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PubMed1986

Pathogenesis of shigella diarrhea. XI. Isolation of a shigella toxin-binding glycolipid from rabbit jejunum and HeLa cells and its identification as globotriaosylceramide.

A glycolipid that specifically binds shigella toxin was isolated from both HeLa cells and rabbit jejunal mucosa and identified as globotriaosylceramide (Gb3) by its identical mobility on HPTLC to authentic erythrocyte Gb3. Toxin also bound to a band tentatively identified as alpha-hydroxylated Gb3. In addition, toxin bound to P1 antigen present in group B human erythrocyte glycolipid extracts. The common feature of the three binding glycolipids is a terminal Gal alpha 1----4Gal disaccharide linked beta 1----4 to either Glc or GlcNAc. Globoisotriaosylceramide, which differs from Gb3 only in possessing a Gal alpha 1----3Gal terminal disaccharide, and LacCer, which lacks the terminal Gal residue of Gb3, were incapable of binding the toxin. Binding was shown to be mediated by the B subunit by the use of isolated toxin A and B subunits and monoclonal subunit-specific antibodies. Gb3-containing liposomes competitively inhibited the binding of toxin to HeLa cell monolayers but did not inhibit toxin-induced cytotoxicity. These studies show an identical carbohydrate-specific glycolipid receptor for shigella toxin in gut and in HeLa cells. The toxin B subunit that mediates this binding has also been shown to recognize a glycoprotein receptor with different sugar specificity. Thus, we have demonstrated that the same small (Mr 6,500) B subunit polypeptide has two distinctive carbohydrate-specific binding sites. The Gal alpha 1----4Gal disaccharide of the glycolipid toxin receptor is also recognized by the Gal-Gal pilus of uropathogenic E. coli. This suggests the possibility that the pilus and toxin B subunit contain homologous sequences. If this is true, it may be possible to use the purified Gal-Gal pilus to produce toxin-neutralizing antibodies.

Animals↗
PubMed2000

In vivo identification of glycolipid antigen-specific T cells using fluorescent CD1d tetramers.

The CD1 family of major histocompatibility complex (MHC)-like molecules specializes in presenting lipid and glycolipid antigens to alpha/beta T lymphocytes, but little is known about the size of the CD1-restricted T cell population or the frequency of T lymphocytes specific for a given glycolipid antigen. Here, we report the generation and use of mouse CD1d1-glycolipid tetramers to visualize CD1d-restricted T cells. In contrast with previous BIAcore-based estimates of very short half-lives for CD1d-glycolipid complexes, we found that the dissociation rate of several different CD1d-glycolipid complexes was very slow. Fluorescent tetramers of mouse CD1d1 complexed with alpha-galactosylceramide (alphaGalCer), the antigen recognized by mouse Valpha14-Jalpha281/Vbeta8 and human Valpha24-JalphaQ/Vbeta11 natural killer T (NKT) cell T cell receptors (TCRs), allowed us for the first time to accurately describe, based on TCR specificity, the entire population of NKT cells in vivo and to identify a previously unrecognized population of NK1.1-negative "NKT" cells, which expressed a different pattern of integrins. In contrast, natural killer (NK) cells failed to bind the tetramers either empty or loaded with alphaGalCer, suggesting the absence of a CD1d-specific, antigen-nonspecific NK receptor. Mouse CD1d1-alphaGalCer tetramers also stained human NKT cells, indicating that they will be useful for probing a range of mouse and human conditions such as insulin-dependent diabetes mellitus, tumor rejection, and infectious diseases where NKT cells play an important role.

Animals↗
PubMed1991

Mycolic acid-containing glycolipid as a possible virulence factor of Rhodococcus equi for mice.

By the use of various Rhodococcus equi strains differing in the length of carbon chains of glycolipid, we examined whether the glycolipid, glucose monomycolate, was contributing to the virulence of R. equi for mice. R. equi strains with longer carbon chain mycolic acid showed a higher virulence as determined by lethality and granuloma formation in mice than those with shorter ones. When purified glycolipid was injected into mice, granuloma formation and liver damage were most prominent with the glycolipid having longer carbon chain mycolic acid. Only a representative strain with longer carbon chain mycolic acid persisted in the spleen of mice after intravenous injection, while a strain with shorter carbon chain mycolic acid was readily eliminated. These results suggested that glycolipid was at least one of the virulence factors of R. equi and that the carbon chain length of mycolic acid might be critical in the expression of virulence.

