Actin tails propel phagosomes after CR3-mediated phagocytosis. (A–C and E) RAW264.7 macrophages stably expressing GFP-actin (A and C) or mCherry-actin (B and E) were examined by confocal microscopy after exposure to complement-coated RBCs (A and E), serum-coated Y. pseudotuberculosis or serum-coated zymosan (B) to trigger CR3-mediated phagocytosis, or IgG-coated RBCs (C) to trigger FcγR-mediated phagocytosis. (D) Quantitation of the percentage of phagosomes that displayed actin tails during the first 15 min after uptake. Data are means ± SEM of at least six individual experiments; a minimum of 70 phagosomes were counted per experiment. (E) PBD-PAK1–YFP was transfected transiently, and its dynamics were monitored in parallel with that of mCherry-actin. (F) Quantitation of the percentage of phagosomes that displayed actin tails during the first 15 min after uptake of complement-coated RBCs in cells transfected with DN forms of Rac1 or Cdc42. Data are means ± SEM of at least four individual experiments; a minimum of 60 phagosomes were counted per experiment. Images in A–C and E are representative of at least 10 individual experiments of each kind. Numbers indicate time in seconds after phagosome formation, and arrows point to the nascent or recently formed phagosomes. Insets illustrate corresponding differential interference contrast images. Bars, 5 µm.