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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

A low dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. (A) Representative images of immunohistochemical staining for TH in the SN at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. Scale bar = 400 μm. (B) Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, *p < 0.05, **p < 0.01, n = 2-3 at 1 week, n = 10-13 at 4 weeks, n = 5-6 at 8 weeks, n = 6 at 16 weeks).
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Fig5: A low dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. (A) Representative images of immunohistochemical staining for TH in the SN at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. Scale bar = 400 μm. (B) Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, *p < 0.05, **p < 0.01, n = 2-3 at 1 week, n = 10-13 at 4 weeks, n = 5-6 at 8 weeks, n = 6 at 16 weeks).

Mentions: As expected, stereological quantification of the number of surviving dopaminergic neurons revealed a milder dopaminergic cell loss at 4 weeks (approximately 40%) compared to the high titer of rAAV2/7-WT α-SYN. At 8 weeks and 16 weeks, in both groups the dopaminergic degeneration was not further progressive, suggesting that with the low titer of rAAV2/7-WT α-SYN the maximum amount of degeneration was already reached at 4 weeks after injection. However, the TH-positive cell loss was again comparable between the parkin−/− and parkin+/+ mice at all time points (e.g. at 4 weeks 35 ± 7% and 41 ± 5% TH-positive cell loss, respectively compared to the non-injected side) (Figure 5A-B). These results confirm that the absence of parkin does not alter the susceptibility to α-SYN induced dopaminergic cell death.Figure 5


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)

A low dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. (A) Representative images of immunohistochemical staining for TH in the SN at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. Scale bar = 400 μm. (B) Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, *p < 0.05, **p < 0.01, n = 2-3 at 1 week, n = 10-13 at 4 weeks, n = 5-6 at 8 weeks, n = 6 at 16 weeks).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4477319&req=5

Fig5: A low dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. (A) Representative images of immunohistochemical staining for TH in the SN at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. Scale bar = 400 μm. (B) Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at 1 week, 4 weeks, 8 weeks and 16 weeks after injection with a low titer of rAAV2/7-WT α-SYN. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, *p < 0.05, **p < 0.01, n = 2-3 at 1 week, n = 10-13 at 4 weeks, n = 5-6 at 8 weeks, n = 6 at 16 weeks).
Mentions: As expected, stereological quantification of the number of surviving dopaminergic neurons revealed a milder dopaminergic cell loss at 4 weeks (approximately 40%) compared to the high titer of rAAV2/7-WT α-SYN. At 8 weeks and 16 weeks, in both groups the dopaminergic degeneration was not further progressive, suggesting that with the low titer of rAAV2/7-WT α-SYN the maximum amount of degeneration was already reached at 4 weeks after injection. However, the TH-positive cell loss was again comparable between the parkin−/− and parkin+/+ mice at all time points (e.g. at 4 weeks 35 ± 7% and 41 ± 5% TH-positive cell loss, respectively compared to the non-injected side) (Figure 5A-B). These results confirm that the absence of parkin does not alter the susceptibility to α-SYN induced dopaminergic cell death.Figure 5

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