Viral Protein R Research Articles

Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment.

Gene therapy involves a substantial loss of hematopoietic stem and progenitor cells (HSPC) during processing and homing. Intra-BM (i.b.m.) transplantation can reduce homing losses, but prior studies have not yielded promising results. We studied the mechanisms involved in homing and engraftment of i.b.m. transplanted and i.v. transplanted genetically modified (GM) human HSPC. We found that i.b.m. HSPC transplantation improved engraftment of hematopoietic progenitor cells (HPC) but not of long-term repopulating hematopoietic stem cells (HSC). Mechanistically, HPC expressed higher functional levels of CXCR4 than HSC, conferring them a retention and homing advantage when transplanted i.b.m. Removing HPC and transplanting an HSC-enriched population i.b.m. significantly increased long-term engraftment over i.v. transplantation. Transient upregulation of CXCR4 on GM HSC-enriched cells, using a noncytotoxic portion of viral protein R (VPR) fused to CXCR4 delivered as a protein in lentiviral particles, resulted in higher homing and long-term engraftment of GM HSC transplanted either i.v. or i.b.m. compared with standard i.v. transplants. Overall, we show a mechanism for why i.b.m. transplants do not significantly improve long-term engraftment over i.v. transplants. I.b.m. transplantation becomes relevant when an HSC-enriched population is delivered. Alternatively, CXCR4 expression on HSC, when transiently increased using a protein delivery method, improves homing and engraftment specifically of GM HSC.

HIV-1 viral protein R decreases malignant behavior of glioma cell U251

Objective To study the effect of recombinant adenovirus mediated transfection of human immunodeficiency virus type 1 viral protein R （Vpr） on TGFβR Ⅲ expression and malignant behavior of glioma cell U251. Methods U251 ceils were divided into the control group, mock group and experiment group, the mock and experiment group were transfected with Ad-GFP and Ad-Vpr, respectively at a multiplicity of infection （MOI） of 100. The expression of Vpr, TGFβR Ⅲ, MMP-2 and MMP-9 were detected by western blot, the malignant biological behavior changes of U251 cells transfected by Ad-Vpr were evaluated by scratch assay and transwell assay. Results Western blot showed that the Vpr protein could be expressed after Ad-Vpr transfection, meanwhile, the expression of TGFβR Ⅲ was up regulated by Ad-Vpr transfection, Relative density values of TGFβRⅢ compared to β-actin in control, Ad-GFP and Ad-Vpr group were0. 71 ±0. 04,0. 83± 0. 09 and 1.13 ±0. 16, respectively, there were significant different in three groups（ P 〈 0. 05 ）. While the expression of MMP-2 and MMP-2 were down regnlated by Ad-Vpr transfection. Relative density values of MMP-2 and MMP-9 compared to 13-actin were 0. 51 ± 0. 11 and 0. 43 ±0. 08 for Ad-Vpr group, 1.11 ±0. 11 and 1.06±0. 18 for control group and 1.23 s0.05 and 1.16 ± 0. 12 for Ad-GFP group, respectively. The expression of MMP-2 and MMP-9 were significantly decreased comparing to control and Ad-GFP group （ P 〈 0. 05 ）. Transwell assay results showed that the average ceils across the membrane were 123.12 ± 10. 82, 118.89 ±12. 65 and 80. 64 ± 7.72 in control, Ad-GFP and Ad-Vpr group, respectively. Compared with control and the Ad-GFP group, the cells across the membrane in Ad-Vpr group were significantly reduced （ P 〈 0. 05 ）. Conclusions Vpr could decrease migratory and invasive behavior of glioma U251 cells probably by upregnlating TGFI3Rm expression. Key words: Glioma; Viral protein R; Transforming growth factor-β receptor Ⅲ

Two Highly Variable Vpr<sub>84</sub>and Vpr<sub>85</sub> Residues within the HIV-1-Vpr C-Terminal Protein Transduction Domain Control Transductionnal Activity and Define a Clade Specific Polymorphism

The virally encoded HIV-1 viral protein R (VPR) is a multifunctional factor that is required for induced HIV-1 pathogenesis. VPR is also a cell-penetrating protein found in biological fluids from HIV-1 infected individuals. In this regard, we previously published that the C-terminal VPR77-92 sequence from HIV-1 89.6, but not from pNL4.3 strain, is a new pro-apoptotic and protein transduction domain (PTD). Here we report on a sequence analysis of VPR77-92 domain using the Los Alamos HIV-1 sequence database. The analysis showed that the two residues of the domain VPR84 and VPR85 are highly variable and differently biased in HIV-1 clade B and HIV-1 clade C. Furthermore, when Jurkat lymphoblastoid cells or PBMC were incubated with chemically synthesized peptides containing distinct VPR77-92 C-terminal sequences from clades B or C, we found that a clade-dependent polymorphism in VPR84 and VPR85 residues controlled the transducing activity of the C-terminal HIV-1 VPR77-92 domain. Together our data indicate that clade-dependent polymorphism in the VPR84 and VPR85 residues defines the transducing properties mediated by the C-terminal domain of HIV-1 VPR. Identification of this VPR polymorphism suggests new approaches to understand the HIV-1 biology and/or pathogenesis.

Inhibition of viral protein r on human colorectal cancer cells and the possible mechanisms

Objective To investigate the inhibitive effects of viral protein r (Vpr) of human immunodeficiency virus 1 ( HIV-1 ) on human colorectal cancer cell line HCT-8,and to find the possible mechanisms.Methods The HCT-8 cells were divided into the control group,adv group and adv-Vpr group.HCT-8 cells were not treated in the control group; HCT-8 cells were treated with Adv or Adv-Vpr at different multiplicity of infection (MOI) in the Adv group or Adv-Vpr group,respectively.Cell proliferation was detected by MTT assay.Cell cycle,apoptosis and mitochondrial membrane potential were detected by flow cytometry.The expression of apoptosisrelated proteins was detected by Western blot.All data were analyzed by using the q test,t test and one-way or two-way analysis of variance.Results The proliferation of HCT-8 cells was significantly inhibited by Vpr.The MTT value of HCT- 8 cells in the Adv-Vpr group was 1.03 ± 0.04,which was significantly lower than 2.46 ± 0.15 in the Adv group and 2.51 ± 0.14 in the control group at 72 hours after Adv-Vpr transfection ( MOI =200) ( F =144.6,P ＜ 0.05).The ratio of HCT-8 cells in the G2/M phase was 37.31％ ± 5.90％ in the Adv-Vpr group,which was significantly higher than 18.30％ ± 6.04％ in the Adv group and 16.66％ ± 3.51％ in the control group ( F =10.08,P ＜ 0.05 ).The ratio of HCT-8 cells with decreased mitochondrial membrane potential was 32.07％ ±5.64％ in the Adv-Vpr group,which was significantly higher than 3.32％ ±0.79％ in the Adv group and 2.76％ ±1.43 ％ in the control group at 48 hours after Adv-Vpr transfection ( MOI =200) ( F =64.45,P ＜ 0.05).The apoptosis rate of HCT-8 cells was 37.62％ ±6.48％ in the Adv-Vpr group,which was significantly higher than 3.44％ ± 1.11％ in the Adv group and 2.93％ ± 1.07％ in the control group at 72 hours after Adv-Vpr transfection ( MOI =200) ( F =122.4,P ＜ 0.05 ).The results of Western blot showed that Vpr induced cleavage and activation of Caspase-9 and Caspase-3 and phosphorylation of Chk1-S345,while the expression levels of Fas,Fas-L,ERK1,ERK2 remained the same at 48 hours after Adv-Vpr treatment ( MOI =200).Conclusions Vpr inhibits the proliferation of the HCT-8 cells in vitro through G2/M phase arrest and apoptosis.Vpr plays its role by activating DNA damaging pathway and initiating mitochondria apoptotic pathway.Vpr is a potential therapeutic agent for colorectal cancer. Key words: Colonic neoplasms; Human immunodeficiency virus 1; Viral protein r gene; G2/M arrest; Cell apoptosis

HIV-1 Viral Protein R (VPR) and its Interactions with Host Cell

Human immunodeficiency virus type 1 (HIV-1) is engaged in dynamic and antagonistic interactions with host cells. Once infected by HIV-1, host cells initiate various antiviral strategies, such as innate antiviral defense mechanisms, to counteract viral invasion. In contrast, the virus has different strategies to suppress these host responses to infection. The final balance between these interactions determines the outcome of the viral infection and disease progression. Recent findings suggest that HIV-1 viral protein R (Vpr) interacts with some of the host innate antiviral factors, such as heat shock proteins, and plays an active role as a viral pathogenic factor. Cellular heat stress response factors counteract Vpr activities and inhibit HIV replication. However, Vpr overcomes these heat-stress-like responses by preventing heat shock factor-1 (HSF-1)-mediated activation of heat shock proteins. In this review, we will focus on the virus-host interactions involving Vpr. In addition to heat stress response proteins, we will discuss interactions of Vpr with other proteins, such as EF2 and Skp1/GSK3, their involvements in cellular responses to Vpr, as well as strategies to develop novel antiviral therapies aimed at enhancing anti-Vpr responses of the host cell.

HIV-1 Mediated Immune Pathogenesis: Spotlight on the Role of Viral Protein R (VPR)

HIV-1 exploits the cellular machinery to replicate in the host cells by targeting a wide range of host factors at different stages of its life cycle. HIV-1 also induces detrimental effects in the infected and uninfected bystander cells resulting in dysregulation including interference in immune effector functions. The latter is specifically linked to the immune evasion strategies of the virus. In addition to the essential roles of structural proteins (Gag, Pol & Env), HIV-1 encoded auxiliary proteins such as Nef, Vif, Vpu, and Vpr through their interaction with the host cellular partners facilitate viral replication and dissemination. HIV-1 Vpr, a virion-associated molecule, has been implicated to play a role in the early events in virus life cycle. Vpr is a pleiotropic protein that exerts a range of effects including inhibition of cell proliferation, induction of apoptosis and modulation of a number of immune molecules. These functions could be in part responsible for Vpr induced immune evasion and virus replication. Appreciating this view is the genetic variation in vpr gene reflected in the form of polymorphisms at the amino acid level that may contribute to the potential CTL escape of the virus. It is likely that Vpr mediated dysregulation of host immune response contributes, in part, to the progression of disease. This review focuses on the recent advances regarding HIV-1 Vpr mediated immunopathogenesis and the mechanistic insight from in vitro and in vivo studies.

