Nigral overexpression of alpha-synuclein in the absence of parkin enhances alpha-synuclein phosphorylation but does not modulate dopaminergic neurodegeneration
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Alpha-synuclein is a key protein in the pathogenesis of Parkinson’s disease. Mutations in the parkin gene are the most common cause of early-onset autosomal recessive Parkinson’s disease, probably through a loss-of-function mechanism. However, the molecular mechanism by which loss of parkin function leads to the development of the disease and the role of alpha-synuclein in parkin-associated Parkinson’s disease is still not elucidated. Conflicting results were reported about the effect of the absence of parkin on alpha-synuclein-mediated neurotoxicity using a transgenic approach. In this study, we investigated the effect of loss of parkin on alpha-synuclein neuropathology and toxicity in adult rodent brain using viral vectors. Therefore, we overexpressed human wild type alpha-synuclein in the substantia nigra of parkin knockout and wild type mice using two different doses of recombinant adeno-associated viral vectors.
No difference was observed in nigral dopaminergic cell loss between the parkin knockout mice and wild type mice up to 16 weeks after viral vector injection. However, the level of alpha-synuclein phosphorylated at serine residue 129 in the substantia nigra was significantly increased in the parkin knockout mice compared to the wild type mice while the total expression level of alpha-synuclein was similar in both groups. The increased alpha-synuclein phosphorylation was confirmed in a parkin knockdown cell line.
These findings support a functional relationship between parkin and alpha-synuclein phosphorylation in rodent brain.
KeywordsParkinson’s disease Alpha-synuclein Alpha-synuclein phosphorylation Parkin Adeno-associated viral vectors Knockout
Analysis of variance
Enhanced green fluorescent protein
parkin wild type
Phosphate buffered saline
- P-S129 α-SYN
α-SYN phosphorylated at serine residue 129
recombinant adeno-associated viral vector
Standard error of the mean
The authors thank Caroline van Heijningen and Sylvie De Swaef for excellent technical assistance and dr. Veerle Janssens for the in-house PP2A monoclonal antibodies. Confocal microscopy was performed at the lab of Molecular Imaging and Photonics at the KU Leuven.
A-SVR is a doctoral fellow supported by the Flemish Research Foundation FWO-Vlaanderen. MOS is a doctoral fellow supported by the European FP7 ITN NEUROMODEL (PITN-GA-2008-215618). This work was supported by the FWO Vlaanderen (G.0768.10), the FP7 RTD project MEFOPA (HEALTH-2009-241791), and the KU Leuven (IOF-KP/07/001, OT/08/052A).
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