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p53- and ERK7-dependent ribosome surveillance response regulates Drosophila insulin-like peptide secretion. PLoS Genet 2014; 10:e1004764. [PMID: 25393288 PMCID: PMC4230838 DOI: 10.1371/journal.pgen.1004764] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 09/19/2014] [Indexed: 01/05/2023] Open
Abstract
Insulin-like signalling is a conserved mechanism that coordinates animal growth and metabolism with nutrient status. In Drosophila, insulin-producing median neurosecretory cells (IPCs) regulate larval growth by secreting insulin-like peptides (dILPs) in a diet-dependent manner. Previous studies have shown that nutrition affects dILP secretion through humoral signals derived from the fat body. Here we uncover a novel mechanism that operates cell autonomously in the IPCs to regulate dILP secretion. We observed that impairment of ribosome biogenesis specifically in the IPCs strongly inhibits dILP secretion, which consequently leads to reduced body size and a delay in larval development. This response is dependent on p53, a known surveillance factor for ribosome biogenesis. A downstream effector of this growth inhibitory response is an atypical MAP kinase ERK7 (ERK8/MAPK15), which is upregulated in the IPCs following impaired ribosome biogenesis as well as starvation. We show that ERK7 is sufficient and essential to inhibit dILP secretion upon impaired ribosome biogenesis, and it acts epistatically to p53. Moreover, we provide evidence that p53 and ERK7 contribute to the inhibition of dILP secretion upon starvation. Thus, we conclude that a cell autonomous ribosome surveillance response, which leads to upregulation of ERK7, inhibits dILP secretion to impede tissue growth under limiting dietary conditions. Ribosome biogenesis is a major consumer of cellular energy and a rate-limiting process during cell growth. The ribosome biogenesis pathway is tightly connected with signaling pathways that regulate tissue growth. For example, nutrient-regulated signaling cues adjust the rate of ribosome biogenesis. On the other hand, the process of ribosome biogenesis is closely monitored by so-called surveillance mechanisms. The best-known ribosome surveillance factor is the transcription factor and tumor suppressor p53. In proliferating cells, activation of p53 upon disturbed ribosome biogenesis leads to cell cycle arrest and inhibition of proliferation. Here we show that ribosome surveillance not only regulates growth locally in proliferating cells, but is also coupled to hormonal growth control through regulation of insulin like peptide (dILPs) secretion. We observed that inhibition of ribosome biogenesis in the Drosophila insulin-producing cells generates a strong cell autonomous signal to inhibit dILP secretion. We identify two downstream effectors of this ribosome surveillance response by showing that p53 as well as an atypical MAP kinase ERK7 are mediators of the inhibition of dILP secretion. We also provide evidence that this ribosome surveillance mechanism contributes to nutrient-dependent regulation of dILP secretion.
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Avet-Rochex A, Carvajal N, Christoforou CP, Yeung K, Maierbrugger KT, Hobbs C, Lalli G, Cagin U, Plachot C, McNeill H, Bateman JM. Unkempt is negatively regulated by mTOR and uncouples neuronal differentiation from growth control. PLoS Genet 2014; 10:e1004624. [PMID: 25210733 PMCID: PMC4161320 DOI: 10.1371/journal.pgen.1004624] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/23/2014] [Indexed: 01/21/2023] Open
Abstract
Neuronal differentiation is exquisitely controlled both spatially and temporally during nervous system development. Defects in the spatiotemporal control of neurogenesis cause incorrect formation of neural networks and lead to neurological disorders such as epilepsy and autism. The mTOR kinase integrates signals from mitogens, nutrients and energy levels to regulate growth, autophagy and metabolism. We previously identified the insulin receptor (InR)/mTOR pathway as a critical regulator of the timing of neuronal differentiation in the Drosophila melanogaster eye. Subsequently, this pathway has been shown to play a conserved role in regulating neurogenesis in vertebrates. However, the factors that mediate the neurogenic role of this pathway are completely unknown. To identify downstream effectors of the InR/mTOR pathway we screened transcriptional targets of mTOR for neuronal differentiation phenotypes in photoreceptor neurons. We identified the conserved gene unkempt (unk), which encodes a zinc finger/RING domain containing protein, as a negative regulator of the timing of photoreceptor differentiation. Loss of unk phenocopies InR/mTOR pathway activation and unk acts downstream of this pathway to regulate neurogenesis. In contrast to InR/mTOR signalling, unk does not regulate growth. unk therefore uncouples the role of the InR/mTOR pathway in neurogenesis from its role in growth control. We also identified the gene headcase (hdc) as a second downstream regulator of the InR/mTOR pathway controlling the timing of neurogenesis. Unk forms a complex with Hdc, and Hdc expression is regulated by unk and InR/mTOR signalling. Co-overexpression of unk and hdc completely suppresses the precocious neuronal differentiation phenotype caused by loss of Tsc1. Thus, Unk and Hdc are the first neurogenic components of the InR/mTOR pathway to be identified. Finally, we show that Unkempt-like is expressed in the developing mouse retina and in neural stem/progenitor cells, suggesting that the role of Unk in neurogenesis may be conserved in mammals. The development of a functional nervous system requires that nerve cells are generated at exactly the right time and place to be correctly integrated. Defects in the timing at which nerve cells are generated, or ‘differentiate’, lead to neurological disorders such as epilepsy and autism. However, very little is known about the identity of the genes that control the timing of nerve cell differentiation. Using developing photoreceptor nerves in the eye of the fruit fly, Drosophila, as a model, we showed previously that a molecular pathway known as ‘mTOR signalling’ is a key regulator of the timing of differentiation. In this study we have identified two new genes, unkempt and headcase, which control the timing of photoreceptor differentiation in Drosophila. The activity of unkempt and headcase is controlled by mTOR signalling and it is through these genes that mTOR is able to control nerve cell differentiation. The proteins encoded by unkempt and headcase form a complex and act synergistically to control the development of Drosophila photoreceptors. mTOR signalling controls a number of important cellular processes, but unkempt and headcase are the first components of this pathway to be identified that control nerve cell differentiation.
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Affiliation(s)
- Amélie Avet-Rochex
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Nancy Carvajal
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | | | - Kelvin Yeung
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Katja T. Maierbrugger
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Carl Hobbs
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Giovanna Lalli
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Umut Cagin
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Cedric Plachot
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Helen McNeill
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Joseph M. Bateman
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
- * E-mail:
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Aramburu J, Ortells MC, Tejedor S, Buxadé M, López-Rodríguez C. Transcriptional regulation of the stress response by mTOR. Sci Signal 2014; 7:re2. [PMID: 24985347 DOI: 10.1126/scisignal.2005326] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The kinase mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation that integrates inputs from growth factor receptors, nutrient availability, intracellular ATP (adenosine 5'-triphosphate), and a variety of stressors. Since early works in the mid-1990s uncovered the role of mTOR in stimulating protein translation, this kinase has emerged as a rather multifaceted regulator of numerous processes. Whereas mTOR is generally activated by growth- and proliferation-stimulating signals, its activity can be reduced and even suppressed when cells are exposed to a variety of stress conditions. However, cells can also adapt to stress while maintaining their growth capacity and mTOR function. Despite knowledge accumulated on how stress represses mTOR, less is known about mTOR influencing stress responses. In this review, we discuss the capability of mTOR, in particular mTOR complex 1 (mTORC1), to activate stress-responsive transcription factors, and we outline open questions for future investigation.
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Affiliation(s)
- Jose Aramburu
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
| | - M Carmen Ortells
- Centre for Genomic Regulation and Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Sonia Tejedor
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Maria Buxadé
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Cristina López-Rodríguez
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain.
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Rehman G, Shehzad A, Khan AL, Hamayun M. Role of AMP-activated protein kinase in cancer therapy. Arch Pharm (Weinheim) 2014; 347:457-68. [PMID: 24677093 DOI: 10.1002/ardp.201300402] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 01/23/2014] [Accepted: 01/31/2014] [Indexed: 11/07/2022]
Abstract
Recent advances in AMP-activated protein kinase (AMPK) as a target in cancer waxed and waned over the past decade of cancer research. AMPK is a cellular energy sensor, present in almost all eukaryotic cells. An elevated AMP/ATP ratio activates the AMPK, which in turn inhibits energy-consuming processes and induces catabolic events that generate ATP to restore the energy homeostasis inside the cell. Several reports have indicated that AMPK regulates several metabolic pathways and may be a potential therapeutic target for the treatment of cancer. Cancer cells have specific metabolic changes that differ from normal cells, and AMPK prevents the deregulated processes in cancer. AMPK may also act to inhibit tumor formation through modulation of cell growth, cell proliferation, autophagy, stress responses, and cell polarity. AMPK has been shown to inhibit mammalian target of rapamycin (mTOR) through tuberous sclerosis complex 2 (TSC2) phosphorylation and phosphatase and tensin homolog (PTEN), considered as central cell growth controller signals in diseases. In response to glucose deprivation, AMPK phosphorylates and activates p53, which induces cell cycle arrest in the G1/S phase of the cell cycle. AMPK has also been reported to block cyclin-dependent kinases through phosphorylation of p27(kip1) , promoting its stabilization and allowing cells to survive metabolic stress via induction of autophagy. Additionally, AMPK induces autophagy by phosphorylation and activation of eEF-2 kinase, and prevents the formation of new proteins. AMPK activators are also used for the treatment of type II diabetes and cancer. This review focuses on AMPK activation and its possible therapeutic role in the treatment of cancer.
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Affiliation(s)
- Gauhar Rehman
- School of Life Science, College of Natural Science, Kyungpook National University, Daegu, South Korea; Department of Zoology, Abdul Wali Khan University, Mardan, K. P. K. Pakistan
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Walker DK, Drummond MJ, Dickinson JM, Borack MS, Jennings K, Volpi E, Rasmussen BB. Insulin increases mRNA abundance of the amino acid transporter SLC7A5/LAT1 via an mTORC1-dependent mechanism in skeletal muscle cells. Physiol Rep 2014; 2:e00238. [PMID: 24760501 PMCID: PMC4002227 DOI: 10.1002/phy2.238] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Abstract Amino acid transporters (AATs) provide a link between amino acid availability and mammalian/mechanistic target of rapamycin complex 1 (mTORC1) activation although the direct relationship remains unclear. Previous studies in various cell types have used high insulin concentrations to determine the role of insulin on mTORC1 signaling and AAT mRNA abundance. However, this approach may limit applicability to human physiology. Therefore, we sought to determine the effect of insulin on mTORC1 signaling and whether lower insulin concentrations stimulate AAT mRNA abundance in muscle cells. We hypothesized that lower insulin concentrations would increase mRNA abundance of select AAT via an mTORC1-dependent mechanism in C2C12 myotubes. Insulin (0.5 nmol/L) significantly increased phosphorylation of the mTORC1 downstream effectors p70 ribosomal protein S6 kinase 1 (S6K1) and ribosomal protein S6 (S6). A low rapamycin dose (2.5 nmol/L) significantly reduced the insulin-(0.5 nmol/L) stimulated S6K1 and S6 phosphorylation. A high rapamycin dose (50 nmol/L) further reduced the insulin-(0.5 nmol/L) stimulated phosphorylation of S6K1 and S6. Insulin (0.5 nmol/L) increased mRNA abundance of SLC38A2/SNAT2 (P ≤ 0.043) and SLC7A5/LAT1 (P ≤ 0.021) at 240 min and SLC36A1/PAT1 (P = 0.039) at 30 min. High rapamycin prevented an increase in SLC38A2/SNAT2 (P = 0.075) and SLC36A1/PAT1 (P ≥ 0.06) mRNA abundance whereas both rapamycin doses prevented an increase in SLC7A5/LAT1 (P ≥ 0.902) mRNA abundance. We conclude that a low insulin concentration increases SLC7A5/LAT1 mRNA abundance in an mTORC1-dependent manner in skeletal muscle cells.
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Affiliation(s)
- Dillon K Walker
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas
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Yamamoto K, Gandin V, Sasaki M, McCracken S, Li W, Silvester J, Elia A, Wang F, Wakutani Y, Alexandrova R, Oo Y, Mullen PJ, Inoue S, Itsumi M, Lapin V, Haight J, Wakeham A, Shahinian A, Ikura M, Topisirovic I, Sonenberg N, Mak T. Largen: A Molecular Regulator of Mammalian Cell Size Control. Mol Cell 2014; 53:904-15. [DOI: 10.1016/j.molcel.2014.02.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 11/26/2013] [Accepted: 02/13/2014] [Indexed: 12/31/2022]
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Schlattner U, Tokarska-Schlattner M, Rousseau D, Boissan M, Mannella C, Epand R, Lacombe ML. Mitochondrial cardiolipin/phospholipid trafficking: the role of membrane contact site complexes and lipid transfer proteins. Chem Phys Lipids 2013; 179:32-41. [PMID: 24373850 DOI: 10.1016/j.chemphyslip.2013.12.008] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/17/2013] [Accepted: 12/19/2013] [Indexed: 11/18/2022]
Abstract
Historically, cellular trafficking of lipids has received much less attention than protein trafficking, mostly because its biological importance was underestimated, involved sorting and translocation mechanisms were not known, and analytical tools were limiting. This has changed during the last decade, and we discuss here some progress made in respect to mitochondria and the trafficking of phospholipids, in particular cardiolipin. Different membrane contact site or junction complexes and putative lipid transfer proteins for intra- and intermembrane lipid translocation have been described, involving mitochondrial inner and outer membrane, and the adjacent membranes of the endoplasmic reticulum. An image emerges how cardiolipin precursors, remodeling intermediates, mature cardiolipin and its oxidation products could migrate between membranes, and how this trafficking is involved in cardiolipin biosynthesis and cell signaling events. Particular emphasis in this review is given to mitochondrial nucleoside diphosphate kinase D and mitochondrial creatine kinases, which emerge to have roles in both, membrane junction formation and lipid transfer.
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Affiliation(s)
- Uwe Schlattner
- Univ. Grenoble-Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA) and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France.
| | - Malgorzata Tokarska-Schlattner
- Univ. Grenoble-Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA) and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France
| | - Denis Rousseau
- Univ. Grenoble-Alpes, Laboratory of Fundamental and Applied Bioenergetics (LBFA) and SFR Environmental and Systems Biology (BEeSy), Grenoble, France; Inserm, U1055, Grenoble, France
| | - Mathieu Boissan
- UPMC Université Paris 06, Paris, France; Inserm, UMRS938, Paris, France; Hôpital Tenon, AP-HP, Service de Biochimie et Hormonologie, Paris, France
| | - Carmen Mannella
- Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Richard Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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Affiliation(s)
- J. William O. Ballard
- School of Biotechnology and Biomolecular Sciences; University of New South Wales; Sydney New South Wales 2052 Australia
| | - Nicolas Pichaud
- School of Biotechnology and Biomolecular Sciences; University of New South Wales; Sydney New South Wales 2052 Australia
- Laboratoire de Biologie Intégrative; Département de Biologie, Chimie et Géographie; Université du Québec à Rimouski; Rimouski Quebec Canada
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PDK1 controls upstream PI3K expression and PIP3 generation. Oncogene 2013; 33:3043-53. [PMID: 23893244 DOI: 10.1038/onc.2013.266] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 04/30/2013] [Accepted: 05/20/2013] [Indexed: 12/17/2022]
Abstract
The PI3K/PDK1/Akt signaling axis is centrally involved in cellular homeostasis and controls cell growth and proliferation. Due to its key function as regulator of cell survival and metabolism, the dysregulation of this pathway is manifested in several human pathologies including cancers and immunological diseases. Thus, current therapeutic strategies target the components of this signaling cascade. In recent years, numerous feedback loops have been identified that attenuate PI3K/PDK1/Akt-dependent signaling. Here, we report the identification of an additional level of feedback regulation that depends on the negative transcriptional control of phosphatidylinositol 3-kinase (PI3K) class IA subunits. Genetic deletion of 3-phosphoinositide-dependent protein kinase 1 (PDK1) or the pharmacological inhibition of its downstream effectors, that is, Akt and mammalian target of rapamycin (mTOR), relieves this suppression and leads to the upregulation of PI3K subunits, resulting in enhanced generation of phosphatidylinositol-3,4,5-trisphosphate (PIP3). Apparently, this transcriptional induction is mediated by the concerted action of different transcription factor families, including the transcription factors cAMP-responsive element-binding protein and forkhead box O. Collectively, we propose that PDK1 functions as a cellular sensor that balances basal PIP3 generation at levels sufficient for survival but below a threshold being harmful to the cell. Our study suggests that the efficiency of therapies targeting the aberrantly activated PI3K/PDK1/Akt pathway might be increased by the parallel blockade of feedback circuits.
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Derecka K, Blythe MJ, Malla S, Genereux DP, Guffanti A, Pavan P, Moles A, Snart C, Ryder T, Ortori CA, Barrett DA, Schuster E, Stöger R. Transient exposure to low levels of insecticide affects metabolic networks of honeybee larvae. PLoS One 2013; 8:e68191. [PMID: 23844170 PMCID: PMC3699529 DOI: 10.1371/journal.pone.0068191] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 05/27/2013] [Indexed: 01/21/2023] Open
Abstract
The survival of a species depends on its capacity to adjust to changing environmental conditions, and new stressors. Such new, anthropogenic stressors include the neonicotinoid class of crop-protecting agents, which have been implicated in the population declines of pollinating insects, including honeybees (Apis mellifera). The low-dose effects of these compounds on larval development and physiological responses have remained largely unknown. Over a period of 15 days, we provided syrup tainted with low levels (2 µg/L(-1)) of the neonicotinoid insecticide imidacloprid to beehives located in the field. We measured transcript levels by RNA sequencing and established lipid profiles using liquid chromatography coupled with mass spectrometry from worker-bee larvae of imidacloprid-exposed (IE) and unexposed, control (C) hives. Within a catalogue of 300 differentially expressed transcripts in larvae from IE hives, we detect significant enrichment of genes functioning in lipid-carbohydrate-mitochondrial metabolic networks. Myc-involved transcriptional response to exposure of this neonicotinoid is indicated by overrepresentation of E-box elements in the promoter regions of genes with altered expression. RNA levels for a cluster of genes encoding detoxifying P450 enzymes are elevated, with coordinated downregulation of genes in glycolytic and sugar-metabolising pathways. Expression of the environmentally responsive Hsp90 gene is also reduced, suggesting diminished buffering and stability of the developmental program. The multifaceted, physiological response described here may be of importance to our general understanding of pollinator health. Muscles, for instance, work at high glycolytic rates and flight performance could be impacted should low levels of this evolutionarily novel stressor likewise induce downregulation of energy metabolising genes in adult pollinators.
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Affiliation(s)
- Kamila Derecka
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, United Kingdom
| | - Martin J. Blythe
- Deep Seq, Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - Sunir Malla
- Deep Seq, Centre for Genetics and Genomics, University of Nottingham, Nottingham, United Kingdom
| | - Diane P. Genereux
- Biology Department, Westfield State University, Westfield, Massachusetts, United States of America
| | | | | | | | - Charles Snart
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, United Kingdom
| | | | - Catharine A. Ortori
- Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - David A. Barrett
- Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - Eugene Schuster
- Institute of Healthy Ageing, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Reinhard Stöger
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire, United Kingdom
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Zou D, Coudron TA, Liu C, Zhang L, Wang M, Chen H. Nutrigenomics in Arma chinensis: transcriptome analysis of Arma chinensis fed on artificial diet and Chinese oak silk moth Antheraea pernyi pupae. PLoS One 2013; 8:e60881. [PMID: 23593338 PMCID: PMC3623872 DOI: 10.1371/journal.pone.0060881] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 03/04/2013] [Indexed: 12/20/2022] Open
Abstract
Background The insect predator, Arma chinensis, is capable of effectively controlling many pests, such as Colorado potato beetle, cotton bollworm, and mirid bugs. Our previous study demonstrated several life history parameters were diminished for A. chinensis reared on an artificial diet compared to a natural food source like the Chinese oak silk moth pupae. The molecular mechanisms underlying the nutritive impact of the artificial diet on A. chinensis health are unclear. So we utilized transcriptome information to better understand the impact of the artificial diet on A. chinensis at the molecular level. Methodology/Principal Findings Illumina HiSeq2000 was used to sequence 4.79 and 4.70 Gb of the transcriptome from pupae-fed and artificial diet-fed A. chinensis libraries, respectively, and a de novo transcriptome assembly was performed (Trinity short read assembler). This resulted in 112,029 and 98,724 contigs, clustered into 54,083 and 54,169 unigenes for pupae-fed and diet-fed A. chinensis, respectively. Unigenes from each sample’s assembly underwent sequence splicing and redundancy removal to acquire non-redundant unigenes. We obtained 55,189 unigenes of A. chinensis, including 12,046 distinct clusters and 43,143 distinct singletons. Unigene sequences were aligned by BLASTx to nr, Swiss-Prot, KEGG and COG (E-value <10−5), and further aligned by BLASTn to nt (E-value <10−5), retrieving proteins of highest sequence similarity with the given unigenes along with their protein functional annotations. Totally, 22,964, 7,898, 18,069, 15,416, 8,066 and 5,341 unigenes were annotated in nr, nt, Swiss-Prot, KEGG, COG and GO, respectively. We compared gene expression variations and found thousands of genes were differentially expressed between pupae-fed and diet-fed A. chinensis. Conclusions/Significance Our study provides abundant genomic data and offers comprehensive sequence information for studying A. chinensis. Additionally, the physiological roles of the differentially expressed genes enable us to predict effects of some dietary ingredients and subsequently propose formulation improvements to artificial diets.
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Affiliation(s)
- Deyu Zou
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Sino-American Biological Control Laboratory, USDA-Agricultural Research Service, Beijing, China
| | - Thomas A. Coudron
- Biological Control of Insects Research Laboratory, USDA-Agricultural Research Service, Columbia, Missouri, United States of America
| | - Chenxi Liu
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Sino-American Biological Control Laboratory, USDA-Agricultural Research Service, Beijing, China
| | - Lisheng Zhang
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Sino-American Biological Control Laboratory, USDA-Agricultural Research Service, Beijing, China
| | - Mengqing Wang
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Sino-American Biological Control Laboratory, USDA-Agricultural Research Service, Beijing, China
| | - Hongyin Chen
- Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Sino-American Biological Control Laboratory, USDA-Agricultural Research Service, Beijing, China
- * E-mail:
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Havula E, Teesalu M, Hyötyläinen T, Seppälä H, Hasygar K, Auvinen P, Orešič M, Sandmann T, Hietakangas V. Mondo/ChREBP-Mlx-regulated transcriptional network is essential for dietary sugar tolerance in Drosophila. PLoS Genet 2013; 9:e1003438. [PMID: 23593032 PMCID: PMC3616910 DOI: 10.1371/journal.pgen.1003438] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 02/25/2013] [Indexed: 11/23/2022] Open
Abstract
Sugars are important nutrients for many animals, but are also proposed to contribute to overnutrition-derived metabolic diseases in humans. Understanding the genetic factors governing dietary sugar tolerance therefore has profound biological and medical significance. Paralogous Mondo transcription factors ChREBP and MondoA, with their common binding partner Mlx, are key sensors of intracellular glucose flux in mammals. Here we report analysis of the in vivo function of Drosophila melanogaster Mlx and its binding partner Mondo (ChREBP) in respect to tolerance to dietary sugars. Larvae lacking mlx or having reduced mondo expression show strikingly reduced survival on a diet with moderate or high levels of sucrose, glucose, and fructose. mlx null mutants display widespread changes in lipid and phospholipid profiles, signs of amino acid catabolism, as well as strongly elevated circulating glucose levels. Systematic loss-of-function analysis of Mlx target genes reveals that circulating glucose levels and dietary sugar tolerance can be genetically uncoupled: Krüppel-like transcription factor Cabut and carbonyl detoxifying enzyme Aldehyde dehydrogenase type III are essential for dietary sugar tolerance, but display no influence on circulating glucose levels. On the other hand, Phosphofructokinase 2, a regulator of the glycolysis pathway, is needed for both dietary sugar tolerance and maintenance of circulating glucose homeostasis. Furthermore, we show evidence that fatty acid synthesis, which is a highly conserved Mondo-Mlx-regulated process, does not promote dietary sugar tolerance. In contrast, survival of larvae with reduced fatty acid synthase expression is sugar-dependent. Our data demonstrate that the transcriptional network regulated by Mondo-Mlx is a critical determinant of the healthful dietary spectrum allowing Drosophila to exploit sugar-rich nutrient sources. Diet displays extreme natural variation between animal species, which range from highly specialized carnivores, herbivores, and nectarivores to flexible dietary generalists. Humans are not identical in this respect either, but the genetic background likely defines the framework for a healthy diet. However, we understand poorly the genetic factors that define the spectrum of healthy diet for a given species or individual. Here we have explored the genetic basis of dietary sugar tolerance of Drosophila melanogaster. D. melanogaster is a generalist fruit breeder that feeds on micro-organisms on decaying fruits and vegetables with varying sugar content. However, mutants lacking the conserved Mondo-Mlx transcription factor complex display striking intolerance towards dietary sucrose, glucose, or fructose. This is manifested in the larvae by the inability to grow and pupate on sugar-rich food, including red grape, which belongs to the normal diet of wild D. melanogaster. Larvae lacking Mondo-Mlx show widespread metabolic imbalance, including highly elevated circulating glucose. Genome-wide gene expression analysis combined with systematic loss-of-function screening of Mlx targets reveal that the genetic network providing sugar tolerance includes a secondary transcriptional effector as well as regulators of glycolysis and detoxification of reactive metabolites.
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Affiliation(s)
- Essi Havula
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Mari Teesalu
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | | | - Heini Seppälä
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Kiran Hasygar
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Petri Auvinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Matej Orešič
- VTT Technical Research Centre of Finland, Espoo, Finland
| | | | - Ville Hietakangas
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Department of Biosciences, University of Helsinki, Helsinki, Finland
- * E-mail:
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63
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Schenone M, Dančík V, Wagner BK, Clemons PA. Target identification and mechanism of action in chemical biology and drug discovery. Nat Chem Biol 2013; 9:232-40. [PMID: 23508189 PMCID: PMC5543995 DOI: 10.1038/nchembio.1199] [Citation(s) in RCA: 628] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 01/28/2013] [Indexed: 12/12/2022]
Abstract
Target-identification and mechanism-of-action studies have important roles in small-molecule probe and drug discovery. Biological and technological advances have resulted in the increasing use of cell-based assays to discover new biologically active small molecules. Such studies allow small-molecule action to be tested in a more disease-relevant setting at the outset, but they require follow-up studies to determine the precise protein target or targets responsible for the observed phenotype. Target identification can be approached by direct biochemical methods, genetic interactions or computational inference. In many cases, however, combinations of approaches may be required to fully characterize on-target and off-target effects and to understand mechanisms of small-molecule action.
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Affiliation(s)
- Monica Schenone
- Proteomics Platform, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| | - Vlado Dančík
- Chemical Biology Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| | - Bridget K Wagner
- Chemical Biology Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
| | - Paul A Clemons
- Chemical Biology Program, Broad Institute of Harvard and MIT, Cambridge, Massachusetts, USA
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64
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mTOR: a link from the extracellular milieu to transcriptional regulation of oligodendrocyte development. ASN Neuro 2013; 5:e00108. [PMID: 23421405 PMCID: PMC3601842 DOI: 10.1042/an20120092] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Oligodendrocyte development is controlled by numerous extracellular signals that regulate a series of transcription factors that promote the differentiation of oligodendrocyte progenitor cells to myelinating cells in the central nervous system. A major element of this regulatory system that has only recently been studied is the intracellular signalling from surface receptors to transcription factors to down-regulate inhibitors and up-regulate inducers of oligodendrocyte differentiation and myelination. The current review focuses on one such pathway: the mTOR (mammalian target of rapamycin) pathway, which integrates signals in many cell systems and induces cell responses including cell proliferation and cell differentiation. This review describes the known functions of mTOR as they relate to oligodendrocyte development, and its recently discovered impact on oligodendrocyte differentiation and myelination. A potential model for its role in oligodendrocyte development is proposed.
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65
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Natarajan R, Trivedi-Vyas D, Wairkar YP. Tuberous sclerosis complex regulates Drosophila neuromuscular junction growth via the TORC2/Akt pathway. Hum Mol Genet 2013; 22:2010-23. [PMID: 23393158 DOI: 10.1093/hmg/ddt053] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mutations in the tuberous sclerosis complex (TSC) are associated with various forms of neurodevelopmental disorders, including autism and epilepsy. The heterodimeric TSC complex, consisting of Tsc1 and Tsc2 proteins, regulates the activity of the TOR (target of rapamycin) complex via Rheb, a small GTPase. TOR, an atypical serine/threonine kinase, forms two distinct complexes TORC1 and TORC2. Raptor and Rictor serve as specific functional components of TORC1 and TORC2, respectively. Previous studies have identified Tsc1 as a regulator of hippocampal neuronal morphology and function via the TOR pathway, but it is unclear whether this is mediated via TORC1 or TORC2. In a genetic screen for aberrant synaptic growth at the neuromuscular junctions (NMJs) in Drosophila, we identified that Tsc2 mutants showed increased synaptic growth. Increased synaptic growth was also observed in rictor mutants, while raptor knockdown did not phenocopy the TSC mutant phenotype, suggesting that a novel role exists for TORC2 in regulating synapse growth. Furthermore, Tsc2 mutants showed a dramatic decrease in the levels of phosphorylated Akt, and interestingly, Akt mutants phenocopied Tsc2 mutants, leading to the hypothesis that Tsc2 and Akt might work via the same genetic pathway to regulate synapse growth. Indeed, transheterozygous analysis of Tsc2 and Akt mutants confirmed this hypothesis. Finally, our data also suggest that while overexpression of rheb results in aberrant synaptic overgrowth, the overgrowth might be independent of TORC2. Thus, we propose that at the Drosophila NMJ, TSC regulates synaptic growth via the TORC2-Akt pathway.
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Affiliation(s)
- Rajalaxmi Natarajan
- Department of Neurology, and George and Cynthia Mitchell Center for Neurodegenerative Diseases, University ofTexas Medical Branch, 301 University Blvd., Galveston, TX 77555, USA
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66
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Malik AR, Urbanska M, Gozdz A, Swiech LJ, Nagalski A, Perycz M, Blazejczyk M, Jaworski J. Cyr61, a matricellular protein, is needed for dendritic arborization of hippocampal neurons. J Biol Chem 2013; 288:8544-8559. [PMID: 23362279 DOI: 10.1074/jbc.m112.411629] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The shape of the dendritic arbor is one of the criteria of neuron classification and reflects functional specialization of particular classes of neurons. The development of a proper dendritic branching pattern strongly relies on interactions between the extracellular environment and intracellular processes responsible for dendrite growth and stability. We previously showed that mammalian target of rapamycin (mTOR) kinase is crucial for this process. In this work, we performed a screen for modifiers of dendritic growth in hippocampal neurons, the expression of which is potentially regulated by mTOR. As a result, we identified Cyr61, an angiogenic factor with unknown neuronal function, as a novel regulator of dendritic growth, which controls dendritic growth in a β1-integrin-dependent manner.
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Affiliation(s)
- Anna R Malik
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Malgorzata Urbanska
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Agata Gozdz
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Lukasz J Swiech
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Andrzej Nagalski
- Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Malgorzata Perycz
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Magdalena Blazejczyk
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
| | - Jacek Jaworski
- Laboratory of Molecular and Cellular Neurobiology, 4 Ks. Trojdena St., 02-109 Warsaw, Poland.
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Chauvin C, Koka V, Nouschi A, Mieulet V, Hoareau-Aveilla C, Dreazen A, Cagnard N, Carpentier W, Kiss T, Meyuhas O, Pende M. Ribosomal protein S6 kinase activity controls the ribosome biogenesis transcriptional program. Oncogene 2013; 33:474-83. [PMID: 23318442 DOI: 10.1038/onc.2012.606] [Citation(s) in RCA: 200] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/21/2012] [Accepted: 11/04/2012] [Indexed: 12/22/2022]
Abstract
S6 kinases (S6Ks) are mechanistic target of rapamycin substrates that participate in cell growth control. S6Ks phosphorylate ribosomal protein S6 (rpS6) and additional proteins involved in the translational machinery, although the functional roles of these modifications remain elusive. Here we analyze the S6K-dependent transcriptional and translational regulation of gene expression by comparing whole-genome microarray of total and polysomal mouse liver RNA after feeding. We show that tissue lacking S6Ks 1 and 2 (S6K1 and S6K2), displays a defect in the ribosome biogenesis (RiBi) transcriptional program after feeding. Over 75% of RiBi factors are controlled by S6K, including Nop56, Nop14, Gar1, Rrp9, Rrp15, Rrp12 and Pwp2 nucleolar proteins. Importantly, the reduced activity of RiBi transcriptional promoters in S6K1;S6K2(-/-) cells is also observed in rpS6 knock-in mutants that cannot be phosphorylated. As ribosomal protein synthesis is not affected by these mutations, our data reveal a distinct and specific aspect of RiBi under the control of rpS6 kinase activity, that is, the RiBi transcriptional program.
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Affiliation(s)
- C Chauvin
- 1] INSERM, U845, Paris, France [2] Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
| | - V Koka
- 1] INSERM, U845, Paris, France [2] Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
| | - A Nouschi
- 1] INSERM, U845, Paris, France [2] Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
| | - V Mieulet
- 1] INSERM, U845, Paris, France [2] Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
| | - C Hoareau-Aveilla
- Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse-UPS and Centre National de La Recherche Scientifique, Toulouse, France
| | - A Dreazen
- Department of Biochemistry and Molecular Biology, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - N Cagnard
- Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
| | - W Carpentier
- Plateforme Post-Génomique Pitié-Salpétrière, Groupe Hospitalier Pitié-Salpétrière, Université Pierre et Marie Curie, Paris, France
| | - T Kiss
- Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse-UPS and Centre National de La Recherche Scientifique, Toulouse, France
| | - O Meyuhas
- Department of Biochemistry and Molecular Biology, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - M Pende
- 1] INSERM, U845, Paris, France [2] Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, UMRS-845, Paris, France
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68
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Malik AR, Urbanska M, Macias M, Skalecka A, Jaworski J. Beyond control of protein translation: what we have learned about the non-canonical regulation and function of mammalian target of rapamycin (mTOR). BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1834:1434-48. [PMID: 23277194 DOI: 10.1016/j.bbapap.2012.12.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Accepted: 12/15/2012] [Indexed: 12/19/2022]
Abstract
Mammalian target of rapamycin (mTOR) is a serine-threonine kinase involved in almost every aspect of mammalian cell function. This kinase was initially believed to control protein translation in response to amino acids and trophic factors, and this function has become a canonical role for mTOR. However, mTOR can form two separate protein complexes (mTORCs). Recent advances clearly demonstrate that both mTORCs can respond to various stimuli and change myriad cellular processes. Therefore, our current view of the cellular roles of TORCs has rapidly expanded and cannot be fully explained without appreciating recent findings about the new modes of mTOR regulation and identification of non-canonical effectors of mTOR that contribute to transcription, cytoskeleton dynamics, and membrane trafficking. This review discusses the molecular details of these newly discovered non-canonical functions that allow mTORCs to control the cellular environment at multiple levels. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).
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Affiliation(s)
- Anna R Malik
- Laboratory of Molecular and Cellular Neurobiology, International Institute of Molecular and Cell Biology in Warsaw, 4 Ks. Trojdena St., 02-109 Warsaw, Poland
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69
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Konarzewski M, Książek A. Determinants of intra-specific variation in basal metabolic rate. J Comp Physiol B 2012; 183:27-41. [PMID: 22847501 PMCID: PMC3536993 DOI: 10.1007/s00360-012-0698-z] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 06/10/2012] [Accepted: 07/13/2012] [Indexed: 12/02/2022]
Abstract
Basal metabolic rate (BMR) provides a widely accepted benchmark of metabolic expenditure for endotherms under laboratory and natural conditions. While most studies examining BMR have concentrated on inter-specific variation, relatively less attention has been paid to the determinants of within-species variation. Even fewer studies have analysed the determinants of within-species BMR variation corrected for the strong influence of body mass by appropriate means (e.g. ANCOVA). Here, we review recent advancements in studies on the quantitative genetics of BMR and organ mass variation, along with their molecular genetics. Next, we decompose BMR variation at the organ, tissue and molecular level. We conclude that within-species variation in BMR and its components have a clear genetic signature, and are functionally linked to key metabolic process at all levels of biological organization. We highlight the need to integrate molecular genetics with conventional metabolic field studies to reveal the adaptive significance of metabolic variation. Since comparing gene expressions inter-specifically is problematic, within-species studies are more likely to inform us about the genetic underpinnings of BMR. We also urge for better integration of animal and medical research on BMR; the latter is quickly advancing thanks to the application of imaging technologies and ‘omics’ studies. We also suggest that much insight on the biochemical and molecular underpinnings of BMR variation can be gained from integrating studies on the mammalian target of rapamycin (mTOR), which appears to be the major regulatory pathway influencing the key molecular components of BMR.
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70
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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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Abstract
The determination of final organ size is a highly coordinated and complex process that relies on the precise regulation of cell number and/or cell size. Perturbation of organ size control contributes to many human diseases, including hypertrophy, degenerative diseases, and cancer. Hippo and TOR are among the key signaling pathways involved in the regulation of organ size through their respective functions in the regulation of cell number and cell size. Here, we review the general mechanisms that regulate organ growth, describe how Hippo and TOR control key aspects of growth, and discuss recent findings that highlight a possible coordination between Hippo and TOR in organ size regulation.
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72
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Belacortu Y, Weiss R, Kadener S, Paricio N. Transcriptional activity and nuclear localization of Cabut, the Drosophila ortholog of vertebrate TGF-β-inducible early-response gene (TIEG) proteins. PLoS One 2012; 7:e32004. [PMID: 22359651 PMCID: PMC3281117 DOI: 10.1371/journal.pone.0032004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 01/17/2012] [Indexed: 01/26/2023] Open
Abstract
Background Cabut (Cbt) is a C2H2-class zinc finger transcription factor involved in embryonic dorsal closure, epithelial regeneration and other developmental processes in Drosophila melanogaster. Cbt orthologs have been identified in other Drosophila species and insects as well as in vertebrates. Indeed, Cbt is the Drosophila ortholog of the group of vertebrate proteins encoded by the TGF-ß-inducible early-response genes (TIEGs), which belong to Sp1-like/Krüppel-like family of transcription factors. Several functional domains involved in transcriptional control and subcellular localization have been identified in the vertebrate TIEGs. However, little is known of whether these domains and functions are also conserved in the Cbt protein. Methodology/Principal Findings To determine the transcriptional regulatory activity of the Drosophila Cbt protein, we performed Gal4-based luciferase assays in S2 cells and showed that Cbt is a transcriptional repressor and able to regulate its own expression. Truncated forms of Cbt were then generated to identify its functional domains. This analysis revealed a sequence similar to the mSin3A-interacting repressor domain found in vertebrate TIEGs, although located in a different part of the Cbt protein. Using β-Galactosidase and eGFP fusion proteins, we also showed that Cbt contains the bipartite nuclear localization signal (NLS) previously identified in TIEG proteins, although it is non-functional in insect cells. Instead, a monopartite NLS, located at the amino terminus of the protein and conserved across insects, is functional in Drosophila S2 and Spodoptera exigua Sec301 cells. Last but not least, genetic interaction and immunohistochemical assays suggested that Cbt nuclear import is mediated by Importin-α2. Conclusions/Significance Our results constitute the first characterization of the molecular mechanisms of Cbt-mediated transcriptional control as well as of Cbt nuclear import, and demonstrate the existence of similarities and differences in both aspects of Cbt function between the insect and the vertebrate TIEG proteins.
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Affiliation(s)
- Yaiza Belacortu
- Departamento de Genética, Facultad CC Biológicas, Universidad de Valencia, Burjasot, Spain
| | - Ron Weiss
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat-Ram, Jerusalem, Israel
| | - Sebastian Kadener
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat-Ram, Jerusalem, Israel
| | - Nuria Paricio
- Departamento de Genética, Facultad CC Biológicas, Universidad de Valencia, Burjasot, Spain
- * E-mail:
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73
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Glatter T, Schittenhelm RB, Rinner O, Roguska K, Wepf A, Jünger MA, Köhler K, Jevtov I, Choi H, Schmidt A, Nesvizhskii AI, Stocker H, Hafen E, Aebersold R, Gstaiger M. Modularity and hormone sensitivity of the Drosophila melanogaster insulin receptor/target of rapamycin interaction proteome. Mol Syst Biol 2011; 7:547. [PMID: 22068330 PMCID: PMC3261712 DOI: 10.1038/msb.2011.79] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 09/09/2011] [Accepted: 09/29/2011] [Indexed: 12/24/2022] Open
Abstract
First systematic analysis of the evolutionary conserved InR/TOR pathway interaction proteome in Drosophila. Quantitative mass spectrometry revealed that 22% of identified protein interactions are regulated by the growth hormone insulin affecting membrane proximal as well as intracellular signaling complexes. Systematic RNA interference linked a significant fraction of network components to the control of dTOR kinase activity. Combined biochemical and genetic data suggest dTTT, a dTOR-containing complex required for cell growth control by dTORC1 and dTORC2 in vivo.
Cellular growth is a fundamental process that requires constant adaptations to changing environmental conditions, like growth factor and nutrient availability, energy levels and more. Over the years, the insulin receptor/target of rapamycin pathway (InR/TOR) emerged as a key signaling system for the control of metazoan cell growth. Genetic screens carried out in the fruit fly Drosophila melanogaster identified key InR/TOR pathway components and their relationships. Phenotypes such as altered cell growth are likely to emerge from perturbed dynamic networks containing InR/TOR pathway components, which stably or transiently interact with other cellular proteins to form complexes and networks thereof. Systematic studies on the topology and dynamics of protein interaction networks become therefore highly relevant to gain systems level understanding of deregulated cell growth. Despite much progress in genetic analysis only few systematic protein interaction studies have been reported for Drosophila, which in most cases lack quantitative information representing the dynamic nature of such networks. Here, we present the first quantitative affinity purification mass spectrometry (AP–MS/MS) analysis on the evolutionary conserved InR/TOR signaling network in Drosophila. Systematic RNAi-based functional analysis of identified network components revealed key components linked to the regulation of the central effector kinase dTOR. This includes also dTTT, a novel dTOR-containing complex required for the control of dTORC1 and dTORC2 in vivo. For systematic AP–MS analysis, we generated Drosophila Kc167 cell lines inducibly expressing affinity-tagged bait proteins previously linked to InR/TOR signaling. Bait expressing Kc167 cell lines were harvested before and after insulin stimulation for subsequent affinity purification. Following LC–MS/MS analysis and probabilistic data filtering using SAINT (Choi et al, 2010), we generated a quantitative network model from 97 high confidence protein–protein interactions and 58 network components (Figure 2). The presented network displayed a high degree of orthologous interactions conserved also in human cells and identified a number of novel molecular interactions with InR/TOR signaling components for future hypothesis driven analysis. To measure insulin-induced changes within the InR/TOR interaction proteome, we applied a recently introduced label-free quantitative MS approach (Rinner et al, 2007). The obtained quantitative data suggest that 22% of all interactions in the network are regulated by insulin. Major changes could be observed within the membrane proximal InR/chico/PI3K signaling complexes, and also in 14-3-3 protein containing signaling complexes and dTORC1, a complex that contains besides dTOR all major orthologous proteins found also in human mTORC1 including the two dTORC1 substrates d4E-BP (Thor) and S6 Kinase (S6K). Insulin triggered both, dissociation and association of dTORC1 proteins. Among the proteins that showed enhanced binding to dTORC1 upon insulin stimulation we found Unkempt, a RING-finger protein with a proposed role in ubiquitin-mediated protein degradation (Lores et al, 2010). Besides dTORC1 our systematic AP–MS analysis also revealed the presence of dTORC2, the second major TOR complex in Drosophila. dTORC2 contains the Drosophila orthologous of human mTORC2 proteins, but in contrast to dTORC1 was not affected upon insulin stimulation. Interestingly, we also found a specific set of proteins that were not linked to the canonical TOR complexes TORC1 and TORC2 in dTOR purifications. These include LqfR (liquid facets related), Pontin, Reptin, Spaghetti and the gene product of CG16908. We found the same set of proteins when we used CG16908 as a bait, suggesting complex formation among the identified proteins. None of the dTORC1/2 components besides dTOR was identified in CG16908 purifications, indicating that these proteins form dTOR complexes distinct from dTORC1 and dTORC2. Based on known interaction information from other species and data obtained from this study we refer to this complex as dTTT (DrosophilaTOR, TELO2, TTI1) (Horejsi et al, 2010; [18]Hurov et al, 2010; [20]Kaizuka et al, 2010). A directed quantitative MS analysis of dTOR complex components suggests that dTORC1 is the most abundant dTOR complex we identified in Kc167 cells. We next studied the potential roles of the identified network components for controlling the activity of the dInR/TOR pathway using systematic RNAi depletion and quantitative western blotting to measure the changes in abundance of phosphorylated substrates of dTORC1 (Thor/d4E-BP, dS6K) and dTORC2 (dPKB) in RNAi-treated cells (Figure 5). Overall, we could identify 16 proteins (out of 58) whose depletion caused an at least 50% increase or decrease in the levels of phosphorylated d4E-BP, S6K and/or PKB compared with control GFP RNAi. Besides established pathway components, we found several novel regulators within the dInR/TOR interaction network. For example, RNAi against the novel insulin-regulated dTORC1 component Unkempt resulted in enhanced phosphorylation of the dTORC1 substrate d4E-BP, which suggests a negative role for Unkempt on dTORC1 activity. In contrast, depletion of CG16908 and LqfR caused hypo-phosphorylation of all dTOR substrates similar to dTOR itself, suggesting a positive role for the dTTT complex on dTOR activity. Subsequently, we tested whether dTTT components also plays a role in dTOR-mediated cell growth in vivo. Depletion of both dTTT components, CG16908 and LqfR, in the Drosophila eye resulted in a substantial decrease in eye size. Likewise, FLP-FRT-mediated mitotic recombination resulted in CG16908 and LqfR mutant clones with a similar reduced growth phenotype as observed in dTOR mutant clones. Hence, the combined biochemical and genetic analysis revealed dTTT as a dTOR-containing complex required for the activity of both dTORC1 and dTORC2 and thus plays a critical role in controlling cell growth. Taken together, these results illustrate how a systematic quantitative AP–MS approach when combined with systematic functional analysis in Drosophila can reveal novel insights into the dynamic organization of regulatory networks for cell growth control in metazoans. Using quantitative mass spectrometry, this study reports how insulin affects the modularity of the interaction proteome of the Drosophila InR/TOR pathway, an evolutionary conserved signaling system for the control of metazoan cell growth. Systematic functional analysis linked a significant number of identified network components to the control of dTOR activity and revealed dTTT, a dTOR complex required for in vivo cell growth control by dTORC1 and dTORC2. Genetic analysis in Drosophila melanogaster has been widely used to identify a system of genes that control cell growth in response to insulin and nutrients. Many of these genes encode components of the insulin receptor/target of rapamycin (InR/TOR) pathway. However, the biochemical context of this regulatory system is still poorly characterized in Drosophila. Here, we present the first quantitative study that systematically characterizes the modularity and hormone sensitivity of the interaction proteome underlying growth control by the dInR/TOR pathway. Applying quantitative affinity purification and mass spectrometry, we identified 97 high confidence protein interactions among 58 network components. In all, 22% of the detected interactions were regulated by insulin affecting membrane proximal as well as intracellular signaling complexes. Systematic functional analysis linked a subset of network components to the control of dTORC1 and dTORC2 activity. Furthermore, our data suggest the presence of three distinct dTOR kinase complexes, including the evolutionary conserved dTTT complex (Drosophila TOR, TELO2, TTI1). Subsequent genetic studies in flies suggest a role for dTTT in controlling cell growth via a dTORC1- and dTORC2-dependent mechanism.
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Affiliation(s)
- Timo Glatter
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
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Vincenzi B, Napolitano A, D'Onofrio L, Frezza AM, Silletta M, Venditti O, Santini D, Tonini G. Targeted therapy in sarcomas: mammalian target of rapamycin inhibitors from bench to bedside. Expert Opin Investig Drugs 2011; 20:1685-705. [DOI: 10.1517/13543784.2011.628984] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Bruno Vincenzi
- University Campus Bio-Medico, Medical Oncology, via Alvaro del Portillo, 200, Rome, Italy
| | - Andrea Napolitano
- University Campus Bio-Medico, Medical Oncology, via Alvaro del Portillo, 200, Rome, Italy
| | - Loretta D'Onofrio
- University Campus Bio-Medico, Medical Oncology, via Alvaro del Portillo, 200, Rome, Italy
| | - Anna Maria Frezza
- University Campus Biomedico, Via Emilio Longoni 69, 155, Rome, Italy
| | - Marianna Silletta
- University Campus Bio-Medico, Medical Oncology, via Alvaro del Portillo, 200, Rome, Italy
| | - Olga Venditti
- University Campus Bio-Medico, Medical Oncology, via Alvaro del Portillo, 200, Rome, Italy
| | - Daniele Santini
- University Campus Biomedico, Via Emilio Longoni 69, 155, Rome, Italy
| | - Giuseppe Tonini
- University Campus Biomedico, Via Emilio Longoni 69, 155, Rome, Italy
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Russell RC, Fang C, Guan KL. An emerging role for TOR signaling in mammalian tissue and stem cell physiology. Development 2011; 138:3343-56. [PMID: 21791526 DOI: 10.1242/dev.058230] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The mammalian target of rapamycin (mTOR) is a kinase that responds to a myriad of signals, ranging from nutrient availability and energy status, to cellular stressors, oxygen sensors and growth factors. The finely tuned response of mTOR to these stimuli results in alterations to cell metabolism and cell growth. Recent studies of conditional knockouts of mTOR pathway components in mice have affirmed the role of mTOR signaling in energy balance, both at the cell and whole organism levels. Such studies have also highlighted a role for mTOR in stem cell homeostasis and lifespan determination. Here, we discuss the molecular mechanisms of TOR signaling and review recent in vitro and in vivo studies of mTOR tissue-specific activities in mammals.
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Affiliation(s)
- Ryan C Russell
- Department of Pharmacology and Moores Cancer Center, University of California at San Diego, La Jolla, CA 92093-0815, USA.
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Alaux C, Dantec C, Parrinello H, Le Conte Y. Nutrigenomics in honey bees: digital gene expression analysis of pollen's nutritive effects on healthy and varroa-parasitized bees. BMC Genomics 2011; 12:496. [PMID: 21985689 PMCID: PMC3209670 DOI: 10.1186/1471-2164-12-496] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 10/10/2011] [Indexed: 12/30/2022] Open
Abstract
Background Malnutrition is a major factor affecting animal health, resistance to disease and survival. In honey bees (Apis mellifera), pollen, which is the main dietary source of proteins, amino acids and lipids, is essential to adult bee physiological development while reducing their susceptibility to parasites and pathogens. However, the molecular mechanisms underlying pollen's nutritive impact on honey bee health remained to be determined. For that purpose, we investigated the influence of pollen nutrients on the transcriptome of worker bees parasitized by the mite Varroa destructor, known for suppressing immunity and decreasing lifespan. The 4 experimental groups (control bees without a pollen diet, control bees fed with pollen, varroa-parasitized bees without a pollen diet and varroa-parasitized bees fed with pollen) were analyzed by performing a digital gene expression (DGE) analysis on bee abdomens. Results Around 36, 000 unique tags were generated per DGE-tag library, which matched about 8, 000 genes (60% of the genes in the honey bee genome). Comparing the transcriptome of bees fed with pollen and sugar and bees restricted to a sugar diet, we found that pollen activates nutrient-sensing and metabolic pathways. In addition, those nutrients had a positive influence on genes affecting longevity and the production of some antimicrobial peptides. However, varroa parasitism caused the development of viral populations and a decrease in metabolism, specifically by inhibiting protein metabolism essential to bee health. This harmful effect was not reversed by pollen intake. Conclusions The DGE-tag profiling methods used in this study proved to be a powerful means for analyzing transcriptome variation related to nutrient intake in honey bees. Ultimately, with such an approach, applying genomics tools to nutrition research, nutrigenomics promises to offer a better understanding of how nutrition influences body homeostasis and may help reduce the susceptibility of bees to (less virulent) pathogens.
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Affiliation(s)
- Cédric Alaux
- INRA, UMR 406 Abeilles et Environnement, Domaine Saint-Paul, 84914 Avignon, France.
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77
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Graham AM, Munday MD, Kaftanoglu O, Page RE, Amdam GV, Rueppell O. Support for the reproductive ground plan hypothesis of social evolution and major QTL for ovary traits of Africanized worker honey bees (Apis mellifera L.). BMC Evol Biol 2011; 11:95. [PMID: 21489230 PMCID: PMC3100260 DOI: 10.1186/1471-2148-11-95] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 04/13/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The reproductive ground plan hypothesis of social evolution suggests that reproductive controls of a solitary ancestor have been co-opted during social evolution, facilitating the division of labor among social insect workers. Despite substantial empirical support, the generality of this hypothesis is not universally accepted. Thus, we investigated the prediction of particular genes with pleiotropic effects on ovarian traits and social behavior in worker honey bees as a stringent test of the reproductive ground plan hypothesis. We complemented these tests with a comprehensive genome scan for additional quantitative trait loci (QTL) to gain a better understanding of the genetic architecture of the ovary size of honey bee workers, a morphological trait that is significant for understanding social insect caste evolution and general insect biology. RESULTS Back-crossing hybrid European x Africanized honey bee queens to the Africanized parent colony generated two study populations with extraordinarily large worker ovaries. Despite the transgressive ovary phenotypes, several previously mapped QTL for social foraging behavior demonstrated ovary size effects, confirming the prediction of pleiotropic genetic effects on reproductive traits and social behavior. One major QTL for ovary size was detected in each backcross, along with several smaller effects and two QTL for ovary asymmetry. One of the main ovary size QTL coincided with a major QTL for ovary activation, explaining 3/4 of the phenotypic variance, although no simple positive correlation between ovary size and activation was observed. CONCLUSIONS Our results provide strong support for the reproductive ground plan hypothesis of evolution in study populations that are independent of the genetic stocks that originally led to the formulation of this hypothesis. As predicted, worker ovary size is genetically linked to multiple correlated traits of the complex division of labor in worker honey bees, known as the pollen hoarding syndrome. The genetic architecture of worker ovary size presumably consists of a combination of trait-specific loci and general regulators that affect the whole behavioral syndrome and may even play a role in caste determination. Several promising candidate genes in the QTL intervals await further study to clarify their potential role in social insect evolution and the regulation of insect fertility in general.
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Affiliation(s)
- Allie M Graham
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27403, USA
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78
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A comprehensive map of the mTOR signaling network. Mol Syst Biol 2011; 6:453. [PMID: 21179025 PMCID: PMC3018167 DOI: 10.1038/msb.2010.108] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 11/12/2010] [Indexed: 02/07/2023] Open
Abstract
The mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation. mTOR signaling is frequently dysregulated in oncogenic cells, and thus an attractive target for anticancer therapy. Using CellDesigner, a modeling support software for graphical notation, we present herein a comprehensive map of the mTOR signaling network, which includes 964 species connected by 777 reactions. The map complies with both the systems biology markup language (SBML) and graphical notation (SBGN) for computational analysis and graphical representation, respectively. As captured in the mTOR map, we review and discuss our current understanding of the mTOR signaling network and highlight the impact of mTOR feedback and crosstalk regulations on drug-based cancer therapy. This map is available on the Payao platform, a Web 2.0 based community-wide interactive process for creating more accurate and information-rich databases. Thus, this comprehensive map of the mTOR network will serve as a tool to facilitate systems-level study of up-to-date mTOR network components and signaling events toward the discovery of novel regulatory processes and therapeutic strategies for cancer.
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79
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Vemulapalli S, Mita A, Alvarado Y, Sankhala K, Mita M. The emerging role of mammalian target of rapamycin inhibitors in the treatment of sarcomas. Target Oncol 2011; 6:29-39. [PMID: 21533543 DOI: 10.1007/s11523-011-0179-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 04/14/2011] [Indexed: 02/03/2023]
Abstract
The mammalian target of rapamycin (mTOR) is a protein kinase that functions as a key regulator of cell growth, proliferation and differentiation, cell-cycle progression, angiogenesis, protein degradation, and apoptosis. Following activation by a number of oncogenic signals such as growth factors, energy and nutrients, mTOR stimulates several downstream effectors including the 40S ribosomal protein S6 kinase (p70s6k) and the eukaryotic initiation factor 4 E binding protein-1 (4 EBP-1), as well as a complex network of regulatory loops. Activation of the mTOR pathway plays a critical role in the development of many tumor types, including renal cell and breast carcinomas, neuroendocrine tumors, and sarcomas. Bone and soft tissue sarcomas are rare, heterogeneous tumors that are curable by local treatments if diagnosed at early stages; however advanced or metastatic sarcomas are rarely curable and very few drugs are efficacious in this setting. Several disruptions in phosphatidylinositol-3 kinase (PI3K)-Akt-mTOR signaling are associated with malignant transformation or progression in various sarcoma sub-types. The PI3K-Akt-mTOR pathway is therefore an exciting target for therapy of sarcomas, and its blockade represents an opportunity to improve outcomes in this poor-prognosis disease. Early studies with mTOR inhibitors have demonstrated promising antitumor activity in patients with metastatic sarcoma who have failed standard treatments. This article discusses the mTOR signaling pathway and summarizes the clinical experience with mTOR inhibitors in patients with advanced or metastatic sarcoma.
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Affiliation(s)
- Sushma Vemulapalli
- Institute for Drug Development, Cancer Therapy and Research Center at The University of Texas Health Science Center, 7979 Wurzbach Road, Zeller Bldg, 4th floor, San Antonio, TX 78229, USA
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Lindquist RA, Ottina KA, Wheeler DB, Hsu PP, Thoreen CC, Guertin DA, Ali SM, Sengupta S, Shaul YD, Lamprecht MR, Madden KL, Papallo AR, Jones TR, Sabatini DM, Carpenter AE. Genome-scale RNAi on living-cell microarrays identifies novel regulators of Drosophila melanogaster TORC1-S6K pathway signaling. Genome Res 2011; 21:433-46. [PMID: 21239477 DOI: 10.1101/gr.111492.110] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The evolutionarily conserved target of rapamycin complex 1 (TORC1) controls cell growth in response to nutrient availability and growth factors. TORC1 signaling is hyperactive in cancer, and regulators of TORC1 signaling may represent therapeutic targets for human diseases. To identify novel regulators of TORC1 signaling, we performed a genome-scale RNA interference screen on microarrays of Drosophila melanogaster cells expressing human RPS6, a TORC1 effector whose phosphorylated form we detected by immunofluorescence. Our screen revealed that the TORC1-S6K-RPS6 signaling axis is regulated by many subcellular components, including the Class I vesicle coat (COPI), the spliceosome, the proteasome, the nuclear pore, and the translation initiation machinery. Using additional RNAi reagents, we confirmed 70 novel genes as significant on-target regulators of RPS6 phosphorylation, and we characterized them with extensive secondary assays probing various arms of the TORC1 pathways, identifying functional relationships among those genes. We conclude that cell-based microarrays are a useful platform for genome-scale and secondary screening in Drosophila, revealing regulators that may represent drug targets for cancers and other diseases of deregulated TORC1 signaling.
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Affiliation(s)
- Robert A Lindquist
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
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81
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Bülow MH, Aebersold R, Pankratz MJ, Jünger MA. The Drosophila FoxA ortholog Fork head regulates growth and gene expression downstream of Target of rapamycin. PLoS One 2010; 5:e15171. [PMID: 21217822 PMCID: PMC3013099 DOI: 10.1371/journal.pone.0015171] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 10/27/2010] [Indexed: 01/05/2023] Open
Abstract
Forkhead transcription factors of the FoxO subfamily regulate gene expression programs downstream of the insulin signaling network. It is less clear which proteins mediate transcriptional control exerted by Target of rapamycin (TOR) signaling, but recent studies in nematodes suggest a role for FoxA transcription factors downstream of TOR. In this study we present evidence that outlines a similar connection in Drosophila, in which the FoxA protein Fork head (FKH) regulates cellular and organismal size downstream of TOR. We find that ectopic expression and targeted knockdown of FKH in larval tissues elicits different size phenotypes depending on nutrient state and TOR signaling levels. FKH overexpression has a negative effect on growth under fed conditions, and this phenotype is not further exacerbated by inhibition of TOR via rapamycin feeding. Under conditions of starvation or low TOR signaling levels, knockdown of FKH attenuates the size reduction associated with these conditions. Subcellular localization of endogenous FKH protein is shifted from predominantly cytoplasmic on a high-protein diet to a pronounced nuclear accumulation in animals with reduced levels of TOR or fed with rapamycin. Two putative FKH target genes, CG6770 and cabut, are transcriptionally induced by rapamycin or FKH expression, and silenced by FKH knockdown. Induction of both target genes in heterozygous TOR mutant animals is suppressed by mutations in fkh. Furthermore, TOR signaling levels and FKH impact on transcription of the dFOXO target gene d4E-BP, implying a point of crosstalk with the insulin pathway. In summary, our observations show that an alteration of FKH levels has an effect on cellular and organismal size, and that FKH function is required for the growth inhibition and target gene induction caused by low TOR signaling levels.
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Affiliation(s)
- Margret H. Bülow
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
- Department of Molecular Brain Physiology and Behavior, Life and Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
- Competence Center for Systems Physiology and Metabolic Diseases (CC-SPMD), Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Ruedi Aebersold
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
- Competence Center for Systems Physiology and Metabolic Diseases (CC-SPMD), Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
- Faculty of Science, University of Zurich, Zurich, Switzerland
| | - Michael J. Pankratz
- Department of Molecular Brain Physiology and Behavior, Life and Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
- * E-mail: (MAJ); (MJP)
| | - Martin A. Jünger
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
- * E-mail: (MAJ); (MJP)
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82
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Belacortu Y, Weiss R, Kadener S, Paricio N. Expression of Drosophila Cabut during early embryogenesis, dorsal closure and nervous system development. Gene Expr Patterns 2010; 11:190-201. [PMID: 21109026 DOI: 10.1016/j.gep.2010.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 11/05/2010] [Accepted: 11/18/2010] [Indexed: 01/21/2023]
Abstract
cabut (cbt) encodes a transcription factor involved in Drosophila dorsal closure (DC), and it is expressed in embryonic epithelial sheets and yolk cell during this process upon activation of the Jun N-terminal kinase (JNK) signaling pathway. Additional studies suggest that cbt may have a role in multiple developmental processes. To analyze Cbt localization through embryogenesis, we generated a Cbt specific antibody that has allowed detecting new Cbt expression patterns. Immunohistochemical analyses on syncytial embryos and S2 cells reveal that Cbt is localized on the surface of mitotic chromosomes at all mitotic phases. During DC, Cbt is expressed in the yolk cell, in epidermal cells and in the hindgut, but also in amnioserosal cells, which also contribute to the process, albeit cbt transcripts were not detected in that tissue. At later embryonic stages, Cbt is expressed in neurons and glial cells in the central nervous system, and is detected in axons of the central and peripheral nervous systems. Most of these expression patterns are recapitulated by GFP reporter gene constructs driven by different cbt genomic regions. Moreover, they have been further validated by immunostainings of embryos from other Drosophila species, thus suggesting that Cbt function during embryogenesis appears to be conserved in evolution.
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Affiliation(s)
- Yaiza Belacortu
- Departamento de Genética, Facultad CC Biológicas, Universidad de Valencia, 46100 Burjasot, Spain
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83
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Baltzer C, Tiefenböck SK, Frei C. Mitochondria in response to nutrients and nutrient-sensitive pathways. Mitochondrion 2010; 10:589-97. [DOI: 10.1016/j.mito.2010.07.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 07/16/2010] [Accepted: 07/23/2010] [Indexed: 11/30/2022]
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Abstract
Mammalian target of rapamycin (mTOR) is a central controller of cell growth, proliferation, metabolism and angiogenesis. mTOR signaling is often dysregulated in various human diseases and thus attracts great interest in developing drugs that target mTOR. Currently it is known that mTOR functions as two complexes, mTOR complex 1/2 (mTORC1/2). Rapamycin and its analogs (all termed rapalogs) first form a complex with the intracellular receptor FK506 binding protein 12 (FKBP12) and then bind a domain separated from the catalytic site of mTOR, blocking mTOR function. Rapalogs are selective for mTORC1 and effective as anticancer agents in various preclinical models. In clinical trials, rapalogs have demonstrated efficacy against certain types of cancer. Recently, a new generation of mTOR inhibitors, which compete with ATP in the catalytic site of mTOR and inhibit both mTORC1 and mTORC2 with a high degree of selectivity, have been developed. Besides, some natural products, such as epigallocatechin gallate (EGCG), caffeine, curcumin and resveratrol, have been found to inhibit mTOR as well. Here, we summarize the current findings regarding mTOR signaling pathway and review the updated data about mTOR inhibitors as anticancer agents.
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Affiliation(s)
- Hongyu Zhou
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
| | - Yan Luo
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
| | - Shile Huang
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
- Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA
- Correspondence: Shile Huang, Ph.D., Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130-3932, USA, Phone: (318) 675-7759; Fax: (318) 675-5180,
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85
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Suganya R, Chen SL, Lu KH. Target of rapamycin in the oriental fruit fly Bactrocera dorsalis (Hendel): its cloning and effect on yolk protein expression. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2010; 75:45-56. [PMID: 20734415 DOI: 10.1002/arch.20383] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Target of rapamycin (TOR), a serine/threonine protein kinase, is involved in regulating a number of growth and developmental processes of an organism, including yolk protein synthesis in insects. In this study, TOR gene was isolated, designated BdTOR (GenBank accession no. FJ167395), from the oriental fruit fly Bactrocera dorsalis (Hendel). Quantitative RT-PCR showed a higher expression of BdTOR in the pupa than in other developmental stages, as well as in ovary than in the fat body. Downregulation of BdTOR activity by rapamycin treatment and RNA interference (RNAi) in vivo resulted in a significant reduction in yolk protein transcripts in both fat body and ovary, with a substantial reduction in ovary size. However, an unexpected increase in the expression of yolk protein gene was observed in adult ovary 9 days after rapamycin treatment. Taken together, the results suggest the involvement of BdTOR in the regulation of yolk protein synthesis in B. dorsalis.
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Affiliation(s)
- R Suganya
- Department of Entomology, National Chung Hsing University, Taichung, Taiwan, Republic of China
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86
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Henriques R, Magyar Z, Monardes A, Khan S, Zalejski C, Orellana J, Szabados L, de la Torre C, Koncz C, Bögre L. Arabidopsis S6 kinase mutants display chromosome instability and altered RBR1-E2F pathway activity. EMBO J 2010; 29:2979-93. [PMID: 20683442 DOI: 10.1038/emboj.2010.164] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 06/29/2010] [Indexed: 12/27/2022] Open
Abstract
The 40S ribosomal protein S6 kinase (S6K) is a conserved component of signalling pathways controlling growth in eukaryotes. To study S6K function in plants, we isolated single- and double-knockout mutations and RNA-interference (RNAi)-silencing lines in the linked Arabidopsis S6K1 and S6K2 genes. Hemizygous s6k1s6k2/++ mutant and S6K1 RNAi lines show high phenotypic instability with variation in size, increased trichome branching, produce non-viable pollen and high levels of aborted seeds. Analysis of their DNA content by flow cytometry, as well as chromosome counting using DAPI staining and fluorescence in situ hybridization, revealed an increase in ploidy and aneuploidy. In agreement with this data, we found that S6K1 associates with the Retinoblastoma-related 1 (RBR1)-E2FB complex and this is partly mediated by its N-terminal LVxCxE motif. Moreover, the S6K1-RBR1 association regulates RBR1 nuclear localization, as well as E2F-dependent expression of cell cycle genes. Arabidopsis cells grown under nutrient-limiting conditions require S6K for repression of cell proliferation. The data suggest a new function for plant S6K as a repressor of cell proliferation and required for maintenance of chromosome stability and ploidy levels.
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Affiliation(s)
- Rossana Henriques
- Royal Holloway, University of London, School of Biological Sciences, Egham Hill, Egham, UK.
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87
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Mechanisms of suspended animation are revealed by transcript profiling of diapause in the flesh fly. Proc Natl Acad Sci U S A 2010; 107:14909-14. [PMID: 20668242 DOI: 10.1073/pnas.1007075107] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Diapause is a widespread adaptation to seasonality across invertebrate taxa. It is critical for persistence in seasonal environments, synchronizing life histories with favorable, resource-rich conditions and mitigating exposure to harsh environments. Despite some promising recent progress, however, we still know very little about the molecular modifications underlying diapause. We used transcriptional profiling to identify key groups of genes and pathways differentially regulated during pupal diapause, dynamically regulated across diapause development, and differentially regulated after diapause was pharmacologically terminated in the flesh fly Sarcophaga crassipalpis. We describe major shifts in stress axes, endocrine signaling, and metabolism that accompany diapause, several of which appear to be common features of dormancy in other taxa. To assess whether invertebrates with different diapause strategies have converged toward similar transcriptional profiles, we use archived expression data to compare the pupal diapause of S. crassipalpis with the adult reproductive diapause of Drosophila melanogaster and the larval dauer of Caenorhabditis elegans. Although dormant invertebrates converge on a few similar physiological phenotypes including metabolic depression and stress resistance, we find little transcriptional similarity among dormancies across species, suggesting that there may be many transcriptional strategies for producing physiologically similar dormancy responses.
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88
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The AAA+ ATPase ATAD3A controls mitochondrial dynamics at the interface of the inner and outer membranes. Mol Cell Biol 2010; 30:1984-96. [PMID: 20154147 DOI: 10.1128/mcb.00007-10] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Dynamic interactions between components of the outer (OM) and inner (IM) membranes control a number of critical mitochondrial functions such as channeling of metabolites and coordinated fission and fusion. We identify here the mitochondrial AAA(+) ATPase protein ATAD3A specific to multicellular eukaryotes as a participant in these interactions. The N-terminal domain interacts with the OM. A central transmembrane segment (TMS) anchors the protein in the IM and positions the C-terminal AAA(+) ATPase domain in the matrix. Invalidation studies in Drosophila and in a human steroidogenic cell line showed that ATAD3A is required for normal cell growth and cholesterol channeling at contact sites. Using dominant-negative mutants, including a defective ATP-binding mutant and a truncated 50-amino-acid N-terminus mutant, we showed that ATAD3A regulates dynamic interactions between the mitochondrial OM and IM sensed by the cell fission machinery. The capacity of ATAD3A to impact essential mitochondrial functions and organization suggests that it possesses unique properties in regulating mitochondrial dynamics and cellular functions in multicellular organisms.
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Tyburczy ME, Kotulska K, Pokarowski P, Mieczkowski J, Kucharska J, Grajkowska W, Roszkowski M, Jozwiak S, Kaminska B. Novel proteins regulated by mTOR in subependymal giant cell astrocytomas of patients with tuberous sclerosis complex and new therapeutic implications. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 176:1878-90. [PMID: 20133820 DOI: 10.2353/ajpath.2010.090950] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Subependymal giant cell astrocytomas (SEGAs) are rare brain tumors associated with tuberous sclerosis complex (TSC), a disease caused by mutations in TSC1 or TSC2, resulting in enhancement of mammalian target of rapamycin (mTOR) activity, dysregulation of cell growth, and tumorigenesis. Signaling via mTOR plays a role in multifaceted genomic responses, but its effectors in the brain are largely unknown. Therefore, gene expression profiling on four SEGAs was performed with Affymetrix Human Genome arrays. Of the genes differentially expressed in TSC, 11 were validated by real-time PCR on independent tumor samples and 3 SEGA-derived cultures. Expression of several proteins was confirmed by immunohistochemistry. The differentially-regulated proteins were mainly involved in tumorigenesis and nervous system development. ANXA1, GPNMB, LTF, RND3, S100A11, SFRP4, and NPTX1 genes were likely to be mTOR effector genes in SEGA, as their expression was modulated by an mTOR inhibitor, rapamycin, in SEGA-derived cells. Inhibition of mTOR signaling affected size of cultured SEGA cells but had no influence on their proliferation, morphology, or migration, whereas inhibition of both mTOR and extracellular signal-regulated kinase signaling pathways led to significant alterations of these processes. For the first time, we identified genes related to the occurrence of SEGA and regulated by mTOR and demonstrated an effective modulation of SEGA growth by pharmacological inhibition of both mTOR and extracellular signal-regulated kinase signaling pathways, which could represent a novel therapeutic approach.
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90
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Li L, Edgar BA, Grewal SS. Nutritional control of gene expression in Drosophila larvae via TOR, Myc and a novel cis-regulatory element. BMC Cell Biol 2010; 11:7. [PMID: 20089194 PMCID: PMC2827378 DOI: 10.1186/1471-2121-11-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 01/20/2010] [Indexed: 11/24/2022] Open
Abstract
Background Nutrient availability is a key determinant of eukaryotic cell growth. In unicellular organisms many signaling and transcriptional networks link nutrient availability to the expression of metabolic genes required for growth. However, less is known about the corresponding mechanisms that operate in metazoans. We used gene expression profiling to explore this issue in developing Drosophila larvae. Results We found that starvation for dietary amino acids (AA's) leads to dynamic changes in transcript levels of many metabolic genes. The conserved insulin/PI3K and TOR signaling pathways mediate nutrition-dependent growth in Drosophila and other animals. We found that many AA starvation-responsive transcripts were also altered in TOR mutants. In contrast, although PI3K overexpression induced robust changes in the expression of many metabolic genes, these changes showed limited overlap with the AA starvation expression profile. We did however identify a strong overlap between genes regulated by the transcription factor, Myc, and AA starvation-responsive genes, particularly those involved in ribosome biogenesis, protein synthesis and mitochondrial function. The consensus Myc DNA binding site is enriched in promoters of these AA starvation genes, and we found that Myc overexpression could bypass dietary AA to induce expression of these genes. We also identified another sequence motif (Motif 1) enriched in the promoters of AA starvation-responsive genes. We showed that Motif 1 was both necessary and sufficient to mediate transcriptional responses to dietary AA in larvae. Conclusions Our data suggest that many of the transcriptional effects of amino acids are mediated via signaling through the TOR pathway in Drosophila larvae. We also find that these transcriptional effects are mediated through at least two mechanisms: via the transcription factor Myc, and via the Motif 1 cis-regulatory element. These studies begin to elucidate a nutrient-responsive signaling network that controls metabolic gene transcription in Drosophila.
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Affiliation(s)
- Ling Li
- Clark H, Smith Brain Tumour Center, Southern Alberta Cancer Research Institute, Calgary, Alberta T2N 4N1, Canada
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91
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Guenin L, Raharijaona M, Houlgatte R, Baba-Aissa F. Expression profiling of prospero in the Drosophila larval chemosensory organ: Between growth and outgrowth. BMC Genomics 2010; 11:47. [PMID: 20085633 PMCID: PMC2826315 DOI: 10.1186/1471-2164-11-47] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Accepted: 01/19/2010] [Indexed: 11/11/2022] Open
Abstract
Background The antenno-maxilary complex (AMC) forms the chemosensory system of the Drosophila larva and is involved in gustatory and olfactory perception. We have previously shown that a mutant allele of the homeodomain transcription factor Prospero (prosVoila1, V1), presents several developmental defects including abnormal growth and altered taste responses. In addition, many neural tracts connecting the AMC to the central nervous system (CNS) were affected. Our earlier reports on larval AMC did not argue in favour of a role of pros in cell fate decision, but strongly suggested that pros could be involved in the control of other aspect of neuronal development. In order to identify these functions, we used microarray analysis of larval AMC and CNS tissue isolated from the wild type, and three other previously characterised prospero alleles, including the V1 mutant, considered as a null allele for the AMC. Results A total of 17 samples were first analysed with hierarchical clustering. To determine those genes affected by loss of pros function, we calculated a discriminating score reflecting the differential expression between V1 mutant and other pros alleles. We identified a total of 64 genes in the AMC. Additional manual annotation using all the computed information on the attributed role of these genes in the Drosophila larvae nervous system, enabled us to identify one functional category of potential Prospero target genes known to be involved in neurite outgrowth, synaptic transmission and more specifically in neuronal connectivity remodelling. The second category of genes found to be differentially expressed between the null mutant AMC and the other alleles concerned the development of the sensory organs and more particularly the larval olfactory system. Surprisingly, a third category emerged from our analyses and suggests an association of pros with the genes that regulate autophagy, growth and insulin pathways. Interestingly, EGFR and Notch pathways were represented in all of these three functional categories. We now propose that Pros could perform all of these different functions through the modulation of these two antagonistic and synergic pathways. Conclusions The current data contribute to the clarification of the prospero function in the larval AMC and show that pros regulates different function in larvae as compared to those controlled by this gene in embryos. In the future, the possible mechanism by which Pros could achieve its function in the AMC will be explored in detail.
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Affiliation(s)
- Laure Guenin
- Université de Bourgogne, Facultés des Sciences, Unité Mixte de Recherche 5548 Associée au Centre National de la Recherche Scientifique, 6, Bd Gabriel, 21 000 Dijon, France
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92
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Bjedov I, Toivonen JM, Kerr F, Slack C, Jacobson J, Foley A, Partridge L. Mechanisms of life span extension by rapamycin in the fruit fly Drosophila melanogaster. Cell Metab 2010; 11:35-46. [PMID: 20074526 PMCID: PMC2824086 DOI: 10.1016/j.cmet.2009.11.010] [Citation(s) in RCA: 726] [Impact Index Per Article: 51.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Revised: 10/13/2009] [Accepted: 11/19/2009] [Indexed: 12/14/2022]
Abstract
The target of rapamycin (TOR) pathway is a major nutrient-sensing pathway that, when genetically downregulated, increases life span in evolutionarily diverse organisms including mammals. The central component of this pathway, TOR kinase, is the target of the inhibitory drug rapamycin, a highly specific and well-described drug approved for human use. We show here that feeding rapamycin to adult Drosophila produces the life span extension seen in some TOR mutants. Increase in life span by rapamycin was associated with increased resistance to both starvation and paraquat. Analysis of the underlying mechanisms revealed that rapamycin increased longevity specifically through the TORC1 branch of the TOR pathway, through alterations to both autophagy and translation. Rapamycin could increase life span of weak insulin/Igf signaling (IIS) pathway mutants and of flies with life span maximized by dietary restriction, indicating additional mechanisms.
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Affiliation(s)
- Ivana Bjedov
- Institute of Healthy Ageing, Department of Genetics, Evolution and Environment, University College London, UK
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93
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Abstract
The insulin signalling pathway is highly conserved from mammals to Drosophila. Insulin signalling in the fly, as in mammals, regulates a number of physiological functions, including carbohydrate and lipid metabolism, tissue growth and longevity. In the present review, I discuss the molecular mechanisms by which insulin signalling regulates metabolism in Drosophila, comparing and contrasting with the mammalian system. I discuss both the intracellular signalling network, as well as the communication between organs in the fly.
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94
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Abstract
Nutrition is a key regulator of tissue growth. In animals, nutritional status is monitored and signaled at both the cellular and systemic levels. The main mediator of cellular nutrient sensing is the protein kinase TOR (target of rapamycin). TOR receives information from levels of cellular amino acids and energy, and it regulates the activity of processes involved in cell growth, such as protein synthesis and autophagy. Insulin-like signaling is the main mechanism of systemic nutrient sensing and mediates its growth-regulatory functions largely through the phosphatidylinositol 3-kinase (PI3K)/AKT protein kinase pathway. Other nutrition-regulated hormonal mechanisms contribute to growth control by modulating the activity of insulin-like signaling. The pathways mediating signals from systemic and cellular levels converge, allowing cells to combine information from both sources. Here we give an overview of the mechanisms that adjust animal tissue growth in response to nutrition and highlight some general features of the signaling pathways involved.
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95
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Bandhakavi S, Kim YM, Ro SH, Xie H, Onsongo G, Jun CB, Kim DH, Griffin TJ. Quantitative nuclear proteomics identifies mTOR regulation of DNA damage response. Mol Cell Proteomics 2009; 9:403-14. [PMID: 19955088 DOI: 10.1074/mcp.m900326-mcp200] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular nutritional and energy status regulates a wide range of nuclear processes important for cell growth, survival, and metabolic homeostasis. Mammalian target of rapamycin (mTOR) plays a key role in the cellular responses to nutrients. However, the nuclear processes governed by mTOR have not been clearly defined. Using isobaric peptide tagging coupled with linear ion trap mass spectrometry, we performed quantitative proteomics analysis to identify nuclear processes in human cells under control of mTOR. Within 3 h of inhibiting mTOR with rapamycin in HeLa cells, we observed down-regulation of nuclear abundance of many proteins involved in translation and RNA modification. Unexpectedly, mTOR inhibition also down-regulated several proteins functioning in chromosomal integrity and up-regulated those involved in DNA damage responses (DDRs) such as 53BP1. Consistent with these proteomic changes and DDR activation, mTOR inhibition enhanced interaction between 53BP1 and p53 and increased phosphorylation of ataxia telangiectasia mutated (ATM) kinase substrates. ATM substrate phosphorylation was also induced by inhibiting protein synthesis and suppressed by inhibiting proteasomal activity, suggesting that mTOR inhibition reduces steady-state (abundance) levels of proteins that function in cellular pathways of DDR activation. Finally, rapamycin-induced changes led to increased survival after radiation exposure in HeLa cells. These findings reveal a novel functional link between mTOR and DDR pathways in the nucleus potentially operating as a survival mechanism against unfavorable growth conditions.
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Affiliation(s)
- Sricharan Bandhakavi
- Department of Biochemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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96
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The Drosophila PGC-1 homologue Spargel coordinates mitochondrial activity to insulin signalling. EMBO J 2009; 29:171-83. [PMID: 19910925 DOI: 10.1038/emboj.2009.330] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 10/07/2009] [Indexed: 01/01/2023] Open
Abstract
Mitochondrial mass and activity must be adapted to tissue function, cellular growth and nutrient availability. In mammals, the related transcriptional coactivators PGC-1alpha, PGC-1beta and PRC regulate multiple metabolic functions, including mitochondrial biogenesis. However, we know relatively little about their respective roles in vivo. Here we show that the Drosophila PGC-1 family homologue, Spargel, is required for the expression of multiple genes encoding mitochondrial proteins. Accordingly, spargel mutants showed mitochondrial respiration defects when complex II of the electron transport chain was stimulated. Spargel, however, was not limiting for mitochondrial mass, but functioned in this respect redundantly with Delg, the fly NRF-2alpha/GABPalpha homologue. More importantly, in the larval fat body, Spargel mediated mitochondrial activity, cell growth and transcription of target genes in response to insulin signalling. In this process, Spargel functioned in parallel to the insulin-responsive transcription factor, dFoxo, and provided a negative feedback loop to fine-tune insulin signalling. Taken together, our data place Spargel at a nodal point for the integration of mitochondrial activity to tissue and organismal metabolism and growth.
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97
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Kent CF, Daskalchuk T, Cook L, Sokolowski MB, Greenspan RJ. The Drosophila foraging gene mediates adult plasticity and gene-environment interactions in behaviour, metabolites, and gene expression in response to food deprivation. PLoS Genet 2009; 5:e1000609. [PMID: 19696884 PMCID: PMC2720453 DOI: 10.1371/journal.pgen.1000609] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Accepted: 07/20/2009] [Indexed: 12/19/2022] Open
Abstract
Nutrition is known to interact with genotype in human metabolic syndromes, obesity, and diabetes, and also in Drosophila metabolism. Plasticity in metabolic responses, such as changes in body fat or blood sugar in response to changes in dietary alterations, may also be affected by genotype. Here we show that variants of the foraging (for) gene in Drosophila melanogaster affect the response to food deprivation in a large suite of adult phenotypes by measuring gene by environment interactions (GEI) in a suite of food-related traits. for affects body fat, carbohydrates, food-leaving behavior, metabolite, and gene expression levels in response to food deprivation. This results in broad patterns of metabolic, genomic, and behavioral gene by environment interactions (GEI), in part by interaction with the insulin signaling pathway. Our results show that a single gene that varies in nature can have far reaching effects on behavior and metabolism by acting through multiple other genes and pathways.
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Affiliation(s)
- Clement F. Kent
- Department of Biology, University of Toronto Mississauga, Ontario, Canada
| | - Tim Daskalchuk
- Phenomenome Discoveries, Saskatoon, Saskatchewan, Canada
| | - Lisa Cook
- Phenomenome Discoveries, Saskatoon, Saskatchewan, Canada
| | - Marla B. Sokolowski
- Department of Biology, University of Toronto Mississauga, Ontario, Canada
- * E-mail:
| | - Ralph J. Greenspan
- The Neurosciences Institute, San Diego, California, United States of America
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98
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Prokupek AM, Kachman SD, Ladunga I, Harshman LG. Transcriptional profiling of the sperm storage organs of Drosophila melanogaster. INSECT MOLECULAR BIOLOGY 2009; 18:465-475. [PMID: 19453766 DOI: 10.1111/j.1365-2583.2009.00887.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The occurrence of female sperm storage across taxa indicates the importance of this complex and dynamic process. Organs responsible for sperm storage (SSOs) and proteins expressed therein, are important in fundamental aspects of reproduction and could play a major role in evolutionary processes such as post-mating sexual selection. Given the essential role of SSOs, it is surprising that the process of sperm storage is so poorly understood. This study investigated the transcriptome of female Drosophila melanogaster SSOs (seminal receptacle and spermathecae). Spermathecae were enriched for proteases and metabolic enzymes while the seminal receptacle was enriched for genes involved in localization, signaling and ion transport. Differences in functional gene categories indicate that these organs play unique roles in sperm storage.
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Affiliation(s)
- A M Prokupek
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
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99
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Chopard A, Hillock S, Jasmin BJ. Molecular events and signalling pathways involved in skeletal muscle disuse-induced atrophy and the impact of countermeasures. J Cell Mol Med 2009; 13:3032-50. [PMID: 19656243 PMCID: PMC4516463 DOI: 10.1111/j.1582-4934.2009.00864.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Disuse-induced skeletal muscle atrophy occurs following chronic periods of inactivity such as those involving prolonged bed rest, trauma and microgravity environments. Deconditioning of skeletal muscle is mainly characterized by a loss of muscle mass, decreased fibre cross-sectional area, reduced force, increased fatigability, increased insulin resistance and transitions in fibre types. A description of the role of specific transcriptional mechanisms contributing to muscle atrophy by altering gene expression during muscle disuse has recently emerged and focused primarily on short period of inactivity. A better understanding of the transduction pathways involved in activation of proteolytic and apoptotic pathways continues to represent a major objective, together with the study of potential cross-talks in these cellular events. In parallel, evaluation of the impact of countermeasures at the cellular and molecular levels in short- and long-term disuse experimentations or microgravity environments should undoubtedly and synergistically increase our basic knowledge in attempts to identify new physical, pharmacological and nutritional targets to counteract muscle atrophy. These investigations are important as skeletal muscle atrophy remains an important neuromuscular challenge with impact in clinical and social settings affecting a variety of conditions such as those seen in aging, cancer cachexia, muscle pathologies and long-term space exploration.
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Affiliation(s)
- Angèle Chopard
- Department of Cellular and Molecular Medicine, Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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100
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Baker DA, Russell S. Gene expression during Drosophila melanogaster egg development before and after reproductive diapause. BMC Genomics 2009; 10:242. [PMID: 19463195 PMCID: PMC2700134 DOI: 10.1186/1471-2164-10-242] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 05/24/2009] [Indexed: 11/30/2022] Open
Abstract
Background Despite the importance of egg development to the female life cycle in Drosophila, global patterns of gene expression have not been examined in detail, primarily due to the difficulty in isolating synchronised developmental stages in sufficient quantities for gene expression profiling. Entry into vitellogenesis is a key stage of oogenesis and by forcing females into reproductive diapause we are able to arrest oogenesis at the pre-vitellogenic stages. Releasing females from diapause allows collection of relatively synchronous developing egg populations and an investigation of some of the transcriptional dynamics apparent before and after reproductive diapause. Results Focusing on gender-biased transcription, we identified mechanisms of egg development suppressed during reproductive dormancy as well as other molecular changes unique to the diapausing female. A microarray based analysis generated a set of 3565 transcripts with at least 2-fold greater expression in females as compared to control males, 1392 such changes were biased during reproductive dormancy. In addition, we also detect 1922 up-regulated transcriptional changes after entry into vitellogenesis, which were classified into discrete blocks of co-expression. We discuss some of the regulatory aspects apparent after re-initiation of egg development, exploring the underlying functions, maternal contribution and evolutionary conservation of co-expression patterns involved in egg production. Conclusion Although much of the work we present is descriptive, fundamental aspects of egg development and gender-biased transcription can be derived from our time-series experiment. We believe that our dataset will facilitate further exploration of the developmental and evolutionary characteristics of oogenesis as well as the nature of reproductive arrest in Drosophila.
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Affiliation(s)
- Dean A Baker
- Department of Genetics, University of Cambridge, Downing Street, Cambridge CB13QA, UK.
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