Forms Of Α-syn Research Articles

α-Synuclein Overexpression Induces Lysosomal Dysfunction and Autophagy Impairment in Human Neuroblastoma SH-SY5Y.

Although the etiology of Parkinson's disease (PD) is multifactorial, it has been linked to abnormal accumulation of α-synuclein (α-syn) in dopaminergic neurons, which could lead to dysfunctions on intracellular organelles, with potential neurodegeneration. Patients with familial early-onset PD frequently present mutation in the α-syn gene (SNCA), which encodes mutant α-syn forms, such as A30P and A53T, which potentially regulate Ca2+ unbalance. Here we investigated the effects of overexpression of wild-type α-syn (WT) and the mutant forms A30P and A53T, on modulation of lysosomal Ca2+ stores and further autophagy activation. We found that in α-syn-overexpressing cells, there was a decrease in Ca2+ released from endoplasmic reticulum (ER) which is related to the increase in lysosomal Ca2+ release, coupled to lysosomal pH alkalization. Interestingly, α-syn-overexpressing cells showed lower LAMP1 levels, and a disruption of lysosomal morphology and distribution, affecting autophagy. Interestingly, all these effects were more evident with A53T mutant isoform when compared to A30P and WT α-syn types, indicating that the pathogenic phenotype for PD is potentially related to impairment of α-syn degradation. Taken together, these events directly impact PD-related dysfunctions, being considered possible molecular targets for neuroprotection.

Alpha Synuclein Connects the Gut-Brain Axis in Parkinson's Disease Patients - A View on Clinical Aspects, Cellular Pathology and Analytical Methodology.

Parkinson’s disease (PD) is marked by different kinds of pathological features, one hallmark is the aggregation of α-synuclein (aSyn). The development of aSyn pathology in the substantia nigra is associated to the manifestation of motor deficits at the time of diagnosis. However, most of the patients suffer additionally from non-motor symptoms, which may occur already in the prodromal phase of the disease years before PD is diagnosed. Many of these symptoms manifest in the gastrointestinal system (GIT) and some data suggest a potential link to the occurrence of pathological aSyn forms within the GIT. These clinical and pathological findings lead to the idea of a gut-brain route of aSyn pathology in PD. The identification of pathological aSyn in the intestinal system, e.g., by GIT biopsies, is therefore of highest interest for early diagnosis and early intervention in the phase of formation and propagation of aSyn. However, reliable methods to discriminate between physiological and pathological forms of enteral aSyn on the cellular and biochemical level are still missing. Moreover, a better understanding of the physiological function of aSyn within the GIT as well as its structure and pathological aggregation pathways are crucial to understand its role within the enteric nervous system and its spreading from the gut to the brain. In this review, we summarize clinical manifestations of PD in the GIT, and discuss biochemical findings from enteral biopsies. The relevance of pathological aSyn forms, their connection to the gut-brain axis and new developments to identify pathologic forms of aSyn by structural features are critically reviewed.

Diphenyl triazine hybrids inhibit α-synuclein fibrillogenesis: Design, synthesis and invitro efficacy studies.

Aggregation of α-synuclein (α-syn) is one of the central hypotheses for Parkinson's disease (PD), therefore, its inhibition and disaggregation is an optimistic approach for the treatment of PD. Here, we report design, synthesis and in-vitro efficacy studies of a series of diphenyl triazine hybrids as potential inhibitors of α-syn fibrillogenesis. From the docking studies, we concluded that compounds A1, A2, A4, A8 and A9 display promising binding affinity with the essential residues of α-syn with binding energy values:-6.0,-7.0,-6.3,-6.6 and-6.7kcal/mol respectively. The target compounds were synthesized using multistep organic synthesis reactions. Compounds A1, A2 A4, A8 and A9 showed a significant lowering of the α-syn fibril formation during Thioflavin-T assay and fluorescence microscopy. In addition, these compounds A1, A2, A4, A8 and A9 also proved to be good disaggregators in the pre-aggregated form of α-syn. Most of the compounds exhibited no cytotoxicity in mouse embryonic fibroblast (MEF) and human adenocarcinomic alveolar basal epithelial cells (A549) except A2. Overall, diphenyl triazine-based compounds can be further investigated for the treatment of synucleinopathies and for Lewy body dementia in which α-syn is predominantly observed.

