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Characterization of M2 muscarinic receptor activation of different G protein subtypes

Ain Uustare1, Johnny Näsman, Karl E O Akerman

  • 1Institute of Organic and Bioorganic Chemistry, University of Tartu, Jakobi Str. 2, EE-51014 Tartu, Estonia.

Neurochemistry International
|September 16, 2003
PubMed

Insights

Insect cells expressing the M2 muscarinic acetylcholine receptor (mAChR) successfully formed functional complexes with Gi and Go proteins. This system is valuable for screening muscarinic receptor ligands, including agonists and antagonists.

Area of Science:

  • Pharmacology
  • Molecular Biology
  • Neuroscience

Background:

  • The M2 muscarinic acetylcholine receptor (mAChR) plays a crucial role in various physiological processes.
  • Understanding its interaction with G proteins is essential for drug development.

Purpose of the Study:

  • To investigate the functional complex formation of M2 mAChR with different G proteins (Gi and Go) in insect cells.
  • To evaluate the utility of this system for screening muscarinic receptor ligands.

Main Methods:

  • Utilized the baculovirus system for M2 mAChR expression in Spodoptera frugiperda (Sf9) insect cells.
  • Coexpressed M2 mAChR with Gi and Go proteins and assessed functional complex formation via [35S]GTPgammaS binding assays.
  • Compared the affinities and efficacies of various muscarinic agonists and partial agonists.

Main Results:

  • M2 mAChR formed active functional complexes with coexpressed Gi and Go proteins, but not with endogenous G proteins.
  • No significant differences in ligand affinities or efficacies were observed between M2/Gi and M2/Go complexes.
  • Constitutive receptor activity was observed with both Gi and Go coexpression.
  • Antagonists acted as inverse agonists, with potencies correlating to binding affinities.

Conclusions:

  • Functional reconstitution of M2 mAChR with Gi or Go proteins in insect cells is feasible.
  • This system serves as a valuable tool for screening the potency and efficacy of muscarinic receptor agonists, partial agonists, and inverse agonists.

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