Mutations in the N-lobe and C-lobe of CaM affect the currents of hSK2 expressed in HEK 293 cells. (A) hSK2 channels were coexpressed with CaM_WT or mutant CaMs (CaM_1,2, CaM_3,4, or CaM_1,2,3,4). Current was recorded before (black trace) and after (red trace) application of apamin (10 nM). (B) Summary data at +60 and −120 mV indicating significant reduction of the SK currents by mutant CaMs (n = 12 cells; *, P < 0.05). (C and D) hSK2 channels were coexpressed with CaM_WT (black bars), CaM_N54I (red bars), CaM_F90L (green bars), CaM_D96V (blue bars), CaM_N98S (cyan bars), and CaM_D130G (magenta bars). (C) Current was recorded before (black trace) and after (red trace) application of apamin (10 nM). (D) Summary data at −120 mV and +60 mV (n = 10–13 cells; *, P < 0.05). For B and D, the colors of the asterisks denote comparisons with the corresponding bar graphs of the same colors, using one-way ANOVA combined with Tukey's test (at −120 mV, P = 0.00001 for all pairwise comparisons except P = 0.04 for CaM_N54I versus CaM_D96V, and P = NS for CaM_D96V versus CaM_D130G and CaM_WT versus CaM_F90L; at +60 mV, P = 0.00001 for all pairwise comparisons except P= NS for CaM_D96V versus CaM_D130G). Data shown represents mean ± SEM.