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Wu M, Tang L, Chen B, Zheng J, Dong F, Su Z, Lin F. Blockade of the mTOR signaling pathway with rapamycin ameliorates aristolochic acid nephropathy. Exp Ther Med 2020; 19:2887-2894. [PMID: 32256773 PMCID: PMC7086201 DOI: 10.3892/etm.2020.8550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 12/03/2019] [Indexed: 12/14/2022] Open
Abstract
Chronic aristolochic acid nephropathy (CAAN) is characterized by widespread apoptosis and interstitial fibrosis, which severely impairs kidney function. mTOR is crucial for cell proliferation and protein synthesis. In the present study, the therapeutic effects of blockade of mTOR activity by rapamycin on aristolochic acid nephropathy were investigated. In vitro experiments to determine cell apoptosis and cell cycle alterations caused by aristolochic acid (AA)-induced injury were conducted on three groups of cells: Untreated control, AAI (treated with aristolochic acid I), and AAI + rapamycin (RMS). In vivo experiments were conducted in a CAAN mouse model. One group of mice was treated with AAI (the CAAN group), while another group was treated with AAI and rapamycin (the treatment group). Kidney function and pathological changes in these mice were assessed by serum creatinine and urea nitrogen analysis. Hematoxylin and eosin staining of renal tissue was performed to evaluate the treatment effects of rapamycin. Western blotting and immunohistochemical staining were used to explore the mechanisms by which rapamycin inhibited cell proliferation, apoptosis and tissue fibrosis. In the in vitro experiments, rapamycin prevented AAI-induced cell apoptosis and G2/M checkpoint cell cycle arrest. In the in vivo experiments, the treatment group exhibited lower serum creatinine and urea nitrogen, less extensive tubular atrophy and increased amount of glomerulus. Additionally, western blotting and immunohistochemical staining showed that the treatment group exhibited decreased expression levels of fibrosis-, proliferation- and apoptosis-related proteins compared with the CAAN group. The findings suggest that rapamycin can ameliorate kidney injury induced by AAI via blockade of mTOR, and thus could be a therapeutic strategy for patients with CAAN.
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Affiliation(s)
- Minmin Wu
- Key Laboratory of Diagnosis and Treatment of Severe Hepato-Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Lili Tang
- Clinical Laboratory, Chinese Medical Hospital of Jining, Jining, Shandong 272037, P.R. China
| | - Bicheng Chen
- Key Laboratory of Diagnosis and Treatment of Severe Hepato-Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Jianjian Zheng
- Key Laboratory of Diagnosis and Treatment of Severe Hepato-Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Fengquan Dong
- Department of Nephrology, Shenzhen University General Hospital, Shenzhen, Guangdong 518055, P.R. China
| | - Zhen Su
- Key Laboratory of Diagnosis and Treatment of Severe Hepato-Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Fan Lin
- Key Laboratory of Diagnosis and Treatment of Severe Hepato-Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China.,Department of Nephrology, Shenzhen University General Hospital, Shenzhen, Guangdong 518055, P.R. China
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Biological Aspects of mTOR in Leukemia. Int J Mol Sci 2018; 19:ijms19082396. [PMID: 30110936 PMCID: PMC6121663 DOI: 10.3390/ijms19082396] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 08/07/2018] [Accepted: 08/10/2018] [Indexed: 02/07/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) is a central processor of intra- and extracellular signals, regulating many fundamental cellular processes such as metabolism, growth, proliferation, and survival. Strong evidences have indicated that mTOR dysregulation is deeply implicated in leukemogenesis. This has led to growing interest in the development of modulators of its activity for leukemia treatment. This review intends to provide an outline of the principal biological and molecular functions of mTOR. We summarize the current understanding of how mTOR interacts with microRNAs, with components of cell metabolism, and with controllers of apoptotic machinery. Lastly, from a clinical/translational perspective, we recapitulate the therapeutic results in leukemia, obtained by using mTOR inhibitors as single agents and in combination with other compounds.
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Hong Z, Pedersen NM, Wang L, Torgersen ML, Stenmark H, Raiborg C. PtdIns3P controls mTORC1 signaling through lysosomal positioning. J Cell Biol 2017; 216:4217-4233. [PMID: 29030394 PMCID: PMC5716264 DOI: 10.1083/jcb.201611073] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 07/04/2017] [Accepted: 08/21/2017] [Indexed: 01/06/2023] Open
Abstract
mTORC1 is activated by lysosome positioning and by amino acid–induced phosphatidylinositol 3-phosphate (PtdIns3P). Hong et al. show that amino acids stimulate recruitment of the PtdIns3P-binding protein FYCO1 to lysosomes and promote contacts between FYCO1 lysosomes and ER that contains the PtdIns3P effector Protrudin, mediating lysosome translocation and facilitating mTORC1 activation. The mechanistic target of rapamycin complex 1 (mTORC1) is a protein kinase complex that localizes to lysosomes to up-regulate anabolic processes and down-regulate autophagy. Although mTORC1 is known to be activated by lysosome positioning and by amino acid–stimulated production of phosphatidylinositol 3-phosphate (PtdIns3P) by the lipid kinase VPS34/PIK3C3, the mechanisms have been elusive. Here we present results that connect these seemingly unrelated pathways for mTORC1 activation. Amino acids stimulate recruitment of the PtdIns3P-binding protein FYCO1 to lysosomes and promote contacts between FYCO1 lysosomes and endoplasmic reticulum that contain the PtdIns3P effector Protrudin. Upon overexpression of Protrudin and FYCO1, mTORC1–positive lysosomes translocate to the cell periphery, thereby facilitating mTORC1 activation. This requires the ability of Protrudin to bind PtdIns3P. Conversely, upon VPS34 inhibition, or depletion of Protrudin or FYCO1, mTORC1-positive lysosomes cluster perinuclearly, accompanied by reduced mTORC1 activity under nutrient-rich conditions. Consequently, the transcription factor EB enters the nucleus, and autophagy is up-regulated. We conclude that PtdIns3P-dependent lysosome translocation to the cell periphery promotes mTORC1 activation.
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Affiliation(s)
- Zhi Hong
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Nina Marie Pedersen
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Ling Wang
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Maria Lyngaas Torgersen
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway.,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
| | - Camilla Raiborg
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, Norway .,Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway
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Erzhi Pill® Repairs Experimental Liver Injury via TSC/mTOR Signaling Pathway Inhibiting Excessive Apoptosis. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2017. [PMID: 28638431 PMCID: PMC5468563 DOI: 10.1155/2017/5653643] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The present study aimed to investigate the mechanism of hepatoprotective effect of Erzhi Pill (EZP) on the liver injury via observing TSC/mTOR signaling pathway activation. The experimental liver injury was induced by 2-acetylaminofluorene (2-AAF) treatment combined with partial hepatectomy (PH). EZP treated 2-AAF/PH-induced liver injury by the therapeutic and prophylactic administration. After the administration of EZP, the activities of aspartic transaminase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AKP), and gamma-glutamyl transpeptidase (γ-GT) were decreased, followed by the decreased levels of hepatocyte apoptosis and caspase-3 expression. However, the secretion of albumin, liver weight, and index of liver weight were elevated. Microscopic examination showed that EZP restored pathological liver injury. Meanwhile, Rheb and mammalian target of rapamycin (mTOR) activation were suppressed, and tuberous sclerosis complex (TSC) expression was elevated in liver tissues induced by 2-AAF/PHx and accompanied with lower-expression of Bax, Notch1, p70S6K, and 4E-EIF and upregulated levels of Bcl-2 and Cyclin D. Hepatoprotective effect of EZP was possibly realized via inhibiting TSC/mTOR signaling pathway to suppress excessive apoptosis of hepatocyte.
