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)

The s-Myc is similar to c-Myc in its ability to induce apoptosis requiring caspase activation. However, s-Myc is distinct from c-Myc in that it has activity to suppress tumor growth and does not require wild-type p53 to induce apoptosis. These facts suggest differential regulation between s-Myc and c-Myc. Here we showed that s-Myc-mediated apoptosis triggered by UV was not inhibited by the inactive form mutant JNK (APF), though c-Myc-mediated apoptosis was. Moreover, we found that JNK did not affect the transactivation activity of s-Myc, but stimulated that of c-Myc. In contrast, both Myc-mediated apoptosis and caspase-3-like protease activation were suppressed by kinase-negative MKK6 and an inactive form mutant p38(AGF). Our results indicate that s-Myc does not require the JNK signaling unlike c-Myc during UV-triggered apoptosis, but the MKK6/p38MAPK pathway might regulate common apoptotic machinery for both s-Myc and c-Myc upstream of caspase.
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PMID:Differential role of the JNK and p38 MAPK pathway in c-Myc- and s-Myc-mediated apoptosis. 1062 2

Chemotherapeutic drugs and energy-rich radiation cause DNA damage, inducing signaling pathways for apoptotic cell death or cell growth arrest. The tumor suppressor gene p53 plays the critical role in the regulation of these DNA damage responses. Human tumor cells can become resistant to chemotherapy through functional inactivation of p53. Thus, it is important to identify p53-independent DNA damage signaling pathways. Here, treatment of cells with chemotherapeutic drugs or UV irradiation potentiated the transcriptional activity of IFN regulatory factor-7 (IRF7), inducing its phosphorylation and its nuclear translocation. Furthermore, IRF7 was activated by the c-Jun NH2-terminal kinase (JNK) in response to DNA-damaging agents. Activation of JNK by mitogen-activated protein kinase kinase-4 stimulated the transcriptional activity of IRF7 and induced its translocation into the nucleus. Thus, activation of IRF7 through the JNK signaling pathway may play a role in the transcriptional regulation of genes in response to DNA-damaging agents.
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PMID:Chemotherapeutic DNA-damaging drugs activate interferon regulatory factor-7 by the mitogen-activated protein kinase kinase-4-cJun NH2-terminal kinase pathway. 1072 64

The tumour suppressor p53 inhibits cell growth through activation of cell-cycle arrest and apoptosis, and most cancers have either mutation within the p53 gene or defects in the ability to induce p53. Activation or re-introduction of p53 induces apoptosis in many tumour cells and may provide effective cancer therapy. One of the key proteins that modulates the apoptotic response is NF-kappaB, a transcription factor that can protect or contribute to apoptosis. Here we show that induction of p53 causes an activation of NF-kappaB that correlates with the ability of p53 to induce apoptosis. Inhibition or loss of NF-kappaB activity abrogated p53-induced apoptosis, indicating that NF-kappaB is essential in p53-mediated cell death. Activation of NF-kappaB by p53 was distinct from that mediated by tumour-necrosis factor-alpha and involved MEK1 and the activation of pp90rsk. Inhibition of MEK1 blocked activation of NF-kappaB by p53 and completely abrogated p53-induced cell death. We conclude that inhibition of NF-kappaB in tumours that retain wild-type p53 may diminish, rather than augment, a therapeutic response.
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PMID:Role of NF-kappaB in p53-mediated programmed cell death. 1078 98

In a previous work we have reported evidences on the mitogenic activity of urokinase-type and tissue-type plasminogen activator (u-PA, t-PA) on serum-deprived human dermal fibroblasts. In this work we have studied the transcription-dependent changes of some cell-cycle related genes associated with the biological activity of PAs, as well as the possible involvement of protein tyr kinases (PTK) and/or protein kinase C (PKC) in the mitogenic signal transduction. The data obtained demonstrate that the growth factor activity of PAs is associated with: - a rapid transient activation of early response genes, c-fos, c-jun and c-myc; - the subsequent coordinated down-regulation of p53 and p21CIP1; - the constant expression of the MEK1 mRNA in every phase of the cell cycle. Quiescent (G0) cells did not express c-fos, c-jun, c-myc and cyclin A, but upon stimulation with mitogens (fetal calf serum (FCS), u-PA, t-PA) the cyclin A mRNA expression was observed in concomitance with the activation of DNA synthesis. Therefore u-PA, t-PA and FCS similarly modulate the expression of c-fos, c-jun, c-myc, p53, p21CIP1 and cyclin A with only slight differences likely related to the time required for activation of DNA synthesis. The PAs mitogenic stimulation of serum-starved cells was associated with the internalization of their molecules, as revealed by immunostaining. The biological activity of u-PA, t-PA, as well as that of limiting concentration of FCS (1%), was mediated by PTK and PKC. Conversely, PTK, but not PKC, was involved in the activation of the proliferative response of basic fibroblast growth factor in the same experimental conditions. In conclusion, u-PA and t-PA can utilize two different pathways, one depending on PTK and the other on PKC in a way similar to the mitogenic activity induced by low concentration of FCS (1%).
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PMID:Gene response of human skin fibroblasts to urokinase- and tissue-type plasminogen activators. 1080 Oct 75

