High-affinity agonism at the P2X7 receptor is mediated by three residues outside the orthosteric pocket
Adam Oken, Nicolas E. Lisi, Ipsita Krishnamurthy, Alanna E. McCarthy, Michael Godsey, Arthur Glasfeld, Steven Mansoor
Abstract
P2X receptors are trimeric ATP-gated ion channels that activate diverse signaling cascades. Due to its role in apoptotic pathways, selective activation of P2X7 is a potential experimental tool and therapeutic approach in cancer biology. However, mechanisms of high-affinity P2X7 activation have not been defined. We report high-resolution cryo-EM structures of wild-type rat P2X7 bound to the high-affinity agonist BzATP as well as significantly improved apo receptor structures in the presence and absence of sodium. Apo structures define molecular details of pore architecture and reveal how a partially hydrated Na+ ion interacts with the conductance pathway in the closed state. Structural, electrophysiological, and direct binding data of BzATP reveal that three residues just outside the orthosteric ATP-binding site are responsible for its high-affinity agonism. This work provides insights into high-affinity agonism for any P2X receptor and lays the groundwork for development of subtype-specific agonists applicable to cancer therapeutics. The P2X7 receptor is an ATP-gated ion channel that mediates inflammasome activation. Here, authors report the structure of P2X7 bound to high-affinity agonist, BzATP, providing a framework to develop small molecules applicable to cancer biology.