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)

To examine the molecular mechanisms by which mechanical stimuli induce protooncogene expression, we cultured rat neonatal cardiocytes in deformable dishes and imposed an in vitro mechanical load by stretching the adherent cells. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos and skeletal alpha-actin followed by activation of protein synthesis. CAT assay indicated that sequences containing a serum response element were required for efficient transcription of c-fos gene by stretching. This accumulation of c-fos mRNA was suppressed by protein kinase C inhibitors at the transcriptional level and was inhibited markedly by down-regulation of protein kinase C. Moreover, myocyte stretching increased inositol phosphate levels. These findings suggest that mechanical stimuli might directly induce protooncogene expression, possibly, via protein kinase C activation. Furthermore, we observed the activation of mitogen activated protein (MAP) kinase by myocyte stretching. This result suggest that MAP kinase activation might increase the efficiency of protein synthesis in ribosomes induced by mechanical stimuli.
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PMID:Role of protein kinase system in the signal transduction of stretch-mediated myocyte growth. 133 62

Adult mammalian ventricular cardiomyocytes are terminally differentiated cells that enlarge adaptively by hypertrophy. In this situation, genes normally expressed in the fetal ventricular cardiomyocyte (e.g. atrial natriuretic factor (ANF), beta-myosin heavy chain (beta-MHC), and skeletal muscle (SkM) alpha-actin) are re-expressed, and there is transient expression of immediate early genes (e.g. c-fos). Using appropriate reporter plasmids, we studied the effects of transfection of the constitutively active or dominant negative mitogen-activated protein kinase kinase MEK1 on ANF, beta-MHC, and SkM alpha-actin promoter activities in cultured ventricular cardiomyocytes. ANF expression was stimulated (maximally 75-fold) by the hypertrophic agonist phenylephrine in a dose-dependent manner (EC50, 10 microM), and this stimulation was inhibited by dominant negative MEK1. Cotransfection of dominant negative MEK1 with a dominant negative mitogen-activated protein kinase (extracellular signal-regulated protein kinase (ERK2)) increased this inhibition. Transfection with constitutively active MEK1 constructs doubled ANF promoter activity. The additional cotransfection of wild-type ERK2 stimulated ANF promoter activity by about 5-fold. Expression of beta-MHC and SkM alpha-actin was also stimulated. Promoter activity regulated by activator protein-1 or c-fos serum response element consensus sequences was also increased. We conclude that the MEK1/ERK2 cascade may play a role in regulating gene expression during hypertrophy.
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PMID:The mitogen-activated protein kinase kinase MEK1 stimulates a pattern of gene expression typical of the hypertrophic phenotype in rat ventricular cardiomyocytes. 749 96

A pyrazolo-quinoline compound, 6-methoxy-4-[2-[(2-hydroxyethoxyl)-ethyl]amino]-3-methyl-1M-pyrazo lo [3,4-b]quinoline (SCH 51344), was identified based on its ability to derepress human smooth muscle alpha-actin promoter activity in ras-transformed cells. In this study, we show that SCH 51344 reverts several key aspects of ras transformation, such as morphological changes, actin filament organization, and anchorage-independent growth, and also inhibits Val-12 Ras-induced maturation of Xenopus oocytes. SCH 51344 is also a potent inhibitor of the anchorage-independent growth of human tumor lines known to contain multiple genetic alterations in addition to activated ras genes. We have sought to determine whether SCH 51344 disrupts the signaling pathway that activates mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK) in normal and ras-transformed fibroblast cells. NIH 3T3 cells transformed by different oncogenes, which have products that participate at different steps of the Ras signaling pathway, were tested in a soft-agar colony formation assay to determine which step of the pathway is inhibited by SCH 51344. Our results indicate that SCH 51344 inhibits the ability of v-abl, v-mos, H-ras, v-raf, and mutant active MAP kinase kinase-transformed NIH 3T3 cells to grow in soft agar. Only v-fos-transformed cells were found to be resistant to the treatment of SCH 51344. SCH 51344 treatment had very little effect, if any, on the activation of MAP kinase kinase, MAP kinase, and p90RSK activity in response to growth factor stimulation. Treatment of ras-transformed cells with SCH 51344 led to stimulation of serum response factor DNA binding activity and activation of serum response element-dependent gene transcription, accounting for its ability to activate alpha-actin promoter activity in ras-transformed cells. Our results indicate that SCH 51344 inhibits ras transformation by a novel mechanism and acts at a point either downstream or parallel to extracellular signal-regulated kinase-dependent Ras signaling pathway.
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PMID:SCH 51344 inhibits ras transformation by a novel mechanism. 758 59

