Biophysical Society Conference | Tahoe 2023

Proton Reactions: From Basic Science to Biomedical Applications

Poster Abstracts

16-POS Board 16 MECHANISMS OF LIGAND REGULATION IN HUMAN VOLTAGE-GATED PROTON CHANNEL HHV1 Shuo Han 1 ; Kimberly Tran 1 ; Samuel Jones 1 ; Shizhen Wang 1 ; 1 University of Missouri-Kansas City, School of Science and Engineering, Division of Biological and Biomedical Systems, Kansas City, MO, USA Voltage-gated proton (Hv) channels are standalone voltage sensors without separate pore forming domains in canonical voltage-gated ion channels. They normally function as acid extruders for their unique voltage- and pH-dependent gating. Aside from voltage and pH, Hv channels are also gated by multiple cellular ligands, including Zn 2+ , polyunsaturated arachidonic acid, albumin, and membrane cholesterol, identified in our recent work. Our previous results indicated that the S4 segment is the central gating machinery in hHv1 channels, with activating voltage enriching its opening conformations while inhibitory ligands, including proton, Zn 2+ and cholesterol, stabilize resting state conformations. How is the function of hHv1 channels regulated in cells? Our functional characterizations on purified hHv1 channels and those expressed in cells indicated that polyunsaturated arachidonic acid strongly activates hHv1 channels and even can eliminate inhibition of both Zn 2+ and cholesterol at physiological levels. Our single-molecule Fluorescence Resonance Energy Transfer (smFRET) measurements further indicated that arachidonic acid activates hHv1 channels by promoting ‘pre-opening’ rather than the opening conformations. In many cells, hHv1 channels are closely associated with NADPH oxidases to compensate for charge/pH imbalances, and both were found in cholesterol-rich lipid rafts. Our results proposed that cell cholesterol level perhaps determines the basal activities of hHv1 channels in cells, while releases of arachidonic acid following irritation or injury may serve as an important mechanism to activate hHv1 channels to promote respiration burst of NADPH oxidases.

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