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Wang XF, Zhang X, Ma W, Li J, Wang X. Host cell restriction factors of equine infectious anemia virus. Virol Sin 2023; 38:485-496. [PMID: 37419416 PMCID: PMC10436108 DOI: 10.1016/j.virs.2023.07.001] [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: 04/13/2023] [Accepted: 07/03/2023] [Indexed: 07/09/2023] Open
Abstract
Equine infectious anemia virus (EIAV) is a member of the lentivirus genus in the Retroviridae family and is considered an animal model for HIV/AIDS research. An attenuated EIAV vaccine, which was successfully developed in the 1970s by classical serial passage techniques, is the first and only lentivirus vaccine that has been widely used to date. Restriction factors are cellular proteins that provide an early line of defense against viral replication and spread by interfering with various critical steps in the viral replication cycle. However, viruses have evolved specific mechanisms to overcome these host barriers through adaptation. The battle between the viruses and restriction factors is actually a natural part of the viral replication process, which has been well studied in human immunodeficiency virus type 1 (HIV-1). EIAV has the simplest genome composition of all lentiviruses, making it an intriguing subject for understanding how the virus employs its limited viral proteins to overcome restriction factors. In this review, we summarize the current literature on the interactions between equine restriction factors and EIAV. The features of equine restriction factors and the mechanisms by which the EIAV counteract the restriction suggest that lentiviruses employ diverse strategies to counteract innate immune restrictions. In addition, we present our insights on whether restriction factors induce alterations in the phenotype of the attenuated EIAV vaccine.
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Affiliation(s)
- Xue-Feng Wang
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Xiangmin Zhang
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Weiwei Ma
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Jiwei Li
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Xiaojun Wang
- State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, China.
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2
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Liang T, Li G, Lu Y, Hu M, Ma X. The Involvement of Ubiquitination and SUMOylation in Retroviruses Infection and Latency. Viruses 2023; 15:v15040985. [PMID: 37112965 PMCID: PMC10144533 DOI: 10.3390/v15040985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/15/2023] [Accepted: 04/16/2023] [Indexed: 04/29/2023] Open
Abstract
Retroviruses, especially the pathogenic human immunodeficiency virus type 1 (HIV-1), have severely threatened human health for decades. Retroviruses can form stable latent reservoirs via retroviral DNA integration into the host genome, and then be temporarily transcriptional silencing in infected cells, which makes retroviral infection incurable. Although many cellular restriction factors interfere with various steps of the life cycle of retroviruses and the formation of viral latency, viruses can utilize viral proteins or hijack cellular factors to evade intracellular immunity. Many post-translational modifications play key roles in the cross-talking between the cellular and viral proteins, which has greatly determined the fate of retroviral infection. Here, we reviewed recent advances in the regulation of ubiquitination and SUMOylation in the infection and latency of retroviruses, focusing on both host defense- and virus counterattack-related ubiquitination and SUMOylation system. We also summarized the development of ubiquitination- and SUMOylation-targeted anti-retroviral drugs and discussed their therapeutic potential. Manipulating ubiquitination or SUMOylation pathways by targeted drugs could be a promising strategy to achieve a "sterilizing cure" or "functional cure" of retroviral infection.
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Affiliation(s)
- Taizhen Liang
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, Guangzhou 511400, China
- Guangzhou Laboratory, Guangzhou International Bio-Island, Guangzhou 510005, China
| | - Guojie Li
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, Guangzhou 511400, China
- Guangzhou Laboratory, Guangzhou International Bio-Island, Guangzhou 510005, China
| | - Yunfei Lu
- Guangzhou Laboratory, Guangzhou International Bio-Island, Guangzhou 510005, China
| | - Meilin Hu
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, Guangzhou 511400, China
- Guangzhou Laboratory, Guangzhou International Bio-Island, Guangzhou 510005, China
| | - Xiancai Ma
- State Key Laboratory of Respiratory Disease, Guangzhou Medical University, Guangzhou 511400, China
- Guangzhou Laboratory, Guangzhou International Bio-Island, Guangzhou 510005, China
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
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3
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Olety B, Peters P, Wu Y, Usami Y, Göttlinger H. HIV-1 propagation is highly dependent on basal levels of the restriction factor BST2. SCIENCE ADVANCES 2021; 7:eabj7398. [PMID: 34714669 PMCID: PMC8555903 DOI: 10.1126/sciadv.abj7398] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/09/2021] [Indexed: 05/22/2023]
Abstract
BST2 is an interferon-inducible antiviral host protein antagonized by HIV-1 Vpu that entraps nascent HIV-1 virions on the cell surface. Unexpectedly, we find that HIV-1 lacking Nef can revert to full replication competence simply by losing the ability to antagonize BST2. Using gene editing together with cell sorting, we demonstrate that even the propagation of wild-type HIV-1 is strikingly dependent on BST2, including in primary human cells. HIV-1 propagation in BST2−/− populations can be fully rescued by exogenous BST2 irrespective of its capacity to signal and even by an artificial BST2-like protein that shares its virion entrapment activity but lacks sequence homology. Counterintuitively, our results reveal that HIV-1 propagation is critically dependent on basal levels of virion tethering by a key component of innate antiviral immunity.
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Retroviral Restriction Factors and Their Viral Targets: Restriction Strategies and Evolutionary Adaptations. Microorganisms 2020; 8:microorganisms8121965. [PMID: 33322320 PMCID: PMC7764263 DOI: 10.3390/microorganisms8121965] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/30/2020] [Accepted: 12/08/2020] [Indexed: 12/17/2022] Open
Abstract
The evolutionary conflict between retroviruses and their vertebrate hosts over millions of years has led to the emergence of cellular innate immune proteins termed restriction factors as well as their viral antagonists. Evidence accumulated in the last two decades has substantially increased our understanding of the elaborate mechanisms utilized by these restriction factors to inhibit retroviral replication, mechanisms that either directly block viral proteins or interfere with the cellular pathways hijacked by the viruses. Analyses of these complex interactions describe patterns of accelerated evolution for these restriction factors as well as the acquisition and evolution of their virus-encoded antagonists. Evidence is also mounting that many restriction factors identified for their inhibition of specific retroviruses have broader antiviral activity against additional retroviruses as well as against other viruses, and that exposure to these multiple virus challenges has shaped their adaptive evolution. In this review, we provide an overview of the restriction factors that interfere with different steps of the retroviral life cycle, describing their mechanisms of action, adaptive evolution, viral targets and the viral antagonists that evolved to counter these factors.
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5
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Schouest B, Leslie GJ, Hoxie JA, Maness NJ. Tetherin downmodulation by SIVmac Nef lost with the H196Q escape variant is restored by an upstream variant. PLoS One 2020; 15:e0225420. [PMID: 32764749 PMCID: PMC7413475 DOI: 10.1371/journal.pone.0225420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 07/13/2020] [Indexed: 01/17/2023] Open
Abstract
The H196 residue in SIVmac239 Nef is conserved across the majority of HIV and SIV isolates, lies immediately adjacent to the AP-2 (adaptor protein 2) binding di-leucine domain (ExxxLM195), and is critical for several described AP-2 dependent Nef functions, including the downregulation of tetherin (BST-2/CD317), CD4, and others. Surprisingly, many stocks of the closely related SIVmac251 swarm virus harbor a nef allele encoding a Q196. In SIVmac239, this variant is associated with loss of multiple AP-2 dependent functions. Publicly available sequences for SIVmac251 stocks were mined for variants linked to Q196 that might compensate for functional defects associated with this residue. Variants were engineered into the SIVmac239 backbone and in Nef expression plasmids and flow cytometry was used to examine surface tetherin expression in primary CD4 T cells and surface CD4 expression in SupT1 cells engineered to express rhesus CD4. We found that SIVmac251 stocks that encode a Q196 residue in Nef uniformly also encode an upstream R191 residue. We show that R191 restores the ability of Nef to downregulate tetherin in the presence of Q196 and has a similar but less pronounced impact on CD4 expression. However, a published report showed Q196 commonly evolves to H196 in vivo, suggesting a fitness cost. R191 may represent compensatory evolution to restore the ability to downregulate tetherin lost in viruses harboring Q196.
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Affiliation(s)
- Blake Schouest
- Division of Microbiology, Tulane National Primate Research Center, Covington, LA, United States of America
| | - George J. Leslie
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
| | - James A. Hoxie
- Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States of America
| | - Nicholas J. Maness
- Division of Microbiology, Tulane National Primate Research Center, Covington, LA, United States of America
- Department of Microbiology and Immunology, School of Medicine, Tulane University Health Sciences Center, New Orleans, LA, United States of America
- * E-mail:
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6
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Giese S, Lawrence SP, Mazzon M, Nijmeijer BM, Marsh M. The Nef Protein of the Macrophage Tropic HIV-1 Strain AD8 Counteracts Human BST-2/Tetherin. Viruses 2020; 12:E459. [PMID: 32325729 PMCID: PMC7232323 DOI: 10.3390/v12040459] [Citation(s) in RCA: 4] [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: 02/10/2020] [Revised: 04/15/2020] [Accepted: 04/15/2020] [Indexed: 12/12/2022] Open
Abstract
Bone Marrow Stromal Cell Antigen 2 (BST-2)/tetherin inhibits the release of numerous enveloped viruses by physically tethering nascent particles to infected cells during the process of viral budding from the cell surface. Tetherin also restricts human immunodeficiency virus (HIV), and pandemic main (M) group HIV type 1s (HIV-1s) are thought to rely exclusively on their Vpu proteins to overcome tetherin-mediated restriction of virus release. However, at least one M group HIV-1 strain, the macrophage-tropic primary AD8 isolate, is unable to express Vpu due to a mutation in its translation initiation codon. Here, using primary monocyte-derived macrophages (MDMs), we show that AD8 Nef protein can compensate for the absence of Vpu and restore virus release to wild type levels. We demonstrate that HIV-1 AD8 Nef reduces endogenous cell surface tetherin levels, physically separating it from the site of viral budding, thus preventing HIV retention. Mechanistically, AD8 Nef enhances internalisation of the long isoform of human tetherin, leading to perinuclear accumulation of the restriction factor. Finally, we show that Nef proteins from other HIV strains also display varying degrees of tetherin antagonism. Overall, we show that M group HIV-1s can use an accessory protein other than Vpu to antagonise human tetherin.
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Affiliation(s)
| | | | | | | | - Mark Marsh
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; (S.G.); (S.P.L.); (M.M.); (B.M.N.)
