751
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Edelstein J, Rockwell P. Okadaic acid induces Akt hyperphosphorylation and an oxidative stress-mediated cell death in serum starved SK-N-SH human neuroblastoma cells that are augmented by rapamycin. Neurosci Lett 2012; 531:74-9. [PMID: 23127854 DOI: 10.1016/j.neulet.2012.10.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 08/06/2012] [Accepted: 10/22/2012] [Indexed: 02/05/2023]
Abstract
Using a neuronal model of serum starved SK-N-SH neuroblastoma cells, we showed previously that the phosphorylation of Akt and the mTOR substrates S6K and S6 through the vascular endothelial growth factor receptor VEGFR2 was enhanced by treatments with the phosphatase PP2A inhibitor okadaic acid (OA). These findings suggested that PP2A inhibition uncouples the regulation of Akt signaling by mTOR and affects cell survival. We therefore examined the effects of mTOR inhibition on Akt phosphorylation at sites threonine 308 (T308) and serine 473 (S473) and survival in OA treated cells. OA induced a loss in cell viability, the accumulation of hyperactivated Akt as monomeric and ubiquitinated forms and an increase in the total levels of ubiquitinated proteins. These events were exacerbated by treatments with an allosteric (rapamycin) but not an active-site inhibitor (PP242) of mTOR. Notably, rapamycin augmented the OA-induced hyperphosphorylation of Akt by suppressing a negative feedback loop of Akt activation through VEGFR2 and its downstream target phosphatidylinositol 3-kinase (PI3K). Treatments with the antioxidant N-acetlycysteine but not the pan caspase inhibitor Z-VAD-FMK promoted survival. Unlike reports that rapamycin promotes survival through increased Akt activation, these findings show that rapamycin-induced hyperphosphorylation of Akt fails to rescue our neuronal model from an oxidative stress-induced and caspase-independent cell death mediated by PP2A inhibition. Moreover, the exacerbation of OA-induced events by rapamycin suggests that mTOR and PP2A work in concert to regulate cell survival, activated Akt and the levels of ubiquitinated proteins.
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Affiliation(s)
- Jacob Edelstein
- Department of Biological Sciences, Hunter College of The City University of New York, 695 Park Avenue, New York, NY 10065, USA
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752
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Henske EP, McCormack FX. Lymphangioleiomyomatosis - a wolf in sheep's clothing. J Clin Invest 2012; 122:3807-16. [PMID: 23114603 DOI: 10.1172/jci58709] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lymphangioleiomyomatosis (LAM) is a rare progressive lung disease of women. LAM is caused by mutations in the tuberous sclerosis genes, resulting in activation of the mTOR complex 1 signaling network. Over the past 11 years, there has been remarkable progress in the understanding of LAM and rapid translation of this knowledge to an effective therapy. LAM pathogenic mechanisms mirror those of many forms of human cancer, including mutation, metabolic reprogramming, inappropriate growth and survival, metastasis via blood and lymphatic circulation, infiltration/invasion, sex steroid sensitivity, and local and remote tissue destruction. However, the smooth muscle cell that metastasizes, infiltrates, and destroys the lung in LAM arises from an unknown source and has an innocent histological appearance, with little evidence of proliferation. Thus, LAM is as an elegant, monogenic model of neoplasia, defying categorization as either benign or malignant.
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Affiliation(s)
- Elizabeth P Henske
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
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753
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Ge Y, Chen J. Mammalian target of rapamycin (mTOR) signaling network in skeletal myogenesis. J Biol Chem 2012; 287:43928-35. [PMID: 23115234 DOI: 10.1074/jbc.r112.406942] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mammalian (or mechanistic) target of rapamycin (mTOR) regulates a wide range of cellular and developmental processes by coordinating signaling responses to mitogens, nutrients, and various stresses. Over the last decade, mTOR has emerged as a master regulator of skeletal myogenesis, controlling multiple stages of the myofiber formation process. In this minireview, we present an emerging view of the signaling network underlying mTOR regulation of myogenesis, which contrasts with the well established mechanisms in the regulation of cell and muscle growth. Current questions for future studies are also highlighted.
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Affiliation(s)
- Yejing Ge
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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754
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Battiprolu PK, Lopez-Crisosto C, Wang ZV, Nemchenko A, Lavandero S, Hill JA. Diabetic cardiomyopathy and metabolic remodeling of the heart. Life Sci 2012; 92:609-15. [PMID: 23123443 DOI: 10.1016/j.lfs.2012.10.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Revised: 09/12/2012] [Accepted: 10/04/2012] [Indexed: 12/16/2022]
Abstract
The incidence and prevalence of diabetes mellitus are both increasing rapidly in societies around the globe. The majority of patients with diabetes succumb ultimately to heart disease, much of which stems from atherosclerotic disease and hypertension. However, the diabetic milieu is itself intrinsically noxious to the heart, and cardiomyopathy can develop independent of elevated blood pressure or coronary artery disease. This process, termed diabetic cardiomyopathy, is characterized by significant changes in the physiology, structure, and mechanical function of the heart. Presently, therapy for patients with diabetes focuses largely on glucose control, and attention to the heart commences with the onset of symptoms. When the latter develops, standard therapy for heart failure is applied. However, recent studies highlight that specific elements of the pathogenesis of diabetic heart disease are unique, raising the prospect of diabetes-specific therapeutic intervention. Here, we review recently unveiled insights into the pathogenesis of diabetic cardiomyopathy and associated metabolic remodeling with an eye toward identifying novel targets with therapeutic potential.
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Affiliation(s)
- Pavan K Battiprolu
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
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755
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mTORC1 enhancement of STIM1-mediated store-operated Ca2+ entry constrains tuberous sclerosis complex-related tumor development. Oncogene 2012; 32:4702-11. [PMID: 23108404 DOI: 10.1038/onc.2012.481] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 08/27/2012] [Accepted: 09/02/2012] [Indexed: 12/14/2022]
Abstract
The protein complex of tuberous sclerosis complex (TSC)1 and TSC2 tumor suppressors is a key negative regulator of mammalian target of rapamycin (mTOR). Hyperactive mTOR signaling due to the loss-of-function of mutations in either TSC1 or TSC2 gene causes TSC, an autosomal dominant disorder featured with benign tumors in multiple organs. As the ubiquitous second messenger calcium (Ca(2+)) regulates various cellular processes involved in tumorigenesis, we explored the potential role of mTOR in modulation of cellular Ca(2+) homeostasis, and in turn the effect of Ca(2+) signaling in TSC-related tumor development. We found that loss of Tsc2 potentiated store-operated Ca(2+) entry (SOCE) in an mTOR complex 1 (mTORC1)-dependent way. The endoplasmic reticulum Ca(2+) sensor, stromal interaction molecule 1 (STIM1), was upregulated in Tsc2-deficient cells, and was suppressed by mTORC1 inhibitor rapamycin. In addition, SOCE repressed AKT1 phosphorylation. Blocking SOCE either by depleting STIM1 or ectopically expressing dominant-negative Orai1 accelerated TSC-related tumor development, likely because of restored AKT1 activity and enhanced tumor angiogenesis. Our data, therefore, suggest that mTORC1 enhancement of store-operated Ca(2+) signaling hinders TSC-related tumor growth through suppression of AKT1 signaling. The augmented SOCE by hyperactive mTORC1-STIM1 cascade may contribute to the benign nature of TSC-related tumors. Application of SOCE agonists could thus be a contraindication for TSC patients. In contrast, SOCE agonists should attenuate mTOR inhibitors-mediated AKT reactivation and consequently potentiate their efficacy in the treatment of the patients with TSC.
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756
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Chiang J, Martinez-Agosto JA. Effects of mTOR Inhibitors on Components of the Salvador-Warts-Hippo Pathway. Cells 2012; 1:886-904. [PMID: 24710534 PMCID: PMC3901137 DOI: 10.3390/cells1040886] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 10/11/2012] [Accepted: 10/12/2012] [Indexed: 01/17/2023] Open
Abstract
The MST/Salvador-Warts-Hippo and mTOR/Akt/PI3K growth signaling pathways have been established as important modulators of cell growth, proliferation and cell survival in controlling organ size in Drosophila and mammals. Here, we sought to determine the role of the MST family of kinases, some of which are components of the Hippo pathway, and their closely related Sterile 20-like kinases (STK) as candidates for mediating cross-talk between the Hippo and mTOR pathways. Expression analysis in the HepG2 and MCF7 cell lines demonstrated common expression of MST1/2/4, MAP4K3/4/5, STK 24 (MST3), STK25, STK39, Pak1, SLK, Stradα/β and TAO2. All components of the Hippo signaling pathway are present in both cell lines except for YAP1 in MCF7 cells. mTOR inhibition via rapamycin decreases TAZ levels in HepG2 but not MCF7 cells and increases TEAD1 levels in MCF7 but not HepG2 cells, suggesting a selective role of the mTOR pathway in regulating these Hippo targets in a cell type-specific manner. Furthermore, the cellular localization of TAZ changes in response to mTORC1/2 inhibitors and Akt inhibition. These findings demonstrate the mTOR-dependent regulation of Hippo signaling at the level of the transcriptional regulators TAZ and TEAD1 and highlight the potential role for mTOR inhibitors in regulating Hippo-signaling dependent tumors.
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Affiliation(s)
- Jonathan Chiang
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Julian A Martinez-Agosto
- Division of Medical Genetics, Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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757
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Copps KD, White MF. Regulation of insulin sensitivity by serine/threonine phosphorylation of insulin receptor substrate proteins IRS1 and IRS2. Diabetologia 2012; 55:2565-2582. [PMID: 22869320 PMCID: PMC4011499 DOI: 10.1007/s00125-012-2644-8] [Citation(s) in RCA: 692] [Impact Index Per Article: 57.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 04/23/2012] [Indexed: 12/11/2022]
Abstract
The insulin receptor substrate proteins IRS1 and IRS2 are key targets of the insulin receptor tyrosine kinase and are required for hormonal control of metabolism. Tissues from insulin-resistant and diabetic humans exhibit defects in IRS-dependent signalling, implicating their dysregulation in the initiation and progression of metabolic disease. However, IRS1 and IRS2 are regulated through a complex mechanism involving phosphorylation of >50 serine/threonine residues (S/T) within their long, unstructured tail regions. In cultured cells, insulin-stimulated kinases (including atypical PKC, AKT, SIK2, mTOR, S6K1, ERK1/2 and ROCK1) mediate feedback (autologous) S/T phosphorylation of IRS, with both positive and negative effects on insulin sensitivity. Additionally, insulin-independent (heterologous) kinases can phosphorylate IRS1/2 under basal conditions (AMPK, GSK3) or in response to sympathetic activation and lipid/inflammatory mediators, which are present at elevated levels in metabolic disease (GRK2, novel and conventional PKCs, JNK, IKKβ, mPLK). An emerging view is that the positive/negative regulation of IRS by autologous pathways is subverted/co-opted in disease by increased basal and other temporally inappropriate S/T phosphorylation. Compensatory hyperinsulinaemia may contribute strongly to this dysregulation. Here, we examine the links between altered patterns of IRS S/T phosphorylation and the emergence of insulin resistance and diabetes.
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Affiliation(s)
- K D Copps
- Howard Hughes Medical Institute, Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, CLS 16020, 300 Longwood Avenue, Boston, MA, 02115, USA
| | - M F White
- Howard Hughes Medical Institute, Division of Endocrinology, Boston Children's Hospital, Harvard Medical School, CLS 16020, 300 Longwood Avenue, Boston, MA, 02115, USA.
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758
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Abstract
Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that functions as a key regulatory protein in normal cell growth, survival, metabolism, development, and angiogenic pathways. Deregulation of these processes is a required hallmark of cancer, and dysregulation of mTOR signaling frequently occurs in a wide variety of malignancies, including lung cancer. Targeting of mTOR is thus an attractive strategy in the development of therapeutic agents against lung cancer. In this review, the mTOR-signaling pathway is described, highlighting opportunities for therapeutic intervention and biomarker analysis, and clinical trials in lung cancer including both non-small cell lung cancer and small cell lung cancer.
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759
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Abstract
The immunological process of clonal selection requires a rapid burst in lymphocyte proliferation, and this involves a metabolic shift to provide energy and the building blocks of new cells. After activation, naive and memory T cells switch from the oxidation of free fatty acids to glycolysis and glutaminolysis to meet these demands. Beyond this, however, the availability of specific metabolites and the pathways that process them interconnect with signaling events in the cell to influence cell cycle, differentiation, cell death and immunological function. Here we define 'metabolic checkpoints' that represent such interconnections and provide examples of how these checkpoints sense metabolic status and transduce signals to affect T lymphocyte responses.
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Affiliation(s)
- Ruoning Wang
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
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760
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Abstract
This review is focusing on a critical mediator of embryonic and postnatal development with multiple implications in inflammation, neoplasia, and other pathological situations in brain and peripheral tissues. These morphogenetic guidance and dependence processes are involved in several malignancies targeting the epithelial and immune systems including the progression of human colorectal cancers. We consider the most important findings and their impact on basic, translational, and clinical cancer research. Expected information can bring new cues for innovative, efficient, and safe strategies of personalized medicine based on molecular markers, protagonists, signaling networks, and effectors inherent to the Netrin axis in pathophysiological states.
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761
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Peng Z, Liao Z, Dziegielewska B, Matsumoto Y, Thomas S, Wan Y, Yang A, Tomkinson AE. Phosphorylation of serine 51 regulates the interaction of human DNA ligase I with replication factor C and its participation in DNA replication and repair. J Biol Chem 2012; 287:36711-9. [PMID: 22952233 DOI: 10.1074/jbc.m112.383570] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human DNA ligase I (hLigI) joins Okazaki fragments during DNA replication and completes excision repair via interactions with proliferating cell nuclear antigen and replication factor C (RFC). Unlike proliferating cell nuclear antigen, the interaction with RFC is regulated by hLigI phosphorylation. To identity of the site(s) involved in this regulation, we analyzed phosphorylated hLigI purified from insect cells by mass spectrometry. These results suggested that serine 51 phosphorylation negatively regulates the interaction with RFC. Therefore, we constructed versions of hLigI in which serine 51 was replaced with either alanine (hLigI51A) to prevent phosphorylation or aspartic acid (hLigI51D) to mimic phosphorylation. hLigI51D but not hLigI51A was defective in binding to purified RFC and in associating with RFC in cell extracts. Although DNA synthesis and proliferation of hLigI-deficient cells expressing either hLig51A or hLig51 was reduced compared with cells expressing wild-type hLigI, cellular senescence was only observed in the cells expressing hLigI51D. Notably, these cells had increased levels of spontaneous DNA damage and phosphorylated CHK2. In addition, although expression of hLigI51A complemented the sensitivity of hLigI-deficient cells to a poly (ADP-ribose polymerase (PARP) inhibitor, expression of hLig151D did not, presumably because these cells are more dependent upon PARP-dependent repair pathways to repair the damage resulting from the abnormal DNA replication. Finally, neither expression of hLigI51D nor hLigI51A fully complemented the sensitivity of hLigI-deficient cells to DNA alkylation. Thus, phosphorylation of serine 51 on hLigI plays a critical role in regulating the interaction between hLigI and RFC, which is required for efficient DNA replication and repair.
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Affiliation(s)
- Zhimin Peng
- Department of Internal Medicine and University of New Mexico Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131, USA
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762
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Shrivastav A, Murphy L. Interactions of PI3K/Akt/mTOR and estrogen receptor signaling in breast cancer. BREAST CANCER MANAGEMENT 2012. [DOI: 10.2217/bmt.12.37] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
SUMMARY Endocrine therapies are used to treat estrogen receptor-positive (ER+) breast cancer; however, patients develop resistance in some cases due to hormone-independent activation of ER signaling. Dysregulation of mTOR, a central hub for various signaling pathways regulated by hormones and growth factors, is a mechanism of endocrine therapy resistance. Activation of kinases in these pathways can cause ligand-independent ER signaling. Phosphorylation of ER regulates activity and predicts clinical outcome in ER+ breast cancer. PI3K/Akt/mTOR pathway activation in breast cancer is common and considered a therapeutic target. PI3K/Akt/mTOR signaling is complex and interacts with ER signaling. mTOR’s downstream target p70S6K negatively regulates Akt on one hand and can phosphorylate ER. Moreover, overexpressed p70S6K activates ER in breast cancer cells. An overall understanding of signaling events, especially those governed by mTOR, is important in deciding treatment protocols for ER+ breast cancers.
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Affiliation(s)
- Anuraag Shrivastav
- Department of Biology, University of Winnipeg, 515 Portage Avenue, Winnipeg, R3B 2E9, MB, Canada
| | - Leigh Murphy
- Department of Biochemistry & Medical Genetics & the Manitoba Institute of Cell Biology, University of Manitoba & CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, R3E 0V9, MB, Canada
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763
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Sikorski TW, Joo YJ, Ficarro SB, Askenazi M, Buratowski S, Marto JA. Proteomic analysis demonstrates activator- and chromatin-specific recruitment to promoters. J Biol Chem 2012; 287:35397-35408. [PMID: 22902623 DOI: 10.1074/jbc.m112.391581] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In-depth characterization of RNA polymerase II preinitiation complexes remains an important and challenging goal. We used quantitative mass spectrometry to explore context-dependent Saccharomyces cerevisiae preinitiation complex formation at the HIS4 promoter reconstituted on naked and chromatinized DNA templates. The transcription activators Gal4-VP16 and Gal4-Gcn4 recruited a limited set of chromatin-related coactivator complexes, namely the chromatin remodeler Swi/Snf and histone acetyltransferases SAGA and NuA4, suggesting that transcription stimulation is mediated through these factors. Moreover, the two activators differentially recruited the coactivator complexes, consistent with specific activator-coactivator interactions. Chromatinized templates suppressed recruitment of basal transcription factors, thereby amplifying the effect of activators, compared with naked DNA templates. This system is sensitive, highly reproducible, and easily applicable to mapping the repertoire of proteins found at any promoter.
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Affiliation(s)
- Timothy W Sikorski
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115; Department of Cancer Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Yoo Jin Joo
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Scott B Ficarro
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115; Department of Cancer Biology, Harvard Medical School, Boston, Massachusetts 02115; Blais Proteomics Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115
| | - Manor Askenazi
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115; Department of Cancer Biology, Harvard Medical School, Boston, Massachusetts 02115; Blais Proteomics Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115
| | - Stephen Buratowski
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
| | - Jarrod A Marto
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115; Department of Cancer Biology, Harvard Medical School, Boston, Massachusetts 02115; Blais Proteomics Center, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
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764
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Covian R, Balaban RS. Cardiac mitochondrial matrix and respiratory complex protein phosphorylation. Am J Physiol Heart Circ Physiol 2012; 303:H940-66. [PMID: 22886415 DOI: 10.1152/ajpheart.00077.2012] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
It has become appreciated over the last several years that protein phosphorylation within the cardiac mitochondrial matrix and respiratory complexes is extensive. Given the importance of oxidative phosphorylation and the balance of energy metabolism in the heart, the potential regulatory effect of these classical signaling events on mitochondrial function is of interest. However, the functional impact of protein phosphorylation and the kinase/phosphatase system responsible for it are relatively unknown. Exceptions include the well-characterized pyruvate dehydrogenase and branched chain α-ketoacid dehydrogenase regulatory system. The first task of this review is to update the current status of protein phosphorylation detection primarily in the matrix and evaluate evidence linking these events with enzymatic function or protein processing. To manage the scope of this effort, we have focused on the pathways involved in energy metabolism. The high sensitivity of modern methods of detecting protein phosphorylation and the low specificity of many kinases suggests that detection of protein phosphorylation sites without information on the mole fraction of phosphorylation is difficult to interpret, especially in metabolic enzymes, and is likely irrelevant to function. However, several systems including protein translocation, adenine nucleotide translocase, cytochrome c, and complex IV protein phosphorylation have been well correlated with enzymatic function along with the classical dehydrogenase systems. The second task is to review the current understanding of the kinase/phosphatase system within the matrix. Though it is clear that protein phosphorylation occurs within the matrix, based on (32)P incorporation and quantitative mass spectrometry measures, the kinase/phosphatase system responsible for this process is ill-defined. An argument is presented that remnants of the much more labile bacterial protein phosphoryl transfer system may be present in the matrix and that the evaluation of this possibility will require the application of approaches developed for bacterial cell signaling to the mitochondria.
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Affiliation(s)
- Raul Covian
- Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute, Bethesda, Maryland 20817, USA
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765
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Labban M, Dyer JR, Sossin WS. Rictor regulates phosphorylation of the novel protein kinase C Apl II in Aplysia sensory neurons. J Neurochem 2012; 122:1108-17. [DOI: 10.1111/j.1471-4159.2012.07865.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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766
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Ma Z, Zhu L, Luo X, Zhai S, Li P, Wang X. Perifosine enhances mTORC1-targeted cancer therapy by activation of GSK3β in NSCLC cells. Cancer Biol Ther 2012; 13:1009-17. [PMID: 22825337 DOI: 10.4161/cbt.20989] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
mTORC1 inhibitors, including rapamycin and its analogs, have been actively studied both pre-clinically and clinically. However, the single treatment of mTORC1 inhibitors has been modest in most cancer types. We have previously demonstrated that the activation of PI3K/Akt and MEK/ERK signaling pathways attenuates the anticancer efficacy of mTORC1 inhibitors. In this study, we report that mTORC1 inhibition also phosphorylates and inactivates GSK3β, which is a tumor suppressor in lung cancer. Moreover, we show that perifosine, as an Akt inhibitor, decreases rapamycin-induced phosphorylation of GSK3β and elevated p-GSK3β levels in rapamycin-resistant cell lines. Combination of perifosine with mTORC1 inhibitors showed enhanced anticancer efficacy both in cell cultures and in a xenograft mouse model. In addition, perifosine inhibits the growth of both rapamycin sensitive and resistant A549 cells. However, inhibition of GSK3β by a selective inhibitor- LiCl, or downregulation of GSK3β expression by siRNA, reverses the growth inhibitory effects of perifosine on rapamycin resistant cells, suggesting the important role of GSK3β activation in enhancing mTORC1 inhibitors efficacy by perifosine. Thus, our results provide a potential therapeutic strategy to enhance mTORC1-targeted cancer therapy by using perifosine or targeting GSK3β.
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Affiliation(s)
- Zhuo Ma
- Department of Pharmacology, Nanjing Medical University, Nanjing, Jiangsu, China
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767
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Analysing signalling networks by mass spectrometry. Amino Acids 2012; 43:1061-74. [PMID: 22821269 DOI: 10.1007/s00726-012-1293-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 04/03/2012] [Indexed: 12/31/2022]
Abstract
Sequence analysis of the human genome and the association of genetic aberrations with diseases have provided a rough framework whereby the impact of individual genotypes can be assessed. To fully understand the effect of individual and co-occurring genetic aberrations, as well as their individual and collected contribution to the development of diseases, it is critical to analyse the matching proteome and to determine how the organisation, expression level and function of protein networks are affected. Sensitive mass spectrometric platforms in combination with innovative workflows allow qualitative and quantitative analyses of the cellular as well as the extracellular proteome. Importantly, in addition to specifically identifying the content of the proteome, several aspects of the proteomic organisation can be analysed including protein complexes, protein modifications, enzymatic activities and subcellular/organelle localisation. Together, these measurements will provide novel insight into the biological effect of disease-causing mutations ultimately coupling genotype and phenotype.
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768
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Xie H, Zhu F, Huang Z, Lee MH, Kim DJ, Li X, Lim DY, Jung SK, Kang S, Li H, Reddy K, Wang L, Ma W, Lubet RA, Bode AM, Dong Z. Identification of mammalian target of rapamycin as a direct target of fenretinide both in vitro and in vivo. Carcinogenesis 2012; 33:1814-21. [PMID: 22798378 PMCID: PMC3515856 DOI: 10.1093/carcin/bgs234] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
N-(4-hydroxyphenyl) retinamide (4HPR, fenretinide) is a synthetic
retinoid that has been tested in clinical trials as a cancer therapeutic and
chemopreventive agent. Although 4HPR has been shown to be cytotoxic to many kinds of
cancer cells, the underlying molecular mechanisms are only partially understood. Until
now, no direct cancer-related molecular target has been reported to be involved in the
antitumor activities of 4HPR. Herein, we found that 4HPR inhibited mammalian target of
rapamycin (mTOR) kinase activity by directly binding with mTOR, which suppressed the
activities of both the mTORC1 and the mTORC2 complexes. The predicted binding mode of 4HPR
with mTOR was based on a homology computer model, which showed that 4HPR could bind in the
ATP-binding pocket of the mTOR protein through hydrogen bonds and hydrophobic
interactions. In vitro studies also showed that 4HPR attenuated mTOR
downstream signaling in a panel of non-small-cell lung cancer cells, resulting in growth
inhibition. Moreover, knockdown of mTOR in cancer cells decreased their sensitivity to
4HPR. Results of an in vivo study demonstrated that i.p. injection of
4HPR in A549 lung tumor-bearing mice effectively suppressed cancer growth. The expression
of mTOR downstream signaling molecules in tumor tissues was also decreased after 4HPR
treatment. Taken together, our results are the first to identify mTOR as a direct
antitumor target of 4HPR both in vitro and in vivo,
providing a valuable rationale for guiding the clinical uses of 4HPR.
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Affiliation(s)
- Hua Xie
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912-3679, USA
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769
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Dalle Pezze P, Sonntag AG, Shanley DP, Thedieck K. Response to Comment on “A Dynamic Network Model of mTOR Signaling Reveals TSC-Independent mTORC2 Regulation”: Building a Model of the mTOR Signaling Network with a Potentially Faulty Tool. Sci Signal 2012. [DOI: 10.1126/scisignal.2003224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Dalle Pezze
et al
. respond to criticisms regarding the specificity of phosphorylation of Ser
2481
of mTOR as a specific readout of mTORC2 activity.
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Affiliation(s)
- Piero Dalle Pezze
- Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne NE4 5PL, UK
| | - Annika G. Sonntag
- Bioinformatics and Molecular Genetics (Faculty of Biology), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
| | - Daryl P. Shanley
- Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne NE4 5PL, UK
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne NE4 5PL, UK
| | - Kathrin Thedieck
- Bioinformatics and Molecular Genetics (Faculty of Biology), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
- Center for Systems Biology (ZBSA), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
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770
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Ho AL, Vasudeva SD, Laé M, Saito T, Barbashina V, Antonescu CR, Ladanyi M, Schwartz GK. PDGF receptor alpha is an alternative mediator of rapamycin-induced Akt activation: implications for combination targeted therapy of synovial sarcoma. Cancer Res 2012; 72:4515-25. [PMID: 22787122 DOI: 10.1158/0008-5472.can-12-1319] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Akt activation by the IGF-1 receptor (IGF-1R) has been posited to be a mechanism of intrinsic resistance to mTORC1 inhibitors (rapalogues) for sarcomas. Here we show that rapamycin-induced phosphorylation of Akt can occur in an IGF-1R-independent manner. Analysis of synovial sarcoma cell lines showed that either IGF-1R or the PDGF receptor alpha (PDGFRA) can mediate intrinsic resistance to rapamycin. Repressing expression of PDGFRA or inhibiting its kinase activity in synovial sarcoma cells blocked rapamycin-induced phosphorylation of Akt and decreased tumor cell viability. Expression profiling of clinical tumor samples revealed that PDGFRA was the most highly expressed kinase gene among several sarcoma disease subtypes, suggesting that PDGFRA may be uniquely significant for synovial sarcomas. Tumor biopsy analyses from a synovial sarcoma patient treated with the mTORC1 inhibitor everolimus and PDGFRA inhibitor imatinib mesylate confirmed that this drug combination can impact both mTORC1 and Akt signals in vivo. Together, our findings define mechanistic variations in the intrinsic resistance of synovial sarcomas to rapamycin and suggest therapeutic strategies to address them.
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Affiliation(s)
- Alan L Ho
- Laboratory of New Drug Development, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 300 East 66th Street, NY 10065, USA.
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771
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Manning BD. Comment on "A Dynamic Network Model of mTOR Signaling Reveals TSC-Independent mTORC2 Regulation": Building a Model of the mTOR Signaling Network with a Potentially Faulty Tool. Sci Signal 2012; 5:lc3; author reply lc4. [DOI: 10.1126/scisignal.2003250] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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772
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Mijakovic I, Macek B. Impact of phosphoproteomics on studies of bacterial physiology. FEMS Microbiol Rev 2012; 36:877-92. [DOI: 10.1111/j.1574-6976.2011.00314.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 10/21/2011] [Accepted: 10/22/2011] [Indexed: 11/27/2022] Open
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773
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Huber TB, Edelstein CL, Hartleben B, Inoki K, Jiang M, Koya D, Kume S, Lieberthal W, Pallet N, Quiroga A, Ravichandran K, Susztak K, Yoshida S, Dong Z. Emerging role of autophagy in kidney function, diseases and aging. Autophagy 2012; 8:1009-31. [PMID: 22692002 PMCID: PMC3429540 DOI: 10.4161/auto.19821] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 02/06/2023] Open
Abstract
Autophagy is a highly conserved process that degrades cellular long-lived proteins and organelles. Accumulating evidence indicates that autophagy plays a critical role in kidney maintenance, diseases and aging. Ischemic, toxic, immunological, and oxidative insults can cause an induction of autophagy in renal epithelial cells modifying the course of various kidney diseases. This review summarizes recent insights on the role of autophagy in kidney physiology and diseases alluding to possible novel intervention strategies for treating specific kidney disorders by modifying autophagy.
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Affiliation(s)
- Tobias B Huber
- Renal Division, University Hospital Freiburg; Freiburg, Germany.
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774
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Yuan E, Tsai PT, Greene-Colozzi E, Sahin M, Kwiatkowski DJ, Malinowska IA. Graded loss of tuberin in an allelic series of brain models of TSC correlates with survival, and biochemical, histological and behavioral features. Hum Mol Genet 2012; 21:4286-300. [PMID: 22752306 DOI: 10.1093/hmg/dds262] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a neurodevelopmental disorder with prominent brain manifestations due to mutations in either TSC1 or TSC2. Here, we describe novel mouse brain models of TSC generated using conditional hypomorphic and null alleles of Tsc2 combined with the neuron-specific synapsin I cre (SynIcre) allele. This allelic series of homozygous conditional hypomorphic alleles (Tsc2(c-del3/c-del3)SynICre(+)) and heterozygote null/conditional hypomorphic alleles (Tsc2(k/c-del3)SynICre(+)) achieves a graded reduction in expression of Tsc2 in neurons in vivo. The mice demonstrate a progressive neurologic phenotype including hunchback, hind limb clasp, reduced survival and brain and cortical neuron enlargement that correlates with a graded reduction in expression of Tsc2 in the two sets of mice. Both models also showed behavioral abnormalities in anxiety, social interaction and learning assays, which correlated with Tsc2 protein levels as well. The observations demonstrate that there are graded biochemical, cellular and clinical/behavioral effects that are proportional to the extent of reduction in Tsc2 expression in neurons. Further, they suggest that some patients with milder manifestations of TSC may be due to persistent low-level expression of functional protein from their mutant allele. In addition, they point to the potential clinical benefit of strategies to raise TSC2 protein expression from the wild-type allele by even modest amounts.
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Affiliation(s)
- Elizabeth Yuan
- Department of Medicine, Brigham and Women’s Hospital, Boston, MA 02115, USA
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775
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Wiza C, Nascimento EBM, Ouwens DM. Role of PRAS40 in Akt and mTOR signaling in health and disease. Am J Physiol Endocrinol Metab 2012; 302:E1453-60. [PMID: 22354785 DOI: 10.1152/ajpendo.00660.2011] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The proline-rich Akt substrate of 40 kDa (PRAS40) acts at the intersection of the Akt- and mammalian target of rapamycin (mTOR)-mediated signaling pathways. The protein kinase mTOR is the catalytic subunit of two distinct signaling complexes, mTOR complex 1 (mTORC1) and mTORC2, that link energy and nutrients to the regulation of cellular growth and energy metabolism. Activation of mTOR in response to nutrients and growth factors results in the phosphorylation of numerous substrates, including the phosphorylations of S6 kinase by mTORC1 and Akt by mTORC2. Alterations in Akt and mTOR activity have been linked to the progression of multiple diseases such as cancer and type 2 diabetes. Although PRAS40 was first reported as substrate for Akt, investigations toward mTOR-binding partners subsequently identified PRAS40 as both component and substrate of mTORC1. Phosphorylation of PRAS40 by Akt and by mTORC1 itself results in dissociation of PRAS40 from mTORC1 and may relieve an inhibitory constraint on mTORC1 activity. Adding to the complexity is that gene silencing studies indicate that PRAS40 is also necessary for the activity of the mTORC1 complex. This review summarizes the regulation and potential function(s) of PRAS40 in the complex Akt- and mTOR-signaling network in health and disease.
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Affiliation(s)
- Claudia Wiza
- Institute of Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, Düsseldorf, Germany
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776
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Roczniak-Ferguson A, Petit CS, Froehlich F, Qian S, Ky J, Angarola B, Walther TC, Ferguson SM. The transcription factor TFEB links mTORC1 signaling to transcriptional control of lysosome homeostasis. Sci Signal 2012; 5:ra42. [PMID: 22692423 DOI: 10.1126/scisignal.2002790] [Citation(s) in RCA: 949] [Impact Index Per Article: 79.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Lysosomes are the major cellular site for clearance of defective organelles and digestion of internalized material. Demand on lysosomal capacity can vary greatly, and lysosomal function must be adjusted to maintain cellular homeostasis. Here, we identified an interaction between the lysosome-localized mechanistic target of rapamycin complex 1 (mTORC1) and the transcription factor TFEB (transcription factor EB), which promotes lysosome biogenesis. When lysosomal activity was adequate, mTOR-dependent phosphorylation of TFEB on Ser(211) triggered the binding of 14-3-3 proteins to TFEB, resulting in retention of the transcription factor in the cytoplasm. Inhibition of lysosomal function reduced the mTOR-dependent phosphorylation of TFEB, resulting in diminished interactions between TFEB and 14-3-3 proteins and the translocation of TFEB into the nucleus, where it could stimulate genes involved in lysosomal biogenesis. These results identify TFEB as a target of mTOR and suggest a mechanism for matching the transcriptional regulation of genes encoding proteins of autophagosomes and lysosomes to cellular need. The closely related transcription factors MITF (microphthalmia transcription factor) and TFE3 (transcription factor E3) also localized to lysosomes and accumulated in the nucleus when lysosome function was inhibited, thus broadening the range of physiological contexts under which this regulatory mechanism may prove important.
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777
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Abstract
The mechanistic target of rapamycin (mTOR) signaling pathway senses and integrates a variety of environmental cues to regulate organismal growth and homeostasis. The pathway regulates many major cellular processes and is implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes, and neurodegeneration. Here, we review recent advances in our understanding of the mTOR pathway and its role in health, disease, and aging. We further discuss pharmacological approaches to treat human pathologies linked to mTOR deregulation.
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778
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Targeting metabolism for cancer treatment and prevention: metformin, an old drug with multi-faceted effects. Oncogene 2012; 32:1475-87. [PMID: 22665053 DOI: 10.1038/onc.2012.181] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Understanding the complexity of cancer and of the underlying regulatory networks provides a new paradigm that tackles cancer development and treatment through a system biology approach, contemporarily acting on various intersecting pathways. Cancer cell metabolism is an old pathogenetic issue that has recently gained new interest as target for therapeutic approaches. More than 70 years ago, Warburg discovered that malignant cells generally have altered metabolism with high rates of glucose uptake and increased glycolysis, even under aerobic condition. Observational studies have provided evidence that impaired metabolism, obesity, hyperglycemia and hyperinsulinemia may have a role in cancer development, progression and prognosis, and actually diabetic and obese patients have increased cancer risk. On the other hand, caloric restriction has been shown to prolong life span and reduce cancer incidence in several animal models, having an impact on different metabolic pathways. Metformin, an antidiabetic drug widely used for over 40 years, mimics caloric restriction acting on cell metabolism at multiple levels, reducing all energy-consuming processes in the cells, including cell proliferation. By overviewing molecular mechanisms of action, epidemiological evidences, experimental data in tumor models and early clinical study results, this review provides information supporting the promising use of metformin in cancer prevention and treatment.
