Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Both hyaluronidase and transforming growth factor (TGF)-beta 1 play a significant role in the development of prostate cancer. In this study, the regulation of tumor necrosis factor (TNF)-mediated cell death by hyaluronidase and TGF-beta 1 was investigated. Preexposure of L929 fibroblasts, prostate LNCaP cells, and epithelial Mv 1 Lu cells to hyaluronidase for a minimum of 12 h resulted in significant enhancement of cell death by TNF. Phosphorylation of p42 and p44 mitogen-activated-protein (MAP) kinases was found by stimulation of L929 cells with hyaluronidase for 30 min, indicating that the Raf/MAP kinase-extracellular signal-regulating protein kinase (MEK)/ MAP kinase pathway was activated. However, blocking the activation of upstream MAP kinase kinase (MEK 1 and 2 kinase) by PD-98059 failed to inhibit the hyaluronidase-enhanced TNF killing of cells, suggesting that hyaluronidase-mediated degradation of extracellular matrix and membrane components may elicit multiple signaling pathways. As a potent stimulator of extracellular matrix protein synthesis, TGF-beta 1 blocked the hyaluronidase-enhanced death of L929 and LNCaP cells mediated by TNF. TGF-beta 1 activated protein-tyrosine kinases in L929 cells, in which the tyrosine kinase inhibitors lavendustin A and tyrphostin blocked the activation as well as the TGF-beta 1 inhibition of hyaluronidase effects. Functional antagonism was also observed between hyaluronidase and TGF-beta 1 in cell growth regulation. For example, TGF-beta 1-mediated suppression of epithelial Mv 1 Lu cell growth was abolished by hyaluronidase. Overall, it is demonstrated in this study that hyaluronidase reciprocally antagonized TGF-beta 1 in the modulation of cell proliferation and TNF-mediated death.
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PMID:Hyaluronidase enhancement of TNF-mediated cell death is reversed by TGF-beta 1. 943 5

Inflammatory cytokines tumor necrosis factor-alpha and interleukin-1 trigger the ceramide signaling pathway, initiated by neutral sphingomyelinase-elicited hydrolysis of cell membrane phospholipid sphingomyelin to ceramide, a new lipid second messenger. Here, we show that triggering the ceramide pathway by sphingomyelinase or C2- and C6-ceramide enhances collagenase-1 (matrix metalloproteinase-1; MMP-1) gene expression by fibroblasts. C2-ceramide activates three distinct mitogen-activated protein kinases (MAPKs) in dermal fibroblasts, i.e. extracellular signal-regulated kinase 1/2 (ERK1/2), stress-activated protein kinase/Jun N-terminal-kinase (SAPK/JNK), and p38. Stimulation of MMP-1 promoter activity by C2-ceramide is dependent on the presence of a functional AP-1 cis-element and is entirely inhibited by overexpression of MAPK inhibitor, dual specificity phosphatase CL100 (MAPK phosphatase-1). Activation of MMP-1 promoter by C2-ceramide is also effectively inhibited by kinase-deficient forms of ERK1/2 kinase (MEK1/2) activator Raf-1, ERK1 and ERK2, SAPK/JNK activator SEK1, or SAPKbeta. In addition, ceramide-dependent induction of MMP-1 expression is potently prevented by PD 98059, a selective inhibitor of MEK1 activation, and by specific p38 inhibitor SB 203580. These results show that triggering the ceramide signaling pathway activates MMP-1 gene expression via three distinct MAPK pathways, i.e. ERK1/2, SAPK/JNK, and p38, and suggest that targeted modulation of the ceramide signaling pathway may offer a novel therapeutic approach for inhibiting collagenolytic activity, e.g. in inflammatory disorders.
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PMID:Enhancement of fibroblast collagenase (matrix metalloproteinase-1) gene expression by ceramide is mediated by extracellular signal-regulated and stress-activated protein kinase pathways. 947 67

