Rapid translocation and insertion of the epithelial Na+ channel in response to RhoA signaling

J Biol Chem. 2006 Sep 8;281(36):26520-7. doi: 10.1074/jbc.M603716200. Epub 2006 Jul 7.

Abstract

Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ absorption across many epithelia. Consequently, ENaC is a central effector impacting systemic blood volume and pressure. Two members of the Ras superfamily of small GTPases, K-Ras and RhoA, activate ENaC. K-Ras activates ENaC via a signaling pathway involving phosphatidylinositol 3-kinase and production of phosphatidylinositol 3,4,5-trisphosphate with the phospholipid directly interacting with the channel to increase open probability. How RhoA increases ENaC activity is less clear. Here we report that RhoA and K-Ras activate ENaC through independent signaling pathways and final mechanisms of action. Activation of RhoA signaling rapidly increases the membrane levels of ENaC likely by promoting channel insertion. This process dramatically increases functional ENaC current, resulting in tight spatial-temporal control of these channels. RhoA signals to ENaC via a transduction pathway, including the downstream effectors Rho kinase and phosphatidylinositol-4-phosphate 5-kinase. Phosphatidylinositol 4,5-biphosphate produced by activated phosphatidylinositol 4-phosphate 5-kinase may play a role in targeting vesicles containing ENaC to the plasma membrane.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • COS Cells
  • Cell Membrane / metabolism*
  • Chlorocebus aethiops
  • Cricetinae
  • Epithelial Sodium Channels / genetics
  • Epithelial Sodium Channels / metabolism*
  • Genes, ras
  • Patch-Clamp Techniques
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction / physiology*
  • rho GTP-Binding Proteins / genetics
  • rho GTP-Binding Proteins / metabolism
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism*

Substances

  • Epithelial Sodium Channels
  • Phosphatidylinositol 4,5-Diphosphate
  • Recombinant Fusion Proteins
  • Phosphotransferases (Alcohol Group Acceptor)
  • 1-phosphatidylinositol-4-phosphate 5-kinase
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein