23155 NOVEL PROTEIN HUMAN 5- alpha REDUCTASES AND USES THEREFOR

Abstract: The invention provides isolated nucleic acid molecules, designated 23155 nucleic acid molecules, which encode novel proteins with homology to a 5- alpha reductase. The invention also provides antisense nucleic acid molecules, recombinant expression vectors containing 23155 nucleic acid molecules, host cells into which the expression vectors have been introduced, and nonhuman transgenic animals in which a 23155 gene has been introduced or disrupted. The invention still further provides isolated 23155 proteins, fusion proteins, antigenic peptides and anti-23155 antibodies. Diagnostic, screening, and therapeutic methods utilizing compositions of the invention are also provided.

Description: 23155 NOVEL PROTEIN HUMAN 5-α REDUCTASES AND USES THEREFOR Background of the Invention The enzyme 5-α reductase (EC 1.3.99.5) is a membrane protein that plays a key role in androgen-dependent target tissues, hi such tissues, 5-c. reductase in target cells reduces the androgen testosterone to c--dihydrotestosterone (DHT) and thus catalyzes the conversion of testosterone into its activated form, DHT. DHT is a steroid that binds to androgen receptors with higher affinity than testosterone. Thus, 5-c. reductase plays an important role relating to androgen levels, which effect the growth and function of many tissues in addition to the reproductive organs. When 5-c. reductase activity is defective, the levels of DHT are reduced and thus, androgen receptors are only partially activated and a full androgen response is not obtained. Those tissues that require high levels of androgens for normal development, such as primordia of external genitalia, do not develop normally and resemble the female phenotype, a clinical condition called male pseudohermaphrodism. (Geoffrey Zubay, Biochemistry 1112-14 (1984)). In contrast, the overproduction of DHT is also associated with human endocrine disorders. Steroidal or non-steroidal inhibitors of 5-c. reductase activity have been used to treat human endocrine disorders such as benign prostatic hyperplasia, a disease that occurs almost universally in males which is characterized by obstructive and irritative urinary voiding symptoms. (Proc Natl Acad Sci U S A 1993 Jun 1; 90 (11):5277-81). Regulation of 5-c. reductase activity may therefore be an important strategy in controlling some types of human endocrine disorders associated with the inhibition or over stimulation of 5-c. reductase activity. Further, testosterone and the steroids metabolized by 5-c. reductase influence processes such as cellular proliferation and cell survival, both of which factor into tumor progression. Regulation of 5-c. reductase activity may therefore be an important strategy in controlling cellular proliferation and cell survival disorders associated with the inhibition or over stimulation of 5-c. reductase activity. Summary of the Invention The present invention is based, at least in part, on the discovery of novel proteins with similarities to known 5-c.reductases, as well as nucleic acid molecules encoding these proteins, referred to herein as "23155". The 23155 nucleic acid and protein molecules of the present invention are useful as modulating agents in regulating a variety of cellular processes affected by androgens, e.g., including the differentiation, growth and maintenance of many tissues in addition to reproductive organs. In particular, 23155 and its related nucleic acids will be useful in treating certain endocrine disorders characterized by abnormal androgen processing, hi addition, overexpression of 32155 in tumor cells exerts an effect on steroid metabolism and intracellular steroid distribution, which In turn affects critical cell processes such as proliferation an survival. Situations where the proteins ofthe invention are of particular advantage are in cases where 5-c. reductase activity is inhibited or reduced, hi cases where cells lack 23155 activity, 23155 can be provided to cells to restore such activity. In other cases where cells overproduce 5-α reductase, 23155 activity, steroid or non-steroid inhibitors of 23155 can be used to reduce excess activity. Examples of such inhibitors include non-steroidal compounds similar to LY191704 (Proc Natl Acad Sci U S A 1993 Jun 1; 90 (11):5277-81), and antibodies specifically recognizing 23155. Such inhibitors are also useful in treating tissues, organs, and subjects that have excess 5-α reductase, 23155 activity. one aspect, this invention provides isolated nucleic acid molecules encoding 23155 proteins or biologically active portions thereof, as well as nucleic acid fragments suitable as primers or hybridization probes for the detection of 23155-encoding nucleic acids. In one embodiment, a 23155 nucleic acid molecule ofthe invention is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or more homologous to a nucleotide sequence (e.g., to the entire length ofthe nucleotide sequence) including SEQ ID NO:l, SEQ ID NO: 3, or a complement thereof. hi a preferred embodiment, a 23155 nucleic acid molecule includes a nucleotide sequence encoding a protein having an amino acid sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 85%, 90%, 95%, 98% or more homologous to an amino acid sequence including SEQ ID NO:2 (e.g., the entire amino acid sequence of SEQ ID NO:2). In another preferred embodiment, an isolated nucleic acid molecule encodes the amino acid sequence of a human 23155. In yet another preferred embodiment, the nucleic acid molecule includes a nucleotide sequence encoding a protein which includes the amino acid sequence of SEQ ID NO:2. In yet another preferred embodiment, the nucleic acid molecule includes a nucleotide sequence encoding a protein having the amino acid sequence of SEQ ID NO:2. Another embodiment ofthe invention features nucleic acid molecules, preferably 23155 nucleic acid molecules, which specifically detect 23155 nucleic acid molecules relative to nucleic acid molecules encoding non-23155 proteins. For example, in one embodiment, such a nucleic acid molecule is at least 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 nucleotides in length and hybridizes under stringent conditions to a nucleic acid molecule comprising the nucleotide sequence shown in SEQ ID NO: 1, or a complement thereof. hi other preferred embodiments, the nucleic acid molecule encodes a naturally occurring allelic variant of a polypeptide which includes the amino acid sequence of SEQ ID NO:2, wherein the nucleic acid molecule hybridizes to a nucleic acid molecule which includes SEQ ID NO:l or SEQ ID NO:3 under stringent conditions. Another embodiment ofthe invention provides an isolated nucleic acid molecule which is antisense to a 23155 nucleic acid molecule, e.g., the coding strand of a 23155 nucleic acid molecule. Another aspect ofthe invention provides a vector comprising a 23155 nucleic acid molecule. In certain embodiments, the vector is a recombinant expression vector, hi another embodiment, the invention provides a host cell containing a vector ofthe invention. The invention also provides a method for producing a protein, preferably a 23155 protein, by culturing in a suitable medium, a host cell, e.g., a mammalian host cell such as a non- human mammalian cell, ofthe invention containing a recombinant expression vector, such that the protein is produced. Another aspect of this invention features isolated or recombinant 23155 proteins and polypeptides. In one embodiment, the isolated protein, preferably a 23155 protein, includes at least one domain conferring 5-α reductase activity and/or a transmembrane domain, h another embodiment, the isolated protein, preferably a 23155 protein, includes at least one domain conferring 5-α reductase activity or a transmembrane domain and has an amino acid sequence which is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 81%, 85%, 90%, 95%, 99% or more homologous to an amino acid sequence including SEQ ID NO:2. In an even further embodiment, the isolated protein, preferably a 23155 protein, includes at least one 5-α reductase domain and plays a role in androgen processing and signalling pathways associated with androgens, e.g., signalling pathways associated with endocrine disorders. In another embodiment, the isolated protein, preferably a 23155 protein, includes at least one 5-α reductase and/or transmembrane domain and is encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l or SEQ ID NO:3. hi another embodiment, the isolated protein, preferably a 23155 protein, has an amino acid sequence sufficiently homologous to the amino acid sequence of SEQ ID NO:2. hi a preferred embodiment, the protein, preferably a 23155 protein, has an amino acid sequence at least about 50%, 55%, 59%, 60%, 65%, 70%, 75%, 80%, 81%, 85%, 90%, 95%, 98% or more homologous to an amino acid sequence including SEQ ID NO:2 (e.g., the entire amino acid sequence of SEQ ID NO:2). hi another embodiment, the invention features fragments ofthe proteins having the amino acid sequence of SEQ ID NO:2, wherein the fragment comprises at least 15 amino acids (e.g., contiguous amino acids) of. the amino acid sequence of SEQ ID NO:2, respectively. In another embodiment, the protein, preferably a 23155 protein, has the amino acid sequence of SEQ ID NO:2. Another embodiment ofthe invention features an isolated protein, preferably a 23155 protein, which is encoded by a nucleic acid molecule having a nucleotide sequence at least about 50%, 55%, 60%, 62%, 65%, 70%, 75%, 78%, 80%, 85%, 86%, 90%, 95%, 97%, 98% or more homologous to a nucleotide sequence (e.g., to the entire length ofthe nucleotide sequence) including SEQ ID NO:l, SEQ ID NO:3, or a complement thereof. This invention further features an isolated protein, preferably a 23155 protein, which is encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, or a complement thereof. The proteins ofthe present invention or biologically active portions thereof, can be operatively linked to a non-23155 polypeptide (e.g., heterologous amino acid sequences) to form fusion proteins. The invention further features antibodies, such as monoclonal or polyclonal antibodies, that specifically bind proteins ofthe invention, preferably 23155 proteins. In addition, the 23155 proteins or biologically active portions thereof can be incorporated into pharmaceutical compositions, which optionally include pharmaceutically acceptable carriers. hi another aspect, the present invention provides a method for detecting the presence of a 23155 nucleic acid molecule, protein or polypeptide in a biological sample by contacting the biological sample with an agent capable of detecting a 23155 nucleic acid molecule, protein or polypeptide such that the presence of a 23155 nucleic acid molecule, protein or polypeptide is detected in the biological sample. another aspect, the present invention provides a method for detecting the presence of 23155 activity in a biological sample by contacting the biological sample with an agent capable of detecting an indicator of 23155 activity such that the presence of 23155 activity is detected in the biological sample. In another aspect, the invention provides a method for modulating 23155 activity comprising contacting a cell capable of expressing 23155 with an agent that modulates 23155 activity such that 23155 activity in the cell is modulated. In one embodiment, the agent inhibits 23155 activity. In another embodiment, the agent stimulates 23155 activity, h one embodiment, the agent is an antibody that specifically binds to a 23155 protein, hi another embodiment, the agent modulates expression of 23155 by modulating transcription of a 23155 gene or translation ofa 23155 mRNA. In yet another embodiment, the agent is a nucleic acid molecule having a nucleotide sequence that is antisense to the coding strand of a 23155 mRNA or a 23155 gene. h one embodiment, the methods ofthe present invention are used to treat a subject having a disorder characterized by aberrant 23155 protein or nucleic acid expression or activity by administering an agent which is a 23155 modulator to the subject, hi one embodiment, the 23155 modulator is a 23155 protein. In another embodiment the 23155 modulator is a 23155 nucleic acid molecule, hi yet another embodiment, the 23155 modulator is a peptide, peptidomimetic, or other small molecule. In a preferred embodiment, the disorder characterized by aberrant 23155 protein or nucleic acid expression is a cellular growth related disorder. The present invention also provides a diagnostic assay for identifying the presence or absence of a genetic alteration characterized by at least one of (i) aberrant modification or mutation of a gene encoding a 23155 protein; (ii) mis-regulation ofthe gene; and (iii) aberrant post-translational modification of a 23155 protein, wherein a wild-type form ofthe gene encodes a protein with a 23155 activity. hi another aspect the invention provides a method for identifying a compound that binds to or modulates the activity of a 23155 protein, by providing an indicator composition comprising a 23155 protein having 23155 activity, contacting the indicator composition with a test compound, and determining the effect ofthe test compound on 23155 activity in the indicator composition to identify a compound that modulates the activity of a 23155 protein. Other features and advantages ofthe invention will be apparent from the following detailed description and claims. Brief Description of the Drawings Figures la-b depict a cDNA sequence (SEQ ID NO:l) and predicted amino acid sequence (SEQ ID NO:2) of human 23155. Figures 2a-b depict the location ofthe metMonine-initiated open reading frame of human 23155 (without the 5' and 3' untranslated regions) indicated as SEQ ID NO:3. Figure 3 depicts a hydropathy plot of human 23155. Relatively hydrophobic residues are shown above the dashed horizontal line, and relatively hydrophilic residues are below the dashed horizontal line. The location ofthe transmembrane domains, and the extracellular and intracellular loops is also indicated. The cysteine residues (cys) and N- glycosylation sites are indicated by short vertical lines just below the hydropathy trace. The numbers corresponding to the amino acid sequence of human 23155 are indicated. Polypeptides ofthe invention include fragments which include: all or part of a hydrophobic sequence, e.g., a sequence above the dashed line, e.g., the sequence from about amino acid 90 to 110, from about 150 to 180, and from about 260 to 270 of SEQ ID NO:2; all or part of a hydrophilic sequence, e.g., a sequence below the dashed line, e.g., the sequence from about amino acid 50 to 70, from about 180 to 190, and from about 295 to 310 of SEQ ID NO:2; a sequence which includes a Cys, or a glycosylation site. Figure 4 depicts an alignment ofthe 5-alpha-reductase domain of human 23155 with a consensus amino acid sequence derived from a hidden Markov model (HMM) from PFAM. The upper sequence is the consensus amino acid sequence (SEQ ID NO:4), while the lower amino acid sequence corresponds to amino acids 145 to 318 of SEQ ID NO:2. Figure 5 depicts a BLAST alignment of human 23155 with a consensus amino acid sequence derived from a ProDomain "steriod 3-oxo-5-alpha-steriod 4-dehydrogenase 5- alpha-reductase SR type oxidoreductase microsome membrane sexual;" (Release 1999.2, http://www.toulouse.inra.fr/prodom.html). The lower sequence is amino acid residues 29 to 146 ofthe 118 amino acid consensus sequence (SEQ ID NO:4), while the upper amino acid sequence corresponds to the "steriod 3-oxo-5-alpha-steriod 4-dehydrogenase 5-alpha- reductase SR type oxidoreductase microsome membrane sexual" domain of human 23155, amino acid residues 201 to 317 of SEQ ID NO:2. Figure 6 is a panel bar graph depicting the relative expression of 23155 RNA relative to a no template control in a panel of human tissues or cells, including but not limited to normal artery, diseased aorta, normal vein, coronary smooth muscle cells (SMC) human umbilical vein endothelial cells (HUVEC), hemangioma, normal heart, coronary heart failure heart tissue, kidney, normal adipose, pancreas, primary osteoblasts, osteoclasts, skin, spinal cord, brain cortex, brain hypofhalarnus, nerve, dorsal root ganglia (DRS), normal breast, breast tumor, normal ovary, ovary tumor, normal prostate and prostate tumor, salivary glands, normal colon and colon tumor, normal lung and lung tumor, lung COPD, colon IBD, normal liver and liver fibrosis, spleen, tonsil, lymph node, small intestine, macrophages, synovium, BM-MNC, activated PBMC, neutrophlis, megakaryocytes, and erythroid, among others, detected using real-time quantitative RT- PCR Taq Man analysis. The graph indicates significant expression in HUVEC, normal human brain cortex, colon tumor and lung tumor. Figure 7 is a panel bar graph depicting the relative expression of 23155 RNA relative to a no template controls in a panel of human tissues or cells, including but not limited to aorta, fetal heart, normal heart, heart/CHF, normal vein, aortic smooth muscle cells (SMC), normal spinal cord, brain cortex, brain hypothalamus, glial cells, brain glioblastoma, normal breast, breast rumor, ovary, pancreas, colon, kidney, liver, lung, spleen, tonsil, lymph node, thymus, epithelial, endothelial, skeletal, fibroblasts, skin, adipose, bone cells (e.g., differentiated and undifferentiated osteoclasts and osteoblasts), aortic SMC (early), aortic SMC (late), shear and static human umbilical vein endothelial cells (HUVEC), among others, detected using real-time quantitative RT-PCR Taq Man analysis. The graph indicates significant expression in brain cortex and hypothalamus, colon tumor, normal fetal liver, lung tumor, epithelial cells and HUVEC. Figure 8 depicts the expression of 23155 RNA relative to a no template control showing the differential expression, in various lung tumor cell lines and lung tissues, which expression was detected using Taq Man analysis. Figure 9 is an oncology panel bar graph depicting the expression of 23155 RNA relative to a no template control showing an increased expression in 4/8 clinical colon tumors in comparison to normal colon tissues, and showing an increased expression in 2/4 liver metastasis in comparison to normal liver tissues, which expression was detected using Taq Man analysis. Figure 10 is a graph of he relative expression of 23155 RNA relative to a no template control in a panel of human clinical angiogenic tissues or cells detected using realtime quantitative RT-PCR Taq Man analysis. Strong positive expression was found in normal brain tissue. Figure 11 is an oncology panel bar graph depicting the expression of 23155 RNA relative to a no template control showing expression in clinical breast tissue samples, which expression was detected using Taq Man analysis. Figure 12 is an oncology panel bar graph depicting the expression of 23155 RNA relative to a no template control showing an increased expression in 2/6 clinical ovary tumors in comparison to normal ovary tissues, which expression was detected using Taq Man analysis. Figure 13 is an oncology panel bar graph depicting the expression of 23155 RNA relative to a no template control showing an increased expression in 7/7 clinical lung tumors in comparison to normal lung tissues, which expression was detected using Taq Man analysis. Detailed Description ofthe Invention The present invention is based, at least in part, on the discovery of novel molecules, referred to herein as "23155" nucleic acid and polypeptide molecules, which play a role in or function in signalling pathways associated with cellular growth, hi one embodiment, the 23155 molecules modulate the activity of one or more proteins involved in cellular growth or differentiation, e.g., cardiac cell growth or differentiation. In another embodiment, the 23155 molecules ofthe present invention are capable of modulating the phosphorylation state of a 23155 molecule or one or more proteins involved in cellular growth or differentiation. The present invention is based, at least in part, on the discovery of novel molecules, referred to herein as 23155 protein and nucleic acid molecules, which comprise a family of molecules having certain conserved structural and functional features. The term "family" when referring to the protein and nucleic acid molecules ofthe invention is intended to mean two or more proteins or nucleic acid molecules having a common structural domain or motif and having sufficient amino acid or nucleotide sequence homology as defined herein. Such family members can be naturally or non-naturally occurring and can be from either the same or different species. For example, a family can contain a first protein of human origin, as well as other, distinct proteins of human origin or alternatively, can contain homologues of non-human origin. Members of a family may also have common functional characteristics. One embodiment ofthe invention features 23155 nucleic acid molecules, preferably human 23155 molecules, e.g., 23155. The 23155 nucleic acid and protein molecules ofthe invention are described in further detail in the following subsections. A. The 23155 Nucleic Acid and Protein Molecules The human 23155 sequence (Figure 1; SEQ ID NO:l), which is approximately 1287 nucleotides long including untranslated regions, contains a predicted methionine-initiated coding sequence of about 957 nucleotides, including the termination codon (nucleotides indicated as coding sequence of SEQ ID NO:l in Fig. 1; SEQ ID NO:3). The coding sequence encodes a 318 amino acid protein (SEQ ID NO:2). The human 23155 protein of SEQ ID NO:2 and Figure 2 includes an amino-terminal hydrophobic amino acid sequence, consistent with a signal sequence, of about 41 amino acids (from amino acid 1 to about amino acid 41 of SEQ ID NO:2, (PSORT, Nakai, K. and Kanehisa, M. (1992) Genomics 14:897-911)), which upon cleavage results in the production of a mature protein form. Human 23155 contains the following regions or other structural features (for general information regarding PFAM identifiers, PS prefix and PF prefix domain identification numbers, refer to Sonnhammer et al. (1997) Protein 28:405-420 and http://www.psc.edu/general/software/packages/pfarn/pfam.html): a 3-oxo-5 -alpha-steroid 4-dehydrogenase domain (PFAM Accession Number PF02544) located at about amino acid residues 145 to 318 of SEQ ID NO:2; seven transmembrane domains (predicted by MEMS AT, Jones et al. (1994) Biochemistry 33:3038-3049) at about amino acids 22 to 46, 75 to 91, 98 to 118, 125 to 141, 156 to 178, 199 to 215 and 260 to 281 of SEQ ID NO:2; one N-glycosylation site (Prosite PS00001) from about amino acids 274 to 277 of SEQ ID NO:2; one protein kinase C phosphorylation sites (Prosite PS00005) at about amino acids 140 to 142, and 191 to 193 of SEQ ID NO:2; one tyrosine kinase phosphorylation site (Prosite PS00007) located at about amino acids 142 to 149 of SEQ ID NO:2; and two N-myristoylation sites (Prosite PS00008) from about amino acids 38 to 43, and 122 to 127 of SEQ ID NO:2. In one embodiment, the isolated proteins ofthe present invention, preferably 23155 proteins, are identified based on the presence of at least one "5-α reductase" domain. As used herein, the term "5-α reductase domain" includes an amino acid sequence of about: 100-400 amino acid residues in length, preferably about 100-300 amino acid residues in length, and more preferably about 100-250 amino acid residues in length, which is conserved in 5-α reductases and having a bit score for the alignment ofthe sequence to the 5-α reductase domain (HMM) of at least about 10, preferably about 15, and more preferably about 25. Short, conserved, stretches of amino acid residues may be present within the 5-α reductase domain, which alternate in sequence with variable-length stretches of amino acid residues which do not exhibit a high level of conservation. The 5-α reductase domain is located after about the fourth transmembrane domain of human 23155 polypeptide and which corresponds to about amino acids 145 to 318 of SEQ ID NO:2. The 5-α reductase domain (1 MM) has been assigned the PFAM Accession Number PF02544 (http://genome.wustl.edu/Pfam/.html). An alignment ofthe 5-α reductase domain (amino acids 145 to 318 of SEQ ID NO:2) of human 23155 with a consensus amino acid sequence (SEQ ID NO:4) derived from a hidden Markov model is depicted in Figure 4. hi a preferred embodiment, a 23155 polypeptide or protein has a "5-α reductase domain" or a region which includes at least about 100-400 more preferably about 100-300 or 100-250 amino acid residues and has at least about 60%, 70% 80% 90% 95%, 99%, or 100% homology with a "5-α reductase domain," e.g., the 5-α reductase domain of human 23155 (e.g., residues 145 to 318 of SEQ ID NO:2). To identify the presence of a "5-α reductase" domain in a 23155 protein sequence, and make the determination that a polypeptide or protein of interest has a particular profile, the amino acid sequence ofthe protein can be searched against the Pfam database of HMMs (e.g., the Pfam database, release 2.1) using the default parameters (http://www.sanger.ac.uk/Software/Pfarn/TTMM_search). For example, the hmmsf program, which is available as part ofthe HMMER package of search programs, is a family specific default program for MILPAT0063 and a score of 15 is the default threshold score for determining a hit. Alternatively, the threshold score for determining a hit can be lowered (e.g., to 8 bits). A description ofthe Pfam database can be found in Sonhammer et al. (1997) Proteins 28:405-420 and a detailed description of HMMs can be found, for example, in Gribskov et al (1990) Meth. Enzymol.183: 146-159; Gribskov et al. (1987) Proc. Natl. Acad. Sci. USA 84:4355-4358; Krogh et α/. (1994) J. Mol. Biol 235:1501-1531; and Srultz et al. (1993) Protein Sci. 2:305-314, the contents of which are incorporated herein by reference. A search was performed against the HMM database resulting in the identification of a "5-α reductase domain" domain in the amino acid sequence of human 23155 at about residues 145 to 318 of SEQ ID NO:2 (see Figure 1). The 5-α reductase domain is homologous to ProDom family "steriod 3-oxo-5-alpha- steriod 4-dehydrogenase 5-alpha-reductase SR type oxidoreductase microsome membrane sexual," SEQ ID NO:5 ProDomain Release 1999.2 http.7/www.toulouse.inra.fr/prodom.html). ProDom (derived from BLAST search) alignments ofthe amino acid sequence of human 23155 revealed that 23155 is similar to the "steriod 3-oxo-5-alpha-steriod 4-dehydrogenase 5-alpha-reductase SR type oxidoreductase microsome membrane sexual" protein. This amino acid molecule is approximately 34% identical to 23155, over amino acids 201 to 317 (SEQ ID NO:5) depicted in Figure 5. To identify the presence of a "5-α reductase" domain in a 23155 protein sequence, and make the determination that a polypeptide or protein of interest has a particular profile, the amino acid sequence ofthe protein can be searched against a database of domains, e.g., the ProDom database (Corpet et al (1999), Nucl Acids Res. 27:263-267). The ProDom protein domain database consists of an automatic compilation of homologous domains. Current versions of ProDom are built using recursive PSI-BLAST searches (Altschul SF et al (1997) Nucleic Acids Res. 25:3389-3402; Gouzy et al. (1999) Computers and Chemistry 23:333-340) ofthe SWISS-PROT 38 and TREMBL protein databases. The database automatically generates a consensus sequence for each domain. A BLAST search was performed against the HMM database resulting in the identification of a "5-α reductase" domain in the amino acid sequence of human 23155 at about residues 201 to 317 of SEQ TD NO:2 (see Figure 1). Isolated proteins ofthe present invention, preferably 23155 proteins, have an amino acid sequence sufficiently homologous to the amino acid sequence