RECEPTOR TYROSINE KINASE GENES

Abstract: The specification describes isolated, purified, or enriched nucleic acid molecules which correspond to particular genes encoding kinases, and to fragments of such genes, as well as the polypeptides encoded by such nucleic acids and antibodies specific for those polypeptides. Also disclosed are methods using such nucleic acid molecules, polypeptides, or antibodies for isolating the full coding sequences for those kinases, for determining the expression patterns and levels for those genes, for screening for agents which modulate the activity of one of the kinases, and for diagnosing or treating a disease associated with one of the kinases.

Description: DESCRIPTION RECEPTOR TYROSINE KINASE GENES Field of the Invention The present invention relates to novel, related tyrosine kinases. In particular, this includes polynucleotide sequences corresponding to human and rodent messenger RNA (mRNA), to the corresponding complementary DNA (cDNA) sequences, and to the encoded polypeptides. Background of the Invention The following description of the background of the invention is provided solely to aid the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the invention. Cellular signal transduction is a fundamental mechanism whereby external stimuli that regulate diverse cellular processes are relayed to the interior of cells. One of the key biochemical mechanisms of signal transduction involves the reversible phosphorylation of proteins, which enables regulation of the activity of mature proteins by altering their structure and function. For reviews, see Posada and Cooper, Mol. Biol. Cell, 3:583-392 (1992) and Hardie, Symp. Soc. Exp. Biol. 44:241-255 (1990)). The best characterized protein kinases in eukaryotes phosphorylate proteins on the alcohol moiety of serine, threonine and tyrosine residues. These kinases largely fall into two groups, those specific for phosphorylating serines and threonines, and those specific for phosphorylating tyrosines. The tyrosine kinases can be further divided into receptor and non-receptor proteins. Protein kinases are one of the largest families of eukaryotic proteins with several hundred known members. Alignment of primary peptide sequences of these proteins shows that they share a 250-300 amino acid domain that can be subdivided into 12 distinct subdomains (I -XII) that comprise the common catalytic core structure. These conserved protein motifs have recently been exploited using PCR-based cloning strategies leading to a significant expansion of the known kinases. Multiple alignment of the sequences in the catalytic domain of protein kinases and subsequent phylogenetic analysis permits their segregation into a phylogenetic tree. In this manner, related kinases are clustered into distinct branches or subfamilies including: tyrosine kinases, cyclic-nucleotide-dependent kinases, calcium/calmodulin kinases, cyclin-dependent kinases and MAP-kinases, as well as several other less defined subfamilies. (See Hanks and Hunter, FASEB J. 9:576-595 (1995). Receptor tyrosine kinases (RTKs) belong to a family of transmembrane proteins and have been implicated in numerous cellular signaling pathways. The predominant biological activity of some RTKs is the stimulation of cell growth and proliferation, while other RTKs are involved in promoting differentiation. In some instances, a single tyrosine kinase can inhibit or stimulate cell proliferation depending on the cellular environment in which it is expressed. RTKs are composed of at least three domains: an extracellular ligand binding domain, a transmembrane domain and a cytoplasmic domain containing at least one enzymatic domain capable of phosphorylating tyrosine residues. Ligand binding to membrane bound receptors induces the formation of receptor dimers and allosteric changes that activate the intracellular kinase domains and result in the self-phosphorylation (autophosphorylation and/or transphosphorylation) of the receptor on tyrosine residues. RTKs are also known to form heterodimers. A possible role for receptor heterodimerizaion is described in Carraway and Cantley, Cell 78:5-8 9 (1994). The non-receptor tyrosine kinases do not contain a transmembrane domain or an extracellular domain and share non-catalytic domains in addition to sharing their catalytic kinase domains. Such non-catalytic domains include the SH2 domain (Src homology domain 2) and SH3 domains (Src homology domain 3). The non-catalytic domains are thought to be important in the regulation of protein-protein interactions during signal transduction. Receptor tyrosine kinases are known to play a role in the proliferation, differentiation and/or survival of many cell types. One example is the Trk family of receptors. The Trks are receptors for several known neurotrophic factors including nerve growth factor (NGF). Binding of NGF to TrkA induces phosphorylation of the receptor and subsequent differentiation of the PC 12 pheochromocytoma cell line, a model for neuronal development. (Kaplan, et al, Science 252:554-558 (1991); Yan, et al, Science 252:561-563 (1991)). Other members of the Trks family include TrkB and TrkC, which are expressed in a variety of structures in nervous system and respond to binding of other neurotrophic factors such as brain-derived neurotrophic factor and neurotrophin-3 (Klein, et al Development 109:845-850 (1990); Glass, et al Cell 66:405-413 (1991); Klein, et al Cell 66:395-403 (1991)). Several RTKs and growth factors were originally identified as activated oncogenes (Aaronson, Science 254:1146-1153 (1991); Bishop, Cell 64:235-248 (1991)) and there has long been a belief that some RTKs may be involved in the development of cancers. Several studies appear to support this notion. These include the high correlation of RTK overexpression with certain human cancers including HER2 with breast and ovarian cancers (Slamon, et al., Science 235:177-182 (1987)), PDGF and its receptors with a high fraction of sarcomas and glially derived neoplasms, and EGF-R with squamous cell carcinomas and glioblastomas (reviewed in Aaronson, (1991)). Several RTKs have been associated with the growth and development of lung cancer cells including c-kit (Hida, et al Int. J. Can. 0 (supp 8):108-109 (1994); Krystal, et al, Can. Res. 56(2);370-376 (1996)), trk (Oelmann, et al Can. Res. 55(10):2212-2219 (1995)), Her2/neu (Tsai, et al Can. Res. 56 (5):1068-1074 (1996)) and EGF-R (Moody, Peptides 17(3):545-555 (1996)). The identification of a lung cancer specific RTK would be advantageous for the development of specific drugs that could inhibit the signal transduction activity of the RTK thereby suppressing the RTK driven growth of the cancer. Summary of the Invention The present invention concerns nucleic acid molecules, each of which corresponds to at least a portion of a unique expressed mammalian gene coding for a tyrosine kinase. Possession of just a portion of a nucleic acid sequence of a gene corresponding to a particular kinase provides a specific probe, allowing the mapping of the gene to a specific chromosome, the mapping of the gene to a position on that chromosome, and identification of clones, such as from a complementary (cDNA) or genomic library, containing the complementary sequence. In addition, possession of a sequence corresponding to a particular gene allows the determination of the expression pattern of that gene, thereby providing valuable information on the biology of relevant tissues. The analysis can also partially characterize some disease states, notably cancers, since cancers represent improperly regulated cell proliferation and, therefore, often involve abnormal kinase gene expression. The genes disclosed herein appear to define a novel group of related receptor tyrosine kinases that are highly expressed in neuronal tissues. Several of these novel genes are also highly expressed in cancerous tissues, in particular lung and ovarian cancers. One gene does not appear to be expressed in any normal tissue but is expressed in a variety of tumor types suggesting it may play a role in forming or maintaining the cancer. Thus, possession of a portion of one of the disclosed sequences or a sequence complementary to a portion of one of those sequences, having a length greater than about 13 or 17 bases in length, preferably, 25, 50, or 100 bases in length, uniquely identifies the corresponding gene, since the sequence of the partial nucleic acid sequence corresponds to a portion of the sequence of the corresponding gene and not to any other gene except essentially equivalent ones. Even if the stated sequence of the partial nucleic acid sequence differs by a small percentage, e.g., by less than about 3% or 1%, from the sequence of the actual nucleotide sequence, the unique identification of the gene is still provided, since the stringency of the hybridization conditions can be adjusted to allow a low level of mismatch. Thus, a probe having the sequence of a portion of one of the stated sequences will still uniquely hybridize with the respective corresponding gene under appropriately stringent hybridizing conditions. In addition, possession of a specific DNA probe provides longer DNA sequences of the gene, including the full length sequence of a cDNA and the full cDNA corresponding to a full-length, mature messenger RNA (mRNA), or a useful portion thereof, or a full-length copy of the genomic gene sequence, because those longer sequences can be obtained by routine procedures utilizing the specific probe. Thus, in this invention, nucleic acid sequences corresponding to specific receptor tyrosine kinase genes are provided. The sequences were identified as coding for tyrosine kinases by sequence analysis based on previously identified tyrosine kinases, as described in detail below. Each sequence is uniquely characteristic of the gene from which it is derived, and provides for the isolation of the complete coding sequence of the gene by standard procedures. Thus, this invention specifically identifies and provides such genes. Such genes can be cloned by standard techniques into vectors and used for screening, diagnostic, or therapeutic procedures, among other uses. Generally, the DNA is cloned into a vector which is specifically designed to express the cloned gene in a useful manner, or to allow specific detection of the desired target nucleic acid. Specifically, in a first aspect, this invention provides purified, enriched or isolated nucleic acid molecules at least 25 nucleotides in length, corresponding to expressed mammalian genes encoding one of a group of related tyrosine kinases. The nucleic acid molecules encode tyrosine kinase polypeptides, each of which has an amino acid sequence which is part of the amino acid sequence of a tyrosine kinase encoded by one of the genes corresponding to one of SEQ ID NO. 1 - 9. Each such nucleic acid molecule has at least 95% sequence identity to the corresponding portion of the gene, or to the complementary sequence. In a related aspect, a purified, isolated, or enriched nucleic acid molecule has at least 95% sequence identity to a portion of one of SEQ ID NO. 1 - 9, or a sequence complementary thereto. Preferably, the sequence identity is higher, for example, at least 97% or 99% or 100%. The nucleic molecules include single strand DNA (ssDNA), double strand DNA (dsDNA), and RNA. The nucleic acid is preferably DNA, and is preferably at least 13 nucleotides in length, more preferably at least 20-30 nucleotides in length, and most preferably at least 50 nucleotides in length. The nucleic acid can specifically hybridize under stringent conditions to a DNA chain having a sequence listed in SEQ ID NO 1 - 9, or a sequence complementary thereto, or to a gene encoding a kinase which corresponds to any of SEQ ID NO. 1 - 9. In preferred embodiments of the above aspects, the nucleic and molecule is longer, such as at least 50, 100, 200, 400 on more nucleotides in length. The sequence of the nucleic acid molecule can be determined and confirmed by redundant sequencing of both complementary strands of a corresponding cDNA using standard, routine sequencing techniques. Such redundant sequencing allows a researcher to eliminate sequence errors which might occur with single pass sequencing and which may be present in some sequences provided herein. Such a nucleic acid molecule is useful as a unique probe for determining the location and expression of a corresponding human gene, cDNA, or mRNA. Therefore, such probe reagents are useful in the analysis of human biology and in the development of new therapeutics as tools to aid mapping and analysis of genes, mRNAs, and polypeptide expression products. Such probes include a nucleic acid sequence of a portion of one of the genes indentified herein, or a sequence complementary thereto, and may also contain additional nucleic acid sequences and/or labels or other components which do not prevent specific hybridization. In addition, such a nucleic acid molecule is useful as a source of primers for copying, transcribing, or reverse transcribing the complementary DNA or RNA. The hybridization of such nucleic acid molecule to the corresponding specific site of the human genomic DNA, cDNA, or mRNA can be performed under commonly used conditions (see e.g. Sambrook, J. et al., Molecular Cloning: A Laboratory Manual ( 1989). Thus, once a person skilled in the art has knowledge of the sequence of any of SEQ ID NO 1 - 9, or possession of a probe based on that sequence, which will specifically hybridize to the corresponding mRNA or cDNA or genomic DNA, that person can readily identify and obtain the corresponding full sequence coding for a polypeptide. Likewise, that person can obtain a cDNA and its sequence which corresponds to the full length of a specific mRNA, and subsequently obtain any of a large number of portions of that cDNA. By a related procedure, that person can also obtain the full length gene and its sequence by an appropriate procedure involving probing, cloning, and sequencing of genomic DNA. Such procedures are well-known and commonly used in the art. As indicated above, the presence of a low level of sequencing errors (if any) in any of SEQ ID NO 1 - 9 creates no difficulties in those procedures, since a probe or primer based on one of the sequences of SEQ ID NO 1 - 9 will still specifically hybridize with the corresponding cDNA, genomic DNA, or mRNA under sufficiently stringent conditions, and can be used to help resequence the DNA to confirm the probe sequence or to discover any errors in the stated sequence. As a result of the sequence relationships indicated above, a cDNA containing a full coding sequence, or a cDNA corresponding to the full length of a mRNA, is obtainable from a shorter, unique probe included in one of the above aspects. If the method for obtaining longer cDNA sequences is properly performed, such longer sequences are obtained with virtual certainty and the inclusion of the complete coding sequence or full-length cDNA can be routinely verified. Therefore, such coding sequences and full length cDNAs are included in this invention. Of course, the full coding sequence or full-length cDNA is not limited to a specific method by which the sequence is obtained. Those skilled in the art will know that a variety of approaches and variations of methods will also provide essentially the same final product. Thus, this invention includes those DNA products, whatever the method used to obtain them. It should be specifically noted that the above aspects include DNA molecules which each include a sequence of nucleotides which codes for a polypeptide which is a portion of a tyrosine kinase. However, the above aspect also includes shorter DNA molecules which may, for example, contain only a portion of a polypeptide-coding sequence. Also, while the nucleic acid molecules of the above aspects can be obtained by standard cloning methods and amplified, such as by PCR, once the desired sequence is known, such molecules (especially DNA chains can also be chemically synthesized by routine methods to provide a specific sequence. This is particularly appropriate for sequences shorter than about 100 nucleotides. Once synthesized, such nucleic acid molecules can be used in the usual way as probes and primers. Thus, from the above aspects, this invention provides nucleic acid molecules which can include full or partial coding sequences or cDNA sequences or mRNA sequences. It also provides nucleic acid molecules which can be used as probes or primers for locating, mapping, identifying, amplifying, and obtaining nucleotide sequences. It also provides probes and primers which can be used for detecting the overall or individual synthetic status of various cellular mRNA and for diagnosing cellular abnormalities due to disease. Similarly, the present invention also provides nucleic acid molecules, preferably DNA molecules, which can be used as probes or primers for detecting the overall or individual synthetic status of various corresponding cellular mRNA. Use of the term "isolated" indicates that a naturally occurring material or organism (e.g., a DNA sequence) has been removed from its normal environment. Thus, an isolated DNA sequence has been removed from its usual cellular environment, and may, for example, be in a cell-free solution or placed in a different cellular environment. For a molecule, such as a DNA sequence, the term does not imply that the molecule (sequence) is the only molecule of that type present. It is also advantageous for some purposes that an organism or molecule (e.g., a nucleotide sequence) be in purified form. The term "purified" does not require absolute purity; instead, it indicates that the sequence, organism, or molecule is relatively purer than in the natural environment. Thus, the claimed DNA could not be obtained directly from total human DNA or from total human RNA. The claimed DNA sequences are not naturally occurring, but rather are obtained via manipulation of a partially purified naturally occurring substance (genomic DNA clones). The construction of a genomic library from chromosomal DNA involves the creation of vectors with genomic DNA inserts and pure individual clones carrying such vectors can be isolated from the library by clonal selection of the cells carrying the library. In the context of this disclosure, "human gene" should be understood to refer to an inheritable unit of genetic material found in a human chromosome. Each gene is composed of a linear chain of deoxyribonucleotides which can be referred to by the sequence of nucleotides forming the chain. Thus, "sequence" is used to indicate both the ordered listing of the nucleotides which form the chain, and the chain, itself, which has that sequence of nucleotides. ("Sequence" is used in the same way in referring to RNA chains, linear chains made of ribonucleotides.) The gene includes regulatory and control sequences, sequences which can be transcribed into an RNA molecule, and may contain sequences with unknown function. Some of the RNA products (products of transcription from DNA) are messenger RNAs (mRNAs) which initially include ribonucleotide sequences (or sequence) which are translated into a polypeptide and ribonucleotide sequences which are not translated. The sequences which are not translated include control sequences and may include some sequences with unknown function. The coding sequences of many mammalian genes are discontinuous, having coding sequences, exons, alternating with non-coding sequences, introns. The introns are present in the mRNA molecule as it is transcribed from the DNA, but the introns are removed and the exons spliced together to form mature mRNA. Thus, mature mRNA is mRNA which is suitable for translation, the introns have been removed and usually other modifications made. It should be recognized that small differences in nucleotide sequence for the same gene can exist between different persons, or between normal cells and cancerous cells, without altering the identity of the gene. Thus, "expressed gene" means that, in the cell or tissue of interest, the gene is transcribed to form RNA molecules and the mature mRNA may be translated to form polypeptides. Expression includes transcription and translation of a nucleic acid. Which genes are expressed in a specific cell line or tissue will depend on factors such as tissue or cell type, stage of development of the cell, tissue, or individual, and whether the cells are normal or transformed into, for example, cancerous cells. Reference to nucleic acid molecules or sequences which "corresponds" to each other, or to a "correspondence" between a polypeptide and a nucleic acid, the correspondence is shown by a transcriptional and/or translational, or reverse transcriptional relationship. As indicated above, many genes can be transcribed to form mRNA molecules. Therefore, there is a correspondence between the DNA sequence of the gene and the mRNA which is, or might be, transcribed from that gene; the correspondence is also present for the reverse relationship, the messenger RNA corresponds with the DNA of the gene. This correspondence is not limited to the relationship between the full sequence of the gene and the full sequence of the mRNA, rather it also exists between a portion or portions of the DNA sequence of the gene and a portion or portions of the RNA sequence of the mRNA. Specifically it should be noted that this correspondence is present between a portion or portions of an mRNA which is not normally translated into polypeptide and all or a portion of the DNA sequence of the gene. Similarly, the correspondence exists between a messenger RNA and a single-strand DNA which is or can be obtained from the mRNA by reverse transcription using a reverse transcriptase. As just described above, the correspondence exists between all or a portion of the DNA and all or a portion of the messenger RNA. Likewise, the correspondence exists between all or a portion of the messenger RNA and all or a portion of a DNA strand which has a sequence complementary to the sequence of the DNA obtained by reverse transcription. Further, the correspondence is present between all or a portion of the messenger RNA and all or a portion of a double-stranded DNA comprising the DNA obtained by reverse transcription and its complementary strand. Similarly, the DNA of a gene or of cDNA, or the RNA of a mRNA "corresponds" to the polypeptide encoded by that gene and mRNA and cDNA. This correspondence between the mRNA and the polypeptide is established through the translational relationship; the nucleotide sequence of the mRNA is translated into the amino acid sequence of the polypeptide. Then, due to the transcription or reverse transcription relationship between the DNA of the gene or the cDNA and the mRNA, there is a "correspondence" between the DNA and the polypeptide. Such a term includes nucleic acid which is analogous or homologous to a reference nucleic acid, as well as complementary nucleic acid. References to a "portion" of a DNA or RNA chain mean a linear chain which has a nucleotide sequence which is the same as a sequential subset of the sequence of the chain to which the portion refers. (Reference to a portion of a polypeptide chain and an amino acid sequence has similar meaning.) Such a subset may contain all of the sequence of the primary chain or may contain only a shorter sequence. The subset will contain at least 13-25, 50, or 100 bases in a single strand, but preferably will contain the full coding sequence from the corresponding mRNA. However, by "same" is meant to include deletions, additions, or substitutions of specific nucleotides of the sequence, or a combination of these changes, which affect a small percentage of the full sequence and still leave the sequences substantially the same. Preferably this percentage of change will be less than 10%, more preferably less than 5%, still more preferably less than 3%, and most preferably less than 1%. Such changes do not affect the property of the protein coded by the sequence. "Same" is therefore distinguished from "identical"; for identical sequences there cannot be any difference in nucleotide sequences. An example of sequences that can be said to be the "same" is sequences encoding homologous proteins from different species which have some similarity in function and have highly similar but not exactly identical sequences. As used above, "complementary" has its usual meaning from molecular biology. Two nucleotide sequences or strands are complementary if they have sequences which would allow base pairing (Watson-Crick or Hoogstein) according to the usual pairing rules. This does not require that the strands would necessarily base pair at every nucleotide; two sequences can still be complementary with a low level (e.g., 1 - 3%) of base mismatch such as that created by deletion, addition, or substitution of one or a few ( e.g., up to 5 in a linear chain of 25 bases) nucleotides, or a combination of such changes. Preferably, however, complementary sequences are exactly complementary, meaning that base pairing can occur for each base of a particular sequence in a chain. In another aspect, the invention provides an isolated or purified nucleic acid molecule encoding a polypeptide expressed in a tissue, obtainable by hybridization under stringent hybridization conditions of a nucleotide sequence selected from the group consisting of SEQ ID NO. 1 - 9 or a sequence complementary thereto, to a mRNA from that tissue. In a further aspect, the invention provides a recombinant nucleic acid molecule having a transcription initiation region functional in a cell, transcriptionally linked with a sequence complementary to an RNA sequence encoding all or at least 25 contiguous amino acids a tyrosine kinase , and a transcription termination region functional in a cell. The tyrosine kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. In addition, it is often advantageous to insert DNA sequences into any of a variety of vectors. Therefore, in further aspects this invention provides DNA of any of the above aspects in a vector. The vector may be selected for a number of different purposes, which can include to produce more DNA with the sequence of the vector insert, but can also specifically include means to translate mRNA transcribed from the vector insert into a polypeptide product, i.e., an expression vector. DNA inserted into an expression vector preferably contains at least 60% of the coding region of the corresponding full-length cDNA, more preferably at least 75%, still more preferably at least 90%, and most preferably all of the coding sequence of the corresponding full-length cDNA. Further, since vectors are usually used by inserting the vector into a cell, these aspects also include a cell containing a vector which has the DNA of any of the above aspects inserted. Within such a cell, the vector may exist extrachromosomally (e.g., as a plasmid or minichromosome), or the vector or part of the vector may be integrated into the host cell chromosome. In this application a "vector" is an agent into which DNA of this invention can be inserted by incorporation into the DNA of the agent. Thus, examples of classes of vectors can be plasmids, cosmids, and viruses (e.g., bacteriophage). Typically, the agents are used to transmit the DNA of the invention into a host cell (e.g., bacterium, yeast, higher eukaryotic cell). A vector may be chosen based on the size of the insert desired, as well as based on the intended use. For preservation of a specific DNA sequence (e.g., in a cDNA library) or for producing a large number of copies of the specific DNA sequence, a cloning vector would be chosen. For transcription of RNA or translation to produce an encoded polypeptide, an expression vector would be chosen. Following transfection of a cell, all or part of the vector DNA, including the insert DNA, may be incorporated into the host cell chromosome, or the vector may be maintained extrachromosomally. In another aspect, the invention concerns an isolated, enriched, or purified kinase polypeptide, where the tyrosine kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 -9 (see Figs. 4A-C). The polypeptide preferably contains at least 25 contiguous amino acids of the amino acid sequence of the tyrosine kinase, more preferably at least 50 amino acids, still more preferably at least 100 amino acids. Most preferably, the polypeptide includes an amino acid sequence which is sufficiently duplicative of the amino acid sequence of the native kinase as to have similar biological activity as the native molecule; this includes a polypeptide which has the full amino acid sequence of the native molecule. Since the disclosed sequence identifies and provides the full coding sequence of each of the corresponding tyrosine kinase genes, this also provides the amino acid sequence of the encoded polypeptide due to the known genetic code such as are shown in SEQ. ID. No. 10 - SEQ. ID. NO. 18 (Figs. 7A-C). Also, possession of a nucleic acid which contains all or part of a full coding sequence enables the production of antibodies which recognize an epitope on the native tyrosine kinase polypeptide. Therefore, in a further aspect the invention provides an antibody having specific binding affinity to a tyrosine kinase polypeptide of SEQ ID NO. 10 - SEQ ID NO. 18. Including both polyclonal and monoclonal antibodies For most uses, it is beneficial if the antibody is purified or isolated. Further, it is often beneficial to produce antibodies in cell culture (i.e., monoclonal antibodies). Therefore, the invention also provides a hybridoma producing such an antibody. In addition, the invention provides testing and screening methods to identify and analyze compounds which bind to and/or affect the activity of kinase polypeptides, such as polypeptides encoded by the kinase genes identified herein. By "comprising" it is meant including, but not limited to, whatever follows the word "comprising". Thus, use of the term "comprising" indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present. By "consisting of is meant including, and limited to, whatever follows the phrase "consisting of. Thus, the phrase "consisting of indicates that the listed elements are required or mandatory, and that no other elements may be present. By "consisting essentially of is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase "consisting essentially of indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they affect the activity or action of the listed elements. Use of the term "comprising" in connection with an embodiment of the invention should be understood to include embodiments "consisting of or "consisting essentially of the specified elements; similarly "consisting essentially of includes "consisting of. Other features and advantages of the invention will be apparent from the following detailed description of the preferred embodiments and from the claims. Brief Description of the Drawings Figure 1 shows the alignment and comparison of the amino acid sequences of the human LMRl , LMR2 and LMR 3 (SEQ ID. NO. 11 , 14, 18) Figure 2 shows the identification and sequences of the oligonucleotides used as primers. Figures 3 A and 3B show expression profiles (Northern blot) of Human normal tissue vs. tumor for LMRl, LMR2 and LMR3. Figure 4 provides the expression analysis (in situ) in rat embryos for LMRl, LMR2 and LMR3. Figure 5 provides the expression analysis (in situ) in adult rat brain for LMRl, LMR2 and LMR3. Figures 6A, 6B, 6C, 6D, 6E, 6F, 6G, 6h, 61 provide nucleotide sequences of LMRs for; LMRl_r (rat), LMRlJh (human), LMRl_m (mouse), LMR2_r (rat), LMR2_h (human), LMR2_m (mouse), LMR3_r (rat), LMR3_h (human), and LMR3_m (mouse). FIG. 7 Provides amino acid sequences of LMRs for; LMRl_r (rat), LMRl h (human), LMRl_m (mouse), LMR2_r (rat), LMR2_h (human), LMR2_m (mouse), LMR3_r (rat), LMR3_h (human), and LMR3_m (mouse). Description of the Preferred Embodiments The present invention relates to mammalian nucleic acids encoding polypeptides having tyrosine kinase activity, the polypeptides encoded by those nucleic acids, cells, tissues and animals containing such nucleic acids, antibodies to such polypeptides, assays utilizing such polypeptides, and methods relating to all of the foregoing. I. Cloning, Probing, and Sequencing In general, as indicated above, the nucleic acids of this invention encode mammalian tyrosine kinases which have sequences characteristic of components of signal transduction pathways. Such nucleic acid sequences can be identified in a number of different ways, including by analyzing sequenced, but unidentified, DNA or RNA or polypeptide sequences from public databases, by probing DNA libraries (e.g., cDNA and genomic libraries) using degenerate probes to sequences conserved in various families and sub-families of such kinases or by PCR-based cloning using degenerate primers based on conserved sequences for various families and sub-families. For the probing or PCR-based approaches, once one or more clones are identified having sequences corresponding to the probe or primers, the genomic or cDNA insert in that clone can be at least partially sequenced by routine methods to confirm that the clone sequence actually corresponds to a tyrosine kinase, and to provide a unique sequence identifying the full gene. Possession of such a unique sequence provides the full gene sequence by following routine techniques. For example, an appropriate probe sequence can be selected and synthesized. The probe can be used to probe cDNA or genomic libraries under stringent hybridization conditions to identify a clone(s) which contain a sequence which contains the complete corresponding open reading frame. Likewise, a probe sequence based on a specific homologous tyrosine kinase sequence from a different mammalian species can be used to detect the corresponding human version of that gene. For example, a probe complementary to a rat gene was used to identify a homologous human kinase sequence as is described in the Example section below. This probe allowed hybridization under sufficiently stringent conditions to a homologous 5' sequence of the clone identified as LMRl . The demonstrated sequence homology over the human, rat, and mouse homologs of the identified genes demonstrates that the invention also provides the other mammalian homologs by routine methods. For example, probe sequences can be obtained based on the genes described herein, preferably from regions of high sequence conservation. Using such probes, and if necessary further degenerate probes, the corresponding genes in other mammalian species can be readily obtained. A homologous gene from a cow has been obtained. II. Gene Identification As indicated above, the tyrosine kinase encoding genes of the present invention are initially identified as having nucleotide sequences characteristic of particular classes of such enzymes, or having sequences corresponding to previously identified homologous genes from one or more other mammalian species. Thus, the genes of the present invention and the corresponding expression products are distinguished and characterized as tyrosine kinases by the sequence relationships with previously known genes or proteins. Such sequence comparisons can be routinely performed using readily available computer-based sequence analysis programs. Such analysis will not generally require full nucleotide or amino acid sequences for an enzyme, as a partial sequence will provide sufficient information to characterize and classify the gene and gene product. Therefore, the identification method described herein allows novel kinase genes to be distinguished from cloned nucleotide sequences, such as in cDNA libraries, as well as from sequence database information of sequenced, but not functionally identified gene sequences. III. Construction of Probes and Primers A nucleic acid probe of the present invention may be used to probe an appropriate chromosomal or cDNA library by usual hybridization methods to obtain another nucleic acid molecule of the present invention. A chromosomal DNA or cDNA library may be prepared from appropriate cells according to recognized methods in the art (see, e.g., "Molecular Cloning: A Laboratory Manual", second edition, edited by Sambrook, Fritsch, & Maniatis, Cold Spring Harbor Laboratory, 1989). In the alternative, chemical synthesis is carried out in order to obtain nucleic acid probes having nucleotide sequences which correspond to N- terminal and C-terminal portions of the amino acid sequence of the polypeptide of interest. Thus, the synthesized nucleic acid probes may be used as primers in a polymerase chain reaction (PCR) carried out in accordance with recognized PCR techniques, essentially according to PCR Protocols, "A Guide to Methods and Applications", edited by Michael et al., Academic Press, 1990, utilizing the appropriate chromosomal or cDNA library to obtain the fragment of the present invention. One skilled in the art can readily design such probes based on the sequence disclosed herein using methods of computer alignment and sequence analysis known in the art (see, e.g., "Molecular Cloning: A Laboratory Manual", second edition, edited by Sambrook, Fritsch, & Maniatis, Cold Spring Harbor Laboratory, 1989). The hybridization probes of the present invention can be labeled by standard labeling techniques such as with a radiolabel, enzyme label, fluorescent label, biotin-avidin label, chemiluminescence, and the like. After hybridization, the probes may be visualized using known methods. The nucleic acid probes of the present invention include RNA, as well as DNA probes, such probes being generated using techniques known in the art. The nucleic acid probe may be immobilized on a solid support. Examples of such solid supports include, but are not limited to, plastics such as polycarbonate, complex carbohydrates such as agarose and sepharose, and acrylic resins, such as polyacrylamide and latex beads. Techniques for coupling nucleic acid probes to such solid supports are well known in the art. The test samples suitable for nucleic acid probing methods of the present invention include, for example, cells or nucleic acid extracts of cells, or biological fluids. The sample used in the above-described methods will vary based on the assay format, the detection method and the nature of the tissues, cells or extracts to be assayed. Methods for preparing nucleic acid extracts of cells are well known in the art and can be readily adapted in order to obtain a sample which is compatible with the method utilized. IV. A Probe Based Method And Kit For Detecting a Disclosed Kinase Gene One method of detecting the presence of one of the disclosed genes in a sample involves (a) contacting a sample with a nucleic acid probe as described above, under conditions such that hybridization occurs, and (b) detecting the presence of the probe bound to the nucleic acid molecule. One skilled in the art would select the nucleic acid probe according to techniques known in the art as described above. Samples to be tested include but should not be limited to RNA samples of human tissue. A kit for detecting the presence of one of the disclosed genes in a sample includes at least one container means containing the above-described nucleic acid probe. The kit may further include other containers containing one or more of the following: wash reagents and reagents capable of detecting the presence of bound nucleic acid probe. Examples of detection reagents include, but are not limited to radiolabeled probes, enzymatic labeled probes (horseradish peroxidase, alkaline phosphatase), and affinity labeled probes (biotin, avidin, or streptavidin). In detail, a compartmentalized kit includes any kit in which reagents are contained in separate containers. Such containers include small glass containers, plastic containers or strips of plastic or paper. Such containers allow the efficient transfer of reagents from one compartment to another compartment such that the samples and reagents are not cross- contaminated and the agents or solutions of each container can be added in a quantitative fashion from one compartment to another. Such containers will include a container which will accept the test sample, a container which contains the probe or primers used in the assay, containers which contain wash reagents (such as phosphate buffered saline, Tris-buffers, and the like), and containers which contain the reagents used to detect the hybridized probe, bound antibody, amplified product, or the like. One skilled in the art will readily recognize that the nucleic acid probes described in the present invention can readily be incorporated into one of the established kit formats which are well known in the art. V. Obtaining Full Length Gene Sequences By utilizing methods well-known to those skilled in the art and portions of the sequences identified in this invention, full length gene sequences can be readily obtained. Such full-length sequence can be complementary DNA (cDNA) sequences or genomic sequences. Probes can be selected according to the usual considerations to provide specific detection of clones containing long DNA inserts. Preferably at least one probe is obtained which binds to a sequence at or near either the 5' or 3' end of the coding sequence. In the case of cDNA clones in a cDNA library, the library vectors can be selected such that vector sequences adjacent to the insert can be utilized as PCR primers, allowing direct amplification and convenient sequencing of the insert by common methods. This process will often provide a full coding sequence, though in some cases it may be necessary to construct a full-length coding sequence using two or more overlapping clones. Similarly, a full genomic sequence can be obtained using a genomic library. However, in this case it will often be necessary to construct a full length sequence based on overlapping clone sequences due to the length added by the introns present in most human genes. VI. Expression Patterns Many human genes are expressed at different levels in different tissues. In some cases, a gene is not expressed at all in some cells or tissues, and at high levels in others. Thus, a variety of different human cell lines from various tissue sources, as well as several different normal human tissues were analyzed for the expression levels of the tyrosine kinase genes identified in this invention. In general, the expression level of a gene was determined by determination of the amount of the corresponding messenger RNA (mRNA) present in the cells, based on hybridization with a labeled probed under specific hybridization conditions. The results of such analyses are discussed in the Example section below. These expression levels suggest the types of diseases and conditions which can be affected by modulation of the activity level of one of the disclosed tyrosine kinases in accord with the understanding of the functions of such specific enzymes. As discussed below, three of the tyrosine kinases of the invention are expressed to some level in tissues of neuronal origin. One, LMR2, is not expressed in normal tissues but is expressed in a variety of cancer tissues. LMR2 is also highly expressed in lung and ovarian tumor samples, suggesting this RTK may play a role in the proliferation of these cancers. VII. Nucleic Acid Sequence Variants Included within the scope of this invention are the functional equivalents of the isolated nucleic acid molecules described herein. The degeneracy of the genetic code permits substitution of certain codons by other codons which specify the same amino acid and hence would give rise to the same protein. The nucleic acid sequence can vary substantially, since, with the exception of methionine and tryptophan, the known amino acids can be coded for by more than one codon. Thus, portions or all of any of the genes disclosed could be synthesized to give a nucleic acid sequence significantly different from that shown in any of SEQ ID NO. 1 - 9. The encoded amino acid sequence would, however, be preserved. In addition, the nucleic acid sequence may comprise a nucleotide sequence which results from the addition, deletion or substitution of at least one nucleotide to the 5'-end and/or the 3'-end of one of the nucleic acid sequences shown, or a derivative thereof. Any nucleotide or polynucleotide may be used in this regard, provided that its addition, deletion or substitution does not alter the amino acid sequence of a polypeptide which is encoded by the nucleotide sequence. For example, the present invention is intended to include any nucleic acid sequence resulting from the addition of ATG as an initiation codon at the 5 '-end of the inventive nucleic acid sequence or its derivative, or from the addition of TTA, TAG or TGA as a termination codon at the 3'-end of the disclosed nucleotide sequence or its derivative. Moreover, the nucleic acid molecule of the present invention may, as necessary, have restriction endonuclease recognition sites added to its 5'-end and/or 3'-end. Such functional alterations of a given nucleic acid sequence afford an opportunity to promote secretion and/or processing of heterologous proteins encoded by foreign nucleic acid sequences fused thereto. All variations of the nucleotide sequence of the disclosed genes and fragments thereof permitted by the genetic code are, therefore, included in this invention. Further, it is possible to delete codons or to substitute one or more codons by codons other than degenerate codons to produce a structurally modified polypeptide, but one which has substantially the same utility or activity of the polypeptide produced by the unmodified nucleic acid molecule. As recognized in the art, the two polypeptides are functionally equivalent, as are the two nucleic acid molecules which give rise to their production, even though the differences between the nucleic acid molecules are not related to degeneracy of the genetic code. VIII. DNA Constructs Comprising a Nucleic Acid Molecule and Cells Containing These Constructs. The present invention also relates to a recombinant DNA molecule comprising, 5' to 3', a promoter effective to initiate transcription in a host cell and the above-described nucleic acid molecules. In addition, the present invention relates to a recombinant DNA molecule comprising a vector and an above-described nucleic acid molecule. The present invention also relates to a nucleic acid molecule comprising a transcriptional region functional in a cell, a sequence complimentary to an mRNA sequence encoding an amino acid sequence corresponding to the above-described polypeptide, and a transcriptional termination region functional in said cell. The above-described molecules may be isolated and/or purified DNA molecules. The present invention also relates to a cell or organism that contains an above-described nucleic acid molecule and.thereby is capable of expressing a peptide. The polypeptide may be purified from cells which have been altered to express the polypeptide. A cell is said to be "altered to express a desired polypeptide" when the cell, through genetic manipulation, is made to produce a protein which it normally does not produce or which the cell normally produces at lower levels. One skilled in the art can readily adapt procedures for introducing and expressing either genomic, cDNA, or synthetic sequences into either eukaryotic or prokaryotic cells. A nucleic acid molecule, such as DNA, is said to be "capable of expressing" a polypeptide if it contains nucleotide sequences which contain transcriptional and translational regulatory information and such sequences are "operably linked" to nucleotide sequences which encode the polypeptide. An operable linkage is a linkage in which the regulatory DNA sequences and the DNA sequence sought to be expressed are connected in such a way as to permit gene sequence expression. The precise nature of the regulatory regions needed for gene sequence expression may vary from organism to organism, but shall in general include a promoter region which, in prokaryotes, contains both the promoter (which directs the initiation