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Xing J, Theune WC, Lukomska A, Frost MP, Damania A, Trakhtenberg EF. Experimental upregulation of developmentally downregulated ribosomal protein large subunits 7 and 7A promotes axon regeneration after injury in vivo. Exp Neurol 2023; 368:114510. [PMID: 37633482 PMCID: PMC10529763 DOI: 10.1016/j.expneurol.2023.114510] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 08/08/2023] [Accepted: 08/23/2023] [Indexed: 08/28/2023]
Abstract
Ribosomal proteins are involved in neurodevelopment and central nervous system (CNS) disease and injury. However, the roles of specific ribosomal protein subunits in developmental axon growth, and their potential as therapeutic targets for treating CNS injuries, are still poorly understood. Here, we show that ribosomal protein large (Rpl) and small (Rps) subunit genes are substantially (56-fold) enriched amongst the genes, which are downregulated during maturation of retinal ganglion cell (RGC) CNS projection neurons. We also show that Rpl and Rps subunits are highly co-regulated in RGCs, and partially re-upregulated after optic nerve crush (ONC). Because developmental downregulation of ribosomal proteins coincides with developmental decline in neuronal intrinsic axon growth capacity, we hypothesized that Rpl/Rps incomplete re-upregulation after injury may be a part of the cellular response which attempts to reactivate intrinsic axon growth mechanisms. We found that experimentally upregulating Rpl7 and Rpl7A promoted axon regeneration after ONC in vivo. Finally, we characterized gene networks associated with Rpl/Rps, and showed that Rpl7 and Rpl7A belong to the cluster of genes, which are shared between translational and neurodevelopmental biological processes (based on gene-ontology) that are co-downregulated in maturing RGCs during the decline in intrinsic axon growth capacity.
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Affiliation(s)
- Jian Xing
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
| | - William C Theune
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
| | - Agnieszka Lukomska
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
| | - Matthew P Frost
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
| | - Ashiti Damania
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA
| | - Ephraim F Trakhtenberg
- Department of Neuroscience, University of Connecticut School of Medicine, 263 Farmington Ave, Farmington, CT 06030, USA.
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2
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Targeting mTOR as a Cancer Therapy: Recent Advances in Natural Bioactive Compounds and Immunotherapy. Cancers (Basel) 2022; 14:cancers14225520. [PMID: 36428613 PMCID: PMC9688668 DOI: 10.3390/cancers14225520] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/01/2022] [Accepted: 11/02/2022] [Indexed: 11/12/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is a highly conserved serine/threonine-protein kinase, which regulates many biological processes related to metabolism, cancer, immune function, and aging. It is an essential protein kinase that belongs to the phosphoinositide-3-kinase (PI3K) family and has two known signaling complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Even though mTOR signaling plays a critical role in promoting mitochondria-related protein synthesis, suppressing the catabolic process of autophagy, contributing to lipid metabolism, engaging in ribosome formation, and acting as a critical regulator of mRNA translation, it remains one of the significant signaling systems involved in the tumor process, particularly in apoptosis, cell cycle, and cancer cell proliferation. Therefore, the mTOR signaling system could be suggested as a cancer biomarker, and its targeting is important in anti-tumor therapy research. Indeed, its dysregulation is involved in different types of cancers such as colon, neck, cervical, head, lung, breast, reproductive, and bone cancers, as well as nasopharyngeal carcinoma. Moreover, recent investigations showed that targeting mTOR could be considered as cancer therapy. Accordingly, this review presents an overview of recent developments associated with the mTOR signaling pathway and its molecular involvement in various human cancer types. It also summarizes the research progress of different mTOR inhibitors, including natural and synthetised compounds and their main mechanisms, as well as the rational combinations with immunotherapies.
