Effect of the Cav1.1 R1086H mutation on DICR activity at 2.5 mM [K ⁺ ]. (A) Resting membrane potential of 5 BV cells in 5 mM or 2.5 mM [K⁺] Krebs solution. Data are the median with individual data points (n = 10, N = 3 for 5 mM [K⁺] and n = 20, N = 3 for 2.5 mM [K⁺]) and were analyzed by the unpaired two-tailed t test with the Mann–Whitney test. (B) Resting ER [Ca²⁺] in WT (black) and R1086H (blue) Cav1.1 cells. Data are means ± SD (n = 12, N = 3) and were analyzed by the two-tailed t test with the Mann–Whitney test. (C) [K⁺] dependence of R-CEPIA1er fluorescence (F/F₀) in WT (black) and R1086H (blue) Cav1.1 cells. Data are means ± SD (n = 9, N = 3). (D and E) Fluorescence change by 61 mM [K⁺] (D) and EC₅₀ values for [K⁺] (E). Data are means ± SD (n = 9, N = 3) and were analyzed by the two-tailed t test with the Mann Whitney test. n is the number of cells (A) or wells (B–E) and N is the number of independent experiments. Related to Fig. 4 D.