Fig. 4.

Model for regulation of actin filament architecture at the lamellipodium. Filaments are nucleated at the cell edge as dendritic branches by Arp2/3 complex and plasma membrane-associated WASp/Scar (not shown). Many of the free barbed ends generated are capped by capping protein binds, which terminates filament growth. Filament crossovers are stabilized by cross-linking proteins such as filamin. As the dendritic network ages and is left behind by the advancing leading edge, disassembly factors such as ADF/cofilin, GMF, and Coronin, debranch Arp2/3 complex-nucleated filaments. Severed filaments at the rear of the lamellipodium are either completely disassembled by ADF/cofilin, working together with Coronin and other factors (e.g. Aip1 and Srv2/CAP, not shown) or cross-linked by fimbrin, α-actinin, and myosin II (not shown) to generate the actin bundles and arcs found in the lamella.