May function as a growth and differentiation factor involved in neuritogenesis. May induce ERBB3 activation. Binds TNR and probably TNC (By similarity). Interacts with ERBB3 and GOPC. Interacts with MDK; this interaction is independent of the presence of chondroitin sulfate chains and promotes elongation of oligodendroglial precursor-like cells (By similarity). In neurons, localizes to synaptic junctions. Also detected in the endoplasmic reticulum and the Golgi. Partially enriched in lipid rafts. Restricted to brain (at protein level). Expressed in brain of 3 months, 5 and 10-year-old individuals. N-glycosylated. O-glycosylated; contains chondroitin sulfate glycans. Part-time proteoglycan, expressed in part as a proteoglycan exhibiting chondroitin sulfate glycans and in part as a non-proteoglycan form. The relative amount of both forms depends on tissues and tissues maturation (By similarity). Phosphorylated; in intracellular and extracellular parts. Different forms of various molecular weight have been observed. Such forms are possibly due to different levels of glycosylation, phosphorylation and/or protein cleavage (By similarity).