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The ribosomal protein S6 in renal cell carcinoma: functional relevance and potential as biomarker. Oncotarget 2016; 7:418-32. [PMID: 26506236 PMCID: PMC4808008 DOI: 10.18632/oncotarget.6225] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/08/2015] [Indexed: 01/09/2023] Open
Abstract
Inhibitors of the mTOR pathway, such as everolimus, are promising compounds to treat patients with renal cell carcinomas (RCCs). However, the precise mechanisms of action are far from clear, and biomarkers predicting the response to mTOR inhibitors are still missing. Here, we provide evidence that in RCCs the rpS6 protein is the major mediator of anti-tumoral effects exerted by everolimus. Inhibition of mTOR signaling results in substantially decreased clonogenicity and proliferation of RCC cells, but did not significantly induce apoptosis. Everolimus effectively blocked protein biosynthesis both in vitro and in a novel ex vivo tissue slice model using fresh vital human RCC tissue. Compared to other components of the mTOR pathway, phosphorylation of rpS6 was most effectively downregulated by everolimus. Importantly, siRNA-mediated downregulation of rpS6, but not of 4ebp1 or p27, abolished the inhibitory effects of everolimus on proliferation and protein synthesis. Moreover, we analyzed the tissue expression of phosphorylated rpS6 (p-rpS6) and non-phosphorylated rpS6 in a large collection of patients with RCCs (n=598 and n=548, respectively). Expression of both proteins qualified as independent negative prognostic markers with a substantially shorter survival of patients with RCCs exhibiting high levels of rpS6 and p-rpS6. Taken together, our functional studies identified rpS6 as a main mediator of the anti-tumoral activity of Everolimus. Therefore, further (pre-)clinical evaluations of rpS6 as a predictive marker for everolimus-based treatment for RCC patients are warranted. Finally, the combined detection of phosphorylated and non-phosphorylated rpS6 could represent a robust prognostic marker to identify patients with high risk RCCs.
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Yamaguchi K, Iglesias-Bartolomé R, Wang Z, Callejas-Valera JL, Amornphimoltham P, Molinolo AA, Cohen EE, Califano JA, Lippman SM, Luo J, Gutkind JS. A synthetic-lethality RNAi screen reveals an ERK-mTOR co-targeting pro-apoptotic switch in PIK3CA+ oral cancers. Oncotarget 2016; 7:10696-709. [PMID: 26882569 PMCID: PMC4905432 DOI: 10.18632/oncotarget.7372] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 01/29/2016] [Indexed: 12/31/2022] Open
Abstract
mTOR inhibition has emerged as a promising strategy for head and neck squamous cell carcinomas (HNSCC) treatment. However, most targeted therapies ultimately develop resistance due to the activation of adaptive survival signaling mechanisms limiting the activity of targeted agents. Thus, co-targeting key adaptive mechanisms may enable more effective cancer cell killing. Here, we performed a synthetic lethality screen using shRNA libraries to identify druggable candidates for combinatorial signal inhibition. We found that the ERK pathway was the most highly represented. Combination of rapamycin with trametinib, a MEK1/2 inhibitor, demonstrated strong synergism in HNSCC-derived cells in vitro and in vivo, including HNSCC cells expressing the HRAS and PIK3CA oncogenes. Interestingly, cleaved caspase-3 was potently induced by the combination therapy in PIK3CA+ cells in vitro and tumor xenografts. Moreover, ectopic expression of PIK3CA mutations into PIK3CA- HNSCC cells sensitized them to the pro-apoptotic activity of the combination therapy. These findings indicate that co-targeting the mTOR/ERK pathways may provide a suitable precision strategy for HNSCC treatment. Moreover, PIK3CA+ HNSCC are particularly prone to undergo apoptosis after mTOR and ERK inhibition, thereby providing a potential biomarker of predictive value for the selection of patients that may benefit from this combination therapy.
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Affiliation(s)
- Kosuke Yamaguchi
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | - Ramiro Iglesias-Bartolomé
- Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Zhiyong Wang
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | | | | | - Alfredo A. Molinolo
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | - Ezra E. Cohen
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | - Joseph A. Califano
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | - Scott M. Lippman
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
| | - Ji Luo
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute (CCR-NCI), National Institutes of Health, Bethesda, MD, USA
| | - J. Silvio Gutkind
- Moores Cancer Center, University of California San Diego, San Diego, CA, USA
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Calastretti A, Gatti G, Quaresmini C, Bevilacqua A. Down-modulation of Bcl-2 sensitizes PTEN-mutated prostate cancer cells to starvation and taxanes. Prostate 2014; 74:1411-22. [PMID: 25111376 DOI: 10.1002/pros.22857] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/17/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND The critical role of PTEN in regulating the PI3K/Akt/mTOR signaling pathway raises the possibility that targeting downstream effectors of the PI3K pathway, such as Bcl-2, might be an effective anti-proliferative strategy for PTEN-deficient prostate cancer cells. METHODS Four prostate cancer cell lines (LNCaP, PC3, DU145, 22Rv1) were assayed for their levels of total Akt and Ser473 phosphorylated Akt (p-Akt) by Western Blotting; their growth rates and sensitivity to different doses of paclitaxel were determined by cell counts after Trypan Blue dye exclusion assay. Cells were subjected to different combinations of starvation (growth factors and/or aminoacids withdrawal), paclitaxel treatment and Bcl-2 silencing by siRNA. Cell viability was evaluated by Trypan Blue dye exclusion assay, Propidium Iodide (PI) and Annexin-V/PI staining. RESULTS We assessed the sensitivity of different prostate cancer cell lines to starvation and we observed a differential response correlated to the levels of Akt activation. The four prostate cancer cell lines also showed different sensitivity to taxol treatments; LNCaP and 22Rv1 cells were more resistant to paclitaxel than DU145 and PC3 cells. Combining taxol with growth factors and aminoacids deprivation leaded to a more than additive reduction of cell viability compared to single treatments in PTEN-mutant LNCaP cells. Down-modulation of anti-apoptotic Bcl-2 protein by siRNA sensitized LNCaP cells to taxanes and starvation induced cell death. CONCLUSIONS Silencing Bcl-2 in PTEN-mutated prostate cancer cells enhances the apoptotic effects of combined starvation and taxol treatments, indicating that inhibition of Bcl-2 may be of significant value in PTEN-mutant tumor therapy.
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Affiliation(s)
- Angela Calastretti
- Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy
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8
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Abstract
Apoptosis contributes to the development of diabetic nephropathy, but the mechanism by which high glucose induces apoptosis is not fully understood. Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Hyperglycemia and high glucose in vitro also lead to apoptosis, a form of programmed cell death. High glucose similar to those seen with hyperglycemia in people with diabetes mellitus, lead to accelerated apoptosis, a form of programmed cell death characterized by cell shrinkage, chromatin condensation and DNA fragmentation, in variety of cell types, including renal proximal tubular epithelial cells.
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9
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Bartlett JMS, A'hern R, Piper T, Ellis IO, Dowsett M, Mallon EA, Cameron DA, Johnston S, Bliss JM, Ellis P, Barrett-Lee PJ. Phosphorylation of AKT pathway proteins is not predictive of benefit of taxane therapy in early breast cancer. Breast Cancer Res Treat 2013; 138:773-81. [PMID: 23535839 DOI: 10.1007/s10549-013-2489-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 03/15/2013] [Indexed: 10/27/2022]
Abstract
Results from the NSABP B-28 trial suggest AKT activation may predict reduced benefit from taxanes following standard anthracycline therapy. Pre-clinical data support a link between PI3 K/AKT signalling and taxane resistance. Using the UK taxotere as adjuvant chemotherapy trial (TACT), we tested the hypothesis that activation of AKT or downstream markers, p70S6K or p90RSK, identifies patients with reduced benefit from taxane chemotherapy. TACT is a multi-centre open-label phase III trial comparing four cycles of standard FEC (fluorouracil, epirubicin, cyclophosphamide) followed by four cycles of docetaxel versus eight cycles of anthracycline-based chemotherapy. Samples from 3,596 patients were available for the current study. We performed immunohistochemical analysis of activation of AKT, p70S6 K and p90RSK. Using a training set with multiple cut-offs for predictive values (10 % increments in expression), we found no evidence for a treatment by marker interaction for pAKT473, pS6 or p90RSK. pAKT473, pS6 and p90RSK expression levels were weakly correlated. A robust, preplanned statistical analysis in the TACT trial found no evidence that pAKT473, pS6 or p90RSK identifies patients deriving reduced benefit from adjuvant docetaxel. This result is consistent with the recent NASBP B28 study where the pAKT473 effect is not statistically significant for the treatment interaction test. Therefore, neither TACT nor NASBP-B28 provides statistically robust evidence of a treatment by marker interaction between pAKT473 and taxane treatment. Alternative methods for selecting patients benefitting from taxanes should be explored.
