Robo1 signaling activates Rho GTPases in transformed cells. Src transformed cells were treated with R5 antibody or control antiserum (IgG) and examined for total and activated Cdc42 and Rac1 GTPases in panels a and b , respectively. Western blotting was performed to detect active (GTP bound) Cdc42 and Rac1, total Cdc42 and Rac1, and GST. Levels of active Cdc42 and Rac1 were quantitated and shown as the percent of untreated control cells (mean+SEM, n=3). Experiments were performed with Cx43Ko and wild type cells, with results from Cx43Ko cells shown. Single and triple asterisks indicate p values less than 0.5 and 0.005, respectively (by t-test).