51
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Haghandish N, Baldwin RM, Morettin A, Dawit HT, Adhikary H, Masson JY, Mazroui R, Trinkle-Mulcahy L, Côté J. PRMT7 methylates eukaryotic translation initiation factor 2α and regulates its role in stress granule formation. Mol Biol Cell 2019; 30:778-793. [PMID: 30699057 PMCID: PMC6589776 DOI: 10.1091/mbc.e18-05-0330] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Protein arginine methyltransferases (PRMTs) are a family of enzymes that modify proteins by methylating the guanidino nitrogen atoms of arginine residues to regulate cellular processes such as chromatin remodeling, pre-mRNA splicing, and signal transduction. PRMT7 is the single type III PRMT solely capable of arginine monomethylation. To date, other than histone proteins, there are very few identified substrates of PRMT7. We therefore performed quantitative mass spectrometry experiments to identify PRMT7’s interactome and potential substrates to better characterize the enzyme’s biological function(s) in cells. These experiments revealed that PRMT7 interacts with and can methylate eukaryotic translation initiation factor 2 alpha (eIF2α), in vitro and in breast cancer cells. Furthermore, we uncovered a potential regulatory interplay between eIF2α arginine methylation by PRMT7 and stress-induced phosphorylation status of eIF2α at serine 51. Finally, we demonstrated that PRMT7 is required for eIF2α-dependent stress granule formation in the face of various cellular stresses. Altogether, our findings implicate PRMT7 as a novel mediator of eIF2α-dependent cellular stress response pathways.
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Affiliation(s)
- Nasim Haghandish
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - R Mitchell Baldwin
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Alan Morettin
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Haben Tesfu Dawit
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Hemanta Adhikary
- Oncology Division, CHU de Québec-Université Laval, Québec City, QC G1R 3S3, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, QC G1V 0A6, Canada
| | - Jean-Yves Masson
- Oncology Division, CHU de Québec-Université Laval, Québec City, QC G1R 3S3, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, QC G1V 0A6, Canada
| | - Rachid Mazroui
- Oncology Division, CHU de Québec-Université Laval, Québec City, QC G1R 3S3, Canada.,Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Québec City, QC G1V 0A6, Canada
| | - Laura Trinkle-Mulcahy
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jocelyn Côté
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
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52
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Yun SJ, Kim H, Jung SH, Kim JH, Ryu JE, Singh NJ, Jeon J, Han JK, Kim CH, Kim S, Jang SK, Kim WJ. The mechanistic insight of a specific interaction between 15d-Prostaglandin-J2 and eIF4A suggests an evolutionary conserved role across species. Biol Open 2018; 7:bio035402. [PMID: 30257829 PMCID: PMC6262856 DOI: 10.1242/bio.035402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/03/2018] [Indexed: 12/24/2022] Open
Abstract
15-deoxy-delta 12,14-prostaglandin J2 (15d-PGJ2) is an anti-inflammatory/anti-neoplastic prostaglandin that functions through covalent binding to cysteine residues of various target proteins. We previously showed that 15d-PGJ2 mediated anti-inflammatory responses are dependent on the translational inhibition through its interaction with eIF4A (Kim et al., 2007). Binding of 15d-PGJ2 to eIF4A specifically blocks the interaction between eIF4G and eIF4A, which leads to the formation of stress granules (SGs), which then cluster mRNAs with inhibited translation. Here, we show that the binding between 15d-PGJ2 and eIF4A specifically blocks the interaction between the MIF4G domain of eIF4G and eIF4A. To reveal the mechanism of this interaction, we used computational simulation-based docking studies and identified that the carboxyl tail of 15d-PGJ2 could stabilize the binding of 15d-PGJ2 to eIF4A through arginine 295 of eIF4A, which is the first suggestion that the 15d-PGJ2 tail plays a physiological role. Interestingly, the putative 15d-PGJ2 binding site on eiF4A is conserved across many species, suggesting a biological role. Our data propose that studying 15d-PGJ2 and its targets may uncover new therapeutic approaches in anti-inflammatory drug discovery.
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Affiliation(s)
- So Jeong Yun
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Hyunjoon Kim
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Seung-Hyun Jung
- Department of Biology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Joon Hyun Kim
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jeong Eun Ryu
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - N Jiten Singh
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jouhyun Jeon
- Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jin-Kwan Han
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Cheol-Hee Kim
- Department of Biology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Sanguk Kim
- Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Sung Key Jang
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Woo Jae Kim
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, K1H 8M5, Canada
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53
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Reineke LC, Cheema SA, Dubrulle J, Neilson JR. Chronic starvation induces noncanonical pro-death stress granules. J Cell Sci 2018; 131:jcs220244. [PMID: 30185525 PMCID: PMC6198455 DOI: 10.1242/jcs.220244] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/20/2018] [Indexed: 01/08/2023] Open
Abstract
Stress granules (SGs) assemble under stress-induced conditions that inhibit protein synthesis, including phosphorylation of eIF2α, inhibition of the RNA helicase eIF4a proteins or inactivation of mTORC1. Classically defined SGs are composed of translation initiation factors, 40S ribosomes, RNA-binding proteins and poly(A)+ mRNAs. As such, they represent an important compartment for storage of mRNAs and regulation of their translation. Emerging work on SGs indicates that these structures might promote cellular survival in diverse disease states. Yet, much work on SG formation and function employs acute stress conditions, which might not accurately reflect the chronic stresses that manifest in human disease. Here, we used prolonged nutrient starvation to model and investigate SG formation and function during chronic stress in a human cell line and mouse embryonic fibroblasts. Surprisingly, we found that SGs that form under chronic nutrient starvation lack 40S ribosomes, do not actively exchange their constituent components with cytoplasmic pools and promote cell death. We named these SGs starvation-induced SGs (stSGs). Our results on stSGs imply that SG assembly and function in the context of prolonged nutrient starvation stress differ significantly from what has been described for acute stress conditions.
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Affiliation(s)
- Lucas C Reineke
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA
| | - Shebna A Cheema
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Graduate Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA
| | - Julien Dubrulle
- Integrated Microscopy Core, Baylor College of Medicine, Houston, TX 77030, USA
| | - Joel R Neilson
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Dan L. Duncan Comprehensive Cancer Center, Baylor College of Medicine, Houston, TX 77030, USA
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54
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Kocaturk NM, Gozuacik D. Crosstalk Between Mammalian Autophagy and the Ubiquitin-Proteasome System. Front Cell Dev Biol 2018; 6:128. [PMID: 30333975 PMCID: PMC6175981 DOI: 10.3389/fcell.2018.00128] [Citation(s) in RCA: 275] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 09/13/2018] [Indexed: 12/16/2022] Open
Abstract
Autophagy and the ubiquitin-proteasome system (UPS) are the two major intracellular quality control and recycling mechanisms that are responsible for cellular homeostasis in eukaryotes. Ubiquitylation is utilized as a degradation signal by both systems, yet, different mechanisms are in play. The UPS is responsible for the degradation of short-lived proteins and soluble misfolded proteins whereas autophagy eliminates long-lived proteins, insoluble protein aggregates and even whole organelles (e.g., mitochondria, peroxisomes) and intracellular parasites (e.g., bacteria). Both the UPS and selective autophagy recognize their targets through their ubiquitin tags. In addition to an indirect connection between the two systems through ubiquitylated proteins, recent data indicate the presence of connections and reciprocal regulation mechanisms between these degradation pathways. In this review, we summarize these direct and indirect interactions and crosstalks between autophagy and the UPS, and their implications for cellular stress responses and homeostasis.
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Affiliation(s)
- Nur Mehpare Kocaturk
- Molecular Biology, Genetics and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey
| | - Devrim Gozuacik
- Molecular Biology, Genetics and Bioengineering Program, Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey
- Center of Excellence for Functional Surfaces and Interfaces for Nano Diagnostics (EFSUN), Sabanci University, Istanbul, Turkey
- Nanotechnology Research and Application Center (SUNUM), Sabanci University, Istanbul, Turkey
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55
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Bakthavachalu B, Huelsmeier J, Sudhakaran IP, Hillebrand J, Singh A, Petrauskas A, Thiagarajan D, Sankaranarayanan M, Mizoue L, Anderson EN, Pandey UB, Ross E, VijayRaghavan K, Parker R, Ramaswami M. RNP-Granule Assembly via Ataxin-2 Disordered Domains Is Required for Long-Term Memory and Neurodegeneration. Neuron 2018; 98:754-766.e4. [PMID: 29772202 DOI: 10.1016/j.neuron.2018.04.032] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 03/07/2018] [Accepted: 04/23/2018] [Indexed: 02/07/2023]
Abstract
Human Ataxin-2 is implicated in the cause and progression of amyotrophic lateral sclerosis (ALS) and type 2 spinocerebellar ataxia (SCA-2). In Drosophila, a conserved atx2 gene is essential for animal survival as well as for normal RNP-granule assembly, translational control, and long-term habituation. Like its human homolog, Drosophila Ataxin-2 (Atx2) contains polyQ repeats and additional intrinsically disordered regions (IDRs). We demonstrate that Atx2 IDRs, which are capable of mediating liquid-liquid phase transitions in vitro, are essential for efficient formation of neuronal mRNP assemblies in vivo. Remarkably, ΔIDR mutants that lack neuronal RNP granules show normal animal development, survival, and fertility. However, they show defects in long-term memory formation/consolidation as well as in C9ORF72 dipeptide repeat or FUS-induced neurodegeneration. Together, our findings demonstrate (1) that higher-order mRNP assemblies contribute to long-term neuronal plasticity and memory, and (2) that a targeted reduction in RNP-granule formation efficiency can alleviate specific forms of neurodegeneration.
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Affiliation(s)
| | - Joern Huelsmeier
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin-2, Ireland
| | | | - Jens Hillebrand
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin-2, Ireland
| | - Amanjot Singh
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India
| | - Arnas Petrauskas
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin-2, Ireland
| | | | | | - Laura Mizoue
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA; HHMI, University of Colorado, Boulder, CO 80309, USA
| | - Eric N Anderson
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Udai Bhan Pandey
- Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Eric Ross
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - K VijayRaghavan
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India
| | - Roy Parker
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA; HHMI, University of Colorado, Boulder, CO 80309, USA
| | - Mani Ramaswami
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India; Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College Dublin, Dublin-2, Ireland.
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56
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Alberti S, Carra S. Quality Control of Membraneless Organelles. J Mol Biol 2018; 430:4711-4729. [PMID: 29758260 DOI: 10.1016/j.jmb.2018.05.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/04/2018] [Accepted: 05/04/2018] [Indexed: 02/06/2023]
Abstract
The formation of membraneless organelles (MLOs) by phase separation has emerged as a new way of organizing the cytoplasm and nucleoplasm of cells. Examples of MLOs forming via phase separation are nucleoli in the nucleus and stress granules in the cytoplasm. The main components of these MLOs are macromolecules such as RNAs and proteins. In order to assemble by phase separation, these proteins and RNAs have to undergo many cooperative interactions. These cooperative interactions are supported by specific molecular features within phase-separating proteins, such as multivalency and the presence of disordered domains that promote weak and transient interactions. However, these features also predispose phase-separating proteins to aberrant behavior. Indeed, evidence is emerging for a strong link between phase-separating proteins, MLOs, and age-related diseases. In this review, we discuss recent progress in understanding the formation, properties, and functions of MLOs. We pay special attention to the emerging link between MLOs and age-related diseases, and we explain how changes in the composition and physical properties of MLOs promote their conversion into an aberrant state. Furthermore, we discuss the key role of the protein quality control machinery in regulating the properties and functions of MLOs and thus in preventing age-related diseases.
