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PubMed1975

Nephritogenic glycoprotein. VI. Induction of proliferative glomerulonephritis with the immunofluorescent 'mesangial pattern' in rats by a single injection of soluble glycoprotein isolated from human urine.

Proliferative glomerulonephritis was induced in rats by a single injection in the hind footpads of the urinary glycoprotein or more purified urinary glycopeptide with Freund's incomplete adjuvant. Although the urinary (water-soluble and non-dialyzable) glycoprotein and glycopeptide were prepared from heterologous urines (human urines), the immunofluorescent pattern of the kidneys was not 'granular' but 'mesangial', as in rats given a single injection of homologous or heterologous renal glycoprotein with nephritogenicity. The pathogenesis of proliferative glomerulonephritis in the present experiments may be explained by the same mechanism as that of rats given a single injection of renal glycoprotein, i.e. by any mechanism other than antigen (heterologous protein)-antibody immune complex and anti-GBM antibody mechanisms.

Animals↗

PubMed1993

The MRP gene associated with a non-P-glycoprotein multidrug resistance encodes a 190-kDa membrane bound glycoprotein.

HL60 cells isolated for resistance to Adriamycin (HL60/ADR) overexpress a 190-kDa ATP binding protein which has a minor sequence homology with P-glycoprotein. It has also been observed that HL60/ADR overexpress the MRP gene which was first identified as a component of a non-P-glycoprotein mediated multidrug resistance of H69/ADR cells [Cole et al., Science (Washington DC), 258: 1650, 1992]. A complementary DNA of MRP has been cloned and based on the deduced sequence encodes a member of the superfamily of proteins which bind ATP and function in various transport processes [Cole et al., Science (Washington DC), 258: 1650, 1992]. In view of this it was of interest to identify the protein encoded by MRP and determine if it may be related to p190. In the present study we have prepared antisera against three synthetic peptides which correspond to the deduced sequence of the MRP protein. Proteins reactive with the antisera have been examined in HL60/ADR cells using Western blot analysis. All antisera react with a 190 kDa protein contained in membranes of resistant but not sensitive cells. One antiserum used for further studies is not reactive with P-glycoprotein contained in membranes of HL60 cells isolated for resistance to vincristine. Analysis of subcellular fractions demonstrates that p190 is present primarily in the endoplasmic reticulum with lower levels also present in plasma membranes. Treatment of HL60/ADR cells with tunicamycin results in the appearance of a 165-kDa resistance associated protein which reacts with the antipeptide serum. The results of this study therefore demonstrate that the MRP gene encodes a 190-kDa membrane bound glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Immunoelectron microscopy of parainfluenza virion glycoproteins with polyclonal and monoclonal antibodies: movement of glycoprotein with monoclonal antibody.

Two glycoproteins (HN and F) of parainfluenza virus were immunogold-labeled with polyclonal and monoclonal antibodies, respectively, and their labeling patterns were compared. Both glycoproteins HN and F were efficiently and homogeneously labeled with polyclonal antibodies, whereas they were labeled much less and heterogeneously with monoclonal antibodies. When either protein was initially labeled with monoclonal antibody, and then the other one, with polyclonal antibody, immunolabels of two glycoproteins were almost completely segregated. Although this segregation deformed virion morphology, it supported the concept of monoclonal antibody-mediated movements of glycoproteins.

Animals↗

PubMed1996

The interaction of the UDP-GLC:glycoprotein glucosyltransferase with the acceptor glycoprotein.

The UDP-Glyc:glycoprotein glucosyltransferase is a soluble protein of the endoplasmic reticulum that in cell-free assays glucosylates denatured but not native glycoproteins. It has been postulated that the enzyme participates in the quality control mechanism of glycoprotein folding in the endoplasmic reticulum by which only properly folded species are transported to the Golgi apparatus. This paper reports studies on the protein determinants that upon recognition by the glucosyltransferase allow the selective glucosylation of denatured glycoproteins. It is shown here that extensive chemical modification of denatured soybean agglutinin does not modify its glucose acceptor capacity, thus suggesting that the protein determinants recognized by the glucosyltransferase are not formed by specific amino acids. Moreover, it is reported that the enzyme binds patches of hydrophobic amino acids exposed in denatured but not in native conformations. As exposure of such residues is the only feature common to all misfolded conformations, it is suggested that binding to hydrophobic amino acids forms part of the recognition mechanism of denatured conformations by the glucosyltransferase.

