Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have reported that the selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib ('Iressa', ZD1839), suppressed intrahepatic metastasis of hepatocellular carcinoma CBO140C12 cells. In this study, we focused on the tumour necrosis factor-alpha (TNF-alpha) signalling pathways. Real-time reverse transcription-polymerase chain reaction showed that TNF-alpha mRNA was expressed in large quantities in the implanted tumour. Gefitinib inhibited EGF- but not hepatocyte growth factor (HGF)-induced activation of mitogen-activated protein kinase (MAPK) cascades, suggesting selectivity of the inhibitor. However, gefitinib inhibited the TNF-alpha-induced activation of MAPKs and Akt. In addition, TNF-alpha-induced metastatic properties including adhesion to fibronectin, mRNA expression of integrin alpha v, production of matrix metalloproteinase-9 and invasion were inhibited by gefitinib without affecting cell proliferation. Furthermore, the TNF-alpha-induced responses except for NF-kappaB activation were blocked by metalloprotease inhibitors, suggesting that gefitinib inhibited the transactivation of EGFR induced by TNF-alpha. These results suggest that the TNF-alpha signalling pathway is a possible target of gefitinib in suppressing the intrahepatic metastasis of hepatocellular carcinoma.
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PMID:Selective inhibition of TNF-alpha-induced activation of mitogen-activated protein kinases and metastatic activities by gefitinib. 1584 Oct 81

Matrix metalloprotease-13 (MMP-13) or collagenase-3 is involved in a number of pathologic processes such as tumor metastasis and angiogenesis, osteoarthritis, rheumatoid arthritis and periodontal diseases. These conditions are associated with extensive degradation of both connective tissue and bone. This report examines gene regulation mechanisms and signal transduction pathways involved in Mmp-13 expression induced by proinflammatory cytokines in periodontal ligament (PDL) fibroblasts. Mmp-13 mRNA expression was increased 10.7 and 9.5 fold after stimulation with IL-1beta (5 ng/mL) and TNF-alpha (10 ng/mL), respectively. However, inhibition of p38 MAPKinase with SB203580 resulted in significant (p<0.001) induction (23.2 and 18.1 fold, respectively) of Mmp-13 mRNA as assessed by real time PCR. Negative regulation of IL-1beta induced Mmp-13 expression was confirmed by inhibiting p38 MAPK gene expression with siRNA. Transient transfection of dominant negative forms of MKK3 and MKK6 also resulted in increased levels of Mmp-13 mRNA after IL-1beta stimulation. Mmp-13 mRNA expression induced by TNF-alpha was decreased by JNK and ERK inhibition. Western blot and zymogram analysis indicated that Mmp-13 protein expression induced by the proinflammatory cytokines were also upregulated by inhibition of p38 MAPK. Reporter gene experiments using stable cell lines harboring 660-bp sequence of the murine Mmp-13 proximal promoter indicated that transcriptional mechanisms were at least partially involved in this negative regulation of Mmp-13 expression by p38 MAPK and upstream MKK3/6. These results suggest a negative transcriptional regulatory mechanism mediated by p38 MAPK and upstream MKK3/6 on Mmp-13 expression induced by proinflammatory cytokines in PDL fibroblasts.
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PMID:MKK3/6-p38 MAPK negatively regulates murine MMP-13 gene expression induced by IL-1beta and TNF-alpha in immortalized periodontal ligament fibroblasts. 1604 11

