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PubMed1994

Comparison of the glycolipid-binding specificities of cholera toxin and porcine Escherichia coli heat-labile enterotoxin: identification of a receptor-active non-ganglioside glycolipid for the heat-labile toxin in infant rabbit small intestine.

The binding specificities of cholera toxin and Escherichia coli heat-labile enterotoxin were investigated by binding of 125I-labelled toxins to reference glycosphingolipids separated on thin-layer chromatograms and coated in microtitre wells. The binding of cholera toxin was restricted to the GM1 ganglioside. The heat-labile toxin showed the highest affinity for GM1 but also bound, though less strongly, to the GM2, GD2 and GD1b gangliosides and to the non-acid glycosphingolipids gangliotetraosylceramide and lactoneotetraosylceramide. The infant rabbit small intestine, a model system for diarrhoea induced by the toxins, was shown to contain two receptor-active glycosphingolipids for the heat-labile toxin, GM1 ganglioside and lactoneotetraosylceramide, whereas only the GM1 ganglioside was receptor-active for cholera toxin. Preliminary evidence was obtained, indicating that epithelial cells of human small intestine also contain lactoneotetraosylceramide and similar sequences. By computer-based molecular modelling, lactoneotetraosylceramide was docked into the active site of the heat-labile toxin, using the known crystal structure of the toxin in complex with lactose. Interactions which may explain the relatively high toxin affinity for this receptor were found.

Animals↗
PubMed1991

Cell adhesion, spreading, and motility of GM3-expressing cells based on glycolipid-glycolipid interaction.

Cell lines expressing varying levels of ganglioside GM3 at the cell surface show different degrees of adhesion and spreading on solid phase coated with such glycosphingolipids (GSLs) as Gg3 (GalNAc beta 1----4Gal beta 1----4Glc beta 1----1Cer), LacCer (Gal beta 1----4Glc beta 1----1Cer), or Gb4 (GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1Cer) (where Cer is ceramide), which may have structures complementary to GM3, but not on solid phase coated with various other GSLs. The degree of cell adhesion and spreading on Gg3 was correlated with the degree of cell-surface GM3 expression, as defined by reactivity with anti-GM3 monoclonal antibody (mAb) DH2. Only cells with high GM3 expression adhered on solid phase coated with LacCer or Gb4. Adhesion of GM3-expressing cells on Gg3-, LacCer-, and Gb4-coated solid phase is based on interaction of GM3 with Gg3 and, to a lesser extent, with LacCer and Gb4, as demonstrated by: (i) the interaction of the GM3 liposome with solid phase coated with Gg3, LacCer, and Gb4, respectively; (ii) the abolition of cell adhesion on each GSL-coated solid phase by treatment of cells with mAb DH2 or sialidase; and (iii) the inhibition of cell adhesion by treatment of GSL-coated solid phase with mAb specific to each GSL. Sialosyllactosyl-lysyllysine conjugate was bound to Gg3 adsorbed on a C18 silica gel column in the presence of bivalent cation, suggesting that the carbohydrate moiety of GM3 is involved in GM3-Gg3 interaction. Not only the adhesion and spreading of GM3-expressing cells, but also their cell motility was greatly enhanced on Gg3-coated solid phase, as determined by Transwell assay and phagokinetic track assay on a gold sol-coated surface. Spreading and motility of GM3-expressing cells on Gg3-coated solid phase were both inhibited by treatment of cells with mAb DH2 or sialidase. These results provide evidence that not only cell adhesion, but also spreading and motility in these cell lines are controlled by complementary GSL-GSL interaction.

Animals↗
PubMed2005

Point mutational analysis of the liganding site in human glycolipid transfer protein. Functionality of the complex.

