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FAK Phosphorylation (fak + phosphorylation)
Selected AbstractsActivation of p21-activated kinase 1 is required for lysophosphatidic acid-induced focal adhesion kinase phosphorylation and cell motility in human melanoma A2058 cellsFEBS JOURNAL, Issue 8 2004In Duk Jung Lysophosphatidic acid (LPA), one of the naturally occurring phospholipids, stimulates cell motility through the activation of Rho family members, but the signaling mechanisms remain to be elucidated. In the present study, we investigated the roles of p21-activated kinase 1 (PAK1) on LPA-induced focal adhesion kinase (FAK) phosphorylation and cell motility. Treatment of human melanoma cells A2058 with LPA increased phosphorylation and activation of PAK1, which was blocked by treatment with pertussis toxin and by inhibition of phosphoinositide 3-kinase (PI3K) with an inhibitor LY294002 or by overexpression of catalytically inactive mutant of PI3K,, indicating that LPA-induced PAK1 activation was mediated via a Gi protein and the PI3K, signaling pathway. In addition, we demonstrated that Rac1/Cdc42 signals acted as upstream effector molecules of LPA-induced PAK activation. However, Rho-associated kinase, MAP kinase kinase 1/2 or phospholipase C might not be involved in LPA-induced PAK1 activation or cell motility stimulation. Furthermore, PAK1 was necessary for FAK phosphorylation by LPA, which might cause cell migration, as transfection of the kinase deficient mutant of PAK1 or PAK auto-inhibitory domain significantly abrogated LPA-induced FAK phosphorylation. Taken together, these findings strongly indicated that PAK1 activation was necessary for LPA-induced cell motility and FAK phosphorylation that might be mediated by sequential activation of Gi protein, PI3K, and Rac1/Cdc42. [source] Cell adhesion regulates platelet-derived growth factor,induced MAP kinase and PI-3 kinase activation in stellate cellsHEPATOLOGY, Issue 3 2002Vinicio Carloni The biologic effects of growth factors are dependent on cell adhesion, and a cross talk occurs between growth factors and adhesion complexes. The aim of the present study was to evaluate the influence of cell adhesion on the major intracellular signaling pathways elicited by platelet-derived growth factor (PDGF) in hepatic stellate cells (HSC). PDGF signaling was investigated in an experimental condition characterized by lack of cell adhesion for different intervals of time. Basal and PDGF-induced focal adhesion kinase (FAK) tyrosine phosphorylation was maintained in a condition of cell suspension for 2, 4, and 6 hours, whereas it was completely lost after 12 and 24 hours. We examined MAP kinase activity at 2 and 24 hours, corresponding to the higher and lower levels of FAK phosphorylation. In these experiments, MAP kinase activity correlated with FAK phosphorylation. Stimulation with PDGF was able to cause Ras-GTP loading only in adherent cells. The ability of PDGF to induce phosphatidylinositol 3-kinase (PI 3-K) activity was abrogated in cells maintained in suspension. The Ser473 phosphorylation of Akt was only marginally affected by the lack of cell adhesion. We then evaluated the association of FAK with c-Src. This association was found to be cell adhesion dependent, and it did not appear to be dependent from phosphorylated FAK. These changes in PDGF-induced intracellular signaling were associated with a remarkable reduction of PDGF-proliferative potential in nonadherent cells, although no marked differences in the apoptotic rate were observed. In conclusion, these results suggest that cell adhesion differentially regulates major signaling pathways activated by PDGF in HSC. [source] Paxillin modulates squamous cancer cell adhesion and is important in pressure-augmented adhesionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2006William C. Conway Abstract Paxillin is an adapter protein regulating signaling and focal adhesion assembly that has been linked to malignant potential in many malignancies. Overexpression of paxillin has been noted in aggressive tumors. Integrin-mediated binding through the focal adhesion complex is important in metastatic adhesion and is upregulated by extracellular pressure in malignant colonocytes through FAK and Src activation. Neither head and neck cancers nor paxillin have been studied in this regard. We hypothesized that paxillin would play a role in modulating squamous cancer adhesion both at baseline and under conditions of increased extracellular pressure. Using SCC25 tongue squamous cancer cells stably transfected with either an empty selection vector or paxillin expression and selection vectors, we studied adhesion to collagen, paxillin, FAK, and Src expression and phosphorylation in cells maintained for 30 min under ambient or 15 mmHg increased pressure conditions. Paxillin-overexpressing cells exhibited adhesion 121,±,2.9% of that observed in vector-only cells (n,=,6, P,<,0.001) under ambient pressure. Paxillin-overexpression reduced FAK phosphorylation. Pressure stimulated adhesion to 118,±,2.3% (n,=,6, P,<,0.001) of baseline in vector-only cells, similar to its effect in the parental line, and induced paxillin, FAK, and Src phosphorylation. However, increased pressure did not stimulate adhesion or phosphorylate paxillin, FAK, or Src further in paxillin-overexpressing cells. Metastasizing squamous cancer cell adhesiveness may be increased by paxillin-overexpression or by paxillin activation by extracellular pressure during surgical manipulation or growth within a constraining compartment. Targeting paxillin in patients with malignancy and minimal tumor manipulation during surgical resection may be important therapeutic adjuncts. J. Cell. Biochem. © 2006 Wiley-Liss, Inc. [source] Transient forebrain ischemia modulates focal adhesion kinase (FAK)-mediated signal transduction in gerbil hippocampusJOURNAL OF NEUROCHEMISTRY, Issue 2003M. Ziemka-Na Focal adhesion kinase (FAK) is thought to play a major role in conveying survival signals from extracellular matrix (ECM). Phosphorylated FAK may interact with other nonreceptor kinases such as Src, and adaptor molecule Cas, perhaps providing a pathway by which ECM may regulate cell viability. In the present study the expression and tyrosine phosphorylation of FAK, Src and Cas after 5 min of global ischemia were investigated. The primary activation/phosphorylation of FAK, observed during first 6 h after ischemic injury, was followed by its profound down-regulation. At 72 h of reperfusion the level of phosphorylated FAK decrease to about 50% of the control. The decrease of FAK phosphorylation coincides with its proteolytic degradation. Cleavage of FAK coincided temporally with the loss of Src and Cas. Ischemia-induced proteolytic processing of the investigated proteins may lead to the interruption of ECM-derived signals and compromise neuronal survival. Acknowledgements:, Sponsored by SCSR 4P05A 08619 and Med. Res. Ctr. [source] | ||||||||||