Modulation of gating currents of the Cav3.1 calcium channel by α2δ2a and γ5 subunits

Modulatory effects of auxiliary γ5 and α2δ2a subunits on intramembrane charge movement originating from the expressed Cav3.1 calcium channel were investigated. Inward current was blocked by 1 mM La3+. Voltage dependences of Qon and Qoff, kinetics of ON- and OFF-charge movement, and Imax/Qmax ratio were measured in the absence and the presence of an auxiliary subunit. The α2δ2a subunit accelerated significantly both ON- and OFF-charge movement. Imax/Qmax ratio and Qon–V, Qoff–V relations were not affected. Coexpression of the α2δ2a subunit may accelerate channel transitions between individual closed states, but not the transition from the last closed channel state into an open state. Coexpression of the γ5 subunit accelerated the decay of the ON-charge transient and enhanced Imax/Qmax ratio. These effects suggest improvement of the coupling between the charge movement and the channel opening due to facilitation of transitions between individual closed states and the transition between the last closed state and an open state.