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:2.7.11.24 (mitogen-activated protein kinase)
95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombin is known to evoke numerous inflammatory and proliferative responses in a wide variety of its target cells. Recent studies have demonstrated morphoregulatory and mitogenic effects of thrombin on astroglial cells (astrocytes). The present study deals with thrombin-induced activation of mitogen-activated protein (MAP) kinase in primary cultures of rat astrocytes. Treatment of serum-starved astrocytes with thrombin resulted in a rapid activation of tyrosine (Tyr) phosphorylation of a set of proteins including a prominent one with a molecular mass of 42 kDa (p42). The identity of p42 with MAP kinase was confirmed by MAP kinase-immunoreactivity of isolated [i.e., immunoprecipitated with anti-phosphotyrosine (PY) antibodies] p42 and by increased myelin basic protein (MBP) kinase activity present in MAP kinase immunoprecipitates of thrombin-treated cultures. Pertussis toxin (PTX) pretreatment failed to inhibit thrombin stimulation of p42 phosphorylation, indicating the lack of involvement of PTX sensitive G proteins in the mechanism of activation of MAP kinase by thrombin. Chronic exposure of cultures to phorbol 12-myristate 13-acetate to down-regulate PKC resulted in an attenuation of thrombin-induced p42 Tyr phosphorylation, although H-7, a known PKC inhibitor, failed to block thrombin effect. However, staurosporine, a nonspecific protein kinase inhibitor, prevented the activation of p42 phosphorylation. It is concluded that thrombin induces MAP kinase activation in astrocytes by a mechanism involving a staurosporine-sensitive pathway.
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PMID:Thrombin activates mitogen-activated protein kinase in primary astrocyte cultures. 759 20

Oocyte meiotic maturation is triggered by different stimuli (hormones, unknown signals through cell interactions) in different species. These stimuli indirectly lead to the activation of a major cell cycle regulating activity, the maturation promoting factor (MPF). Other factors, such as the product of the proto-oncogene c-mos or enzymes of the MAP kinase family, are also involved in the process of maturation. MAP kinase activation occurs during meiotic maturation in oocytes from different species with different kinetics. The relationships between MPF activation and MAP kinase activation have been well studied in species such as clam and Xenopus. In this paper, we study the precise timing of MAP kinase activation (as measured by phosphorylation of exogenous myelin basic protein and shifts in mobility of ERK 1 and ERK 2) versus MPF activation (as measured by phosphorylation of exogenous histone H1) during mouse oocyte maturation and, in parallel, morphological events such as changes in microtubule organization and chromatin condensation. We observed that MAP kinase activation was delayed after MPF activation and that this activity persisted throughout maturation whereas MPF activity dropped between the two meiotic metaphases. After parthenogenetic activation of ovulated eggs, MAP kinase inactivation was very slow compared to MPF inactivation. During the first mitotic cell cycle, a rise in myelin basic protein kinase activity at M-phase was observed but it was not related to MAP kinase activation. Furthermore, microtubules and chromatin remained in a metaphase-like state during the complete period of maturation (including the period between the two meiotic metaphases) and a few hours after activation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Microtubule and chromatin behavior follow MAP kinase activity but not MPF activity during meiosis in mouse oocytes. 760 Sep 50

