α-Synuclein aggregation and modulating factors

Intramolecular interaction kinetically regulates fibril formation by human and mouse α-synuclein

Regulation of α-synuclein (αS) fibril formation is a potent therapeutic strategy for αS-related neurodegenerative disorders. αS, an intrinsically disordered 140-residue intraneural protein, comprises positively charged N-terminal, hydrophobic non-amyloid β component (NAC), and negatively charged C-terminal regions. Although mouse and human αS share 95% sequence identity, mouse αS forms amyloid fibrils faster than human αS. To evaluate the kinetic regulation of αS fibrillation, we examined the effects of mismatched residues in human and mouse αS on fibril formation and intramolecular interactions. Thioflavin T fluorescence assay using domain-swapped or C-terminal-truncated αS variants revealed that mouse αS exhibited higher nucleation and fibril elongation than human αS. In mouse αS, S87N substitution in the NAC region rather than A53T substitution is dominant for enhanced fibril formation. Fӧrester resonance energy transfer analysis demonstrated that the intramolecular interaction of the C-terminal region with the N-terminal and NAC regions observed in human αS is perturbed in mouse αS. In mouse αS, S87N substitution is responsible for the perturbed interaction. These results indicate that the interaction of the C-terminal region with the N-terminal and NAC regions suppresses αS fibril formation and that the human-to-mouse S87N substitution in the NAC region accelerates αS fibril formation by perturbing intramolecular interaction.

Accurate Detection of α-Synuclein Seeds in Cerebrospinal Fluid from Isolated Rapid Eye Movement Sleep Behavior Disorder and Patients with Parkinson's Disease in the DeNovo Parkinson (DeNoPa) Cohort

BACKGROUND

Misfolded α-synuclein (αSyn) aggregates (αSyn-seeds) in cerebrospinal fluid (CSF) are biomarkers for synucleinopathies such as Parkinson's disease (PD). αSyn-seeds have been detected in prodromal cases with isolated rapid eye movement sleep behavior disorder (iRBD).

OBJECTIVES

The objective of this study was to determine the accuracy of the αSyn-seed amplification assay (αS-SAA) in a comprehensively characterized cohort with a high proportion of PD and iRBD CSF samples collected at baseline.

METHODS

We used a high-throughput αS-SAA to analyze 233 blinded CSF samples from 206 participants of the DeNovo Parkinson Cohort (DeNoPa) (113 de novo PD, 64 healthy controls, 29 iRBD confirmed by video polysomnography). Results were compared with the final diagnosis, which was determined after up to 10 years of longitudinal clinical evaluations, including dopamine-transporter-single-photon emission computed tomography (DAT-SPECT) at baseline, CSF proteins, Movement Disorder Society-Unified Parkinson's Disease Rating Scale, and various cognitive and nonmotor scales.

RESULTS

αS-SAA detected αSyn-seeds in baseline PD-CSF with 98% accuracy. αSyn-seeds were detected in 93% of the iRBD cases. αS-SAA results showed higher agreement with the final than the initial diagnosis, as 14 patients were rediagnosed as non-αSyn aggregation disorder. For synucleinopathies, αS-SAA showed higher concordance with the final diagnosis than DAT-SPECT. Statistically significant correlations were found between assay parameters and disease progression.

CONCLUSIONS

Our results confirm αS-SAA accuracy at the first clinical evaluation when a definite diagnosis is most consequential. αS-SAA conditions reported here are highly sensitive, enabling the detection of αSyn-seeds in CSF from iRBD just months after the first symptoms, suggesting that αSyn-seeds are present in the very early prodromal phase of synucleinopathies. Therefore, αSyn-seeds are clear risk markers for synuclein-related disorders, but not for time of phenoconversion. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A Conceptual Study on the Peripheral Clearance of Brain-Derived α-Synuclein in Humans

BACKGROUND

Abnormal intracellular expression and aggregation of α-synuclein (α-syn) is the histopathological hallmark of several neurodegenerative diseases especially Parkinson's disease. However, safe and efficient approaches to clear α-syn remain unavailable.