Mammalian glycolipid transfer proteins (GLTPs) facilitate the selective transfer of glycolipids between lipid vesicles in vitro. Recent structural determinations of the apo- and glycolipid-liganded forms of human GLTP have provided the first insights into the molecular architecture of the protein and its glycolipid binding site (Malinina, L., Malakhova, M. L., Brown, R. E., and Patel, D. J. (2004) Nature 430, 1048-1053). In the present study, we have evaluated the functional consequences of point mutation of the glycolipid liganding site of human GLTP within the context of a carrier-based mechanism of glycolipid intermembrane transfer. Different approaches were developed to rapidly and efficiently assess the uptake and release of glycolipid by GLTP. They included the use of glass-immobilized, glycolipid films to load GLTP with glycolipid and separation of GLTP/glycolipid complexes from vesicles containing glycolipid (galactosylceramide or lactosylceramide) or from monosialoganglioside dispersions by employing nickel-nitrilotriacetic acid-based affinity or gel filtration strategies. Point mutants of the sugar headgroup recognition center (Trp-96, Asp-48, Asn-52) and of the ceramide-accommodating hydrophobic tunnel (Phe-148, Phe-183, Leu-136) were analyzed for their ability to acquire and release glycolipid ligand. Two manifestations of point mutation within the liganding site were apparent: (i) impaired formation of the GLTP/glycolipid complex; (ii) impaired acquisition and release of bound glycolipid by GLTP. The results are consistent with a carrier-based mode of GLTP action to accomplish the intermembrane transfer of glycolipid. Also noteworthy was the inefficient release of glycolipid by wtGLTP into phosphatidylcholine acceptor vesicles, raising the possibility of a function other than intermembrane glycolipid transfer in vivo.

Animals↗
PubMed1981

Chemical characterization of neutral glycolipids in the human myeloid leukemias.

Human neutrophils and lymphocytes have been shown to have different classes of neutral glycolipids. We have investigated alterations of glycolipids in the human myeloid leukemias to see how their neutral glycolipids differ from those of normal neutrophils. The chemical structures of the neutral glycolipids from large numbers of homogeneously purified leukemia cells were determined using column and thin-layer chromatography, gas-liquid chromatography (GLC), GLC-mass spectrometry, and direct probe mass spectrometry. Our results showed that cells from patients with acute myelogenous leukemia (AML) had less than half the amount of neutral glycolipid per cell than did cells from patients with chronic myelogenous leukemia (CML). Chromatographic mapping of the neutral glycolipids from these cells showed that AML cells had less of the polar, long-chain neutral glycolipids than did CML cells. The studies confirmed that over 99% of the neutral glycolipids were contained in a population of compounds with 1, 2, 3, and 4 sugar-containing neutral glycolipids whose structures are: Glc 1 --> 1 ceramide; Gal 1 --> 1 ceramide; Gal 1 --> 4 Glc 1 --> 1 ceramide; Gal 1 --> 4 Gal 1 --> 1 ceramide; GlcNAc 1 --> 3 Gal 1 --> 4 Glc 1 --> 1 ceramide; and Gal 1 --> 4 GlcNAc 1 --> 3 Gal 1 --> 4 Glc 1 --> 1 ceramide. Lactosyl ceramide was the major glycolipid in both AML and CML cells. The studies show that human myeloid leukemia cells have the same neutral glycolipids as normal neutrophils. The alterations in neutral glycolipid distribution in leukemia suggest that they might be useful as "differentiation markers", with the morphologically more "mature" leukemias having more complex glycolipids. We were unable to detect novel or "malignancy-associated" neutral glycolipids in any of the leukemias we studied.-Klock, J. C., J. L. D'Angona, and B. A. Macher. Chemical characterization of neutral glycolipids in the human myeloid leukemias.

Carbohydrate Conformation↗
PubMed1974

Comparison of the chemical structure and biological activities of the glycolipids of Salmonella minnesota R595 and Salmonella typhimurium SL1102.

