Α-synuclein Inclusions Research Articles

α-Synuclein aggregation decreases cortico-amygdala connectivity and impairs social behavior in mice

Abnormal accumulation of insoluble α-synuclein (α-Syn) inclusions in neurons, neurites, and glial cells is the defining neuropathology of synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy. Accumulation of α-Syn inclusions in the amygdala has been well-documented in post-mortem studies of PD and DLB brains, as well as preclinical animal models of these conditions. Though α-Syn pathology is closely associated with neurodegeneration, there is a poor correlation between neuronal loss in the amygdala and the clinical features of PD and DLB. Moreover, functional interaction between the cerebral cortex and the amygdala is critical to regulating emotion, motivation, and social behaviors. The cortico-amygdala functional interaction is likely to be disrupted by the development of α-Syn pathology in the brain. Thus, we hypothesize that neuronal α-Syn inclusions disrupt cortical modulation of the amygdala circuits and are sufficient to drive social behavioral deficits. In the present work, we designed a series of longitudinal studies to rigorously measure the time courses of neurodegeneration, functional impairment of cortico-amygdala connectivity, and development of amygdala-dependent social behavioral deficits to test this hypothesis. We injected α-Syn preformed fibrils (PFFs) into the dorsal striatum to induce α-Syn aggregation in the amygdala and the medial prefrontal cortex (mPFC) of C57BL6 mice of both sexes, followed by a detailed analysis of temporal development of α-Syn pathology, synaptic deficits, and neuronal loss in the amygdala, as well as behavioral deficits at 3–12 months post injections. Development of α-Syn inclusions caused losses of cortical axon terminals and cell death in the basolateral amygdala (BLA) at 6- and 12-months post injections, respectively. At a relatively early stage of 3 months post injections, the connection strength of the mPFC-BLA synapse was decreased in PFFs-injection mice compared to controls. Meanwhile, the PFFs-injected mice showed impaired social interaction behavior, which was rescued by chemogenetic stimulation of mPFC-BLA connections. Altogether, we presented a series of evidence to delineate circuit events in the amygdala associated with the accumulation of α-Syn inclusions in the mouse brain, highlighting that functional impairment of the amygdala is sufficient to cause social behavior deficits. The present work further suggests that early circuit modulation could be an effective approach to alleviate symptoms associated with α-Syn pathology, necessitating studies of functional consequences of α-Syn aggregation.

Rapid iPSC inclusionopathy models shed light on formation, consequence, and molecular subtype of α-synuclein inclusions

The heterogeneity of protein-rich inclusions and its significance in neurodegeneration is poorly understood. Standard patient-derived iPSC models develop inclusions neither reproducibly nor in a reasonable time frame. Here, we developed screenable iPSC "inclusionopathy" models utilizing piggyBac or targeted transgenes to rapidly induce CNS cells that express aggregation-prone proteins at brain-like levels. Inclusions and their effects on cell survival were trackable at single-inclusion resolution. Exemplar cortical neuron α-synuclein inclusionopathy models were engineered through transgenic expression of α-synuclein mutant forms or exogenous seeding with fibrils. We identified multiple inclusion classes, including neuroprotective p62-positive inclusions versus dynamic and neurotoxic lipid-rich inclusions, both identified in patient brains. Fusion events between these inclusion subtypes altered neuronal survival. Proteome-scale α-synuclein genetic- and physical-interaction screens pinpointed candidate RNA-processing and actin-cytoskeleton-modulator proteins like RhoA whose sequestration into inclusions could enhance toxicity. These tractable CNS models should prove useful in functional genomic analysis and drug development for proteinopathies.

Excitatory synaptic structural abnormalities produced by templated aggregation of α-syn in the basolateral amygdala

