Fig. 4.
Rsu1 binds to Rac1 and affects actin dynamics in Drosophila S2 cells. (A and B) Rsu1 binds to (A) both the GTP-locked forms of Rac1 (Rac1CA) and GDP-locked forms of Rac1 (Rac1DN) but (B) not to Rho1 GTP- (Rho1CA) or GDP-locked (Rho1DN) forms. (C) Rac1.GTP pull-down experiments shows that RNAi-mediated knockdown of Rsu1 leads to increased Rac1.GTP loading. (D and E) Globular (G) to filamentous (F) actin assay measuring the ratio of actin in free globular to assembled filamentous form showing that RNAi-mediated knockdown of Rsu1 causes an approximately threefold decrease in G/F actin ratio, whereas overexpression of constitutive active Rac1CA causes an approximately ninefold decrease in G/F actin ratios compared with controls. The actin stabilizer phalloidin also decreases the G/F ratio and served as a positive control. IP, immunoprecipitation. ***P < 0.001 (n = 4–9).