REGULATION OF HUMAN PLC DELTA-1

Abstract: Reagents which regulate human PLC delta-1 activity and reagents which bind to human PLC delta-1 gene products can be used, <i>inter alia</i>,to treat COPD, congestive heart failure, hypertension, and cancer, and a variety of conditions in which signal transduction is impaired.

Description: REGULATION OF HUMAN PLC PELTA-1 This application incorporates by reference co-pending application Serial No. 60/207,277 filed May 30, 2000. TECHNICAL FIELD OF THE INVENTION The invention relates to the regulation of human PLC delta- 1 activity for therapeutic effects. BACKGROUND OF THE INVENTION Phospholipase C Phospholipase C (PLC) belongs to a family of enzymes, also known as disulfide isomerases, which play a very important role in transmembrane signal transduction (see U.S. Patent 5,587,306). Many extracellular signaling molecules including hormones, growth factors, neurotransmitters, and immunoglobulms bind to their respective cell surface receptors and activate PLCs. The role of an activated PLC is to catalyze the hydrolysis of phosphatidylinositol-4, 5-bisphosphate (PIP2), a minor component of the plasma membrane to produce diacylglycerol and inositol 1, 4, 5-trisphosphate (IP3). In their respective biochemical pathways, IP3 and diacylglycerol serve as second messengers and trigger a series of intracellular responses. IP3 induces the release of Ca " " " from internal cellular storage, and diacylglycerol activates protein kinase C (PKC). Both pathways are part of transmembrane signal transduction mechanisms which regulate cellular processes which include secretion, neural activity, metabolism, and proliferation. For example, interleukin 4 receptor signaling in human monocytes involves activation of PLC (Ho et al, J. Exp. Med. 180, 1457-69, 1994). Several distinct isoforms of PLC have been identified and are categorized as PLC-beta, PLC-gamma, and PLC-delta. Subtypes are designated by adding Arabic numbers after the Greek letters, e.g. PLC-beta- 1. PLCs have a molecular mass of 62-68 kDa, and their amino acid sequences show two regions of significant similarity. The first region designated X has about 170 amino acids, and the second or Y region contains about 260 amino acids. The Mechanism of G Protein-Mediated Transmembrane Signaling The activation of a particular PLC is mediated by a guanine nucleotide binding-regulatory protein (G-protein) or by the intrinsic tyrosine kinase activity of cell surface receptors. Many plasma membrane-bound receptors, including the hormone receptors, activate the cell's G proteins. Each G protein can act as a molecular switch turning on one or more membrane-bound effectors such as adenylate cyclase, ion channels, or phospholipase C. G proteins are heterotrimers with alpha, beta, and gamma subunits. Inactive G proteins have guanine diphosphate (GDP) molecule bound tightly to their alpha subunit. When a G-protein linked receptor binds an extracellular ligand, such as a hormone, the hormone-receptor complex causes dissociation of GDP from the alpha-subunit. Immediately thereafter, GTP molecules fill the site, and activity of the alpha subunit's intrinsic ATPase causes dissociation of the G protein from the hormone-receptor complex. Simultaneously, GTP binding reduces the affinities between the alpha-, beta- and gamma-subunits and frees the beta-gamma complex. In some systems, the beta-gamma complex then activates PLC beta-2 (Katz et al, Nature 360, 686-89, 1992). Phospholipase Isoforms and Their Cellular Activity The catalytic activities of the three isoforms of PLC are dependent upon Ca "1-1" . It has been suggested that the binding sites for Ca " " " in the PLCs are located in the Y-region, one of two conserved regions. The hydrolysis of common inositol-containing phospholipids—phosphatidylinositol (PI), phosphatidylinositol 4-monophosphate (PIP), and phosphatidylinositol 4, 5-bisphosphate (PIP2) by any of the isoforms yields cyclic and noncyclic inositol phosphates. A large number of hormones and related molecules are known to activate phospholipases. PLC-beta Isoforms Both beta-1 and beta-2 isoforms of PLC are activated by certain subtypes of G-proteins and related G protein alpha-subunits during the transduction of signals from cell surface receptors to PLC. There may be two distinct types of G proteins, one pertussis toxin sensitive and the other insensitive, which activate the beta-1 isoform. Katz et al, supra, suggest that the beta subunit of the G protein may also activate PLC beta-1. The activation of PLCs is achieved by increasing their intrinsic activity rather than by reducing the PLCs requirement of Ca "1"4" in the cytosol. PLC-gamma Isoforms The PLC gamma- 1 isoform is mainly phosphorylated and activated by growth factor receptors belonging to the tyrosine kinase family. In addition, the growth factor receptors associate with the gamma- 1 isoform before any tyrosine phosphorylation occurs. The major sites of tyrosine phosphorylation by the receptors for epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and nerve growth factor (NGF) appear to be Tyr-771, Tyr-783, and Tyr-1254 in the PLC amino acid sequence. Phosphorylation of Tyr-783 in the gamma- 1 isoform by the receptor tyrosine kinase is essential for the activation of the gamma- 1 isoform. Other evidence suggests that non-receptor protein tyrosine kinases can also phosphorylate and activate the gamma- 1 isoform in response to certain cell surface receptors in leukocytes. For instance, the T cell antigen receptors complex can recognize antigens and transduce signals across the plasma membrane. Likewise, it appears that non-receptor protein tyrosine kinases can activate the gamma-2 isoform. Evidence suggests that the activation of the gamma-2 isoform is necessary for stimulation of phospholipase D by platelet-derived growth factor (Yeo et al, J. Biol. Chem. 269, 27823-26, 1994). Other evidence suggests that B cell surface antigen CD20 is associated with tyrosine and serine kinases and involved in tyrosine phosphorylation and activation of the gamma-1 and gamma-2 isoforms (Deans et al, J. Immunol 151, 4494-504, 1993). Growth factor-induced activation of PLCs appears to be independent of G-protein mediation. Marrero et al, J. Biol. Chem. 269, 10935-39, 1994), however, reported an exception in rat aortic vascular smooth muscle cells where PLC-gamma- 1 was activated by a G-protein-coupled receptor. PLC-delta Neither receptors nor transducers of the PLC-delta isoforms have been identified. Inhibition of PLCs by Protein Kinases Evidence suggests that the activation of protein kinases may serve as negative feed back signals and attenuate receptor-coupled PLC activity including the magnitude and duration in certain types of cells. For instance, the phosphorylation of Thr-654 in the EGF receptors by protein kinase prevents activation of the gamma-1 isoform by reducing the capacity of the receptor tyrosine kinase to phosphorylate the gamma-1 isoform. In addition, PKC activators such as cAMP and phorbol 12-myristate 13-acetate (PMA) attenuate the PIP2 hydrolysis induced by T cell antigen receptors. Likewise, the beta-1 isoform of PLC appears to be regulated by PKC in certain cells. Effects of The Second Messengers and Calcium Cations Inositol t sphosphate Once activated, PLCs catalyze the hydrolysis of phosphatidylinositol-4, 5-bisphosphate (PIP2) to produce diacylglycerol and inositol 1, 4, 5-trisphosphate (IP3), all of which serve as second messengers. Inositol tnsphosphate releases Ca 1-1- from intracellular stores and increases the influx of Ca " " " from the extracellular fluid. Ca " " " directly regulates target enzymes and indirectly affects other enzymes by functioning as a second messenger and interacting with Ca^-binding proteins, such as troponin C and calmodulin. Deactivation of the inositol tnsphosphate pathway is achieved by active transport of Ca ++ into cells and extrusion of ions by plasma membrane-bound, Ca^-pumping ATPases. Likewise, sequential phosphorylation degrades inositol trisphosphate. Diacylglycerol Diacylglycerol, a product of the hydrolysis by PLCs, acts as a second messenger by activating protein kinase C. After protein kinase C binds to diacylglycerol, the requirement of Ca by protein kinase C decreases to the level of free Ca found in the cytosol. Activated protein kinase C phosphorylates a great number of intracellular proteins. The termination of the diacylglycerol effect is achieved by enzymatic recycling to form phosphatidylinositol. Alternatively, a diacylglycerol lipase breaks down diacylglycerol. PLC and Diseases Evidence indicates that a high percentage of primary human mammary carcinomas concomitantly show increased levels of receptor EGF and PLC-gamma- 1. Likewise, studies on spontaneous hypertensive rats have suggested that one of the main causes for the hypertension is an abnormal activation of PLC-delta- 1 resulting from point mutations in the X and Y regions of the PLC amino acid sequence. The biology of PLC is reviewed, inter alia, in Isselbacher et al, HARRISON'S PRINCIPLES OF INTERNAL MEDICINE, McGraw-Hill, New York City, 1994; Kuruvilla et al, J. Immunol. 151, 637-48, 1993; and Rhee & Choi, J Biol. Chem. 267, 12393-96, 1994. Because of the important role of PLC enzymes, there is a need in the art to identify additional members of this enzyme family which can be regulated to provide therapeutic effects. SUMMARY OF THE INVENTION It is an object of the invention to provide reagents and methods of regulating a human PLC delta- 1. This and other objects of the invention are provided by one or more of the embodiments described below. One embodiment of the invention is a PLC delta- 1 polypeptide comprising an amino acid sequence selected from the group consisting of: amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 2; the amino acid sequence shown in SEQ ID NO: 2; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 4; the amino acid sequence shown in SEQ ID NO:4; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 9; the amino acid sequence shown in SEQ ID NO: 9; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 13; and the amino acid sequence shown in SEQ ID NO: 13. Yet another embodiment of the invention is a method of screening for agents which decrease extracellular matrix degradation. A test compound is contacted with a PLC delta- 1 polypeptide comprising an amino acid sequence selected from the group consisting of: amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 2; the amino acid sequence shown in SEQ ID NO: 2; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 4; the amino acid sequence shown in SEQ ID NO:4; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 9; the amino acid sequence shown in SEQ ID NO: 9; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 13; and the amino acid sequence shown in SEQ ID NO: 13. Binding between the test compound and the PLC delta- 1 polypeptide is detected. A test compound which binds to the PLC delta- 1 polypeptide is thereby identified as a potential agent for decreasing extracellular matrix degradation. The agent can work by decreasing the activity of the PLC delta- 1. Another embodiment of the invention is a method of screening for agents which decrease extracellular matrix degradation. A test compound is contacted with a polynucleotide encoding a PLC delta-1 polypeptide, wherein the polynucleotide comprises a nucleotide sequence selected from the group consisting of: nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 1; the nucleotide sequence shown in SEQ ID NO: 1; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 3; the nucleotide sequence shown in SEQ ID NO: 3; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 5; the nucleotide sequence shown in SEQ ID NO:5; nucleotide sequences which are at least about 50%ι identical to the nucleotide sequence shown in SEQ ID NO: 6; the nucleotide sequence shown in SEQ ID NO: 6; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 7; the nucleotide sequence shown in SEQ ID NO: 7; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 8; the nucleotide sequence shown in SEQ ID NO:8; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 10; and the nucleotide sequence shown in SEQ ID NO: 10. Binding of the test compound to the polynucleotide is detected. A test compound which binds to the polynucleotide is identified as a potential agent for decreasing extracellular matrix degradation. The agent can work by decreasing the amount of the PLC delta- 1 through interacting with the PLC delta- 1 mRNA. Another embodiment of the invention is a method of screening for agents which regulate extracellular matrix degradation. A test compound is contacted with a PLC delta- 1 polypeptide comprising an amino acid sequence selected from the group consisting of: amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 2; the amino acid sequence shown in SEQ ID NO: 2; amino acid sequences which are at least about 50%ι identical to the amino acid sequence shown in SEQ ID NO: 4; the amino acid sequence shown in SEQ ID NO:4; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 9; the amino acid sequence shown in SEQ ID NO: 9; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 13; and the amino acid sequence shown in SEQ ID NO: 13. A PLC delta- 1 activity of the polypeptide is detected. A test compound which increases PLC delta- 1 activity of the polypeptide relative to PLC delta- 1 activity in the absence of the test compound is thereby identified as a potential agent for increasing extracellular matrix degradation. A test compound which decreases PLC delta- 1 activity of the polypeptide relative to PLC delta- 1 activity in the absence of - li ¬ the test compound is thereby identified as a potential agent for decreasing extracellular matrix degradation. Even another embodiment of the invention is a method of screening for agents which decrease extracellular matrix degradation. A test compound is contacted with a PLC delta- 1 product of a polynucleotide which comprises a nucleotide sequence selected from the group consisting of: nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 1; the nucleotide sequence shown in SEQ ID NO: 1; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO : 3 ; the nucleotide sequence shown in SEQ ID NO: 3; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 5; the nucleotide sequence shown in SEQ ID NO: 5; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 6; the nucleotide sequence shown in SEQ ID NO: 6; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 7; the nucleotide sequence shown in SEQ ID NO: 7; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 8; the nucleotide sequence shown in SEQ ID NO: 8; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 10; and the nucleotide sequence shown in SEQ ID NO: 10. Binding of the test compound to the PLC delta- 1 product is detected. A test compound which binds to the PLC delta- 1 product is thereby identified as a potential agent for decreasing extracellular matrix degradation. Still another embodiment of the invention is a method of reducing extracellular matrix degradation. A cell is contacted with a reagent which specifically binds to a polynucleotide encoding a PLC delta- 1 polypeptide or the product encoded by the polynucleotide, wherein the polynucleotide comprises a nucleotide sequence selected from the group consisting of: nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 1; the nucleotide sequence shown in SEQ ID NO: 1; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 3; the nucleotide sequence shown in SEQ ID NO: 3; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 5; the nucleotide sequence shown in SEQ ID NO:5; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ LD NO: 6; the nucleotide sequence shown in SEQ ID NO: 6; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 7; the nucleotide sequence shown in SEQ ID NO: 7; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 8; the nucleotide sequence shown in SEQ ID NO: 8; nucleotide sequences which are at least about 50% identical to the nucleotide sequence shown in SEQ ID NO: 10; and the nucleotide sequence shown in SEQ ID NO: 10. PLC delta- 1 activity in the cell is thereby decreased. The invention thus provides reagents and methods for regulating human PLC delta- 1 which can be used ter alia, to treat COPD, congestive heart failure, hypertension, and cancer, and a variety of conditions in which signal transduction is impaired. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the DNA-sequence encoding a PLC delta- 1 polypeptide. Fig. 2 shows the amino acid sequence deduced from the DNA-sequence of Fig.1. Fig. 3 shows the DNA-sequence encoding a PLC delta- 1 polypeptide. Fig. 4 shows the amino acid sequence deduced from the DNA-sequence of Fig. 3. Fig. 5 shows the DNA-sequence encoding a PLC delta- 1 polypeptide. Fig. shows the DNA-sequence encoding a PLC delta- 1 polypeptide. Fig.7 shows the DNA-sequence encoding a PLC delta-1 polypeptide. Fig.8 shows the DNA-sequence encoding a PLC delta-1 polypeptide. Fig.9 shows the amino acid sequecne of a PLC delta-1 polypeptide. Fig.10 shows the DNA-sequence encoding a PLC delta-1 polypeptide. Fig.11 shows the amino acid sequence of the rat protein identified with SwissProt Accession No. P10688. Fig.12 shows the amino acid sequence of the rat protein identified with SwissProt Accssion No. P10688. Fig.l shows the BLASTP alignment of the PLC delta-1 polypeptide of Fig. 4 with the rat protein identified with SwissProt Accession No. PI 0688 of Fig. 11. The pleckstrin homology domain is indicated in bold. Fig.14 shows the HMMPFAM alignment of the PLC delta-1 polypeptide of Fig. 4 with pfam|hmm|PH of Fig. 12; PFAM is a large collection of multiple sequence alignments and hidden Markov models (HMM) covering many common protein domains. Fig.15 shows the tBLASTn alignment of the rat protein identified with SwissProt Accession No. P10688 of Fig. 12 with the PLC delta-1 polypeptide of Fig. 9. Fig.16 shows the relative expression of human PLC delta-1 in various human tissues. Fig.17 shows the relative expression of human PLC delta-1 in various human respiratory tissues and cells. Fig. 18 shows the amino acid sequence deduced from the DNA-sequence of Fig. 10. Fig. 19 shows the BLAST alignment of 101_ext_TRl against swiss /P51178/ PIP6_HUMAN. Fig. 20 shows the HMMPFAM alignment of 101_ext_TRl against pfam/hmm/PI- PLC-X. Fig.21 shows the HMMPFAM alignment of 101_ext_TRl against pfam/ rmm/PI- PLC-Y. Fig. 22 shows the HMMPFAM alignment of 101_ext_TRl against ρfam/hmm/C2. DETAILED DESCRIPTION OF THE INVENTION The invention relates to an isolated polynucleotide encoding a PLC delta-1 polypeptide and being selected from the group consisting of: a) a polynucleotide encoding a PLC delta-1 polypeptide comprising an amino acid sequence selected from the group consisting of: amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 2; the amino acid sequence shown in SEQ ID NO: 2; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 4; the amino acid sequence shown in SEQ ID NO:4; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 9; the amino acid sequence shown in SEQ ID NO: 9; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 13; and the amino acid sequence shown in SEQ ID NO: 13. b) a polynucleotide comprising the sequence of SEQ ID NOS: 1, 3, 5, 6, 7, 8 or 10; c) a polynucleotide which hybridizes under stringent conditions to a polynucleotide specified in (a) and (b); d) a polynucleotide the sequence of which deviates from the polynucleotide sequences specified in (a) to (c) due to the degeneration of the genetic code; and e) a polynucleotide which represents a fragment, derivative or allelic variation of a polynucleotide sequence specified in (a) to (d). Furthermore, it has been discovered by the present applicant that a novel l-phosphatidylinositol-4,5-bisphosphate phosphodiesterase delta 1 (PLC delta-1), particularly a human PLC delta-1, is a discovery of the present invention. Human PLC delta-1 is 43 % identical over 117 amino acids to the rat protein identified with SwissProt Accession No. P10688 (SEQ ID NO: 11) and annotated as a 1 -phosphatidylinositol- 4,5-bisphosphate phosphodiesterase delta 1 (Fig. 1). The SwissProt entry of PI 0688 (SEQ ID NO: 11) bears the following annotations: "Hydrolase; Lipid degradation; Transducer; Calcium-binding." The alignment of human PLC delta-1 with this rat homolog covers the pleckstrin homology (PH) domain, which is responsible for high affinity binding to PI3 or PIP2. Human PLC delta-1 thus is likely to be useful for the same purposes as previously identified PLC delta-1 proteins. Polypeptides PLC delta-1 polypeptides according to the invention comprise at least 25, 50, or 100 contiguous amino acids of SEQ ID NO:2 or a biologically active variant thereof, as defined below. A PLC delta-1 polypeptide of the invention therefore can be a portion of a PLC delta-1 molecule, a full-length PLC delta-1 molecule, or a fusion protein comprising all or a portion of a PLC delta-1 molecule. Biologically Active Variants PLC delta-1 variants which are biologically active, e.g.., retain a PLC delta-1 activity, also are PLC delta-1 polypeptides. Preferably, naturally or non-naturally occurring PLC delta-1 variants have amino acid sequences which are at least about 50, preferably about 75, 90, 96, or 98% identical to an amino acid sequence shown in SEQ ID NOS:2, 4, 9 or 13. Percent identity between a putative PLC delta-1 variant and an amino acid sequence of SEQ ID NO: 2, 4, or 9 is determined using the Needleman and Wunsch algorithm (Needleman and Wunsch, J.Mol. Biol. 48; 443- 453, 1970) with the substitution-matrix BLOSUM62 (S. Henikoff and J.G. Henikoff, Proc. Natl. Acad. Sci. USA 89:10915-10919, 1992) using a gap creation penalty" of 8 and a gap extension penalty of 2. Variations in percent identity can be due, for example, to amino acid substitutions, insertions, or deletions. Amino acid substitutions are defined as one for one amino acid replacements. They are conservative in nature when the substituted amino acid has similar structural and/or chemical properties. Examples of conservative replacements are substitution of a leucine with an isoleucine or valine, an aspartate with a glutamate, or a threonine with a serine. Amino acid insertions or deletions are changes to or within an amino acid sequence. They typically fall in the range of about 1 to 5 amino acids. Guidance in determining which amino acid residues can be substituted, inserted, or deleted without abolishing biological or immunological activity can be found using computer programs well known in the art, such as DNASTAR software. Whether an amino acid change results in a biologically active PLC delta-1 polypeptide can readily be determined by assaying for fibronectin binding or for PLC delta-1 activity, as is known in the art and described, for example, in the specific examples below. Fusion Proteins Fusion proteins are useful for generating antibodies against PLC delta-1 amino acid sequences and for use in various assay systems. For example, fusion proteins can be used to identify proteins which interact with portions of a PLC delta-1 polypeptide, including its active site and fibronectin domains. Methods such as protein affinity chromatography or library-based assays for protein-protein interactions, such as the yeast two-hybrid or phage display systems, can be used for this purpose. Such methods are well known in the art and also can be used as drug screens. A PLC delta-1 fusion protein comprises two protein segments fused together by means of a peptide bond. Contiguous amino acids for use in a fusion protein can be selected from the amino acid sequences shown in SEQ ID NO:2, 4, 9 or 13 or from a biologically active variant thereof, such as those described above. For example, the first protein segment can comprise at least 25, 50, or 100 contiguous amino acids of SEQ ID NO:2 or a biologically active variant thereof. Preferably, a fusion protein comprises the active site of the PLC delta-1 or the pleckstrin domain shown in FIG. 1. The first protein segment also can comprise full-length PLC delta-1. The second protein segment can be a full-length protein or a protein fragment or polypeptide. Proteins commonly used in fusion protein construction include β- galactosidase, β-glucuronidase, green fluorescent protein (GFP), autofluorescent proteins, including blue fluorescent protein (BFP), glutathione-S ransferase (GST), luciferase, horseradish peroxidase (HRP), and chloramphenicol acetyltransferase (CAT). Additionally, epitope tags are used in fusion protein constructions, including histidine (His) tags, FLAG tags, influenza hemagglutinin (HA) tags, Myc tags, VSV- G tags, and thioredoxin (Trx) tags. Other fusion constructions can include maltose binding protein (MBP), S-tag, Lex a DNA binding domain (DBD) fusions, GAL4 DNA binding domain fusions, and herpes simplex virus (HSV) BP16 protein fusions. A fusion protein also can be engineered to contain a cleavage site located between the PLC delta-1 polypeptide-encoding sequence and the heterologous protein sequence, so that the PLC delta-1 polypeptide can be cleaved and purified away from the heterologous moiety. A fusion protein can be synthesized chemically, as is known in the art. Preferably, a fusion protein is produced by covalently linking two protein segments or by standard procedures in the art of molecular biology. Recombinant DNA methods can be used to prepare fusion proteins, for example, by making a DNA construct which comprises PLC delta-1 coding sequences disclosed herein in proper reading frame with nucleotides encoding the second protein segment and expressing the DNA construct in a host cell, as is known in the art. Many kits for constructing fusion proteins are available from companies such as Promega Corporation (Madison, WI), Stratagene (La Jolla, CA), CLONTECH (Mountain View, CA), Santa Cruz Biotechnology (Santa Cruz, CA), MBL International Corporation (MIC; Watertown, MA), and Quantum Biotechnologies (Montreal, Canada; 1-888-DNA-KITS). Identification of Species Homologs Species homologs of human PLC delta-1 can be obtained using PLC delta-1 polynucleotides (described below) to make suitable probes or primers to screening cDNA expression libraries from other species, such as mice, monkeys, or yeast, identifying cDNAs which encode homologs of PLC delta-1, and expressing the cDNAs as is known in the art. Polynucleotides A PLC delta-1 polynucleotide can be single- or double-stranded and comprises a coding sequence or the complement of a coding sequence for a PLC delta-1 polypeptide. A nucleotide sequence encoding the human PLC delta-1 polypeptide shown in SEQ ID NO:13 is shown in SEQ ID NO:10. Degenerate nucleotide sequences encoding human PLC delta-1 polypeptides, as well as homologous nucleotide sequences which are at least about 50, preferably about 75, 90, 96, or 98%) identical to the PLC delta-1 coding sequences nucleotide sequence shown in SEQ ID NO: 10 also are PLC delta-1 polynucleotides. Percent sequence identity between the sequences of two polynucleotides is determined using computer programs such as ALIGN which employ the FASTA algorithm, using an affine gap search with a gap open penalty of -12 and a gap extension penalty of -2. Complementary DNA (cDNA) molecules, species homologs, and variants of PLC delta-1 polynucleotides which encode biologically active PLC delta-1 polypeptides also are PLC delta-1 polynucleotides. Identification of Variants and Homologs Variants and homologs of the PLC delta-1 polynucleotides disclosed above also are PLC delta-1 polynucleotides. Typically, homologous PLC delta-1 polynucleotide sequences can be identified by hybridization of candidate polynucleotides to known PLC delta-1 polynucleotides under stringent conditions, as is known in the art. For example, using the following wash conditions~2X SSC (0.3 M NaCl, 0.03 M sodium citrate, pH 7.0), 0.1% SDS, room temperature twice, 30 minutes each; then 2X SSC, 0.1% SDS, 50 °C once, 30 minutes; then 2X SSC, room temperature twice, 10 minutes each— homologous sequences can be identified which contain at most about 25-30% basepair mismatches. More preferably, homologous nucleic acid strands contain 15-25% basepair mismatches, even more preferably 5-15% basepair mismatches. Species homologs of the PLC delta-1 polynucleotides disclosed herein can be identified by making suitable probes or primers and screening cDNA expression libraries from other species, such as mice, monkeys, or yeast. Human variants of PLC delta-1 polynucleotides can be identified, for example, by screening human cDNA expression libraries. It is well known that the T m of a double-stranded DNA decreases by 1-1.5 °C with every 1% decrease in homology (Bonner et al, J. Mol. Biol 81, 123 (1973). Variants of human PLC delta-1 polynucleotides or PLC delta-1 polynucleotides of other species can therefore be identified, for example, by hybridizing a putative homologous PLC delta-1 polynucleotide with a polynucleotide having a nucleotide sequence of SEQ ID NO:l, 5, or 7 or the complement of SEQ ID NO:3 to form a test hybrid. The melting temperature of the test hybrid is compared with the melting temperature of a hybrid comprising PLC delta-1 polynucleotides having perfectly complementary nucleotide sequences, and the number or percent of basepair mismatches within the test hybrid is calculated. Nucleotide sequences which hybridize to PLC delta-1 polynucleotides or their complements following stringent hybridization and/or wash conditions are also PLC delta-1 polynucleotides. Stringent wash conditions are well known and understood in the art and are disclosed, for example, in Sambrook et al, MOLECULAR CLONING: A LABORATORY MANUAL, 2d ed., 1989, at pages 9.50-9.51. Typically, for stringent hybridization conditions a combination of temperature and salt concentration should be chosen that is approximately 12-20 °C below the calculated T m of the hybrid under study. The T m of a hybrid between a PLC delta-1 polynucleotide having a coding sequence disclosed herein and a polynucleotide se- quence which is at least about 50, preferably about 75, 90, 96, or 98% identical to that nucleotide sequence can be calculated, for example, using the equation of Bolton and McCarthy, Proc. Natl Acad. Sci. U.S.A. 48, 1390 (1962): T m - 81.5 °C - 16.6(log 10 [Na + ]) + 0.41(%G + C) - 0.63(%formamide) - 600/1), where / = the length of the hybrid in basepairs. Stringent wash conditions include, for example, 4X SSC at 65 °C, or 50% formamide, 4X SSC at 42 °C, or 0.5X SSC, 0.1% SDS at 65 °C. Highly stringent wash conditions include, for example, 0.2X SSC at 65 °C. Preparation of Polynucleotides A naturally occurring PLC delta-1 polynucleotide can be isolated free of other cellular components such as membrane components, proteins, and lipids. Polynucleotides can be made by a cell and isolated using standard nucleic acid purification techniques, synthesized using an amplification technique, such as the polymerase chain reaction (PCR), or synthesized using an automatic synthesizer. Methods for isolating polynucleotides are routine and are known in the art. Any such technique for obtaining a polynucleotide can be used to obtain isolated PLC delta-1 polynucleotides. For example, restriction enzymes and probes can be used to isolate polynucleotide fragments which comprise PLC delta-1 nucleotide sequences. Isolated polynucleotides are in preparations which are free or at least 70, 80, or 90% free of other molecules. PLC delta-1 cDNA molecules can be made with standard molecular biology techniques, using PLC delta-1 mRNA as a template. PLC delta-1 cDNA molecules can thereafter be replicated using molecular biology techniques known in the art and disclosed in manuals such as Sambrook et al. (1989). An amplification technique, such as PCR, can be used to obtain additional copies of PLC delta-1 polynucleotides, using either human genomic DNA or cDNA as a template. Alternatively, synthetic chemistry techniques can be used to synthesize PLC delta-1 polynucleotides. The degeneracy of the genetic code allows alternate nucleotide sequences to be synthesized which will encode a PLC delta-1 polypeptide having, for example, the amino acid sequence shown in SEQ ID NO:2 or 13 or a biologically active variant thereof. Obtaining Full-Length Polynucleotides The partial sequences of SEQ ID NOS.T, 3, and 5-8 or their complements can be used to identify the corresponding full length gene from which they were derived. The partial sequences can be nick-translated or end-labeled with 32 P using polynucleotide kinase using labeling methods known to those with skill in the art (BASIC METHODS IN MOLECULAR BIOLOGY, Davis et al, eds., Elsevier Press, N.Y., 1986). A lambda library prepared from human tissue can be directly screened with the labeled sequences of interest or the library can be converted en masse to pBluescript (Stratagene Cloning Systems, La Jolla, Calif. 92037) to facilitate bacterial colony screening (see Sambrook et al, 19.89, pg. 1.20). Both methods are well known in the art. Briefly, filters with bacterial colonies containing the library in pBluescript or bacterial lawns containing lambda plaques are denatured, and the DNA is fixed to the filters. The filters are hybridized with the labeled probe using hybridization conditions described by Davis et al, 1986. The partial sequences, cloned into lambda or pBluescript, can be used as positive controls to assess background binding and to adjust the hybridization and washing stringencies necessary for accurate clone identification. The resulting autoradiograms are compared to duplicate plates of colonies or plaques; each exposed spot corresponds to a positive colony or plaque. The colonies or plaques are selected and expanded, and the DNA is isolated from the colonies for further analysis and sequencing. Positive cDNA clones are analyzed to determine the amount of additional sequence they contain using PCR with one primer from the partial sequence and the other primer from the vector. Clones with a larger vector-insert PCR product than the original partial sequence are analyzed by restriction digestion and DNA sequencing to determine whether they contain an insert of the same size or similar as the mRNA size determined from Northern blot Analysis. Once one or more overlapping cDNA clones are identified, the complete sequence of the clones can be determined, for example after exonuclease III digestion (McCombie et al, Methods 3, 33-40, 1991). A series of deletion clones are generated, each of which is sequenced. The resulting overlapping sequences are assembled into a single contiguous sequence of high redundancy (usually three to five overlapping sequences at each nucleotide position), resulting in a highly accurate final sequence. Various PCR-based methods can be used to extend the nucleic acid sequences encoding the disclosed portions of human PLC delta-1 to detect upstream sequences such as promoters and regulatory elements. For example, restriction-site PCR uses universal primers to retrieve unknown sequence adjacent to a known locus (Sarkar, PCR Methods Applic. 2, 318-322, 1993). Genomic DNA is first amplified in the presence of a primer to a linker sequence and a primer specific to the known region. The amplified sequences are then subjected to a second round of PCR with the same linker primer and another specific primer internal to the first one. Products of each round of PCR are transcribed with an appropriate RNA polymerase and sequenced using reverse transcriptase. Inverse PCR also can be used to amplify or extend sequences using divergent primers based on a known region (Triglia et al, Nucleic Acids Res. 16, 8186, 1988). Primers can be designed using commercially available software, such as OLIGO 4.06 Primer Analysis software (National Biosciences Inc., Plymouth, Minn.), to be 22-30 nucleotides in length, to have a GC content of 50% or more, and to anneal to the target sequence at temperatures about 68 - 72 °C. The method uses several restriction enzymes to generate a suitable fragment in the known region of a gene. The fragment is then circularized by intramolecular ligation and used as a PCR template. Another method which can be used is capture PCR, which involves PCR amplification of DNA fragments adjacent to a known sequence in human and yeast artificial chromosome DNA (Lagerstrom et al, PCR Methods Applic. 