Cell surface receptor that plays a functionally redundant role in the inhibition of neurite outgrowth mediated by MAG (PubMed:15673660). 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 (By similarity). Protects motoneurons against apoptosis; protection against apoptosis is probably mediated by MAG (PubMed:26335717). 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). Interacts with MAG (PubMed:15673660, PubMed:19420245, PubMed:21308849). Does not interact with OMG and RTN4 (PubMed:15673660). Localized to the surface of neurons, including axons (PubMed:12694398, PubMed:15673660). Detected close to synapses, but is excluded from synapses (By similarity). Detected in adult brain, in neocortex, hippocampus, striatum and dorsal root ganglion neurons, and in retina (at protein level) (PubMed:15673660). In brain, detected in cerebral cortex and hippocampus. Weak or no expression detected in the cerebellum, thalamus or striatum (PubMed:12694398). Expression is high in adult, but very low in neonate dorsal root ganglion neurons (at protein level). 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 (PubMed:19420245, PubMed:21308849). O-glycosylated (PubMed:19420245). Contains terminal sialic acid groups on its glycan chains (PubMed:19420245). Belongs to the Nogo receptor family.