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Focal Adhesion Kinase (focal + adhesion_kinase)
Selected AbstractsRegulation of focal adhesion targeting and inhibitory functions of the FAK related protein FRNK using a novel estrogen receptor "switch"CYTOSKELETON, Issue 2 2002Karen H. Martin Abstract Focal adhesion kinase (FAK) is a regulator of numerous adhesion-dependent processes including cell migration, cell proliferation, and cell survival. The C-terminal domain of FAK, FAK-related nonkinase (FRNK), is autonomously expressed and functions as an inhibitor of FAK signaling. Previous attempts to use FRNK as a tool to dissect FAK signaling have been limited because of an inability to temporally regulate the inhibitory functions of FRNK. In this report, we describe and characterize a conditionally targeted form of FRNK that was created by fusing the hormone-binding domain of the estrogen receptor (ER*) to the C-terminus of FRNK. In the absence of added hormone, FRNK-ER* was diffusely distributed throughout the cytoplasm of cells. Upon addition of hormone, the cytoplasmic pool of FRNK-ER* was rapidly redistributed to focal adhesions. We demonstrate that cells expressing FRNK-ER* show a hormone-dependent decrease in FAK tyrosine phosphorylation and cell migration. Furthermore, when cells expressing of FRNK-ER* were treated with hormone, the cells responded with a dramatic change in cell morphology, suggesting a role for FAK in the regulation of the adhesive properties of focal adhesions. Cell Motil. Cytoskeleton 51:76,88, 2002. © 2002 Wiley-Liss, Inc. [source] The effect of focal adhesion kinase gene silencing on 5-fluorouracil chemosensitivity involves an Akt/NF-,B signaling pathway in colorectal carcinomasINTERNATIONAL JOURNAL OF CANCER, Issue 1 2010Yuying Chen Abstract Multicellular resistance (MCR) is produced because multicellular spheroids (MCSs) are formed with a broad cell,cell connection when cultured in three-dimensions, which limits the clinical treatment efficacy in solid tumors. Focal adhesion kinase (FAK) plays an important role in apoptosis, survival and cell adhesion between cells and their extracellular matrix. In this study, we investigated the expressions of FAK, Akt and NF-,B in human colorectal cancer (CRC), and the effects of FAK gene silencing on MCSs formation and 5-fluorouracil (5-FU) chemosensitivity in colon carcinoma MCSs culture cells. In CRC samples, FAK, Akt and NF-,B were overexpressed. The positive expression of FAK correlated notably with lymph node metastasis and cellular differentiation. Positive expressions of Akt and NF-,B were significantly related to cellular differentiation and lymph node metastasis, respectively. Furthermore, positive expression of FAK correlated with that of Akt and NF-,B. The expression of FAK was inhibited significantly by a small hairpin RNA targeting FAK. Knockdown of FAK reversed the formation and aggregation of MCSs, significantly decreased the 50% inhibitory concentration of 5-FU, and markedly increased MCS culture cells apoptosis. These effects were associated with reduced levels of Akt and NF-,B. These results indicate that suppressing FAK expression potentiated 5-FU-induced cytotoxicity and contributed to its chemosensitizing effect by suppressing Akt/NF-,B signaling in colon carcinoma MCS culture cells. These data also imply that FAK mediates MCR of CRC through the survival signaling pathway FAK/Akt/NF-,B. [source] Integrin signaling through FAK in the regulation of mammary stem cells and breast cancerIUBMB LIFE, Issue 4 2010Jun-Lin Guan Abstract Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase identified as a key mediator of intracellular signaling by integrins, a major family of cell surface receptors for extracellular matrix, in the regulation of different cellular functions in a variety of cells. Upon activation by integrins through disruption of an autoinhibitory mechanism, FAK undergoes autophosphorylation and forms a complex with Src and other cellular proteins to trigger downstream signaling through its kinase activity or scaffolding function. A number of integrins are identified as surface markers for mammary stem cells (MaSCs), and both integrins and FAK are found to play crucial roles in the maintenance of MaSCs in studies using mouse models, suggesting that integrin signaling through FAK may serve as a functional marker for MaSCs. Consistent with previous studies linking increased expression and activation of FAK to human breast cancer, these findings suggest a novel cellular mechanism of FAK promotion of mammary tumorigenesis by maintaining the pools of MaSCs as targets of oncogenic transformation. Furthermore, FAK inactivation in mouse models of breast cancer also reduced the pool of mammary cancer stem cells (MaCSCs), decreased their self-renewal in vitro, and compromised their tumorigenicity and maintenance in vivo, suggesting a potential role of integrin signaling through FAK in breast cancer growth and progression through its functions in MaCSCs. This review discusses these recent advances and future studies into the mechanism of integrin signaling through FAK in breast cancer through regulation of MaCSCs that may lead to development of novel therapies for this deadly disease. © 2010 IUBMB IUBMB Life, 62(4): 268,276, 2010 [source] New concepts regarding focal