Review Identification, localization and function of a novel neuropeptide, 26RFa, and its cognate receptor, GPR103, in the avian hypothalamus

摘要

Several neuropeptides possessing the RFamide motif at their C-termini (designated RFamide peptides) have been characterized in the hypothalamus of a variety of vertebrates. Since the discovery of the 26-amino acid RFamide peptide (termed 26RFa) from the frog brain, 26RFa has been shown to exert orexi-genic activity in mammals and to be a ligand of the previously identified orphan G protein-coupled receptor GPR103. Recently, we have identified 26RFa in the avian brain by molecular cloning of the cDNA encoding the 26RFa precursor and mass spectrometry analysis of the mature peptide. 26RFa-producing neurons are exclusively located in the hypothalamus whereas GPR103 is widely distributed in the avian brain. Furthermore, avian 26RFa stimulates feeding behavior in broiler chicks. This review summarizes the advances in the identification, localization, and functions of 26RFa and its cognate receptor GPR103 in vertebrates and highlights recent progress made in birds. Since the initial identification of the cardioexdtatory peptide Phe-Met-Arg-Phe-NH2 (FMRFamide) from the ganglia of the Venus clam Macrocallista nimbosa (Price and Greenberg, 1977), a number of RFamide peptides have been characterized in invertebrates and these peptides seem to act as neurotransmitters and neuromodula-tors (for reviews, see Chartrel et al., 2002, 2006a; Tsutsui and Ukena, 2006; Ukena and Tsutsui, 2005; Walker and Papaioannou, 2009). RFamide peptides constitute a family of biologically active peptides that possess the Arg-Phe-NH2 motif at their C-termini. To date, five groups of the RFamide peptide family have been identified in vertebrates: the neuropeptide FF (NPFF) group, the prolac-tin-releasing peptide (PrRP) group, the gonadotropin-inhibitory hormone (GnIH) group, the kisspeptin group, and the 26RFa group (for reviews, see Bruzzone et al., 2006; Chartrel et al., 2011; Osugi et al., 2006; Tsutsui, 2009; Tsutsui and Ukena, 2006; Tsutsui et al., 2010a,b; Ukena and Tsutsui, 2005). This review summarizes the current knowledge on 26RFa, the latest member of the RFamide peptide family discovered in vertebrates, and focuses on recent data pertaining to 26RFa in birds.