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Expression of mutant alpha-synucleins enhances dopamine transporter-mediated MPP+ toxicity in vitro
Vera Lehmensiek1, Eva-Maria Tan, Johannes Schwarz
1Department of Neurology, University of Ulm, Oberer Eselsberg 45, 89081 Ulm, Germany.
Abstract:
Mutations in the alpha-synuclein gene (A30P and A53T) are reported to cause familial Parkinson's disease (PD), but it is not known how they result in selective dopaminergic cell death. Here we report on effects of mutant alpha-synucleins on dopamine transporter (DAT)-mediated toxicity of the selective dopaminergic neurotoxin 1-methyl-4-phenylpyridinium ion (MPP+) in vitro. We established human embryonic kidney HEK-293 cell lines stably co-expressing each alpha-synuclein isoform and the human DAT. We demonstrate that expression of all alpha-synuclein isoforms enhances toxicity of general complex I inhibition (rotenone), but only the expression of mutant alpha-synucleins induces significant increased DAT-dependent toxicity of very low concentrations of MPP+ compared to wild-type protein. Proteasomal inhibition by lactacystin does not alter MPP+-toxicity in all cell lines. Our data suggest a new mechanism of MPP+-induced dopaminergic toxicity by an interaction between mutant alpha-synucleins and the DAT, which is independent of the function of the proteasome.
Insights
Mutant alpha-synucleins enhance toxicity of the neurotoxin MPP+ by interacting with the dopamine transporter (DAT). This interaction specifically increases cell death in dopaminergic neurons, offering new insights into Parkinson's disease pathogenesis.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- Familial Parkinson's disease (PD) is linked to alpha-synuclein gene mutations (A30P, A53T).
- The precise mechanism causing selective dopaminergic cell death in PD remains unclear.
Purpose of the Study:
- To investigate how mutant alpha-synucleins influence the toxicity of MPP+ mediated by the dopamine transporter (DAT).
- To explore potential interactions between alpha-synuclein variants and DAT in dopaminergic neurotoxicity.
Main Methods:
- Established human embryonic kidney (HEK-293) cell lines co-expressing alpha-synuclein isoforms and human DAT.
- Assessed toxicity of MPP+ and rotenone under conditions of wild-type and mutant alpha-synuclein expression.
- Investigated the role of proteasomal inhibition using lactacystin.
Main Results:
- All alpha-synuclein isoforms enhanced rotenone toxicity (complex I inhibition).
- Mutant alpha-synucleins significantly increased DAT-dependent MPP+ toxicity at low concentrations compared to wild-type.
- Proteasomal inhibition did not consistently alter MPP+ toxicity across cell lines.
Conclusions:
- Mutant alpha-synucleins interact with DAT, leading to enhanced susceptibility to MPP+ toxicity.
- This interaction presents a novel mechanism for MPP+-induced dopaminergic neurotoxicity, independent of proteasomal function.
- Findings suggest a direct role for mutant alpha-synuclein and DAT interaction in familial Parkinson's disease pathology.