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779
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Zaytseva YY, Valentino JD, Gulhati P, Mark Evers B. mTOR inhibitors in cancer therapy. Cancer Lett 2012; 319:1-7. [DOI: 10.1016/j.canlet.2012.01.005] [Citation(s) in RCA: 198] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 12/22/2011] [Accepted: 01/10/2012] [Indexed: 01/01/2023]
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780
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Abstract
Amino acid availability is a rate-limiting factor in the regulation of protein synthesis. When amino acid supplies become restricted, mammalian cells employ homeostatic mechanisms to rapidly inhibit processes such as protein synthesis, which demands high levels of amino acids. Muscle cells in particular are subject to high protein turnover rates to maintain amino acid homeostasis. Mammalian target of rapamycin complex 1 (mTORC1) is an evolutionary conserved multiprotein complex that coordinates a network of signaling cascades and functions as a key mediator of protein translation, gene transcription, and autophagy. Signal transduction through mTORC1, which is centrally involved in muscle growth through enhanced protein translation, is governed by intracellular amino acid supply. The branched-chain amino acid leucine is critical for muscle growth and acts in part through activation of mTORC1. Recent research has revealed that mTORC1 signaling is coordinated primarily at the lysosomal membranes. This discovery has sparked a wealth of research in this field, revealing several different signaling molecules involved in transducing the amino acid signal to mTORC1, including the Rag GTPases, MAP4K3, and Vps34/ULK1. This review evaluates the current knowledge regarding cellular mechanisms that control and sense the intracellular amino acid pool. We discuss the role of leucine and mTORC1 in the regulation of amino acid transport via the system L and system A transporters such as LAT1 and SNAT2, as well as protein degradation via autophagic and proteasomal pathways. We also describe the complexities of energy homeostasis via AMPK and cell receptor-mediated growth signals that also converge on mTORC1. Leucine is a particularly potent regulator of protein turnover, to the extent where leucine stimulation alone is sufficient to stimulate mTORC1 signal transduction. The significance of leucine in this context is not yet known; however, recent advancements in this area will also be covered within this review.
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Affiliation(s)
- Kayleigh M Dodd
- Institute of Medical Genetics, Cardiff University, Heath Park, Cardiff, Wales, UK
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781
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Wahdan-Alaswad RS, Bane KL, Song K, Shola DT, Garcia JA, Danielpour D. Inhibition of mTORC1 kinase activates Smads 1 and 5 but not Smad8 in human prostate cancer cells, mediating cytostatic response to rapamycin. Mol Cancer Res 2012; 10:821-33. [PMID: 22452883 PMCID: PMC3557528 DOI: 10.1158/1541-7786.mcr-11-0615] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Although hyperactivated mTOR is well recognized as being pivotal to prostate cancer growth and progression, the underlying mechanisms by which it promotes such responses remain incompletely understood. Here, we show that rapamycin activates Smads 1 and 5 in human prostate cancer cells and tissues through blocking mTORC1 kinase. Small hairpin RNA-based gene silencing and gene overexpression approaches reveal that Smads 1 and 5 mediate, whereas Smad8 represses, rapamycin-induced cell death and expression of the bone morphogenetic protein (BMP) transcriptional target Id1 in human prostate cancer cell lines. Moreover, such phospho-Smad1/5-mediated rapamycin responses were blocked by LDN-193189 (a BMPRI kinase inhibitor) or Noggin (a BMP antagonist) in LNCaP prostate cancer cells. Likewise, the mTOR kinase inhibitors Ku-0063794 and WYE-354 each enhanced phosphorylation of Smad1/5. Intriguingly, silencing raptor alone enhanced, whereas silencing rictor repressed, the phosphorylation of Smad1/5, indicating that mTORC1 represses, whereas mTORC2 activates, BMP signaling. Immunohistochemical analysis showed increased levels of phospho-Smad1/5 concomitant with suppression of phospho-S6 and survivin levels in PC3 human prostate cancer xenografts in athymic mice administered rapamycin (intraperitoneally, 5 mg/kg/d, 2-6 days). Moreover, we show that compared with prostate tumor tissue from untreated patients, levels of phospho-Smad1/5 were significantly elevated in the prostate tumor tissue of patients with high-risk prostate cancer who received 8 weeks of the rapalog everolimus as part of a neoadjuvant clinical trial before undergoing local definitive therapy by radical prostatectomy. Taken together, our data implicate Smads 1, 5 and 8 as potential prognostic markers and therapeutic targets for mTOR inhibition therapy of prostate cancer.
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Affiliation(s)
- Reema S. Wahdan-Alaswad
- Case Comprehensive Cancer Center Research Laboratories, The Division of General Medical Sciences-Oncology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Pharmacology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Kara L. Bane
- Case Comprehensive Cancer Center Research Laboratories, The Division of General Medical Sciences-Oncology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Kyung Song
- Case Comprehensive Cancer Center Research Laboratories, The Division of General Medical Sciences-Oncology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Dorjee T.N. Shola
- Case Comprehensive Cancer Center Research Laboratories, The Division of General Medical Sciences-Oncology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Molecular Biology and Microbiology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Jorge A. Garcia
- Department of Solid Tumor Oncology and Urology, Cleveland Clinic Taussig Cancer Institute
- Glickman Urological & Kidney Institute Cleveland Clinic, Cleveland, Ohio
| | - David Danielpour
- Case Comprehensive Cancer Center Research Laboratories, The Division of General Medical Sciences-Oncology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Pharmacology, Case Western Reserve University, at Case Western Reserve University School of Medicine, Cleveland, Ohio
- Department of Urology, University Hospitals of Cleveland, Ohio
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782
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Adegoke OA, Abdullahi A, Tavajohi-Fini P. mTORC1 and the regulation of skeletal muscle anabolism and mass. Appl Physiol Nutr Metab 2012; 37:395-406. [DOI: 10.1139/h2012-009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The mass and integrity of skeletal muscle is vital to whole-body substrate metabolism and health. Indeed, defects in muscle metabolism and functions underlie or exacerbate diseases like diabetes, rheumatoid arthritis, and cancer. Physical activity and nutrition are the 2 most important environmental factors that can affect muscle health. At the molecular level, the mammalian target of rapamycin complex 1 (mTORC1) is a critical signalling complex that regulates muscle mass. In response to nutrition and resistance exercise, increased muscle mass and activation of mTORC1 occur in parallel. In this review, we summarize recent findings on mTORC1 and its regulation in skeletal muscle in response to resistance exercise, alone or in combination with intake of protein or amino acids. Because increased activity of the complex is implicated in the development of muscle insulin resistance, obesity, and some cancers (e.g., ovarian, breast), drugs that target mTORC1 are being developed or are in clinical trials. However, various cancers are associated with extensive muscle wasting, due in part to tumour burden and malnutrition. This muscle wasting may also be a side effect of anticancer drugs. Because loss of muscle mass is associated not only with metabolic abnormalities but also dose limiting toxicity, we review the possible implications for skeletal muscle of long-term inhibition of mTORC1, especially in muscle wasting conditions.
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Affiliation(s)
- Olasunkanmi A.J. Adegoke
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
| | - Abdikarim Abdullahi
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
| | - Pegah Tavajohi-Fini
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, 4700 Keele Street, Toronto ON M3J 5P3, Canada
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783
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Abstract
PURPOSE OF REVIEW The implication of the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) in promoting protein synthesis has been well described. Over the past years, several studies revealed that mTORC1 also plays a crucial role in promoting lipid biosynthesis and that such connection could be linked to diseases including obesity, nonalcoholic fatty liver disease (NAFLD), and cancer. Here, we review the mechanisms by which mTORC1 regulates lipid synthesis by focusing on the key signaling events that trigger hepatic de-novo lipogenesis in response to nutrients and insulin. RECENT FINDINGS mTORC1 promotes lipid synthesis by activating the transcription factor sterol regulatory element binding protein 1 (SREBP-1). Recent studies indicate that mTORC1 regulates SREBP-1 activation at multiple levels. Although mTORC1 was originally shown to be necessary and sufficient to activate SREBP-1 in vitro, new studies indicate that hyperactivation of mTORC1 is insufficient to trigger SREBP-1 activation and lipid biogenesis in vivo. These findings reveal that the molecular connection between mTORC1 and SREBP-1 is more complex than originally envisioned. SUMMARY The discovery of a connection between mTORC1 and SREBP-1 opens a new chapter in our understanding of the molecular mechanisms regulating de-novo lipogenesis. A better comprehension of these mechanisms is key for the development of new tools to treat NAFLD and its complications.
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Affiliation(s)
- Inan Bakan
- Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec (CRIUCPQ), Faculté de Médecine, Université Laval, Québec G1V 4G5, Canada
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784
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Hoshii T, Tadokoro Y, Naka K, Ooshio T, Muraguchi T, Sugiyama N, Soga T, Araki K, Yamamura KI, Hirao A. mTORC1 is essential for leukemia propagation but not stem cell self-renewal. J Clin Invest 2012; 122:2114-29. [PMID: 22622041 DOI: 10.1172/jci62279] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 04/04/2012] [Indexed: 12/11/2022] Open
Abstract
Although dysregulation of mTOR complex 1 (mTORC1) promotes leukemogenesis, how mTORC1 affects established leukemia is unclear. We investigated the role of mTORC1 in mouse hematopoiesis using a mouse model of conditional deletion of Raptor, an essential component of mTORC1. Raptor deficiency impaired granulocyte and B cell development but did not alter survival or proliferation of hematopoietic progenitor cells. In a mouse model of acute myeloid leukemia (AML), Raptor deficiency significantly suppressed leukemia progression by causing apoptosis of differentiated, but not undifferentiated, leukemia cells. mTORC1 did not control cell cycle or cell growth in undifferentiated AML cells in vivo. Transplantation of Raptor-deficient undifferentiated AML cells in a limiting dilution revealed that mTORC1 is essential for leukemia initiation. Strikingly, a subset of AML cells with undifferentiated phenotypes survived long-term in the absence of mTORC1 activity. We further demonstrated that the reactivation of mTORC1 in those cells restored their leukemia-initiating capacity. Thus, AML cells lacking mTORC1 activity can self-renew as AML stem cells. Our findings provide mechanistic insight into how residual tumor cells circumvent anticancer therapies and drive tumor recurrence.