Actinomycetales Infections↗
PubMed1970

Role of Glycolipids and Phosphatidylglycerol in the Serological Activity of Mycoplasma pneumoniae.

Mycoplasma pneumoniae lipids were fractionated by combined silicic acid and diethylaminoethyl-cellulose chromatography. The lipid fractions were tested for complement-fixing activity and for blocking of metabolism-inhibiting antibodies in human and rabbit antisera to M. pneumoniae. Thin-layer chromatography and carbohydrate analysis of hydrolysates of the lipid fractions indicated that glycolipids were responsible for the specific serological activities of the lipid extracts of the organism. Phosphatidylglycerol, which accompanied the glycolipids, was serologically inactive when isolated free from glycolipids. Phosphatidylglycerol considerably enhanced the serological activity of the glycolipids, serving as an auxiliary lipid. Because of this auxiliary effect, minute quantities of contaminating glycolipids sufficed to render serological activity to "purified" phosphatidylgylcerol preparations, providing an explanation to the previous identification of the active lipid as a phospholipid.

Journal Article↗
PubMed1992

Structural characterization of free glycolipids which are potential precursors for glycophosphatidylinositol anchors in mouse thymoma cell lines.

Biosynthesis of glycophosphatidylinositol-anchored membrane glycoproteins proceeds through the attachment of a preformed glycolipid onto a C-terminal amino acid rapidly after translation. Here we describe the structural analysis of two very polar glycolipids which can be observed after metabolic labeling of lymphoma cell lines S1A and EL-4 with either tritiated myo-inositol, mannose, or ethanolamine. These lipids are not made by mutant cells deficient in the biosynthesis of glycophosphatidylinositol anchors. The lipids were isolated, and their carbohydrate moiety was characterized using hydrofluoric acid dephosphorylation, nitrous acid deamination, acetolysis, exoglycosidase treatments, and combinations thereof to produce labeled fragments which could be analyzed by paper chromatography. Results are compatible with the structure (X-->)Man alpha 1,2 Man alpha 1,6(Y-->)Man alpha-GlcN-acylinositol, X and Y being hydrofluoric acid-sensitive substituents (most likely phosphoethanolamine). The anchor oligosaccharide of the glycophosphatidylinositol protein anchors of S1A cells was isolated, similarly characterized, and found to contain the identical carbohydrate structure. Pulse-chase experiments indicate that the very polar glycolipids have half-lives which are much longer than the one of phosphatidylinositol. The results suggest that these very polar glycolipids represent supernumerary precursor glycolipids which did not get transferred onto proteins or represent processed forms of such precursors.

Animals↗
PubMed1986

Identification of a glycolipid precursor of the Trypanosoma brucei variant surface glycoprotein.

The variant surface glycoprotein (VSG) of Trypanosoma brucei has a glycolipid covalently attached to its C terminus. This glycolipid, which anchors the protein to the cell membrane, is attached to the VSG polypeptide within 1 min after translation (Bangs, J. D. Hereld, D., Krakow, J.L., Hart, G. W., and Englund, P. T. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 3207-3211). This rapid processing suggests that, prior to incorporation, the glycolipid may exist in the cell as a preformed precursor which is transferred to the VSG polypeptide en bloc. We have isolated a molecule which has properties consistent with it being a VSG glycolipid precursor. It is highly polar and can be labeled by [3H] myristate but not by [3H]palmitate. It reaches steady state during continuous labeling with [3H]myristate and shows rapid turnover in pulse-chase experiments, suggesting that it is a metabolic intermediate rather than an end product. When treated with HNO2 it liberates phosphatidylinositol, as does VSG (Ferguson, M. A. J., Low, M. G., and Cross, G. A. M. (1985) J. Biol. Chem. 260, 14547-14555). Also, like VSG, it releases a compound which co-migrates on thin layer chromatography with dimyristylglycerol when treated with the purified endogenous phospholipase C from trypanosomes. After treatment with this lipase, the putative precursor can be immunoprecipitated by antibodies directed against the C-terminal cross-reactive antigenic determinant of the VSG. These data provide strong evidence that this glycolipid is a VSG precursor.

