The role of mechanical stretching in the activation and localization of adhesion proteins and related intracellular molecules. Boccafoschi, F, et al. J. Cell. Biochem., 112: 1403-9 (2011)
2011
Show Abstract
The molecular complexity of the processes which lead to cell adhesion includes membrane and cytoskeletal proteins, involved in the focal adhesion formation, as well as signaling molecules tightly associated with the main intracellular regulatory cascades (Akt/PKB and MAPK/Erk). Dynamic environments, which create substrate deformations at determined frequencies and timing, have significant influences on adhesion mechanisms and in general in cellular behavior. In this work, we investigated the role of mechanical stretching (10% substrate deformation, 1 Hz frequency applied up to 60 min) on adhesion proteins (vinculin and focal adhesion kinase-FAK), related RhoGTPases (Rac1 and RhoA), and intracellular pathways (Akt/PKB and MAPK/Erk) in terms of activation and membrane recruitment in relation with cytoskeletal changes observed (membrane ruffling and filopodia formation). These changes are due to intracellular molecular rearrangements, acting with sequential concerted dynamics, able to modify the cytoskeletal conformation. The observed cellular response adds some important issues for better understanding the cellular behavior in environment which mimic as close as possible the physiological conditions. J. Cell. Biochem. 112: 1403-1409, 2011. © 2011 Wiley-Liss, Inc. | | | 21321993
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Focal adhesion assembly in myofibroblasts fosters a microenvironment that promotes tumor growth. Kang N, Yaqoob U, Geng Z, Bloch K, Liu C, Gomez T, Billadeau D, Shah V Am J Pathol
177
1888-900. Epub 2010 Aug 27.
2010
Show Abstract
Cells within the tumor microenvironment influence tumor growth through multiple mechanisms. Pericytes such as hepatic stellate cells are an important cell within the tumor microenvironment; their transformation into highly motile myofibroblasts leads to angiogenesis, stromal cell recruitment, matrix deposition, and ensuing tumor growth. Thus, a better understanding of mechanisms that regulate motility of pericytes is required. Focal adhesions (FAs) form a physical link between the extracellular environment and the actin cytoskeleton, a requisite step for cell motility. FAs contain a collection of proteins including the Ena/VASP family member, vasodilator-stimulated phosphoprotein (VASP); however, a role for VASP in FA development has been elusive. Using a comprehensive siRNA knockdown approach and a variety of VASP mutants coupled with complementary cell imaging methodologies, we demonstrate a requirement of VASP for optimal development of FAs and cell spreading in LX2 liver myofibroblasts, which express high levels of endogenous VASP. Rac1, a binding partner of VASP, acts in tandem with VASP to regulate FAs. In vivo, perturbation of Ena/VASP function in tumor myofibroblast precursor cells significantly reduces pericyte recruitment to tumor vasculature, myofibroblastic transformation, tumor angiogenesis, and tumor growth, providing in vivo pathobiologic relevance to these findings. Taken together, our results identify Ena/VASP as a significant modifier of tumor growth through regulation of FA dynamics and ensuing pericyte/myofibroblast function within the tumor microenvironment. Full Text Article | | | 20802179
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Edaravone mimics sphingosine-1-phosphate-induced endothelial barrier enhancement in human microvascular endothelial cells. Omori, Kazuyoshi, et al. Am. J. Physiol., Cell Physiol., 293: C1523-31 (2007)
2007
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Nox1-dependent reactive oxygen generation is regulated by Rac1 Cheng, Guangjie, et al. J. Biol. Chem., 281:17718-17726 (2006)
2006
| | Human | 16636067
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Incorporation of CXCR4 into membrane lipid rafts primes homing-related responses of hematopoietic stem/progenitor cells to an SDF-1 gradient. Marcin Wysoczynski, Ryan Reca, Janina Ratajczak, Magda Kucia, Neeta Shirvaikar, Marek Honczarenko, Michael Mills, Jens Wanzeck, Anna Janowska-Wieczorek, Mariusz Z Ratajczak Blood
105
40-8
2005
Show Abstract
We found that supernatants of leukapheresis products (SLPs) of patients mobilized with granulocyte-colony-stimulating factor (G-CSF) or the various components of SLPs (fibrinogen, fibronectin, soluble vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule-1 [ICAM-1], and urokinase plasminogen activator receptor [uPAR]) increase the chemotactic responses of hematopoietic stem/progenitor cells (HSPCs) to stromal-derived factor-1 (SDF-1). However, alone they do not chemoattract HSPCs, but they do increase or prime the cells' chemotactic responses to a low or threshold dose of SDF-1. We observed that SLPs increased calcium flux, phosphorylation of mitogen-activated protein kinase (MAPK) p42/44 and AKT, secretion of matrix metalloproteinases, and adhesion to endothelium in CD34+ cells. Furthermore, SLPs increased SDF-dependent actin polymerization and significantly enhanced the homing of human cord blood (CB)- and bone marrow (BM)-derived CD34+ cells in a NOD/SCID mouse transplantation model. Moreover, the sensitization or priming of