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Kang H, Kang T, Jackson L, Murphy A, Nitta T. Evidence for Involvement of ADP-Ribosylation Factor 6 in Intracellular Trafficking and Release of Murine Leukemia Virus Gag. Cells 2024; 13:270. [PMID: 38334661 PMCID: PMC10854678 DOI: 10.3390/cells13030270] [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: 12/07/2023] [Revised: 01/29/2024] [Accepted: 01/29/2024] [Indexed: 02/10/2024] Open
Abstract
Murine leukemia viruses (MuLVs) are simple retroviruses that cause several diseases in mice. Retroviruses encode three basic genes: gag, pol, and env. Gag is translated as a polyprotein and moves to assembly sites where viral particles are shaped by cleavage of poly-Gag. Viral release depends on the intracellular trafficking of viral proteins, which is determined by both viral and cellular factors. ADP-ribosylation factor 6 (Arf6) is a small GTPase that regulates vesicular trafficking and recycling of different types of cargo in cells. Arf6 also activates phospholipase D (PLD) and phosphatidylinositol-4-phosphate 5-kinase (PIP5K) and produces phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). We investigated how Arf6 affected MuLV release with a constitutively active form of Arf6, Arf6Q67L. Expression of Arf6Q67L impaired Gag release by accumulating Gag at PI(4,5)P2-enriched compartments in the cytoplasm. Treatment of the inhibitors for PLD and PIP5K impaired or recovered MuLV Gag release in the cells expressing GFP (control) and Arf6Q67L, implying that regulation of PI(4,5)P2 through PLD and PIP5K affected MuLV release. Interference with the phosphoinositide 3-kinases, mammalian target of rapamycin (mTOR) pathway, and vacuolar-type ATPase activities showed further impairment of Gag release from the cells expressing Arf6Q67L. In contrast, mTOR inhibition increased Gag release in the control cells. The proteasome inhibitors reduced viral release in the cells regardless of Arf6Q67L expression. These data outline the differences in MuLV release under the controlled and overactivated Arf6 conditions and provide new insight into pathways for MuLV release.
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Affiliation(s)
- Hyokyun Kang
- Department of Biology, Savannah State University, Savannah, GA 31404, USA; (H.K.); (T.K.); (L.J.); (A.M.)
| | - Taekwon Kang
- Department of Biology, Savannah State University, Savannah, GA 31404, USA; (H.K.); (T.K.); (L.J.); (A.M.)
| | - Lauryn Jackson
- Department of Biology, Savannah State University, Savannah, GA 31404, USA; (H.K.); (T.K.); (L.J.); (A.M.)
| | - Amaiya Murphy
- Department of Biology, Savannah State University, Savannah, GA 31404, USA; (H.K.); (T.K.); (L.J.); (A.M.)
| | - Takayuki Nitta
- Department of Biology, Savannah State University, Savannah, GA 31404, USA; (H.K.); (T.K.); (L.J.); (A.M.)
- Department of Molecular Biology and Biochemistry, Cancer Research Institute, University of California, Irvine, CA 92697, USA
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Bussienne C, Marquet R, Paillart JC, Bernacchi S. Post-Translational Modifications of Retroviral HIV-1 Gag Precursors: An Overview of Their Biological Role. Int J Mol Sci 2021; 22:ijms22062871. [PMID: 33799890 PMCID: PMC8000049 DOI: 10.3390/ijms22062871] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/06/2021] [Accepted: 03/09/2021] [Indexed: 11/24/2022] Open
Abstract
Protein post-translational modifications (PTMs) play key roles in eukaryotes since they finely regulate numerous mechanisms used to diversify the protein functions and to modulate their signaling networks. Besides, these chemical modifications also take part in the viral hijacking of the host, and also contribute to the cellular response to viral infections. All domains of the human immunodeficiency virus type 1 (HIV-1) Gag precursor of 55-kDa (Pr55Gag), which is the central actor for viral RNA specific recruitment and genome packaging, are post-translationally modified. In this review, we summarize the current knowledge about HIV-1 Pr55Gag PTMs such as myristoylation, phosphorylation, ubiquitination, sumoylation, methylation, and ISGylation in order to figure out how these modifications affect the precursor functions and viral replication. Indeed, in HIV-1, PTMs regulate the precursor trafficking between cell compartments and its anchoring at the plasma membrane, where viral assembly occurs. Interestingly, PTMs also allow Pr55Gag to hijack the cell machinery to achieve viral budding as they drive recognition between viral proteins or cellular components such as the ESCRT machinery. Finally, we will describe and compare PTMs of several other retroviral Gag proteins to give a global overview of their role in the retroviral life cycle.
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3
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Ziegler CM, Dang L, Eisenhauer P, Kelly JA, King BR, Klaus JP, Manuelyan I, Mattice EB, Shirley DJ, Weir ME, Bruce EA, Ballif BA, Botten J. NEDD4 family ubiquitin ligases associate with LCMV Z's PPXY domain and are required for virus budding, but not via direct ubiquitination of Z. PLoS Pathog 2019; 15:e1008100. [PMID: 31710650 PMCID: PMC6874086 DOI: 10.1371/journal.ppat.1008100] [Citation(s) in RCA: 12] [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: 04/27/2019] [Revised: 11/21/2019] [Accepted: 09/20/2019] [Indexed: 12/20/2022] Open
Abstract
Viral late domains are used by many viruses to recruit the cellular endosomal sorting complex required for transport (ESCRT) to mediate membrane scission during viral budding. Unlike the P(S/T)AP and YPX(1–3)L late domains, which interact directly with the ESCRT proteins Tsg101 and ALIX, the molecular linkage connecting the PPXY late domain to ESCRT proteins is unclear. The mammarenavirus lymphocytic choriomeningitis virus (LCMV) matrix protein, Z, contains only one late domain, PPXY. We previously found that this domain in LCMV Z, as well as the ESCRT pathway, are required for the release of defective interfering (DI) particles but not infectious virus. To better understand the molecular mechanism of ESCRT recruitment by the PPXY late domain, affinity purification-mass spectrometry was used to identify host proteins that interact with the Z proteins of the Old World mammarenaviruses LCMV and Lassa virus. Several Nedd4 family E3 ubiquitin ligases interact with these matrix proteins and in the case of LCMV Z, the interaction was PPXY-dependent. We demonstrated that these ligases directly ubiquitinate LCMV Z and mapped the specific lysine residues modified. A recombinant LCMV containing a Z that cannot be ubiquitinated maintained its ability to produce both infectious virus and DI particles, suggesting that direct ubiquitination of LCMV Z alone is insufficient for recruiting ESCRT proteins to mediate virus release. However, Nedd4 ligases appear to be important for DI particle release suggesting that ubiquitination of targets other than the Z protein itself is required for efficient viral ESCRT recruitment. Enveloped viruses derive their lipid bilayer from either the cellular plasma membrane or an intracellular organelle during the process of viral budding in which a virus particle is formed at a membrane. Many enveloped viruses recruit the cellular endosomal sorting complex required for transport (ESCRT) in order to efficiently cut the membrane that connects a newly budded, but not released, virus particle from its parent membrane. Late domains, which are short protein motifs found in numerous enveloped viruses, specifically recruit ESCRT for this process. Two types of late domains accomplish this by binding directly to ESCRT proteins. A third late domain, PPXY, recruits ESCRT proteins through an unknown, indirect linkage. In this study, we sought to identify proteins that may bridge the PPXY late domain and ESCRT proteins. We found that Nedd4 family ubiquitin ligases interact with the PPXY domain in the mammarenavirus Z protein resulting in ubiquitination of Z at two lysine residues. However, Z ubiquitination was largely dispensable for the virus. Conversely, Nedd4 ubiquitin ligases were critical during infection suggesting that the most important contribution made to virus release by Nedd4 ligases is not direct ubiquitination of the viral matrix protein, but possibly the ubiquitination of cellular proteins or other viral proteins.
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Affiliation(s)
- Christopher M. Ziegler
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Loan Dang
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Philip Eisenhauer
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Jamie A. Kelly
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Benjamin R. King
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Joseph P. Klaus
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Inessa Manuelyan
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
- Cellular, Molecular and Biomedical Sciences Graduate Program, University of Vermont, Burlington, Vermont, United States of America
| | - Ethan B. Mattice
- Cellular, Molecular and Biomedical Sciences Graduate Program, University of Vermont, Burlington, Vermont, United States of America
| | - David J. Shirley
- Ixis LLC, Data Science Division, Burlington, Vermont, United States of America
| | - Marion E. Weir
- Department of Biology, University of Vermont, Burlington, Vermont, United States of America
| | - Emily A. Bruce
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
| | - Bryan A. Ballif
- Department of Biology, University of Vermont, Burlington, Vermont, United States of America
| | - Jason Botten
- Department of Medicine, Division of Immunobiology, University of Vermont, Burlington, Vermont, United States of America
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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Coren LV, Nagashima K, Ott DE. A PLPPV sequence in the p8 region of Gag provides late domain function for mouse mammary tumor virus. Virology 2019; 535:272-278. [PMID: 31357166 PMCID: PMC6952571 DOI: 10.1016/j.virol.2019.07.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 02/07/2023]
Abstract
The late (L) domain sequence used by mouse mammary tumor virus (MMTV) remains undefined. Similar to other L domain-containing proteins, MMTV p8 and p14NC proteins are monoubiquitinated, suggesting L domain function. Site-directed mutagenesis of p8, PLPPV, and p14NC, PLPPL, sequences in MMTV Gag revealed a requirement only for the PLPPV sequence in virion release in a position-dependent manner. Electron microscopy of a defective Gag mutant confirmed an L domain budding defect morphology. The equine infectious anemia virus (EIAV) YPDL core L domain sequence and PLPPV provided L domain function in reciprocal MMTV and EIAV Gag exchange mutants, respectively. Alanine scanning of the PLPPV sequence revealed a strict requirement for the valine residue but only minor requirements for any one of the other residues. Thus, PLPPV provides MMTV L domain function, representing a fourth type of retroviral L domain that enables MMTV Gag proteins to co-opt cellular budding pathways for release.
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Affiliation(s)
- Lori V Coren
- AIDS and Cancer Virus Program, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA.
| | - Kunio Nagashima
- Advanced Technology Program, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA
| | - David E Ott
- AIDS and Cancer Virus Program, National Cancer Institute at Frederick, Frederick, MD, 21702-1201, USA
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Wapling J, Srivastava S, Shehu-Xhilaga M, Tachedjian G. Targeting Human Immunodeficiency Virus Type 1 Assembly, Maturation and Budding. Drug Target Insights 2017. [DOI: 10.1177/117739280700200020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Johanna Wapling
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia
- Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia
| | - Seema Srivastava
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia
| | - Miranda Shehu-Xhilaga
- Department of Medicine, Monash University, Prahran, Victoria 3181, Australia
- Infectious Diseases Unit, Alfred Hospital, Prahran, Victoria 3181, Australia
| | - Gilda Tachedjian
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia
- Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia
- Department of Medicine, Monash University, Prahran, Victoria 3181, Australia
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6
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Hijacking of the Ubiquitin/Proteasome Pathway by the HIV Auxiliary Proteins. Viruses 2017; 9:v9110322. [PMID: 29088112 PMCID: PMC5707529 DOI: 10.3390/v9110322] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 10/26/2017] [Accepted: 10/30/2017] [Indexed: 02/08/2023] Open
Abstract
The ubiquitin-proteasome system (UPS) ensures regulation of the protein pool in the cell by ubiquitination of proteins followed by their degradation by the proteasome. It plays a central role in the cell under normal physiological conditions as well as during viral infections. On the one hand, the UPS can be used by the cell to degrade viral proteins, thereby restricting the viral infection. On the other hand, it can also be subverted by the virus to its own advantage, notably to induce degradation of cellular restriction factors. This makes the UPS a central player in viral restriction and counter-restriction. In this respect, the human immunodeficiency viruses (HIV-1 and 2) represent excellent examples. Indeed, many steps of the HIV life cycle are restricted by cellular proteins, some of which are themselves components of the UPS. However, HIV itself hijacks the UPS to mediate defense against several cellular restriction factors. For example, the HIV auxiliary proteins Vif, Vpx and Vpu counteract specific restriction factors by the recruitment of cellular UPS components. In this review, we describe the interplay between HIV and the UPS to illustrate its role in the restriction of viral infections and its hijacking by viral proteins for counter-restriction.
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7
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Cross- and Co-Packaging of Retroviral RNAs and Their Consequences. Viruses 2016; 8:v8100276. [PMID: 27727192 PMCID: PMC5086612 DOI: 10.3390/v8100276] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 10/03/2016] [Accepted: 10/03/2016] [Indexed: 12/23/2022] Open
Abstract
Retroviruses belong to the family Retroviridae and are ribonucleoprotein (RNP) particles that contain a dimeric RNA genome. Retroviral particle assembly is a complex process, and how the virus is able to recognize and specifically capture the genomic RNA (gRNA) among millions of other cellular and spliced retroviral RNAs has been the subject of extensive investigation over the last two decades. The specificity towards RNA packaging requires higher order interactions of the retroviral gRNA with the structural Gag proteins. Moreover, several retroviruses have been shown to have the ability to cross-/co-package gRNA from other retroviruses, despite little sequence homology. This review will compare the determinants of gRNA encapsidation among different retroviruses, followed by an examination of our current understanding of the interaction between diverse viral genomes and heterologous proteins, leading to their cross-/co-packaging. Retroviruses are well-known serious animal and human pathogens, and such a cross-/co-packaging phenomenon could result in the generation of novel viral variants with unknown pathogenic potential. At the same time, however, an enhanced understanding of the molecular mechanisms involved in these specific interactions makes retroviruses an attractive target for anti-viral drugs, vaccines, and vectors for human gene therapy.
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8
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Sabino Cunha M, Lima Sampaio T, Peterlin BM, Jesus da Costa L. A Truncated Nef Peptide from SIVcpz Inhibits the Production of HIV-1 Infectious Progeny. Viruses 2016; 8:v8070189. [PMID: 27399760 PMCID: PMC4974524 DOI: 10.3390/v8070189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 06/08/2016] [Accepted: 06/14/2016] [Indexed: 12/02/2022] Open
Abstract
Nef proteins from all primate Lentiviruses, including the simian immunodeficiency virus of chimpanzees (SIVcpz), increase viral progeny infectivity. However, the function of Nef involved with the increase in viral infectivity is still not completely understood. Nonetheless, until now, studies investigating the functions of Nef from SIVcpz have been conducted in the context of the HIV-1 proviruses. In an attempt to investigate the role played by Nef during the replication cycle of an SIVcpz, a Nef-defective derivative was obtained from the SIVcpzWTGab2 clone by introducing a frame shift mutation at a unique restriction site within the nef sequence. This nef-deleted clone expresses an N-terminal 74-amino acid truncated peptide of Nef and was named SIVcpz-tNef. We found that the SIVcpz-tNef does not behave as a classic nef-deleted HIV-1 or simian immunodeficiency virus of macaques SIVmac. Markedly, SIVcpz-tNef progeny from both Hek-293T and Molt producer cells were completely non-infectious. Moreover, the loss in infectivity of SIVcpz-tNef correlated with the inhibition of Gag and GagPol processing. A marked accumulation of Gag and very low levels of reverse transcriptase were detected in viral lysates. Furthermore, these observations were reproduced once the tNef peptide was expressed in trans both in SIVcpzΔNef and HIV-1WT expressing cells, demonstrating that the truncated peptide is a dominant negative for viral processing and infectivity for both SIVcpz and HIV-1. We demonstrated that the truncated Nef peptide binds to GagPol outside the protease region and by doing so probably blocks processing of both GagPol and Gag precursors at a very early stage. This study demonstrates for the first time that naturally-occurring Nef peptides can potently block lentiviral processing and infectivity.
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Affiliation(s)
- Marcela Sabino Cunha
- Departamento de Virologia-Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373-CCS-Bloco I, Rio de Janeiro 21941-902, Brazil.
| | - Thatiane Lima Sampaio
- Departamento de Virologia-Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373-CCS-Bloco I, Rio de Janeiro 21941-902, Brazil.
| | - B Matija Peterlin
- Departments of Medicine, Microbiology and Immunology, University of California, San Francisco, 533 Parnassus Avenue, San Francisco, CA 94143, USA.
| | - Luciana Jesus da Costa
- Departamento de Virologia-Instituto de Microbiologia, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373-CCS-Bloco I, Rio de Janeiro 21941-902, Brazil.
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9
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Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag. Viruses 2016; 8:117. [PMID: 27120610 PMCID: PMC4848609 DOI: 10.3390/v8040117] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 03/29/2016] [Accepted: 04/18/2016] [Indexed: 12/15/2022] Open
Abstract
The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (l-) domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane.
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10
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Calistri A, Munegato D, Carli I, Parolin C, Palù G. The ubiquitin-conjugating system: multiple roles in viral replication and infection. Cells 2014; 3:386-417. [PMID: 24805990 PMCID: PMC4092849 DOI: 10.3390/cells3020386] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Revised: 04/23/2014] [Accepted: 04/24/2014] [Indexed: 12/17/2022] Open
Abstract
Through the combined action of ubiquitinating and deubiquitinating enzymes, conjugation of ubiquitin to a target protein acts as a reversible post-translational modification functionally similar to phosphorylation. Indeed, ubiquitination is more and more recognized as a central process for the fine regulation of many cellular pathways. Due to their nature as obligate intracellular parasites, viruses rely on the most conserved host cell machineries for their own replication. Thus, it is not surprising that members from almost every viral family are challenged by ubiquitin mediated mechanisms in different steps of their life cycle and have evolved in order to by-pass or exploit the cellular ubiquitin conjugating system to maximize their chance to establish a successful infection. In this review we will present several examples of the complex interplay that links viruses and the ubiquitin conjugation machinery, with a special focus on the mechanisms evolved by the human immunodeficiency virus to escape from cellular restriction factors and to exit from infected cells.
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Affiliation(s)
- Arianna Calistri
- Department of Molecular Medicine, University of Padova, via Gabelli 63, Padova 35121, Italy.
| | - Denis Munegato
- Department of Molecular Medicine, University of Padova, via Gabelli 63, Padova 35121, Italy.
| | - Ilaria Carli
- Department of Molecular Medicine, University of Padova, via Gabelli 63, Padova 35121, Italy.
| | - Cristina Parolin
- Department of Molecular Medicine, University of Padova, via Gabelli 63, Padova 35121, Italy.
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padova, via Gabelli 63, Padova 35121, Italy.
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11
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Klinger PP, Schubert U. The ubiquitin–proteasome system in HIV replication: potential targets for antiretroviral therapy. Expert Rev Anti Infect Ther 2014; 3:61-79. [PMID: 15757458 DOI: 10.1586/14787210.3.1.61] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Since the discovery of HIV approximately 20 years ago, more than 60 million individuals have been infected, and AIDS still remains one of the most devastating diseases humankind has ever faced. Unfortunately, there is little hope that an effective vaccine will be developed in the near future. Current antiretroviral treatment is based on drugs that either target the viral enzymes (protease and reverse transcriptase) or the attachment and entry of the virus. Although the introduction of highly active antiretroviral therapy in the mid-1990s has led to a profound reduction in HIV-related morbidity and mortality, the complete eradication of the virus from infected individuals has never been achieved. In addition, these antiviral drugs can induce serious adverse effects, particularly when administered in combination over prolonged treatment periods. A further drawback to these treatments is that with the high mutation rate of HIV, drug-resistant mutants are evolving, particularly when antiretroviral treatment only suppresses virus replication to marginal levels in latently infected cells making up the virus reservoirs in vivo. Cellular genes have much lower mutation rates, and drug-mediated modulation of specific cellular pathways represents an attractive antiviral strategy. Recent findings showing that proteasome inhibitors interfere with budding, maturation and infectivity of HIV have triggered intensive investigation of the hitherto unappreciated function of the ubiquitin-proteasome system in HIV replication. It was also observed that, like several other retroviruses, HIV-1 virions contain a small amount of mono-ubiquitinylated Gag proteins. Currently, two E3-type ubiquitin ligases, in addition to one E3-like protein, have been identified as regulators of HIV budding. These ligases might represent interesting targets for therapeutic intervention.
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Affiliation(s)
- Patricia P Klinger
- University of Erlangen-Nuremberg, Institute of Clinical and Molecular Virology, Schlossgarten 4, 91054 Erlangen, Germany
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12
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Watanabe H, Tanaka Y, Shimazu Y, Sugahara F, Kuwayama M, Hiramatsu A, Kiyotani K, Yoshida T, Sakaguchi T. Cell-Specific Inhibition of Paramyxovirus Maturation by Proteasome Inhibitors. Microbiol Immunol 2013; 49:835-44. [PMID: 16172538 DOI: 10.1111/j.1348-0421.2005.tb03672.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Effects of proteasome inhibitors on the replication of a paramyxovirus in comparison with the effects on replication of an orthomyxovirus and rhabdovirus were investigated. Treatment of Sendai virus (SeV)-infected LLC-MK2 cells with 50 microM MG132 reduced virus growth to ca. 1/10,000, and treatment with different concentrations of MG132 reduced virus growth in a dose-dependent manner. Released amounts of viral proteins were reduced in correspondence with decrease in infectivity. The inhibition of virus maturation was confirmed by an SeV-like particle formation system. Lactacystin also impaired SeV growth and zLL impaired the growth to a lesser extent, suggesting involvement of proteasomes in the restriction of virus growth. In the presence of MG132, localizations of the M protein and viral F and HN glycoproteins on the cell membrane appeared to be partly dissociated, although the viral glycoproteins were normally transported to the cell surface. These results suggest that an early step of SeV assembly was disturbed by proteasome inhibitors. The relationship of the results with ubiquitin is also discussed. SeV maturation was less susceptible and resistant to MG132 in CV1 cells and A549 cells, respectively, indicating cell specificity of the drug effect. Release of vesicular stomatitis virus also showed high susceptibility to MG132 and release of influenza virus A/WSN/33 was only mildly susceptible to the drug in LLC-MK2 cells. Effects of proteasome inhibitors on virus maturation are thus highly cell-specific and partly virus-specific.
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Affiliation(s)
- Hitoshi Watanabe
- Department of Virology, Graduate School of Biomedical Sciences, Hiroshima University 1-2-3 Kasumi, Minami-ku, Hiroshima, Japan
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13
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Rabi SA, Laird GM, Durand CM, Laskey S, Shan L, Bailey JR, Chioma S, Moore RD, Siliciano RF. Multi-step inhibition explains HIV-1 protease inhibitor pharmacodynamics and resistance. J Clin Invest 2013; 123:3848-60. [PMID: 23979165 DOI: 10.1172/jci67399] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 05/30/2013] [Indexed: 11/17/2022] Open
Abstract
HIV-1 protease inhibitors (PIs) are among the most effective antiretroviral drugs. They are characterized by highly cooperative dose-response curves that are not explained by current pharmacodynamic theory. An unresolved problem affecting the clinical use of PIs is that patients who fail PI-containing regimens often have virus that lacks protease mutations, in apparent violation of fundamental evolutionary theory. Here, we show that these unresolved issues can be explained through analysis of the effects of PIs on distinct steps in the viral life cycle. We found that PIs do not affect virion release from infected cells but block entry, reverse transcription, and post-reverse transcription steps. The overall dose-response curves could be reconstructed by combining the curves for each step using the Bliss independence principle, showing that independent inhibition of multiple distinct steps in the life cycle generates the highly cooperative dose-response curves that make these drugs uniquely effective. Approximately half of the inhibitory potential of PIs is manifest at the entry step, likely reflecting interactions between the uncleaved Gag and the cytoplasmic tail (CT) of the Env protein. Sequence changes in the CT alone, which are ignored in current clinical tests for PI resistance, conferred PI resistance, providing an explanation for PI failure without resistance.
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Affiliation(s)
- S Alireza Rabi
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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14
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Zhou Y, Gao L, Shi H, Xia H, Gao L, Lian C, Chen L, Yao Q, Chen K, Liu X. Microarray analysis of gene expression profile in resistant and susceptible Bombyx mori strains reveals resistance-related genes to nucleopolyhedrovirus. Genomics 2013; 101:256-62. [PMID: 23434630 DOI: 10.1016/j.ygeno.2013.02.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 02/05/2013] [Accepted: 02/07/2013] [Indexed: 01/28/2023]
Abstract
To investigate the molecular mechanism of silkworm resistance to BmNPV infection, we constructed a near-isogenic line (BC8) with BmNPV resistance using highly resistant (NB) and highly susceptible parental strains (306). We investigated variations in the gene expression in the midguts of BmNPV-infected BC8 and 306 at 12 h pi using the microarray. 92 differentially expressed genes were identified. Real-time qPCR analysis confirmed that 10 genes were significantly up-regulated or down-regulated in the midguts of BC8 and NB compared to 306. To our knowledge, we first defined the role of the amino acid transporter and 26S proteasome in insect antiviral. However, serine protease was not completely consistent with data of reported previously in insect antiviral. The role of the 5 genes (Bm123, Bm122, COP β', aquaporin, glycoside hydrolases) was also demonstrated in insect antiviral. Our results provided new insights into the molecular mechanism of the Bombyx mori immune response against BmNPV infection.
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Affiliation(s)
- Yang Zhou
- Institute of Life Sciences, Jiangsu University, China
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15
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Budding of Enveloped Viruses: Interferon-Induced ISG15-Antivirus Mechanisms Targeting the Release Process. Adv Virol 2012; 2012:532723. [PMID: 22666250 PMCID: PMC3362814 DOI: 10.1155/2012/532723] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 03/12/2012] [Indexed: 11/17/2022] Open
Abstract
Pathogenic strains of viruses that infect humans are encapsulated in membranes derived from the host cell in which they infect. After replication, these viruses are released by a budding process that requires cell/viral membrane scission. As such, this represents a natural target for innate immunity mechanisms to interdict enveloped virus spread and recent advances in this field will be the subject of this paper.
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16
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Abstract
Ubiquitin is important for the budding of many retroviruses and other enveloped viruses, but the precise role of ubiquitin in virus budding remains unclear. Here, we characterized the ubiquitination of the matrix (M) protein of a paramyxovirus, parainfluenza virus 5 (PIV5). The PIV5 M protein (but not the PIV5 nucleocapsid protein) was found to be targeted for monoubiquitination in transfected mammalian cells. Major sites of ubiquitin attachment identified by mass spectrometry analysis were lysine residues at amino acid positions 79/80, 130, and 247. The cumulative mutation of lysine residues 79, 80, and 130 to arginines led to an altered pattern of M protein ubiquitination and impaired viruslike particle (VLP) production. However, the cumulative mutation of lysine residues 79, 80, 130, and 247 to arginines restored M protein ubiquitination and VLP production, suggesting that ubiquitin is attached to alternative sites on the M protein when the primary ones have been removed. Additional lysine residues were targeted for mutagenesis based on the UbiPred algorithm. An M protein with seven lysine residues changed to arginines exhibited altered ubiquitination and poor VLP production. A recombinant virus encoding an M protein with seven lysines mutated was generated, and this virus exhibited a 6-fold-reduced maximum titer, with the defect being attributed mainly to the budding of noninfectious particles. The recombinant virus was assembly deficient, as judged by the redistribution of viral M and hemagglutinin-neuraminidase proteins in infected cells. Similar assembly defects were observed for the wild-type (wt) virus after treatment with a proteasome inhibitor. Collectively, these findings suggest that the monoubiquitination of the PIV5 M protein is important for proper virus assembly and for the budding of infectious particles.
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17
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Systemic analysis of heat shock response induced by heat shock and a proteasome inhibitor MG132. PLoS One 2011; 6:e20252. [PMID: 21738571 PMCID: PMC3127947 DOI: 10.1371/journal.pone.0020252] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 04/28/2011] [Indexed: 11/19/2022] Open
Abstract
The molecular basis of heat shock response (HSR), a cellular defense mechanism against various stresses, is not well understood. In this, the first comprehensive analysis of gene expression changes in response to heat shock and MG132 (a proteasome inhibitor), both of which are known to induce heat shock proteins (Hsps), we compared the responses of normal mouse fibrosarcoma cell line, RIF- 1, and its thermotolerant variant cell line, TR-RIF-1 (TR), to the two stresses. The cellular responses we examined included Hsp expressions, cell viability, total protein synthesis patterns, and accumulation of poly-ubiquitinated proteins. We also compared the mRNA expression profiles and kinetics, in the two cell lines exposed to the two stresses, using microarray analysis. In contrast to RIF-1 cells, TR cells resist heat shock caused changes in cell viability and whole-cell protein synthesis. The patterns of total cellular protein synthesis and accumulation of poly-ubiquitinated proteins in the two cell lines were distinct, depending on the stress and the cell line. Microarray analysis revealed that the gene expression pattern of TR cells was faster and more transient than that of RIF-1 cells, in response to heat shock, while both RIF-1 and TR cells showed similar kinetics of mRNA expression in response to MG132. We also found that 2,208 genes were up-regulated more than 2 fold and could sort them into three groups: 1) genes regulated by both heat shock and MG132, (e.g. chaperones); 2) those regulated only by heat shock (e.g. DNA binding proteins including histones); and 3) those regulated only by MG132 (e.g. innate immunity and defense related molecules). This study shows that heat shock and MG132 share some aspects of HSR signaling pathway, at the same time, inducing distinct stress response signaling pathways, triggered by distinct abnormal proteins.
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18
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Hahn S, Setz C, Wild J, Schubert U. The PTAP sequence within the p6 domain of human immunodeficiency virus type 1 Gag regulates its ubiquitination and MHC class I antigen presentation. THE JOURNAL OF IMMUNOLOGY 2011; 186:5706-18. [PMID: 21482733 DOI: 10.4049/jimmunol.1003764] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Endogenous peptides presented by MHC class I (MHC-I) molecules are mostly derived from de novo synthesized, erroneous proteins, so-called defective ribosomal products (DRiPs), which are rapidly degraded via the ubiquitin-proteasome pathway. We have previously shown that the HIV-1 Gag protein represents a bona fide substrate for the DRiP pathway and that the amount of Gag-DRiPs can be enhanced by the introduction of an N-end rule degradation signal, leading to increased MHC-I presentation and immunogenicity of Gag. Based on these findings, we sought to identify a naturally occurring sequence motif within Gag that regulates its entry into the DRiP pathway. As the PTAP late assembly domain motif in the C-terminal p6 domain of Gag has been shown to negatively regulate the ubiquitination of Gag, we analyzed the correlation between ubiquitination and MHC-I presentation of PTAP-deficient Gag. Intriguingly, mutation of PTAP not only reduces the release of virus-like particles, but also increases ubiquitination of Gag and, consistently, enhances MHC-I presentation of a Gag-derived epitope. Although the half-life of the PTAP mutant was only mildly reduced, the entry into the DRiP pathway was significantly increased, as demonstrated by short-term pulse-chase analyses under proteasome inhibition. Collectively, these results indicate that, besides driving virus release, the PTAP motif regulates the entry of Gag into the DRiP pathway and, thus, into the MHC-I pathway. Although there are no naturally occurring PTAP mutants of HIV-1, mutations of PTAP might enhance the immunogenicity of Gag and, thus, be considered for the improvement of vaccine development.
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Affiliation(s)
- Sabine Hahn
- Institute of Clinical and Molecular Virology, Friedrich Alexander University, 91054 Erlangen, Germany
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19
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Abstract
The host innate immune response, including the production of type-I IFN, represents the primary line of defense against invading viral pathogens. Of the hundreds of IFN-stimulated genes (ISGs) discovered to date, ISG15 was one of the first identified and shown to encode a ubiquitin-like protein that functions, in part, as a modifier of protein function. Evidence implicating ISG15 as an innate immune protein with broad-spectrum antiviral activity continues to accumulate rapidly. This review will summarize recent findings on the innate antiviral activity of ISG15, with a focus on the interplay between ubiquitination and ISGylation pathways resulting in modulation of RNA virus assembly/budding. Indeed, ubiquitination is known to be proviral for some RNA viruses, whereas the parallel ISGylation pathway is known to be antiviral. A better understanding of the antiviral activities of ISG15 will enhance our fundamental knowledge of host innate responses to viral pathogens and may provide insight useful for the development of novel therapeutic approaches designed to enhance the immune response against such pathogens.
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Affiliation(s)
- Ronald N Harty
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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20
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The interferon-induced gene ISG15 blocks retrovirus release from cells late in the budding process. J Virol 2010; 84:4725-36. [PMID: 20164219 DOI: 10.1128/jvi.02478-09] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The release of retroviruses from cells requires ubiquitination of Gag and recruitment of cellular proteins involved in endosome sorting, including the ESCRT-III proteins and the Vps4 ATPase. In response to infection, cells have evolved an interferon-induced mechanism to block virus replication through expression of the interferon-stimulated gene 15 (ISG15), a dimer homologue of ubiquitin, which interferes with ubiquitin pathways in cells. Previously, it has been reported that ISG15 expression inhibited the E3 ubiquitin ligase, Nedd4, and prevented association of the ESCRT-I protein Tsg101 with human immunodeficiency virus type 1 (HIV-1) Gag. The budding of avian sarcoma leukosis virus and HIV-1 Gag virus-like particles containing L-domain mutations can be rescued by fusion to ESCRT proteins, which cause entry into the budding pathway beyond these early steps. The release of these fusions from cells was susceptible to inhibition by ISG15, indicating that there was a block late in the budding process. We now demonstrate that the Vps4 protein does not associate with the avian sarcoma leukosis virus or the HIV-1 budding complexes when ISG15 is expressed. This is caused by a loss in interaction between Vps4 with its coactivator protein LIP5 needed to promote the formation of the ESCRT-III-Vps4 double-hexamer complex required for membrane scission and virus release. The inability of LIP5 to interact with Vps4 is the probable result of ISG15 conjugation to the ESCRT-III protein, CHMP5, which regulates the availability of LIP5. Thus, there appear to be multiple levels of ISG15-induced inhibition acting at different stages of the virus release process.
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21
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Abstract
This mini review covers the drug discovery aspect of both proteasome activators and inhibitors. The proteasome is involved in many essential cellular functions, such as regulation of cell cycle, cell differentiation, signal transduction pathways, antigen processing for appropriate immune responses, stress signaling, inflammatory responses, and apoptosis. Due to the importance of the proteasome in cellular functions, inhibition or activation of the proteasome could become a useful therapeutic strategy for a variety of diseases. Many proteasome inhibitors have been identified and can be classified into two groups according to their source: chemically synthesized small molecules and compounds derived from natural products. A successful example of development of a proteasome inhibitor as a clinically useful drug is the peptide boronate, PS341 (Bortezomib), was approved for the treatment of multiple myeloma. In contrast to proteasome inhibitors, small molecules that can activate or enhance proteasome activity are rare and are not well studied. The fact that over-expression of the cellular proteasome activator PA28 exhibited beneficial effects on the Huntington's disease neuronal model cells raised the prospect that small molecule proteasome activators could become useful therapeutics. The beneficial effect of oleuropein, a small molecule proteasome activator, on senescence of human fibroblasts also suggested that proteasome activators might have the potential to be developed into anti-aging agents.
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Affiliation(s)
- Li Huang
- Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA
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22
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Pincetic A, Leis J. The Mechanism of Budding of Retroviruses From Cell Membranes. Adv Virol 2009; 2009:6239691-6239699. [PMID: 19865606 PMCID: PMC2768365 DOI: 10.1155/2009/623969] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 12/18/2008] [Indexed: 11/17/2022] Open
Abstract
Retroviruses have evolved a mechanism for the release of particles from the cell membrane that appropriates cellular protein complexes, referred to as ESCRT-I, -II, -III, normally involved in the biogenesis of multivesicular bodies. Three different classes of late assembly (L) domains encoded in Gag, with core sequences of PPXY, PTAP, and YPXL, recruit different components of the ESCRT machinery to form a budding complex for virus release. Here, we highlight recent progress in identifying the role of different ESCRT complexes in facilitating budding, ubiquitination, and membrane targeting of avian sarcoma and leukosis virus (ASLV) and human immunodeficiency virus, type 1 (HIV-1). These findings show that retroviruses adopt parallel budding pathways by recruiting different host factors from common cellular machinery for particle release.
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Affiliation(s)
- Andrew Pincetic
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Jonathan Leis
- Department of Microbiology and Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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23
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Premature processing of mouse mammary tumor virus Gag polyprotein impairs intracellular capsid assembly. Virology 2008; 384:33-7. [PMID: 19046754 DOI: 10.1016/j.virol.2008.10.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 04/09/2008] [Accepted: 10/24/2008] [Indexed: 11/24/2022]
Abstract
Mouse mammary tumor virus (MMTV) is the prototypical member of the Betaretrovirus genus, but the processes of its morphogenesis are poorly characterized. In this report, we describe an unusual intracellular processing of MMTV Gag polyprotein in human 293T cells transiently expressing MMTV from heterologous promoter. The same specific cleavage products of the viral protease were seen for the wild type as well as for nonmyristylated mutant of MMTV Gag polyprotein completely defective in the particle release. Inactivation of the viral protease resulted in more stable Gag polyprotein and in accumulation of intracytoplasmic particles for nonmyristylated Gag. The intracellular processing of nonmyristylated MMTV Gag indicates that protease activation in betaretrovirus can occur independently of budding.
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24
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Abstract
It has been known for some time that HIV-1 virions contain cellular proteins in addition to proteins encoded by the viral genome. Recent studies have vastly increased the number of host proteins detected in HIV-1. This review summarises the current findings on several cellular proteins present in these virions, including some functional studies on their potential roles in the viral replication cycle and pathogenesis. Because retroviruses require extensive assistance from host proteins and pathways, the data from biochemical characterisations of HIV-1 serve as an important starting point for understanding the role of cellular proteins that act in or influence the biology of HIV-1. Additionally, a better understanding of the interactions between cellular proteins and viral components might provide more targets for anti-HIV therapeutic intervention and provide for a better understanding of how HIV-1 alters the immune system. The extensive study of HIV-1 has already brought new insights to the fields of immunology and vaccine science. In the same way, knowledge of viral--cellular protein interactions might assist our understanding of important cellular pathways.
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Affiliation(s)
- David E Ott
- AIDS Vaccine Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD 21702-1201, USA.
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25
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Neznanov N, Dragunsky EM, Chumakov KM, Neznanova L, Wek RC, Gudkov AV, Banerjee AK. Different effect of proteasome inhibition on vesicular stomatitis virus and poliovirus replication. PLoS One 2008; 3:e1887. [PMID: 18382670 PMCID: PMC2268745 DOI: 10.1371/journal.pone.0001887] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 02/26/2008] [Indexed: 12/22/2022] Open
Abstract
Proteasome activity is an important part of viral replication. In this study, we examined the effect of proteasome inhibitors on the replication of vesicular stomatitis virus (VSV) and poliovirus. We found that the proteasome inhibitors significantly suppressed VSV protein synthesis, virus accumulation, and protected infected cells from toxic effect of VSV replication. In contrast, poliovirus replication was delayed, but not diminished in the presence of the proteasome inhibitors MG132 and Bortezomib. We also found that inhibition of proteasomes stimulated stress-related processes, such as accumulation of chaperone hsp70, phosphorylation of eIF2α, and overall inhibition of translation. VSV replication was sensitive to this stress with significant decline in replication process. Poliovirus growth was less sensitive with only delay in replication. Inhibition of proteasome activity suppressed cellular and VSV protein synthesis, but did not reduce poliovirus protein synthesis. Protein kinase GCN2 supported the ability of proteasome inhibitors to attenuate general translation and to suppress VSV replication. We propose that different mechanisms of translational initiation by VSV and poliovirus determine their sensitivity to stress induced by the inhibition of proteasomes. To our knowledge, this is the first study that connects the effect of stress induced by proteasome inhibition with the efficiency of viral infection.
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Affiliation(s)
- Nickolay Neznanov
- Department of Molecular Genetics, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, United States of America.
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26
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Abstract
A functional ubiquitin proteasome system is essential for all eukaryotic cells and therefore any alteration to its components has potential pathological consequences. Though the exact underlying mechanism is unclear, an age-related decrease in proteasome activity weakens cellular capacity to remove oxidatively modified proteins and favours the development of neurodegenerative and cardiac diseases. Up-regulation of proteasome activity is characteristic of muscle wasting conditions including sepsis, cachexia and uraemia, but may not be rate limiting. Meanwhile, enhanced presence of immunoproteasomes in aging brain and muscle tissue could reflect a persistent inflammatory defence and anti-stress mechanism, whereas in cancer cells, their down-regulation reflects a means by which to escape immune surveillance. Hence, induction of apoptosis by synthetic proteasome inhibitors is a potential treatment strategy for cancer, whereas for other diseases such as neurodegeneration, the use of proteasome-activating or -modulating compounds could be more effective. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).
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Affiliation(s)
- Burkhardt Dahlmann
- Institut für Biochemie, Charité-Universitätsmedizin-Berlin, Monbijoustr, 2, 10117 Berlin, Germany.
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27
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Calistri A, Sette P, Salata C, Cancellotti E, Forghieri C, Comin A, Göttlinger H, Campadelli-Fiume G, Palù G, Parolin C. Intracellular trafficking and maturation of herpes simplex virus type 1 gB and virus egress require functional biogenesis of multivesicular bodies. J Virol 2007; 81:11468-78. [PMID: 17686835 PMCID: PMC2045546 DOI: 10.1128/jvi.01364-07] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The biogenesis of multivesicular bodies (MVBs) is topologically equivalent to virion budding. Hence, a number of viruses exploit the MVB pathway to build their envelope and exit from the cell. By expression of dominant negative forms of Vps4 and Vps24, two components of the MVB pathway, we observed an impairment in infectious herpes simplex virus (HSV) assembly/egress, in agreement with a recent report showing the involvement in HSV envelopment of Vps4, the MVB-specific ATPase (C. M. Crump, C. Yates, and T. Minson, J. Virol. 81:7380-7387). Furthermore, HSV infection resulted in morphological changes to MVBs. Glycoprotein B (gB), one of the most highly conserved glycoproteins across the Herpesviridae family, was sorted to MVB membranes. In cells expressing the dominant negative form of Vps4, the site of intracellular gB accumulation was altered; part of gB accumulated as an endoglycosidase H-sensitive immature form at a calreticulin-positive compartment, indicating that gB traffic was dependent on a functional MVB pathway. gB was ubiquitinated in both infected and transfected cells. Ubiquitination was in part dependent on ubiquitin lysine 63, a signal for cargo sorting to MVBs. Partial deletion of the gB cytoplasmic tail resulted in a dramatic reduction of ubiquitination, as well as of progeny virus assembly and release to the extracellular compartment. Thus, HSV envelopment/egress and gB intracellular trafficking are dependent on functional MVB biogenesis. Our data support the view that the sorting of gB to MVB membranes may represent a critical step in HSV envelopment and egress and that modified MVB membranes constitute a platform for HSV cytoplasmic envelopment or that MVB components are recruited to the site(s) of envelopment.
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Affiliation(s)
- Arianna Calistri
- Department of Histology, Microbiology and Medical Biotechnologies, via Gabelli 63, 35121 Padova, Italy.
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28
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Wapling J, Srivastava S, Shehu-Xhilaga M, Tachedjian G. Targeting human immunodeficiency virus type 1 assembly, maturation and budding. Drug Target Insights 2007; 2:159-82. [PMID: 21901072 PMCID: PMC3155237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The targets for licensed drugs used for the treatment of human immunodeficiency virus type 1 (HIV-1) are confined to the viral reverse transcriptase (RT), protease (PR), and the gp41 transmembrane protein (TM). While currently approved drugs are effective in controlling HIV-1 infections, new drug targets and agents are needed due to the eventual emergence of drug resistant strains and drug toxicity. Our increased understanding of the virus life-cycle and how the virus interacts with the host cell has unveiled novel mechanisms for blocking HIV-1 replication. This review focuses on inhibitors that target the late stages of virus replication including the synthesis and trafficking of the viral polyproteins, viral assembly, maturation and budding. Novel approaches to blocking the oligomerization of viral enzymes and the interactions between viral proteins and host cell factors, including their feasibility as drug targets, are discussed.
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Affiliation(s)
- Johanna Wapling
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia,Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia
| | - Seema Srivastava
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia
| | - Miranda Shehu-Xhilaga
- Department of Medicine, Monash University, Prahran, Victoria 3181, Australia,Infectious Diseases Unit, Alfred Hospital, Prahran, Victoria 3181, Australia
| | - Gilda Tachedjian
- Molecular Interactions Group, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, 3004, Australia,Department of Microbiology, Monash University, Clayton, Victoria 3168, Australia,Department of Medicine, Monash University, Prahran, Victoria 3181, Australia,Correspondence: Gilda Tachedjian, Ph.D., Molecular Interactions Group, The Macfarlane Burnet Institute for Medical Research and Public Health, GPO Box 2284, Melbourne, Victoria, 3001, Australia. Tel: 61 3 9282 2256; Fax: 61 3 9282 2100;
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29
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Heidecker G, Lloyd PA, Soheilian F, Nagashima K, Derse D. The role of WWP1-Gag interaction and Gag ubiquitination in assembly and release of human T-cell leukemia virus type 1. J Virol 2007; 81:9769-77. [PMID: 17609263 PMCID: PMC2045422 DOI: 10.1128/jvi.00642-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The PPPY motif in the matrix (MA) domain of human T-cell leukemia virus type 1 (HTLV-1) Gag associates with WWP1, a member of the HECT domain containing family of E3 ubiquitin ligases. Mutation of the PPPY motif arrests particle assembly at an early stage and abolishes ubiquitination of MA. Similar effects are seen when Gag is expressed in the presence of a truncated form of WWP1 that lacks the catalytically active HECT domain (C2WW). To understand the role of ubiquitination in budding, we mutated the four lysines in MA to arginines and identified lysine 74 as the unique site of ubiquitination. Virus-like particles produced by the K74R mutant did not contain ubiquitinated MA and showed a fourfold reduction in the release of infectious particles. Furthermore, the K74R mutation rendered assembly hypersensitive to C2WW inhibition; K74R Gag budding was inhibited at significantly lower levels of expression of C2WW compared with wild-type Gag. This finding indicates that the interaction between Gag and WWP1 is required for functions other than Gag ubiquitination. Additionally, we show that the PPPY(-) mutant Gag exerts a strong dominant-negative effect on the budding of wild-type Gag, further supporting the importance of recruitment of WWP1 to achieve particle assembly.
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Affiliation(s)
- Gisela Heidecker
- National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA.
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30
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Borissenko L, Groll M. 20S proteasome and its inhibitors: crystallographic knowledge for drug development. Chem Rev 2007; 107:687-717. [PMID: 17316053 DOI: 10.1021/cr0502504] [Citation(s) in RCA: 332] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ljudmila Borissenko
- Charité (CCM), Institut für Biochemie, AG Strukturforschung, Monbijoustrasse 2, 10117 Berlin, Germany
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31
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Agarwal S, Harada J, Schreifels J, Lech P, Nikolai B, Yamaguchi T, Chanda SK, Somia NV. Isolation, characterization, and genetic complementation of a cellular mutant resistant to retroviral infection. Proc Natl Acad Sci U S A 2006; 103:15933-8. [PMID: 17043244 PMCID: PMC1636844 DOI: 10.1073/pnas.0602674103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By using a genetic screen, we have isolated a mammalian cell line that is resistant to infection by retroviruses that are derived from the murine leukemia virus, human immunodeficiency virus type 1, and feline immunodeficiency virus. We demonstrate that the cell line is genetically recessive for the resistance, and hence it is lacking a factor enabling infection by retroviruses. The block to infection is early in the life cycle, at the poorly understood uncoating stage. We implicate the proteasome at uncoating by completely rescuing the resistant phenotype with the proteasomal inhibitor MG-132. We further report on the complementation cloning of a gene (MRI, modulator of retrovirus infection) that can also act to reverse the inhibition of infection in the mutant cell line. These data implicate a role for the proteasome during uncoating, and they suggest that MRI is a regulator of this activity. Finally, we reconcile our findings and other published data to suggest a model for the involvement of the proteasome in the early phase of the retroviral life cycle.
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Affiliation(s)
- Sumit Agarwal
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
| | - Josephine Harada
- Genomics Institute, Novartis Research Foundation, San Diego, CA 92121
| | - Jeffrey Schreifels
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
| | - Patrycja Lech
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
| | - Bryan Nikolai
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
| | - Tomoyuki Yamaguchi
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
| | - Sumit K. Chanda
- Genomics Institute, Novartis Research Foundation, San Diego, CA 92121
| | - Nikunj V. Somia
- *Department of Genetics, Cell Biology, and Development, and the Institute of Human Genetics, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455; and
- To whom correspondence should be addressed. E-mail:
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32
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Gottwein E, Jäger S, Habermann A, Kräusslich HG. Cumulative mutations of ubiquitin acceptor sites in human immunodeficiency virus type 1 gag cause a late budding defect. J Virol 2006; 80:6267-75. [PMID: 16775314 PMCID: PMC1488962 DOI: 10.1128/jvi.02177-05] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The p6 domain of human immunodeficiency virus type 1 (HIV-1) Gag has long been known to be monoubiquitinated. We have previously shown that the MA, CA, and NC domains are also monoubiquitinated at low levels (E. Gottwein and H. G. Krausslich, J. Virol. 79:9134-9144, 2005). While several lines of evidence support a role for ubiquitin in virus release, the relevance of Gag ubiquitination is unclear. To directly address the function of Gag ubiquitination, we constructed Gag variants in which lysine residues in the NC, SP2, and p6 domains were mutated to arginine either in individual domains or in combination. Using these mutants, we showed that in addition to MA, CA, NC, and p6, SP2 is also mono- or di-ubiquitinated at levels comparable to those of the other domains. Replacement of all lysine residues in only one of the domains had minor effects on virus release, while cumulative mutations in NC and SP2 or in NC and p6 resulted in an accumulation of late budding structures, as observed by electron microscopy analysis. Strikingly, replacement of all lysine residues downstream of CA led to a significant reduction in virus release kinetics and a fivefold accumulation of late viral budding structures compared to wild-type levels. These results indicate that ubiquitination of lysine residues in Gag in the vicinity of the viral late domain is important for HIV-1 budding, while no specific lysine residue may be needed and individual domains can functionally substitute. This is consistent with Gag ubiquitination being functionally involved in a transient protein interaction network at the virus budding site.