adhesion kinase promotion of cell migration and proliferationJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2006Braden D. Cox Abstract Focal adhesion kinase (FAK) is a non-receptor cytoplasmic tyrosine kinase that plays a key role in the regulation of proliferation and migration of normal and tumor cells. FAK associates with integrin receptors and recruits other molecules to the site of this interaction thus forming a signaling complex that transmits signals from the extracellular matrix to the cell cytoskeleton. Crk-associated substrate (CAS) family members appear to play a pivotal role in FAK regulation of cell migration. Cellular Src bound to FAK phosphorylates CAS proteins leading to the recruitment of a Crk family adaptor molecule and activation of a small GTPase and c-Jun N-terminal kinase (JNK) promoting membrane protrusion and cell migration. The relocalization of CAS and signaling through specific CAS family members appears to determine the outcome of this pathway. FAK also plays an important role in regulating cell cycle progression through transcriptional control of the cyclin D1 promoter by the Ets B and Kruppel-like factor 8 (KLF8) transcription factors. FAK regulation of cell cycle progression in tumor cells requires Erk activity, cyclin D1 transcription, and the cyclin-dependent kinase (cdk) inhibitor p27Kip1. The ability of FAK to integrate integrin and growth factor signals resulting in synergistic promotion of cell migration and proliferation, and its potential regulation by nuclear factor kappa B (NF,B) and p53 and a ubiquitously expressed inhibitory protein, suggest that it is remarkable in its capacity to integrate multiple extracellular and intracellular stimuli. 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] Focal adhesion kinase mediates human leukocyte histocompatibility antigen class II-induced signaling in gingival fibroblastsJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2007S. Yoshizawa Background and Objective:, The role of human leukocyte antigen class II molecules on nonantigen-presenting cells has been a matter of controversy. We previously reported that human leukocyte antigen class II molecules on human gingival fibroblasts do not present antigens, but transduce signals into the cells by making a complex with antigenic peptide T-cell receptor or by stimulating cell surface human leukocyte antigen-DR molecules with human leukocyte antigen-DR antibody (L243), which mimics the formation of the human leukocyte antigen class II,antigenic peptide T-cell receptor complex, resulting in the expression of several cytokines. The aim of this study was to detect human leukocyte antigen class II-associated molecules mediating human leukocyte antigen class II-induced signals into the cells. Material and Methods:, Antibody-based protein-microarray analysis was performed to detect activated signaling molecules in gingival fibroblasts stimulated via human leukocyte antigen class II molecules. Then, we examined if these molecules structurally associate with human leukocyte antigen class II and actually transduce signals into the cells. Results:, Stimulation of human leukocyte antigen class II on gingival fibroblasts by L243 resulted in enhanced phosphorylation of focal adhesion kinase. Focal adhesion kinase was co-immunoprecipitated with human leukocyte antigen-DR by L243. Stimulation of gingival fibroblasts with L243 induced phosphorylation of focal adhesion kinase. Luteolin, a putative focal adhesion kinase inhibitor, suppressed phosphorylation of focal adhesion kinase and dose dependently inhibited human leukocyte antigen class II-induced cytokine production. Conclusion:, Focal adhesion kinase is structurally associated with human leukocyte antigen-DR and mediates human leukocyte antigen class II-induced signals in gingival fibroblasts. [source] FAK silencing inhibits leukemogenesis in BCR/ABL-transformed hematopoietic cells,AMERICAN JOURNAL OF HEMATOLOGY, Issue 5 2009Yi Le Focal adhesion kinase (FAK) is constitutively activated and tyrosine phosphorylated in BCR/ABL-transformed hematopoietic cells, but the role it plays during leukemogenesis remains unclear. Here, we examined the effects of RNA interference-mediated FAK silencing on leukemogenesis induced by a BCR/ABL-transformed cell line. Transduction of BCR/ABL-BaF3 cells with FAK shRNA inhibited FAK expression and reduced STAT5 phosphorylation, but induced caspase-3 activation. In vitro studies showed that treatment with FAK shRNA resulted in impaired cell proliferation and colony formation, while increasing cell apoptosis. Mice that received transplants of BCR/ABL-BaF3 cells with FAK shRNA displayed significantly prolonged survival time and diminished leukemia progression. In addition, FAK silencing enhanced in vitro and in vivo efficacy of ABL tyrosine kinase inhibitor imatinib in BCR/ABL-BaF3 cells. Our results suggest that FAK is critical for leukemogenesis and might be a potential target for leukemia therapy. Am. J. Hematol. 2009. © 2009 Wiley-Liss, Inc. [source] Nucleotides and epidermal growth factor induce parallel cytoskeletal rearrangements and migration in cultured adult murine neural stem cellsACTA PHYSIOLOGICA, Issue 2 2010I. Grimm Abstract Aim:, The adult subventricular zone (SVZ) contains neural stem cells that generate neuroblasts migrating to the olfactory bulb (OB) and differentiating into interneurones. The molecular cues controlling essential functions within the neurogenesis pathway such as proliferation, short and long distance migration, functional integration and cell survival are poorly understood. We have previously shown that cultured adult neural stem cells express a considerable variety of nucleotide receptors and that nucleotides and epidermal growth factor (EGF) induce converging intracellular signalling pathways that carry potential for synergism in the control of neural stem cell proliferation and cell survival. Here we investigate the role of EGF and the nucleotides ATP, ADP,S and UTP in neural stem cell migration. Methods:, Neural stem cells were prepared from adult mice and subjected to adherent culture. Labelling of F-actin was performed with tetramethylrhodamine isothiocyanate-phalloidin. Images were processed for quantitative evaluation of fluorescence labelling. Agonist-induced phosphorylation of AKT and focal adhesion kinase was analysed by quantitative Western blotting. Agonist-dependent cell migration was assayed using 48-well microchemotaxis chambers. Results:, Nucleotides and EGF induce the formation of stress fibres, an increase in the cortical actin cytoskeleton and in cell spreading. This is associated with increased phosphorylation of AKT and focal adhesion kinase. Using microchemotaxis chambers we demonstrate a parallel increase in cell migration. Conclusion:, Our results suggest that nucleotides and EGF acting as paracrine or autocrine signalling substances can be of relevance for structuring and maintaining the cytoarchitecture of the SVZ and the stream of neuroblasts migrating to the OB. [source] Overexpression of profilin reduces the migration of invasive breast cancer cellsCYTOSKELETON, Issue 2 2004Partha Roy Abstract The exact role profilin plays in cell migration is not clear. In this study, we have evaluated the effect of overexpression of profilin on the migration of breast cancer cells. Overexpression was carried out by stably expressing GFP-profilin in BT474 cells. It was observed that even a moderate level of overexpression of profilin significantly impaired the ability of BT474 cells to spread on fibronectin-coated substrate and migrate in response to EGF. GFP-profilin expressing cells also showed increased resistance to detachment in response to trypsin and increased tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin compared to the parental and GFP-expressing (control) cell lines. These results suggest that perturbation of profilin levels may offer a good strategy for controlling the metastatic potential of breast cancer cells. Cell Motil. Cytoskeleton 57:84,95, 2004. © 2004 Wiley-Liss, Inc. [source] Aberrant methylation of GTPase regulator associated with the focal adhesion kinase (GRAF) promoter is an adverse prognostic factor in myelodysplastic syndromeEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 2 2010Jun Qian No abstract is available for this article. [source] A pseudosymmetric cell adhesion regulatory domain in the ,7 tail of the integrin ,4,7 that interacts with focal adhesion kinase and srcEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 8 2006Geoffrey Abstract The ,7 integrins ,4,7 and ,E,7 play key roles in forming the gut-associated lymphoid tissue, and contribute to chronic inflammation. The ,4,7 integrin-mediated adhesion of activated lymphocytes is largely due to a transient increase in avidity from ligand-induced clustering of ,4,7 at the cell-surface. Here, we report that L and D enantiomers of a cell-permeable peptide YDRREY encompassing residues 735,740 of the cytoplasmic tail of the ,7 subunit inhibit the adhesion of T cells to ,7 integrin ligands. The YDRREY peptide abrogated mucosal addressin cell adhesion molecule-1-induced clustering of ,4,7 on the surface of activated T cells. A mutated form of the YDRREY peptide carrying either single or double conservative mutations at Tyr735Phe and Tyr740Phe was unable to inhibit T cell adhesion, suggesting that both tandem tyrosines are critical for activity. The YDRREY peptide was bound and phosphorylated by focal adhesion kinase and src, which may serve to sequester cytoskeletal proteins to the cytoplasmic domain of ,4,7. The quasi-palindromic sequence YDRREY within the ,7 cytoplasmic tail constitutes a cell adhesion regulatory domain that modulates the interaction of ,7-expressing leukocytes with their endothelial and epithelial ligands. Cell-permeable peptidomimetics based on this motif have utility as anti-inflammatory reagents for the treatment of chronic inflammatory disease. [source] Fibrinogen-CD11b/CD18 interaction activates the NF-,B pathway and delays apoptosis in human neutrophilsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2003Carolina Rubel Abstract The regulation of neutrophil half-life by members of the coagulation cascade is critical for the resolution of the inflammatory response. We have demonstrated that soluble fibrinogen (sFbg) delays human neutrophil (PMN) apoptosis through a mechanism that involves CD11b interactions, and phosphorylation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase,1/2 (ERK1/2). Since NF-,B is a key element in the regulation of apoptotic mechanisms in several immune cells, we investigated whether NF-,B is involved in the control of PMN survival by sFbg. We showthat sFbg triggers inhibitor protein ,B (I,B-,) degradation and NF-,B activation. Furthermore, pharmacological inhibition of NF-,B abrogates sFbg effects on apoptosis. In addition, specific inhibition of MAPK ERK1/2 significantly reduces NF-,B translocation by sFbg, suggesting a relationship between ERK1/2 and NF-,B activation. Similar results are obtained when granulocytic-differentiated HL-60 cells are treated with sFbg, making this model highly attractive for integrin-induced gene expression studies. It can be concluded that NF-,B participates in the prevention of apoptosis induced by sFbg with the participation of MAPK ERK1/2. These results shed light on the molecular mechanisms that control human granulocyte apoptosis, and suggest that NF-,B regulation may be of benefit for the resolution of the inflammatory response. [source] Activation 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] The first CH domain of affixin activates Cdc42 and Rac1 through ,PIX, a Cdc42/Rac1-specific guanine nucleotide exchanging factorGENES TO CELLS, Issue 3 2004Wataru Mishima Rho GTPases, Cdc42 and Rac1, play pivotal roles in cell migration by efficiently integrating cell-substrate adhesion and actin polymerization. Although it has been suggested that integrins stimulate these Rho GTPases via some of integrin binding proteins such as focal adhesion kinase (FAK) and paxillin, the precise molecular mechanism is largely unknown. In this study, we showed that the over-expression of RP1 corresponding to the first CH domain (CH1) of affixin, an integrin-linked kinase (ILK)-binding protein, induced a significant actin reorganization in MDCK cells by activating Cdc42/Rac1. Affixin full length and RP1 co-immunoprecipitated with ,PIX, a Cdc42/Rac1-specific guanine nucleotide exchanging factor (GEF), and they co-localized at the tips of lamellipodia in motile cells. The involvement of ,PIX in the RP1-induced Cdc42 activation was demonstrated by the significant dominant negative effect of a point mutant of ,PIX, ,PIX (L383R, L384S), lacking GEF activity. Our data strongly support that ILK and affixin provide a novel signalling pathway that links integrin signalling to Cdc42/Rac1 activation. [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] Leupaxin Is a Critical Adaptor Protein in the Adhesion Zone of the Osteoclast,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2003Anandarup Gupta Abstract Leupaxin is a cytoskeleton adaptor protein that was first identified in human macrophages and was found to share homology with the focal adhesion protein, paxillin. Leupaxin possesses several protein-binding domains that have been implicated in targeting proteins such as focal adhesion kinase (pp125FAK) to focal adhesions. Leupaxin can be detected in monocytes and osteoclasts, both cells of hematopoietic origin. We have identified leupaxin to be a component of the osteoclast podosomal signaling complex. We have found that leupaxin in murine osteoclasts is associated with both PYK2 and pp125FAK in the osteoclast. Treatment of osteoclasts with TNF-, and soluble osteopontin were found to stimulate tyrosine phosphorylation of both leupaxin and leupaxin-associated PYK2. Leupaxin was found to co-immunoprecipitate with the protein tyrosine phosphatase PTP-PEST. The cellular distribution of leupaxin, PYK2, and protein tyrosine phosphorylation-PEST co-localized at or near the osteoclast podosomal complex. Leupaxin was also found to associate with the ARF-GTPase-activating protein, paxillin kinase linker p95PKL, thereby providing a link to regulators of cytoskeletal dynamics in the osteoclast. Overexpression of leupaxin by transduction into osteoclasts evoked numerous cytoplasmic projections at the leading edge of the cell, resembling a motile phenotype. Finally, in vitro inhibition of leupaxin expression in the osteoclast led to a decrease in resorptive capacity. Our data suggest that leupaxin may be a critical nucleating component of the osteoclast podosomal signaling complex. [source] Bone Mineralization and Osteoblast Differentiation Are Negatively Modulated by Integrin ,v,3JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2001Su-Li Cheng Abstract Numerous bone matrix proteins can interact with ,v-containing integrins including ,v,3. To elucidate the net effects of the interaction between these proteins and ,v,3 on osteoblast function, we developed a murine osteoblastic cell line that overexpressed human ,v,3. Human ,v,3-integrin was expressed on cell membrane, in which its presence did not alter the surface level of endogenous mouse ,v,3. The expressed human ,v,3 was functional because cell adhesion to osteopontin was increased and this increment was abolished by antibody against human ,v,3. The proliferation rate of cells overexpressing ,v,3 (,v,3-cells) was increased whereas matrix mineralization was decreased. To elucidate the mechanisms leading to inhibition of matrix mineralization, the expression of proteins important for mineralization was analyzed. Alkaline phosphatase activity and the expression of osteocalcin, type I collagen, and bone sialoprotein (BSP) were decreased whereas osteopontin was stimulated in ,v,3-cells. The regulation of osteopontin, osteocalcin, and BSP expression was mediated via transcriptional mechanism because their promoter activities were altered. Examination of molecules involved in integrin signaling indicated that activator protein-1 (AP-1) and extracellular signal-regulated kinase (Erk) activities were enhanced whereas c-jun N -terminal kinase (JNK) activity was decreased in ,v,3-cells. The activity of p38 and the levels of focal adhesion kinase (FAK) and vinculin were not altered. Moreover, the adhesions of ,v,3-cells to type I collagen and fibronectin were inhibited, which was attributed to decreased ,1-integrin levels on cell surface. In conclusion, overexpressing ,v,3-integrin in osteoblasts stimulated cell proliferation but retarded differentiation, which were derived via altered integrin-matrix interactions, signal transduction, and matrix protein expression. [source] Mechanically Strained Cells of the Osteoblast Lineage Organize Their Extracellular Matrix Through Unique Sites of ,V,3 -Integrin ExpressionJOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2000Magdalena Wozniak Abstract Bone cells transduce mechanical signals into anabolic biochemical responses. However, the mechanisms of mechanotransduction are unknown. To address this issue, we performed studies in primary cells of the human osteoblast lineage grown on collagen/vitronectin-coated supports. We discovered that mechanical strain stimulated a redistribution of the ,v,3 -integrin to irregular plaque-like areas at the cell-extracellular matrix surface. Proteins involved in integrin-matrix interactions in focal adhesions, vinculin and talin, did not localize to the plaque-like areas of ,v,3 -expression, but signaling molecules such as focal adhesion kinase (FAK) did. Mechanical strain increased the number and size of the plaques defined by surface expression of ,v,3 -integrin. Osteopontin was secreted as a cross-linked macromolecular complex, likely through the action of tissue transglutaminase that also was found in the plaques of ,v,3 -integrin cell-matrix interaction. Mechanical strain increased mineralization of the extracellular matrix that developed in these plaques in ,v,3 -integrin-dependent manner. Because the plaque-like areas of cell-matrix interaction exhibit macromolecular assembly and mineralization, we conclude that they may represent subcellular domains of bone formation and that ,v,3 -integrin activation represents one mechanism by which mechanical strain stimulates bone formation. [source] Disruption of FRNK expression by gene targeting of the intronic promoter within the focal adhesion kinase geneJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2007Haruko Hayasaka Abstract FRNK, a non-catalytic variant of focal adhesion kinase (FAK), is expressed in major blood vessels throughout mouse development and is postulated to play a role in regulating cell adhesion and signaling in vascular smooth muscle cells (VSMCs). The FRNK transcriptional start site lies within an intron of the FAK gene, suggesting that the FRNK gene is a "gene within a gene". Here, we identified a 1 kb intronic sequence of the FAK gene that is necessary for endogenous FRNK expression. Deletion of this sequence in gene-targeted mice abolished FRNK expression, showing the direct involvement of the FAK intron in the regulation of FRNK expression. The level of FAK expression was normal in the FRNK-deficient mice, indicating that FAK and FRNK are transcriptionally regulated by distinct promoters. The FRNK-deficient mice were viable, fertile, and displayed no obvious histological abnormalities in any of the major blood vessels. Western blot analysis showed that FRNK,deficient and wild-type (WT) cells had comparable levels of steady-state and adhesion-dependent FAK autophosphorylation. Despite the fact that ectopic expression of FRNK suppresses focal adhesion formation in cultured cells, these results suggest that endogenous FRNK is not essential for development or the formation of the mouse vasculature. J. Cell. Biochem. 102: 947,954, 2007. © 2007 Wiley-Liss, Inc. [source] FRNK, the autonomously expressed C-terminal region of focal adhesion kinase, is uniquely regulated in vascular smooth muscle: Analysis of expression in transgenic miceJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2005Haruko Hayasaka Abstract FRNK, the autonomously expressed carboxyl-terminal region of focal adhesion kinase (FAK), is expressed in tissues that are rich in vascular smooth muscle cells (VSMCs). Here we report the generation of transgenic mice harboring the putative FRNK promoter fused to LacZ and examine the promoter activity in situ via expression of ,-galactosidase. The transgenic mice exhibited expression of ,-galactosidase predominantly in arterial VSMCs in large and small blood vessels of major organs. Upregulation of ,-galactosidase activity was observed in tunica media following carotid injury, indicating that the FRNK promoter is activated in VSMCs in response to injury. Robust expression of ,-galactosidase in blood vessels was also detected in the developing embryo. However, expression was also observed in the midline, the nose and skin epidermis, indicating distinct transcriptional regulation of the FRNK promoter in embryogenesis. To analyze FRNK expression in vitro, we identified a 116 bp sequence in the FRNK promoter that was sufficient to function as an enhancer when fused to the minimal actin promoter and expressed in cultured smooth muscle cells. Mutation of AP-1 and NF-E2 binding consensus sequences within this element abrogated enhancer activity, supporting the involvement of this promoter element in VSMC expression of FRNK. © 2005 Wiley-Liss, Inc. [source] Vascular smooth muscle cell growth-promoting factor/F-spondin inhibits angiogenesis via the blockade of integrin ,v,3 on vascular endothelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2001Yoshito Terai Vascular smooth muscle cell growth-promoting factor (VSGP) was originally isolated from bovine ovarian follicular fluid as a stimulator of vascular smooth muscle cell proliferation. Homology searches indicate that bovine and human VSGPs are orthologs of rat F-spondin. Here, we examined whether recombinant human VSGP/F-spondin affected the biological activities of endothelial cells. VSGP/F-spondin did not affect the proliferation of human umbilical vein endothelial cells (HUVECs); however, it did inhibit VEGF- or bFGF-stimulated HUVEC migration. To clarify the mechanism of this inhibitory effect, we examined the adhesion of HUVECs to extracellular matrix proteins. VSGP/F-spondin specifically inhibited the spreading of HUVECs on vitronectin via the functional blockade of integrin ,v,3. As a result, VSGP/F-spondin inhibited the tyrosine phosphorylation of focal adhesion kinase (FAK) when HUVECs were plated on vitronectin. Moreover, VSGP/F-spondin inhibited the activation of Akt when HUVECs on vitronectin were stimulated with VEGF. VSGP/F-spondin inhibited tube formation by HUVECs in vitro and neovascularization in the rat cornea in vivo. These results indicate that VSGP/F-spondin inhibits angiogenesis at least in part by the blockade of endothelial integrin ,v,3. © 2001 Wiley-Liss, Inc. [source] Defective ,1 -integrins expression in arsenical keratosis and arsenic-treated cultured human keratinocytesJOURNAL OF CUTANEOUS PATHOLOGY, Issue 2 2006Chih-Hung Lee Background:, ,1 -integrins, which localize to the basolateral surface of basal keratinocytes, are important in the differentiation control and proliferation of the epidermis. Many cutaneous diseases with perturbed differentiation, including arsenical keratosis, show altered patterns of integrin distribution and expression. Arsenic may induce arsenical keratosis through the differentiation and apoptosis aberration by integrins. The purpose of this study is to investigate the role of integrin and arsenic in the pathogenesis of arsenical keratosis. Methods:, Twenty-five specimens obtained from 25 patients with arsenical keratosis disease were studied. Immunohistochemistry staining to ,1, ,2,1, or ,3,1 integrins was performed in arsenical keratosis and clinically normal perilesional skin. Western blotting was used to assess the expression of integrin ,1 and focal adhesion kinase (FAK) in arsenic-treated cultured keratinocytes. Results:, A decreased expression of ,1, ,2,1, or ,3,1 integrins was demonstrated in arsenical keratosis and clinical normal perilesional skin in a large proportion of arsenical keratosis cases studied. The expressions of integrin ,1 and FAK were both decreased in arsenic-treated keratinocytes. Conclusions:, Our results suggest that arsenic induces abnormal differentiation in arsenical keratosis via the effects of integrin expression in keratinocytes. [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] Integrins mediate ,-amyloid-induced cell-cycle activation and neuronal deathJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2008Giuseppina Frasca Abstract Early intracellular events responsible for cell-cycle induction by ,-amyloid (A,) in neurons have not been identified yet. Extracellular signal,regulated kinases 1/2 (ERK1/2) have been identified in this pathway, and inhibition of ERK activity prevents cell-cycle activation and reduces neuronal death induced by A,. To identify upstream events responsible for ERK activation, attention has been focused on integrins. Treatment of SH-SY5Y cells, differentiated by long-term exposure to 10 ,M retinoic acid with a neutralizing anti-,1-integrin antibody significantly reduced A,-induced neuronal death. However, cell-cycle analysis showed that treatment with anti-,1-integrin per se produced changes in the distribution of cell populations, thus hampering any effect on A,-induced cell-cycle activation. 4-Amino-5-(4-chlorophenyl)-7(t-butyl)pyrazol(3,4- D)pyramide, an inhibitor of src protein kinases that colocalizes with focal adhesion kinase (FAK) and is involved in integrin signaling, was effective in reducing activation of the cell cycle and preventing induction of neuronal death by A, while inhibiting ERK1/2 phosphorylation. Similar results were obtained when FAK expression was down-regulated by siRNA silencing. The present study identifies a sequence of early events in the toxic effect of A, in neuronal cultures that involves interaction with integrins, activation of FAK/src, enhanced phosphorylation of ERK1/2, and induction of the cell cycle, all leading to neuronal death. © 2007 Wiley-Liss, Inc. [source] Focal adhesion kinase mediates human leukocyte histocompatibility antigen class II-induced signaling in gingival fibroblastsJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2007S. Yoshizawa Background and Objective:, The role of human leukocyte antigen class II molecules