Inositol 1,4,5-trisphosphate signaling pathway (IP3 signaling pathway)

The Inositol 1,4,5-trisphosphate (IP3) signaling pathway is a fundamental intracellular mechanism that translates extracellular signals into calcium-mediated cellular responses (Berridge, 1993). It begins when ligands bind to G protein-coupled receptors or receptor tyrosine kinases, activating phospholipase C to cleave PIP2 into IP3 and diacylglycerol (Alzayady et al., 2016). IP3 acts as a second messenger, diffusing to the endoplasmic reticulum where it binds to IP3 receptors to release stored calcium into the cytosol (StatPearls, 2023). This rise in calcium regulates diverse functions such as neurotransmission, gene expression, and muscle contraction (Berridge, 2016). Dysregulation of this pathway is a hallmark of several conditions, including bipolar disorder, cardiac hypertrophy, and neurodegenerative diseases like Alzheimer's (Berridge, 2016). While the pathway itself is a complex network rather than a single protein, its components like IP3 receptors and PLC enzymes are major areas of pharmacological interest. Drugs such as lithium modulate this pathway by inhibiting inositol recycling, though the widespread nature of calcium signaling poses significant challenges for achieving therapeutic specificity (PubMed, 2022).

Other names

Phosphoinositide signaling pathwayPLC-IP3-DAG pathwayIP3/Ca2+ signaling pathwayPhosphatidylinositol signaling system

The pathway is initiated by the activation of phospholipase C (PLC), which hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 then binds to IP3 receptors (IP3Rs) on the endoplasmic reticulum, triggering the release of sequestered calcium ions into the cytoplasm to activate downstream signaling effectors (Berridge, 1993; StatPearls, 2023).