Figure 2.

Collaboration between Arf and Rho GTPases to potentiate actin assembly via WRC. The Wave regulatory complex (WRC) exists in an inactive state i.e. the VCA domain of WAVE is not free to bind to the Arp2/3 complex to induce actin polymerization. Upon external stimuli, such as effector protein delivery by Salmonella or on EGF stimulation, Arf6 recruits and activates ARNO that in turn stimulates the exchange of GDP (white circle) bound to Arf1 for GTP (blue circle). Activated Arf1 consequently anchors via its exposed myristoylation moiety (black lines) to the plasma membrane. The Arf1 binding partner remains unclear, but nevertheless membrane-anchored active Arf1 and Rac1 work in cooperation to recruit and activate the WRC (i.e., release the VCA domain) that induces Arp2/3-dependent polymerization of actin filaments (pink).