Presence of Clathrin at Adhesion Sites in Phagocytosing Macrophages

Phagocytosis of particles by macrophages may be similar to cell spreading on a substratum, in that a dense network of actin filaments appears beneath the plasma membrane in both cases. When viewed in broken-open or detergent- extracted cells, cytoskeletal filaments are observed to form focal attachments to the plasma membrane and to the cytoplasmic surface of phagosomes. Hartwig et al. have presented a model of phagocytosis in which an actin-binding protein alters the organization of subplasmalemma1 actin filaments in such a way that the plasma membrane is forced up over the particle to form the phagosome. Their evidence indicates that similar actin-binding proteins may function during cell spreading.