Lysosomal dysfunction causes neurodegeneration in mucolipidosis II 'knock-in' mice.

Mucolipidosis II is a neurometabolic lysosomal trafficking disorder of infancy caused by loss of mannose 6-phosphate targeting signals on lysosomal proteins, leading to lysosomal dysfunction and accumulation of non-degraded material. However, the identity of storage material and mechanisms of neurodegeneration in mucolipidosis II are unknown. We have generated 'knock-in' mice with a common mucolipidosis II patient mutation that show growth retardation, progressive brain atrophy, skeletal abnormalities, elevated lysosomal enzyme activities in serum, lysosomal storage in fibroblasts and brain and premature death, closely mimicking the mucolipidosis II disease in humans. The examination of affected mouse brains at different ages by immunohistochemistry, ultrastructural analysis, immunoblotting and mass spectrometric analyses of glycans and anionic lipids revealed that the expression and proteolytic processing of distinct lysosomal proteins such as α-l-fucosidase, ß-hexosaminidase, α-mannosidase or Niemann-Pick C2 protein are more significantly impacted by the loss of mannose 6-phosphate residues than enzymes reaching lysosomes independently of this targeting mechanism. As a consequence, fucosylated N-glycans, GM2 and GM3 gangliosides, cholesterol and bis(monoacylglycero)phosphate accumulate progressively in the brain of mucolipidosis II mice. Prominent astrogliosis and the accumulation of organelles and storage material in focally swollen axons were observed in the cerebellum and were accompanied by a loss of Purkinje cells. Moreover, an increased neuronal level of the microtubule-associated protein 1 light chain 3 and the formation of p62-positive neuronal aggregates indicate an impairment of constitutive autophagy in the mucolipidosis II brain. Our findings demonstrate the essential role of mannose 6-phosphate for selected lysosomal proteins to maintain the capability for degradation of sequestered components in lysosomes and autophagolysosomes and prevent neurodegeneration. These lysosomal proteins might be a potential target for a valid therapeutic approach for mucolipidosis II disease.

Glycoprotein lysosomal storage disorders: alpha- and beta-mannosidosis, fucosidosis and alpha-N-acetylgalactosaminidase deficiency.

Glycoproteinoses belong to the lysosomal storage disorders group. The common feature of these diseases is the deficiency of a lysosomal protein that is part of glycan catabolism. Most of the lysosomal enzymes involved in the hydrolysis of glycoprotein carbohydrate chains are exo-glycosidases, which stepwise remove terminal monosaccharides. Thus, the deficiency of a single enzyme causes the blockage of the entire pathway and induces a storage of incompletely degraded substances inside the lysosome. Different mutations may be observed in a single disease and in all cases account for the nonexpression of lysosomal glycosidase activity. Different clinical phenotypes generally characterize a specific disorder, which rather must be described as a continuum in severity, suggesting that other biochemical or environmental factors influence the course of the disease. This review provides details on clinical features, genotype-phenotype correlations, enzymology and biochemical storage of four human glycoprotein lysosomal storage disorders, respectively alpha- and beta-mannosidosis, fucosidosis and alpha-N-acetylgalactosaminidase deficiency. Moreover, several animal disorders of glycoprotein metabolism have been found and constitute valuable models for the understanding of their human counterparts.

Effect of okadaic acid on O-linked N-acetylglucosamine levels in a neuroblastoma cell line.

O-Linked N-Acetylglucosamine (O-GlcNAc) is a major form of post-translational modification found in nuclear and cytoplasmic proteins. Several authors have advanced the hypothesis according to which phosphorylation and O-GlcNAc glycosylation are reciprocally related to one another [1,2]. In order to test this hypothesis we have investigated the effect of a broad spectrum phosphatase inhibitor, okadaic acid (OA), generally used to induce protein hyperphosphorylation, on the GlcNAc content of cellular glycoproteins. We demonstrate that in neuronal cells lines OA decreases the level of O-GlcNAc in both nuclear and cytoplasmic proteins with a greater effect in the nuclear fraction. This phenomenon was demonstrated by the use of three different procedures for the detection of O-GlcNAc in conjunction with a systematic treatment with PNGase F. O-Linked GlcNAc was characterized using respectively lectin staining with WGA, galactosyltransferase labeling and metabolic labeling of cultured cells with [3H]glucosamine. Although the effects on individual proteins varied, a less pronounced effect was observed on HeLa or COS cell total homogenates. When Kelly cells were treated with OA, the major observation was a decrease in O-GlcNAc content of nuclear proteins. The measurement of the UDP-GlcNAc level clearly demonstrates that the decrease on the O-GlcNAc level in the neuroblastoma cell line after treatment with okadaic acid is not a consequence of the modification of the UDP-GlcNAc pool.

