Two Vanilloid Ligand Bindings Per Channel Are Required to Transduce Capsaicin-Activating Stimuli

Abstract

The tetrameric capsaicin receptor transient receptor potential vanilloid 1 (TRPV1) in mammals has evolved the capability to integrate pain signal arising from harmful temperature and chemical irritants. The four repetitions of TRPV1 subunits result in an ion channel with excellent pain sensitivity, allowing this ionotropic receptor to differentiate graded injuries. We manipulated the stoichiometry and relative steric coordination of capsaicin-bound structures at the molecular level to determine the rules by which the receptor codes pain across a broad range of intensities. By introducing capsaicin-insensitive S512F mutant subunits into the TRPV1 channel, we found that binding of the first ligand results in low but clear channel activation. Maximal agonist-induced activation is already apparent in tetramers harboring two or three wild-type TRPV1 subunits, which display comparable activity to wild-type tetramer. The non-vanilloid agonist 2-aminoethoxydiphenyl borate (2-APB) differs from that of capsaicin in the TRPV1 channel opening mechanism activating all S512F-mutated TRPV1 channels. Two or more wild-type TRPV1 subunits are also required for full anandamide-induced channel activation, a cannabinoid that shares overlapping bindingpocket to capsaicin. Our results demonstrate that the stoichiometry of TRPV1 activation is conserved for two types of agonists.

TRPV1: Structure, Endogenous Agonists, and Mechanisms

“…More recently, details on the stoichiometry of TRPV1 activation by capsaicin were provided by Liu and collaborators [45]. These authors used microfluorometry to measure intracellular Ca 2+ increases in HEK293 cells that expressed linked tetrameric TRPV1 receptors with different subunit compositions that contained the capsaicin-insensitive S512F mutant and/or wild-type subunits.…”

“…These authors used microfluorometry to measure intracellular Ca 2+ increases in HEK293 cells that expressed linked tetrameric TRPV1 receptors with different subunit compositions that contained the capsaicin-insensitive S512F mutant and/or wild-type subunits. The authors covalently linked the subunits in order to produce all possible tetrameric compositions containing one single wild-type repeat and observed that the mutant channels could be partially opened by capsaicin and that the binding of two vanilloid molecules (i.e., two wild-type and two mutant subunits) is required in order to fully transduce capsaicin-dependent stimuli [45].…”

The Effect of the Trpv1 Agonist, Capsaicin, on the Developing Rat Brain: A Mini Review

“…However, the multifunctional nature of the TRPV1 channel also poses considerable challenges for targeted drug design. Recent studies on the molecular mechanism of activation of the TRPV1 channel by capsaicin 54,55 may provide clues for new approaches to drug design.…”