Subtype-Specific Ligand Binding and Activation Gating in Homomeric and Heteromeric P2X Receptors

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• P2X receptors are ATP-gated cation channels crucial for sensory signaling, inflammation, and pain.
• Understanding P2X receptor activation mechanisms, including ligand binding and conformational changes, is vital.
• Magnesium ions (Mg2+) modulate ATP-induced P2X receptor activity.

Purpose of the Study:

• To investigate subtype-specific ligand potency and efficacy on human P2X2, P2X3, and P2X2/3 receptors using novel fluorescent ATP derivatives.
• To explore the relationship between ligand binding and activation gating in P2X receptors under varying Mg2+ concentrations.
• To assess the utility of fluorescent ATP derivatives (fATP and α,βMe-fATP) as tools for studying P2X receptor function.

Main Methods:

• Utilized two novel fluorescently labelled ATP derivatives: 2-[DY-547P1]-AHT-ATP (fATP) and 2-[DY-547P1]-AHT-α,βMe-ATP (α,βMe-fATP).
• Examined ligand potency and efficacy on human P2X2, P2X3, and P2X2/3 receptors.
• Investigated the influence of Mg2+ concentration on P2X receptor activation and ligand binding.

Main Results:

• Demonstrated subtype-specific patterns of ligand potency and efficacy across P2X2, P2X3, and P2X2/3 receptors.
• Observed Mg2+-dependent reduction in P2X2 receptor activation with robust binding, while P2X3 receptors showed decreased activation and increased binding at high Mg2+.
• The P2X2/3 heteromer exhibited a hybrid Mg2+ effect, distinct from homomeric receptors.

Conclusions:

• Novel fluorescent ATP derivatives are effective tools for dissecting P2X receptor mechanisms.
• Mg2+ significantly and differentially modulates P2X receptor subtype activation and binding, impacting ligand-receptor interactions.
• Findings advance the understanding of P2X receptor function in sensory signaling, inflammation, and pain pathways.