of RNA transcription) as well as the DNA sequences which, when transcribed into RNA, will signal synthesis initiation. Such regions will normally include those 5 '-non-coding sequences involved with initiation of transcription and translation, such as the TATA box, capping sequence, CAAT sequence, and the like. If desired, the non-coding region 3' to the coding sequence of any of the disclosed genes may be obtained by the above-described methods. This region may be retained for its transcriptional termination regulatory sequences, such as termination and polyadenylation. Thus, by retaining the 3 '-region naturally contiguous to the DNA sequence encoding one of the disclosed genes, the transcriptional termination signals may be provided. Where the transcriptional termination signals are not satisfactorily functional in the expression host cell, then a 3' region functional in the host cell may be substituted. Two DNA sequences (such as a promoter region sequence and a coding sequence) are said to be operably linked if the nature of the linkage between the two DNA sequences does not (1) result in the introduction of a frame-shift mutation, (2) interfere with the ability of the promoter region sequence to direct the transcription of a gene sequence, or (3) interfere with the ability of the a gene sequence to be transcribed by the promoter region sequence. Thus, a promoter region would be operably linked to a DNA sequence if the promoter were capable of effecting transcription of that DNA sequence. Thus, to express one of the disclosed genes, transcriptional and translational signals recognized by an appropriate host are necessary. The present invention encompasses the expression of one of the disclosed genes (or a functional derivative thereof) in either prokaryotic or eukaryotic cells. Prokaryotic hosts are, generally, very efficient and convenient for the production of recombinant proteins and are, therefore, one type of preferred expression system for one of the disclosed genes. Prokaryotes most frequently are represented by various strains of E. coli. However, other microbial strains may also be used, including other bacterial strains. In prokaryotic systems, plasmid vectors that contain replication sites and control sequences derived from a species compatible with the host may be used. Examples of suitable plasmid vectors may include pBR322, pUCl 18, pUCl 19 and the like; suitable phage or bacteriophage vectors may include lambda gtlO, lambda gtl 1 and the like; and suitable virus vectors may include pMAM-neo, pKRC and the like. Preferably, the selected vector of the present invention has the capacity to replicate in the selected host cell. Recognized prokaryotic hosts include bacteria such as E. coli, Bacillus, Streptomyces, Pseudomonas, Salmonella, Serratia, and the like. However, under such conditions, the peptide will not be glycosylated. The prokaryotic host must be compatible with the replicon and control sequences in the expression plasmid. To express one of the disclosed genes (or a functional derivative thereof) in a prokaryotic cell, the coding sequence is operably linked to a functional prokaryotic promoter. Such promoters may be either constitutive or, more preferably, regulatable (i.e., inducible or derepressible). Examples of constitutive promoters include the int promoter of bacteriophage lambda, the bla promoter of the beta-lactamase gene sequence of pBR322, and the CAT promoter of the chloramphenicol acetyl transferase gene sequence of pPR325, and the like. Examples of inducible prokaryotic promoters include the major right and left promoters of bacteriophage lambda (PL and PR), the trp, recA, beta lacZ, lad, and gal promoters of E. coli, the beta-amylase (Ulmanen et at., J Bacteriol 162:176-182(1985)) and the (-28- specific promoters of B. subtilis (Gilman et at., Gene Sequence 32:11-20(1984)), the promoters of the bacteriophages of Bacillus (Gryczan, In: The Molecular Biology of the Bacilli, Academic Press, Inc., NY (1982)), and Streptomyces promoters (Ward et at., Mol. Gen. Genet. 203:468-478(1986)). Prokaryotic promoters are reviewed by Glick (J. Ind. Microbiot. 1 :277- 282(1987)); Cenatiempo (Biochimie 68:505-516(1986)); and Gottesman (Ann. Rev. Genet. 18:415-442 (1984)). Proper expression in a prokaryotic cell also requires the presence of a ribosome binding site upstream of the gene sequence-encoding sequence. Such ribosome binding sites are disclosed, for example, by Gold et at. (Ann. Rev. Microbiol 35:365-404(1981)). The selection of control sequences, expression vectors, transformation methods, and the like, are dependent on the type of host cell used to express the gene. As used herein, "cell", "cell line", and "cell culture" may be used interchangeably and all such designations include progeny. Thus, the words "transformants" or "transformed cells" include the primary subject cell and cultures derived therefrom, without regard to the number of transfers. It is also understood that all progeny may not be precisely identical in DNA content, due to deliberate or inadvertent mutations. However, as defined, mutant progeny have the same functionality as that of the originally transformed cell. Host cells which may be used in the expression systems of the present invention are not strictly limited, provided that they are suitable for use in the expression of the peptide of interest. Suitable hosts may often include eukaryotic cells. Preferred eukaryotic hosts include, for example, yeast, fungi, insect cells, mammalian cells either in vivo, or in tissue culture. Mammalian cells which may be useful as hosts include HeLa cells, cells of fibroblast origin such as VERO or CHO-K1, or cells of lymphoid origin and their derivatives. Preferred mammalian host cells include SP2/0 and J558L, as well as neuroblastoma cell lines such as IMR 332 which may provide better capacities for correct post-translational processing. In addition, plant cells are also available as hosts, and control sequences compatible with plant cells are available, such as the cauliflower mosaic virus 35S and 19S, and nopaline synthase promoter and polyadenylation signal sequences. Another preferred host is an insect cell, for example the Drosophila larvae. Using insect cells as hosts, the Drosophila alcohol dehydrogenase promoter can be used. Rubin, Science 240:1453-1459(1988). Alternatively, baculovirus vectors can be engineered to express large amounts of one of the genes of interest in insect cells (Jasny, Science 238:1653 (1987); Miller et al., In: Genetic Engineering (1986), Setlow, J.K., et al, eds., Plenum, Vol. 8, pp. 277-297). Any of a series of yeast gene sequence expression systems can be utilized which incorporate promoter and termination elements from the actively expressed gene sequences coding for glycolytic enzymes which are produced in large quantities when yeast are grown in mediums rich in glucose. Known glycolytic gene sequences can also provide very efficient transcriptional control signals. Yeast provides substantial advantages in that it can also carry out post-translational peptide modifications. A number of recombinant DNA strategies exist which utilize strong promoter sequences and high copy number of plasmids which can be utilized for production of the desired proteins in yeast. Yeast recognizes leader sequences on cloned mammalian gene sequence products and secretes peptides bearing leader sequences (i.e., pre-peptides). For a mammalian host, several possible vector systems are available for the expression of one of the disclosed genes. A wide variety of transcriptional and translational regulatory sequences may be employed, depending upon the nature of the host. The transcriptional and translational regulatory signals may be derived from viral sources, such as adenovirus, bovine papilloma virus, cytomegalovirus, simian virus, or the like, where the regulatory signals are associated with a particular gene sequence which has a high level of expression. Alternatively, promoters from mammalian expression products, such as actin, collagen, myosin, and the like, may be employed. Transcriptional initiation regulatory signals may be selected which allow for repression or activation, so that expression of the gene sequences can be modulated. Of interest are regulatory signals which are temperature-sensitive so that by varying the temperature, expression can be repressed or initiated, or are subject to chemical (such as metabolite) regulation. Expression of one of the disclosed genes in eukaryotic hosts requires the use of eukaryotic regulatory regions. Such regions will, in general, include a promoter region sufficient to direct the initiation of RNA synthesis. Preferred eukaryotic promoters include, for example, the promoter of the mouse metallothionein I gene sequence (Hamer et al., J. Mol. Appl. Gen. 1 :273-288(1982)); the TK promoter of Herpes virus (McKnight, Cell 31 :355-365 (1982)); the SV40 early promoter (Benoist et al., Nature (London) 290:304-310(1981)); the yeast gal4 gene sequence promoter (Johnston et al., Proc. Natl. Acad. Sci. (USA) 79:6971-6975(1982); Silver et al., Proc. Natl. Acad. Sci. (USA) 81 :5951-5955 (1984)). Translation of eukaryotic mRNA is initiated at the codon which encodes the first methionine. For this reason, it is preferable to ensure that the linkage between a eukaryotic promoter and a DNA sequence which encodes a kinase (or a functional derivative thereof) does not contain any intervening codons which are capable of encoding a methionine (i.e., AUG). The presence of such codons results either in a formation of a fusion protein (if the AUG codon is in the same reading frame as the coding sequence) or a frame-shift mutation (if the AUG codon is not in the same reading frame as the coding sequence). A nucleic acid molecule and an operably linked promoter may be introduced into a recipient prokaryotic or eukaryotic cell either as a nonreplicating DNA (or RNA) molecule, which may either be a linear molecule or, more preferably, a closed covalent circular molecule. Since such molecules are incapable of autonomous replication, the expression of the gene may occur through the transient expression of the introduced sequence. Alternatively, permanent expression may occur through the integration of the introduced DNA sequence into the host chromosome. A vector may be employed which is capable of integrating the desired gene sequences into the host cell chromosome. Cells which have stably integrated the introduced DNA into their chromosomes can be selected by also introducing one or more markers which allow for selection of host cells which contain the expression vector. The marker may provide for prototrophy to an auxotrophic host, biocide resistance, e.g., antibiotics, or heavy metals, such as copper, or the like. The selectable marker gene sequence can either be directly linked to the DNA gene sequences to be expressed, or introduced into the same cell by co-transfection. Additional elements may also be needed for optimal synthesis of single chain binding protein mRNA. These elements may include splice signals, as well as transcription promoters, enhancers, and termination signals. cDNA expression vectors incorporating such elements include those described by Okayama, Molec. Cell. Biol. 3:280(1983). The introduced nucleic acid molecule can be incorporated into a plasmid or viral vector capable of autonomous replication in the recipient host. Any of a wide variety of vectors may be employed for this purpose. Factors of importance in selecting a particular plasmid or viral vector include: the ease with which recipient cells that contain the vector may be recognized and selected from those recipient cells which do not contain the vector; the number of copies of the vector which are desired in a particular host; and whether it is desirable to be able to "shuttle" the vector between host cells of different species. Preferred prokaryotic vectors include plasmids such as those capable of replication in E. coli (such as, for example, pBR322, ColΕl, pSClOl , pACYC 184, "VX. Such plasmids are, for example, disclosed by Sambrook (see, e.g., "Molecular Cloning: A Laboratory Manual", second edition, edited by Sambrook, Fritsch, & Maniatis, Cold Spring Harbor Laboratory, (1989)). Bacillus plasmids include pC194, pC221, pT127, and the like. Such plasmids are disclosed by Gryczan (In: The Molecular Biology of the Bacilli, Academic Press, NY (1982), pp. 307-329). Suitable Streptomyces plasmids include plJlOl (Kendall et al., J. Bacteriol. 169:4177-4183 (1987)), and streptomyces bacteriophages such as .C31 (Chater et al., In: Sixth International Symposium on Actinomycetales Biology, Akademiai Kaido, Budapest, Hungary (1986), pp. 45-54). Pseudomonas plasmids are reviewed by John et al. (Rev. Infect. Dis. 8:693-704(1986)), and Izaki (Jpn. J. Bacteriol. 33:729-742(1978)). Preferred eukaryotic plasmids include, for example, BPV, vaccinia, SV40, 2-micron circle, and the like, or their derivatives. Such plasmids are well known in the art (Botstein et al, Miami Wntr. Symp. 19:265- 274(1982); Broach, In: "The Molecular Biology of the Yeast Saccharomyces: Life Cycle and Inheritance", Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, p. 445-470 (1981); Broach, Cell 28:203-204 (1982); Bollon et at., J. Ctin. Hematol. Oncol. 10:39-48 (1980); Maniatis, In: Cell Biology: A Comprehensive Treatise, Vol. 3, Gene Sequence Expression, Academic Press, NY, pp. 563-608(1980). Once the vector or nucleic acid molecule containing the construct(s) has been prepared for expression, the DNA construct(s) may be introduced into an appropriate host cell by any of a variety of suitable means, i.e., transformation, transfection, conjugation, protoplast fusion, electroporation, particle gun technology, calcium phosphate-precipitation, direct microinjection, and the like. After the introduction of the vector, recipient cells are grown in a selective medium, which selects for the growth of vector-containing cells. Expression of the cloned gene molecule(s) results in the production of the encoded amino acid sequence. This can take place in the transformed cells as such, or following the induction of these cells to differentiate (for example, by administration of bromodeoxyuracil to neuroblastoma cells or the like). A variety of incubation conditions can be used to form the peptide of the present invention. The most preferred conditions are those which mimic physiological conditions. IX. Purified Polypeptides A variety of methodologies known in the art can be utilized to obtain the peptide of the present invention. The peptide may be purified from tissues or cells which naturally produce the peptide. Alternatively, the above-described isolated nucleic acid fragments could be used to express the kinase protein in any organism. The samples of the present invention include cells, protein extracts or membrane extracts of cells, or biological fluids. The sample will vary based on the assay format, the detection method and the nature of the tissues, cells or extracts used as the sample. Any eukaryotic organism can be used as a source for the peptide of the invention, as long as the source organism naturally contains such a peptide. As used herein, "source organism" refers to the original organism from which the amino acid sequence of the subunit is derived, regardless of the organism the subunit is expressed in and ultimately isolated from. One skilled in the art can readily follow known methods for isolating proteins in order to obtain the peptide free of natural contaminants. These include, but are not limited to: size-exclusion chromatography, HPLC, ion-exchange chromatography, and immuno-affinity chromatography. X. An Antibody Having Binding Affinity To A Kinase Polypeptide And A Hybridoma Containing the Antibody. The present invention relates to an antibody having binding affinity to one of the identified tyrosine kinase polypeptide. The polypeptide may have the amino acid sequence shown in SEQ ID NO. 10 - SEQ ID NO. 18, or functional derivative thereof, or at