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

Light Microscopy. Immunofluorescence microscopy with the 9E10 mAb that recognizes the myc-tagged ␣2,3 SAT (O) of the MTSV1-7 3ST and T47D 3ST cell lines gave the expected pattern of staining. The ␣2,3 sialyltransferase gave a perinuclear staining, often located to one side of the nucleus, characteristic of Golgi apparatus staining (Fig. 8 a) . No staining was observed elsewhere in the cell and staining of unfixed cells showed no positive surface staining (data not shown). To confirm the localization in the Golgi apparatus, the cells were double labeled using a polyclonal antibody to mannosidase II, a resident of the Golgi medial cisternae, and 9E10. Fig. 8 b shows that these enzymes are coexpressed, as shown by the yellow staining resulting from the overlapping of fluorescein and rhodamine second antibodies, thus confirming localization to the Golgi apparatus of the recombinantly expressed ␣2,3 sialyltransferase.