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PubMed1985

Mannoside storage and axonal dystrophy in sensory neurones of swainsonine-treated rats: morphogenesis of lesions.

Young rats were treated with swainsonine for up to 200 days at a dose rate that restricted neuronal mannoside storage to neurones not protected by the blood/brain barrier. In lumbar dorsal root ganglion neurones, mannoside storage in the cell body developed in parallel to dystrophic changes at the extremities of peripherally and centrally directed axons. The dystrophic process involved the accumulation of autophagic structures. In the CNS, axonal dystrophy was confined to areas receiving long processes from affected neurones. The results suggest that axonal dystrophy is a direct consequence of the lysosomal storage process in parent cell bodies. The possible relationship of axonal dystrophy to neuronal lysosomal function is discussed.

Alkaloids↗
PubMed2004

Synthesis of cluster mannosides via a Ugi four-component reaction and their inhibition against the binding of yeast mannan to concanavalin A.

The Ugi four-component reaction (U-4CR) was utilized to prepare divalent and trivalent cluster mannosides with different scaffolds. The glycoclusters obtained were tested for their relative inhibitory potency against the binding of yeast mannan to concanavalin A by solid-phase enzyme-linked lectin assays (ELLA) using methyl alpha-D-mannopyranoside as a standard. Among them, a divalent mannoside containing aromatic groups showed the strongest binding affinity to concanavalin A.

Concanavalin A↗
PubMed1999

Molecular recognition of concanavalin A on mannoside diacetylene lipid monolayer at the air-water interface.

The interaction of p-10,12-pentacosadiyne-1-n-phenylamide alpha-D-mannopyranoside (MPDA) with protein concanavalin A (Con A) was studied at the air/water interface. The expansion of molecular area of PDA (10,12-pentacosadiynoic acid)/MPDA mixed monolayer after injection of Con A in subphase shows strong interaction between Con A and the monolayer. The maximum expansion of molecular area decreases as the molar ratio of MPDA increases due to the steric hindrance effect. By using enzyme mannosidase to cut-off the mannoside headgroup of MPDA, expansion of molecular area was greatly reduced, indicating that the binding of Con A is specific to the mannoside headgroup. The kinetics of the binding fits to the first order bimolecular reaction model. Fluorescence quenching of fluorescein isothiocyanate labeled Con A after injection into the subphase gives a direct proof of the molecular recognition.

Air↗
PubMed1997

4,6-di-O-benzoyl-3-O-benzyl-alpha-D-arabino-hexo-pyranos-2-ulosyl bromide: a conveniently accessible glycosyl donor for the expedient construction of diantennary beta-D-mannosides branched at O-3 and O-6.

A concise practical, large scale-adaptable six-step sequence has been developed for the transformation of diacetone-glucose into 4,6-di-O-benzoyl-3-O-benzyl-alpha-D-arabino-hexopyranos-2-ulosy l bromide (7), a most useful indirect beta-D-mannosyl donor as its blocking group pattern allows the construction of biologically relevant beta-D-mannosides branched at O-3 and O-6. The broad utility of this new ulosyl bromide 7 resides in its high anomeric reactivity, and in the ease and uniformity with which beta-stereocontrol can be achieved over both, glycosidations and carbonyl reduction of the beta-ulosides formed: Koenigs-Knorr conditions exclusively provide beta-glycosiduloses, hydride reduction of their carbonyl functions proceeds with high stereoselectivities (> 20:1) in favor of the beta-D-mannosides. These preparatively auspicious properties are materialized in an efficient, straightforward synthesis of alpha-D-Manp-(1-->6)-[alpha-D-Manp-(1-->3)]-beta-D-Manp++ +-(1-->O)-Octyl, the 3,6-O-branched core-mannotrioside carrying an octyl spacer instead of the chitobiosyl unit.

Carbohydrate Sequence↗
PubMed2005

Efficient installation of beta-mannosides using a dehydrative coupling strategy.

[reaction: see text]. A new coupling procedure for the construction of the challenging beta-mannosidic bond is described. Dehydrative mannosylation using 4,6-O-benzylidene mannopyranoses allows for the formation of beta-mannosides in excellent yield. The stereoselectivity is generally good but influenced by the exact nature of the glycosylating agent and the nucleophile.

Combinatorial Chemistry Techniques↗
PubMed1998

Transport of free polymannose-type oligosaccharides from the endoplasmic reticulum into the cytosol is inhibited by mannosides and requires a thapsigargin-sensitive calcium store.

The transport of free polymannose-type oligosaccharides from the lumen of the endoplasmic reticulum into the cytosol has been recently demonstrated (Moore,S.E.H., et al., 1995, EMBO J., 14, 6034-6042), but at present little is known of the characteristics of this process. Here, it is shown that inhibition of the transport of endogenously synthesized metabolically radiolabeled free oligosaccharides out of the endoplasmic reticulum into the cytosol of permeabilized HepG2 cells occurs when assays are conducted in the presence of mannose (IC50, 4.9 mM), or its derivatives modified at the first carbon (C1) of the sugar ring; alpha-methyl mannoside (IC50, 2.0 mM), mannoheptulose (IC50, 1.6 mM), and alpha-benzyl mannoside (IC50, 0.8 mM), whereas other monosaccharides (50 mM), differing from mannose at position; C2 (glucose), C3 (altrose), C4 (talose), C5 (l-rhamnose), and C6 (mannoheptose), have little effect. N-Acetylglucosamine does not inhibit oligosaccharide transport and, furthermore, although mannobioses and a mannotriose inhibit free oligosaccharide transport, di-N-acetylchitobiose is without effect. It is also shown that if the transport assay buffer is either depleted of calcium ions, or supplemented with the Ca2+/Mg2+ATPase inhibitor, thapsigargin, or with calcium ionophores, free oligosaccharide transport out of the endoplasmic reticulum is inhibited. These results demonstrate that the terminal nonreducing mannosyl residues of free polymannose-type oligosaccharides and not their N-acetylglucosamine-containing reducing termini, play an important role in the interaction of the free oligosaccharide with the transport machinery, and that this transport process requires the presence of calcium sequestered in the lumen of the endoplasmic reticulum.

Adenosine Triphosphate↗
PubMed1987

Ultrastructural localization of mannoside residues on tissue sections: comparative evaluation of the enzyme-gold and the lectin-gold approaches.

Mannoside residues were revealed at the ultrastructural level in different cellular and extracellular compartments by means of the enzyme-gold and the lectin-gold approaches. For the enzyme-gold technique, an alpha-mannosidase-gold complex was prepared and conditions for the preparation of this complex as well as for its application were determined. Labeling was found over the rough endoplasmic reticulum mainly at the level of the membranes, the lumen of the cisternae being devoid of labeling. In the nucleus, the dense chromatin and the edge of the fibrillar threads in the nucleolus were intensely labeled. Few gold particles were present over the Golgi apparatus and mitochondria. The secretory granules in pancreatic cells, the peroxisomes in liver and the mucin in duodenal goblet cells were devoid of labeling. In the extracellular space, the basal lamina was labeled. Over the glomerular basal lamina, the labeling was mainly towards the epithelial side, in close contact with the podocytes. The results with the concanavalin A horseradish peroxidase (Con A-HRP)-gold technique were similar to those found with the enzyme-gold approach. Some differences were, however, detected at the level of the rough endoplasmic reticulum and the nucleus. In the endoplasmic reticulum, Con A-HRP-gold labeling was present over both the membranes and the lumen of the cisternae. In the nucleus, the labeling was mainly over the dispersed chromatin. These differences may be due to the binding of Con A not only to mannoside but also to other sugar residues as well as to the affinity of HRP-gold for some nucleoplasmic components.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Purification of an acidic alpha-D-mannosidase from Aspergillus saitoi and specific cleavage of 1,2-alpha-D-mannosidic linkage in yeast mannan.

An acidic alpha-D-mannosidase (alpha-D-mannoside mannohydrolase, EC 3.2.1.24) has been isolated from culture filtrate of Aspergillus saitoi. The extracellular alpha-mannosidase was homogeneous in polyacrylamide gel electrophoresis. The molecular weight of the enzyme was 51 000 and the isoelectric point pH 4.5. The purified enzyme has a pH optimum of 5.0, a Km of 0.45 mM with baker's yeast mannan and has no activity towards p-nitrophenyl-alpha-D-mannoside. The mode of action of the enzyme has been studied with baker's yeast mannan and saké yeast mannan. The enzyme cleaves specifically the 1,2-alpha-linked side chain, producing free mannose.

