title: Cofilin contributes to phagocytosis of IgG-opsonized particles but not non-opsonized particles in RAW264 macrophages.
abstract: Cofilin is an actin-binding protein that severs actin filaments. It plays a key role in regulating actin cytoskeletal remodeling, thereby contributing to diverse cellular functions. However, the involvement of cofilin in phagocytosis remains to be elucidated. We examined the spatiotemporal localization of cofilin during phagocytosis of IgG-opsonized erythrocytes, IgG-opsonized latex beads and non-opsonized latex beads. Live-cell imaging showed that GFP-cofilin accumulates in the sites of IgG-opsonized particle binding and in phagocytic cups. Moreover, immunofluorescence microscopy revealed that endogenous cofilin localizes to phagocytic cups engulfing IgG-opsonized particles, but not non-opsonized latex beads. Scanning electron microscopy demonstrated a notable difference in morphology between phagocytic structures in IgG-dependent and IgG-independent phagocytosis. In phagocytosis of IgG-opsonized particles, sheet-like pseudopodia extended along the surface of IgG-opsonized particles to form phagocytic cups. In contrast, in opsonin-independent phagocytosis, long finger-like filopodia captured non-opsonized latex beads. Importantly, non-opsonized beads sank into the cells without extending phagocytic cups. Our analysis of cofilin mutant expression demonstrates that phagocytosis of IgG-opsonized particles is enhanced in cells expressing wild-type cofilin or active mutant cofilin-S3A, whereas the uptake of non-opsonized latex beads is not. These data suggest that cofilin promotes actin cytoskeletal remodeling to form phagocytic cups by accelerating actin turnover and thereby facilitating phagosome formation. In contrast, cofilin is not involved in opsonin-independent phagocytosis of latex beads.
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan Laboratory of Electron Microscopy, Southern Medical University, Guangzhou 510515, China.
authors.forename: Yanmeng
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan Department of Information Technology, School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Cao
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
authors.forename: Youhei
authors.initials: Y
authors.lastname: Egami
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Kawai
authors.affiliation: Department of Histology and Cell Biology, School of Medicine, Kagawa University, Miki, Kagawa 761-0793, Japan naraki@med.kagawa-u.ac.jp.
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Araki
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D007074:Immunoglobulin G / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D008863:Microspheres; D009895:Opsonin Proteins / Q000378:metabolism*; D010587:Phagocytosis / Q000276:immunology*; D000067996:RAW 264.7 Cells
chemical_list: D051339:Actin Depolymerizing Factors; D007074:Immunoglobulin G; D009895:Opsonin Proteins
keywords: cofilin; electron microscopy; latex beads; live-cell imaging; macrophages; phagocytosis