Cloning and characterization of rabbit neuropeptide Y receptor subtypes

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) are structurally related peptides that have numerous functions in both neural and endocrine signaling. These effects are mediated by the NPY receptor family and five members of this family have been cloned in mammals. To better characterize these receptor subtypes, we cloned and expressed the Y1, Y2, Y4 and Y5 receptor subtypes from the rabbit. Comparison of these sequences with human orthologs revealed that the Y1, Y2 and Y5 receptors have generally strong amino-acid sequence conservation, with 91-96% identity, while Y4 receptor showed relatively weak similarity with 82% identity, as with other species. Particularly in the transmembrane regions, Y1, Y2, and Y5 receptor subtypes showed remarkable conservation, with 98-99% amino acid identity. Competitive binding studies by NPY-family peptides and analogs showed that Y1, Y2 and Y5 receptors had similar pharmacological profiles between the respective rabbit and human receptor subtypes. Interestingly, all the tested peptides had a greater affinity for rabbit Y4 receptor than human Y4 receptor. These results suggest that rabbit and human Y1, Y2 and Y5 receptor subtypes are well conserved, whereas Y4 receptors are less well conserved.