Rac1 activation comes full circle

The Rac1 small GTPase is responsive to a large array of extracellular signals and in turn controls a wide variety of cellular functions-including actin dynamics. New findings add an additional layer of intricacy to the already complex process of regulating Rac1 activity, via a positive feedback loop involving the actin-binding protein coronin 1A, the Rac1 exchange factor ArhGEF7, the Rac1 effector Pak1 and the Rac1 inhibitor RhoGDI alpha. This complex shows remarkable versatility, integrating Rac1 translocation, release from RhoGDI and, possibly, nucleotide exchange.