Internalization of pancreatic polypeptide Y4 receptors: correlation of receptor intake and affinity

Abstract

Unlike neuropeptide Y receptors, the pancreatic polypeptide Y4 receptors display considerable differences in sequence and ligand-binding affinity across mammalian species. This could produce different receptor turnover rates in the same cellular membrane environment. Comparing rat, human and guinea-pig Y4 receptors expressed in Chinese hamster ovary (CHO) cells ( K d with human pancreatic polypeptide 14, 45 and 116 pM, respectively), we indeed found human pancreatic polypeptide internalization in the rank order of receptor affinities. A large fraction of the internalized human pancreatic polypeptide, similar across the Y4 species, was associated with secondary endosomes (density≈1.05 in Percoll gradients) and lysosomes (density≈1.11). For all Y4 receptors examined, this intake was potently and selectively inhibited by cholesterol-complexing polyene antibiotic filipin III and also by clathrin lattice formation inhibitor, phenylarsine oxide. Internalization differences found across Y4 receptor species to a degree compare with those observed for the cloned guinea-pig neuropeptide Y Y1 and human neuropeptide Y Y5 receptors and, generally, support ligand-binding affinities as important determinants of internalization for neuropeptide receptors.