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Affiliation(s)
- Simon Alberti
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
| | - Serena Carra
- Department of Biomedical, Metabolic and Neural Science, University of Modena and Reggio Emilia, Center for Neuroscience and Neurotechnology, 41125 Modena, Italy.
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57
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Aguilera-Gomez A, Zacharogianni M, van Oorschot MM, Genau H, Grond R, Veenendaal T, Sinsimer KS, Gavis ER, Behrends C, Rabouille C. Phospho-Rasputin Stabilization by Sec16 Is Required for Stress Granule Formation upon Amino Acid Starvation. Cell Rep 2018; 20:935-948. [PMID: 28746877 DOI: 10.1016/j.celrep.2017.06.042] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 04/22/2017] [Accepted: 06/16/2017] [Indexed: 12/15/2022] Open
Abstract
Most cellular stresses induce protein translation inhibition and stress granule formation. Here, using Drosophila S2 cells, we investigate the role of G3BP/Rasputin in this process. In contrast to arsenite treatment, where dephosphorylated Ser142 Rasputin is recruited to stress granules, we find that, upon amino acid starvation, only the phosphorylated Ser142 form is recruited. Furthermore, we identify Sec16, a component of the endoplasmic reticulum exit site, as a Rasputin interactor and stabilizer. Sec16 depletion results in Rasputin degradation and inhibition of stress granule formation. However, in the absence of Sec16, pharmacological stabilization of Rasputin is not enough to rescue the assembly of stress granules. This is because Sec16 specifically interacts with phosphorylated Ser142 Rasputin, the form required for stress granule formation upon amino acid starvation. Taken together, these results demonstrate that stress granule formation is fine-tuned by specific signaling cues that are unique to each stress. These results also expand the role of Sec16 as a stress response protein.
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Affiliation(s)
- Angelica Aguilera-Gomez
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Margarita Zacharogianni
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Marinke M van Oorschot
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Heide Genau
- Institute of Biochemistry II, Medical School Goethe University, 60323 Frankfurt am Main, Germany
| | - Rianne Grond
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands
| | - Tineke Veenendaal
- Department of Cell Biology, UMC Utrecht, 3584 CT Utrecht, the Netherlands
| | - Kristina S Sinsimer
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Elizabeth R Gavis
- Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Christian Behrends
- Institute of Biochemistry II, Medical School Goethe University, 60323 Frankfurt am Main, Germany
| | - Catherine Rabouille
- Hubrecht Institute-KNAW & University Medical Center (UMC) Utrecht, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Cell Biology, UMC Utrecht, 3584 CT Utrecht, the Netherlands; Department of Cell Biology, UMC Groningen, 9713 GZ Groningen, the Netherlands.
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58
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Perez-Pepe M, Fernández-Alvarez AJ, Boccaccio GL. Life and Work of Stress Granules and Processing Bodies: New Insights into Their Formation and Function. Biochemistry 2018; 57:2488-2498. [PMID: 29595960 DOI: 10.1021/acs.biochem.8b00025] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The dynamic formation of stress granules (SGs), processing bodies (PBs), and related RNA organelles regulates diverse cellular processes, including the coordination of functionally connected messengers, the translational regulation at the synapse, and the control of viruses and retrotransposons. Recent studies have shown that pyruvate kinase and other enzymes localize in SGs and PBs, where they become protected from stress insults. These observations may have implications for enzyme regulation and metabolic control exerted by RNA-based organelles. The formation of these cellular bodies is governed by liquid-liquid phase separation (LLPS) processes, and it needs to be strictly controlled to prevent pathogenic aggregation. The intracellular concentration of key metabolites, such as ATP and sterol derivatives, may influence protein solubility, thus affecting the dynamics of liquid organelles. LLPS in vitro depends on the thermal diffusion of macromolecules, which is limited inside cells, where the condensation and dissolution of membrane-less organelles are helped by energy-driven processes. The active transport by the retrograde motor dynein helps SG assembly, whereas the anterograde motor kinesin mediates SG dissolution; a tug of war between these two molecular motors allows transient SG formation. There is evidence that the efficiency of dynein-mediated transport increases with the number of motor molecules associated with the cargo. The dynein-dependent transport may be influenced by cargo size as larger cargos can load a larger number of motors. We propose a model based on this emergent property of dynein motors, which would be collectively stronger during SG condensation and weaker during SG breakdown, thus allowing kinesin-mediated dispersion.
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Affiliation(s)
- Marcelo Perez-Pepe
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
| | - Ana J Fernández-Alvarez
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
| | - Graciela L Boccaccio
- Instituto Leloir and Instituto de Investigaciones Bioquı́micas de Buenos Aires (IIBBA)-CONICET , Buenos Aires , Argentina
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59
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Jauhari A, Singh T, Yadav S. Expression of miR-145 and Its Target Proteins Are Regulated by miR-29b in Differentiated Neurons. Mol Neurobiol 2018; 55:8978-8990. [PMID: 29619741 DOI: 10.1007/s12035-018-1009-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 03/15/2018] [Indexed: 12/21/2022]
Abstract
MicroRNAs (miRNAs) are emerging as the most potential regulator of neuronal development. Recent studies from our lab and elsewhere have demonstrated a direct role of miRNAs in regulating neuronal differentiation and synaptogenesis. MicroRNA-145, a miRNA identified to regulate pluripotency of stem cells, downregulates the protein levels of reprogramming transcription factors (RTFs) like OCT4, SOX2, and KLF4 (cell, 137,647-658,2009). Studies have shown that miR-145 is multifunctional and crucial for fate determination of neurons. In our recently published study, we have identified a set of miRNAs including miR-145 and miR-29b families differentially expressed in SH-SY5Y cells exposed sequentially with retinoic acid + brain-derived neurotrophic factor (RA+BDNF) for differentiation into mature neurons (Mol Neurobiol (2016) doi: https://doi.org/10.1007/s12035-016-0042-9 ). In the present study, we have identified the role of miR-29b in upregulation of miR-145, which is upregulated after exposure of RA+BDNF in a P53-dependent manner. In differentiating SH-SY5Y cells, expression of miR-29b downregulates expression of P85α, a P53 inhibitor, which results in upregulation of miR-145 and downregulation of RTF proteins. Ectopic expression of miR-145 and miR-29b in amounts equivalent to their endogenous expression has induced G1 phase cell cycle arrest. In conclusion, our studies have identified miR-29b as an upstream regulator of miR-145 and targets its RTF genes during differentiation of SH-SY5Y cells.
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Affiliation(s)
- Abhishek Jauhari
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR- Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31 Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, -226001, India.,Academy of Scientific and Innovative Research (AcSIR), CSIR- IITR Campus, New Delhi, India
| | - Tanisha Singh
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR- Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31 Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, -226001, India.,Department of Biochemistry, School of Dental Sciences, Babu Banarasi Das University, Lucknow, Uttar Pradesh, India
| | - Sanjay Yadav
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR- Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhawan, 31 Mahatma Gandhi Marg, Lucknow, Uttar Pradesh, -226001, India.
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60
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Berson A, Sartoris A, Nativio R, Van Deerlin V, Toledo JB, Porta S, Liu S, Chung CY, Garcia BA, Lee VMY, Trojanowski JQ, Johnson FB, Berger SL, Bonini NM. TDP-43 Promotes Neurodegeneration by Impairing Chromatin Remodeling. Curr Biol 2017; 27:3579-3590.e6. [PMID: 29153328 PMCID: PMC5720388 DOI: 10.1016/j.cub.2017.10.024] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/20/2017] [Accepted: 10/09/2017] [Indexed: 12/12/2022]
Abstract
Regulation of chromatin structure is critical for brain development and function. However, the involvement of chromatin dynamics in neurodegeneration is less well understood. Here we find, launching from Drosophila models of amyotrophic lateral sclerosis and frontotemporal dementia, that TDP-43 impairs the induction of multiple key stress genes required to protect from disease by reducing the recruitment of the chromatin remodeler Chd1 to chromatin. Chd1 depletion robustly enhances TDP-43-mediated neurodegeneration and promotes the formation of stress granules. Conversely, upregulation of Chd1 restores nucleosomal dynamics, promotes normal induction of protective stress genes, and rescues stress sensitivity of TDP-43-expressing animals. TDP-43-mediated impairments are conserved in mammalian cells, and, importantly, the human ortholog CHD2 physically interacts with TDP-43 and is strikingly reduced in level in temporal cortex of human patient tissue. These findings indicate that TDP-43-mediated neurodegeneration causes impaired chromatin dynamics that prevents appropriate expression of protective genes through compromised function of the chromatin remodeler Chd1/CHD2. Enhancing chromatin dynamics may be a treatment approach to amyotrophic lateral scleorosis (ALS)/frontotemporal dementia (FTD).
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Affiliation(s)
- Amit Berson
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ashley Sartoris
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Raffaella Nativio
- Epigenetics Institute, Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Vivianna Van Deerlin
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jon B Toledo
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sílvia Porta
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shichong Liu
- Epigenetics Institute, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Chia-Yu Chung
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Benjamin A Garcia
- Epigenetics Institute, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Virginia M-Y Lee
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - F Brad Johnson
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Shelley L Berger
- Epigenetics Institute, Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nancy M Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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61
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Effects of oxidative and thermal stresses on stress granule formation in human induced pluripotent stem cells. PLoS One 2017; 12:e0182059. [PMID: 28746394 PMCID: PMC5528897 DOI: 10.1371/journal.pone.0182059] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 07/11/2017] [Indexed: 12/14/2022] Open
Abstract
Stress Granules (SGs) are dynamic ribonucleoprotein aggregates, which have been observed in cells subjected to environmental stresses, such as oxidative stress and heat shock (HS). Although pluripotent stem cells (PSCs) are highly sensitive to oxidative stress, the role of SGs in regulating PSC self-renewal and differentiation has not been fully elucidated. Here we found that sodium arsenite (SA) and HS, but not hydrogen peroxide (H2O2), induce SG formation in human induced (hi) PSCs. Particularly, we found that these granules contain the well-known SG proteins (G3BP, TIAR, eIF4E, eIF4A, eIF3B, eIF4G, and PABP), were found in juxtaposition to processing bodies (PBs), and were disassembled after the removal of the stress. Moreover, we showed that SA and HS, but not H2O2, promote eIF2α phosphorylation in hiPSCs forming SGs. Analysis of pluripotent protein expression showed that HS significantly reduced all tested markers (OCT4, SOX2, NANOG, KLF4, L1TD1, and LIN28A), while SA selectively reduced the expression levels of NANOG and L1TD1. Finally, in addition to LIN28A and L1TD1, we identified DPPA5 (pluripotent protein marker) as a novel component of SGs. Collectively, these results provide new insights into the molecular cues of hiPSCs responses to environmental insults.
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62
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Cinti A, Le Sage V, Milev MP, Valiente-Echeverría F, Crossie C, Miron MJ, Panté N, Olivier M, Mouland AJ. HIV-1 enhances mTORC1 activity and repositions lysosomes to the periphery by co-opting Rag GTPases. Sci Rep 2017; 7:5515. [PMID: 28710431 PMCID: PMC5511174 DOI: 10.1038/s41598-017-05410-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 05/30/2017] [Indexed: 12/20/2022] Open
Abstract
HIV-1 co-opts several host machinery to generate a permissive environment for viral replication and transmission. In this work we reveal how HIV-1 impacts the host translation and intracellular vesicular trafficking machineries for protein synthesis and to impede the physiological late endosome/lysosome (LEL) trafficking in stressful conditions. First, HIV-1 enhances the activity of the master regulator of protein synthesis, the mammalian target of rapamycin (mTOR). Second, the virus commandeers mTOR-associated late endosome/lysosome (LEL) trafficking and counteracts metabolic and environmental stress-induced intracellular repositioning of LEL. We then show that the small Rag GTPases, RagA and RagB, are required for the HIV-1-mediated LEL repositioning that is likely mediated by interactions between the Rags and the viral proteins, Gag and Vif. siRNA-mediated depletion of RagA and RagB leads to a loss in mTOR association to LEL and to a blockade of viral particle assembly and release at the plasma membrane with a marked concomitant reduction in virus production. These results show that HIV-1 co-opts fundamental mechanisms that regulate LEL motility and positioning and support the notion that LEL positioning is critical for HIV-1 replication.
