A persulfidation-based mechanism controls aquaporin-8 conductance

Area of Science:

• Cellular Biology
• Biochemistry
• Molecular Physiology

Background:

• Tyrosine kinase receptor engagement activates NADPH-oxidases, releasing extracellular hydrogen peroxide (H2O2).
• Aquaporin-8 (AQP8) facilitates H2O2 transport across the plasma membrane, with gating modulating signal strength during cellular stress.
• Previous work established AQP8's role in H2O2 transport and its reversible gating.

Purpose of the Study:

• To elucidate the molecular mechanism underlying AQP8 gating.
• To identify the specific modification and regulatory molecules involved in AQP8 channel activity.
• To understand how H2O2 transport is modulated under cellular stress conditions.

Main Methods:

• Investigated AQP8 gating using molecular modeling and biochemical assays.
• Examined the role of cysteine 53 (C53) persulfidation in AQP8 channel function.
• Utilized gene silencing (siRNA) of cystathionine β-synthase (CBS) to assess its contribution to H2S production and AQP8 gating.

Main Results:

• Demonstrated that persulfidation of cysteine 53 (C53) mediates AQP8 gating.
• Showed that hydrogen sulfide (H2S) treatment blocks H2O2 entry via AQP8 in unstressed cells.
• Found that silencing CBS prevents AQP8 closure, identifying CBS as the primary source of H2S regulating AQP8.
• Molecular modeling revealed C53 persulfidation displaces a histidine residue in the channel's pore.

Conclusions:

• Proposed a mechanism where H2O2 transport through AQP8 leads to C53 sulfenylation, making it susceptible to H2S.
• H2S, produced by CBS, mediates AQP8 gating by persulfidating C53, thus tuning H2O2 transport.
• This regulatory pathway controls H2O2 signaling and potentially limits oxidative stress.