Results 1 - 10 of 152

Rho-stimulated contractility drives the formation of stress fibers and focal adhesions

by Magdalena Chrzanowska-wodnicka, Keith Burridge - J. Cell Biol , 1996
"... Abstract. Activated rhoA, a ras-related GTP-binding protein, stimulates the appearance of stress fibers, focal adhesions, and tyrosine phosphorylation in quiescent cells (Ridley, A.J., and A. Hall, 1992. Cell. 70:389-399). The pathway by which rho triggers these events has not been elucidated. Many ..."
Abstract - Cited by 309 (5 self) - Add to MetaCart
Abstract. Activated rhoA, a ras-related GTP-binding protein, stimulates the appearance of stress fibers, focal adhesions, and tyrosine phosphorylation in quiescent cells (Ridley, A.J., and A. Hall, 1992. Cell. 70:389-399). The pathway by which rho triggers these events has not been elucidated. Many of the agents that activate rho (e.g., vasopressin, endothelin, lysophosphatidic acid) stimulate the contractility of smooth muscle and other cells. We have investigated whether rho's induction of stress fibers, focal adhesions, and tyrosine phosphorylation is the result of its stimulation of contractility. We demonstrate that stimulation of fibroblasts with lysophosphatidic acid, which activates rho, induces myosin light chain phosphorylation. This precedes the forma-tion of stress fibers and focal adhesions and is accompanied by increased contractility. Inhibition of contractility by several different mechanisms leads to inhibition of rho-induced stress fibers, focal adhesions, and tyrosine phosphorylation. In addition, when contractility is inhibited, integrins disperse from focal adhesions as stress fibers and focal adhesions disassemble. Conversely, upon stimulation of contractility, diffusely distributed integrins are aggregated into focal adhesions. These results suggest that activated rho stimulates contractility, driving the formation of stress fibers and focal adhesions and elevating tyrosine phosphorylation. A model is proposed to account for how contractility could promote these events. F OCAL adhesions are sites where cells in culture adhere strongly to the underlying extracellular matrix (ECM) 1 via specific members of the integrin family of ECM receptors (Burridge et al., 1988; Jockusch et al., 1995). At their cytoplasmic face, focal adhesions provide attachment for bundles of actin filaments (stress fibers). More than just sites of structural linkage between the ECM on the outside and the cytoskeleton on the inside, focal adhesions are regions of signal transduction. Components involved in multiple signal transduction pathways have been identified in focal adhesions (Hynes, 1992;
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Integrin-mediated signals regulated by members of the rho family of GTPases

by Edwin A. Clark, Warren G. King, Joan S. Brugge, Marc Symons, Richard O. Hynes - J , 1998
"... Abstract. The organization of the actin cytoskeleton can be regulated by soluble factors that trigger signal transduction events involving the Rho family of GTPases. Since adhesive interactions are also capable of organizing the actin-based cytoskeleton, we examined the role of Cdc42-, Rac-, and Rho ..."
Abstract - Cited by 102 (3 self) - Add to MetaCart
Abstract. The organization of the actin cytoskeleton can be regulated by soluble factors that trigger signal transduction events involving the Rho family of GTPases. Since adhesive interactions are also capable of organizing the actin-based cytoskeleton, we examined the role of Cdc42-, Rac-, and Rho-dependent signaling pathways in regulating the cytoskeleton during integrin-mediated adhesion and cell spreading using dominant-inhibitory mutants of these GTPases. When Rat1 cells initially adhere to the extracellular matrix protein fibronectin, punctate focal complexes form at the cell periphery. Concomitant with focal complex formation, we observed some phosphorylation of the focal adhesion kinase (FAK) and Src, which occurred independently of Rho family GTPases. However, subsequent
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The assembly of integrin adhesion complexes require both extracellular matrix and intracellular Rho/Rac GTPases

by Neil A. Hotchin, Alan Hall - J. Cell Biol , 1995
"... Abstract. Interaction of cells with extracellular matrix via integrin adhesion receptors plays an important role in a wide range of cellular functions, for example cell growth, movement, and differentiation. Upon interaction with substrate, integrins cluster and associate with a variety of cytoplasm ..."
Abstract - Cited by 76 (4 self) - Add to MetaCart
Abstract. Interaction of cells with extracellular matrix via integrin adhesion receptors plays an important role in a wide range of cellular functions, for example cell growth, movement, and differentiation. Upon interaction with substrate, integrins cluster and associate with a variety of cytoplasmic proteins to form focal complexes and with the actin cytoskeleton. Although the intracellular signals induced by integrins are at present undefined, it is thought that they are mediated by proteins recruited to the focal complexes. It has been suggested, for example, that after recruitment to focal adhesions p125 FAK can activate the ERK1/2 MAP kinase cascade. We have previously reported that members of the rho family of small GTPases can trigger the assembly of focal complexes when activated in cells. Using
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Autophosphorylation of the focal adhesion kinase, pp125 FAK , directs SH2-dependent binding of pp60 src