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Affiliation(s)
- Takayuki Hoshii
- Division of Molecular Genetics, Cancer and Stem Cell Research Program, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
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785
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Lamming DW, Sabatini DM, Baur JA. Pharmacologic Means of Extending Lifespan. JOURNAL OF CLINICAL & EXPERIMENTAL PATHOLOGY 2012; Suppl 4:7327. [PMID: 25379357 PMCID: PMC4219537 DOI: 10.4172/2161-0681.s4-002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Dudley W. Lamming
- Department of Biology, MIT, Cambridge, MA 02139, Howard
Hughes Medical Institute, MIT, Cambridge, MA 02139; Whitehead Institute for
Biomedical Research, Cambridge MA 02142, Broad Institute of Harvard and MIT, Seven
Cambridge Center, Cambridge, MA 02142, The David H. Koch Institute for Integrative
Cancer Research at MIT, Cambridge, MA 02139, USA
| | - David M. Sabatini
- Department of Biology, MIT, Cambridge, MA 02139, Howard
Hughes Medical Institute, MIT, Cambridge, MA 02139; Whitehead Institute for
Biomedical Research, Cambridge MA 02142, Broad Institute of Harvard and MIT, Seven
Cambridge Center, Cambridge, MA 02142, The David H. Koch Institute for Integrative
Cancer Research at MIT, Cambridge, MA 02139, USA
| | - Joseph A. Baur
- Department of Physiology, Institute for Diabetes, Obesity,
and Metabolism, Perelman School of Medicine, University of Pennsylvania,
Philadelphia PA 19104, USA
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786
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Logue JS, Morrison DK. Complexity in the signaling network: insights from the use of targeted inhibitors in cancer therapy. Genes Dev 2012; 26:641-50. [PMID: 22474259 DOI: 10.1101/gad.186965.112] [Citation(s) in RCA: 201] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cancer often arises when normal cellular growth goes awry due to defects in critical signal transduction pathways. A growing number of inhibitors that target specific components of these pathways are in clinical use, but the success of these agents has been limited by the resistance to inhibitor therapy that ultimately develops. Studies have now shown that cancer cells respond to chronic drug treatment by adapting their signaling circuitry, taking advantage of pathway redundancy and routes of feedback and cross-talk to maintain their function. This review focuses on the compensatory signaling mechanisms highlighted by the use of targeted inhibitors in cancer therapy.
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Affiliation(s)
- Jeremy S Logue
- Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA
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787
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Abstract
The mammalian target of rapamycin (mTOR) and the phosphoinositide 3-kinase (PI3K) signaling pathways are commonly deregulated in cancers and promote cellular growth, proliferation, and survival. mTOR is part of two complexes, mTORC1 and mTORC2, with different biochemical structures and substrates specificity. PI3K/AKT activation may result from genetic hits affecting different components of the pathway, whereas the mechanisms leading to constitutive mTORC1 activation remain globally unknown. The connections between the PI3K and mTOR kinases are multiple and complex, including common substrates, negative feedback loops, or direct activation mechanisms. First-generation allosteric mTOR inhibitors (eg, rapamycin) are mainly active on mTORC1 and mostly display cytostatic anti-tumor activity. Recently, second-generation catalytic mTOR inhibitors targeting both mTOR complexes 1 and 2 have been developed. Some of them also inhibit class IA PI3K. Here, we highlight recent data generated with these new inhibitors against cancer cells and their potential as anti-cancer drugs.
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788
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Kazdoba TM, Sunnen CN, Crowell B, Lee GH, Anderson AE, D'Arcangelo G. Development and characterization of NEX- Pten, a novel forebrain excitatory neuron-specific knockout mouse. Dev Neurosci 2012; 34:198-209. [PMID: 22572802 DOI: 10.1159/000337229] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 02/13/2012] [Indexed: 01/15/2023] Open
Abstract
The phosphatase and tensin homolog located on chromosome 10 (PTEN) suppresses the activity of the phosphoinositide-3-kinase/Akt/mammalian target of rapamycin (mTOR) pathway, a signaling cascade critically involved in the regulation of cell proliferation and growth. Human patients carrying germ line PTEN mutations have an increased predisposition to tumors, and also display a variety of neurological symptoms and increased risk of epilepsy and autism, implicating PTEN in neuronal development and function. Consistently, loss of Pten in mouse neural cells results in ataxia, seizures, cognitive abnormalities, increased soma size and synaptic abnormalities. To better understand how Pten regulates the excitability of principal forebrain neurons, a factor that is likely to be altered in cognitive disorders, epilepsy and autism, we generated a novel conditional knockout mouse line (NEX-Pten) in which Cre, under the control of the NEX promoter, drives the deletion of Pten specifically in early postmitotic, excitatory neurons of the developing forebrain. Homozygous mutant mice exhibited a massive enlargement of the forebrain, and died shortly after birth due to excessive mTOR activation. Analysis of the neonatal cerebral cortex further identified molecular defects resulting from Pten deletion that likely affect several aspects of neuronal development and excitability.
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Affiliation(s)
- Tatiana M Kazdoba
- Department of Cell Biology and Neuroscience, The State University of New Jersey, Piscataway, NJ 08854, USA
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789
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Robida-Stubbs S, Glover-Cutter K, Lamming DW, Mizunuma M, Narasimhan SD, Neumann-Haefelin E, Sabatini DM, Blackwell TK. TOR signaling and rapamycin influence longevity by regulating SKN-1/Nrf and DAF-16/FoxO. Cell Metab 2012; 15:713-24. [PMID: 22560223 PMCID: PMC3348514 DOI: 10.1016/j.cmet.2012.04.007] [Citation(s) in RCA: 470] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 12/13/2011] [Accepted: 04/06/2012] [Indexed: 11/25/2022]
Abstract
The TOR kinase, which is present in the functionally distinct complexes TORC1 and TORC2, is essential for growth but associated with disease and aging. Elucidation of how TOR influences life span will identify mechanisms of fundamental importance in aging and TOR functions. Here we show that when TORC1 is inhibited genetically in C. elegans, SKN-1/Nrf, and DAF-16/FoxO activate protective genes, and increase stress resistance and longevity. SKN-1 also upregulates TORC1 pathway gene expression in a feedback loop. Rapamycin triggers a similar protective response in C. elegans and mice, but increases worm life span dependent upon SKN-1 and not DAF-16, apparently by interfering with TORC2 along with TORC1. TORC1, TORC2, and insulin/IGF-1-like signaling regulate SKN-1 activity through different mechanisms. We conclude that modulation of SKN-1/Nrf and DAF-16/FoxO may be generally important in the effects of TOR signaling in vivo and that these transcription factors mediate an opposing relationship between growth signals and longevity.
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Affiliation(s)
- Stacey Robida-Stubbs
- Joslin Diabetes Center, Harvard Stem Cell Institute, and Department of Genetics, Harvard Medical School, Boston, MA 02215, USA
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790
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Blagosklonny MV. Once again on rapamycin-induced insulin resistance and longevity: despite of or owing to. Aging (Albany NY) 2012; 4:350-8. [PMID: 22683661 PMCID: PMC3384435 DOI: 10.18632/aging.100461] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
Calorie restriction (CR), which deactivates the nutrient-sensing mTOR pathway, slows down aging and prevents age-related diseases such as type II diabetes. Compared with CR, rapamycin more efficiently inhibits mTOR. Noteworthy, severe CR and starvation cause a reversible condition known as "starvation diabetes." As was already discussed, chronic administration of rapamycin can cause a similar condition in some animal models. A recent paper published in Science reported that chronic treatment with rapamycin causes a diabetes-like condition in mice by indirectly inhibiting mTOR complex 2. Here I introduce the notion of benevolent diabetes and discuss whether starvation-like effects of chronic high dose treatment with rapamycin are an obstacle for its use as an anti-aging drug.
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791
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Valcourt JR, Lemons JMS, Haley EM, Kojima M, Demuren OO, Coller HA. Staying alive: metabolic adaptations to quiescence. Cell Cycle 2012; 11:1680-96. [PMID: 22510571 DOI: 10.4161/cc.19879] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Quiescence is a state of reversible cell cycle arrest that can grant protection against many environmental insults. In some systems, cellular quiescence is associated with a low metabolic state characterized by a decrease in glucose uptake and glycolysis, reduced translation rates and activation of autophagy as a means to provide nutrients for survival. For cells in multiple different quiescence model systems, including Saccharomyces cerevisiae, mammalian lymphocytes and hematopoietic stem cells, the PI3Kinase/TOR signaling pathway helps to integrate information about nutrient availability with cell growth rates. Quiescence signals often inactivate the TOR kinase, resulting in reduced cell growth and biosynthesis. However, quiescence is not always associated with reduced metabolism; it is also possible to achieve a state of cellular quiescence in which glucose uptake, glycolysis and flux through central carbon metabolism are not reduced. In this review, we compare and contrast the metabolic changes that occur with quiescence in different model systems.
