Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Like other enveloped viruses, HIV-1 uses cellular machinery to bud from infected cells. We now show that Tsg101 protein, which functions in vacuolar protein sorting (Vps), is required for HIV-1 budding. The UEV domain of Tsg101 binds to an essential tetrapeptide (PTAP) motif within the p6 domain of the structural Gag protein and also to ubiquitin. Depletion of cellular Tsg101 by small interfering RNA arrests HIV-1 budding at a late stage, and budding is rescued by reintroduction of Tsg101. Dominant negative mutant Vps4 proteins that inhibit vacuolar protein sorting also arrest HIV-1 and MLV budding. These observations suggest that retroviruses bud by appropriating cellular machinery normally used in the Vps pathway to form multivesicular bodies.
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PMID:Tsg101 and the vacuolar protein sorting pathway are essential for HIV-1 budding. 1159 85

The authors examined multiple brain sections from 15 autopsy cases of AIDS for the vascular changes, presence of amyloid plaques and signs of axonal damage. The mean patients age was 33.8 years (range 24-48 years). Neuropathological findings included: HIV-specific changes (5), opportunistic infections (7), lymphoma (1) and two cases with nonspecific changes. All sections were stained with hematoxylin-eosin (H-E), selected sections were stained with Masson trichrome, Gomori reticulin, Congo red and thioflavine S method. Two sections from each case were immunostained for the presence of beta-amyloid (4G8). ubiquitin, alpha-smooth muscle actin and CD31. The different forms of vascular changes were found in all cases. The common changes were: lymphocytic perivascular or transmural infiltrations and hyalinization, thickening or fibrosis of the arterial and arteriolar wall. The perivascular space widening up to status lacunaris was a frequent phenomenon in the basal ganglia and deep white matter. Some of the cortical arterioles formed little multiluminal structures. Immunohistochemical examination revealed features of hypertrophy of the vascular muscular layer and signs of the slight endothelial cells proliferation. In three cases 4G8 immunopositive. Congo red and thioflavine S-negative, diffuse beta-amyloid deposits were present in the gray matter, focally their localization was perivascular. Ubiquitin immunoreactivity presented as numerous dot-like structures or focal bundles of positive widened axons in the white matter, spheroids and scattered positive neurons were also found. The authors suggest that some of morphological changes within the brain and consecutive neuropsychological symptoms in AIDS are of the vascular origin. Presence of amyloid plaques and axonal damage are the elements of the complex degenerative and inflammatory process in the brain caused by chronic inflammatory stimulation in HIV infection.
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PMID:Vasculopathy and amyloid beta reactivity in brains of patients with acquired immune deficiency (AIDS). 1169 22

HIV-1 budding appears to require Vps4 and Tsg101-two proteins that have links to endosomal sorting machinery. A picture emerges wherein divergent viruses recruit endosomal proteins like Tsg101 to gain access to ubiquitin processes that play a crucial role during viral budding.
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PMID:Resistance is futile: assimilation of cellular machinery by HIV-1. 1172 31

HIV-1 is a fundamentally difficult target for vaccines due to its high mutation rate and its repertoire of immunoevasive strategies. To address these difficulties, a multivalent, proteasome-targeted, live genetic vaccine was recently developed against HIV-1 using the expression library immunization approach. In this HIV-1 vaccine all open reading frames of HIV-1 are expressed from 32 plasmids as Ag fragments fused to the ubiquitin protein to increase Ag targeting to the proteasome to enhance CTL responses. In this work we demonstrate the ability of the HIV-1 library vaccine to simultaneously provoke robust HLA-A*0201-restricted T cell responses against all 32 HIV-1 library vaccine Ags after single immunization by gene gun. These CD8 T cell responses included HLA-A*0201-restricted CTL activity, CD8/IFN-gamma T cell responses, and HLA tetramer binding against defined immunodominant epitopes in gag, pol, env, and nef as well as potent CD8/IFN-gamma responses against undefined HLA-A*0201-restricted epitopes in all remaining Ags of the library. CD8 responses mediated by single gag, pol, env, and nef plasmids from the vaccine demonstrated little reduction in specific T cell responses when these plasmids were diluted into the context of the full 32-plasmid library, suggesting that Ag dominance or immune interference is not an overt problem to limit the efficacy of this complex vaccine. Therefore, this work demonstrates the ability of the HIV-1 library vaccine to generate robust multivalent genome-wide T cell responses as one approach to control the highly mutable and immunoevasive HIV-1 virus.
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PMID:Generation of genome-wide CD8 T cell responses in HLA-A*0201 transgenic mice by an HIV-1 ubiquitin expression library immunization vaccine. 1175 84

Efficient budding of HIV-1 from the plasma membrane of infected cells requires the function of a 6-kDa protein known as p6. A highly conserved Pro-Thr-Ala-Pro (PTAP) motif (the "late" or "L" domain), is critical for the virus-budding activity of p6. Recently, it was demonstrated that the product of tumor susceptibility gene 101 (TSG101), which contains at its N terminus a domain highly related to ubiquitin-conjugating (E2) enzymes, binds HIV-1 Gag in a p6-dependent fashion. We examined the impact of overexpressing the N-terminal region of TSG101 on HIV-1 particle assembly and release. We observed that this domain (referred to as TSG-5') potently inhibits virus production. Examination of cells coexpressing HIV-1 Gag and TSG-5' by electron microscopy reveals a defect in virus budding reminiscent of that observed with p6 L domain mutants. In addition, the effect of TSG-5' depends on an intact p6 L domain; the assembly and release of virus-like particles produced by Gag mutants lacking a functional p6 PTAP motif is not significantly affected by TSG-5'. Furthermore, assembly and release of murine leukemia virus and Mason-Pfizer monkey virus are insensitive to TSG-5'. TSG-5' is incorporated into virions, confirming the Gag/TSG101 interaction in virus-producing cells. Mutations that inactivate the p6 L domain block TSG-5' incorporation. These data demonstrate a link between the E2-like domain of TSG101 and HIV-1 L domain function, and indicate that TSG101 derivatives can act as potent and specific inhibitors of HIV-1 replication by blocking virus budding.
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PMID:Overexpression of the N-terminal domain of TSG101 inhibits HIV-1 budding by blocking late domain function. 1180 36

Host factors that associate retrovirus replication also play an important role in regulating cellular physiological conditions. Therefore, a discovery of HIV related cellular proteins might open up understanding mechanisms for essential cellular machinery. Recent advances in biotechnology have shed new light on the molecular mechanism of HIV replication. We choose three topics about HIV replication and discuss them; a role of ubiquitin and vacuolar protein sorting pathway during virus budding, new players, integrase and central DNA flap, that regulate the translocation of preintegration complex into nucleus, and a relationship between basic model for core formation and fullerene molecule.
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PMID:[Molecular mechanism of HIV-1 replication]. 1196 70

Retroviral Gag polyproteins contain regions that promote the separation of virus particles from the plasma membrane and from each other. These Gag regions are often referred to as late assembly (L) domains. The L domain of human immunodeficiency virus type 1 (HIV-1) is in the C-terminal p6(gag) domain and harbors an essential P(T/S)APP motif, whereas the L domains of oncoretroviruses are in the N-terminal half of the Gag precursor and have a PPXY core motif. We recently observed that L domains induce the ubiquitination of a minimal HIV-1 Gag construct and that point mutations which abolish L domain activity prevent Gag ubiquitination. In that study, a peptide from the Ebola virus L domain with overlapping P(T/S)APP and PPXY motifs showed exceptional activity in promoting Gag ubiquitination and the release of virus-like particles. We now show that a substitution which disrupts the PPXY motif but leaves the P(T/S)APP motif intact abolishes L domain activity in the minimal Gag context, but not in the context of a near full-length HIV-1 Gag precursor. Our results reveal that the P(T/S)APP motif does not function autonomously and indicate that the HIV-1 nucleocapsid-p1 region, which is proximal to p6(gag), can cooperate with the conserved L domain core motif. We have also examined the effects of ubiquitin mutants on virus-like particle production, and the results indicate that residues required for the endocytosis function of ubiquitin are also involved in virus budding.
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PMID:Late assembly domain function can exhibit context dependence and involves ubiquitin residues implicated in endocytosis. 1199 75

Human Tsg101 plays key roles in HIV budding and in cellular vacuolar protein sorting (VPS). In performing these functions, Tsg101 binds both ubiquitin (Ub) and the PTAP tetrapeptide 'late domain' motif located within the viral Gag protein. These interactions are mediated by the N-terminal domain of Tsg101, which belongs to the catalytically inactive ubiquitin E2 variant (UEV) family. We now report the structure of Tsg101 UEV and chemical shift mapping of the Ub and PTAP binding sites. Tsg101 UEV resembles canonical E2 ubiquitin conjugating enzymes, but has an additional N-terminal helix, an extended beta-hairpin that links strands 1 and 2, and lacks the two C-terminal helices normally found in E2 enzymes. PTAP-containing peptides bind in a hydrophobic cleft exposed by the absence of the C-terminal helices, whereas ubiquitin binds in a novel site surrounding the beta-hairpin. These studies provide a structural framework for understanding how Tsg101 mediates the protein-protein interactions required for HIV budding and VPS.
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PMID:Structure and functional interactions of the Tsg101 UEV domain. 1200 92

UBA domains are a commonly occurring sequence motif of approximately 45 amino acid residues that are found in diverse proteins involved in the ubiquitin/proteasome pathway, DNA excision-repair, and cell signaling via protein kinases. The human homologue of yeast Rad23A (HHR23A) is one example of a nucleotide excision-repair protein that contains both an internal and a C-terminal UBA domain. The solution structure of HHR23A UBA(2) showed that the domain forms a compact three-helix bundle. We report the structure of the internal UBA(1) domain of HHR23A. Comparison of the structures of UBA(1) and UBA(2) reveals that both form very similar folds and have a conserved large hydrophobic surface patch. The structural similarity between UBA(1) and UBA(2), in spite of their low level of sequence conservation, leads us to conclude that the structural variability of UBA domains in general is likely to be rather small. On the basis of the structural similarities as well as analysis of sequence conservation, we predict that this hydrophobic surface patch is a common protein-interacting surface present in diverse UBA domains. Furthermore, accumulating evidence that ubiquitin binds to UBA domains leads us to the prediction that the hydrophobic surface patch of UBA domains interacts with the hydrophobic surface on the five-stranded beta-sheet of ubiquitin. Detailed comparison of the structures of the two UBA domains, combined with previous mutagenesis studies, indicates that the binding site of HIV-1 Vpr on UBA(2) does not completely overlap the ubiquitin binding site.
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PMID:Solution structures of UBA domains reveal a conserved hydrophobic surface for protein-protein interactions. 1207 61

Cancer cells frequently show high constitutive activity of the antiapoptotic transcription factor nuclear factor kappaB (NF-kappaB), which results in their enhanced survival. Activation of NF-kappaB classically depends on degradation of its inhibitor IkappaBalpha by the 26s proteasome. Specific proteasome inhibitors induce apoptosis in cancer cells and, at nonlethal concentrations, sensitize cells to the cytotoxic effects of ionizing radiation and chemotherapeutic drugs. Recently, the protease coded by the HIV-I virus has been shown to share cleavage activities with the proteasome. For this reason, we investigated whether the HIV-I protease inhibitor saquinavir can inhibit NF-kappaB activation, block 26s proteasome activity in prostate cancer cells, and promote their apoptosis. The effect of saquinavir on LPS/IFN-gamma-induced activation of NF-kappaB was assessed by gel-shift assays and by Western analysis of corresponding IkappaBalpha-levels. Its effect on 20s and 26s proteasome activity was analyzed with a fluorogenic peptide assay using whole cell lysates from LnCaP, DU-145, and PC-3 prostate cancer cells pretreated with saquinavir for 9 h. Proteasome inhibition in living cells was assessed using ECV 304 cells stably transfected with an expression plasmid for an ubiquitin/green fluorescence protein fusion protein (ECV 304/10). Apoptosis was monitored morphologically and by flow cytometry. Saquinavir treatment prevented LPS/IFN-gamma-induced activation of NF-kappaB in RAW cells and stabilized expression of IkappaBalpha. It inhibited 20s and 26s proteasome activity in lysates from LnCaP, DU-145, and PC-3 prostate cancer cells with an IC(50) of 10 micro M and caused the accumulation of an ubiquitin/green fluorescence protein fusion protein in living ECV 304/10 cells. Incubation of PC-3 and DU-145 prostate cancer, U373 glioblastoma, and K562 and Jurkat leukemia cells with saquinavir caused a concentration-dependent induction of apoptosis. In the case of PC-3 and DU-145, saquinavir sensitized the surviving cells to ionizing radiation. We conclude that saquinavir inhibits proteasome activity in mammalian cells as well as acting on the HIV-I protease. Because saquinavir induced apoptosis in human cancer cells, HIV-I protease inhibitors might become a new class of cytotoxic drugs, alone or in combination with radiation or chemotherapy.
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PMID:The human immunodeficiency virus (HIV)-1 protease inhibitor saquinavir inhibits proteasome function and causes apoptosis and radiosensitization in non-HIV-associated human cancer cells. 1223 89


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