Calcium Signaling
Ca²⁺ as a universal second messenger controlling diverse cellular processes.
Overview
Intracellular Ca²⁺ concentration is maintained at ~100 nM versus ~1.5 mM extracellular by Ca²⁺-ATPases (SERCA, PMCA) and Na⁺/Ca²⁺ exchangers. Signaling occurs when Ca²⁺ is released from ER stores (via IP3R or RyR) or enters through plasma membrane channels (VGCC, CRAC, TRP). Ca²⁺ binds calmodulin, which activates CaMK kinases, calcineurin, and other effectors. Temporal patterns (oscillations, waves) encode signal specificity.
Cellular Location
Cytoplasm, ER, mitochondria
Clinical Significance
Controls muscle contraction, neurotransmitter release, gene expression, and cell death; calcineurin inhibitors (cyclosporine, tacrolimus) used in transplantation.
Key Molecules
Key Enzymes
Related Pathways
G Protein-Coupled Receptor (GPCR) Signaling
Seven-transmembrane receptors activating heterotrimeric G proteins.
Ion Channel Signaling
Selective ion flux through membrane channels driving electrical and chemical signals.
Synaptic Transmission
Chemical neurotransmission across synaptic clefts between neurons.