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Biochimica Et Biophysica Acta Oct 1999Aspartylglucosaminuria (AGU, McKusick 208400) is an autosomal recessive lysosomal storage disease caused by defective degradation of Asn-linked glycoproteins. AGU... (Review)
Review
Aspartylglucosaminuria (AGU, McKusick 208400) is an autosomal recessive lysosomal storage disease caused by defective degradation of Asn-linked glycoproteins. AGU mutations occur in the gene (AGA) for glycosylasparaginase, the enzyme necessary for hydrolysis of the protein oligosaccharide linkage in Asn-linked glycoprotein substrates undergoing metabolic turnover. Loss of glycosylasparaginase activity leads to accumulation of the linkage unit Asn-GlcNAc in tissue lysosomes. Storage of this fragment affects the pathophysiology of neuronal cells most severely. The patients notably suffer from decreased cognitive abilities, skeletal abnormalities and facial grotesqueness. The progress of the disease is slower than in many other lysosomal storage diseases. The patients appear normal during infancy and generally live from 25 to 45 years. A specific AGU mutation is concentrated in the Finnish population with over 200 patients. The carrier frequency in Finland has been estimated to be in the range of 2.5-3% of the population. So far there are 20 other rare family AGU alleles that have been characterized at the molecular level in the world's population. Recently, two knockout mouse models for AGU have been developed. In addition, the crystal structure of human leukocyte glycosylasparaginase has been determined and the protein has a unique alphabetabetaalpha sandwich fold shared by a newly recognized family of important enzymes called N-terminal nucleophile (Ntn) hydrolases. The nascent single-chain precursor of glycosylase araginase self-cleaves into its mature alpha- and beta-subunits, a reaction required to activate the enzyme. This interesting biochemical feature is also shared by most of the Ntn-hydrolase family of proteins. Many of the disease-causing mutations prevent proper folding and subsequent activation of the glycosylasparaginase.
Topics: Acetylglucosamine; Amino Acid Sequence; Animals; Aspartylglucosylaminase; Base Sequence; DNA, Complementary; Disease Models, Animal; Evolution, Molecular; Finland; Gene Deletion; Gene Rearrangement; Glycoproteins; Humans; Lysosomal Storage Diseases; Lysosomes; Molecular Sequence Data; Mutation; Mutation, Missense
PubMed: 10571008
DOI: 10.1016/s0925-4439(99)00076-9 -
JIMD Reports 2017
Erratum to: White Matter Microstructure and Subcortical Gray Matter Structure Volumes in Aspartylglucosaminuria; a 5-Year Follow-up Brain MRI Study of an Adolescent with Aspartylglucosaminuria and His Healthy Twin Brother.
PubMed: 28341936
DOI: 10.1007/8904_2017_18 -
Molecular Therapy : the Journal of the... Mar 2021Aspartylglucosaminuria (AGU) is an autosomal recessive lysosomal storage disease caused by loss of the enzyme aspartylglucosaminidase (AGA), resulting in AGA substrate...
Aspartylglucosaminuria (AGU) is an autosomal recessive lysosomal storage disease caused by loss of the enzyme aspartylglucosaminidase (AGA), resulting in AGA substrate accumulation. AGU patients have a slow but progressive neurodegenerative disease course, for which there is no approved disease-modifying treatment. In this study, AAV9/AGA was administered to Aga mice intravenously (i.v.) or intrathecally (i.t.), at a range of doses, either before or after disease pathology begins. At either treatment age, AAV9/AGA administration led to (1) dose dependently increased and sustained AGA activity in body fluids and tissues; (2) rapid, sustained, and dose-dependent elimination of AGA substrate in body fluids; (3) significantly rescued locomotor activity; (4) dose-dependent preservation of Purkinje neurons in the cerebellum; and (5) significantly reduced gliosis in the brain. Treated mice had no abnormal neurological phenotype and maintained body weight throughout the whole experiment to 18 months old. In summary, these results demonstrate that treatment of Aga mice with AAV9/AGA is effective and safe, providing strong evidence that AAV9/AGA gene therapy should be considered for human translation. Further, we provide a direct comparison of the efficacy of an i.v. versus i.t. approach using AAV9, which should greatly inform the development of similar treatments for other related lysosomal storage diseases.
