Stimulation of protein glycosylation in cultured hepatoma cells by polyprenyl phosphates

The aim of this work was to selectively stimulate N-glycosylation of proteins in cultured AH 70Btc hepatoma cells. Dolichyl phosphate, alpha-dihydrodecaprenyl phosphate and solanesyl phosphate were entrapped in egg lecithin liposomes and supplied to the cells. After treatment with 0.6-15 nmol of the polyprenyl phosphates/3 ml/dish for 48 hr, the incorporations of [14C]glucosamine into N-linked saccharide chains of glycoproteins and into lipid intermediates were increased to various extents. The stimulation by alpha-dihydrodecaprenyl phosphate was most significant and 15 nmol of the lipid/dish increased the incorporation into N-linked saccharide chains of glycoproteins by about 80%. The incorporations of [14C]glucosamine into O-linked saccharide chains and of [14C]leucine into proteins were not changed significantly by alpha-dihydrodecaprenyl phosphate. When the N-linked glycopeptides prepared from the cells and those from the cells treated with the polyprenyl phosphate were compared by Sephadex G-50 column chromatography, no significant difference was observed. Analysis of reduced cellular glycoproteins by sodium dodecyl sulfate/polyacrylamide-gel electrophoresis showed that alpha-dihydrodecaprenyl phosphate increased the incorporation of [14C]glucosamine into N-linked saccharide chains of certain high-molecular-weight glycoproteins. In addition, the polyprenyl phosphate enhanced the adhesiveness of the cells to the substratum, probably as a result of the stimulation of N-glycosylation of proteins.