Molecular Mechanism for H 2 S-Induced Activation of K ATP Channels

Abstract

Hydrogen sulfide (H₂S) is an endogenous opener of K_ATP channels in many different types of cells. However, the molecular mechanism for an interaction between H₂S and K_ATP channel proteins remains unclear. The whole-cell patch-clamp technique and mutagenesis approach were used to examine the effects of H₂S on different K_ATP channel subunits, rvKir6.1 and rvSUR1, heterologously expressed in HEK-293 cells. H₂S stimulated coexpressed rvKir6.1/rvSUR1 K_ATP channels, but had no effect on K_ATP currents generated by rvKir6.1 expression alone. Intracellularly applied sulfhydryl alkylating agent (N-ethylmaleimide, NEM), oxidizing agent (chloramine T, CLT), and a disulfide bond–oxidizing enzyme (protein disulfide isomerase) did not alter H₂S effects on this recombinant channels. CLT, but not NEM, inhibited basal rvKir6.1/rvSUR1 currents, and both abolished the stimulatory effects of H₂S on K_ATP currents, when applied extracellularly. After selective cysteine residues (C6S and C26S but not C1051S and C1057S) in the extracellular loop of rvSUR1 subunits were point-mutated, H₂S lost its stimulatory effects on rvKir6.1/rvSUR1 currents. Our results demonstrate that H₂S interacts with Cys6 and Cys26 residues of the extracellular N terminal of rvSUR1 subunit of K_ATP channel complex. Direct chemical modification of rvSUR1 subunit protein constitutes a molecular mechanism for the activation of K_ATP channels by H₂S. Antioxid. Redox Signal. 12, 1167–1178.