of SEQ ID NO:2 or are encoded by a nucleotide sequence sufficiently homologous to SEQ ID NO:l or SEQ ID NO:3. As used herein, the term "sufficiently homologous" refers to a first amino acid or nucleotide sequence which contains a sufficient or minimum number of identical or equivalent (e.g., an amino acid residue which has a similar side chain) amino acid residues or nucleotides to a second amino acid or nucleotide sequence such that the first and second amino acid or nucleotide sequences share common structural domains or motifs and/or a common functional activity. For example, amino acid or nucleotide sequences which share common structural domains have at least 30%, 40%, or 50% homology, preferably 60% homology, more preferably 70%-80%, and even more preferably 90-95% homology across the amino acid sequences ofthe domains and contain at least one and preferably two structural domains or motifs, are defined herein as sufficiently homologous. Furthermore, amino acid or nucleotide sequences which share at least 30%, 40%, or 50%, preferably 60%, more preferably 70-80%, or 90-95% homology and share a common functional activity are defined herein as sufficiently homologous. A 23155 polypeptide can include at least one, two, three, four, five, six, and preferably seven "transmembrane domains" or regions homologous with "transmembrane domains". As used herein, the term "transmembrane domain" includes an amino acid sequence of about 10 to 40 amino acid residues in length and spans the plasma membrane. Transmembrane domains are rich in hydrophobic residues, e.g., at least 50%, 60%, 70%, 80%, 90%, 95% or more ofthe amino acids of a transmembrane domain are hydrophobic, e.g., leucines, isoleucines, tyrosines, or tryptophans. Transmembrane domains typically have alpha-helical structures and are described in, for example, Zagotta, W.N. et al., (1996) Annual Rev. Neuroscl 19:235-263, the contents of which are incorporated herein by reference. i a preferred embodiment, a 23155 polypeptide or protein has at least one, two, three, four, five, six and preferably seven "transmembrane domains" or regions which include at least about 12 to 35 more preferably about 14 to 30 or 15 to 25 amino acid residues and has at least about 60%, 70% 80% 90% 95%, 99%, or 100% homology with a "transmembrane domain," e.g., the transmembrane domains of human 23155 (e.g., residues 22 to 46, 75 to 91, 98 to 118, 125 to 141, 156 to 178, 199 to 215 and 260 to 281 of SEQ ID NO:2). The transmembrane domain of human 23155 is visualized in the hydropathy plot (Figure 3) as regions of about 15 to 25 amino acids where the hydropathy trace is mostly above the horizontal line. To identify the presence of a "transmembrane" domain in a 23155 protein sequence, and make the determination that a polypeptide or protein of interest has a particular profile, the amino acid sequence ofthe protein can be analyzed by a transmembrane prediction method that predicts the secondary structure and topology of integral membrane proteins based on the recognition of topological models (MEMSAT, Jones et al., (1994) Biochemistry 33:3038- 3049). A 23155 polypeptide can include at least one, two, three, four, five, six, seven, eight preferably nine "non-transmembrane regions." As used herein, the term "non-transmembrane region" includes an amino acid sequence not identified as a transmembrane domain. The non- transmembrane regions in 23155 are located at about amino acids 1 to 21, 47 to 74, 92 to 97, 119 to 124, 142 to 155, 179 to 198, 216 to 259, and 281 to 318 of SEQ ID NO:2. The non-transmembrane regions of 23155 include at least one, two or three, preferably four cytoplasmic regions. When located at the C-terminus, the cytoplasmic region is referred to herein as the "C-terminal cytoplasmic domain." As used herein, an "C-terminal cytoplasmic domain" includes an amino acid sequence having about 1 to 50, preferably about 1 to 45, more preferably about 1 to 40, or even more preferably about 1 to 37 amino acid residues in length and is located inside of a cell or within the cytoplasm of a cell. The C- terminal amino acid residue of an "C-terminal cytoplasmic domain" is adjacent to an C- terminal amino acid residue of a transmembrane domain in a 23155 protein. For example, an C-terminal cytoplasmic domain is located at about amino acid residues 282 to 318 of SEQ ID NO:2. In a preferred embodiment, a polypeptide or protein has an C-terminal cytoplasmic domain or a region which includes at least about 5, preferably about 1 to 30, and more preferably about 1 to 37 amino acid residues and has at least about 60%, 70% 80% 90% 95%, 99%, or 100% homology with an "C-terminal cytoplasmic domain," e.g., the C-terminal cytoplasmic domain of human 23155 (e.g., residues 282 to 318 of SEQ ID NO:2). In another embodiment, a 23155 protein includes at least one, two and preferably three cytoplasmic loops. As used herein, the term "loop" includes an amino acid sequence that resides outside of a phospholipid membrane, having a length of at least about 5, preferably about 5 to 50, more preferably about 7 to 28 amino acid residues, and has an amino acid sequence that connects two transmembrane domains within a protein or polypeptide. Accordingly, the N-terminal amino acid of a loop is adjacent to a C-terminal amino acid of a transmembrane domain in a 23155 molecule, and the C-terminal amino acid of a loop is adjacent to an N-terminal amino acid of a transmembrane domain in a 23155 molecule. As used herein, a "cytoplasmic loop" includes a loop located inside of a cell or within the cytoplasm of a cell. For example, a "cytoplasmic loop" can be found at about amino acid residues 47 to 74, 119 to 124, or 179 to 198 of SEQ ID NO:2. In a preferred embodiment, a 23155 polypeptide or protein has a cytoplasmic loop or a region which includes at least about 5, preferably about 5 to 50, more preferably about 7 to 28 amino acid residues and has at least about 60%, 70% 80% 90% 95%, 99%, or 100% homology with a cytoplasmic loop," e.g., a cytoplasmic loop of human 23155 (e.g., residues 47 to 74, 119 to 124, or 179 to 198 of SEQ ID NO:2). hi another embodiment, a 23155 protein includes at least one, preferably two non- cytoplasmic loops. As used herein, a "non-cytoplasmic loop" includes an amino acid sequence located outside of a cell or within an intracellular organelle. Non-cytoplasmic loops include extracellular domains (i.e., outside ofthe cell) and intracellular domains (i.e., within the cell). When referring to membrane-bound proteins found in intracellular organelles (e.g., mitochondria, endoplasmic reticulum, peroxisomes microsomes, vesicles, endosomes, and lysosomes), non-cytoplasmic loops include those domains ofthe protein that reside in the lumen ofthe organelle or the matrix or the intermembrane space. For example, a "non- cytoplasmic loop" can be found at about amino acid residues 92 to 97, 142 to 155, and 216 to 259, of SEQ ID NO:2. In a preferred embodiment, a 23155 polypeptide or protein has at least one non- cytoplasmic loop or a region which includes at least about 5, preferably about 5 to 50, more preferably about 6 to 44 amino acid residues and has at least about 60%, 70% 80% 90% 95%, 99%, or 100% homology with a "non-cytoplasmic loop," e.g., at least one non-cytoplasmic loop of human 23155 (e.g., residues 92 to 97, 142 to 155, and 216 to 259 of SEQ ID NO:2). A 23155 family member can include at least one 3 -oxo-5 -alpha-steroid 4- dehydrogenase domain or a 5-α reductase domain or at least one, two, three, four, five, six, seven, eight and preferably nine transmembrane or non-transmembrane domains. Furthermore, a 23155 family member can include at least one N-glycosylation site (PS00001); at least one, preferably two protein kinase C phosphorylation sites (PS00005); at least one tyrosine kinase phosphorylation site (PS00007); or at least one and preferably two N-myristoylation sites (PS00008). As used interchangeably herein a "23155 activity", "biological activity of 23155" or "functional activity of 23155", refers to an activity exerted by a 23155 protein, polypeptide or nucleic acid molecule on a 23155 responsive cell or a 23155 protein substrate, as determined in vivo, or in vitro, according to standard techniques. The biological activity of 23155 is described herein. Accordingly, another embodiment ofthe invention features isolated 23155 proteins and polypeptides having a 23155 activity. Preferred proteins are 23155 proteins having at least one 5-α reductase activity, preferably, a 23155 activity. Additional preferred proteins have at least one 5-α reductase domain and are, preferably, encoded by a nucleic acid molecule having a nucleotide sequence which hybridizes under stringent hybridization conditions to a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l or SEQ ID NO:3. A 23155 activity can also be an indirect activity, e.g., a cellular signaling activity mediated by interaction ofthe 23155 protein with a 23155 receptor. Based on the above- described sequence structures and similarities to molecules of known function, the 23155 molecules ofthe present invention have similar biological activities as 5-α reductase family members. For example, the 23155 proteins ofthe present invention can have one or more ofthe following activities: (1) regulating a variety of cellular processes affected by androgens, e.g., including the differentiation, growth and maintenance of many tissues in addition to reproductive organs; (2) modulating endocrine functions characterized by abnormal androgen processing; (3) steroid metabolism e.g. converting testosterone into its activated form (dihydrotestosterone); (4) modulating cellular proliferation and cell survival; and (5) the ability to antagonize or inhibit, competitively or non-competitively, any or all of (l)-(5). Thus, the 23155 molecules can act as novel diagnostic targets and therapeutic agents for controlling one or more cancers or disorders relating to cellular proliferation and cell survival. Examples of such disorders, e.g., 5-αreductase-associated or other 23155- associated disorders, include but are not limited to, cellular proliferative and/or differentiative disorders, disorders associated with bone metabolism, immune e.g., inflammatory, disorders, cardiovascular disorders, including endothelial cell disorders, liver disorders, viral diseases, pain or metabolic disorders, and preferably cellular proliferative and/or differentiative disorders. Examples of cellular proliferative and/or differentiative disorders include cancer, e.g., carcinoma, sarcoma, metastatic disorders or hematopoietic neoplastic disorders, e.g., leukemias. A metastatic tumor can arise from a multitude of primary tumor types, including but not limited to those of prostate, colon, lung, breast and liver origin. As used herein, the term "cancer" (also used interchangeably with the terms, "hyperproliferative" and "neoplastic") refers to cells having the capacity for autonomous growth, i.e., an abnormal state or condition characterized by rapidly proliferating cell growth. Cancerous disease states maybe categorized as pathologic, i.e., characterizing or constituting a disease state, e.g., malignant tumor growth, or may be categorized as non- pathologic, i.e., a deviation from normal but not associated with a disease state, e.g., cell proliferation associated with wound repair. The term is meant to include all types of cancerous growths or oncogenic processes, metastatic tissues or malignantly transformed cells, tissues, or organs, irrespective of histopathologic type or stage of invasiveness. The term "cancer" includes malignancies ofthe various organ systems, such as those affecting lung, breast, thyroid, lymphoid, gastrointestinal, and genito-urinary tract, as well as adenocarcinomas which include malignancies such as most colon cancers, renal-cell carcinoma, prostate cancer and/or testicular tumors, non-small cell carcinoma ofthe lung, cancer ofthe small intestine and cancer ofthe esophagus. The term "carcinoma" is art recognized and refers to malignancies of epithelial or endocrine tissues including respiratory system carcinomas, gastrointestinal system carcinomas, genitourinary system carcinomas, testicular carcinomas, breast carcinomas, prostatic carcinomas, endocrine system carcinomas, and melanomas. Exemplary carcinomas include those forming from tissue ofthe cervix, lung, prostate, breast, head and neck, colon and ovary. The term "carcinoma" also includes carcinosarcomas, e.g., which include malignant tumors composed of carcinomatous and sarcomatous tissues. An "adenocarcinoma" refers to a carcinoma derived from glandular tissue or in which the tumor cells form recognizable glandular structures. The term "sarcoma" is art recognized and refers to malignant tumors of mesenchymal derivation. The 23155 molecules ofthe invention can be used to monitor, treat and/or diagnose a variety of proliferative disorders. Such disorders include hematopoietic neoplastic disorders. As used herein, the term "hematopoietic neoplastic disorders" includes diseases involving hyperplastic/neoplastic cells of hematopoietic origin, e.g., arising from myeloid, lymphoid or erythroid lineages, or precursor cells thereof. Preferably, the diseases arise from poorly differentiated acute leukemias, e.g., erythroblastic leukemia and acute megakaryoblastic leukemia. Additional exemplary myeloid disorders include, but are not limited to, acute promyeloid leukemia (APML), acute myelogenous leukemia (AML) and chronic myelogenous leukemia (CML) (reviewed in Vaickus, L. (1991) Crit Rev. in Oncol. Hemotol. 11:267-97); lymphoid malignancies include, but are not limited to acute lymphoblastic leukemia (ALL) which includes B-lineage ALL and T-lineage ALL, chronic lymphocytic leukemia (CLL), prolymphocytic leukemia (PLL), hairy cell leukemia (HLL) and Waldenstrom's macroglobulinemia (WM). Additional forms of malignant lymphomas include, but are not limited to non-Hodgkin lymphoma and variants thereof, peripheral T cell lymphomas, adult T cell leukemia/lymphoma (ATL), cutaneous T-cell lymphoma (CTCL), large granular lymphocytic leukemia (LGF), Hodgkin's disease and Reed- Sternberg disease. The nucleotide sequence ofthe isolated human 23155 cDNA and the predicted amino acid sequence ofthe human 23155 polypeptide are shown in Figures 1-2 and in SEQ ID NOs: 1 and 2, respectively. A plasmid containing the nucleotide sequence encoding human 23155 was deposited with American Type Culture Collection (ATCC), 10801 University Boulevard, Manassas, VA 20110-2209, on and assigned Accession Number . This deposit will be maintained under the terms ofthe Budapest Treaty on the International Recognition ofthe Deposit of Microorganisms for the Purposes of Patent Procedure. This deposit was made merely as a convenience for those of skill in the art and is not an admission that a deposit is required under 35 U.S.C. §112. The 23155 gene, which is approximately 1287 nucleotides in length, encodes a protein having a molecular weight of approximately 35.1 kD and which is approximately 318 amino acid residues in length. The 23155 gene is expressed predominantly in the brain and protate epithelium as well as lung tumors, colon tumors, and ovarian tumors. Various aspects ofthe invention are described in further detail in the following subsections: I. Isolated Nucleic Acid Molecules One aspect ofthe invention pertains to isolated nucleic acid molecules that encode 23155 proteins or biologically active portions thereof, as well as nucleic acid fragments sufficient for use as hybridization probes to identify 23155-encoding nucleic acids (e.g., 23155 mRNA) and fragments for use as PCR primers for the amplification or mutation of 23155 nucleic acid molecules. As used herein, the term "nucleic acid molecule" is intended to include DNA molecules (e.g., cDNA or genomic DNA) and RNA molecules (e.g., mRNA) and analogs ofthe DNA or RNA generated using nucleotide analogs. The nucleic acid molecule can be single-stranded or double-stranded, but preferably is double-stranded DNA. An "isolated" nucleic acid molecule is one which is separated from other nucleic acid molecules which are present in the natural source ofthe nucleic acid. For example, with regards to genomic DNA, the term "isolated" includes nucleic acid molecules which are separated from the chromosome with which the genomic DNA is naturally associated. Preferably, an "isolated" nucleic acid is free of sequences which naturally flank the nucleic acid (i.e., sequences located at the 5' and 3' ends ofthe nucleic acid) in the genomic DNA ofthe organism from which the nucleic acid is derived. For example, in various embodiments, the isolated 23155 nucleic acid molecule can contain less than about 5 kb, 4kb, 3kb, 2kb, 1 kb, 0.5 kb or 0.1 kb of nucleotide sequences which naturally flank the nucleic acid molecule in genomic DNA ofthe cell from which the nucleic acid is derived. Moreover, an "isolated" nucleic acid molecule, such as a cDNA molecule, can be substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized. A nucleic acid molecule ofthe present invention, e.g., a nucleic acid molecule having the nucleotide sequence of SEQ ID NO: 1 or SEQ ID NO:3, or a portion thereof, can be isolated using standard molecular biology techniques and the sequence information provided herein. For example, using all or portion ofthe nucleic acid sequence of SEQ ID NO:l, or the nucleotide sequence of SEQ ID NO:3, as a hybridization probe, nucleic acid molecules can be isolated using standard hybridization and cloning techniques (e.g., as described in Sambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989). Moreover, a nucleic acid molecule encompassing all or a portion of SEQ ID NO:l or SEQ ID NO:3 can be isolated by the polymerase chain reaction (PCR) using synthetic oligonucleotide primers designed based upon the sequence of SEQ ID NO:l or SEQ ID NO:3, respectively. A nucleic acid ofthe invention can be amplified using cDNA, mRNA or alternatively, genomic DNA, as a template and appropriate oligonucleotide primers according to standard PCR amplification techniques. The nucleic acid so amplified can be cloned into an appropriate vector and characterized by DNA sequence analysis. Furthermore, oligonucleotides corresponding to 23155 nucleotide sequences can be prepared by standard synthetic techniques, e.g., using an automated DNA synthesizer. In a preferred embodiment, an isolated nucleic acid molecule ofthe invention comprises the nucleotide sequence shown in SEQ ID NO: 1. The sequence of SEQ ID NO: 1 corresponds to the partial human 23155 cDNA. This cDNA comprises sequences encoding the human 23155 protein (i.e., "the coding region", as shown in SEQ ID NO:3), as well as 5' untranslated sequences (98 nucleotides before the coding region) and 3' untranslated sequences (232 nucleotides after the coding region). Alternatively, the nucleic acid molecule can comprise only the coding region of SEQ ID NO:l (e.g., corresponding to SEQ ID NO:3). In another preferred embodiment, an isolated nucleic acid molecule ofthe invention comprises a nucleic acid molecule which is a complement ofthe nucleotide sequence shown in SEQ ID NO: 1 or SEQ ID NO:3, or a portion of any of these nucleotide sequences. A nucleic acid molecule which is complementary to the nucleotide sequence shown in SEQ ID NO:l or SEQ ID NO:3, is one which is sufficiently complementary to the nucleotide sequence shown in SEQ ID NO.T or SEQ ID NO:3, respectively, such that it can hybridize to the nucleotide sequence shown in SEQ ID NO:l or SEQ ID NO:3, respectively, thereby forming a stable duplex. In still another preferred embodiment, an isolated nucleic acid molecule ofthe present invention comprises a nucleotide sequence which is at least about 50%, 54%, 55%, 60%, 62%, 65%, 70%, 75%, 78%, 80%, 85%, 86%, 90%, 95%, 97%, 98% or more homologous to the nucleotide sequence (e.g., to the entire length ofthe nucleotide sequence) shown in SEQ ID NO:l or SEQ ID NO:3, or a portion of any of these nucleotide sequences. Moreover, the nucleic acid molecule ofthe invention can comprise only a portion of the nucleic acid sequence of SEQ ID NO: 1 or SEQ ID NO:3, for example a fragment which can be used as a probe or primer or a fragment encoding a biologically active portion of a 23155 protein. The nucleotide sequence determined from the cloning ofthe 23155 gene allows for the generation of probes and primers designed for use in identifying and/or cloning other 23155 family members, as well as 23155 homologues from other species. The probe/primer typically comprises substantially purified oligonucleotide. The oligonucleotide typically comprises a region of nucleotide sequence that hybridizes under stringent conditions to at least about 12 or 15, preferably about 20 or 25, more preferably about 30, 35, 40, 45, 50, 55, 60, 65, or 75 consecutive nucleotides of a sense sequence of SEQ ID NO:l or SEQ ID NO:3, of an anti-sense sequence of SEQ ID NO:l or SEQ ID NO:3, or of a naturally occurring allelic variant or mutant of SEQ JD NO:l or SEQ ID NO:3. In an exemplary embodiment, a nucleic acid molecule ofthe present invention comprises a nucleotide sequence which is at least 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 nucleotides in length and hybridizes under stringent hybridization conditions to a nucleic acid molecule of SEQ ID NO:l or SEQ ID NO:3. Probes based on the 23155 nucleotide sequences can be used to detect transcripts or genomic sequences encoding the same or homologous proteins. In preferred embodiments, the probe further comprises a label group attached thereto, e.g., the label group can be a radioisotope, a fluorescent compound, an enzyme, or an enzyme co-factor. Such probes can be used as a part of a diagnostic test kit for identifying cells or tissues which misexpress a 23155 protein, such as by measuring a level of a 23155 encoding nucleic acid in a sample of cells from a subject e.g., detecting 23155 mRNA levels or determining whether a genomic 23155 gene has been mutated or deleted. A nucleic acid fragment encoding a "biologically active portion of a 23155 protein" can be prepared by isolating a portion ofthe nucleotide sequence of SEQ ID NO:l or SEQ ID NO:3, which encodes a polypeptide having a 23155 biological activity (the biological activities ofthe 23155 proteins are described herein), expressing the encoded portion ofthe 23155 protein (e.g., by recombinant expression in vitro) and assessing the activity ofthe encoded portion ofthe 23155 protein. The invention further encompasses nucleic acid molecules that differ from the nucleotide sequence shown in SEQ ID NO:l or SEQ ID NO:3, due to the degeneracy ofthe genetic code and, thus, encode the same 23155 proteins as those encoded by the nucleotide sequence shown in SEQ ID NO: 1 or SEQ ID NO:3. In another embodiment, an isolated nucleic acid molecule ofthe invention has a nucleotide sequence encoding a protein having an amino acid sequence shown in SEQ ID NO:2. In addition to the 23155 nucleotide sequences shown in SEQ ID NO:l or SEQ JJD NO:3, it will be appreciated by those skilled in the art that DNA sequence polymorphisms that lead to changes in the amino acid sequences ofthe 23155 proteins may exist within a population (e.g., the human population). Such genetic polymorphism in the 23155 genes may exist among individuals within a population due to natural allelic variation. As used herein, the terms "gene" and "recombinant gene" refer to nucleic acid molecules which include an open reading frame encoding an 23155 protein, preferably a mammalian 23155 protein, and can further include non-coding regulatory sequences, and introns. Such natural allelic variations include both functional and non-functional 23155 proteins and can typically result in 1-5% variance in the nucleotide sequence of a 23155 gene. Any and all such nucleotide variations and resulting amino acid polymorphisms in 23155 genes that are the result of natural allelic variation and that do not alter the functional activity of a 23155 protein are intended to be within the scope ofthe invention. Moreover, nucleic acid molecules encoding other 23155 family members and, thus, which have a nucleotide sequence which differs from the 23155 sequences of SEQ ID NO:l or SEQ ID NO:3 are intended to be within the scope ofthe invention. For example, another 23155 cDNA can be identified based on the nucleotide sequence of human 23155. Moreover, nucleic acid molecules encoding 23155 proteins from different species, and thus which have a nucleotide sequence which differs from the 23155 sequences of SEQ ID NO: 1 or SEQ ID NO:3 are intended to be within the scope ofthe invention. For example, a mouse 23155 cDNA can be identified based on the nucleotide sequence of a human 23155. Nucleic acid molecules corresponding to natural allelic variants and homologues of the 23155 cDNAs ofthe invention can be isolated based on their homology to the 23155 nucleic acids disclosed herein using the cDNAs disclosed herein, or a portion thereof, as a hybridization probe according to standard hybridization techniques under stringent hybridization conditions. Accordingly, in another embodiment, an isolated nucleic acid molecule ofthe invention is at least 15, 20, 25, 30 or more nucleotides in length and hybridizes under stringent conditions to the nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l or SEQ TD NO:3. hi other embodiment, the nucleic acid is at least 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600 nucleotides in length. As used herein, the term "hybridizes under stringent conditions" is intended to describe conditions for hybridization and washing under which nucleotide sequences at least 30%, 40%, 50%, or 60% homologous to each other typically remain hybridized to each other. Preferably, the conditions are such that sequences at least about 70%, more preferably at least about 80%, even more preferably at least about 85% or 90% homologous to each other typically remain hybridized to each other. Such stringent conditions are known to those skilled in the art and can be found in Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1-6.3.6. A preferred, non-limiting example of stringent hybridization conditions are hybridization in 6X sodium chloride/sodium citrate (SSC) at about 45°C, followed by one or more washes in 0.2 X SSC, 0.1% SDS at 50-65°C. Preferably, an isolated nucleic acid molecule ofthe invention that hybridizes under stringent conditions to the sequence of SEQ ID NO:l or SEQ ID NO:3 corresponds to a naturally-occurring nucleic acid molecule. As used herein, a "naturally-occurring" nucleic acid molecule refers to an RNA or DNA molecule having a nucleotide sequence that occurs in nature (e.g., encodes a natural protein). i addition to naturally-occurring allelic variants of the 23155 sequences that may exist in the population, the skilled artisan will further appreciate that changes can be introduced by mutation into the nucleotide sequences of SEQ ID NO: 1 or SEQ ID NO:3, thereby leading to changes in the amino acid sequence ofthe encoded 23155 proteins, without altering the functional ability ofthe 23155 proteins. For example, nucleotide substitutions leading to amino acid substitutions at "non-essential" amino acid residues can be made in the sequence of SEQ ID NO:l or SEQ ID NO:3. A "non-essential" amino acid residue is a residue that can be altered from the wild-type sequence of 23155 (e.g., the sequence of SEQ ID NO:2) without altering the biological activity, whereas an "essential" amino acid residue is required for biological activity. For example, amino acid residues that are conserved among the 23155 proteins ofthe present invention, are predicted to be particularly unamenable to alteration. Furthermore, additional amino acid residues that are conserved between the 23155 proteins ofthe present invention and