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Query: UMLS:C0001511 (Adhesion)
 5,955 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adhesion to extracellular matrix mediates cell cycle progression in mid-late G1; this effect involves an integrin-dependent organization of the cytoskeleton and a consequent change in cell shape. In an effort to identify potential signal-transducing agents that are associated with integrin-dependent shape changes, we looked for kinase activities that were stimulated by long-term adhesion of G0-synchronized NIH-3T3 cells to fibronectin-coated dishes. Several kinase activities were stimulated by this procedure, two of which migrated at 42 and 44 kDa and phosphorylated myelin basic protein in vitro. Blotting with anti-phosphotyrosine and anti-mitogen-activated protein (MAP) kinase antibodies identified these enzymes as ERK 1 and ERK 2. In contrast to the rapid and transient activation of these MAP kinases by platelet-derived growth factor, stimulation of MAP kinase activity by fibronectin was gradual, persistent, and associated with cell spreading rather than cell attachment itself. Cytochalasin D blocked the activation of MAP kinase activity that was induced by the binding of cells to fibronectin. Moreover, MAP kinase was also activated by adhesion of cells to vitronectin and type IV collagen; these effects were also associated with cell spreading. These results distinguish the regulation of G1 phase MAP kinase activity by soluble mitogens and extracellular matrix. They also implicate MAP kinase in shape-dependent cell cycle progression.
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PMID:Integrin-dependent activation of MAP kinase: a link to shape-dependent cell proliferation. 761 63

Adhesion of human monocytes (MOs) results in the rapid transcriptional activation of cytokine genes that are dependent on nuclear factor (NF)-kappaB. Several pathways leading to activation of NF-kappaB have been described, including those involving reactive oxygen intermediates (ROIs) and members of the mitogen-activated protein (MAP) kinase superfamily. To investigate the involvement of tyrosine phosphorylation (TP) and oxidant generation in interleukin (IL)-8 and GRO messenger RNA induction, MOs and human alveolar macrophages (AMs) were adhered to plastic or exposed to a particulate pollutant, residual oil fly ash (ROFA). Both stimuli caused rapid TP and ROI production in MOs and AMs. However, neither NF-kappaB translocation nor IL-8 gene induction occurred in adhered or ROFA-exposed AMs. Analysis of MAP kinase activation found phosphorylation of Jun amino-terminal kinase (JNK) and p38 in the AMs, but not of extracellular regulated kinase/MAP kinase (ERK/MAPK). AMs stimulated with lipopolysaccharide activated ERK/MAPK, in addition to JNK and p38, and showed translocation of NF-kappaB. In contrast to AMs, MO adhesion or exposure to ROFA particles in suspension rapidly activated p38, JNK, and ERK/MAPK, and activated NF-kappaB binding as well as IL-8 mRNA expression. Pretreatment with the tyrosine kinase inhibitors genistein or herbimycin A before adherence had no effect on transcriptional activation in MOs, whereas adherence and ROFA-induced oxidant generation was inhibited in both MOs and AMs. Taken together, these data indicate that NF-kappaB activation or generalized transcriptional activation of cytokine genes are independent of changes in oxidant stress imposed on phagocytes by adhesion. Furthermore, the data suggest that certain environmental responses in AMs may be uncoupled from activation of NF-kappaB.
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PMID:Adhesion and pollution particle-induced oxidant generation is neither necessary nor sufficient for cytokine induction in human alveolar macrophages. 1065 41

Integrin-mediated substrate adhesion of endothelial cells leads to intracellular signaling, including the activation of ERK 1/2 (extracellular regulated kinases 1 and 2), members of the mitogen-activated protein kinase (MAPK) family. MKP-1 is a dual-specificity protein phosphatase that may play an important role in regulating MAPK activity through dephosphorylation of threonine and tyrosine. Adhesion of human umbilical vein endothelial cells to fibronectin increased MKP-1 protein and mRNA levels, which reached a maximum at 60 min, while MAPK activity was maximal at 30 min. The MEK inhibitor PD98059 blocked activation of MAPK as well as the induction of MKP-1 during adhesion. The transcription inhibitor actinomycin D blocked MKP-1 induction and produced prolonged MAPK activation during adhesion. In contrast, endothelial adhesion to poly-L-lysine did not alter MAPK activity or MKP-1 levels. These findings demonstrate that integrin-mediated adhesion of endothelial cells to fibronectin results in transcriptional activation of MKP-1 through a MAPK-dependent mechanism. Regulation of MKP-1 by MAPK likely represents an important negative-feedback mechanism.
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PMID:Adhesion to fibronectin enhances MKP-1 activation in human endothelial cells. 1087 41

Adhesion to extracellular matrix (ECM) induces intracellular signals that modulate cell proliferation, survival and differentiation. To study signalling events triggered by cell-ECM interactions in vivo we used transgenic mice exhibiting reduced mammary epithelial cell proliferation and increased apoptosis rates during the growth phase in pregnancy and lactation due to expression of a beta1-integrin dominant-negative mutant in the mammary gland epithelium. Here we show that ERK and JNK MAPKs were markedly less activated in lactating transgenic glands thereby accounting for the growth defects. The FAK pathway was not affected suggesting a mechanism of activation additional to the ECM signal. On the contrary, the significant decrease of Shc phosphorylation, Grb2 recruitment and the reduced phosphorylation level of Akt Thr308 and Akt substrates FKHR and Bad detected in transgenic glands show that activation of the Shc and the Akt pathways require intact cell-ECM interactions. These results provide an insight into the mechanisms of growth control by integrin-mediated adhesion that operate in vivo.
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PMID:Growth defects induced by perturbation of beta1-integrin function in the mammary gland epithelium result from a lack of MAPK activation via the Shc and Akt pathways. 1137 36

Proper stimulation of cell cycle progression and DNA synthesis requires cooperating signals from integrin and growth factor receptors. We previously found that the proinflammatory peptide, macrophage migration inhibitory factor (MIF), functions as an autocrine mediator of growth factor-dependent ERK MAP kinase activation and cell cycle progression. We now report that MIF secretion is induced by cell adhesion to fibronectin in quiescent mouse fibroblasts. Adhesion-mediated release of MIF subsequently promotes integrin-dependent activation of MAP kinase, cyclin D1 expression, and DNA synthesis. Secretion of MIF requires protein kinase C activity, and recombinant MIF reconstitutes the activation of MAP kinases in the presence of protein kinase C inhibition. Finally, we show that cells deficient in MIF have significantly higher retinoblastoma tumor suppressor and lower E2F transcriptional activities. These results suggest that MIF is an important autocrine mediator of adhesion-dependent signaling events and may provide mechanistic insight into how MIF regulates proliferative and oncogenic processes.
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PMID:Adhesion-dependent signaling by macrophage migration inhibitory factor (MIF). 1229 13

The development of fibrosis is a common response to a variety of injuries and results in the net accumulation of matrix proteins and impairment of normal organ function. We previously reported that the integrin alpha8beta1 is expressed by alveolar interstitial cells in normal lung and is upregulated during the development of fibrosis. TGFbeta1 is an important mediator of the inflammatory response in pulmonary fibrosis. TGFbeta1 is secreted as a latent protein that is non-covalently associated with latency-associated peptide (LAP) and requires activation to exert its effects. LAP-TGFbeta1 and LAP-TGFbeta3 contain the tripeptide sequence, arginine-glycine-aspartic acid (RGD), a known integrin recognition motif. The integrin alpha8beta1 binds to several ligands such as fibronectin and vitronectin through the RGD sequence. Recent reports demonstrate that the integrins alphavbeta1, alphavbeta6 and alphavbeta8 adhere to LAP-TGFbeta1 through the RGD site. Therefore, we asked whether LAP-TGFbeta1 might be a ligand for alpha8beta1 and whether this may be important in the development of fibrosis. We found that cell lines transfected with alpha8 subunit were able to spread on and adhere to recombinant LAP-TGFbeta1 significantly better than mock transfected cell lines. alpha8-transfected cells were also able to adhere to LAP-TGFbeta3 significantly better than mock transfected cells. Adhesion to LAP-TGFbeta1 was enhanced by activation of alpha8beta1 by Mn(2+), or 8A2, an integrin beta1 activating antibody. Furthermore, cell adhesion was abolished when we used a recombinant LAP-TGFbeta1 protein in which the RGD site was mutated to RGE. alpha8beta1 binding to LAP-TGFbeta1 increased cell proliferation and phosphorylation of FAK and ERK, but did not activate of TGFbeta1. These data strongly suggest that LAP-TGFbeta1 is a ligand of alpha8beta1 and interaction of alpha8beta1 with LAP-TGFbeta1 may influence cell behavior.
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PMID:Integrin alpha8beta1 mediates adhesion to LAP-TGFbeta1. 1241 8