OBJECTIVE

This study aimed to investigate the process of peripheral catabolism of brain-derived α-syn.

METHODS

Thirty patients with atrioventricular reentrant tachycardia (AVRT) (left accessory pathways) who underwent radiofrequency catheter ablation (RFCA) were enrolled in this study. Blood was collected via catheters from superior vena cava (SVC), inferior vena cava (IVC) proximal to the hepatic vein (HV), the right femoral vein (FV), and femoral artery (FA) simultaneously during RFCA. Plasma α-syn levels of AVRT patients and soluble α-syn levels of the brain samples were measured using enzyme-linked immunosorbent assay kits.

RESULTS

The α-syn concentrations in different locations of veins were divided by time-matched arterial α-syn concentrations to generate the venous/arterial (V/A) ratio. The V/A ratio of α-syn from the SVC was 1.204 (1.069-1.339, 95% CI), while the V/A ratio of α-syn from IVC was 0.831 (0.734-0.928, 95% CI), suggesting that brain-derived α-syn in the arterial blood was physiologically cleared while going through the peripheral organs and tissues. And it was estimated that about half of brain soluble α-syn could efflux and be cleared in the periphery. Moreover, the glomerular filtration rate was found correlated with V-A difference (FA-ICV) (p = 0.0272).

CONCLUSION

Under physiological conditions, brain-derived α-syn could efflux into and be catabolized by the peripheral system. The kidney may play a potential role in the clearance of α-syn.

Pathogenic Impact of α-Synuclein Phosphorylation and Its Kinases in α-Synucleinopathies

α-Synuclein is a protein with a molecular weight of 14.5 kDa and consists of 140 amino acids encoded by the SNCA gene. Missense mutations and gene duplications in the SNCA gene cause hereditary Parkinson’s disease. Highly phosphorylated and abnormally aggregated α-synuclein is a major component of Lewy bodies found in neuronal cells of patients with sporadic Parkinson’s disease, dementia with Lewy bodies, and glial cytoplasmic inclusion bodies in oligodendrocytes with multiple system atrophy. Aggregated α-synuclein is cytotoxic and plays a central role in the pathogenesis of the above-mentioned synucleinopathies. In a healthy brain, most α-synuclein is unphosphorylated; however, more than 90% of abnormally aggregated α-synuclein in Lewy bodies of patients with Parkinson’s disease is phosphorylated at Ser129, which is presumed to be of pathological significance. Several kinases catalyze Ser129 phosphorylation, but the role of phosphorylation enzymes in disease pathogenesis and their relationship to cellular toxicity from phosphorylation are not fully understood in α-synucleinopathy. Consequently, this review focuses on the pathogenic impact of α-synuclein phosphorylation and its kinases during the neurodegeneration process in α-synucleinopathy.

A Matrigel-based 3D construct of SH-SY5Y cells models the α-synuclein pathologies of Parkinson's disease

Parkinson's disease (PD) is associated with α-synuclein-based Lewy body pathology, which has been difficult to observe in conventional two-dimensional (2D) cell culture and even in animal models. We herein aimed to develop a three-dimensional (3D) cellular model of PD to recapitulate the α-synuclein pathologies. All-trans-retinoic acid-differentiated human SH-SY5Y cells and Matrigel were optimized for 3D construction. The 3D cultured cells displayed higher tyrosine hydroxylase expression than 2D cells and improved dopaminergic-like phenotypes, as suggested by RNA-sequencing analyses. Multiple forms of α-synuclein, including monomer, and low- and high-molecular mass oligomers, were differentially present in the 2D and 3D cells, but mostly remained unchanged upon N-methyl-4-phenyl pyridine or rotenone treatment. Phosphorylated α-synuclein was accumulated, and detergent-insoluble α-synuclein fraction was observed, in the neurotoxin-treated 3D cells. Importantly, Lewy body-like inclusions were captured in the 3D system, including proteinase K-resistant α-synuclein aggregates, ubiquitin aggregation, and β-amyloid and β-sheet protein deposition. The study provides a unique and convenient 3D model of PD that recapitulates critical α-synuclein pathologies and should be useful in multiple PD-associated applications.

Summary: This study provides a convenient 3D model of Parkinson's disease (PD), which recapitulates α-synuclein pathologies in human cells and could be used to investigate PD mechanisms and screen drugs.

The Neuroprotective Effect of Steroid Receptor Coactivator-Interacting Protein (SIP) in Astrocyte Model of 1-Methyl-4-Phenylpyridinium (MPP⁺)-Induced Parkinson's Disease

Background

The purpose of this study was to investigate the role and mechanism of steroid receptor coactivator-interacting protein (SIP) in an astrocyte model of 1-methyl-4-phenylpyridinium (MPP⁺)-induced Parkinson’s disease.

Material/Methods

To perform our study, a Parkinson’s disease cell model was established by treating the rat glioblastoma cell line C6 with MPP⁺. SIP was overexpressed in C6 cells using SIP-plasmid. Cell viability and apoptosis were analyzed using MTT assay and flow cytometer respectively. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels were detected using enzyme linked immunosorbent assay and quantitative reverse transcription PCR. Besides, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) production, and superoxide dismutase (SOD) enzyme activity were determined in the present study. For protein and mRNA detection, western blot assay, and qRT-PCR were performed respectively.

Results

SIP was decreased in MPP⁺-induced C6 cells. SIP overexpression relieved MPP⁺-induced cytotoxicity of C6 cells, displayed as increased cell viability and reduced cell apoptosis and reduced LDH release. Besides, SIP inhibited MPP⁺-induced inflammatory response and oxidative stress, evidenced by decreased levels of inflammatory factors (TNF-α and IL-1β), reduced ROS generation and enhanced SOD activity. Moreover, MPP⁺-induced nuclear factor-κB activation was inhibited by SIP overexpression.

Conclusions

SIP was downregulated in Parkinson’s disease and it played a protective role in the development Parkinson’s disease, thus may be a promising target for Parkinson’s disease treatment.

α-Synuclein in Parkinson's disease: causal or bystander?

Parkinson's disease (PD) comprises a spectrum of disorders with differing subtypes, the vast majority of which share Lewy bodies (LB) as a characteristic pathological hallmark. The process(es) underlying LB generation and its causal trigger molecules are not yet fully understood. α-Synuclein (α-syn) is a major component of LB and SNCA gene missense mutations or duplications/triplications are causal for rare hereditary forms of PD. As typical sporadic PD is associated with LB pathology, a factor of major importance is the study of the α-syn protein and its pathology. α-Syn pathology is, however, also evident in multiple system atrophy (MSA) and Lewy body disease (LBD), making it non-specific for PD. In addition, there is an overlap of these α-synucleinopathies with other protein-misfolding diseases. It has been proven that α-syn, phosphorylated tau protein (pτ), amyloid beta (Aβ) and other proteins show synergistic effects in the underlying pathogenic mechanisms. Multiple cell death mechanisms can induce pathological protein-cascades, but this can also be a reverse process. This holds true for the early phases of the disease process and especially for the progression of PD. In conclusion, while rare SNCA gene mutations are causal for a minority of familial PD patients, in sporadic PD (where common SNCA polymorphisms are the most consistent genetic risk factor across populations worldwide, accounting for 95% of PD patients) α-syn pathology is an important feature. Conversely, with regard to the etiopathogenesis of α-synucleinopathies PD, MSA and LBD, α-syn is rather a bystander contributing to multiple neurodegenerative processes, which overlap in their composition and individual strength. Therapeutic developments aiming to impact on α-syn pathology should take this fact into consideration.

