Pale neurites, premature α-synuclein aggregates with centripetal extension from axon collaterals.
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ABSTRACT:
SUBMITTER: Kanazawa T
PROVIDER: S-EPMC8029413 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Parkinson's disease (PD) is characterized neuropathologically by intracellular aggregates of fibrillar α-synuclein, termed Lewy bodies (LBs). Approximately 90% of α-synuclein deposited as LBs is phosphorylated at Ser129 in brains with PD. In contrast, only 4% of total α-synuclein is phosphorylated at Ser129 in brains with normal individuals. It is unclear why extensive phosphorylation occurs in the pathological process of PD. To address this issue, we investigated a mechanism and role of Ser129-phosphorylation in regulating accumulation of α-synuclein. In CHO cells, the levels of Ser129-phosphorylated soluble α-synuclein were maintained constantly to those of total α-synuclein in intracellular and extracellular spaces. In SH-SY5Y cells and rat primary cortical neurons, mitochondrial impairment by rotenone or MPP+ enhanced Ser129-phosphorylation through increased influx of extracellular Ca2+. This elevation was suppressively controlled by targeting Ser129-phosphorylated α-synuclein to the proteasome pathway. Rotenone-induced insoluble α-synuclein was also targeted by Ser129-phosphoryation to the proteasome pathway. Experiments with epoxomicin and chloroquine showed that proteasomal targeting of insoluble Ser129-phosphorylated α-synuclein was enhanced under lysosome inhibition and it reduced accumulation of insoluble total α-synuclein. However, in a rat AAV-mediated α-synuclein overexpression model, there was no difference in the number of total α-synuclein aggregates between A53T mutant and A53T plus S129A double mutant α-synuclein, although Ser129-phosphorylated α-synuclein-positive aggregates were increased in rats expressing A53T α-synuclein. These findings suggest that Ser129-phosphorylation occurs against stress conditions, which increases influx of extracellular Ca2+, and it prevents accumulation of insoluble α-synuclein by evoking proteasomal clearance complementary to lysosomal one. However, Ser129-phosphorylation may provide an ineffective signal for degradation-resistant aggregates, causing extensive phosphorylation in aggregates.
| S-EPMC5472914 | biostudies-literature
Project description:Parkinson's disease (PD) is one of the most common neurodegenerative diseases. It is characterized pathologically by the aggregation of α-synuclein (αS) in the form of Lewy bodies and Lewy neurites. A major challenge in PD therapy is poor efficiency of drug delivery to the brain due to the blood-brain barrier (BBB). For this reason, nanomaterials, with significant advantages in drug delivery, have gained attention. On the other hand, recent studies have shown that nanoparticles can promote αS aggregation in salt solution. Therefore, we tested if nanoparticles could have the same effect in cell models. We found that nanoparticle can induce cells to form αS inclusions as shown in immunocytochemistry, and detergent-resistant αS aggregates as shown in biochemical analysis; and nanoparticles of smaller size can induce more αS inclusions. Moreover, the induction of αS inclusions is in part dependent on endolysosomal impairment and the affinity of αS to nanoparticles. More importantly, we found that the abnormally high level of endogenous lysosomotropic biomolecules (e.g., sphingosine), due to impairing the integrity of endolysosomes could be a determinant factor for the susceptibility of cells to nanoparticle-induced αS aggregation; and deletion of GBA1 gene to increase the level of intracellular sphingosine can render cultured cells more susceptible to the formation of αS inclusions in response to nanoparticle treatment. Ultrastructural examination of nanoparticle-treated cells revealed that the induced inclusions contained αS-immunopositive membranous structures, which were also observed in inclusions seeded by αS fibrils. These results suggest caution in the use of nanoparticles in PD therapy. Moreover, this study further supports the role of endolysosomal impairment in PD pathogenesis and suggests a possible mechanism underlying the formation of membrane-associated αS pathology.
