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Nigral overexpression of alpha-synuclein in the absence of parkin enhances alpha-synuclein phosphorylation but does not modulate dopaminergic neurodegeneration.

Van Rompuy AS, Oliveras-Salvá M, Van der Perren A, Corti O, Van den Haute C, Baekelandt V - Mol Neurodegener (2015)

Bottom Line: Conflicting results were reported about the effect of the absence of parkin on alpha-synuclein-mediated neurotoxicity using a transgenic approach.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neurobiology and Gene Therapy, Department of Neurosciences, KU Leuven, Flanders, Belgium. annexsophie.vanrompuy@uzleuven.be.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: These findings support a functional relationship between parkin and alpha-synuclein phosphorylation in rodent brain.

No MeSH data available.


Related in: MedlinePlus

High transduction efficiency of mouse dopaminergic neurons with rAAV2/7-WT α-SYN and rAAV2/7-eGFP. Fluorescent double stainings for TH and α-SYN at 1 week or TH and eGFP at 4 weeks after injection of rAAV2/7-WT α-SYN or rAAV2/7-eGFP respectively, demonstrate that the majority of the dopaminergic neurons of the injected side of the SN is transduced. Scale bar = 25 μm.
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Fig2: High transduction efficiency of mouse dopaminergic neurons with rAAV2/7-WT α-SYN and rAAV2/7-eGFP. Fluorescent double stainings for TH and α-SYN at 1 week or TH and eGFP at 4 weeks after injection of rAAV2/7-WT α-SYN or rAAV2/7-eGFP respectively, demonstrate that the majority of the dopaminergic neurons of the injected side of the SN is transduced. Scale bar = 25 μm.

Mentions: Immunohistochemical stainings for α-SYN and eGFP revealed high transgene expression in the SN for both vectors (Figure 1). With confocal analysis we observed a transduction efficiency of the dopaminergic neurons of approximately 85% (Figure 2). To investigate the degree of dopaminergic neurodegeneration, we stereologically quantified the number of tyrosine hydroxylase (TH)-positive cells in the SN. At 4 weeks after injection, the rAAV2/7-WT α-SYN induced a dopaminergic lesion of 59 ± 6% compared to the non-injected side in the parkin+/+ mice, which is in agreement with our previous study [33] (Figure 1 and 3A). In the parkin−/− mice a comparable dopaminergic cell loss of 52 ± 6% was observed. The rAAV2/7-eGFP injected mice did not show any loss of TH-positive cells (Figure 1 and 3B). The loss of dopaminergic terminals in the striatum was comparable between parkin+/+ (24 ± 5.2%) and parkin−/− (33 ± 6.9%) mice (Figure 3C). Thus, we conclude that the sensitivity of parkin−/− mice and parkin+/+ mice to dopaminergic degeneration induced by a high dose of rAAV2/7-WT α-SYN is similar.Figure 1


Nigral overexpression of alpha-synuclein in the absence of parkin enhances alpha-synuclein phosphorylation but does not modulate dopaminergic neurodegeneration.

Van Rompuy AS, Oliveras-Salvá M, Van der Perren A, Corti O, Van den Haute C, Baekelandt V - Mol Neurodegener (2015)

High transduction efficiency of mouse dopaminergic neurons with rAAV2/7-WT α-SYN and rAAV2/7-eGFP. Fluorescent double stainings for TH and α-SYN at 1 week or TH and eGFP at 4 weeks after injection of rAAV2/7-WT α-SYN or rAAV2/7-eGFP respectively, demonstrate that the majority of the dopaminergic neurons of the injected side of the SN is transduced. Scale bar = 25 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4477319&req=5

Fig2: High transduction efficiency of mouse dopaminergic neurons with rAAV2/7-WT α-SYN and rAAV2/7-eGFP. Fluorescent double stainings for TH and α-SYN at 1 week or TH and eGFP at 4 weeks after injection of rAAV2/7-WT α-SYN or rAAV2/7-eGFP respectively, demonstrate that the majority of the dopaminergic neurons of the injected side of the SN is transduced. Scale bar = 25 μm.
Mentions: Immunohistochemical stainings for α-SYN and eGFP revealed high transgene expression in the SN for both vectors (Figure 1). With confocal analysis we observed a transduction efficiency of the dopaminergic neurons of approximately 85% (Figure 2). To investigate the degree of dopaminergic neurodegeneration, we stereologically quantified the number of tyrosine hydroxylase (TH)-positive cells in the SN. At 4 weeks after injection, the rAAV2/7-WT α-SYN induced a dopaminergic lesion of 59 ± 6% compared to the non-injected side in the parkin+/+ mice, which is in agreement with our previous study [33] (Figure 1 and 3A). In the parkin−/− mice a comparable dopaminergic cell loss of 52 ± 6% was observed. The rAAV2/7-eGFP injected mice did not show any loss of TH-positive cells (Figure 1 and 3B). The loss of dopaminergic terminals in the striatum was comparable between parkin+/+ (24 ± 5.2%) and parkin−/− (33 ± 6.9%) mice (Figure 3C). Thus, we conclude that the sensitivity of parkin−/− mice and parkin+/+ mice to dopaminergic degeneration induced by a high dose of rAAV2/7-WT α-SYN is similar.Figure 1

Bottom Line: Conflicting results were reported about the effect of the absence of parkin on alpha-synuclein-mediated neurotoxicity using a transgenic approach.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Neurobiology and Gene Therapy, Department of Neurosciences, KU Leuven, Flanders, Belgium. annexsophie.vanrompuy@uzleuven.be.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: These findings support a functional relationship between parkin and alpha-synuclein phosphorylation in rodent brain.

No MeSH data available.


Related in: MedlinePlus