A secret that underlies Parkinson's disease: The damaging cycle

Parkinson's disease (PD) is a movement disorder, and its common characteristics include the loss of dopaminergic neurons and the accumulation of a special type of cytoplasmic inclusions called Lewy bodies in the substantia nigra pars compacta, which are more prevalent in the elderly. However, the pathophysiology of PD is still elusive. In this review, we summarized five common factors involved in PD, namely, (i) oxidative stress, (ii) mitochondrial dysfunction, (iii) inflammation, (iv) abnormal α-synuclein, and (v) endogenous neurotoxins, and proposed a hypothesis involving a damaging cycle. Oxidative stress-triggered aldehydes react with biogenic amines to produce endogenous neurotoxins. They cause mitochondrial dysfunction and the formation of inflammasomes, which induce the activation of neuroglial cells and the infiltration of T lymphocytes. The synergistic effect of these processes fosters chronic inflammation and α-synuclein aggregation and further exacerbates the impact of oxidative stress to establish a damaging cycle that eventually results in the degeneration of dopaminergic neurons. This damaging cycle provides an explanation of progressive neuronal death during the pathogenesis of PD and provides new potential targets beneficial for developing new drugs and approaches for clinical neuroprotection.

Naja mossambica mossambica Cobra Cardiotoxin Targets Mitochondria to Disrupt Mitochondrial Membrane Structure and Function

Cobra venom cardiotoxins (CVCs) can translocate to mitochondria to promote apoptosis by eliciting mitochondrial dysfunction. However, the molecular mechanism(s) by which CVCs are selectively targeted to the mitochondrion to disrupt mitochondrial function remains to be elucidated. By studying cardiotoxin from Naja mossambica mossambica cobra (cardiotoxin VII4), a basic three-fingered S-type cardiotoxin, we hypothesized that cardiotoxin VII4 binds to cardiolipin (CL) in mitochondria to alter mitochondrial structure/function and promote neurotoxicity. By performing confocal analysis, we observed that red-fluorescently tagged cardiotoxin rapidly translocates to mitochondria in mouse primary cortical neurons and in human SH-SY5Y neuroblastoma cells to promote aberrant mitochondrial fragmentation, a decline in oxidative phosphorylation, and decreased energy production. In addition, by employing electron paramagnetic resonance (EPR) and protein nuclear magnetic resonance (¹H-NMR) spectroscopy and phosphorescence quenching of erythrosine in model membranes, our compiled biophysical data show that cardiotoxin VII4 binds to anionic CL, but not to zwitterionic phosphatidylcholine (PC), to increase the permeability and formation of non-bilayer structures in CL-enriched membranes that biochemically mimic the outer and inner mitochondrial membranes. Finally, molecular dynamics simulations and in silico docking studies identified CL binding sites in cardiotoxin VII4 and revealed a molecular mechanism by which cardiotoxin VII4 interacts with CL and PC to bind and penetrate mitochondrial membranes.

Conformation-specific antibodies against multiple amyloid protofibril species from a single amyloid immunogen

We engineered and employed a chaperone‐like amyloid‐binding protein Nucleobindin 1 (NUCB1) to stabilize human islet amyloid polypeptide (hIAPP) protofibrils for use as immunogen in mice. We obtained multiple monoclonal antibody (mAb) clones that were reactive against hIAPP protofibrils. A secondary screen was carried out to identify clones that cross‐reacted with amyloid beta‐peptide (Aβ42) protofibrils, but not with Aβ40 monomers. These mAbs were further characterized in several in vitro assays, in immunohistological studies of a mouse model of Alzheimer's disease (AD) and in AD patient brain tissue. We show that mAbs obtained by immunizing mice with the NUCB1‐hIAPP complex cross‐react with Aβ42, specifically targeting protofibrils and inhibiting their further aggregation. In line with conformation‐specific binding, the mAbs appear to react with an intracellular antigen in diseased tissue, but not with amyloid plaques. We hypothesize that the mAbs we describe here recognize a secondary or quaternary structural epitope that is common to multiple amyloid protofibrils. In summary, we report a method to create mAbs that are conformation‐sensitive and sequence‐independent and can target more than one type of protofibril species.

