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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 high dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at (A) 1 week and 4 weeks after injection with a high titer of rAAV2/7-WT α-SYN and at (B) 4 weeks after injection with rAAV2/7-eGFP. (C) quantification of TH staining in striatum (injected over non-injected side) of parkin+/+ and parkin−/− mice 4 weeks after injection. Asterisks depict significant decrease respective to 1 week, unless specified otherwise. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, ** p < 0.01 ***p < 0.001, 1 week rAAV2/7-WT α-SYN: n = 4; 4 weeks rAAV2/7-WT α-SYN: n = 15-16; 4 weeks rAAV2/7-eGFP: n = 5-6).
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Fig3: A high dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at (A) 1 week and 4 weeks after injection with a high titer of rAAV2/7-WT α-SYN and at (B) 4 weeks after injection with rAAV2/7-eGFP. (C) quantification of TH staining in striatum (injected over non-injected side) of parkin+/+ and parkin−/− mice 4 weeks after injection. Asterisks depict significant decrease respective to 1 week, unless specified otherwise. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, ** p < 0.01 ***p < 0.001, 1 week rAAV2/7-WT α-SYN: n = 4; 4 weeks rAAV2/7-WT α-SYN: n = 15-16; 4 weeks rAAV2/7-eGFP: n = 5-6).

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)

A high dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at (A) 1 week and 4 weeks after injection with a high titer of rAAV2/7-WT α-SYN and at (B) 4 weeks after injection with rAAV2/7-eGFP. (C) quantification of TH staining in striatum (injected over non-injected side) of parkin+/+ and parkin−/− mice 4 weeks after injection. Asterisks depict significant decrease respective to 1 week, unless specified otherwise. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, ** p < 0.01 ***p < 0.001, 1 week rAAV2/7-WT α-SYN: n = 4; 4 weeks rAAV2/7-WT α-SYN: n = 15-16; 4 weeks rAAV2/7-eGFP: n = 5-6).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4477319&req=5

Fig3: A high dose of rAAV2/7-WT α-SYN induces similar dopaminergic degeneration in parkin−/− and parkin+/+ mice. Stereological quantification of the number of TH-positive neurons in the SN of parkin+/+ and parkin−/− mice at (A) 1 week and 4 weeks after injection with a high titer of rAAV2/7-WT α-SYN and at (B) 4 weeks after injection with rAAV2/7-eGFP. (C) quantification of TH staining in striatum (injected over non-injected side) of parkin+/+ and parkin−/− mice 4 weeks after injection. Asterisks depict significant decrease respective to 1 week, unless specified otherwise. (Mean ± SEM, two-way ANOVA followed by Bonferroni post-hoc test, ** p < 0.01 ***p < 0.001, 1 week rAAV2/7-WT α-SYN: n = 4; 4 weeks rAAV2/7-WT α-SYN: n = 15-16; 4 weeks rAAV2/7-eGFP: n = 5-6).
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