The Ste20p protein kinase was immunopurified from yeast cells and analyzed in an in vitro assay system. Ste20p immune complexes exhibited autophosphorylating activity at serine and threonine residues and specifically phosphorylated a bacterially expressed glutathione S-transferase (GST) fusion of Ste11p (a mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase homologue) at serine and threonine residues. In contrast, GST fusions either of Ste7p (a MEK homologue) or the beta-subunit of the mating response G-protein and immunoprecipitated Ste5p were not phosphorylated by the Ste20p immune complexes. Myelin basic protein was identified as an excellent in vitro substrate, whereas histone H1 was only poorly phosphorylated. Evidence was obtained that autophosphorylation might play a regulatory role for the in vitro kinase activity. The in vitro activity was found to be Ca(2+)-independent. Both the in vivo and in vitro activities were abolished by mutational changes of either the conserved lysine residue 649 within the ATP binding site or threonine 777 between the catalytic subdomains VII and VIII. Wild-type Ste20p and the catalytically inactive T777A mutant were identified as phosphoproteins in vivo. The phosphorylation occurred at serine and threonine residues independent of pheromone stimulation. Based on the genetically determined significance of Ste20p in pheromone signal transduction and on our in vitro studies, we propose the model that Ste20p represents a yeast MEK kinase kinase whose function is to link G-protein-coupled receptors through G beta gamma to a mitogen-activated protein kinase module.
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PMID:Molecular characterization of Ste20p, a potential mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase kinase from Saccharomyces cerevisiae. 760 57

Adhesion to extracellular matrix mediates cell cycle progression in mid-late G1; this effect involves an integrin-dependent organization of the cytoskeleton and a consequent change in cell shape. In an effort to identify potential signal-transducing agents that are associated with integrin-dependent shape changes, we looked for kinase activities that were stimulated by long-term adhesion of G0-synchronized NIH-3T3 cells to fibronectin-coated dishes. Several kinase activities were stimulated by this procedure, two of which migrated at 42 and 44 kDa and phosphorylated myelin basic protein in vitro. Blotting with anti-phosphotyrosine and anti-mitogen-activated protein (MAP) kinase antibodies identified these enzymes as ERK 1 and ERK 2. In contrast to the rapid and transient activation of these MAP kinases by platelet-derived growth factor, stimulation of MAP kinase activity by fibronectin was gradual, persistent, and associated with cell spreading rather than cell attachment itself. Cytochalasin D blocked the activation of MAP kinase activity that was induced by the binding of cells to fibronectin. Moreover, MAP kinase was also activated by adhesion of cells to vitronectin and type IV collagen; these effects were also associated with cell spreading. These results distinguish the regulation of G1 phase MAP kinase activity by soluble mitogens and extracellular matrix. They also implicate MAP kinase in shape-dependent cell cycle progression.
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PMID:Integrin-dependent activation of MAP kinase: a link to shape-dependent cell proliferation. 761 63

Insulin stimulated a concentration-dependent increase in protein synthesis in L6 myoblasts which was significant at 1 nM. This response was not prevented by the transcription inhibitor, actinomycin D. The protein kinase C (PKC) inhibitor, Ro-31-8220, and downregulation of PKC by prolonged incubation of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), had no effect on the ability of insulin to stimulate protein synthesis whilst completely blocking the response to TPA. In contrast, insulin failed to enhance protein synthesis significantly in the presence of either ibuprofen, a selective cyclooxygenase inhibitor or rapamycin, an inhibitor of the 70 kDa S6 kinase. When cell extracts were prepared and assayed for total myelin basic protein kinase activity, a stimulatory effect of insulin was not observed until the concentration approached 100-fold (i.e. 100 nM) that required to elicit increases in protein synthesis. Upon fractionation on a Mono-Q column, 100 nM insulin increased the activity of 3 peaks which phosphorylated myelin basic protein. Two of these peaks were identified as the 42 and 44 kDa forms of Mitogen Activated Protein (MAP) kinase by immunoblotting. In contrast, 1 nM insulin had no effect on the activity of these peaks. The data suggest that physiologically relevant concentrations of insulin do not stimulate translation in L6 cells through either PKC or the 42/44 kDa isoforms of MAP kinase and that this response is, at least in part, mediated through the activation of the 70 kDa S6 kinase by cyclooxygenase metabolites.
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PMID:Evidence that protein kinase C and mitogen activated protein kinase are not involved in the mechanism by which insulin stimulates translation in L6 myoblasts. 764 90

