Depletion of membrane cholesterol modifies structure, dynamic and activation of Na1.7.

Cholesterol is a major component of plasma membranes and plays a significant role in actively regulating the functioning of several membrane proteins in humans. In this study, we focus on the role of cholesterol depletion on the voltage-gated sodium channel Na1.7, which is primarily expressed in the peripheral sensory neurons and linked to various chronic inherited pain syndromes. Coarse-grained molecular dynamics simulations revealed key dynamic changes of Na1.7 upon membrane cholesterol depletion: A loss of rigidity in the structural motifs linked to activation and fast-inactivation is observed, suggesting an easier transition of the channel between different gating states. In-vitro whole-cell patch clamp experiments on HEK293t cells expressing Na1.7 validated these predictions at the functional level: Hyperpolarizing shifts in the voltage-dependence of activation and fast-inactivation were observed along with an acceleration of the time to peak and onset kinetics of fast inactivation. These results underline the critical role of membrane composition, and of cholesterol in particular, in influencing Na1.7 gating characteristics. Furthermore, our results also point to cholesterol-driven changes of the geometry of drug-binding regions, hinting to a key role of the membrane environment in the regulation of drug effects.