Role of putative voltage-sensor countercharge D4 in regulating gating properties of CaV1.2 and CaV1.3 calcium channels

ABSTRACTVoltage-dependent calcium channels (CaV) activate over a wide range of membrane potentials, and the voltage-dependence of activation of specific channel isoforms is exquisitely tuned to their diverse functions in excitable cells. Alternative splicing further adds to the stunning diversity of gating properties. For example, developmentally regulated insertion of an alternatively spliced exon 29 in the fourth voltage-sensing domain (VSD IV) of CaV1.1 right-shifts voltage-dependence of activation by 30 mV and decreases the current amplitude several-fold. Previously we demonstrated that this regulation of gating properties depends on interactions between positive gating charges (R1, R2) and a negative countercharge (D4) in VSD IV of CaV1.1. Here we investigated whether this molecular mechanism plays a similar role in the VSD IV of CaV1.3 and in VSDs II and IV of CaV1.2 by introducing charge-neutralizing mutations (D4N or E4Q) in the corresponding positions of CaV1.3 and in two splice variants of CaV1....