Pathological Endogenous α-Synuclein Accumulation in Oligodendrocyte Precursor Cells Potentially Induces Inclusions in Multiple System Atrophy.
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ABSTRACT:
SUBMITTER: Kaji S
PROVIDER: S-EPMC5830961 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description: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/p25?. However, the role of oligodendroglial aSyn and p25? 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 p25?-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 p25? 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 p25? 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 p25? 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.
| S-EPMC7289399 | biostudies-literature
Project description:α-Synuclein (αsyn) aggregates into toxic fibrils in multiple neurodegenerative diseases where these fibrils form characteristic pathological inclusions such as Lewy bodies (LBs). The mechanisms initiating αsyn aggregation into fibrils are unclear, but ubiquitous post-translational modifications of αsyn present in LBs may play a role. Specific C-terminally (C)-truncated forms of αsyn are present within human pathological inclusions and form under physiological conditions likely in lysosome-associated pathways, but the roles for these C-truncated forms of αsyn in inclusion formation and disease are not well understood. Herein, we characterized the in vitro aggregation properties, amyloid fibril structures, and ability to induce full-length (FL) αsyn aggregation through prion-like mechanisms for eight of the most common physiological C-truncated forms of αsyn (1-115, 1-119, 1-122, 1-124, 1-125, 1-129, 1-133, and 1-135). In vitro, C-truncated αsyn aggregated more readily than FL αsyn and formed fibrils with unique morphologies. The presence of C-truncated αsyn potentiated aggregation of FL αsyn in vitro through co-polymerization. Specific C-truncated forms of αsyn in cells also exacerbated seeded aggregation of αsyn. Furthermore, in primary neuronal cultures, co-polymers of C-truncated and FL αsyn were potent prion-like seeds, but polymers composed solely of the C-truncated protein were not. These experiments indicated that specific physiological C-truncated forms of αsyn have distinct aggregation properties, including the ability to modulate the prion-like aggregation and seeding activity of FL αsyn. Proteolytic formation of these C-truncated species may have an important role in both the initiation of αsyn pathological inclusions and further progression of disease with strain-like properties.
| S-EPMC6295729 | biostudies-literature
Project description:Synucleinopathies, neurodegenerative disorders with alpha-synuclein (α-syn) accumulation, are the second leading cause of neurodegeneration in the elderly, however no effective disease-modifying alternatives exist for these diseases. Multiple system atrophy (MSA) is a fatal synucleinopathy characterized by the accumulation of toxic aggregates of α-syn within oligodendroglial cells, leading to demyelination and neurodegeneration, and the reduction of this accumulation might halt the fast progression of MSA. In this sense, the involvement of microRNAs (miRNAs) in synucleinopathies is yet poorly understood, and the potential of manipulating miRNA levels as a therapeutic tool is underexplored. In this study, we analyzed the levels of miRNAs that regulate the expression of autophagy genes in MSA cases, and investigated the mechanistic correlates of miRNA dysregulation in in vitro models of synucleinopathy. We found that microRNA-101 (miR-101) was significantly increased in the striatum of MSA patients, together with a reduction in the expression of its predicted target gene RAB5A. Overexpression of miR-101 in oligodendroglial cell cultures resulted in a significant increase in α-syn accumulation, along with autophagy deficits. Opposite results were observed upon expression of an antisense construct targeting miR-101. Stereotaxic delivery of a lentiviral construct expressing anti-miR-101 into the striatum of the MBP-α-syn transgenic (tg) mouse model of MSA resulted in reduced oligodendroglial α-syn accumulation and improved autophagy. These results suggest that miRNA dysregulation contributes to MSA pathology, with miR-101 alterations potentially mediating autophagy impairments. Therefore, therapies targeting miR-101 may represent promising approaches for MSA and related neuropathologies with autophagy dysfunction.