Characterization of Le(x), Le(y) and A Le(y) antigen determinants in KDN-containing O-linked glycan chains from Pleurodeles waltlii jelly coat eggs.

Novel acidic oligosaccharides were isolated in large amounts by reductive alkaline treatment of the jelly coat of Pleurodeles waltlii (Michah) eggs. The oligosaccharides were found to contain the newly described KDN as acidic monosaccharide and possess either the Le(x), Le(y) and A Le(y) antigenic determinants. Occurrence of Le(x) and Le(y) determinants previously recognized as tumor-associated antigen (TAA) demonstrates that mucins of lower animals may represent a rich and easily available source for preparing TAA. Moreover, it reinforces the hypothesis according to which TAA are evolution markers.

Purification of human intrinsic factor using high-performance ion-exchange chromatography as the final step.

Human intrinsic factor was purified 1430-fold from gastric juice with a yield of 75% using two steps: labile ligand affinity chromatography and high-performance ion-exchange chromatography. Intrinsic factor precipitated in the presence of specific autoantibodies and 15% sodium sulfate, had an estimated Mr of 59 000 in 5% SDS electrophoresis and could bind to the specific ileal receptor in vitro. Its carbohydrate composition could be related to N-lactosaminic and O-glycosidic chains. High-performance ion-exchange chromatography was a mild, rapid and efficient procedure to separate completely intrinsic factor from haptocorrin (another glycoprotein of gastric juice which binds cobalamin) and from other contaminating proteins.

Excretion of cobalamin and haptocorrin in the meconium of cystic fibrosis, premature, and control neonates.

Excretion of haptocorrin (R binder), cobalamin, and other corrinoids was studied in meconium from cystic fibrosis (n = 4), premature (n = 3), and control neonates (n = 13). Corrinoids content was 1.67 +/- 0.92 pmol/mg protein in meconium of cystic fibrosis (CF) neonates but only 0.33 +/- 0.37 and 0.48 +/- 0.47 pmol/mg protein, respectively, in that of prematures and controls. Considering its molecular mass (110,100 +/- 10,100) and its mean isoelectric point (3.67 +/- 0.20), haptocorrin remained undergraded in the meconium of CF neonates whereas it was partially degraded in the meconium of prematures and in most of the meconium from controls. Sequestration of cobalamin by undergraded haptocorrin can explain its increased excretion in CF meconium. Cobalamin-binding capacity of haptocorrin was 22.13 +/- 15.50 pmol/mg protein in CF meconium and about 400-fold lower in meconium of prematures and controls. This may correspond to a fetal intestinal hypersecretion in cases of CF.

Ganglioside storage, hexosaminidase lability, and urinary oligosaccharides in adult Sandhoff's disease.

Two adult sisters with severe spinocerebellar degeneration were deficient in hexosaminidase A and B. GM2 ganglioside storage in brain tissue obtained by autopsy from one patient was most pronounced in the cerebellum. Hexosaminidase activity in brain tissue was negligible, but fibroblasts from the second patient contained relatively high amounts of heat-labile activities of both isoenzymes. Pulse-chase experiments showed synthesis of precursor alpha- and beta-chains of hexosaminidase, maturation of the alpha-chain, but only a very small amount of mature beta-chain. These data indicate a destabilizing mutation in the beta-locus. Substrate-specific effects of this mutation were demonstrated by the urinary oligosaccharide pattern.