other 23155 family members are not likely to be amenable to alteration. Accordingly, another aspect ofthe invention pertains to nucleic acid molecules encoding 23155 proteins that contain changes in amino acid residues that are not essential for activity. Such 23155 proteins differ in amino acid sequence from SEQ ID NO:2, yet retain biological activity. J-n one embodiment, the isolated nucleic acid molecule comprises a nucleotide sequence encoding a protein, wherein the protein comprises an amino acid sequence at least about 41%, 42%, 45%, 50%, 55%, 59%, 60%, 65%, 70%, 75%, 80%, 81%, 85%, 90%, 95%, 98% or more homologous to the amino acid sequence of SEQ ID NO:2 (e.g., the entire amino acid sequence of SEQ ID NO:2). An isolated nucleic acid molecule encoding a 23155 protein homologous to the protein of SEQ ID NO:2 can be created by introducing one or more nucleotide substitutions, additions or deletions into the nucleotide sequence of SEQ ID NO:l, respectively, such that one or more amino acid substitutions, additions or deletions are introduced into the encoded protein. Mutations can be introduced into SEQ ID NO:l by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis. Preferably, conservative amino acid substitutions are made at one or more predicted non- essential amino acid residues. A "conservative amino acid substitution" is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Thus, a predicted nonessential amino acid residue in a 23155 protein is preferably replaced with another amino acid residue from the same side chain family. Alternatively, in another embodiment, mutations can be introduced randomly along all or part of a 23155 coding sequence, such as by saturation mutagenesis, and the resultant mutants can be screened for 23155 biological activity to identify mutants that retain activity. Following mutagenesis of SEQ ID NO: 1, the encoded protein can be expressed recombinantly and the activity ofthe protein can be determined. In a preferred embodiment, a mutant 23155 protein can be assayed for the ability to reduce androgens or other steroid compounds. hi addition to the nucleic acid molecules encoding 23155 proteins described above, another aspect ofthe invention pertains to isolated nucleic acid molecules which are antisense thereto. An "antisense" nucleic acid comprises a nucleotide sequence which is complementary to a "sense" nucleic acid encoding a protein, e.g., complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence. Accordingly, an antisense nucleic acid can hydrogen bond to a sense nucleic acid. The antisense nucleic acid can be complementary to an entire 23155 coding strand, or only to a portion thereof. In one embodiment, an antisense nucleic acid molecule is antisense to a "coding region" ofthe coding strand of a nucleotide sequence encoding 23155. The term "coding region" refers to the region ofthe nucleotide sequence comprising codons which are translated into amino acid residues (e.g., the coding region of human 23155 corresponds to SEQ ID NO:3). In another embodiment, the antisense nucleic acid molecule is antisense to a "noncoding region" ofthe coding strand of a nucleotide sequence encoding 23155. The term "noncoding region" refers to 5' and 3' sequences which flank the coding region that are not translated into amino acids (i.e., also referred to as 5' and 3' untranslated regions). Given the coding strand sequences encoding 23155 disclosed herein (e.g., SEQ ID NO:3), antisense nucleic acids ofthe invention can be designed according to the rules of Watson and Crick base pairing. The antisense nucleic acid molecule can be complementary to the entire coding region of 23155 mRNA, but more preferably is an oligonucleotide which is antisense to only a portion ofthe coding or noncoding region of 23155 mRNA. For example, the antisense oligonucleotide can be complementary to the region surrounding the translation start site of 23155 mRNA. An antisense oligonucleotide can be, for example, about 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 nucleotides in length. An antisense nucleic acid ofthe invention can be constructed using chemical synthesis and enzymatic ligation reactions using procedures known in the art. For example, an antisense nucleic acid (e.g., an antisense oligonucleotide) can be chemically synthesized using naturally occurring nucleotides or variously modified nucleotides designed to increase the biological stability ofthe molecules or to increase the physical stability ofthe duplex formed between the antisense and sense nucleic acids, e.g., phosphorothioate derivatives and acridine substituted nucleotides can be used. Examples of modified nucleotides which can be used to generate the antisense nucleic acid include 5-fluorouracil, 5-bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xantine, 4-acetylcytosine, 5-(carboxyhydroxylmethyl) uracil, 5- carboxymethylaminomethyl-2-thiouridine, 5-carboxymethylaminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6-isopentenyladenine, 1- methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine, 2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-adenine, 7-methylguanine, 5- methylaminomethyluracil, 5 -methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine, 5 '-methoxycarboxymethyluracil, 5-methoxyuracil, 2-methylthio-N6-isopentenyladenine, uracil-5-oxyacetic acid (v), wybutoxosine, pseudouracil, queosine, 2-thiocytosine, 5- methyl-2-thiouracil, 2-thiouracil, 4-thiouracil, 5-methyluracil, uracil-5- oxyacetic acid methylester, uracil-5-oxyacetic acid (v), 5-methyl-2-thiouracil, 3-(3-amino-3-N-2- carboxypropyl) uracil, (acp3)w, and 2,6-diaminopurine. Alternatively, the antisense nucleic acid can be produced biologically using an expression vector into which a nucleic acid has been subcloned in an antisense orientation (i.e., RNA transcribed from the inserted nucleic acid will be of an antisense orientation to a target nucleic acid of interest, described further in the following subsection). The antisense nucleic acid molecules ofthe invention are typically administered to a subject or generated in situ such that they hybridize with or bind to cellular mRNA and/or genomic DNA encoding a 23155 protein to thereby inhibit expression ofthe protein, e.g., by inhibiting transcription and/or translation. The hybridization can be by conventional nucleotide complementarity to form a stable duplex, or, for example, in the case of an antisense nucleic acid molecule which binds to DNA duplexes, through specific interactions in the major groove ofthe double helix. An example of a route of administration of antisense nucleic acid molecules ofthe invention include direct injection at a tissue site. Alternatively, antisense nucleic acid molecules can be modified to target selected cells and then administered systemically. For example, for systemic administration, antisense molecules can be modified such that they specifically bind to receptors or antigens expressed on a selected cell surface, e.g., by linking the antisense nucleic acid molecules to peptides or antibodies which bind to cell surface receptors or antigens. The antisense nucleic acid molecules can also be delivered to cells using the vectors described herein. To achieve sufficient intracellular concentrations ofthe antisense molecules, vector constructs in which the antisense nucleic acid molecule is placed under the control of a strong pol II or pol in promoter are prefened. In yet another embodiment, the antisense nucleic acid molecule ofthe invention is an α-anomeric nucleic acid molecule. An α-anomeric nucleic acid molecule forms specific double-stranded hybrids with complementary RNA in which, contrary to the usual β-units, the strands run parallel to each other (Gaultier et al. (1987) Nucleic Acids. Res. 15:6625- 6641). The antisense nucleic acid molecule can also comprise a 2'-o-methylribonucleotide (Inoue et al (1987) Nucleic Acids Res. 15:6131-6148) or a chimeric RNA-DNA analogue (Inoue et al. (1987) FEBS Lett. 215:327-330). In still another embodiment, an antisense nucleic acid ofthe invention is a ribozyme. Ribozymes are catalytic RNA molecules with ribonuclease activity which are capable of cleaving a single-stranded nucleic acid, such as an mRNA, to which they have a complementary region. Thus, ribozymes (e.g., hammerhead ribozymes (described in Haselhoff and Gerlach (1988) Nature 334:585-591)) can be used to catalytically cleave 23155 mRNA transcripts to thereby inhibit translation of 23155 mRNA. A ribozyme having specificity for a 23155 encoding nucleic acid can be designed based upon the nucleotide sequence of a 23155 cDNA disclosed herein (i.e., SEQ ID NO:l or SEQ ID NO:3). For example, a derivative of a Tetrahymena L-19 TVS RNA can be constructed in which the nucleotide sequence ofthe active site is complementary to the nucleotide sequence to be cleaved in a 23155 encoding mRNA. See, e.g., Cech et al U.S. Patent No. 4,987,071; and Cech et al U.S. Patent No. 5,116,742. Alternatively, 23155 mRNA can be used to select a catalytic RNA having a specific ribonuclease activity from a pool of RNA molecules. See, e.g., Bartel, D. and Szostak, J.W. (1993) Science 261:1411-1418. Alternatively, 23155 gene expression can be inhibited by targeting nucleotide sequences complementary to the regulatory region ofthe 23155 (e.g., the 23155 promoter and/or enhancers) to form triple helical structures that prevent transcription ofthe 23155 gene in target cells. See generally, Helene, C. (1991) Anticancer Drug Des. 6(6):569-84; Helene, C. et al. (1992) Ann. N.Y. Acad. Sci. 660:27-36; and Maher, L.J. (1992) Bioassays 14(12):807-15. In yet another embodiment, the 23155 nucleic acid molecules ofthe present invention can be modified at the base moiety, sugar moiety or phosphate backbone to improve, e.g., the stability, hybridization, or solubility ofthe molecule. For example, the deoxyribose phosphate backbone ofthe nucleic acid molecules can be modified to generate peptide nucleic acids (see Hyrup B. et al (1996) Bioorganic & Medicinal Chemistry 4 (1): 5-23). As used herein, the terms "peptide nucleic acids" or "PNAs" refer to nucleic acid mimics, e.g., DNA mimics, in which the deoxyribose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA oligomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup B. et al. (1996) supra; Perry-O'Keefe et al Proc. Natl. Acad. Sci. 93: 14670-675. PNAs of 23155 nucleic acid molecules can be used in therapeutic and diagnostic applications. For example, PNAs can be used as antisense or antigene agents for sequence- specific modulation of gene expression by, for example, inducing transcription or translation arrest or inhibiting replication. PNAs of 23155 nucleic acid molecules can also be used in the analysis of single base pair mutations in a gene, (e.g., by PNA-directed PCR clamping); as 'artificial restriction enzymes' when used in combination with other enzymes, (e.g., SI nucleases (Hyrup B. (1996) supra)); or as probes or primers for DNA sequencing or hybridization (Hyrup B. et al. (1996) supra; Perry-O'Keefe supra). In another embodiment, PNAs of 23155 can be modified, (e.g., to enhance their stability or cellular uptake), by attaching lipophilic or other helper groups to PNA, by the formation of PNA-DNA chimeras, or by the use of liposomes or other techniques of drug delivery known in the art. For example, PNA-DNA chimeras of 23155 nucleic acid molecules can be generated which may combine the advantageous properties of PNA and DNA. Such chimeras allow DNA recognition enzymes, (e.g., RNAse H and DNA polymerases), to interact with the DNA portion while the PNA portion would provide high binding affinity and specificity. PNA-DNA chimeras can be linked using linkers of appropriate lengths selected in terms of base stacking, number of bonds between the nucleobases, and orientation (Hyrup B. (1996) supra). The synthesis of PNA-DNA chimeras can be performed as described in Hyrup B. (1996) supra and Finn P.J. et al. (1996) Nucleic Acids Res. 24 (17): 3357-63. For example, a DNA chain can be synthesized on a solid support using standard phosphoramidite coupling chemistry and modified nucleoside analogs, e.g., 5'-(4-methoxy lyl)amino-5'-deoxy-thymidine phosphoramidite, can be used as a between the PNA and the 5' end of DNA (Mag, M. et al. (1989) Nucleic Acid Res. 17: 5973-88). PNA monomers are then coupled in a stepwise manner to produce a chimeric molecule with a 5' PNA segment and a 3' DNA segment (Finn P.J. et al. (1996) supra). Alternatively, chimeric molecules can be synthesized with a 5' DNA segment and a 3' PNA segment (Peterser, K.H. et al. (1975) Bioorganic Med. Chem. Lett. 5: 1119-11124). hi other embodiments, the oligonucleotide may include other appended groups such as peptides (e.g., for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e.g., Letsinger et al. (1989) Proc. Natl. Acad. Sci. US. 86:6553-6556; Lemairre et al (1987) Proc. Natl Acad. Sci. USA 84:648-652; PCT Publication No. W088/09810) or the blood-brain barrier (see, e.g., PCT Publication No. W089/10134). In addition, oligonucleotides can be modified with hybridization-triggered cleavage agents (See, e.g., Krol et al. (1988) Bio-Techniques 6:958-976) or intercalating agents. (See, e.g., Zon (1988) Pharm. Res. 5:539-549). To this end, the oligonucleotide may be conjugated to another molecule, (e.g., a peptide, hybridization triggered cross- linking agent, transport agent, or hybridization-triggered cleavage agent). II. Isolated 23155 Proteins and Anti-23155 Antibodies One aspect ofthe invention pertains to isolated 23155 proteins, and biologically active portions thereof, as well as polypeptide fragments suitable for use as immunogens to raise anti-23155 antibodies. In one embodiment, native 23155 proteins can be isolated from cells or tissue sources by an appropriate purification scheme using standard protein purification techniques, hi another embodiment, 23155 proteins are produced by recombinant DNA techniques. Alternative to recombinant expression, a 23155 protein or polypeptide can be synthesized chemically using standard peptide synthesis techniques. An "isolated" or "purified" protein or biologically active portion thereof is substantially free of cellular material or other contaminating proteins from the cell or tissue source from which the 23155 protein is derived, or substantially free from chemical precursors or other chemicals when chemically synthesized. The language "substantially free of cellular material" includes preparations of 23155 protein in which the protein is separated from cellular components ofthe cells from which it is isolated or recombinantly produced. In one embodiment, the language "substantially free of cellular material" includes preparations of 23155 protein having less than about 30% (by dry weight) of non- 23155 protein (also refened to herein as a "contaminating protein"), more preferably less than about 20% of non-23155 protein, still more preferably less than about 10% of non- 23155 protein, and most preferably less than about 5% non-23155 protein. When the 23155 protein or biologically active portion thereof is recombinantly produced, it is also preferably substantially free of culture medium, i.e., culture medium represents less than about 20%, more preferably less than about 10%, and most preferably less than about 5% of the volume ofthe protein preparation. The language "substantially free of chemical precursors or other chemicals" includes preparations of 23155 protein in which the protein is separated from chemical precursors or other chemicals which are involved in the synthesis ofthe protein. In one embodiment, the language "substantially free of chemical precursors or other chemicals" includes preparations of 23155 protein having less than about 30% (by dry weight) of chemical precursors or non-23155 chemicals, more preferably less than about 20% chemical precursors or non-23155 chemicals, still more preferably less than about 10% chemical precursors or non-23155 chemicals, and most preferably less than about 5% chemical precursors or non-23155 chemicals. Biologically active portions of a 23155 protein include peptides comprising amino acid sequences sufficiently homologous to or derived from the amino acid sequence ofthe 23155 protein, e.g., the amino acid sequence shown in SEQ ID NO:2, which include less amino acids than the full length 23155 proteins, and exhibit at least one activity of a 23155 protein. Typically, biologically active portions comprise a domain or motif with at least one activity of the 23155 protein. A biologically active portion of a 23155 protein can be a polypeptide which is, for example, at least 10, 25, 50, 100 or more amino acids in length. In a preferred embodiment, the 23155 protein has an amino acid sequence shown in SEQ ID NO:2. In other embodiments, the 23155 protein is substantially homologous to SEQ ID NO:2, and retains the functional activity ofthe protein of SEQ ID NO:2, yet differs in amino acid sequence due to natural allelic variation or mutagenesis, as described in detail in subsection I above. Accordingly, in another embodiment, the 23155 protein is a protein which comprises an amino acid sequence at least about 41%, 42%, 45%, 50%, 55%, 59%, 60%, 65%, 70%, 75%, 80%, 81%, 85%, 90%, 95%, 98% or more homologous to the amino acid sequence of SEQ ID NO:2 (e.g., the entire amino acid sequence of SEQ ID NO:2). To determine the percent identity of two amino acid sequences or of two nucleic acid sequences, the sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in one or both of a first and a second amino acid or nucleic acid sequence for optimal alignment and non-homologous sequences can be disregarded for comparison purposes). In a prefened embodiment, the length of a reference sequence aligned for comparison purposes is at least 30%, preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, and even more preferably at least 70%, 80%, or 90% of the length ofthe reference sequence (e.g., when aligning a second sequence to the 23155, amino acid sequence of SEQ ID NO:2 having 318 amino acid residues, at least about 95, preferably at least 130, more preferably at least 160, even more preferably at least 190, and even more preferably at least 220, 260 or 290 amino acid residues are aligned). The amino acid residues or nucleotides at conesponding amino acid positions or nucleotide positions are then compared. When a position in the first sequence is occupied by the same amino acid residue or nucleotide as the conesponding position in the second sequence, then the molecules are identical at that position (as used herein amino acid or nucleic acid "identity" is equivalent to amino acid or nucleic acid "homology"). The percent identity between the two sequences is a function ofthe number of identical positions shared by the sequences, taking into account the number of gaps, and the length of each gap, which need to be introduced for optimal alignment ofthe two sequences. The comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm, hi a prefened embodiment, the percent identity between two amino acid sequences is determined using the GAP program in the GCG software package (available at http://www.gcg.com), using either a Blossom 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6. In yet another prefened embodiment, the percent identity between two nucleotide sequences is determined using the GAP program in the GCG software package (available at http://www.gcg.com), using a NWSgapdna.CMP matrix and a gap weight of 40, 50, 60, 70, or 80 and a length weight of 1, 2, 3, 4, 5, or 6. The nucleic acid and protein sequences ofthe present invention can further be used as a "query sequence" to perform a search against public databases to, for example, identify other family members or related sequences. Such searches can be performed using the NBLAST and XBLAST programs (version 2.0) of Altschul, et al. (1990) J. Mol. Biol 215:403-10. BLAST nucleotide searches can be performed with the NBLAST program, score = 100, wordlength = 12 to obtain nucleotide sequences homologous to 23155 nucleic acid molecules ofthe invention. BLAST protein searches can be performed with the XBLAST program, score = 50, wordlength = 3 to obtain amino acid sequences homologous to 23155 protein molecules ofthe invention. To obtain gapped alignments for comparison purposes, Gapped BLAST can be utilized as described in Altschul et al, (1997) Nucleic Acids Res. 25(17):3389-3402. When utilizing BLAST and Gapped BLAST programs, the default parameters ofthe respective programs (e.g., XBLAST and NBLAST) can be used. See http://www.ncbi.nlm.nih.gov. The invention also provides 23155 chimeric or fusion proteins. As used herein, a 23155 "chimeric protein" or "fusion protein" comprises a 23155 polypeptide operatively linked to a non-23155 polypeptide. An "23155 polypeptide" refers to a polypeptide having an amino acid sequence conesponding to 23155, whereas a "non-23155 polypeptide" refers to a polypeptide having an amino acid sequence conesponding to a protein which is not substantially homologous to the 23155 protein, e.g., a protein which is different from the 23155 protein and which is derived from the same or a different organism. Within a 23155 fusion protein the 23155 polypeptide can conespond to all or a portion of a 23155 protein, hi a prefened embodiment, a 23155 fusion protein comprises at least one biologically active portion of a 23155 protein. In another prefened embodiment, a 23155 fusion protein comprises at least two biologically active portions of a 23155 protein. Within the fusion protein, the term "operatively linked" is intended to indicate that the 23155 polypeptide and the non-23155 polypeptide are fused in-frame to each other. The non-23155 polypeptide can be fused to the N-terminus or C-terminus ofthe 23155 polypeptide. For example, in one embodiment, the fusion protein is a GST-23155 fusion protein in which the 23155 sequences are fused to the C-terminus ofthe GST sequences. Such fusion proteins can facilitate the purification of recombinant 23155. In another embodiment, the fusion protein is a 23155 protein containing a heterologous signal sequence at its N-terminus. In certain host cells (e.g., mammalian host cells), expression and/or secretion of 23155 can be increased through use of a heterologous signal sequence. The 23155 fusion proteins ofthe invention can be incorporated into pharmaceutical compositions and administered to a subject in vivo. The 23155 fusion proteins can be used to affect the bioavailability of a 23155 substrate. Use of 23155 fusion proteins may be useful therapeutically for the treatment of cellular growth related disorders, e.g., cardiovascular disorders. Moreover, the 23155 fusion proteins ofthe invention can be used as immunogens to produce anti-23155 antibodies in a subject, to purify 23155 ligands and in screening assays to identify molecules which inhibit the interaction of 23155 with a 23155 substrate. Preferably, a 23155 chimeric or fusion protein ofthe invention is produced by standard recombinant DNA techniques. For example, DNA fragments coding for the different polypeptide sequences are ligated together in-frame in accordance with conventional techniques, for example by employing blunt-ended or stagger-ended termini for ligation, restriction enzyme digestion to provide for appropriate termini, filling-in of cohesive ends as appropriate, alkaline phosphatase treatment to avoid undesirable joining, and enzymatic ligation. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of gene fragments can be carried out using anchor primers which give rise to complementary overhangs between two consecutive gene fragments which can subsequently be annealed and reamplified to generate a chimeric gene sequence (see, for example, Current Protocols in Molecular Biology, eds. Ausubel et al. John Wiley & Sons: 1992). Moreover, many expression vectors are commercially available that already encode a fusion moiety (e.g., a GST polypeptide). A 23155 encoding nucleic acid can be cloned into such an expression vector such that the fusion moiety is linked in-frame to the 23155 protein. The present invention also pertains to variants of the 23155 proteins which function as either 23155 agonists (mimetics) or as 23155 antagonists. Variants ofthe 23155 proteins can be generated by mutagenesis, e.g., discrete point mutation or truncation of a 23155 protein. An agonist ofthe 23155 proteins can retain substantially the same, or a subset, of the biological activities ofthe naturally occurring form of a 23155 protein. An antagonist of a 23155 protein can inhibit one or more ofthe activities ofthe naturally occurring form ofthe 23155 protein by, for example, competitively modulating a cardiovascular system activity of a 23155 protein. Thus, specific biological effects can be elicited by treatment with a variant of limited function. In one embodiment, treatment of a subject with a variant having a subset ofthe biological activities ofthe naturally occurring form ofthe protein has fewer side effects in a subject relative to treatment with the naturally occurring form ofthe 23155 protein. hi one embodiment, variants of a 23155 protein which function as either 23155 agonists (mimetics) or as 23155 antagonists respectively can be identified by screening combinatorial libraries of mutants, e.g., truncation mutants, of a 23155 protein for 23155 protein agonist or antagonist activity, hi one embodiment, a variegated library of 23155 variants is generated by combinatorial mutagenesis at the nucleic acid level and is encoded by a variegated gene library. A variegated library of 23155 variants can be produced by, for example, enzymatically ligating a mixture of synthetic oligonucleotides into gene sequences such that a degenerate set of potential 23155 sequences is expressible as individual polypeptides, or alternatively, as a set of larger fusion proteins (e.g., for phage display) containing the set of 23155 sequences therein. There are a variety of methods which can be used to produce libraries of potential 23155 variants from a degenerate oligonucleotide sequence. Chemical synthesis of a degenerate gene sequence can be performed in an automatic DNA synthesizer, and the synthetic gene then ligated into an appropriate expression vector. Use of a degenerate set of genes allows for the provision, in one mixture, of all ofthe sequences encoding the desired set of potential 23155 sequences. Methods for synthesizing degenerate oligonucleotides are known in the art (see, e.g., Narang, S.A. (1983) Tetrahedron 39:3; Itakura et α/. (1984) Annu. Rev. Biochem. 