Calcium sensors in regulated exocytosis.
Neurotransmitter release, hormone secretion and a variety of other secretory process are tightly regulated with exocytotic fusion of secretory vesicles being triggered by a rise in cytosolic Ca2+ concentration. A series of proteins that act as part of a conserved core machinery for vesicle docking and fusion throughout the cell have been identified. In regulated exocytosis this core machinery must be controlled by Ca(2+)-sensor proteins that allow rapid activation of the fusion process following elevation of cytosolic Ca2+ concentration. The properties of such Ca2+ sensors are known from physiological studies but their molecular identity remains to be unequivocally established. The multiple Ca(2+)-dependent steps in the exocytotic pathway suggest the likely involvement of several Ca(2+)-binding proteins with distinct properties. Functional evidence for the role of various Ca(2+)-binding proteins and their possible sites of action is accumulating but a definitive identification of the major Ca(2+)-sensor in the final step of Ca(2+)-triggered membrane fusion in different cell types awaits further analysis.
Burgoyne
R D
RD
Physiological Laboratory, University of Liverpool, UK. burgoyne@liverpool.ac.uk
Morgan
A
A
D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D011506:Proteins / Q000378:metabolism
D011506:Proteins; D002118:Calcium