Atomic Force Microscopy Reveals the Architecture of the Epithelial Sodium Channel (ENaC)

作者：Stewart Andrew P; Haerteis Silke; Diakov Alexei; Korbmacher Christoph; Edwardson J Michael^*

来源：Journal of Biological Chemistry, 2011, 286(37): 31944-31952.

DOI：10.1074/jbc.M111.275289

The epithelial sodium channel (ENaC) is a member of the ENaC/degenerin superfamily. ENaC is a heteromultimer containing three homologous subunits (alpha, beta, and gamma); 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 alpha-, beta- and gamma-subunits. We show that for alpha-, beta- and gamma-ENaC alone, pairs of antibodies decorate the channel at an angle of 120 degrees, indicating that the individual subunits assemble as homotrimers. A similar approach demonstrates that alpha beta gamma-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.

• 出版日期2011-9-16