Investigation of α-Synuclein Amyloid Fibrils Using the Fluorescent Probe Thioflavin T

In this work, α-synuclein amyloid fibrils—the formation of which is a biomarker of Parkinson’s disease—were investigated using the fluorescent probe thioflavin T (ThT). The experimental conditions of protein fibrillogenesis were chosen so that a sufficient number of continuous measurements could be performed to characterize and analyze all stages of this process. The reproducibility of fibrillogenesis and the structure of the obtained aggregates (which is a critical point for further investigation) were proven using a wide range of physical-chemical methods. For the determination of ThT-α-synuclein amyloid fibril binding parameters, the sample and reference solutions were prepared using equilibrium microdialysis. By utilizing absorption spectroscopy of these solutions, the ThT-fibrils binding mode with a binding constant of about 10⁴ M⁻¹ and stoichiometry of ThT per protein molecule of about 1:8 was observed. Fluorescence spectroscopy of the same solutions with the subsequent correction of the recorded fluorescence intensity on the primary inner filter effect allowed us to determine another mode of ThT binding to fibrils, with a binding constant of about 10⁶ M⁻¹ and stoichiometry of about 1:2500. Analysis of the photophysical characteristics of the dye molecules bound to the sites of different binding modes allowed us to assume the possible localization of these sites. The obtained differences in the ThT binding parameters to the amyloid fibrils formed from α-synuclein and other amyloidogenic proteins, as well as in the photophysical characteristics of the bound dye, confirmed the hypothesis of amyloid fibril polymorphism.

Proteasome impairment by α-synuclein

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder worldwide and characterized by the loss of dopaminergic neurons in the patients’ midbrains. Both the presence of the protein α-synuclein in intracellular protein aggregates in surviving neurons and the genetic linking of the α-synuclein encoding gene point towards a major role of α-synuclein in PD etiology. The exact pathogenic mechanisms of PD development are not entirely described to date, neither is the specific role of α-synuclein in this context. Previous studies indicate that one aspect of α-synuclein-related cellular toxicity might be direct proteasome impairment. The 20/26S proteasomal machinery is an important instrument of intracellular protein degradation. Thus, direct proteasome impairment by α-synuclein might explain or at least contribute to the formation of intracellular protein aggregates. Therefore this study investigates direct proteasomal impairment by α-synuclein both in vitro using recombinant α-synuclein and isolated proteasomes as well as in living cells. Our experiments demonstrate that the impairment of proteasome activity by α-synuclein is highly dependent upon the cellular background and origin. We show that recombinant α-synuclein oligomers and fibrils scarcely affect 20S proteasome function in vitro, neither does transient α-synuclein expression in U2OS ps 2042 (Ubi(G76V)-GFP) cells. However, stable expression of both wild-type and mutant α-synuclein in dopaminergic SH-SY5Y and PC12 cells results in a prominent impairment of the chymotrypsin-like 20S/26S proteasomal protein cleavage. Thus, our results support the idea that α-synuclein in a specific cellular environment, potentially present in dopaminergic cells, cannot be processed by the proteasome and thus contributes to a selective vulnerability of dopaminergic cells to α-synuclein pathology.

An enhanced recombinant amino-terminal acetylation system and novel in vivo high-throughput screen for molecules affecting α-synuclein oligomerisation

Amino‐terminal acetylation is a ubiquitous protein modification affecting the majority of eukaryote proteins to regulate stability and function. We describe an optimised recombinant expression system for rapid production of amino terminal‐acetylated proteins within bacteria. We go on to describe the system's use in a fluorescence based in vivo assay for use in the high‐throughput screen to identify drugs that impact amino‐terminal acetylation‐dependent oligomerisation. These new tools and protocols will allow researchers to enhance routine recombinant protein production and identify new molecules for use in research and clinical applications.

