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Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding
10:13

Measuring G-protein-coupled Receptor Signaling via Radio-labeled GTP Binding

Published on: June 9, 2017

Antagonists show GTP-sensitive high-affinity binding to the sigma-1 receptor.

J M Brimson1, C A Brown, S T Safrany

  • 1Department of Pharmacy and Pharmacology, University of Bath, Bath, UK.

British Journal of Pharmacology
|April 14, 2011
PubMed
Summary

Sigma-1 receptor antagonists bind to high- and low-affinity states, unlike agonists. Functional responses require binding to an unidentified low-affinity target, suggesting a revised understanding of sigma-1 receptor activity.

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Area of Science:

  • Pharmacology
  • Cell Biology
  • Neuroscience

Background:

  • Sigma-1 receptors possess atypical characteristics, including potentially two transmembrane domains.
  • Antagonists typically require higher doses than their affinities suggest for biological effects.

Purpose of the Study:

  • To reassess the binding characteristics of sigma-1 receptor ligands.
  • To investigate the distinct binding states of sigma-1 receptor antagonists and agonists.
  • To explore the relationship between ligand binding and functional responses.

Main Methods:

  • Radioligand saturation and competition binding assays using [³H]-(+)-pentazocine.
  • Assessment of metabolic activity via MTS assay.
  • Analysis of calcium signaling using Fura-2 dye.

Main Results:

  • Sigma-1 receptor antagonists exhibit GTP- and suramin-sensitive high-affinity binding, distinct from agonists.
  • Functional responses, including calcium signaling and metabolic activity, are linked to sigma-1 receptor binding.
  • These functional responses necessitate binding to an unidentified, low-affinity target.

Conclusions:

  • Sigma-1 receptors are coupled to G proteins, an interaction evident during antagonist binding analysis.
  • The specific G protein involved in this coupling remains to be identified.
  • The established concepts of agonist and antagonist actions at the sigma-1 receptor warrant re-evaluation.