Agonist internalization by cloned Y1 neuropeptide Y (NPY) receptor in Chinese hamster ovary cells shows strong preference for NPY, endosome-linked entry and fast receptor recycling.

In Chinese hamster ovary (CHO) cells expressing the cloned guinea-pig Y1 receptor, the saturable, receptor-linked internalization of NPY (NPY)-related peptides showed the rank order of human/rat neuropeptide Y (hNPY)>pig/rat peptide YY (pPYY)>=(Pro34)human PYY>(Leu31,Pro34)hNPY>(Leu31,Pro34)hPYYmuch greater-thanBVD-11 (a selective Y1 antagonist). All agonists accessed similar numbers of Y1 sites in particulates from disrupted cells, with relatively small affinity variation. The rate of internalization could significantly depend on the overall interactivity of the agonist peptide (reflected in sensitivity to chaotropic agents, as well as in the level of non-saturable binding and internalization). Concentration-dependent inhibition of the agonist-driven CHO-Y1 internalization was found with filipin III (a cholesterol-complexing macrolide), and confirmed with inhibitors of clathrin lattice formation, phenylarsine oxide (PAO) and sucrose. In the concentration range affecting Y1 internalization, none of the above treatments or agents significantly alter agonist affinity for Y1 cell surface or particulate receptors. Largely similar responses to the above inhibitors were observed in CHO-Y1 cells for internalization of human transferrin. Internalization of CHO-Y1 receptor apparently is driven by NPY in strong preference to other naturally encountered agonists. At 37 °C, most of the internalized receptor is rapidly recycled through endosome-like membrane elements, detectable in Percoll gradients.