Objective:To study whether Abba1’s C-terminal region might participate in the formation of membrane ruffling. Methods:Several recombinant plasmids,such as pEGFP,pEGFP-hAbba1,pEGFP-hAbba1-IMD,pEGFP-hAbba1-del-357-722aa-WH2 were prepared. COS7 cells were transiently transfected with these plasmids,respectively. Immunofluorescent microscopy was carried out to detect the formation of membrane protrusions. And GTP-bound Rac1(GTP-Rac1)in cell lysates was determined by pull-down with GST-PAK-CRIB followed by Western blot with Rac1 antibody. Results:From immunofluorescent microscopy,unlike overexpression of Abba1 inducing the formation of membrane ruffling,cells overexpressing Abba1-IMD or Abba1-del-357-722aa-WH2 displayed microspikes. Pull-down combined Western blot analysis revealed that the relative level of GTP-Rac1 was increased in the cells with overexpression of Abba1. However,the level was decreased in cells transfected with Abba1-IMD and Abba1-del-357-722aa-WH2. Conclusion:The data indicated that C-terminal region affected Abba1 inducing membrane ruffling in COS7 cells,which was connected with the decrescent level of GTP-Rac1.