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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Integrin receptor binding to extracellular matrix proteins generates intracellular signals via enhanced tyrosine phosphorylation events that are important for cell growth, survival, and migration. This review will focus on the functions of the focal adhesion kinase (FAK) protein-tyrosine kinase (PTK) and its role in linking integrin receptors to intracellular signaling pathways. FAK associates with several different signaling proteins such as Src-family PTKs, p130Cas, Shc, Grb2, PI 3-kinase, and paxillin. This enables FAK to function within a network of integrin-stimulated signaling pathways leading to the activation of targets such as the ERK and JNK/mitogen-activated protein kinase pathways. Focus will be placed on the structural domains and sites of FAK tyrosine phosphorylation important for FAK-mediated signaling events and how these sites are conserved in the FAK-related PTK, Pyk2. We will review what is known about FAK activation by integrin receptor-mediated events and also non-integrin stimuli. In addition, we discuss the emergence of a consensus FAK substrate phosphorylation sequence. Emphasis will also be placed on the role of FAK in generating cell survival signals and the cleavage of FAK during caspase-mediated apoptosis. An in-depth discussion will be presented of integrin-stimulated signaling events occurring in the FAK knockout fibroblasts (FAK-) and how these cells exhibit deficits in cell migration. FAK re-expression in the FAK- cells confirms the role of this PTK in the regulation of cell morphology and in promoting cell migration events. In addition, these results reinforce the potential role for FAK in promoting an invasive phenotype in human tumors.
Prog Biophys Mol Biol 1999
PMID:Signaling through focal adhesion kinase. 1035 9

Signaling pathways mediated by adhesive molecules are tightly associated with cytoskeletal organization and cell growth regulation. Focal adhesion kinase (FAK) plays a prominent role in the adhesion signaling pathway through its tyrosine kinase activity and protein-protein interaction with other signaling molecules, including src, paxillin, and p130CAS, and other proteins. We explored the roles of these signaling molecules in the transformation of B104-1-1 cells, an NIH/3T3-derived cell line transformed by activated rat p185neu. The cytoskeletal organization of the p185neu-transformed cells was disrupted, and their morphology was dramatically altered. FAK, paxillin, and p130CAS appeared to be tyrosine phosphorylated in both NIH/3T3 and B104-1-1. However, the phosphorylation levels of paxillin and p130CAS were lower in B104-1-1 cells than in NIH/3T3 cells. Surprisingly, the association between FAK and paxillin was enhanced in B104-1-1 cells, suggesting reorganization of protein-protein interaction modulated by protein phosphorylation. Our results showed that even though cellular transformation by src and neu has similar consequences, such as focal adhesion disassembly and increased metastasis potential, the molecular events underlying the signaling pathways can be dramatically different.
Mol Carcinog 1999 Jun
PMID:Inhibition of focal contact formation in cells transformed by p185neu. 1036 17

Glomerular permeability for macromolecules depends partially on proper attachment of the glomerular epithelial cells (GEC) to the glomerular basement membrane (GBM). The latter requires integrity of the actin cytoskeleton, which in turn is regulated by specific actin-associated proteins. Since several glomerulopathies characterized by heavy proteinuria are associated with increased glomerular tumor necrosis factor alpha (TNF-alpha) expression, we studied the interaction of TNF-alpha with the actin cytoskeleton of cultured rat GEC. Incubation of GEC with 10 ng/ml TNF-alpha for variable time periods ranging from 15 min to 24 hr demonstrated a marked accentuation and redistribution of actin microfilaments, as shown by direct fluorescence analysis and confocal laser scanning microscopy. Quantitative biochemical determination of the G/total-actin ratio confirmed the above observations. Indeed, this ratio was significantly reduced, indicating substantial polymerization of G-actin and formation of F-actin. Concurrently, TNF-alpha rapidly induced tyrosine phosphorylation of both paxillin and focal adhesion kinase, without affecting the expression levels of these two proteins. In addition, tyrosine phosphorylation of vinculin became evident, indicating involvement of this focal adhesion marker in the observed actin reorganization. Inhibition of tyrosine phosphorylation by genistein prevented the reorganization of the actin cytoskeleton by TNF-alpha. We conclude that TNF-alpha induces substantial reorganization of actin cytoskeleton and focal adhesions. These effects occur simultaneously, with a prompt TNF-alpha-induced tyrosine phosphorylation of paxillin and focal adhesion kinase, indicating that these proteins, known to regulate actin polymerization and formation of focal adhesions, may be directly involved in the mechanism controlling the observed actin redistribution. These findings suggest that the observed TNF-alpha-actin cytoskeleton interactions may relate to the pathogenesis of glomerulopathies with heavy proteinuria, in which increased glomerular expression of TNF-alpha is associated with disturbances in the attachment of podocytes to the GBM.
Mol Med 1999 Jun
PMID:TNF-alpha induces actin cytoskeleton reorganization in glomerular epithelial cells involving tyrosine phosphorylation of paxillin and focal adhesion kinase. 1041 63

