Molecular principles of assembly, activation, and inhibition in epithelial sodium channel
- Oregon Health and Science University, United States
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.
Article and author information
Author details
Isabelle Baconguis
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.
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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Molecular principles of assembly, activation, and inhibition in epithelial sodium channel
eLife 9:e59038.
https://doi.org/10.7554/eLife.59038
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