Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HIV Envelope Protein gp160”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2001

Inhibition of the calcium release-activated calcium (CRAC) current in Jurkat T cells by the HIV-1 envelope protein gp160.

The HIV-1 envelope glycoprotein gp120/160 has pleiotropic effects on T cell function. We investigated whether Ca(2+) signaling, a crucial step for T cell activation, was altered by prolonged exposure of Jurkat T cells to gp160. Microfluorometric measurements showed that Jurkat cells incubated with gp160 had smaller (approximately 40%) increases in [Ca(2+)](i) in response to phytohemagglutinin and had a reduced Ca(2+) influx (approximately 25%). gp160 had similar effects on Jurkat cells challenged with thapsigargin. We used the patch clamp technique to record the Ca(2+) current, which is responsible for Ca(2+) influx and has properties of the calcium release-activated Ca(2+) current (I(CRAC)). gp160 reduced I(CRAC) by approximately 40%. The inhibitory effects of gp160 were antagonized by staurosporine (0.1 microm), an inhibitor of protein-tyrosine kinases and protein kinase Cs (PKCs), and by Gö 6976 (5 microm), an inhibitor acting especially on PKC alpha and PKC beta I. 12-O-Tetradecanoyl phorbol 13-acetate (16 nm), a PKC activator, reproduced the effects of gp160 in untreated cells. A Western blotting analysis of PKC isoforms alpha, beta I, delta, and zeta showed that only the cellular distribution of PKC alpha and -beta I were significantly modified by gp160. In addition, gp160 was able to modify the subcellular distribution of PKC alpha and PKC beta I caused by phytohemagglutinin. Therefore the reduction in I(CRAC) caused by prolonged incubation with gp160 is probably mediated by PKC alpha or -beta I.

Calcium↗
PubMed1991

Identification of membrane anchorage domains of the HIV-1 gp160 envelope glycoprotein precursor.

The gp41 transmembrane protein of human immunodeficiency virus type 1 (HIV-1) contains a hydrophobic membrane-spanning domain that serves to anchor the gp120-gp41 complex on the surface of infected cells and virions. To study the requirements for membrane anchorage, conservative amino acid substitutions in three residues at a time were made within this hydrophobic gp41 region. The complete gp160 precursor as well as the gp120 exterior envelope glycoprotein were exported into the supernatant of expressing cells for two mutants with amino acid substitutions in residues 687-689 and 697-699. The soluble gp160 molecules exhibited a binding ability for CD4 on the surface of SupT1 cells that was 33-36% that of the soluble gp120 glycoproteins. These results implicate residues 687-689 and 697-699 as important components of the stop-transfer signal that anchors the gp160 envelope glycoprotein precursor in the membrane. The data also suggest that characteristics in addition to hydrophobicity are required for stop-transfer signals.

Amino Acid Sequence↗
PubMed1993

Role of HIV-1 envelope V3 loop cleavage in cell tropism.

The envelope protein is an important determinant of HIV-1 cell-specific tropism. The gp160 envelope precursor proteins from macrophage-tropic or T lymphoid cell line-tropic strains of HIV-1 were expressed in recombinant vaccinia virus-infected cell lines or primary lymphocytes or macrophages. No significant differences in the kinetics of synthesis of gp160, processing into gp120 and gp41 proteins, N-linked glycosylation, or release of gp120 into the medium were noted with the different envelope proteins. However, gp120 envelope protein shed into the medium was found to be at least partially cleaved at a site within the V3 loop. The gp120 envelope proteins from macrophage-tropic isolates exhibited lower rates of cleavage than those from lymphoid cell line-tropic strains in all cell types examined. Cell-free protease digestion studies also demonstrated relative resistance of the envelopes from macrophage-tropic compared to lymphoid cell line-tropic strains. All recombinant envelope proteins were recognized by monoclonal antibodies directed at gp41 or the C-terminal gp120 epitopes, and no differences in binding to CD4 were noted.

Amino Acid Sequence↗
PubMed1997

HIV-1 gp160 envelope protein modulates proliferation and apoptosis in mesangial cells.