Lysosomal catabolic pathway of N-glycosylprotein glycans.

In vitro study of the initiation steps of catabolism of N-glycosylproteins in rat liver lysosomes has led to the evidence that the degradation of the carbohydrate chain is an ordered and bi-directional phenomenon: 1) The first one starts at the reducing terminus, immediately follows the degradation of the peptidic backbone by proteases and involves a serial reaction of 3 enzymes, respectively, 1) an alpha-L-fucosidase, 2) an aspartylglucosaminidase, and 3) an acidic 'oligosaccharide specific' endo-N-acetyl-beta-D-hexosaminidase, that we propose calling endo-chitobiase. 2) The second one is the commonly admitted sequential recurrent degradation by exoglycosidases. This process explains the presence of oligosaccharides sharing a single terminal reducing N-acetylglucosamine residue in human lysosomal storage diseases. Using a model glycoasparagine as a substrate, we followed the above mentioned hydrolysis reactions by 1H NMR spectroscopy. The kinetic data revealed a rapid hydrolysis of the substrate via pathway 1 prior to the action of exoglycosidases. Moreover, the latter act at different rates on the different antennae of the substrate.

1H and 13C-NMR assignments for sialylated oligosaccharide-alditols related to mucins. Study of thirteen components from hen ovomucin and swallow nest mucin.

Four hundred MHz 1H-NMR and 100 MHz 13C-NMR spectra of thirteen sialylated oligosaccharide-alditols isolated from hen ovomucin and swallow nests (Collocalia mucin) were studied. The resonance assignments were determined by combining multiple-relayed coherence-transfer chemical-shift-correlated spectroscopy (multiple-Relay-Cosy) and 1H/13C chemical-shift-correlated 2-D experiments.

The SPASIBA force field as an essential tool for studying the structure and dynamics of saccharides.

The SPASIBA force field has been applied to the determination of the structure and dynamical properties of various disaccharides. It has been shown that the experimental properties (structure, dipole moment, conformational relative energies) are satisfactorily predicted. The anomeric and exo-anomeric effects are confidently reproduced without specific terms for the alpha and beta anomers and the type of glycosidic linkages.

Association of ATP synthase alpha-chain with neurofibrillary degeneration in Alzheimer's disease.

Amyloid deposits and neurofibrillary tangles (NFT) are the two hallmarks that characterize Alzheimer's disease (AD). In order to find the molecular partners of these degenerating processes, we have developed antibodies against insoluble AD brain lesions. One clone, named AD46, detects only NFT. Biochemical and histochemistry analyses demonstrate that the labeled protein accumulating in the cytosol of Alzheimer degenerating neurons is the alpha-chain of the ATP synthase. The cytosolic accumulation of the alpha-chain of ATP synthase is observed even at early stages of neurofibrillary degenerating process. It is specifically observed in degenerating neurons, either alone or tightly associated with aggregates of tau proteins, suggesting that it is a new molecular event related to neurodegeneration. Overall, our results strongly suggest the implication of the alpha-chain of ATP synthase in neurofibrillary degeneration of AD that is illustrated by the cytosolic accumulation of this mitochondrial protein, which belongs to the mitochondrial respiratory system. This regulatory subunit of the respiratory complex V of mitochondria is thus a potential target for therapeutic and diagnostic strategies.

Lectin activities of cytokines and growth factors: function and implications for pathology.

The discovery that certain cytokines have carbohydrate-binding (lectin) properties opens new concepts in the understanding of their mechanism of action. The carbohydrate-recognition domain, which is localized opposite to the receptor-binding domain, makes these molecules bi-functional. The expression of the biological activity of the cytokine relies on its carbohydrate-binding activity which allows the association of the cytokine receptor with molecular complexes comprising the specific kinase involved in receptor phosphorylation and in specific signal transduction. It is expected that blood accumulation of free or membrane-bound glucan ligands of cytokines may dramatically perturb their endogenous function inducing specific immunodeficiencies.

Macular cherry-red spot and myoclonus syndrome. Juvenile form of sialidosis.

