[Investigation of the action mechanisms of poly-ADP-ribosylation in hexavalent chromium induced cell damage]

OBJECTIVE

To investigate the effect of poly-ADP-ribosylation in hexavalent chromium Cr(VI) induced cell damage.

METHODS

The study object, poly (ADP-ribose) glycohydrolase (PARG) deficient human bronchial epithelial cells (16HBE cells), was constructed previously by our research group. Normal 16HBE cells and PARG-deficient cells were treated with different doses of Cr (VI) for 24 h to compare the differences to Cr (VI) toxicity, meanwhile set up the solvent control group. On this basis, 5.0 µmol/L of Cr (VI) was selected as the exposure dose, after the exposure treatment, total proteins of both cells were extracted for two dimension fluorescence difference gel electrophoresis (2D-DIGE) separation, statistically significant differential protein spots were screened and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS/MS), and further validated by Western blot.

RESULTS

After Cr (VI) treatment, the survival rate of PARG-deficient cells was higher than normal 16HBE cells. When the doses reached up to 5.0 µmol/L, the survival rate of 16HBE cells and PARG-deficient cells were respectively (59.67 ± 6.43)% and (82.00 ± 6.25)%, the difference between which was significant (t = -4.32, P < 0.05). 18 protein spots were selected and successfully identified after 2D-DIGE comparison of differential proteins between normal 16HBE cells and PARG-deficient cells before and after exposure. The function of those proteins was involved in the maintenance of cell shape, energy metabolism, DNA damage repair and regulation of gene expression. The differential expression of cofilin-1 was successfully validated by Western blot. The expression level of cofilin-1 in the 16HBE cells increased after Cr (VI) exposure with the relative expression quantity of 1.41 ± 0.04 in treated group and 1.00 ± 0.01 in control group, the difference of which was statistically significant (t = -18.00, P < 0.05), while the expression level in PARG-deficient cells had no statistically significant difference (t = -8.61, P > 0.05).

CONCLUSION

Most of the identified differential proteins are closely related to tumorigenesis, suggesting that poly-ADP-ribosylation reaction may resist the cytotoxicity of Cr(VI) by inhibiting Cr (VI) induced tumorigenesis, which provides important reference data to clarify the mechanisms of poly-ADP-ribosylation in Cr (VI) induced cell damage.

Parg deficiency confers radio-sensitization through enhanced cell death in mouse ES cells exposed to various forms of ionizing radiation

Poly(ADP-ribose) glycohydrolase (Parg) is the main enzyme involved in poly(ADP-ribose) degradation. Here, the effects of Parg deficiency on sensitivity to low and high linear-energy-transfer (LET) radiation were investigated in mouse embryonic stem (ES) cells. Mouse Parg(-/-) and poly(ADP-ribose) polymerase-1 deficient (Parp-1(-/-)) ES cells were used and responses to low and high LET radiation were assessed by clonogenic survival and biochemical and biological analysis methods. Parg(-/-) cells were more sensitive to γ-irradiation than Parp-1(-/-) cells. Transient accumulation of poly(ADP-ribose) was enhanced in Parg(-/-) cells. Augmented levels of phosphorylated H2AX (γ-H2AX) from early phase were observed in Parg(-/-) ES cells. The induction level of p53 phophorylation at ser18 was similar in wild-type and Parp-1(-/-) cells and apoptotic cell death process was mainly observed in the both genotypes. These results suggested that the enhanced sensitivity of Parg(-/-) ES cells to γ-irradiation involved defective repair of DNA double strand breaks. The effects of Parg and Parp-1 deficiency on the ES cell response to carbon-ion irradiation (LET13 and 70 keV/μm) and Fe-ion irradiation (200 keV/μm) were also examined. Parg(-/-) cells were more sensitive to LET 70 keV/μm carbon-ion irradiation than Parp-1(-/-) cells. Enhanced apoptotic cell death also accompanied augmented levels of γ-H2AX in a biphasic manner peaked at 1 and 24h. The induction level of p53 phophorylation at ser18 was not different between wild-type and Parg(-/-) cells. The augmented level of poly(ADP-ribose) accumulation was noted after carbon-ion irradiation compared to γ-irradiation even in the wild-type cells. An enhanced poly(ADP-ribose) accumulation was further observed in Parg(-/-) cells. Both Parg(-/-) cells and Parp-1(-/-) cells did not show sensitization to Fe-ion irradiation. Parg deficiency sensitizes mouse ES cells to a wide therapeutic range of LET radiation through the effects on DNA double strand break repair responses and enhanced cell death.

