PTH1R AND PTH3R RECEPTORS

Abstract: The present invention relates to novel parathyroid hormone (PTH) and parathyroid hormone related protein (PTHrP) receptors (PTH1R and PTH3R) isolated from zebrafish. The receptors of the present invention share homology with previously identified parathyroid hormone (PTH)/parathyroid related protein (PTHrP) receptors. Isolated nucleic acid molecules are provided encoding the zebrafish PTH1R and PTH3R receptors. PTH1R and PTH3R receptor polypeptides are also provided, as are vectors, host cells and recombinant methods for producing the same. The invention further relates to screening methods for identifying agonists and antagonists of PTH1R and PTH3R receptor activity and to diagnostic and therapeutic methods.

Description: PTHIR and PTH3R Receptors Background of the Invention Statement as to Rights to Inventions Made Under Federally-Sponsored Research and Development Part of the work performed during development of this invention utilized U.S. Government funds. The U.S. Government has certain rights in this invention. Field of the Invention The present invention is related to the fields of molecular biology, developmental biology, physiology, neurobiology and medicine. The invention provides polynucleotides encoding the zebrafish PTHIR receptor and polynucleotides for a novel zebrafish PTH3R receptor, as well as vectors and cells containing said polynucleotides. The invention further provides polypeptides for the PTHIR and PTH3R receptors. The polynucleotides and polypeptides of the invention are useful for the identification of agonist and antagonists of PTHIR or PTH3R receptor function and as reagents in the treatment of diseases or disorders associated with PTHIR or PTH3R function. Related Art The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PTHIR) mediates in mammals and frogs the actions of PTH and PTHrP. Both peptides, most likely evolved through a gene duplication event from a common ancestral gene, and have retained limited homology within the amino-terminal region. Because of their structural conservation, PTH and PTHrP bind with similar affinity to the PTH1 R, and activate this common receptor with similar or indistinguishable efficacy. Due to this unusual ligand-specificity, the PTHIR mediates the endocrine actions of PTH, the most important peptide regulator of calcium homeostasis in mammals, and the autocrine/paracrine actions of PTHrP, which is important for normal chondrocyte proliferation and differentiation (Karaplis, et al, (1997)); Lanske, et al, (1996)), and most likely for other, still incompletely defined functions including pancreas, skin, and breast development, as well as tooth eruption (Wysolmerski, et al, (1996)). In addition to the PTHIR, a PTH type-2 receptor (PTH2R) has been isolated from mammals and teleosts (Usdin, et al. , (1995); Rubin, et al. (1999)), and at least the human PTH2R is activated by PTH and a recently isolated hypothalamus peptide (Usdin, et al, (1999)). Its biological importance remains uncertain, as does the importance of additional receptors for which there is growing biological and pharmacological evidence. For example, receptors with specificity for amino-terminal PTH and PTHrP have been described for keratinocytes, squamous carcinoma cell lines, and central nervous system cells (Orloff et al, (1995 and 1996); Fukayama, et al, (1995)), and there is evidence for a PTHrP-selective receptor in the mammalian supraoptic nucleus (Yamamoto et al, (1997) and (1998)). In addition, the midregional portion of PTHrP stimulates an increase in intracellular free calcium in some cell lines and increases placental calcium transport (Kovacs et al, (1996); Wu et al, (1996); Orloff et al. , (1996)), and the carboxy-terminal portion of PTH binds to a distinct receptor on clonal cell lines (Inomata, et al, (1995); Takasu, et al, (1998)). Research on the parathyroid hormone (PTH) has been extensive. Formulations of PTH and compounds with PTH activity have been described (see US Patent Nos. 5,496,801; 5,814,603; 5,208041;), and methods to produce the same are also known (see US Patent Nos. 5,616,560 and 5,010,010). In addition, analogs and inhibitors of PTH may be found in the prior art (see US Patent Nos. 4,423,037; 5,693616; 5,695,955 and 5,798,225). Thus, the invention furthers the art by focusing on PTH receptors and providing reagents and methods that are distinct and separate from PTH. Summary of the Invention The present invention provides isolated nucleic acid molecules comprising a polynucleotide encoding a novel PTHIR receptor having the amino acid sequence shown in Figure 2A (SEQ ID NO:2) or the amino acid sequence encoded by the cDNA clone deposited in a bacterial host with the ATCC as patent deposit PTA-916 on November 4, 1999. The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of PTH 1 R polypeptides or peptides by recombinant techniques . The invention further provides an isolated PTHIR polypeptide having an amino acid sequence encoded by a polynucleotide described herein. The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding a novel PTH3R receptor having the amino acid sequence shown in Figure 2B (SEQ ID NO:4) or the amino acid sequence encoded by the cDNA clone deposited in a bacterial host with the ATCC as patent deposit PTA-915 on November 4, 1999. The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of PTH3R polypeptides or peptides by recombinant techniques. The invention further provides an isolated PTH3R polypeptide having an amino acid sequence encoded by a polynucleotide described herein. The present invention also provides a screening method for identifying compounds capable of enhancing or inhibiting a cellular response induced by the PTHIR or PTH3R receptor, which involves contacting cells which express the PTHIR or PTH3R receptor with the candidate compound, assaying a cellular response, and comparing the cellular response to a standard cellular response, the standard being assayed when contact is made in absence of the candidate compound; whereby, an increased cellular response over the standard indicates that the compound is an agonist and a decreased cellular response over the standard indicates that the compound is an antagonist. In another aspect, a screening assay for agonists and antagonists is provided which involves determining the effect a candidate compound has on PTH or PTHrP binding to the PTHIR or PTH3R receptor. In particular, the method involves contacting the PTH1 R or PTH3R receptor with a PTH or PTHrP polypeptide and a candidate compound and determining whether PTH or PTHrP polypeptide binding to the PTHIR or PTH3R receptor is increased or decreased due to the presence of the candidate compound. An additional aspect of the invention is related to a method for treating an individual in need of an increased level of PTHIR or PTH3R activity in the body comprising administering to such an individual a composition comprising a therapeutically effective amount of an isolated PTH 1 R or PTH3R polypeptide of the invention or an agonist thereof. A still further aspect of the invention is related to a method for treating an individual in need of a decreased level of PTHIR or PTH3R receptor activity in the body comprising, administering to such an individual a composition comprising a therapeutically effective amount of an PTHIR or PTH3R antagonist. The invention further provides a diagnostic method useful during diagnosis or prognosis of diseases and disorders associated with PTHIR or PTH3R receptor expression or function. Brief Description of the Figures Figure 1. A) Schematic representation of exons M6/7 and M7 (A), and of the cDNA encoding the PTHIR or the PTH3R (B). Vertical boxes depict the predicted location of the membrane-spanning helices; recognition sites for restriction enzymes are shown by //. For and Rev arrows indicate the approximate location of primers used for RT-PCR, 5' RACE, and 3' RACE for zPTHIR and zPTH3R. C) The nucleotide sequence of the PTH3R receptor cDNA. D) The nucleotide sequence of the PTH3R receptor cDNA. •$=, degenerate primers; <— , zPTHlR-specific; <-, zPTH3R-specifιc; ς, potential sites for N-linked glycosylation. Figure 2 A) The amino acid sequence of the PTHIR receptor; B) The amino acid sequence of the PTH3R receptor. Figure 3 Alignment of the amino acid sequences of the zPTHIR, zPTH2R, and zPTH3R. The sequences were aligned using the GAP and pileup algorithms of the GCG package (Genetics Computer Group, Wisconsin). Conserved consensus sites for potential N-glycosylation are identified by #; Gaps were introduced to maximize sequence homology. The seventeen residues which are lacking in one splice variant of the characterized zPTH2R (Rubin et al, (1999)) are boxed; the residues which are predicted to comprise the signal peptide are outlined with a stippled box; and those residues which are likely to be PTH3R-specific are boxed. Figure 4A-D. COS-7 cells transiently expressing the zPTHIR or the zPTH3R were evaluated for competitive inhibition of radioligand binding (A,B) and agonist-stimulated cAMP production (C,D). Binding studies (as described in Materials and Methods) used either 125 I-[Nle 8 - 21 ,Tyr 34 ]rPTH-(l-34)amide (Panel A) or 125 I-[Tyr 36 ]hPTHrP-(l-36)amide (Panel B) as radioligand and varying amounts of unlabeled peptide. Data are expressed as % of maximal binding. Cyclic AMP accumulation is expressed as % of maximal for the zPTHIR (C) or the zPTH3R (D); basal cAMP accumulation was 3-4 pmol/well for either receptor; maximal accumulation of 106.2 pmol/well for the zPTHIR, and 285.4 pmol/well for the zPTH3R. BD, PTH; ΦO, PTHrP; filled symbols represent zPTHIR, open symbols represent zPTH3R. All data represent the mean ± SEM of at least three independent transfections. RECTIFIED SHEET (RULE 91) ISA/EP Figure 5. Accumulation of total IP in COS-7 cells transiently expressing the zPTHIR, or the zPTH3R or the hPTHlR. Hydrolysis of total IPs was assessed as described in the absence or presence of PTHrP (10 "6 M) or PTH (10 "6 M). Data are expressed as fold above basal and represent the mean ± SEM of at least two independent experiments. Figure 6. A phylogenetic analysis, as described in Materials and Methods, indicated that the single most parsimonious tree had a length of 1549 steps, and a consistency index excluding uninformative characters of 0.863. The bootstrap confidence intervals are shown next to the branch points and indicate the percentage of trials which support a given branch in 100 branch-and-bound iterations. Figure 7. Southern blot analysis of wild-type (left lane) and PTH/PTHrP receptor knock out mouse genomic DNA (right lane) probed with PTH3R. Detailed Description of the Preferred Embodiments The present invention provides novel PTH receptor nucleic acids and proteins (Rubin and Juppner, (1999)). More specifically, the present invention provides isolated nucleic acid molecules comprising a polynucleotide encoding a novel PTHIR polypeptide having the amino acid sequence shown in Figure 2 A (SEQ ID NO:2), which was determined by sequencing a cloned cDNA. The PTHIR protein of the present invention shares sequence homology with previously identified PTHIR and PTH2R sequences. The nucleotide sequence of SEQ ID NO:l was obtained by sequencing a cDNA clone (zPTHIR), which was deposited on November 4, 1999 at the American Type Culture Collection, 10801 University Boulevard, Manassas, Virginia 20110-2209, and given accession number PTA-916. The cDNA was inserted between the EcoRI and Sphl site of plasmid pcDNAI/Amp (Invitrogen). RECTIFIED SHEET (RULE 91) ISA/EP The present invention also provides isolated nucleic acid molecules comprising a polynucleotide encoding a novel PTH3R polypeptide having the amino acid sequence shown in Figure 2B (SEQ ID NO:4), which was determined by sequencing a cloned cDNA. The PTH3R protein of the present invention shares sequence homology with the PTH 1 R protein sequence of the invention and other PTH 1 R and PTH2R protein sequences previously. The nucleotide sequence shown in Figure ID (SEQ ID NO:3) was obtained by sequencing a cDNA clone(zPTH3R), which was deposited on November 4, 1999 at the American Type Culture Collection, 10801 University Boulevard, Manassas, Virginia 20110- 2209, and given accession number PTA-915. The cDNA was inserted between the BamHI and Notl site of plasmid pcDNAI/Amp (Invitrogen). Nucleic Acid Molecules Unless otherwise indicated, all nucleotide sequences determined by sequencing a DNA molecule herein were determined by manual sequencing, and all amino acid sequences of polypeptides encoded by DNA molecules determined herein were predicted by translation of a DNA sequence determined as above. Therefore, as is known in the art for any DNA sequence determined by this approach, any nucleotide sequence determined herein may contain some errors. Nucleotide sequences determined by manual sequencing are typically at least about 95% to at least about 99.9% identical to the actual nucleotide sequence of the sequenced DNA molecule. As is also known in the art, a single insertion or deletion in a determined nucleotide sequence compared to the actual sequence will cause a frame shift in translation of the nucleotide sequence such that the predicted amino acid sequence encoded by a determined nucleotide sequence will be completely different from the amino acid sequence actually encoded by the sequenced DNA molecule, beginning at the point of such an insertion or deletion. Using the information provided herein, such as the nucleotide sequence of SEQ ID NO:l or SEQ ID NO:3, a nucleic acid molecule of the present RECTIFIED SHEET (RULE 91) ISA/EP invention encoding a PTHIR or PTH3R polypeptide, respectively, may be obtained using standard cloning and screening procedures, such as those for cloning cDNAs using mRNA as starting material. Illustrative of the invention, the nucleic acid molecule described in SEQ ID NO:l was discovered using oligonucleotide primers in a polymerase chain reaction (PCR) with total RNA isolated from adult zebrafish. The determined nucleotide sequence of the PTH 1 R cDNA of SEQ ID NO:l contains an open reading frame encoding a protein of about 536 amino acid residues, with a predicted leader sequence of about 24 amino acid residues, and a deduced molecular weight of about 61.4 kDa for the non-glycosylated form. The amino acid sequence of the predicted mature PTHIR receptor is shown in Figure 2A from amino acid residue about 25 to residue about 536. The PTHIR protein shown in Figure 2A (SEQ ID NO:2) is about 76 % identical to human PTHIR sequence and about 68 % identical to human PTH2R sequence. Also illustrative of the invention is the nucleic acid molecule described in Figure ID (SEQ ID NO:3) was discovered in a zebrafish cDNA library (Clontech). The determined nucleotide sequence of the Figure ID (SEQ ID NO:3) contains an open reading frame encoding a protein of about 542 amino acid residues, with a predicted leader sequence of about 21 amino acid residues, and a deduced molecular weight of about 59.2 kDa. The PTH3R protein shown inFigure 2B (SEQ IDNO:4) is about 68% and 57% similar to human PTHlRand human PTH2R, respectively. As indicated, the present invention also provides the mature form(s) of the PTHIR and PTH3R receptors of the present invention. According to the signal hypothesis, proteins secreted by mammalian cells have a signal or secretory leader sequence which is cleaved from the mature protein once export of the growing protein chain across the rough endoplasmic reticulum has been initiated. Most mammalian cells and even insect cells cleave secreted proteins with the same specificity. However, in some cases, cleavage of a secreted protein is not entirely uniform, which results in two or more mature species on the protein. Further, it RECTIFIED SHEET (RULE 91) ISA/EP has long been known that the cleavage specificity of a secreted protein is ultimately determined by the primary structure of the complete protein, that is, it is inherent in the amino acid sequence of the polypeptide. Therefore, the present invention provides a nucleotide sequence encoding the mature PTHIR polypeptides having the amino acid sequence encoded by the cDNA clone deposited in a bacterial host with the ATCC as patent deposit PTA-916 on November 4, 1999 and as shown in Figure 2A (SEQ ID NO:2). The present invention also provides a nucleotide sequence encoding the mature PTH3R polypeptides having the amino acid sequence encoded by the cDNA clone deposited in a bacterial host with the ATCC as patent deposit PTA-915 on November 4, 1999 and as shown in Figure 2B (SEQ ID NO:4). By the mature PTHIR protein having the amino acid sequence encoded by the cDNA clone contained in the bacterial host deposited with the ATCC as patent deposit PTA- 916 is meant the mature form(s) of the PTHIR receptor produced by expression in a mammalian cell (e.g., COS cells, as described below) of the complete open reading frame encoded by the zebrafish DNA sequence of the clone contained in the vector in the deposited host. By the mature PTH3R protein having the amino acid sequence encoded by the cDNA clone contained in the bacterial host deposited with the ATCC as patent deposit PTA-915 is meant the mature