by M D Schaller, J D Hildebr, J D Shannon, J W Fox, R R Vines, Michael D. Schaller, Jeffrey D. Hildebrand, John D. Shannon, Jay W. Fox, Richard R. Vines, J. Thomas Parsons , 1994
"... Autophosphorylation of the focal adhesion kinase, pp125FAK, directs SH2-dependent binding of pp60src. ..."
Abstract - Cited by 73 (10 self) - Add to MetaCart
Autophosphorylation of the focal adhesion kinase, pp125FAK, directs SH2-dependent binding of pp60src.
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Tyrosine phosphorylation of focal adhesion kinase at sites in the catalytic domain regulates kinase activity: a role for Src family kinases

by M B Calalb, T R Polte, S K Hanks, Mol Cell Biol, Mihail B. Calalb, Thomas R. Polte, Steven K. Hanks , 1995
"... Tyrosine phosphorylation of focal adhesion kinase at sites in the catalytic domain regulates kinase activity: a role for Src family kinases. ..."
Abstract - Cited by 65 (3 self) - Add to MetaCart
Tyrosine phosphorylation of focal adhesion kinase at sites in the catalytic domain regulates kinase activity: a role for Src family kinases.
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Deficiency of Src family kinases p59/61 hck and p58 c-fgr results in defective adhesion-dependent neutrophil functions

by Clifford A. Lowell, Laura Fumagalli, Giorgio Berton - J. Cell Biol , 1996
"... Abstract. Cross-linking of the neutrophi1132- or 133-related leukocyte response integrins by extracellular matrix (ECM) proteins or monoclonal antibodies (mAb) stimulates cytoskeletal rearrangement leading to cell spreading and respiratory burst. Tyrosine phosphorylation of a variety of proteins and ..."
Abstract - Cited by 57 (9 self) - Add to MetaCart
Abstract. Cross-linking of the neutrophi1132- or 133-related leukocyte response integrins by extracellular matrix (ECM) proteins or monoclonal antibodies (mAb) stimulates cytoskeletal rearrangement leading to cell spreading and respiratory burst. Tyrosine phosphorylation of a variety of proteins and activation of the Src family kinases within polymorphonuclear leukocytes (PMN) have recently been implicated in the intracellular signaling pathways generated by leukocyte integrins (Yan, S.R., L. Fumagalli, and G. Berton. 1995. J. Inflammation. 45:217-311.) To directly test whether these functional responses are dependent on the Src family kinases p59/61 hCk and p58 c-fgr, we examined adhesiondependent respiratory burst in PMNs isolated from hck-/-, fgr-/-, and hck-/-fgr-/- knockout mice. Purified
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Signal transduction of mechanical stresses in the vascular wall. Hypertension 32: 338–345

by Alain Tedgui , 1998
"... Abstract—The vascular wall is constantly subjected to a variety of mechanical forces in the form of stretch (tensile stress), due to blood pressure, and shear stress, due to blood flow. Alterations in either of these stresses are known to result in vascular remodeling, an adaptation characterized by ..."
Abstract - Cited by 56 (2 self) - Add to MetaCart
Abstract—The vascular wall is constantly subjected to a variety of mechanical forces in the form of stretch (tensile stress), due to blood pressure, and shear stress, due to blood flow. Alterations in either of these stresses are known to result in vascular remodeling, an adaptation characterized by modified morphology and function of the blood vessels, allowing the vessels to cope with physiological or pathological conditions. The processes involved in vascular remodeling include cellular hypertrophy and hyperplasia, as well as enhanced protein synthesis or extracellular matrix protein reorganiza-tion. In vitro studies using vascular cells have attempted to identify the mechanisms behind structural alterations. Possible pathways include ion channels, integrin interaction between cells and the extracellular matrix, activation of various tyrosine kinases (such as c-Src, focal adhesion kinase, and mitogen-activated protein kinases), and autocrine production and release of growth factors. These pathways lie upstream of de novo synthesis of immediate response genes and total protein synthesis, both of which are likely to be involved in the process of vascular remodeling. (Hypertension. 1998;32:338-345.) Key Words: shear stress n stretch n muscle, smooth n endothelium n MAP kinases Blood vessels are permanently subjected to mechanicalforces in the form of stretch, which because of the pulsatile nature of blood flow exposes vessels to cyclic mechanical strain, and shear stress. Blood pressure is the

