1. Structural Biology and Molecular Biophysics
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Molecular principles of assembly, activation, and inhibition in epithelial sodium channel

  1. Sigrid Noreng
  2. Richard Posert
  3. Arpita Bharadwaj
  4. Alexandra Houser
  5. Isabelle Baconguis  Is a corresponding author
  1. Oregon Health and Science University, United States
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Cite this article as: eLife 2020;9:e59038 doi: 10.7554/eLife.59038

Abstract

The molecular bases of heteromeric assembly and link between Na+ self-inhibition and protease-sensitivity in epithelial sodium channels (ENaCs) are not fully understood. Previously, we demonstrated that ENaC subunits – α, β, and γ – assemble in a counterclockwise configuration when viewed from outside the cell with the protease-sensitive GRIP domains in the periphery (Noreng et al., 2018). Here we describe the structure of ENaC resolved by cryo-electron microscopy at 3 Å. We find that a combination of precise domain arrangement and complementary hydrogen bonding network defines the subunit arrangement. Furthermore, we determined that the α subunit has a primary functional module consisting of the finger and GRIP domains. The module is bifurcated by the α2 helix dividing two distinct regulatory sites: Na+ and the inhibitory peptide. Removal of the inhibitory peptide perturbs the Na+ site via the α2 helix highlighting the critical role of the α2 helix in regulating ENaC function.

Data availability

All cryo-EM maps have been deposited in the Electron Microscopy Data Bank under the accession code EMD-21896 for ENaC. Model coordinates have been deposited in the Protein Data Bank under the accession code 6WTH.

The following data sets were generated

Article and author information

Author details

  1. Sigrid Noreng

    Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5767-1399
  2. Richard Posert

    Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9010-2104
  3. Arpita Bharadwaj

    Vollum Institute, Oregon Health and Science University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3867-7610
  4. Alexandra Houser

    Neuroscience Graduate Program, Oregon Health and Science University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Isabelle Baconguis

    Vollum Institute, Oregon Health and Science University, Portland, United States
    For correspondence
    bacongui@ohsu.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-5440-2289

Funding

National Institutes of Health (DP5OD017871)

  • Isabelle Baconguis

American Heart Association (19TPA34760754)

  • Isabelle Baconguis

American Heart Association (18PRE33990205)

  • Sigrid Noreng

National Science Foundation (DGE-1937961)

  • Alexandra Houser

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Sriram Subramaniam, University of British Columbia, Canada

Publication history

  1. Received: May 26, 2020
  2. Accepted: July 29, 2020
  3. Accepted Manuscript published: July 30, 2020 (version 1)
  4. Version of Record published: August 7, 2020 (version 2)

Copyright

© 2020, Noreng et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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