title: Regulation of Rho family GTPases by cell-cell and cell-matrix adhesion.
abstract: Integrins and cadherins are transmembrane adhesion receptors that are necessary for cells to interact with the extracellular matrix or adjacent cells, respectively. Integrins and cadherins initiate signaling pathways that modulate the activity of Rho family GTPases. The Rho proteins Cdc42, Rac1, and RhoA regulate the actin cytoskeleton. Cdc42 and Rac1 are primarily involved in the formation of protrusive structures, while RhoA generates myosin-based contractility. Here we examine the differential regulation of RhoA, Cdc42, and Rac1 by integrin and cadherin signaling. Integrin and cadherin signaling leads to a decrease in RhoA activity and activation of Cdc42 and Rac1. When the normal RhoA suppression is antagonized or RhoA signaling is increased, cells exhibited impaired spreading on the matrix protein fibronectin and decreased cell-cell adhesion. Spreading on fibronectin and the formation of cell-cell adhesions is decreased in cells expressing dominant negative forms of Cdc42 or Rac1. These data demonstrate that integrins and cadherins regulate Rho proteins in a comparable manner and lead us to speculate that these changes in Rho protein activity participate in a feedback mechanism that promotes further cell-matrix or cell-cell interaction, respectively.
authors.affiliation: Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. warthur@med.unc.edu
authors.forename: William T
authors.initials: WT
authors.lastname: Arthur
authors.forename: Nicole K
authors.initials: NK
authors.lastname: Noren
authors.forename: Keith
authors.initials: K
authors.lastname: Burridge
mesh_terms: D000818:Animals; D015820:Cadherins / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology; D002450:Cell Communication / Q000502:physiology*; D021982:Cell-Matrix Junctions / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000502:physiology; D020741:rho GTP-Binding Proteins / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000502:physiology
chemical_list: D015820:Cadherins; D016023:Integrins; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein