PKCε phosphorylates α₄β₂ nicotinic ACh receptors and promotes recovery from desensitization

Background and Purpose Nicotinic (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 PKCε phosphorylation of α₄β₂ nAChRs regulates receptor recovery from desensitization. Experimental Approach Receptor recovery from desensitization was investigated by electrophysiological characterization of human α₄β₂ nAChRs. Phosphorylation of the α₄ 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 Results Inhibiting PKCε impaired the magnitude of α₄β₂ nAChR recovery from desensitization. We identified five putative PKCε phosphorylation sites in the large intracellular loop of the α₄ subunit, and mutating four sites to alanines also impaired recovery from desensitization. α₄ nAChR subunit phosphorylation was reduced in synaptosomes from Prkce^-/- mice. Sazetidine-A-induced hypothermia, which is mediated by α₄β₂ nAChR desensitization, was more severe and prolonged in Prkce^-/- than in wild-type mice. Conclusions and Implications PKCε phosphorylates the α₄ nAChR subunit and regulates recovery from receptor desensitization. This study illustrates the importance of phosphorylation in regulating α₄β₂ receptor function, and suggests that reducing phosphorylation prolongs receptor desensitization and decreases the number of receptors available for activation.