title: Regulation of GPCR expression through an interaction with CCT7, a subunit of the CCT/TRiC complex.
abstract: Mechanisms that prevent aggregation and promote folding of nascent G protein-coupled receptors (GPCRs) remain poorly understood. We identified chaperonin containing TCP-1 subunit eta (CCT7) as an interacting partner of the β-isoform of thromboxane A2receptor (TPβ) by yeast two-hybrid screening. CCT7 coimmunoprecipitated with overexpressed TPβ and β2-adrenergic receptor (β2AR) in HEK 293 cells, but also with endogenous β2AR. CCT7 depletion by small interfering RNA reduced total and cell-surface expression of both receptors and caused redistribution of the receptors to juxtanuclear aggresomes, significantly more so for TPβ than β2AR. Interestingly, Hsp90 coimmunoprecipitated with β2AR but virtually not with TPβ, indicating that nascent GPCRs can adopt alternative folding pathways. In vitro pull-down assays showed that both receptors can interact directly with CCT7 through their third intracellular loops and C-termini. We demonstrate that Trp334in the TPβ C-terminus is critical for the CCT7 interaction and plays an important role in TPβ maturation and cell-surface expression. Of note, introducing a tryptophan in the corresponding position of the TPα isoform confers the CCT7-binding and maturation properties of TPβ. We show that an interaction with a subunit of the CCT/TCP-1 ring complex (TRiC) chaperonin complex is involved in regulating aggregation of nascent GPCRs and in promoting their proper maturation and expression.
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CR-CHUS), and Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
authors.forename: Samuel
authors.initials: S
authors.lastname: Génier
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CR-CHUS), and Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
authors.forename: Jade
authors.initials: J
authors.lastname: Degrandmaison
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CR-CHUS), and Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
authors.forename: Pierrick
authors.initials: P
authors.lastname: Moreau
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CR-CHUS), and Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
authors.forename: Pascale
authors.initials: P
authors.lastname: Labrecque
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada.
authors.forename: Terence E
authors.initials: TE
authors.lastname: Hébert
authors.affiliation: Service de Rhumatologie, Département de Médecine, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Centre de Recherche du Centre Hospitalier Universitaire de Sherbrooke (CR-CHUS), and Institut de Pharmacologie de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada jean-luc.parent@usherbrooke.ca.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Parent
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D056404:Chaperonin Containing TCP-1 / Q000378:metabolism* / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: C533333:CCT7 protein, human; D002352:Carrier Proteins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D018343:Receptors, Adrenergic, beta-2; D043562:Receptors, G-Protein-Coupled; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D056404:Chaperonin Containing TCP-1