FIG. 10.

Sra1, Nap1, and Abi are required for cadherin-dependent adhesion. (A) A431 cells were transfected with control or Sra1-specific siRNAs, and after 48 h, cells were fixed and stained with anti-β-catenin antibody (left panels) (bar, 10 μm) or subjected to cell lysis (right panels). Total cell lysates were analyzed by Western blotting with the indicated antibodies. (B) A431 cells transfected with the indicated siRNAs were allowed to adhere for 1 h on E-cad-Fc-coated wells, and adherent cells were counted (upper panel). Results represent the means ± SEMs of at least three independent experiments. *, significant decrease for control siRNA versus Sra1 siRNA, Nap1 siRNA, or Abi1/2 siRNA (P < 0.01). A431 cells transfected with the indicated siRNAs were lysed, and cell lysates were analyzed by blotting with the indicated antibodies (lower panel). (C) Proposed model for the role of Abi in the regulation of cell-cell junctions through distinct types of actin nucleation complexes. Active Rac1 and RhoA may promote the recruitment of distinct Abi/Dia and Abi/Wave protein complexes. The Abi/Dia complex is required for junction formation and stability, whereas the Abi/Wave/Arp2/3 complex is involved in lamellipodial protrusions during the formation of nascent junctions.