Molecular Mechanisms of Large-Conductance Ca2+-Activated Potassium Channel Activation by Ginseng Gintonin
Figure 4
Involvement of PKC but not PKA in gintonin-mediated BKCa channel activation. (a) Gintonin or ginsenoside Rg3 induces activation of BKCa channels in oocytes. ((b)–(d)) Time-current relationships show the effects of gintonin or ginsenoside Rg3 in the pretreatment of PMA (1 μM) for 10 min, calphostin (Cal 1.5 μM) for 10 min, or the mutation of the PKC phosphorylation site (S1061A). Peak outward currents were recorded during bath application of gintonin (10 μg/mL). 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 presence of PMA, calphostin, or mutant BKCa channels. (e) Time-current relationships following the application of gintonin (10 μg/mL) or ginsenoside Rg3 (100 μM) for 30 s in oocytes expressing S939A mutant BKCa channels. (f) Concentration dependency of wild-type and S939A mutant BKCa channels on gintonin-mediated BKCa channel activation. (g) Summary histograms show that peak outward BKCa channel currents (mean ± S.E.M; -12 oocytes each) recorded in oocytes expressing the BKCa channel in the absence or presence of the indicated agents or mutation (*, compared to gintonin alone).
