Analysis of dolichyl pyrophosphoryl oligosaccharides in purified storage cytosomes from ovine ceroid-lipofuscinosis.

Ovine ceroid-lipofuscinosis is an inherited neurodegenerative disorder characterised by the accumulation of storage cytosomes in brain and visceral organs. Phosphorylated dolichol-containing compounds, largely in the form of dolichyl pyrophosphoryl oligosaccharides, have been shown to constitute 1-2% of the dry weight of storage cytosomes isolated from brain and pancreas, and 0.5 and 0.1% respectively of storage cytosomes isolated from liver and kidney. The carbohydrate portion of these glyconjugates in storage cytosomes isolated from brain, pancreas and liver consisted of a series of oligosaccharides of composition Man2-9GlcNAc2, with Man5-8GlcNAc2 predominating. The concentrations of dolichyl pyrophosphoryl oligosaccharides in storage cytosomes from ovine ceroid-lipofuscinosis are much higher than has been reported for endoplasmic reticulum, their normal functional location.

Stored dolichyl pyrophosphoryl oligosaccharides in Batten disease.

Each of the 3 childhood forms of Batten disease, juvenile (JB), late-infantile (LIB), and infantile (IB), have abnormally high brain concentrations of dolichyl pyrophosphoryl oligosaccharides (Dol-PP-OS). In this study, the carbohydrate portions of Dol-PP-OS were analysed: in JB and LIB, they range in size from Man2GlcNAc2 to Glc3Man9GlcNAc2, predominant components being Man5-7GlcNAc2 and Glc3Man7GlcNAc2. In IB, they range from Man6-9GlcNAc2, no glucose containing oligosaccharides being identified. In Batten disease, the main subcellular location of Dol-PP-OS is within storage material, where it represents up to 7% of the dry weight. [3H]-Mannose incorporation experiments with cultured fibroblasts show that synthesis of Dol-PP-OS in JB is normal. We infer that the glycosylation intermediate Glc3Man9GlcNAc2-PP-dolichol is synthesised normally within the endoplasmic reticulum in Batten disease, but that catabolic derivatives accumulate within the lysosomes. It is unclear whether this process is central to the pathogenesis of the disease, though in IB a defect in the release of mannose residues from Dol-PP-OS is a distinct possibility.

Mitochondrial ATP synthase subunit c storage in the ceroid-lipofuscinoses (Batten disease).

The ceroid-lipofuscinoses (Batten disease) are neurodegenerative inherited lysosomal storage diseases of children and animals. A common finding is the occurrence of fluorescent storage bodies (lipopigment) in cells. These have been isolated from tissues of affected sheep. Direct protein sequencing established that the major component is identical to the dicyclohexylcarbodiimide (DCCD) reactive proteolipid, subunit c, of mitochondrial ATP synthase and that this protein accounts for at least 50% of the storage body mass. No other mitochondrial components are stored. Direct sequencing of storage bodies isolated from tissues of children with juvenile and late infantile ceroid-lipofuscinosis established that they also contain large amounts of complete and normal subunit c. It is also stored in the disease in cattle and dogs but is not present in storage bodies from the human infantile form. Subunit c is normally found as part of the mitochondrial ATP synthase complex and accounts for 2-4% of the inner mitochondrial membrane protein. Mitochondria from affected sheep contain normal amounts of this protein. The P1 and P2 genes that code for it are normal as are mRNA levels. Oxidative phosphorylation is also normal. These findings suggest that ovine ceroid-lipofuscinosis is caused by a specific failure in the degradation of subunit c after its normal inclusion into mitochondria, and its consequent abnormal accumulation in lysosomes. This implies a unique pathway for subunit c degradation. It is probable that the human late infantile and juvenile diseases and the disease in cattle and dogs involve lesions in the same pathway.

Accumulation of phosphorylated dolichol in several tissues in ceroid-lipofuscinosis (Batten disease).

The concentrations of phosphorylated dolichol (P-dolichol) and of non-phosphorylated dolichol were estimated in a number of different tissues from ceroid-lipofuscinosis (CL) and control cases. The P-dolichol contents of four tissues, brain, pancreas, muscle and kidney were significantly greater than control values. Liver and spleen showed little or no increase in P-dolichol content. Though non-phosphorylated dolichol levels were higher in CL tissues than in control tissues, the differences were significant only for brain and pancreas. In control muscle, a linear age-related increase in non-phosphorylated dolichol content was observed. The relative amounts of the major homologs of P-dolichol and of non-phosphorylated dolichol were estimated. Each tissue has a characteristic homolog size-distribution, and there is close similarity between the size-distribution profiles of P-dolichol and of non-phosphorylated dolichol for each tissue.

A high performance liquid chromatography method for the analysis of 35S-cystine: application to the diagnosis of cystinosis.

