Ca_V3.1 channel pore pseudo-symmetry revealed by selectivity filter mutations in its domains I/II

There is growing evidence indicating that the pore structure of voltage-gated ion channels (VGICs) influences gating besides their conductance. Regarding low voltage-activated (LVA) Ca²⁺ channels, it has been demonstrated that substitutions of the pore aspartate (D) by a glutamate (D-to-E substitution) in domains III and IV alter channel gating properties such as a positive shift in the channel activation voltage dependence. In the present report, we evaluated the effects of E-to-D substitution in domains I and II on the Ca_V3.1 channel gating properties. Our results indicate that substitutions in these two domains differentially modify the gating properties of Ca_V3.1 channels. The channel with a single mutation in domain I (DEDD) presented slower activation and faster inactivation kinetics and a slower recovery from inactivation, as compared with the WT channel. In contrast, the single mutant in domain II (EDDD) presented a small but significant negative shift of activation voltage dependence with faster activation and slower inactivation kinetics. Finally, the double mutant channel (DDDD) presented somehow intermediate properties with respect to the two single mutants but with fastest deactivation kinetics. Overall, our results indicate that single amino acid modification of the selectivity filter of LVA Ca²⁺ channels in distinct domains differentially influence their gating properties, supporting a pore pseudo-symmetry.