title: Novel evolutionary lineages of the invertebrate oxytocin/vasopressin superfamily peptides and their receptors in the common octopus (Octopus vulgaris).
abstract: The common octopus, Octopus vulgaris, is the first invertebrate species that was shown to possess two oxytocin/vasopressin (OT/VP) superfamily peptides, octopressin (OP) and cephalotocin (CT). Previously, we cloned a GPCR (G-protein-coupled receptor) specific to CT [CTR1 (CT receptor 1)]. In the present study, we have identified an additional CTR, CTR2, and a novel OP receptor, OPR. Both CTR2 and OPR include domains and motifs typical of GPCRs, and the intron- exon structures are in accord with those of OT/VP receptor genes. CTR2 and OPR expressed in Xenopus oocytes induced calcium-mediated inward chloride current in a CT- and OP-specific manner respectively. Several regions and residues, which are requisite for binding of the vertebrate OT/VP receptor family with their ligands, are highly conserved in CTRs, but not in OPR. These different sequences between CTRs and OPR, as well as the amino acid residues of OP and CT at positions 2-5, were presumed to play crucial roles in the binding selectivity to their receptors, whereas the difference in the polarity of OT/VP family peptide residues at position 8 confers OT and VP with the binding specificity in vertebrates. CTR2 mRNA was present in various peripheral tissues, and OPR mRNA was detected in both the nervous system and peripheral tissues. Our findings suggest that the CT and OP genes, similar to the OT/VP family, evolved through duplication, but the ligand-receptor selectivity were established through different evolutionary lineages from those of their vertebrate counterparts.
authors.affiliation: Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamoto, Mishima, Osaka 618-8503, Japan.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Kanda
authors.forename: Honoo
authors.initials: H
authors.lastname: Satake
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kawada
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Minakata
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D003001:Cloning, Molecular / Q000379:methods; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D049831:Octopodiformes / Q000235:genetics*; D009865:Oocytes / Q000737:chemistry / Q000378:metabolism; D010121:Oxytocin / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D014667:Vasopressins / Q000235:genetics*; D014981:Xenopus / Q000235:genetics
chemical_list: D043562:Receptors, G-Protein-Coupled; D014667:Vasopressins; D010121:Oxytocin