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Liu X, Hu C, He Q, Bai Y, Zhang X, Fu Z, Ma X, Xu M, Liang Z, Mao Q. Research progress on immune mechanism and control strategy of dsRNA impurities in mRNA vaccine. Expert Rev Vaccines 2025. [PMID: 40401819 DOI: 10.1080/14760584.2025.2510335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2025] [Revised: 05/19/2025] [Accepted: 05/20/2025] [Indexed: 05/23/2025]
Abstract
INTRODUCTION Double-stranded RNA (dsRNA) is a key impurities of mRNA vaccines prepared by in vitro transcription (IVT) and is primarily transcribed by T7 RNA polymerase. It can trigger innate immunity and induce a series of side effects that may influence the safety of mRNA vaccines. AREAS COVERED This manuscript summarizes dsRNA generation mechanisms and immunity activation and analyzes the current challenges in dsRNA detection and control strategies. Regulatory standards for dsRNA impurities in mRNA vaccines have also been discussed. EXPERT OPINION dsRNA as a critical quality attribute (CQA), the structural heterogeneity of it (including length and structure) and its precise immunomodulatory mechanisms affecting vaccine safety are poorly understood. Regulatory authorities have not released specific standards for dsRNA. Additionally, there is a lack of comparative analysis data on different corporate testing methods. Therefore, to ensure the safety of dsRNA containing mRNA vaccines, and improve mRNA-based platforms, it is of great significance to establish standardized detection methods and standards for dsRNA; to design mRNA production with low dsRNA impurities by adopting the quality by design (QbD) approach; and to evaluate the immune stimulation mechanism of dsRNA impurities in mRNA vaccines.
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Affiliation(s)
- Xinjun Liu
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Chaoying Hu
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Qian He
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Yu Bai
- Sinovac Life Sciences Co, Ltd. Beijing, China
| | - Xuanxuan Zhang
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Zhihao Fu
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Xiao Ma
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Miao Xu
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Zhenglun Liang
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
| | - Qunying Mao
- State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, NMPA Key Laboratory for Quality Research and Evaluation of Biological Products, Research Units of innovative Vaccine Quality Evaluation and Standardization, Chinese Academy of Medical Sciences, National institutes for Food and Drug Control, Beijing, China
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2
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Pennisi R, Sciortino MT. HSV-1 Triggers an Antiviral Transcriptional Response during Viral Replication That Is Completely Abrogated in PKR -/- Cells. Pathogens 2023; 12:1126. [PMID: 37764935 PMCID: PMC10536113 DOI: 10.3390/pathogens12091126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 08/29/2023] [Accepted: 09/01/2023] [Indexed: 09/29/2023] Open
Abstract
The activation of the innate immune response during HSV-1 infection stimulates several transcription factors, such as NF-κB and IRF3, which are critical regulators of IFN-β expression. The released IFN-β activates the ISGs, which encode antiviral effectors such as the PKR. We found that HSV-1 triggers an antiviral transcriptional response during viral replication by activating TBK1-IRF3-NF-κB network kinetically. In contrast, we reported that infected PKR-/- cells fail to activate the transcription of TBK1. Downstream, TBK1 was unable to activate the transcription of IRF3 and NF-κB. These data suggested that in PKR-/- cells, HSV-1 replication counteracts TBK1-IRF3-NF-κB network. In this scenario, a combined approach of gene knockout and gene silencing was used to determine how the lack of PKR facilitates HSV-1 replication. We reported that in HEp-2-infected cells, PKR can influence the TBK1-IRF3-NF-κB network, consequently interfering with viral replication. Otherwise, an abrogated PKR-mediated signaling sustains the HSV-1 replication. Our result allows us to add additional information on the complex HSV-host interaction network by reinforcing the concept of the PKR role in the innate response-related networks during HSV replication in an in vitro model.
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Affiliation(s)
- Rosamaria Pennisi
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Maria Teresa Sciortino
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d’Alcontres 31, 98166 Messina, Italy
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3
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Gao H, Lin Y, Huang C, Li X, Diamond MS, Liu C, Zhang R, Zhang P. A genome-wide CRISPR screen identifies HuR as a regulator of apoptosis induced by dsRNA and virus. J Cell Sci 2022; 135:274702. [PMID: 35112703 DOI: 10.1242/jcs.258855] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 01/24/2022] [Indexed: 11/20/2022] Open
Abstract
We performed an unbiased whole-genome CRISPR/Cas9 screen in A549 cells to identify potential regulators involved in cell death triggered by dsRNA. Of several top candidate genes, we identified the RNA binding protein ELAV like protein 1 (ELAVL1) that encodes Hu antigen R (HuR). Depletion of HuR led to less cell death induced by dsRNA. HuR is mainly involved in the apoptosis, and all of its RNA recognition motifs are essential for its proapoptotic function. We further showed that the HuR depletion had no influence on the mRNA level of an anti-apoptotic gene, BCL2, instead downregulated its translation in a cap-independent way. Polysome fractionation studies showed that HuR retarded the BCL2 mRNA in the non-translating pool of polysomes. Moreover, protection from dsRNA-induced apoptosis by HuR depletion required the presence of BCL2, indicating that the proapoptotic function of HuR is executed by suppressing BCL2. Consistently, HuR regulated apoptosis induced by infection of encephalomyocarditis or Semliki Forest virus. Collectively, our work identified a suite of proteins that regulate dsRNA-induced cell death, and elucidated the mechanism by which HuR acts as a pro-apoptotic factor.
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Affiliation(s)
- Huixin Gao
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Yuxia Lin
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Changbai Huang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Xiaobo Li
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Michael S Diamond
- Departments of Medicine, Molecular Microbiology, Pathology & Immunology, Washington University School of Medicine, Saint Louis, MO, USA
| | - Chao Liu
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Rong Zhang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Ping Zhang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
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4
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Lin Y, Huang C, Gao H, Li X, Lin Q, Zhou S, Huo Z, Huang Y, Liu C, Zhang P. AMBRA1 promotes apoptosis induced by dsRNA and virus through interacting with and stabilizing MAVS. J Cell Sci 2021; 135:273618. [PMID: 34859815 DOI: 10.1242/jcs.258910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 11/11/2021] [Indexed: 10/19/2022] Open
Abstract
Apoptosis is an important cellular response to viral infection. In current study, we identified activating molecule in Beclin1-regulated autophagy protein 1 (AMBRA1) as a positive regulator of apoptosis triggered by dsRNA. Depletion of AMBRA1 by gene editing significantly reduced dsRNA-induced apoptosis, which was largely restored by trans-complementation of AMBRA1. Mechanistically, AMBRA1 interacts with mitochondrial antiviral-signaling protein (MAVS), a key mitochondrial adaptor in the apoptosis pathway induced by dsRNA and viral infection. Further Co-IP analysis demonstrated that the mitochondrial localization of MAVS was essential for their interaction. The impact of AMBRA1 on dsRNA-induced apoptosis relied on the presence of MAVS and caspase-8. AMBRA1 was involved in the stabilization of MAVS through preventing its proteasomal degradation induced by dsRNA. Consistently, AMBRA1 upregulated the apoptosis induced by Semliki Forest virus infection. Taken together, our work illustrated a role of AMBRA1 in the virus-induced apoptosis through interacting with and stabilizing MAVS.
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Affiliation(s)
- Yuxia Lin
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Changbai Huang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Huixin Gao
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Xiaobo Li
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Quanshi Lin
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Shili Zhou
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Zhiting Huo
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Yanxia Huang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Chao Liu
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Microbiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Ping Zhang
- Key Laboratory of Tropical Diseases Control (Sun Yat-sen University), Ministry of Education, Guangzhou 510080, China.,Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
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Gioti K, Kottaridi C, Voyiatzaki C, Chaniotis D, Rampias T, Beloukas A. Animal Coronaviruses Induced Apoptosis. Life (Basel) 2021; 11:185. [PMID: 33652685 PMCID: PMC7996831 DOI: 10.3390/life11030185] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/21/2021] [Accepted: 02/22/2021] [Indexed: 02/06/2023] Open
Abstract
Apoptosis is a form of programmed death that has also been observed in cells infected by several viruses. It is considered one of the most critical innate immune mechanisms that limits pathogen proliferation and propagation before the initiation of the adaptive immune response. Recent studies investigating the cellular responses to SARS-CoV and SARS-CoV-2 infection have revealed that coronaviruses can alter cellular homeostasis and promote cell death, providing evidence that the modulation of apoptotic pathways is important for viral replication and propagation. Despite the genetic diversity among different coronavirus clades and the infection of different cell types and several hosts, research studies in animal coronaviruses indicate that apoptosis in host cells is induced by common molecular mechanisms and apoptotic pathways. We summarize and critically review current knowledge on the molecular aspects of cell-death regulation during animal coronaviruses infection and the viral-host interactions to this process. Future research is expected to lead to a better understanding of the regulation of cell death during coronavirus infection. Moreover, investigating the role of viral proteins in this process will help us to identify novel antiviral targets related to apoptotic signaling pathways.
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Affiliation(s)
- Katerina Gioti
- Department of Biomedical Sciences, University of West Attica, 12243 Athens, Greece; (K.G.); (C.K.); (C.V.); (D.C.)
| | - Christine Kottaridi
- Department of Biomedical Sciences, University of West Attica, 12243 Athens, Greece; (K.G.); (C.K.); (C.V.); (D.C.)
- Department of Genetics, Development and Molecular Biology, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
| | - Chrysa Voyiatzaki
- Department of Biomedical Sciences, University of West Attica, 12243 Athens, Greece; (K.G.); (C.K.); (C.V.); (D.C.)
| | - Dimitrios Chaniotis
- Department of Biomedical Sciences, University of West Attica, 12243 Athens, Greece; (K.G.); (C.K.); (C.V.); (D.C.)
| | - Theodoros Rampias
- Biomedical Research Foundation of the Academy of Athens, Basic Research Center, 11527 Athens, Greece
| | - Apostolos Beloukas
- Department of Biomedical Sciences, University of West Attica, 12243 Athens, Greece; (K.G.); (C.K.); (C.V.); (D.C.)