The focal adhesion kinase (FAK) is discretely localized to focal adhesions via its C-terminal focal adhesion-targeting (FAT) sequence. FAK is regulated by integrin-dependent cell adhesion and can regulate tyrosine phosphorylation of downstream substrates, like paxillin. By the use of a mutational strategy, the regions of FAK that are required for cell adhesion-dependent regulation and for inducing tyrosine phosphorylation of paxillin were determined. The results show that the FAT sequence was the single region of FAK that was required for each function. Furthermore, the FAT sequence of FAK was replaced with a focal adhesion-targeting sequence from vinculin, and the resulting chimera exhibited cell adhesion-dependent tyrosine phosphorylation and could induce paxillin phosphorylation like wild-type FAK. These results suggest that subcellular localization is the major determinant of FAK function.
Mol Biol Cell 1999 Aug
PMID:Focal adhesion targeting: the critical determinant of FAK regulation and substrate phosphorylation. 1043 8

Tyrosine phosphorylation of focal adhesion kinase (FAK) creates a high-affinity binding site for the src homology 2 domain of the Src family of tyrosine kinases. Assembly of a complex between FAK and Src kinases may serve to regulate the subcellular localization and the enzymatic activity of members of the Src family of kinases. We show that simultaneous overexpression of FAK and pp60(c-src) or p59(fyn) results in the enhancement of the tyrosine phosphorylation of a limited number of cellular substrates, including paxillin. Under these conditions, tyrosine phosphorylation of paxillin is largely cell adhesion dependent. FAK mutants defective for Src binding or focal adhesion targeting fail to cooperate with pp60(c-src) or p59(fyn) to induce paxillin phosphorylation, whereas catalytically defective FAK mutants can direct paxillin phosphorylation. The negative regulatory site of pp60(c-src) is hypophosphorylated when in complex with FAK, and coexpression with FAK leads to a redistribution of pp60(c-src) from a diffuse cellular location to focal adhesions. A FAK mutant defective for Src binding does not effectively induce the translocation of pp60(c-src) to focal adhesions. These results suggest that association with FAK can alter the localization of Src kinases and that FAK functions to direct phosphorylation of cellular substrates by recruitment of Src kinases.
Mol Biol Cell 1999 Oct
PMID:Complex formation with focal adhesion kinase: A mechanism to regulate activity and subcellular localization of Src kinases. 1051 82

