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)

Nrf2 (NF-E2-related factor 2) is a central transcription factor involved in the transcriptional activation of many genes encoding phase II drug-metabolizing enzymes via the antioxidant response element. Nrf2 has previously been found to undergo nuclear translocation by a phosphorylation-dependent mechanism mediated by protein kinase C in HepG2 cells treated with tert-butylhydroquinone, beta-naphthoflavone, or 12-O-tetradecanoylphorbol-13-acetate. In the present report, we have found that the levels of Nrf2 were increased in cells treated with tert-butylhydroquinone or beta-naphthoflavone by a post-transcriptional mechanism. Treatment of HepG2 cells with cycloheximide resulted in the loss of Nrf2 within 30 min. By contrast, treatment with the proteasome inhibitors (lactacystin or MG-132) caused an accumulation of Nrf2 as well as an induction of reporter gene activity in cells transfected with the GSTA2 antioxidant response element-chloramphenicol acetyl transferase construct. Similarly, the protein phosphatase inhibitor okadaic acid also caused an accumulation of Nrf2, whereas the reverse effects were observed with PD 98059 and U 0126, two compounds that block the activation of the MAPK/ERK signaling cascade. These data suggest that Nrf2 is degraded by the ubiquitin-dependent pathway and that phosphorylation of Nrf2 leads to an increase in its stability and subsequent transactivation activity.
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PMID:Increased protein stability as a mechanism that enhances Nrf2-mediated transcriptional activation of the antioxidant response element. Degradation of Nrf2 by the 26 S proteasome. 1244 95

IFN-gamma induction of C1 inhibitor (C1INH) is mediated by an IFN-gamma-activated sequence (GAS), via binding of signal transducer and activator of transcription 1 (STAT1). These studies focused on the factors responsible for down-regulation of nuclear STAT1 in hepatocytes, the primary site of synthesis of C1INH. The activity of nuclear STAT1 following stimulation with IFN-gamma was sustained with the phosphatase inhibitor, pervanadate, or the proteasome inhibitor, lactacystin. Pervanadate prolonged STAT1 activation and blocked the inactivation of nuclear STAT1. Binding of ubiquitin to phosphorylated STAT1 was detectable in cells treated with lactacystin. Staurosporine only moderately decreased the prolongation of nuclear phosphorylated STAT1 after pretreatment with pervanadate or lactacystin. An antisense mitogen-activated protein kinase phosphatase (MKP-1) oligonucleotide prolonged the accumulation of phosphorylated STAT1. These data are consistent with the hypothesis that down-regulation of IFN-gamma-mediated nuclear STAT1 binding in hepatocytes involves both dephosphorylation by MKP-1 and degradation via proteolysis by the ubiquitin-dependent proteasome pathway.
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PMID:Nuclear phosphatases and the proteasome in suppression of STAT1 activity in hepatocytes. 1245 77

The ubiquitin-proteasome pathway is an intracellular protein degradation pathway responsible for degradation of many regulatory proteins that must be rapidly eliminated normally. Some recent studies reported that a proteasome dysfunction was involved in the pathogenesis of neurodegenerative diseases. Thus, there is now considerable interest in the possible role of proteasome in this regard. Here we show that inhibition of proteasomal function by Lactacystin-induced cell death in a neuronal differentiated Neuro2a (nN2a) cell line but not in an undifferentiated Neuro2a (N2a) cell line. Cell death was accompanied by both the activation of c-Jun N-terminal kinase, p38 and caspase-3. A pan-caspase inhibitor, Z-VAD-FMK, or SB203580, a p38 inhibitor could not inhibit cell death induced by Lactacystin, whereas nN2a cell lines with stable expression of the dominant negative mutant of c-Jun N-terminal kinase showed a remarkable suppression of cell death. Lactacystin-induced cell death is mediated through the c-Jun N-terminal kinase pathway but not the caspase-dependent pathway in a nN2a cell line. Our results shed light on the association among the proteasomal dysfunction, JNK pathway and neuronal cell death, leading to the elucidation of its possible role in the pathogenesis of neurodegenerative diseases.
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PMID:c-Jun N-terminal kinase pathway mediates Lactacystin-induced cell death in a neuronal differentiated Neuro2a cell line. 1248 Jan 74