Animals↗
PubMed1985

Lea-active heptaglycosylceramide, a hybrid of type 1 and type 2 chain, and the pattern of glycolipids with Lea, Leb, X (Lex), and Y (Ley) determinants in human blood cell membranes (ghosts). Evidence that type 2 chain can elongate repetitively but type 1 chain cannot.

Two major glycolipids reactive with the monoclonal anti-Lea antibody have been isolated from human blood cell membranes. One component was identified as lactofucopentaosyl(II)ceramide and the other as a ceramide heptassaccharide with the structure described below: (formula; see text) The structure includes the Lea determinant (type 1 chain) linked to lactoneotetraosylceramide (type 2 chain); thus, it is regarded to be a hybrid between type 1 and 2 chain. In addition, a minor component having the thin-layer chromatographic mobility of a ceramide nonasaccharide, which was reactive to anti-Lea antibody, was detected. No other component with a thin-layer chromatographic mobility slower than the above components and reactive to the anti-Lea antibody was detected. In contrast, a series of slowly migrating glycolipids having X (Lex) determinant (Gal beta 1----4(Fuc alpha 1----3)GlcNAc) was detected. A similar series of long chain glycolipids having Y (Ley) determinant (Fuc alpha 1----2Gal beta 1----4(Fuc1----3)GlcNAc) was detected in human blood cells; in contrast, only one major Leb glycolipid was found with the mobility of a ceramide hexasaccharide. No glycolipid with a long carbohydrate chain composed exclusively of type 1 chain was detected. Thus, chain elongation may proceed through type 2 chain, but not through type 1 chain. Lea and X (Lex) haptens are distributed equally among blood group A, B, and O red blood cells, whereas the quantity of Leb and Y (Ley) haptens is much lower in A and B blood cells than in O blood cells.

ABO Blood-Group System↗
PubMed1997

Le(y) glycolipid acts as a co-factor for tumor procoagulant activity.

We have generated a monoclonal antibody (MAb), FS01, which inhibits the procoagulant activity (CCA-1) produced by a human squamous cell carcinoma cell line, LK52. Expression of the antigen recognized by FS01 MAb in various cancer cell lines correlated well with the procoagulant activities of the expressing cell lines. Our objective was to characterize the molecule reacting with FS01 MAb and to analyze its involvement in the CCA-1 procoagulant activity. The molecule was identified as a glycolipid and found to be involved in the procoagulant activity because both procoagulant activity and reactivity to FS01 MAb were lost after endoglycoceramidase treatment of CCA-1. Furthermore, FS01 MAb recognized the Lewis Y (Le[y]) antigen. To confirm the involvement of a glycolipid incorporating the Le(y) antigen in the procoagulant activity, we attempted to purify CCA-1 from LK52 culture supernatant. In one of the purification steps, a fraction containing low procoagulant activity (CCA-1p) separated from the Le(y)-positive fraction (CCA-1c). Although CCA-1c alone did not show procoagulant activity, the procoagulant activity of CCA-1p was augmented by CCA-1c and this augmentation was inhibited by FS01 MAb. Furthermore, CCA-1c enhanced the procoagulant activity of 33 cell lines tested as well as CCA-1p. In addition, purified Le(y) glycolipid from canine intestine augmented the procoagulant activity of CCA-1p, and this augmentation also could be inhibited by FS01 MAb. We conclude that Le(y) glycolipid is a co-factor for the procoagulant activity derived from cancer cells.

Animals↗
PubMedDate not supplied

Characterization of protein-glycolipid recognition at the membrane bilayer.

