Abstract
Calcium (Ca(2+)) and cyclic AMP (cAMP) signaling cross talk and synergize to stimulate the cardinal functions of exocrine cells, regulated exocytosis, and fluid and electrolyte secretion. This physiological process requires the organization of the two signaling pathways into complexes at defined cellular domains and close placement. Such domains are formed by membrane contact sites (MCS). This review discusses the basic properties of Ca(2+) signaling in exocrine cells, the role of MCS in the organization of cell signaling and in cross talk and synergism between the Ca(2+) and cAMP signaling pathways and, finally, the mechanism by which the Ca(2+) and cAMP pathways synergize to stimulate epithelial fluid and electrolyte secretion.