Inhibition of hK2P3.1 (TASK-1) Potassium Channels by the Tyrosine Kinase Inhibitor Genistein

Two-pore-domain (K2P) channels mediate potassium background currents, controlling excitability by stabilizing membrane potential below firing threshold and expediting repolarization. Inhibition of K2P currents permits membrane potential depolarization and excitation. Signaling via protein tyrosine kinases has been implicated in ion channel modulation. The objective of this study was to investigate tyrosine kinase regulation of K2P3.1 channels. The two-electrode voltage clamp technique was used to record K2P currents in Xenopus oocytes, and K2P3.1 channels were studied in CHO cells using the whole cell patch clamp technique. Human K2P3.1 (TASK-1) was blocked by the tyrosine kinase inhibitor, genistein, in Xenopus oocytes (IC50 = 10.7 μM) and in Chinese hamster ovary cells (IC50 = 12.3 μM). The channel was not affected by genistin, an inactive analogue of genistein. Perorthovanadate, an inhibitor of tyrosine phosphatase activity, slightly attenuated the inhibitory effect of genistein. Current reduction was voltage-independent and did not require channel protonation at position H98. Genistein-associated blockade occurred independently of channel phosphorylation at the single tyrosine kinase phosphorylation site, Y323, suggesting that tyrosine kinase activity does not directly affect K2P3.1 channel function. In addition to K2P3.1, genistein also reduced K2P6.1 (TWIK-2), K2P9.1 (TASK-3), and K2P13.1 (THIK-1) currents, respectively. Modulation of K2P channels by genistein is revealed to be a novel mechanism to alter background K+ channel function.