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Li S, Xie Y, Yu C, Zheng C, Xu Z. The battle between host antiviral innate immunity and immune evasion by cytomegalovirus. Cell Mol Life Sci 2024; 81:341. [PMID: 39120730 DOI: 10.1007/s00018-024-05369-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 07/10/2024] [Accepted: 07/17/2024] [Indexed: 08/10/2024]
Abstract
Cytomegalovirus (CMV) has successfully established a long-lasting latent infection in humans due to its ability to counteract the host antiviral innate immune response. During coevolution with the host, the virus has evolved various evasion techniques to evade the host's innate immune surveillance. At present, there is still no vaccine available for the prevention and treatment of CMV infection, and the interaction between CMV infection and host antiviral innate immunity is still not well understood. However, ongoing studies will offer new insights into how to treat and prevent CMV infection and its related diseases. Here, we update recent studies on how CMV evades antiviral innate immunity, with a focus on how CMV proteins target and disrupt critical adaptors of antiviral innate immune signaling pathways. This review also discusses some classic intrinsic cellular defences that are crucial to the fight against viral invasion. A comprehensive review of the evasion mechanisms of antiviral innate immunity by CMV will help investigators identify new therapeutic targets and develop vaccines against CMV infection.
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Affiliation(s)
- Shuang Li
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Yuanyang Xie
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Changyin Yu
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China.
- The Collaborative Innovation Center of Tissue Damage Repair and Regeneration Medicine, Zunyi Medical University, Zunyi, China.
| | - Chunfu Zheng
- Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB, Canada.
| | - Zucai Xu
- Department of Neurology, Affiliated Hospital of Zunyi Medical University, Zunyi, China.
- The Collaborative Innovation Center of Tissue Damage Repair and Regeneration Medicine, Zunyi Medical University, Zunyi, China.
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2
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Kim JY, Min YJ, Lee MH, An YR, Ashktorab H, Smoot DT, Kwon SW, Lee SK. Ceramide promotes lytic reactivation of Epstein-Barr virus in gastric carcinoma. J Virol 2024; 98:e0177623. [PMID: 38197630 PMCID: PMC10878077 DOI: 10.1128/jvi.01776-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 12/11/2023] [Indexed: 01/11/2024] Open
Abstract
Epstein-Barr virus (EBV) has a lifelong latency period after initial infection. Rarely, however, when the EBV immediate early gene BZLF1 is expressed by a specific stimulus, the virus switches to the lytic cycle to produce progeny viruses. We found that EBV infection reduced levels of various ceramide species in gastric cancer cells. As ceramide is a bioactive lipid implicated in the infection of various viruses, we assessed the effect of ceramide on the EBV lytic cycle. Treatment with C6-ceramide (C6-Cer) induced an increase in the endogenous ceramide pool and increased production of the viral product as well as BZLF1 expression. Treatment with the ceramidase inhibitor ceranib-2 induced EBV lytic replication with an increase in the endogenous ceramide pool. The glucosylceramide synthase inhibitor Genz-123346 inhibited C6-Cer-induced lytic replication. C6-Cer induced extracellular signal-regulated kinase 1/2 (ERK1/2) and CREB phosphorylation, c-JUN expression, and accumulation of the autophagosome marker LC3B. Treatment with MEK1/2 inhibitor U0126, siERK1&2, or siCREB suppressed C6-Cer-induced EBV lytic replication and autophagy initiation. In contrast, siJUN transfection had no impact on BZLF1 expression. The use of 3-methyladenine (3-MA), an inhibitor targeting class III phosphoinositide 3-kinases (PI3Ks) to inhibit autophagy initiation, resulted in reduced beclin-1 expression, along with suppressed C6-Cer-induced BZLF1 expression and LC3B accumulation. Chloroquine, an inhibitor of autophagosome-lysosome fusion, increased BZLF1 protein intensity and LC3B accumulation. However, siLC3B transfection had minimal effect on BZLF1 expression. The results suggest the significance of ceramide-related sphingolipid metabolism in controlling EBV latency, highlighting the potential use of drugs targeting sphingolipid metabolism for treating EBV-positive gastric cancer.IMPORTANCEEpstein-Barr virus remains dormant in the host cell but occasionally switches to the lytic cycle when stimulated. However, the exact molecular mechanism of this lytic induction is not well understood. In this study, we demonstrate that Epstein-Barr virus infection leads to a reduction in ceramide levels. Additionally, the restoration of ceramide levels triggers lytic replication of Epstein-Barr virus with increase in phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and CREB. Our study suggests that the Epstein-Barr virus can inhibit lytic replication and remain latent through reduction of host cell ceramide levels. This study reports the regulation of lytic replication by ceramide in Epstein-Barr virus-positive gastric cancer.
