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Differential stability of the crystallographic interfaces of mu- and kappa-opioid receptors.

ABSTRACT: The recent mu-opioid receptor (MOPr) and kappa-opioid receptor (KOPr) crystal structures have inspired hypotheses of physiologically relevant dimerization contacts, specifically: a closely packed interface involving transmembrane (TM) helices TM5 and TM6, and a less compact interface, involving TM1, TM2, and helix 8 (H8). While the former was only found in MOPr crystals, similar arrangements of the latter were identified for both KOPr and MOPr. The relevance of these interfaces outside of a crystal lattice is called into question by the possibility that they might be influenced by the specific crystallization conditions. In this study, we have employed umbrella sampling molecular dynamics simulations of coarse-grained representations of the interacting MOPr or KOPr crystallographic structures, in the absence of the T4 lysozyme, and in an explicit lipid-water environment, to determine the strength of receptor dimerization at the different crystallographic interfaces. We note that the shape of the interface plays a dominant role in the strength of the interaction, and the pattern of contacting residues defines the shape of the potential of mean force. This information can be used to guide experiments aimed at exploring the role of dimerization in opioid receptor function.

SUBMITTER: Johnston JM

PROVIDER: S-EPMC3944890 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Differential stability of the crystallographic interfaces of mu- and kappa-opioid receptors.

Johnston Jennifer M JM Filizola Marta M

PloS one 20140228 2

The recent mu-opioid receptor (MOPr) and kappa-opioid receptor (KOPr) crystal structures have inspired hypotheses of physiologically relevant dimerization contacts, specifically: a closely packed interface involving transmembrane (TM) helices TM5 and TM6, and a less compact interface, involving TM1, TM2, and helix 8 (H8). While the former was only found in MOPr crystals, similar arrangements of the latter were identified for both KOPr and MOPr. The relevance of these interfaces outside of a crys ...[more]

PMID: 24651466

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Project description:Although participation of opioids in antinociception induced by cannabinoids has been documented, there is little information regarding the participation of cannabinoids in the antinociceptive mechanisms of opioids. The aim of the present study was to determine whether endocannabinoids could be involved in peripheral antinociception induced by activation of mu-, delta- and kappa-opioid receptors.Nociceptive thresholds to mechanical stimulation of rat paws treated with intraplantar prostaglandin E2 (PGE2, 2 microg) to induce hyperalgesia were measured 3 h after injection using an algesimetric apparatus. Opioid agonists morphine (200 microg), (+)-4-[(alphaR)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80) (80 microg), bremazocine (50 microg); cannabinoid receptor antagonists N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251) (20-80 microg), 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl(4-methoxyphenyl) methanone (AM630) (12.5-100 microg); and an inhibitor of methyl arachidonyl fluorophosphonate (MAFP) (1-4 microg) were also injected in the paw.The CB1-selective cannabinoid receptor antagonist AM251 completely reversed the peripheral antinociception induced by morphine in a dose-dependent manner. In contrast, the CB2-selective cannabinoid receptor antagonist AM630 elicited partial antagonism of this effect. In addition, the administration of the fatty acid amide hydrolase inhibitor, MAFP, enhanced the antinociception induced by morphine. The cannabinoid receptor antagonists AM251 and AM630 did not modify the antinociceptive effect of SNC80 or bremazocine. The antagonists alone did not cause any hyperalgesic or antinociceptive effect.Our results provide evidence for the involvement of endocannabinoids, in the peripheral antinociception induced by the mu-opioid receptor agonist morphine. The release of cannabinoids appears not to be involved in the peripheral antinociceptive effect induced by kappa- and delta-opioid receptor agonists.

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Dataset Information

Differential stability of the crystallographic interfaces of mu- and kappa-opioid receptors.

Publications

Differential stability of the crystallographic interfaces of mu- and kappa-opioid receptors.

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