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

The hepatitis C virus NS5A protein plays a critical role in virus replication, conferring interferon resistance to the virus through perturbation of multiple intracellular signaling pathways. Since NS5A is a phosphoprotein, it is of considerable interest to understand the role of phosphorylation in NS5A function. In this report, we investigated the phosphorylation of NS5A by taking advantage of 119 glutathione S-transferase-tagged protein kinases purified from Saccharomyces cerevisiae to perform a global screening of yeast kinases capable of phosphorylating NS5A in vitro. A database BLAST search was subsequently performed by using the sequences of the yeast kinases that phosphorylated NS5A in order to identify human kinases with the highest sequence homologies. Subsequent in vitro kinase assays and phosphopeptide mapping studies confirmed that several of the homologous human protein kinases were capable of phosphorylating NS5A. In vivo phosphopeptide mapping revealed phosphopeptides common to those generated in vitro by AKT, p70S6K, MEK1, and MKK6, suggesting that these kinases may phosphorylate NS5A in mammalian cells. Significantly, rapamycin, an inhibitor commonly used to investigate the mTOR/p70S6K pathway, reduced the in vivo phosphorylation of specific NS5A phosphopeptides, strongly suggesting that p70S6 kinase and potentially related members of this group phosphorylate NS5A inside the cell. Curiously, certain of these kinases also play a major role in mRNA translation and antiapoptotic pathways, some of which are already known to be regulated by NS5A. The findings presented here demonstrate the use of high-throughput screening of the yeast kinome to facilitate the major task of identifying human NS5A protein kinases for further characterization of phosphorylation events in vivo. Our results suggest that this novel approach may be generally applicable to the screening of other protein biochemical activities by mechanistic class.
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PMID:High-throughput screening of the yeast kinome: identification of human serine/threonine protein kinases that phosphorylate the hepatitis C virus NS5A protein. 1501 73

Depending on the type of external signals, T cells can initiate multiple intracellular signaling pathways that can be broadly classified into two groups based on their sensitivity to the immunosuppressive drug cyclosporin A (CsA). Interleukin (IL)-12-mediated interferon (IFN)-gamma production by activated T cells has been shown to be CsA-insensitive. In this report, we demonstrate that the IL-12-induced CsA-resistant pathway of IFN-gamma production is sensitive to rapamycin. Rapamycin treatment resulted in the aberrant recruitment of Stat3, Stat4, and phospho-c-Jun to the genomic promoter region resulting in decreased IFN-gamma transcription. IL-12-induced phosphorylation of Stat3 on Ser-727 was affected by rapamycin, which may be due to the effect of rapamycin on the IL-12-induced interaction between mammalian target of rapamycin (mTOR) and Stat3. In accordance with this, reduction in the mTOR protein level by small interfering RNA resulted in suppression of Stat3 phosphorylation and decreased production of IFN-gamma after IL-12 stimulation. These results suggest that mTOR may play a major role in IL-12-induced IFN-gamma production by activated T cells.
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PMID:Interleukin-12-induced interferon-gamma production by human peripheral blood T cells is regulated by mammalian target of rapamycin (mTOR). 1552 80

The mainstay of any curative treatment in renal cell carcinoma (RCC) is surgery. In case of metastatic disease at presentation a radical nephrectomy is recommended to good performance status patients prior to start of interferon-alfa treatment. Interferon-alpha (IFN-alpha) offers in a small but significant percentage of patients advantage in overall survival; interleukin-2 (IL-2) based therapy gives similar survival rates. To date hormonal and chemotherapy do not have a proven impact on survival. The recent new insights in the molecular biology of clear RCC has revealed a key-role for vascular endothelial growth factor (VEGF) in the stimulation of angiogenesis in this highly vascularized tumour. This opens interesting new treatment strategies including: blockage of VEGF with the monoclonal antibody bevacizumab and inhibition of VEGF receptor tyrosine kinases (with small oral molecules such as SU11248 or PTK787). Likewise, inhibition of the Raf kinase pathway (with oral Bay 43-9006) or inhibition of the mTOR pathway (with i.v. CCI-779) are under investigation. Preliminary clinical results with all these compounds are interesting and the results of ongoing phase III studies will become available in the next years.
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PMID:Novel treatments for metastatic renal cell carcinoma. 1597 88