An HPLC method for the measurement of radioactively labelled cystine is described. This method has been applied to studies of the uptake and retention of 35S-cystine by cultured cells. Radioactive cystine was measured, as a proportion of the non-protein labelled products in cultured cells incubated with medium containing 35S-cystine. Cells from healthy individuals contained less than 7% cystine whereas cells from cases of cystinosis contained at least 19% cystine. The method has been applied to the prenatal diagnosis of cystinosis. The use of flow radioactivity detection provides the advantages of rapid diagnosis and quantitation of metabolites.

Glycoconjugates in storage cytosomes from ceroid-lipofuscinosis (Batten's disease) and in lipofuscin from old-age brain.

The ceroid-lipofuscinoses (CL) are a group of inherited diseases characterised by the accumulation, in brain, of autofluorescent storage cytosomes which have similar histochemical staining properties to lipofuscin, the neuronal wear and tear pigment of old-age brain. The storage cytosomes stain strongly with periodic acid-Schiff reagent (PAS), indicating the presence of carbohydrate. In brain from each childhood form of CL, concentrations of phosphorylated dolichol (Dol-P) are 10- to 20- fold higher than in age-matched controls. Brain Dol-P concentrations are also increased between 2 and 5- fold in several different lipidoses and in elderly subjects. Much of the Dol-P which accumulates is located within the storage cytosomes. Dol-P constitutes 2-3% of the dry weight of storage cytosomes from juvenile and late-infantile CL, and 0.3-0.7% of storage cytosomes from infantile CL, ovine CL and of lipofuscin isolated from old age brain. The bulk of the Dol-P in CL brain and in isolated storage cytosomes is present as dolichyl pyrophosphoryl oligosaccharides (Dol-PP-OS). The constitutions of the oligosaccharide moieties differ in the various forms of the disease. Histochemical analysis of frozen sections of unfixed brain after extraction by various lipid solvents indicates that the major part of the PAS positive intraneuronal material in CL brain and in old-age brain has the extraction properties of Dol-PP-OS. Carbohydrate represents 4-7% of the dry weight of CL storage cytosomes and of lipofuscin. The major monosaccharide components are mannose, N-acetyl glucosamine, glucose and galactose. Depending on the form of the disease studied, up to 40% of this material can be accounted for by Dol-PP-OS. Polyacrylamide gel electrophoresis of storage cytosomes followed by lectin blotting demonstrates several low molecular weight components which bind concanavalin A. These do not coelute with the major protein components and may well be Dol-PP-OS. We conclude that Dol-PP-OS are concentrated in storage cytosomes in CL and are one of their major glycoconjugate components.

Lysosomal storage of the DCCD reactive proteolipid subunit of mitochondrial ATP synthase in human and ovine ceroid lipofuscinoses.

The ceroid lipofuscinoses (Batten's disease) are a group of neuro-degenerative lysosomal storage diseases of children and animals that are recessively inherited. In the diseased individuals fluorescent storage bodies accumulate in a wide variety of cells, including neurons. The material stored in the cells of sheep affected with ceroid lipofuscinosis is two-thirds protein. The stored material does not arise from lipid peroxidation or a defect in lipid metabolism, and the lipid content is consistent with a lysosomal origin for the storage bodies. The major protein stains poorly with Coomassie blue dye and is soluble in organic solvents. It has an apparent molecular weight of 3,500 and its amino acids sequence is identical to that of the dicyclohexylcarbodiimide (DCCD) reactive proteolipid, subunit c, of mammalian mitochondrial ATP synthases. Apart from removal of mitochondrial import sequences, it has not been modified post-translationally. At least 50% of the mass of the storage bodies is composed of this protein. A minor protein sequence related to the 17-kDa subunit of vacuolar H(+)-ATPase is also found in storage bodies isolated from pancreas. As in humans and cattle, the ovine protein is the product of two expressed genes named P1 and P2. In normal and diseased animals there are no differences in sequences between P1 cDNAs or P2 cDNAs, nor do levels of mRNAs in liver for P1 or P2 differ substantially between normal and diseased animals. Both normal and diseased sheep also express a spliced pseudogene encoding amino acids 1 to 31 of the mitochondrial import presequence. The peptides they encode differ by one amino acid; arginine-23 is changed to glutamine in the diseased sheep. Storage bodies isolated from brains and pancreas of children affected with the juvenile and late infantile forms of ceroid lipofuscinosis also contain large amounts of material that is identical to subunit c of ATP synthase. However, the protein is not present in storage bodies isolated from brains of patients affected with the infantile form of the disease, and these storage bodies contain other unidentified proteins. It is possible that the cause of ovine, juvenile and late infantile ceroid lipofuscinoses is related to a defect in degradation of the subunit c of mitochondrial ATP synthase.