Parkinson's disease (PD) and Dementia with Lewy bodies (DLB) are characterized by neuronal α-synuclein (α-syn) inclusions termed Lewy Pathology, which are abundant in the amygdala. The basolateral amygdala (BLA), in particular, receives projections from the thalamus and cortex. These projections play a role in cognition and emotional processing, behaviors which are impaired in α-synucleinopathies. To understand if and how pathologic α-syn impacts the BLA requires animal models of α-syn aggregation. Injection of α-syn pre-formed fibrils (PFFs) into the striatum induces robust α-syn aggregation in excitatory neurons in the BLA that corresponds with reduced contextual fear conditioning. At early time points after aggregate formation, cortico-amygdala excitatory transmission is abolished. The goal of this project was to determine if α-syn inclusions in the BLA induce synaptic degeneration and/or morphological changes. In this study, we used C57BL/6 J mice injected bilaterally with PFFs in the dorsal striatum to induce α-syn aggregate formation in the BLA. A method was developed using immunofluorescence and three-dimensional reconstruction to analyze excitatory cortico-amygdala and thalamo-amygdala presynaptic terminals closely juxtaposed to postsynaptic densities. The abundance and morphology of synapses were analyzed at 6- or 12-weeks post-injection of PFFs. α-Syn aggregate formation in the BLA did not cause a significant loss of synapses, but cortico-amygdala and thalamo-amygdala presynaptic terminals and postsynaptic densities with aggregates of α-syn show increased volumes, similar to previous findings in human DLB cortex, and in non-human primate models of PD. Transmission electron microscopy showed that asymmetric synapses in mice with PFF-induced α-syn aggregates have reduced synaptic vesicle intervesicular distances, similar to a recent study showing phospho-serine-129 α-syn increases synaptic vesicle clustering. Thus, pathologic α-syn causes major alterations to synaptic architecture in the BLA, potentially contributing to behavioral impairment and amygdala dysfunction observed in synucleinopathies.

Disease progression in proposed brain-first and body-first Parkinson’s disease subtypes

A new Parkinson’s disease (PD) subtyping model has been recently proposed based on the initial location of α-synuclein inclusions, which divides PD patients into the brain-first subtype and the body-first subtype. Premotor RBD has proven to be a predictive marker of the body-first subtype. We found compared to PD patients without possible RBD (PDpRBD–, representing the brain-first subtype), PD patients with possible premotor RBD (PDpRBD+, representing the body-first subtype) had lower Movement Disorders Society Unified Parkinson’s Disease Rating Scale part III (MDS UPDRS-III) score (p = 0.022) at baseline but presented a faster progression rate (p = 0.009) in MDS UPDRS-III score longitudinally. The above finding indicates the body-first subtype exhibited a faster disease progression in motor impairments compared to the brain-first subtype and further validates the proposed subtyping model.

Recent advances in stem cells therapy: efficacy, ethics, safety concerns and future directions focusing on neurodegenerative disorders- a review

Neurodegeneration refers to the gradual loss of neurons and extensive changes occur in glial cells like tau inclusions in astrocytes and oligodendrocytes, α-synuclein inclusions in oligodendrocytes and SOD1 aggregates in astrocytes along with deterioration in the motor, cognition, learning, and behaviour. Common neurodegenerative disorders are Alzheimer’s Disease (AD), Parkinson’s Disease (PD), Amyotrophic Lateral Sclerosis (ALS), Huntington’s disease (HD), Spinocerebellar Ataxia (SCAs), and Supranuclear palsy are some common one. There is a lack of effective treatment for neurodegenerative diseases, and scientists are putting their efforts into developing therapies against them. Stem cell therapy has emerged as a hope for neurodegenerative disorders since it is not only the damaged neurons that might be replaced, but other neuromodulators and neuroprotectors are secreted. Stem cell terminal differentiation before implantation ensures the implantation of correct cells and molecular markers like carbonic anhydrase II, CNPase (2′,3′-cyclic nucleotide 3′-phosphohydrolase), myelin basic protein (MBP), and myelin oligodendrocyte glycoprotein ​(MOG) elucidate the differentiation. Secretion of various growth factors like epidermal growth factor (EGF), keratinocyte growth factor (KGF), vascular endothelial growth factor-α (VEGF-α), transforming growth factor (TGF) and macrophage inflammatory protein (MIP) supports cell survival, cell proliferation, blood vessel formation, axon regeneration, and neuroglial functional connection formation at the site of degeneration. Adverse effects of stem cell therapy, like teratogenicity and differentiation in different cells other than the desired one under the influence of microenvironment, are a few key concerns. Post-transplantation improved synaptic plasticity, apoptosis inhibition, and reduction in tau-phosphorylation and Amyloid beta (Aβ) production has been observed in Alzheimer’s patients.A large number of experimental, preclinical, and clinical studies have been conducted, and encouraging results have been obtained. The present review exhaustively discusses various kinds of stem cells, their usage in treating neurodegenerative disorders, limitations and challenges, and ethical issues related to stem cell therapy.