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Tavakoli-Tameh A, Janaka SK, Zarbock K, O’Connor S, Crosno K, Capuano S, Uno H, Lifson JD, Evans DT. Loss of tetherin antagonism by Nef impairs SIV replication during acute infection of rhesus macaques. PLoS Pathog 2020; 16:e1008487. [PMID: 32302364 PMCID: PMC7190186 DOI: 10.1371/journal.ppat.1008487] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 04/29/2020] [Accepted: 03/21/2020] [Indexed: 12/13/2022] Open
Abstract
Most simian immunodeficiency viruses use Nef to counteract the tetherin proteins of their nonhuman primate hosts. Nef also downmodulates cell-surface CD4 and MHC class I (MHC I) molecules and enhances viral infectivity by counteracting SERINC5. We previously demonstrated that tetherin antagonism by SIV Nef is genetically separable from CD4- and MHC I-downmodulation. Here we show that disruption of tetherin antagonism by Nef impairs virus replication during acute SIV infection of rhesus macaques. A combination of mutations was introduced into the SIVmac239 genome resulting in three amino acid substitutions in Nef that impair tetherin antagonism, but not CD3-, CD4- or MHC I-downmodulation. Further characterization of this mutant (SIVmac239AAA) revealed that these changes also result in partial sensitivity to SERINC5. Separate groups of four rhesus macaques were infected with either wild-type SIVmac239 or SIVmac239AAA, and viral RNA loads in plasma and sequence changes in the viral genome were monitored. Viral loads were significantly lower during acute infection in animals infected with SIVmac239AAA than in animals infected with wild-type SIVmac239. Sequence analysis of the virus population in plasma confirmed that the substitutions in Nef were retained during acute infection; however, changes were observed by week 24 post-infection that fully restored anti-tetherin activity and partially restored anti-SERINC5 activity. These observations reveal overlap in the residues of SIV Nef required for counteracting tetherin and SERINC5 and selective pressure to overcome these restriction factors in vivo.
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Affiliation(s)
- Aidin Tavakoli-Tameh
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sanath Kumar Janaka
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Katie Zarbock
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Shelby O’Connor
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kristin Crosno
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Saverio Capuano
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Hajime Uno
- Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Jeffrey D. Lifson
- AIDS and Cancer Virus Program, Leidos Biomedical Research Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
| | - David T. Evans
- Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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8
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Abstract
The accessory protein Nef of human immunodeficiency virus (HIV) is a primary determinant of viral pathogenesis. Nef is abundantly expressed during infection and reroutes a variety of cell surface proteins to disrupt host immunity and promote the viral replication cycle. Nef counteracts host defenses by sequestering and/or degrading its targets via the endocytic and secretory pathways. Nef does this by physically engaging a number of host trafficking proteins. Substantial progress has been achieved in identifying the targets of Nef, and a structural and mechanistic understanding of Nef's ability to command the protein trafficking machinery has recently started to coalesce. Comparative analysis of HIV and simian immunodeficiency virus (SIV) Nef proteins in the context of recent structural advances sheds further light on both viral evolution and the mechanisms whereby trafficking is hijacked. This review describes how advances in cell and structural biology are uncovering in growing detail how Nef subverts the host immune system, facilitates virus release, and enhances viral infectivity.
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9
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Suppression of µ1 subunit of the adaptor protein complex 2 reduces dengue virus release. Virus Genes 2019; 56:27-36. [PMID: 31720911 DOI: 10.1007/s11262-019-01710-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 10/28/2019] [Indexed: 01/16/2023]
Abstract
Dengue virus (DENV) requires clathrin-mediated endocytosis for its entry into the cells where the adaptor protein complex (AP) is vital for the clathrin-coated vesicle formation. The role of AP-2 was previously examined in the early stages of DENV infection; however, the role of AP-2 in the late stage of DENV infection was not determined. The µ1 subunit of AP-2 (AP2M1) is one of the most important cytoplasmic carrier domains in clathrin-mediated endocytosis and the phosphorylation of this subunit by the kinase enzyme, AP-2 associated protein kinase 1 (AAK1), stimulates clathrin and supports the cell surface receptor incorporation. In the present study, we primarily aimed to investigate the role of AP2M1 by gene silencing approach as well as using naked DENV RNA transfection into AP2M1 knockdown cells. Secondarily, an inhibitor of AAK1, sunitinib was used to investigate whether AAK1 could influence the virus production in DENV-infected Huh7 cells. The knockdown of AP2M1 in the DENV-infected Huh7 cells displayed a reduction in the viral titer at 24 h post-infection. Furthermore, experiments were conducted to bypass the DENV internalization using a naked DENV RNA transfection into the AP2M1 knockdown cells. Higher intracellular DENV RNA, DENV E protein, and intracellular virion were observed, whereas the extracellular virion production was comparably less than that of control. Treatment with sunitinib in DENV-infected Huh7 cells was able to reduce extracellular virion production and was consistent with all four serotypes of DENV. Therefore, our findings demonstrate the role of AP2M1 in the exocytosis step of DENV replication leading to infectious DENV production and the efficacy of sunitinib in suppressing virus production during the infection with different serotypes of DENV.
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Johnson WE, McCarthy KR. Complex Problems Require Ternary Solutions: Another Lesson from SIV Nef. Cell Host Microbe 2019; 26:299-300. [PMID: 31513765 DOI: 10.1016/j.chom.2019.08.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this issue of Cell Host & Microbe, Buffalo et al. describe a cryo-EM structure of SIV Nef complexed with AP-2 and tetherin. The structure helps explain why human tetherin is Nef-resistant and why lentiviruses that successfully emerged in humans (HIV-1 and HIV-2) had to evolve novel anti-tetherin strategies.
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Affiliation(s)
- Welkin E Johnson
- Biology Department, Boston College, Chestnut Hill, MA 02467, USA.
| | - Kevin R McCarthy
- Laboratory of Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Buffalo CZ, Stürzel CM, Heusinger E, Kmiec D, Kirchhoff F, Hurley JH, Ren X. Structural Basis for Tetherin Antagonism as a Barrier to Zoonotic Lentiviral Transmission. Cell Host Microbe 2019; 26:359-368.e8. [PMID: 31447307 DOI: 10.1016/j.chom.2019.08.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 07/05/2019] [Accepted: 07/31/2019] [Indexed: 12/25/2022]
Abstract
Tetherin is a host defense factor that physically prevents virion release from the plasma membrane. The Nef accessory protein of simian immunodeficiency virus (SIV) engages the clathrin adaptor AP-2 to downregulate tetherin via its DIWK motif. As human tetherin lacks DIWK, antagonism of tetherin by Nef is a barrier to simian-human transmission of non-human primate lentiviruses. To determine the molecular basis for tetherin counteraction, we reconstituted the AP-2 complex with a simian tetherin and SIV Nef and determined its structure by cryoelectron microscopy (cryo-EM). Nef refolds the first α-helix of the β2 subunit of AP-2 to a β hairpin, creating a binding site for the DIWK sequence. The tetherin binding site in Nef is distinct from those of most other Nef substrates, including MHC class I, CD3, and CD4 but overlaps with the site for the restriction factor SERINC5. This structure explains the dependence of SIVs on tetherin DIWK and consequent barrier to human transmission.
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Affiliation(s)
- Cosmo Z Buffalo
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Christina M Stürzel
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Elena Heusinger
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Dorota Kmiec
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - James H Hurley
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - Xuefeng Ren
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.
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12
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Current advances in HIV vaccine preclinical studies using Macaque models. Vaccine 2019; 37:3388-3399. [PMID: 31088747 DOI: 10.1016/j.vaccine.2019.04.094] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 04/02/2019] [Accepted: 04/30/2019] [Indexed: 02/06/2023]
Abstract
The macaque simian or simian/human immunodeficiency virus (SIV/SHIV) challenge model has been widely used to inform and guide human vaccine trials. Substantial advances have been made recently in the application of repeated-low-dose challenge (RLD) approach to assess SIV/SHIV vaccine efficacies (VE). Some candidate HIV vaccines have shown protective effects in preclinical studies using the macaque SIV/SHIV model but the model's true predictive value for screening potential HIV vaccine candidates needs to be evaluated further. Here, we review key parameters used in the RLD approach and discuss their relevance for evaluating VE to improve preclinical studies of candidate HIV vaccines.
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13
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Morris KL, Buffalo CZ, Stürzel CM, Heusinger E, Kirchhoff F, Ren X, Hurley JH. HIV-1 Nefs Are Cargo-Sensitive AP-1 Trimerization Switches in Tetherin Downregulation. Cell 2019; 174:659-671.e14. [PMID: 30053425 DOI: 10.1016/j.cell.2018.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 04/27/2018] [Accepted: 07/03/2018] [Indexed: 01/08/2023]
Abstract
The HIV accessory protein Nef counteracts immune defenses by subverting coated vesicle pathways. The 3.7 Å cryo-EM structure of a closed trimer of the clathrin adaptor AP-1, the small GTPase Arf1, HIV-1 Nef, and the cytosolic tail of the restriction factor tetherin suggested a mechanism for inactivating tetherin by Golgi retention. The 4.3 Å structure of a mutant Nef-induced dimer of AP-1 showed how the closed trimer is regulated by the dileucine loop of Nef. HDX-MS and mutational analysis were used to show how cargo dynamics leads to alternative Arf1 trimerization, directing Nef targets to be either retained at the trans-Golgi or sorted to lysosomes. Phosphorylation of the NL4-3 M-Nef was shown to regulate AP-1 trimerization, explaining how O-Nefs lacking this phosphosite counteract tetherin but most M-Nefs do not. These observations show how the higher-order organization of a vesicular coat can be allosterically modulated to direct cargoes to distinct fates.
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Affiliation(s)
- Kyle L Morris
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Cosmo Z Buffalo
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Christina M Stürzel
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Elena Heusinger
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Xuefeng Ren
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.
| | - James H Hurley
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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14
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Strain-Specific Antagonism of the Human H1N1 Influenza A Virus against Equine Tetherin. Viruses 2018; 10:v10050264. [PMID: 29772683 PMCID: PMC5977257 DOI: 10.3390/v10050264] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/11/2018] [Accepted: 05/14/2018] [Indexed: 12/16/2022] Open
Abstract
Tetherin/BST-2/CD317 is an interferon-induced host restriction factor that can block the budding of enveloped viruses by tethering them to the cell surface. Many viruses use certain proteins to counteract restriction by tetherin from their natural hosts, but not from other species. The influenza A virus (FLUAV) has a wide range of subtypes with different host tropisms. Human tetherin (huTHN) has been reported to restrict only specific FLUAV strains and the viral hemagglutinin (HA) and neuraminidase (NA) genes determine the sensitivity to huTHN. Whether tetherins from other hosts can block human FLUAV is still unknown. Here, we evaluate the impact of equine tetherin (eqTHN) and huTHN on the replication of A/Sichuan/1/2009 (H1N1) and A/equine/Xinjiang/1/2007 (H3N8) strains. Our results show that eqTHN had higher restriction activity towards both viruses, and its shorter cytoplasmic tail contributed to that activity. We further demonstrated that HA and NA of A/Hamburg/4/2009 (H1N1) could counteract eqTHN. Notably, our results indicate that four amino acids, 13T and 49L of HA and 32T and 80V of NA, were involved in blocking the restriction activity of eqTHN. These findings reveal interspecies restriction by eqTHN towards FLUAV, and the role of the HA and NA proteins in overcoming this restriction.
