Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51812 (mitogen-activated protein)
 10,636 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adhesion molecules such as VLA-4 are important not only for monocyte adhesion to extracellular matrix proteins, but also for subsequent cell activation. Monocyte adherence to fibronectin or engagement of VLA-4 has been demonstrated to stimulate production of potent inflammatory mediators such as tumor necrosis factor-alpha, interleukin-1, and the procoagulant tissue factor protein. However, the intracellular signaling cascades leading to gene expression have not been elucidated. Using the human monocytic THP-1 cell line, VLA-4 cross-linking by monoclonal antibodies directed against its alpha4 and beta1 subunits produced a time-dependent increase in tyrosine phosphorylation of a broad range of cellular proteins. Using Western blot analysis directed against the phosphorylated form of the extracellular signal-related kinase (ERK) mitogen-activated protein (MAP) kinase proteins, as well as immunoprecipitation and in vitro kinase assays, we found that VLA-4 cross-linking increased ERK1/ERK2 tyrosine phosphorylation and activity. In conjunction, integrin cross-linking also increased NF-kappaB nuclear translocation and 4-h expression of tissue factor. Inhibition of tyrosine kinase activity with genistein (10 microg/ml) as well as selective MAP kinase inhibition with the MEK-1 inhibitor PD98059 abolished the VLA-4-dependent ERK tyrosine phosphorylation, inhibited NF kappaB nuclear binding, and abrogated tissue factor expression induced by both VLA-4 cross-linking and adhesion to fibronectin in THP-1 cells and human peripheral blood monocytes. These studies point to the involvement of the MAP kinase pathway in the activation of monocytic cells during transmigration to inflammatory sites.
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PMID:VLA-4 integrin cross-linking on human monocytic THP-1 cells induces tissue factor expression by a mechanism involving mitogen-activated protein kinase. 909 80

The paradigm for the response to hypoxia is erythropoietin gene expression; activation of hypoxia-inducible factor-1 (HIF-1) results in erythropoietin production. Previously, we found that oxygen deprivation induced tissue factor, especially in mononuclear phagocytes, by an early growth response (Egr-1)-dependent pathway without involvement of HIF-1 (Yan, S.-F., Zou, Y.-S., Gao, Y., Zhai, C., Mackman, N., Lee, S., Milbrandt, J., Pinsky, D., Kisiel, W., and Stern, D. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 8298-8303). Now, we show that cultured monocytes subjected to hypoxia (pO2 approximately 12 torr) displayed increased Egr-1 expression because of de novo biosynthesis, with a approximately 10-fold increased rate of transcription. Transfection of monocytes with Egr-1 promoter-luciferase constructs localized elements responsible for hypoxia-enhanced expression to -424/-65, a region including EBS (ets binding site)-SRE (serum response element)-EBS and SRE-EBS-SRE sites. Further studies with each of these regions ligated to the basal thymidine kinase promoter and luciferase demonstrated that EBS sites in the element spanning -424/-375 were critical for hypoxia-enhanceable gene expression. These data suggested that an activated ets factor, such as Elk-1, in complex with serum response factor, was the likely proximal trigger of Egr-1 transcription. Indeed, hypoxia induced activation of Elk-1, and suppression of Elk-1 blocked up-regulation of Egr-1 transcription. The signaling cascade preceding Elk-1 activation in response to oxygen deprivation was traced to activation of protein kinase C-betaII, Raf, mitogen-activated protein kinase/extracellular signal-regulated protein kinase kinase and mitogen-activated protein kinases. Comparable hypoxia-mediated Egr-1 induction and activation were observed in cultured hepatoma-derived cells deficient in HIF-1beta and wild-type hepatoma cells, indicating that the HIF-1 and Egr-1 pathways are initiated independently in response to oxygen deprivation. We propose that activation of Egr-1 in response to hypoxia induces a different facet of the adaptive response than HIF-1, one component of which causes expression of tissue factor, resulting in fibrin deposition.
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PMID:Hypoxia-associated induction of early growth response-1 gene expression. 1032 6

