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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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Morrison JH, Poeschla EM. The Feline Immunodeficiency Virus Envelope Signal Peptide Is a Tetherin Antagonizing Protein. mBio 2023; 14:e0016123. [PMID: 36927083 PMCID: PMC10128041 DOI: 10.1128/mbio.00161-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/23/2023] [Indexed: 03/18/2023] Open
Abstract
Signal peptides are N-terminal peptides, generally less than 30 amino acids in length, that direct translocation of proteins into the endoplasmic reticulum and secretory pathway. The envelope glycoprotein (Env) of the nonprimate lentivirus feline immunodeficiency virus (FIV) contains the longest signal peptide of all eukaryotic, prokaryotic, and viral proteins (175 amino acids), yet the reason is unknown. Tetherin is a dual membrane-anchored host protein that inhibits the release of enveloped viruses from cells. Primate lentiviruses have evolved three antagonists: the small accessory proteins Vpu and Nef, and in the case of HIV-2, Env. Here, we identify the FIV Env signal peptide (Fsp) as the FIV tetherin antagonist. A short deletion in the central portion of Fsp had no effect on viral replication in the absence of tetherin, but severely impaired virion budding in its presence. Fsp is necessary and sufficient, acting as an autonomous accessory protein with the rest of Env dispensable. In contrast to primate lentivirus tetherin antagonists, its mechanism is to stringently block the incorporation of this restriction factor into viral particles rather than by degrading it or downregulating it from the plasma membrane. IMPORTANCE The study of species- and virus-specific differences in restriction factors and their antagonists has been central to deciphering the nature of these key host defenses. FIV is an AIDS-causing lentivirus that has achieved pandemic spread in the domestic cat. We now identify its tetherin antagonist as the signal sequence of the Envelope glycoprotein, thus identifying the fourth lentiviral anti-tetherin protein and the first new lentiviral accessory protein in decades. Fsp is necessary and sufficient and functions by stringently blocking particle incorporation of tetherin, which differs from the degradation or surface downregulation mechanisms used by primate lentiviruses. Fsp also is a novel example of signal peptide dual function, being both a restriction factor antagonist and a mediator of protein translocation into the endoplasmic reticulum.
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Affiliation(s)
- James H Morrison
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Eric M Poeschla
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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3
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Prion-like low complexity regions enable avid virus-host interactions during HIV-1 infection. Nat Commun 2022; 13:5879. [PMID: 36202818 PMCID: PMC9537594 DOI: 10.1038/s41467-022-33662-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 09/27/2022] [Indexed: 12/24/2022] Open
Abstract
Cellular proteins CPSF6, NUP153 and SEC24C play crucial roles in HIV-1 infection. While weak interactions of short phenylalanine-glycine (FG) containing peptides with isolated capsid hexamers have been characterized, how these cellular factors functionally engage with biologically relevant mature HIV-1 capsid lattices is unknown. Here we show that prion-like low complexity regions (LCRs) enable avid CPSF6, NUP153 and SEC24C binding to capsid lattices. Structural studies revealed that multivalent CPSF6 assembly is mediated by LCR-LCR interactions, which are templated by binding of CPSF6 FG peptides to a subset of hydrophobic capsid pockets positioned along adjoining hexamers. In infected cells, avid CPSF6 LCR-mediated binding to HIV-1 cores is essential for functional virus-host interactions. The investigational drug lenacapavir accesses unoccupied hydrophobic pockets in the complex to potently impair HIV-1 inside the nucleus without displacing the tightly bound cellular cofactor from virus cores. These results establish previously undescribed mechanisms of virus-host interactions and antiviral action.
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Cano-Ortiz L, Gu Q, de Sousa-Pereira P, Zhang Z, Chiapella C, Penda Twizerimana A, Lin C, Cláudia Franco A, VandeWoude S, Luedde T, Baldauf HM, Münk C. Feline Leukemia Virus-B Envelope together with its GlycoGag and Human Immunodeficiency Virus-1 Nef Mediate Resistance to Feline SERINC5. J Mol Biol 2021; 434:167421. [DOI: 10.1016/j.jmb.2021.167421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 12/17/2021] [Accepted: 12/18/2021] [Indexed: 11/29/2022]
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5
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Rebensburg SV, Wei G, Larue RC, Lindenberger J, Francis AC, Annamalai AS, Morrison J, Shkriabai N, Huang SW, KewalRamani V, Poeschla EM, Melikyan GB, Kvaratskhelia M. Sec24C is an HIV-1 host dependency factor crucial for virus replication. Nat Microbiol 2021; 6:435-444. [PMID: 33649557 PMCID: PMC8012256 DOI: 10.1038/s41564-021-00868-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 01/20/2021] [Indexed: 01/31/2023]
Abstract
Early events of the human immunodeficiency virus 1 (HIV-1) lifecycle, such as post-entry virus trafficking, uncoating and nuclear import, are poorly characterized because of limited understanding of virus-host interactions. Here, we used mass spectrometry-based proteomics to delineate cellular binding partners of curved HIV-1 capsid lattices and identified Sec24C as an HIV-1 host dependency factor. Gene deletion and complementation in Jurkat cells revealed that Sec24C facilitates infection and markedly enhances HIV-1 spreading infection. Downregulation of Sec24C in HeLa cells substantially reduced HIV-1 core stability and adversely affected reverse transcription, nuclear import and infectivity. Live-cell microscopy showed that Sec24C co-trafficked with HIV-1 cores in the cytoplasm during virus ingress. Biochemical assays demonstrated that Sec24C directly and specifically interacted with hexameric capsid lattices. A 2.3-Å resolution crystal structure of Sec24C228-242 in the complex with a capsid hexamer revealed that the Sec24C FG-motif bound to a pocket comprised of two adjoining capsid subunits. Combined with previous data1-4, our findings indicate that a capsid-binding FG-motif is conserved in unrelated proteins present in the cytoplasm (Sec24C), the nuclear pore (Nup153; refs. 3,4) and the nucleus (CPSF6; refs. 1,2). We propose that these virus-host interactions during HIV-1 trafficking across different cellular compartments are crucial for productive infection of target cells.
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Affiliation(s)
- Stephanie V Rebensburg
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Guochao Wei
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Ross C Larue
- College of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Jared Lindenberger
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Ashwanth C Francis
- Department of Pediatrics, Infectious Diseases, Emory University, Atlanta, GA, USA
| | - Arun S Annamalai
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - James Morrison
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Nikoloz Shkriabai
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Szu-Wei Huang
- Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Vineet KewalRamani
- Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Eric M Poeschla
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Gregory B Melikyan
- Department of Pediatrics, Infectious Diseases, Emory University, Atlanta, GA, USA
| | - Mamuka Kvaratskhelia
- Division of Infectious Diseases, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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6
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Waheed AA, Swiderski M, Khan A, Gitzen A, Majadly A, Freed EO. The viral protein U (Vpu)-interacting host protein ATP6V0C down-regulates cell-surface expression of tetherin and thereby contributes to HIV-1 release. J Biol Chem 2020; 295:7327-7340. [PMID: 32291285 PMCID: PMC7247306 DOI: 10.1074/jbc.ra120.013280] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/09/2020] [Indexed: 12/11/2022] Open
Abstract
Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. The HIV-1 accessory protein viral protein U (Vpu) enhances release of the virus from host cells by down-regulating the cell-surface expression of the host restriction factor tetherin. However, the exact mechanism of Vpu-mediated suppression of antiviral host responses is unclear. To further understand the role of host proteins in Vpu's function, here we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated tetherin degradation, resulting in defective HIV-1 release. We also observed that ATP6V0C overexpression stabilizes tetherin expression. This stabilization effect was specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C″, had no effect on tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization experiments revealed that the ATP6V0C-stabilized tetherin is sequestered in a CD63- and lysosome-associated membrane protein 1 (LAMP1)-positive intracellular compartment. These results indicate that the Vpu-interacting protein ATP6V0C plays a role in down-regulating cell-surface expression of tetherin and thereby contributes to HIV-1 assembly and release.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702.
| | - Maya Swiderski
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ali Khan
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ariana Gitzen
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Ahlam Majadly
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Dynamics and Replication Program, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
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Interferon γ and α Have Differential Effects on SAMHD1, a Potent Antiviral Protein, in Feline Lymphocytes. Viruses 2019; 11:v11100921. [PMID: 31600877 PMCID: PMC6832628 DOI: 10.3390/v11100921] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/05/2019] [Accepted: 10/06/2019] [Indexed: 12/15/2022] Open
Abstract
Sterile alpha motif and histidine/aspartic domain-containing protein 1 (SAMHD1) is a protein with anti-viral, anti-neoplastic, and anti-inflammatory properties. By degrading cellular dNTPs to constituent deoxynucleoside and free triphosphate, SAMHD1 limits viral DNA synthesis and prevents replication of HIV-1 and some DNA viruses such as HBV, vaccinia, and HSV-1. Recent findings suggest SAMHD1 is broadly active against retroviruses in addition to HIV-1, such as HIV-2, FIV, BIV, and EIAV. Interferons are cytokines produced by lymphocytes and other cells that induce a wide array of antiviral proteins, including some with activity again lentiviruses. Here we evaluated the role of IFNs on SAMHD1 gene expression, transcription, and post-translational modification in a feline CD4+ T cell line (FeTJ) and in primary feline CD4+ T lymphocytes. SAMHD1 mRNA in FetJ cells increased in a dose-related manner in response to IFNγ treatment concurrent with increased nuclear localization and phosphorylation. IFNα treatment induced SAMHD1 mRNA but did not significantly alter SAMHD1 protein detection, phosphorylation, or nuclear translocation. In purified primary feline CD4+ lymphocytes, IL2 supplementation increased SAMHD1 expression, but the addition of IFNγ did not further alter SAMHD1 protein expression or nuclear localization. Thus, the effect of IFNγ on SAMHD1 expression is cell-type dependent, with increased translocation to the nucleus and phosphorylation in FeTJ but not primary CD4+ lymphocytes. These findings imply that while SAMH1 is inducible by IFNγ, overall activity is cell type and compartment specific, which is likely relevant to the establishment of lentiviral reservoirs in quiescent lymphocyte populations.
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8
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Generous AR, Harrison OJ, Troyanovsky RB, Mateo M, Navaratnarajah CK, Donohue RC, Pfaller CK, Alekhina O, Sergeeva AP, Indra I, Thornburg T, Kochetkova I, Billadeau DD, Taylor MP, Troyanovsky SM, Honig B, Shapiro L, Cattaneo R. Trans-endocytosis elicited by nectins transfers cytoplasmic cargo, including infectious material, between cells. J Cell Sci 2019; 132:jcs235507. [PMID: 31331966 PMCID: PMC6737912 DOI: 10.1242/jcs.235507] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 07/12/2019] [Indexed: 12/13/2022] Open
Abstract
Here, we show that cells expressing the adherens junction protein nectin-1 capture nectin-4-containing membranes from the surface of adjacent cells in a trans-endocytosis process. We find that internalized nectin-1-nectin-4 complexes follow the endocytic pathway. The nectin-1 cytoplasmic tail controls transfer: its deletion prevents trans-endocytosis, while its exchange with the nectin-4 tail reverses transfer direction. Nectin-1-expressing cells acquire dye-labeled cytoplasmic proteins synchronously with nectin-4, a process most active during cell adhesion. Some cytoplasmic cargo remains functional after transfer, as demonstrated with encapsidated genomes of measles virus (MeV). This virus uses nectin-4, but not nectin-1, as a receptor. Epithelial cells expressing nectin-4, but not those expressing another MeV receptor in its place, can transfer infection to nectin-1-expressing primary neurons. Thus, this newly discovered process can move cytoplasmic cargo, including infectious material, from epithelial cells to neurons. We name the process nectin-elicited cytoplasm transfer (NECT). NECT-related trans-endocytosis processes may be exploited by pathogens to extend tropism. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Alex R Generous
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
- Virology and Gene Therapy Track, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Oliver J Harrison
- Departments of Biochemistry and Molecular Biophysics, Systems Biology and Medicine, Zuckerman Mind, Brain, Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Regina B Troyanovsky
- Department of Dermatology, Northwestern University, The Feinberg School of Medicine, Chicago, IL 60611
| | - Mathieu Mateo
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Chanakha K Navaratnarajah
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Ryan C Donohue
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
- Virology and Gene Therapy Track, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Christian K Pfaller
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
- Virology and Gene Therapy Track, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Olga Alekhina
- Department of Immunology, Mayo Clinic, Rochester, MN 55905, USA
| | - Alina P Sergeeva
- Departments of Biochemistry and Molecular Biophysics, Systems Biology and Medicine, Zuckerman Mind, Brain, Behavior Institute, Columbia University, New York, NY 10032, USA
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Indrajyoti Indra
- Department of Dermatology, Northwestern University, The Feinberg School of Medicine, Chicago, IL 60611
| | - Theresa Thornburg
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT 59717, USA
| | - Irina Kochetkova
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT 59717, USA
| | | | - Matthew P Taylor
- Department of Microbiology & Immunology, Montana State University, Bozeman, MT 59717, USA
| | - Sergey M Troyanovsky
- Department of Dermatology, Northwestern University, The Feinberg School of Medicine, Chicago, IL 60611
| | - Barry Honig
- Departments of Biochemistry and Molecular Biophysics, Systems Biology and Medicine, Zuckerman Mind, Brain, Behavior Institute, Columbia University, New York, NY 10032, USA
- Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Lawrence Shapiro
- Departments of Biochemistry and Molecular Biophysics, Systems Biology and Medicine, Zuckerman Mind, Brain, Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Roberto Cattaneo
- Department of Molecular Medicine, Mayo Clinic, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
- Virology and Gene Therapy Track, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
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9
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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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10
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Pfaller CK, Donohue RC, Nersisyan S, Brodsky L, Cattaneo R. Extensive editing of cellular and viral double-stranded RNA structures accounts for innate immunity suppression and the proviral activity of ADAR1p150. PLoS Biol 2018; 16:e2006577. [PMID: 30496178 PMCID: PMC6264153 DOI: 10.1371/journal.pbio.2006577] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 10/26/2018] [Indexed: 01/09/2023] Open
Abstract
The interferon (IFN)-mediated innate immune response is the first line of defense against viruses. However, an IFN-stimulated gene, the adenosine deaminase acting on RNA 1 (ADAR1), favors the replication of several viruses. ADAR1 binds double-stranded RNA and converts adenosine to inosine by deamination. This form of editing makes duplex RNA unstable, thereby preventing IFN induction. To better understand how ADAR1 works at the cellular level, we generated cell lines that express exclusively either the IFN-inducible, cytoplasmic isoform ADAR1p150, the constitutively expressed nuclear isoform ADAR1p110, or no isoform. By comparing the transcriptome of these cell lines, we identified more than 150 polymerase II transcripts that are extensively edited, and we attributed most editing events to ADAR1p150. Editing is focused on inverted transposable elements, located mainly within introns and untranslated regions, and predicted to form duplex RNA structures. Editing of these elements occurs also in primary human samples, and there is evidence for cross-species evolutionary conservation of editing patterns in primates and, to a lesser extent, in rodents. Whereas ADAR1p150 rarely edits tightly encapsidated standard measles virus (MeV) genomes, it efficiently edits genomes with inverted repeats accidentally generated by a mutant MeV. We also show that immune activation occurs in fully ADAR1-deficient (ADAR1KO) cells, restricting virus growth, and that complementation of these cells with ADAR1p150 rescues virus growth and suppresses innate immunity activation. Finally, by knocking out either protein kinase R (PKR) or mitochondrial antiviral signaling protein (MAVS)—another protein controlling the response to duplex RNA—in ADAR1KO cells, we show that PKR activation elicits a stronger antiviral response. Thus, ADAR1 prevents innate immunity activation by cellular transcripts that include extensive duplex RNA structures. The trade-off is that viruses take advantage of ADAR1 to elude innate immunity control. The innate immune response is a double-edged sword. It must protect the host from pathogens while avoiding accidental recognition of “self” molecular patterns, which can lead to autoimmune reactions. Double-stranded RNA is among the most potent inducers of cellular stress and interferon responses. We characterize here a mechanism that prevents autoimmune activation and show that an RNA virus, measles virus, can exploit it to elude innate immune responses. This mechanism relies on the enzyme adenosine deaminase acting on RNA 1 (ADAR1), which converts adenosine residues within duplex RNA structures to inosine. We identify duplex RNA structures in the 3′ untranslated regions of over 150 cellular transcripts and show that they are heavily edited in ADAR1-expressing cells. We detect the same type of editing in duplex RNA–forming defective genomes accidentally generated by measles virus. Loss of RNA editing causes strong innate immune responses and is detrimental to viral replication. Thus, by keeping the amount of duplex RNA in cells below an immune activation threshold, ADAR1 prevents autoimmunity while also favoring pathogens.
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Affiliation(s)
- Christian K. Pfaller
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Ryan C. Donohue
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota, United States of America
| | - Stepan Nersisyan
- Tauber Bioinformatics Research Center, University of Haifa, Haifa, Israel
- Lomonosov Moscow State University, Moscow, Russia
| | - Leonid Brodsky
- Tauber Bioinformatics Research Center, University of Haifa, Haifa, Israel
| | - Roberto Cattaneo
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Mayo Clinic Graduate School of Biomedical Sciences, Rochester, Minnesota, United States of America
- * E-mail:
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11
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Preadaptation of Simian Immunodeficiency Virus SIVsmm Facilitated Env-Mediated Counteraction of Human Tetherin by Human Immunodeficiency Virus Type 2. J Virol 2018; 92:JVI.00276-18. [PMID: 29976668 DOI: 10.1128/jvi.00276-18] [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: 02/16/2018] [Accepted: 06/23/2018] [Indexed: 12/14/2022] Open
Abstract
The host restriction factor tetherin inhibits virion release from infected cells and poses a significant barrier to successful zoonotic transmission of primate lentiviruses to humans. While most simian immunodeficiency viruses (SIV), including the direct precursors of human immunodeficiency virus type 1 (HIV-1) and HIV-2, use their Nef protein to counteract tetherin in their natural hosts, they fail to antagonize the human tetherin ortholog. Pandemic HIV-1 group M and epidemic group O strains overcame this hurdle by adapting their Vpu and Nef proteins, respectively, whereas HIV-2 group A uses its envelope (Env) glycoprotein to counteract human tetherin. Whether or how the remaining eight groups of HIV-2 antagonize this antiviral factor has remained unclear. Here, we show that Nef proteins from diverse groups of HIV-2 do not or only modestly antagonize human tetherin, while their ability to downmodulate CD3 and CD4 is highly conserved. Experiments in transfected cell lines and infected primary cells revealed that not only Env proteins of epidemic HIV-2 group A but also those of a circulating recombinant form (CRF01_AB) and rare groups F and I decrease surface expression of human tetherin and significantly enhance progeny virus release. Intriguingly, we found that many SIVsmm Envs also counteract human as well as smm tetherin. Thus, Env-mediated tetherin antagonism in different groups of HIV-2 presumably stems from a preadaptation of their SIVsmm precursors to humans. In summary, we identified a phenotypic trait of SIVsmm that may have facilitated its successful zoonotic transmission to humans and the emergence of HIV-2.IMPORTANCE HIV-2 groups A to I resulted from nine independent cross-species transmission events of SIVsmm to humans and differ considerably in their prevalence and geographic spread. Thus, detailed characterization of these viruses offers a valuable means to elucidate immune evasion mechanisms and human-specific adaptations determining viral spread. In a systematic comparison of rare and epidemic HIV-2 groups and their simian SIVsmm counterparts, we found that the ability of Nef to downmodulate the primary viral entry receptor CD4 and the T cell receptor CD3 is conserved, while effects on CD28, CD74, and major histocompatibility complex class I surface expression vary considerably. Furthermore, we show that not only the Env proteins of HIV-2 groups A, AB, F, and I but also those of some SIVsmm isolates antagonize human tetherin. This finding helps to explain why SIVsmm has been able to cross the species barrier to humans on at least nine independent occasions.
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12
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de Pablo-Maiso L, Doménech A, Echeverría I, Gómez-Arrebola C, de Andrés D, Rosati S, Gómez-Lucia E, Reina R. Prospects in Innate Immune Responses as Potential Control Strategies against Non-Primate Lentiviruses. Viruses 2018; 10:v10080435. [PMID: 30126090 PMCID: PMC6116218 DOI: 10.3390/v10080435] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 08/08/2018] [Accepted: 08/10/2018] [Indexed: 02/06/2023] Open
Abstract
Lentiviruses are infectious agents of a number of animal species, including sheep, goats, horses, monkeys, cows, and cats, in addition to humans. As in the human case, the host immune response fails to control the establishment of chronic persistent infection that finally leads to a specific disease development. Despite intensive research on the development of lentivirus vaccines, it is still not clear which immune responses can protect against infection. Viral mutations resulting in escape from T-cell or antibody-mediated responses are the basis of the immune failure to control the infection. The innate immune response provides the first line of defense against viral infections in an antigen-independent manner. Antiviral innate responses are conducted by dendritic cells, macrophages, and natural killer cells, often targeted by lentiviruses, and intrinsic antiviral mechanisms exerted by all cells. Intrinsic responses depend on the recognition of the viral pathogen-associated molecular patterns (PAMPs) by pathogen recognition receptors (PRRs), and the signaling cascades leading to an antiviral state by inducing the expression of antiviral proteins, including restriction factors. This review describes the latest advances on innate immunity related to the infection by animal lentiviruses, centered on small ruminant lentiviruses (SRLV), equine infectious anemia virus (EIAV), and feline (FIV) and bovine immunodeficiency viruses (BIV), specifically focusing on the antiviral role of the major restriction factors described thus far.
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MESH Headings
- Animals
- Cats
- Cattle
- Dendritic Cells/immunology
- Dendritic Cells/virology
- Gene Expression Regulation/immunology
- Goats
- Horses
- Immunity, Innate
- Immunodeficiency Virus, Bovine/immunology
- Immunodeficiency Virus, Bovine/pathogenicity
- Immunodeficiency Virus, Feline/immunology
- Immunodeficiency Virus, Feline/pathogenicity
- Infectious Anemia Virus, Equine/immunology
- Infectious Anemia Virus, Equine/pathogenicity
- Interferon Regulatory Factors/genetics
- Interferon Regulatory Factors/immunology
- Killer Cells, Natural/immunology
- Killer Cells, Natural/virology
- Lentivirus Infections/genetics
- Lentivirus Infections/immunology
- Lentivirus Infections/virology
- Macrophages/immunology
- Macrophages/virology
- Pathogen-Associated Molecular Pattern Molecules/immunology
- Receptors, Pattern Recognition/genetics
- Receptors, Pattern Recognition/immunology
- Sheep
- T-Lymphocytes/immunology
- T-Lymphocytes/virology
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Affiliation(s)
- Lorena de Pablo-Maiso
- Instituto de Agrobiotecnología (IdAB), UPNA-CSIC-Gobierno de Navarra, Navarra 31192, Spain.
| | - Ana Doménech
- Dpto. Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid 28040, Spain.
| | - Irache Echeverría
- Instituto de Agrobiotecnología (IdAB), UPNA-CSIC-Gobierno de Navarra, Navarra 31192, Spain.
| | - Carmen Gómez-Arrebola
- Instituto de Agrobiotecnología (IdAB), UPNA-CSIC-Gobierno de Navarra, Navarra 31192, Spain.
| | - Damián de Andrés
- Instituto de Agrobiotecnología (IdAB), UPNA-CSIC-Gobierno de Navarra, Navarra 31192, Spain.
| | - Sergio Rosati
- Malattie Infettive degli Animali Domestici, Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Torino 10095, Italy.
| | - Esperanza Gómez-Lucia
- Dpto. Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid 28040, Spain.
| | - Ramsés Reina
- Instituto de Agrobiotecnología (IdAB), UPNA-CSIC-Gobierno de Navarra, Navarra 31192, Spain.
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Properties and Functions of Feline Immunodeficiency Virus Gag Domains in Virion Assembly and Budding. Viruses 2018; 10:v10050261. [PMID: 29772651 PMCID: PMC5977254 DOI: 10.3390/v10050261] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 05/13/2018] [Accepted: 05/14/2018] [Indexed: 01/11/2023] Open
Abstract
Feline immunodeficiency virus (FIV) is an important cat pathogen worldwide whose biological and pathophysiological properties resemble those of human immunodeficiency virus type 1 (HIV-1). Therefore, the study of FIV not only benefits its natural host but is also useful for the development of antiviral strategies directed against HIV-1 infections in humans. FIV assembly results from the multimerization of a single but complex viral polypeptide, the Gag precursor. In this review, we will first give an overview of the current knowledge of the proteins encoded by the FIV pol, env, rev, vif, and orf-A genes, and then we will describe and discuss in detail the critical roles that each of the FIV Gag domains plays in virion morphogenesis. Since retroviral assembly is an attractive target for therapeutic interventions, gaining a better understanding of this process is highly desirable.
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Feline APOBEC3s, Barriers to Cross-Species Transmission of FIV? Viruses 2018; 10:v10040186. [PMID: 29642583 PMCID: PMC5923480 DOI: 10.3390/v10040186] [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: 03/27/2018] [Revised: 04/06/2018] [Accepted: 04/07/2018] [Indexed: 02/07/2023] Open
Abstract
The replication of lentiviruses highly depends on host cellular factors, which defines their species-specific tropism. Cellular restriction factors that can inhibit lentiviral replication were recently identified. Feline immunodeficiency virus (FIV) was found to be sensitive to several feline cellular restriction factors, such as apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3 (APOBEC3) and tetherin, but FIV evolved to counteract them. Here, we describe the molecular mechanisms by which feline APOBEC3 restriction factors inhibit FIV replication and discuss the molecular interaction of APOBEC3 proteins with the viral antagonizing protein Vif. We speculate that feline APOBEC3 proteins could explain some of the observed FIV cross-species transmissions described in wild Felids.
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15
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Eckstrand CD, Sparger EE, Murphy BG. Central and peripheral reservoirs of feline immunodeficiency virus in cats: a review. J Gen Virol 2017; 98:1985-1996. [DOI: 10.1099/jgv.0.000866] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Chrissy D. Eckstrand
- Veterinary Microbiology and Pathology, College of Veterinary Medicine, 4003 Animal Disease Biotechnology Facility, Washington State University, Pullman, WA 99163, USA
| | - Ellen E. Sparger
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, 3115 Tupper Hall, Davis, CA 95616, USA
| | - Brian G. Murphy
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, 4206 Vet Med 3A, University of California, Davis, CA 95616, USA
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Feline Immunodeficiency Virus Neuropathogenesis: A Model for HIV-Induced CNS Inflammation and Neurodegeneration. Vet Sci 2017; 4:vetsci4010014. [PMID: 29056673 PMCID: PMC5606611 DOI: 10.3390/vetsci4010014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 12/11/2022] Open
Abstract
Feline Immunodeficiency virus (FIV), similar to its human analog human immunodeficiency virus (HIV), enters the central nervous system (CNS) soon after infection and establishes a protected viral reservoir. The ensuing inflammation and damage give rise to varying degrees of cognitive decline collectively known as HIV-associated neurocognitive disorders (HAND). Because of the similarities to HIV infection and disease, FIV has provided a useful model for both in vitro and in vivo studies of CNS infection, inflammation and pathology. This mini review summarizes insights gained from studies of early infection, immune cell trafficking, inflammation and the mechanisms of neuropathogenesis. Advances in our understanding of these processes have contributed to the development of therapeutic interventions designed to protect neurons and regulate inflammatory activity.
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Li SX, Barrett BS, Guo K, Santiago ML. Tetherin/BST-2: Restriction Factor or Immunomodulator? Curr HIV Res 2016; 14:235-46. [PMID: 26957198 DOI: 10.2174/1570162x14999160224102752] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/10/2015] [Accepted: 08/11/2015] [Indexed: 11/22/2022]
Abstract
BACKGROUND Cell-mediated immune (CMI) responses are critical for the control of HIV-1 infection and their importance was highlighted by the existence of viral proteins, particularly Vpu and Nef, that antagonize these responses. Pandemic HIV-1 Vpu counteracts Tetherin/BST-2, a host factor that could prevent the release of HIV-1 virions by tethering virions on the cell surface, but a link between Tetherin and HIV-1 CMI responses has not yet been demonstrated in vivo. In vitro, the virological and immunological impact of Tetherin-mediated accumulation of virions ranged from enhanced or diminished cell-to-cell spread to enhanced recognition by virus-specific antibodies for natural killer cellmediated lysis. However, Tetherin-restricted virions could be internalized through an endocytosis motif in the Tetherin cytoplasmic tail. METHODS Given the uncertainties on which in vitro results manifest in vivo and the dearth of knowledge on how Tetherin influences retroviral immunity, in vivo retrovirus infections in mice encoding wild-type, null and endocytosis-defective Tetherin were performed. Here, we review and highlight the results from these in vivo studies. RESULTS Current data suggests that endocytosis-defective Tetherin functions as a potent innate restriction factor. By contrast, endocytosis-competent Tetherin, the form found in most mammals including humans and the form counteracted by HIV-1 Vpu, was linked to stronger CMI responses in mice. CONCLUSION We propose that the main role of endocytosis-competent Tetherin is not to directly restrict retroviral replication, but to promote a more effective CMI response against retroviruses.
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Affiliation(s)
| | | | | | - Mario L Santiago
- Division of Infectious Diseases, University of Colorado Denver, Mail Stop B-168, 12700 E 19th Avenue, Aurora, CO 80045, USA.
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18
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Antagonism of BST-2/Tetherin Is a Conserved Function of the Env Glycoprotein of Primary HIV-2 Isolates. J Virol 2016; 90:11062-11074. [PMID: 27681141 DOI: 10.1128/jvi.01451-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 09/22/2016] [Indexed: 11/20/2022] Open
Abstract
Although HIV-2 does not encode a vpu gene, the ability to antagonize bone marrow stromal antigen 2 (BST-2) is conserved in some HIV-2 isolates, where it is controlled by the Env glycoprotein. We previously reported that a single-amino-acid difference between the laboratory-adapted ROD10 and ROD14 Envs controlled the enhancement of virus release (referred to here as Vpu-like) activity. Here, we investigated how conserved the Vpu-like activity is in primary HIV-2 isolates. We found that half of the 34 tested primary HIV-2 Env isolates obtained from 7 different patients enhanced virus release. Interestingly, most HIV-2 patients harbored a mixed population of viruses containing or lacking Vpu-like activity. Vpu-like activity and Envelope functionality varied significantly among Env isolates; however, there was no direct correlation between these two functions, suggesting they evolved independently. In comparing the Env sequences from one HIV-2 patient, we found that similar to the ROD10/ROD14 Envs, a single-amino-acid change (T568I) in the ectodomain of the TM subunit was sufficient to confer Vpu-like activity to an inactive Env variant. Surprisingly, however, absence of Vpu-like activity was not correlated with absence of BST-2 interaction. Taken together, our data suggest that maintaining the ability to antagonize BST-2 is of functional relevance not only to HIV-1 but also to HIV-2 as well. Our data show that as with Vpu, binding of HIV-2 Env to BST-2 is important but not sufficient for antagonism. Finally, as observed previously, the Vpu-like activity in HIV-2 Env can be controlled by single-residue changes in the TM subunit. IMPORTANCE Lentiviruses such as HIV-1 and HIV-2 encode accessory proteins whose function is to overcome host restriction mechanisms. Vpu is a well-studied HIV-1 accessory protein that enhances virus release by antagonizing the host restriction factor BST-2. HIV-2 does not encode a vpu gene. Instead, the HIV-2 Env glycoprotein was found to antagonize BST-2 in some isolates. Here, we cloned multiple Env sequences from 7 HIV-2-infected patients and found that about half were able to antagonize BST-2. Importantly, most HIV-2 patients harbored a mixed population of viruses containing or lacking the ability to antagonize BST-2. In fact, in comparing Env sequences from one patient combined with site-directed mutagenesis, we were able to restore BST-2 antagonism to an inactive Env protein by a single-amino-acid change. Our data suggest that targeting BST-2 by HIV-2 Env is a dynamic process that can be regulated by simple changes in the Env sequence.
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Nishitsuji H, Sugiyama R, Abe M, Takaku H. ATP1B3 Protein Modulates the Restriction of HIV-1 Production and Nuclear Factor κ Light Chain Enhancer of Activated B Cells (NF-κB) Activation by BST-2. J Biol Chem 2015; 291:4754-62. [PMID: 26694617 DOI: 10.1074/jbc.m115.679357] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Indexed: 11/06/2022] Open
Abstract
Here, we identify ATP1B3 and fibrillin-1 as novel BST-2-binding proteins. ATP1B3 depletion in HeLa cells (BST-2-positive cells), but not 293T cells (BST-2-negative cells), induced the restriction of HIV-1 production in a BST-2-dependent manner. In contrast, fibrillin-1 knockdown reduced HIV-1 production in 293T and HeLa cells in a BST-2-independent manner. Moreover, NF-κB activation was enhanced by siATP1B3 treatment in HIV-1- and HIV-1ΔVpu-infected HeLa cells. In addition, ATP1B3 silencing induced high level BST-2 expression on the surface of HeLa cells. These results indicate that ATP1B3 is a co-factor that accelerates BST-2 degradation and reduces BST-2-mediated restriction of HIV-1 production and NF-κB activation.
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Affiliation(s)
- Hironori Nishitsuji
- From the Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Chiba 272-8516
| | - Ryuichi Sugiyama
- the Department of Life and Environmental Sciences and the Department of Microbiology, Yokohama City University School of Medicine, Kanagawa 236-0004, Japan
| | - Makoto Abe
- the Department of Life and Environmental Sciences and
| | - Hiroshi Takaku
- the Department of Life and Environmental Sciences and Research Institute, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba 275-0016, Japan, and
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20
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Painter MM, Morrison JH, Zoecklein LJ, Rinkoski TA, Watzlawik JO, Papke LM, Warrington AE, Bieber AJ, Matchett WE, Turkowski KL, Poeschla EM, Rodriguez M. Antiviral Protection via RdRP-Mediated Stable Activation of Innate Immunity. PLoS Pathog 2015; 11:e1005311. [PMID: 26633895 PMCID: PMC4669089 DOI: 10.1371/journal.ppat.1005311] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 11/05/2015] [Indexed: 01/09/2023] Open
Abstract
For many emerging and re-emerging infectious diseases, definitive solutions via sterilizing adaptive immunity may require years or decades to develop, if they are even possible. The innate immune system offers alternative mechanisms that do not require antigen-specific recognition or a priori knowledge of the causative agent. However, it is unclear whether effective stable innate immune system activation can be achieved without triggering harmful autoimmunity or other chronic inflammatory sequelae. Here, we show that transgenic expression of a picornavirus RNA-dependent RNA polymerase (RdRP), in the absence of other viral proteins, can profoundly reconfigure mammalian innate antiviral immunity by exposing the normally membrane-sequestered RdRP activity to sustained innate immune detection. RdRP-transgenic mice have life-long, quantitatively dramatic upregulation of 80 interferon-stimulated genes (ISGs) and show profound resistance to normally lethal viral challenge. Multiple crosses with defined knockout mice (Rag1, Mda5, Mavs, Ifnar1, Ifngr1, and Tlr3) established that the mechanism operates via MDA5 and MAVS and is fully independent of the adaptive immune system. Human cell models recapitulated the key features with striking fidelity, with the RdRP inducing an analogous ISG network and a strict block to HIV-1 infection. This RdRP-mediated antiviral mechanism does not depend on secondary structure within the RdRP mRNA but operates at the protein level and requires RdRP catalysis. Importantly, despite lifelong massive ISG elevations, RdRP mice are entirely healthy, with normal longevity. Our data reveal that a powerfully augmented MDA5-mediated activation state can be a well-tolerated mammalian innate immune system configuration. These results provide a foundation for augmenting innate immunity to achieve broad-spectrum antiviral protection.
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Affiliation(s)
- Meghan M. Painter
- Mayo Graduate School of Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - James H. Morrison
- Department of Molecular Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Division of Infectious Diseases, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Laurie J. Zoecklein
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Tommy A. Rinkoski
- Department of Molecular Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Jens O. Watzlawik
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Louisa M. Papke
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Arthur E. Warrington
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Allan J. Bieber
- Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota, United State of America
| | - William E. Matchett
- Mayo Graduate School of Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Kari L. Turkowski
- Mayo Graduate School of Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Eric M. Poeschla
- Department of Molecular Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Division of Infectious Diseases, University of Colorado School of Medicine, Aurora, Colorado, United States of America
- Department of Immunology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Moses Rodriguez
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Immunology, Mayo Clinic, Rochester, Minnesota, United States of America
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21
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Takeuchi JS, Ren F, Yoshikawa R, Yamada E, Nakano Y, Kobayashi T, Matsuda K, Izumi T, Misawa N, Shintaku Y, Wetzel KS, Collman RG, Tanaka H, Hirsch VM, Koyanagi Y, Sato K. Coevolutionary dynamics between tribe Cercopithecini tetherins and their lentiviruses. Sci Rep 2015; 5:16021. [PMID: 26531727 PMCID: PMC4631996 DOI: 10.1038/srep16021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 10/08/2015] [Indexed: 02/03/2023] Open
Abstract
Human immunodeficiency virus, a primate lentivirus (PLV), causes AIDS in humans, whereas most PLVs are less or not pathogenic in monkeys. These notions suggest that the co-evolutionary process of PLVs and their hosts associates with viral pathogenicity, and therefore, that elucidating the history of virus-host co-evolution is one of the most intriguing topics in the field of virology. To address this, recent studies have focused on the interplay between intrinsic anti-viral proteins, such as tetherin, and viral antagonists. Through an experimental-phylogenetic approach, here we investigate the co-evolutionary interplay between tribe Cercopithecini tetherin and viral antagonists, Nef and Vpu. We reveal that tribe Cercopithecini tetherins are positively selected, possibly triggered by ancient Nef-like factor(s). We reconstruct the ancestral sequence of tribe Cercopithecini tetherin and demonstrate that all Nef proteins are capable of antagonizing ancestral Cercopithecini tetherin. Further, we consider the significance of evolutionary arms race between tribe Cercopithecini and their PLVs.
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Affiliation(s)
- Junko S Takeuchi
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Fengrong Ren
- Department of Bioinformatics, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 1138510, Japan
| | - Rokusuke Yoshikawa
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Eri Yamada
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Yusuke Nakano
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan.,Department of Medical Virology, Faculty of Life Sciences, Kumamoto University, Kumamoto 8608556, Japan
| | - Tomoko Kobayashi
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Kenta Matsuda
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Taisuke Izumi
- Department of Microbiology, Institute of Health Biosciences, The University of Tokushima, Tokushima 7708503, Japan
| | - Naoko Misawa
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Yuta Shintaku
- Wildlife Research Center, Kyoto University, Kyoto 6068203, Japan.,Japan Monkey Centre, Aichi 4840081, Japan
| | - Katherine S Wetzel
- Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Ronald G Collman
- Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | - Hiroshi Tanaka
- Department of Bioinformatics, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 1138510, Japan
| | - Vanessa M Hirsch
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Yoshio Koyanagi
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan
| | - Kei Sato
- Laboratory of Viral Pathogenesis, Institute for Virus Research, Kyoto University, Kyoto 6068507, Japan.,CREST, Japan Science and Technology Agency, Saitama 3220012, Japan
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22
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HIV-1 Adapts To Replicate in Cells Expressing Common Marmoset APOBEC3G and BST2. J Virol 2015; 90:725-40. [PMID: 26512082 DOI: 10.1128/jvi.02431-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/16/2015] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Previous studies have shown that a major block to HIV-1 replication in common marmosets operates at the level of viral entry and that this block can be overcome by adaptation of the virus in tissue-cultured cells. However, our current studies indicate that HIV-1 encounters additional postentry blocks in common marmoset peripheral blood mononuclear cells. Here, we show that the common marmoset APOBEC3G (A3G) and BST2 proteins block HIV-1 in cell cultures. Using a directed-evolution method that takes advantage of the natural ability of HIV-1 to mutate during replication, we have been able to overcome these blocks in tissue-cultured cells. In the adapted viruses, specific changes were observed in gag, vif, env, and nef. The contribution of these changes to virus replication in the presence of the A3G and BST2 restriction factors was studied. We found that certain amino acid changes in Vif and Env that arise during adaptation to marmoset A3G and BST2 allow the virus to replicate in the presence of these restriction factors. The changes in Vif reduce expression levels and encapsidation of marmoset APOBEC3G, while the changes in Env increase viral fitness and discretely favor cell-to-cell transmission of the virus, allowing viral escape from these restriction factors. IMPORTANCE HIV-1 can infect only humans and chimpanzees. The main reason for this narrow tropism is the presence in many species of dominant-acting factors, known as restriction factors, that block viral replication in a species-specific way. We have been exploring the blocks to HIV-1 in common marmosets, with the ultimate goal of developing a new animal model of HIV-1 infection in these monkeys. In this study, we observed that common marmoset APOBEC3G and BST2, two known restriction factors, are able to block HIV-1 in cell cultures. We have adapted HIV-1 to replicate in the presence of these restriction factors and have characterized the mechanisms of escape. These studies can help in the development of a novel animal model for in vivo infection of marmosets with HIV-1-like viruses.
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Lv M, Zhang B, Shi Y, Han Z, Zhang Y, Zhou Y, Zhang W, Niu J, Yu XF. Identification of BST-2/tetherin-induced hepatitis B virus restriction and hepatocyte-specific BST-2 inactivation. Sci Rep 2015; 5:11736. [PMID: 26119070 PMCID: PMC4484258 DOI: 10.1038/srep11736] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 05/05/2015] [Indexed: 12/25/2022] Open
Abstract
BST-2/tetherin is an interferon-inducible antiviral protein that blocks the release of various enveloped viruses, including HIV-1. Hepatitis B virus (HBV), a major cause of liver disease, belongs to the Hepadnaviridae family of enveloped DNA viruses. Whether BST-2 regulates HBV production is largely unknown. In this report, we have demonstrated that HBV particle release is modulated by BST-2 in a cell type-dependent fashion. In HEK293T cells, ectopically expressed or interferon-induced BST-2 strongly inhibited HBV release. BST-2 co-localized with HBV surface protein at multivesicular bodies (MVBs) and physically interacted with HBV particles. However, exogenous BST-2-induced HBV restriction was weak in Huh-7 hepatoma cells, and the interferon-induced anti-HBV effect was independent of BST-2 induction in hepatic L02 cells. Notably, HBV could promote HIV-1 ΔVpu virus release from BST-2-positive HepG2 hepatoma cells but not HeLa cells, whereas Vpu failed to efficiently inhibit BST-2-induced HBV restriction. HBx exhibited an enhanced interaction and co-localization with BST-2 in hepatocytes. These observations indicate that BST-2 restricts HBV production at intracellular MVBs but is inactivated by HBV through a novel mechanism requiring hepatocyte-specific cellular co-factors or a hepatocyte-specific environment. Further understanding of BST-2-induced HBV restriction may provide new therapeutic targets for future HBV treatments.
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Affiliation(s)
- Mingyu Lv
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] Department of Hepatology, First Hospital of Jilin University, Changchun, P. R. China
| | - Biao Zhang
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] School of Pharmaceutical Sciences, Jilin University, Changchun, P. R. China
| | - Ying Shi
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Zhu Han
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Yan Zhang
- School of Life Sciences, Jilin University, Changchun, P. R. China
| | - Yulai Zhou
- School of Pharmaceutical Sciences, Jilin University, Changchun, P. R. China
| | - Wenyan Zhang
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Junqi Niu
- Department of Hepatology, First Hospital of Jilin University, Changchun, P. R. China
| | - Xiao-Fang Yu
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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Tedbury PR, Freed EO. The cytoplasmic tail of retroviral envelope glycoproteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:253-84. [PMID: 25595807 DOI: 10.1016/bs.pmbts.2014.10.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Retroviruses comprise a large, diverse group that infects a broad range of host organisms. Pathogenicity varies widely; the human immunodeficiency virus is the causative agent of acquired immunodeficiency syndrome, one of the world's leading infectious causes of death, while many nonhuman retroviruses cause cancer in the host. Retroviruses have been studied intensively, and great strides have been made in understanding aspects of retroviral biology. While the principal functions of the viral structural proteins are well understood, there remain many incompletely characterized domains. One of these is the cytoplasmic tail (CT) of the envelope glycoprotein. Several functions of the CT are highly conserved, whereas other properties are unique to a specific retrovirus. For example, the lentiviruses encode envelope glycoproteins with particularly large cytoplasmic domains. The functions of the long lentiviral envelope CT are still being deciphered. The reported functions of retroviral envelope CTs are discussed in this chapter.
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Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
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25
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Waheed AA, Kuruppu ND, Felton KL, D’Souza D, Freed EO. In COS cells Vpu can both stabilize tetherin expression and counteract its antiviral activity. PLoS One 2014; 9:e111628. [PMID: 25360760 PMCID: PMC4216104 DOI: 10.1371/journal.pone.0111628] [Citation(s) in RCA: 8] [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: 06/25/2014] [Accepted: 10/03/2014] [Indexed: 01/12/2023] Open
Abstract
The interferon-inducible cellular protein tetherin (CD317/BST-2) inhibits the release of a broad range of enveloped viruses. The HIV-1 accessory protein Vpu enhances virus particle release by counteracting this host restriction factor. While the antagonism of human tetherin by Vpu has been associated with both proteasomal and lysosomal degradation, the link between Vpu-mediated tetherin degradation and the ability of Vpu to counteract the antiviral activity of tetherin remains poorly understood. Here, we show that human tetherin is expressed at low levels in African green monkey kidney (COS) cells. However, Vpu markedly increases tetherin expression in this cell line, apparently by sequestering it in an internal compartment that bears lysosomal markers. This stabilization of tetherin by Vpu requires the transmembrane sequence of human tetherin. Although Vpu stabilizes human tetherin in COS cells, it still counteracts the ability of tetherin to suppress virus release. The enhancement of virus release by Vpu in COS cells is associated with a modest reduction in cell-surface tetherin expression, even though the overall expression of tetherin is higher in the presence of Vpu. This study demonstrates that COS cells provide a model system in which Vpu-mediated enhancement of HIV-1 release is uncoupled from Vpu-mediated tetherin degradation.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
- * E-mail:
| | - Nishani D. Kuruppu
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Kathryn L. Felton
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Darren D’Souza
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
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26
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The HERV-K human endogenous retrovirus envelope protein antagonizes Tetherin antiviral activity. J Virol 2014; 88:13626-37. [PMID: 25210194 DOI: 10.1128/jvi.02234-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Endogenous retroviruses are the remnants of past retroviral infections that are scattered within mammalian genomes. In humans, most of these elements are old degenerate sequences that have lost their coding properties. The HERV-K(HML2) family is an exception: it recently amplified in the human genome and corresponds to the most active proviruses, with some intact open reading frames and the potential to encode viral particles. Here, using a reconstructed consensus element, we show that HERV-K(HML2) proviruses are able to inhibit Tetherin, a cellular restriction factor that is active against most enveloped viruses and acts by keeping the viral particles attached to the cell surface. More precisely, we identify the Envelope protein (Env) as the viral effector active against Tetherin. Through immunoprecipitation experiments, we show that the recognition of Tetherin is mediated by the surface subunit of Env. Similar to Ebola glycoprotein, HERV-K(HML2) Env does not mediate Tetherin degradation or cell surface removal; therefore, it uses a yet-undescribed mechanism to inactivate Tetherin. We also assessed all natural complete alleles of endogenous HERV-K(HML2) Env described to date for their ability to inhibit Tetherin and found that two of them (out of six) can block Tetherin restriction. However, due to their recent amplification, HERV-K(HML2) elements are extremely polymorphic in the human population, and it is likely that individuals will not all possess the same anti-Tetherin potential. Because of Tetherin's role as a restriction factor capable of inducing innate immune responses, this could have functional consequences for individual responses to infection. IMPORTANCE Tetherin, a cellular protein initially characterized for its role against HIV-1, has been proven to counteract numerous enveloped viruses. It blocks the release of viral particles from producer cells, keeping them tethered to the cell surface. Several viruses have developed strategies to inhibit Tetherin activity, allowing them to efficiently infect and replicate in their host. Here, we show that human HERV-K(HML2) elements, the remnants of an ancient retroviral infection, possess an anti-Tetherin activity which is mediated by the envelope protein. It is likely that this activity was an important factor that contributed to the recent, human-specific amplification of this family of elements. Also, due to their recent amplification, HERV-K(HML2) elements are highly polymorphic in the human population. Since Tetherin is a mediator of innate immunity, interindividual variations among HERV-K(HML2) Env genes may result in differences in immune responses to infection.
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27
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Yin X, Guo M, Gu Q, Wu X, Wei P, Wang X. Antiviral potency and functional analysis of tetherin orthologues encoded by horse and donkey. Virol J 2014; 11:151. [PMID: 25158826 PMCID: PMC4152588 DOI: 10.1186/1743-422x-11-151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 08/22/2014] [Indexed: 12/11/2022] Open
Abstract
Background Tetherin is an interferon-inducible host cell factor that blocks the viral particle release of the enveloped viruses. Most knowledge regarding the interaction between tetherin and viruses has been obtained using the primate lentiviral system. However, much less is known about the functional roles of tetherin on other lentiviruses. Equine infectious anemia virus (EIAV) is an important macrophage-tropic lentivirus that has been widely used as a practical model for investigating the evolution of the host-virus relationship. The host range of EIAV is reported to include all members of the Equidae family. However, EIAV has different clinical responses in horse and donkey. It’s intriguing to investigate the similarities and differences between the tetherin orthologues encoded by horse and donkey. Results We report here that there are two equine tetherin orthologues. Compared to horse tetherin, there are three valine amino acid deletions within the transmembrane domain and three distinct mutations within the ectodomain of donkey tetherin. However, the antiviral activity of donkey tetherin was not affected by amino acid deletion or substitution. In addition, both tetherin orthologues encoded by horse and donkey are similarly sensitive to EIAV Env protein, and equally activate NF-κB signaling. Conclusion Our data suggest that both tetherin orthologues encoded by horse and donkey showed similar antiviral activities and abilities to induce NF-κB signaling. In addition, the phenomenon about the differential responses of horses and donkeys to infection with EIAV was not related with the differences in the structure of the corresponding tetherin orthologues.
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Affiliation(s)
| | | | | | | | - Ping Wei
- College of Veterinary Medicine, Northeast Agricultural University, Harbin, China.
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28
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TALEN knockout of the PSIP1 gene in human cells: analyses of HIV-1 replication and allosteric integrase inhibitor mechanism. J Virol 2014; 88:9704-17. [PMID: 24942577 DOI: 10.1128/jvi.01397-14] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED HIV-1 utilizes the cellular protein LEDGF/p75 as a chromosome docking and integration cofactor. The LEDGF/p75 gene, PSIP1, is a potential therapeutic target because, like CCR5, depletion of LEDGF/p75 is tolerated well by human CD4+ T cells, and knockout mice have normal immune systems. RNA interference (RNAi) has been useful for studying LEDGF/p75, but the potent cofactor activity of small protein residua can be confounding. Here, in human cells with utility for HIV research (293T and Jurkat), we used transcription activator-like effector nucleases (TALENs) to completely eradicate all LEDGF/p75 expression. We performed two kinds of PSIP1 knockouts: whole-gene deletion and deletion of the integrase binding domain (IBD)-encoding exons. HIV-1 integration was inhibited, and spreading viral replication was severely impaired in PSIP1-/- Jurkat cells infected at high multiplicity. Furthermore, frameshifting the gene in the first coding exon with a single TALEN pair yielded trace LEDGF/p75 levels that were virologically active, affirming the cofactor's potency and the value of definitive gene or IBD exon segment deletion. Some recent studies have suggested that LEDGF/p75 may participate in HIV-1 assembly. However, we determined that assembly of infectious viral particles is normal in PSIP1-/- cells. The potency of an allosteric integrase inhibitor, ALLINI-2, for rendering produced virions noninfectious was also unaffected by total eradication of cellular LEDGF/p75. We conclude that HIV-1 particle assembly and the main ALLINI mechanism are LEDGF/p75 independent. The block to HIV-1 propagation in PSIP1-/- human CD4+ T cells raises the possibility of gene targeting PSIP1 combinatorially with CCR5 for HIV-1 cure. IMPORTANCE LEDGF/p75 dependence is universally conserved in the retroviral genus Lentivirus. Once inside the nucleus, lentiviral preintegration complexes are thought to attach to the chromosome when integrase binds to LEDGF/p75. This tethering process is largely responsible for the 2-fold preference for integration into active genes, but the cofactor's full role in the lentiviral life cycle is not yet clear. Effective knockdowns are difficult because even trace residua of this tightly chromatin-bound protein can support integration cofactor function. Here, in experimentally useful human cell lines, we used TALENs to definitively eradicate LEDGF/p75 by deleting either all of PSIP1 or the exons that code for the integrase binding domain. HIV-1 replication was severely impaired in these PSIP1 knockout cells. Experiments in these cells also excluded a role for LEDGF/p75 in HIV-1 assembly and showed that the main ALLINI mechanism is LEDGF/p75 independent. Site-specific gene targeting of PSIP1 may have therapeutic potential for HIV-1 disease.
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29
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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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