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15
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Maintenance of AP-2-Dependent Functional Activities of Nef Restricts Pathways of Immune Escape from CD8 T Lymphocyte Responses. J Virol 2018; 92:JVI.01822-17. [PMID: 29237831 DOI: 10.1128/jvi.01822-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 12/02/2017] [Indexed: 01/28/2023] Open
Abstract
Nef-specific CD8+ T lymphocytes (CD8TL) are linked to extraordinary control of primate lentiviral replication, but the mechanisms underlying their efficacy remain largely unknown. The immunodominant, Mamu-B*017:01+-restricted Nef195-203MW9 epitope in SIVmac239 partially overlaps a sorting motif important for interactions with host AP-2 proteins and, hence, downmodulation of several host proteins, including Tetherin (CD317/BST-2), CD28, CD4, SERINC3, and SERINC5. We reasoned that CD8TL-driven evolution in this epitope might compromise Nef's ability to modulate these important molecules. Here, we used deep sequencing of SIV from nine B*017:01+ macaques throughout infection with SIVmac239 to characterize the patterns of viral escape in this epitope and then assayed the impacts of these variants on Nef-mediated modulation of multiple host molecules. Acute variation in multiple Nef195-203MW9 residues significantly compromised Nef's ability to downregulate surface Tetherin, CD4, and CD28 and reduced its ability to prevent SERINC5-mediated reduction in viral infectivity but did not impact downregulation of CD3 or major histocompatibility complex class I, suggesting the selective disruption of immunomodulatory pathways involving Nef AP-2 interactions. Together, our data illuminate a pattern of viral escape dictated by a selective balance to maintain AP-2-mediated downregulation while evading epitope-specific CD8TL responses. These data could shed light on mechanisms of both CD8TL-driven viral control generally and on Mamu-B*017:01-mediated viral control specifically.IMPORTANCE A rare subset of humans infected with HIV-1 and macaques infected with SIV can control the virus without aid of antiviral medications. A common feature of these individuals is the ability to mount unusually effective CD8 T lymphocyte responses against the virus. One of the most formidable aspects of HIV is its ability to evolve to evade immune responses, particularly CD8 T lymphocytes. We show that macaques that target a specific peptide in the SIV Nef protein are capable of better control of the virus and that, as the virus evolves to escape this response, it does so at a cost to specific functions performed by the Nef protein. Our results help show how the virus can be controlled by an immune response, which could help in designing effective vaccines.
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Foster TL, Pickering S, Neil SJD. Inhibiting the Ins and Outs of HIV Replication: Cell-Intrinsic Antiretroviral Restrictions at the Plasma Membrane. Front Immunol 2018; 8:1853. [PMID: 29354117 PMCID: PMC5758531 DOI: 10.3389/fimmu.2017.01853] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 12/07/2017] [Indexed: 01/01/2023] Open
Abstract
Like all viruses, human immunodeficiency viruses (HIVs) and their primate lentivirus relatives must enter cells in order to replicate and, once produced, new virions need to exit to spread to new targets. These processes require the virus to cross the plasma membrane of the cell twice: once via fusion mediated by the envelope glycoprotein to deliver the viral core into the cytosol; and secondly by ESCRT-mediated scission of budding virions during release. This physical barrier thus presents a perfect location for host antiviral restrictions that target enveloped viruses in general. In this review we will examine the current understanding of innate host antiviral defences that inhibit these essential replicative steps of primate lentiviruses associated with the plasma membrane, the mechanism by which these viruses have adapted to evade such defences, and the role that this virus/host battleground plays in the transmission and pathogenesis of HIV/AIDS.
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Affiliation(s)
- Toshana L Foster
- Department of Infectious Disease, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Suzanne Pickering
- Department of Infectious Disease, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
| | - Stuart J D Neil
- Department of Infectious Disease, School of Immunology and Microbial Sciences, King's College London, London, United Kingdom
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17
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Stoneham CA, Singh R, Jia X, Xiong Y, Guatelli J. Endocytic activity of HIV-1 Vpu: Phosphoserine-dependent interactions with clathrin adaptors. Traffic 2017; 18:545-561. [PMID: 28504462 DOI: 10.1111/tra.12495] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 05/09/2017] [Accepted: 05/10/2017] [Indexed: 10/19/2022]
Abstract
HIV-1 Vpu modulates cellular transmembrane proteins to optimize viral replication and provide immune-evasion, triggering ubiquitin-mediated degradation of some targets but also modulating endosomal trafficking to deplete them from the plasma membrane. Interactions between Vpu and the heterotetrameric clathrin adaptor protein (AP) complexes AP-1 and AP-2 have been described, yet the molecular basis and functional roles of such interactions are incompletely defined. To investigate the trafficking signals encoded by Vpu, we fused the cytoplasmic domain (CD) of Vpu to the extracellular and transmembrane domains of the CD8 α-chain. CD8-VpuCD was rapidly endocytosed in a clathrin- and AP-2-dependent manner. Multiple determinants within the Vpu CD contributed to endocytic activity, including phosphoserines of the β-TrCP binding site and a leucine-based ExxxLV motif. Using recombinant proteins, we confirmed ExxxLV-dependent binding of the Vpu CD to the α/σ2 subunit hemicomplex of AP-2 and showed that this is enhanced by serine-phosphorylation. Remarkably, the Vpu CD also bound directly to the medium (μ) subunits of AP-2 and AP-1; this interaction was dependent on serine-phosphorylation of Vpu and on basic residues in the μ subunits. We propose that the flexibility with which Vpu binds AP complexes broadens the range of cellular targets that it can misdirect to the virus' advantage.
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Affiliation(s)
- Charlotte A Stoneham
- Department of Medicine, University of California at San Diego, La Jolla, California.,VA San Diego Healthcare System, San Diego, California
| | - Rajendra Singh
- Department of Medicine, University of California at San Diego, La Jolla, California.,VA San Diego Healthcare System, San Diego, California
| | - Xiaofei Jia
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - John Guatelli
- Department of Medicine, University of California at San Diego, La Jolla, California.,VA San Diego Healthcare System, San Diego, California
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18
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Tetherin Antagonism by HIV-1 Group M Nef Proteins. J Virol 2016; 90:10701-10714. [PMID: 27654287 DOI: 10.1128/jvi.01465-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 09/12/2016] [Indexed: 12/20/2022] Open
Abstract
Although Nef is the viral gene product used by most simian immunodeficiency viruses to overcome restriction by tetherin, this activity was acquired by the Vpu protein of HIV-1 group M due to the absence of sequences in human tetherin that confer susceptibility to Nef. Thus, it is widely accepted that HIV-1 group M uses Vpu instead of Nef to counteract tetherin. Challenging this paradigm, we identified Nef alleles of HIV-1 group M isolates with significant activity against human tetherin. These Nef proteins promoted virus release and tetherin downmodulation from the cell surface and, in the context of vpu-deleted HIV-1 recombinants, enhanced virus replication and resistance to antibody-dependent cell-mediated cytotoxicity (ADCC). Further analysis revealed that the Vpu proteins from several of these viruses lack antitetherin activity, suggesting that under certain circumstances, HIV-1 group M Nef may acquire the ability to counteract tetherin to compensate for the loss of this function by Vpu. These observations illustrate the remarkable plasticity of HIV-1 in overcoming restriction by tetherin and challenge the prevailing view that all HIV-1 group M isolates use Vpu to counteract tetherin. IMPORTANCE Most viruses of HIV-1 group M, the main group of HIV-1 responsible for the global AIDS pandemic, use their Vpu proteins to overcome restriction by tetherin (BST-2 or CD317), which is a transmembrane protein that inhibits virus release from infected cells. Here we show that the Nef proteins of certain HIV-1 group M isolates can acquire the ability to counteract tetherin. These results challenge the current paradigm that HIV-1 group M exclusively uses Vpu to counteract tetherin and underscore the importance of tetherin antagonism for efficient viral replication.
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A pilot study on interaction between donkey tetherin and EIAV stains with different virulent and replication characteristics. Microb Pathog 2016; 106:65-68. [PMID: 27816678 DOI: 10.1016/j.micpath.2016.10.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Revised: 09/27/2016] [Accepted: 10/31/2016] [Indexed: 11/22/2022]
Abstract
Tetherin (BST-2) is an important host restriction factor that can inhibit the release of a diverse array of enveloped viruses from infected cells. Conversely, to facilitate their release and spread, many viruses have evolved various strategies to overcome the antiviral effect of tetherin in a species-specific manner. During the development of an attenuated equine infectious anemia virus (EIAV) vaccine in our laboratory, we found that serial passage of a field-isolated virulent EIAV strains in horse and donkey as well as the cultivated donkey cells, produces several typical EIAV strains, including EIAVDV, EIAVDLV, and EIAVFDDV, which exhibit distinct virulence and replication features in vivo and in vitro. However, the role of host restriction factors in EIAV evolution during the serial passage is not well understood. This study aimed to evaluate whether these newly generated strains adapt differently to donkey tetherin (do-tetherin) based on their virulence. We found that do-tetherin exerts an inhibition on the release of the viral particles produced by all three strains, albeit with varying intensity: EIAVDV < EIAVDLV < EIAVFDDV. Additionally, all three EIAV strains could counteract the restriction mediated by do-tetherin via their envelope proteins (Env) with varying strength: EIAVDV > EIAVDLV > EIAVFDDV. These results indicate that donkey tetherin is involved in shaping of EIAV evolution during serial passage.
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Differential Control of BST2 Restriction and Plasmacytoid Dendritic Cell Antiviral Response by Antagonists Encoded by HIV-1 Group M and O Strains. J Virol 2016; 90:10236-10246. [PMID: 27581991 DOI: 10.1128/jvi.01131-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/29/2016] [Indexed: 12/15/2022] Open
Abstract
BST2/tetherin is a type I interferon (IFN-I)-stimulated host factor that restricts the release of HIV-1 by entrapping budding virions at the cell surface. This membrane-associated protein can also engage and activate the plasmacytoid dendritic cell (pDC)-specific immunoglobulin-like transcript 7 (ILT7) inhibitory receptor to downregulate the IFN-I response by pDCs. Pandemic HIV-1 group M uses Vpu (M-Vpu) to counteract the two BST2 isoforms (long and short) that are expressed in human cells. M-Vpu efficiently downregulates surface long BST2, while it displaces short BST2 molecules away from viral assembly sites. We recently found that this attribute is used by M-Vpu to activate the BST2/ILT7-dependent negative-feedback pathway and to suppress pDC IFN-I responses during sensing of infected cells. However, whether this property is conserved in endemic HIV-1 group O, which has evolved Nef (O-Nef) to counteract specifically the long BST2 isoform, remains unknown. In the present study, we validated that O-Nefs have the capacity to downregulate surface BST2 and enhance HIV-1 particle release although less efficiently than M-Vpu. In contrast to M-Vpu, O-Nef did not efficiently enhance viral spread in T cell culture or displace short BST2 from viral assembly sites to prevent its occlusion by tethered HIV-1 particles. Consequently, O-Nef impairs the ability of BST2 to activate negative ILT7 signaling to suppress the IFN-I response by pDC-containing peripheral blood mononuclear cells (PBMCs) during sensing of infected cells. These distinctive features of BST2 counteraction by O-Nefs may in part explain the limited spread of HIV-1 group O in the human population. IMPORTANCE The geographical distributions and prevalences of different HIV-1 groups show large variations. Understanding drivers of distinctive viral spread may aid in the development of therapeutic strategies for controlling the spread of HIV-1 pandemic strains. The differential spread of HIV-1 groups appears to be linked to their capacities to antagonize the long and short isoforms of the BST2 restriction factor. We found that the endemic HIV-1 group O-encoded BST2 antagonist Nef is unable to counteract the restriction mediated by short BST2, a condition that impairs its ability to activate ILT7 and suppress pDC antiviral responses. This is in contrast to the pandemic HIV-1 group M-specified BST2 countermeasure Vpu, which displays a diverse array of mechanisms to counteract short and long BST2 isoforms, an attribute that allows the effective control of pDC antiviral responses. These findings may help explain the limited spread of HIV-1 group O as well as the continued predominance of HIV-1 group M throughout the world.