Mesangial cell (MC) hyperplasia and accumulation of extracellular matrix are the predominant features of HIV-associated nephropathy (HIVAN). Since mice transgenic for HIV-1 genes show renal lesions mimicking HIVAN, we studied the effect of HIV-1 gp160 protein on cultured murine MC (MMC) proliferation and apoptosis. HIV-1 gp160 protein stimulated (p < 0.001) MMC proliferation when compared with control MMCs. This effect of gp160 protein peaked at a concentration of 0.01 microg/ml. MMCs treated with a higher concentration of gp160 protein (0.1 microg/ml) or for a prolonged period of time (72 h) showed apoptosis rather than cell proliferation. These studies were further confirmed by DNA fragmentation and end labeling assays. gp160 also enhanced apoptosis in human MCs. Tumor necrosis factor (TNF)-alpha enhanced (p < 0.001) MMC apoptosis, and anti-TNF-alpha antibodies inhibited gp160-induced MMC apoptosis. In addition, gp160 protein attenuated MMC expression of Bcl-2 mRNA expression. These results suggest that gp160-induced apoptosis may be affected in part by the release of TNF-alpha and associated with attenuated mRNA expression of Bcl-2 by MMCs.

AIDS-Associated Nephropathy↗
PubMed1995

Enhanced proteolytic processing of the human immunodeficiency virus type 1 envelope protein in murine Ltk(-) cells.

Proteolytic processing of the human immunodeficiency virus type 1 (HIV-1) envelope (Env) precursor glycoprotein (gp160) to produce the mature gp120 and gp41 proteins is required for virus infection and virus-induced cell fusion. It has also been suggested that cleavage of gp120 at the immunodominant V3 loop region is required for virus-to-cell and cell-to-cell fusion. In this investigation we have studied the proteolytic processing of the HIV-1 Env in cells of various origins (human, monkey, and mouse) infected with a vaccinia virus recombinant expressing the entire gp160 protein (VV-env-1). We have observed that in murine Ltk(-) cells, in addition to the proteolytic cleavage of gp160 at the gp120/gp41 site, there is also extensive intracellular proteolytic processing of gp160 at the V3 loop and at a novel site located at the C terminus of gp41. Similar proteolytic processing of the Env precursor was observed after treatment of extracts of VV-env-1-infected monkey cells with thrombin, a trypsin-like protease that has been shown to cleave the gp120 at the V3 loop. Our findings suggest that murine Ltk(-) cells could be a good model system for structural studies of Env with different HIV isolates and in searches for proteinase inhibitors that could prevent HIV-1 infection of susceptible cells by blocking proteolysis of Env.

Animals↗
PubMed1992

Sulfation of the human immunodeficiency virus envelope glycoprotein.

Sulfation is a posttranslational modification of proteins which occurs on either the tyrosine residues or the carbohydrate moieties of some glycoproteins. In the case of secretory proteins, sulfation has been hypothesized to act as a signal for export from the cell. We have shown that the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein precursor (gp160) as well as the surface (gp120) and transmembrane (gp41) subunits can be specifically labelled with 35SO42-. Sulfated HIV-1 envelope glycoproteins were identified in H9 cells infected with the IIIB isolate of HIV-1 and in the cell lysates and culture media of cells infected with vaccinia virus recombinants expressing a full-length or truncated, secreted form of the HIV-1 gp160 gene. N-glycosidase F digestion of 35SO4(2-)-labelled envelope proteins removed virtually all radiolabel from gp160, gp120, and gp41, indicating that sulfate was linked to the carbohydrate chains of the glycoprotein. The 35SO42-label was at least partially resistant to endoglycosidase H digestion, indicating that some sulfate was linked to complex carbohydrates. Brefeldin A, a compound that inhibits the endoplasmic reticulum to Golgi transport of glycoproteins, was found to inhibit the sulfation of the envelope glycoproteins. Envelope glycoproteins synthesized in cells treated with chlorate failed to incorporate 35SO42-. However, HIV glycoproteins were still secreted from cells in the presence of chlorate, indicating that sulfation is not a requirement for secretion of envelope glycoproteins. Sulfation of HIV-2 and simian immunodeficiency virus envelope glycoproteins has also been demonstrated by using vaccinia virus-based expression systems. Sulfation is a major determinant of negative charge and could play a role in biological functions and antigenic properties of HIV glycoproteins.

Antiviral Agents↗
PubMed1993

Augmentation of human immunodeficiency virus type 1 neutralizing antibody by priming with gp160 recombinant vaccinia and boosting with rgp160 in vaccinia-naive adults. The NIAID AIDS Vaccine Clinical Trials Network.

