Elucidating the roles of voltage sensors in NaV1.9 activation and inactivation through a spider toxin

Abstract

The gating process of voltage-gated sodium (Na_V) channels is extraordinary intrinsic and involves numerous factors, such as voltage-sensing domain (VSD), the N-terminus and C-terminus, and the auxiliary subunits. To date, the gating mechanism of Na_V channel has not been clearly elucidated. Na_V1.9 has garnered significant attention due to its slow gating kinetics. Due to the challenges of Na_V1.9 heterologous expression, research on its gating mechanism is relatively limited. Whether there are any differences in the functions of the four VSDs in Na_V1.9 compared to those in other subtypes remains an open question. Here, we employed the established chimera method to transplant the S3b-S4 motif from the VSDIV of the toxin-sensitive donor channel (Na_V1.9) into the receptor channel (Na_V1.9/1.8 DIV S3b-S4 chimera). This modification imparted animal toxin sensitivity to the other three VSDs. Our results demonstrate that all four VSDs of Na_V1.9 are involved in channel opening, VSDIII and VSDIV are primarily involved in regulating fast inactivation, and VSDII also regulates the steady-state inactivation of channels. These findings provide a new insight into the gating mechanism of Na_V1.9.