Aspergillus↗
PubMed1995

The human UDP-N-acetylglucosamine: alpha-6-D-mannoside-beta-1,2- N-acetylglucosaminyltransferase II gene (MGAT2). Cloning of genomic DNA, localization to chromosome 14q21, expression in insect cells and purification of the recombinant protein.

UDP-GlcNAc:alpha-6-D-mannoside [GlcNAc to Man alpha 1-6] beta-1,2-N-acetylglucosaminyltransferase II (GlcNAc-T II, EC 2.4.1.143) is a Golgi enzyme catalyzing an essential step in the conversion of oligomannose to complex N-glycans. A 1.2-kb probe from a rat liver cDNA encoding GlcNAc-T II was used to screen a human genomic DNA library in lambda EMBL3. Southern analysis of restriction endonuclease digests of positive phage clones identified two hybridizing fragments (3.0 and 3.5 kb) which were subcloned into pBlueScript. The inserts of the resulting plasmids (pHG30 and pHG36) are over-lapping clones containing 5.5 kb of genomic DNA. The pHG30 insert (3.0 kb) contains a 1341-bp open reading frame encoding a 447-amino-acid protein, 250 bp of G + C-rich 5'-upstream sequence and 1.4 kb of 3'-downstream sequence. The pHG36 insert (3.5 kb) contains 2.75 kb of 5'-upstream sequence and 750 bp of the 5'-end of the open reading frame. The protein sequence showed the domain structure typical of all previously cloned glycosyltransferases, i.e. a short 9-residue putative cytoplasmic N-terminal domain, a 20-residue hydrophobic non-cleavable putative signal-anchor domain and a 418-residue C-terminal catalytic domain. Northern analysis of human tissues showed a major message at 3 kb and minor signals at 2 and 4.5 kb. There is no sequence similarity to any previously cloned glycosyltransferases including human UDP-GlcNAc:alpha-3-D-mannoside [GlcNAc to Man alpha 1-3] beta-1,2-N-acetylglucosaminyltransferase I (GlcNAc-T I) which has 445 amino acids with a 418-residue C-terminal catalytic domain. The human GlcNAc-T I and II genes (MGAT1 and MGAT2) map to chromosome bands 5q35 and 14q21, respectively, by fluorescence in situ hybridization. The entire coding regions of human GlcNAc-T I and II are each on a single exon. There is 92% identity between the amino acid sequences of the catalytic domains of human and rat GlcNAc-T II. Southern analysis of restriction enzyme digests of human genomic DNA indicates that there is only a single copy of the MGAT2 gene. The full-length coding region of GlcNAc-T II has been expressed in the baculovirus/Sf9 insect cell system, the recombinant enzyme has been purified to near homogeneity with a specific activity of about 20 mumol.min-1.mg-1 and the product synthesized by the recombinant enzyme has been identified by high-resolution 1H-NMR spectroscopy and mass spectrometry.

Amino Acid Sequence↗
PubMed1995

Identification of a 148-kDa surface lectin from Giardia lamblia with specificity for alpha-methyl-D-mannoside.

A lectin specific for alpha-methyl-D-mannoside was purified from the membrane extract of Giardia lamblia by a combination of gel filtration chromatography on Sephadex G-75 and Superose 6-HR 10/30. The homogeneity of the lectin was established by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular mass of the native protein was 148 kDa. The lectin agglutinated rabbit erythrocytes in the presence of Ca2+ at 37 degrees C and pH 7.0. The maximum activity of the lectin was obtained after trypsin treatment. The inhibition study clearly suggests that the binding site of the lectin recognizes alpha-methyl-D-mannoside as the immunodominant sugar.

Animals↗
PubMed1984

Control of glycoprotein synthesis. IX. A terminal Man alpha l-3Man beta 1- sequence in the substrate is the minimum requirement for UDP-N-acetyl-D-glucosamine: alpha-D-mannoside (GlcNAc to Man alpha 1-3) beta 2-N-acetylglucosaminyltransferase I.