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Affiliation(s)
- Alessandro Cinti
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada
| | - Valerie Le Sage
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada
| | - Miroslav P Milev
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada
| | - Fernando Valiente-Echeverría
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada.,Molecular and Cellular Virology Laboratory, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Independencia, 834100, Santiago, Chile
| | - Christina Crossie
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada
| | - Marie-Joelle Miron
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada
| | - Nelly Panté
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Martin Olivier
- Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada.,Department of Microbiology and Immunology, McGill University, Montréal, Québec, H3A 2B4, Canada
| | - Andrew J Mouland
- HIV-1 RNA Trafficking Laboratory, Lady Davis Institute at the Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada. .,Department of Medicine and the Division of Experimental Medicine, McGill University, Montréal, Québec, H3A 0G4, Canada. .,Department of Microbiology and Immunology, McGill University, Montréal, Québec, H3A 2B4, Canada.
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63
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Yenigun VB, Sirito M, Amcheslavky A, Czernuszewicz T, Colonques-Bellmunt J, García-Alcover I, Wojciechowska M, Bolduc C, Chen Z, López Castel A, Krahe R, Bergmann A. (CCUG) n RNA toxicity in a Drosophila model of myotonic dystrophy type 2 (DM2) activates apoptosis. Dis Model Mech 2017. [PMID: 28623239 PMCID: PMC5560059 DOI: 10.1242/dmm.026179] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The myotonic dystrophies are prototypic toxic RNA gain-of-function diseases. Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are caused by different unstable, noncoding microsatellite repeat expansions – (CTG)DM1 in DMPK and (CCTG)DM2 in CNBP. Although transcription of mutant repeats into (CUG)DM1 or (CCUG)DM2 appears to be necessary and sufficient to cause disease, their pathomechanisms remain incompletely understood. To study the mechanisms of (CCUG)DM2 toxicity and develop a convenient model for drug screening, we generated a transgenic DM2 model in the fruit fly Drosophila melanogaster with (CCUG)n repeats of variable length (n=16 and 106). Expression of noncoding (CCUG)106, but not (CCUG)16, in muscle and retinal cells led to the formation of ribonuclear foci and mis-splicing of genes implicated in DM pathology. Mis-splicing could be rescued by co-expression of human MBNL1, but not by CUGBP1 (CELF1) complementation. Flies with (CCUG)106 displayed strong disruption of external eye morphology and of the underlying retina. Furthermore, expression of (CCUG)106 in developing retinae caused a strong apoptotic response. Inhibition of apoptosis rescued the retinal disruption in (CCUG)106 flies. Finally, we tested two chemical compounds that have shown therapeutic potential in DM1 models. Whereas treatment of (CCUG)106 flies with pentamidine had no effect, treatment with a PKR inhibitor blocked both the formation of RNA foci and apoptosis in retinae of (CCUG)106 flies. Our data indicate that expression of expanded (CCUG)DM2 repeats is toxic, causing inappropriate cell death in affected fly eyes. Our Drosophila DM2 model might provide a convenient tool for in vivo drug screening. Summary: A Drosophila model of myotonic dystrophy type 2 (DM2) recapitulates several features of the human disease, identifies apoptosis as a contributing factor to DM2, and is likely to provide a convenient tool for drug screening.
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Affiliation(s)
- Vildan Betul Yenigun
- Department of Biochemistry & Molecular Biology, University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Departments of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Graduate Programs in Genes & Development, University of Texas Graduate School in Biomedical Sciences at Houston, Houston, TX, USA
| | - Mario Sirito
- Departments of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Alla Amcheslavky
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Tomek Czernuszewicz
- Departments of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | | | | | - Marzena Wojciechowska
- Departments of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Clare Bolduc
- Department of Biochemistry & Molecular Biology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Zhihong Chen
- Department of Biochemistry & Molecular Biology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | | | - Ralf Krahe
- Departments of Genetics, University of Texas MD Anderson Cancer Center, Houston, TX, USA .,Graduate Programs in Genes & Development, University of Texas Graduate School in Biomedical Sciences at Houston, Houston, TX, USA.,Graduate Programs in Human & Molecular Genetics, University of Texas Graduate School in Biomedical Sciences at Houston, Houston, Texas, USA
| | - Andreas Bergmann
- Department of Biochemistry & Molecular Biology, University of Texas MD Anderson Cancer Center, Houston, TX, USA .,Graduate Programs in Genes & Development, University of Texas Graduate School in Biomedical Sciences at Houston, Houston, TX, USA.,Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA, USA
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64
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Riback JA, Katanski CD, Kear-Scott JL, Pilipenko EV, Rojek AE, Sosnick TR, Drummond DA. Stress-Triggered Phase Separation Is an Adaptive, Evolutionarily Tuned Response. Cell 2017; 168:1028-1040.e19. [PMID: 28283059 DOI: 10.1016/j.cell.2017.02.027] [Citation(s) in RCA: 543] [Impact Index Per Article: 77.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 12/17/2016] [Accepted: 02/16/2017] [Indexed: 01/08/2023]
Abstract
In eukaryotic cells, diverse stresses trigger coalescence of RNA-binding proteins into stress granules. In vitro, stress-granule-associated proteins can demix to form liquids, hydrogels, and other assemblies lacking fixed stoichiometry. Observing these phenomena has generally required conditions far removed from physiological stresses. We show that poly(A)-binding protein (Pab1 in yeast), a defining marker of stress granules, phase separates and forms hydrogels in vitro upon exposure to physiological stress conditions. Other RNA-binding proteins depend upon low-complexity regions (LCRs) or RNA for phase separation, whereas Pab1's LCR is not required for demixing, and RNA inhibits it. Based on unique evolutionary patterns, we create LCR mutations, which systematically tune its biophysical properties and Pab1 phase separation in vitro and in vivo. Mutations that impede phase separation reduce organism fitness during prolonged stress. Poly(A)-binding protein thus acts as a physiological stress sensor, exploiting phase separation to precisely mark stress onset, a broadly generalizable mechanism.
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Affiliation(s)
- Joshua A Riback
- Graduate Program in the Biophysical Sciences, University of Chicago, Chicago, IL 60673, USA
| | - Christopher D Katanski
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA
| | - Jamie L Kear-Scott
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA
| | - Evgeny V Pilipenko
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA
| | - Alexandra E Rojek
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA
| | - Tobin R Sosnick
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA; Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60673, USA; Institute of Molecular Engineering, University of Chicago, Chicago, IL 60673, USA
| | - D Allan Drummond
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago, IL 60673, USA; Department of Human Genetics, University of Chicago, Chicago, IL 60673, USA.
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65
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Lo Piccolo L, Yamaguchi M. RNAi of arcRNA hsrω affects sub-cellular localization of Drosophila FUS to drive neurodiseases. Exp Neurol 2017; 292:125-134. [PMID: 28342748 DOI: 10.1016/j.expneurol.2017.03.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 03/01/2017] [Accepted: 03/21/2017] [Indexed: 02/08/2023]
Abstract
Defective RNA metabolism is common pathogenic mechanisms involved in neurological disorders. Indeed, a conspicuous feature of some neurodegenerative diseases is the loss of nuclear activities of RNA-binding proteins (RBPs) like Fused in sarcoma (FUS) and eventually, their accumulation in cytoplasmic proteinaceous inclusions. Long non-coding RNAs (lncRNAs) are emerging as important regulators of tissue physiology and disease processes, including neurological disorders. A subset of these lncRNAs is the core of nuclear bodies (NBs), which are the sites of RNA processing and sequestration of specific ribonucleoproteins (RNPs) complexes. In Drosophila melanogaster the lncRNA hsrω is the architectural RNA (arcRNA) of the NB omega speckles (ω-speckles). Here, we show that the neuron-specific and motor neuron-specific knockdown of hsrω impairs locomotion in larval and adult flies and induces anatomical defects in presynaptic terminals of motor neurons, suggesting a novel role of arcRNA hsrω in development of neuromuscular junctions. Since RBPs are recognized as important regulators of neuronal activities, to examine the molecular mechanism of such neurodegeneration, we analysed interaction between hsrω and Drosophila orthologue of human FUS (dFUS). Strictly, we found that dFUS genetically and physically interacts with the arcRNA hsrω. Moreover, we revealed that a fine regulation of gene expression occurs between hsrω and dFUS and surprisingly, we uncover that depletion of hsrω affects the sub-cellular compartmentalization of dFUS thus, enhancing its cytoplasmic localization and inducing its loss of nuclear function. The model we propose shows the role of arcRNA in diseases affecting the nervous system and in particular it elucidates the molecular mechanism underlying the loss of dFUS nuclear function in the absence of its mutations. Our new findings could provide new insights into the pathogenesis of neurodegenerative disease dependent on mis-function or mis-localization of aggregation prone RNA binding proteins like FUS in Amyotrophic Lateral Sclerosis.
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Affiliation(s)
- Luca Lo Piccolo
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
| | - Masamitsu Yamaguchi
- Department of Applied Biology, The Center for Advanced Insect Research, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
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66
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Dissecting the molecular mechanisms that impair stress granule formation in aging cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:475-486. [DOI: 10.1016/j.bbamcr.2016.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 11/21/2016] [Accepted: 12/09/2016] [Indexed: 01/20/2023]
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67
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Casein Kinase 2 Is Linked to Stress Granule Dynamics through Phosphorylation of the Stress Granule Nucleating Protein G3BP1. Mol Cell Biol 2017; 37:MCB.00596-16. [PMID: 27920254 DOI: 10.1128/mcb.00596-16] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 11/29/2016] [Indexed: 12/27/2022] Open
Abstract
Stress granules (SGs) are large macromolecular aggregates that contain translation initiation complexes and mRNAs. Stress granule formation coincides with translational repression, and stress granules actively signal to mediate cell fate decisions by signaling to the translation apparatus to (i) maintain translational repression, (ii) mount various transcriptional responses, including innate immunity, and (iii) repress apoptosis. Previous work showed that G3BP1 is phosphorylated at serine 149, which regulates G3BP1 oligomerization, stress granule assembly, and RNase activity intrinsic to G3BP1. However, the kinase that phosphorylates G3BP1 was not identified, leaving a key step in stress granule regulation uncharacterized. Here, using chemical inhibition, genetic depletion, and overexpression experiments, we show that casein kinase 2 (CK2) promotes stress granule dynamics. These results link CK2 activity with SG disassembly. We also show that casein kinase 2 phosphorylates G3BP1 at serine 149 in vitro and in cells. These data support a role for casein kinase 2 in regulation of protein synthesis by downregulating stress granule formation through G3BP1.
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68
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Mahboubi H, Stochaj U. Cytoplasmic stress granules: Dynamic modulators of cell signaling and disease. Biochim Biophys Acta Mol Basis Dis 2017; 1863:884-895. [PMID: 28095315 DOI: 10.1016/j.bbadis.2016.12.022] [Citation(s) in RCA: 187] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 12/15/2016] [Accepted: 12/26/2016] [Indexed: 12/14/2022]
Abstract
Stress granule (SG) assembly is a conserved cellular strategy to minimize stress-related damage and promote cell survival. Beyond their fundamental role in the stress response, SGs have emerged as key players for human health. As such, SG assembly is associated with cancer, neurodegenerative disorders, ischemia, and virus infections. SGs and granule-related signaling circuits are therefore promising targets to improve therapeutic intervention for several diseases. This is clinically relevant, because pharmacological drugs can affect treatment outcome by modulating SG formation. As membraneless and highly dynamic compartments, SGs regulate translation, ribostasis and proteostasis. Moreover, they serve as signaling hubs that determine cell viability and stress recovery. Various compounds can modulate SG formation and dynamics. Rewiring cell signaling through SG manipulation thus represents a new strategy to control cell fate under various physiological and pathological conditions.
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Affiliation(s)
- Hicham Mahboubi
- Department of Physiology, McGill University, Montreal, Canada
| | - Ursula Stochaj
- Department of Physiology, McGill University, Montreal, Canada.
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69
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Bai Y, Dong Z, Shang Q, Zhao H, Wang L, Guo C, Gao F, Zhang L, Wang Q. Pdcd4 Is Involved in the Formation of Stress Granule in Response to Oxidized Low-Density Lipoprotein or High-Fat Diet. PLoS One 2016; 11:e0159568. [PMID: 27454120 PMCID: PMC4959751 DOI: 10.1371/journal.pone.0159568] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 07/04/2016] [Indexed: 12/26/2022] Open
Abstract
Stress granules (SGs) in response to various stresses have been reported in many diseases. We previously reported the implication of programmed cell death 4 (Pdcd4) in obesity-induced stress responses, but the possible link between Pdcd4 and SGs remains lacking. In this study we showed that oxidized low-density lipoprotein (ox-LDL) or high-fat diet (HFD) induced SG formation in mouse macrophages and liver tissues, and Pdcd4 deficiency in mice remarkably reduced its formation. In response to ox-LDL, either endogenous or ectopic Pdcd4 displayed granule-like expression and co-localized with SG markers including T-cell-restricted intracellular antigen-1, fragile X mental retardation-related protein 1, and eukaryotic initiation factor 4A. Ectopic expression of truncated Pdcd4 that depleted specific RNA-binding motif significantly disrupted the SG formation, suggesting the direct involvement of Pdcd4 in ox-LDL-induced SGs through its RNA-binding activity. Additionally, Pdcd4 deficiency drove AKT activation and suppression of eIF2α phosphorylation, thereby contributing to the resistance to ox-LDL or HFD-induced SG formation. Collectively, our data suggest that Pdcd4 as a crucial regulator in SGs induced by ox-LDL or HFD maybe a potential target for mitigating SG-associated stress responses in obesity and related diseases.
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Affiliation(s)
- Yang Bai
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Zhaojing Dong
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Qianwen Shang
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Hui Zhao
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Liyang Wang
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Chun Guo
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Fei Gao
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Public Health, Qilu Hospital, Shandong University, Jinan 250012, Shandong, China
| | - Lining Zhang
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
| | - Qun Wang
- Department of Immunology, Shandong University School of Medicine, Jinan 250012, Shandong, China
- * E-mail:
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70
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Gleason LU, Burton RS. Genomic evidence for ecological divergence against a background of population homogeneity in the marine snail Chlorostoma funebralis. Mol Ecol 2016; 25:3557-73. [PMID: 27199218 DOI: 10.1111/mec.13703] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 04/29/2016] [Accepted: 05/03/2016] [Indexed: 12/19/2022]
Abstract
The balance between natural selection, gene flow and genetic drift is difficult to resolve in marine invertebrates with extensive dispersal and fluctuating population sizes. The intertidal snail Chlorostoma funebralis has planktonic larvae and previous work using mtDNA polymorphism reported no genetic population structure. Nevertheless, recent studies have documented differences in thermal tolerance and transcriptomic responses to heat stress between northern and southern California, USA, populations. To gain insight into the dynamics influencing adaptive divergence, we used double-digest restriction site-associated DNA (ddRAD) sequencing to identify 1861 genomewide, quality-filtered single-nucleotide polymorphism (SNP) loci for C. funebralis collected from three northern and three southern California sites (15 individuals per population). Considering all SNPs, there was no evidence for genetic differentiation among populations or regions (average FST = 0.0042). However, outlier tests revealed 34 loci putatively under divergent selection between northern and southern populations, and structure and SNP tree analyses based on these outliers show clear genetic differentiation between geographic regions. Three of these outliers are known or hypothesized to be involved in stress granule formation, a response to environmental stress such as heat. Combined with previous work that found thermally tolerant southern populations show high baseline expression of stress response genes, these results further suggest that thermal stress is a strong selective pressure across C. funebralis populations. Overall, this study increases our understanding of the factors constraining local adaptation in marine organisms, while suggesting that ecologically driven, strong differentiation can occur at relevant loci in a species with planktonic larvae.
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Affiliation(s)
- Lani U Gleason
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, 92093-0202, USA.,Department of Biology, Loyola Marymount University, Los Angeles, CA, 90045, USA
| | - Ronald S Burton
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, 92093-0202, USA
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71
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Ravel-Chapuis A, Klein Gunnewiek A, Bélanger G, Crawford Parks TE, Côté J, Jasmin BJ. Staufen1 impairs stress granule formation in skeletal muscle cells from myotonic dystrophy type 1 patients. Mol Biol Cell 2016; 27:1728-39. [PMID: 27030674 PMCID: PMC4884064 DOI: 10.1091/mbc.e15-06-0356] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 03/25/2016] [Indexed: 11/11/2022] Open
Abstract
Myotonic dystrophy (DM1) is caused by an expansion of CUG repeats (CUG(exp)) in the DMPK mRNA 3'UTR. CUG(exp)-containing mRNAs become toxic to cells by misregulating RNA-binding proteins. Here we investigated the consequence of this RNA toxicity on the cellular stress response. We report that cell stress efficiently triggers formation of stress granules (SGs) in proliferating, quiescent, and differentiated muscle cells, as shown by the appearance of distinct cytoplasmic TIA-1- and DDX3-containing foci. We show that Staufen1 is also dynamically recruited into these granules. Moreover, we discovered that DM1 myoblasts fail to properly form SGs in response to arsenite. This blockage was not observed in DM1 fibroblasts, demonstrating a cell type-specific defect. DM1 myoblasts display increased expression and sequestration of toxic CUG(exp) mRNAs compared with fibroblasts. Of importance, down-regulation of Staufen1 in DM1 myoblasts rescues SG formation. Together our data show that Staufen1 participates in the inhibition of SG formation in DM1 myoblasts. These results reveal that DM1 muscle cells fail to properly respond to stress, thereby likely contributing to the complex pathogenesis of DM1.
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Affiliation(s)
- Aymeric Ravel-Chapuis
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Amanda Klein Gunnewiek
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Guy Bélanger
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Tara E Crawford Parks
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jocelyn Côté
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Bernard J Jasmin
- Department of Cellular and Molecular Medicine and Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
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72
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Temporal Regulation of Distinct Internal Ribosome Entry Sites of the Dicistroviridae Cricket Paralysis Virus. Viruses 2016; 8:v8010025. [PMID: 26797630 PMCID: PMC4728584 DOI: 10.3390/v8010025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 01/08/2016] [Accepted: 01/11/2016] [Indexed: 01/04/2023] Open
Abstract
Internal ribosome entry is a key mechanism for viral protein synthesis in a subset of RNA viruses. Cricket paralysis virus (CrPV), a member of Dicistroviridae, has a positive-sense single strand RNA genome that contains two internal ribosome entry sites (IRES), a 5′untranslated region (5′UTR) and intergenic region (IGR) IRES, that direct translation of open reading frames (ORF) encoding the viral non-structural and structural proteins, respectively. The regulation of and the significance of the CrPV IRESs during infection are not fully understood. In this study, using a series of biochemical assays including radioactive-pulse labelling, reporter RNA assays and ribosome profiling, we demonstrate that while 5′UTR IRES translational activity is constant throughout infection, IGR IRES translation is delayed and then stimulated two to three hours post infection. The delay in IGR IRES translation is not affected by inhibiting global translation prematurely via treatment with Pateamine A. Using a CrPV replicon that uncouples viral translation and replication, we show that the increase in IGR IRES translation is dependent on expression of non-structural proteins and is greatly stimulated when replication is active. Temporal regulation by distinct IRESs within the CrPV genome is an effective viral strategy to ensure optimal timing and expression of viral proteins to facilitate infection.
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73
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Fan AC, Leung AKL. RNA Granules and Diseases: A Case Study of Stress Granules in ALS and FTLD. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 907:263-96. [PMID: 27256390 DOI: 10.1007/978-3-319-29073-7_11] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
RNA granules are microscopically visible cellular structures that aggregate by protein-protein and protein-RNA interactions. Using stress granules as an example, we discuss the principles of RNA granule formation, which rely on the multivalency of RNA and multi-domain proteins as well as low-affinity interactions between proteins with prion-like/low-complexity domains (e.g. FUS and TDP-43). We then explore how dysregulation of RNA granule formation is linked to neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), and discuss possible strategies for therapeutic intervention.
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Affiliation(s)
- Alexander C Fan
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
| | - Anthony K L Leung
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
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74
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Wallace EWJ, Kear-Scott JL, Pilipenko EV, Schwartz MH, Laskowski PR, Rojek AE, Katanski CD, Riback JA, Dion MF, Franks AM, Airoldi EM, Pan T, Budnik BA, Drummond DA. Reversible, Specific, Active Aggregates of Endogenous Proteins Assemble upon Heat Stress. Cell 2015; 162:1286-98. [PMID: 26359986 DOI: 10.1016/j.cell.2015.08.041] [Citation(s) in RCA: 327] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 06/19/2015] [Accepted: 08/05/2015] [Indexed: 01/03/2023]
Abstract
Heat causes protein misfolding and aggregation and, in eukaryotic cells, triggers aggregation of proteins and RNA into stress granules. We have carried out extensive proteomic studies to quantify heat-triggered aggregation and subsequent disaggregation in budding yeast, identifying >170 endogenous proteins aggregating within minutes of heat shock in multiple subcellular compartments. We demonstrate that these aggregated proteins are not misfolded and destined for degradation. Stable-isotope labeling reveals that even severely aggregated endogenous proteins are disaggregated without degradation during recovery from shock, contrasting with the rapid degradation observed for many exogenous thermolabile proteins. Although aggregation likely inactivates many cellular proteins, in the case of a heterotrimeric aminoacyl-tRNA synthetase complex, the aggregated proteins remain active with unaltered fidelity. We propose that most heat-induced aggregation of mature proteins reflects the operation of an adaptive, autoregulatory process of functionally significant aggregate assembly and disassembly that aids cellular adaptation to thermal stress.
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Affiliation(s)
- Edward W J Wallace
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Jamie L Kear-Scott
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Evgeny V Pilipenko
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Michael H Schwartz
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Pawel R Laskowski
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Alexandra E Rojek
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Christopher D Katanski
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Joshua A Riback
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Michael F Dion
- FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA
| | | | - Edoardo M Airoldi
- FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA; Department of Statistics, Harvard University, Cambridge, MA 02138, USA
| | - Tao Pan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Bogdan A Budnik
- FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA
| | - D Allan Drummond
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA.