1, 111-119, 1991). In this method, multiple restriction enzyme digestions and ligations are used to place an engineered double-stranded sequence into an unknown fragment of the DNA molecule before performing PCR. Another method which can be used to retrieve unknown sequences is that of Parker et al, Nucleic Acids Res. 19, 3055-3060, 1991. Additionally, PCR, nested primers, and PROMOTERFINDER libraries (CLONTECH, Palo Alto, Calif.) can be used to walk genomic DNA. This process avoids the need to screen libraries and is useful in finding intron/exon junctions. When screening for full-length cDNAs, it is preferable to use libraries that have been size-selected to include larger cDNAs. Also, random-primed libraries are preferable, in that they will contain more sequences which contain the 5' regions of genes. Use of a randomly primed library may be especially preferable for situations in which an oligo d(T) library does not yield a full-length cDNA. Genomic libraries can be useful for extension of sequence into 5' non-transcribed regulatory regions. Commercially available capillary electrophoresis systems can be used to analyze the size or confirm the nucleotide sequence of PCR or sequencing products. For example, capillary sequencing can employ flowable polymers for electrophoretic separation, four different fluorescent dyes (one for each nucleotide) which are laser activated, and detection of the emitted wavelengths by a charge coupled device camera. Output/light intensity can be converted to electrical signal using appropriate software (e.g. GENOTYPER and Sequence NAVIGATOR, Perkin Elmer), and the entire process from loading of samples to computer analysis and electronic data display can be computer controlled. Capillary electrophoresis is especially preferable for the sequencing of small pieces of DNA which might be present in limited amounts in a particular sample. Obtaining Polypeptides PLC delta-1 polypeptides can be obtained, for example, by purification from human cells, by expression of PLC delta-1 polynucleotides, or by direct chemical synthesis. Protein Purification PLC delta-1 polypeptides can be purified from cells, including cells which have been transfected with PLC delta-1 expression constructs. Senescent fibroblasts, colon, and brain anaplastic oligodendroglioma are especially useful sources of PLC delta-1 polypeptides. A purified PLC delta-1 polypeptide is separated from other compounds which normally associate with the PLC delta-1 polypeptide in the cell, such as certain proteins, carbohydrates, or lipids, using methods well-known in the art. Such methods include, but are not limited to, size exclusion chromatography, ammonium sulfate fractionation, ion exchange chromatography, affinity chromatography, and preparative gel electrophoresis. A preparation of purified PLC delta-1 polypeptides is at least 80% pure; preferably, the preparations are 90%, 95%, or 99% pure. Purity of the preparations can be assessed by any means known in the art, such as SDS-polyacrylamide gel electrophoresis. Enzymatic activity of the purified preparations can be assayed, for example, as described in the specific examples, below. Expression of Polynucleotides To express a PLC delta-1 polypeptide, a PLC delta-1 polynucleotide can be inserted into an expression vector which contains the necessary elements for the transcription and translation of the inserted coding sequence. Methods which are well known to those skilled in the art can be used to construct expression vectors containing sequences encoding PLC delta-1 polypeptides and appropriate transcriptional and translational control elements. These methods include in vitro recombinant DNA techniques, synthetic techniques, and in vivo genetic recombination. Such techniques are described, for example, in Sambrook et al. (1989) and Ausubel et al, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, New York, N.Y, 1989. A variety of expression vector/host systems can be utilized to contain and express sequences encoding a PLC delta-1 polypeptide. These include, but are not limited to, microorganisms, such as bacteria transformed with recombinant bacteriophage, plasmid, or cosmid DNA expression vectors; yeast transformed with yeast expression vectors, insect cell systems infected with virus expression vectors (e.g., baculovirus), plant cell systems transformed with virus expression vectors (e.g., cauliflower mosaic virus, CaMV; tobacco mosaic virus, TMV) or with bacterial expression vectors (e.g., Ti or pBR322 plasmids), or animal cell systems. The control elements or regulatory sequences are those non-translated regions of the vector — enhancers, promoters, 5' and 3' untranslated regions — which interact with host cellular proteins to carry out transcription and translation. Such elements can vary in their strength and specificity. Depending on the vector system and host utilized, any number of suitable transcription and translation elements, including constitutive and inducible promoters, can be used. For example, when cloning in bacterial systems, inducible promoters such as the hybrid lacZ promoter of the BLUESCRIPT phagemid (Stratagene, LaJolla, Calif.) or pSPORTl plasmid (Life Technologies) and the like can be used. The baculovirus polyhedrin promoter can be used in insect cells. Promoters or enhancers derived from the genomes of plant cells (e.g., heat shock, RUBISCO, and storage protein genes) or from plant viruses (e.g., viral promoters or leader sequences) can be cloned into the vector. In mam- malian cell systems, promoters from mammalian genes or from mammalian viruses are preferable. If it is necessary to generate a cell line that contains multiple copies of a nucleotide sequence encoding a PLC delta-1 polypeptide, vectors based on SV40 or EBV can be used with an appropriate selectable marker. Bacterial and Yeast Expression Systems In bacterial systems, a number of expression vectors can be selected depending upon the use intended for the PLC delta-1 polypeptide. For example, when a large quantity of a PLC delta-1 polypeptide is needed for the induction of antibodies, vectors which direct high level expression of fusion proteins that are readily purified can be used. Such vectors include, but are not limited to, multifunctional E. coli cloning and expression vectors such as BLUES CREPT (Stratagene), in which the sequence encoding the PLC delta-1 polypeptide can be ligated into the vector in frame with sequences for the amino-terminal Met and the subsequent 7 residues of β- galactosidase so that a hybrid protein is produced. pLN vectors (Van Heeke & Schuster, J. Biol. Chem. 264, 5503-5509, 1989 or pGEX vectors (Promega, Madison, Wis.) can be used to express foreign polypeptides as fusion proteins with glutathione S-transferase (GST). In general, such fusion proteins are soluble and can easily be purified from lysed cells by adsorption to glutathione-agarose beads followed by elution in the presence of free glutathione. Proteins made in such systems can be designed to include heparin, thrombin, or Factor Xa protease cleavage sites so that the cloned polypeptide of interest can be released from the GST moiety at will. In the yeast Saccharomyces cerevisiae, a number of vectors containing constitutive or inducible promoters such as alpha factor, alcohol oxidase, and PGH can be used. For reviews, see Ausubel et al. (1989) and Grant et al, Methods Enzymol. 153, 516-544, 1987. Plant and Insect Expression Systems If plant expression vectors are used, the expression of sequences encoding PLC delta- 1 polypeptides can be driven by any of a number of promoters. For example, viral promoters such as the 35S and 19S promoters of CaMV can be used alone or in combination with the omega leader sequence from TMV (Takamatsu EMBO J. 6, 307-311, 1987). Alternatively, plant promoters such as the small subunit of RUBISCO or heat shock promoters can be used (Coruzzi et al, EMBO J. 3, 1671-1680, 1984; Broglie et al, Science 224, 838-843, 1984; Winter et al, Results Probl. Cell Differ. 17, 85-105, 1991). These constructs can be introduced into plant cells by direct DNA transformation or by pathogen-mediated transfection. Such techniques are described in a number of generally available reviews (see, for example, Hobbs or Murray, in MCGRAW HILL YEARBOOK OF SCIENCE AND TECHNOLOGY, McGraw Hill, New York, N.Y., pp. 191-196, 1992). An insect system also can be used to express a PLC delta-1 polypeptide. For example, in one such system Autographa californica nuclear polyhedrosis virus (AcNPV) is used as a vector to express foreign genes in Spodoptera frugiperda cells or in Trichoplusia larvae. Sequences encoding PLC delta-1 polypeptides can be cloned into a non-essential region of the virus, such as the polyhedrin gene, and placed under control of the polyhedrin promoter. Successful insertion of PLC delta-1 polypeptides will render the polyhedrin gene inactive and produce recombinant virus lacking coat protein. The recombinant viruses can then be used to infect, for example, &. frugiperda cells or Trichoplusia larvae in which PLC delta-1 polypeptides can be expressed (Engelhard et al, Proc. Nat. Acad. Sci. 91, 3224-3227, 1994). Mammalian Expression Systems A number of viral-based expression systems can be utilized in mammalian host cells. For example, if an adenovirus is used as an expression vector, sequences encoding PLC delta-1 polypeptides can be ligated into an adenovirus transcription/translation complex consisting of the late promoter and tripartite leader sequence. Insertion in a non-essential El or E3 region of the viral genome can be used to obtain a viable virus which is capable of expressing a PLC delta-1 polypeptide in infected host cells (Logan & Shenk, Proc. Natl Acad. Sci. 81, 3655-3659, 1984). In addition, transcription enhancers, such as the Rous sarcoma virus (RSV) enhancer, can be used to increase expression in mammalian host cells. Human artificial chromosomes (HACs) also can be used to deliver larger fragments of DNA than can be contained and expressed in a plasmid. HACs of 6M to 10M are constructed and delivered to cells via conventional delivery methods (e.g., liposomes, polycationic amino polymers, or vesicles). Specific initiation signals also can be used to achieve more efficient translation of sequences encoding PLC delta-1 polypeptides. Such signals include the ATG initiation codon and adjacent sequences. In cases where sequences encoding a PLC delta-1 polypeptide, its initiation codon, and upstream sequences are inserted into the appropriate expression vector, no additional transcriptional or translational control signals may be needed. However, in cases where only coding sequence, or a fragment thereof, is inserted, exogenous translational control signals (including the ATG initiation codon) should be provided. The initiation codon should be in the correct reading frame to ensure translation of the entire insert. Exogenous translational elements and initiation codons can be of various origins, both natural and synthetic. The efficiency of expression can be enhanced by the inclusion of enhancers which are appropriate for the particular cell system which is used (see Sc arf et al, Results Probl. Cell Differ. 20, 125-162, 1994). Host Cells A host cell strain can be chosen for its ability to modulate the expression of the inserted sequences or to process an expressed PLC delta-1 polypeptide in the desired fashion. Such modifications of the polypeptide include, but are not limited to, acetylation, carboxylation, glycosylation, phosphorylation, lipidation, and acylation. Post-translational processing which cleaves a "prepro" form of the polypeptide also can be used to facilitate correct insertion, folding and/or function. Different host cells which have specific cellular machinery and characteristic mechanisms for post-translational activities (e.g., CHO, HeLa, MDCK, HEK293, and WI38), are available from the American Type Culture Collection (ATCC; 10801 University Boulevard, Manassas, VA 20110-2209) and can be chosen to ensure the correct modification and processing of the foreign protein. Stable expression is preferred for long-term, high-yield production of recombinant proteins. For example, cell lines which stably express PLC delta-1 polypeptides can be transformed using expression vectors which can contain viral origins of replication and/or endogenous expression elements and a selectable marker, gene on the same or on a separate vector. Following the introduction of the vector, cells can be allowed to grow for 1-2 days in an enriched medium before they are switched to a selective medium. The purpose of the selectable marker is to confer resistance to selection, and its presence allows growth and recovery of cells which successfully express the introduced PLC delta-1 sequences. Resistant clones of stably transformed cells can be proliferated using tissue culture techniques appropriate to the cell type. Any number of selection systems can be used to recover transformed cell lines. These include, but are not limited to, the herpes simplex virus thymidme kinase (Wigler et al, Cell 11, 223-32, 1977) and adenine phosphoribosyltransferase (Lowy et al, Cell 22, 817-23, 1980). Genes which can be employed in tk ~ or aprf cells, respectively. Also, antimetabolite, antibiotic, or herbicide resistance can be used as the basis for selection. For example, dhfr confers resistance to methotrexate (Wigler et al, Proc. Natl. Acad. Sci. 77, 3567-70, 1980); npt confers resistance to the amino- glycosides, neomycin and G-418 (Colbere-Garapin et al, J. Mol Biol. 150, 1-14, 1981); and als and pat confer resistance to chlorsulfuron and phosphinotricin acetyl- transferase, respectively (Murray, 1992 supra). Additional selectable genes have been described, for example trpB, which allows cells to utilize indole in place of tryptophan, or hisD, which allows cells to utilize histinol in place of histidine (Hartman & Mulligan, Proc. Natl. Acad. Sci. 85, 8047-51, 1988). Visible markers such as anthocyanins, β-glucuronidase and its substrate GUS, and luciferase and its substrate luciferin, can be used to identify transformants and to quantify the amount of transient or stable protein expression attributable to a specific vector system (Rhodes et al, Methods Mol. Biol. 55, 121-131, 1995). Detecting Expression of Polypeptides Although the presence of marker gene expression suggests that the PLC delta-1 polynucleotide is also present, its presence and expression may need to be confirmed. For example, if a sequence encoding a PLC delta-1 polypeptide is inserted within a marker gene sequence, transformed cells containing sequences which encode a PLC delta-1 polypeptide can be identified by the absence of marker gene function. Alternatively, a marker gene can be placed in tandem with a sequence encoding a PLC delta-1 polypeptide under the control of a single promoter. Expression of the marker gene in response to induction or selection usually indicates expression of the PLC delta-1 polynucleotide. Alternatively, host cells which contain a PLC delta-1 polynucleotide and which express a PLC delta-1 polypeptide can be identified by a variety of procedures known to those of skill in the art. These procedures include, but are not limited to, DNA-DNA or DNA-RNA hybridizations and protein bioassay or immunoassay techniques which include membrane, solution, or chip-based technologies for the detection and/or quantification of nucleic acid or protein. The presence of a polynucleotide sequence encoding a PLC delta-1 polypeptide can be detected by DNA-DNA or DNA-RNA hybridization or amplification using probes or fragments or fragments of polynucleotides encoding a PLC delta-1 polypeptide. Nucleic acid amplification-based assays involve the use of oligonucleotides selected from sequences encoding a PLC delta-1 polypeptide to detect transformants which contain a PLC delta-1 polynucleotide. A variety of protocols for detecting and measuring the expression of a PLC delta-1 polypeptide, using either polyclonal or monoclonal antibodies specific for the polypeptide, are known in the art. Examples include enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and fluorescence activated cell sorting (FACS). A two-site, monoclonal-based immunoassay using monoclonal antibodies reactive to two non-interfering epitopes on a PLC delta-1 polypeptide can be used, or a competitive binding assay can be employed. These and other assays are described in Hampton et al, SEROLOGICAL METHODS: A LABORATORY MANUAL, APS Press, St. Paul, Minn., 1990) and Maddox et al, J. Exp. Med. 158, 1211-1216, 1983). A wide variety of labels and conjugation techniques are known by those skilled in the art and can be used in various nucleic acid and amino acid assays. Means for producing labeled hybridization or PCR probes for detecting sequences related to polynucleotides encoding PLC delta-1 polypeptides include oligolabeling, nick trans- lation, end-labeling, or PCR amplification using a labeled nucleotide. Alternatively, sequences encoding a PLC delta-1 polypeptide can be cloned into a vector for the production of an mRNA probe. Such vectors are known in the art, are commercially available, and can be used to synthesize RNA probes in vitro by addition of labeled nucleotides and an appropriate RNA polymerase, such as T7, T3, or SP6. These procedures can be conducted using a variety of commercially available kits (Amersham Pharmacia Biotech, Promega, and US Biochemical). Suitable reporter molecules or labels which can be used for ease of detection include radionuclides, enzymes, fluorescent, chemiluminescent, or chromogenic agents, as well as substrates, cofactors, inhibitors, magnetic particles, and the like. Expression and Purification of Polypeptides Host cells transformed with nucleotide sequences encoding a PLC delta-1 polypeptide can be cultured under conditions suitable for the expression and recovery of the protein from cell culture. The polypeptide produced by a transformed cell can be secreted or contained intracellularly depending on the sequence and/or the vector used. As will be understood by those of skill in the art, expression vectors containing polynucleotides which encode PLC delta-1 polypeptides can be designed to contain signal sequences which direct secretion of PLC delta-1 polypeptides through a prokaryotic or eukaryotic cell membrane. Other constructions can be used to join a sequence encoding a PLC delta-1 polypeptide to a nucleotide sequence encoding a polypeptide domain which will facilitate purification of soluble proteins. Such purification facilitating domains include, but are not limited to, metal chelating peptides such as histidine-tryptophan modules that allow purification on immobilized metals, protein A domains that allow purification on immobilized immunoglobulin, and the domain utilized in the FLAGS extension/affinity purification system (Immunex Corp., Seattle, Wash.). The inclusion of cleavable linker sequences such as those specific for Factor Xa or entero- kinase (Invitrogen, San Diego, CA) between the purification domain and the PLC delta-1 polypeptide can be used to facilitate purification. One such expression vector provides for expression of a fusion protein containing a PLC delta-1 polypeptide and 6 histidine residues preceding a thioredoxin or an enterokinase cleavage site. The histidine residues facilitate purification on IMAC (immobilized metal ion affinity chromatography as described in Porath et al, Prot. Exp. Purif 3, 263-281, 1992), while the enterokinase cleavage site provides a means for purifying the PLC delta-1 polypeptide from the fusion protein. Vectors which contain fusion proteins are disclosed in Kroll et al, DNA Cell Biol. 12, 441-453, 1993). Chemical Synthesis Sequences encoding a PLC delta-1 polypeptide can be synthesized, in whole or in part, using chemical methods well known in the art (see Caruthers et al, Nucl. Acids Res. Symp. Ser. 215-223, 1980; Horn et al. Nucl. Acids Res. Symp. Ser. 225-232, 1980). Alternatively, a PLC delta-1 polypeptide itself can be produced using chemical methods to synthesize its amino acid sequence. For example, PLC delta-1 polypeptides can be produced by direct peptide synthesis using solid-phase techniques (Merrifield, J Am. Chem. Soc. 85, 2149-2154, 1963; Roberge et al, Science 269, 202-204, 1995). Protein synthesis can be performed using manual techniques or by automation. Automated synthesis can be achieved, for example, using Applied Biosystems 431 A Peptide Synthesizer (Perkin Elmer). Various fragments of PLC delta-1 polypeptides can be separately synthesized and combined using chemical methods to produce a full-length molecule. The newly synthesized peptide can be substantially purified by preparative high per- formance liquid chromatography (e.g., Creighton, PROTEINS: STRUCTURES AND MOLECULAR PRINCIPLES, WH Freeman and Co., New York, N.Y., 1983). The composition of a synthetic PLC delta-1 polypeptide can be confirmed by amino acid analysis or sequencing (e.g., the Edman degradation procedure; see Creighton, supra). Additionally, any portion of the amino acid sequence of the PLC delta-1 polypeptide can be altered during direct synthesis and/or combined using chemical methods with sequences from other proteins to produce a variant polypeptide or a fusion protein. Production of Altered Polypeptides As will be understood by those of skill in the art, it may be advantageous to produce PLC delta-1 polypeptide-encoding nucleotide sequences possessing non-naturally occurring codons. For example, codons preferred by a particular prokaryotic or eukaryotic host can be selected to increase the rate of protein expression or to produce an RNA transcript having desirable properties, such as a half-life which is longer than that of a transcript generated from the naturally occurring sequence. The nucleotide sequences disclosed herein can be engineered using methods generally known in the art to alter PLC delta-1 polypeptide-encoding sequences for a variety of reasons, including modification of the cloning, processing, and/or expression of the gene product. DNA shuffling by random fragmentation and PCR reassembly of gene fragments and synthetic oligonucleotides can be used to engineer the nucleotide sequences. For example, site-directed mutagenesis can be used to insert new restriction sites, alter glycosylation patterns, change codon preference, produce splice variants, introduce mutations, and so forth. Antibodies Any type of antibody known in the art can be generated to bind specifically to an epitope of a PLC delta-1 polypeptide. "Antibody" as used