P2X1

P2X1 is a subunit of the P2X receptor family, a class of ATP-gated cation channels. It is encoded by the P2RX1 gene in humans.

Each subunit has two transmembrane helices with a large extracellular loop that binds ATP. P2X receptors assemble as homo- or heterotrimeric channels; P2X1 commonly forms homomeric channels that gate Na+, K+, and Ca2+ when ATP binds.

P2X1 is highly expressed in platelets and vascular smooth muscle, and is also found in the urinary bladder and some neuronal populations. Activation by extracellular ATP leads to rapid Ca2+ influx and membrane depolarization, promoting platelet shape change and aggregation and triggering smooth muscle contraction.

Pharmacology of P2X1 includes inhibition by antagonists such as suramin and PPADS; more selective antagonists have been described, including NF449. P2X1 channels can desensitize with sustained ATP exposure, and they tend to show fast activation with relatively rapid desensitization compared with some other P2X subtypes.

Research and clinical relevance: P2X1 participates in purinergic signaling in cardiovascular and urinary systems and is a potential target for disorders involving platelet activation and smooth muscle function. It is also studied for possible roles in pain signaling and inflammatory responses.