Tissue factor (TF) assembled with activated factor VII (FVIIa) initiates the coagulation cascade. We recently showed that TF was essential for FVIIa-induced vascular endothelial growth factor (VEGF) production by human fibroblasts. We investigated whether this production resulted from TF activation by its binding to FVIIa or from the production of clotting factors activated downstream. Incubation of fibroblasts with a plasma-derived FVIIa concentrate induced the generation of activated factor X (FXa) and thrombin and the secretion of VEGF, which was inhibited by hirudin and FXa inhibitors. By contrast, the addition of recombinant FVIIa to fibroblasts did not induce VEGF secretion unless factor X was present. Moreover, thrombin and FXa induced VEGF secretion and VEGF mRNA accumulation, which were blocked by hirudin and FXa inhibitors, respectively. The effect of thrombin was mediated by its specific receptor, protease-activated receptor-1; in contrast, the effect of FXa did not appear to involve effector cell protease receptor-1, because it was not affected by an anti-effector cell protease receptor-1 antibody. An increase in intracellular calcium with the calcium ionophore A23187 or intracellular calcium chelation by BAPTA-AM had no effect on either basal or FXa-induced VEGF secretion, suggesting that the calcium signaling pathway was not sufficient to induce VEGF secretion. Finally, FVIIa, by itself, had no effect on mitogen-activated protein (MAP) kinase activation, contrary to thrombin and FXa, which activate the p44/p42 MAP kinase pathway, as shown by the blocking effect of PD 98059 and by Western blotting of activated MAP kinases. These findings indicate that FVIIa protease induction of VEGF expression is mediated by thrombin and FXa generated in response to FVIIa binding to TF-expressing fibroblasts; they also exclude a direct signaling involving MAP kinase activation via the intracellular domain of TF when expressed by these cells.
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PMID:Vascular endothelial growth factor production by fibroblasts in response to factor VIIa binding to tissue factor involves thrombin and factor Xa. 1080 56

Tissue factor (TF), apart from activating the extrinsic pathway of the blood coagulation, is a principal regulator of embryonic angiogenesis and oncogenic neoangiogenesis, but also influences inflammation, leukocyte diapedesis and tumor progression. The intracellular domain of TF lacks homology to other classes of receptors and hence the signaling mechanism is poorly understood. Here we demonstrate that factor VIIa (the natural ligand for TF) induces the activation of the Src family members c-Src, Lyn, and Yes, and subsequently phosphatidylinositol 3-kinase (PI3K), followed by stimulation of c-Akt/protein kinase B as well as the small GTPases Rac and Cdc42. In turn Rac mediates p38 mitogen-activated protein (MAP) kinase activation and cytoskeletal reorganization, whereas factor VIIa-induced p42/p44 MAP kinase stimulation required PI3K enzymatic activity but was not inhibited by dominant negative Rac proteins. We propose that this Src family member/PI3K/Rac-dependent signaling pathway is a major mediator of factor VIIa/TF effects in pathophysiology.
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PMID:Factor VIIa/tissue factor-induced signaling via activation of Src-like kinases, phosphatidylinositol 3-kinase, and Rac. 1084 1

Vascular endothelial growth factor (VEGF) is not only essential for vasculogenesis and angiogenesis but is also capable of inducing tissue factor, the prime initiator of coagulation, in endothelial cells. In this study we have analyzed the VEGF-elicited pathways involved in the induction of tissue factor in human umbilical cord vein endothelial cells. Using specific low molecular weight inhibitors we could demonstrate a crucial role of the p38 and Erk-1/2 mitogen-activated protein (MAP) kinases. In contrast, treatment with wortmannin or LY294002, inhibitors of phosphatidylinositol 3 (PI3)-kinase, resulted in a strong enhancement of the VEGF-induced tissue factor production, indicating a negative regulatory role of the PI3-kinase on tissue factor-inducing pathways. Accordingly, transduction with constitutively active Akt led to a reduction of VEGF-induced tissue factor production. Western blot analyses using antibodies specific for phosphorylated p38 showed an enhanced activation of this MAP kinase in human umbilical cord vein endothelial cells when stimulated with VEGF in the presence of wortmannin in comparison to either agent alone. Thus, the negative regulation of the PI3-kinase pathway on endothelial tissue factor activity can be explained at least in part by a suppression of this MAP kinase-signaling pathway. This is the first demonstration of a reciprocal relationship between procoagulant activity and the PI3-kinase-Akt signaling pathway, and it reveals a novel mechanism by which tissue factor expression can be controlled in endothelial cells.
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PMID:An inhibitory role of the phosphatidylinositol 3-kinase-signaling pathway in vascular endothelial growth factor-induced tissue factor expression. 1144 86