least 9 contiguous amino acids thereof (preferably, at least 20, 30, 35, or 40 contiguous amino acids thereof). The present invention also relates to an antibody having specific binding affinity to a polypeptide encoded by one of the disclosed genes. Such an antibody may be isolated by comparing its binding affinity to a particular encoded polypeptide with its binding affinity to another polypeptide. Those which bind selectively to the particular encoded polypeptide would be chosen for use in methods requiring a distinction between that particular polypeptide and other polypeptides. Such methods could include, but should not be limited to, the analysis of altered expression of the particular polypeptide in tissue containing other polypeptides. The tyrosine kinase proteins of the present invention can be used in a variety of procedures and methods, such as for the generation of antibodies, for use in identifying pharmaceutical compositions, and for studying DNA/protein interaction. The peptides of the present invention can be used to produce antibodies or hybridomas. One skilled in the art will recognize that if an antibody is desired, such a peptide would be generated as described herein and used as an immunogen. The antibodies of the present invention include monoclonal and polyclonal antibodies, as well fragments of these antibodies, and humanized forms. Humanized forms of the antibodies of the present invention may be generated using one of the procedures known in the art such as chimerization or CDR grafting. The present invention also relates to a hybridoma which produces the above-described monoclonal antibody, or binding fragment thereof. A hybridoma is an immortalized cell line which is capable of secreting a specific monoclonal antibody. In general, techniques for preparing monoclonal antibodies and hybridomas are well known in the art (Campbell, "Monoclonal Antibody Technology: Laboratory Techniques in Biochemistry and Molecular Biology," Elsevier Science Publishers, Amsterdam, The Netherlands (1984); St. Groth et al., J Immunol. Methods 35:1-21(1980)). Any animal (mouse, rabbit, and the like) which is known to produce antibodies can be immunized with the selected polypeptide. Methods for immunization are well known in the art. Such methods include subcutaneous or intraperitoneal injection of the polypeptide. One skilled in the art will recognize that the amount of polypeptide used for immunization will vary based on the animal which is immunized, the antigenicity of the polypeptide and the site of injection. The polypeptide may be modified or administered in an adjuvant in order to increase the peptide antigenicity. Methods of increasing the antigenicity of a polypeptide are well known in the art. Such procedures include coupling the antigen with a heterologous protein (such as globulin or β- galactosidase) or through the inclusion of an adjuvant during immunization. For monoclonal antibodies, spleen cells from the immunized animals are removed, fused with myeloma cells, such as SP2/0-Agl4 myeloma cells, and allowed to become monoclonal antibody producing hybridoma cells. Any one of a number of methods well known in the art can be used to identify the hybridoma cell which produces an antibody with the desired characteristics. These include screening the hybridomas with an ELISA assay, western blot analysis, or radioimmunoassay (Lutz et al., Exp. Cell Res. 175:109-124(1988)). Hybridomas secreting the desired antibodies are cloned and the class and subclass is determined using procedures known in the art (Campbell, "Monoclonal Antibody Technology: Laboratory Techniques in Biochemistry and Molecular Biology", supra (1984)). For polyclonal antibodies, antibody containing antisera is isolated from the immunized animal and is screened for the presence of antibodies with the desired specificity using one of the above-described procedures. The above-described antibodies may be detectably labeled. Antibodies can be detectably labeled through the use of radioisotopes, affinity labels (such as biotin, avidin, and the like), enzymatic labels (such as horse radish peroxidase, alkaline phosphatase, and the like) fluorescent labels (such as FITC or rhodamine, and the like), paramagnetic atoms, and the like. Procedures for accomplishing such labeling are well-known in the art, for example, see (Stemberger et al., J. Histochem. Cytochem. 18:315 (1970); Bayer et al., Immumnol. 109:129(1972); Goding, J. Immunol. Meth. 13:215(1976)). The labeled antibodies of the present invention can be used for in vitro, in vivo, and in situ assays to identify cells or tissues which express a specific peptide. The above-described antibodies may also be immobilized on a solid support. Examples of such solid supports include plastics such as polycarbonate, complex carbohydrates such as agarose and sepharose, acrylic resins and such as polyacrylamide and latex beads. Techniques for coupling antibodies to such solid supports are well known in the art (Weir et al., "Handbook of Experimental Immunology" 4th Ed., Blackwell Scientific Publications, Oxford, England, Chapter 10(1986); Jacoby et al., Meth. Enzym. 34, Academic Press, N.Y. (1974)). The immobilized antibodies of the present invention can be used for in vitro, in vivo, and in situ assays as well as in immunochromotography. Furthermore, one skilled in the art can readily adapt currently available procedures, as well as the techniques, methods and kits disclosed above with regard to antibodies, to generate peptides capable of binding to a specific peptide sequence in order to generate rationally designed antipeptide peptides, for example see Hurby et al., "Application of Synthetic Peptides: Antisense Peptides", In Synthetic Peptides, A User's Guide, W.H. Freeman, NY, pp. 289-307(1992), and Kaspczak et al., Biochemistry 28:9230-8(1989). Anti-peptide peptides can be generated by replacing the basic amino acid residues found in a peptide sequence encoded by one of the disclosed genes with acidic residues, while maintaining hydrophobic and uncharged polar groups. For example, lysine, arginine, and/or histidine residues are replaced with aspartic acid or glutamic acid and glutamic acid residues are replaced by lysine, arginine or histidine. XL An Antibody Based Method And Kit The present invention encompasses a method of detecting a polypeptide encoded by one of the disclosed genes in a sample, by: (a) contacting the sample with an above-described antibody, under conditions such that immunocomplexes form, and (b) detecting the presence of said antibody bound to the polypeptide. In detail, the methods involves incubating a test sample with one or more of the antibodies of the present invention and assaying whether the antibody binds to the test sample. Altered levels of a kinase in a sample as compared to normal levels may indicate disease. Conditions for incubating an antibody with a test sample vary. Incubation conditions depend on the format employed in the assay, the detection methods employed, and the type and nature of the antibody used in the assay. One skilled in the art will recognize that any one of the commonly available immunological assay formats (such as radioimmunoassays, enzyme-linked immunosorbent assays, diffusion based Ouchterlony, or rocket immunofluorescent assays) can readily be adapted to employ the antibodies of the present invention. Examples of such assays can be found in Chard, "An Introduction to Radioimmunoassay and Related Techniques" Elsevier Science Publishers, Amsterdam, The Netherlands (1986); Bullock et al., "Techniques in Immunocytochemistry," Academic Press, Orlando, FL Vol. 1(1982), Vol. 2 (1983), Vol. 3 (1985); Tijssen, "Practice and Theory of Enzyme Immunoassays: Laboratory Techniques in Biochemistry and Molecular Biology," Elsevier Science Publishers, Amsterdam, The Netherlands (1985). The immunological assay test samples of the present invention include cells, protein or membrane extracts of cells, or biological fluids such as blood, serum, plasma, or urine. The test sample used in the above-described method will vary based on the assay format, nature of the detection method and the tissues, cells or extracts used as the sample to be assayed. Methods for preparing protein extracts or membrane extracts of cells are well known in the art and can be readily be adapted in order to obtain a sample which is capable with the system utilized. A kit contains all the necessary reagents to carry out the previously described methods of detection. The kit may comprise: (i) a first container means containing an above-described antibody, and (ii) second container means containing a conjugate comprising a binding partner of the antibody and a label. In another preferred embodiment, the kit further comprises one or more other containers comprising one or more of the following: wash reagents and reagents capable of detecting the presence of bound antibodies. Examples of detection reagents include, but are not limited to, labeled secondary antibodies, or in the alternative, if the primary antibody is labeled, the chromophoric, enzymatic, or antibody binding reagents which are capable of reacting with the labeled antibody. The compartmentalized kit may be as described above for nucleic acid probe kits. One skilled in the art will readily recognize that the antibodies described in the present invention can readily be incorporated into one of the established kit formats which are well known in the art. XII. Isolation of Compounds Which Interact With Identified RTKs. The present invention also relates to a method of detecting a compound capable of binding to a RTK polypeptide from one of the identified kinase genes by incubating the compound with the polypeptide and detecting the presence of the compound bound to the polypeptide. The compound may be present within a complex mixture, for example, serum, body fluid, or cell extracts. Binding assay methods may have a variety of different formats, including competition binding assays in which the effect of the presence of a test compound or compound mixture on the binding of a labeled known binding compound is determined. Other formats include detection of receptor activation, detection of binding of labeled or spectrophotometrically detectable test compound to the kinase. Depending on whether a particular kinase is naturally membrane bound or free in the cytoplasm, the binding assays can be performed with isolated membranes, with intact cells, or in a cell and membrane-free solution or attached to a solid support. Additionally, membrane-bound kinases can often be freed from the membrane, such as by removing a transmembrane portion, and assayed for binding in solution or attached to a solid support. The present invention also relates to a method of detecting an agonist or antagonist of RTK activity or RTK binding partner activity by incubating cells that produce a particular RTK in the presence of a compound and detecting changes in the level of activity of the particular RTK or RTK binding partner activity. The compounds thus identified would produce a change in activity indicative of the presence of the compound. The compound may be present within a complex mixture, for example, serum, body fluid, or cell extracts. Once the compound is identified it can be isolated using techniques well known in the art. The present invention also encompasses a method of agonizing (stimulating) or antagonizing activity associated with particular RTKs in a mammal by administering to a mammal an agonist or antagonist to the particular RTK(s)in an amount sufficient to effect the agonism or antagonism. A method of treating diseases in a mammal with an agonist or antagonist of activity related to a particular RTK(s) by administering the agonist or antagonist to a mammal in an amount sufficient to agonize or antagonize RTK associated functions is also encompassed in the present application. XIII. Transgenic Animals. A variety of methods are available for the production of transgenic animals associated with this invention. DNA can be injected into the pronucleus of a fertilized egg before fusion of the male and female pronuclei, or injected into the nucleus of an embryonic cell (e.g., the nucleus of a two-cell embryo) following the initiation of cell division (Brinster et al., Proc. Nat. Acad. Sci. USA 82: 4438-4442 (1985)). Embryos can be infected with viruses, especially retroviruses, modified to carry inorganic-ion receptor nucleotide sequences of the invention. Pluripotent stem cells derived from the inner cell mass of the embryo and stabilized in culture can be manipulated in culture to incorporate nucleotide sequences of the invention. A transgenic animal can be produced from such cells through implantation into a blastocyst that is implanted into a foster mother and allowed to come to term. Animals suitable for transgenic experiments can be obtained from standard commercial sources such as Charles River (Wilmington, MA), Taconic (Germantown, NY), Harlan Sprague Dawley (Indianapolis, IN), etc. The procedures for manipulation of the rodent embryo and for microinjection of DNA into the pronucleus of the zygote are well known to those of ordinary skill in the art (Hogan et al., supra). Microinjection procedures for fish, amphibian eggs and birds are detailed in Houdebine and Chourrout, Experientia 47: 897-905 (1991). Other procedures for introduction of DNA into tissues of animals are described in U.S. Patent No., 4,945,050 (Sandford et al., July 30, 1990). By way of example only, to prepare a transgenic mouse, female mice are induced to superovulate. Females are placed with males, and the mated females are sacrificed by CO 2 asphyxiation or cervical dislocation and embryos are recovered from excised oviducts. Surrounding cumulus cells are removed. Pronuclear embryos are then washed and stored until the time of injection. Randomly cycling adult female mice are paired with vasectomized males. Recipient females are mated at the same time as donor females. Embryos then are transferred surgically. The procedure for generating transgenic rats is similar to that of mice. See Hammer et al, Cell 63:1099-1112 (1990). Methods for the culturing of embryonic stem (ES) cells and the subsequent production of transgenic animals by the introduction of DNA into ES cells using methods such as electroporation, calcium phosphate/DNA precipitation and direct injection also are well known to those of ordinary skill in the art. See, for example, Teratocarcinomas and Embryonic Stem Cells, A Practical Approach, E.J. Robertson, ed., IRL Press (1987). In cases involving random gene integration, a clone containing the sequence(s) of the invention is co-transfected with a gene encoding resistance. Alternatively, the gene encoding neomycin resistance is physically linked to the sequence(s) of the invention. Transfection and isolation of desired clones are carried out by any one of several methods well known to those of ordinary skill in the art (E.J. Robertson, supra). DNA molecules introduced into ES cells can also be integrated into the chromosome through the process of homologous recombination. Capecchi, Science 244: 1288-1292 (1989). Methods for positive selection of the recombination event (i.e., neo resistance) and dual positive-negative selection (i.e., neo resistance and gancyclovir resistance) and the subsequent identification of the desired clones by PCR have been described by Capecchi, supra and Joyner et al., Nature 338: 153-156 (1989), the teachings of which are incorporated herein. The final phase of the procedure is to inject targeted ES cells into blastocysts and to transfer the blastocysts into pseudopregnant females. The resulting chimeric animals are bred and the offspring are analyzed by Southern blotting to identify individuals that carry the transgene. Procedures for the production of non-rodent mammals and other animals have been discussed by others. See Houdebine and Chourrout, supra; Pursel et al, Science 244:1281-1288 (1989); and Simms et al., Bio/Technology 6:179-183 (1988). Thus, the