POROSOMES: CURRENT CONCEPTS OF THE MECHANISM OF EXOCYTOSIS

Secretion is a basic process in all cells and is involved in important functions such as the release of hormones from endocrine and neuroendocrine cells, in neurotransmission, the release of digestive enzymes and acid secretion, etc, having an important role in the physiology of many metabolic processes of tissues and organs. Contrary to an accepted belief of more than 60 years that the final step in the process of secretion is the total incorporation of secretory granule membrane into the cell plasma membrane for the delivery of secretory product to the outside of the cell, studies made in the last 25 years demonstrated a completely different molecular mechanism of secretion, this being a highly regulated process. Discovery of a new cellular structure, the "porosome", in principal with the aid of atomic force microscopy (AFM) and transmission electron microscopy (TEM), and the discovery of SNARE (Soluble NSF Attachment Protein REceptor) and SNAREs-induced membrane fusion, and the regulated expulsion of secretory product via secretory vesicle swelling with Aquaporin 1 (AQ1) and Ca2+ implicated, has finally provided us with an understanding of cell secretion at the molecular level. The current study was undertaken to present this new concept regarding the cellular process of secretion, using original illustration of our researches.