Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Skeletal muscle loss during aging leads to an increased risk of falls, fractures, and eventually loss of independence. Resistance exercise is a useful intervention to prevent sarcopenia; however, the muscle protein synthesis (MPS) response to resistance exercise is less in elderly compared with young subjects. On the other hand, essential amino acids (EAA) increase MPS equally in both young and old subjects when sufficient EAA is ingested. We hypothesized that EAA ingestion following a bout of resistance exercise would stimulate anabolic signaling and MPS similarly between young and old men. Each subject ingested 20 g of EAA 1 h following leg resistance exercise. Muscle biopsies were obtained before and 1, 3, and 6 h after exercise to measure the rate of MPS and signaling pathways that regulate translation initiation. MPS increased early in young (1-3 h postexercise) and later in old (3-6 h postexercise). At 1 h postexercise, ERK1/2 MNK1 phosphorylation increased and eIF2alpha phosphorylation decreased only in the young. mTOR signaling (mTOR, S6K1, 4E-BP1, eEF2) was similar between groups at all time points, but MNK1 phosphorylation was lower at 3 h and AMP-activated protein kinase-alpha (AMPKalpha) phosphorylation was higher in old 1-3 h postexercise. We conclude that the acute MPS response after resistance exercise and EAA ingestion is similar between young and old men; however, the response is delayed with aging. Unresponsive ERK1/2 signaling and AMPK activation in old muscle may be playing a role in the delayed activation of MPS. Notwithstanding, the combination of resistance exercise and EAA ingestion should be a useful strategy to combat sarcopenia.
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PMID:Skeletal muscle protein anabolic response to resistance exercise and essential amino acids is delayed with aging. 1832 67

During pregnancy a high rate of beta-cell proliferation occurs, making of this a useful model for the study of islet cell expansion in vivo. We used the murine pregnancy model to assess the effect of Rapamycin treatment on islet cell proliferation in vivo. Rapamycin is routinely used for the prevention of graft rejection in transplanted patients, including islet transplant recipients. As expected, pregnancy led to increased beta-cell proliferation, islet yield and skewing in size distribution after isolation and pancreatic insulin content, when compared to non-pregnant females. Rapamycin treatment resulted in reduced beta cell proliferation in pregnant mice, while minimal effects of Rapamycin treatment were observed on islet function both in vivo and in vitro. Rapamycin treatment of islets resulted in reduced phosphorylation of p70s6k, a downstream effector molecule of mTOR and increased ERK1/2 phosphorylation. In conclusion, beta-cell replication is reduced under Rapamycin treatment in vivo, suggesting that this mechanism may be operational and impair beta-cell renewal in transplanted patients.
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PMID:Rapamycin impairs beta-cell proliferation in vivo. 1837 93

Cysteine-rich 61 (Cyr61/CCN1), one of the members of CCN family, has been implicated in the progression of human malignancies. Previously, our studies have demonstrated that Cyr61/CCN1 has a role in promoting gastric cancer cell invasion, but the mechanism is not clear yet. Here, we found that hypoxia-inducing factor-1alpha (HIF-1alpha) protein, but not mRNA, expression was significantly elevated in gastric cancer cells overexpressing Cyr61. Supportively, a profound reduction of endogenous HIF-1alpha protein was noted in one highly invasive cell line, TSGH, when transfected with antisense Cyr61. By comparison, the induction kinetics of HIF-1alpha protein by recombinant Cyr61 (rCyr61) was distinct from that of insulin-like growth factor-1 and CoCl(2) treatment, both well known for induction of HIF-1alpha. Using cycloheximide and MG132, we demonstrated that the Cyr61-mediated HIF-1alpha up-regulation was through de novo protein synthesis, rather than increased protein stability. rCyr61 could also activate the PI3K/AKT/mTOR and ERK1/2 signaling pathways, both of which were essential for HIF-1alpha protein accumulation. Blockage of HIF-1alpha activity in Cyr61-expressing cells by transfecting with a dominant negative (DN)-HIF-1alpha strongly inhibited their invasion ability, suggesting that elevation in HIF-1alpha protein is vital for Cyr61-mediated gastric cancer cell invasion. In addition, several HIF-1alpha-regulated invasiveness genes were examined, and we found that only plasminogen activator inhibitor-1 (PAI-1) showed a significant increase in mRNA and protein levels in cells overexpressing Cyr61. Treatment with PAI-1-specific antisense oligonucleotides or function-neutralizing antibodies abolished the invasion ability of the Cyr61-overexpressing cells. Transfection with dominant negative-HIF-1alpha to block HIF-1alpha activity also effectively reduced the elevated PAI-1 level. In conclusion, our data provide a detailed mechanism by which Cyr61 promoted gastric cancer cell invasive ability via an HIF-1alpha-dependent up-regulation of PAI-1.
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PMID:Involvement of hypoxia-inducing factor-1alpha-dependent plasminogen activator inhibitor-1 up-regulation in Cyr61/CCN1-induced gastric cancer cell invasion. 2803 33

Reactive oxygen species (ROS) have been implicated in the pathogenesis of a variety of diseases, and antioxidant treatment is currently being investigated as a potential therapy to attenuate the detrimental effects of ROS-mediated oxidative stress. Melatonin is a potent naturally produced antioxidant, which acts through various mechanisms to ameliorate the toxic effects of ROS. However, little is known about the mechanisms of signaling pathways through which melatonin acts to reverse the effects of ROS. In the present study, the effect of melatonin treatment on the hydrogen peroxide (H(2)O(2))-induced activation of the mitogen-activated protein kinase (MAPK) and mammalian target of rapamycin (mTOR) signaling pathways was assessed in H4IIE hepatoma cells. It was found that melatonin strongly attenuated H(2)O(2)-induced activation of the ERK1/2 and p38 MAP kinases, as well as several of their downstream targets. Melatonin also attenuated the H(2)O(2)-induced phosphorylation of Akt and the Akt substrate mTOR, as well as a downstream target of mTOR action, 4E-BP1. Upregulation of ERK1/2, p38, and Akt signaling by H(2)O(2) was accompanied by activation of Ras, an effect that was blocked by melatonin. Overall, the results suggest that melatonin acts to prevent many of the H(2)O(2)-induced alterations in the MAPK and mTOR signaling pathways through inhibition of Ras, at least in H4IIE hepatoma cells.
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PMID:Melatonin represses oxidative stress-induced activation of the MAP kinase and mTOR signaling pathways in H4IIE hepatoma cells through inhibition of Ras. 1841 May 86

Phytochemical-rich foods have been shown to be effective at reversing age-related deficits in memory in both animals and humans. We show that a supplementation with a blueberry diet (2% w/w) for 12 weeks improves the performance of aged animals in spatial working memory tasks. This improvement emerged within 3 weeks and persisted for the remainder of the testing period. Memory performance correlated well with the activation of cAMP-response element-binding protein (CREB) and increases in both pro- and mature levels of brain-derived neurotrophic factor (BDNF) in the hippocampus. Changes in CREB and BDNF in aged and blueberry-supplemented animals were accompanied by increases in the phosphorylation state of extracellular signal-related kinase (ERK1/2), rather than that of calcium calmodulin kinase (CaMKII and CaMKIV) or protein kinase A. Furthermore, age and blueberry supplementation were linked to changes in the activation state of Akt, mTOR, and the levels of Arc/Arg3.1 in the hippocampus, suggesting that pathways involved in de novo protein synthesis may be involved. Although causal relationships cannot be made among supplementation, behavior, and biochemical parameters, the measurement of anthocyanins and flavanols in the brain following blueberry supplementation may indicate that changes in spatial working memory in aged animals are linked to the effects of flavonoids on the ERK-CREB-BDNF pathway.
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PMID:Blueberry-induced changes in spatial working memory correlate with changes in hippocampal CREB phosphorylation and brain-derived neurotrophic factor (BDNF) levels. 1845 78

Fragile X syndrome is a common form of cognitive deficit caused by the functional absence of fragile X mental retardation protein (FMRP), a dendritic RNA-binding protein that represses translation of specific messages. Although FMRP is phosphorylated in a group I metabotropic glutamate receptor (mGluR) activity-dependent manner following brief protein phosphatase 2A (PP2A)-mediated dephosphorylation, the kinase regulating FMRP function in neuronal protein synthesis is unclear. Here we identify ribosomal protein S6 kinase (S6K1) as a major FMRP kinase in the mouse hippocampus, finding that activity-dependent phosphorylation of FMRP by S6K1 requires signaling inputs from mammalian target of rapamycin (mTOR), ERK1/2, and PP2A. Further, the loss of hippocampal S6K1 and the subsequent absence of phospho-FMRP mimic FMRP loss in the increased expression of SAPAP3, a synapse-associated FMRP target mRNA. Together these data reveal a S6K1-PP2A signaling module regulating FMRP function and place FMRP phosphorylation in the mGluR-triggered signaling cascade required for protein-synthesis-dependent synaptic plasticity.
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PMID:S6K1 phosphorylates and regulates fragile X mental retardation protein (FMRP) with the neuronal protein synthesis-dependent mammalian target of rapamycin (mTOR) signaling cascade. 1847 9

Hypoxia-inducible factor-1 (HIF-1) is the central mediator of cellular responses to low oxygen and vital to many aspects of cancer biology. In a search for HIF-1 inhibitors, we identified a quassinoid 6alpha-tigloyloxychaparrinone (TCN) as an inhibitor of HIF-1 activation from Ailantus altissima. We here demonstrated the effect of TCN on HIF-1 activation induced by hypoxia or CoCl2. TCN showed the potent inhibitory activity against HIF-1 activation induced by hypoxia in various human cancer cell lines. This compound markedly decreased the hypoxia-induced accumulation of HIF-1alpha protein dose-dependently, whereas it did not affect the expressions of HIF-1beta and topoisomerase-I. Furthermore, TCN prevented hypoxia-induced expression of HIF-1 target genes for vascular endothelial growth factor (VEGF) and erythropoietin. Further analysis revealed that TCN strongly inhibited HIF-1alpha protein synthesis, without affecting the expression level of HIF-1alpha mRNA or degradation of HIF-1alpha protein. Moreover, the levels of phosphorylation of extracellular signal-regulated kinase-1/2 (ERK1/2), mitogen-activated protein (MAP) kinase-interacting protein kinase-1 (MNK1) and eukaryotic initiation factor 4E (eIF4E) were significantly suppressed by the treatment of TCN, without changing the total levels of these proteins. Our data suggested that TCN may exhibit anticancer activity by inhibiting HIF-1alpha translation through the inhibition of eIF4E phosphorylation pathway and thus provide a novel mechanism for the anticancer activity of quassinoids. TCN could be a new HIF-1-targeted anticancer agent and be effective on mammalian target of rapamycin (mTOR)-targeted cancer therapy, in which mTOR inhibition increases eIF4E phosphorylation.
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PMID:A quassinoid 6alpha-tigloyloxychaparrinone inhibits hypoxia-inducible factor-1 pathway by inhibition of eukaryotic translation initiation factor 4E phosphorylation. 1863 43

The great diversity of the expression sites and proposed function of the oxytocin (OXT) receptor (OXTR) is paralleled by a diversity of its signalling pathways, many of which have still remained unexplored. We have used different approaches to discover novel pathways. By means of a phosphoproteomics approach, we have detected several distinct OXT-induced changes in tyrosine as well as threonine phosphorylation states of intracellular protein in myometrial cells. The most prominent change involved dephosphorylation of a 95-kDa phosphothreonine moiety. By N-terminal amino acid microsequence analysis, this moiety was shown to correspond to eukaryotic translation factor eEF2. This protein is a key regulator of protein synthesis and mediates, upon dephosphorylation, the translocation step of peptide chain elongation. These findings define a novel mechanism by which OXT assumes a so far unrecognized trophic function. We next elucidated the intracellular pathway(s) involved. We found that this effect is not mediated by any of the known pathways known to induce eEF2 dephosphorylation (mTOR, ERK1/2 or p38) but by protein kinase C. Consistent with this idea, we also found that direct stimulation of protein kinase C with a phorbol ester induced eEF2 dephosphorylation in myometrial cells. Using phosphoERK antibodies, we discovered by Western blotting that OXT induced phosphorylation of a higher molecular weight ERK-related protein. We were able to show that this band corresponded to "big MAP kinase1" or ERK5. ERK5 is part of a distinct MAPK cascade and promotes expression of the myosin light chain gene and plays an obligatory role in muscle cell development and differentiation. The role of ERK5 in myometrium has remained unexplored, but it is likely to represent an important novel pathway mediating OXT's effects on smooth muscle function. Further elucidation of these novel signalling pathways will have significant relevance for the development of novel pathway-specific OXTR agonists and antagonists.
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PMID:Oxytocin receptor signalling. 1865 81

Preclinical studies using human gastric adenocarcinoma (GAC) cell lines have shown that the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, can inhibit tumor growth and that the extracellular signal-regulated kinase (ERK) of the Ras/Raf kinase/ERK pathway is related to chemoresistance and apoptosis. We examined the state of activation of components of mTOR, Ras/Raf kinase/ERK, and nuclear factor (NF)-kappaB signal transduction pathways, as well as cell cycle protein analyte correlates in GAC cases. Formalin-fixed paraffin-embedded tissue microarray blocks containing samples from 210 cases of GAC were examined. Immunohistochemistry was utilized to detect the following antigens: S100P, upstream stimulator of ERK, and NF-kappaB pathways; phosphorylated (p)-mTOR (Ser 2448), p-ERK-1/2 (Thr 202/Tyr 204), and one of their common down-stream effectors, p-p70S6K(Thr 389); p-NF-kappaBp65(Ser 536); and cell cycle associated proteins, Ki-67, and S phase kinase-associated protein (Skp)2. Immunoreactivity (0 to 4+) of protein expression and compartmentalization were assessed by bright-field microscopy. The majority of cases showed positive (1+ to 4+) cytoplasmic/plasmalemmal p-mTOR (88%), and moderate-strong (2+ to 4+) nuclear p-p70S6K (93%) and nuclear S100P (81%) expression. A subset of cases exhibited moderate-strong nuclear p-ERK-1/2 (15%) and p-NF-kappaBp65 (36%) expression. The majority of cases showed concomitant moderate-strong (2+ to 4+) nuclear Ki-67 (71%) and Skp2 (68%). Nuclear expression levels of p-ERK-1/2 and p-NF-kappaBp65, of p-p70S6K and p-NF-kappaB, and of Ki-67 and Skp2, respectively, showed significant linear correlations in GAC (p <0.001). Additionally, there were statistically significant differences in the mean expression levels of p-ERK-1/2 and p-NF-kappaBp65 in diffuse vs intestinal types of GAC, with higher levels of both in the diffuse type ( p = 0.001 and p <0.0001, respectively). In summary, morphoproteomic analysis reveals constitutive activation of mTOR and to some extent, Ras/Raf kinase and NF-kappaB pathways in GAC, as evidenced by increased cytoplasmic p-mTOR, nuclear translocation of p-p70S6K and p-ERK-1/2 phosphorylated at putative sites of activation (Ser 2448, Thr 389, and Thr 202/Tyr 204, respectively), as well as correlative expression of cell cycle analytes, Ki-67, and Skp2. These results suggest that a prospective study is warranted to evaluate the use of morphoproteomic profiling of individual patients with GAC in order to design combinatorial treatment strategies that target the mTOR, Ras/Raf kinase/ERK, and/or NF-kappaB pathways.
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PMID:Morphoproteomic profile of mTOR, Ras/Raf kinase/ERK, and NF-kappaB pathways in human gastric adenocarcinoma. 1871 46

Gastrointestinal stromal tumours (GISTs) with deletions in KIT exon 11 are characterized by higher proliferation rates and shorter disease-free survival times, compared to GISTs with KIT exon 11 point mutations. Up-regulation of cyclin D is a crucial event for entry into the G1 phase of the cell cycle, and links mitogenic signalling to cell proliferation. Signalling from activated KIT to cyclin D is directed through the RAS/RAF/ERK, PI3K/AKT/mTOR/EIF4E, and JAK/STATs cascades. ERK and STATs initiate mRNA transcription of cyclin D, whereas EIF4E activation leads to increased translation efficiency and reduced degradation of cyclin D protein. The aim of the current study was to analyse the mRNA and protein expression as well as protein phosphorylation of central hubs of these signalling cascades in primary GISTs, to evaluate whether tumours with KIT exon 11 deletions and point mutations differently utilize these pathways. GISTs with KIT exon 11 deletions had significantly higher mitotic counts, higher proliferation rates, and shorter disease-free survival times. In line with this, they had significantly higher expression of cyclin D on the mRNA and protein level. Furthermore, there was a significantly higher amount of phosphorylated ERK1/2, and a higher protein amount of STAT3, mTOR, and EIF4E. PI3K and phosphorylated AKT were also up-regulated, but this was not significant. Ultimately, GISTs with KIT exon 11 deletions had significantly higher phosphorylation of the central negative cell-cycle regulator RB. Phosphorylation of RB is accomplished by activated cyclin D/CDK4/6 complex, and marks a central event in the release of the cell cycle. Altogether, these observations suggest increased KIT signalling with up-regulation of cyclin D as the basis for the unfavourable clinical course in GISTs with KIT exon 11 deletions.
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PMID:Increased KIT signalling with up-regulation of cyclin D correlates to accelerated proliferation and shorter disease-free survival in gastrointestinal stromal tumours (GISTs) with KIT exon 11 deletions. 1872 75


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