The small GTPase RALA controls JNK-mediated FOXO activation by regulation of a JIP1 scaffold complex

Abstract Forkhead box O (FOXO) transcription factors are tumor suppressors and increase lifespan of model organisms. Cellular stress, in particular oxidative stress due to an increase in levels of reactive oxygen species (ROS), activates FOXOs through JNK-mediated phosphorylation. Importantly, JNK regulation of FOXO is evolutionary conserved. Here we identified the pathway that mediates ROS-induced JNK-dependent FOXO regulation. Following increased ROS, RALA is activated by the exchange factor RLF, which is in complex with JIP1 and JNK. Active RALA consequently regulates assembly and activation of MLK3, MKK4 and JNK onto the JIP1 scaffold. Furthermore, regulation of FOXO by RALA and JIP1 is conserved in C.elegans, where both ral-1 and jip-1 depletion impairs heat shock-induced nuclear translocation of the FOXO orthologue DAF16.