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A more recent version of this article appeared on December 1, 2007
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Submitted on December 22, 2006
Revised on July 18, 2007
Accepted on September 11, 2007
*Centre National de la Recherche Scientifique, Unité Mixte de Recherche 144, Paris F-75248, France;
Institut Curie, Centre de Recherche, Paris F-75248, France;
Hybrigenics, 75014 Paris, France;
Centre National de la Recherche Scientifique, Centre de Recherche de Biochimie Macromoléculaire, 34293 Montpellier Cedex 5, France
Monitoring Editor: Martin A. Schwartz
The mechanisms underlying functional interactions between ERM (Ezrin, Radixin, Moesin) proteins and Rho GTPases are not well understood. Here we characterized the interaction between ezrin and a novel Rho guanine nucleotide exchange factor, PLEKHG6. We show that ezrin recruits PLEKHG6 to the apical pole of epithelial cells where PLEKHG6 induces the formation of microvilli and membrane ruffles. These morphological changes are inhibited by dominant negative forms of RhoG. Indeed, we found that PLEKHG6 activates RhoG and to a much lesser extent Rac1. In addition we show that ezrin forms a complex with PLEKHG6 and RhoG. Furthermore, we detected a ternary complex between ezrin, PLEKHG6 and the RhoG effector ELMO. We demonstrate that PLEKHG6 and ezrin are both required in macropinocytosis. Following down-regulation of either PLEKHG6 or ezrin expression we observed an inhibition of dextran uptake in EGF-stimulated A431 cells. Altogether, our data indicate that ezrin allows the local activation of RhoG at the apical pole of epithelial cells by recruiting upstream and downstream regulators of RhoG and that both PLEKHG6 and ezrin are required for efficient macropinocytosis.
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