Identification of PUFA interaction site on ASIC3 suggests a complex regulatory mechanism

Abstract

Inflammatory 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 eliminates the DHA-mediated slowing of channel desensitization and also modestly reduces the effect PUFAs have on the proton sensitivity of channel 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.