Endogenous oligodendroglial alpha-synuclein and TPPP/p25α orchestrate alpha-synuclein pathology in experimental multiple system atrophy models
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Multiple system atrophy (MSA) is characterized by the presence of distinctive glial cytoplasmic inclusions (GCIs) within oligodendrocytes that contain the neuronal protein alpha-synuclein (aSyn) and the oligodendroglia-specific phosphoprotein TPPP/p25α. However, the role of oligodendroglial aSyn and p25α in the formation of aSyn-rich GCIs remains unclear. To address this conundrum, we have applied human aSyn (haSyn) pre-formed fibrils (PFFs) to rat wild-type (WT)-, haSyn-, or p25α-overexpressing oligodendroglial cells and to primary differentiated oligodendrocytes derived from WT, knockout (KO)-aSyn, and PLP-haSyn-transgenic mice. HaSyn PFFs are readily taken up by oligodendroglial cells and can recruit minute amounts of endogenous aSyn into the formation of insoluble, highly aggregated, pathological assemblies. The overexpression of haSyn or p25α accelerates the recruitment of endogenous protein and the generation of such aberrant species. In haSyn PFF-treated primary oligodendrocytes, the microtubule and myelin networks are disrupted, thus recapitulating a pathological hallmark of MSA, in a manner totally dependent upon the seeding of endogenous aSyn. Furthermore, using oligodendroglial and primary cortical cultures, we demonstrated that pathology-related S129 aSyn phosphorylation depends on aSyn and p25α protein load and may involve different aSyn “strains” present in oligodendroglial and neuronal synucleinopathies. Importantly, this hypothesis was further supported by data obtained from human post-mortem brain material derived from patients with MSA and dementia with Lewy bodies. Finally, delivery of haSyn PFFs into the mouse brain led to the formation of aberrant aSyn forms, including the endogenous protein, within oligodendroglia and evoked myelin decompaction in WT mice, but not in KO-aSyn mice. This line of research highlights the role of endogenous aSyn and p25α in the formation of pathological aSyn assemblies in oligodendrocytes and provides in vivo evidence of the contribution of oligodendroglial aSyn in the establishment of aSyn pathology in MSA.
KeywordsAlpha-synuclein Multiple system atrophy Myelin Oligodendrocytes Seeding Tubulin polymerization promoting protein
The authors would like to thank the BRFAA biological imaging facility for their valuable contribution to confocal imaging and image analysis, George Tzanoukos (M.Sc., Head of the Biomedical Engineering Department, BRFAA) for technical assistance, and the BRFAA Animal Facility. The authors would also like to thank Dr. Nadia Stefanova (Innsbruck University) for providing the C57BL6 PLP-haSyn transgenic mice and Imago Pharmaceuticals for providing the 11A5 antibody. The authors also like to thank Dr. Lee Clough for editing the manuscript. PHJ was supported by the Lundbeck foundation Grant R223-2015-4222 and R248-2016-25. This work was supported by an MSA Coalition grant and a Bodossaki Grant to MX. Partial support was provided by an NIH grant NS1000876 to BG and by the Innovative Medicines Initiative 2 Joint Undertaking under Grant agreement No. 116060 (IMPRiND) to LS. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation program and EFPIA. This work was supported by the Swiss State Secretariat for Education‚ Research and Innovation (SERI) under contract number 17.00038. The opinions expressed and arguments employed herein do not necessarily reflect the official views of these funding bodies.
PM carried out the experiments, analyzed and interpreted the data, generated the figures, and participated in the study design, and in writing the manuscript. FA carried out the immunohistochemical analysis of the hPFF-injected mouse brains. AKK performed the initial experiments with the uptake of hPFFs in the OLN cell lines. MV carried out additional experiments required for resubmission. IK performed the EM analysis. MZ, KG, and SB generated the haSyn PFFs. ZS and BG performed immunohistochemical staining and comparative analyses of human brain tissue. PHJ provided the OLN cells, p25α plasmid, and p25α antibody. LS participated in study design, data interpretation, and in writing the manuscript. MX conceived the hypothesis, coordinated and led the study, and participated in study design, data interpretation and in writing the manuscript.
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Conflict of interest
The authors have declared that no conflict of interest exists.
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