Abstract
Understanding of the mechanisms of modulation of voltage-gated Na
+
(Na
V
) channels by general anesthetic agents such as sevoflurane is critical to interpret their role in general anesthesia. By using the bacterial Na
V
channel analogue NaChBac plus a combination of computational and electrophysiological analyses, this work strongly suggests a multisite mechanism of sevoflurane action on Na
V
channels. Furthermore, computer simulations suggest specific putative anesthetic sites worthy of further investigation.
Halogenated inhaled general anesthetic agents modulate voltage-gated ion channels, but the underlying molecular mechanisms are not understood. Many general anesthetic agents regulate voltage-gated Na
+
(Na
V
) channels, including the commonly used drug sevoflurane. Here, we investigated the putative binding sites and molecular mechanisms of sevoflurane action on the bacterial Na
V
channel NaChBac by using a combination of molecular dynamics simulation, electrophysiology, and kinetic analysis. Structural modeling revealed multiple sevoflurane interaction sites possibly associated with NaChBac modulation. Electrophysiologically, sevoflurane favors activation and inactivation at low concentrations (0.2 mM), and additionally accelerates current decay at high concentrations (2 mM). Explaining these observations, kinetic modeling suggests concurrent destabilization of closed states and low-affinity open channel block. We propose that the multiple effects of sevoflurane on NaChBac result from simultaneous interactions at multiple sites with distinct affinities. This multiple-site, multiple-mode hypothesis offers a framework to study the structural basis of general anesthetic action.