Topics: Animals; Aspartylglucosaminuria; Aspartylglucosylaminase; Body Weight; Dependovirus; Disease Models, Animal; Female; Genetic Therapy; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Purkinje Cells
PubMed: 33186692
DOI: 10.1016/j.ymthe.2020.11.012 -
FEBS Letters Aug 2018Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by defects of the hydrolase glycosylasparaginase (GA). Previously, we showed that a Canadian AGU...
UNLABELLED
Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by defects of the hydrolase glycosylasparaginase (GA). Previously, we showed that a Canadian AGU mutation disrupts an obligatory intramolecular autoprocessing with the enzyme trapped as an inactive precursor. Here, we report biochemical and structural characterizations of a model enzyme corresponding to a Finnish AGU allele, the T234I variant. Unlike the Canadian counterpart, the Finnish variant is capable of a slow autoprocessing to generate detectible hydrolyzation activity of the natural substrate of GA. We have determined a 1.6 Å-resolution structure of the Finnish AGU model and built an enzyme-substrate complex to provide a structural basis for analyzing the negative effects of the point mutation on K and k of the mature enzyme.
ENZYME
Glycosylasparaginase or aspartylglucosaminidase, EC3.5.1.26.
Topics: Alleles; Amino Acid Sequence; Amino Acid Substitution; Aspartylglucosaminuria; Aspartylglucosylaminase; Crystallography, X-Ray; Finland; Homeostasis; Humans; Lysosomal Storage Diseases; Models, Molecular; Point Mutation; Protein Structure, Secondary; Proteolysis
PubMed: 29993127
DOI: 10.1002/1873-3468.13190 -
Orphanet Journal of Rare Diseases Jan 2021Oligosaccharidoses are storage disorders due to enzymatic defects involved in the breakdown of the oligosaccharidic component of glycosylated proteins. The defect cause...
BACKGROUND
Oligosaccharidoses are storage disorders due to enzymatic defects involved in the breakdown of the oligosaccharidic component of glycosylated proteins. The defect cause the accumulation of oligosaccharides (OS) and, depending on the lacking enzyme, results in characteristic profiles which are helpful for the diagnosis. We developed a new tandem mass spectrometry method for the screening of urinary OS which was applied to identify a large panel of storage disorders.
METHODS
The method was set-up in urine and dried urine spots (DUS). Samples were analysed, without derivatization and using maltoheptaose as internal standard, by UHPLC-MS/MS with MRM acquisition of target OS transitions, including Glc4, the biomarker of Pompe disease. The chromatographic run was < 30 min. Samples from patients with known storage disorders were used for clinical validation.
RESULTS
The method allowed to confirm the diagnosis of oligosaccharidoses (sialidosis, α-/β-mannosidosis, fucosidosis, aspartylglucosaminuria) and of GM1 and GM2 (Sandhoff type) gangliosidosis, by detecting specific OS profiles. In other storage disorders (mucolipidosis II and III, mucopolysaccharidosis type IVB) the analyisis revealed abnormal OS excretion with non-specific profiles. Besides Pompe disease, the tetrasaccharide Glc4 was increased also in disorders of autophagy (Vici syndrome, Yunis-Varon syndrome, and Danon disease) presenting cardiomuscular involvement with glycogen storage. Overall, results showed a clear separation between patients and controls, both in urine and in DUS.
CONCLUSION
This new UHPLC/MS-MS method, which is suitable for rapid and easy screening of OS in urine and DUS, expands the detection of storage disorders from oligosaccharidoses to other diseases, including the novel category of inherited disorders of autophagy.
