title: Cannabinoid receptor 2 expression modulates Gβ(1)γ(2) protein interaction with the activator of G protein signalling 2/dynein light chain protein Tctex-1.
abstract: The activator of G protein signalling AGS2 (Tctex-1) forms protein complexes with Gβγ, and controls cell proliferation by regulating cell cycle progression. A direct interaction of Tctex-1 with various G protein-coupled receptors has been reported. Since the carboxyl terminal portion of CB2 carries a putative Tctex-1 binding motif, we investigated the potential interplay of CB2 and Tctex-1 in the absence and presence of Gβγ. The supposed interaction of cannabinoid receptor CB2 with Tctex-1 and the influence of CB2 on the formation of Tctex-1-Gβγ-complexes were studied by co- and/or immunoprecipitation experiments in transiently transfected HEK293 cells. The analysis on Tctex-1 protein was performed in the absence and presence of the ligands JWH 133, 2-AG, and AM 630, the protein biosynthesis inhibitor cycloheximide or the protein degradation blockers MG132, NH4Cl/leupeptin or bafilomycin. Our results show that CB2 neither directly nor indirectly via Gβγ interacts with Tctex-1, but competes with Tctex-1 in binding to Gβγ. The Tctex-1-Gβγ protein interaction was disrupted by CB2 receptor expression resulting in a release of Tctex-1 from the complex, and its degradation by the proteasome and partly by lysosomes. The decrease in Tctex-1 protein levels is induced by CB2 expression "dose-dependently" and is independent of stimulation by agonist or blocking by an inverse agonist treatment. The results suggest that CB2 receptor expression independent of its activation by agonists is sufficient to competitively disrupt Gβγ-Tctex-1 complexes, and to initiate Tctex-1 degradation. These findings implicate that CB2 receptor expression modifies the stability of intracellular protein complexes by a non-canonical pathway.
authors.affiliation: Neuronal and Cellular Signal Transduction, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf (UKE), 20246 Hamburg, Germany; Institute of Pharmacology and Toxicology, Ulm University, 89081 Ulm, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Nagler
authors.affiliation: Institute of Physiological Chemistry, Ulm University, 89081 Ulm, Germany.
authors.forename: Lysann
authors.initials: L
authors.lastname: Palkowitsch
authors.affiliation: Neuronal and Cellular Signal Transduction, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf (UKE), 20246 Hamburg, Germany; Institute of Pharmacology and Toxicology, Ulm University, 89081 Ulm, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rading
authors.affiliation: Institute of Pharmacology and Toxicology, Ulm University, 89081 Ulm, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Moepps
authors.affiliation: Neuronal and Cellular Signal Transduction, Center for Molecular Neurobiology Hamburg (ZMNH), University Medical Center Hamburg-Eppendorf (UKE), 20246 Hamburg, Germany; Institute of Pharmacology and Toxicology, Ulm University, 89081 Ulm, Germany. Electronic address: meliha.karsak@zmnh.uni-hamburg.de.
authors.forename: Meliha
authors.initials: M
authors.lastname: Karsak
mesh_terms: D054314:Drug Inverse Agonism; D004398:Dyneins / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D011485:Protein Binding / Q000502:physiology; D043885:Receptor, Cannabinoid, CB2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
chemical_list: C588309:CNR2 protein, human; C533386:Dynlt1b protein, mouse; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D007211:Indoles; D043885:Receptor, Cannabinoid, CB2; D004398:Dyneins; C094023:iodopravadoline
keywords: 2-AG (PubChem CID: 5282280); AM 630 (PubChem CID: 4302963); Ammonium chloride (PubChem CID: 25517); Bafilomycin A1 (PubChem CID: 25517); Cannabinoid receptor (CB(2)); Cycloheximide (PubChem CID: 6197); G protein subunit; G protein-coupled receptor (GPCR); JWH 133 (PubChem CID: 6918505); Leupeptin hemisulfate (PubChem CID: 2733491); MG132 (PubChem CID: 462382); Protein degradation; Tctex-1