| S-EPMC8565355 | biostudies-literature
Project description:Aggregation of ?-synuclein is a hallmark of Parkinson's disease and dementia with Lewy bodies. We here investigate the relationship between cytosolic Ca2+ and ?-synuclein aggregation. Analyses of cell lines and primary culture models of ?-synuclein cytopathology reveal an early phase with reduced cytosolic Ca2+ levels followed by a later Ca2+ increase. Aggregated but not monomeric ?-synuclein binds to and activates SERCA in vitro, and proximity ligation assays confirm this interaction in cells. The SERCA inhibitor cyclopiazonic acid (CPA) normalises both the initial reduction and the later increase in cytosolic Ca2+ CPA protects the cells against ?-synuclein-aggregate stress and improves viability in cell models and in Caenorhabditis elegans in vivo Proximity ligation assays also reveal an increased interaction between ?-synuclein aggregates and SERCA in human brains affected by dementia with Lewy bodies. We conclude that ?-synuclein aggregates bind SERCA and stimulate its activity. Reducing SERCA activity is neuroprotective, indicating that SERCA and down-stream processes may be therapeutic targets for treating ?-synucleinopathies.
| S-EPMC5934765 | biostudies-literature
Project description:ObjectiveAutonomic nervous system is involved at the onset of Parkinson disease (PD), and alpha-synuclein (?-Syn) and its phosphorylated form (p-?Syn) have been detected in dermal autonomic nerve fibers of PD. We assessed disease specific conformation variant of ?-Syn immunoreactivity in cutaneous nerves and characterized skin denervation patterns in PD and atypical parkinsonism (AP).MethodsWe enrolled 49 subjects, 19 with PD, 17 age-matched healthy controls, and 13 with AP. The manifestations of disease were rated on clinical scales. Skin biopsies from ankle, thigh, and neck were analyzed by immunofluorescence for p-?Syn, 5G4 as a conformation specific antibody to pathogenic ?-Syn and PGP9.5 as axonal marker. Intraepidermal nerve fiber density was measured in all anatomical sites as marker of neurodegeneration. Thirteen of the 19 PD underwent a 1 year follow-up visit plus skin biopsies.ResultsPD subjects displayed more severe cervical skin denervation (P < 0.03), which correlated to disease duration and worsened between initial and follow-up examination (P < 0.001). p-?Syn and 5G4 were equally sensitive and specific for the diagnosis of PD (area under the ROC was 0.839 for p-?Syn and 0.886 for 5G4). PD and AP with possible alpha-synucleinopathies share the features of marked cervical denervation and the presence of 5G4. In contrast AP with possible tauopathies were normal.InterpretationConformational specific forms of ?-Syn are detectable in skin biopsy by immunofluorescence in PD, with a promising diagnostic efficiency similar to p-?Syn. Cervical cutaneous denervation correlates with disease duration and increases over time standing out as a potential biomarker of PD progression.
| S-EPMC6243385 | biostudies-literature
Project description:α-Synuclein aggregates, a key hallmark of the pathogenesis of Parkinson's disease, can be amplified by using their seeding activity, and the evaluation of the seeding activity of cerebrospinal fluid (CSF) is reportedly useful for diagnosis. However, conventional shaking-based assays are time-consuming procedures, and the clinical significance of the diversity of seeding activity among patients remains to be clarified. Previously, we reported a high-throughput ultrasonication-induced amyloid fibrillation assay. Here, we adapted this assay to amplify and detect α-synuclein aggregates from CSF, and investigated the correlation between seeding activity and clinical indicators. We confirmed that this assay could detect α-synuclein aggregates prepared in vitro and also aggregates released from cultured cells. The seeding activity of CSF correlated with the levels of α-synuclein oligomers measured by an enzyme-linked immunosorbent assay. Moreover, the seeding activity of CSF from patients with Parkinson's disease was higher than that of control patients. Notably, the lag time of patients with Parkinson's disease was significantly correlated with the MIBG heart-to-mediastinum ratio. These findings showed that our ultrasonication-based assay can rapidly amplify misfolded α-synuclein and can evaluate the seeding activity of CSF.