Macular cherry-red spot, myoclonus and progressive mental deterioration are described in a man of 16 years. Morphological examination of the liver, bone marrow and fibroblasts showed numerous vacuoles containing storage material in the cytoplasm of the cells. Twelve different oligosaccharides were isolated from urine and their structures were determined. All have N-acetylglucosamine in a reducing end and (2--3) and 2--6) neuraminic acid in the terminal position. This abnormal urinary oligosaccharide excretion is due to absence of (2--6) neuraminidase which was not detected in fibroblast culture. This case is discussed in relationship to other cases with macular cherry-red spot, myoclonus and oligosaccharide urinary excretion.

Abnormal galactoside excretion in urine of a patient with early myoclonic epileptic encephalopathy.

An abnormal carbohydrate pattern was found in urine of a patient with early myoclonic epileptic encephalopathy. Three major oligosaccharides have been isolated from the urine; structural studies including sugar analyses, methylation procedure and enzymatic hydrolysis allow us to propose the following structures: beta-Gal-(1 leads to 3)-Gal beta-Gal-(1 leads to 3)-beta-Gal-(1 leads to 3)-Glc beta-Gal-(1 leads to 3)-beta-Gal-(1 leads to 3)-Gal Such oligosaccharide structures have not previously been described in any biological fluid. The origin of these compounds, and the possibility of a specific metabolic defect are discussed.

Cobalamin R binder as a possible model molecule for glycoprotein study in cystic fibrosis.

The isoprotein pattern of semi-purified R binder (an acidic glycoprotein which binds cobalamin) from saliva and sera of 8 cystic fibrosis patients was compared to that of R binder from samples of 5 healthy children. In cases of cystic fibrosis, the mean isoelectric point of salivary R binder was increased from 3.78 up to 4.34 and its microheterogeneity was reduced. These significant physicochemical modifications were not observed with R binder from cystic fibrosis sera and they did not correlate with the beta-galactosidase, alpha-mannosidase, alpha-L-fucosidase nor neuraminidase activity of saliva. We propose the R binder as a model molecule to study the glycoprotein metabolism in cystic fibrosis since it contains 30-40% carbohydrate, is easily complexed with cyano[57Co]cobalamin and is present in most tissues and fluids of the human organism.

Structure of the phosphopeptidomannans from flocculent and non-flocculent yeast Kluyveromyces lactis.

After extraction from whole cells, and purification by gel filtration, the chemical composition and molecular mass estimation of the cell-wall phosphopeptidomannan (PPM) showed no significant difference respectively between flocculent, weakly, very weakly and non-flocculent Kluyveromyces lactis yeast strains. However, when PPMs were tested as ligands of a lectin, extracted from the flocculent strain, the PPM isolated from the flocculent and weakly flocculent strain were recognized to a higher degree than those isolated from the non and very weakly flocculent strains. Acetolysis of PPM extracted from the four strains produced five oligosaccharide fractions corresponding to mono-, di-, tri-, penta-and hexa-saccharides. The flocculent strain was characterised by a high content of di-and penta-saccharides. The 1H NMR analysis of the oligosaccharides demonstrated that the flocculent strain contained equivalent levels of the two mannobioses: Man(alpha 1-->2)Man and Man(alpha 1-->3)Man and of the two mannotrioses Man(alpha 1-->2)Man(alpha 1-->2)Man and Man(alpha 1-->3)Man(alpha 1-->2)Man. In contrast, the non-flocculent and the very weakly flocculent strains contained a single type of mannobiose Man(alpha 1-->2)Man and one type of mannotriose Man(alpha 1-->2)Man(alpha 1-->2)Man.

Primary structure of four human milk octa-, nona-, and undeca-saccharides established by 1H- and 13C-nuclear magnetic resonance spectroscopy.