on nonantigen-presenting cells has been a matter of controversy. We previously reported that human leukocyte antigen class II molecules on human gingival fibroblasts do not present antigens, but transduce signals into the cells by making a complex with antigenic peptide T-cell receptor or by stimulating cell surface human leukocyte antigen-DR molecules with human leukocyte antigen-DR antibody (L243), which mimics the formation of the human leukocyte antigen class II,antigenic peptide T-cell receptor complex, resulting in the expression of several cytokines. The aim of this study was to detect human leukocyte antigen class II-associated molecules mediating human leukocyte antigen class II-induced signals into the cells. Material and Methods:, Antibody-based protein-microarray analysis was performed to detect activated signaling molecules in gingival fibroblasts stimulated via human leukocyte antigen class II molecules. Then, we examined if these molecules structurally associate with human leukocyte antigen class II and actually transduce signals into the cells. Results:, Stimulation of human leukocyte antigen class II on gingival fibroblasts by L243 resulted in enhanced phosphorylation of focal adhesion kinase. Focal adhesion kinase was co-immunoprecipitated with human leukocyte antigen-DR by L243. Stimulation of gingival fibroblasts with L243 induced phosphorylation of focal adhesion kinase. Luteolin, a putative focal adhesion kinase inhibitor, suppressed phosphorylation of focal adhesion kinase and dose dependently inhibited human leukocyte antigen class II-induced cytokine production. Conclusion:, Focal adhesion kinase is structurally associated with human leukocyte antigen-DR and mediates human leukocyte antigen class II-induced signals in gingival fibroblasts. [source] Expression and Cytoskeletal Association of Integrin Subunits Is Selectively Increased in Rat Perivenous Hepatocytes After Chronic Ethanol AdministrationALCOHOLISM, Issue 12 2001Courtney S. Schaffert Background: For normal function and survival, hepatocytes require proper cell,extracellular matrix (ECM) contacts mediated by integrin receptors and focal adhesions. Previous studies have shown that chronic ethanol consumption selectively impairs perivenous (PV) hepatocyte attachment and spreading on various ECM substrates but increases expression of the ,1 integrin subunit, the common , subunit for two major hepatocyte-ECM receptors, ,1,1 and ,5,1 integrins. This study examined the effects of ethanol treatment on the expression and cytoskeletal distribution of ,1, ,5, and ,1 integrin subunits, the epidermal growth factor receptor (EGF-R), and the cytoskeletal proteins focal adhesion kinase, paxillin, vinculin, and actin in periportal and PV hepatocytes. Methods: Periportal and PV hepatocytes were isolated from control and ethanol-fed rats. For expression analysis, lysates were examined by SDS-PAGE and immunoblotting procedures. For cytoskeletal distribution studies, Triton-soluble and -insoluble (cytoskeletal) fractions from hepatocytes cultured on collagen IV were analyzed by SDS-PAGE and immunoblotting. Results: Chronic ethanol administration caused PV-specific increases in expression and cytoskeletal association of the integrin subunits. Although ethanol treatment did not affect expression of the EGF-R in either cell type, it did increase the association of the EGF-R with the cytoskeleton selectively in PV hepatocytes. Ethanol treatment had no significant effect on either the expression or the cytoskeletal distribution of focal adhesion kinase, paxillin, vinculin, or actin in either cell type. Conclusions: The increases in integrin expression and cytoskeletal association observed after chronic ethanol administration suggest that a process downstream of integrin-ECM interactions is impaired selectively in PV hepatocytes, possibly involving altered focal adhesion assembly or turnover, processes essential for efficient cell-ECM adhesion. Alterations in these processes could contribute to the impaired hepatocyte function and structure observed after chronic ethanol administration. [source] Involvement of the ,3 E749ATSTFTN756 region in stabilizing integrin ,IIb,3 -ligand interactionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2003P. E. M. H. Litjens Summary., Platelet integrin ,IIb,3 must be activated via intracellular mechanisms before it binds soluble ligands, and it is thought to be activated at its extracellular site by surface-bound ligands. Integrin activation is associated with rearrangement of the cytoskeleton and phosphorylation of proteins that become localized in focal contacts. In these processes, the cytoplasmic tail of the ,-subunit plays a central role. We introduced peptides homologous to the E749ATSTFTN756 domain (E,N peptide) and the T755NITYRGT762 domain (T,T peptide) of ,3 in streptolysin O-permeabilized platelets and analyzed the initial interaction with soluble fibronectin, fibrinogen and PAC-1 after stimulation with thrombin. E,N peptide left the initial binding of fibronectin intact but interfered with stable receptor occupancy. E,N peptide also inhibited fibrinogen binding, thereby reducing the formation of large aggregates. Strikingly, E,N peptide did not disturb the binding of PAC-1, which is known to reflect activation of the integrin. E,N peptide also inhibited