Beneficial effects of cysteamine in Thy1-α-Syn mice and induced pluripotent stem cells with a SNCA gene triplication

A number of publications have reported that cysteamine has significant therapeutic effects on several aspects of Parkinson's disease (PD)-related pathology but none of these studies have evaluated its impact on pathological forms of α-Synuclein (α-Syn), one of the main hallmarks of PD. We therefore tested the efficacy of cysteamine on the Thy1-α-Syn mouse model which over-expresses full-length human wild-type α-Syn. Two-month (early stage disease) and 6-month old (late stage disease) mice and littermate controls were treated daily with cysteamine (20 mg/kg, i.p.) to assess the protective and restorative properties of this compound. After 6 weeks of treatment, animals were tested using a battery of motor tests. Cysteamine-treated transgenic mice displayed significant improvements in motor performance as compared to saline-treated transgenic littermates. Post-mortem readouts revealed a reduction in fibrillation, phosphorylation and total levels of overexpresed human α-Syn. To determine if such outcomes extended to human cells, the benefits of cysteamine were additionally tested using 6-hydroxydopamine (6-OHDA) treated neurons differentiated from induced pluripotent stem cells (iPSCs) derived from a PD patient harbouring a triplication of the SNCA gene. SNCA neurons treated with cysteamine exhibited significantly more intact/healthy neurites than cells treated with 6-OHDA alone. Additionally, SNCA neurons treated with cysteamine in the absence of 6-OHDA showed a trend towards lower total α-Syn levels. Overall, our in vivo and in vitro findings suggest that cysteamine can act as a disease-modifying molecule by enhancing -the survival of dopaminergic neurons and reducing pathological forms of α-Syn.

Role of alpha-synuclein phosphorylation at Serine 129 in methamphetamine-induced neurotoxicity in vitro and in vivo.

The phosphorylation and aggregation of alpha-synuclein (α-Syn) play a key role in methamphetamine (METH)-induced dopaminergic neurotoxicity. The exact mechanism underlying the interaction between METH-induced neurotoxicity and α-Syn was poorly clarified. We aimed to figure out the role of serine 129 phosphorylation (pS129) of α-Syn on its aggregation and neurotoxicity in vitro and in vivo. In this study, we examined pS129 α-Syn expression in vitro and in vivo at the protein phosphorylation and genetic levels and evaluated its effect on METH-induced neurotoxicity. Here, we found that pS129 α-Syn was significantly increased after METH treatment; moreover, the neuronal α-Syn aggregation and apoptosis caused by METH exposure were significantly attenuated after inhibiting α-Syn phosphorylation. We demonstrate that pS129 α-Syn contributes to the aggregation of α-Syn, and that phosphorylated and aggregated forms of α-Syn play an important role in METH-induced neurotoxicity in dopaminergic neurons and SH-SY5Y cells, supporting a potential insight into the treatment of METH-induced neurotoxicity.

Lipids: Key Players That Modulate α-Synuclein Toxicity and Neurodegeneration in Parkinson's Disease.

Parkinson’s disease (PD) is the second most common neurodegenerative disease; it is characterized by the loss of dopaminergic neurons in the midbrain and the accumulation of neuronal inclusions, mainly consisting of α-synuclein (α-syn) fibrils in the affected regions. The prion-like property of the pathological forms of α-syn transmitted via neuronal circuits has been considered inherent in the nature of PD. Thus, one of the potential targets in terms of PD prevention is the suppression of α-syn conversion from the functional form to pathological forms. Recent studies suggested that α-syn interacts with synaptic vesicle membranes and modulate the synaptic functions. A series of studies suggest that transient interaction of α-syn as multimers with synaptic vesicle membranes composed of phospholipids and other lipids is required for its physiological function, while an α-syn-lipid interaction imbalance is believed to cause α-syn aggregation and the resultant pathological α-syn conversion. Altered lipid metabolisms have also been implicated in the modulation of PD pathogenesis. This review focuses on the current literature reporting the role of lipids, especially phospholipids, and lipid metabolism in α-syn dynamics and aggregation processes.

