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)

To examine the role of clathrin-coated vesicle endocytosis in insulin receptor signaling and GLUT4 trafficking, we used recombinant adenovirus to express a dominant interfering mutant of dynamin (K44A/dynamin) in 3T3L1 adipocytes. Functional expression of K44A/dynamin, as measured by inhibition of transferrin receptor internalization, did not affect insulin-stimulated insulin receptor autophosphorylation, Shc tyrosine phosphorylation, or mitogen-activated protein kinase activation. Although the tyrosine phosphorylation of insulin receptor substrate-1 was slightly reduced, correlating with a 25% decrease in insulin receptor substrate-1-associated phosphatidylinositol 3-kinase activity, insulin-stimulated Akt kinase activation was unaffected. In contrast, expression of K44A/dynamin resulted in the cell-surface accumulation of GLUT4 under basal conditions and an inhibition of GLUT4 endocytosis without affecting insulin-stimulated GLUT4 exocytosis. These data demonstrate that disruption of clathrin-mediated endocytosis does not significantly perturb insulin receptor signal transduction pathways. Furthermore, K44A/dynamin expression causes an accumulation of GLUT4 at the cell surface, suggesting that GLUT4 vesicles exist in at least two distinct intracellular compartments, one that undergoes continuous recycling and a second that is responsive to insulin.
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PMID:Expression of a dominant interfering dynamin mutant in 3T3L1 adipocytes inhibits GLUT4 endocytosis without affecting insulin signaling. 973 14

The trefoil gene family of mucus cell-secreted proteins is a critical mediator of gastrointestinal mucosal restitution. Transcription of trefoil genes is induced during mucosal repair, but the regulatory mechanisms involved are unknown. Mice deficient in the intestine-specific peptide intestinal trefoil factor (ITF), in which colonic restitution is lethally impaired, showed reduced expression of the gastric trefoil genes SP and pS2, suggesting that trefoil peptides may individually regulate transcription of the entire family. In gastric cell lines, the trefoils were shown to act in a manner suggestive of immediate-early genes capable of auto- and cross-induction through cis-acting regulatory regions. Trefoil-mediated transcriptional regulation required activation of the Ras/MEK/MAP kinase signal transduction pathway. EGF receptor (EGF-R) activation was also necessary for trefoil auto- and cross-induction, and both spasmolytic polypeptide (SP) and ITF stimulation of gastric cell lines led to phosphorylation of EGF-R. Nevertheless, ITF and ITF-thioredoxin cell surface binding at 4 degrees C colocalized not with EGF-R, but with CD71, which is found in clathrin-coated pits, suggesting that integration of trefoil peptide responses may occur after internalization. As EGF-R expression is itself strongly induced after mucosal damage, the trefoil/EGF-R relationship may be pivotal in the generation and maintenance of the mucosal repair phenotype.
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PMID:The trefoil gene family are coordinately expressed immediate-early genes: EGF receptor- and MAP kinase-dependent interregulation. 1022 80

Heme oxygenase (HO) is responsible for the physiological breakdown of heme into equimolar amounts of biliverdin, carbon monoxide, and iron. Three isoforms (HO-1, HO-2, and HO-3) have been identified. HO-1 is ubiquitous and its mRNA and activity can be increased several-fold by heme, other metalloporphyrins, transition metals, and stimuli that induce cellular stress. HO-1 is recognized as a major heat shock/stress response protein. Recent work from our laboratory has demonstrated several potential consensus regulatory elements in the 5'-untranslated region (UTR) of HO-1, including activator protein 1 (AP-1), metal responsive element (MRE), oncogene c-myc/max heterodimer binding site (Myc/Max), antioxidant response element (ARE), and GC box binding (Sp1) sites. Using deletion-reporter gene constructs, we have mapped sites that mediate the arsenite-dependent induction of HO-1, and we have shown that components of the extracellular signal-regulated kinase (ERK) and p38 (a homologue of the yeast HOG1 kinase), but not c-jun N-terminal kinase (JNK), mitogen-activated protein (MAP) kinase pathways are involved in arsenite-dependent upregulation. In contrast, HO-2 is present chiefly in the brain and testes and is virtually uninducible. HO-3 has very low activity; its physiological function probably involves heme binding. Products of the HO reaction have important effects: carbon monoxide is a potent vasodilator, which is thought to play a key role in the modulation of vascular tone, especially in the liver under physiological conditions, and in many organs under "stressful" conditions associated with HO-1 induction. Biliverdin and its product bilirubin, formed in most mammals, are potent antioxidants. In contrast, "free" iron increases oxidative stress and regulates the expression of many mRNAs (e.g., DCT-1, ferritin, and transferrin receptor) by affecting the conformation of iron regulatory protein (IRP)-1 and its binding to iron regulatory elements (IREs) in the 5'- or 3'-UTRs of the mRNAs.
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PMID:Heme oxygenase: recent advances in understanding its regulation and role. 1051 65

