FIGURE 3.

YopO blocks Rac activation during FcγR phagocytosis. A, COS-7 cells were transiently transfected with FcγRIIA and either GFP or GFP-YopOwt and then challenged with IgG-opsonized sRBC for 10 min at 37 °C after synchronization at 4 °C. Cells were lysed at 0 and 10 min and incubated with GST-PAK CRIB immobilized on glutathione-Sepharose beads. Bead eluates and lysates were analyzed by SDS-PAGE and Western blot probing for Rac. A representative experiment is shown. B, fold activation of Rac was quantified and shown relative to activation levels at 0 min (GFP-expressing cells). Data are mean ± S.E. of three independent experiments. * indicates p < 0.05.