The authors have examined the role of the src-family of protein tyrosine kinases in leukotriene B(4) (LTB(4))-induced activation of guinea-pig eosinophils. Western blot analysis identified the src-like protein tyrosine kinases p53(lyn), p56(lyn), p56/59(hck), p55(fgr), and p56(lck) whereas p60(src), p62(yes), p55(blk), and p59(fyn) were not detected. LTB(4) promoted a rapid increase in p53/56(lyn) activity in eosinophils, which peaked at 5 seconds and remained elevated at 60 seconds; hck, fgr, and lck were not activated. A role for p53/56(lyn) in eosinophil activation was investigated with the use of the src-selective inhibitor PP1 (1 micromol/L to 10 micromol/L), which attenuated LTB(4)-stimulated p53/56(lyn) activity and the phosphorylation of extracellular signal-regulated kinase-2 in intact cells. At comparable concentrations, PP1 was also shown to attenuate LTB(4)-induced nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) oxidase activation, chemotaxis, and Ca(++)-dependent [(3)H]arachidonic acid (AA) release. Moreover, an inhibitor of mitogen-activated protein kinase kinase-1, PD 098059, significantly inhibited LTB(4)-induced chemotaxis but had no effect on oxidant production or [(3)H]AA release. Collectively, these results implicate lyn kinase in LTB(4)-induced eosinophil activation through the recruitment of divergent cell-signaling pathways.
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PMID:Pleiotropic role of lyn kinase in leukotriene B(4)-induced eosinophil activation. 1082 41

Activating mutations of RAS are thought to be early events in the evolution of thyroid follicular neoplasms. We used a doxycycline-inducible expression system to explore the acute effects of H-RAS12 on genomic stability in thyroid PCCL3 cells. At 2-3 days (first or second cell cycle) there was a significant increase in the frequency of micronucleation. Treatment of cells with YVAD-CHO inhibited RAS-induced apoptosis, but had no effect on micronucleation. The effects of H-RAS(V12) were mediated by activation of MAPK, as treatment with PD98059 at concentrations verified to selectively inhibit MEK1 reduced the frequency of prevalence of cells with micronuclei. In addition, doxycycline-inducible expression of a constitutively active MEK1, but not of a mutant RAC1, mimicked the effects of H-RAS(V12). The effects of H-RAS(V12) on genome destabilization were apparent even though the sequence of p53 in PCCL3 cells was confirmed to be wild-type. Acute activation of H-RAS(V12) evoked a proportional increase in both CREST negative and CREST positive micronuclei, indicating that both clastogenic and aneugenic effects were involved. H-RAS(V12) and activated MEK1 also induced centrosome amplification, and chromosome misalignment. Evidence that acute expression of constitutively activated RAS destabilizes the genome of PCCL3 cells is consistent with a mode of tumor initiation in which this oncogene promotes phenotypic progression by predisposing to large scale genomic abnormalities.
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PMID:The RAS oncogene induces genomic instability in thyroid PCCL3 cells via the MAPK pathway. 1095 88

Astrogliosis is a hallmark of prion diseases. Finding ways of inhibiting astrocyte proliferation may be beneficial to treating these diseases. PrP106-126 a peptide fragment of the prion protein induces proliferation of astrocytes. The mechanism of its action was studied in detail. Induction of astrocyte proliferation in culture requires cytokines interleukin-1 and interleukin-6 released from microglia in the presence of PrP106-126. However, the increased release of these cytokines is insufficient without direct effects of PrP106-126 on astrocytes. PrP106-126 induces increased progression through the cell cycle to late G1 and enhances the level of both p53 and phosphorylated ERKs in astrocytes. PrP106-126-induced proliferation of astrocytes in culture can be inhibited by antibodies to cytokines or by MEK inhibitors.
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PMID:A model for the mechanism of astrogliosis in prion disease. 1099 49

