Comparative efficacy of VIP and analogs on activation and internalization of the recombinant VPAC2 receptor expressed in CHO cells.

Using a monoclonal antibody interacting with the extracellular amino-terminus of the human VPAC2 receptor but that did not interfere with ligand binding, we measured by flow cytometry receptor internalization and trafficking induced by full agonists, partial agonists and an antagonist in Chinese hamster ovary cells expressing the recombinant receptor. The agonists, but not the antagonist, induced a rapid, dose-dependent receptor internalization blocked by hypertonic sucrose that was more pronounced for the VIP analog N-hexanoyl-VIP (80%) than for VIP and Ro 25-1553 (50%) and the [A11]-VIP (20%). Re-expression of the receptors at the membrane was achieved within two hours after exposure to VIP and Ro 25-1553 was blocked by 25 microM monensin but not by 10 microg/ml cycloheximide. Re-expression was much slower after exposure to the acylated peptide and was blocked by preincubation with 25 microM monensin and 10 microg/ml cycloheximide.