Drug effects on B-fragment transport to the Golgi apparatus. HeLa cells were incubated with fluorophore-labeled B-fragment for 1 h at 19.5°C, before being shifted to 37°C (A) in the absence (CTL) or presence of 1 μM Bafi or 1 μM CytoD, or (B) in the presence of 5 μg/ ml BFA. The cells were then fixed and labeled with CTR433 antibody (A) or anti-TfR antibody (B). (C) BFA inhibits B-fragment transport to dispersed Golgi cisternae in Noc-treated HeLa cells. HeLa cells were pretreated for 1 h with 10 μM Noc. The cells were then transferred on ice and incubated with fluorophore-labeled B-fragment for 30 min, washed, and then shifted for 30 min to 37°C in the absence (top row) or presence (bottom row) of 5 μg/ml BFA and in the continued presence of Noc. The cells were then fixed and stained for the Golgi marker CTR433. Note that in the absence of BFA, B-fragment associated with the dispersed cisternae of the Golgi apparatus (top), while in the presence of the drug, the CTR433-positive cisternae were devoid of B-fragment (bottom). Four optical slices were obtained by confocal microscopy.