Glucosylceramide Associated with Gaucher Disease Forms Amyloid-like Twisted Ribbon Fibrils That Induce α-Synuclein Aggregation.
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ABSTRACT:
SUBMITTER: Paul A
PROVIDER: S-EPMC8397424 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Parkinson's disease (PD) is characterized by a progressive loss of dopaminergic neurons, a process that current therapeutic approaches cannot prevent. In PD, the typical pathological hallmark is the accumulation of intracellular protein inclusions, known as Lewy bodies and Lewy neurites, which are mainly composed of ?-synuclein. Here, we exploited a high-throughput screening methodology to identify a small molecule (SynuClean-D) able to inhibit ?-synuclein aggregation. SynuClean-D significantly reduces the in vitro aggregation of wild-type ?-synuclein and the familiar A30P and H50Q variants in a substoichiometric molar ratio. This compound prevents fibril propagation in protein-misfolding cyclic amplification assays and decreases the number of ?-synuclein inclusions in human neuroglioma cells. Computational analysis suggests that SynuClean-D can bind to cavities in mature ?-synuclein fibrils and, indeed, it displays a strong fibril disaggregation activity. The treatment with SynuClean-D of two PD Caenorhabditis elegans models, expressing ?-synuclein either in muscle or in dopaminergic neurons, significantly reduces the toxicity exerted by ?-synuclein. SynuClean-D-treated worms show decreased ?-synuclein aggregation in muscle and a concomitant motility recovery. More importantly, this compound is able to rescue dopaminergic neurons from ?-synuclein-induced degeneration. Overall, SynuClean-D appears to be a promising molecule for therapeutic intervention in Parkinson's disease.
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Project description:C-terminal truncations of monomeric wild-type alpha-synuclein (henceforth WT-αS) have been shown to enhance the formation of amyloid aggregates both in vivo and in vitro and have been associated with accelerated progression of Parkinson's disease (PD). The correlation with PD may not solely be a result of faster aggregation, but also of which fibril polymorphs are preferentially formed when the C-terminal residues are deleted. Considering that different polymorphs are known to result in distinct pathologies, it is important to understand how these truncations affect the organization of αS into fibrils. Here we present high-resolution microscopy and advanced vibrational spectroscopy studies that indicate that the C-terminal truncation variant of αS, lacking residues 109-140 (henceforth referred to as 1-108-αS), forms amyloid fibrils with a distinct structure and morphology. The 1-108-αS fibrils have a unique negative circular dichroism band at ∼230 nm, a feature that differs from the canonical ∼218 nm band usually observed for amyloid fibrils. We show evidence that 1-108-αS fibrils consist of strongly twisted β-sheets with an increased inter-β-sheet distance and a higher solvent exposure than WT-αS fibrils, which is also indicated by the pronounced differences in the 1D-IR (FTIR), 2D-IR, and vibrational circular dichroism spectra. As a result of their distinct β-sheet structure, 1-108-αS fibrils resist incorporation of WT-αS monomers.
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Project description:Amyloid deposits from several human diseases have been found to contain membrane lipids. Co-aggregation of lipids and amyloid proteins in amyloid aggregates, and the related extraction of lipids from cellular membranes, can influence structure and function in both the membrane and the formed amyloid deposit. Co-aggregation can therefore have important implications for the pathological consequences of amyloid formation. Still, very little is known about the mechanism behind co-aggregation and molecular structure in the formed aggregates. To address this, we study in vitro co-aggregation by incubating phospholipid model membranes with the Parkinson's disease-associated protein, α-synuclein, in monomeric form. After aggregation, we find spontaneous uptake of phospholipids from anionic model membranes into the amyloid fibrils. Phospholipid quantification, polarization transfer solid-state NMR and cryo-TEM together reveal co-aggregation of phospholipids and α-synuclein in a saturable manner with a strong dependence on lipid composition. At low lipid to protein ratios, there is a close association of phospholipids to the fibril structure, which is apparent from reduced phospholipid mobility and morphological changes in fibril bundling. At higher lipid to protein ratios, additional vesicles adsorb along the fibrils. While interactions between lipids and amyloid-protein are generally discussed within the perspective of different protein species adsorbing to and perturbing the lipid membrane, the current work reveals amyloid formation in the presence of lipids as a co-aggregation process. The interaction leads to the formation of lipid-protein co-aggregates with distinct structure, dynamics and morphology compared to assemblies formed by either lipid or protein alone.
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Project description:OBJECTIVE:Alpha-synuclein (?-syn) is a major component of Lewy bodies, which are the pathological hallmark in Parkinson's disease, and its genetic mutations cause familial forms of Parkinson's disease. Patients with ?-syn G51D mutation exhibit severe clinical symptoms. However, in vitro studies showed low propensity for ?-syn with the G51D mutation. We studied the mechanisms associated with severe neurotoxicity of ?-syn G51D mutation using a murine model generated by G51D ?-syn fibril injection into the brain. METHODS:Structural analysis of wild-type and G51D ?-syn-fibrils were performed using Fourier transform infrared spectroscopy. The ability of ?-syn fibrils forming aggregates was first assessed in in vitro mammalian cells. An in vivo mouse model with an intranigral injection of ?-syn fibrils was then used to evaluate the propagation pattern of ?-syn and related cellular changes. RESULTS:We found that G51D ?-syn fibrils have higher ?-sheet contents than wild-type ?-syn fibrils. The addition of G51D ?-syn fibrils to mammalian cells overexpressing ?-syn resulted in the formation of phosphorylated ?-syn inclusions at a higher rate. Similarly, an injection of G51D ?-syn fibrils into the substantia nigra of a mouse brain induced more widespread phosphorylated ?-syn pathology. Notably, the mice injected with G51D ?-syn fibrils exhibited progressive nigral neuronal loss accompanied with mitochondrial abnormalities and motor impairment. CONCLUSION:Our findings indicate that the structural difference of G51D ?-syn fibrils plays an important role in the rapidly developed and more severe neurotoxicity of G51D mutation-linked Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.
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