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Pattoo TS, Khanday FA. Corelating the molecular structure of BAG3 to its oncogenic role. Cell Biol Int 2024; 48:1080-1096. [PMID: 38924608 DOI: 10.1002/cbin.12199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/22/2024] [Accepted: 05/31/2024] [Indexed: 06/28/2024]
Abstract
BAG3 is a multifaceted protein characterised by having WW domain, PXXP motif and BAG domain. This protein gets upregulated during malignant transformation of cells and has been associated with poorer survival of patients. Procancerous activity of BAG domain of BAG3 is well documented. BAG domain interacts with ATPase domain of Hsp-70 preventing protein delivery to proteasome. This impediment results in enhanced cell survival, proliferation, resistance to apoptosis and chemoresistance. Besides BAG domain other two domains/motifs of BAG3 are under research vigilance to explore its further oncogenic role. This review summarises the role of different structural determinants of BAG3 in elevating oncogenesis. Based on the already existing findings, more interacting partners of BAG3 are anticipated. The anticipated partners of BAG3 can shed a wealth of information into the mechanistic insights of its proproliferative role. Proper insights into the mechanistic details adopted by BAG3 to curtail/elaborate activity of anticipated interacting partners can serve as a potent target for development of therapeutic interventions.
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Affiliation(s)
| | - Firdous A Khanday
- Department of Biotechnology, University of Kashmir, Srinagar, Jammu and Kashmir, India
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2
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Lin HS, Li CH, Chen LW, Wang SS, Chen LY, Hung CH, Lin CL, Chang PJ. The varicella-zoster virus ORF16 protein promotes both the nuclear transport and the protein abundance of the viral DNA polymerase subunit ORF28. Virus Res 2024; 345:199379. [PMID: 38643859 PMCID: PMC11061344 DOI: 10.1016/j.virusres.2024.199379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/19/2024] [Accepted: 04/19/2024] [Indexed: 04/23/2024]
Abstract
Although all herpesviruses utilize a highly conserved replication machinery to amplify their viral genomes, different members may have unique strategies to modulate the assembly of their replication components. Herein, we characterize the subcellular localization of seven essential replication proteins of varicella-zoster virus (VZV) and show that several viral replication enzymes such as the DNA polymerase subunit ORF28, when expressed alone, are localized in the cytoplasm. The nuclear import of ORF28 can be mediated by the viral DNA polymerase processivity factor ORF16. Besides, ORF16 could markedly enhance the protein abundance of ORF28. Noteworthily, an ORF16 mutant that is defective in nuclear transport still retained the ability to enhance ORF28 abundance. The low abundance of ORF28 in transfected cells was due to its rapid degradation mediated by the ubiquitin-proteasome system. We additionally reveal that radicicol, an inhibitor of the chaperone Hsp90, could disrupt the interaction between ORF16 and ORF28, thereby affecting the nuclear entry and protein abundance of ORF28. Collectively, our findings imply that the cytoplasmic retention and rapid degradation of ORF28 may be a key regulatory mechanism for VZV to prevent untimely viral DNA replication, and suggest that Hsp90 is required for the interaction between ORF16 and ORF28.
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Affiliation(s)
- Huang-Shen Lin
- Department of Internal Medicine, Division of Infectious Diseases, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan; Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Cheng-Han Li
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Lee-Wen Chen
- Department of Respiratory Care, Chang Gung University of Science and Technology, Chiayi 61363, Taiwan; Department of Pediatric Surgery, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Shie-Shan Wang
- Department of Pediatric Surgery, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan; School of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Li-Yu Chen
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Chien-Hui Hung
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Chun-Liang Lin
- Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Pey-Jium Chang
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan; Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan.
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Li W, You G, Haiyilati A, Wang H, Jiao H, Wang Y, Gao L, Cao H, Li X, Zheng SJ. Critical Role of Viral Protein Hexon in Hypervirulent Fowl Adenovirus Serotype-4-Induced Autophagy by Interaction with BAG3 and Promotion of Viral Replication in LMH Cells. J Virol 2023; 97:e0028423. [PMID: 37255472 PMCID: PMC10308884 DOI: 10.1128/jvi.00284-23] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 05/13/2023] [Indexed: 06/01/2023] Open
Abstract
Hepatitis-pericardial syndrome (HHS) is an acute highly infectious avian disease caused by fowl adenovirus serotype 4 (FAdV-4), characterized by fulminant hepatitis and hydropericardium in broilers. Since 2015, a widespread epidemic has occurred in China due to the emergence of hypervirulent FAdV-4 (HPFAdV-4), causing huge losses to the stakeholders. However, the pathogenesis of HPFAdV-4 and the host responses to its infection remain elusive. Here, we show that infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy in cells and that the autophagy induced by recombinant HPFAdV-4-ON1 (rHPFAdV-4-ON1), a viral strain generated by replacing the hexon gene of wild-type HPFAdV-4 (HPFAdV-4-WT) with the one of nonpathogenic strain FAdV-4-ON1, was remarkably mitigated compared to that of the rHPFAdV-4-WT control, suggesting that HPFAdV-4 hexon is responsible for virus-induced autophagy. Importantly, we found that hexon interacted with a cellular protein, BAG3, a host protein that initiates autophagy, and that BAG3 expression increased in cells infected with HPFAdV-4. Furthermore, knockdown of BAG3 by RNA interference (RNAi) significantly inhibited HPFAdV-4- or hexon-induced autophagy and suppressed viral replication. On the contrary, expression of hexon markedly upregulated the expression of BAG3 via activating the P38 signaling pathway, triggering autophagy. Thus, these findings reveal that HPFAdV-4 hexon interacts with the host protein BAG3 and promotes BAG3 expression by activating P38 signaling pathway, thereby inducing autophagy and enhancing viral proliferation, which immensely furthers our understanding of the pathogenesis of HPFAdV-4 infection. IMPORTANCE HHS, mainly caused by HPFAdV-4, has caused large economic losses to the stakeholders in recent years. Infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy that is essential for HPFAdV-4 replication. By a screening strategy, the viral protein hexon was found responsible for virus-induced autophagy in cells. Importantly, hexon was identified as a factor promoting viral replication by interaction with BAG3, an initiator of host cell autophagy. These findings will help us to better understand the host response to HPFAdV-4 infection, providing a novel insight into the pathogenesis of HPFAdV-4 infection.
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Affiliation(s)
- Wei Li
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Guangju You
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Areayi· Haiyilati
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Hongnuan Wang
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Huixuan Jiao
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Yongqiang Wang
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Li Gao
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Hong Cao
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Xiaoqi Li
- College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Shijun J. Zheng
- National Key Laboratory of Veterinary Public Health Security, China Agricultural University, Beijing, China
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, China Agricultural University, Beijing, China
- College of Veterinary Medicine, China Agricultural University, Beijing, China
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Wu S, Zhao Y, Wang D, Chen Z. Mode of Action of Heat Shock Protein (HSP) Inhibitors against Viruses through Host HSP and Virus Interactions. Genes (Basel) 2023; 14:genes14040792. [PMID: 37107550 PMCID: PMC10138296 DOI: 10.3390/genes14040792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 03/29/2023] Open
Abstract
Misfolded proteins after stress-induced denaturation can regain their functions through correct re-folding with the aid of molecular chaperones. As a molecular chaperone, heat shock proteins (HSPs) can help client proteins fold correctly. During viral infection, HSPs are involved with replication, movement, assembly, disassembly, subcellular localization, and transport of the virus via the formation of macromolecular protein complexes, such as the viral replicase complex. Recent studies have indicated that HSP inhibitors can inhibit viral replication by interfering with the interaction of the virus with the HSP. In this review, we describe the function and classification of HSPs, the transcriptional mechanism of HSPs promoted by heat shock factors (HSFs), discuss the interaction between HSPs and viruses, and the mode of action of HSP inhibitors at two aspects of inhibiting the expression of HSPs and targeting the HSPs, and elaborate their potential use as antiviral agents.
