Figure 2. LQTS CaM mutants diminish CDI in HEK293 cells.

A, Exemplar currents evoked by 30-mV voltage step (top) in cells co-transfected with Ca_V1.2 and CaM_WT. CDI manifests as the stronger decay in Ca²⁺ (red) current as compared to Ba²⁺ (black). Ba²⁺ trace is scaled downward to match the peak of the Ca²⁺ trace, thus facilitating comparison of decay kinetics, and the scale bar for current references the Ca²⁺ trace, here and throughout.

B, Average normalized peak current versus voltage relation obtained with Ba²⁺ for the same cells as in A. Data are plotted as mean ± SEM here and throughout.

C, Population data for CDI across voltages. r₃₀₀ measures the current remaining after 300 ms, after normalization to peak current. f₃₀₀ is the difference between Ca²⁺ and Ba²⁺ at 30 mV, after normalization by the Ba²⁺ r₃₀₀ value.

D, Expression of CaM_D96V severely blunts CDI of Ca_V1.2.

E, The current-voltage relation for the CaM_D96V scenario remains unaltered.

F, Population data bears out the CaM_D96V reduction of CDI across voltages. For reference, the Ca²⁺ r₃₀₀ curve for CaM_WT is reproduced in gray.

G–L, CaM_D130G and CaMF142L also induce dramatic CDI deficits. Format as in D–F.