Part of the WAVE complex that regulates lamellipodia formation. The WAVE complex regulates actin filament reorganization via its interaction with the Arp2/3 complex. Actin remodeling activity is regulated by RAC1 (By similarity). Plays a role in neural tube closure. At the interface between the lamellipodial actin meshwork and the membrane. Belongs to the HEM-1/HEM-2 family.