Molecular mechanism of protein kinase C modulation of sodium channel α-subunits expressed in Xenopus oocytes

The mechanism of modulation of sodium channel α-subunits (Type IIA) by a protein kinase C (PKC) activator was studied on single channel level. It was found that: (i) time constants for channel activation were prolonged; (ii) inactivation remained virtually unchanged; (iii) peak sodium inward current was reduced as evidenced by calculation of average sodium currents; and (iv) time constants for current activation and decay were prolonged. (i), (iii) and (iv) were voltage dependent, being most prominent at threshold potentials. The data show that a voltage dependent action on the activation gate can account for the observed reduction of peak inward sodium current and prolongation of current decay in macroscopic experiments.