Structural basis of pH-dependent activation in a CLC transporter

Area of Science:

• Structural biology
• Molecular biophysics
• Ion channel function

Background:

• Chloride channels (CLCs) are dimeric transporters regulating vital cellular processes.
• Common gating controls CLC activity, with mutations causing dominant genetic disorders.
• The structural basis of common gating remains largely unknown.

Purpose of the Study:

• To elucidate the structural rearrangements underlying common gating in CLC channels.
• To investigate the mechanism of pH-dependent activation in CLC-ec1.
• To correlate structural findings with disease-causing mutations in human CLCs.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) of CLC-ec1.
• Analysis of structural rearrangements under activating conditions.
• Mutational analysis of CLC-ec1 and human CLC-7.

Main Results:

• Identified large-scale structural rearrangements in CLC-ec1 upon activation.
• Demonstrated pH-dependent remodeling of the dimer interface, facilitating H+ transport.
• Observed that water wire formation in the H+ pathway precedes Cl- pore opening.
• Showed disease-associated mutations enhance CLC-ec1 activation and CLC-7 common gate opening.

Conclusions:

• The pH activation mechanism of CLC-ec1 involves concerted opening of intracellular H+ pathways via dimer interface remodeling.
• Structural insights into CLC-ec1 activation provide a framework for understanding common gating in human CLCs.
• The findings link structural dynamics to ion transport and disease mechanisms in CLC channels.