Preferential Interaction between the dopamine D2 receptor and Arrestin2 in neostriatal neurons

Dopamine D2 receptor interactions with arrestins and arrestin-dependent internalization have been characterized using heterologously expressed D2 receptor and arrestins. The purpose of this study was to investigate D2 receptor interaction with endogenous arrestins. Arrestin2 and arrestin3 in striatal homogenates bound to the third cytoplasmic loop of the D2 receptor, and purified arrestin2 and arrestin3 bound to the second and third loops and C terminus of the D2 receptor, in a glutathione S-transferase pull-down assay. In NS20Y neuroblastoma cells expressing an enhanced green-fluorescent protein-tagged D2 receptor (D2-EGFP), 2-h D2 agonist stimulation enhanced the colocalization of D2-EGFP with endogenous arrestin2 and arrestin3. These results suggest that the D2 receptor has the intrinsic ability to bind both nonvisual arrestins. Agonist treatment of D2-EGFP NS20Y cells induced D2 receptor internalization (36-46%) that was maximal within 20 min, but that was prevented by small interfering RNA-induced depletion of arrestin2 and arrestin3. In neostriatal neurons, 2-h agonist treatment selectively increased the colocalization of the endogenous D2 receptor with arrestin2, whereas receptor colocalization with arrestin3 was reduced. Agonist stimulation caused translocation of arrestin2, but not arrestin3, to the membrane in neurons and selectively enhanced the coimmunoprecipitation of the D2 receptor and arrestin2. All three measures of receptor/arrestin interaction (colocalization, translocation, and coprecipitation) demonstrated selective agonist-induced interaction between the D2 receptor and arrestin2 in neurons.