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Affiliation(s)
- Jun Yeob Kim
- Department of Medical Life Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
- Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Young Jin Min
- College of Pharmacy, Seoul National University, Seoul, South Korea
| | - Min-Hyeok Lee
- Department of Medical Life Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
- Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Yea Rim An
- Department of Medical Life Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
- Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | | | - Duane T. Smoot
- Department of Medicine, Howard University, Washington, DC, USA
| | - Sung Won Kwon
- College of Pharmacy, Seoul National University, Seoul, South Korea
| | - Suk Kyeong Lee
- Department of Medical Life Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
- Department of Biomedicine & Health Sciences, College of Medicine, The Catholic University of Korea, Seoul, South Korea
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3
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Thinwa JW, Zou Z, Parks E, Sebti S, Hui K, Wei Y, Goodarzi M, Singh V, Urquhart G, Jewell JL, Pfeiffer JK, Levine B, Reese TA, Shiloh MU. CDKL5 regulates p62-mediated selective autophagy and confers protection against neurotropic viruses. J Clin Invest 2024; 134:e168544. [PMID: 37917202 PMCID: PMC10760973 DOI: 10.1172/jci168544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 10/31/2023] [Indexed: 11/04/2023] Open
Abstract
Virophagy, the selective autophagosomal engulfment and lysosomal degradation of viral components, is crucial for neuronal cell survival and antiviral immunity. However, the mechanisms leading to viral antigen recognition and capture by autophagic machinery remain poorly understood. Here, we identified cyclin-dependent kinase-like 5 (CDKL5), known to function in neurodevelopment, as an essential regulator of virophagy. Loss-of-function mutations in CDKL5 are associated with a severe neurodevelopmental encephalopathy. We found that deletion of CDKL5 or expression of a clinically relevant pathogenic mutant of CDKL5 reduced virophagy of Sindbis virus (SINV), a neurotropic RNA virus, and increased intracellular accumulation of SINV capsid protein aggregates and cellular cytotoxicity. Cdkl5-knockout mice displayed increased viral antigen accumulation and neuronal cell death after SINV infection and enhanced lethality after infection with several neurotropic viruses. Mechanistic studies demonstrated that CDKL5 directly binds the canonical selective autophagy receptor p62 and phosphorylates p62 at T269/S272 to promote its interaction with viral capsid aggregates. We found that CDKL5-mediated phosphorylation of p62 facilitated the formation of large p62 inclusion bodies that captured viral capsids to initiate capsid targeting to autophagic machinery. Overall, these findings identify a cell-autonomous innate immune mechanism for autophagy activation to clear intracellular toxic viral protein aggregates during infection.
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Affiliation(s)
| | | | | | | | - Kelvin Hui
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Center for iPS Cell Research and Application, Kyoto University, Kyoto, Japan
| | - Yongjie Wei
- Cancer Research Institute, Guangzhou Medical University, Guangzhou, China
| | | | | | - Greg Urquhart
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jenna L. Jewell
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | | | - Beth Levine
- Department of Internal Medicine
- Department of Microbiology
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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4
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Pena-Francesch M, Vanoaica LD, Zhu GF, Stumpe M, Sankar DS, Nowag H, Valencia-Camargo AD, Hammerschmidt W, Dengjel J, Ligeon LA, Münz C. The autophagy machinery interacts with EBV capsids during viral envelope release. Proc Natl Acad Sci U S A 2023; 120:e2211281120. [PMID: 37579175 PMCID: PMC10451551 DOI: 10.1073/pnas.2211281120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 06/02/2023] [Indexed: 08/16/2023] Open
Abstract
Autophagy serves as a defense mechanism against intracellular pathogens, but several microorganisms exploit it for their own benefit. Accordingly, certain herpesviruses include autophagic membranes into their infectious virus particles. In this study, we analyzed the composition of purified virions of the Epstein-Barr virus (EBV), a common oncogenic γ-herpesvirus. In these, we found several components of the autophagy machinery, including membrane-associated LC3B-II, and numerous viral proteins, such as the capsid assembly proteins BVRF2 and BdRF1. Additionally, we showed that BVRF2 and BdRF1 interact with LC3B-II via their common protein domain. Using an EBV mutant, we identified BVRF2 as essential to assemble mature capsids and produce infectious EBV. However, BdRF1 was sufficient for the release of noninfectious viral envelopes as long as autophagy was not compromised. These data suggest that BVRF2 and BdRF1 are not only important for capsid assembly but together with the LC3B conjugation complex of ATG5-ATG12-ATG15L1 are also critical for EBV envelope release.