53:323; Itakura et al. (1984) Science 198:1056; Ike et al. (1983) Nucleic Acid Res. 11:477. In addition, libraries of fragments of a 23155 protein coding sequence can be used to generate a variegated population of 23155 fragments respectively for screening and subsequent selection of variants of a 23155 protein. In one embodiment, a library of coding sequence fragments can be generated by treating a double stranded PCR fragment of a 23155 coding sequence with a nuclease under conditions wherein nicking occurs only about once per molecule, denaturing the double stranded DNA, renaturing the DNA to form double stranded DNA which can include sense/antisense pairs from different nicked products, removing single stranded portions from reformed duplexes by treatment with SI nuclease, and ligating the resulting fragment library into an expression vector. By this method, an expression library can be derived which encodes N-terminal, C-terminal and internal fragments of various sizes of the 23155 protein. Several techniques are known in the art for screening gene products of combinatorial libraries made by point mutations or truncation, and for screening cDNA libraries for gene products having a selected property. Such techniques are adaptable for rapid screening ofthe gene libraries generated by the combinatorial mutagenesis of 23155 proteins. The most widely used techniques, which are amenable to high through-put analysis, for screening large gene libraries typically include cloning the gene library into replicable expression vectors, transforming appropriate cells with the resulting library of vectors, and expressing the combinatorial genes under conditions in which detection of a desired activity facilitates isolation ofthe vector encoding the gene whose product was detected. Recrusive ensemble mutagenesis (REM), a new technique which enhances the frequency of functional mutants in the libraries, can be used in combination with the screening assays to identify 23155 variants (Arkin and Yourvan (1992) Proc. Natl Acad. Sci. USA 89:7811-7815; Delgrave et al. (1993) Protein Engineering 6(3):327-331). hi one embodiment, cell based assays can be exploited to analyze a variegated 23155 library. For example, a library of expression vectors can be transfected into a cell line which ordinarily synthesizes and secretes 23155. The transfected cells are then cultured such that 23155 and a particular mutant 23155 are secreted and the effect of expression ofthe mutant on 23155 activity in cell supernatants can be detected, e.g., by any of a number of enzymatic assays. Plasmid DNA can then be recovered from the cells which score for inhibition, or alternatively, potentiation of 23155 activity, and the individual clones further characterized. An isolated 23155 protein, or a portion or fragment thereof, can be used as an immunogen to generate antibodies that bind 23155 using standard techniques for polyclonal and monoclonal antibody preparation. A full-length 23155 protein can be used or, alternatively, the invention provides antigenic peptide fragments of 23155 for use as immunogens. The antigenic peptide of 23155 comprises at least 8 amino acid residues of the amino acid sequence shown in SEQ ID NO:2 and encompasses an epitope of 23155 such that an antibody raised against the peptide forms a specific immune complex with 23155. Preferably, the antigenic peptide comprises at least 10 amino acid residues, more preferably at least 15 amino acid residues, even more preferably at least 20 amino acid residues, and most preferably at least 30 amino acid residues. Prefened epitopes encompassed by the antigenic peptide are regions of 23155 that are located on the surface ofthe protein, e.g., hydrophilic regions. A 23155 immunogen typically is used to prepare antibodies by immunizing a suitable subject, (e.g., rabbit, goat, mouse or other mammal) with the immunogen. An appropriate immunogenic preparation can contain, for example, recombinantly expressed 23155 protein or a chemically synthesized 23155 polypeptide. The preparation can further include an adjuvant, such as Freund's complete or incomplete adjuvant, or similar immunostimulatory agent. Immunization of a suitable subject with an immunogenic 23155 preparation induces a polyclonal anti-23155 antibody response. Accordingly, another aspect ofthe invention pertains to anti-23155 antibodies. The term "antibody" as used herein refers to immunoglobulin molecules and immunologically active portions of immunoglobulin molecules, i.e., molecules that contain an antigen binding site which specifically binds (immunoreacts with) an antigen, such as 23155. Examples of immunologically active portions of immunoglobulin molecules include F(ab) and F(ab')2 fragments which can be generated by treating the antibody with an enzyme such as pepsin. The invention provides polyclonal and monoclonal antibodies that bind 23155. The term "monoclonal antibody" or "monoclonal antibody composition", as used herein, refers to a population of antibody molecules that contain only one species of an antigen binding site capable of immunoreacting with a particular epitope of 23155. A monoclonal antibody composition thus typically displays a single binding affinity for a particular 23155 protein with which it immunoreacts. Polyclonal anti-23155 antibodies can be prepared as described above by immunizing a suitable subject with a 23155 immunogen. The anti-23155 antibody titer in the immunized subject can be monitored over time by standard techniques, such as with an enzyme linked immunosorbent assay (ELISA) using immobilized 23155. If desired, the antibody molecules directed against 23155 can be isolated from the mammal (e.g., from the blood) and further purified by well known techniques, such as protein A chromatography to obtain the IgG fraction. At an appropriate time after immunization, e.g., when the anti- 23155 antibody titers are highest, antibody-producing cells can be obtained from the subject and used to prepare monoclonal antibodies by standard techniques, such as the hybridoma technique originally described by Kohler and Milstein (1975) Nature 256:495-497) (see also, Brown et al. (1981) J Immunol 127:539-46; Brown et al (1980) J. Biol Chem .255:4980-83; Yeh et al. (1976) Proc. Natl. Acad. Sci. USA 76:2927-31; and Yeh et al. (1982) Int. J. Cancer 29:269-75), the more recent human B cell hybridoma technique (Kozbor et al. (1983) Immunol Today 4:72), the EBV-hybridoma technique (Cole et al. (1985), Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, Inc., pp. 77-96) or rrioma techniques. The technology for producing monoclonal antibody hybridomas is well known (see generally R. H. Kenneth, in Monoclonal Antibodies: A New Dimension In Biological Analyses, Plenum Publishing Corp., New York, New York (1980); E. A. Lerner (1981) Yale J. Biol Med, 54:387-402; M. L. Gefter et al. (1977) Somatic Cell Genet. 3:231-36). Briefly, an immortal cell line (typically a myeloma) is fused to lymphocytes (typically splenocytes) from a mammal immunized with a 23155 immunogen as described above, and the culture supernatants ofthe resulting hybridoma cells are screened to identify a hybridoma producing a monoclonal antibody that binds 23155. Any ofthe many well known protocols used for fusing lymphocytes and immortalized cell lines can be applied for the purpose of generating an anti-23155 monoclonal antibody (see, e.g., G. Galfre et al. (1977) Nature 266:55052; Gefter et al. Somatic Cell Genet., cited supra; Lerner, Yale J. Biol. Med., cited supra; Kenneth, Monoclonal Antibodies, cited supra). Moreover, the ordinarily skilled worker will appreciate that there are many variations of such methods which also would be useful. Typically, the immortal cell line (e.g., a myeloma cell line) is derived from the same mammalian species as the lymphocytes. For example, murine hybridomas can be made by fusing lymphocytes from a mouse immunized with an immunogenic preparation ofthe present invention with an immortalized mouse cell line. Prefened immortal cell lines are mouse myeloma cell lines that are sensitive to culture medium containing hypoxanthine, aminopterin and thymidine ("HAT medium"). Any of a number of myeloma cell lines can be used as a fusion partner according to standard techniques, e.g., the P3-NSl/l-Ag4-l, P3- x63-Ag8.653 or Sp2/O-Agl4 myeloma lines. These myeloma lines are available from ATCC. Typically, HAT-sensitive mouse myeloma cells are fused to mouse splenocytes using polyethylene glycol ("PEG"). Hybridoma cells resulting from the fusion are then selected using HAT medium, which kills unfused and unproductively fused myeloma cells (unfused splenocytes die after several days because they are not transformed). Hybridoma cells producing a monoclonal antibody ofthe invention are detected by screening the hybridoma culture supernatants for antibodies that bind 23155, e.g., using a standard ELISA assay. Alternative to preparing monoclonal antibody-secreting hybridomas, a monoclonal anti-23155 antibody can be identified and isolated by screening a recombinant combinatorial immunoglobulin library (e.g., an antibody phage display library) with 23155 to thereby isolate immunoglobulin library members that bind 23155. Kits for generating and screening phage display libraries are commercially available (e.g., the Pharmacia Recombinant Phage Antibody System, Catalog No. 27-9400-01; and the Stratagene SurfZAP™ Phage Display Kit, Catalog No. 240612). Additionally, examples of methods and reagents particularly amenable for use in generating and screening antibody display library can be found in, for example, Ladner et al U.S. Patent No. 5,223,409; Kang et al. PCT International Publication No. WO 92/18619; Dower et al PCT International Publication No. WO 91/17271; Winter et al. PCT International Publication WO 92/20791; Markland et al. PCT International Publication No. WO 92/15679; Breitling et al. PCT International Publication WO 93/01288; McCafferty et al. PCT International Publication No. WO 92/01047; Ganard et al. PCT International Publication No. WO 92/09690; Ladner et al. PCT International Publication No. WO 90/02809; Fuchs et al. (1991) Bio/Technology 9:1370-1372; Hay et al. (1992) Hum. Antibod. Hybridomas 3:81-85; Huse et al. (1989) Science 246:1275-1281; Griffiths et al. (1993) EMBO J 12:125-134; Hawkins et al. (1992) J. Mol Biol 226:889-896; Clarkson et al (1991) Nature 352:624-628; Gram et al. (1992) Proc. Natl Acad. Sci. USA 89:3576-3580; Ganad et al. (1991) Bio/Technology 9:1373- 1377; Hoogenboom et al. (1991) Nuc. Acid Res. 19:4133-4137; Barbas et al. (1991) Proc. Natl Acad. Sci. USA 88:7978-7982; and McCafferty et al Nature (1990) 348:552-554. Additionally, recombinant anti-23155 antibodies, such as chimeric and humanized monoclonal antibodies, comprising both human and non-human portions, which can be made using standard recombinant DNA techniques, are within the scope ofthe invention. Such chimeric and humanized monoclonal antibodies can be produced by recombinant DNA techniques known in the art, for example using methods described in Robinson et al. International Application No. PCT/US86/02269; Akira, et al. European Patent Application 184,187; Taniguchi, M., European Patent Application 171,496; Morrison et al. European Patent Application 173,494; Neuberger et al. PCT hitemational Publication No. WO 86/01533; Cabilly et al. U.S. Patent No. 4,816,567; Cabilly et al. European Patent Application 125,023; Better et al. (1988) Science 240:1041-1043; Liu et al. (1987) Proc. Natl Acad. Sci. USA 84:3439-3443; Liu et al. (1987) J. Immunol 139:3521-3526; Sun et al. (1987) Proc. Natl. Acad. Sci. USA 84:214-218; Nishimura et al. (1987) Cane. Res. 47:999-1005; Wood et al (1985) Natur 314:446-449; and Shaw et al. (1988) J Natl Cancer Inst. 80:1553-1559); Morrison, S. L. (1985) Science 229:1202-1207; Oi et al. (1986) BioTechniques 4:214; Winter U.S. Patent 5,225,539; Jones et al. (1986) Nature 321:552-525; Verhoeyan et al (1988) Science 239:1534; and Beidler et al. (1988) J. Immunol 141:4053-4060. An anti-23155 antibody (e.g., monoclonal antibody) can be used to isolate 23155 by standard techniques, such as affinity chromatography or immunoprecipitation. An anti- 23155 antibody can facilitate the purification of natural 23155 from cells and of recombinantly produced 23155 expressed in host cells. Moreover, an anti-23155 antibody can be used to detect 23155 protein (e.g., in a cellular lysate or cell supernatant) in order to evaluate the abundance and pattern of expression ofthe 23155 protein. Anti-23155 antibodies can be used diagnostically to monitor protein levels in tissue as part of a clinical testing procedure, e.g., to, for example, determine the efficacy of a given treatment regimen. Detection can be facilitated by coupling (i.e., physically linking) the antibody to a detectable substance. Examples of detectable substances include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, bioluminescent materials, and radioactive materials. Examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, -galactosidase, or acetylcholinesterase; examples of suitable prosthetic group complexes include streptavidin/biotin and avidin/biotin; examples of suitable fluorescent materials include umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; an example of a luminescent material includes luminol; examples of bioluminescent materials include luciferase, luciferin, and aequorin, and examples of suitable radioactive material include 175 I, 131 I, S or 3 H. HI. Recombinant Expression Vectors and Host Cells Another aspect ofthe invention pertains to vectors, preferably expression vectors, containing a nucleic acid encoding a 23155 protein (or a portion thereof). As used herein, the term "vector" refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One type of vector is a "plasmid", which refers to a circular double stranded DNA loop into which additional DNA segments can be ligated. Another type of vector is a viral vector, wherein additional DNA segments can be ligated into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are refened to herein as "expression vectors". In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, "plasmid" and "vector" can be used interchangeably as the plasmid is the most commonly used form of vector. However, the invention is intended to include such other forms of expression vectors, such as viral vectors (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions. The recombinant expression vectors ofthe invention comprise a nucleic acid ofthe invention in a form suitable for expression ofthe nucleic acid in a host cell, which means that the recombinant expression vectors include one or more regulatory sequences, selected on the basis ofthe host cells to be used for expression, which is operatively linked to the nucleic acid sequence to be expressed. Within a recombinant expression vector, "operably linked" is intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a manner which allows for expression ofthe nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell). The term "regulatory sequence" is intended to includes promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Such regulatory sequences are described, for example, in Goeddel; Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990). Regulatory sequences include those which direct constitutive expression of a nucleotide sequence in many types of host cell and those which direct expression ofthe nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences). It will be appreciated by those skilled in the art that the design ofthe expression vector can depend on such factors as the choice ofthe host cell to be transformed, the level of expression of protein desired, and the like. The expression vectors ofthe invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as described herein (e.g., 23155 proteins, mutant forms of 23155 proteins, fusion proteins, and the like). The recombinant expression vectors ofthe invention can be designed for expression of 23155 proteins in prokaryotic or eukaryotic cells. For example, 23155 proteins can be expressed in bacterial cells such as E. coli, insect cells (using baculovirus expression vectors) yeast cells or mammalian cells. Suitable host cells are discussed further in Goeddel, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990). Alternatively, the recombinant expression vector can be transcribed and translated in vitro, for example using T7 promoter regulatory sequences and T7 polymerase. Expression of proteins in prokaryotes is most often carried out in E. coli with vectors containing constitutive or inducible promoters directing the expression of either fusion or non-fusion proteins. Fusion vectors add a number of amino acids to a protein encoded therein, usually to the amino terminus ofthe recombinant protein. Such fusion vectors typically serve three purposes: 1) to increase expression of recombinant protein; 2) to increase the solubility ofthe recombinant protein; and 3) to aid in the purification ofthe recombinant protein by acting as a ligand in affinity purification. Often, in fusion expression vectors, a proteolytic cleavage site is introduced at the junction ofthe fusion moiety and the recombinant protein to enable separation ofthe recombinant protein from the fusion moiety subsequent to purification ofthe fusion protein. Such enzymes, and their cognate recognition sequences, include Factor Xa, thrombin and enterokinase. Typical fusion expression vectors include pGEX (Pharmacia Biotech Inc; Smith, D.B. and Johnson, K.S. (1988) Gene 67:31-40), pMAL (New England Biolabs, Beverly, MA) andpRIT5 (Pharmacia, Piscataway, NJ) which fuse glutathione S-transferase (GST), maltose E binding protein, or protein A, respectively, to the target recombinant protein. Purified fusion proteins can be utilized in 23155 activity assays, (e.g., direct assays or competitive assays described in detail below), or to generate antibodies specific for 23155 proteins, for example. In a prefened embodiment, a 23155 fusion protein expressed in a retroviral expression vector ofthe present invention can be utilized to infect bone manow cells which are subsequently transplanted into inadiated recipients. The pathology ofthe subject recipient is then examined after sufficient time has passed (e.g., six (6) weeks). Examples of suitable inducible non-fusion E. coli expression vectors include pTrc (Amann et al, (1988) Gene 69:301-315) and pET lid (Srudier et al, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, California (1990) 60-89). Target gene expression from the pTrc vector relies on host RNA polymerase transcription from a hybrid trp-lac fusion promoter. Target gene expression from the pET l id vector relies on transcription from a T7 gnlO-lac fusion promoter mediated by a coexpressed viral RNA polymerase (T7 gnl). This viral polymerase is supplied by host strains BL21(DE3) or HMS174(DE3) from a resident prophage harboring a T7 gnl gene under the transcriptional control ofthe lacUV 5 promoter. One strategy to maximize recombinant protein expression in E. coli is to express the protein in a host bacteria with an impaired capacity to proteolytically cleave the recombinant protein (Gottesman, S., Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, California (1990) 119-128). Another strategy is to alter the nucleic acid sequence ofthe nucleic acid to be inserted into an expression vector so that the individual codons for each amino acid are those preferentially utilized in E. coli (Wada et al, (1992) Nucleic Acids Res. 20:2111-2118). Such alteration of nucleic acid sequences ofthe invention can be carried out by standard DNA synthesis techniques. hi another embodiment, the 23155 expression vector is a yeast expression vector. Examples of vectors for expression in yeast S. cerevisiae include pYepSecl (Baldari, et al, (1987) Embo J. 6:229-234), pMFa (Kurjan and Herskowitz, (1982) Cell 30:933-943), pJRY88 (Schultz et al, (1987) Gene 54:113-123), pYES2 (Invitrogen Corporation, San Diego, CA), and picZ (hiVitrogen Corp, San Diego, CA). Alternatively, 23155 proteins can be expressed in insect cells using baculovirus expression vectors. Baculovirus vectors available for expression of proteins in cultured insect cells (e.g., Sf 9 cells) include the pAc series (Smith et al. (1983) Mol. Cell Biol. 3:2156-2165) and the pVL series (Lucklow and Summers (1989) Virology 170:31-39). In yet another embodiment, a nucleic acid ofthe invention is expressed in mammalian cells using a mammalian expression vector. Examples of mammalian expression vectors include pCDM8 (Seed, B. (1987) Nature 329:840) and pMT2PC (Kaufman et al. (1987) EMBO J. 6:187-195). When used in mammalian cells, the expression vector's control functions are often provided by viral regulatory elements. For example, commonly used promoters are derived from polyoma, Adenovirus 2, cytomegalovirus and Simian Virus 40. For other suitable expression systems for both prokaryotic and eukaryotic cells see chapters 16 and 17 of Sambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989. hi another embodiment, the recombinant mammalian expression vector is capable of directing expression ofthe nucleic acid preferentially in a particular cell type (e.g., tissue-specific regulatory elements are used to express the nucleic acid). Tissue-specific regulatory elements are known in the art. Non-limiting examples of suitable tissue-specific promoters include the albumin promoter (liver-specific; Pinkert et al. (1987) Genes Dev. 1:268-277), lymphoid-specific promoters (Calame and Eaton (1988) Adv. Immunol. 43:235- 275), in particular promoters of T cell receptors (Winoto and Baltimore (1989) EMBO J. 8:729-733) and immunoglobulins (Banerji et al. (1983) Cell 33:729-740; Queen and Baltimore (1983) Cell 33:741-748), neuron-specific promoters (e.g., the neurofilament promoter; Byrne and Ruddle (1989) Proc. Natl. Acad. Sci. USA 86:5473-5477), pancreas- specific promoters (Edlund et al. (1985) Science 230:912-916), and mammary gland- specific promoters (e.g., milk whey promoter; U.S. Patent No. 4,873,316 and European Application Publication No. 264,166). Developmentally-regulated promoters are also encompassed, for example the murine hox promoters (Kessel and Grass (1990) Science 249:374-379) and the α-fetoprotein promoter (Campes and Tilghman (1989) Genes Dev. 3:537-546). The invention further provides a recombinant expression vector comprising a DNA molecule ofthe invention cloned into the expression vector in an antisense orientation. That is, the DNA molecule is operatively linked to a regulatory sequence in a manner which allows for expression (by transcription ofthe DNA molecule) of an RNA molecule which is antisense to 23155 mRNA. Regulatory sequences operatively linked to a nucleic acid cloned in the antisense orientation can be chosen which direct the continuous expression of the antisense RNA molecule in a variety of cell types, for instance viral promoters and/or enhancers, or regulatory sequences can be chosen which direct constitutive, tissue specific or cell type specific expression of antisense RNA. The antisense expression vector can be in the form of a recombinant plasmid, phagemid or attenuated virus in which antisense nucleic acids are produced under the control of a high efficiency regulatory region, the activity of which can be determined by the cell type into which the vector is introduced. For a discussion ofthe regulation of gene expression using antisense genes see Weintraub, H. et al, Antisense RNA as a molecular tool for genetic analysis, Reviews - Trends in Genetics, Vol. 1(1) 1986. Another aspect ofthe invention pertains to host cells into which a recombinant expression vector ofthe invention has been introduced. The terms "host cell" and "recombinant host cell" are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope ofthe term as used herein. A host cell can be any prokaryotic or eukaryotic cell. For example, a 23155 protein can be expressed in bacterial cells such as E. coli, insect cells, yeast or mammalian cells (such as Chinese hamster ovary cells (CHO) or COS cells). Other suitable host cells are known to those skilled in the art. Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques. As used herein, the terms "transformation" and "transfection" are intended to refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, or electroporation. Suitable methods for transforming or transfecting host cells can be found in Sambrook, et al. (Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989), and other laboratory manuals. For stable transfection of mammalian cells, it is known that, depending upon the expression vector and transfection technique used, only a small fraction of cells may integrate the foreign DNA into their genome. In order to identify and select these integrants, a gene that encodes a selectable marker (e.g., resistance to antibiotics) is generally introduced into the host cells along with the gene of interest. Prefened selectable markers include those which confer resistance to drugs, such as G418, hygromycin and methotrexate. Nucleic acid encoding a selectable marker can be introduced into a host cell on the same vector as that encoding a 23155 protein or can be introduced on a separate vector. Cells stably transfected with the introduced nucleic acid can be identified by drug selection (e.g., cells that have incorporated the selectable marker gene will survive, while the other cells die). A host cell ofthe invention, such as a prokaryotic or eukaryotic host cell in culture, can be used to produce (i.e., express) a 23155 protein. Accordingly, the invention further provides methods for producing a 23155 protein using the host cells ofthe invention. In one embodiment, the method comprises culturing the host cell of invention (into which a recombinant expression vector encoding a 23155 protein has been introduced) in a suitable medium such that a 23155 protein is produced, hi another embodiment, the method further comprises isolating a 23155 protein from the medium or the host cell. The host cells ofthe invention can also be used to produce non-human transgenic animals. For example, in one embodiment, a host cell ofthe invention is a fertilized oocyte or an embryonic stem cell into which 23155coding sequences have been introduced. Such host cells can then be used to create non-human transgenic animals in which exogenous 23155 sequences have been introduced into their genome or homologous recombinant animals in which endogenous 23155 sequences have been altered. Such animals are useful for studying the function and/or activity of a 23155 and for identifying and/or evaluating modulators of 23155 activity. As used herein, a "transgenic animal" is a non-human animal, preferably a mammal, more preferably a rodent such as a rat or mouse, in which one or more ofthe cells ofthe animal includes a transgene. Other examples of transgenic animals include non-human primates, sheep, dogs, cows, goats, chickens, amphibians, and the like. A transgene is exogenous DNA which is integrated into the genome of a cell from which a transgenic animal develops and which remains in the genome ofthe mature animal, thereby directing the expression of an encoded gene product in one or more cell types or tissues ofthe transgenic animal. As used herein, a "homologous recombinant animal" is a non-human animal, preferably a mammal, more preferably a mouse, in which an endogenous 23155 gene has been altered by homologous recombination between the endogenous gene and an exogenous DNA molecule introduced into a cell ofthe animal, e.g., an embryonic cell ofthe animal, prior to development of he animal. A transgenic animal ofthe invention can be created by introducing a 23155 encoding nucleic acid into the male pronuclei of a fertilized oocyte, e.g., by microinjection, retroviral infection, and allowing the oocyte to develop in a pseudopregnant female foster animal. The 23155 cDNA sequence of SEQ ID NO: 1 can be introduced as a transgene into the genome of a non-human animal. Alternatively, a nonhuman homologue of a human 23155 gene, such as a mouse or rat 23155 gene, can be used as a transgene. Alternatively, a 23155 gene homologue, such as another 23155 family member, can be isolated based on hybridization to the 23155 cDNA sequences of SEQ ID NO:l or SEQ ID NO:3 (described further in subsection I above) and used as a transgene. tronic sequences and polyadenylation signals can also be included in the transgene to increase the efficiency of expression ofthe transgene. A tissue-specific regulatory sequence(s) can be operably linked to a 23155 transgene to direct expression of a 23155 protein to particular cells. Methods for generating transgenic animals via embryo manipulation and microinjection, particularly animals such as mice, have become conventional in the art and are described, for example, in U.S. Patent Nos. 4,736,866 and 4,870,009, both by Leder et al, U.S. Patent No. 4,873,191 by Wagner et al. and in Hogan, B., Manipulating the Mouse Embryo, (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1986). Similar