High-affinity agonism at the P2X₇ receptor is mediated by three residues outside the orthosteric pocket

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• P2X receptors are ATP-gated ion channels regulating cellular signaling.
• P2X7 receptor activation is implicated in cancer biology via apoptotic pathways.
• Understanding P2X7 high-affinity activation mechanisms is critical for therapeutic development.

Purpose of the Study:

• To elucidate the structural mechanisms underlying high-affinity activation of the P2X7 receptor.
• To define the molecular details of the P2X7 receptor's pore architecture in its closed state.
• To identify specific residues responsible for high-affinity agonism by BzATP.

Main Methods:

• High-resolution cryo-electron microscopy (cryo-EM) to determine receptor structures.
• Electrophysiological recordings to assess receptor function.
• Direct binding assays to quantify agonist interactions.

Main Results:

• Determined cryo-EM structures of wild-type rat P2X7 with BzATP and apo states.
• Revealed molecular details of pore architecture and Na+ ion interaction in the closed state.
• Identified three specific residues outside the ATP-binding site crucial for BzATP's high-affinity agonism.

Conclusions:

• The study provides atomic-level insights into P2X7 receptor activation by high-affinity agonists.
• Structural and functional data pave the way for developing subtype-specific P2X7 agonists.
• These findings support the potential of P2X7 receptor modulation in cancer therapeutics.