It has been suggested that phosphorylation of a 40S ribosomal protein, S6, regulates protein synthesis. Two distinct families of S6 kinase have been identified, the rsk-encoded 85- to 92-kD S6 kinase (RSK) and the 70- or 85-kD S6 kinase (p70S6K). We have previously shown that hypertrophic stimuli, such as angiotensin II (Ang II), rapidly activate RSK in cardiac myocytes. However, RSK and p70S6K are regulated by distinct mechanisms, and p70S6K, but not RSK, is the physiological S6 kinase in vivo in other cell types. Using cultured neonatal rat ventricular myocytes, we examined whether Ang II activates p70S6K and investigated the effect of rapamycin, a potent yet indirect inhibitor of p70S6K, on the Ang II-induced hypertrophic response. Immunoblot analyses indicate that cardiac myocytes express the 70- and 85-kD forms of p70s6K. Ang II caused a rapid and sustained activation of p70S6K through the type I Ang II receptor. Rapamycin inhibited Ang II-induced activation of p70S6K in a dose-dependent manner, with an IC50 of 0.14 ng/mL (0.15 nmol/L). Rapamycin did not inhibit Ang II-induced activation of tyrosine kinase, mitogen-activated protein kinase, RSK, and protein kinase C. The effect of rapamycin is unlikely to be mediated by its effect on p34cdc2 and p33cdk2 because Ang II did not activate these cell cycle-dependent kinases in cardiac myocytes. In contrast, a dose-dependent inhibition of p70S6K by rapamycin is very closely correlated with its inhibition of the Ang II-induced increase in protein synthesis. Interestingly, rapamycin did not affect the Ang II-induced activation of specific gene expression, including the immediate-early gene c-fos and fetal type genes, such as atrial natriuretic factor and skeletal alpha-actin. Moreover, rapamycin did not suppress Ang II-induced phenotypic changes at the protein level, such as increased atrial natriuretic factor secretion, expression of beta-myosin heavy chain, and organization of actin into sarcomeric units. These results indicate that p70S6K is activated by Ang II and that a rapamycin-sensitive signaling mechanism, most likely p70S6K, plays an essential role in the Ang II-induced increase in overall protein synthesis but not in Ang II-induced specific phenotypic changes in cardiac myocytes.
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PMID:Rapamycin selectively inhibits angiotensin II-induced increase in protein synthesis in cardiac myocytes in vitro. Potential role of 70-kD S6 kinase in angiotensin II-induced cardiac hypertrophy. 758 15

Vascular smooth muscle cells have been shown to exist in two phenotypic states which have been designated proliferative and contractile. The properties of rat aortic vascular smooth muscle cells grown on Matrigel were compared with cells grown on untreated plastic culture dishes. Cells grown on Matrigel manifested at least four important properties characteristic of the contractile phenotype as compared with cells grown on plastic. The cells grown on Matrigel had altered morphology similar to in vivo studies of contractile vascular smooth muscle. The cells had a low proliferative index, showed enhanced levels of the smooth muscle isoform of alpha-actin, and had an enhanced contractile response to the vasoconstrictor arginine vasopressin. All of these changes were maintained through at least five passages and could be reversed by replating cells grown on Matrigel back to uncoated plastic dishes. Changes in post-receptor signaling pathways which could account for the altered physiologic responses of the cells were investigated. Cells grown on Matrigel showed no alterations in agonist-induced mobilization of intracellular Ca2+ or agonist-stimulated cAMP levels. However, stimulation of mitogen-activated protein kinase (MAP kinase) by both vasoconstrictors and growth factors was inhibited by 50% in cells grown on Matrigel as compared with plastic. This decrease in agonist-induced MAP kinase was associated with a decrease in the levels of both p42 and p44 MAP kinase protein and a decrease in tyrosine phosphorylation of both isoforms in cells grown on Matrigel. Alterations in MAP kinase activation can account at least in part for the observed physiologic responses of contractile vascular smooth muscle. Growth of vascular smooth muscle cells on Matrigel represents a useful model to examine phenotypic-dependent alterations in post-receptor signaling.
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PMID:Vascular smooth muscle cells grown on Matrigel. A model of the contractile phenotype with decreased activation of mitogen-activated protein kinase. 803 34

