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Klaus Strebel - One of the best experts on this subject based on the ideXlab platform.
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antagonism of bst 2 tetherin is a conserved function of the env glycoprotein of primary hiv 2 isolates
Journal of Virology, 2016Co-Authors: Chiayen Chen, Sarah Welbourn, Masashi Shingai, Malcolm A Martin, Pedro Borrego, Nuno Taveira, Klaus StrebelAbstract:ABSTRACT Although HIV-2 does not encode a vpu gene, the ability to antagonize bone marrow stromal antigen 2 (BST-2) is conserved in some HIV-2 isolates, where it is controlled by the Env glycoprotein. We previously reported that a single-amino-acid difference between the laboratory-adapted ROD10 and ROD14 Envs controlled the enhancement of Virus Release (referred to here as Vpu-like) activity. Here, we investigated how conserved the Vpu-like activity is in primary HIV-2 isolates. We found that half of the 34 tested primary HIV-2 Env isolates obtained from 7 different patients enhanced Virus Release. Interestingly, most HIV-2 patients harbored a mixed population of Viruses containing or lacking Vpu-like activity. Vpu-like activity and Envelope functionality varied significantly among Env isolates; however, there was no direct correlation between these two functions, suggesting they evolved independently. In comparing the Env sequences from one HIV-2 patient, we found that similar to the ROD10/ROD14 Envs, a single-amino-acid change (T568I) in the ectodomain of the TM subunit was sufficient to confer Vpu-like activity to an inactive Env variant. Surprisingly, however, absence of Vpu-like activity was not correlated with absence of BST-2 interaction. Taken together, our data suggest that maintaining the ability to antagonize BST-2 is of functional relevance not only to HIV-1 but also to HIV-2 as well. Our data show that as with Vpu, binding of HIV-2 Env to BST-2 is important but not sufficient for antagonism. Finally, as observed previously, the Vpu-like activity in HIV-2 Env can be controlled by single-residue changes in the TM subunit. IMPORTANCE LentiViruses such as HIV-1 and HIV-2 encode accessory proteins whose function is to overcome host restriction mechanisms. Vpu is a well-studied HIV-1 accessory protein that enhances Virus Release by antagonizing the host restriction factor BST-2. HIV-2 does not encode a vpu gene. Instead, the HIV-2 Env glycoprotein was found to antagonize BST-2 in some isolates. Here, we cloned multiple Env sequences from 7 HIV-2-infected patients and found that about half were able to antagonize BST-2. Importantly, most HIV-2 patients harbored a mixed population of Viruses containing or lacking the ability to antagonize BST-2. In fact, in comparing Env sequences from one patient combined with site-directed mutagenesis, we were able to restore BST-2 antagonism to an inactive Env protein by a single-amino-acid change. Our data suggest that targeting BST-2 by HIV-2 Env is a dynamic process that can be regulated by simple changes in the Env sequence.
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positioning of cysteine residues within the n terminal portion of the bst 2 tetherin ectodomain is important for functional dimerization of bst 2
Journal of Biological Chemistry, 2015Co-Authors: Sarah Welbourn, Amy J Andrew, Sandra Kao, Kelly E Du Pont, Christopher E Berndsen, Klaus StrebelAbstract:BST-2/tetherin is a cellular host factor capable of restricting the Release of a variety of enveloped Viruses, including HIV-1. Structurally, BST-2 consists of an N-terminal cytoplasmic domain, a transmembrane domain, an ectodomain, and a C-terminal membrane anchor. The BST-2 ectodomain encodes three cysteine residues in its N-terminal half, each of which can contribute to the formation of cysteine-linked dimers. We previously reported that any one of the three cysteine residues is sufficient to produce functional BST-2 dimers. Here we investigated the importance of cysteine positioning on the ectodomain for functional dimerization of BST-2. Starting with a cysteine-free monomeric form of BST-2, individual cysteine residues were reintroduced at various locations throughout the ectodomain. The resulting BST-2 variants were tested for expression, dimerization, surface presentation, and inhibition of HIV-1 Virus Release. We found significant flexibility in the positioning of cysteine residues, although the propensity to form cysteine-linked dimers generally decreased with increasing distance from the N terminus. Interestingly, all BST-2 variants, including the one lacking all three ectodomain cysteines, retained the ability to form non-covalent dimers, and all of the BST-2 variants were efficiently expressed at the cell surface. Importantly, not all BST-2 variants capable of forming cysteine-linked dimers were functional, suggesting that cysteine-linked dimerization of BST-2 is necessary but not sufficient for inhibiting Virus Release. Our results expose new structural constraints governing the functional dimerization of BST-2, a property essential to its role as a restriction factor tethering Viruses to the host cell.
