Structural Basis of a Point Mutation that Causes the Genetic Disease Aspartylglucosaminuria

Sui, Lufei; Lakshminarasimhan, Damodharan; Pande, Suchita; Guo, Hongjie

doi:10.1016/j.str.2014.09.014

Cited by 10 publications

(38 citation statements)

References 33 publications

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“…In the case of the mutant AGA precursors, this rearrangement is severely reduced, preventing the cleavage into subunits. It has been shown that dimerization of two precursor molecules is a prerequisite for the cleavage, and some AGU mutations in the dimer interface prevent dimerization and thus activation22930. However, this appears not to be the case with T122K and AGU-Fin, which both become processed into subunits when coexpressed with the wildtype AGA.…”

Section: Discussionmentioning

confidence: 99%

Identification of Small Molecule Compounds for Pharmacological Chaperone Therapy of Aspartylglucosaminuria

Banning

Gülec

Rouvinen

et al. 2016

Sci Rep

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Aspartylglucosaminuria (AGU) is a lysosomal storage disorder that is caused by genetic deficiency of the enzyme aspartylglucosaminidase (AGA) which is involved in glycoprotein degradation. AGU is a progressive disorder that results in severe mental retardation in early adulthood. No curative therapy is currently available for AGU. We have here characterized the consequences of a novel AGU mutation that results in Thr122Lys exchange in AGA, and compared this mutant form to one carrying the worldwide most common AGU mutation, AGU-Fin. We show that T122K mutated AGA is expressed in normal amounts and localized in lysosomes, but exhibits low AGA activity due to impaired processing of the precursor molecule into subunits. Coexpression of T122K with wildtype AGA results in processing of the precursor into subunits, implicating that the mutation causes a local misfolding that prevents the precursor from becoming processed. Similar data were obtained for the AGU-Fin mutant polypeptide. We have here also identified small chemical compounds that function as chemical or pharmacological chaperones for the mutant AGA. Treatment of patient fibroblasts with these compounds results in increased AGA activity and processing, implicating that these substances may be suitable for chaperone mediated therapy for AGU.

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Section: Discussionmentioning

confidence: 99%

Identification of Small Molecule Compounds for Pharmacological Chaperone Therapy of Aspartylglucosaminuria

Banning

Gülec

Rouvinen

et al. 2016

Sci Rep

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“…We also propose a plausible explanation for its low activity based on comparison of substrate bound complexes of the mutant model with the wildtype GA model. Since a precursor structure of the same mutant in complex with β-AHA has also been reported previously [17], in this study we further built a GA-β-AHA model complex by superposing a few GA structures: the current model, the precursor-β-AHA complex, and the wild-type GA structures [7, 17]. This allows us to analyze catalysis of β-AHA as a non-chitobiose substrate of GA.…”

Section: Introductionmentioning

confidence: 86%

“…The β-AHA-GA complex model was generated by superimposing secondary structure of G172D-β-AHA complex (precursor structure, PDB code 4R4Y) [17] with the previously published T152C GA-NAcGlc-Asn complex (GA-substrate structure, PDB code 2GL9) [23]. The coordinates of the β-AHA were then placed in the active site of the wild-type GA structure, built as described previously (2GAW) [7].…”

Section: Methodsmentioning

confidence: 99%

“…In an AGU allele of a Canadian family, a mutation has been reported that is caused by the change of a nucleotide from G to A in exon 6 [16, 17], causing complex clinical presentation [18]. This mutation leads to two alternative splicing forms, resulting in two different lengths of transcripts: one with the normal length, whereas the other with a truncation of about 90 nucleotides due to exon 6 skipping.…”

Section: Introductionmentioning

confidence: 99%

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Crystal structure of a mutant glycosylasparaginase shedding light on aspartylglycosaminuria-causing mechanism as well as on hydrolysis of non-chitobiose substrate

