Cell 178, 1362–1374 (2019)

Most known agonists of the TRPA1 ion channel are reactive electrophiles that covalently modify cysteine residues in a cytoplasmic domain of the channel called the allosteric nexus. Although some non-covalent TRPA1 agonists have been identified, these are typically of low potency and specificity, limiting their use for analgesic drug development. To identify new TRPA1 agonists, Lin King et al. screened a collection of arachnid venoms and identified a scorpion disulfide-linked peptide toxin, WaTx (wasabi receptor toxin), as exhibiting potent and selective activity with TRPA1 in cells but lacking electrophilic character. Patch-clamp and FRET assays indicated that WaTx crosses membranes to access the cytoplasmic side of the TRPA1 channel, likely enabled by a basic patch at one end of the peptide’s helical structure. Surprisingly, a series of mutagenesis and protein-interaction experiments localized the WaTx-binding site to the same allosteric nexus targeted by electrophilic agonists. However, channel activation kinetics and permeability differ upon binding of WaTx versus electrophilic agonists, suggesting that they operate through distinct mechanisms of action. The discovery of a potent non-electrophilic TRPA1 agonist could provide a route to further understanding and treatment of pain.