Cells detect external stimuli through cell-surface receptors. In cases where the stimulus is a cytokine or a growth factor, the cell responds by inducing modifications in the actin cytoskeleton. These changes are mediated through the Rho family of GTPases. Among these GTPases, RhoA, Rac1 and Cdc42 have been extensively studied. The activity of these proteins is closely monitored and tightly regulated through Guanine-nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) that turn the “switch” on and off respectively. Crosstalk between Rho GTPases has been long studied; yet many questions are raised regarding the spatiotemporal regulation of these GTPases, particularly RhoA and Rac1. This review sheds a light on the antagonistic relationship between both GTPases and puts emphasis on the importance of cycling of RhoA activation at the focal adhesions for optimal cell migration.

细胞通过细胞表面受体检测外部刺激。在刺激是细胞因子或生长因子的情况下，细胞通过诱导肌动蛋白细胞骨架的修饰而作出反应。这些变化是通过GTPases的Rho家族介导的。在这些GTPases中，已经广泛研究了RhoA，Rac1和Cdc42。这些蛋白质的活性通过分别打开和关闭“开关”的鸟嘌呤核苷酸交换因子（GEF）和GTPase激活蛋白（GAP）进行密切监控和严格调节。Rho GTPases之间的串扰已被长期研究；关于这些GTP酶的时空调节，尤其是RhoA和Rac1，提出了许多问题。