Cytosolic and intra-organellar Ca2+ oscillations: mechanisms and function

A rise in cytosolic Ca2+ concentration is a universal signalling mechanism that regulates myriad physiological responses including exocytosis, contraction, cell growth and cell death. Cytosolic Ca2+ signals often occur in the form of repetitive Ca2+ transients, or oscillations, particularly following activation of G-protein-coupled receptors that engage the phospholipase C pathway. Ca oscillations have also been seen within organelles including mitochondria and the nucleus. It is well established that signalling information is contained within the amplitude and frequency of the Ca2+ oscillations but recent studies reveal that the spatial profile of the Ca2+ transients is also used to selectively activate downstream responses.