Neuronal phosphoprotein that coats synaptic vesicles, and binds to the cytoskeleton. Acts as a regulator of synaptic vesicles trafficking, involved in the control of neurotransmitter release at the pre-synaptic terminal. Also involved in the regulation of axon outgrowth and synaptogenesis. The complex formed with NOS1 and CAPON proteins is necessary for specific nitric-oxide functions at a presynaptic level 