Evolution of calcium homeostasis: From birth of the first cell to an omnipresent signalling system

Specific Ca2+ homeostatic system appeared very early in the history of the cell, as a survival system preventing Ca2+-mediated cell damage. This homeostatic system produced a steep (similar to 20,000 times) concentration gradient between extracellular and intracellular compartments, which has both survival importance (even relatively short increases in cytosolic Ca2+ concentrations higher then 100 nM are incompatible with life) and signalling function. Evolution utilised this gradient together with an ability of Ca2+ to interact with many biological molecules to create the most widespread and versatile signalling system, controlling the majority of cellular processes and executing complex routines of intercellular communications. (c) 2007 Elsevier Ltd. All rights reserved.