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Affiliation(s)
- James R Valcourt
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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792
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Fonslow BR, Niessen SM, Singh M, Wong CCL, Xu T, Carvalho PC, Choi J, Park SK, Yates JR. Single-step inline hydroxyapatite enrichment facilitates identification and quantitation of phosphopeptides from mass-limited proteomes with MudPIT. J Proteome Res 2012; 11:2697-709. [PMID: 22509746 DOI: 10.1021/pr300200x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Herein we report the characterization and optimization of single-step inline enrichment of phosphopeptides directly from small amounts of whole cell and tissue lysates (100-500 μg) using a hydroxyapatite (HAP) microcolumn and Multidimensional Protein Identification Technology (MudPIT). In comparison to a triplicate HILIC-IMAC phosphopeptide enrichment study, ∼80% of the phosphopeptides identified using HAP-MudPIT were unique. Similarly, analysis of the consensus phosphorylation motifs between the two enrichment methods illustrates the complementarity of calcium- and iron-based enrichment methods and the higher sensitivity and selectivity of HAP-MudPIT for acidic motifs. We demonstrate how the identification of more multiply phosphorylated peptides from HAP-MudPIT can be used to quantify phosphorylation cooperativity. Through optimization of HAP-MudPIT on a whole cell lysate we routinely achieved identification and quantification of ca. 1000 phosphopeptides from a ∼1 h enrichment and 12 h MudPIT analysis on small quantities of material. Finally, we applied this optimized method to identify phosphorylation sites from a mass-limited mouse brain region, the amygdala (200-500 μg), identifying up to 4000 phosphopeptides per run.
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Affiliation(s)
- Bryan R Fonslow
- Department of Chemical Physiology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, California 92037, USA
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793
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Riera MF, Regueira M, Galardo MN, Pellizzari EH, Meroni SB, Cigorraga SB. Signal transduction pathways in FSH regulation of rat Sertoli cell proliferation. Am J Physiol Endocrinol Metab 2012; 302:E914-23. [PMID: 22275758 DOI: 10.1152/ajpendo.00477.2011] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The final number of Sertoli cells reached during the proliferative periods determines sperm production capacity in adulthood. It is well known that FSH is the major Sertoli cell mitogen; however, little is known about the signal transduction pathways that regulate the proliferation of Sertoli cells. The hypothesis of this investigation was that FSH regulates proliferation through a PI3K/Akt/mTORC1 pathway, and additionally, AMPK-dependent mechanisms counteract FSH proliferative effects. The present study was performed in 8-day-old rat Sertoli cell cultures. The results presented herein show that FSH, in addition to increasing p-Akt, p-mTOR, and p-p70S6K levels, increases p-PRAS40 levels, probably contributing to improving mTORC1 signaling. Furthermore, the decrease in FSH-stimulated p-Akt, p-mTOR, p-p70S6K, and p-PRAS40 levels in the presence of wortmannin emphasizes the participation of PI3K in FSH signaling. Additionally, the inhibition of FSH-stimulated Sertoli cell proliferation by the effect of wortmannin and rapamycin point to the relevance of the PI3K/Akt/mTORC1 signaling pathway in the mitotic activity of FSH. On the other hand, by activating AMPK, several interesting observations were made. Activation of AMPK produced an increase in Raptor phosphorylation, a decrease in p70S6K phosphorylation, and a decrease in FSH-stimulated Sertoli cell proliferation. The decrease in FSH-stimulated cell proliferation was accompanied by an increased expression of the cyclin-dependent kinase inhibitors (CDKIs) p19INK4d, p21Cip1, and p27Kip1. In summary, it is concluded that FSH regulates Sertoli cell proliferation with the participation of a PI3K/Akt/mTORC1 pathway and that AMPK activation may be involved in the detention of proliferation by, at least in part, a decrease in mTORC1 signaling and an increase in CDKI expression.
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Affiliation(s)
- María F Riera
- Centro de Investigaciones Endocrinológicas (CEDIE-CONICET), Hospital de Niños "R. Gutiérrez," Gallo, Buenos Aires, Argentina.
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794
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Radford EJ, Isganaitis E, Jimenez-Chillaron J, Schroeder J, Molla M, Andrews S, Didier N, Charalambous M, McEwen K, Marazzi G, Sassoon D, Patti ME, Ferguson-Smith AC. An unbiased assessment of the role of imprinted genes in an intergenerational model of developmental programming. PLoS Genet 2012; 8:e1002605. [PMID: 22511876 PMCID: PMC3325178 DOI: 10.1371/journal.pgen.1002605] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 02/03/2012] [Indexed: 11/18/2022] Open
Abstract
Environmental factors during early life are critical for the later metabolic health of the individual and of future progeny. In our obesogenic environment, it is of great socioeconomic importance to investigate the mechanisms that contribute to the risk of metabolic ill health. Imprinted genes, a class of functionally mono-allelic genes critical for early growth and metabolic axis development, have been proposed to be uniquely susceptible to environmental change. Furthermore, it has also been suggested that perturbation of the epigenetic reprogramming of imprinting control regions (ICRs) may play a role in phenotypic heritability following early life insults. Alternatively, the presence of multiple layers of epigenetic regulation may in fact protect imprinted genes from such perturbation. Unbiased investigation of these alternative hypotheses requires assessment of imprinted gene expression in the context of the response of the whole transcriptome to environmental assault. We therefore analyse the role of imprinted genes in multiple tissues in two affected generations of an established murine model of the developmental origins of health and disease using microarrays and quantitative RT–PCR. We demonstrate that, despite the functional mono-allelicism of imprinted genes and their unique mechanisms of epigenetic dosage control, imprinted genes as a class are neither more susceptible nor protected from expression perturbation induced by maternal undernutrition in either the F1 or the F2 generation compared to other genes. Nor do we find any evidence that the epigenetic reprogramming of ICRs in the germline is susceptible to nutritional restriction. However, we propose that those imprinted genes that are affected may play important roles in the foetal response to undernutrition and potentially its long-term sequelae. We suggest that recently described instances of dosage regulation by relaxation of imprinting are rare and likely to be highly regulated. Environmental perturbations during early life are known to affect one's risk of metabolic disease many years later. Furthermore, that risk can be inherited by future generations, although the mechanisms responsible are poorly understood. Imprinted genes are unusual as only one of the two copies is expressed in a parent-of-origin–specific manner. As only one copy is active, imprinted gene dosage has been hypothesised to be uniquely vulnerable to environmental change. Therefore, it has been suggested that imprinted genes may play an important role in the developmental origins of health and disease. Alternatively, the opposite may be true—imprinted genes may be more tightly safeguarded from perturbation. To test these two hypotheses, we analysed the expression of imprinted genes in the context of all active genes in two affected generations of a mouse model of the developmental origins of health and disease. Our data show that imprinted genes as a class are neither more nor less susceptible to expression change, but a subset of imprinted genes may be involved in the adaptation of the conceptus. Furthermore, imprints in the developing germline are not affected and imprinted genes are largely stable in the second generation. This is important, as it is the first time that this hypothesis has been tested in an unbiased fashion.
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Affiliation(s)
- Elizabeth J. Radford
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Elvira Isganaitis
- Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Josep Jimenez-Chillaron
- Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joshua Schroeder
- Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael Molla
- Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Simon Andrews
- Bioinformatics Group, The Babraham Institute, Cambridge, United Kingdom
| | - Nathalie Didier
- Myology Group-UMR S 787, INSERM and Université Paris VI/Pierre et Marie Curie, Paris, France
| | - Marika Charalambous
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Kirsten McEwen
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Giovanna Marazzi
- Myology Group-UMR S 787, INSERM and Université Paris VI/Pierre et Marie Curie, Paris, France
| | - David Sassoon
- Myology Group-UMR S 787, INSERM and Université Paris VI/Pierre et Marie Curie, Paris, France
| | - Mary-Elizabeth Patti
- Research Division, Joslin Diabetes Center and Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (ACF-S); (M-EP)
| | - Anne C. Ferguson-Smith
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (ACF-S); (M-EP)
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795
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Turan N, Ghalwash MF, Katari S, Coutifaris C, Obradovic Z, Sapienza C. DNA methylation differences at growth related genes correlate with birth weight: a molecular signature linked to developmental origins of adult disease? BMC Med Genomics 2012; 5:10. [PMID: 22498030 PMCID: PMC3359247 DOI: 10.1186/1755-8794-5-10] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 04/12/2012] [Indexed: 12/26/2022] Open
Abstract
Background Infant birth weight is a complex quantitative trait associated with both neonatal and long-term health outcomes. Numerous studies have been published in which candidate genes (IGF1, IGF2, IGF2R, IGF binding proteins, PHLDA2 and PLAGL1) have been associated with birth weight, but these studies are difficult to reproduce in man and large cohort studies are needed due to the large inter individual variance in transcription levels. Also, very little of the trait variance is explained. We decided to identify additional candidates without regard for what is known about the genes. We hypothesize that DNA methylation differences between individuals can serve as markers of gene "expression potential" at growth related genes throughout development and that these differences may correlate with birth weight better than single time point measures of gene expression. Methods We performed DNA methylation and transcript profiling on cord blood and placenta from newborns. We then used novel computational approaches to identify genes correlated with birth weight. Results We identified 23 genes whose methylation levels explain 70-87% of the variance in birth weight. Six of these (ANGPT4, APOE, CDK2, GRB10, OSBPL5 and REG1B) are associated with growth phenotypes in human or mouse models. Gene expression profiling explained a much smaller fraction of variance in birth weight than did DNA methylation. We further show that two genes, the transcriptional repressor MSX1 and the growth factor receptor adaptor protein GRB10, are correlated with transcriptional control of at least seven genes reported to be involved in fetal or placental growth, suggesting that we have identified important networks in growth control. GRB10 methylation is also correlated with genes involved in reactive oxygen species signaling, stress signaling and oxygen sensing and more recent data implicate GRB10 in insulin signaling. Conclusions Single time point measurements of gene expression may reflect many factors unrelated to birth weight, while inter-individual differences in DNA methylation may represent a "molecular fossil record" of differences in birth weight-related gene expression. Finding these "unexpected" pathways may tell us something about the long-term association between low birth weight and adult disease, as well as which genes may be susceptible to environmental effects. These findings increase our understanding of the molecular mechanisms involved in human development and disease progression.
