Neurodegenerative diseases are characterized by the formation and propagation of protein aggregates, especially amyloid fibrils. However, what normally suppresses protein misfolding and aggregation ...in metazoan cells remains incompletely understood. Here, we show that TRIM11, a member of the metazoan tripartite motif (TRIM) family, both prevents the formation of protein aggregates and dissolves pre-existing protein deposits, including amyloid fibrils. These molecular chaperone and disaggregase activities are ATP independent. They enhance folding and solubility of normal proteins and cooperate with TRIM11 SUMO ligase activity to degrade aberrant proteins. TRIM11 abrogates α-synuclein fibrillization and restores viability in cell models of Parkinson’s disease (PD). Intracranial adeno-associated viral delivery of TRIM11 mitigates α-synuclein-mediated pathology, neurodegeneration, and motor impairments in a PD mouse model. Other TRIMs can also function as ATP-independent molecular chaperones and disaggregases. Thus, we define TRIMs as a potent and multifunctional protein quality-control system in metazoa, which might be applied to treat neurodegenerative diseases.
Display omitted
•TRIM11 prevents and reverses protein aggregation in an ATP-independent manner•These molecular chaperone and disaggregase activities enhance protein solubility•They also act together with TRIM11 SUMO ligase activity to degrade defective proteins•TRIM11 mitigates pathology, neurodegeneration, and motor defects in a mouse PD model
Zhu at al. show that TRIM11 possesses ATP-independent molecular chaperone and disaggregase activities. These activities enhance the solubility of proteins and cooperate with TRIM11 SUMO ligase activity to degrade defective proteins. TRIM11 abrogates fibrillization of α-synuclein in vitro and in cells and rescues a mouse model of Parkinson’s disease.
Preclinical assessment of the therapeutic potential of dopamine (DA) neuron replacement in Parkinson’s disease (PD) has primarily been performed in the 6-hydroxydopamine toxin model. While this is a ...good model to assess graft function, it does not reflect the pathological features or progressive nature of the disease. In this study, we establish a humanized transplantation model of PD that better recapitulates the main disease features, obtained by coinjection of preformed human α-synuclein (α-syn) fibrils and adeno-associated virus (AAV) expressing human wild-type α-syn unilaterally into the rat substantia nigra (SN). This model gives rise to DA neuron dysfunction and progressive loss of DA neurons from the SN and terminals in the striatum, accompanied by extensive α-syn pathology and a prominent inflammatory response, making it an interesting and relevant model in which to examine long-term function and integrity of transplanted neurons in a PD-like brain. We transplanted DA neurons derived from human embryonic stem cells (hESCs) into the striatum and assessed their survival, growth, and function over 6 to 18 wk. We show that the transplanted cells, even in the presence of ongoing pathology, are capable of innervating the DA-depleted striatum. However, on closer examination of the grafts, we found evidence of α-syn pathology in the form of inclusions of phosphorylated α-syn in a small fraction of the grafted DA neurons, indicating host-to-graft transfer of α-syn pathology, a phenomenon that has previously been observed in PD patients receiving fetal tissue grafts but has not been possible to demonstrate and study in toxin-based animal models.
