Ras couples phosphoinositide 3-OH kinase to the epithelial Na+ channel

Alexander Staruschenko, Oleh M. Pochynyuk, Qiusheng Tong, James D. Stockand

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Aldosterone induces the expression of the small G protein K-Ras. Both K-Ras and its 1st effector phosphoinositide 3-OH kinase (PI3-K) are necessary and sufficient for the activation of ENaC increasing channel open probability. The cell signaling mechanism by which K-Ras enhances ENaC activity, however, is uncertain. We demonstrate here that K-Ras significantly activates human ENaC reconstituted in Chinese hamster ovary cells ∼3-fold. Activation in response to K-Ras was sensitive to the irreversible PI3-K inhibitor wortmannin but not the competitive LY294002 inhibitor of this phospholipid kinase. Similarly, a PI3-K 1st effector-specific Ras mutant (G12:C40) enhanced ENaC activity in a wortmannin but not LY294002 sensitive manner. Constitutively active PI3-K also enhanced ENaC activity but in a wortmannin and LY294002 sensitive manner with the effects of PI3-K and K-Ras not being additive. The activation of ENaC by PI3-K was also sensitive to intracellular GDPβS. Constitutively active PI3-K that is incapable of interacting with K-Ras (K227E p110α) acted as dominant negative with respect to the regulation of ENaC even in the presence of K-Ras. K-Ras is known to directly interact with PI3-K with aldosterone promoting this interaction. Here we demonstrate that K-Ras also interacts with ENaC through an, as yet, undetermined mechanism. We conclude that K-Ras enhances ENaC activity by localizing PI3-K near the channel and stimulating of PI3-K activity.

Original languageEnglish (US)
Pages (from-to)108-115
Number of pages8
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1669
Issue number2
DOIs
StatePublished - May 20 2005

Keywords

  • ENaC activation
  • K-Ras
  • Phosphoinositide 3-OH kinase

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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