Twenty low molecular weight compounds were tested as substrates for UDP-GlcNAc:alpha-D-mannoside (GlcNAc to Man alpha 1-3) beta 2-N-acetylglucosaminyltransferase I (GlcNAc-transferase I) purified from bovine colostrum. This enzyme is at a key control point in the biosynthetic path leading to complex Asn-linked oligosaccharides. The highest activity was obtained with the substrate Man alpha 1-3(R1 alpha 1-6)Man beta 1-R2 where R1 was Man alpha 1-3(Man alpha 1-6)Man- (Km = 0.20 mM) and R2 was -4GlcNAc beta 1-4GlcNAc-Asn. Somewhat less effective were substrates in which R1 was Man- (Km = 0.4-0.6 mM) and R2 was either-4GlcNAc or -4GlcNAc beta 1-4(Fuc alpha 1-6)GlcNAc-Asn. Removal of the Man alpha 1-6 arm (R1 = H-) or replacing R2 with an isopropyl group had no effect on Vmax but increased the Km about 10-fold, thereby leading to an 85% reduction in enzyme activity as measured under standard conditions. An 85% reduction in activity was also observed if R2 was replaced with N-acetylglucosaminitol. Enzyme activity was reduced 33% if R1 was Gal beta 1-4GlcNAc beta 1-2Man-. Any compounds lacking a Man alpha 1-3- terminus or in which the beta-linked Man had been replaced with an alpha-linked Man were totally inactive. It was concluded that a terminal Man alpha 1-3Man beta 1-sequence is a minimal structural requirement for a GlcNAc-transferase I substrate. The only effective substrate for partially purified UDP-GlcNAc:alpha-D-mannoside (GlcNAc to Man alpha 1-6) beta 2-N-acetylglucosaminyltransferase II (GlcNAc-transferase II) from bovine colostrum was R1-GlcNAc beta 1-2Man alpha 1-3(Man alpha 1-6)Man beta 1-R2 where R1 = H-. The absence of a terminal GlcNAc beta 1-2- residue or masking this residue by making R1 = Gal beta 1-4-, both prevented enzyme activity, indicating that GlcNAc-transferase I action must precede GlcNAc-transferase II action during biosynthesis of complex Asn-linked oligosaccharides.

Animals↗
PubMed2001

Effect of alpha1,2-mannosidic linkage located in a alpha1,3-branch of Man6GlcNAc2 oligosaccharide on enzyme activity of recombinant human Man9-mannosidase produced in Escherichia coli.

We produced the human kidney Man9-mannosidase in Escherichia coli and studied the effect of the alpha-1,2-mannosidic linkage located in the alpha branch of Manalpha1-6(Manalpha1-2Manalpha1-3)Manalpha1-6(Manalpha1-3)Manbeta1-4GlcNAcbeta1-4-GlcNAc, an N-linked oligosaccharide, on the enzyme activity. The alpha1,2-mannose residue influenced the rate of hydrolysis of and substrate preference for other alpha-1,2-mannosidic linkages.

Journal Article↗
PubMed1982

Maximizing differences in the concanavalin A-induced blastogenic responses of lymphocytes from breast cancer patients and controls by the use of alpha-methyl-D-mannoside.

In an attempt to magnify differences in the immune responses of potentially immunosuppressed cancer patients and normal controls, an assessment was made on the effects of the competitive inhibitor alpha-methyl-D-mannoside on the concanavalin A (Con A)-induced blastogenic responses of lymphocytes from each of these populations. Lymphocytes from breast cancer patients with metastatic disease were significantly deficient in their capability to undergo blast transformation regardless of whether the monosaccharide inhibitor was added to the assay cultures. In contrast, lymphocytes from breast cancer patients who did not display metastatic disease were capable of normal blastogenic responses to Con A. The addition of alpha-methyl-D-mannoside to lymphocyte cultures caused a significantly greater inhibition of the blastogenic responses of these patients' cells as compared to cells of normal controls. Thus the monosaccharide seems to serve as a useful reagent for optimizing differences between lymphocyte blastogenic responses of normal donors and those of immunodepressed donors. The results suggest that lymphocytes from breast cancer patients without clinically evident metastases possess some modification of their cell membrane. One possibility discussed was that the number or distribution of receptors for Con A on the membrane of lymphocytes of these patients is deficient.

Binding, Competitive↗
PubMed2006

Phosphatidylinositol mannosides: synthesis and adjuvant properties of phosphatidylinositol di- and tetramannosides.

Phosphatidylinositol mannosides (PIMs) isolated from mycobacteria have been identified as an important class of glycolipids with significant immune modulating properties. We present here the syntheses of phosphatidylinositol dimannoside (PIM2, 1) and phosphatidylinositol tetramannoside (PIM4, 2) and evaluate their adjuvant properties in a transgenic mouse model. The key step in the synthetic methodology for the synthesis of 2 relies on the selective glycosylation of diol 3 with mannosyl donor 11. Both synthetic PIMs were effective at enhancing IFN-gamma when given as adjuvants with a model antigen, with PIM2 being the more active. These data suggest that in this assay the PIM core structure is responsible for the observed biological activity.

