G protein-coupling and ligand selectivity of the D_2L and D₃ dopamine receptors

Lane, J.R., Powney, B., Wise, A., Rees, S. and Milligan, G. (2008) G protein-coupling and ligand selectivity of the D_2L and D₃ dopamine receptors. Journal of Pharmacology and Experimental Therapeutics, 325(1), pp. 319-330. (doi: 10.1124/jpet.107.134296)

Abstract

The human dopamine D_2L receptor couples promiscuously to multiple members of the Gα_i/o subfamily. Despite the high homology of the D_2L and D₃ receptors, the G protein-coupling specificity of the human D₃ receptor is less clearly characterized. The primary aim of this study, then, was the parallel characterization of the G protein coupling specificity of the D_2L and D₃ receptors. By employing both receptor-G protein fusion proteins and stable cell lines in which pertussis toxin-resistant mutants of individual Gα_i-family G proteins were expressed in an inducible fashion we demonstrated highly selective coupling of the D₃ receptor to Gα_o1. Furthermore, by using the fusion proteins to ensure identical stoichiometry of receptor to G protein for each pairing, a range of ligands displayed higher potency and, for partial agonists, higher efficacy at the D3 receptor when coupled to G_o1 as compared to the D_2L receptor. The second aim of this study was to investigate the molecular basis of the above differential G protein-coupling specificity. The importance of a twelve amino acid sequence from the C-terminal end of the third intracellular loop of the D_2L receptor in providing promiscuity in G protein coupling was demonstrated using a chimeric D₃/D₂ receptor in which the equivalent region of the D₃ receptor was exchanged for this sequence. This chimera displayed D₃-like affinity for [³H] spiperone and potency for agonists, but gained D₂-like ability to couple to each of Gα_i1-3 as well as Gα_o1.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Milligan, Professor Graeme
• Authors: Lane, J.R., Powney, B., Wise, A., Rees, S., and Milligan, G.
• Subjects: Q Science > QH Natural history > QH345 Biochemistry
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: Journal of Pharmacology and Experimental Therapeutics
• ISSN: 0022-3565