May be involved in the regulation of neurotransmitter release and synaptogenesis. Interacts with CAPON. Peripheral membrane protein localized to the cytoplasmic surface of synaptic vesicles. Neuron specific. Detected predominantly in brain. The A region binds phospholipids with a preference for negatively charged species. Phosphorylation at Ser-9 dissociates synapsins from synaptic vesicles. Regulated by calcium. Calcium inhibits ATP binding to the C-domain. Belongs to the synapsin family.