It has been assumed in the past that the lipid moieties of endotoxic lipopolysaccharides are quite similar if not identical. This has been tested in the reported work here, where the chemical composition and biological activities of the glycolipids of two heptoseless Re mutants, Salmonella minnesota R595 and Salmonella typhimurium SL1102, have been studied and compared. The two glycolipids, extracted with chloroform-methanol (4:1), showed identical thin-layer chromatographic patterns. The molar ratios for hexosamine, fatty acids, phosphorus, 2-keto-3-deoxyoctonate, total amines, and total nitrogen of the purified glycolipids were in the same range, but small differences could be established. Both glycolipids contained the same major fatty acids, i.e., lauric, myristic, palmitic, and 3-hydroxymyristic acids, in similar but not identical ratios. On paper electrophoresis, the acid hydrolysates of the two glycolipids showed analogous components. In the determination of molecular weight, whereas S. minnesota R595 glycolipid did not show concentration dependence, the molecular weight measured for S. typhimurium SL1102 increased with its concentration. The molecular weight of the fully endotoxic R595 glycolipid has been found to be 17,000 +/- 1,500. Both glycolipids showed similar activities in the Shwartzman skin reaction, Limulus-lysate clotting assay, mouse lethality, and enhancement of nonspecific resistance, but the R595 preparation appeared to be more active on a weight basis in some parameters than SL1102. Using passive hemagglutination, we observed cross-reactivity between the glycolipids. In the gel-diffusion test, they revealed clear identity. The antiserum against S. minnesota R595 neutralized the Shwartzman skin reactivity not only of R595 but also of SL1102 glycolipid. These results confirm that there are identical immunodeterminant group(s) in the two glycolipids. On the other hand, chemical analytical data for two glycolipids showed only similarities, indicating that although both glycolipids are of comparable chemical nature, differences between them exist.

Antibodies, Bacterial↗
PubMed1996

Expression and localization of Lewis(x) glycolipids and GD1a ganglioside in human glioma cells.

We analysed the glycolipid composition of glioma cells (N-370 FG cells), which are derived from a culture of transformed human fetal glial cells. The neutral and acidic glycolipid fractions were isolated by column chromatography on DEAE-Sephadex and analysed by high-performance thin-layer chromatography (HPTLC). The neutral glycolipid fraction contained 1.6 micrograms of lipid-bound glucose/galactose per mg protein and consisted of GlcCer (11.4% of total neutral glycolipids), GalCer (21.5%), LacCer (21.4%), Gb4 (21.1%), and three unknown neutral glycolipids (23%). These unknown glycolipids were characterized as Lewis(x) (fucosylneolactonorpentaosyl ceramide; Le(x)), difucosylneolactonorhexaosyl ceramide (dimeric Le(x)), and neolactonorhexaosyl ceramide (nLc6) by an HPTLC-overlay method for glycolipids using specific mouse anti-glycolipid antibodies against glycolipid and/or liquid-secondary ion (LSI) mass spectrometry. The ganglioside fraction contained 0.6 micrograms of lipid-bound sialic acid per mg protein with GD1a as the predominant ganglioside species (83% of the total gangliosides) and GM3, GM2, and GM1 as minor components. Trace amounts of sialyl-Le(x) and the complex type of sialyl-Le(x) derivatives were also present. Immunocytochemical studies revealed that GD1a and GalCer were primarily localized on the surface of cell bodies. Interestingly, Le(x) glycolipids and sialyl-Le(x) were localized not only on the cell bodies but also on short cell processes. Especially, sialyl-Le(x) glycolipid was located on the tip of fine cellular processes. The unique localization of the Le(x) glycolipids suggests that they may be involved in cellular differentiation and initiation of cellular growth in this cell line.

Animals↗
PubMed1991

Glycolipids in rat cochlea.

In recent years, the functions of glycolipids have been intensively studied. Before the research of the roles of glycolipids in the inner ear, it seemed to be necessary to demonstrate the composition of glycolipids at first. Therefore, rat cochlea has been examined for glycolipid composition in the present study. Glycolipids extracted from 200 cochlea samples were separated into neutral and acidic glycolipid fractions. Each fraction was analyzed by thin-layer chromatography. The neutral glycolipid was almost exclusively galactosylceramide (cerebroside) with trace amounts of globoside and unidentified glycolipids. In acidic glycolipids, sulfated galactosylceramide (cerebroside sulfate) was most abundant. Of the gangliosides (sialic acid-containing glycolipids), ganglioside GM3 (51.8%) was the predominant component, and GM2 (6.0%), GM1 (8.8%), GD3 (10.7%), GD1a (8.7%), GD1b (5.9%), and GT1b (3.6%) were also detected. In addition to these, rat cochlea also contained several, minor, unidentified gangliosides. This pattern of the cochlear acidic glycolipids is very similar to that of the renal acidic glycolipids. This finding seems to be very interesting when considering that the toxic side effects of aminoglycosides occur only in the kidney and the inner ear.

Animals↗
PubMed1999

Leb glycolipids present in the lumen of the gastrointestinal tract of rats do not enter the plasma compartment.

We orally administered to rats several times more Leb glycolipids than is proportionally found in the gastrointestinal tract of humans. This was done in an effort to study two potential phenomena: the possibility that glycolipids in plasma may originate from glycolipids derived from the lumen of the gastrointestinal tract, and to investigate the potential to secondarily modify in vivo the glycolipid profile of gastrointestinal tract epithelial cells, a phenomenon clearly established for human erythrocytes, leukocytes, and platelets. We were able to establish that some of the orally administered glycolipids can be detected at the surface of the upper region mucosa of the gastrointestinal tract for more than 24 hours and are essentially excreted intact in stools in less than 72 hours. Some fecal degradation of the Leb glycolipids into Lea and H type 1 did occur. Although we clearly established that the glycolipids were present in the mucus layer adherent to the cell surface, we could not conclusively establish if the glycolipids had inserted into the epithelial cell membrane. This, however, could not be excluded. The fact that the fed glycolipids remained in the mucus layer of the upper region of the gastrointestinal tract for at least 24 hours may have some pharmacological value. Using sensitive techniques, including red cell serology, immunohistology, and immunochemistry of glycolipids isolated from plasma and red cells, there was no evidence that the fed Leb glycolipids reached the plasma compartment, thus suggesting that glycolipids present in the lumen of the gastrointestinal tract cannot reach the circulation.

Journal Article↗
PubMed1984

Glycolipid-dependent interaction between human migration-inhibitory factor and mononuclear phagocytes.

It has been previously established in the guinea pig that the response of peritoneal macrophages to migration inhibitory factor (MIF) is enhanced by a macrophage glycolipid and that gangliosides reversibly bind MIF. This suggests that glycolipids function as cell surface receptors for MIF. In this report, it is demonstrated that the response of human peripheral blood monocytes to human MIF is augmented by preincubation of these cells with glycolipid-enriched material extracted from the human macrophage-like cell line U937 or human peripheral blood monocytes and with a purified glycolipid from guinea pig peritoneal macrophages. In addition, a mixed ganglioside preparation from bovine brain shows the same effect. In contrast, the pure gangliosides, GM1 and GD1a, and glycolipids from the HL-60 cell line, which is a MIF-unresponsive cell line, were not able to enhance the response to human MIF. The specificity of enhancement by particular glycolipids could not be attributed to an increased uptake of only enhancing glycolipids since there was no significant difference between the association of monocytes with radioactive liposomes containing biologically active or inactive glycolipids. Pronase treatment did not affect the enhancing activity of the U937 glycolipid-enriched material. Incubation of cells with glycolipids results in enhancement only if done at 37 degrees C and not at 4 degrees C. Therefore, the association of lipid with the monocyte surface appears to be dependent on temperature. Further evidence for the receptor nature of these enhancing glycolipids is provided by experiments involving affinity purification experiments. Coupling of bovine brain mixed gangliosides to agarose resulted in a matrix capable of reversibly binding MIF. GD1a-agarose was inactive in this respect.

Animals↗
PubMed1994

Age-related resistance to 987P fimbria-mediated colonization correlates with specific glycolipid receptors in intestinal mucus in swine.

Strains of enterotoxigenic Escherichia coli that produce 987P fimbriae (987P+ strains) colonize the small intestines and cause diarrhea in neonatal (< 6-day-old) pigs but not in weaned pigs. However, 987P+ E. coli strains adhere in vitro to intestinal epithelial cells from pigs of both ages. Two intestinal components, designated 987R and 987M, bind 987P fimbriae (987P) on Western blots (immunoblots). We examined brush borders (BB) and intestinal washes (IW) from pigs to determine if they contain glycolipids which bind 987P. Total glycolipid extracts from BB and IW of 4-week-old pigs were separated on thin-layer chromatograms and overlaid with purified 987P. Bound 987P were detected with 987P-specific antiserum. 987P bound to at least one moiety in both BB and IW glycolipids and also bound to several purified glycolipids, including gangliotetraosylceramide, lactosylceramide (CDH), sulfatide (SFT), gangliotriaosylceramide, and galactosylceramide (listed in order of decreasing affinity). Strain 987, but not the isogenic 987P- strain I36, bound to these same glycolipids, indicating that the fimbriae contain the adhesin required for binding to these lipids. Glycolipids extracted from BB and IW isolated from 3- and 4-week-old pigs and from BB isolated from 1-day-old pigs contained similar amounts of glycolipids like CDH and SFT that bound 987P. Finally, 987P bound to CDH, SFT, and total BB glycolipids separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to Immobilon, and these glycolipids had mobilities similar to that of 987M. Thus, 987M may contain 987P-binding glycolipids. We hypothesize that glycolipid receptors for 987P, most likely CDH or SFT, in the mucus of older pigs bind 987P and inhibit 987P- mediated intestinal colonization by preventing the attachment of 987P+ E. coli to 987P receptors on the intestinal epithelium.

Adhesins, Escherichia coli↗
PubMed1981

Complex carbohydrates as differentiation markers in malignant blood cells: glycolipids in the human leukemias.

This article summarizes the data on chemical sequencing of human leukocyte cell surface glycolipids that we have obtained over the last 3 years. The purpose of the work was to determine if these cell surface glycoconjugates differ among different leukocyte populations and at different stages of development. In homogeneous form we purified large numbers of leukocytes from normal persons and persons with acute and chronic leukemias of myeloid and lymphoid types, using continuous flow centrifugation leukapheresis. We extracted the glycolipids from these cells and used thin-layer chromatography, gas-liquid chromatography, gas chromatography-mass spectrometry, direct probe mass spectrometry, and enzyme treatment to obtain complete structural information on these compounds. Twenty glycolipids were identified and sequenced, representing over 99% of the glycolipids of human leukocytes. The major findings are that human leukocytes possess glycolipid patterns that distinguish them from other blood cells. Additionally, leukocytes of "myeloid' and "lymphoid' types can be distinguished by their glycolipid type. Glycolipids in human leukemic cells show two main features: (1) even though the cells appear morphologically "undifferentiated', all leukemias can be classified on the basis of their glycolipids as "myeloid' or "lymphoid'; (2) the complexity of their cell surface glycolipids is correlated with their degree of morphologic "differentiation', the more differentiated leukemias having more complex structures. No glycolipids were found in leukemic leukocytes that were not found in the normal cells. Glycolipids would therefore appear to be useful as both cell- and possibly differentiation-specific markers in human blood cells. The antigenic differences seen in human leukemic cells may be due in part to an altered distribution of complex carbohydrates at the cell surface.

Antigens, Surface↗
PubMed1994

The role of glycolipid C in the GPI biosynthetic pathway in Trypanosoma brucei bloodstream forms.

The glycosylphosphatidylinositol (GPI) biosynthetic pathway in Trypanosoma brucei bloodstream forms includes the formation of glycolipid C. This molecule is the inositol-acylated form of the GPI anchor precursor, glycolipid A. There is no evidence for the transfer of glycolipid C to protein in vivo and the role of glycolipid C is unclear. In this paper we show that glycolipid C is not synthesised in the presence of phenylmethylsulphonyl fluoride (PMSF) and that glycolipid C is not an obligatory intermediate on the pathway to the formation of glycolipid A. Using pulse-chase experiments we show that glycolipid A and glycolipid C are in a dynamic equilibrium and we suggest that only the forward reaction (glycolipid A conversion to glycolipid C) is inhibited by PMSF.

Animals↗