Mdm2 acts as a major regulator of the tumor suppressor p53 by targeting its destruction. Here, we show that the mdm2 gene is also regulated by the Ras-driven Raf/MEK/MAP kinase pathway, in a p53-independent manner. Mdm2 induced by activated Raf degrades p53 in the absence of the Mdm2 inhibitor p19ARF. This regulatory pathway accounts for the observation that cells transformed by oncogenic Ras are more resistant to p53-dependent apoptosis following exposure to DNA damage. Activation of the Ras-induced Raf/MEK/MAP kinase may therefore play a key role in suppressing p53 during tumor development and treatment. In primary cells, Raf also activates the Mdm2 inhibitor p19ARF. Levels of p53 are therefore determined by opposing effects of Raf-induced p19ARF and Mdm2.
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PMID:Opposing effects of Ras on p53: transcriptional activation of mdm2 and induction of p19ARF. 1105 4

Three-dimensional tumor growth is dependent on the perpetual recruitment of host blood vessels to the tumor site. This recruitment process (mainly via angiogenesis) is thought to be triggered, at least in part, by the very same set of genetic alterations (activated oncogenes, inactivated/lost tumor suppressor genes) as those responsible for other aspects of malignant transformation (e.g., aberrant mitogenesis, resistance to apoptosis). Potent oncogenes are able to deregulate expression of both angiogenesis stimulators and inhibitors in cancer cells. For example, mutant ras expression is associated with increased production of vascular endothelial growth factor (VEGF) and downregulation of thrombospondin-1 (TSP-1). Upregulation of VEGF and angiogenesis can also be induced by constitutive activation of other oncogenic proteins (e.g., EGFR, Raf, MEK, PI3K) acting at various levels on the Ras signaling pathway. The mode and the magnitude of such proangiogenic influences can be significantly modified by cell type (fibroblastic or epithelial origin), epigenetic factors (hypoxia, changes in cell density), and/or presence of additional genetic lesions (e.g., preceding loss of p16 or p53 tumor suppressor genes). Activated oncogenes (e.g., ras, src, HER-2) induce co-expression of angiogenic properties concomitantly with several highly selectable traits (increased mitogenesis, resistance to apoptosis), a circumstance that may accelerate selection of the angiogenic phenotype at the cell population level. On the other hand oncogene-induced reduction in growth requirements may also endow tumor cells with a diminished (albeit not abrogated) dependence on (close) proximity to blood vessels, i.e., with reduced vascular dependence. Thus, oncogenes can impact several interconnected aspects of cellular growth, survival, and angiogenesis. Experimental evidence suggests that, in principle, many of these properties (including angiogenesis) can be simultaneously suppressed (and tumor stasis or regression induced) by effective use of the specific oncogene antagonists and signal transduction inhibitors.
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PMID:Oncogenes and angiogenesis: signaling three-dimensional tumor growth. 1114 71

Resveratrol, a phytoalexin found in grapes, berries, and peanuts, is one of the most promising agents for cancer prevention. Our previous study showed that the antitumor activity of resveratrol occurs through p53-mediated apoptosis. In this study, we have elucidated the potential signaling components underlying resveratrol-induced p53 activation and induction of apoptosis. We found that in a mouse JB6 epidermal cell line, resveratrol activated extracellular-signal-regulated protein kinases (ERKs), c-Jun NH2-terminal kinases (JNKs), and p38 kinase and induced serine 15 phosphorylation of p53. Stable expression of a dominant negative mutant of ERK2 or p38 kinase or their respective inhibitor, PD98059 or SB202190, repressed the phosphorylation of p53 at serine 15. In contrast, overexpression of a dominant negative mutant of JNKI had no effect on the phosphorylation. Most importantly, ERKs and p38 kinase formed a complex with p53 after treatment with resveratrol. Strikingly, resveratrol-activated ERKs and p38 kinase, but not JNKs, phosphorylated p53 at serine 15 in vitro. Furthermore, pretreatment of the cells with PD98059 or SB202190 or stable expression of a dominant negative mutant of ERK2 or p38 kinase impaired resveratrol-induced p53-dependent transcriptional activity and apoptosis, whereas constitutively active MEK1 increased the transcriptional activity of p53. These data strongly suggest that both ERKs and p38 kinase mediate resveratrol-induced activation of p53 and apoptosis through phosphorylation of p53 at serine 15.
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PMID:Resveratrol-induced activation of p53 and apoptosis is mediated by extracellular-signal-regulated protein kinases and p38 kinase. 1124 72


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