Figure 9.

Proteasome inhibition prevents loss of FcγRIIA from the phagosome. CHO cells stably transfected with FcγRIIA-GFP were either left untreated (A) or pretreated with 10 μM MG-132 for 3 h (C) before phagocytosis of opsonized beads for 40 min. The cells were then fixed and the distribution of FcγRIIA-GFP was analyzed by laser confocal microscopy (A and C). Corresponding DIC images appear in B and D. (E and F) Quantitation of results of experiments like those in A–D. The fluorescence pattern of each phagosome was categorized as being continuous around the phagosome, patchy (discontinuous) or absent from the phagosome. The fraction of each type is shown in E for both conditions. (F) The ratio of the fluorescence intensity of phagosomes of cells treated with MG-132 divided by phagosomes of control cells, measured as in Figure 5. Data are means ± SE of three experiments, each counting a minimum of 60 phagosomes. Size bar, 5 μm.