Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Both MAP kinases and the protein kinase p74raf-1 are activated by many growth factors in a c-ras-dependent manner and by oncogenic p21ras. We were therefore interested in determining the relationship between MAP kinases and raf. The MAP kinase ERK2 is activated by expression of oncogenically activated raf, independently of cellular ras. Overexpressed p74raf-1 potentiates activation of ERK2 by EGF and TPA. MAP kinase kinase inactivated by phosphatase 2A treatment is phosphorylated and reactivated by incubation with p74raf-1 immunoprecipitated from phorbol ester-treated cells. We conclude that raf protein kinase is upstream of MAP kinases and is either a MAP kinase kinase kinase or a MAP kinase kinase kinase kinase.
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PMID:Activation of the MAP kinase pathway by the protein kinase raf. 133 Mar 21

When quiescent dog thyroid epithelial cells in primary culture are stimulated for 48 h with thyrotropin (TSH), forskolin acting through cAMP, or with cAMP-independent mitogens including epidermal growth factor (EGF), hepatocyte growth factor (HGF), and a tumor promoting phorbol ester (TPA), only 30-60% of cells progress through the cell cycle. A more general growth response requires the combination of EGF and TSH or forskolin. In this study we ask whether this intercellular heterogeneity in mitogen sensitivity could depend on a similar heterogeneity at early stages of the mitogenic stimulation process, i.e., at the levels of p42/p44 MAP kinase nuclear translocation and c-Fos protein appearance. We used indirect immunofluorescence microscopy with photometric quantitation and corroborated data using Western blotting. We analyzed the double staining of c-Fos and p42/p44 MAP kinases, since the nuclear translocation of these MAP kinases has been suggested as a key step for the stimulation of c-fos transcription. (i) EGF and HGF induced c-Fos accumulation and MAP kinase translocation in variable fractions of the cell population that corresponded to their relative potency as mitogens. c-Fos appearance and MAP kinase translocation poorly correlated in individual cells. Many cells accumulated c-Fos without any detectable p42/p44 MAP kinase translocation. The heterogeneity of proliferative responses to EGF could be due to the lack of c-Fos or MAP kinase responsiveness of many cells. (ii) TPA induced c-Fos accumulation and MAP kinase translocation within the whole cell population, which did not explain the heterogeneity of the growth response to this factor and showed that these events are not sufficient to elicit DNA synthesis, (iii) TSH and forskolin induced a weak c-Fos accumulation in only a minority of cells but, as previously shown, no p42/p44 MAP kinase phosphorylation and translocation. An important c-Fos expression was thus dispensable for the strong DNA synthesis stimulation exerted by cAMP-dependent mitogens. (iv) Forskolin potentiated the EGF effect on c-Fos expression but not on p42/p44 MAP kinase phosphorylation and translocation. This reflected the fact that EGF induced c-Fos accumulation in 90% of cells in the presence of forskolin but in 30-50% of cells in its absence. This kind of potentiation, which specifically implies an increase in the fraction of responding cells, is termed "generalization" in the present study.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Intercellular heterogeneity of early mitogenic events: cAMP generalizes the EGF effect on c-Fos protein appearance but not on MAP kinase phosphorylation and nuclear translocation in dog thyroid epithelial cells. 758 41