[Nutrition support of patients with celiac disease and deficiency of carbohydrases of the small intestinal mucosa]

The treatment policy of nutritive support for patients with different types of celiac disease is still actual issue. The difficulty of treatment policy implementation associated with villus atrophy, that brings on not only small intestine malabsorption function, but secretory process disorder (particularly, some of intestinal ferments production, including carbohydrases. The work objective is different types of celiac disease (typical, latent, torpid) nutritive correction improvement based on study of small intestine mucous membrane morphofunctional features at different stages of its atrophy, its carbohydrase activity that identifies clinic manifestation features, including nutritional disorders. We suppose, that such phermentopathy correction by means of directional action composites will have a wholesome effect on elimination of different nutritive disorder at celiac disease.

Characterization of pullulanase (PUL)-deficient mutants of rice (Oryza sativa L.) and the function of PUL on starch biosynthesis in the developing rice endosperm

Rice (Oryza sativa) allelic sugary1 (sug1) mutants defective in isoamylase 1 (ISA1) accumulate varying levels of starch and phytoglycogen in their endosperm, and the activity of a pullulanase-type of a debranching enzyme (PUL) was found to correlate closely with the severity of the sug1 phenotype. Thus, three PUL-deficient mutants were generated to investigate the function of PUL in starch biosynthesis. The reduction of PUL activity had no pleiotropic effects on the other enzymes involved in starch biosynthesis. The short chains (DP < or = 13) of amylopectin in PUL mutants were increased compared with that of the wild type, but the extent of the changes was much smaller than that of sug1 mutants. The alpha-glucan composition [amylose, amylopectin, water-soluble polysaccharide (WSP)] and the structure of the starch components (amylose and amylopectin) of the PUL mutants were essentially the same, although the average chain length of the B(2-3) chains of amylopectin in the PUL mutant was approximately 3 residues longer than that of the wild type. The double mutants between the PUL-null and mild sug1 mutants still retained starch in the outer layer of endosperm tissue, while the amounts of WSP and short chains (DP < or = 7) of amylopectin were higher than those of the sug1 mutant; this indicates that the PUL function partially overlaps with that of ISA1 and its deficiency has a much smaller effect on the synthesis of amylopectin than ISA1 deficiency and the variation of the sug1 phenotype is not significantly dependent on the PUL activities.

Poly(ADP-ribose) polymerase 1 accelerates single-strand break repair in concert with poly(ADP-ribose) glycohydrolase

Single-strand breaks are the commonest lesions arising in cells, and defects in their repair are implicated in neurodegenerative disease. One of the earliest events during single-strand break repair (SSBR) is the rapid synthesis of poly(ADP-ribose) (PAR) by poly(ADP-ribose) polymerase (PARP), followed by its rapid degradation by poly(ADP-ribose) glycohydrolase (PARG). While the synthesis of poly(ADP-ribose) is important for rapid rates of chromosomal SSBR, the relative importance of poly(ADP-ribose) polymerase 1 (PARP-1) and PARP-2 and of the subsequent degradation of PAR by PARG is unclear. Here we have quantified SSBR rates in human A549 cells depleted of PARP-1, PARP-2, and PARG, both separately and in combination. We report that whereas PARP-1 is critical for rapid global rates of SSBR in human A549 cells, depletion of PARP-2 has only a minor impact, even in the presence of depleted levels of PARP-1. Moreover, we identify PARG as a novel and critical component of SSBR that accelerates this process in concert with PARP-1.

PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion

Poly (ADP-ribosyl)ation, an early post-translational modification in response to DNA damage, is catalyzed by poly (ADP-ribose) polymerase (PARP-1) and catabolized by poly(ADP-ribose) glycohydrolase (PARG). The aim of this study was to investigate the role of PARG on the modulation of the inflammatory response caused by splanchnic ischemia and reperfusion. SAO shock in rats and wild-type (WT) mice was associated with a significant neutrophil infiltration in the ileum and production of tumor necrosis factor-alpha (TNF-alpha). Reperfused ileum tissue sections from SAO-shocked WT mice and rats showed positive staining for P-selectin and ICAM-1 localized mainly in the vascular endothelial cells. Genetic disruption of the PARG gene in mice or pharmacological inhibition of PARG by PARG inhibitors significantly improved the histological status of the reperfused tissues associated with reduced expression of P-selectin and ICAM-1, neutrophil infiltration into the reperfused intestine, and TNF-alpha production. These results suggest that PARG activity modulates the inflammatory response in ischemia/reperfusion and participates in end (target) organ damage under these conditions.