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Kachaev ZM, Ivashchenko SD, Kozlov EN, Lebedeva LA, Shidlovskii YV. Localization and Functional Roles of Components of the Translation Apparatus in the Eukaryotic Cell Nucleus. Cells 2021; 10:3239. [PMID: 34831461 PMCID: PMC8623629 DOI: 10.3390/cells10113239] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 12/15/2022] Open
Abstract
Components of the translation apparatus, including ribosomal proteins, have been found in cell nuclei in various organisms. Components of the translation apparatus are involved in various nuclear processes, particularly those associated with genome integrity control and the nuclear stages of gene expression, such as transcription, mRNA processing, and mRNA export. Components of the translation apparatus control intranuclear trafficking; the nuclear import and export of RNA and proteins; and regulate the activity, stability, and functional recruitment of nuclear proteins. The nuclear translocation of these components is often involved in the cell response to stimulation and stress, in addition to playing critical roles in oncogenesis and viral infection. Many components of the translation apparatus are moonlighting proteins, involved in integral cell stress response and coupling of gene expression subprocesses. Thus, this phenomenon represents a significant interest for both basic and applied molecular biology. Here, we provide an overview of the current data regarding the molecular functions of translation factors and ribosomal proteins in the cell nucleus.
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Affiliation(s)
- Zaur M. Kachaev
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
- Center for Genetics and Life Science, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Sergey D. Ivashchenko
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Eugene N. Kozlov
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Lyubov A. Lebedeva
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
| | - Yulii V. Shidlovskii
- Department of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, 119334 Moscow, Russia; (Z.M.K.); (S.D.I.); (E.N.K.); (L.A.L.)
- Center for Genetics and Life Science, Sirius University of Science and Technology, 354340 Sochi, Russia
- Department of Biology and General Genetics, Sechenov First Moscow State Medical University (Sechenov University), 119992 Moscow, Russia
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Zhou X, Zhong Y, Molinar-Inglis O, Kunkel MT, Chen M, Sun T, Zhang J, Shyy JYJ, Trejo J, Newton AC, Zhang J. Location-specific inhibition of Akt reveals regulation of mTORC1 activity in the nucleus. Nat Commun 2020; 11:6088. [PMID: 33257668 PMCID: PMC7705703 DOI: 10.1038/s41467-020-19937-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 10/27/2020] [Indexed: 12/13/2022] Open
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) integrates growth, nutrient and energy status cues to control cell growth and metabolism. While mTORC1 activation at the lysosome is well characterized, it is not clear how this complex is regulated at other subcellular locations. Here, we combine location-selective kinase inhibition, live-cell imaging and biochemical assays to probe the regulation of growth factor-induced mTORC1 activity in the nucleus. Using a nuclear targeted Akt Substrate-based Tandem Occupancy Peptide Sponge (Akt-STOPS) that we developed for specific inhibition of Akt, a critical upstream kinase, we show that growth factor-stimulated nuclear mTORC1 activity requires nuclear Akt activity. Further mechanistic dissection suggests that nuclear Akt activity mediates growth factor-induced nuclear translocation of Raptor, a regulatory scaffolding component in mTORC1, and localization of Raptor to the nucleus results in nuclear mTORC1 activity in the absence of growth factor stimulation. Taken together, these results reveal a mode of regulation of mTORC1 that is distinct from its lysosomal activation, which controls mTORC1 activity in the nuclear compartment.
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Affiliation(s)
- Xin Zhou
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Yanghao Zhong
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA, USA
| | | | - Maya T Kunkel
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Mingyuan Chen
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Tengqian Sun
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Jiao Zhang
- Division of Cardiology, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - John Y-J Shyy
- Division of Cardiology, Department of Medicine, University of California San Diego, La Jolla, CA, USA
| | - JoAnn Trejo
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Alexandra C Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Jin Zhang
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA.
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.
- Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA, USA.
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5
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Turi Z, Lacey M, Mistrik M, Moudry P. Impaired ribosome biogenesis: mechanisms and relevance to cancer and aging. Aging (Albany NY) 2020; 11:2512-2540. [PMID: 31026227 PMCID: PMC6520011 DOI: 10.18632/aging.101922] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 04/04/2019] [Indexed: 02/06/2023]
Abstract
The biosynthesis of ribosomes is a complex process that requires the coordinated action of many factors and a huge energy investment from the cell. Ribosomes are essential for protein production, and thus for cellular survival, growth and proliferation. Ribosome biogenesis is initiated in the nucleolus and includes: the synthesis and processing of ribosomal RNAs, assembly of ribosomal proteins, transport to the cytoplasm and association of ribosomal subunits. The disruption of ribosome biogenesis at various steps, with either increased or decreased expression of different ribosomal components, can promote cell cycle arrest, senescence or apoptosis. Additionally, interference with ribosomal biogenesis is often associated with cancer, aging and age-related degenerative diseases. Here, we review current knowledge on impaired ribosome biogenesis, discuss the main factors involved in stress responses under such circumstances and focus on examples with clinical relevance.
