Meta-Biol

• Pathways

The organized movements of membranes and the actin cytoskeleton are coordinated in phagocytosis by small GTPases of the Rho family. Specifically, RAC1 and CDC42 are known to be stimulated upon engagement of FCGR and are essential for the extension of the pseudopods that surround and engulf the phagocytic particle (Scott et al 2005). RAC1 is known to regulate actin dynamics. It is active throughout the phagocytic cup and activated RAC1 is necessary to assemble F actin. However, closing the phagocytic cup requires RAC1 to be deactivated (Naakaya et al 2007). Deletion of RAC1 prevents FCGR mediated phagocytosis (Hall et al 2006). RAC1 activation involves transition from an inactive GDP bound to an active GTP bound state catalysed by guanine exchanges factors (GEFs). VAV has been implicated in the activation of RAC1 (Patel et al 2002).