Exocytosis: the role of Ca2+, GTP and ATP as regulators and modulators in the rat mast cell model.

Cells and tissues release preformed materials contained in secretory granules into the extracellular environment by the mechanism of exocytosis which involves selective fusion of perigranular membranes with the plasma membrane. While the mechanism is believed to be shared between all cells that undergo exocytotic secretion, the molecular details of the interaction between the two fusing membranes are far from being understood. Recent advances have been based on the technique of membrane permeabilization which allows the composition of the cytosol to be precisely controlled. A role for a previously unsuspected GTP-binding protein (GE) in the regulation of the terminal steps of exocytosis has thereby been revealed. Among mammalian secretory cells, the mast cell has proved to be particularly amenable for investigations in this area.