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Affiliation(s)
- Zsofia Turi
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Matthew Lacey
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Martin Mistrik
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
| | - Pavel Moudry
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacky University, 779 00 Olomouc, Czech Republic
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6
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Temprine K, Campbell NR, Huang R, Langdon EM, Simon-Vermot T, Mehta K, Clapp A, Chipman M, White RM. Regulation of the error-prone DNA polymerase Polκ by oncogenic signaling and its contribution to drug resistance. Sci Signal 2020; 13:13/629/eaau1453. [PMID: 32345725 DOI: 10.1126/scisignal.aau1453] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The DNA polymerase Polκ plays a key role in translesion synthesis, an error-prone replication mechanism. Polκ is overexpressed in various tumor types. Here, we found that melanoma and lung and breast cancer cells experiencing stress from oncogene inhibition up-regulated the expression of Polκ and shifted its localization from the cytoplasm to the nucleus. This effect was phenocopied by inhibition of the kinase mTOR, by induction of ER stress, or by glucose deprivation. In unstressed cells, Polκ is continually transported out of the nucleus by exportin-1. Inhibiting exportin-1 or overexpressing Polκ increased the abundance of nuclear-localized Polκ, particularly in response to the BRAFV600E-targeted inhibitor vemurafenib, which decreased the cytotoxicity of the drug in BRAFV600E melanoma cells. These observations were analogous to how Escherichia coli encountering cell stress and nutrient deprivation can up-regulate and activate DinB/pol IV, the bacterial ortholog of Polκ, to induce mutagenesis that enables stress tolerance or escape. However, we found that the increased expression of Polκ was not excessively mutagenic, indicating that noncatalytic or other functions of Polκ could mediate its role in stress responses in mammalian cells. Repressing the expression or nuclear localization of Polκ might prevent drug resistance in some cancer cells.
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Affiliation(s)
- Kelsey Temprine
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.,Gerstner Sloan Kettering Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Nathaniel R Campbell
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.,Tri-Institutional M.D./Ph.D. Program, Weill Cornell Medical College, New York, NY 10065, USA
| | - Richard Huang
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Erin M Langdon
- University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA
| | - Theresa Simon-Vermot
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Krisha Mehta
- Division of General Internal Medicine, Department of Medicine, Weill Cornell Medical College, New York, NY 10065, USA
| | | | - Mollie Chipman
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.,Gerstner Sloan Kettering Graduate School of Biomedical Sciences, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Richard M White
- Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
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7
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Prioretti L, Carriere F, Field B, Avilan L, Montané MH, Menand B, Gontero B. Targeting TOR signaling for enhanced lipid productivity in algae. Biochimie 2019; 169:12-17. [PMID: 31265860 DOI: 10.1016/j.biochi.2019.06.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 06/26/2019] [Indexed: 01/21/2023]
Abstract
Microalgae can produce large quantities of triacylglycerols (TAGs) and other neutral lipids that are suitable for making biofuels and as feedstocks for green chemistry. However, TAGs accumulate under stress conditions that also stop growth, leading to a trade-off between biomass production and TAG yield. Recently, in the model marine diatom Phaeodactylum tricornutum it was shown that inhibition of the target of rapamycin (TOR) kinase boosts lipid productivity by promoting TAG production without stopping growth. We believe that basic knowledge in this emerging field is required to develop innovative strategies to improve neutral lipid accumulation in oleaginous microalgae. In this minireview, we discuss current research on the TOR signaling pathway with a focus on its control on lipid homeostasis. We first provide an overview of the well characterized roles of TOR in mammalian lipogenesis, adipogenesis and lipolysis. We then present evidence of a role for TOR in controlling TAG accumulation in microalgae, and draw parallels between the situation in animals, plants and microalgae to propose a model of TOR signaling for TAG accumulation in microalgae.
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Affiliation(s)
- Laura Prioretti
- Aix Marseille Univ, CNRS, BIP UMR 7281, 31 Chemin Joseph Aiguier, 13402, Marseille, Cedex 09, France
| | - Frédéric Carriere
- Aix Marseille Univ, CNRS, BIP UMR 7281, 31 Chemin Joseph Aiguier, 13402, Marseille, Cedex 09, France
| | - Ben Field
- Aix Marseille Univ, CEA, CNRS, UMR 7265 BIAM, 163 Avenue de Luminy, 13288, Marseille, France
| | - Luisana Avilan
- Aix Marseille Univ, CNRS, BIP UMR 7281, 31 Chemin Joseph Aiguier, 13402, Marseille, Cedex 09, France
| | - Marie-Hélène Montané
- Aix Marseille Univ, CEA, CNRS, UMR 7265 BIAM, 163 Avenue de Luminy, 13288, Marseille, France
| | - Benoît Menand
- Aix Marseille Univ, CEA, CNRS, UMR 7265 BIAM, 163 Avenue de Luminy, 13288, Marseille, France.
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, BIP UMR 7281, 31 Chemin Joseph Aiguier, 13402, Marseille, Cedex 09, France.
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von Walden F. Ribosome biogenesis in skeletal muscle: coordination of transcription and translation. J Appl Physiol (1985) 2019; 127:591-598. [PMID: 31219775 DOI: 10.1152/japplphysiol.00963.2018] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Skeletal muscle mass responds in a remarkable manner to alterations in loading and use. It has long been clear that skeletal muscle hypertrophy can be prevented by inhibiting RNA synthesis. Since 80% of the cell's total RNA has been estimated to be rRNA, this finding indicates that de novo production of rRNA via transcription of the corresponding genes is important for such hypertrophy to occur. Transcription of rDNA by RNA Pol I is the rate-limiting step in ribosome biogenesis, indicating in turn that this biogenesis strongly influences the hypertrophic response. The present minireview focuses on 1) a brief description of the key steps in ribosome biogenesis and the relationship of this process to skeletal muscle mass and 2) the coordination of ribosome biogenesis and protein synthesis for growth or atrophy, as exemplified by the intracellular AMPK and mTOR pathways.
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Affiliation(s)
- Ferdinand von Walden
- Division of Pediatric Neurology, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden
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9
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Montané MH, Menand B. TOR inhibitors: from mammalian outcomes to pharmacogenetics in plants and algae. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:2297-2312. [PMID: 30773593 DOI: 10.1093/jxb/erz053] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 02/05/2019] [Indexed: 05/19/2023]
Abstract
Target of rapamycin (TOR) is a conserved eukaryotic phosphatidylinositol 3-kinase-related kinase that regulates growth and metabolism in response to environment in plants and algae. The study of the plant and algal TOR pathway has largely depended on TOR inhibitors first developed for non-photosynthetic eukaryotes. In animals and yeast, fundamental work on the TOR pathway has benefited from the allosteric TOR inhibitor rapamycin and more recently from ATP-competitive TOR inhibitors (asTORis) that circumvent the limitations of rapamycin. The asTORis, developed for medical application, inhibit TOR complex 1 (TORC1) more efficiently than rapamycin and also inhibit rapamycin-resistant TORCs. This review presents knowledge on TOR inhibitors from the mammalian field and underlines important considerations for plant and algal biologists. It discusses the use of rapamycin and asTORis in plants and algae and concludes with guidelines for physiological studies and genetic screens with TOR inhibitors.