form(s) of the PTH3R receptor produced by expression in a mammalian cell (e.g., COS cells, as described below) of the complete open reading frame encoded by the zebrafish DNA sequence of the clone contained in the vector in the deposited host. As indicated below, the mature PTHIR receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916 may or may not differ from the predicted "mature' THlR protein shown in Figure 2A (amino acids from about 25 to about 536) depending on the accuracy of the predicted cleavage. The mature PTH3R receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915 may or may not differ from the predicted "mature" PTH3R protein shown in Figure 2B (amino acids from about 22 to about 542) depending on the accuracy of the predicted cleavage site. Methods for predicting whether a protein has a secretory leader as well as the cleavage point for that leader sequence are available. For instance, the methods of McGeoch (Virus Res. 3:271-286 (1985)) and von Heinje (Nucleic Acids Res. 74:4683-4690 (1986)) can be used. The accuracy of predicting the cleavage points of known mammalian secretory proteins for each of these methods is in the range of 75-80%. von Heinje, supra. However, the two methods do not always produce the same predicted cleavage point(s) for a given protein. A computational method may be found in the computer program "PSORT" (K. Nakai and M. Kanehisa. Genomics 14:897-911 (1992)), which is an expert system for predicting the cellular location of a protein based on the amino acid sequence. As part of this computational prediction of localization, the methods of McGeoch and von Heinje are incorporated. In the present case, the predicted amino acid sequence of the complete PTHIR and PTH3R polypeptides of the present invention were analyzed for structural properties by comparison to the rat PTHIR sequence. This analysis provided predicted a cleavage site between amino acids 24 and 25 in Figure 2A (SEQ ID NO:2) and a cleavage site between amino acids 21 and 22 in Figure 2B (SEQ ID NO:4). Thus, the leader sequence for the PTHIR receptor protein is predicted to consist of amino acid residues 1-24 in Figure 2A (amino acids 1 to 24 in SEQ ID NO:2) , while the predicted mature PTHIR protein consists of residues 25-536 (amino acids 25 to 536 in SEQ ID NO:2). The leader sequence for the PTH3R receptor protein is predicted to consist of amino acid residues 1-21 in Figure 2B (amino acids 1-21 in SEQ ID NO:4), while the predicted mature PTH3R protein consists of residues 22-542 (amino acids 22 to 542 in SEQ ID NO:4). As indicated, nucleic acid molecules of the present invention may be in the form of RNA, such as mRNA, or in the form of DNA, including, for instance, cDNA and genomic DNA obtained by cloning or produced synthetically. The DNA may be double-stranded or single-stranded. Single-stranded DNA or RNA may be the coding strand, also known as the sense strand, or it may be the non-coding strand, also referred to as the anti-sense strand. As one of ordinary skill would appreciate, however, due to the possibilities of sequencing errors, the PTHIR receptor polypeptide encoded by the deposited cDNA comprises about 536 amino acids, but may be anywhere in the range of 510-561 amino acids; and the leader sequence of this protein is about 24 amino acids, but may be anywhere in the range of about 10 to about 30 amino acids. As one of ordinary skill would also appreciate, however, due to the possibilities of sequencing errors, the PTH3R receptor polypeptide encoded by the deposited cDNA comprises about 542 amino acids, but may be anywhere in the range of 500-550 amino acids; and the leader sequence of this protein is about 24 amino acids, but may be anywhere in the range of about 15 to about 35 amino acids. As indicated, nucleic acid molecules of the present invention may be in the form of RNA, such as mRNA, or in the form of DNA, including, for instance, cDNA and genomic DNA obtained by cloning or produced synthetically. The DNA may be double-stranded or single-stranded. Single-stranded DNA or RNA may be the coding strand, also known as the sense strand, or it may be the non-coding strand, also referred to as the anti-sense strand. By "isolated" nucleic acid molecule(s) is intended a nucleic acid molecule, DNA or RNA, which has been removed from its native environment. For example, recombinant DNA molecules contained in a vector are considered isolated for the purposes of the present invention. Further examples of isolated DNA molecules include recombinant DNA molecules maintained in heterologous host cells or purified (partially or substantially) DNA molecules in solution. Isolated RNA molecules include in vivo or in vitro RNA transcripts of the DNA molecules of the present invention. Isolated nucleic acid molecules according to the present invention further include such molecules produced synthetically. Isolated nucleic acid molecules of the present invention include DNA molecules comprising an open reading frame (ORF) shown in SEQ ID NO:l or SEQ ID NO:3; DNA molecules comprising the coding sequence for the PTHIR receptor shown in Figure 2A (SEQ ID NO:2) or the PTH3R receptor shown Figure 2B (SEQ ID NO:4); and DNA molecules which comprise a sequence substantially different from those described above but which, due to the degeneracy of the genetic code, still encode the PTHIR or the PTH3R receptor. Of course, the genetic code is well known in the art. Thus, it would be routine for one skilled in the art to generate such degenerate variants. In another aspect, the invention provides isolated nucleic acid molecules encoding the PTHIR polypeptide having an amino acid sequence encoded by the cDNA clone contained in the plasmid deposited with the ATCC as patent deposit PTA-916 on November 4, 1999. Another aspect, the invention provides isolated nucleic acid molecules encoding the PTH3R polypeptide having an amino acid sequence encoded by the cDN A clone contained in the plasmid deposited with the ATCC as patent deposit PTA-915 on November 4, 1999. Preferably, these nucleic acid molecules will encode the mature polypeptides encoded by the above-described deposited cDNA clones. In a further embodiment, nucleic acid molecules are provided encoding the PTHIR or the PTH3R polypeptide or the PTHIR or the PTH3R polypeptide lacking the N-terminal methionine. The invention also provides an isolated nucleic acid molecule having the nucleotide sequence shown in SEQ ID NO:l or the nucleotide sequence of the PTHIR cDNA contained in the above-described deposited clone, or a nucleic acid molecule having a sequence complementary to one of the above sequences. Such isolated molecules, particularly DNA molecules, are useful as probes for gene mapping, by in situ hybridization with chromosomes, and for detecting expression of the PTHIR gene in human tissue, for instance, by Northern blot analysis. The invention also provides an isolated nucleic acid molecule having the nucleotide sequence shown in SEQ ID NO:3 or the nucleotide sequence of the cDNA contained in the above-described deposited clone, or a nucleic acid molecule RECTIFIED SHEET (RULE 91) ISA/EP having a sequence complementary to one of the above sequences. Such isolated molecules, particularly DNA molecules, are useful as probes for gene mapping, by in situ hybridization with chromosomes, and for detecting expression of the gene in human tissue, for instance, by Northern blot analysis. The present invention is further directed to fragments of the isolated nucleic acid molecules described herein. By a fragment of an isolated nucleic acid molecule having the nucleotide sequence of the deposited cDNAs or the nucleotide sequence shown in SEQ ID NO:l or SEQ ID NO:3 is intended fragments at least about 15 nt, and more preferably at least about 20 nt, still more preferably at least about 30 nt, and even more preferably, at least about 40 nt in length which are useful as diagnostic probes and primers as discussed herein. Of course, larger fragments of about 50-1550 nt in length, and more preferably at fragments least about 600 nt in length are also useful according to the present invention as are fragments corresponding to most, if not all, of the nucleotide sequence of the deposited cDNAs or as shown in SEQ ID NO: 1 or SEQ ID NO:3. By a fragment at least 20 nt in length, for example, is intended fragments which include 20 or more contiguous bases from the nucleotide sequence of the deposited cDNAs or the nucleotide sequence as shown in or SEQ ID NO:l or SEQ ID NO:3. Preferred nucleic acid fragments of the present invention include nucleic acid molecules encoding: a polypeptide comprising the PTHIR receptor extracellular domain (predicted to constitute amino acid residues from about 25 to about 147 in Figure 2 A (or amino acid residues from about 25 to about 147 in SEQ ID NO:2)); a polypeptide comprising the PTHIR receptor transmembrane domain (predicted to constitute amino acid residues from about 148 to about 416 in Figure 2 A (or amino acid residues from about 148 to about 416 in SEQ ID NO:2)); and a polypeptide comprising the PTHIR receptor extracellular domain with all or part of the transmembrane domain deleted. As above with the leader sequence, the amino acid residues constituting the PTHIR receptor extracellular and transmembrane domains have been predicted. Thus, as one of ordinary skill RECTIFIED SHEET (RULE 91) ISA/EP would appreciate, the amino acid residues constituting these domains may vary slightly (e.g., by about 1 to about 15 amino acid residues) depending on the criteria used to define each domain. Preferred nucleic acid fragments of the present invention also include nucleic acid molecules encoding: a polypeptide comprising the PTH3R receptor extracellular domain (predicted to constitute amino acid residues from about 22 to about 145 in Figure 2B (or amino acid residues from about 22 to about 145 in SEQ ID NO:4); a polypeptide comprising the PTH3R receptor transmembrane domain (predicted to constitute amino acid residues from about 146 to about 402 in Figure 2B (or amino acid residues from about 146 to about 402 in SEQ ID NO:4); and a polypeptide comprising the PTH3R receptor extracellular domain with all or part of the transmembrane domain deleted. As above with the leader sequence, the amino acid residues constituting the PTH3R receptor extracellular and transmembrane domains have been predicted by computer analysis. Thus, as one of ordinary skill would appreciate, the amino acid residues constituting these domains may vary slightly (e.g., by about 1 to about 15 amino acid residues) depending on the criteria used to define each domain. Preferred nucleic acid fragments of the present invention also include nucleic acid molecules encoding epitope-bearing portions of the PTHIR or PTH3R receptor protein. As one skilled in the art would know, a nucleic acid sequence may be used to predict the polypeptide sequence encoded therein. Such information may then be used to predict antigenic determinants in the polypeptide that may be related to the corresponding polynucleotide regions encoding the antigenic determinants identified by the analysis. Methods for predicting the antigenic determinants of a polypeptide are well known in the art. Methods for determining other such epitope-bearing portions of the PTHIR or the PTH3R protein are described in detail below. In another aspect, the invention provides an isolated nucleic acid molecule comprising a polynucleotide which hybridizes under stringent hybridization conditions to a portion of the polynucleotide in a nucleic acid molecule of the invention described above, for instance, the cDNA clones contained in the bacterial hosts deposited with the ATCC as patent deposit PTA-915 or patent deposit PTA-916. By "stringent hybridization conditions" is intended overnight incubation at 42° C in a solution comprising: 50% formamide, 5x SSC (150 mM NaCl, 15mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10% dextran sulfate, and 20 g/ml denatured, sheared salmon sperm DNA, followed by washing the filters in 0.1 x SSC at about 65 °C. In another aspect, the invention provides an isolated nucleic acid molecule comprising a polynucleotide which hybridizes under low stringency hybridization conditions to a portion of the polynucleotide in a nucleic acid molecule of the invention described above, for instance, the cDNA clones contained in the bacterial hosts deposited with the ATCC as patent deposit PTA-915 or patent deposit PTA-916. By "low stringency hybridization conditions" is intended overnight incubation at 42 °C in a solution comprising: 30% formamide, 5x SSC (150 mM NaCl, 15mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10% dextran sulfate, and 20 g/ml denatured, sheared salmon sperm DNA, followed by washing the filters in a solution of 2x SSC or lx SSC or 0 .5x SSC at about 55 °C or 60 °C or 65 °C. By a polynucleotide which hybridizes to a "portion" of a polynucleotide is intended a polynucleotide (either DNA or RNA) hybridizing to at least about 15 nucleotides (nt), and more preferably at least about 20 nt, still more preferably at least about 30 nt, and even more preferably about 30-70 nt of the reference polynucleotide. These are useful as diagnostic probes and primers as discussed above and in more detail below. By a portion of a polynucleotide of "at least 20 nt in length," for example, is intended 20 or more contiguous nucleotides from the nucleotide sequence of the reference polynucleotide (e.g., the deposited cDNAs or the nucleotide sequence as shown in SEQ ID NO:l or SEQ ID NO:3). Of course, a polynucleotide which hybridizes only to a poly A sequence (such as the 3' terminal poly(A) tract of the PTHIR receptor cDNA shown in RECTIFIED SHEET (RULE 91) ISA/EP SEQ ID NO:l or the 3' terminal poly(A) tract of the PTH3R receptor cDNA shown in SEQ ID NO:3), or to a complementary stretch of T (or U) resides, would not be included in a polynucleotide of the invention used to hybridize to a portion of a nucleic acid of the invention, since such a polynucleotide would hybridize to any nucleic acid molecule containing a poly (A) stretch or the complement thereof (e.g., practically any double-stranded cDNA clone). As indicated, nucleic acid molecules of the present invention which encode a PTHIR or PTH3R polypeptide may include, but are not limited to those encoding the amino acid sequence of the mature polypeptides, by themselves; the coding sequence for the mature polypeptides and additional sequences, such as those encoding the amino acid leader or secretory sequence, such as apre-, or pro- or prepro- protein sequence; the coding sequence of the mature polypeptide, with or without the aforementioned additional coding sequences, together with additional, non-coding sequences, including for example, but not limited to introns and non-coding 5' and 3 ' sequences, such as the transcribed, non-translated sequences that play a role in transcription, mRNA processing, including splicing and polyadenylation signals, for example - ribosome binding and stability of mRNA; an additional coding sequence which codes for additional amino acids, such as those which provide additional functionalities. Thus, the sequence encoding the polypeptide may be fused to a marker sequence, such as a sequence encoding a peptide which facilitates purification of the fused polypeptide. In certain preferred embodiments of this aspect of the invention, the marker amino acid sequence is a hexa-histidine peptide, such as the tag provided in a pQE vector (Qiagen, Inc.), among others, many of which are commercially available. As described in Gentz et al, Proc. Natl. Acad. Sci. USA 5 :821-824 (1989), for instance, hexa-histidine provides for convenient purification of the fusion protein. The "HA" tag is another peptide useful for purification which corresponds to an epitope derived from the influenza hemagglutinin protein, which has been described by Wilson et al, Cell 37: 767 (1984). As discussed RECTIFIED SHEET (RULE 91) ISA/EP below, other such fusion proteins include the PTHIR receptor fused to Fc at the N- or C -terminus. The present invention further relates to variants of the nucleic acid molecules of the present invention, which encode portions, analogs or derivatives of the PTHIR or PTH3R receptor. Variants may occur naturally, such as a natural allelic variant. By an "allelic variant" is intended one of several alternate forms of a gene occupying a given locus on a chromosome of an organism. Genes II, Lewin, B., ed., John Wiley & Sons, New York (1985). Non-naturally occurring variants may be produced using art-known mutagenesis techniques. Such variants include those produced by nucleotide substitutions, deletions or additions, which may involve one or more nucleotides. The variants may be altered in coding regions, non-coding regions, or both. Alterations in the coding regions may produce conservative or non-conservative amino acid substitutions, deletions or additions. Especially preferred among these are silent substitutions, additions and deletions, which do not alter the properties and activities of the PTHIR or PTH3R receptor or portions thereof. Also especially preferred in this regard are conservative substitutions. Further embodiments of the invention include isolated nucleic acid molecules comprising a polynucleotide having a nucleotide sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to (a) a nucleotide sequence encoding the full-length PTH 1 R polypeptide having the complete amino acid sequence in SEQ ID NO:2, including the predicted leader sequence; (b) a nucleotide sequence encoding the polypeptide having the amino acid sequence in SEQ ID NO:2, but lacking the N-terminal methionine; (c) a nucleotide sequence encoding the mature PTHIR receptor (full-length polypeptide with the leader removed) having the amino acid sequence at positions from about 25 to about 536 in SEQ ID NO:2; (d) a nucleotide sequence encoding the full-length PTH 1 R polypeptide having the complete amino acid sequence including the leader encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (e) a nucleotide sequence encoding the mature PTHIR receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (f) a nucleotide sequence encoding the PTHIR receptor extracellular domain; (g) a nucleotide sequence encoding the PTHIR receptor transmembrane domain; (h) a nucleotide sequence encoding the PTHIR receptor extracellular domain with all or part of the transmembrane domain deleted; and (i) a nucleotide sequence complementary to any of the nucleotide sequences in (a), (b), (c), (d), (e), (f), (g) or (h). Embodiments of the invention also include isolated nucleic acid molecules comprising a polynucleotide having a nucleotide sequence at least 50%, 55%, 60%, 65%, 70%, 75%. 