Beta-Hexosaminidase is a key enzyme required for the lysosomal degradation of glycolipids, glycoproteins and glycosaminoglycans. Biosynthesis of active enzyme entails numerous posttranslational modifications of its two subunits, including association into dimers. Only the alpha-beta heterodimer (A isoenzyme) is able to hydrolyze GM2 ganglioside. Mutations in the genes encoding the alpha- and beta-subunits give rise to the catastrophic neurodegenerative disorders, Tay-Sachs disease and Sandhoff disease, respectively, as well as to GM2 gangliosidoses of later onset and milder course. Such mutations, already known to be very heterogeneous, will be characterized at the level of the genes and the proteins in order to understand the molecular basis of this class of diseases and to provide better diagnosis and carrier detection. Additional mutations will be engineered at specific sites of the alpha- and beta-subunit cDNAs to determine the effect of structural alterations on transport, dimerization and catalysis. The effect of premature translation termination on the metabolism of alpha-subunit cDNA will be examined because of its relevance to the major Tay-Sachs disease mutation. To remedy the current lack of knowledge of the three-dimensional structure of the enzyme, the disulfide bridges, which lock the subunits into their folded state, will be mapped and their biosynthetic pathway determined; an overexpression system will be developed to generate homogeneous enzyme for crystallographic studies. The goal is to fully understand structure/function relationships in the beta-hexosaminidase protein and their disruption in genetic disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS022376-10
Application #
2264489
Study Section
Biochemistry Study Section (BIO)
Project Start
1985-07-01
Project End
1997-06-30
Budget Start
1994-07-01
Budget End
1995-06-30
Support Year
10
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of California Los Angeles
Department
Biochemistry
Type
Schools of Medicine
DUNS #
119132785
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Ryazantsev, Sergey; Yu, Wei-Hong; Zhao, Hui-Zhi et al. (2007) Lysosomal accumulation of SCMAS (subunit c of mitochondrial ATP synthase) in neurons of the mouse model of mucopolysaccharidosis III B. Mol Genet Metab 90:393-401
Jordan, Maria C; Zheng, Yi; Ryazantsev, Sergey et al. (2005) Cardiac manifestations in the mouse model of mucopolysaccharidosis I. Mol Genet Metab 86:233-43
Zheng, Yi; Ryazantsev, Sergey; Ohmi, Kazuhiro et al. (2004) Retrovirally transduced bone marrow has a therapeutic effect on brain in the mouse model of mucopolysaccharidosis IIIB. Mol Genet Metab 82:286-95
Ohmi, Kazuhiro; Greenberg, David S; Rajavel, Kavitha S et al. (2003) Activated microglia in cortex of mouse models of mucopolysaccharidoses I and IIIB. Proc Natl Acad Sci U S A 100:1902-7
Li, Hong Hua; Zhao, Hui-Zhi; Neufeld, Elizabeth F et al. (2002) Attenuated plasticity in neurons and astrocytes in the mouse model of Sanfilippo syndrome type B. J Neurosci Res 69:30-8
Rajavel, K S; Neufeld, E F (2001) Nonsense-mediated decay of human HEXA mRNA. Mol Cell Biol 21:5512-9
Yu, W H; Zhao, K W; Ryazantsev, S et al. (2000) Short-term enzyme replacement in the murine model of Sanfilippo syndrome type B. Mol Genet Metab 71:573-80
Zhao, K W; Neufeld, E F (2000) Purification and characterization of recombinant human alpha-N-acetylglucosaminidase secreted by Chinese hamster ovary cells. Protein Expr Purif 19:202-11
Li, H H; Yu, W H; Rozengurt, N et al. (1999) Mouse model of Sanfilippo syndrome type B produced by targeted disruption of the gene encoding alpha-N-acetylglucosaminidase. Proc Natl Acad Sci U S A 96:14505-10
Schmidtchen, A; Greenberg, D; Zhao, H G et al. (1998) NAGLU mutations underlying Sanfilippo syndrome type B. Am J Hum Genet 62:64-9

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