Functional and Structural Divergence in Human TRPV1 Channel Subunits by Oxidative Cysteine Modification

Area of Science:

• Ion channel biophysics
• Molecular neuroscience
• Redox signaling

Background:

• Transient Receptor Potential Vanilloid 1 (TRPV1) channels are key sensors of noxious stimuli and inflammatory mediators.
• Cysteine oxidation is implicated in TRPV1's response to oxidative stress, but the precise mechanism is unclear.

Purpose of the Study:

• To elucidate the biochemical basis of cysteine oxidation in TRPV1 channel activation.
• To characterize the role of cysteine residues in TRPV1 redox sensing and channel stability.

Main Methods:

• Non-reducing SDS-PAGE to detect disulfide bonds.
• Electrophysiology to assess channel function.
• Mass spectrometry to identify oxidized cysteine residues in human TRPV1 (hTRPV1).

Main Results:

• Identified a stable intersubunit disulfide bond between Cys-258 and Cys-742 in hTRPV1, forming dimers.
• Mutants lacking this bond (C258S, C742S) exhibited reduced protein half-life.
• The C258S mutant showed abolished response to oxidants, and Cys-258 was highly sensitive to hydrogen peroxide.
• Mass spectrometry revealed heterogeneous modification of Cys-258 residues, with some free thiols and others involved in disulfide bonds.

Conclusions:

• The intersubunit disulfide bond involving Cys-258 and Cys-742 is critical for hTRPV1 stability and dimerization.
• Cys-258 plays a dual role: sensing oxidation via its free thiol and contributing to dimerization via disulfide bond formation.
• hTRPV1 exhibits heterogeneous subunit composition regarding redox status and function, influencing its overall activity.