PIP₂regulates the ionic current of P2X receptors and P2X ₇ receptor-mediated cell death

P2X₇ receptors are non-selective cation channels gated by extracellular ATP. Prolonged stimulation of the P2X₇ receptor leads to an increase in cell permeability, cytokine release and apoptosis/necrosis. Application of PIP₂ to inside-out patches strongly activated all homomeric members of the P2X receptor family, including P2X₇ channels. Blockade of PIP₂ re-synthesis or induction of PIP ₂ hydrolysis diminished ATP-gated P2X₇ currents. Several positively charged residues in the proximal C-terminus of P2X₇ were found to be important for PIP₂ interactions, as mutation of these sites reduced the apparent affinity for PIP₂ and enhanced current inhibition by PIP₂ depletion. In addition, we demonstrated the dependence of ATP-mediated cell death on P2X₇ receptor interaction with PIP₂ in three different cell systems: HEK cells stably transfected with P2X₇, primary T cells and a macrophage cell line. These results identify PIP₂ as a critical regulator of the function of the extracellular ligand-gated P2X receptor/channels and provide a novel way to control ATP-mediated cell death.