| S-EPMC5650998 | biostudies-literature
Project description:The molecular architecture of α-Synuclein (α-Syn) inclusions, pathognomonic of various neurodegenerative disorders, remains unclear. α-Syn inclusions were long thought to consist mainly of α-Syn fibrils, but recent reports pointed to intracellular membranes as the major inclusion component. Here, we use cryo-electron tomography (cryo-ET) to image neuronal α-Syn inclusions in situ at molecular resolution. We show that inclusions seeded by α-Syn aggregates produced recombinantly or purified from patient brain consist of α-Syn fibrils crisscrossing a variety of cellular organelles. Using gold-labeled seeds, we find that aggregate seeding is predominantly mediated by small α-Syn fibrils, from which cytoplasmic fibrils grow unidirectionally. Detailed analysis of membrane interactions revealed that α-Syn fibrils do not contact membranes directly, and that α-Syn does not drive membrane clustering. Altogether, we conclusively demonstrate that neuronal α-Syn inclusions consist of α-Syn fibrils intermixed with membranous organelles, and illuminate the mechanism of aggregate seeding and cellular interaction.
| S-EPMC8046968 | biostudies-literature
Project description:The Parkinson's disease (PD)-associated kinase Leucine-Rich Repeat Kinase 2 (LRRK2) is a crucial modulator of the autophagy-lysosome pathway, but unclarity exists on the precise mechanics of its role and the direction of this modulation. In particular, LRRK2 is involved in the degradation of pathological alpha-synuclein, with pathogenic mutations precipitating neuropathology in cellular and animal models of PD, and a significant proportion of LRRK2 patients presenting Lewy neuropathology. Defects in autophagic processing and lysosomal degradation of alpha-synuclein have been postulated to underlie its accumulation and onset of neuropathology. Thus, it is critical to obtain a comprehensive knowledge on LRRK2-associated pathology. Here, we investigated a G2019S-LRRK2 recombinant cell line exhibiting accumulation of endogenous, phosphorylated alpha-synuclein. We found that G2019S-LRRK2 leads to accumulation of LC3 and abnormalities in lysosome morphology and proteolytic activity in a kinase-dependent fashion, but independent from constitutively active Rab10. Notably, LRRK2 inhibition was ineffective upon upstream blockade of autophagosome-lysosome fusion events, highlighting this step as critical for alpha-synuclein clearance.
| S-EPMC7280235 | biostudies-literature
Project description:Posttranslational modifications by phosphorylation, ubiquitination, neddylation and other pathways have emerged as major regulators of cellular functions. NEDD8 ultimate buster 1, NUB1, is an adaptor protein, which negatively regulates the levels of the ubiquitin-like protein NEDD8 as well as neddylated proteins through proteasomal degradation. We previously reported that NUB1 is highly involved in the pathogenesis of synucleinopathy including Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). In general, since phosphorylation is strongly related to the alteration of protein propensity, we examined if the fundamental function of NUB1 can be modulated by its phosphorylation. We created a series of phosphomimic mutants of NUB1. Among them, we found that phosphorylation of NUB1 at S46 (P-NUB46) efficiently degrades aggregates using a cell-based assay. Immunohistochemical studies have shown that specific antibodies against P-NUB46 reacted with Lewy bodies in PD and DLB but not with glial cytoplasmic inclusions in MSA. Moreover, P-NUB46 levels were significantly higher in the brains of patients with DLB than in control brains, and P-NUB46 was extracted in an insoluble fraction of DLB. These findings suggest that the phosphorylation of NUB1 is modulated during the pathological process of Lewy body disease.
| S-EPMC8028632 | biostudies-literature
Project description:Multiple system atrophy (MSA), a progressive neurodegenerative disease characterized by autonomic dysfunction and motor impairment, is caused by the self-templated misfolding of the protein ?-synuclein. With no treatment currently available, we sought to characterize the spread of ?-synuclein in a transgenic mouse model of MSA prion propagation to support drug discovery programs for synucleinopathies. Brain homogenates from MSA patient samples or mouse-passaged MSA were inoculated either by standard freehand injection or stereotactically into TgM83+/- mice, which express human ?-synuclein with the A53T mutation. Following disease onset, brains from the mice were tested for biologically active ?-synuclein prions using a cell-based assay and examined for ?-synuclein neuropathology. Inoculation studies using homogenates prepared from brain regions lacking detectable ?-synuclein neuropathology transmitted neurological disease to mice. Terminal animals contained similar concentrations of ?-synuclein prions; however, a time-course study where mice were terminated every five days through disease progression revealed that the kinetics of ?-synuclein prion replication in the mice were variable. Stereotactic inoculation into the thalamus reduced variability in disease onset in the mice, although incubation times were consistent with standard inoculations. Using human samples with and without neuropathological lesions, we observed that ?-synuclein prion formation precedes neuropathology in the brain, suggesting that disease in patients is not limited to brain regions containing neuropathological lesions.
| S-EPMC6999861 | biostudies-literature
Project description:Multiple system atrophy (MSA) is a neurodegenerative disease caused by an accumulation of alpha-synuclein (alpha-syn) in oligodendrocytes. Little is known about the cellular mechanisms by which alpha-syn accumulation causes neuronal degeneration in MSA. Our previous research, however, revealed that in a mouse model of MSA, oligodendrocytic inclusions of alpha-syn induced neuronal accumulation of alpha-syn, as well as progressive neuronal degeneration. Here we identify the mechanisms that underlie neuronal accumulation of alpha-syn in a mouse MSA model. We found that the alpha-syn protein binds to beta-III tubulin in microtubules to form an insoluble complex. The insoluble alpha-syn complex progressively accumulates in neurons and leads to neuronal dysfunction. Furthermore, we demonstrated that the neuronal accumulation of insoluble alpha-syn is suppressed by treatment with a microtubule depolymerizing agent. The underlying pathological process appeared to also be inhibited by this treatment, providing promise for future therapeutic approaches.
| S-EPMC2671377 | biostudies-literature
Project description:AimsMultiple system atrophy (MSA) is a fatal neurodegenerative disease. Similar to Parkinson's disease (PD), MSA is an α-synucleinopathy, and its pathological hallmark consists of glial cytoplasmic inclusions (GCIs) containing α-synuclein (SNCA) in oligodendrocytes. We previously identified consistent changes in myelin-associated oligodendrocyte basic protein (MOBP) and huntingtin interacting protein 1 (HIP1) DNA methylation status in MSA. We hypothesized that if differential DNA methylation at these loci is mechanistically relevant for MSA, it should have downstream consequences on gene regulation.MethodsWe investigated the relationship between MOBP and HIP1 DNA methylation and mRNA levels in cerebellar white matter from MSA and healthy controls. Additionally, we analysed protein expression using western blotting, immunohistochemistry and proximity ligation assays.ResultsWe found decreased MOBP mRNA levels significantly correlated with increased DNA methylation in MSA. For HIP1, we found a distinct relationship between DNA methylation and gene expression levels in MSA compared to healthy controls, suggesting this locus may be subjected to epigenetic remodelling in MSA. Although soluble protein levels for MOBP and HIP1 in cerebellar white matter were not significantly different between MSA cases and controls, we found striking differences between MSA and other neurodegenerative diseases, including PD and Huntington's disease. We also found that MOBP and HIP1 are mislocalized into the GCIs in MSA, where they appear to interact with SNCA.ConclusionsThis study supports a role for DNA methylation in downregulation of MOBP mRNA in MSA. Most importantly, the identification of MOBP and HIP1 as new constituents of GCIs emphasizes the relevance of these two loci to the pathogenesis of MSA.
| S-EPMC8219819 | biostudies-literature
Project description:Spinal muscular atrophy, the most prevalent hereditary motor neuron disease, is caused by mutations in the survival motor neuron (SMN) 1 gene. A significant reduction in the encoded SMN protein leads to the degeneration of motor neurons. However, the molecular events leading to this process are not well understood. The present study uses a previously developed neuronal cell culture model of spinal muscular atrophy for a multiplex transcriptome analysis. Furthermore, gene expression analysis was performed on in vitro cell cultures, as well as tissue samples of spinal muscular atrophy patients and transgenic mice. RNA and subsequent Western blot protein analyses suggest that low SMN levels are associated with significantly lower alpha-synuclein expression. Examination of two genes related to vesicular transport showed a similar though less dramatic decrease in expression. The 140-amino acid protein alpha-synuclein, dominant mutations of which have previously been associated with an autosomal dominant form of Parkinson's disease, is strongly expressed in select neurons of the brain. Although not well understood, the physiologic functions of alpha-synuclein have been linked to synaptic vesicular neurotransmitter release and neuroprotection, suggesting a possible contribution to Smn-deficient motor neuron pathology. Furthermore, alpha-synuclein may be a genetic modifier or biomarker of spinal muscular atrophy.
| S-EPMC3918138 | biostudies-literature