invention provides transgenic, nonhuman mammals containing a transgene encoding a polypeptide encoded by one of the disclosed genes, or a gene effecting the expression of a such a polypeptide. Such transgenic nonhuman mammals are particularly useful as an in vivo test system for studying the effects of introducing such a polypeptide, regulating the expression of such a polypeptide (i.e., through the introduction of additional genes, antisense nucleic acids, or ribozymes). A "transgenic animal" is an animal having cells that contain DNA which has been artificially inserted into a cell, which DNA becomes part of the genome of the animal which develops from that cell. Preferred transgenic animals are primates, mice, rats, cows, pigs, horses, goats, sheep, dogs and cats. The transgenic DNA may encode for a human polypeptide encoded by one of the disclosed genes. Native expression in an animal may be reduced by providing an amount of anti-sense RNA or DNA effective to reduce expression of the receptor. XIV. Gene Therapy Genetic sequences corresponding to the disclosed genes will also be useful in gene therapy (reviewed in Miller, Nature 357:455-460, (1992). Miller states that advances have resulted in practical approaches to human gene therapy that have demonstrated positive initial results. The basic science of gene therapy is described in Mulligan, Science 260:926-931, (1993). In one preferred embodiment, an expression vector containing a coding sequence of one of the disclosed genes is inserted into cells, the cells are grown in vitro and then infused in large numbers into patients. In another preferred embodiment, a DNA segment containing a promoter of choice (for example a strong promoter) is transferred into cells containing an endogenous copy of one of the disclosed genes in such a manner that the promoter segment enhances expression of the endogenous gene (for example, the promoter segment is transferred to the cell such that it becomes directly linked to the endogenous gene). The gene therapy may involve the use of an adenovirus containing cDNA corresponding to one of the disclosed genes targeted to a tumor, systemic increase of expression of one of the disclosed genes by implantation of engineered cells, injection with virus having a recombinant form of one of the disclosed genes, or injection of naked DNA of one of the disclosed genes into appropriate tissues. Target cell populations may be modified by introducing altered forms of one or more components of the protein complexes in order to modulate the activity of such complexes. For example, by reducing or inhibiting a complex component activity within target cells, an abnormal signal transduction event(s) leading to a condition may be decreased, inhibited, or reversed. Deletion or missense mutants of a component, that retain the ability to interact with other components of the protein complexes but cannot function in signal transduction may be used to inhibit an abnormal, deleterious signal transduction event. Expression vectors derived from viruses such as retroviruses, vaccinia virus, adenovirus, adeno-associated virus, herpes viruses, several RNA viruses, or bovine papilloma virus, may be used for delivery of nucleotide sequences (e.g., cDNA) encoding recombinant protein into the targeted cell population (e.g., tumor cells). Methods which are well known to those skilled in the art can be used to construct recombinant viral vectors containing coding sequences. See, for example, the techniques described in Maniatis et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, N.Y. (1989), and in Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley Interscience, N.Y. (1989). Alternatively, recombinant nucleic acid molecules encoding protein sequences can be used as naked DNA or in reconstituted system e.g., liposomes or other lipid systems for delivery to target cells (See e.g., Feigner et al., Nature 337:387-8, 1989). Several other methods for the direct transfer of plasmid DNA into cells exist for use in human gene therapy and involve targeting the DNA to receptors on cells by complexing the plasmid DNA to proteins. See, Miller, supra. In its simplest form, gene transfer can be performed by simply injecting minute amounts of DNA into the nucleus of a cell, through a process of microinjection. Capecchi MR, Cell 22:479-88 (1980). Once recombinant genes are introduced into a cell, they can be recognized by the cells normal mechanisms for transcription and translation, and a gene product will be expressed. Other methods have also been attempted for introducing DNA into larger numbers of cells. These methods include: transfection, wherein DNA is precipitated with CaPO4 and taken into cells by pinocytosis (Chen C. and Okayama H, Mol. Cell Biol. 7:2745-52 (1987)); electroporation, wherein cells are exposed to large voltage pulses to introduce holes into the membrane (Chu G. et al., Nucleic Acids Res., 15:1311-26 (1987)); lipofection/liposome fusion, wherein DNA is packaged into lipophilic vesicles which fuse with a target cell (Feigner PL., et al., Proc. Natl. Acad. Sci. USA. 84:7413-7 (1987)); and particle bombardment using DNA bound to small projectiles (Yang NS. et al., Proc. Natl. Acad. Sci. 87:9568-72 (1990)). Another method for introducing DNA into cells is to couple the DNA to chemically modified proteins. It has also been shown that adenovirus proteins are capable of destabilizing endosomes and enhancing the uptake of DNA into cells. The admixture of adenovirus to solutions containing DNA complexes, or the binding of DNA to polylysine covalently attached to adenovirus using protein crosslinking agents substantially improves the uptake and expression of the recombinant gene. Curiel DT et al., Am. J. Respir. Cell. Mol. Biol, 6:247-52 (1992). As used herein "gene transfer" means the process of introducing a foreign nucleic acid molecule into a cell. Gene transfer is commonly performed to enable the expression of a particular product encoded by the gene. The product may include a protein, polypeptide, anti-sense DNA or RNA, or enzymatically active RNA. Gene transfer can be performed in cultured cells or by direct administration into animals. Generally gene transfer involves the process of nucleic acid contact with a target cell by non-specific or receptor mediated interactions, uptake of nucleic acid into the cell through the membrane or by endocytosis, and release of nucleic acid into the cytoplasm from the plasma membrane or endosome. Expression may require, in addition, movement of the nucleic acid into the nucleus of the cell and binding to appropriate nuclear factors for transcription. As used herein "gene therapy" is a form of gene transfer and is included within the definition of gene transfer as used herein and specifically refers to gene transfer to express a therapeutic product from a cell in vivo or in vitro. Gene transfer can be performed ex vivo on cells which are then transplanted into a patient, or can be performed by direct administration of the nucleic acid or nucleic acid-protein complex into the patient. In another preferred embodiment, a vector having nucleic acid sequences of one of the disclosed genes is provided, in which the nucleic acid sequence is expressed only in specific tissue. Methods of achieving tissue-specific gene expression are set forth, for example, in International Publication No. WO 93/09236, filed November 3, 1992 and published May 13, 1993. In all of the preceding vectors set forth above, a further aspect of the invention is that the nucleic acid sequence contained in the vector may include additions, deletions or modifications to some or all of the sequence of the nucleic acid, as defined above. In another preferred embodiment, a method of gene replacement is set forth. "Gene replacement" as used herein means supplying a nucleic acid sequence which is capable of being expressed in vivo in an animal and thereby providing or augmenting the function of an endogenous gene which is missing or defective in the animal. EXAMPLES The examples below are non-limiting and are merely representative of various aspects and features of the present invention. The examples below demonstrate the isolation, and characterization of the gene sequences corresponding to a group of novel, related tyrosine kinases. EXAMPLE 1 ISOLATION OF cDNAs ENCODING THREE NOVEL HUMAN RTKs Protein kinases are one of the largest families of eukaryotic protiens with several hundred known members. These proteins share a 250-300 amino acid domain that can be subdivided into 12 distinct subdomains that comprise the common catalytic core structure. These conserved protein motifs have recently been exploited using PCR-based cloning strategies leading to a significant expansion of the known kinases. Multiple alignment of the sequences in the catalytic domain of protein kinases and subsequent phylogentic analysis permits their segregation into a phylogentic tree. In this manner, related kinases are clustered into distinct branches or subfamilies including: tyrosine kinases, cyclic-nucleotide-dependent kinases, calcium/calmodulin kinases, cyclin-dependent kinases and MAP-kinases, as well as several other less defined subfamilies. Initially we set out to identify homologues of TRK, a receptor that represents a distinct family of tyrosine kinases. We designed degenerate primers to conserved sequences within kinase subdomains I and VIII of this family of three mammalian receptors. Subdomain I is at the N-terminus of the kinase domain and contains the consensus motif GXGXXGXV which is involved in anchoring ATP to the catalytic unit of all classes of kinases. Subdomain VIII contains a highly conserved APE motif, upstream of which are residues that are well conserved between members of the same class of kinases (serine kinases, cytoplasmic tyrosine kinases, or receptor tyrosine kinases). Based on comparison of all known protein kinases, we designed degenerate oligonucleotide primers to subdomains I and VIII that would pick up only the three TRK kinases. MATERIALS AND METHODS CELLS LINES and CULTURE CONDITIONS All cell lines were obtained from the American Type Culture Collection (ATCC) or from the NCI and were grown according to their recommendations. MOLECULAR CLONING Total RNAs were isolated using the Guanidine Salts/Phenol extraction protocol of Chomczynski and Sacchi (P. Chomczynski and N. Sacchi, Anal. Biochem. 162, 156 (1987) from human, rat or mouse tissues, and from human tumor cell lines originating from specific tissue types. These RNAs were used as templates to generate single-stranded cDNAs using the Superscript Preamplification System for First Strand Synthesis kit purchased from GibcoBRL (Life Technologies, U.S.A.; Gerard, GF et al. (1989), FOCUS 11, 66) under conditions recommended by manufacturer. A typical reaction used 10 ug total RNA or 2 ug poly(A) + RNA with 1.5 ug oligo(dT) !2 _ 18 in a reaction volume of 60 ul. The product was treated with RNaseH and diluted to 100 ul with H20. For subsequent PCR amplification, 1-4 ul of these sscDNAs were used in each reaction. Oligonucleotides were synthesized on an Applied Biosystems 394 DNA synthesizer using established phosphoramidite chemistry and were used unpurified after precipitation with ethanol. The degenerate oligonucleotide primers are listed in Table I. Also listed for each degenerate oligonucleotide is the length, orientation, nucleotide sequence, and the amino acid sequence to which the primer is derived. Degenerate nucleotide residue designations are: N = A, C, G,or T; R = A or G; and Y = C or T. Using TRK as a template, these primers produce products of 550 bp. A PCR reaction was performed using Primers TRKa and TRKb applied to several of the single-stranded sources listed above. The primers were added at a final concentration of 5 uM each to a mixture containing 10 mM TrisHCl (pH8.3), 50 mM KC1, 1.5 mM MgCl 2 , 200 uM each deoxynucleoside triphosphate, 0.001% gelatin, and 1.5 U AmpliTaq DNA Polymerase (Perkin-Elmer/Cetus), and 1- 4 ul cDNA. Following 3 min denaturation at 95°C, the cycling conditions were 94°C for 30 s, 50°C for 1 min, and 72°C for lmin 45 s for 35 cycles. PCR fragments migrating at between 450-550 bp were isolated from 2% agaorse gels using GeneClean, blunt cloned into pBlueScript SKII+ at the EcoRV site (Stratagene). Colonies were selected for mini plasmid DNA-preparations using Qiagen columns and the plasmid DNAs were sequenced using cycle sequencing dye-terminator kit with AmpliTaq DNA Polymerase, FS (ABI, Foster City, CA). Sequencing reaction products were run on an ABI Prism 377 DNA Sequencer, and analyzed using the BLAST alignment algorithm (Altschul, S.F. et al., J. Mol. Biol 215:403-10). A novel clone (#135-31-2) was isolated by PCR with primers TRKa and TRKb on single-stranded cDNA from rat adult brain substantia nigra as a template. This clone was subsequently designated as a fragment of rat LMRl. A rat PC 12 cDNA library in pCDNA (Clontech) and a rat fetal brain lambda gtl 1 cDNA library (Clontech) were screened with this fragment as a probe, leading to isolation of several larger cDNA clones. DNA sequence analysis of LMRl_r demonstrated its homology to several tyrosine kinase receptors, and it had all the motifs characteristic of this class of enzymes. The 5' end of this sequence encodes two hydrophobic regions, consistent with the presence of the signal sequence and transmembrane domain of a Type la transmembrane protein. The region between these two hydrophobic domains is only 18 amino acids, suggesting this protein contains an extremely short extracellular domain. LMRljr has several atypical amino acid substitutions at highly conserved sites in the putative tyrosine kinase domain. These include a VAVK to VVVK change in domain II, a DFG to DYG change in domain VII, and a SDVW to SNVW change in domain IX. We designed several additional primers to some of the unique motfis of LMRl_r to combine with other primers specific to the unrelated receptor tyrosine kinases TEK and ROS. The primer sequences are shown in Figure 2. Multiple combinations of these primers were applied to single stranded cDNA from several rat, mouse, and human sources, leading to the isolation of additional homologues of LMR 1. NORTHERN BLOT ANALYSIS Northern blots were prepared by running 10 ug total RNA isolated from 60 human tumor cell lines and 26 normal human tissues on a denaturing formaldehyde 1.2% agarose gel and transferring to nylon membranes. Filters were hybridized with random prime [α 32 P]dCTP-labeled probes synthesized from the inserts of human LMRl, LMR2 and LMR3. Hybridization was performed at 42°C overnight in 6XSSC, 0.1% SDS, IX Denhardt's solution, 100 μg/ml denatured herring sperm DNA with 1-2 x 10 6 cpm/ml of 32 P-labeled DNA probes. The filters were washed in O.lXSSC/0.1% SDS, 65°C, and exposed on a Molecular Dynamics phosphorimager. SEMI-QUANTITATIVE PCR DETECTION OF LMRl RNA was isolated from a variety of rat cell lines and fresh frozen tissues. Single stranded cDNA was synthesized from 10 μg of each RNA as described above using the Superscript Preamplification System (GibcoBRL). These single strand templates were then used in a 25 cycle PCR reaction with two LMRljr specific oligonucleotides. 