FIGURE 7.
D2R activation promotes HTT Ser-421 dephosphorylation in vivo. A, STHdhQ7/7 cells were transfected or not transfected (NT) with HA-D2R. 48 h after transfection, the cells were serum-starved 6 h prior to agonist stimulation. In 7 sets of independent experiments, the cells were pretreated or not pretreated with cadmium chloride (5 μm, 6 h in serum-deprived DMEM) before apomorphine (Apo) stimulation (20 μm apomorphine, 35 min). Then the full-length HTT was immunoprecipitated. Western blots and densitometry analysis of phospho-Ser-421 HTT relative levels are shown. B and C, wild type mice were injected with a saline solution or NPA (3 mg/kg, intraperitoneal, 15/20 min) (B) or raclopride (Raclo, 2 mg/kg, intraperitoneal, 30 min) (C). Then the full-length striatal HTT was immunoprecipitated, and the phospho-Ser-421 was assessed. D, D2R knock-out mice were injected with a saline solution or NPA (3 mg/kg, intraperitoneal, 15/20 min), and then the full-length striatal HTT was immunoprecipitated, and the phospho-Ser-421 was assessed. E, analysis of the phospho-Ser-421 HTT relative levels in the striatum of β-arrestin 2 knock-out (BARR2 KO) mice versus wild type littermates under basal condition was conducted as stated above.