GTPase-activating protein for p21-rac and a phorbol ester receptor. Involved in the assembly of neuronal locomotor circuits as a direct effector of EPHA4 in axon guidance. Interacts with EPHA4; effector of EPHA4 in axon guidance linking EPHA4 activation to RAC1 regulation. In neurons in brain regions that are involved in learning and memory processes. Increases in amount during brain development coincident with synaptogenesis. Phosphorylated. Phosphorylation is EPHA4 kinase activity-dependent (By similarity).