Noxious compounds activate TRPA1 ion channels through covalent modification of cysteines

Abstract

The nervous system senses peripheral damage through nociceptive neurons that transmit a pain signal. TRPA1 is a member of the Transient Receptor Potential (TRP) family of ion channels and is expressed in nociceptive neurons. TRPA1 is activated by a variety of noxious stimuli, including cold temperatures, pungent natural compounds, and environmental irritants. How such diverse stimuli activate TRPA1 is not known. We observed that most compounds known to activate TRPA1 are able to covalently bind cysteine residues. Here we use click chemistry to show that derivatives of two such compounds, mustard oil and cinnamaldehyde, covalently bind mouse TRPA1. Structurally unrelated cysteine-modifying agents such as iodoacetamide (IA) and (2-aminoethyl)methanethiosulphonate (MTSEA) also bind and activate TRPA1. We identified by mass spectrometry fourteen cytosolic TRPA1 cysteines labelled by IA, three of which are required for normal channel function. In excised patches, reactive compounds activated TRPA1 currents that were maintained at least 10 min after washout of the compound in calcium-free solutions. Finally, activation of TRPA1 by disulphide-bond-forming MTSEA is blocked by the reducing agent dithiothreitol (DTT). Collectively, our data indicate that covalent modification of reactive cysteines within TRPA1 can cause channel activation, rapidly signalling potential tissue damage through the pain pathway.

TRPA1 channel activation induces cholecystokinin release via extracellular calcium

“…AITC present in mustard oils as well as in wasabi (a japanese horseradish), is a membrane permeable electrophilic compound which activates TRPA1 [20,21]. Stimulation of STC-1 cells with AITC lead to a robust increase in intracellular calcium levels and stimulation of CCK release.…”

Inhaled ethanol potentiates the cough response to capsaicin in patients with airway sensory hyperreactivity

“…Hopefully, specific TRPV1 antagonists could be useful in treating disorders such as pain, chronic cough, and irritable bowl syndrome [31]. Also the ion channel TRPA1 (Transient receptor potential channel ankyrin subunit 1) is activated by a variety of noxious stimuli, including cold temperatures, pungent natural compounds, and environmental irritants [32]. Many "sensory compounds" presumed to be specific have a promiscuous relationship with different TRP channels [33].…”

Exploiting Quorum Sensing To Confuse Bacterial Pathogens

“…The proposed mechanism of action for cinnamaldehyde is disruption of protein-DNA interactions of the QS-responsive master regulatory protein, LuxR (not to be confused with LuxR-type AHL receptors), with targeted promoter sequences. SAR studies found that cinnamaldehyde analogues disrupted, modestly, LuxR's interaction with the LuxR consensus binding sequence (281); however, mechanisms explaining these effects have not been clear, and the knowledge that cinnamaldehyde is able to covalently modify cysteine residues of various proteins (285) leaves open the possibility that other targets are at play. The decreased toxicity of food and herbal extracts compared with other better-studied but cytotoxic QS inhibitors offers a practical rationale to mine natural dietary substances for novel QSI compounds.…”