CaM-induced shift of inactivation in hNaV1.4 channels.
Representative Na+ currents and I–V relationships for wild type (A) and hNaV1.4F1705I channels (B) elicited by the same pulse protocol shown in the inset of Figure 1B. CaM and CaM1234 over expression significantly (p<0.05) shifts the wild type but not the hNaV1.4F1705I I–V in the depolarizing direction. (C) Representative steady-state inactivation currents elicited from different holding potentials. (D, E) Plots of the steady-state inactivation and activation relationships of wild type hNaV1.4 (D) and hNaV1.4F1705I channels (E). The solid lines are the fits to steady-state inactivation data with CaM and CaM1234 over expression. There is a significant (p<0.005) depolarizing shift of the inactivation curve by CaM and CaM1234 compared to the expression of hNaV1.4F1705I alone. The symbols and colors are the same in all panels of the figure.