[Molecular diagnosis of congenital disorders of glycosylation]

Congenital disorders of glycosylation are a group of inherited disorders, characterized by a central nervous system dysfunction and multiorgan failure associated with defective N-glycosylation. CDG-I comprises all defects in the assembly of the dolichol-linked glycan and its transfer to the protein, whereas CDG-II refers to defects in the processing of the protein-bound glycans. The diagnosis is done by the presence of hypoglycosylated glycoproteins in the serum and typing by enzymatic assay (available for CDG-Ia and Ib) and/or mutation detection. We give an overview of the latest results of molecular diagnosis from the French CDG I families. We report novel mutations and their functional study. In addition we looked for a founder effect for the most frequent mutations observed in the French population.

Failure to degrade poly(ADP-ribose) causes increased sensitivity to cytotoxicity and early embryonic lethality

The metabolism of poly(ADP-ribose) (PAR) is critical for genomic stability in multicellular eukaryotes. Here, we show that the failure to degrade PAR by means of disruption of the murine poly(ADP-ribose) glycohydrolase (PARG) gene unexpectedly causes early embryonic lethality and enhanced sensitivity to genotoxic stress. This lethality results from the failure to hydrolyze PAR, because PARG null embryonic day (E) 3.5 blastocysts accumulate PAR and concurrently undergo apoptosis. Moreover, embryonic trophoblast stem cell lines established from early PARG null embryos are viable only when cultured in medium containing the poly(ADP-ribose) polymerase inhibitor benzamide. Cells lacking PARG also show reduced growth, accumulation of PAR, and increased sensitivity to cytotoxicity induced by N-methyl-N'-nitro-N-nitrosoguanidine and menadione after benzamide withdrawal. These results provide compelling evidence that the failure to degrade PAR has deleterious consequences. Further, they define a role for PARG in embryonic development and a protective role in the response to genotoxic stress.

Loss of poly(ADP-ribose) glycohydrolase causes progressive neurodegeneration in Drosophila melanogaster

Poly(ADP-ribosyl)ation has been suggested to be involved in regulation of DNA repair, transcription, centrosome duplication, and chromosome stability. However, the regulation of degradation of poly(ADP-ribose) and its significance are not well understood. Here we report a loss-of-function mutant Drosophila with regard to poly(ADP-ribose) glycohydrolase, a major hydrolyzing enzyme of poly(ADP-ribose). The mutant lacks the conserved catalytic domain of poly(ADP-ribose) glycohydrolase, and exhibits lethality in the larval stages at the normal development temperature of 25 degrees C. However, one-fourth of the mutants progress to the adult stage at 29 degrees C but showed progressive neurodegeneration with reduced locomotor activity and a short lifespan. In association with this, extensive accumulation of poly(ADP-ribose) could be detected in the central nervous system. These results suggest that poly(ADP-ribose) metabolism is required for maintenance of the normal function of neuronal cells. The phenotypes observed in the parg mutant might be useful to understand neurodegenerative conditions such as the Alzheimer's and Parkinson's diseases that are caused by abnormal accumulation of substances in nervous tissue.

Production of long-chain levan by a sacC insertional mutant from Bacillus subtilis 327UH

A hyper extracellular protein producer, Bacillus subtilis 327UH, produced large amounts of levan in a medium containing 20% sucrose, and the yield of levan after 10 hours was more than 60%, when based on the fructose amount of sucrose. After transformation of 327UH with a levanase-deficient 168SC (sacC::Cm(r)) chromosomal DNA, a Cm(r) transformant 327UHSC (sacC::Cm(r) degSU(Hy)) produced 3 times longer levan than that of the wild type.

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.

Defective lymphocyte glycosidases in the macrophage activation cascade of juvenile osteopetrosis

Generation of macrophage-activating factor requires a precursor protein, Gc protein (serum vitamin D3-binding protein), as well as participation of beta-galactosidase of inflammation-primed B lymphocytes and sialidase of T lymphocytes. The treatment of human peripheral blood mononuclear cells with an inflammatory lysophospholipid induced beta-galactosidase and sialidase activity of lymphocytes, leading to the generation of macrophage-activating factor and activation of monocytes/macrophages. However, lysophospholipid treatment of peripheral blood mononuclear cells from three infantile patients with osteopetrosis resulted in no significant activation of monocytes/macrophages. The lysophospholipid-inducible beta-galactosidase activity of B lymphocytes as well as that of the sialidase of T lymphocytes was found to be defective in these patients.