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hiv 1 vpu targets cell surface markers cd4 and bst 2 through distinct mechanisms
Molecular Aspects of Medicine, 2010Co-Authors: Amy J Andrew, Klaus StrebelAbstract:Abstract Vpu is a small integral membrane protein encoded by HIV-1 and some SIV isolates. The protein is known to induce degradation of the viral receptor molecule CD4 and to enhance the Release of newly formed virions from the cell surface. Vpu accomplishes these two functions through two distinct mechanisms. In the case of CD4, Vpu acts as a molecular adaptor to connect CD4 to an E3 ubiquitin ligase complex resulting in CD4 degradation by cellular proteasomes. This requires signals located in Vpu’s cytoplasmic domain. Enhancement of Virus Release on the other hand involves the neutralization of a cellular host factor, BST-2 (also known as CD317, HM1.24, or tetherin) and requires Vpu’s TM domain. The current review discusses recent advances on the role of Vpu in controlling degradation of CD4 and in regulating Virus Release.
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the formation of cysteine linked dimers of bst 2 tetherin is important for inhibition of hiv 1 Virus Release but not for sensitivity to vpu
Retrovirology, 2009Co-Authors: Amy J Andrew, Eri Miyagi, Sandra Kao, Klaus StrebelAbstract:The Human Immunodeficiency Virus type 1 (HIV-1) Vpu protein enhances Virus Release from infected cells and induces proteasomal degradation of CD4. Recent work identified BST-2/CD317 as a host factor that inhibits HIV-1 Virus Release in a Vpu sensitive manner. A current working model proposes that BST-2 inhibits Virus Release by tethering viral particles to the cell surface thereby triggering their subsequent endocytosis. Here we defined structural properties of BST-2 required for inhibition of Virus Release and for sensitivity to Vpu. We found that BST-2 is modified by N-linked glycosylation at two sites in the extracellular domain. However, N-linked glycosylation was not important for inhibition of HIV-1 Virus Release nor did it affect surface expression or sensitivity to Vpu. Rodent BST-2 was previously found to form cysteine-linked dimers. Analysis of single, double, or triple cysteine mutants revealed that any one of three cysteine residues present in the BST-2 extracellular domain was sufficient for BST-2 dimerization, for inhibition of Virus Release, and sensitivity to Vpu. In contrast, BST-2 lacking all three cysteines in its ectodomain was unable to inhibit Release of wild type or Vpu-deficient HIV-1 virions. This defect was not caused by a gross defect in BST-2 trafficking as the mutant protein was expressed at the cell surface of transfected 293T cells and was down-modulated by Vpu similar to wild type BST-2. While BST-2 glycosylation was functionally irrelevant, formation of cysteine-linked dimers appeared to be important for inhibition of Virus Release. However lack of dimerization did not prevent surface expression or Vpu sensitivity of BST-2, suggesting Vpu sensitivity and inhibition of Virus Release are separable properties of BST-2.
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vpu enhances hiv 1 Virus Release in the absence of bst 2 cell surface down modulation and intracellular depletion
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Eri Miyagi, Amy J Andrew, Sandra Kao, Klaus StrebelAbstract:HIV-1 Vpu enhances the Release of virions from infected cells. Recent work identified Bst-2/CD317/tetherin as a host factor whose inhibitory activity on viral Release is counteracted by Vpu. A current working model proposes that Bst-2 inhibits Virus Release by tethering viral particles to the cell surface. Here, we analyzed endogenous Bst-2 with respect to its effect on Virus Release from HeLa cells, T cells, and macrophages. We noted significant cell type-dependent variation in Bst-2 expression. Vpu caused a reduction in Bst-2 expression in transfected HeLa cells and long-term infected macrophages. However, Vpu expression did not result in cell surface down-modulation of Bst-2 or a reduction in intracellular Bst-2 expression in CEMx174 or H9 cells, yet Virus replication in these cells was Vpu-responsive. Surprisingly, Bst-2 was undetectable in cell-free virions that were recovered from the surface of HeLa cells by physical shearing, suggesting that a tethering model may not explain all of the functional properties of Bst-2. Taken together we conclude that enhancement of Virus Release by Vpu does not, at least in CEMx174 and H9 cells, require cell surface down-modulation or intracellular depletion of Bst-2, nor does it entail exclusion of Bst-2 from viral particles.
Chen Liang - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH Open Access Tetherin inhibits prototypic foamy Virus Release
2013Co-Authors: Juan Tan, Chen Liang, Ruikang Liu, Yunqi Geng, Wentao QiaoAbstract:Background: Tetherin (also known as BST-2, CD317, and HM1.24) is an interferon- induced protein that blocks the Release of a variety of enveloped Viruses, such as retroViruses, filoViruses and herpesViruses. However, the relationship between tetherin and foamy Viruses has not been clearly demonstrated. Results: In this study, we found that tetherin of human, simian, bovine or canine origin inhibits the production of infectious prototypic foamy Virus (PFV). The inhibition of PFV by human tetherin is counteracted by human immunodeficiency Virus type 1 (HIV-1) Vpu. Furthermore, we generated human tetherin transmembrane domain deletion mutant (delTM), glycosyl phosphatidylinositol (GPI) anchor deletion mutant (delGPI), and dimerization and glycosylation deficient mutants. Compared with wild type tetherin, the delTM and delGPI mutants only moderately inhibited PFV production. In contrast, the dimerization and glycosylation deficient mutants inhibit PFV production as efficiently as the wild type tetherin. Conclusions: These results demonstrate that tetherin inhibits the Release and infectivity of PFV, and this inhibition is antagonized by HIV-1 Vpu. Both the transmembrane domain and the GPI anchor of tetherin are important for the inhibition of PFV, whereas the dimerization and the glycosylation of tetherin are dispensable. Backgroun
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the transmembrane domain of bst 2 determines its sensitivity to down modulation by human immunodeficiency Virus type 1 vpu
Journal of Virology, 2009Co-Authors: Liwei Rong, Renepierre Lorgeoux, Claudette Aloysius, Jennifer Lu, Jianyong Zhang, Chen Liang, Mark A. WainbergAbstract:Bone marrow stromal cell antigen 2 (BST-2, also known as tetherin) restricts the production of a number of enveloped Viruses by blocking Virus Release from the cell surface. This antiviral activity is counteracted by such viral factors as Vpu of human immunodeficiency Virus type 1 (HIV-1). Here, we report that Vpu antagonizes human BST-2 but not BST-2 derived from African green monkeys. The determinants of susceptibility to Vpu map to the transmembrane domain of BST-2. In accordance with this, expression of human BST-2 containing a modified transmembrane domain effectively blocks the replication of wild-type Vpu-expressing HIV-1 in CD4+ T cells. Furthermore, these BST-2 variants, as opposed to wild-type human BST-2, are refractory to Vpu-mediated down-regulation as a result of an attenuated interaction with Vpu. In view of the work by others pointing to a key role of the transmembrane domain of Vpu in promoting Virus Release, our data suggest that a direct interaction through the transmembrane domain of each of these two proteins is a prerequisite for Vpu to down-modulate BST-2.
Eric O. Freed - One of the best experts on this subject based on the ideXlab platform.
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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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mutations in the feline immunodeficiency Virus envelope glycoprotein confer resistance to a dominant negative fragment of tsg101 by enhancing infectivity and cell to cell Virus transmission
Biochimica et Biophysica Acta, 2014Co-Authors: Benjamin G Luttge, Prashant Panchal, Vinita Puri, Mary Ann Checkley, Eric O. FreedAbstract:Abstract The Pro-Ser-Ala-Pro (PSAP) motif in the p2 domain of feline immunodeficiency Virus (FIV) Gag is required for efficient Virus Release, Virus replication, and Gag binding to the ubiquitin-E2-variant (UEV) domain of Tsg101. As a result of this direct interaction, expression of an N-terminal fragment of Tsg101 containing the UEV domain (referred to as TSG-5′) inhibits FIV Release. In these respects, the FIV p2 Gag PSAP motif is analogous to the PTAP motif of HIV-1 p6 Gag . To evaluate the feasibility of a late domain-targeted inhibition of Virus replication, we created an enriched Crandell-Rees feline kidney (CRFK) cell line (T5′ hi ) that stably expresses high levels of TSG-5′. Here we show that mutations in either the V3 loop or the second heptad repeat (HR2) domain of the FIV envelope glycoprotein (Env) rescue FIV replication in T5′ hi cells without increasing FIV Release efficiency. TSG-5′-resistance mutations in Env enhance virion infectivity and the cell–cell spread of FIV when diffusion is limited using a semi-solid growth medium. These findings show that mutations in functional domains of Env confer TSG-5′-resistance, which we propose enhances specific infectivity and the cell–cell transmission of Virus to counteract inefficient Virus Release. This article is part of a Special Issue entitled: Viral Membrane Proteins—Channels for Cellular Networking.
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Distribution of ESCRT Machinery at HIV Assembly Sites Reveals Virus Scaffolding of ESCRT Subunits
Science (New York N.Y.), 2014Co-Authors: Schuyler B. Van Engelenburg, Gleb Shtengel, Harald F Hess, Prabuddha Sengupta, Kayoko Waki, Michal Jarnik, Sherimay D. Ablan, Eric O. Freed, Jennifer Lippincott-schwartzAbstract:The human immunodeficiency Virus (HIV) hijacks the endosomal sorting complexes required for transport (ESCRT) to mediate Virus Release from infected cells. The nanoscale organization of ESCRT machinery necessary for mediating viral abscission is unclear. Here, we applied three-dimensional superresolution microscopy and correlative electron microscopy to delineate the organization of ESCRT components at HIV assembly sites. We observed ESCRT subunits localized within the head of budding virions and Released particles, with head-localized levels of CHMP2A decreasing relative to Tsg101 and CHMP4B upon Virus abscission. Thus, the driving force for HIV Release may derive from initial scaffolding of ESCRT subunits within the viral bud interior followed by plasma membrane association and selective remodeling of ESCRT subunits.
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beyond tsg101 the role of alix in escrting hiv 1
Nature Reviews Microbiology, 2007Co-Authors: Ken Fujii, James H Hurley, Eric O. FreedAbstract:The limited coding capacity of retroviral genomes forces these Viruses to rely heavily on the host-cell machinery for their replication. This phenomenon is particularly well illustrated by the interaction between retroViruses and components of the endosomal budding machinery that occurs during Virus Release. Here, we focus on the use of host-cell factors during HIV-1 budding and highlight recent progress in our understanding of the role of one such factor, Alix, in both viral and cellular membrane budding and fission events.
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the late domain of human immunodeficiency Virus type 1 p6 promotes Virus Release in a cell type dependent manner
Journal of Virology, 2002Co-Authors: Dimiter G Demirov, Jan M Orenstein, Eric O. FreedAbstract:The p6 domain of human immunodeficiency Virus type 1 (HIV-1) is located at the C terminus of the Gag precursor protein Pr55(Gag). Previous studies indicated that p6 plays a critical role in HIV-1 particle budding from Virus-expressing HeLa cells. In this study, we performed a detailed mutational analysis of the N terminus of p6 to map the sequences required for efficient Virus Release. We observed that the highly conserved P-T/S-A-P motif located near the N terminus of p6 is remarkably sensitive to change; even conservative mutations in this sequence imposed profound Virus Release defects in HeLa cells. In contrast, single and double amino acid substitutions outside the P-T/S-A-P motif had no significant effect on particle Release. The introduction of stop codons one or two residues beyond the P-T/S-A-P motif markedly impaired virion Release, whereas truncation four residues beyond P-T/S-A-P had no effect on particle production in HeLa cells. By examining the effects of p6 mutation in biological and biochemical analyses and by electron microscopy, we defined the role of p6 in particle Release and Virus replication in a panel of T-cell and adherent cell lines and in primary lymphocytes and monocyte-derived macrophages. We demonstrated that the effects of p6 mutation on Virus replication are markedly cell type dependent. Intriguingly, even in T-cell lines and primary lymphocytes in which p6 mutations block Virus replication, these changes had little or no effect on particle Release. However, p6-mutant particles produced in T-cell lines and primary lymphocytes exhibited a defect in virion-virion detachment, resulting in the production of tethered chains of virions. Virus Release in monocyte-derived macrophages was markedly inhibited by p6 mutation. To examine further the cell type-specific Virus Release defect in HeLa versus T cells, transient heterokaryons were produced between HeLa cells and the Jurkat T-cell line. These heterokaryons display a T-cell-like phenotype with respect to the requirement for p6 in particle Release. The results described here define the role of p6 in Virus replication in a wide range of cell types and reveal a strong cell type-dependent requirement for p6 in Virus particle budding.
Amy J Andrew - One of the best experts on this subject based on the ideXlab platform.
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positioning of cysteine residues within the n terminal portion of the bst 2 tetherin ectodomain is important for functional dimerization of bst 2
Journal of Biological Chemistry, 2015Co-Authors: Sarah Welbourn, Amy J Andrew, Sandra Kao, Kelly E Du Pont, Christopher E Berndsen, Klaus StrebelAbstract:BST-2/tetherin is a cellular host factor capable of restricting the Release of a variety of enveloped Viruses, including HIV-1. Structurally, BST-2 consists of an N-terminal cytoplasmic domain, a transmembrane domain, an ectodomain, and a C-terminal membrane anchor. The BST-2 ectodomain encodes three cysteine residues in its N-terminal half, each of which can contribute to the formation of cysteine-linked dimers. We previously reported that any one of the three cysteine residues is sufficient to produce functional BST-2 dimers. Here we investigated the importance of cysteine positioning on the ectodomain for functional dimerization of BST-2. Starting with a cysteine-free monomeric form of BST-2, individual cysteine residues were reintroduced at various locations throughout the ectodomain. The resulting BST-2 variants were tested for expression, dimerization, surface presentation, and inhibition of HIV-1 Virus Release. We found significant flexibility in the positioning of cysteine residues, although the propensity to form cysteine-linked dimers generally decreased with increasing distance from the N terminus. Interestingly, all BST-2 variants, including the one lacking all three ectodomain cysteines, retained the ability to form non-covalent dimers, and all of the BST-2 variants were efficiently expressed at the cell surface. Importantly, not all BST-2 variants capable of forming cysteine-linked dimers were functional, suggesting that cysteine-linked dimerization of BST-2 is necessary but not sufficient for inhibiting Virus Release. Our results expose new structural constraints governing the functional dimerization of BST-2, a property essential to its role as a restriction factor tethering Viruses to the host cell.
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hiv 1 vpu targets cell surface markers cd4 and bst 2 through distinct mechanisms
Molecular Aspects of Medicine, 2010Co-Authors: Amy J Andrew, Klaus StrebelAbstract:Abstract Vpu is a small integral membrane protein encoded by HIV-1 and some SIV isolates. The protein is known to induce degradation of the viral receptor molecule CD4 and to enhance the Release of newly formed virions from the cell surface. Vpu accomplishes these two functions through two distinct mechanisms. In the case of CD4, Vpu acts as a molecular adaptor to connect CD4 to an E3 ubiquitin ligase complex resulting in CD4 degradation by cellular proteasomes. This requires signals located in Vpu’s cytoplasmic domain. Enhancement of Virus Release on the other hand involves the neutralization of a cellular host factor, BST-2 (also known as CD317, HM1.24, or tetherin) and requires Vpu’s TM domain. The current review discusses recent advances on the role of Vpu in controlling degradation of CD4 and in regulating Virus Release.
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the formation of cysteine linked dimers of bst 2 tetherin is important for inhibition of hiv 1 Virus Release but not for sensitivity to vpu
Retrovirology, 2009Co-Authors: Amy J Andrew, Eri Miyagi, Sandra Kao, Klaus StrebelAbstract:The Human Immunodeficiency Virus type 1 (HIV-1) Vpu protein enhances Virus Release from infected cells and induces proteasomal degradation of CD4. Recent work identified BST-2/CD317 as a host factor that inhibits HIV-1 Virus Release in a Vpu sensitive manner. A current working model proposes that BST-2 inhibits Virus Release by tethering viral particles to the cell surface thereby triggering their subsequent endocytosis. Here we defined structural properties of BST-2 required for inhibition of Virus Release and for sensitivity to Vpu. We found that BST-2 is modified by N-linked glycosylation at two sites in the extracellular domain. However, N-linked glycosylation was not important for inhibition of HIV-1 Virus Release nor did it affect surface expression or sensitivity to Vpu. Rodent BST-2 was previously found to form cysteine-linked dimers. Analysis of single, double, or triple cysteine mutants revealed that any one of three cysteine residues present in the BST-2 extracellular domain was sufficient for BST-2 dimerization, for inhibition of Virus Release, and sensitivity to Vpu. In contrast, BST-2 lacking all three cysteines in its ectodomain was unable to inhibit Release of wild type or Vpu-deficient HIV-1 virions. This defect was not caused by a gross defect in BST-2 trafficking as the mutant protein was expressed at the cell surface of transfected 293T cells and was down-modulated by Vpu similar to wild type BST-2. While BST-2 glycosylation was functionally irrelevant, formation of cysteine-linked dimers appeared to be important for inhibition of Virus Release. However lack of dimerization did not prevent surface expression or Vpu sensitivity of BST-2, suggesting Vpu sensitivity and inhibition of Virus Release are separable properties of BST-2.
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vpu enhances hiv 1 Virus Release in the absence of bst 2 cell surface down modulation and intracellular depletion
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Eri Miyagi, Amy J Andrew, Sandra Kao, Klaus StrebelAbstract:HIV-1 Vpu enhances the Release of virions from infected cells. Recent work identified Bst-2/CD317/tetherin as a host factor whose inhibitory activity on viral Release is counteracted by Vpu. A current working model proposes that Bst-2 inhibits Virus Release by tethering viral particles to the cell surface. Here, we analyzed endogenous Bst-2 with respect to its effect on Virus Release from HeLa cells, T cells, and macrophages. We noted significant cell type-dependent variation in Bst-2 expression. Vpu caused a reduction in Bst-2 expression in transfected HeLa cells and long-term infected macrophages. However, Vpu expression did not result in cell surface down-modulation of Bst-2 or a reduction in intracellular Bst-2 expression in CEMx174 or H9 cells, yet Virus replication in these cells was Vpu-responsive. Surprisingly, Bst-2 was undetectable in cell-free virions that were recovered from the surface of HeLa cells by physical shearing, suggesting that a tethering model may not explain all of the functional properties of Bst-2. Taken together we conclude that enhancement of Virus Release by Vpu does not, at least in CEMx174 and H9 cells, require cell surface down-modulation or intracellular depletion of Bst-2, nor does it entail exclusion of Bst-2 from viral particles.
Mark Marsh - One of the best experts on this subject based on the ideXlab platform.
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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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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.
