Molecular characterization of structure and tissue distribution of chicken neurotensin receptor.

Neurotensin, a tridecapeptide, is distributed in a wide range of tissues and exhibits multiple functions through its receptors. Hitherto molecular characterization of the neurotensin receptor has been reported in mammalian, amphibian, and fish species but not in avian species. In this study, we cloned the cDNA encoding chicken neurotensin receptor from the duodenum and characterized its primary structure, biological activity and distribution in the gastrointestinal tract. The cDNA encoded a protein consisting of 399 amino acids that had significant overall sequence homology to other vertebrate neurotensin receptor 1 with higher extent in the seven transmembrane domains. Chicken neurotensin increased intracellular Ca(2+) concentrations in human embryonic kidney 293 cells transiently expressing the chicken neurotensin receptor 1. Real-time PCR analysis showed that chicken neurotensin receptor 1 mRNA is expressed throughout the gastrointestinal tract with markedly higher level in the colon/rectum. These results indicate that the chicken neurotensin receptor 1 is involved in gastrointestinal functions through an intracellular signaling pathway accompanied by an increase in Ca(2+) levels.

Molecular characterization of sequence and expression of chicken GPR39.

GPR39 has been recently proposed to be a specific receptor for a novel anorexic peptide, obestatin, isolated from rat stomach. Obestatin is generated from the proprotein for ghrelin by proteolytic cleavage and shows opposing action to ghrelin in the regulation of food intake and gastrointestinal movement. In this study, we performed cDNA cloning for chicken GPR39 and characterized expression profiles of its mRNA in chicken tissues. Chicken GPR39 cDNA encoding 462 amino acids was cloned from chick duodenum. The amino acid sequence showed high homology to human (62.6%), mouse (62.6%), and rat (65.3%) GPR39. A computer-assisted search for chicken GPR39 cDNA sequence in the chicken genome database revealed that chicken GPR39 gene consists of two exons separated by an intron. Real-time PCR analysis revealed the expression of GPR39 mRNA in a wide range of tissues with the highest level in the duodenum in chicks and hens. The expression level in the duodenum rapidly increased during the early post-hatch period. Interestingly, relatively higher expression was observed in the oviduct, vagina and uterus in hen. These findings suggest that GPR39 is involved in the regulation of gastrointestinal and reproductive functions in chicken.