cell chemotaxis to an SDF-1 gradient was dependent on cholesterol content in the cell membrane and on the incorporation of the SDF-1 binding receptor CXCR4 and the small GTPase Rac-1 into membrane lipid rafts. This colocalization of CXCR4 and Rac-1 in lipid rafts facilitated guanosine triphosphate (GTP) binding/activation of Rac-1. Hence, we postulate that CXCR4 could be primed by various factors related to leukapheresis and mobilization that increase its association with membrane lipid rafts, allowing the HSPCs to better sense the SDF-1 gradient. This may partially explain why HSPCs from mobilized peripheral blood leukapheresis products engraft more quickly in patients than do those from BM or CB. Based on our findings, we suggest that the homing of HSPCs is optimal when CXCR4 is incorporated in membrane lipid rafts and that ex vivo priming of HSPCs with some of the SLP-related molecules before transplantation could increase their engraftment. | | | 15328152
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Fc{epsilon}RI-mediated mast cell degranulation requires calcium-independent microtubule-dependent translocation of granules to the plasma membrane. Nishida, Keigo, et al. J. Cell Biol., 170: 115-26 (2005)
2005
Show Abstract
The aggregation of high affinity IgE receptors (Fcepsilon receptor I [FcepsilonRI]) on mast cells is potent stimulus for the release of inflammatory and allergic mediators from cytoplasmic granules. However, the molecular mechanism of degranulation has not yet been established. It is still unclear how FcepsilonRI-mediated signal transduction ultimately regulates the reorganization of the cytoskeleton and how these events lead to degranulation. Here, we show that FcepsilonRI stimulation triggers the formation of microtubules in a manner independent of calcium. Drugs affecting microtubule dynamics effectively suppressed the FcepsilonRI-mediated translocation of granules to the plasma membrane and degranulation. Furthermore, the translocation of granules to the plasma membrane occurred in a calcium-independent manner, but the release of mediators and granule-plasma membrane fusion were completely dependent on calcium. Thus, the degranulation process can be dissected into two events: the calcium-independent microtubule-dependent translocation of granules to the plasma membrane and calcium-dependent membrane fusion and exocytosis. Finally, we show that the Fyn/Gab2/RhoA (but not Lyn/SLP-76) signaling pathway plays a critical role in the calcium-independent microtubule-dependent pathway. | Activation Assay | | 15998803
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The survival kinase Mirk/dyrk1B is activated through Rac1-MKK3 signaling. Kideok Jin, Seunghwan Lim, Stephen E Mercer, Eileen Friedman The Journal of biological chemistry
280
42097-105
2005
Show Abstract
The serine/threonine kinase Mirk/dyrk1B is activated in several solid tumors where it mediates cell survival, but the mechanism by which Mirk is activated in tumors is unknown. We now demonstrate that Mirk is activated as a kinase by signaling from Rac1 to the mitogen-activated protein kinase kinase MKK3. Rac is a Ras superfamily GTPase that, when activated, functions downstream of Ras oncoproteins to promote cell survival, transformation, and membrane ruffling. The constitutively active mutant Rac1QL activated Mirk in several cell types through MKK3, which in turn activated Mirk by phosphorylation. Dominant negative Rac1, dominant negative MKK3, and knockdown of MKK3 by RNA interference inhibited the kinase activity of co-expressed Mirk. E-cadherin ligation in confluent Madin-Darby canine kidney (MDCK) epithelial cells is known to transiently activate Rac1. Mirk was activated by endogenous Rac1 following E-cadherin ligation in confluent MDCK epithelial cells, whereas treatment of confluent MDCK cells with an Rac1 inhibitor decreased Mirk activity. Disruption of cadherin ligation by EGTA or prevention of cadherin ligation by maintenance of cells at subconfluent density blocked activation of Mirk. Engagement of cadherin molecules on subconfluent cells by an E-cadherin/Fc chimeric molecule transiently activated both Rac1 and Mirk with a similar time course. Rac activity is up-regulated in many human tumors and mediates survival signals, which enable tumor cells to evade apoptosis. This study characterizes a new anti-apoptotic signaling pathway that connects Rac1 with a novel downstream effector, Mirk kinase, which has recently been demonstrated to mediate survival in human tumors. | | | 16257974
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FARP2 triggers signals for Sema3A-mediated axonal repulsion. Toyofuku, Toshihiko, et al. Nat. Neurosci., 8: 1712-9 (2005)
2005
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CD28-dependent HIV-1 Transcription Is Associated with Vav, Rac, and NF-{kappa}B Activation Cook, J. A., et al J Biol Chem, 278:35812-35818 (2003)
2003
| Activation Assay | | 12842899
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Adhesion-related kinase repression of gonadotropin-releasing hormone gene expression requires Rac activation of the extracellular signal-regulated kinase pathway Allen, M. P., et al J Biol Chem, 277:38133-40 (2002)
2002
| Activation Assay | | 12138087
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