The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Stuart J D Neil - One of the best experts on this subject based on the ideXlab platform.
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serine phosphorylation of hiv 1 vpu and its binding to Tetherin regulates interaction with clathrin adaptors
PLOS Pathogens, 2015Co-Authors: Tonya Kueck, Suzanne Pickering, Julia Weinelt, Toshana L Foster, Jonathan Sumner, Stuart J D NeilAbstract:HIV-1 Vpu prevents incorporation of Tetherin (BST2/ CD317) into budding virions and targets it for ESCRT-dependent endosomal degradation via a clathrin-dependent process. This requires a variant acidic dileucine-sorting motif (ExxxLV) in Vpu. Structural studies demonstrate that recombinant Vpu/Tetherin fusions can form a ternary complex with the clathrin adaptor AP-1. However, open questions still exist about Vpu’s mechanism of action. Particularly, whether endosomal degradation and the recruitment of the E3 ubiquitin ligase SCFβTRCP1/2 to a conserved phosphorylated binding site, DSGNES, are required for antagonism. Re-evaluation of the phenotype of Vpu phosphorylation mutants and naturally occurring allelic variants reveals that the requirement for the Vpu phosphoserine motif in Tetherin antagonism is dissociable from SCFβTRCP1/2 and ESCRT-dependent Tetherin degradation. Vpu phospho-mutants phenocopy ExxxLV mutants, and can be rescued by direct clathrin interaction in the absence of SCFβTRCP1/2 recruitment. Moreover, we demonstrate physical interaction between Vpu and AP-1 or AP-2 in cells. This requires Vpu/Tetherin transmembrane domain interactions as well as the ExxxLV motif. Importantly, it also requires the Vpu phosphoserine motif and adjacent acidic residues. Taken together these data explain the discordance between the role of SCFβTRCP1/2 and Vpu phosphorylation in Tetherin antagonism, and indicate that phosphorylation of Vpu in Vpu/Tetherin complexes regulates promiscuous recruitment of adaptors, implicating clathrin-dependent sorting as an essential first step in Tetherin antagonism.
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retroviral retention activates a syk dependent hemitam in human Tetherin
Cell Host & Microbe, 2014Co-Authors: Rui Pedro Galao, Suzanne Pickering, Rachel Curnock, Stuart J D NeilAbstract:Tetherin (BST2/CD317) restricts the release of enveloped viral particles from infected cells. Coupled to this virion retention, hominid Tetherins induce proinflammatory gene expression via activating NF-κB. We investigated the events initiating this Tetherin-induced signaling and show that physical retention of retroviral particles induces the phosphorylation of conserved tyrosine residues in the cytoplasmic tails of Tetherin dimers. This phosphorylation induces the recruitment of spleen tyrosine kinase (Syk), which is required for downstream NF-κB activation, indicating that the Tetherin cytoplasmic tail resembles the hemi-immunoreceptor tyrosine-based activation motifs (hemITAMs) found in C-type lectin pattern recognition receptors. Retroviral-induced Tetherin signaling is coupled to the cortical actin cytoskeleton via the Rac-GAP-containing protein RICH2 (ARHGAP44), and a naturally occurring Tetherin polymorphism with reduced RICH2 binding exhibits decreased phosphorylation and NF-κB activation. Thus, upon virion retention, this linkage to the actin cytoskeleton likely triggers Tetherin phosphorylation and subsequent signal transduction to induce an antiviral state.
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Differential sensitivities of Tetherin isoforms to counteraction by primate lentiviruses.
Journal of virology, 2014Co-Authors: Julia Weinelt, Stuart J D NeilAbstract:ABSTRACT The mammalian antiviral membrane protein Tetherin (BST2/CD317) can be expressed as two isoforms derived from differential translational initiation. The shorter isoform of the human protein (S-Tetherin) lacks the first 12 amino acids of the longer (L-Tetherin) cytoplasmic tail, which includes a tyrosine motif that acts as both an endocytic recycling signal and a determinant of virus-induced NF-κB activation. S-Tetherin is also reported to be less sensitive to the prototypic viral antagonist human immunodeficiency virus type 1 (HIV-1) Vpu. Here we analyzed the relative sensitivities of L- and S-Tetherins to primate lentiviral countermeasures. We show that the reduced sensitivity of S-Tetherin to HIV-1 Vpu is a feature of all group M proteins, including those of transmitted founder viruses, primarily because it cannot be targeted for endosomal degradation owing to the truncation of its cytoplasmic tail. In contrast, both isoforms of the human and rhesus macaque Tetherins display the same sensitivity to nondegradative lentiviral countermeasures of HIV-2 and SIVmac, respectively. Surprisingly, however, the Vpu proteins encoded by simian immunodeficiency viruses (SIVs) of African guenons, as well as that from recently isolated highly pathogenic HIV-1 group N, do not discriminate between Tetherin isoforms. Together, these data suggest that the group M HIV-1 Vpu primarily adapted to target L-Tetherin upon zoonotic transmission from chimpanzees, and further, we speculate that functions specifically associated with this isoform, such as proinflammatory signaling, play key roles in human Tetherin9s antiviral function in vivo . IMPORTANCE The ability of HIV-1 and related viruses to counteract a host antiviral protein, Tetherin, is strictly maintained. The adaptation of the HIV-1 Vpu protein to counteract human Tetherin is thought to have been one of the key events in the establishment of the HIV/AIDS pandemic. Recent evidence shows that Tetherin is expressed as two isoforms and that Vpu preferentially targets the longer form. Here we show that unlike other virus-encoded countermeasures, such as those from primate viruses related to HIV-1, the enhanced ability to counteract the long Tetherin isoform is conserved among HIV-1 strains that make up the majority of the human pandemic. This correlates with the ability of Vpu to induce long Tetherin degradation. We speculate that functions associated with the human version of this isoform, such as an inflammatory signaling capacity, selected for Vpu9s enhanced targeting of long Tetherin during its adaptation to humans.
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innate sensing of hiv 1 assembly by Tetherin induces nfκb dependent proinflammatory responses
Cell Host & Microbe, 2012Co-Authors: Rui Pedro Galao, Anna Le Tortorec, Suzy Pickering, Tonya Kueck, Stuart J D NeilAbstract:Antiviral proteins that recognize pathogen-specific or aberrantly located molecular motifs are perfectly positioned to act as pattern-recognition receptors and signal to the immune system. Here we investigated whether the interferon-induced viral restriction factor Tetherin (CD317/BST2), which is known to inhibit HIV-1 particle release by physically Tethering virions to the cell surface, has such a signaling role. We find that upon restriction of Vpu-defective HIV-1, Tetherin acts as a virus sensor to induce NFκB-dependent proinflammatory gene expression. Signaling requires both Tetherin's extracellular domain involved in virion retention and determinants in the cytoplasmic tail, including an endocytic motif, although signaling is independent of virion endocytosis. Furthermore, recruitment of the TNF-receptor-associated factor TRAF6 and activation of the mitogen-activated protein kinase TAK1 are critical for signaling. Human Tetherin's ability to mediate efficient signaling may have arisen as a result of a five amino acid deletion that occurred in hominids after their divergence from chimpanzees.
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release of filamentous and spherical influenza a virus is not restricted by Tetherin
Journal of General Virology, 2012Co-Authors: Emily A Bruce, Stuart J D Neil, Rui Pedro Galao, Ruth Rollason, Helen M Wise, George Banting, Truus E M Abbink, Paul DigardAbstract:The cellular protein Tetherin is thought to act as a ‘leash’ that anchors many enveloped viruses to the plasma membrane and prevents their release. We found that replication of multiple strains of influenza A virus was generally insensitive to alteration of Tetherin levels, as assessed by output titre or scanning electron microscopy of cell-associated virions. This included human, swine, avian and equine isolates, strains that form filamentous or spherical particles and viruses that lack the M2 or NS1 proteins. Levels of cell-surface Tetherin were not reduced by influenza infection, but Tetherin and the viral haemagglutinin co-localized on the plasma membrane. However, Tetherin could not be detected in filamentous virions, suggesting that influenza may possess a mechanism to exclude it from virions. Overall, if influenza does encode a specific antagonist of Tetherin, it is not M2 or NS1 and we find no evidence for a role in host range specificity.
Eric O. Freed - One of the best experts on this subject based on the ideXlab platform.
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the viral protein u vpu interacting host protein atp6v0c down regulates cell surface expression of Tetherin and thereby contributes to hiv 1 release
Journal of Biological Chemistry, 2020Co-Authors: Abdul Waheed, Maya Swiderski, Ariana Gitzen, Ahlam Majadly, Ali Khan, Eric O. FreedAbstract:Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. The HIV-1 accessory protein viral protein U (Vpu) enhances release of the virus from host cells by down-regulating the cell-surface expression of the host restriction factor Tetherin. However, the exact mechanism of Vpu-mediated suppression of antiviral host responses is unclear. To further understand the role of host proteins in Vpu's function, here we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated Tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated Tetherin degradation, resulting in defective HIV-1 release. We also observed that ATP6V0C overexpression stabilizes Tetherin expression. This stabilization effect was specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C", had no effect on Tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization experiments revealed that the ATP6V0C-stabilized Tetherin is sequestered in a CD63- and lysosomal-associated membrane protein 1 (LAMP1)-positive intracellular compartment. These results indicate that the Vpu-interacting protein ATP6V0C plays a role in down-regulating cell-surface expression of Tetherin and thereby contributes to HIV-1 assembly and release.
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the viral protein u vpu interacting host protein atp6v0c down regulates cell surface expression of Tetherin and thereby contributes to hiv 1 release
Journal of Biological Chemistry, 2020Co-Authors: Abdul A. Waheed, Maya Swiderski, Ariana Gitzen, Ahlam Majadly, Ali Khan, Eric O. FreedAbstract:Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. The HIV-1 accessory protein viral protein U (Vpu) enhances release of the virus from host cells by down-regulating the cell-surface expression of the host restriction factor Tetherin. However, the exact mechanism of Vpu-mediated suppression of antiviral host responses is unclear. To further understand the role of host proteins in Vpu's function, here we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated Tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated Tetherin degradation, resulting in defective HIV-1 release. We also observed that ATP6V0C overexpression stabilizes Tetherin expression. This stabilization effect was specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C″, had no effect on Tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization experiments revealed that the ATP6V0C-stabilized Tetherin is sequestered in a CD63- and lysosome-associated membrane protein 1 (LAMP1)-positive intracellular compartment. These results indicate that the Vpu-interacting protein ATP6V0C plays a role in down-regulating cell-surface expression of Tetherin and thereby contributes to HIV-1 assembly and release.
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the vpu interacting protein atp6v0c regulates expression of Tetherin and hiv 1 release
bioRxiv, 2020Co-Authors: Abdul Waheed, Maya Swiderski, Ariana Gitzen, Ahlam Majadly, Ali R Khan, Eric O. FreedAbstract:Abstract The HIV-1 accessory protein Vpu enhances virus release by down-regulating cell surface expression of the host restriction factor Tetherin. To further understand the role of host proteins in Vpu function, we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated Tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated Tetherin degradation, resulting in a defect in HIV-1 release. We also observed that overexpression of ATP6V0C stabilizes Tetherin expression. This stabilization is specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C”, had no effect on Tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization studies showed that the ATP6V0C-stabilized Tetherin is sequestered in a CD63- and LAMP1-positive intracellular compartment. These data demonstrate that the Vpu-interacting protein ATP6V0C plays a role in regulating Tetherin expression and HIV-1 assembly and release.
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the vpu interacting protein sgta regulates expression of a non glycosylated Tetherin species
Scientific Reports, 2016Co-Authors: Abdul Waheed, Maya Swiderski, Scott Macdonald, Maisha Khan, Megan Mounts, Yue Xu, Yihong Ye, Eric O. FreedAbstract:The HIV-1 accessory protein Vpu enhances virus release by counteracting the host restriction factor Tetherin. To further understand the role of host cell proteins in Vpu function, we carried out yeast two-hybrid screening and identified a previously reported Vpu-interacting host factor, small glutamine-rich tetratricopeptide repeat-containing protein (SGTA). While RNAi-mediated depletion of SGTA did not significantly affect levels of Tetherin or virus release efficiency, we observed that overexpression of SGTA inhibited HIV-1 release in a Vpu- and Tetherin-independent manner. Overexpression of SGTA in the presence of Vpu, but not in its absence, resulted in a marked stabilization and cytosolic relocalization of a 23-kDa, non-glycosylated Tetherin species. Coimmunoprecipitation studies indicated that non-glycosylated Tetherin is stabilized through the formation of a ternary SGTA/Vpu/Tetherin complex. This accumulation of non-glycosylated Tetherin is due to inhibition of its degradation, independent of the ER-associated degradation (ERAD) pathway. Because the SGTA-stabilized Tetherin species is partially localized to the cytosol, we propose that overexpression of SGTA in the presence of Vpu blocks the translocation of Tetherin across the ER membrane, resulting in cytosolic accumulation of a non-glycosylated Tetherin species. Although our results do not provide support for a physiological function of SGTA in HIV-1 replication, they demonstrate that SGTA overexpression regulates Tetherin expression and stability, thus providing insights into the function of SGTA in ER translocation and protein degradation.
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Vpu induces the degradation of human Tetherin in 293T cells but stabilizes its expression in COS cells.
2014Co-Authors: Abdul A. Waheed, Nishani D. Kuruppu, Kathryn L. Felton, Darren D’souza, Eric O. FreedAbstract:293T (A) or COS (B) cells were transfected with vectors expressing HA-tagged human, mouse, rhesus, and agm Tetherins without or with Vpu expression vector at a Tetherin:Vpu DNA ratio of 1∶5. Total transfected DNA was held constant with empty vector. Truncated human Tetherins that lack the cytoplasmic tail (delCT) or putative GPI anchor (delGPI) were also used to identify the regions of Tetherin required for Vpu-mediated degradation. One day posttransfection, cells were lysed and subjected to western blot analysis with the indicated antibodies. Vpu decreased Tetherin expression by 3.1 fold in 293T cells whereas it increased Tetherin expression by ∼5-fold in COS cells; levels of the delCT mutant were increased ∼3-fold in COS cells and 1.6 fold in 293T cells by Vpu. (C) COS cells were transfected with HA-tagged human Tetherin expression vector and cell lysates were subjected to western blot analysis with anti-HA or anti-tubulin antibodies. Vpu was also co-expressed to compare the pattern of Tetherin expression. Molecular mass markers are shown on the right (in kDa). In this experiment, proteasomal inhibitors (MG132 and ALLN) increased the expression of the ∼23 kDa Tetherin species by 3.2 fold, whereas lysosomal inhibitors (bafilomycin and concanamycin) rescued the expression of the ∼26 kDa Tetherin species by 2.6 fold and the ∼23 kDa Tetherin species by 1.7 fold compared to the no inhibitor control. Co-expression of Vpu increased the expression of the ∼26 kDa Tetherin species by 5.2 fold and the ∼23 kDa Tetherin species by 1.7 fold. (D) 293T, COS, and Vero cells were transfected with HA-tagged human Tetherin expression vector in the absence and presence of Vpu expression vector, and one-day posttransfection cells were lysed and subjected to Western blot analysis as above. Vpu reduced the expression of Tetherin by 2.4 fold in 293T cells, whereas the levels were increased by ∼20-fold in COS cells and ∼4-fold in Vero cells. Similar results were obtained in an independent experiment.
Paul D. Bieniasz - One of the best experts on this subject based on the ideXlab platform.
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Tetherin Inhibits Cell-free Virus Dissemination and Retards Murine Leukemia Virus Pathogenesis
Journal of virology, 2017Co-Authors: Rachel A. Liberatore, Emily J. Mastrocola, Chelsea Powell, Paul D. BieniaszAbstract:The relative contributions of cell-free virion circulation and direct cell-to-cell transmission to retroviral dissemination and pathogenesis are unknown. Tetherin/Bst2 is an antiviral protein that blocks enveloped virion release into the extracellular milieu but may not inhibit cell-to-cell virus transmission. We developed live-cell imaging assays which show that Tetherin does not affect Moloney murine leukemia virus (MoMLV) spread, and only minimally affects vesicular stomatitis virus (VSV) spread, to adjacent cells in a monolayer. Conversely, cell-free MLV and VSV virion yields and VSV spread to distal cells were dramatically reduced by Tetherin. To elucidate the roles of Tetherin and cell-free virions during in vivo viral dissemination and pathogenesis, we developed mice carrying an inducible human Tetherin (hTetherin) transgene. While ubiquitous hTetherin expression was detrimental to the growth and survival of mice, restriction of hTetherin expression to hematopoietic cells gave apparently healthy mice. The expression of hTetherin in hematopoietic cells had little or no effect on the number of MoMLV-infected splenocytes and thymocytes. However, hTetherin expression significantly reduced cell-free plasma viremia and also delayed MoMLV-induced disease. Overall, these results suggest that MoMLV spread within hematopoietic tissues and cell monolayers involves cell-to-cell transmission that is resistant to Tetherin but that virion dissemination via plasma is inhibited by Tetherin and is required for full MoMLV pathogenesis.IMPORTANCE Retroviruses are thought to spread primarily via direct cell-to-cell transmission, yet many have evolved to counteract an antiviral protein called Tetherin, which may selectively inhibit cell-free virus release. We generated a mouse model with an inducible Tetherin transgene in order to study how Tetherin affects retroviral dissemination and on which cell types its expression is required to do so. We first developed a novel in vitro live-cell imaging assay to demonstrate that while Tetherin does indeed dramatically reduce cell-free virus spreading, it has little to no effect on direct cell-to-cell transmission of either vesicular stomatitis virus (VSV) or the retrovirus MoMLV. Using our transgenic mouse model, we found that Tetherin expression on hematopoietic cells resulted in the specific reduction of MoMLV cell-free plasma viremia but not the number of infected hematopoietic cells. The delay in disease associated with this scenario suggests a role for cell-free virus in retroviral disease progression.
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origins and evolution of Tetherin an orphan antiviral gene
Cell Host & Microbe, 2016Co-Authors: Daniel Blancomelo, Siddarth Venkatesh, Paul D. BieniaszAbstract:Summary Tetherin encodes an interferon-inducible antiviral protein that traps a broad spectrum of enveloped viruses at infected cell surfaces. Despite the absence of any clearly related gene or activity, we describe possible scenarios by which Tetherin arose that exemplify how protein modularity, evolvability, and robustness can create and preserve new functions. We find that Tetherin genes in various organisms exhibit no sequence similarity and share only a common architecture and location in modern genomes. Moreover, Tetherin is part of a cluster of three potential sister genes encoding proteins of similar architecture, some variants of which exhibit antiviral activity while others can be endowed with antiviral activity by a simple modification. Only in slowly evolving species (e.g., coelacanths) does Tetherin exhibit sequence similarity to one potential sister gene. Neofunctionalization, drift, and genetic conflict appear to have driven a near complete loss of sequence similarity among modern Tetherin genes and their sister genes.
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Tetherin promotes the innate and adaptive cell mediated immune response against retrovirus infection in vivo
Journal of Immunology, 2014Co-Authors: Bradley S Barrett, Rachel A. Liberatore, Paul D. Bieniasz, Karl J Heilman, Ronald J Messer, George Kassiotis, Kim J Hasenkrug, Mario L SantiagoAbstract:Tetherin/BST-2 is a host restriction factor that could directly inhibit retroviral particle release by Tethering nascent virions to the plasma membrane. However, the immunological impact of Tetherin during retrovirus infection remains unknown. We now show that Tetherin influences antiretroviral cell-mediated immune responses. In contrast to the direct antiviral effects of Tetherin, which are dependent on cell surface expression, the immunomodulatory effects are linked to the endocytosis of the molecule. Mice encoding endocytosis-competent C57BL/6 Tetherin exhibited lower viremia and pathology at 7 d postinfection with Friend retrovirus (FV) compared with mice encoding endocytosis-defective NZW/LacJ Tetherin. Notably, antiretroviral protection correlated with stronger NK cell responses. In addition, Friend retrovirus infection levels were significantly lower in wild-type C57BL/6 mice than in Tetherin knockout mice at 2 wk postinfection, and antiretroviral protection correlated with stronger NK cell and virus-specific CD8+ T cell responses. The results demonstrate that Tetherin acts as a modulator of the cell-mediated immune response against retrovirus infection in vivo.
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mechanism of hiv 1 virion entrapment by Tetherin
PLOS Pathogens, 2013Co-Authors: Siddarth Venkatesh, Paul D. BieniaszAbstract:Tetherin, an interferon-inducible membrane protein, inhibits the release of nascent enveloped viral particles from the surface of infected cells. However, the mechanisms underlying virion retention have not yet been fully delineated. Here, we employ biochemical assays and engineered Tetherin proteins to demonstrate conclusively that virion tethers are composed of the Tetherin protein itself, and to elucidate the configuration and topology that Tetherin adopts during virion entrapment. We demonstrate that Tetherin dimers adopt an "axial" configuration, in which pairs of transmembrane domains or pairs of glycosylphosphatidyl inositol anchors are inserted into assembling virion particles, while the remaining pair of membrane anchors remains embedded in the infected cell membrane. We use quantitative western blotting to determine that a few dozen Tetherin dimers are used to tether each virion particle, and that there is ∼3- to 5-fold preference for the insertion of glycosylphosphatidyl inositol anchors rather than transmembrane domains into tethered virions. Cumulatively, these results demonstrate that axially configured Tetherin homodimers are directly responsible for trapping virions at the cell surface. We suggest that insertion of glycosylphosphatidyl inositol anchors may be preferred so that effector functions that require exposure of the Tetherin N-terminus to the cytoplasm of infected cells are retained.
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vpu binds directly to Tetherin and displaces it from nascent virions
PLOS Pathogens, 2013Co-Authors: Matthew W Mcnatt, Trinity Zang, Paul D. BieniaszAbstract:Tetherin (Bst2/CD317/HM1.24) is an interferon-induced antiviral host protein that inhibits the release of many enveloped viruses by Tethering virions to the cell surface. The HIV-1 accessory protein, Vpu, antagonizes Tetherin through a variety of proposed mechanisms, including surface downregulation and degradation. Previous studies have demonstrated that mutation of the transmembrane domains (TMD) of both Vpu and Tetherin affect antagonism, but it is not known whether Vpu and Tetherin bind directly to each other. Here, we use cysteine-scanning mutagenesis coupled with oxidation-induced cross-linking to demonstrate that Vpu and Tetherin TMDs bind directly to each other in the membranes of living cells and to map TMD residues that contact each other. We also reveal a property of Vpu, namely the ability to displace Tetherin from sites of viral assembly, which enables Vpu to exhibit residual Tetherin antagonist activity in the absence of surface downregulation or degradation. Elements in the cytoplasmic tail domain (CTD) of Vpu mediate this displacement activity, as shown by experiments in which Vpu CTD fragments were directly attached to Tetherin in the absence of the TMD. In particular, the C-terminal α-helix (H2) of Vpu CTD is sufficient to remove Tetherin from sites of viral assembly and is necessary for full Tetherin antagonist activity. Overall, these data demonstrate that Vpu and Tetherin interact directly via their transmembrane domains enabling activities present in the CTD of Vpu to remove Tetherin from sites of viral assembly.
David T. Evans - One of the best experts on this subject based on the ideXlab platform.