Alpha4 phosphoprotein in the mTOR pathway is a prolactin (PRL)-downregulated gene product that interacts with the catalytic subunit of serine/threonine protein phosphatase 2A (PP2Ac) in rat Nb2 lymphoma cells. Transient overexpression of alpha4 in COS-1 cells inhibited PRL-inducible interferon-regulatory-1 (IRF-1) promoter activity, but the mechanism underlying this inhibition was not known. The present study showed a stable alpha4-PP2Ac complex that was not dissociated by rapamycin in COS-1 cells. Transient overexpression of alpha4 in COS-1 cells had no effect on endogenous PP2Ac protein levels but significantly increased PP2Ac carboxymethylation and PP2A activity as compared to controls. The increased PP2A activity was accompanied by decreased phosphorylation of eukaryotic initiation factor 4E-binding protein (4E-BP1) but had no effect on Stat phosphorylation. However, overexpressed alpha4 decreased arginine methylation of Stat1alpha and increased Stat1alpha binding to the Stat1alpha-specific inhibitor, PIAS1. In summary, ectopic alpha4 increased PP2A activity in COS-1 cells and this was accompanied by Stat1alpha hypomethylation and increased Stat1alpha-PIAS1 association. These events would inhibit Stat action and ultimately inhibit PRL-inducible IRF-1 promoter activity.
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PMID:Overexpression of the mTOR alpha4 phosphoprotein activates protein phosphatase 2A and increases Stat1alpha binding to PIAS1. 1708 18

The mechanisms regulating initiation of mRNA translation for the generation of protein products that mediate interferon (IFN) responses are largely unknown. We have previously shown that both Type I and II IFNs engage the mammalian target of rapamycin (mTOR), resulting in downstream phosphorylation and deactivation of the translational repressor 4E-BP1 (eIF4E-binding protein 1). In the current study, we provide direct evidence that such regulation of 4E-BP1 by IFNalpha or IFNgamma results in sequential dissociation of 4E-BP1 from eukaryotic initiation factor-4E and subsequent formation of a functional complex between eukaryotic initiation factor-4E and eukaryotic initiation factor-4G, to allow initiation of mRNA translation. We also demonstrate that the induction of key IFNalpha- or IFNgamma-inducible proteins (ISG15 (interferon-stimulated gene 15) and CXCL10) that mediate IFN responses are enhanced in 4E-BP1 (4E-BP1(-/-)) knockout MEFs, as compared with wild-type 4E-BP1(+/+) MEFs. On the other hand, IFN-dependent transcriptional regulation of the Isg15 and Cxcl10 genes is intact in the absence of 4E-BP1, as determined by real time reverse transcriptase-PCR assays and promoter assays for ISRE and GAS, establishing that 4E-BP1 plays a selective negative regulatory role in IFN-induced mRNA translation. Interestingly, the induction of expression of ISG15 and CXCL10 proteins by IFNs was also strongly enhanced in cells lacking expression of the tuberin (TSC2(-/-)) or hamartin (TSC1(-/-)) genes, consistent with the known negative regulatory effect of the TSC1-TSC2 complex on mTOR activation. In other work, we demonstrate that the induction of an IFN-dependent antiviral response is strongly enhanced in cells lacking expression of 4E-BP1 and TSC2, demonstrating that these elements of the IFN-activated mTOR pathway exhibit important regulatory effects in the generation of IFN responses. Taken altogether, our data suggest an important role for mTOR-dependent pathways in IFN signaling and identify 4E-BP1 and TSC1-TSC2 as key components in the generation of IFN-dependent biological responses.
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PMID:Regulatory effects of mammalian target of rapamycin-activated pathways in type I and II interferon signaling. 1711 81

The year 2006 will mark a turning point in the daily management of patients with metastatic renal cell carcinoma. The impact of immunotherapy with interferon-alpha or interleukin-2 has been shown to be restricted to a minority of patients. The growing understanding of molecular mechanisms involved in the pathogenesis of the disease, especially clear-cell carcinoma, has led to the development of multiple targeted therapies with significant clinical benefits. Two compounds that predominantly inhibit the tyrosine kinase activity of the vascular endothelial growth factor receptor have been shown to improve the progression-free survival of patients in first- (sunitinib versus interferon-alpha) or second-line (sorafenib versus placebo) treatment. Temsirolimus, an agent that inhibits the serine-threonine kinase activity of the mammalian target of rapamycin, offers better overall survival than interferon in patients with poor-risk characteristics. Further studies are needed to determine the optimal combinations of these agents in metastatic disease and to assess their impact in the adjuvant setting.
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PMID:Targeted therapies in metastatic renal cell carcinoma: the light at the end of the tunnel. 1718 90

