P2X2 receptor subunit interfaces are missense variant hotspots, where mutations tend to increase apparent ATP...

Area of Science:

• Ion channel biophysics
• Molecular genetics
• Human population genetics

Background:

• P2X receptors are trimeric ligand-gated ion channels crucial for physiological functions like nociception and hearing.
• While P2X receptor structure is known, human genetic variations and their functional impact remain understudied.
• Seven P2X subtypes exist, forming homo- or heterotrimeric complexes.

Purpose of the Study:

• To investigate the impact of P2X2 receptor inter-subunit missense variants on channel function.
• To analyze variants found in the human population and those predicted by structural models.
• To explore the functional consequences of single and double mutations at subunit interfaces.

Main Methods:

• Electrophysiological recordings to assess channel activity.
• Biochemical assays to evaluate protein interactions and stability.
• Analysis of human population genetic data and structural predictions.

Main Results:

• Extracellular inter-subunit interfaces of P2X2 receptors exhibit a high density of missense variations.
• Mutations disrupting inter-subunit interactions often lead to increased apparent ATP affinity.
• Double mutants at subunit interfaces demonstrate significant energetic coupling, especially when in close proximity.

Conclusions:

• This study provides the first structural map of human population-wide mutations in a ligand-gated ion channel.
• Mutation distribution suggests evolutionary selection acting at the protein domain level.
• P2X2 receptors may possess an intrinsically high activation threshold for modulation or protection against overstimulation.