Peptidases in Drosophila melanogaster. I. Characterization of dipeptidase and leucine aminopeptidase activities.

Four major peptidases of Drosophila melanogaster have been described and distinguished by their electrophoretic mobilities, molecular weights, net electrical charges, and substrate specificities. The previously described leucine aminopeptidase, LAP D, consists of at least two isozymes, designated here LAP P and LAP G. In pupae most LAP activity results from LAP P (pupal); in larvae and adults, in contrast, most LAP activity results from LAP G (gut). These two LAPs may be separated by electrophoresis in the presence of the nonionic detergent Triton X-100. A specific assay for LAP P, which exploits the large difference between the net electrical charge of LAP P and that of LAP G, is described. The activity levels of two dipeptidases, Dip A and Dip B, were high in all the postembryonic stages examined. Specific assays for Dip A and Dip B were used to show that for each of these isozymes, the activity in an adult is proportional to gene dosage.

Accumulation of dolichol-linked oligosaccharides in ceroid-lipofuscinosis (Batten disease).

The accumulation of phosphorylated dolichol compounds in a number of tissues from cases of ceroid-lipofuscinosis (CL) is documented, together with an analysis of their complex carbohydrate structures. Oligosaccharides were released from dolichyl pyrophosphoryl compounds, partially purified from brain, either by mild acid hydrolysis or endoglucosaminidase digestion. The molar amounts of oligosaccharides released corresponded to the levels of P-dolichol in each brain analysed. Qualitative analysis indicated that the oligosaccharides from brain consist of a number of different components, ranging in size from four to fourteen monosaccharide units and containing chitobiose at the reducing terminal, and that the species containing seven or eight monosaccharides can be fully digested to a trisaccharide by alpha-mannosidase. The compounds that accumulate in CL tissues probably represent some of the lipid-linked intermediates known to be involved in the glycosylation of proteins, together with metabolites derived from these intermediates. The results suggest that CL might result from an impairment of the ability to metabolize dolichyl pyrophosphoryl oligosaccharides.

Dolichol and phosphorylated dolichol content of tissues in ceroid-lipofuscinosis.

Concentrations of free dolichol, total non-phosphorylated dolichol, and total phosphorylated dolichol were measured in autopsy specimens of brain and liver from ceroid-lipofuscinosis (CL) and control cases. Levels of non-phosphorylated dolichol, mainly as free dolichol, were increased approximately two-fold in late-infantile CL brain. No increase was observed for CL liver. In late-infantile and juvenile CL brain, the increase in phosphorylated dolichol was at least ten-fold, but no significant difference was found for CL liver. A substantial part of the increase in phosphorylated dolichol in CL brain appeared to be due to lipid-linked oligosaccharides. The results suggest that CL might involve a defect in the metabolism of dolichol-linked oligosaccharides.

A high-performance liquid chromatography method for the analysis of picomole amounts of oligosaccharides.

A method for the high-performance liquid chromatography separation of tritium-reduced, acetylated oligosaccharides is described. Their highly sensitive detection in column eluant is facilitated by the use of a flow radioactivity detector. The method differentiates some structural isomers and provides resolution of high-mannose oligosaccharides comparable or superior to that of other high-performance liquid chromatography methods. The detection limit is 0.3 pmol of oligosaccharide. For the detection of radioactive oligosaccharides this method is much less laborious than scintillation counting of collected peak fractions. Generation of a continuous chromatographic trace offers a particular advantage in the detection of partially resolved peaks and the visualization of peak shape. A study of some of the factors influencing acetylation and reduction has led to the development of a robust analytical method.

Ratios for very-long-chain fatty acids in plasma of subjects with peroxisomal disorders, as determined by HPLC and validated by gas chromatography-mass spectrometry.

We describe an HPLC method for measurement of ratios of concentrations of very-long-chain fatty acids (VLCFA) in plasma. The method, which involves ultraviolet detection of p-bromophenacyl derivatives of fatty acids, is validated by comparison with a gas chromatographic-mass spectrometric (GC-MS) method. The correlation between the ratios of 24-carbon fatty acids to 22-carbon fatty acids (C24/C22) estimated by the two methods was close (r = 0.976) as was the correlation for the C26/C22 ratios (r = 0.947). Increased VLCFA ratios could be demonstrated by either technique in patients with adrenoleukodystrophy, Zellweger syndrome, and infantile Refsum's disease. The HPLC method also measures phytanate concentrations in plasma. Control VLCFA ratios (for subjects without peroxisomal disorders) obtained by the two methods agree well with those reported by Moser et al. (Ann Neurol 1984; 16:628-41). For subjects younger than one year, ratios for C24/C22 and C26/C22 fatty acids were significantly greater than in older subjects.