A growing number of important molecular recognition events are being shown to involve the interactions between proteins and glycolipids. Glycolipids are molecules in which one or more monosaccharides are glycosidically linked to a lipid moiety. The lipid moiety is generally buried in the cell membrane or other bilayer, leaving the oligosaccharide moiety exposed but in close proximity to the bilayer surface. This presents a unique environment for protein-carbohydrate interactions, and studies to determine the influence of the bilayer on these phenomena are in their infancy. One important property of the bilayer is the ability to orient and cluster glycolipid species, as strong interactions in biological systems are often achieved through multivalency arising from the simultaneous association of two or more proteins and receptors. This is especially true of protein-carbohydrate binding because of the unusually low affinities that characterize the monovalent interactions. More recent studies have also shown that the composition of the lipid bilayer is a critical parameter in protein-glycolipid recognition. The fluidity of the bilayer allows for correct geometric positioning of the oligosaccharide head group relative to the binding sites on the protein. In addition, there are activity-based and structural data demonstrating the impact of the bilayer microenvironment on the modulation of oligosaccharide presentation. The use of model membranes in biosensor-based methods has supplied decisive evidence of the importance of the membrane in receptor presentation. These data can be correlated with three-dimensional structural information from X-ray crystallography, NMR, and molecular mechanics to provide insight into specific protein-carbohydrate inter--actions at the bilayer.

Antibodies, Monoclonal↗
PubMed1999

Self glycolipids as T-cell autoantigens.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by discrete areas of demyelination. An autoimmune response against components of myelin is thought to contribute to disease pathogenesis. Here we identify glycolipids as new targets recognized by T cells in multiple sclerosis patients. Circulating T cells reactive with glycolipids are more frequent in MS patients than in control donors as shown by enzyme-linked immunospot assay. They specifically recognize different types of glycolipids, such as gangliosides, sulfatide and galactosylceramide and release IFN-gamma and TNF-alpha. T cells specific for gangliosides were found to be CD8+, TCR alphabeta+, restricted by the MHC-like CD1b molecule and specific for epitopes residing in the carbohydrate moiety of gangliosides. Our findings suggest that in addition to self proteins, self glycolipids may represent potential source of autoantigens recognized by T cells in autoimmune diseases.

Adult↗
PubMed1989

Analysis of glycolipids by fast atom bombardment mass spectrometry.

The positive and negative ion fast atom bombardment (FAB) mass spectra of four glycolipids obtained from microbial cultures are reported. The spectra of the glycolipids in the positive ion mode are characterized by abundant [M + Na]+, [M + Na + matrix]+ and [M + 2Na - H]+ species. In negative FAB conditions the molecules yield [M - H]-. Our understanding of the FAB behaviour of glycolipids in both positive and negative modes has been considerably aided in the structure elucidation, without any derivatization or degradation reaction of the compounds studied. The technique allows unambiguous molecular weight determination of low-microgram amounts of these glycolipids purified from biological sources and provides useful fragmentation information.

Glycolipids↗
PubMed1983

In vitro induction of tumor-specific immunity by highly purified VSV grown in SV40-transformed cells and tumor glycolipids incorporated into liposomes.

Cytotoxic effector lymphocytes (CL) were induced by in vitro immunization of spleen cells from normal Syrian hamsters to syngeneic tumor cells, either SV40-transformed (EH-SV) or spontaneously transformed (EH-N). The lymphocyte reactivity was measured in a direct 51Cr release cytotoxicity assay performed with EH-SV- and EH-N-labelled targets. A specific cytotoxic effect against tumor cells carrying the sensitizing antigens was observed. Cytotoxic effector lymphocytes were also induced by in vitro immunization of hamster spleen cells to highly purified vesicular stomatitis virus (VSV) grown either in syngeneic SV40-transformed fibroblasts or in "normal" fibroblasts. Purified virus possessing an intact envelope or virus subparticles devoid of their glycoprotein spikes stimulated the cellular immune responses against host tumor antigens present within the viral envelope. Cytotoxicity assays have revealed two tumor-specific antigens (TSA), one induced by SV40 and present in SV40-transformed cell lines and the other present in "normal" cells. CL were also induced by in vitro sensitization of spleen cells from normal hamsters to liposomes containing the polar glycolipid fraction from EH-SV and/or EH-N cells. A specific cytotoxic effect against tumor cells that have supplied the glycolipid extract was observed, suggesting specific recognition of glycolipid antigens characteristic for each tumor line. This study supports the view that surface glycolipids act as tumor-specific antigens implicated in the destruction of SV40-induced tumors in Syrian hamsters.

Animals↗
PubMed1994

Glycosylphosphatidylinositol membrane anchors in Saccharomyces cerevisiae: absence of ceramides from complete precursor glycolipids.

Glycosylphosphatidylinositol (GPI) anchoring of membrane proteins occurs through two distinct steps, namely the assembly of a precursor glycolipid and its subsequent transfer onto newly synthesized proteins. To analyze the structure of the yeast precursor glycolipid we made use of the pmi40 mutant that incorporates very high amounts of [3H]mannose. Two very polar [3H]mannose-labeled glycolipids named CP1 and CP2 qualified as GPI precursor lipids since their carbohydrate head group, Man alpha 1,2(X-->PO4-->6)Man alpha 1,2Man alpha 1,6Man alpha-GlcN-inositol (with X most likely being ethanolamine) comprises the core structure which is common to all GPI anchors described so far. CP1 predominates in cells grown at 24 degrees C whereas CP2 is induced by stress conditions. The apparent structural identity of the head groups suggests that CP1 and CP2 contain different lipid moieties. The lipid moieties of both CP1 and CP2 can be removed by mild alkaline hydrolysis although the protein-bound GPI anchors made by the pmi40 cells under identical labeling conditions contain mild base resistant ceramides. These findings imply that the ceramide moiety found on the majority of yeast GPI anchored proteins is added through a lipid remodeling step that occurs after the addition of the GPI precursor glycolipids to proteins.

Alkalies↗
PubMed1987

Human teratocarcinoma stem cells: glycolipid antigen expression and modulation during differentiation.

Teratocarcinomas are germ cell tumors in which pluripotent stem cells, embryonal carcinoma (EC) cells, undergo differentiation along the pathways resembling those occurring during early embryogenesis. Human EC cell lines established in vitro provide a model for studying embryonic cellular differentiation in a way that is pertinent to early human development. The predominant glycolipid antigens expressed by EC cells of both humans and mice have globoseries core structures; in humans they are terminally modified to yield the monoclonal antibody-defined stage-specific embryonic antigens SSEA-3 and SSEA-4, and also globo-ABH antigens; in the mouse terminal modification yields the Forssman antigen rather than SSEA-3 and -4. These observations focus attention on the possible role of the P-blood group system, which regulates synthesis of globoseries oligosaccharides, in the behavior of cells in the early embryo and in teratocarcinomas. Marked changes in the core structures of the cell surface glycolipids occur as the EC cells differentiate; thus globoseries structures rapidly diminish and are replaced by lactoseries and then by ganglioseries glycolipids. During differentiation of the NTERA-2 line of pluripotent human EC cells into neurons and other cell types, the various subsets of differentiated cells that arise are distinguished by their differential expression of new glycolipid antigens, particularly ganglioside GT3 (recognized by antibody A2B5), and ganglioside 9-0-acetyl GD3 (recognized by antibody ME311). Neurons are found among the A2B5+/ME311- cells.

Antigens, Differentiation↗
PubMed1988

Glycolipid induced proliferation of lipopolysaccharide hyporesponsive C3H/HeJ splenocytes.

Although the C3H/HeJ mouse is hyporesponsive to lipopolysaccharides (LPS), certain forms of the lipid A fraction have been shown to stimulate cells from this mouse strain. To determine the role of the oligosaccharide chain length on the lipid A-induced proliferation of C3H/HeJ splenocytes, a panel of glycolipids from R-chemotypes (Re, Rc, and Rd) and a nontoxic monophosphoryl lipid A (MPL) were tested. The MPL cells isolated from the MPL of Salmonella minnesota, Salmonella typhimurium, and the Reglycolipids isolated from Escherichia coli were found to be effective at stimulating the LPS-hyporesponsive spleen cells. A Re-glycolipid isolated from a different strain of E. coli cells was inactive, as were the S. minnesota Rc and Rd chemotypes. Proliferation induced by MPL and the active Re preparations was dose dependent and was inhibited by polymyxin B. Thus, if contamination of the Re-LPS or MPL with lipid A-associated protein occurred, it was below functional levels. The data suggest that the C3H/HeJ spleen cells are capable of responding to certain glycolipids, but they may lack the ability to convert native LPS into a stimulatory signal. In addition, a monosaccharide precursor of lipid A (lipid X), and a monoacyl glucosamine phospholipid derivative of lipid X (MaGP), were capable of inhibiting the proliferation induced by the MPL and Re-glycolipids. These data are compatible with the existence of a spleen cell receptor for lipid A.

Animals↗
PubMed2003

Influence of spacer length on the agglutination of glycolipid-incorporated liposomes by ConA as model membrane.

Through a systematic investigation of the agglutination of long chain mannolipid and glucolipid incorporated liposomes by concanavalin A (ConA) it was found that the agglutination was dependent on different factors. The studied factors reported here are (1) spacer length and (2) ground lipid matrix. The threshold and the relative saturating ConA binding concentration (saturation point to attain the binding saturation condition) of glycosides with varying spacer length for agglutination are dependent on the spacer length of the glycolipid. These concentrations decrease with the increasing number of in-built ethyleneoxy spacer length in the glycolipid and find its minimum with 6 spacer units; it increases then more and more with increasing number of spacer units (>6 units). This is supposed to be due to the requirement of a proper distance of the hydrophilic determinant from the liposome surface for the response by ConA (response invoking distance), which may be most favorable in case of 6 spacer units. Further increase in number of spacer units (>6) results to an increasing probability of the bending of the spacer chain along with the terminal polar head group more and more towards the liposome surface; this leads to a reduction of the factual distance of the terminal hydrophilic head group from the liposome surface, weakening the response for ConA binding. The threshold concentration or saturation point decreases also with the rigidity of the ground lipid matrix. Increased rigidity of the ground matrix leads to a phase separation and localized 'Domain' formation with the glycolipid inside the ground matrix layer due to their immiscibility, invoking better response resulting to a reduction of required incorporated glycolipid concentration.

Concanavalin A↗
PubMed1994

A novel chemical procedure for the selective removal of nonreducing terminal N-acetyl hexosamine residues from glycolipids.

A two-step oxidative hydrolysis procedure is described for the selective removal of nonreducing terminal N-acetylhexosamine residues from glycolipids. The procedure gives a 50-60% yield of the n-1 hexosyl ceramide, the remainder being peeling products (n-2, n-3, etc.). The reaction is dependent on the selective deacetylation of nonreducing terminal N-acetyl hexosamine residues by aqueous base hydrolysis. Deglycosylation then occurs in the presence of hydrogen peroxide. Glycolipids containing internal or no N-acetylhexosamine residues are unaltered in these reactions. This method is suitable for the large-scale deglycosylation of appropriate glycolipids and may also be used as an adjunct in structural determination of unknown amino sugar-containing glycolipids.

Acetylation↗
PubMed1996

Detection of glycolipids as biotinylated derivatives using enhanced chemiluminescence.

A new method for the detection of glycolipids as biotinylated derivatives is presented. This method is based on the detection of lipids by enhanced chemiluminescence (ECL) following conjugation with streptavidin-horseradish peroxidase (SHRP). Partial biotinylation of glycolipids is achieved after mild oxidation of the glycan moiety with Na-meta-periodate to increase the availability of biotin-reactive sites. There are several significant advantages of the glycolipid ECL detection: it avoids the need for radio-labeling; it provides the possibility of antibody probing; it allows reprobing of SHRP conjugate to adjust background and luminol light emission levels; it permits easy and accurate quantification of glycolipids at low concentrations; and it involves nondestructive staining, thereby enabling further molecular analysis.

Biotin↗