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Figueiredo VC, McCarthy JJ. Regulation of Ribosome Biogenesis in Skeletal Muscle Hypertrophy. Physiology (Bethesda) 2019; 34:30-42. [PMID: 30540235 PMCID: PMC6383632 DOI: 10.1152/physiol.00034.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 01/22/2023] Open
Abstract
The ribosome is the enzymatic macromolecular machine responsible for protein synthesis. The rates of protein synthesis are primarily dependent on translational efficiency and capacity. Ribosome biogenesis has emerged as an important regulator of skeletal muscle growth and maintenance by altering the translational capacity of the cell. Here, we provide evidence to support a central role for ribosome biogenesis in skeletal muscle growth during postnatal development and in response to resistance exercise training. Furthermore, we discuss the cellular signaling pathways regulating ribosome biogenesis, discuss how myonuclear accretion affects translational capacity, and explore future areas of investigation within the field.
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Affiliation(s)
- Vandré Casagrande Figueiredo
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Rehabilitation Sciences, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - John J McCarthy
- The Center for Muscle Biology, College of Health Sciences, University of Kentucky , Lexington, Kentucky
- Department of Physiology, University of Kentucky , Lexington, Kentucky
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2
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Schmidt N, Irle I, Ripkens K, Lux V, Nelles J, Johannes C, Parry L, Greenow K, Amir S, Campioni M, Baldi A, Oka C, Kawaichi M, Clarke AR, Ehrmann M. Epigenetic silencing of serine protease HTRA1 drives polyploidy. BMC Cancer 2016; 16:399. [PMID: 27388476 PMCID: PMC4936022 DOI: 10.1186/s12885-016-2425-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 06/27/2016] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Increased numbers and improperly positioned centrosomes, aneuploidy or polyploidy, and chromosomal instability are frequently observed characteristics of cancer cells. While some aspects of these events and the checkpoint mechanisms are well studied, not all players have yet been identified. As the role of proteases other than the proteasome in tumorigenesis is an insufficiently addressed question, we investigated the epigenetic control of the widely conserved protease HTRA1 and the phenotypes of deregulation. METHODS Mouse embryonal fibroblasts and HCT116 and SW480 cells were used to study the mechanism of epigenetic silencing of HTRA1. In addition, using cell biological and genetic methods, the phenotypes of downregulation of HTRA1 expression were investigated. RESULTS HTRA1 is epigenetically silenced in HCT116 colon carcinoma cells via the epigenetic adaptor protein MBD2. On the cellular level, HTRA1 depletion causes multiple phenotypes including acceleration of cell growth, centrosome amplification and polyploidy in SW480 colon adenocarcinoma cells as well as in primary mouse embryonic fibroblasts (MEFs). CONCLUSIONS Downregulation of HTRA1 causes a number of phenotypes that are hallmarks of cancer cells suggesting that the methylation state of the HtrA1 promoter may be used as a biomarker for tumour cells or cells at risk of transformation.
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Affiliation(s)
- Nina Schmidt
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Inga Irle
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Kamilla Ripkens
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Vanda Lux
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Jasmin Nelles
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Christian Johannes
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
| | - Lee Parry
- />School of Biosciences, Cardiff University, Cardiff, CF10 3US UK
| | - Kirsty Greenow
- />School of Biosciences, Cardiff University, Cardiff, CF10 3US UK
| | - Sarah Amir
- />School of Biosciences, Cardiff University, Cardiff, CF10 3US UK
| | - Mara Campioni
- />Department of Biochemistry and Biophysics, Section of Pathology, Second University of Naples, 80100 Naples, Italy
| | - Alfonso Baldi
- />Department of Biochemistry and Biophysics, Section of Pathology, Second University of Naples, 80100 Naples, Italy
| | - Chio Oka
- />Division of Gene Function in Animals, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 Japan
| | - Masashi Kawaichi
- />Division of Gene Function in Animals, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 Japan
| | - Alan R. Clarke
- />School of Biosciences, Cardiff University, Cardiff, CF10 3US UK
| | - Michael Ehrmann
- />Centre for Medical Biotechnology, Faculty of Biology and Geography, University Duisburg-Essen, Universitaetsstrasse, D-45117 Essen, Germany
- />School of Biosciences, Cardiff University, Cardiff, CF10 3US UK
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3
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Adams GR, Bamman MM. Characterization and regulation of mechanical loading-induced compensatory muscle hypertrophy. Compr Physiol 2013; 2:2829-70. [PMID: 23720267 DOI: 10.1002/cphy.c110066] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In mammalian systems, skeletal muscle exists in a dynamic state that monitors and regulates the physiological investment in muscle size to meet the current level of functional demand. This review attempts to consolidate current knowledge concerning development of the compensatory hypertrophy that occurs in response to a sustained increase in the mechanical loading of skeletal muscle. Topics covered include: defining and measuring compensatory hypertrophy, experimental models, loading stimulus parameters, acute responses to increased loading, hyperplasia, myofiber-type adaptations, the involvement of satellite cells, mRNA translational control, mechanotransduction, and endocrinology. The authors conclude with their impressions of current knowledge gaps in the field that are ripe for future study.
