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Recognition of schistosome glycolipids by immunoglobulin E: possible role in immunity.

To investigate the role of antibody responses to (glyco)lipids in immunity to schistosome infection, lipids extracted from Schistosoma mansoni eggs and adult worms were fractionated, and the antibody isotype profile reactive to the fractionated lipids in a well-characterized S. haematobium-infected population was investigated. In tests of 10 plasma samples it was found that immunoglobulin G (IgG) reactivity was highest to the fraction containing ceramidepolyhexosides, whereas IgE reactivity was most prominent to both cerebroside- and ceramidepolyhexoside-containing fractions. The fraction containing ceramidepolyhexosides was then tested for reactivity with IgG subclasses and IgE in plasma samples from 66 S. haematobium-infected patients. Considering IgG4 and IgE, isotypes of particular interest in helminth infections, we found that both isotypes recognized egg (glyco)proteins in more than 90% of the infected subjects. However, in the case of glycolipids, IgE reactivity was much more prominent than IgG4 reactivity (found in 80 and 41% of the subjects, respectively). Furthermore, worm glycolipid-specific IgE prior to treatment of the subjects with praziquantel was negatively correlated with egg counts at 2 years posttreatment, indicating that IgE directed towards glycolipids could play an important role in resistance to reinfection.

Adolescent↗

A novel phenolic glycolipid from Mycobacterium leprae possibly involved in immunogenicity and pathogenicity.

A phenolic glycolipid was obtained in high amounts (2% of dry weight) from Mycobacterium leprae isolated from infected armadillo liver. Infrared and nuclear magnetic resonance spectroscopy showed that it is closely related to "mycoside A" from Mycobacterium kansasii and is therefore a glycosylphenolic phthiocerol diester. The crucial difference between the two products is in the composition of the attached trisaccharide. Gas-liquid chromatography-mass spectroscopy showed that the product from M. kansasii is composed of 2,4-di-O-methylrhamnose, 2-O-methylrhamnose, and 2-O-methylfucose, whereas that from M. leprae contains 2,3-di-O-methylrhamnose, 3-O-methylrhamnose, and 3,6-di-O-methylglucose. The distinct composition of the oligosaccharide segment of the glycolipid from M. leprae may make it useful for the chemical and serological differentiation of this organism from other mycobacteria. Surprisingly large quantities (2.2 mg/g of dry liver) of the glycolipid were also found in infected liver residue freed of M. leprae, suggesting that it may be responsible for the electron-transparent "foam" surrounding the organism in infected lepromatous tissue.

Chemical Phenomena↗

High levels of glycolipid and low levels of phospholipid in a marine caulobacter.

Studies of the lipid composition of the marine bacterium Caulobacter halobacteroides revealed the presence of glycolipid as the predominant lipid constituent. The presence of minor amounts of phospholipid was confirmed with the incorporation of 14C- and 32P-labeled compounds. Other marine caulobacters had similar lipid compositions. Five chromatographically separable glycolipids were detected, two of which were identified as mono- and diglycosyldiglycerides. Glycolipid constituted 90 to 99% of the total extractable lipid based on 14C-acetate incorporation into six marine caulobacter strains. In addition, comparisons were made with the lipid extracts of the nonmarine Caulobacter crescentus and Micrococcus lysodeikticus, which contain substantial amounts of phospholipid. Studies of lipid composition during growth showed the maximum amount of phospholipid during early logarithmic growth (2.9%) with a decrease to 0.3% in the early stationary phase. The finding of a group of organisms in which phospholipid is not a major constituent of the lipid fraction is unique and generates many questions about the lipid requirements for membrane structure and function.

Acetates↗

Flavone-enhanced accumulation and symbiosis-related biological activity of a diglycosyl diacylglycerol membrane glycolipid from Rhizobium leguminosarum biovar trifolii.