Twelve vaccinia-naive volunteers were inoculated with recombinant vaccinia virus expressing the human immunodeficiency virus type 1 (HIV-1) strain IIIB (HIV-1IIIB) envelope glycoprotein gp160 and subsequently immunized with 640 micrograms of recombinant (r) gp160 protein produced in baculovirus. After booster immunization with rgp160, the sera of all vaccinees showed strong antibody responses detected by Western blot and ELISA; 8 had neutralizing activity and 5 had fusion inhibition activity against the homologous strain; 5 blocked binding of CD4 cells to gp120. Cross-reactive neutralization of HIV-1MN was detected in 3 of 8 sera that neutralized HIV-1IIIB. The combination of live recombinant vaccinia followed by subunit booster immunization was more immunogenic than either product alone and represents a promising approach for HIV-1 immunoprophylaxis. Further definition of recombinant vaccinia safety and augmentation of immune responses to geographically prevalent HIV-1 strains will be necessary before expanding clinical trials to high-risk groups.

AIDS Vaccines↗
PubMed1997

Comparative functional role of PC7 and furin in the processing of the HIV envelope glycoprotein gp160.

The intracellular proteolytic processing of HIV envelope glycoprotein gp160 into gp120/gp41 is an essential step for virus infectivity. Several convertases, belonging to the pro-protein convertase family, have been proposed as candidate gp160 processing enzymes. Here we demonstrate using RT-PCR that resting human T4 lymphocytes weakly express PC7, furin, and PC5 mRNA whereas lymphocytes activated under conditions favoring HIV replication express 5-10-fold higher levels of furin and PC7. In this report, we examined the capability of the newly cloned convertase PC7 to cleave gp160 into gp120/gp41 and compared it to furin. This was carried out in a cell-based assay whereby both gp160 and the cognate convertase were co-expressed in the constitutively secreting BSC40 cells and in the regulated AtT20 cells, as well as using two in vitro assays which examined the cleavage of gp160 or of a synthetic peptide spanning the cleavage site. The data demonstrate that PC7 can cleave specifically and in a cell-type specific manner gp160 into gp120gp41, suggesting that both furin and PC7 are so far the major PC-like candidate gp160 convertase in T4 lymphocytes.

Amino Acid Sequence↗
PubMed1997

Human immunodeficiency virus type 1 and 2 envelope glycoproteins oligomerize through conserved sequences.

Hetero-oligomerization between human immunodeficiency virus type 2 (HIV-2) envelope glycoprotein (Env) truncation mutants and epitope-tagged gp160 is dependent on the presence of gp41 transmembrane protein (TM) amino acids 552 to 589, a putative amphipathic alpha-helical sequence. HIV-2 Env truncation mutants containing this sequence were also able to form cross-type hetero-oligomers with HIV-1 Env. HIV-2/HIV-1 hetero-oligomerization was, however, more sensitive to disruption by mutagenesis or increased temperature. The conservation of the Env oligomerization function of the HIV-1 and HIV-2 alpha-helical sequences suggests that retroviral TM alpha-helical motifs may have a universal role in oligomerization.

Amino Acid Sequence↗
PubMed2000

Design and intracellular activity of a human single-chain antibody to human immunodeficiency virus type 1 conserved gp41 epitope.

A human lymphoid cell line (F172-D8) excreting a human immunodeficiency virus type 1 (HIV-1) anti-gp41 monoclonal antibody was used to construct a plasmid containing the cDNA of the single-chain variable fragment (scFvD8) corresponding to this antibody. A stable human osteosarcoma cell line was obtained which expressed the scFvD8 protein in the cytoplasm. Whereas a cell line transfected with a control construct (pCI-neo) was readily and productively infected with laboratory (Ba-L) or primary HIV-1 isolates, the scFvD8 cell line did not support productive infection. Binding of the virus, internalization, and reverse transcription were not altered by scFvD8 expression, but gp160 expression was dramatically reduced. These data suggest that cytoplasmic expression of this artificial single-chain antibody can interfere with gp160 expression, thereby reducing the production of mature viral envelope proteins.

Cell Line↗
PubMed1991

The assembly of the HIV-1 env glycoprotein into dimers and tetramers.

The envelope (env) glycoprotein of human immunodeficiency virus 1 (HIV-1), initially synthesized as a precursor molecule termed gp160, is cleaved into two noncovalently associated subunits prior to delivery to the plasma membrane. We have studied the oligomeric structure of this protein using chemical cross-linking, velocity gradient sedimentation, and SDS-resistance. We find that gp160 forms stable homodimers after synthesis. After cleavage to gp120/gp41 the molecule becomes less stable to detergent solubilization and centrifugation but remains dimeric. Interactions between the 129 amino terminal residues in the ectodomains of adjoining gp41 subunits are both sufficient and necessary for assembly. In addition, tetramers composed of two dimers were also formed. Larger structures were not observed. The tetrameric paramyxovirus F protein, which has structural and functional similarities to the HIV-1 env protein, also forms a dimer of dimers.