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Liu Y, Li M, Zhang D, Zhang M, Hu Q. HSV-2 glycoprotein gD targets the CC domain of tetherin and promotes tetherin degradation via lysosomal pathway. Virol J 2016; 13:154. [PMID: 27630089 PMCID: PMC5024446 DOI: 10.1186/s12985-016-0610-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/08/2016] [Indexed: 11/16/2022] Open
Abstract
Background HSV-2 is the major cause of genital herpes. We previously demonstrated that the host viral restriction factor tetherin restricts HSV-2 release and is antagonized by several HSV-2 glycoproteins. However, the mechanisms underlying HSV-2 glycoproteins mediated counteraction of tetherin remain unclear. In this study, we investigated whether tetherin restricts the cell-to-cell spread of HSV-2 and the mechanisms underlying HSV-2 gD mediated antagonism of tetherin. Methods Infectious center assays were used to test whether tetherin could affect cell-to-cell spread of HSV-2. Coimmunoprecipitation assays were performed to map the tetherin domains required for HSV-2 gD-mediated downregulation. Immunoflurence assays were performed to detect the accumulation of tetherin in lysosomes or proteasomes. All experiments were repeated for at least three times and the data were performed statistical analysis. Results 1) Tetherin restricts cell-to-cell spread of HSV-2; 2) HSV-2 gD specifically interacts with the CC domain of tetherin; 3) HSV-2 gD promotes tetherin to the lysosomal degradation pathway. Conclusions Tetherin not only restricts HSV-2 release but also its cell-to-cell spread. In turn, HSV-2 gD targets the CC domain of tetherin and promotes its degradation in the lysosome. Findings in this study have increased our understanding of tetherin restriction and viral countermeasures.
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Affiliation(s)
- Yalan Liu
- State Key Laboratory of Virology, Chinese Academy of Sciences, Wuhan Institute of Virology, Wuhan, 430071, China.
| | - Mei Li
- State Key Laboratory of Virology, Chinese Academy of Sciences, Wuhan Institute of Virology, Wuhan, 430071, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Di Zhang
- State Key Laboratory of Virology, Chinese Academy of Sciences, Wuhan Institute of Virology, Wuhan, 430071, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Mudan Zhang
- State Key Laboratory of Virology, Chinese Academy of Sciences, Wuhan Institute of Virology, Wuhan, 430071, China
| | - Qinxue Hu
- State Key Laboratory of Virology, Chinese Academy of Sciences, Wuhan Institute of Virology, Wuhan, 430071, China.,Institute for Infection and Immunity, St George's University of London, London, SW17 0RE, UK
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22
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Kong N, Meng Q, Wu Y, Wang Z, Zuo Y, Tong W, Zheng H, Li G, Yang S, Yu H, Shan T, Zhou EM, Tong G. Monoclonal Antibody to Bone Marrow Stromal Cell Antigen 2 Protein of Swine. Monoclon Antib Immunodiagn Immunother 2016; 35:172-6. [PMID: 27148642 DOI: 10.1089/mab.2016.0007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The bone marrow stromal cell antigen 2 (BST-2) protein was identified as a novel virus restriction factor that potently restricts the replication and egress of enveloped viruses. In this study, we generated monoclonal antibodies (MAbs) against porcine BST-2 encoding 34-112 aa of porcine BST-2, which was cloned and inserted into the prokaryotic expression vector pCold-I to construct a recombinant plasmid pCold-pBST-2. The recombinant porcine BST-2 protein (rpBST-2 protein) was induced by isopropyl-β-D-thiogalactoside in Escherichia coli BL21 (DE3). Then, BALB/c mice were immunized with the purified rpBST-2 protein to prepare MAbs of BST-2. After subcloning, one strain of hybridoma cells named 1B2 secreting porcine BST-2 protein monoclonal antibody (MAb) was obtained. Indirect immunofluorescence assay and western blot analysis showed that the MAb was specifically reacted with the overexpressed porcine BST-2 protein in Vero cells. The specific MAb of porcine BST-2 provides a valuable tool for further studies of BST-2 to restrict virus infection.
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Affiliation(s)
- Ning Kong
- 1 Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University , Yangling, China .,2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Qiong Meng
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Yongguang Wu
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Zhongze Wang
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Yewen Zuo
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Wu Tong
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - Hao Zheng
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - Guoxin Li
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - Shen Yang
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - Hai Yu
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - Tongling Shan
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
| | - En-Min Zhou
- 1 Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University , Yangling, China
| | - Guangzhi Tong
- 2 Department of Swine Infectious Disease, Shanghai Veterinary Research Institute , Chinese Academy of Agricultural Sciences, Shanghai, China .,3 Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses , Yangzhou, China
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23
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Mahauad-Fernandez WD, Okeoma CM. BST-2: at the crossroads of viral pathogenesis and oncogenesis. Future Virol 2016. [DOI: 10.2217/fvl.15.113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BST-2 is a moonlight protein with several protective and deleterious functions. Regulation of virus restriction and tumor aggressiveness are the most studied aspects of BST-2 function and thus, the main focus of this perspective. Virus inhibition roles of BST-2 have therapeutic potential that, if properly harnessed, could result in near broad spectrum antiviral. However, the involvement of BST-2 in cancer calls for additional studies on BST-2 biology and re-evaluation of the overall role of BST-2 in host protection, as it appears that BST-2 has pleiotropic effects in the host. Here, we analyze the antiviral and protumor roles of BST-2. We also discuss potential therapeutic options for BST-2 against viral infection and cancer.
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Affiliation(s)
- Wadie D Mahauad-Fernandez
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Interdisciplinary Program in Molecular & Cellular Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Chioma M Okeoma
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
- Interdisciplinary Program in Molecular & Cellular Biology, University of Iowa, Iowa City, IA 52242, USA
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Ohta K, Goto H, Yumine N, Nishio M. Human parainfluenza virus type 2 V protein inhibits and antagonizes tetherin. J Gen Virol 2015; 97:561-570. [PMID: 26675672 DOI: 10.1099/jgv.0.000373] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tetherin (BST-2/CD317/HM1.24) is an antiviral membrane protein that prevents the release of enveloped viruses from the cell surface. We found that the growth of human parainfluenza virus type 2 (hPIV-2), but not that of V protein-deficient recombinant hPIV-2, was inhibited by tetherin. V protein immunoprecipitates with tetherin, and this interaction requires its C-terminal Trp residues. The glycosyl phosphatidylinositol attachment signal of tetherin, but not its cytoplasmic tail, was necessary for its binding with V. The distribution of the V protein clearly changed when co-expressed with tetherin in plasmid-transfected cells. hPIV-2 infection of HeLa cells reduced cell surface tetherin without affecting total cellular tetherin. This reduction also occurred in HeLa cells constitutively expressing V, whereas mutated V protein did not affect the cell surface tetherin. Our results suggest that hPIV-2 V protein antagonizes tetherin by binding it and reducing its presence at the cell surface.
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Affiliation(s)
- K Ohta
- Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayama, Japan
| | - H Goto
- Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayama, Japan
| | - N Yumine
- Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayama, Japan
| | - M Nishio
- Department of Microbiology, School of Medicine, Wakayama Medical University, Wakayama, Japan
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Mahauad-Fernandez WD, Okeoma CM. The role of BST-2/Tetherin in host protection and disease manifestation. IMMUNITY INFLAMMATION AND DISEASE 2015; 4:4-23. [PMID: 27042298 PMCID: PMC4768070 DOI: 10.1002/iid3.92] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/07/2015] [Accepted: 11/09/2015] [Indexed: 12/21/2022]
Abstract
Host cells respond to viral infections by activating immune response genes that are not only involved in inflammation, but may also predispose cells to cancerous transformation. One such gene is BST‐2, a type II transmembrane protein with a unique topology that endows it tethering and signaling potential. Through this ability to tether and signal, BST‐2 regulates host response to viral infection either by inhibiting release of nascent viral particles or in some models inhibiting viral dissemination. However, despite its antiviral functions, BST‐2 is involved in disease manifestation, a function linked to the ability of BST‐2 to promote cell‐to‐cell interaction. Therefore, modulating BST‐2 expression and/or activity has the potential to influence course of disease.
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Affiliation(s)
- Wadie D Mahauad-Fernandez
- Department of MicrobiologyCarver College of MedicineUniversity of IowaIowa CityIA52242USA; Interdisciplinary Program in Molecular and Cellular BiologyUniversity of IowaIowa CityIA52242USA
| | - Chioma M Okeoma
- Department of MicrobiologyCarver College of MedicineUniversity of IowaIowa CityIA52242USA; Interdisciplinary Program in Molecular and Cellular BiologyUniversity of IowaIowa CityIA52242USA
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Mussil B, Javed A, Töpfer K, Sauermann U, Sopper S. Increased BST2 expression during simian immunodeficiency virus infection is not a determinant of disease progression in rhesus monkeys. Retrovirology 2015; 12:92. [PMID: 26554913 PMCID: PMC4641394 DOI: 10.1186/s12977-015-0219-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 10/23/2015] [Indexed: 12/21/2022] Open
Abstract
Background Bone marrow stromal cell antigen 2 (BST2), also known as tetherin, HM1.24 or CD317 represents a type 2 integral membrane protein, which has been described to restrict the production of some enveloped viruses by inhibiting the virus release from the cell surface. This innate antiviral mechanism is counteracted by the HIV-1 viral factor Vpu, targeting BST2 for cellular degradation. Since antiviral BST2 activity has been mainly confirmed by in vitro data, we investigated its role in vivo on the disease progression using the SIV/macaque model for AIDS. We determined BST2 expression in PBMC and leukocyte subsets of uninfected and SIV-infected rhesus macaques by real-time PCR and flow cytometry and correlated it with disease progression and viral load. Results Compared to pre-infection levels, we found increased BST2 expression in PBMC, purified CD4+ lymphocytes and CD14+ monocytes of SIV-infected animals, which correlated with viral load. Highest BST2 levels were found in progressors and lowest levels comparable to uninfected macaques were observed in long-term non-progressors (LTNPs). During acute viremia, BST2 mRNA increased in parallel with MX1, a prototype interferon-stimulated gene. This association was maintained during the whole disease course. Conclusion The detected relationship between BST2 expression and viral load as well as with MX1 indicate a common regulation by the interferon response and suggest rather limited influence of BST2 in vivo on the disease outcome. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0219-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Bianka Mussil
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Aneela Javed
- Unit of Infection Models, German Primate Centre, Goettingen, Germany. .,Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Science and Technology (NUST), H12, Islamabad, Pakistan.
| | - Katharina Töpfer
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Ulrike Sauermann
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Sieghart Sopper
- Department of Hematology and Oncology, Medical University Innsbruck, ZVG 7G5 009A, Anichstr. 35, 6020, Innsbruck, Austria. .,Tyrolean Cancer Research Institute, Innsbruck, Austria.
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The KT Jeang Retrovirology prize 2015: Paul Bieniasz. Retrovirology 2015; 12:84. [PMID: 26438335 PMCID: PMC4595249 DOI: 10.1186/s12977-015-0208-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 09/18/2015] [Indexed: 11/13/2022] Open
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Serine Phosphorylation of HIV-1 Vpu and Its Binding to Tetherin Regulates Interaction with Clathrin Adaptors. PLoS Pathog 2015; 11:e1005141. [PMID: 26317613 PMCID: PMC4552633 DOI: 10.1371/journal.ppat.1005141] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 08/11/2015] [Indexed: 02/07/2023] Open
Abstract
HIV-1 Vpu prevents incorporation of tetherin (BST2/ CD317) into budding virions and targets it for ESCRT-dependent endosomal degradation via a clathrin-dependent process. This requires a variant acidic dileucine-sorting motif (ExxxLV) in Vpu. Structural studies demonstrate that recombinant Vpu/tetherin fusions can form a ternary complex with the clathrin adaptor AP-1. However, open questions still exist about Vpu’s mechanism of action. Particularly, whether endosomal degradation and the recruitment of the E3 ubiquitin ligase SCFβTRCP1/2 to a conserved phosphorylated binding site, DSGNES, are required for antagonism. Re-evaluation of the phenotype of Vpu phosphorylation mutants and naturally occurring allelic variants reveals that the requirement for the Vpu phosphoserine motif in tetherin antagonism is dissociable from SCFβTRCP1/2 and ESCRT-dependent tetherin degradation. Vpu phospho-mutants phenocopy ExxxLV mutants, and can be rescued by direct clathrin interaction in the absence of SCFβTRCP1/2 recruitment. Moreover, we demonstrate physical interaction between Vpu and AP-1 or AP-2 in cells. This requires Vpu/tetherin transmembrane domain interactions as well as the ExxxLV motif. Importantly, it also requires the Vpu phosphoserine motif and adjacent acidic residues. Taken together these data explain the discordance between the role of SCFβTRCP1/2 and Vpu phosphorylation in tetherin antagonism, and indicate that phosphorylation of Vpu in Vpu/tetherin complexes regulates promiscuous recruitment of adaptors, implicating clathrin-dependent sorting as an essential first step in tetherin antagonism. Counteraction of tetherin, a host antiviral protein that blocks viral release from infected cells, is an essential attribute of HIV-1 and its related viruses. The HIV-1 accessory protein Vpu binds to tetherin, preventing its incorporation into viral particles, and targets it for ubiquitin-dependent degradation. This involves mis-trafficking of tetherin by a Vpu-dependent mechanism through the engagement of clathrin adaptor proteins. Although structural evidence exists for Vpu and tetherin interacting with clathrin adaptor 1 (AP-1), evidence that it is required for Vpu-mediated tetherin counteraction is still lacking. Tetherin degradation by Vpu also requires an E3 ubiquitin ligase, SCFβTRCP1/2 that binds to phosphorylated serine residues in the Vpu cytoplasmic tail. Again, discrepancies exist about the importance of this interaction in tetherin’s counteraction. Here we show that Vpu phosphorylation, in combination with its physical interaction with tetherin, regulates interaction with both AP-1 and the other major cellular clathrin adaptor, AP-2. These interactions can be decoupled from SCFβTRCP1/2 recruitment, thus indicating clathrin-dependent mis-trafficking as a critical step in tetherin antagonism by Vpu. Additionally, the ability to interact both with AP-1 and AP-2 in a tetherin-dependent manner indicates a redundancy in host cofactors used by Vpu that explains disparate previous observations of its mechanism of action.
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Bego MG, Côté É, Aschman N, Mercier J, Weissenhorn W, Cohen ÉA. Vpu Exploits the Cross-Talk between BST2 and the ILT7 Receptor to Suppress Anti-HIV-1 Responses by Plasmacytoid Dendritic Cells. PLoS Pathog 2015; 11:e1005024. [PMID: 26172439 PMCID: PMC4501562 DOI: 10.1371/journal.ppat.1005024] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 06/16/2015] [Indexed: 11/25/2022] Open
Abstract
Plasmacytoid dendritic cells (pDCs) constitute a major source of type-I interferon (IFN-I) production during acute HIV infection. Their activation results primarily from TLR7-mediated sensing of HIV-infected cells. However, the interactions between HIV-infected T cells and pDCs that modulate this sensing process remain poorly understood. BST2/Tetherin is a restriction factor that inhibits HIV release by cross-linking virions onto infected cell surface. BST2 was also shown to engage the ILT7 pDC-specific inhibitory receptor and repress TLR7/9-mediated IFN-I production by activated pDCs. Here, we show that Vpu, the HIV-1 antagonist of BST2, suppresses TLR7-mediated IFN-I production by pDC through a mechanism that relies on the interaction of BST2 on HIV-producing cells with ILT7. Even though Vpu downregulates surface BST2 as a mean to counteract the restriction on HIV-1 release, we also find that the viral protein re-locates remaining BST2 molecules outside viral assembly sites where they are free to bind and activate ILT7 upon cell-to-cell contact. This study shows that through a targeted regulation of surface BST2, Vpu promotes HIV-1 release and limits pDC antiviral responses upon sensing of infected cells. This mechanism of innate immune evasion is likely to be important for an efficient early viral dissemination during acute infection. Plasmacytoid dendritic cells (pDCs) produce large quantities of type I interferon (IFN-I) upon stimulation by many viruses, including HIV. Their activation is very effective following cell contacts with HIV-1-infected CD4+ T cells. We investigated whether HIV-1 could regulate the antiviral responses of pDCs triggered upon sensing of infected cells. We show that HIV-1 suppresses the levels of IFN-I produced by pDCs through a process that requires expression of the Vpu accessory protein in virus-producing cells. A well-described role of Vpu is to promote efficient HIV-1 production by counteracting BST2, a host factor that entraps nascent viral particle at the cell surface. Apart from its antiviral activity, BST2 was reported to inhibit IFN-I production by pDCs through binding and activation of the ILT7 pDC-specific inhibitory receptor. Our results reveal that through a highly sophisticated targeted regulation of BST2 levels at the surface of infected cells, Vpu promotes HIV-1 release and limits IFN-I production by pDCs via the negative signaling exerted by the BST2-ILT7 pair. Overall, this study sheds light on a novel Vpu-BST2 interaction that allows HIV-1 to escape pDC antiviral responses. This modulation of pDC antiviral response by HIV Vpu may facilitate the initial viral expansion during acute infection.
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Affiliation(s)
- Mariana G. Bego
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
| | - Édouard Côté
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
| | - Nick Aschman
- Université Grenoble Alpes, Unit of Virus Host Cell Interactions (UVHCI), CNRS, UVHCI, Grenoble, France
| | - Johanne Mercier
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
| | - Winfried Weissenhorn
- Université Grenoble Alpes, Unit of Virus Host Cell Interactions (UVHCI), CNRS, UVHCI, Grenoble, France
| | - Éric A. Cohen
- Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Department of Microbiology, Infectiology and Immunology, Université de Montréal, Montreal, Quebec, Canada
- * E-mail:
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Abstract
Tetherin represents an important barrier for successful cross-species transmissions of primate lentiviruses. HIV-1 overcame this obstacle by using Vpu as a countermeasure. However, Kluge and collaborators now show that HIV-1 group O uses Nef to antagonize tetherin, and that this activity may have contributed to its spread in West-Central Africa.
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Affiliation(s)
- Ruth Serra-Moreno
- Department of Biological Sciences, College of Arts and Sciences, Texas Tech University, 8(th) and Canton Avenue, Lubbock, TX 79409-3131, USA.
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Kluge SF, Mack K, Iyer SS, Pujol FM, Heigele A, Learn GH, Usmani SM, Sauter D, Joas S, Hotter D, Bibollet-Ruche F, Plenderleith LJ, Peeters M, Geyer M, Sharp PM, Fackler OT, Hahn BH, Kirchhoff F. Nef proteins of epidemic HIV-1 group O strains antagonize human tetherin. Cell Host Microbe 2014; 16:639-50. [PMID: 25525794 PMCID: PMC4274627 DOI: 10.1016/j.chom.2014.10.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 08/13/2014] [Accepted: 09/18/2014] [Indexed: 01/06/2023]
Abstract
Most simian immunodeficiency viruses use their Nef protein to antagonize the host restriction factor tetherin. A deletion in human tetherin confers Nef resistance, representing a hurdle to successful zoonotic transmission. HIV-1 group M evolved to utilize the viral protein U (Vpu) to counteract tetherin. Although HIV-1 group O has spread epidemically in humans, it has not evolved a Vpu-based tetherin antagonism. Here we show that HIV-1 group O Nef targets a region adjacent to this deletion to inhibit transport of human tetherin to the cell surface, enhances virion release, and increases viral resistance to inhibition by interferon-α. The Nef protein of the inferred common ancestor of group O viruses is also active against human tetherin. Thus, Nef-mediated antagonism of human tetherin evolved prior to the spread of HIV-1 group O and likely facilitated secondary virus transmission. Our results may explain the epidemic spread of HIV-1 group O.
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Affiliation(s)
- Silvia F Kluge
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Katharina Mack
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Shilpa S Iyer
- Departments of Medicine and Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - François M Pujol
- Department of Infectious Diseases, Integrative Virology, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Anke Heigele
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Gerald H Learn
- Departments of Medicine and Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Shariq M Usmani
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Daniel Sauter
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Simone Joas
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Dominik Hotter
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Frederic Bibollet-Ruche
- Departments of Medicine and Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | | | - Martine Peeters
- UMI233, TransVIHMI, Institut de Recherche pour le Développement (IRD) and Université Montpellier, Montpellier 34394, France
| | - Matthias Geyer
- Group Physical Biochemistry, Center of Advanced European Studies and Research, 53175 Bonn, Germany
| | - Paul M Sharp
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK
| | - Oliver T Fackler
- Department of Infectious Diseases, Integrative Virology, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Beatrice H Hahn
- Departments of Medicine and Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
| | - Frank Kirchhoff
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany.
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Wang X, Li C, Zhou L, Zhang N, Wang X, Ge X, Guo X, Yang H. Porcine reproductive and respiratory syndrome virus counteracts the porcine intrinsic virus restriction factors-IFITM1 and Tetherin in MARC-145 cells. Virus Res 2014; 191:92-100. [PMID: 25102331 DOI: 10.1016/j.virusres.2014.07.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/22/2014] [Accepted: 07/25/2014] [Indexed: 12/12/2022]
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) has been recognized to modulate the innate immune response of host. However, little is known about the effects of PRRSV infection on porcine intrinsic virus-restriction factors. This study presents the first demonstration that the nonstructural protein 3 (Nsp3) or envelope (E) protein of PRRSV interacted with porcine intrinsic virus-restriction factor IFITM1 or Tetherin. Next, in PRRSV-infected MARC-145 cells and the transfected cells with the IFITM1- or Tetherin-expressing plasmid, IFITM1 was shown to be mainly distributed perinuclear, and Tetherin was proposed to be partially removed away from cell surface. Moreover, the overexpression of IFITM1 and Tetherin were shown to have no obvious effects on the replication of PRRSV in MARC-145 cells. The Nsp3 of PRRSV was demonstrated to induce the proteasome-dependent degradation of IFITM1 upon PRRSV infection. These findings suggest that PRRSV might counteract the antiviral functions of IFITM1 and Tetherin by the interaction of the Nsp3 with IFITM1 and the E protein with Tetherin, providing a novel clue for exploring possible mechanisms associated with the evasion of PRRSV from immune recognition of host.
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Affiliation(s)
- Xiaolong Wang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Congcong Li
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Lei Zhou
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Ning Zhang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Xingchen Wang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Xinna Ge
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Xin Guo
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China
| | - Hanchun Yang
- Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, People's Republic of China.
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Characterization of red-capped mangabey tetherin: implication for the co-evolution of primates and their lentiviruses. Sci Rep 2014; 4:5529. [PMID: 24984862 PMCID: PMC4078312 DOI: 10.1038/srep05529] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 06/11/2014] [Indexed: 11/11/2022] Open
Abstract
Primate lentiviruses including human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency viruses (SIVs) evolved through the acquisition of antagonists against intrinsic host restriction factors, such as tetherin. It is widely accepted that HIV-1 has emerged by zoonotic transmission of SIV in chimpanzee (SIVcpz), and that SIVcpz Nef protein antagonizes chimpanzee tetherin. Although Nef of SIVcpz shares a common ancestor with that of SIVrcm, an SIV in red-capped mangabey (Cercocebus torquatus), it remains unclear whether SIVrcm Nef can antagonize tetherin of its natural host. In this study, we determine the sequence of red-capped mangabey tetherin for the first time and directly demonstrate that SIVrcm Nef is the bona fide antagonist of red-capped mangabey tetherin. These findings suggest that SIVrcm Nef is the functional ancestor of SIVcpz Nef. Moreover, molecular phylogenetic analyses reveal that tetherins of the genus Cercocebus have experienced adaptive evolution, which is presumably promoted by primate lentiviruses.
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Nityanandam R, Serra-Moreno R. BCA2/Rabring7 targets HIV-1 Gag for lysosomal degradation in a tetherin-independent manner. PLoS Pathog 2014; 10:e1004151. [PMID: 24852021 PMCID: PMC4031200 DOI: 10.1371/journal.ppat.1004151] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 04/14/2014] [Indexed: 12/04/2022] Open
Abstract
BCA2 (Rabring7, RNF115 or ZNF364) is a RING-finger E3 ubiquitin ligase that was identified as a co-factor in the restriction imposed by tetherin/BST2 on HIV-1. Contrary to the current model, in which BCA2 lacks antiviral activity in the absence of tetherin, we found that BCA2 possesses tetherin-independent antiviral activity. Here we show that the N-terminus of BCA2 physically interacts with the Matrix region of HIV-1 and other retroviral Gag proteins and promotes their ubiquitination, redistribution to endo-lysosomal compartments and, ultimately, lysosomal degradation. The targeted depletion of BCA2 in tetherin-expressing and tetherin-deficient cells results in a significant increase in virus release and replication, indicating that endogenous BCA2 possesses antiviral activity. Therefore, these results indicate that BCA2 functions as an antiviral factor that targets HIV-1 Gag for degradation, impairing virus assembly and release. Tetherin (also known as BST2, CD317 or HM1.24) is an interferon-inducible cellular factor that interferes with the release of enveloped viruses from infected cells. A recent study identified BCA2 (Breast Cancer-Associated gene 2, also known as RNF115, ZNF364 or Rabring7), a RING-finger E3 ubiquitin ligase, as a co-factor in the tetherin-mediated restriction of HIV-1. According to this model, BCA2 interacts with sequences in the N-terminus of tetherin to promote the internalization and lysosomal degradation of tethered HIV-1 particles, with no apparent antiviral activity in cells not expressing tetherin. However, here we show for the first time that BCA2 inhibits virus production for HIV-1 and other retroviruses in a tetherin-independent manner by reducing the cellular levels of Gag – the precursor of the structural proteins Matrix, Capsid, Nucleocapsid and p6. Hence, contrary to its reported role as a tetherin co-factor, BCA2 functions as a tetherin-independent antiviral factor that impairs virus assembly and release.
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Affiliation(s)
- Ramya Nityanandam
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
| | - Ruth Serra-Moreno
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail:
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Jia X, Weber E, Tokarev A, Lewinski M, Rizk M, Suarez M, Guatelli J, Xiong Y. Structural basis of HIV-1 Vpu-mediated BST2 antagonism via hijacking of the clathrin adaptor protein complex 1. eLife 2014; 3:e02362. [PMID: 24843023 PMCID: PMC4018625 DOI: 10.7554/elife.02362] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BST2/tetherin, an antiviral restriction factor, inhibits the release of enveloped viruses from the cell surface. Human immunodeficiency virus-1 (HIV-1) antagonizes BST2 through viral protein u (Vpu), which downregulates BST2 from the cell surface. We report the crystal structure of a protein complex containing Vpu and BST2 cytoplasmic domains and the core of the clathrin adaptor protein complex 1 (AP1). This, together with our biochemical and functional validations, reveals how Vpu hijacks the AP1-dependent membrane trafficking pathways to mistraffick BST2. Vpu mimics a canonical acidic dileucine-sorting motif to bind AP1 in the cytosol, while simultaneously interacting with BST2 in the membrane. These interactions enable Vpu to build on an intrinsic interaction between BST2 and AP1, presumably causing the observed retention of BST2 in juxtanuclear endosomes and stimulating its degradation in lysosomes. The ability of Vpu to hijack AP-dependent trafficking pathways suggests a potential common theme for Vpu-mediated downregulation of host proteins. DOI:http://dx.doi.org/10.7554/eLife.02362.001 HIV is a retrovirus that attacks the immune system, making the body increasingly susceptible to opportunistic infections and disease and eventually leading to AIDS. While antiretroviral drugs have allowed people with AIDS to live longer, there is no cure or vaccine for HIV. Two types of HIV exist, with HIV-1 being much more common and pathogenic than HIV-2. Like other ‘complex’ retroviruses, the HIV-1 genome contains genes that encode various proteins that allow the virus to disrupt the immune response of the host it is attacking. Viral protein u is a protein encoded by HIV-1 (but not HIV-2) that counteracts an antiviral protein called BST2 in the host. BST2, which is part of the host's innate immune response, prevents newly formed viruses from leaving the surface of infected cells. By counteracting BST2, viral protein u allows the virus to spread in the host more efficiently. Like many proteins, newly produced BST2 is packaged inside structures called vesicles in a part of the cell called the trans-Golgi network, and then sent to its destination. Complexes formed by various proteins make sure that the vesicles take their cargo to their correct destinations within the cell. Two adaptor protein complexes—known as AP1 and AP2—are thought to be involved the transport of BST2. However, it is not known how viral protein u stops BST2 from reaching the cell surface, or how it decreases the amount of BST2 in the cell as a whole. Jia et al. show how viral protein u and BST2 jointly interact with AP1. This interaction leads to the mistrafficking and degradation of BST2 and the counteraction of its antiviral activity. DOI:http://dx.doi.org/10.7554/eLife.02362.002
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Affiliation(s)
- Xiaofei Jia
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Erin Weber
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Andrey Tokarev
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Mary Lewinski
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Maryan Rizk
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Marissa Suarez
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - John Guatelli
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
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Abstract
Myxovirus resistance 2 (Mx2/MxB) has recently been uncovered as an effector of the anti-HIV-1 activity of type I interferons (IFNs) that inhibits HIV-1 at an early stage postinfection, after reverse transcription but prior to proviral integration into host DNA. The mechanistic details of Mx2 antiviral activity are not yet understood, but a few substitutions in the HIV-1 capsid have been shown to confer resistance to Mx2. Through a combination of in vitro evolution and unbiased mutagenesis, we further map the determinants of sensitivity to Mx2 and reveal that multiple capsid (CA) surfaces define sensitivity to Mx2. Intriguingly, we reveal an unanticipated sensitivity determinant within the C-terminal domain of capsid. We also report that Mx2s derived from multiple primate species share the capacity to potently inhibit HIV-1, whereas selected nonprimate orthologs have no such activity. Like TRIM5α, another CA targeting antiretroviral protein, primate Mx2s exhibit species-dependent variation in antiviral specificity against at least one extant virus and multiple HIV-1 capsid mutants. Using a combination of chimeric Mx2 proteins and evolution-guided approaches, we reveal that a single residue close to the N terminus that has evolved under positive selection can determine antiviral specificity. Thus, the variable N-terminal region can define the spectrum of viruses inhibited by Mx2. Importance: Type I interferons (IFNs) inhibit the replication of most mammalian viruses. IFN stimulation upregulates hundreds of different IFN-stimulated genes (ISGs), but it is often unclear which ISGs are responsible for inhibition of a given virus. Recently, Mx2 was identified as an ISG that contributes to the inhibition of HIV-1 replication by type I IFN. Thus, Mx2 might inhibit HIV-1 replication in patients, and this inhibitory action might have therapeutic potential. The mechanistic details of how Mx2 inhibits HIV-1 are currently unclear, but the HIV-1 capsid protein is the likely viral target. Here, we determine the regions of capsid that specify sensitivity to Mx2. We demonstrate that Mx2 from multiple primates can inhibit HIV-1, whereas Mx2 from other mammals (dogs and sheep) cannot. We also show that primate variants of Mx2 differ in the spectrum of lentiviruses they inhibit and that a single residue in Mx2 can determine this antiviral specificity.
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Sauter D. Counteraction of the multifunctional restriction factor tetherin. Front Microbiol 2014; 5:163. [PMID: 24782851 PMCID: PMC3989765 DOI: 10.3389/fmicb.2014.00163] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 03/26/2014] [Indexed: 01/28/2023] Open
Abstract
The interferon-inducible restriction factor tetherin (also known as CD317, BST-2 or HM1.24) has emerged as a key component of the antiviral immune response. Initially, tetherin was shown to restrict replication of various enveloped viruses by inhibiting the release of budding virions from infected cells. More recently, it has become clear that tetherin also acts as a pattern recognition receptor inducing NF-κB-dependent proinflammatory gene expression in virus infected cells. Whereas the ability to restrict virion release is highly conserved among mammalian tetherin orthologs and thus probably an ancient function of this protein, innate sensing seems to be an evolutionarily recent activity. The potent and broad antiviral activity of tetherin is reflected by the fact that many viruses evolved means to counteract this restriction factor. A continuous arms race with viruses has apparently driven the evolution of different isoforms of tetherin with different functional properties. Interestingly, tetherin has also been implicated in cellular processes that are unrelated to immunity, such as the organization of the apical actin network and membrane microdomains or stabilization of the Golgi apparatus. In this review, I summarize our current knowledge of the different functions of tetherin and describe the molecular strategies that viruses have evolved to antagonize or evade this multifunctional host restriction factor.
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Affiliation(s)
- Daniel Sauter
- Institute of Molecular Virology, Ulm University Medical Center Ulm, Germany
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Differential sensitivities of tetherin isoforms to counteraction by primate lentiviruses. J Virol 2014; 88:5845-58. [PMID: 24623426 DOI: 10.1128/jvi.03818-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED The mammalian antiviral membrane protein tetherin (BST2/CD317) can be expressed as two isoforms derived from differential translational initiation. The shorter isoform of the human protein (S-tetherin) lacks the first 12 amino acids of the longer (L-tetherin) cytoplasmic tail, which includes a tyrosine motif that acts as both an endocytic recycling signal and a determinant of virus-induced NF-κB activation. S-tetherin is also reported to be less sensitive to the prototypic viral antagonist human immunodeficiency virus type 1 (HIV-1) Vpu. Here we analyzed the relative sensitivities of L- and S-tetherins to primate lentiviral countermeasures. We show that the reduced sensitivity of S-tetherin to HIV-1 Vpu is a feature of all group M proteins, including those of transmitted founder viruses, primarily because it cannot be targeted for endosomal degradation owing to the truncation of its cytoplasmic tail. In contrast, both isoforms of the human and rhesus macaque tetherins display the same sensitivity to nondegradative lentiviral countermeasures of HIV-2 and SIVmac, respectively. Surprisingly, however, the Vpu proteins encoded by simian immunodeficiency viruses (SIVs) of African guenons, as well as that from recently isolated highly pathogenic HIV-1 group N, do not discriminate between tetherin isoforms. Together, these data suggest that the group M HIV-1 Vpu primarily adapted to target L-tetherin upon zoonotic transmission from chimpanzees, and further, we speculate that functions specifically associated with this isoform, such as proinflammatory signaling, play key roles in human tetherin's antiviral function in vivo. IMPORTANCE The ability of HIV-1 and related viruses to counteract a host antiviral protein, tetherin, is strictly maintained. The adaptation of the HIV-1 Vpu protein to counteract human tetherin is thought to have been one of the key events in the establishment of the HIV/AIDS pandemic. Recent evidence shows that tetherin is expressed as two isoforms and that Vpu preferentially targets the longer form. Here we show that unlike other virus-encoded countermeasures, such as those from primate viruses related to HIV-1, the enhanced ability to counteract the long tetherin isoform is conserved among HIV-1 strains that make up the majority of the human pandemic. This correlates with the ability of Vpu to induce long tetherin degradation. We speculate that functions associated with the human version of this isoform, such as an inflammatory signaling capacity, selected for Vpu's enhanced targeting of long tetherin during its adaptation to humans.
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Abstract
In the fields of virology and innate immunity, BST-2/tetherin is well known for its ability to block the egress of enveloped viruses from infected cells. This appears to be accomplished by 'tethering' virions to the cell surface, thereby limiting virion release. In the past year, several groups have discovered that BST-2/tetherin can activate NF-κB, a transcriptional activator that leads to the rapid expression of both proinflammatory cytokines and proteins involved in cell survival. While this new BST-2 function has been interpreted as a possible viral-sensing mechanism, there may also be broader implications for HIV gene regulation. This article reviews the evidence for BST-2-dependent NF-κB activation, and explores the significance of these exciting new results.
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Affiliation(s)
- Jean K Gustin
- Vaccine & Gene Therapy Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA
| | - Janet L Douglas
- Vaccine & Gene Therapy Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA
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40
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Assisted evolution enables HIV-1 to overcome a high TRIM5α-imposed genetic barrier to rhesus macaque tropism. PLoS Pathog 2013; 9:e1003667. [PMID: 24086139 PMCID: PMC3784476 DOI: 10.1371/journal.ppat.1003667] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 08/13/2013] [Indexed: 01/07/2023] Open
Abstract
Diversification of antiretroviral factors during host evolution has erected formidable barriers to cross-species retrovirus transmission. This phenomenon likely protects humans from infection by many modern retroviruses, but it has also impaired the development of primate models of HIV-1 infection. Indeed, rhesus macaques are resistant to HIV-1, in part due to restriction imposed by the TRIM5α protein (rhTRIM5α). Initially, we attempted to derive rhTRIM5α-resistant HIV-1 strains using two strategies. First, HIV-1 was passaged in engineered human cells expressing rhTRIM5α. Second, a library of randomly mutagenized capsid protein (CA) sequences was screened for mutations that reduced rhTRIM5α sensitivity. Both approaches identified several individual mutations in CA that reduced rhTRIM5α sensitivity. However, neither approach yielded mutants that were fully resistant, perhaps because the locations of the mutations suggested that TRIM5α recognizes multiple determinants on the capsid surface. Moreover, even though additive effects of various CA mutations on HIV-1 resistance to rhTRIM5α were observed, combinations that gave full resistance were highly detrimental to fitness. Therefore, we employed an ‘assisted evolution’ approach in which individual CA mutations that reduced rhTRIM5α sensitivity without fitness penalties were randomly assorted in a library of viral clones containing synthetic CA sequences. Subsequent passage of the viral library in rhTRIM5α-expressing cells resulted in the selection of individual viral species that were fully fit and resistant to rhTRIM5α. These viruses encoded combinations of five mutations in CA that conferred complete or near complete resistance to the disruptive effects of rhTRIM5α on incoming viral cores, by abolishing recognition of the viral capsid. Importantly, HIV-1 variants encoding these CA substitutions and SIVmac239 Vif replicated efficiently in primary rhesus macaque lymphocytes. These findings demonstrate that rhTRIM5α is difficult to but not impossible to evade, and doing so should facilitate the development of primate models of HIV-1 infection. Retroviruses such as HIV-1 often exhibit limited capacity to infect species other than their natural hosts. This phenomenon is partly due to the existence of antiviral proteins that protect against infection by viruses that have not adapted to a particular species. For example, the resistance of rhesus macaques, the monkey species most commonly used in medical research, to HIV-1 infection is partly attributable to the vulnerability of HIV-1 to TRIM5α. Rhesus macaque TRIM5α (rhTRIM5α) blocks HIV-1 infection by recognition of the viral capsid following its entry into the cell, and it has proven difficult to derive HIV-1 strains that are resistant to rhTRIM5α. However, by devising an ‘assisted evolution’ approach, we identified particular combinations of mutations that render HIV-1 resistant to rhTRIM5α. These mutations enable HIV-1 to evade rhTRIM5α by abolishing recognition of the capsid. Notably, introduction of rhTRIM5α-resistant capsids into an HIV-1 that was also engineered to avoid the rhesus macaque APOBEC3 antiviral proteins, allowed efficient HIV-1 replication in rhesus macaque lymphocytes. These discoveries have the potential to advance the development of rhesus macaque models of HIV-1 infection.
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41
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Compton AA, Malik HS, Emerman M. Host gene evolution traces the evolutionary history of ancient primate lentiviruses. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120496. [PMID: 23938749 DOI: 10.1098/rstb.2012.0496] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Simian immunodeficiency viruses (SIVs) have infected primate species long before human immunodeficiency virus has infected humans. Dozens of species-specific lentiviruses are found in African primate species, including two strains that have repeatedly jumped into human populations within the past century. Traditional phylogenetic approaches have grossly underestimated the age of these primate lentiviruses. Instead, here we review how selective pressures imposed by these viruses have fundamentally altered the evolutionary trajectory of hosts genes and, even in cases where there now remains no trace of the viruses themselves, these evolutionary signatures can reveal the types of viruses that were once present. Examination of selection by ancient viruses on the adaptive evolution of host genes has been used to derive minimum age estimates for modern primate lentiviruses. This type of data suggests that ancestors of modern SIV existed in simian primates more than 10 Ma. Moreover, examples of host resistance and viral adaptation have implications not only for estimating the age and host range of ancient primate lentiviruses, but also the pathogenic potential of their modern counterparts.
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Affiliation(s)
- Alex A Compton
- Molecular and Cellular Biology Graduate Program, University of Washington, , Seattle, WA 98195, USA
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42
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Humphries AC, Way M. The non-canonical roles of clathrin and actin in pathogen internalization, egress and spread. Nat Rev Microbiol 2013; 11:551-60. [PMID: 24020073 DOI: 10.1038/nrmicro3072] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The role of clathrin in pathogen entry has received much attention and has highlighted the adaptability of clathrin during internalization. Recent studies have now uncovered additional roles for clathrin and have put the spotlight on its role in pathogen spread. Here, we discuss the manipulation of clathrin by pathogens, with specific attention to the processes that occur at the plasma membrane. In the majority of cases, both clathrin and the actin cytoskeleton are hijacked, so we also examine the interplay between these two systems and their role during pathogen internalization, egress and spread.
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Affiliation(s)
- Ashley C Humphries
- Cancer Research UK London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, UK
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43
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Abstract
Tetherin, an interferon-inducible membrane protein, inhibits the release of nascent enveloped viral particles from the surface of infected cells. However, the mechanisms underlying virion retention have not yet been fully delineated. Here, we employ biochemical assays and engineered tetherin proteins to demonstrate conclusively that virion tethers are composed of the tetherin protein itself, and to elucidate the configuration and topology that tetherin adopts during virion entrapment. We demonstrate that tetherin dimers adopt an “axial” configuration, in which pairs of transmembrane domains or pairs of glycosylphosphatidyl inositol anchors are inserted into assembling virion particles, while the remaining pair of membrane anchors remains embedded in the infected cell membrane. We use quantitative western blotting to determine that a few dozen tetherin dimers are used to tether each virion particle, and that there is ∼3- to 5-fold preference for the insertion of glycosylphosphatidyl inositol anchors rather than transmembrane domains into tethered virions. Cumulatively, these results demonstrate that axially configured tetherin homodimers are directly responsible for trapping virions at the cell surface. We suggest that insertion of glycosylphosphatidyl inositol anchors may be preferred so that effector functions that require exposure of the tetherin N-terminus to the cytoplasm of infected cells are retained. The cellular restriction factor, tetherin, prevents HIV-1 and other enveloped virus particles from being disseminated into the extracellular milieu by infiltrating their envelopes and by physically crosslinking them to the cell surface. It is known that tetherin consists of pairs of membrane anchors, situated at either end of a rod-shaped molecule, but how tetherin causes virion tethering has been difficult to unambiguously determine. In this work, we develop genetic and biochemical approaches to probe tetherin molecules that have infiltrated tethered virions. We show that tetherin adopts an “axial” configuration in its functional state, with a pair of membrane anchors situated at one end of the rod-like structure inserted into a tethered virion. While either end of the rod can be inserted into a virion, there is a preference for the insertion of its lipid (glycosylphosphatidyl inositol) modified carboxyl-terminus into virion envelopes. These studies demonstrate unequivocally that the tetherin molecule itself is directly responsible for trapping virions, and dissect the molecular mechanism underpinning its antiviral activity.
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44
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Serra-Moreno R, Zimmermann K, Stern LJ, Evans DT. Tetherin/BST-2 antagonism by Nef depends on a direct physical interaction between Nef and tetherin, and on clathrin-mediated endocytosis. PLoS Pathog 2013; 9:e1003487. [PMID: 23853598 PMCID: PMC3708871 DOI: 10.1371/journal.ppat.1003487] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Accepted: 05/28/2013] [Indexed: 11/30/2022] Open
Abstract
Nef is the viral gene product employed by the majority of primate lentiviruses to overcome restriction by tetherin (BST-2 or CD317), an interferon-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. Although the mechanisms of tetherin antagonism by HIV-1 Vpu and HIV-2 Env have been investigated in detail, comparatively little is known about tetherin antagonism by SIV Nef. Here we demonstrate a direct physical interaction between SIV Nef and rhesus macaque tetherin, define the residues in Nef required for tetherin antagonism, and show that the anti-tetherin activity of Nef is dependent on clathrin-mediated endocytosis. SIV Nef co-immunoprecipitated with rhesus macaque tetherin and the Nef core domain bound directly to a peptide corresponding to the cytoplasmic domain of rhesus tetherin by surface plasmon resonance. An analysis of alanine-scanning substitutions identified residues throughout the N-terminal, globular core and flexible loop regions of Nef that were required for tetherin antagonism. Although there was significant overlap with sequences required for CD4 downregulation, tetherin antagonism was genetically separable from this activity, as well as from other Nef functions, including MHC class I-downregulation and infectivity enhancement. Consistent with a role for clathrin and dynamin 2 in the endocytosis of tetherin, dominant-negative mutants of AP180 and dynamin 2 impaired the ability of Nef to downmodulate tetherin and to counteract restriction. Taken together, these results reveal that the mechanism of tetherin antagonism by Nef depends on a physical interaction between Nef and tetherin, requires sequences throughout Nef, but is genetically separable from other Nef functions, and leads to the removal of tetherin from sites of virus release at the plasma membrane by clathrin-mediated endocytosis. Tetherin (BST-2, CD317 or HM1.24) is an interferon-inducible cellular restriction factor that prevents the release of enveloped viruses from infected cells. Human and simian immunodeficiency viruses have evolved to use different viral proteins to overcome the anti-viral effects of tetherin. Whereas HIV-1 Vpu and HIV-2 Env counteract human tetherin, most SIVs use the accessory protein Nef to counteract tetherin in their non-human primate hosts. Here we show that the mechanism of tetherin antagonism by SIV Nef involves a direct physical interaction between the core domain of Nef and the cytoplasmic domain of tetherin, which results in the removal of tetherin from sites of virus assembly and release on the cell surface by a mechanism that depends on clathrin and dynamin 2. The Nef-mediated internalization of tetherin leads to the accumulation of tetherin within lysosomal compartments, suggesting that, similar to CD4− and MHC I-downregulation, Nef promotes the lysosomal degradation of tetherin.
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Affiliation(s)
- Ruth Serra-Moreno
- Division of Microbiology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail: (RSM); (DTE)
| | - Kerstin Zimmermann
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Lawrence J. Stern
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - David T. Evans
- Division of Microbiology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail: (RSM); (DTE)
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45
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McNatt MW, Zang T, Bieniasz PD. Vpu binds directly to tetherin and displaces it from nascent virions. PLoS Pathog 2013; 9:e1003299. [PMID: 23633949 PMCID: PMC3635990 DOI: 10.1371/journal.ppat.1003299] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 02/25/2013] [Indexed: 12/27/2022] Open
Abstract
Tetherin (Bst2/CD317/HM1.24) is an interferon-induced antiviral host protein that inhibits the release of many enveloped viruses by tethering virions to the cell surface. The HIV-1 accessory protein, Vpu, antagonizes Tetherin through a variety of proposed mechanisms, including surface downregulation and degradation. Previous studies have demonstrated that mutation of the transmembrane domains (TMD) of both Vpu and Tetherin affect antagonism, but it is not known whether Vpu and Tetherin bind directly to each other. Here, we use cysteine-scanning mutagenesis coupled with oxidation-induced cross-linking to demonstrate that Vpu and Tetherin TMDs bind directly to each other in the membranes of living cells and to map TMD residues that contact each other. We also reveal a property of Vpu, namely the ability to displace Tetherin from sites of viral assembly, which enables Vpu to exhibit residual Tetherin antagonist activity in the absence of surface downregulation or degradation. Elements in the cytoplasmic tail domain (CTD) of Vpu mediate this displacement activity, as shown by experiments in which Vpu CTD fragments were directly attached to Tetherin in the absence of the TMD. In particular, the C-terminal α-helix (H2) of Vpu CTD is sufficient to remove Tetherin from sites of viral assembly and is necessary for full Tetherin antagonist activity. Overall, these data demonstrate that Vpu and Tetherin interact directly via their transmembrane domains enabling activities present in the CTD of Vpu to remove Tetherin from sites of viral assembly.
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Affiliation(s)
- Matthew W. McNatt
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Trinity Zang
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Paul D. Bieniasz
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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46
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Abstract
Tetherin (BST2/CD317) has emerged as a key host cell defense molecule, inhibiting the release and spread of diverse enveloped virions from infected cells. In this chapter, I review the molecular and cellular basis for tetherin's antiviral activities and the function of virally encoded countermeasures that disrupt its function. I further describe recent advances in our understanding of tetherin's associated role in viral pattern recognition and the evidence for its role in limiting viral pathogenesis in vivo.
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Affiliation(s)
- Stuart J D Neil
- Department of Infectious Disease, King's College London School of Medicine, London, UK.
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47
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Blanco-Melo D, Venkatesh S, Bieniasz PD. Intrinsic cellular defenses against human immunodeficiency viruses. Immunity 2012; 37:399-411. [PMID: 22999946 DOI: 10.1016/j.immuni.2012.08.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Indexed: 10/27/2022]
Abstract
Viral infections are often detrimental to host survival and reproduction. Consequently, hosts have evolved a variety of mechanisms to defend themselves against viruses. A component of this arsenal is a set of proteins, termed restriction factors, which exhibit direct antiviral activity. Among these are several classes of proteins (APOBEC3, TRIM5, Tetherin, and SAMHD1) that inhibit the replication of human and simian immunodeficiency viruses. Here, we outline the features, mechanisms, and evolution of these defense mechanisms. We also speculate on how restriction factors arose, how they might interact with the conventional innate and adaptive immune systems, and how an understanding of these intrinsic cellular defenses might be usefully exploited.
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Affiliation(s)
- Daniel Blanco-Melo
- Howard Hughes Medical Institute, Laboratory of Retrovirology, Aaron Diamond AIDS Research Center, The Rockefeller University 455 First Avenue New York, NY, 10016
| | - Siddarth Venkatesh
- Howard Hughes Medical Institute, Laboratory of Retrovirology, Aaron Diamond AIDS Research Center, The Rockefeller University 455 First Avenue New York, NY, 10016
| | - Paul D Bieniasz
- Howard Hughes Medical Institute, Laboratory of Retrovirology, Aaron Diamond AIDS Research Center, The Rockefeller University 455 First Avenue New York, NY, 10016
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48
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Abstract
Cellular proteins called "restriction factors" can serve as powerful blockades to HIV replication, but the virus possesses elaborate strategies to circumvent these barriers. First, we discuss general hallmarks of a restriction factor. Second, we review how the viral Vif protein protects the viral genome from lethal levels of cDNA deamination by promoting APOBEC3 protein degradation; how the viral Vpu, Env, and Nef proteins facilitate internalization and degradation of the virus-tethering protein BST-2/tetherin; and how the viral Vpx protein prevents the premature termination of reverse transcription by degrading the dNTPase SAMHD1. These HIV restriction and counter-restriction mechanisms suggest strategies for new therapeutic interventions.
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Affiliation(s)
- Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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49
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Abstract
Studies of retroviruses have been instrumental in revealing the existence of an array of antiviral proteins, or restriction factors, and the mechanisms by which they function. Some restriction factors appear to specifically inhibit retrovirus replication, while others have a broader antiviral action. Here, we briefly review current understanding of the mechanisms by which several such proteins exert antiviral activity. We also discuss how retroviruses have evolved to evade or antagonize antiviral proteins, including through the action of viral accessory proteins. Restriction factors, their viral targets and antagonists have exerted evolutionary pressure on each other, resulting in specialization and barriers to cross-species transmission. Potentially, this recently revealed intrinsic system of antiviral immunity might be mobilized for therapeutic benefit.
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Affiliation(s)
- Theodora Hatziioannou
- Aaron Diamond AIDS Research Center, The Rockefeller University, New York, NY 10016, United States
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50
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Kueck T, Neil SJD. A cytoplasmic tail determinant in HIV-1 Vpu mediates targeting of tetherin for endosomal degradation and counteracts interferon-induced restriction. PLoS Pathog 2012; 8:e1002609. [PMID: 22479182 PMCID: PMC3315493 DOI: 10.1371/journal.ppat.1002609] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 02/11/2012] [Indexed: 01/12/2023] Open
Abstract
The HIV-1 accessory protein Vpu counteracts tetherin (BST-2/CD317) by preventing its incorporation into virions, reducing its surface expression, and ultimately promoting its degradation. Here we characterize a putative trafficking motif, EXXXLV, in the second alpha helix of the subtype-B Vpu cytoplasmic tail as being required for efficient tetherin antagonism. Mutation of this motif prevents ESCRT-dependent degradation of tetherin/Vpu complexes, tetherin cell surface downregulation, but not its physical interaction with Vpu. Importantly, this motif is required for efficient cell-free virion release from CD4+ T cells, particularly after their exposure to type-1 interferon, indicating that the ability to reduce surface tetherin levels and promote its degradation is important to counteract restriction under conditions that the virus likely encounters in vivo. Vpu EXXXLV mutants accumulate with tetherin at the cell surface and in endosomal compartments, but retain the ability to bind both β-TrCP2 and HRS, indicating that this motif is required for a post-binding trafficking event that commits tetherin for ESCRT-dependent degradation and prevents its transit to the plasma membrane and viral budding zones. We further found that while Vpu function is dependent on clathrin, and the entire second alpha helix of the Vpu tail can be functionally complemented by a clathrin adaptor binding peptide derived from HIV-1 Nef, none of the canonical clathrin adaptors nor retromer are required for this process. Finally we show that residual activity of Vpu EXXXLV mutants requires an intact endocytic motif in tetherin, suggesting that physical association of Vpu with tetherin during its recycling may be sufficient to compromise tetherin activity to some degree. Tetherin inhibits the release of several diverse enveloped viruses from infected cells and is counteracted by the HIV-1 accessory gene Vpu. Vpu prevents tetherin's incorporation into nascent viral particles, promotes its downregulation from the cell surface and targets tetherin for degradation. Here we identify a determinant that resembles an acidic-dileucine-based sorting sequence in the Vpu cytoplasmic tail that is required for efficient counteraction of tetherin activity, particularly in CD4+ T cells treated with type-1 interferon. Mutation of this motif prevents cell-surface downregulation and degradation of Vpu/tetherin complexes but does not affect their interaction. Rather, in its absence, Vpu accumulates in early endosomes and at the cell surface where it becomes incorporated into assembling virions with tetherin, indicating that this motif modulates sub-cellular trafficking of tetherin. Furthermore Vpu activity is clathrin-dependent and can be reconstituted by replacing a portion of the cytoplasmic tail encompassing this motif with one derived from HIV-1 Nef that is known to bind several clathrin adaptors. Finally, we demonstrate that residual function of the mutant Vpu requires a trafficking motif in tetherin, suggesting that physical interaction of tetherin with Vpu during its recycling to the cell-surface can interfere with its function to a variable extent.
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Affiliation(s)
| | - Stuart J. D. Neil
- Department of Infectious Disease, King's College London School of Medicine, Guy's Hospital, London, United Kingdom
- * E-mail:
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