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Affiliation(s)
- Marie-Hélène Montané
- Aix Marseille Université, CEA, CNRS, BIAM, Laboratoire de génétique et biophysique des plantes, Marseille, F-13009, France
| | - Benoît Menand
- Aix Marseille Université, CEA, CNRS, BIAM, Laboratoire de génétique et biophysique des plantes, Marseille, F-13009, France
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Jhanwar-Uniyal M, Wainwright JV, Mohan AL, Tobias ME, Murali R, Gandhi CD, Schmidt MH. Diverse signaling mechanisms of mTOR complexes: mTORC1 and mTORC2 in forming a formidable relationship. Adv Biol Regul 2019; 72:51-62. [PMID: 31010692 DOI: 10.1016/j.jbior.2019.03.003] [Citation(s) in RCA: 154] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/25/2019] [Accepted: 03/25/2019] [Indexed: 02/07/2023]
Abstract
Activation of Mechanistic target of rapamycin (mTOR) signaling plays a crucial role in tumorigenesis of numerous malignancies including glioblastoma (GB). The Canonical PI3K/Akt/mTOR signaling cascade is commonly upregulated due to loss of the tumor suppressorm PTEN, a phosphatase that acts antagonistically to the kinase (PI3K) in conversion of PIP2 to PIP3. mTOR forms two multiprotein complexes, mTORC1 and mTORC2 which are composed of discrete protein binding partners to regulate cell growth, motility, and metabolism. These complexes are sensitive to distinct stimuli, as mTORC1 is sensitive to nutrients while mTORC2 is regulated via PI3K and growth factor signaling. The main function of mTORC1 is to regulate protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. On the other hand, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK and it also plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. mTORC1 and mTORC2 regulate each other, as shown by the fact that Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Allosteric inhibitors of mTOR, rapamycin and rapalogs, remained ineffective in clinical trials of Glioblastoma (GB) patients, in part due to their incomplete inhibition of mTORC1 as well as unexpected activation of mTOR via the loss of negative feedback loops. In recent years, novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6KSer235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKTSer473. Furthermore by these novel combined mTORC1/mTORC2 inhibitors reduced the proliferation and self-renewal of GB cancer stem cells. However, a search of more effective way to target mTOR has generated a third generation inhibitor of mTOR, "Rapalink", that bivalently combines rapamycin with an ATP-binding inhibitor, which effectively abolishes the mTORC1 activity. All in all, the effectiveness of inhibitors of mTOR complexes can be judged by their ability to suppress both mTORC1/mTORC2 and their ability to impede both cell proliferation and migration along with aberrant metabolic pathways.
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Affiliation(s)
- Meena Jhanwar-Uniyal
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA.
| | - John V Wainwright
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Avinash L Mohan
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Michael E Tobias
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Raj Murali
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Chirag D Gandhi
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
| | - Meic H Schmidt
- Department of Neurosurgery, Westchester Medical Center / New York Medical College, Valhalla, NY, 10595, USA
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11
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Meneguello L, Barbosa NM, Pereira KD, Proença ARG, Tamborlin L, Simabuco FM, Iwai LK, Zanelli CF, Valentini SR, Luchessi AD. The polyproline-motif of S6K2: eIF5A translational dependence and importance for protein-protein interactions. J Cell Biochem 2019; 120:6015-6025. [PMID: 30320934 DOI: 10.1002/jcb.27888] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 09/20/2018] [Indexed: 12/18/2022]
Abstract
Ribosomal S6 kinase 1 (S6K1) and S6K2 proteins are effectors of the mammalian target of rapamycin complex 1 pathway, which control the process of protein synthesis in eukaryotes. S6K2 is associated with tumor progression and has a conserved C-terminus polyproline rich motif predicted to be important for S6K2 interactions. It is noteworthy that the translation of proteins containing sequential prolines has been proposed to be dependent of eukaryotic translation initiation factor 5A (eIF5A) translation factor. Therefore, we investigated the importance of polyproline-rich region of the S6K2 for its intrinsic phosphorylation activity, protein-protein interaction and eIF5A role in S6K2 translation. In HeLa cell line, replacing S6K2 polyproline by the homologous S6K1-sequence did not affect its kinase activity and the S6K2 endogenous content was maintained after eIF5A gene silencing, even after near complete depletion of eIF5A protein. Moreover, no changes in S6K2 transcript content was observed, ruling out the possibility of compensatory regulation by increasing the mRNA content. However, in the budding yeast model, we observed that S6K2 production was impaired when compared with S6K2∆Pro, after reduction of eIF5A protein content. These results suggest that although the polyproline region of S6K2 is capable of generating ribosomal stalling, the depletion of eIF5A in HeLa cells seems to be insufficient to cause an expressive decrease in the content of endogenous S6K2. Finally, coimmunoprecipitation assays revealed that the replacement of the polyproline motif of S6K2 alters its interactome and impairs its interaction with RPS6, a key modulator of ribosome activity. These results evidence the importance of S6K2 polyproline motif in the context of S6Ks function.
