Identification of a novel V1-type AVP receptor based on the molecular recognition theory

Background: The molecular recognition theory predicts that binding domains of peptide hormones and their corresponding receptor binding domains evolve d from complementary strands of genomic DNA, and that a process of selectiv e evolutionary mutational events within these primordial domains gave rise to the high affinity and high specificity of peptide hormone-receptor inter actions observed today in different peptide hormone-receptor systems. Moreo ver, this theory has been broadened as a general hypothesis that could expl ain the evolution of intermolecular protein-protein and intramolecular pept ide interactions. Materials and Methods: Applying a molecular cloning strategy based on the m olecular recognition theory, we screened a rat kidney cDNA library with a v asopressin (AVP) antisense oligonucleotide probe, expecting to isolate pote ntial AVP receptors. Results: We isolated a rat kidney cDNA encoding a functional VI-type vasopr essin receptor. Structural analysis identified a 135 amino acid-long polype ptide with a single transmembrane domain, quite distinct from the rhodopsin -based G protein-coupled receptor superfamily. Functional analysis of the e xpressed VI-type receptor in Cos-1 cells revealed AVP-specific binding, AVP -specific coupling to Ca2+ mobilizing transduction system, and characterist ic VI-type antagonist inhibition. Conclusions: This is the second AVP receptor cDNA isolated using AVP antipe ptide-based oligonucleotide screening, thus providing compelling evidence i n support of the molecular recognition theory as the basis of the evolution of this peptide hormone-receptor system, as well as adds molecular complex ity and diversity to AVP receptor systems.