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Liang Z, Zhang S, Zou Z, Li J, Wu R, Xia L, Shi G, Cai J, Tang J, Jian J. Functional characterization of BAG3 in orange-spotted grouper (Epinephelus coioides) during viral infection. FISH & SHELLFISH IMMUNOLOGY 2022; 122:465-475. [PMID: 35218970 DOI: 10.1016/j.fsi.2022.02.044] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 01/23/2022] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
Bcl-2-associated athanogene 3 (BAG3) is a cochaperone protein that interacts with Bcl-2 and mediate cell death. However, little is known about the roles of fish BAG3 during viral infection. In this study, we characterized a BAG3 homolog from orange-spotted grouper (Epinephelus coioides) (EcBAG3) and investigated its roles during viral infection. The EcBAG3 protein encoded 579 amino acids with typical WW, PXXP and BAG domains, which shared high identities with reported fish BAG3. Quantitative real-time PCR (qRT-PCR) analysis revealed that EcBAG3 was highly expressed in brain and heart. And the expression of EcBAG3 was significantly up-regulated after red-spotted grouper nervous necrosis virus (RGNNV) stimulation in vitro. EcBAG3 overexpression could promoted the expression of viral genes (coat protein (CP) and RNA-dependent RNA polymerase (RdRp)), which was enhanced by co-transfection with Hsp70 and Hsp22. Also, EcBAG3 overexpression up-regulated the expression of LC3-Ⅱ and down-regulated the expression of Bax and BNIP3, the IFN- (IRF1, IRF3, IRF7, IFP35, Mx1) or inflammation-related (IL-1β and TNFα) factors, as well as decreased the activities of NF-κB, ISRE and IFN-3. While knockdown of EcBAG3 decreased the transcripts of RGNNV CP gene and RdRp gene. Further studies showed that EcBAG3 knockdown impaired the expression level of autophagy factor LC3-Ⅱ, and promoted the expression level of Bax and BNIP3, inflammatory factors and interferon factors. These data indicate that EcBAG3 can affect viral infection through modulating virus-induced cell death, regulating the expression of IFN- and inflammation-related factors, which will be helpful to further explore the immune response of fish during viral infection.
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Affiliation(s)
- Zhenyu Liang
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China
| | - Shuping Zhang
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China
| | - Zihong Zou
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China
| | - Jinze Li
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China
| | - Rimin Wu
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China
| | - Liqun Xia
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China
| | - Gang Shi
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China
| | - Jia Cai
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, PR China; Guangxi Key Lab for Marine Natural Products and Combinational Biosynthesis Chemistry, Guangxi Beibu Gulf Marine Research Centre, Guangxi Academy of Sciences, Nanning, 530007, PR China.
| | - Jufen Tang
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China
| | - Jichang Jian
- College of Fishery, Guangdong Ocean University, Zhanjiang, 524088, PR China; Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Zhanjiang, 524088, PR China; Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Zhanjiang, 524088, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhanjiang), 524002, PR China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, PR China
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Lin H, Koren SA, Cvetojevic G, Girardi P, Johnson GV. The role of BAG3 in health and disease: A "Magic BAG of Tricks". J Cell Biochem 2022; 123:4-21. [PMID: 33987872 PMCID: PMC8590707 DOI: 10.1002/jcb.29952] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 04/25/2021] [Indexed: 01/03/2023]
Abstract
The multi-domain structure of Bcl-2-associated athanogene 3 (BAG3) facilitates its interaction with many different proteins that participate in regulating a variety of biological pathways. After revisiting the BAG3 literature published over the past ten years with Citespace software, we classified the BAG3 research into several clusters, including cancer, cardiomyopathy, neurodegeneration, and viral propagation. We then highlighted recent key findings in each cluster. To gain greater insight into the roles of BAG3, we analyzed five different published mass spectrometry data sets of proteins that co-immunoprecipitate with BAG3. These data gave us insight into universal, as well as cell-type-specific BAG3 interactors in cancer cells, cardiomyocytes, and neurons. Finally, we mapped variable BAG3 SNPs and also mutation data from previous publications to further explore the link between the domains and function of BAG3. We believe this review will provide a better understanding of BAG3 and direct future studies towards understanding BAG3 function in physiological and pathological conditions.
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Affiliation(s)
- Heng Lin
- Department of Anesthesiology and Perioperative Medicine, University of Rochester Medical Center, Rochester NY 14642 USA
| | - Shon A. Koren
- Department of Anesthesiology and Perioperative Medicine, University of Rochester Medical Center, Rochester NY 14642 USA
| | - Gregor Cvetojevic
- Department of Anesthesiology and Perioperative Medicine, University of Rochester Medical Center, Rochester NY 14642 USA
| | - Peter Girardi
- Department of Anesthesiology and Perioperative Medicine, University of Rochester Medical Center, Rochester NY 14642 USA
| | - Gail V.W. Johnson
- Department of Anesthesiology and Perioperative Medicine, University of Rochester Medical Center, Rochester NY 14642 USA
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Wei J, Sun Y, Wang TT, Zhu G, Liu WH, He XH, Li Z. The Regulation of Prototype Foamy Virus 5'Long Terminal Repeats and Internal Promoter by Endogenous Transcription Factors. Intervirology 2021; 65:17-28. [PMID: 34438397 DOI: 10.1159/000517539] [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: 11/11/2020] [Accepted: 06/01/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND For foamy virus, the transactivator of spumaretrovirus (Tas) could bind directly to target DNA sequences termed as Tas responsive elements and trigger the viral internal promoter (IP) and long terminal repeat (LTR) promoters. The cellular endogenous factors also play an important role in viral gene expressions. We hypothesized that except the viral transcription factor Tas, the cellular endogenous factors also affect the viral gene expression. METHODS The full length of the prototype foamy virus (PFV) genome (U21247) was used to predict the potential binding sites of the transcription factors by online software JASPAR (http://jaspar.genereg.net) and Softberry (http://linux1.softberry.com/berry.phtml?topic=index&group=programs&subgroup=promoter). The Dual-Luciferase® Reporter Assay System (Promega, USA) was used to confirm the relative luciferase activities of the test groups. The different representative activating agents or inhibitors of each canonical signal pathway were used to identify the impact of these pathways on PFV 5'LTR and IP promoters. RESULTS The results showed different cellular endogenous factors might have respective effects on PFV 5'LTR and IP. It is worth mentioning that activator protein-1 and BCL2-associated athanogene 3, 2 kinds of vital proteins associated with NF-κB and PKC pathways, could activate the basal activity of 5'LTR and IP promoters but inhibit the Tas-regulated activity of both promoters. Furthermore, PFV Tas was identified to trigger the transcription of the NF-κB promoter. CONCLUSION NF-κB had a negative effect on PFV 5'LTR and IP promoter activities, the PKC pathway might upregulate 5'LTR and IP promoter activities, and the JNK and NF-AT signal pathway could increase the Tas-regulated promoter activity of PFV 5'LTR. This study sheds light on the interaction between PFV and the host cell and may help utilize the viral promoters in retroviral vectors designed for gene transfer experiments.
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Affiliation(s)
- Jie Wei
- College of Life Sciences, Shaanxi Normal University, Xi'an, China,
| | - Yan Sun
- College of Life Sciences, Shaanxi Normal University, Xi'an, China
| | - Ting-Ting Wang
- College of Life Sciences, Shaanxi Normal University, Xi'an, China
| | - Gui Zhu
- College of Life Sciences, Shaanxi Normal University, Xi'an, China
| | - Wan-Hong Liu
- School of Medicine, Wuhan University, Wuhan, China
| | - Xiao-Hua He
- School of Medicine, Wuhan University, Wuhan, China
| | - Zhi Li
- College of Life Sciences, Shaanxi Normal University, Xi'an, China
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Abstract
In the following continuation article, the author will expand on how the mechanisms discussed in Part One capitalise on host characteristics to produce the organ specific damage seen in severe coronavirus disease (COVID-19), with specific reference to pulmonary and cardiac manifestations. Pneumonia is the primary manifestation of COVID-19; presentation varies from a mild, self-limiting pneumonitis to a fulminant and progressive respiratory failure. Features of disease severity tend to directly correlate with patient age, with elderly populations faring poorest. Advancing age parallels an increasingly pro-oxidative pulmonary milieu, a consequence of increasing host expression of phospholipase A2 Group IID. Virally induced expression of NADPH oxidase intensifies this pro-oxidant environment. The virus avails of the host response by exploiting caveolin-1 to assist in disabling host defenses and adopting a glycolytic metabolic pathway to self-replicate.
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Lyu C, Li WD, Wang SW, Peng JM, Yang YB, Tian ZJ, Cai XH. Host BAG3 Is Degraded by Pseudorabies Virus pUL56 C-Terminal 181L- 185L and Plays a Negative Regulation Role during Viral Lytic Infection. Int J Mol Sci 2020; 21:ijms21093148. [PMID: 32365661 PMCID: PMC7247713 DOI: 10.3390/ijms21093148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 04/23/2020] [Accepted: 04/23/2020] [Indexed: 11/16/2022] Open
Abstract
Bcl2-associated athanogene (BAG) 3, which is a chaperone-mediated selective autophagy protein, plays a pivotal role in modulating the life cycle of a wide variety of viruses. Both positive and negative modulations of viruses by BAG3 were reported. However, the effects of BAG3 on pseudorabies virus (PRV) remain unknown. To investigate whether BAG3 could modulate the PRV life cycle during a lytic infection, we first identified PRV protein UL56 (pUL56) as a novel BAG3 interactor by co-immunoprecipitation and co-localization analyses. The overexpression of pUL56 induced a significant degradation of BAG3 at protein level via the lysosome pathway. The C-terminal mutations of 181L/A, 185L/A, or 181L/A-185L/A in pUL56 resulted in a deficiency in pUL56-induced BAG3 degradation. In addition, the pUL56 C-terminal mutants that lost Golgi retention abrogated pUL56-induced BAG3 degradation, which indicates a Golgi retention-dependent manner. Strikingly, BAG3 was not observed to be degraded in either wild-type or UL56-deleted PRV infected cells as compared to mock infected ones, whereas the additional two adjacent BAG3 cleaved products were found in the infected cells in a species-specific manner. Overexpression of BAG3 significantly suppressed PRV proliferation, while knockdown of BAG3 resulted in increased viral yields in HEK293T cells. Thus, these data indicated a negative regulation role of BAG3 during PRV lytic infection. Collectively, our findings revealed a novel molecular mechanism on host protein degradation induced by PRV pUL56. Moreover, we identified BAG3 as a host restricted protein during PRV lytic infection in cells.
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Aviner R, Frydman J. Proteostasis in Viral Infection: Unfolding the Complex Virus-Chaperone Interplay. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a034090. [PMID: 30858229 DOI: 10.1101/cshperspect.a034090] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Viruses are obligate intracellular parasites that rely on their hosts for protein synthesis, genome replication, and viral particle production. As such, they have evolved mechanisms to divert host resources, including molecular chaperones, facilitate folding and assembly of viral proteins, stabilize complex structures under constant mutational pressure, and modulate signaling pathways to dampen antiviral responses and prevent premature host death. Biogenesis of viral proteins often presents unique challenges to the proteostasis network, as it requires the rapid and orchestrated production of high levels of a limited number of multifunctional, multidomain, and aggregation-prone proteins. To overcome such challenges, viruses interact with the folding machinery not only as clients but also as regulators of chaperone expression, function, and subcellular localization. In this review, we summarize the main types of interactions between viral proteins and chaperones during infection, examine evolutionary aspects of this relationship, and discuss the potential of using chaperone inhibitors as broad-spectrum antivirals.
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Affiliation(s)
- Ranen Aviner
- Department of Biology, Stanford University, Stanford, California 94305
| | - Judith Frydman
- Department of Biology, Stanford University, Stanford, California 94305.,Department of Genetics, Stanford University, Stanford, California 94305
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Mohseni Ahooyi T, Torkzaban B, Shekarabi M, Tahrir FG, Decoppet EA, Cotto B, Langford D, Amini S, Khalili K. Perturbation of synapsins homeostasis through HIV-1 Tat-mediated suppression of BAG3 in primary neuronal cells. Cell Death Dis 2019; 10:473. [PMID: 31209204 PMCID: PMC6572798 DOI: 10.1038/s41419-019-1702-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/06/2019] [Accepted: 03/14/2019] [Indexed: 02/02/2023]
Abstract
HIV-1 Tat is known to be released by HIV infected non-neuronal cells in the brain, and after entering neurons, compromises brain homeostasis by impairing pro-survival pathways, thus contributing to the development of HIV-associated CNS disorders commonly observed in individuals living with HIV. Here, we demonstrate that synapsins, phosphoproteins that are predominantly expressed in neuronal cells and play a vital role in modulating neurotransmitter release at the pre-synaptic terminal, and neuronal differentiation become targets for Tat through autophagy and protein quality control pathways. We demonstrate that the presence of Tat in neurons results in downregulation of BAG3, a co-chaperone for heat shock proteins (Hsp70/Hsc70) that is implicated in protein quality control (PQC) processes by eliminating mis-folded and damaged proteins, and selective macroautophagy. Our results show that treatment of cells with Tat or suppression of BAG3 expression by siRNA in neuronal cells disturbs subcellular distribution of synapsins and synaptotagmin 1 (Syt1) leading to their accumulation in the neuronal soma and along axons in a punctate pattern, rather than being properly distributed at axon-terminals. Further, our results revealed that synapsins partially lost their stability and their removal via lysosomal autophagy was noticeably impaired in cells with low levels of BAG3. The observed impairment of lysosomal autophagy, under this condition, is likely caused by cells losing their ability to process LC3-I to LC3-II, in part due to a decrease in the ATG5 levels upon BAG3 knockdown. These observations ascribe a new function for BAG3 in controlling synaptic communications and illuminate a new downstream target for Tat to elicit its pathogenic effect in impacting neuronal cell function and behavior.
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Affiliation(s)
- Taha Mohseni Ahooyi
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA.
| | - Bahareh Torkzaban
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Masoud Shekarabi
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Farzaneh G Tahrir
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Emilie A Decoppet
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Bianca Cotto
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Dianne Langford
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Shohreh Amini
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA
| | - Kamel Khalili
- Department of Neuroscience Center for Neurovirology, Lewis Katz School of Medicine at Temple University, 3500N. Broad Street, Philadelphia, PA, 19140, USA.
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12
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Ravindran MS. Molecular chaperones: from proteostasis to pathogenesis. FEBS J 2018; 285:3353-3361. [PMID: 29890022 PMCID: PMC7164077 DOI: 10.1111/febs.14576] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/12/2018] [Accepted: 06/07/2018] [Indexed: 12/13/2022]
Abstract
Maintaining protein homeostasis (proteostasis) is essential for a functional proteome. A wide range of extrinsic and intrinsic factors perturb proteostasis, causing protein misfolding, misassembly, and aggregation. This compromises cellular integrity and leads to aging and disease, including neurodegeneration and cancer. At the cellular level, protein aggregation is counteracted by powerful mechanisms comprising of a cascade of enzymes and chaperones that operate in a coordinated multistep manner to sense, prevent, and/or dispose of aberrant proteins. Although these processes are well understood for soluble proteins, there is a major gap in our understanding of how cells handle misfolded or aggregated membrane proteins. This article provides an overview of cellular proteostasis with emphasis on membrane protein substrates and suggests host–virus interaction as a tool to clarify outstanding questions in proteostasis.
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Affiliation(s)
- Madhu Sudhan Ravindran
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
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13
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BIS overexpression does not affect the sensitivity of HEK 293T cells against apoptosis. Mol Cell Toxicol 2017. [DOI: 10.1007/s13273-017-0010-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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14
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Liang J, Sagum CA, Bedford MT, Sidhu SS, Sudol M, Han Z, Harty RN. Chaperone-Mediated Autophagy Protein BAG3 Negatively Regulates Ebola and Marburg VP40-Mediated Egress. PLoS Pathog 2017; 13:e1006132. [PMID: 28076420 PMCID: PMC5226679 DOI: 10.1371/journal.ppat.1006132] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 12/15/2016] [Indexed: 12/18/2022] Open
Abstract
Ebola (EBOV) and Marburg (MARV) viruses are members of the Filoviridae family which cause outbreaks of hemorrhagic fever. The filovirus VP40 matrix protein is essential for virus assembly and budding, and its PPxY L-domain motif interacts with WW-domains of specific host proteins, such as Nedd4 and ITCH, to facilitate the late stage of virus-cell separation. To identify additional WW-domain-bearing host proteins that interact with VP40, we used an EBOV PPxY-containing peptide to screen an array of 115 mammalian WW-domain-bearing proteins. Using this unbiased approach, we identified BCL2 Associated Athanogene 3 (BAG3), a member of the BAG family of molecular chaperone proteins, as a specific VP40 PPxY interactor. Here, we demonstrate that the WW-domain of BAG3 interacts with the PPxY motif of both EBOV and MARV VP40 and, unexpectedly, inhibits budding of both eVP40 and mVP40 virus-like particles (VLPs), as well as infectious VSV-EBOV recombinants. BAG3 is a stress induced protein that regulates cellular protein homeostasis and cell survival through chaperone-mediated autophagy (CMA). Interestingly, our results show that BAG3 alters the intracellular localization of VP40 by sequestering VP40 away from the plasma membrane. As BAG3 is the first WW-domain interactor identified that negatively regulates budding of VP40 VLPs and infectious virus, we propose that the chaperone-mediated autophagy function of BAG3 represents a specific host defense strategy to counteract the function of VP40 in promoting efficient egress and spread of virus particles.
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Affiliation(s)
- Jingjing Liang
- Department of Pathobiology, School Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
- Laboratory of Animal Infectious Diseases, College of Animal Sciences and Veterinary Medicine; State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
| | - Cari A. Sagum
- Department of Epigenetics & Molecular Carcinogenesis, M.D. Anderson Cancer Center, University of Texas Smithville, Smithville, TX, United States of America
| | - Mark T. Bedford
- Department of Epigenetics & Molecular Carcinogenesis, M.D. Anderson Cancer Center, University of Texas Smithville, Smithville, TX, United States of America
| | - Sachdev S. Sidhu
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Marius Sudol
- Department of Physiology, National University of Singapore, Mechanobiology Institute and Institute for Molecular and Cell Biology (IMCB, A*STAR), Republic of Singapore
| | - Ziying Han
- Department of Pathobiology, School Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
| | - Ronald N. Harty
- Department of Pathobiology, School Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
- * E-mail:
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15
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Cotugno R, Basile A, Romano E, Gallotta D, Belisario MA. BAG3 down-modulation sensitizes HPV18(+) HeLa cells to PEITC-induced apoptosis and restores p53. Cancer Lett 2014; 354:263-71. [PMID: 25175321 PMCID: PMC7116956 DOI: 10.1016/j.canlet.2014.08.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 07/28/2014] [Accepted: 08/18/2014] [Indexed: 12/19/2022]
Abstract
BAG3 down-modulation by siRNA technology restored p53. Reduced BAG3 expression sensitized HeLa but not C33A (HPV-negative) cells to PEITC. Reduced BAG3 expression was associated with a decrease of E6 viral protein levels.
BAG3 is a multi-functional component of tumor cell pro-survival machinery, and its biological functions have been largely associated to proteasome system. Here, we show that BAG3 down-modulation resulted in reduced cell viability and enhanced PEITC-induced apoptosis largely more extensively in HeLa (HPV18+) rather than in C33A (HPV−) cervical carcinoma cell lines. Moreover, we demonstrate that BAG3 suppression led to a decrease of viral E6 oncoprotein and a concomitant recovery of p53 tumor suppressor, the best recognized target of E6 for proteasome degradation. E6 and p53 expression were modulated at protein level, since their respective mRNAs were unaffected. Taken together our findings reveal a novel role for BAG3 as host protein contributing to HPV18 E6-activated pro-survival strategies, and suggest a possible relevance of its expression levels in drug/radiotherapy-resistance of HPV18-bearing cervical carcinomas.
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Affiliation(s)
- Roberta Cotugno
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n.132, Fisciano, 84084, Salerno, Italy
| | - Anna Basile
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n.132, Fisciano, 84084, Salerno, Italy
| | - Elena Romano
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n.132, Fisciano, 84084, Salerno, Italy
| | - Dario Gallotta
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n.132, Fisciano, 84084, Salerno, Italy
| | - Maria Antonietta Belisario
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n.132, Fisciano, 84084, Salerno, Italy.
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16
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Regulated transport into the nucleus of herpesviridae DNA replication core proteins. Viruses 2013; 5:2210-34. [PMID: 24064794 PMCID: PMC3798897 DOI: 10.3390/v5092210] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 12/11/2022] Open
Abstract
The Herpesvirdae family comprises several major human pathogens belonging to three distinct subfamilies. Their double stranded DNA genome is replicated in the nuclei of infected cells by a number of host and viral products. Among the latter the viral replication complex, whose activity is strictly required for viral replication, is composed of six different polypeptides, including a two-subunit DNA polymerase holoenzyme, a trimeric primase/helicase complex and a single stranded DNA binding protein. The study of herpesviral DNA replication machinery is extremely important, both because it provides an excellent model to understand processes related to eukaryotic DNA replication and it has important implications for the development of highly needed antiviral agents. Even though all known herpesviruses utilize very similar mechanisms for amplification of their genomes, the nuclear import of the replication complex components appears to be a heterogeneous and highly regulated process to ensure the correct spatiotemporal localization of each protein. The nuclear transport process of these enzymes is controlled by three mechanisms, typifying the main processes through which protein nuclear import is generally regulated in eukaryotic cells. These include cargo post-translational modification-based recognition by the intracellular transporters, piggy-back events allowing coordinated nuclear import of multimeric holoenzymes, and chaperone-assisted nuclear import of specific subunits. In this review we summarize these mechanisms and discuss potential implications for the development of antiviral compounds aimed at inhibiting the Herpesvirus life cycle by targeting nuclear import of the Herpesvirus DNA replicating enzymes.
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17
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Cotugno R, Gallotta D, d'Avenia M, Corteggio A, Altamura G, Roperto F, Belisario MA, Borzacchiello G. BAG3 protects bovine papillomavirus type 1-transformed equine fibroblasts against pro-death signals. Vet Res 2013; 44:61. [PMID: 23876161 PMCID: PMC3729419 DOI: 10.1186/1297-9716-44-61] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/08/2013] [Indexed: 01/19/2023] Open
Abstract
In human cancer cells, BAG3 protein is known to sustain cell survival. Here, for the first time, we demonstrate the expression of BAG3 protein both in equine sarcoids in vivo and in EqS04b cells, a sarcoid-derived fully transformed cell line harbouring bovine papilloma virus (BPV)-1 genome. Evidence of a possible involvement of BAG3 in equine sarcoid carcinogenesis was obtained by immunohistochemistry analysis of tumour samples. We found that most tumour samples stained positive for BAG3, even though to a different grade, while normal dermal fibroblasts from healthy horses displayed very weak staining pattern for BAG3 expression. By siRNA technology, we demonstrate in EqS04b the role of BAG3 in counteracting basal as well as chemical-triggered pro-death signals. BAG3 down-modulation was indeed shown to promote cell death and cell cycle arrest in G0/G1. In addition, we found that BAG3 silencing sensitized EqS04b cells to phenethylisothiocyanate (PEITC), a promising cancer chemopreventive/chemotherapeutic agent present in edible cruciferous vegetables. Notably, such a pro-survival role of BAG3 was less marked in E. Derm cells, an equine BPV-negative fibroblast cell line taken as a normal counterpart. Altogether our findings might suggest a mutual cooperation between BAG3 and viral oncoproteins to sustain cell survival.
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Affiliation(s)
- Roberta Cotugno
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II n,132, 84084, Fisciano, Salerno, Italy.
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18
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Chen Y, Yang LN, Cheng L, Tu S, Guo SJ, Le HY, Xiong Q, Mo R, Li CY, Jeong JS, Jiang L, Blackshaw S, Bi LJ, Zhu H, Tao SC, Ge F. Bcl2-associated athanogene 3 interactome analysis reveals a new role in modulating proteasome activity. Mol Cell Proteomics 2013; 12:2804-19. [PMID: 23824909 DOI: 10.1074/mcp.m112.025882] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bcl2-associated athanogene 3 (BAG3), a member of the BAG family of co-chaperones, plays a critical role in regulating apoptosis, development, cell motility, autophagy, and tumor metastasis and in mediating cell adaptive responses to stressful stimuli. BAG3 carries a BAG domain, a WW domain, and a proline-rich repeat (PXXP), all of which mediate binding to different partners. To elucidate BAG3's interaction network at the molecular level, we employed quantitative immunoprecipitation combined with knockdown and human proteome microarrays to comprehensively profile the BAG3 interactome in humans. We identified a total of 382 BAG3-interacting proteins with diverse functions, including transferase activity, nucleic acid binding, transcription factors, proteases, and chaperones, suggesting that BAG3 is a critical regulator of diverse cellular functions. In addition, we characterized interactions between BAG3 and some of its newly identified partners in greater detail. In particular, bioinformatic analysis revealed that the BAG3 interactome is strongly enriched in proteins functioning within the proteasome-ubiquitination process and that compose the proteasome complex itself, suggesting that a critical biological function of BAG3 is associated with the proteasome. Functional studies demonstrated that BAG3 indeed interacts with the proteasome and modulates its activity, sustaining cell survival and underlying resistance to therapy through the down-modulation of apoptosis. Taken as a whole, this study expands our knowledge of the BAG3 interactome, provides a valuable resource for understanding how BAG3 affects different cellular functions, and demonstrates that biologically relevant data can be harvested using this kind of integrated approach.
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Affiliation(s)
- Ying Chen
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China
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19
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Ulbricht A, Arndt V, Höhfeld J. Chaperone-assisted proteostasis is essential for mechanotransduction in mammalian cells. Commun Integr Biol 2013; 6:e24925. [PMID: 23986815 PMCID: PMC3737759 DOI: 10.4161/cib.24925] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 05/03/2013] [Accepted: 05/03/2013] [Indexed: 12/28/2022] Open
Abstract
Maintaining the dynamic proteome of a living cell in the face of an ever-changing environment depends on a fine-tuned balance of protein synthesis and protein degradation. Molecular chaperones exert key functions during protein homeostasis (proteostasis). They associate with nonnative client proteins following synthesis or damage and facilitate client sorting and folding. When client proteins are terminally misfolded, chaperones cooperate with protein degradation systems to dispose of such clients. This dual proteostasis activity of chaperones is essential for maintaining cell function under normal growth conditions and becomes even more important under stress conditions such as heat and oxidative stress. The recent identification of chaperone-assisted selective autophagy (CASA) as a tension-induced autophagy pathway highlights the critical role of molecular chaperones in mechanically strained cells and tissues. The CASA complex, assembled by the cochaperone BAG3, coordinates protein degradation and protein synthesis in response to mechanical force. Here we describe the composition and function of this chaperone complex in mammals and discuss its relevance for tissue homeostasis and the regulation of cell adhesion, migration and proliferation. We provide a unifying concept for the function of BAG3, which integrates its involvement in muscle maintenance, tumor formation and virus infection.
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Affiliation(s)
- Anna Ulbricht
- Institute for Cell Biology; University of Bonn; Bonn, Germany
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20
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Liu BQ, Du ZX, Zong ZH, Li C, Li N, Zhang Q, Kong DH, Wang HQ. BAG3-dependent noncanonical autophagy induced by proteasome inhibition in HepG2 cells. Autophagy 2013; 9:905-16. [PMID: 23575457 DOI: 10.4161/auto.24292] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Emerging lines of evidence have shown that blockade of ubiquitin-proteasome system (UPS) activates autophagy. The molecular players that regulate the relationship between them remain to be elucidated. Bcl-2 associated athanogene 3 (BAG3) is a member of the BAG co-chaperone family that regulates the ATPase activity of heat shock protein 70 (HSP70) chaperone family. Studies on BAG3 have demonstrated that it plays multiple roles in physiological and pathological processes, including antiapoptotic activity, signal transduction, regulatory role in virus infection, cell adhesion and migration. Recent studies have attracted much attention on its role in initiation of autophagy. The current study, for the first time, demonstrates that proteasome inhibitors elicit noncanonical autophagy, which was not suppressed by inhibitors of class III phosphatidylinositol 3-kinase (PtdIns3K) or shRNA against Beclin 1 (BECN1). In addition, we demonstrate that BAG3 is ascribed to activation of autophagy elicited by proteasome inhibitors and MAPK8/9/10 (also known as JNK1/2/3 respectively) activation is also implicated via upregulation of BAG3. Moreover, we found that noncanonical autophagy mediated by BAG3 suppresses responsiveness of HepG2 cells to proteasome inhibitors.
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Affiliation(s)
- Bao-Qin Liu
- Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, China
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21
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Geller R, Taguwa S, Frydman J. Broad action of Hsp90 as a host chaperone required for viral replication. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1823:698-706. [PMID: 22154817 DOI: 10.1016/j.bbamcr.2011.11.007] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 11/21/2011] [Accepted: 11/22/2011] [Indexed: 02/06/2023]
Abstract
Viruses are intracellular pathogens responsible for a vast number of human diseases. Due to their small genome size, viruses rely primarily on the biosynthetic apparatus of the host for their replication. Recent work has shown that the molecular chaperone Hsp90 is nearly universally required for viral protein homeostasis. As observed for many endogenous cellular proteins, numerous different viral proteins have been shown to require Hsp90 for their folding, assembly, and maturation. Importantly, the unique characteristics of viral replication cause viruses to be hypersensitive to Hsp90 inhibition, thus providing a novel therapeutic avenue for the development of broad-spectrum antiviral drugs. The major developments in this emerging field are hereby discussed. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).
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Affiliation(s)
- Ron Geller
- Department of Biology and BioX Program, Stanford University, Stanford, CA, USA
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22
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Wang HQ, Meng X, Liu BQ, Li C, Gao YY, Niu XF, Li N, Guan Y, Du ZX. Involvement of JNK and NF-κB pathways in lipopolysaccharide (LPS)-induced BAG3 expression in human monocytic cells. Exp Cell Res 2011; 318:16-24. [PMID: 22020323 DOI: 10.1016/j.yexcr.2011.10.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 10/02/2011] [Accepted: 10/04/2011] [Indexed: 12/16/2022]
Abstract
Lipopolysaccharide (LPS) is an outer-membrane glycolipid component of Gram-negative bacteria known for its fervent ability to activate monocytic cells and for its potent proinflammatory capabilities. Bcl-2-associated athanogene 3 (BAG3) is a survival protein that has been shown to be stimulated during cell response to stressful conditions, such as exposure to high temperature, heavy metals, proteasome inhibition, and human immunodeficiency virus 1 (HIV-1) infection. In addition, BAG3 regulates replication of Varicella-Zoster Virus (VZV) and Herpes Simplex Virus (HSV) replication, suggesting that BAG3 could participate in the host response to infection. In the current study, we found that LPS increased the expression of BAG3 in a dose- and time-dependent manner. Actinomycin D completely blocked the LPS-induced BAG3 accumulation, as well as LPS activated the proximal promoter of BAG3 gene, supported that the induction by LPS occurred at the level of gene transcription. LPS-induced BAG3 expression was blocked by JNK or NF-κB inhibition, suggesting that JNK and NF-κB pathways participated in BAG3 induction by LPS. In addition, we also found that induction of BAG3 was implicated in monocytic cell adhesion to extracellular matrix induced by LPS. Overall, the data support that BAG3 is induced by LPS via JNK and NF-κB-dependent signals, and involved in monocytic cell-extracellular matrix interaction, suggesting that BAG3 may have a role in the host response to LPS stimulation.
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Affiliation(s)
- Hua-Qin Wang
- Department of Biochemistry & Molecular Biology, China Medical University, Shenyang 110001, China.
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23
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Abstract
Bcl2-associated athanogene 3 (BAG3) protein is a member of BAG family of co-chaperones that interacts with the ATPase domain of the heat shock protein (Hsp) 70 through BAG domain (110–124 amino acids). BAG3 is the only member of the family to be induced by stressful stimuli, mainly through the activity of heat shock factor 1 on bag3 gene promoter. In addition to the BAG domain, BAG3 contains also a WW domain and a proline-rich (PXXP) repeat, that mediate binding to partners different from Hsp70. These multifaceted interactions underlie BAG3 ability to modulate major biological processes, that is, apoptosis, development, cytoskeleton organization and autophagy, thereby mediating cell adaptive responses to stressful stimuli. In normal cells, BAG3 is constitutively present in a very few cell types, including cardiomyocytes and skeletal muscle cells, in which the protein appears to contribute to cell resistance to mechanical stress. A growing body of evidence indicate that BAG3 is instead expressed in several tumor types. In different tumor contexts, BAG3 protein was reported to sustain cell survival, resistance to therapy, and/or motility and metastatization. In some tumor types, down-modulation of BAG3 levels was shown, as a proof-of-principle, to inhibit neoplastic cell growth in animal models. This review attempts to outline the emerging mechanisms that can underlie some of the biological activities of the protein, focusing on implications in tumor progression.
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Gout E, Gutkowska M, Takayama S, Reed JC, Chroboczek J. Co-chaperone BAG3 and adenovirus penton base protein partnership. J Cell Biochem 2011; 111:699-708. [PMID: 20607728 PMCID: PMC7166384 DOI: 10.1002/jcb.22756] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The BAG family of Hsp70/Hsc70 co‐chaperones is characterised by the presence of a conserved BAG domain at the carboxyl‐terminus. BAG3 protein is the only member of this family containing also the N‐terminally located WW domain. We describe here the identification of adenovirus (Ad) penton base protein as the first BAG3 partner recognising BAG3 WW domain. Ad penton base is the viral capsid constituent responsible for virus internalisation. It contains in the N‐terminal part two conserved PPxY motifs, known ligands of WW domains. In cells producing Ad penton base protein, cytoplasmic endogenous BAG3 interacts with it and co‐migrates to the nucleus. Preincubation of BAG3 with Ad base protein results in only slight modulation of BAG3 co‐chaperone activity, suggesting that this interaction is not related to the classical BAG3 co‐chaperone function. However, depletion of BAG3 impairs the cell entry of the virus and viral progeny production in Ad‐infected cells, suggesting that the interaction between virus penton base protein and cellular co‐chaperone BAG3 positively influences virus life cycle. These results thus demonstrate a novel host–pathogen interaction, which contributes to the successful infectious life cycle of adenoviruses. In addition, these data enrich our knowledge about the multifunctionality of the BAG3 co‐chaperone. J. Cell. Biochem. 111: 699–708, 2010. © 2010 Wiley‐Liss, Inc.
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Affiliation(s)
- E Gout
- Institut de Biologie Structurale, 41 rue Jules Horowitz, CEA, CNRS, Université Joseph Fourier, 38027 Grenoble, France
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25
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Quantitative proteomics analysis reveals BAG3 as a potential target to suppress severe acute respiratory syndrome coronavirus replication. J Virol 2010; 84:6050-9. [PMID: 20392858 DOI: 10.1128/jvi.00213-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The discovery of a novel coronavirus (CoV) as the causative agent of severe acute respiratory syndrome (SARS) has highlighted the need for a better understanding of CoV replication. The replication of SARS-CoV is highly dependent on host cell factors. However, relatively little is known about the cellular proteome changes that occur during SARS-CoV replication. Recently, we developed a cell line expressing a SARS-CoV subgenomic replicon and used it to screen inhibitors of SARS-CoV replication. To identify host proteins important for SARS-CoV RNA replication, the protein profiles of the SARS-CoV replicon cells and parental BHK21 cells were compared using a quantitative proteomic strategy termed "stable-isotope labeling by amino acids in cell culture-mass spectrometry" (SILAC-MS). Our results revealed that, among the 1,081 host proteins quantified in both forward and reverse SILAC measurements, 74 had significantly altered levels of expression. Of these, significantly upregulated BCL2-associated athanogene 3 (BAG3) was selected for further functional studies. BAG3 is involved in a wide variety of cellular processes, including cell survival, cellular stress response, proliferation, migration, and apoptosis. Our results show that inhibition of BAG3 expression by RNA interference led to significant suppression of SARS-CoV replication, suggesting the possibility that upregulation of BAG3 may be part of the machinery that SARS-CoV relies on for replication. By correlating the proteomic data with these functional studies, the findings of this study provide important information for understanding SARS-CoV replication.
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Herpes simplex virus type 1 immediate-early protein ICP22 is required for VICE domain formation during productive viral infection. J Virol 2009; 84:2384-94. [PMID: 20032172 DOI: 10.1128/jvi.01686-09] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During productive infection, herpes simplex virus type 1 (HSV-1) induces the formation of discrete nuclear foci containing cellular chaperone proteins, proteasomal components, and ubiquitinated proteins. These structures are known as VICE domains and are hypothesized to play an important role in protein turnover and nuclear remodeling in HSV-1-infected cells. Here we show that VICE domain formation in Vero and other cells requires the HSV-1 immediate-early protein ICP22. Since ICP22 null mutants replicate efficiently in Vero cells despite being unable to induce VICE domain formation, it can be concluded that VICE domain formation is not essential for HSV-1 productive infection. However, our findings do not exclude the possibility that VICE domain formation is required for viral replication in cells that are nonpermissive for ICP22 mutants. Our studies also show that ICP22 itself localizes to VICE domains, suggesting that it could play a role in forming these structures. Consistent with this, we found that ICP22 expression in transfected cells is sufficient to reorganize the VICE domain component Hsc70 into nuclear inclusion bodies that resemble VICE domains. An N-terminal segment of ICP22, corresponding to residues 1 to 146, is critical for VICE domain formation in infected cells and Hsc70 reorganization in transfected cells. We previously found that this portion of the protein is dispensable for ICP22's effects on RNA polymerase II phosphorylation. Thus, ICP22 mediates two distinct regulatory activities that both modify important components of the host cell nucleus.
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27
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Pockley AG, Calderwood SK, Santoro MG. Role of Heat Shock Proteins in Viral Infection. PROKARYOTIC AND EUKARYOTIC HEAT SHOCK PROTEINS IN INFECTIOUS DISEASE 2009; 4. [PMCID: PMC7121897 DOI: 10.1007/978-90-481-2976-8_3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
One of the most intriguing and less known aspects of the interaction between viruses and their host is the impact of the viral infection on the heat shock response (HSR). While both a positive and a negative role of different heat shock proteins (HSP) in the control of virus replication has been hypothesized, HSP function during the virus replication cycle is still not well understood. This chapter describes different aspects of the interactions between viruses and heat shock proteins during infection of mammalian cells: the first part focuses on the modulation of the heat shock response by human viral pathogens; the second describes the interactions of HSP and other chaperones with viral components, and their function during different steps of the virus replication cycle; the last part summarizes our knowledge on the effect of hyperthermia and HSR modulators on virus replication.
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Affiliation(s)
- A. Graham Pockley
- School of Medicine & Biomedical Science, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX United Kingdom
| | - Stuart K. Calderwood
- Beth Israel Deaconess Medical Center, Harvard Medical School, Burlington Avenue 21-27, Boston, 02215 U.S.A
| | - M. Gabriella Santoro
- Dipto. Biologia, Università di Roma, Tor Vergata, Via della Ricerca Scientifica 1, Roma, 00133 Italy
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Virus-Induced Chaperone-Enriched (VICE) domains function as nuclear protein quality control centers during HSV-1 infection. PLoS Pathog 2009; 5:e1000619. [PMID: 19816571 PMCID: PMC2752995 DOI: 10.1371/journal.ppat.1000619] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Accepted: 09/14/2009] [Indexed: 12/11/2022] Open
Abstract
Virus-Induced Chaperone-Enriched (VICE) domains form adjacent to nuclear viral replication compartments (RC) during the early stages of HSV-1 infection. Between 2 and 3 hours post infection at a MOI of 10, host protein quality control machinery such as molecular chaperones (e.g. Hsc70), the 20S proteasome and ubiquitin are reorganized from a diffuse nuclear distribution pattern to sequestration in VICE domains. The observation that VICE domains contain putative misfolded proteins suggests that they may be similar to nuclear inclusion bodies that form under conditions in which the protein quality control machinery is overwhelmed by the presence of misfolded proteins. The detection of Hsc70 in VICE domains, but not in nuclear inclusion bodies, indicates that Hsc70 is specifically reorganized by HSV-1 infection. We hypothesize that HSV-1 infection induces the formation of nuclear protein quality control centers to remodel or degrade aberrant nuclear proteins that would otherwise interfere with productive infection. Detection of proteolytic activity in VICE domains suggests that substrates may be degraded by the 20S proteasome in VICE domains. FRAP analysis reveals that GFP-Hsc70 is dynamically associated with VICE domains, suggesting a role for Hsc70 in scanning the infected nucleus for misfolded proteins. During 42°C heat shock, Hsc70 is redistributed from VICE domains into RC perhaps to remodel viral replication and regulatory proteins that have become insoluble in these compartments. The experiments presented in this paper suggest that VICE domains are nuclear protein quality control centers that are modified by HSV-1 to promote productive infection. Protein quality control is a protective cellular mechanism by which damaged proteins are refolded or degraded so that they cannot interfere with essential cellular processes. In the event that protein quality control machinery cannot refold or degrade damaged proteins, sequestration of misfolded protein is an alternative protective mechanism for reducing the toxic effects of misfolded protein. Several neurological diseases result from the accumulation of toxic misfolded proteins that cannot be efficiently refolded or degraded. In neurons from patients afflicted with Huntington's disease, misfolded huntingtin protein is sequestered in large aggregates in the nucleus called inclusion bodies. Inclusion bodies also contain protein quality control machinery including molecular chaperones, the proteasome and ubiquitin. Here we report that analogous structures called Virus-Induced Chaperone-Enriched (VICE) domains form in the nucleus of cells infected with Herpes Simplex Virus type 1 (HSV-1). VICE domains contain misfolded protein, chaperones and protein degradation activity. VICE domain formation is efficient in infected cells taxed with high levels of viral protein production. We hypothesize that misfolded proteins that arise in HSV-1-infected cells are sequestered in VICE domains to promote remodeling of misfolded proteins.
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Kyratsous CA, Walters MS, Panagiotidis CA, Silverstein SJ. Complementation of a herpes simplex virus ICP0 null mutant by varicella-zoster virus ORF61p. J Virol 2009; 83:10637-43. [PMID: 19656893 PMCID: PMC2753114 DOI: 10.1128/jvi.01144-09] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Accepted: 07/26/2009] [Indexed: 01/06/2023] Open
Abstract
The herpes simplex virus (HSV) ICP0 protein acts to overcome intrinsic cellular defenses that repress viral alpha gene expression. In that vein, viruses that have mutations in ICP0's RING finger or are deleted for the gene are sensitive to interferon, as they fail to direct degradation of promyelocytic leukemia protein (PML), a component of host nuclear domain 10s. While varicella-zoster virus is also insensitive to interferon, ORF61p, its ICP0 ortholog, failed to degrade PML. A recombinant virus with each coding region of the gene for ICP0 replaced with sequences encoding ORF61p was constructed. This virus was compared to an ICP0 deletion mutant and wild-type HSV. The recombinant degraded only Sp100 and not PML and grew to higher titers than its ICP0 null parental virus, but it was sensitive to interferon, like the virus from which it was derived. This analysis permitted us to compare the activities of ICP0 and ORF61p in identical backgrounds and revealed distinct biologic roles for these proteins.
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Affiliation(s)
- Christos A Kyratsous
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 W. 168th St., New York, NY 10032, USA
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Kyratsous CA, Silverstein SJ. Components of nuclear domain 10 bodies regulate varicella-zoster virus replication. J Virol 2009; 83:4262-74. [PMID: 19211749 PMCID: PMC2668482 DOI: 10.1128/jvi.00021-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 02/04/2009] [Indexed: 11/20/2022] Open
Abstract
PML, Sp100, and Daxx are proteins that normally reside within nuclear domains 10 (ND10s). They associate with DNA virus genomes and repress the very early stages of the DNA virus replication cycle. Virus-encoded proteins counteract this innate antiviral response. ICP0, a herpes simplex virus (HSV) immediate-early protein, is necessary and sufficient to dissociate ND10s and target their two major components, PML and Sp100, for proteasomal degradation. In this report, we show that ORF61p, the varicella-zoster virus (VZV) ortholog of ICP0, does not degrade PML and alters Sp100 levels only slightly. Furthermore, we demonstrate that other virus proteins cannot substitute for this lack of function during infection. By using short interfering RNAs, we depleted PML, Sp100, and Daxx and studied their roles in plaquing efficiency, virus protein accumulation, infectious-center titer, and virus spread. The results of these studies show that components of ND10s can accelerate VZV replication but do not ultimately control cell-associated virus titers. We conclude that while both ICP0 and ORF61p activate virus gene expression, they modulate host innate repression mechanisms in two different ways. As a result, HSV and VZV commandeer their host cells by distinct mechanisms to ensure their replication and spread.
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Affiliation(s)
- Christos A Kyratsous
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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Kyratsous CA, Silverstein SJ, DeLong CR, Panagiotidis CA. Chaperone-fusion expression plasmid vectors for improved solubility of recombinant proteins in Escherichia coli. Gene 2009; 440:9-15. [PMID: 19328840 DOI: 10.1016/j.gene.2009.03.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 03/13/2009] [Accepted: 03/15/2009] [Indexed: 11/18/2022]
Abstract
The enteric bacterium Escherichia coli is the most extensively used prokaryotic organism for production of proteins of therapeutic or commercial interest. However, it is common that heterologous over-expressed recombinant proteins fail to properly fold resulting in formation of insoluble aggregates known as inclusion bodies. Complex systems have been developed that employ simultaneous over-expression of chaperone proteins to aid proper folding and solubility during bacterial expression. Here we describe a simple method whereby a protein of interest, when fused in frame to the E. coli chaperones DnaK or GroEL, is readily expressed in large amounts in a soluble form. This system was tested using expression of the mouse prion protein PrP, which is normally insoluble in bacteria. We show that while in trans over-expression of the chaperone DnaK failed to alter partitioning of PrP from the insoluble inclusion body fraction to the soluble cytosol, expression of a DnaK-PrP fusion protein yielded large amounts of soluble protein. Similar results were achieved with a fragment of insoluble Varicella Zoster virus protein ORF21p. In theory this approach could be applied to any protein that partitions with inclusion bodies to render it soluble for production in E. coli.
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Affiliation(s)
- Christos A Kyratsous
- Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, Thessaloniki, 54124, Greece.
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Abstract
Viruses as obligate intracellular parasites use host cell proteins to ensure efficient replication and spread. Cellular proteins are required for several stages of a virus life cycle. Here, we identify BAG3, a co-chaperone, as a regulator of herpes virus immediate early gene expression. We report that a herpes simplex virus lacking the gene encoding a potent transcriptional activator, ICP0, is compromised for replication in cells silenced for BAG3 in a multiplicity of infection-dependent manner. We also show a requirement for BAG3 to augment virus gene expression and demonstrate that the co-chaperone acts independently of promyelocytic leukemia to increase herpes simplex virus replication.
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Youn DY, Lee DH, Lim MH, Yoon JS, Lim JH, Jung SE, Yeum CE, Park CW, Youn HJ, Lee JS, Lee SB, Ikawa M, Okabe M, Tsujimoto Y, Lee JH. Bis deficiency results in early lethality with metabolic deterioration and involution of spleen and thymus. Am J Physiol Endocrinol Metab 2008; 295:E1349-57. [PMID: 18840758 DOI: 10.1152/ajpendo.90704.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Bcl-2 interacting cell death suppressor (Bis), also known as Bag3 or CAIR-1, is involved in antistress and antiapoptotic pathways. In addition to Bcl-2, Bis binds to several proteins, suggesting it has diverse functions in normal and pathological conditions. To better define the physiological function of Bis in vivo, we developed bis-deficient mice with a cre-loxP system. Targeted disruption of exon 4 of the bis gene was demonstrated by Southern blotting and PCR, and Western blotting showed that no intact or truncated Bis protein was synthesized in bis(-/-) mice. While heterozygotes were fertile and appeared normal, Bis-deficient mice showed growth retardation and died by 3 wk after birth. The relative weight of the thymus and spleen was reduced and the total numbers of white blood cells, splenocytes, and thymocytes were significantly reduced compared with wild-type littermates. Serum profiles indicated significant hypoglycemia as well as decrease in triglyceride and cholesterol levels. Expression profiles of metabolic genes indicated that gluconeogenesis and beta-oxidation are activated in the liver of bis(-/-) mice. This activation, as well as a decrease in peripheral fat and an induction of fatty liver, appears to be an adaptive response to hypoglycemia. Our study reveals that the absence of Bis has considerable influences on postnatal growth and survival, possibly due to a nutritional impairment.
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Affiliation(s)
- Dong-Ye Youn
- Department of Biochemistry, Catholic University of Korea, Korea
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TRIM28 mediates primer binding site-targeted silencing of Lys1,2 tRNA-utilizing retroviruses in embryonic cells. Proc Natl Acad Sci U S A 2008; 105:12521-6. [PMID: 18713861 DOI: 10.1073/pnas.0805540105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Murine leukemia viruses (MLVs) and related retroelements are potently restricted in embryonic cells by postintegration transcriptional silencing, likely to protect the germ line from insertional mutagenesis. This silencing is in large part attributable to the presence of a nuclear repression complex, which targets a sequence element of the proviral DNA, the repressor-binding site. The repressor-binding site closely overlaps the tRNA primer binding site, a highly conserved sequence essential for virus replication and defining the site of initiation of DNA synthesis during reverse transcription. We have recently demonstrated that the cellular corepressor TRIM28 is recruited to the proline tRNA primer-binding site used by many MLVs and is required to mediate this silencing. Here, we show that TRIM28 is also required for the restriction of retroviruses using a completely distinct tRNA for the priming of their DNA synthesis, namely Lys-1,2 tRNA. These results generalize the role of TRIM28 in retroviral restriction and suggest that this system has evolved to restrict multiple retroviruses.
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Nuclear import of the varicella-zoster virus latency-associated protein ORF63 in primary neurons requires expression of the lytic protein ORF61 and occurs in a proteasome-dependent manner. J Virol 2008; 82:8673-86. [PMID: 18562514 DOI: 10.1128/jvi.00685-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Varicella-zoster virus (VZV) open reading frame (ORF) 63 protein (ORF63p) is one of six VZV ORFs shown to be transcribed and translated in latently infected human dorsal root ganglia. ORF63p accumulates exclusively in the cytoplasm of latently infected sensory neurons, whereas it is both nuclear and cytoplasmic during lytic infection and following reactivation from latency. Here, we demonstrate that infection of primary guinea pig enteric neurons (EN) with an adenovirus expressing ORF63p results in the exclusive cytoplasmic localization of the protein reminiscent of its distribution during latent VZV infection in humans. We show that the addition of the simian virus 40 large-T-antigen nuclear localization signal (NLS) results in the nuclear import of ORF63p in EN and that the ORF63p endogenous NLSs are functional in EN when fused to a heterologous protein. These data suggest that the cytoplasmic localization of ORF63p in EN results from the masking of the NLSs, thus blocking nuclear import. However, the coexpression of ORF61p, a strictly lytic VZV protein, and ORF63p in EN results in the nuclear import of ORF63p in a proteasome-dependent manner, and both ORF63p NLSs are required for this event. We propose that the cytoplasmic localization of ORF63p in neurons results from NLS masking and that the expression of ORF61p removes this block, allowing nuclear import to proceed.
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