Cys-27 variant of human delta-opioid receptor modulates maturation and cell surface delivery of Phe-27 variant via heteromerization.
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Leskela TT, Lackman JJ, Vierimaa MM, Kobayashi H, Bouvier M, Petaja-Repo UE
Cys-27 variant of human delta-opioid receptor modulates maturation and cell surface delivery of Phe-27 variant via heteromerization.
J Biol Chem. 2012 Feb 10;287(7):5008-20. doi: 10.1074/jbc.M111.305656. Epub 2011 Dec 19.
- PubMed ID
- 22184124 [ View in PubMed]
- Abstract
The important role of G protein-coupled receptor homo/heteromerization in receptor folding, maturation, trafficking, and cell surface expression has become increasingly evident. Here we investigated whether the human delta-opioid receptor (hdeltaOR) Cys-27 variant that shows inherent compromised maturation has an effect on the behavior of the more common Phe-27 variant in the early secretory pathway. We demonstrate that hdeltaOR-Cys-27 acts in a dominant negative manner and impairs cell surface delivery of the co-expressed hdeltaOR-Phe-27 and impairs conversion of precursors to the mature form. This was demonstrated by metabolic labeling, Western blotting, flow cytometry, and confocal microscopy in HEK293 and human SH-SY5Y neuroblastoma cells using differentially epitope-tagged variants. The hdeltaOR-Phe-27 precursors that were redirected to the endoplasmic reticulum-associated degradation were, however, rescued by a pharmacological chaperone, the opioid antagonist naltrexone. Co-immunoprecipitation of metabolically labeled variants revealed that both endoplasmic reticulum-localized precursors and mature receptors exist as homo/heteromers. The existence of homo/heteromers was confirmed in living cells by bioluminescence resonance energy transfer measurements, showing that the variants have a similar propensity to form homo/heteromers. By forming both homomers and heteromers, the hdeltaOR-Cys-27 variant may thus regulate the levels of receptors at the cell surface, possibly leading to altered responsiveness to opioid ligands in individuals carrying the Cys-27 variant.