A Transfected Sialyltransferase That Is Elevated in Breast Cancer and Localizes to the medial/trans-Golgi Apparatus Inhibits the Development of core-2–based O-Glycans

Whitehouse, Caroline; Burchell, Joy; Gschmeissner, Stephen; Brockhausen, Inka; Lloyd, Kenneth O.; Taylor-Papadimitriou, Joyce

We have previously shown that most of the O-glycans added to MUC1 produced by T47D cells have either the core-1 structure (Gal␤1,3 GalNAc) or sialylated core-1. On the other hand, 64% of the O-glycans added to MUC1 produced by MTSV1-7 cells are disialylated core-2-based structures, the rest being mainly unsialylated core-1 (Lloyd et al., 1996) . The same method was now used to analyze the oligosaccharide side chains on MUC1 produced by T47D transfectants. The cells were metabolically labeled with [ 3 H]glucosamine and MUC1 immunoprecipitated with the polyclonal antibody, CT1 (Pemberton et al., 1992) . Since CT1 reacts with the cytoplasmic tail of MUC1, its binding is not influenced by the carbohydrate attached to the extracellular domain, and therefore all the glycoforms of MUC1 are precipitated. Fig. 5 shows the HPAEC profiles of the reduced oligosaccharides released from the MUC1 immunoprecipitates. In wild-type T47D and T47D neo, the labeled oligosaccharides were equally distributed between peaks 1 Enzyme assays were carried out as described previously (Brockhausen et al., 1995) .