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Affiliation(s)
- Leticia Meneguello
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Natália M Barbosa
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Karina D Pereira
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - André R G Proença
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
| | - Leticia Tamborlin
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
| | - Fernando M Simabuco
- Laboratory of Functional Properties in Foods, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
| | - Leo K Iwai
- Special Laboratory of Applied Toxinology, Center of Toxins, Immune-Response and Cell Signaling, LETA/ CeTICS, Butantan Institute, Butanta, Brazil
| | - Cleslei F Zanelli
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Sandro R Valentini
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara, Brazil
| | - Augusto D Luchessi
- Laboratory of Biotechnology, School of Applied Sciences, University of Campinas (UNICAMP), Limeira, Brazil
- Institute of Biosciences, Department of Biology, São Paulo State University (UNESP), Rio Claro, Brazil
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Lie S, Banks P, Lawless C, Lydall D, Petersen J. The contribution of non-essential Schizosaccharomyces pombe genes to fitness in response to altered nutrient supply and target of rapamycin activity. Open Biol 2019; 8:rsob.180015. [PMID: 29720420 PMCID: PMC5990653 DOI: 10.1098/rsob.180015] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 04/06/2018] [Indexed: 12/12/2022] Open
Abstract
Nutrient fluctuations in the cellular environment promote changes in cell metabolism and growth to adapt cell proliferation accordingly. The target of rapamycin (TOR) signalling network plays a key role in the coordination of growth and cell proliferation with the nutrient environment and, importantly, nutrient limitation reduces TOR complex 1 (TORC1) signalling. We have performed global quantitative fitness profiling of the collection of Schizosaccharomyces pombe strains from which non-essential genes have been deleted. We identified genes that regulate fitness when cells are grown in a nutrient-rich environment compared with minimal environments, with varying nitrogen sources including ammonium, glutamate and proline. In addition, we have performed the first global screen for genes that regulate fitness when both TORC1 and TORC2 signalling is reduced by Torin1. Analysis of genes whose deletions altered fitness when nutrients were limited, or when TOR signalling was compromised, identified a large number of genes that regulate transmembrane transport, transcription and chromatin organization/regulation and vesicle-mediated transport. The ability to tolerate reduced TOR signalling placed demands upon a large number of biological processes including autophagy, mRNA metabolic processing and nucleocytoplasmic transport. Importantly, novel biological processes and all processes known to be regulated by TOR were identified in our screens. In addition, deletion of 62 genes conserved in humans gave rise to strong sensitivity or resistance to Torin1, and 29 of these 62 genes have novel links to TOR signalling. The identification of chromatin and transcriptional regulation, nutritional uptake and transport pathways in this powerful genetic model now paves the way for a molecular understanding of how cells adapt to the chronic and acute fluctuations in nutrient supply that all eukaryotes experience at some stage, and which is a key feature of cancer cells within solid tumours.
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Affiliation(s)
- Shervi Lie
- Flinders Centre for Innovation in Cancer, College of Medicine & Public Health, Flinders University, Bedford Park, Adelaide, South Australia 5042, Australia
| | - Peter Banks
- High Throughput Screening Facility, Newcastle Biomedicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Conor Lawless
- Institute for Cell & Molecular Biosciences, Newcastle University Medical School, Newcastle upon Tyne NE2 4HH, UK
| | - David Lydall
- Institute for Cell & Molecular Biosciences, Newcastle University Medical School, Newcastle upon Tyne NE2 4HH, UK
| | - Janni Petersen
- Flinders Centre for Innovation in Cancer, College of Medicine & Public Health, Flinders University, Bedford Park, Adelaide, South Australia 5042, Australia .,South Australia Health and Medical Research Institute, North Terrace, PO Box 11060, Adelaide, South Australia 5000, Australia
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Napolitano G, Esposito A, Choi H, Matarese M, Benedetti V, Di Malta C, Monfregola J, Medina DL, Lippincott-Schwartz J, Ballabio A. mTOR-dependent phosphorylation controls TFEB nuclear export. Nat Commun 2018; 9:3312. [PMID: 30120233 PMCID: PMC6098152 DOI: 10.1038/s41467-018-05862-6] [Citation(s) in RCA: 236] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/25/2018] [Indexed: 01/17/2023] Open
Abstract
During starvation the transcriptional activation of catabolic processes is induced by the nuclear translocation and consequent activation of transcription factor EB (TFEB), a master modulator of autophagy and lysosomal biogenesis. However, how TFEB is inactivated upon nutrient refeeding is currently unknown. Here we show that TFEB subcellular localization is dynamically controlled by its continuous shuttling between the cytosol and the nucleus, with the nuclear export representing a limiting step. TFEB nuclear export is mediated by CRM1 and is modulated by nutrient availability via mTOR-dependent hierarchical multisite phosphorylation of serines S142 and S138, which are localized in proximity of a nuclear export signal (NES). Our data on TFEB nucleo-cytoplasmic shuttling suggest an unpredicted role of mTOR in nuclear export.
