Functional and molecular interactions between Rac1 and FE65.

FE65 is reported to act as an adaptor protein with several protein-interaction domains, including one WW domain and two phosphotyrosine interaction/binding domains. Through these binding domains, FE65 was considered to recruit various binding partners together to form functional complexes in a certain cellular compartment. In this study, we demonstrated that Rac1, a member of the Rho family GTPases, bound with FE65. We also elucidated that Rac1 inhibitor significantly suppressed FE65 expression, and Rac1 small interfering RNA transduction significantly decreased FE65 expression. FE65 small interfering RNA, however, did not influence Rac1 expression and its activity. Taken together, our results reveal that Rac1 interacts with FE65, and Rac1 activity regulates FE65 expression.