Molecular Mechanisms of Large-Conductance Ca2+-Activated Potassium Channel Activation by Ginseng Gintonin
Figure 5
Involvement of calmodulin and CaM kinase II in gintonin-mediated BKCa channel activation. ((a) and (b)) Oocytes expressing the BKCa channel were incubated in the absence (a) or presence (b) of calmidazolium (1.5 μM) for 10 min. Insets, the representative gintonin-mediated or ginsenoside Rg3-mediated peak outward current amplitude at +40 mV from a holding potential of −80 mV was measured in the absence or presence of calmidazolium. (c) Summary histograms show peak outward BKCa channel currents recorded in oocytes expressing the BKCa channel in the absence or presence of the calmidazolium (CMZ) (mean ± S.E.M; -14 oocytes each; , compared to gintonin alone). (d) The oocytes expressing mutant BKCa channel at the CaM kinase II phosphorylation site (T462A or S521A) were treated with gintonin by bathing application for 60 s. Mutation of CaM kinase II phosphorylation sites resulted in a rightward shift of the gintonin concentration-response curve (mean ± S.E.M; –12 oocytes each). (e) Summary histograms show that the gintonin-mediated peak outward BKCa channel currents recorded in oocytes expressing mutant BKCa channel at the CaM kinase II phosphorylation site (T462A or S521A) were significantly attenuated (mean ± S.E.M; –12 oocytes each; *, compared to wild-type).
