A G protein-coupled receptor from zebrafish is activated by human parathyroid hormone and not by human or teleost parathyroid hormone-related peptide. Implications for the evolutionary conservation of calcium-regulating peptide hormones.
Genomic and cDNA clones encoding portions of a putative catfish parathyroid hormone (PTH) 2 receptor (PTH2R) led to the isolation of a cDNA encoding a full-length zebrafish PTH2R (zPTH2R). The zPTH2R shared 63 and 60% amino acid sequence identity with human and rat PTH2Rs, respectively, 47-52% identity with mammalian and frog PTH/PTHrP receptors (PTH1R), and less than 37% with other members of this family of G protein-coupled receptors. COS-7 cells expressing zPTH2R(43), a 5' splice variant that lacked 17 amino acids in the amino-terminal extracellular domain, showed cAMP accumulation when challenged with [Tyr(34)]hPTH(1-34)-amide (hPTH) (EC(50), 1.64 +/- 0. 95 nM) and [Ile(5),Trp(23),Tyr(36)]hPTHrP-(1-36)-amide ([Ile(5), Trp(23)]hPTHrP) (EC(50), 46.8 +/- 12.1 nM) but not when stimulated with [Tyr(36)]hPTHrP-(1-36)-amide (hPTHrP), [Trp(23), Tyr(36)]hPTHrP-(1-36)-amide ([Trp(23)]hPTHrP), or [Ala(29),Glu(30), Ala(34),Glu(35),Tyr(36)]fugufish PTHrP-(1-36)amide (fuguPTHrP). FuguPTHrP also failed to activate the human PTH2R but had similar efficiency and efficacy as hPTH and hPTHrP when tested with cells expressing the human PTH1R. Agonist-dependent activation of zPTH2R was less efficient than that of zPTH2R(43), and both receptor variants showed no cAMP accumulation when stimulated with either secretin, growth hormone-releasing hormone, or calcitonin. The zPTH2R thus has ligand specificity similar to that of the human homolog, which raises the possibility that a PTH-like molecule exists in zebrafish, species which lack parathyroid glands.
Rubin
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Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Hellman
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Zon
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Lobb
C J
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Bergwitz
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Jüppner
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D015139:Blotting, Southern; D003001:Cloning, Molecular; D015342:DNA Probes; D018076:DNA, Complementary; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007059:Ictaluridae; D008969:Molecular Sequence Data; D010281:Parathyroid Hormone / Q000235:genetics / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D051381:Rats; D044183:Receptor, Parathyroid Hormone, Type 2; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015027:Zebrafish
D015342:DNA Probes; D018076:DNA, Complementary; C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D044183:Receptor, Parathyroid Hormone, Type 2; D018016:Receptors, Parathyroid Hormone; D019204:GTP-Binding Proteins