Stimulation of human polymorphonuclear neutrophils with the chemotactic peptide FMLP induces an increase in the phosphorylation of several proteins on tyrosine residues. Immunoblotting of whole cell lysates with antiphosphotyrosine antibodies demonstrated this increase to be predominant in two proteins with apparent m.w. of 40,000 and 42,000, respectively. We identify these two proteins as members of the mitogen-activated-protein (MAP) kinase family. These results are based on comigration of the tyrosine phosphorylated proteins with two proteins of same apparent m.w., recognized by a series of antibodies raised against sequences contained within members of this family. This was further confirmed by immunoprecipitation with either an antiphosphotyrosine antibody or a MAP kinase-specific antibody. To assess whether neutrophil stimulation with FMLP increased MAP kinase activity, the cells were stimulated with various doses of FMLP and the phosphotransferase activity in cell lysates was measured against two identified substrates of MAP kinase: myelin basic protein and T-669, the epidermal growth factor receptor Thr 669 synthetic peptide modeled after the major site of phosphorylation of the receptor. A dose- and time-dependent increase in MAP kinase activity was detected in the lysates from FMLP-stimulated PMN, which closely correlated with the dose and time course of tyrosine phosphorylation of the 40- and 42-kDa proteins. Additionally, the MAP kinases in crude lysates were enriched by DEAE-cellulose chromatography and further resolved on a MonoQ column by fast performance liquid chromatography. The respective eluates contained the two proteins, each recognized by anti-MAP kinase antibodies and, after stimulation, each was phosphorylated on tyrosine residues and expressed T-669 phosphotransferase activity. Treatment with genistein, a tyrosine kinase inhibitor, reduced the tyrosine phosphorylation of the 40- and 42-kDa proteins in a dose-dependent manner, decreased the activation of the MAP kinases, and inhibited the production of superoxide anion by FMLP-stimulated neutrophils. Therefore, this study demonstrates that human polymorphonuclear neutrophils contain two distinct members of the MAP kinase family, antigenically related to sea star p44mpk and rat p43erk1 and that both MAP kinase isoforms are implicated in the cascade of protein phosphorylation induced by neutrophil stimulation with FMLP. Furthermore, these data suggest that tyrosine phosphorylation and activation of these two enzymes may play a regulatory role in the signal transduction pathway leading to the respiratory burst induced by FMLP.
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PMID:Stimulation of human neutrophils with formyl-methionyl-leucyl-phenylalanine induces tyrosine phosphorylation and activation of two distinct mitogen-activated protein-kinases. 767 31

Treatment of 3T3-L1 adipocytes with insulin resulted in activation of 2-deoxyglucose transport activity and translocation of glucose transporters (GLUT4 and GLUT1) from the cytoplasmic space to the plasma membrane. ML-9 (a myosin light chain kinase inhibitor) inhibited insulin stimulation of 2-deoxyglucose transport activity by 80% at 100 microM (IC50 = 27 microM) without affecting 2-deoxyglucose transport activity in the basal state. The inhibition was independent of extracellular Ca2+ concentration and almost fully reversible at 40 microM ML-9. ML-9 did not inhibit insulin-stimulated tyrosine phosphorylation of 95-kDa protein in the wheat germ agglutinin-purified preparation and of 95- and 160-kDa proteins in intact cells. However, ML-9 inhibited insulin-induced translocation of both GLUT4 and GLUT1 in a dose-dependent manner. The dose-response curves were similar to those observed for the inhibition of insulin stimulation of 2-deoxyglucose transport activity. Neither insulin nor ML-9 affected the phosphorylation state of both heavy and light chains of myosin. Therefore, it seems likely that ML-9 inhibits the insulin-induced translocation of glucose transporters at a step beyond the insulin receptor kinase activity by a mechanism different from that affecting phosphorylation of the myosin light chain. Phosphorylating activity of microtubule-associated protein 2 and myelin basic protein was stimulated by insulin, and this stimulation was not affected by ML-9. ML-9, however, inhibited the phosphorylating activity in vitro and insulin stimulation of the phosphorylating activity of ribosomal protein S6 in intact cells in a dose-dependent manner similar to that observed for the inhibition of insulin stimulation of glucose transport. These results suggest that mitogen-activated protein kinase may be one of the constituents in intracellular insulin signaling to the glucose transport system.
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PMID:Effects of ML-9 on insulin stimulation of glucose transport in 3T3-L1 adipocytes. 768 Mar 48