methods are used for production of other transgenic animals. A transgenic founder animal can be identified based upon the presence of a 23155 transgene in its genome and or expression of 23155 mRNA in tissues or cells ofthe animals. A transgenic founder animal can then be used to breed additional animals carrying the transgene. Moreover, transgenic animals carrying a transgene encoding a 23155 protein can further be bred to other transgenic animals carrying other transgenes. To create a homologous recombinant animal, a vector is prepared which contains at least a portion of a 23155 gene into which a deletion, addition or substitution has been introduced to thereby alter, e.g., functionally disrupt, the 23155 gene. The 23155 gene can be a human gene (e.g., the SEQ ID NO: 1), but more preferably, is a non-human homologue of a human 23155 gene (e.g., a cDNA isolated by stringent hybridization with the nucleotide sequence of SEQ ID NO: 1). For example, a mouse 23155 gene can be used to construct a homologous recombination vector suitable for altering an endogenous 23155 gene in the mouse genome, hi a prefened embodiment, the vector is designed such that, upon homologous recombination, the endogenous 23155 gene is functionally disrupted (i.e., no longer encodes a functional protein; also refened to as a "knock out" vector). Alternatively, the vector can be designed such that, upon homologous recombination, the endogenous 23155 gene is mutated or otherwise altered but still encodes a functional protein (e.g., the upstream regulatory region can be altered to thereby alter the expression of the endogenous 23155 protein). In the homologous recombination vector, the altered portion ofthe 23155 gene is flanked at its 5' and 3' ends by additional nucleic acid sequence ofthe 23155 gene to allow for homologous recombination to occur between the exogenous 23155 gene carried by the vector and an endogenous 23155 gene in an embryonic stem cell. The additional flanking 23155 nucleic acid sequence is of sufficient length for successful homologous recombination with the endogenous gene. Typically, several kilobases of flanking DNA (both at the 5' and 3' ends) are included in the vector (see e.g., Thomas, K.R. and Capecchi, M. R. (1987) Cell 51:503 for a description of homologous recombination vectors). The vector is introduced into an embryonic stem cell line (e.g., by electroporation) and cells in which the introduced 23155 gene has homologously recombined with the endogenous 23155 gene are selected (see, e.g., Li, E. et al (1992) Cell 69:915). The selected cells are then injected into a blastocyst of an animal (e.g., a mouse) to form aggregation chimeras (see e.g., Bradley, A. in Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, E.J. Robertson, ed. (IRL, Oxford, 1987) pp. 113-152). A chimeric embryo can then be implanted into a suitable pseudopregnant female foster animal and the embryo brought to term. Progeny harboring the homologously recombined DNA in their germ cells can be used to breed animals in which all cells ofthe animal contain the homologously recombined DNA by germline transmission ofthe transgene. Methods for constructing homologous recombination vectors and homologous recombinant animals are described further in Bradley, A. (1991) Current Opinion in Biotechnology 2:823-829 and in PCT International Publication Nos.: WO 90/11354 by Le Mouellec et al; WO 91/01140 by Smithies et al; WO 92/0968 by Zijlstra et al; and WO 93/04169 by Berns et α/. hi another embodiment, transgenic non-humans animals can be produced which contain selected systems which allow for regulated expression ofthe transgene. One example of such a system is the cre/loxP recombinase system of bacteriophage PI. For a description ofthe cre/loxP recombinase system, see, e.g., Lakso et al. (1992) Proc. Natl. Acad. Sci. USA 89:6232-6236. Another example of a recombinase system is the FLP recombinase system of Saccharomyces cerevisiae (O' Gorman et al. (1991) Science 251:1351-1355. If a cre/loxP recombinase system is used to regulate expression ofthe transgene, animals containing transgenes encoding both the Cre recombinase and a selected protein are required. Such animals can be provided through the construction of "double" transgenic animals, e.g., by mating two transgenic animals, one containing a transgene encoding a selected protein and the other containing a transgene encoding a recombinase. Clones ofthe non-human transgenic animals described herein can also be produced according to the methods described in Wihnut, I. et al. (1997) Nature 385:810-813 and PCT International Publication Nos. WO 97/07668 and WO 97/07669. In brief, a cell, e.g., a somatic cell, from the transgenic animal can be isolated and induced to exit the growth cycle and enter G 0 phase. The quiescent cell can then be fused, e.g., through the use of electrical pulses, to an enucleated oocyte from an animal ofthe same species from which the quiescent cell is isolated. The reconstructed oocyte is then cultured such that it develops to morula or blastocyte and then transfened to pseudopregnant female foster animal. The offspring borne of this female foster animal will be a clone ofthe animal from which the cell, e.g., the somatic cell, is isolated. IV. Use of 23155 Molecules as Surrogate Markers The 23155 molecules ofthe invention are also useful as markers of disorders or disease states, as markers for precursors of disease states, as markers for predisposition of disease states, as markers of drug activity, or as markers ofthe pharmacogenomic profile of a subject. Using the methods described herein, the presence, absence and/or quantity ofthe 23155 molecules ofthe invention can be detected, and can be conelated with one or more biological states in vivo. For example, the 23155 molecules ofthe invention can serve as sunogate markers for one or more disorders or disease states or for conditions leading up to disease states. As used herein, a "sunogate marker" is an objective biochemical marker which conelates with the absence or presence of a disease or disorder, or with the progression of a disease or disorder (e.g., with the presence or absence of a tumor). The presence or quantity of such markers is independent ofthe disease. Therefore, these markers can serve to indicate whether a particular course of treatment is effective in lessening a disease state or disorder. Surrogate markers are of particular use when the presence or extent of a disease state or disorder is difficult to assess through standard methodologies (e.g., early stage tumors), or when an assessment of disease progression is desired before a potentially dangerous clinical endpoint is reached (e.g., an assessment of cardiovascular disease can be made using cholesterol levels as a surrogate marker, and an analysis of HIV infection can be made using HIV RNA levels as a sunogate marker, well in advance ofthe undesirable clinical outcomes of myocardial infarction or fully-developed AIDS). Examples ofthe use of sunogate markers in the art include: Koomen et al. (2000) J. Mass. Spectrom. 35: 258-264; and James (1994) AIDS Treatment News Archive 209. The 23155 molecules ofthe invention are also useful as pharmacodynamic markers. As used herein, a "pharmacodynamic marker" is an objective biochemical marker which conelates specifically with drug effects. The presence or quantity of a pharmacodynamic marker is not related to the disease state or disorder for which the drug is being administered; therefore, the presence or quantity ofthe marker is indicative ofthe presence or activity ofthe drug in a subject. For example, a pharmacodynamic marker can be indicative ofthe concentration ofthe drug in a biological tissue, in that the marker is either expressed or transcribed or not expressed or transcribed in that tissue in relationship to the level ofthe drag. In this fashion, the distribution or uptake ofthe drug can be monitored by the pharmacodynamic marker. Similarly, the presence or quantity ofthe pharmacodynamic marker can be related to the presence or quantity ofthe metabolic product of a drug, such that the presence or quantity ofthe marker is indicative ofthe relative breakdown rate ofthe drug in vivo. Pharmacodynamic markers are of particular use in increasing the sensitivity of detection of drug effects, particularly when the drug is administered in low doses. Since even a small amount of a drag can be sufficient to activate multiple rounds of marker (e.g., a 23155 marker) transcription or expression, the amplified marker can be in a quantity which is more readily detectable than the drag itself. Also, the marker can be more easily detected due to the nature ofthe marker itself; for example, using the methods described herein, anti-23155 antibodies can be employed in an immune-based detection system for a 23155 protein marker, or 23155-specific radiolabeled probes can be used to detect a 23155 mRNA marker. Furthermore, the use of a pharmacodynamic marker can offer mechanism- based prediction of risk due to drug treatment beyond the range of possible direct observations. Examples ofthe use of pharmacodynamic markers in the art include: Matsuda et al. US 6,033,862; Hattis et al. (1991) Env. Health Perspect. 90: 229-238; Schentag (1999) Am. J. Health-Syst. Pharm. 56 Suppl. 3: S21-S24; and Nicolau (1999) Am. J. Health-Syst. Pharm. 56 Suppl. 3: S16-S20. The 23155 molecules ofthe invention are also useful as pharmacogenomic markers. As used herein, a "pharmacogenomic marker" is an objective biochemical marker which conelates with a specific clinical drag response or susceptibility in a subject (see, e.g., McLeod et al. (1999) Eωr. J. Cancer 35:1650-1652). The presence or quantity ofthe pharmacogenomic marker is related to the predicted response ofthe subject to a specific drag or class of drugs prior to administration ofthe drug. By assessing the presence or quantity of one or more pharmacogenomic markers in a subject, a drug therapy which is most appropriate for the subject, or which is predicted to have a greater degree of success, can be selected. For example, based on the presence or quantity of RNA, or protein (e.g., 23155 protein or RNA) for specific tumor markers in a subject, a drag or course of treatment can be selected that is optimized for the treatment ofthe specific tumor likely to be present in the subject. Similarly, the presence or absence of a specific sequence mutation in 23155 DNA can conelate with a 23155 drug response. The use of pharmacogenomic markers therefore permits the application ofthe most appropriate treatment for each subject without having to administer the therapy. V. Pharmaceutical Compositions The 23155 nucleic acid molecules, 23155 proteins, and anti-23155 antibodies (also refened to herein as "active compounds") ofthe invention can be incoφorated into pharmaceutical compositions suitable for administration. Such compositions typically comprise the nucleic acid molecule, protein, or antibody and a pharmaceutically acceptable carrier. As used herein the language "pharmaceutically acceptable carrier" is intended to include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the compositions is contemplated. Supplementary active compounds can also be incorporated into the compositions. A pharmaceutical composition ofthe invention is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral, e.g., intravenous, intradermal, subcutaneous, oral (e.g., inhalation), transdermal (topical), transmucosal, and rectal administration. Solutions or suspensions used for parenteral, intradermal, or subcutaneous application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. pH can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. For intravenous administration, suitable carriers include physiological saline, bacteriostatic water, Cremophor EL™ (BASF, Parsippany, NJ) or phosphate buffered saline (PBS). In all cases, the composition must be sterile and should be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance ofthe required particle size in the case of dispersion and by the use of surfactants. Prevention ofthe action of microorganisms can be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as manitol, sorbitol, sodium chloride in the composition. Prolonged absorption ofthe injectable compositions can be brought about by including in the composition an agent which delays absorption, for example, aluminum monostearate and gelatin. Sterile injectable solutions can be prepared by incorporating the active compound (e.g., a 23155 protein or anti-23155 antibody) in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle which contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the prefened methods of preparation are vacuum drying and freeze-drying which yields a powder ofthe active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof. Oral compositions generally include an inert diluent or an edible carrier. They can be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic achninistration, the active compound can be incorporated with excipients and used in the form of tablets, troches, or capsules. Oral compositions can also be prepared using a fluid carrier for use as a mouthwash, wherein the compound in the fluid carrier is applied orally and swished and expectorated or swallowed. Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part ofthe composition. The tablets, pills, capsules, troches and the like can contain any ofthe following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring. For administration by inhalation, the compounds are delivered in the form of an aerosol spray from pressured container or dispenser which contains a suitable propellant, e.g., a gas such as carbon dioxide, or a nebulizer. Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, detergents, bile salts, and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays or suppositories. For transdermal administration, the active compounds are formulated into ointments, salves, gels, or creams as generally known in the art. The compounds can also be prepared in the form of suppositories (e.g., with conventional suppository bases such as cocoa butter and other glycerides) or retention enemas for rectal delivery. In one embodiment, the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation and Nova Pharmaceuticals, hie. Liposomal suspensions (including liposomes targeted to infected cells with monoclonal antibodies to viral antigens) can also be used as pharmaceutically acceptable carriers. These can be prepared according to methods known to those skilled in the art, for example, as described in U.S. Patent No. 4,522,811. It is especially advantageous to formulate oral or parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subject to be treated; each unit containing a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms ofthe invention are dictated by and directly dependent on the unique characteristics ofthe active compound and the particular therapeutic effect to be achieved, and the limitations inherent in the art of compounding such an active compound for the treatment of individuals. Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the dose lethal to 50% ofthe population) and the ED50 (the dose therapeutically effective in 50% ofthe population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Compounds which exhibit large therapeutic indices are prefened. While compounds that exhibit toxic side effects may be used, care should be taken to design a delivery system that targets such compounds to the site of affected tissue in order to minimize potential damage to uninfected cells and, thereby, reduce side effects. The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the method ofthe invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose may be formulated in animal models to achieve a circulating plasma concentration range that includes the IC50 (i.e., the concentration ofthe test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma may be measured, for example, by high performance liquid chromatography. The nucleic acid molecules ofthe invention can be inserted into vectors and used as gene therapy vectors. Gene therapy vectors can be delivered to a subject by, for example, intravenous injection, local administration (see U.S. Patent 5,328,470) or by stereotactic injection (see e.g., Chen et al. (1994) Proc. Natl. Acad. Sci. USA 91:3054-3057). The pharmaceutical preparation ofthe gene therapy vector can include the gene therapy vector in an acceptable diluent, or can comprise a slow release matrix in which the gene delivery vehicle is imbedded. Alternatively, where the complete gene delivery vector can be produced intact from recombinant cells, e.g., retroviral vectors, the pharmaceutical preparation can include one or more cells which produce the gene delivery system. The pharmaceutical compositions can be included in a container, pack, or dispenser together with instructions for administration. VI. Uses and Methods ofthe Invention The nucleic acid molecules, proteins, protein homologues, and antibodies described herein can be used in one or more ofthe following methods: a) screening assays; b) predictive medicine (e.g., diagnostic assays, prognostic assays, monitoring clinical trials, and pharmacogenetics); and c) methods of treatment (e.g., therapeutic and prophylactic). The isolated nucleic acid molecules ofthe invention can be used, for example, to express 23155 protein (e.g., via a recombinant expression vector in a host cell in gene therapy applications), to detect 23155 mRNA (e.g., in a biological sample) or a genetic alteration in a 23155 gene, and to modulate 23155 activity, as described further below. The 23155 proteins can be used to treat disorders characterized by insufficient or excessive production of a 23155 substrate or production of 23155 inhibitors. In addition, the 23155 proteins can be used to screen for naturally occurring 23155 substrates, to screen for drags or compounds which modulate 23155 activity, as well as to treat disorders characterized by insufficient or excessive production of 23155 protein or production of 23155 protein forms which have decreased or abenant activity compared to 23155 wild type protein. Moreover, the anti-23155 antibodies ofthe invention can be used to detect and isolate 23155 proteins, regulate the bioavailability of 23155 proteins, and modulate 23155 activity. A. Screening Assays: The invention provides a method (also refened to herein as a "screening assay") for identifying modulators, i.e., candidate or test compounds or agents (e.g., peptides, peptidomimetics, small molecules or other drugs) which bind to 23155 proteins, have a stimulatory or inhibitory effect on, for example, 23155 expression or 23155 activity, or have a stimulatory or inhibitory effect on, for example, the expression or activity of a 23155 substrate. In one embodiment, the invention provides assays for screening candidate or test compounds which are substrates of a 23155 protein or polypeptide or biologically active portion thereof. In another embodiment, the invention provides assays for screening candidate or test compounds which bind to or modulate the activity of a 23155 protein or polypeptide or biologically active portion thereof, e.g., modulate the ability of 23155 to interact with its cognate ligand. The test compounds ofthe present invention can be obtained using any ofthe numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the 'one-bead one- compound' library method; and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam, K.S. (1997) Anticancer Drug Des. 12:145). Examples of methods for the synthesis of molecular libraries can be found in the art, for example in: DeWitt et al. (1993) Proc. Natl. Acad. Sci. U.S.A. 90:6909; Erb et al. (1994) Proc. Natl Acad. Sci. USA 91:11422; Zuckermann et al. (1994). J. Med. Chem. 37:2678; Cho et al. (1993) Science 261:1303; Canell et al. (1994) Angew. Chem. Int. Ed. Engl 33:2059; Carell et al. (1994) Angew. Chem. Int. Ed. Engl 33:2061; and in Gallop et al (1994) J. Med. Chem. 37:1233. Libraries of compounds may be presented in solution (e.g., Houghten (1992) Biotechniques 13:412-421), or on beads (Lam (1991) Nature 354:82-84), chips (Fodor (1993) Nature 364:555-556), bacteria (Ladner USP 5,223,409), spores (Ladner USP '409), plasmids (Cull et al. (1992) Proc Natl Acad Sci USA 89:1865-1869) or on phage (Scott and Smith (1990) Science 249:386-390); (Devlin (1990) Science 249:404-406); (Cwrrla et al. (1990) Proc. Natl Acad. Sci. 87:6378-6382); (Felici (1991) J. Mol Biol 222:301-310); (Ladner supra.). i another embodiment, an assay is a cell-based assay comprising contacting a cell expressing a 23155 target molecule (e.g., a 23155 phosphorylation substrate) with a test compound and determining the ability ofthe test compound to modulate (e.g. stimulate or inhibit) the activity ofthe 23155 target molecule. Determining the ability ofthe test compound to modulate the activity of a 23155 target molecule can be accomplished, for example, by determining the ability ofthe 23155 protein to bind to or interact with the 23155 target molecule, or by determining the ability ofthe 23155 protein to phosphorylate the 23155 target molecule. Determining the ability ofthe 23155 protein to bind to or interact with a 23155 target molecule can be accomplished by determining direct binding. Determining the ability ofthe 23155 protein to bind to or interact with a 23155 target molecule can be accomplished, for example, by coupling the 23155 protein with a radioisotope or enzymatic label such that binding ofthe 23155 protein to a 23155 target molecule can be determined by detecting the labeled 23155 protein in a complex. For example, 23155 molecules, e.g., 23155 proteins, can be labeled with ^^1, 3$S, ^C, or ^H, either directly or indirectly, and the radioisotope detected by direct counting of radioemission or by scintillation counting. Alternatively, 23155 molecules can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product. It is also within the scope of this invention to determine the ability of a compound to modulate the interaction between 23155 and its target molecule, without the labeling of any ofthe interactants. For example, a microphysiometer can be used to detect the interaction of 23155 with its target molecule without the labeling of either 23155 or the target molecule. McConnell, H. M. et al. (1992) Science 257:1906-1912. As used herein, a "microphysiometer" (e.g., Cytosensor) is an analytical instrument that measures the rate at which a cell acidifies its environment using a light-addressable potentiometric sensor (LAPS). Changes in this acidification rate can be used as an indicator ofthe interaction between compound and receptor. hi a prefened embodiment, determining the ability ofthe 23155 protein to bind to or interact with a 23155 target molecule can be accomplished by determining the activity of the target molecule. For example, the activity ofthe target molecule can be determined by detecting induction of a cellular second messenger ofthe target (e.g., intracellular Ca2+ diacylglycerol, IP3, etc.), detecting catalytic/enzymatic activity ofthe target an appropriate substrate, detecting the induction of a reporter gene (comprising a target-responsive regulatory element operatively linked to a nucleic acid encoding a detectable marker, e.g., chloramphenicol acetyl transferase), or detecting a target-regulated cellular response. In yet another embodiment, an assay ofthe present invention is a cell-free assay in which a 23155 protein or biologically active portion thereof is contacted with a test compound and the ability ofthe test compound to bind to the 23155 protein or biologically active portion thereof is determined. Binding ofthe test compound to the 23155 protein can be determined either directly or indirectly as described above. In a prefened embodiment, the assay includes contacting the 23155 protein or biologically active portion thereof with a known compound which binds 23155 to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability ofthe test compound to interact with a 23155 protein, wherein determining the ability ofthe test compound to interact with a 23155 protein comprises determining the ability ofthe test compound to preferentially bind to 23155 or biologically active portion thereof as compared to the known compound. In another embodiment, the assay is a cell-free assay in which a 23155 protein or biologically active portion thereof is contacted with a test compound and the ability ofthe test compound to modulate (e.g., stimulate or inhibit) the activity ofthe 23155 protein or biologically active portion thereof is determined. Determining the ability ofthe test compound to modulate the activity of a 23155 protein can be accomplished, for example, by determining the ability ofthe 23155 protein to bind to a 23155 target molecule by one of the methods described above for determining direct binding. Determining the ability ofthe 23155 protein to bind to a 23155 target molecule can also be accomplished using a technology such as real-time Biomolecular Interaction Analysis (BIA). Sjolander, S. and Urbaniczky, C. (1991) Anal Chem. 63:2338-2345 and Szabo et al. (1995) Curr. Opin. Struct. Biol. 5:699-705. As used herein, "BIA" is a technology for studying biospecific interactions in real time, without labeling any ofthe interactants (e.g., BIAcore). Changes in the optical phenomenon of surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules. hi an alternative embodiment, determining the ability ofthe test compound to modulate the activity of a 23155 protein can be accomplished by determining the ability of the 23155 protein to further modulate the activity of a 23155 target molecule (e.g., a 23155 mediated signal transduction pathway component). For example, the activity ofthe effector molecule on an appropriate target can be determined, or the binding ofthe effector to an appropriate target can be determined as previously described. In yet another embodiment, the cell-free assay involves contacting a 23155 protein or biologically active portion thereof with a known compound which binds the 23155 protein to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability ofthe test compound to interact with the 23155 protein, wherein determining the ability ofthe test compound to interact with the 23155 protein comprises determining the ability ofthe 23155 protein to preferentially bind to or modulate the activity of a 23155 target molecule. The cell-free assays ofthe present invention are amenable to use of both soluble and/or membrane-bound forms of proteins (e.g., 23155 proteins or biologically active portions thereof, or receptors to which 23155 binds). In the case of cell-free assays in which a membrane-bound form a protein is used (e.g., a cell surface 23155 receptor) it may be desirable to utilize a solubilizing agent such that the membrane-bound form ofthe protein is maintained in solution. Examples of such solubilizing agents include non-ionic detergents such as n-octylglucoside, n-dodecylglucoside, n-dodecylmaltoside, octanoyl- N-methylglucamide, decanoyl-N-methylglucamide, Triton® X-100, Triton® X-114, Thesif®, Isotridecypoly(ethylene glycol ether) n , 3-[(3-cholamidoρropyl)dimethylamminio]- 1-propane sulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylamminio]-2-hydroxy-l- propane sulfonate (CHAPSO), or N-dodecyl=N,N-dimethyl-3-ammonio-l -propane sulfonate. In more than one embodiment ofthe above assay methods ofthe present invention, it may be desirable to immobilize either 23155 or its target molecule to facilitate separation of complexed from uncomplexed forms of one or both ofthe proteins, as well as to accommodate automation ofthe assay. Binding of a test compound to a 23155 protein, or interaction of a 23155 protein with a target molecule in the presence and absence of a candidate compound, can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtitre plates, test tubes, and microcentrifuge tubes. In one embodiment, a fusion protein can be provided which adds a domain that allows one or both ofthe proteins to be bound to a matrix. For example, glutathione-S-transferase/ 23155 fusion proteins or glutathione-S-transferase/target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, MO) or glutathione derivatized microtitre plates, which are then combined with the test compound or the test compound and either the non-adsorbed target protein or 23155 protein, and the mixture incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtitre plate wells are washed to remove any unbound components, the matrix immobilized in the case of beads, complex determined either directly or indirectly, for example, as described above. Alternatively, the complexes can be dissociated from the matrix, and the level of 23155 binding or activity determined using standard techniques. Other techniques for immobilizing proteins on matrices can also be used in the screening assays ofthe invention. For example, either a 23155 protein or a 23155 target molecule can be immobilized utilizing conjugation of biotin and sfreptavidin. Biotinylated 23155 protein or target molecules can be prepared from biotin-NHS (N-hydroxysuccinimide) using techniques well known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, IL), and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemical). Alternatively, antibodies reactive with 23155 protein or target molecules but which do not interfere with binding of the 23155 protein to its target molecule can be derivatized to the wells ofthe plate, and unbound target or 23155 protein trapped in the wells by antibody conjugation. Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include immunodetection of complexes using antibodies reactive with the 23155 protein or target molecule, as well as enzyme-linked assays which rely on detecting an enzymatic activity associated with the 23155 protein or target molecule. In another embodiment, modulators of 23155 expression are identified in a method wherein a cell is contacted ith a candidate compound and the expression of 23155 mRNA or protein in the cell is determined. The level of expression of 23155 mRNA or protein in the presence ofthe candidate compound is compared to the level of expression of 23155 mRNA or protein in the absence ofthe candidate compound. The candidate compound can then be identified as a modulator of 23155 expression based on this comparison. For example, when expression of 23155 mRNA or protein is greater (statistically significantly greater) in the presence ofthe candidate compound than in its absence, the candidate compound is identified as a stimulator of 23155 RNA or protein expression. Alternatively, when expression of 23155 mRNA or protein is less (statistically significantly less) in the presence ofthe candidate compound than in its absence, the candidate compound is identified as an inhibitor of 23155 mRNA or protein expression. The level of 23155 mRNA or protein expression in the cells can be determined by methods described herein for detecting 23155 mRNA or protein. In yet another aspect ofthe invention, the 23155 proteins can be used as "bait proteins" in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Patent No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993) J. Biol Chem. 268:12046- 12054; Barrel et al. (1993) Biotechniques 14:920-924; Iwabuchi et al. (1993) Oncogene 8: 1693-1696; and Brent WO94/10300), to identify other proteins, which bind to or interact with 23155 ("23155 binding proteins" or "23155bρ") and are involved in 23155 activity. Such 23155 binding proteins are also likely to be involved in the propagation of signals by the 23155 proteins or 23155 targets as, for example, downstream elements of a 23155mediated signaling pathway. Alternatively, such 23155 binding proteins are likely to be 23155 inhibitors. The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. In one construct, the gene that codes for a 23155 protein is fused to a gene encoding the DNA binding domain of a known transcription factor (e.g., GAL-4). In the other construct, a DNA sequence, from a library of DNA sequences, that encodes an unidentified protein ("prey" or "sample") is fused to a gene that codes for the activation domain ofthe known transcription factor. If the "bait" and the "prey" proteins are able to interact, in vivo, forming a 23155dependent complex, the DNA-binding and activation domains ofthe transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ) which is operably linked to a transcriptional regulatory site responsive to the transcription factor. Expression ofthe reporter gene can be detected and cell colomes containing the functional transcription factor can be isolated and used to obtain the cloned gene which encodes the protein which interacts with the 23155 protein. This invention further pertains to novel agents identified by the above-described screening assays. Accordingly, it is within the scope of this invention to further use an agent identified as described herein in an appropriate animal model. For example, an agent identified as described herein (e.g., a 23155 modulating agent, an antisense 23155 nucleic acid molecule, a 23155 specific antibody, or a 23155 binding partner) can be used in an animal model to determine the efficacy, toxicity, or side effects of treatment with such an agent. Alternatively, an agent identified as described herein can be used in an animal model to determine the mechanism of action of such an agent. Furthermore, this invention pertains to uses of novel agents identified by the above-described screening assays for treatments as described herein. B. Detection Assays Portions or fragments ofthe cDNA sequences identified herein (and the conesponding complete gene sequences) can be used in numerous ways as polynucleotide reagents. For example, these sequences can be used to: (i) map their respective genes on a chromosome; and, thus, locate gene regions associated with genetic disease; (ii) identify an individual from a minute biological sample (tissue typing); and (iii) aid in forensic identification of a biological sample. These applications are described in the subsections below. 1. Chromosome Mapping Once the sequence (or a portion ofthe sequence) of a gene has been isolated, this sequence can be used to map the location ofthe gene on a chromosome. This process is called chromosome mapping. Accordingly, portions or fragments ofthe 23155 nucleotide sequences, described herein, can be used to map the location ofthe 23155 genes on a chromosome. The mapping ofthe 23155 sequences to chromosomes is an important first step in conelating these sequences with genes associated with disease. Briefly, 23155 genes can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp in length) from the 23155 nucleotide sequences. Computer analysis of the 23155 sequences can be used to predict primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers can then be used for PCR screening of somatic cell hybrids containing individual human chromosomes. Only those hybrids containing the human gene conesponding to the 23155 sequences will yield an amplified fragment. Somatic cell hybrids are prepared by fusing somatic cells from different mammals (e.g., human and mouse cells). As hybrids of human and mouse cells grow and divide, they gradually lose human chromosomes in random order, but retain the mouse chromosomes. By using media in which mouse cells cannot grow, because they lack a particular enzyme, but human cells can, the one human chromosome that contains the gene encoding the needed enzyme, will be retained. By using various media, panels of hybrid cell lines can be established. Each cell line in a panel contains either a single human chromosome or a small number of human chromosomes, and a full set of mouse chromosomes, allowing easy mapping of individual genes to specific human chromosomes. (D'Eustachio P. et al. (1983) Science 220:919-924). Somatic cell hybrids containing only fragments of human chromosomes can also be produced by using human chromosomes with translocations and deletions. PCR mapping of somatic cell hybrids is a rapid procedure for assigning a particular sequence to a particular chromosome. Three or more sequences can be assigned per day using a single thermal cycler. Using the 23155 nucleotide sequences to design oligonucleotide primers, sublocalization can be achieved with panels of fragments from specific chromosomes. Other mapping strategies which can similarly be used to map a 9o, lp, or lv sequence to its chromosome include in situ hybridization (described in Fan, Y. et al. (1990) Proc. Natl. Acad. Sci. USA, 87:6223-27), pre-screening with labeled flow-sorted chromosomes, and pre-selection by hybridization to chromosome specific cDNA libraries. Fluorescence in situ hybridization (FISH) of a DNA sequence to a metaphase chromosomal spread can further be used to provide a precise chromosomal location in one step. Chromosome spreads can be made using cells whose division has been blocked in metaphase by a chemical such as colcemid that disrupts the mitotic spindle. The chromosomes can be treated briefly with trypsin, and then stained with Giemsa. A pattern of light and dark bands develops on each chromosome, so that the chromosomes can be identified individually. The FISH technique can be used with a DNA sequence as short as 500 or 600 bases. However, clones larger than 1,000 bases have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. Preferably 1,000 bases, and more preferably 2,000 bases will suffice to get good results at a reasonable amount of time. For a review of this technique, see Verma et al, Human Chromosomes: A Manual of Basic Techniques (Pergamon Press, New York 1988). Reagents for chromosome mapping can be used individually to mark a single chromosome or a single site on that chromosome, or panels of reagents can be used for marking multiple sites and/or multiple chromosomes. Reagents conesponding to noncoding regions ofthe genes actually are prefened for mapping purposes. Coding sequences are more likely to be conserved within gene families, thus increasing the chance of cross hybridizations during chromosomal mapping. Once a sequence has been mapped to a precise chromosomal location, the physical position ofthe sequence on the chromosome can be conelated with genetic map data. (Such data are found, for example, in V. McKusick, Mendelian Inheritance in Man, available on-line through Johns Hopkins University Welch Medical Library). The relationship between a gene and a disease, mapped to the same chromosomal region, can then be identified through linkage analysis (co-inheritance of physically adjacent genes), described in, for example, Egeland, J. et al. (1987) Nature, 325:783-787. Moreover, differences in the DΝA sequences between individuals affected and unaffected with a disease associated with the 23155 gene, can be determined. If a mutation is observed in some or all ofthe affected individuals but not in any unaffected individuals, then the mutation is likely to be the causative agent ofthe particular disease. Comparison of affected and unaffected individuals generally involves first looking for structural alterations in the chromosomes, such as deletions or translocations that are visible from chromosome spreads or detectable using PCR based on that DNA sequence. Ultimately, complete sequencing of genes from several individuals can be performed to confirm the presence of a mutation and to distinguish mutations from polymorphisms. 2. Tissue Typing The 23155 sequences ofthe present invention can also be used to identify individuals from minute biological samples. The United States military, for example, is considering the use of restriction fragment length polymorphism (RFLP) for identification of its personnel. In this technique, an individual's genomic DNA is digested with one or more restriction enzymes, and probed on a Southern blot to yield unique bands for identification. This method does not suffer from the cunent limitations of "Dog Tags" which can be lost, switched, or stolen, making positive identification difficult. The sequences ofthe present invention are useful as additional DNA markers for RFLP (described in U.S. Patent 5,272,057). Furthermore, the sequences ofthe present invention can be used to provide an alternative technique which determines the actual base-by-base DNA sequence of selected portions of an individual's genome. Thus, the 23155 nucleotide sequences described herein can be used to prepare two PCR primers from the 5' and 3' ends ofthe sequences. These primers can then be used to amplify an individual's DNA and subsequently sequence it. Panels of conesponding DNA sequences from individuals, prepared in this manner, can provide unique individual identifications, as each individual will have a unique set of such DNA sequences due to allelic differences. The sequences ofthe present invention can be used to obtain such identification sequences from individuals and from tissue. The 23155 nucleotide sequences ofthe invention uniquely represent portions ofthe human genome. Allelic variation occurs to some degree in the coding regions of these sequences, and to a greater degree in the noncoding regions. It is estimated that allelic variation between individual humans occurs with a frequency of about once per each 500 bases. Each ofthe sequences described herein can, to some degree, be used as a standard against which DNA from an individual can be compared for identification purposes. Because greater numbers of polymorphisms occur in the noncoding regions, fewer sequences are necessary to differentiate individuals. The noncoding sequences of SEQ ID NO: 1, can comfortably provide positive individual identification with a panel of perhaps 10 to 1,000 primers which each yield a noncoding amplified sequence of 100 bases. If predicted coding sequences, such as those in SEQ ID NO:3 are used, a more appropriate number of primers for positive individual identification would be 500-2,000. If a panel of reagents from 23155 nucleotide sequences described herein is used to generate a unique identification database for an individual, those same reagents can later be used to identify tissue from that individual. Using the unique identification database, positive identification ofthe individual, living or dead, can be made from extremely small tissue samples. 3. Use of Partial 23155 Sequences in Forensic Biology DNA-based identification techniques can also be used in forensic biology. Forensic biology is a scientific field employing genetic typing of biological evidence found at a crime scene as a means for positively identifying, for example, a perpetrator of a crime. To make such an identification, PCR technology can be used to amplify DNA sequences taken from very small biological samples such as tissues, e.g., hair or skin, or body fluids, e.g., blood, saliva, or semen found at a crime scene. The amplified sequence can then be compared to a standard, thereby allowing identification ofthe origin ofthe biological sample. The sequences ofthe present invention can be used to provide polynucleotide reagents, e.g., PCR primers, targeted to specific loci in the human genome, which can enhance the reliability of DNA-based forensic identifications by, for example, providing another "identification marker" (i.e. another DNA sequence that is unique to a particular individual). As mentioned above, actual base sequence information can be used for identification as an accurate alternative to patterns formed by restriction enzyme generated fragments. Sequences targeted to noncoding regions of SEQ ID NO:l are particularly appropriate for this use as greater numbers of polymorphisms occur in the noncoding regions, making it easier to differentiate individuals using this technique. Examples of polynucleotide reagents include the 23155 nucleotide sequences or portions thereof, e.g., fragments derived from the noncoding regions of SEQ ID NO:l, having a length of at least 20 bases, preferably at least 30 bases. The 23155 nucleotide sequences described herein can further be used to provide polynucleotide reagents, e.g., labeled or labelable probes which can be used in, for example, an in situ hybridization technique, to identify a specific tissue, e.g., brain tissue. This can be very useful in cases where a forensic pathologist is presented with a tissue of unknown origin. Panels of such 23155 probes can be used to identify tissue by species and/or by organ type. In a similar fashion, these reagents, e.g., 23155 primers or probes can be used to screen tissue culture for contamination (i.e. screen for the presence of a mixture of different types of cells in a culture). C. Predictive Medicine: The present invention also pertains to the field of predictive medicine in which diagnostic assays, prognostic assays, and monitoring clinical trials are used for prognostic (predictive) purposes to thereby treat an individual prophylactically. Accordingly, one aspect ofthe present invention relates to diagnostic assays for determining 23155 protein and/or nucleic acid expression as well as 23155 activity, in the context of a biological sample (e.g., blood, serum, cells, tissue) to thereby determine whether an individual is afflicted with a disease or disorder, or is at risk of developing a disorder, associated with abenant 23155 expression or activity. The invention also provides for prognostic (or predictive) assays for determining whether an individual is at risk of developing a disorder associated with 23155 protein, nucleic acid expression or activity. For example, mutations in a 23155 gene can be assayed in a biological sample. Such assays can be used for prognostic or predictive purpose to thereby prophylactically treat an individual prior to the onset of a disorder characterized by or associated with 23155 protein, nucleic acid expression or activity. Another aspect ofthe invention pertains to monitoring the influence of agents (e.g., drags, compounds) on the expression or activity of 23155 in clinical trials. These and other agents are described in further detail in the following sections. 1. Diagnostic Assays An exemplary method for detecting the presence or absence of 23155 protein or nucleic acid in a biological sample involves obtaining a biological sample from a test subject and contacting the biological sample with a compound or an agent capable of detecting 23155 protein or nucleic acid (e.g., RNA, genomic DNA) that encodes 23155 protein such that the presence of 23155 protein or nucleic acid is detected in the biological sample. A prefened agent for detecting 23155 mRNA or genomic DNA is a labeled nucleic acid probe capable of hybridizing to 23155 mRNA or genomic DNA. The nucleic acid probe can be, for example, a human 23155 nucleic acid, such as the nucleic acid of SEQ JO NO:l, or a portion thereof, such as an oligonucleotide of at least 15, 30, 50, 100, 250 or 500 nucleotides in length and sufficient to specifically hybridize under stringent conditions to 23155 mRNA or genomic DNA. Other suitable probes for use in the diagnostic assays ofthe invention are described herein. A prefened agent for detecting 23155 protein is an antibody capable of binding to 23155 protein, preferably an antibody with a detectable label. Antibodies can be polyclonal, or more preferably, monoclonal. An intact antibody, or a fragment thereof (e.g., Fab or F(ab')2) can be used. The term "labeled", with regard to the probe or antibody, is intended to encompass direct labeling ofthe probe or antibody by coupling (i.e., physically linking) a detectable substance to the probe or antibody, as well as indirect labeling ofthe probe or antibody by reactivity with another reagent that is directly labeled. Examples of indirect labeling include detection of a primary antibody using a fluorescently labeled secondary antibody and end-labeling of a DNA probe with biotin such that it can be detected with fluorescently labeled streptavidin. The term "biological sample" is intended to include tissues, cells and biological fluids isolated from a subject, as well as tissues, cells and fluids present within a subject. That is, the detection method ofthe invention can be used to detect 23155 mRNA, protein, or genomic DNA in a biological sample in vitro as well as in vivo. For example, in vitro techniques for detection of 23155 mRNA include Northern hybridizations and in situ hybridizations. In vitro techniques for detection of 23155 protein include enzyme linked immunosorbent assays (ELISAs), Western blots, immunoprecipitations and immunofluorescence. In vitro techniques for detection of 23155 genomic DNA include Southern hybridizations. Furthermore, in vivo techniques for detection of 23155 protein include introducing into a subject a labeled anti-23155 antibody. For example, the antibody can be labeled with a radioactive marker whose presence and location in a subject can be detected by standard imaging techniques. In one embodiment, the biological sample contains protein molecules from the test subject. Alternatively, the biological sample can contain mRNA molecules from the test subject or genomic DNA molecules from the test subject. A prefened biological sample is a serum sample isolated by conventional means from a subject. In another embodiment, the methods further involve obtaining a control biological sample from a control subject, contacting the control sample with a compound or agent capable of detecting 23155 protein, mRNA, or genomic DNA, such that the presence of 23155 protein, mRNA or genomic DNA is detected in the biological sample, and comparing the presence of 23155 protein, mRNA or genomic DNA in the control sample with the presence of 23155 protein, mRNA or genomic DNA in the test sample. The invention also encompasses kits for detecting the presence of 23155 in a biological sample. For example, the kit can comprise a labeled compound or agent capable of detecting 23155 protein or mRNA in a biological sample; means for determimng the amount of 23155 in the sample; and means for comparing the amount of 23155 in the sample with a standard. The compound or agent can be packaged in a suitable container. The kit can further comprise instructions for using the kit to detect 23155 protein or nucleic acid. 2. Prognostic Assays The diagnostic methods described herein can furthermore be utilized to identify subjects having or at risk of developing a disease or disorder associated with abenant 23155 expression or activity. For example, the assays described herein, such as the preceding diagnostic assays or the following assays, can be utilized to identify a subject having or at risk of developing a disorder associated with 23155 protein, nucleic acid expression or activity. Thus, the present invention provides a method for identifying a disease or disorder associated with abenant 23155 expression or activity in which a test sample is obtained from a subject and 23155 protein or nucleic acid (e.g., mRNA, genomic DNA) is detected, wherein the presence of 23155 protein or nucleic acid is diagnostic for a subject having or at risk of developing a disease or disorder associated with abenant 23155 expression or activity. As used herein, a "test sample" refers to a biological sample obtained from a subject of interest. For example, a test sample can be a biological fluid (e.g., serum), cell sample, or tissue. Furthermore, the prognostic assays described herein can be used to determine whether a subject can be administered an agent (e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drug candidate) to treat a disease or disorder associated with abenant 23155 expression or activity. Thus, the present invention provides methods for determining whether a subject can be effectively treated with an agent for a disorder associated with abenant 23155 expression or activity in which a test sample is obtained and 23155 protein or nucleic acid expression or activity is detected (e.g., wherein the abundance of 23155 protein or nucleic acid expression or activity is diagnostic for a subject that can be administered the agent to treat a disorder associated with abenant 23155 expression or activity). The methods ofthe invention can also be used to detect genetic alterations in a 23155 gene, thereby determimng if a subject with the altered gene is at risk for a disorder associated with the 23155 gene. In prefened embodiments, the methods include detecting, in a sample of cells from the subject, the presence or absence of a genetic alteration characterized by at least one of an alteration affecting the integrity of a gene encoding a 23155 protein, or the mis-expression ofthe 23155 gene. For example, such genetic alterations can be detected by ascertaining the existence of at least one of 1) a deletion of one or more nucleotides from a 23155 gene; 2) an addition of one or more nucleotides to a 23155 gene; 3) a substitution of one or more nucleotides of a 23155 gene, 4) a chromosomal reanangement of a 23155 gene; 5) an alteration in the level of a messenger RNA transcript of a 23155 gene, 6) abenant modification of a 23155 gene, such as ofthe methylation pattern ofthe genomic DNA, 7) the presence of a non- wild type splicing pattern of a messenger RNA transcript of a 23155 gene, 8) a non-wild type level of a 23155 protein, 9) allelic loss of a 23155 gene, and 10) inappropriate post-translational modification of a 23155 protein. As described herein, there are a large number of assay techniques known in the art which can be used for detecting alterations in a 23155 gene. A prefened biological sample is a tissue or serum sample isolated by conventional means from a subject. In certain embodiments, detection ofthe alteration involves the use of a probe/primer in a polymerase chain reaction (PCR) (see, e.g., U.S. Patent Nos. 4,683,195 and 4,683,202), such as anchor PCR or RACE PCR, or, alternatively, in a ligation chain reaction (LCR) (see, e.g., Landegran et al. (1988) Science 241:1077-1080; and Nakazawa et al. (1994) Proc. Natl Acad. Sci. USA 91:360-364), the latter of which can be particularly useful for detecting point mutations in the 23155 gene (see Abravaya et al. (1995) Nucleic Acids Res .23:675-682). This method can include the steps of collecting a sample of cells from a patient, isolating nucleic acid (e.g., genomic, mRNA or both) from the cells ofthe sample, contacting the nucleic acid sample with one or more primers which specifically hybridize to a 23155 gene under conditions such that hybridization and amplification ofthe 23155 gene (if present) occurs, and detecting the presence or absence of an amplification product, or detecting the size ofthe amplification product and comparing the length to a control sample. It is anticipated that PCR and/or LCR may be desirable to use as a preliminary amplification step in conjunction with any ofthe techniques used for detecting mutations described herein. Alternative amplification methods include: self sustained sequence replication (Guatelli, J.C. et al, (1990) Proc. Natl. Acad. Sci. USA 87:1874-1878), transcriptional amplification system (Kwoh, D.Y. et al, (1989) Proc. Natl Acad. Sci. USA 86:1173-1177), Q-Beta Replicase (Lizardi, P.M. et al. (1988) Bio-Technology 6:1191), or any other nucleic acid amplification method, followed by the detection ofthe amplified molecules using techniques well known to those of skill in the art. These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present in very low numbers. hi an alternative embodiment, mutations in a 23155 gene from a sample cell can be identified by alterations in restriction enzyme cleavage patterns. For example, sample and control DNA is isolated, amplified (optionally), digested with one or more restriction endonucleases, and fragment length sizes are determined by gel electrophoresis and compared. Differences in fragment length sizes between sample and control DNA indicates mutations in the sample DNA. Moreover, the use of sequence specific ribozymes (see, for example, U.S. Patent No. 5,498,531) can be used to score for the presence of specific mutations by development or loss of a ribozyme cleavage site. In other embodiments, genetic mutations in 23155 can be identified by hybridizing a sample and control nucleic acids, e.g., DNA or RNA, to high density anays containing hundreds or thousands of oligonucleotides probes (Cronin, M.T. et al. (1996) Human Mutation 1: 244-255; Kozal, M.J. et al. (1996) Nature Medicine 2: 753-759). For example, genetic mutations in 23155 can be identified in two dimensional anays containing light- generated DNA probes as described in Cronin, M.T. et al. supra. Briefly, a first hybridization array of probes can be used to scan through long stretches of DNA in a sample and control to identify base changes between the sequences by making linear anays of sequential overlapping probes. This step allows the identification of point mutations. This step is followed by a second hybridization anay that allows the characterization of specific mutations by using smaller, specialized probe anays complementary to all variants or mutations detected. Each mutation anay is composed of parallel probe sets, one complementary to the wild-type gene and the other complementary to the mutant gene. In yet another embodiment, any of a variety of sequencing reactions known in the art can be used to directly sequence the 23155 gene and detect mutations by comparing the sequence ofthe sample 23155 with the conesponding wild-type (control) sequence. Examples of sequencing reactions include those based on techniques developed by Maxam and Gilbert ((1977) Proc. Natl Acad. Sci. USA 74:560) or Sanger ((1977) Proc. Natl Acad. Sci. USA 74:5463). It is also contemplated that any of a variety of automated sequencing procedures can be utilized when performing the diagnostic assays ((1995) Biotechniques 19:448), including sequencing by mass spectrometry (see, e.g., PCT International Publication No. WO 94/16101; Cohen et al. (1996) Adv. Chromatogr. 