FIGURE 5.

CK2 phosphorylation mutations of CaM modified KCNQ2 current and PIP₂ susceptibility. A, representative current traces of KCNQ2 currents expressed in CHO cells in the presence of CaM(WT), CaM(3D), or CaM(3A) as well as KCNQ2(F24A) + CaM(WT). At a holding potential of −80 mV, KCNQ2 currents were activated by 500-ms step depolarizations up to +30 mV, followed by −60 mV. B, KCNQ2 current density at −10 mV. ***, p < 0.001 by nonparametric ANOVA followed by Dunn's multiple comparisons test. C, voltage clamp current traces showing Ci-VSP-induced rundown of KCNQ2 current. Step depolarizations (10 s), which activated noninactivating current when KCNQ2 channel was expressed alone (upper traces), showed depolarization-dependent run-down (lower traces) when co-expressed with Ci-VSP. D, average current traces ± S.E. (shaded) of scaled currents showing that the Ci-VSP-induced rundown of the KCNQ2 current was reduced by co-expression of CaM(3D) or in KCNQ2(F24A) channel. Shaded area surrounding each trace shows S.E. The data were collected from 10-s depolarization steps to +30 mV. E, histogram of relative KCNQ2 currents at t = 10 s shown in D. ***, p < 0.001 by nonparametric ANOVA followed by Dunn's multiple comparisons test. Error bars show S.E.