Nanomolar oligomerization and selective co-aggregation of α-synuclein pathogenic mutants revealed by single-molecule fluorescence

Protein aggregation is a hallmark of many neurodegenerative diseases, notably Alzheimer's and Parkinson's disease. Parkinson's disease is characterized by the presence of Lewy bodies, abnormal aggregates mainly composed of α-synuclein. Moreover, cases of familial Parkinson's disease have been linked to mutations in α-synuclein. In this study, we compared the behavior of wild-type (WT) α-synuclein and five of its pathological mutants (A30P, E46K, H50Q, G51D and A53T). To this end, single-molecule fluorescence detection was coupled to cell-free protein expression to measure precisely the oligomerization of proteins without purification, denaturation or labelling steps. In these conditions, we could detect the formation of oligomeric and pre-fibrillar species at very short time scale and low micromolar concentrations. The pathogenic mutants surprisingly segregated into two classes: one group forming large aggregates and fibrils while the other tending to form mostly oligomers. Strikingly, co-expression experiments reveal that members from the different groups do not generally interact with each other, both at the fibril and monomer levels. Together, this data paints a completely different picture of α-synuclein aggregation, with two possible pathways leading to the development of fibrils.

Subcellular Parkinson's Disease-Specific Alpha-Synuclein Species Show Altered Behavior in Neurodegeneration

Parkinson's disease and other synucleinopathies are characterized by the presence of intra-neuronal protein aggregates enriched in the presynaptic protein α-synuclein. α-synuclein is considered an intrinsically disordered 14 kDa monomer, and although poorly understood, its transition to higher-order multimeric species may play central roles in healthy neurons and during Parkinson's disease pathogenesis. In this study, we demonstrate that α-synuclein exists as defined, subcellular-specific species that change characteristics in response to oxidative stress in neuroblastoma cells and in response to Parkinson's disease pathogenesis in human cerebellum and frontal cortex. We further show that the phosphorylation patterns of different α-synuclein species are subcellular specific and dependent on the oxidative environment. Using high-performance liquid chromatography and mass spectrometry, we identify a Parkinson's disease enriched, cytosolic ~36-kDa α-synuclein species which can be recapitulated in Parkinson's disease model neuroblastoma cells. The characterization of subcellular-specific α-synuclein features in neurodegeneration will allow for the identification of neurotoxic α-synuclein species, which represent prime targets to reduce α-synuclein pathogenicity.

Atp13a2 Deficiency Aggravates Astrocyte-Mediated Neuroinflammation via NLRP3 Inflammasome Activation

AIM

Atp13a2 (Park9) gene encodes a transmembrane lysosomal P5-type ATPase (ATP13A2), and its missense or truncation mutations leads to lysosomal dysfunction and consequently results in neuronal death in the pathogenesis of Parkinson's disease (PD). Nevertheless, the roles of ATP13A2 in the biological features of astrocytes, especially in the regulation of PD-related neuroinflammation, have not been investigated.

METHODS

We cultured primary neurons and astrocytes from mouse midbrain to investigate the mechanisms for astrocyte ATP13A2-regulated lysosomal function and neuroinflammation following 1-methyl-4-phenylpyridinium (MPP(+) ) treatment.

RESULTS

We found that astrocytes expressed considerable levels of ATP13A2 and deficiency of ATP13A2 in astrocyte-induced intense inflammation, which exacerbated dopaminergic neuron damage after exposure to MPP(+) . Notably, lack of ATP13A2 increased lysosomal membrane permeabilization and cathepsin B release, which in turn exacerbated activation of nod-like receptor protein 3 (NLRP3) inflammasome to produce excess IL-1β from astrocytes. Furthermore, overexpression of ATP13A2 reversed MPP(+) -induced cathepsin B release and NLRP3 inflammasome activation in astrocytes.

CONCLUSIONS

Our results have revealed a novel role of ATP13A2 in modulating astrocyte-mediated neuroinflammation via NLRP3 inflammasome activation, thus bringing to light of a direct link between astrocyte lysosome and neuroinflammation in the pathological model of PD.