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to (a) a nucleotide sequence encoding the full-length PTH3R polypeptide having the complete amino acid sequence in Figure 2B (SEQ ID NO:4), including the predicted leader sequence; (b) a nucleotide sequence encoding the polypeptide having the amino acid sequence in SEQ ID NO:4, but lacking the N-terminal methionine; (c) a nucleotide sequence encoding the mature PTH3R receptor (full-length polypeptide with the leader removed) having the amino acid sequence at positions from about 22 to about 542 in SEQ ID NO:4; (d) a nucleotide sequence encoding the full-length PTH3R polypeptide having the complete amino acid sequence including the leader encoded by the cDNA clone deposited with the ATCC as patent deposit PTA- 915; (e) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence encoded by the cDNA deposited with the ATCC as patent deposit PTA-915; (f) a nucleotide sequence encoding the PTH3R receptor extracellular domain; (g) a nucleotide sequence encoding the PTH3R receptor transmembrane domain; (h) a nucleotide sequence encoding the PTH3R receptor extracellular domain with all or part of the transmembrane domain deleted; and (i) a nucleotide sequence complementary to any of the nucleotide sequences in (a), (b), (c), (d), (e), (f), (g), or (h). By a polynucleotide having a nucleotide sequence at least, for example, 95% "identical" to a reference nucleotide sequence encoding a PTHl R or PTH3R polypeptide is intended that the nucleotide sequence of the polynucleotide is identical to the reference sequence except that the polynucleotide sequence may include up to five point mutations per each 100 nucleotides of the reference nucleotide sequence encoding the PTHIR or PTH3R receptor. In other words, to obtain a polynucleotide having a nucleotide sequence at least 95% identical to a reference nucleotide sequence, up to 5% of the nucleotides in the reference sequence may be deleted or substituted with another nucleotide, or a number of nucleotides up to 5% of the total nucleotides in the reference sequence may be inserted into the reference sequence. These mutations of the reference sequence may occur at the 5 ' or 3 ' terminal positions of the reference nucleotide sequence or anywhere between those terminal positions, interspersed either individually among nucleotides in the reference sequence or in one or more contiguous groups within the reference sequence. As a practical matter, whether any particular nucleic acid molecule is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%o, 97%, 98%, or 99% identical to, for instance, the nucleotide sequence shown in SEQ ID NO:l or SEQ ID NO:3 or to the nucleotides sequence of the deposited cDNA clones can be determined conventionally using known computer programs such as the Bestfit program (Wisconsin Sequence Analysis Package, Version 8 for Unix, Genetics Computer Group, University Research Park, 575 Science Drive, Madison, WI 53711. Bestfit uses the local homology algorithm of Smith and Waterman, Advances in Applied Mathematics 2: 482-489 (1981), to find the best segment of homology between two sequences. When using Bestfit or any other sequence alignment program to determine whether a particular sequence is, for instance, 95% identical to a reference sequence according to the present invention, the parameters are set, of course, such that the percentage of identity is calculated over the full length of the reference nucleotide RECTIFIED SHEET (RULE 91) ISA EP sequence and that gaps in homology of up to 5% of the total number of nucleotides in the reference sequence are allowed. The present application is directed to nucleic acid molecules at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence shown in SEQ ID NO: 1 or SEQ ID NO: 3 or to the nucleic acid sequence of the deposited cDNAs, irrespective of whether they encode a polypeptide having PTHIR or PTH3R receptor activity. This is because even where a particular nucleic acid molecule does not encode a polypeptide having PTHIR or PTH3R receptor activity, one of skill in the art would still know how to use the nucleic acid molecule, for instance, as a hybridization probe or a polymerase chain reaction (PCR) primer. Uses of the nucleic acid molecules of the present invention that do not encode a polypeptide having PTHIR or PTH3R receptor activity include, inter alia, (1) isolating the PTHIR or PTH3R receptor gene or allelic variants thereof in a cDNA library; (2) in situ hybridization (e.g., "FISH") to metaphase chromosomal spreads to provide precise chromosomal location of the PTHIR or PTH3R receptor gene, as described in Verma et al, Human Chromosomes: A Manual of Basic Techniques, Pergamon Press, New York (1988); and (3) Northern Blot analysis for detecting PTHIR or PTH3R receptor mRNA expression in specific tissues. Preferred, however, are nucleic acid molecules having sequences at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to the nucleic acid sequence shown in SEQ ID NO:l or SEQ ID NO:3 or to the nucleic acid sequence of the deposited cDNA which do, in fact, encode a polypeptide having PTHIR or PTH3R receptor activity. By "a polypeptide having PTHIR or PTH3R receptor activity" is intended polypeptides exhibiting activity similar, but not necessarily identical, to an activity of the PTHIR or PTH3R receptor of the invention, as measured in a particular biological assay. For example, PTHIR or PTH3Rreceptor activity can be measured using competition binding experiments of labeled PTH or PTHrP to RECTIFIED SHEET (RULE 91) ISA EP cells expressing the candidate PTHIR or PTH3R polypeptide as described in Treanor etal, Nature 552:80-83 (1996) or Jing eta , Cell 85: 1113-1124 (1996). As demonstrated in Examples 3 and 4 herein, assays to address PTHIR and PTH3R function are well known in the art. Any cell line expressing the PTHIR or PTH3R receptor, or variants thereof, may be used to assay ligand binding and second messenger activation as described in Examples 3 and 4. Of course, due to the degeneracy of the genetic code, one of ordinary skill in the art will immediately recognize that a large number of the nucleic acid molecules having a sequence at least 95%), 96%, 97%, 98%, or 99% identical to the nucleic acid sequence of the deposited cDNAs or the nucleic acid sequence shown in SEQ ID NO:l or SEQ ID NO:3 will encode a polypeptide "having PTHIR or PTH3R receptor activity." In fact, since degenerate variants of these nucleotide sequences all encode the same polypeptide, this will be clear to the skilled artisan even without performing the above described comparison assay. It will be further recognized in the art that, for such nucleic acid molecules that are not degenerate variants, a reasonable number will also encode a polypeptide having PTHIR or PTH3R protein activity. This is because the skilled artisan is fully aware of amino acid substitutions that are either less likely or not likely to significantly effect protein function (e.g., replacing one aliphatic amino acid with a second aliphatic amino acid). For example, guidance concerning how to make phenotypically silent amino acid substitutions is provided in Bowie, J. U. et al, "Deciphering the Message in Protein Sequences: Tolerance to Amino Acid Substitutions," Science 247: 1306- 1310 (1990), wherein the authors indicate that proteins are surprisingly tolerant of amino acid substitutions. The invention also provides a method for the isolation of a nucleic acid molecule comprising: (a) selecting a fragment of SEQ ID NO:3 as a nucleic acid probe; (b) hybridizing said probe overnight to at least one test sequence by incubation at 42°C in a solution of 30% formamide, 5x SSC (150 mM NaCl, RECTIFIED SHEET (RULE 91) ISA/EP 15mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10% dextran sulfate, and 20 g/ml denatured, sheared salmon sperm DNA; (c) removing nonhydridized probe by washing with a solution of 2x SSC or lx SSC or 0 .5x SSC at about 55 °C or 60°C or 65 °C; and (d) identifying a target sequence bound by said probe; wherein said identified target sequence is at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to a sequence selected from the group consisting of: (e) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence at positions from about 1 to about 542 in (SEQ ID NO:4); (f) a nucleotide sequence encoding the PTH3R receptor having the amino acid sequence at positions from about 2 to about 542 in (SEQ ID NO:4); (g) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence at positions from about 22 to about 542 in (SEQ ID NO:4); (h) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915 ; (i) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (j) a nucleotide sequence encoding the PTH3R extracellular domain; (k) a nucleotide sequence encoding the PTH3R transmembrane domain; and (1) a nucleotide sequence complementary to any of the nucleotide sequences in (e), (f), (g), (h), (i), (j) or (k). The invention also provides a method for the isolation of a nucleic acid molecule comprising: (a) selecting a fragment of SEQ ID NO:l as a nucleic acid probe; (b) hybridizing said probe overnight to at least one test sequence by incubation at 42 °C in a solution of 30% formamide, 5x SSC (150 mM NaCl, 15mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10%) dextran sulfate, and 20 g/ml denatured, sheared salmon sperm DNA; (c) removing nonhydridized probe by washing with a solution of 2x SSC or lx SSC or 0 .5x SSC at about 55°C or 60°C or 65°C; and (d) identifying a target sequence bound by said probe; wherein said identified target sequence is at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to a sequence selected from the group consisting of: (e) a nucleotide sequence encoding the PTHIR receptor having the complete amino acid sequence at positions from about 1 to about 536 in SEQ ID NO:2; (f) a nucleotide sequence encoding the PTHl R receptor having the amino acid sequence at positions from about 2 to about 536 in SEQ ID NO:2; (g) a nucleotide sequence encoding the mature PTHl R receptor having the amino acid sequence at positions from about 25 to about 536 in SEQ ID NO:2; (h) a nucleotide sequence encoding the PTHIR receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (i) a nucleotide sequence encoding the mature PTH 1 R receptor having the amino acid sequence encoded by the cDNA deposited with the ATCC as patent deposit PTA-916; (j) a nucleotide sequence encoding the PTHIR extracellular domain; (k) a nucleotide sequence encoding the PTHIR transmembrane domain; and (1) a nucleotide sequence complementary to any of the nucleotide sequences in (e), (f), (g), (h), (i), (j) or (k). Vectors and Host Cells The present invention also relates to vectors which include the isolated DNA molecules of the present invention, host cells which are genetically engineered with the recombinant vectors, and the production of PTHIR or PTH3R polypeptides or fragments thereof by recombinant techniques. The polynucleotides may be joined to a vector containing a selectable marker for propagation in a host. Generally, a plasmid vector is introduced in a precipitate, such as a calcium phosphate precipitate, or in a complex with a charged lipid. If the vector is a virus, it may be packaged in vitro using an appropriate packaging cell line and then transduced into host cells. The DNA insert should be operatively linked to an appropriate promoter, such as the phage lambda PL promoter, the E coli lac, trp and tac promoters, the SV40 early and late promoters and promoters of retroviral LTRs, to name a few. Other suitable promoters will be known to the skilled artisan. The expression constructs will further contain sites for transcription initiation, termination and, in the transcribed region, a ribosome binding site for translation. The coding portion of the mature transcripts expressed by the constructs will preferably include a translation initiating at the beginning and a termination codon (UAA, UGA or UAG) appropriately positioned at the end of the polypeptide to be translated. As indicated, the expression vectors will preferably include at least one selectable marker. Such markers include dihydrofolate reductase or neomycin resistance for eukaryotic cell culture and tetracycline or ampicillin resistance genes for culturing in E. coli and other bacteria. Representative examples of appropriate hosts include, but are not limited to, bacterial cells, such as E. coli, Streptomyces and Salmonella typhimurium cells; fungal cells, such as yeast cells; insect cells such as Drosophila S2 and Spodoptera Sf9 cells; animal cells such as CHO, COS and Bowes melanoma cells; and plant cells. Appropriate culture mediums and conditions for the above-described host cells are known in the art. Among vectors preferred for use in bacteria include pQΕ70, pQE60 and pQE-9, available from Qiagen; pBS vectors, Phagescript vectors, Bluescript vectors, pNH8A, pNHlόa, pNH18A, pNH46A, available from Stratagene; and ptrc99a, pKK223-3, pKK233-3, pDR540, pRIT5 available from Pharmacia. Among preferred eukaryotic vectors are pWLNEO, pSV2CAT, pOG44, pXTl and pSG available from Stratagene; and pSVK3, pBPV, pMSG and pSVL available from Pharmacia. Other suitable vectors will be readily apparent to the skilled artisan. Introduction of the construct into the host cell can be effected by calcium phosphate transfection, DEAE-dextran mediated transfection, cationic lipid-mediated transfection, electroporation, transduction, infection or other methods. Such methods are described in many standard laboratory manuals, such as Davis et al, Basic Methods In Molecular Biology (1986). The polypeptide may be expressed in a modified form, such as a fusion protein, and may include not only secretion signals, but also additional heterologous functional regions. For instance, a region of additional amino acids, particularly charged amino acids, may be added to the N-terminus of the polypeptide to improve stability and persistence in the host cell, during purification, or during subsequent handling and storage. Also, peptide moieties may be added to the polypeptide to facilitate purification. Such regions may be removed prior to final preparation of the polypeptide. The addition of peptide moieties to polypeptides to engender secretion or excretion, to improve stability and to facilitate purification, among others, are familiar and routine techniques in the art. A preferred fusion protein comprises a heterologous region from immunoglobulin that is useful to solubilize proteins. For example, EP-A-O 464 533 (Canadian counterpart 2045869) discloses fusion proteins comprising various portions of constant region of immunoglobin molecules together with another human protein or part thereof. In many cases, the Fc part in a fusion protein is thoroughly advantageous for use in therapy and diagnosis and thus results, for example, in improved pharmacokinetic properties (EP-A 0232262). On the other hand, for some uses it would be desirable to be able to delete the Fc part after the fusion protein has been expressed, detected and purified in the advantageous manner described. This is the case when Fc portion proves to be a hindrance to use in therapy and diagnosis, for example when the fusion protein is to be used as antigen for immunizations. In drug discovery, for example, human proteins, such as, hIL5-receptor has been fused with Fc portions for the purpose of high-throughput screening assays to identify antagonists of hIL-5. See, D. Bennett et al, Journal of Molecular Recognition, Vol. 8:52-58 (1995) and K. Johanson et al, The Journal of Biological Chemistry, Vol. 270, No. 16:9459-9471 (1995). The PTHIR or PTH3R receptor can be recovered and purified from recombinant cell cultures by well-known methods including ammonium sulfate or ethanol precipitation, acid extraction, anion or cation exchange chromatography, phosphocellulose chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxylapatite chromatography and lectin chromatography. Most preferably, high performance liquid chromatography ("HPLC") is employed for purification. Polypeptides of the present invention include naturally purified products, products of chemical synthetic procedures, and products produced by recombinant techniques from a prokaryotic or eukaryotic host, including, for example, bacterial, yeast, higher plant, insect and mammalian cells. Depending upon the host employed in a recombinant production procedure, the polypeptides of the present invention may be glycosylated or may be non-glycosylated. In addition, polypeptides of the invention may also include an initial modified methionine residue, in some cases as a result of host-mediated processes. PTHIR and PTH3R Polypeptides and Fragments The invention further provides an isolated PTH 1 R or PTH3R polypeptide having the amino acid sequence encoded by the deposited cDNAs, or the amino acid sequence in Figure 2A (SEQ ID NO:2) or Figure 2B (SEQ ID NO:4), or a peptide or polypeptide comprising a portion of the above polypeptides. It will be recognized in the art that some amino acid sequences of the PTHIR or PTH3R receptor can be varied without significant effect of the structure or function of the protein. If such differences in sequence are contemplated, it should be remembered that there will be critical areas on the protein which determine activity. Thus, the invention further includes variations of the PTHIR or PTH3R receptor which show substantial PTHIR or PTH3R receptor activity or which include regions of PTHIR or PTH3R protein such as the protein portions discussed below. Such mutants include deletions, insertions, inversions, repeats, and type substitutions. As indicated above, guidance concerning which amino acid changes are likely to be phenotypically silent can be found in Bowie, J.U., et al, "Deciphering the Message in Protein Sequences: Tolerance to Amino Acid Substitutions," Science 247. 