Negatively regulates RAC1 signaling and RAC1-driven cytoskeletal remodeling. Regulates chemotaxis, cell migration and epithelial polarization by controlling the polarity, plasticity, duration and extent of protrusions. Limits Rac1 mediated activation of the Scar/WAVE complex, focuses protrusion signals and regulates pseudopod complexity by inhibiting Scar/WAVE-induced actin polymerization. Protects against Salmonella bacterial infection. Attenuates processes such as macropinocytosis, phagocytosis and cell migration and restrict sopE-mediated bacterial entry (By similarity). Restricts also infection mediated by Mycobacterium tuberculosis and Listeria monocytogenes (By similarity). Involved in the regulation of mitochondrial dynamics and oxidative stress (By similarity). Interacts with RAC1 (GTP-bound form preferentially). Ubiquitinated at Lys-74 upon Salmonella bacterial infection. Belongs to the CYRI family.