Journal Article

Cryo-EM structures of the DCPIB-inhibited volume-regulated anion channel LRRC8A in lipid nanodiscs

Kern, David M, Brohawn, Stephen G, Oh, SeCheol, Hite, Richard K

2019

Overview

Hypoosmotic conditions activate volume-regulated anion channels in vertebrate cells. These channels are formed by leucine-rich repeat-containing protein 8 (LRRC8) family members and contain LRRC8A in homo- or hetero-hexameric assemblies. Here, we present single-particle cryo-electron microscopy structures of Mus musculus LRRC8A in complex with the inhibitor DCPIB reconstituted in lipid nanodiscs. DCPIB plugs the channel like a cork in a bottle - binding in the extracellular selectivity filter and sterically occluding ion conduction. Constricted and expanded structures reveal coupled dilation of cytoplasmic LRRs and the channel pore, suggesting a mechanism for channel gating by internal stimuli. Conformational and symmetry differences between LRRC8A structures determined in detergent micelles and lipid bilayers related to reorganization of intersubunit lipid binding sites demonstrate a critical role for the membrane in determining channel structure. These results provide insight into LRRC8 gating and inhibition and the role of lipids in the structure of an ionic-strength sensing ion channel.

• Publisher: eLife Sciences Publications Ltd,eLife Sciences Publications, Ltd
• Subject: Animals / Anion channels / Anions - chemistry / Biology / Cell Size / Channel gating / Conduction / cryo-EM / Cryoelectron Microscopy / Cyclopentanes - chemistry / Cytoplasm - chemistry / Electron microscopy / Humans / Indans - chemistry / ion channel / Leucine / Lipid bilayers / Lipid Bilayers - chemistry / Lipids / Lipids - chemistry / LRRC8 / Membrane Proteins - chemistry / Membrane Proteins - ultrastructure / Mice / Nanostructures - chemistry / Neuroscience / Osmolar Concentration / Protein Conformation / Structural Biology and Molecular Biophysics / Symmetry / volume regulation / VRAC