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 CB 2 carries a putative Tctex-1 binding motif, we investigated the potential interplay of CB 2 and Tctex-1 in the absence and presence of Gβγ. The supposed interaction of cannabinoid receptor CB 2 with Tctex-1 and the influence of CB 2 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, NH 4 Cl/leupeptin or bafilomycin. Our results show that CB 2 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 CB 2 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 CB 2 expression “dose-dependently” and is independent of stimulation by agonist or blocking by an inverse agonist treatment. The results suggest that CB 2 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 CB 2 receptor expression modifies the stability of intracellular protein complexes by a non-canonical pathway.