Calciummediated

Calciummediated refers to biological processes that depend on calcium ions (Ca2+) acting as intracellular second messengers. In these processes, transient increases in cytosolic free Ca2+ concentration—from basal nanomolar levels to micromolar peaks—trigger rapid responses and can influence longer-term cellular changes. Calcium signaling is highly versatile and occurs in virtually all cell types.

Calcium signals arise from release of Ca2+ from internal stores (primarily the endoplasmic or sarcoplasmic reticulum via IP3 receptors and ryanodine receptors) and from Ca2+ entry across the plasma membrane through channels such as voltage-gated calcium channels, receptor-operated channels, and store-operated calcium entry mediated by STIM and Orai proteins. Calcium is buffered and concentrated within microdomains by calcium-binding proteins (for example calmodulin, calbindin, and parvalbumin) and then taken up by organelles like mitochondria and re-sequestered by pumps such as SERCA in the ER/SR membrane and MCU in mitochondria. Plasma membrane pumps and exchangers (PMCA and NCX) work to restore basal Ca2+ levels after signaling events.

Calcium exerts its effects through a cadre of calcium-binding proteins and calcium-dependent enzymes. Calmodulin is a key sensor that activates a family of kinases (CaMKs) and the phosphatase calcineurin; classical protein kinase C and other effectors also respond to Ca2+. The downstream outcomes include exocytosis (for neurotransmitters and hormones), muscle contraction, enzyme activity modulation, and regulation of gene expression via signaling pathways such as NFAT and CREB.

Precise control of calcium signaling is essential, and disruptions can contribute to disease. Aberrant Ca2+ signaling is linked to cardiac arrhythmias, neurodegenerative disorders, and metabolic dysfunction. Research tools such as calcium-sensitive fluorescent indicators are used to study calciummediated processes.