Cell surface receptor that plays a functionally redundant role in the inhibition of neurite outgrowth mediated by MAG (By similarity). Plays a functionally redundant role in postnatal brain development. Contributes to normal axon migration across the brain midline and normal formation of the corpus callosum. Does not seem to play a significant role in regulating axon regeneration in the adult central nervous system. Protects motoneurons against apoptosis; protection against apoptosis is probably mediated by MAG (By similarity). Like other family members, plays a role in restricting the number dendritic spines and the number of synapses that are formed during brain development (PubMed:22325200). Signaling mediates activation of Rho and downstream reorganization of the actin cytoskeleton (PubMed:22325200). Interaction with MAG is controversial, and may be indirect (Probable). Does not interact with MAG, OMG and RTN4 (PubMed:12839991). Interacts with MAG (By similarity). Localized to the surface of neurons, including axons. Detected close to synapses, but is excluded from synapses. Highly expressed in brain and liver. Expressed at lower levels in kidney, mammary gland, placenta, skeletal muscle, spleen and thyroid. Undergoes zinc metalloproteinase-mediated ectodomain shedding in neuroblastoma cells; is released both as a full-length ectodomain and an N-terminal fragment containing the leucine-rich repeat (LRR) region of the protein. N-glycosylated. Belongs to the Nogo receptor family.