Rhizobium leguminosarum bv. trifolii is the bacterial symbiont which induces nitrogen-fixing root nodules on the leguminous host, white clover (Trifolium repens L.). In this plant-microbe interaction, the host plant excretes a flavone, 4',7-dihydroxyflavone (DHF), which activates expression of modulation genes, enabling the bacterial symbiont to elicit various symbiosis-related morphological changes in its roots. We have investigated the accumulation of a diglycosyl diacylglycerol (BF-7) in wild-type R. leguminosarum bv. trifolii ANU843 when grown with DHF and the biological activities of this glycolipid bacterial factor on host and nonhost legumes. In vivo labeling studies indicated that wild-type ANU843 cells accumulate BF-7 in response to DHF, and this flavone-enhanced alteration in membrane glycolipid composition was suppressed in isogenic nodA::Tn5 and nodD::Tn5 mutant derivatives. Seedling bioassays performed under microbiologically controlled conditions indicated that subnanomolar concentrations of purified BF-7 elicit various symbiosis-related morphological responses on white clover roots, including thick short roots, root hair deformation, and foci of cortical cell divisions. Roots of the nonhost legumes alfalfa and vetch were much less responsive to BF-7 at these low concentrations. A structurally distinct diglycosyl diacylglycerol did not induce these responses on white clover, indicating structural constraints in the biological activity of BF-7 on this legume host. In bioassays using aminoethoxyvinylglycine to suppress plant production of ethylene, BF-7 elicited a meristematic rather than collaroid type of mitogenic response in the root cortex of white clover. These results indicate an involvement of flavone-activated nod expression in membrane accumulation of BF-7 and a potent ability of this diglycosyl diacylglycerol glycolipid to perform as a bacterial factor enabling R. leguminosarum bv. trifolii to activate segments of its host's symbiotic program during early development of the root nodule symbiosis.

Bacterial Proteins↗

The hglK gene is required for localization of heterocyst-specific glycolipids in the cyanobacterium Anabaena sp. strain PCC 7120.

Mutant strain 543 of the cyanobacterium Anabaena sp. strain PCC 7120 was originally isolated as a Fox- mutant following chemical mutagenesis. Ultrastructural analysis shows that in nitrogen-replete media the vegetative cells of the mutant are more cylindrical and have thicker septa than those of the wild type, while in nitrogen-free media the mutant heterocysts lack the normal glycolipid layer external to the cell wall. Although this layer is absent, strain 543 heterocysts nevertheless contain heterocyst-specific glycolipids, as determined by thin-layer chromatography. The mutation in strain 543 is in a gene we have named hglK, encoding a protein of 727 amino acids. The wild-type HglK protein appears to contain four membrane-spanning regions followed by 36 repeats of a degenerate pentapeptide sequence, AXLXX. The mutation in strain 543 introduces a termination codon immediately upstream of the pentapeptide repeat region. A mutant constructed by insertion of an antibiotic resistance cassette near the beginning of the hglK gene has the same phenotype as strain 543. We propose that hglK encodes a protein necessary for the localization of heterocyst glycolipids and that this function requires the pentapeptide repeats of the HglK protein.

Amino Acid Sequence↗

Anabaena sp. strain PCC 7120 gene devH is required for synthesis of the heterocyst glycolipid layer.

In response to deprivation for fixed nitrogen, the filamentous cyanobacterium Anabaena sp. strain PCC 7120 provides a microoxic intracellular environment for nitrogen fixation through the differentiation of semiregularly spaced vegetative cells into specialized cells called heterocysts. The devH gene is induced during heterocyst development and encodes a product with characteristics of a trans-acting regulatory protein. A devH mutant forms morphologically distinguishable heterocysts but is Fox(-), incapable of nitrogen fixation in the presence of oxygen. We demonstrate that rearrangements of nitrogen fixation genes take place normally in the devH mutant and that it is Fix(+), i.e., has nitrogenase activity under anoxic conditions. The Fox(-) phenotype was shown by ultrastructural studies to be associated with the absence of the glycolipid layer of the heterocyst envelope. The expression of glycolipid biosynthetic genes in the mutant is greatly reduced, and heterocyst glycolipids are undetectable.

Aerobiosis↗

Chemotypes of Mycobacterium malmoense based on glycolipid profiles.

