Fig. 2. Secretory traffic of VSVG-FP in the absence of microtubules. Confocal images of fixed COS7 cells coexpressing VSVG-YFP (green, A-B) and either the ER marker Srβ-CFP (A, red) or the ER exit site marker Sec31-CFP (B, red). For complete microtubule depolymerization, cells were transferred to ice for 20 minutes following a 24 hour incubation at the nonpermissive temperature (40°C) to accumulate VSVG in the ER. Nocodazole (1 µg/ml) was added and the cells were incubated at the permissive temperature (34°C) for the indicated times before addition of formaldehyde. Arrowheads indicate reticular and flat ER membranes. Scale bars: 10 µm.