NMR and computational studies of interactions between remote residues in gangliosides

Conformational preferences of the gangliosides GM1, GM1b, and GD1a have been investigated by using a systematic combination of NMR distance constraints and molecular mechanics calculations. These gangliosides share a common four-sugar core but differ in the number or placement of sialic acid residues attached to the core. Placement of the sialic acid residues is shown to influence the preferred core conformation. The origin of these effects is postulated to be intramolecular interactions of the sialic acid residues with other remote residues. In the case of GM1, hydrogen bonds between the internal sialic acid and an N-acetyl group on GalNAc are suggested. In the case of GD1a, a hydrogen-bonding network between the terminal and internal sialic acids is suggested to play a role.     

Disialogangliosides and their interaction with cholera toxin - investigation by molecular modeling, molecular mechanics and molecular dynamics

Molecular mechanics and molecular dynamics studies are performed to investigate the conformational preference of cell surface disialogangliosides (GD1A, GD1B and GD3) in aqueous environment. The molecular mechanics calculation reveals that water mediated hydrogen bonding network plays a significant role in the structural stabilization of GD1A, GD1B and GD3. These water mediated hydrogen bonds not only exist between neighboring residues but also exist between residues that are separated by 2 to 3 residues in between. The conformational energy difference between different conformational states of gangliosides correlates very well with the number of water mediated and direct hydrogen bonds. The spatial flexibility of NeuNAc of gangliosides at the binding site of cholera toxin is worked out. The NeuNAc has a limited allowed eulerian space at the binding site of Cholera Toxin (2.4%). The molecular modeling, molecular mechanics and molecular dynamics of disialoganglioside-cholera toxin complex reveal that cholera toxin can accommodate the disialoganglioside GD1A in three different modes. A single mode of binding is permissible for GD1B and GD3. Direct and water mediated hydrogen bonding interactions stabilizes these binding modes and play an essential role in defining the order of specificity for different disialogangliosides towards cholera toxin. This study not only provides models for the disialoganglioside-cholera toxin complexes but also identifies the NeuNAc binding site as a site for design of inhibitors that can restrict the pathogenic activity of cholera toxin.     

Disialogangliosides and Their Interaction with Cholera Toxin—Investigation by Molecular Modeling,Molecular Mechanics and Molecular Dynamics

Abstract

Molecular mechanics and molecular dynamics studies are performed to investigate the conformational preference of cell surface disialogangliosides (GD1A, GD1B and GD3) in aqueous environment. The molecular mechanics calculation reveals that water mediated hydrogen bonding network plays a significant role in the structural stabilization of GD1A, GD1B and GD3. These water mediated hydrogen bonds not only exist between neighboring residues but also exist between residues that are separated by 2 to 3 residues in between. The conformational energy difference between different conformational states of gangliosides correlates very well with the number of water mediated and direct hydrogen bonds. The spatial flexibility of NeuNAc of gangliosides at the binding site of cholera toxin is worked out. The NeuNAc has a limited allowed eulerian space at the binding site of Cholera Toxin (2.4%). The molecular modeling, molecular mechanics and molecular dynamics of disialo- ganglioside-cholera toxin complex reveal that cholera toxin can accommodate the disialo- ganglioside GD1A in three different modes. A single mode of binding is permissible for GD1B and GD3. Direct and water mediated hydrogen bonding interactions stabilizes these binding modes and play an essential role in defining the order of specificity for different disialogangliosides towards cholera toxin. This study not only provides models for the disialoganglioside-cholera toxin complexes but also identifies the NeuNAc binding site as a site for design of inhibitors that can restrict the pathogenic activity of cholera toxin.     

Neuraminic acid-specific modification and tritium labelling of gangliosides.