To examine the molecular mechanisms by which mechanical stimuli induce protooncogene expression and hypertrophy of cardiac myocytes directly, we cultured rat neonatal cardiac myocytes in deformable dishes and imposed mechanical load on adherent cultured cardiac myocytes by stretching the dishes. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos and skeletal alpha-actin followed by the amino acid incorporation into cardiac proteins. CAT assay analysis indicated that the sequences containing serum response element were required for the efficient transcription of c-fos gene by stretching. This accumulation of c-fos mRNA by myocyte stretching was inhibited markedly by down-regulation of protein kinase C. Moreover, myocyte stretching increased inositol phosphate levels. These findings suggests that mechanical stimuli might directly induce protooncogene expression possibly via protein kinase C activation. Furthermore, we observed the activation of MAP kinase by myocytes stretching. This result suggests that MAP kinase activation induced by mechanical stimuli might increase the efficiency of protein synthesis on ribosomes induced by mechanical stimuli.
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PMID:Role of protein kinase system in the signal transduction of stretch-mediated protooncogene expression and hypertrophy of cardiac myocytes. 838 96

Transfected Jurkat cells overexpressing extracellular signal-regulated kinase (ERK1), also referred to as mitogen-activated protein (MAP) kinase, were selected by Western blotting assay using anti-ERK1 and antiphosphotyrosine antibodies in combination with a functional MAP kinase assay. We then asked whether enhanced ERK1 expression had any effect on induction of T-cell cytokine genes. The results show that overexpression of ERK1 enhances expression of T-cell interleukin-2 (IL-2), IL-3, and granulocyte-macrophage colony-stimulating factor mRNA; no change was seen in expression of the alpha-actin gene. DNA-binding activities of the transcription factors AP1, NF-AT, and NF-kB were specifically increased twofold to fourfold in ERK1-overexpressing clones relative to nontransformed or vector-transformed cells, whereas no enhancement of CK1-CK2 protein DNA binding activity was detected after ERK1 overexpression. Additionally, increased NF-AT DNA binding activity was associated with functional enhancement of NF-AT transactivating activity in ERK1-overexpressing cells. These results provide direct evidence for the role of MAP kinase in the regulation of cytokine gene expression and indicate that such regulation is likely mediated through the enhanced DNA binding activity of specific nuclear transcription factors.
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PMID:Overexpression of mitogen-activated protein kinase (ERK1) enhances T-cell cytokine gene expression: role of AP1, NF-AT, and NF-KB. 840 Feb 95

We have previously shown that extracellular ATP, like norepinephrine (NE) and many other hypertrophy-inducing agents, increases expression of the immediate-early genes c-fos and junB in cultured neonatal cardiac myocytes but that the intracellular signaling pathways activated by ATP and responsible for these changes differ from those stimulated by NE. Furthermore, whereas NE increases incorporation of [14C]phenylalanine (14C-Phe) and cell size in neonatal cardiomyocytes, ATP does not. Since ATP is coreleased with NE from sympathetic nerve endings in the heart, we investigated whether ATP could modulate cardiac hypertrophy induced by adrenergic agonists, such as NE. We report in the present study that extracellular ATP inhibited the increase in incorporation of 14C-Phe into cellular protein and the increase in cell size in neonatal rat cardiac myocytes that was induced by NE, phenylephrine (PE), basic fibroblast growth factor, or endothelin-1. This inhibition was dose dependent, occurred predominantly through P2 purinergic receptors, and was observed even when cells were treated with ATP for as little as 1 hour before the addition of the hypertrophy-inducing agent. ATP also selectively affected changes in gene expression associated with hypertrophy. It prevented PE-stimulated increases in atrial natriuretic factor and myosin light chain-2 mRNA levels, while appearing to augment basal and PE-stimulated skeletal alpha-actin mRNA levels. ATP alone increased sarcoplasmic reticulum Ca2+-ATPase mRNA levels but had no effect when added with PE. ATP did not significantly affect the level of the constitutively expressed mRNA for GAPDH. Neither the PE-stimulated increase in immediate-early gene expression nor the initial induction of mitogen-activated protein kinase activity by PE was inhibited by ATP. These results demonstrate that extracellular ATP can inhibit hypertrophic growth of neonatal cardiac myocytes and differentially alter the changes in gene expression that accompany hypertrophy.
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PMID:Extracellular ATP inhibits adrenergic agonist-induced hypertrophy of neonatal cardiac myocytes. 863 9

