Characterization of GM3 Gangliosides in Human Milk throughout Lactation: Insights from the Analysis with the Use of Reversed-Phase Liquid Chromatography Coupled to Quadrupole Time-Of-Flight Mass Spectrometry

Gangliosides are complex lipids found in human milk that play important structural and biological functions. In this study, we utilized reversed-phase liquid chromatography coupled to quadrupole time-of-flight mass spectrometry to evaluate the molecular distribution of GM3 in human milk samples collected at distinct lactation stages, ranging from colostrum to advanced lactation samples. Throughout lactation, GM3 d40:1 emerged as the most abundant GM3 species, except in colostrum, where GM3 d42:2 prevailed. The relative content of GM3 species containing very long N-fatty acyl (N-FA) substituents with >22 carbon atoms decreased, while the content of GM3 species containing 14:0, 18:0, 18:1, and 20:0 N-FA substituents increased in the later months of lactation. These findings highlight the divergence of GM3 profiles across the lactation period. Moreover, considerable interindividual variance was observed among the analyzed samples. The assessment of the GM3 profiles contributes to our understanding of the dynamic composition of human milk.

High-coverage targeted lipidomics revealed dramatic lipid compositional changes in asthenozoospermic spermatozoa and inverse correlation of ganglioside GM3 with sperm motility

BACKGROUND

It has been previously demonstrated that cholesterol content and cholesterol/phospholipid ratio were significantly higher in asthenozoospermia and oligoasthenoteratozoospermia. The majority of published studies have investigated the fatty acid composition of phospholipids rather than lipids themselves. This study evaluated the lipid composition of asthenozoospermic and normozoospermic spermatozoa, and identified the exact lipid species that correlated with sperm motility.

METHODS

A total of 12 infertile asthenozoospermia patients and 12 normozoospermia subjects with normal sperm motility values were tested for semen volume, sperm concentration, count, motility, vitality and morphology. High-coverage targeted lipidomics with 25 individual lipid classes was performed to analyze the sperm lipid components and establish the exact lipid species that correlated with sperm motility.

RESULTS

A total of 25 individual lipid classes and 479 lipid molecular species were identified and quantified. Asthenozoospermic spermatozoa showed an increase in the level of four lipid classes, including Cho, PE, LPI and GM3. A total of 48 lipid molecular species were significantly altered between normozoospermic and asthenozoospermic spermatozoa. Furthermore, the levels of total GM3 and six GM3 molecular species, which were altered in normozoospermic spermatozoa versus asthenozoospermic spermatozoa, were inversely correlated with sperm progressive and total motility.

CONCLUSIONS

Several unique lipid classes and lipid molecular species were significantly altered between asthenozoospermic and normozoospermic spermatozoa, revealing new possibilities for further mechanistic pursuits and highlighting the development needs of culture medium formulations to improve sperm motility.

GM2-GM3 gangliosides ratio is dependent on GRP94 through down-regulation of GM2-AP cofactor in brain metastasis cells

GRP94 is an ATP-dependent chaperone able to regulate pro-oncogenic signaling pathways. Previous studies have shown a critical role of GRP94 in brain metastasis (BrM) pathogenesis and progression. In this work, an untargeted lipidomic analysis revealed that some lipid species were altered in GRP94-deficient cells, specially GM2 and GM3 gangliosides. The catalytic pathway of GM2 is affected by the low enzymatic activity of β-Hexosaminidase (HexA), responsible for the hydrolysis of GM2 to GM3. Moreover, a deficiency of the GM2-activator protein (GM2-AP), the cofactor of HexA, is observed without alteration of gene expression, indicating a post-transcriptional alteration of GM2-AP in the GRP94-ablated cells. One plausible explanation of these observations is that GM2-AP is a client of GRP94, resulting in defective GM2 catabolic processing and lysosomal accumulation of GM2 in GRP94-ablated cells. Overall, given the role of gangliosides in cell surface dynamics and signaling, their imbalance might be linked to modifications of cell behaviour acquired in BrM progression. This work indicates that GM2-AP could be an important factor in ganglioside balance maintenance. These findings highlight the relevance of GM3 and GM2 gangliosides in BrM and reveal GM2-AP as a promising diagnosis and therapeutic target in BrM research.

Increased catabolism and decreased unsaturation of ganglioside in patients with inflammatory bowel disease

AIM: To investigate whether accelerated catabolism of ganglioside and decreased ganglioside content contribute to the etiology of pro-inflammatory intestinal disease.

METHODS: Intestinal mucosa from terminal ileum or colon was obtained from patients with ulcerative colitis or inflammatory Crohn’s disease (n = 11) undergoing bowel resection and compared to control samples of normal intestine from patients with benign colon polyps (n = 6) and colorectal cancer (n = 12) in this observational case-control study. Gangliosides and phospholipids of intestinal mucosa were characterized by class and ceramide or fatty acid composition using liquid chromatography triple-quad mass spectrometry. Content and composition of ganglioside classes GM1, GM3, GD3, GD1a, GT1 and GT3 were compared among subject groups. Content and composition of phospholipid classes phosphatidylcholine (PC) and phosphatidylethanolamine were compared among subject groups. Unsaturation index of individual ganglioside and phospholipid classes was computed and compared among subject groups. Ganglioside catabolism enzymes beta-hexosaminidase A (HEXA) and sialidase-3 (NEU3) were measured in intestinal mucosa using western blot and compared among subject groups.

RESULTS: Relative GM3 ganglioside content was 2-fold higher (P < 0.05) in intestine from patients with inflammatory bowel disease (IBD) compared to control intestine. The quantity of GM3 and ratio of GM3/GD3 was also higher in IBD intestine than control tissue (P < 0.05). Control intestine exhibited 3-fold higher (P < 0.01) relative GD1a ganglioside content than IBD intestine. GD3 and GD1a species of ganglioside containing three unsaturated bonds were present in control intestine, but were not detected in IBD intestine. The relative content of PC containing more than two unsaturated bonds was 30% lower in IBD intestine than control intestine (P < 0.05). The relative content of HEXA in IBD intestine was increased 1.7-fold (P < 0.05) and NEU3 was increased 8.3-fold (P < 0.01) compared to normal intestine. Intestinal mucosa in IBD is characterized by increased GM3 content, decreased GD1a, and a reduction in polyunsaturated fatty acid constituents in GD3, GD1a and PC.

CONCLUSION: This study suggests a new paradigm by proposing that IBD occurs as a consequence of increased metabolism of specific gangliosides.

Mass spectrometric analysis of the glycosphingolipid-derived glycans from miniature pig endothelial cells and islets: identification of NeuGc epitope in pig islets

Glycosphingolipid (GSL) is a major component of the plasma membrane in eukaryotic cells that is involved directly in a variety of immunological events via cell-to-cell or cell-to-protein interactions. In this study, qualitative and quantitative analyses of GSL-derived glycans on endothelial cells and islets from a miniature pig were performed and their glycosylation patterns were compared. A total of 60 and 47 sialylated and neutral GSL-derived glycans from the endothelial cells and islets, respectively, were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and collision-induced fragmentation using positive-ion electrospray ionization (ESI) ion-trap tandem mass spectrometry (MS/MS). In accordance with previous immunohistochemistry studies, the alpha-Gal-terminated GSL was not detected but NeuGc-terminated GSLs were newly detected from miniature pig islets. In addition, the neutral GSL-derived glycans were relatively quantified by derivatization with carboxymethyl trimethylammonium hydrazide (so called Girard's T reagent) and MALDI-TOF MS. The structural information of the GSL-derived glycans from pig endothelial cells and islets suggests that special attention should be paid to all types of glycoconjugates expressed on pig tissues or cells for successful clinical xenotransplantation.

Ganglioside GM3 modulates tumor suppressor PTEN-mediated cell cycle progression--transcriptional induction of p21(WAF1) and p27(kip1) by inhibition of PI-3K/AKT pathway

The simple ganglioside GM3 has been shown to have anti-proliferative effects in several in vitro and in vivo cancer models. Although the exogenous ganglioside GM3 has an inhibitory effect on cancer cell proliferation, the exact mechanism by which it prevents cell proliferation remains unclear. Previous studies showed that MDM2 is an oncoprotein that controls tumorigenesis through both p53-dependent and p53-independent mechanisms, and tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a dual-specificity phosphatase that antagonizes phosphatidylinositol 3-kinase (PI-3K)/AKT signaling, is capable of blocking MDM2 nuclear translocation and destabilizing the MDM2 protein. Results from our current study show that GM3 treatment dramatically increases cyclin-dependent kinase (CDK) inhibitor (CKI) p21(WAF1) expression through the accumulation of p53 protein by the PTEN-mediated inhibition of the PI-3K/AKT/MDM2 survival signaling in HCT116 colon cancer cells. Moreover, the data herein clearly show that ganglioside GM3 induces p53-dependent transcriptional activity of p21(WAF1), as evidenced by the p21(WAF1) promoter-driven luciferase reporter plasmid (full-length p21(WAF1) promoter and a construct lacking the p53-binding sites). Additionally, ganglioside GM3 enhances expression of CKI p27(kip1) through the PTEN-mediated inhibition of the PI-3K/AKT signaling. Furthermore, the down-regulation of the cyclin E and CDK2 was clearly observed in GM3-treated HCT116 cells, but the down-regulation of cyclin D1 and CDK4 was not. On the contrary, suppression of PTEN levels by RNA interference restores the enhanced expression of p53-dependent p21(WAF1) and p53-independent p27(kip1) through inactivating the effect of PTEN on PI-3K/AKT signaling modulated by ganglioside GM3. These results suggest that ganglioside GM3-stimulated PTEN expression modulates cell cycle regulatory proteins, thus inhibiting cell growth. We conclude that ganglioside GM3 represents a modulator of cancer cell proliferation and may have potential for use in colorectal cancer therapy.

A liquid chromatography/tandem mass spectrometric approach for the determination of gangliosides GD3 and GM3 in bovine milk and infant formulae

A liquid chromatographic/tandem mass spectrometric method using pneumatically assisted electrospray ionisation (LC/ESI-MS/MS) was developed for the determination of gangliosides GD3 and GM3 in milk and infant formulae. The gangliosides were extracted in a chloroform/methanol/water environment and cleaned up by solid-phase extraction (SPE) on an end-capped C8 sorbent. The gangliosides were detected in negative ion mode after separation on a reversed-phase (RP) C5 analytical column. From the different ganglioside molecular species, product ions at m/z 290 corresponding to an N-acetylneuraminic acid fragment were produced in the collision cell and used in selected reaction monitoring. A standard addition technique was applied for quantification. The relative repeatability standard deviations were less than 5% for GD3 (level 10 mg/L) and 14% for GM3 (level 0.1-0.2 mg/L).

Pathophysiological implication of ganglioside GM3 in early mouse embryonic development through apoptosis

Apoptosis may occur in early embryos where the execution of essential developmental events has failed, and gangliosides, sialic acid-conjugated glycosphingolipids, are proposed to regulate cell differentiation and growth. To evaluate the regulatory roles of ganglioside GM3 in early embryonic development, this study examined its expressional patterns in apoptotic cells during early embryonic development in mice. Pre-implanted embryos were obtained by in vitro fertilization, which were treated at the 4-cell stage with three the apoptosis inducers, actinomycin D, camptothecin and cycloheximide, for 15 h. All three inducers significantly increased the percentage of apoptotic cells, as measured using a TUNEL method, but remarkably reduced the total cell numbers. The numbers of morula and blastocyst stages were significantly decreased by treatment of the embryos with the three apoptosis inducers compared with the control, with a similar result also observed in the number of blastomeres. Staining of early embryos with Hoechst 33342 revealed a significant percentage of apoptotic nuclei. Prominent immunofluorescence microscopy revealed a significant difference in the ganglioside GM3 expression in apoptotic embryos compared with the control, and RT-PCR also demonstrated a dramatic increase in ganglioside GM3 synthase mRNA in the apoptotic embryos. These results suggest that ganglioside GM3 may be pathophysiologically implicated in the regulation of early embryonic development through an apoptotic mechanism.

human and bovine milk gangliosides differ in their fatty acid composition

Gangliosides are considered bioactive components in human infant nutrition, and their fatty acid composition alters their biological effects. We used matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) MS and GLC to analyze the fatty acid composition of the predominant gangliosides, the monosialoganglioside GM(3) [sialic acid (Sia) alpha2-3 galactose (Gal) beta1-4 glucose (Glc) beta1-1 ceramide] and the disialoganglioside GD(3) (Sia alpha2-8 Sia alpha2-3 Gal beta1-4 Glc beta1-1 ceramide), in pooled human and bovine milk, the latter being a source for gangliosides in infant formula. Compared with whole milk lipids, both human and bovine milk gangliosides were selectively enriched with certain fatty acids, and the fatty acid composition of milk gangliosides in the 2 species was significantly different. The amount of long-chain fatty acids (> or =20 C atoms) was higher in bovine milk gangliosides (GM(3): 73.71 +/- 3.39%; GD(3): 79.19 +/- 2.79%) than in human milk gangliosides (GM(3): 51.25 +/- 0.65%; GD(3): 34.04 +/- 1.80%). Tricosanoic acid (23:0) dominated in bovine milk gangliosides (GM(3): 24.05 +/- 1.37%; GD(3): 26.66 +/- 1.24%), whereas it only played a minor role in human milk gangliosides (GM(3): 2.88 +/- 0.10%; GD(3): 1.84 +/- 0.29%). We hypothesized that the differences in the fatty acid composition of milk gangliosides result in physiological distinctions between breast-fed and formula-fed infants and therefore are of importance for human infant nutrition.

Ceramides and glycosphingolipids in maturation process: leukemic cells as an experimental model

Leukemic cells were used as experimental material to demonstrate changes in the content of GSLs during the development and maturation of neutrophils. The most abundant cellular GSL is LacCer. An elevation in the LacCer level occurs twice during the maturation process: initially, on formation of azurophil granules, and subsequently, (a more significant rise) on formation of specific granules. The formation of the latter is accompanied by an increase in the level of GalGalCer. During the maturation of myeloblasts, there is a simultaneous growth in the content of LacCer and GM3 as well as that of their common precursors, that is, free ceramides. Like other tumor cells, GM3 rich myeloblasts in the peripheral blood from patients with AML are characterized by shedding of gangliosides. The quantitative Cer/GlcCer ratio in these cells seems to be advantageous for the efficacy of chemotherapy in the induction of apoptosis. Myelo- and metamyelocytes achieve the highest level of GSLs. Their entry into the full maturity stage is accompanied by a decrease in the level of GSLs. Patterns of GSLs expression change greatly during development and maturation. However, with respect to the composition and content of GSLs, there are no significant differences between normal and leukemic mature neutrophils. At each stage of the development and maturation of myelogenous leukemic cells, as well as in normal mature neutrophils, there occurs the synthesis of the same molecular species both free ceramides and ceramide portions of LacCer, precursor of more complex GSLs.

Enhanced expression of a-series gangliosides in fibroblasts of patients with peroxisome biogenesis disorders

Peroxisome biogenesis disorders (PBD) are classified into Zellweger syndrome (ZS), infantile Refsum disease (IRD) and neonatal adrenoleukodystrophy. Disturbances in the differentiation of neural cells such as migration arrest are characteristic of PBD. So far the pathogenesis of these disturbances is not clearly understood. We describe an altered metabolism of glycosphingolipids in PBD which has not yet been investigated. We observed an increased amount of a-series gangliosides, GM2, GM1 and GD1a, in the fibroblasts of patients with ZS and IRD. Gangliosides GM1 and GD1a were not present in detectable amounts in normal subjects. A key step in the synthesis of a-series gangliosides is a transfer of GalNAc to ganglioside GM3, so we determined the level of ganglioside GM3 by immunohistochemical methods. We found a granular structure, which was positive toward anti-ganglioside GM3 antibody in the cytoplasm of the patients' fibroblasts. In control cells, the cell membrane was slightly positive toward anti-GM3 antibody. These results may help to clarify the pathogenesis of PBD with respect to the functional roles of glycosphingolipids in cell differentiation, proliferation and apoptosis.

Phenotype determination of anti-GM3 positive cells in atherosclerotic lesions of the human aorta. Hypothetical role of ganglioside GM3 in foam cell formation

Earlier we reported that atherosclerotic plaques contain cells which were specifically and very intensively stained with anti-GM3 antibodies although no GM3 positive cells were detected in the normal non-diseased arterial intima. Because of their lipid inclusions, GM3 positive cells in atherosclerotic lesions seemed to be foam cells but their origin needed clarification. Using an immunohistochemical technique in the present work, we showed that some of these foam cells contained CD68 antigen. However, the most intense accumulation of GM3 occurred in the areas composed of foam cells which did not stain with any cell type-specific antibodies, including antibodies to macrophages (anti-CD68) and smooth muscle cells (anti-smooth muscle alpha-actin), perhaps, because the cell type-specific antigens were lost during the transformation of intimal cells into foam cells. Ultrastructural analysis of the areas where foam cells overexpressed GM3 demonstrated that some foam cells lacked both a basal membrane and myofilaments but contained a large number of secondary lysosomes and phagolysosomes, morphological features which might indicate their macrophage origin. Other foam cells contained a few myofilaments and fragments of basal membrane around their plasmalemmal membrane, suggesting a smooth muscle cell origin. These observations indicate that accumulation of excessive amounts of GM3 occurs in different cell types transforming into foam cells. We suggest that up-regulation of GM3 synthesis in intimal cells might be an essential event in foam cell formation. Shedding of a large number of membrane-bound microvesicles from the cell surface of foam cells was observed in areas of atherosclerotic lesions corresponding to extracellular GM3 accumulation. We speculate that extracellularly localised GM3 might affect the differentiation and modification of intimal cells in atherosclerotic lesions.

Identification of GM3 as a marker of therapy-resistant periradicular lesions

The purpose of this study was to analyze the profile of glycosphingolipids (GSLs) in periradicular lesions refractory to endodontic treatment. Sixteen periapical lesions were removed surgically from patients (experimental group) and compared with 10 samples of periodontal ligament removed from extracted intact third molars (control group). After the GSLs extraction and purification procedures were performed the neutral and acidic GSL fractions were analyzed by high-performance thin-layer chromatography and quantified by densitometry. Data reported herein show that: (i) tissues in the experimental group presented about twice as much GSLs as the control group; (ii) lesion tissues express lactoneotetraosylceramide, and lactofucopentaosyl (IV) ceramide, whereas these neutral GSLs are absent in normal tissues; and (iii) normal tissues express GT1b, whereas lesions cells do not express this ganglioside. In contrast lesion tissues express GM3, which is conspicuously absent in normal tissues.

Studies on the specificity and sensitivity of the influenza C virus binding assay for 9-O-acetylated sialic acids and its application to human melanomas

The sensitivity and specificity of two influenza C virus assays, solid-phase and overlay assays, were investigated using naturally occurring 9-O-acetylated GD(3), rat serum glycoproteins containing 60% of N-acetyl-9-O-acetylneuraminic acid, and synthetically O-acetylated sialylated compounds. The sensitivity of the solid-phase assay was higher for glycoproteins containing N-acetyl-9-O-acetylneuraminic acid than for gangliosides, and also differed for various 9-O-acetylated gangliosides. The overlay assay was less sensitive for all glycoconjugates tested. For virus recognition the presentation of the sialic acid within the molecule and the structure of the sialic acid are essential. Investigation of gangliosides from human melanomas and normal skin with the influenza C virus assay showed an increase of O-acetylation of sialic acids in most tumour samples and the occurrence of several O-acetylated gangliosides.

A distinct ganglioside composition of rat pancreatic islets

Gangliosides in rat pancreatic tissue and isolated pancreatic islets were examined by methods including glycolipid-overlay techniques. The content of gangliosides in isolated pancreatic islets was approximately 6-fold higher than that in pancreatic tissue when compared on a protein basis. While N-glycolylneuraminic acid amounted to 7.2% of total lipid-bound sialic acids of pancreatic tissue, this molecular species was not detected in that of pancreatic islets. A remarkable difference in ganglioside composition was observed between pancreatic tissue and pancreatic islets. Pancreatic tissue showed a complex ganglioside pattern with GM3 as the largest ganglioside component, whereas isolated pancreatic islets had a simpler ganglioside profile without detectable amounts of GM3 and some other components. Pancreatic gangliosides were further examined by thin-layer chromatographic immunostaining with a monoclonal antibody A2B5 that reacts specifically with c-series gangliosides. Pancreatic tissue and pancreatic islets showed almost identical ganglioside patterns consisting of GT3, GT2, GQ1c, and GP1c. The concentration of c-series gangliosides in pancreatic islets was calculated to be more than 250-fold higher than that of pancreatic tissue. These results shows that pancreatic islet cells have a distinct ganglioside composition in rat pancreas.

Variation of the ganglioside compositions of human milk, cow's milk and infant formulas

The ganglioside compositions of human milk, cow's milk and infant formulas were compared. The results showed that there was a drastic change in the ganglioside composition from the colostrum to later human milk, and that both the patterns and contents of gangliosides in human milk, cow's milk and infant formulas differed markedly. In human milk, the total lipid-bound sialic acid level was two times higher than those in cow's milk and infant formulas. The major ganglioside in the later human milk, GM3 (27.7%), was only a minor component in the colostrum, cow's milk and infant formulas (3.3, 2.8 and 0.4-2.6%, respectively). GD3 represented 49.0, 61.0 and 72.4-86.6%, respectively, of the colostrum, cow's milk and infant formulas, compared to 31.8% of the later human milk gangliosides. Another four gangliosides, which were assumed to be c-series gangliosides, were detected in the colostrum and the later human milk. They represented 33-38% of total lipid-bound sialic acid, and were tentatively designated as GX1, GX2, GX3 and GX4, respectively. However, only GX1 and GX2 were observed in cow's milk and infant formulas. The variation of the gangliosides in human and cow's milk, and infant formulas might have some biological significance regarding neonatal brain development, allergies, infant growth and non-immunoglobulin prophylactic activities against some bacterial toxins.

Expression of mouse sialic acid on gangliosides of a human glioma grown as a xenograft in SCID mice

Ganglioside sialic acid content was examined in the U87-MG human glioma grown as cultured cells and as a xenograft in severe combined immunodeficiency (SCID) mice. The cultured cells and the xenograft possessed N-glycolylneuraminic acid (NeuGc)-containing gangliosides, despite the inability of human cells to synthesize NeuGc. Human cells express only N-acetylneuraminic acid (NeuAc)-containing gangliosides, whereas mouse cells express both NeuAc- and NeuGc-containing gangliosides. Small amounts of NeuGc ganglioside sialic acid (2-3% of total ganglioside sialic acid) were detected in the cultured cells, whereas large amounts (66% of total ganglioside sialic acid) were detected in the xenograft. The NeuGc in gangliosides of the cultured cells was derived from gangliosides in the fetal bovine serum of the culture medium, whereas that in the U87-MG xenograft was derived from gangliosides of the SCID host. The chromatographic distribution of U87-MG gangliosides differed markedly between the in vitro and in vivo growth environments. The neutral glycosphingolipids in the U87-MG cells consisted largely of glucosylceramide, galactosylceramide, and lactosylceramide, and their distribution also differed in the two growth environments. Asialo-GM1 (Gg4Cer) was not present in the cultured tumor cells but was expressed in the xenograft, suggesting an origin from infiltrating cells (macrophages) from the SCID host. The infiltration of mouse host cells and the expression of mouse sialic acid on human tumor cell glycoconjugates may alter the biochemical and immunogenic properties of xenografts.

Chronological changes in the ganglioside composition of human milk during lactation

The normal chronological changes in the ganglioside composition of human milk during lactation were examined by means of a high-performance thin-layer chromatography (HPTLC) micro-method with 1 ml of milk from each lactation. Six human milk ganglioside compositions were found, which were designated as GM3, GD3, GX1, GX2, GX3 and GX4. GX1-GX4, which had not been described previously, were tentatively assumed to be gangliosides of the c-series because they did not react to the GA1 antibody after sialidase treatment. GD3 was the major composition of the colostrum (GD3, 42-56%; GM3, 2.22-6.5%). GM3 increased sharply at eight days postpartum (GD3, 32.22%; GM3, 27.79%) and then increased gradually after eight days until examined at seven weeks postpartum (GM3/GD3, 0.84-2.67). The newly found GX1-GX4 showed some variability in the percentage composition between individuals, and there were no distinct differences between the colostrum and the later milk. The drastic compositional changes in GM3 and GD3 during lactation might have some biological significance, such as in immunological activity, somatic growth and the nervous system.

Atherosclerotic aortic gangliosides enhance integrin-mediated platelet adhesion to collagen

Gangliosides, sialic acid-containing glycosphingolipids, accumulate in atherosclerotic vessels. Their role in the pathogenesis of atherosclerosis is unknown. Gangliosides isolated from tumor cells promote collagen-stimulated platelet aggregation and ATP secretion and enhance platelet adhesion to immobilized collagen. These activities are all mediated by ganglioside effects on the platelet integrin collagen receptor alpha2beta1. Therefore, we hypothesized that gangliosides isolated from atherosclerotic plaques would enhance platelet adhesion to immobilized collagen, a major component of the subendothelial matrix of blood vessels. Furthermore, we questioned whether this effect of atherosclerotic gangliosides might play a role in the pathogenesis of atherosclerosis. To test this hypothesis, we isolated the gangliosides from postmortem aortas of patients with extensive atherosclerotic disease and examined their effects on platelet adhesion. Samples of aortic tissue taken from areas involved with atherosclerotic plaque demonstrated accumulation of gangliosides (64.9+/-6.5 nmol/g wet weight) compared with gangliosides isolated from control normal aortic tissue taken from children who died of noncardiac causes (NAGs; 21.1+/-6.4 nmol/g wet weight). Interestingly, samples of tissue taken from diseased aortas but from areas not involved with gross plaque formation also demonstrated ganglioside accumulation (47.6+/-12.8 nmol/g wet weight). Next, the activity of each of these gangliosides on platelet adhesion to immobilized type I collagen was studied. Atherosclerotic aortic gangliosides (AAGs) as well as those isolated from grossly unaffected areas of the same aorta (UAGs) both increased platelet adhesion compared with control NAGs (OD570, 0. 37+/-0.11 and 0.29+/-0.14 versus 0.16+/-0.07, respectively; P<0.01 and P<0.05, respectively). These OD570 values corresponded to 9x10(5), 8x10(4), and 6x10(3) platelets per well after preincubation with 5 micromol/L AAG, UAG, and NAG, respectively. Increased adhesion was observed after preincubation with as little as 0.5 micromol/L AAG, and maximal adhesion was seen at 2.5 micromol/L, with a plateau extending to the highest concentration tested, 10 micromol/L. The effect of AAGs on platelet adhesion to collagen was abrogated by incubation of treated platelets with F-17 anti-alpha2 monoclonal antibody (OD570, 0.13+/-0.02). Finally, the effects of the major individual gangliosides isolated from atherosclerotic tissues, GM3 and GD3, were tested. GM3 increased adhesion to collagen (OD570, 0.415+/-0.06) as did GD3 (0.31+/-0.08). Similar to that of AAGs, the effect of both molecules was blocked by F-17 (0. 09+/-0.04 and 0.13+/-0.06, respectively). These experiments demonstrate that accumulated atherosclerotic gangliosides promote platelet adhesion to collagen, the major component of the subendothelial matrix. Furthermore, this activity is mediated by an effect of the gangliosides on the collagen-binding integrin alpha2beta1. This activity may provide a mechanism for the development of platelet thrombi at sites where atherosclerotic gangliosides accumulate and help to explain the role of platelets in the process of atherosclerotic disease progression.

Distribution of gangliosides, GM1 and GM3, in the rat oviduct

It is known that gangliosides, being ubiquitous membrane components, play important roles in cell-cell recognition, differentiation and transmembrane signalling. GM3, GM1 and GD1a were detected in the rat oviduct as major gangliosides by thin-layer chromatography (TLC) analysis. The total amounts of gangliosides from the oviducts at various times after hormone injection were not much changed. In order to identify their distribution and possible changes during ovulation, frozen sections of the rat oviducts were stained with specific monoclonal antibodies (MAbs) against the ganglio-series gangliosides. GM3 and GM1 were expressed in a different manner, but GD1a and other gangliosides were not immunohistochemically detected. In the ampullar region, GM3 was expressed in all the stroma and epithelial cells, but not GM1. GM1 was also not observed in epithelial cells. Staining by anti-GM1 monoclonal antibodies revealed long and minute thread-like structures in some of the stroma cells, whereas anti-GM3 monoclonal antibodies stained the entire cytoplasm, but not the nucleus, of all the stroma and epithelial cells. Other ganglio-series gangliosides, including GD1a, were not detected to some extent in the ampullar region by immunohistochemistry. Thus, these data suggest that GM3 and GM1 are oviduct-specific gangliosides.

GT1b in human metastatic brain tumors: GT1b as a brain metastasis-associated ganglioside

We studied ganglioside expression in 12 human metastatic brain tumors metastasized from colon (4), renal (3), lung (2), esophagus (1), pancreas (1), and mammary (1) carcinomas. GM3 was the major common ganglioside expressed in brain metastatic tumor tissues, and GT1b was also present in all the metastatic brain tumor tissues. The latter was identified by TLC-immunostaining and characterized structurally by secondary ion mass spectrometry combined with 'Far-Eastern blot'. The immunohistochemical analysis of frozen tissue sections confirmed localization of GT1b in the tumor cell membrane or cytosol. GT1b was shown to be expressed both in the primary colon carcinoma and the metastasis of a single patient by immunohistochemical procedure. In systemic carcinomas without brain metastasis, GM3 was a common major component, but no GT1b was detected. These findings indicate that GT1b is a brain metastasis-associated ganglioside. We speculate that the presence of GT1b would be a useful marker for estimating metastatic potentials to the brain.

Isolation and culture of bovine endothelial cells of endoneurial origin

Penetration of immunoglobulins and/or migration of activated lymphocytes into peripheral nervous system (PNS) parenchyma are the initial key steps to develop immunological disorders of PNS including Guillain-Barré syndrome, IgM neuropathy and chronic inflammatory demyelinating polyradiculoneuropathy. Hence, it is important to know the cellular property of endothelial cells of endoneurial tissue origin (PnMEC) because these cells constitute the bulk of the blood-nerve barrier (BNB). For this purpose, we developed a method to isolate and culture pure populations of PnMECs from bovine cauda equina. PnMECs were identified by their cobblestone appearance, immunoreactivity against Factor VIII/von Willebrand factor (vWF) antigen, and positive uptake of DiI-Ac-LDL. The glucose transporter type 1 (GLUT1) expression of these cells was rapidly down-regulated in vitro. Other than GM3(NeuAc) and GM3(NeuGc) as major glycosphingolipids, PnMECs comprise GM1, GD1a, GD1b and GT1b, which are shared by PNS parenchyma, and sialyl lactosaminyl paragloboside (SLPG) as minor species. Because bovine PnMECs proliferate rapidly and a large mass of cells could be obtained, this method should contribute to the biochemical analysis of surface molecules in PnMECs that might play a key role in the formation of BNB as well as in pathological conditions involving the PNS.

A close association of GM3 with c-Src and Rho in GM3-enriched microdomains at the B16 melanoma cell surface membrane: a preliminary note

B16 melanoma is characterized by high content of GM3 ganglioside, which has been recognized as a melanoma-associated antigen defined by specific monoclonal antibodies. We report now that GM3 is present predominantly (>90%) in the 1% Triton X-100-insoluble, low-density microvesicular fraction ("detergent-insoluble glycosphingolipid-enriched microdomain"; DIGEM) separated on sucrose density-gradient centrifugation. Associated with DIGEM, many signal transducer molecules such as c-Src, FAK, and the low-molecular-weight G-proteins Rho A and H-Ras were also found. Rho A and FAK were found in part, and PLC-beta2 and G alphas were found exclusively, in the high-density fraction. Immunoprecipitation of GM3 present in DIGEM by anti-GM3 antibody DH2, followed by Western blotting, revealed co-precipitation of Rho A and c-Src with GM3. These findings suggest (i) a specific organization of GM3 in close association with Rho A and c-Src within DIGEM at the melanoma cell surface; and (ii) such organizational units may be directly involved in signal transduction, in which glycosphingolipids receive signals which are subsequently transduced by associated transducer molecules.

Developmental changes in carbohydrate antigens in embryonic rat lens

The functions of glycosphingolipids, especially those containing the alpha-galactosyl epitope, were investigated during the development and differentiation of rat lens. Glycosphingolipids in embryonic lens tissue were mainly composed of neolacto-series glycosphingolipids and sialic acid-containing ganglio-series gangliosides GM3 and GD3. These glycosphingolipids and gangliosides were widely expressed on cell membranes in the lens vesicle and the elongating lens fibers. In particular, the expression of neolacto-series glycosphingolipids with the alpha-galactosyl epitope was found to be associated with the differentiation and interaction of lens fibers. Glycoproteins with the alpha-galactosyl epitope was also involved in the elongation of lens fibers. The expression of the glycoproteins was highly specific in elongating lens fibers when these were examined in head sections obtained at various embryonic stages. Thus, the alpha-galactosyl epitope on glycosphingolipids and glycoproteins appears to be associated with the differentiation and elongation of lens fibers in the rat. Evolution-related changes in the expression of carbohydrate antigens are also discussed in relation to the development and cell-to-cell interaction of lens fibers in mammals.

Human medulloblastoma gangliosides

To establish a model system for the study of ganglioside metabolism of the human brain tumor, medulloblastoma, we have chemically characterized the gangliosides of the Daoy cell line. These cells contain a high concentration of gangliosides (143 +/- 13 nmol LBSA/10(8) cells). The major species have been structurally confirmed to be GM2 (65.9%), GM3 (13.0%), and GD1a (10.3%). Isolation of individual gangliosides homogeneous in both carbohydrate and ceramide moieties by reversed-phase HPLC and analysis by negative-ion fast atom bombardment collisionally activated dissociation tandem mass spectrometry have allowed us to unequivocally characterize ceramide structures. In the case of GM2, 10 major ceramide subspecies were identified: d18:1-hC16:0, d18:1-C16:0, d18:0-C16:0, d18:1-C18:0, d18:1-C20:0, d18:1-C22:0, d18:2-C24:1, d18:1-C23:1, d18:1-C24:1, and d18:1-C24:0. Taken together with previous studies, these findings in buman medulloblastoma cells support the view that high expression and marked heterogeneity of ceramide structure are general characteristics of tumor gangliosides, molecules which are shed by the tumor cells and which are biologically active in vivo.

Evidence for the existence of ganglioside-enriched plasma membrane domains in human peripheral lymphocytes

In human peripheral blood lymphocytes (PBL) monosialoganglioside GM3 appears to be the major ganglioside on the cell plasma membrane. We have analyzed the expression and distribution pattern of GM3 molecules on the lymphocyte plasma membrane by flow cytometry, immunofluorescence, and immunoelectron microscopy, using an anti-GM3 monoclonal antibody. Both CD4+ and CD8+ T lymphocyte subpopulations showed substantial GM3 expression, as determined by thin-layer chromatography and flow cytometric analysis. A clustered distribution of GM3 molecules on the cell surface, revealed by immunofluorescence and immunogold electron microscopy, clearly indicated the presence of GM3 molecule-enriched plasma membrane domains. To better define these domains, we analyzed the ganglioside and protein composition of buoyant low-density Triton-insoluble (LDTI) lymphocyte fractions. The results show that GM3 is enriched approximately 20-fold in LDTI fraction, as compared with total cell lysates. In addition, CD4 and lck molecules are selectively recovered in the same LDTI fraction isolated from human PBL. These findings, together with the observation that anti-CD4 co-immunoprecipitated GM3, support the hypothesis of a possible GM3-CD4 interaction and suggest a role for gangliosides as structural components of the membrane multimolecular signaling complex involved in T-cell activation, antigen recognition, and other dynamic lymphocytic plasma membrane functions.

Ganglioside content of human platelets--differences in resting and activated platelets

Gangliosides may play functional roles in platelet physiology, therefore this study has been designed to evaluate whether changes in ganglioside composition may occur as a consequence of platelet activation. The results obtained indicate that lactosylceramide and GM3 are the major glycosphingolipids of human platelets. The lipid-bound sialic acid (LBSA) content was 1.27 +/- 0.04 micrograms/mg of protein. Resting platelets did not express GD3; GD3 was synthesized upon platelet activation (24 +/- 8 ng/mg of protein). The stimulation of platelets with adenosine diphosphate showed the appearance of GD3 even in the absence of degranulation. Finally, incorporation of pyrene-labeled GM3 into platelet membranes, followed by stimulation with adenosine diphosphate, resulted in the appearance of a fluorescent band comigrating with GD3. The present studies indicate that sialytransferase activation may occur as an early event following platelet stimulation, leading to GD3 synthesis mainly from the GM3 pool.

Anti-GM3 (II3Neu5Ac-lactosylceramide) ganglioside antibody labels human fetal Purkinje neurons during the critical stage of cerebellar development

The ganglioside GM3 (II3Neu5Ac-lactosylceramide) represents a minor ganglioside in normal human brain compared to major gangliosides with gangliotetraose-backbone. In this study the presence of GM3 in three 23 and 24 weeks of gestation old human cerebella was demonstrated by immunostaining extracted gangliosides on thin-layer chromatography plate as well as by immunohistochemical analysis of cerebellar cryosections. During this stage of brain development GM3 was found to be dominantly expressed on cells corresponding to Purkinje neurons. Delipidation of histological sections with chloroform/methanol caused significant reduction of anti-GM3 immunostaining, thus confirming the prevalent ganglioside nature of this antigen. These results give evidence that (1) GM3 ganglioside is associated with a specific subset of human fetal cerebellar neurons during the critical development stage, and (2) a definite ganglioside in general is distributed to a specific subset of cells in normal human brain.

Ganglioside composition of the rat choriocarcinoma cell line, Rcho-1

The Rcho-1 cell line, originally established from a rat choriocarcinoma, shows differentiation into placental trophoblastic giant cell-like cells and has been used to study the mechanism of placental function control. In the present study, we analysed the ganglioside composition of Rcho-1 cells by HPTLC orcinol/H2So4, TLC/ immunostaining and immunohistochemistry. Rcho-1 cells expressed GM3 and GD3 as the major gangliosides and CTH as major neutral glycolipid when they were cultured in growth medium (20% FCS) or transplanted beneath the kidney capsule. The expression of these gangliosides was strong in the undifferentiated small cells, whereas the completely differentiated giant cells showed poor staining with antibodies against the gangliosides. Under culture conditions to induce cell differentiation using horse serum (1-20% HS), the expression of GD3 was suppressed and re-expressed when the medium was changed to growth medium, suggesting that a change of ganglioside components may trigger and define the direction of terminal differentiation. Thus the composition of glycolipids is conserved in Rcho-1 cells and is similar to that of the rat placenta, where GM3 is dominant in mid-pregnancy and decreased in late pregnancy, whereas GD3 is low in mid-pregnancy and increased in late pregnancy.

Evidence for the existence of ganglioside molecules in the antigen of Entamoeba histolytica

Gangliosides were found to be present in Entamoeba histolytica. They were extracted from lyophilized trophozoites of the pathogenic strain HM-1:IMSS and purified by high performance thin-layer chromatography. Two resorcinol-positive bands, comigrating with GM2 and GD1a were demonstrated, revealing the existence of ganglioside molecules in Entamoeba histolytica. The GM2 content, determined as lipid-bound sialic acid, was 1.5 micrograms/10(8) amoebae, the content of the GD1a comigrating band was 0.32 microgram/10(8) amoebae. The identity of the GM2 comigrating band was confirmed by TLC immunostaining, using the monoclonal anti-GM2 antibody GMB28. Furthermore, six out of ten anti-amoeba positive sera selectively reacted with the GM2 comigrating band, as revealed by immunostaining on TLC plates. Absorption tests revealed that preincubation of anti-amoeba positive sera with standard GM2 was followed by a significant decrease in the reaction with amoeba trophozoites by indirect immunofluorescence. These results demonstrate that a GM2 comigrating component of Entamoeba histolytica may be one of the antigens responsible for the appearance of circulating antibodies in patients with amoebiasis.

Ganglioside GM1 and GM3 in early human brain development: an immunocytochemical study

The distribution of GM1 and GM3 gangliosides in human brain development between gestational week (g.w.) 6 and 15 was demonstrated by an immunocytochemical approach using polyclonal anti-GM1 and anti-GM3 antibodies. The first appearance of GM1- and GM3-positive cells was recorded as early as in g.w.6. Both antibodies labeled the cells in the ventricular zone of the telencephalic wall, with radially oriented fibers toward the pial surface, which represent radial glia cells with glia fibers. The intensive GM3 immunoreactivity was also exhibited in proliferating cells in the ventricular zone between g.w.6 and 12. During the period from g.w. 12 to 15, characterized by a rapid multiplication of neurons and glia cells, an increased number of GM1- and GM3-positive cells was observed. Prominent GM1 ganglioside staining was observed at the surface of the cell bodies in the ventricular zone. Besides surface labeling in migrating cells, GM1 immunoreactivity was identified inside the soma in the regions of cortical plate and subplate. GM1 immunoreactivity was more pronounced on the membrane of neuronal cells migrating along radial glia fibers, especially at the contact site between neuronal and glial cells. The GM3 ganglioside was localized mostly inside the soma, showing a granular immunoreactivity pattern. Our observations confirm the presence of GM1 and GM3 gangliosides in neuronal and glial cells in early human brain development. The involvement, especially of GM1 ganglioside in glia-neuronal contacts during migration of neuroblasts to their final destination, as well as the presence of GM3 ganglioside in proliferative cells in the ventricular zone of the telencephalic wall was also recorded.

New data on content and distribution of gangliosides in human milk

The content and distribution of gangliosides, and total lipid content, were studied in human milk samples from different periods of lactation. We found a significant correlation (r = 0.5564; p = 0.0165) between ganglioside and total lipid contents. There was a selective change in the relative concentrations of GD3 and GM3 during lactation. The most abundant ganglioside in samples from the first three weeks of lactation was GD3, whereas after the first month, GM3 was the major ganglioside. In addition to GD3 and GM3, previously known to be present in human milk, we detected several previously unreported highly polar gangliosides.

Ganglioside profiles of experimental melanomas and of their melanosomal fractions

We compared ganglioside profiles of animal tumours (B16 and Cloudman S91 murine melanomas, Bomirski Syrian hamster melanoma), which are widely used as models of human melanoma, and of their melanosomal fractions. A ganglioside fraction was extracted and purified and the amount of each component ganglioside was assessed by thin-layer chromatography. GM3 was the dominant ganglioside species in the murine melanomas studied. Unlike human melanomas, the GD3 expression in mouse melanomas was low. GD3 and GM3 were major gangliosides in Bomirski hamster melanoma. Alkali-labile O-acetyl-GD3, a melanoma-specific ganglioside, was detected only in Bomirski melanoma. GD2, which in human melanoma is seen as a distinct signal of tumour progression, was not found in the animal melanomas studied. Melanosomes isolated from B16 and Bomirski melanomas contained GM3 and GD3 as their major ganglioside components. These data extend the group of common antigenic determinants shared by melanosomes and cell surface of pigment cells.

Expression of de-N-acetyl-gangliosides in human melanoma cells is induced by genistein or nocodazole

Neuraminic acid is the core structure of most known sialic acids. In natural systems, the amino group at the 5 position of neuraminic acid residues is usually assumed to be acylated. Previously, synthetic de-N-acetyl-gangliosides (with free amino groups at the 5 position of neuraminic acids) have been shown to modulate cellular proliferation and tyrosine phosphokinase reactions. While indirect evidence has suggested that traces of these molecules exist naturally in certain tumor cells, further exploration has been hampered by the lack of a system showing consistent expression at an easily detectable level. Using synthetic compounds as antigens, we have developed highly specific monoclonal antibodies against de-N-acetyl-GM3 and de-N-acetyl-GD3 that require both the free amino group and the exocyclic side chain of sialic acids for recognition. Cultured human melanoma cells showed low but variably detectable levels of reactivity with these antibodies. The ability of various biologically active molecules to stimulate this reactivity was explored. Of many compounds tested, only the tyrosine kinase inhibitor genistein induced reactivity in a dose-dependent manner. Antibody reactivity with ganglioside extracts from genistein-treated cells was abolished by chemical re-N-acetylation and/or truncation of sialic acid side chains by mild periodate oxidation. High performance thin layer chromatography immuno-overlay analysis confirmed the presence of the novel compound de-N-acetyl-GD3 in these extracts. Several other tyrosine kinase inhibitors tested did not give the same increase in de-N-acetyl-ganglioside expression. However, the microtubule inhibitor nocodazole caused a similar accumulation of these molecules, particularly in non-adherent cells expected to be arrested at metaphase. Thus, genistein may induce de-N-acetyl-ganglioside expression by virtue of its known ability to arrest cells in the G2M phase, rather than as a general consequence of tyrosine kinase inhibition. These studies also provide a system in which to analyze the enzymatic basis of de-N-acetyl-ganglioside expression and their potential roles as growth regulating molecules.

Glycoprotein and ganglioside changes in human trophoblasts after exposure to pulsed Doppler ultrasound

Changes in glycoprotein and ganglioside composition in human trophoblasts (eighth week of gestation) after in vitro exposure to pulsed Doppler ultrasound (pulse duration 1.22 microseconds; repetition frequency 11.1 kHz; center frequency 4 MHz; ISPPA = 175.5 W/cm2; ISPTA = 0.59 W/cm2) were investigated. Evacuated trophoblasts were divided in two halves and insonated for 10 min on top of a 6-cm layer of 5% gelatin in 50-mL tubes (Falcon) at 37 degrees C. One half of each trophoblast was sham insonated and served as an internal control. After insonation trophoblasts were maintained at 37 degrees C for 24 h. Glycoproteins were detected using alpha-D-mannose specific lectins from Galanthus nivalis and Narcissus pseudonarcissus. A decrease in the expression of mannose containing glycoprotein mgp47 and an increase in expression of mgp54 were observed. Ganglioside composition was also significantly altered. Concentrations of two gangliosides migrating similarly to GM2, and one similarly to GQ1, decreased by more than 75%. At the same time, concentrations of one ganglioside migrating similarly to GM3, and two other unidentified gangliosides increased two- to fourfold.

Gangliosides as diagnostic markers of human astrocytomas and primitive neuroectodermal tumors

BACKGROUND

Limitations of classification schemes for brain tumors based solely on morphology have stimulated searches for molecular markers of nosologic and prognostic value. Gangliosides are logical candidates because there are high concentrations of them in the nervous system, there is evidence of their roles in regulation of growth and differentiation, and data from small series suggest correlations between ganglioside composition and glioma type.

METHODS

Ganglioside compositions were determined for 70 primary human brain tumors: 16 low grade astrocytomas (LG), 12 anaplastic astrocytomas (AA), 34 glioblastoma multiformes (GBM), and 8 primitive neuroectodermal tumors (PNET). This method involved identification and quantitation of specific gangliosides using chemical analysis and immunoanalysis.

RESULTS

Among all tumor types, histologic grade correlated with a progressive loss of 1b gangliosides (P < 0.0001). GQ1b was higher in LGs than in AAs (P < 0.001). Both GT1b and GD1b were higher in AAs than GBMs (P < 0.01 and 0.05, respectively) and lower in PNETs than in GBMs (P < 0.05). GM3 was higher in PNETs than in any astrocytoma group and higher in GBMs than in either AAs or LGs. There was a significant difference in the content of 3'-LM1 among all groups (P < 0.005), between AAs and GBMs (P < 0.05), and between low grade ordinary and juvenile pilocytic astrocyomas (P < 0.01). The lacto-series ganglioside 3'-isoLM1 was present in all groups except PNET.

CONCLUSIONS

These results indicate that patterns of gangliosides could be of considerable value in refining the classification and diagnosis of primary human brain tumors.

Association of the GPI-anchored leucocyte surface glycoproteins with ganglioside GM3

The major glycolipid co-immunopurifying with the glycosylphosphatidylinositol-anchored leucocyte surface glycoprotein CD59 from detergent lysates of human T cell lines HPB ALL, Jurkat and myeloid line HL-60 was identified as the glycosphingolipid GM3. Monoclonal antibodies to GM3 immunoprecipitated the same large detergent-resistant, protein-tyrosine kinase containing "GPI-complexes" as antibodies to several GPI-anchored proteins. Therefore GM3 is another component of these large membrane complexes potentially involved in signalling through GPI-anchored receptors or through some glycolipids.

Expression of gangliosides GM3 (NeuAc) and GM3 (NeuGc) in myelomas and hybridomas of mouse, rat, and human origin

In this study gangliosides from various myelomas and hybridomas of mouse, rat, and human origin were characterized by thin-layer and high-performance liquid chromatography, immunological methods (overlay technique) and fast atom bombardment mass spectrometry. Exclusively GM3 substituted with C24:1- and C16:0-fatty acid, was found in all B cell-derived cell lines. C18 sphingosine was the single long chain base in each GM3 ceramide portion. The mouse myeloma (NS-1) and all hybridomas, obtained by fusion of mouse, rat, or human B lymphocytes with murine myelomas, showed high GM3 (NeuGc) content (> 75%) and low GM3 (NeuAc) expression. Absolute amounts of GM3 ranged from 0.2 up to 0.8 mg x 10(-9) cells. Normally, human cells do not express NeuGc, and an Epstein-Barr virus-transformed human B lymphocyte line analyzed in this study retained this sialylation status, expressing exclusively GM3 (NeuAc) (100%). The fusion of human B lymphocytes with mouse myelomas led to high GM3 (NeuGc) expression (average about 85%) in all mouse/human heterohybridomas examined. Our results indicate the chromosomal gene "transfer" and/or the activation of enzymes involved in NeuGc-biosynthesis due to the somatic cell fusion process, which might explain the mouse dominance in the manifestation of the NeuGc-phenotype in hybridomas of human origin.

Characterization and use of biotinylated Escherichia coli K99 lectin

K99 lectin from Escherichia coli was purified and biotinylated via the amino groups of lysine residues using N-biotinyl-6-amino-caproic acid N-hydroxysuccinimide ester (BcapNHS). Biotin was detected on Lys-47 and Lys-87. It was previously demonstrated (Jacobs, A.A.C., Van den Berg, P.A., Bak, H.J. and De Graaf, F.K. (1986) Biochim. Biophys. Acta 872, 92-97) that modification of lysine residues 132 and 133 with 4-chloro-3,5-dinitrobenzoate (CDNB) resulted in the loss of the binding capacity of K99 fimbriae. Due to the higher size of the biotin derivative compared to CDNB, Lys-132 or Lys-133, essential for the biological activity, were not modified. The biotinylation did not cause the loss of the haemagglutinating activity but was sufficient to permit detection of the lectin by streptavidin. A flow cytometric analysis was used for the detection of the receptors on the surface of erythrocytes.

Glycosphingolipids in cultured lens epithelial cells from dog and rhesus monkey

Vertebrate lens tissues contain several species of acidic and neutral glycosphingolipids in relatively high amounts. However, the epithelia with capsule from dog and rhesus monkey lenses had a simpler composition and lower content of glycosphingolipids than whole lenses. Gangliosides and neutral glycosphingolipids in monolayer cultures of lens epithelial cells were also different from those in whole lenses. Although alpha-galactosyl (Gal alpha 1-3Gal-R) or Lewis(x) (Gal beta 1-4[Fuc alpha 1-3]GlcNAc-R) epitopes were found in glycosphingolipids from whole lenses, they were not detected in those from monolayer cultures of dog and rhesus monkey lens cells. In addition, significant changes in ganglio-series gangliosides were induced in monolayer cultures of both cells, where GM3 and GD3 were predominant. Immunofluorescence study revealed a characteristic distribution of cell surface gangliosides in confluent monolayers. These findings suggest that glycosphingolipid synthesis in lens epithelia is intrinsically different from that in cortical and nuclear fibres, and that the expression of Lewis(x) and alpha-galactosyl epitopes in glycosphingolipids appears to be associated with the differentiation of epithelial cells to fibres.

Protein kinase C substrates and ganglioside inhibitors in bovine mammary nuclei

In cow mammary gland, unlike in other tissues, gangliosides (putative physiologic regulators of protein kinase C) may be distributed in nuclei and on the cell surface. This study was designed to determine whether gangliosides and the protein kinase C system (the enzyme and its substrate proteins) are present in cow mammary gland nuclei and to examine the effect of gangliosides detected in nuclei on protein phosphorylation catalyzed by protein kinase C. Gangliosides GM3, GD3, and GT1b were detected in the highly purified nuclear fraction. The nuclear ganglioside pattern was different from those of whole tissue and cytosol, thereby suggesting the presence of the gangliosides in nuclei. Protein kinase C and its substrate proteins (120, 97, 56, 43, 38, and 36 kDa) were extracted by Triton X-100 treatment of nuclei. Both protein kinase C activity (histone phosphorylation) and the nuclear substrate phosphorylation were effectively inhibited by the three gangliosides. Of the gangliosides, GT1b was the most potent in inhibiting phosphorylation, followed by GD3 and GM3. These results suggest that signal transduction mediated by protein kinase C in cow mammary gland nuclei may be regulated by gangliosides.

Molecular cloning of a human monoclonal antibody reactive to ganglioside GM3 antigen on human cancers

In this study we report the characterization of a human monoclonal antibody (HuMab), L612, that reacts with ganglioside GM3 and has therapeutic application for the treatment of human neoplasms, particularly melanoma. A permanent IgM-secreting Epstein-Barr virus-transformed B-cell line L612 was established. L612 HuMab bound specifically to neoplastic cell lines in culture and in tissue biopsy specimens such as melanoma, colon, breast, and lung cancer. The antibody did not bind to normal cells or biopsy tissue. HuMab L612 showed the highest reactivity to melanoma cells, particularly to those with high concentrations of GM3. Immunostaining on high-performance thin-layer chromatography plates demonstrated that L612 HuMab bound to GM3 purified from melanoma cells. Removal of the sialic acid from GM3 abolished antibody binding. HuMab L612 also reacted to GM4 purified from egg yolk, indicating that it recognizes an NeuAc alpha 2-3 galactose antigen determinant. HuMab L612 heavy and light chains were sequenced and determined to belong to the mu heavy chain variable subgroup III and kappa chain variable subgroup IV families, respectively. The studies indicate that the L612 HuMab has significant therapeutic potential for a wide variety of human cancers.

Ganglioside composition of subcellular fractions, including pre- and postsynaptic membranes, from Torpedo electric organ

Gangliosides were isolated from four subcellular fractions of the electric organ of Torpedo marmorata: synaptosomes, presynaptic membranes, postsynaptic membranes, and synaptic vesicle membranes. This exploited a principal advantage offered by this tissue: facile separation of pre-and postsynaptic elements. Total ganglioside concentration in presynaptic membranes was approximately twice that of synaptosomes and 15 times that of postsynaptic membranes (47.7, 24.4, and 3.21 micrograms of lipid sialic acid per mg protein, respectively). Synaptic vesicle membranes had the highest overall concentration (78.9) relative to protein, but a concentration approximately comparable to that of presynaptic membranes when expressed relative to phospholipid. The thin-layer patterns of these two fractions were similar, both in terms of total pattern and the specific pattern of gangliotetraose structures as revealed by overlay with cholera toxin B subunit; these were notable for the paucity of monosialo structures and the virtual absence of GM1. Postsynaptic membranes, on the other hand, had a significantly higher content of monosialogangliosides including the presence of GM1. The synaptosomal pattern resembled that of the presynaptic membranes and synaptic vesicles. Thus, a clear difference in ganglioside pattern could be discerned between the pre- and postsynaptic elements of the electric organ.

[Ganglioside lactones in human stomach and breast tumors]

Ganglioside lactones absent in homologous normal tissues have been found in minute amounts in human gastric and mammary tumours. In mammary gland tumours only the ganglioside GM3 lactone has been identified. Gastric tumours also contain the GM3 lactone; in one case a ganglioside GD3 lactone was identified.

Expression of ganglioside GM3 and H-2 antigens in clones with different metastatic and growth potentials isolated from Lewis lung carcinoma (3LL) cell line

In view of the evidence that cell expression of gangliosides in several tumors is positively involved in the metastatic phenotype, Lewis lung carcinoma (3LL) cell line, expressing GM3 as the major ganglioside, was analysed for the cell surface expression of GM3. An indirect immunofluorescence assay, using a M2590 monoclonal antibody recognizing GM3, was used for this purpose. Since the parental 3LL cells consist of heterogenous subpopulations differing in the degrees of GM3 expression, we have developed clones of this cell line with different degrees of metastatic potentials by using an in vitro non-selective procedure in order to investigate whether the expression of GM3 is associated with metastatic potential. The degree of cell surface expression of GM3 among the clones correlated well with their total cellular content of this ganglioside. However, we were unable to confirm the report of increased level of GM3 in high metastatic 3LL clones, nor did a decreased level correlate with weak metastatic ability. In our recent work, an inhibitor of glucosylceramide synthase, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), was found to decrease the levels of all cellular glucosphingolipids and cause the accumulation of the precursors of glucosylceramide. The present study does not, however, rule out the possible involvement of this lipid family in metastatic dissemination, since treatment of 3LL cells with D-PDMP resulted in significant inhibition of their experimental metastatic potential. Clones expressing very low GM3 grew slowly in culture dishes, suggesting that GM3 may have a regulatory role in cell proliferation. The low metastatic clones expressed high levels of H-2Kb antigen, while the expression of the same antigen on the high metastatic clones was relatively low, confirming the previous observation of this tumor system. Moreover, a clone showing the lowest tumorigenic potency revealed both a high cell surface expression of H-2Kb and a high H-2Kb/H-2Db ratio.

Myelin gangliosides of human peripheral nervous system: an enrichment of GM1 in the motor nerve myelin isolated from cauda equina

Myelins of the PNS were isolated from human motor and sensory nerves of cauda equina, and their ganglioside compositions were compared. The predominant ganglioside in the human PNS myelins, both from motor and sensory nerves, was LM1 (sialosylneolactotetraosylceramide). Sialosyl-nLc6Cer and disialosyl-nLc4Cer, GD3, GM3, and GD1b were detected as common components of the two nerve myelins. Furthermore, it was revealed that the motor nerve myelin contained GM1 (about 15% of total gangliosides), whereas sensory nerve myelin contained only a trace amount of GM1 (less than 5%), by TLC analyses together with TLC immunostaining using anti-GM1 antibody. As for the disialoganglioside fraction, the content of GD1a, as well as that of GM1, differed in motor and sensory nerves. Thus, the different contents of the ganglioseries gangliosides in human motor and sensory nerve myelins were demonstrated.

Common phenotypic expression of gangliosides GM3 and GD3 in normal human tissues and neoplastic skin lesions

The expression of gangliosides in non-malignant tissues (epidermis and pigmented nevus) and neoplastic lesions (melanoma, squamous cell carcinoma [SCC] and basal cell carcinoma [BCS]) of the human skin was analyzed immunohistochemically and biochemically to characterize the features associated with malignancy. Immunohistochemical staining with an anti-II3NeuAc-LacCer (GM3) monoclonal antibody (M2590 mAb) and an anti-II3(NeuAc)2-LacCer (GD3) mAb (R24) showed the expression of the gangliosides GM3 and GD3 to vary among the different tissues. M2590 clearly stained epidermal keratinocytes and the tumor cells of BCC and SCC, and strongly stained melanocytes and melanoma cells. In contrast, R24 did not stain epidermal keratinocytes and only faintly stained SCC cells, while it clearly stained BCC cells, and intensely stained melanocytes and melanoma cells. GM3 showed a similar level of staining among the tissue specimens, while the level of GD3 staining was quite variable among the tumor specimens. Biochemical analysis by thin-layer chromatography (TLC) with resorcinol staining and TLC immunostaining with either M2590 or R24 showed both GM3 and GD3 to be commonly expressed by both the normal and malignant skin tissues, including SCC. There was no close correlation between the intensity of immunohistochemical staining and the biochemically detected amounts of these gangliosides. This may have been partly due to the so-called cryptic expression of cell membrane gangliosides. Our results thus suggest that analysis of the tumor-associated expression of gangliosides requires several methods, since the sensitivity of the methods used may have a considerable effect on the diagnostic value of gangliosides as skin cancer markers.

Solution conformations of GM3 gangliosides containing different sialic acid residues as revealed by NOE-based distance mapping, molecular mechanics, and molecular dynamics calculations

The conformation of the GM3 ganglioside, Neu5Ac alpha 2-3Gal beta 1-4Glc beta 1-1 Cer, and its analogs containing the Neu5Gc or Neu4Ac5Gc residues (Gc = glycolyl, CH2OHCO) was investigated in Me2SO-d6 solution with the aid of a distance-mapping procedure based on rotating-frame NOE contacts, with hydroxyl protons being used as long-range sensors defining the distance constraints. A pronounced flexibility found for both the Neu-Gal and Gal-Glc linkages was confirmed by 1000-ps molecular dynamics simulations. Similar results, although based on a smaller number of NOE constraints, were obtained for GM3 gangliosides anchored in mixed D2O/dodecylphosphocholine-d38 micelles and for the Neu5Ac-, Neu5Gc-, and Neu5,9Ac2-sialyllactoses dissolved in D2O. No noteworthy differences in conformational behavior of the glycan chains of the three gangliosides or sialyllactoses were observed in either of the media.