Lewy-like aggregation of α-synuclein reduces protein phosphatase 2A activity in vitro and in vivo

Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Neuroscience (Impact Factor: 3.36). 01/2012; 207:288-97. DOI: 10.1016/j.neuroscience.2012.01.028
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α-synuclein (α-Syn) is a chaperone-like protein that is highly implicated in Parkinson's disease (PD) as well as in dementia with Lewy bodies (DLB). Rare forms of PD occur in individuals with mutations of α-Syn or triplication of wild type α-Syn, and in both PD and DLB the intraneuronal inclusions known as Lewy bodies contain aggregated α-Syn that is highly phosphorylated on serine 129. In neuronal cells and in the brains of α-Syn overexpressing transgenic mice, soluble α-Syn stimulates the activity of protein phosphatase 2A (PP2A), a major serine/threonine phosphatase. Serine 129 phosphorylation of α-Syn attenuates its stimulatory effects on PP2A and also accelerates α-Syn aggregation; however, it is unknown if aggregation of α-Syn into Lewy bodies impairs PP2A activity. To assess for this, we measured the impact of α-Syn aggregation on PP2A activity in vitro and in vivo. In cell-free assays, aggregated α-Syn had ∼50% less PP2A stimulatory effects than soluble recombinant α-Syn. Similarly in DLB and α-Syn triplication brains, which contain robust α-Syn aggregation with high levels of serine 129 phosphorylation, PP2A activity was also ∼50% attenuated. As α-Syn normally stimulates PP2A activity, our data suggest that overexpression of α-Syn or sequestration of α-Syn into Lewy bodies has the potential to alter the phosphorylation state of key PP2A substrates; raising the possibility that all forms of synucleinopathy will benefit from treatments aimed at optimizing PP2A activity.

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Available from: Ruth G. Perez, Apr 19, 2014
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    • "Samples were assayed at 650 nm relative to fresh standards by malachite green assay (17-127; Millipore/Upstate). Inhibitors for specificity included: 50 nM protein-phosphataseinhibitor 2 (PP1-specific), 3 nM fostriecin (PP2A/PP4-specific), 50 nM cantharidin (PP4-specific), and 10 nM okadaic acid as previously described (Peng et al. 2005; Lou et al. 2010; Wu et al. 2012). "
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