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polymorphisms in rhesus macaque Tetherin are associated with differences in acute viremia in simian immunodeficiency virus δnef infected animals
Journal of Virology, 2018Co-Authors: Sanath Kumar Janaka, Ruth Serramoreno, William J Neidermyer, Aidin Tavakolitameh, James A Hoxie, Ronald C Desrosiers, Paul R Johnson, Jeffrey D Lifson, Steven M Wolinsky, David T. EvansAbstract:Tetherin (BST-2 or CD317) is an interferon-inducible transmembrane protein that inhibits virus release from infected cells. To determine the extent of sequence variation and the impact of polymorphisms in rhesus macaque Tetherin on simian immunodeficiency virus (SIV) infection, Tetherin alleles were sequenced from 146 rhesus macaques, including 68 animals infected with wild-type SIVmac239 and 47 animals infected with SIVmac239Δnef Since Nef is the viral gene product of SIV that counteracts restriction by Tetherin, these groups afford a comparison of the effects of Tetherin polymorphisms on SIV strains that are, and are not, resistant to Tetherin. We identified 15 alleles of rhesus macaque Tetherin with dimorphic residues at 9 positions. The relationship between these alleles and plasma viral loads was compared during acute infection, prior to the onset of adaptive immunity. Acute viremia did not differ significantly among the wild-type SIV-infected animals; however, differences in acute viral loads were associated with polymorphisms in Tetherin among the animals infected with SIVΔnef In particular, polymorphisms at positions 43 and 111 (P43 and H111) were associated with lower acute-phase viral loads for SIVΔnef infection. These observations reveal extensive polymorphism in rhesus macaque Tetherin, maintained perhaps as a consequence of variability in the selective pressure of diverse viral pathogens, and identify Tetherin alleles that may have an inherently greater capacity to restrict SIV replication in the absence of Nef.IMPORTANCE As a consequence of ongoing evolutionary conflict with viral pathogens, Tetherin has accumulated numerous species-specific differences that represent important barriers to the transmission of viruses between species. This study reveals extensive polymorphism in rhesus macaque Tetherin and identifies specific alleles that are associated with lower viral loads during the first few weeks after infection with nef-deleted SIV. These observations suggest that the variable selective pressure of viral pathogens, in addition to driving the diversification of Tetherin among species, also operates within certain species to maintain sequence variation in Tetherin.
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polymorphisms in rhesus macaque Tetherin are associated with differences in acute viremia in simian immunodeficiency virus δ nef infected animals
Journal of Virology, 2018Co-Authors: Sanath Kumar Janaka, Ruth Serramoreno, William J Neidermyer, Aidin Tavakolitameh, James A Hoxie, Ronald C Desrosiers, Paul R Johnson, Jeffrey D Lifson, Steven M Wolinsky, David T. EvansAbstract:Tetherin (BST-2 or CD317) is an interferon-inducible transmembrane protein that inhibits virus release from infected cells. To determine the extent of sequence variation and the impact of polymorphisms in rhesus macaque Tetherin on simian immunodeficiency virus (SIV) infection, Tetherin alleles were sequenced from 146 rhesus macaques, including 68 animals infected with wild-type SIVmac239 and 47 animals infected with SIVmac239Δnef Since Nef is the viral gene product of SIV that counteracts restriction by Tetherin, these groups afford a comparison of the effects of Tetherin polymorphisms on SIV strains that are, and are not, resistant to Tetherin. We identified 15 alleles of rhesus macaque Tetherin with dimorphic residues at 9 positions. The relationship between these alleles and plasma viral loads was compared during acute infection, prior to the onset of adaptive immunity. Acute viremia did not differ significantly among the wild-type SIV-infected animals; however, differences in acute viral loads were associated with polymorphisms in Tetherin among the animals infected with SIVΔnef In particular, polymorphisms at positions 43 and 111 (P43 and H111) were associated with lower acute-phase viral loads for SIVΔnef infection. These observations reveal extensive polymorphism in rhesus macaque Tetherin, maintained perhaps as a consequence of variability in the selective pressure of diverse viral pathogens, and identify Tetherin alleles that may have an inherently greater capacity to restrict SIV replication in the absence of Nef.IMPORTANCE As a consequence of ongoing evolutionary conflict with viral pathogens, Tetherin has accumulated numerous species-specific differences that represent important barriers to the transmission of viruses between species. This study reveals extensive polymorphism in rhesus macaque Tetherin and identifies specific alleles that are associated with lower viral loads during the first few weeks after infection with nef-deleted SIV. These observations suggest that the variable selective pressure of viral pathogens, in addition to driving the diversification of Tetherin among species, also operates within certain species to maintain sequence variation in Tetherin.
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Tetherin Antagonism by HIV-1 Group M Nef Proteins
Journal of virology, 2016Co-Authors: Juan F. Arias, Ruth Serra-moreno, Marta Colomer-lluch, Benjamin Von Bredow, Justin M. Greene, Julie Macdonald, David H. O’connor, David T. EvansAbstract:Although Nef is the viral gene product used by most simian immunodeficiency viruses to overcome restriction by Tetherin, this activity was acquired by the Vpu protein of HIV-1 group M due to the absence of sequences in human Tetherin that confer susceptibility to Nef. Thus, it is widely accepted that HIV-1 group M uses Vpu instead of Nef to counteract Tetherin. Challenging this paradigm, we identified Nef alleles of HIV-1 group M isolates with significant activity against human Tetherin. These Nef proteins promoted virus release and Tetherin downmodulation from the cell surface and, in the context of vpu-deleted HIV-1 recombinants, enhanced virus replication and resistance to antibody-dependent cell-mediated cytotoxicity (ADCC). Further analysis revealed that the Vpu proteins from several of these viruses lack antiTetherin activity, suggesting that under certain circumstances, HIV-1 group M Nef may acquire the ability to counteract Tetherin to compensate for the loss of this function by Vpu. These observations illustrate the remarkable plasticity of HIV-1 in overcoming restriction by Tetherin and challenge the prevailing view that all HIV-1 group M isolates use Vpu to counteract Tetherin. IMPORTANCE Most viruses of HIV-1 group M, the main group of HIV-1 responsible for the global AIDS pandemic, use their Vpu proteins to overcome restriction by Tetherin (BST-2 or CD317), which is a transmembrane protein that inhibits virus release from infected cells. Here we show that the Nef proteins of certain HIV-1 group M isolates can acquire the ability to counteract Tetherin. These results challenge the current paradigm that HIV-1 group M exclusively uses Vpu to counteract Tetherin and underscore the importance of Tetherin antagonism for efficient viral replication.
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Tetherin antagonism by vpu protects hiv infected cells from antibody dependent cell mediated cytotoxicity
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Juan F. Arias, Benjamin Von Bredow, Lisa N Heyer, Kim L Weisgrau, Brian Moldt, Dennis R Burton, Eva G Rakasz, David T. EvansAbstract:Tetherin is an IFN-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. HIV-1 overcomes this restriction factor by expressing HIV-1 viral protein U (Vpu), which down-regulates and degrades Tetherin. We report that mutations in Vpu that impair Tetherin antagonism increase the susceptibility of HIV-infected cells to antibody-dependent cell-mediated cytotoxicity (ADCC), and conversely that RNAi knockdown of Tetherin, but not other cellular proteins down-modulated by Vpu, decreases the susceptibility of HIV-infected cells to ADCC. These results reveal that Vpu protects HIV-infected cells from ADCC as a function of its ability to counteract Tetherin. By serving as link between innate and adaptive immunity, the antiviral activity of Tetherin may be augmented by virus-specific antibodies, and hence much greater than previously appreciated.
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Tetherin bst 2 antagonism by nef depends on a direct physical interaction between nef and Tetherin and on clathrin mediated endocytosis
PLOS Pathogens, 2013Co-Authors: Ruth Serramoreno, Kerstin Zimmermann, Lawrence J. Stern, David T. EvansAbstract:Nef is the viral gene product employed by the majority of primate lentiviruses to overcome restriction by Tetherin (BST-2 or CD317), an interferon-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. Although the mechanisms of Tetherin antagonism by HIV-1 Vpu and HIV-2 Env have been investigated in detail, comparatively little is known about Tetherin antagonism by SIV Nef. Here we demonstrate a direct physical interaction between SIV Nef and rhesus macaque Tetherin, define the residues in Nef required for Tetherin antagonism, and show that the anti-Tetherin activity of Nef is dependent on clathrin-mediated endocytosis. SIV Nef co-immunoprecipitated with rhesus macaque Tetherin and the Nef core domain bound directly to a peptide corresponding to the cytoplasmic domain of rhesus Tetherin by surface plasmon resonance. An analysis of alanine-scanning substitutions identified residues throughout the N-terminal, globular core and flexible loop regions of Nef that were required for Tetherin antagonism. Although there was significant overlap with sequences required for CD4 downregulation, Tetherin antagonism was genetically separable from this activity, as well as from other Nef functions, including MHC class I-downregulation and infectivity enhancement. Consistent with a role for clathrin and dynamin 2 in the endocytosis of Tetherin, dominant-negative mutants of AP180 and dynamin 2 impaired the ability of Nef to downmodulate Tetherin and to counteract restriction. Taken together, these results reveal that the mechanism of Tetherin antagonism by Nef depends on a physical interaction between Nef and Tetherin, requires sequences throughout Nef, but is genetically separable from other Nef functions, and leads to the removal of Tetherin from sites of virus release at the plasma membrane by clathrin-mediated endocytosis.
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The nef protein of the macrophage tropic HIV-1 strain AD8 counteracts human BST-2/Tetherin
Viruses, 2020Co-Authors: Sebastian Giese, Scott P. Lawrence, Michela Mazzon, Bernadien M. Nijmeijer, Mark MarshAbstract:Bone Marrow Stromal Cell Antigen 2 (BST-2)/Tetherin inhibits the release of numerous enveloped viruses by physically Tethering nascent particles to infected cells during the process of viral budding from the cell surface. Tetherin also restricts human immunodeficiency virus (HIV), and pandemic main (M) group HIV type 1s (HIV-1s) are thought to rely exclusively on their Vpu proteins to overcome Tetherin-mediated restriction of virus release. However, at least one M group HIV-1 strain, the macrophage-tropic primary AD8 isolate, is unable to express Vpu due to a mutation in its translation initiation codon. Here, using primary monocyte-derived macrophages (MDMs), we show that AD8 Nef protein can compensate for the absence of Vpu and restore virus release to wild type levels. We demonstrate that HIV-1 AD8 Nef reduces endogenous cell surface Tetherin levels, physically separating it from the site of viral budding, thus preventing HIV retention. Mechanistically, AD8 Nef enhances internalisation of the long isoform of human Tetherin, leading to perinuclear accumulation of the restriction factor. Finally, we show that Nef proteins from other HIV strains also display varying degrees of Tetherin antagonism. Overall, we show that M group HIV-1s can use an accessory protein other than Vpu to antagonise human Tetherin.
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The Nef protein of the macrophage tropic HIV-1 strain AD8 counteracts human Bst-2/Tetherin
2020Co-Authors: Sebastian Giese, Scott P. Lawrence, Michela Mazzon, Bernadien M. Nijmeijer, Mark MarshAbstract:Abstract Bst-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.
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Tetherin Can Restrict Cell-Free and Cell-Cell Transmission of HIV from Primary Macrophages to T Cells
PLoS Pathogens, 2014Co-Authors: Sebastian Giese, Mark MarshAbstract:Bst-2/Tetherin inhibits the release of HIV by Tethering newly formed virus particles to the plasma membrane of infected cells. Although the mechanisms of Tetherin-mediated restriction are increasingly well understood, the biological relevance of this restriction in the natural target cells of HIV is unclear. Moreover, whether Tetherin exerts any restriction on the direct cell-cell spread of HIV across intercellular contacts remains controversial. Here we analyse the restriction endogenous Tetherin imposes on HIV transmission from primary human macrophages, one of the main targets of HIV in vivo. We find that the mRNA and protein levels of Tetherin in macrophages are comparable to those in T cells from the same donors, and are highly upregulated by type I interferons. Improved immunocytochemistry protocols enable us to demonstrate that Tetherin localises to the cell surface, the trans-Golgi network, and the macrophage HIV assembly compartments. Tetherin retains budded virions in the assembly compartments, thereby impeding the release and cell-free spread of HIV, but it is not required for the maintenance of these compartments per se. Notably, using a novel assay to quantify cell-cell spread, we show that Tetherin promotes the transfer of virus clusters from macrophages to T cells and thereby restricts the direct transmission of a dual-tropic HIV-1. Kinetic analyses provide support for the notion that this direct macrophage-T cell spread is mediated, at least in part, by so-called virological synapses. Finally, we demonstrate that the viral Vpu protein efficiently downregulates the cell surface and overall levels of Tetherin, and thereby abrogates this HIV restriction in macrophages. Together, our study shows that Tetherin, one of the most potent HIV restriction factors identified to date, can inhibit virus spread from primary macrophages, regardless of the mode of transmission.
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Tetherin Restricts Herpes Simplex Virus 1 and Is Antagonized by Glycoprotein M
Journal of virology, 2013Co-Authors: Caroline Blondeau, Mark Marsh, Annegret Pelchen-matthews, Petra Mlcochova, Richard S. B. Milne, Greg J. TowersAbstract:Tetherin is a broadly active antiviral effector that works by Tethering nascent enveloped virions to a host cell membrane, thus preventing their release. In this study, we demonstrate that herpes simplex virus 1 (HSV-1) is targeted by Tetherin. We identify the viral envelope glycoprotein M (gM) as having moderate anti-Tetherin activity. We show that gM but not gB or gD efficiently removes Tetherin from the plasma membrane and can functionally substitute for the human immunodeficiency virus type 1 (HIV-1) Vpu protein, the prototypic viral Tetherin antagonist, in rescuing HIV-1 release from Tetherin-expressing cells. Our data emphasize that Tetherin is a broadly active antiviral effector and contribute to the emerging hypothesis that viruses must suppress or evade an array of host cell countermeasures in order to establish a productive infection.
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the escrt 0 component hrs is required for hiv 1 vpu mediated bst 2 Tetherin down regulation
PLOS Pathogens, 2011Co-Authors: Mark Marsh, Katy Janvier, Annegret Pelchen Matthews, Jeanbaptiste Renaud, Marina Caillet, Clarisse BerlioztorrentAbstract:The Endosomal Sorting Complexes Required for Transport (ESCRT) machinery, a highly conserved set of four hetero-oligomeric protein complexes, is required for multivesicular body formation, sorting ubiquitinylated membrane proteins for lysosomal degradation, cytokinesis and the final stages of assembly of a number of enveloped viruses, including the human immunodeficiency viruses. Here, we show an additional role for the ESCRT machinery in HIV-1 release. BST-2/Tetherin is a restriction factor that impedes HIV release by Tethering mature virus particles to the plasma membrane. We found that HRS, a key component of the ESCRT-0 complex, promotes efficient release of HIV-1 and that siRNA-mediated HRS depletion induces a BST-2/Tetherin phenotype. This activity is related to the ability of the HIV-1 Vpu protein to down-regulate BST-2/Tetherin. We found that BST-2/Tetherin undergoes constitutive ESCRT-dependent sorting for lysosomal degradation and that this degradation is enhanced by Vpu expression. We demonstrate that Vpu-mediated BST-2/Tetherin down-modulation and degradation require HRS (ESCRT-0) function and that knock down of HRS increases cellular levels of BST-2/Tetherin and restricts virus release. Furthermore, HRS co-precipitates with Vpu and BST-2. Our results provide further insight into the mechanism by which Vpu counteracts BST-2/Tetherin and promotes HIV-1 dissemination, and they highlight an additional role for the ESCRT machinery in virus release.
