Scinderin and cortical F-actin are components of the secretory machinery

Secretory vesicle exocytosis is the mechanism of release of neurotransmitte rs and neuropeptides. Secretory vesicles are localized in at least two morp hologically and functionally distinct compartments: the reserve pool and th e release-ready pool. Filamentous actin networks play an important role in this compartmentalization and in the trafficking of vesicles between these compartments. The cortical F-actin network constitutes a barrier (negative clamp) to the movement of secretory vesicles to release sites, and it must be locally disassembled to allow translocation of secretory vesicles in pre paration for exocytosis. The disassembly of the cortical F-actin network is controlled by scinderin (a Ca2+-dependent F-actin severing protein) upon a ctivation by Ca2+ entering the cells during stimulation. There are several factors that regulate scinderin activation (i.e., Ca2+ levels, phosphatidyl inositol 4,5-bisphosphate (PIP2), etc.). The results suggest that scinderin and the cortical F-actin network are components of the secretory machinery .