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Affiliation(s)
- John M S Bartlett
- Ontario Institute for Cancer Research, MaRS Centre, South Tower, 101 College Street, Suite 800, Toronto, ON M5G 0A3, Canada.
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Bodur C, Kutuk O, Tezil T, Basaga H. Inactivation of Bcl-2 through IκB kinase (IKK)-dependent phosphorylation mediates apoptosis upon exposure to 4-hydroxynonenal (HNE). J Cell Physiol 2012; 227:3556-65. [PMID: 22262057 DOI: 10.1002/jcp.24057] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Apoptosis of macrophage foam cells loaded with modified/oxidized lipids is implicated in destabilization of advanced atherosclerotic plaques in humans. Concentration of HNE, main aldehydic product of plasma LDL peroxidation, elevates in atherosclerotic lesions as well as in cultured cells under oxidative stress. Although this reactive aldehyde has been shown to promote apoptosis with the involvement of p38 MAPK and JNK in various mammalian cell lines, roles of B-cell lymphoma 2 (Bcl-2) family proteins remain to be deciphered. We demonstrated that HNE-induced apoptosis was accompanied by concurrent downregulations of antiapoptotic Bcl-x(L) and Mcl-1 as well as upregulation of proapoptotic Bak. Furthermore, phoshorylation of Bcl-2 at Thr56, Ser70, and probably more phosphorylation sites located on N-terminal loop domain associated with HNE-induced apoptosis in both U937 and HeLa cells while ectopic expression of a phospho-defective Bcl-2 mutant significantly attenuated apoptosis. In parallel to this, HNE treatment caused release of proapoptotic Bax from Bcl-2. Pharmacological inhbition of IKK inhibited HNE-induced Bcl-2 phosphorylation. Similarly, silencing IKKα and -β both ended up with abrogation of Bcl-2 phosphorylation along with attenuation of apoptosis. Moreover, both IKKα and -β coimmunoprecipitated with Bcl-2 and in vitro kinase assay proved the ability of IKK to phosphorylate Bcl-2. In view of these findings and considering HNE inhibits DNA-binding activity of nuclear factor-κB (NF-κB) through prevention of IκB phosphorylation/ubiquitination/proteolysis, IKK appears to directly interfere with Bcl-2 activity through phosphorylation in HNE-mediated apoptosis independent of NF-κB signaling.
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Affiliation(s)
- Cagri Bodur
- Biological Sciences and Bioengineering Program, Sabanci University, Orhanli, Tuzla, Istanbul, Turkey
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Chae S, Kim YB, Lee JS, Cho H. Resistance to paclitaxel in hepatoma cells is related to static JNK activation and prohibition into entry of mitosis. Am J Physiol Gastrointest Liver Physiol 2012; 302:G1016-24. [PMID: 22323130 DOI: 10.1152/ajpgi.00449.2011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hepatocellular carcinoma (HCC) generally shows chemoresistant features to anticancer agents. Paclitaxel has been clinically used in the treatment of various cancers. However, effect of paclitaxel on HCC has not been adequately addressed. Here, we found two categories of hepatoma cells in response to paclitaxel. Paclitaxel effectively decreased the cell viability of SNU475, Hep3B, and SNU387 HCC cells and Chang liver cells (death prone). In contrast, the other five hepatoma cell lines (SNU449, SNU398, SUN368, SNU354, and HepG2 cells) were resistant to paclitaxel (death reluctant). In response to paclitaxel, Bcl-2 was highly phosphorylated in death-prone cells, whereas much less Bcl-2 was phosphorylated in death-reluctant cells. Cotreatment with SP600125, an inhibitor JNK, significantly reduced the phosphorylated Bcl-2 in death-prone cells and caused a significant reduction in cell death. The reduced cell death was due to prohibition into mitotic entry as evidenced by low cyclin B(1)/Cdk1 kinase activity. In death-reluctant cells, inbuild-phospho-JNK levels were high but no longer activated in response to paclitaxel. We found that paclitaxel combined with caffeine or UCN-01, inhibitors of G(2) DNA damage checkpoint, was able to partially overcome resistance to paclitaxel in these cells. Thus our data provide the molecular basis of paclitaxel resistance in hepatoma cells, and appropriate combination therapy may increase treatment efficacy.
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Affiliation(s)
- Sunyoung Chae
- Department of Biochemistry, Ajou University School of Medicine, Suwon, Korea
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Craddock TJA, Tuszynski JA, Chopra D, Casey N, Goldstein LE, Hameroff SR, Tanzi RE. The zinc dyshomeostasis hypothesis of Alzheimer's disease. PLoS One 2012; 7:e33552. [PMID: 22457776 PMCID: PMC3311647 DOI: 10.1371/journal.pone.0033552] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 02/13/2012] [Indexed: 11/20/2022] Open
Abstract
Alzheimer's disease (AD) is the most common form of dementia in the elderly. Hallmark AD neuropathology includes extracellular amyloid plaques composed largely of the amyloid-β protein (Aβ), intracellular neurofibrillary tangles (NFTs) composed of hyper-phosphorylated microtubule-associated protein tau (MAP-tau), and microtubule destabilization. Early-onset autosomal dominant AD genes are associated with excessive Aβ accumulation, however cognitive impairment best correlates with NFTs and disrupted microtubules. The mechanisms linking Aβ and NFT pathologies in AD are unknown. Here, we propose that sequestration of zinc by Aβ-amyloid deposits (Aβ oligomers and plaques) not only drives Aβ aggregation, but also disrupts zinc homeostasis in zinc-enriched brain regions important for memory and vulnerable to AD pathology, resulting in intra-neuronal zinc levels, which are either too low, or excessively high. To evaluate this hypothesis, we 1) used molecular modeling of zinc binding to the microtubule component protein tubulin, identifying specific, high-affinity zinc binding sites that influence side-to-side tubulin interaction, the sensitive link in microtubule polymerization and stability. We also 2) performed kinetic modeling showing zinc distribution in extra-neuronal Aβ deposits can reduce intra-neuronal zinc binding to microtubules, destabilizing microtubules. Finally, we 3) used metallomic imaging mass spectrometry (MIMS) to show anatomically-localized and age-dependent zinc dyshomeostasis in specific brain regions of Tg2576 transgenic, mice, a model for AD. We found excess zinc in brain regions associated with memory processing and NFT pathology. Overall, we present a theoretical framework and support for a new theory of AD linking extra-neuronal Aβ amyloid to intra-neuronal NFTs and cognitive dysfunction. The connection, we propose, is based on β-amyloid-induced alterations in zinc ion concentration inside neurons affecting stability of polymerized microtubules, their binding to MAP-tau, and molecular dynamics involved in cognition. Further, our theory supports novel AD therapeutic strategies targeting intra-neuronal zinc homeostasis and microtubule dynamics to prevent neurodegeneration and cognitive decline.