5'-TGAAAGTGGGAGATTACGGAATA and 5'- GTTACTATACTTAGTCTGATCTGC. Reaction products were electrophoresed on 2% agarose gels, stained with ethidium bromide and photographed on a UV light box. The relative intensity of the LMRl -specific bands were estimated for each sample. IN SITU HYBRIDIZATION ANALYSIS Cryostat sections of OCT-embedded frozen rat embryos (El 6, E20), and adult rat brain were placed on poly-lysine coated slides and fixed in 4% paraformaldehyde in PBS at 4oC. The slides were treated with 0.25% acetic anhydride/O.lM TEA for 10 min at room temperature, rinsed in 2XSSC and dehydrated by rinsing for 15 seconds each in water, followed by 30%, 50%, 85%, 95%o and 100% EtOH. The slides were then air dried and prehybridized by transfering to PBS/5 mM MgC12 for 10 min followed by 0.25M Tris/O.IM glycine for 10 min, and 50% formamide/2XSET at 37oC for 10 min. The slides were then hybridized in hybridization buffer (50% formamide/2X SET /10X Denhardt's/0.5 mg per ml tRNA/ 100 mM DTT) containing 2 million cpm of [35 S] CTP-labeled sense and antisense riboprobes generated from 300-500 bp fragments encoding rat LMRl, LMR2, or LMR3. Six drops of the hybridization mix was added per slide and incubated for 4 hours at 45oC. The slides were rinsed in 4X SSC followed by 50%) formamide/2XSET for 15 min at 60oC. The slides were again rinsed in 4X SSC prior to treating with 20 ug/ml RNAase A in 4X SET at 37oC for 20 min and then rinsed in IX SSC. The slides were then dehydrated in 30% EtOH/0.3 M NH4HOAC, 50% EtOH/0.3 M NH4HOAc, 70% EtOH/0.3 M NH4HOAc, 85% EtOH, 95% EtOH, 100% EtOH, air dried, and stored in an airtight box with dessicant at room temperature. Slides were dipped in Kodak NTB2 emulsion, and exposed for 2-5 weeks prior to developing. CHROMOSOMAL LOCALIZATION AND GENOMIC CLONING OF LMR2 A pair of oligonucleotides primers were derived from the sequence of the 3 '-untranslated region of human LMR2 for amplification of a 521 bp LMR2 specific fragment from genomic DNA. The primers span nucleotides 8232-8254 (sense) and 8732-8752 (antisense) of the human LMR2 sequence. This primer pair was applied to the Stanford Human Genome Center G3 radiation hybrid panel (Research Genetics, Huntsville, AL) and to a library of human bacterial artifical chromosome (BAC) DNA pools (Release III, Research Genetics, Huntsville, AL). PCR reactions were performed with a 64oC annealing temperature for 30-35 cycles as recommended by the distributor. In addition, a 158 bp Xhol-Pstl fragment from the 5' end of human LMR2 was used to probe a human placenta genomic DNA library in lambda FIXII in order to isolate a genomic clone spanning the 5' end of the LMR2 cDNA clones. RESULTS SEQUENCE ANALYSIS OF cDNA CLONES ENCODING THREE NOVEL RTKs We designed degenerate primers TRKa and TRKb based on conserved residues within the kinase domain of the receptor tyrosine kinase TRK, to use for identification of novel kinases using polymerase chain reaction (PCR). When applied to rat substantia nigra sscDNA as a template, multiple copies of TRKA, TRKB and TRKC cDNA were isolated as well as a several novel DNA fragments with homology to serine kinases. A novel 550 bp clone (135-31-2) had sequence that was most similar to the RTKs, Insulin receptor, IGF 1 -receptor, TRKA, and ROS was named LMRl_r. Using this fragment as a probe, we screened RNAs from a number rat sources by Northern blot, demonstrating an apparent selectivity in expression of this clone in rat brain. The LMRl_r probe was also used to screen a cDNA library constructed from rat PC 12 cell line RNA to isolate overlapping clones spanning the 3'-end ofLMRl_r. The 2,572 bp LMRl_r nucleotide sequence (SEQ ID NO. 1) is shown in FIG. 7 and contains a single open reading frame encoding a polypeptide of 848 amino acids. Additional 3' clones will be required to resolve the complete sequence of LMRl_r, however the C-terminal portion of LMRl was subsequently isolated from a human cDNA library (see below). LMRl_r amino acid sequence (SEQ ID NO. 10) conserves all 12 subdomains characteristic of eukaryotic protein kinases. It does have atypical substititions in three highly conserved residues within the catalytic domain of other protein kinases, as described below. Upstream of the putative protein kinase domain are two hydrophobic stretches characteristic of a signal sequence and transmembrane domain. We designed several additional primers to some of the unique motfis of LMRl _r to combine with other primers specific to the unrelated receptor tyrosine kinases TEK and ROS. The primer sequences are shown in Table I. Multiple combinations of these primers were applied to single stranded cDNA from several rat, mouse, and human sources, leading to the isolation of additional homologues of LMRl . Specifically, we identified fragments coresponding to the human and mouse counterparts of LMRl_r (LMRl_h from human cerebellum, isolated with primers IROSD3 and IROS D6; LRMl_m using the same primers on mouse day 11 embryo cDNA). Seven additional unique fragments were isolated by PCR with various pairs of these degenerate primers. Sequence comparison suggests that these seven clones represent two additional human genes and their orthologues from rat or mouse. Specifically they are referred to as LMR2_h (primers IROSD3 and IROSD6 on OVCAR-3 ovarian tumor cell line cDNA), LMR2_m (primers ROS1 and IROSD5 on mouse day 10 embryo cDNA), LRM2_r (primers IROSD3 and IROSD6 on rat PC 12 cDNA), LMR2_h (primers IROSD3 and IROSD5 on human heart cDNA), LMR2_r (primers IROSD3 and IROSD5 on rat PC 12 cDNA), LMR3_h (primers IROSD3 and IROSD6 on human fetal brain cDNA), and LMR3_m (primers TEK1 and IROSD5 on mouse day 12 embryo cDNA). The partial cDNA clones from human LMRl, LMR2, and LMR3 were then used to probe cDNA libraries in order to isolate full length human cDNA clones. A 5,048 bp clone of LMRl i (SEQ ID NO. 2) was isolated from a lambda ZAP cDNA library constructed from SNB75 cell line RNA. This clone spans all but the first 27 amino acids of the predicted 1384 amino acid human LMRl protein (SEQ ID NO. 11). The true N-terminus of LMRl however is contained on the rat cDNA clone. Two LMR2_h cDNA clones of 4,349 bp and 5,482 bp were isolated from an NCI-H460 human lung carcinoma cell line cDNA library and the SNB75 cDNA library, respectively. Together these clones span the complete 8,982 bp human LMR2 cDNA (SEQ ID NO. 5) and encode a protein of 1504 amino acids (SEQ ID NO. 14). Finally, a 1,583 bp clone of LMR3_h (SEQ ID NO. 8) was isolated from a lambda gtl 1 human brain cDNA library. This clone spans the N- terminal 473 amino acids of human LMR3 (SEQ ID NO. 17). Additional screening is ongoing to isolate the 3' end of the human LMR3 cDNA. Each of the three LMR proteins begin with two closely spaced hydrophobic regions. The first hydrophobic stretch of LMRl (aa 1-20), LMR2 (aa 1-26), and LMR3 (aa 1-20) meets the criteria signal peptide domains, with discriminant scores of 8.78, 18.95, and 10.76 respectively using the method of McGeoch (D. J. McGeoch, Virus Research, 3, 271, 1985), and with weight matrix scores of +3.45, 9.03, and 8.66 respectively (threshold = 3.5) using the von Heijne algorithm (G. von Heijne, Nucl. Acids Res., 14, 4683, 1986). The second hydrophobic region of LMRl (aa 38-64), LMR2 (aa 39-69), and LMR3 (aa 35-62) generate likelihood scores of -9.18, -17.09, and -11.25 (threshold = -2.0) respectively, using the ALOM method of Klein et al. (P. Klein, M. Kanehisa, and C. DeLisi, Biochim. Biophys. Acta, 815, 468, 1985) to predict transmembrane domains. Based on these analyses, LMRl, LMR2, and LMR3 are all predicted to be type la membrane proteins with very short extracellular domains of 18 (AFSSHFDPDGAPLSELSW), 12 (APLPQTGAGEAP), and 14 (SPAHPDGFALGRAP) amino acids respectively. Conceivably, these receptors may contain an additional co-receptor as present in many GPI-anchored cytokine receptors, GDNF-receptors, or contactin-related adhesion molecules. Co- immunoprecipitation studies will allow us to address this issue. LMRl, LMR2, and LMR3 all share a domain that conserves all 12 subdomains characteristic of eukaryotic protein kinases. The three human proteins share 52-59%) amino acid sequence identity within this putative kinase domain whereas the rat, mouse, and human orthologues of LMRl share 92-93% amino acid identity. The putative kinase domain of the LMRs is most related to that of other receptor tyrosine kinases. They share 33-36%) amino acid identity with TRKA, TRKB, and TRKC and 31-35% identity with insulin receptor, IGF1R, Musk, Tyro 10, DDR, and ROS. However two cytoplasmic tyrosine kinases, ITK and BMX are 33-34% identical to the kinase-like domain of LMR2. This analysis suggests the LMR receptors will likely represent a unique class or classes of RTKs. The kinase- like domain of the three LMRs do contain three atypical substitutions at residues that are highly conserved among all protein kinases: VAVK to V(V/I)VK in kinase domain II (aa 163-166 in LMR2), DFG to DYG (aa 281-283 in LMR2), and DVWS to NVWS (aa 329-332 in LMR2). The first substitution is a contact residue for the adenosine ring of ATP, and the presence of a hydrophobic residue in this position is unique to all known protein kinases. The remaining two substitutions are not known to be directly involved in the catalytic function of kinases and are present in other active kinases such as PIM1, and PKC. Whether these substitutions affect activity or specificity of the kinase-like domain can be addressed through in vitro kinase and FSBA-binding experiments. The C-terminal domains of LMRl, and LMR2, are 975 and 1093 amino acids respectively. The C-terminal domain of LMR3 is at least 153 aa (sequence analysis of the remaining C-terminal region of LMR3 is ongoing). These proteins were named Lemurs (LMR) as a reflection of their unusually long extracatalytic C-terminal tails. Within the C-tails are several conserved pockets of amino acid identity that contain 7 tyrosine residues (Fig. 1). Each of these may function as potential tyrosine phosphorylation sites, and may be of significance for LMR-specific signaling. These "tails" are also very hydrophilic and negatively charged, but otherwise lack significant homology to other proteins. Numerous isoforms have been identified for LMRl and LMR2, resulting from alternative splicing or addition of a single base resulting in a frameshift and truncation of the C- terminal domain. EXPRESSION PROFILE of HUMAN LMRs Northern blots of RNA from adult human tissue samples and human tumor cell lines were hybridized with DNA probes specific to human LMRl, LMR2, and LMR3. A single mRNA transcript was identified for each gene (LMRl = 7 kb; LMR2 = 9kb; LMR3 = 5.1 kb), and all had distinct and restricted expression in specific cell types (Figs 3 A and B). LMRl was also analyzed by quantitatvie PCR on a variety of rat tissues RNA samples. LMRl, LMR2 and LMR3 expression in normal adult tissues was restricted to those of neuronal origin (adult brain, cortex, and cerebellum) and was absent from all other adult tissues examined. LMRl was expressed at low levels in cell lines from 3 lung tumors, 1 CNS tumor, 1 colon tumor, and 2 melanomas. LMR3 expression was not detected in any of the 59 tumor cell lines. In contrast, LMR2 was widely and abundantely expressed in numerous tumor cell lines, particularly those of lung, breast, and colon origin. IN SITU ANALYSIS of LMR EXPRESSION LMRl, LMR2, and LMR3 developmental expression was analyzed by in situ hybridization on day 16 rat embryos (Fig. 4). LMRl expression was tightly restricted to the dorsal root ganglia (DRGs) and the projecting nerves, and absent from all other neuronal and non-neuronal tissues examined. LMR3 was also abundantely expressed in DRGs, but had comparable expression in other embryonic neuronal structures including the spinal cord, thalamus, and brainstem, and lower levies in the specific regions of the midbrain and cortex. LMR3 was also expressed in the embryonic stomach and colon. LMR2 had a much broader expression profile than LMRl or LMR3 in the day 16 rat embryo. LMR2 was expressed at high levels in the same neuronal tissues as LMR3 (DRGs, spinal cord, brainstem, thalamus, midbrain, and cortex), but LMR2 expression was also strong in the trigeminal nucleus, neuroretina, and the olfactory epithelium. LMR2 was also abundantely expressed in a variety of non-neuronal embyronic tissues including the stomach, intestine, and colon, the lung, kidney, liver and pancreas. Expression of LMRl, LMR2, and LMR3 was also analyzed by in situ hybridization in coronal and saggital sections of the adult rat brain (Fig. 5). LMRl was weakly expressed in the cerebellum, cortex, thalamic and amygdaloid nuclei, and brainstem. LMR3 was more abundantly expressed in the adult brain with highest expression in the hippocampus, cerebellum, anterior cortex, amygdaloid, thalamic, caudate, facial and supramammilary nuclei. LMR2 expression in the adult rat brain was stronger than that of LMRl or LMR3, particularly in the purkinje layer of the cerebellum, the outer cortex, hippocampus, and in the thalmic, caudate/putamen, amygdaloid, facial, and trigeminal nuclei. LMR2 was also detected in the region of the piriform cortex, and substantia nigra. Overall, the expression of LMRl and LMR3 are highly restricted to neuronal tissues with minimal expression in other adult or embryonic organs or in human tumor cell lines. In contrast, LMR2 expression is limited to adult neuronal tissues, but is also very abundantly expressed in other non-neuronal fetal tissues and in numerous tumor cell lines. The onco-fetal pattern of LMR2 expression suggests it may serve as a selective target for cancer therapy. GENOMIC ANALYSIS AND CHROMOSOMAL LOCALIZATION of LMR2 PCR primer pairs were designed to specifically recognize LMR2 from genomic DNA. These primers were then be used to screen the Stanford G3 radiation hybrid panel of DNAs isolated from hamster-human somatic cell hybrids, in order to postionally map the LMR2 gene. LMR2 was mapped to chromosome 7q22.1. This chromosomal region had been reported to be amplified in pancreatic cancer, multiple-drug resistant cells, and in malignant solid tumors. Translocations in the region of 7q22 have been seen in myeloid leukemias, and endometrial polyps, and chromosome loss has been reported in breast, ovarian, prostate, and espophageal cancer, and in uterine leiomyomas. Analysis of the LMR2 gene/sequence from specimens isolated from these tumor sources will be necessary to validate LMR2's involvement in any of these tumor types. The LMR2-specific primers were also used to isolate a -130 kb BAC (bacterial artificial chromosome) clone spanning the entire human LMR2 gene. In total, 4 BAC clones were identified to contain the 3' UTR of the LMR2 gene (Plate pool 345-352/Row B/Column 10; Plate pool 457-464/Row J/Column 22; Plate pool 569-576/Row N/Column 18; and Plate pool 9-16/Row L/Column 6). The latter of these BAC clones was found to also contain the 5' end of the LMR2 cDNA clone. An additional 12 kb lambda human genomic clone containing the 5' most region of the cDNA clone was also isolated. Partial sequence analysis of the BAC clone revealed the location of numerous exons in LMR2, proving that the C-terminal isoforms of LMR2 were alternatively spliced transcripts. Additional sequence analysis of the lambda genomic clone and BAC clone identified two small introns in the N-terminal coding region of LMR2 (one near the junction of the predicted signal sequence), and revealed that the predicted 5' UTR of LMR2 was contiguous with the predicted start methionine, and that a stop codon is present in frame just upstream of our furthest cDNA clone. No upstream introns were obvious and a consensus "TATA Box" lies 259 bp upstream of the 5' most cDNA sequence suggestive that this may be the upstream LMR2 promoter region. In summary, the analysis of the genomic and cDNA clones suggest that the sequence presented (SEQ ID NO. 5) represents the complete coding sequence of human LMR2, and that it has an unusual membrane configuration, with a very short extracellular domain. This conclusion is further supported by the consistent presence of start methionine followed by a predicted signal peptide in the LMRl and LMR3 clones. However, confirmation that these clones represent the entire LMR2 coding region awaits verification that the recombinant protein encodes a polypeptide of the same size as endogenous LMR2 and that immunolocalization studies demonstrate LMR2 toe a cell surface receptor (see below). EXAMPLE 2 RECOMBINANT EXPRESSION OF NOVEL RTKs MATERIALS AND METHODS EXPRESSION VECTOR CONSTRUCTION Several expression constructs were generated from the human LMR2 cDNA including: a) full length LMR2_h in a pCDNA expression vector; b) a chimera between chicken TrkA extracellular domain and the transmembrane and cytoplasmic domains of human LMR2 in