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Opioid efficacy in a C6 glioma cell line stably expressing the human kappa opioid receptor

A E Remmers1, M J Clark, A Mansour

  • 1Department of Pharmacology, University of Michigan, Ann Arbor 48109- 0632, USA. aremmers@umich.edu

The Journal of Pharmacology and Experimental Therapeutics
|January 26, 1999
PubMed

Insights

This study characterizes the human kappa opioid receptor (kappaOR) using a transfected C6 glioma cell line. Researchers found these cells effectively assess kappaOR efficacy and G protein activation by various opioid ligands.

Area of Science:

  • Pharmacology
  • Neuroscience
  • Molecular Biology

Background:

  • The kappa opioid receptor (kappaOR) plays a crucial role in pain modulation and other physiological processes.
  • Understanding kappaOR ligand interactions is essential for developing targeted therapeutics.
  • Characterizing receptor binding and downstream signaling pathways provides insights into opioid receptor function.

Purpose of the Study:

  • To characterize kappa opioid receptor (kappaOR) binding and G protein activation using a C6 glioma cell line stably expressing human kappaOR.
  • To evaluate the efficacy of a comprehensive series of opioid ligands at the kappaOR.
  • To investigate potential alternative mechanisms of drug action beyond direct kappaOR agonism.

Main Methods:

  • Utilized a C6 glioma cell line stably transfected with the human kappa opioid receptor (kappaOR).
  • Assessed ligand-binding affinity using radioligand binding assays (e.g., [3H]U69593).
  • Measured G protein activation via [35S]GTPgammaS binding assays, assessing agonist and antagonist activities of various opioid ligands.

Main Results:

  • The kappaOR ligand-binding affinity in the transfected cells mirrored that observed in monkey brain membranes.
  • Both peptide and nonpeptide agonists maximally stimulated [35S]GTPgammaS binding, which was blocked by pertussis toxin, confirming G protein coupling.
  • Several ligands acting as antagonists at mu opioid receptors showed partial kappaOR agonism, suggesting complex drug actions. Stereoselectivity was observed for benzomorphan and benzodiazepine derivatives.

Conclusions:

  • The C6 glioma cell line expressing homogeneous kappaOR populations provides a robust model for studying kappaOR pharmacology.
  • The [35S]GTPgammaS binding properties of these cells are suitable for assessing kappaOR ligand efficacy.
  • The findings highlight the complexity of opioid ligand interactions and potential for off-target or alternative signaling mechanisms.

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