[Disorders of glycoprotein degradation]

Glycoprotein consist of oligosaccharides chains covalently attached to the polypeptide backbone. They are synthesized by two pathways; sugar nucleotide pathway and dolichol pathway. The degradation of glycoproteins occurs predominantly in the lysosomes through the ordered actions of lysosomal proteases, glycosidases, and aspartylglucosaminidase. Genetic deficiencies of these enzymes cause progressive accumulation of partially degraded oligosaccharides and glycopeptides, resulting in specific lysosomal storage diseases. Clinically, the diseases are characterized by the various degree of mental retardation, coarse facies, dysostosis multiplex, and visceromegaly. Although the urinary screening test for storage compounds is highly supportive, the definitive diagnosis of the disease is based on the measurement of lysosomal enzyme activity. This paper presents the review of clinical and biochemical features of this group of diseases including alpha-mannosidosis, beta-mannosidosis, fucosidosis, sialidosis, and aspartylglucosaminuria. Recent advances in molecular genetics in fucosidosis and aspartylglucosaminuria are also reviewed.

Genes encoding xylan and beta-glucan hydrolysing enzymes in Bacillus subtilis: characterization, mapping and construction of strains deficient in lichenase, cellulase and xylanase

The gene encoding extracellular xylanase (xynA) was amplified as a 770 bp DNA fragment from Bacillus subtilis 168 chromosomal DNA by PCR. The genes encoding endo-beta-1,4-glucanase (eglS) and endo-beta-1,3-1,4-glucanase (bglS) were isolated from a genomic library of B. subtilis 168. The sequences of xynA and eglS were identical to those of the xylanase and cellulase genes from B. subtilis PAP115. Integrative plasmids containing DNA fragments with deletions in the coding region of the genes were constructed and used to replace the chromosomal eglS, bglS and xynA genes of B. subtilis 168. Strains without any detectable activity against xylan (Xyn-), carboxymethylcellulose (Egl-) or mixed linked beta-1,3-1,4-glucan (Egl- Bgl-) were obtained. The genes were mapped at 170 degrees (eglS), 175 degrees (xynA) and 340 degrees (bglS) on the B. subtilis chromosome.

Characteristics and cariogenicity of a fructanase-defective Streptococcus mutants strain

Polymers of D-fructose produced by a variety of oral bacteria are believed to function as extracellular carbohydrate reserves. Degradation of these polysaccharides in plaque following exhaustion of dietary carbohydrates is thought to contribute to the extent and duration of the acid challenge to the tooth surface and thus to the initiation and progression of dental caries. Streptococcus mutans produces a fructanase, the product of the fruA gene, which is capable of degrading beta(2,6)- and beta(2,1)-linked fructans that are commonly synthesized by dental plaque microorganisms. To evaluate the role of the FruA protein in exopolysaccharide metabolism and to assess the contribution of this enzyme to the pathogenic potential of S. mutans, a fructanase-deficient strain of S. mutans was constructed. Inactivation of a cloned fruA gene was accomplished in Escherichia coli by using a mini-Mu dE transposon, and then an isogenic mutant of S. mutans UA159 was constructed by allelic exchange. Successful inactivation of fruA was confirmed through the use of biochemical assays, Western blotting (immunoblotting) with anti-recombinant FruA antisera, and Southern hybridization. The data indicated that FruA was the only fructan hydrolase produced by S. mutans UA159. Inactivation of fruA had no significant effects on glucosyltransferase or fructosyltransferase activity. In the rat caries model using animals fed a high-sucrose diet and ad libitum, there were no significant differences in the number or severity of smooth surface, sulcal, or root caries elicited by the fruA mutant and the wild-type organism.

4-Trifluoromethylumbelliferyl glycosides as new substrates for revealing diseases connected with hereditary deficiency of lysosome glycosidases

The following glycosides of 4-trifluoromethylumbelliferone: alpha-D-mannopyranoside, alpha-L-fucopyranoside, alpha-D-glucopyranoside, beta-D-glucopyranoside, alpha-D-galactopyranoside, beta-D-galactopyranoside, alpha-L-iduronide and beta-D-glucuronide were studied. 4-Trifluoromethylumbelliferyl glycosides were shown to be substrates for glycosidases. Some of them were cleaved even better than the corresponding methylumbelliferyl glycosides. 4-Trifluoromethylumbelliferyl glycosides were applied for revealing the corresponding enzyme deficiencies upon diagnosis of Gaucher and Hurler diseases as well as GM1 gangliosidosis and alpha-mannosidosis. 4-Trifluoromethylumbelliferone released after enzymatic hydrolysis of 4-trifluoromethylumbelliferyl glycosides exhibits more contrast yellow fluorescence in UV-light than the blue one of methylumbelliferone upon exposure of enzyme activity on solid supports. Therefore 4-trifluoromethylumbelliferyl glycosides are convenient substrates for revealing glycosidase activity directly in tissue samples, e.g. in placenta, and thus for fast prenatal diagnosis of lysosomal diseases.

