1. Academic Validation
  2. Atomic force microscopy reveals the architecture of the epithelial sodium channel (ENaC)

Atomic force microscopy reveals the architecture of the epithelial sodium channel (ENaC)

  • J Biol Chem. 2011 Sep 16;286(37):31944-52. doi: 10.1074/jbc.M111.275289.
Andrew P Stewart 1 Silke Haerteis Alexei Diakov Christoph Korbmacher J Michael Edwardson
Affiliations

Affiliation

  • 1 Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
Abstract

The epithelial Sodium Channel (ENaC) is a member of the ENaC/degenerin superfamily. ENaC is a heteromultimer containing three homologous subunits (α, β, and γ); however, the subunit stoichiometry is still controversial. Here, we addressed this issue using atomic force microscopy imaging of complexes between isolated ENaC and Antibodies/Fab fragments directed against specific epitope tags on the α-, β- and γ-subunits. We show that for α-, β- and γ-ENaC alone, pairs of Antibodies decorate the channel at an angle of 120°, indicating that the individual subunits assemble as homotrimers. A similar approach demonstrates that αβγ-ENaC assembles as a heterotrimer containing one copy of each subunit. Intriguingly, all four subunit combinations also produce higher-order structures containing two or three individual trimers. The trimer-of-trimers organization would account for earlier reports that ENaC contains eight to nine subunits.

Figures