Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51812 (mitogen-activated protein)
 10,636 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Sublethal concentrations of reactive oxygen intermediates including H2O2 can alter human T cell function and inhibit proliferative responses but relatively little is known about the effects of low levels of oxidant stress on signaling pathways. In the present study, we investigated whether the exposure of Jurkat T cells to micromolar concentrations of H2O2 might influence the activity of certain serine/threonine kinases and protein phosphatases important for T cell signaling as well as initiation of nuclear events. Jurkat cells treated with 100-200 microM H2O2 exhibited rapid increases in cytosolic protein kinase C (PKC) activity without detectable translocation of PKC to the membrane/particulate compartment. The stimulation of PKC activity by H2O2 was associated with an increase in the activation of kinases phosphorylating myelin basic protein (MBP), a substrate for mitogen-activated protein (MAP) kinase and RRLSSLRA (S6 peptide; a substrate for the approximately 90-kDa ribosomal S6 kinases). Optimal activation of MAP kinase in cells treated with H2O2 was preceded by increases in protein tyrosine phosphorylations and occurred at sublethal concentrations of H2O2 which did not markedly deplete intracellular ATP. Pretreatment of cells with the PKC inhibitors sangivamycin and H7 suppressed but did not block the stimulation of MAP kinase activity in response to H2O2 or phytohemagglutinin. The activities of both protein tyrosine phosphatase (PTP) and protein phosphatase 2A (PP2A) were reduced after H2O2 treatment of intact cells. Furthermore, kinetic studies showed that H2O2 was capable of suppressing the activities of PTP and PP2A before inducing optimal increases in MAP kinase activity. These results demonstrate that the exposure of T cells to sublethal levels of oxidant stress acutely stimulates the MAP kinase cascade and suggest that this activation may involve PKC-dependent and -independent pathways as well as inhibition of certain protein phosphatases.
 ...
PMID:Sublethal levels of oxidant stress stimulate multiple serine/threonine kinases and suppress protein phosphatases in Jurkat T cells. 777 89

We have shown that hyperoxic exposure of immature rats induces airway smooth muscle layer thickening and cell turnover parallel to that found in the airways of patients with bronchopulmonary dysplasia and chronic, severe asthma. We hypothesized that reactive oxygen species could promote the observed airway remodeling by directly stimulating signal transduction pathways that regulate cell growth. To test this hypothesis in cultured cells, we assessed the effects of hydrogen peroxide (H2O2) on mitogen-activated protein (MAP) kinase activation in bovine tracheal myocytes. The MAP kinases are a family of 40 to 46 kD cytosolic serine/threonine kinases that participate in the transduction of mitogenic signals to the cell nucleus. Quiescent cells were exposed to H2O2 (25 to 200 microns; 2 to 60 min), after which SDS-PAGE of cell extracts was performed. Western analysis using an anti-MAP kinase antiserum revealed a decrease in the mobility of the 42 and 44 kD MAP kinase bands after H2O2 exposures of 5 to 30 min, reflecting the phosphorylation at threonine and tyrosine residues required for enzymatic activity. MAP kinase activation was demonstrated by kinase renaturation assays, which showed an almost 4-fold increase in 42 and 44 kD MAP kinase activity. Down-regulation of protein kinase C (PKC) with phorbol 12,13-dibutyrate (PDBu) partially reduced H2O2-stimulated MAP kinase activity, suggesting that H2O2 induces MAP kinase activation via both PKC-dependent and PKC-independent pathways. Western analysis using a phosphotyrosine monoclonal antibody revealed increased tyrosine phosphorylation of proteins with approximate molecular weights of 72 and 125 kD after H2O2 exposure, demonstrating that H2O2 can stimulate the tyrosine phosphorylation of multiple cytosolic proteins, including MAP kinase.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Hydrogen peroxide stimulates mitogen-activated protein kinase in bovine tracheal myocytes: implications for human airway disease. 794 86