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Affiliation(s)
- Gregory R Adams
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, USA.
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4
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Effect of different resistance-training regimens on the WNT-signaling pathway. Eur J Appl Physiol 2011; 111:2535-45. [DOI: 10.1007/s00421-011-1874-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 02/14/2011] [Indexed: 10/18/2022]
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5
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Montagne J, Lecerf C, Parvy JP, Bennion JM, Radimerski T, Ruhf ML, Zilbermann F, Vouilloz N, Stocker H, Hafen E, Kozma SC, Thomas G. The nuclear receptor DHR3 modulates dS6 kinase-dependent growth in Drosophila. PLoS Genet 2010; 6:e1000937. [PMID: 20463884 PMCID: PMC2865512 DOI: 10.1371/journal.pgen.1000937] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 04/02/2010] [Indexed: 12/25/2022] Open
Abstract
S6 kinases (S6Ks) act to integrate nutrient and insulin signaling pathways and, as such, function as positive effectors in cell growth and organismal development. However, they also have been shown to play a key role in limiting insulin signaling and in mediating the autophagic response. To identify novel regulators of S6K signaling, we have used a Drosophila-based, sensitized, gain-of-function genetic screen. Unexpectedly, one of the strongest enhancers to emerge from this screen was the nuclear receptor (NR), Drosophila hormone receptor 3 (DHR3), a critical constituent in the coordination of Drosophila metamorphosis. Here we demonstrate that DHR3, through dS6K, also acts to regulate cell-autonomous growth. Moreover, we show that the ligand-binding domain (LBD) of DHR3 is essential for mediating this response. Consistent with these findings, we have identified an endogenous DHR3 isoform that lacks the DBD. These results provide the first molecular link between the dS6K pathway, critical in controlling nutrient-dependent growth, and that of DHR3, a major mediator of ecdysone signaling, which, acting together, coordinate metamorphosis.
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Affiliation(s)
- Jacques Montagne
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Centre de Génétique Moléculaire, CNRS UPR 2167, Gif-sur-Yvette, France
- Université Paris-Sud, Orsay, France
- Université Pierre et Marie Curie-Paris 6, Paris, France
- * E-mail: (JM); (GT)
| | - Caroline Lecerf
- Centre de Génétique Moléculaire, CNRS UPR 2167, Gif-sur-Yvette, France
- Université Paris-Sud, Orsay, France
- Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Jean-Philippe Parvy
- Centre de Génétique Moléculaire, CNRS UPR 2167, Gif-sur-Yvette, France
- Université Paris-Sud, Orsay, France
- Université Pierre et Marie Curie-Paris 6, Paris, France
| | - Janis M. Bennion
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Thomas Radimerski
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Marie-Laure Ruhf
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio, United States of America
| | | | - Nicole Vouilloz
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Hugo Stocker
- ETH, Institut für Molekulare Systembiologie, Zürich, Switzerland
| | - Ernst Hafen
- ETH, Institut für Molekulare Systembiologie, Zürich, Switzerland
| | - Sara C. Kozma
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - George Thomas
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Metabolic Diseases Institute, University of Cincinnati, Cincinnati, Ohio, United States of America
- * E-mail: (JM); (GT)
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Kurabe N, Arai S, Nishijima A, Kubota N, Suizu F, Mori M, Kurokawa J, Kondo-Miyazaki M, Ide T, Murakami K, Miyake K, Ueki K, Koga H, Yatomi Y, Tashiro F, Noguchi M, Kadowaki T, Miyazaki T. The death effector domain-containing DEDD supports S6K1 activity via preventing Cdk1-dependent inhibitory phosphorylation. J Biol Chem 2008; 284:5050-5. [PMID: 19106089 DOI: 10.1074/jbc.m808598200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell cycle regulation and biochemical responses upon nutrients and growth factors are the major regulatory mechanisms for cell sizing in mammals. Recently, we identified that the death effector domain-containing DEDD impedes mitotic progression by inhibiting Cdk1 (cyclin-dependent kinase 1) and thus maintains an increase of cell size during the mitotic phase. Here we found that DEDD also associates with S6 kinase 1 (S6K1), downstream of phosphatidylinositol 3-kinase, and supports its activity by preventing inhibitory phosphorylation of S6K1 brought about by Cdk1 during the mitotic phase. DEDD(-/-) cells showed reduced S6K1 activity, consistently demonstrating decreased levels in activating phosphorylation at the Thr-389 site. In addition, levels of Cdk1-dependent inhibitory phosphorylation at the C terminus of S6K1 were enhanced in DEDD(-/-) cells and tissues. Consequently, as in S6K1(-/-) mice, the insulin mass within pancreatic islets was reduced in DEDD(-/-) mice, resulting in glucose intolerance. These findings suggest a novel cell sizing mechanism achieved by DEDD through the maintenance of S6K1 activity prior to cell division. Our results also suggest that DEDD may harbor important roles in glucose homeostasis and that its deficiency might be involved in the pathogenesis of type 2 diabetes mellitus.
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Affiliation(s)
- Nobuya Kurabe
- Division of Molecular Biomedicine for Pathogenesis, Center for Disease Biology and Integrative Medicine, University of Tokyo, Tokyo, Japan
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Abstract
Satellite cells are small, mononuclear cells found in close association with striated skeletal muscles cells (myofibers). These cells appear to function as reserve myoblasts. A critical role for these cells in the process of muscle regeneration following injury has been clearly established. In that role, satellite cells have been shown to proliferate extensively. Some of the progeny of these cells then fuse with each other to form replacement myofibers, whereas others return to quiescence, thereby maintaining this reserve population. In response to injury, activated satellite cells can also fuse with damaged but viable myofibers to promote repair and regeneration. It has also been observed that satellite cells are activated during periods of significantly increased muscle loading and that some of these cells fuse with apparently undamaged myofibers as part of the hypertrophy process. The observation that the inactivation of satellite cell proliferation prevents most of the hypertrophy response to chronic increases in loading has lead to the hypothesis that a limitation to the expansion of myofiber size is imposed by the number of myonuclei present. Recent evidence suggests that a potential limitation to muscle hypertrophy, in the absence of a reserve supply of myonuclei, may be the inability to sustain increases in ribosomes, thereby limiting translational capacity.
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Affiliation(s)
- Gregory R Adams
- Department of Physiology and Biophysics, Medical Science I D335, University of California, Irvine, CA 92697, USA.
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8
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Arai S, Miyake K, Voit R, Nemoto S, Wakeland EK, Grummt I, Miyazaki T. Death-effector domain-containing protein DEDD is an inhibitor of mitotic Cdk1/cyclin B1. Proc Natl Acad Sci U S A 2007; 104:2289-94. [PMID: 17283331 PMCID: PMC1793902 DOI: 10.1073/pnas.0611167104] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Accumulating evidence has shown that many molecules, including some cyclin-dependent kinases (Cdks) and cyclins, as well as the death-effector domain (DED)-containing FADD, function for both apoptosis and cell cycle. Here we identified that DEDD, which also possesses the DED domain, acts as a novel inhibitor of the mitotic Cdk1/cyclin B1 complex. DEDD associates with mitotic Cdk1/cyclin B1 complexes via direct binding to cyclin B1 and reduces their function. In agreement, kinase activity of nuclear Cdk1/cyclin B1 in DEDD-null (DEDD-/-) embryonic fibroblasts is increased compared with that in DEDD+/+ cells, which results in accelerated mitotic progression, thus exhibiting a shortened G2/M stage. Interestingly, DEDD-/- cells also demonstrated decreased G1 duration, which perhaps enhanced the overall reduction in rRNA amounts and cell volume, primarily caused by the rapid termination of rRNA synthesis before cell division. Likewise, DEDD-/- mice show decreased body and organ weights relative to DEDD+/+ mice. Thus, DEDD is an impeder of cell mitosis, and its absence critically influences cell and body size via modulation of rRNA synthesis.