Topics: Chromatography, High Pressure Liquid; Fucosidosis; Glycogen Storage Disease Type II; Humans; Lysosomal Storage Diseases; Oligosaccharides; Tandem Mass Spectrometry
PubMed: 33422100
DOI: 10.1186/s13023-020-01662-8 -
Annals of Clinical and Translational... Dec 2018Aspartylglucosaminuria is a lysosomal storage disorder enriched in Finland. We report on a pair of non-Finnish siblings with aspartylglucosaminuria with autofluorescent...
Aspartylglucosaminuria is a lysosomal storage disorder enriched in Finland. We report on a pair of non-Finnish siblings with aspartylglucosaminuria with autofluorescent inclusion bodies on optical coherence tomography, a finding not previously reported in this disorder. We performed a record review, neurological and neuropsychological evaluation, brain MRI, and optical coherence tomography for each patient. They are compound heterozygous for a 34-kb deletion and a c.365C>A novel variant of the gene. Autofluorescent inclusion bodies were found on optical coherence tomography in the older, more severely affected brother. We hypothesize the finding represents a noninvasive biomarker of disease severity for aspartylglucosaminuria.
PubMed: 30564628
DOI: 10.1002/acn3.672 -
Brain Sciences Sep 2020Aspartylglucosaminuria (AGU) is a rare lysosomal storage disorder causing developmental delay, intellectual disability, and eventual death. A distinct feature in AGU is...
Aspartylglucosaminuria (AGU) is a rare lysosomal storage disorder causing developmental delay, intellectual disability, and eventual death. A distinct feature in AGU is iron accumulation within the thalamus. Our aim is to demonstrate that susceptibility-weighted images (SWI) could be used as an MRI biomarker to evaluate the response within the AGU population to newly evolving treatments. SWI from 16 patients with AGU and 16 age-matched controls were used in the analysis. Thalamic volume with an iron accumulation was identified using a permutation test. Group differences were investigated for both the complete thalamus and the iron accumulation regions. Group-wise age correlation within these volumes were assessed with analysis of variance and multivariate regression. We found a statistically significant and large difference (-value = 0.01, Cohen's D = 0.97) for the whole thalamus comparison and an even greater difference in the iron accumulation regions (-value < 0.01, Cohen's D = 3.52). Furthermore, we found strong evidence for iron accumulation as a linear function of age with R = 0.65 only for AGU. The statistical analysis of SWI provides tools for assessing the degree of iron accumulation. This method could be used to study the response to treatments, in that a successful treatment would be expected to result in a decline in iron accumulation.
PubMed: 32992453
DOI: 10.3390/brainsci10100677 -
Biochimica Et Biophysica Acta.... Mar 2018Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by mutations in the gene for aspartylglucosaminidase (AGA). This enzyme participates in glycoprotein...
Aspartylglucosaminuria (AGU) is a lysosomal storage disorder caused by mutations in the gene for aspartylglucosaminidase (AGA). This enzyme participates in glycoprotein degradation in lysosomes. AGU results in progressive mental retardation, and no curative therapy is currently available. We have here characterized the consequences of AGA gene mutations in a compound heterozygous patient who exhibits a missense mutation producing a Ser72Pro substitution in one allele, and a nonsense mutation Trp168X in the other. Ser72 is not a catalytic residue, but is required for the stabilization of the active site conformation. Thus, Ser72Pro exchange impairs the autocatalytic activation of the AGA precursor, and results in a considerable reduction of the enzyme activity and in altered AGA precursor processing. Betaine, which can partially rescue the AGA activity in AGU patients carrying certain missense mutations, turned out to be ineffective in the case of Ser72Pro substitution. The Trp168X nonsense allele results in complete lack of AGA polypeptide due to nonsense-mediated decay (NMD) of the mRNA. Amlexanox, which inhibits NMD and causes a translational read-through, facilitated the synthesis of a full-length, functional AGA protein from the nonsense allele. This could be demonstrated as presence of the AGA polypeptide and increased enzyme activity upon Amlexanox treatment. Furthermore, in the Ser72Pro/Trp168X expressing cells, Amlexanox induced a synergistic increase in AGA activity and polypeptide processing due to enhanced processing of the Ser72Pro polypeptide. Our data show for the first time that Amlexanox might provide a valid therapy for AGU.
