Overexpression of different isoforms of glucosaminyl N-deacetylase/N-sulfotransferase results in distinct heparan sulfate N-sulfation patterns

Functional interactions of heparan sulfate (HS) with selected proteins depe nd on distinct saccharide sequences which are generated during biosynthesis of the polysaccharide. Glucosaminyl N-deacetylase/N-sulfotransferases (NDS Ts) catalyze both the N-deacetylation and N-sulfation reactions that initia te the modification of the (GlcNAc-GlcA)(n) polysaccharide backbone. The N- acety/N-sulfate exchange is restricted to certain regions of the polysaccha ride chains, and only these can be further modified by glucuronyl C5-epimer ization and O-sulfation at various positions. To investigate whether NDST i soforms influenced differently the structure of HS, murine NDST-1 was overe xpressed in human kidney 293 cells, and the structure of the HS produced wa s compared to HS from NDST-2 overexpressing cells [Cheung, W. F., Eriksson, I., Kusche-Gullberg M., Lindahl, U., and Kjellen, L. (1996) Biochemistry 3 5, 5250-5256], The level of N-sulfation increased from 40% in control cells to 60% and 80%, respectively, in NDST-1 and NDST-2 transfected cells. Inte restingly, the increase in N-sulfation was accompanied by an increased chai n length, while no effect on IdoA content or O-sulfation was seen. The most extended N-sulfated domains were found in HS synthesized by NDST-2 transfe cted cells. Since both the N-deacetylase and the N-sulfotransferase activit ies were lower in these cells than in the NDST-1 overexpressing cells, we c onclude that, in addition to the level of enzyme expression, the NDST isofo rm also is important in determining the N-sulfation pattern in HS.