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Affiliation(s)
- Satoko Arai
- *Division of Molecular Biomedicine for Pathogenesis, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Center for Immunology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, NA7200, Dallas, TX 75390-9093; and
| | - Katsuhisa Miyake
- Center for Immunology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, NA7200, Dallas, TX 75390-9093; and
| | - Renate Voit
- Department of Molecular Biology of the Cell II, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Shino Nemoto
- *Division of Molecular Biomedicine for Pathogenesis, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Edward K. Wakeland
- Center for Immunology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, NA7200, Dallas, TX 75390-9093; and
| | - Ingrid Grummt
- Department of Molecular Biology of the Cell II, German Cancer Research Center, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | - Toru Miyazaki
- *Division of Molecular Biomedicine for Pathogenesis, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- Center for Immunology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, NA7200, Dallas, TX 75390-9093; and
- To whom correspondence should be addressed. E-mail:
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9
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Armstrong DD, Esser KA. Wnt/beta-catenin signaling activates growth-control genes during overload-induced skeletal muscle hypertrophy. Am J Physiol Cell Physiol 2005; 289:C853-9. [PMID: 15888552 DOI: 10.1152/ajpcell.00093.2005] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Beta-catenin is a transcriptional activator shown to regulate the embryonic, postnatal, and oncogenic growth of many tissues. In most research to date, beta-catenin activation has been the unique downstream function of the Wnt signaling pathway. However, in the heart, a Wnt-independent mechanism involving Akt-mediated phosphorylation of glycogen synthase kinase (GSK)-3beta was recently shown to activate beta-catenin and regulate cardiomyocyte growth. In this study, results have identified the activation of the Wnt/beta-catenin pathway during hypertrophy of mechanically overloaded skeletal muscle. Significant increases in beta-catenin were determined during skeletal muscle hypertrophy. In addition, the Wnt receptor, mFrizzled (mFzd)-1, the signaling mediator disheveled-1, and the transcriptional co-activator, lymphocyte enhancement factor (Lef)-1, are all increased during hypertrophy of the overloaded mouse plantaris muscle. Experiments also determined an increased association between GSK-3beta and the inhibitory frequently rearranged in advanced T cell-1 protein with no increase in GSK-3beta phosphorylation (Ser9). Finally, skeletal muscle overload resulted in increased nuclear beta-catenin/Lef-1 expression and induction of the transcriptional targets c-Myc, cyclin D1, and paired-like homeodomain transcription factor 2. Thus this study provides the first evidence that the Wnt signaling pathway induces beta-catenin/Lef-1 activation of growth-control genes during overload induced skeletal muscle hypertrophy.
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10
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Rouzaire-Dubois B, Malo M, Milandri JB, Dubois JM. Cell size-proliferation relationship in rat glioma cells. Glia 2004; 45:249-57. [PMID: 14730698 DOI: 10.1002/glia.10320] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The homeostasis of the central nervous system is highly controlled by glial cells and is dramatically altered in the case of glioma. In this respect, the complex connection between cell size and division is of particular importance and needs clarifying. In order to investigate this connection, cell number and volume were measured in C6 rat glioma cells under different experimental conditions, including continuous cell culture, Cl- channel blockade, and anisotonicity, and in the presence of an inhibitory conditioned medium collected from cell cultures or in a medium containing a low level of fetal calf serum. The rate of cell proliferation changed with cell volume in a bell-shaped manner, so that it is optimal within a cell volume window and appears to be controlled by low and high cell size checkpoints. The cell size-proliferation relationship can be defined by Boltzmann-like equations, which may reflect the effects of macromolecular crowding on proteins controlling the cell cycle progression. Altogether, these observations indicate that glioma cell proliferation is controlled predominantly but not exclusively by cell size-dependent mechanisms.
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Perrin L, Benassayag C, Morello D, Pradel J, Montagne J. Modulo is a target of Myc selectively required for growth of proliferative cells in Drosophila. Mech Dev 2003; 120:645-55. [PMID: 12834864 DOI: 10.1016/s0925-4773(03)00049-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In Drosophila, the homologue of the proto-oncogene Myc is a key regulator of both cell size and cell growth. The identities and roles of dMyc target genes in these processes, however, remain largely unexplored. Here, we investigate the function of the modulo (mod) gene, which encodes a nucleolus localized protein. In gain of function or loss of function experiments, we demonstrate that mod is directly controlled by dMyc. Strikingly, in proliferative imaginal cells, mod loss-of-function impairs both cell growth and cell size, whereas larval endoreplicative tissues grow normally. In contrast to dMyc, over-expressing Mod in wing imaginal discs is not sufficient to induce cell growth. Taken together, our results indicate that mod does not possess the full spectrum of dMyc activities, but is required selectively in proliferative cells to sustain their growth and to maintain their specific size.
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Affiliation(s)
- Laurent Perrin
- Institut de Génétique Humaine, 141 rue de la Cardonille, 34396 Montpellier Cedex 5, France.
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12
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Felton-Edkins ZA, Fairley JA, Graham EL, Johnston IM, White RJ, Scott PH. The mitogen-activated protein (MAP) kinase ERK induces tRNA synthesis by phosphorylating TFIIIB. EMBO J 2003; 22:2422-32. [PMID: 12743036 PMCID: PMC155998 DOI: 10.1093/emboj/cdg240] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2002] [Revised: 03/21/2003] [Accepted: 03/24/2003] [Indexed: 01/01/2023] Open
Abstract
RNA polymerase (pol) III transcription increases within minutes of serum addition to growth-arrested fibroblasts. We show that ERK mitogen-activated protein kinases regulate pol III output by directly binding and phosphorylating the BRF1 subunit of transcription factor TFIIIB. Blocking the ERK signalling cascade inhibits TFIIIB binding to pol III and to transcription factor TFIIIC2. Chromatin immunoprecipitation shows that the association of BRF1 and pol III with tRNA(Leu) genes in cells decreases when ERK is inactivated. Furthermore, mutation of an ERK docking domain or phosphoacceptor site in BRF1 prevents serum induction of pol III transcription. These data identify a novel target for ERK, and suggest that its ability to stimulate biosynthetic capacity and growth involves direct transcriptional activation of tRNA and 5S rRNA genes.
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Affiliation(s)
- Zoe A Felton-Edkins
- Institute of Biomedical and Life Sciences, Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, UK
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13
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Abstract
NFAT5/TonEBP, the most recently described member of the rel/NFkappaB/NFAT family of signal-dependent transcription factors, is activated by extracellular hypertonicity-a cellular stress of particular and perhaps unique physiologic relevance to cells of the renal medulla. Accumulating evidence suggests that NFAT5/TonEBP also functions in vivo under isotonic conditions as part of a ubiquitous regulatory mechanism that senses and adjusts available intracellular volume during cell growth to establish an intracellular environment appropriate for optimal cell proliferation.
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Affiliation(s)
- Steffan N Ho
- Department of Pathology, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0644, USA.
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14
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Uchihara T, Iwabuchi K, Funata N, Yagishita S. Attenuated nuclear shrinkage in neurons with nuclear aggregates--a morphometric study on pontine neurons of Machado-Joseph disease brains. Exp Neurol 2002; 178:124-8. [PMID: 12460614 DOI: 10.1006/exnr.2002.8028] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nuclear aggregates (NAs) and neurodegeneration in brains from patients with Machado-Joseph disease (MJD) are both triggered by pathological expansion of CAG/polyglutamine repeat in ataxin-3, but it remains to be clarified whether NA formation is associated with accelerated neurodegeneration. In an attempt to clarify a possible influence of NAs on neurons in human brains, we quantified the size and deformity of neuronal nuclei (those with or without NAs, separately) cross-sectioned on pontine preparations of autopsied brains from four patients with MJD and five controls. Nuclear shrinkage and deformity were more marked in MJD brains than in controls, and these changes were attenuated in neurons harboring NAs. NAs of MJD are presumably linked to a mechanism that attenuates rather than accelerates nuclear shrinkage and deformity. This finding leads us to consider that NAs are not necessarily toxic to neurons in diseased human brains.
