Voltage-gated sodium channels (VGSCs)

Voltage-gated sodium channels (VGSCs) are integral membrane proteins essential for initiating and propagating action potentials in excitable cells. They consist of a large alpha subunit (~230 kDa) and auxiliary beta subunits (~25-45 kDa). The alpha subunit has four homologous domains (I-IV), each with six transmembrane segments (S1-S6). The architecture includes a pore domain for ion selectivity and permeation, and four voltage-sensing domains (VSDs) (S1-S4). VGSCs exist in closed, open, and inactivated states. Upon membrane depolarization, positively charged S4 segments move, causing a conformational change that opens the channel and allows sodium influx. Rapid inactivation follows, preventing further influx until repolarization. Nine mammalian alpha subunits (Nav1.1-Nav1.9) are encoded by distinct genes and classified by tetrodotoxin (TTX) sensitivity (sensitive and resistant). VGSCs are significant therapeutic targets, particularly in pain management, with specific isoforms (Nav1.3, Nav1.7, Nav1.8, Nav1.9) implicated. Mutations lead to channelopathies associated with various disorders including pain, muscle issues, epilepsy, and neurological conditions. Nav1.7 is a key target for pain due to its role in inherited pain syndromes. Recent structural studies using cryo-EM and X-ray crystallography have provided high-resolution insights into their structure-function relationships, aiding drug development.

Other names

VGSCs

Modulation of channel states (closed, open, inactivated) via interaction with the pore or voltage-sensing domains, thereby altering sodium ion flux and cellular excitability.