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

The BCR/ABL chimeric protein plays a central role in the pathogenesis of chronic myelogenous leukemia (CML). Intensive research has elucidated many signal transduction pathways activated by BCR/ABL. However, few studies addressed BCR/ABL-dependent alterations in gene expression that may contribute to the pathobiology of CML. To additionally define such downstream genes, we performed a subtractive hybridization between cord blood (CB) CD34(+) cells transduced with an MSCV-retrovirus vector containing either enhanced green fluorescent protein (eGFP) alone or p210(BCR/ABL)-internal ribosome entry site-eGFP. Thirty-four subtracted clones expressed in p210-eGFP but not eGFP-transduced CD34(+) cells have been confirmed by Northern blot and sequenced. Fifty-nine percent represent novel proteins, and 41% are homologous to known genes. Quantitative real-time PCR analysis confirmed that 14 of 14 genes tested were also overexpressed in additional populations of p210(BCR/ABL)-transduced CB CD34(+) cells, as well as in CD34(+) cells from primary newly diagnosed CML patients versus GFP-transduced CB or samples from normal donors. Western blot analysis showed that the known sequences were also overexpressed at the protein level. Treatment of BCR/ABL(+) cells with the Abl-specific tyrosine kinase inhibitor STI571 decreased expression at the mRNA as well as protein level of some but not all of the gene products. This suggests that increased gene expression is in some cases tyrosine kinase-independent. Some of the overexpressed genes are implicated in cellular processes known to be disturbed in CML, including the mitogen-activated protein kinase or the ubiquitin pathway, whereas overexpression of other genes, including RAN and NUP98, may implicate new cellular pathways involved in CML. Additional characterization of downstream genes activated by BCR/ABL may lead to important new insights in the molecular mechanisms underlying CML and identify potentially novel therapeutic targets for CML.
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PMID:BCR/ABL-mediated increased expression of multiple known and novel genes that may contribute to the pathogenesis of chronic myelogenous leukemia. 1258 34

Transcriptional regulation of downstream gene expression by thyroid hormone (T(3)) is mediated by the thyroid hormone receptor (TR). T(3) binding induces a complicated transition, where TR converts from a transcriptional repressor into a transcriptional activator and instigates downstream gene transcription. Binding of T(3) to TR also induces the degradation of TR, resulting in desensitization of the cells to further T(3) treatment. It has been shown that phosphorylation of TR plays a critical role in its activity and stability after T(3) binding. However, the kinases in control of phosphorylating TR in the nucleus have not been identified. In this study we demonstrate that MAPKs are possible candidates responsible for the nuclear phosphorylation of TR. Suppression of MAPKs with specific inhibitors repressed TR transcriptional activity and antagonized okadeic acid-induced TR transcriptional activity potentiation. Overexpression of the MAPK activator, MKK6, and its constitutively active mutant, MKK6EE, significantly increased TR activity and protected TR from degradation. Involvement of the 26S ubiquitin proteasome in hormone binding-induced TR degradation was also examined. We found that MAPKs enhanced the DNA binding affinity of TR. Our results suggest that MAPKs are the major kinases responsible for the nuclear phosphorylation of TR and are critical factors modulating the transcriptional activity and protein stability of TR subsequent to ligand binding.
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PMID:Mitogen-activated protein kinases potentiate thyroid hormone receptor transcriptional activity by stabilizing its protein. 1263 24