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Affiliation(s)
- Toshiki Uchihara
- Department of Neuropathology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashi-dai, Fuchu, Tokyo 183-8526, Japan.
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15
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Adams GR, Caiozzo VJ, Haddad F, Baldwin KM. Cellular and molecular responses to increased skeletal muscle loading after irradiation. Am J Physiol Cell Physiol 2002; 283:C1182-95. [PMID: 12225982 DOI: 10.1152/ajpcell.00173.2002] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Irradiation of rat skeletal muscles before increased loading has been shown to prevent compensatory hypertrophy for periods of up to 4 wk, possibly by preventing satellite cells from proliferating and providing new myonuclei. Recent work suggested that stem cell populations exist that might allow irradiated muscles to eventually hypertrophy over time. We report that irradiation essentially prevented hypertrophy in rat muscles subjected to 3 mo of functional overload (OL-Ir). The time course and magnitude of changes in cellular and molecular markers of anabolic and myogenic responses were similar in the OL-Ir and the contralateral nonirradiated, overloaded (OL) muscles for the first 3-7 days. These markers then returned to control levels in OL-Ir muscles while remaining elevated in OL muscles. The number of myonuclei and amount of DNA were increased markedly in OL but not OL-Ir muscles. Thus it appears that stem cells were not added to the irradiated muscles in this time period. These data are consistent with the theory that the addition of new myonuclei may be required for compensatory hypertrophy in the rat.
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Affiliation(s)
- Gregory R Adams
- Department of Physiology and Biophysics, Medical Sciences IC308, College of Medicine, University of California, Irvine, CA 92697, USA.
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16
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Mizukami Y. A matter of size: developmental control of organ size in plants. CURRENT OPINION IN PLANT BIOLOGY 2001; 4:533-9. [PMID: 11641070 DOI: 10.1016/s1369-5266(00)00212-0] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The intrinsic size of plant organs is determined by developmental signals, yet the molecular and genetic mechanisms that control organ size are largely unknown. Ongoing functional analysis of Arabidopsis genes is defining important regulators involved in these mechanisms. Key features of this control are the coordinated activation of growth and cell division by growth regulators and the maintenance of meristematic competence by the ANT gene, which acts as an organ-size checkpoint. Alterations of genome size by polyploidization and endoreduplication can reset this checkpoint by ploidy-dependent, epigenetically regulated differential gene expression. In addition, the regulation of polarized growth and phytohormone signaling also affect final organ size. These findings reveal unique aspects of plant organ-size control that are distinct from animal organ-size control.
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Affiliation(s)
- Y Mizukami
- Department of Plant and Microbial Biology, University of California, 231 Koshland Hall, Berkeley, California 94720, USA.
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17
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Abstract
In this issue of Molecular Cell, Stefanovsky et al. demonstrate that the activation of the ERK1/2 MAP kinases by growth factors leads to induction of ribosomal gene transcription, through a mechanism dependent on phosphorylation of the upstream binding factor (UBF). This provides a connection between growth factor signaling and increased translation.
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Affiliation(s)
- E D Gallagher
- Department of Pharmacology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Montagne J, Radimerski T, Thomas G. Insulin Signaling: Lessons from the Drosophila Tuberous Sclerosis Complex, a Tumor Suppressor. Sci Signal 2001. [DOI: 10.1126/scisignal.1052001pe36] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Montagne J, Radimerski T, Thomas G. Insulin signaling: lessons from the Drosophila tuberous sclerosis complex, a tumor suppressor. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2001; 2001:pe36. [PMID: 11675514 DOI: 10.1126/stke.2001.105.pe36] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The genes that encode the proteins composing the tuberous sclerosis complex (TSC) are tumor suppressors. Experiments in the model organism Drosophila melanogaster have provided insight into the identity of these genes and their functions in regulating cell size and proliferation. Montagne et al. describe the various genetic interactions that show TSC to be a regulator of the insulin signaling pathway and a regulator of progression through the cell cycle, which explains its effects on cell size and tissue and tumor growth.
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Affiliation(s)
- J Montagne
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66 Basel, CH-4058, Switzerland
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