Recently we reported a novel means of regulating LIM domain protein function. Paxillin LIM zinc-finger phosphorylation in response to cell adhesion regulates the subcellular localization of this cytoskeletal adaptor protein to focal adhesions, and also modulates cell adhesion to fibronectin (Brown et al. [1998] Mol. Biol. Cell 9:1803-1816). In the present study, we characterize further the protein kinases that phosphorylate paxillin LIM2 on threonine and LIM3 on serine. Analysis of the subcellular distribution of the LIM kinases demonstrated that the LIM3 protein kinase, but not the LIM2 kinase, resides within a detergent-insoluble fraction. The activities of the paxillin LIM domain kinases are differentially regulated during embryogenesis, and analysis of tissue distribution indicated a specificity in expression patterns between the LIM2 and LIM3 kinases. In addition, these protein kinases were refractory to inhibition by a panel of broad-spectrum serine/threonine kinase inhibitors, suggesting a novel derivation. The paxillin protein kinase activities were stimulated in serum-starved CHO.K1 cells by the mitogen phorbol myristate acetate (PMA), and by PMA and angiotensin II in rat aortic smooth muscle cells. In vivo labeling, phosphoamino acid analysis, and phosphopeptide mapping of paxillin immunoprecipitated from angiotensin II-stimulated smooth muscle cells confirmed an induction of paxillin serine/threonine phosphorylation and supports the contention that these newly identified paxillin kinases are dynamic components of growth factor signaling through the cytoskeleton.
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PMID:Characterization of paxillin LIM domain-associated serine threonine kinases: activation by angiotensin II in vascular smooth muscle cells. 1058 Oct 4

We have expressed the beta1B integrin subunit in beta1-deficient GD25 cells to examine beta1B functions without the interference of endogenous beta1A expression. As previously reported [Retta et al., 1998, Mol. Biol. Cell 9, 715-731], the beta1B integrins did not mediate cell adhesion under normal culture conditions, while the presence of 0.3 mM Mn(2+) allowed beta1B integrins to support adhesion. Mn(2+), as well as the small soluble peptide GRGDS, induced a beta1B conformation, which was recognized by the mAb 9EG7, a marker for active or ligand-bound integrins. beta1B integrins were found to localize to a subset of focal contacts in a ligand-independent manner on fibronectin, but not on vitronectin. However, clustering of beta1B did not induce tyrosine phosphorylation of FAK, p130(Cas), or paxillin, as studied by beta1B-mediated adhesion, to fibronectin in the presence of Mn(2+) or to anti-beta1 antibody in DMEM. Induction of ligand-occupied conformation by the GRGDS peptide during the adhesion to anti-beta1 antibody also failed to trigger FAK phosphorylation. Stimulation of tyrosine phosphorylation on FAK, p130(Cas), and paxillin by adhesion via integrin alphaVbeta3 to fibronectin or vitronectin was not disturbed in GD25-beta1B cells compared to the untransfected GD25 cells, nor were any negative effects of beta1B observed on alphaVbeta3-mediated cell attachment, spreading, and actin organization, or on the cell proliferation rate. These results show that the reported negative effects of beta1B on adhesive events do not apply to alphaVbeta3-dependent interactions and suggest that they may specifically act on beta1 integrins.
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PMID:Expression of integrin subunit beta1B in integrin beta1-deficient GD25 cells does not interfere with alphaVbeta3 functions. 1062 65

We have previously shown that dexamethasone (DEX) stimulates rapid polymerization of actin and stabilization of microfilaments in human endometrial adenocarcinoma cells. As the content of total cellular actin and the concentration of the actin transcript did not change, we concluded that polymerization of actin by glucocorticoids involves nongenomic mechanisms. However, the signaling events by which the latter is achieved remain unknown. In the present study we evaluated whether tyrosine phosphorylation is required for the rapid, nongenomic DEX effect on actin assembly. In cells preincubated with the tyrosine kinase inhibitors, genistein or erbstatin analogue (EA), before adding DEX the G-/total actin ratio remained unchanged, whereas DEX in the absence of both inhibitors reduced the ratio by 25%. In addition, when cells were preincubated with the protein tyrosine phosphatase inhibitor pervanadate and subsequently incubated with DEX, the G-/total actin ratio was dramatically reduced by 65%. Furthermore, DEX increased transiently the levels of tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin within 2 to 15 min, without a change in their expression levels. Pervanadate mimicked this effect of DEX and enhanced tyrosine phosphorylation of both proteins. In addition, when cells were exposed to the anticytoskeletal agent cytochalasin B, the basal levels of tyrosine phosphorylation of both proteins were reduced. This effect was reversed by DEX, indicating that actin cytoskeleton integrity is required for the effect of DEX on tyrosine phosphorylation of FAK and paxillin. Finally, we documented enhanced expression of the Ras-related GTP-binding protein Rho-B after long-term (12- and 24-hr) treatment with DEX, whereas Rho-B levels remained unchanged after short-term (3- and 6-hr) treatment. Our observations demonstrate a novel mechanism through which the rapid nongenomic effect of DEX on actin assembly requires tyrosine phosphorylation of the cytoskeleton-associated proteins FAK and paxillin. We also propose that the DEX-induced actin polymerization may constitute a mechanism for transduction of signals resulting in tyrosine phosphorylation of FAK and paxillin. Moreover, the enhanced Rho-B levels observed after long-term treatment with DEX imply a mechanism for the well-described, long-term effects of glucocorticoids on actin cytoskeleton.
Mol Med 1999 Nov
PMID:Tyrosine phosphorylation of focal adhesion kinase and paxillin regulates the signaling mechanism of the rapid nongenomic action of dexamethasone on actin cytoskeleton. 1065 75