Phorbol ester tumor promoters (TPA) activate the endogenous erk/MAP kinases and Rsk S6 kinases but not the p70S6 kinase in COS cells. DNA sequences encoding the rat Rsk-1 S6 kinase (homologous to Xenopus rsk alpha), modified by insertion of a peptide epitope at the polypeptide aminoterminus, were expressed transiently in COS cells. TPA stimulates the 40S and peptide kinase activity of the recombinant epitope-tagged Rsk-1, as well as the extent of Rsk-1 autophosphorylation in vitro (32P-Ser >> 32P-Thr). Indications that the conformation of the recombinant Rsk-1 polypeptide is substantially changed after activation by TPA in situ include a retarded mobility of the Rsk-1 polypeptide on SDS-PAGE and the appearance of new 32P-peptides during autophosphorylation in vitro. All these features of the TPA-activated Rsk-1 S6 kinase are abolished by dephosphorylation of the kinase in vitro with Ser/Thr phosphatase-2A. TPA increases 32P incorporation into recombinant Rsk-1 by 2-3-fold (32P-Ser >> 32P-Thr). Peptide mapping exhibits a single major 32P-peptide in Rsk-1 isolated from unstimulated cells and 10-12 additional 32P peptides after TPA treatment in situ. Phosphorylation of basal or phosphatase-2A-treated recombinant Rsk-1 in vitro with erk2/MAP kinase increases Rsk-1 40S kinase, peptide kinase, and autophosphorylating activity, retards migration of Rsk-1 polypeptides on SDS-PAGE, and generates new sites of Rsk-1 autophosphorylation in vitro. By contrast, TPA-activated Rsk-1 is not altered in these properties by autophosphorylation in vitro. By contrast, TPA-activated Rsk-1 is not altered in these properties by phosphorylation in vitro with erk2/MAP kinase. Activation of Rsk-1 in situ with TPA diminishes by over 90% the extent of Rsk-1 phosphorylation achieved in vitro by erk2/MAP kinase, as compared to the parallel phosphorylation of a phosphatase-2A-treated Rsk-1; basal Rsk-1 is intermediate. Peptide maps of phosphatase-2A-treated Rsk-1 after phosphorylation in vitro with erk2/MAP kinase exhibit 32P-peptides that comigrate with nearly all of the 32P-peptides present in TPA-activated-32P Rsk-1 labeled in situ, plus several 32P-peptides characteristic of Rsk-1 autophosphorylation in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of an epitope-tagged recombinant Rsk-1 S6 kinase by phorbol ester and erk/MAP kinase. 768 67

The phorbol ester PMA/TPA (phorbol 12-myristate 13-acetate) is a potent tumor promoter which mimics distinct intracellular signalling events triggered by activated growth factor receptors, e.g. the activation of MAP kinases. The largest known family of TPA-binding proteins comprise members of the protein kinase C (PKC) family although other TPA-binding proteins outside the PKC family have recently been identified. In this report we addressed the mechanism and the pathway by which TPA induces the activation of MAPkinases. Using recombinant proteins and in vitro phosphorylation reactions we identified the components in the signal transduction pathway from TPA to MAPkinase and we show that the activation of MAPkinase by TPA requires the presence of protein kinase C, c-raf and the MAPkinase activator MEK. We also find that the activation of raf autophosphorylation in vitro correlates with the ability of Raf to signal to MAPkinase. Thus the activation of Raf by PKC apparently can trigger the same signalling pathway as oncogenic Raf or Raf activation by ras in combination with tyrosine phosphorylation.
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PMID:Signalling from TPA to MAP kinase requires protein kinase C, raf and MEK: reconstitution of the signalling pathway in vitro. 793 44

We have studied in cultured rat astroglial cells MAP kinases, known for their role in intracellular signal transduction. The MAP kinase activity was stimulated by growth factors (FGFb, FGFa, EGF, PDGF, and IGF1), by a phorbol ester (TPA) activating-protein kinase C (PKC), by a neuropeptide (endothelin-1), and by a neuromediator (carbachol). Astrocytes pretreated for 18 h with TPA were still stimulated by growth factors and endothelin, suggesting that down-regulated isoforms of PKC are not involved in MAP kinase activation. In contrast, the small effect of carbachol was suppressed by TPA pretreatment. Astrocytes contained two proteins (p41 and p44) recognized by MAP kinase antibody. These proteins were phosphorylated on tyrosine residues in the cytosols of stimulated astrocytes. The kinetics of MAP kinase activation by FGFb and IGF1 were very different. FGFb promoted a rapid activation of MAP kinase (about 10 min) plus a prolonged phase that lasted at least 12 h. IGF1 produced only a rapid transient peak of activation at about 20 min. Hence, extracellular signals might generate different effects in astrocytes by differentially modulating the MAP kinase cascade. On a Mono Q column the growth factor-stimulated MAP kinase activity was separated into two peaks containing p41 and p44. Stimulation of astrocytes altered the elution pattern of p44 as a result of its phosphorylation. An ATP-dependent MAP kinase activator (MW = 40-45 kDa) was found in fractions of FGFb-stimulated cells which were not retained on Mono Q column, indicating the existence of a MAP kinase kinase (MEK) in astrocytes. C-Raf, identified in other cells as a MAP kinase kinase kinase, was also present in astrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:MAP kinase cascade in astrocytes. 816 69

