Aspartylglucosaminuria (AGU) is a lysosomal storage disease caused by a metabolic disorder in glycoprotein degradation. AGU results in accumulation of glycoasparagines in the lysosomes of virtually all cell types, with severe clinical symptoms such as progressive neurodegeneration and mental retardation, coarse facial features, skeletal abnormalities, and connective tissue lesions. AGU mutations occur in the gene for glycosylasparaginase (GA), a lysosomal enzyme required to hydrolyze glycoasparagines. AGU has been reported worldwide, with 26 different AGU alleles found so far, but still no treatment available for this disease. However, during the past few years, there has been significant progress in the identification and characterization of AGU causative mutations. Thus development of an effective AGU therapy would make this genetic disease amenable to newborn screening for an early treatment. Our crystallographic studies on GA reveal that a surface loop (named precursor P-loop) blocks the catalytic center of mature hydrolase. Autoproteolysis is thus required to remove this P-loop in order to open up the catalytic center. Nonetheless, AGU mutations cause misprocessing and mistargeting of GA precursors, thus prevents their autoactivation for the hydrolase activity. High-resolution structural studies of GA and AGU molecules will greatly enhance our understanding of the structural consequences of these AGU mutations but have so far been hampered by the inability to obtain sufficient amounts of highly purified human GA. Nonetheless, we have overcome this hurdle by purifying and crystallizing bacterial GA, which has been demonstrated to have identical structural features and use the same mechanism to autoactivate its hydrolase activity. Our preliminary results indicate that small molecules with structures similar to glycine can enhance autoproteolytic and hydrolase activity of AGU mutants. Building on our recent progress on GA autoprocessing, we propose in this application to 1) characterize molecular pathogenesis of AGU mutations;2) push forward our structural and mechanistic studies of GA autoproteolytic activation;3) study structural consequences of AGU mutations;and 4) develop small molecules to stimulate autoprocessing of AGU molecules. The broad, long- term objective of this application is to develop small molecules as therapeutics to ameliorate the AGU misprocessing and mistargeting defect and thus alleviate the suffering of AGU patients and their families.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK075294-02
Application #
7554622
Study Section
Special Emphasis Panel (ZRG1-BST-Q (52))
Program Officer
Mckeon, Catherine T
Project Start
2008-02-01
Project End
2013-01-31
Budget Start
2009-02-01
Budget End
2010-01-31
Support Year
2
Fiscal Year
2009
Total Cost
$275,839
Indirect Cost
Name
Boston University
Department
Physiology
Type
Schools of Medicine
DUNS #
604483045
City
Boston
State
MA
Country
United States
Zip Code
02118
Pande, Suchita; Bizilj, William; Guo, Hwai-Chen (2018) Biochemical and structural insights into an allelic variant causing the lysosomal storage disorder - aspartylglucosaminuria. FEBS Lett 592:2550-2561
Pande, Suchita; Lakshminarasimhan, Damodharan; Guo, Hwai-Chen (2017) Crystal structure of a mutant glycosylasparaginase shedding light on aspartylglycosaminuria-causing mechanism as well as on hydrolysis of non-chitobiose substrate. Mol Genet Metab 121:150-156
Sui, Lufei; Lakshminarasimhan, Damodharan; Pande, Suchita et al. (2014) Structural basis of a point mutation that causes the genetic disease aspartylglucosaminuria. Structure 22:1855-1861
Wang, Yeming; Guo, Hwai-Chen (2010) Crystallographic snapshot of glycosylasparaginase precursor poised for autoprocessing. J Mol Biol 403:120-30
Sun, Yixin; Guo, Hwai-Chen (2008) Structural constraints on autoprocessing of the human nucleoporin Nup98. Protein Sci 17:494-505