An SH3 domaincontaining GTPase-activating protein for Rho and Cdc42 associates with focal adhesion kinase

by Jeffrey D. Hildebrand, Joan M. Taylor, J. Thomas Parsons , 1996
"... The integrin family of cell surface receptors mediates cell adhesion to components of the extracellular matrix (ECM). Integrin engagement with the ECM initiates signaling cascades that regulate the organization of the actin-cytoskeleton and changes in gene expression. The Rho subfamily of Ras-relate ..."
Abstract - Cited by 45 (4 self) - Add to MetaCart
The integrin family of cell surface receptors mediates cell adhesion to components of the extracellular matrix (ECM). Integrin engagement with the ECM initiates signaling cascades that regulate the organization of the actin-cytoskeleton and changes in gene expression. The Rho subfamily of Ras-related low-molecular-weight GTP-binding proteins and several protein tyrosine kinases have been implicated in mediating various aspects of integrin-dependent alterations in cell homeostasis. Focal adhesion kinase (FAK or pp125 FAK) is one of the tyrosine kinases predicted to be a critical component of integrin signaling. To elucidate the mechanisms by which FAK participates in integrin-mediated signaling, we have used expression cloning to identify cDNAs that encode potential FAK-binding proteins. We report here the identification of a cDNA that encodes a new member of the GTPase-activating protein (GAP) family of GTPase regulators. This GAP, termed Graf (for GTPase regulator associated with FAK), binds to the C-terminal domain of FAK in an SH3 domain-dependent manner and preferentially stimulates the GTPase activity of the GTP-binding proteins RhoA and Cdc42. Subcellular localization studies using Graf-transfected chicken embryo cells indicates that Graf colocalizes with actin stress fibers, cortical actin structures, and focal adhesions. Graf mRNA is expressed in a variety of avian tissues and is particularly abundant in embryonic brain and liver. Graf represents the first example of a regulator of the Rho family of small GTP-binding proteins that exhibits binding to a protein tyrosine kinase.
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Identification of LIM3 as the principal determinant of paxillin focal adhesion localization and characterization of a novel motif on paxillin directing vinculin and focal adhesion kinase binding

by Michael C. Brown, Joseph A. Perrotta, Christopher E. Turner - J. Cell Biol , 1996
"... Abstract. Paxillin is a 68-kD focal adhesion phosphoprotein that interacts with several proteins including members of the src family of tyrosine kinases, the transforming protein v-crk, and the cytoskeletal proteins vinculin and the tyrosine kinase, focal adhesion kinase (FAK). This suggests a funct ..."
Abstract - Cited by 38 (7 self) - Add to MetaCart
Abstract. Paxillin is a 68-kD focal adhesion phosphoprotein that interacts with several proteins including members of the src family of tyrosine kinases, the transforming protein v-crk, and the cytoskeletal proteins vinculin and the tyrosine kinase, focal adhesion kinase (FAK). This suggests a function for paxillin as a molecular adaptor, responsible for the recruitment of structural and signaling molecules to focal adhesions. The current study defines the vinculin- and FAK-interaction domains on paxillin and identifies the principal paxillin focal adhesion targeting motif. Using truncation and deletion mutagenesis, we have localized the vinculin-binding site on paxillin to a contiguous stretch of 21 amino acids spanning residues 143-164. In contrast, maximal binding of FAK to paxillin requires, in
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Physical state of the extracellular matrix regulates the structure and molecular composition of the cell-matrix adhesions

by Ben-zion Katz, Eli Zamir, Er Bershadsky, Zvi Kam, Kenneth M. Yamada, Benjamin Geiger , 2000
"... This study establishes that the physical state of the extracellular matrix can regulate integrinmediated cytoskeletal assembly and tyrosine phosphorylation to generate two distinct types of cell-matrix adhesions. In primary fibroblasts, � 5 � 1 integrin associates mainly with fibronectin fibrils an ..."
Abstract - Cited by 34 (0 self) - Add to MetaCart
This study establishes that the physical state of the extracellular matrix can regulate integrinmediated cytoskeletal assembly and tyrosine phosphorylation to generate two distinct types of cell-matrix adhesions. In primary fibroblasts, � 5 � 1 integrin associates mainly with fibronectin fibrils and forms adhesions structurally distinct from focal contacts, independent of actomyosinmediated cell contractility. These “fibrillar adhesions ” are enriched in tensin, but contain low levels of the typical focal contact components paxillin, vinculin, and tyrosine-phosphorylated proteins. However, when the fibronectin is covalently linked to the substrate, � 5 � 1 integrin forms highly tyrosine-phosphorylated, “classical ” focal contacts containing high levels of paxillin and vinculin. These experiments indicate that the physical state of the matrix, not just its molecular composition, is a critical factor in defining cytoskeletal organization and phosphorylation at adhesion sites. We propose that molecular organization of adhesion sites is controlled by at least two mechanisms: 1) specific integrins associate with their ligands in transmembrane complexes with appropriate cytoplasmic anchor proteins (e.g., fibronectin– � 5 � 1 integrin–tensin complexes), and 2) physical properties (e.g., rigidity) of the extracellular matrix regulate local tension at adhesion sites and activate local tyrosine phosphorylation, recruiting a variety of plaque molecules
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