Severe acute pancreatitis and normal serum amylase activity due to pancreatic isoamylase deficiency

A 31-year-old man with a primary attack of severe acute alcohol-induced pancreatitis presenting with a low to normal amylase activity in serum is described. The diagnosis was confirmed surgically and, further, by studies of immunoreactive trypsin in serum, which was elevated. Analysis of pancreatic isoamylase in serum during the convalescence showed very low activity. The patient is thought to represent a case of pancreatic isoamylase deficiency.

Chromosomal mapping of lysosomal enzyme structural genes in the domestic cat

A panel of 42 rodent x cat somatic cell hybrids has been used to assign seven structural genes for lysosomal enzymes to specific chromosomes in the domestic cat. The assignments include alpha-glucosidase (GANAB) to chromosome D1, alpha-galactosidase (GLA) to the X chromosome, beta-galactosidase 1 (GLB1) to chromosome B3, beta-glucuronidase (GUSB) to chromosome E3, alpha-mannosidase A (MANA) to chromosome B3, alpha-L-fucosidase (FUCA) to chromosome C1, and hexosaminidase A (HEXA) to chromosome B3. In all cases, the feline lysosomal enzyme genes were located in linkage groups which were syntenic with their homologous positions in the human gene map. These assignments expand the genetic map of the cat and reaffirm the extensive syntenic homology between the chromosome maps of man and cat.

[Characteristics of biogenesis and substrate specificity of lysosomal glycosidases under normal conditions and in glycosidoses]

Main steps are considered of posttranslational modification of lysosomal hydrolases, which are glycoproteins. Processing of the enzymatic carbohydrate moiety in various compartments of endoplasmic reticulum and Golgi apparatus is discussed. Importance of mannose-6-phosphate groups formed during the processing is revealed by studies on binding of these enzymes with specific receptor responsible for their transport into lysosomes. Specificity of lysosomal glycosidases and their isoforms, catalyzing hydrolysis of carbohydrate chains of glycoconjugates and of synthetic substrates dissimilar in the structure, is discussed. Complex structural organization of these enzymes in lysosomes (protein activators and stabilizing factors, presence of marker sites etc) was studied using as an example lysosomal diseases of accumulation, glycosidoses, developed in hereditary deficiency of glycosidases. The data on elevated activity of the majority of lysosomal enzymes in glycosidoses, which are not involved in the primary genetic defect, suggest the possibility of general unspecific response of cells to accumulation of unhydrolyzed compounds.

Neuropathological and clinical correlations in Hurler disease

We report studies on two patients (1 and 2) with Hurler disease. They both had all of the non-neurological features of Hurler disease to a similar and extreme degree and similar signs of brain damage on computed tomography. However, intellectual function was unusually well-preserved in patient 1, but seriously and typically impaired in patient 2. The reason for this discrepancy has been investigated by reference to the neuropathological findings, the results of alpha-L-iduronidase assays using different substrates and comparisons to other cases (patients 3 and 4). We suggest that patient 1 is an unusual variant of the disease who may have had a very low residual alpha-L-iduronidase activity in neuronal cells only, and that this could not be demonstrated by either enzyme assays on whole brain using the 4-methylumbelliferyliduronide substrate (Crow et al., 1983) or in studies on fibroblast lysates using a radioactive disaccharide substrate.

The deficiency of B-glycosidases in leukocytes from patients with non-insulin dependent diabetes mellitus

The activity and intracellular localization of two B-glycosidases i.e., N-acetyl-beta-D-glucosaminidase (NAG) and beta-glucuronidase (GR) was estimated by means of semi-quantitative histochemical methods in the peripheral blood neutrophils and lymphocytes from 52 patients with non-insulin dependent diabetes mellitus and compared with that in 67 healthy subjects of similar age and sex. The total neutrophil and lymphocyte count did not differ in the patients from that in the controls. The GR and the NAG activity indexes were significantly lower in the neutrophils from patients as compared with that in the control group. The number of lymphocytes with GR-positive and NAG-positive intact lysosomes were 200-fold and respectively 40-fold lower in the patients than in the healthy subjects. The authors discuss the significance of their observations with regard to the relationship between the enzymatic activity of the cells studied and their functional capabilities.

