Noxious compounds activate TRPA1 ion channels through covalent modification of cysteines

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Nociceptive neurons detect peripheral damage, transmitting pain signals via the nervous system.
• TRPA1 (Transient Receptor Potential channel A1) is expressed in nociceptive neurons and activated by diverse noxious stimuli like cold and irritants.
• The precise mechanism of TRPA1 activation by various stimuli remains largely unknown.

Purpose of the Study:

• To investigate the role of covalent modification of cysteine residues in TRPA1 channel activation.
• To elucidate how diverse stimuli activate TRPA1 channels.

Main Methods:

• Utilized click chemistry to demonstrate covalent binding of mustard oil and cinnamaldehyde derivatives to mouse TRPA1.
• Employed cysteine-modifying agents like iodoacetamide (IA) and (2-aminoethyl)methanethiosulphonate (MTSEA) to probe TRPA1 activation.
• Identified specific TRPA1 cysteine residues involved in channel function using mass spectrometry.
• Performed electrophysiological recordings in excised patches to assess TRPA1 currents and the effect of reactive compounds, washout, and reducing agents (DTT).

Main Results:

• Mustard oil and cinnamaldehyde derivatives covalently bind to mouse TRPA1.
• Structurally unrelated agents IA and MTSEA also bind and activate TRPA1.
• Mass spectrometry identified fourteen cytosolic TRPA1 cysteines modified by IA, with three crucial for normal function.
• Reactive compounds induced TRPA1 currents maintained after washout; MTSEA-induced activation was blocked by DTT.

Conclusions:

• Covalent modification of reactive cysteines in TRPA1 is a key mechanism for channel activation.
• This covalent modification rapidly signals potential tissue damage through the pain pathway.
• Understanding TRPA1's cysteine reactivity provides insights into pain signaling and potential therapeutic targets.