Comparative Modeling of Viral Protein R (VpR) from Human Immunodeficiency Virus 1 (HIV 1)

AbstractDuring Human Immunodeficiency Virus infection interactions take place between host and the pathogen. This interac-tion mainly determines the efficiency of viral infection and the disease progression. Human Immunodeficiency Virus infectedcells responds to several antiviral immune mechanisms such as innate, cellular and humoral immune antiviral defense. Thisvirus has also gained resistance to suppress these host cellular responses. Out of many self resistance mechanisms, Viral prote inR (VpR) occupies a significant role, such as nuclear transport of the viral pre-integration complex, activation of viral transc rip-tion, induction of cell cycle and apoptosis of the host cells. Apart from these specific roles, the function of VpR remains mys teryfor the structural bioinformatics. The comparative modeling approach is used to predict the structure of a VpR using NMRstructure of the HIV-1 regulatory protein as the template (PDB ID: 1ESX: A). The theoretical structure of VpR is generatedusing Modeller9v1, a program for comparative modeling of protein using special restraints. This theoretical structure believesto paves the way for the novel lead synthesis.Keywords

HIV-1 Viral Protein-R (VPR) Protects against Lethal Superantigen Challenge While Maintaining Homeostatic T Cell Levels in Vivo

The HIV-1 accessory protein Vpr exhibits many interesting features related to macrophage and T cell biology. As a viral protein or as a soluble molecule it can suppress immune cell activation and cytokine production in vitro in part by targeted inhibition of NF-κB. In this regard we sought to test its effects in vivo on an NF-κB-dependent immune pathway. We examined the activity of Vpr in a lethal toxin-mediated challenge model in mice. Intravenous delivery of Vpr was sufficient to protect mice from lethal challenge with staphylococcal endotoxin B (SEB). Furthermore, Vpr protected host CD4+ T cells from in vivo depletion likely by preventing induction of AICD of SEB-exposed cells in a post-toxin-binding fashion. Understanding the biology of Vpr's activities in this model may allow for new insight into potential mechanisms of hyperinflammatory disease and into Vpr pathobiology in the context of HIV infection.

Partner molecules of accessory protein Vpr of the human immunodeficiency virus type 1.

Vpr (Viral protein-R) of the Human Immunodeficiency Virus type-1 is a 14-kDa virion-associated protein, conserved in HIV-1, -2 and the Simian Immunodeficiency Virus (SIV). Vpr is incorporated into the virion, travels to the nucleus, and has multiple activities including promoter activation, cell cycle arrest at the G2/M transition and apoptosis induction. Through these activities, Vpr is thought to influence not only viral replication but also numerous host cell functions. These functions may be categorized in three groups depending on the domains of Vpr that support them: (1) functions mediated by the amino terminal portion of Vpr, like virion packaging; (2) functions mediated by the carboxyl terminal portion such as cell cycle arrest; and (3) functions that depend on central alpha-helical structures such as transcriptional activation, apoptosis and subcellular shuttling. Association of these activities to specific regions of the Vpr molecule appears to correlate to the host/viral molecules that interact with corresponding portion of Vpr. They include Gag, host transcription factors/coactivators such as SP1, the glucocorticoid receptor, p300/CREB-binding protein and TFIIB, apoptotic adenine nucleotide translocator, cyclophilin A and 14-3-3 proteins. The properties of Vpr molecule has made it difficult to assess its function and determine the true cellular interactors. Further studies on Vpr function are needed to fully assess the function of this important early regulatory molecule of HIV and other lentiviruses.

Hybrid lentivirus vectors.

Lentivirus vectors are promising tools for gene transfer (,). Retroviral vectors in general offer the unique advantage of stably integrating into the genome of the host cell, thus providing the basis for sustained gene expression. In contrast to the classical oncoretrovirus-derived vectors, lentivirus vectors are highly efficient at infection of nondividing cells. This unique ability is owing to the presence of nuclear localization signals on several virion associated proteins, which include matrix (MA), viral protein R (VPR), and integrase (IN) () and a cis-acting element termed the central polypurine tract (cPPT) (,).

Human immunodeficiency virus type I viral protein R (VPR) induces cell-cycle arrest in cervical cancer cells

Human immunodeficiency virus type I viral protein R (VPR) induces cell-cycle arrest in cervical cancer cells

Viral protein R of human immunodeficiency virus types 1 and 2 is dispensable for replication and cytopathogenicity in lymphoid cells

Viral protein R (VPR) is conserved in human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2). To assess its function, we have constructed mutations within the vpr coding regions of HIV-1 and HIV-2 predicted to express truncated VPR products. Infectious virus was produced by each proviral clone and showed similar replication kinetics and cytopathogenicity when compared with the corresponding parental proviral clone.