- Institute of Infection & Global Health, University of Liverpool, Liverpool L69 7BE, UK
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6
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Brechin V, Shinohara F, Saito JI, Seitz H, Tomari Y. Mechanistic analysis of the enhanced RNAi activity by 6-mCEPh-purine at the 5' end of the siRNA guide strand. RNA (NEW YORK, N.Y.) 2021; 27:151-162. [PMID: 33177187 PMCID: PMC7812867 DOI: 10.1261/rna.073775.119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 10/15/2020] [Indexed: 05/05/2023]
Abstract
A key approach for improving siRNA efficacy is chemical modifications. Through an in silico screening of modifications at the 5'-end nucleobase of the guide strand, an adenine-derived compound called 6-(3-(2-carboxyethyl)phenyl)-purine (6-mCEPh-purine) was identified to improve the RNAi activity in cultured human cells and in vivo mouse models. Nevertheless, it remains unclear how this chemical modification enhances the siRNA potency. Here, we used a series of biochemical approaches to quantitatively evaluate the effect of the 6-mCEPh-purine modification at each step in the assembly of the RNAi effector complex called RISC. We found that the modification improves the formation of mature RISC at least in two different ways, by fixing the loading orientation of siRNA duplexes and increasing the stability of mature RISC after passenger strand ejection. Our data will provide a molecular platform for further development of chemically modified siRNA drugs.
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Affiliation(s)
- Vincent Brechin
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Fumikazu Shinohara
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Research Function Unit, R&D Division, Kyowa Kirin Co. Ltd., Chiyoda-ku, Tokyo 100-0004, Japan
| | - Jun-Ichi Saito
- Research Function Unit, R&D Division, Kyowa Kirin Co. Ltd., Chiyoda-ku, Tokyo 100-0004, Japan
| | - Hervé Seitz
- Institut de Génétique Humaine, UMR 9002 CNRS and Université de Montpellier, 34396 Montpellier, France
| | - Yukihide Tomari
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
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7
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Reovirus σ3 Protein Limits Interferon Expression and Cell Death Induction. J Virol 2020; 94:JVI.01485-20. [PMID: 32847863 DOI: 10.1128/jvi.01485-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 08/20/2020] [Indexed: 01/31/2023] Open
Abstract
Induction of necroptosis by mammalian reovirus requires both type I interferon (IFN)-signaling and viral replication events that lead to production of progeny genomic double-stranded RNA (dsRNA). The reovirus outer capsid protein μ1 negatively regulates reovirus-induced necroptosis by limiting RNA synthesis. To determine if the outer capsid protein σ3, which interacts with μ1, also functions in regulating necroptosis, we used small interfering RNA (siRNA)-mediated knockdown. Similarly to what was observed in diminishment of μ1 expression, knockdown of newly synthesized σ3 enhances necroptosis. Knockdown of σ3 does not impact reovirus RNA synthesis. Instead, this increase in necroptosis following σ3 knockdown is accompanied by an increase in IFN production. Furthermore, ectopic expression of σ3 is sufficient to block IFN expression following infection. Surprisingly, the capacity of σ3 protein to bind dsRNA does not impact its capacity to diminish production of IFN. Consistent with this, infection with a virus harboring a mutation in the dsRNA binding domain of σ3 does not result in enhanced production of IFN or necroptosis. Together, these data suggest that σ3 limits the production of IFN to control innate immune signaling and necroptosis following infection through a mechanism that is independent of its dsRNA binding capacity.IMPORTANCE We use mammalian reovirus as a model to study how virus infection modulates innate immune signaling and cell death induction. Here, we sought to determine how viral factors regulate these processes. Our work highlights a previously unknown role for the reovirus outer capsid protein σ3 in limiting the induction of a necrotic form of cell death called necroptosis. Induction of cell death by necroptosis requires production of interferon. The σ3 protein limits the induction of necroptosis by preventing excessive production of interferon following infection.
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Urban C, Welsch H, Heine K, Wüst S, Haas DA, Dächert C, Pandey A, Pichlmair A, Binder M. Persistent Innate Immune Stimulation Results in IRF3-Mediated but Caspase-Independent Cytostasis. Viruses 2020; 12:v12060635. [PMID: 32545331 PMCID: PMC7354422 DOI: 10.3390/v12060635] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 06/09/2020] [Accepted: 06/09/2020] [Indexed: 01/19/2023] Open
Abstract
Persistent virus infection continuously produces non-self nucleic acids that activate cell-intrinsic immune responses. However, the antiviral defense evolved as a transient, acute phase response and the effects of persistently ongoing stimulation onto cellular homeostasis are not well understood. To study the consequences of long-term innate immune activation, we expressed the NS5B polymerase of Hepatitis C virus (HCV), which in absence of viral genomes continuously produces immune-stimulatory RNAs. Surprisingly, within 3 weeks, NS5B expression declined and the innate immune response ceased. Proteomics and functional analyses indicated a reduced proliferation of those cells most strongly stimulated, which was independent of interferon signaling but required mitochondrial antiviral signaling protein (MAVS) and interferon regulatory factor 3 (IRF3). Depletion of MAVS or IRF3, or overexpression of the MAVS-inactivating HCV NS3/4A protease not only blocked interferon responses but also restored cell growth in NS5B expressing cells. However, pan-caspase inhibition could not rescue the NS5B-induced cytostasis. Our results underline an active counter selection of cells with prolonged innate immune activation, which likely constitutes a cellular strategy to prevent persistent virus infections.
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Affiliation(s)
- Christian Urban
- Institute of Virology, School of Medicine, Technical University of Munich, 81675 Munich, Germany; (C.U.); (D.A.H.)
| | - Hendrik Welsch
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
- Faculty of Biosciences, Heidelberg University, 69117 Heidelberg, Germany
| | - Katharina Heine
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
| | - Sandra Wüst
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
| | - Darya A. Haas
- Institute of Virology, School of Medicine, Technical University of Munich, 81675 Munich, Germany; (C.U.); (D.A.H.)
| | - Christopher Dächert
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
- Faculty of Biosciences, Heidelberg University, 69117 Heidelberg, Germany
| | - Aparna Pandey
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
| | - Andreas Pichlmair
- Institute of Virology, School of Medicine, Technical University of Munich, 81675 Munich, Germany; (C.U.); (D.A.H.)
- German Center for Infection Research (DZIF), Munich Partner Site, 81675 Munich, Germany
- Correspondence: (A.P.); (M.B.)
| | - Marco Binder
- Research Group “Dynamics of Early Viral Infection and the Innate Antiviral Response”, Division Virus-Associated Carcinogenesis (F170), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany; (H.W.); (K.H.); (S.W.); (C.D.); (A.P.)
- Correspondence: (A.P.); (M.B.)
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9
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Hu S, Sun H, Yin L, Li J, Mei S, Xu F, Wu C, Liu X, Zhao F, Zhang D, Huang Y, Ren L, Cen S, Wang J, Liang C, Guo F. PKR-dependent cytosolic cGAS foci are necessary for intracellular DNA sensing. Sci Signal 2019; 12:eaav7934. [PMID: 31772125 DOI: 10.1126/scisignal.aav7934] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cyclic GMP-AMP synthase (cGAS) is a major sensor of cytosolic DNA from invading pathogens and damaged cellular organelles. Activation of cGAS promotes liquid-like phase separation and formation of membraneless cytoplasmic structures. Here, we found that cGAS bound G3BP1, a double-stranded nucleic acid helicase involved in the formation of stress granules. Loss of G3BP1 blocked subcellular cGAS condensation and suppressed the interferon response to intracellular DNA and DNA virus particles in cells. Furthermore, an RNA-dependent association with PKR promoted G3BP1 foci formation and cGAS-dependent interferon responses. Together, these results indicate that PKR promotes the formation of G3BP1-dependent, membraneless cytoplasmic structures necessary for the DNA-sensing function of cGAS in human cells. These data suggest that there is a previously unappreciated link between nucleic acid sensing pathways, which requires the formation of specialized subcellular structures.
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Affiliation(s)
- Siqi Hu
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Hong Sun
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Lijuan Yin
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Jian Li
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Shan Mei
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Fengwen Xu
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Chao Wu
- NHC Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB-Fondation Mérieux, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Xiaoman Liu
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Fei Zhao
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Di Zhang
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Yu Huang
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Lili Ren
- NHC Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB-Fondation Mérieux, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China
| | - Shan Cen
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, P. R. China
| | - Jianwei Wang
- NHC Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB-Fondation Mérieux, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China.
| | - Chen Liang
- McGill University AIDS Centre, Lady Davis Institute, Jewish General Hospital, Montreal H3T 1E2, Canada.
| | - Fei Guo
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology and Center for AIDS Research, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, P. R. China.
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10
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Wang Y, Jia J, Wang Y, Li F, Song X, Qin S, Wang Z, Kitazato K, Wang Y. Roles of HSV-1 infection-induced microglial immune responses in CNS diseases: friends or foes? Crit Rev Microbiol 2019; 45:581-594. [PMID: 31512533 DOI: 10.1080/1040841x.2019.1660615] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Microglia, as brain-resident macrophages, are the first line of defense against brain invading pathogens. Further, their dysfunction has been recognized to be closely associated with mounting CNS diseases. Of note, chronic HSV-1 infection leads to the persistent activation of microglia, which elicit a comprehensive response by generating certain factors with neurotoxic and neuroprotective effects. CNS infection with HSV-1 results in herpes simplex encephalitis and herpes simplex keratitis. Microglial immune response plays a crucial role in the development of these diseases. Moreover, HSV-1 infection is strongly associated with several CNS diseases, especially Alzheimer's disease and schizophrenia. These CNS diseases can be effectively ameliorated by eliciting an appropriate immune response, such as inhibition of microglial proliferation and activation. Therefore, it is crucial to reassess the positive and negative roles of microglia in HSV-1 CNS infection for a more comprehensive and detailed understanding of the relationship between microglia and CNS diseases. Hence, the present review focuses on the dual roles of microglia in mediating HSV-1 CNS infection, as well as on the strategy of targeting microglia to ameliorate CNS diseases. Further research in this field can help comprehensively elucidate the dual role of the microglial immune response in HSV-1 CNS infection, providing a theoretical basis for identifying therapeutic targets against overactive microglia in CNS diseases and HSV-1 infection.
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Affiliation(s)
- Yiliang Wang
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China
| | - Jiaoyan Jia
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China
| | - Yun Wang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Feng Li
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China
| | - Xiaowei Song
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China.,College of Pharmacy, Jinan University, Guangzhou, China
| | - Shurong Qin
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China.,College of Pharmacy, Jinan University, Guangzhou, China
| | - Zhaoyang Wang
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China.,Key Laboratory of Bioengineering Medicine of Guangdong Province, Jinan University, Guangzhou, China
| | - Kaio Kitazato
- Division of Molecular Pharmacology of Infectious Agents, Department of Molecular Microbiology and Immunology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan
| | - Yifei Wang
- Guangzhou Jinan Biomedicine Research and Development Center, Institute of Biomedicine, College of Life Science and Technology, Jinan University, Guangzhou, China.,Key Laboratory of Virology of Guangzhou, Jinan University, Guangzhou, China
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11
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Hirata Y, Iwasaki T, Makimura Y, Okajima S, Oh-Hashi K, Takemori H. Inhibition of double-stranded RNA-dependent protein kinase prevents oxytosis and ferroptosis in mouse hippocampal HT22 cells. Toxicology 2019; 418:1-10. [PMID: 30817950 DOI: 10.1016/j.tox.2019.02.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 01/26/2019] [Accepted: 02/22/2019] [Indexed: 01/20/2023]
Abstract
Double-stranded RNA-dependent protein kinase (PKR) is a component of signal transduction pathways mediating various stress signals including oxidative stress and endoplasmic reticulum (ER) stress and is suggested to be implicated in several neurodegenerative diseases. Cell death in neurodegenerative conditions has been linked to oxidative stress; however, the involvement of PKR in endogenous oxidative stress such as oxytosis and ferroptosis which is quite distinct from classical apoptosis remains unknown. We investigated here the effect of a PKR inhibitor C16 (an imidazole-oxindole derivative) on oxytosis and ferroptosis in cultured HT22 mouse hippocampal cells. C16 prevented glutamate- and erastin-induced cell death, reactive oxygen species accumulation, Ca2+ influx, phosphorylation of inositol-requiring enzyme 1 (IRE1), one of the three branches of ER stress signaling and its downstream signaling components. On the other hand, C16 did not prevent oxidative stress-induced heme oxygenase-1 expression; instead, C16 activated the extracellular signal-regulated kinase pathway. The protective effect of C16 is diminished in PKR knockout HT22 cells. Real time measurements of the oxygen consumption rate and extracellular acidification rate over a long period of time leading to cell death showed that C16 partially prevented erastin-induced mitochondrial and glycolytic dysfunction. These results suggest that PKR is an important component of oxytosis and ferroptosis and the inhibition of PKR is neuroprotective against endogenous oxidative stress-induced cell death and provide an effective strategy for neuroprotection.
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Affiliation(s)
- Yoko Hirata
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan.
| | - Takuya Iwasaki
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Yukimi Makimura
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Sayaka Okajima
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Kentaro Oh-Hashi
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan
| | - Hiroshi Takemori
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan; United Graduate School of Drug Discovery and Medical Information Sciences, Gifu University, Yanagido, Gifu 501-1193, Japan.
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12
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An "Old" protein with a new story: Coronavirus endoribonuclease is important for evading host antiviral defenses. Virology 2018; 517:157-163. [PMID: 29307596 PMCID: PMC5869138 DOI: 10.1016/j.virol.2017.12.024] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 12/21/2017] [Accepted: 12/22/2017] [Indexed: 12/19/2022]
Abstract
Here we review the evolving story of the coronavirus endoribonuclease (EndoU). Coronavirus EndoU is encoded within the sequence of nonstructural protein (nsp) 15, which was initially identified as a component of the viral replication complex. Biochemical and structural studies revealed the enzymatic nature of nsp15/EndoU, which was postulated to be essential for the unique replication cycle of viruses in the order Nidovirales. However, the role of nsp15 in coronavirus replication was enigmatic as EndoU-deficient coronaviruses were viable and replicated to near wild-type virus levels in fibroblast cells. A breakthrough in our understanding of the role of EndoU was revealed in recent studies, which showed that EndoU mediates the evasion of viral double-stranded RNA recognition by host sensors in macrophages. This new discovery of nsp15/EndoU function leads to new opportunities for investigating how a viral EndoU contributes to pathogenesis and exploiting this enzyme for therapeutics and vaccine design against pathogenic coronaviruses.
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13
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Coronavirus nonstructural protein 15 mediates evasion of dsRNA sensors and limits apoptosis in macrophages. Proc Natl Acad Sci U S A 2017; 114:E4251-E4260. [PMID: 28484023 DOI: 10.1073/pnas.1618310114] [Citation(s) in RCA: 270] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Coronaviruses are positive-sense RNA viruses that generate double-stranded RNA (dsRNA) intermediates during replication, yet evade detection by host innate immune sensors. Here we report that coronavirus nonstructural protein 15 (nsp15), an endoribonuclease, is required for evasion of dsRNA sensors. We evaluated two independent nsp15 mutant mouse coronaviruses, designated N15m1 and N15m3, and found that these viruses replicated poorly and induced rapid cell death in mouse bone marrow-derived macrophages. Infection of macrophages with N15m1, which expresses an unstable nsp15, or N15m3, which expresses a catalysis-deficient nsp15, activated MDA5, PKR, and the OAS/RNase L system, resulting in an early, robust induction of type I IFN, PKR-mediated apoptosis, and RNA degradation. Immunofluorescence imaging of nsp15 mutant virus-infected macrophages revealed significant dispersal of dsRNA early during infection, whereas in WT virus-infected cells, the majority of the dsRNA was associated with replication complexes. The loss of nsp15 activity also resulted in greatly attenuated disease in mice and stimulated a protective immune response. Taken together, our findings demonstrate that coronavirus nsp15 is critical for evasion of host dsRNA sensors in macrophages and reveal that modulating nsp15 stability and activity is a strategy for generating live-attenuated vaccines.
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14
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A new role of GCN2 in the nucleolus. Biochem Biophys Res Commun 2017; 485:484-491. [DOI: 10.1016/j.bbrc.2017.02.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Accepted: 02/07/2017] [Indexed: 01/06/2023]
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15
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Kalra J, Dhar A. Double-stranded RNA-dependent protein kinase signalling and paradigms of cardiometabolic syndrome. Fundam Clin Pharmacol 2017; 31:265-279. [PMID: 27992964 DOI: 10.1111/fcp.12261] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Revised: 11/30/2016] [Accepted: 12/16/2016] [Indexed: 12/28/2022]
Affiliation(s)
- Jaspreet Kalra
- Department of Pharmacy; Birla Institute of Technology and Sciences Pilani, Hyderabad Campus; Jawahar Nagar Shameerpet, Hyderabad Andhra Pradesh 500078 India
| | - Arti Dhar
- Department of Pharmacy; Birla Institute of Technology and Sciences Pilani, Hyderabad Campus; Jawahar Nagar Shameerpet, Hyderabad Andhra Pradesh 500078 India
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16
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Yoon J, Park K, Hwang DS, Rhee K. Importance of eIF2α phosphorylation as a protective mechanism against heat stress in mouse male germ cells. Mol Reprod Dev 2017; 84:265-274. [PMID: 28067447 DOI: 10.1002/mrd.22778] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 12/27/2016] [Indexed: 01/27/2023]
Abstract
Mammalian male germ cells are exceptionally labile to heat stress. A temporal arrest of translation is one immediate response to heat, which involves heat-induced phosphorylation of eukaryotic initiation factor 2α (eIF2α) to block the formation of the translational initiation complex. Here, we investigated the protective mechanisms against heat stress in mouse male germ cells. All known eIF2α kinases were expressed in lineage- and developmental stage-specific manners in the testis; noteworthy was the presence of Gcn2 (General control nonderepressible 2 kinase) in spermatocytes of all seminiferous tubules. Multiple eIF2α kinases are likely activated upon heat stress in male germ cells. ISRIB (Integrated stress response inhibitor) was then used to determine the events downstream of eIF2α phosphorylation. ISRIB significantly reduced the rate of stress granule formation in spermatocytes at early-stage (III-IV) seminiferous tubules, and induced a number of apoptotic germ cells at late-stage (XI-XII) seminiferous tubules near the onset of meiosis. Thus, stress granule formation is a downstream event of eIF2α phosphorylation that may not directly protect cells from apoptosis, at least in spermatocytes of seminiferous tubules in early stages. Mol. Reprod. Dev. 84: 265-274, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jungbin Yoon
- Department of Biological Sciences, Seoul National University, Seoul, Korea
| | - Kyosun Park
- Department of Biological Sciences, Seoul National University, Seoul, Korea
| | - Deog Su Hwang
- Department of Biological Sciences, Seoul National University, Seoul, Korea
| | - Kunsoo Rhee
- Department of Biological Sciences, Seoul National University, Seoul, Korea
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17
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Abstract
Cell death is a common outcome of virus infection. In some cases, cell death curbs virus replication. In others, cell death enhances virus dissemination and contributes to tissue injury, exacerbating viral disease. Three forms of cell death are observed following virus infection-apoptosis, necroptosis, and pyroptosis. In this review, I describe the core machinery needed for each of these forms of cell death. Using representative viruses, I highlight how distinct stages of virus replication initiate signaling pathways that elicit these forms of cell death. I also discuss viral strategies to overcome the deleterious effects of cell death on virus propagation and the consequences of cell death for host physiology.
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Affiliation(s)
- Pranav Danthi
- Department of Biology, Indiana University, Bloomington, Indiana 47405;
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18
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The estrogen metabolite 2-methoxyestradiol regulates eukaryotic initiation factor 4E (eIF4E) and inhibits protein synthesis in MG63 osteosarcoma cells. Genes Dis 2016; 3:153-158. [PMID: 30258883 PMCID: PMC6147162 DOI: 10.1016/j.gendis.2016.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/10/2016] [Indexed: 12/23/2022] Open
Abstract
Osteosarcoma is a primary bone tumor that affects children and young adults. The estrogen metabolite 2-methoxyestradiol (2-ME) induces cell death in osteosarcoma cells. To determine whether 2-ME actions involve the control of protein synthesis, we studied the effect of 2-ME on eukaryotic initiation factor 4E (eIF4E) and eIF4E-binding protein 1 (4E-BP1) in MG63 osteosarcoma cells. Our results show that 2-ME treatment increases the association of eIF4E with 4E-BP1 in osteosarcoma cells. Also, 2-ME decreases the binding of eIF4E protein to 7-methyl-guanosine cap structure, indicating that 2-ME treatment results in the inhibition of translational initiation. These findings are further supported by the inhibition of protein synthesis in 2-ME-treated osteosarcoma cells. Taken together, our studies show that 2-ME-mediated antitumor effects in osteosarcoma cells involve the regulation of protein synthesis, and translational machinery could serve as a target in the treatment of osteosarcoma.
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19
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Koyama S, Omura T, Yonezawa A, Imai S, Nakagawa S, Nakagawa T, Yano I, Matsubara K. Gefitinib and Erlotinib Lead to Phosphorylation of Eukaryotic Initiation Factor 2 Alpha Independent of Epidermal Growth Factor Receptor in A549 Cells. PLoS One 2015; 10:e0136176. [PMID: 26288223 PMCID: PMC4545731 DOI: 10.1371/journal.pone.0136176] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 07/31/2015] [Indexed: 01/01/2023] Open
Abstract
Gefitinib and erlotinib are anticancer agents, which inhibit epidermal growth factor receptor (EGFR) tyrosine kinase. Interstitial lung disease (ILD) occurs in patients with non-small cell lung cancer receiving EGFR inhibitors. In the present study, we examined whether gefitinib- and erlotinib-induced lung injury related to ILD through endoplasmic reticulum (ER) stress, which is a causative intracellular mechanism in cytotoxicity caused by various chemicals in adenocarcinomic human alveolar basal epithelial cells. These two EGFR inhibitors increased Parkinson juvenile disease protein 2 and C/EBP homologous protein mRNA expressions, and activated the eukaryotic initiation factor (eIF) 2α/activating transcription factor 4 pathway without protein kinase R-like ER kinase activation in A549 cells. Gefitinib and erlotinib caused neither ER stress nor cell death; however, these agents inhibited cell growth via the reduction of cyclin-D1 expression. Tauroursodeoxycholic acid, which is known to suppress eIF2α phosphorylation, cancelled the effects of EGFR inhibitors on cyclin-D1 expression and cell proliferation in a concentration-dependent manner. The results of an EGFR-silencing study using siRNA showed that gefitinib and erlotinib affected eIF2α phosphorylation and cyclin-D1 expression independent of EGFR inhibition. Therefore, the inhibition of cell growth by these EGFR inhibitors might equate to impairment of the alveolar epithelial cell repair system via eIF2α phosphorylation and reduced cyclin-D1 expression.
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Affiliation(s)
- Satoshi Koyama
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Tomohiro Omura
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Atsushi Yonezawa
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Satoshi Imai
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Shunsaku Nakagawa
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Takayuki Nakagawa
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Ikuko Yano
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
| | - Kazuo Matsubara
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, Kyoto, Japan
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20
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RNase L Cleavage Products Promote Switch from Autophagy to Apoptosis by Caspase-Mediated Cleavage of Beclin-1. Int J Mol Sci 2015; 16:17611-36. [PMID: 26263979 PMCID: PMC4581211 DOI: 10.3390/ijms160817611] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 07/17/2015] [Accepted: 07/27/2015] [Indexed: 01/03/2023] Open
Abstract
Autophagy and apoptosis share regulatory molecules enabling crosstalk in pathways that affect cellular homeostasis including response to viral infections and survival of tumor cells. Ribonuclease L (RNase L) is an antiviral endonuclease that is activated in virus-infected cells and cleaves viral and cellular single-stranded RNAs to produce small double-stranded RNAs with roles in amplifying host responses. Activation of RNase L induces autophagy and apoptosis in many cell types. However, the mechanism by which RNase L mediates crosstalk between these two pathways remains unclear. Here we show that small dsRNAs produced by RNase L promote a switch from autophagy to apoptosis by caspase-mediated cleavage of Beclin-1, terminating autophagy. The caspase 3-cleaved C-terminal fragment of Beclin-1 enhances apoptosis by translocating to the mitochondria along with proapoptotic protein, Bax, and inducing release of cytochrome C to the cytosol. Cleavage of Beclin-1 determines switch to apoptosis since expression of caspase-resistant Beclin-1 inhibits apoptosis and sustains autophagy. Moreover, inhibiting RNase L-induced autophagy promotes cell death and inhibiting apoptosis prolongs autophagy in a cross-inhibitory mechanism. Our results demonstrate a novel role of RNase L generated small RNAs in cross-talk between autophagy and apoptosis that impacts the fate of cells during viral infections and cancer.
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21
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Shin U, Williams DE, Kozakov D, Hall DR, Beglov D, Vajda S, Andersen RJ, Pelletier J. Stimulators of translation identified during a small molecule screening campaign. Anal Biochem 2014; 447:6-14. [PMID: 24513115 DOI: 10.1016/j.ab.2013.10.026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 10/14/2013] [Accepted: 10/16/2013] [Indexed: 10/26/2022]
Abstract
In screening a library of natural and synthetic products for eukaryotic translation modulators, we identified two natural products, isohymenialdisine and hymenialdisine, that exhibit stimulatory effects on translation. The characterization of these compounds led to the insight that mRNA used to program the translation extracts during high-throughput assay setup was leading to phosphorylation of eIF2α, a potent negative regulatory event that is mediated by one of four kinases. We identified double-stranded RNA-dependent protein kinase (PKR) as the eIF2α kinase that was being activated by exogenously added mRNA template. Characterization of the mode of action of isohymenialdisine revealed that it directly acts on PKR by inhibiting autophosphorylation, perturbs the PKR-eIF2α phosphorylation axis, and can be modeled into the PKR ATP binding site. Our results identify a source of "false positives" for high-throughput screen campaigns using translation extracts, raising a cautionary note for this type of screen.
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22
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Wang X, Dong JH, Zhang WZ, Leng JJ, Cai SW, Chen MY, Yang X. Double stranded RNA-dependent protein kinase promotes the tumorigenic phenotype in HepG2 hepatocellular carcinoma cells by activating STAT3. Oncol Lett 2014; 8:2762-2768. [PMID: 25360179 PMCID: PMC4214393 DOI: 10.3892/ol.2014.2560] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 08/12/2014] [Indexed: 01/08/2023] Open
Abstract
Previously known as a first-response protein upon viral infection and other stress signals, double-stranded RNA-dependent protein kinase (PKR, also termed EIF2AK2) has been found to be differentially expressed in multiple types of tumor, including hepatocellular carcinoma, suggesting that PKR may be involved in tumor initiation and development. However, whether and how PKR promotes or suppresses the development of hepatocellular carcinoma remains controversial. In the present study, PKR expression was investigated using qPCR and western blot analysis, which revealed that PKR expression was upregulated in liver tumor tissues, when compared to that of adjacent normal tissues, which were obtained from four primary liver cancer patients. Furthermore, in vitro cellular assays revealed that PKR exerts a key role in maintaining the proliferation and migration of HepG2 human hepatocellular carcinoma cells. Mouse models with xenograft transplantations also confirmed a tumorigenic role of PKR in HepG2 cells. Furthermore, a transcription factor, signal transducer and activator of transcription 3 (STAT3), was revealed to mediate the tumor-promoting function of PKR in HepG2 cells, as shown by in vitro cellular proliferation and migration assays. In conclusion, the results suggested a tumorigenic role of PKR in liver cancer and a detailed mechanism involving an oncogenic transcription factor, STAT3, is described. Therefore, PKR may present a potential novel therapeutic target for the treatment of liver cancer.
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Affiliation(s)
- Xun Wang
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Jia-Hong Dong
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Wen-Zhi Zhang
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Jian-Jun Leng
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Shou-Wang Cai
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Ming-Yi Chen
- Department of Hepatobiliary Surgery, The General Hospital of Chinese People's Liberation Army, Beijing 100853, P.R. China
| | - Xuerui Yang
- MOE Key Laboratory of Bioinformatics, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, P.R. China
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23
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Fang L, Cho HJ, Chan C, Feig M. Binding site multiplicity with fatty acid ligands: implications for the regulation of PKR kinase autophosphorylation with palmitate. Proteins 2014; 82:2429-42. [PMID: 24862841 DOI: 10.1002/prot.24607] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/17/2014] [Accepted: 05/09/2014] [Indexed: 01/09/2023]
Abstract
Saturated long chain-free fatty acids (FFAs), especially palmitate, have been implicated in apoptosis by inhibiting the activity of PKR (double-stranded RNA-dependent protein kinase). We recently found evidence that palmitate interacts directly with the kinase domain of PKR, subsequently inhibiting the autophosphorylation of PKR. To investigate the interactions of palmitate with PKR and its effects on PKR autophosphorylation, we performed extensive unbiased MD simulations combined with biochemical and biophysical experiments. The simulations predict multiple putative binding sites of palmitate on both the phosphorylated and unphosphorylated PKR with similar binding affinities. Ligand-protein interactions involving a large variety of different binding modes challenge the conventional view of highly specific, single binding sites. Key interactions of palmitate involve the αC-helix of PKR, especially near residue R307. Experimental mutation of R307 was found to affect palmitate binding and reduce its inhibitory effect. Based on this study a new allosteric mechanism is proposed where palmitate binding to the αC-helix prevents the inactive-to-active transition of PKR and subsequently reduces its ability to autophosphorylate.
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Affiliation(s)
- Liang Fang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, 48824
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24
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Acunzo J, Baylot V, So A, Rocchi P. TCTP as therapeutic target in cancers. Cancer Treat Rev 2014; 40:760-9. [PMID: 24650927 DOI: 10.1016/j.ctrv.2014.02.007] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 02/19/2014] [Accepted: 02/21/2014] [Indexed: 01/07/2023]
Abstract
The translationally controlled tumor protein (TCTP) is a highly conserved protein present in eukaryotic organisms. This protein, located both in the cytoplasmic and the nucleus, is expressed in various tissues and is regulated in response to a wide range of extracellular stimuli. TCTP interacts with itself and other protein including MCL1 and p53. TCTP has been shown to play an important role in physiological events, such as cell proliferation, cell death and immune responses but also in stress response and tumor reversion. Moreover, TCTP expression is associated with malignancy and chemoresistance. In this review, we will evaluate pathways regulated by TCTP and current inhibitory strategy to target TCTP in cancerous diseases.
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Affiliation(s)
- Julie Acunzo
- (a)Inserm, U1068, CRCM, Marseille F-13009, France; (b)Institut Paoli-Calmettes, Marseille F-13009, France; (c)Aix-Marseille Univ., Marseille F-13284, France; (d)CNRS, UMR7258, Marseille F-13009, France
| | - Virginie Baylot
- (a)Inserm, U1068, CRCM, Marseille F-13009, France; (b)Institut Paoli-Calmettes, Marseille F-13009, France; (c)Aix-Marseille Univ., Marseille F-13284, France; (d)CNRS, UMR7258, Marseille F-13009, France
| | - Alan So
- (e)University of British Columbia, The Vancouver Prostate Centre 2660- Oak St Vancouver, BC V6H3Z6, Canada
| | - Palma Rocchi
- (a)Inserm, U1068, CRCM, Marseille F-13009, France; (b)Institut Paoli-Calmettes, Marseille F-13009, France; (c)Aix-Marseille Univ., Marseille F-13284, France; (d)CNRS, UMR7258, Marseille F-13009, France.
