Regulation of two-pore-domain (K2P) potassium leak channels by the tyrosine kinase inhibitor genistein.
OBJECTIVE
Two-pore-domain potassium (K2P) channels mediate potassium background (or 'leak') currents, controlling excitability by stabilizing membrane potential below firing threshold and expediting repolarization. Inhibition of K2P currents permits membrane potential depolarization and excitation. As expected for key regulators of excitability, leak channels are under tight control from a plethora of stimuli. Recently, signalling via protein tyrosine kinases (TKs) has been implicated in ion channel modulation. The objective of this study was to investigate TK regulation of K2P channels.


METHODS
The two-electrode voltage clamp technique was used to record K2P currents in Xenopus oocytes. In addition, K2P channels were studied in Chinese hamster ovary (CHO) cells using the whole-cell patch clamp technique.


RESULTS
Here, we report inhibition of human K2P3.1 (TASK-1) currents by the TK antagonist, genistein, in Xenopus oocytes (IC50=10.7 microM) and in CHO cells (IC50=12.3 microM). The underlying molecular mechanism was studied in detail. hK2P3.1 was not affected by genistin, an inactive analogue of genistein. Perorthovanadate, an inhibitor of tyrosine phosphatase activity, reduced the inhibitory effect of genistein. Current reduction was voltage independent and did not require channel protonation at position H98 or phosphorylation at the single TK phosphorylation site, Y323. Among functional hK2P family members, genistein also reduced K2P6.1 (TWIK-2), K2P9.1 (TASK-3) and K2P13.1 (THIK-1) currents, respectively.


CONCLUSIONS
Modulation of K2P channels by the TK inhibitor, genistein, represents a novel molecular mechanism to alter background K+ currents.
Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.
J
J
Gierten
E
E
Ficker
R
R
Bloehs
K
K
Schlömer
S
S
Kathöfer
E
E
Scholz
E
E
Zitron
C
C
Kiesecker
A
A
Bauer
R
R
Becker
H A
HA
Katus
C A
CA
Karle
D
D
Thomas
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004594:Electrophysiology; D019833:Genistein / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010766:Phosphorylation; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors* / Q000187:drug effects / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D015398:Signal Transduction; D014982:Xenopus laevis
C486603:KCNK13 protein, human; C118290:KCNK6 protein, human; C498655:KCNK9 protein, human; D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; D047428:Protein Kinase Inhibitors; C420132:potassium channel subfamily K member 3; D019833:Genistein