Gem associates with Ezrin and acts via the Rho-GAP protein Gmip to down-regulate the Rho pathway.
Gem is a protein of the Ras superfamily that plays a role in regulating voltage-gated Ca2+ channels and cytoskeletal reorganization. We now report that GTP-bound Gem interacts with the membrane-cytoskeleton linker protein Ezrin in its active state, and that Gem binds to active Ezrin in cells. The coexpression of Gem and Ezrin induces cell elongation accompanied by the disappearance of actin stress fibers and collapse of most focal adhesions. The same morphological effect is elicited when cells expressing Gem alone are stimulated with serum and requires the expression of ERM proteins. We show that endogenous Gem down-regulates the level of active RhoA and actin stress fibers. The effects of Gem downstream of Rho, i.e., ERM phosphorylation as well as disappearance of actin stress fibers and most focal adhesions, require the Rho-GAP partner of Gem, Gmip, a protein that is enriched in membranes under conditions in which Gem induced cell elongation. Our results suggest that Gem binds active Ezrin at the plasma membrane-cytoskeleton interface and acts via the Rho-GAP protein Gmip to down-regulate the processes dependent on the Rho pathway.
Hatzoglou
Anastassia
A
Institut Curie-Centre de Recherche and Inserm U528, Paris F-75248, France. hatzoglo@cict.fr
Ader
Isabelle
I
Splingard
Anne
A
Flanders
James
J
Saade
Evelyne
E
Leroy
Ingrid
I
Traver
Sabine
S
Aresta
Sandra
S
de Gunzburg
Jean
J
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D015536:Down-Regulation; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000235:genetics; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D000099149:Ezrin
D000199:Actins; D003598:Cytoskeletal Proteins; D020690:GTPase-Activating Proteins; D017874:Immediate-Early Proteins; D020559:Monomeric GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D000099149:Ezrin; C474310:GMIP protein, human; C000602556:Gmip protein, mouse; C490245:GEM protein, human; C088119:Gem protein, mouse