Principles of the Ca2+ Homeostatic/Signalling System

Calcium ions are the most ubiquitous and pluripotent signalling molecules, which regulate a wide array of physiological and pathological reactions. The specific system, controlling cellular Ca²⁺ homeostasis appeared very early in the evolution, being initially survival system preventing Ca²⁺ -mediated cell damage. Subsequently, the steep Ca²⁺ gradients maintained by Ca²⁺ homeostatic molecular cascades became the basis for Ca²⁺ signalling. This signalling system utilises Ca²⁺ channels and transporters localised in plasmalemma and intracellular membranes to create highly organised and compartmentalised cytosolic Ca²⁺ fluctuations occurring within the spatial and temporal domains. Changes in cytosolic Ca²⁺ concentrations regulate a multitude of Ca²⁺ -dependent proteins, which serve as “Ca²⁺ sensors” and thus the effectors of Ca²⁺ signalling system.