Thin-layer chromatographic analysis of 72 Finnish clinical mycobacterial isolates presumptively identified as Mycobacterium malmoense revealed four major glycolipid profiles with two minor variations. An additional glycolipid profile was found in three British M. malmoense-like strains. No clear distinction between the strains could be made by means of gas chromatography of cellular fatty acids. The two M. malmoense-specific constituents, 2-methyleicosanoate and 2,4,6-trimethyltetracosanoate, were detected in all strains. The frequency of chemotypes other than that of the type strain was 8% among the Finnish isolates. This variation should be recognized when confirmative identification of mycobacteria is based on thin-layer chromatography of glycolipid extracts.

Bacterial Typing Techniques↗

Production of monoclonal antibody to a phenolic glycolipid of Mycobacterium tuberculosis and its use in detection of the antigen in clinical isolates.

A monoclonal antibody (MAbIII604) specific to phenolic glycolipid Tb (PGL-Tb), a Mycobacterium tuberculosis-specific antigen, was produced and used in the detection of the antigen. MAbIII604 reacted with the PGL-Tb antigen but not with other phenolic glycolipids from Mycobacterium leprae, M. bovis, and M. kansasii, thus indicating the specificity of the monoclonal antibody to PGL-Tb. A dot enzyme-linked immunosorbent assay with MAbIII604 was employed to detect the PGL-Tb antigen in lipids purified from M. tuberculosis clinical isolates. Of 50 isolates, 32 (64.0%) showed clear evidence of the PGL-Tb antigen by the dot enzyme-linked immunosorbent assay, but there were marked variations in the intensities and sizes of spots. This suggests differences in PGL-Tb antigen production among M. tuberculosis strains even when they are grown in the same culture media and conditions. This was most evident from the fact that in only eight (16.0%) of the isolates examined was the PGL-Tb antigen detectable by thin-layer chromatography, which is much less sensitive for the detection of glycolipid antigens. This study shows that monoclonal antibodies specific to PGL-Tb are useful in detecting the antigen in lipid extracts and that there is a marked variation in the PGL-Tb production among M. tuberculosis clinical isolates.

Antibodies, Bacterial↗

Signals determining protein tyrosine kinase and glycosyl-phosphatidylinositol-anchored protein targeting to a glycolipid-enriched membrane fraction.

Glycosyl-phosphatidylinositol (GPI)-anchored membrane proteins and certain protein tyrosine kinases associate with a Triton X-100-insoluble, glycolipid-enriched membrane fraction in MDCK cells. Also, certain protein tyrosine kinases have been shown to associate with GPI-anchored proteins in other cell types. To characterize the interaction between GPI-anchored proteins and protein tyrosine kinases, GPI-anchored proteins were coexpressed with p56lck in HeLa cells. Both proteins were shown to target independently to the glycolipid-enriched membranes. Coimmunoprecipitation of GPI-anchored proteins and p56lck occurred only when both proteins were located in the glycolipid-enriched membranes, and gentle disruption of these membranes abolished the interaction. The GPI anchor was found to be the targeting signal for this membrane fraction in GPI-anchored proteins. Analysis of mutants indicated that p56lck was nearly quantitatively palmitoylated at Cys-5 but not palmitoylated at Cys-3. The nonpalmitoylated cysteine at position 3 was very important for association of p56lck with the membrane fraction, while palmitoylation at Cys-5 promoted only a low level of interaction. Because other src family protein tyrosine kinases that are associated with GPI-anchored proteins always contain a Cys-3, we propose that this residue, in addition to the N-terminal myristate, is part of a common signal targeting these proteins to a membrane domain that has been linked to transmembrane signaling.

Amino Acid Sequence↗

Colon carcinoma cell glycolipids, integrins, and other glycoproteins mediate adhesion to HUVECs under flow.

