EFFECT OF RETINOIC ACID ON THE STRUCTURE OF N-GLYCANS ON THE SURFACE OF HUMAN HEPATOCARCINOMA CELLS AND ITS ENZYMATIC MECHANISM

In order to study the effect of retinoic acid on the structure of N-gl ycans on the cell surface, the N-glycans of glycoproteins on the surfa ce of 7721 human hepatocarcinoma cells were labelled with [H-3] mannos e, added to the culture medium. The H-3-labelled N-glycans were prepar ed from cell-surface glycoproteins, desialylated, and subjected to seq uential chromatography on concanavalin A and Datura stranonium aggluti nin affinity columns to separate the glycans into four fractions of di fferent type and different antennary number. It was found that the per centage of C2C2 biantennary complex type N-glycans was increased, but the high-mannose type as well as the tri- and tetraantennary complex t ypes, especially that with a C-2,C-6 branched structure, were decrease d after the cells had been treated with retinoic acid for 3-5 days. Us ing a Lens culinar is agglutinin affinity column, it was discovered th at the core fucose in the biantennary glycan was also decreased. The e nzymatic mechanisms of the above changes were revealed in further stud y to involve the decrease of N-acetylglucosaminyl-transferase V and co re alpha-1,6-fucosyltransferase by retinoic acid.