Bandarupalli, R. | Search bioRxiv

bioRxiv2026

PUFA modulation of ASIC3 involves both specific and lipid solvent-like interactions

AbstractInflammatory mediators including polyunsaturated fatty acids (PUFAs) potentiate ASIC3 by altering channel gating, yet the molecular basis for their interactions remains poorly defined. Using all-atom MD simulations and electrophysiology, we show that DHA accumulates around ASIC3 through interactions with a membrane-facing electropositive region along the outer leaflet of TM1. In the open state, a more buried binding site for the lipid is exposed that allows the carboxylate head group to bind a critical arginine along with nearby polar residues. Mutation of this site prevents the slowing of channel desensitization but only reduces the effect PUFAs have on the pH dependence of activation. The same mutations do not prevent regulation by other lipid classes like N-acyl amino acids or lysophosphatidyl choline. Our results provide the first detailed description of a PUFA binding site on ASICs, offering new insights into lipid modulation and potential strategies for developing novel treatments for inflammatory pain.

biophysics↗

bioRxiv2024

Molecular Insights into Single Chain Lipid Modulation of Acid-Sensing Ion Channel 3

Polyunsaturated fatty acids (PUFAs) and their analogs play a significant role in modulating the activity of diverse ion channels, and recent studies show that these lipids potentiate acid-sensing ion channels (ASICs), leading to increased activity. The potentiation of the channel stems from multiple gating changes, but the exact mechanism of these effects remains uncertain. We posit a mechanistic explanation for one of these changes in channel function, the increase in the maximal current, by applying a combination of electrophysiology and all-atom molecular dynamics simulations on the open-state hASIC3. Microsecond-scale simulations were performed on open-state hASIC3 in the absence and presence of a PUFA, docosahexaenoic acid (DHA), and a PUFA analog, N-arachidonyl glycine (AG). Intriguingly, our simulations in the absence of PUFA or PUFA analogs reveal that a tail from the membrane phospholipid POPC inserts itself into the pore of the channel through lateral fenestrations on the sides of the transmembrane segments, obstructing ion permeation through the channel. The binding of either DHA or AG prevented POPC from accessing the pore in our simulations, relieving the block of ionic conduction by phospholipids. Finally, we use the single-channel recording to show that DHA increases the amplitude of the single-channel currents in ASIC3, which is consistent with our hypothesis that PUFAs relieve the pore block of the channel induced by POPCs. Together, these findings offer a potential mechanistic explanation of how PUFAs modulate ASIC maximal current, revealing a novel mechanism of action for PUFA-induced modulation of ion channels.

biophysics↗