Several inflammatory effects of tumor necrosis factor (TNF) are known to be mediated through activation of a nuclear transcription factor NF-kappaB, but how TNF activates NF-kappaB is incompletely understood. In the present report, we examined the role of protein tyrosine kinases (PTK) in TNF-mediated NF-kappaB activation by using genistein and erbstatin, two potent inhibitors of PTK. The treatment of human myeloid U-937 cells with either inhibitor completely suppressed the TNF-induced NF-kappaB activation in a dose- and time-dependent manner. Suppression correlated with PTK activity, since among the structural analogues of genistein, only an active inhibitor of PTK, quercetin blocked TNF-induced NF-kappaB activation and not daidzein, an inactive inhibitor. Inhibition of NF-kappaB activation was not limited to myeloid cells, as it was observed with T cells and epithelial cells. Both the PTK inhibitors blocked the degradation of IkappaBalpha, the inhibitory subunit of NF-kappaB, and the consequent translocation of the p65 subunit without any significant effect on p50 or on c-Rel. The PTK inhibitors did not interfere with NF-kappaB binding to DNA. The NF-kappaB-dependent CAT reporter gene expression in transient transfection assays was also suppressed by the PTK inhibitors. Both PTK inhibitors abolished TNF-induced activation of N-terminal c-Jun kinase and mitogen-activated protein kinase kinase. Overall, our results suggest that a genistein- and erbstatin-sensitive PTK is involved in the pathway leading to NF-kappaB activation and gene expression by TNF and thus could be used as a target for development of antiinflammatory drugs.
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PMID:Protein tyrosine kinase inhibitors block tumor necrosis factor-induced activation of nuclear factor-kappaB, degradation of IkappaBalpha, nuclear translocation of p65, and subsequent gene expression. 952 14

We report the cloning of a novel human activator of c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase kinase 7 (MKK7). The mRNA for MKK7 is widely expressed in humans and mice and encodes a 47-kDa protein (419 amino acids), as determined by immunoblotting endogenous MKK7 with an antibody raised against its N terminus. The kinase domain of MKK7 is closely related to a Drosophila JNK kinase dHep (69% identity) and to a newly identified ortholog from Caenorhabditis elegans (54% identity), and was more distantly related to MKK4, MKK3, and MKK6. MKK7 phosphorylated and activated JNK1 but failed to activate p38 MAPK in co-expression studies. In hematopoietic cells, endogenous MKK7 was activated by treatment with the growth factor interleukin-3 (but not interleukin-4), or by ligation of CD40, the B-cell antigen receptor, or the receptor for the Fc fragment of immunoglobulin. MKK7 was also activated when cells were exposed to heat, UV irradiation, anisomycin, hyperosmolarity or the pro-inflammatory cytokine tumor necrosis factor-alpha. Co-expression of constitutively active mutants of RAS, RAC, or CDC42 in HeLa epithelial cells or of RAC or CDC42 in Ba/F3 factor-dependent hematopoietic cells also activated MKK7, suggesting that MKK7 will be involved in many physiological pathways.
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PMID:Human mitogen-activated protein kinase kinase 7 (MKK7) is a highly conserved c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activated by environmental stresses and physiological stimuli. 953 30

Several recently identified intracellular proteins associate with the tumor necrosis factor (TNF) receptor and activate nuclear transcription factor (NF)-kappaB, c-Jun kinase, and apoptosis. However, the mechanism is not understood. In the present report, we investigated the role of reactive oxygen intermediates in TNF-induced signaling. Overexpression of manganese superoxide dismutase (Mn-SOD) in human breast cancer MCF-7 cells completely abolished TNF-mediated NF-kappaB activation, IkappaB alpha degradation, p65 nuclear translocation, and NF-kappaB-dependent reporter gene expression. Besides TNF, phorbol ester-, okadaic acid-, ceramide-, and lipopolysaccharide-induced activation of NF-kappaB was blocked by Mn-SOD, indicating a common pathway of activation. H2O2-induced NF-kappaB activation, however, was potentiated. In addition, Mn-SOD blocked the TNF-mediated activation of activated protein-1, stress-activated c-Jun protein kinase, and mitogen-activated protein kinase kinase. TNF-induced antiproliferative effects and caspase-3 activation, indicators of apoptosis, were also completely suppressed by transfection of cells with Mn-SOD. Suppression of apoptosis induced by okadaic acid, H2O2, and taxol was also inhibited by Mn-SOD but not that induced by vincristine, vinblastine, or daunomycin. Overall, these results demonstrate that, in addition to several recently identified signaling molecules, reactive oxygen intermediates play a critical role in activation of NF-kappaB, activated protein-1, c-Jun kinase, and apoptosis induced by TNF and other agents.
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PMID:Overexpression of manganese superoxide dismutase suppresses tumor necrosis factor-induced apoptosis and activation of nuclear transcription factor-kappaB and activated protein-1. 958 69