Carboxy-terminal truncation and phosphorylation of α-synuclein elongates survival in a prion-like seeding mouse model of synucleinopathy

Pathologic intracellular inclusions formed from polymers of misfolded α-synuclein (αsyn) protein define a group of neurodegenerative diseases termed synucleinopathies which includes Parkinson’s disease (PD). Prion-like recruitment of endogenous cellular αsyn has been demonstrated to occur in animal models of synucleinopathy, whereby misfolded αsyn can induce further pathologic αsyn inclusions to form through a prion-like mechanism. It has been suggested that misfolded αsyn may assume differing conformations which lead to varied clinical and pathological manifestations of disease; this phenomenon bears similarities to that of prion strains whereby the same misfolded protein can produce unique diseases. It is unclear what factors influence the development of unique αsyn strains, however post-translational modifications (PTMs) such as phosphorylation and truncation that are present in misfolded αsyn in disease may play a role due to their modulation of biochemical and structural αsyn properties. Herein, we investigate the prion-like properties of misfolded αsyn polymers containing either phosphomimetic (S129E) αsyn, 5 different major carboxy (C)-truncated forms of αsyn (1-115, 1-119, 1-122, 1-125, and 1-129 αsyn), or a mixture of these PTM containing αsyn forms compared to full-length (FL) αsyn in HEK293T cells and M83 transgenic mice overexpressing A53T αsyn. It is demonstrated that upon peripheral intramuscular injection of these C-truncated or S129E αsyn polymers into M83 mice, prion-like progression and time to disease onset in this mouse model is elongated when any of these PTMs are present, demonstrating that common modifications to the C-terminus of αsyn present in disease modulates the prion-like seeding properties of αsyn.

Phosphorylated Alpha-Synuclein in Red Blood Cells as a Potential Diagnostic Biomarker for Multiple System Atrophy: A Pilot Study.

Diagnosis of multiple system atrophy (MSA) remains a challenge, due to the complexity and overlapping of its symptoms with other Parkinsonian disorders. The critical role of alpha-synuclein (α-syn) in the pathogenesis of MSA makes it an ideal biomarker for the diagnosis of MSA. Although α-syn alterations in cerebrospinal fluid (CSF) and blood plasma have been extensively assessed for the utility in diagnosing MSA, inconsistent results have been obtained, presumably due to the contamination by hemolysis and other confounding factors. In this study, levels of serine 129-phosphorylated α-syn (pS-α-syn), a major pathologic form of α-syn, in red blood cells (RBCs), were measured using ELISA in a Chinese cohort consisting of 107 MSA patients and 220 healthy controls. A significant increase in the levels of pS-α-syn in RBCs (pS-α-syn-RBC) was observed in MSA patients than in healthy controls (14.02 ± 4.02 ng/mg versus 11.89 ± 3.57 ng/mg; p < 0.0001). Receiver operating characteristic curve (ROC) indicated that pS-α-syn-RBC discriminated the patients well from the controls with a sensitivity of 80.37% (95% confidence interval (CI): 71.58%–87.42%), a specificity of 88.64% (95% CI: 83.68%–92.51%), and an area under the curve (AUC) of 0.91 (95% CI: 0.87–0.94). The levels of pS-α-syn-RBC were negatively correlated with RBD-HK scores and differed between MSA-P and MSA-C subtypes (13.27 ± 1.91 versus 12.19 ± 3.04; p=0.025). The difference between subtypes was seen at Hoehn and Yahr stages 3 and 4, and the age at onset (AAO) between 60 and 69 years (p=0.016). The results suggest that pS-α-syn-RBC is increased in MSA patients and can be used as a potential diagnostic biomarker for MSA.