Inhibition of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, by the irreversible inhibitor alpha-difluoromethylornithine (DFMO) has been shown to decrease the invasiveness of metastatic human breast cancer cell lines. However, the mechanism by which DFMO acts to reduce invasiveness is unclear. Using the human breast cancer cell line MDA-MB-435, the effect of DFMO on metalloprotease gene expression was investigated. DFMO treatment decreases the expression of the metalloprotease meprin alpha, while concurrent treatment with DFMO and the polyamine putrescine partially restored meprin alpha expression levels. Expression of MMP-7 mRNA was reduced by DFMO, while MMPs-1, -2, -3, -14, and meprin beta were unaffected. Treatment of cells with a second inhibitor of polyamine biosynthesis, the S-adenosylmethionine decarboxylase (SAMDC) inhibitor SAM486A, also resulted in a dosage dependent decrease in meprin alpha and MMP-7 mRNA. In addition, DFMO treatment decreased meprin alpha at the protein level by 2 days of treatment, and MMP-7 protein levels at 4 and 6 days. Previous studies have shown that DFMO treatment increases ERK phosphorylation and signaling through the MAP kinase pathway. The decrease in meprin alpha expression was reversed with the MEK inhibitor PD98059, demonstrating that MAP kinase signaling mediates the effect of DFMO and SAM486A. MDA-MB-435 cells treated with the meprin alpha inhibitor actinonin (5 nM) were less invasive in vitro, indicating that meprin alpha is mechanistically involved in invasion. The decrease in meprin alpha expression in DFMO and SAM486A-treated cells indicates a means by which these compounds can decrease the invasiveness of metastatic breast cancer cells.
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PMID:Inhibitors of polyamine biosynthesis decrease the expression of the metalloproteases meprin alpha and MMP-7 in hormone-independent human breast cancer cells. 1617 Jun 69

Pulmonary cavitation is vital to the persistence and spread of Mycobacterium tuberculosis (MTb), but mechanisms underlying this lung destruction are poorly understood. Fibrillar type I collagen provides the lung's tensile strength, and only matrix metalloproteinases (MMPs) can degrade it at neutral pH. We investigated MTb-infected lung tissue and found that airway epithelial cells adjacent to tuberculosis (Tb) granulomas expressed a high level of MMP-1 (interstitial collagenase). Conditioned media from MTb-infected monocytes (CoMTb) up-regulated epithelial cell MMP-1 promoter activity, gene expression, and secretion, whereas direct MTb infection did not. CoMTb concurrently suppressed tissue inhibitor of metalloprotease-1 (TIMP-1) secretion, further promoting matrix degradation, and in Tb patients very low TIMP-1 expression was detected. MMP-1 up-regulation required synergy between TNF-alpha and G protein-coupled receptor signaling pathways. CoMTb stimulated p38 MAPK phosphorylation, and this is the point of TNF-alpha synergy with G protein-coupled receptor activation. Furthermore, p38 phosphorylation was the switch up-regulating MMP-1 activity and decreasing TIMP-1 secretion. Activated p38 localized to MMP-1-secreting airway epithelial cells in Tb patients. These data reveal a monocyte-epithelial cell network whereby MTb may drive tissue destruction, and they demonstrate that p38 phosphorylation is a key regulatory point in the generation of a matrix-degrading phenotype.
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PMID:Mycobacterium tuberculosis up-regulates matrix metalloproteinase-1 secretion from human airway epithelial cells via a p38 MAPK switch. 1621 Jun 39

Vascular endothelial dysfunction is thought to play a prominent role in systemic anthrax pathogenesis. We examined the effect of anthrax lethal toxin (LTx), a key virulence factor of Bacillus anthracis, on the expression of vascular cell adhesion molecule-1 (VCAM-1) on normal and cytokine-stimulated human lung microvascular endothelial cells. Confluent endothelial monolayers were treated with lethal factor (LF), protective antigen (PA), or both (LTx) in the presence or absence of tumor necrosis factor-alpha (TNFalpha). LTx enhanced cytokine-induced VCAM-1 expression and monocyte adhesion. LTx alone had no effect on VCAM-1 expression. LF, PA or the combination of a catalytically inactive mutant LF and PA failed to enhance cytokine-induced VCAM-1 expression. Treatment with inhibitors of mitogen-activated protein kinase kinases (MEKs) and mitogen-activated protein kinases did not reproduce the VCAM-1 enhancement effect of LTx, a known MEK metalloprotease, suggesting LTx-mediated MEK cleavage may not be a contributing factor.
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PMID:Anthrax lethal toxin enhances cytokine-induced VCAM-1 expression on human endothelial cells. 1624 17