tyrosine phosphorylation of focal adhesion kinase, a response known to be dependent on ,IIb,3. T,T peptide did not affect these processes. In a model for outside-in integrin activation, E,N peptide disrupted the binding of CHO cells expressing ,IIb,3 to surface-bound ligand. Again, T,T peptide had no effect. We conclude that the E749ATSTFTN756 region of the ,3 -tail stabilizes the binding of soluble and surface-bound ligand to integrin ,IIb,3 via a mechanism that involves the phosphorylation of FAK. [source] A novel strategy to inhibit FAK and IGF-1R decreases growth of pancreatic cancer xenograftsMOLECULAR CARCINOGENESIS, Issue 2 2010Donghang Zheng Abstract Deregulation of insulin-like growth factor-1 receptor (IGF-1R) and focal adhesion kinase (FAK) signaling pathways plays an important role in cancer cell proliferation and metastasis. In pancreatic cancer cells, the crosstalk and compensatory mechanisms between these two pathways reduce the efficacy of the treatments that target only one of the pathways. Ablation of IGF-1R signaling by siRNA showed minimal effects on the survival and growth of pancreatic cancer cells. An increased activity of FAK pathway was seen in these cells after IGF-1R knockdown. Further inhibition of FAK pathway using Y15 significantly decreased cell survival, adhesion, and promoted apoptosis. The combination of Y15 treatment and IGF-1R knockdown also showed significant antitumor effect in vivo. The current study demonstrates the importance of dual inhibition of both these signaling pathways as a novel strategy to decrease both in vitro and in vivo growth of human pancreatic cancer. © 2009 Wiley-Liss, Inc. [source] Laminin acts via focal adhesion kinase/phosphatidylinositol-3, kinase/protein kinase B to down-regulate ,1 -adrenergic receptor signalling in cat atrial myocytesTHE JOURNAL OF PHYSIOLOGY, Issue 3 2009Y. G. Wang We previously reported that short-term (2 h) plating of cat atrial myocytes on the extracellular matrix protein, laminin (LMN) decreases adenylate cyclase activity and ,1 -adrenergic receptor (,1 -AR) stimulation of L-type Ca2+ current (ICa,L). The present study sought to determine whether LMN-mediated down-regulation of ,1 signalling is due to down-regulation of adenylate cyclase and to gain insight into the signalling mechanisms responsible. ,1 -AR stimulation was achieved by 0.01 ,m isoproterenol (isoprenaline) plus 0.1 ,m ICI 118551, a selective ,2 -AR antagonist. Atrial myocytes were plated for at least 2 h on uncoated cover-slips (,LMN) or cover-slips coated with LMN (+LMN). As previously reported, ,1 -AR stimulation of ICa,L was significantly smaller in +LMN compared to ,LMN atrial myocytes. In ,LMN myocytes, 10 ,m LY294002 (LY), a specific inhibitor of PI-(3)K, had no effect on ,1 -AR stimulation of ICa,L. In +LMN myocytes, however, LY significantly increased ,1 -AR stimulation of ICa,L. Western blots revealed that compared with ,LMN myocytes, +LMN myocytes showed a significant increase in Akt phosphorylation at Ser-473, which was prevented by LY. In another approach, +LMN myocytes were infected (multiplicity of infection (MOI), 100; 24 h) with replication-defective adenoviruses (Adv) expressing dominant-negative inhibitors of focal adhesion kinase (FAK) (Adv-FRNK or Adv-Y397F-FAK) or Akt (Adv-dnAkt). Compared with control cells infected with Adv-,-galactosidase, cells infected with Adv-FRNK, Adv-Y397F-FAK or Adv-dnAkt each exhibited a significantly greater ,1 -AR stimulation of ICa,L. In ,LMN myocytes LY had no effect on forskolin (FSK)-stimulated ICa,L. However, in +LMN myocytes LY significantly increased FSK-stimulated ICa,L. Similar results were obtained in +LMN atrial myocytes infected with Adv-FRNK. We conclude that LMN binding to ,1 -integrin receptors acts via FAK/PI-(3)K/Akt to inhibit adenylate cyclase activity and thereby down-regulates ,1 -AR-mediated stimulation of ICa,L. These findings provide new insight into the cellular mechanisms by which the extracellular matrix can modulate atrial ,-AR signalling. [source] Effects of Fibronectin, VEGF and Angiostatin on the Expression of MMPs through Different Signaling Pathways in the JEG-3 CellsAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 4 2003Jian Zhang Problem: The objective of this study was to evaluate the possible signal pathway of fibronectin (FN), vascular endothelial growth factor (VEGF) and angiostatin (AS) on the expression of matrix metalloproteinases (MMPs) in JEG-3 cells. Methods of study: JEG-3 cells were cultured and were examined for the effect of FN, VEGF and AS on the expression of MMPs by immunocytochemistry, gelatin zymography, Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). Results: We found that up-regulation of the expression of MMPs was induced by FN and VEGF through the focal adhesion kinase (FAK)/mitogen-activated protein kinase (MAPK) and Flt-1/p38SAPK/MAPKAPK2 signaling pathways, respectively. Furthermore, AS down-regulated the expression of MMPs through the integrin ,V,3/FAK signaling pathway independent of the integrin-binding motif Arg-Gly-Asp (RGD). Conclusion: These data indicate that the expression of MMPs is regulated by many independent factors (such as FN, VEGF and AS) through different signaling pathways which influence the behavior of trophoblast cells. [source] | |||||||||||||||||||||||||||||||