Molecular principles of assembly, activation, and inhibition in epithelial sodium channel
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
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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