Oleic acid blocks the calcium-activated chloride channel TMEM16A/ANO1

• Published in: Biochimica et biophysica acta. Molecular and cell biology of lipids Vol. 1867; no. 5; p. 159134
• Main Authors: Leon-Aparicio, Daniel, Sánchez-Solano, Alfredo, Arreola, Jorge, Perez-Cornejo, Patricia
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2022
• Subjects: HEK293 cells; Methyl-oleate; Oleic acid; Patch-clamp; TMEM16A; Methyl-oleate; TMEM16A; HEK293 cells; Patch-clamp; Oleic acid
• ISSN: 1388-1981; 1879-2618
• DOI: 10.1016/j.bbalip.2022.159134

The calcium-activated chloride channel TMEM16A (ANO1) supports the passive movement of chloride ions across membranes and controls critical cell functions. Here we study the block of wild-type and mutant TMEM16A channels expressed in HEK293 cells by oleic acid, a monounsaturated omega-9 fatty acid beneficial for cardiovascular health. We found that oleic acid irreversibly blocks TMEM16A in a dose- and voltage-dependent manner at low intracellular Ca2+. We tested whether oleic acid interacted with the TMEM16A pore, varying the permeant anion concentration and mutating pore residues. Lowering the permeating anion concentration in the intracellular side did nothing but the blockade was intensified by increasing the anion concentration in the extracellular side. However, the blockade of the pore mutants E633A and I641A was voltage-independent, and the I641A IC50, a mutant with the inner hydrophobic gate in disarray, increased 16-fold. Furthermore, the uncharged methyl-oleate blocked 20–24% of the wild-type and I641A channels regardless of voltage. Our findings suggest that oleic acid inhibits TMEM16A by an allosteric mechanism after the electric field drives oleic acid's charged moiety inside the pore. Block of TMEM16A might be why oleic acid has a beneficial impact on the cardiovascular system. •Oleic acid blocks the TMEM16A/ANO1 channel in a dose and voltage-dependent manner.•The block became voltage-independent after mutating pore residues E633 and I641.•The block becomes voltage-independent at high intracellular Ca2+ concentration.•Half-maximal inhibition was 0.66 and 10.4 μM for WT and I641A channels.•Oleic acid behaves as an allosteric blocker that can plug the pore.