title: Endogenous RhoG is dispensable for integrin-mediated cell spreading but contributes to Rac-independent migration.
abstract: Rac activation by integrins is essential for cell spreading, migration, growth and survival. Based mainly on overexpression of dominant-negative mutants, RhoG has been proposed to mediate integrin-dependent Rac activation upstream of ELMO and Dock180. RhoG-knockout mice, however, display no significant developmental or functional abnormalities. To clarify the role of RhoG in integrin-mediated signaling, we developed a RhoG-specific antibody, which, together with shRNA-mediated knockdown, allowed analysis of the endogenous protein. Despite dramatic effects of dominant-negative constructs, nearly complete RhoG depletion did not substantially inhibit cell adhesion, spreading, migration or Rac activation. Additionally, RhoG was not detectably activated by adhesion to fibronectin. Using Rac1(-/-) cells, we found that constitutively active RhoG induced membrane ruffling via both Rac-dependent and -independent pathways. Additionally, endogenous RhoG was important for Rac-independent cell migration. However, RhoG did not significantly contribute to cell spreading even in these cells. These data therefore clarify the role of RhoG in integrin signaling and cell motility.
authors.affiliation: Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Meller
authors.forename: Luis
authors.initials: L
authors.lastname: Vidali
authors.forename: Martin Alexander
authors.initials: MA
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D002464:Cell Migration Inhibition; D002465:Cell Movement / Q000502:physiology*; D022081:Cell Surface Extensions / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D034741:RNA, Small Interfering; D015398:Signal Transduction; D014162:Transfection; D020744:rac GTP-Binding Proteins / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: C099818:DOCK1 protein, human; D016023:Integrins; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins