Shear force sensing of epithelial Na+ channel (ENaC) relies on N-glycosylated asparagines in the palm and knuckle domains of αENaC

Proc Natl Acad Sci U S A. 2020 Jan 7;117(1):717-726. doi: 10.1073/pnas.1911243117. Epub 2019 Dec 23.

Abstract

Mechanosensitive ion channels are crucial for normal cell function and facilitate physiological function, such as blood pressure regulation. So far little is known about the molecular mechanisms of how channels sense mechanical force. Canonical vertebrate epithelial Na+ channel (ENaC) formed by α-, β-, and γ-subunits is a shear force (SF) sensor and a member of the ENaC/degenerin protein family. ENaC activity in epithelial cells contributes to electrolyte/fluid-homeostasis and blood pressure regulation. Furthermore, ENaC in endothelial cells mediates vascular responsiveness to regulate blood pressure. Here, we provide evidence that ENaC's ability to mediate SF responsiveness relies on the "force-from-filament" principle involving extracellular tethers and the extracellular matrix (ECM). Two glycosylated asparagines, respectively their N-glycans localized in the palm and knuckle domains of αENaC, were identified as potential tethers. Decreased SF-induced ENaC currents were observed following removal of the ECM/glycocalyx, replacement of these glycosylated asparagines, or removal of N-glycans. Endothelial-specific overexpression of αENaC in mice induced hypertension. In contrast, expression of αENaC lacking these glycosylated asparagines blunted this effect. In summary, glycosylated asparagines in the palm and knuckle domains of αENaC are important for SF sensing. In accordance with the force-from-filament principle, they may provide a connection to the ECM that facilitates vascular responsiveness contributing to blood pressure regulation.

Keywords: N-glycosylation; epithelial Na+ channel (ENaC); extracellular tether; mechanotransduction; shear force.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Asparagine / chemistry
  • Asparagine / metabolism*
  • Disease Models, Animal
  • Endothelial Cells
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / pathology
  • Endothelium, Vascular / physiopathology
  • Epithelial Sodium Channels / chemistry
  • Epithelial Sodium Channels / genetics
  • Epithelial Sodium Channels / metabolism*
  • Extracellular Matrix / metabolism*
  • Female
  • Glycosylation
  • HEK293 Cells
  • Humans
  • Hypertension / etiology
  • Hypertension / pathology
  • Hypertension / physiopathology
  • Male
  • Mice
  • Mice, Transgenic
  • Mutagenesis, Site-Directed
  • Oocytes
  • Patch-Clamp Techniques
  • Point Mutation
  • Polysaccharides / chemistry
  • Protein Domains / genetics*
  • Stress, Mechanical
  • Xenopus laevis

Substances

  • Epithelial Sodium Channels
  • Polysaccharides
  • SCNN1A protein, human
  • Scnn1a protein, mouse
  • Scnn1a protein, rat
  • Asparagine