Several studies have demonstrated that intrastriatal injections of fibrillar α-synuclein in rodent brain induced a Parkinson's disease-like propagation of Lewy body pathology with significant ...nigrostriatal neurodegeneration. This study evaluated the pathological features when exogenous α-synuclein preformed fibrils were injected into the putamen of non-human primates. Eight cynomolgus monkeys received unilateral intraputamen injections of α-synuclein preformed fibrils and four monkeys received sham surgery. Monkeys were assessed with 123I-PE2I single-photon emission computerized tomography scans targeting the dopamine transprter at baseline, 3, 6, 9, 12, and 15 months. Imaging revealed a robust increase in dopamine transporter binding, an effect confirmed by port-mortem immunohistochemical analyses, suggesting that upregulation of dopamine transporter occurs as part of an early pathological process. Histochemistry and immunohistochemistry revealed that α-synuclein preformed fibrils injections into the putamen induced intraneuronal inclusions positive for phosphorylated α-synuclein in ipsilateral substantia nigra and adjacent to the injection site. α-Synuclein inclusions were thioflavin-S-positive suggesting that the inclusions induced by α-synuclein preformed fibrils exhibited pathological properties similar to amyloid-like Lewy body pathology in Parkinson's disease brains. The α-synuclein preformed fibrils resulted in Lewy pathology in the ipsilateral substantia nigra with significant reduction (-29.30%) of dopaminergic neurons as compared with controls. Nigral neurons with α-synuclein inclusions exhibited a phenotypic downregulation of the dopamine markers tyrosine hydroxylase and Nurr1. Taken together, our findings demonstrate that α-synuclein preformed fibrils induce a synucleinopathy in non-human primates with authentic Lewy pathology and nigrostriatal changes indicative of early Parkinson's disease.
Parkinson's disease is a progressive neurodegenerative disorder characterized by the intracellular accumulation of insoluble alpha-synuclein aggregates into Lewy bodies and neurites. Increasing ...evidence indicates that Parkinson's disease progression results from the spread of pathologic alpha-synuclein through neuronal networks. However, the exact mechanisms underlying the propagation of abnormal proteins in the brain are only partially understood. The objective of this study was first to describe the long-term spatiotemporal distributions of Lewy-related pathology in mice injected with alpha-synuclein preformed fibrils and then to recreate these patterns using a computational model that simulates in silico the spread of pathologic alpha-synuclein. In this study, 87 2-3-month-old non-transgenic mice were injected with alpha-synuclein preformed fibrils to generate a comprehensive post-mortem dataset representing the long-term spatiotemporal distributions of hyperphosphorylated alpha-synuclein, an established marker of Lewy pathology, across the 426 regions of the Allen Mouse Brain Atlas. The mice were injected into either the caudoputamen, nucleus accumbens or hippocampus, and followed over 24 months with pathologic alpha-synuclein quantified at seven intermediate time points. The pathologic patterns observed at each time point in this high-resolution dataset were then compared to those generated using a Susceptible-Infected-Removed (SIR) computational model, an agent-based model that simulates the spread of pathologic alpha-synuclein for every brain region taking simultaneously into account the effect of regional brain connectivity and Snca gene expression. Our histopathological findings showed that differentially targeted seeding of pathological alpha-synuclein resulted in unique propagation patterns over 24 months and that most brain regions were permissive to pathology. We found that the SIR model recreated the observed distributions of pathology over 24 months for each injection site. Null models showed that both Snca gene expression and connectivity had a significant influence on model fit. In sum, our study demonstrates that the combination of normal alpha-synuclein concentration and brain connectomics contributes to making brain regions more vulnerable to the pathological process, providing support for a prion-like spread of pathologic alpha-synuclein. We propose that this rich dataset and the related computational model will help test new hypotheses regarding mechanisms that may alter the spread of pathologic alpha-synuclein in the brain.
Parkinson's disease (PD) is a neurodegenerative disorder that is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies), markers of neuroinflammation and the ...progressive loss of nigrostriatal dopamine (DA) neurons. These pathological features can be recapitulated in vivo using the α-syn preformed fibril (PFF) model of synucleinopathy. We have previously determined that microglia proximal to PFF-induced nigral α-syn inclusions increase in soma size, upregulate major-histocompatibility complex-II (MHC-II) expression, and increase expression of a suite of inflammation-associated transcripts. This microglial response is observed months prior to degeneration, suggesting that microglia reacting to α-syn inclusion may contribute to neurodegeneration and could represent a potential target for novel therapeutics. The goal of this study was to determine whether colony stimulating factor-1 receptor (CSF1R)-mediated microglial depletion impacts the magnitude of α-syn aggregation, nigrostriatal degeneration, or the response of microglial in the context of the α-syn PFF model.
