P2X: The ionotropic receptor for extracellular ATP

Studies made during the past four years have reported the cDNA cloning of P2X receptors and their electrophysiologic evaluation. More recently, mutagenesis and protein biochemistry approaches have begun to assign functions to specific regions in these proteins. These functions include the agonist and antagonist binding profiles of different P2X receptors and their ability to form nonselective cationic channels. The work has also shed light on how the physiologic ligand for P2X receptors, extracellular ATP, can have effects in both the nervous and immune systems. One member of the P2X receptor family, i.e., P2X(7), is selectively expressed in the immune system. This receptor is a bifunctional molecule, generating both a cationic channel and a macromolecular pore, whose activation can result in permeabilization of the cell. Drug Dev. Res. 45:125-129, 1998. (C) 1998 Wiley-Liss, Inc.