Elucidating the role of α-synuclein on dopamine homeostasis using improved human dopaminergic cell models

• Main Author: Lourenço Venda, Lara Patricia Mateus
• Other Authors: Wade-Martins, Richard
• Published: University of Oxford 2010
• Subjects: 616.833
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558331

Parkinson's disease (PD) is a devastating neurodegenerative disorder with cardinal motor symptoms linked to death of nigrostriatal dopaminergic neurons. Several findings place the protein cc-synuclein firmly at the centre of PD research. First, co-synuclein is the main component of Lewy bodies, the defining inclusion in PD. Second, missense muta- tions and duplication or triplication of the SNCA locus cause autosomal dominant PD. Finally, recent genome-wide association studies revealed the involvement of SNCA vari- ants in sporadic PD, providing a central link between genetics and neurodegeneration in PD. The aim of this study is to elucidate the role of cc-synuclein on dopamine homeos tasis. To this end, two approaches to modulate cc-synuclein gene expression have been developed in a relevant human dopaminergic cell line: (i) RNAi-mediated knockdown of cc-synuclein and (ii) expression from a BAC vector carrying the entire human SNCA genomic locus under the control of endogenous promoter sequences. Modulation of «-synuclein expression caused several functional changes. cc-Synuclein was shown to influence cellular dopamine levels, specifically acting on dopamine biosyn- the tic enzymes TH and AADC. Suppression of cc-synuclein increased dopamine content, whereas modest overexpression of cc-synuclein was sufficient to dramatically reduce to- tal dopamine content. At the same time, the presence of A53T cc-synuclein mutation reduced TH activity. Changes in DAT function were also observed. Consistent with pre- vious findings, suppression of cc-synuclein led to a 50% decrease in dopamine uptake. A53T-mutated cc-synuclein also altered DAT activity, causing a reduction in dopamine uptake velocity coupled with a decrease in dopamine affinity for the transporter. This could be due to altered DAT post-translational modifications and consequently changes in DAT trafficking. This work highlights important roles for cc-synuclein in maintaining dopamine home- ostasis and demonstrates that modulation of cc-synuclein expression has complex effects on dopaminergic neuronal function.