The neural cell adhesion molecule (NCAM) plays a key role in neural development, regeneration and synaptic plasticity. This study describes a novel function of NCAM140 in stimulating integrin-dependent cell migration. Expression of NCAM140 in rat B35 neuroblastoma cells resulted in increased migration toward the extracellular matrix proteins fibronectin, collagen IV, vitronectin, and laminin. NCAM-potentiated cell migration toward fibronectin was dependent on beta1 integrins and required extracellular-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) activity. NCAM140 in B35 neuroblastoma cells was subject to ectodomain cleavage resulting in a 115 kDa soluble fragment released into the media and a 30 kDa cytoplasmic domain fragment remaining in the cell membrane. NCAM140 ectodomain cleavage was stimulated by the tyrosine phosphatase inhibitor pervanadate and inhibited by the broad spectrum metalloprotease inhibitor GM6001, characteristic of a metalloprotease. Moreover, treatment of NCAM140-B35 cells with GM6001 reduced NCAM140-stimulated cell migration toward fibronectin and increased cellular attachment to fibronectin to a small but significant extent. These results suggested that metalloprotease-induced cleavage of NCAM140 from the membrane promotes integrin- and ERK1/2-dependent cell migration to extracellular matrix proteins.
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PMID:NCAM140 stimulates integrin-dependent cell migration by ectodomain shedding. 1627 15

The causative agent of anthrax, Bacillus anthracis, produces two toxins that contribute in part to its virulence. Lethal toxin is a metalloprotease that cleaves upstream mitogen-activated protein kinase kinases. Edema toxin is a calmodulin-dependent adenylate cyclase. Previous studies demonstrated that the anthrax toxins are important immunomodulators that promote immune evasion of the bacterium by suppressing activation of macrophages and dendritic cells. Here we showed that injection of sublethal doses of either lethal or edema toxin into mice directly inhibited the subsequent activation of T lymphocytes by T-cell receptor-mediated stimulation. Lymphocytes were isolated from toxin-injected mice after 1 or 4 days and stimulated with antibodies against CD3 and CD28. Treatment with either toxin inhibited the proliferation of T cells. Injection of lethal toxin also potently inhibited cytokine secretion by stimulated T cells. The effects of edema toxin on cytokine secretion were more complex and were dependent on the length of time between the injection of edema toxin and the isolation of lymphocytes. Treatment with lethal toxin blocked multiple kinase signaling pathways important for T-cell receptor-mediated activation of T cells. Phosphorylation of the extracellular signal-regulated kinase and the stress-activated kinase p38 was significantly decreased. In addition, phosphorylation of the serine/threonine kinase AKT and of glycogen synthase kinase 3 was inhibited in T cells from lethal toxin-injected mice. Thus, anthrax toxins directly act on T lymphocytes in a mouse model. These findings are important for future anthrax vaccine development and treatment.
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PMID:Direct inhibition of T-lymphocyte activation by anthrax toxins in vivo. 1629 24