herein includes intact immunoglobulin molecules, as well as fragments thereof, such as Fab, F(ab') 2 , and Fv, which are capable of binding an epitope of a PLC delta-1 polypeptide. Typically, at least 6, 8, 10, or 12 contiguous amino acids are required to form an epitope. However, epitopes which involve non-contiguous amino acids may require more, e.g., at least 15, 25, or 50 amino acids. An antibody which specifically binds to an epitope of a PLC delta-1 polypeptide can be used therapeutically, as well as in immunochemical assays, including but not limited to Western blots, ELISAs, radioimmunoassays, immunohistochemical assays, immunoprecipitations, or other immunochemical assays known in the art. Various immunoassays can be used to identify antibodies having the desired specificity. Numerous protocols for competitive binding or immunoradiometric assays are well known in the art. Such immunoassays typically involve the measurement of complex formation between an immunogen and an antibody which specifically binds to the immunogen. Typically, an antibody which specifically binds to a PLC delta-1 polypeptide provides a detection signal at least 5-, 10-, or 20-fold higher than a detection signal provided with other proteins when used in an immunochemical assay. Preferably, antibodies which specifically bind to PLC delta-1 polypeptides do not detect other proteins in immunochemical assays and can immunoprecipitate a PLC delta-1 polypeptide from solution. PLC delta-1 polypeptides can be used to immunize a mammal, such as a mouse, rat, rabbit, guinea pig, monkey, or human, to produce polyclonal antibodies. If desired, a PLC delta-1 polypeptide can be conjugated to a carrier protein, such as bovine serum albumin, thyroglobulin, and keyhole limpet hemocyanin. Depending on the host species, various adjuvants can be used to increase the immunological response. Such adjuvants include, but are not limited to, Freund's adjuvant, mineral gels (e.g., aluminum hydroxide), and surface active substances (e.g. lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanin, and dinitrophenol). Among adjuvants used in humans, BCG (bacilli Calmette-Guerin) and Corynebacterium parvum are especially useful. Monoclonal antibodies which specifically bind to a PLC delta-1 polypeptide can be prepared using any technique which provides for the production of antibody molecules by continuous cell lines in culture. These techniques include, but are not limited to, the hybridoma technique, the human B-cell hybridoma technique, and the EBV-hybridoma technique (Kohler et al, Nature 256, 495-497, 1985; Kozbor et al, J. Immunol. Methods 81, 31-42, 1985; Cote et al, Proc. Natl. Acad. Sci. 80, 2026-2030, 1983; Cole et al, Mol. Cell Biol. 62, 109-120, 1984). In addition, techniques developed for the production of "chimeric antibodies," the splicing of mouse antibody genes to human antibody genes to obtain a molecule with appropriate antigen specificity and biological activity, can be used (Morrison et al, Proc. Natl. Acad. Sci. 81, 6851-6855, 1984; Neuberger et al, Nature 312, 604-608, 1984; Takeda et al, Nature 314, 452-454, 1985). Monoclonal and other antibodies also can be "humanized" to prevent a patient from mounting an immune response against the antibody when it is used therapeutically. Such antibodies may be sufficiently similar in sequence to human antibodies to be used directly in therapy or may require alteration of a few key residues. Sequence differences between rodent anti- bodies and human sequences can be minimized by replacing residues which differ from those in the human sequences by site directed mutagenesis of individual residues or by grating of entire complementarity determining regions. Alternatively, one can produce humanized antibodies using recombinant methods, as described in GB2188638B. Antibodies which specifically bind to a PLC delta-1 polypeptide can contain antigen binding sites which are either partially or fully humanized, as disclosed in U.S. 5,565,332. Alternatively, techniques described for the production of single chain antibodies can be adapted using methods known in the art to produce single chain antibodies which specifically bind to PLC delta-1 polypeptides. Antibodies with related specificity, but of distinct idiotypic composition, can be generated by chain shuffling from random combinatorial immunoglobin libraries (Burton, Proc. Natl. Acad. Sci. 88, 11120-23, 1991). Single-chain antibodies also can be constructed using a DNA amplification method, such as PCR, using hybridoma cDNA as a template (Thirion et al, 1996, Eur. J. Cancer Prev. 5, 507-11). Single-chain antibodies can be mono- or bispecific, and can be bivalent or tetravalent. Construction of tetravalent, bispecific single-chain antibodies is taught, for example, in Coloma & Morrison, 1997, Nat. Biotechnol. 15, 159-63. Construction of bivalent, bispecific single-chain antibodies is taught in Mallender & Voss, 1994, J Biol. Chem. 269, 199-206. A nucleotide sequence encoding a single-chain antibody can be constructed using manual or automated nucleotide synthesis, cloned into an expression construct using standard recombinant DNA methods, and introduced into a cell to express the coding sequence, as described below. Alternatively, single-chain antibodies can be produced directly using, for example, filamentous phage technology. Verhaar et al, 1995, Int. J. Cancer 61, 497-501; Nicholls et al, 1993, J Immunol. Meth. 165, 81- 91. Antibodies which specifically bind to PLC delta-1 polypeptides also can be produced by inducing in vivo production in the lymphocyte population or by screening immunoglobulin libraries or panels of highly specific binding reagents as disclosed in the literature (Orlandi et al, Proc. Natl. Acad. Sci. 86, 3833-3837, 1989; Winter et al, Nature 349, 293-299, 1991). Other types of antibodies can be constructed and used therapeutically in methods of the invention. For example, chimeric antibodies can be constructed as disclosed in WO 93/03151. Binding proteins which are derived from immunoglobulms and which are multivalent and multispecific, such as the "diabodies" described in WO 94/13804, also can be prepared. Antibodies of the invention can be purified by methods well known in the art. For example, antibodies can be affinity purified by passage over a column to which a PLC delta-1 polypeptide is bound. The bound antibodies can then be eluted from the column using a buffer with a high salt concentration. Antisense Oligonucleotides Antisense oligonucleotides are nucleotide sequences which are complementary to a specific DNA or RNA sequence. Once introduced into a cell, the complementary nucleotides combine with natural sequences produced by the cell to form complexes and block either transcription or translation. Preferably, an antisense oligonucleotide is at least 11 nucleotides in length, but can be at least 12, 15, 20, 25, 30, 35, 40, 45, or 50 or more nucleotides long. Longer sequences also can be used. Antisense oligonucleotide molecules can be provided in a DNA construct and introduced into a cell as described above to decrease the level of PLC delta-1 gene products in the cell. Antisense oligonucleotides can be deoxyribonucleotides, ribonucleotides, or a combination of both. Oligonucleotides can be synthesized manually or by an auto- mated synthesizer, by covalently linking the 5' end of one nucleotide with the 3' end of another nucleotide with non-phosphodiester internucleotide linkages such alkyl- phosphonates, phosphorothioates, phosphorodithioates, alkylphosphonothioates, alkylphosphonates, phosphoramidates, phosphate esters, carbamates, acetamidate, carboxymethyl esters, carbonates, and phosphate triesters. See Brown, Meth. Mol. Biol. 20, 1-8, 1994; Sonveaux, Meth. Mol. Biol. 26, 1-72, 1994; Uhlmann et al, Chem. Rev. 90, 543-583, 1990. Modifications of PLC delta-1 gene expression can be obtained by designing antisense oligonucleotides which will form duplexes to the control, 5', or regulatory regions of the PLC delta-1 gene. Oligonucleotides derived from the transcription initiation site, e.g., between positions -10 and +10 from the start site, are preferred. Similarly, inhibition can be achieved using "triple helix" base-pairing methodology. Triple helix pairing is useful because it causes inhibition of the ability of the double helix to open sufficiently for the binding of polymerases, transcription factors, or chaperons. Therapeutic advances using triplex DNA have been described in the literature (e.g., Gee et al, in Huber & Carr, MOLECULAR AND IMMUNOLOGIC APPROACHES, Futura Publishing Co., Mt. Kisco, N.Y., 1994). An antisense oligonucleotide also can be designed to block translation of mRNA by preventing the transcript from binding to ribosomes. Precise complementarity is not required for successful duplex formation between an antisense oligonucleotide and the complementary sequence of a PLC delta-1 polynucleotide. Antisense oligonucleotides which comprise, for example, 2, 3, 4, or 5 or more stretches of contiguous nucleotides which are precisely complementary to a PLC delta-1 polynucleotide, each separated by a stretch of contiguous nucleotides which are not complementary to adjacent PLC delta-1 nucleotides, can provide targeting specificity for PLC delta-1 mRNA. Preferably, each stretch of complementary- contiguous nucleotides is at least 4, 5, 6, 7, or 8 or more nucleotides in length. Non- complementary intervening sequences are preferably 1, 2, 3, or 4 nucleotides in length. One skilled in the art can easily use the calculated melting point of an anti- sense-sense pair to determine the degree of mismatching which will be tolerated between a particular antisense oligonucleotide and a particular PLC delta-1 polynucleotide sequence. Antisense oligonucleotides can be modified without affecting their ability to hybridize to a PLC delta-1 polynucleotide. These modifications can be internal or at one or both ends of the antisense molecule. For example, internucleoside phosphate linkages can be modified by adding cholesteryl or diamine moieties with varying numbers of carbon residues between the amino groups and terminal ribose. Modified bases and/or sugars, such as arabinose instead of ribose, or a 3', 5 '-substituted oligonucleotide in which the 3' hydroxyl group or the 5' phosphate group are substituted, also can be employed in a modified antisense oligonucleotide. These modified oligonucleotides can be prepared by methods well known in the art. See, e.g., Agrawal et al, Trends Biotechnol 10, 152-158, 1992; Uhlmann et al, Chem. Rev. 90, 543-584, 1990; Uhlmann et al, Tetrahedron. Lett. 215, 3539-3542, 1987. Ribozymes Ribozymes are RNA molecules with catalytic activity. See, e.g., Cech, Science 236, 1532-1539; 1987; Cech, Ann. Rev. Biochem. 59, 543-568; 1990, Cech, Curr. Opin. Struct. Biol 2, 605-609; 1992, Couture & Stinchcomb, Trends Genet. 12, 510-515, 1996. Ribozymes can be used to inhibit gene function by cleaving an RNA sequence, as is known in the art (e.g., Haseloff et al, U.S. Patent 5,641,673). The mechanism of ribozyme action involves sequence-specific hybridization of the ribozyme molecule to complementary target RNA, followed by endonucleolytic cleavage. Examples include engineered hammerhead motif ribozyme molecules that can specifically and efficiently catalyze endonucleolytic cleavage of specific nucleotide sequences. The coding sequence of a PLC delta-1 polynucleotide can be used to generate ribozymes which will specifically bind to mRNA transcribed from the PLC delta-1 polynucleotide. Methods of designing and constructing ribozymes which can cleave other RNA molecules in trans in a highly sequence specific manner have been developed and described in the art (see Haseloff et al. Nature 334, 585-591, 1988). For example, the cleavage activity of ribozymes can be targeted to specific RNAs by engineering a discrete "hybridization" region into the ribozyme. The hybridization region contains a sequence complementary to the target RNA and thus specifically hybridizes with the target (see, for example, Gerlach et al, EP 321,201). Specific ribozyme cleavage sites within a PLC delta-1 RNA target are initially identified by scanning the RNA molecule for ribozyme cleavage sites which include the following sequences: GUA, GUU, and GUC. Once identified, short RNA sequences of between 15 and 20 ribonucleotides corresponding to the region of the PLC delta-1 target RNA containing the cleavage site can be evaluated for secondary structural features which may render the target inoperable. The suitability of candidate targets also can be evaluated by testing accessibility to hybridization with complementary oligonucleotides using ribonuclease protection assays. Longer complementary sequences can be used to increase the affinity of the hybridization sequence for the target. The hybridizing and cleavage regions of the ribozyme can be integrally related; thus, upon hybridizing to the PLC delta-1 target RNA through the complementary regions, the catalytic region of the ribozyme can cleave the target. Ribozymes can be introduced into cells as part of a DNA construct. Mechanical methods, such as microinjection, liposome-mediated transfection, electroporation, or calcium phosphate precipitation, can be used to introduce a ribozyme-containing DNA construct into cells in which it is desired to decrease PLC delta-1 expression. Alternatively, if it is desired that the cells stably retain the DNA construct, it can be supplied on a plasmid and maintained as a separate element or integrated into the genome of the cells, as is known in the art. The DNA construct can include transcriptional regulatory elements, such as a promoter element, an enhancer or UAS element, and a transcriptional terminator signal, for controlling transcription of ribozymes in the cells. As taught in Haseloff et al, U.S. Patent 5,641,673, ribozymes can be engineered so that ribozyme expression will occur in response to factors which induce expression of a target gene. Ribozymes also can be engineered to provide an additional level of regulation, so that destruction of PLC delta-1 mRNA occurs only when both a ribozyme and a target gene are induced in the cells. Differentially Expressed Genes Described herein are methods for the identification of genes whose products interact with human PLC delta-1. Such genes may represent genes that are differentially expressed in disorders including, but not limited to, COPD, congestive heart failure, hypertension, and cancer. Further, such genes may represent genes that are differentially regulated in response to manipulations relevant to the progression or treatment of such diseases. Additionally, such genes may have a temporally modulated expression, increased or decreased at different stages of tissue or organism development. A differentially expressed gene may also have its expression modulated under control versus experimental conditions. In addition, the human PLC delta-1 gene or gene product may itself be tested for differential expression. The degree to which expression differs in a normal versus a diseased state need only be large enough to be visualized via standard characterization techniques such as differential display techniques. Other such standard characterization techniques by which expression differences may be visualized include but are not limited to, quantitative RT (reverse transcriptase), PCR, and Northern analysis. Identification of Differentially Expressed Genes To identify differentially expressed genes total RNA or, preferably, mRNA is isolated from tissues of interest. For example, RNA samples are obtained from tissues of experimental subjects and from corresponding tissues of control subjects. Any RNA isolation technique that does not select against the isolation of mRNA may be utilized for the purification of such RNA samples. See, for example, Ausubel et al, ed., CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, Inc. New York, 1987-1993. Large numbers of tissue samples may readily be processed using techniques well known to those of skill in the art, such as, for example, the single-step RNA isolation process of Chomczynski, U.S. Patent 4,843,155. Transcripts within the collected RNA samples that represent RNA produced by differentially expressed genes are identified by methods well known to those of skill in the art. They include, for example, differential screening (Tedder et al, Proc. Natl. Acad. Sci. U.S.A. 85, 208-12, 1988), subrractive hybridization (Hedrick et al, Nαtwre 308, 149-53; Lee et al, Proc. Natl. Acad. Sci. U.S.A. 88, 2825, 1984), and differential display (Liang & Pardee, Science 257, 967-71, 1992; U.S. Patent 5,262,311), and microarrays. The differential expression information may itself suggest relevant methods for the treatment of disorders involving the human PLC delta-1. For example, treatment may include a modulation of expression of the differentially expressed genes and/or the gene encoding the human PLC delta-1. The differential expression information may indicate whether the expression or activity of the differentially expressed gene or gene product or the human PLC delta-1 gene or gene product are up-regulated or down-regulated. Screening Methods The invention provides methods for identifying modulators, i.e., candidate or test compounds which bind to PLC delta-1 polypeptides or polynucleotides and/or have a stimulatory or inhibitory effect on, for example, expression or activity of the PLC delta-1 polypeptide or polynucleotide, so as to regulate degradation of the extracellular matrix. Decreased extracellular matrix degradation is useful for preventing or suppressing malignant cells from metastasizing. Increased extracellular matrix degradation may be desired, for example, in developmental disorders characterized by inappropriately low levels of extracellular matrix degradation or in regeneration. The invention provides assays for screening test compounds which bind to or modulate the activity of a PLC delta-1 polypeptide or a PLC delta-1 polynucleotide. A test compound preferably binds to a PLC delta-1 polypeptide or polynucleotide. More preferably, a test compound decreases a PLC delta-1 activity of a PLC delta-1 polypeptide or expression of a PLC delta-1 polynucleotide by at least about 10, preferably about 50, more preferably about 75, 90, or 100% relative to the absence of the test compound. rest Compounds Test compounds can be pharmacologic agents already known in the art or can be compounds previously unknown to have any pharmacological activity. The compounds can be naturally occurring or designed in the laboratory. They can be isolated from microorganisms, animals, or plants, and can be produced recombinantly, or synthesized by chemical methods known in the art. If desired, test compounds can be obtained using any of the numerous combinatorial library methods known in the art, including but not limited to, biological libraries, spatially addressable parallel solid phase or solution phase libraries, synthetic library methods requiring deconvolution, the "one-bead one-compound" library method, and synthetic library methods using affinity chromatography selection. The biological library approach is limited to polypeptide libraries, while the other four approaches are applicable to polypeptide, non-peptide oligomer, or small molecule libraries of compounds. See Lam, Anticancer Drug Des. 12, 145, 1997. Methods for the synthesis of molecular libraries are well known in the art (see, for example, DeWitt et al, Proc. Natl. Acad. Sci. U.S.A. 90, 6909, 1993; Erb et al Proc. Natl. Acad. Sci. U.S.A. 91, 11422, 1994; Zuckermann et /., J. Med. Chem. 37, 2678, 1994; Cho et al, Science 