Figure 4.

GRASP55 is not required for Golgi stacking or protein secretion. (A) HeLa cells were transfected with either control or GR55 siRNA oligo. After 72 h, cells were fixed in 1% glutaraldehyde and processed for electron microscopy. The stacking of Golgi cisternae is not affected by GRASP55 depletion. Cisternae numbers range from three to five cisternae per Golgi stack both in control and GRASP55-depleted cells. (B) Cell surface VSV-G was determined using the anti-VSV-G mAb 8G5F11, which is specific for the extracellular domain of VSV-G. FACS sorting revealed that VSV-G surface expression was not affected in both control and siRNA-transfected cells. Likewise, the secretion of ss-HRP was monitored as described previously (Bard et al., 2006). Secreted HRP was assayed using ECL and found to be at comparable levels at all time points tested in control and GRASP55-depleted cells.