Ceramide glycanase from leech, Hirudo medicinalis, and earthworm, Lumbricus terrestris

Counter effects of Asiaticosids-D through putative neurotransmission on rotenone induced cerebral ganglionic injury in Lumbricus terrestris

Asiaticoside-D (AD) was shown to efficacy of ganglionic degenerated Lumbricus terrestris as a pioneering observation in our earlier research. Though, extract molecular mechanisms of AD for degenerative diseases (DDs) remains largely unknown. We investigated the neuroprotective effects of AD against ROT in cerebral ganglions (CGs) of degenerative L. terrestris. Worms were exposed to 0.4 ppm ROT for 7 days were subjected to co- treatment with 15 ppm of AD. After, CGs was removed. The levels oxidant, non-antioxidant, antioxidant status, ganglioside, ceramide and ceramide glycanase (CGase) were estimated. The m-RNA levels of dopamine transporter (DAT), octopamine transporter (OAT), innexins-9 (inx-9), ionotropic glutamate receptor 3 (iGlu3), heat shock proteins (hsp70), XPRLamide neuropeptide precursor, tyramine beta-hydroxylase (tbh-1) and β- adrenergic receptor kinase-2 (β-ARK2-3) by semi-qRT- PCR. The expression pattern of tyramine beta hydroxylase (TBH), glutamate receptor (iGluR), serotonin transporter (SERT), dopamine transporters (DAT), nerve growth factors (NGF), cytochrome C oxidase (COC), NADH dehydogenase subunit-1 (ND-1), neurotrophin receptor p75 (p75NTR), neuronal nitric oxiside synthase (nNOs) interleukin 1- beta (IL1-β) and tumor necrosis factor alpha (TNF-α) by western blotting. Glutaminergic, serotogenic and dopaminergic toxicity variations were also performed. The levels of oxidant, non-antioxidant, antioxidant status, lipids, proteins and m-RNAs were significantly altered (p < 0.001) on ROT-induced (group II) and their levels were significantly changes (p < 0.05) by ROT+AD in CGs. The sensitive study plan concluded the neuroprotective effects of AD against ROT induced degeneration in worms and suggest that the AD deserves future studies for its use as an effective alternative medicine that could minimize the morbidity of ganglionic degenerative diseases patients.

19q13.12 microdeletion syndrome fibroblasts display abnormal storage of cholesterol and sphingolipids in the endo-lysosomal system

Microdeletions in 19q12q13.12 cause a rare and complex haploinsufficiency syndrome characterized by intellectual deficiency, developmental delays, and neurological movement disorders. Variability in the size and interval of the deletions makes it difficult to attribute the complex clinical phenotype of this syndrome to an underlying gene(s). As an alternate approach, we examined the biochemical and metabolic features of fibroblasts from an affected individual to derive clues as to the molecular basis for the syndrome. Immunofluorescence and electron microscopy of affected fibroblasts revealed an abnormal endo-lysosomal compartment that was characterized by rapid accumulation of lysosomotropic dyes, elevated LAMP1 and LAMP2 expression and vacuoles containing membrane whorls, common features of lysosomal lipid storage disorders. The late endosomes-lysosomes (LE/LY) of affected fibroblasts accumulated low-density lipoprotein cholesterol, and displayed reduced cholesterol esterification and increased de novo cholesterol synthesis, indicative of defective cholesterol transport to the endoplasmic reticulum. Affected fibroblasts also had increased ceramide and sphingolipid mass, altered glycosphingolipid species and accumulation of a fluorescent lactosylceramide probe in LE/LY. Autophagosomes also accumulated in affected fibroblasts because of decreased fusion with autolysosomes, a defect associated with other lysosomal storage diseases. Attempts to correct the cholesterol/sphingolipid storage defect in fibroblasts with cyclodextrin, sphingolipid synthesis inhibitors or by altering ion transport were unsuccessful. Our data show that 19q13.12 deletion fibroblasts have abnormal accumulation of cholesterol and sphingolipids in the endo-lysosomal system that compromises organelle function and could be an underlying cause of the clinical features of the syndrome.

Verification and refinement of cellular glycosphingolipid profiles using HPLC

Glycosphingolipids (GSLs) are hybrid molecules consisting of the sphingolipid ceramide linked to a mono- or oligo-saccharide. In comparison to other membrane lipids, the family of GSLs stands out because of the extensive variation in the carbohydrate headgroup. GSLs are cell surface binding partners, in cis with growth factor receptors, and in trans with bacterial toxins and viruses, and are among the host-derived membrane components of viral particles, including those of HIV. In spite of their biological relevance, GSL profiles of commonly used cell lines have been analyzed to different degrees. Here, we directly compare the GSL complements from CHO-K1, COS-7, HeLa, HEK-293, HEPG2, Jurkat, and SH-SY5Y cells using an HPLC-based method requiring modest amounts of material. Compared to previous studies, the HPLC-based analyses provided more detailed information on the complexity of the cellular GSL complement, qualitatively as well as quantitatively. In particular for cells expressing multiple GSLs, we found higher numbers of GSL species, and different levels of abundance. Our study thus extends our knowledge of biologically relevant lipids in widely used cell lines.

Preparation and characterization of EGCase I, applicable to the comprehensive analysis of GSLs, using a rhodococcal expression system

Endoglycoceramidase (EGCase) is a glycosidase capable of hydrolyzing the β -glycosidic linkage between the oligosaccharides and ceramides of glycosphingolipids (GSLs). Three molecular species of EGCase differing in specificity were found in the culture fluid of Rhodococcus equi (formerly Rhodococcus sp. M-750) and designated EGCase I, II, and III. This study describes the molecular cloning of EGCase I and characterization of the recombinant enzyme, which was highly expressed in a rhodococcal expression system using Rhodococcus erythropolis. Kinetic analysis revealed the turnover number (k(cat)) (k(cat)) of the recombinant EGCase I to be 22- and 1,200-fold higher than that of EGCase II toward GM1a and Gb3Cer, respectively, although the K(m) of both enzymes was almost the same for these substrates. Comparison of the three-dimensional structure of EGCase I (model) and EGCase II (crystal) indicated that a flexible loop hangs over the catalytic cleft of EGCase II but not EGCase I. Deletion of the loop from EGCase II increased the k(cat) of the mutant enzyme, suggesting that the loop is a critical factor affecting the turnover of substrates and products in the catalytic region. Recombinant EGCase I exhibited broad specificity and good reaction efficiency compared with EGCase II, making EGCase I well-suited to a comprehensive analysis of GSLs.

Diverse endogenous antigens for mouse NKT cells: self-antigens that are not glycosphingolipids

NKT cells with an invariant Ag receptor (iNKT cells) represent a highly conserved and unique subset of T lymphocytes having properties of innate and adaptive immune cells. They have been reported to regulate a variety of immune responses, including the response to cancers and the development of autoimmunity. The development and activation of iNKT cells is dependent on self-Ags presented by the CD1d Ag-presenting molecule. It is widely believed that these self-Ags are glycosphingolipids (GSLs), molecules that contain ceramide as the lipid backbone. In this study, we used a variety of methods to show that mammalian Ags for mouse iNKT cells need not be GSLs, including the use of cell lines deficient in GSL biosynthesis and an inhibitor of GSL biosynthesis. Presentation of these Ags required the expression of CD1d molecules that could traffic to late endosomes, the site where self-Ag is acquired. Extracts of APCs contain a self-Ag that could stimulate iNKT cells when added to plates coated with soluble, rCD1d molecules. The Ag(s) in these extracts are resistant to sphingolipid-specific hydrolase digestion, consistent with the results using live APCs. Lyosphosphatidylcholine, a potential self-Ag that activated human iNKT cell lines, did not activate mouse iNKT cell hybridomas. Our data indicate that there may be more than one type of self-Ag for iNKT cells, that the self-Ags comparing mouse and human may not be conserved, and that the search to identify these molecules should not be confined to GSLs.

Glycan profiling of urine, amniotic fluid and ascitic fluid from galactosialidosis patients reveals novel oligosaccharides with reducing end hexose and aldohexonic acid residues

Urine, amniotic fluid and ascitic fluid samples of galactosialidosis patients were analyzed and structurally characterized for free oligosaccharides using capillary high-performance anion-exchange chromatography with pulsed amperometric detection and online mass spectrometry. In addition to the expected endo-beta-N-acetylglucosaminidase-cleaved products of complex-type sialylated N-glycans, O-sulfated oligosaccharide moieties were detected. Moreover, novel carbohydrate moieties with reducing-end hexose residues were detected. On the basis of structural features such as a hexose-N-acetylhexosamine-hexose-hexose consensus sequence and di-sialic acid units, these oligosaccharides are thought to represent, at least in part, glycan moieties of glycosphingolipids. In addition, C(1)-oxidized, aldohexonic acid-containing versions of most of these oligosaccharides were observed. These observations suggest an alternative catabolism of glycosphingolipids in galactosialidosis patients: oligosaccharide moieties from glycosphingolipids would be released by a hitherto unknown ceramide glycanase activity. The results show the potential and versatility of the analytical approach for structural characterization of oligosaccharides in various body fluids.

