The movement of proteins and lipids from one intracellular compartment to another is carried out by a well-orchestrated process of transport vesicle formation, vesicle docking with a target compartment, and finally vesicle-target membrane fusion. The proteins that catalyze membrane fusion are termed SNAREs. In the brain, synaptic vesicle/presynaptic plasma membrane fusion requires the formation of a ternary SNARE complex composed of one member of the VAMP-family on synaptic secretory granules and one member of the Syntaxin family together with SNAP-25 on the pre-synaptic membrane proteins. SNARE complexes regulate fusion in all eukaryotic cells, including yeast, however there was one key to the SNARE hypothesis that was missing: SNAP-25 is only expressed in neurons and it was assumed there were SNAP-25 homolog(s) that served the role of SNAP-25 in SNARE complex assembly and membrane fusion in non-neuronal cells. My lab discovered this missing link, which we named SNAP-23, and over the years both in my lab and in collaborations we have shown that SNAP-23 is a key modulator of regulated exocytosis (and other membrane-membrane fusion events) in mast cells, platelets, neurons, epithelial cells, and endothelial cells. We have generated a conditional knock-out of the SNAP-23 gene using Cre/lox technology and found the deletion of SNAP-23 in any given cell type leads to the death of those cells. By transiently deleting SNAP-23 in fibroblasts we have found that SNAP-23 deletion leads to rapid cell death, demonstrating an essential role for SNAP-23 in regulating cell survival. Some of our published major accomplishments in the field of regulated exocytosis are: -SNAP-23 controls exocytosis in a diverse array of secretory cells. Together with collaborators in a variety of fields we have shown that SNAP-23 is an essential regulator of a variety of membrane membrane fusion events. We have shown that SNAP-23 de-phosphorylation, presumably by protein phosphatase 2B, regulates secretion of von Willebrand factor from endothelial cells. We also found perturbation of SNAP-23 suppresses Rab5a-dependent homotypic secretory granule fusion during compound exocytosis, revealing a novel mechanism of SNAP-23 regulation of exocytosis in mast cells.
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