HYPERGLYCOSYLATION OF EOSINOPHIL RIBONUCLEASES IN A PROMYELOCYTIC LEUKEMIA-CELL LINE AND IN DIFFERENTIATED PERIPHERAL-BLOOD PROGENITOR CELLS

We evaluated two independent models of eosinophil differentiation for their ability to synthesize the ribonuclease toxins eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP), Cells from th e clone 15 subline of HL-60 (human promyelocytic leukemia) produced bo th EDN and ECP; production of EDN increased in response to butyric aci d (BA), CD34(+) peripheral blood progenitor cells (PBPCs) gown with cy tokines promoting eosinophil differentiation also produced EDN, EDN fr om both the clone 15 and PBPCs was more heterogeneous and heavily glyc osylated ((s)imilar to 22-45 kDa) than EDN from mature peripheral bloo d eosinophils (18-25 kDa), The heterogeneity of EDN from the clone 15 cells was not altered by endoglycosidase Hf, whereas treatment with pe ptide-N-glycosidase F (PNGase F) produced a single-band immunoreactive band ((s)imilar to 15 kDa), In contrast, only the highest molecular w eight forms of EDN from differentiated PBPCs were eliminated by PNGase F (reduced to 22-35 kDa), suggesting the presence of uncharacteristic forms of posttranslational modification, Synthesis of hyperglycosylat ed proteins has not been previously reported in PBPCs and is a feature shared with tumor cells and cell lines.