Nitric oxide activates TRP channels by cysteine S-nitrosylation

Abstract

Intracellular Ca²⁺ concentration elevation is essential for activation of Ca²⁺-dependent NO synthases (NOSs). However, molecular components eliciting this mechanism remain unclear. Here, we report a novel activation mechanism mediated by cysteine S-nitrosylation in transient receptor potential (TRP) channels. Recombinant TRPC5 and TRPV1, which are commonly classified as receptor-activated channel and thermosensor channel respectively, induce entry of Ca²⁺ into cells in response to nitric oxide (NO). Labeling and functional assays using cysteine mutants, together with membrane sidedness in activating reactive disulfides, show that cytoplasmically accessible Cys553 and nearby Cys558 are nitrosylation sites mediating NO sensitivity in TRPC5. The responsive TRP proteins have conserved cysteines on the same N-terminal side of the pore region. Notably, nitrosylation of native TRPC5 upon G protein-coupled ATP receptor stimulation elicits entry of Ca²⁺ into endothelial cells. These findings suggest that native TRPC5 is essential for Ca²⁺ influx activated by NO via eNOS upon receptor stimulation in endothelial cells. Forthermore, the group of native S-nitrosylation-sensitive TRP channels mediates a ubiquitous mechanism that is critical for feedback regulation of Ca²⁺ signals by NO. [J Physiol Sci. 2007;57 Suppl:S224]