Phosphatase and feedback regulation of Raf-1 signaling.

The Raf-1 kinase is an effector of Ras GTPases that lies at the apex of the three-tier Raf/MEK/ERK pathway. Raf-1 activation is a complex process that entails two major events--relief of autoinhibition imposed by the regulatory domain and kinase domain activation. Recent studies indicate that the transition of Raf-1 from an active to an inactive state bears similar complexity to the activation process. Both these events require dynamic changes in Raf-1 phosphorylation. Here, we discuss the critical role of phosphatases and feedback phosphorylation during activation and inactivation of Raf-1 signaling.