1306-1310 (1990). Thus, the fragment, derivative or analog of the polypeptide of Figure 2A (SEQ ID NO:2) or Figure 2B (SEQ ID NO:4), or that encoded by the deposited cDNAs, may be (i) one in which one or more of the amino acid residues are substituted with a conserved or non-conserved amino acid residue (preferably a conserved amino acid residue) and such substituted amino acid residue may or may not be one encoded by the genetic code, or (ii) one in which one or more of the amino acid residues includes a substituent group, or (iii) one in which the mature polypeptide is fused with another compound, such as a compound to increase the half-life of the polypeptide (for example, polyethylene glycol), or (iv) one in which the additional amino acids are fused to the mature polypeptide, such as an IgG Fc fusion region peptide or leader or secretory sequence or a sequence which is employed for purification of the mature polypeptide or a proprotein sequence. Such fragments, derivatives and analogs are deemed to be within the scope of those skilled in the art from the teachings herein. Of particular interest are substitutions of charged amino acids with another charged amino acid and with neutral or negatively charged amino acids. The latter results in proteins with reduced positive charge to improve the characteristics of the PTHIR or PTH3R protein. The prevention of aggregation is highly desirable. Aggregation of proteins not only results in a loss of activity but can also be problematic when preparing pharmaceutical formulations, because they can be immunogenic. (Pinckard et al, Clin Exp. Immunol. 2:331-340 (1967); Robbins et al, Diabetes 3(5:838-845 (1987); Cleland et al. Crit. Rev. Therapeutic Drug Carrier Systems 70:307-377 (1993)). The replacement of amino acids can also change the selectivity of binding to cell surface receptors. Ostade et al, Nature 361:266-26 (1993) describes certain mutations resulting in selective binding of TNF-α to only one of the two known types of TNF receptors. Thus, the PTHIR or PTH3R receptor of the present invention may include one or more amino acid substitutions, deletions or additions, either from natural mutations or human manipulation. As indicated, changes are preferably of a minor nature, such as conservative amino acid substitutions that do not significantly affect the folding or activity of the protein (see Table 1). TABLE 1. Conservative Amino Acid Substitutions. Amino acids in the PTH 1 R or PTH3R protein of the present invention that are essential for function can be identified by methods known in the art, such as site-directed mutagenesis or alanine-scanning mutagenesis (Cunningham and Wells, Science 244:1081-1085 (1989)). The latter procedure introduces single alanine mutations at every residue in the molecule. The resulting mutant molecules are then tested for biological activity such as receptor binding or in vitro proliferative activity. Sites that are critical for ligand-receptor binding can also be determined by structural analysis such as crystallization, nuclear magnetic resonance or photoaffinity labeling (Smith et al, J. Mol. Biol. 224:899-904 (1992) and de Vos et al. Science 255:306-312 (1992)). The polypeptides of the present invention are preferably provided in an isolated form. By "isolated polypeptide" is intended a polypeptide removed from its native environment. Thus, a polypeptide produced and/or contained within a recombinant host cell is considered isolated for purposes of the present invention. Also intended as an "isolated polypeptide" are polypeptides that have been purified, partially or substantially, from a recombinant host cell. For example, a recombinantly produced version of the antimicrobial peptide polypeptide can be substantially purified by the one-step method described in Smith and Johnson, Gene 67:31-40 (1988). The polypeptides of the present invention are preferably provided in an isolated form, and preferably are substantially purified. A recombinantly produced version of the PTHIR or PTH3R receptor can be substantially purified by the one-step method described in Smith and Johnson, Gene 67:31-40 (1988). The polypeptides of the present invention also include the polypeptide encoded by the deposited PTHIR cDNA including the leader, the polypeptide encoded by the deposited the cDNA minus the leader (i.e., the mature protein), the polypeptide of Figure 2A (SEQ ID NO:2) including the leader, the polypeptide of Figure 2A (SEQ ID NO:2) minus the leader, the extracellular domain, the transmembrane domain, a polypeptide comprising amino acids about 1 to about 536 in SEQ ID NO:2, and a polypeptide comprising amino acids about 2 to about 536 in SEQ ID NO:2, as well as polypeptides which are at least 95% identical, still more preferably at least 96%, 97%, 98% or 99% identical to the polypeptides described above, and also include portions of such polypeptides with at least 30 amino acids and more preferably at least 50 amino acids. The polypeptides of the present invention also include the polypeptide encoded by the deposited PTH3R cDNA including the leader, the polypeptide encoded by the deposited the cDNA minus the leader (i.e., the mature protein), the polypeptide of Figure 2 (SEQ ID NO:4) including the leader, the polypeptide of Figure 4 (SEQ ID NO:4) minus the leader, the extracellular domain, the transmembrane domain, a polypeptide comprising amino acids about 1 to about 542 in SEQ ID NO:4, and a polypeptide comprising amino acids about 2 to about 542 in SEQ ID NO:4, as well as polypeptides which are at least 95% identical, still more preferably at least 96%, 97%, 98% or 99% identical to the polypeptides described above, and also include portions of such polypeptides with at least 30 amino acids and more preferably at least 50 amino acids. By a polypeptide having an amino acid sequence at least, for example, 95% "identical" to a reference amino acid sequence of a PTHIR or PTH3R polypeptide is intended that the amino acid sequence of the polypeptide is identical to the reference sequence except that the polypeptide sequence may include up to five amino acid alterations per each 100 amino acids of the reference amino acid of the PTHl R or PTH3R receptor. In other words, to obtain a polypeptide having an amino acid sequence at least 95% identical to a reference amino acid sequence, up to 5% of the amino acid residues in the reference sequence may be deleted or substituted with another amino acid, or a number of amino acids up to 5% of the total amino acid residues in the reference sequence may be inserted into the reference sequence. These alterations of the reference sequence may occur at the amino or carboxy terminal positions of the reference amino acid sequence or anywhere between those terminal positions, interspersed either individually among residues in the reference sequence or in one or more contiguous groups within the reference sequence. As a practical matter, whether any particular polypeptide is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to, for instance, the amino acid sequence shown in Figure 2A (SEQ ID NO:2) or Figure 2B (SEQ ID NO:4) or to the amino acid sequence encoded by deposited cDNA clones can be determined conventionally using known computer programs such the Bestfit program (Wisconsin Sequence Analysis Package, Version 8 for Unix, Genetics Computer Group, University Research Park, 575 Science Drive, Madison, WI 53711). When using Bestfit or any other sequence alignment program to determine whether a particular sequence is, for instance, 95% identical to a reference sequence according to the present invention, the parameters are set, of course, such that the percentage of identity is calculated over the full length of the reference amino acid sequence and that gaps in homology of up to 5% of the total number of amino acid residues in the reference sequence are allowed. The polypeptide of the present invention could be used as a molecular weight marker on SDS-PAGE gels or on molecular sieve gel filtration columns using methods well known to those of skill in the art. As described in detail below, the polypeptides of the present invention can also be used to raise polyclonal and monoclonal antibodies, which are useful in assays for detecting PTHIR or PTH3R expression as described below or as agonists and antagonists capable of enhancing or inhibiting PTHIR or PTH3R receptor function. Further, such polypeptides can be used in the yeast two-hybrid system to "capture" PTHIR or PTH3R receptor binding proteins which are also candidate agonist and antagonist according to the present invention. The yeast two hybrid system is described in Fields and Song, Nature 340:245-246 (1989). In another aspect, the invention provides a peptide or polypeptide comprising an epitope-bearing portion of a polypeptide of the invention. The epitope of this polypeptide portion is an immunogenic or antigenic epitope of a polypeptide described herein. An "immunogenic epitope" is defined as a part of a protein that elicits an antibody response when the whole protein is the immunogen. On the other hand, a region of a protein molecule to which an antibody can bind is defined as an "antigenic epitope." The number of immunogenic epitopes of a protein generally is less than the number of antigenic epitopes. See, for instance, Geysen et al, Proc. Natl. Acad. Sci. USA 57:3998- 4002 (1983). As to the selection of peptides or polypeptides bearing an antigenic epitope (i.e., that contain a region of a protein molecule to which an antibody can bind), it is well known in that art that relatively short synthetic peptides that mimic part of a protein sequence are routinely capable of eliciting an antiserum that reacts with the partially mimicked protein. See, for instance, Sutcliffe, J. G., Shinnick, T. M., Green, N. and Learner, R.A. (1983) Antibodies that react with predetermined sites on proteins. Science 219:660-666. Peptides capable of eliciting protein-reactive sera are frequently represented in the primary sequence of a protein, can be characterized by a set of simple chemical rules, and are confined neither to immunodominant regions of intact proteins (i.e., immunogenic epitopes) nor to the amino or carboxyl terminals. Antigenic epitope-bearing peptides and polypeptides of the invention are therefore useful to raise antibodies, including monoclonal antibodies, that bind specifically to a polypeptide of the invention. See, for instance, Wilson et al, Cell 37:767-77% (1984) at 777. Antigenic epitope-bearing peptides and polypeptides of the invention preferably contain a sequence of at least seven, more preferably at least nine and most preferably between at least about 15 to about 30 amino acids contained within the amino acid sequence of a polypeptide of the invention. Thus, one skilled in the art will have the requisite knowledge to select antigenic epitope bearing regions from the polypeptides in Figure 2A (SEQ ID NO:2) and Figure 2B (SEQ ID NO:4). The epitope-bearing peptides and polypeptides of the invention may be produced by any conventional means. For example, Houghten provides a general method for the rapid solid-phase synthesis of large numbers of peptides: specificity of antigen-antibody interaction at the level of individual amino acids Houghten, R. A., Proc. Natl. Acad. Sci. USA 52:5131-5135 (1985)). This "Simultaneous Multiple Peptide Synthesis (SMPS)" process is further described in U.S. Patent No. 4,631,211 to Houghten et al. (1986). As one of skill in the art will appreciate, PTHIR or PTH3R polypeptides of the present invention and the epitope-bearing fragments thereof described above can be combined with parts of the constant domain of immunoglobulins (IgG), resulting in chimeric polypeptides. These fusion proteins facilitate purification and show an increased half-life in vivo. This has been shown, e.g., for chimeric proteins consisting of the first two domains of the human CD4-polypeptide and various domains of the constant regions of the heavy or light chains of mammalian immunoglobulins (EPA 394,827; Traunecker et al, Nature 331:84- 86 (1988)). Fusion proteins that have a disulfide-linked dimeric structure due to the IgG part can also be more efficient in binding and neutralizing other molecules than the monomeric PTHIR or PTH3R protein or protein fragment alone (Fountoulakis et al, J. Biochem 270:3958-3964 (1995)). Diagnosis and Prognosis It is believed that certain tissues in mammals with certain diseases and disorders express significantly decreased levels of the PTH 1 R or PTH3R receptor and mRNA encoding the PTHIR or PTH3R receptor when compared to a corresponding "standard" mammal, i.e., amammal ofthe same species not having the disorder. Further, it is believed that enhanced levels ofthe PTHIR or PTH3R receptor can be detected in certain body fluids (e.g., sera, plasma, urine, and spinal fluid) from mammals with cancer when compared to sera from mammals of the same species not having the disorder. Thus, the invention provides a diagnostic method useful during diagnosis of diseases and disorders, for example, which involves assaying the expression level ofthe gene encoding the PTHl R or PTH3R receptor in mammalian cells or body fluid and comparing the gene expression level with a standard PTHIR or PTH3R receptor gene expression level, whereby an decrease in the gene expression level over the standard is indicative of certain disorders. Where a diagnosis of a disorder has already been made according to conventional methods, the present invention is useful as a prognostic indicator, whereby patients exhibiting decreased PTHIR or PTH3R gene expression will experience a worse clinical outcome relative to patients expressing the gene at a higher level. By "assaying the expression level of the gene encoding the PTHIR or PTH3R protein" is intended qualitatively or quantitatively measuring or estimating the level ofthe PTHIR or PTH3R protein or the level ofthe mRNA encoding the PTHIR or PTH3R receptor in a first biological sample either directly (e.g., by determining or estimating absolute protein level or mRNA level) or relatively (e.g., by comparing to the PTHIR or PTH3R protein level or mRNA level in a second biological sample). Preferably, the PTHl R or PTH3R protein level or mRNA level in the first biological sample is measured or estimated and compared to a standard PTHIR or PTH3R protein level or mRNA level, the standard being taken from a second biological sample obtained from an individual not having the cancer. As will be appreciated in the art, once a standard PTHIR or PTH3R protein level or mRNA level is known, it can be used repeatedly as a standard for comparison. By "biological sample" is intended any biological sample obtained from an individual, cell line, tissue culture, or other source which contains PTHIR or PTH3R protein or mRNA. Biological samples include mammalian body fluids (such as sera, plasma, urine, synovial fluid and spinal fluid) which contain PTHIR or PTH3R protein, and ovarian, prostate, heart, placenta, pancreas liver, spleen, lung, breast, neural, and umbilical tissue. The present invention is useful for detecting disorders in mammals. In particular the invention is useful during diagnosis of diseases and disorders in mammals involving PTHIR or PTH3R receptor expression or function. Mutations that affect PTHIR or PTH3R sequence and/or expression levels of PTHIR or PTH3R could be diagnostic for patients with diseases or disorders of a developmental, physiological or neurological nature. Preferred mammals include monkeys, apes, cats, dogs, cows, pigs, horses, rabbits and humans. Particularly preferred are humans. Total cellular RNA can be isolated from a biological sample using the single-step guanidinium-thiocyanate-phenol-chloroform method described in Chomczynski and Sacc i, Anal. Biochem. 