Reduced actin polymerization response and Rac1 activation upon cAMP stimulation in YopE expressing cells. (A) Relative F-actin content as determined by TRITC-phalloidin staining of aggregation competent cells fixed at the indicated time points after stimulation with 1 μM cAMP. Control cells are non-induced cells carrying the GFP-YopE plasmid. The amount of F-actin was normalized relative to the F-actin level of unstimulated cells. Data are average ± standard deviation of 5 independent experiments. For simplicity, error bars are depicted only in one direction. *P < 0.05, Student's t-test. (B) Activation of Rac1 upon cAMP stimulation in cells expressing GFP-YopE. Rac1-GTP was separated using a pulldown assay. A representative blot of each strain is shown. Data are average ± standard deviation of four independent pull down experiments. *P < 0.05, Student's t-test.