1. A crude ganglioside mixture and pure GM1 and GD1a from bovine brain grey matter were prepared on a large scale. 2. The C7- and G8-analogues of NeuNAc were prepared from Collocalia mucoid and their structures established by gas-liquid chromatography and mass spectrometry. 3. Using model compounds in addition to various gangliosides, the conditions for the periodate oxidation and subsequent borohydride reduction of gangliosides were investigated with regard to the yield of C7- and C8-analogues of NeuNAc and the integrity of other monosaccharides in the oligosaccharide chain. These conditions were optimised to yield maximum C8-NeuNAc production and low C7-NeuNAc formation. Thus products were obtained which closely resemble the native gangliosides. 4. Using boro [3H] hydride, ganglioside derivatives with high specific radioactivity were prepared for the first time, containing either NeuNAc and labelled C8-NeuNAc or mainly labelled C7-NeuNAc depending on the prevailing conditions.     

Monosialogangliosides and Their Interaction with Cholera Toxin—Investigation by Molecular Modeling and Molecular Mechanics

Abstract

Molecular mechanics and molecular dynamics studies are performed to investigate the conformational preference of cell surface monosialogangliosides (GM3, GM2 and GM1) in aqueous environment. Water mediated hydrogen bonding network plays a significant role in the structural stabilization of GM3, GM2 and GM1. The spatial flexibility of NeuNAc of gangliosides at the binding site of cholera toxin reveals a limited allowed eulerian space of 2.4% with a much less allowed eulerian space (1.4%) for external galactose of GM1. The molecular mechanics of monosialoganglioside-cholera toxin complex reveals that cholera toxin can accommodate the monosialogangliosides in three different modes. Direct and water mediated hydrogen bonding interactions stabilize these binding modes and play an essential role in defining the order of specificity for different monosialogangliosides towards cholera toxin. This study identifies the NeuNAc binding site as a site for design of inhibitors that can restrict the pathogenic activity of cholera toxin.     

Theoretical studies on the conformations of higher gangliosides

The possible conformations of higher gangliosides (GD3, GT1a. GT1b, GQ1b) have been determined by computing their potential energy using semi-empirical potential functions. The favoured conformation of the disialic acid fragment in these gangliosides is independent of its position (internal or terminal). The favoured conformations of these gangliosides have also been correlated to their biological activity. The results suggest that tetanus toxin and sendai virus may have a large binding site which can accommodate at least four sugar residues.     

Monosialogangliosides and their interaction with cholera toxin - investigation by molecular modeling and molecular mechanics

Molecular mechanics and molecular dynamics studies are performed to investigate the conformational preference of cell surface monosialogangliosides (GM3, GM2 and GM1) in aqueous environment. Water mediated hydrogen bonding network plays a significant role in the structural stabilization of GM3, GM2 and GM1. The spatial flexibility of NeuNAc of gangliosides at the binding site of cholera toxin reveals a limited allowed eulerian space of 2.4% with a much less allowed eulerian space (1.4%) for external galactose of GM1. The molecular mechanics of monosialoganglioside-cholera toxin complex reveals that cholera toxin can accommodate the monosialogangliosides in three different modes. Direct and water mediated hydrogen bonding interactions stabilize these binding modes and play an essential role in defining the order of specificity for different monosialogangliosides towards cholera toxin. This study identifies the NeuNAc binding site as a site for design of inhibitors that can restrict the pathogenic activity of cholera toxin.     

Biosynthesis in vitro of mono- and di-sialosylgangliosides from gangliotetraosylceramide by cultured cell lines and young rat brain. Structure of the products, and activity and specificity of sialosyltransferase