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75
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Aulas A, Vande Velde C. Alterations in stress granule dynamics driven by TDP-43 and FUS: a link to pathological inclusions in ALS? Front Cell Neurosci 2015; 9:423. [PMID: 26557057 PMCID: PMC4615823 DOI: 10.3389/fncel.2015.00423] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/06/2015] [Indexed: 12/12/2022] Open
Abstract
Stress granules (SGs) are RNA-containing cytoplasmic foci formed in response to stress exposure. Since their discovery in 1999, over 120 proteins have been described to be localized to these structures (in 154 publications). Most of these components are RNA binding proteins (RBPs) or are involved in RNA metabolism and translation. SGs have been linked to several pathologies including inflammatory diseases, cancer, viral infection, and neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). In ALS and FTD, the majority of cases have no known etiology and exposure to external stress is frequently proposed as a contributor to either disease initiation or the rate of disease progression. Of note, both ALS and FTD are characterized by pathological inclusions, where some well-known SG markers localize with the ALS related proteins TDP-43 and FUS. We propose that TDP-43 and FUS serve as an interface between genetic susceptibility and environmental stress exposure in disease pathogenesis. Here, we will discuss the role of TDP-43 and FUS in SG dynamics and how disease-linked mutations affect this process.
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Affiliation(s)
- Anaïs Aulas
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal Montréal, QC, Canada ; Department of Biochemistry, Université de Montréal Montréal, QC, Canada
| | - Christine Vande Velde
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal Montréal, QC, Canada ; Department of Neurosciences, Université de Montréal Montréal, QC, Canada
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76
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Jevtov I, Zacharogianni M, van Oorschot MM, van Zadelhoff G, Aguilera-Gomez A, Vuillez I, Braakman I, Hafen E, Stocker H, Rabouille C. TORC2 mediates the heat stress response in Drosophila by promoting the formation of stress granules. J Cell Sci 2015; 128:2497-508. [PMID: 26054799 PMCID: PMC4510851 DOI: 10.1242/jcs.168724] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/03/2015] [Indexed: 12/29/2022] Open
Abstract
The kinase TOR is found in two complexes, TORC1, which is involved in growth control, and TORC2, whose roles are less well defined. Here, we asked whether TORC2 has a role in sustaining cellular stress. We show that TORC2 inhibition in Drosophila melanogaster leads to a reduced tolerance to heat stress, whereas sensitivity to other stresses is not affected. Accordingly, we show that upon heat stress, both in the animal and Drosophila cultured S2 cells, TORC2 is activated and is required for maintaining the level of its known target, Akt1 (also known as PKB). We show that the phosphorylation of the stress-activated protein kinases is not modulated by TORC2 nor is the heat-induced upregulation of heat-shock proteins. Instead, we show, both in vivo and in cultured cells, that TORC2 is required for the assembly of heat-induced cytoprotective ribonucleoprotein particles, the pro-survival stress granules. These granules are formed in response to protein translation inhibition imposed by heat stress that appears to be less efficient in the absence of TORC2 function. We propose that TORC2 mediates heat resistance in Drosophila by promoting the cell autonomous formation of stress granules.
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Affiliation(s)
- Irena Jevtov
- Institute of Molecular Systems Biology, ETH Zurich, Zurich 8093, Switzerland
| | | | - Marinke M van Oorschot
- Hubrecht Institute of the KNAW and UMC Utrecht, Uppsalalaan 8, Utrecht 3584 CT, Netherlands
| | - Guus van Zadelhoff
- Cellular Protein Chemistry, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | | | - Igor Vuillez
- Institute of Molecular Systems Biology, ETH Zurich, Zurich 8093, Switzerland
| | - Ineke Braakman
- Cellular Protein Chemistry, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands
| | - Ernst Hafen
- Institute of Molecular Systems Biology, ETH Zurich, Zurich 8093, Switzerland
| | - Hugo Stocker
- Institute of Molecular Systems Biology, ETH Zurich, Zurich 8093, Switzerland
| | - Catherine Rabouille
- Hubrecht Institute of the KNAW and UMC Utrecht, Uppsalalaan 8, Utrecht 3584 CT, Netherlands Department of Cell Biology, UMC Utrecht, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands
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77
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Ivanova E, Berger A, Scherrer A, Alkalaeva E, Strub K. Alu RNA regulates the cellular pool of active ribosomes by targeted delivery of SRP9/14 to 40S subunits. Nucleic Acids Res 2015; 43:2874-87. [PMID: 25697503 PMCID: PMC4357698 DOI: 10.1093/nar/gkv048] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The human genome contains about 1.5 million Alu elements, which are transcribed into Alu RNAs by RNA polymerase III. Their expression is upregulated following stress and viral infection, and they associate with the SRP9/14 protein dimer in the cytoplasm forming Alu RNPs. Using cell-free translation, we have previously shown that Alu RNPs inhibit polysome formation. Here, we describe the mechanism of Alu RNP-mediated inhibition of translation initiation and demonstrate its effect on translation of cellular and viral RNAs. Both cap-dependent and IRES-mediated initiation is inhibited. Inhibition involves direct binding of SRP9/14 to 40S ribosomal subunits and requires Alu RNA as an assembly factor but its continuous association with 40S subunits is not required for inhibition. Binding of SRP9/14 to 40S prevents 48S complex formation by interfering with the recruitment of mRNA to 40S subunits. In cells, overexpression of Alu RNA decreases translation of reporter mRNAs and this effect is alleviated with a mutation that reduces its affinity for SRP9/14. Alu RNPs also inhibit the translation of cellular mRNAs resuming translation after stress and of viral mRNAs suggesting a role of Alu RNPs in adapting the translational output in response to stress and viral infection.
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Affiliation(s)
- Elena Ivanova
- Département de biologie cellulaire, Université de Genève, Sciences III, 1211 Genève, Switzerland
| | - Audrey Berger
- Département de biologie cellulaire, Université de Genève, Sciences III, 1211 Genève, Switzerland
| | - Anne Scherrer
- Département de biologie cellulaire, Université de Genève, Sciences III, 1211 Genève, Switzerland
| | - Elena Alkalaeva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Katharina Strub
- Département de biologie cellulaire, Université de Genève, Sciences III, 1211 Genève, Switzerland
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78
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Puscheck EE, Awonuga AO, Yang Y, Jiang Z, Rappolee DA. Molecular biology of the stress response in the early embryo and its stem cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 843:77-128. [PMID: 25956296 DOI: 10.1007/978-1-4939-2480-6_4] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Stress is normal during early embryogenesis and transient, elevated stress is commonplace. Stress in the milieu of the peri-implantation embryo is a summation of maternal hormones, and other elements of the maternal milieu, that signal preparedness for development and implantation. Examples discussed here are leptin, adrenaline, cortisol, and progesterone. These hormones signal maternal nutritional status and provide energy, but also signal stress that diverts maternal and embryonic energy from an optimal embryonic developmental trajectory. These hormones communicate endocrine maternal effects and local embryonic effects although signaling mechanisms are not well understood. Other in vivo stresses affect the embryo such as local infection and inflammation, hypoxia, environmental toxins such as benzopyrene, dioxin, or metals, heat shock, and hyperosmotic stress due to dehydration or diabetes. In vitro, stresses include shear during handling, improper culture media and oxygen levels, cryopreservation, and manipulations of the embryo to introduce sperm or mitochondria. We define stress as any stimulus that slows stem cell accumulation or diminishes the ability of cells to produce normal and sufficient parenchymal products upon differentiation. Thus stress deflects downwards the normal trajectories of development, growth and differentiation. Typically stress is inversely proportional to embryonic developmental and proliferative rates, but can be proportional to induction of differentiation of stem cells in the peri-implantation embryo. When modeling stress it is most interesting to produce a 'runting model' where stress exposures slow accumulation but do not create excessive apoptosis or morbidity. Windows of stress sensitivity may occur when major new embryonic developmental programs require large amounts of energy and are exacerbated if nutritional flow decreases and removes energy from the normal developmental programs and stress responses. These windows correspond to zygotic genome activation, the large mRNA program initiated at compaction, ion pumping required for cavitation, the differentiation of the first lineages, integration with the uterine environment at implantation, rapid proliferation of stem cells, and production of certain lineages which require the highest energy and are most sensitive to mitochondrial inhibition. Stress response mechanisms insure that stem cells for the early embryo and placenta survive at lower stress exposures, and that the organism survives through compensatory and prioritized stem cell differentiation, at higher stress exposures. These servomechanisms include a small set of stress enzymes from the 500 protein kinases in the kinome; the part of the genome coding for protein kinases that hierarchically regulate the activity of other proteins and enzymes. Important protein kinases that mediate the stress response of embryos and their stem cells are SAPK, p38MAPK, AMPK, PI3K, Akt, MEK1/2, MEKK4, PKA, IRE1 and PERK. These stress enzymes have cytosolic function in cell survival at low stress exposures and nuclear function in modifying transcription factor activity at higher stress exposures. Some of the transcription factors (TFs) that are most important in the stress response are JunC, JunB, MAPKAPs, ATF4, XBP1, Oct1, Oct4, HIFs, Nrf2/KEAP, NFKB, MT1, Nfat5, HSF1/2 and potency-maintaining factors Id2, Cdx2, Eomes, Sox2, Nanog, Rex1, and Oct4. Clearly the stress enzymes have a large number of cytosolic and nuclear substrates and the TFs regulate large numbers of genes. The interaction of stress enzymes and TFs in the early embryo and its stem cells are a continuing central focus of research. In vitro regulation of TFs by stress enzymes leads to reprogramming of the stem cell when stress diminishes stem cell accumulation. Since more differentiated product is produced by fewer cells, the process compensates for fewer cells. Coupled with stress-induced compensatory differentiation of stem cells is a tendency to prioritize differentiation by increasing the first essential lineage and decreasing later lineages. These mechanisms include stress enzymes that regulate TFs and provide stress-specific, shared homeostatic cellular and organismal responses of prioritized differentiation.
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Affiliation(s)
- Elizabeth E Puscheck
- Department of Ob/Gyn, REI Division, Wayne State University School of Medicine, Detroit, MI, USA
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79
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Sumoylation is Required for the Cytoplasmic Accumulation of a Subset of mRNAs. Genes (Basel) 2014; 5:982-1000. [PMID: 25333844 PMCID: PMC4276922 DOI: 10.3390/genes5040982] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 09/26/2014] [Accepted: 10/04/2014] [Indexed: 12/17/2022] Open
Abstract
In order to discover novel proteins that promote the nuclear export of newly synthesized mRNAs in mammalian cells, we carried out a limited RNAi screen for proteins required for the proper cytoplasmic distribution of a model intronless mRNA. From this screen we obtained two hits, Ubc9 (SUMO-conjugating E2 enzyme) and GANP (germinal center-associated nuclear protein). Depletion of Ubc9 inhibited the proper cytoplasmic distribution of certain overexpressed intronless mRNAs, while depletion of GANP affected all tested mRNAs. Depletion of Sae1, which is also required for sumoylation, partially inhibited the cytoplasmic distribution of our model mRNA. Interestingly, the block in cytoplasmic accumulation in Ubc9-depleted cells could be overcome if an intron was incorporated into the mRNA. Surprisingly, Ubc9-depleted cells had normal nuclear export of newly synthesized intronless mRNAs, indicating that the observed accumulation of the model mRNA in the nuclei of transfected cells was likely due to some more general perturbation. Indeed, depletion of Ubc9, coupled with the overexpression of the intronless mRNAs, caused the redistribution of the nuclear speckle protein SC35 to cytoplasmic foci. Our results suggest that sumoylation may play a role in the proper assembly of mRNPs and/or the distribution of key RNA binding proteins, and may thus contribute to general protein expression patterns.
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80
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Casci I, Pandey UB. A fruitful endeavor: modeling ALS in the fruit fly. Brain Res 2014; 1607:47-74. [PMID: 25289585 DOI: 10.1016/j.brainres.2014.09.064] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 09/26/2014] [Accepted: 09/27/2014] [Indexed: 12/11/2022]
Abstract
For over a century Drosophila melanogaster, commonly known as the fruit fly, has been instrumental in genetics research and disease modeling. In more recent years, it has been a powerful tool for modeling and studying neurodegenerative diseases, including the devastating and fatal amyotrophic lateral sclerosis (ALS). The success of this model organism in ALS research comes from the availability of tools to manipulate gene/protein expression in a number of desired cell-types, and the subsequent recapitulation of cellular and molecular phenotypic features of the disease. Several Drosophila models have now been developed for studying the roles of ALS-associated genes in disease pathogenesis that allowed us to understand the molecular pathways that lead to motor neuron degeneration in ALS patients. Our primary goal in this review is to highlight the lessons we have learned using Drosophila models pertaining to ALS research. This article is part of a Special Issue entitled ALS complex pathogenesis.