Widespread nuclear lamina injuries defeat proteostatic purposes of α-synuclein amyloid inclusions.

Biogenesis of inclusion bodies (IBs) facilitates protein quality control (PQC). Canonical aggresomes execute degradation of misfolded proteins while non-degradable amyloids sequester into insoluble protein deposits. Lewy bodies (LBs) are filamentous amyloid inclusions of α-synuclein, but PQC benefits and drawbacks associated with LB-like IBs remain underexplored. Here, we report that crosstalk between filamentous LB-like IBs and aggresome-like IBs of α-synuclein (Syn-aggresomes) buffer the load, aggregation state, and turnover of the amyloidogenic protein in mouse primary neurons and HEK293T cells. Filamentous LB-like IBs possess unorthodox PQC capacities of self-quarantining α-synuclein amyloids and being degradable upon receding fresh amyloidogenesis. Syn-aggresomes equilibrate biogenesis of filamentous LB-like IBs by facilitating spontaneous degradation of α-synuclein and conditional turnover of disintegrated α-synuclein amyloids. Thus, both types of IB primarily contribute to PQC. Incidentally, the overgrown perinuclear LB-like IBs become degenerative once these are misidentified by BICD2, a cargo-adapter for the cytosolic motor-protein dynein. Microscopy indicates that microtubules surrounding the perinuclear filamentous inclusions are also distorted, misbalancing the cytoskeleton-nucleoskeleton tension leading to widespread lamina injuries. Together, nucleocytoplasmic mixing, DNA damage, and deregulated transcription of stress chaperones defeat the proteostatic purposes of the filamentous amyloids of α-synuclein.

Reduced progranulin increases tau and α-synuclein inclusions and alters mouse tauopathy phenotypes via glucocerebrosidase

Comorbid proteinopathies are observed in many neurodegenerative disorders including Alzheimer’s disease (AD), increase with age, and influence clinical outcomes, yet the mechanisms remain ill-defined. Here, we show that reduction of progranulin (PGRN), a lysosomal protein associated with TDP-43 proteinopathy, also increases tau inclusions, causes concomitant accumulation of α-synuclein and worsens mortality and disinhibited behaviors in tauopathy mice. The increased inclusions paradoxically protect against spatial memory deficit and hippocampal neurodegeneration. PGRN reduction in male tauopathy attenuates activity of β-glucocerebrosidase (GCase), a protein previously associated with synucleinopathy, while increasing glucosylceramide (GlcCer)-positive tau inclusions. In neuronal culture, GCase inhibition enhances tau aggregation induced by AD-tau. Furthermore, purified GlcCer directly promotes tau aggregation in vitro. Neurofibrillary tangles in human tauopathies are also GlcCer-immunoreactive. Thus, in addition to TDP-43, PGRN regulates tau- and synucleinopathies via GCase and GlcCer. A lysosomal PGRN–GCase pathway may be a common therapeutic target for age-related comorbid proteinopathies.

Stochastic Optical Reconstruction Microscopy Imaging of Multiple System Atrophy Inclusions Suggests Stepwise α-Synuclein Aggregation.

The architecture and composition of glial (GCI) and neuronal (NCI) α-synuclein inclusions observed in multiple system atrophy (MSA) remain to be precisely defined to better understand the disease. Here, we used stochastic optical reconstruction microscopy (STORM) to characterize the nanoscale organization of glial (GCI) and neuronal (NCI) α-synuclein inclusions in cryopreserved brain sections from MSA patients. STORM revealed a dense cross-linked internal structure of α-synuclein in all GCI and NCI. The internal architecture of hyperphosphorylated α-synuclein (p-αSyn) inclusions was similar in glial and neuronal cells, suggesting a common aggregation mechanism. A similar sequence of p-αSyn stepwise intracellular aggregation was defined in oligodendrocytes and neurons, starting from the perinuclear area and growing inside the cells. Consistent with this hypothesis, we found a higher mitochondrial density in GCI and NCI compared to oligodendrocytes and neurons from unaffected donors (P < 0.01), suggesting an active recruitment of the organelles during the aggregation process. These first STORM images of GCI and NCI suggest stepwise α-synuclein aggregation in MSA. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Anionic nanoplastic contaminants promote Parkinson's disease-associated α-synuclein aggregation.

