Prolonged treatment with pramipexole promotes physical interaction of striatal dopamine D3 autoreceptors with dopamine transporters to reduce dopamine uptake

•Prolonged PPX treatment induces physical interaction between D3 autoreceptor and DAT.•PPX also promotes DAT dimer formation and DAT interaction with D2R and α-syn.•Changes in DAT interactions are associated with a decrease in DAT affinity for DA.•The changes induced by PPX in DAT interactions and function are D3R-dependent.

The dopamine (DA) transporter (DAT), a membrane glycoprotein expressed in dopaminergic neurons, clears DA from extracellular space and is regulated by diverse presynaptic proteins like protein kinases, α-synuclein, D2 and D3 autoreceptors. DAT dysfunction is implicated in Parkinson's disease and depression, which are therapeutically treated by dopaminergic D2/D3 receptor (D2/D3R) agonists. It is, then, important to improve our understanding of interactions between D3R and DAT. We show that prolonged administration of pramipexole (0.1 mg/kg/day, 6 to 21 days), a preferential D3R agonist, leads to a decrease in DA uptake in mouse striatum that reflects a reduction in DAT affinity for DA in the absence of any change in DAT density or subcellular distribution. The effect of pramipexole was absent in mice with genetically-deleted D3R (D3R−/−), yet unaffected in mice genetically deprived of D2R (D2R−/−). Pramipexole treatment induced a physical interaction between D3R and DAT, as assessed by co-immunoprecipitation and in situ proximity ligation assay. Furthermore, it promoted the formation of DAT dimers and DAT association with both D2R and α-synuclein, effects that were abolished in D3R−/− mice, yet unaffected in D2R−/− mice, indicating dependence upon D3R. Collectively, these data suggest that prolonged treatment with dopaminergic D3 agonists provokes a reduction in DA reuptake by dopaminergic neurons related to a hitherto-unsuspected modification of the DAT interactome. These observations provide novel insights into the long-term antiparkinson, antidepressant and additional clinical actions of pramipexole and other D3R agonists.

Graphical abstractSchematic drawing summarizing the effects of prolonged PPX treatment (0.1 mg/kg/day; 6 days) on DAT at dopaminergic terminals in mouse striatum. PPX promotes the formation of DAT dimers, and the physical interaction of DAT with its protein partners α-synuclein, D2 and D3 autoreceptors. These changes are associated with a decline in dopamine uptake, resulting in an increase in extracellular dopamine and a decrease in intracellular dopamine. Extra, extracellular space; Intra, intracellular space.Figure optionsDownload full-size imageDownload as PowerPoint slide