Signaling adapter molecule involved in p75NTR/NGFR signaling. Plays a role in cell cycle progression and neuronal differentiation. Inhibits neuronal differentiation in response to nerve growth factor (NGF). May act as a link between the cell cycle and neurotrophic factor signaling, possibly by functioning as an upstream modulator of receptor signaling, coordinating biological responses to external signals with internal cellular states (By similarity). Interacts with neurotrophin receptor p75NTR/NGFR. Interacts with OMP (By similarity). Shuttles between the cytoplasm and the nucleus. Phosphorylated. Phosphorylation of Ser-105 protects it from the proteasome (By similarity). Ubiquitinated. Degraded by the proteasome (By similarity). Belongs to the BEX family.