Neurochemical characterization of canine alpha-L-iduronidase deficiency disease (model of human mucopolysaccharidosis I)

This report presents the neurochemical findings on the first dog to die with deficiency of alpha-L-iduronidase (mucopolysaccharide alpha-L-iduronohydrolase; EC 3.2.1.76). The principal findings were (a) markedly increased glycosaminoglycan content in all neural tissues examined (from threefold in sciatic nerve to 15-fold in brainstem), (b) a modest increase in levels of gangliosides GM2, GM3, and GD3, particularly in gray matter, (c) excessive accumulation of glycosaminoglycans in the CSF, (d) the increased glycosaminoglycans were dermatan sulfate and heparan sulfate, and (e) the molecular weights of the liver glycosaminoglycans were shifted toward smaller sizes, indicating partial degradation. The canine disorder thus resembles mucopolysaccharidosis I in all aspects.

[Psychotic symptoms during the evolution of dementia in muco- polysaccharidosis of Hurler-Scheie phenotype]

The case reported concerns a 17 1/2 year-old adolescent presenting with complete alpha-L-iduronidase deficiency. Its phenotype intermediate between Hurler's and Scheie's syndromes and the occurrence of a delirious and hallucinatory condition evolving with acute exacerbations on a constant subdelirious and excited state made this case particular. This case report is compared to the 30 in the Anglo-Saxon literature which shows, in addition to the rarity of psychiatric symptoms (one single case), the multiplicity of the possible phenotypes, reinforcing the hypothesis of a polyallelic or even non allelic mutation.

The clinical spectrum of alpha-L-iduronidase deficiency

We present five patients with alpha-L-iduronidase deficiency who do not have the typical Hurler or Scheie phenotypes; they are compared to 28 similarly atypical cases from the literature. Phenotypic differences are pointed out and intrafamilial similarities stressed. Among the various possible explanations for this situation, the existence of genetic compounds seems acceptable for some of the cases, but others seem to be caused by different mutations. The elucidation of these alternative possibilities from recent biochemical research is discussed.

alpha-L-Iduronidase deficiency in mucopolysaccharidosis type I against a radiolabelled sulfated disaccharide substrate derived from dermatan sulfate

alpha-L-Iduronidase activity was assayed by incubation of a radiolabelled disaccharide, O-(alpha-L-idopyranosyluronic acid)-(1----3)-2,5 anhydro-D-[1,3H]-talitol 4-sulfate (IdoA-anT4S) derived from dermatan sulfate, with homogenates of leucocytes, cultured amniotic cells and skin fibroblasts from normal individuals and patients affected with an alpha-L-iduronidase-deficiency disorder (mucopolysaccharidosis type I, MPS I), parents of such patients and patients affected with other mucopolysaccharidoses. The assay clearly distinguished affected homozygotes from normal controls, heterozygotes and other mucopolysaccharidosis types. Preliminary results show that fibroblast homogenates from patients with the MPS I Hurler phenotype were virtually unable to hydrolyse IdoA-anT4S, whereas fibroblast homogenates from a patient with a relatively mild (Scheie) phenotype exhibited a residual activity with Vmax value of 2.5 pmol/min/mg protein and an apparent Km of 21 mumol/l compared to a range of 1020-2105 pmol/min/mg for Vmax and 12-35 mumol/l for Km for fibroblasts from normal controls.

Heparan sulfate and dermatan sulfate from the liver of a patient with Hurler syndrome: high performance liquid chromatography of their degradation products after incubation with alpha-L-iduronidase-deficient fibroblasts

Using a high performance liquid chromatography method, degradation products of heparan sulfate (HS) and dermatan sulfate (DS) were investigated after incubation of control and alpha-L-iduronidase-deficient fibroblasts with HS or DS. Characteristic elution profiles of the degradation products were obtained from the respective alpha-L-iduronidase-deficient fibroblasts. Moreover, alpha-L-iduronidase in control fibroblasts was resolved into two distinct components, forms A and B, on DEAE-cellulose column chromatography. Form A alpha-L-iduronidase could degrade HS, but not DS. Conversely, form B alpha-L-iduronidase could not degrade HS, but could degrade DS.

