P2X4 Receptors in Immunity and Inflammation

The P2X4 receptor is an ATP-gated cation channel that is widely expressed in cells of the immune system. It is able to form heterotrimers by combining with P2X2, P2X5, and/or P2X6. Signal transduction is accompanied by fast influx of Ca2+ and Na+ and efflux of K+. This receptor differs from other members of the P2X family since it is one of the most sensitive purinergic receptors (at nanomolar ATP concentrations), about 1,000 times more than the archetypal P2X7. In the immune system, this receptor has been implicated in the processing and release of cytokines as well as in the modulation of several immune cell activities.