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-glycans on the cell surface, the N-glycans of glycoproteins on the surface of 7721 human hepatocarcinoma cells were labelled with [3H] mannose, added to the culture medium. The 3H-labelled N-glycans were prepared from cell-surface glycoproteins, desialylated, and subjected to sequential chromatography on concanavalin A and Datura stranonium agglutinin affinity columns to separate the glycans into four fractions of different type and different antennary number. It was found that the percentage of C2C2 biantennary complex type N-glycans was increased, but the high-mannose type as well as the tri- and tetraantennary complex types, especially that with a C2.6 branched structure, were decreased after the cells had been treated with retinoic acid for 3-5 days. Using a Lens culinaris agglutinin affinity column, it was discovered that the core fucose in the biantennary glycan was also decreased. The enzymatic mechanisms of the above changes were revealed in further study to involve the decrease of N-acetylglucosaminyl-transferase V and core alpha-1,6-fucosyltransferase by retinoic acid.