Porosome
Porosomes vary in size depending on the cell type. Porosome in the exocrine pancreas and in endocrine and neuroendocrine cells range from 100 nm to 180 nm in diameter while in neurons they range from 10 nm to 15 nm (about 1/10 the size of pancreatic porosomes). When a secretory vesicle containing v-SNARE docks at the porosome base containing t-SNARE, membrane continuity (ring complex) is formed between the two. The size of the t/v-SNARE complex is directly proportional to the size of the vesicle. These vesicles contain dehydrated proteins (non-active) which are activated once  they are hydrated. GTP is required for the transport of water through the water channels or Aquaporins, and ions through ion channels to hydrate the vesicle. Once the vesicle fuses at the porosome base, the contents of the vesicle at high pressure are ejected from the cell. Generally the porosomes are opened and closed by actin, however, neurons require a fast response therefore they have central plugs that open to release contents and close to stop the release (the composition of the central plug is yet to be discovered). Porosomes have been demonstrated to be the universal secretory machinery in  cells. The neuronal porosome proteome has been solved, providing the possible molecular architecture and the complete composition of the machinery. History of discovery. The porosome was discovered in the early to mid-1990s by a team led by Professor Bhanu Pratap Jena at Yale University School of Medicine, using atomic force microscopy.