Compartmentalized signalling: Ca2+ compartments, microdomains and the many facets of Ca2+ signalling

Ca2+ regulates a multitude of cellular processes and does so by partitioning its actions in space and time. In this review, we discuss how Ca2+ responses are constructed from small quantal (elementary) events that have the potential to propagate to produce large pan-cellular responses. We review how Ca2+ is compartmentalized both physically and functionally, and describe how each organelle has its own distinct Ca2+-handling properties. We explain how coordination of the movement of Ca2+ between organelles is used to shape and hone Ca2+ signals. Finally, we provide a number of specific examples of where compartmentation and localization of Ca2+ are crucial to cell function.