Incubations in vitro of GA1, labeled with 3H in the terminal D-galactopyranosyl group, with nonradioactive CMP-NeuNAc in the presence of homogenates of C21 rat brain glial cells, NIE mouse neuroblastoma cells, 3T3 mouse fibroblasts, SV 40-transformed 3T3 cells, chick embryo fibroblasts, Rous sarcoma virus-transformed chick embryo fibroblasts, and 9-day old rat brain resulted in all cases in the formation in high yield of GM1b, in which the neuraminidase-labile NeuNAc group is linked at O-3 of the terminal D-galactosyl residue, as shown by permethylation studies. No trace of the naturally occurring neuraminidase-stable GM1a was detected in any case. In addition, with NIE cells, and normal and RSV-transformed chick embryo fibroblasts, a disialosylganglioside (GD1) differing from GD1a and GD1b, and bearing only one substituent at O-3 of the terminal D-galactopyranosyl residue was formed. It was also biosynthesized from GM1b and CMP-NeuNAc by NIE and chick embryo cells but not by C21 cells, or rat brain. However, C21 cells and rat brain were capable of synthesizing GD1a from GM1a. Periodate oxidation degraded both NeuNAc groups in GD1 to a 7-carbon fragm:nt, indicating lack of substitution at O-8. GM1b could not be detected as a natural product in rat brain.     

GD3 Prevalence in Adult Rat Retina Correlates with the Maintenance of a High GD3-/GM2-Synthase Activity Ratio Throughout Development

Unlike neurons from avian retina and other regions of avian and mammalian brain, neurons from mammalian retina not only contain gangliosides of the gangliotetraosyl ceramide series but also maintain a prevalence of GD3, a ganglioside of the lactosylceramide series characteristic of proliferative neural cells, when they are fully differentiated. We show here that GD3 is prevalent at all developmental periods of the rat retina from birth [50% of total gangliosidic N-acetylneuraminic acid (NeuNAc)] to adult (30% of total gangliosidic NeuNAc). GD3-synthase specific activity increased about 1.5-fold from birth to day 7 and essentially plateaued thereafter. The GD3-/GM2-synthase specific activity ratio was compared in rat and chicken retina at early and late developmental stages. In chicken retina the ratio was about 0.7 at early (when GD3 is prevalent) and decreased to 0.07 at late (when GD1a is prevalent) developmental stages. In rat retina the ratio was about 13 and 6 at, respectively, early and late developmental stages. These findings suggest that the prevalence of GD3 and of other "b" pathway gangliosides in adult rat retina neurons could be due in part to the maintenance of a high GD3-/GM2-synthase activity ratio throughout development of the tissue.     

Occurrence of glycosylation and deglycosylation of exogenously administered ganglioside GM1 in mouse liver.

Ganglioside GM1, 3H-labelled at the level of terminal galactose or of sphingosine, was intravenously injected into Swiss albino mice and some steps in its metabolic fate in the liver were investigated. After administration of [3H]sphingosine-labelled GM1 all major liver gangliosides [GM3, GM2, GM1, GD1a-(NeuAc,NeuGl)] became radioactive, the radioactivity residing in all cases on the sphingosine moiety. The specific radioactivity was highest in GM1, which carried about 53% of the radioactivity incorporated into gangliosides, followed by GM2, with 34.5% of incorporated radioactivity, GM3 and GD1a-(NeuAc,NeuGl), both with about 5% of incorporated radioactivity. After administration of [3H]galactose-labelled GM1 the only radioactive gangliosides present in the liver were GM1 and GD1a-(NeuAc,NeuGl), the former carrying about 95% of the total ganglioside-incorporated radioactivity, the latter about 3%. Both gangliosides were radioactive exclusively in the terminal galactose residue. According to these results exogenously administered GM1, after being taken up by the liver, is mainly degraded to GM2 and GM3, a part being, however, sialylated to GD1a-(NeuAc,NeuGl). All this suggests that exogenous GM1 may be involved in the metabolic routes of endogenous liver gangliosides.     

GANGLIOSIDE1−COMPOSITION OF BRAIN IN TAY-SACHS DISEASE: INCREASED AMOUNTS OF GD2 AND N-ACETYL-β-D-GALACTOSAMINYL GD1a GANGLIOSIDE

Abstract— The ganglioside composition of the brain of a patient with Tay-Sachs disease (TS-brain) was determined by a newly developed ganglioside-mapping procedure and compared with that of an age-matched control brain. GM2 ganglioside was the predominant component in TS-brain and the following gangliosides were also found, GM1, GD1a, GD1b and GT1 (major gangliosides in normal brain), and GM3, GD3, GD2 and GD1a-GAN (minor or undetectable components of normal brain). Individual gangliosides were isolated by column chromatography using a combination of DEAE-Sepharose, Iatrobeads and Silica Gel 60 and their structures were confirmed by comparing them with authentic standards using TLC, analysing their carbohydrate compositions by gas-liquid chromatography and cleaving them sequentially with glycosidases. The amounts of individual components were measured by quantitative densitometric scanning of the thin-layer plates. As a reflection of myelin breakdown, no sialosylgalactosyl ceramide was detectable in TS-brain. Although the total amounts of all gangliosides except GM2 in TS-brain were low, there were normal molar ratios of the main gangliosides in normal brain, that is, GM1, GD1a, GD1b and GT1. In comparison with the amount of GDla ganglioside, the amounts of GM2, GD2 and GD1a-GAN, which contain N-acetylgalactosamine as a terminal carbohydrate residue, were all elevated in TS-brain. The long chain bases of individual gangliosides contained both C-18 and C-20 sphingosine in different ratios and the ratio of C-20 to C-18 increased in the gangliosides in the order: GM2 < GM1 < GD1a < GD1a-GAN < GD1b < GT1 in both normal brain and TS-brain. In contrast, GD2 and GD3 gangliosides consisted mainly of C-18 sphingosine. The C-20 to C-18 ratios of individual gangliosides in the TS-brain were lower than those of age-matched control brain. Hexosaminidase from Turbo cornutus showed the same specific activity and K_m value in catalysing the cleavage of terminal N-acetylgalactosaminyl residues from GM2, GD2 and GD1a-GAN, suggesting that the brain gangliosides that increase in Tay-Sachs disease may be cleaved by the same enzyme.     

Neuraminidase in Calf Retinal Outer Segment Membranes

Abstract: An enzyme catalyzing the hydrolysis of sialic acid ( N -acetylneuraminic acid: NeuNAc)-containing glycoconjugates has been found in bovine retinal rod outer segment (ROS) membranes. The enzymatic activity is optimal at pH 4.0 and is stimulated by 0.15% Triton X-100. Total activity was determined by the release of NeuNAc from endogenous and exogenous substrates (GDla). The ROS enzyme preferentially hydrolyses the ROS gangliosides, possibly because they are more accessible than the glycoproteins as substrates for the neuraminidase. Release of NeuNAc from gangliosides leads to important changes in the ganglioside patterns; whereas the amounts of GM1 increased throughout the incubation, the levels of polysialogangliosides GTlb and GD3 diminished owing to their rapid hydrolysis. The finding that gangliosides are hydrolysed more extensively than glycoproteins suggests that endogenous ROS gangliosides may be the principal source of metabolically available sialic acid in ROS. It was also observed that the activity of ROS neuraminidase is not affected by illumination of the membranes.     

Generation of murine monoclonal antibodies specific for N-glycolylneuraminic acid-containing gangliosides.

We generated two murine monoclonal antibodies (MAbs) specific for mono- and disialylgangliosides having N-glycolylneuraminic acid (NeuGc) as their sialic acid moiety, respectively, by immunizing C3H/HeN mice with these purified gangliosides adsorbed to Salmonella minnesota followed by fusion with mouse myeloma cells. By use of a wide variety of glycolipids, including NeuGc-containing gangliosides, the precise structures recognized by these two antibodies were elucidated through enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatography. One MAb, GMR8, which was generated by immunizing the mice with purified GM3(NeuGc), reacted specifically with gangliosides having NeuGc alpha 2----3Gal- terminal structures, such as GM3(NeuGc), IV3NeuGc alpha-Gg4Cer, IV3NeuGc alpha-nLc4Cer, V3NeuGc alpha-Gb5Cer, and GD1a(NeuGc, NeuGc). None of the other gangliosides having internal NeuGc alpha2----3Gal- sequences, such as GM2(NeuGc) and GM1(NeuGc), nor corresponding gangliosides having NeuAc alpha 2----3Gal- sequences, nor neutral glycolipids were recognized. Thus, the epitope structures recognized by the MAb were found to be strictly NeuGc alpha 2----3Gal- terminal structures. In contrast, the other MAb, GMR3, which was generated by immunizing the mice with purified GD3(NeuGc-NeuGc-) adsorbed to the bacteria, reacted specifically with gangliosides having NeuGc alpha 2----8NeuGc alpha 2----3Gal- terminal sequences, such as GD3(NeuGc-NeuGc-), IV3NeuGc alpha 2-Gg4Cer, IV3NeuGc alpha 2-nLc4Cer, and V3NeuGc alpha 2-Gb5Cer, but did not react with corresponding gangliosides having NeuAc as their sialic acid moiety or with the neutral glycolipids tested. The epitope structures recognized by the MAb were suggested to be NeuGc alpha 2----8NeuGc alpha 2----3Gal- terminal structures. Using these MAbs, we determined the distribution of such gangliosides in the spleen, kidney, and liver of several mice strains. Novel gangliosides reactive with these MAbs were detected in these tissues.     

Characterization of the cholera toxin receptor on Balb/c 3T3 cells as a ganglioside similar to, or identical with, ganglioside GM1. No evidence for galactoproteins with receptor activity.

Balb/c 3T3 cells contain a large number [(0.8-1.6) x 10(6)] of high-affinity (half-maximal binding at 0.2 nM) binding sites for cholera toxin that are resistant to proteolysis, but are quantitatively extracted with chloroform/methanol. The following evidence rigorously establishes that the receptor is a ganglioside similar to, or identical with, ganglioside GM1 by the galactose oxidase/NaB3H4 technique on intact cells was inhibited by cholera toxin. (2) Ganglioside GM1 was specifically adsorbed from Nonidet P40 extracts of both surface- (galactose oxidase/NaB3H4 technique) and metabolically ([1-14C]palmitate) labelled cells in the presence of cholera toxin, anti-toxin and Staphylococcus aureus. (3) Ganglioside GM1 was the only ganglioside labelled when total cellular gangliosides separated on silica-gel sheets were overlayed with 125I-labelled cholera toxin, although GM3 and GD1a were the major gangliosides present. In contrast no evidence for a galactoprotein with receptor activity was obtained. Cholera toxin did not protect the terminal galactose residues of cell-surface glycoproteins from labelling by the galactose oxidase/NaB3H4 technique. No toxin-binding proteins could be identified in Nonidet P40 extracts of [35S]-methionine-labelled cells by immunochemical means. After sodium dodecyl sulphate/polyacrylamide-gel electrophoresis none of the major cellular galactoproteins identified by overlaying gels with 125I-labelled ricin were able to bind 125I-labelled cholera toxin. It is concluded that the cholera toxin receptor on Balb/c 3T3 cells is exclusively ganglioside GM1 (or a related species), and that cholera toxin can therefore be used to probe the function and organisation of gangliosides in these cells as previously outlined [Critchley, Ansell, Perkins, Dilks & Ingram (1979) J. Supramol. Struct. 12, 273-291].     

Monoclonal antibody detects monosialogangliosides having a sialic acid alpha 2----3-galactosyl residue

A murine monoclonal antibody (mAb), designated mAb 202, was generated using a human melanoma cell line, UCLASO-M14 as the immunogen. mAb 202 reacted with two (GM2 and GM3) of the four (GM2, GM3, GD2, and GD3) gangliosides expressed by M14. Several authentic monosialogangliosides, including GM4, GM3, GM2, GM1, GM1b, and sialylparagloboside were then tested for their binding to 202 mAb by the immune adherence inhibition assay, TLC-enzyme immunostaining, and enzyme-linked immunosorbent assay. All showed positive binding but in varying degrees. GM4 showed the strongest affinity. No significant differences of reactivity were observed between the sialic acid derivatives, N-acetyl and N-glycolyl, in these gangliosides. Disialogangliosides such as GD3, GD2, GD1a, and GD1b, trisialoganglioside GT1b, and neutral glycolipids including GlcCer, GalCer, LacCer, GbOs3Cer, GbOs4Cer, GgOs3Cer, GgOs4Cer, and nLcOs4Cer were all negative. These results indicate that the 202 mAb detects sialyl alpha 2----3Gal residue in the monosialoganglioside, irrespective of the internal structure. Since GM4 is not expressed by M14 cells, the terminal disaccharide (sialyl alpha 2----3Gal) in GM3 and/or GM2 must have been the epitope responsible for the generation of the antibody.     

Subcellular distribution and biosynthesis of rat liver gangliosides

Gangliosides have generally been assumed to be localized primarily in the plasma membrane. Analysis of gangliosides from isolated subcellular membrane fractions of rat liver indicated that 76% of the total ganglioside sialic acid was present in the plasma membrane. Mitochondria and endoplasmic reticulum fractions, while containing only low levels of gangliosides on a protein basis, each contained approx. 10% of total ganglioside sialic acid. Gangliosides also were present in the Golgi apparatus and nuclear membrane fractions, and soluble gangliosides were in the supernatant. Individual gangliosides were non-homogeneously distributed and each membrane fraction was characterized by a unique ganglioside composition. Plasma membrane contained only 14 and 28% of the total GD1a and GD3, respectively, but 80-90% of the GM1, GD1b, GT1b and GQ1b. Endoplasmic reticulum, when corrected for plasma membrane contamination, contained only trace amounts of GM1, GD1b, GT1b and GQ1b, but 11 and 5% of the total GD1a and GD3, respectively. The ganglioside composition of highly purified endoplasmic reticulum was similar. Ganglioside biosynthetic enzymes were concentrated in the Golgi apparatus. However, low levels of these enzymes were present in the highly purified endoplasmic reticulum fractions. Pulse-chase experiments with [3H]galactose revealed that total gangliosides were labeled first in the Golgi apparatus, mitochondria and supernatant within 10 min. Labeled gangliosides were next observed at 30 min in the endoplasmic reticulum, plasma membrane and nuclear membrane fractions. Analysis of the individual gangliosides also revealed that GM3, GM1, GD1a and GD1b were labeled first in the Golgi apparatus at 10 min. These studies indicate that gangliosides synthesized in the Golgi apparatus may be transported not only to the plasma membrane, but to the endoplasmic reticulum and to other internal endomembranes as well.     

Gangliosides from human melanoma immunomodulate response of T cells to interleukin-2

The gangliosides expressed by normal melanocytes are predominantly GM3 (greater than 90%) and GD3 (less than 5%). Malignant melanoma can express several other types of gangliosides in significant quantities, including GM2 and GD2. Melanoma patients can develop an immune response against some of these ganglioside antigens on autologous melanoma cells. The four major gangliosides expressed by human melanoma cells (GM3, GD3, GM2, and GD2) were examined for their immunomodulatory effect on lymph node lymphocytes from melanoma patients. Gangliosides were added exogenously to lymphocytes grown in the presence of IL-2. Preferential interactions of specific melanoma gangliosides on IL-2 stimulation were found. While GM2 and GD2 enhanced the lymphocyte response to IL-2, GM3 and GD3 significantly inhibited this response. GM2 and GD2 differ from GM3 and GD3 by the presence of a terminal N-acetylgalactosamine. Since different gangliosides can up-regulate and down-regulate lymphocyte responses to IL-2, the ganglioside phenotype of melanoma cells may play a major role in determining whether an individual tumor causes immune stimulation or suppression.     

Asymmetric distribution of gangliosides in rat renal brush-border and basolateral membranes

Highly enriched brush-border and basolateral membranes isolated from rat renal cortex were used to study the distribution of endogenous gangliosides in the two distinct plasma membrane domains of epithelial cells. These two membrane domains differed in their glycolipid composition. The basolateral membranes contained more of both neutral and acidic glycolipids, expressed on a protein basis. In both membranes, the neutral glycolipids corresponding to mono-, di-, tri- and tetraglycosylceramides were present. The basolateral membranes contained more diglycosylceramide than the brush-border membranes. The major gangliosides found were GM4, GM3, and GD3 with minor amounts of GM1 and GD1a. The latter were identified and quantified by sensitive iodinated cholera toxin binding assays. When the distribution of individual gangliosides was calculated as a percent of total gangliosides, the brush-border membranes were enriched with GM3, GM1 and GD1a compared to the basolateral membranes, which were enriched with GD3 and GM4. The observation of a distinct distribution of glycolipids between brush-border and basolateral membranes of the same epithelial cell suggests that there may be a specific sorting and insertion process for epithelial plasma membrane glycolipids. In turn, asymmetric glycolipid biogenesis may reflect differences in glycolipid function between the two domains of the epithelial plasma membrane.     

Selective shedding of gangliosides by cells of mouse ascitic sarcoma-37

The profile and content of gangliosides associated with tumour cells of mouse sarcoma-37 and exfoliated from the cell surface were determined. It was shown that 20% of tumour gangliosides shed from the cell surface and only about 7% of all the shed gangliosides were contained in plasma membrane fragments. When incubated in vitro at 37 degrees C for 1 hour, the tumour cells were found to release less than 2% of cellular gangliosides. The main components of cellular gangliosides corresponded in their chromatographic behaviour to GM2 (31-32% of the total ganglioside content), GD3 (17-18%), GD1a (9-11%), GD2 (16-17%) and hematosides (19-21%). The profiles of in vivo and in vitro shed gangliosides were similar but strongly differed from those of cellular gangliosides: the relative content of GM2 was 70-75% and the other gangliosides were found in negligible amounts. The data show that GM2 accumulation in extracellular spaces is rather the result of its selective shedding than the shedding of products of "incomplete" cellular ganglioside synthesis.     

Differences in liver ganglioside patterns in various inbred strains of mice

The ganglioside patterns in the liver of different inbred and hybrid strains of mice were investigated. The inbred strains were Balb/cAnNCr1BR, C57BL/6NCr1BR, DBA/2NCr1BR. C3H/HeNCr1BR; the hybrid strain was the Swiss albino. The following major gangliosides were found to be present in mouse liver: GM3-NeuAc; GM3-NeuGl, GM2 [a mixture of one species carrying N-acetylneuraminic acid (NeuAc) and one carrying N-glycollylneuraminic acid (NeuGl)], GM1 and GD1a-(NeuAc,NeuGl). The qualitative and quantitative patterns of liver gangliosides were markedly different in the various inbred strains of mice; in Balb/cAnNCr1BR strain, ganglioside GM2 was preponderant (99.2% of total ganglioside content); in C57BL/6NCr1BR, the major ganglioside was GM2 (90.4%), followed by GM3-NeuAc (5.6%) and GM3-NeuGl (4.0%); in DBA/2NCr1BR, GM2 accounted for 77.1%, GD1a-(NeuAc,NeuGl) 18.9% and GM1 3.1% of gangliosides; in C3H/HeNCr1BR, GM2 constituted 50.6%, GM1 22.8% and GD1a-(NeuAc,NeuGl) 22.1%. In the hybrid Swiss albino mice, liver ganglioside composition markedly varied from one animal to another, GM3-NeuGl, GM2 and GD1a-(NeuAc,NeuGl) being the predominant gangliosides in the various cases.