Pande

Lakshminarasimhan

Guo

2017

Molecular Genetics and Metabolism

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Glycosylasparaginase (GA) is an amidase that cleaves Asn-linked glycoproteins in lysosomes. Deficiency of this enzyme causes accumulation of glycoasparagines in lysosomes of cells, resulting in a genetic condition called aspartylglycosaminuria (AGU). To better understand the mechanism of a disease-causing mutation with a single residue change from a glycine to an aspartic acid, we generated a model mutant enzyme at the corresponding position (named G172D mutant). Here we report a 1.8Å resolution crystal structure of mature G172D mutant and analyzed the reason behind its low hydrolase activity. Comparison of mature G172D and wildtype GA models reveals that the presence of Asp 172 near the catalytic site affects substrate catabolism in mature G172D, making it less efficient in substrate processing. Also recent studies suggest that GA is capable of processing substrates that lack a chitobiose (Glycan, N-acetylchiobios, NAcGlc) moiety, by its exo-hydrolase activity. The mechanism for this type of catalysis is not yet clear. L-aspartic acid β-hydroxamate (β-AHA) is a non-chitobiose substrate that is known to interact with GA. To study the underlying mechanism of non-chitobiose substrate processing, we built a GA-β-AHA complex structure by comparing to a previously published G172D mutant precursor in complex with a β-AHA molecule. A hydrolysis mechanism of β-AHA by GA is proposed based on this complex model.

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“…Site-directed mutagenesis and expression studies in COS cells demonstrated that only the cysteine to serine substitution (C163S) causes the deficiency of glycosylasparaginase activity [30]. The mutation destroys a disulfide bond [31] and leads to conformational changes in the inactive prercursor enzyme protein preventing its autocleavage into subunits and an active enzyme protein [32]. …”

Section: Molecular Geneticsmentioning

confidence: 99%

Aspartylglycosaminuria: a review

Arvio

Mononen

2016

Orphanet J Rare Dis

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Aspartylglucosaminuria (AGU), a recessively inherited lysosomal storage disease, is the most common disorder of glycoprotein degradation with a high prevalence in the Finnish population. It is a lifelong condition affecting on the patient’s appearance, cognition, adaptive skills, physical growth, personality, body structure, and health. An infantile growth spurt and development of macrocephalia associated to hernias and respiratory infections are the key signs to an early identification of AGU. Progressive intellectual and physical disability is the main symptom leading to death usually before the age of 50 years.The disease is caused by the deficient activity of the lysosomal enzyme glycosylasparaginase (aspartylglucosaminidase, AGA), which leads to a disorder in the degradation of glycoasparagines – aspartylglucosamine or other glycoconjugates with an aspartylglucosamine moiety at their reducing end – and accumulation of these undegraded glycoasparagines in tissues and body fluids. A single nucleotide change in the AGA gene resulting in a cysteine to serine substitution (C163S) in the AGA enzyme protein causes the deficiency of the glycosylasparaginase activity in the Finnish population. Homozygosity for the single nucleotide change causing the C163S mutation is responsible for 98% of the AGU cases in Finland simplifying the carrier detection and prenatal diagnosis of the disorder in the Finnish population. A mouse strain, which completely lacks the Aga activity has been generated through targeted disruption of the Aga gene in embryonic stem cells. These Aga-deficient mice share most of the clinical, histopathologic and biochemical characteristics of human AGU disease. Treatment of AGU mice with recombinant AGA resulted in rapid correction of the pathophysiologic characteristics of AGU in non-neuronal tissues of the animals. The accumulation of aspartylglucosamine was reduced by up to 40% in the brain tissue of the animals depending on the age of the animals and the therapeutic protocol. Enzyme replacement trials on human AGU patients have not been reported so far. Allogenic stem cell transplantation has not proved effective in curing AGU.

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Structural Basis of a Point Mutation that Causes the Genetic Disease Aspartylglucosaminuria

Cited by 10 publications

References 33 publications

Identification of Small Molecule Compounds for Pharmacological Chaperone Therapy of Aspartylglucosaminuria

Identification of Small Molecule Compounds for Pharmacological Chaperone Therapy of Aspartylglucosaminuria

Crystal structure of a mutant glycosylasparaginase shedding light on aspartylglycosaminuria-causing mechanism as well as on hydrolysis of non-chitobiose substrate

Aspartylglycosaminuria: a review

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