Regulated exocytosis in immune function: are SNARE-proteins involved?

Inflammation is an important feature in the pathogenesis of most chronic lung diseases. It is characterized by tissue infiltration with various inflammatory cells, including eosinophils, mast cells, basophils, macrophages, neutrophils, T- and B-lymphocytes and dendritic cells (1). In the tissue granulocytes release their toxic granule proteins after being stimulated by soluble mediators released by other inflammatory cells (2). Therefore, it is important to characterize the intracellular mechanisms regulating the transport of the granule contents in inflammatory cells. Intracellular vesicle-traffic in mammalian cells is mediated by transport vesicles that emerge from donor compartments and are specifically targeted to acceptor compartments where they deliver their contents after membrane fusion (3). This traffic leads to three types of fusion: vesicle-intracellular membranes, vesicle-vesicle or vesicle-plasma membrane. The process leading to fusion of vesicle-plasma membrane is called exocytosis, and it delivers proteins to the cell surface (receptors e.g. CD11b, CD18) and exports soluble molecules (mediators e.g. ECP) from the cell. A number of key proteins involved in regulated exocytosis have been identified from inflammatory cells. This review is a brief summary of these proteins and it includes recent results from studies on regulated exocytosis in inflammatory cells.