Dynamic conformational changes of acid-sensing ion channels in different desensitizing conditions

Area of Science:

• Neuroscience
• Molecular Biology
• Biophysics

Background:

• Acid-sensing ion channels (ASICs) are crucial for neuronal functions like synaptic transmission and pain sensing.
• ASIC1a exhibits multiple desensitization mechanisms (acute, steady-state, tachyphylaxis) that regulate channel activity.
• Understanding the dynamic conformational changes underlying ASIC1a desensitization is essential but remains incomplete.

Purpose of the Study:

• To investigate the dynamic conformational changes in ASIC1a during different desensitization states.
• To elucidate the role of the β11-12 linker and the N414K mutation in ASIC1a desensitization.

Main Methods:

• Electrophysiology and voltage-clamp fluorometry were employed to monitor functional and conformational changes.
• Cysteine-labeled fluorophores were used to track conformational shifts in the extracellular and transmembrane domains.
• Site-directed mutagenesis (N414K) was introduced to study its impact on ASIC1a function.

Main Results:

• The N414K mutation in ASIC1a impaired acute desensitization and significantly affected steady-state desensitization and tachyphylaxis.
• While the mutant's extracellular domain retained pH sensitivity and conformational changes, these did not always correlate with desensitization.
• The N414K mutation reduced, but did not abolish, desensitization, as evidenced by preserved sensitivity to a known peptide modulator.

Conclusions:

• The N414K mutation highlights the intricate relationship between extracellular domain conformational changes and pore function in ASIC1a desensitization.
• This study provides critical insights into the molecular mechanisms governing ASIC1a channel gating and modulation.
• The findings advance the fundamental understanding of ASIC1a's role in physiological and pathological processes.