Treatment of rat 3Y1 fibroblasts with vasopressin (AVP) results in a transient activation of MAP kinase as potent as with EGF and serum. An antagonist of vasopressin receptor V1, but not an antagonist of V2, inhibited the AVP-induced activation of MAP kinases, indicating that AVP activates MAP kinases through V1 receptor. Prolonged TPA treatment of cells resulted in partial MAP kinase activation, indicating the presence of PKC-independent pathway. The pathway was inhibited by wortmannin, an inhibitor of PI3-kinase. The results suggest that wortmannin-sensitive molecules such as PI3-kinase, are involved in the V1 receptor-mediated activation of the MAP kinase pathway independent of TPA-sensitive PKC.
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PMID:Wortmannin inhibits the activation of MAP kinase following vasopressin V1 receptor stimulation. 854 62

Insulin-induced glucose transport stimulation, which results from the translocation of glucose transporter 4 (GLUT 4)-containing vesicles, is completely blocked after prolonged insulin treatment of 3T3-L1 adipocytes. Since GLUT 4 expression was reduced by only 30%, we looked at the insulin signaling pathway in this insulin-resistant model. Insulin-induced tyrosine phosphorylation of the major insulin receptor substrate IRS 1 was reduced by 50 +/- 7%, while its expression was decreased by 70 +/- 4%. When cells were treated with worthmannin (a PI3-kinase inhibitor) together with insulin, the expression of IRS 1 diminished to a much lower extent. Associated with the decrease in IRS 1 expression and phosphorylation, the activation by insulin of anti-phosphotyrosine immunoprecipitable PI3-kinase activity and of p44mapk activities was altered. However, the expression of these proteins was normal and p44mapk activity remained responsive to the tumour promoter TPA. Those results indicate that prolonged insulin treatment of 3T3-L1 adipocytes induces an insulin-resistant state with a reduced ability of insulin to stimulate the PI3-kinase and the MAP-kinases and a blockade of glucose transporter translocation.
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PMID:Alterations in insulin signalling pathway induced by prolonged insulin treatment of 3T3-L1 adipocytes. 869 Jan 66

The ERK, JNK/SAPK and p38/RK MAP kinase subtypes are differentially activated by physiological, pharmacological and stress stimuli; all three subtypes are implicated in immediate-early (IE) gene induction by these agents. Here, we have asked whether inhibition of a single MAP kinase subtype under these conditions would generally alter induction of several IE genes in a similar way or whether this would differentially up- and down-regulate particular IE genes, an issue which bears on the question of whether individual MAP kinases are strictly targeted to specific IE genes, or whether they might catalyse phosphorylation events that affect several IE genes in the same way. SB 203580, an inhibitor of p38/RK, has been used to analyse the role of this kinase in the induction of five IE genes (c-fos, fosB, c-jun, junB and junD) under diverse conditions of stimulation. In C3H 10T1/2 cells, p38/RK and its downstream kinase MAPKAP K-2 are activated by all stimuli used with the exception of TPA. The specificity of SB 203580 as a p38/RK inhibitor in these cells is demonstrated; it does not affect ERKs or JNK/SAPKs but does result in a small increase in the activity of the upstream kinase MKK6, the principal p38/RK activator in these cells. We find that inhibition of p38/RK under these conditions produces general effects on all five IE genes as a group in three ways. First, induction of all five genes in response to okadaic acid or tumour necrosis factor-alpha (TNF-alpha) is not significantly altered by SB 203580. Second, in cells stimulated with anisomycin or U.V. radiation, SB 203580 potently inhibits all of the induced IE genes. Finally, SB 203580 enhances induction of all five IE genes in EGF-treated cells; these enhanced mRNA levels are not due to stabilisation of labile mRNA transcripts. The significance of these results to current thinking on the relationship between distinct MAP kinase subtypes and specific IE genes is discussed.
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PMID:Effects of the inhibition of p38/RK MAP kinase on induction of five fos and jun genes by diverse stimuli. 939 76