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Affiliation(s)
- Nahid Turan
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA
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796
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Franz-Wachtel M, Eisler SA, Krug K, Wahl S, Carpy A, Nordheim A, Pfizenmaier K, Hausser A, Macek B. Global detection of protein kinase D-dependent phosphorylation events in nocodazole-treated human cells. Mol Cell Proteomics 2012; 11:160-70. [PMID: 22496350 DOI: 10.1074/mcp.m111.016014] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Protein kinase D (PKD) is a cytosolic serine/threonine kinase implicated in regulation of several cellular processes such as response to oxidative stress, directed cell migration, invasion, differentiation, and fission of the vesicles at the trans-Golgi network. Its variety of functions must be mediated by numerous substrates; however, only a couple of PKD substrates have been identified so far. Here we perform stable isotope labeling of amino acids in cell culture-based quantitative phosphoproteomic analysis to detect phosphorylation events dependent on PKD1 activity in human cells. We compare relative phosphorylation levels between constitutively active and kinase dead PKD1 strains of HEK293 cells, both treated with nocodazole, a microtubule-depolymerizing reagent that disrupts the Golgi complex and activates PKD1. We identify 124 phosphorylation sites that are significantly down-regulated upon decrease of PKD1 activity and show that the PKD target motif is significantly enriched among down-regulated phosphorylation events, pointing to the presence of direct PKD1 substrates. We further perform PKD1 target motif analysis, showing that a proline residue at position +1 relative to the phosphorylation site serves as an inhibitory cue for PKD1 activity. Among PKD1-dependent phosphorylation events, we detect predominantly proteins with localization at Golgi membranes and function in protein sorting, among them several sorting nexins and members of the insulin-like growth factor 2 receptor pathway. This study presents the first global detection of PKD1-dependent phosphorylation events and provides a wealth of information for functional follow-up of PKD1 activity upon disruption of the Golgi network in human cells.
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797
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Montero JC, Chen X, Ocaña A, Pandiella A. Predominance of mTORC1 over mTORC2 in the Regulation of Proliferation of Ovarian Cancer Cells: Therapeutic Implications. Mol Cancer Ther 2012; 11:1342-52. [DOI: 10.1158/1535-7163.mct-11-0723] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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798
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Song MS, Salmena L, Pandolfi PP. The functions and regulation of the PTEN tumour suppressor. Nat Rev Mol Cell Biol 2012; 13:283-96. [PMID: 22473468 DOI: 10.1038/nrm3330] [Citation(s) in RCA: 1450] [Impact Index Per Article: 120.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The importance of the physiological function of phosphatase and tensin homologue (PTEN) is illustrated by its frequent disruption in cancer. By suppressing the phosphoinositide 3-kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway through its lipid phosphatase activity, PTEN governs a plethora of cellular processes including survival, proliferation, energy metabolism and cellular architecture. Consequently, mechanisms regulating PTEN expression and function, including transcriptional regulation, post-transcriptional regulation by non-coding RNAs, post-translational modifications and protein-protein interactions, are all altered in cancer. The repertoire of PTEN functions has recently been expanded to include phosphatase-independent activities and crucial functions within the nucleus. Our increasing knowledge of PTEN and pathologies in which its function is altered will undoubtedly inform the rational design of novel therapies.
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Affiliation(s)
- Min Sup Song
- Cancer Genetics Program, Beth Israel Deaconess Cancer Center, Department of Medicine and Pathology, Harvard Medical School, Boston, Massachuchetts 02215, USA.
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799
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Fonseca BD, Diering GH, Bidinosti MA, Dalal K, Alain T, Balgi AD, Forestieri R, Nodwell M, Rajadurai CV, Gunaratnam C, Tee AR, Duong F, Andersen RJ, Orlowski J, Numata M, Sonenberg N, Roberge M. Structure-activity analysis of niclosamide reveals potential role for cytoplasmic pH in control of mammalian target of rapamycin complex 1 (mTORC1) signaling. J Biol Chem 2012; 287:17530-17545. [PMID: 22474287 DOI: 10.1074/jbc.m112.359638] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) signaling is frequently dysregulated in cancer. Inhibition of mTORC1 is thus regarded as a promising strategy in the treatment of tumors with elevated mTORC1 activity. We have recently identified niclosamide (a Food and Drug Administration-approved antihelminthic drug) as an inhibitor of mTORC1 signaling. In the present study, we explored possible mechanisms by which niclosamide may inhibit mTORC1 signaling. We tested whether niclosamide interferes with signaling cascades upstream of mTORC1, the catalytic activity of mTOR, or mTORC1 assembly. We found that niclosamide does not impair PI3K/Akt signaling, nor does it inhibit mTORC1 kinase activity. We also found that niclosamide does not interfere with mTORC1 assembly. Previous studies in helminths suggest that niclosamide disrupts pH homeostasis of the parasite. This prompted us to investigate whether niclosamide affects the pH balance of cancer cells. Experiments in both breast cancer cells and cell-free systems demonstrated that niclosamide possesses protonophoric activity in cells and in vitro. In cells, niclosamide dissipated protons (down their concentration gradient) from lysosomes to the cytosol, effectively lowering cytoplasmic pH. Notably, analysis of five niclosamide analogs revealed that the structural features of niclosamide required for protonophoric activity are also essential for mTORC1 inhibition. Furthermore, lowering cytoplasmic pH by means other than niclosamide treatment (e.g. incubation with propionic acid or bicarbonate withdrawal) recapitulated the inhibitory effects of niclosamide on mTORC1 signaling, lending support to a possible role for cytoplasmic pH in the control of mTORC1. Our data illustrate a potential mechanism for chemical inhibition of mTORC1 signaling involving modulation of cytoplasmic pH.
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Affiliation(s)
- Bruno D Fonseca
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada; Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada.
| | - Graham H Diering
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michael A Bidinosti
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Kush Dalal
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Tommy Alain
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Aruna D Balgi
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Roberto Forestieri
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Matt Nodwell
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Charles V Rajadurai
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Cynthia Gunaratnam
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Andrew R Tee
- Institute of Medical Genetics, Wales College of Medicine, Cardiff University, Heath Park Way, Cardiff CF14 4XN, United Kingdom
| | - Franck Duong
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Raymond J Andersen
- Departments of Chemistry and Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - John Orlowski
- Department of Physiology, 3655 Promenade Sir William Osler, Bellini Building, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Masayuki Numata
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, 1160 Pine Avenue West, Rosalind and Morris Goodman Cancer Centre, McGill University, Montreal, Quebec H3A 1A3, Canada
| | - Michel Roberge
- Department of Biochemistry and Molecular Biology, 2350 Health Sciences Mall, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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800
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Xie J, Herbert TP. The role of mammalian target of rapamycin (mTOR) in the regulation of pancreatic β-cell mass: implications in the development of type-2 diabetes. Cell Mol Life Sci 2012; 69:1289-304. [PMID: 22068611 PMCID: PMC11114779 DOI: 10.1007/s00018-011-0874-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/20/2011] [Accepted: 10/20/2011] [Indexed: 12/22/2022]
Abstract
Type-2 diabetes mellitus (T2DM) is a disorder that is characterized by high blood glucose concentration in the context of insulin resistance and/or relative insulin deficiency. It causes metabolic changes that lead to the damage and functional impairment of organs and tissues resulting in increased morbidity and mortality. It is this form of diabetes whose prevalence is increasing at an alarming rate due to the 'obesity epidemic', as obesity is a key risk factor in the development of insulin resistance. However, the majority of individuals who have insulin resistance do not develop diabetes due to a compensatory increase in insulin secretion in response to an increase in insulin demand. This adaptive response is sustained by an increase in both β-cell function and mass. Importantly, there is increasing evidence that the Serine/Threonine kinase mammalian target of rapamycin (mTOR) plays a key role in the regulation of β-cell mass and therefore likely plays a critical role in β-cell adaptation. Therefore, the primary focus of this review is to summarize our current understanding of the role of mTOR in stimulating pancreatic β-cell mass and thus, in the prevention of type-2 diabetes.
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Affiliation(s)
- Jianling Xie
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
| | - Terence P. Herbert
- Department of Cell Physiology and Pharmacology, University of Leicester, The Henry Wellcome Building, University Road, Leicester, LE1 9HN UK
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