Amino Acid Sequence↗

PubMed1995

P-glycoprotein epitope mapping. II. The murine monoclonal antibody MM6.15 to human multidrug-resistant cells binds with three distinct loops in the MDR1-P-glycoprotein extracellular domain.

A new murine monoclonal antibody (MAb), MM6.15, to human MDR1 P-glycoprotein was found to be reactive in ELISA with synthetic peptides selected from the predicted sequences of the first, fourth and sixth extracellular loop of MDR1-P-glycoprotein. In order to precisely define the MM6.15-binding site, a peptide library of overlapping 5- to 9-mer residues covering the entire sixth extracellular loop of both human and rodent class-1 P-glycoproteins was synthesized on polyethylene pins and tested for MAb binding. The results of this ELISA demonstrated that the MAb MM6.15 reacts only with human synthetic peptides and that the critical component of the MAb recognition is made up of the amino-acid sequence LVAHKL (residues 963-968 of the MDR1-P-glycoprotein) with histidine (H), lysine (K) and possibly leucine (L), key residues of this immunogenic domain.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

The effect of cytoplasmic domain mutations on membrane anchoring and glycoprotein processing of herpes simplex virus type 1 glycoprotein C.

The predicted amino acid sequence of herpes simplex virus type 1 glycoprotein C (HSV-1 gC) shows that it has the features of a typical type 1 integral membrane protein: a cleavable N-terminal signal sequence, a glycosylated ectodomain, a single transmembrane domain, and a small, charged cytoplasmic domain. In an earlier investigation of the function of the gC cytoplasmic domain, it was shown that the gC synthesized by a gC mutant, dl2, which lacked the last three residues of the transmembrane domain and the entire cytoplasmic domain, was initially synthesized as a membrane bound glycoprotein, but was not stably anchored in the plasma membrane. In this study, we generated a panel of four HSV-1 gC mutants with novel cytoplasmic domains in order to further delineate the role of this domain in stable anchoring and to investigate the role of charged residues in this process. The cytoplasmic domain mutants produced significant quantities of a novel precursor (pgC-86K), approximately 6K smaller than the wild-type gC precursor. The quantity of pgC-86K correlated with the number of positive charges in the cytoplasmic domain. Although the nature of the novel form of the precursor is unclear, its correlation with cytoplasmic domain charge suggests that an important function of this domain is to influence gC processing. Significantly, restoration of the carboxy-terminal 3 amino acids of the gC transmembrane domain restored the wild-type anchoring phenotype to gC, indicating that the cytoplasmic domain is not required for membrane anchoring. Further characterization of dl2 gC confirmed that this glycoprotein is not released from the membrane by proteolysis. We suggest that the addition of three additional hydrophobic residues to the dl2 transmembrane domain increases its hydrophobicity enough to stabilize membrane anchoring of the glycoprotein.

Amidohydrolases↗

PubMed1995

alpha 1-Acid glycoprotein binds human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein via N-linked glycans.

In the present study, we demonstrate a specific low-affinity interaction between recombinant precursor gp160 (rgp160) or surface unit gp120 (rgp120) of human immunodeficiency virus type 1 (HIV-1) and alpha 1-acid glycoprotein (AGP), a human glycoprotein displaying complex type N-glycans. Binding of rgp160/rgp120 to agarose-coupled AGP was dose-dependent, saturable, calcium-, pH- and temperature-dependent. Binding was inhibited by soluble AGP, asialo-AGP, fetuin, beta-D-GlcNAc47-BSA, alpha-D-Man20-BSA, mannan, complex-type asialo-agalacto-tetraanternary precursor oligosaccharide from human AGP and oligomannose 9 from porcine thyroglobulin; fully deglycosylated AGP was not inhibitory. The three AGP glycoforms separated on immobilized ConA bound rgp160 to the same extent as did unfractionated AGP. These findings extend our previous results on the carbohydrate-binding properties of HIV-1 envelope (Env) glycoprotein in that they demonstrate the involvement of AGP glycan moieties in the binding to rgp160/rgp120. Preincubation of rgp160 with AGP or mannan significantly reduced its binding to monocyte-derived macrophages (MDM), suggesting that AGP may play a role in preventing binding of soluble or virus-bound Env glycoprotein to CD4+ monocytic cells.

