The actin-cytoskeleton plays a critical role in various biological processes, including cell migration, development, tissue remodeling, and memory formation. Both extracellular and intracellular signals regulate reorganization of the actin-cytoskeleton to modulate tissue architecture and cellular morphology in a spatiotemporal manner. Since the discovery that activation of Rho family GTPases induces actin-cytoskeleton reorganization, the mode of action of Rho family GTPases has been extensively

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... studied and individual effectors have been characterized. The actin-binding protein IQGAP1 was identified as an effector of Rac and Cdc42 and is the founding member of the IQGAP family with two additional isoforms. The IQGAP family shows conserved domain organization, and each member displays a specific expression pattern in mammalian tissues. IQGAPs regulate the actin-cytoskeleton alone and with their binding partners, thereby controlling diverse cellular processes, such as cell migration and adhesion. Here, we introduce IQGAPs as an actin-cytoskeleton regulator. -associated protein 1; VCA, verprolin-homology, cofilin-homology and acidic domain; WAVE, Wiskott-Aldrich syndrome protein (WASP) verprolin homologous. researchers, including us, have been intensively studying the mode of action of the Rho family GTPases. Biochemical and genetic screens have identified critical effectors of Rho family GTPases that mediate the activation of the Rho family GTPases and the reorganization of the actincytoskeleton. These effectors include IQGAPs, Specifically Rac1-associated protein 1 (Sra-1, also known cytoplasmic FMR1 interacting protein 1), Rho-kinase (also known ROK, ROCK), Dia (Diaphanous related formin), p21activating kinase (PAK), Wiskott-Aldrich syndrome protein (WASP) verprolin homologous (WAVE) complex, and WASP/N-WASP. In this review, we focus on the role of IQGAPs in the regulation of the actin-cytoskeleton. The mode of action of Rho family GTPases and their other effectors in the regulation of actin-cytoskeleton is discussed in several excellent reviews (Kaibuchi et al. IQGAPs and the Actin-cytoskeleton