Tissue factor (TF), a transmembrane receptor for the serine protease coagulation factor VII(a) (FVIIa), is the main initiator of the coagulation cascade. Through incompletely elucidated mechanisms, TF serves additional functions in tumor-associated angiogenesis and metastasis. We have studied interleukin-8 (IL-8) as a possible link between TF-FVIIa complex formation and subsequent processes. Recombinant human FVIIa induced the up-regulation of both IL-8 mRNA and protein in a FVIIa dose- and time-dependent fashion. A neutralizing antibody to TF reduced this induction by 93 +/- 5%. Active site-inhibited FVIIa had no stimulatory effect and completely blocked that of FVIIa. This confirms that the increased IL-8 production was dependent on the formation of TF-FVIIa complexes and the proteolytic activity of FVIIa. The IL-8 promoter contains DNA binding sites for nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). In response to FVIIa, the DNA binding activity of both NF-kappaB and AP-1 was enhanced in an electrophoretic mobility shift assay. In addition, the IL-8 promoter was transcriptionally activated both in a luciferase reporter system and a nuclear run-off assay. Moreover, IL-8 mRNA stability was significantly enhanced by FVIIa-induced activation of the mitogen-activated protein kinases ERK1/2 and p38. Taken together, TF-FVIIa signaling induced increased transcription as well as mRNA stabilization leading to the significant up-regulation of IL-8 protein synthesis.
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PMID:Factor VIIa induces tissue factor-dependent up-regulation of interleukin-8 in a human keratinocyte line. 1197 37

The expression of tissue factor (TF) by monocytes that have transmigrated across the endothelium to sites of extravascular inflammation acts both to focus and amplify the inflammatory response. Because clustering of the integrins responsible for endothelial adhesion and transmigration induces tyrosine phosphorylation and activation of the mitogen-activated protein (MAP) kinases, we postulated that transmigration might lead to monocyte activation and TF production. Monocytes were migrated across TNFalpha-primed ECV304 cells grown on fibronectin-coated Transwell chambers in response to FMLP (10(-8) M). After transmigration, monocytes showed a time-dependent increase in surface TF expression and biological procoagulant activity. TF expression was dependent on monocyte adhesion to ECV304 cells. Specifically, TF was not induced by FMLP treatment of suspended monocytes, by migration across fibronectin alone, or by soluble factors induced during migration, whereas monocyte-ECV304 adhesion was sufficient to stimulate TF. Antibodies against CD29 (beta1 integrin), but not against CD18 (beta2 integrin) or CD31 (PECAM-1), inhibited TF expression. Monocyte adhesion to ECV304 cells induced tyrosine phosphorylation of cellular proteins and specifically of the ERK and p38 MAP kinases. Tyrosine kinase inhibition with genistein (10 microg/mL) blocked transmigration, whereas selective ERK inhibition with PD98059 (50 microM) or p38 inhibition with SB203580 (20 microM) did not. However, both ERK and p38 inhibition dose dependently abolished TF expression. These studies suggest that an extravascular focus of infection or inflammation can promote both intravascular thrombosis and extravascular fibrin deposition during the process of adhesion and transmigration across the endothelial barrier. The selective inhibition of the mitogen-activated protein kinases may offer a novel therapeutic means of modulating this inflammatory sequence.
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PMID:Monocyte adhesion and transmigration induce tissue factor expression: role of the mitogen-activated protein kinases. 1209 34

Vascular endothelial growth factor (VEGF) is an angiogenic hormone that increases the growth of many malignant tumors. Tissue factor (TF), the initiator of blood coagulation, is implicated in VEGF regulation. We recently reported that hemoglobin (Hb) upregulates TF on malignant cells. Therefore, to explore the role of Hb in angiogenesis, we examined its effect on VEGF production in A375 melanoma and J82 bladder carcinoma (TF+) and KG1 myeloid leukemia (TF-) cells. Hb (0.50 mg/ml) induced VEGF expression and secretion in TF+ malignant cells. VEGF secretion was inhibited by cycloheximide (85%) and the specific inhibitors of protein tyrosine kinase, genistein (71+/-0.74 and 55+/-4.90%) and mitogen-activated protein (MAP)-kinase, PD098059 (82+/-2.0 and 59+/-6.7%) in A375 and J82 cells respectively. In contrast, Hb (2.0 mg/ml) did not increase VEGF in KG1 cells. Hb-induced VEGF was purified from the culture medium of J82 cells using immunoaffinity chromatography and two isoforms (46 and 30 kd) identified. We conclude that Hb-induced synthesis of VEGF in TF-bearing malignant cells is mediated by protein tyrosine kinase and by MAP-kinase pathways.
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PMID:Hemoglobin induces the expression and secretion of vascular endothelial growth factor from human malignant cells. 1239 45