Male Fischer 344 rats were injected intrastriatally with either α-syn PFFs or saline. Rats were continuously administered Pexidartinib (PLX3397B, 600 mg/kg), a CSF1R inhibitor, to deplete microglia for a period of either 2 or 6 months.
CSF1R inhibition resulted in significant depletion (~ 43%) of ionized calcium-binding adapter molecule 1 immunoreactive (Iba-1ir) microglia within the SNpc. However, CSF1R inhibition did not impact the increase in microglial number, soma size, number of MHC-II immunoreactive microglia or microglial expression of Cd74, Cxcl10, Rt-1a2, Grn, Csf1r, Tyrobp, and Fcer1g associated with phosphorylated α-syn (pSyn) nigral inclusions. Further, accumulation of pSyn and degeneration of nigral neurons was not impacted by CSF1R inhibition. Paradoxically, long term CSF1R inhibition resulted in increased soma size of remaining Iba-1ir microglia in both control and PFF rats, as well as expression of MHC-II in extranigral regions.
Collectively, our results suggest that CSF1R inhibition does not impact the microglial response to nigral pSyn inclusions and that CSF1R inhibition is not a viable disease-modifying strategy for PD.
Many risk loci for Parkinson's disease (PD) have been identified by genome-wide association studies (GWASs), but target genes and mechanisms remain largely unknown. We linked the GWAS-derived ...chromosome 7 locus (sentinel single-nucleotide polymorphism rs199347) to
through colocalization analyses of expression quantitative trait locus and PD risk signals, confirmed by allele-specific expression studies in the human brain. In cells, glycoprotein nonmetastatic melanoma protein B (GPNMB) coimmunoprecipitated and colocalized with α-synuclein (aSyn). In induced pluripotent stem cell-derived neurons, loss of
resulted in loss of ability to internalize aSyn fibrils and develop aSyn pathology. In 731 PD and 59 control biosamples, GPNMB was elevated in PD plasma, associating with disease severity. Thus,
represents a PD risk gene with potential for biomarker development and therapeutic targeting.
The accumulation of misfolded α-synuclein (aSyn) and neuron loss define several neurodegenerative disorders including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). However, the ...precise relationship between pathology and neurotoxicity and why these processes disproportionately affect certain neuron subpopulations are poorly understood. We show here that Math2-expressing neurons in the hippocampal
Cornu ammonis
(CA), a region significantly affected by aSyn pathology in advanced PD and DLB, are highly susceptible to pathological seeding with pre-formed fibrils (PFFs), in contrast to dentate gyrus neurons, which are relatively spared. Math2
+
neurons also exhibited more rapid and severe cell loss in both in vitro and in vivo models of synucleinopathy. Toxicity resulting from PFF exposure was dependent on endogenous aSyn and could be attenuated by
N
-acetyl-cysteine through a glutathione-dependent process. Moreover, aSyn expression levels strongly correlate with relative vulnerability among hippocampal neuron subtypes of which Math2
+
neurons contained the highest amount. Consistent with this, antisense oligonucleotide (ASO)-mediated knockdown of aSyn reduced the neuronal pathology in a time-dependent manner. However, significant neuroprotection was observed only with early ASO intervention and a substantial reduction of aSyn pathology, indicating toxicity occurs after a critical threshold of pathological burden is exceeded in vulnerable neurons. Together, our findings reveal considerable heterogeneity in endogenous aSyn levels among hippocampal neurons and suggest that this may contribute to the selective vulnerability observed in the context of synucleinopathies.
