New insights into the regulation and cellular functions of the ARP2/3 complex

The ARP2/3 complex, which nucleates branched actin filament networks, is itself activated by nucleation-promoting factors (NPFs). New understanding is being gained into NPF control of ARP2/3 and the biological roles of ARP2/3 branched actin. The actin-related protein 2/3 (ARP2/3) complex nucleates branched actin filament networks, but requires nucleation promoting factors (NPFs) to stimulate this activity. NPFs include proteins such as Wiskott–Aldrich syndrome protein (WASP), neural WASP (NWASP), WASP family verprolin-homologous protein (WAVE; also known as SCAR) and the recently identified WASP and SCAR homologue (WASH) complex. The mechanisms underlying NPF-dependent regulation and the cellular functions of ARP2/3 are being unravelled using new chemical and genetic approaches. Of particular interest is the role of the ARP2/3 complex in vesicular trafficking and directional cell motility.