Topics: Amino Acid Substitution; Aminopyridines; Aspartylglucosaminuria; Aspartylglucosylaminase; Cells, Cultured; Child; Codon, Nonsense; Female; HEK293 Cells; HeLa Cells; Humans; Lysosomal Storage Diseases; Mutation, Missense
PubMed: 29247835
DOI: 10.1016/j.bbadis.2017.12.014 -
Proceedings of the National Academy of... Dec 1991Aspartylglucosaminuria (AGU) is an inherited lysosomal storage disorder caused by the deficiency of aspartylglucosaminidase. We have earlier reported a single missense...
Aspartylglucosaminuria (AGU) is an inherited lysosomal storage disorder caused by the deficiency of aspartylglucosaminidase. We have earlier reported a single missense mutation (Cys163----Ser) to be responsible for 98% of the AGU alleles in the isolated Finnish population, which contains about 90% of the reported AGU patients. Here we describe the spectrum of 10 AGU mutations found in unrelated patients of non-Finnish origin. Since 11 out of 12 AGU patients were homozygotes, consanguinity has to be a common denominator in most AGU families. The mutations were distributed over the entire coding region of the aspartylglucosaminidase cDNA, except in the carboxyl-terminal 17-kDa subunit in which they were clustered within a 46-amino acid region. Based on the character of the mutations, most of them are prone to affect the folding and stability and not to directly affect the active site of the aspartylglucosaminidase enzyme.
Topics: Acetylglucosamine; Adolescent; Adult; Alleles; Aspartylglucosaminuria; Aspartylglucosylaminase; Base Sequence; Cell Line; Child; Child, Preschool; Chromosome Deletion; Codon; DNA; DNA Transposable Elements; Fibroblasts; Humans; Infant; Leukocytes; Molecular Sequence Data; Mutation; Oligodeoxyribonucleotides; Polymerase Chain Reaction; Polymorphism, Genetic; RNA; RNA Splicing
PubMed: 1722323
DOI: 10.1073/pnas.88.24.11222 -
JIMD Reports Sep 2021Aspartylglucosaminuria (AGU) (OMIM #208400) is a recessively inherited disorder of glycoprotein catabolism, a subset of the lysosomal storage disorders (LSDs)....
Aspartylglucosaminuria (AGU) (OMIM #208400) is a recessively inherited disorder of glycoprotein catabolism, a subset of the lysosomal storage disorders (LSDs). Deficiency of the enzyme (E.C. 3.5.1.26) leads to accumulation of aspartylglucosamine in various organs and its excretion in the urine. The disease is characterized by an initial period of normal development in infancy, a plateau in childhood, and subsequent regression in adolescence and adulthood. No curative treatments are currently available, leading to a protracted period of significant disability prior to early death. Hematopoietic stem cell transplantation (HSCT) has demonstrated efficacy in other LSDs, by providing enzyme replacement therapy in somatic viscera and decreasing substrate accumulation. Moreover, donor-derived monocytes cross the blood-brain barrier, differentiate into microglia, and secrete enzyme in the central nervous system (CNS). This has been shown to improve neurocognitive outcomes in other LSDs. The evidence to date for HSCT in AGU is varied, with marked improvement in glycosylasparaginase enzyme activity in the CNS in mice models, but varying neurocognitive outcomes in humans. We present a case series of four children with AGU who underwent HSCT at different ages (9 years, 5 years, 5 months, and 7 months of age), with long-term follow-up post-transplant (over 10 years). These cases demonstrate similar neurodevelopmental heterogeneity based on formal developmental assessments. The third case, transplanted prior to the onset of neurocognitive involvement, is developing normally despite a severe phenotype in other family members. This suggests that further research should examine the role of early HSCT in management of AGU.
PubMed: 34485011
DOI: 10.1002/jmd2.12222