Serum and glucocorticoid-regulated kinase modulates Nedd4-2-mediated inhibition of the epithelial Na+ channel

J Biol Chem. 2002 Jan 4;277(1):5-8. doi: 10.1074/jbc.C100623200. Epub 2001 Nov 5.

Abstract

The epithelial Na+ channel (ENaC) forms the pathway for Na+ absorption across epithelia, including the kidney collecting duct, where it plays a critical role in Na+ homeostasis and blood pressure control. Na+ absorption is regulated in part by mechanisms that control the expression of ENaC at the apical cell surface. Nedd4 family members (e.g. Nedd4, Nedd4-2) bind to the channel and decrease its surface expression by catalyzing its ubiquitination and degradation. Conversely, serum and glucocorticoid-regulated kinase (SGK), a downstream mediator of aldosterone, increases the expression of ENaC at the cell surface. Here we show that SGK and human Nedd4-2 (hNedd4-2) converge in a common pathway to regulate epithelial Na+ absorption. Consistent with this model, we found that SGK bound to hNedd4-2 and hNedd4. A PY motif in SGK mediated the interaction and was required for SGK to stimulate ENaC. SGK phosphorylated hNedd4-2 (but not hNedd4), altering hNedd4-2 function; phosphorylation reduced the binding of hNedd4-2 to alphaENaC, and hence, the hNedd4-2-mediated inhibition of Na+ absorption. These data suggest that SGK regulates epithelial Na+ absorption in part by modulating the function of hNedd4-2.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • COS Cells
  • Calcium-Binding Proteins / physiology*
  • Endosomal Sorting Complexes Required for Transport
  • Epithelial Sodium Channels
  • Immediate-Early Proteins
  • Ligases / physiology*
  • Nedd4 Ubiquitin Protein Ligases
  • Nuclear Proteins*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / physiology*
  • Sodium / metabolism
  • Sodium Channel Blockers*
  • Sodium Channels / physiology
  • Ubiquitin-Protein Ligases*

Substances

  • Calcium-Binding Proteins
  • Endosomal Sorting Complexes Required for Transport
  • Epithelial Sodium Channels
  • Immediate-Early Proteins
  • Nuclear Proteins
  • Sodium Channel Blockers
  • Sodium Channels
  • Sodium
  • Nedd4 Ubiquitin Protein Ligases
  • Nedd4 protein, human
  • Nedd4L protein, human
  • Ubiquitin-Protein Ligases
  • Protein Serine-Threonine Kinases
  • serum-glucocorticoid regulated kinase
  • Ligases