Modification of pentasaccharide core of surface N-glycans during differentiation of HL-60 cells.

All-trans retinoic acid (ATRA) or phorbol-12-myristate-13-acetate (PMA) are two representative inducers which induce the differentiation of HL-60 cells to myelocytes and monocytes respectively. Structural modifications of the pentasaccharide core portion of N-glycans on cell surface glycoproteins during differentiation of HL-60 cells induced by these two agents and the enzymatic mechanism of the structural modifications were studied. Both ATRA and PMA enhanced the incorporation of [3H]-labeled mannose into N-glycans of glycoproteins from cell surface. By using E-PHA and WGA lectin affinity chromatography to analyze [3H]-N-glycans prepared from the surface of control, ATRA- and PMA-treated cells, it was found that the content of bisecting GlcNAc (bis-GlcNAc) attached to the core of N-glycans decreased in ATRA-treated cells, but increased in PMA-treated cells. Since GlcNAc T-III is the enzyme responsible for the synthesis of bis-GlcNAc, the change of bis-GlcNAc was consistent with the alteration of GlcNAc T-III activities in ATRA- and PMA-treated cells. Core alpha-1,6 fucose of surface N-glycans decreased during differentiation which was determined by AAL affinity chromatography. This was also compatible with the reduced activity of alpha-1,6 Fuc T. the enzyme catalyzing the synthesis of core Fuc, in ATRA- and PMA-treated cells. The increase of GlcNAc T-III activity and bis-GlcNAc content in N-glycans may be related to cell adhesion observed in monocytic differentiation.