The effect of constitutive expression of mitogen-activated protein kinase (MAPK) phosphatase 1 (MKP-1) on gene expression in response to hypertrophic agonists was examined in cultured neonatal rat ventricular myocytes. Luciferase (LUX) reporter genes linked to promoters for atrial natriuretic factor, ventricular myosin light chain 2, beta-myosin heavy chain, skeletal muscle alpha-actin (SkM alpha-actin) and serum response element-regulated c-fos (c-fos-SRE) were transfected into cardiomyocytes. Phenylephrine (PE; 10 microM), phorbol 12-myristate 13-acetate (1 microM) and endothelin 1 (10 nM) stimulated the expression of these various reporter genes by 2. 5-20-fold. MKP-1 inhibited these effects by 60-85%. In contrast, MKP-1 had no effect on the expression of a constitutively active Rous sarcoma virus-LUX reporter gene. A catalytically inactive mutant MKP-1CS (cysteine-->serine mutation) and the broad-specificity protein tyrosine phosphatase 1B (PTP-1B) had no significant effect on any reporter gene tested. MKP-1 had much less effect on the morphological features accompanying agonist-induced cardiac hypertrophy. PE (10 microM) increased myocyte area by 59% but this effect was only decreased by one-third by MKP-1 and was also partly decreased (by 25%) by expression of PTP-1B. PE also altered cell shape but this was unaffected by MKP-1. There was also no clear effect of MKP-1 on the organization of the contractile apparatus into sarcomeric structures in the presence of 10 microM PE. We conclude that the transcriptional responses accompanying cardiac myocyte hypertrophy are dependent on an MKP-1-sensitive step, presumably the activation of one or members of the MAPK family, but that cell size, shape and myofibrillar organization are much less sensitive to inhibition by MKP-1.
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PMID:Mitogen-activated protein kinase phosphatase 1 inhibits the stimulation of gene expression by hypertrophic agonists in cardiac myocytes. 916 18

RAS controls at least two signaling pathways, one regulating extracellular signal-regulated kinase (ERK) activation and the other controlling membrane ruffling formation. Activating RAS mutations are commonly found in human tumors, making RAS and its downstream signaling pathways important targets for tumor therapeutics. We have developed a reporter-gene based assay system, utilizing transformation sensitive alpha-actin promoter, to identify compounds that inhibit the transforming activity of RAS either directly or indirectly. SCH51344 is a pyrazolo-quinoline derivative, identified based on its ability to depreprses alpha-actin promoter in RAS-transformed cells and shown to be a potent inhibitor of RAS-transformation. However, this compound had very little effect on the activities of the proteins in the ERK pathway, suggesting that it inhibits RAS-transformation by a novel mechanism and acts on a signaling pathway distinct from ERK pathway. Recently, in collaboration with Dr. Dafna Bar-Sagi's group, we have shown that SCH51344 inhibits membrane ruffling induced by activated forms of H-RAS, K-RAS, N-RAS and RAC. Treatment of fibroblast cells with this compound had very little effect on RAS-mediated activation of ERK and Jun kinase activities. Our results indicate that SCH51344 inhibits a critical component of the membrane ruffling pathway downstream from RAC and suggest that targeting the membrane ruffling pathway may be an effective approach to inhibit transformation by RAS.
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PMID:[Inhibition of RAS-transformation by SCH51344]. 930 48


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