Recent studies have identified increasing levels of nanoplastic pollution in the environment. Here, we find that anionic nanoplastic contaminants potently precipitate the formation and propagation of α-synuclein protein fibrils through a high-affinity interaction with the amphipathic and non-amyloid component (NAC) domains in α-synuclein. Nanoplastics can internalize in neurons through clathrin-dependent endocytosis, causing a mild lysosomal impairment that slows the degradation of aggregated α-synuclein. In mice, nanoplastics combine with α-synuclein fibrils to exacerbate the spread of α-synuclein pathology across interconnected vulnerable brain regions, including the strong induction of α-synuclein inclusions in dopaminergic neurons in the substantia nigra. These results highlight a potential link for further exploration between nanoplastic pollution and α-synuclein aggregation associated with Parkinson's disease and related dementias.

Treatment of Parkinson's disease with biologics that penetrate the blood-brain barrier via receptor-mediated transport.

Parkinson's disease (PD) is characterized by neurodegeneration of nigral-striatal neurons in parallel with the formation of intra-neuronal α-synuclein aggregates, and these processes are exacerbated by neuro-inflammation. All 3 components of PD pathology are potentially treatable with biologics. Neurotrophins, such as glial derived neurotrophic factor or erythropoietin, can promote neural repair. Therapeutic antibodies can lead to disaggregation of α-synuclein neuronal inclusions. Decoy receptors can block the activity of pro-inflammatory cytokines in brain. However, these biologic drugs do not cross the blood-brain barrier (BBB). Biologics can be made transportable through the BBB following the re-engineering of the biologic as an IgG fusion protein, where the IgG domain targets an endogenous receptor-mediated transcytosis (RMT) system within the BBB, such as the insulin receptor or transferrin receptor. The receptor-specific antibody domain of the fusion protein acts as a molecular Trojan horse to ferry the biologic into brain via the BBB RMT pathway. This review describes the re-engineering of all 3 classes of biologics (neurotrophins, decoy receptor, therapeutic antibodies) for BBB delivery and treatment of PD. Targeting the RMT pathway at the BBB also enables non-viral gene therapy of PD using lipid nanoparticles (LNP) encapsulated with plasmid DNA encoding therapeutic genes. The surface of the lipid nanoparticle is conjugated with a receptor-specific IgG that triggers RMT of the LNP across the BBB in vivo.

Formation of templated inclusions in a forebrain α-synuclein mouse model is independent of LRRK2

Leucine-rich repeat kinase 2 (LRRK2) and α-synuclein share enigmatic roles in the pathobiology of Parkinson's disease (PD). LRRK2 mutations are a common genetic cause of PD which, in addition to neurodegeneration, often present with abnormal deposits of α-synuclein in the form of Lewy-related pathology. As Lewy-related pathology is a prominent neuropathologic finding in sporadic PD, the relationship between LRRK2 and α-synuclein has garnered considerable interest. However, whether and how LRRK2 might influence the accumulation of Lewy-related pathology remains poorly understood. Through stereotactic injection of mouse α-synuclein pre-formed fibrils (PFF), we modeled the spread of Lewy-related pathology within forebrain regions where LRRK2 is most highly expressed. The impact of LRRK2 genotype on the formation of α-synuclein inclusions was evaluated at 1-month post-injection. Neither deletion of LRRK2 nor G2019S LRRK2 knockin appreciably altered the burden of α-synuclein pathology at this early timepoint. These observations fail to provide support for a robust pathophysiologic interaction between LRRK2 and α-synuclein in the forebrain in vivo. There was, however, a modest reduction in microglial activation induced by PFF delivery in the hippocampus of LRRK2 knockout mice, suggesting that LRRK2 may contribute to α-synuclein-induced neuroinflammation. Collectively, our data indicate that the pathological accumulation of α-synuclein in the mouse forebrain is largely independent of LRRK2.

