E-cadherin–catenin–Arp2/3 puncta marked sites of actin assembly on purified membranes. (a) Purified membranes were incubated with increasing concentrations of rhodamine-labeled G-actin. Although the total amounts of actin incorporated increased with actin concentration (unscaled), the sizes and numbers of membrane actin puncta were the same (scaled). Bar, 10 µm. (b) Immunofluorescence staining showing colocalization of actin puncta with E-cadherin, α-catenin, β-catenin, and Arp2/3 but not PI3K p110-γ. Bar, 5 µm. (c) Western blot of total liver homogenate and purified membrane fraction (see Materials and methods).