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Affiliation(s)
- Ian Casci
- Department of Pediatrics, Child Neurology and Neurobiology, Children׳s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224, USA; Human Genetics Graduate Program, University of Pittsburgh School of Public Health, Pittsburgh, PA 15261, USA
| | - Udai Bhan Pandey
- Department of Pediatrics, Child Neurology and Neurobiology, Children׳s Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA 15224, USA.
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81
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Seguin SJ, Morelli FF, Vinet J, Amore D, De Biasi S, Poletti A, Rubinsztein DC, Carra S. Inhibition of autophagy, lysosome and VCP function impairs stress granule assembly. Cell Death Differ 2014; 21:1838-51. [PMID: 25034784 PMCID: PMC4227144 DOI: 10.1038/cdd.2014.103] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 06/05/2014] [Accepted: 06/06/2014] [Indexed: 12/15/2022] Open
Abstract
Stress granules (SGs) are mRNA-protein aggregates induced during stress, which accumulate in many neurodegenerative diseases. Previously, the autophagy-lysosome pathway and valosin-containing protein (VCP), key players of the protein quality control (PQC), were shown to regulate SG degradation. This is consistent with the idea that PQC may survey and/or assist SG dynamics. However, despite these observations, it is currently unknown whether the PQC actively participates in SG assembly. Here, we describe that inhibition of autophagy, lysosomes and VCP causes defective SG formation after induction. Silencing the VCP co-factors UFD1L and PLAA, which degrade defective ribosomal products (DRIPs) and 60S ribosomes, also impaired SG assembly. Intriguingly, DRIPs and 60S, which are released from disassembling polysomes and are normally excluded from SGs, were significantly retained within SGs in cells with impaired autophagy, lysosome or VCP function. Our results suggest that deregulated autophagy, lysosomal or VCP activities, which occur in several neurodegenerative (VCP-associated) diseases, may alter SG morphology and composition.
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Affiliation(s)
- S J Seguin
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Universita' di Modena e Reggio Emilia, Modena, Italy
| | - F F Morelli
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Universita' di Modena e Reggio Emilia, Modena, Italy
| | - J Vinet
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Universita' di Modena e Reggio Emilia, Modena, Italy
| | - D Amore
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Universita' di Modena e Reggio Emilia, Modena, Italy
| | - S De Biasi
- Dipartimento Chirurgico, Medico, Odontoiatrico e di Scienze Morfologiche, Universita' di Modena e Reggio Emilia, Modena, Italy
| | - A Poletti
- Dipartimento di Scienze Farmacologiche e Biomolecolari (DiSFeB), Universita' di Milano, Milan, Italy
| | - D C Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge, UK
| | - S Carra
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Universita' di Modena e Reggio Emilia, Modena, Italy
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82
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Clayton CE. Networks of gene expression regulation in Trypanosoma brucei. Mol Biochem Parasitol 2014; 195:96-106. [PMID: 24995711 DOI: 10.1016/j.molbiopara.2014.06.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 06/19/2014] [Accepted: 06/23/2014] [Indexed: 10/25/2022]
Abstract
Regulation of gene expression in Kinetoplastids relies mainly on post-transcriptional mechanisms. Recent high-throughput analyses, combined with mathematical modelling, have demonstrated possibilities for transcript-specific regulation at every stage: trans splicing, polyadenylation, translation, and degradation of both the precursor and the mature mRNA. Different mRNA degradation pathways result in different types of degradation kinetics. The original idea that the fate of an mRNA - or even just its degradation kinetics - can be defined by a single "regulatory element" is an over-simplification. It is now clear that every mRNA can bind many different proteins, some of which may compete with each other. Superimposed upon this complexity are the interactions of those proteins with effectors of gene expression. The amount of protein that is made from a gene is therefore determined by a complex network of interactions.
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Affiliation(s)
- C E Clayton
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
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83
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Adjibade P, Mazroui R. Control of mRNA turnover: implication of cytoplasmic RNA granules. Semin Cell Dev Biol 2014; 34:15-23. [PMID: 24946962 DOI: 10.1016/j.semcdb.2014.05.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 05/21/2014] [Indexed: 12/15/2022]
Abstract
The control of mRNA turnover is essential for the cell to rationalize its mRNA content both under physiological conditions and upon stress. Several mechanisms involved in the control of mRNA turnover have been elucidated. These include surveillance mechanisms such as nonsense-mediated decay, non-stop mediated decay and non-go-mediated decay that eliminate aberrant mRNAs, and regulatory mechanisms including AU-mediated decay, GU-mediated decay, and CDE-mediated decay that ensure mRNA plasticity. In general, the mechanisms of RNA decay rely on interactions between specific cis-acting RNA elements and selected RNA-binding proteins that either prevent the degradation of mRNA targets or induce the recruitment of decaying effectors leading to mRNA degradation. Formation of cytoplasmic RNA granules including processing bodies, stress granules, UV granules, and exosome granules have recently emerged as an additional mechanism that control mRNA turnover of selected mRNAs. Here we will review briefly review the main mechanisms that control mRNA decay and highlight possible implication of RNA granules in such mechanisms.
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Affiliation(s)
- Pauline Adjibade
- Centre de recherche du CHU de Québec, Département de biologie moléculaire, biochimie médicale et pathologie, Université Laval, Québec, PQ, Canada
| | - Rachid Mazroui
- Centre de recherche du CHU de Québec, Département de biologie moléculaire, biochimie médicale et pathologie, Université Laval, Québec, PQ, Canada.
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84
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Coudert L, Adjibade P, Mazroui R. Analysis of translation initiation during stress conditions by polysome profiling. J Vis Exp 2014. [PMID: 24893838 DOI: 10.3791/51164] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Precise control of mRNA translation is fundamental for eukaryotic cell homeostasis, particularly in response to physiological and pathological stress. Alterations of this program can lead to the growth of damaged cells, a hallmark of cancer development, or to premature cell death such as seen in neurodegenerative diseases. Much of what is known concerning the molecular basis for translational control has been obtained from polysome analysis using a density gradient fractionation system. This technique relies on ultracentrifugation of cytoplasmic extracts on a linear sucrose gradient. Once the spin is completed, the system allows fractionation and quantification of centrifuged zones corresponding to different translating ribosomes populations, thus resulting in a polysome profile. Changes in the polysome profile are indicative of changes or defects in translation initiation that occur in response to various types of stress. This technique also allows to assess the role of specific proteins on translation initiation, and to measure translational activity of specific mRNAs. Here we describe our protocol to perform polysome profiles in order to assess translation initiation of eukaryotic cells and tissues under either normal or stress growth conditions.
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Affiliation(s)
- Laëtitia Coudert
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University; CHU de Quebec Research Center
| | - Pauline Adjibade
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University; CHU de Quebec Research Center
| | - Rachid Mazroui
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University; CHU de Quebec Research Center;
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85
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Sudestada1, a Drosophila ribosomal prolyl-hydroxylase required for mRNA translation, cell homeostasis, and organ growth. Proc Natl Acad Sci U S A 2014; 111:4025-30. [PMID: 24550463 DOI: 10.1073/pnas.1314485111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Genome sequences predict the presence of many 2-oxoglutarate (2OG)-dependent oxygenases of unknown biochemical and biological functions in Drosophila. Ribosomal protein hydroxylation is emerging as an important 2OG oxygenase catalyzed pathway, but its biological functions are unclear. We report investigations on the function of Sudestada1 (Sud1), a Drosophila ribosomal oxygenase. As with its human and yeast homologs, OGFOD1 and Tpa1p, respectively, we identified Sud1 to catalyze prolyl-hydroxylation of the small ribosomal subunit protein RPS23. Like OGFOD1, Sud1 catalyzes a single prolyl-hydroxylation of RPS23 in contrast to yeast Tpa1p, where Pro-64 dihydroxylation is observed. RNAi-mediated Sud1 knockdown hinders normal growth in different Drosophila tissues. Growth impairment originates from both reduction of cell size and diminution of the number of cells and correlates with impaired translation efficiency and activation of the unfolded protein response in the endoplasmic reticulum. This is accompanied by phosphorylation of eIF2α and concomitant formation of stress granules, as well as promotion of autophagy and apoptosis. These observations, together with those on enzyme homologs described in the companion articles, reveal conserved biochemical and biological roles for a widely distributed ribosomal oxygenase.
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86
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FMRP and Ataxin-2 function together in long-term olfactory habituation and neuronal translational control. Proc Natl Acad Sci U S A 2013; 111:E99-E108. [PMID: 24344294 DOI: 10.1073/pnas.1309543111] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) and Ataxin-2 (Atx2) are triplet expansion disease- and stress granule-associated proteins implicated in neuronal translational control and microRNA function. We show that Drosophila FMRP (dFMR1) is required for long-term olfactory habituation (LTH), a phenomenon dependent on Atx2-dependent potentiation of inhibitory transmission from local interneurons (LNs) to projection neurons (PNs) in the antennal lobe. dFMR1 is also required for LTH-associated depression of odor-evoked calcium transients in PNs. Strong transdominant genetic interactions among dFMR1, atx2, the deadbox helicase me31B, and argonaute1 (ago1) mutants, as well as coimmunoprecitation of dFMR1 with Atx2, indicate that dFMR1 and Atx2 function together in a microRNA-dependent process necessary for LTH. Consistently, PN or LN knockdown of dFMR1, Atx2, Me31B, or the miRNA-pathway protein GW182 increases expression of a Ca2+/calmodulin-dependent protein kinase II (CaMKII) translational reporter. Moreover, brain immunoprecipitates of dFMR1 and Atx2 proteins include CaMKII mRNA, indicating respective physical interactions with this mRNA. Because CaMKII is necessary for LTH, these data indicate that fragile X mental retardation protein and Atx2 act via at least one common target RNA for memory-associated long-term synaptic plasticity. The observed requirement in LNs and PNs supports an emerging view that both presynaptic and postsynaptic translation are necessary for long-term synaptic plasticity. However, whereas Atx2 is necessary for the integrity of dendritic and somatic Me31B-containing particles, dFmr1 is not. Together, these data indicate that dFmr1 and Atx2 function in long-term but not short-term memory, regulating translation of at least some common presynaptic and postsynaptic target mRNAs in the same cells.
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87
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Coordination of translational control and protein homeostasis during severe heat stress. Curr Biol 2013; 23:2452-62. [PMID: 24291094 DOI: 10.1016/j.cub.2013.09.058] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/05/2013] [Accepted: 09/27/2013] [Indexed: 11/24/2022]
Abstract
BACKGROUND Exposure of cells to severe heat stress causes not only misfolding and aggregation of proteins but also inhibition of translation and storage of mRNA in cytosolic heat stress granules (heat-SGs), limiting newly synthesized protein influx into overloaded proteome repair systems. How these two heat stress responses connect is unclear. RESULTS Here, we show that both S. cerevisiae and D. melanogaster heat-SGs contain mRNA, translation machinery components (excluding ribosomes), and molecular chaperones and that heat-SGs coassemble with aggregates of misfolded, heat-labile proteins. Components in these mixed assemblies exhibit distinct molecular motilities reflecting differential trapping. We demonstrate that heat-SG disassembly and restoration of translation activity during heat stress recovery is intimately linked to disaggregation of damaged proteins present in the mixed assemblies and requires Hsp104 and Hsp70 activity. CONCLUSIONS Chaperone-driven protein disaggregation directly coordinates timing of translation reinitiation with protein folding capacity during cellular protein quality surveillance, enabling efficient protein homeostasis.