Abstract
Synucleinopathies are composed of Parkinson disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Alpha-synuclein (α-Syn) forms aggregates mainly in neurons in PD ...and DLB, while oligodendroglial α-Syn aggregates are characteristic of MSA. Recent studies have demonstrated that injections of synthetic α-Syn preformed fibrils (PFFs) into the brains of wild-type (WT) animals induce intraneuronal α-Syn aggregates and the subsequent interneuronal transmission of α-Syn aggregates. However, injections of α-Syn PFFs or even brain lysates of patients with MSA have not been reported to induce oligodendroglial α-Syn aggregates, raising questions about the pathogenesis of oligodendroglial α-Syn aggregates in MSA. Here, we report that WT mice injected with mouse α-Syn (m-α-Syn) PFFs develop neuronal α-Syn pathology after short postinjection (PI) intervals on the scale of weeks, while oligodendroglial α-Syn pathology emerges after longer PI intervals of several months. Abundant oligodendroglial α-Syn pathology in white matter at later time points is reminiscent of MSA. Furthermore, comparison between young and aged mice injected with m-α-Syn PFFs revealed that PI intervals rather than aging correlate with oligodendroglial α-Syn aggregation. These results provide novel insights into the pathological mechanisms of oligodendroglial α-Syn aggregation in MSA.
Reactive microglia are observed with aging and in Lewy body disorders, including within the olfactory bulb of men with Parkinson's disease. However, the functional impact of microglia in these ...disorders is still debated. Resetting these reactive cells by a brief dietary pulse of the colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 may hold therapeutic potential against Lewy-related pathologies. To our knowledge, withdrawal of PLX5622 after short-term exposure has not been tested in the preformed α-synuclein fibril (PFF) model, including in aged mice of both sexes. Compared to aged female mice, we report that aged males on the control diet showed higher numbers of phosphorylated α-synuclein+ inclusions in the limbic rhinencephalon after PFFs were injected in the posterior olfactory bulb. However, aged females displayed larger inclusion sizes compared to males. Short-term (14-day) dietary exposure to PLX5622 followed by control chow reduced inclusion numbers and levels of insoluble α-synuclein in aged males—but not females—and unexpectedly raised inclusion sizes in both sexes. Transient delivery of PLX5622 also improved spatial reference memory in PFF-infused aged mice, as evidenced by an increase in novel arm entries in a Y-maze. Superior memory was positively correlated with inclusion sizes but negatively correlated with inclusion numbers. Although we caution that PLX5622 delivery must be tested further in models of α-synucleinopathy, our data suggest that larger-sized—but fewer—α-synucleinopathic structures are associated with better neurological outcomes in PFF-infused aged mice.
•We leveraged a mouse model of preformed fibril-seeded, limbic alpha-synucleinopathy.•Aged female mice had fewer but larger-sized inclusions than aged males.•Transient PLX5622 reduced inclusion counts and insoluble α-synuclein in aged males.•Transient PLX5622 raised inclusion sizes and improved spatial reference memory.•Superior memory was linked to larger-sized but fewer inclusions.
The synucleinopathies are a diverse group of neurodegenerative disorders characterized by the accumulation of aggregated alpha-synuclein (aSyn) in vulnerable populations of brain cells. Oxidative ...stress is both a cause and a consequence of aSyn aggregation in the synucleinopathies; however, noninvasive methods for detecting oxidative stress in living animals have proven elusive. In this study, we used the reactive oxygen species (ROS)-sensitive positron emission tomography (PET) radiotracer
FROStrace to detect increases in oxidative stress in the widely-used A53T mouse model of synucleinopathy. A53T-specific elevations in
FROStrace signal emerged at a relatively early age (6-8 months) and became more widespread within the brain over time, a pattern which paralleled the progressive development of aSyn pathology and oxidative damage in A53T brain tissue. Systemic administration of lipopolysaccharide (LPS) also caused rapid and long-lasting elevations in
FROStrace signal in A53T mice, suggesting that chronic, aSyn-associated oxidative stress may render these animals more vulnerable to further inflammatory insult. Collectively, these results provide novel evidence that oxidative stress is an early and chronic process during the development of synucleinopathy and suggest that PET imaging with
FROStrace holds promise as a means of detecting aSyn-associated oxidative stress noninvasively.
PDF
