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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 165 (1998), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the H. influenzae type b (Hib) genome, two putative adhesin B genes, HI0119 and HI0362, have been identified on the basis of homology to the adhesin B (FimA) of Streptococcus parasanguis. We expressed and characterized one of them, HI0119, from a non-typeable H. influenzae strain (NTHI). This 37 kDa protein was selectively isolated from an H. influenzae surface protein (water) extract by elution from a celite matrix with EDTA. The adhesin B protein is 97.7% identical to that of H. influenzae, strain Rd, has 23.7% identity and 47.8% similarity to FimA of Streptococcus parasanguis but is distinguished from the FimA family by the absence of the N-terminal lipid anchor consensus sequence LXXC, the presence of a C-terminal disulfide-bonded domain, and a central histidine-rich domain. Recombinant fusion protein bound specifically to celite. Antisera raised against fusion protein recognized a 37 kDa protein from whole cell extracts of H. influenzae on Western blots. A truncated mutant lacking the C-terminal disulfide-bonded domain and a Cys308 to Ser mutant were constructed and expressed as fusion proteins. Both mutants retained celite binding. However, purified fusion proteins could not, unlike H. influenzae, bind Hep2 cells, suggesting that HI0119 may not be an adhesin in this organism.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4986
    Keywords: glycolipid recognition ; carbohydrate exposure ; conformation ; solid phase binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The importance of the surrounding lipid environment on the availability of glycolipid carbohydrate for ligand binding was demonstrated by studying the influence of phosphatidylcholine fatty acid chain length on binding of verotoxins (VT1 and VT2c) to their specific cell surface receptor, globotriaosylceramide (Gb3) in the presence of auxiliary lipids both in a microtitre plate surface bilayer film and in a liposome membrane model system. In the microtitre assay, both VT1 and VT2c binding to Gb3 was increased as a function of decreasing PC acyl chain length likely resulting in increased Gb3 exposure. In the liposome assay VT1 binding was similarly modulated, however the effect on VT2c binding was more complex and did not follow a simple function of increased carbohydrate exposure. Earlier work established that C22:1 and C18:1Gb3 fatty acid homologues were the preferred Gb3 receptor isoforms in the microtitre assay for VT1 and VT2c respectively. This selectivity was maintained in C16PC containing liposomes, but in C14PC liposomes, binding to C22:1Gb3 (but not C18:1Gb3) was elevated such that this Gb3 species now became the preferred receptor for both toxins. This change in verotoxin/Gb3 homologue binding selectivity in the presence of C14PC did not occur in the microtitre bilayer format. These results are consistent with our proposal that these toxins recognize different epitopes on the Gb3 oligosaccharide. We infer that relative availability of these epitopes for toxin binding in an artificial bilayer is influenced not only by the exposure due to the discrepancy between the fatty acyl chain lengths of Gb3 and PC, but by the physical mode of presentation of the bilayer structure. Such acyl chain length differences have a more marked effect in a supported bilayer film whereas only the largest discrepancies affect Gb3 receptor function in liposomes. The basis of phospholipid modulation of glycolipid carbohydrate accessibility for receptor function is likely complex and will involve phase separation, gel/liquid crystalline transition, packing and lateral mobility within the bilayer, suggesting that such parameters should be considered in the assessment of glycolipid receptor function in cells.
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  • 3
    ISSN: 1573-4986
    Keywords: B lymphocytes ; Cell Surface Molecules ; Glycosphingolipid ; Cytokines ; FACS ; CD77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previous studies have indicated that globotriaosyl ceramide (Gb3 or CD77) plays a role in α-interferon signal transduction and CD19-mediated homotypic adhesion in B cell lines derived from Burkitt's lymphoma. These roles for Gb3 may involve the proteins IFNAR-1 (subunit 1 of the interferon-α receptor) and CD19, respectively, both of which have potential Gb3-binding sites in their extracellular domains which resemble those of the verotoxin (Shiga toxin and Shiga-like toxin) B subunit. The majority of this work was performed using wild-type Daudi cells and a single, Gb3-deficient mutant cell line, VT500. In the present investigations, these and additional Daudi-derived cells with varying degrees of sensitivity to interferon-α were examined for Gb3 expression, interferon-induced growth inhibition and CD19 expression. The degree of interferon-induced growth inhibition and CD19 expression correlated with Gb3 expression in the various cell lines tested. In addition, reconstitution of the VT500 cell line with Gb3 but not other glycolipids partially restored the sensitivity of cells to IFN-induced growth inhibition. The degree to which reconstitution restored sensitivity to growth inhibition was similar to the results of previous studies in which Gb3 reconstitution restored sensitivity to verotoxin-induced cytotoxicity. These results demonstrate that Gb3 is specifically required for IFN-induced growth inhibition in Daudi cells and provide further evidence of a role for Gb3 in CD19 expression and function in these cells.
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The pentameric B subunit of verotoxin (VT) mediates the attachment to cell surface globotriaosyl ceramide (Gb3) to facilitate receptor-mediated endocytosis of the toxin. In highly toxin-sensitive tumor cells, the holotoxin and VT1 B subunit is targeted intracellularly to elements of the endoplasmic reticulum (ER)/nuclear membrane. In less sensitive cells, the toxin is targeted to components of the Golgi apparatus. We have studied two cell systems: the induced VT hypersensitivity of human astrocytoma cell lines cultured in the presence of sodium butyrate (compared to sodium propionate and capronate) and the increased VT sensitivity of multiple drug-resistant mutants as compared to parental human ovarian carcinoma cells. In both cases, a difference in the intracellular retrograde transport of the receptor-bound internalized toxin to the ER/nuclear envelope, as opposed to the Golgi, correlated with a 〉1,000-fold increase in cell sensitivity to VT. This change in intracellular routing may be due to sorting of Gb3 fatty acid isoforms, since nuclear targeting was found in turn to correlate with the preferential synthesis of Gb3 containing shorter chain (primarily C16) fatty acid species. We propose that the isoform-dependent traffic of Gb3 from the cell surface to the ER/nuclear membrane provides a new signal transduction pathway for Gb3 binding proteins. J Cell Physiol 177:646-660, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 462-466 
    ISSN: 1040-452X
    Keywords: Sulfogalactoglycerolipid ; Insulin-like growth factor 1 ; Spermatogenesis ; Phosphorylation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The synthesis of sulfogalactosyl-glycerolipid (SGG) is a differentiation marker in spermatogenesis restricted to the zygotene and early pachytene spermatocytes. The galactolipid sulfotransferase responsible for the synthesis of SGG is regulated by a phosphorylation mechanism. The activity of this enzyme is reduced in cells later in spermatogenesis by a low molecular weight inhibitor, which can be extracted in organic solvents and purified by reverse phase high pressure liquid chromatography (HPLC). This purified inhibitor is a potent postreceptor insulin-mimetic, which stimulates adipocyte lipogenesis more effectively than does insulin. Phosphoinositol (PI) glycolipids have been proposed as second messengers of the insulin phosphorylation cascade. These species contain a nonacetylated glucosamine, which renders them liable to cleavage by deamidation. The activity of the sulfotransferase inhibitor was lost following nitrous acid deamidation and was labile to PI specific phospholipase C digestion. Insulin and insulin-like growth factor I were found to inhibit germ cell synthesis of SGG in vitro to some degree but had no direct effect on the testicular galacto-lipid sulfotransferase assay. These results indicate that the sulfotransferase inhibitor is a glycosyl phosphoinositide similar to the lipid species, which mediate insulin signal transduction and suggest that germ cell SGG biosynthesis may be regulated by a receptor-mediated phosphorylation pathway. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 632-639 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Infection with Verotoxin producing Escherichia coli (VTEC) has been implicated in hemolytic uremic syndrome, the leading cause of pediatric renal failure. Verotoxin (VT) binds to globotriaosylceramide (Galα1-4Galβ1-4GlcCer Gb3) in susceptible cells. Gb3 is required for cytotoxicity and toxin-resistant cells deficient in Gb3 can be sensitized to VT cytotoxicity by incorporation of exogenous Gb3 into the cells. However, the absolute Gb3 content of cell lines does not necessarily correspond directly with the degree of sensitivity to VT. The present study demonstrates that susceptibility to VT is a function of cell growth and that stationary phase cells are resistant to VT. Using chemically synchronized Vero cells, we have also found a tenfold difference in susceptibility to VT during the cell cycle. Our experiments define a maximal sensitivity “window” of 1-2 hours from the G1/S boundary. This corresponds to increased VT binding without change in overall Gb3 content. Cell surface labelling indicated that cyclic turnover and exposure of Gb3 may be the critical parameter in determining VT sensitivity. Such changes during the cell cycle may also be of relevance in vivo in determining toxin pathology during VTEC infections and the physiology of plasma membrane Gb3.
    Additional Material: 7 Ill.
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  • 7
    Publication Date: 2011-04-03
    Print ISSN: 1552-4450
    Electronic ISSN: 1552-4469
    Topics: Biology , Chemistry and Pharmacology
    Published by Springer Nature
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  • 8
  • 9
    Publication Date: 1996-04-01
    Print ISSN: 0282-0080
    Electronic ISSN: 1573-4986
    Topics: Chemistry and Pharmacology
    Published by Springer
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  • 10
    Publication Date: 2009-05-14
    Description: Several human histo-blood groups are glycosphingolipids, including P/P1/Pk. Glycosphingolipids are implicated in HIV-host-cell-fusion and some bind to HIV-gp120 in vitro. Based on our previous studies on Fabry disease, where Pk accumulates and reduces infection, and a soluble Pk analog that inhibits infection, we investigated cell surface–expressed Pk in HIV infection. HIV-1 infection of peripheral blood–derived mononuclear cells (PBMCs) from otherwise healthy persons, with blood group P1k, where Pk is overexpressed, or blood group p, that completely lacks Pk, were compared with draw date–matched controls. Fluorescence-activated cell sorter analysis and/or thin layer chromatography were used to verify Pk levels. P1k PBMCs were highly resistant to R5 and X4 HIV-1 infection. In contrast, p PBMCs showed 10- to 1000-fold increased susceptibility to HIV-1 infection. Surface and total cell expression of Pk, but not CD4 or chemokine coreceptor expression, correlated with infection. Pk liposome–fused cells and CD4+ HeLa cells manipulated to express high or low Pk levels confirmed a protective effect of Pk. We conclude that Pk expression strongly influences susceptibility to HIV-1 infection, which implicates Pk as a new endogenous cell-surface factor that may provide protection against HIV-1 infection.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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