Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/7023
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Type: Journal article
Title: Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome): A Y210C mutation causes either altered protein handling or altered protein function of N-acetylgalactosamine 4-sulfatase at multiple points in the vacuolar network
Author: Bradford, T.
Litjens, T.
Parkinson, E.
Hopwood, J.
Brooks, D.
Citation: Biochemistry, 2002; 41(15):4962-4971
Publisher: Amer Chemical Soc
Issue Date: 2002
ISSN: 0006-2960
1520-4995
Abstract: The lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (4-sulfatase) is required for the degradation of the glycosaminoglycan substrates dermatan and chondroitin sulfate. A 4-sulfatase deficiency results in the accumulation of undegraded substrate and causes the severe lysosomal storage disorder mucopolysaccharidosis type VI (MPS VI) or Maroteaux-Lamy syndrome. A wide variation in clinical severity is observed between MPS VI patients and reflects the number of different 4-sulfatase mutations that can cause the disorder. The most common 4-sulfatase mutation, Y210C, was detected in approximately 10% of MPS VI patients and has been associated with an attenuated clinical phenotype when compared to the archetypical form of MPS VI. To define the molecular defect caused by this mutation, Y210C 4-sulfatase was expressed in Chinese hamster ovary (CHO-K1) cells for protein and cell biological analysis. Biosynthetic studies revealed that Y210C 4-sulfatase was synthesized at a comparable molecular size and amount to wild-type 4-sulfatase, but there was evidence of delayed processing, traffic, and stability of the mutant protein. Thirty-three percent of the intracellular Y210C 4-sulfatase remained as a precursor form, for at least 8 h post labeling and was not processed to the mature lysosomal form. However, unlike other 4-sulfatase mutations causing MPS VI, a significant amount of Y210C 4-sulfatase escaped the endoplasmic reticulum and was either secreted from the expression cells or underwent delayed intracellular traffic. Sixty-seven percent of the intracellular Y210C 4-sulfatase was processed to the mature form (43, 8, and 7 kDa molecular mass forms) by a proteolytic processing step known to occur in endosomes-lysosomes. Treatment of Y210C CHO-K1 cells with the protein stabilizer glycerol resulted in increased amounts of Y210C 4-sulfatase in endosomes, which was eventually trafficked to the lysosome after a long, 24 h chase time. This demonstrated delayed traffic of Y210C 4-sulfatase to the lysosomal compartment. The endosomal Y210C 4-sulfatase had a low specific activity, suggesting that the mutant protein also had problems with stability. Treatment of Y210C CHO-K1 cells with the protease inhibitor ALLM resulted in an increased amount of mature Y210C 4-sulfatase localized in lysosomes, but this protein had a very low level of activity. This indicated that the mutant protein was being inactivated and degraded at an enhanced rate in the lysosomal compartment. Biochemical analysis of Y210C 4-sulfatase revealed a normal pH optimum for the mutant protein but demonstrated a reduced enzyme activity with time, also consistent with a protein stability problem. This study indicated that multiple subcellular and biochemical processes can contribute to the biogenesis of mutant protein and may in turn influence the clinical phenotype of a patient. In MPS VI patients with a Y210C allele, the composite effect of different stages of intracellular processing/handling and environment has been shown to cause a reduced level of Y210C 4-sulfatase protein and activity, resulting in an attenuated clinical phenotype.
Keywords: CHO Cells
Lysosomes
Vacuoles
Animals
Rabbits
Humans
Mucopolysaccharidosis VI
N-Acetylgalactosamine-4-Sulfatase
Recombinant Proteins
Antibodies
Antibodies, Monoclonal
Blotting, Northern
Transfection
Amino Acid Substitution
Protein Conformation
Kinetics
Mutation
Models, Molecular
Cricetinae
DOI: 10.1021/bi0121149
Published version: http://dx.doi.org/10.1021/bi0121149
Appears in Collections:Aurora harvest
Paediatrics publications

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