261, 1303, 1993; Carell et al, Angew. Chem. Int. Ed. Engl. 33, 2059, 1994; Carell et al, Angew. Chem. Int. Ed. Engl. 33, 2061; Gallop et al, J. Med. Chem. 37, 1233, 1994). Libraries of compounds can be presented in solution (see, e.g., Houghten, BioTechniques 13, 412-421, 1992), or on beads (Lam, Nature 354, 82-84, 1991), chips (Fodor, Nature 364, 555-556, 1993), bacteria or spores (Ladner, U.S. Patent 5,223,409), plasmids (Cull et al, Proc. Natl. Acad. Sci. U.S.A. 89, 1865-1869, 1992), or phage (Scott & Smith, Science 249, 386-390, 1990; Devlin, Science 249, 404-406, 1990); Cwirla et al, Proc. Natl. Acad. Sci. 97, 6378-6382, 1990; Felici, J Mol. Biol. 222, 301-310, 1991; and Ladner, U.S. Patent 5,223,409). High Throughput Screening Test compounds can be screened for the ability to bind to PLC delta-1 polypeptides or polynucleotides or to affect PLC delta-1 activity or PLC delta-1 gene expression using high throughput screening. Using high throughput screening, many discrete compounds can be tested in parallel so that large numbers of test compounds can be quickly screened. The most widely established techniques utilize 96-well microtiter plates. The wells of the microtiter plates typically require assay volumes that range from 50 to 500 μl. In addition to the plates, many instruments, materials, pipettors, robotics, plate washers, and plate readers are commercially available to fit the 96-well format. Alternatively, "free format assays," or assays that have no physical barrier between samples, can be used. For example, an assay using pigment cells (melanocytes) in a simple homogeneous assay for combinatorial peptide libraries is described by jayawickreme et al, Proc. Natl. Acad. Sci. U.S.A. 19, 1614-18 (1994). The cells are placed under agarose in petri dishes, then beads that carry combinatorial compounds are placed on the surface of the agarose. The combinatorial compounds are partially released the compounds from the beads. Active compounds can be visualized as dark pigment areas because, as the compounds diffuse locally into the gel matrix, the active compounds cause the cells to change colors. Another example of a free format assay is described by Chelsky, "Strategies for Screening Combinatorial Libraries: Novel and Traditional Approaches," reported at the First Annual Conference of The Society for Biomolecular Screening in Philadelphia, Pa. (Nov. 7-10, 1995). Chelsky placed a simple homogenous enzyme assay for carbonic anhydrase inside an agarose gel such that the enzyme in the gel would cause a color change throughout the gel. Thereafter, beads carrying combinatorial compounds via a photolinker were placed inside the gel and the compounds were partially released by UV-light. Compounds that inhibited the enzyme were observed as local zones of inhibition having less color change. Yet another example is described by Salmon et al, Molecular Diversity 2, 57-63 (1996). In this example, combinatorial libraries were screened for compounds that had cytotoxic effects on cancer cells growing in agar. Another high throughput screening method is described in Beutel et al, U.S. Patent 5,976,813. In this method, test samples are placed in a porous matrix. One or more assay components are then placed within, on top of, or at the bottom of a matrix such as a gel, a plastic sheet, a filter, or other form of easily manipulated solid support. When samples are introduced to the porous matrix they diffuse sufficiently slowly, such that the assays can be performed without the test samples running together. Binding Assays For binding assays, the test compound is preferably a small molecule which binds to and occupies the active site or the fad-like domain of the PLC delta-1 polypeptide, thereby making the active site or fibronectin domain inaccessible to substrate such that normal biological activity is prevented. Examples of such small molecules include, but are not limited to, small peptides or peptide-like molecules. In binding assays, either the test compound or the PLC delta-1 polypeptide can comprise a detectable label, such as a fluorescent, radioisotopic, chemiluminescent, or enzymatic label, such as horseradish peroxidase, alkaline phosphatase, or luciferase. Detection of a test compound which is bound to the PLC delta-1 polypeptide can then be accomplished, for example, by direct counting of radioemmission, by scintillation counting, or by determining conversion of an appropriate substrate to a detectable product. Alternatively, binding of a test compound to a PLC delta-1 polypeptide can be determined without labeling either of the interactants. For example, a microphysiometer can be used to detect binding of a test compound with a target polypeptide. A microphysiometer (e.g., Cytosensor™) is an analytical instrument that measures the rate at which a cell acidifies its environment using a light-addressable potentiometric sensor (LAPS). Changes in this acidification rate can be used as an indicator of the interaction between a test compound and a PLC delta-1 polypeptide. (McConnell et al, Science 257, 1906-1912, 1992). Determining the ability of a test compound to bind to a PLC delta-1 polypeptide also can be accomplished using a technology such as real-time Bimolecular Interaction Analysis (BIA). Sjolander & Urbaniczky, Anal. Chem. 63, 2338-2345, 1991, and Szabo et al, Curr. Opin. Struct. Biol. 5, 699-705, 1995. BIA is a technology for studying biospecific interactions in real time, without labeling any of the interactants (e.g., BIAcore™). Changes in the optical phenomenon surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules. In yet another aspect of the invention, a PLC delta-1 polypeptide can be used as a "bait protein" in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Patent 5,283,317; Zervos et al, Cell 72, 223-232, 1993; Madura et al, J. Biol. Chem. 268, 12046-12054, 1993; Bartel et al, BioTechniques 14, 920-924, 1993; Iwabuchi et al, Oncogene 8, 1693-1696, 1993; and Brent W094/10300), to identify other proteins which bind to or interact with the PLC delta-1 polypeptide and modulate its activity. The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. For example, in one construct a polynucleotide encoding a PLC delta-1 polypeptide is fused to a polynucleotide encoding the DNA binding domain of a known transcription factor (e.g., GAL-4). In the other construct, a DNA sequence that encodes an unidentified protein ("prey" or "sample") is fused to a polynucleotide that codes for the activation domain of the known transcription factor. If the "bait" and the "prey" proteins are able to interact in vivo to form a protein-dependent complex, the DNA-binding and activation domains of the transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ), which is operably linked to a transcriptional regulatory site responsive to the transcription factor. Expression of the reporter gene can be detected, and cell colonies containing the functional transcription factor can be isolated and used to obtain the DNA sequence encoding the protein which interacts with the PLC delta-1 polypeptide. It may be desirable to immobilize either the PLC delta-1 polypeptide (or polynucleotide) or the test compound to facilitate separation of bound from unbound forms of one or both of the interactants, as well as to accommodate automation of the assay. Thus, either the PLC delta-1 polypeptide (or polynucleotide) or the test compound can be bound to a solid support. Suitable solid supports include, but are not limited to, glass or plastic slides, tissue culture plates, microtiter wells, tubes, silicon chips, or particles such as beads (including, but not limited to, latex, polystyrene, or glass beads). Any method known in the art can be used to attach the PLC delta-1 polypeptide (or polynucleotide) or test compound to a solid support, including use of covalent and non-covalent linkages, passive absorption, or pairs of binding moieties attached respectively to the polypeptide or test compound and the solid support. Test compounds are preferably bound to the solid support in an array, so that the location of individual test compounds can be tracked. Binding of a test compound to a PLC delta-1 polypeptide (or polynucleotide) can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtiter plates, test tubes, and microcentrifuge tubes. In one embodiment, a PLC delta-1 polypeptide is a fusion protein comprising a domain that allows the PLC delta-1 polypeptide to be bound to a solid support. For example, glutathione-S-transferase fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) or glutathione derivatized microtiter plates, which are then combined with the test compound or the test compound and the non-adsorbed PLC delta-1 polypeptide; the mixture is then incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtiter plate wells are washed to remove any unbound components. Binding of the interactants can be determined either directly or indirectly, as described above. Alternatively, the complexes can be dissociated from the solid support before binding is determined. Other techniques for immobilizing polypeptides or polynucleotides on a solid support also can be used in the screening assays of the invention. For example, either a PLC delta-1 polypeptide (or polynucleotide) or a test compound can be immobilized utilizing conjugation of biotin and streptavidin. Biotinylated PLC delta-1 polypeptides or test compounds can be prepared from biotin-NHS(N-hydroxysuccin- imide) using techniques well known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, 111.) and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemical). Alternatively, antibodies which specifically bind to a PLC delta-1 polypeptide polynucleotides, or a test compound, but which do not interfere with a desired binding site, such as the active site or a fibronectin domain of the PLC delta-1 polypeptide, can be derivatized to the wells of the plate. Unbound target or protein can be trapped in the wells by antibody conjugation. Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include irnmunodetection of complexes using antibodies which specifically bind to the PLC delta-1 polypeptide (or polynucleotides) or test compound, enzyme-linked assays which rely on detecting a PLC delta-1 activity of the PLC delta-1 polypeptide, and SDS gel electrophoresis under non-reducing conditions. Screening for test compounds which bind to a PLC delta-1 polypeptide or polynucleotide also can be carried out in an intact cell. Any cell which comprises a PLC delta-1 polynucleotide or polypeptide can be used in a cell-based assay system. A PLC delta-1 polynucleotide can be naturally occurring in the cell or can be introduced using techniques such as those described above. Either a primary culture or an established cell line, including neoplastic cell lines such as the colon cancer cell lines HCT116, DLD1, HT29, Caco2, SW837, SW480, and RKO, breast cancer cell lines 21-PT, 21-MT, MDA-468, SK-BR3, and BT-474, the A549 lung cancer cell line, and the H392 glioblastoma cell line, can be used. An intact cell is contacted with a test compound. Binding of the test compound to a PLC delta-1 polypeptide or polynucleotide is determined as described above, after lysing the cell to release the PLC delta-1 polypeptide-test compound complex. Enzyme Assays Test compounds can be tested for the ability to increase or decrease a PLC delta-1 activity of a PLC delta-1 polypeptide. PLC delta-1 activity can be measured as is known in the art, for example, using the method described in Grobler & Hurley, Protein Sci. 5, 680-86, 1996. PLC delta-1 activity can be measured after contacting either a purified PLC delta-1 polypeptide, a cell extract, or an intact cell with a test compound. A test compound which decreases PLC delta-1 activity by at least about 10, preferably about 50, more preferably about 75, 90, or 100% is identified as a potential therapeutic agent for decreasing human PLC delta-1 activity. A test compound which increases PLC delta-1 activity by at least about 10, preferably about 50, more preferably about 75, 90, or 100% is identified as a potential therapeutic agent for increasing human PLC delta-1 activity. Gene Expression In another embodiment, test compounds which increase or decrease PLC delta-1 gene expression are identified. A PLC delta-1 polynucleotide is contacted with a test compound, and the expression of an RNA or polypeptide product of the PLC delta-1 polynucleotide is determined. The level of expression of PLC delta-1 mRNA or polypeptide in the presence of the test compound is compared to the level of expression of PLC delta-1 mRNA or polypeptide in the absence of the test compound. The test compound can then be identified as a modulator of expression based on this comparison. For example, when expression of PLC delta-1 mRNA or polypeptide is greater in the presence of the test compound than in its absence, the test compound is identified as a stimulator or enhancer of PLC delta-1 mRNA or polypeptide is less expression. Alternatively, when expression of the mRNA or protein is less in the presence of the test compound than in its absence, the test compound is identified as an inhibitor of PLC delta-1 mRNA or polypeptide expression. The level of PLC delta-1 mRNA or polypeptide expression in the cells can be determined by methods well known in the art for detecting mRNA or protein. Either qualitative or quantitative methods can be used. The presence of polypeptide products of a PLC delta-1 polynucleotide can be determined, for example, using a variety of techniques known in the art, including immunochemical methods such as radioimmunoassay, Western blotting, and irnmunohistochemistry. Alternatively, polypeptide synthesis can be determined in vivo, in a cell culture, or in an in vitro translation system by detecting incorporation of labeled amino acids into a PLC delta-1 polypeptide. Such screening can be carried out either in a cell-free assay system or in an intact cell. Any cell which expresses a PLC delta-1 polynucleotide can be used in a cell- based assay system. The PLC delta-1 polynucleotide can be naturally occurring in the cell or can be introduced using techniques such as those described above. Either a primary culture or an established cell line, including neoplastic cell lines such as the colon cancer cell lines HCT116, DLD1, HT29, Caco2, SW837, SW480, and RKO, breast cancer cell lines 21-PT, 21-MT, MDA-468, SK-BR3, and BT-474, the A549 lung cancer cell line, and the H392 glioblastoma cell line, can be used. Pharmaceutical Compositions The invention also provides pharmaceutical compositions which can be administered to a patient to achieve a therapeutic effect. Pharmaceutical compositions of the invention can comprise a PLC delta-1 polypeptide, PLC delta-1 polynucleotide, antibodies which specifically bind to a PLC delta-1 polypeptide, or mimetics, agonists, antagonists, or inhibitors of a PLC delta-1 polypeptide. The compositions can be administered alone or in combination with at least one other agent, such as stabilizing compound, which can be administered in any sterile, biocompatible pharmaceutical carrier, including, but not limited to, saline, buffered saline, dextrose, and water. The compositions can be administered to a patient alone, or in combination with other agents, drugs or hormones. In addition to the active ingredients, these pharmaceutical compositions can contain suitable pharmaceutically-acceptable carriers comprising excipients and auxiliaries which facilitate processing of the active compounds into preparations which can be used pharmaceutically. Pharmaceutical compositions of the invention can be administered by any number of routes including, but not limited to, oral, intravenous, intramuscular, intra-arterial, intramedullary, intrathecal, intraventricular, transdermal, subcutaneous, intraperitoneal, intranasal, parenteral, topical, sublingual, or rectal means. Pharmaceutical compositions for oral administration can be formulated using pharmaceutically acceptable carriers well known in the art in dosages suitable for oral administration. Such carriers enable the pharmaceutical compositions to be formulated as tablets, pills, dragees, capsules, liquids, gels, syrups, slurries, suspensions, and the like, for ingestion by the patient. Pharmaceutical preparations for oral use can be obtained through combination of active compounds with solid excipient, optionally grinding a resulting mixture, and processing the mixture of granules, after adding suitable auxiliaries, if desired, to obtain tablets or dragee cores. Suitable excipients are carbohydrate or protein fillers, such as sugars, including lactose, sucrose, mannitoL or sorbitol; starch from corn, wheat, rice, potato, or other plants; cellulose, such as methyl cellulose, hydroxy- propy-lmethyl-cellulose, or sodium carboxymethylcellulose; gums including arabic and tragacanth; and proteins such as gelatin and collagen. If desired, disintegrating or solubilizing agents can be added, such as the cross-linked polyvinyl pyrrolidone, agar, alginic acid, or a salt thereof, such as sodium alginate. Dragee cores can be used in conjunction with suitable coatings, such as concentrated sugar solutions, which also can contain gum arabic, talc, polyvinylpyrrolidone, carbopol gel, polyethylene glycol, and/or titanium dioxide, lacquer solutions, and suitable organic solvents or solvent mixtures. Dyesruffs or pigments can be added to the tablets or dragee coatings for product identification or to characterize the quantity of active compound, i.e., dosage. Pharmaceutical preparations which can be used orally include push-fit capsules made of gelatin, as well as soft, sealed capsules made of gelatin and a coating, such as glycerol or sorbitol. Push-fit capsules can contain active ingredients mixed with a filler or binders, such as lactose or starches, lubricants, such as talc or magnesium stearate, and, optionally, stabilizers. In soft capsules, the active compounds can be dissolved or suspended in suitable liquids, such as fatty oils, liquid, or liquid polyethylene glycol with or without stabilizers. Pharmaceutical formulations suitable for parenteral administration can be formulated in aqueous solutions, preferably in physiologically compatible buffers such as Hanks' solution, Ringer's solution, or physiologically buffered saline. Aqueous in- jection suspensions can contain substances which increase the viscosity of the suspension, such as sodium carboxymethyl cellulose, sorbitol, or dextran. Additionally, suspensions of the active compounds can be prepared as appropriate oily injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl oleate or triglycerides, or liposomes. Non-lipid polycationic amino polymers also can be used for delivery. Optionally, the suspension also can contain suitable stabilizers or agents which in- crease the solubility of the compounds to allow for the preparation of highly concentrated solutions. For topical or nasal administration, penetrants appropriate to the particular barrier to be permeated are used in the formulation. Such penetrants are generally known in the art. The pharmaceutical compositions of the present invention can be manufactured in a manner that is known in the art, e.g., by means of conventional mixing, dissolving, granulating, dragee-making, levigating, emulsifying, encapsulating, entrapping, or lyophilizing processes. The pharmaceutical composition can be provided as a salt and can be formed with many acids, including but not limited to, hydrochloric, sulfuric, acetic, lactic, tartaric, malic, succinic, etc. Salts tend to be more soluble in aqueous or other protonic solvents than are the