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The disorder of hyaluronic acid metabolism in cultured skin fibroblasts derived from a patient with the Hurler syndrome.

The metabolism of hyaluronic acid in cultured skin fibroblasts derived from a patient with the Hurler syndrome and from a normal subject was examined. 1. An increased net incorporation of [(3)H]glucose into the hyaluronic acid fraction of the Hurler-syndrome cells occurred when compared with normal cells. 2. During a ;chase' period, approx. 35% of the radioactivity derived from glucose was lost from the hyaluronic acid fraction of the Hurler-syndrome cells, whereas the normal cells retained all their radioactivity. 3. Although the Hurler-syndrome cells contained a ninefold greater amount of hyaluronic acid than normal cells, simultaneous determination of the specific radioactivity derived from the label revealed a value for the Hurler-syndrome cells one-half that of normal cells. These results are taken to indicate that the Hurler cells synthesize hyaluronic acid de novo at a higher rate than do normal cells. 4. Exposure of Hurler-syndrome cultured fibroblasts to a crude urine corrective-factor preparation (Neufeld & Cantz, 1971), now known to contain alpha-l-iduronidase, the specific Hurler-syndrome corrective factor (Bach et al., 1972), decreased the hyaluronic acid content to near-normal values before any effect was observed on [(3)H]glucose incorporation into the hyaluronic acid fraction. 5. In addition, the hyaluronic acid content of the normal cells decreased after exposure to the corrective factor of urine. 6. The mobilization of hyaluronic acid in Hurler-syndrome and normal cells exposed to the crude corrective-factor preparation of urine caused a decrease in specific radioactivity in the ;corrected' Hurler-syndrome cells and an increase in specific radioactivity in the ;corrected' normal cells.

Biological Transport↗

Identification of glu-277 as the catalytic nucleophile of Thermoanaerobacterium saccharolyticum beta-xylosidase using electrospray MS.

Thermoanaerobacterium saccharolyticum beta-xylosidase is a member of family 39 of the glycosyl hydrolases. This grouping comprises both retaining beta-d-xylosidases and alpha-l-iduronidases. T. saccharolyticum beta-xylosidase catalyses the hydrolysis of short xylo-oligosaccharides into free xylose via a covalent xylosyl-enzyme intermediate. Incubation of T. saccharolyticum beta-xylosidase with 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-d-xyloside resulted in time-dependent inactivation of the enzyme (inactivation rate constant ki=0.089 min-1, dissociation constant for the inactivator Ki=65 microM) through the accumulation of a covalent 2-deoxy-2-fluoro-alpha-d-xylosyl-enzyme, as observed by electrospray MS. Removal of excess inactivator and regeneration of the free enzyme through transglycosylation with either xylobiose or thiobenzyl xyloside demonstrated that the covalent intermediate was kinetically competent. Peptic digestion of the 2-deoxy-2-fluoro-alpha-d-xylosyl-enzyme intermediate and subsequent analysis by electrospray ionization triple-quadrupole MS in the neutral-loss mode indicated the presence of a 2-deoxy-2-fluoro-alpha-d-xylosyl peptide. Sequence determination of the labelled peptide by tandem MS in the daughter-ion scan mode permitted the identification of Glu-277 (bold and underlined) as the catalytic nucleophile within the sequence IILNSHFPNLPFHITEY.

Amino Acid Sequence↗

Murine marrow-derived mesenchymal stem cell: isolation, in vitro expansion, and characterization.

In spite of the attention given to the study of mesenchymal stem cells (MSCs) derived from the bone marrow (BM) of humans and other species, there is a lack of information about murine MSCs. We describe the establishment of conditions for the in vitro expansion of plastic-adherent cells from murine BM for over 50 passages, and provide their characterization regarding morphology, surface marker profile and growth kinetics. These cells were shown to differentiate along osteogenic and adipogenic pathways, and to support the growth and differentiation of haematopoietic stem cells, and were thus operationally defined as murine mesenchymal stem cells (mMSCs). mMSCs were positive for the surface markers CD44, CD49e, CD29 and Sca-1, and exhibited a homogeneous, distinctive morphology. Their frequency in the BM of adult BALB/c and C57Bl/6 mice, normal or knockout for the alpha-L-iduronidase (IDUA) gene, was preliminarily estimated to be 1 per 11,300-27,000 nucleated cells. The emergence of a defined methodology for the culture of mMSCs, as well as a comprehensive understanding of their biology, will make the development of cellular and genetic therapy protocols in murine models possible, and provide new perspectives in the field of adult stem cells research.

Animals↗

Mucopolysaccharidosis VI in a Siamese/short-haired European cat.

A 3-year-old Siamese/short-haired European cat was referred for clinical disease characterized by dwarfism, facial dysmorphia, paralysis, small and curled ears, corneal clouding and large areas of alopecia. X-ray examination showed multiple bone dysplasia. On the basis of clinical features a form of mucopolysaccharidosis was suspected. The cat, killed at the owner's request, presented several severe skeletal deformities such as long caudal limbs, enlarged thorax with sunken breastbone, vertebral ankylosis in many spinal segments and visceral involvement. Histologically, the cat showed diffuse vacuolization and enlargement of cells in cartilage, bone and visceral organs. Ultrastructurally, membrane-bound vacuoles were filled with fibrillar and fluffy-material or concentrically whorled lamellae. Arylsulphatase B activity was 3.24 nm/mg/h in the affected cat and 30.6 in a normal age-matched control (NC). The L-iduronidase activity was slightly increased. Quantitation of total glycosaminoglycans (GAGs) revealed a 4.5-fold increase in the affected cat as compared with NC, while electrophoretic run of specific GAGs [chondroitin sulphate (CA); hyaluronan (HA); heparan sulphate (HS); dermatan sulphate (DS); keratan sulphate (KS)] performed on a cellulose acetate sheet, showed a striking increase in the DS band. On densitometric analysis of the electrophoretic run stained with Alcian Blue 8GX, the absorption of DS was eight-fold increased as compared with NC. The clinical and morphological features, and the biochemical findings, were consistent with the diagnosis of feline mucopolysaccharidosis VI.

Animals↗

[Mucopolysaccharidosis I-S (Scheie's disease) (author's transl)].

Mucopolysaccharidosis I-S in two encygotic twin sisters. The disease is characterised by opacification of the cornea, hepatospenomegaly, carpal tunnel syndrome, flexion contractures of the fingers and toes, valvar heart disease, normal intelligence and essentially normal behaviour. The biochemical defect consists of deficiency of the lysosomal hydrolase alpha-L-iduronidase. Urinary dermatan-sulphate excretion is raised. The muscles are also involved:the electron microscopic revelas interstitial storage of glycosaminoglycan-like substance. There is no specific treatment.

Adult↗

Activated microglia in cortex of mouse models of mucopolysaccharidoses I and IIIB.

Alpha-N-acetylglucosaminidase deficiency (mucopolysaccharidosis IIIB, MPS IIIB) and alpha-l-iduronidase deficiency (MPS I) are heritable lysosomal storage diseases; neurodegeneration is prominent in MPS IIIB and in severe cases of MPS I. We have obtained morphologic and molecular evidence for the involvement of microglia in brain pathology of mouse models of the two diseases. In the cortex, a subset of microglia (sometimes perineuronal) consists of cells that are probably phagocytic; they have large storage vacuoles, react with MOMA-2 (monoclonal antibody against macrophages) and Griffonia simplicifolia isolectin IB(4), and stain intensely for the lysosomal proteins Lamp-1, Lamp-2, and cathepsin D as well as for G(M3) ganglioside. MOMA-2-positive cells appear at 1 and 6 months in MPS IIIB and MPS I mice, respectively, but though their number increases with age, they remain sparse. However, a profusion of cells carrying the macrophage CD68/macrosialin antigen appear in the cortex of both mouse models at 1 month. mRNA encoding CD68/macrosialin also increases at that time, as shown by microarray and Northern blot analyses. Ten other transcripts elevated in both mouse models are associated with macrophage functions, including complement C4, the three subunits of complement C1q, lysozyme M, cathepsins S and Z, cytochrome b558 small subunit, macrophage-specific protein 1, and DAP12. An increase in IFN-gamma and IFN-gamma receptor was observed by immunohistochemistry. These functional increases may represent activation of resident microglia, an influx and activation of blood monocytes, or both. They show an inflammatory component of brain disease in the two MPS, as is known for many neurodegenerative disorders.