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Affiliation(s)
- Eva Gottwein
- Abteilung Virologie, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
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Agromayor M, Martin-Serrano J. Interaction of AMSH with ESCRT-III and deubiquitination of endosomal cargo. J Biol Chem 2006; 281:23083-91. [PMID: 16760479 DOI: 10.1074/jbc.m513803200] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The "class E" vacuolar protein sorting (VPS) pathway mediates sorting of ubiquitinated cargo into the forming vesicles of the multivesicular bodies (MVB), and it is essential for down-regulation of signaling by growth factors and budding of enveloped viruses such as Ebola and HIV-1. Work in yeast has identified DOA4 as a gene that is recruited by the class E machinery to remove ubiquitin from the endosomal cargo before it is incorporated into MVB vesicles, but the identity of the mammalian counterpart is unclear. Here we report the interaction of AMSH (associated molecule with the SH3 domain of STAM), an endosomal deubiquitinating enzyme, with the endodomal sorting complex required for transport (ESCRT-III) subunits CHMP1A, CHMP1B, CHMP2A, and CHMP3. We also show that a catalytically inactive AMSH inhibits retroviral budding in a dominant-negative manner and induces the accumulation of ubiquitinated forms of an endosomal cargo, namely murine leukemia virus Gag. Finally, VPS4 and AMSH compete for binding to the C-terminal regions of CHMP1A and CHMP1B, revealing a coordinated interaction with ESCRT-III. Taken together, these results are consistent with a role of AMSH in the deubiquitination of the endosomal cargo preceding lysosomal degradation.
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Affiliation(s)
- Monica Agromayor
- Department of Infectious Diseases, King's College London School of Medicine at Guy's, King's College, and St. Thomas' Hospitals, London SE1 9RT, United Kingdom
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Bieniasz PD. Late budding domains and host proteins in enveloped virus release. Virology 2006; 344:55-63. [PMID: 16364736 DOI: 10.1016/j.virol.2005.09.044] [Citation(s) in RCA: 286] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Accepted: 09/14/2005] [Indexed: 12/17/2022]
Affiliation(s)
- Paul D Bieniasz
- Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, 455 First Avenue, New York, NY 10016, USA.
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35
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Stanke N, Stange A, Lüftenegger D, Zentgraf H, Lindemann D. Ubiquitination of the prototype foamy virus envelope glycoprotein leader peptide regulates subviral particle release. J Virol 2006; 79:15074-83. [PMID: 16306578 PMCID: PMC1316034 DOI: 10.1128/jvi.79.24.15074-15083.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Foamy virus (FV) particle egress is unique among retroviruses because of its essential requirement for Gag and Env coexpression for budding and particle release. The FV glycoprotein undergoes a highly unusual biosynthesis resulting in the generation of three particle-associated, mature subunits, leader peptide (LP), surface (SU), and transmembrane (TM), derived from a precursor protein by posttranslational proteolysis mediated by furin or furinlike proteases. Previously at least three LP products of different molecular weights were detected in purified FV particles. Here we demonstrate that the higher-molecular-weight forms gp28LP and gp38LP are ubiquitinated variants of the major gp18LP cleavage product, which has a type II membrane topology. Furthermore, we show that all five lysine residues located within the N-terminal 60-amino-acid cytoplasmic domain of gp18LP can potentially be ubiquitinated, however, there seems to be a preference for using the first three. Inactivation of ubiquitination sites individually resulted in no obvious phenotype. However, simultaneous inactivation of the first three or all five ubiquitination sites in gp18LP led to a massive increase in subviral particles released by these mutant glycoproteins that were readily detectable by electron microscopy analysis upon expression of the ubiquitination-deficient glycoprotein by itself or in a proviral context. Surprisingly, only the quintuple ubiquitination mutant showed a two- to threefold increase in single-cycle infectivity assays, whereas all other mutants displayed infectivities similar to that of the wild type. Taken together, these data suggest that the balance between viral and subviral particle release of FVs is regulated by ubiquitination of the glycoprotein LP.
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Affiliation(s)
- Nicole Stanke
- Institut für Virologie, Medizinische Fakultät "Carl Gustav Carus," Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany
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36
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Abstract
Ubiquitin is important for the release of human immunodeficiency virus type 1 (HIV-1) and several other retroviruses, but the functional significance of Gag ubiquitination is unknown. To address this problem, we decided to analyze Gag ubiquitination in detail. A low percentage of the HIV-1 p6 protein has previously been shown to be ubiquitinated, and published mutagenesis data suggested that Gag ubiquitination is largely lost upon mutation of the two lysine residues in p6. In this study, we show that Gag proteins lacking the p6 domain or the two lysine residues within p6 are ubiquitinated at levels comparable to those of the wild-type Gag protein. We detected monoubiquitinated forms of the matrix (MA), capsid (CA), and nucleocapsid (NC) proteins in mature virus preparations. Protease digestion of Gag polyproteins extracted from immature virions indicated that ubiquitinated MA, CA, and possibly NC are as abundant as ubiquitinated p6. The HIV-1 late-domain motifs PTAP and LRSLF were not required for Gag ubiquitination, and mutation of the PTAP motif even resulted in an increase in the amount of Gag-Ub conjugates detected. Finally, at steady state, ubiquitinated Gag proteins were not enriched in either membrane-associated or virus-derived Gag fractions. In summary, these results indicate that HIV-1 Gag can be monoubiquitinated in all domains and that ubiquitination of lysine residues outside p6 may thus contribute to viral release and/or infectivity.
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Affiliation(s)
- Eva Gottwein
- Abteilung Virologie, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
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Ott DE, Coren LV, Gagliardi TD, Nagashima K. Heterologous late-domain sequences have various abilities to promote budding of human immunodeficiency virus type 1. J Virol 2005; 79:9038-45. [PMID: 15994797 PMCID: PMC1168796 DOI: 10.1128/jvi.79.14.9038-9045.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Retroviral late (L) domains present within Gag act in conjunction with cellular proteins to efficiently release virions from the surface of the cell. Three different critical core sequences have been identified as required elements for L-domain function: PPPY, PTAP (also PSAP), and YPDL, with different retroviruses utilizing one or two of these core sequences. The human immunodeficiency virus type 1 (HIV-1) L domain is centered around a PTAP sequence in the p6 region of Gag. To assess the ability of heterologous L-domain sequences to be functionally interchanged for those in full-length HIV-1, we produced a series of constructs that replaced PTAP-containing p6(Gag) sequences with those of PPPY- or YPDL-based L domains. While previous studies had found that L domains are interchangeable in other retroviruses, most of the sequences introduced into p6(Gag) failed to substitute for PTAP-mediated L-domain function. One exception was the 11-amino-acid p2b sequence of Rous sarcoma virus (RSV) Gag, which could fully restore HIV-1 budding, while a PPPPY sequence exchange alone did not. This suggests that the RSV L domain consists of more than simply its core L-domain sequence. The HIV-p2b chimera was as infectious as the wild type, produced normal virions, and was sensitive to proteasome inhibitors. These results show that L-domain sequences are not necessarily interchangeable. Thus, HIV-1 Gag might have a more stringent requirement for L-domain function than the other retroviruses previously studied.
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Affiliation(s)
- David E Ott
- Basic Research Program, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, Maryland 21702-1201, USA.
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38
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Segura-Morales C, Pescia C, Chatellard-Causse C, Sadoul R, Bertrand E, Basyuk E. Tsg101 and Alix interact with murine leukemia virus Gag and cooperate with Nedd4 ubiquitin ligases during budding. J Biol Chem 2005; 280:27004-12. [PMID: 15908698 DOI: 10.1074/jbc.m413735200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retroviruses use endosomal machinery to bud out of infected cells, and various Gag proteins recruit this machinery by interacting with either of three cellular factors as follows: ubiquitin ligases of the Nedd4 family, Tsg101, or Alix/Aip1. Here we show that the murine leukemia virus Gag has the unique ability to interact with all three factors. Small interfering RNAs against Tsg101 or Alix and dominant-negative forms of Nedd4 can all reduce production of virus-like particles. However, inactivating the Nedd4-binding site abolishes budding, whereas disrupting Tsg101 or Alix binding has milder effects. Nedd4 ubiquitin ligases are therefore essential, and Tsg101 and Alix play auxiliary roles. Most interestingly, overexpression of Alix can stimulate the release of Gag, and this occurs independently of most Alix partners Tsg101, Cin85, Alg-2, and endophilins. In addition, Gag mutants that do not bind Tsg101 or Alix concentrate on late endosomes and become very sensitive to dominant-negative forms of Nedd4 that do not conjugate ubiquitin. This suggests that the direct interaction of Gag with Tsg101 and Alix favors budding from the plasma membrane and relieves a requirement for ubiquitination by Nedd4.1. Other Nedd4-dependent Gag proteins also contain binding sites for Tsg101 or Alix, suggesting that this could be a common feature of retroviruses.
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Schmitt AP, Leser GP, Morita E, Sundquist WI, Lamb RA. Evidence for a new viral late-domain core sequence, FPIV, necessary for budding of a paramyxovirus. J Virol 2005; 79:2988-97. [PMID: 15709019 PMCID: PMC548478 DOI: 10.1128/jvi.79.5.2988-2997.2005] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Enveloped virus budding has been linked to both the ubiquitin-proteasome pathway and the vacuolar protein-sorting pathway of cells. We show here for the paramyxovirus SV5 that proteasome inhibitors and expression of dominant-negative VPS4(E228Q) ATPase blocks budding. The SV5 matrix (M) protein lacks previously defined late domains (e.g., P[T/S]AP, PPxY, YPDL) that recruit cellular factors. We identified a new motif for budding (core sequence FPIV) that can compensate functionally for lack of a PTAP late domain in budding human immunodeficiency virus type 1 virus-like particles (VLPs). Mutagenesis experiments suggest the more general sequence O-P-x-V. The proline residue was found to be critically important for function of this sequence, as substitution of this proline in the SV5 M protein resulted in poor budding of SV5 VLPs and failure of recombinant SV5 virus to replicate normally. Adaptation of mutant virus occurred rapidly, resulting in new proline residues elsewhere in the M protein. We hypothesize that these proline residues act to partially restore virus budding by generation of new motifs that act as suboptimal late domains.
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Affiliation(s)
- Anthony P Schmitt
- Northwestern University, 2205 Tech Dr., Evanston, IL 60208-3500, USA
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Abstract
The release of retrovirus particles from the infected cell is greatly stimulated by short motifs, known as "late" or "L" domains, present within the Gag precursor protein. Three distinct classes of L domains have been identified; these bear the core sequence: Pro-Thr/Ser-Ala-Pro [P(T/S)AP], Pro-Pro-x-Tyr (PPxY), or Tyr-Pro-x-Leu (YPxL). A number of recent studies have demonstrated that L domains function by interacting with components of the machinery responsible for sorting cellular proteins into the multivesicular body (MVB) pathway. This review traces the history of L domain discovery and characterization, and highlights the relationship between L domain activity, retrovirus release, and the host endosomal sorting machinery.
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Affiliation(s)
- Dimiter G Demirov
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, Bldg. 535/Rm. 124, Frederick, MD 21702-1201, USA
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Martin-Serrano J, Eastman SW, Chung W, Bieniasz PD. HECT ubiquitin ligases link viral and cellular PPXY motifs to the vacuolar protein-sorting pathway. ACTA ACUST UNITED AC 2004; 168:89-101. [PMID: 15623582 PMCID: PMC2171676 DOI: 10.1083/jcb.200408155] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Many enveloped viruses exploit the class E vacuolar protein-sorting (VPS) pathway to bud from cells, and use peptide motifs to recruit specific class E VPS factors. Homologous to E6AP COOH terminus (HECT) ubiquitin ligases have been implicated as cofactors for PPXY motif–dependent budding, but precisely which members of this family are responsible, and how they access the VPS pathway is unclear. Here, we show that PPXY-dependent viral budding is unusually sensitive to inhibitory fragments derived from specific HECT ubiquitin ligases, namely WWP1 and WWP2. We also show that WWP1, WWP2, or Itch ubiquitin ligase recruitment promotes PPXY-dependent virion release, and that this function requires that the HECT ubiquitin ligase domain be catalytically active. Finally, we show that several mammalian HECT ubiquitin ligases, including WWP1, WWP2, and Itch are recruited to class E compartments induced by dominant negative forms of the class E VPS ATPase, VPS4. These data indicate that specific HECT ubiquitin ligases can link PPXY motifs to the VPS pathway to induce viral budding.
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Affiliation(s)
- Juan Martin-Serrano
- Aaron Diamond AIDS Research Center and The Rockefeller University, New York, NY 10021, USA
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Spidel JL, Craven RC, Wilson CB, Patnaik A, Wang H, Mansky LM, Wills JW. Lysines close to the Rous sarcoma virus late domain critical for budding. J Virol 2004; 78:10606-16. [PMID: 15367628 PMCID: PMC516377 DOI: 10.1128/jvi.78.19.10606-10616.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Accepted: 05/19/2004] [Indexed: 12/18/2022] Open
Abstract
The release of retroviruses from the plasma membrane requires host factors that are believed to be recruited to the site of budding by the late (L) domain of the virus-encoded Gag protein. The L domain of Rous sarcoma virus (RSV) has been shown to interact with a ubiquitin (Ub) ligase, and budding of this virus is dependent on Ub. RSV is similar to other retroviruses in that it contains approximately 100 molecules of Ub, but it is unique in that none of these molecules has been found to be conjugated to Gag. If transient ubiquitination of RSV Gag is required for budding, then replacement of the target lysine(s) with arginine should prevent the addition of Ub and reduce budding. Based on known sites of ubiquitination in other viruses, the important lysines would likely reside near the L domain. In RSV, there are five lysines located just upstream of the L domain in a region of the matrix (MA) protein that is dispensable for membrane binding, and replacement of these with arginine (mutant 1-5KR) reduced budding 80 to 90%. The block to budding was found to be on the plasma membrane; however, the few virions that were released had normal size, morphology, and infectivity. Budding was restored when any one of the residues was changed back to lysine or when lysines were inserted in novel positions, either within this region of MA or within the downstream p10 sequence. Moreover, the 1-5KR mutant could be rescued into particles by coexpression of budding-competent Gag molecules. These data argue that the phenotype of mutant 1-5KR is not due to a conformational defect. Consistent with the idea that efficient budding requires a specific role for lysines, human T-cell leukemia virus type 1, which does not bud well compared to RSV and lacks lysines close to its L domain, was found to be released at a higher level upon introduction of lysines near its L domain. This report strongly supports the hypothesis that ubiquitination of the RSV Gag protein (and perhaps those of other retroviruses) is needed for efficient budding.
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Affiliation(s)
- Jared L Spidel
- Department of Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Dr., P.O. Box 850, Hershey, PA 17033, USA
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Szymkiewicz I, Shupliakov O, Dikic I. Cargo- and compartment-selective endocytic scaffold proteins. Biochem J 2004; 383:1-11. [PMID: 15219178 PMCID: PMC1134037 DOI: 10.1042/bj20040913] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Accepted: 06/24/2004] [Indexed: 01/05/2023]
Abstract
The endocytosis of membrane receptors is a complex and tightly controlled process that is essential for maintaining cellular homoeostasis. The removal of receptors from the cell surface can be constitutive or ligand-induced, and occurs in a clathrin-dependent or -independent manner. The recruitment of receptors into specialized membrane domains, the formation of vesicles and the trafficking of receptors together with their ligands within endocytic compartments are regulated by reversible protein modifications, and multiple protein-protein and protein-lipid interactions. Recent reports describe a variety of multidomain molecules that facilitate receptor endocytosis and function as platforms for the assembly of protein complexes. These scaffold proteins typically act in a cargo-specific manner, recognizing one or more receptor types, or function at the level of endocytic cellular microcompartments by controlling the movement of cargo molecules and linking endocytic machineries to signalling pathways. In the present review we summarize present knowledge on endocytic scaffold molecules and discuss their functions.
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Key Words
- cargo
- endocytosis
- microcompartment
- scaffold
- alix, alg-2 (apoptosis-linked gene 2)-interacting protein x
- anth domain, ap180 n-terminal homology domain
- ap-2, adaptor protein-2
- arh, autosomal recessive hypercholesterolaemia
- bar domain, bin/amphiphysin/rvs domain
- cd2ap, cd2-associated protein
- cin85, cbl-interacting protein of 85 kda
- dab2, disabled-2
- eea1, early endosome antigen 1
- egfr, epidermal growth factor receptor
- eh domain, eps15 homology domain
- enth domain, epsin n-terminal homology domain
- escrt, endosomal sorting complexes required for transport
- fyve, fab1p, yotb, vac1p and eea1
- gap, gtpase-activating protein
- gpcr, g-protein-coupled receptor
- hrs, hepatocyte growth factor-regulated tyrosine kinase substrate
- lbpa, lysobiphosphatidic acid
- ldl, low-density lipoprotein
- lnx, ligand of numb protein x
- mvb, multivesicular body
- nak, numb-associated kinase
- nsf, n-ethylmaleimide-sensitive fusion protein
- pon, partner of numb
- ptb domain, phosphotyrosine-binding domain
- rtk, receptor tyrosine kinase
- sh3, src homology 3
- snare, soluble nsf attachment protein receptor
- stam, signal-transducing adaptor molecule
- tcr, t-cell receptor
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Affiliation(s)
- Iwona Szymkiewicz
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
| | - Oleg Shupliakov
- †Department of Neuroscience, CEDB, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Ivan Dikic
- *Institute of Biochemistry II, Goethe University Medical School, 60590 Frankfurt, Germany
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Amit I, Yakir L, Katz M, Zwang Y, Marmor MD, Citri A, Shtiegman K, Alroy I, Tuvia S, Reiss Y, Roubini E, Cohen M, Wides R, Bacharach E, Schubert U, Yarden Y. Tal, a Tsg101-specific E3 ubiquitin ligase, regulates receptor endocytosis and retrovirus budding. Genes Dev 2004; 18:1737-52. [PMID: 15256501 PMCID: PMC478194 DOI: 10.1101/gad.294904] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The tumor suppressor gene 101 (tsg101) regulates vesicular trafficking processes in yeast and mammals. We report a novel protein, Tal (Tsg101-associated ligase), whose RING finger is necessary for multiple monoubiquitylation of Tsg101. Bivalent binding of Tsg101 to a tandem tetrapeptide motif (PTAP) and to a central region of Tal is essential for Tal-mediated ubiquitylation of Tsg101. By studying endocytosis of the epidermal growth factor receptor and egress of the human immunodeficiency virus, we conclude that Tal regulates a Tsg101-associated complex responsible for the sorting of cargo into cytoplasm-containing vesicles that bud at the multivesicular body and at the plasma membrane.
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Affiliation(s)
- Ido Amit
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel
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45
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Golab J, Bauer TM, Daniel V, Naujokat C. Role of the ubiquitin-proteasome pathway in the diagnosis of human diseases. Clin Chim Acta 2004; 340:27-40. [PMID: 14734194 DOI: 10.1016/j.cccn.2003.10.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The ubiquitin-proteasome pathway constitutes the major system for nuclear and extralysosomal cytosolic protein degradation in eukaryotic cells. A plethora of cell proteins implicated in the maintenance and regulation of essential cellular processes undergoes processing and functional modification by proteolytic degradation via the ubiquitin-proteasome pathway. Deregulations of the pathway have been shown to contribute to the pathogenesis of several human diseases, such as cancer, neurodegenerative, autoimmune, genetic and metabolic disorders, most of them exhibiting abnormal accumulation and altered composition of components of the pathway that is suitable for diagnostic proceedings. While the ubiquitin-proteasome pathway is currently exploited to develop novel therapeutic strategies, it is less regarded as a diagnostic area. Future research should lead to an improved understanding of the pathophysiology of the ubiquitin-proteasome pathway with the aim of allowing the development of subtle diagnostic strategies.
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Affiliation(s)
- Jakub Golab
- Department of Immunology, Center of Biostructure Research, The Medical University of Warsaw, Warsaw, Poland
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46
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Ros C, Kempf C. The ubiquitin-proteasome machinery is essential for nuclear translocation of incoming minute virus of mice. Virology 2004; 324:350-60. [PMID: 15207621 DOI: 10.1016/j.virol.2004.04.016] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Revised: 03/11/2004] [Accepted: 04/01/2004] [Indexed: 02/08/2023]
Abstract
Minute virus of mice (MVM) infection is disrupted by proteasome inhibitors. Here, we show that inhibition of the ubiquitin-proteasome pathway did not affect viral entry and had influence neither on the natural proteolytic cleavage of VP2 to VP3 nor on the externalization of the N terminal of VP1. In both MG132-treated and untreated cells, MVM particles accumulated progressively in the perinuclear region. However, in MG132-treated cells, MVM was not able to penetrate into the nuclei, remaining blocked in the perinuclear region without capsid disassembly. MVM was similarly sensitive to MG132 in the two cell lines tested, A9 and NB324K. After releasing from the reversible MG132 block, MVM recovered the ability to translocate to the nuclei and replicate. Analysis of viral capsid proteins during internalization showed no evidence of capsid ubiquitination or degradation. We examined the effect of MG132 on two other parvoviruses, canine (CPV) and bovine parvovirus (BPV). Similarly to MVM, CPV infection was sensitive to MG132; however, BPV infection, as previously shown for adeno-associated viruses (AAVs), was not disturbed. These findings suggest that parvoviruses follow divergent strategies for nuclear transport, some of them requiring active proteasomes.
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Affiliation(s)
- Carlos Ros
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.
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47
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Martin-Serrano J, Perez-Caballero D, Bieniasz PD. Context-dependent effects of L domains and ubiquitination on viral budding. J Virol 2004; 78:5554-63. [PMID: 15140952 PMCID: PMC415830 DOI: 10.1128/jvi.78.11.5554-5563.2004] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Many enveloped viruses encode late assembly domains, or L domains, that facilitate virion egress. PTAP-type L domains act by recruiting the ESCRT-I (endosomal sorting complex required for transport I) component Tsg101, and YPXL/LXXLF-type L domains recruit AIP-1/ALIX, both of which are class E vacuolar protein sorting (VPS) factors, normally required for the generation of vesicles within endosomes. The binding cofactors for PPXY-type L domains have not been unambiguously resolved but may include Nedd4-like ubiquitin ligases. Largely because they act as autonomous binding sites for host factors, L domains are generally transferable and active in a context-independent manner. Ebola virus matrix protein (EbVP40) contains two overlapping L-domain motifs within the sequence ILPTAPPEYMEA. Here, we show that both motifs are required for efficient EbVP40 budding. However, upon transplantation into two different retroviral contexts, the relative contributions of the PTAP and PPEY motifs differ markedly. In a murine leukemia virus carrying the EbVP40 sequence, both motifs contributed to overall L domain activity, and budding proceeded in a partly Tsg101-independent manner. Conversely, when transplanted into the context of human immunodeficiency virus type 1 (HIV-1), EbVP40 L-domain activity was entirely due to a PTAP-Tsg101 interaction. In fact, a number of PPXY-type L domains were inactive in the context of HIV-1. Surprisingly, PTAP and YPXL-type L domains that simulated HIV-1 budding reduced the amount of ubiquitin conjugated to Gag, while inactive PPXY-type L domains increased Gag ubiquitination. These observations suggest that active L domains recruit deubiquitinating enzymes as a consequence of class E VPS factor recruitment. Moreover, context-dependent L-domain function may reflect distinct requirements for host functions during the morphogenesis of different viral particles or the underlying presence of additional, as yet undiscovered L domains.
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Heidecker G, Lloyd PA, Fox K, Nagashima K, Derse D. Late assembly motifs of human T-cell leukemia virus type 1 and their relative roles in particle release. J Virol 2004; 78:6636-48. [PMID: 15163754 PMCID: PMC416494 DOI: 10.1128/jvi.78.12.6636-6648.2004] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2003] [Accepted: 03/11/2004] [Indexed: 11/20/2022] Open
Abstract
Three late assembly domain consensus motifs, namely PTAP, PPPY, and LYPXL, have been identified in different retroviruses. They have been shown to interact with the cellular proteins TSG101, Nedd4, and AP2 or AIP, respectively. Human T-cell leukemia virus type 1 (HTLV-1) has a PPPY and a PTAP motif, separated by two amino acids, located at the end of MA, but only the PPPY motif is conserved in the deltaretrovirus group. Like other retroviral peptides carrying the late motif, MA is mono- or di-ubiquitinated. A mutational analysis showed that 90% of PPPY mutant particles were retained in the cell compared to 15% for the wild-type virus. Mutations of the PTAP motif resulted in a 20% decrease in particle release. In single-cycle infectivity assays, the infectious titers of late motif mutants correlated with the amounts of released virus, as determined by an enzyme-linked immunosorbent assay. We observed binding of MA to the WW domains of the Nedd4 family member WWP1 but not to the amino-terminal ubiquitin E2 variant domain of TSG101 in mammalian two-hybrid analyses. The binding to WWP1 was eliminated when the PPPY motif was mutated. However, MA showed binding to TSG101 in the yeast two-hybrid system that was dependent on an intact PTAP motif. A dominant-negative (DN) mutant of WWP1 could inhibit budding of the intact HTLV-1 virus. In contrast, DN TSG101 only affected the release of virus-like particles encoded by Gag expression plasmids. Electron and fluorescent microscopy showed that Gag accumulates in large patches in the membranes of cells expressing viruses with PPPY mutations. Very few tethered immature particles could be detected in these samples, suggesting that budding is impaired at an earlier step than in other retroviruses.
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Affiliation(s)
- Gisela Heidecker
- Molecular Biology of Retroviruses Section, Basic Research Lab, National Cancer Institute/NIH, NCI-Frederick, Bldg. 567, Rm. 155, Frederick, MD 21702-1201, USA.
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Irie T, Licata JM, McGettigan JP, Schnell MJ, Harty RN. Budding of PPxY-containing rhabdoviruses is not dependent on host proteins TGS101 and VPS4A. J Virol 2004; 78:2657-65. [PMID: 14990685 PMCID: PMC353768 DOI: 10.1128/jvi.78.6.2657-2665.2004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Viral matrix proteins of several enveloped RNA viruses play important roles in virus assembly and budding and are by themselves able to bud from the cell surface in the form of lipid-enveloped, virus-like particles (VLPs). Three motifs (PT/SAP, PPxY, and YxxL) have been identified as late budding domains (L-domains) responsible for efficient budding. L-domains can functionally interact with cellular proteins involved in vacuolar sorting (VPS4A and TSG101) and endocytic pathways (Nedd4), suggesting involvement of these pathways in virus budding. Ebola virus VP40 has overlapping PTAP and PPEY motifs, which can functionally interact with TSG101 and Nedd4, respectively. As for vesicular stomatitis virus (VSV), a PPPY motif within M protein can interact with Nedd4. In addition, M protein has a PSAP sequence downstream of the PPPY motif, but the function of PSAP in budding is not clear. In this study, we compared L-domain functions between Ebola virus and VSV by constructing a chimeric M protein (M40), in which the PPPY motif of VSV M is replaced by the L domains of VP40. The budding efficiency of M40 was 10-fold higher than that of wild-type (wt) M protein. Overexpression of a dominant negative mutant of VPS4A or depletion of cellular TSG101 reduced the budding of only M40-containing VLPs but not that of wt M VLPs or live VSV. These findings suggest that the PSAP motif of M protein is not critical for budding and that there are fundamental differences between PTAP-containing viruses (Ebola virus and human immunodeficiency virus type 1) and PPPY-containing viruses (VSV and rabies virus) regarding their dependence on specific host factors for efficient budding.
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Affiliation(s)
- Takashi Irie
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Wang H, Machesky NJ, Mansky LM. Both the PPPY and PTAP motifs are involved in human T-cell leukemia virus type 1 particle release. J Virol 2004; 78:1503-12. [PMID: 14722305 PMCID: PMC321366 DOI: 10.1128/jvi.78.3.1503-1512.2004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In retroviruses, the late (L) domain has been defined as a conserved motif in the Gag polyprotein precursor that, when mutated, leads to the emergence of virus particles that fail to pinch off from the plasma membrane. These domains have been observed to contain the PPXY, PTAP, or YXXL motifs. The deltaretroviruses, which include bovine leukemia virus (BLV) and human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2, have a conserved PPPY motif in the C-terminal region of the matrix (MA) domain of Gag, while HTLV-1 also encodes a PTAP motif in MA. In this study, we analyzed the roles of the PPPY and PTAP motifs in the C terminus of MA in HTLV-1 particle release. Mutation of either motif (i.e., PPPY changed to APPY or PTAP changed to PTRP) reduced budding efficiencies. Particle buds and electron-dense regions of plasma membrane were observed by electron microscopy. When the locations of PPPY and PTAP were switched, particle release was eliminated. Intriguingly, the replacement of the PTAP motif with either the PPPY or YPDL motifs did not influence the release of virus particles, but the replacement of the PPPY motif with either PTAP or YPDL eliminated particle production. This indicates that the role that PPPY plays in HTLV-1 budding cannot be replaced with either PTAP or YPDL. A similar observation was made with the BLV PPPY motif. Finally, HTLV-1 particle release was found to be sensitive to proteasome inhibitors, implicating a role for ubiquitin in HTLV-1 budding. In summary, our observations indicate that (i) the PPPY motif plays a crucial role in virus budding and (ii) the PTAP motif plays a more subtle role in HTLV-1 particle release. Each of these motifs may play an important role in virus release from specific cell types and therefore be important in efficient virus spread and transmission.
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Affiliation(s)
- Huating Wang
- Department of Molecular Virology, Cellular and Developmental Biology Graduate Program, Ohio State University, Columbus, Ohio 43210, USA
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