MOLECULAR EVOLUTION OF VERTEBRATE VIP RECEPTORS AND FUNCTIONAL-CHARACTERIZATION OF A VIP RECEPTOR FROM GOLDFISH CARASSIUS-AURATUS

Vasoactive intestinal polypeptide (VIP) is a neuropeptide that has num erous physiological actions and is widely distributed in the body. How ever, as yet, there is no sequence information about VIP receptors in lower vertebrates. Partial cDNA fragments spanning transmembrane domai ns 2 to 6 of VIP receptors were isolated from six nonmammalian vertebr ate species, including chicken, pigeon, frog, lizard, salmon, and gold fish. Sequence comparison of these receptors revealed essential struct ural motifs responsible for receptor function. In addition, the first nonmammalian full-length VIP receptor cDNA was obtained by screening a goldfish brain and pituitary cDNA library. Functional expression of t his receptor in mammalian COS-7 cells showed that it is coupled to cAM P production in a VIP and PACAP concentration-dependent manner; the EC (50) of VIP was determined to be 1 nM. At 100 nM peptide, the relative potency of various peptides in stimulating cAMP in the transfected ce lls was VIP > PACAP > GHRH = secretin > PHM > PTH > glucagon > GLP-1 > GIP. Characterization of the VIP receptors in lower vertebrates shoul d enhance our understanding of the molecular evolution and physiology of VIP in vertebrates. (C) 1997 Academic Press.