Shark rectal gland vasoactive intestinal peptide receptor: cloning, functional expression, and regulation of CFTR chloride channels.
Vasoactive intestinal peptide (VIP) is a secretagogue that mediates chloride secretion in intestinal epithelia. We determined the relative potency of VIP and related peptides in the rectal gland of the elasmobranch dogfish shark and cloned and expressed the VIP receptor (sVIP-R) from this species. In the perfused rectal gland, VIP (5 nM) stimulated chloride secretion from 250 +/- 66 to 2,604 +/- 286 microeq x h(-1) x g(-1); the relative potency of peptide agonists was VIP > PHI = GHRH > PACAP > secretin, where PHI is peptide histidine isoleucine amide, GHRH is growth hormone-releasing hormone, and PACAP is pituitary adenylate cylase activating peptide. The cloned sVIP-R from shark rectal gland (SRG) is only 61% identical to the human VIP-R1. It maintains a long, extracellular NH2 terminus with seven cysteine residues, and has three N-glycosylation sites and eight other residues implicated in VIP binding. Two amino acids considered important for peptide binding in mammals are not present in the shark orthologue. When sVIP-R and the CFTR chloride channel were coexpressed in Xenopus oocytes, VIP increased chloride conductance from 11.3 +/- 2 to 127 +/- 34 microS. The agonist affinity for activating chloride conductance by the cloned receptor was VIP > GHRH = PHI > PACAP > secretin, a profile mirroring that in the perfused gland. The receptor differs from previously cloned VIP-Rs in having a low affinity for PACAP. Expression of both sVIP-R and CFTR mRNA was detected by quantitative PCR in shark rectal gland, intestine, and brain. These studies characterize a unique G protein-coupled receptor from the shark rectal gland that is the oldest cloned VIP-R.
Bewley
Marie S
MS
Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Pena
John T G
JT
Plesch
Florian N
FN
Decker
Sarah E
SE
Weber
Gerhard J
GJ
Forrest
John N
JN
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D004284:Dogfish / Q000502:physiology*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D010802:Phylogeny; D018005:Receptors, Vasoactive Intestinal Peptide / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012491:Salt Gland / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D014982:Xenopus laevis
D018797:Cell Cycle Proteins; D002712:Chlorides; D018005:Receptors, Vasoactive Intestinal Peptide; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D014660:Vasoactive Intestinal Peptide; D004706:Endodeoxyribonucleases; C078472:mENase protein, Coprinus cinereus