Molecular characterization of three NPY receptors (Y2, Y5 and Y7) in chickens: Gene structure, tissue expression, promoter identification, and functional analysis.

Six neuropeptide Y (NPY) receptors are suggested to mediate the biological actions of NPY, peptide YY (PYY), and pancreatic polypeptide (PP), such as food intake in birds, however, information regarding the structure and signaling of avian NPY receptors are rather limited. In this study, we investigated the gene structure, tissue expression and signaling property of three NPY receptors (cY2, cY5 and cY7) in chickens. The results showed that 1) cY2, cY5 and cY7 contain novel non-coding exons upstream of their start codon and alternative mRNA splicing in their 5'-UTR results in the formation of multiple transcript variants; 2) cY2, cY5 and cY7 transcripts were detected to be widely expressed in adult chicken tissues including various brain regions by RT-PCR, and their expression is controlled by a promoter(s) near exon 1, which display promoter activity in DF-1 cells as demonstrated by Dual-luciferase reporter assay; 3) cY2, cY5 and cY7 expressed in HEK293 cells were preferentially (or potently) activated by cNPY1-36 and cPYY1-37, but not by cPP1-36, and their activation led to the inhibition of cAMP/PKA signaling pathway and activation of MAPK/ERK signaling pathway, monitored by the cell-based luciferase reporter systems or western blots, indicating that the three NPY receptors are functional and capable of transmitting signals effectively. On the whole, our data establishes a molecular basis to elucidate the actions of three functional NPY receptors (cY2, cY5 and cY7) and their ligands in birds, which helps to uncover the conserved roles of these ligand-receptor pairs in vertebrates.