Fingerprinting of large oligosaccharides linked to ceramide by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: highly heterogeneous polyglycosylceramides of human erythrocytes with receptor activity for Helicobacter pylori

Highly microheterogeneous polyglycosylceramides (PGCs) of human erythrocytes with an average composition of about 25 monosaccharides linked to ceramide were analyzed by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The human gastric pathogen Helicobacter pylori was earlier shown to bind this glycosphingolipid mixture by thin-layer chromatogram binding assay. The receptor activity was present along the whole nonresolved chromatographic interval. Mass spectra of intact PGCs were compared with corresponding spectra of oligosaccharides enzymatically released from the ceramides. Two subfractions of PGCs containing less than one and more than one sialic acid residue per molecule were used. MALDI-MS spectra were recorded in both linear and reflectron mode with the accuracies of </=0.08% and </=0.02%, respectively, which allowed determination of the constituent parts of the detected ions in form of ceramide and number of hexoses, N-acetylhexosamines, fucoses and sialic acids. Molecular species were found based on ceramide with mainly sphingosine and fatty acids 24:0 and 24:1 (with less amounts of 22:0), and with a total number of monosaccharides ranging from 11 (neutral, m/z = 2605 for [M+Na](+)) to 41 (one sialic acid, m/z = 8057 for [M-H](-)). The saccharide composition obtained supported a successively extended and branched N -acetyllactosamine core with substitutions of fucoses (0 up to 8) and sialic acid (0 to 1). The reliable molecular analysis of large oligosaccharides linked to ceramide using this approach will be of great help for the further structure analysis in order to define the epitope for the sialic acid-dependent binding by the bacterium.

Glycotargeting: the preparation of glyco-amino acids and derivatives from unprotected reducing sugars

Lectins are present on the surface of many cells. Many lectins actively recycle from membrane to endosomes and efficiently take up glycoconjugates in a sugar-dependent manner. On this basis, glycoconjugates, specially those obtained by chemical means, are good candidates as carriers of drugs, oligonucleotides or genes. In this paper, we present a panel of methods suitable to transform unprotected reducing oligosaccharides into glycosynthons designed to be easily linked to therapeutic agents. All the glycosynthons presented here are glycosylamines or derivatives, mainly glyco-amino acids or glycopeptides. Glycosylamines are easy to obtain, but they are very labile in slightly acidic or neutral medium; they must be stabilized, by acylation for instance. The coupling efficiency of a reducing sugar with ammonia as well as an alkylamine or an arylamine is higher at high temperature, however, because of the Amadori rearrangement, special conditions have to be selected to prepare the expected glycosylamine derivative with a high yield. Glycosylamines are easily acylated by N-protected amino acids, or by halogeno acids which can then be transformed into amino acids. Alternatively, unprotected reducing oligosaccharides may very efficiently be transformed into N-glycosyl-amino acids and then protected by N-acylation. With a glutamyl derivative having both the alpha-amino and the gamma-carboxylic groups free, the coupling and the acylation, which is intramolecular, are roughly quantitative. N-oligosaccharyl-amino acid derivatives are interesting glycosynthons, because their sugar moiety bears the specificity towards membrane lectins while the amino acid part has the capacity to easily substitute a therapeutic agent.

Synthesis of aryl 3'-sulfo-beta-lactosides as fluorogenic and chromogenic substrates for ceramide glycanases

We have previously reported that 4-methylumbelliferyl 6'-O-benzyl-beta-lactoside (2) is a useful substrate for a fluorometric assay of ceramide glycanase (CGase) (L.-X. Wang, N. V. Pavlova, S.-C. Li, Y.-T. Li and Y. C. Lee, Glycoconjugate J., 13 (1996) 359-365). The introduction of a 6-O-benzyl group at the terminal Gal efficiently protected the substrate from its hydrolysis by exo-galactosidase, permitting the assay of CGase in crude biological materials. However, a drawback of this substrate is its low water-solubility and relatively high Km (at a mM level). Introduction of a sulfate group into 4-methylumbelliferyl beta-lactoside (1) led to the formation of 4-methylumbelliferyl 3'-O-sulfo-beta-lactoside (3), which was found to be a more effective substrate than 2. Moreover, the presence of a 3'-O-sulfate group not only increases the water solubility tremendously, but also protects the substrate from cleavage by exo-beta-galactosidase as the 6'-O-benzyl group in 2 does. In addition to the fluorogenic substrate (3), two sulfated chromogenic substrates, N-tetradecanoyl-4-O(3'-sulfo-beta-lactosyl)-3-nitro-L-tyrosine methyl ester (9) and 2-N-(tetradecanoylamino)-4-nitro-phenyl 3'-sulfo-beta-lactoside (12), were synthesized and their suitability for a photometric assay of CGase was evaluated. Substrates 9 and 12, with a long fatty acid chain attached to the aglycon part, have a Km value close to that of the natural substrate GM1 (at a microM level).

