Incorporation of the hexose analogue 2-deoxy- d-galactose into membrane glycoproteins in HepG2 cells

Abstract

The incorporation of 2-deoxy- d-galactose into the oligosaccharide moieties of glycoproteins and the consequences of 2-deoxy- d-galactose treatment on the fucosylation of glycoproteins were investigated in the human hepatoma cell line HepG2. Using different methods, it was shown that treatment of HepG2 cells with 2-deoxy- d-galactose leads to an incorporation of 2-deoxy- d-galactose and a decrease of l-fucose incorporation into the oligosaccharides of glycoproteins. The extent of labeling by l-[ 3H]fucose was determined by removing l-[ 3H]fucose from labeled cells with the aid of a purified α1,2-fucosidase from Aspergillus niger. Using this method, it was shown that 2-deoxy- d-galactose markedly inhibits α1,2-fucosylation. Measurement of the amount of 2-deoxy- d-galactose incorporated, however, showed that replacement of d-galactose by 2-deoxy- d-galactose does not entirely account for the decrease in α1,2-fucosylation. In addition, a hitherto unreported compensatory increase of α1,3/α1,4-fucosylation was found to occur when α-1,2-fucosylation was inhibited by treatment with 2-deoxy- d-galactose.