762. 156-159(1987). LevelsofmRNA encoding the PTHIR or PTH3R receptor are then assayed using any appropriate method. These include Northern blot analysis (Harada et al, Cell 63.'303-312 (1990)), SI nuclease mapping (Fujita et al, Cell 49:357- 367 (1987)), the polymerase chain reaction (PCR), reverse transcription in combination with the polymerase chain reaction (RT-PCR) (Fujita et al, Cell 49:357- 367 (1987)), and reverse transcription in combination with the ligase chain reaction (RT-LCR). Assaying PTHIR or PTH3R protein levels in a biological sample can occur using antibody-based techniques. For example, PTHIR or PTH3R protein expression in tissues can be studied with classical immunohistological methods (Jalkanen, M., et al, J. Cell. Biol. 707:976-985 (1985); Jalkanen, M., et al, J. Cell. Biol. 705:3087-3096 (1987)). Other antibody-based methods useful for detecting PTHIR or PTH3R receptor gene expression include immunoassays, such as the enzyme linked immunosorbent assay (ELISA) and the radioimmunoassay (RIA). Suitable labels are known in the art and include enzyme labels, such as glucose oxidase, and radioisotopes, such as iodine ( 125 1, 12, I), carbon ( 14 C), sulfur ( 35 S), tritium ( 3 H), indium ( l l2 In), and technetium ( 99m Tc), and fluorescent labels, such as fluorescein and rhodamine, and biotin. Agonists and Antagonists ofthe PTHIR or PTH3R The present invention also provides a screening method for identifying compounds capable of enhancing or inhibiting a cellular response induced by the PTHIR or PTH3R receptor, which involves contacting cells which express the PTHIR or PTH3R receptor with the candidate compound, assaying a cellular response, and comparing the cellular response to a standard cellular response, the standard being assayed when contact is made in absence of the candidate compound; whereby, an increased cellular response over the standard indicates that the compound is an agonist and a decreased cellular response over the standard indicates that the compound is an antagonist. In another aspect, a screening assay for agonists and antagonists is provided which involves determining the effect a candidate compound has on PTH or PTHrP binding to the PTHIR or PTH3R receptor. In particular, the method involves contacting the PTHIR or PTH3R receptor with a PTH or a PTHrP polypeptide and a candidate compound and determining whether PTH or PTHrP polypeptide binding to the PTHIR or PTH3R receptor is increased or decreased due to the presence ofthe candidate compound. By "agonist" is intended naturally occurring and synthetic compounds capable of enhancing or potentiating PTHIR or PTH3R receptor response (e.g. , signaling through the cAMP or inositol phosphate pathway). By "antagonist" is intended naturally occurring and synthetic compounds capable of inhibiting PTHIR or PTH3R receptor response (e.g., signaling through the cAMP or inositol phosphate pathway). Whether any candidate "agonist" or "antagonist" of the present invention can enhance or inhibit PTH 1 R or PTH3R receptor activity can be determined using art-known competition binding assays, including those described in more detail below. One such screening procedure involves the use of melanophores which are transfected to express a receptor of the present invention. Such a screening technique is described in PCT WO 92/01810, published February 6, 1992. Such an assay may be employed, for example, for screening for a compound which inhibits (or enhances) activation of the PTHIR or PTH3R receptor polypeptide of the present invention by contacting the melanophore cells which encode the receptor with both PTH or PTHrP as a ligand and the candidate antagonist (or agonist). Inhibition or enhancement of the signal generated by the ligand indicates that the compound is an antagonist or agonist of the ligand/receptor signaling pathway. Other screening techniques include the use of cells which express the receptor (for example, transfected CHO cells) in a system which measures extracellular pH changes caused by receptor activation, for example, as described in Science 246: 181-296 (October 1989). For example, compounds may be contacted with a cell which expresses the PTH 1 R or PTH3 R receptor polypeptide of the present invention and a second messenger response, e.g., signal transduction or pH changes, may be measured to determine whether the potential compound activates or inhibits the receptor. Another such screening technique involves introducing RNA encoding the PTHIR or PTH3R receptor into Xenopus oocytes to transiently express the receptor. The receptor oocytes may then be contacted with the receptor ligand and a compound to be screened, followed by detection of inhibition or activation of a calcium signal in the case of screening for compounds which are thought to inhibit activation ofthe receptor. Another screening technique involves expressing in cells a construct wherein the receptor is linked to a phospholipase C or D. Such cells include endothelial cells, smooth muscle cells, embryonic kidney cells, etc. The screening may be accomplished as hereinabove described by detecting activation of the PTHIR or PTH3R receptor or inhibition of activation of the PTHIR or PTH3R receptor from the phospholipase signal. Another method involves screening for compounds which inhibit activation of the receptor polypeptide of the present invention antagonists by determining inhibition of binding of labeled ligand to cells which have the receptor on the surface thereof. Such a method involves transfecting a eukaryotic cell with DNA encoding the PTHIR or PTH3R receptor such that the cell expresses the receptor on its surface and contacting the cell with a compound in the presence of a labeled form of a known ligand. The ligand can be labeled, e.g., by radioactivity. The amount of labeled ligand bound to the receptors is measured, e.g., by measuring radioactivity of the receptors. If the compound binds to the receptor as determined by a reduction of labeled ligand which binds to the receptors, the binding of labeled ligand to the receptor is inhibited. Further screening assays for agonist and antagonist of the present invention are described in Tartaglia, L.A., and Goeddel, D.V., J Biol. Chem. 267 (7):4304-4307(\992). Thus, in a further aspect, a screening method is provided for determining whether a candidate agonist or antagonist is capable of enhancing or inhibiting a cellular response to PTH or PTHrP. The method involves contacting cells which express the PTHIR or PTH3R polypeptide with a candidate compound and the PTH or PTHrP ligand, assaying a cellular response, and comparing the cellular response to a standard cellular response, the standard being assayed when contact is made with the ligand in absence of the candidate compound, whereby an increased cellular response over the standard indicates that the candidate compound is an agonist ofthe ligand/receptor signaling pathway and a decreased cellular response compared to the standard indicates that the candidate compound is an antagonist ofthe ligand/receptor signaling pathway. By "assaying a cellular response" is intended qualitatively or quantitatively measuring a cellular response to a candidate compound and/or PTH or PTHrP (e.g., determining or estimating an increase or decrease in cell proliferation or tritiated thymidine labeling). By the invention, a cell expressing the PTHIR or PTH3R polypeptide can be contacted with either an endogenous or exogenously administered PTH or PTHrP. Agonist according to the present invention include naturally occurring and synthetic compounds such as, for example, PTH or PTHrP peptide fragments, or other known compounds that behave as PTH or PTHrP agonist. Preferred agonist include chemotherapeutic drugs such as, for example, cisplatin, doxorubicin, bleomycin, cytosine arabinoside, nitrogen mustard, methotrexate and vincristine. Others include ethanol and β-amyloid peptide. (Science 2(57:1457-1458 (1995)). Further preferred agonist include polyclonal and monoclonal antibodies raised against the PTHIR or PTH3R polypeptide, or a fragment thereof. Antagonist according to the present invention include naturally occurring and synthetic compounds such as, for example, the CD40 ligand, neutral amino acids, zinc, estrogen, androgens, viral genes (such as Adenovirus EIB, Baculovirus p35 and IAP, Cowpox virus crmA, Epstein-Barr virus BHRF1, LMP-1, African swine fever virus LMW5-HL, and Herpesvirus yl 34.5), calpain inhibitors, cysteine protease inhibitors, and tumor promoters (such as PMA, Phenobarbital, and α-Hexachlorocyclohexane). Other potential antagonists include antisense molecules. Antisense technology can be used to control gene expression through antisense DNA or RNA or through triple-helix formation. Antisense techniques are discussed, for example, in Okano, J. Neurochem. 56:560 (1991); Oligodeoxynucleotides as Antisense Inhibitors of Gene Expression, CRC Press, Boca Raton, FL (1988). Triple helix formation is discussed in, for instance Lee et al, Nucleic Acids Research (5:3073 (1979); Cooney et al, Science 241:456 (1988); and Dervan et al, Science 257:1360 (1991). The methods are based on binding of a polynucleotide to a complementary DNA or RNA. For example, the 5' coding portion of a polynucleotide that encodes the mature polypeptide ofthe present invention may be used to design an antisense RNA oligonucleotide of from about 10 to 40 base pairs in length. A DNA oligonucleotide is designed to be complementary to a region ofthe gene involved in transcription thereby preventing transcription and the production of the receptor. The antisense RNA oligonucleotide hybridizes to the mRNA in vivo and blocks translation of the mRNA molecule into receptor polypeptide. The oligonucleotides described above can also be delivered to cells such that the antisense RNA or DNA may be expressed in vivo to inhibit production of the receptor. Further antagonist according to the present invention include soluble forms of PTHIR or PTH3R fragments that include the ligand binding domain from the extracellular region ofthe full length receptor. Such soluble forms of the receptor, which may be naturally occurring or synthetic, antagonize PTHIR or PTH3R mediated signaling by competing with the cell surface PTHIR or PTH3R for binding to PTH or PTHrP. These are preferably expressed as dimers or trimers, since these have been shown to be superior to monomeric forms of soluble receptor as antagonists, e.g., IgGFc-PTHlR or IgGFc-PTH3R receptor family fusions. Modes of administration It will be appreciated that conditions caused by a decrease in the standard or normal level of PTHIR or PTH3R receptor activity in an individual, can be treated by administration of PTHIR or PTH3R protein. Thus, the invention further provides a method of treating an individual in need of an increased level of PTHIR or PTH3R receptor activity comprising administering to such an individual a pharmaceutical composition comprising an effective amount of an isolated PTHl R or PTH3R polypeptide ofthe invention, effective to increase the PTHIR or PTH3R receptor activity level in such an individual. The invention also relates to a method of treating an individual in need of an increased level of PTHIR or PTH3R receptor activity comprising administering to such an individual a pharmaceutical composition comprising an effective amount of an agonist for PTHIR or PTH3R. The invention further relates to a method of treating an individual in need of a decreased level of PTHIR or PTH3R receptor activity comprising administering to such an individual a pharmaceutical composition comprising an effective amount of an antagonist for PTHIR or PTH3R. As a general proposition, the total pharmaceutically effective amount of PTHIR or PTH3R polypeptide or its agonists or antagonists administered parenterally per dose will be in the range of about 1 μg/kg/day to 10 mg/kg/day of patient body weight, although, as noted above, this will be subject to therapeutic discretion. More preferably, this dose is at least 0.01 mg/kg/day, and most preferably for humans between about 0.01 and 1 mg/kg/day for the hormone. If given continuously, the PTHIR or PTH3R polypeptide is typically administered at a dose rate of about 1 μg/kg/hour to about 50 μg/kg/hour, either by 1-4 injections per day or by continuous subcutaneous infusions, for example, using a mini-pump. An intravenous bag solution may also be employed. Pharmaceutical compositions containing the PTHIR or PTH3R polypeptide(s)of the invention or its agonists or antagonsits may be administered orally, rectally, parenterally, intracistemally, intravaginally, intraperitoneally, topically (as by powders, ointments, drops or transdermal patch), bucally, or as an oral or nasal spray. By "pharmaceutically acceptable carrier" is meant a non- toxic solid, semisolid or liquid filler, diluent, encapsulating material or formulation auxiliary of any type. The term "parenteral" as used herein refers to modes of administration which include intravenous, intramuscular, intraperitoneal, intrasternal, subcutaneous and intraarticular injection and infusion. Chromosome Assays The nucleic acid molecules ofthe present invention are also valuable for chromosome identification. The sequence is specifically targeted to and can hybridize with a particular location on an individual human chromosome. The mapping of DNAs to chromosomes according to the present invention is an important first step in correlating those sequences with genes associated with disease. In certain preferred embodiments in this regard, the cDNA herein disclosed is used to clone genomic DNA of a PTHIR or PTH3R receptor gene. This can be accomplished using a variety of well known techniques and libraries, which generally are available commercially. The genomic DNA then is used for in situ chromosome mapping using well known techniques for this purpose. In addition, in some cases, sequences can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp) from the cDNA. Computer analysis ofthe 3 ' untranslated region ofthe gene is used to rapidly select primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers are then used for PCR screening of somatic cell hybrids containing individual human chromosomes. Fluorescence in situ hybridization ("FISH") of a cDNA clone to a metaphase chromosomal spread can be used to provide a precise chromosomal location in one step. This technique can be used with probes from the cDNA as short as 50 or 60 bp. For a review of this technique, see Verma et al, Human Chromosomes: A Manual Of Basic Techniques, Pergamon Press, New York (1988). Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data. Such data are found, for example, in V. McKusick, Mendelian Inheritance In Man, available on-line through Johns Hopkins University, Welch Medical Library. The relationship between genes and diseases that have been mapped to the same chromosomal region are then identified through linkage analysis (coinheritance of physically adjacent genes). Next, it is necessary to determine the differences in the cDNA or genomic sequence between affected and unaffected individuals. If a mutation is observed in some or all ofthe affected individuals but not in any normal individuals, then the mutation is likely to be the causative agent ofthe disease. Having generally described the invention, the same will be more readily understood by reference to the following examples, which are provided by way of illustration and are not intended as limiting. Examples Example 1: Isolation of Genomic DNA Clones Encoding the Zebrafish PTHIR and a novel type-3 receptor, PTH3R Using zebrafish genomic DNA and several degenerate forward and reverse primers (Figure 1), two distinct products of approximately 200 and 840 bp, respectively were obtained under stringent conditions. Forward (For) and reverse (Rev) degenerate primers (synthesized by the MGH Polymer core facility) for nested PCR (nPCR) were based on previously isolated mammalian and frog PTHIR sequences. Primers were located in exon M6/7 which encodes in mammals the third extracellular loop and the amino-terminal portion of transmembrane (TM) helix 7, and exon M7 which encodes the carboxy-terminal portion of TM7 and the beginning of the intracellular tail (Kong, et al, (1994); Schipani, et al, (1995)) (Figure 1). The primers for the first PCR reaction were the following: For M6a (5 'TTYGGIGTSCAYTAYATHGTVTT; (SEQ ID NO:26) 576-fold degenerate), or For M6b (5'GTSYTBRTGCCICTHYTYGG; (SEQ ID NO:6) 1152-fold degenerate), and Rev M7 (CTCDCCATTRCAGWARCAGTADAT; (SEQ ID NO:7) 72-fold degenerate) (Fig. 1 ). PCR was performed using 1 mg of zebrafish (Danio rerio) genomic DNA, Gibco Taq (5 units), and the following PCR profile [initial denaturation at 95 ° for 3 min, (denature at 94 ° for 1 min, anneal at 50 ° for 1 min, and polymerize at 72° for 4 or 6 min) for 35 cycles] on an MJ research thermal cycler (Watertown, MA). nPCR was performed using 2 μl of a 1 :100 dilution of the initial PCR product with a degenerate nested primer Rev M7#2 (5'GTADATRATDGMMACAAARAADCC; (SEQ ID NO:8) 432-fold degenerate), and either For M6a or For M6b using the same PCR profile as before (Fig. 1). nPCR products were identified on a 1.5% agarose gel with ethidium bromide, and DNA species of approximately 210 bp and 850 bp were excised, spun through a spin column (Biol 01, La Jolla, CA), ethanol precipitated overnight [(1/10 vol of 3M sodium acetate was added, 2 vol of ethanol, 1 μl of glycogen (Pharmacia, Uppsala, Sweden)], and ligated into pGEM-T (Promega, Madison, WI). After transformation of competent DH5a E. coli cells (Gibco, Grand Island, NY), plasmid DNA from single colonies was purified using standard protocols, and sequenced by 33 P cycle sequencing (Amersham, Arlington Heights, IL) on an 8M urea 6% polyacrylamide field gradient gel (Rubin et al. , 1998). The DNA sequences, from the nested PCRs using For M6a or For M6b, were analyzed by the GCG package program (GCG, Univ. WI) and subsequently refered to as zPTHlR(TM6/7)/GEM-T and zPTH3R(TM6/7)/GEM-T, respectively. Nucleotide sequence analysis revealed that both clones showed significant homology at their 5' and 3' ends with the hPTHlR (78% and 73% identity, respectively). While clone #1, zPTHlR(TM6/7), contained 84 bp of intronic sequence (compared to 81 bp ofthe hPTH 1 R) (Schipani, et al., (\ 995)), clone #2, zPTH3R(TM6/7), contained an intron of more than 700 bp. These findings indicated that portions of two distinct genes had been isolated which both share higher homology with PTHIR than with PTH2R (64% and 70% identity, respectively). Example 2: Isolation of partial cDNA clones encoding zPTHIR and zPTH3R Total RNA from adult zebrafish was isolated as previously described (Rubin et al. , (1999)) and used as a template for RT-PCR (Gibco). For and Rev primers for RT-PCR were based on either zPTHIR or zPTH3R genomic DNA sequences corresponding to the mammalian exons M6/7 and M7, zPTHlR(TM6/7)/GEM-T and zPTH3R(TM6/7)/GEM-T, respectively (Fig. 1). Reverse transcription (RT) was performed using Superscript II RNAase H reverse transcriptase and 5 μg total RNA at 42° C with zPTHlR/Rev 6(1) (5'GCATTTCATAATGCATCTGGATTTG) (SEQ ID NO:9), or zPTH3R/Rev 6(1 ) (5 'CTGTGAAGAATTGAAGAGCATCTC) (SEQ ID NO: 10), respectively. PCR, using the For 313 (5'ACMAACTACTAYTGGATYCTGGTG (SEQ ID NO: 11); 8 -fold degenerate) and either ofthe two Rev 6(1 ) primers was performed using Gibco Taq (5 units) and the following PCR profile [initial denaturation at 95° for 3 min, (denature at 94° for 1 min, anneal at 56° for 1 min, and polymerize at 72° for 2 min) for 35 cycles]. nPCR was performed using 2 μl of a 1 : 100 dilution from the initial zPTH 1 R or zPTH3R RT-PCR product, and either zPTHlR/Rev 6(2) (5'AGAAACTTCTGTGTAAGGCATCGC) (SEQ ID NO: 12) or zPTH3R/Rev 6(2) (5 ΑAGAGCCATGAACAGCATGTAATG) (SEQ ID NO:13), and the For 313 primer using the previous PCR profile except for 35 cycles. zPTHIR and zPTH3R PCR products were identified on a 1.5% agarose gel with ethidium bromide, cDNA species of approximately 450 bp were cloned, as described above, into pGEM-T to yield zPTHlR(TM3/6)/pGEMT and zPTH3R(TM3/6)/pGEMT, respectively. Example 3: Isolation of full-length cDNAs encoding the zPTHIR RT-PCR using For313 and primers specific for zPTHlR(TM6/7) produced a 450 bp cDN A, zPTH 1 R(TM3/6), corresponding to TM3 through TM6 of the mammalian PTHIR. Subsequently, 5' and 3' RACE reactions were performed to generate overlapping sequences, and a full-length zPTHIR clone was constructed using a unique Mfel endonuclease restriction site (Fig. 1). 5 ' and 3 ' RACE reactions (Gibco) were performed using total RNA, and primers based on zPTHlR(TM3/6)/pGEMT nucleotide sequence. RT for 5' RACE was performed, as described above, except that Rev 6(2) was used. The first 5 ' RACE P C R was performe d us ing Rev 6 (3 ) (5'GAAGACTATGTAGTGAACACCGAA) (SEQ ID NO: 14), Gibco Taq (2.5 units) and the following PCR profile [initial denaturation at 95° for 3 min, (denature at 94° for 1 min, anneal at 55° for 1 min, and polymerize at 72° for 2 min) for 7 cycles, followed by 28 cycles with annealing at 64°. The first nPCR was performed using 5 μl of a 1 :100 dilution from the previous PCR, Rev TM5 primer (5 ΑTATTGTTGTCTGGTGTCACATCT) (SEQ ID NO: 15), (KlenTaq, 5.0 units) (Clontech, CA), and the following PCR profile [initial denaturation at 95° for 3 min, [(denature at 94° for 1 min, anneal at 62° for 1 min, and polymerize at 72° for 2 min) for 35 cycles} with a final extension of 10 min at 72°]. A second nPCR was performed using 5 μl ofa 1 : 100 dilution from the first nPCR, Rev 4x primer (5'CGCATTTGTTTCTCGAAGTTTTGTTGC) (SEQ ID NO: 16), Gibco Taq (5.0 units) and the same PCR profile as the first nPCR. The second nPCR products were purified as described above and ligated into pGEM-T EASY (Promega) to yield zPTHlR(5')/pGEMTeasy, for transformation of TOP 10 E. coli cells (Invitrogen). For 3 ' RACE, RT was performed as before but with an oligo-dT anchor primer (Gibco). PCR was performed using the For TM3 primer (5'ATCTTCATGACCTTCTTCTCAGAC) (SEQ ID NO: 17), Gibco Taq (2.5 units) and the following profile [initial denaturation at 95 ° for 3 min, [(denature at 94° for 1 min, anneal at 64° for 1 min, and polymerize at 72° for 3 min) for 35 cycles} with a final extension of 10 min at 72°]. nPCR was performed using the previous PCR profile with 5 μl of a 1 : 100 dilution from the previous PCR, and For 4(1) (5'AGGAAGTACCTCTGGGGCTTCA) (SEQ ID NO: 18). The 3' RACE nPCR products were purified and cloned to yield Z PTH1R(3 ')/pGEMTeasy. Midiprep DNA o f zPTH l R( 5 ' )/pGEMTeasy and zPTHlR(3')/pGEMTeasy were digested with Mfe I and Nde I (New England Biolabs, Beverly, MA), and a 1.0 Kb fragment from ZPTH1R(3 ') was ligated into an approximately 4.5 Kb fragment from zPTHlR(5')/pGEMTeasy to yield the full length zPTH I R clone, zPTHl R(FL)/pGEMTeasy. The zPTHlR(FL)/pGEMTeasy plasmid DNA was digested with EcoRI and Sad, and cloned into the corresponding sites in pGEM-3 (Promega) to yield zPTHlR(FL)/pGEM3. Subsequently, an EcoRI/Sphl fragment, from the insert of zPTHlR(FL)/pGEM3 which comprises the entire coding region, of the zPTHIR was cloned into the corresponding sites of pcDNAI/Amp (Invitrogen) to yield zPTHlR(FL)/pcDNAI/Amp (zPTHIR). The 5 ' RACE reactions generated two PCR products which contained an identical Kozak sequence and coding region (including the putative signal sequence) but varied in the length of the 5' UT; 5'RACE#29 was 149 bp and 5'RACE#25 was 391 bp. Both clones, ZPTH1R#25 and zPTHlR#29, were characterized by radioligand assay, total IP generation, and cAMP accumulation. The amino acid sequence encoded by zPTHIR cDNA (536 residues, Fig. 2 A) showed highest sequence homology to the frog and mammalian PTHlRs (Bergwitz, etal, (1998); Kong, etal, (1994)). The overall amino acid sequence homology with the hPTHlR was 76% but only 68% when compared to the hPTH2R. Similar to the mammalian PTHlRs, the 3 ' non-coding region of zPTHIR did not contain a typical polyadenylation signal sequence, however, an imperfect sequence was found (TAT AAA) 49 bp upstream ofthe poly A (n) tail. Example 4: Isolation of full-length cDNAs encoding the zPTH3R The genomic clone, zPTH3R(TM6/7), contained, at the 5' and 3' end, nucleotide sequences which were similar to but distinct from zPTHIR and zPTH2R, and contained approximately 700 bp, rather than 84 bp, of intronic sequence. This information indicated that portions of a novel gene had been isolated, subsequently refered to as zPTH3R. RT-PCR using For313 and primers specific for zPTH3R(TM6/7) produced a 450 bp cDNA clone, zPTH3R(TM3/6), which encodes TM3 through TM6 ofthe zPTH3R. A zebrafish 1 gtl l cDNA library (Clontech) was screened by plaque hybridization using a 450 bp 32 P-radiolabeled cDNA probe which was generated by PCR from zPTH3R(TM3/6)/pGEMT. Filters containing 1.5 x 10 6 pfu were hybridized (42° for 18 hrs) in 50% formamide (Rubin et al, 1999), and washes were performed for 30 min each at RT, 50°, and at 55°, respectively, with lx SSC/0.1% SDS. Autoradiography was performed for 5 days at -70° with a DuPont Cronex intensifying screen and Kodak XAR film. A single phage was plaque-purified and subcloned into the EcoRI site of pcDNAI/Amp using the λ TRAP phage kit (Clontech) to yield zeb3-37pcDNAI/Amp. 5' RACE reactions (Gibco) were performed as above using three s u c c e s s i v e r e v e r s e z P T H 3 R p r i m e r s [ T M 1 ( 5 ' GAAGAGGTGGATGTGGATGTAGTT) (SEQ ID NO: 19), G (5' GCAGTGGAGACGTTTGAAATA) (SEQ ID NO:20), and E3 (5' CCAGTTACCTGATGC ATC AC AGTG) (SEQ ID NO :21 )] . The cDN A products were ligated to pGEMT-EASY (yielding zeb3-5 VpGEMT), minipreped, and their sequences analysed for homology to the known PTH receptors using GCG. Inserts which were determined to contain a nucleotide sequence with homology to the signal sequence of the mammalian PTHlRs were ligated into zeb3- 37pcDNAI/Amp using sites for BamHI, ApaLI, and Notl to yield zPTH3R(FL)/pcDNAI/Amp (zPTH3R). From 1.5 x 10 6 screened PFUs, a single phage clone was identified and the 2.5 Kb insert was subcloned to yield zeb3-37pcDNAI/Amp. Sequence analysis showed that the clone was closely related to the known PTHlRs from the region corresponding to the mammalian exon El through the carboxy -terminal region encoded by exon T (Kong, et al. , ( 1994)). However, the cDNA portion encoding the amino-terminal, extracellular domain and most ofthe 3' untranslated region immediately following the termination codon were missing. 5 'RACE on total zebrafish RNA revealed the presence of several putative splice variants which is similar to the findings with the zPTH2R (Rubin et al. , (1999)). Seven ofthe ten zeb3-5' clones were identified as containing cDNA sequences similar to the mammalian exons E3 and El, which encode portions of the amino-terminal extracellular domain of the PTHlRs. These clones also contained a Kozak sequence and a nucleotide sequence with homology to the signal peptide sequence found in the mammalian PTH 1 Rs (Kong, et al. , ( 1994); Schipani, et al. , ( 1995)). Three other zeb3-5' clones, which also contained the E3 and El equivalent, had different 5 ' ends and could therefore represent putative splice variants. Similar to the zPTH2R (Rubin et al, (1999)) and the human PTHIR (Joun et al. (1997), Bettoun et al, (1997)), one of these zPTH3R putative splice variants lacked a signal peptide sequence but did contain an initiator AUG two codons upstream ofthe exon El equivalent. The second putative splice variant lacked a Kozak sequence, an initiator AUG, and contained a highly charged sequence upstream of the equivalent of El which is unlikel;y to represent a signal peptide. Only those clones which contained a Kozak sequence, an inframe AUG, and a 5' coding region with homology to the zPTHl R, were ligated into the ApaLI site of zeb3-37pcDNAI/Amp to yield the full-length zPTH3R (Fig. 1 ). Overall, the sequence encoded by this novel receptor (542 residues, Fig. 2B) shared 66% AA similarity and 59% AA identity with zPTHIR, but only 55% similarity with the zPTH2R. Similar to the frog PTHlRs, zPTHIR and zPTH3R lacked the equivalent of the cDNA encoded by exon E2, suggesting that the appearance of this non-essential exon represents a mammalian evolutionary innovation (Lee, et al, (1994)). In contrast to this mammalian E2 apomorphy, zPTHIR and zPTH3R contain the same eight extracellular cysteines as all known mammalian and non- mammalian members of this family of G protein-coupled receptors as well as several other "signature residues" (G protein coupled receptor database: Http://www.gcrdb.uthacsa.edu). However, there are differences in the number of consensus sequences (N-X-S or N-X-T) for potential N-glycosylation between zPTHIR and zPTH3R; only two are conserved for all zebrafish PTH receptors (Fig. 2C). Furthermore, analysis of the intracellular tail residues indicates that this region has a higher rate of sequence variation between PTH receptor subtypes and was therefore used for further comparison (Table 2). For example, the homology between zPTHIR and hPTHlR in this region is 56%>, which is similar to the 58%) AA similarity for zPTH2R and hPTH2R. In contrast, the homology between the tail regions of zPTH3R and hPTHlR is 38%, and 28% when compared to hPTH2R (Table 2). The zPTH3R was therefore identified as a novel member within the PTH/PTHrP receptor family. Example 5: Functional characterization ofzPTHIR and zPTH3R in COS-7 cells Plasmid DNAs encoding the two full length zPTH 1 Rs (#25 and #29) and the zPTH3R were transiently expressed in COS-7 cells. COS-7 African green monkey kidney cells (approximately 200,000 cells/well in a 24-well plate) were cultured and transfected with plasmid DNA (200 ng/well) as described (Rubin et al, (1998)). After transfection, cells were cultured for 72 hrs at 37° with daily exchanges of medium, followed by an additional 24 hrs at 33 ° (Gardella et al. , (1997)) until they were functionally evaluated after 96 hrs. Radioligand studies with COS-7 cells expressing either zPTHIR or zPTH3R were performed as described using either , 25 I-labeled [Nle 8 ' 21 ,Tyr 34 ]rPTH-(l-34)amide (rPTH) (SEQ ID NO:22) or ,25 I-labeled [Tyr 36 ]hPTHrP-(l-36)amide (PTHrP) (SEQ ID NO:23), and increasing concentrations of either [Tyr 34 ]hPTH(l-34)amide (PTH) (SEQ ID NO:24), or [Tyr 36 ]hPTHrP(l-36)amide (PTHrP) (SEQ ID NO:25) (Bergwitz et al, (1997)). Peptides were synthesized by the MGH polymer core facility as described (Gardella et al, (1996)). Specific binding was calculated by subtracting radioligand binding in the presence of excess unlabeled peptide from the total binding. All points represent mean ± S.E.M. of two to three replicates from two or more independent experiments. IC 50 values (dose of a competing ligand which resulted in 50% inhibition of radioligand binding) were calculated as previously described (Gardella et al. , (1996)). In order to assess agonist-dependent cAMP accumulation of COS-7 cells expressing zPTHIR and zPTH3R, experiments were done in 24-well plates with COS-7 cells stimulated in the presence of increasing concentrations of either PTH or PTHrP, and intracellular cAMP was determined as described (Bergiwtz et al. ,( 1998)). EC 50 values were determined as previously described (Gardella et al. , (1996)). In order to determine total inositol phosphate turnover for COS-7 cells expressing zPTHIR, zPTH3R, and hPTHlR, cells were grown in 6-well plates with COS-7 cells (approximately 200,00 cells/well transfected with either 1 μg/well of zPTHIR, zPTH3R, or hPTHlR (stina)). Cells were cultured for 3 days in DMEM/7% fetal bovine serum (FBS) at 37°C with daily exchanges of medium. The cells were then preloaded with 3 μCi/ml myo-[ 3 H]inositol (New England Nuclear, Boston, MA) in inositol-free DMEM (Gibco)/7% FBS (33°C for 18 hr). The following day, plates were rinsed and then incubated with 10 "6 M of either PTH, PTHrP in DMEM/0.1 % BSA, or with DMEM/0.1 % BSA alone (40 min at 37°C), in the presence of 30 mM LiCl. Total inositol phosphate (IPs) were isolated by anion exchange column chromatography as previously described (Iida-Klein et al, (1994 and 1995)), and 1 ml of the eluate (l/8th of total) was counted in a liquid scintillation counter (model LS 6000IC, Beckman, Fullerton, CA). All points represent mean ± S.E.M. of two to three replicates from two or more independent experiments. Both zPTHIR clones showed high affinity binding of radiolabeled rPTH and PTHrP (Table 2, Fig. 4). Apparently, due to the shorter 5' UT, zPTHlR#29 showed in comparison to #25 slightly higher expression levels and higher maximal cAMP accumulation (101.6 pmole/well for hPTHrP and 106.2 pmole/well for hPTH versus 92.4 pmole/well for hPTHrP and 90.4 pmole/well for hPTH; see Table 2), but otherwise both clones were indistinguishable. Only the functional data for zPTHlR#29 are therefore presented (figure 3, Table 3). Interestingly, zPTH3R showed a higher specific binding for radiolabeled PTHrP than rPTH. Furthermore, the zPTH3R showed a higher apparent Kd for PTHrP than PTH (approximately 3nM versus approximately lOOnM, respectively). These results indicate that zPTH3R preferentially interacts with PTHrP. Similar to these binding data, COS-7 cells expressing the zPTHIR showed very similar EC 50s for cAMP accumulation in response to either PTH or PTHrP which is similar to the findings with mammalian PTHlRs (EC 50 : 0.8 ± 0.03 nM for PTH and 0.3 ± 0.04 nM for PTHrP, Table 2). The zPTH3R showed a higher maximal cAMP accumulation (285.4 nM for PTH and 227.4 for PTHrP nM), but in contrast to the zPTH 1 R, zPTH3R showed a reduced efficacy for PTH (EC 50s : 5.98 ± 0.24 nM for PTH and 0.49 ± 0.17 