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Jiang Z, Fletcher NM, Ali-Fehmi R, Diamond MP, Abu-Soud HM, Munkarah AR, Saed GM. Modulation of redox signaling promotes apoptosis in epithelial ovarian cancer cells. Gynecol Oncol 2011; 122:418-23. [PMID: 21620448 DOI: 10.1016/j.ygyno.2011.04.051] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Revised: 04/27/2011] [Accepted: 04/29/2011] [Indexed: 01/16/2023]
Abstract
OBJECTIVE Epithelial ovarian cancer (EOC) cells are known to be resistant to apoptosis through a mechanism that may involve alteration in their redox balance. NADPH oxidase is a major source of intracellular superoxide, which is converted to the less toxic product by superoxide dismutase (SOD). Superoxide contributes to hypoxia inducible factor (HIF)-1α stabilization. We sought to determine the effects of inhibiting the generation of intracellular reactive oxygen species (ROS) on apoptosis of EOC cells. METHODS Diphenyleneiodonium (DPI), an irreversible ROS inhibitor, was used to inhibit the generation of ROS in EOC cell lines, SKOV-3 and MDAH-2774, followed by assessment of apoptosis, NADPH oxidase, SOD3 and HIF-1α expression. A combination of immunohistochemistry, immunoprecipitation/western blot, and real-time RT-PCR were utilized to evaluate the expression of these enzymes in EOC cells as well as normal ovarian tissue and ovarian cancer tissue specimens. RESULTS DPI treatment significantly induced apoptosis in both EOC cell lines as evident by increased caspase-3 activity and TUNEL assay. Additionally, both EOC cell lines were found to express NADPH oxidase, HIF-1α, and SOD3, which were highly sensitive to DPI treatment. DPI treatment resulted in reduced NADPH oxidase, SOD3 and HIF-1α levels. Furthermore, ovarian cancer tissues were found to manifest higher NADPH oxidase levels as compared to normal ovarian tissues. CONCLUSIONS These data suggest that lowering oxidative stress, possibly through the inhibition of NADPH oxidase, induces apoptosis in ovarian cancer cells and may serve as a potential target for cancer therapy.
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Affiliation(s)
- Zhongliang Jiang
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI 48201, USA
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Velagapudi C, Bhandari BS, Abboud-Werner S, Simone S, Abboud HE, Habib SL. The tuberin/mTOR pathway promotes apoptosis of tubular epithelial cells in diabetes. J Am Soc Nephrol 2011; 22:262-73. [PMID: 21289215 DOI: 10.1681/asn.2010040352] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Apoptosis contributes to the development of diabetic nephropathy, but the mechanism by which high glucose (HG) induces apoptosis is not fully understood. Because the tuberin/mTOR pathway can modulate apoptosis, we studied the role of this pathway in apoptosis in type I diabetes and in cultured proximal tubular epithelial (PTE) cells exposed to HG. Compared with control rats, diabetic rats had more apoptotic cells in the kidney cortex. Induction of diabetes also increased phosphorylation of tuberin in association with mTOR activation (measured by p70S6K phosphorylation), inactivation of Bcl-2, increased cytosolic cytochrome c expression, activation of caspase 3, and cleavage of PARP; insulin treatment prevented these changes. In vitro, exposure of PTE cells to HG increased phosphorylation of tuberin and p70S6K, phosphorylation of Bcl-2, expression of cytosolic cytochrome c, and caspase 3 activity. High glucose induced translocation of the caspase substrate YY1 from the cytoplasm to the nucleus and enhanced cleavage of PARP. Pretreatment the cells with the mTOR inhibitor rapamycin reduced the number of apoptotic cells induced by HG and the downstream effects of mTOR activation noted above. Furthermore, gene silencing of tuberin with siRNA decreased cleavage of PARP. These data show that the tuberin/mTOR pathway promotes apoptosis of tubular epithelial cells in diabetes, mediated in part by cleavage of PARP by YY1.
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Affiliation(s)
- Chakradhar Velagapudi
- The University of Texas Health Science Center, Department of Medicine-MSC 7882, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA.
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15
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Shafer A, Zhou C, Gehrig PA, Boggess JF, Bae-Jump VL. Rapamycin potentiates the effects of paclitaxel in endometrial cancer cells through inhibition of cell proliferation and induction of apoptosis. Int J Cancer 2010; 126:1144-54. [PMID: 19688827 PMCID: PMC2818608 DOI: 10.1002/ijc.24837] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mammalian target of rapamycin (mTOR) inhibitors modulate signaling pathways involved in cell cycle progression, and recent phase II trials demonstrate activity in patients with endometrial cancer. Our objective was to examine the effects of combination therapy with rapamycin and paclitaxel in endometrial cancer cell lines. Paclitaxel inhibited proliferation in a dose-dependent manner in both cell lines with IC(50) values of 0.1-0.5 nM and 1-5 nM for Ishikawa and ECC-1 cells, respectively. To assess synergy of paclitaxel and rapamycin, the combination index (CI) was calculated by the method of Chou and Talalay. Simultaneous exposure of cells to various doses of paclitaxel in combination with rapamycin (1 nM) resulted in a significant synergistic anti-proliferative effect (CI <1, range 0.131-0.920). Rapamycin alone did not induce apoptosis, but combined treatment with paclitaxel increased apoptosis over that of paclitaxel alone. Treatment with rapamycin and paclitaxel resulted in decreased phosphorylation of S6 and 4E-BP1, two critical downstream targets of the mTOR pathway. Rapamycin decreased hTERT mRNA expression by real-time RT-PCR while paclitaxel alone had no effect on telomerase activity. Paclitaxel increased polymerization and acetylation of tubulin, and rapamycin appeared to enhance this effect. Thus, in conclusion, we demonstrate that rapamycin potentiates the effects of paclitaxel in endometrial cancer cells through inhibition of cell proliferation, induction of apoptosis and potentially increased polymerization and acetylation of tubulin. This suggests that the combination of rapamycin and paclitaxel may be a promising effective targeted therapy for endometrial cancer.
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Affiliation(s)
- Aaron Shafer
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of North Carolina, Chapel Hill, NC
| | - Chunxiao Zhou
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of North Carolina, Chapel Hill, NC
| | - Paola A. Gehrig
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of North Carolina, Chapel Hill, NC
| | - John F. Boggess
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of North Carolina, Chapel Hill, NC
| | - Victoria L. Bae-Jump
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of North Carolina, Chapel Hill, NC
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16
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Cyclin-dependent kinase 1-mediated Bcl-xL/Bcl-2 phosphorylation acts as a functional link coupling mitotic arrest and apoptosis. Mol Cell Biol 2009; 30:640-56. [PMID: 19917720 DOI: 10.1128/mcb.00882-09] [Citation(s) in RCA: 185] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Despite detailed knowledge of the components of the spindle assembly checkpoint, a molecular explanation of how cells die after prolonged spindle checkpoint activation, and thus how microtubule inhibitors and other antimitotic drugs ultimately elicit their lethal effects, has yet to emerge. Mitotically arrested cells typically display extensive phosphorylation of two key antiapoptotic proteins, Bcl-x(L) and Bcl-2, and evidence suggests that phosphorylation disables their antiapoptotic activity. However, the responsible kinase has remained elusive. In this report, evidence is presented that cyclin-dependent kinase 1 (CDK1)/cyclin B catalyzes mitotic-arrest-induced Bcl-x(L)/Bcl-2 phosphorylation. Furthermore, we show that CDK1 transiently and incompletely phosphorylates these proteins during normal mitosis. When mitosis is prolonged in the absence of microtubule inhibition, Bcl-x(L) and Bcl-2 become highly phosphorylated. Transient overexpression of nondegradable cyclin B1 caused apoptotic death, which was blocked by a phosphodefective Bcl-x(L) mutant but not by a phosphomimetic Bcl-x(L) mutant, confirming Bcl-x(L) as a key target of proapoptotic CDK1 signaling. These findings suggest a model whereby a switch in the duration of CDK1 activation, from transient during mitosis to sustained during mitotic arrest, dramatically increases the extent of Bcl-x(L)/Bcl-2 phosphorylation, resulting in inactivation of their antiapoptotic function. Thus, phosphorylation of antiapoptotic Bcl-2 proteins acts as a sensor for CDK1 signal duration and as a functional link coupling mitotic arrest to apoptosis.
