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)

Protein expression in the heart is altered following periods of myocardial ischemia. The changes in protein expression are associated with increased cell size that can be maladaptive. There is little information regarding the regulation of protein expression through the process of mRNA translation during ischemia and reperfusion in the heart. Therefore, the purpose of this study was to identify changes in signaling pathways and downstream regulatory mechanisms of mRNA translation in an in vivo model of myocardial ischemia and reperfusion. Hearts were collected from rats whose left main coronary arteries had either been occluded for 25 min or reversibly occluded for 25 min and subsequently reperfused for 15 min. Following reperfusion, both the phosphoinositide 3-kinase and mitogen-activated protein kinase pathways were activated, as evidenced by increased phosphorylation of Akt (PKB), extracellular signal-regulated kinase 1/2, and p38 mitogen-activated protein kinase. Activation of Akt stimulated signaling through the protein kinase mammalian target of rapamycin, as evidenced by increased phosphorylation of two of its effectors, the ribosomal protein S6 kinase and the eukaryotic initiation factor eIF4E binding protein 1. Ischemia and reperfusion also resulted in increased phosphorylation of eIF2 and eIF2B. These changes in protein phosphorylation suggest that control of mRNA translation following ischemia and reperfusion is modulated through a number of signaling pathways and regulatory mechanisms.
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PMID:Activation of signaling pathways and regulatory mechanisms of mRNA translation following myocardial ischemia-reperfusion. 1669 Jul 84

The minimal adipose phenotype of hormone-sensitive lipase (HSL)-null mice suggested that other hormonally responsive lipase(s) were present in adipocytes. Recent studies have characterized a new adipose tissue triglyceride lipase, ATGL/PNPLA2/destnutrin/iPLA2zeta/TTS2.2 (ATGL). We had previously cloned a novel adipose-enriched transcript by differential screening and recently determined its identity with murine ATGL. We report here on the regulation of ATGL by TNF-alpha and insulin in 3T3-L1 adipocytes and identify ATGL as a target for transcriptional activation by the key adipogenic transcription factor PPARgamma. Insulin at 100 nM resulted in a marked decrease in ATGL transcript that was effectively blocked by inhibitors for PI 3-kinase and p70 ribosomal protein S6 kinase. TNF-alpha treatment decreased ATGL transcript in a time-dependent manner that paralleled TNF-alpha downregulation of PPARgamma with a maximal decrease noted by 6 h. TNF-alpha effects on ATGL were attenuated by pretreatment with PD-98059, LY-294002, or rapamycin, suggesting involvement of the p44/42 MAP kinase, PI 3-kinase, and p70 ribosomal protein S6 kinase signals. To study transcriptional regulation of ATGL, we cloned 2,979 bp of the murine ATGL 5'-flanking region. Compared with promoterless pGL2-Basic, the -2979/+21 ATGL luciferase construct demonstrated 120- and 40-fold increases in activity in white and brown adipocytes, respectively. Luciferase reporter activities for a series of eight ATGL promoter deletions revealed that the -928/+21, -1738/+21, -1979/+21, and -2979/+21 constructs were transactivated by PPARgamma. Our findings identify the novel lipase ATGL to be a target gene for TNF-alpha and insulin action in adipocytes and reveal that it is subject to transcriptional control by PPARgamma-mediated signals.
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PMID:The adipose tissue triglyceride lipase ATGL/PNPLA2 is downregulated by insulin and TNF-alpha in 3T3-L1 adipocytes and is a target for transactivation by PPARgamma. 1670 60

