Two distinct cytoplasmic regions of the beta2 integrin chain regulate RhoA function during phagocytosis.
AlphaMbeta2 integrins mediate phagocytosis of opsonized particles in a process controlled by RhoA, Rho kinase, myosin II, Arp2/3, and actin polymerization. AlphaMbeta2, Rho, Arp2/3, and F-actin accumulate underneath bound particles; however, the mechanism regulating Rho function during alphaMbeta2-mediated phagocytosis is poorly understood. We report that the binding of C3bi-opsonized sheep red blood cells (RBCs) to alphaMbeta2 increases Rho-GTP, but not Rac-GTP, levels. Deletion of the cytoplasmic domain of beta2, but not of alphaM, abolished Rho recruitment and activation, as well as phagocytic uptake. Interestingly, a 16-amino acid (aa) region in the membrane-proximal half of the beta2 cytoplasmic domain was necessary for activating Rho. Three COOH-terminal residues (aa 758-760) were essential for beta2-induced accumulation of Rho at complement receptor 3 (CR3) phagosomes. Activation of Rho was necessary, but not sufficient, for its stable recruitment underneath bound particles or for uptake. However, recruitment of active Rho was sufficient for phagocytosis. Our data shed light on the mechanism of outside-in signaling, from ligated integrins to the activation of Rho GTPase signaling.
Division of Cell and Molecular Biology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, England, UK.
Agnès
A
Wiedemann
Jayesh C
JC
Patel
Jenson
J
Lim
Andy
A
Tsun
Yvette
Y
van Kooyk
Emmanuelle
E
Caron
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018821:CD18 Antigens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D003179:Complement C3b / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000737:chemistry / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013912:Threonine / Q000235:genetics; D014162:Transfection; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D000199:Actins; D018821:CD18 Antigens; D016177:Macrophage-1 Antigen; D013912:Threonine; D003179:Complement C3b; D006160:Guanosine Triphosphate; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D013755:Tetradecanoylphorbol Acetate