Proton block of proton-activated TRPV1 current

Area of Science:

• Neuroscience
• Molecular Biology
• Physiology

Background:

• The TRPV1 cation channel is a key sensor for heat, capsaicin, and pH.
• In physiological conditions, H+ ions activate TRPV1, mediating pain and vasodilation.
• A significant increase in TRPV1 current is observed upon H+ removal, a phenomenon not fully explained by current models.

Purpose of the Study:

• To elucidate the mechanism behind the paradoxical increase in TRPV1 current upon H+ removal.
• To investigate how H+ ions modulate TRPV1 channel activity beyond simple activation.
• To understand the implications of these complex H+ interactions on nociceptive signaling.

Main Methods:

• Electrophysiological recordings of TRPV1 channel currents.
• Site-directed mutagenesis of acidic residues in the ion selectivity filter.
• Voltage-dependence and ion-dependence studies of H+ inhibition.

Main Results:

• H+ ions inhibit TRPV1 currents by interfering with ion permeation, not just gating.
• The inhibition is voltage and permeant ion dependent.
• Mutations in acidic residues partially rescue the inhibition, indicating their role in the permeation block.

Conclusions:

• The prominent "OFF" response of TRPV1 is due to rapid recovery from H+ permeation inhibition.
• Complex interplay between H+-mediated gating and permeation effects shapes TRPV1 channel behavior.
• These findings have significant implications for understanding nociception and TRPV1-related conditions.