(1) Fractalkine is a CX(3)C chemokine for mononuclear leukocytes that is expressed mainly by vascular cells, and regulated by pro-inflammatory cytokines. This study investigated signal transduction mechanisms by which tumor necrosis factor (TNF)-alpha stimulated fractalkine expression in cultured rat vascular smooth muscle cells (VSMCs), and the modulatory effect of a haemorrheologic agent, pentoxifylline, on its production. (2) TNF-alpha (1-50 ng ml(-1)) stimulated fractalkine mRNA and protein expression in concentration- and time-dependent manners. Pretreatment with calphostin C (0.4 micro M, a selective inhibitor of protein kinase C (PKC), and PD98059 (40 micro M), a specific inhibitor of p42/44 mitogen-activated protein kinase (MAPK) kinase, attenuated TNF-alpha-stimulated fractalkine mRNA and protein expression. In contrast, H-89 (2 micro M), a selective inhibitor of cAMP-dependent protein kinase, wortmannin (0.5 micro M), a selective inhibitor of phosphatidylinositol 3-kinase, and SB203580 (40 micro M), a specific inhibitor of p38 MAPK, had no discernible effect. (3) The ubiquitin/proteosome inhibitors, MG132 (10 micro M) and pyrrolidine dithiocarbamate (200 micro M), suppressed activation of NF-kappaB as well as stimulation of fractalkine mRNA and protein expression by TNF-alpha. (4) TNF-alpha-activated phosphorylation of PKC was blocked by calphostin C, whereas TNF-alpha-augmented phospho-p42/44 MAPK and phospho-c-Jun levels were reduced by PD98059. Neither calphostin C nor PD98059 affected TNF-alpha-induced degradation of I-kappaBalpha or p65 nuclear translocation. (5) Pretreatment with pentoxifylline (0.1-1 mg ml(-1)) decreased TNF-alpha-stimulated fractalkine mRNA and protein expression, which was preceded by a reduction in TNF-alpha-activated phosphorylation of PKC, p42/44 MAPK and c-Jun as well as degradation of I-kappaBalpha and p65/NF-kappaB nuclear translocation. (6) These data indicate that activation of PKC, p42/44 MAPK kinase, and NF-kappaB are involved in TNF-alpha-stimulated fractalkine production in VSMCs. Down-regulation of the PKC, p42/44 MAPK, and p65/NF-kappaB signals by PTX may be therapeutically relevant and provide an explanation for the anti-fractalkine effect of this drug.
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PMID:Inhibition by pentoxifylline of TNF-alpha-stimulated fractalkine production in vascular smooth muscle cells: evidence for mediation by NF-kappa B down-regulation. 1264 97

Both the ERK and phosphatidylinositol 3'-kinase (PI3K) signaling pathways can protect cells from apoptosis following withdrawal of survival factors. We have previously shown that the ERK1/2 pathway acts independently of PI3K to block expression of the BH3-only protein, BimEL, and prevent serum withdrawal-induced cell death, although the precise mechanism by which ERK reduced BimEL levels was unclear. By comparing Bim mRNA and Bim protein, expression we now show that the rapid expression of BimEL following serum withdrawal cannot be accounted for simply by increases in mRNA following inhibition of PI3K. In cells maintained in serum BimEL is a phosphoprotein. We show that activation of the ERK1/2 pathway is both necessary and sufficient to promote BimEL phosphorylation and that this leads to a substantial increase in turnover of the BimEL protein. ERK1/2-dependent degradation of BimEL proceeds via the proteasome pathway because it is blocked by proteasome inhibitors and is defective at the restrictive temperature in cells with a temperature-sensitive mutation in the E1 component of the ubiquitin-conjugating system. Finally, co-transfection of BimEL and FLAG-ubiquitin causes the accumulation of polyubiquitinated forms of Bim, and this requires the ERK1/2 pathway. Our findings provide new insights into the regulation of Bim and the role of the ERK pathway in cell survival.
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PMID:Activation of the ERK1/2 signaling pathway promotes phosphorylation and proteasome-dependent degradation of the BH3-only protein, Bim. 1264 60

The proteasome is a multisubunit proteolytic enzyme comprising activator complexes bound to the 20 S catalytic core. The functions of the proteasomal activator (PA) 700 in ubiquitin/ATP-dependent protein degradation and of the PA28 alpha/beta activators in antigen presentation are well defined. However, the function of a third PA, PA28 gamma, remains elusive. We now show that mitogen-activated protein kinase (MAPK)/extracellular-signal-regulated kinase (ERK) kinase kinase 3 (MEKK3), a MAPK kinase kinase (MAPKKK) involved in MAPK kinase 7 (MKK7)-c-Jun N-terminal kinase ('JNK') and MKK6-p38 signalling, can bind PA28 gamma but not PA28 alpha. In contrast, B-Raf, a MAPKKK specific for the MAPK/ERK kinase ('MEK')-ERK module, binds PA28 gamma and alpha. The PA28 gamma-binding domain of MEKK3 is located within its N-terminal regulatory domain (amino acids 1-178). Expression of MEKK3 in Cos-7 cells led to an increase in endogenous and co-expressed PA28 gamma protein levels, whereas kinase-deficient MEKK3 had no effect on PA28 gamma expression. Furthermore, in vitro assays indicated that PA28 gamma was a MEKK3 substrate. MEKK3 represents the first protein kinase capable of binding and phosphorylating a PA, and provides a potential mechanism to link stress-activated protein kinase signalling with the PA28 gamma-dependent proteasome.
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PMID:MEKK3 interacts with the PA28 gamma regulatory subunit of the proteasome. 1265 Jun 40