Sphingosine 1-phosphate (S1P), a bioactive lipid, is produced and stored in platelets and is released from activated platelets during blood coagulation activation. Thrombin, which is also generated during blood coagulation, has been shown to induce tissue factor (TF), the initiator of blood coagulation, in endothelial cells (ECs); however, the effect of S1P on this process is not evaluated. Here we demonstrated that S1P strongly potentiated thrombin-induced TF expression in ECs and that S1P itself did not induce TF expression. Among signaling lipids, platelet-activating factor slightly enhanced thrombin-induced TF expression; other lipids, including lysophosphatidic acid, lysophosphatidylcholine, sphingosine, and C2-ceramide exert no effect on TF expression. S1P enhanced TF expression at the transcriptional level, possibly via promoting the activation of transcription factors nuclear factor-kappaB (NF-kappaB) and Egr-1. Thrombin weakly and S1P strongly activated extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein (MAP) kinase and, in the presence of both stimulants, enhanced and sustained activation of this kinase was observed. The ERK1/2-specific inhibitor PD98059 significantly inhibited enhanced TF expression induced by both stimulants but only weakly inhibited thrombin-induced TF expression, thus indicating the requirement of the ERK1/2 pathway in synergistic induction of TF expression. In addition, we found that thrombin and S1P rapidly up-regulated the expression of S1P receptors, endothelial differentiation gene-1 (EDG-1) and EDG-3, thereby suggesting that the effect of S1P on TF expression and other EC functions may be enhanced by thrombin and S1P itself. The present data reveal the synergistic effect of S1P on thrombin-induced TF expression in ECs, which may promote further thrombin and S1P generation, thus propagating a positive feedback reaction.
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PMID:Synergistic effect of sphingosine 1-phosphate on thrombin-induced tissue factor expression in endothelial cells. 1273 Jan

Matrix metalloproteinase-9 (MMP-9) plays a crucial role in both angiogenesis and tumor invasion. Vascular endothelial growth factor (VEGF) has been shown to up-regulate the expression of MMP-9 in vascular smooth muscle cells. We recently reported that hemoglobin (Hb) enhances the expression of tissue factor (TF) and VEGF on TF-positive human malignant cells. Therefore, to explore the relationship between tumor cell angiogenic protein VEGF and MMP-9, we studied the effect of Hb on MMP-9 production in human A375 malignant melanoma and J82 bladder carcinoma (TF+) cells and in KG1 myeloid leukemia (TF-) cells. Malignant cells were incubated with varying concentrations (0-1.0 mg/ml) of Hb and analyzed for released MMP-9 by gelatin zymography, dot immunoblotting, enzyme-linked immunosorbent assay, and Western blotting. Hb (0.50 mg/ml) induced an almost two-fold increase of MMP-9 in both A375 malignant melanoma (398 +/- 62 versus 233 +/- 61.0 ng/ml, P = 0.027) and J82 bladder carcinoma cells (1.55 +/- 0.12 versus 0.80 +/- 0.004 ng/ml, P = 0.004), compared with cells incubated without Hb. This release of MMP-9 was significantly inhibited by cycloheximide (95%) and by the specific inhibitors of protein tyrosine kinase, genistein (70 +/- 3.0%, P = 0.00027 and 67 +/- 1.0%, P = 0.00005) and mitogen-activated protein (MAP)-kinase, PD98059 (56 +/- 2.0%, P = 0.0001 and 62 +/- 1.0%, P = 0.00003) in A375 and J82 cells, respectively. In contrast, Hb (2.0 mg/ml) did not increase MMP-9 in KG1 cells. We conclude that Hb-induced synthesis of active MMP-9 in TF-bearing malignant cells is due to de novo synthesis of newly formed protein and is mediated by protein tyrosine kinase and by mitogen-activated protein kinase pathways.
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PMID:Hemoglobin induces the production and release of matrix metalloproteinase-9 from human malignant cells. 1285 30


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