corresponding free base forms. In other cases, the preferred preparation can be a lyophilized powder which can contain any or all of the following: 1-50 mM histidine, 0.1%-2% sucrose, and 2-7% mannitol, at a pH range of 4.5 to 5.5, that is combined with buffer prior to use. Further details on techniques for formulation and administration can be found in the latest edition of REMINGTON'S PHARMACEUTICAL SCIENCES (Maack Publishing Co., Easton, Pa.). After pharmaceutical compositions have been prepared, they can be placed in an appropriate container and labeled for treatment of an indicated condition. Such labeling would include amount, frequency, and method of administration. Diagnostic Methods The human PLC delta-1 and polynucleotides encoding it can be used in diagnostic assays for detecting diseases and abnormalities or susceptibility to diseases and abnormalities related to the presence of mutations in the nucleic acid sequences which encode the enzyme. For example, differences can be determined between the cDNA or genomic sequence encoding human PLC delta-1 in individuals afflicted with a disease and in normal individuals. If a mutation is observed in some or all of the afflicted individuals but not in normal individuals, then the mutation is likely to be the causative agent of the disease. Sequence differences between a reference gene and a gene having mutations can be revealed by the direct DNA sequencing method. In addition, cloned DNA segments can be employed as probes to detect specific DNA segments. The sensitivity of this method is greatly enhanced when combined with PCR. For example, a sequencing primer can be used with a double-stranded PCR product or a single-stranded template molecule generated by a modified PCR. The sequence determination is performed by conventional procedures using radiolabeled nucleotides or by automatic sequencing procedures using fluorescent tags. Genetic testing based on DNA sequence differences can be carried out by detection of alteration in electrophoretic mobility of DNA fragments in gels with or without denaturing agents. Small sequence deletions and insertions can be visualized, for example, by high resolution gel electrophoresis. DNA fragments of different sequences can be distinguished on denaturing formamide gradient gels in which the mobilities of different DNA fragments are retarded in the gel at different positions according to their specific melting or partial melting temperatures (see, e.g., Myers et al, Science 230, 1242, 1985). Sequence changes at specific locations can also be revealed by nuclease protection assays, such as RNase and SI protection or the chemical cleavage method (e.g., Cotton et al, Proc. Natl Acad. Sci. USA 85, 4397-4401, 1985). Thus, the detection of a specific DNA sequence can be performed by methods such as hybridization, RNase protection, chemical cleavage, direct DNA sequencing or the use of restriction enzymes and Southern blotting of genomic DNA. In addition to direct methods such as gel-electrophoresis and DNA sequencing, mutations can also be detected by in situ analysis. Altered levels of human PLC delta-1 also can be detected in various tissues. Assays used to detect levels of the receptor polypeptides in a body sample, such as blood or a tissue biopsy, derived from a host are well known to those of skill in the art and include radioimmunoassays, competitive binding assays, Western blot analysis, and ELISA assays. Therapeutic Indications and Methods Diseases or conditions in which signal transduction is aberrant may be treated using molecules which regulate the activity of human PLC delta-1. Human PLC delta-1 can be regulated to treat COPD, congestive heart failure, hypertension, and cancer. Chronic obstructive pulmonary (or airways) disease (COPD) is a condition defined physiologically as airflow obstruction that generally results from a mixture of emphysema and peripheral airway obstruction due to chronic bronchitis (Senior & Shapiro, Pulmonary Diseases and Disorders, 3d ed., New York, McGraw-Hill, 1998, pp. 659-681, 1998; Barnes, Chest 117, 10S-14S, 2000). Emphysema is characterized by destruction of alveolar walls leading to abnormal enlargement of the air spaces of the lung. Chronic bronchitis is defined clinically as the presence of chronic productive cough for three months in each of two successive years. In COPD, airflow obstruction is usually progressive and is only partially reversible. By far the most important risk factor for development of COPD is cigarette smoking, although the disease does occur in non-smokers. Chronic inflammation of the airways is a key pathological feature of COPD (Senior & Shapiro, 1998). The inflammatory cell population comprises increased numbers of macrophages, neutrophils, and CD8 + lymphocytes. Inhaled irritants, such as cigarette smoke, activate macrophages which are resident in the respiratory tract, as well as epithelial cells leading to release of chemokines (e.g., interleukin-8) and other chemotactic factors. These chemotactic factors act to increase the neutrophil/mono- cyte trafficking from the blood into the lung tissue and airways. Neutrophils and monocytes recruited into the airways can release a variety of potentially damaging mediators such as proteolytic enzymes and reactive oxygen species. Matrix degradation and emphysema, along with airway wall thickening, surfactant dys- function, and mucus hypersecretion, all are potential sequelae of this inflammatory response that lead to impaired airflow and gas exchange. Congestive heart failure results in alterations of the level of PLC isozymes, including PLC delta-1 (Tappia et al, Am. J. Physiol. 227, H40-9, 1999); correction of PLC delta-1 levels may therefore be useful to treat congestive heart failure. Heart failure is defined as a pathophysiologic state in which an abnormality of cardiac function is responsible for the failure of the heart to pump blood at a rate commensurate with the requirement of the metabolizing tissue. It includes all forms of pumping failure such as high-output and low-output, acute and chronic, right-sided or left-sided, systolic or diastolic, independent of the underlying cause. Studies on spontaneous hypertensive rats have suggested that one of the main causes for the hypertension is an abnormal activation of PLC delta-1 resulting from point mutations in the X and Y regions of the PLC amino acid sequence. Thus, regulation of human PLC delta-1 can be used to treat hypertension. Hypertensive vascular diseases include primary as well as all kinds of secondary arterial hypertension (renal, endocrine, neurogenic, others). Human PLC delta-1 may therefore be used as a drug target for the treatment of hypertension as well as for the prevention of all complications. Human PLC delta-1 also may be useful for treating cancer. Cancer is a disease fundamentally caused by oncogenic cellular transformation. There are several hallmarks of transformed cells that distinguish them from their normal counterparts and underlie the pathophysiology of cancer. These include uncontrolled cellular proliferation, unresponsiveness to normal death-inducing signals (immortalization), increased cellular motility and invasiveness, increased ability to recruit blood supply through induction of new blood vessel formation (angiogenesis), genetic instability, and dysregulated gene expression. Various combinations of these aberrant physiolo- gies, along with the acquisition of drug-resistance frequently lead to an intractable disease state in which organ failure and patient death ultimately ensue. Most standard cancer therapies target cellular proliferation and rely on the differential proliferative capacities between transformed and normal cells for their efficacy. This approach is hindered by the facts that several important normal cell types are also highly proliferative and that cancer cells frequently become resistant to these agents. Thus, the therapeutic indices for traditional anti-cancer therapies rarely exceed 2.0. The advent of genomics-driven molecular target identification has opened up the possibility of identifying new cancer-specific targets for therapeutic intervention that will provide safer, more effective treatments for cancer patients. Thus, newly discovered tumor-associated genes and their products can be tested for their role(s) in disease and used as tools to discover and develop innovative therapies. Genes playing important roles in any of the physiological processes outlined above can be characterized as cancer targets. Genes or gene fragments identified through genomics can readily be expressed in one or more heterologous expression systems to produce functional recombinant proteins. These proteins are characterized in vitro for their biochemical properties and then used as tools in high-throughput molecular screening programs to identify chemical modulators of their biochemical activities. Agonists and/or antagonists of target protein activity can be identified in this manner and subsequently tested in cellular and in vivo disease models for anti-cancer activity. Optimization of lead compounds with iterative testing in biological models and detailed pharmacokinetic and toxicological analyses form the basis for drug development and subsequent testing in humans. The invention further pertains to the use of novel agents identified by the screening assays described above. Accordingly, it is within the scope of this invention to use a test compound identified as described herein in an appropriate animal model. For ex- ample, an agent identified as described herein (e.g., a modulating agent, an antisense nucleic acid molecule, a specific antibody, ribozyme, or a polypeptide-binding partner) can be used in an animal model to determine the efficacy, toxicity, or side effects of treatment with such an agent. Alternatively, an agent identified as described herein can be used in an animal model to determine the mechanism of action of such an agent. Furthermore, this invention pertains to uses of novel agents identi- fied by the above-described screening assays for treatments as described herein. A reagent which affects PLC delta-1 activity can be administered to a human cell, either in vitro or in vivo, to reduce PLC delta-1 activity. The reagent preferably binds to an expression product of a human PLC delta-1 gene. If the expression product is a polypeptide, the reagent is preferably an antibody. For treatment of human cells ex vivo, an antibody can be added to a preparation of stem cells which have been removed from the body. The cells can then be replaced in the same or another human body, with or without clonal propagation, as is known in the art. In one embodiment, the reagent is delivered using a liposome. Preferably, the liposome is stable in the animal into which it has been administered for at least about 30 minutes, more preferably for at least about 1 hour, and even more preferably for at least about 24 hours. A liposome comprises a lipid composition that is capable of targeting a reagent, particularly a polynucleotide, to a particular site in an animal, such as a human. Preferably, the lipid composition of the liposome is capable of targeting to a specific organ of an animal, such as the lung or liver. A liposome useful in the present invention comprises a lipid composition that is capable of fusing with the plasma membrane of the targeted cell to deliver its contents to the cell. Preferably, the transfection efficiency of a liposome is about 0.5 μg of DNA per 16 nmole of liposome delivered to about 10 cells, more preferably about 1.0 μg of DNA per 16 nmol of liposome delivered to about 10 6 cells, and even more preferably about 2.0 μg of DNA per 16 nmol of liposome delivered to about 10 δ cells. Preferably, a liposome is between about 100 and 500 nm, more preferably between about 150 and 450 nm, and even more preferably between about 200 and 400 nm in diameter. Suitable liposomes for use in the present invention include those liposomes standardly used in, for example, gene delivery methods known to those of skill in the art. More preferred liposomes include liposomes having a polycationic lipid compo- sition and/or liposomes having a cholesterol backbone conjugated to polyethylene glycol. Optionally, a liposome comprises a compound capable of targeting the liposome to a tumor cell, such as a tumor cell ligand exposed on the outer surface of the liposome. Complexing a liposome with a reagent such as an antisense oligonucleotide or ribozyme can be achieved using methods which are standard in the art (see, for example, U.S. Patent 5,705,151). Preferably, from about 0.1 μg to about 10 μg of polynucleotide is combined with about 8 nmol of liposomes, more preferably from about 0.5 μg to about 5 μg of polynucleotides are combined with about 8 nmol liposomes, and even more preferably about 1.0 μg of polynucleotides is combined with about 8 nmol liposomes. In another embodiment, antibodies can be delivered to specific tissues in vivo using receptor-mediated targeted delivery. Receptor-mediated DNA delivery techniques are taught in, for example, Findeis et al Trends in Biotechnol 11, 202-05 (1993); Chiou et al, GENE THERAPEUTICS: METHODS AND APPLICATIONS OF DIRECT GENE TRANSFER (J.A. Wolff, ed.) (1994); Wu & Wu, J. Biol Chem. 263, 621-24 (1988); Wu et al, J. Biol. Chem. 269, 542-46 (1994); Zenke et al, Proc. Natl Acad. Sci. U.S.A. 87, 3655-59 (1990); Wu et al., J. Biol. Chem. 266, 338-42 (1991). If the reagent is a single-chain antibody, polynucleotides encoding the antibody can be constructed and introduced into a cell either ex vivo or in vivo using well- established techniques including, but not limited to, transferrin-polycation-mediated DNA transfer, transfection with naked or encapsulated nucleic acids, liposome- mediated cellular fusion, intracellular transportation of DNA-coated latex beads, protoplast fusion, viral infection, electroporation, "gene gun," and DEAE- or calcium phosphate-mediated transfection. Determination of a Therapeutically Effective Dose The determination of a therapeutically effective dose is well within the capability of those skilled in the art. A therapeutically effective dose refers to that amount of active ingredient which increases or decreases extracellular matrix degradation relative to that which occurs in the absence of the therapeutically effective dose. For any compound, the therapeutically effective dose can be estimated initially either in cell culture assays or in animal models, usually mice, rabbits, dogs, or pigs. The animal model also can be used to determine the appropriate concentration range and route of administration. Such information can then be used to determine useful doses and routes for administration in humans. Therapeutic efficacy and toxicity, e.g., ED 50 (the dose therapeutically effective in 50% of the population) and LD 50 (the dose lethal to 50% of the population), can be determined by standard pharmaceutical procedures in cell cultures or experimental animals. The dose ratio of toxic to therapeutic effects is the therapeutic index, and it can be expressed as the ratio, LD 50 /ED 50 . Pharmaceutical compositions which exhibit large therapeutic indices are preferred. The data obtained from cell culture assays and animal studies is used in formulating a range of dosage for human use. The dosage contained in such compositions is preferably within a range of circulating concentrations that include the ED 50 with little or no toxicity. The dosage varies within this range depending upon the dosage form employed, sensitivity of the patient, and the route of administration. The exact dosage will be determined by the practitioner, in light of factors related to the subject that requires treatment. Dosage and administration are adjusted to provide sufficient levels of the active ingredient or to maintain the desired effect. Factors which can be taken into account include the severity of the disease state, general health of the subject, age, weight, and gender of the subject, diet, time and frequency of administration, drug combination(s), reaction sensitivities, and tolerance/response to therapy. Long-acting pharmaceutical compositions can be administered every 3 to 4 days, every week, or once every two weeks depending on the half-life and clearance rate of the particular formulation. Normal dosage amounts can vary from 0.1 to 100,000 micrograms, up to a total dose of about 1 g, depending upon the route of administration. Guidance as to particular dosages and methods of delivery is provided in the literature and generally available to practitioners in the art. Those skilled in the art will employ different formulations for nucleotides than for proteins or their inhibitors. Similarly, delivery of polynucleotides or polypeptides will be specific to particular cells, conditions, locations, etc. Effective in vivo dosages of an antibody are in the range of about 5 μg to about 50 μg/kg, about 50 μg to about 5 mg/kg, about 100 μg to about 500 μg/kg of patient body weight, and about 200 to about 250 μg/kg of patient body weight. For administration of polynucleotides encoding single-chain antibodies, effective in vivo dosages are in the range of about 100 ng to about 200 ng, 500 ng to about 50 mg, about 1 μg to about 2 mg, about 5 μg to about 500 μg, and about 20 μg to about 100 μg of DNA. If the expression product is mRNA, the reagent is preferably an antisense oligonucleotide or a ribozyme. Polynucleotides which express antisense oligonucleotides or ribozymes can be introduced into cells by a variety of methods, as described above. Preferably, a reagent reduces expression of a PLC delta-1 polynucleotide or activity of a PLC delta-1 polypeptide by at least about 10, preferably about 50, more prefer- ably about 75, 90, or 100% relative to the absence of the reagent. The effectiveness of the mechanism chosen to decrease the level of expression of a PLC delta-1 polynucleotide or the activity of a PLC delta-1 polypeptide can be assessed using methods well known in the art, such as hybridization of nucleotide probes to PLC delta-1 -specific mRNA, quantitative RT-PCR, immunologic detection of a PLC delta-1 polypeptide, or measurement of PLC delta-1 activity. In any of the embodiments described above, any of the pharmaceutical compositions of the invention can be administered in combination with other appropriate therapeutic agents. Selection of the appropriate agents for use in combination therapy can be made by one of ordinary skill in the art, according to conventional pharmaceutical principles. The combination of therapeutic agents can act syner- gistically to effect the treatment or prevention of the various disorders described above. Using this approach, one may be able to achieve therapeutic efficacy with lower dosages of each agent, thus reducing the potential for adverse side effects. Any of the therapeutic methods described above can be applied to any subject in need of such therapy, including, for example, mammals such as dogs, cats, cows, horses, rabbits, monkeys, and most preferably, humans. The above disclosure generally describes the present invention, and all patents and patent applications cited in this disclosure are expressly incorporated herein. A more complete understanding can be obtained by reference to the following specific examples which are provided for purposes of illustration only and are not intended to limit the scope of the invention. EXAMPLE 1 Detection of PLC delta-1 activity The polynucleotide of SEQ ID NO: 10 is inserted into the expression vector ρCEV4 and the expression vector pCEV4-PLC delta 1 polypeptide obtained is transfected into human embryonic kidney 293 