α-Synuclein propagation leads to synaptic abnormalities in the cortex through microglial synapse phagocytosis

The major neuropathologic feature of Parkinson’s disease is the presence of widespread intracellular inclusions of α-synuclein known as Lewy bodies. Evidence suggests that these misfolded protein inclusions spread through the brain with disease progression. Changes in synaptic function precede neurodegeneration, and this extracellular α-synuclein can affect synaptic transmission. However, whether and how the spreading of α-synuclein aggregates modulates synaptic function before neuronal loss remains unknown. In the present study, we investigated the effect of intrastriatal injection of α-synuclein preformed fibrils (PFFs) on synaptic activity in the somatosensory cortex using a combination of whole-cell patch-clamp electrophysiology, histology, and Golgi-Cox staining. Intrastriatal PFF injection was followed by formation of phosphorylated α-synuclein inclusions in layer 5 of the somatosensory cortex, leading to a decrease in synapse density, dendritic spines, and spontaneous excitatory post-synaptic currents, without apparent neuronal loss. Additionally, three-dimensional reconstruction of microglia using confocal imaging showed an increase in the engulfment of synapses. Collectively, our data indicate that propagation of α-synuclein through neural networks causes abnormalities in synaptic structure and dynamics prior to neuronal loss.

Parkinson's disease pathology is directly correlated to SIRT3 in human subjects and animal models: Implications for AAV.SIRT3-myc as a disease-modifying therapy

In Parkinson's disease (PD), post-mortem studies in affected brain regions have demonstrated a decline in mitochondrial number and function. This combined with many studies in cell and animal models suggest that mitochondrial dysfunction is central to PD pathology. We and others have shown that the mitochondrial protein deacetylase, SIRT3, has neurorestorative effects in PD models. In this study, to determine whether there is a link between PD pathology and SIRT3, we analysed SIRT3 levels in human subjects with PD, and compared to age-matched controls. In the SNc of PD subjects, SIRT3 was reduced by 56.8 ± 15.5% compared to control, regardless of age (p < 0.05, R = 0.6539). Given that age is the primary risk factor for PD, this finding suggests that reduced SIRT3 may contribute to PD pathology. Next, we measured whether there was a correlation between α-synuclein and SIRT3. In a parallel study, we assessed the disease-modifying potential of SIRT3 over-expression in a seeding model of α-synuclein. In PFF rats, infusion of rAAV1.SIRT3-myc reduced abundance of α-synuclein inclusions by 30.1 ± 18.5%. This was not observed when deacetylation deficient SIRT3H248Y was transduced, demonstrating the importance of SIRT3 deacetylation in reducing α-synuclein aggregation. These studies confirm that there is a clear difference in SIRT3 levels in subjects with PD compared to age-matched controls, suggesting a link between SIRT3 and the progression of PD. We also demonstrate that over-expression of SIRT3 reduces α-synuclein aggregation, further validating AAV.SIRT3-myc as a potential disease-modifying solution for PD.

A small molecule 20C from Gastrodia elata inhibits α-synuclein aggregation and prevents progression of Parkinson’s disease

Parkinson’s disease (PD) is pathologically manifested by the aggregation of α-synuclein, which has been envisioned as a promising disease-modifying target for PD. Here, we identified 20C, a bibenzyl compound derived from Gastrodia elata, able to inhibit the aggregation of A53T variants of α-synuclein directly in vitro. Computational analysis revealed that 20C binds to cavities in mature α-synuclein fibrils, and it indeed displays a strong interaction with α-synuclein and reduced their β-sheet structure by microscale thermophoresis and circular dichroism, respectively. Moreover, incubating neural cells with 20C reduced the amounts of α-synuclein inclusions significantly. The treatment of A53T α-Syn transgenic mice with 20C significantly reduces the toxic α-synuclein levels, improves behavioral performance, rescues dopaminergic neuron, and enhances functional connections between SNc and PD associated brain areas. The transcriptome analysis of SNc demonstrated that 20C improves mitochondrial dynamics, which protects mitochondrial morphology and function against α-synuclein induced degeneration. Overall, 20C appears to be a promising candidate for the treatment of PD.