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88
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Thedieck K, Holzwarth B, Prentzell MT, Boehlke C, Kläsener K, Ruf S, Sonntag AG, Maerz L, Grellscheid SN, Kremmer E, Nitschke R, Kuehn EW, Jonker JW, Groen AK, Reth M, Hall MN, Baumeister R. Inhibition of mTORC1 by astrin and stress granules prevents apoptosis in cancer cells. Cell 2013; 154:859-74. [PMID: 23953116 DOI: 10.1016/j.cell.2013.07.031] [Citation(s) in RCA: 219] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 04/03/2013] [Accepted: 07/23/2013] [Indexed: 12/21/2022]
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) controls growth and survival in response to metabolic cues. Oxidative stress affects mTORC1 via inhibitory and stimulatory inputs. Whereas downregulation of TSC1-TSC2 activates mTORC1 upon oxidative stress, the molecular mechanism of mTORC1 inhibition remains unknown. Here, we identify astrin as an essential negative mTORC1 regulator in the cellular stress response. Upon stress, astrin inhibits mTORC1 association and recruits the mTORC1 component raptor to stress granules (SGs), thereby preventing mTORC1-hyperactivation-induced apoptosis. In turn, balanced mTORC1 activity enables expression of stress factors. By identifying astrin as a direct molecular link between mTORC1, SG assembly, and the stress response, we establish a unifying model of mTORC1 inhibition and activation upon stress. Importantly, we show that in cancer cells, apoptosis suppression during stress depends on astrin. Being frequently upregulated in tumors, astrin is a potential clinically relevant target to sensitize tumors to apoptosis.
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Affiliation(s)
- Kathrin Thedieck
- Faculty of Biology, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany.
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89
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Jones BL, VanLoozen J, Kim MH, Miles SJ, Dunham CM, Williams LD, Snell TW. Stress granules form in Brachionus manjavacas (Rotifera) in response to a variety of stressors. Comp Biochem Physiol A Mol Integr Physiol 2013; 166:375-84. [PMID: 23856158 DOI: 10.1016/j.cbpa.2013.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 02/05/2023]
Abstract
Many eukaryotes share a common response to environmental stresses. The responses include reorganization of cellular organelles and proteins. Similar stress responses between divergent species suggest that these protective mechanisms may have evolved early and been retained from the earliest eukaryotic ancestors. Many eukaryotic cells have the capacity to sequester proteins and mRNAs into transient stress granules (SGs) that protect most cellular mRNAs (Anderson and Kedersha, 2008). Our observations extend the phylogenetic range of SGs from trypanosomatids, insects, yeast and mammalian cells, where they were first described, to a species of the lophotrochozoan animal phylum Rotifera. We focus on the distribution of three proteins known to be associated with both ribosomes and SG formation: eukaryotic initiation factors eIF3B, eIF4E and T-cell-restricted intracellular antigen 1. We found that these three proteins co-localize to SGs in rotifers in response to temperature stress, osmotic stress and nutrient deprivation as has been described in other eukaryotes. We have also found that the large ribosomal subunit fails to localize to the SGs in rotifers. Furthermore, the SGs in rotifers disperse once the environmental stress is removed as demonstrated in yeast and mammalian cells. These results are consistent with SG formation in trypanosomatids, insects, yeast and mammalian cells, further supporting the presence of this protective mechanism early in the evolution of eukaryotes.
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Affiliation(s)
- Brande L Jones
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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90
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Grousl T, Ivanov P, Malcova I, Pompach P, Frydlova I, Slaba R, Senohrabkova L, Novakova L, Hasek J. Heat shock-induced accumulation of translation elongation and termination factors precedes assembly of stress granules in S. cerevisiae. PLoS One 2013; 8:e57083. [PMID: 23451152 PMCID: PMC3581570 DOI: 10.1371/journal.pone.0057083] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 01/17/2013] [Indexed: 12/26/2022] Open
Abstract
In response to severe environmental stresses eukaryotic cells shut down translation and accumulate components of the translational machinery in stress granules (SGs). Since they contain mainly mRNA, translation initiation factors and 40S ribosomal subunits, they have been referred to as dominant accumulations of stalled translation preinitiation complexes. Here we present evidence that the robust heat shock-induced SGs of S. cerevisiae also contain translation elongation factors eEF3 (Yef3p) and eEF1Bγ2 (Tef4p) as well as translation termination factors eRF1 (Sup45p) and eRF3 (Sup35p). Despite the presence of the yeast prion protein Sup35 in heat shock-induced SGs, we found out that its prion-like domain is not involved in the SGs assembly. Factors eEF3, eEF1Bγ2 and eRF1 were accumulated and co-localized with Dcp2 foci even upon a milder heat shock at 42°C independently of P-bodies scaffolding proteins. We also show that eEF3 accumulations at 42°C determine sites of the genuine SGs assembly at 46°C. We suggest that identification of translation elongation and termination factors in SGs might help to understand the mechanism of the eIF2α factor phosphorylation-independent repression of translation and SGs assembly.
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Affiliation(s)
- Tomas Grousl
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Pavel Ivanov
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Ivana Malcova
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Petr Pompach
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Ivana Frydlova
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Renata Slaba
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | | | - Lenka Novakova
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
| | - Jiri Hasek
- Institute of Microbiology of AS CR, v.v.i., Prague, Czech Republic
- * E-mail:
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91
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Gareau C, Houssin E, Martel D, Coudert L, Mellaoui S, Huot ME, Laprise P, Mazroui R. Characterization of fragile X mental retardation protein recruitment and dynamics in Drosophila stress granules. PLoS One 2013; 8:e55342. [PMID: 23408971 PMCID: PMC3567066 DOI: 10.1371/journal.pone.0055342] [Citation(s) in RCA: 23] [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: 09/04/2012] [Accepted: 12/21/2012] [Indexed: 01/27/2023] Open
Abstract
The RNA-binding protein Fragile X Mental Retardation (FMRP) is an evolutionarily conserved protein that is particularly abundant in the brain due to its high expression in neurons. FMRP deficiency causes fragile X mental retardation syndrome. In neurons, FMRP controls the translation of target mRNAs in part by promoting dynamic transport in and out neuronal RNA granules. We and others have previously shown that upon stress, mammalian FMRP dissociates from translating polysomes to localize into neuronal-like granules termed stress granules (SG). This localization of FMRP in SG is conserved in Drosophila. Whether FMRP plays a key role in SG formation, how FMRP is recruited into SG, and whether its association with SG is dynamic are currently unknown. In contrast with mammalian FMRP, which has two paralog proteins, Drosophila FMR1 (dFMRP) is encoded by a single gene that has no paralog. Using this genetically simple model, we assessed the role of dFMRP in SG formation and defined the determinants required for its recruitment in SG as well as its dynamics in SG. We show that dFMRP is dispensable for SG formation in vitro and ex vivo. FRAP experiments showed that dFMRP shuttles in and out SG. The shuttling activity of dFMRP is mediated by a protein-protein interaction domain located at the N-terminus of the protein. This domain is, however, dispensable for the localization of dFMRP in SG. This localization of dFMRP in SG requires the KH and RGG motifs which are known to mediate RNA binding, as well as the C-terminal glutamine/asparagine rich domain. Our studies thus suggest that the mechanisms controlling the recruitment of FMRP into SG and those that promote its shuttling between granules and the cytosol are uncoupled. To our knowledge, this is the first demonstration of the regulated shuttling activity of a SG component between RNA granules and the cytosol.
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Affiliation(s)
- Cristina Gareau
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Elise Houssin
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - David Martel
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Laetitia Coudert
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Samia Mellaoui
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Marc-Etienne Huot
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Patrick Laprise
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
| | - Rachid Mazroui
- Department of Molecular Biology, Medical Biochemistry, and Pathology, Faculty of Medicine, Laval University, Centre de recherche le CHU de Quebec, Quebec, Canada
- * E-mail:
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92
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Nishida KM, Miyoshi K, Ogino A, Miyoshi T, Siomi H, Siomi MC. Roles of R2D2, a cytoplasmic D2 body component, in the endogenous siRNA pathway in Drosophila. Mol Cell 2013; 49:680-91. [PMID: 23375501 DOI: 10.1016/j.molcel.2012.12.024] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 11/16/2012] [Accepted: 12/26/2012] [Indexed: 11/17/2022]
Abstract
Endogenous small interfering RNAs (endo-siRNAs) in Drosophila are processed by Dicer-2 (Dcr-2) and loaded onto Ago2 by the Dcr-2/R2D2 heterodimer. In r2d2 mutants, the level of endo-siRNAs is unchanged, but endo-siRNAs are misloaded onto Ago1. However, the mechanism underlying the control of endo-siRNA sorting by R2D2 remains unknown. Here, we show that R2D2 controls endo-siRNA sorting by localizing Dcr-2, and presumably endo-siRNA duplexes, to cytoplasmic foci, D2 bodies. Ago2, but not Ago1, localized to D2 bodies. dsRNA-binding-deficient mutant, but not wild-type, R2D2 failed to localize D2 bodies and caused endo-siRNA misdirection to Ago1 in R2D2-depleted cells. However, R2D2 was dispensable for sorting miRNAs and exogenous siRNAs onto Ago1 and Ago2, respectively, in vivo. Endo- and exo-siRNA guide selection also occurred R2D2 independently. The functions of R2D2 are required to avoid endo-siRNA misdirection to Ago1, because Ago1 is capable of loading incompletely complementary miRNA duplexes and endo-siRNA duplexes.
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Affiliation(s)
- Kazumichi M Nishida
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan
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93
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Schwede A, Kramer S, Carrington M. How do trypanosomes change gene expression in response to the environment? PROTOPLASMA 2012; 249:223-238. [PMID: 21594757 PMCID: PMC3305869 DOI: 10.1007/s00709-011-0282-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 05/02/2011] [Indexed: 05/30/2023]
Abstract
All organisms are able to modulate gene expression in response to internal and external stimuli. Trypanosomes represent a group that diverged early during the radiation of eukaryotes and do not utilise regulated initiation of transcription by RNA polymerase II. Here, the mechanisms present in trypanosomes to alter gene expression in response to stress and change of host environment are discussed and contrasted with those operating in yeast and cultured mammalian cells.
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Affiliation(s)
- Angela Schwede
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW UK
| | - Susanne Kramer
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW UK
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QW UK
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94
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TDP-43 aggregation in neurodegeneration: are stress granules the key? Brain Res 2012; 1462:16-25. [PMID: 22405725 DOI: 10.1016/j.brainres.2012.02.032] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2011] [Revised: 02/04/2012] [Accepted: 02/06/2012] [Indexed: 12/12/2022]
Abstract
The RNA-binding protein TDP-43 is strongly linked to neurodegeneration. Not only are mutations in the gene encoding TDP-43 associated with ALS and FTLD, but this protein is also a major constituent of pathological intracellular inclusions in these diseases. Recent studies have significantly expanded our understanding of TDP-43 physiology. TDP-43 is now known to play important roles in neuronal RNA metabolism. It binds to and regulates the splicing and stability of numerous RNAs encoding proteins involved in neuronal development, synaptic function and neurodegeneration. Thus, a loss of these essential functions is an attractive hypothesis regarding the role of TDP-43 in neurodegeneration. Moreover, TDP-43 is an aggregation-prone protein and, given the role of toxic protein aggregates in neurodegeneration, a toxic gain-of-function mechanism is another rational hypothesis. Importantly, ALS related mutations modulate the propensity of TDP-43 to aggregate in cell culture. Several recent studies have documented that cytoplasmic TDP-43 aggregates co-localize with stress granule markers. Stress granules are cytoplasmic inclusions that repress translation of a subset of RNAs in times of cellular stress, and several proteins implicated in neurodegeneration (i.e. Ataxin-2 and SMN) interact with stress granules. Thus, understanding the interplay between TDP-43 aggregation, stress granules and the effect of ALS-associated TDP-43 mutations may be the key to understanding the role of TDP-43 in neurodegeneration. We propose two models of TDP-43 aggregate formation. The "independent model" stipulates that TDP-43 aggregation is independent of stress granule formation, in contrast to the "precursor model" which presents the idea that stress granule formation contributes to a TDP-43 aggregate "seed" and that chronic stress leads to concentration-dependent TDP-43 aggregation. This article is part of a Special Issue entitled: RNA-Binding Proteins.