In addition to their role in bacterial killing, reactive oxygen intermediates (ROI) produced by the NADPH oxidase may participate in the regulation of intracellular pathways. We have recently demonstrated that ROI produced by the oxidase regulate tyrosine phosphorylation in neutrophils, possibly by alterations in the cellular redox state. The purpose of the present study was to characterize the identities of certain of the redox-sensitive tyrosine-phosphorylated substrates and the significance of the increased phosphorylation. As a prominent 42-44-kDa phosphorylated band was noted in oxidant-treated cells, we investigated the possible phosphorylation and activation of mitogen-activated protein (MAP) kinase under these conditions. Immunoprecipitation of MAP kinase followed by immunoblotting with anti-phosphotyrosine antibodies indicated that a 42-44-kDa polypeptide was tyrosine-phosphorylated in response to treatment of cells, either with the oxidizing agent diamide or with H2O2 in cells where catalase was inhibited. Using an in vitro renaturation assay with myelin basic protein as the substrate, oxidant-induced stimulation of kinase activity of a 42-44-kDa band was observed in both whole cell extracts and in MAP kinase immunoprecipitates. The mechanism of redox-sensitive activation of MAP kinase was examined. First, exposure of cells to oxidants caused a significant increase in the activity of MEK (the putative activator of MAP kinase), as determined by an in vitro kinase assay using recombinant catalytically inactive glutathione S-transferase-MAP kinase as the substrate. Additionally, oxidant treatment of cells resulted in inhibition of the activity of CD45, a protein tyrosine phosphatase known to dephosphorylate and inactivate MAP kinase. We conclude that oxidant treatment of neutrophils can activate MAP kinase by stimulating its tyrosine and (presumably) threonine phosphorylation via MEK activation, a response that may be potentiated by inhibition of MAP kinase dephosphorylation by phosphatases such as CD45.
 ...
PMID:Activation of the mitogen-activated protein kinase signaling pathway in neutrophils. Role of oxidants. 798 67

Extracellular signal-regulated kinases (ERKs), also known as mitogen-activated protein (MAP) kinases, are rapidly phosphorylated and activated in response to a number of external factors which promote growth and differentiation (T. G. Boulton, S. H. Nye, D. J. Robbins, N. Y. Ip, E. Radziejewska, S. D. Morgenbesser, R. A. DePinho, N. Panayotatos, M. H. Cobb, and G. D. Yancopoulos, Cell, 65: 663-675, 1991; S. L. Pelech and S. S. Jasbinder, Science (Washington DC), 257: 1355-1356, 1992; G. Thomas, Cell, 68: 3-6, 1992). We have identified two novel stimulators of MAP kinase activity, ionizing radiation and H2O2. Both radiation and H2O2, as well as the known agonist 12-O-tetradecanoylphorbol 13-acetate activate MAP kinase through the production of reactive oxygen intermediates. Our results demonstrate a direct link between the MAP kinase signal transduction pathway and reactive oxygen species and provide a unifying mechanism for activation of early- and late-response genes by inducers of oxidative stress.
 ...
PMID:X-irradiation, phorbol esters, and H2O2 stimulate mitogen-activated protein kinase activity in NIH-3T3 cells through the formation of reactive oxygen intermediates. 826 31

Chromium is an important industrial metal, an environmental pollutant, and a human carcinogen. To investigate the mechanisms of chromium-induced carcinogenesis, activation of mitogen-activated protein (MAP) kinases ERK1 and ERK2 was examined in rat hepatoma cells following exposure to hexavalent chromium (Cr(VI)). Cr(VI) was found to activate both forms of MAP kinase in a dose- and time-dependent manner. In contrast to the protein kinase C (PKC) agonist, phorbol 12-myristate 13-acetate, which induced a transient activation of MAP kinases, Cr(VI) caused persistent activation of these enzymes. Furthermore, unlike phorbol 12-myristate 13-acetate, the ability of chromium to activate MAP kinases was found to be independent of PKC since chromium-induced MAP kinase activation occurred in PKC-depleted cells. Stimulation of ERK1 and ERK2 was associated with the ability of Cr(VI) to increase cellular peroxide levels as determined using the H2O2-sensitive fluorescent probe 2',7'-dichlorofluorescein diacetate and flow cytometry. Furthermore, the activation of these kinases by chromium was enhanced in cells treated with the glutathione-depleting agent, L-buthionine-[S,R]-sulfoximine, and attenuated in cells pretreated with an agent that elevates cellular levels of glutathione (i.e., N-acetyl-L-cysteine). The ability of chromium to modulate MAP kinase activity in this manner suggests a mechanism of chromium-induced carcinogenesis that involves the persistent stimulation of cellular regulatory pathways.
 ...
PMID:Chromium induces a persistent activation of mitogen-activated protein kinases by a redox-sensitive mechanism in H4 rat hepatoma cells. 861 49

