Extracellular ATP

Extracellular ATP (adenosine triphosphate) is a key signaling molecule outside cells, distinct from its role as the primary intracellular energy currency. In the extracellular space, ATP acts as a potent messenger involved in diverse physiological and pathological processes, including neurotransmission, inflammation, immune responses, and cancer biology. It signals through P2X (ligand-gated ion channels) and P2Y (G-protein-coupled receptors) purinergic receptors. Extracellular ATP is rapidly degraded by ectonucleotidases into ADP, AMP, and adenosine, which also act on P1 receptors. Release occurs through vesicular exocytosis, channel-mediated release, and cell damage. It plays roles in neurotransmission, immune response, inflammation, and cancer biology.

Agonist of P2X and P2Y receptors; precursor to adenosine which acts on P1 receptors