title: Dissociation of recruitment and activation of the small G-protein Rac during Fcgamma receptor-mediated phagocytosis.
abstract: Rho-family proteins play a central role in most actin-dependent processes, including the control and maintenance of cell shape, adhesion, motility, and phagocytosis. Activation of these GTP-binding proteins is tightly regulated spatially and temporally; however, very little is known of the mechanisms involved in their recruitment and activation in vivo. Because of its inducible, restricted signaling, phagocytosis offers an ideal physiological system to delineate the pathways linking surface receptors to actin remodeling via Rho GTPases. In this study, we investigated the involvement of early regulators of Fcgamma receptor signaling in Rac recruitment and activation. Using a combination of receptor mutagenesis, cellular, molecular, and pharmacological approaches, we show that Src family and Syk kinases control Rac and Vav function during phagocytosis. Importantly, both the immunoreceptor tyrosine-based activation motif within Fcgamma receptor cytoplasmic domain and Src kinase control the recruitment of Vav and Rac. However, Syk activity is dispensable for Vav and Rac recruitment. Moreover, we show that Rac and Cdc42 activities coordinate F-actin accumulation at nascent phagosomes. Our results provide new insights in the understanding of the spatiotemporal regulation of Rho-family GTPase function, and of Rac in particular, during phagocytosis. We believe they will contribute to a better understanding of more complex cellular processes, such as cell adhesion and migration.
authors.affiliation: Centre for Molecular Microbiology and Infection, and Division of Cell and Molecular Cell biology, Faculty of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: Céline
authors.initials: C
authors.lastname: Cougoule
authors.forename: Saiko
authors.initials: S
authors.lastname: Hoshino
authors.forename: Anna
authors.initials: A
authors.lastname: Dart
authors.forename: Jenson
authors.initials: J
authors.lastname: Lim
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Caron
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D016650:Fluorescein-5-isothiocyanate; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008954:Models, Biological; D009895:Opsonin Proteins / Q000494:pharmacology; D010587:Phagocytosis; D010590:Phalloidine; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav / Q000032:analysis / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism*; D000072377:Syk Kinase; D020744:rac GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; D047908:Intracellular Signaling Peptides and Proteins; D009895:Opsonin Proteins; D051567:Proto-Oncogene Proteins c-vav; D017452:Receptors, IgG; C496619:Vav1 protein, mouse; D010590:Phalloidine; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D019061:src-Family Kinases; D020744:rac GTP-Binding Proteins; D016650:Fluorescein-5-isothiocyanate