Stimulation of c-Jun transcriptional activity via phosphorylation mediated by the stress-activated or c-Jun amino-terminal (SAPK/JNK) subgroup of mitogen-activated protein kinases (MAP kinases) is thought to depend on a kinase-docking site (the delta region) within the amino-terminal activation domain, which is deleted from the oncogenic derivative, v-Jun [1] [2] [3]. This mutation markedly enhances v-Jun oncogenicity [4] [5]; however, its transcriptional consequences have not been resolved. In part, this reflects uncertainty as to whether binding of SAPK/JNK inhibits c-Jun function directly [6] [7] or, alternatively, serves to facilitate and maintain the specificity of positive regulatory phosphorylation [8]. Using a two-hybrid approach, we show that SAPK/JNK stimulates c-Jun transactivation in yeast and that this depends on both catalytic activity and physical interaction between the kinase and its substrate. Furthermore, c-Jun is active when tethered to DNA via SAPK/JNK, demonstrating that kinase binding does not preclude transactivation. Taken together, these results suggest that SAPK/JNK acts primarily as a positive regulator of c-Jun transactivation in situ, and that loss of the docking site physically uncouples v-Jun from this control. This loss-of-function model accounts for the deficit of v-Jun regulatory phosphorylation and repression of TPA response element (TRE)-dependent transcription observed in v-Jun-transformed cells and predicts that an important property of the oncoprotein is to antagonise SAPK/JNK-dependent gene expression.
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PMID:An oncogenic mutation uncouples the v-Jun oncoprotein from positive regulation by the SAPK/JNK pathway in vivo. 942 47

By performing in vitro kinase assays we found in papilloma producing 308 mouse keratinocytes that okadaic acid elevated activities of extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinases (MAPKs). This okadaic acid mediated activation of MAP kinases correlated with increased AP-1 binding to a consensus TPA responsive element (TRE) and elevated TRE dependent transcription. To determine the role of p38 MAP kinases in these processes we employed the specific p38 MAP kinase inhibitor SB 203580. Using orthophosphate labeling we showed a decrease in phosphorylation of MAPK activated protein kinase-2 (MAPKAP-K2) indicating reduced activity of p38 MAPKs utilizing this kinase as substrate. In contrast, we found that SB 203580 raised activities of ERK-1/2 and JNKs. Electrophoretic mobility shift assays revealed an increase in TRE binding activity in response to SB 203580 most likely resulting from increased expression of the major TRE binding components JunD and FosB as indicated by Western blot analyses. Increased TRE DNA binding failed to lead to increased transactivation correlating with the inability of SB 203580 to increase phosphorylation of these AP-1 proteins. These data indicate that SB 203580 sensitive p38 MAP kinases are not involved in okadaic acid mediated increases in TRE DNA binding and transactivation.
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PMID:Inhibition of p38 MAP kinase increases okadaic acid mediated AP-1 expression and DNA binding but has no effect on TRE dependent transcription. 1038 Aug 84


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