The effect of stress on the production of cytokine-induced neutrophil chemoattractant (CINC) was examined in rat C6 glioma cells. We studied the production of CINC, an interleukin-8 (IL-8) family protein, with bacterial endotoxin, H2O2, and tumor necrosis factor-alpha (TNF-alpha). Each stress induced CINC mRNA in a concentration-dependent manner. Since stress activates the protein kinases regulating nuclear transcription factors, we examined the effects of protein kinase inhibitors and the over-expression of dominant-negative Ras on CINC mRNA expression. Neither over-expression of dominant-negative Ras nor pretreatment with PD98059 (MEK-1 inhibitor), SB203580 (p38MAPK inhibitor), or GF109203X (protein kinase C (PKC) inhibitor) altered stress-induced CINC mRNA expression. This suggests that the Ras-MAPK, p38MAPK, and PKC pathways are not involved in CINC mRNA expression in glial cells. On the other hand, pretreatment with herbimycin A, a potent tyrosine kinase inhibitor, or Ro31-8220, a non-selective serine/threonine kinase inhibitor, suppressed stress-induced CINC mRNA expression. This indicates that stress-induced CINC mRNA expression is mediated by herbimycin A-, or Ro31-8220-sensitive kinases in glial cells. Since stress activates NF-kappaB and NF-IL6, we examined that the effect of herbimycin A, which suppresses CINC mRNA expression, on NF-kappaB and NF-IL6 activation. Herbimycin A suppressed NF-kappaB but not NF-IL6. These results suggest that in rat glial cells, the factors that induce CINC mRNA expression are mediated by herbimycin A-sensitive NF-kappaB activation, but not through the PKC, Ras-MAPK or p38 MAPK pathways.
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PMID:Induction of cytokine-induced neutrophil chemoattractant in response to various stresses in rat C6 glioma cells. 959 44

The pathways involved in the cellular responses to the insulin-like growth factors (IGFs) are numerous and vary according to cell type. Following activation of the IGF-I receptor, the mitogen-activated protein kinase and phosphatidylinositide 3'-kinase (PI3'K) pathways are activated and result in cellular proliferation and inhibition of apoptosis. In this study, we analyzed the IGF-I effect on the stress-activated protein kinase/c-Jun N-terminal kinase (JNK) activity using human embryonic kidney 293 cells, 293 cells transiently expressing hemagglutinin-JNK, and 293 cells stably expressing a hemagglutinin-JNK transgene. In all cell types, endogenous or transfected JNK activity was strongly stimulated by anisomycin or tumor necrosis factor-alpha, and 10 nM IGF-I pretreatment suppressed the induced JNK activity. To determine whether the effect of IGF-I on JNK activity involves the mitogen-activated protein kinase or PI3'K pathway, we used the specific MEK1 inhibitor PD098059 and the PI3'K inhibitor LY 294002. PD098059 did not alter the IGF-I suppressive effect on stressor-induced JNK activity, but LY 294002 suppressed the IGF-I effect. Moreover, in transiently transfected parental 293 cells expressing dominant-negative Akt, anisomycin-increased JNK activity was not suppressed by pretreatment with IGF-I. Our results demonstrate that the action of IGF-I on JNK in these cells is via PI3'K and Akt.
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PMID:Insulin-like growth factor-I inhibits the stress-activated protein kinase/c-Jun N-terminal kinase. 974 73

The stress-activated protein kinase (SAPK) and mitogen-activated protein kinase (MAPK) cascades mediate cytotoxic and cytoprotective functions, respectively, in the regulation of leukemic cell survival. Involvement of these signaling systems in the cytotoxicity of 1-beta-D-arabinofuranosylcytosine (ara-C) and modulation of ara-C lethality by protein kinase C PKC inhibition/down-regulation was examined in HL-60 promyelocytic leukemia cells. Exposure to ara-C (10 microM) for 6 hr promoted extensive apoptotic DNA damage and cell death, as well as activation of PKC. This response was accompanied by downstream activation of the SAPK and MAPK cascades. PKC-dependent MAPK activity seemed to limit ara-C action in that the toxicity of ara-C was enhanced by pharmacological reductions of PKC, MAPK, or both. Thus, ara-C action was (1) partially attenuated by diradylglycerols, which stimulated PKC and MAPK, but (2) dramatically amplified by sphingoid bases, which inhibited PKC and MAPK. The cytotoxicity of ara-C also was substantially increased by pharmacological reductions of PKC, including down-regulation of PKC by chronic preexposure to the macrocyclic lactone bryostatin 1 or inhibition of PKC by acute coexposure to the dihydrosphingosine analog safingol. Significantly, both of these manipulations prevented activation of MAPK by ara-C. Moreover, acute disruption of the MAPK module by AMF, a selective inhibitor of MEK1, suppressed both basal and drug-stimulated MAPK activity and sharply increased the cytotoxicity of ara-C, suggesting the direct involvement of MAPK as a downstream antiapoptotic effector for PKC. None of these chemopotentiating agents enhanced ara-CTP formation. Ceramide-driven SAPK activity did not seem to mediate drug-induced apoptosis, given that (1) neutralization of endogenous tumor necrosis factor-alpha with monoclonal antibodies or soluble tumor necrosis factor receptor substantially reduced ceramide generation and SAPK activation by ara-C, whereas the induction of apoptosis was unaffected; (2) pharmacological inhibition of sphingomyelinase by 3-O-methoxysphingomyelin reduced ceramide generation and SAPK activation without limiting the drug's cytotoxicity; and (3) potentiation of ara-C action by bryostatin 1 or safingol was not associated with further stimulation of SAPK. These observations collectively suggest a primary role for decreased MAPK, rather than increased SAPK, in the potentiation of ara-C cytotoxicity by interference with PKC-dependent signaling.
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PMID:Evidence for involvement of mitogen-activated protein kinase, rather than stress-activated protein kinase, in potentiation of 1-beta-D-arabinofuranosylcytosine-induced apoptosis by interruption of protein kinase C signaling. 980 19

