Induction of a storage phenotype and abnormal intracellular localization of apical glycoproteins are two independent responses to GalNAcalpha-O-bn.

Our previous studies on an inhibitor of O-glycosylation of glycoproteins, GalNAcalpha-O-bn, in the model of enterocytic HT-29 cells, have shown at the cellular level an alteration of the normal localization of apical glycoproteins, and at the biochemical level an in situ synthesis and storage of sialylated GalNAcalpha-O-bn oligosaccharides. The purpose of this study was to examine if a relation existed between these two events, using different cell lines. Intracellular storage of GalNAcalpha-O-bn metabolites occurred in HT-29 and CAPAN-1 cells but not in Caco-2 cells. On the other hand, an accumulation of endosomal/lysosomal compartments was observed in HT-29 and CAPAN-1 cells but not in Caco-2 cells. These data focused on a GalNAcalpha-O-bn-derived storage phenotype in HT-29 and CAPAN-1 cells. The apical membrane glycoproteins MUC1 and CEA showed an abnormal localization inside intracytoplasmic vesicles in HT-29 cells, whereas they kept their normal localization in Caco-2 and CAPAN-1 cells. Studies on the glycosylation of these apical glycoproteins showed that GalNAcalpha-O-bn inhibited the glycosylation in a cell-specific manner. The alteration in the apical targeting of glycoproteins, and the appearance of a GalNAcalpha-O-bn-derived storage phenotype are two independent and cell type-specific events. The former depends on the inhibition pattern of the glycosylation of endogenous glycoproteins, whereas the latter is connected to the intracellular accumulation of GalNAcalpha-O-bn metabolites.