title: Molecular basis for genistein-induced inhibition of Kir2.3 currents.
abstract: Inwardly rectifying potassium channels play an important role in the maintenance of membrane potential in neurons and myocardium. Identification of functional regulation mechanisms concerning these channels may lead to the development of specific modulators for these channels. Genistein is an isoflavone with potent inhibitory activity on protein tyrosine kinase. In this study, we have found that among three members of the Kir family (Kir2.3, Kir2.1, and Kir3.4* [a highly active mutant of Kir3.4, Kir3.4-S143T]) we tested, genistein significantly inhibited Kir2.3 currents. Using the two-electrode voltage clamp technique, we have demonstrated that micromole concentrations of genistein concentration-dependently and reversibly inhibited the currents of Kir2.3 channel expressed in Xenopus oocytes with an IC50 of 16.9+/-2.8 microM. Using the whole-cell patch-clamp technique, genistein also inhibited the currents of Kir2.3 channel expressed in HEK293 cells with an IC50 of 19.3+/-3.2 microM. Genistein had little or no effect on Kir2.1 and Kir3.4* currents. The effect of genistein on Kir2.3 currents was not affected by vanadate, a potent protein tyrosine phosphatase inhibitor. Furthermore, the effect of genistein was not mimicked by daidzein, an inactive analogue of genistein, or another potent tyrosine kinase inhibitor, tyrphostin 23. Chimeras between Kir2.3 and Kir2.1 channels were constructed to identify molecular basis that distinguished the effect of genistein on these channels. It was found that the transmembrane domains and the pore region of Kir2.3 channel were important determinant for high sensitivity for genistein inhibition.
authors: Department of Pharmacology, Hebei Medical University, 361 Zhongshan East Road, Shijiazhuang, Hebei 050017, China.
authors: Zhiying
authors: Z
authors: Zhao
authors: Boyi
authors: B
authors: Liu
authors: Guohong
authors: G
authors: Zhang
authors: Zhanfeng
authors: Z
authors: Jia
authors: Qingzhong
authors: Q
authors: Jia
authors: Xian
authors: X
authors: Geng
authors: Hailin
authors: H
authors: Zhang
mesh_terms: D000818:Animals; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D004791:Enzyme Inhibitors; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D007529:Isoflavones; C489457:KCNJ2 protein, human; C099489:KCNJ4 protein, human; C484274:KCNJ5 protein, human; D019269:Phosphatidylinositol 4,5-Diphosphate; D024661:Potassium Channels, Inwardly Rectifying; D047428:Protein Kinase Inhibitors; D020032:Tyrphostins; C004742:daidzein; D019833:Genistein; C060641:tyrphostin A23