cells. Cells at 80-90% confluence, in 24-well multiwells, are labeled overnight with myo-[2-3H] inositol (1 μCi mil, 0,5 ml/well) in medium M199 with 25 IU ml-1 penicillin, 25 μg ml-1 streptomycin, at 37°C in 5% CO 2 . To the 0,5 ml of labeling medium is added 50 μl of 11 -fold final concentration of LiCl (110 mM) in balanced salt solution. After further incubation for 15 min with agonists, total [3H] inositol (poly)phosphates are extracted and separated on small Dowex-1 (C1-) columns. It is shown that the polypeptide of SEQ ID NO.: 13 has PLC delta-1 activity. EXAMPLE 2 Expression of a recombinant DNA sequence encoding a human PLC delta-1 polypeptide in yeast cells (Pichia pastoris) To produce large quantities of human PLC delta-1 polypeptides in yeast, the Pichia pastoris expression vector pPICZB (Invitrogen, San Diego, CA) is used. The human PLC delta-1 encoding DNA sequence is the nucleotide sequence shown in SEQ ID NO: 10. Before insertion into vector pPICZB, the DNA sequence is modified by well known methods in such a way that it contains at its 5 '-end an initiation codon and at its 3 '-end an enterokinase cleavage site, a His6 reporter tag, and a termination codon. Recognition sequences for restriction endonucleases are added at both termini. After digestion of the multiple cloning site of pPICZ B with the corresponding restriction enzymes, the modified human PLC delta-1 polypeptide-encoding DNA sequence is ligated into pPICZB. This expression vector is designed for inducible expression in Pichia pastoris, and expression is driven by a yeast promoter. The resulting pPICZ/md-His6 vector is used to transform the yeast. The yeast is cultivated under usual conditions in shake flasks, and the recombinantly produced protein is isolated from the culture by affinity chromatography (Ni-NTA-Resin) in the presence of 8 M urea. The bound polypeptide is eluted with buffer, pH 3.5, and neutralized. Separation of the human PLC delta-1 polypeptide from the His6 reporter tag is accomplished by site-specific proteolysis using enterokinase (Invitrogen, San Diego, CA) according to manufacturer s instructions. Purified human PLC delta-1 polypeptide is obtained. EXAMPLE 3 Identification of a test compound which binds to a PLC delta-1 polypeptide Purified PLC delta-1 polypeptides comprising a glutathione-S-transferase protein and absorbed onto glutathione-derivatized wells of 96-well microtiter plates are contacted with test compounds from a small molecule library at pH 7.0 in a physiological buffer solution. PLC delta-1 polypeptides consist essentially of the amino acid sequence shown in SEQ ID NO: 13. The test compounds comprise a fluorescent tag. The samples are incubated for 5 minutes to one hour. Control samples are incubated in the absence of a test compound. The buffer solution containing the test compounds is washed from the wells. Binding of a test compound to a PLC delta-1 polypeptide is detected by fluorescence measurements of the contents of the wells. A test compound which increases the fluorescence in a well by at least 15% relative to fluorescence of a well in which a test compound was not incubated is identified as a compound which binds to a PLC delta-1 polypeptide. EXAMPLE 4 Identification of a test compound which decreases PLC delta-1 activity Cellular extracts from cells comprising human PLC delta-1 are contacted with test compounds from a small molecule library and assayed for PLC delta-1 activity. Control extracts, in the absence of a test compound, also are assayed. Phospholipase activity can be measured, for example, as described in Grobler & Hurley, Protein Sci. 5, 680-86, 1996. A test compound which decreases PLC delta-1 activity of the extract relative to the control extract by at least 20% is identified as a PLC delta-1 inhibitor. EXAMPLE 5 Identification of a test compound which decreases PLC delta-1 gene expression A test compound is administered to a culture of the breast tumor cell line MDA-468 and incubated at 37 °C for 10 to 45 minutes. A culture of the same type of cells incubated for the same time without the test compound provides a negative control. RNA is isolated from the two cultures as described in Chirgwin et al, Biochem. 18, 5294-99, 1979). Northern blots are prepared using 20 to 30 μg total RNA and hybridized with a 32 P-labeled PLC delta-1 -specific probe at 65 ° C in Express-hyb (CLONTECH). The probe comprises at least 11 contiguous nucleotides selected from the complement of SEQ ID NO: 10. A test compound which decreases the PLC delta-1 -specific signal relative to the signal obtained in the absence of the test compound is identified as an inhibitor of PLC delta-1 gene expression. EXAMPLE 6 Treatment of hypertension with a reagent which specifically binds to a human PLC delta-1 gene product Synthesis of antisense human PLC delta-1 oligonucleotides comprising at least 11 contiguous nucleotides selected from the complement of SEQ ID NO: 10 is performed on a Pharmacia Gene Assembler series synthesizer using the phosphor- amidite procedure (Uhlmann et al, Chem. Rev. 90, 534-83, 1990). Following assembly and deprotection, oligonucleotides are ethanol-precipitated twice, dried, and suspended in phosphate-buffered saline (PBS) at the desired concentration. Purity of these oligonucleotides is tested by capillary gel electrophoreses and ion exchange HPLC. Endotoxin levels in the oligonucleotide preparation are determined using the Limulus Amebocyte Assay (Bang, Biol. Bull. (Woods Hole, Mass.) 105, 361-362, 1953). An aqueous composition containing the antisense oligonucleotides at a concentration of 0.1-100 μM is administered to a patient with hypertension. The severity of the patient's hypertension is decreased. EXAMPLE 7 In vivo testing of compounds/target validation 1. Acute Mechanistic Assays 1.1. Reduction in Mitogenic Plasma Hormone Levels This non-tumor assay measures the ability of a compound to reduce either the endogenous level of a circulating hormone or the level of hormone produced in response to a biologic stimulus. Rodents are administered test compound (p.o., i.p., i.v., i.m., or s.c). At a predetermined time after administration of test compound, blood plasma is collected. Plasma is assayed for levels of the hormone of interest. If the normal circulating levels of the hormone are too low and/or variable to provide consistent results, the level of the hormone may be elevated by a pre-treatment with a biologic stimulus (i.e., LHRH may be injected i.m. into mice at a dosage of 30 ng/mouse to induce a burst of testosterone synthesis). The timing of plasma collection would be adjusted to coincide with the peak of the induced hormone response. Compound effects are compared to a vehicle-treated control group. An F- test is preformed to deteπnine if the variance is equal or unequal followed by a Student's t-test. Significance is p value < 0.05 compared to the vehicle control group. 1.2. Hollow Fiber Mechanism of Action Assay Hollow fibers are prepared with desired cell line(s) and implanted intraperitoneally and/or subcutaneously in rodents. Compounds are administered p.o., i.p., i.v., i.m., or s.c. Fibers are harvested in accordance with specific readout assay protocol, these may include assays for gene expression (bDNA, PCR, or Taqman), or a specific biochemical activity (i.e., cAMP levels. Results are analyzed by Student's t-test or Rank Sum test after the variance between groups is compared by an F-test, with significance at p < 0.05 as compared to the vehicle control group. 2. Subacute Functional In Vivo Assays 2.1. Reduction in Mass of Hormone Dependent Tissues This is another non-tumor assay that measures the ability of a compound to reduce the mass of a hormone dependent tissue (i.e., seminal vesicles in males and uteri in females). Rodents are administered test compound (p.o., i.p., i.v., i.m., or s.c.) according to a predetermined schedule and for a predetermined duration (i.e., 1 week). At termination of the study, animals are weighed, the target organ is excised, any fluid is expressed, and the weight of the organ is recorded. Blood plasma may also be collected. Plasma may be assayed for levels of a hormone of interest or for levels of test agent. Organ weights may be directly compared or they may be normalized for the body weight of the animal. Compound effects are compared to a vehicle-treated control group. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t-test. Significance is p value < 0.05 compared to the vehicle control group. 2.2. Hollow Fiber Proliferation Assay Hollow fibers are prepared with desired cell line(s) and implanted intraperitoneally and/or subcutaneously in rodents. Compounds are administered p.o., i.p., i.v., i.m., or s.c. Fibers are harvested in accordance with specific readout assay protocol. Cell proliferation is determined by measuring a marker of cell number (i.e., MTT or LDH). The cell number and change in cell number from the starting inoculum are analyzed by Student's t-test or Rank Sum test after the variance between groups is compared by an F-test, with significance at p < 0.05 as compared to the vehicle control group. 2.3. Anti-angiogenesis Models 2.3.1. Corneal Angiogenesis Hydron pellets with or without growth factors or cells are implanted into a micropocket surgically created in the rodent cornea. Compound administration may be systemic or local (compound mixed with growth factors in the hydron pellet). Corneas are harvested at 7 days post implantation immediately following intracardiac infusion of colloidal carbon and are fixed in 10% formalin. Readout is qualitative scoring and/or image analysis. Qualitative scores are compared by Rank Sum test. Image analysis data is evaluated by measuring the area of neovascularization (in pixels) and group averages are compared by Student's t-test (2 tail). Significance is p < 0.05 as compared to the growth factor or cells only group. 2.3.2. Matrigel Angϊogenesis Matrigel, containing cells or growth factors, is injected subcutaneously. Compounds are administered p.o., i.p., i.v., i.m., or s.c. Matrigel plugs are harvested at predetermined time point(s) and prepared for readout. Readout is an ELISA-based assay for hemoglobin concentration and/or histological examination (i.e. vessel count, special staining for endothelial surface markers: CD31, factor-8). Readouts are analyzed by Student's t-test, after the variance between groups is compared by an F-test, with significance determined at p < 0.05 as compared to the vehicle control group. 3. Primary Antitumor Efficacy 3.1. Early Therapy Models 3.1.1. Subcutaneous Tumor Tumor cells or fragments are implanted subcutaneously on Day 0. Vehicle and/or compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule starting at a time, usually on Day 1, prior to the ability to measure the tumor burden. Body weights and tumor measurements are recorded 2-3 times weekly. Mean net body and tumor weights are calculated for each data collection day. Antitumor efficacy may be initially determined by comparing the size of treated (T) and control (C) tumors on a given day by a Student's t-test, after the variance between groups is compared by an F-test, with significance determined at p < 0.05. The experiment may also be continued past the end of dosing in which case tumor measurements would continue to be recorded to monitor tumor growth delay. Tumor growth delays are expressed as the difference in the median time for the treated and control groups to attain a predetermined size divided by the median time for the control group to attain that size. Growth delays are compared by generating Kaplan- Meier curves from the times for individual tumors to attain the evaluation size. Significance is p < 0.05. 3.1.2. Intraperitoneal/Intracranial Tumor Models Tumor cells are injected intraperitoneally or intracranially on Day 0. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule starting on Day 1. Observations of morbidity and/or mortality are recorded twice daily. Body weights are measured and recorded twice weekly. Morbidity/mortality data is expressed in terms of the median time of survival and the number of long- term survivors is indicated separately. Survival times are used to generate Kaplan- Meier curves. Significance is p < 0.05 by a log-rank test compared to the control group in the experiment. 3.2. Established Disease Model Tumor cells or fragments are implanted subcutaneously and grown to the desired size for treatment to begin. Once at the predetermined size range, mice are randomized into treatment groups. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Tumor and body weights are measured and recorded 2-3 times weekly. Mean tumor weights of all groups over days post inoculation are graphed for comparison. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t-test to compare tumor sizes in the treated and control groups at the end of treatment. Significance is p < 0.05 as compared to the control group. Tumor measurements may be recorded after dosing has stopped to monitor tumor growth delay. Tumor growth delays are expressed as the difference in the median time for the treated and control groups to attain a predetermined size divided by the median time for the control group to attain that size. Growth delays are compared by generating Kaplan-Meier curves from the times for individual tumors to attain the evaluation size. Significance is p value <_0.05 compared to the vehicle control group. 3.3. Orthotopic Disease Models 3.3.1. Mammary Fat Pad Assay Tumor cells or fragments, of mammary adenocarcinoma origin, are implanted directly into a surgically exposed and reflected mammary fat pad in rodents. The fat pad is placed back in its original position and the surgical site is closed. Hormones may also be administered to the rodents to support the growth of the tumors. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Tumor and body weights are measured and recorded 2-3 times weekly. Mean tumor weights of all groups over days post inoculation are graphed for comparison. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t-test to compare tumor sizes in the treated and control groups at the end of treatment. Significance is p < 0.05 as compared to the control group. Tumor measurements may be recorded after dosing has stopped to monitor tumor growth delay. Tumor growth delays are expressed as the difference in the median time for the treated and control groups to attain a predetermined size divided by the median time for the control group to attain that size. Growth delays are compared by generating Kaplan-Meier curves from the times for individual tumors to attain the evaluation size. Significance is p value< 0.05 compared to the vehicle control group. In addition, this model provides an opportunity to increase the rate of spontaneous metastasis of this type of tumor. Metastasis can be assessed at termination of the study by counting the number of visible foci per target organ, or measuring the target organ weight. The means of these endpoints are compared by Student's t-test after conducting an F-test, with significance determined at p < 0.05 compared to the control group in the experiment. 3.3.2. Intraprostatic Assay Tumor cells or fragments, of prostatic adenocarcinoma origin, are implanted directly into a surgically exposed dorsal lobe of the prostate in rodents. The prostate is externalized through an abdominal incision so that the tumor can be implanted specifically in the dorsal lobe while verifying that the implant does not enter the seminal vesicles. The successfully inoculated prostate is replaced in the abdomen and the incisions throught e abdomen and skin are closed. Hormones may also be administered to the rodents to support the growth of the tumors. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Body weights are measured and recorded 2-3 times weekly. At a predetermined time, the experiment is terminated and the animal is dissected. The size of the primary tumor is measured in three dimensions using either a caliper or an ocular micrometer attached to a dissecting scope. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t-test to compare tumor sizes in the treated and control groups at the end of treatment. Significance is p < 0.05 as compared to the control group. This model provides an opportunity to increase the rate of spontaneous metastasis of this type of tumor. Metastasis can be assessed at termination of the study by counting the number of visible foci per target organ (i.e., the lungs), or measuring the target organ weight (i.e., the regional lymph nodes). The means of these endpoints are compared by Student's t-test after conducting an F-test, with significance determined at p < 0.05 compared to the control group in the experiment. 3.3.3. Intrabronchial Assay Tumor cells of pulmonary origin may be implanted intrabronchially by making an incision through the skin and exposing the trachea. The trachea is pierced with the beveled end of a 25 gauge needle and the tumor cells are inoculated into the main bronchus using a flat-ended 27 gauge needle with a 90° bend. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Body weights are measured and recorded 2-3 times weekly. At a predetermined time, the experiment is terminated and the animal is dissected. The size of the primary tumor is measured in three dimensions using either a caliper or an ocular micrometer attached to a dissecting scope. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t-test to compare tumor sizes in the treated and control groups at the end of treatment. Significance is p < 0.05 as compared to the control group. This model provides an opportunity to increase the rate of spontaneous metastasis of this type of tumor. Metastasis can be assessed at termination of the study by counting the number of visible foci per target organ (i.e., the contralateral lung), or measuring the target organ weight. The means of these endpoints are compared by Student's t-test after conducting an F-test, with significance determined at p < 0.05 compared to the control group in the experiment. 3.3.4. Intracecal Assay Tumor cells of gastrointestinal origin may be implanted intracecally by making an abdominal incision through the skin and externalizing the intestine. Tumor cells are inoculated into the cecal wall without penetrating the lumen of the intestine using a 27 or 30 gauge needle. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Body weights are measured and recorded 2-3 times weekly. At a predetermined time, the experiment is terminated and the animal is dissected. The size of the primary tumor is measured in three dimensions using either a caliper or an ocular micrometer attached to a dissecting scope. An F-test is preformed to determine if the variance is equal or unequal followed by a Student's t- test to compare tumor sizes in the treated and control groups at the end of treatment. Significance is p < 0.05 as compared to the control group. This model provides an opportunity to increase the rate of spontaneous metastasis of this type of tumor. Metastasis can be assessed at termination of the study by counting the number of visible foci per target organ (i.e., the liver), or measuring the target organ weight. The means of these endpoints are compared by Student's t-test after conducting an F-test, with significance determined at p < 0.05 compared to the control group in the experiment. 4. Secondary (Metastatic) Antitumor Efficacy 4.1. Spontaneous Metastasis Tumor cells are inoculated s.c. and the tumors allowed to grow to a predetermined range for spontaneous metastasis studies to the lung or liver. These primary tumors are then excised. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule which may include the period leading up to the excision of the primary tumor to evaluate therapies directed at inhibiting the early stages of tumor metastasis. Observations of morbidity and/or mortality are recorded daily. Body weights are measured and recorded twice weekly. Potential endpoints include survival time, numbers of visible foci per target organ, or target organ weight. When survival time is used as the endpoint the other values are not determined. Survival data is used to generate Kaplan-Meier curves. Significance is p < 0.05 by a log-rank test compared to the control group in the experiment. The mean number of visible tumor foci, as determined under a dissecting microscope, and the mean target organ weights are compared by Student's t-test after conducting an F-test, with significance detennined at p < 0.05 compared to the control group in the experiment for both of these endpoints. 4.2. Forced Metastasis Tumor cells are injected into the tail vein, portal vein, or the left ventricle of the heart in experimental (forced) lung, liver, and bone metastasis studies, respectively. Compounds are administered p.o., i.p., i.v., i.m., or s.c. according to a predetermined schedule. Observations of morbidity and/or mortality are recorded daily. Body weights are measured and recorded twice weekly. Potential endpoints include survival time, numbers of visible foci per target organ, or target organ weight. When survival time is used as the endpoint the other values are not determined. Survival data is used to generate Kaplan-Meier curves. Significance is p < 0.05 by a log-rank test compared to the control group in the experiment. The mean number of visible tumor foci, as determined under a dissecting microscope, and the mean target organ weights are compared by Student's t-test after conducting an F-test, with significance at p < 0.05 compared to the vehicle control group in the experiment for both endpoints. EXAMPLE 8 Tissue-specific expression of human PLC delta-1 As a first step to establishing a role for human PLC delta-1 in the pathogenesis of COPD, expression profiling of the gene was done using real-time quantitative PCR (TaqMan) with RNA samples isolated from a wide range of human cells and tissues. Total RNA samples were either purchased from commercial suppliers or purified in- house. Two panels of RNAs were used for profiling: a whole body organ panel (Table 1) and a respiratory specific panel (Table 2). Real-time quantitative PCR. This technique is a development of the kinetic analysis of PCR first described by Higuchi et al. (BioTechnology 10, 413-17, 1992; BioTechnology 11, 1026-30, 1993). The principle is that at any given cycle within the exponential phase of PCR, the amount of product is proportional to the initial number of template copies. PCR amplification is performed in the presence of an oligonucleotide probe (TaqMan probe) that is complementary to the target sequence and labeled with a fluorescent reporter dye and a quencher dye. During the extension phase of PCR, the probe is cleaved by the 5 '-3' endonuclease activity of Taq DNA polymerase, releasing the fluorophore from the effect of the quenching dye (Holland et al, Proc. Natl. Acad. Sci. U.S.A. 88, 7276-80, 1991). Because the fluorescence emission increases in direct proportion to the amount of the specific amplified product, the exponential growth phase of PCR product can be detected and used to determine the initial template concentration (Heid et al, Genome Res. 6, 986-94, 1996, and Gibson et al, Genome Res. 6, 995-1001, 1996). RNA extraction and cDNA preparation. Total RNA from each of the 'in-house' samples listed in Table 2 was isolated using Qiagen's (Crawley, West Sussex, UK) RNeasy system according to the manufacturer's protocol. The concentration of purified RNA was determined using RiboGreen RNA quantitation kit (Molecular Probes Europe, The Netherlands). RNA concentrations of the samples purchased from commercial suppliers were also determined using RiboGreen. For the preparation of cDNA, lμg of total RNA was reverse transcribed using 200U of SUPERSCRIPT™ II RNaseH " Reverse Transcriptase (Life Technologies, Paisley, UK), lOmM dithiothreitol, 0.5mM of each dNTP, and 5μM random hexamers (PE Applied Biosystems, Warrington, Cheshire, UK) in a final volume of 20μl according to the manufacturer's protocol. TaqMan quantitative analysis. Specific primers and probe were designed according to the recommendations of PE Applied Biosystems and are listed below: Forward primer: 5'- CTGAGCGTGTGGTTCCAGC -3' Reverse primer: 5'- CAGGCCCTCGGACTGGT-3' Probe: 5'-(FAM)-ACATCTTCTTCGTGCAGCACATCGAGG-3' where FAM = 6-carboxy-fluorescein. Quantitative PCR was performed with 10 ng of reverse transcribed RNA from each sample. Each determination was done in duplicate. The assay reaction mix was as follows: IX final TaqMan Universal PCR Master Mix (from 2X stock) (PE Applied Biosystems, CA); 900 nM forward primer; 900nM reverse primer; 200 nM probe; 10 ng cDNA; and water to 25μl. Each of the following steps were carried out once: pre PCR, 2 minutes at 50° C, and 10 minutes at 95°C. The following steps are carried out 40 times: denaturation, 15 seconds at 95 °C, annealing/extension, 1 minute at 60°C. Real-time quantitative PCR was done using an ABI Prism 7700 Sequence Detector. The C T value generated for each reaction was used to determine the initial template concentration (copy number) by interpolation from a universal standard curve. The level of expression of the target gene in each sample was calculated relative to the sample with the lowest expression of the gene. The relative expression of human PLC delta-1 across various human tissues is shown in FIG. 16. Expression of the gene was detected in many tissues and was especially high in colon and testis. Abundant expression of human PLC delta-1 in lung was observed -although much lower than in colon and testis-, and is of particular interest. This was investigated further by analyzing the expression of the gene in some of the constituent cell types of the lung. In these samples expression was essentially limited to epithelial cells, with small airway epithelial cells and the Clara-like cell line H441 exhibiting the highest levels (FIG. 17). Expression in inflammatory cells was absent or very low. Table 1. Human organ RNA panel used for real-time quantitative PCR. All samples were obtained from Clontech UK Ltd, Basingstoke, UK. Table 2. Human respiratory specific RNA panel used for real-time quantitative PCR.

Claims: CLAIMS 1. An isolated polynucleotide encoding a PLC delta-1 polypeptide and being selected from the group consisting of: a) a polynucleotide encoding a PLC delta-1 polypeptide comprising an amino acid sequence selected form the group consisting of: amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 2; the amino acid sequence shown in SEQ ID NO: 2 amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 4; the amino acid sequence shown in SEQ ID NO: 4; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 9; the amino acid sequence shown in SEQ ED NO: 9; amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO: 13; and the amino acid sequence shown in SEQ ID NO: 13. b) a polynuecleotide comprising the sequence of SEQ ID NOS: 1, 3, 5, 6, 7, 8 or 10; c) a polynucleotide which hybridizes under stringent conditions to a polynucleotide specified in (a) and (b); d) a polynucleotide the sequence of which deviates from the polynucleotide sequences specified in (a) to (c) due to the degeneration of the genetic code; and e) a polynucleotide which represents a fragment, derivative or allelic variation of a polynucleotide sequence specified in (a to (d). 2. An expression vector containing any polynucleotide of claim 1. 3. A host cell containing the expression vector of claim 2. 4. A substantially purified PLC delta-1 polypeptide encoded by a polynucleotide of claim 1. 5. A method for producing a PLC delta-1 polypeptide, wherein the method comprises the following steps: a) culturing the host cell of claim 3 under conditions suitable for the expression of the PLC delta-1 polypeptide; and b) recovering the PLC delta-1 polypeptide from the host cell culture. 6. A method for detection of a polynucleotide encoding a PLC delta-1 polypeptide in a biological sample comprising the following steps: a) hybridizing any polynucleotide of claim 1 to a nucleic acid material of a biological sample, thereby forming a hybridization complex; and b) detecting said hybridization complex. 7. The method of claim 6, wherein before hybridization, the nucleic acid material of the biological sample is amplified. 8. A method for the detection of a polynucleotide of claim 1 or a PLC delta-1 polypeptide of claim 4 comprising the steps of: contacting a biological sample with a reagent which specifically interacts with the polynucleotide or the PLC delta-1 polypeptide. A diagnostic kit for conducting the method of any one of claims 6 to 8. 10. A method of screening for agents which decrease the activity of a PLC delta- 1, comprising the steps of: contacting a test compound with any PLC delta-1 polypeptide encoded by any polynucleotide of claim 1; detecting binding of the test compound to the PLC delta-1 polypeptide, wherein a test compound which binds to the polypeptide is identified as a potential therapeutic agent for decreasing the activity of a PLC delta-1. 11. A method of screening for agents which regulate the activity of a PLC delta- 1, comprising the steps of: contacting a test compound with a PLC delta-1 polypeptide encoded by any polynucleotide of claim 1; and detecting a PLC delta-1 activity of the polypeptide, wherein a test compound which increases the PLC delta-1 activity is identified as a potential therapeutic agent for increasing the activity of the PLC delta-1, and wherein a test compound which decreases the PLC delta-1 activity of the polypeptide is identified as a potential therapeutic agent for decreasing the activity of the PLC delta-1. 12. A method of screening for agents which decrease the activity of a PLC delta- 1, comprising the steps of: contacting a test compound with any polynucleotide of claim 1 and detecting binding of the test compound to the polynucleotide, wherein a test compound which binds to the polynucleotide is identified as a potential therapeutic agent for decreasing the activity of PLC delta-1. A method of reducing the activity of PLC delta-1, comprising the steps of: contacting a cell with a reagent which specifically binds to any polynucleotide of claim 1 or any PLC delta-1 polypeptide of claim 4, whereby the activity of PLC delta-1 is reduced. A reagent that modulates the activity of a PLC delta-1 polypeptide or a polynucleotide wherein said reagent is identified by the method of any of the claim 10 to 12. A pharmaceutical composition, comprising : the expression vector of claim 2 or the reagent of claim 14 and a pharmaceutically acceptable carrier. Use of the pharmaceutical composition of claim 15 for modulating the activity of a PLC delta-1 in a disease. Use of claim 16 wherein the disease is COPD, congestive heart failure, hyper- tension, cancer or conditions in which PLC delta-1 signal transduction is impaired. A cDNA encoding a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13. The cDNA of claim 18 which comprises SEQ ID NO:l, 3, 5, 6, 7, 8 or 10. The cDNA of claim 18 which consists of SEQ ID NO:l, 3, 5, 6, 7, 8 or 10. 21. An expression vector comprising a polynucleotide which encodes a polypeptide comprising the amino acid sequence shown in SEQ LD NO:2, 4, 9 or 13. 22. The expression vector of claim 21 wherein the polynucleotide consists of SEQ ID NO:l, 3, 5, 6, 7, 8 or 10. 23. A host cell comprising an expression vector which encodes a polypeptide comprising the amino acid sequence shown in SEQ ED NO:2, 4, 9 or 13. 24. The host cell of claim 23 wherein the polynucleotide consists of SEQ ID NO: 1, 3, 5, 6, 7, 8 or 10. 25. A purified polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13. 26. The purified polypeptide of claim 25 which consists of the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13. 27. A fusion protein comprising a polypeptide having the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13. 28. A method of producing a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13, comprising the steps of: culturing a host cell comprising an expression vector which encodes the polypeptide under conditions whereby the polypeptide is expressed; and isolating the polypeptide. 29. The method of claim 28 wherein the expression vector comprises SEQ ID NO:l, 3, 5, 6, 7, 8 or 10. 30. A method of detecting a coding sequence for a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13, comprising the steps of: hybridizing a polynucleotide comprising 11 contiguous nucleotides of SEQ ID NO:l, 3, 5, 6, 7, 8 or 10 to nucleic acid material of a biological sample, thereby forming a hybridization complex; and detecting the hybridization complex. 31. The method of claim 30 further comprising the step of amplifying the nucleic acid material before the step of hybridizing. 32. A kit for detecting a coding sequence for a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13, comprising: a polynucleotide comprising 11 contiguous nucleotides of SEQ ID NO:l, 3, 5, 6, 7, 8 or 10; and instructions for the method of claim 30. 33. A method of detecting a polypeptide comprising the amino acid sequence shown in SEQ ED NO:2, 4, 9 or 13, comprising the steps of: contacting a biological sample with a reagent that specifically binds to the polypeptide to form a reagent-polypeptide complex; and detecting the reagent-polypeptide complex. 34. The method of claim 33 wherein the reagent is an antibody. 35. A kit for detecting a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13, comprising: an antibody which specifically binds to the polypeptide; and instructions for the method of claim 33. A method of screening for agents which can modulate the activity of a human PLC delta-1, comprising the steps of: contacting a test compound with a polypeptide comprising an amino acid sequence selected from the group consisting of: (1) amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13 and (2) the amino acid sequence shown in SEQ D NO:2, 4, 9 or 13; and detecting binding of the test compound to the polypeptide, wherein a test compound which binds to the polypeptide is identified as a potential agent for regulating activity of the human PLC delta- 1. The method of claim 36 wherein the step of contacting is in a cell. The method of claim 36 wherein the cell is in vitro. The method of claim 36 wherein the step of contacting is in a cell-free system. The method of claim 36 wherein the polypeptide comprises a detectable label. The method of claim 36 wherein the test compound comprises a detectable label. The method of claim 36 wherein the test compound displaces a labeled ligand which is bound to the polypeptide. 43. The method of claim 36 wherein the polypeptide is bound to a solid support. 44. The method of claim 36 wherein the test compound is bound to a solid support. 45. A method of screening for agents which modulate an activity of a human PLC delta-1, comprising the steps of: contacting a test compound with a polypeptide comprising an amino acid se- quence selected from the group consisting of: (1) amino acid sequences which are at least about 50% identical to the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13 and (2) the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13; and detecting an activity of the polypeptide, wherein a test compound which increases the activity of the polypeptide is identified as a potential agent for increasing the activity of the human PLC delta-1, and wherein a test compound which decreases the activity of the polypeptide is identified as a potential agent for decreasing the activity of the human PLC delta-1. 46. The method of claim 45 wherein the step of contacting is in a cell. 47. The method of claim 45 wherein the cell is in vitro. 48. The method of claim 45 wherein the step of contacting is in a cell-free system. 49. The method of claim 45 wherein the activity is cyclic AMP formation. 50. The method of claim 45 wherein the activity is mobilization of intracellular calcium. 51. The method of claim 45 wherein the activity is phosphoinositide metabolism. 52. A method of screening for agents which modulate an activity of a human PLC delta-1, comprising the steps of: contacting a test compound with a product encoded by a polynucleotide which comprises the nucleotide sequence shown in SEQ ID NO:l, 3, 5, 6, 7, 8 or 10; and detecting binding of the test compound to the product, wherein a test compound which binds to the product is identified as a potential agent for regulating the activity of the human PLC delta-1. 53. The method of claim 52 wherein the product is a polypeptide. 54. The method of claim 52 wherein the product is RNA. 55. A method of reducing activity of a human PLC delta-1, comprising the step of: contacting a cell with a reagent which specifically binds to a product encoded by a polynucleotide comprising the nucleotide sequence shown in SEQ ID NO:l, 3, 5, 6, 7, 8 or 10, whereby the activity of a human PLC delta-1 is reduced. 56. The method of claim 55 wherein the product is a polypeptide. 57. The method of claim 56 wherein the reagent is an antibody. 58. The method of claim 55 wherein the product is RNA. 59. The method of claim 58 wherein the reagent is an antisense oligonucleotide. 60. The method of claim 59 wherein the reagent is a ribozyme. 61. The method of claim 55 wherein the cell is in vitro. 62. The method of claim 55 wherein the cell is in vivo. 63. A pharmaceutical composition, comprising: a reagent which specifically binds to a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13; and a pharmaceutically acceptable carrier. 64. The pharmaceutical composition of claim 63 wherein the reagent is an antibody. 65. A pharmaceutical composition, comprising: a reagent which specifically binds to a product of a polynucleotide comprising the nucleotide sequence shown in SEQ ED NO:l, 3, 5, 6, 7, 8 or 10; and a pharmaceutically acceptable carrier. 66. The pharmaceutical composition of claim 65 wherein the reagent is a ribozyme. 67. The pharmaceutical composition of claim 65 wherein the reagent is an antisense oligonucleotide. The pharmaceutical composition of claim 65 wherein the reagent is an antibody. A pharmaceutical composition, comprising: an expression vector encoding a polypeptide comprising the amino acid sequence shown in SEQ ID NO:2, 4, 9 or 13; and a pharmaceutically acceptable carrier. The pharmaceutical composition of claim 69 wherein the expression vector comprises SEQ ID NO:l, 3, 5, 6, 7, 8 or 10. A method of treating a PLC delta-1 dysfunction related disease, comprising the step of: administering to a patient in need thereof a therapeutically effective dose of a reagent that modulates a function of a human PLC delta-1, whereby symptoms of the PLC delta-1 dysfunction related disease are ameliorated. The method of claim 71 wherein the reagent is identified by the method of claim 36. The method of claim 71 wherein the reagent is identified by the method of claim 45. The method of claim 71 wherein the reagent is identified by the method of claim 52. The method of claim 71 wherein the disease is COPD, congestive heart failure, hypertension, cancer or conditions in which PLC delta-1 signal transduction is impaired.

Inventors: XIAO YONGHONG, XIAO, YONGHONG
Applicants: BAYER AG, XIAO YONGHONG, BAYER AKTIENGESELLSCHAFT, XIAO, YONGHONG
Application year: 2001
Main classification: C12N9
IPC codes: A61K38, C12N9, C12N15