calciumflux

Calcium flux refers to the movement of calcium ions (Ca2+) across cellular membranes or within cells, producing changes in intracellular calcium concentration. Ca2+ is a universal second messenger involved in many physiological processes, including muscle contraction, neurotransmitter release, enzyme activity, and gene regulation. The dynamics of calcium flux are tightly regulated to maintain low resting cytosolic Ca2+ levels (about 100 nM) while enabling rapid, localized elevations when signaling is required.

Influx and efflux across the plasma membrane are mediated by diverse channels and transporters. Calcium can enter the cell through voltage-gated calcium channels, ligand-gated channels, receptor-operated channels, and store-operated calcium entry, which is activated when endoplasmic reticulum Ca2+ stores are depleted. Ca2+ is extruded from the cell mainly by plasma membrane Ca2+-ATPases (PMCA) and the sodium/calcium exchanger (NCX). Intracellular calcium stores release Ca2+ through IP3 receptors and ryanodine receptors on the endoplasmic reticulum, while mitochondria can take up Ca2+ via the mitochondrial calcium uniporter (MCU), shaping local signaling microdomains.

Calcium flux is buffered by calcium-binding proteins and buffered reservoirs, ensuring precise signaling. Dysregulation of Ca2+ flux is implicated in various conditions, including cardiac arrhythmias, neurodegenerative diseases, and certain cancers. Researchers measure flux using calcium-sensitive fluorescent indicators and imaging, electrophysiological approaches, or biochemical assays to quantify changes in Ca2+ concentrations over time.

In summary, calcium flux describes controlled movements of Ca2+ that translate electrical or chemical stimuli into diverse cellular responses.