This study was undertaken to investigate the molecular constituents mediating LS174T colon adenocarcinoma cell adhesion to 4-h TNF-alpha-stimulated human umbilical vein endothelial cells (HUVECs) under flow. At 1 dyn/cm(2), approximately 57% of cells rolled and then became firmly adherent, whereas others continuously rolled on endothelium. Initial cell binding was primarily mediated by endothelial E-selectin. By using neuraminidase, glycolipid biosynthesis inhibitor d,l-threo-1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol. HCl, trypsin, and flow cytometry, LS174T cells were shown to express sialyl Lewis(x) (sLe(x))- and di-sLe(x)-decorated, but not sLe(a)-decorated, glycolipid and glycoprotein ligands for E-selectin. The cells preferentially employed sialylated glycoproteins over glycolipids in adhesion as measured by conversion of rolling to firm adhesion, resistance to detachment by increased shear stress, and rolling velocity. However, a nonsialylated E-selectin counterreceptor also exists. Furthermore, LS174T alpha(2), alpha(6), and beta(1) integrins support a minor pathway in adhesion to HUVECs. Finally, tumor cell attachment specifically increases HUVEC endocytosis of E-selectin. Altogether, the data indicate the complexity of carcinoma cell-endothelium adhesion via sialylated glycoconjugates, integrins, and their respective counterreceptors.

Cell Adhesion↗

Expression of glycolipids and myelin-associated glycoprotein during the differentiation of oligodendrocytes: comparison of the CG-4 glial cell line to primary cultures.

The expression of cerebrosides, sulfatides, gangliosides and the myelin-associated glycoprotein (MAG) during differentiation of the CG-4 line of oligodendrocyte progenitors [Louis et al.: J. Neurosci Res 31: 193, 1992] was compared with their expression in primary cultures of oligodendrocyte precursors [McCarthy and de Vellis: J Cell Biol 85: 890, 1980]. When the CG-4 cells differentiated from bipolar progenitors to oligodendrocytes, there was a decrease of glucosylcerebroside synthesis and an increase in galactosylcerebroside and sulfatide synthesis. However, even after differentiation, the incorporation of [3H]galactose into these glycolipids, the amounts of galactosylcerebroside and sulfatide, and the galactocerebroside/sulfatide ratio were all much less than in primary cultures of differentiating oligodendrocytes. The major gangliosides in differentiated primary oligodendrocyte cultures were GM3 and GD3, and GD3 was also a major ganglioside in the CG-4 line. However, unlike primary cultures of O-2A lineage cells in which GM3 synthesis increased dramatically during differentiation to oligodendrocytes, the CG-4 cells expressed very little GM3. Also, the CG-4 cells expressed larger amounts of more complex gangliosides, e.g. GD1b and GT1b, which were almost entirely restricted to the b-series. The amount of MAG expressed by the CG-4 cells increased substantially when they differentiated to oligodendrocytes, and it was almost all the large immature isoform. However, even after differentiation, the amount expressed was less than in differentiated primary oligodendrocyte cultures. Overall, the lower expression of myelin-related glycolipids and MAG by the CG-4 line suggests a lesser degree of differentiation in comparison to primary oligodendrocytes under the culture conditions of these experiments, but the larger amounts of cells available from the CG-4 line should be useful for investigating glycolipid and MAG function related to the early stages of myelinogenesis.

Animals↗

Immunohistochemical and biochemical demonstration of the change in glycolipid composition of the intestinal epithelial cell surface in mice in relation to epithelial cell differentiation and bacterial association.

We have previously demonstrated the appearance of fucosyl asialo-GM1 (FGA1) in the small-intestinal epithelial cells of germ-free mice via the induction of GDP-fucose: asialo-GM1 (GA1) alpha(1 leads to 2) fucosyltransferase (FT) after the conventionalization of these animals (Umesaki Y, Sakata T, Yajima T: Biochem Biophys Res Commun 105:439, 1982). The present study, based on this earlier work, demonstrates the changes in the glycolipid antigens of the small-intestinal epithelial-cell membrane as shown immunohistochemically with specific antibodies raised against asialo GM1 (GA1) and FGA1. In germ-free mice, GA1 was localized both in the villus cells and in the crypt cells. In the process of conventionalization, FGA1 appeared in the villus cells while the GA1 content of these cells was decreased. Four to 5 days after the conventionalization procedure, the fluorescence produced by anti-FGA1 was strongest in the villus cells, while that produced by anti-GA1 was detected only in the crypt cells. At this same time the FT activity of the small-intestinal mucosa was highest, with most of the GA1 apparently being converted into FGA1, as shown in the paper cited above. Thereafter, the GA1 content of both the villus and crypt cells again increased greatly. On the other hand, the fluorescence produced with anti-FGA1 decreased, and could no longer be detected 14 days after conventionalization. The activity of FT, measured biochemically in epithelial cells differentially isolated from the villus tip to the crypt, was greater in the villus than in the crypt region. This confirmed the intense staining with anti-FGA1 that was seen in villus cells. The fluorescence produced by the two anti-glycolipid antibodies used in the study distributed not only in the microvillus membrane but also to some extent in the basolateral membrane. The localization of the respective glycolipids contrasted with that of the glycoprotein sucrase--isomaltase enzyme complex, the fluorescence of which was exclusively confined to the microvillus-membrane side of the villus cells.

Animals↗

Relationship between antidepressants and glycolipids in the forced swimming test in mice.

GalNAc alpha 1-3GalNAc-lipids induce an antidepressive-like effect in mice in the forced swimming test. In the present study, the relationship between the effects of several antidepressants and serum glycolipid reactivities were investigated. The antidepressants imipramine, maprotiline, paroxetine, trazodone and mianserin induced an effect in forced swimming in mice after 1 or 6 h but not 15 min after treatment. The GalNAc alpha 1-3GalNAc-lipid globopentaosylceramide dose-dependently induced the effect only 15 min after treatment, and the glycolipid reactivities were found in the serum dose-dependently at the period that the mice showed the antidepressive-like climbing behavior. The results strongly suggest that glycolipid production, and not the central neurological activities of the antidepressants, induce the antidepressive effect in mice.

Animals↗

Influence of high-protein diets on brain phospholipid, ganglioside and monogalactosyl glycolipid content previously altered by long-term low-protein and ethanol administration.

A previous study was undertaken to determine the influence of the combined effects of ethanol consumption and a low-protein diet on brain membrane (phospholipids and gangliosides) and myelin (monogalactosyl glycolipids) lipids. Male Wistar rats chronically consuming ethanol were fed isoenergetic diets containing 22% protein (controls) or 6% protein (protein-deprived) from 60 to 240 days of age. Protein malnutrition initiated at 60 days of age affected phosphatidylglycerol, sphingophospholipid, monosialoganglioside GM1 and cerebroside containing nervonic fatty acid by 240 days of age. Among the effects of ethanol was an increase of the relative proportion of lipid galactose in monogalactosyl glycolipids and of N-acetylneuraminic acid in the trisialoganglioside GT1b, while there was decrease of the lipid phosphorus in the investigated phospholipids and of the disialoganglioside GD1a. The low-protein diet generally interfered with ethanol effects except for monosialo GM3, GM2 and GM1 gangliosides. The present study was carried out to investigate whether the ethanol-induced effect on these brain lipids could be elevated when we switched these animals to diets with 21 or 34% protein during the following 90 days. It was found that increasing protein intake and cessation of drinking ethanol returned the investigated brain phospholipids, monogalactosyl glycolipids and gangliosides to control values.

Animals↗

iNKT-cell responses to glycolipids.

Invariant natural killer T (iNKT) cells are an unusual group of T lymphocytes that recognize glycolipid antigens presented by the major histocompatibility complex class I-related protein CD1d. Because iNKT cells play a regulatory role in the immune system, they are attractive targets for immunotherapy. The marine-sponge-derived glycolipid alpha-galactosylceramide (alpha-GalCer) potently activates iNKT cells. In vivo administration of alpha-GalCer to mice or humans results in rapid and robust cytokine secretion by iNKT cells, followed by the activation of a variety of cell types of the innate and adaptive immune systems. These potent immunomodulatory activities of alpha-GalCer are being exploited for therapeutic purposes. Preclinical studies in mice have demonstrated that alpha-GalCer and related glycolipids can protect mice against a variety of diseases, including cancer, infections, and several autoimmune and inflammatory conditions. Although alpha-GalCer treatment of mice is associated with unwanted side-effects, it has been proven safe in clinical trials with cancer patients. These studies have raised significant enthusiasm for the development of effective and safe iNKT-cell-based immunotherapies for a variety of human diseases.

Animals↗

Therapeutic potential of glycolipid ligands for natural killer (NK) T cells in the suppression of autoimmune diseases.

NKT cells emerge as important regulatory cells in autoimmune responses. Abnormalities in the numbers and functions of natural killer T (NKT) cells have been observed in patients with autoimmune diseases as well as in a variety of mouse strains that are genetically predisposed for development of autoimmune diseases. Unlike conventional T cells that recognize peptides in association with major histocompatibility complex (MHC), NKT cells recognize glycolipid antigens presented by the non-polymorphic MHC class I-like protein, CD1d. Recently, we and other groups have demonstrated that administration of glycolipid ligands such as alpha-galactosylceramide (alpha-GC ) or its sphingosine truncated derivative, OCH suppressed autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE), diabetes in NOD mice and collagen-induced arthritis (CIA) by inducing T helper (Th) 2 bias of autoimmune T cells. OCH is a unique ligand to stimulate NKT cells to selectively produce Th2 cytokines whereas alpha-GC induces both interleukin (IL)-4 and interferon (IFN)-gamma, and is more beneficial for treatment of a wide variety of Th1-mediated autoimmune diseases. The lack of polymorphism of CD1d and cross-reactive responses of mouse and human NKT cells to the same ligand indicates that targeting NKT cells with this ligand may be an attractive means for intervening in human autoimmune diseases such as type I diabetes (T1D), multiple sclerosis (MS) and rheumatoid arthritis (RA). The present review will focus on the potential roles of NKT cells in the pathogenesis of autoimmune diseases and the recent advances in glycolipid therapy for autoimmune disease models. The molecular mechanism of OCH-induced Th2-selective cytokine secretion will also be discussed.

Animals↗

NKT cell-stimulating synthetic glycolipids as potential therapeutics for autoimmune disease.

Although T cells were previously believed to recognize only peptide antigen associated with the major histocompatibility complex (MHC), recent studies have shown that there are unique T cells specialized for recognition of lipid or glycolipid antigens bound to the MHC class I-like CD1 molecules (CD1a, b, c or d). Among these lipid-specific T cells, CD1d-restricted T cells, also referred to as natural killer (NK) T cells, are of special interest as a target of drug development, since their role in immunoregulation has been indicated in various physiological or disease conditions including autoimmunity. They are unique in their homogeneous ligand specificity for alpha-glycosylated sphingolipid and secrete large amounts of regulatory cytokines shortly after T cell receptor (TCR) engagement. The first glycolipid identified as an NKT cell ligand was alpha-galactosylceramide (alpha-GalCer) derived from marine sponges. alpha-GalCer exhibits significant immunomodulatory effects by stimulating NKT cells. However, we found that an altered analogue of alpha-GalCer with a shorter sphingosine chain (OCH), is more useful than alpha-GalCer for treatment of autoimmune disease models, because of its ability to selectively induce IL-4, a key cytokine for control of autoimmunity. As such, altered glycolipid ligands (AGL) of alpha-GalCer appear to be promising reagents for treatment of human autoimmune diseases.

Animals↗

Ley glycolipid-recognizing monoclonal antibody inhibits procoagulant activity and metastasis of human adenocarcinoma.

Tumor procoagulant is associated with cancer at advanced stages of malignancy such as infiltration and metastasis. In the present study, we investigated the role of Ley glycolipid in the mechanism of cancer metastasis. Ley glycolipid acts as an important cofactor in the expression of the blood-coagulating activity of cancer cell-derived coagulating activity 1 (CCA-1), which is one of the known tumor procoagulants. Monoclonal antibody (MoAb) FS01, which serves as the Ley-recognizing epitope, inhibits the procoagulant activity of CCA-1 was found to dose-dependently inhibit the procoagulant activity of normal plasma induced by the human lung adenocarcinoma cell line, HAL8, which shows a high level of Ley expression. It did not, however, inhibit the procoagulant activity of the human colon cancer cell line, RPMI4788, which does not express Ley. Administration of FS01 MoAb inhibited lung metastasis of HAL8 cells, but not that of RPMI4788. The absence of antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity of FS01 MoAb against the HAL8 cell line suggests that the inhibition of HAL8 metastasis by FS01 MoAb derives from the inhibition of blood-coagulating activity of the latter. These findings indicate that Ley glycolipid plays an important role in the mechanism of cancer metastasis via the procoagulant activity of CCA-1.

Adenocarcinoma↗