Redistribution of secretory granule components precedes that of synaptic vesicle proteins during differentiation of a neuronal cell line in serum-free medium

Incubation of the rat sensory neuron-derived cell line ND7 in serum-free medium results in the arrest of mitosis and the appearance of numerous neuronal processes. During this differentiation event, secretory granule components such as chromogranins, neuropeptide Y and the C-flanking peptide of pro-neuropeptide Y move to the tips of the majority of the neuronal processes regardless of process length. In contrast, the synaptic vesicle component, synaptophysin, is found only at the tips of the very long processes which appear following prolonged periods of culture in serum-free medium. A similar restriction of synaptophysin to long processes is also observed following differentiation and process formation induced by other treatments such as incubation in reduced serum or treatment with cyclic AMP or phorbol myristate acetate. Hence the regulated secretory pathway associated with the chromogranins and neuropeptides appears to be segregated into the processes at an earlier stage of ND7 differentiation than the synaptophysin-associated synaptic vesicle pathway. ND7 cells therefore provide a model system for studying the processes regulating these pathways and the redistribution of their components during neuronal differentiation.