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This Article Accepted manuscript (PDF) Supplemental Figure All Versions of this Article: JME-08-0083v1 41/5/343    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wu, S. Articles by Sherwood, N. PubMed PubMed Citation Articles by Wu, S. Articles by Sherwood, N.

S Wu, Biology, University of Victoria, Victoria, British Columbia, V8P 5C2 , Canada
G Roch, Biology, University of Victoria, Victoria, British Columbia, Canada
L Cervini, Peptide Biology Laboratory, The Salk Institute, La Jolla, United States
J Rivier, Peptide Biology Laboratory, The Salk Institute, La Jolla, United States
N Sherwood, Victoria, British Columbia, Canada

Correspondence: Sheng Wu, Email: sheng.w.wu{at}gmail.com

Abstract

A group of ten hormones in humans are structurally related and known as the secretin superfamily. These hormones bind to G-protein-coupled receptors that activate the cAMP pathway and are clustered as the secretin or B family. We used molecular techniques to clone two full length receptor cDNAs in zebrafish, which were analyzed for amino acid sequence and ligand-binding motifs, phylogenetic position, synteny, tissue expression, functional response, and signaling pathway. Evidence is provided that the two cDNAs are the peptide histidine-isoleucine (PHI) receptor and PRP receptor, which is known as growth hormone-releasing hormone-like peptide (GHRH-LP) receptor in non-mammals. Further we cloned a zebrafish cDNA encoding the peptides PHI and vasoactive intestinal peptide (VIP). The PHI-R cDNA, transfected into COS7 cells, responded to zebrafish PHI in a sensitive and dose-dependent manner (EC50 = 1.8 X 10-9M) but not to PACAP and VIP. The GHRH-LP receptor responded to both zebrafish GHRH-LP1 and GHRH with a 3.5 fold greater response to the former. For comparison, two zebrafish receptors (PAC1 & VPAC1) and two human receptors (VPAC2 & GHRH) were tested with human and/or zebrafish peptides. Unexpectedly, zebrafish VIP activated its PAC1 receptor suggesting that in evolution, PAC1 is not always a specific receptor for PACAP. We conclude that zebrafish, like goldfish, have a specific receptor for PHI and GHRH-LP. Our evidence that zebrafish PHI is more potent than human PHM in activating the human VPAC2 receptor (EC50 = 7.4 X 10-9M) supports our suggestion that the VPAC2R and PHI-R shared a common ancestral receptor.