nM for PTHrP, Table 2, Fig. 4). Furthermore, in addition to being more efficiently activated by PTHrP, the zPTH3R showed a significant activation at 10 " " M (Fig. 4). These results confirmed the radioreceptor studies which had indicated that the zPTH3R interacts preferentially with PTHrP. Similar to the mammalian PTHlRs, COS-7 cells expressing the zPTHIR showed an equivalent increase of IP accumulation (2-fold) when stimulated with either PTH or PTHrP. In contrast, despite higher expression levels, no IP accumulation was detectable when challenged with either ligand (Fig. 5). The lack of signaling through this second messenger may be related to significant structural alterations in the second intracellular loop of zPTH3R (Fig. 4). Previous studies with the rat PTHIR have shown that this portion ofthe receptor is important for IP signaling, since replacement of some residues in this "EKKY" cassette either impaired or abolished phospholipase C activation. While the zPTHIR contains a conserved DRKY sequence instead of the mammalian EKKY, the corresponding AA residues ofthe zPTH3R are DKNC (Fig. 3). The two most important residues are therefore altered in the novel receptor which could explain the signaling selectivity ofthe zPTH3R. The zPTH3R is therefore a naturally occurring PTH/PTHrP receptor which appears to be incapable of signaling through IP. Example 6: Southern Blot Analysis of Zebrafish Genomic DNA To confirm that zPTHIR and zPTH3R are encoded by distinct genes, three infrequently cutting restriction endonucleases were utilized to digest zebrafish genomic DNA to completion (data not shown). Approximately 16 μg of zebrafish genomic DNA was digested to completion with either BamHI, EcoRI, or Hindlll, split into two equal aliquots for electrophoresis through a 0.8% agarose gel containing ethidium bromide, and transferred onto a nitrocellulose membrane (MSI, Westborough, MA). After baking in vacuo for 2 hr at 80° C, the blots were hybridized in 50% formamide (42 ° for 18 hrs) with PCR-generated 32 P-labeled probes (Schowalter and Sommer, 1989) encoding either the carboxy- terminal tail of zPTHIR or zPTH3R (240 and 335 bp, respectively). Washes were performed for 30 min each at RT and 42° in lx SSC/0.1% SDS, and at 50° in 0.5x SSC/0.1% SDS followed by autoradiography at -70° for 7 days with a DuPont Cronex intensifying screen and Kodak XAR film. Initial Southern blot data using probes corresponding to TM3 through TM6 of either receptor showed multiple hybridizing DNA species, indicating that these probes cross hybridized with each others gene or with closely related genes (data not shown). To increase the specificity for either subtype, hybridizations were performed with radiolabeled probes comprising only the tail region of each receptor, zPTHlR tail or zPTH3R/tail, which showed the highest rates of sequence variation between PTH receptor subtypes. For each digest the tail probes hybridized, under stringent conditions, to a single but different genomic DNA fragment indicating that distinct genes encode zPTHIR and zPTH3R (data not shown). Example 7: Phylogenetic and Structural Analyses of All Known PTHRs Alignment of all known PTHlRs, PTH2Rs, the goldfish VIP receptor (#U56391), and the human CRF receptor (#P34998) sequences was performed as previously described (Rubin et al. , ( 1999)). Sequences were subsequently aligned within MacClade 3.0 (Maddison and Maddison, 1992) and gaps were entered to maximize the homology of the native proteins. Each AA was treated as an unweighted character when analyzed using the branch-and-bound search option of PAUP 3.1 (Swofford, 1993). A bootstrapping analysis using the branch-and- bound option on 100 replicates (Hedges, (1992)) was performed and only groups which were compatible with the 50% majority-rule consensus were retained (Swofford and Olsen, (1990); Swofford, (1993)). GCG was used for comparing the tail regions of zPTHIR, zPTH2R, zPTH3R, hPTHlR, and hPTH2R. A further analysis was performed within MacClade to determine unambiguous residues which may be character-dependent for each PTH/PTHrP receptor subtype (Madison and Maddison, 1992; Swofford, 1993; Rubin et al, 1999). The single most parsimonious Bootstrap consensus tree revealed two statistically significant PTH/PTHrP receptor clades; the PTH1R/PTH3R clade and the PTH2R clade (Fig. 7). Furthermore, within the PTHl R/PTH3R clade, the PTHIR groups significantly different from PTH3R and, at least for the PTHIR, the terminal branches contained within are congruent with morphologically based phylogenies (Pough, et al, (1989)). Whereas the overall amino acid conservation between zPTHIR and zPTH3R is relatively high, particularly within the transmembrane region, multivariate analysis led to the identification of amino acid residues that may be specific for PTH3Rs (Fig. 3). Although additional PTH3R sequences from other species are required to confirm the receptor specificity of these residues, the limited number of amino acid changes may already allow mutational studies to explore their functional importance, particularly with regard to phospholipase C activation. Example 7: Southern Blot Analysis of Mouse Genomic DNA In order to establish the occurrence of PTH3R in mammals, Southern blot analysis was done with genomic DNA from a wild-type mouse (Figure 7, left lane, 10 μg) and from a mouse lacking both copies ofthe PTH/PTHrP receptor gene (Figure 7, right lane 2 μg). Briefly, genomic DNAs were digested to completion with the restriction enzyme BamHI, subjected to agarose gel electrophoresis and transferred to a membrane for probing with radiolabeled PTH3R DNA (approximately 300 bp encoding the tail portion ofthe zPTH3R). Hybridization was performed under conditions of 30% formamide at 42 degrees Celsius overnight. The blot was subjected to a final wash of lxSSC at 60 degrees Celsius. Radiography was performed by exposing the blot to film for 3 days at -80 C with an intensifying screen. The detection of a band in the PTH/PTHrP receptor knockout (KO) DNA indicates the presence of PTH3R in mouse genomic DNA. Table 2. Comparisons ofthe Amino Acid sequences ofthe Intracellular, Carboxy-Terminal Tail of Different PTH Receptors Residues comprising the tail region of the zPTHIR and zPTH3R were compared to corresponding regions of the zPTH2R, and the human PTHIR or PTH2R. Percent similarity and percent identity are indicated. Table 2 Table 3. Binding and cAMP Signaling Properties of PTH and PTHrP Analogs on the zPTHIR and the zPTH3R Competitive binding and cAMP stimulation assays were performed at room temperature with intact COS-7 cells that expressed either the zPTHIR or the zPTH3R, as described in Materials and Methods. Homologous binding reactions utilized ' 25 I-rPTH with unlabeled rPTH, and l25 I-hPTHrP with unlabeled hPTHrP, heterologous binding reactions utilized 125 I-hPTH with unlabeled rPTH. EC 50 and IC 50 values were determined as previously described (Gardella et al. , 1996). Values are the mean ± SEM of at least three independent transfections. ND, not determined. Table 3 List of Other References Cited Herein: 1. Potts, J.T., Jr., Jϋppner, H.: Parathyroid hormone and parathyroid hormone-related peptide in calcium homeostasis, bone metabolism, and bone development: the proteins, their genes, and receptors. In: Avioli LV, Krane SM, eds. Metabolic Bone Disease, 3 ed. New York: Academic Press, 1997; 51-94. 2. Bergwitz, C, Klein, P., Kohno, H., Forman, S.A., Lee, K., Rubin, D., Jiippner, H. (1998). Identification, functional characterization, and developmental expression of two nonallelic parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor isoforms in Xenopus laevis (Daudin). Endocrinology 139, 723-732 3. Broadus, A.E., Stewart, A.F.: Parathyroid hormone-related protein: Structure, processing, and physiological actions. In: Bilezikian JP, Levine MA, Marcus R, eds. The parathyroids. Basic and Clinical Concepts. New York: Raven Press, 1994; 259-294. 4. Karaplis, A.C., Luz, A., Glowacki, J., Bronson, R., Tybulewicz, V., Kronenberg, H.M., Mulligan, R.C. (1994). Lethal skeletal dysplasia from targeted disruption of the parathyroid hormone-related peptide gene. Genes Develop 8, 277-289. 5. Lanske, B., Karaplis, A.C., Luz, A., Vortkamp, A., Pirro, A., Karperien, M., Defize, L.H.K., Ho, C, Mulligan, R.C, Abou-Samra, A.B., Jϋppner, H., Segre, G.V., Kronenberg, H.M. (1996). PTH/PTHrP receptor in early development and Indian hedgehog-regulated bone growth. Science 273, 663-666. 6. Wysolmerski, J.J., Broadus, A.E., Zhou, J., Fuchs, E., Milstone, L.M., Philbrick, W.M. (1994). Overexpression of parathyroid hormone-related protein in the skin of transgenic mice interferes with hair follicle development. Proc. Natl. Acad. Sci. USA 91, 1133-1137. 7. Wysolmerski, J.J., McCaughern-Carucci, J.F., Daifotis, A.G., Broadus, A.E., Philbrick, W.M. (1996). Overexpression of parathyroid hormone-related protein or parathyroid hormone in transgenic mice impairs branching morphogenesis during mammary gland development. Development 121, 3539-3547. 8. Weir, E.C, Philbrick, W.M., Amling, M., Neff, L.A., Baron, R., Broadus, A.E. (1996). Targeted overexpression of parathyroid hormone-related peptide in chondrocytes causes skeletal dysplasia and delayed endochondral bone formation. Proc. Natl. Acad. Sci. USA 93, 10240-10245. 9. Philbrick, W.M., Dreyer, B.E., Nakchbandi, LA., Karaplis, A.C (1998). Parathyroid hormone-related protein is required for tooth eruption. Proc. Natl. Acad. Sci. USA 95, 11846-11851. 10. Usdin, T.B., Gruber, C, Bonner, T.I. (1995). Identification and functional expression of a receptor selectively recognizing parathyroid hormone, the PTH2 receptor. J. Biol. Chem. 270, 15455-15458. 11. Usdin, T.B., Bonner, T.I., Harta, G., Mezey, E. (1996). Distribution of PTH-2 receptor messenger RNA in rat. Endocrinology 137, 4285-4297. 12. Rubin, D.A., Hellman, P., Zon, L.I., Lobb, C.J., Bergwitz, C, Jϋppner, H. (1999). A teleost parathyroid hormone type-2 receptor is activated by PTH and not PTHrP: implications for the evolutionary conservation of calcium-regulating peptide hormones. J. Bio. Chem. 271, 23035-23042. 13. Usdin, T.B. (1997). Evidence for a parathyroid hormone-2 receptor selective ligand in the hypothalamus. Endocrinology 138, 831-834. 14. Orloff, J.J., Ganz, M.B., Ribaudo, A.E., Burtis, W.J., Reiss, M., Milstone, L.M., Stewart, A.F. (1992). Analysis of PTHrP binding and signal transduction mechanisms in benign and malignant squamous cells. Am J Physiol 262, E599-607. 15. Gaich, G., Orloff, J.J., Atillasoy, E.J., Burtis, W.J., Ganz, M.B., Stewart, A.F. (1993). Amino-terminal parathyroid hormone-related portein: specific binding and cytosolic calcium responses in rat insulinoma cells. Endocrinology 132, 1402-1409. 16. Orloff, J.J., Kats, Y., Urena, P., Schipa i, E., Vasavada, R.C, Philbrick, W.M., Behal, A., Abou-Samra, A.B., Segre, G.V., Jϋppner, H. (1995). Further evidence for a novel receptor for amino-terminal parathyroid hormone-related protein on keratinocytes and squamous carcinoma cell lines. Endocrinology 136, 3016-3023. 17. Fukayama, S., Tashjian, A.H., Davis, J.N. (1995). Signaling by N- and C-terminal sequences of parathyroid hormone-related protein in hippocampal neurons. Proc. Natl. Acad. Sci. USA 92, 10182-10886. 18. Yamamoto, S., Morimoto, I., Yanagihara, N., Zeki, K., Fujihira, T., Izumi, F., Yamashita, H., Eto, S. (1997). Parathyroid hormone-related peptide-(l-34) [PTHrP-(l-34)] induces vasopressin release from the rat supraoptic nucleus in vitro through a novel receptor distinct from a type I or type II PTH/PTHrP receptor. Endocrinology 138, 2066-2072. 19. Yamamoto, S., Morimoto, I., Zeki, K., Ueta, Y., Yamashita, H., Kannan, H., Eto, S. (1998). Centrally administered parathyroid hormone (PTH)-related protein (1-34) but not PTH(l-34) stimulates arginine-vasopressin secretion and its messenger ribonucleoic acid expression in supraoptic nucleus ofthe conscious rats. Endocrinology 139, 383-388. 20. Kovacs, C.S., Lanske, B., Hunzelman, J.L., Guo, J., Karaplis, A.C., Kronenberg, H.M. (1996). Parathyroid hormone-related peptide (PTHrP) regulates fetal placental calcium transport through a receptor distinct from the PTH/PTHrP receptor. Proc. Natl. Acad. Sci. USA 93, 15233-15238. 21. Wu, T.L., Vasavada, R.C, Yang, K., Massfelder, T., Ganz, M., Abbas, S.K., Care, A.D., Stewart, A.F. (1996). Structural and physiological characterization of the mid-region secretory species of parathyroid hormone-related protein. J. Biol. Chem. 271, 24371-24381. 22. Orloff, J.J., Ganz, M.B., Nathanson, H., Moyer, M.S., Kats, Y., Mitnick, M., Behal, A., Gasalla-Herraiz, J., Isales, CM. (1996). A midregion parathyroid hormone-related peptide mobilizes cytosolic calcium and stimulates formation of inositol trisphosphate in a squamous carcinoma cell line. Endocrinology 137, 5376-5385. 23. Inomata, N., Akiyama, M., Kubota, N., Jϋppner, H. (1995). Characterization of a novel PTH-receptor with specificity for the carboxyl-terminal region of PTH(l-84). Endocrinology 136, 4732-4740. 24. Takasu, H., Baba, H., Inomata, N., Uchiyama, Y., Kubota, N., Kumaki, K., Matsumoto, A., Nakajima, K., Kimura, T., Sakakibara, S., Fujita, T., Chihara, K., Nagai, I. (1996). The 69-84 amino acid region of the parathyroid hormone molecule is essential for the interaction of the hormone with the binding sites with carboxyl-terminal specificity. Endocrinology 137, 5537-5543. 25. Gardella, T.J., Luck, M.D., Jensen, G.S., Usdin, T.B., Jϋppner, H. (1996). Converting parathyroid hormone-related peptide (PTHrP) into a potent PTH-2 receptor agonist. J. Biol. Chem. 271, 19888-19893. 26. Bergwitz, C, Jusseaume, S.A., Luck, M.D., Jϋppner, H., Gardella, TJ. (1997). Residues in the membrane-spanning and extracellular regions of the parathyroid hormone (PTH)-2 receptor determine signaling selectivity for PTH and PTH-related peptide. J. Biol. Chem. 272, 28861-28868. 27. Schipani, E., Karga, H., Karaplis, A.C., Potts, J.T., Jr., Kronenberg, H.M., Segre, G.V., Abou-Samra, A.B., Jϋppner, H. (1993). Identical complementary deoxyribonucleic acids encode a human renal and bone parathyroid hormone (PTH)/PTH-related peptide receptor. Endocrinology 132, 2157-2165. 28. Iida-Klein, A., Guo, J., Drake, M.T., Kronenberg, H.M., Abou-Samra, A.B., Bringhurst, F.R., Segre, G.V. (1994). Structural requirements of PTH/PTHrP receptors for phospholipase C activation and regulation of phosphate uptake. J. Bone Miner. Res. 29. Iida-Klein, A., Guo, J., Xie, L. Y., Jϋppner, H., Potts, J.T., Jr., Kronenberg, H.M., Bringhurst, F.R., Abou-Samra, A.B., Segre, G.V. (1995). Truncation of the carboxyl-terminal region ofthe parathyroid hormone (PTH)/PTH-related peptide receptor enhances PTH stimulation of adenylate cyclase but not phospholipase C. J. Biol. Chem. 270, 8458-8465. 30. Kong, X.F., Schipani, E., Lanske, B., Joun, H., Karperien, M., Defize, L.H.K., Jϋppner, H., Potts, J.T., Segre, G.V., Kronenberg, H.M., Abou-Samra, A.B. (1994). The rat, mouse and human genes encoding the receptor for parathyroid hormone and parathyroid hormone-related peptide are highly homologous. Biochem. Biophys. Res. Comm. 200, 1290-1299. 31. Schipani, E., Weinstein, L.S., Bergwitz, C, Iida-Klein, A., Kong, X.F., Stuhrmann, M., Kruse, K., Whyte, M.P., Murray, T., Schmidtke, J., van Dop, C, Brickman, A.S., Crawford, J.D., Potts, J.T., Jr., Kronenberg, H.M., Abou-Samra, A.B., Segre, G.V., Jϋppner, H. (1995). Pseudohypoparathyroidism type lb is not caused by mutations in the coding exons of the human parathyroid hormone (PTHVPTH-related peptide receptor gene. J. Clin. Endocrinol. Metab. 80, 1611-1621. 32. Joun, H., Lanske, B., Karperien, M., Qian, F., Defize, L., Abou-Samra, A. (1997). Tissue-specific transcription start sites and alternative splicing of the parathyroid hormone (PTHVPTH-related peptide (PTHrP) receptor gene: a new PTH/PTHrP receptor splice variant that lacks the signal peptide. Endocrinology 138, 1742-1749. 33. Bettoun, J.D., Minagawa, M., Kwan, M.Y., Lee, H.S., Yasuda, T., Hendy, G.N., Goltzman, D., White, J.H. (1997). Cloning and characterization of the promoter regions ofthe human parathyroid hormone (PTH)/PTH-related peptide receptor gene: analysis of deoxyribonucleic acid from normal subjects and patients with pseudohypoparathyroidism type lb. J. Clin. Endocrinol. Metab. 82, 1031-1040. 34. Bettoun, J.D., Minagawa, M., Hendy, G.N., Alpert, L.C, Goodyer, C.G., Goltzman, D., White, J.H. (1998). Developmental upregulation of the human parathyroid hormone (PTH)/PTH-related peptide receptor gene expression from conserved and human-specific promoters. J. Clin. Invest. 102, 958-967. 35. Lee, C, Gardella, T.J., Abou-Samra, A.B., Nussbaum, S.R., Segre, G.V., Potts, J.T., Jr., Kronenberg, H.M., Jϋppner, H. (1994). Role ofthe extracellular regions of the parathyroid hormone (PTH)/PTH-related peptide receptor in hormone binding. Endocrinology 135, 1488-1495. 36. Maddison, W.P., and Maddison, M.D. (1992) McClade, 3 rd Ed., Sinauer Associates, Inc., Sunderland, MA. 37. Hedges, S.B., (1992) Mol. Cell. Evol. 9: 366-369. 