INHIBITION OF N-LINKED GLYCOSYLATION INDUCES EARLY APOPTOSIS IN HUMANPROMYELOCYTIC HL-60 CELLS

Inhibition of protein N-glycosylation by tunicamycin induced morpholog ical changes characteristic of apoptosis in human promyelocytic HL-60 cells. Internucleosomal DNA fragmentation could be detected after shor t-time incubation (between 6 and 9 h) of HL-60 cells with low doses of tunicamycin (0.05 mu g/ml). Under these conditions the synthesis of g lycoproteins was reduced to 17% of control values, while no significan t changes in the rates of total protein synthesis could be observed. T unicamycin ability to induce DNA fragmentation was in good correlation with its potency as glycosylation inhibitor in several myeloid cell l ines. Tunicamycin-induced apoptosis was potentiated by activation of p rotein kinease C (PKC) by phorbol esters and partially prevented by th e PKC inhibitor staurosporine. Inhibitors of RNA and protein synthesis displayed a protective effect. Treatment of HL-60 cells with tunicamy cin did not elicit the expression of cell surface differentiation anti gens or their ability to generate superoxide anion. In contrast, tunic amycin significantly inhibited these processes during dimethyl sulfoxi de (DMSO)-induced myeloid differentiation. These observations indicate that the main effect of tunicamycin in HL-60 cells is the induction o f apoptosis. (C) 1995 Wiley-Liss, Inc.