Modulated I _Ca,L in adult Flag-RadΔCT murine cardiomyocytes. (A) Representative family of I_Ca,L currents. Voltage protocol schematic above current traces. (B) Current density–voltage relationship for peak I_Ca,L from Flag-Rad and Flag-RadΔCT ex vivo cardiomyocytes. (C) Conductance transforms of the current–voltage curve. Smooth curves are Boltzmann distribution fitted to data. Mean maximal conductance was significantly increased 5.2-fold in Flag-RadΔCT (614.8, 95% CI 528.4, 701.2) compared with Flag-Rad (118.0, 95% CI 30.7, 205.2) (estimated marginal means). Statistical significance was determined by a linear mixed model, nesting cells into the random factor mouse. Genotype as a main effect was significantly different (P = 0.002, F = 62.856). (D) To highlight the shift in activation midpoint, the conductance–voltage curves were normalized to maximum conductance. The mean activation midpoint was significantly shifted negatively at 11.3 mV in Flag-RadΔCT (−14.2, 95% CI −17.6, −10.9) relative to Flag-Rad (−3.0, 95% CI −5.9, 0.02) (estimated marginal means). Statistical significance was determined by a linear mixed model, nesting cells into the random factor mouse. Genotype as a main effect was significantly different (P = 0.018, F = 24.419). Mice are shown to the left and cells to the right. For mice, means and SEM are plotted; for cells, medians, and IQR. For Flag-Rad (N = 3 mice, n = 13 cells); for Flag-RadΔCT (N = 3 mice, n = 14 cells). (E) Western blot for Ca_V1.2 expression in protein lysates from Flag-Rad and Flag-RadΔCT whole heart lysates. Median relative expression of Ca_V1.2 (normalized to total protein) was not significantly different (Mann–Whitney U test, P = 0.5476, U = 6). Source data are available for this figure: SourceData F3.