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17
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Ondrousková E, Slovácková J, Pelková V, Procházková J, Soucek K, Benes P, Smarda J. Heavy metals induce phosphorylation of the Bcl-2 protein by Jun N-terminal kinase. Biol Chem 2008; 390:49-58. [PMID: 19007308 DOI: 10.1515/bc.2009.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The Bcl-2 protein is one of the key components of biochemical pathways controlling programmed cell death. The function of this protein can be regulated by posttranslational modifications. Phosphorylation of Bcl-2 has been considered to be significantly associated with cell cycle arrest in the G2/M phase of the cell cycle, and with cell death caused by defects of microtubule dynamics. This study shows that phosphorylation of Bcl-2 can be induced by heavy metals due to activation of the Jun N-terminal kinase pathway that is not linked to the G2/M cell cycle arrest. Furthermore, we demonstrate that hyperphosphorylated Bcl-2 protein is a more potent inhibitor of zinc-induced cell death than its hypophosphorylated mutant form. These data suggest that regulation of Bcl-2 protein function by phosphorylation is an important part of cell responses to stress.
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Affiliation(s)
- Eva Ondrousková
- Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlárská 2, CZ-611 37 Brno, Czech Republic
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18
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Hamano T, Gendron TF, Causevic E, Yen SH, Lin WL, Isidoro C, DeTure M, Ko LW. Autophagic-lysosomal perturbation enhances tau aggregation in transfectants with induced wild-type tau expression. Eur J Neurosci 2008; 27:1119-30. [DOI: 10.1111/j.1460-9568.2008.06084.x] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Abstract
The mammalian target of rapamycin mTOR is a central element in an evolutionary conserved signalling pathway that regulates cell growth, survival and proliferation, orchestrating signals originating from growth factors, nutrients or particular stress stimuli. Two important modulators of mTOR activity are the AKT and ERK/MAPK signalling pathways. Many studies have shown that mTOR plays an important role in the biology of malignant cells, including deregulation of the cell cycle, inactivation of apoptotic machinery and resistance to chemotherapeutic agents. The development of several mTOR inhibitors, in addition to rapamycin, has facilitated studies of the role of mTOR in cancer, and verified the antitumour effect of mTOR inhibition in many types of neoplasms, including lymphomas. Clinical trials of rapamycin derivatives in lymphoma patients are already in development and there are encouraging preliminary results, such as the substantial response of a subset of mantle cell lymphoma patients to the rapamycin analogue temsirolimus. Based on results obtained from in vitro and in vivo studies of the mTOR pathway in lymphomas, it seems that better understanding of mTOR regulation will reveal aspects of lymphomagenesis and contribute to the development of more powerful, targeted therapies for lymphoma patients.
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20
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Carpentier DC, Griffiths CM, King LA. The baculovirus P10 protein of Autographa californica nucleopolyhedrovirus forms two distinct cytoskeletal-like structures and associates with polyhedral occlusion bodies during infection. Virology 2008; 371:278-91. [DOI: 10.1016/j.virol.2007.09.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Revised: 09/24/2007] [Accepted: 09/28/2007] [Indexed: 11/28/2022]
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21
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Priulla M, Calastretti A, Bruno P, Azzariti A, Amalia A, Paradiso A, Canti G, Nicolin A. Preferential chemosensitization of PTEN-mutated prostate cells by silencing the Akt kinase. Prostate 2007; 67:782-9. [PMID: 17373720 DOI: 10.1002/pros.20566] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND In prostate cancer, mutations of the phosphatase PTEN can activate the kinase cascade PI3K/Akt/mTOR which induces drug resistance. METHODS Chemosensitization by siRNA targeting Akt was studied in HEK293 cells forced to express CA-Akt or kinase-dead DN-Akt. To decrease drug resistance, Akt was silenced with siRNA in human prostate DU-145 cell line expressing the normal PTEN or in LNCaP and PC3 cell lines expressing mutated-PTEN. Taxol was used for the chemosensitization studies. RESULTS Silencing Akt in the drug-resistant CA-Akt cells efficiently sensitized cells to antitubule agents, whereas silencing drug-responsive DN-Akt cells did not. Only minor effects were obtained in wild-type HEK293 cells. Potentiation by siRNA of taxol cytotoxicity was significantly greater in mutated-PTEN cells than in prostate cells expressing wild-type PTEN. The apoptotic program induced by taxol was preferentially potentiated by Akt siRNA in PTEN-mutated cell lines as regards the DU-145 cell line. CONCLUSIONS Silencing Akt in PTEN-mutated prostate cancer cells enhances the antitumor effects of taxol. No siRNA chemosensitization was obtained in prostate cells with wild type PTEN.
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22
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Bevilacqua A, Ghisolfi L, Franzi S, Maresca G, Gherzi R, Capaccioli S, Nicolin A, Canti G. Stabilization of cellular mRNAs and up-regulation of proteins by oligoribonucleotides homologous to the Bcl2 adenine-uridine rich element motif. Mol Pharmacol 2007; 71:531-8. [PMID: 17077270 DOI: 10.1124/mol.106.029041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adenine-uridine rich elements (AREs) play an important role in modulating mRNA stability, being the target site of many ARE-binding proteins (AUBPs) that are involved in the decay process. Three 26-mer 2'-O-methyl oligoribonucleotides (ORNs) homologous to the core region of ARE of bcl2 mRNA have been studied for decoy-aptamer activity in UV cross-linking assays. Sense-oriented ORNs competed with the ARE motif for the interaction with both destabilizing and stabilizing AUBPs in cell-free systems and in cell lines. Moreover, ORNs induced mRNA stabilization and up-regulated both Bcl2 mRNA and protein levels in the cells. Bcl2 ORNs stabilized other ARE-containing transcripts and up-regulated their expression. These results indicate that Bcl2 ORNs compete for AUBP-ARE interactions independently of ARE class and suggest that in the cell, the default labile status of ARE-containing mRNAs depends on the combined interaction of such transcripts with destabilizing AUBPs.
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Affiliation(s)
- Annamaria Bevilacqua
- Department of Pharmacology, University of Milan, Via Vanvitelli 32, 20129 Milan, Italy
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23
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Lafay-Chebassier C, Pérault-Pochat MC, Page G, Rioux Bilan A, Damjanac M, Pain S, Houeto JL, Gil R, Hugon J. The immunosuppressant rapamycin exacerbates neurotoxicity of Abeta peptide. J Neurosci Res 2007; 84:1323-34. [PMID: 16955484 DOI: 10.1002/jnr.21039] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease of the central nervous system characterized by two major lesions: extracellular senile plaques and intraneuronal neurofibrillary tangles. beta-Amyloid (Abeta) is known to play a major role in the pathogenesis of AD. Protein synthesis and especially translation initiation are modulated by different factors, including the PKR/eIF2 and the mTOR/p70S6K pathways. mRNA translation is altered in the brain of AD patients. Very little is known about the translation control mediated by mTOR in AD, although mTOR is a central regulator of translation initiation and also ribosome biogenesis and cell growth and proliferation. In this study, by using Western blotting, we show that mTOR pathway is down-regulated by Abeta treatment in human neuroblastoma cells, and the underlying mechanism explaining a transient activation of p70S6K is linked to cross-talk between mTOR and ERK1/2 at this kinase level. This phenomenon is associated with caspase-3 activation, and inhibition of mTOR by the inhibitor rapamycin enhances Abeta-induced cell death. Moreover, in our cell model, insulin-like growth factor-1 is able to increase markedly the p70S6K phosphorylation controlled by mTOR and reduces the caspase-3 activity, but its protective effect on Abeta cell death is mediated via an mTOR-independent pathway. These results demonstrate that mTOR plays an important role as a cellular survival pathway in Abeta toxicity and could represent a possible target for modulating Abeta toxicity.