Hippocampal subfield vulnerability to α-synuclein pathology precedes neurodegeneration and cognitive dysfunction

Cognitive dysfunction is a salient feature of Parkinson’s disease (PD) and Dementia with Lewy bodies (DLB). The onset of dementia reflects the spread of Lewy pathology throughout forebrain structures. The mere presence of Lewy pathology, however, provides limited indication of cognitive status. Thus, it remains unclear whether Lewy pathology is the de facto substrate driving cognitive dysfunction in PD and DLB. Through application of α-synuclein fibrils in vivo, we sought to examine the influence of pathologic inclusions on cognition. Following stereotactic injection of α-synuclein fibrils within the mouse forebrain, we measured the burden of α-synuclein pathology at 1-, 3-, and 6-months post-injection within subregions of the hippocampus and cortex. Under this paradigm, the hippocampal CA2/3 subfield was especially susceptible to α-synuclein pathology. Strikingly, we observed a drastic reduction of pathology in the CA2/3 subfield across time-points, consistent with the consolidation of α-synuclein pathology into dense somatic inclusions followed by neurodegeneration. Silver-positive degenerating neurites were observed prior to neuronal loss, suggesting that this might be an early feature of fibril-induced neurotoxicity and a precursor to neurodegeneration. Critically, mice injected with α-synuclein fibrils developed progressive deficits in spatial learning and memory. These findings support that the formation of α-synuclein inclusions in the mouse forebrain precipitate neurodegenerative changes that recapitulate features of Lewy-related cognitive dysfunction.

Monitoring α-synuclein Aggregation Induced by Preformed α-synuclein Fibrils in an In Vitro Model System.

Parkinson's disease (PD) is characterized by the presence of α-synuclein (α-syn) inclusions in the brain and the degeneration of dopamine-producing neurons. There is evidence to suggest that the progression of PD may be due to the prion-like spread of α-syn aggregates, so understanding and limiting α-syn propagation is a key area of research for developing PD treatments. Several cellular and animal model systems have been established to monitor α-syn aggregation and propagation. In this study, we developed an in vitro model using A53T α-syn-EGFP overexpressing SH-SY5Y cells and validated its usefulness for high-throughput screening of potential therapeutic targets. Treatment with preformed recombinant α-syn fibrils induced the formation of aggregation puncta of A53T α-syn-EGFP in these cells, which were analyzed using four indices: number of dots per cell, size of dots, intensity of dots, and percentage of cells containing aggregation puncta. Four indices are reliable indicators of the effectiveness of interventions against α-syn propagation in a one-day treatment model to minimize the screening time. This simple and efficient in vitro model system can be used for high-throughput screening to discover new targets for inhibiting α-syn propagation.

The G51D SNCA mutation generates a slowly progressive α-synuclein strain in early-onset Parkinson’s disease

Unique strains of α-synuclein aggregates have been postulated to underlie the spectrum of clinical and pathological presentations seen across the synucleinopathies. Whereas multiple system atrophy (MSA) is associated with a predominance of oligodendroglial α-synuclein inclusions, α-synuclein aggregates in Parkinson’s disease (PD) preferentially accumulate in neurons. The G51D mutation in the SNCA gene encoding α-synuclein causes an aggressive, early-onset form of PD that exhibits clinical and neuropathological traits reminiscent of both PD and MSA. To assess the strain characteristics of G51D PD α-synuclein aggregates, we performed propagation studies in M83 transgenic mice by intracerebrally inoculating patient brain extracts. The properties of the induced α-synuclein aggregates in the brains of injected mice were examined using immunohistochemistry, a conformational stability assay, and by performing α-synuclein seed amplification assays. Unlike MSA-injected mice, which developed a progressive motor phenotype, G51D PD-inoculated animals remained free of overt neurological illness for up to 18 months post-inoculation. However, a subclinical synucleinopathy was present in G51D PD-inoculated mice, characterized by the accumulation of α-synuclein aggregates in restricted regions of the brain. The induced α-synuclein aggregates in G51D PD-injected mice exhibited distinct properties in a seed amplification assay and were much more stable than those present in mice injected with MSA extract, which mirrored the differences observed between human MSA and G51D PD brain samples. These results suggest that the G51D SNCA mutation specifies the formation of a slowly propagating α-synuclein strain that more closely resembles α-synuclein aggregates associated with PD than MSA.

New SNCA mutation and structures of α-synuclein filaments from juvenile-onset synucleinopathy

A 21-nucleotide duplication in one allele of SNCA was identified in a previously described disease with abundant α-synuclein inclusions that we now call juvenile-onset synucleinopathy (JOS). This mutation translates into the insertion of MAAAEKT after residue 22 of α-synuclein, resulting in a protein of 147 amino acids. Both wild-type and mutant proteins were present in sarkosyl-insoluble material that was extracted from frontal cortex of the individual with JOS and examined by electron cryo-microscopy. The structures of JOS filaments, comprising either a single protofilament, or a pair of protofilaments, revealed a new α-synuclein fold that differs from the folds of Lewy body diseases and multiple system atrophy (MSA). The JOS fold consists of a compact core, the sequence of which (residues 36–100 of wild-type α-synuclein) is unaffected by the mutation, and two disconnected density islands (A and B) of mixed sequences. There is a non-proteinaceous cofactor bound between the core and island A. The JOS fold resembles the common substructure of MSA Type I and Type II dimeric filaments, with its core segment approximating the C-terminal body of MSA protofilaments B and its islands mimicking the N-terminal arm of MSA protofilaments A. The partial similarity of JOS and MSA folds extends to the locations of their cofactor-binding sites. In vitro assembly of recombinant wild-type α-synuclein, its insertion mutant and their mixture yielded structures that were distinct from those of JOS filaments. Our findings provide insight into a possible mechanism of JOS fibrillation in which mutant α-synuclein of 147 amino acids forms a nucleus with the JOS fold, around which wild-type and mutant proteins assemble during elongation.

Rotenone-Induced Model of Parkinson's Disease: Beyond Mitochondrial Complex I Inhibition.

Parkinson's disease (PD) is usually diagnosed through motor symptoms that make the patient incapable of carrying out daily activities; however, numerous non-motor symptoms include olfactory disturbances, constipation, depression, excessive daytime sleepiness, and rapid eye movement at sleep; they begin years before motor symptoms. Therefore, several experimental models have been studied to reproduce several PD functional and neurochemical characteristics; however, no model mimics all the PD motor and non-motor symptoms to date, which becomes a limitation for PD study. It has become increasingly relevant to find ways to study the disease from its slowly progressive nature. The experimental models most frequently used to reproduce PD are based on administering toxic chemical compounds, which aim to imitate dopamine deficiency. The most used toxic compounds to model PD have been 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which inhibit the complex I of the electron transport chain but have some limitations. Another toxic compound that has drawn attention recently is rotenone, the classical inhibitor of mitochondrial complex I. Rotenone triggers the progressive death of dopaminergic neurons and α-synuclein inclusions formation in rats; also, rotenone induces microtubule destabilization. This review presents information about the experimental model of PD induced by rotenone, emphasizing its molecular characteristics beyond the inhibition of mitochondrial complex I.

PARKINSON'S DISEASE — OVERVIEW OF MODERN TREATMENT METHODS

Introduction. Parkinson's disease (PD) is a neurodegenerative neurological disease with a slowly progressive course. In particular, it manifests as a movement disorder that includes rest tremor, rigidity, bradykinesia, and postural instability. Movement disorder in patients with PD mainly occurs due to the selective loss of pigmented dopaminergic neurons of the compact area of the substantia nigra, as a result of the depletion of dopamine in the striatum. The pathogenetic feature of this disease is the presence of intraneuronal aggregates and inclusions of α-synuclein. To date, there are no proven treatments for Parkinson's disease, but a number of medications exist offering benefits in terms of controlling movement disorders. Although they can significantly improve motor function, they can also lead to problematic side effects, especially as the disease progresses. Materials and methods. To analyze the main directions of modern methods of Parkinson's disease treatment and to conduct a profound review and analysis of literature research data on the modern methods of Parkinson's disease treatment over the past 10 years. The results. It has been established that modern treatment methods are based mainly on exogenous administration of drugs with dopaminergic activity and inhibitors of endogenous dopamine metabolism. Although levodopa has been used in the treatment of Parkinson's disease since its inception, numerous experimental therapeutic and neurosurgical approaches are now being investigated. These include drugs aiming at the inhibition and degradation of α-synuclein aggregation, which is considered the driving force of neurodegeneration in Parkinson's disease. They raise expectations that a disease-modifying agent will be discovered in the short-term future. Thus, in combination with a number of regenerative and neurosurgical approaches, including stem cell and gene therapy and deep brain stimulation, significant progress will be made in the treatment of Parkinson's disease in the coming years and a number of new effective options will become available.