OCCURRENCE OF 2 TYPES OF SECRETORY VESICLES IN THE HUMAN NEUROBLASTOMA SH-SY5Y

Western blot analysis showed that the human neuroblastoma SH-SY5Y expr esses the proteins synaptotagmin I, synaptobrevin, synapsin I, rab3a, syntaxin, SNAP-25, NSF, alpha-SNAP, and munc-18, which have been impli cated in the movement, docking, and fusion of vesicles during exocytos is from other neuroendocrine cells, The subcellular localization of se cretogranins I and II, synaptotagmin I, neuropeptide Y, rab3a, synapto brevin, synaptophysin, and syntaxin was investigated by immunofluoresc ence microscopy and revealed punctate staining patterns characteristic of secretory vesicles. The comigration of noradrenaline, secretograni n II, and dopamine-beta-hydroxylase on sucrose-D2O gradient fractions indicates the presence of a population of noradrenaline-containing lar ge dense-cored vesicles (LDCVs). In addition, a lighter vesicle popula tion is also present that does not appear to be noradrenergic and cont ains a 48-kDa synaptophysin antigen absent from the large dense-cored vesicles. Immunocytochemical experiments show that not all of the vesi cles that express synaptotagmin I contain secretogranin II. Thus, our studies suggest that two types of vesicle are present in SH-SY5Y cells , one of which, the LDCVs, contains noradrenaline. These findings conf irm our previous studies suggesting that depolarization-evoked release of noradrenaline from SH-SY5Y occurs by LDCV exocytosis. This enhance s the value of SH-SY5Y as a cell line in which to study the mechanism by which noradrenaline release is regulated.