Myelin-associated glycoprotein (MAG), a nervous system cell adhesion molecule, is an I-type lectin that binds to sialylated glycoconjugates, including gangliosides bearing characteristic structural determinants. Preferentially binds to alpha-2,3-linked sialic acid. Binds ganglioside Gt1b. Adhesion molecule that mediates interactions between myelinating cells and neurons by binding to neuronal sialic acid-containing gangliosides and to the glycoproteins RTN4R and RTN4RL2. Protection against apoptosis is probably mediated via interaction with neuronal RTN4R and RTN4RL2. In dorsal root ganglion neurons the inhibition is mediated primarily via binding to neuronal RTN4R or RTN4RL2 and to a lesser degree via binding to neuronal gangliosides. In cerebellar granule cells the inhibition is mediated primarily via binding to neuronal gangliosides. In sensory neurons, inhibition of neurite extension depends only partially on RTN4R, RTN4RL2 and gangliosides.