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Tang X, Pu Y, Peng H, Li K, Faouzi S, Lu T, Pu D, Cerezo M, Xu J, Li L, Robert C, Shen S. Spatial patterns of the cap-binding complex eIF4F in human melanoma cells. Comput Struct Biotechnol J 2023; 21:1157-1168. [PMID: 36789267 PMCID: PMC9918392 DOI: 10.1016/j.csbj.2023.01.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 01/27/2023] [Accepted: 01/29/2023] [Indexed: 02/01/2023] Open
Abstract
As a central node of protein synthesis, the cap-binding complex, eukaryotic translation initiation factor 4 F (eIF4F), is involved in cell homeostasis, development and tumorigenesis. A large body of literature exists on the regulation and function of eIF4F in cancer cells, however the intracellular localization patterns of this complex are largely unknown. Since different subsets of mRNAs are translated in distinct subcellular compartments, understanding the distribution of translation initiation factors in the cell is of major interest. Here, we developed an in situ detection method for eIF4F at the single cell level. By using an image-based spot feature analysis pipeline as well as supervised machine learning, we identify five distinct spatial patterns of the eIF4F translation initiation complex in human melanoma cells. The quantity of eIF4F complex per cell correlated with the global mRNA translation activity, and its variation is dynamically regulated by cell state or extracellular stimuli. In contrast, the spatial patterns of eIF4F complexes at the single cell level could distinguish melanoma cells harboring different oncogenic driver mutations. This suggests that different tumorigenic contexts differentially regulate the subcellular localization of mRNA translation, with specific localization of eIF4F potentially associated with melanoma cell chemoresistance.
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Affiliation(s)
- Xinpu Tang
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
- Department of Neurosurgery, West China Hospital of Sichuan University, Chengdu, China
- National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
| | - Yi Pu
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
- Department of Burn Surgery, West China Hospital of Sichuan University, Chengdu, China
| | - Haoning Peng
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
- Department of Thoracic Surgery, West China Hospital of Sichuan University, Chengdu, China
| | - Kaixiu Li
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
| | - Sara Faouzi
- INSERM U981, Gustave Roussy Cancer Campus, Villejuif, France
| | - Tianjian Lu
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
- Department of Thoracic Surgery, West China Hospital of Sichuan University, Chengdu, China
| | - Dan Pu
- Lung Cancer Center, West China Hospital of Sichuan University, Chengdu, China
| | - Michael Cerezo
- Université Côte d′Azur, Nice, France
- Centre Méditerranéen de Médicine Moléculaire (C3M), INSERM U1065, Equipe 12, Nice, France
| | - Jianguo Xu
- Department of Neurosurgery, West China Hospital of Sichuan University, Chengdu, China
| | - Lu Li
- Lung Cancer Center, West China Hospital of Sichuan University, Chengdu, China
- Corresponding author.
| | - Caroline Robert
- INSERM U981, Gustave Roussy Cancer Campus, Villejuif, France
- Dermatology Unit, Gustave Roussy Cancer Campus, Villejuif, France
- Corresponding author at: INSERM U981, Gustave Roussy Cancer Campus, Villejuif, France.
| | - Shensi Shen
- Institute of Thoracic Oncology, West China Hospital of Sichuan University, Chengdu, China
- National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China
- Department of Thoracic Surgery, West China Hospital of Sichuan University, Chengdu, China
- Correspondence to: Institute of Thoracic Oncology and National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, China.
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Ayama-Canden S, Tondo R, Piñeros L, Ninane N, Demazy C, Dieu M, Fattaccioli A, Tabarrant T, Lucas S, Bonifazi D, Michiels C. IGDQ motogenic peptide gradient induces directional cell migration through integrin (αv)β3 activation in MDA-MB-231 metastatic breast cancer cells. Neoplasia 2022; 31:100816. [PMID: 35763908 PMCID: PMC9241093 DOI: 10.1016/j.neo.2022.100816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 06/08/2022] [Accepted: 06/13/2022] [Indexed: 11/02/2022] Open
Abstract
In the context of breast cancer metastasis study, we have shown in an in vitro model of cell migration that IGDQ-exposing (IsoLeu-Gly-Asp-Glutamine type I Fibronectin motif) monolayers (SAMs) on gold sustain the adhesion of breast cancer MDA-MB-231 cells by triggering Focal Adhesion Kinase and integrin activation. Such tunable scaffolds are used to mimic the tumor extracellular environment, inducing and controlling cell migration. The observed migratory behavior induced by the IGDQ-bearing peptide gradient along the surface allows to separate cell subpopulations with a "stationary" or "migratory" phenotype. In this work, we knocked down the integrins α5(β1) and (αv)β since they are already known to be implicated in cell migration. To this aim, a whole proteomic analysis was performed in beta 3 integrin (ITGB3) or alpha 5 integrin (ITGA5) knock-down MDA-MB-231 cells, in order to highlight the pathways implied in the integrin-dependent cell migration. Our results showed that i) ITGB3 depletion influenced ITGA5 mRNA expression, ii) ITGB3 and ITGA5 were both necessary for IGDQ-mediated directional single cell migration and iii) integrin (αv)β3 was activated by IGDQ fibronectin type I motif. Finally, the proteomic analysis suggested that co-regulation of recycling transport of ITGB3 by ITGA5 is potentially necessary for directional IGDQ-mediated cell migration.
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Affiliation(s)
- Sophie Ayama-Canden
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Rodolfo Tondo
- School of Chemistry, Cardiff University, Park Place, Main Building, CF10 3AT, Cardiff, Wales, United Kingdom
| | - Liliana Piñeros
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Noëlle Ninane
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Catherine Demazy
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Marc Dieu
- MaSUN, Mass Spectrometry Facility, University of Namur, 61, rue de Bruxelles, 5000 Namur, Belgium
| | - Antoine Fattaccioli
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Tijani Tabarrant
- LARN - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Stéphane Lucas
- LARN - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
| | - Davide Bonifazi
- School of Chemistry, Cardiff University, Park Place, Main Building, CF10 3AT, Cardiff, Wales, United Kingdom; Institute of Organic Chemistry, University of Vienna, Währinger Str. 38, 1090 Vienna, Austria
| | - Carine Michiels
- URBC - NARILIS, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium.
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Lashkevich KA, Dmitriev SE. mRNA Targeting, Transport and Local Translation in Eukaryotic Cells: From the Classical View to a Diversity of New Concepts. Mol Biol 2021; 55:507-537. [PMID: 34092811 PMCID: PMC8164833 DOI: 10.1134/s0026893321030080] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 02/26/2021] [Accepted: 03/12/2021] [Indexed: 12/28/2022]
Abstract
Spatial organization of protein biosynthesis in the eukaryotic cell has been studied for more than fifty years, thus many facts have already been included in textbooks. According to the classical view, mRNA transcripts encoding secreted and transmembrane proteins are translated by ribosomes associated with endoplasmic reticulum membranes, while soluble cytoplasmic proteins are synthesized on free polysomes. However, in the last few years, new data has emerged, revealing selective translation of mRNA on mitochondria and plastids, in proximity to peroxisomes and endosomes, in various granules and at the cytoskeleton (actin network, vimentin intermediate filaments, microtubules and centrosomes). There are also long-standing debates about the possibility of protein synthesis in the nucleus. Localized translation can be determined by targeting signals in the synthesized protein, nucleotide sequences in the mRNA itself, or both. With RNA-binding proteins, many transcripts can be assembled into specific RNA condensates and form RNP particles, which may be transported by molecular motors to the sites of active translation, form granules and provoke liquid-liquid phase separation in the cytoplasm, both under normal conditions and during cell stress. The translation of some mRNAs occurs in specialized "translation factories," assemblysomes, transperons and other structures necessary for the correct folding of proteins, interaction with functional partners and formation of oligomeric complexes. Intracellular localization of mRNA has a significant impact on the efficiency of its translation and presumably determines its response to cellular stress. Compartmentalization of mRNAs and the translation machinery also plays an important role in viral infections. Many viruses provoke the formation of specific intracellular structures, virus factories, for the production of their proteins. Here we review the current concepts of the molecular mechanisms of transport, selective localization and local translation of cellular and viral mRNAs, their effects on protein targeting and topogenesis, and on the regulation of protein biosynthesis in different compartments of the eukaryotic cell. Special attention is paid to new systems biology approaches, providing new cues to the study of localized translation.
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Affiliation(s)
- Kseniya A Lashkevich
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119234 Moscow, Russia.,Faculty of Bioengineering and Bioinformatics, Moscow State University, 119234 Moscow, Russia
| | - Sergey E Dmitriev
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, 119234 Moscow, Russia.,Faculty of Bioengineering and Bioinformatics, Moscow State University, 119234 Moscow, Russia.,Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia
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Batool W, Shabbir A, Lin L, Chen X, An Q, He X, Pan S, Chen S, Chen Q, Wang Z, Norvienyeku J. Translation Initiation Factor eIF4E Positively Modulates Conidiogenesis, Appressorium Formation, Host Invasion and Stress Homeostasis in the Filamentous Fungi Magnaporthe oryzae. FRONTIERS IN PLANT SCIENCE 2021; 12:646343. [PMID: 34220879 PMCID: PMC8244596 DOI: 10.3389/fpls.2021.646343] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 05/21/2021] [Indexed: 05/14/2023]
Abstract
Translation initiation factor eIF4E generally mediates the recognition of the 5'cap structure of mRNA during the recruitment of the ribosomes to capped mRNA. Although the eIF4E has been shown to regulate stress response in Schizosaccharomyces pombe positively, there is no direct experimental evidence for the contributions of eIF4E to both physiological and pathogenic development of filamentous fungi. We generated Magnaporthe oryzae eIF4E (MoeIF4E3) gene deletion strains using homologous recombination strategies. Phenotypic and biochemical analyses of MoeIF4E3 defective strains showed that the deletion of MoeIF4E3 triggered a significant reduction in growth and conidiogenesis. We also showed that disruption of MoeIF4E3 partially impaired conidia germination, appressorium integrity and attenuated the pathogenicity of ΔMoeif4e3 strains. In summary, this study provides experimental insights into the contributions of the eIF4E3 to the development of filamentous fungi. Additionally, these observations underscored the need for a comprehensive evaluation of the translational regulatory machinery in phytopathogenic fungi during pathogen-host interaction progression.
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Affiliation(s)
- Wajjiha Batool
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ammarah Shabbir
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Lili Lin
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaomin Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qiuli An
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiongjie He
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shu Pan
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shuzun Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qinghe Chen
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
| | - Zonghua Wang
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
- *Correspondence: Zonghua Wang,
| | - Justice Norvienyeku
- Fujian University Key Laboratory for Plant-Microbe Interaction, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, The School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
- Justice Norvienyeku, ;
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Böhm BB, Fehrl Y, Janczi T, Schneider N, Burkhardt H. Cell adhesion-induced transient interaction of ADAM15 with poly(A) binding protein at the cell membrane colocalizes with mRNA translation. PLoS One 2018; 13:e0203847. [PMID: 30265671 PMCID: PMC6161846 DOI: 10.1371/journal.pone.0203847] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/28/2018] [Indexed: 12/15/2022] Open
Abstract
The regulation of temporo-spatial compartmentalization of protein synthesis is of crucial importance for a variety of physiologic cellular functions. Here, we demonstrate that the cell membrane-anchored disintegrin metalloproteinase ADAM15, upregulated in a variety of aggressively growing tumor cells, in the hyperproliferative synovial membrane of inflamed joints as well as in osteoarthritic chondrocytes, transiently binds to poly(A) binding protein 1 (PABP) in cells undergoing adhesion. The cytoplasmic domain of ADAM15 was shown to selectively interact with the proline-rich linker of PABP. Immunostainings of adhesion-triggered cells demonstrate an ADAM15-dependent recruitment of PABP to cell membrane foci coinciding with ongoing mRNA translation as visualized by the detection of puromycin-terminated polypeptides. Moreover, the increase in cell membrane-associated neosynthesis of puromycylated proteins upon induction of cell adhesion was proven linked to ADAM15 expression in HeLa and ADAM15-transfected chondrocytic cells. Thus, down regulation of ADAM15 by siRNA and/or the use of a cell line transfected with a mutant ADAM15-construct lacking the cytoplasmic tail resulted in a considerable reduction in the amount of cell membrane-associated puromycylated proteins formed during induced cell adhesion. These results provide first direct evidence for a regulatory role of ADAM15 on mRNA translation at the cell membrane that transiently emerges in response to triggering cell adhesion and might have potential implications under pathologic conditions of matrix remodeling associated with ADAM15 upregulation.
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Affiliation(s)
- Beate B. Böhm
- Division of Rheumatology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany
| | - Yuliya Fehrl
- Division of Rheumatology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany
| | - Tomasz Janczi
- Division of Rheumatology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany
| | - Nadine Schneider
- Project Group Translational Medicine & Pharmacology TMP, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Frankfurt am Main, Germany
| | - Harald Burkhardt
- Division of Rheumatology, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany
- Project Group Translational Medicine & Pharmacology TMP, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Frankfurt am Main, Germany
- * E-mail:
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Abstract
RNA-binding proteins are often multifunctional, interact with a variety of protein partners and display complex localizations within cells. Mammalian cytoplasmic poly(A)-binding proteins (PABPs) are multifunctional RNA-binding proteins that regulate multiple aspects of mRNA translation and stability. Although predominantly diffusely cytoplasmic at steady state, they shuttle through the nucleus and can be localized to a variety of cytoplasmic foci, including those associated with mRNA storage and localized translation. Intriguingly, PABP sub-cellular distribution can alter dramatically in response to cellular stress or viral infection, becoming predominantly nuclear and/or being enriched in induced cytoplasmic foci. However, relatively little is known about the mechanisms that govern this distribution/relocalization and in many cases PABP functions within specific sites remain unclear. Here we discuss the emerging evidence with respect to these questions in mammals.
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Royall E, Doyle N, Abdul-Wahab A, Emmott E, Morley SJ, Goodfellow I, Roberts LO, Locker N. Murine norovirus 1 (MNV1) replication induces translational control of the host by regulating eIF4E activity during infection. J Biol Chem 2015; 290:4748-4758. [PMID: 25561727 PMCID: PMC4335213 DOI: 10.1074/jbc.m114.602649] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Protein synthesis is a tightly controlled process responding to several stimuli, including viral infection. As obligate intracellular parasites, viruses depend on the translation machinery of the host and can manipulate it by affecting the availability and function of specific eukaryotic initiation factors (eIFs). Human norovirus is a member of the Caliciviridae family and is responsible for gastroenteritis outbreaks. Previous studies on feline calicivirus and murine norovirus 1 (MNV1) demonstrated that the viral protein, genome-linked (VPg), acts to direct translation by hijacking the host protein synthesis machinery. Here we report that MNV1 infection modulates the MAPK pathway to activate eIF4E phosphorylation. Our results show that the activation of p38 and Mnk during MNV1 infection is important for MNV1 replication. Furthermore, phosphorylated eIF4E relocates to the polysomes, and this contributes to changes in the translational state of specific host mRNAs. We propose that global translational control of the host by eIF4E phosphorylation is a key component of the host-pathogen interaction.
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Affiliation(s)
- Elizabeth Royall
- University of Surrey, Faculty of Health and Medical Sciences, School of Biosciences and Medicine, Guildford GU2 7HX, United Kingdom
| | - Nicole Doyle
- University of Surrey, Faculty of Health and Medical Sciences, School of Biosciences and Medicine, Guildford GU2 7HX, United Kingdom
| | - Azimah Abdul-Wahab
- University of Surrey, Faculty of Health and Medical Sciences, School of Biosciences and Medicine, Guildford GU2 7HX, United Kingdom
| | - Ed Emmott
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, United Kingdom
| | - Simon J Morley
- Department of Biochemistry and Molecular Biology, School of Life Sciences, University of Sussex, JMS Building, Brighton BN1 9RH, United Kingdom
| | - Ian Goodfellow
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, United Kingdom
| | - Lisa O Roberts
- University of Surrey, Faculty of Health and Medical Sciences, School of Biosciences and Medicine, Guildford GU2 7HX, United Kingdom
| | - Nicolas Locker
- University of Surrey, Faculty of Health and Medical Sciences, School of Biosciences and Medicine, Guildford GU2 7HX, United Kingdom.
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Gosselin P, Martineau Y, Morales J, Czjzek M, Glippa V, Gauffeny I, Morin E, Le Corguillé G, Pyronnet S, Cormier P, Cosson B. Tracking a refined eIF4E-binding motif reveals Angel1 as a new partner of eIF4E. Nucleic Acids Res 2013; 41:7783-92. [PMID: 23814182 PMCID: PMC3763552 DOI: 10.1093/nar/gkt569] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The initiation factor 4E (eIF4E) is implicated in most of the crucial steps of the mRNA life cycle and is recognized as a pivotal protein in gene regulation. Many of these roles are mediated by its interaction with specific proteins generally known as eIF4E-interacting partners (4E-IPs), such as eIF4G and 4E-BP. To screen for new 4E-IPs, we developed a novel approach based on structural, in silico and biochemical analyses. We identified the protein Angel1, a member of the CCR4 deadenylase family. Immunoprecipitation experiments provided evidence that Angel1 is able to interact in vitro and in vivo with eIF4E. Point mutation variants of Angel1 demonstrated that the interaction of Angel1 with eIF4E is mediated through a consensus eIF4E-binding motif. Immunofluorescence and cell fractionation experiments showed that Angel1 is confined to the endoplasmic reticulum and Golgi apparatus, where it partially co-localizes with eIF4E and eIF4G, but not with 4E-BP. Furthermore, manipulating Angel1 levels in living cells had no effect on global translation rates, suggesting that the protein has a more specific function. Taken together, our results illustrate that we developed a powerful method for identifying new eIF4E partners and open new perspectives for understanding eIF4E-specific regulation.
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Affiliation(s)
- Pauline Gosselin
- UPMC Univ Paris 06, UMR 7150, Mer et Santé, Station Biologique, F-29680 Roscoff, France, CNRS, UMR 7150, Mer et Santé, Station Biologique, F-29680 Roscoff, France. Université Européenne de Bretagne, Bretagne, Roscoff, France, INSERM, UMR 1037, Centre de Recherche en Cancérologie de Toulouse, Toulouse 31432, France, UPMC Univ Paris 06, UMR 7139, Végétaux Marins et Biomolécules, Station Biologique, F-29680 Roscoff, France, CNRS, UMR 7139, Végétaux Marins et Biomolécules, Station Biologique, F-29680 Roscoff, France, UPMC Univ Paris 06, FR2424, ABiMS, Station Biologique, F-29680 Roscoff, France and CNRS, FR2424, ABiMS, Station Biologique, F-29680 Roscoff, France
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9
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Geiger T, Zaidel-Bar R. Opening the floodgates: proteomics and the integrin adhesome. Curr Opin Cell Biol 2012; 24:562-8. [DOI: 10.1016/j.ceb.2012.05.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Accepted: 05/22/2012] [Indexed: 01/09/2023]
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10
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Klemke RL. Trespassing cancer cells: 'fingerprinting' invasive protrusions reveals metastatic culprits. Curr Opin Cell Biol 2012; 24:662-9. [PMID: 22980730 DOI: 10.1016/j.ceb.2012.08.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 07/24/2012] [Accepted: 08/20/2012] [Indexed: 10/27/2022]
Abstract
Metastatic cancer cells produce invasive membrane protrusions called invadopodia and pseudopodia, which play a central role in driving cancer cell dissemination in the body. Malignant cells use these structures to attach to and degrade extracellular matrix proteins, generate force for cell locomotion, and to penetrate the vasculature. Recent work using unique subcellular fractionation methodologies combined with spatial genomic, proteomic, and phosphoproteomic profiling has provided insight into the invadopodiome and pseudopodiome signaling networks that control the protrusion of invasive membranes. Here I highlight how these powerful spatial 'omics' approaches reveal important signatures of metastatic cancer cells and possible new therapeutic targets aimed at treating metastatic disease.
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Affiliation(s)
- Richard L Klemke
- Department of Pathology and Moores Cancer Center, University of California San Diego, La Jolla, CA 92093-0612, United States.
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11
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The ezrin metastatic phenotype is associated with the initiation of protein translation. Neoplasia 2012; 14:297-310. [PMID: 22577345 DOI: 10.1593/neo.11518] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 03/13/2012] [Accepted: 03/16/2012] [Indexed: 12/14/2022] Open
Abstract
We previously associated the cytoskeleton linker protein, Ezrin, with the metastatic phenotype of pediatric sarcomas, including osteosarcoma and rhabdomyosarcoma. These studies have suggested that Ezrin contributes to the survival of cancer cells after their arrival at secondary metastatic locations. To better understand this role in metastasis, we undertook two noncandidate analyses of Ezrin function including a microarray subtraction of high-and low-Ezrin-expressing cells and a proteomic approach to identify proteins that bound the N-terminus of Ezrin in tumor lysates. Functional analyses of these data led to a novel and unifying hypothesis that Ezrin contributes to the efficiency of metastasis through regulation of protein translation. In support of this hypothesis, we found Ezrin to be part of the ribonucleoprotein complex to facilitate the expression of complex messenger RNA in cells and to bind with poly A binding protein 1 (PABP1; PABPC1). The relevance of these findings was supported by our identification of Ezrin and components of the translational machinery in pseudopodia of highly metastatic cells during the process of cell invasion. Finally, two small molecule inhibitors recently shown to inhibit the Ezrin metastatic phenotype disrupted the Ezrin/PABP1 association. Taken together, these results provide a novel mechanistic basis by which Ezrin may contribute to metastasis.
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12
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Zaborowska I, Kellner K, Henry M, Meleady P, Walsh D. Recruitment of host translation initiation factor eIF4G by the Vaccinia Virus ssDNA-binding protein I3. Virology 2012; 425:11-22. [PMID: 22280895 DOI: 10.1016/j.virol.2011.12.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 12/09/2011] [Accepted: 12/23/2011] [Indexed: 11/15/2022]
Abstract
Poxviruses are large double-stranded DNA viruses that replicate exclusively in the cytoplasm of infected cells within discrete compartments termed viral factories. Recent work has shown that the prototypical poxvirus, Vaccinia Virus (VacV) sequesters components of the eukaryotic translation initiation complex eIF4F within viral factories while also stimulating formation of eIF4F complexes. However, the forces that govern these events remain unknown. Here, we show that maximal eIF4F formation requires viral DNA replication and the formation of viral factories, suggesting that sequestration functions to promote eIF4F assembly, and identify the ssDNA-binding protein, I3 as a viral factor that interacts and co-localizes with the eIF4F scaffold protein, eIF4G. Although it did not adversely affect host or viral protein synthesis, I3 specifically mediated the binding of eIF4G to ssDNA. Combined, our findings offer an explanation for the specific pattern and temporal process of eIF4G redistribution and eIF4F complex assembly within VacV-infected cells.
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Affiliation(s)
- Izabela Zaborowska
- National Institute for Cellular Biotechnology, Dublin City University, Dublin 9, Ireland
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Ziegler ME, Souda P, Jin YP, Whitelegge JP, Reed EF. Characterization of the endothelial cell cytoskeleton following HLA class I ligation. PLoS One 2012; 7:e29472. [PMID: 22247778 PMCID: PMC3256144 DOI: 10.1371/journal.pone.0029472] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 11/29/2011] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Vascular endothelial cells (ECs) are a target of antibody-mediated allograft rejection. In vitro, when the HLA class I molecules on the surface of ECs are ligated by anti-HLA class I antibodies, cell proliferation and survival pathways are activated and this is thought to contribute to the development of antibody-mediated rejection. Crosslinking of HLA class I molecules by anti-HLA antibodies also triggers reorganization of the cytoskeleton, which induces the formation of F-actin stress fibers. HLA class I induced stress fiber formation is not well understood. METHODOLOGY AND PRINCIPAL FINDINGS The present study examines the protein composition of the cytoskeleton fraction of ECs treated with HLA class I antibodies and compares it to other agonists known to induce alterations of the cytoskeleton in endothelial cells. Analysis by tandem mass spectrometry revealed unique cytoskeleton proteomes for each treatment group. Using annotation tools a candidate list was created that revealed 12 proteins, which were unique to the HLA class I stimulated group. Eleven of the candidate proteins were phosphoproteins and exploration of their predicted kinases provided clues as to how these proteins may contribute to the understanding of HLA class I induced antibody-mediated rejection. Three of the candidates, eukaryotic initiation factor 4A1 (eIF4A1), Tropomyosin alpha 4-chain (TPM4) and DDX3X, were further characterized by Western blot and found to be associated with the cytoskeleton. Confocal microscopy analysis showed that class I ligation stimulated increased eIF4A1 co-localization with F-actin and paxillin. CONCLUSIONS/SIGNIFICANCE Colocalization of eIF4A1 with F-actin and paxillin following HLA class I ligation suggests that this candidate protein could be a target for understanding the mechanism(s) of class I mediated antibody-mediated rejection. This proteomic approach for analyzing the cytoskeleton of ECs can be applied to other agonists and various cells types as a method for uncovering novel regulators of cytoskeleton changes.
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Affiliation(s)
- Mary E. Ziegler
- The Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Puneet Souda
- The Pasarow Mass Spectrometry Laboratory, The Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Yi-Ping Jin
- The Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Julian P. Whitelegge
- The Pasarow Mass Spectrometry Laboratory, The Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Elaine F. Reed
- The Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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14
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Translation initiation factors and active sites of protein synthesis co-localize at the leading edge of migrating fibroblasts. Biochem J 2011; 438:217-27. [PMID: 21539520 DOI: 10.1042/bj20110435] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cell migration is a highly controlled essential cellular process, often dysregulated in tumour cells, dynamically controlled by the architecture of the cell. Studies involving cellular fractionation and microarray profiling have previously identified functionally distinct mRNA populations specific to cellular organelles and architectural compartments. However, the interaction between the translational machinery itself and cellular structures is relatively unexplored. To help understand the role for the compartmentalization and localized protein synthesis in cell migration, we have used scanning confocal microscopy, immunofluorescence and a novel ribopuromycylation method to visualize translating ribosomes. In the present study we show that eIFs (eukaryotic initiation factors) localize to the leading edge of migrating MRC5 fibroblasts in a process dependent on TGN (trans-Golgi network) to plasma membrane vesicle transport. We show that eIF4E and eIF4GI are associated with the Golgi apparatus and membrane microdomains, and that a proportion of these proteins co-localize to sites of active translation at the leading edge of migrating cells.
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15
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Di Florio A, Adesso L, Pedrotti S, Capurso G, Pilozzi E, Corbo V, Scarpa A, Geremia R, Delle Fave G, Sette C. Src kinase activity coordinates cell adhesion and spreading with activation of mammalian target of rapamycin in pancreatic endocrine tumour cells. Endocr Relat Cancer 2011; 18:541-54. [PMID: 21712346 DOI: 10.1530/erc-10-0153] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Pancreatic endocrine tumours (PETs) are rare and heterogeneous neoplasms, often diagnosed at metastatic stage, for which no cure is currently available. Recently, activation of two pathways that support proliferation and invasiveness of cancer cells, the Src family kinase (SFK) and mammalian target of rapamycin (mTOR) pathways, was demonstrated in PETs. Since both pathways represent suitable targets for therapeutic intervention, we investigated their possible interaction in PETs. Western blot and immunofluorescence analyses indicated that SFK and mTOR activity correlate in PET cell lines. We also found that SFKs coordinate cell adhesion and spreading with activation of the mTOR pathway in PET cells. Live cell metabolic labelling and biochemical studies demonstrated that SFK activity enhance mTOR-dependent translation initiation. Furthermore, microarray analysis of the mRNAs associated with polyribosomes revealed that SFKs regulate mTOR-dependent translation of specific transcripts, with an enrichment in mRNAs encoding cell cycle proteins. Importantly, a synergic inhibition of proliferation was observed in PET cells concomitantly treated with SFK and mTOR inhibitors, without activation of the phosphatidylinositol 3-kinase/AKT pro-survival pathway. Tissue microarray analysis revealed activation of Src and mTOR in some PET samples, and identified phosphorylation of 4E-BP1 as an independent marker of poor prognosis in PETs. Thus, our work highlights a novel link between the SFK and mTOR pathways, which regulate the translation of mRNAs for cell cycle regulators, and suggest that crosstalk between these pathways promotes PET cell proliferation.
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Affiliation(s)
- Alessia Di Florio
- Department of Public Health and Cell Biology, University of Rome Tor Vergata, Italy
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16
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Localization of ribosomes and translation initiation factors to talin/beta3-integrin-enriched adhesion complexes in spreading and migrating mammalian cells. Biol Cell 2010; 102:265-76. [PMID: 19929852 DOI: 10.1042/bc20090141] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND INFORMATION The spatial localization of translation can facilitate the enrichment of proteins at their sites of function while also ensuring that proteins are expressed in the proximity of their cognate binding partners. RESULTS Using human embryonic lung fibroblasts and employing confocal imaging and biochemical fractionation techniques, we show that ribosomes, translation initiation factors and specific RNA-binding proteins localize to nascent focal complexes along the distal edge of migrating lamellipodia. 40S ribosomal subunits appear to associate preferentially with beta3 integrin in focal adhesions at the leading edges of spreading cells, with this association strongly augmented by a synergistic effect of cell engagement with a mixture of extracellular matrix proteins. However, both ribosome and initiation factor localizations do not require de novo protein synthesis. CONCLUSIONS Taken together, these findings demonstrate that repression, complex post-transcriptional regulation and modulation of mRNA stability could potentially be taking place along the distal edge of migrating lamellipodia.
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Wolf A, Krause-Gruszczynska M, Birkenmeier O, Ostareck-Lederer A, Hüttelmaier S, Hatzfeld M. Plakophilin 1 stimulates translation by promoting eIF4A1 activity. ACTA ACUST UNITED AC 2010; 188:463-71. [PMID: 20156963 PMCID: PMC2828926 DOI: 10.1083/jcb.200908135] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
p120 armadillo protein plakophilin 1 binds to eukaryotic translation factor eIF4A1, recruiting it into cap-binding complexes and stimulating translation. Plakophilins 1–3 (PKP1–3) are desmosomal proteins of the p120ctn family of armadillo-related proteins that are essential for organizing the desmosomal plaque. Recent findings identified PKPs in stress granules, suggesting an association with the translational machinery. However, a role of PKPs in controlling translation remained elusive so far. In this study, we show a direct association of PKP1 with the eukaryotic translation initiation factor 4A1 (eIF4A1). PKP1 stimulated eIF4A1-dependent translation via messenger RNA cap and encephalomyocarditis virus internal ribosomal entry site (IRES) structures, whereas eIF4A1-independent translation via hepatitis C virus IRES was not affected. PKP1 copurified with eIF4A1 in the cap complex, and its overexpression stimulated eIF4A1 recruitment into cap-binding complexes. At the molecular level, PKP1 directly promoted eIF4A1 adenosine triphosphatase activity. The stimulation of translation upon PKP1 overexpression correlated with the up-regulation of proliferation and cell size. In conclusion, these findings identify PKP1 as a regulator of translation and proliferation via modulation of eIF4A1 activity and suggest that PKP1 controls cell growth in physiological and pathological conditions.
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Affiliation(s)
- Annika Wolf
- Division of Pathobiochemistry, Martin Luther University Halle-Wittenberg, 06097 Halle, Germany
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18
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Subcellular localization of mRNA and factors involved in translation initiation. Biochem Soc Trans 2008; 36:648-52. [PMID: 18631134 DOI: 10.1042/bst0360648] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Both the process and synthesis of factors required for protein synthesis (or translation) account for a large proportion of cellular activity. In eukaryotes, the most complex and highly regulated phase of protein synthesis is that of initiation. For instance, across eukaryotes, at least 12 factors containing 22 or more proteins are involved, and there are several regulated steps. Recently, the localization of mRNA and factors involved in translation has received increased attention. The present review provides a general background to the subcellular localization of mRNA and translation initiation factors, and focuses on the potential functions of localized translation initiation factors. That is, as genuine sites for translation initiation, as repositories for factors and mRNA, and as sites of regulation.
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Eukaryotic translation initiation factor 4F architectural alterations accompany translation initiation factor redistribution in poxvirus-infected cells. Mol Cell Biol 2008; 28:2648-58. [PMID: 18250159 DOI: 10.1128/mcb.01631-07] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Despite their self-sufficient ability to generate capped mRNAs from cytosolic DNA genomes, poxviruses must commandeer the critical eukaryotic translation initiation factor 4F (eIF4F) to recruit ribosomes. While eIF4F integrates signals to control translation, precisely how poxviruses manipulate the multisubunit eIF4F, composed of the cap-binding eIF4E and the RNA helicase eIF4A assembled onto an eIF4G platform, remains obscure. Here, we establish that the poxvirus infection of normal, primary human cells destroys the translational repressor eIF4E binding protein (4E-BP) and promotes eIF4E assembly into an active eIF4F complex bound to the cellular polyadenylate-binding protein (PABP). Stimulation of the eIF4G-associated kinase Mnk1 promotes eIF4E phosphorylation and enhances viral replication and protein synthesis. Remarkably, these eIF4F architectural alterations are accompanied by the concentration of eIF4E and eIF4G within cytosolic viral replication compartments surrounded by PABP. This demonstrates that poxvirus infection redistributes, assembles, and modifies core and associated components of eIF4F and concentrates them within discrete subcellular compartments. Furthermore, it suggests that the subcellular distribution of eIF4F components may potentiate the complex assembly.
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Control of protein translation by phosphorylation of the mRNA 5′-cap-binding complex. Biochem Soc Trans 2007; 35:1634-7. [DOI: 10.1042/bst0351634] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Initiation of mRNA translation is a key regulatory step in the control of gene expression. Microarray analysis indicates that total mRNA levels do not always reflect protein levels, since mRNA association with polyribosomes is necessary for protein synthesis. Phosphorylation of translation initiation factors offers a cost-effective and rapid way to adapt to physiological and environmental changes, and there is increasing evidence that many of these factors are subject to multiple regulatory phosphorylation events. The present article focuses on the nature of reversible phosphorylation and the function of the 5′-cap-binding complex in plants.
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Abstract
Prolonged sepsis and exposure to an inflammatory milieu decreases muscle protein synthesis and reduces muscle mass. As a result of its ability to integrate diverse signals, including hormones and nutrients, the mammalian target of rapamycin (mTOR) is a dominant regulator in the translational control of protein synthesis. Under postabsorptive conditions, sepsis decreases mTOR kinase activity in muscle, as evidenced by reduced phosphorylation of both eukaryotic initiation factor (eIF)4E-binding protein (BP)-1 and ribosomal S6 kinase (S6K)1. These sepsis-induced changes, along with the redistribution of eIF4E from the active eIF4E.eIF4G complex to the inactive eIF4E.4E-BP1 complex, are preventable by neutralization of tumor necrosis factor (TNF)-alpha but not by antagonizing glucocorticoid action. Although the ability of mTOR to respond to insulin-like growth factor (IGF)-I is not disrupted by sepsis, the ability of leucine to increase 4E-BP1 and S6K1 phosphorylation is greatly attenuated. This "leucine resistance" results from a cooperative interaction between both TNF-alpha and glucocorticoids. Finally, although septic animals are not IGF-I resistant, the anabolic actions of IGF-I are nonetheless reduced because of the development of growth hormone resistance, which decreases both circulating and muscle IGF-I. Herein, we highlight recent advances in the mTOR signaling network and emphasize their connection to the atrophic response observed in skeletal muscle during sepsis. Although many unanswered questions remain, understanding the cellular basis of the sepsis-induced decrease in translational activity will contribute to the rational development of therapeutic interventions and thereby minimize the debilitating affects of the atrophic response that impairs patient recovery.
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Affiliation(s)
- Charles H Lang
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
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Hewett JW, Tannous B, Niland BP, Nery FC, Zeng J, Li Y, Breakefield XO. Mutant torsinA interferes with protein processing through the secretory pathway in DYT1 dystonia cells. Proc Natl Acad Sci U S A 2007; 104:7271-6. [PMID: 17428918 PMCID: PMC1855419 DOI: 10.1073/pnas.0701185104] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Indexed: 01/06/2023] Open
Abstract
TorsinA is an AAA(+) protein located predominantly in the lumen of the endoplasmic reticulum (ER) and nuclear envelope responsible for early onset torsion dystonia (DYT1). Most cases of this dominantly inherited movement disorder are caused by deletion of a glutamic acid in the carboxyl terminal region of torsinA. We used a sensitive reporter, Gaussia luciferase (Gluc) to evaluate the role of torsinA in processing proteins through the ER. In primary fibroblasts from controls and DYT1 patients most Gluc activity (95%) was released into the media and processed through the secretory pathway, as confirmed by inhibition with brefeldinA and nocodazole. Fusion of Gluc to a fluorescent protein revealed coalignment and fractionation with ER proteins and association of Gluc with torsinA. Notably, fibroblasts from DYT1 patients were found to secrete markedly less Gluc activity as compared with control fibroblasts. This decrease in processing of Gluc in DYT1 cells appear to arise, at least in part, from a loss of torsinA activity, because mouse embryonic fibroblasts lacking torsinA also had reduced secretion as compared with control cells. These studies demonstrate the exquisite sensitivity of this reporter system for quantitation of processing through the secretory pathway and support a role for torsinA as an ER chaperone protein.
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Affiliation(s)
- Jeffrey W. Hewett
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
| | - Bakhos Tannous
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
| | - Brian P. Niland
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
| | - Flavia C. Nery
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
| | - Juan Zeng
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
| | - Yuqing Li
- Department of Neurology and Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Xandra O. Breakefield
- *Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital, and Program in Neuroscience, Harvard Medical School, Boston, MA 02114; and
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