Molecular control of δ-opioid receptor signalling

Nature (Impact Factor: 41.46). 01/2014; 506(7487). DOI: 10.1038/nature12944
Source: PubMed


Opioids represent widely prescribed and abused medications, although their signal transduction mechanisms are not well understood. Here we present the 1.8 Å high-resolution crystal structure of the human δ-opioid receptor (δ-OR), revealing the presence and fundamental role of a sodium ion in mediating allosteric control of receptor functional selectivity and constitutive activity. The distinctive δ-OR sodium ion site architecture is centrally located in a polar interaction network in the seven-transmembrane bundle core, with the sodium ion stabilizing a reduced agonist affinity state, and thereby modulating signal transduction. Site-directed mutagenesis and functional studies reveal that changing the allosteric sodium site residue Asn 131 to an alanine or a valine augments constitutive β-arrestin-mediated signalling. Asp95Ala, Asn310Ala and Asn314Ala mutations transform classical δ-opioid antagonists such as naltrindole into potent β-arrestin-biased agonists. The data establish the molecular basis for allosteric sodium ion control in opioid signalling, revealing that sodium-coordinating residues act as 'efficacy switches' at a prototypic G-protein-coupled receptor.

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    • "This residue resides in the ''message domain'' of KOR (Portoghese, 1989; Vardy et al., 2013), and D138A mutations have been reported to nearly abolish the binding of all known KOR agonists without affecting the affinity or potency of SALA (Kane et al., 2006; Vardy et al., 2013). Furthermore, recent high-resolution crystal structures of related opioid receptors (Fenalti et al., 2014, 2015) implied that this residue is also essential for the interaction of other classes of opioids including opioid peptides and opioid antagonists. We reasoned, therefore, that changing the negative charge to a polar residue via a D138N mutation would further decrease the potency of endogenous peptide ligands and enhance the potency of SALB and SALA. "

    • "The insertion of b 562 RIL into ICL3 of the smoothened receptor has also been proposed as a reason for the lack of structural rearrangements at the cytoplasmic surface upon agonist binding (Wang et al., 2013b). Finally, comparison of the murine d-opioid receptor structure solved with an ICL3 T4L fusion (Granier et al., 2012) and the human d-opioid receptor with an N-terminal b 562 RIL fusion (Fenalti et al., 2014) shows a high degree of structural similarity, with the main deviations occurring proximal to the sites of fusion. "
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    ABSTRACT: G protein-coupled receptor (GPCR) structural biology has progressed dramatically in the last decade. There are now over 120 GPCR crystal structures deposited in the Protein Data Bank of 32 different receptors from families scattered across the phylogenetic tree, including Class B, C, and Frizzled GPCRs. These structures have been obtained in combination with a wide variety of ligands, and captured in a range of conformational states. This surge in structural knowledge has enlightened research into the molecular recognition of biologically active molecules, the mechanisms of receptor activation, the dynamics of functional selectivity, and fuelled structure- based drug design efforts for GPCRs. Here we summarize the innovations in both protein engineering/molecular biology and crystallography techniques that have led to these advances in GPCR structural biology, and discuss how they may influence the resulting structural models. We also provide a brief molecular pharmacologist's guide to GPCR X-ray crystallography, outlining some key aspects in the process of structure determination, with the goal to encourage non-crystallographers to interrogate structures at the molecular level. Finally we show how chemogenomics approaches can be used to marry the wealth of existing receptor pharmacology data with the expanding repertoire of structures, providing a deeper understanding of the mechanistic details of GPCR function. The American Society for Pharmacology and Experimental Therapeutics.
    Molecular pharmacology 07/2015; 88(3). DOI:10.1124/mol.115.099663 · 4.13 Impact Factor
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    • "The several recent crystal structures that show interacting parallel receptors in the crystal unit cell (Fig. 3) have been used as an argument in favor of GPCR dimerization, although the possibility exists that these are crystallographic artifacts and/or they do not necessarily represent physiologically relevant interfaces. Two of the five available opioid receptor crystal structures (Fenalti et al., 2014; Granier et al., 2012; Manglik et al., 2012; Thompson et al., 2012; Wu et al., 2012), specifically the structures of μ (Manglik et al., 2012) and κ (Wu et al., 2012) receptors, also reveal parallel arrangements of interacting receptors. As shown in Fig. 3, these correspond to two different interfaces in the case of μ receptor, one of which is also seen in the κ receptor crystal "
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    ABSTRACT: Opioid receptors are important drug targets for pain management, addiction, and mood disorders. Although substantial research on these important subtypes of G protein-coupled receptors has been conducted over the past two decades to discover ligands with higher specificity and diminished side effects, currently used opioid therapeutics remain suboptimal. Luckily, recent advances in structural biology of opioid receptors provide unprecedented insights into opioid receptor pharmacology and signaling. We review here a few recent studies that have used the crystal structures of opioid receptors as a basis for revealing mechanistic details of signal transduction mediated by these receptors, and for the purpose of drug discovery. Copyright © 2015. Published by Elsevier B.V.
    European journal of pharmacology 05/2015; 763. DOI:10.1016/j.ejphar.2015.05.012 · 2.53 Impact Factor
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