38. Swofford, D.L., (1993) PAUP: Phylogenetic Analysis Using Parsimony, 3.1 ED., Illinois Natural History Survey, Champaign, IL. 39. Swofford, D.L., and Olsen, G.J., (1990) in Molecular Systematics (Hillis, D.M., and Moritz, C, eds.) pp 411-501, Sinauer Associates, Inc., Sunderland, MA. 40. Rubin, D.A., and Jϋppner, H., (1999) Zebrafish Express the Common Parathyroid Hormone /Parathyroid Hormone-related Peptide (PTHIR) and a Novel Receptor (PTH3R) That Is Preferentially Activated by Mammalian and Fugufish Parathyroid Hormone-related Peptide. J. Bio. Chem.274: 28185-28190. 41. Pough, F.H., Heiser, J.B., and McFarland, W.N. (1989) Vertebrate Life, 3 rd Ed., Macmillan, New York. 42. Usdin, T.B., Hoare, S.R.J., Wang, T., Mezey, E., and Kowalak, J.A. (1999) TIP39: A New Neuropeptide and PTH2 -receptor Agonist From Hypothalamus Nature Neuroscience 2: 941-943. 64. 1 INDICATIONS RELATING TO DEPOSITED MICROORGANISM OR OTHER BIOLOGICAL MATERIAL (PCT Rule I3bιs) A. The indications made below relate to the microorganism referred to in the description on page 6 , hne 25_ B. IDENTIFICATION OF DEPOSIT Further deposits are identified on an additional sheet S Name ol depositary institution Amei ican Type Culluic Collection (ATCC) Address ot depositary institution I including postal code and countrs ) 10801 Univei sity Boulevard Manassas. V n ginia 201 10-2209 United States ot America Date ot deposit November 4. 1999 Accession Number ATTC - PTA-916 C. ADDITIONAL INDICATIONS (leave blank if not applicable) This information is continued on an additional sheet d Plasmid in Escherichia coli ZPTHIR D. DESIGNATED STATES FOR VVHICII INDICATIONS ARE MADE at ,iw mdu aimm are no, / ,,, all donated Sia -i E. SEPARATE FURNISHING OF INDICATIONS ,/ t «u υimύ „ n„, , ψ a ω e , The indications listed below w ill be submitted to the international Bureau latei (specifv the general naluic oj the indications, e v . "Accession Numbei oj Deposit") For receiving Office use onlv For International Bureau use onlv ^This sheet was received with the international application □ This sheet was received by the International Bureau on χει __ Authorized officer Form PCT/RO/134 (July 1998) 009pc05 torml34( I ) 64. 2 INDICATIONS RELATING TO DEPOSITED MICROORGANISM OR OTHER BIOLOGICAL MATERIAL (PCT Rule I3bιs) A. The indications made below relate to the microorganism referred to in the description on page 7 , line B. IDENTIFICATION OF DEPOSIT Further deposits are identified on an additional sheet S Name of depositary institution Amciican Type Culture Collection (ATCC) Address ot depositary institution (including postal code and country) 10801 University Boulevard Manassas. Virginia 201 10-2209 United States ot ' Ameπca Date ot deposit November 4. 1999 Accession Number ATTC - PTA-915 C. ADDITIONAL INDICATIONS (leave blank if not applicable) χ hls forma t ion is continued on an additional sheet □ Plasmid in Escherichia coli ZPTH3R D. DESIGNATED STATES FOR WHICH INDICATIONS ARE MADE (if the indu atw are not tor alt designated bates E. SEPARATE FURNISHING OF INDICATIONS , leave blank „ no, „ PP ι uπb iei The indications listed below will be submitted to the international Bureau later (specify the general nature ofthe indications, e g . "Accession Numbei of Deposit") Form PCT/RO/134 (July 1998) 474pc01 forml34( 2 )

Claims: -65- What Is Claimed Is: 1. An isolated nucleic acid molecule comprising a polynucleotide having a nucleotide sequence at least 95% identical to a sequence selected from the group consisting of: (a) a nucleotide sequence encoding the PTHIR receptor having the complete amino acid sequence at positions from about 1 to about 536 in SEQ ID NO:2; (b) a nucleotide sequence encoding the PTHIR receptor having the amino acid sequence at positions from about 2 to about 536 in SEQ ID NO:2; (c) a nucleotide sequence encoding the mature PTHIR receptor having the amino acid sequence at positions from about 25 to about 536 in SEQ ID NO:2; (d) a nucleotide sequence encoding the PTHIR receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (e) a nucleotide sequence encoding the mature PTHIR receptor having the amino acid sequence encoded by the cDNA deposited with the ATCC as patent deposit PTA-916; (f) a nucleotide sequence encoding the PTHIR extracellular domain; (g) a nucleotide sequence encoding the PTH 1 R transmembrane domain; and (h) a nucleotide sequence complementary to any of the nucleotide sequences in (a), (b), (c), (d), (e), (f) or (g). 2. The nucleic acid molecule of claim 1 wherein said polynucleotide has the complete nucleotide sequence of SEQ ID NO:l. RECTIFIED SHEET (RULE 91) ISA/EP -66- 3. The nucleic acid molecule of claim 1 wherein said polynucleotide has the nucleotide sequence of SEQ ID NO:l encoding the PTHIR receptor having the complete amino acid sequence in Figure 2A (SEQ ID NO:2). 4. The nucleic acid molecule of claim 1 wherein said polynucleotide has the nucleotide sequence of SEQ ID NO:l encoding the mature PTHIR receptor having the amino acid sequence in Figure 2A (SEQ ID NO:2). 5. The nucleic acid molecule of claim 1 wherein said polynucleotide has the complete nucleotide sequence of the cDNA clone deposited with the ATCC as patent deposit PTA-916. 6. The nucleic acid molecule of claim 1 wherein said polynucleotide has the nucleotide sequence encoding the PTHIR receptor having the complete amino acid sequence encoded by the cDNA deposited with the ATCC as patent deposit PTA-916. 7. The nucleic acid molecule of claim 1 wherein said polynucleotide has the nucleotide sequence encoding the mature PTHIR receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916. 8. An isolated nucleic acid molecule comprising a polynucleotide which hybridizes under stringent hybridization conditions to a polynucleotide having a nucleotide sequence identical to a nucleotide sequence in (a), (b), (c), (d), (e), (f) or (g) of claim 1 wherein said polynucleotide which hybridizes does not hybridize under stringent hybridization conditions to a polynucleotide having a nucleotide sequence consisting of only A residues or of only T residues. RECTIFIED SHEET (RULE 91) ISA/EP -67- 9. An isolated nucleic acid molecule comprising a polynucleotide which encodes the amino acid sequence of an epitope-bearing portion of a PTHIR receptor having an amino acid sequence in (a), (b), (c), (d), (e), (f) or (g) of claim 1. 10. The isolated nucleic acid molecule of claim 1 , which encodes the PTHIR receptor extracellular domain. 1 1. The isolated nucleic acid molecule of claim 1 , which encodes the PTHIR receptor transmembrane domain. 12. A method for making a recombinant vector comprising inserting an isolated nucleic acid molecule of claim 1 into a vector. 13. A recombinant vector produced by the method of claim 12. 14. A method of making a recombinant host cell comprising introducing the recombinant vector of claim 13 into a host cell. 15. A recombinant host cell produced by the method of claim 14. 16. A recombinant method for producing a PTHIR polypeptide, comprising culturing the recombinant host cell of claim 15 under conditions such that said polypeptide is expressed and recovering said polypeptide. 17. An isolated PTHIR polypeptide having an amino acid sequence at least 95% identical to a sequence selected from the group consisting of: (a) the amino acid sequence ofthe PTHIR polypeptide having the complete amino acid sequence at positions from about 1 to about 536 in SEQ ID NO:2; -68- (b) the amino acid sequence ofthe PTH 1 R polypeptide having the amino acid sequence at positions from about 2 to about 536 in SEQ ID NO:2; (c) the amino acid sequence ofthe mature PTH 1 R polypeptide having the amino acid sequence at positions from about 25 to about 536 in SEQ ID NO:2; (d) the amino acid sequence ofthe PTH 1 R polypeptide having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (e) the amino acid sequence ofthe mature PTH 1 R polypeptide having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-916; (f) the amino acid sequence of the PTHIR receptor extracellular domain; (g) the amino acid sequence of the PTHIR receptor transmembrane domain; and (h) the amino acid sequence of an epitope-bearing portion of any one ofthe polypeptides of (a), (b), (c), (d), (e), (f), or (g). 18. An isolated polypeptide comprising an epitope-bearing portion of the PTHIR receptor protein. 19. An isolated antibody that binds specifically to a PTHl R receptor polypeptide of claim 17. 20. A method of treating diseases and disorders associated with the decreased PTHIR activity comprising administering an effective amount ofthe polypeptide as claimed in claim 17, or an agonist thereof to a patient in need thereof. -69- 21. A method of treating diseases and disorders associated with increased PTHIR activity comprising administering an effective amount an antagonist ofthe polypeptide as claimed in claim 17 to a patient in need thereof. 22. An isolated nucleic acid molecule comprising a polynucleotide having a nucleotide sequence at least 95% identical to a sequence selected from the group consisting of: (a) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence at positions from about 1 to about 542 in (SEQ ID NO:4); (b) a nucleotide sequence encoding the PTH3R receptor having the amino acid sequence at positions from about 2 to about 542 in (SEQ ID NO:4); (c) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence at positions from about 22 to about 542 in (SEQ ID NO:4); (d) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (e) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (f) a nucleotide sequence encoding the PTH3R extracellular domain; (g) a nucleotide sequence encoding the PTH3R transmembrane domain; (h) a nucleotide sequence complementary to any of the nucleotide sequences in (a), (b), (c), (d), (e), (f) or (g). -70- 23. The nucleic acid molecule of claim 22 wherein said polynucleotide has the complete nucleotide sequence in Figure ID (SEQ ID NO:3). 24. The nucleic acid molecule of claim 22 wherein said polynucleotide has the nucleotide sequence in Figure ID (SEQ ID NO:3) encoding the PTH3R receptor having the complete amino acid sequence in Figure 2B (SEQ ID NO:4). 25. The nucleic acid molecule of claim 22 wherein said polynucleotide has the nucleotide sequence in Figure ID (SEQ ID NO:3) encoding the mature PTH3R receptor having the amino acid sequence in Figure 2B (SEQ ID NO:4). 26. The nucleic acid molecule of claim 22 wherein said polynucleotide has the complete nucleotide sequence of the cDNA clone deposited with the ATCC as patent deposit PTA-915. 27. The nucleic acid molecule of claim 22 wherein said polynucleotide has the nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915. 28. The nucleic acid molecule of claim 22 wherein said polynucleotide has the nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915. 29. An isolated nucleic acid molecule comprising a polynucleotide which hybridizes under stringent hybridization conditions to a polynucleotide having a nucleotide sequence identical to a nucleotide sequence in (a), (b), (c), (d), (e), (f), (g), or (h) of claim 22 wherein said polynucleotide which hybridizes -71- does not hybridize under stringent hybridization conditions to a polynucleotide having a nucleotide sequence consisting of only A residues or of only T residues. 30. An isolated nucleic acid molecule comprising a polynucleotide which encodes the amino acid sequence of an epitope-bearing portion of a PTH3R receptor having an amino acid sequence in (a), (b), (c), (d), (e), (f), (g), or (h) of claim 22. 31. The isolated nucleic acid molecule of claim 22, which encodes the PTH3R receptor extracellular domain. 32. The isolated nucleic acid molecule of claim 22, which encodes the PTH3R receptor transmembrane domain. 33. A method for making a recombinant vector comprising inserting an isolated nucleic acid molecule of claim 22 into a vector. 34. A recombinant vector produced by the method of claim 33. 35. A method of making a recombinant host cell comprising introducing the recombinant vector of claim 34 into a host cell. 36. A recombinant host cell produced by the method of claim 35. 37. A recombinant method for producing a PTH3R polypeptide, comprising culturing the recombinant host cell of claim 36 under conditions such that said polypeptide is expressed and recovering said polypeptide. 38. An isolated PTH3R polypeptide having an amino acid sequence at least 95% identical to a sequence selected from the group consisting of: -72- (a) the amino acid sequence ofthe PTH3 R polypeptide having the complete amino acid sequence at positions from about 1 to about 542 in (SEQ ID NO:4); (b) the amino acid sequence ofthe PTH3 R polypeptide having the amino acid sequence at positions from about 2 to about 542 in (SEQ ID NO:4); (c) the amino acid sequence ofthe mature PTH3R polypeptide having the amino acid sequence at positions from about 22 to about 542 in(SEQ ID NO:4); (d) the amino acid sequence ofthe PTH3 R polypeptide having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (e) the amino acid sequence ofthe mature PTH3R polypeptide having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (f) the amino acid sequence of the PTH3R receptor extracellular domain; (g) the amino acid sequence of the PTH3R receptor transmembrane domain; (h) the amino acid sequence of an epitope-bearing portion of any one ofthe polypeptides of (a), (b), (c), (d), (e), (f), or (g). 39. An isolated polypeptide comprising an epitope-bearing portion of the PTH3R receptor protein. 40. An isolated antibody that binds specifically to a PTH3R receptor polypeptide of claim 38 41. A method of treating diseases and disorders associated with the decreased PTH3R activity comprising administering an effective amount ofthe -73- polypeptide as claimed in claim 38, or an agonist thereof to a patient in need thereof. 42. A method of treating diseases and disorders associated with increased PTH3R activity comprising administering an effective amount an antagonist ofthe polypeptide as claimed in claim 38 to a patient in need thereof. 43. An isolated polynucleotide encoding a modified PTH3R protein, wherein, except for at least one conservative amino acid substitution, said modified protein has an amino acid sequence that is identical to a member selected from the group consisting of: (a) amino acids 1 to 542 of SEQ ID NO:4; (b) amino acids 2 to 542 of SEQ ID NO:4; and (c) amino acids 22 to 542 of SEQ ID NO:4. 44. A modified PTH3R protein, wherein, except for at least one conservative amino acid substitution, said modified protein has an amino acid sequence that is identical to a member selected from the group consisting of: (a) amino acids 1 to 542 of SEQ ID NO:4; (b) amino acids 2 to 542 of SEQ ID NO:4; and (c) amino acids 22 to 542 of SEQ ID NO:4. 45. An isolated polynucleotide encoding a modified PTH 1 R protein, wherein, except for at least one conservative amino acid substitution, said modified protein has an amino acid sequence that is identical to a member selected from the group consisting of: (a) amino acids 1 to 536 of SEQ ID NO:2; (b) amino acids 2 to 536 of SEQ ID NO:2; and (c) amino acids 25 to 536 of SEQ ID NO:2. -74- 46. A modified PTHIR protein, wherein, except for at least one conservative amino acid substitution, said modified protein has an amino acid sequence that is identical to a member selected from the group consisting of: (a) amino acids 1 to 536 of SEQ ID NO:2; (b) amino acids 2 to 536 of SEQ ID NO:2; and (c) amino acids 25 to 536 of SEQ ID NO:2. 47. A method for the isolation of a nucleic acid molecule comprising (a) selecting a fragment of SEQ ID NO: 3 as a nucleic acid probe; (b) hybridizing said probe overnight to at least one test sequence by incubation at 42 °C in a solution of 30% formamide, 5x SSC (150 mM NaCl, 15mM trisodium citrate), 50 mM sodium phosphate (pH 7.6), 5x Denhardt's solution, 10% dextran sulfate, and 20 g/ml denatured, sheared salmon sperm DNA; and (c) removing nonhydridized probe by washing with a solution of 2x SSC or lx SSC or 0 .5x SSC at about 55 °C or 60°C or 65 °C; (d) identifying a target sequence bound by said probe; wherein said identified target sequence is at least about 70% identical to a sequence selected from the group consisting of: (e) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence at positions from about 1 to about 523 in (SEQ ID NO:4); (f) a nucleotide sequence encoding the PTH3R receptor having the amino acid sequence at positions from about 2 to about 523 in (SEQ ID NO:4); (g) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence at positions from about 22 to about 523 in (SEQ ID NO:4); -75- (h) a nucleotide sequence encoding the PTH3R receptor having the complete amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (i) a nucleotide sequence encoding the mature PTH3R receptor having the amino acid sequence encoded by the cDNA clone deposited with the ATCC as patent deposit PTA-915; (j) a nucleotide sequence encoding the PTH3R extracellular domain; (k) a nucleotide sequence encoding the PTH3R transmembrane domain; (1) a nucleotide sequence complementary to any of the nucleotide sequences in (e), (f), (g), (h), (i), (j) or (k).

Inventors: JUEPPNER HARALD, RUBIN DAVID A, JUEPPNER, HARALD, RUBIN, DAVID, A.
Applicants: JUEPPNER HARALD, RUBIN DAVID A, JUEPPNER, HARALD, RUBIN, DAVID, A.
Application year: 1999
Main classification: C12N15
IPC codes: A61K38, A61K45, A61P5, C07K14, C07K16, C12N1, C12N5, C12N15, C12P21, C12Q1, G01N33