Nr-CAM, a cell-cell adhesion molecule of the immunoglobulin-like cell adhesion molecule family, known for its function in neuronal outgrowth and guidance, was recently identified as a target gene of beta-catenin signaling in human melanoma and colon carcinoma cells and tissue. Retrovirally mediated transduction of Nr-CAM into fibroblasts induces cell motility and tumorigenesis. We investigated the mechanisms by which Nr-CAM can confer properties related to tumor cell behavior and found that Nr-CAM expression in NIH3T3 cells protects cells from apoptosis in the absence of serum by constitutively activating the extracellular signal-regulated kinase and AKT signaling pathways. We detected a metalloprotease-mediated shedding of Nr-CAM into the culture medium of cells transfected with Nr-CAM, and of endogenous Nr-CAM in B16 melanoma cells. Conditioned medium and purified Nr-CAM-Fc fusion protein both enhanced cell motility, proliferation, and extracellular signal-regulated kinase and AKT activation. Moreover, Nr-CAM was found in complex with alpha4beta1 integrins in melanoma cells, indicating that it can mediate, in addition to homophilic cell-cell adhesion, heterophilic adhesion with extracellular matrix receptors. Suppression of Nr-CAM levels by small interfering RNA in B16 melanoma inhibited the adhesive and tumorigenic capacities of these cells. Stable expression of the Nr-CAM ectodomain in NIH3T3 cells conferred cell transformation and tumorigenesis in mice, suggesting that the metalloprotease-mediated shedding of Nr-CAM is a principal route for promoting oncogenesis by Nr-CAM.
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PMID:The shed ectodomain of Nr-CAM stimulates cell proliferation and motility, and confers cell transformation. 1635 71

We have shown that the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib ('Iressa', ZD1839) inhibits the development of intrahepatic metastases of hepatocellular carcinoma CBO140C12, and EGFR transactivation by tumor necrosis factor-alpha is a possible target of gefitinib. In the present study, we focused on the fibronectin (FN)-dependent signaling pathway to further elucidate the antimetastatic activity of gefitinib in CBO140C12 cells. We initially observed that FN induced activation of extracellular signal-regulated kinase (ERK), p38 and Akt, as well as cell proliferation and CBO140C12 cell invasion. These responses were mediated by EGFR tyrosine kinase, because gefitinib inhibited these effects of FN. FN-induced ERK, p38 and Akt activation was partly blocked by the Arg-Gly-Asp (RGD)-pseudo-peptide FC-336, anti-alphav integrin antibody RMV-7, the broad-spectrum matrix metalloprotease inhibitor GM6001 and the broad spectrum a disintegrin and metalloprotease (ADAM) inhibitor TAPI-1. But these inhibitors had no effect on EGF-induced signaling pathways, suggesting that integrins and ADAM may be upstream components of EGFR in these responses. These results suggest that FN-induced activation of ERK, p38, Akt, cell proliferation and invasion was mediated, at least in part, via integrins, ADAM and EGFR, and that this FN-induced signaling pathway might be involved in the antimetastatic activity of gefitinib.
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PMID:Activation of MEK/ERK and PI3K/Akt pathways by fibronectin requires integrin alphav-mediated ADAM activity in hepatocellular carcinoma: a novel functional target for gefitinib. 1644 27

Many bacterial toxins act on conserved components of essential host-signaling pathways. One consequence of this conservation is that genetic model organisms such as Drosophila melanogaster can be used for analyzing the mechanism of toxin action. In this study, we characterize the activities of two anthrax virulence factors, lethal factor (LF) and edema factor, in transgenic Drosophila. LF is a zinc metalloprotease that cleaves and inactivates most human mitogen-activated protein kinase (MAPK) kinases (MAPKKs). We found that LF similarly cleaves the Drosophila MAPK kinases Hemipterous (Hep) and Licorne in vitro. Consistent with these observations, expression of LF in Drosophila inhibited the Hep/c-Jun N-terminal kinase pathway during embryonic dorsal closure and the related process of adult thoracic closure. Epistasis experiments confirmed that LF acts at the level of Hep. We also found that LF inhibits Ras/MAPK signaling during wing development and that LF acts upstream of MAPK and downstream of Raf, consistent with LF acting at the level of Dsor. In addition, we found that edema factor, a potent adenylate cyclase, inhibits the hh pathway during wing development, consistent with the known role of cAMP-dependent PKA in suppressing the Hedgehog response. These results demonstrate that anthrax toxins function in Drosophila as they do in mammalian cells and open the way to using Drosophila as a multicellular host system for studying the in vivo function of diverse toxins and virulence factors.
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PMID:Anthrax lethal factor and edema factor act on conserved targets in Drosophila. 1649 49


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