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Quantifying Agonist Activity at G Protein-coupled Receptors
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Quantifying Agonist Activity at G Protein-coupled Receptors

Published on: December 26, 2011

A simple method for quantifying functional selectivity and agonist bias

Terry Kenakin1, Christian Watson, Vanessa Muniz-Medina

  • 1Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA. Kenakin@email.unc.edu

ACS Chemical Neuroscience
|August 4, 2012
PubMed

Insights

New methods quantify biased agonism for seven-transmembrane (7TM) receptors, addressing cell-type variability in drug discovery. This approach aids in optimizing drug candidates by evaluating receptor activation and signaling pathway bias.

Area of Science:

  • Pharmacology and Drug Discovery
  • Molecular and Cellular Biology
  • Biochemistry

Background:

  • Seven-transmembrane (7TM) receptors exhibit functional selectivity, where agonists activate specific signaling pathways, leading to biased responses.
  • Cell type-dependent variability in agonist responses complicates drug profiling and medicinal chemistry efforts for targeted therapies.
  • Understanding and quantifying agonist bias is crucial for developing effective therapeutics that leverage specific receptor signaling.

Purpose of the Study:

  • To develop a quantitative scale based on the Black and Leff operational model to describe 7TM receptor agonism.
  • To introduce a 'transduction coefficient' (log(τ/K(A))) for statistically evaluating selective agonist effects and guiding drug discovery.
  • To address the challenge of cell type dependence in agonist profiling for therapeutic applications.

Main Methods:

  • Utilized the Black and Leff operational model to define a scale incorporating receptor affinity (K(A) (-1)) and signaling pathway efficacy (τ).
  • Introduced and applied a 'transduction coefficient' (log(τ/K(A))) to quantify agonist bias.
  • Quantified the bias of four chemokines for CCR5-mediated inositol phosphate production versus internalization.

Main Results:

  • Developed a statistically robust scale for evaluating 7TM receptor agonism and functional selectivity.
  • Demonstrated the practical application of the 'transduction coefficient' in quantifying chemokine bias for CCR5.
  • Confirmed the method's independence from receptor density and discussed statistical confidence estimates.

Conclusions:

  • The proposed scale and transduction coefficient provide a valuable tool for assessing agonist bias in a manner that can inform structure-activity relationship studies.
  • This quantitative approach aids in the selection and optimization of drug candidates by characterizing their specific signaling profiles.
  • The method offers a statistically sound framework for understanding and exploiting functional selectivity in drug development.
Keywords:
Biased agonismdrug discoveryfunctional selectivityreceptor methodsreceptor theorystimulus bias

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