Dendritic branching and homogenization of actin networks mediated by arp2/3 complex.

The cytoskeleton of motile cells exploits accessory proteins to locally modulate its organization and micromechanics. Here, we demonstrate that the Arp2/3 complex plays the role, unique among other cytoskeleton proteins, of an actin network "homogenizer," promoting the extremely rapid formation of homogeneous and stiff networks. Nanotracking of microspheres imbedded in F-actin networks reveals that the Arp2/3 complex promotes the formation of networks that are remarkably more homogeneous than control networks, a distinctive feature that coordinates a dramatic burst of elasticity. These results suggest that the Arp2/3 complex possesses a unique function of stabilizing membrane protrusions through the formation of homogeneous and stiff actin cytoskeleton at the leading edge of crawling cells.