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Yapo V, Majumder K, Tedbury PR, Wen X, Ong YT, Johnson MC, Sarafianos SG. HIV-2 inhibits HIV-1 gene expression via two independent mechanisms during cellular co-infection. J Virol 2023; 97:e0187022. [PMID: 37991365 PMCID: PMC10734542 DOI: 10.1128/jvi.01870-22] [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: 12/16/2022] [Accepted: 06/28/2023] [Indexed: 11/23/2023] Open
Abstract
IMPORTANCE Twenty-five years after the first report that HIV-2 infection can reduce HIV-1-associated pathogenesis in dual-infected patients, the mechanisms are still not well understood. We explored these mechanisms in cell culture and showed first that these viruses can co-infect individual cells. Under specific conditions, HIV-2 inhibits HIV-1 through two distinct mechanisms, a broad-spectrum interferon response and an HIV-1-specific inhibition conferred by the HIV-2 TAR. The former could play a prominent role in dually infected individuals, whereas the latter targets HIV-1 promoter activity through competition for HIV-1 Tat binding when the same target cell is dually infected. That mechanism suppresses HIV-1 transcription by stalling RNA polymerase II complexes at the promoter through a minimal inhibitory region within the HIV-2 TAR. This work delineates the sequence of appearance and the modus operandi of each mechanism.
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Affiliation(s)
- Vincent Yapo
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Kinjal Majumder
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Philip R. Tedbury
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Xin Wen
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Yee T. Ong
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Marc C. Johnson
- CS Bond Life Sciences Center, University of Missouri, Columbia, Missouri, USA
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, Missouri, USA
| | - Stefan G. Sarafianos
- Center for ViroScience and Cure, Laboratory of Biochemical Pharmacology, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
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Hogan V, Johnson WE. Unique Structure and Distinctive Properties of the Ancient and Ubiquitous Gamma-Type Envelope Glycoprotein. Viruses 2023; 15:v15020274. [PMID: 36851488 PMCID: PMC9967133 DOI: 10.3390/v15020274] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/13/2023] [Accepted: 01/15/2023] [Indexed: 01/20/2023] Open
Abstract
After the onset of the AIDS pandemic, HIV-1 (genus Lentivirus) became the predominant model for studying retrovirus Env glycoproteins and their role in entry. However, HIV Env is an inadequate model for understanding entry of viruses in the Alpharetrovirus, Gammaretrovirus and Deltaretrovirus genera. For example, oncogenic model system viruses such as Rous sarcoma virus (RSV, Alpharetrovirus), murine leukemia virus (MLV, Gammaretrovirus) and human T-cell leukemia viruses (HTLV-I and HTLV-II, Deltaretrovirus) encode Envs that are structurally and functionally distinct from HIV Env. We refer to these as Gamma-type Envs. Gamma-type Envs are probably the most widespread retroviral Envs in nature. They are found in exogenous and endogenous retroviruses representing a broad spectrum of vertebrate hosts including amphibians, birds, reptiles, mammals and fish. In endogenous form, gamma-type Envs have been evolutionarily coopted numerous times, most notably as placental syncytins (e.g., human SYNC1 and SYNC2). Remarkably, gamma-type Envs are also found outside of the Retroviridae. Gp2 proteins of filoviruses (e.g., Ebolavirus) and snake arenaviruses in the genus Reptarenavirus are gamma-type Env homologs, products of ancient recombination events involving viruses of different Baltimore classes. Distinctive hallmarks of gamma-type Envs include a labile disulfide bond linking the surface and transmembrane subunits, a multi-stage attachment and fusion mechanism, a highly conserved (but poorly understood) "immunosuppressive domain", and activation by the viral protease during virion maturation. Here, we synthesize work from diverse retrovirus model systems to illustrate these distinctive properties and to highlight avenues for further exploration of gamma-type Env structure and function.
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Ruiz-Jiménez F, Pérez-Olais JH, Raymond C, King BJ, McClure CP, Urbanowicz RA, Ball JK. Challenges on the development of a pseudotyping assay for Zika glycoproteins. J Med Microbiol 2021; 70:001413. [PMID: 34499027 PMCID: PMC8697511 DOI: 10.1099/jmm.0.001413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 07/15/2021] [Indexed: 11/18/2022] Open
Abstract
Introduction. Zika virus (ZIKV) emerged as a public health concern on the American continent during late 2015. As the number of infected grew so did the concerns about its capability to cause long-term damage especially with the appearance of the congenital Zika syndrome (CZS). Proteins from the TAM family of receptor tyrosine kinases (RTKs) were proposed as the cellular receptors, however, due to the ability of the virus to infect a variety of cell lines different strategies to elucidate the tropism of the virus should be investigated.Hypothesis. Pseudotyping is a powerful tool to interrogate the ability of the glycoprotein (GP) to permit entry of viruses.Aim. We aimed to establish a highly tractable pseudotype model using lenti- and retro-viral backbones to investigate the entry pathway of ZIKV.Methodology. We used different glycoprotein constructs and different lenti- or retro-viral backbones, in a matrix of ratios to investigate production of proteins and functional pseudotypes.Results. Varying the ratio of backbone and glycoprotein plasmids did not yield infectious pseudotypes. Moreover, the supplementation of the ZIKV protease or the substitution of the backbone had no positive impact on the infectivity. We showed production of the proteins in producer cells implying the lack of infectious pseudotypes is due to a lack of successful glycoprotein incorporation, rather than lack of protein production.Conclusion. In line with other reports, we were unable to successfully produce infectious pseudotypes using the variety of methods described. Other strategies may be more suitable in the development of an efficient pseudotype model for ZIKV and other flaviviruses.
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Affiliation(s)
| | | | - Chidinma Raymond
- School of Life Sciences, The University of Nottingham, Nottingham, UK
| | - Barnabas J King
- School of Life Sciences, The University of Nottingham, Nottingham, UK
| | | | - Richard A. Urbanowicz
- School of Life Sciences, The University of Nottingham, Nottingham, UK
- Department of Infection Biology and Microbiomes, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
| | - Jonathan K. Ball
- School of Life Sciences, The University of Nottingham, Nottingham, UK
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An infectious Rous Sarcoma Virus Gag mutant that is defective in nuclear cycling. J Virol 2021; 95:e0064821. [PMID: 34319154 DOI: 10.1128/jvi.00648-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
During retroviral replication, unspliced viral genomic RNA (gRNA) must escape the nucleus for translation into viral proteins and packaging into virions. "Complex" retroviruses such as Human Immunodeficiency Virus (HIV) use cis-acting elements on the unspliced gRNA in conjunction with trans-acting viral proteins to facilitate this escape. "Simple" retroviruses such as Mason-Pfizer Monkey Virus (MPMV) and Murine Leukemia Virus (MLV) exclusively use cis-acting elements on the gRNA in conjunction with host nuclear export proteins for nuclear escape. Uniquely, the simple retrovirus Rous Sarcoma Virus (RSV) has a Gag structural protein that cycles through the nucleus prior to plasma membrane binding. This trafficking has been implicated in facilitating gRNA nuclear export and is thought to be a required mechanism. Previously described mutants that abolish nuclear cycling displayed enhanced plasma membrane binding, enhanced virion release, and a significant loss in genome incorporation resulting in loss of infectivity. Here, we describe a nuclear cycling deficient RSV Gag mutant that has similar plasma membrane binding and genome incorporation to WT virus and surprisingly, is replication competent albeit with a slower rate of spread compared to WT. This mutant suggests that RSV Gag nuclear cycling is not strictly required for RSV replication. Importance While mechanisms for retroviral Gag assembly at the plasma membrane are beginning to be characterized, characterization of intermediate trafficking locales remain elusive. This is in part due to the difficulty of tracking individual proteins from translation to plasma membrane binding. RSV Gag nuclear cycling is a unique phenotype that may provide comparative insight to viral trafficking evolution and may present a model intermediate to cis- and trans-acting mechanisms for gRNA export.
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Influence of Different Glycoproteins and of the Virion Core on SERINC5 Antiviral Activity. Viruses 2021; 13:v13071279. [PMID: 34209034 PMCID: PMC8310182 DOI: 10.3390/v13071279] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/22/2021] [Accepted: 06/28/2021] [Indexed: 11/25/2022] Open
Abstract
Host plasma membrane protein SERINC5 is incorporated into budding retrovirus particles where it blocks subsequent entry into susceptible target cells. Three structurally unrelated proteins encoded by diverse retroviruses, human immunodeficiency virus type 1 (HIV-1) Nef, equine infectious anemia virus (EIAV) S2, and ecotropic murine leukemia virus (MLV) GlycoGag, disrupt SERINC5 antiviral activity by redirecting SERINC5 from the site of virion assembly on the plasma membrane to an internal RAB7+ endosomal compartment. Pseudotyping retroviruses with particular glycoproteins, e.g., vesicular stomatitis virus glycoprotein (VSV G), renders the infectivity of particles resistant to inhibition by virion-associated SERINC5. To better understand viral determinants for SERINC5-sensitivity, the effect of SERINC5 was assessed using HIV-1, MLV, and Mason-Pfizer monkey virus (M-PMV) virion cores, pseudotyped with glycoproteins from Arenavirus, Coronavirus, Filovirus, Rhabdovirus, Paramyxovirus, and Orthomyxovirus genera. SERINC5 restricted virions pseudotyped with glycoproteins from several retroviruses, an orthomyxovirus, a rhabdovirus, a paramyxovirus, and an arenavirus. Infectivity of particles pseudotyped with HIV-1, amphotropic-MLV (A-MLV), or influenza A virus (IAV) glycoproteins, was decreased by SERINC5, whether the core was provided by HIV-1, MLV, or M-PMV. In contrast, particles pseudotyped with glycoproteins from M-PMV, parainfluenza virus 5 (PIV5), or rabies virus (RABV) were sensitive to SERINC5, but only with particular retroviral cores. Resistance to SERINC5 did not correlate with reduced SERINC5 incorporation into particles, route of viral entry, or absolute infectivity of the pseudotyped virions. These findings indicate that some non-retroviruses may be sensitive to SERINC5 and that, in addition to the viral glycoprotein, the retroviral core influences sensitivity to SERINC5.
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Structural Domains of the Herpes Simplex Type 1 gD Protein that Restrict HIV-1 Particle Infectivity. J Virol 2021; 95:JVI.02355-20. [PMID: 33536165 PMCID: PMC8103709 DOI: 10.1128/jvi.02355-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, we showed that the presence of the herpes simplex virus type 1 (HSV-1) gD glycoprotein but not gB potently restricted HIV-1 particle infectivity. This restriction was characterized by incorporation of HSV-1 gD and the exclusion of the HIV-1 gp120/gp41 from budding virus particles. To determine the structural domains involved in gD restriction of HIV-1, a series of deletion mutants and chimeric proteins between gD and the non-restrictive gB were generated. Our results show that deletion of the cytoplasmic tail domain (CTD) of gD or that replacement of the transmembrane domain (TMD) with the TMD from gB slightly reduced restriction activity. However, replacement of the gD CTD with that of gB resulted in lower cell surface expression, significantly less incorporation into HIV-1 particles, and inefficient restriction of the release of infectious HIV-1. Analysis of gB/gD chimeric proteins revealed that removal of the gB CTD or replacement with gD CTD resulted in enhanced surface expression and an increase in restriction activity. Finally, we show that expression of gD without other HSV-1 proteins resulted in gD fractionation into detergent resistant membranes (DRM) and that gD co-localized with the raft marker GM1, which may partially explain its incorporation into budding virus particles. Taken together, our results suggest that expression of gD at the cell surface is likely a major factor but that other intrinsic properties are also involved in the gD-mediated restriction of HIV-1 particle infectivity.IMPORTANCE Previously, we showed that unlike the HSV-1, the presence of the gD glycoprotein in virus producer cells but not gB potently restricted HIV-1 particle infectivity. To better understand the relationship between cell surface expression, virus incorporation and restriction of HIV-1, we analyzed a series of deletion mutants and chimeric proteins in which domains of gD and gB were swapped. Our results indicate that: a) gD/gB chimeras having the cytoplasmic domain (CTD) of gB significantly reduced cell surface expression, release from cells, incorporation into virus, and reduced HIV-1 restriction; b) removal of the gB CTD or replacement with the gD CTD resulted in better surface expression, incorporation into HIV-1, and enhanced restriction; and c) the transmembrane domain of gB can influence transport and ultimately effect incorporation of gB into HIV-1. Overall, these data support a role for gD surface expression as crucial to restriction of infectious HIV-1 release.
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Elucidating the Basis for Permissivity of the MT-4 T-Cell Line to Replication of an HIV-1 Mutant Lacking the gp41 Cytoplasmic Tail. J Virol 2020; 94:JVI.01334-20. [PMID: 32938764 DOI: 10.1128/jvi.01334-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 09/07/2020] [Indexed: 12/11/2022] Open
Abstract
HIV-1 encodes an envelope glycoprotein (Env) that contains a long cytoplasmic tail (CT) harboring trafficking motifs implicated in Env incorporation into virus particles and viral transmission. In most physiologically relevant cell types, the gp41 CT is required for HIV-1 replication, but in the MT-4 T-cell line the gp41 CT is not required for a spreading infection. To help elucidate the role of the gp41 CT in HIV-1 transmission, in this study, we investigated the viral and cellular factors that contribute to the permissivity of MT-4 cells to gp41 CT truncation. We found that the kinetics of HIV-1 production and virus release are faster in MT-4 than in the other T-cell lines tested, but MT-4 cells express equivalent amounts of HIV-1 proteins on a per-cell basis relative to cells not permissive to CT truncation. MT-4 cells express higher levels of plasma-membrane-associated Env than nonpermissive cells, and Env internalization from the plasma membrane is less efficient than that from another T-cell line, SupT1. Paradoxically, despite the high levels of Env on the surface of MT-4 cells, 2-fold less Env is incorporated into virus particles produced from MT-4 than SupT1 cells. Contact-dependent transmission between cocultured 293T and MT-4 cells is higher than in cocultures of 293T with most other T-cell lines tested, indicating that MT-4 cells are highly susceptible to cell-to-cell infection. These data help to clarify the long-standing question of how MT-4 cells overcome the requirement for the HIV-1 gp41 CT and support a role for gp41 CT-dependent trafficking in Env incorporation and cell-to-cell transmission in physiologically relevant cell lines.IMPORTANCE The HIV-1 Env cytoplasmic tail (CT) is required for efficient Env incorporation into nascent particles and viral transmission in primary CD4+ T cells. The MT-4 T-cell line has been reported to support multiple rounds of infection of HIV-1 encoding a gp41 CT truncation. Uncovering the underlying mechanism of MT-4 T-cell line permissivity to gp41 CT truncation would provide key insights into the role of the gp41 CT in HIV-1 transmission. This study reveals that multiple factors contribute to the unique ability of a gp41 CT truncation mutant to spread in cultures of MT-4 cells. The lack of a requirement for the gp41 CT in MT-4 cells is associated with the combined effects of rapid HIV-1 protein production, high levels of cell-surface Env expression, and increased susceptibility to cell-to-cell transmission compared to nonpermissive cells.
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8
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Sequence Determinants in Gammaretroviral Env Cytoplasmic Tails Dictate Virus-Specific Pseudotyping Compatibility. J Virol 2019; 93:JVI.02172-18. [PMID: 30894464 DOI: 10.1128/jvi.02172-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 03/13/2019] [Indexed: 12/11/2022] Open
Abstract
Viruses can incorporate foreign glycoproteins to form infectious particles through a process known as pseudotyping. However, not all glycoproteins are compatible with all viruses. Despite the fact that viral pseudotyping is widely used, what makes a virus/glycoprotein pair compatible is poorly understood. To study this, we chose to analyze a gammaretroviral glycoprotein (Env) whose compatibility with different viruses could be modulated through small changes in its cytoplasmic tail (CT). One form of this glycoprotein is compatible with murine leukemia virus (MLV) particles but incompatible with human immunodeficiency virus type 1 (HIV-1) particles, while the second is compatible with HIV-1 particles but not with MLV particles. To decipher the factors affecting virus-specific Env incompatibility, we characterized Env incorporation, maturation, cell-to-cell fusogenicity, and virus-to-cell fusogenicity of each Env. The HIV-1 particle incompatibility correlated with less efficient cleavage of the R peptide by HIV-1 protease. However, the MLV particle incompatibility was more nuanced. MLV incompatibility appeared to be caused by lack of incorporation into particles, yet incorporation could be restored by further truncating the CT or by using a chimeric MLV Gag protein containing the HIV-1 MA without fully restoring infectivity. The MLV particle incompatibility appeared to be caused in part by fusogenic repression in MLV particles through an unknown mechanism. This study demonstrates that the Env CT can dictate functionality of Env within particles in a virus-specific manner.IMPORTANCE Viruses utilize viral glycoproteins to efficiently enter target cells during infection. How viruses acquire viral glycoproteins has been studied to understand the pathogenesis of viruses and develop safer and more efficient viral vectors for gene therapies. The CTs of viral glycoproteins have been shown to regulate various stages of glycoprotein biogenesis, but a gap still remains in understanding the molecular mechanism of glycoprotein acquisition and functionality regarding the CT. Here, we studied the mechanism of how specific mutations in the CT of a gammaretroviral envelope glycoprotein distinctly affect infectivity of two different viruses. Different mutations caused failure of glycoproteins to function in a virus-specific manner due to distinct fusion defects, suggesting that there are virus-specific characteristics affecting glycoprotein functionality.
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Polpitiya Arachchige S, Henke W, Kalamvoki M, Stephens EB. Analysis of herpes simplex type 1 gB, gD, and gH/gL on production of infectious HIV-1: HSV-1 gD restricts HIV-1 by exclusion of HIV-1 Env from maturing viral particles. Retrovirology 2019; 16:9. [PMID: 30940160 PMCID: PMC6444546 DOI: 10.1186/s12977-019-0470-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 03/23/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND We previously showed that the gM of HSV-1 could restrict the release of infectious HIV-1 from cells. In this study, we analyzed if the four HSV-1 glycoproteins (gD, gB, and gH/gL), which are the minimum glycoproteins required for HSV-1 entry, restricted the release of infectious HIV-1. RESULTS Of these four glycoproteins, gD and gH/gL restricted the production of infectious HIV-1 from cells transfected with an infectious molecular clone of HIV-1 (strain NL4-3) while gB had no significant effect. Pulse-chase analyses indicated that gD did not affect the biosynthesis and processing of gp160 into gp120/gp41, the transport of the gp120/gp41 to the cell surface, or the release of HIV-1 particles from the cell surface. Our analyses revealed that gD was incorporated into HIV-1 virus particles while gp120/gp41 was excluded from released virus particles. Truncated mutants of gD revealed that the cytoplasmic domain was dispensable but that a membrane bound gD was required for the restriction of release of infectious HIV-1. Finally, cell lines expressing gD also potently restricted the release of infectious virus. CONCLUSIONS Due to its ability to exclude HIV-1 gp120/gp41 from maturing virus, gD may provide a useful tool in deciphering mechanisms of Env incorporation into maturing virus particles.
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Affiliation(s)
- Sachith Polpitiya Arachchige
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, 2000 Hixon Hall, 3901 Rainbow Blvd., Kansas City, KS, 66160, USA
| | - Wyatt Henke
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, 2000 Hixon Hall, 3901 Rainbow Blvd., Kansas City, KS, 66160, USA
| | - Maria Kalamvoki
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, 2000 Hixon Hall, 3901 Rainbow Blvd., Kansas City, KS, 66160, USA
| | - Edward B Stephens
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, 2000 Hixon Hall, 3901 Rainbow Blvd., Kansas City, KS, 66160, USA.
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Klug YA, Schwarzer R, Rotem E, Charni M, Nudelman A, Gramatica A, Zarmi B, Rotter V, Shai Y. The HIV gp41 Fusion Protein Inhibits T-Cell Activation through the Lentiviral Lytic Peptide 2 Motif. Biochemistry 2019; 58:818-832. [PMID: 30602116 DOI: 10.1021/acs.biochem.8b01175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The human immunodeficiency virus enters its host cells by membrane fusion, initiated by the gp41 subunit of its envelope protein. gp41 has also been shown to bind T-cell receptor (TCR) complex components, interfering with TCR signaling leading to reduced T-cell activation. This immunoinhibitory activity is suggested to occur during the membrane fusion process and is attributed to various membranotropic regions of the gp41 ectodomain and to the transmembrane domain. Although extensively studied, the cytosolic region of gp41, termed the cytoplasmic tail (CT), has not been examined in the context of immune suppression. Here we investigated whether the CT inhibits T-cell activation in different T-cell models by utilizing gp41-derived peptides and expressed full gp41 proteins. We found that a conserved region of the CT, termed lentiviral lytic peptide 2 (LLP2), specifically inhibits the activation of mouse, Jurkat, and human primary T-cells. This inhibition resulted in reduced T-cell proliferation, gene expression, cytokine secretion, and cell surface expression of CD69. Differential activation of the TCR signaling cascade revealed that CT-based immune suppression occurs downstream of the TCR complex. Moreover, LLP2 peptide treatment of Jurkat and primary human T-cells impaired Akt but not NFκB and ERK1/2 activation, suggesting that immune suppression occurs through the Akt pathway. These findings identify a novel gp41 T-cell suppressive element with a unique inhibitory mechanism that can take place post-membrane fusion.
