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

Golgi apparatus profiles were selected at random, photographed, and printed at a final magnification of 75,000. The compartments of the Golgi apparatus were defined as described previously (Nilsson et al., 1993) . Briefly, the trans cisternae were defined as the last continuous cisternae that la-beled for Gal-T, and the TGN comprises the tubuloreticular network adjacent to the trans side of the Golgi apparatus stack. The boundary of the Golgi cisternae and TGN (defined as the interface between the outermost membranes of the tubular network and the adjacent cytoplasm) (Rabouille et al., 1995) was drawn on each micrograph. Gold particles over the TGN and the Golgi cisternae were directly counted and included gold over budding vesicles but not structures such as vacuolar endosomes, which can be found in the TGN and were excluded.