title: RhoA/ROCK-mediated switching between Cdc42- and Rac1-dependent protrusion in MTLn3 carcinoma cells.
abstract: Rho GTPases are versatile regulators of cell shape that act on the actin cytoskeleton. Studies using Rho GTPase mutants have shown that, in some cells, Rac1 and Cdc42 regulate the formation of lamellipodia and filopodia, respectively at the leading edge, whereas RhoA mediates contraction at the rear of moving cells. However, recent reports have described a zone of RhoA/ROCK activation at the front of cells undergoing motility. In this study, we use a FRET-based RhoA biosensor to show that RhoA activation localizes to the leading edge of EGF-stimulated cells. Inhibition of Rho or ROCK enhanced protrusion, yet markedly inhibited cell motility; these changes correlated with a marked activation of Rac-1 at the cell edge. Surprisingly, whereas EGF-stimulated protrusion in control MTLn3 cells is Rac-independent and Cdc42-dependent, the opposite pattern is observed in MTLn3 cells after inhibition of ROCK. Thus, Rho and ROCK suppress Rac-1 activation at the leading edge, and inhibition of ROCK causes a switch between Cdc42 and Rac-1 as the dominant Rho GTPase driving protrusion in carcinoma cells. These data describe a novel role for Rho in coordinating signaling by Rac and Cdc42.
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Mirvat
authors.initials: M
authors.lastname: El-Sibai
authors.forename: Olivier
authors.initials: O
authors.lastname: Pertz
authors.forename: Huan
authors.initials: H
authors.lastname: Pang
authors.forename: Shu-Chin
authors.initials: SC
authors.lastname: Yip
authors.forename: Mike
authors.initials: M
authors.lastname: Lorenz
authors.forename: Marc
authors.initials: M
authors.lastname: Symons
authors.forename: John S
authors.initials: JS
authors.lastname: Condeelis
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Hahn
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Backer
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002277:Carcinoma / Q000201:enzymology* / Q000473:pathology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002465:Cell Movement / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D021381:Protein Transport / Q000187:drug effects; D011554:Pseudopodia / Q000187:drug effects / Q000201:enzymology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D011725:Pyridines; C108830:Y 27632; D004815:Epidermal Growth Factor; D054460:rho-Associated Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein