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

Elife. 2019 Feb 18;8:e42636. doi: 10.7554/eLife.42636.

Abstract

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.

Keywords: LRRC8; VRAC; cryo-EM; ion channel; molecular biophysics; mouse; neuroscience; structural biology; volume regulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anions / chemistry
  • Cell Size
  • Cryoelectron Microscopy
  • Cyclopentanes / chemistry
  • Cytoplasm / chemistry
  • Humans
  • Indans / chemistry
  • Lipid Bilayers / chemistry
  • Lipids / chemistry*
  • Membrane Proteins / chemistry
  • Membrane Proteins / ultrastructure*
  • Mice
  • Nanostructures / chemistry
  • Osmolar Concentration
  • Protein Conformation*

Substances

  • 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-one-5-yl)oxybutyric acid
  • Anions
  • Cyclopentanes
  • Indans
  • LRRC8A protein, mouse
  • Lipid Bilayers
  • Lipids
  • Membrane Proteins