Animals↗

The defect in the Hunter syndrome: deficiency of sulfoiduronate sulfatase.

Skin fibroblasts cultured from patients affected with the Hunter syndrome are deficient in the activity of a protein, named the "Hunter corrective factor," that is required for degradation of dermatan and heparan sulfates. We now show that this factor, purified from human urine, removes about 2% of the sulfate residues from [(35)S]mucopolysaccharide accumulated within Hunter fibroblasts; these groups are derived from "oversulfated" regions of the polymer. Acetone-powder extracts of fibroblasts derived from patients with the Hunter syndrome are deficient in this sulfatase, in contrast to similar extracts from fibroblasts of individuals of other genotype. Hunter corrective factor coupled to alpha-L-iduronidase (or alternatively, mixed extracts from Hurler and Hunter fibroblasts) release iduronic acid from 4-O-alpha-L-sulfoiduronosyl-D-sulfoanhydromannose. We conclude that the Hunter corrective factor is a sulfatase for sulfated iduronic acid residues.

Carbohydrate Metabolism, Inborn Errors↗

Experimental animal model for mucopolysaccharidosis: suramin-induced glycosaminoglycan and sphingolipid accumulation in the rat.

Intracerebral injection of the trypanocidal drug suramin in rats caused the formation of membranous neuronal and neuroglial inclusions. Here we show that intravenous administration suramin, 500 mg/kg, to 2-month-old rats causes a 5- to 8-fold increase of glycosaminoglycan concentration in the liver within 10 days and a 6-fold increase in urinary glycosaminoglycan excertion. The excess glycosaminoglycans consist of heparan sulfate and dermatan sulfate. Intracerebral injection of 250 micrograms of suramin results in a small increase of glycosaminoglycan and larger increase of ganglioside GM2, GM3, and GD3 concentrations in the treated region of the brain. The activities of the lysosomal enzymes iduronate sulfatase, beta-glucuronidase, and hyaluronidase in the liver of the suramin-treated mature rats were consistently decreased, whereas those of alpha-L-iduronidase, heparan N-sulfatase, arylsulfatase B, and others were considerably increased. The activity of iduronate sulfatase was completely inhibited in vitro by suramin at concentrations of 50 microM or higher. The activity of beta-glucuronidase was also strongly inhibited by low concentrations of suramin, but this inhibition was partially decreased at higher concentrations of the drug. The inhibition of both enzymes by suramin was noncompetitive. The suramin-treated rat may be a useful experimental animal model of mucopolysaccharidosis.

Age Factors↗

Rat brain contains high levels of mannose-6-phosphorylated glycoproteins including lysosomal enzymes and palmitoyl-protein thioesterase, an enzyme implicated in infantile neuronal lipofuscinosis.

Mannose 6-phosphate (Man-6-P) is a posttranslational carbohydrate modification typical of newly synthesized acid hydrolases that signals targeting from the Golgi apparatus to the lysosome via Man-6-P receptors (MPRs). Using iodinated cation independent MPR as a probe in a Western blot assay, we surveyed levels of Man-6-P glycoproteins in a number of different rat tissues. Considerable variation was observed with respect to total amounts and types of Man-6-P glycoproteins in the different tissues. Brain contained 2-8-fold more Man-6-P glycoproteins than other tissues, with relative abundance being brain >> testis approximately heart > lung approximately kidney approximately ovary approximately spleen > skeletal muscle approximately liver approximately serum. Analysis of 16 different lysosomal enzyme activities revealed that brain contains lower activities than other tissues which suggested that decreased removal of Man-6-P results in increased levels of Man-6-P glycoproteins. This was directly demonstrated by comparing activities of phosphorylated lysosomal enzymes, purified by immobilized MPR affinity chromatography, with total activities. The phosphorylated forms accounted for a considerable proportion of the MPR-targeted activities measured in brain (on average, 36.2%) but very little in lung, kidney, and liver (on average, 5.5, 2.3, and 0. 7%, respectively). Man-6-P glycoproteins were also isolated from rat brain by MPR affinity chromatography on a preparative scale. Of the 18 bands resolvable by SDS-polyacrylamide gel electrophoresis, seven bands were NH2-terminally sequenced and identified as the known lysosomal enzymes cathepsin L, cathepsin A, cathepsin D, alpha-galactosidase A, arylsulfatase A, and alpha-iduronidase. One of the major Man-6-P glycoproteins was identified as palmitoyl protein thioesterase, which was not previously thought to be lysosomal. This finding raises important questions about the cellular location and function of palmitoyl protein thioesterase, mutations in which result in the neurodegenerative disorder, infantile neuronal ceroid lipofuscinosis.