The crystal structure of a Fab fragment to the melanoma-associated GD2 ganglioside

The GD2 ganglioside is a cell-surface component that appears on the surface of metastatic melanoma cells and is a marker for the progression of the disease. The ME36.1 monoclonal antibody binds to the GD2 ganglioside and has shown potential as a therapeutic antibody. ME36.1 is a possible alternative therapy to radiation, which is often ineffective in late-stage melanoma. The crystal structure of the Fab fragment of ME36.1 has been determined using molecular replacement and refined to an R factor of 20.4% at 2.8 A resolution. The model has good geometry with root-mean-square deviations of 0.008 A from ideal bond lengths and 1.7 degrees from ideal bond angles. The crystal structure of the ME36.1 Fab shows that its complementarity determining region forms a groove-shaped binding site rather than the pocket-type observed in other sugar binding Fabs. Molecular modeling has placed a four-residue sugar, representative of GD2, in the antigen binding site. The GD2 sugar moiety is stabilized by a network of hydrogen bonds that define the specificity of ME36.1 toward its antigen.

A fluorometric assay of ceramide glycanase with 4-methylumbelliferyl beta-D-lactoside derivatives

4-Methylumbelliferyl 6'-O-benzyl-beta-D-lactoside (6'Bn-MU-Lac) and some related compounds were synthesized via different selective reactions including phase-transfer glycosylation. Their suitability as substrates for a fluorometric assay of ceramide glycanase (CGase) was evaluated. Among others, the 6'Bn-MU-Lac, which is resistant to exogalactosidase, was found to be a suitable substrate for routine assay of the CGase activity. For American leech CGase, the K(m) value is 0.232 mM at pH 5.

Fluorophore-assisted carbohydrate electrophoresis in the separation, analysis, and sequencing of carbohydrates

Carbohydrate analysis has traditionally been viewed as a specialty science, performed only in a few well-established laboratories using conventional carbohydrate analysis technology (e.g. NMR, gas chromatography-mass spectroscopy, high-performance liquid chromatography, capillary electrophoresis) combined with the specialized technical training that has been essential for accurate interpretation of the data. This tradition of specialized laboratories is changing, due primarily to an increase in the number of scientists performing routine carbohydrate analysis. As a result, many scientists who are not trained in traditional carbohydrate analytical techniques now need to be able to perform accurate carbohydrate analysis in their own laboratories. This has created a need for technically simple and inexpensive methods of carbohydrate analysis. In this review, we present application vignettes of a technically simple, yet analytically powerful method called fluorophore-assisted carbohydrate electrophoresis (FACE). FACE can be used for performing routine oligosaccharide profiling, monosaccharide analysis, and sequencing of a variety of carbohydrates.

Capillary electrophoresis of carboxylated carbohydrates. Part 2. Selective precolumn derivatization of sialooligosaccharides derived from gangliosides with 7-aminonaphthalene-1,3-disulfonic acid fluorescing tag

The most suitable conditions for selective precolumn derivatization of sialooligosaccharides, derived from gangliosides, with 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) and the subsequent separation of the derivatives by capillary electrophoresis are described. ANDSA-sialooligosaccharide derivatives, which fluoresce at 420 nm when excited at 315 nm, were readily detected in capillary electrophoresis using an on-column lamp-operated fluorescence detector. In addition, the precolumn derivatization described here, which exploited the reactivity of the carboxylic acid group of the sialic acid residue of the oligosaccharides, replaced each weak carboxylic acid group of the parent sugar by two strong sulfonic acid groups. This allowed for electrophoresis over a wide range of pH and improved the resolution of the derivatives when compared to those obtained with underivatized sialooligosaccharides under identical separation conditions. The separation of sialooligosaccharides was best achieved when 75 mM borate, pH 10.0, was used as the running electrolyte. The derivatization and separation conditions described herein are expected to be readily transposed to the capillary electrophoresis of other sialooligosaccharides such as those derived from glycoproteins.