title: Involvement of the coatomer protein complex I in the intracellular traffic of the delta opioid receptor.
abstract: The delta opioid receptor (DOPr) is known to be mainly expressed in intracellular compartments. It remains unknown why DOPr is barely exported to the cell surface, but it seems that a substantial proportion of the immature receptor is trapped within the endoplasmic reticulum (ER) and the Golgi network. In the present study, we performed LC-MS/MS analysis to identify putative protein partners involved in the retention of DOPr. Analysis of the proteins co-immunoprecipitating with Flag-DOPr in transfected HEK293 cells revealed the presence of numerous subunits of the coatomer protein complex I (COPI), a vesicle-coating complex involved in recycling resident proteins from the Golgi back to the ER. Further analysis of the amino acid sequence of DOPr identified multiple consensus di-lysine and di-arginine motifs within the intracellular segments of DOPr. Using cell-surface ELISA and GST pulldown assays, we showed that DOPr interacts with COPI through its intracellular loops 2 and 3 (ICL2 and ICL3, respectively) and that the mutation of the K164AK166(ICL2) or K250EK252(ICL3) putative COPI binding sites increased the cell-surface expression of DOPr in transfected cells. Altogether, our results indicate that COPI is a binding partner of DOPr and provide a putative mechanism to explain why DOPr is highly retained inside the cells.
authors.affiliation: Département de pharmacologie-physiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Étienne
authors.initials: É
authors.lastname: St-Louis
authors.affiliation: Département de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Jade
authors.initials: J
authors.lastname: Degrandmaison
authors.affiliation: Département de pharmacologie-physiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Grastilleur
authors.affiliation: Département de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Samuel
authors.initials: S
authors.lastname: Génier
authors.affiliation: Département de pharmacologie-physiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Véronique
authors.initials: V
authors.lastname: Blais
authors.affiliation: Département de pharmacologie-physiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Lavoie
authors.affiliation: Département de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada. Electronic address: Jean-Luc.Parent@USherbrooke.ca.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Parent
authors.affiliation: Département de pharmacologie-physiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Département d'anesthésiologie, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de pharmacologie de Sherbrooke, Université de Sherbrooke, Sherbrooke, Québec, Canada; Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada; Centre de recherche du CHUS, Sherbrooke, Québec, Canada; Quebec Pain Research Network, Québec, Canada. Electronic address: Louis.Gendron@USherbrooke.ca.
authors.forename: Louis
authors.initials: L
authors.lastname: Gendron
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D022181:COP-Coated Vesicles / Q000378:metabolism; D020755:Coat Protein Complex I / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D011485:Protein Binding; D021382:Protein Sorting Signals; D021381:Protein Transport; D017465:Receptors, Opioid, delta / Q000737:chemistry / Q000378:metabolism*
chemical_list: D020755:Coat Protein Complex I; D021382:Protein Sorting Signals; D017465:Receptors, Opioid, delta
keywords: Coatomer protein complex I; Delta opioid receptor; Endoplasmic reticulum export; G protein-coupled receptor; Protein sorting; Receptor trafficking; cis-Golgi