Carboxy-terminal truncations of mouse α-synuclein alter aggregation and prion-like seeding.

α-synuclein (αsyn) forms pathologic inclusions in several neurodegenerative diseases termed synucleinopathies. The inclusions are comprised of αsyn fibrils harboring prion-like properties. Prion-like activity of αsyn has been studied by intracerebral injection of fibrils into mice, where the presence of a species barrier requires the use of mouse αsyn. Post-translational modifications to αsyn such as carboxy (C)-terminal truncation occur in synucleinopathies, and their implications for prion-like aggregation and seeding are under investigation. Herein, C-truncated forms of αsyn found in human disease are recapitulated in mouse αsyn to study their seeding activity invitro, in HEK293T cells, in neuronal-glial culture, and in nontransgenic mice. The results show that C-truncation of mouse αsyn accelerates aggregation of αsyn but alters prion-like seeding of inclusion formation.

Unique \u03b1-synuclein pathology within the amygdala in Lewy body dementia: implications for disease initiation and progression

The protein α-synuclein (αsyn) forms pathologic aggregates in a number of neurodegenerative diseases including Lewy body dementia (LBD) and Parkinson’s disease (PD). It is unclear why diseases such as LBD may develop widespread αsyn pathology, while in Alzheimer’s disease with amygdala restricted Lewy bodies (AD/ALB) the αsyn aggregates remain localized. The amygdala contains αsyn aggregates in both LBD and in AD/ALB; to understand why αsyn pathology continues to progress in LBD but not in AD/ALB, tissue from the amygdala and other regions were obtained from 14 cases of LBD, 9 cases of AD/ALB, and 4 controls for immunohistochemical and biochemical characterization. Utilizing a panel of previously characterized αsyn antibodies, numerous unique pathologies differentiating LBD and AD/ALB were revealed; particularly the presence of dense neuropil αsyn aggregates, astrocytic αsyn, and αsyn-containing dystrophic neurites within senile plaques. Within LBD, these unique pathologies were predominantly present within the amygdala. Biochemically, the amygdala in LBD prominently contained specific carboxy-truncated forms of αsyn which are highly prone to aggregate, suggesting that the amygdala may be prone to initiate development of αsyn pathology. Similar to carboxy-truncated αsyn, it was demonstrated herein that the presence of aggregation prone A53T αsyn is sufficient to drive misfolding of wild-type αsyn in human disease. Overall, this study identifies within the amygdala in LBD the presence of unique strain-like variation in αsyn pathology that may be a determinant of disease progression.

The molecular tweezer CLR01 reduces aggregated, pathologic, and seeding-competent α-synuclein in experimental multiple system atrophy

Multiple system atrophy (MSA) is a fatal, adult-onset neurodegenerative disorder that has no cure and very limited treatment options. MSA is characterized by deposition of fibrillar α-synuclein (α-syn) in glial cytoplasmic inclusions in oligodendrocytes. Similar to other synucleinopathies, α-syn self-assembly is thought to be a key pathologic event and a prominent target for disease modification in MSA. Molecular tweezers are broad-spectrum nanochaperones that prevent formation of toxic protein assemblies and enhance their clearance. The current lead compound, CLR01, has been shown to inhibit α-syn aggregation but has not yet been tested in the context of MSA. To fill this gap, here, we conducted a proof-of-concept study to assess the efficacy of CLR01 in remodeling MSA-like α-syn pathology in the PLP-α-syn mouse model of MSA. Six-month-old mice received intracerebroventricular CLR01 (0.3 or 1 mg/kg per day) or vehicle for 32 days. Open-field test revealed a significant, dose-dependent amelioration of an anxiety-like phenotype. Subsequently, immunohistochemical and biochemical analyses showed dose-dependent reduction of pathological and seeding-competent forms of α-syn, which correlated with the behavioral phenotype. CLR01 treatment also promoted dopaminergic neuron survival in the substantia nigra. To our knowledge, this is the first demonstration of an agent that reduces formation of putative high-molecular-weight oligomers and seeding-competent α-syn in a mouse model of MSA, supporting the view that these species are key to the neurodegenerative process and its cell-to-cell progression in MSA. Our study suggests that CLR01 is an attractive therapeutic candidate for disease modification in MSA and related synucleinopathies, supporting further preclinical development.