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Affiliation(s)
- Gennaro Napolitano
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
- Medical Genetics Unit, Department of Medical and Translational Science, Federico II University, Via Pansini 5, 80131, Naples, Italy
| | - Alessandra Esposito
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Heejun Choi
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA, 20147, USA
| | - Maria Matarese
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Valerio Benedetti
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Chiara Di Malta
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Jlenia Monfregola
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Diego Luis Medina
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy
| | - Jennifer Lippincott-Schwartz
- Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA, 20147, USA
- National Institute of Child Health and Development, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Andrea Ballabio
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078, Pozzuoli, Naples, Italy.
- Medical Genetics Unit, Department of Medical and Translational Science, Federico II University, Via Pansini 5, 80131, Naples, Italy.
- Department of Molecular and Human Genetics and Neurological Research Institute, Baylor College of Medicine, Houston, TX, 77030, USA.
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The roles of RRP15 in nucleolar formation, ribosome biogenesis and checkpoint control in human cells. Oncotarget 2017; 8:13240-13252. [PMID: 28099941 PMCID: PMC5355092 DOI: 10.18632/oncotarget.14658] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 12/27/2016] [Indexed: 01/05/2023] Open
Abstract
The nucleolus controls ribosome biogenesis and its perturbation induces nucleolar stress that inhibits cell cycle progression and activates checkpoint responses. Here, we investigate the roles of ribosomal RNA processing protein, RRP15, in nucleolar formation, ribosome biogenesis, cell cycle progression and checkpoint control in human cells. RRP15 is localized in the nucleolus and required for nucleolar formation. In contrast to the budding yeast Rrp15p that was reported as a component of pre-60S subunits, RRP15 is found in both pre-40S and pre-60S subunits and involved in regulating rRNA transcription and ribosome biogenesis. Perturbation of RRP15 induces nucleolar stress that activates RPL5/RPL11/5S rRNA (RP)-Mdm2-p53 axis checkpoint response and arrests cells at G1-G1/S in p53-proficient non-transformed RPE1 cells but not in p53-deficient HeLa and MCF7 tumor cells. Instead, p53-deficient HeLa and MCF7 cells with RRP15-dependent nucleolar stress enter S-phase with S-phase perturbation that activates ATR-Chk1- γH2AX axis DNA replication/damage checkpoint response, delaying S-G2/M progression and, ultimately, causing cell death. The selective checkpoint response, cell cycle inhibition and/or cytotoxicity induced by RRP15-dependent nucleolar stress in p53-proficient non-transformed cells and p53-deficient tumor cells suggest that RRP15 might be a potential target for cancer therapy.