Protein tyrosine phosphorylation events play determinant roles in cellular processes such as proliferation and differentiation. We have recently reported that hydrogen peroxide, an active oxygen species and a cellular oxidant, stimulates growth response events in vascular smooth muscle cells (VSMC). To understand the mechanisms by which oxidant stress modulates these growth response events, we have studied the effect of hydrogen peroxide on protein tyrosine phosphorylation events in VSMC. Our findings show that hydrogen peroxide stimulates tyrosine phosphorylation of several proteins including epidermal growth factor receptor (EGFR) in VSMC. Hydrogen peroxide-induced tyrosine phosphorylation of EGFR was found to be time dependent; with a threefold increase at 5 min and a 20-fold increase at 30 min of treatment as compared to control levels. Hydrogen peroxide treatment of VSMC also resulted in a time-dependent increase in tyrosine phosphorylation of SHC proteins. In addition, hydrogen peroxide-induced tyrosine-phosphorylated EGFR formed a complex with SHC-Grb2-SOS. These events were followed by activation of Ras and extracellular signal-regulated protein kinases (ERKs) group of mitogen-activated protein kinases (MAPKs). Together these findings demonstrate for the first time that hydrogen peroxide, a cellular oxidant, possess the ability to activate EGFR-mediated signaling events in VSMC. These EGFR-mediated signaling events may be important in oxidant stress-induced cellular responses.
 ...
PMID:Hydrogen peroxide induces complex formation of SHC-Grb2-SOS with receptor tyrosine kinase and activates Ras and extracellular signal-regulated protein kinases group of mitogen-activated protein kinases. 876 Dec 92

Vascular endothelial cells are constantly in contact with oxyradicals and must be especially well equipped to resist their toxic effects and generate appropriate physiological responses. Despite the importance of oxyradicals in the physiopathology of the vascular endothelium, the mechanisms regulating the oxidative response of endothelial cells are poorly understood. In the present study, we observed that H2O2 in concentrations that induced severe fragmentation of F-actin in fibroblasts rather induced a reorganization of F-actin in primary cultures of human umbilical vein endothelial cells (HUVECs) that was characterized by the accumulation of stress fibers, the recruitment of vinculin to focal adhesions, and the loss of membrane ruffles, H2O2 also induced in these cells a strong (10- to 14-fold) activation of the p38 mitogen-activated protein (MAP) kinase, which resulted in activation of MAP kinase-activated protein kinase-2/3 and phosphorylation of the F-actin polymerization modulator, heat shock protein 27 (HSP27). The MAP kinases extracellular-regulated kinase, and c-Jun N-terminal kinase/stress-activated protein kinase were only slightly increased by these treatments. Inhibiting p38 activity with the highly specific inhibitor SB203580 blocked the H2O2-induced endothelial microfilament responses. Moreover, fibroblasts acquired an endothelium-like SB203580-sensitive actin response when HSP27 concentration was increased by gene transfection to the same high level as found in HUVECs. The results indicate that activation of p38 MAP kinase in cells such as endothelial cells, which naturally express high level of HSP27, plays a central role in modulating microfilament responses to oxidative stress. Consequently, the p38 MAP kinase pathway may participate in the several oxyradical-activated functions of the endothelium that are associated with reorganization of microfilament network.
 ...
PMID:Oxidative stress-induced actin reorganization mediated by the p38 mitogen-activated protein kinase/heat shock protein 27 pathway in vascular endothelial cells. 904 59

Hydrogen peroxide stimulated tyrosine phosphorylation of several proteins in growth-arrested vascular smooth muscle cells (VSMC). One of these proteins was identified as fibroblast growth factor receptor type I (FGFR1). In addition, induced tyrosine phosphorylation of FGFR1 by hydrogen peroxide resulted in complex formation with Grb2. Hydrogen peroxide also caused a time-dependent activation of extracellular signal-regulated protein kinases (ERKs; p42&p44) group of mitogen-activated protein kinases (MAPKs) in VSMC. The time courses of the hydrogen peroxide-stimulated FGFR1 tyrosine phosphorylation and ERKs activation were followed by induced expression of c-fos and c-jun. Genistein, a potent inhibitor of protein tyrosine kinases, significantly blunted the hydrogen peroxide-induced FGFR1 tyrosine phosphorylation, ERKs activation and c-fos and c-jun expression. PD98059, a specific inhibitor of MEK1, attenuated the hydrogen peroxide-induced ERKs activation and c-fos and c-jun expression. Together, these results suggest that oxidants such as hydrogen peroxide stimulate tyrosine phosphorylation of receptor tyrosine kinases and these, in turn, mediate the down-stream signalling events including the recruitment of Grb2 by the receptor, activation of ERKs and induction of c-fos and c-jun expression.
 ...
PMID:Protein tyrosine kinase activity is required for oxidant-induced extracellular signal-regulated protein kinase activation and c-fos and c-jun expression. 911 18

