Rho, Rac and Cdc42

Abstract

Phagocytosis is a major host defense mechanism that is mediated by at least two receptors in macrophages: complement receptor 3 (CR3) and the Fc γ receptors (Fc γRs). Caron and Hall have dissected the involvement of Rho, Rac and Cdc42 in FcγR- and CR3-mediated phagocytosis 1 Caron E. Hall A. Identification of two distinct mechanisms of phagocytosis controlled by different Rho GTPases. Science. 1998; 282: 1717-1721 Crossref PubMed Scopus (782) Google Scholar . These three small GTPases act as molecular switches in the reorganization of the actin cytoskeleton. By co-expressing FcγR or CR3 receptors and dominant negative mutants of Rho, Rac and Cdc42 in different cell lines, two mechanisms of phagocytosis have been identified: type I phagocytosis is mediated by FcγRs and requires Cdc42 and Rac, whereas type II phagocytosis is mediated by CR3 and requires Rho only. Interestingly, during type I phagocytosis, all three GTPases are recruited to the phagocytic compartment, probably following the activation of Cdc42, but only Rho is recruited during type II phagocytosis. Rho, Rac and Cdc42 are well known for controlling different aspects of morphological reorganization in the cell. The different GTPases recruited to the phagocytic compartment might therefore pertain to the morphological and physiological (in particular, the inflammatory response) differences that are observed during FcγR- and CR3-mediated phagocytosis.