Properties of alpha-L-iduronidase in cultured skin fibroblasts from alpha-L-iduronidase-deficient patients

On DEAE cellulose column chromatography, alpha-L-iduronidase in cultured skin fibroblasts was resolved into two distinct components, forms A and B. They had similar Km values for 4-methylumbelliferyl-alpha-L-iduronide, but differed in pH optima and thermal stability. Form B was more heat-stable than form A. Residual alpha-L-iduronidase activity in Hurler fibroblasts was heat-stable, while that in Scheie fibroblasts was heat-labile, and moreover, that in Hurler-Scheie compound fibroblasts lay intermediate between Hurler and Scheie syndromes. These findings demonstrated that Hurler syndrome, Scheie syndrome and Hurler-Scheie compound were enzymatically distinguishable.

A canine model of human alpha-L-iduronidase deficiency

A disease discovered in three Plott Hound littermates was found to be associated with a profound and specific deficiency of alpha-L-iduronidase (mucopolysaccharide alpha-L-iduronohydrolase; EC 3.2.1.76) in fibroblasts and leukocytes. The pedigree was consistent with autosomal recessive inheritance. A markedly increased amount of dermatan sulfate and heparan sulfate was excreted in urine. Fibroblasts cultured from the skin of the affected dogs accumulated excessive 35S-labeled mucopolysaccharide; this accumulation could be decreased to a normal level by exogenous human high-uptake alpha-L-iduronidase (Hurler corrective factor) as well as by secretions of normal human or canine fibroblasts. The correction was inhibited by mannose 6-phosphate. Maturation of alpha-L-iduronidase in normal canine fibroblasts followed the pathway previously observed in human fibroblasts; no cross-reactive material was observed in the cells or in secretions from the fibroblasts of the affected dogs. The canine disorder thus resembles mucopolysaccharidosis I in all biochemical parameters tested; the clinical appearance of the animals is closest to Hurler-Scheie syndrome, a form of alpha-L-iduronidase deficiency of intermediate severity. The animal model should prove valuable for therapeutic experiments.

[Mucolipidosis II or I-cell disease in the neonatal period]

A newborn with the clinical, radiological and biochemical features of mucolipidosis II or "I cell disease" is presented. Some aspects of differential diagnosis in neonatal period and of the outcome are commented. The infant had also a single right kidney and agammaglobulinemia without further alteration of the humoral or cellular immunity at 10 months of age.

Biochemical and histopathological studies on patients with mucopolysaccharidoses, two of whom had been treated by fibroblast transplantation

Biochemical and pathological observations on tissues from two patients with Hurler disease (mucopolysaccharidosis IH; alpha-L-iduronidase deficiency) who had been treated by fibroblast transplants as a means of enzyme replacement treatment are reported. These results and those obtained in three surgical specimens [ligamentum flavum with dura mater from a case of Scheie disease (mucopolysaccharidosis IS; alpha-L-iduronidase deficiency); a fetus with Hurler disease; and tonsil from a patient with Hunter disease (mucopolysaccharidosis II; alpha-L-idurono-2-sulphate sulphatase deficiency)] illustrate the inadequacy of routine histological processing to demonstrate the abnormal glycosaminoglycan accumulation in this group of diseases. A combined approach using histochemistry and electron microscopy enables the extent of both extracellular and intracellular involvement to be assessed. The fetus (20 wk gestation) already showed evidence of Hurler disease. The pathological appearances in both of the fibroblast-transplanted patients were those which would have been expected in patients dying with unmodified Hurler disease. There was no detectable alpha-L-iduronidase activity in the brain, liver, kidney or in fibroblasts cultured from either the transplantation sites or from remote subcutaneous sites in either of the transplanted patients. These results are discussed from the viewpoint of their bearing on the pathophysiology of the mucopolysaccharidoses and proposals for their treatment by enzyme replacement.

Canine alpha-L-iduronidase deficiency. A model of mucopolysaccharidosis I

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[Cultivation of amniotic fluid cells for the purpose of diagnosing certain metabolic diseases]

A method for preparing amniotic fluid cell culture has been developed. The optimal conditions for the culture involved the incubation period averaging 17.9 days. Normal activity values were obtained for 8 glycosidases whose deficiency is responsible for the development of hereditary accumulation diseases. The data obtained allow a prenatal diagnosis of glycolipidoses (Tay-Sachs, Fabrys, Gaucher's diseases, etc.). The evidence on prenatal diagnosis of Tay-Sach's disease is presented.

Post- and pre-natal assessment of alpha-L-iduronidase deficiency with a radiolabelled natural substrate

1. α-l-Iduronidase activity was assayed by incubation of iduronosyl anhydro[1-3H]mannitol 6-sulphate with homogenates of cultured skin fibroblasts, amniotic cells and leucocytes derived from normal individuals, patients affected with α-l-iduronidase deficiency disorder (mucopolysaccharidosis type I: Hurler, Scheie and Hurler-Scheie compound) and parents of such patients.

