Fig. 4. Time-lapse sequences of living RAW264.1 macrophages transfected with pEGFP-actin, showing actin dynamics during phagocytosis of IgG-Es. (A) In a control cell, IgG-Es induced F-actin assembly where they were bound, resulting in phagocytic-cup formation. It was noteworthy that the IgG-Es was deformed during phagocytic-cup formation, suggesting that the F-actin ring constricted the phagocytic cup and squeezed the IgG-Es. Subsequently, the F-actin ring seemed to close at the top of the cup. F-actin disappeared immediately after phagocytic cups closed into intracellular phagosomes. (B) In a ML-7-treated cell, F-actin assembly and phagocytic-cup extension occurred, but the process was slower and the cup was shallower than in control. Even though phagocytic cups were formed, they did not constrict or close. The time interval between frames is 10 seconds. Bars, 10 µm. The supplemental video materials are available in the online version [Video 1 (http://www.jcs.biologists.org/supplemental)].