Adjuvants, Immunologic↗
PubMed2006

Multivalent glycomimetics: synthesis of nonavalent mannoside clusters with variation of spacer properties.

Oligosaccharide mimetics are important tools in the glycosciences. In this work, we have employed spaced glycodendrons for the synthesis of oligomannoside mimetics. Starting from a number of trivalent, branched molecular wedges, the preparation of nonavalent cluster mannosides was accomplished, which were varied with regard to the chemical characteristics of their spacer moieties and spacer lengths. For ligation of the various trivalent dendrons to the nonavalent target molecules peptide coupling was employed.

Bacterial Adhesion↗
PubMed2000

Association of concentration of asbestos and asbestos-like fibers with the patient's survival and the binding capacity of lung parenchyma to galectin-1 and natural alpha-galactoside- and alpha-mannoside-binding immunoglobulin G subfractions from human serum.

Our aim in this study was to search for lung parenchyma alterations associated with asbestos and/or asbestos-like fiber concentration. This was done by means of immuno- or glycohistochemistry. The hot-ashing technique determined the asbestos and asbestos-like fiber concentrations in the lung tissues of 100 patients of whom 52 were treated for primary lung and 25 for secondary lung tumors; fiber concentration was also measured for 23 patients whose disease was benign. The results were correlated to smoking habits, survival of the patients, and expression of binding capacities for endogenous lectins, natural carbohydrate-binding and lectin-specific antibodies. The cohort with proven asbestos exposure revealed a mean fiber concentration 114 f/g compared to 95 f/g in the non-exposed group. An increased asbestos fiber concentration was correlated to galectin-1-binding and the presence of epitopes for natural immunoglobulin G subfractions with selectivity to alpha-galactosides and alpha-mannosides. The survival of patients with primary and secondary lung tumors was negatively associated with the fiber concentration. The data indicate that increased presence of asbestos is correlated with an alteration of defined glycohistochemical features of alveolar lining cells.

Adult↗
PubMed2001

Synthetic mannosides act as acceptors for mycobacterial alpha1-6 mannosyltransferase.

A series of synthetic mannosides was screened in a cell-free system for their ability to act as acceptor substrates for mycobacterial mannosyltransferases. Evaluation of these compounds demonstrated the incorporation of [14C]Man from GDP-[14C]Man into a radiolabeled organic-soluble fraction and analysis by thin layer chromatography and autoradiography revealed the formation of two radiolabeled products. Each synthetic acceptor was capable of accepting one or two mannose residues, resulting in a major and a minor mannosylated product. Both products from each acceptor were isolated and their mass was confirmed by fast-atom bombardment-mass spectrometry (FABMS). Characterization of each mannosylated product by exo-glycosidase digestion. acetolysis and linkage analysis by gas chromatography mass spectrometry of partially per-O-methylated alditols, revealed only alpha1-6-linked products. In addition. the antibiotic amphomycin selectively inhibited the formation of mannosylated products suggesting polyprenolmonophosphate-mannose (C15 50-P-Man) was the immediate mannose donor in all mannosylation reactions observed. The ability of synthetic disaccharides to act as acceptor substrates in this system, is most likely due to the action of a mycobacterial polyprenol-P-Man:mannan alpha1-6 mannosyltransferase involved in the biosynthesis of linear alpha1-6-linked lipomannan.

Carbohydrate Sequence↗
PubMed2006

Total synthesis of phosphatidylinositol mannosides of Mycobacterium tuberculosis.

The total synthesis of phosphatidylinositol mannosides (PIMs), a key class of antigenic glycolipids found on the cell wall of Mycobacterium tuberculosis, is described. The synthetic strategy relied on a [4 + 3] glycosylation of tetramannoside 1 and pseudotrisaccharide 2, which allowed for convergent access to the glycan backbone of the phosphatidylinositol dimannoside (PIM2) and hexamannoside (PIM6). A short practical synthesis of tuberculostearic acid was achieved based on a copper-catalyzed cross-coupling reaction. Union of the glycan and lipid parts resulted in the first total synthesis of native PIM2 and PIM6.

Carbohydrate Sequence↗