Gating and anion selectivity are reciprocally regulated in TMEM16A (ANO1)

Numerous essential physiological processes depend on the TMEM16A-mediated Ca2+-activated chloride fluxes. Extensive structure-function studies have helped to elucidate the Ca2+ gating mechanism of TMEM16A, revealing a Ca2+-sensing element close to the anion pore that alters conduction. However, subs...

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Bibliographic Details
Published in:	The Journal of general physiology Vol. 154; no. 8; p. 1
Main Authors:	De Jesús-Pérez, José J, López-Romero, Ana E, Posadas, Odalys, Segura-Covarrubias, Guadalupe, Aréchiga-Figueroa, Iván, Gutiérrez-Medina, Braulio, Pérez-Cornejo, Patricia, Arreola, Jorge
Format:	Journal Article
Language:	English
Published:	United States Rockefeller University Press 01-08-2022
Subjects:	Animals Anions Anions - metabolism Anoctamin-1 - genetics Binding sites Biophysics Calcium - metabolism Calcium channels (voltage-gated) Calcium chloride Calcium-binding protein Cellular Physiology Channel gating Chloride Channels - chemistry Chloride Channels - genetics Communication HEK293 Cells Humans Hydrophobicity Ion Channel Gating Ions Membrane Transport Mice Neoplasm Proteins - metabolism Permeability Site-directed mutagenesis Structure-function relationships
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Summary:	Numerous essential physiological processes depend on the TMEM16A-mediated Ca2+-activated chloride fluxes. Extensive structure-function studies have helped to elucidate the Ca2+ gating mechanism of TMEM16A, revealing a Ca2+-sensing element close to the anion pore that alters conduction. However, substrate selection and the substrate-gating relationship in TMEM16A remain less explored. Here, we study the gating-permeant anion relationship on mouse TMEM16A expressed in HEK 293 cells using electrophysiological recordings coupled with site-directed mutagenesis. We show that the apparent Ca2+ sensitivity of TMEM16A increased with highly permeant anions and SCN- mole fractions, likely by stabilizing bound Ca2+. Conversely, mutations at crucial gating elements, including the Ca2+-binding site 1, the transmembrane helix 6 (TM6), and the hydrophobic gate, impaired the anion permeability and selectivity of TMEM16A. Finally, we found that, unlike anion-selective wild-type channels, the voltage dependence of unselective TMEM16A mutant channels was less sensitive to SCN-. Therefore, our work identifies structural determinants of selectivity at the Ca2+ site, TM6, and hydrophobic gate and reveals a reciprocal regulation of gating and selectivity. We suggest that this regulation is essential to set ionic selectivity and the Ca2+ and voltage sensitivities in TMEM16A.
Bibliography:	J.J. De Jesús-Pérez’s current address is Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA. G. Segura-Covarrubias’s current address is Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH.
ISSN:	0022-1295 1540-7748
DOI:	10.1085/jgp.202113027