The putative core protein of hepatitis C virus (HCV) regulates cellular growth and a number of cellular promoters. To further understand its effect, we investigated the role of the core protein in the endogenous regulation of two distinct transcription factors, nuclear factor-kappaB (NF-kappaB) and activating protein-1 (AP-1), and the related mitogen-activated protein kinase kinase (MAPKK) and c-Jun N-terminal kinase (JNK). Stable cell transfectants expressing the HCV core protein suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation. Supershift analysis revealed that NF-kappaB consists of p50 and p65 subunits. This correlated with inhibition of the degradation of IkappaBalpha, the inhibitory subunit of NF-kappaB. The effect was not specific to TNF, as suppression in core protein-expressing cells was also observed in response to a number of other inflammatory agents known to activate NF-kappaB. In contrast to the effect on NF-kappaB, the HCV core protein constitutively activated AP-1, which correlated with the activation of JNK and MAPKK, which are known to regulate AP-1. These observations indicated that the core protein targets transcription factors known to be involved in the regulation of inflammatory responses and the immune system.
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PMID:Ectopic expression of hepatitis C virus core protein differentially regulates nuclear transcription factors. 981 6

To clarify the differences of the signaling pathways used by granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor- (TNF), we investigated activation of mitogen-activated protein kinase (MAPK) subtype cascades in human neutrophils stimulated by these cytokines. G-CSF exclusively tyrosine-phosphorylated extracellular signal-regulated kinase (ERK). GM-CSF tyrosine-phosphorylated ERK strongly and p38 MAPK weakly, whereas TNF tyrosine-phosphorylated p38 MAPK strongly and ERK weakly. Consistent with these findings, MEK, an upstream kinase of ERK, was phosphorylated by G-CSF, GM-CSF, and TNF, whereas MKK3/MKK6, an upstream kinase of p38 MAPK, was phosphorylated by GM-CSF and TNF, but not by G-CSF. The potency of these cytokines to phosphorylate ERK and MEK was GM-CSF > G-CSF > TNF, whereas that to phosphorylate p38 MAPK and MKK3/MKK6 was TNF > GM-CSF. C-Jun amino-terminal kinase (JNK) was not tyrosine-phosphorylated by any cytokine despite the existence of JNK proteins in human neutrophils, whereas it was tyrosine-phosphorylated by TNF in undifferentiated and all-trans retinoic acid-differentiated HL-60 cells. Increased phosphorylation of ERK or p38 MAPK was detected within 1 to 5 minutes after stimulation with each cytokine and was dependent on the concentrations of cytokines used. MEK inhibitor (PD98059) reduced tyrosine phosphorylation of ERK, but not p38 MAPK, induced by G-CSF, GM-CSF, or TNF. GM-CSF- or TNF-induced superoxide (O2-) release was inhibited by p38 MAPK inhibitor (SB203580) in a dose-dependent manner, suggesting the possible involvement of p38 MAPK in GM-CSF- or TNF-induced O2- release. The results indicate that G-CSF, GM-CSF, and TNF activate the overlapping but distinct MAPK subtype cascades in human neutrophils and suggest that the differential activation of ERK and p38 MAPK cascades may explain the differences of the effects of these cytokines on human neutrophil functions.
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PMID:Cytokine-specific activation of distinct mitogen-activated protein kinase subtype cascades in human neutrophils stimulated by granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha. 986 79


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