2. The assay for α-l-iduronidase, described for use with these cell types, clearly distinguished affected homozygotes from heterozygotes and normal controls.

3. The mean specific activity of α-l-iduronidase in homogenates prepared from cultured skin fibroblasts and leucocytes from more than seven obligate heterozygotes for mucopolysaccharidosis type I was found to be about one-half of the mean of more than 40 normal controls. A number of heterozygotes had α-l-iduronidase activity that identified them as carriers; others had values clearly within the normal range. Thus heterozygote detection of mucopolysaccharidosis type I is not certain.

4. With iduronosyl anhydro[1-3H]mannitol 6-sulphate used as substrate, cell types from five pregnancies at risk for α-l-iduronidase deficiency were examined; each foetus was predicted to be unaffected. For one foetus it was not possible from measurements of total enzyme activity alone to distinguish between the heterozygous carrier state and affected homozygote. The difficulty was resolved by comparing Michaelis-Menten kinetics of this enzyme in fibroblasts derived from the propositus, mother and normal controls with the kinetics of the enzyme in amniotic cells isolated from the foetus at risk and from normal controls.

Neuraminidase in cultured fibroblasts and leucocytes of homozygotes and heterozygotes for the mucolipidosis II gene (I-cell disease)

The significance of neuraminidase deficiency reported to be the primary defect in mucolipidosis II has been evaluated by determination of this enzyme activity in cultured fibroblasts, culture medium, and leucocytes from homozygote and heterozygous carriers of the disease. A new and sensitive fluorometric assay of neuraminidase was used with sodium (4-methylumbeliferyl-alpha-D-N-acetylneuraminate) as substrate. We report: 1) nearly total deficiency of neuraminidase in mucolipidosis fibroblasts, 2) partial deficiency of this enzyme in leucocytes of one patient, 3) this decreased activity ceases to exist following Triton X-100 treatment, and 4) intermediary mean neuraminidase activity in fibroblasts and leucocytes from obligate heterozygotes. Although these results would be consistent with the suggestion that neuraminidase deficiency is the primary defect in this disease, evidence from the work of other authors suggests that the enzyme deficiency results from a secondary effect of the mucolipidosis II mutation.

Multiple glycosidase deficiencies in a case of juvenile (type 3) Gaucher disease

Biochemical investigations were performed on autopsy tissues obtained from an 11-year-old girl who died with the juvenile, subacute neuropathic form of Gaucher disease. In addition to the expected deficiency of glucocerebrosidase activity, extracts of both liver and kidney from this individual displayed a profound (greater than or equal to 90%) deficiency of "soluble" beta-glucosidase, beta-xylosidase, and beta-galactosidase activities. Fibroblasts obtained from this individual also contained markedly reduced levels of beta-xylosidase activity but normal levels of beta-D-fucosidase and beta-galactosidase activity. Because the soluble beta-glucosidase, beta-xylosidase, and a portion of the beta-galactosidase activities from control human liver all cochromatographed on a gel filtration column of Sephadex G-200, it is suggested that these activities all reside in a single enzyme, analogous to the situation described in a number of nonhuman, mammalian tissues. This demonstration of multiple glycosidase deficiencies in addition to the deficiency of glucocerebrosidase in a case of subacute neuropathic Gaucher disease suggests that other biochemical aberrations, in addition to a deficiency of glucocerebrosidase, might contribute to pathology in some cases of Gaucher disease.

Diagnosis of the mucopolysaccharidoses using cultured skin fibroblasts and amniotic fluid cells

Assay of alpha-L-iduronidase, heparin sulphamidase, N-acetyl-alpha-D-glucosaminidase, arylsulphatase B, alpha-L-fucosidase, beta-glucuronidase, beta-galactosidase and alpha-D-mannosidase in cultured cells is described. Activities in deficient fibroblast strains are compared to control fibroblast strains. The first case of Sanfilippo B in the United Kingdom is reported. A comparison of enzyme activities in cultured fibroblasts and amniotic fluid cells is made.

Glycosphingolipid hydrolases: properties and molecular genetics

This is a review of the properties and molecular genetics of six lysosomal hydrolases: beta-galactosidase, hexosaminidases A and B, alpha-galactosidase, beta-glucosidase and alpha-fucosidase. Each enzyme is discussed with regards to isoenzymes and substrate specificity, subunit structure, genetic relationship of isoenzymes and genetic variants. The molecular genetics of human diseases caused by deficiencies of each enzyme are discussed.