36:127-162; and Griffin et al. (1993) Appl Biochem. Biotechnol 38:147-159). Other methods for detecting mutations in the 23155 gene include methods in which protection from cleavage agents is used to detect mismatched bases in RNA/RNA or RNA/DNA heteroduplexes (Myers et al. (1985) Science 230:1242). In general, the art technique of "mismatch cleavage" starts by providing heteroduplexes formed by hybridizing (labeled) RNA or DNA containing the wild-type 23155 sequence with potentially mutant RNA or DNA obtained from a tissue sample. The double-stranded duplexes are treated with an agent which cleaves single-stranded regions ofthe duplex such as which will exist due to basepair mismatches between the control and sample strands. For instance, RNA DNA duplexes can be treated with RNase and DNA/DNA hybrids treated with SI nuclease to enzymatically digesting the mismatched regions. In other embodiments, either DNA/DNA or RNA/DNA duplexes can be treated with hydroxylamine or osmium tetroxide and with piperidine in order to digest mismatched regions. After digestion ofthe mismatched regions, the resulting material is then separated by size on denaturing polyacrylamide gels to determine the site of mutation. See, for example, Cotton et al. (1988) Proc. Natl Acad Sci USA 85:4397; Saleeba et al. (1992) Methods Enzymol 217:286-295. In a prefened embodiment, the control DNA or RNA can be labeled for detection. hi still another embodiment, the mismatch cleavage reaction employs one or more proteins that recognize mismatched base pairs in double-stranded DNA (so called "DNA mismatch repair" enzymes) in defined systems for detecting and mapping point mutations in 23155 cDNAs obtained from samples of cells. For example, the mutY enzyme of E. coli cleaves A at G/A mismatches and the thymidine DNA glycosylase from HeLa cells cleaves T at G/T mismatches (Hsu et al. (1994) Carcinogenesis 15:1657-1662). According to an exemplary embodiment, a probe based on a 23155 sequence, e.g., a wild-type 23155 sequence, is hybridized to a cDNA or other DNA product from a test cell(s). The duplex is treated with a DNA mismatch repair enzyme, and the cleavage products, if any, can be detected from electrophoresis protocols or the like. See, for example, U.S. Patent No. 5,459,039. In other embodiments, alterations in electrophoretic mobility will be used to identify mutations in 23155 genes. For example, single strand conformation polymorphism (SSCP) may be used to detect differences in electrophoretic mobility between mutant and wild type nucleic acids (Orita et al. (1989) Proc Natl. Acad. Sci USA: 86:2766, see also Cotton (1993) Mutat Res 285:125-144; and Hayashi (1992) Genet Anal Tech Appl 9:73-79). Single-stranded DNA fragments of sample and control 23155 nucleic acids will be denatured and allowed to renature. The secondary stracture of single-sfranded nucleic acids varies according to sequence, the resulting alteration in electrophoretic mobility enables the detection of even a single base change. The DNA fragments may be labeled or detected with labeled probes. The sensitivity ofthe assay may be enhanced by using RNA (rather than DNA), in which the secondary structure is more sensitive to a change in sequence. In a prefened embodiment, the subject method utilizes heteroduplex analysis to separate double stranded heteroduplex molecules on the basis of changes in electrophoretic mobility (Keen et al (1991) Trends Genet 7:5). hi yet another embodiment the movement of mutant or wild-type fragments in polyacrylamide gels containing a gradient of denaturant is assayed using denaturing gradient gel electrophoresis (DGGE) (Myers et al (1985) Nature 313:495). When DGGE is used as the method of analysis, DNA will be modified to insure that it does not completely denature, for example by adding a GC clamp of approximately 40 bp of high- melting GC-rich DNA by PCR. In a further embodiment, a temperature gradient is used in place of a denaturing gradient to identify differences in the mobility of control and sample DNA (Rosenbaum and Reissner (1987) Biophys Chem 265:12753). Examples of other techniques for detecting point mutations include, but are not limited to, selective oligonucleotide hybridization, selective amplification, or selective primer extension. For example, oligonucleotide primers may be prepared in which the known mutation is placed centrally and then hybridized to target DNA under conditions which permit hybridization only if a perfect match is found (Saiki et al. (1986) Nature 324:163); Saiki et al. (1989) Proc. Natl Acad. Sci USA 86:6230). Such allele specific oligonucleotides are hybridized to PCR amplified target DNA or a number of different mutations when the oligonucleotides are attached to the hybridizing membrane and hybridized with labeled target DNA. Alternatively, allele specific amplification technology which depends on selective PCR amplification may be used in conjunction with the instant invention. Oligonucleotides used as primers for specific amplification may carry the mutation of interest in the center of the molecule (so that amplification depends on differential hybridization) (Gibbs et al. (1989) Nucleic Acids Res. 17:2437-2448) or at the extreme 3' end of one primer where, under appropriate conditions, mismatch can prevent, or reduce polymerase extension (Prossner et al (1993) Tibtech 11 :238). hi addition it may be desirable to introduce a novel restriction site in the region ofthe mutation to create cleavage-based detection (Gasparini et al. (1992) Mol. Cell Probes 6:1). It is anticipated that in certain embodiments amplification may also be performed using Taq ligase for amplification (Barany (1991) Proc. Natl. Acad. Sci USA 88:189). h such cases, ligation will occur only if there is a perfect match at the 3' end ofthe 5' sequence making it possible to detect the presence of a known mutation at a specific site by looking for the presence or absence of amplification. The methods described herein may be performed, for example, by utilizing prepackaged diagnostic kits comprising at least one probe nucleic acid or antibody reagent described herein, which maybe conveniently used, e.g., in clinical settings to diagnose patients exhibiting symptoms or family history of a disease or illness involving a 23155 gene. Furthermore, any cell type or tissue in which 23155 is expressed may be utilized in the prognostic assays described herein. 3. Monitoring of Effects During Clinical Trials Monitoring the influence of agents (e.g., drugs or compounds) on the expression or activity of a 23155 protein can be applied not only in basic drag screening, but also in clinical trials. For example, the effectiveness of an agent determined by a screening assay as described herein to increase 23155 gene expression, protein levels, or upregulate 23155 activity, can be monitored in clinical trials of subjects exhibiting decreased 23155 gene expression, protein levels, or downregulated 23155 activity. Alternatively, the effectiveness of an agent determined by a screening assay to decrease 23155 gene expression, protein levels, or downregulate 23155 activity, can be monitored in clinical trials of subjects exhibiting increased 23155 gene expression, protein levels, or upregulated 23155 activity, hi such clinical trials, the expression or activity of a 23155 gene, and preferably, other genes that have been implicated in a disorder can be used as a "read out" or markers ofthe phenotype of a particular cell. For example, and not by way of limitation, genes, including 23155, that are modulated in cells by treatment with an agent (e.g., compound, drag or small molecule) which modulates 23155 activity (e.g., identified in a screening assay as described herein) can be identified. Thus, to study the effect of agents on a 23155 associated disorder, for example, in a clinical trial, cells can be isolated and RNA prepared and analyzed for the levels of expression of 23155 and other genes implicated in the 23155 associated disorder, respectively. The levels of gene expression (i.e., a gene expression pattern) can be quantified by Northern blot analysis or RT-PCR, as described herein, or alternatively by measuring the amount of protein produced, by one ofthe methods as described herein, or by measuring the levels of activity of 23155 or other genes. In this way, the gene expression pattern can serve as a marker, indicative ofthe physiological response ofthe cells to the agent. Accordingly, this response state may be determined before, and at various points during treatment ofthe individual with the agent. In a prefened embodiment, the present invention provides a method for monitoring the effectiveness of treatment of a subject with an agent (e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drug candidate identified by the screening assays described herein) comprising the steps of (i) obtaining a pre-administration sample from a subject prior to administration ofthe agent; (ii) detecting the level of expression of a 23155 protein, mRNA, or genomic DNA in the pre- administration sample; (iii) obtaining one or more post-administration samples from the subject; (iv) detecting the level of expression or activity ofthe 23155 protein, mRNA, or genomic DNA in the post-administration samples; (v) comparing the level of expression or activity ofthe 23155 protein, mRNA, or genomic DNA in the pre-administration sample with the 23155 protein, mRNA, or genomic DNA in the post administration sample or samples; and (vi) altering the administration ofthe agent to the subject accordingly. For example, increased administration ofthe agent maybe desirable to increase the expression or activity of 23155 to higher levels than detected, i.e., to increase the effectiveness ofthe agent. Alternatively, decreased administration ofthe agent maybe desirable to decrease expression or activity of 23155 to lower levels than detected, i.e. to decrease the effectiveness ofthe agent. According to such an embodiment, 23155 expression or activity may be used as an indicator ofthe effectiveness of an agent, even in the absence of an observable phenotypic response. C. Methods of Treatment: The present invention provides for both prophylactic and therapeutic methods of treating a subject at risk of (or susceptible to) a disorder or having a disorder associated with abenant 23155 expression or activity. With regards to both prophylactic and therapeutic methods of treatment, such treatments maybe specifically tailored or modified, based on knowledge obtained from the field of pharmacogenomics. As used herein, the term "treatment" is defined as the application or administration of a therapeutic agent to a patient, or application or administration of a therapeutic agent to an isolated tissue or cell line from a patient, who has a disease, a symptom of disease or a predisposition toward a disease, with the purpose to cure, heal, alleviate, relieve, alter, remedy, ameliorate, improve or affect the disease, the symptoms of disease or the predisposition toward disease. A therapeutic agent includes, but is not limited to, small molecules, peptides, antibodies, ribozymes and antisense oligonucleotides. "Pharmacogenomics", as used herein, refers to the application of genomics technologies such as gene sequencing, statistical genetics, and gene expression analysis to drugs in clinical development and on the market. More specifically, the term refers the study of how a patient's genes determine his or her response to a drug (e.g., a patient's "drug response phenotype", or "drug response genotype".) Thus, another aspect ofthe invention provides methods for tailoring an individual's prophylactic or therapeutic treatment with either the 23155 molecules ofthe present invention or 23155 modulators according to that individual's drag response genotype. Pharmacogenomics allows a clinician or physician to target prophylactic or therapeutic treatments to patients who will most benefit from the treatment and to avoid treatment of patients who will experience toxic drag-related side effects. The 23155 molecules can act as novel diagnostic targets and therapeutic agents for controlling one or more of cellular proliferative and/or differentiative disorders, disorders associated with bone metabolism, immune, e.g., inflammatory, disorders, cardiovascular disorders, including endothelial cell disorders, liver disorders, viral diseases, pain or metabolic disorders. Abenant expression and/or activity of 23155 molecules can mediate disorders associated with bone metabolism. "Bone metabolism" refers to direct or indirect effects in the formation or degeneration of bone structures, e.g., bone formation, bone resorption, etc., which can ultimately affect the concentrations in serum of calcium and phosphate. This term also includes activities mediated by 23155 molecules effects in bone cells, e.g. osteoclasts and osteoblasts, that can in turn result in bone formation and degeneration. For example, 23155 molecules can support different activities of bone resorbing osteoclasts such as the stimulation of differentiation of monocytes and mononuclear phagocytes into osteoclasts. Accordingly, 23155 molecules that modulate the production of bone cells can influence bone formation and degeneration, and thus can be used to treat bone disorders. Examples of such disorders include, but are not limited to, osteoporosis, osteodystrophy, osteomalacia, rickets, osteitis fibrosa cystica, renal osteodystrophy, osteosclerosis, anti- convulsant treatment, osteopenia, fibrogenesis-imperfecta ossium, secondary hypeφarathyrodism, hypoparafhyroidism, hypeφarathyroidism, cirrhosis, obstructive jaundice, drug induced metabolism, medullary carcinoma, chronic renal disease, rickets, sarcoidosis, glucocorticoid antagonism, malabsoφtion syndrome, steatonhea, tropical sprue, idiopathic hypercalcemia and milk fever. The 23155 nucleic acid and protein ofthe invention can be used to treat and/or diagnose a variety of immune, e.g., inflammatory, (e.g. respiratory inflammatory) disorders. Examples of immune disorders or diseases include, but are not limited to, autoimmune diseases (including, for example, diabetes mellitus, arthritis (including rheumatoid arthritis, juvenile rheumatoid arthritis, osteoarthritis, psoriatic arthritis), multiple sclerosis, encephalomyelitis, myasthenia gravis, systemic lupus erythematosis, autoimmune thyroiditis, dermatitis (including atopic dermatitis and eczematous dermatitis), psoriasis, Sjδgren's Syndrome, inflammatory bowel disease, e.g. Crohn's disease and ulcerative colitis, aphthous ulcer, iritis, conjunctivitis, keratoconjunctivitis, asthma, allergic asthma, chronic obstructive pulmonary disease, cutaneous lupus erythematosus, scleroderma, vaginitis, proctitis, drug eruptions, leprosy reversal reactions, erythema nodosum leprosum, autoimmune uveitis, allergic encephalomyelitis, acute necrotizing hemonhagic encephalopathy, idiopathic bilateral progressive sensorineural hearing loss, aplastic anemia, pure red cell anemia, idiopathic thrombocytopenia, polychondritis, Wegener's granulomatosis, chronic active hepatitis, Stevens- Johnson syndrome, idiopathic sprue, lichen planus, Graves' disease, sarcoidosis, primary biliary cinhosis, uveitis posterior, and interstitial lung fibrosis), graft- versus-host disease, cases of transplantation, and allergy such as, atopic allergy. Examples of disorders involving the heart or "cardiovascular disorder" include, but are not limited to, a disease, disorder, or state involving the cardiovascular system, e.g., the heart, the blood vessels, and/or the blood. A cardiovascular disorder can be caused by an imbalance in arterial pressure, a malfunction ofthe heart, or an occlusion of a blood vessel, e.g., by a thrombus. Examples of cardiovascular disorders include but are not limited to, hypertension, atherosclerosis, coronary artery spasm, coronary artery disease, anhythmias, heart failure, including but not limited to, cardiac hypertrophy, left-sided heart failure, and right-sided heart failure; ischemic heart disease, including but not limited to angina pectoris, myocardial infarction, chronic ischemic heart disease, and sudden cardiac death; hypertensive heart disease, including but not limited to, systemic (left-sided) hypertensive heart disease and pulmonary (right-sided) hypertensive heart disease; valvular heart disease, including but not limited to, valvular degeneration caused by calcification, such as calcification of a congenitally bicuspid aortic valve, and mitral annular calcification, and myxomatous degeneration ofthe mitral valve (mitral valve prolapse), rheumatic fever and rheumatic heart disease, infective endocarditis, and noninfected vegetations, such as nonbacterial thrombotic endocarditis and endocarditis of systemic lupus erythematosus (Libman-Sacks disease), carcinoid heart disease, and complications of artificial valves; myocardial disease, including but not limited to dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and myocarditis; pericardial disease, including but not limited to, pericardial effusion and hemopericardium and pericarditis, including acute pericarditis and healed pericarditis, and rheumatoid heart disease; neoplastic heart disease, including but not limited to, primary cardiac tumors, such as myxoma, lipoma, papillary fibroelastoma, rhabdomyoma, and sarcoma, and cardiac effects of noncardiac neoplasms; congenital heart disease, including but not limited to, left-to-right shunts—late cyanosis, such as atrial septal defect, ventricular septal defect, patent ductus arteriosus, and atrio ventricular septal defect, right-to-left shunts— early cyanosis, such as tetralogy of fallot, transposition of great arteries, truncus arteriosus, tricuspid atresia, and total anomalous pulmonary venous connection, obstructive congenital anomalies, such as coarctation of aorta, pulmonary stenosis and atresia, and aortic stenosis and atresia, disorders involving cardiac transplantation, and congestive heart failure. A cardiovasular disease or disorder also includes an endothelial cell disorder. As used herein, an "endothelial cell disorder" includes a disorder characterized by abenant, unregulated, or unwanted endothelial cell activity, e.g., proliferation, migration, angiogenesis, or vascularization; or abenant expression of cell surface adhesion molecules or genes associated with angiogenesis, e.g., TIE-2, FLT and FLK. Endothelial cell disorders include tumorigenesis, tumor metastasis, psoriasis, diabetic retinopathy, endometriosis, Grave's disease, ischemic disease (e.g., atherosclerosis), and chronic inflammatory diseases (e.g., rheumatoid arthritis). Disorders which can be treated or diagnosed by methods described herein include, but are not limited to, disorders associated with an accumulation in the liver of fibrous tissue, such as that resulting from an imbalance between production and degradation ofthe extracellular matrix accompanied by the collapse and condensation of preexisting fibers. The methods described herein can be used to diagnose or treat hepatocellular necrosis or injury induced by a wide variety of agents including processes which disturb homeostasis, such as an inflammatory process, tissue damage resulting from toxic injury or altered hepatic blood flow, and infections (e.g., bacterial, viral and parasitic). For example, the methods can be used for the early detection of hepatic injury, such as portal hypertension or hepatic fibrosis. In addition, the methods can be employed to detect liver fibrosis attributed to inborn enors of metabolism, for example, fibrosis resulting from a storage disorder such as Gaucher's disease (lipid abnormalities) or a glycogen storage disease, Al-antitrypsin deficiency; a disorder mediating the accumulation (e.g., storage) of an exogenous substance, for example, hemochromatosis (iron-overload syndrome) and copper storage diseases (Wilson's disease), disorders resulting in the accumulation of a toxic metabolite (e.g., tyrosinemia, fructosemia and galactosemia) and peroxisomal disorders (e.g., Zellweger syndrome). Additionally, the methods described herein can be used for the early detection and treatment of liver injury associated with the administration of various chemicals or drugs, such as for example, methofrexate, isonizaid, oxyphenisatin, methyldopa, chloφromazine, tolbutamide or alcohol, or which represents a hepatic manifestation of a vascular disorder such as obstruction of either the intrahepatic or extrahepatic bile flow or an alteration in hepatic circulation resulting, for example, from chronic heart failure, veno-occlusive disease, portal vein thrombosis or Budd-Chiari syndrome. Additionally, 23155 molecules can play an important role in the etiology of certain viral diseases, including but not limited to Hepatitis B, Hepatitis C and Heφes Simplex Virus (HSV). Modulators of 23155 activity could be used to control viral diseases. The modulators can be used in the treatment and/or diagnosis of viral infected tissue or virus- associated tissue fibrosis, especially liver and liver fibrosis. Also, 23155 modulators can be used in the treatment and/or diagnosis of virus-associated carcinoma, especially hepatocellular cancer. Additionally, 23155 can play an important role in the regulation of metabolism or pain disorders. Diseases of metabolic imbalance include, but are not limited to, obesity, anorexia nervosa, cachexia, lipid disorders, and diabetes. Examples of pain disorders include, but are not limited to, pain response elicited during various forms of tissue injury, e.g., inflammation, infection, and ischemia, usually refened to as hyperalgesia (described in, for example, Fields, H.L. (1987) Pain, New York:McGraw-Hill); pain associated with musculoskeletal disorders, e.g., joint pain; tooth pain; headaches; pain associated with surgery; pain related to irritable bowel syndrome; or chest pain. 1. Prophylactic Methods In one aspect, the invention provides a method for preventing in a subject, a disease or condition associated with an abenant 23155 expression or activity, by administering to the subject a 23155 or an agent which modulates 23155 expression or at least one 23155 activity. Subjects at risk for a disease which is caused or contributed to by abenant 23155 expression or activity can be identified by, for example, any or a combination of diagnostic or prognostic assays as described herein. Administration of a prophylactic agent can occur prior to the manifestation of symptoms characteristic ofthe 23155 abenancy, such that a disease or disorder is prevented or, alternatively, delayed in its progression. Depending on the type of 23155 abenancy, for example, a 23155, 23155 agonist or 23155 antagonist agent can be used for treating the subject. The appropriate agent can be determined based on screening assays described herein. 2. Therapeutic Methods Another aspect ofthe invention pertains to methods of modulating 23155 expression or activity for therapeutic puφoses. Accordingly, in an exemplary embodiment, the modulatory method ofthe invention involves contacting a cell with a 23155 or agent that modulates one or more ofthe activities of 23155 protein activity associated with the cell. An agent that modulates 23155 protein activity can be an agent as described herein, such as a nucleic acid or a protein, a naturally-occurring target molecule of a 23155 protein (e.g., a 23155 phosphorylation substrate), a 23155 antibody, a 23155 agonist or antagonist, a peptidomimetic of a 23155 agonist or antagonist, or other small molecule, hi one embodiment, the agent stimulates one or more 23155 activities. Examples of such stimulatory agents include active 23155 protein and a nucleic acid molecule encoding 23155 that has been introduced into the cell. In another embodiment, the agent inhibits one or more 23155 activities. Examples of such inhibitory agents include antisense 23155 nucleic acid molecules, anti-23155 antibodies, and 23155 inhibitors. These modulatory methods can be performed in vitro (e.g., by culturing the cell with the agent) or, alternatively, in vivo (e.g., by administering the agent to a subject). As such, the present invention provides methods of treating an individual afflicted with a disease or disorder characterized by abenant expression or activity of a 23155 protein or nucleic acid molecule. In one embodiment, the method involves administering an agent (e.g., an agent identified by a screening assay described herein), or combination of agents that modulates (e.g., upregulates or downregulates) 23155 expression or activity. In another embodiment, the method involves administering a 23155 protein or nucleic acid molecule as therapy to compensate for reduced or abenant 23155 expression or activity. Stimulation of 23155 activity is desirable in situations in which 23155 is abnormally downregulated and/or in which increased 23155 activity is likely to have a beneficial effect. For example, stimulation of 23155 activity is desirable in situations in which a 23155 is downregulated and/or in which increased 23155 activity is likely to have a beneficial effect. Likewise, inhibition of 23155 activity is desirable in situations in which 23155 is abnormally upregulated and/or in which decreased 23155 activity is likely to have a beneficial effect. 