Molecular Characterization of Arylsulfatase G: EXPRESSION,PROCESSING, GLYCOSYLATION,TRANSPORT, AND ACTIVITY* |
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Authors: | Bj?rn Kowalewski Torben Lübke Katrin Kollmann Thomas Braulke Thomas Reinheckel Thomas Dierks Markus Damme |
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Institution: | From the ‡Department of Chemistry, Biochemistry I, Bielefeld University, 33615 Bielefeld.;the §Department of Biochemistry, Children''s Hospital, University Medical Center Hamburg-Eppendorf, Hamburg 20246, and ;the ¶Institute of Molecular Medicine and Cell Research and BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg 79104, Germany |
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Abstract: | Arylsulfatase G (ARSG) is a recently identified lysosomal sulfatase that was shown to be responsible for the degradation of 3-O-sulfated N-sulfoglucosamine residues of heparan sulfate glycosaminoglycans. Deficiency of ARSG leads to a new type of mucopolysaccharidosis, as described in a mouse model. Here, we provide a detailed molecular characterization of the endogenous murine enzyme. ARSG is expressed and proteolytically processed in a tissue-specific manner. The 63-kDa single-chain precursor protein localizes to pre-lysosomal compartments and tightly associates with organelle membranes, most likely the endoplasmic reticulum. In contrast, proteolytically processed ARSG fragments of 34-, 18-, and 10-kDa were found in lysosomal fractions and lost their membrane association. The processing sites and a disulfide bridge between the 18- and 10-kDa chains could be roughly mapped. Proteases participating in the processing were identified as cathepsins B and L. Proteolytic processing is dispensable for hydrolytic sulfatase activity in vitro. Lysosomal transport of ARSG in the liver is independent of mannose 6-phosphate, sortilin, and Limp2. However, mutation of glycosylation site N-497 abrogates transport of ARSG to lysosomes in human fibrosarcoma cells, due to impaired mannose 6-phosphate modification. |
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Keywords: | Enzyme Processing Heparan Sulfate Lysosomal Glycoprotein Lysosomal Storage Disease Lysosome Arylsulfatase G Mannose 6-Phosphate Mucopolysaccharidosis Proteolytic Processing Sulfatase |
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