Ha-Ras is modified by isoprenoid on Cys(186) and by reversibly attached palmitates at Cys(181) and Cys(184). Ha-Ras loses 90% of its transforming activity if Cys(181) and Cys(184) are changed to serines, implying that palmitates make important contributions to oncogenicity. However, study of dynamic acylation is hampered by an absence of methods for acutely manipulating Ha-Ras palmitoylation in living cells. S-nitrosocysteine (SNC) and, to a more modest extent, S-nitrosoglutathione were found to rapidly increase [(3)H]palmitate incorporation into cellular or oncogenic Ha-Ras in NIH 3T3 cells. In contrast, SNC decreased [(3)H]palmitate labeling of the transferrin receptor and caveolin. SNC accelerated loss of [(3)H]palmitate from Ha-Ras, implying that SNC stimulated deacylation and permitted subsequent reacylation of Ha-Ras. SNC also decreased Ha-Ras GTP binding and inhibited phosphorylation of the kinases ERK1 and ERK2 in NIH 3T3 cells. Thus, SNC altered two important properties of Ha-Ras activation state and lipidation. These results identify SNC as a new tool for manipulating palmitate turnover on Ha-Ras and for studying requirements of repalmitoylation and the relationship between palmitate cycling, membrane localization, and signaling by Ha-Ras.
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PMID:S-Nitrosocysteine increases palmitate turnover on Ha-Ras in NIH 3T3 cells. 1080 23

Intracellular iron homeostasis is regulated, in part, by interactions between iron-regulatory proteins (IRP1 and IRP2) and iron-responsive elements (IREs) in ferritin and transferrin receptor mRNAs. In addition to iron, cellular oxidative stress induced by H(2)O(2), nitric oxide, and hypoxia, and hormonal activation by thyroid hormone and erythropoeitin have each been shown to regulate IRP binding to IREs. Hormonal signals, in particular mediated through protein kinase C (PKC), play a central role in the modulation of IRP/IRE interactions since phorbol esters were shown to activate IRP binding (Eisenstein, R. S., Tuazon, P. T., Schalinske, K. L., Anderson, S. A., and Traugh, J. A. (1993) J. Biol. Chem. 268, 27363-27370). In pituitary thyrotrophs (TtT97), we found that thyrotropin releasing hormone (TRH) and epidermal growth factor (EGF) increased IRP binding to a ferritin IRE, dependent on PKC and mitogen-activated protein kinase (MAPK) activity. In contrast, TRH and EGF decreased IRP binding in pituitary lactotrophs (GH3), despite activation of PKC and MAPK. IRP1 and IRP2 levels remained constant and IRP2 binding was predominant throughout. TRH and EGF markedly decreased IRP binding in MAPK kinase inhibitor-treated GH3 cells, whereas, they increased IRP binding in phosphatase inhibitor-treated GH3 cells. IRE-dependent CAT reporter translational expression closely reflected IRP binding to the ferritin IRE in both GH3 and TtT97 cells. Interestingly, ferritin protein levels were regulated similarly by TRH in both cell lines. These data link two different cell receptor systems to common signaling pathways that regulate IRP binding and ferritin expression. Remarkably, for TRH and EGF, these effects may be PKC-dependent or -independent determined by the cell type.
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PMID:Thyrotropin-releasing hormone and epidermal growth factor regulate iron-regulatory protein binding in pituitary cells via protein kinase C-dependent and -independent signaling pathways. 1088 93

We previously identified intersectin, a multiple EH and SH3 domain-containing protein, as a component of the endocytic machinery. Overexpression of the SH3 domains of intersectin blocks transferrin receptor endocytosis, possibly by disrupting targeting of accessory proteins of clathrin-coated pit formation. More recently, we identified mammalian Sos, a guanine-nucleotide exchange factor for Ras, as an intersectin SH3 domain-binding partner. We now demonstrate that overexpression of intersectin's SH3 domains blocks activation of Ras and MAP kinase in various cell lines. Several studies suggest that activation of MAP kinase downstream of multiple receptor types is dependent on endocytosis. Thus, the dominant-negative effect of the SH3 domains on Ras/MAP kinase activation may be indirectly mediated through a block in endocytosis. Consistent with this idea, incubating cells at 4 degrees C or with phenylarsine oxide, treatments previously established to inhibit EGF receptor endocytosis, blocks EGF-dependent activation of MAP kinase. However, under these conditions, Ras activity is unaffected and overexpression of the SH3 domains of intersectin is still able to block Ras activation. Thus, intersectin SH3 domain overexpression can effect EGF-mediated MAP kinase activation directly through a block in Ras, consistent with a functional role for intersectin in Ras activation.
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PMID:Intersectin can regulate the Ras/MAP kinase pathway independent of its role in endocytosis. 1089 62

Ets-family genes have been implicated in leukemia, as well as in normal hematopoiesis. ERF is an ets-related gene that represses transcription and is regulated by MAPK phosphorylation through its effect on ERF sub-cellular localization. Using pluripotent human cell lines, we studied the effect of ERF on erythroid differentiation. K562 and HEL cells expressing ERF expressed elevated levels of the erythroid-specific markers CD71 and Glycophorin A, as well as hemoglobin and GATA1. Treatment with the Erk kinase inhibitor PD98058 further enhanced the erythroid phenotype in ERF-expressing cells and cells expressing a non-phosphorylatable ERF mutant exhibited an even more enhanced phenotype. These results are consistent with the fact that ERF function is regulated by MAPK, and suggest that the effect of the MAPK pathway in erythroid differentiation is partially mediated by ERF. The effect of ERF is similar to the one shown for ETS1 and opposite to the FLI1 function in these cells, suggesting that several ets genes may play key roles in hematopoietic differentiation.
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PMID:ERF, an ETS-related transcriptional repressor, can induce erythroid differentiation. 1289 89

The AMP-activated protein kinase (AMPK) pathway participates in the metabolic effects of contraction on muscle glucose uptake. We have shown that contraction increases both GLUT4 translocation to the cell surface and p38 mitogen-activated protein kinase (p38 MAPK) activity. The latter pathway may be involved in the activation of GLUT4. Here we investigated whether the AMPK activator AICAR increases glucose uptake by inducing translocation of GLUT4 and/or by activating the p38 MAPK pathway. AICAR infusion into glucose-clamped rats increased muscle glucose uptake and GLUT4 translocation from an intracellular fraction to the plasma membrane but not to T-tubules. AICAR also caused recruitment of the transferrin receptor to the plasma membrane and increased [125I]-transferrin uptake in isolated muscle. AICAR treatment in vivo or in vitro activated both p38 MAPKalpha and beta (1.6- to 2.8-fold) in EDL muscles with a time course identical to that of stimulation of AMPK and glucose transport. The p38 MAPK inhibitor SB203580 abrogated the stimulatory effect of AICAR on glucose uptake. These results suggest that AICAR increases muscle glucose uptake by two mechanisms: 1) inducing selective recruitment of GLUT4 to the plasma membrane, and 2) activating p38 MAPKalpha and beta, which may be involved in the activation of GLUT4.
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PMID:The AMP-activated protein kinase activator AICAR does not induce GLUT4 translocation to transverse tubules but stimulates glucose uptake and p38 mitogen-activated protein kinases alpha and beta in skeletal muscle. 1295 72

We developed an in vivo model for cadmium-induced bone loss in which mice excrete bone mineral in feces beginning 8 h after cadmium gavage. Female mice of three strains [CF1, MTN (metallothionein-wild-type), and MT1,2KO (MT1,2-deficient)] were placed on a low-calcium diet for 2 weeks. Each mouse was gavaged with 200 microg Cd or vehicle only. Fecal calcium was monitored daily for 9 days, beginning 4 days before cadmium gavage, to document the bone response. For CF1 mice, bones were taken from four groups: +/- Cd, 2 h after Cd and +/- Cd, 4 h after Cd. MTN and MT1,2KO strains had two groups each: +/-Cd, 4 h after Cd. PolyA+ RNA preparations from marrow-free shafts of femura and tibiae of each +/- Cd pair were submitted to Incyte Genomics for microarray analysis. Fecal Ca results showed that bone calcium excreted after cadmium differed for the three mouse strains: CF1, 0.24 +/- 0.08 mg; MTN, 0.92 +/- 0.22 mg; and MT1,2KO, 1.7 +/- 0.4 mg. Gene array results showed that nearly all arrayed genes were unaffected by cadmium. However, MT1 and MT2 had Cd+/Cd- expression ratios >1 in all four groups, while all ratios for MT3 were essentially 1, showing specificity. Both probes for MAPK 14 (p38 MAPK) had expression ratios >1, while no other MAPK responded to cadmium. Vacuolar proton pump ATPase and integrin alpha v (osteoclast genes), transferrin receptor, and src-like adaptor protein genes were stimulated by Cd; other src-related genes were unaffected. Genes for bone formation, stress response, growth factors, and signaling molecules showed little or no response to cadmium. Results support the hypothesis that Cd stimulates bone demineralization via a p38 MAPK pathway involving osteoclast activation.
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PMID:Microarray analysis of changes in bone cell gene expression early after cadmium gavage in mice. 1367 60

1-Methyl-4-phenylpyridinium (MPP(+)) is a neurotoxin that causes Parkinson's disease in experimental animals and humans. Despite the fact that intracellular iron was shown to be crucial for MPP(+)-induced apoptotic cell death, the molecular mechanisms for the iron requirement remain unclear. We investigated the role of transferrin receptor (TfR) and iron in modulating the expression of alpha-synuclein (alpha-syn) in MPP(+)-induced oxidative stress and apoptosis. Results show that MPP(+) inhibits mitochondrial complex-1 and aconitase activities leading to enhanced H(2)O(2) generation, TfR expression and alpha-syn expression/aggregation. Pretreatment with cell-permeable iron chelators, TfR antibody (that inhibits TfR-mediated iron uptake), or transfection with glutathione peroxidase (GPx1) enzyme inhibits intracellular oxidant generation, alpha-syn expression/aggregation, and apoptotic signaling as measured by caspase-3 activation. Cells overexpressing alpha-syn exacerbated MPP(+) toxicity, whereas antisense alpha-syn treatment totally abrogated MPP(+)-induced apoptosis in neuroblastoma cells without affecting oxidant generation. The increased cytotoxic effects of alpha-syn in MPP(+)-treated cells were attributed to inhibition of mitogen-activated protein kinase and proteasomal function. We conclude that MPP(+)-induced iron signaling is responsible for intracellular oxidant generation, alpha-syn expression, proteasomal dysfunction, and apoptosis. Relevance to Parkinson's disease is discussed.
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PMID:Alpha-synuclein up-regulation and aggregation during MPP+-induced apoptosis in neuroblastoma cells: intermediacy of transferrin receptor iron and hydrogen peroxide. 1474 48


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