| S-EPMC6461702 | biostudies-literature
Project description:Here we describe the use of an organotypic hippocampal slice model for studying ?-synuclein aggregation and inter-neuronal spreading initiated by microinjection of pre-formed ?-synuclein fibrils (PFFs). PFF injection at dentate gyrus (DG) templates the formation of endogenous ?-synuclein aggregates in axons and cell bodies of this region that spread to CA3 and CA1 regions. Aggregates are insoluble and phosphorylated at serine-129, recapitulating Lewy pathology features found in Parkinson's disease and other synucleinopathies. The model was found to favor anterograde spreading of the aggregates. Furthermore, it allowed development of slices expressing only serine-129 phosphorylation-deficient human ?-synuclein (S129G) using an adeno-associated viral (AAV) vector in ?-synuclein knockout slices. The processes of aggregation and spreading of ?-synuclein were thereby shown to be independent of phosphorylation at serine-129. We provide methods and highlight crucial steps for PFF microinjection and characterization of aggregate formation and spreading. Slices derived from genetically engineered mice or manipulated using viral vectors allow testing of hypotheses on mechanisms involved in the formation of ?-synuclein aggregates and their prion-like spreading.
| S-EPMC6924077 | biostudies-literature
Project description:Misfolded alpha-synuclein (αSyn) is a major constituent of Lewy bodies and Lewy neurites, which are pathological hallmarks of Parkinson's disease (PD). The contribution of αSyn to PD is well established, but the detailed mechanism remains obscure. Using a model in which αSyn aggregation in primary neurons was seeded by exogenously added, preformed αSyn amyloid fibrils (PFF), we found that a majority of pathogenic αSyn (indicated by serine 129 phosphorylated αSyn, ps-αSyn) was membrane-bound and associated with mitochondria. In contrast, only a minuscule amount of physiological αSyn was mitochondrial bound. In vitro, αSyn PFF displayed a stronger binding to purified mitochondria than did αSyn monomer, revealing a preferential mitochondria binding by aggregated αSyn. This selective mitochondrial ps-αSyn accumulation was confirmed in other neuronal and animal αSyn aggregation models that do not require exogenously added PFF and, more importantly, in postmortem brain tissues of patients suffering from PD and other neurodegenerative diseases with αSyn aggregation (α-synucleinopathies). We also showed that the mitochondrial ps-αSyn accumulation was accompanied by defects in cellular respiration in primary neurons, suggesting a link to mitochondrial dysfunction. Together, our results show that, contrary to physiological αSyn, pathogenic αSyn aggregates preferentially bind to mitochondria, indicating mitochondrial dysfunction as the common downstream mechanism for α-synucleinopathies. Our findings suggest a plausible model explaining the formation and the peculiar morphology of Lewy body and reveal that disrupting the interaction between ps-αSyn and the mitochondria is a therapeutic target for α-synucleinopathies.
| S-EPMC6419482 | biostudies-literature
Project description:Alpha-synuclein (α-Syn) aggregates are the main component of Lewy bodies, which are the characteristic pathological feature in Parkinson's disease (PD) brain. Evidence that α-Syn aggregation can be propagated between neurones has led to the suggestion that this mechanism is responsible for the stepwise progression of PD pathology. Decreasing α-Syn expression is predicted to attenuate this process and is thus an attractive approach to delay or halt PD progression. We have used α-Syn small interfering RNA (siRNA) to reduce total and aggregated α-Syn levels in mouse brains. To achieve widespread delivery of siRNAs to the brain we have peripherally injected modified exosomes expressing Ravies virus glycoprotein loaded with siRNA. Normal mice were analyzed 3 or 7 days after injection. To evaluate whether this approach can decrease α-Syn aggregates, we repeated the treatment using transgenic mice expressing the human phosphorylation-mimic S129D α-Syn, which exhibits aggregation. In normal mice we detected significantly reduced α-Syn messenger RNA (mRNA) and protein levels throughout the brain 3 and 7 days after treatment with RVG-exosomes loaded with siRNA to α-Syn. In S129D α-Syn transgenic mice we found a decreased α-Syn mRNA and protein levels throughout the brain 7 days after injection. This resulted in significant reductions in intraneuronal protein aggregates, including in dopaminergic neurones of the substantia nigra. This study highlights the therapeutic potential of RVG-exosome delivery of siRNA to delay and reverse brain α-Syn pathological conditions.
