Using voltage‐sensor toxins and their molecular targets to investigate Na_V1.8 gating

Abstract

Voltage-gated sodium (Na ) channel gating is a complex phenomenon which involves a distinct contribution of four integral voltage-sensing domains (VSDI, VSDII, VSDIII and VSDIV). Utilizing accrued pharmacological and structural insights, we build on an established chimera approach to introduce animal toxin sensitivity in each VSD of an acceptor channel by transferring in portable S3b-S4 motifs from the four VSDs of a toxin-susceptible donor channel (Na 1.2). By doing so, we observe that in Na 1.8, a relatively unexplored channel subtype with distinctly slow gating kinetics, VSDI-III participate in channel opening whereas VSDIV can regulate opening as well as fast inactivation. These results illustrate the effectiveness of a pharmacological approach to investigate the mechanism underlying gating of a mammalian Na channel complex.

Shared and unique aspects of ligand‐ and voltage‐gated ion‐channel gating

“…). In the current issue of The Journal , Gilchrist and Bosmans present an original research article detailing how animal toxins can be used to understand the slow gating kinetics of Nav1.8 (Gilchrist & Bosmans, ), a Nav channel implicated in pain mechanisms (Han et al . ).…”

“…To do this, the authors introduced toxin sensitivity into each of the four voltage sensor domains of Nav1.8 by exchanging their sequences with those of Nav1.2 to probe their role in channel gating and inactivation. Using this chimera approach, Gilchrist and Bosmans conclude that the voltage sensor domains I–III participate in channel opening, whereas voltage sensor domain IV regulates channel opening as well as the onset of fast inactivation (Gilchrist & Bosmans, ).…”

“…Given all of this, the Nav channel community has been developing a comprehensive understanding of how the structural architecture J Physiol 596.10 of Nav channels relates to their functional behaviour (Ahern et al 2016). In the current issue of The Journal, Gilchrist and Bosmans present an original research article detailing how animal toxins can be used to understand the slow gating kinetics of Nav1.8 (Gilchrist & Bosmans, 2018), a Nav channel implicated in pain mechanisms (Han et al 2016). To do this, the authors introduced toxin sensitivity into each of the four voltage sensor domains of Nav1.8 by exchanging their sequences with those of Nav1.2 to probe their role in channel gating and inactivation.…”

“…To do this, the authors introduced toxin sensitivity into each of the four voltage sensor domains of Nav1.8 by exchanging their sequences with those of Nav1.2 to probe their role in channel gating and inactivation. Using this chimera approach, Gilchrist and Bosmans conclude that the voltage sensor domains I-III participate in channel opening, whereas voltage sensor domain IV regulates channel opening as well as the onset of fast inactivation (Gilchrist & Bosmans, 2018). Dr Marc Gielen presented a compelling account of his postdoctoral work with Dr Trevor Smart at University College London where he performed a comprehensive analysis of Cys-loop GABA A and glycine receptor desensitization (Gielen et al 2015).…”

Identification and characterization of novel proteins from Arizona bark scorpion venom that inhibit Nav1.8, a voltage-gated sodium channel regulator of pain signaling

“…Progress has been hindered by a lack of venom proteins that modify Nav1.8 gating. In an effort to use gating modifier toxins to study Nav1.8 gating properties, Gilchrist and Bosmans exchanged Nav1.8 voltage sensors with Nav1.2, a toxin-sensitive channel [48]. Arizona (AZ) bark scorpion ( Centruroides sculpturatus ) venom proteins inhibit Nav1.8 activity and block pain in natural populations of predatory mice (Grasshopper mice, Onychomys torridus ) that feed on scorpions [49].…”