an adenovirus expression vector; c) a GST- fusion construct containing the juxtamembrane and cytoplasmic domain of LMR2 fused to the C-terminal end of a GST expression cassette; d) the kinase domain of LMR2_h fused to a GyrB expression cassette; e) a full length LMR2_h construct with a Lys to Ala (K to A) mutation at the predicted ATP binding site of the LMR2 kinase domain, inserted in the pCDNA vector; f) various truncated LMR2 constructs in the pCDNA vector, containing progressively larger C-terminal deletions. The "K to A" mutant and the C-terminal truncation mutants of LMR2 might function as dominant negative constructs, and will be used to elucidate the function of LMR2. GENERATION OF SPECIFIC IMMUNOREAGENTS TO THE THREE NOVEL RTKs Specific immunoreagents were raised in rabbits against KLH- or MAP-conjugated synthetic peptides corresponding to human LMR2. C-terminal peptides were conjugated to KLH with gluteraldehyde, leaving a free C-terminus. Internal peptides were MAP-conjugated with a blocked N-terminus. Additional immunoreagents can also generated by immunizing rabbits with the bacterially expressed GST-fusion protiens containing the cytoplasmic domains of LMRl, LMR2, and LMR3. For LMR2, a GST fusion construct was genereated that encoded amino acids 71-840 of the human LMR2 protein. Peptide immunogens for human LMR2 include: TRANSIENT EXPRESSION OF the LMRl .2.3 in MAMMALIAN CELLS The pcDNA expression plasmids (lOug DNA/ 100 mm plate) containing the LMR2 constructs are introduced into 293 cells with lipofectamine (Gibco BRL). After 72 hours, the cells are harvested in 0.5 ml solubilization buffer (20 mM HEPES pH7.35, 150 mM NaCl, 10% glycerol, 1% Triton X-100, 1.5 mM MgCl 2 , 1 mM EGTA, 2 mM phenylmethylsulfonyl fluoride, 1 μg/ml aprotinin). Sample aliquots were resolved by SDS polyacrylamide gel electrophoresis (PAGE) on 6%acrylamide/0.5% bis-acrylamide gels and electrophoretically transferred to nitrocellulose. Non-specific binding is blocked by preincubating blots in Blotto (phosphate buffered saline containing 5% w/v non-fat dried milk and 0.2% v/v nonidet P-40 (Sigma)), and recombinant protein was detected using the various anti- peptide or anti-GST-fusion specific antisera. IMMUNOSTAINING Cells expressing endogenous LMRs, based on immunoblot analysis, were plated on glass slides and stained with LMR-specific antisera to determine the subcellular location of endogenous protein. Cells were fixed in methacarnes (60% Methanol/30% chloroform 10% glacial acetic acid) for 20 min, then post-fixed in 0.25% Tween20 in PBS. Slides were then blocked in 5% normal goat serum in PBS/0.25% Tween20 for 45 min. Slides were then incubated with a 1 :500 dilution of LMR2-specific antisera from the 5th bleed of rabbits immunized with peptide 494A or 497A for 45 min at room temperature, washed 5x in PBS/0.25% Tween20. A 1 :500 dilution of goat anti-rabbit F(ab')2 IgG-cyanine CY3 (Jackson Immunoresearch laboratories, West Grove, PA) was added for 30 min, followed by 6 washes in PBS/0.25% Tween20, and 2x in H2O. Slides were then air dried and mounted for analysis by fluroscent microscopy. IN VITRO KINASE ASSAYS Three days after transfection with the LMR2 expression contracts, a 10 cm plate of 293 cells was washed with PBS and solubilized on ice with 2 ml PBSTDS containing phosphatase inhibitors (10 mM NaHPO4, 7.25, 150 mM NaCl, 1% Triton X-100, 0.5% deoxycholate, 0.1% SDS, 0.2% sodium azide, 1 mM NaF, 1 mM EGTA, 4 mM sodium orthovanadate, 1% aprotinin, 5 μg/ml leupeptin). Cell debris was removed by centrifugation (12000 x g, 15 min, 4°C) and the lysate was precleared by two successive incubations with 50 ul of a 1 :1 slurry of protein A sepharose for 1 hour each. One-half ml of the cleared supernatant was reacted with 10 ul of protein A purified LMR2 antisera (generated from the GST fusion protein) plus 50 ul of a 1 :1 slurry of protein A-sepharose for 2 hr at 4°C. The beads were then washed 2 times in PBSTDS, and 2 times in HNTG (20mM HEPES, pH7.5/150 mM NaCl, 0,1% Triton X-100, 10% glycerol). The immunopurified LMR2 on sepharose beads was resuspended in 20 ul HNTG plus 30 mM MgC12, 10 mM MnC12, and 20 uCi [g32P]ATP (3000 Ci/mmol). The kinase reaction was run for 30 min at room temperature, and stopped by addition of HNTG supplemented with 50 mM EDTA. The samples were washed 6 times in HNTG, boiled 5 min in SDS sample buffer and analyzed by 6% SDS-PAGE followed by autoradiography. Phosphoamino acid analysis was performed by standard 2D methods on 32P-labeled LMR2 excised from the SDS-PAGE gel. FSBA labeling Immunoprecipitated LMR2 was labeled with the ATP-analogue FSBA as described by Anostario, M Jr et al (Anal. Biochem 190,60-65, 1990) in the presence or absence of ATP competitor. FSBA-bound LMR2 was detected by immunoblot with anti-FSBA antibodies (Boehringer Mannheim). RESULTS The apparent molecular weight of each of the three novel RTKs can be determined by transient expression in human 293 embryonic kidney epithelial cells followed by immunoblotting with LMR-specific antisera. Surprisingly, the full length LMR2 cDNA construct encodes a protein that migrates at -230 kDa on an 6% SDS-PAGE gel, whereas the cDNA predicts an unmodified protein of 164.9 kDa. The chimeric TrkA-LMR2 construct encodes a protein that migrates at above 250 kDa on an 6% SDS-PAGE gel, whereas the cDNA predicts a protein of -207 kDa (plus 13 potential glycosylation sites). Since there the predicted extracellular domain of LMR2 is only 12 amino acids, with no sites for glycosylation, the cause of the slower gel mobility is unclear. Based on a series of C-terminal deletion mutants it appears the discrepancy between calculated and apparent gel mobility is a result of the presence of the long, negatively charged C-terminal tail of LMR2. However, this analysis confirms the recombinant protein can be stabley produced in mammalian cells and provides a source of recombinant protein to confirm the specificity of the antisera. The anti-GST fusion and peptide antisera were tested for their sensitivity and specificity on recombinant protein. The LMRl and LMR2 anti-GST fusion antibodies were both confirmed to specifically recognize the appropriate recombinant protein in immunoprecipitation and Western blot. However their Western reactivity was weak, and they performed poorly on immunostaining. Anti- peptide antisera derived from LMR2 peptides 489 A and 491 A (SEQ ID NO.19, and 20) worked on Western blots, but not for immunoprecipitation, whereas LMR2 peptides 494A and 497A (SEQ ID NO.21, and 22) worked in Western blots, immunoprecipitation, and for cellular immunostaining. All LMR2 immunoreagents recognized a 230 kDa recombinant protein, whereas the 497 A peptide antisera also detected an additional 130 kDa band on Western blot. All expression constructs were confirmed to produce the encoded protein by Western blots and immunoprecipitation. A panel of human tumor cell lines were screened for expression of endogenous LMR2 by Western blot. The Western blot analysis concurred with the Northerns, with highest endogenous LMR2 expression detected in NCI-H441, COLO205, and MCF7 cells. The endogenous protein migrated at -230 kDa, indistinguishable from the recombinant LMR2, further supporting that this cDNA encodes the full length LMR2 and that the protein has an unusually slow mobility in a reducing SDS-PAGE gel. These cells lines will be useful for characterization of the activity and biology of LMR2. Immunolocalization of recombinant LMR2 in transient and stabley transfected 293 cells suggests it is both membrane and endoplasmic reticulum- associated. Assessment of the location of endogenous LMR2 in H441 cells is underway. In vivo and in vitro phosphorylation assays were performed with recombinant and endogenous LMR2 following immunoprecipitation with LMR2- specific antisera. To date only serine and threonine phosphorylation has been detected associated with LMR2. Several distinct antibodies all detect comparable activity, suggesting the activity is associated with LMR2 and not due to antisera cross-reactivity. However, a similar amount of phosphorylation was also observed with the "kinase dead" K to A construct. These results suggest that either the "kinase dead" construct is still active, or that the activity is due to a serine kinase that is very tightly associated with LMR2. Experiments are underway to reassess kinase activity under different assay conditions (pH 5-8, variable ATP concentration, and presence of irreversible phosphatase inhibitors) and to determine if LMR2 can bind the the ATP-analogue FSBA. The LMR2-specific antisera can also be used to co-immunoprecipate, substrates or co-receptors that associate with LMR2 from 35S-methionine/cysteine or 32P-labeled lysates. Since LMR2 has such an unusually short extracellular domain, the presence of an associated co-receptor could allow it access to modulation by a solbule or extracellular associated ligand. Owing to the presence of potential tyrosine phosphorylation sites in the stretches of amino acids that are conserved between LMRl , LMR2, and LMR3, it seems likely that these proteins may have uniquely specific substrates. Co-immunoprecipitation, random peptide libraries, phage display, and yeast two-hybrid techniques are all methods for identifying LMR2-selective substrates. LMRl, LMR2, and LMR3 define a novel family of receptors that are structurally related to receptor tyrosine kinases. While their inherent catalytic activity is still under investigation, they all share the distinct motifs that typically characterize this class of enzymes. In addition, they possess extremely short extracellular domains and C-terminal tails of unprecidented length among RTKs. These structural features, along with several conserved C-terminal potential tyrosine phosphorylation sites suggests their biology may be unique among other receptors. Based on the restricted expression of all three LMRs to adult neuronal tissues and the upregulation of LMR2 in a wide variety of tumor cell lines, these proteins may be critical targets for neurodegenerative disorders or cancer. Ongoing experiments will characterize their effect on growth rate, DNA synthesis, cell-contact inhibition (foci formation), anchorage-independent growth (soft agar assays), and tumorigenicity in nude mice, and for their role in cell survival, apoptosis, or neurite outgrowth. Furthermore, the dominant negative constructs, neutralizing antisera, or antisense oligonucleotides can be used to address the inolvement of these novel RTKs in various biologic processess, both in normal development and disease. One skilled in the art would readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The molecular complexes and the methods, procedures, treatments, molecules, specific compounds described herein are presently representative of preferred embodiments are exemplary and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention are defined by the scope of the claims. It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. All patents and publications mentioned in the specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein. Thus, for example, in each instance herein any of the terms "comprising", "consisting essentially of and "consisting of may be replaced with either of the other two terms. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group. For example, if X is described as selected from the group consisting of bromine, chlorine, and iodine, claims for X being bromine and claims for X being bromine and chlorine are fully described. Those references not previously incorporated herein by reference, including both patent and non-patent references, are expressly incorporated herein by reference for all purposes. Other embodiments are within the following claims.

Claims: CLAIMS What is claimed is: 1. A purified, isolated, or enriched nucleic acid molecule at least 25 nucleotides in length, wherein the sequence of said nucleic acid molecule has at least 95%) sequence identity or complementarity to a portion of a gene encoding a kinase, wherein said gene is selected from the group consisting of the genes corresponding to any of SEQ ID NO. 1 - 9. 2. The nucleic acid molecule of claim 1, wherein said nucleic acid molecule has at least 95% sequence identity to a sequence which encodes at least 50 contiguous amino acids of said gene. 3. The nucleic acid molecule of claim 2, wherein said nucleic acid molecule has at least 95%> sequence identity to a sequence which encodes at least 100 contiguous amino acids of said gene. 4. A purified, isolated, or enriched nucleic acid molecule at least 25 nucleotides in length, wherein the sequence of said nucleic acid molecule has at least 95% sequence identity to a portion of a sequence selected from SEQ ID NO. 1 - 9 or a sequence complementary thereto. 5. A nucleic acid probe for the detection of nucleic acid encoding a kinase polypeptide in a sample, wherein said kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 6. The nucleic acid probe of claim 5, wherein said probe comprises a sequence at least 25 nucleotides in length complementary to a portion of said nucleic acid. 7. The nucleic acid probe of claim 6, wherein said probe comprises a sequence at least 50 nucleotides in length complementary to a portion of said nucleic acid. 8. An isolated or purified nucleic acid molecule encoding a human polypeptide expressed in a human tissue, obtainable by hybridization under stringent hybridization conditions of a nucleotide sequence selected from the group consisting of SEQ ID NO. 1 - 9 or a sequence complementary thereto, to mRNA from said human tissue. 9. A recombinant nucleic acid molecule comprising a transcriptional initiation region functional in a cell, transcriptionally linked with a sequence complementary to an RNA sequence encoding a kinase polypeptide and a transcriptional termination region functional in a cell, wherein said kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 10. The recombinant nucleic acid molecule of claim 9, wherein said kinase polypeptide comprises the amino acid sequence of said kinase encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 11. An isolated, enriched or purified kinase polypeptide, wherein said kinase is encoded by a gene or portion of a gene corresponding to any of SEQ ID NO. 1 - 9, and wherein said polypeptide comprises at least 25 contiguous amino acids of the amino acid sequence of said kinase. 12. The kinase polypeptide of claim 11 , wherein said polypeptide comprises at least 50 contiguous amino acids of the amino acid sequence of said kinase. 13. The kinase polypeptide polypeptide of claim 12, wherein said polypeptide comprises at least 100 contiguous amino acids of the amino acid sequence of said kinase . 14. The kinase polypeptide polypeptide of claim 13, wherein said polypeptide comprises the full amino acid sequence of said kinase. 15. The kinase polypeptide of claim 14, wherein said polypeptide comprises the amino acid sequence encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 16. An antibody having specific binding affinity to a kinase polypeptide, wherein said kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 17. The antibody of claim 16, wherein said kinase polypeptide comprises at least 3 contiguous amino acids of the amino acid sequence of said kinase. 18. The antibody of claim 17, wherein said kinase polypeptide comprises at least 25 contiguous amino acids of the amino acid sequence of said kinase. 19. A hybridoma which produces an antibody having specific binding affinity to a kinase polypeptide, wherein said kinase is encoded by a gene corresponding to any of SEQ ID NO. 1 - 9. 20. The hybridoma of claim 19, wherein said kinase polypeptide comprises at least 25 contiguous amino acids of the amino acid sequence of said kinase .

Inventors: JOHO KEITH E, PLOWMAN GREGORY D, JOHO, KEITH, E., PLOWMAN, GREGORY, D.
Applicants: SUGEN INC, SUGEN, INC.
Application year: 1997
Main classification: C07K14
IPC codes: A61K48, C07K14, C07K16, C12N5, C12N9, C12N15, C12P21, C12Q1, C12R1