A single nucleotide polymorphic mutation in the human mu-opioid receptor severely impairs receptor signaling

Item Type:	Article
Title:	A single nucleotide polymorphic mutation in the human mu-opioid receptor severely impairs receptor signaling
Creators Name:	Befort, K. and Filliol, D. and Decaillot, F.M. and Gaveriaux-Ruff, C. and Hoehe, M.R. and Kieffer, B.L.
Abstract:	Large scale sequencing of the human μ-opioid receptor (hMOR) gene has revealed polymorphic mutations that occur within the coding region. We have investigated whether the mutations N40D in the extracellular N-terminal region, N152D in the third transmembrane domain, and R265H and S268P in the third intracellular loop alter functional properties of the receptor expressed in mammalian cells. The N152D receptor was produced at low densities. Binding affinities of structurally diverse opioids (morphine, diprenorphine, DAMGO and CTOP) and the main endogenous opioid peptides (β-endorphin, [Met]enkephalin, and dynorphin A) were not markedly changed in mutant receptors (<3-fold). Receptor signaling was strongly impaired in the S268P mutant, with a reduction of efficacy and potency of several agonists (DAMGO, β-endorphin, and morphine) in two distinct functional assays. Signaling at N40D and R265H mutants was highly similar to wild type, and none of the mutations induced detectable constitutive activity. DAMGO-induced down-regulation of receptor-binding sites, following 20 h of treatment, was identical in wild-type and mutant receptors. Our data show that natural sequence variations in hMOR gene have little influence on ligand binding or receptor down-regulation but could otherwise modify receptor density and signaling. Importantly, the S268P mutation represents a loss-of-function mutation for the human μ-opioid receptor, which may have an incidence on opioid-regulated behaviors or drug addiction in vivo.
Keywords:	Ala(2)-MePhe(4)-Gly(5)-Enkephalin, Asparagine, Aspartic Acid, COS Cells, Cultured Cells, Cyclic AMP, Guanosine 5'-O-(3-Thiotriphosphate), Mu Opioid Receptors, Narcotics, Opioid Analgesics, Proline, Serine, Signal Transduction, Site-Directed Mutagenesis, Single Nucleotide Polymorphism, Sulfur Radioisotopes, Animals
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	276
Number:	5
Page Range:	3130-3137
Date:	1 January 2001
Official Publication:	https://doi.org/10.1074/jbc.M006352200
PubMed:	View item in PubMed

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