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Discrete signaling mechanisms of mTORC1 and mTORC2: Connected yet apart in cellular and molecular aspects. Adv Biol Regul 2017; 64:39-48. [PMID: 28189457 DOI: 10.1016/j.jbior.2016.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 12/23/2016] [Accepted: 12/23/2016] [Indexed: 12/19/2022]
Abstract
Activation of PI3K/Akt/mTOR (mechanistic target of rapamycin) signaling cascade has been shown in tumorigenesis of numerous malignancies including glioblastoma (GB). This signaling cascade is frequently upregulated due to loss of the tumor suppressor PTEN, a phosphatase that functions antagonistically to PI3K. mTOR regulates cell growth, motility, and metabolism by forming two multiprotein complexes, mTORC1 and mTORC2, which are composed of special binding partners. These complexes are sensitive to distinct stimuli. mTORC1 is sensitive to nutrients and mTORC2 is regulated via PI3K and growth factor signaling. mTORC1 regulates protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. Also, mTORC2 is responsive to growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases like Akt and SGK. mTORC2 plays a crucial role in maintenance of normal and cancer cells through its association with ribosomes, and is involved in cellular metabolic regulation. Both complexes control each other as Akt regulates PRAS40 phosphorylation, which disinhibits mTORC1 activity, while S6K regulates Sin1 to modulate mTORC2 activity. Another significant component of mTORC2 is Sin1, which is crucial for mTORC2 complex formation and function. Allosteric inhibitors of mTOR, rapamycin and rapalogs, have essentially been ineffective in clinical trials of patients with GB due to their incomplete inhibition of mTORC1 or unexpected activation of mTOR via the loss of negative feedback loops. Novel ATP binding inhibitors of mTORC1 and mTORC2 suppress mTORC1 activity completely by total dephosphorylation of its downstream substrate pS6KSer235/236, while effectively suppressing mTORC2 activity, as demonstrated by complete dephosphorylation of pAKTSer473. Furthermore, proliferation and self-renewal of GB cancer stem cells are effectively targetable by these novel mTORC1 and mTORC2 inhibitors. Therefore, the effectiveness of inhibitors of mTOR complexes can be estimated by their ability to suppress both mTORC1 and 2 and their ability to impede both cell proliferation and migration.
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Tokheim C, Bhattacharya R, Niknafs N, Gygax DM, Kim R, Ryan M, Masica DL, Karchin R. Exome-Scale Discovery of Hotspot Mutation Regions in Human Cancer Using 3D Protein Structure. Cancer Res 2016; 76:3719-31. [PMID: 27197156 DOI: 10.1158/0008-5472.can-15-3190] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 04/01/2016] [Indexed: 12/12/2022]
Abstract
The impact of somatic missense mutation on cancer etiology and progression is often difficult to interpret. One common approach for assessing the contribution of missense mutations in carcinogenesis is to identify genes mutated with statistically nonrandom frequencies. Even given the large number of sequenced cancer samples currently available, this approach remains underpowered to detect drivers, particularly in less studied cancer types. Alternative statistical and bioinformatic approaches are needed. One approach to increase power is to focus on localized regions of increased missense mutation density or hotspot regions, rather than a whole gene or protein domain. Detecting missense mutation hotspot regions in three-dimensional (3D) protein structure may also be beneficial because linear sequence alone does not fully describe the biologically relevant organization of codons. Here, we present a novel and statistically rigorous algorithm for detecting missense mutation hotspot regions in 3D protein structures. We analyzed approximately 3 × 10(5) mutations from The Cancer Genome Atlas (TCGA) and identified 216 tumor-type-specific hotspot regions. In addition to experimentally determined protein structures, we considered high-quality structural models, which increase genomic coverage from approximately 5,000 to more than 15,000 genes. We provide new evidence that 3D mutation analysis has unique advantages. It enables discovery of hotspot regions in many more genes than previously shown and increases sensitivity to hotspot regions in tumor suppressor genes (TSG). Although hotspot regions have long been known to exist in both TSGs and oncogenes, we provide the first report that they have different characteristic properties in the two types of driver genes. We show how cancer researchers can use our results to link 3D protein structure and the biologic functions of missense mutations in cancer, and to generate testable hypotheses about driver mechanisms. Our results are included in a new interactive website for visualizing protein structures with TCGA mutations and associated hotspot regions. Users can submit new sequence data, facilitating the visualization of mutations in a biologically relevant context. Cancer Res; 76(13); 3719-31. ©2016 AACR.
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Affiliation(s)
- Collin Tokheim
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Rohit Bhattacharya
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Noushin Niknafs
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | | | - Rick Kim
- In Silico Solutions, Fairfax, Virginia
| | | | - David L Masica
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Rachel Karchin
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland. Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland.
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Chen X, Zhu Y, Wang Z, Zhu H, Pan Q, Su S, Dong Y, Li L, Zhang H, Wu L, Lou X, Liu S. mTORC1 alters the expression of glycolytic genes by regulating KPNA2 abundances. J Proteomics 2016; 136:13-24. [DOI: 10.1016/j.jprot.2016.01.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 01/14/2016] [Accepted: 01/30/2016] [Indexed: 12/14/2022]
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