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24
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Lakshmana MK, Hara H, Tabira T. Amyloid beta protein-related death-inducing protein induces G2/M arrest: Implications for neurodegeneration in Alzheimer's disease. J Neurosci Res 2007; 85:2262-71. [PMID: 17510977 DOI: 10.1002/jnr.21351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Amyloid beta protein (Abeta)-related death-inducing protein (AB-DIP) is a novel Abeta binding protein expressed ubiquitously. Here we demonstrate that overexpression of AB-DIP in SH-SY5Y neuroblastoma cells causes G2/M arrest. By deletion mutant analysis, we have identified the minimal region within AB-DIP required for G2/M arrest. We have also shown that microtubule-interfering agents (MIAs) such as nocodazole, vinblastine, paclitaxel, and vincristine, known to arrest cells at G2/M, also phosphorylate AB-DIP. However, etoposide, which causes genotoxic stress; tunicamycin, an ER stress inducer; and rotenone, which causes mitochondrial damage, fail to phosphorylate AB-DIP, implying that phosphorylation of AB-DIP is specific to microtubule-disruption-induced G2/M arrest. By using different classes of kinase inhibitors, we also demonstrate that a putative tyrosine kinase phosphorylates AB-DIP. Mono- or multisite mutations of tyrosine or serine/threonine residues confirmed that mutation of tyrosine residues but not serine/threonine residues greatly reduces nocodazole-induced phosphorylation of AB-DIP. Furthermore, phosphorylation of AB-DIP can be induced in MCF-7 cells that lack functional p53, suggesting that AB-DIP phosphorylation is independent of p53. Mounting experimental evidence continues to support the role of cell cycle abnormalities in the pathogenesis of Alzheimer's disease, and our results suggest that AB-DIP might provide a mechanistic link between microtubule disruption, mitotic abnormalities, neuronal dysfunction, and death. Therefore, interfering with AB-DIP may have therapeutic applications in conditions such as Alzheimer's disease, in which microtubule disruption and mitotic abnormalities have been suggested to play a pathological role.
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Affiliation(s)
- Madepalli K Lakshmana
- Department of Neuroscience, University of California, San Diego, Leichtag Biomedical Research, La Jolla, California 92093, USA.
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25
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Abstract
There is currently a high level of interest in signalling through the mammalian target of rapamycin (mTOR). This reflects both its key role in many cell functions and its involvement in disease states such as cancers. The best understood targets for mTOR signalling are proteins involved in controlling the translational machinery, including the ribosomal protein S6 kinases and proteins that regulate the initiation and elongation phases of translation. Indeed, there is compelling evidence that at least one of these targets of mTOR (eukaryotic initiation factor eIF4E) plays a key role in tumorigenesis. It is regulated through the mTOR-dependent phosphorylation of inhibitory proteins such as eIF4E-binding protein 1. Thus, targeting mTOR signalling may be an effective anticancer strategy, in at least a significant subset of tumours. Not all effects of mTOR are sensitive to the classical anti-mTOR drug rapamycin, and this compound also interferes with other processes besides eIF4E function. Developing new approaches to targeting mTOR for cancer therapy requires more detailed knowledge of signalling downstream of mTOR. Such advances are likely to come from further work to understand the regulation of mTOR targets such as components of the translational apparatus.
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Affiliation(s)
- J Averous
- Unité de Nutrition Humaine, INRA de Theix, Saint Genès Champanelle, France
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26
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Faivre S, Kroemer G, Raymond E. Current development of mTOR inhibitors as anticancer agents. Nat Rev Drug Discov 2006; 5:671-88. [PMID: 16883305 DOI: 10.1038/nrd2062] [Citation(s) in RCA: 744] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mammalian target of rapamycin (mTOR) is a kinase that functions as a master switch between catabolic and anabolic metabolism and as such is a target for the design of anticancer agents. The most established mTOR inhibitors--rapamycin and its derivatives--showed long-lasting objective tumour responses in clinical trials, with CCI-779 being a first-in-class mTOR inhibitor that improved the survival of patients with advanced renal cell carcinoma. This heralded the beginning of extensive clinical programmes to further evaluate mTOR inhibitors in several tumour types. Here we review the clinical development of this drug class and look at future prospects for incorporating these agents into multitarget or multimodality strategies against cancer.
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Affiliation(s)
- Sandrine Faivre
- Service Inter Hospitalier de Cancrologie, Beaujon University Hospital, 100 Boulevard du General Leclerc, 92118 Clichy Cedex, France
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27
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Bergstralh DT, Ting JPY. Microtubule stabilizing agents: Their molecular signaling consequences and the potential for enhancement by drug combination. Cancer Treat Rev 2006; 32:166-79. [PMID: 16527420 DOI: 10.1016/j.ctrv.2006.01.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/28/2022]
Abstract
Microtubule stabilization by chemotherapy is a powerful weapon in the war against cancer. Disruption of the mitotic spindle activates a number of signaling pathways, with consequences that may protect the cell or lead to its death via apoptosis. Taxol, the first microtubule stabilizing drug to be identified, has been utilized successfully in the treatment of solid tumors for two decades. Several features, however, make this drug less than ideal, and the search for next generation stabilizing drugs with increased efficacy has been intense and fruitful. Microtubule stabilizing agents (MSAs), including the taxanes, the epothilones, discodermolide, laulimalide, and eleutherobin, form an important and expanding family of chemotherapeutic agents. A strong understanding of their molecular signaling consequences is essential to their value, particularly in regard to their potential for combinatorial chemotherapy - the use of multiple agents to enhance the efficacy of cancer treatment. Here we present a critical review of research on the signaling mechanisms induced by MSAs, their relevance to apoptosis, and their potential for exploitation by combinatorial therapy.
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Affiliation(s)
- Daniel T Bergstralh
- Lineberger Comprehensive Cancer Center, Curriculum in Genetics and Molecular Biology, Campus Box #7295, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA
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28
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Voorzanger-Rousselot N, Alberti L, Blay JY. CD40L induces multidrug resistance to apoptosis in breast carcinoma and lymphoma cells through caspase independent and dependent pathways. BMC Cancer 2006; 6:75. [PMID: 16545138 PMCID: PMC1435764 DOI: 10.1186/1471-2407-6-75] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Accepted: 03/18/2006] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND CD40L was found to reduce doxorubicin-induced apoptosis in non Hodgkin's lymphoma cell lines through caspase-3 dependent mechanism. Whether this represents a general mechanism for other tumor types is unknown. METHODS The resistance induced by CD40L against apoptosis induced by a panel of cytotoxic chemotherapeutic drugs in non Hodgkin's lymphoma and breast carcinoma cell lines was investigated. RESULTS Doxorubicin, cisplatyl, etoposide, vinblastin and paclitaxel increased apoptosis in a dose-dependent manner in breast carcinoma as well as in non Hodgkin's lymphoma cell lines. Co-culture with irradiated L cells expressing CD40L significantly reduced the percentage of apoptotic cells in breast carcinoma and non Hodgkin's lymphoma cell lines treated with these drugs. In breast carcinoma cell lines, these 5 drugs induced an inconsistent increase of caspase-3/7 activity, while in non Hodgkin's lymphoma cell lines all 5 drugs increased caspase-3/7 activity up to 28-fold above baseline. Co-culture with CD40L L cells reduced (-39% to -89%) the activation of caspase-3/7 induced by these agents in all 5 non Hodgkin's lymphoma cell lines, but in none of the 2 breast carcinoma cell lines. Co culture with CD40L L cells also blocked the apoptosis induced by exogenous ceramides in breast carcinoma and non Hodgkin's lymphoma cell lines through a caspase-3-like, 8-like and 9-like dependent pathways. CONCLUSION These results indicate that CD40L expressed on adjacent non tumoral cells induces multidrug resistance to cytotoxic agents and ceramides in both breast carcinoma and non Hodgkin's lymphoma cell lines, albeit through a caspase independent and dependent pathway respectively.