Human polymorphonuclear neutrophils exhibit a low level of the microtubule-associated protein kinase (MAPK) activity. This enzymic activity is enhanced up to 3-fold upon cell stimulation with the human haematopoietic hormone granulocyte-macrophage colony-stimulating factor (GM-CSF). This is demonstrated both in whole-cell lysates and in DEAE-anion-exchange semi-purified fractions prepared from GM-CSF-stimulated neutrophils, by assaying the kinase activity against either myelin basic protein or a phosphoacceptor peptide that bears the specific phosphorylation site of the MAPK natural substrate. Similarly, phosphorylation of MAPK in tyrosine residues, as found in immunoblots using anti-phosphotyrosine antibodies, follows similar time- and dose-response curves as the kinase activation. Pretreatment of the cells with the tyrosine kinase inhibitor genistein abrogates the above-mentioned effect, whereas the phosphatase inhibitor okadaic acid enhances both the basal and the GM-CSF-stimulated kinase activities. Likewise, MAPK tyrosine phosphorylation is diminished in genistein-treated neutrophils, and enhanced in okadaic acid-treated cells. We conclude that MAPK activity is present in human neutrophils, and that it is stimulated by GM-CSF. This stimulation of the activity is most likely due to the phosphorylation of MAPK in tyrosine residues triggered upon binding of GM-CSF to its receptors.
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PMID:Direct stimulation by tyrosine phosphorylation of microtubule-associated protein (MAP) kinase activity by granulocyte-macrophage colony-stimulating factor in human neutrophils. 768 11

PTP1C, a protein-tyrosine-phosphatase (protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) containing two src homology 2 domains, is poorly active when assayed with various protein substrates in vitro. Its activity is stimulated > 1000-fold by anionic phospholipids when myelin basic protein or mitogen-activated protein kinase is used as substrate but reduced in the presence of several other substrates. Data are presented to indicate a direct interaction of the enzyme with phospholipids. Enzyme stimulation directed only toward certain specific substrates is interpreted by assuming that these compounds also bind to the phospholipid vesicles where they will be subjected to rapid enzymatic attack. A possible regulation of PTP1C by its translocation to the cell membrane is hypothesized.
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PMID:Stimulation by phospholipids of a protein-tyrosine-phosphatase containing two src homology 2 domains. 768 30

Mitogen-activated protein kinase (MAP kinase) plays a role in the cascade of protein kinase activation in cultured cells. To investigate the involvement of MAP kinase in meiotic maturation, we measured MAP kinase activity, using myelin basic protein as a substrate, with histone H1 kinase activity, in mouse oocytes. MAP kinase activity was low 1 h after isolation from follicles (when oocytes lost their germinal vesicle), increased abruptly at 2 h, and remained high until the second metaphase (13 h after isolation from follicles). Histone H1 kinase activity increased gradually from 2 to 7 h after isolation. When immature oocytes were treated with puromycin, MAP kinase activity did not increase after isolation from follicles. In the presence of 3-isobutyl-1-methylxanthine, the treatment of immature oocytes with okadaic acid, a specific inhibitor of protein phosphatase 1 and 2A, induced germinal vesicle breakdown and activation of MAP kinase. These results suggest that MAP kinase is involved in the regulation of meiotic maturation, and that the activation of MAP kinase requires protein synthesis and is inhibited by the protein phosphatase during meiotic maturation in mouse oocytes.
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PMID:Activation of mitogen-activated protein kinase during meiotic maturation in mouse oocytes. 768 86


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