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Isomura M, Kotake Y, Masuda K, Miyara M, Okuda K, Samizo S, Sanoh S, Hosoi T, Ozawa K, Ohta S. Tributyltin-induced endoplasmic reticulum stress and its Ca2+-mediated mechanism. Toxicol Appl Pharmacol 2013; 272:137-46. [DOI: 10.1016/j.taap.2013.05.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 05/15/2013] [Accepted: 05/24/2013] [Indexed: 11/16/2022]
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Kim B, Park K, Rhee K. Heat stress response of male germ cells. Cell Mol Life Sci 2013; 70:2623-36. [PMID: 23007846 PMCID: PMC11113252 DOI: 10.1007/s00018-012-1165-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 08/19/2012] [Accepted: 09/10/2012] [Indexed: 01/09/2023]
Abstract
The vast majority of mammalian testes are located outside the body cavity for proper thermoregulation. Heat has an adverse effect on mammalian spermatogenesis and eventually leads to sub- or infertility. Recent studies have provided insights into the molecular response of male germ cells to high temperatures. Here, we review the effects of heat on male germ cells and discuss the mechanisms underlying germ cell loss and impairment. We also discuss the role of translational control in male germ cells as a potential protective mechanism against heat-induced germ cell apoptosis.
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Affiliation(s)
- Byunghyuk Kim
- Department of Biological Sciences, Seoul National University, Seoul, 151-747 Korea
| | - Kyosun Park
- Department of Biological Sciences, Seoul National University, Seoul, 151-747 Korea
| | - Kunsoo Rhee
- Department of Biological Sciences, Seoul National University, Seoul, 151-747 Korea
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Prognostic significance of combinations of RNA-dependent protein kinase and EphA2 biomarkers for NSCLC. J Thorac Oncol 2013; 8:301-8. [PMID: 23370317 DOI: 10.1097/jto.0b013e318282def7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
INTRODUCTION RNA-dependent protein kinase (PKR) is an independent prognostic variable in patients with non-small-cell lung cancer (NSCLC). In the current study, we investigated the correlation between PKR and 25 other biomarkers for NSCLC, identified the markers that could further improve the prognostic significance of PKR and elucidated the mechanisms of interaction between these markers and PKR. METHODS Tissue microarray samples obtained from 218 patients with lung cancer were stained with an anti-PKR antibody and antibodies against 25 biomarkers. Immunohistochemical expression was scored and used for Kaplan-Meier survival analysis. The interaction between PKR and EphA2 in NSCLC cell lines was examined. RESULTS We found that PKR was associated with EphA2 and that the prognostic information regarding NSCLC provided by the combination of PKR and EphA2 (P/E) was significantly more accurate than that provided by either marker alone. The 5-year overall survival rate in patients with PKR/EphA2 (20%) was significantly lower than that of patients with PKR/EphA2 (74%), patients with PKR/EphA2 (55%), and patients with PKR/EphA2 (55%) (p < 0.0001). We also found that the PKR:EphA2 (P/E) ratio was significantly associated with prognosis (p < 0.0001). Univariate and multivariate Cox analyses revealed that this P/E combination or ratio was an independent predictor of overall survival. In addition, induction of PKR expression reduced EphA2 protein expression levels in NSCLC cell lines. CONCLUSIONS PKR/EphA2 is a significant predictor of prognosis for NSCLC. PKR/EphA2 may be a promising approach to improving screening efficiency and predicting prognosis in patients with NSCLC.
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Taghavi N, Samuel CE. RNA-dependent protein kinase PKR and the Z-DNA binding orthologue PKZ differ in their capacity to mediate initiation factor eIF2α-dependent inhibition of protein synthesis and virus-induced stress granule formation. Virology 2013; 443:48-58. [PMID: 23706307 DOI: 10.1016/j.virol.2013.04.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 04/03/2013] [Accepted: 04/22/2013] [Indexed: 02/07/2023]
Abstract
Protein kinase R (PKR), a regulator of translation in mammalian cells, possesses two ds-RNA binding domains responsible for kinase activation. Protein kinase Z (PKZ), a PKR-like kinase present in fish, possesses two Z-DNA binding domains. A complementation strategy with cells stably deficient in PKR was used to compare the functions of PKR and PKZ. We found reporter expression was inhibited by wildtype (WT) PKR but not by either catalytic (K296R) or RNA-binding (K64E) mutants. PKZ, like PKR, more potently inhibited 5' cap-dependent compared to IRES-dependent reporter expression. However, in contrast to PKR-expressing cells, phosphorylation of initiation factor eIF2α was not detectably increased in PKZ-expressing cells. Furthermore, virus-induced stress granule formation was observed in PKR-deficient cells complemented with WT PKR but not K296R mutant PKR or WT PKZ. These results suggest that PKR and PKZ function by distinguishable mechanisms to modulate host responses including protein synthesis inhibition and stress granule formation.
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Affiliation(s)
- Nora Taghavi
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA
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29
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Handy I, Patel RC. STAT1 requirement for PKR-induced cell cycle arrest in vascular smooth muscle cells in response to heparin. Gene 2013; 524:15-21. [PMID: 23597922 DOI: 10.1016/j.gene.2013.03.124] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Revised: 03/18/2013] [Accepted: 03/27/2013] [Indexed: 11/27/2022]
Abstract
Interferons (IFNs) are a family of cytokines that exhibit antiviral, antiproliferative, and immunomodulatory properties. PKR (protein kinase, RNA activated) is of central importance in mediating the antiproliferative actions of IFNs. Our research has established that PKR inhibits vascular smooth muscle cell (VSMC) proliferation by regulating G1 to S transition. Many cardiovascular diseases result from complications of atherosclerosis, a chronic and progressive inflammatory condition often characterized by excessive proliferation of VSMC. Thus, an effective method for inhibiting VSMC proliferation is likely to arrest atherosclerosis and restenosis at early stages. Our research establishes that PKR activation in VSMC leads to a G1 arrest brought about by an inhibition of cyclin-dependent kinase 2 (Cdk2) activity by p27(kip1). In quiescent VSMC, p27(kip1) levels are high and when stimulated by serum/growth factors, p27(kip1) levels drop by destabilization of the protein. Under conditions that lead to activation of PKR, there is a marked inhibition of p27(kip1) down-regulation due to increased stability of p27(kip1) protein. In order to understand the mechanism of heparin-induced stabilization of p27(kip1) in VSMC, we examined the involvement of the Signal Transducer and Activator of Transcription-1 (STAT1), which is an important player in mediating antiproliferative effects of IFNs. Our results demonstrate that PKR overexpression in VSMC leads to an increase in p27(kip1) protein levels and this increase requires the catalytic activity of PKR. PKR activation induced by antiproliferative agent heparin leads to phosphorylation of STAT1 on serine 727, which is essential for the cell cycle block. STAT1 null VSMCs are largely defective in heparin-induced cell cycle arrest and in PKR null cells the STAT1 phosphorylation in response to heparin was absent. These results establish that heparin causes STAT1 phosphorylation on serine 727 via activation of PKR and that this event is required for the G1 arrest in VSMC.
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Affiliation(s)
- Indhira Handy
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208,USA
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30
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Yang C, Shogren KL, Goyal R, Bravo D, Yaszemski MJ, Maran A. RNA-dependent protein kinase is essential for 2-methoxyestradiol-induced autophagy in osteosarcoma cells. PLoS One 2013; 8:e59406. [PMID: 23527187 PMCID: PMC3602192 DOI: 10.1371/journal.pone.0059406] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 02/16/2013] [Indexed: 11/26/2022] Open
Abstract
Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Surgical resection and adjunctive chemotherapy are the only widely available options of treatment for this disease. Anti-tumor compound 2-Methoxyestradiol (2-ME) triggers cell death through the induction of apoptosis in osteosarcoma cells, but not in normal osteoblasts. In this report, we have investigated whether autophagy plays a role in 2-ME actions on osteosarcoma cells. Transmission electron microscopy imaging shows that 2-ME treatment leads to the accumulation of autophagosomes in human osteosarcoma cells. 2-ME induces the conversion of the microtubule-associated protein LC3-I to LC3-II, a biochemical marker of autophagy that is correlated with the formation of autophagosomes. Conversion to LC3-II is accompanied by protein degradation in 2-ME-treated cells. 2-ME does not induce autophagosome formation in normal primary human osteoblasts. In addition, 2-ME-dependent autophagosome formation in osteosarcoma cells requires ATG7 expression. Furthermore, 2-ME does not induce accumulation of autophagosomes in osteosarcoma cells that express dominant negative mutant RNA-dependent protein kinase (PKR) and are resistant to anti-proliferative and anti-tumor effects of 2-ME. Taken together, our study shows that 2-ME treatment induces PKR-dependent autophagy in osteosarcoma cells, and that autophagy could play an important role in 2-ME-mediated anti-tumor actions and in the control of osteosarcoma.
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Affiliation(s)
- Caihong Yang
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Orthopedic, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Kristen L. Shogren
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Ribu Goyal
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Dalibel Bravo
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Michael J. Yaszemski
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Avudaiappan Maran
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota, United States of America
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Abstract
RNA interference (RNAi) is a cellular mechanism to inhibit the expression of gene products in a highly specific manner. In recent years, RNAi has become the cornerstone of gene function studies, shortening the otherwise long process of target identification and validation. In addition, small interfering RNA (siRNA) and short-hairpin RNA (shRNA) therapies are being developed for the treatment of a variety of human diseases. Despite its huge potential for gene silencing, a hurdle to safe and effective RNAi is the activation of innate immune responses. Induction of innate immunity is dose- and sequence-dependent, and is also influenced by target tissue and delivery vehicle. Research on the molecular mechanisms mediating this response is helping to improve the design of the RNAi molecules. Nevertheless, appropriate testing for the presence of this undesired effect is needed prior to making conclusions on the outcome of the silencing treatment.
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Affiliation(s)
- Núria Morral
- Department of Medical and Molecular Genetics, and Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Ishibashi O, Ali MM, Luo SS, Ohba T, Katabuchi H, Takeshita T, Takizawa T. Short RNA duplexes elicit RIG-I-mediated apoptosis in a cell type- and length-dependent manner. Sci Signal 2011; 4:ra74. [PMID: 22067459 DOI: 10.1126/scisignal.2001614] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Short double-stranded RNAs (dsRNAs) induce type I interferon (IFN)-mediated innate immune responses. In functional studies with short interfering RNAs or synthetic mimics of microRNA precursors in vitro, we found that short dsRNAs readily induced apoptosis in cells derived from human granulosa cell tumors, but not in other cell types. Apoptosis was independent of the sequence of the dsRNA, but depended on its length, and was induced by 23- and 24-nucleotide (nt) dsRNAs, but not by shorter dsRNAs (< 22 nt) or by the long dsRNA polyinosinic-polycytidylic acid. Microarray analysis revealed that apoptosis was accompanied by the increased expression of IFN-stimulated genes; however, several lines of evidence showed that IFNs did not directly induce apoptosis. Subsequent analyses revealed that the short dsRNAs increased the expression of retinoic acid-inducible gene I (RIG-I) through dsRNA-activated protein kinase (PKR). Although these dsRNAs bore 3' overhangs and nontriphosphate 5' termini, which are not thought to be RIG-I-activating structures, the dsRNAs bound to RIG-I and triggered proapoptotic signaling mostly by activating RIG-I, which was followed by activation of the mitogen-activated protein kinase p38. Thus, we suggest that ligand recognition and subsequent signaling by RNA sensors are more complicated than previously believed. In addition, short dsRNAs may serve as pharmacological agents to target specific tumors, such as granulosa cell tumors.
