TY - JOUR T1 - Benzoquinone Reveals a Cysteine-dependent Desensitization Mechanism of TRPA1. JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.112.084194 SP - mol.112.084194 AU - Yessenia Ibarra AU - Nathaniel T Blair Y1 - 2013/01/01 UR - http://molpharm.aspetjournals.org/content/early/2013/03/11/mol.112.084194.abstract N2 - The transient receptor potential ankyrin 1 (TRPA1) non-selective cation channel has a conserved function as a noxious chemical sensor throughout much of Metazoa. Electrophilic chemicals activate both insect and vertebrate TRPA1 via covalent modification of cysteine residues in the amino terminal region. Although naturally occurring electrophilic plant compounds, such as mustard oil and cinnamaldehyde, are TRPA1 agonists, it is unknown whether arthropod-produced electrophiles activate mammalian TRPA1. We characterized the effects of the electrophilic arthropod defensive compound, para-benzoquinone (pBQN), on the human TRPA1 channel. We used whole-cell recordings of HEK cells heterologously expressing either wild-type TRPA1 or TRPA1 with three serine substituted cysteines crucial for electrophile activation (C621S, C641S, C665S). We found that pBQN activates TRPA1 starting at 10 nM and peaking at 300 nM; higher concentrations caused rapid activation followed by a fast decline. Activation by pBQN required reactivity with cysteine residues, but ones that are distinct from those previously reported to be the key targets of electrophiles. The current reduction we found at higher pBQN concentrations was a cysteine-dependent desensitization of TRPA1, and did not require prior activation. The cysteines required for desensitization are not accessible to all electrophiles as iodoacetamide and internally applied MTSET failed to cause desensitization (despite large activation). Interestingly, following pBQN desensitization, wild-type TRPA1 had dramatically reduced response to the non-electrophile agonist carvacrol, whereas the triple cysteine mutant TRPA1 retained its full response. Our results suggest that modification of multiple cysteine residues by electrophilic compounds can generate both activation and desensitization of the TRPA1 channel. ER -