Binding, Competitive↗

PubMed2000

Effect of semisynthetic analog of alpha(1)-acid glycoprotein on immunomodulatory and antiinflammatory activity of natural glycoprotein.

Pseudo-alpha(1)-acid glycoprotein with carbohydrate chain ratio typical of native form was synthesized by a previously developed original technique of quantitative transfer of alpha(1)-acid glycoprotein carbohydrate chains to other polymeric carrier. Similarly to native glycoprotein, the semisynthetic analog inhibited lymphocyte proliferation and stimulated the production of antiinflammatory cytokines by peripheral blood mononuclear leukocytes. However, it possessed no antioxidant activity and did not inhibit complement activation by the alternative pathway. The role of carbohydrate and protein components of alpha(1)-acid glycoprotein molecule in the realization of its biological effects is discussed.

Drug Interactions↗

PubMed1997

Acquisition of taxol resistance via P-glycoprotein- and non-P-glycoprotein-mediated mechanisms in human ovarian carcinoma cells.

Taxol-resistant clones from a human ovarian carcinoma cell line (2008) were selected by an initial exposure to 0.05 microM (2008/13) or 0.5 microM (2008/17) taxol. Thereafter, a series of clones with increasing taxol resistance were derived from the 2008/17 and 2008/13 cells by stepwise sequential exposure to increasing concentrations of taxol. The 2008/17 clones displayed a classical P-glycoprotein-mediated drug-resistance phenotype. In contrast, the 2008/13 clones followed the classical P-glycoprotein-mediated resistance phenotype until a 245-fold taxol-resistant clone (2008/13/2) was obtained, which was followed by a further increase in the degree of resistance but significant down-regulation of P-glycoprotein expression in the 252-fold taxol-resistant 2008/13/4 cells. This clone (2008/13/4) also accumulated significantly higher intracellular levels of taxol than those expressing the P-glycoprotein. No correlation between the expression of the multidrug resistance-associated protein and taxol resistance was observed. Verapamil increased the sensitivity of all drug-resistant clones to taxol, and this was probably related to the ability of verapamil to increase the intracellular concentration of taxol (except in the case of 2008/13/4 cells). The 2008/17 clones were highly cross-resistant to Adriamycin, etoposide, and vincristine. They also displayed a low level of cross-resistance to camptothecin but were not cross-resistant to cisplatin. The taxol-resistant 2008/13 clones displayed a similar pattern of cross-resistance for all drugs (except Adriamycin). The 2008/13 clones were only 2-to 4-fold cross-resistant Adriamycin. The levels of alpha-tubulin and beta-tubulin were similar in the parental 2008 and taxol-resistant 2008/13/4 cells. Furthermore, the in vitro binding of [3H]taxol to semipurified microtubule preparations derived from the parental 2008 and the taxol-resistant 2008/13/2 and 2008/13/4 cells was similar. These results show that in human ovarian carcinoma cells resistance to taxol can be acquired via as yet undescribed mechanisms.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2002

Shiga-like toxin II modifies brain distribution of a P-glycoprotein substrate, doxorubicin, and P-glycoprotein expression in mice.

The effect of Shiga-like toxin II (SLT-II), which was derived from Escherichia coli O157:H7, on doxorubicin transport across the blood-brain barrier (BBB) and P-glycoprotein function, was investigated in ddY mice. Doxorubicin (30 mg kg(-1)) was administered intravenously or fluorescein isothiocyanate labeled dextran (FD-4) was infused (20 microg min(-1)) to the mice, who had received an intravenous injection of SLT-II (0.2 microg/animal) 6 or 24 h earlier. Blood and brain were removed 4 h after injection of doxorubicin or 60 min after infusion of FD-4. SLT-II significantly elevated the brain concentration and brain-to-plasma concentration ratio (K(p)) of doxorubicin and FD-4 24 h after injection, but did not alter 6 h after. Cyclosporin A (200 mg kg(-1)) significantly increased the K(p) value of doxorubicin in the control mice, but did not alter it in mice treated 24 h earlier with SLT-II. Pentoxifylline (100 mg kg(-1)) a TNF-alpha production inhibitor, ameliorated SLT-II-induced increases in the brain concentrations of both drugs and the K(p) value of FD-4, suggesting that TNF-alpha, at least in part, causes damage to the brain capillaries. Western blot analysis revealed that SLT-II increased the protein level of P-glycoprotein in the brain of mice 6 h after injection and the increased level remained unchanged for 24 h. SLT-II did not change ATP content in the brain of mice. These results suggest that the increased P-glycoprotein level cannot explain SLT-II-induced increase in the doxorubicin accumulation in brain. The present findings indicate that SLT-II impairs the BBB function and doxorubicin transport across the BBB, while it overexpresses P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1981

Amino acid and carbohydrate structural variants of glycoprotein products (M-N glycoproteins) of the M-N allelic locus.

Major glycoprotein of MgM, MM Miltenberger III (MiIII), and M-N erythrocyte membranes from individual donors were cleaved with CNBr and their amino-terminal octapeptides were examined with respect to amino acid and carbohydrate composition. The amino-terminal octapeptides from the heterozygous MgM donor were resolved into two types, A and A'. MgM A was identical to octapeptide A from MM glycoproteins in carbohydrate and amino acid compositions. MgM A' exhibited amino acid composition similar to NN peptide A except for a single substitution of an Asx for a Thr and, as a result, was not glycosylated. MM(MiIII) octapeptide A was identical to M peptide A in amino acid composition, but differed in carbohydrate content. This glycopeptide contained three O-glycosidically linked carbohydrate units, one of which contained GlcNAc bound to a core of NeuAc, Gal, and GalNAc. About two such units were also present in the CNBr glycopeptide B of the glycoprotein, and on the basis of studies with alkaline borohydride and alkaline sulfite degradations, these units are believed to have the following structure: (formula see text) The Mg is an allelomorph of the M-N locus, likely evolved from a single base substitution in the N gene. The resulting single amino acid substitution effects the posttranslational carbohydration of neighboring Ser and Thr residues. The MM(MiIII) appears to be a product of the M gene that undergoes sequences of posttranslational glycosylations different from those of the M-N glycoproteins.

Alleles↗

PubMed2003

Functional evolution of the HIV-1 envelope glycoprotein 120 association site of glycoprotein 41.

Protein-protein interaction surfaces can exhibit structural plasticity, a mechanism whereby an interface adapts to mutations as binding partners coevolve. The HIV-1 envelope glycoprotein gp120-gp41 complex, which is responsible for receptor attachment and membrane fusion, represents an extreme example of a coevolving complex as up to 35% amino acid sequence divergence has been observed in these proteins among HIV-1 isolates. In this study, the function of conserved gp120 contact residues, Leu593, Trp596, Gly597, Lys601, and Trp610 within the disulfide-bonded region of gp41, was examined in envelope glycoproteins derived from diverse HIV-1 isolates. We found that the gp120-gp41 association function of the disulfide-bonded region is conserved. However, the contribution of individual residues to gp41 folding and/or stability, gp120-gp41 association, membrane fusion function, and viral entry varied from isolate to isolate. In gp120-gp41 derived from the dual-tropic isolate, HIV-189.6, the importance of Trp596 for fusion function was dependent on the chemokine receptor utilized as a fusion cofactor. Thus, the engagement of alternative chemokine receptors may evoke distinct fusion-activation signals involving the site of gp120-gp41 association. An examination of chimeric glycoproteins revealed that the isolate-specific functional contributions of particular gp120-contact residues are influenced by the sequence of gp120 hypervariable regions 1, 2, and 3. These data indicate that the gp120-gp41 association site is structurally and functionally adaptable, perhaps to maintain a functional glycoprotein complex in a setting of host selective pressures driving the rapid coevolution of gp120 and gp41.

Amino Acid Sequence↗

PubMed1996

The paramyxovirus simian virus 5 hemagglutinin-neuraminidase glycoprotein, but not the fusion glycoprotein, is internalized via coated pits and enters the endocytic pathway.

The hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins of the paramyxovirus simian virus 5 (SV5) are expressed on the surface of virus-infected cells. Although the F protein was found to be expressed stably, the HN protein was internalized from the plasma membrane. HN protein lacks known internalization signals in its cytoplasmic domain that are common to many integral membrane proteins that are internalized via clathrin-coated pits. Thus, the cellular pathway of HN protein internalization was examined. Biochemical analysis indicated that HN was lost from the cell surface with a t1/2 of approximately 45-50 min and turned over with a t1/2 of approximately 2 h. Immunofluorescent analysis showed internalized SV5 HN in vesicle-like structures in a juxtanuclear pattern coincident with the localization of ovalbumin. In contrast the SV5 F glycoprotein and the HN glycoprotein of the highly related parainfluenza virus 3 (hPIV-3) were found only on the cell surface. Immunogold staining of HN on the surface of SV5-infected CV-1 cells and examination using electron microscopy, showed heavy surface labeling that gradually decreased with time. Concomitantly, gold particles were detected in the endosomal system and with increasing time, gold-labeled structures having the morphology of lysosomes were observed. On the plasma membrane approximately 5% of the gold-labeled HN was found in coated pits. The inhibition of the pinching-off of coated pits from the plasma membrane by cytosol acidification significantly reduced HN internalization. Internalized HN was co-localized with gold-conjugated transferrin, a marker for the early endosomal compartments, and with gold-conjugated bovine serum albumin, a marker for late endosomal compartments. Taken together, these data strongly suggest that the HN glycoprotein is internalized via clathrin-coated pits and delivered to the endocytic pathway.

Cell Line↗

PubMed1991

Properties and evolutionary relationships of the Marek's disease virus homologues of protein kinase, glycoprotein D and glycoprotein I of herpes simplex virus.

The deduced amino acid sequences of the open reading frames (ORFs) mapping in the short unique segment (US) of Marek's disease virus (MDV) reported in the accompanying paper have been analysed using computer programs to determine their relationships to herpesvirus proteins. Analysis of the catalytic domains of protein kinases showed that the MDV kinase (MDV PK) was closely related to the alphaherpesvirus protein kinase mapping in US. The results also showed that the MDV PK was more closely related to the cellular kinases that control cell division than to the proto-oncogenes c-src and c-mos and it was predicted that the MDV PK would phosphorylate serine/threonine. The MDV homologue of herpes simplex virus (HSV) glycoprotein D (gD) contained several residues that were conserved in mammalian herpesviruses. In particular, six cysteines were perfectly aligned in all the gDs and there were numerous conservative substitutions. Although only approximately 65% of the MDV homologue of glycoprotein I (gI) of HSV has been sequenced, it was clear that a significant number of amino acid residues including four cysteines were conserved in the gI homologues of MDV and mammalian herpesviruses. Further analysis suggested that MDV gD was more closely related to the gDs of pseudorabies virus (PRV) and equine herpesvirus 1 than to the gD of HSV-1 and HSV-2. It was noted that HSV-2 glycoprotein G (gG), PRV gX and MDV gD were related and that MDV ORF4 was related to MDV gD and probably to HSV-1 gG. The results have shown a clear relationship between the genes of MDV and their counterparts in mammalian alphaherpesviruses and are consistent with the idea that MDV glycoprotein genes in US might have arisen by a process of gene duplication and independent evolution.

Amino Acid Sequence↗

PubMed1994

The equine herpesvirus type 1 glycoprotein homologous to herpes simplex virus type 1 glycoprotein M is a major constituent of the virus particle.

Glycoprotein 45 is a major envelope glycoprotein of equine herpesvirus type 1. The gene encoding this protein is located between map units 0.615 and 0.636 on the virus genome and evidence has suggested that it is encoded by gene 52, one of four genes within this region. Using PCR we have amplified gene 52 and subsequently cloned it into a mammalian expression vector under the control of the human cytomegalovirus immediate early gene promoter. The gene was expressed in COS-7 cells and its product was detected by immunofluorescence and Western blotting. The results indicate that glycoprotein 45 is encoded by gene 52, and that it is the homologue of herpes simplex virus type 1 glycoprotein M.

Base Sequence↗

PubMed1999

N- and C-terminal external domains of human herpesvirus-6 glycoprotein H affect a fusion-associated conformation mediated by glycoprotein L binding the N terminus.

Human herpesvirus-6 (HHV-6), like other betaherpesviruses, shows cell fusion with wild-type strains, and this cellular spread is mediated by the glycoprotein gH/gL complex. Anti-fusion monoclonal antibodies (MAbs) specific for HHV-6 glycoprotein gH inhibit infection and prevent cellular spread by syncytia formation. Reactivity of these MAbs with gH deletion mutants suggests a conserved C-terminal fusion-associated domain. A conserved motif here has an N-glycosylation site and characteristics of a beta turn. Motif deletion abrogated MAb recognition while co-expression with glycoprotein gL restored this conformational epitope, indicating the importance of folding and not glycosylation at this site. Our previous studies showed gL binding to gH at an N-terminal domain specific for betaherpesviruses. To further examine the function of this N-terminal domain, a betaherpesvirus-specific motif was deleted. This mutant gH still bound gL, and was recognized by the anti-fusion MAbs; however, recognition was now primarily in the immature form and reduced during processing to the mature form. A model is discussed whereby gL binding gH at the N-terminal domain acts to draw together the C-terminal extracellular domain and this interaction affects a functional conformation during glycoprotein maturation.

Animals↗

PubMed1983

Insertion mutants of herpes simplex virus have a duplication of the glycoprotein D gene and express two different forms of glycoprotein D.

We produced insertion mutants of herpes simplex virus (HSV) that contain two functional copies of genes encoding different forms of glycoprotein D (gD). These viruses have the gene for HSV type 2 (HSV-2) gD at the normal locus and the gene for HSV-1 gD inserted into the thymidine kinase locus. Results of immunoprecipitation experiments done with monoclonal antibodies revealed that both gD genes were expressed by these viruses, regardless of orientation of the inserted HSV-1 gD gene, and that maximal synthesis of both glycoproteins depended on viral DNA replication. This apparently normal expression of the inserted HSV-1 gD gene was from a DNA fragment (SacI fragment, 0.906 to 0.924 map units) containing nucleotide sequences extending from approximately 400 base pairs upstream of the 5' end of the gD mRNA to about 200 base pairs upstream of the 3' end. The glycoproteins expressed from both genes were incorporated into the surfaces of infected cells. Electrophoretic analyses of purified virions and neutralization studies suggest that both glycoproteins were also incorporated into virions. This nonpreferential utilization of both gene products makes these viruses ideal strains for the generation and characterization of a variety of mutations.

Animals↗

PubMed1992

The transmembrane glycoprotein of human immunodeficiency virus type 1 induces syncytium formation in the absence of the receptor binding glycoprotein.

To study the intracellular transport and biological properties of the human immunodeficiency virus type 1 (HIV-1) transmembrane glycoprotein (TM; gp41), we constructed a truncated envelope gene in which the majority of the coding sequences for the surface glycoprotein (SU; gp120) were deleted. Transient expression of this truncated env gene in primate cells resulted in the biosynthesis of two proteins with M(r)s of 52,000 and 41,000, respectively. Immunofluorescence studies with antibodies to the HIV-1 TM protein indicated that the intracellular and surface localization of these proteins were indistinguishable from those of the native HIV-1 gp120-gp41 complex. These results indicate that the oligosaccharide processing and cell surface transport of the HIV-1 TM protein were not dependent on the presence of the receptor binding subunit, gp120. Syncytium formation was readily detected upon expression of the deleted HIV-1 env gene into COS and CD4+ HeLa cell lines, suggesting that in the absence of gp120, the TM protein retained biological activity. This observation was confirmed by infection of primate and mouse cell lines with a recombinant vaccinia virus (vvgp41) expressing the truncated HIV-1 env gene. These results strongly suggest that (i) the two biological activities of the HIV-1 envelope glycoprotein can occur independently and (ii) the association of the two glycoprotein subunits may restrict the fusion activity of the transmembrane component to CD4+ cells.

Amino Acid Sequence↗