Sustained extracellular signal-regulated kinase 1/2 (ERK1/2) activation does not always correlate with its upstream Ras-Raf-mitogen-activated protein kinase kinase 1/2 (MKK1/2) signal cascade in cancer cells, and the mechanism remains elusive. Here we report a novel mechanism by which sustained ERK1/2 activation is established. We demonstrate that Pb(II), a carcinogenic metal, persistently induces ERK1/2 activity in CL3 human lung cancer cells and that Ras-Raf-MKK1/2 signaling cannot fully account for such activation. It is intriguing that Pb(II) treatment reduces mitogen-activated protein kinase phosphatase 1 (MKP-1) protein levels in time- and dose-dependent manners, which correlates with sustained ERK1/2 activation, and that Pb(II) also induces mRNA and de novo protein synthesis of MKP-1. In Pb(II)-treated cells, MKP-1 is polyubiquitinated, and proteasome inhibitors markedly alleviate the ubiquitination and degradation of MKP-1. Inhibiting the Pb(II)-induced ERK1/2 activation by PD98059 greatly suppresses MKP-1 ubiquitination and degradation. It is remarkable that constitutive activation of MKK1/2 triggers endogenous MKP-1 ubiquitination and degradation in various mammalian cell lines. Furthermore, expression of functional MKP-1 decreases ERK1/2 activation and the c-Fos protein level and enhances cytotoxicity under Pb(II) exposure. Taken together, these results demonstrate that activated ERK1/2 can trigger MKP-1 degradation via the ubiquitin-proteasome pathway, thus facilitating long-term activation of ERK1/2 against cytotoxicity.
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PMID:ERK1/2 achieves sustained activation by stimulating MAPK phosphatase-1 degradation via the ubiquitin-proteasome pathway. 1267 37

Recent advances in high-density DNA microarray technique allow the possibility to analyze thousands of genes simultaneously for their differential gene expression patterns in various biologic processes. Through clustering analysis and pattern recognition, the significance of these differentially expressed genes can be recognized and correlated with the biologic events that may take place inside the cell and tissue. High-density DNA microarray nylon membranes were used to explore gene expression and regulation associated with smoke- and hydrogen peroxide-induced injury and repair in differentiated human bronchial epithelial cells in vitro. At least three phases of change in gene expression could be recognized. The first phase seems to be an immediate event in response to oxidant injury. This phase includes the induction of bcl-2 and mdm2 genes that are involved in the regulation of apoptosis, and the mitogen-activated protein kinase phosphatase 1 that functions as a regulator for various mitogen-activated protein kinase activities. The second phase, usually 5 h later, includes the induction of various stress proteins and ubiquitin, which are important in providing the chaperone mechanism and the turnover of damaged macromolecules. The third phase, which is 5 to 10 h later, includes the induction of genes that seem to be involved in reducing oxidative stress by metabolizing the cellular level of reactive oxygen species. In this phase, enzymes associated with tissue and cell remodeling are also elevated. These results demonstrated a complex gene expression array by bronchial epithelial cells in response to a single insult of oxidants that are relevant to environmental pollutants.
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PMID:Application of high-density DNA microarray to study smoke- and hydrogen peroxide-induced injury and repair in human bronchial epithelial cells. 1287 47

Familial Alzheimer's Disease (AD) has been linked to amyloid beta protein precursor (AbetaPP) and presenilin gene mutations. In sporadic AD, which accounts for the vast majority of cases, the pathogenesis of neurodegeneration is unknown; however, recent evidence suggests a role for oxidative stress. The present study demonstrates that transient hypoxic injury to cortical neurons causes several of the molecular and biochemical abnormalities that occur in AD including, mitochondrial dysfunction, impaired membrane integrity, increased levels of DNA damage, reactive oxygen species, phospho-tau, phospho-MAP-1B, and ubiquitin immunoreactivity, and AbetaPP cleavage with accumulation of Abeta-immunoreactive products. These abnormalities were associated with activation of kinases that phosphorylate tau, including glycogen synthase kinase 3beta (GSK-3beta), mitogen-activated protein kinase (MAPK), and cyclin-dependent kinase 5 (Cdk-5). Further studies showed that significant neuro-protection with sparing of mitochondrial function and membrane integrity could be achieved by pre-treating the cortical neurons with N-acetyl cysteine, glutathione, or inhibitors of GSK-3beta, MAP kinase, or AbetaPP gamma-secretase. Therefore, in the absence of underlying gene mutations, oxidative stress can cause AD-type abnormalities, including aberrant post-translational processing of neuronal cytoskeletal proteins and APP. Our results also suggest that pre-treatment with agents that block specific components of the AD neurodegeneration cascade may provide neuroprotection against oxidative stress-induced impairments in membrane integrity, mitochondrial function, and viability.
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PMID:Transient hypoxia causes Alzheimer-type molecular and biochemical abnormalities in cortical neurons: potential strategies for neuroprotection. 1475 39

