Serum starved HeLa cells were stimulated with 100 ng/ml of EGF for 4 h, 50 ng/ml of PDGF for 3 h or left untreated as a control. Cells were subsequently immunostained with antibodies to the Golgi complex marker TGN46 (AC’, AG’, AK’, BC’, BG’ and BK’), the ER marker calnexin (cnx) (AA’, AE’, AI’, BA’, BE’, and BI’) and either endogenous GalNAc-T1 (AB’, AF’, and AJ’) or GalNAc-T2 (BB’, BF’ and BJ’). Merged channels (AD’, AH’, AL’, BD’, BH’, and BL’) demonstrate that growth factor treatments have no effect on GalNAc-T1 or—T2 Golgi complex localization. Insets depicting a magnified view of merged imaging channels. Individual maximum projections of 30 confocal sections shown in (A) are representative of 95, 74 and 78 cells for Control, EGF and PDGF treatments, respectively, from two independent experiments. Images in (B) are representative of 73, 79, and 61 cells for Control, EGF and PDGF treatments, respectively, from two independent experiments. Scale bars, 10 μm. (C) Manders’ correlation coefficient was used to quantitate the degree of coincidence between GalNAc-T1 or—T2 with TGN46 (Golgi complex) and GalNAc-T1 or—T2 with calnexin (ER) in control, EGF and PDGF treated cells from confocal sections acquired over the entire volume of each cell. Values represent the mean ± S.D. from the number of cells described in (A) and (B).