Since the effects of progesterone are mediated mainly via estrogen-dependent progesterone receptor (PR), the expression of the effects of progesterone may be masked or overridden by the influence of estrogen under conditions in which priming with estrogens is required. We have established a PR-positive but estrogen receptor-alpha (ER-alpha) negative breast cancer cell model by transfecting PR cDNA into ER-alpha- and PR-negative MDA-MB-231 cells in order that the functions of progesterone can be studied independently of estrogens. We have demonstrated using this model that progesterone markedly inhibited cell growth. We have also discovered that progesterone induced remarkable changes in cell morphology and specific adhesion structures. Progesterone-treated cells became considerably more flattened and well spread than vehicle-treated control cells. This was associated with a striking increase of stress fibers, both in number and diameter, and increased focal contacts as shown by the staining of focal adhesion proteins paxillin and talin. There were also distinct increases in tyrosine phosphorylation of focal adhesion protein paxillin and focal adhesion kinase in association with increased focal adhesion. The staining of tyrosine-phosphorylated proteins was concentrated at focal adhesions in progesterone-treated cells. More interestingly, monoclonal antibody (Ab) to beta1 integrin was able to inhibit progesterone-induced cell spreading and formation of actin cytoskeleton. To our knowledge, this is the first report describing a direct effect of progesterone in inducing spreading and adhesion of breast cancer cells, and beta1-integrin appeared to play an essential role in the effect. It is known that the initial step of tumor metastasis is the breakaway of tumor cells from primary tumor mass when they lose the ability to attach. Hence, progesterone-induced cell spreading and adhesion may have significant implications in tumor metastasis.
Mol Endocrinol 2000 Mar
PMID:Progesterone induces focal adhesion in breast cancer cells MDA-MB-231 transfected with progesterone receptor complementary DNA. 1070 53

By using differential display, we cloned the human counterpart of the murine gene Hic-5 from senescent human keratinocytes. The full-length cDNA contained a short GC-stretch proceeding a consensus Kozak sequence followed by a single open reading frame of 1338 bp encoding a 461-amino acid protein with a predicted molecular weight of 50 kDa. The expression of this gene was prominent in cells of epithelial origin but low or absent in lymphoid tissues and hematopoietic cells. The deduced protein contained four LIM domains at the carboxyl-terminal end and four LD motifs at the amino-terminal half, sharing high similarities with the focal adhesion protein paxillin. Hic-5 may therefore function, like paxillin, as a potential adapter for the recruitment of structural and signaling molecules to certain subcellular sites or in focal adhesions. Isolation of the genomic sequence revealed that the gene covered a segment of 6 kb and spanned 11 exons from the translation initiation site ATG to the termination signal TGA. Fluorescent in situ hybridization by using a human Hic-5 specific probe localized the gene to human chromosome 16p11.
Mol Carcinog 2000 Mar
PMID:Molecular cloning of human Hic-5, a potential regulator involved in signal transduction and cellular senescence. 1070 79


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