Abstract
The receptor-evoked Ca(2+) signal in secretory epithelia mediate many cellular functions essential for cell survival and their most fundamental functions of secretory granules exocytosis and fluid and electrolyte secretion. Ca(2+) influx is a key component of the receptor-evoked Ca(2+) signal in secretory cell and is mediated by both TRPC and the STIM1-activated Orai1 channels that mediates the Ca(2+) release-activated current (CRAC) I(crac). The core components of the receptor-evoked Ca(2+) signal are assembled at the ER/PM junctions where exchange of materials between the plasma membrane and internal organelles take place, including transfer of lipids and Ca(2+). The Ca(2+) signal generated at the confined space of the ER/PM junctions is necessary for activation of the Ca(2+)-regulated proteins and ion channels that mediate exocytosis with high fidelity and tight control. In this review we discuss the general properties of Ca(2+) signaling, PI(4,5)P(2) and other lipids at the ER/PM junctions with regard to secretory cells function and disease caused by uncontrolled Ca(2+) influx.