Cloning and characterization of an arginine vasotocin receptor from the euryhaline flounder Platichthys flesus

A sequence coding for an arginine vasotocin (AVT) receptor has been identif ied by the screening of a hepatic cDNA library from the teleost Platichthys flesus. The 2701-bp receptor sequence is predicted to yield a 384-amino ac id peptide, analysis of which indicates a seven-transmembrane spanning sequ ence typical of G-protein-coupled receptors with the N terminus on the oute r surface of the cell membrane. Sequence analysis showed this sequence to h ave a high homology with the Catostomus commersoni AVT receptor (76%) and m ammalian vasopressin V-1-type receptor (62%), but only 55% homology with th e C. commersoni isotocin receptor. A two-electrode voltage clamp was used t o characterize the receptor expressed in Xenopus laevis oocytes. AVT induce d an inward current which was dose dependent over the range 16.7 fmol to 5 pmol; isotocin was without effect over the same dose range. The mammalian v asopressin V-1-type receptor agonist ([Phe(2), Orn(8)] oxytocin) induced an inward current but was less potent than AVT, whereas the mammalian vasopre ssin V-1-type receptor agonist ([Deamino(1), Val(4), D-Arg(8)] AVP) was wit hout effect. Injection of oocytes with heparin or BAPTA suppressed the resp onse to AVT, indicating receptor linkage to the phospholipase C-phosphatidy linositol pathway. Northern analysis demonstrated the presence of this AVT receptor mRNA in the brain, kidney, and gill of flounder. (C) 2001 Academic Press.