Tetramethylpyrazine Analogue T-006 Promotes the Clearance of Alpha-synuclein by Enhancing Proteasome Activity in Parkinson's Disease Models.

Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide and is characterized in part by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). The main pathological hallmark of PD is the intraneuronal accumulation of misfolded α-synuclein (α-syn) aggregates. Mutations in the SNCA gene (encoding α-syn) and variations in its copy number are associated with some forms of familial PD. In the present study, T-006, a new tetramethylpyrazine (TMP) derivative with recently reported anti-Alzheimer activity, is shown to significantly promote α-syn degradation in a cellular PD model. Moreover, we illustrate that T-006 inhibits the accumulation of both Triton-soluble and -insoluble forms of α-syn and protects against α-syn-induced neurotoxicity in A53T-α-syn transgenic mice. The mechanism of action of T-006 was verified by evaluation of a potential protein degradation pathway. We found that T-006 promotes α-syn degradation in a proteasome-dependent and autophagy-independent manner. We further confirmed that T-006 enhances proteasome activity by upregulating 20S proteasome subunit β5i (LMP7) protein expression. A functional study revealed that T-006 activates the PKA/Akt/mTOR/p70S6K pathway to trigger LMP7 expression and enhance chymotrypsin-like proteasomal activity. These findings indicate that T-006 is a potent proteasome activator and a potential therapeutic agent for the prevention and treatment of PD and related diseases.

Oxyphylla A Promotes Degradation of α-Synuclein for Neuroprotection via Activation of Immunoproteasome.

Parkinson’s disease (PD), the second most common neurodegenerative disorder, is neuropathologically characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and the presence of Lewy bodies in surviving neurons. α-synuclein (α-syn) is the major component of Lewy bodies and its deposition in neurons is critical pathological event in the pathogenesis of PD. Herein, we reported that Oxyphylla A, a novel lead compound from the fruit of Alpinia oxyphylla, significantly promoted α-syn degradation in a cellular PD model. When exploring the molecular pathways, we found that Oxyphylla A promoted α-syn degradation in a ubiquitin proteasome system (UPS)-dependent and autophagy-independent manner. We further confirmed that Oxyphylla A enhanced UPS activity by upregulating 20S subunit PSMB8 expression. A mechanism study revealed that Oxyphylla A activated the PKA/Akt/mTOR pathway to trigger PSMB8 expression and enhance UPS activity. Finally, we illustrated that Oxyphylla A alleviated the accumulation of both Triton-soluble and Triton-insoluble forms of α-syn and protected against α-syn-induced neurotoxicity in A53T α-syn transgenic mice. These findings suggest that the activation of UPS, via small molecular UPS enhancers including Oxyphylla A, may be a therapeutic strategy for intervention against PD and related diseases.

Spreading of α-Synuclein and Tau: A Systematic Comparison of the Mechanisms Involved.

Alzheimer's disease (AD) and Parkinson's disease (PD) are age-associated neurodegenerative disorders characterized by the misfolding and aggregation of alpha-synuclein (aSyn) and tau, respectively. The coexistence of aSyn and tau aggregates suggests a strong overlap between tauopathies and synucleinopathies. Interestingly, misfolded forms of aSyn and tau can propagate from cell to cell, and throughout the brain, thereby templating the misfolding of native forms of the proteins. The exact mechanisms involved in the propagation of the two proteins show similarities, and are reminiscent of the spreading characteristic of prion diseases. Recently, several models were developed to study the spreading of aSyn and tau. Here, we discuss the mechanisms involved, the similarities and differences between the spreading of the two proteins and that of the prion protein, and the different cell and animal models used for studying these processes. Ultimately, a deeper understanding of the molecular mechanisms involved may lead to the identification of novel targets for therapeutic intervention in a variety of devastating neurodegenerative diseases.

