Calcium microdomains: Organization and function

Microdomains of Ca2+, which are formed at sites where Ca2+ enters the cytoplasm either at the cell surface or at the internal stores, are a key element of Ca2+ signalling. The term microdomain includes the elementary events that are the basic building blocks of Ca2+ signals. As Ca2+ enters the cytoplasm, it produces a local plume of Ca2+ that has been given different names (sparks, puffs, sparklets and syntillas). These elementary events can combine to produce larger microdomains. The significance of these localized domains of Ca2+ is that they can regulate specific cellular processes in different regions of the cell. Such microdomains are particularly evident in neurons where both pre- and postsynaptic events are controlled by highly localized pulses of Ca2+. The ability of single neurons to process enormous amounts of information depends upon such miniaturization of the Ca2+ signalling system. Control of cardiac cell contraction and gene transcription provides another example of how the parallel processing of Ca2+ signalling can occur through microdomains of intracellular Ca2+.