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Affiliation(s)
- Yoel A Klug
- Department of Biomolecular Sciences , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Roland Schwarzer
- Gladstone Institute for Virology and Immunology , University of California, San Francisco , San Francisco , California 94158 , United States
| | - Etai Rotem
- Department of Biomolecular Sciences , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Meital Charni
- Department of Molecular Cell Biology , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Alon Nudelman
- Department of Biomolecular Sciences , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Andrea Gramatica
- Gladstone Institute for Virology and Immunology , University of California, San Francisco , San Francisco , California 94158 , United States
| | - Batya Zarmi
- Department of Biomolecular Sciences , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Varda Rotter
- Department of Molecular Cell Biology , Weizmann Institute of Science , Rehovot 7610001 , Israel
| | - Yechiel Shai
- Department of Biomolecular Sciences , Weizmann Institute of Science , Rehovot 7610001 , Israel
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11
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King B, Tarr AW. How have retrovirus pseudotypes contributed to our understanding of viral entry? Future Virol 2017. [DOI: 10.2217/fvl-2017-0062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Study of virus entry into host cells is important for understanding viral tropism and pathogenesis. Studying the entry of in vitro cultured viruses is not always practicable. Study of highly pathogenic viruses, viruses that do not grow in culture, and viruses that rapidly change phenotype in vitro can all benefit from alternative models of entry. Retrovirus particles can be engineered to display the envelope proteins of heterologous enveloped viruses. This approach, broadly termed ‘pseudotyping’, is an important technique for interrogating virus entry. In this perspective we consider how retrovirus pseudotypes have addressed these challenges and improved our understanding of the entry pathways of diverse virus species, including Ebolavirus, human immunodeficiency virus and hepatitis C virus.
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Affiliation(s)
- Barnabas King
- National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & the University of Nottingham, Nottingham, UK
- School of Life Sciences, Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, UK
| | - Alexander W Tarr
- National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, Nottingham University Hospitals NHS Trust & the University of Nottingham, Nottingham, UK
- School of Life Sciences, Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, UK
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12
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Walsh SR, de Jong JG, van Vloten JP, Gerpe MCR, Santry LA, Wootton SK. Truncation of the enzootic nasal tumor virus envelope protein cytoplasmic tail increases Env-mediated fusion and infectivity. J Gen Virol 2017; 98:108-120. [PMID: 27902399 DOI: 10.1099/jgv.0.000654] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Enzootic nasal tumor virus (ENTV) and Jaagsiekte sheep retrovirus (JSRV) are highly related ovine betaretroviruses that induce nasal and lung tumours in small ruminants, respectively. While the ENTV and JSRV envelope (Env) glycoproteins mediate virus entry using the same cellular receptor, the glycosylphosphatidylinositol-linked protein hyaluronoglucosaminidase, ENTV Env pseudovirions mediate entry into cells from a much more restricted range of species than do JSRV Env pseudovirions. Unlike JSRV Env, ENTV Env does not induce cell fusion at pH 5.0 or above, but rather requires a much lower pH (4.0-4.5) for fusion to occur. The cytoplasmic tail of retroviral envelope proteins is a key modulator of envelope-mediated fusion and pseudotype efficiency, especially in the context of virions composed of heterologous Gag proteins. Here we report that progressive truncation of the ENTV Env cytoplasmic tail improves transduction efficiency of pseudotyped retroviral vectors and that complete truncation of the ENTV Env cytoplasmic tail increases transduction efficiency to wild-type JSRV Env levels by increasing fusogenicity without affecting sensitivity to inhibition by lysosomotropic agents, subcellular localization or efficiency of inclusion into virions. Truncation of the cytoplasmic domain of ENTV Env resulted in a significant advantage in viral entry into all cell types tested, including foetal ovine lung and nasal cells. Taken together, we demonstrate that the cytoplasmic tail modulates the fusion activity of the ENTV Env protein and that truncation of this region enhances Eenv-mediated entry into target cells.
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Affiliation(s)
- Scott R Walsh
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Jondavid G de Jong
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Jacob P van Vloten
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | | | - Lisa A Santry
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Sarah K Wootton
- Present address: McMaster Immunology Research Centre, McMaster University, Hamilton, ON, Canada.,Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
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13
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Distinct Particle Morphologies Revealed through Comparative Parallel Analyses of Retrovirus-Like Particles. J Virol 2016; 90:8074-84. [PMID: 27356903 DOI: 10.1128/jvi.00666-16] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/21/2016] [Indexed: 12/29/2022] Open
Abstract
UNLABELLED The Gag protein is the main retroviral structural protein, and its expression alone is usually sufficient for production of virus-like particles (VLPs). In this study, we sought to investigate-in parallel comparative analyses-Gag cellular distribution, VLP size, and basic morphological features using Gag expression constructs (Gag or Gag-YFP, where YFP is yellow fluorescent protein) created from all representative retroviral genera: Alpharetrovirus, Betaretrovirus, Deltaretrovirus, Epsilonretrovirus, Gammaretrovirus, Lentivirus, and Spumavirus. We analyzed Gag cellular distribution by confocal microscopy, VLP budding by thin-section transmission electron microscopy (TEM), and general morphological features of the VLPs by cryogenic transmission electron microscopy (cryo-TEM). Punctate Gag was observed near the plasma membrane for all Gag constructs tested except for the representative Beta- and Epsilonretrovirus Gag proteins. This is the first report of Epsilonretrovirus Gag localizing to the nucleus of HeLa cells. While VLPs were not produced by the representative Beta- and Epsilonretrovirus Gag proteins, the other Gag proteins produced VLPs as confirmed by TEM, and morphological differences were observed by cryo-TEM. In particular, we observed Deltaretrovirus-like particles with flat regions of electron density that did not follow viral membrane curvature, Lentivirus-like particles with a narrow range and consistent electron density, suggesting a tightly packed Gag lattice, and Spumavirus-like particles with large envelope protein spikes and no visible electron density associated with a Gag lattice. Taken together, these parallel comparative analyses demonstrate for the first time the distinct morphological features that exist among retrovirus-like particles. Investigation of these differences will provide greater insights into the retroviral assembly pathway. IMPORTANCE Comparative analysis among retroviruses has been critically important in enhancing our understanding of retroviral replication and pathogenesis, including that of important human pathogens such as human T-cell leukemia virus type 1 (HTLV-1) and HIV-1. In this study, parallel comparative analyses have been used to study Gag expression and virus-like particle morphology among representative retroviruses in the known retroviral genera. Distinct differences were observed, which enhances current knowledge of the retroviral assembly pathway.
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In Vivo Analysis of Infectivity, Fusogenicity, and Incorporation of a Mutagenic Viral Glycoprotein Library Reveals Determinants for Virus Incorporation. J Virol 2016; 90:6502-14. [PMID: 27147747 DOI: 10.1128/jvi.00804-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 12/14/2022] Open
Abstract
UNLABELLED Enveloped viruses utilize transmembrane surface glycoproteins to gain entry into target cells. Glycoproteins from diverse viral families can be incorporated into nonnative viral particles in a process termed pseudotyping; however, the molecular mechanisms governing acquisition of these glycoproteins are poorly understood. For murine leukemia virus envelope (MLV Env) glycoprotein, incorporation into foreign viral particles has been shown to be an active process, but it does not appear to be caused by direct interactions among viral proteins. In this study, we coupled in vivo selection systems with Illumina next-generation sequencing (NGS) to test hundreds of thousands of MLV Env mutants for the ability to be enriched in viral particles and to perform other glycoprotein functions. NGS analyses on a subset of these mutants predicted that the residues important for incorporation are in the membrane-proximal external region (MPER), particularly W127 and W137, and the residues in the membrane-spanning domain (MSD) and also immediately flanking it (T140 to L163). These predictions were validated by directly measuring the impact of mutations in these regions on fusogenicity, infectivity, and incorporation. We suggest that these two regions dictate pseudotyping through interactions with specific lipid environments formed during viral assembly. IMPORTANCE Researchers from numerous fields routinely exploit the ability to manipulate viral tropism by swapping viral surface proteins. However, this process, termed pseudotyping, is poorly understood at the molecular level. For murine leukemia virus envelope (MLV Env) glycoprotein, incorporation into foreign viral particles is an active process, but it does not appear to occur through direct viral protein-protein interactions. In this study, we tested hundreds of thousands of MLV Env mutants for the ability to be enriched in viral particles as well as perform other glycoprotein functions. Our analyses on a subset of these mutants predict that the glycoprotein regions embedded in and immediately flanking the viral membrane dictate active incorporation into viral particles. We suggest that pseudotyping occurs through specific lipid-protein interactions at the viral assembly site.
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Trimer Enhancement Mutation Effects on HIV-1 Matrix Protein Binding Activities. J Virol 2016; 90:5657-5664. [PMID: 27030269 DOI: 10.1128/jvi.00509-16] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 03/25/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The HIV-1 matrix (MA) protein is the amino-terminal domain of the HIV-1 precursor Gag (Pr55Gag) protein. MA binds to membranes and RNAs, helps transport Pr55Gag proteins to virus assembly sites at the plasma membranes of infected cells, and facilitates the incorporation of HIV-1 envelope (Env) proteins into virions by virtue of an interaction with the Env protein cytoplasmic tails (CTs). MA has been shown to crystallize as a trimer and to organize on membranes in hexamer lattices. MA mutations that localize to residues near the ends of trimer spokes have been observed to impair Env protein assembly into virus particles, and several of these are suppressed by the 62QR mutation at the hubs of trimer interfaces. We have examined the binding activities of wild-type (WT) MA and 62QR MA variants and found that the 62QR mutation stabilized MA trimers but did not alter the way MA proteins organized on membranes. Relative to WT MA, the 62QR protein showed small effects on membrane and RNA binding. However, 62QR proteins bound significantly better to Env CTs than their WT counterparts, and CT binding efficiencies correlated with trimerization efficiencies. Our data suggest a model in which multivalent binding of trimeric HIV-1 Env proteins to MA trimers contributes to the process of Env virion incorporation. IMPORTANCE The HIV-1 Env proteins assemble as trimers, and incorporation of the proteins into virus particles requires an interaction of Env CT domains with the MA domains of the viral precursor Gag proteins. Despite this knowledge, little is known about the mechanisms by which MA facilitates the virion incorporation of Env proteins. To help elucidate this process, we examined the binding activities of an MA mutant that stabilizes MA trimers. We found that the mutant proteins organized similarly to WT proteins on membranes, and that mutant and WT proteins revealed only slight differences in their binding to RNAs or lipids. However, the mutant proteins showed better binding to Env CTs than the WT proteins, and CT binding correlated with MA trimerization. Our results suggest that multivalent binding of trimeric HIV-1 Env proteins to MA trimers contributes to the process of Env virion incorporation.
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Abstract
UNLABELLED We have examined the interactions of wild-type (WT) and matrix protein-deleted (ΔMA) HIV-1 precursor Gag (PrGag) proteins in virus-producing cells using a biotin ligase-tagging approach. To do so, WT and ΔMA PrGag proteins were tagged with the Escherichia coli promiscuous biotin ligase (BirA*), expressed in cells, and examined. Localization patterns of PrGag proteins and biotinylated proteins overlapped, consistent with observations that BirA*-tagged proteins biotinylate neighbor proteins that are in close proximity. Results indicate that BirA*-tagged PrGag proteins biotinylated themselves as well as WT PrGag proteins in trans. Previous data have shown that the HIV-1 Envelope (Env) protein requires an interaction with MA for assembly into virions. Unexpectedly, ΔMA proteins biotinylated Env, whereas WT BirA*-tagged proteins did not, suggesting that the presence of MA made Env inaccessible to biotinylation. We also identified over 50 cellular proteins that were biotinylated by BirA*-tagged PrGag proteins. These included membrane proteins, cytoskeleton-associated proteins, nuclear transport factors, lipid metabolism regulators, translation factors, and RNA-processing proteins. The identification of these biotinylated proteins offers new insights into HIV-1 Gag protein trafficking and activities and provides new potential targets for antiviral interference. IMPORTANCE We have employed a novel strategy to analyze the interactions of the HIV-1 structural Gag proteins, which involved tagging wild-type and mutant Gag proteins with a biotin ligase. Expression of the tagged proteins in cells allowed us to analyze proteins that came in close proximity to the Gag proteins as they were synthesized, transported, assembled, and released from cells. The tagged proteins biotinylated proteins encoded by the HIV-1 pol gene and neighbor Gag proteins, but, surprisingly, only the mutant Gag protein biotinylated the HIV-1 Envelope protein. We also identified over 50 cellular proteins that were biotinylated, including membrane and cytoskeletal proteins and proteins involved in lipid metabolism, nuclear import, translation, and RNA processing. Our results offer new insights into HIV-1 Gag protein trafficking and activities and provide new potential targets for antiviral interference.
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Tedbury PR, Freed EO. The cytoplasmic tail of retroviral envelope glycoproteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:253-84. [PMID: 25595807 DOI: 10.1016/bs.pmbts.2014.10.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Retroviruses comprise a large, diverse group that infects a broad range of host organisms. Pathogenicity varies widely; the human immunodeficiency virus is the causative agent of acquired immunodeficiency syndrome, one of the world's leading infectious causes of death, while many nonhuman retroviruses cause cancer in the host. Retroviruses have been studied intensively, and great strides have been made in understanding aspects of retroviral biology. While the principal functions of the viral structural proteins are well understood, there remain many incompletely characterized domains. One of these is the cytoplasmic tail (CT) of the envelope glycoprotein. Several functions of the CT are highly conserved, whereas other properties are unique to a specific retrovirus. For example, the lentiviruses encode envelope glycoproteins with particularly large cytoplasmic domains. The functions of the long lentiviral envelope CT are still being deciphered. The reported functions of retroviral envelope CTs are discussed in this chapter.
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Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
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Basic motifs target PSGL-1, CD43, and CD44 to plasma membrane sites where HIV-1 assembles. J Virol 2014; 89:454-67. [PMID: 25320329 DOI: 10.1128/jvi.02178-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED HIV-1 incorporates various host membrane proteins during particle assembly at the plasma membrane; however, the mechanisms mediating this incorporation process remain poorly understood. We previously showed that the HIV-1 structural protein Gag localizes to the uropod, a rear-end structure of polarized T cells, and that assembling Gag copatches with a subset, but not all, of the uropod-directed proteins, i.e., PSGL-1, CD43, and CD44, in nonpolarized T cells. The latter observation suggests the presence of a mechanism promoting virion incorporation of these cellular proteins. To address this possibility and identify molecular determinants, in the present study we examined coclustering between Gag and the transmembrane proteins in T and HeLa cells using quantitative two-color superresolution localization microscopy. Consistent with the findings of the T-cell copatching study, we found that basic residues within the matrix domain of Gag are required for Gag-PSGL-1 coclustering. Notably, the presence of a polybasic sequence in the PSGL-1 cytoplasmic domain significantly enhanced this coclustering. We also found that polybasic motifs present in the cytoplasmic tails of CD43 and CD44 also promote their coclustering with Gag. ICAM-1 and ICAM-3, uropod-directed proteins that do not copatch with Gag in T cells, and CD46, a non-uropod-directed protein, showed no or little coclustering with Gag. However, replacing their cytoplasmic tails with the cytoplasmic tail of PSGL-1 significantly enhanced their coclustering with Gag. Altogether, these results identify a novel mechanism for host membrane protein association with assembling HIV-1 Gag in which polybasic sequences present in the cytoplasmic tails of the membrane proteins and in Gag are the major determinants. IMPORTANCE Nascent HIV-1 particles incorporate many host plasma membrane proteins during assembly. However, it is largely unknown what mechanisms promote the association of these proteins with virus assembly sites within the plasma membrane. Notably, our previous study showed that HIV-1 structural protein Gag colocalizes with a group of uropod-directed transmembrane proteins, PSGL-1, CD43, and CD44, at the plasma membrane of T cells. The results obtained in the current study using superresolution localization microscopy suggest the presence of a novel molecular mechanism promoting the association of PSGL-1, CD43, and CD44 with assembling HIV-1 which relies on polybasic sequences in HIV-1 Gag and in cytoplasmic domains of the transmembrane proteins. This information advances our understanding of virion incorporation of host plasma membrane proteins, some of which modulate virus spread positively or negatively, and suggests a possible new strategy to enrich HIV-1-based lentiviral vectors with a desired transmembrane protein.
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Tedbury PR, Freed EO. The role of matrix in HIV-1 envelope glycoprotein incorporation. Trends Microbiol 2014; 22:372-8. [PMID: 24933691 DOI: 10.1016/j.tim.2014.04.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/21/2014] [Accepted: 04/24/2014] [Indexed: 11/19/2022]
Abstract
Incorporation of the viral envelope (Env) glycoprotein is a critical requirement for the production of infectious HIV-1 particles. It has long been appreciated that the matrix (MA) domain of the Gag polyprotein and the cytoplasmic tail of Env are central players in the process of Env incorporation, but the precise mechanisms have been elusive. Several recent developments have thrown light on the contributions of both proteins, prompting a re-evaluation of the role of MA during Env incorporation. The two domains appear to play distinct but complementary roles, with the cytoplasmic tail of Env responsible for directing Env to the site of assembly and the matrix domain accommodating the cytoplasmic tail of Env in the Gag lattice.
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Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
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Alfadhli A, Barklis E. The roles of lipids and nucleic acids in HIV-1 assembly. Front Microbiol 2014; 5:253. [PMID: 24917853 PMCID: PMC4042026 DOI: 10.3389/fmicb.2014.00253] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 05/08/2014] [Indexed: 11/23/2022] Open
Abstract
During HIV-1 assembly, precursor Gag (PrGag) proteins are delivered to plasma membrane (PM) assembly sites, where they are triggered to oligomerize and bud from cells as immature virus particles. The delivery and triggering processes are coordinated by the PrGag matrix (MA) and nucleocapsid (NC) domains. Targeting of PrGag proteins to membranes enriched in cholesterol and phosphatidylinositol-4,5-bisphosphate (PI[4,5]P2) is mediated by the MA domain, which also has been shown to bind both RNA and DNA. Evidence suggests that the nucleic-acid-binding function of MA serves to inhibit PrGag binding to inappropriate intracellular membranes, prior to delivery to the PM. At the PM, MA domains putatively trade RNA ligands for PI(4,5)P2 ligands, fostering high-affinity membrane binding. Triggering of oligomerization, budding, and virus particle release results when NC domains on adjacent PrGag proteins bind to viral RNA, leading to capsid (CA) domain oligomerization. This process leads to the assembly of immature virus shells in which hexamers of membrane-bound MA trimers appear to organize above interlinked CA hexamers. Here, we review the functions of retroviral MA proteins, with an emphasis on the nucleic-acid-binding capability of the HIV-1 MA protein, and its effects on membrane binding.
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Affiliation(s)
- Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University Portland, OR, USA
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Sciences University Portland, OR, USA
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Basmaciogullari S, Pizzato M. The activity of Nef on HIV-1 infectivity. Front Microbiol 2014; 5:232. [PMID: 24904546 PMCID: PMC4033043 DOI: 10.3389/fmicb.2014.00232] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 04/30/2014] [Indexed: 12/29/2022] Open
Abstract
The replication and pathogenicity of lentiviruses is crucially modulated by “auxiliary proteins” which are expressed in addition to the canonical retroviral ORFs gag, pol, and env. Strategies to inhibit the activity of such proteins are often sought and proposed as possible additions to increase efficacy of the traditional antiretroviral therapy. This requires the acquisition of an in-depth knowledge of the molecular mechanisms underlying their function. The Nef auxiliary protein is expressed uniquely by primate lentiviruses and plays an important role in virus replication in vivo and in the onset of AIDS. Among its several activities Nef enhances the intrinsic infectivity of progeny virions through a mechanism which remains today enigmatic. Here we review the current knowledge surrounding such activity and we discuss its possible role in HIV biology.
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Affiliation(s)
- Stéphane Basmaciogullari
- Hôpital Necker-Enfants Malades, Sorbonne Paris Cité, Université Paris Descartes Paris, France ; INSERM U845 Paris, France
| | - Massimo Pizzato
- Centre for Integrative Biology, University of Trento Trento, Italy
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Gregory DA, Olinger GY, Lucas TM, Johnson MC. Diverse viral glycoproteins as well as CD4 co-package into the same human immunodeficiency virus (HIV-1) particles. Retrovirology 2014; 11:28. [PMID: 24708808 PMCID: PMC3985584 DOI: 10.1186/1742-4690-11-28] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 03/19/2014] [Indexed: 12/17/2022] Open
Abstract
Background Retroviruses can acquire not only their own glycoproteins as they bud from the cellular membrane, but also some cellular and foreign viral glycoproteins. Many of these non-native glycoproteins are actively recruited to budding virions, particularly other viral glycoproteins. This observation suggests that there may be a conserved mechanism underlying the recruitment of glycoproteins into viruses. If a conserved mechanism is used, diverse glycoproteins should localize to a single budding retroviral particle. On the other hand, if viral glycoproteins have divergent mechanisms for recruitment, the different glycoproteins could segregate into different particles. Results To determine if co-packaging occurs among different glycoproteins, we designed an assay that combines virion antibody capture and a determination of infectivity based on a luciferase reporter. Virions were bound to a plate with an antibody against one glycoprotein, and then the infectivity was measured with cells that allow entry only with a second glycoprotein. We tested pairings of glycoproteins from HIV, murine leukemia virus (MLV), Rous sarcoma virus (RSV), vesicular stomatitis virus (VSV), and Ebola virus. The results showed that glycoproteins that were actively recruited into virions were co-packaged efficiently with each other. We also tested cellular proteins and found CD4 also had a similar correlation between active recruitment and efficient co-packaging, but other cellular proteins did not. Conclusion Glycoproteins that are actively incorporated into HIV-1 virions are efficiently co-packaged into the same virus particles, suggesting that the same general mechanism for recruitment may act in many viruses.
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Affiliation(s)
| | | | | | - Marc C Johnson
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA.
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Tedbury PR, Ablan SD, Freed EO. Global rescue of defects in HIV-1 envelope glycoprotein incorporation: implications for matrix structure. PLoS Pathog 2013; 9:e1003739. [PMID: 24244165 PMCID: PMC3828165 DOI: 10.1371/journal.ppat.1003739] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 09/05/2013] [Indexed: 02/01/2023] Open
Abstract
The matrix (MA) domain of HIV-1 Gag plays key roles in membrane targeting of Gag, and envelope (Env) glycoprotein incorporation into virions. Although a trimeric MA structure has been available since 1996, evidence for functional MA trimers has been elusive. The mechanism of HIV-1 Env recruitment into virions likewise remains unclear. Here, we identify a point mutation in MA that rescues the Env incorporation defects imposed by an extensive panel of MA and Env mutations. Mapping the mutations onto the putative MA trimer reveals that the incorporation-defective mutations cluster at the tips of the trimer, around the perimeter of a putative gap in the MA lattice into which the cytoplasmic tail of gp41 could insert. By contrast, the rescue mutation is located at the trimer interface, suggesting that it may confer rescue of Env incorporation via modification of MA trimer interactions, a hypothesis consistent with additional mutational analysis. These data strongly support the existence of MA trimers in the immature Gag lattice and demonstrate that rescue of Env incorporation defects is mediated by modified interactions at the MA trimer interface. The data support the hypothesis that mutations in MA that block Env incorporation do so by imposing a steric clash with the gp41 cytoplasmic tail, rather than by disrupting a specific MA-gp41 interaction. The importance of the trimer interface in rescuing Env incorporation suggests that the trimeric arrangement of MA may be a critical factor in permitting incorporation of Env into the Gag lattice. One of the enduring problems in HIV-1 research is the mechanism of incorporation of the viral envelope (Env) glycoprotein into viral particles. Several models have been proposed ranging from an entirely passive process to a requirement for binding of Env by the matrix (MA) domain of the Gag precursor polyprotein. It is clear that specific regions within MA and Env play important roles, as mutations in these domains can prevent Env incorporation. We have identified a point mutation in MA that rescues a broad range of Env-incorporation defective mutations, located both in MA and in Env. Our investigations into the mechanism of rescue have revealed the importance of interactions between MA monomers at a trimeric interface. Our results are consistent with previously published crystallographic models and now provide functional support for the existence of MA trimers in the immature Gag lattice. Furthermore, as the modification of trimer interactions plays a role in the rescue of Env incorporation, we propose that MA trimerization and the organization of the MA lattice may be critical factors in Env incorporation.
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Affiliation(s)
- Philip R. Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Sherimay D. Ablan
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- * E-mail:
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Retrovirus glycoprotein functionality requires proper alignment of the ectodomain and the membrane-proximal cytoplasmic tail. J Virol 2013; 87:12805-13. [PMID: 24049172 DOI: 10.1128/jvi.01847-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nonnative viral glycoproteins, including Friend murine leukemia virus envelope (F-MLV Env) are actively recruited to HIV-1 assembly sites by an unknown mechanism. Because interactions with the lipid microenvironment at budding sites could contribute to recruitment, we examined the contribution of the hydrophobicity of the F-MLV Env membrane-spanning domain (MSD) to its incorporation into HIV-1 particles. A series of F-MLV Env mutants that added or deleted one, two, or three leucines in the MSD were constructed. All six mutants retained the ability to be incorporated into HIV-1 particles, but the -1L, -2L, -3L, +1L, and +2L mutants were not capable of producing infectious particles. Surprisingly, the +3L Env glycoprotein was able to produce infectious particles and was constitutively fusogenic. However, when the cytoplasmic tail domains (CTDs) in the Env constructs were deleted, all six of the MSD mutants were able to produce infectious particles. Further mutational analyses revealed that the first 10 amino acids of the CTD is a critical regulator of infectivity. A similar phenotype was observed in HIV-1 Env upon addition of leucines in the MSD, with +1 and +2 leucine mutations greatly reducing Env activity, but +3 leucine mutations behaving similar to the wild type. Unlike F-MLV Env (+1L and +2L), HIV-1 Env (+1L and +2L) infectivity was not restored by deletion of the CTD. We hypothesize that the CTD forms a coiled-coil that disrupts the protein's functionality if it is not in phase with the trimer interface of the ectodomain.
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Quan Y, Xu H, Wainberg MA. Defective HIV-1 quasispecies in the form of multiply drug-resistant proviral DNA within cells can be rescued by superinfection with different subtype variants of HIV-1 and by HIV-2 and SIV. J Antimicrob Chemother 2013; 69:21-7. [PMID: 23963235 DOI: 10.1093/jac/dkt326] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES HIV-1 generates swarms of similar, but genetically distinct, variants termed quasispecies and many of these variants can be defective. A relevant question is whether such defective species can contribute to viral pathogenesis. Indeed, we previously reported that a presumed recombination of defective proviral DNA with other complementary defective proviral DNA or with wild-type viral DNA in the aftermath of superinfection could lead to the rescue of defective provirus and the production of replication-competent virus. We then wished to determine whether such rescue could be affected by viruses of different subtypes or even by other members of the retrovirus family. METHODS Here, we have used drug resistance mutations within the HIV genome as markers of potential recombination. RESULTS We show that a defective proviral DNA within cells can be rescued by the superinfection of MT2 cells by various subtypes of HIV-1, and by HIV-2 and simian immunodeficiency virus, but not by human T cell leukaemia virus type 1 or by human herpes virus-6. The drug-resistance phenotype of the rescued HIV was confirmed in a second round of infection. CONCLUSIONS Defective proviral HIV-1 can be rescued by the infection by different variants of HIV-1 and by several other retroviruses as well.
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Affiliation(s)
- Yudong Quan
- McGill University AIDS Centre, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, McGill University, Montréal, Québec, Canada
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Bohl CR, Abrahamyan LG, Wood C. Human Ubc9 is involved in intracellular HIV-1 Env stability after trafficking out of the trans-Golgi network in a Gag dependent manner. PLoS One 2013; 8:e69359. [PMID: 23861967 PMCID: PMC3704627 DOI: 10.1371/journal.pone.0069359] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 06/07/2013] [Indexed: 01/03/2023] Open
Abstract
The cellular E2 Sumo conjugase, Ubc9 interacts with HIV-1 Gag, and is important for the assembly of infectious HIV-1 virions. In the previous study we demonstrated that in the absence of Ubc9, a defect in virion assembly was associated with decreased levels of mature intracellular Envelope (Env) that affected Env incorporation into virions and virion infectivity. We have further characterized the effect of Ubc9 knockdown on HIV Env processing and assembly. We found that gp160 stability in the endoplasmic reticulum (ER) and its trafficking to the trans-Golgi network (TGN) were unaffected, indicating that the decreased intracellular mature Env levels in Ubc9-depleted cells were due to a selective degradation of mature Env gp120 after cleavage from gp160 and trafficked out of the TGN. Decreased levels of Gag and mature Env were found to be associated with the plasma membrane and lipid rafts, which suggest that these viral proteins were not trafficked correctly to the assembly site. Intracellular gp120 were partially rescued when treated with a combination of lysosome inhibitors. Taken together our results suggest that in the absence of Ubc9, gp120 is preferentially degraded in the lysosomes likely before trafficking to assembly sites leading to the production of defective virions. This study provides further insight in the processing and packaging of the HIV-1 gp120 into mature HIV-1 virions.
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Affiliation(s)
- Christopher R. Bohl
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Levon G. Abrahamyan
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Charles Wood
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
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Santos da Silva E, Mulinge M, Perez Bercoff D. The frantic play of the concealed HIV envelope cytoplasmic tail. Retrovirology 2013; 10:54. [PMID: 23705972 PMCID: PMC3686653 DOI: 10.1186/1742-4690-10-54] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 05/01/2013] [Indexed: 11/18/2022] Open
Abstract
Lentiviruses have unusually long envelope (Env) cytoplasmic tails, longer than those of other retroviruses. Whereas the Env ectodomain has received much attention, the gp41 cytoplasmic tail (gp41-CT) is one of the least studied parts of the virus. It displays relatively high conservation compared to the rest of Env. It has been long established that the gp41-CT interacts with the Gag precursor protein to ensure Env incorporation into the virion. The gp41-CT contains distinct motifs and domains that mediate both intensive Env intracellular trafficking and interactions with numerous cellular and viral proteins, optimizing viral infectivity. Although they are not fully understood, a multiplicity of interactions between the gp41-CT and cellular factors have been described over the last decade; these interactions illustrate how Env expression and incorporation into virions is a finely tuned process that has evolved to best exploit the host system with minimized genetic information. This review addresses the structure and topology of the gp41-CT of lentiviruses (mainly HIV and SIV), their domains and believed functions. It also considers the cellular and viral proteins that have been described to interact with the gp41-CT, with a particular focus on subtype-related polymorphisms.
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Clustering and mobility of HIV-1 Env at viral assembly sites predict its propensity to induce cell-cell fusion. J Virol 2013; 87:7516-25. [PMID: 23637402 DOI: 10.1128/jvi.00790-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
HIV-1 Env mediates virus attachment to and fusion with target cell membranes, and yet, while Env is still situated at the plasma membrane of the producer cell and before its incorporation into newly formed particles, Env already interacts with the viral receptor CD4 on target cells, thus enabling the formation of transient cell contacts that facilitate the transmission of viral particles. During this first encounter with the receptor, Env must not induce membrane fusion, as this would prevent the producer cell and the target cell from separating upon virus transmission, but how Env's fusion activity is controlled remains unclear. To gain a better understanding of the Env regulation that precedes viral transmission, we examined the nanoscale organization of Env at the surface of producer cells. Utilizing superresolution microscopy (stochastic optical reconstruction microscopy [STORM]) and fluorescence recovery after photobleaching (FRAP), we quantitatively assessed the clustering and dynamics of Env upon its arrival at the plasma membrane. We found that Gag assembly induced the aggregation of small Env clusters into larger domains and that these domains were completely immobile. Truncation of the cytoplasmic tail (CT) of Env abrogated Gag's ability to induce Env clustering and restored Env mobility at assembly sites, both of which correlated with increased Env-induced fusion of infected and uninfected cells. Hence, while Env trapping by Gag secures Env incorporation into viral particles, Env clustering and its sequestration at assembly sites likely also leads to the repression of its fusion function, and thus, by preventing the formation of syncytia, Gag helps to secure efficient transfer of viral particles to target cells.
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Qi M, Williams JA, Chu H, Chen X, Wang JJ, Ding L, Akhirome E, Wen X, Lapierre LA, Goldenring JR, Spearman P. Rab11-FIP1C and Rab14 direct plasma membrane sorting and particle incorporation of the HIV-1 envelope glycoprotein complex. PLoS Pathog 2013; 9:e1003278. [PMID: 23592992 PMCID: PMC3616983 DOI: 10.1371/journal.ppat.1003278] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2012] [Accepted: 02/12/2013] [Indexed: 11/19/2022] Open
Abstract
The incorporation of the envelope glycoprotein complex (Env) onto the developing particle is a crucial step in the HIV-1 lifecycle. The long cytoplasmic tail (CT) of Env is required for the incorporation of Env onto HIV particles in T cells and macrophages. Here we identify the Rab11a-FIP1C/RCP protein as an essential cofactor for HIV-1 Env incorporation onto particles in relevant human cells. Depletion of FIP1C reduced Env incorporation in a cytoplasmic tail-dependent manner, and was rescued by replenishment of FIP1C. FIP1C was redistributed out of the endosomal recycling complex to the plasma membrane by wild type Env protein but not by CT-truncated Env. Rab14 was required for HIV-1 Env incorporation, and FIP1C mutants incapable of binding Rab14 failed to rescue Env incorporation. Expression of FIP1C and Rab14 led to an enhancement of Env incorporation, indicating that these trafficking factors are normally limiting for CT-dependent Env incorporation onto particles. These findings support a model for HIV-1 Env incorporation in which specific targeting to the particle assembly microdomain on the plasma membrane is mediated by FIP1C and Rab14. Enveloped viruses must develop strategies to ensure that a sufficient quantity of their receptor-binding envelope proteins are incorporated onto the surface of viruses as they form. The HIV envelope glycoprotein is specifically incorporated onto assembling virions in relevant cells such as T lymphocytes in a manner that requires its long cytoplasmic tail. The mechanism underlying this specific incorporation has remained unknown. Here, we identify a cellular trafficking pathway that is required for the incorporation of HIV envelope onto virions. A combination of the adaptor protein Rab11-FIP1C and Rab14 directs the envelope protein onto assembling virions, and loss of either of these host factors results in the production of virus particles lacking envelope. We also found that FIP1C was required for replication in T cell lines. This study identifies a trafficking complex required for HIV envelope incorporation and for the formation of infectious HIV particles.
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Affiliation(s)
- Mingli Qi
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Janice A. Williams
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Hin Chu
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Xuemin Chen
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Jaang-Jiun Wang
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Lingmei Ding
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Ehiole Akhirome
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Xiaoyun Wen
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Lynne A. Lapierre
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - James R. Goldenring
- Departments of Surgery and Cell and Developmental Biology, Epithelial Biology Center, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail: (JRG); (PS)
| | - Paul Spearman
- Department of Pediatrics, Children's Healthcare of Atlanta and Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail: (JRG); (PS)
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Super-resolution microscopy reveals specific recruitment of HIV-1 envelope proteins to viral assembly sites dependent on the envelope C-terminal tail. PLoS Pathog 2013; 9:e1003198. [PMID: 23468635 PMCID: PMC3585150 DOI: 10.1371/journal.ppat.1003198] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Accepted: 01/03/2013] [Indexed: 12/13/2022] Open
Abstract
The inner structural Gag proteins and the envelope (Env) glycoproteins of human immunodeficiency virus (HIV-1) traffic independently to the plasma membrane, where they assemble the nascent virion. HIV-1 carries a relatively low number of glycoproteins in its membrane, and the mechanism of Env recruitment and virus incorporation is incompletely understood. We employed dual-color super-resolution microscopy visualizing Gag assembly sites and HIV-1 Env proteins in virus-producing and in Env expressing cells. Distinctive HIV-1 Gag assembly sites were readily detected and were associated with Env clusters that always extended beyond the actual Gag assembly site and often showed enrichment at the periphery and surrounding the assembly site. Formation of these Env clusters depended on the presence of other HIV-1 proteins and on the long cytoplasmic tail (CT) of Env. CT deletion, a matrix mutation affecting Env incorporation or Env expression in the absence of other HIV-1 proteins led to much smaller Env clusters, which were not enriched at viral assembly sites. These results show that Env is recruited to HIV-1 assembly sites in a CT-dependent manner, while Env(ΔCT) appears to be randomly incorporated. The observed Env accumulation surrounding Gag assemblies, with a lower density on the actual bud, could facilitate viral spread in vivo. Keeping Env molecules on the nascent virus low may be important for escape from the humoral immune response, while cell-cell contacts mediated by surrounding Env molecules could promote HIV-1 transmission through the virological synapse.
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Lucas TM, Janaka SK, Stephens EB, Johnson MC. Vpu downmodulates two distinct targets, tetherin and gibbon ape leukemia virus envelope, through shared features in the Vpu cytoplasmic tail. PLoS One 2012; 7:e51741. [PMID: 23284757 PMCID: PMC3526647 DOI: 10.1371/journal.pone.0051741] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/09/2012] [Indexed: 11/21/2022] Open
Abstract
During human immunodeficiency virus-1 (HIV-1) assembly, the host proteins CD4 (the HIV-1 receptor) and tetherin (an interferon stimulated anti-viral protein) both reduce viral fitness. The HIV-1 accessory gene Vpu counteracts both of these proteins, but it is thought to do so through two distinct mechanisms. Modulation of CD4 likely occurs through proteasomal degradation from the endoplasmic reticulum. The exact mechanism of tetherin modulation is less clear, with possible roles for degradation and alteration of protein transport to the plasma membrane. Most investigations of Vpu function have used different assays for CD4 and tetherin. In addition, many of these investigations used exogenously expressed Vpu, which could result in variable expression levels. Thus, few studies have investigated these two Vpu functions in parallel assays, making direct comparisons difficult. Here, we present results from a rapid assay used to simultaneously investigate Vpu-targeting of both tetherin and a viral glycoprotein, gibbon ape leukemia virus envelope (GaLV Env). We previously reported that Vpu modulates GaLV Env and prevents its incorporation into HIV-1 particles through a recognition motif similar to that found in CD4. Using this assay, we performed a comprehensive mutagenic scan of Vpu in its native proviral context to identify features required for both types of activity. We observed considerable overlap in the Vpu sequences required to modulate tetherin and GaLV Env. We found that features in the cytoplasmic tail of Vpu, specifically within the cytoplasmic tail hinge region, were required for modulation of both tetherin and GaLV Env. Interestingly, these same regions features have been determined to be critical for CD4 downmodulation. We also observed a role for the transmembrane domain in the restriction of tetherin, as previously reported, but not of GaLV Env. We propose that Vpu may target both proteins in a mechanistically similar manner, albeit in different cellular locations.
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Affiliation(s)
- Tiffany M. Lucas
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
| | - Sanath K. Janaka
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
| | - Edward B. Stephens
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Marc C. Johnson
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
- * E-mail:
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32
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Multiple Gag domains contribute to selective recruitment of murine leukemia virus (MLV) Env to MLV virions. J Virol 2012; 87:1518-27. [PMID: 23152533 DOI: 10.1128/jvi.02604-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Retroviruses, like all enveloped viruses, must incorporate viral glycoproteins to form infectious particles. Interactions between the glycoprotein cytoplasmic tail and the matrix domain of Gag are thought to direct recruitment of glycoproteins to native virions for many retroviruses. However, retroviruses can also incorporate glycoproteins from other viruses to form infectious virions known as pseudotyped particles. The glycoprotein murine leukemia virus (MLV) Env can readily form pseudotyped particles with many retroviruses, suggesting a generic mechanism for recruitment. Here, we sought to identify which components of Gag, particularly the matrix domain, contribute to recruitment of MLV Env into retroviral particles. Unexpectedly, we discovered that the matrix domain of HIV-1 Gag is dispensable for generic recruitment, since it could be replaced with a nonviral membrane-binding domain without blocking active incorporation of MLV Env into HIV virions. However, MLV Env preferentially assembles with MLV virions. When MLV and HIV particles are produced from the same cell, MLV Env is packaged almost exclusively by MLV particles, thus preventing incorporation into HIV particles. Surprisingly, the matrix domain of MLV Gag is not required for this selectivity, since MLV Gag containing the matrix domain from HIV is still able to outcompete HIV particles for MLV Env. Although MLV Gag is sufficient for selective incorporation to occur, no single Gag domain dictates the selectivity. Our findings indicate that Env recruitment is more complex than previously believed and that Gag assembly/budding sites have fundamental properties that affect glycoprotein incorporation.
