Dynamin-2 associates with the dopamine receptor signalplex and regulates internalization of activated D2 receptors

Dopamine receptors (DRs) are implicated in modulating a variety of important neuronal processes including those involved in development and plasticity. Although dopamine receptors are known to be internalized in response to ligand activation, the mechanisms regulating this process have not been clearly defined. Here, we show that D2 dopamine receptors (D2Rs) undergo dynamin-2-dependent internalization in response to agonist treatment. Using a cleavable biotin assay to quantify receptor internalization, we found that expression of dynamin-2 mutants defective in GTPase function virtually abolished agonist-induced D2R internalization. In contrast, expression of a dynamin-1 mutant did not alter D2R internalization. In human embryonic kidney (HEK) 293 cells and primary striatal neurons, dynamin-2 was found to localize to sites of D2R internalization. Dynamin/D2R association was examined in adult rat forebrain using subcellular fractionation and coimmunoprecipitation methods. D2Rs and dynamin-2 were coexpressed in non-synaptosomal fractions, and dynamin-2 was found to coimmunoprecipitate with the D2R signalling complex (signalplex). Taken together, our findings suggest that dynamin-2 regulates D2R internalization and thus is likely to play an important role in D2R mediated dopaminergic transmission.