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Synergistic influence of phosphorylation and metal ions on tau oligomer formation and coaggregation with α-synuclein at the single molecule level.

Nübling G, Bader B, Levin J, Hildebrandt J, Kretzschmar H, Giese A - Mol Neurodegener (2012)

Bottom Line: While tau fibril formation is well-characterized, factors influencing tau oligomerization and molecular interactions of tau and α-synuclein are not well understood.We used a novel approach applying confocal single-particle fluorescence to investigate the influence of tau phosphorylation and metal ions on tau oligomer formation and its coaggregation with α-synuclein at the level of individual oligomers.Moreover, tau phosphorylation and Al3+ as well as Fe3+ enhanced both formation of mixed oligomers and recruitment of α-synuclein in pre-formed tau oligomers.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Neuropathology and Prion Research, Ludwig-Maximilians-Universität, Feodor-Lynen-Str, 23, 81377, Munich, Germany.

ABSTRACT

Background: Fibrillar amyloid-like deposits and co-deposits of tau and α-synuclein are found in several common neurodegenerative diseases. Recent evidence indicates that small oligomers are the most relevant toxic aggregate species. While tau fibril formation is well-characterized, factors influencing tau oligomerization and molecular interactions of tau and α-synuclein are not well understood.

Results: We used a novel approach applying confocal single-particle fluorescence to investigate the influence of tau phosphorylation and metal ions on tau oligomer formation and its coaggregation with α-synuclein at the level of individual oligomers. We show that Al3+ at physiologically relevant concentrations and tau phosphorylation by GSK-3β exert synergistic effects on the formation of a distinct SDS-resistant tau oligomer species even at nanomolar protein concentration. Moreover, tau phosphorylation and Al3+ as well as Fe3+ enhanced both formation of mixed oligomers and recruitment of α-synuclein in pre-formed tau oligomers.

Conclusions: Our findings provide a new perspective on interactions of tau phosphorylation, metal ions, and the formation of potentially toxic oligomer species, and elucidate molecular crosstalks between different aggregation pathways involved in neurodegeneration.

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Related in: MedlinePlus

Al3+promotes the formation of SDS stable tau oligomers more efficiently after tau phosphorylation.A. Cross-correlation amplitudes (G (0)) show mild proaggregatory activity of the organic solvent DMSO, which was significantly higher for mTau. Al3+ promotes intense protein oligomerization. Measurements were taken from 15 independent samples; each sample was measured four times. B. 2D histograms of detected photons indicate the formation of smaller oligomers in presence of DMSO (mean 76 monomers per oligomer for mTau, 26 monomers for pTau) compared to Al3+ (mean 220 to 240 monomers per oligomer). C. Cross correlation amplitude immediately before (T0) and 100 min after (T100) addition of SDS to the aggregation assay. Significant reductions of aggregation levels at T100 are indicated by the symbols over the error bars, while significant differences between pTau and mTau are indicated by the symbols over the wide bars. Measurements were taken from 7 independent samples. D. Cross correlation amplitude at T100 normalized against T0 shows increased SDS-resistance of Al3+ induced oligomers compared to DMSO. Levels of significance are displayed as * = p < 0.05; ** = p < 0.01; ‡ = p < 0.001.
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Figure 2: Al3+promotes the formation of SDS stable tau oligomers more efficiently after tau phosphorylation.A. Cross-correlation amplitudes (G (0)) show mild proaggregatory activity of the organic solvent DMSO, which was significantly higher for mTau. Al3+ promotes intense protein oligomerization. Measurements were taken from 15 independent samples; each sample was measured four times. B. 2D histograms of detected photons indicate the formation of smaller oligomers in presence of DMSO (mean 76 monomers per oligomer for mTau, 26 monomers for pTau) compared to Al3+ (mean 220 to 240 monomers per oligomer). C. Cross correlation amplitude immediately before (T0) and 100 min after (T100) addition of SDS to the aggregation assay. Significant reductions of aggregation levels at T100 are indicated by the symbols over the error bars, while significant differences between pTau and mTau are indicated by the symbols over the wide bars. Measurements were taken from 7 independent samples. D. Cross correlation amplitude at T100 normalized against T0 shows increased SDS-resistance of Al3+ induced oligomers compared to DMSO. Levels of significance are displayed as * = p < 0.05; ** = p < 0.01; ‡ = p < 0.001.

Mentions: Our previous studies revealed that the organic solvent DMSO and the metal ion aluminium (Al3+) induce the formation of distinct tau oligomer species [49]. In order to evaluate the influence of protein phosphorylation on the effects of these aggregation inducers, we employed GSK-3β to create phosphorylated tau (pTau) and compared its aggregation behavior to mock phosphorylated tau (mTau). Our findings show that oligomerization of both pTau and mTau can be induced by 1% DMSO, with mTau showing a higher rate of aggregation than pTau (p < 0.001, Figure 2A). Conversely, in presence of 10 μM Al3+, pTau oligomerization exceeds mTau (p < 0.05), with the overall aggregation level being distinctly higher compared to DMSO for both pTau and mTau (also see Additional files 1 and 2).


Synergistic influence of phosphorylation and metal ions on tau oligomer formation and coaggregation with α-synuclein at the single molecule level.

Nübling G, Bader B, Levin J, Hildebrandt J, Kretzschmar H, Giese A - Mol Neurodegener (2012)

Al3+promotes the formation of SDS stable tau oligomers more efficiently after tau phosphorylation.A. Cross-correlation amplitudes (G (0)) show mild proaggregatory activity of the organic solvent DMSO, which was significantly higher for mTau. Al3+ promotes intense protein oligomerization. Measurements were taken from 15 independent samples; each sample was measured four times. B. 2D histograms of detected photons indicate the formation of smaller oligomers in presence of DMSO (mean 76 monomers per oligomer for mTau, 26 monomers for pTau) compared to Al3+ (mean 220 to 240 monomers per oligomer). C. Cross correlation amplitude immediately before (T0) and 100 min after (T100) addition of SDS to the aggregation assay. Significant reductions of aggregation levels at T100 are indicated by the symbols over the error bars, while significant differences between pTau and mTau are indicated by the symbols over the wide bars. Measurements were taken from 7 independent samples. D. Cross correlation amplitude at T100 normalized against T0 shows increased SDS-resistance of Al3+ induced oligomers compared to DMSO. Levels of significance are displayed as * = p < 0.05; ** = p < 0.01; ‡ = p < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472288&req=5

Figure 2: Al3+promotes the formation of SDS stable tau oligomers more efficiently after tau phosphorylation.A. Cross-correlation amplitudes (G (0)) show mild proaggregatory activity of the organic solvent DMSO, which was significantly higher for mTau. Al3+ promotes intense protein oligomerization. Measurements were taken from 15 independent samples; each sample was measured four times. B. 2D histograms of detected photons indicate the formation of smaller oligomers in presence of DMSO (mean 76 monomers per oligomer for mTau, 26 monomers for pTau) compared to Al3+ (mean 220 to 240 monomers per oligomer). C. Cross correlation amplitude immediately before (T0) and 100 min after (T100) addition of SDS to the aggregation assay. Significant reductions of aggregation levels at T100 are indicated by the symbols over the error bars, while significant differences between pTau and mTau are indicated by the symbols over the wide bars. Measurements were taken from 7 independent samples. D. Cross correlation amplitude at T100 normalized against T0 shows increased SDS-resistance of Al3+ induced oligomers compared to DMSO. Levels of significance are displayed as * = p < 0.05; ** = p < 0.01; ‡ = p < 0.001.
Mentions: Our previous studies revealed that the organic solvent DMSO and the metal ion aluminium (Al3+) induce the formation of distinct tau oligomer species [49]. In order to evaluate the influence of protein phosphorylation on the effects of these aggregation inducers, we employed GSK-3β to create phosphorylated tau (pTau) and compared its aggregation behavior to mock phosphorylated tau (mTau). Our findings show that oligomerization of both pTau and mTau can be induced by 1% DMSO, with mTau showing a higher rate of aggregation than pTau (p < 0.001, Figure 2A). Conversely, in presence of 10 μM Al3+, pTau oligomerization exceeds mTau (p < 0.05), with the overall aggregation level being distinctly higher compared to DMSO for both pTau and mTau (also see Additional files 1 and 2).

Bottom Line: While tau fibril formation is well-characterized, factors influencing tau oligomerization and molecular interactions of tau and α-synuclein are not well understood.We used a novel approach applying confocal single-particle fluorescence to investigate the influence of tau phosphorylation and metal ions on tau oligomer formation and its coaggregation with α-synuclein at the level of individual oligomers.Moreover, tau phosphorylation and Al3+ as well as Fe3+ enhanced both formation of mixed oligomers and recruitment of α-synuclein in pre-formed tau oligomers.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Neuropathology and Prion Research, Ludwig-Maximilians-Universität, Feodor-Lynen-Str, 23, 81377, Munich, Germany.

ABSTRACT

Background: Fibrillar amyloid-like deposits and co-deposits of tau and α-synuclein are found in several common neurodegenerative diseases. Recent evidence indicates that small oligomers are the most relevant toxic aggregate species. While tau fibril formation is well-characterized, factors influencing tau oligomerization and molecular interactions of tau and α-synuclein are not well understood.

Results: We used a novel approach applying confocal single-particle fluorescence to investigate the influence of tau phosphorylation and metal ions on tau oligomer formation and its coaggregation with α-synuclein at the level of individual oligomers. We show that Al3+ at physiologically relevant concentrations and tau phosphorylation by GSK-3β exert synergistic effects on the formation of a distinct SDS-resistant tau oligomer species even at nanomolar protein concentration. Moreover, tau phosphorylation and Al3+ as well as Fe3+ enhanced both formation of mixed oligomers and recruitment of α-synuclein in pre-formed tau oligomers.

Conclusions: Our findings provide a new perspective on interactions of tau phosphorylation, metal ions, and the formation of potentially toxic oligomer species, and elucidate molecular crosstalks between different aggregation pathways involved in neurodegeneration.

Show MeSH
Related in: MedlinePlus