PKCε phosphorylates 42 nicotinic ACh receptors and promotes recovery from desensitization

Background and PurposeNicotinic (ACh) receptor recovery from desensitization is modulated by PKC, but the PKC isozymes and the phosphorylation sites involved have not been identified. We investigated whether PKC epsilon phosphorylation of (42) nAChRs regulates receptor recovery from desensitization. Experimental ApproachReceptor recovery from desensitization was investigated by electrophysiological characterization of human (42) nAChRs. Phosphorylation of the (4) nAChR subunit was assessed by immunoblotting of mouse synaptosomes. Hypothermia induced by sazetidine-A and nicotine was measured in Prkce(-/-) and wild-type mice. Key ResultsInhibiting PKC epsilon impaired the magnitude of (42) nAChR recovery from desensitization. We identified five putative PKC epsilon phosphorylation sites in the large intracellular loop of the (4) subunit, and mutating four sites to alanines also impaired recovery from desensitization. (4) nAChR subunit phosphorylation was reduced in synaptosomes from Prkce(-/-) mice. Sazetidine-A-induced hypothermia, which is mediated by (42) nAChR desensitization, was more severe and prolonged in Prkce(-/-) than in wild-type mice. Conclusions and ImplicationsPKC epsilon phosphorylates the (4) nAChR subunit and regulates recovery from receptor desensitization. This study illustrates the importance of phosphorylation in regulating (42) receptor function, and suggests that reducing phosphorylation prolongs receptor desensitization and decreases the number of receptors available for activation.