Propagation of conformational changes during mu-opioid receptor activation

Article

关键词: PROTEIN-COUPLED RECEPTOR;    BETA(2)-ADRENERGIC RECEPTOR;    CRYSTAL-STRUCTURE;    NMR-SPECTROSCOPY;    DYNAMIC PROCESS;    ANALGESIA;    EFFICACY;    RHODOPSIN;    AGONIST;    COMPLEX;   

DOI  :  10.1038/nature14680

来源: SCIE

【 摘 要 】

mu-Opioid receptors (mu ORs) are G-protein-coupled receptors that are activated by a structurally diverse spectrum of natural and synthetic agonists including endogenous endorphin peptides, morphine and methadone. The recent structures of the mu OR in inactive(1) and agonist-induced active states (Huang et al., ref. 2) provide snapshots of the receptor at the beginning and end of a signalling event, but little is known about the dynamic sequence of events that span these two states. Here we use solution-state NMR to examine the process of mu OR activation using a purified receptor (mouse sequence) preparation in an amphiphile membrane-like environment. We obtain spectra of the mu OR in the absence of ligand, and in the presence of the high-affinity agonist BU72 alone, or with BU72 and a G protein mimetic nanobody. Our results show that conformational changes in transmembrane segments 5 and 6 (TM5 and TM6), which are required for the full engagement of a G protein, are almost completely dependent on the presence of both the agonist and the G protein mimetic nanobody, revealing a weak allosteric coupling between the agonist-binding pocket and the G-protein-coupling interface (TM5 and TM6), similar to that observed for the beta 2-adrenergic receptor(3). Unexpectedly, in the presence of agonist alone, we find larger spectral changes involving intracellular loop 1 and helix 8 compared to changes in TM5 and TM6. These results suggest that one or both of these domains may play a role in the initial interaction with the G protein, and that TM5 and TM6 are only engaged later in the process of complex formation. The initial interactions between the G protein and intracellular loop 1 and/or helix 8 may be involved in G-protein coupling specificity, as has been suggested for other family A G-protein-coupled receptors.

【 授权许可】

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