Characterisation of Oxidative Stress, DNA Damage and Inflammation in a Cellular Model of Parkinson’s Disease

Background: Parkinson’s disease (PD) is the second most commonly occurring neurodegenerative disease and is classed as a synucleinopathy due to the critical role of α-synuclein (α-Syn) in its pathology. α-Syn is able to translocate from the cytoplasm to the nucleus and cause DNA damage. Methods: SH-SY5Y cells were stably transfected with plasmids containing wildtype α-Syn and A53T mutant α-Syn as fusion proteins with EGFP and an EGFP only control vector. The cells were treated with hydrogen peroxide (H2O2) and analysed in a differentiated state for the effects of oxidative stress using flow cytometry, DNA damage using H2A.X staining and inflammatory and senescence markers using qPCR. Results: Cells expressing the A53T mutation exhibited a higher sensitivity to treatment with H2O2 with significantly higher amounts of DNA damage. Importantly, WT α-Syn seemed to have a protective effect in differentiated cells under increased stress with no increase in DNA damage after H2O2 treatment. In line with these results, inflammatory markers of COX-2, IL-6 and TNF-α as well as stress-and senescence markers p21 and p16 were all significantly increased in differentiated treated cells expressing mutated α-Syn while there were no changes in cells expressing wildtype α-Syn. Interestingly, both forms of α-Syn increased the levels of mitochondrial ROS already in untreated conditions while there were no differences between the two α-Syn forms. Conclusions: Our data demonstrate a higher stress sensitivity of SH-SY5Y neuroblastoma cells harbouring an A53T mutant α-Syn for DNA damage and selected inflammatory marker. In contrast, wildtype α-Syn seemed to provide protection against oxidative stress in a neurone-like cellular model. Thus, these neuroblastoma cells differentiated with retinoid acid seem to be a good model for studying various pathological effects of α-Syn.

Unbiased Screens for Modifiers of Alpha-Synuclein Toxicity.

We provide an overview about unbiased screens to identify modifiers of alpha-synuclein (αSyn)-induced toxicity, present the models and the libraries that have been used for screening, and describe how hits from primary screens were selected and validated. Screens can be classified as either genetic or chemical compound modifier screens, but a few screens do not fit this classification. Most screens addressing αSyn-induced toxicity, including genome-wide overexpressing and deletion, were performed in yeast. More recently, newer methods such as CRISPR-Cas9 became available and were used for screening purposes. Paradoxically, given that αSyn-induced toxicity plays a role in neurological diseases, there is a shortage of human cell-based models for screening. Moreover, most screens used mutant or fluorescently tagged forms of αSyn and only very few screens investigated wild-type αSyn. Particularly, no genome-wide αSyn toxicity screen in human dopaminergic neurons has been published so far. Most unbiased screens for modifiers of αSyn toxicity were performed in yeast, and there is a lack of screens performed in human and particularly dopaminergic cells.

Autophagy\u2013lysosome pathway alterations and alpha-synuclein up-regulation in the subtype of neuronal ceroid lipofuscinosis, CLN5 disease

Neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative lysosomal storage disorders. CLN5 deficiency causes a subtype of NCL, referred to as CLN5 disease. CLN5 is a soluble lysosomal protein with an unclear function in the cell. Increased levels of the autophagy marker protein LC3-II have been reported in several subtypes of NCLs. In this report, we examine whether autophagy is altered in CLN5 disease. We found that the basal level of LC3-II was elevated in both CLN5 disease patient fibroblasts and CLN5-deficient HeLa cells. Further analysis using tandem fluorescent mRFP-GFP-LC3 showed the autophagy flux was increased. We found the alpha-synuclein (α-syn) gene SNCA was highly up-regulated in CLN5 disease patient fibroblasts. The aggregated form of α-syn is well known for its role in the pathogenicity of Parkinson’s disease. Higher α-syn protein levels confirmed the SNCA up-regulation in both patient cells and CLN5 knockdown HeLa cells. Furthermore, α-syn was localized to the vicinity of lysosomes in CLN5 deficient cells, indicating it may have a lysosome-related function. Intriguingly, knocking down SNCA reversed lysosomal perinuclear clustering caused by CLN5 deficiency. These results suggest α-syn may affect lysosomal clustering in non-neuronal cells, similar to its role in presynaptic vesicles in neurons.

α-Synuclein and Glia in Parkinson's Disease: A Beneficial or a Detrimental Duet for the Endo-Lysosomal System?

Accumulation of α-synuclein (α-syn) species in dopaminergic neurons is one of the main hallmarks of Parkinson's disease (PD). Several factors have been associated with α-syn aggregation process, including an impairment of the proper protein degradation, which might drive the neurons toward an alternative and/or additional clearance mechanism that involves the release of undigested material from the cell. It has been reported that extracellular α-syn, released by stressed and/or degenerating neurons, might widely contribute to the neuronal toxicity and degeneration. Therefore, the uptake and clearance of misfolded/aggregated proteins is a key process to control extracellular deposition of α-syn aggregates, the spreading and progression of the disease. All the main brain cell types, neurons, astrocytes and microglia are able to internalize and degrade extracellular α-syn, however, glial cells appear to be the most efficient scavengers. Accumulating evidence indicates that the endocytosis of α-syn species might be conformation-sensitive, cell- and receptor-type specific, making the scenario highly complex. In this review, we will shed light on the different endocytosis mechanisms and receptors recruited for the uptake and clearance of pathological α-syn forms with a special focus on glial cells. Moreover, we will discuss how PD-related genes, in addition to α-syn itself, may alter the endo-lysosomal pathway causing an impairment of clearance, which, in turn, lead to accumulation of toxic species, dysfunctions of glia physiology and progression of the disease.

Physiological C-terminal truncation of α-synuclein potentiates the prion-like formation of pathological inclusions

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.

Development of an aggregate-selective, human-derived α-synuclein antibody BIIB054 that ameliorates disease phenotypes in Parkinson's disease models

Aggregation of α-synuclein (α-syn) is neuropathologically and genetically linked to Parkinson's disease (PD). Since stereotypic cell-to-cell spreading of α-syn pathology is believed to contribute to disease progression, immunotherapy with antibodies directed against α-syn is considered a promising therapeutic approach for slowing disease progression. Here we report the identification, binding characteristics, and efficacy in PD mouse models of the human-derived α-syn antibody BIIB054, which is currently under investigation in a Phase 2 clinical trial for PD. BIIB054 was generated by screening human memory B-cell libraries from healthy elderly individuals. Epitope mapping studies conducted using peptide scanning, X-ray crystallography, and mutagenesis show that BIIB054 binds to α-syn residues 1–10. BIIB054 is highly selective for aggregated forms of α-syn with at least an 800-fold higher apparent affinity for fibrillar versus monomeric recombinant α-syn and a strong preference for human PD brain tissue. BIIB054 discriminates between monomers and oligomeric/fibrillar forms of α-syn based on high avidity for aggregates, driven by weak monovalent affinity and fast binding kinetics. In efficacy studies in three different mouse models with intracerebrally inoculated preformed α-syn fibrils, BIIB054 treatment attenuated the spreading of α-syn pathology, rescued motor impairments, and reduced the loss of dopamine transporter density in dopaminergic terminals in striatum. The preclinical data reported here provide a compelling rationale for clinical development of BIIB054 for the treatment and prevention of PD.