| S-EPMC4204174 | biostudies-literature
Project description:α-Synuclein aggregation at the synapse is an early event in Parkinson's disease and is associated with impaired striatal synaptic function and dopaminergic neuronal death. The cysteine string protein (CSPα) and α-synuclein have partially overlapping roles in maintaining synaptic function and mutations in each cause neurodegenerative diseases. CSPα is a member of the DNAJ/HSP40 family of co-chaperones and like α-synuclein, chaperones the SNARE complex assembly and controls neurotransmitter release. α-Synuclein can rescue neurodegeneration in CSPαKO mice. However, whether α-synuclein aggregation alters CSPα expression and function is unknown. Here we show that α-synuclein aggregation at the synapse is associated with a decrease in synaptic CSPα and a reduction in the complexes that CSPα forms with HSC70 and STGa. We further show that viral delivery of CSPα rescues in vitro the impaired vesicle recycling in PC12 cells with α-synuclein aggregates and in vivo reduces synaptic α-synuclein aggregates increasing monomeric α-synuclein and restoring normal dopamine release in 1-120hαSyn mice. These novel findings reveal a mechanism by which α-synuclein aggregation alters CSPα at the synapse, and show that CSPα rescues α-synuclein aggregation-related phenotype in 1-120hαSyn mice similar to the effect of α-synuclein in CSPαKO mice. These results implicate CSPα as a potential therapeutic target for the treatment of early-stage Parkinson's disease.
| S-EPMC8320296 | biostudies-literature
Project description:PurposeDeposition of misfolded alpha-synuclein (αSYN) aggregates in the human brain is one of the major hallmarks of synucleinopathies. However, a target-specific tracer to detect pathological aggregates of αSYN remains lacking. Here, we report the development of a positron emission tomography (PET) tracer based on anle138b, a compound shown to have therapeutic activity in animal models of neurodegenerative diseases.MethodsSpecificity and selectivity of [3H]MODAG-001 were tested in in vitro binding assays using recombinant fibrils. After carbon-11 radiolabeling, the pharmacokinetic and metabolic profile was determined in mice. Specific binding was quantified in rats, inoculated with αSYN fibrils and using in vitro autoradiography in human brain sections of Lewy body dementia (LBD) cases provided by the Neurobiobank Munich (NBM).Results[3H]MODAG-001 revealed a very high affinity towards pure αSYN fibrils (Kd = 0.6 ± 0.1 nM) and only a moderate affinity to hTau46 fibrils (Kd = 19 ± 6.4 nM) as well as amyloid-β1-42 fibrils (Kd = 20 ± 10 nM). [11C]MODAG-001 showed an excellent ability to penetrate the mouse brain. Metabolic degradation was present, but the stability of the parent compound improved after selective deuteration of the precursor. (d3)-[11C]MODAG-001 binding was confirmed in fibril-inoculated rat striata using in vivo PET imaging. In vitro autoradiography showed no detectable binding to aggregated αSYN in human brain sections of LBD cases, most likely, because of the low abundance of aggregated αSYN against background protein.ConclusionMODAG-001 provides a promising lead structure for future compound development as it combines a high affinity and good selectivity in fibril-binding assays with suitable pharmacokinetics and biodistribution properties.
| S-EPMC8113290 | biostudies-literature