Analysis of SNARE-Mediated Exocytosis Using a Cell Fusion Assay

Exocytosis is the fusion of transport vesicles with the plasma membrane. By exocytosis, eukaryotic cells secrete soluble proteins and endogenous chemicals to the extracellular space, and deliver new membrane proteins and lipids to the plasma membrane. A large body of work has demonstrated that the interactions of SNARE (soluble N-ethylmaleimidesensitive factor attachment protein receptor) proteins on vesicles (v-SNAREs) and on target membranes (t-SNAREs) catalyze intracellular vesicle fusion events, including exocytosis (Bonifacino and Glick, 2004; Jahn et al., 2003; Rothman, 1994) (Fig. 1). The vesicle-associated membrane proteins (VAMPs), i.e., VAMPs 1, 2, 3, 4, 5, 7 and 8, are v-SNAREs that reside in various post-Golgi vesicular compartments, and have been implicated in exocytosis. In this chapter, we review recent progress of using a novel cell fusion assay to analyze the specificity and membrane fusion activities of VAMPs (Hasan et al., 2010).