Gene Products, env↗
PubMed1988

Expression of membrane-associated and secreted variants of gp160 of human immunodeficiency virus type 1 in vitro and in continuous cell lines.

The gene encoding the 856-amino-acid envelope glycoprotein, gp160, of human immunodeficiency virus type 1 was mutagenized and transfected into Chinese hamster ovary cells. Continuous cell lines that constitutively produced gp160 variants were isolated and used to study the biosynthesis and orientation of gp160 in cellular membranes. In vivo studies of gp160 variants failed to reveal domains upstream of amino acid residue 665 that could serve as stop transfer sequences. Analyses of gp160 variants expressed in vitro in a translation-coupled translocation system were consistent with the in vivo studies and provided evidence that gp160 is a simple bitopic membrane protein. A model for the orientation and function of gp160 in cellular membranes is presented. The cell lines described provide a convenient source of the gp120-gp41 complex.

AIDS-Related Complex↗
PubMed1993

Normal T cell receptor-mediated signaling in T cell lines stably expressing HIV-1 envelope glycoproteins.

A series of T cell lines transfected to stably express HIV-1 envelope (env) glycoproteins were analyzed for viability and for T cell signaling. One transfectant was distinguished by its stable expression of gp120 and gp41, whereas the remainder of the T cell lines were similar to previously reported env-expressing T cells in synthesizing predominantly unprocessed env glycoprotein gp160. All of the transfectants were additionally constructed to express tat and rev proteins. None of these cell lines displayed growth abnormalities or spontaneous cell fusion, although the cell line synthesizing env gp120/gp41 could be induced to fuse and die when cocultured with a second cell expressing surface CD4. A cell line expressing only gp160 and the transfectant expressing gp160, gp120, and gp41 could be triggered normally via CD3-cross-linking as measured by protein tyrosine phosphorylation and by the induction of the CD69 activation marker. At levels of env protein expression sufficient to mediate syncytium formation and to kill cells, these HIV-1 env transfectants displayed no intrinsic T cell signaling abnormalities, suggesting that mechanisms other than a direct intracellular action of the tat or env proteins may be contributing to the deficit in Ag-specific T cell activation described subsequent to HIV infection in vivo and in vitro.

CD4-Positive T-Lymphocytes↗
PubMed1991

Computer analysis of human immunodeficiency virus-1 envelope glycoprotein: functional topogenic domains as signals for transfer and cleavage.

Analysis of human immunodeficiency virus-1 (HIV-1) gp160 amino acid sequences by computer programs that provide information on the possible conformation, hydrophilicity, and surface probability was used to identify possible functional domains. Amino acid domains that serve as signals for transfer of the polypeptide chain through the cell membrane were identified. Stop-transfer amino acid domains present in gp160 made possible the identification of the membrane anchorage hydrophobic amino acid sequence. The characterization of amino acid domains that serve as signals for proteolytic cleavage suggest that gp41 might be cleaved in a number of positions in the polypeptide chain, releasing parts of the carboxy-terminus amino acid sequence from that part of gp41 anchored in the cell membrane. The computer analysis deals with the mode of insertion of gp160 into the cell membrane by the cellular signal recognition protein system and subsequent processing of the gp160 to gp120 and gp41 (and subpeptides). The model for the positioning of these peptides is used to predict the organization of the processed envelope proteins in the viral envelope. The possible function of domains in gp120 and gp41 during the interaction with host cells during virus infection is discussed.

Amino Acid Sequence↗
PubMed1993

Induction of human immunodeficiency virus-specific T cell responses in rhesus monkeys by synthetic peptides from gp160.

We have previously identified several synthetic peptides from conserved regions of the human immunodeficiency virus (HIV) envelope protein gp160 that have the capacity to induce broadly reactive T cell responses against gp160 in mice of several major histocompatibility complex (MHC) haplotypes. In the present investigation three rhesus monkeys were immunized with a mixture of eight synthetic peptides that are capable of inducing T cell activity in mice. Peripheral blood mononuclear cells (PBMCs) from these monkeys were monitored every 2 weeks for a period of 34 weeks for proliferative responses against individual peptides and recombinant gp160. Peripheral blood mononuclear cells from all three rhesus monkeys showed good proliferative responses with peptides 104 (aa 45-55), 111 (aa 118-130), and 63 (aa 519-543), whereas weak responses were observed with peptides 113 (aa 204-216) and 116 (aa 240-252). Two of the three rhesus monkey-derived PBMC preparations also showed good proliferative responses with peptide 61 (aa 586-598). Significant responses were not observed with peptides 105 (aa 48-61) and R15K (aa 315-329) in any of the monkeys immunized. However, PBMCs from all three monkeys showed significantly high proliferative responses with recombinant gp160, the HIV-1 envelope protein precursor. These results demonstrate that mixtures of synthetic peptides from HIV env gene product can prime gp160-specific T cell responses in rhesus monkeys.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Enhanced immunity to human immunodeficiency virus (HIV) envelope elicited by a combined vaccine regimen consisting of priming with a vaccinia recombinant expressing HIV envelope and boosting with gp160 protein.

Transmission studies have suggested that an optimal human immunodeficiency virus type 1 (HIV-1) vaccine should induce both neutralizing antibodies and cytolytic T cells to eliminate free virus and infected cells. A phase I trial in healthy HIV-1-seronegative persons was conducted with a combination HIV-1 vaccine regimen (strain IIIB) consisting of priming with a recombinant vaccinia (vac/env) virus expressing HIV-1 envelope and boosting with a gp160 glycoprotein derived from a recombinant baculovirus (rgp160). T-cell and antibody responses detected after immunization with either vac/env alone or rgp160 alone were generally of low magnitude and transient, and no subject developed neutralizing antibodies. In contrast, recipients of the combination regimen demonstrated in vitro T-cell proliferative responses to homologous HIV-1 antigens that were 3- to 10-fold higher than responses with either vaccine alone, and these responses were sustained for > 18 months in 75% of recipients. Moreover, both CD8+ and CD4+ cytolytic T cells were detected. Antibody responses (titer, 1:800 to 1:102,400) to homologous HIV envelope developed in all recipients of the combination regimen, and neutralizing antibodies were detected in 7 of 13. Thus, immunization with a live virus vaccine followed by boosting with a soluble protein offers promise for inducing the broad immunity needed in an HIV vaccine.

Baculoviridae↗
PubMed1995

Priming of class I-restricted cytotoxic T lymphocytes by vaccination with recombinant protein antigens.

We investigated the specific priming of MHC class I-restricted cytotoxic T lymphocytes (CTL) by different protein antigen preparations in mice. The recombinant viral protein antigens tested are of potential relevance for the design of subunit vaccines. They include the hepatitis B virus (HBV) surface antigen (S-antigen), the HIV-1 gp160 envelope protein, and a chimeric HIV-1 Pr55-gag/V3-3 retrovirus-like particle. In addition, ovalbumin (OVA) was tested. The native or denatured particulate (multimeric) or monomeric form of these protein antigens was injected by various routes into mice. Class I-restricted CTL were efficiently primed by a single low-dose injection of HBV S-antigen particles or the chimeric HIV-1 Pr55-gag/V3-3 particles. After SDS-denaturation, gel-purified monomeric S-antigen and monomeric Pr55-gag/V3-3 fusion protein were still very efficient in priming CTL. CTL sensitization was not detected in a (primary or boosted) response to even high doses of native OVA or native HIV-1 gp160. Denaturation of these two antigens by detergent strikingly increased their immunogenicity for CTL. Immunization of mice with non-treated or SDS-denatured antigenic peptides representing the relevant CTL-defined epitopes of the tested protein antigens did not prime CTL. These data indicate that native, particulate and denatured, monomeric protein antigens efficiently stimulate a class I-restricted CTL response.

Amino Acid Sequence↗
PubMed1999

Repeated immunization with recombinant gp160 human immunodeficiency virus (HIV) envelope protein in early HIV-1 infection: evaluation of the T cell proliferative response.

This longitudinal study was designed to evaluate cellular immunity in early-stage, asymptomatic human immunodeficiency virus (HIV)-1-infected persons (CD4 cell count,>400/mm3; median, 625/mm3) who were immunized with either recombinant (r) gp160 or placebo every 2 months for 5 years. Proliferative responses were assessed against rgp160, rp24, and a panel of recall antigens and mitogens. Despite good reactivity to recall antigens, at baseline approximately 33% had proliferative responses to gp160, and approximately 42% showed p24 gag responses. There was no statistical difference between vaccine and placebo groups for antigens or mitogens. After 1 year, approximately 73% of the subjects in the vaccine arm had new or boosted responses to gp160, versus approximately 18% in the placebo arm. Statistical significance was maintained throughout the study. Recurrent vaccination with recombinant gp160 was proven to be persistently immunogenic, increasing significantly the ability of HIV-1-infected persons to mount new proliferative responses to the vaccine.

AIDS Vaccines↗