Adhesion to type 1 collagen can elicit different cellular responses dependent upon whether the collagen is in a fibrillar form (gel) or monomeric form (film). Hepatocytes adherent to collagen film spread extensively, express cyclin D1, and increase DNA synthesis in response to epidermal growth factor, whereas hepatocytes adherent to collagen gel have increased differentiated function, but lower DNA synthesis. The signaling mechanisms by which different forms of type I collagen modulate cell cycle progression are unknown. When ERK MAP kinase activation was analyzed in hepatocytes attached to collagen film, two peaks of ERK activity were demonstrated. Only the second peak, which correlated with an increase of cyclin D1, was required for G1-S progression. Notably, this second peak of ERK activity was absent in cells adherent to collagen gel, but not required in the presence of exogenous cyclin D1. Expression of activated mutants of the Ras/Raf/MEK signaling pathway in cells adherent to collagen gel restored ERK phosphorylation and DNA synthesis, but differentially affected cell shape. Although Ras, Raf, and MEK all increased expression of cyclin D1 on collagen film, only Ras and Raf significantly up-regulated cyclin D1 levels on collagen gel. These results demonstrate that adhesion to polymerized collagen induces growth arrest by inhibiting the Ras/ERK-signaling pathway to cyclin D1 required in late G1.
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PMID:The role of collagen structure in mitogen stimulation of ERK, cyclin D1 expression, and G1-S progression in rat hepatocytes. 1279 85

SWAP-70, an unusual phosphatidylinositol-3-kinase-dependent protein that interacts with the RhoGTPase Rac, is highly expressed in mast cells. Cultured bone marrow mast cells (BMMC) from SWAP-70(-/-) mice are reduced in FcepsilonRI-triggered degranulation. This report describes the hitherto-unknown role of SWAP-70 in c-kit receptor signaling, a key proliferation and differentiation pathway in mast cells. Consistent with the role of Rac in cell motility and regulation of the actin cytoskeleton, mutant cells show abnormal actin rearrangements and are deficient in migration in vitro and in vivo. SWAP-70(-/-) BMMC are impaired in calcium flux, in proper translocation and activity of Akt kinase (required for mast cell activation and survival), and in translocation of Rac1 and Rac2 upon c-kit stimulation. Adhesion to fibronectin is reduced, but homotypic cell association induced through c-kit is strongly increased in SWAP-70(-/-) BMMC. Homotypic association requires extracellular Ca(2+) and depends on the integrin alpha(L)beta(2) (LFA-1). ERK is hyperactivated upon c-kit signaling in adherent and dispersed mutant cells. Together, we suggest that SWAP-70 is an important regulator of specific effector pathways in c-kit signaling, including mast cell activation, migration, and cell adhesion.
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PMID:SWAP-70 regulates c-kit-induced mast cell activation, cell-cell adhesion, and migration. 1554 37

The fact that small cell lung cancer (SCLC) is commonly incurable despite being initially responsive to chemotherapy, combined with disappointing results from a recent SCLC clinical trial with imatinib, has intensified efforts to identify mechanisms of SCLC resistance. Adhesion to extracellular matrix (ECM) is one mechanism that can increase therapeutic resistance in SCLC cells. To address whether adhesion to ECM increases resistance through modulation of signaling pathways, a series of SCLC cell lines were plated on various ECM components, and activation of two signaling pathways that promote cellular survival, the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway and the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) pathway, was assessed. Although differential activation was observed, adhesion to laminin increased Akt activation, increased cellular survival after serum starvation, and caused the cells to assume a flattened, epithelial morphology. Inhibitors of the PI3K/Akt/mTOR pathway (LY294002, rapamycin) but not the MEK/ERK pathway (U0126) abrogated laminin-mediated survival. SCLC cells plated on laminin were not only resistant to serum starvation-induced apoptosis but were also resistant to apoptosis caused by imatinib. Combining imatinib with LY294002 or rapamycin but not U0126 caused greater than additive increases in apoptosis compared with apoptosis caused by the inhibitor or imatinib alone. Similar results were observed when adenoviruses expressing mutant Akt were combined with imatinib, or when LY294002 was combined with cisplatin or etoposide. These studies identify laminin-mediated activation of the PI3K/Akt/mTOR pathway as a mechanism of cellular survival and therapeutic resistance in SCLC cells and suggest that inhibition of the PI3K/Akt/mTOR pathway is one strategy to overcome SCLC resistance mediated by ECM.
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PMID:Inhibition of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway but not the MEK/ERK pathway attenuates laminin-mediated small cell lung cancer cellular survival and resistance to imatinib mesylate or chemotherapy. 1616 21

Adhesion to the extracellular matrix (ECM) proteins collagen I and vitronectin is sufficient to drive human mesenchymal stem cells (hMSCs) into an osteogenic differentiation pathway, but the mechanisms underlying this stimulation are not well understood. We found that addition of beta1 and alpha(v)beta3 integrin blocking antibodies inhibited ECM-induced ERK activation, while addition of the MEK inhibitor PD98059 blocked ERK activation, serine phosphorylation of the osteogenic transcription factor runx2/cbfa-1, osteogenic gene expression, and calcium deposition. These results suggest that ERK plays an important role in driving the ECM-induced osteogenic differentiation of hMSC.
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PMID:ERK signaling pathways regulate the osteogenic differentiation of human mesenchymal stem cells on collagen I and vitronectin. 1619 81


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