The propofol binding sites of prokaryotic voltage-gated sodium channels

Abstract

Propofol, one of the most commonly used intravenous general anesthetics, modulates neuronal function by interacting with ion channels. The mechanisms that link propofol binding to the modulation of distinct ion channel states, however, are not understood. To tackle this problem, we investigated prokaryotic ancestors of eukaryotic voltage-gated Na+ channels (Navs) using unbiased photoaffinity labeling with a photoacitivatable propofol analog (AziPm), electrophysiological methods and mutagenesis. The results directly demonstrate conserved propofol binding sites involving the S4 voltage sensors and the S4-S5 linkers in NaChBac and NavMs, and also suggest state-dependent changes at these sites. Then, using molecular dynamics simulations to elucidate the structural basis of propofol modulation, we show that the S4 voltage sensors and the S4-S5 linkers shape two distinct propofol binding sites in a conformation-dependent manner. These interactions help explain how propofol binding promotes activation-coupled inactivation to inhibit Nav channel function.

Propofol directly binds and inhibits skeletal muscle ryanodine receptor 1 (RyR1)

“…Propofol inhibition of channels with TMDs similar to that of the RyR1 is not a unique phenomenon (29)(30)(31)(32)(33)(34). Moreover, binding in or around the conserved S4-5 linker domain appears to be a canonical feature in ion channels such as NaChBac, NavMs, and Kv1.2 (35)(36)(37)(38). Given the existence of multiple propofol binding sites distributed among different domains in this very large protein, we hypothesize that an allosteric mechanism at least partly underlies its effects, although this is conjectural.…”