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Affiliation(s)
- Osamu Ishibashi
- Department of Molecular Medicine and Anatomy, Nippon Medical School, 1-1-5 Sendagi, Tokyo 113-8602, Japan
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Ill-Raga G, Palomer E, Wozniak MA, Ramos-Fernández E, Bosch-Morató M, Tajes M, Guix FX, Galán JJ, Clarimón J, Antúnez C, Real LM, Boada M, Itzhaki RF, Fandos C, Muñoz FJ. Activation of PKR causes amyloid ß-peptide accumulation via de-repression of BACE1 expression. PLoS One 2011; 6:e21456. [PMID: 21738672 PMCID: PMC3125189 DOI: 10.1371/journal.pone.0021456] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 06/02/2011] [Indexed: 12/13/2022] Open
Abstract
BACE1 is a key enzyme involved in the production of amyloid ß-peptide (Aß) in Alzheimer's disease (AD) brains. Normally, its expression is constitutively inhibited due to the presence of the 5′untranslated region (5′UTR) in the BACE1 promoter. BACE1 expression is activated by phosphorylation of the eukaryotic initiation factor (eIF)2-alpha, which reverses the inhibitory effect exerted by BACE1 5′UTR. There are four kinases associated with different types of stress that could phosphorylate eIF2-alpha. Here we focus on the double-stranded (ds) RNA-activated protein kinase (PKR). PKR is activated during viral infection, including that of herpes simplex virus type 1 (HSV1), a virus suggested to be implicated in the development of AD, acting when present in brains of carriers of the type 4 allele of the apolipoprotein E gene. HSV1 is a dsDNA virus but it has genes on both strands of the genome, and from these genes complementary RNA molecules are transcribed. These could activate BACE1 expression by the PKR pathway. Here we demonstrate in HSV1-infected neuroblastoma cells, and in peripheral nervous tissue from HSV1-infected mice, that HSV1 activates PKR. Cloning BACE1 5′UTR upstream of a luciferase (luc) gene confirmed its inhibitory effect, which can be prevented by salubrinal, an inhibitor of the eIF2-alpha phosphatase PP1c. Treatment with the dsRNA analog poly (I∶C) mimicked the stimulatory effect exerted by salubrinal over BACE1 translation in the 5′UTR-luc construct and increased Aß production in HEK-APPsw cells. Summarizing, our data suggest that PKR activated in brain by HSV1 could play an important role in the development of AD.
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Affiliation(s)
- Gerard Ill-Raga
- Laboratory of Molecular Physiology and Channelopathies, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Catalonia, Spain
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Cho H, Mukherjee S, Palasuberniam P, Pillow L, Bilgin B, Nezich C, Walton SP, Feig M, Chan C. Molecular mechanism by which palmitate inhibits PKR autophosphorylation. Biochemistry 2011; 50:1110-9. [PMID: 21192654 PMCID: PMC3035770 DOI: 10.1021/bi101923r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
PKR (double-stranded RNA-activated protein kinase) is an important component of the innate immunity, antiviral, and apoptotic pathways. Recently, our group found that palmitate, a saturated fatty acid, is involved in apoptosis by reducing the autophosphorylation of PKR at the Thr451 residue; however, the molecular mechanism by which palmitate reduces PKR autophosphorylation is not known. Thus, we investigated how palmitate affects the phosphorylation of the PKR protein at the molecular and biophysical levels. Biochemical and computational studies show that palmitate binds to PKR, near the ATP-binding site, thereby inhibiting its autophosphorylation at Thr451 and Thr446. Mutation studies suggest that Lys296 and Asp432 in the ATP-binding site on the PKR protein are important for palmitate binding. We further confirmed that palmitate also interacts with other kinases, due to the conserved ATP-binding site. A better understanding of how palmitate interacts with the PKR protein, as well as other kinases, could shed light onto possible mechanisms by which palmitate mediates kinase signaling pathways that could have implications on the efficacy of current drug therapies that target kinases.
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Affiliation(s)
- Hyunju Cho
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
| | - Shayantani Mukherjee
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Pratheeba Palasuberniam
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Lisa Pillow
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
| | - Betul Bilgin
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
| | - Catherine Nezich
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - S. Patrick Walton
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
| | - Michael Feig
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Christina Chan
- Department of Chemical Engineering and Material Science, Michigan State University, East Lansing, MI 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
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Shen L, Lan Z, Sun X, Shi L, Liu Q, Ni J. Proteomic analysis of lanthanum citrate-induced apoptosis in human cervical carcinoma SiHa cells. Biometals 2010; 23:1179-89. [PMID: 20814718 DOI: 10.1007/s10534-010-9368-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 07/20/2010] [Indexed: 11/30/2022]
Abstract
Lanthanides possess diverse biological effect and have been shown to promote cell proliferation and induce apoptosis. Our previous studies showing that lanthanide citrate complex has significant antitumor activity in human cervical cancer HeLa cells. This study aims at determining if [LaCit(2)](3-) have the activity against another type of human cervical cancer cell line SiHa and the changes in protein expression that contribute to the mechanism(s) of [LaCit(2)](3-)-mediated apoptosis in SiHa cells. Cell growth inhibition was measured by MTT method, and apoptosis was detected by means of Hoechst 33258 staining and flow cytometry analysis. After [LaCit(2)](3-)-treatment the results show that the growth of SiHa cells was inhibited, the cells displayed typical apoptosis morphological changes, and increase in the rates of apoptosis. Using proteomics approaches, a variety of differentially expressed proteins were identified in SiHa cells before and after treatment with [LaCit(2)](3-). There were profound changes in 10 proteins relating to mitochondrial function and oxidative stress, suggesting that mitochondrial dysfunction plays a key role in [LaCit(2)](3-)-induced apoptosis. This was confirmed by a decrease in the mitochondrial transmembrane potential (Δψ(m)), and increases in H(2)O(2) generation in [LaCit(2)](3-)-treated cells. Among them the alerted proteins, Prx I, ANXA1 and TRAF5 were validated by western blotting analyses. These results suggest that there is an intrinsic molecular pathway of cell apoptosis in [LaCit(2)](3-)-treated SiHa cells. This observation is in accordance with our previous reports about the effects of [LaCit(2)](3-) and [YbCit(2)](3-) on HeLa cells and it provide a molecular mechanism underlying lanthanide citrate complex-mediated cell apoptosis.
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Affiliation(s)
- Liming Shen
- College of Life Sciences, Shenzhen University, Shenzhen, 518060, People's Republic of China
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Fournier MJ, Gareau C, Mazroui R. The chemotherapeutic agent bortezomib induces the formation of stress granules. Cancer Cell Int 2010; 10:12. [PMID: 20429927 PMCID: PMC2873330 DOI: 10.1186/1475-2867-10-12] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 04/29/2010] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Cytoplasmic stress granules (SGs) are specialized storage sites of untranslated mRNAs whose formation occurs under different stress conditions and is often associated with cell survival. SGs-inducing stresses include radiations, hypoxia, viral infections, and chemical inhibitors of specific translation initiation factors. The FDA-approved drug bortezomib (Velcade(R)) is a peptide boronate inhibitor of the 26S proteasome that is very efficient for the treatment of myelomas and other hematological tumors. Solid tumors are largely refractory to bortezomib. In the present study, we investigated the formation of SGs following bortezomib treatment. RESULTS We show that bortezomib efficiently induces the formation of SGs in cancer cells. This process involves the phosphorylation of translation initiation factor eIF2alpha by heme-regulated inhibitor kinase (HRI). Depletion of HRI prevents bortezomib-induced formation of SGs and promotes apoptosis. CONCLUSIONS This is the first study describing the formation of SGs by a chemotherapeutic compound. We speculate that the activation of HRI and the formation of SGs might constitute a mechanism by which cancer cells resist bortezomib-mediated apoptosis.
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Affiliation(s)
- Marie-Josée Fournier
- Centre de recherche de l'hôpital St-François d'Assise (CHUQ/CRSFA), 10 rue de l'Espinay, Quebec, QC G1L 3L5, Canada.
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Jiang Z, Belforte JE, Lu Y, Yabe Y, Pickel J, Smith CB, Je HS, Lu B, Nakazawa K. eIF2alpha Phosphorylation-dependent translation in CA1 pyramidal cells impairs hippocampal memory consolidation without affecting general translation. J Neurosci 2010; 30:2582-94. [PMID: 20164343 PMCID: PMC2836228 DOI: 10.1523/jneurosci.3971-09.2010] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 12/08/2009] [Accepted: 01/05/2010] [Indexed: 11/21/2022] Open
Abstract
Protein synthesis inhibitor antibiotics are widely used to produce amnesia, and have been recognized to inhibit general or global mRNA translation in the basic translational machinery. For instance, anisomycin interferes with protein synthesis by inhibiting peptidyl transferase or the 80S ribosomal function. Therefore, de novo general or global protein synthesis has been thought to be necessary for long-term memory formation. However, it is unclear which mode of translation-gene-specific translation or general/global translation-is actually crucial for the memory consolidation process in mammalian brains. Here, we generated a conditional transgenic mouse strain in which double-strand RNA-dependent protein kinase (PKR)-mediated phosphorylation of eIF2alpha, a key translation initiation protein, was specifically increased in hippocampal CA1 pyramidal cells by the chemical inducer AP20187. Administration of AP20187 significantly increased activating transcription factor 4 (ATF4) translation and concomitantly suppressed CREB-dependent pathways in CA1 cells; this led to impaired hippocampal late-phase LTP and memory consolidation, with no obvious reduction in general translation. Conversely, inhibition of general translation by low-dose anisomycin failed to block hippocampal-dependent memory consolidation. Together, these results indicated that CA1-restricted genetic manipulation of particular mRNA translations is sufficient to impair the consolidation and that consolidation of memories in CA1 pyramidal cells through eIF2alpha dephosphorylation depends more on transcription/translation of particular genes than on overall levels of general translation. The present study sheds light on the critical importance of gene-specific translations for hippocampal memory consolidation.
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Affiliation(s)
- Zhihong Jiang
- Unit on the Genetics of Cognition and Behavior, Mood and Anxiety Disorders Program
| | - Juan E. Belforte
- Unit on the Genetics of Cognition and Behavior, Mood and Anxiety Disorders Program
| | - Yuan Lu
- Gene, Cognition, and Psychosis Program
| | - Yoko Yabe
- Unit on the Genetics of Cognition and Behavior, Mood and Anxiety Disorders Program
| | | | - Carolyn Beebe Smith
- Unit on Neuroadaptation and Protein Metabolism, Laboratory of Cerebral Metabolism, National Institute of Mental Health, and
| | - Hyun-Soo Je
- Laboratory of Cellular and Synaptic Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Bai Lu
- Gene, Cognition, and Psychosis Program
- Laboratory of Cellular and Synaptic Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Kazu Nakazawa
- Unit on the Genetics of Cognition and Behavior, Mood and Anxiety Disorders Program
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Bommer UA, Heng C, Perrin A, Dash P, Lobov S, Elia A, Clemens MJ. Roles of the translationally controlled tumour protein (TCTP) and the double-stranded RNA-dependent protein kinase, PKR, in cellular stress responses. Oncogene 2009; 29:763-73. [PMID: 19901967 DOI: 10.1038/onc.2009.380] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Translationally controlled tumour protein (TCTP) is a highly conserved protein present in all eukaryotic organisms. Various cellular functions and molecular interactions have been ascribed to this protein, many related to its growth-promoting and antiapoptotic properties. TCTP levels are highly regulated in response to various cellular stimuli and stresses. We have shown recently that the double-stranded RNA-dependent protein kinase, PKR, is involved in translational regulation of TCTP. Here we extend these studies by demonstrating that TCTP is downregulated in response to various proapoptotic treatments, in particular agents that induce Ca(++) stress, in a PKR-dependent manner. This regulation requires phosphorylation of protein synthesis factor eIF2alpha. Since TCTP has been characterized as an antiapoptotic and Ca(++)-binding protein, we asked whether it is involved in protecting cells from Ca(++)-stress-induced apoptosis. Overexpression of TCTP partially protects cells against thapsigargin-induced apoptosis, as measured using caspase-3 activation assays, a nuclear fragmentation assay, using fluorescence-activated cell sorting analysis, and time-lapse video microscopy. TCTP also protects cells against the proapoptotic effects of tunicamycin and etoposide, but not against those of arsenite. Our results imply that cellular TCTP levels influence sensitivity to apoptosis and that PKR may exert its proapoptotic effects at least in part through downregulation of TCTP via eIF2alpha phosphorylation.
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Affiliation(s)
- U-A Bommer
- Division of Basic Medical Sciences, St George's, University of London, London, UK.
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Conrady CD, Drevets DA, Carr DJJ. Herpes simplex type I (HSV-1) infection of the nervous system: is an immune response a good thing? J Neuroimmunol 2009; 220:1-9. [PMID: 19819030 DOI: 10.1016/j.jneuroim.2009.09.013] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 09/15/2009] [Accepted: 09/15/2009] [Indexed: 02/06/2023]
Abstract
Herpes simplex virus type 1 (HSV-1) can induce a robust immune response initially thru the activation of pattern recognition receptors and subsequent type I interferon production that then shapes, along with other innate immune components, the adaptive immune response to the insult. While this response is necessary to quell virus replication, drive the pathogen into a "latent" state, and likely hinder viral reactivation, collateral damage can ensue with demonstrable cell death and foci of tissue pathology in the central nervous system (CNS) as a result of the release of inflammatory mediators including reactive oxygen species. Although rare, HSV-1 is the leading cause of frank sporadic encephalitis that, if left untreated, can result in death. A greater understanding of the contribution of resident glial cells and infiltrating leukocytes within the CNS in response to HSV-1 invasion is necessary to identify candidate molecules as targets for therapeutic intervention to reduce unwarranted inflammation coinciding with the maintenance of the anti-viral state.
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Affiliation(s)
- Christopher D Conrady
- Department of Microbiology, Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, United States
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Robert F, Williams C, Yan Y, Donohue E, Cencic R, Burley SK, Pelletier J. Blocking UV-induced eIF2alpha phosphorylation with small molecule inhibitors of GCN2. Chem Biol Drug Des 2009; 74:57-67. [PMID: 19519745 DOI: 10.1111/j.1747-0285.2009.00827.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The eIF2alpha kinase general control non-depressible 2 integrates translation initiation rates to amino acid availability. General control non-depressible 2 also regulates translation initiation during synaptic plasticity and GCN2(-/-) mice show improved memory compared with wild-type mice with a reduced threshold for triggering late long-term potentiation. This property suggests that inhibiting general control non-depressible 2 function might represent a therapeutic avenue for improving memory. We screened for general control non-depressible 2 inhibitors using a small library of known kinase inhibitors and ATP-analogs and identified three compounds--indirubin-3'-monoxime, SP600125 and a SyK inhibitor with activity against general control non-depressible 2. All three compounds inhibit the ability of general control non-depressible 2 to phosphorylate eIF2alphain vitro as well as in vivo following UV-treatment of mouse embryonic fibroblasts. Using computer-assisted modeling, we modeled the binding of the inhibitors in the ATP-binding site of general control non-depressible 2. This work provides the molecular basis for undertaking structure-activity relationships of these compounds in order to develop specific inhibitors of general control non-depressible 2.
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Affiliation(s)
- Francis Robert
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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Ke ZJ, Wang X, Fan Z, Luo J. Ethanol promotes thiamine deficiency-induced neuronal death: involvement of double-stranded RNA-activated protein kinase. Alcohol Clin Exp Res 2009; 33:1097-103. [PMID: 19382901 PMCID: PMC3093711 DOI: 10.1111/j.1530-0277.2009.00931.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Heavy alcohol consumption causes cerebellar degeneration, and the underlying mechanism is unclear. Chronic alcoholism is usually associated with thiamine deficiency (TD) which is known to induce selective neurodegeneration in the brain. However, the role of TD in alcohol-induced cerebellar degeneration remains to be elucidated. The double-stranded RNA-activated protein kinase (PKR) is a potent antiviral protein. Viral infection or binding to dsRNA causes PKR autophosphorylation and subsequent phosphorylation of the alpha-subunit of eukaryotic translation factor-2alpha, leading to inhibition of translation or apoptosis. PKR can also be activated by cellular stresses. METHODS In this study, we used an in vitro model, cultured cerebellar granule neurons (CGNs), to investigate the interaction between TD and ethanol and evaluate the contribution of their interaction to neuronal loss. TD was induced by treatment with amprolium in association with ethanol. Cell viability was determined by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide assay. PKR expression/phosphorylation and subcellular distribution was analyzed with immunoblotting and immunocytochemistry. RESULTS Thiamine deficiency caused death of CGNs but ethanol did not. However, TD plus ethanol induced a much greater cell loss than TD alone. TD-induced PKR phosphorylation and ethanol exposure significantly promoted TD-induced PKR phosphorylation as well as its nuclear translocation. A selective PKR inhibitor not only protected CGNs against TD toxicity, but also abolished ethanol potentiation of TD-induced loss of CGNs. CONCLUSIONS Ethanol promoted TD-induced PKR activation and neuronal death. PKR may be a convergent protein that mediates the interaction between TD and ethanol.
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Affiliation(s)
- Zun-Ji Ke
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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Yang X, Chan C. Repression of PKR mediates palmitate-induced apoptosis in HepG2 cells through regulation of Bcl-2. Cell Res 2009; 19:469-86. [PMID: 19259124 PMCID: PMC2664847 DOI: 10.1038/cr.2009.25] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The present study shows that double-stranded RNA-dependent protein kinase (PKR) regulates the protein expression level and phosphorylation of Bcl-2 and plays an anti-apoptotic role in human hepatocellular carcinoma cells (HepG2). In various types of cells, saturated free fatty acids (FFAs), such as palmitate, have been shown to induce cellular apoptosis by several mechanisms. Palmitate down-regulates the activity of PKR and thereby decreases the level of Bcl-2 protein, mediated in part by reduced activation of the NF-kappaB transcription factor. In addition to the level of Bcl-2 protein, the phosphorylation of Bcl-2 at different amino acid residues, such as Ser70 and Ser87, is also important in regulating cellular apoptosis. The decrease in the phosphorylation of Bcl-2 at Ser70 upon exposure to palmitate is mediated by inhibition of PKR and possibly by c-Jun N-terminal kinase (JNK), whereas the phosphorylation of Bcl-2 at Ser87 is unaffected by palmitate or PKR. In summary, PKR mediates the regulation of the protein level and the phosphorylation status of Bcl-2, providing a novel mechanism of palmitate-induced apoptosis in HepG2 cells.
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Affiliation(s)
- Xuerui Yang
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
| | - Christina Chan
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, MI 48824
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824
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Kakugawa S, Shimojima M, Goto H, Horimoto T, Oshimori N, Neumann G, Yamamoto T, Kawaoka Y. Mitogen-activated protein kinase-activated kinase RSK2 plays a role in innate immune responses to influenza virus infection. J Virol 2009; 83:2510-7. [PMID: 19129453 PMCID: PMC2648281 DOI: 10.1128/jvi.02416-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 12/29/2008] [Indexed: 11/20/2022] Open
Abstract
Viral infections induce signaling pathways in mammalian cells that stimulate innate immune responses and affect cellular processes, such as apoptosis, mitosis, and differentiation. Here, we report that the ribosomal protein S6 kinase alpha 3 (RSK2), which is activated through the "classical" mitogen-activated protein kinase pathway, plays a role in innate immune responses to influenza virus infection. RSK2 functions in the regulation of cell growth and differentiation but was not known to play a role in the cellular antiviral response. We have found that knockdown of RSK2 enhanced viral polymerase activity and growth of influenza viruses. Influenza virus infection stimulates NK-kappaB- and beta interferon-dependent promoters. This stimulation was reduced in RSK2 knockdown cells, suggesting that RSK2 executes its effect through innate immune response pathways. Furthermore, RSK2 knockdown suppressed influenza virus-induced phosphorylation of the double-stranded RNA-activated protein kinase PKR, a known antiviral protein. These findings establish a role for RSK2 in the cellular antiviral response.
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MESH Headings
- Animals
- Cell Line
- Dogs
- Gene Knockdown Techniques
- Humans
- Immunity, Innate
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/growth & development
- Influenza A Virus, H1N1 Subtype/immunology
- Influenza A Virus, H5N1 Subtype/genetics
- Influenza A Virus, H5N1 Subtype/growth & development
- Influenza A Virus, H5N1 Subtype/immunology
- Interferons/biosynthesis
- Models, Biological
- NF-kappa B p52 Subunit/biosynthesis
- Ribosomal Protein S6 Kinases, 90-kDa/genetics
- Ribosomal Protein S6 Kinases, 90-kDa/physiology
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Affiliation(s)
- Satoshi Kakugawa
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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Epithelial cell survival by activating transcription factor 3 (ATF3) in response to chemical ribosome-inactivating stress. Biochem Pharmacol 2009; 77:1105-15. [DOI: 10.1016/j.bcp.2008.11.028] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 11/25/2008] [Accepted: 11/26/2008] [Indexed: 12/14/2022]
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Pataer A, Swisher SG, Roth JA, Logothetis CJ, Corn PG. Inhibition of RNA-dependent protein kinase (PKR) leads to cancer cell death and increases chemosensitivity. Cancer Biol Ther 2009; 8:245-52. [PMID: 19106640 PMCID: PMC2854203 DOI: 10.4161/cbt.8.3.7386] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
RNA-dependent protein kinase is an interferon-induced, double-stranded (ds), RNA-activated serine/threonine protein kinase involved in the eukaryotic response to viral infection. While PKR also functions in cellular differentiation, growth control and apoptosis, its role in human cancer remains poorly understood. To explore a role for PKR in human cancer, we evaluated PKR expression and function in a series of cancer cell lines from different tumor types. We observed that PKR protein expression is high in various cancer cells and low in normal cells. Knockdown of PKR protein expression by PKR siRNA induced cell death, indicating a PKR-dependent survival pathway under normal growth conditions. Inhibition of PKR signaling using a dominant negative adenoviral PKR mutant (Ad-Delta6PKR) also induced cancer cell apoptosis via a mechanism that blocks activation of AKT-mediated survival while simultaneously inducing ER stress. ER stress-mediated apoptosis was evidenced by unregulated expression of phosphorylated JNK (p-JNK), phosphorylated cJun (p-cJun), and caspase-4 and was significantly reduced in cancer cells treated with JNK and caspase-4 inhibitors. We further demonstrated that inhibition of PKR signaling via either siRNA or Ad-Delta6PKR sensitizes cancer cells to etoposide or cisplatin-mediated cell death. Our results suggest a rationale to develop therapeutic strategies that target PKR signaling in human cancer cells.
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Affiliation(s)
- Abujiang Pataer
- Department of Thoracic and Cardiovascular Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 , USA.
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Rothenburg S, Seo EJ, Gibbs JS, Dever TE, Dittmar K. Rapid evolution of protein kinase PKR alters sensitivity to viral inhibitors. Nat Struct Mol Biol 2009; 16:63-70. [PMID: 19043413 PMCID: PMC3142916 DOI: 10.1038/nsmb.1529] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Accepted: 11/18/2008] [Indexed: 12/23/2022]
Abstract
Protein kinase PKR (also known as EIF2AK2) is activated during viral infection and phosphorylates the alpha subunit of eukaryotic translation initiation factor 2 (eIF2), leading to inhibition of translation and viral replication. We report fast evolution of the PKR kinase domain in vertebrates, coupled with positive selection of specific sites. Substitution of positively selected residues in human PKR with residues found in related species altered sensitivity to PKR inhibitors from different poxviruses. Species-specific differences in sensitivity to poxviral pseudosubstrate inhibitors were identified between human and mouse PKR, and these differences were traced to positively selected residues near the eIF2alpha binding site. Our findings indicate how an antiviral protein evolved to evade viral inhibition while maintaining its primary function. Moreover, the identified species-specific differences in the susceptibility to viral inhibitors have important implications for studying human infections in nonhuman model systems.
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Affiliation(s)
- Stefan Rothenburg
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Su N, Kilberg MS. C/EBP homology protein (CHOP) interacts with activating transcription factor 4 (ATF4) and negatively regulates the stress-dependent induction of the asparagine synthetase gene. J Biol Chem 2008; 283:35106-17. [PMID: 18940792 DOI: 10.1074/jbc.m806874200] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C/EBP homology protein (CHOP), a stress-induced transcription factor, is involved in transcriptional regulation, cell cycle, and apoptosis. The present studies identified CHOP as an interacting partner of activating transcription factor (ATF) 4 in a yeast two-hybrid screen and confirmed their interaction in HEK293T cells. CHOP protein levels rose modestly and transiently during amino acid deprivation, whereas endoplasmic reticulum stress caused a much higher and sustained expression of CHOP protein. Exogenous CHOP expression enhanced the TRB3 gene induction by amino acid deprivation. Conversely, CHOP suppressed the induction of the endogenous asparagine synthetase (ASNS) gene and inhibited transcription from a reporter gene driven by the ASNS promoter following activation by ATF4 or amino acid deprivation. Short interfering RNA-mediated knockdown of CHOP further enhanced the induction of ASNS by either amino acid deprivation or endoplasmic reticulum stress. The CHOP-dependent repression of the ASNS gene required the entire CHOP protein, arguing against the possibility of simple sequestration of ATF4 by the CHOP leucine zipper domain, and chromatin immunoprecipitation analysis showed association of CHOP with the ASNS and TRB3 promoters. Interestingly, chromatin immunoprecipitation also showed that CHOP was associated with the C/EBP-ATF composite site regions of the SNAT2, VEGF, and CAT-1 genes, despite no significant effect on their expression after exogenous CHOP overexpression. Collectively, the results document that CHOP is a member of the transcription factor network that controls the stress-induced regulation of specific C/EBP-ATF-containing genes, such as ASNS.
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Affiliation(s)
- Nan Su
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610, USA
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Cardin E, Larose L. Nck-1 interacts with PKR and modulates its activation by dsRNA. Biochem Biophys Res Commun 2008; 377:231-5. [PMID: 18835251 DOI: 10.1016/j.bbrc.2008.09.112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Accepted: 09/23/2008] [Indexed: 11/19/2022]
Abstract
Activation of the double-stranded RNA (dsRNA)-activated protein kinase PKR results in inhibition of general translation through phosphorylation of the eukaryotic initiation factor 2 alpha-subunit on serine 51 (eIF2alphaSer51). Previously, we have reported that the adaptor protein Nck-1 modulates eIF2alphaSer51 phosphorylation by a subset of eIF2alpha kinases, including PKR. Herein, we demonstrate that Nck-1 prevents efficient activation of PKR by dsRNA, revealing that Nck-1 acts at the level of PKR. In agreement, Nck-1 impairs p38MAPK activation and attenuates cell death induced by dsRNA, in addition to diminish eIF2alphaSer51 phosphorylation. Our data show that the inhibitory effect of Nck-1 on PKR is reversible, as it could be overcome by increasing levels of dsRNA. Interestingly, we found that Nck-1 interacts with the inactive form of PKR, independently of its Src homology domains. Furthermore, we uncovered that Nck-1 is substrate of PKR in vitro. All together, our data provide the first evidence identifying Nck-1 as a novel endogenous regulator of PKR and support the notion that Nck-1-PKR interaction could be a way to limit PKR activation.
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Affiliation(s)
- Eric Cardin
- Experimental Medicine Department, Polypeptide Laboratory, McGill University, Montreal, Que, Canada
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Maran A, Shogren KL, Benedikt M, Sarkar G, Turner RT, Yaszemski MJ. 2-methoxyestradiol-induced cell death in osteosarcoma cells is preceded by cell cycle arrest. J Cell Biochem 2008; 104:1937-45. [PMID: 18384113 PMCID: PMC2821714 DOI: 10.1002/jcb.21758] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
2-Methoxyestradiol (2-ME), a naturally occurring mammalian metabolite of 17beta-Estradiol (E2), induces cell death in osteosarcoma cells. To further understand the molecular mechanisms of action, we have investigated cell cycle progression in 2-ME-treated human osteosarcoma (MG63, SaOS-2 and LM7 [corrected]) cells. At 5 microM, 2-ME induced growth arrest by inducing a block in cell cycle; 2-ME-treatment resulted in 2-fold increases in G1 phase cells and a decrease in S phase cells in MG63 and SaOS-2 osteosarcoma cell lines, compared to the appropriate vehicle controls. 2-ME-treatment induced a threefold increase in the G2 phase in LM7 [corrected] osteosarcoma cells. The results demonstrated steroid specificity, as the tumorigenic metabolite, 16alpha-hydroxyestradiol (16-OHE), did not have any effect on cell cycle progression in osteosarcoma cells. The cell cycle arrest coincided with an increase in expression of the cell cycle markers p21, p27 and p53 proteins in 2-ME-treated osteosarcoma cells. Also, MG63 cells, transiently transfected with cDNA for a 'loss of function mutant' RNA-dependent protein kinase (PKR) protein, were resistant to 2-ME-induced cell cycle arrest. These results suggest that 2-ME works in concert with factors regulating cell cycle progression, and cell cycle arrest precedes cell death in 2-ME-treated osteosarcoma cells.
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Affiliation(s)
- Avudaiappan Maran
- Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905, USA.
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50
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Narasimhan J, Joyce BR, Naguleswaran A, Smith AT, Livingston MR, Dixon SE, Coppens I, Wek RC, Sullivan WJ. Translation regulation by eukaryotic initiation factor-2 kinases in the development of latent cysts in Toxoplasma gondii. J Biol Chem 2008; 283:16591-601. [PMID: 18420584 DOI: 10.1074/jbc.m800681200] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A key problem in the treatment of numerous pathogenic eukaryotes centers on their development into latent forms during stress. For example, the opportunistic protist Toxoplasma gondii converts to latent cysts (bradyzoites) responsible for recrudescence of disease. We report that Toxoplasma eukaryotic initiation factor-2alpha (TgIF2alpha) is phosphorylated during stress and establish that protozoan parasites utilize translation control to modulate gene expression during development. Importantly, TgIF2alpha remains phosphorylated in bradyzoites, explaining how these cells maintain their quiescent state. Furthermore, we have characterized novel eIF2 kinases; one in the endoplasmic reticulum and a likely regulator of the unfolded protein response (TgIF2K-A) and another that is a probable responder to cytoplasmic stresses (TgIF2K-B). Significantly, our data suggest that 1) the regulation of protein translation through eIF2 kinases is associated with development, 2) eIF2alpha phosphorylation is employed by cells to maintain a latent state, and 3) endoplasmic reticulum and cytoplasmic stress responses evolved in eukaryotic cells before the early diverging Apicomplexa. Given its importance to pathogenesis, eIF2 kinase-mediated stress responses may provide opportunities for novel therapeutics.
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Affiliation(s)
- Jana Narasimhan
- Department of Pharmacology and Toxicology and Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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