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. Interacts with OMP (By similarity). Interacts with neurotrophin receptor p75NTR/NGFR. Shuttles between the cytoplasm and the nucleus. Predominantly nuclear. Expressed in the central nervous system. Expressed in Schwann cells from newborn sciatic nerve. Oscillates during the cell cycle, being lowest at G1 and highest at S phase (at protein level). Phosphorylated. Phosphorylation of Ser-105 protects it from the proteasome. Ubiquitinated (Probable). Degraded by the proteasome (By similarity). Belongs to the BEX family.