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Marincowitz C, Genis A, Goswami N, De Boever P, Nawrot TS, Strijdom H. Vascular endothelial dysfunction in the wake of HIV and ART. FEBS J 2018; 286:1256-1270. [PMID: 30220106 DOI: 10.1111/febs.14657] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 08/30/2018] [Accepted: 09/12/2018] [Indexed: 01/18/2023]
Abstract
Mounting evidence points to increased rates of cardiovascular disease (CVD) among people living with HIV/AIDS (PLWHA). Endothelial dysfunction (loss of endothelium-dependent vascular relaxation in response to provasodilatory stimuli) constitutes an early pathophysiological event in atherogenesis and CVD. Both HIV-1 infection and antiretroviral therapy (ART) are implicated in the development of endothelial dysfunction; however, conclusions are frequently drawn from associations shown in epidemiological studies. In this narrative review of mainly in vitro and animal studies, we report on the current understanding of how various HIV-1 proteins, HIV-1-induced proinflammatory cytokines and common antiretroviral drugs directly impact vascular endothelial cells. Proposed cellular mechanisms underlying the switch to a dysfunctional state are discussed, including oxidative stress, impaired expression and regulation of endothelial nitric oxide (NO) synthase (eNOS) and increased expression of vascular adhesion molecules. From the literature, it appears that increased reactive oxygen species (ROS) production, linked to decreased NO bioavailability and ensuing endothelial dysfunction, may be proposed as a putative final common pathway afflicting the vascular endothelium in PLWHA. The HIV-1-proteins Tat, Gp120 and Nef in particular, the proinflammatory cytokine, TNF-α, and the antiretroviral drugs Efavirenz and Lopinavir, most commonly postulated to be primary causal agents of endothelial dysfunction, are also discussed. We conclude that, despite existing evidence from basic research papers, a significant gap remains in terms of the exact underlying cellular mechanisms involved in HIV-1 and ART induced endothelial dysfunction. Bridging this gap could help pave the way for future strategies to prevent and treat early cardiovascular changes in PLWHA.
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Affiliation(s)
- Clara Marincowitz
- Division of Medical Physiology, Stellenbosch University, Cape Town, South Africa
| | - Amanda Genis
- Division of Medical Physiology, Stellenbosch University, Cape Town, South Africa
| | - Nandu Goswami
- Department of Physiology and Otto Loewi Research Centre, Medical University of Graz, Austria
| | - Patrick De Boever
- Health Unit, Flemish Institute for Technological Research (VITO), Mol, Belgium.,Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium
| | - Tim S Nawrot
- Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium.,Centre for Environment and Health, Department for Public Health and Primary Care, KU Leuven, Belgium
| | - Hans Strijdom
- Division of Medical Physiology, Stellenbosch University, Cape Town, South Africa
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Raposo RAS, Abdel-Mohsen M, Holditch SJ, Kuebler PJ, Cheng RG, Eriksson EM, Liao W, Pillai SK, Nixon DF. Increased expression of intrinsic antiviral genes in HLA-B*57-positive individuals. J Leukoc Biol 2013; 94:1051-9. [PMID: 23929683 DOI: 10.1189/jlb.0313150] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The genetic background of HIV-1-infected subjects, particularly the HLA class I haplotype, appears to be critical in determining disease progression rates, thought to be a result of the role of HIV-1-specific CD8(+) T cell responses. The HLA-B*57 allele is strongly associated with viremic suppression and slower disease progression. However, there is considerable heterogeneity in HIV-1 disease progression rates among HLA-B*57-positive subjects, suggesting that additional factors may help to contain viral replication. In this report, we investigated the association between host restriction factors, other established immunological parameters, and HLA type in HIV-1-seronegative individuals. Our results demonstrate that healthy, uninfected HLA-B*57-positive individuals exhibit significantly higher gene-expression levels of host restriction factors, such as APOBEC3A, APOBEC3B, BST-2/tetherin, and ISG15. Interestingly, HLA-B*57 individuals have significantly lower CD4(+) T cell frequencies but harbor slightly more activated CD4(+) T cells compared with their HLA-B*35 counterparts. We detected significant correlations between CD4(+) T cell activation and expression of several APOBEC3 family members, BST-2/tetherin, SAMHD1, and TRIM5α in HLA-B*57-positive individuals. To our knowledge, this is the first report showing distinct associations between host restriction factors and HLA class I genotype. Our results provide insights into natural protection mechanisms and immunity against HIV-1 that fall outside of classical HLA-mediated effects.
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Affiliation(s)
- Rui André Saraiva Raposo
- 2.Division of Experimental Medicine, 1001 Potrero Ave., Bldg. 3, Room 603, Box 1234, San Francisco, CA 94110, USA.
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Lucas TM, Janaka SK, Stephens EB, Johnson MC. Vpu downmodulates two distinct targets, tetherin and gibbon ape leukemia virus envelope, through shared features in the Vpu cytoplasmic tail. PLoS One 2012; 7:e51741. [PMID: 23284757 PMCID: PMC3526647 DOI: 10.1371/journal.pone.0051741] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/09/2012] [Indexed: 11/21/2022] Open
Abstract
During human immunodeficiency virus-1 (HIV-1) assembly, the host proteins CD4 (the HIV-1 receptor) and tetherin (an interferon stimulated anti-viral protein) both reduce viral fitness. The HIV-1 accessory gene Vpu counteracts both of these proteins, but it is thought to do so through two distinct mechanisms. Modulation of CD4 likely occurs through proteasomal degradation from the endoplasmic reticulum. The exact mechanism of tetherin modulation is less clear, with possible roles for degradation and alteration of protein transport to the plasma membrane. Most investigations of Vpu function have used different assays for CD4 and tetherin. In addition, many of these investigations used exogenously expressed Vpu, which could result in variable expression levels. Thus, few studies have investigated these two Vpu functions in parallel assays, making direct comparisons difficult. Here, we present results from a rapid assay used to simultaneously investigate Vpu-targeting of both tetherin and a viral glycoprotein, gibbon ape leukemia virus envelope (GaLV Env). We previously reported that Vpu modulates GaLV Env and prevents its incorporation into HIV-1 particles through a recognition motif similar to that found in CD4. Using this assay, we performed a comprehensive mutagenic scan of Vpu in its native proviral context to identify features required for both types of activity. We observed considerable overlap in the Vpu sequences required to modulate tetherin and GaLV Env. We found that features in the cytoplasmic tail of Vpu, specifically within the cytoplasmic tail hinge region, were required for modulation of both tetherin and GaLV Env. Interestingly, these same regions features have been determined to be critical for CD4 downmodulation. We also observed a role for the transmembrane domain in the restriction of tetherin, as previously reported, but not of GaLV Env. We propose that Vpu may target both proteins in a mechanistically similar manner, albeit in different cellular locations.
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Affiliation(s)
- Tiffany M. Lucas
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
| | - Sanath K. Janaka
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
| | - Edward B. Stephens
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Marc C. Johnson
- Department of Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri-School of Medicine, Columbia, Missouri, United States of America
- * E-mail:
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Abstract
The transmembrane domains (TMDs) of integral membrane proteins do not merely function as membrane anchors but play active roles in many important biological processes. The downregulation of the CD4 coreceptor by the Vpu protein of HIV-1 is a prime example of a process that is dependent on specific properties of TMDs. Here we report the identification of Trp22 in the Vpu TMD and Gly415 in the CD4 TMD as critical determinants of Vpu-induced targeting of CD4 to endoplasmic reticulum (ER)-associated degradation (ERAD). The two residues participate in different aspects of ERAD targeting. Vpu Trp22 is required to prevent assembly of Vpu into an inactive, oligomeric form and to promote CD4 polyubiquitination and subsequent recruitment of the VCP-UFD1L-NPL4 dislocase complex. In the presence of a Vpu Trp22 mutant, CD4 remains integrally associated with the ER membrane, suggesting that dislocation from the ER into the cytosol is impaired. CD4 Gly415, on the other hand, contributes to CD4-Vpu interactions. We also identify two residues, Val20 and Ser23, in the Vpu TMD that mediate retention of Vpu and, by extension, CD4 in the ER. These findings highlight the exploitation of several TMD-mediated mechanisms by HIV-1 Vpu in order to downregulate CD4 and thus promote viral pathogenesis.
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The HIV-1 Vpu viroporin inhibitor BIT225 does not affect Vpu-mediated tetherin antagonism. PLoS One 2011; 6:e27660. [PMID: 22110710 PMCID: PMC3215742 DOI: 10.1371/journal.pone.0027660] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 10/21/2011] [Indexed: 12/14/2022] Open
Abstract
Among its many roles, the HIV-1 accessory protein Vpu performs a viroporin function and also antagonizes the host cell restriction factor tetherin through its transmembrane domain. BIT225 is a small molecule inhibitor that specifically targets the Vpu viroporin function, which, in macrophages, resulted in late stage inhibition of virus release and decreased infectivity of released virus, a phenotype similar to tetherin-mediated restriction. Here, we investigated whether BIT225 might mediate its antiviral function, at least in part, via inhibition of Vpu-mediated tetherin antagonism. Using T-cell lines inducible for tetherin expression, we found that BIT225 does not exert its antiviral function by inhibiting Vpu-mediated tetherin downmodulation from the cell surface, the main site of action of tetherin activity. In addition, results from a bioluminescence resonance energy transfer (BRET) assay showed that the Vpu-tetherin interaction was not affected by BIT225. Our data provide support for the concept that tetherin antagonism and viroporin function are separable on the Vpu transmembrane and that viroporin function might be cell-type dependent. Further, this work contributes to the characterization of BIT225 as an inhibitor that specifically targets the viroporin function of Vpu.
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Abstract
Assembly and release of human immunodeficiency virus type 1 (HIV-1) particles is mediated by the viral Gag polyprotein precursor. Gag is synthesized in the cytosol and rapidly translocates to membrane to orchestrate particle production. The cell biology of HIV-1 Gag trafficking is currently one of the least understood aspects of HIV-1 replication. In this review, we highlight the current understanding of the cellular machinery involved in Gag trafficking and virus assembly.
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Affiliation(s)
- Muthukumar Balasubramaniam
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, Maryland
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Serine-threonine ubiquitination mediates downregulation of BST-2/tetherin and relief of restricted virion release by HIV-1 Vpu. J Virol 2010; 85:51-63. [PMID: 20980512 DOI: 10.1128/jvi.01795-10] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The HIV-1 protein Vpu counteracts the antiviral activity of the innate restriction factor BST-2/tetherin by a mechanism that partly depends on its interaction with β-TrCP, a substrate adaptor for an SCF (Skp-Cullin 1-F box) E3 ubiquitin ligase complex. This suggests that Vpu stimulates the ubiquitination of BST-2 and that this underlies the relief of restriction. Here, we show that Vpu stimulates ubiquitination of BST-2. Mutation of all potential ubiquitination sites in the cytoplasmic domain of BST-2, including lysines, cysteines, serines, and threonines, abrogates Vpu-mediated ubiquitination. However, a serine-threonine-serine sequence specifically mediates the downregulation of BST-2 from the cell surface and the optimal relief of restricted virion release. Serine-threonine ubiquitination of BST-2 is likely part of the mechanism by which Vpu counteracts innate defenses.
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