Faculty Collaboration Database

Ras couples phosphoinositide 3-OH kinase to the epithelial Na+ channel. Biochim Biophys Acta 2005 May 20;1669(2):108-15

Date

05/17/2005

Pubmed ID

15893513

DOI

10.1016/j.bbamem.2005.01.005

Scopus ID

2-s2.0-18944373042 (requires institutional sign-in at Scopus site)   31 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 approximately 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 GDPbetaS. Constitutively active PI3-K that is incapable of interacting with K-Ras (K227E p110alpha) 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.

Author List

Staruschenko A, Pochynyuk OM, Tong Q, Stockand JD

MESH terms used to index this publication - Major topics in bold

Aldosterone
Animals
CHO Cells
Cricetinae
Cricetulus
Epithelial Sodium Channels
GTP-Binding Proteins
Humans
Phosphatidylinositol 3-Kinases
Signal Transduction
Sodium Channels
ras Proteins