The secret life of calcium in cell signaling

The concentration of Ca2+ ions inside the cytosol is about the same as outside (1–2 mM). But nearly all of it is buffered such that the free cytosolic concentration is some 10,000-fold lower at ~100 nM. This steep gradient of Ca2+ across the plasma membrane (and organellar Ca2+ stores) is tapped into during cell stimulation when the cytosolic concentration of Ca2+ rapidly rises, entraining a series of events that ultimately influence cell function. What is quite remarkable is the diversity of the stimuli that use Ca2+. These include electrical activity and numerous neurotransmitters and hormones. Equally diverse are the downstream Ca2+-dependent events such Calcium is an abundant alkaline earth metal. In the body, it is found as calcium ions (Ca2+), and most of it is deposited in hard tissues such as bones and teeth. But less well known is the role of Ca2+ as a messenger within cells. Here, I provide an overview of this hidden but critical function of Ca2+.