The mitogen activated protein (MAP) kinase module: (Raf -->MEK-->ERKs) is central to the control of cell growth, cell differentiation and cell survival. The fidelity of signalling and the spatio-temporal activation are key determinants in generating precise biological responses. The fidelity is ensured by scaffold proteins - protein kinase 'insulators' - and by specific docking sites. The duration and the intensity of the response are in part controlled by the compartmentalization of the signalling molecules. Growth factors promote rapid nuclear translocation and persistent activation of p42/p44 MAP kinases, respectively and ERK2/ERK1, during the entire G1 period with an extinction during the S-phase. These features are exquisitely controlled by the temporal induction of the MAP kinase phosphatases, MKP1-3. MKP1 and 2 induction is strictly controlled by the activation of the MAP kinase module providing evidence for an auto-regulatory mechanism. This negative regulatory loop is further enhanced by the capacity of p42/p44 MAPK to phosphorylate MKP1 and 2. This action reduces the degradation rate of MKPs through the ubiquitin-proteasomal system. Whereas the two upstream kinases of the module (Raf and MEK) remain cytoplasmic, ERKs (anchored to MEK in the cytoplasm of resting cells) rapidly translocate to the nucleus upon mitogenic stimulation. This latter process is rapid, reversible and controlled by the strict activation of the MAPK cascade. Following long-term MAPK stimulation, p42/p44 MAPKs progressively accumulate in the nucleus in an inactive form. Therefore we propose that the nucleus represents a site for ERK action, sequestration and signal termination. With the generation of knockdown mice for each of the ERK isoforms, we will illustrate that besides controlling cell proliferation the ERK cascade also controls cell differentiation and cell behaviour.
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PMID:Fidelity and spatio-temporal control in MAP kinase (ERKs) signalling. 1289 87

The cyclin-dependent kinase (CDK) inhibitor p27Kip1 plays a key role in growth and development of the mammary epithelium and in breast cancer. p27Kip1 levels are regulated through ubiquitin/proteasome-mediated proteolysis, promoted by CDK2 and the F box protein Skp2 at the G1/S transition, and independent of Skp2 in mid-G1. We investigated the respective roles of Skp2 and subcellular localization of p27Kip1 in down-regulation of p27Kip1 induced in MCF-7 cells by estrogens. 17beta-Estradiol treatment increased Skp2 expression in MCF-7 cells; however, this increase was prevented by G1 blockade mediated by p16Ink4a or the CDK inhibitor roscovitine, whereas down-regulation of p27Kip1 was maintained. Exogenous Skp2 prevented growth arrest of MCF-7 cells by antiestrogen, coinciding with decreased p27Kip1 expression. Under conditions of G1 blockade, p27Kip1 was stabilized by inhibition of CRM1-dependent nuclear export with leptomycin B or by mutation of p27Kip1 (Ser10 --> Ala; S10A) interfering with CRM1/p27Kip1 interaction. Antisense Skp2 oligonucleotides and a dominant-interfering Cul-1(1-452) mutant prevented down-regulation of p27Kip1S10A, whereas Skp2 overexpression elicited its destruction in mitogen-deprived cells. Active mediators of the extracellular signal-regulated kinase (ERK) pathway including Raf-1caax induced cytoplasmic localization of p27Kip1 in antiestrogen-treated cells and prevented accumulation of p27Kip1 in these cells independent of Skp2 expression and coinciding with ERK activation. Genetic or chemical blockade of the ERK pathway prevented down-regulation and cytoplasmic localization of p27Kip1 in response to estrogen. Our studies indicate that estrogens elicit down-regulation of p27Kip1 in MCF-7 cells through Skp2-dependent and -independent mechanisms that depend upon subcellular localization of p27Kip1 and require the participation of mediators of the Ras/Raf-1/ERK signaling pathway.
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PMID:Estrogens down-regulate p27Kip1 in breast cancer cells through Skp2 and through nuclear export mediated by the ERK pathway. 1290 6


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