Amino Acid Sequence↗

The iodothyronine selenodeiodinases are thioredoxin-fold family proteins containing a glycoside hydrolase clan GH-A-like structure.

The three iodothyronine selenodeiodinases catalyze the initiation and termination of thyroid hormone effects in vertebrates. Structural analyses of these proteins have been hindered by their integral membrane nature and the inefficient eukaryotic-specific pathway for selenoprotein synthesis. Hydrophobic cluster analysis used in combination with Position-specific Iterated BLAST reveals that their extramembrane portion belongs to the thioredoxin-fold superfamily for which experimental structure information exists. Moreover, a large deiodinase region imbedded in the thioredoxin fold shares strong similarities with the active site of iduronidase, a member of the clan GH-A-fold of glycoside hydrolases. This model can explain a number of results from previous mutagenesis analyses and permits new verifiable insights into the structural and functional properties of these enzymes.

Amino Acid Sequence↗

Active-site motifs of lysosomal acid hydrolases: invariant features of clan GH-A glycosyl hydrolases deduced from hydrophobic cluster analysis.

The clan GH-A is a group of more than 200 proteins representing nine established families of glycosyl hydrolases that act on a large variety of substrates. This clan includes five enzymes implicated in lysosomal storage diseases: beta-glucuronidase (Sly disease), beta-glucocerebrosidase (Gaucher disease), beta-galactosidase (Landing disease and Morquito type B disease), beta-mannosidase (mannosidosis) and alpha-L-iduronidase (Hurler-Scheie disease). Examination of known 3D structures from some families of the clan allowed us to deduce structural and functional features shared by these proteins. We then used the hydrophobic cluster analysis method to study the protein sequences of the entire clan. Our results reveal that, despite low levels of sequence identity, all the proteins of the clan (including the aforementioned lysosomal enzymes) likely share a similar catalytic domain consisting of an (alpha/beta)8 barrel with conserved functional amino acids located at the C-terminal ends of six of the eight strands constituting the beta-barrel. Interestingly, several mutations reported to be responsible for lysosomal storage diseases are located within these conserved regions of the lysosomal enzyme catalytic domains.

Amino Acid Sequence↗

Gene for autosomal dominant congenital stationary night blindness maps to the same region as the gene for the beta-subunit of the rod photoreceptor cGMP phosphodiesterase (PDEB) in chromosome 4p16.3.

We studied a large multigeneration Danish family with autosomal dominant congenital stationary night blindness. Both electrophysiological and psychophysical findings in affected family members were identical to those reported in patients from the 'Nougaret family'. The disease locus in the Danish family has now been mapped by demonstrating close linkage without recombination (Q = 0.00 at Zmax = 14.4) to the locus for alpha-L-iduronidase assigned to chromosome 4p16.3. Interestingly the gene for the beta-subunit of the rod photoreceptor cGMP-specific phosphodiesterase maps to the very same chromosomal region.

Chromosome Mapping↗

Purification and some properties of human liver iduronate sulfatase.

Iduronate sulfatase was purified from human liver for an investigation of the degradative pathway of dermatan sulfate. An overall 80-fold purification was achieved and, more importantly, the preparation was free of alpha-L-iduronidase, beta-glucuronidase, N-acetylgalactosamine 4-sulfate sulfatase (arylsulfatase B) and highly enriched in beta-N-acetylhexosaminidase. The liver enzyme appeared to be composed of several molecular species. The enzyme activity was optimal at pH 4.0 and its Km was 10--20 microM with sulfoiduronyl sulfoanhydromannitol. Chloride was inhibitory at high concentration and among divalent metal ions, only copper was inhibitory. Nitrocatechol sulfate was not a substrate, but did show competitive inhibition. Its Ki for iduronate sulfatase was similar to its Km for arylsulfatase, suggesting a similarity in the substrate binding sites of iduronate sulfatase and arylsulfatases.