3. Pharmacogenomics The 23155 molecules ofthe present invention, as well as agents, or modulators which have a stimulatory or inhibitory effect on 23155 activity (e.g., 23155 gene expression) as identified by a screening assay described herein can be administered to individuals to treat (prophylactically or therapeutically) disorders (e.g., cardiovascular disorders such as congestive heart failure) associated with abenant 23155 activity. In conjunction with such treatment, pharmacogenomics (i.e., the study ofthe relationship between an individual's genotype and that individual's response to a foreign compound or drug) may be considered. Differences in metabolism of therapeutics can lead to severe toxicity or therapeutic failure by altering the relation between dose and blood concentration ofthe pharmacologically active drag. Thus, a physician or clinician may consider applying knowledge obtained in relevant pharmacogenomics studies in determining whether to administer a 23155 molecule or 23155 modulator as well as tailoring the dosage and/or therapeutic regimen of treatment with a 23155 molecule or 23155 modulator. Pharmacogenomics deals with clinically significant hereditary variations in the response to drags due to altered drag disposition and abnormal action in affected persons. See, for example, Eichelbaum, M. et al. (1996) Clin. Exp. Pharmacol Physiol. 23(10-11) :983-985 and Linder, M.W. et al. (1997) Clin. Chem. 43(2):254-266. In general, two types of pharmacogenetic conditions can be differentiated. Genetic conditions transmitted as a single factor altering the way drugs act on the body (altered drug action) or genetic conditions transmitted as single factors altering the way the body acts on drags (altered drug metabolism). These pharmacogenetic conditions can occur either as rare genetic defects or as naturally-occurring polymoφhisms. For example, glucose-6-phosphate dehydrogenase deficiency (G6PD) is a common inherited enzymopathy in which the main clinical complication is haemolysis after ingestion of oxidant drugs (anti-malarials, sulfonamides, analgesics, nitrofurans) and consumption of fava beans. One pharmacogenomics approach to identifying genes that predict drag response, known as "a genome-wide association", relies primarily on a high-resolution map ofthe human genome consisting of already known gene-related markers (e.g., a "bi-allelic" gene marker map which consists of 60,000-100,000 polymoφhic or variable sites on the human genome, each of which has two variants.) Such a high-resolution genetic map can be compared to a map ofthe genome of each of a statistically significant number of patients taking part in a Phase TUTTT drug trial to identify markers associated with a particular observed drug response or side effect. Alternatively, such a high resolution map can be generated from a combination of some ten-million known single nucleotide polymoφhisms (SNPs) in the human genome. As used herein, a "SNP" is a common alteration that occurs in a single nucleotide base in a stretch of DNA. For example, a SNP may occur once per every 1000 bases of DNA. A SNP may be involved in a disease process, however, the vast majority may not be disease-associated. Given a genetic map based on the occunence of such SNPs, individuals can be grouped into genetic categories depending on a particular pattern of SNPs in their individual genome, i such a manner, treatment regimens can be tailored to groups of genetically similar individuals, taking into account traits that maybe common among such genetically similar individuals. Alternatively, a method termed the "candidate gene approach", can be utilized to identify genes that predict a drug response. According to this method, if a gene that encodes a drug target is known (e.g., a 23155 protein or 23155 receptor ofthe present invention), all common variants of that gene can be fairly easily identified in the population and it can be determined if having one version ofthe gene versus another is associated with a particular drug response. As an illustrative embodiment, the activity of drag metabolizing enzymes is a major determinant of both the intensity and duration of drug action. The discovery of genetic polymoφhisms of drug metabolizing enzymes (e.g., N-acetyltransferase 2 (NAT 2) and cytochrome P450 enzymes CYP2D6 and CYP2C19) has provided an explanation as to why some patients do not obtain the expected drug effects or show exaggerated drug response and serious toxicity after taking the standard and safe dose of a drag. These polymoφhisms are expressed in two phenotypes in the population, the extensive metabolizer (EM) and poor metabolizer (PM). The prevalence of PM is different among different populations. For example, the gene coding for CYP2D6 is highly polymoφhic and several mutations have been identified in PM, which all lead to the absence of functional CYP2D6. Poor metabolizers of CYP2D6 and CYP2C19 quite frequently experience exaggerated drug response and side effects when they receive standard doses. If a metabolite is the active therapeutic moiety, PM show no therapeutic response, as demonstrated for the analgesic effect of codeine mediated by its CYP2D6-formed metabolite moφhine. The other extreme are the so called ultra-rapid metabolizers who do not respond to standard doses. Recently, the molecular basis of ultra-rapid metabolism has been identified to be due to CYP2D6 gene amplification. Alternatively, a method termed the "gene expression profiling", can be utilized to identify genes that predict drug response. For example, the gene expression of an animal dosed with a drag (e.g., a 23155 molecule or 23155 modulator ofthe present invention) can give an indication whether gene pathways related to toxicity have been turned on. Information generated from more than one ofthe above pharmacogenomics approaches can be used to determine appropriate dosage and treatment regimens for prophylactic or therapeutic treatment an individual. This knowledge, when applied to dosing or drug selection, can avoid adverse reactions or therapeutic failure and thus enhance therapeutic or prophylactic efficiency when treating a subject with a 23155 molecule or 23155 modulator, such as a modulator identified by one ofthe exemplary screening assays described herein. This invention is further illustrated by the following examples which should not be construed as limiting. The contents of all references, patents and published patent applications cited throughout this application are incoφorated herein by reference. EXAMPLES Example 1: Identification and Characterization of Human 23155 cDNAs The human 23155 sequence (Figure la-b; SEQ ED NO:l), which is approximately 1287 nucleotides long including untranslated regions, contains a predicted methionine- initiated coding sequence (SEQ J-D NO:3, Figure 2a-b) of about 957 nucleotides (nucleotides 1-957 of SEQ ID NO:l). The coding sequence encodes a 318 amino acid protein (SEQ ID NO:2). Example 2: Expression and Tissue Distribution of 23155 mRNA Northern blot hybridizations with various RNA samples can be performed under standard conditions and washed under stringent conditions, i.e., 0.2xSSC at 65°C. A DNA probe conesponding to all or a portion ofthe 23155 cDNA (SEQ ID NO: 1) can be used. The DNA is radioactively labeled with 32 P-dCTP using the Prime-It Kit (Stratagene, La Jolla, CA) according to the instructions ofthe supplier. Filters containing mRNA from mouse hematopoietic and endocrine tissues, and cancer cell lines (Clontech, Palo Alto, CA) can be probed in ExpressHyb hybridization solution (Clontech) and washed at high stringency according to manufacturer's recommendations. TaqMan real-time quantitative RT-PCR is used to detect the presence of RNA transcript conesponding to human 23155 in several tissues. It is found that the conesponding orthologs of 23155 are expressed in a variety of tissues. The results ofthe screening for 23155, are shown in Figures 6-13. Reverse Transcriptase PCR (RT-PCR) was used to detect the presence of RNA transcript conesponding to human 23155 in RNA prepared from tumor and normal tissues. Figures 6-7 illustrate the relative expression levels and tissue distribution ofthe 23155 gene in various tissues using Taq Man PCR. If a subject has a disease characterized by underexpression or overexpression of a 23155 gene, modulators which have a stimulatory or inhibitory effect on protein 5-α reductase activity (e.g., protein 5-α reductase gene expression) can be administered to individuals to treat (prophylactically or therapeutically) protein 5-αreductase-associated disorders. Figures 6-7 illustrates the ubiquitous relative expression levels of 23155 in various tissues using TaqMan PCR, and significant expression in in HUVEC, normal human brain cortex, colon tumor, and lung tumor tissues (Figure 6) as well as brain cortex and hypothalamus, colon tumor, normal fetal liver, lung tumor, epithelial cells and HUVEC (Figure 7). Variable expression was found in lung tumor cell lines and tissues as shown in Figure 8 for 23155. The highest expression for 23155 was found in the lung tumor cell line, NCIH 67. Figure 9 shows some 23155 expression in colon and normal tumor with increased expression in 4/8 colon tumor samples in comparison to normal colon tissue samples and increased expression in 2/4 liver metastasis in comparison to normal liver tissues. n an angiogenic panel, the results of which are shown in Figure 10, variable expression was found in all tissues. Figure 11 shows variable expression in breast tumor and normal breast tissue samples. Decreased 23155 expression was found in 2/6 ovary tumor samples in comparison to normal ovary samples as shown in Figure 12. Figure 13 shows increased expression in 7/7 lung tumor samples in comparison to normal lung tissue samples. Again, expression was detected using Taq Man analysis. Expression profiling results using in situ hybridization techniques have shown that 23155 mRNA has been detected in human lung, colon, ovary and breast tissues. Positive expression of 23155 has been shown in 6/8 lung tumors and lung inflammatory cells in comparison with lack of expression, 0/2, in normal lung tissue samples. In addition, positive expression of 23155 has been shown in 2/2 colon tumors and some metastases (2/4) in comparison with low expression, 1/2, in normal colon tissue samples. Further, 23155 has been shown to be expressed both in tumors and normal tissues, of normal ovarian stroma (1/2) and tumors (2/4). Regarding breast tissue, negative expression of 23155 was found in both normal (0/1) and tumor (0/2). As seen by these results, 23155 molecules have been found to be overexpressed in some tumors or cells, where the molecules may be inappropriately propagating either cell proliferation or cell survival signals or have abenant protein 5-α reductase activity. As such, 23155 molecules may serve as specific and novel identifiers of such tumor cells or disorders. Further, modulators ofthe 23155 molecules are useful for the treatment of cancer. For example, inhibitors ofthe 23155 molecules are useful for the treatment of cancer where 23155 is upregulated in tumor cells such as lung, colon, breast, and ovarian cancer and in particular lung cancer, and are useful as a diagnostic. Example 3: Recombinant Expression of 23155 in Bacterial Cells In this example, 23155 is expressed as a recombinant glutathione-S-transferase (GST) fusion polypeptide in E. coli and the fusion polypeptide is isolated and characterized. Specifically, 23155 is fused to GST and this fusion polypeptide is expressed in E. coli, e.g., strain PEB199. Expression ofthe GST-3714, -16742, -23546, or -13887 fusion protein in PEB 199 is induced with EPTG. The recombinant fusion polypeptide is purified from crude bacterial lysates ofthe induced PEB 199 strain by affinity chromatography on glutathione beads. Using polyacrylamide gel electrophoretic analysis ofthe polypeptide purified from the bacterial lysates, the molecular weight ofthe resultant fusion polypeptide is determined. Example 4: Expression of Recombinant 23155 Protein in COS Cells To express the 23155 gene in COS cells, the pcDNA/Amp vector by Invitrogen Coφoration (San Diego, CA) is used. This vector contains an SV40 origin of replication, an ampicillin resistance gene, an E. coli replication origin, a CMV promoter followed by a polylihker region, and an SV40 intron and polyadenylation site. A DNA fragment encoding the entire 23155 protein and an HA tag (Wilson et al. (1984) Cell 37:767) or a FLAG tag fused in-frame to its 3' end ofthe fragment is cloned into the polylinker region ofthe vector, thereby placing the expression ofthe recombinant protein under the confrol ofthe CMV promoter. To construct the plasmid, the 23155 DNA sequence is amplified by PCR using two primers. The 5' primer contains the restriction site of interest followed by approximately twenty nucleotides ofthe 23155 coding sequence starting from the initiation codon; the 3' end sequence contains complementary sequences to the other restriction site of interest, a translation stop codon, the HA tag or FLAG tag and the last 20 nucleotides ofthe 23155 coding sequence. The PCR amplified fragment and the pCDNA/Amp vector are digested with the appropriate restriction enzymes and the vector is dephosphorylated using the CIAP enzyme (New England Biolabs, Beverly, MA). Preferably the two restriction sites chosen are different so that the 23155 gene is inserted in the conect orientation. The ligation mixture is transformed into E. coli cells (strains HBIOI, DH5α, SURE, available from Stratagene Cloning Systems, La Jolla, CA, can be used), the transformed culture is plated on ampicillin media plates, and resistant colonies are selected. Plasmid DNA is isolated from transformants and examined by restriction analysis for the presence ofthe conect fragment. COS cells are subsequently transfected with the 23155-pcDNA Amp plasmid DNA using the calcium phosphate or calcium chloride co-precipitation methods, DEAE-dextran- mediated transfection, lipofection, or electroporation. Other suitable methods for transfecting host cells can be found in Sambrook, J., Fritsh, E. F., and Maniatis, T. Molecular Cloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989. The expression of the 23155 polypeptide is detected by radiolabelling ( 35 S-methionine or 35 S-cysteine available from NEN, Boston, MA, can be used) and immunoprecipitation (Harlow, E. and Lane, D. Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1988) using an HA specific monoclonal antibody. Briefly, the cells are labeled for 8 hours with 35 S-methionine (or 35 S-cysteine). The culture media are then collected and the cells are lysed using detergents (RIPA buffer, 150 mM NaCl, 1% NP-40, 0.1% SDS, 0.5% DOC, 50 mM Tris, pH 7.5). Both the cell lysate and the culture media are precipitated with an HA specific monoclonal antibody. Precipitated polypeptides are then analyzed by SDS-PAGE. Alternatively, DNA containing the 23155 coding sequence is cloned directly into the polylinker ofthe pCDNA/Amp vector using the appropriate restriction sites. The resulting plasmid is transfected into COS cells in the manner described above, and the expression of the 23155 polypeptide is detected by radiolabelling and immunoprecipitation using a 23155 specific monoclonal antibody. Equivalents Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments ofthe invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims: What is claimed is: 1. An isolated 23155 nucleic acid molecule selected from the group consisting of: a) a nucleic acid molecule comprising a nucleotide sequence which is at least 60% identical to the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, or the nucleotide sequence ofthe DNA insert ofthe plasmid deposited with ATCC as Accession Number ; b) a nucleic acid molecule comprising a fragment of at least 15 nucleotides ofthe nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, or the nucleotide sequence ofthe DNA insert ofthe plasmid deposited with ATCC as Accession Number c) a nucleic acid molecule which encodes a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number ; d) a nucleic acid molecule which encodes a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the fragment comprises at least 15 contiguous amino acids of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number ; e) a nucleic acid molecule which encodes a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the nucleic acid molecule hybridizes to a nucleic acid molecule comprising SEQ ID NO:l, SEQ ID NO:3, or a complement thereof, under stringent conditions; f) a nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:l, SEQ ID NO:3, or the nucleotide sequence ofthe DNA insert ofthe plasmid deposited with ATCC as Accession Number ; and g) a nucleic acid molecule which encodes a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert o the plasmid deposited with the ATCC as Accession Number . 2. The isolated nucleic acid molecule of claim 1, which is the nucleotide sequence SEQ ID NO: 1. 3. A host cell which contains the nucleic acid molecule of claim 1. 4. An isolated 23155 polypeptide selected from the group consisting of: a) a polypeptide which is encoded by a nucleic acid molecule comprising a nucleotide sequence which is at least 60% identical to a nucleic acid comprising the nucleotide sequence of SEQ ED NO:l, SEQ D NO:3, or the nucleotide sequence ofthe DNA insert ofthe plasmid deposited with ATCC as Accession Number , or a complement thereof; b) a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ ID NO:l, SEQ ID NO:3, or a complement thereof under stringent conditions; c) a fragment of a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the fragment comprises at least 15 contiguous amino acids of SEQ ED NO:2; and d) the amino acid sequence of SEQ TD NO:2. 5. An antibody which selectively binds to a polypeptide of claim 4. 6. A method for producing a polypeptide selected from the group consisting of: a) a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number ; b) a polypeptide comprising a fragment ofthe amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the fragment comprises at least 15 contiguous amino acids of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number ; c) a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ID NO:2, or the amino acid sequence encoded by the cDNA insert ofthe plasmid deposited with the ATCC as Accession Number , wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ ID NO:l or SEQ ID NO:3; and d) the amino acid sequence of SEQ ED NO:2; comprising culturing the host cell of claim 3 under conditions in which the nucleic acid molecule is expressed. 7. A method for detecting the presence of a nucleic acid molecule of claim 1 or a polypeptide encoded by the nucleic acid molecule in a sample, comprising: a) contacting the sample with a compound which selectively hybridizes to the nucleic acid molecule of claim 1 or binds to the polypeptide encoded by the nucleic acid molecule; and b) determining whether the compound hybridizes to the nucleic acid or binds to the polypeptide in the sample. 8. A kit comprising a compound which selectively hybridizes to a nucleic acid molecule of claim 1 or binds to a polypeptide encoded by the nucleic acid molecule and instructions for use. 9. A method for identifying a compound which binds to a polypeptide or modulates the activity ofthe polypeptide of claim 4 comprising the steps of: a) contacting a polypeptide, or a cell expressing a polypeptide of claim 4 with a test compound; and b) determining whether the polypeptide binds to the test compound or determining the effect ofthe test compound on the activity ofthe polypeptide. 10. A method for modulating the activity of a polypeptide of claim 4 comprising contacting the polypeptide or a cell expressing the polypeptide with a compound which binds to the polypeptide in a sufficient concentration to modulate the activity ofthe polypeptide. 11. A method of identifying a nucleic acid molecule associated with cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample from a subject with or at risk of developing cancer or a cellular proliferation and/or differentiation disorder comprising nucleic acid molecules with a hybridization probe comprising at least 25 contiguous nucleotides of SEQ ID NO: 1 defined in claim 2; and b) detecting the presence of a nucleic acid molecule in the sample that hybridizes to the probe, thereby identifying a nucleic acid molecule associated with cancer or a cellular proliferation and or differentiation disorder. 12. A method of identifying a nucleic acid associated with cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample from a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk of developing a cancer or a cellular proliferation and/or differentiation disorder comprising nucleic acid molecules with a first and a second amplification primer, the first primer comprising at least 25 contiguous nucleotides of SEQ ED NO:l defined in claim 2 and the second primer comprising at least 25 contiguous nucleotides from the complement of SEQ ED NO:l; b) incubating the sample under conditions that allow nucleic acid amplification; and c) detecting the presence of a nucleic acid molecule in the sample that is amplified, thereby identifying the nucleic acid molecule associated with cancer or a cellular proliferation and/or differentiation disorder. 13. A method of identifying a polypeptide associated with cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample comprising polypeptides with a 23155 binding partner ofthe 23155 polypeptide defined in claim 4; and b) detecting the presence of a polypeptide in the sample that binds to the 23155 binding partner, thereby identifying the polypeptide associated with cancer or a cellular proliferation and/or differentiation disorder. 14. A method of identifying a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample obtained from the subject comprising nucleic acid molecules with a hybridization probe comprising at least 25 contiguous nucleotides of SEQ ID NO: 1 defined in claim 2; and b) detecting the presence of a nucleic acid molecule in the sample that hybridizes to the probe, thereby identifying a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing a cancer or a cellular proliferation and/or differentiation disorder. 15. A method of identifying a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing a cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample obtained from the subject comprising nucleic acid molecules with a first and a second amplification primer, the first primer comprising at least 25 contiguous nucleotides of SEQ ID NO: 1 defined in claim 2 and the second primer comprising at least 25 contiguous nucleotides from the complement of SEQ ID NO:l; b) incubating the sample under conditions that allow nucleic acid amplification; and c) detecting the presence of a nucleic acid molecule in the sample that is amplified, thereby identifying a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing cancer or a cellular proliferation and/or differentiation disorder. 16. A method of identifying a subj ect having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing cancer or a cellular proliferation and/or differentiation disorder comprising: a) contacting a sample obtained from the subject comprising polypeptides with a 23155 binding partner ofthe 23155 polypeptide defined in claim 4; and b) detecting the presence of a polypeptide in the sample that binds to the 23155 binding partner, thereby identifying a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk for developing cancer or a cellular proliferation and/or differentiation disorder. 17. A method for identifying a compound capable of treating cancer or a cellular proliferation and/or differentiation disorder characterized by abenant 23155 nucleic acid expression or 23155 polypeptide activity comprising assaying the ability ofthe compound to modulate 23155 nucleic acid expression or 23155 polypeptide activity, thereby identifying a compound capable of " treating cancer or a cellular proliferation and/or differentiation disorder characterized by abenant 23155 nucleic acid expression or 23155 polypeptide activity. 18. A method for treating a subject having cancer or a cellular proliferation and/or differentiation disorder or at risk of developing cancer or a cellular proliferation and/or differentiation disorder comprising administering to the subject a 23155 modulator ofthe nucleic acid molecule defined in claim 1 or the polypeptide encoded by the nucleic acid molecule or contacting a cell with a 23155 modulator. 19. The method of claim 18, wherein the 23155 modulator is a) a small molecule; b) peptide; c) phosphopeptide; d) anti-23155 antibody; e) a 23155 polypeptide comprising the amino acid sequence of SEQ ID NO:2, or a fragment thereof; f) a 23155 polypeptide comprising an amino acid sequence which is at least 90 percent identical to the amino acid sequence of SEQ ID NO:2, wherein the percent identity is calculated using the ALIGN program for comparing amino acid sequences, a PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4; or g) an isolated naturally occurring allelic variant of a polypeptide consisting ofthe amino acid sequence of SEQ ID NO:2, wherein the polypeptide is encoded by a nucleic acid molecule which hybridizes to a complement of a nucleic acid molecule consisting of SEQ ED NO: 1 at 6X SSC at 45°C, followed by one or more washes in 0.2X SSC, 0.1% SDS at 65°C. 20. The method of claim 18, wherein the 23155 modulator is a) an antisense 23155 nucleic acid molecule; b) is a ribozyme; c) the nucleotide sequence of SEQ ID NO: 1 , or a fragment thereof; d) a nucleic acid molecule encoding a polypeptide comprising an amino acid sequence which is at least 90 percent identical to the amino acid sequence of SEQ ID NO:2, wherein the percent identity is calculated using the ALIGN program for comparing amino acid sequences, a PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4; e) a nucleic acid molecule encoding a naturally occurring allelic variant of a polypeptide comprising the amino acid sequence of SEQ ED NO:2, wherein the nucleic acid molecule which hybridizes to a complement of a nucleic acid molecule consisting of SEQ TD NO:l at 6X SSC at 45°C, followed by one or more washes in 0.2X SSC, 0.1% SDS at 65°C; or f) a gene therapy vector. 21. A method for evaluating the efficacy of a freatment of cancer or a cellular proliferation and/or differentiation disorder, in a subject, comprising: treating a subject with a protocol under evaluation; assessing the expression level of a 23155 nucleic acid molecule defined in claim 1 or 23155 polypeptide encoded by the 23155 nucleic acid molecule, wherein a change in the expression level of 23155 nucleic acid or 23155 polypeptide after the treatment, relative to the level before the treatment, is indicative ofthe efficacy ofthe treatment of cancer or a cellular proliferation and/or differentiation disorder. 22. A method of diagnosing cancer or a cellular proliferation and/or differentiation disorder in a subject, comprising: evaluating the expression or activity of a 23155 nucleic acid molecule defined in claim 1 or a 23155 polypeptide encoded by the 23155 nucleic acid molecule, such that a difference in the level of 23155 nucleic acid or 23155 polypeptide relative to a normal subject or a cohort of normal subjects is indicative of cancer or a cellular proliferation and/or differentiation disorder. 23. The method defined in claim 18 wherein the cancer or a cellular proliferation and/or differentiation disorder is colon, liver, lung, or ovarian cancer. 24. The method defined in claim 23 wherein the cancer or a cellular proliferation and/or differentiation disorder is lung cancer.

Inventors: HUNTER JOHN JOSEPH, MEYERS RACHEL, HUNTER, JOHN, JOSEPH, MEYERS, RACHEL
Applicants: HUNTER JOHN JOSEPH, MEYERS RACHEL, MILLENNIUM PHARM INC, HUNTER, JOHN, JOSEPH, MEYERS, RACHEL, MILLENNIUM PHARMACEUTICALS, INC.
Application year: 2001
Main classification: C12N15
IPC codes: C12N9, C12N15