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Affiliation(s)
| | - Laurent Alberti
- Equipe Cytokines et Cancer, Unité INSERM U590, Centre Léon Bérard, 28 rue Laënnec, 69373 LYON cedex 08, France
| | - Jean-Yves Blay
- Equipe Cytokines et Cancer, Unité INSERM U590, Centre Léon Bérard, 28 rue Laënnec, 69373 LYON cedex 08, France
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Teachey DT, Obzut DA, Cooperman J, Fang J, Carroll M, Choi JK, Houghton PJ, Brown VI, Grupp SA. The mTOR inhibitor CCI-779 induces apoptosis and inhibits growth in preclinical models of primary adult human ALL. Blood 2006; 107:1149-55. [PMID: 16195324 PMCID: PMC1895910 DOI: 10.1182/blood-2005-05-1935] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Accepted: 09/23/2005] [Indexed: 01/08/2023] Open
Abstract
Acute lymphoblastic leukemia (ALL) in adult patients is often resistant to current therapy, making the development of novel therapeutic agents paramount. We investigated whether mTOR inhibitors (MTIs), a class of signal transduction inhibitors, would be effective in primary human ALL. Lymphoblasts from adult patients with precursor B ALL were cultured on bone marrow stroma and were treated with CCI-779, a second generation MTI. Treated cells showed a dramatic decrease in cell proliferation and an increase in apoptotic cells, compared to untreated cells. We also assessed the effect of CCI-779 in a NOD/SCID xenograft model. We treated a total of 68 mice generated from the same patient samples with CCI-779 after establishment of disease. Animals treated with CCI-779 showed a decrease in peripheral-blood blasts and in splenomegaly. In dramatic contrast, untreated animals continued to show expansion of human ALL. We performed immunoblots to validate the inhibition of the mTOR signaling intermediate phospho-S6 in human ALL, finding down-regulation of this target in xenografted human ALL exposed to CCI-779. We conclude that MTIs can inhibit the growth of adult human ALL and deserve close examination as therapeutic agents against a disease that is often not curable with current therapy.
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Affiliation(s)
- David T Teachey
- Division of Oncology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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30
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Parmar S, Smith J, Sassano A, Uddin S, Katsoulidis E, Majchrzak B, Kambhampati S, Eklund EA, Tallman MS, Fish EN, Platanias LC. Differential regulation of the p70 S6 kinase pathway by interferon alpha (IFNalpha) and imatinib mesylate (STI571) in chronic myelogenous leukemia cells. Blood 2005; 106:2436-2443. [PMID: 15790787 PMCID: PMC1895266 DOI: 10.1182/blood-2004-10-4003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Accepted: 03/16/2005] [Indexed: 01/30/2023] Open
Abstract
The precise mechanisms by which imatinib mesylate (STI571) and interferon alpha (IFNalpha) exhibit antileukemic effects are not known. We examined the effects of IFNs or imatinib mesylate on signaling pathways regulating initiation of mRNA translation in BCR-ABL-expressing cells. Treatment of IFN-sensitive KT-1 cells with IFNalpha resulted in phosphorylation/activation of mammalian target of rapamycin (mTOR) and downstream activation of p70 S6 kinase. The IFN-activated p70 S6 kinase was found to regulate phosphorylation of S6 ribosomal protein, which regulates translation of mRNAs with oligopyrimidine tracts in the 5'-untranslated region. In addition, IFNalpha treatment resulted in an mTOR- and/or phosphatidyl-inositol 3'(PI 3') kinase-dependent phosphorylation of 4E-BP1 repressor of mRNA translation on sites that are required for its deactivation and dissociation from the eukaryotic initiation factor-4E (eIF4E) complex. In contrast to the effects of IFNs, imatinib mesylate suppressed p70 S6 kinase activity, consistent with inhibition of BCR-ABL-mediated activation of the mTOR/p70 S6 kinase pathway. Moreover, the mTOR inhibitor rapamycin enhanced the suppressive effects of imatinib mesylate on primary leukemic granulocyte macrophage-colony-forming unit (CFU-GM) progenitors from patients with chronic myelogenous leukemia (CML). Taken altogether, our data demonstrate that IFNs and imatinib mesylate differentially regulate PI 3' kinase/mTOR-dependent signaling cascades in BCR-ABL-transformed cells, consistent with distinct effects of these agents on pathways regulating mRNA translation. They also support the concept that combined use of imatinib mesylate with mTOR inhibitors may be an appropriate future therapeutic strategy for the treatment of CML.
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MESH Headings
- 5' Untranslated Regions
- Androstadienes/pharmacology
- Benzamides
- Cell Line
- Cell Line, Tumor
- Cell Survival
- Eukaryotic Initiation Factor-4E/metabolism
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Neoplastic
- Granulocytes/cytology
- Granulocytes/metabolism
- Humans
- Imatinib Mesylate
- Immunoblotting
- Interferon-alpha/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/enzymology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphorylation
- Piperazines/pharmacology
- Protein Biosynthesis
- Protein Kinases/metabolism
- Pyrimidines/pharmacology
- RNA, Messenger/metabolism
- Ribosomal Protein S6 Kinases, 70-kDa/biosynthesis
- Ribosomal Protein S6 Kinases, 70-kDa/genetics
- Signal Transduction
- Sirolimus/pharmacology
- Stem Cells
- TOR Serine-Threonine Kinases
- Time Factors
- Wortmannin
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Affiliation(s)
- Simrit Parmar
- Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School, Lakeside Veterans Administration Medical Center, Section of Hematology-Oncology, University of Chicago, IL, USA
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Vignot S, Faivre S, Aguirre D, Raymond E. mTOR-targeted therapy of cancer with rapamycin derivatives. Ann Oncol 2005; 16:525-37. [PMID: 15728109 DOI: 10.1093/annonc/mdi113] [Citation(s) in RCA: 485] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Rapamycin and its derivatives (CCI-779, RAD001 and AP23576) are immunosuppressor macrolides that block mTOR (mammalian target of rapamycin) functions and yield antiproliferative activity in a variety of malignancies. Molecular characterization of upstream and downstream mTOR signaling pathways is thought to allow a better selection of rapamycin-sensitive tumours. For instance, a loss of PTEN functions results in Akt phosphorylation, cell growth and proliferation; circumstances that can be blocked using rapamycin derivatives. From recent studies, rapamycin derivatives appear to display a safe toxicity profile with skin rashes and mucositis being prominent and dose-limiting. Sporadic activity with no evidence of dose-effect relationship has been reported. Evidence suggests that rapamycin derivatives could induce G1-S cell cycle delay and eventually apoptosis depending on inner cellular characteristics of tumour cells. Surrogate molecular markers that could be used to monitor biological effects of rapamycin derivatives and narrow down biologically active doses in patients, such as the phosphorylation of P70S6K or expression of cyclin D1 and caspase 3, are currently evaluated. Since apoptosis induced by rapamycin is blocked by BCL-2, strategies aimed at detecting human tumours that express BCL-2 and other anti-apoptotic proteins might allow identification of rapamycin-resistant tumours. Finally, we discuss current and future placements of rapamycin derivatives and related translational research into novel therapeutic strategies against cancer.
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Affiliation(s)
- S Vignot
- Department of Oncology, Hospital Saint Louis, Paris Department of Medical Oncology, Beaujon University Hospital, Clichy, France
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Du L, Lyle CS, Chambers TC. Characterization of vinblastine-induced Bcl-xL and Bcl-2 phosphorylation: evidence for a novel protein kinase and a coordinated phosphorylation/dephosphorylation cycle associated with apoptosis induction. Oncogene 2004; 24:107-17. [PMID: 15531923 DOI: 10.1038/sj.onc.1208189] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Bcl-xL and Bcl-2 are phosphorylated in response to microtubule inhibitors, but the kinase(s) responsible and the functional significance have remained unclear. In this study, we investigated the characteristics of Bcl-xL and Bcl-2 phosphorylation in KB-3 carcinoma cells treated with vinblastine. In both asynchronous and synchronous cell cultures, Bcl-xL and Bcl-2 underwent a well-defined and coordinated cycle of phosphorylation and dephosphorylation, with a lengthy period of phosphorylation preceding apoptosis induction, and with dephosphorylation closely correlated with initiation of apoptosis. Internally, validated inhibitors of JNK, ERK, p38(MAPK), or CDK1 failed to inhibit vinblastine-induced phosphorylation of Bcl-xL or Bcl-2. In vitro, Bcl-xL and Bcl-2 were poor substrates relative to c-Jun and ATF2 for active recombinant JNK1. Both Bcl-xL and Bcl-2 were localized primarily to the mitochondrial fraction in both control and vinblastine-treated cells, indicating that phosphorylation did not promote subcellular redistribution. Bcl-xL kinase activity was demonstrated in mitochondrial extracts from vinblastine-treated, but not control, cells. These findings suggest that phosphorylation of these key antiapoptotic proteins may be catalysed by a novel or unsuspected kinase that is activated or induced in response to microtubule damage. Furthermore, the same kinase and phosphatase system may be operating in tandem on both proteins, and phosphorylation appears to maintain their antiapoptotic function, whereas dephosphorylation may trigger apoptosis. These results provide evidence for a novel signaling pathway connecting microtubule damage to apoptosis induction, and help to clarify some of the controversy concerning the role of Bcl-2 phosphorylation in microtubule inhibitor-induced apoptosis.
