Opioid receptors from a lower vertebrate (Catostomus commersoni): Sequence, pharmacology, coupling to a G-protein-gated inward-rectifying potassium channel (GIRK1), and evolution

Darlison, Mark G.; Greten, Florian R.; Harvey, Robert J.; Kreienkamp, Hans-J�rgen; St�hmer, Thorsten; Zwiers, Henk; Lederis, Karl; Richter, Dietmar

Abstract

The molecular evolution of the opioid receptor family has been studied by isolating cDNAs that encode six distinct opioid receptor-like proteins from a lower vertebrate, the teleost fish Catostomus commersoni. One of these, which has been obtained in full-length form, encodes a 383-amino acid protein that exhibits greatest sequence similarity to mammalian μ-opioid receptors; the corresponding gene is expressed predominantly in brain and pituitary. Transfection of the teleost cDNA into HEK 293 cells resulted in the appearance of a receptor having high affinity for the μ-selective agonist [d-Ala2, MePhe4-Gly-ol5]enkephalin (DAMGO) (Kd = 0.63 ± 0.15 nM) and for the nonselective antagonist naloxone (Kd = 3.1 ± 1.3 nM). The receptor had negligible affinity for U50488 and [d-Pen2, d-Pen5]enkephalin (DPDPE), which are κ- and δ-opioid receptor selective agonists, respectively. Stimulation of transfected cells with 1 μM DAMGO lowered forskolin-induced cAMP levels, an effect that could be reversed by naloxone. Experiments in Xenopus oocytes have demonstrated that the fish opioid receptor can, in an agonist-dependent fashion, activate a coexpressed mouse G-protein-gated inward-rectifying potassium channel (GIRK1). The identification of six distinct fish opioid receptor-like proteins suggests that additional mammalian opioid receptors remain to be identified at the molecular level. Furthermore, our data indicate that the μ-opioid receptor arose very early in evolution, perhaps before the appearance of vertebrates, and that the pharmacological and functional properties of this receptor have been conserved over a period of ≈400 million years implying that it fulfills an important physiological role.

Citation

Darlison, M. G., Greten, F. R., Harvey, R. J., Kreienkamp, H.-J., Stühmer, T., Zwiers, H., Lederis, K., & Richter, D. (1997). Opioid receptors from a lower vertebrate (Catostomus commersoni): Sequence, pharmacology, coupling to a G-protein-gated inward-rectifying potassium channel (GIRK1), and evolution. Proceedings of the National Academy of Sciences, 94(15), 8214-8219

• Journal Article Type: Article
• Acceptance Date: May 29, 1997
• Online Publication Date: Jul 22, 1997
• Publication Date: 1997
• Deposit Date: Jul 26, 2016
• Journal: Proceedings of the National Academy of Sciences
• Publisher: National Academy of Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 94
• Issue: 15
• Pages: 8214-8219
• Public URL: http://researchrepository.napier.ac.uk/Output/316317