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  • 1
    Electronic Resource
    Electronic Resource
    Verotoxins inhibit the growth of and induce apoptosis in human astrocytoma cells (1998)
    Springer
    Journal of neuro-oncology 40 (1998), S. 137-150 
    Details
    ISSN: 1573-7373
    Keywords: glycolipid receptor ; globotriaosyl ceramide ; α2 interferon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Verotoxin 1 (VT1) is an E. coli toxin comprising an A subunit with N-glycanase activity, and five smaller B subunits capable of binding to the functional receptor globotriaosylceramide (Galα1-4-Galβ1-4-Glcceramide-Gb3). VT is implicated in hemorrhagic colitis and the more serious hemolytic uremic syndrome. VT1 is active against various tumor cell lines in vitro and in vivo. To extend the anti-cancer spectrum of activity of VT to human brain tumors, in the present analysis we studied the effects of VT on the growth of 6 permanent human astrocytoma cell lines. All astrocytoma cell lines analyzed express Gb3 and were sensitive to VT-1 at a dose of 50 ng/ml, but sensitivity was not proportional to the relative Gb3 concentration. VT induced apoptosis in these cells was shown by electron microscopy. Morphological evidence (nuclear shrinkage and chromatin condensation) of apoptosis could be clearly distinguished 1.5 hrs after toxin addition. Ultrastructural preservation of organelles was observed in conjunction with blebbing of the plasma membrane, condensation of chromatin within the nucleus and nuclear shrinkage. Apoptosis was also induced by the recombinant toxin B subunit alone, suggesting that the ligation of Gb3 is the primary induction mechanism. These studies indicate that verotoxin/Gb3 targetting may provide a novel basis for the inhibition of astrocytoma tumour cell growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006010019064
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  • 2
    Electronic Resource
    Electronic Resource
    The expression and characterization of a putative adhesin B from H. influenzae (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 165 (1998), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb13137.x
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of phospholipid chain length on verotoxin/globotriaosyl ceramide binding in model membranes: comparison of a supported bilayer film and liposomes (1996)
    Springer
    Glycoconjugate journal 13 (1996), S. 159-166 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731490
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  • 4
    Electronic Resource
    Electronic Resource
    Globotriaosyl ceramide modulates interferon-α-induced growth inhibition and CD19 expression in Burkitt's lymphoma cells (1999)
    Springer
    Glycoconjugate journal 16 (1999), S. 821-828 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007145420116
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  • 5
    Electronic Resource
    Electronic Resource
    Intracellular targeting of the endoplasmic reticulum/nuclear envelope by retrograde transport may determine cell hypersensitivity to verotoxin via globotriaosyl ceramide fatty acid isoform traffic (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 177 (1998), S. 646-660 
    Details
    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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Developmentally regulated testicular galactolipid sulfotransferase inhibitor is a phosphoinositol glycerolipid and insulin-mimetic (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 462-466 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370414
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  • 7
    Electronic Resource
    Electronic Resource
    Susceptibility to verotoxin as a function of the cell cycle (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 632-639 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041500324
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