Add to ORKG[First paragraph] In eukaryotic cells, variations in the levels of cytosolic free calcium regulate processes as important and disparate as chemotaxis, chromosome segregation, fertilization, ion transport, muscle contraction, passage through cell cycle transition points, proteolysis, secretion, and substrate uptake (7). Cytosolic free calcium concentration is tightly controlled by the action of specific pumps and channels in the plasma membrane and subcellular organelles (8, 83). Response to increased cytosolic free calcium concentration is mediated by either direct binding to calcium-sensitive enzymes, such as protein kinase C (49) and calpain (72), or activation of a protein transducer, such as calmodulin (15)