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Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels
16:36

Proteomics to Identify Proteins Interacting with P2X2 Ligand-Gated Cation Channels

Published on: May 18, 2009

Kinetics of antagonist actions at rat P2X2/3 heteromeric receptors

Valeria Spelta1, Lin-Hua Jiang, Annmarie Surprenant

  • 1Institute of Molecular Physiology, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK.

British Journal of Pharmacology
|March 22, 2002
PubMed

Insights

This study investigated the binding kinetics of three antagonists—TNP-ATP, suramin, and PPADS—to heteromeric P2X(2/3) receptors. PPADS demonstrated the slowest association and dissociation rates, indicating unique interactions with these receptors.

Area of Science:

  • Pharmacology
  • Molecular Biology
  • Neuroscience

Background:

  • P2X receptors are ligand-gated ion channels involved in various physiological processes.
  • Heteromeric P2X(2/3) receptors play a role in pain signaling and neurotransmission.
  • Understanding receptor-ligand interactions is crucial for developing targeted therapeutics.

Purpose of the Study:

  • To characterize the binding kinetics of three antagonists (TNP-ATP, suramin, PPADS) on heteromeric P2X(2/3) receptors.
  • To determine the association and dissociation rate constants for these antagonists.
  • To elucidate the mechanisms underlying the affinity of these compounds for the P2X(2/3) receptor.

Main Methods:

  • Human embryonic kidney cells expressing P2X(2) and P2X(3) subunits were utilized.
  • alpha,beta-methylene-ATP was used as the agonist at concentrations ≤30 microM.
  • Antagonist-agonist interaction kinetics were measured by varying pre-application and co-application times.

Main Results:

  • TNP-ATP exhibited high affinity (K(D) ≈ 2 nM) due to rapid binding (k(+1) ≈ 100 μM⁻¹s⁻¹).
  • Suramin (K(D) ≈ 1 μM) showed a 100-fold slower association rate than TNP-ATP but similar dissociation.
  • PPADS (K(D) ≈ 0.1 μM) displayed significantly slower association and dissociation kinetics compared to TNP-ATP and suramin.

Conclusions:

  • The binding kinetics of TNP-ATP, suramin, and PPADS to P2X(2/3) receptors differ significantly.
  • PPADS exhibits unique slow binding and unbinding characteristics, suggesting distinct interaction modes.
  • These findings provide valuable insights into P2X(2/3) receptor pharmacology and potential drug development.

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