Next to water, tea is the most popular beverage in the world, and the cancer-preventive effects of this beverage have been suggested. Epidemiological studies have shown decreased cancer occurrence in those individuals who drink green tea regularly. A wealth of research suggests numerous mechanisms of action to explain these observations. The most abundant and popular compound studied in tea research is (-)-epigallocatechin-3-gallate (EGCG), which acts as a powerful antioxidant and can inhibit a number of tumor cell proliferation- and survival-related proteins. Tea polyphenols are known to inhibit the large multi-catalytic protease (the proteasome) and metaloproteionases, involved in tumor survival and metastasis, respectively. Additionally, tea polyphenols inhibit the activities of many tumor-associated protein kinases, including epidermal growth factor receptor, vascular endothelial growth factor receptor, platelet-derived growth factor receptor, mitogen-activated protein kinase, and IkB kinase. Tea polyphenols have also been found to inhibit some cancer-related proteins that regulate DNA replication and transformation. At present, it is not known which of these activities of tea polyphenols are required for its cancer-preventive effects. However, by understanding the in vivo concentrations of tea polyphenols required to inhibit each of these activities, we may start to sort out in the future the mechanisms responsible for the cancer-preventive effects of tea.
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PMID:Potential molecular targets of tea polyphenols in human tumor cells: significance in cancer prevention. 1249 82

WR1065 is an aminothiol with selective cytoprotective effects in normal cells compared with cancer cells. In a previous study (North, S., El-Ghissassi, F., Pluquet, O., Verhaegh, G., and Hainaut, P. (2000) Oncogene 19, 1206-1214), we have shown that WR1065 activates wild-type p53 in cultured cells. Here we show that WR1065 induces p53 to accumulate through escape from proteasome-dependent degradation. This accumulation is not prevented by inhibitors of phosphatidylinositol 3-kinases and is not accompanied by phosphorylation of Ser-15, -20, or -37, which are common targets of the kinases activated in response to DNA damage. Furthermore, WR1065 activates the JNK (c-Jun N-terminal kinase), decreases complex formation between p53 and inactive JNK, and phosphorylates p53 at Thr-81, a known site of phosphorylation by JNK. A dominant negative form of JNK (JNK-APF) reduces by 50% the activation of p53 by WR1065. Thus, WR1065 activates p53 through a JNK-dependent signaling pathway. This pathway may prove useful for pharmacological modulation of p53 activity through non-genotoxic mechanisms.
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PMID:The cytoprotective aminothiol WR1065 activates p53 through a non-genotoxic signaling pathway involving c-Jun N-terminal kinase. 1253 96

Experience-dependent remodeling of the postsynaptic density (PSD) is critical for synapse formation and plasticity in the mammalian brain. Here, in cultured rat hippocampal neurons, I found long-lasting, global changes in the molecular composition of the PSD dictated by synaptic activity. These changes were bidirectional, reversible, modular, and involved multiple classes of PSD proteins. Moreover, activity-dependent remodeling was accompanied by altered protein turnover, occurred with corresponding increases or decreases in ubiquitin conjugation of synaptic proteins and required proteasome-mediated degradation. These modifications, in turn, reciprocally altered synaptic signaling to the downstream effectors CREB (cyclic AMP response element binding protein) and ERK-MAPK (extracellular signal regulated kinase-MAP kinase). These results indicate that activity regulates postsynaptic composition and signaling through the ubiquitin-proteasome system, providing a mechanistic link between synaptic activity, protein turnover and the functional reorganization of synapses.
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PMID:Activity level controls postsynaptic composition and signaling via the ubiquitin-proteasome system. 3025 Feb 64

Sprouty was originally identified in a genetic screen in Drosophila as an antagonist of fibroblast (FGF) and epidermal growth factor (EGF) signaling. Subsequently, four vertebrate homologs were discovered; among these, the human homolog Sprouty 2 (hSpry2) contains the highest degree of sequence homology to the Drosophila protein. It has been shown that hSpry2 interacts directly with c-Cbl, an E3-ubiquitin ligase, which promotes the downregulation of receptor tyrosine kinases (RTKs). In this study, we have investigated the functional consequences of the association between hSpry2 and c-Cbl. We have found that hSpry2 is ubiquitinated by c-Cbl in an EGF-dependent manner. EGF stimulation induces the tyrosine phosphorylation of hSpry2, which in turn enhances the interaction of hSpry2 with c-Cbl. The c-Cbl-mediated ubiquitination of hSpry2 targets the protein for degradation by the 26S proteasome. An enhanced proteolytic degradation of hSpry2 is also observed in response to FGF stimulation. The FGF-induced degradation of hSpry2 limits the duration of the inhibitory effect of hSpry2 on extracellular signal-regulated kinase (ERK) activation and enables the cells to recover their sensitivity to FGF stimulation. Our results indicate that the interaction of hSpry2 with c-Cbl might serve as a mechanism for the downregulation of hSpry2 during receptor tyrosine kinase signaling.
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PMID:hSpry2 is targeted to the ubiquitin-dependent proteasome pathway by c-Cbl. 1259 96

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

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


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