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

Abstract

A sequence coding for an arginine vasotocin (AVT) receptor has been identified 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 acid peptide, analysis of which indicates a seven-transmembrane spanning sequence typical of G-protein-coupled receptors with the N terminus on the outer surface of the cell membrane. Sequence analysis showed this sequence to have a high homology with the Catostomus commersoni AVT receptor (76%) and mammalian vasopressin V(1)-type receptor (62%), but only 55% homology with the C. commersoni isotocin receptor. A two-electrode voltage clamp was used to characterize the receptor expressed in Xenopus laevis oocytes. AVT induced 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 vasopressin V(1)-type receptor agonist ([Phe(2), Orn(8)] oxytocin)() induced an inward current but was less potent than AVT, whereas the mammalian vasopressin V(2)-type receptor agonist ([Deamino(1), Val(4), D-Arg(8)] AVP) was without effect. Injection of oocytes with heparin or BAPTA suppressed the response to AVT, indicating receptor linkage to the phospholipase C-phosphatidylinositol pathway. Northern analysis demonstrated the presence of this AVT receptor mRNA in the brain, kidney, and gill of flounder.