A novel mechanism of neurokinin-1 receptor resensitization.
Prolonged or repeated activation of many G protein-coupled receptors induces rapid desensitization followed by a period during which receptors are resensitized. In this study, concanavalin A (Con A) and monensin were used to investigate the mechanisms of desensitization and resensitization of the neurokinin-1 receptor. Con A inhibits internalization, whereas monensin prevents receptor recycling. The effects of Con A and monensin on desensitization, resensitization, receptor phosphorylation, endocytosis, and recycling of the neurokinin-1 receptor were assessed. Desensitization was defined as the decrease in the ability of substance P (SP) to elicit an intracellular Ca2+ response after a prolonged SP exposure. Resensitization was characterized as the return of SP responsiveness. Under control conditions, desensitization occurred after a 5-min exposure to agonist. Resensitization was evident 30 min after agonist washout. Neither monensin nor Con A prevented desensitization. Monensin completely inhibited resensitization, whereas Con A decreased but did not completely block resensitization. Receptor phosphorylation was increased after agonist activation and returned to basal levels after a recovery period. Neither Con A nor monensin altered the amount of agonist-specific receptor phosphorylation. Receptor binding analysis showed that plasma membrane receptors were internalized after a 5-min agonist exposure. Receptor recycling was not observed after a 1-h recovery period; however, resensitization was apparent. Taken together, these results suggest that rapid neurokinin-1 receptor desensitization can occur without receptor internalization and that resensitization occurs before receptor recycling.
Bennett
V J
VJ
Department of Neurobiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio, USA.
Perrine
S A
SA
Simmons
M A
MA
D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology; D006224:Cricetinae; D008985:Monensin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D018040:Receptors, Neurokinin-1 / Q000819:agonists* / Q000378:metabolism*
D018040:Receptors, Neurokinin-1; D003208:Concanavalin A; D008985:Monensin