scholarly journals Ebola Virus Glycoprotein Counteracts BST-2/Tetherin Restriction in a Sequence-Independent Manner That Does Not Require Tetherin Surface Removal

2010 ◽  
Vol 84 (14) ◽  
pp. 7243-7255 ◽  
Author(s):  
Lisa A. Lopez ◽  
Su Jung Yang ◽  
Heiko Hauser ◽  
Colin M. Exline ◽  
Kevin G. Haworth ◽  
...  
Keyword(s):  
Cell Surface ◽  
Ebola Virus ◽  
Independent Manner ◽  
Specific Sequence ◽  
Surface Population ◽  
Human Tetherin ◽  
Infected Cells ◽  
Inducible Protein ◽  
Tm Domain ◽  
Hiv 1

ABSTRACT BST-2/tetherin is an interferon-inducible protein that restricts the release of enveloped viruses from the surface of infected cells by physically linking viral and cellular membranes. It is present at both the cell surface and in a perinuclear region, and viral anti-tetherin factors including HIV-1 Vpu and HIV-2 Env have been shown to decrease the cell surface population. To map the domains of human tetherin necessary for both virus restriction and sensitivity to viral anti-tetherin factors, we constructed a series of tetherin derivatives and assayed their activity. We found that the cytoplasmic tail (CT) and transmembrane (TM) domains of tetherin alone produced its characteristic cellular distribution, while the ectodomain of the protein, which includes a glycosylphosphatidylinositol (GPI) anchor, was sufficient to restrict virus release when presented by the CT/TM regions of a different type II membrane protein. To counteract tetherin restriction and remove it from the cell surface, HIV-1 Vpu required the specific sequence present in the TM domain of human tetherin. In contrast, the HIV-2 Env required only the ectodomain of the protein and was sensitive to a point mutation in this region. Strikingly, the anti-tetherin factor, Ebola virus GP, was able to overcome restriction conferred by both tetherin and a series of functional tetherin derivatives, including a wholly artificial tetherin molecule. Moreover, GP overcame restriction without significantly removing tetherin from the cell surface. These findings suggest that Ebola virus GP uses a novel mechanism to circumvent tetherin restriction.

scholarly journals The Nef protein of the macrophage tropic HIV-1 strain AD8 counteracts human Bst-2/tetherin

2020 ◽  
Author(s):  
Sebastian Giese ◽  
Scott P. Lawrence ◽  
Michela Mazzon ◽  
Bernadien M. Nijmeijer ◽  
Mark Marsh
Keyword(s):  
Cell Surface ◽  
Virus Release ◽  
Viral Budding ◽  
Primary Monocyte ◽  
Human Tetherin ◽  
Human Immunodeficiency Viruses ◽  
Infected Cells ◽  
Translation Initiation Codon ◽  
Hiv 1 ◽  
Tetherin Antagonism

AbstractBst-2/tetherin inhibits the release of numerous enveloped viruses by physically attaching nascent particles to infected cells during the process of viral budding from the cell surface. Tetherin also restricts human immunodeficiency viruses (HIV), and pandemic main (M) group HIV-1s are thought to exclusively rely on their Vpu proteins to overcome tetherin-mediated restriction of virus release. However, at least one M group HIV-1 strain, the macrophage-tropic primary AD8 isolate, is unable to express vpu due to a mutation in its translation initiation codon. Here, using primary monocyte-derived macrophages (MDMs), we show that AD8 was able to use its Nef protein to compensate for the absence of Vpu and restore virus release to wild type levels. We demonstrate that HIV-1 AD8 Nef reduces endogenous tetherin levels from the cell surface, physically separating it from the site of viral budding and thus preventing HIV retention. Mechanistically, AD8 Nef enhances l-tetherin internalisation, leading to perinuclear accumulation of the restriction factor. Finally, we show that Nef proteins from other HIV strains also display varying degrees of tetherin antagonism. Overall, this is the first report showing that M group HIV-1s can use an accessory protein other than Vpu to antagonise human tetherin.

scholarly journals The Nef Protein of the Macrophage Tropic HIV-1 Strain AD8 Counteracts Human BST-2/Tetherin

Viruses ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 459 ◽  
Author(s):  
Sebastian Giese ◽  
Scott P. Lawrence ◽  
Michela Mazzon ◽  
Bernadien M. Nijmeijer ◽  
Mark Marsh
Keyword(s):  
Cell Surface ◽  
Virus Release ◽  
Viral Budding ◽  
Primary Monocyte ◽  
Human Tetherin ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Translation Initiation Codon ◽  
Hiv 1 ◽  
Tetherin Antagonism

