Abstract
Cell migration involves many steps, including membrane protrusion and the development of new adhesions. Here we have investigated whether there is a link between actin polymerization and integrin engagement. In response to signals that trigger membrane protrusion, the actin-related protein (Arp)2/3 complex transiently binds to vinculin, an integrin-associated protein. The interaction is regulated, requiring phosphatidylinositol-4,5-bisphosphate and Rac1 activation, and is sufficient to recruit the Arp2/3 complex to new sites of integrin aggregation. Binding of the Arp2/3 complex to vinculin is direct and does not depend on the ability of vinculin to associate with actin. We have mapped the binding site for the Arp2/3 complex to the hinge region of vinculin, and a point mutation in this region selectively blocks binding to the Arp2/3 complex. Compared with WT vinculin, expression of this mutant in vinculin-null cells results in diminished lamellipodial protrusion and spreading on fibronectin. The recruitment of the Arp2/3 complex to vinculin may be one mechanism through which actin polymerization and membrane protrusion are coupled to integrin-mediated adhesion.
Publication types
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Comparative Study
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Actin-Related Protein 2
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Actin-Related Protein 3
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Actins / metabolism
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Androstadienes / pharmacology
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Animals
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Binding Sites / genetics
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Cell Adhesion*
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Cell Line
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Cell Movement
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Cells, Cultured
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Cytoskeletal Proteins / metabolism*
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Embryo, Mammalian
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Epidermal Growth Factor / pharmacology
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Extracellular Matrix / metabolism
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Fibronectins / physiology
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Green Fluorescent Proteins
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HeLa Cells
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Humans
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Integrins / metabolism
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Luminescent Proteins / metabolism
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Mice
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Phosphatidylinositol 3-Kinases / pharmacology
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Phosphoinositide-3 Kinase Inhibitors
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Point Mutation
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Protein Binding
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Pseudopodia / metabolism*
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Recombinant Fusion Proteins / metabolism
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Vinculin / antagonists & inhibitors
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Vinculin / chemistry
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Vinculin / genetics
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Vinculin / metabolism*
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Wortmannin
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rac1 GTP-Binding Protein / metabolism
Substances
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ACTR2 protein, human
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ACTR3 protein, human
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Actin-Related Protein 2
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Actin-Related Protein 3
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Actins
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Actr2 protein, mouse
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Actr3 protein, mouse
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Androstadienes
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Cytoskeletal Proteins
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Fibronectins
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Integrins
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Luminescent Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Recombinant Fusion Proteins
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Vinculin
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Green Fluorescent Proteins
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Epidermal Growth Factor
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rac1 GTP-Binding Protein
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Wortmannin