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

James M Brimson, C A Brown, Stephen T Safrany

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

BACKGROUND AND PURPOSE: Sigma-1 receptors are atypical receptors with potentially two transmembrane domains. Antagonists require doses significantly higher than their published affinities to have biological effects. We have reassessed the binding characteristics of these ligands and found antagonists bind to high-and low-affinity states not distinguished by agonists.

EXPERIMENTAL APPROACH: The affinities of sigma-1 receptor ligands was assessed using radioligand saturation and competition binding of [(3)H]-(+)-pentazocine to permeabilized MDA-MB-468 cells. This was compared with the effect of ligands on metabolic activity using an MTS-based assay and calcium signalling using cells loaded with the calcium dye, Fura-2.

KEY RESULTS: Sigma-1 receptor antagonists, but not agonists, show GTP- and suramin-sensitive high-affinity binding. Functional responses (calcium signalling and metabolic activity), while associated with sigma-1 receptor binding, required binding to an unidentified, low-affinity target.

CONCLUSIONS AND IMPLICATIONS: Sigma-1 receptors are coupled to G proteins. This interaction is only observed when analysing antagonist binding. The identity of the G protein remains to be resolved. The concept of agonist and antagonist at the sigma-1 receptor needs to be revisited.

Original languageEnglish
Pages (from-to)772-780
Number of pages9
JournalBritish Journal of Pharmacology
Volume164
Issue number2B
DOIs
Publication statusPublished - Sep 2011

Keywords

  • IPAG
  • MTS
  • calcium
  • rimcazole
  • cholera toxin
  • Sigma-1 receptor
  • G protein
  • antagonist
  • agonist

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