Postsynaptic adhesion molecule that binds to presynaptic neurexins to mediate both excitatory and inhibitory synapse formation. Promotes synapse development by acting as a cell adhesion molecule at the postsynaptic membrane, which associates with both neurexin-alpha and neurexin-beta proteins at the presynaptic membrane (By similarity). Regulates the balance between excitatory and inhibitory synapses by inhibiting formation of excitatory parallel-fiber synapses and promoting formation of inhibitory synapses in the same neuron (By similarity). May also be involved in ascorbate (vitamin C) uptake via its interaction with SLC23A2/SVCT2. Complex formation with APBA2 and APP, stabilizes APP metabolism and enhances APBA2-mediated suppression of beta-APP40 secretion, due to the retardation of intracellular APP maturation (By similarity).
Subcellular locations: Postsynaptic cell membrane, Endoplasmic reticulum membrane, Golgi apparatus membrane, Cell projection, Dendrite
Most prominent in the postsynaptic specializations of asymmetric (type I) synapses with both axodendritic and axospinous localization.