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| Subject Categories: Signal Transduction |
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| The EMBO Journal
(2008) 27, 1321–1332, doi:10.1038/emboj.2008.64 Published online 3 April 2008 |
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| Functioning of the dimeric GABAB receptor extracellular domain revealed by glycan wedge scanning |
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| Philippe Rondard1, 6, Siluo Huang2, 6, Carine Monnier1, Haijun Tu2, Bertrand Blanchard1, Nadia Oueslati1, Fanny Malhaire1, Ying Li2, Eric Trinquet3, Gilles Labesse4, 5, Jean-Philippe Pin1 and Jianfeng Liu2 |
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1 CNRS, UMR 5203, Institut de Génomique Fonctionnelle, Montpellier, France and INSERM, U661, Montpellier, France and Université Montpellier 1, 2, Montpellier, France 2 Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, China 3 CisBio International, Parc technologique Marcel Boiteux, Bagnols/Cèze, France 4 Centre de Biochimie Structurale, CNRS, UMR5048, Université Montpellier 1, Montpellier, France 5 INSERM U414, Montpellier, France To whom correspondence should be addressed Jean-Philippe Pin, CNRS, UMR 5203, Institut de Génomique Fonctionnelle, Montpellier, France, and INSERM, U661, Montpellier, France, and Université Montpellier 1,2, Montpellier 34000, France. Tel.: +33 467 14 2988; Fax: +33 467 54 2432; E-mail: jppin@igf.cnrs.fr Jianfeng Liu, Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, China. Tel.: +86 278 779 2031; Fax: +86 278 779 2024; E-mail: jfliu@mail.hust.edu.cn 6 These authors contributed equally to this work Received 31 August 2007; Accepted 5 March 2008; Published online 3 April 2008. |
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| Abstract |
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| The G-protein-coupled receptor (GPCR) activated by the neurotransmitter GABA is made up of two subunits, GABAB1 and GABAB2. GABAB1 binds agonists, whereas GABAB2 is required for trafficking GABAB1 to the cell surface, increasing agonist affinity to GABAB1, and activating associated G proteins. These subunits each comprise two domains, a Venus flytrap domain (VFT) and a heptahelical transmembrane domain (7TM). How agonist binding to the GABAB1 VFT leads to GABAB2 7TM activation remains unknown. Here, we used a glycan wedge scanning approach to investigate how the GABAB VFT dimer controls receptor activity. We first identified the dimerization interface using a bioinformatics approach and then showed that introducing an N-glycan at this interface prevents the association of the two subunits and abolishes all activities of GABAB2, including agonist activation of the G protein. We also identified a second region in the VFT where insertion of an N-glycan does not prevent dimerization, but blocks agonist activation of the receptor. These data provide new insight into the function of this prototypical GPCR and demonstrate that a change in the dimerization interface is required for receptor activation. |
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| Keywords: allosteric modulators, anxiety, baclofen, class C GPCRs, drug addiction |
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