The structures of two octasaccharides, one nonasaccharide, and one undecasaccharide, isolated from human milk, have been investigated by 1H- and 13C-nuclear magnetic resonance spectroscopy. The structures of these oligosaccharides are: beta-D-Galp-(1----4)-[alpha-L-Fucp- (1----3)]-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-[alpha-L-Fucp+ ++- (1----3)]-beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-D-Glc; beta-D-GALp-(1----3)-[alpha-L-Fucp-(1----4)]-beta-D-GlcpNAc-(1---- 3)-beta-D - Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1----3)-beta -D-Galp- (1----4)-D-Glc; beta-D-Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1---- 6)-(alpha - L-Fucp-(1----2)-beta-D-Gal-(1----3)-[alpha-L-Fucp-(1----4)]- beta-D-GlcpNAc- (1----3))-beta-D-Galp-(1----4)-D-Glc; and alpha-L-Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3) -beta-D- Galp-(1----4)-[alpha-L-Fucp-(1----3)]-beta-D-GlcpNAc-(1----6)-[alp ha-L- Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-(1----3)]-beta-D -Galp- (1----4)-D-Glc. The two octasaccharides have been previously isolated from human milk as a mixture, and in a pure form from new-born feces, but the n.m.r. data were not provided. These two octasaccharides display the di-Lewis X and the composite Lewis A-Lewis X antigenic determinant, previously described as neo-antigens of adenocarcinoma cell lines.

Complete 1H- and 13C-resonance assignments for D-mannooligosaccharides of the beta-D-(1-->2)-linked series released from the phosphopeptidomannan of Candida albicans VW.32 (serotype A).

D-Mannooligosaccharides (dp 1 to > 17) were released by mild acid hydrolysis from the phosphopeptidomannan of a Candida albicans strain of A serotype (VW.32). Among these, mannooligosaccharides ranging from bi- to hepta-ose, which were obtained in appreciable amounts, were structurally investigated and found to belong to the beta-D-(1-->2)-linked series. The occurrence of such compounds has already been reported in other Candida albicans strains. The complete 1H- and 13C-resonance assignments for manno-tri- to manno-hepta-ose are reported and general rules applicable for the 1NMR spectrum analysis of linear mannooligosaccharide of the general structure, beta-D-Man p-(1-->2)-[beta-D-Man p-(1-->2)]n-beta-D-Man p are proposed.

The structures of six urinary oligosaccharides that are characteristic for a patient with Morquio syndrome type B.

Morquio syndrome type B is an inherited, lysosomal storage disease characterised by a marked deficiency in acid beta-D-galactosidase, while the 2-acetamido-2-deoxy-beta-D-galactose 6-sulphate sulphatase activity is normal. Urinary oligosaccharides were studied in order to evaluate the effect of the diminished beta-D-galactosidase activity on the catabolism of glycoconjugates and to compare their structure with those excreted by patients with GM1-gangliosidosis. The following oligosaccharides were isolated: beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)-beta-D-Manp-(1 leads to 4)-D-GlcpNac(1), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)-[alpha-D-Manp-(1 leads to 3)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (2a), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (2b), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (3), beta-D-Galp-(1 leads to 4)-beta-D-Glcp-NAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-(beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-[beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 6)]-alpha-D-Manp-(1 leads to 6))-beta-D-Manp-(1 leads to 4)-D-GlcpNAc (4), beta-D-Galp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 3)-[beta-D-GlcpNAc-(1 leads to 4)]-[beta-D-Glap-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-D-Glcp-NAc (5). Significant differences between Morquio syndrome type B and GM1- gangliosidosis have been observed, with regard to the excretion rate and the specific structures of urinary oligosaccharides. Compounds 2a, 2b, and 5 are novel members of the series of oligosaccharides isolated from the urine of patients with inherited lysosomal storage diseases.

Horse erythrocyte gangliosides: preparation of the major hematoside NeuNG1-Lac-Cer.

A simple method for the isolation of hematoside NeuNG1-Lac-Cer from horse erythrocytes is described. An aliquot of the crude ganglioside fraction was labeled by tritiated sodium borohydride after mild periodate oxidation. The compounds obtained were used as radioactive tracers in column chromatography. Gangliosides were applied onto a silicic acid column and eluted stepwise by solvents of steadily increasing polarity. The major ganglioside, NeuNG1-Lac-Cer, was eluted in a high yield by the solvent mixture chloroform/methanol/water (60:35:8, v/v/v).