Chemical Phenomena↗

Dense peripheral corneal clouding in Scheie syndrome.

A 28-year-old woman with Scheie syndrome (MPS I-S) presented with the unusual feature of extremely dense peripheral corneal clouding, allowing maintenance of good central visual acuity. Characteristic systemic features, an abnormal electroretinogram result, and absent alpha-L-iduronidase activity confirmed the diagnosis despite the unusual corneal pattern of clouding.

Adult↗

Meningiomas in young cats with mucopolysaccharidosis I.

Meningiomas are the most common central nervous system tumor of the cat, with an age at diagnosis of greater than nine years in 73% of the affected animals. Four of seven cats with alpha-L-iduronidase deficient mucopolysaccharidosis I had meningiomas at postmortem examination. All four cats were less than three years of age. The relationship between the meningiomas and the metabolic defect of MPS I is not clear.

Animals↗

Hurler's syndrome: dental findings in a case treated with bone marrow transplantation in infancy.

Hurler's syndrome, also known as mucopolysaccharidosis I (MPS I-H), is a rare condition inherited as an autosomal recessive trait. It is caused by a deficiency in alpha-L-iduronidase, an enzyme that participates in the degradation of the glycosaminoglycans (GAGs) heparin sulphate and dermatan sulphate. Children with Hurler's syndrome appear nearly normal at birth but, left untreated, show a progressive mental and physical deterioration caused by a build-up of GAGs in all organs of the body. Death is often caused by cardiac or respiratory failure and usually occurs before the second decade of life. In recent years, bone marrow transplantation (BMT) has been employed in the management of patients with Hurler's syndrome. However, the dental findings observed in these cases have not previously been reported in the dental literature. Here we report a patient aged 11 years and 6 months, presented to a Specialist Paediatric Dentistry Unit, who was successfully treated by BMT at 18 months of age.

Anodontia↗

Full expression of Hunter's disease in a female with an X-chromosome deletion leading to non-random inactivation.

A 2.5-year-old girl who presented with abdominal distension, hepatomegaly, coarse facies, hirsutism and contraction deformities was investigated for mucopolysaccharidoses. Urinary excretion showed increased total glycosaminoglycans (105 mg/mmol creatinine; normal for age 9-20 mg/mmol) with marked increases of dermatan and heparan sulphates. A number of lysosomal enzyme activities were measured on leucocytes, serum and cultured fibroblasts. Normal or high activities were found for alpha-iduronidase, N-acetylgalactosamine-6-sulphatase, beta-galactosidase, arylsulphatase B and beta-glucuronidase. However a marked deficiency of iduronate sulphate sulphatase activity was observed, consistent with a diagnosis of Hunter's disease. Activities were reduced to less than 2% of mean control values in the patient's leucocytes, serum and cultured fibroblasts. Normal activities were measured in samples from the father and younger sister but a partial deficiency (43% of control serum) was found in the mother. Chromosome studies on the patient revealed a partial deletion of the long arm of one X-chromosome, most probably of band Xq25, which was not inherited from either parent. Studies using BrdU indicated that the deleted X chromosome was consistently late replicating, and as a result the Hunter gene was fully expressed on the other X chromosome.

Child, Preschool↗

Hurler syndrome with severe complication in post-bone marrow transplantation course: life threatening interstitial pneumonitis and hypertension.

Bone marrow transplantation (BMT) was performed in a 3 year old patient with Hurler syndrome. The post-BMT course was complicated by interstitial pneumonitis and severe hypertension, which were life threatening. The patient responded well to therapy and recovered. BMT in this patient resulted in significant clinical improvement in the signs and symptoms of Hurler syndrome. Biochemical improvement, including elevated alpha-L-iduronidase activity in white blood cells and decreased urinary glycosaminoglycan excretion was significant. However, skeletal and neurological impairment were not improved. We conclude that BMT for Hurler syndrome should be performed at an earlier stage, before severe neuronal damage has occurred. Moreover, BMT is a high risk procedure and there will always be a possibility that life threatening complications will occur, as in our case.

Bone Marrow Transplantation↗