Expression of heparan sulphate L-iduronyl 2-O-sulphotransferase in human kidney 293 cells results in increased D-glucuronyl 2-O-sulphation

Functionally important interactions between heparan sulphate and a variety of proteins depend on the precise location of O-sulphate groups. Such resid ues occur at C-2 of L-iduronic (IdoA) and D-glucuronic acid (GlcA) units, a nd at C-3 and C-6 of D-glucosamine (GlcN) units. Stable transfection of hum an embryonic kidney 293 cells with a cDNA encoding mouse mastocytoma IdoA 2 -O-sulphotransferase resulted in an approx. 6-fold increase in O-sulphotran sferase activity, compared with control cells, as determined using O-desulp hated heparin as an acceptor. Structural analysis of endogenous heparan sul phate in the transfected cells, following metabolic labelling with either [ H-3]GlcN or [S-35]sulphate, showed appreciable formation of -GlcA(2-OSO3)-G lcNSO(3)- disaccharide units (6% of total disaccharide units; 17% of total O-sulphated disaccharide units) that were essentially absent from heparan s ulphate from control cells. The increase in GlcA 2-O-sulphation was accompa nied by a decrease in the amount of IdoA formed, whereas overall 2-O-sulpha tion or 6-O-sulphation remained largely unaffected. These findings indicate that 2-O-sulphation of IdoA and GlcA residues is catalysed by the same enz yme in heparan sulphate biosynthesis.