Aminosulfonate modulated pH-induced conformational changes in connexin26 hemichannels

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• Gap junction channels are crucial for intercellular communication, mediating the passage of ions and molecules.
• Acidification is known to close gap junction channels, but the precise molecular mechanism remains unclear.
• Previous studies suggest aminosulfonates directly inhibit connexin channel activity.

Purpose of the Study:

• To investigate the direct effect of acidification on connexin26 gap junction channels.
• To elucidate the mechanism by which pH influences connexin channel gating.

Main Methods:

• High-resolution atomic force microscopy (AFM) was used to analyze force-dissected connexin26 gap junctions.
• Experiments were conducted in HEPES buffer and compared with non-aminosulfonate buffers at varying pH levels.

Main Results:

• Connexin26 gap junction channels closed at pH < 6.5 and reopened reversibly at pH 7.6 in HEPES buffer.
• This pH-dependent closure was not observed in non-aminosulfonate buffers, indicating a role for the buffer composition.
• AFM revealed a gradual increase in pore diameter with increasing pH, without changes in outer connexon diameter or significant lobe rotation.

Conclusions:

• Acidification directly inhibits connexin26 gap junction channel activity in an isoform-specific manner.
• The mechanism involves direct interaction with the connexin protein, distinct from Ca2+-induced closure.
• HEPES buffer facilitates pH-dependent channel gating through protonated aminosulfonates.