title: Integrins regulate GTP-Rac localized effector interactions through dissociation of Rho-GDI.
abstract: The proper function of Rho GTPases requires precise spatial and temporal regulation of effector interactions. Integrin-mediated cell adhesion modulates the interaction of GTP-Rac with its effectors by controlling GTP-Rac membrane targeting. Here, we show that the translocation of GTP-Rac to membranes is independent of effector interactions, but instead requires the polybasic sequence near the carboxyl terminus. Cdc42 also requires integrin-mediated adhesion for translocation to membranes. A recently developed fluorescence resonance energy transfer (FRET)-based assay yields the surprising result that, despite its uniform distribution, the interaction of activated V12-Rac with a soluble, cytoplasmic effector domain is enhanced at specific regions near cell edges and is induced locally by integrin stimulation. This enhancement requires Rac membrane targeting. We show that Rho-GDI, which associates with cytoplasmic GTP-Rac, blocks effector binding. Release of Rho-GDI after membrane translocation allows Rac to bind to effectors. Thus, Rho-GDI confers spatially restricted regulation of Rac-effector interactions.
authors.affiliation: Division of Vascular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, USA. mdelpozo@scripps.edu
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Del Pozo
authors.forename: William B
authors.initials: WB
authors.lastname: Kiosses
authors.forename: Nazilla B
authors.initials: NB
authors.lastname: Alderson
authors.forename: Nahum
authors.initials: N
authors.lastname: Meller
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Hahn
authors.forename: Martin Alexander
authors.initials: MA
authors.lastname: Schwartz
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D016023:Integrins; D011993:Recombinant Fusion Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins