Isolation and structural characterization of a mono-sulfated isoglobotetraosylceramide, the first sulfoglycosphingolipid of the isoglobo-series, from rat kidney

The Structural Diversity of Natural Glycosphingolipids (GSLs)

Glycosphingolipids (GSLs) are a subclass of glycolipids made of a glycan and a ceramide that, in turn, is composed of a sphingoid base moiety and a fatty acyl group. GSLs represent the vast majority of glycolipids in eukaryotes, and as an essential component of the cell membrane, they play an important role in many biological and pathological processes. Therefore, they are useful targets for the development of novel diagnostic and therapeutic methods for human diseases. Since sphingosine was first described by J. L. Thudichum in 1884, several hundred GSL species, not including their diverse lipid forms that can further amplify the number of individual GSLs by many folds, have been isolated from natural sources and structurally characterized. This review tries to provide a comprehensive survey of the major GSL species, especially those with distinct glycan structures and modification patterns, and the ceramides with unique modifications of the lipid chains, that have been discovered to date. In particular, this review is focused on GSLs from eukaryotic species. This review has listed 251 GSL glycans with different linkages, 127 glycans with unique modifications, 46 sphingoids, and 43 fatty acyl groups. It should be helpful for scientists who are interested in GSLs, from isolation and structural analyses to chemical and enzymatic syntheses, as well as their biological studies and applications.

Total syntheses of disulphated glycosphingolipid SB1a and the related monosulphated SM1a

Total syntheses of two natural sulphoglycolipids, disulphated glycosphingolipid SB1a and the structurally related monosulphated SM1a, are described. They have common glycan sequences and ceramide moieties and are associated with human epithelial carcinomas. The syntheses featured efficient glycan assembly and the glucosyl ceramide cassette as a versatile building block. The binding of the synthetic sulphoglycolipids by the carcinoma-specific monoclonal antibody AE3 was investigated using carbohydrate microarray technology.

The repertoire of glycan determinants in the human glycome

The number of glycan determinants that comprise the human glycome is not known. This uncertainty arises from limited knowledge of the total number of distinct glycans and glycan structures in the human glycome, as well as limited information about the glycan determinants recognized by glycan-binding proteins (GBPs), which include lectins, receptors, toxins, microbial adhesins, antibodies, and enzymes. Available evidence indicates that GBP binding sites may accommodate glycan determinants made up of 2 to 6 linear monosaccharides, together with their potential side chains containing other sugars and modifications, such as sulfation, phosphorylation, and acetylation. Glycosaminoglycans, including heparin and heparan sulfate, comprise repeating disaccharide motifs, where a linear sequence of 5 to 6 monosaccharides may be required for recognition. Based on our current knowledge of the composition of the glycome and the size of GBP binding sites, glycoproteins and glycolipids may contain approximately 3000 glycan determinants with an additional approximately 4000 theoretical pentasaccharide sequences in glycosaminoglycans. These numbers provide an achievable target for new chemical and/or enzymatic syntheses, and raise new challenges for defining the total glycome and the determinants recognized by GBPs.

Metabolism of sulfolipids in isolated renal tubules from rat

Proximal-rich tubules were prepared from rat kidneys by using collagenase treatment. The isolated rat renal tubules were compared with the intact kidney on the following characteristics. (1) Composition of the sulfoglycolipid. (2) Sulfoglycolipid metabolism based on incorporation of [35S]sulfate or some properties of sulfoglycolipid metabolism, including the activities of anabolic and catabolic enzymes. The results indicated following characteristics of the isolated renal tubules in comparison to the kidney in vivo. (1) The sulfoglycolipid compositions are qualitatively similar, except that the content of glucosyl sulfatide, Gg3Cer II3-sulfate, and GM4 was slightly higher in the isolated tubules. (2) The apparent half-lives (15-55 min) of sulfoglycolipids in the isolated tubules could indicate the existence of a rapid turnover pool of these lipids. (3) The sulfotransferase and sulfatase activities related to sulfoamphiphiles in the renal tubule were similar to those reported for the whole kidney. Based on the above criteria, we conclude that the isolated rat renal tubule should be a useful metabolic system for clarification of the short-term physiological events, up to 90 min, of proximal tubular sulfoglycolipids. By using the present system, we showed that biosynthesis of the renal total sulfoglycolipid was significantly elevated in rats deprived of water for 24 h.

Glycosphingolipid structural analysis and glycosphingolipidomics

Sphingosines, or sphingoids, are a family of naturally occurring long-chain hydrocarbon derivatives sharing a common 1,3-dihydroxy-2-amino-backbone motif. The majority of sphingolipids, as their derivatives are collectively known, can be found in cell membranes in the form of amphiphilic conjugates, each composed of a polar head group attached to an N-acylated sphingoid, or ceramide. Glycosphingolipids (GSLs), which are the glycosides of either ceramide or myo-inositol-(1-O)-phosphoryl-(O-1)-ceramide, are a structurally and functionally diverse sphingolipid subclass; GSLs are ubiquitously distributed among all eukaryotic species and are found in some bacteria. Since GSLs are secondary metabolites, direct and comprehensive analysis (metabolomics) must be considered an essential complement to genomic and proteomic approaches for establishing the structural repertoire within an organism and deducing its possible functional roles. The glycosphingolipidome clearly comprises an important and extensive subset of both the glycome and the lipidome, but the complexities of GSL structure, biosynthesis, and function form the outlines of a considerable analytical problem, especially since their structural diversity confers by extension an enormous variability with respect to physicochemical properties. This chapter covers selected developments and applications of techniques in mass spectrometric (MS) that have contributed to GSL structural analysis and glycosphingolipidomics since 1990. Sections are included on basic characteristics of ionization and fragmentation of permethylated GSLs and of lithium-adducted nonderivatized GSLs under positive-ion electrospray ionization mass spectrometry (ESI-MS) and collision-induced mass spectrometry (CID-MS) conditions; on the analysis of sulfatides, mainly using negative-ion techniques; and on selected applications of ESI-MS and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to emerging GSL structural, functional, and analytical issues. The latter section includes a particular focus on evolving techniques for analysis of gangliosides, GSLs containing sialic acid, as well as on characterizations of GSLs from selected nonmammalian eukaryotes, such as dipterans, nematodes, cestodes, and fungi. Additional sections focus on the issue of whether it is better to leave GSLs intact or remove the ceramide; on development and uses of thin-layer chromatography (TLC) blotting and TLC-MS techniques; and on emerging issues of high-throughput analysis, including the use of flow injection, liquid chromatography mass spectrometry (LC-MS), and capillary electrophoresis mass spectrometry (CE-MS).

Occurrence and tissue distribution of c-series gangliosides in the common squid Todarodes pacificus

We have recently demonstrated that the common squid Todarodes pacificus express acidic lipids that were reactive with a monoclonal antibody A2B5. In the present study, two A2B5-reactive acidic lipids were isolated from squid hepatopancreatic tissue and characterized for their structures by methods including glycolipid overlay analysis, product analysis after sialidase treatment, and electrospray ionization-mass spectrometry (ESI-MS). Accordingly, the two acidic lipid were identified as GT3 and GQ1c, respectively. Another A2B5-reactive acidic lipid in the tissue was tentatively assigned to GT2 based upon its reactivity to A2B5 and chromatographic mobility on thin-layer chromatography. The composition and concentration of c-series gangliosides significantly differed among squid tissues (i.e. hepatopancreas, cerebral ganglion, eye lens, and mantle tissue). Interestingly, the percentages of c-series gangliosides within total gangliosides of hepatopancreas and cerebral ganglion were even higher than that of cod fish brain, which is known to be highly enriched with this ganglioside species. These findings strongly support the hypothesis that c-series gangliosides in squid tissues are not derived from ganglioside-containing food intake, but biosynthesized in a tissue-specific manner.

The specificity of monoclonal antibody A2B5 to c-series gangliosides

To examine the specificity of monoclonal antibody A2B5, four A2B5-reactive gangliosides (designated as G-1, G-2, G-3 and G-4) were purified from bonito fish brain. Ganglioside-1, -2, and -3 migrated above GD1b, below GQ1b, and far below GQ1b on thin-layer chromatography. Ganglioside-4 had the slowest chromatographic mobility and migrated below G-3. The structures of these gangliosides were characterized by overlay analysis with glycolipid-specific ligands, product analysis after sialidase or mild acid treatment, and electrospray ionization-mass spectrometry (ESI-MS). Accordingly, G-1, G-2 and G-3 were identified to be GT3, GQ1c and GP1c, respectively. The ganglioside G-4 was shown to have the following structure: NeuAc-NeuAc-NeuAc-Galbeta1-3Gal NAcbeta1-4(NeuAc-NeuAc-NeuAcalpha2-3)Galbeta1-4Glcbeta1-1'Cer. The antibody A2B5 reacted with these c-series gangliosides, but not with GD3 and other gangliosides and neutral glycosphingolipids. The antigenic epitope for A2B5 was assumed to include the trisialosyl residue connected to the inner galactose of the hemato- or ganglio-type oligosaccharide structure of gangliosides. Phylogenetic analysis of brain gangliosides using the A2B5 preparation demonstrated that c-series gangliosides are enriched in lower animals, especially bony fish of different species. The monoclonal antibody A2B5 would be a useful tool for examining the distribution and function of c-series gangliosides.

Structural analysis and immunohistochemical localization of two acidic glycosphingolipids from the porcine, parasitic nematode, Ascaris suum

The acidic glycolipid fraction (AF) of the porcine, parasitic nematode, Ascaris suum , consisted of two subfractions. The major component AF II reacted with orcinol-sulfuric acid and molybdate, while the minor component AF I gave a positive reaction with azure-A, a cationic dye specific for sulfatides. Sugar constituent analysis, methanolysis, methylation analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, liquid secondary-ion mass spectrometry, and gas-liquid chromatography/mass spectrometry specified AF II to be an unusual phosphoinositolglycosphingolipid (Galalpha1-Ins-P-1ceramide) and the minor component AF I to be a 3-sulfogalactosylcerebroside (HSO3-3Galss1-1ceramide). The ceramide moiety of both components consisted of lignoceric (C24:0) and cerebronic (C24h:0) acids and mainly C17 iso-branched sphingosine. Immunohistochemical localization studies of the glycolipid-bound antigenic determinants with a polyclonal antiserum against AF II and an anti-sulfatide monoclonal antibody against AF I revealed the presence of the AF II-epitope in the intestine, whereas the AF I-epitope was found in the hypodermis, contractile zone of somatic muscle cells and the external musculature of the uterus. To our knowledge, this is the first report of the presence of a sulfatide in an invertebrate.

Isolation and characterization of a unique sulfated ganglioside, sulfated GM1a, from rat kidney

A novel class of sulfoglycosphingolipid, a sulfate analog of ganglioside, was isolated from mammals for the first time. This sulfated ganglioside was purified from rat kidney by column chromatographies on anion exchangers and silica beads. One-dimensional 1H NMR, compositional and permethylation analyses showed that this glycolipid has a Gg4Cer core with 1 mol each of sulfate ester and N- glycolylneuraminic acid (NeuGc) at C-3 of galactose. The major ceramide consisted of nonhydroxy fatty acids (24:0 and 22:0) and 4-hydroxysphinganine (t18:0), deduced from the compositional analysis and negative liquid secondary ion mass spectrometry (LSIMS). Mild acid hydrolysis and solvolysis produced compounds which correspond to Gg4Cer IV3-sulfate (SM1b) and II3NeuGcalpha-Gg4Cer (GM1a (NeuGc)), respectively. The abundant ions characteristic for sulfated mono- and disaccharides in high-energy collision-induced dissociation (CID) spectra were consistent with the structure at the non-reducing terminus, HSO3 -O- Hex -O- HexNAc- rather than the alternative structure, NeuGc -O- Hex -O- HexNAc-. The two-dimensional 1H NMR further evidenced the presence of a 3 -O- sulfated galactose in the molecule. From these results the complete structure was proposed to be HSO3-3Galbeta-3GalNAcbeta-4(NeuGcalpha-3)Galb eta-4Glcbeta-1Cer (II3NeuGcalpha-Gg4Cer IV3-sulfate).

Structure of a novel phosphocholine-containing aminoglycoglycerolipid of Mycoplasma fermentans

Mycoplasma fermentans is thought to be a pathogen of rheumatoid arthritis or a cofactor of AIDS (acquired immunodeficiency syndrome). To elucidate the possible involvement of membrane constituents in the pathogenesis of these diseases, we studied its lipid components. Several alkali labile glycophospholipids were detected and named glycoglycerophospholipids (GGPLs). Previously, we purified and determined the structure of one of them as 6'-O-phosphocholine-alpha-glucopyranosyl-(1'-3)-1,2-diacyl-sn-glycerol (GGPL-I). The present paper describes the purification and structural characterization of GGPL-III, the major GGPL of M. fermentans using 1H-, 13C- and 31P-nuclear magnetic resonance spectroscopy, and mass-spectroscopy as 1"-phosphocholine,2"-amino dihydroxypropane-3"-phospho-6'-alpha-glucopyranosyl-(1'-3)-1,2-dia cyl-glycerol.

Negative-ion fast atom bombardment and electrospray ionization tandem mass spectrometry for characterization of sulfated and sialyl Lewis-type glycosphingolipids

Structural characterization of sulfated and sialyl Lewis (Le)-type glycosphingolipids performed by fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometry is described. Both FAB and ESI collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of acidic glycosphingolipids allowed identification of the sulfated or sialyl sugar, and provided information on the saccharide chain sequence. The negative-ion tandem FABMS of sulfated Le-type glycosphingolipids having the non-reducing end trisaccharide ion as the precursor can be used to differentiate the Le(a)- and Le(x)-type oligosaccharides. The ESI CID-MS/MS of multiple-charged ions provided even more detailed structural information, and some of the useful daughter ions appeared with higher m/z values than the precursor because of a lower charge-state. These methodologies can be applied to the structural analyses of glycoconjugates with much larger molecular masses and higher polarity, such as the poly-sulfated and sialyl analogues.

Structural characterization of a novel mono-sulfated gangliotriaosylceramide containing a 3-O-sulfated N-acetylgalactosamine from rat kidney

A novel mono-sulfated glycosphingolipid based on the gangliotriaose core structure was isolated from rat kidney. The isolation procedure involved extraction of lipids with chloroform/methanol, mild alkaline methanolysis, column chromatographies with anion exchangers and silica beads. The structure was characterized by compositional analysis, FTIR spectroscopy, methylation analysis, 1H-NMR spectroscopy and negative-ion liquid secondary ion mass spectrometry (LSMIS) using the intact glycolipid and its desulfation product. The two dimensional chemical shift correlated spectroscopy provided information on the sugar sequence as well as anomeric configurations, and indicated the presence of a 3-O-sulfated N-acetylgalactosamine within the molecule. Negative-ion LSIMS with high- and low-energy collision-induced dissociation defined the sugar sequence and ceramide composition, confirming the presence of a sulfated N-acetylgalactosamine at the non-reducing terminus. From these results, the complete structure was proposed to be HSO3-3GalNAc beta 1-4Gal beta 1-4Glc beta 1-1Cer (Gg3Cer III3-sulfate, SM2b).

Structural analysis of mono- and bis-sulfated glycosphingolipids by negative liquid secondary ion mass spectrometry with high- and low-energy collision-induced dissociation

Several underivatized mono- and bis-sulfated glycosphingolipids having gangliotriaose or gangliotetraose core structure were analyzed by negative liquid secondary ion mass spectrometry (LSIMS) with high- and low-energy collision-induced dissociation (CID). In the normal negative LSIMS spectra, each mono-sulfated glycolipid gave abundant [M - H]- ions and each bis-sulfated glycolipid gave abundant [M + Na - 2H]- ions as well as the hydrogen sulfate anion [OSO3H]-. In high-energy CID spectra of the deprotonated molecule, only ions containing a sulfate ester were clearly observed. When a sulfate was present on the non-reducing terminal saccharide residue, a series of ions corresponding to sulfated mono- to tetra-saccharides, resulting from sequential cleavage of glycosidic bonds, were observed. If the sulfate was attached to an internal hexose of the sugar chain, the product ions corresponding to the non-sulfated, non-reducing terminal residue were absent. In contrast, the low-energy CID resulted in extremely simple spectra that contained only one or two major product ions characteristic of each sulfated glycolipid. These results provided clear information on the overall sugar and ceramide compositions, and allowed saccharide structures differing in location and number of sulfate esters to be distinguished.

Accumulation of isogloboside and ganglio-N-tetraosyl ceramide having blood group B determinant in the hepatomas of female LEC rats

We have studied the neutral glycolipid composition of spontaneous hepatomas in LEC female rats. Neutral lipid fractions were isolated and purified by column chromatographies on DEAE-Toyopearl 650(M) and Iatrobeads. The neutral glycolipid fraction contained 3.2 to 4.4 micrograms lipid-bound glucose (Glc) per mg protein, and consisted of isogloboside (iso-Gb4, 50.8% of total neutral glycolipids) and IV3Gal, IV2Fuc, GgOse4Cer (asialo-BGM1, 13.5%) as the major neutral glycolipids and Gb3 and iso-Gb3 (9.2%), GlcCer (7.2%), LacCer (6.1%) as the other species. The structure of iso-Gb4 was elucidated by gas-liquid chromatography (GLC), permethylation study, liquid secondary ion (LSI) mass spectrometry, and nuclear Overhauser enhancement spectroscopy (NOESY) and that for asialo-BGM1 by GLC, LSI mass spectrometry, and high-performance thin-layer chromatography (HPTLC)-overlay method using anti-asialo-BGM1 antibody. Isogloboside and asialo-BGM1 which are found in negligible amounts in normal liver tissues may represent excellent markers for studying tumor metastasis and cellular adhesion.

A novel mono-sulfated pentaglycosylceramide with the isoglobo-series core structure in rat kidney

A five-sugar sulfated glycosphingolipid containing an isoglobo-series carbohydrate core was isolated from rat kidney and its structure characterized by compositional analysis, FTIR spectroscopy, methylation analysis and 1H NMR spectroscopy of the intact glycolipid and its limited degradation products, and negative liquid secondary ion mass spectrometry (LSIMS). The two dimensional chemical shift correlated spectroscopy and NOE spectroscopy provided information on the sugar sequence and linkage as well as anomeric configurations, so as to establish the presence of a 3-O-sulfated galactose and a Gal alpha 1-3Gal structure within the molecule. Negative LSIMS with collision-induced dissociation defined the sugar sequence and ceramide composition, allowing to confirm the presence, and indicating the position, of the sulfate group. The glycosphingolipid was found to be a mono-sulfated derivative of the isoglobo-series core, with the following structure: HSO3(-)-3Gal beta 1-3GalNAc beta 1-3Gal alpha 1-3Gal beta 1-4Glc beta 1-1Cer (iGb5Cer V3-sulfate).