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Affiliation(s)
- Maria Pena-Francesch
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
| | - Liliana Danusia Vanoaica
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
| | - Gao-Feng Zhu
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
| | - Michael Stumpe
- Department of Biology, University of Fribourg, Fribourg1700, Switzerland
| | | | - Heike Nowag
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
| | | | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München, German Research Center for Environmental Health and German Center for Infection Research, D-81377Munich, Germany
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, Fribourg1700, Switzerland
| | - Laure-Anne Ligeon
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
| | - Christian Münz
- Viral Immunobiology, Institute of Experimental Immunology, University of Zürich, Zürich8057, Switzerland
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5
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Kim HJ, Lee Y, Lee S, Park B. HCMV-encoded viral protein US12 promotes autophagy by inducing autophagy flux. Biochem Biophys Res Commun 2023; 654:94-101. [PMID: 36898229 DOI: 10.1016/j.bbrc.2023.03.004] [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: 02/20/2023] [Accepted: 03/01/2023] [Indexed: 03/06/2023]
Abstract
The human cytomegalovirus (HCMV)-encoded US12 gene family is a group of ten predicted seven-transmembrane domain proteins that are structurally similar to G-protein-coupled receptors or transmembrane Bax inhibitor-1 motif-containing proteins; however, the roles of US12 family proteins in virus-host interactions remain to be discovered. Here, we suggest a new function of the US12 protein in regulating cellular autophagy. US12 is predominantly located to the lysosome and interacts with the lysosomal membrane protein 2 (LAMP2). A liquid chromatography-mass spectrometry (MS)/MS-based targeted proteomics analysis shows that US12 is tightly correlated with autophagy. US12 induces autophagy via upregulating ULK1 phosphorylation and subsequent LC3-II conversion, thereby accelerating autophagic flux. Moreover, HeLa cells overexpressing US12 displays intense LC3-specific staining and autolysosome formation even under nutrient-sufficient conditions. Furthermore, the physical interaction of p62/SQSTM1 with US12 is involved in the resistance to the degradation of p62/SQSTM1 by autophagy, despite the induction of both autolysosome formation and autophagic flux. Although the effect of US12 expression in HCMV infection on autophagy remains undetermined, these findings provide new insights into the viral drivers of host autophagy during HCMV evolution and pathogenesis.
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Affiliation(s)
- Hyung Jin Kim
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul, 03722, South Korea
| | - Yoora Lee
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul, 03722, South Korea
| | - Sungwook Lee
- Division of Tumor Immunology, Research Institute, National Cancer Center, Goyang, 10408, South Korea
| | - Boyoun Park
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul, 03722, South Korea.
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6
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Ghosh AK, Su YP, Forman M, Keyes RF, Smith BC, Hu X, Ferrer M, Arav-Boger R. Harnessing the Noncanonical Keap1-Nrf2 Pathway for Human Cytomegalovirus Control. J Virol 2023; 97:e0016023. [PMID: 36939350 PMCID: PMC10134830 DOI: 10.1128/jvi.00160-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Accepted: 03/02/2023] [Indexed: 03/21/2023] Open
Abstract
Host-derived cellular pathways can provide an unfavorable environment for virus replication. These pathways have been a subject of interest for herpesviruses, including the betaherpesvirus human cytomegalovirus (HCMV). Here, we demonstrate that a compound, ARP101, induces the noncanonical sequestosome 1 (SQSTM1)/p62-Keap1-Nrf2 pathway for HCMV suppression. ARP101 increased the levels of both LC3 II and SQSTM1/p62 and induced phosphorylation of p62 at the C-terminal domain, resulting in its increased affinity for Keap1. ARP101 treatment resulted in Nrf2 stabilization and translocation into the nucleus, binding to specific promoter sites and transcription of antioxidant enzymes under the antioxidant response element (ARE), and HCMV suppression. Knockdown of Nrf2 recovered HCMV replication following ARP101 treatment, indicating the role of the Keap1-Nrf2 axis in HCMV inhibition by ARP101. SQSTM1/p62 phosphorylation was not modulated by the mTOR kinase or casein kinase 1 or 2, indicating ARP101 engages other kinases. Together, the data uncover a novel antiviral strategy for SQSTM1/p62 through the noncanonical Keap1-Nrf2 axis. This pathway could be further exploited, including the identification of the responsible kinases, to define the biological events during HCMV replication. IMPORTANCE Antiviral treatment for human cytomegalovirus (HCMV) is limited and suffers from the selection of drug-resistant viruses. Several cellular pathways have been shown to modulate HCMV replication. The autophagy receptor sequestosome 1 (SQSTM1)/p62 has been reported to interact with several HCMV proteins, particularly with components of HCMV capsid, suggesting it plays a role in viral replication. Here, we report on a new and unexpected role for SQSTM1/p62, in HCMV suppression. Using a small-molecule probe, ARP101, we show SQSTM1/p62 phosphorylation at its C terminus domain initiates the noncanonical Keap1-Nrf2 axis, leading to transcription of genes under the antioxidant response element, resulting in HCMV inhibition in vitro. Our study highlights the dynamic nature of SQSTM1/p62 during HCMV infection and how its phosphorylation activates a new pathway that can be exploited for antiviral intervention.
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Affiliation(s)
- Ayan K. Ghosh
- Department of Pediatrics, Division of Infectious Disease, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Yu-Pin Su
- Department of Pediatrics, Division of Infectious Disease, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Michael Forman
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Robert F. Keyes
- Department of Biochemistry, Program in Chemical Biology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Brian C. Smith
- Department of Biochemistry, Program in Chemical Biology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Xin Hu
- National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, Rockville, Maryland, USA
| | - Marc Ferrer
- National Center for Advancing Translational Sciences (NCATS), National Institutes of Health, Rockville, Maryland, USA
| | - Ravit Arav-Boger
- Department of Pediatrics, Division of Infectious Disease, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
- Department of Pediatrics, Division of Infectious Disease, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Chen T, Tu S, Ding L, Jin M, Chen H, Zhou H. The role of autophagy in viral infections. J Biomed Sci 2023; 30:5. [PMID: 36653801 PMCID: PMC9846652 DOI: 10.1186/s12929-023-00899-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/10/2023] [Indexed: 01/20/2023] Open
Abstract
Autophagy is an evolutionarily conserved catabolic cellular process that exerts antiviral functions during a viral invasion. However, co-evolution and co-adaptation between viruses and autophagy have armed viruses with multiple strategies to subvert the autophagic machinery and counteract cellular antiviral responses. Specifically, the host cell quickly initiates the autophagy to degrade virus particles or virus components upon a viral infection, while cooperating with anti-viral interferon response to inhibit the virus replication. Degraded virus-derived antigens can be presented to T lymphocytes to orchestrate the adaptive immune response. Nevertheless, some viruses have evolved the ability to inhibit autophagy in order to evade degradation and immune responses. Others induce autophagy, but then hijack autophagosomes as a replication site, or hijack the secretion autophagy pathway to promote maturation and egress of virus particles, thereby increasing replication and transmission efficiency. Interestingly, different viruses have unique strategies to counteract different types of selective autophagy, such as exploiting autophagy to regulate organelle degradation, metabolic processes, and immune responses. In short, this review focuses on the interaction between autophagy and viruses, explaining how autophagy serves multiple roles in viral infection, with either proviral or antiviral functions.
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Affiliation(s)
- Tong Chen
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
| | - Shaoyu Tu
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
| | - Ling Ding
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
| | - Meilin Jin
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
| | - Huanchun Chen
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
| | - Hongbo Zhou
- grid.35155.370000 0004 1790 4137State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430030 China ,grid.35155.370000 0004 1790 4137Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430030 China
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Penner I, Büscher N, Dejung M, Freiwald A, Butter F, Plachter B. Subviral Dense Bodies of Human Cytomegalovirus Induce an Antiviral Type I Interferon Response. Cells 2022; 11:cells11244028. [PMID: 36552792 PMCID: PMC9777239 DOI: 10.3390/cells11244028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022] Open
Abstract
(1) Background: Cells infected with the human cytomegalovirus (HCMV) produce subviral particles, termed dense bodies (DBs), both in-vitro and in-vivo. They are released from cells, comparable to infectious virions, and are enclosed by a membrane that resembles the viral envelope and mediates the entry into cells. To date, little is known about how the DB uptake influences the gene expression in target cells. The purpose of this study was to investigate the impact of DBs on cells, in the absence of a viral infection. (2) Methods: Mass spectrometry, immunoblot analyses, siRNA knockdown, and a CRISPR-CAS9 knockout, were used to investigate the changes in cellular gene expression following a DB exposure; (3) Results: A number of interferon-regulated genes (IRGs) were upregulated after the fibroblasts and endothelial cells were exposed to DBs. This upregulation was dependent on the DB entry and mediated by the type I interferon signaling through the JAK-STAT pathway. The induction of IRGs was mediated by the sensing of the DB-introduced DNA by the pattern recognition receptor cGAS. (4) Conclusions: The induction of a strong type I IFN response by DBs is a unique feature of the HCMV infection. The release of DBs may serve as a danger signal and concomitantly contribute to the induction of a strong, antiviral immune response.
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Affiliation(s)
- Inessa Penner
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Nicole Büscher
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Mario Dejung
- Institute for Molecular Biology, 55128 Mainz, Germany
| | - Anja Freiwald
- Institute for Molecular Biology, 55128 Mainz, Germany
| | - Falk Butter
- Institute for Molecular Biology, 55128 Mainz, Germany
| | - Bodo Plachter
- Institute for Virology, University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany
- Correspondence:
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Borst EM, Harmening S, Sanders S, Caragliano E, Wagner K, Lenac Roviš T, Jonjić S, Bosse JB, Messerle M. A Unique Role of the Human Cytomegalovirus Small Capsid Protein in Capsid Assembly. mBio 2022; 13:e0100722. [PMID: 36066102 PMCID: PMC9600257 DOI: 10.1128/mbio.01007-22] [Citation(s) in RCA: 2] [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: 04/13/2022] [Accepted: 08/11/2022] [Indexed: 11/20/2022] Open
Abstract
Morphogenesis of herpesvirus particles is highly conserved; however, the capsid assembly and genome packaging of human cytomegalovirus (HCMV) exhibit unique features. Examples of these include the essential role of the small capsid protein (SCP) and the existence of the β-herpesvirus-specific capsid-associated protein pp150. SCP and pp150, as well as the UL77 and UL93 proteins, are important capsid constituents, yet their precise mechanism of action is elusive. Here, we analyzed how deletion of the open reading frames (ORFs) encoding pUL77, pUL93, pp150, or SCP affects the protein composition of nuclear capsids. This was achieved by generating HCMV genomes lacking the respective genes, combined with a highly efficient transfection technique that allowed us to directly analyze these mutants in transfected cells. While no obvious effects were observed when pUL77, pUL93, or pp150 was missing, the absence of SCP impeded capsid assembly due to strongly reduced amounts of major capsid protein (MCP). Vice versa, when MCP was lacking, SCP became undetectable, indicating a mutual dependence of SCP and MCP for establishing appropriate protein levels. The SCP domain mediating stable MCP levels could be narrowed down to a C-terminal helix known to convey MCP binding. Interestingly, an SCP-EGFP (enhanced green fluorescent protein) fusion protein which also impaired the production of infectious progeny acted in a different manner, as capsid assembly was not abolished; however, SCP-EGFP-harboring capsids were devoid of DNA and trapped in paracrystalline nuclear structures. These results indicate that SCP is essential in HCMV because of its impact on MCP levels and reveal SCP as a potential target for antiviral inhibitors. IMPORTANCE Human cytomegalovirus (HCMV) is a ubiquitous pathogen causing life-threatening disease in immunocompromised individuals. Virus-specific processes such as capsid assembly and genome packaging can be exploited to design new antiviral strategies. Here, we report on a novel function of the HCMV small capsid protein (SCP), namely, ensuring stable levels of major capsid protein (MCP), thereby governing capsid assembly. Furthermore, we discovered a mutual dependence of the small and major capsid proteins to guarantee appropriate levels of the other respective protein and were able to pin down the SCP domain responsible for this effect to a region previously shown to mediate binding to the major capsid protein. In summary, our data contribute to the understanding of how SCP plays an essential part in the HCMV infection cycle. Moreover, disrupting the SCP-MCP interface may provide a starting point for the development of novel antiviral drugs.
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Affiliation(s)
- Eva Maria Borst
- Department of Virology, Hannover Medical School, Hannover, Germany
| | - Sarah Harmening
- Department of Virology, Hannover Medical School, Hannover, Germany
| | - Saskia Sanders
- Department of Virology, Hannover Medical School, Hannover, Germany
- Leibniz-Institute for Experimental Virology, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
| | - Enrico Caragliano
- Department of Virology, Hannover Medical School, Hannover, Germany
- Leibniz-Institute for Experimental Virology, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
| | - Karen Wagner
- Department of Virology, Hannover Medical School, Hannover, Germany
| | - Tihana Lenac Roviš
- Center for Proteomics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
| | - Stipan Jonjić
- Center for Proteomics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
| | - Jens Bernhard Bosse
- Department of Virology, Hannover Medical School, Hannover, Germany
- Leibniz-Institute for Experimental Virology, Hamburg, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
| | - Martin Messerle
- Department of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research, Partner Site Hannover Braunschweig, Hannover, Germany
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10
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Li X, Huang Z, Zhu L, Yu F, Feng M, Gu A, Jiang J, Wang G, Huang D. Prognostic Model and Nomogram Construction and Validation With an Autophagy-Related Gene Signature in Low-Grade Gliomas. Front Genet 2022; 13:905751. [PMID: 35923699 PMCID: PMC9342864 DOI: 10.3389/fgene.2022.905751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 06/03/2022] [Indexed: 11/30/2022] Open
Abstract
Background: Autophagy plays a vital role in cancer development. However, the prognostic value of autophagy-related genes (ARGs) in low-grade gliomas (LGG) is unclear. This research aimed to investigate whether ARGs correlated with overall survival (OS) in LGG patients. Methods: RNA-sequencing data were obtained from The Cancer Genome Atlas (TCGA) TARGET GTEx database. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis of ARGs were performed by the “clusterprofile” R package. Cox regression with the wald χ2 test was employed to identify prognostic significant ARGs. Next, the receiver operator characteristic curves were established to evaluate the feasibility of risk score (riskscore=h0(t)exp(∑j=1nCoefj×Xj)) and other clinical risk factors to predict prognosis. A nomogram was constructed. Correlations between clinical features and ARGs were further verified by a t-test or Kruskal–Wallis test. In addition, the correlations between autophagy and immune cells were assessed through the single-sample gene set enrichment analysis (ssGSEA) and tumor immune estimation resource database. Last, the prediction model was verified by LGG data downloaded from the Chinese Glioma Genome Atlas (CGGA) database. Results: Overall, 35 DE-ARGs were identified. Functional enrichment analysis showed that these genes were mainly related to oxidative stress and regulation of autophagy. Nine ARGs (BAX, BIRC5, CFLAR, DIRAS3, GRID2, MAPK9, MYC, PTK6, and TP53) were significantly associated with OS. Age (Hazard ratio (HR) = 1.063, 95% CI: 1.046–1.080), grade (HR = 3.412, 95% CI: 2.164–5.379), histological type (HR = 0.556, 95% CI: 0.346–0.893), and risk score (HR = 1.135, 95% CI: 1.104–1.167) were independent prognostic risk factors (all p < 0.05). In addition, BIRC5, CFLAR, DIRAS3, TP53, and risk scores were found to correlate significantly with age and tumor grade (all p < 0.05). Immune cell enrichment analysis demonstrated that the types of immune cells and their expression levels in the high-risk group were significantly different from those in the low-risk group (all p < 0.05). A prognostic nomogram was constructed to predict 1-, 3-, and 5-year survival, and the prognostic value of sorted ARGs were verified in the CGGA database and clinical samples. Conclusion: Our findings suggest that the 9 DE-ARGs’ risk score model could serve as diagnostic and prognostic biomarkers. The prognostic nomograms could be useful for individualized survival prediction and improved treatment strategies.
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Affiliation(s)
- Xinrui Li
- Department of Neurology, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Zhiyuan Huang
- Research Center for Translational Medicine, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
- Department of Thoracic Surgery, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Lei Zhu
- Department of Neurosurgery, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Fei Yu
- Department of Neurology, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Minghao Feng
- Department of Thoracic Surgery, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Aiqin Gu
- Department of Neurosurgery, Taizhou People’s Hospital Affiliated to Nanjing Medical University, Taizhou, China
| | - Jianxin Jiang
- Department of Neurosurgery, Taizhou People’s Hospital Affiliated to Nanjing Medical University, Taizhou, China
- *Correspondence: Jianxin Jiang, ; Guangxue Wang, ; Dongya Huang,
| | - Guangxue Wang
- Research Center for Translational Medicine, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
- *Correspondence: Jianxin Jiang, ; Guangxue Wang, ; Dongya Huang,
| | - Dongya Huang
- Department of Neurology, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China
- *Correspondence: Jianxin Jiang, ; Guangxue Wang, ; Dongya Huang,
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11
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Schweiger L, Lelieveld-Fast LA, Mikuličić S, Strunk J, Freitag K, Tenzer S, Clement AM, Florin L. HPV16 Induces Formation of Virus-p62-PML Hybrid Bodies to Enable Infection. Viruses 2022; 14:v14071478. [PMID: 35891458 PMCID: PMC9315800 DOI: 10.3390/v14071478] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/24/2022] [Accepted: 06/29/2022] [Indexed: 11/29/2022] Open
Abstract
Human papillomaviruses (HPVs) inflict a significant burden on the human population. The clinical manifestations caused by high-risk HPV types are cancers at anogenital sites, including cervical cancer, as well as head and neck cancers. Host cell defense mechanisms such as autophagy are initiated upon HPV entry. At the same time, the virus modulates cellular antiviral processes and structures such as promyelocytic leukemia nuclear bodies (PML NBs) to enable infection. Here, we uncover the autophagy adaptor p62, also known as p62/sequestosome-1, as a novel proviral factor in infections by the high-risk HPV type 16 (HPV16). Proteomics, imaging and interaction studies of HPV16 pseudovirus-treated HeLa cells display that p62 is recruited to virus-filled endosomes, interacts with incoming capsids, and accompanies the virus to PML NBs, the sites of viral transcription and replication. Cellular depletion of p62 significantly decreased the delivery of HPV16 viral DNA to PML NBs and HPV16 infection rate. Moreover, the absence of p62 leads to an increase in the targeting of viral components to autophagic structures and enhanced degradation of the viral capsid protein L2. The proviral role of p62 and formation of virus-p62-PML hybrid bodies have also been observed in human primary keratinocytes, the HPV target cells. Together, these findings suggest the previously unrecognized virus-induced formation of p62-PML hybrid bodies as a viral mechanism to subvert the cellular antiviral defense, thus enabling viral gene expression.
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Affiliation(s)
- Linda Schweiger
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
| | - Laura A. Lelieveld-Fast
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
| | - Snježana Mikuličić
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
| | - Johannes Strunk
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
| | - Kirsten Freitag
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
| | - Stefan Tenzer
- Institute of Immunology, University Medical Center, Johannes Gutenberg University of Mainz, 55131 Mainz, Germany;
| | - Albrecht M. Clement
- Institute of Pathobiochemistry, University Medical Center, Johannes Gutenberg University of Mainz, Duesbergweg 6, 55128 Mainz, Germany;
| | - Luise Florin
- Institute for Virology and Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg University of Mainz, Obere Zahlbacher Strasse 67, 55131 Mainz, Germany; (L.S.); (L.A.L.-F.); (S.M.); (J.S.); (K.F.)
- Correspondence: ; Tel.: +49-(0)-6131-179083
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12
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Vinogradskaya GR, Ivanov AV, Kushch AA. Mechanisms of Survival of Cytomegalovirus-Infected Tumor Cells. Mol Biol 2022; 56:668-683. [PMID: 36217337 PMCID: PMC9534468 DOI: 10.1134/s0026893322050132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/19/2022] [Accepted: 04/19/2022] [Indexed: 11/04/2022]
Abstract
Human cytomegalovirus (HCMV) DNA and proteins are often detected in malignant tumors, warranting studies of the role that HCMV plays in carcinogenesis and tumor progression. HCMV proteins were shown to regulate the key processes involved in tumorigenesis. While HCMV as an oncogenic factor just came into focus, its ability to promote tumor progression is generally recognized. The review discusses the viral factors and cell molecular pathways that affect the resistance of cancer cells to therapy. CMV inhibits apoptosis of tumor cells, that not only promotes tumor progression, but also reduces the sensitivity of cells to antitumor therapy. Autophagy was found to facilitate either cell survival or cell death in different tumor cells. In leukemia cells, HCMV induces a "protective" autophagy that suppresses apoptosis. Viral factors that mediate drug resistance and their interactions with key cell death pathways are necessary to further investigate in order to develop agents that can restore the tumor sensitivity to anticancer drugs.
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Affiliation(s)
- G. R. Vinogradskaya
- Konstantinov St. Petersburg Institute of Nuclear Physics, National Research Center “Kurchatov Institute”, 188300 Gatchina, Leningrad oblast Russia
| | - A. V. Ivanov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia
| | - A. A Kushch
- Gamaleya National Research Center of Epidemiology and Microbiology, Ministry of Health of the Russian Federation, 123098 Moscow, Russia
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13
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Häge S, Büscher N, Pakulska V, Hahn F, Adrait A, Krauter S, Borst EM, Schlötzer-Schrehardt U, Couté Y, Plachter B, Marschall M. The Complex Regulatory Role of Cytomegalovirus Nuclear Egress Protein pUL50 in the Production of Infectious Virus. Cells 2021; 10:3119. [PMID: 34831342 PMCID: PMC8625744 DOI: 10.3390/cells10113119] [Citation(s) in RCA: 6] [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] [Received: 10/07/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 11/30/2022] Open
Abstract
The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recruits several viral and cellular factors by direct and indirect contacts. Recently, we generated an ORF-UL50-deleted recombinant HCMV in pUL50-complementing cells and obtained first indications of putative additional functions of pUL50. In this study, we produced purified ΔUL50 particles under both complementing (ΔUL50C) and non-complementing (ΔUL50N) conditions and performed a phenotypical characterization. Findings were as follows: (i) ΔUL50N particle preparations exhibited a clear replicative defect in qPCR-based infection kinetics compared to ΔUL50C particles; (ii) immuno-EM analysis of ΔUL50C did not reveal major changes in nuclear distribution of pUL53 and lamin A/C; (iii) mass spectrometry-based quantitative proteomics showed a large concordance of protein contents in the NIEP fractions of ΔUL50C and ΔUL50N particles, but virion fraction was close to the detection limit for ΔUL50N; (iv) confocal imaging of viral marker proteins of immediate early (IE) and later phases of ΔUL50N infection indicated a very low number of cells showing an onset of viral lytic protein expression; and, finally (v) quantitative measurements of encapsidated genomes provided evidence for a substantial reduction in the DNA contents in ΔUL50N compared to ΔUL50C particles. In summary, the results point to a complex and important regulatory role of the HCMV nuclear egress protein pUL50 in the maturation of infectious virus.
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Affiliation(s)
- Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Nicole Büscher
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Victoria Pakulska
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Annie Adrait
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Steffi Krauter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School (MHH), 30625 Hannover, Germany;
| | | | - Yohann Couté
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Bodo Plachter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
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14
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Yan JM, Zhang WK, Yan LN, Jiao YJ, Zhou CM, Yu XJ. Bunyavirus SFTSV exploits autophagic flux for viral assembly and egress. Autophagy 2021; 18:1599-1612. [PMID: 34747299 PMCID: PMC9298452 DOI: 10.1080/15548627.2021.1994296] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2022] Open
Abstract
Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging negatively stranded enveloped RNA bunyavirus that causes SFTS with a high case fatality rate of up to 30%. Macroautophagy/autophagy is an evolutionarily conserved process involved in the maintenance of host homeostasis, which exhibits anti-viral or pro-viral responses in reaction to different viral challenges. However, the interaction between the bunyavirus SFTSV and the autophagic process is still largely unclear. By establishing various autophagy-deficient cell lines, we found that SFTSV triggered RB1CC1/FIP200-BECN1-ATG5-dependent classical autophagy flux. SFTSV nucleoprotein induced BECN1-dependent autophagy by disrupting the BECN1-BCL2 association. Importantly, SFTSV utilized autophagy for the viral life cycle, which not only assembled in autophagosomes derived from the ERGIC and Golgi complex, but also utilized autophagic vesicles for exocytosis. Taken together, our results suggest a novel virus-autophagy interaction model in which bunyavirus SFTSV induces classical autophagy flux for viral assembly and egress processes, suggesting that autophagy inhibition may be a novel therapy for treating or releasing SFTS.
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Affiliation(s)
- Jia-Min Yan
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, China
| | - Wen-Kang Zhang
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, China
| | - Li-Na Yan
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, China
| | - Yong-Jun Jiao
- Nhc Key laboratory of Enteric Pathogenic Microbiology, Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China, Nanjing, China
| | - Chuan-Min Zhou
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, China.,Department of Infectious Diseases, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Xue-Jie Yu
- State Key Laboratory of Virology, School of Public Health, Wuhan University, Wuhan, China
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15
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The Autophagy-Initiating Protein Kinase ULK1 Phosphorylates Human Cytomegalovirus Tegument Protein pp28 and Regulates Efficient Virus Release. J Virol 2021; 95:JVI.02346-20. [PMID: 33328309 DOI: 10.1128/jvi.02346-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 12/08/2020] [Indexed: 02/06/2023] Open
Abstract
Autophagy is a catabolic process contributing to intrinsic cellular defense by degrading viral particles or proteins; however, several viruses hijack this pathway for their own benefit. The role of autophagy during human cytomegalovirus (HCMV) replication has not been definitely clarified yet. Utilizing small interfering RNA (siRNA)-based screening, we observed that depletion of many autophagy-related proteins resulted in reduced virus release, suggesting a requirement of autophagy-related factors for efficient HCMV replication. Additionally, we could show that the autophagy-initiating serine/threonine protein kinase ULK1 as well as other constituents of the ULK1 complex were upregulated at early times of infection and stayed upregulated throughout the replication cycle. We demonstrate that indirect interference with ULK1 through inhibition of the upstream regulator AMP-activated protein kinase (AMPK) impaired virus release. Furthermore, this result was verified by direct abrogation of ULK1 kinase activity utilizing the ULK1-specific kinase inhibitors SBI-0206965 and ULK-101. Analysis of viral protein expression in the presence of ULK-101 revealed a connection between the cellular kinase ULK1 and the viral tegument protein pp28 (pUL99), and we identified pp28 as a novel viral substrate of ULK1 by in vitro kinase assays. In the absence of ULK1 kinase activity, large pp28- and pp65-positive structures could be detected in the cytoplasm at late time points of infection. Transmission electron microscopy demonstrated that these structures represent large perinuclear protein accumulations presumably representing aggresomes. Our results indicate that HCMV manipulates ULK1 and further components of the autophagic machinery to ensure the efficient release of viral particles.IMPORTANCE The catabolic program of autophagy represents a powerful immune defense against viruses that is, however, counteracted by antagonizing viral factors. Understanding the exact interplay between autophagy and HCMV infection is of major importance since autophagy-related proteins emerged as promising targets for pharmacologic intervention. Our study provides evidence for a proviral role of several autophagy-related proteins suggesting that HCMV has developed strategies to usurp components of the autophagic machinery for its own benefit. In particular, we observed strong upregulation of the autophagy-initiating protein kinase ULK1 and further components of the ULK1 complex during HCMV replication. In addition, both siRNA-mediated depletion of ULK1 and interference with ULK1 protein kinase activity by two chemically different inhibitors resulted in impaired viral particle release. Thus, we propose that ULK1 kinase activity is required for efficient HCMV replication and thus represents a promising novel target for future antiviral drug development.
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