Published 27 March 2006. doi:10.1083/jcb.200508075
The Rockefeller University Press, 0021-9525 $8.00
JCB, Volume 172, Number 7, 1069-1079
Two distinct cytoplasmic regions of the ß2 integrin chain regulate RhoA function during phagocytosis
Agnès Wiedemann,
Jayesh C. Patel,
Jenson Lim,
Andy Tsun,
Yvette van Kooyk, and
Emmanuelle Caron
Division of Cell and Molecular Biology, Centre for Molecular Microbiology and Infection, Imperial College London, London SW7 2AZ, England, UK
Correspondence to Emmanuelle Caron: e.caron{at}imperial.ac.uk
Mß2 integrins mediate phagocytosis of opsonized particles in a process controlled by RhoA, Rho kinase, myosin II, Arp2/3, and actin polymerization.
Mß2, Rho, Arp2/3, and F-actin accumulate underneath bound particles; however, the mechanism regulating Rho function during
Mß2-mediated phagocytosis is poorly understood. We report that the binding of C3bi-opsonized sheep red blood cells (RBCs) to
Mß2 increases Rho-GTP, but not Rac-GTP, levels. Deletion of the cytoplasmic domain of ß2, but not of
M, abolished Rho recruitment and activation, as well as phagocytic uptake. Interestingly, a 16amino acid (aa) region in the membrane-proximal half of the ß2 cytoplasmic domain was necessary for activating Rho. Three COOH-terminal residues (aa 758760) were essential for ß2-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.
Abbreviations used in this paper: CR3, complement receptor 3; PAK, p21-activated kinase; RBC, sheep red blood cell; RBD, Rho-binding domain of rhotekin; wt, wild-type.

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