Molecular characterization of arylsulfatase G – Molecular characterization of arylsulfatase G – expression, processing, glycosylation, transport and activity [Glycobiology and Extracellular Matrices]

August 18th, 2014 by Kowalewski, B., Lubke, T., Kollmann, K., Braulke, T., Reinheckel, T., Dierks, T., Damme, M.

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 propably 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 N497 abrogates transport of ARSG to lysosomes in human fibrosarcoma cells, due to impaired mannose 6-phosphate modification.
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