Epidermal Growth Factor Receptor Tyrosine Kinase Stimulates Human Inward Rectifier Potassium (Kir2.3) Channels

Abstract

Protein tyrosine kinases (PTKs), in addition to the mediation of cellular events such as cell growth, differentiation, etc., regulate ion channels. Although Kir2.3 channel plays a crucial role in the repolarization and membrane potential stabilization of neurons and myocardium, modulation of this channel is not fully understood. The present study investigated whether/how human Kir2.3 channel is modulated by PTKs and protein tyrosine phosphatases (PTPs) in HEK 239 cells stably expressing Kir2.3 gene using approaches of whole-cell patch voltage clamp, immunoprecipitation and Western blot, and site-directed mutagenesis. We found that epidermal growth factor (EGF, 100 ng/ml) and PTPs inhibitor orthovanadate (1 mM) significantly enhanced Kir2.3 channel current, while the broad spectrum PTKs inhibitor genistein and the selective EGF receptor kinase inhibitor AG556, but not the Src-family PTK inhibitor PP2 or the platelet-derived growth factor receptor kinase inhibitor AG1295, suppressed the current. The inhibitory effect of Kir2.3 current by genistein or AG556 was fully countered by EGF or orthovanadate. In addition, tyrosine phosphorylation level of Kir2.3 channel was increased by EGF or orthovanadate, but decreased by genistein or AG556. The reduced phosphorylation level by genistein or AG556 was reversed by EGF or orthovanadate. Interestingly, the response of Kir2.3 channel to EGF or AG556 disappeared in Kir2.3 Y234A mutant. Our results demonstrate the novel information that human Kir2.3 channel is stimulated by EGFR tyrosine kinase via phosphorylating the channel at Tyr234.