Identification, Localisation and Functional Implication of 26RFa Orthologue Peptide in the Brain of Zebra Finch (Taeniopygia guttata)

Abstract

Several neuropeptides with the C-terminal Arg-Phe-NH(2) (RFa) sequence have been identified in the hypothalamus of a variety of vertebrates. The present study was conducted to isolate novel RFa peptides from the zebra finch brain. Peptides were isolated by immunoaffinity purification using an antibody that recognises avian RFa peptides. The isolated peptide consisted of 25 amino acids with RFa at its C-terminus. The sequence was SGTLGNLAEEINGYNRRKGGFTFRFa. Alignment of the peptide with vertebrate 26RFa has revealed that the identified peptide is the zebra finch 26RFa. We also cloned the precursor cDNA encoding this peptide. Synteny analysis of the gene showed a high conservation of this gene among vertebrates. In addition, we cloned the cDNA encoding a putative 26RFa receptor, G protein-coupled receptor 103 (GPR103) in the zebra finch brain. GPR103 cDNA encoded a 432 amino acid protein that has seven transmembrane domains. In situ hybridisation analysis in the brain showed that the expression of 26RFa mRNA is confined to the anterior-medial hypothalamic area, ventromedial nucleus of the hypothalamus and the lateral hypothalamic area, the brain regions that are involved in the regulation of feeding behaviour, whereas GPR103 mRNA is distributed throughout the brain in addition to the hypothalamic nuclei. When administered centrally in free-feeding male zebra finches, 26RFa increased food intake 24 h after injection without body mass change. Diencephalic GPR103 mRNA expression was up-regulated by fasting for 10 h. Our data suggest that the hypothalamic 26RFa-its receptor system plays an important role in the central control of food intake and energy homeostasis in the zebra finch.

MOLECULAR EVOLUTION OF GPCRS: 26Rfa/GPR103

“…Furthermore, in situ hybridization has shown specific expression of 26RFa/QRFP mRNA in the anterior hypothalamic nucleus in the chick brain, and the distribution of 26RFa/QRFP mRNA-containing perikarya clearly matches with that of 26RFa/QRFP-immunoreactive neurons (Ukena et al 2010). In the zebra finch, in situ hybridization analysis has revealed that expression of 26RFa/QRFP mRNA is localized to the anterior-medial hypothalamic area, the ventromedial nucleus of the hypothalamus, and the lateral hypothalamic area (Tobari et al 2011). These neuroanatomical data suggest that, in birds, 26RFa/QRFP produced in the hypothalamus participates in the control of feeding behavior, as shown previously in rodents (Chartrel et al 2006b, Do Régo et al 2006, Moriya et al 2006, Primeaux et al 2008.…”

“…Taken together, it appears that the C-terminal region of 26RFa/QRFP is responsible for the biological activity of the peptide. In addition to the chick data, it has been reported that central injection of 26RFa/QRFP in free-feeding male zebra finches stimulates food intake for 24 h, without a change in body mass (Tobari et al 2011). These results also indicate that 26RFa/QRFP exerts an orexigenic activity in various avian species.…”

“…As the N-terminal amino acid was pyroglutamic acid, this RFamide peptide was also named pyroglutamylated RFamide peptide (QRFP; Fukusumi et al 2003). Subsequently, the cDNAs encoding the 26RFa/QRFP precursors have been characterized in goldfish (Liu et al 2009), quail (Ukena et al 2010), chicken (Ukena et al 2010), and zebra finch (Tobari et al 2011) (Fig. 2B).…”

“…2A). More recently, a 26RFa/QRFP ortholog, consisting of 25 amino acids, and the related cDNA have been characterized in the brain of zebra finch (Tobari et al 2011;Fig. 2).…”

“…In birds, the cDNAs encoding QRFPR have been characterized in the brain of chicken and zebra finch (Ukena et al 2010, Tobari et al 2011. The sequence of chicken QRFPR is highly similar to those of human and rat QRFPR (Fig.…”