Turnover of Heparan Sulfate Depends on 2-O-Sulfation of Uronic Acids

摘要: To study how the pattern of sulfation along a heparan sulfate chain affects its turnover, we examined catabolism in wild-type Chinese hamster ovary cells and mutant pgsF-17, defective 2-O-sulfation uronic acid residues (Bai, X., Esko, J. D. (1996) Biol. Chem. 271, 17711-17717). Heparan from contains normal amounts 6-O-sulfated glucosamine iduronic somewhat higher levels N-sulfated but lacks any 2-O-sulfated or glucuronic residues. Pulse-chase experiments showed that both transport newly synthesized proteoglycans to plasma membrane, where they shed into medium move cell through endocytosis. Internalization cell-associated molecules leads sequential endoglycosidase (heparanase) fragmentation chains eventual lysosomal degradation. In cells, begin degrade within 1 h, leading accumulation intermediate (10-20-kDa) small (4-7-kDa) oligosaccharides. Mutant did not generate these intermediates, although internalization intracellular trafficking appeared normal, degraded with kinetics. This difference was due heparanase activities mutant, since cytoplasmic extracts cleaved vitro. Instead, were relatively resistant degradation by cellular heparanases. These findings suggest are important for cleavage endogenous heparanases overall chains.