Reactive oxygen species modulate major cellular functions by mechanisms which are still poorly understood. Recently, H2O2 has been reported to stimulate the activity of the mitogen-activated protein kinases (MAPKs) ERK and JNK, and the expression of the proto-oncogenes c-fos and c-jun. As their expression is enhanced by H2O2 in astrocytes, we studied whether these MAPKs were stimulated by H2O2 in primary cultured astrocytes. The result was positive, a maximum of stimulation being reached with 200 microM H2O2 (0.3 pmol H2O2/cell) for both ERK and JNK. ERK was previously reported to stimulate cytosolic phospholipase A2 phosphorylation and activity. H2O2 stimulated the release of arachidonic acid in astrocytes, as already reported in other cell types. We found also that cPLA2 phosphorylation was increased by H2O2. Moreover, the stimulation by H2O2 of ERK and JNK was decreased by phospholipase A2 activity inhibitors. When astrocytes were incubated first with eicosatetraynoic acid, a structural analogue competing in arachidonic acid metabolism, the stimulation of JNK by H2O was also inhibited, suggesting the involvement of arachidonic acid metabolites. Cyclooxygenase or cytochrome P450 monooxygenase inhibitors failed in decreasing the MAPK stimulation by H2O2, whereas lipoxygenase inhibitors completely abolished that of JNK. Mitogenicity has been reported to be stimulated by H2O2 in other cell types. Although ERK was strongly and durably stimulated by 200 microM H2O2 in astrocytes, at the same extent as by mitogenic growth factors, basal thymidine incorporation rate was decreased by more than 80% after 12-15 h. Moreover, the stimulation of thymidine incorporation induced by basic fibroblast growth factor was transiently abolished by H2O2. Furthermore, H2O2 likely induced the expression of CL100/PAC1/MKP-1, a dual specificity phosphatase which has been implicated in ERK and JNK inactivation in the nucleus. Finally, the prior treatment of astrocytes with MK886, a 5-lipoxygenase-activating protein inhibitor, prevented JNK from stimulation, but did not prevent thymidine incorporation from inhibition, both induced by H2O2. These results strongly suggest an involvement of arachidonic acid and/or its metabolites in the stimulation of both ERK and JNK following the oxidative stress evoked by H2O2, which induced a cell cycle arrest probably independent of the stimulation of JNK.
 ...
PMID:Mediation by arachidonic acid metabolites of the H2O2-induced stimulation of mitogen-activated protein kinases (extracellular-signal-regulated kinase and c-Jun NH2-terminal kinase). 911 28

Recently, three mammalian mitogen-activated protein (MAP) kinases, ERK, SAPK/JNK, and p38/HOG-1 have been identified, each with apparently unique signal transduction pathways. The p38 MAP kinase mediates an intracellular stress-activated signaling pathway by regulating down-stream molecules, such as MAP kinase-activated protein (MAPKAP) kinase 2. To study the tissue specificity of MAPKAP kinase 2, mRNA blots containing multiple human tissues were hybridized with a specific oligonucleotide probe corresponding to human MAPKAP kinase 2. The Northern blot analysis revealed that two mRNA species of MAPKAP kinase 2, with sizes of 4.8 and 3.3 kb, were expressed in high levels in both human heart and skeletal muscle tissues. To better understand how MAPKAP kinase 2 is regulated in myocardium, cultured rat cardiac myoblast (H9c2) cells were stimulated with heat shock, H2O2-induced oxidative stress, or phorbol ester (PMA). Enzymatic activity of cellular MAPKAP kinase 2 in the cell lysates was evaluated using an in vitro kinase assay. Exposure of H9c2 cells to heat shock or oxidative stress induced a transient increase of cellular MAPKAP kinase 2 activity, which reached its peak level within 5 min. In contrast, stimulation of H9c2 cells with PMA, a potential myocardial hypertrophic factor, induced a sustained increase of cellular MAPKAP kinase 2 activity that was detectable for over 1 h. In addition, in vitro protein phosphorylation analysis with recombinant MAPKAP kinase 2 showed that small heat shock protein (hsp25) served as a major substrate molecule for the kinase in H9c2 cells and the protein phosphorylation of cellular hsp25 was stimulated by H2O2-induced oxidative stress or PMA treatment in intact H9c2 cells. Moreover, exposure of H9c2 cells to H2O2-induced oxidative stress or PMA rapidly activated cellular p38 MAP kinase as detected by the induced protein phosphorylation of the kinase. Taken together, these results strongly suggest that MAPKAP kinase 2 may be involved in stress-activated signal transduction in myocardium.
 ...
PMID:High expression and activation of MAP kinase-activated protein kinase 2 in cardiac muscle cells. 928 47


1 2 3 4 5 6 7 8 9 10 Next >>