Bone Marrow Stromal Cell Antigen 2 (BST-2)/tetherin inhibits the release of numerous enveloped viruses by physically tethering nascent particles to infected cells during the process of viral budding from the cell surface. Tetherin also restricts human immunodeficiency virus (HIV), and pandemic main (M) group HIV type 1s (HIV-1s) are thought to rely exclusively on their Vpu proteins to overcome tetherin-mediated restriction of virus release. However, at least one M group HIV-1 strain, the macrophage-tropic primary AD8 isolate, is unable to express Vpu due to a mutation in its translation initiation codon. Here, using primary monocyte-derived macrophages (MDMs), we show that AD8 Nef protein can compensate for the absence of Vpu and restore virus release to wild type levels. We demonstrate that HIV-1 AD8 Nef reduces endogenous cell surface tetherin levels, physically separating it from the site of viral budding, thus preventing HIV retention. Mechanistically, AD8 Nef enhances internalisation of the long isoform of human tetherin, leading to perinuclear accumulation of the restriction factor. Finally, we show that Nef proteins from other HIV strains also display varying degrees of tetherin antagonism. Overall, we show that M group HIV-1s can use an accessory protein other than Vpu to antagonise human tetherin.

scholarly journals Determinants of Tetherin Antagonism in the Transmembrane Domain of the Human Immunodeficiency Virus Type 1 Vpu Protein

2010 ◽  
Vol 84 (24) ◽  
pp. 12958-12970 ◽  
Author(s):  
Raphaël Vigan ◽  
Stuart J. D. Neil
Keyword(s):  
Human Immunodeficiency Virus ◽  
Amino Acid ◽  
Cell Surface ◽  
Human Immunodeficiency Virus Type ◽  
Transmembrane Domain ◽  
Human Tetherin ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Tetherin Antagonism

ABSTRACT Tetherin (BST2/CD317) potently restricts the particle release of human immunodeficiency virus type 1 (HIV-1) mutants defective in the accessory gene vpu. Vpu antagonizes tetherin activity and induces its cell surface downregulation and degradation in a manner dependent on the transmembrane (TM) domains of both proteins. We have carried out extensive mutagenesis of the HIV-1 NL4.3 Vpu TM domain to identify three amino acid positions, A14, W22, and, to a lesser extent, A18, that are required for tetherin antagonism. Despite the mutants localizing indistinguishably from the wild-type (wt) protein and maintaining the ability to multimerize, mutation of these positions rendered Vpu incapable of coimmunoprecipitating tetherin or mediating its cell surface downregulation. Interestingly, these amino acid positions are predicted to form one face of the Vpu transmembrane alpha helix and therefore potentially contribute to an interacting surface with the transmembrane domain of tetherin either directly or by modulating the conformation of Vpu oligomers. While the equivalent of W22 is invariant in HIV-1/SIVcpz Vpu proteins, the positions of A14 and A18 are highly conserved among Vpu alleles from HIV-1 groups M and N, but not those from group O or SIVcpz that lack human tetherin (huTetherin)-antagonizing activity, suggesting that they may have contributed to the adaption of HIV-1 to human tetherin.

scholarly journals HIV-1 Vpr up-regulates expression of ligands for the activating NKG2D receptor and promotes NK cell–mediated killing

Blood ◽  
2010 ◽  
Vol 115 (7) ◽  
pp. 1354-1363 ◽  
Author(s):  
Jonathan Richard ◽  
Sardar Sindhu ◽  
Tram N. Q. Pham ◽  
Jean-Philippe Belzile ◽  
Éric A. Cohen
Keyword(s):  
Dna Damage ◽  
Cell Surface ◽  
Nk Cell ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Target Cells ◽  
Nkg2d Ligands ◽  
Infected Cells ◽  
Nkg2d Receptor ◽  
Hiv 1

AbstractHIV up-regulates cell-surface expression of specific ligands for the activating NKG2D receptor, including ULBP-1, -2, and -3, but not MICA or MICB, in infected cells both in vitro and in vivo. However, the viral factor(s) involved in NKG2D ligand expression still remains undefined. HIV-1 Vpr activates the DNA damage/stress-sensing ATR kinase and promotes G2 cell-cycle arrest, conditions known to up-regulate NKG2D ligands. We report here that HIV-1 selectively induces cell-surface expression of ULBP-2 in primary CD4+ T lymphocytes by a process that is Vpr dependent. Importantly, Vpr enhanced the susceptibility of HIV-1–infected cells to NK cell–mediated killing. Strikingly, Vpr alone was sufficient to up-regulate expression of all NKG2D ligands and thus promoted efficient NKG2D-dependent NK cell–mediated killing. Delivery of virion-associated Vpr via defective HIV-1 particles induced analogous biologic effects in noninfected target cells, suggesting that Vpr may act similarly beyond infected cells. All these activities relied on Vpr ability to activate the ATR-mediated DNA damage/stress checkpoint. Overall, these results indicate that Vpr is a key determinant responsible for HIV-1–induced up-regulation of NKG2D ligands and further suggest an immunomodulatory role for Vpr that may not only contribute to HIV-1–induced CD4+ T-lymphocyte depletion but may also take part in HIV-1–induced NK-cell dysfunction.

scholarly journals Human Immunodeficiency Virus Type 1 Vpr Protein Does Not Modulate Surface Expression of the CD4 Receptor

2002 ◽  
Vol 76 (8) ◽  
pp. 4125-4130 ◽  
Author(s):  
Enrique Argañaraz ◽  
María José Cortés ◽  
Sydney Leibel ◽  
Juan Lama
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Cell Surface ◽  
Target Cells ◽  
Viral Receptor ◽  
Cd4 Receptor ◽  
Immunodeficiency Virus ◽  
Infected Cells ◽  
Hiv 1

ABSTRACT The CD4 receptor is required for the entry of human immunodeficiency virus (HIV) into target cells. It has long been known that Nef, Env, and Vpu participate in the removal of the viral receptor from the cell surface. Recently, it has been proposed that the HIV type 1 (HIV-1) Vpr protein may also play a role in the downmodulation of CD4 from the surfaces of infected cells (L. Conti, B. Varano, M. C. Gauzzi, P. Matarrese, M. Federico, W. Malorani, F. Belardelli, and S. Gessani, J. Virol. 74:10207-10211, 2000). To investigate the possible role of Vpr in the downregulation of the viral receptor Vpr alleles from HIV-1 and simian immunodeficiency virus were transiently expressed in transformed T cells and in 293T fibroblasts, and their ability to modulate surface CD4 was evaluated. All Vpr alleles efficiently arrested cells in the G2 stage of the cell cycle. However, none of the tested Vpr proteins altered the expression of CD4 on the cell surface. In comparison, HIV-1 Nef efficiently downmodulated surface CD4 in all the experimental settings. Transformed T cells and primary lymphocytes were challenged with wild-type, Nef-defective, and Vpr-defective viruses. A significant reduction in the HIV-induced downmodulation of surface CD4 was observed in viruses lacking Nef. However, Vpr-deletion-containing viruses showed no defect in their ability to remove CD4 from the surfaces of infected cells. Our results indicate that Vpr does not play a role in the HIV-induced downmodulation of the CD4 receptor.

scholarly journals HIV-1 Envelope Glycoprotein Cell Surface Localization Is Associated with Antibody-Induced Internalization

Viruses ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1953
Author(s):  
Sai Priya Anand ◽  
Jérémie Prévost ◽  
Jade Descôteaux-Dinelle ◽  
Jonathan Richard ◽  
Dung N. Nguyen ◽  
...  
Keyword(s):  
Cell Surface ◽  
Neutralizing Antibodies ◽  
Surface Expression ◽  
Broadly Neutralizing Antibodies ◽  
Open Conformation ◽  
Surface Localization ◽  
Infected Cells ◽  
Cell Surface Localization ◽  
Underlying Mechanisms ◽  
Hiv 1

To minimize immune responses against infected cells, HIV-1 has evolved different mechanisms to limit the surface expression of its envelope glycoproteins (Env). Recent observations suggest that the binding of certain broadly neutralizing antibodies (bNAbs) targeting the ‘closed’ conformation of Env induces its internalization. On the other hand, non-neutralizing antibodies (nNAbs) that preferentially target Env in its ‘open’ conformation, remain bound to Env on the cell surface for longer periods of time. In this study, we attempt to better understand the underlying mechanisms behind the differential rates of antibody-mediated Env internalization. We demonstrate that ‘forcing’ open Env using CD4 mimetics allows for nNAb binding and results in similar rates of Env internalization as those observed upon the bNAb binding. Moreover, we can identify distinct populations of Env that are differentially targeted by Abs that mediate faster rates of internalization, suggesting that the mechanism of antibody-induced Env internalization partially depends on the localization of Env on the cell surface.

scholarly journals Functional Analysis of the Transmembrane (TM) Domain of the Autographa californica Multicapsid Nucleopolyhedrovirus GP64 Protein: Substitution of Heterologous TM Domains

2008 ◽  
Vol 82 (7) ◽  
pp. 3329-3341 ◽  
Author(s):  
Zhaofei Li ◽  
Gary W. Blissard
Keyword(s):  
Membrane Proteins ◽  
Cell Surface ◽  
Membrane Fusion ◽  
Low Ph ◽  
Autographa Californica ◽  
Virus Infectivity ◽  
Type I ◽  
Gpi Anchor ◽  
Tm Domain ◽  
Hiv 1

ABSTRACT GP64, the major envelope glycoprotein of the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) budded virion, is important for host cell receptor binding and mediates low-pH-triggered membrane fusion during entry by endocytosis. In the current study, we examined the functional role of the AcMNPV GP64 transmembrane (TM) domain by replacing the 23-amino-acid GP64 TM domain with corresponding TM domain sequences from a range of viral and cellular type I membrane proteins, including Orgyia pseudotsugata MNPV (OpMNPV) GP64 and F, thogotovirus GP75, Lymantria dispar MNPV (LdMNPV) F, human immunodeficiency virus type 1 (HIV-1) GP41, human CD4 and glycophorin A (GpA), and influenza virus hemagglutinin (HA), and with a glycosylphosphatidylinositol (GPI) anchor addition sequence. In transient expression experiments with Sf9 cells, chimeric GP64 proteins containing either a GPI anchor or TM domains from LdMNPV F or HIV-1 GP41 failed to localize to the cell surface and thus appear to be incompatible with either GP64 structure or cell transport. All of the mutant constructs detected at the cell surface mediated hemifusion (outer leaflet merger) upon low-pH treatment, but only those containing TM domains from CD4, GpA, OpMNPV GP64, and thogotovirus GP75 mediated pore formation and complete membrane fusion activity. This supports a model in which partial fusion (hemifusion) proceeds by a mechanism that is independent of the TM domain and the TM domain participates in the enlargement or expansion of fusion pores after hemifusion. GP64 proteins containing heterologous TM domains mediated virion budding with dramatically differing levels of efficiency. In addition, chimeric GP64 proteins containing TM domains from CD4, GpA, HA, and OpMNPV F were incorporated into budded virions but were unable to rescue the infectivity of a gp64 null virus, whereas those with TM domains from OpMNPV GP64 and thogotovirus GP75 rescued infectivity. These results show that in addition to its basic role in membrane anchoring, the GP64 TM domain is critically important for GP64 trafficking, membrane fusion, virion budding, and virus infectivity. These critical functions were replaced only by TM domains from related viral membrane proteins.

scholarly journals 2549 Characterizing the expression kinetics of HIV-1 envelope protein

2018 ◽  
Vol 2 (S1) ◽  
pp. 7-7
Author(s):  
Djin-Ye Oh ◽  
Lihong Liu ◽  
Benjamin Trinité ◽  
En-Wei Hu-Van Wright ◽  
Vincent Sahi ◽  
...  
Keyword(s):  
Cell Surface ◽  
Virus Production ◽  
Cellular Level ◽  
Hiv Treatment ◽  
Cell Surface Expression ◽  
Substantial Impact ◽  
Infected Cells ◽  
Kinetics Of ◽  
Hiv 1 ◽  
Expression Kinetics

OBJECTIVES/SPECIFIC AIMS: Characterize the expression kinetics of HIV-1 Envelope and their relationship to virus production at the cellular level. METHODS/STUDY POPULATION: In vitro and ex vivo laboratory analyses. RESULTS/ANTICIPATED RESULTS: Initial studies addressing the kinetics of cell surface. Envelope (Env) expression reveal that Env expression to peaks on day 2 post infection. Next steps include a series of experiments to compare the kinetics of Env cell surface expression with broadly neutralizing antibody (bNAb)-mediated ADCC and the characterization of virus production kinetics in this same context. To be maximally effective, ADCC elimination of infected cells should occur before peak Env expression. DISCUSSION/SIGNIFICANCE OF IMPACT: Potent bNAbs to HIV-1 recognize vulnerable sites on the HIV-1 Envelope (Env) protein and are of great clinical interest due to their potential use in the prevention and treatment of HIV-1 infection. Their effectiveness depends not only on the neutralization of viral infectivity, but also on the elimination of productively infected cells via antibody-dependent cellular cytotoxicity (ADCC). On a cellular level, ADCC dynamics are determined by the timing and level of Env expression on the surface of HIV-infected cells. This study aims to delineate the expression kinetics of HIV-1 Envelope and their relationship to virus production. We expect that it will provide new insights into the utility of bNAb-mediated ADCC in treating and possibly curing HIV-1 infection; therefore results might have substantial impact on future HIV treatment strategies.

scholarly journals MARCH8 Restricts Ebola Virus Replication by Blocking the Viral Glycoprotein Processing and Glycosylation

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 123
Author(s):  
Changqing Yu ◽  
Sunan Li ◽  
Omid Madadgar ◽  
Iqbal Ahmad ◽  
Xianfeng Zhang ◽  
...  
Keyword(s):  
Cell Surface ◽  
Fusion Protein ◽  
Fusion Proteins ◽  
Ebola Virus ◽  
Class I ◽  
Class Iii ◽  
Viral Glycoprotein ◽  
E3 Ligases ◽  
Glycosylation Sites ◽  
Hiv 1

Ebola virus (EBOV) glycoprotein (GP) is a class I fusion protein whose maturation is dependent on furin-mediated processing. EBOV-GP is heavily glycosylated, with glycans constituting ~50% of its molecular mass. Compared with 15 N-linked glycosylation sites, EBOV-GP1 has ~80 potential O-linked glycosylation sites in the mucin-like domain (MLD), suggesting that O-linked glycans are dominated. The membrane-associated RING-CH (MARCH) family consists of 11 members that are RING-finger ubiquitin E3 ligases. Recently, human MARCH1, MARCH2, and MARCH8 were reported to inhibit HIV-1 replication by targeting its Env. Here, we show that human MARCH8 also inhibits EBOV replication by blocking GP incorporation into virions via downregulating its cell surface expression. To understand how the downregulation occurs, we investigated EBOV-GP subcellular localization, processing, glycosylation, and intracellular trafficking in the presence of human MARCH8. We find that MARCH8 interacts with GP and retains GP in the Golgi. MARCH8 also interacts with the homoB domain of furin that blocks its convertase activity. In consequence, MARCH8 blocks GP processing in an MLD-independent manner. Consistently, MARCH8 also blocks the O-linked, but not the N-linked glycosylation of GP. Importantly, in the presence of MARCH8, the shedding of GP1 but not the secreted GP (sGP) is blocked, suggesting that MARCH8 targets the GP1 C-terminal region. The MARCH8 activity is extended to its orthologs from Bos taurus and mice, and its paralogs MARCH1 and MARCH2. In addition, MARCH8 inhibits the processing of two other class I fusion proteins, including HIV-1 Env and IAV HA, and it triggers the degradation of the class III fusion protein VSV-G. We conclude that MARCH8 exerts a very broad and conserved antiviral activity by inhibiting the maturation of class I fusion proteins, which blocks their secretion to the cell surface and incorporation into virions. It should also target class III fusion proteins by triggering their degradation.

scholarly journals Envelope-Dependent, Cyclophilin-Independent Effects of Glycosaminoglycans on Human Immunodeficiency Virus Type 1 Attachment and Infection

2002 ◽  
Vol 76 (12) ◽  
pp. 6332-6343 ◽  
Author(s):  
Yi-jun Zhang ◽  
Theodora Hatziioannou ◽  
Trinity Zang ◽  
Douglas Braaten ◽  
Jeremy Luban ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Cell Surface ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Target Cells ◽  
Independent Manner ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Cell surface glycosaminoglycans (GAGs), in particular heparan sulfate (HS), have been proposed to mediate the attachment of human immunodeficiency virus type 1 (HIV-1) to target cells prior to virus entry, and both the viral gp120 envelope protein and virion-associated cyclophilin A (CypA) have been shown to directly interact with HS and its analogues. To determine the role of GAGs in HIV attachment and infection, we generated HIV-susceptible derivatives of CHO cell lines that either express high levels of GAGs (CHO-K1) or lack GAGs (pgsA745). Using a panel of HIV-1 envelopes, we found that cell surface GAG-mediated effects on virion attachment and infection vary in an envelope strain-dependent but coreceptor-independent manner. In fact, cell surface GAG-mediated enhancement of infection is confined to isolates that contain a highly positively charged V3-loop sequence, while infection by most strains is apparently inhibited by the presence of GAGs. Moreover, the enhancing and inhibitory effects of polycations and polyanions on HIV-1 infection are largely dependent on the presence of cell surface GAGs. These observations are consistent with a model in which GAGs influence in vitro HIV-1 infection primarily by modifying the charge characteristics of the target cell surface. Finally, the effects of GAGs on HIV-1 infection are observed to an equivalent extent whether CypA is present in or absent from virions. Overall, these data exclude a major role for GAGs in mediating the attachment of many HIV-1 strains to target cells via interactions with virion-associated gp120 or CypA.

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