Differential activation of kiss receptors by Kiss1 and Kiss2 peptides in the sea bass

Abstract

Two forms ofkissgene (kiss1andkiss2) have been described in the teleost sea bass. This study assesses the cloning and characterization of two Kiss receptor genes, namelykissr2andkissr3(known asgpr54-1bandgpr54-2b, respectively), and their signal transduction pathways in response to Kiss1 and Kiss2 peptides. Phylogenetic and synteny analyses indicate that these paralogs originated by duplication of an ancestral gene before teleost specific duplication. Thekissr2andkissr3mRNAs encode proteins of 368 and 378 amino acids, respectively, and share 53.1% similarity in amino acid sequences.In silicoanalysis of the putative promoter regions of the sea bass Kiss receptor genes revealed conserved flanking regulatory sequences among teleosts. Bothkissr2andkissr3are predominantly expressed in brain and gonads of sea bass, medaka and zebrafish. In the testis, the expression levels of sea bass kisspeptins and Kiss receptors point to a significant variation during the reproductive cycle.In vitrofunctional analyses revealed that sea bass Kiss receptor signals are transduced both via the protein kinase C and protein kinase A pathway. Synthetic sea bass Kiss1–15 and Kiss2–12 peptides activated Kiss receptors with different potencies, indicating a differential ligand selectivity. Our data suggest that Kissr2 and Kissr3 have a preference for Kiss1 and Kiss2 peptides, respectively, thus providing the basis for future studies aimed at establishing their physiologic roles in sea bass.