The role of the AMP-activated kinase (AMPK) as a metabolic sensor in skeletal muscle has been far better characterized for glucose and fat metabolism than for protein metabolism. Therefore, the studies presented here were designed to examine the effects of 5-aminoimidazole-4-carboxamide-1-beta-d-ribonucleoside (AICAR)-induced AMPK signaling on effector mechanisms of mRNA translation and protein synthesis in cultures of C(2)C(12) myotubes. The findings show that, following AICAR (2 mM) treatment, AMPK phosphorylation was increased within 15 min and remained elevated throughout a 60-min time course. In association with the increase in AMPK phosphorylation, global rates of protein synthesis declined to 90, 70, and 63% of the control values at the 15-, 30-, and 60-min time points, respectively. By 60 min, polysomes disaggregated into free ribosomal subunits, suggesting an inhibition of initiation of mRNA translation. However, phosphorylation of eukaryotic elongation factor 2 was increased at 15 and 30 min but then declined to control values by 60 min, suggesting a transient inhibition of translation elongation. The decline in protein synthesis and changes in mRNA translation were associated with a repression of the mammalian target of rapamycin (mTOR) signaling pathway, as indicated by increased association of Hamartin with Tuberin, increased association of regulatory associated protein of mTOR with mTOR, and dephosphorylation of the downstream targets ribosomal protein S6 kinase-1 and eukaryotic initiation factor 4E-binding protein-1. They were also associated with activation of the MAPK signaling pathway, as indicated by increased phosphorylation of MEK1/2 and ERK1/2 and the downstream target eIF4E. Overall, the data support the conclusion that AICAR-induced AMPK activation suppresses protein synthesis through concurrent repression of mTOR signaling and activation of MAPK signaling, the combination of which modulates transient changes in the initiation and elongation phases of mRNA translation.
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PMID:Time course changes in signaling pathways and protein synthesis in C2C12 myotubes following AMPK activation by AICAR. 1676 Mar 36

Although p90 ribosomal S6 kinase (RSK) is known as an important downstream effector of the ribosomal protein S6 kinase/extracellular signal-regulated kinase (Ras/ERK) pathway, its endogenous role, and precise molecular function remain unclear. Using gain-of-function and null mutants of RSK, its physiological role was successfully characterized in Drosophila. Surprisingly, RSK-null mutants were viable, but exhibited developmental abnormalities related to an enhanced ERK-dependent cellular differentiation such as ectopic photoreceptor- and vein-cell formation. Conversely, overexpression of RSK dramatically suppressed the ERK-dependent differentiation, which was further augmented by mutations in the Ras/ERK pathway. Consistent with these physiological phenotypes, RSK negatively regulated ERK-mediated developmental processes and gene expressions by blocking the nuclear localization of ERK in a kinase activity-independent manner. In addition, we further demonstrated that the RSK-dependent inhibition of ERK nuclear migration is mediated by the physical association between ERK and RSK. Collectively, our study reveals a novel regulatory mechanism of the Ras/ERK pathway by RSK, which negatively regulates ERK activity by acting as a cytoplasmic anchor in Drosophila.
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PMID:Inhibition of ERK-MAP kinase signaling by RSK during Drosophila development. 1676 54

In response to traumatic brain injury (TBI), neurons initiate neuroplastic processes through the activation of intracellular signaling pathways. However, the molecular mechanisms underlying neuroplasticity after TBI are poorly understood. To study this, we utilized the fluid-percussion brain injury (FPI) model to investigate alterations in the mammalian target of rapamycin (mTOR) signaling pathways in response to TBI. Mammalian target of rapamycin stimulates mRNA translation through phosphorylation of eukaryotic initiation factor 4E binding protein-1 (4E-BP1), p70 ribosomal S6 kinase (p70S6K), and ribosomal protein S6 (rpS6). These pathways coordinate cell growth and neuroplasticity via dendritic protein synthesis. Rats received sham surgery or moderate parasagittal FPI on the right side of the parietal cortex, followed by 15 mins, 30 mins, 4 h, 24 h, or 72 h of recovery. Using Western blot analysis, we found that mTOR, p70S6K, rpS6, and 4E-BP1 phosphorylation levels were significantly increased in the ipsilateral parietal cortex and hippocampus from 30 mins to 24 h after TBI, whereas total protein levels were unchanged. Using confocal microscopy to localize these changes, we found that rpS6 phosphorylation was increased in the parietal cortex and all subregions of the hippocampus. In accordance with these results, eIF4E, a key, rate-limiting mRNA translation factor, was also phosphorylated by mitogen-activated protein kinase-interacting kinase 1 (Mnk1) 15 mins after TBI. Together, these results suggest that changes in mRNA translation may be one mechanism that neurons use to respond to trauma and may contribute to the neuroplastic changes observed after TBI.
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PMID:Alterations in mammalian target of rapamycin signaling pathways after traumatic brain injury. 1695 78

Autocrine tumour growth factor alpha (TGFalpha)/epidermal growth factor receptor (EGFR) stimulation in colorectal carcinoma (CRC) cells regulates cell adhesion and invasiveness via ribosomal protein S6 kinase (S6K) phosphorylation in pre-clinical studies. The aim of this study was to evaluate whether TGFalpha and EGFR expression might be correlated with a higher metastatic behaviour in human tumours. Paraffin-embedded material was retrospectively collected from 101 primitive CRCs including all stage IV patients at diagnosis treated at our Institution from 1999 to 2004 (50 cases, Group B) and 51 stage II-III control cases (Group A). EGFR and TGFalpha expression, together with signalling molecules (including signal transducer and activator of transcription [STAT3], serine-treonine kinase [Akt], mitogen-activated protein kinase [MAPK], mammalian target of rapamycin [mTOR] and S6K) in selected samples, was evaluated by immunohistochemistry using the EGFR Dako antibody. A total of 68/101 (67.3%) cases were EGFR positive and 79/101 (78.2%) cases were TGFalpha positive. EGFR/TGFalpha co-expression differed significantly (p = 0.02) between Group A and Group B tumours (23/51, 45.1% vs 34/50, 68.0%, respectively), whereas no differences in STAT, Akt, mTOR expression was evident between the two groups. Conversely, there was a significantly higher expression of phosphorylated S6K in stage IV cases (Group B) than in the controls (Group A; 70.4% vs 38.7%; p = 0.02). In agreement with in vitro data, EGFR, TGFalpha and S6K co-expression in human CRC was significantly higher in patients with advanced stage at diagnosis.
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PMID:Co-expression of EGF receptor, TGFalpha and S6 kinase is significantly associated with colorectal carcinomas with distant metastases at diagnosis. 1726 80

An important function of growth hormone (GH) is to promote cell and tissue growth, and a key component of these effects is the stimulation of protein synthesis. In this study, we demonstrate that, in H4IIE hepatoma cells, GH acutely activated protein synthesis through signaling via the mammalian target of rapamycin (mTOR) and specifically through the rapamycin-sensitive mTOR complex 1 (mTORC1). GH treatment enhanced the phosphorylation of two targets of mTOR signaling, 4E-BP1 and ribosomal protein S6. Phosphorylation of S6 and 4E-BP1 was maximal at 30-45 min and 10-20 min after GH stimulation, respectively. Both proteins modulate components of the translational machinery. The GH-induced phosphorylation of 4E-BP1 led to its dissociation from eIF4E and increased binding of eIF4E to eIF4G to form (active) eIF4F complexes. The ability of GH to stimulate the phosphorylation of S6 and 4E-BP1 was blocked by rapamycin. GH also led to the dephosphorylation of a third translational component linked to mTORC1, the elongation factor eEF2. Its regulation followed complex biphasic kinetics, both phases of which required mTOR signaling. GH rapidly activated both the MAP kinase (ERK) and PI 3-kinase pathways. Signaling through PI 3-kinase alone was, however, sufficient to activate the downstream mTORC1 pathway. Consistent with this, GH increased the phosphorylation of TSC2, an upstream regulator of mTORC1, at sites that are targets for Akt/PKB. Finally, the activation of overall protein synthesis by GH in H4IIE cells was essentially completely inhibited by wortmannin or rapamycin. These results demonstrate for the first time that mTORC1 plays a major role in the rapid activation of protein synthesis by GH.
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PMID:The rapid activation of protein synthesis by growth hormone requires signaling through mTOR. 1728 72

Autophagy is a response of cancer cells to various anticancer therapies. It is designated as programmed cell death type II and characterized by the formation of autophagic vacuoles in the cytoplasm. The Akt/mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K) and the extracellular signal-regulated kinases 1/2 (ERK1/2) pathways are two major pathways that regulate autophagy induced by nutrient starvation. These pathways are also frequently associated with oncogenesis in a variety of cancer cell types, including malignant gliomas. However, few studies have examined both of these signal pathways in the context of anticancer therapy-induced autophagy in cancer cells, and the effect of autophagy on cell death remains unclear. Here, we examined the anticancer efficacy and mechanisms of curcumin, a natural compound with low toxicity in normal cells, in U87-MG and U373-MG malignant glioma cells. Curcumin induced G(2)/M arrest and nonapoptotic autophagic cell death in both cell types. It inhibited the Akt/mTOR/p70S6K pathway and activated the ERK1/2 pathway, resulting in induction of autophagy. It is interesting that activation of the Akt pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the ERK1/2 pathway inhibited curcumin-induced autophagy and induced apoptosis, thus resulting in enhanced cytotoxicity. These results imply that the effect of autophagy on cell death may be pathway-specific. In the subcutaneous xenograft model of U87-MG cells, curcumin inhibited tumor growth significantly (P < 0.05) and induced autophagy. These results suggest that curcumin has high anticancer efficacy in vitro and in vivo by inducing autophagy and warrant further investigation toward possible clinical application in patients with malignant glioma.
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PMID:Evidence that curcumin suppresses the growth of malignant gliomas in vitro and in vivo through induction of autophagy: role of Akt and extracellular signal-regulated kinase signaling pathways. 1739 90

A defect in protein turnover underlies multiple forms of cell atrophy. Since S6 kinase (S6K)-deficient cells are small and display a blunted response to nutrient and growth factor availability, we have hypothesized that mutant cell atrophy may be triggered by a change in global protein synthesis. By using mouse genetics and pharmacological inhibitors targeting the mammalian target of rapamycin (mTOR)/S6K pathway, here we evaluate the control of translational target phosphorylation and protein turnover by the mTOR/S6K pathway in skeletal muscle and liver tissues. The phosphorylation of ribosomal protein S6 (rpS6), eukaryotic initiation factor-4B (eIF4B), and eukaryotic elongation factor-2 (eEF2) is predominantly regulated by mTOR in muscle cells. Conversely, in liver, the MAPK and phosphatidylinositol 3-kinase pathways also play an important role, suggesting a tissue-specific control. S6K deletion in muscle mimics the effect of the mTOR inhibitor rapamycin on rpS6 and eIF4B phosphorylation without affecting eEF2 phosphorylation. To gain insight on the functional consequences of these modifications, methionine incorporation and polysomal distribution were assessed in muscle cells. Rates and rapamycin sensitivity of global translation initiation are not altered in S6K-deficient muscle cells. In addition, two major pathways of protein degradation, autophagy and expression of the muscle-specific atrophy-related E3 ubiquitin ligases, are not affected by S6K deletion. Our results do not support a role for global translational control in the growth defect due to S6K deletion, suggesting specific modes of growth control and translational target regulation downstream of mTOR.
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PMID:S6 kinase inactivation impairs growth and translational target phosphorylation in muscle cells maintaining proper regulation of protein turnover. 1749 29

Epidemiological data suggest that epigallocatechin-3-gallate (EGCG) possesses chemopreventive properties against cancer. In this study, we examined the molecular mechanisms of EGCG in human pancreatic cancer cells. EGCG caused growth arrest at G1 stage of cell cycle through regulation of cyclin D1, cdk4, cdk6, p21/WAF1/CIP1 and p27/KIP1, and induced apoptosis through generation of reactive oxygen species and activation of caspase-3 and caspase-9. EGCG inhibited expressions of Bcl-2 and Bcl-XL and induced expressions of Bax, Bak, Bcl-XS and PUMA. Mouse embryonic fibroblasts (MEFs) derived from Bax and Bak double knockout mice exhibited greater protection against EGCG-induced apoptosis than wild-type or single knockout MEFs. EGCG caused Bax activation in p53 -/- MEFs, suggesting that EGCG can induce apoptosis in the absence of p53. Furthermore, the activities of Ras, Raf-1 and ERK1/2 were inhibited, whereas the activities of MEKK1, JNK1/2 and p38 MAP kinases were induced by EGCG. Inhibition of cRaf-1 or ERK enhanced EGCG-induced apoptosis, whereas inhibition of JNK or p38 MAP kinase inhibited EGCG-induced apoptosis. EGCG inhibited the activation of p90 ribosomal protein S6 kinase, and induced the activation of cJUN. Our results suggest that EGCG induces growth arrest and apoptosis through multiple mechanisms, and can be used for pancreatic cancer prevention.
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PMID:Epigallocatechin-3-gallate inhibits cell cycle and induces apoptosis in pancreatic cancer. 1756 28


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