Metastatic clear cell renal cell cancer has traditionally been treated with cytokines (interferon or interleukin-2). Improved understanding of biology has engendered novel targeted therapeutic agents that have radically altered the outlook. Vascular endothelial growth factor, the related receptor and the mTOR signal transduction pathway have particularly been exploited. Sunitinib malate, sorafenib and temsirolimus have improved clinical outcomes compared with interferon in randomized trials. Other multitargeted tyrosine kinase inhibitors (lapatinib, axatinib and pazopanib) and antiangiogenic agents (bevacizumab and lenalidomide) have also demonstrated activity in early studies. Combinations of these agents are being evaluated. The future of the therapy of renal cancer appears promising owing to the efficacy of these novel agents. Clinical trials designed to further assess these and other agents need to be vigorously supported.
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PMID:Recent advances in the therapy of renal cancer. 1725 Apr 61

Patients with metastatic gastrointestinal neuroendocrine tumors have traditionally been faced with few effective treatment options. Somatostatin analogs often successfully control symptoms of hormonal hypersecretion but seldom result in tumor regression. Some patients with hepatic metastases are also candidates for ablative therapies such as surgical debulking or embolization. The role of systemic agents such as interferon alfa or cytotoxic chemotherapy remains ill defined. The more prevalent use of these modalities has been restricted by low tumor response rates and the potential for toxicity. Novel agents, including radiolabeled somatostatin analogs, inhibitors of the vascular endothelial growth factor pathway, and inhibitors of mammalian target of rapamycin, have shown promising activity in recent clinical studies. Continued investigation of these agents should render a better understanding of their efficacy in patients with advanced neuroendocrine tumors.
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PMID:New developments in the treatment of gastrointestinal neuroendocrine tumors. 1743 Jun 88

Management of renal cell carcinoma (RCC) has made considerable progress in recent years, and new emerging strategies are being developed. On the basis of the results of two randomised studies in the early 2000s, nephrectomy has now become the standard as cytoreductive surgery before embarking on systemic treatment with cytokines. Interleukin (IL)-2 and interferon were the standard treatment in metastatic RCC (MRCC) until 2006. The efficacy of these two drugs, which have now been used for >20 years in MRCC, is still controversial. On the basis of many studies, these drugs should not be given to patients with a poor prognosis. In patients with good prognostic factors, a cytokine-based regimen should remain the standard as either a high-dose IL-2 or subcutaneous regimen. In patients with intermediate risk, the results of the French Percy Quattro study encourage the use of new targeted therapies as first-line therapy. Development of targeted therapies in RCC has been necessary largely because the Von Hippel-Lindau (VHL) gene is often mutated in sporadic RCC. VHL protein abnormalities lead to accumulation of hypoxia-inducible factor (HIF)-alpha and activation of a series of genes, including vascular endothelial growth factor (VEGF), thus inducing angiogenesis. Results from many recent studies with new agents that block the VEGF pathway have been reported and offer new strategic options for patients with MRCC. Sunitinib and sorafenib, two tyrosine kinase inhibitors, improve progression-free survival in RCC compared with standard treatment and have been recently approved. Temsirolimus, a mammalian target of rapamycin inhibitor regulating HIF-alpha, improves survival in RCC patients with poor risk features. Bevacizumab, a monoclonal antibody against VEGF, has shown very promising efficacy. Overall, treatment of MRCC is currently moving from the cytokine era to the targeted agent era. However, many questions still remain regarding the efficacy of combination treatments and on the best way to achieve complete remission, which is probably the best hope of curing MRCC.
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PMID:Advanced renal cell carcinoma: current and emerging management strategies. 1754 70

Metastatic clear cell renal cell cancer has traditionally been treated with cytokines (interferon or interleukin-2). Improved understanding of biology has engendered novel targeted therapeutic agents that have altered the natural history of this disease. The vascular endothelial growth factor and its related receptor and the mTOR signal transduction pathway have particularly been exploited. Sunitinib malate, sorafenib tosylate, temsirolimus, and bevacizumab have improved clinical outcomes in randomized trials. Other multitargeted tyrosine kinase inhibitors (lapatinib, axitinib, pazopanib) and antiangiogenic agents (VEGF Trap, lenalidomide) have also demonstrated activity in early studies. Combinations of these agents are being evaluated. The future of the therapy of renal cancer appears promising owing to the efficacy of these novel agents.
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PMID:Targeted therapy for renal cell carcinoma: a new treatment paradigm. 1763 78


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