The Clathrin-Dependent Localization of Dopamine Transporter to Surface Membranes Is Affected by α-Synuclein

Abstract

Parkinson's disease (PD) is a progressive age-dependent neurodegenerative disorder, predominantly affecting the dopamine-producing neurons residing at the substantia nigra. Abnormalities in α-synuclein (α-Syn) and dopamine transporter (DAT) are implicated in the pathogenesis of PD. We tested the hypothesis that α-Syn regulates surface DAT localization and DAT activity, in cultured cells co-expressing α-Syn and DAT, and in brains of mice modeling PD, transgenic for the mutant A53T α-Syn form. The results indicate that α-Syn expression affects the partitioning of DAT between the cell surface and intracellular compartments, resulting in lower surface DAT levels. Accordingly, lower uptake of tritiated dopamine was measured in synaptosomes of A53T α-Syn transgenic mouse brains. Importantly, we show that the effect of α-Syn on surface DAT is mediated by clathrin. Downregulation of clathrin by specific siRNAs directed against its heavy chain abolished the effect of α-Syn on phorbol 12-myristate 13-acetate-induced DAT internalization. These results suggest that α-Syn plays a role in regulating dopamine homeostasis through its involvement in clathrin-mediated endocytosis.

Decision letter: Loss of the transcription factor Meis1 prevents sympathetic neurons target-field innervation and increases susceptibility to sudden cardiac death

“…In vitro, proximal axonal growth in double Eng1/2 mutant is unaffected whereas in vivo, the projections of these neurons toward the basal telencephalon are missing. Interestingly, in Eng1/Eng2 double mutants, neuronal apoptosis is preceded by a loss of a-synuclein expression (Simon et al, 2001), a vesicular protein able to modulate clathrin-dependent endocytosis, vesicle trafficking and recycling (Kuwahara et al, 2008;Ben Gedalya et al, 2009;Nemani et al, 2010;Cheng et al, 2011;Kisos et al, 2014;Vargas et al, 2014). Thus, the neuronal phenotypes we report following Meis1 inactivation strikingly resemble the phenotypes reported for Eng mutation in mesencephalic dopaminergic neurons.…”

Role of the endolysosomal system in Parkinson’s disease

“…This was also seen upon transgenic expression of α‐synuclein (Xu et al ; Eguchi et al ). Over‐expression of mutant α‐synuclein also affects dopamine transporter trafficking on the pre‐synaptic membrane, leading to dopamine dyshomeostasis (Kisos et al ). The observations that over‐expression and deletion of synucleins have similar effects on SV exo‐ and endocytosis (Lautenschlager et al ) suggest that SV cycling is exquisitely sensitive to α‐synuclein levels.…”

α-Synuclein – Regulator of Exocytosis, Endocytosis, or Both?

“…On the one hand, a-synuclein is thought to be associated with clathrin-mediated endocytosis of synaptic vesicles ( Figure 3A) because triple synuclein knockout led to changes in CME protein expression in mice and because increased numbers of clathrin-coated pits have been seen after stimulation of triple synuclein knockout synapses [48]. In addition, early studies on receptor-mediated endocytosis of transferrin suggested a role for a-synuclein in CME [61][62][63]. Furthermore, the study in lamprey synapses displayed disturbances of CME and increased bulk endocytosis [50].…”