Ras activates the epithelial Na+ channel through phosphoinositide 3-OH kinase signaling

Alexander Staruschenko, Pravina Patel, Qiusheng Tong, Jörge L. Medina, James D. Stockand

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

Aldosterone induces expression and activation of the GTP-dependent signaling switch K-Ras. This small monomeric G protein is both necessary and sufficient for activation of the epithelial Na+ channel (ENaC). The mechanism by which K-Ras enhances ENaC activity, however, is uncertain. We demonstrate here that K-Ras activates human ENaC reconstituted in Chinese hamster ovary cells in a GTP-dependent manner. K-Ras influences ENaC activity most likely by affecting open probability. Inhibition of phosphoinositide 3-OH kinase (PI3K) abolished K-Ras actions on ENaC. In contrast, inhibition of other K-Ras effector cascades, including the MAPK and Ral/Rac/Rho cascades, did not affect K-Ras actions on ENaC. Activation of ENaC by K-Ras, moreover, was sensitive to co-expression of dominant negative p85PI3K. The G12:C40 effector-specific double mmtant of Ras, which preferentially activates PI3K, enhanced ENaC activity in a manner sensitive to inhibition of PI3K. Other effector-specific mutants preferentially activating MAPK and RalGDS signaling had no effect. Constitutively active PI3K activated ENaC independent of K-Ras with the effects of PI3K and K-Ras on ENaC not being additive. We conclude that K-Ras activates ENaC via the PI3K cascade.

Original languageEnglish (US)
Pages (from-to)37771-37778
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number36
DOIs
StatePublished - Sep 3 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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