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Retroviral env glycoprotein trafficking and incorporation into virions. Mol Biol Int 2012; 2012:682850. [PMID: 22811910 PMCID: PMC3395148 DOI: 10.1155/2012/682850] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/08/2012] [Accepted: 05/31/2012] [Indexed: 11/17/2022] Open
Abstract
Together with the Gag protein, the Env glycoprotein is a major retroviral structural protein and is essential for forming infectious virus particles. Env is synthesized, processed, and transported to certain microdomains at the plasma membrane and takes advantage of the same host machinery for its trafficking as that used by cellular glycoproteins. Incorporation of Env into progeny virions is probably mediated by the interaction between Env and Gag, in some cases with the additional involvement of certain host factors. Although several general models have been proposed to explain the incorporation of retroviral Env glycoproteins into virions, the actual mechanism for this process is still unclear, partly because structural data on the Env protein cytoplasmic tail is lacking. This paper presents the current understanding of the synthesis, trafficking, and virion incorporation of retroviral Env proteins.
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Baluyot MF, Grosse SA, Lyddon TD, Janaka SK, Johnson MC. CRM1-dependent trafficking of retroviral Gag proteins revisited. J Virol 2012; 86:4696-700. [PMID: 22318151 PMCID: PMC3318649 DOI: 10.1128/jvi.07199-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 01/27/2012] [Indexed: 11/20/2022] Open
Abstract
We analyzed the nuclear trafficking ability of Gag proteins from six retroviral genera. Contrary to a previous report, human immunodeficiency virus type 1 (HIV-1) Gag showed no propensity to cycle through the nucleus. The only Gag protein that displayed CRM1-dependent nuclear cycling was that of Rous sarcoma virus (RSV). Surprisingly, this cycling could be eliminated without compromising infectivity by replacing the RSV Gag N-terminal matrix (MA) domain with HIV MA.
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Affiliation(s)
| | - Sarah A. Grosse
- Rosalind Franklin University of Medicine and Science, Chicago, Illinois, USA
| | - Terri D. Lyddon
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
| | - Sanath K. Janaka
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
| | - Marc C. Johnson
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
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35
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Jiang J, Ablan S, Derebail S, Hercík K, Soheilian F, Thomas JA, Tang S, Hewlett I, Nagashima K, Gorelick RJ, Freed EO, Levin JG. The interdomain linker region of HIV-1 capsid protein is a critical determinant of proper core assembly and stability. Virology 2011; 421:253-65. [PMID: 22036671 PMCID: PMC3573886 DOI: 10.1016/j.virol.2011.09.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/17/2011] [Accepted: 09/14/2011] [Indexed: 11/20/2022]
Abstract
The HIV-1 capsid protein consists of two independently folded domains connected by a flexible peptide linker (residues 146-150), the function of which remains to be defined. To investigate the role of this region in virus replication, we made alanine or leucine substitutions in each linker residue and two flanking residues. Three classes of mutants were identified: (i) S146A and T148A behave like wild type (WT); (ii) Y145A, I150A, and L151A are noninfectious, assemble unstable cores with aberrant morphology, and synthesize almost no viral DNA; and (iii) P147L and S149A display a poorly infectious, attenuated phenotype. Infectivity of P147L and S149A is rescued specifically by pseudotyping with vesicular stomatitis virus envelope glycoprotein. Moreover, despite having unstable cores, these mutants assemble WT-like structures and synthesize viral DNA, although less efficiently than WT. Collectively, these findings demonstrate that the linker region is essential for proper assembly and stability of cores and efficient replication.
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Affiliation(s)
- Jiyang Jiang
- Section on Viral Gene Regulation, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Building 6B, Room 216, 6 Center Drive, Bethesda, MD 20892-2780, USA
| | - Sherimay Ablan
- Virus-Cell Interaction Section, Drug Resistance Program, National Cancer Institute Frederick, Frederick, MD 21702-1201, USA
| | - Suchitra Derebail
- Section on Viral Gene Regulation, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Building 6B, Room 216, 6 Center Drive, Bethesda, MD 20892-2780, USA
| | - Kamil Hercík
- Section on Viral Gene Regulation, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Building 6B, Room 216, 6 Center Drive, Bethesda, MD 20892-2780, USA
| | - Ferri Soheilian
- Image Analysis Laboratory, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
| | - James A. Thomas
- AIDS and Cancer Virus Program, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
| | - Shixing Tang
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
| | - Indira Hewlett
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA
| | - Kunio Nagashima
- Image Analysis Laboratory, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
| | - Robert J. Gorelick
- AIDS and Cancer Virus Program, SAIC-Frederick, Inc., National Cancer Institute-Frederick, Frederick, MD 21702-1201, USA
| | - Eric O. Freed
- Virus-Cell Interaction Section, Drug Resistance Program, National Cancer Institute Frederick, Frederick, MD 21702-1201, USA
| | - Judith G. Levin
- Section on Viral Gene Regulation, Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health, National Institutes of Health, Building 6B, Room 216, 6 Center Drive, Bethesda, MD 20892-2780, USA
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Gag induces the coalescence of clustered lipid rafts and tetraspanin-enriched microdomains at HIV-1 assembly sites on the plasma membrane. J Virol 2011; 85:9749-66. [PMID: 21813604 DOI: 10.1128/jvi.00743-11] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The HIV-1 structural protein Gag associates with two types of plasma membrane microdomains, lipid rafts and tetraspanin-enriched microdomains (TEMs), both of which have been proposed to be platforms for HIV-1 assembly. However, a variety of studies have demonstrated that lipid rafts and TEMs are distinct microdomains in the absence of HIV-1 infection. To measure the impact of Gag on microdomain behaviors, we took advantage of two assays: an antibody-mediated copatching assay and a Förster resonance energy transfer (FRET) assay that measures the clustering of microdomain markers in live cells without antibody-mediated patching. We found that lipid rafts and TEMs copatched and clustered to a greater extent in the presence of membrane-bound Gag in both assays, suggesting that Gag induces the coalescence of lipid rafts and TEMs. Substitutions in membrane binding motifs of Gag revealed that, while Gag membrane binding is necessary to induce coalescence of lipid rafts and TEMs, either acylation of Gag or binding of phosphatidylinositol-(4,5)-bisphosphate is sufficient. Finally, a Gag derivative that is defective in inducing membrane curvature appeared less able to induce lipid raft and TEM coalescence. A higher-resolution analysis of assembly sites by correlative fluorescence and scanning electron microscopy showed that coalescence of clustered lipid rafts and TEMs occurs predominantly at completed cell surface virus-like particles, whereas a transmembrane raft marker protein appeared to associate with punctate Gag fluorescence even in the absence of cell surface particles. Together, these results suggest that different membrane microdomain components are recruited in a stepwise manner during assembly.
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Abstract
The replication cycle of HIV proceeds within an infected cell and imaging techniques allow us to focus on the pathogen in this cellular environment. During recent years, both electron microscopy and fluorescence microscopy have evolved from methods providing two-dimensional still images to techniques that can resolve native, three-dimensional structures at resolutions down to approximately 20 Å, or allow direct real-time observation of dynamic intracellular events, respectively, thereby yielding numerous novel insights into HIV biology. Future technological developments are expected to narrow the gap between electron microscopy (high spatial and structural resolution, but no information about dynamics) and fluorescence microscopy (high temporal resolution and high throughput, but low spatial resolution), providing detailed views that will deepen our understanding of HIV–cell interactions.
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Affiliation(s)
- Barbara Müller
- Department of Infectious Diseases, Virology, University Hospital of Heidelberg, Im Neuenheimer Feld 324, D-69120 Heidelberg, Germany
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38
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Checkley MA, Luttge BG, Freed EO. HIV-1 envelope glycoprotein biosynthesis, trafficking, and incorporation. J Mol Biol 2011; 410:582-608. [PMID: 21762802 PMCID: PMC3139147 DOI: 10.1016/j.jmb.2011.04.042] [Citation(s) in RCA: 328] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 04/14/2011] [Accepted: 04/15/2011] [Indexed: 12/13/2022]
Abstract
The HIV-1 envelope (Env) glycoproteins play an essential role in the virus replication cycle by mediating the fusion between viral and cellular membranes during the entry process. The Env glycoproteins are synthesized as a polyprotein precursor (gp160) that is cleaved by cellular proteases to the mature surface glycoprotein gp120 and the transmembrane glycoprotein gp41. During virus assembly, the gp120/gp41 complex is incorporated as heterotrimeric spikes into the lipid bilayer of nascent virions. These gp120/gp41 complexes then initiate the infection process by binding receptor and coreceptor on the surface of target cells. Much is currently known about the HIV-1 Env glycoprotein trafficking pathway and the structure of gp120 and the extracellular domain of gp41. However, the mechanism by which the Env glycoprotein complex is incorporated into virus particles remains incompletely understood. Genetic data support a major role for the cytoplasmic tail of gp41 and the matrix domain of Gag in Env glycoprotein incorporation. Still to be defined are the identities of host cell factors that may promote Env incorporation and the role of specific membrane microdomains in this process. Here, we review our current understanding of HIV-1 Env glycoprotein trafficking and incorporation into virions.
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Affiliation(s)
- Mary Ann Checkley
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
| | - Benjamin G. Luttge
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program National Cancer Institute Frederick, MD 21702
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Abstract
Retrovirus transmission via direct cell-cell contact is more efficient than diffusion through the extracellular milieu. This is believed to be due to the ability of viruses to efficiently coordinate several steps of the retroviral life cycle at cell-cell contact sites (D. C. Johnson et al., J. Virol. 76:1-8, 2002; D. M. Phillips, AIDS 8:719-731, 1994; Q. Sattenau, Nat. Rev. Microbiol. 6:815-826, 2008). Using the murine leukemia virus (MLV) as a model retrovirus, we have previously shown that interaction between viral envelope (Env) and receptor directs viral assembly to cell-cell contact sites to promote efficient viral spreading (J. Jin et al., PLoS Biol. 7:e1000163, 2009). In addressing the underlying mechanism, we observed that Env cytoplasmic tail directs this contact-induced polarized assembly. We present here the viral determinants in the Env cytoplasmic tail and Gag that are important in this process. A tyrosine residue within the cytoplasmic tail of Env was identified, which directs polarized assembly. MLV matrix-mediated membrane targeting is required for Gag recruitment to sites of cell-cell contact. Our results suggest that MLV polarized assembly is mediated by a direct or indirect interaction between both domains, thereby coupling Gag recruitment and virus assembly to Env accumulation at the cell-cell interface. In contrast, HIV Gag that assembles outside of cell-cell interfaces can subsequently be drawn into contact zones mediated by MLV Env and receptor, a finding that is consistent with the previously observed lateral movement of HIV into the virological synapse (W. Hubner et al., Science 323:1743-1747, 2009; D. Rudnicka et al., J. Virol. 83:6234-6246, 2009). As such, we observed two distinct modes of virus cell-to-cell transmission that involve either polarized or nonpolarized assembly, but both result in virus transmission.
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Abstract
A mandatory step in the formation of an infectious retroviral particle is the acquisition of its envelope glycoprotein (Env). This step invariably occurs by Env positioning itself in the host membrane at the location of viral budding and being incorporated along with the host membrane into the viral particle. In some ways, this step of the viral life cycle would appear to be imprecise. There is no specific sequence in Env or in the retroviral structural protein, Gag, that is inherently required for the production of an infectious Env-containing particle. Additionally, Env-defective proviruses can efficiently produce infectious particles with any of a number of foreign retroviral Env glycoproteins or even glycoproteins from unrelated viral families, a process termed pseudotyping. However, mounting evidence suggests that Env incorporation is neither passive nor random. Rather, several redundant mechanisms appear to contribute to the carefully controlled process of Env acquisition, many of which are apparently used by a wide variety of enveloped viruses. This review presents and discusses the evidence for these different mechanisms contributing to incorporation.
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Affiliation(s)
- Marc C Johnson
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, 65211, USA.
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41
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R5 HIV env and vesicular stomatitis virus G protein cooperate to mediate fusion to naive CD4+ T Cells. J Virol 2010; 85:644-8. [PMID: 20980513 DOI: 10.1128/jvi.01851-10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Naïve CD4(4) T cells are resistant to both HIV R5 env and vesicular stomatitis virus G protein (VSV-G)-mediated fusion. However, viral particles carrying both HIV R5 env and VSV-G infect naïve cells by an unexplained mechanism. We show that VSV-G-pseudotyped virus cannot fuse to unstimulated cells because the viral particles cannot be endocytosed. However, virions carrying both HIV R5 env and VSV-G can fuse because CD4 binding allows viral uptake. Our findings reveal a unique mechanism by which R5 HIV env and VSV-G cooperate to allow entry to naïve CD4(+) T cells, providing a tool to target naïve CD4(+) T cells with R5 HIV to study HIV coreceptor signaling and latency.
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Lucas TM, Lyddon TD, Grosse SA, Johnson MC. Two distinct mechanisms regulate recruitment of murine leukemia virus envelope protein to retroviral assembly sites. Virology 2010; 405:548-55. [PMID: 20655565 DOI: 10.1016/j.virol.2010.06.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 04/24/2010] [Accepted: 06/08/2010] [Indexed: 12/12/2022]
Abstract
The cytoplasmic tail domain (CTD) of retroviral envelope (Env) proteins has been implicated in modulating Env incorporation into viral particles. We generated a panel of murine leukemia virus (MLV) Env mutants and analyzed their ability to be recruited to human immunodeficiency virus-1 (HIV-1) assembly sites. Surprisingly, the entire CTD was dispensable for recruitment to assembly sites, but a mutation that disrupted the furin cleavage site in Env abolished recruitment. To determine if MLV Env can show selectivity for homologous assembly sites, cells were co-transfected with both HIV-1 and MLV assembly components along with each MLV Env construct and assayed for infectious particle production. MLV Env selectively formed infectious particles with the MLV components at the expense of infectious HIV-1 infectious particle production, but truncation of the CTD progressively reduced this selectivity. Collectively these data suggest that there are two separable mechanisms that govern MLV Env recruitment to viral assembly sites.
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Affiliation(s)
- Tiffany M Lucas
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri- School of Medicine, Columbia, MO 65211, USA
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Abstract
Retroviruses undergo several critical steps to complete a replication cycle. These include the complex processes of virus entry, assembly, and budding that often take place at the plasma membrane of the host cell. Both virus entry and release involve membrane fusion/fission reactions between the viral envelopes and host cell membranes. Accumulating evidence indicates important roles for lipids and lipid microdomains in virus entry and egress. In this review, we outline the current understanding of the role of lipids and membrane microdomains in retroviral replication.
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Abstract
Advances in cell biology and biophysics revealed that cellular membranes consist of multiple microdomains with specific sets of components such as lipid rafts and TEMs (tetraspanin-enriched microdomains). An increasing number of enveloped viruses have been shown to utilize these microdomains during their assembly. Among them, association of HIV-1 (HIV type 1) and other retroviruses with lipid rafts and TEMs within the PM (plasma membrane) is well documented. In this review, I describe our current knowledge on interrelationships between PM microdomain organization and the HIV-1 particle assembly process. Microdomain association during virus particle assembly may also modulate subsequent virus spread. Potential roles played by microdomains will be discussed with regard to two post-assembly events, i.e., inhibition of virus release by a raft-associated protein BST-2/tetherin and cell-to-cell HIV-1 transmission at virological synapses.
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Lei Y, Joo KI, Zarzar J, Wong C, Wang P. Targeting lentiviral vector to specific cell types through surface displayed single chain antibody and fusogenic molecule. Virol J 2010; 7:35. [PMID: 20149250 PMCID: PMC2830192 DOI: 10.1186/1743-422x-7-35] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 02/11/2010] [Indexed: 02/07/2023] Open
Abstract
Background Viral delivery remains one of the most commonly used techniques today in the field of gene therapy. However, one of the remaining hurdles is the off-targeting effect of viral delivery. To overcome this obstacle, we recently developed a method to incorporate an antibody and a fusogenic molecule (FM) as two distinct molecules into the lentiviral surface. In this report, we expand this strategy to utilize a single chain antibody (SCAb) for targeted transduction. Results Two versions of the SCAb were generated to pair with our various engineered FMs by linking the heavy chain and the light chain variable domains of the anti-CD20 antibody (αCD20) via a GS linker and fusing them to the hinge-CH2-CH3 region of human IgG. The resulting protein was fused to either a HLA-A2 transmembrane domain or a VSVG transmembrane domain for anchoring purpose. Lentiviral vectors generated with either version of the SCAb and a selected FM were then characterized for binding and fusion activities in CD20-expressing cells. Conclusion Certain combinations of the SCAb with various FMs could result in an increase in viral transduction. This two-molecule lentiviral vector system design allows for parallel optimization of the SCAb and FMs to improve targeted gene delivery.
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Affiliation(s)
- Yuning Lei
- Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA
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46
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Pseudotyping incompatibility between HIV-1 and gibbon ape leukemia virus Env is modulated by Vpu. J Virol 2009; 84:2666-74. [PMID: 20042505 DOI: 10.1128/jvi.01562-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The Env protein from gibbon ape leukemia virus (GaLV) has been shown to be incompatible with human immunodeficiency virus type 1 (HIV-1) in the production of infectious pseudotyped particles. This incompatibility has been mapped to the C-terminal cytoplasmic tail of GaLV Env. Surprisingly, we found that the HIV-1 accessory protein Vpu modulates this incompatibility. The infectivity of HIV-1 pseudotyped with murine leukemia virus (MLV) Env was not affected by Vpu. However, the infectivity of HIV-1 pseudotyped with an MLV Env with the cytoplasmic tail from GaLV Env (MLV/GaLV Env) was restricted 50- to 100-fold by Vpu. A Vpu mutant containing a scrambled membrane-spanning domain, Vpu(RD), was still able to restrict MLV/GaLV Env, but mutation of the serine residues at positions 52 and 56 completely alleviated the restriction. Loss of infectivity appeared to be caused by reduced MLV/GaLV Env incorporation into viral particles. The mechanism of this downmodulation appears to be distinct from Vpu-mediated CD4 downmodulation because Vpu-expressing cells that failed to produce infectious HIV-1 particles nonetheless continued to display robust surface MLV/GaLV Env expression. In addition, if MLV and HIV-1 were simultaneously introduced into the same cells, only the HIV-1 particle infectivity was restricted by Vpu. Collectively, these data suggest that Vpu modulates the cellular distribution of MLV/GaLV Env, preventing its recruitment to HIV-1 budding sites.
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47
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Bieniasz PD. The cell biology of HIV-1 virion genesis. Cell Host Microbe 2009; 5:550-8. [PMID: 19527882 DOI: 10.1016/j.chom.2009.05.015] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2009] [Revised: 05/20/2009] [Accepted: 05/28/2009] [Indexed: 10/20/2022]
Abstract
Recent work has illuminated three critical aspects of the cell biology of HIV-1 particle genesis. First, we have come to understand which cellular membranes are selected as platforms for virus particle assembly and how this occurs. Second, an understanding of how the host ESCRT pathway enables virion budding is accruing. Third, it has become apparent that a host inhibitor can block HIV-1 particle release and that antagonism of this inhibitor underlies the ability of HIV and SIV accessory genes to facilitate particle release. Here, I review recent progress in these three areas.
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Affiliation(s)
- Paul D Bieniasz
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center, New York, NY 10016, USA.
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Waheed AA, Freed EO. Lipids and membrane microdomains in HIV-1 replication. Virus Res 2009; 143:162-76. [PMID: 19383519 DOI: 10.1016/j.virusres.2009.04.007] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 04/01/2009] [Accepted: 04/03/2009] [Indexed: 10/20/2022]
Abstract
Several critical steps in the replication cycle of human immunodeficiency virus type 1 (HIV-1) - entry, assembly and budding - are complex processes that take place at the plasma membrane of the host cell. A growing body of data indicates that these early and late steps in HIV-1 replication take place in specialized plasma membrane microdomains, and that many of the viral and cellular components required for entry, assembly, and budding are concentrated in these microdomains. In particular, a number of studies have shown that cholesterol- and sphingolipid-enriched microdomains known as lipid rafts play important roles in multiple steps in the virus replication cycle. In this review, we provide an overview of what is currently known about the involvement of lipids and membrane microdomains in HIV-1 replication.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA.
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