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95
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Damgaard CK, Lykke-Andersen J. Translational coregulation of 5'TOP mRNAs by TIA-1 and TIAR. Genes Dev 2011; 25:2057-68. [PMID: 21979918 DOI: 10.1101/gad.17355911] [Citation(s) in RCA: 169] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The response of cells to changes in their environment often requires coregulation of gene networks, but little is known about how this can occur at the post-transcriptional level. An important example of post-transcriptional coregulation is the selective translational regulation in response to growth conditions of mammalian mRNAs that encode protein biosynthesis factors and contain hallmark 5'-terminal oligopyrimidine tracts (5'TOP). However, the responsible trans-factors and the mechanism by which they coregulate 5'TOP mRNAs have remained elusive. Here we identify stress granule-associated TIA-1 and TIAR proteins as key factors in human 5'TOP mRNA regulation, which upon amino acid starvation assemble onto the 5' end of 5'TOP mRNAs and arrest translation at the initiation step, as evidenced by TIA-1/TIAR-dependent 5'TOP mRNA translation repression, polysome release, and accumulation in stress granules. This requires starvation-mediated activation of the GCN2 (general control nonderepressible 2) kinase and inactivation of the mTOR (mammalian target of rapamycin) signaling pathway. Our findings provide a mechanistic explanation to the long-standing question of how the network of 5'TOP mRNAs are coregulated according to amino acid availability, thereby allowing redirection of limited resources to mount a nutrient deprivation response. This presents a fundamental example of how a group of mRNAs can be translationally coregulated in response to changes in the cellular environment.
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Affiliation(s)
- Christian Kroun Damgaard
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA.
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96
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Abstract
hSMG-1 is a member of the phosphoinositide 3 kinase-like kinase (PIKK) family with established roles in nonsense-mediated decay (NMD) of mRNA containing premature termination codons and in genotoxic stress responses to DNA damage. We report here a novel role for hSMG-1 in cytoplasmic stress granule (SG) formation. Exposure of cells to stress causing agents led to the localization of hSMG-1 to SG, identified by colocalization with TIA-1, G3BP1, and eIF4G. hSMG-1 small interfering RNA and the PIKK inhibitor wortmannin prevented formation of a subset of SG, while specific inhibitors of ATM, DNA-PK(cs), or mTOR had no effect. Exposure of cells to H(2)O(2) and sodium arsenite induced (S/T)Q phosphorylation of proteins. While Upf2 and Upf1, an essential substrate for hSMG-1 in NMD, were present in SG, NMD-specific Upf1 phosphorylation was not detected in SG, indicating hSMG-1's role in SG is separate from classical NMD. Thus, SG formation appears more complex than originally envisaged and hSMG-1 plays a central role in this process.
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97
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Chow C, Cloutier S, Dumas C, Chou MN, Papadopoulou B. Promastigote to amastigote differentiation of Leishmania is markedly delayed in the absence of PERK eIF2alpha kinase-dependent eIF2alpha phosphorylation. Cell Microbiol 2011; 13:1059-77. [DOI: 10.1111/j.1462-5822.2011.01602.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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98
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Beerman RW, Jongens TA. A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms. Neuroscience 2011; 181:48-66. [PMID: 21333716 DOI: 10.1016/j.neuroscience.2011.02.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 02/10/2011] [Accepted: 02/12/2011] [Indexed: 02/07/2023]
Abstract
Fragile X syndrome is caused by the loss of expression of the fragile X mental retardation protein (FMRP). As a RNA binding protein, FMRP functions in translational regulation, localization, and stability of its neuronal target transcripts. The Drosophila homologue, dFMR1, is well conserved in sequence and function with respect to human FMRP. Although dFMR1 is known to express two main isoforms, the mechanism behind production of the second, more slowly migrating isoform has remained elusive. Furthermore, it remains unknown whether the two isoforms may also contribute differentially to dFMR1 function. We have found that this second dFMR1 isoform is generated through an alternative translational start site in the dfmr1 5'UTR. This 5'UTR coding sequence is well conserved in the melanogaster group. Translation of the predominant, smaller form of dFMR1 (dFMR1-S(N)) begins at a canonical start codon (ATG), whereas translation of the minor, larger form (dFMR1-L(N)) begins upstream at a non-canonical start codon (CTG). To assess the contribution of the N-terminal extension toward dFMR1 activity, we generated transgenic flies that exclusively express either dFMR1-S(N) or dFMR1-L(N). Expression analyses throughout development revealed that dFMR1-S(N) is required for normal dFMR1-L(N) expression levels in adult brains. In situ expression analyses showed that either dFMR1-S(N) or dFMR1-L(N) is individually sufficient for proper dFMR1 localization in the nervous system. Functional studies demonstrated that both dFMR1-S(N) and dFMR1-L(N) can function independently to rescue dfmr1 null defects in synaptogenesis and axon guidance. Thus, dfmr1 encodes two functional isoforms with respect to expression and activity throughout neuronal development.
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Affiliation(s)
- R W Beerman
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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99
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Thomas MG, Loschi M, Desbats MA, Boccaccio GL. RNA granules: the good, the bad and the ugly. Cell Signal 2011; 23:324-34. [PMID: 20813183 PMCID: PMC3001194 DOI: 10.1016/j.cellsig.2010.08.011] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 08/20/2010] [Indexed: 12/13/2022]
Abstract
Processing bodies (PBs) and Stress Granules (SGs) are the founding members of a new class of RNA granules, known as mRNA silencing foci, as they harbour transcripts circumstantially excluded from the translationally active pool. PBs and SGs are able to release mRNAs thus allowing their translation. PBs are constitutive, but respond to stimuli that affect mRNA translation and decay, whereas SGs are specifically induced upon cellular stress, which triggers a global translational silencing by several pathways, including phosphorylation of the key translation initiation factor eIF2alpha, and tRNA cleavage among others. PBs and SGs with different compositions may coexist in a single cell. These macromolecular aggregates are highly conserved through evolution, from unicellular organisms to vertebrate neurons. Their dynamics is regulated by several signaling pathways, and depends on microfilaments and microtubules, and the cognate molecular motors myosin, dynein, and kinesin. SGs share features with aggresomes and related aggregates of unfolded proteins frequently present in neurodegenerative diseases, and may play a role in the pathology. Virus infections may induce or impair SG formation. Besides being important for mRNA regulation upon stress, SGs modulate the signaling balancing apoptosis and cell survival. Finally, the formation of Nuclear Stress Bodies (nSBs), which share components with SGs, and the assembly of additional cytosolic aggregates containing RNA -the UV granules and the Ire1 foci-, all of them induced by specific cell damage factors, contribute to cell survival.
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Key Words
- atxn2, ataxin-2
- bicd, bicaudal d
- cbp, creb binding protein
- cpeb, cytoplasmic polyadenylation element binding protein
- dhc, dynein heavy chain
- dic, dynein intermediate chain
- fak, focal adhesion kinase
- fus/tls/hnrnp p2, fused in sarcoma
- g3bp, ras-gap sh3 domain binding protein
- gcn2, general control nonderepressible-2
- grb7, growth factor receptor-bound protein 7
- hap, hnrnp a1 interacting protein
- hdac6, histone deacetylase 6
- hri, heme-regulated inhibitor
- hsf, heat shock transcription factor
- khc, kinesin heavy chain
- klc, kinesin light chain
- mln51, metastatic lymph node 51
- nmd, nonsense mediated decay
- nsbs, nuclear stress bodies
- ogfod1, 2–14 oxoglutarate and fe(ii)-dependent oxygenase domain containing 1
- pb, processing body
- perk, pancreatic endoplasmic reticulum eif2alpha kinase
- pkr/eif2ak2, double stranded rna-dependent protein kinase
- pp1, protein phosphatase 1
- prp, prion protein
- rbp, rna binding protein
- rnp, ribonucleoparticle
- sam68, src associated in mitosis 68 kda
- member of star, signal transducer and activator of rna
- sca, spinocerebellar ataxia
- sg, stress granule
- sma, spinal muscular atrophy
- fmrp, fragile x mental retardation protein
- smn, survival of motor neuron
- tdp43, tar dna-binding protein 43
- traf2, tnf receptor associated factor 2
- uvgs, uv rna granules
- processing body
- stress granule
- kinesin
- dynein
- bicaudal d
- aggresome
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Affiliation(s)
- María Gabriela Thomas
- Instituto Leloir, Av. Patricias Argentinas 435, C1405 BWE Buenos Aires, Argentina
- CONICET, Buenos Aires, Argentina
| | - Mariela Loschi
- Instituto Leloir, Av. Patricias Argentinas 435, C1405 BWE Buenos Aires, Argentina
- CONICET, Buenos Aires, Argentina
| | - María Andrea Desbats
- Instituto Leloir, Av. Patricias Argentinas 435, C1405 BWE Buenos Aires, Argentina
| | - Graciela Lidia Boccaccio
- Instituto Leloir, Av. Patricias Argentinas 435, C1405 BWE Buenos Aires, Argentina
- CONICET, Buenos Aires, Argentina
- University of Buenos Aires
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Khong A, Jan E. Modulation of stress granules and P bodies during dicistrovirus infection. J Virol 2011; 85:1439-51. [PMID: 21106737 PMCID: PMC3028890 DOI: 10.1128/jvi.02220-10] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 11/16/2010] [Indexed: 11/20/2022] Open
Abstract
Stress granules (SGs) are dynamic cytosolic aggregates composed of ribonucleoproteins that are induced during cellular stress when protein synthesis is inhibited. The function of SGs is poorly understood, but they are thought to be sites for reorganizing mRNA and protein. Several viruses can modulate SG formation, suggesting that SGs have an impact on virus infection. In this study, we have investigated the relationship of SG formation in Drosophila S2 cells infected by cricket paralysis virus (CrPV), a member of the Dicistroviridae family. Despite a rapid shutoff of host translation during CrPV infection, several hallmark SG markers such as the Drosophila TIA-1 and G3BP (RasGAP-SH3-binding protein) homologs, Rox8 and Rin, respectively, do not aggregate in CrPV-infected cells, even when challenged with potent SG inducers such as heat shock, oxidative stress, and pateamine A treatment. Furthermore, we demonstrate that a subset of P body markers become moderately dispersed at late times of infection. In contrast, as shown by fluorescent in situ hybridization, poly(A)(+) RNA granules still form at late times of infection. These poly(A)(+) RNA granules do not contain viral RNA nor do they colocalize with P body markers. Finally, our results demonstrate that the CrPV viral 3C protease is sequestered to SGs under cellular stress but not during virus infection. In summary, we propose that dicistrovirus infection leads to the selective inhibition of distinct SGs so that viral proteins are available for viral processing.
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Affiliation(s)
- Anthony Khong
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver BC V6T 1Z3, Canada
| | - Eric Jan
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver BC V6T 1Z3, Canada
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