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Affiliation(s)
- Lihua Du
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Asnaghi L, Calastretti A, Bevilacqua A, D'Agnano I, Gatti G, Canti G, Delia D, Capaccioli S, Nicolin A. Bcl-2 phosphorylation and apoptosis activated by damaged microtubules require mTOR and are regulated by Akt. Oncogene 2004; 23:5781-91. [PMID: 15208671 DOI: 10.1038/sj.onc.1207698] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The serine/threonine kinase mTOR, the major sensor of cell growth along the PI3K/Akt pathway, can be activated by agents acting on microtubules. Damaged microtubules induce phosphorylation of the Bcl-2 protein and lower the threshold of programmed cell death, both of which are inhibited by rapamycin. In HEK293 cells expressing Akt mutants, the level of Bcl-2 phosphorylation and the threshold of apoptosis induced by taxol or by nocodazole are significantly modified. In cells expressing dominant-negative Akt (DN-Akt), Bcl-2 phosphorylation and p70S6KThr421/Ser424 phosphorylation induced by taxol or nocodazole were significantly enhanced as compared to cells expressing constitutively active Akt (CA-Akt) and inhibited by rapamycin. Moreover, DN-Akt cells were more sensitive to antitubule agents than CA-Akt cells. In nocodazole-treated HEK293 cells sorted according to cell cycle, the p70S6KThr421/Ser424 phosphorylation was associated to the G2/M fraction. More relevant, nocodazole inhibited, in a dose-response manner, mTOR phosphorylation at Ser2448. This activity, potentiated in DN-Akt cells, was not detectable in CA-Akt cells. Our results suggest that death signals originating from damaged microtubules in G2/M can compete with G1 survival pathways at the level of mTOR. These findings have implications for cancer therapy and drug resistance.
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Affiliation(s)
- Laura Asnaghi
- Department of Pharmacology, University of Milan, Via Vanvitelli 32, 20129 Milan, Italy
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Shah OJ, Ghosh S, Hunter T. Mitotic regulation of ribosomal S6 kinase 1 involves Ser/Thr, Pro phosphorylation of consensus and non-consensus sites by Cdc2. J Biol Chem 2003; 278:16433-42. [PMID: 12586835 DOI: 10.1074/jbc.m300435200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During mitosis, the cyclin-dependent kinase, Cdc2, signals the inactivation of major anabolic processes such as transcription, mRNA processing, translation, and ribosome biogenesis, thereby providing energy needed for the radical and energetically costly structural reorganization of the cell. This is accomplished by phosphorylation and inactivation of several key anabolic elements, including TFIIIB, TFIID, RNA polymerase II, poly(A) polymerase, and translation elongation factor 1gamma. We report here that ribosomal S6 kinase 1 (S6K1), a protein kinase linked to the translation of ribosomal protein mRNAs, is also subject to regulation by Cdc2 in mitosis. In mitotic HeLa cells, when the activity of Cdc2 is high, S6K1 is phosphorylated at multiple Ser/Thr, Pro (S/TP) sites, including Ser(371), Ser(411), Thr(421), and Ser(424). Concomitant with this, the phosphorylation of the hydrophobic motif site, Thr(389), is reduced resulting in a decrease in the specific activity of S6K1. The mitotic S/TP phosphorylation sites are readily phosphorylated by Cdc2.cyclin B in vitro. These proline-directed phosphorylations are sensitive to chemical inhibitors of Cdc2 but not to inhibitors of mammalian target of rapamycin, phosphatidylinositol 3-kinase, MEK1/2, or p38. In murine FT210 cells arrested in mitosis, conditional inactivation of Cdc2 reduces phosphorylation of S6K1 at S/TP sites while simultaneously increasing phosphorylation of Thr(389) and of the S6K1 substrate, RPS6. A physical interaction exists between Cdc2 and S6K1, and this interaction is enhanced in mitotic cells. These results suggest that Cdc2 provides a signal that triggers inactivation of S6K1 in mitosis, presumably serving to spare energy for costly mitotic processes at the expense of ribosomal protein synthesis.
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Affiliation(s)
- O Jameel Shah
- Molecular and Cellular Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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von Haefen C, Wieder T, Essmann F, Schulze-Osthoff K, Dörken B, Daniel PT. Paclitaxel-induced apoptosis in BJAB cells proceeds via a death receptor-independent, caspases-3/-8-driven mitochondrial amplification loop. Oncogene 2003; 22:2236-47. [PMID: 12700660 DOI: 10.1038/sj.onc.1206280] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Caspase-8 is a key effector of death-receptor-triggered apoptosis. In a previous study, we demonstrated, however, that caspase-8 can also be activated in a death receptor-independent manner via the mitochondrial apoptosis pathway, downstream of caspase-3. Here, we show that caspases-3 and -8 mediate a mitochondrial amplification loop that is required for the optimal release of cytochrome c, mitochondrial permeability shift transition, and cell death during apoptosis induced by treatment with the microtubule-damaging agent paclitaxel (Taxol). In contrast, Smac release from mitochondria followed a different pattern, and therefore seems to be regulated independently from cytochrome c release. Taxol-induced cell death was inhibited by the use of synthetic, cell-permeable caspase-3- (zDEVD-fmk) or caspase-8-specific (zIETD-fmk) inhibitors. Apoptosis signaling was not affected by a dominant-negative FADD mutant (FADD-DN), thereby excluding a role of death receptor signaling in the amplification loop and drug-induced apoptosis. The inhibitor experiments were corroborated by the use of BJAB cells overexpressing the natural serpin protease inhibitor, cytokine response modifier A. These data demonstrate that the complete activation of mitochondria, release of cytochrome c, and execution of drug-induced apoptosis require a mitochondrial amplification loop that depends on caspases-3 and -8 activation. In addition, this is the first report to demonstrate death receptor-independent caspase-8 autoprocessing in vivo.
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Affiliation(s)
- Clarissa von Haefen
- Department of Hematology, Oncology and Tumor Immunology, University Medical Center Charité, University of Berlin, Germany
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Basu A, Haldar S. Identification of a novel Bcl-xL phosphorylation site regulating the sensitivity of taxol- or 2-methoxyestradiol-induced apoptosis. FEBS Lett 2003; 538:41-7. [PMID: 12633850 DOI: 10.1016/s0014-5793(03)00131-5] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Bcl-xL, a close homolog of Bcl2, is an important regulator of apoptosis and is overexpressed in human cancer. Phosphorylation of Bcl-xL can be induced by microtubule-damaging drugs such as taxol or 2-methoxyestradiol (2-ME). By site-directed mutagenesis studies, we have identified that serine 62 is the necessary site for taxol- or 2-ME-induced Bcl-xL phosphorylation in prostate cancer cells. Further studies with the inhibitor of Jun kinase (JNK) and phosphorylation null mutant of Bcl-xL reveal the augmentative role of JNK-mediated Bcl-xL phosphorylation in apoptosis of prostate cancer cells. In summary, our studies suggest that the phosphorylation of Bcl-xL by stress response kinase signaling might oppose the anti-apoptotic function of Bcl-xL to permit prostate cancer cells to die by apoptosis.
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Affiliation(s)
- Aruna Basu
- Department of Research, Pharmacology, Ireland Cancer Center, MetroHealth Medical Center, Case Western Reserve University, R456, Rammelkamp Building, 2500 MetroHealth Drive, Cleveland, OH 44109, USA
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Castedo M, Ferri KF, Kroemer G. Mammalian target of rapamycin (mTOR): pro- and anti-apoptotic. Cell Death Differ 2002; 9:99-100. [PMID: 11840159 DOI: 10.1038/sj.cdd.4400978] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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