Interaction of α-synuclein with biomembranes in Parkinson's disease--role of cardiolipin

One of the key molecular events underlying the pathogenesis of Parkinson's disease (PD) is the aberrant misfolding and aggregation of the α-synuclein (αS) protein into higher-order oligomers that play a key role in neuronal dysfunction and degeneration. A wealth of experimental data supports the hypothesis that the neurotoxicity of αS oligomers is intrinsically linked with their ability to interact with, and disrupt, biological membranes; especially those membranes having negatively-charged surfaces and/or lipid packing defects. Consequences of αS-lipid interaction include increased membrane tension, permeation by pore formation, membrane lysis and/or leakage due to the extraction of lipids from the bilayer. Moreover, we assert that the interaction of αS with a liquid-disordering phospholipid uniquely enriched in mitochondrial membranes, namely cardiolipin (1,3-diphosphatidyl-sn-glycerol, CL), helps target the αS oligomeric complexes intracellularly to mitochondria. Binding mediated by CL may thus represent an important pathomechanism by which cytosolic αS could physically associate with mitochondrial membranes and disrupt their integrity. Impaired mitochondrial function culminates in a cellular bioenergetic crisis and apoptotic death. To conclude, we advocate the accelerated discovery of new drugs targeting this pathway in order to restore mitochondrial function in PD.

Comparison between α-synuclein wild-type and A53T mutation in a progressive Parkinson's disease model

BACKGROUND AND AIMS

Vector based over-expression of α-synuclein is a newly developed method to establish animal Parkinson's disease (PD) model. In this paper, we inject the rat brain with recombinant adeno-associated virus (rAAV) to express α-synuclein wild-type and A53T mutation, and compared the degeneration of dopaminergic neurons between them.

METHOD AND RESULTS

The rAAV vectors were injected into the substantia nigra pars compacta (SNpc) of rat brain. In different time point, immunohistochemistry was used to detect the expression of α-synuclein. The expression level was lower in the 3rd and 6th week and increased from the 9th week. α-synuclein spread around the neurons in SNpc in the 12th week. The loss of dopaminergic neurons was increasing along the expression of α-synuclein, and damage extent was more serious in the A53T group than the WT group. In the A53T group, there were more insoluble inclusions can be detected, and the phosphorylation of α-synuclein was also higher.

CONLUSION

The result of comparison between the two types of α-synuclein showed that A53T mutated α-synuclein was more effective to establish PD model, and the model based A53T mutated α-synuclein was a suitable model to early-onset PD.

DJ-1 interactions with α-synuclein attenuate aggregation and cellular toxicity in models of Parkinson's disease

Parkinson's disease (PD) is a devastating neurodegenerative disorder characterized by the loss of neurons in the substantia nigra pars compacta and the presence of Lewy bodies in surviving neurons. These intracellular protein inclusions are primarily composed of misfolded α-synuclein (aSyn), which has also been genetically linked to familial and sporadic forms of PD. DJ-1 is a small ubiquitously expressed protein implicated in several pathways associated with PD pathogenesis. Although mutations in the gene encoding DJ-1 lead to familial early-onset PD, the exact mechanisms responsible for its role in PD pathogenesis are still elusive. Previous work has found that DJ-1--which has protein chaperone-like activity--modulates aSyn aggregation. Here, we investigated possible physical interactions between aSyn and DJ-1 and any consequent functional and pathological relevance. We found that DJ-1 interacts directly with aSyn monomers and oligomers in vitro, and that this also occurs in living cells. Notably, several PD-causing mutations in DJ-1 constrain this interaction. In addition, we found that overexpression of DJ-1 reduces aSyn dimerization, whereas mutant forms of DJ-1 impair this process. Finally, we found that human DJ-1 as well as yeast orthologs of DJ-1 reversed aSyn-dependent cellular toxicity in Saccharomyces cerevisiae. Taken together, these data suggest that direct interactions between DJ-1 and aSyn constitute the basis for a neuroprotective mechanism and that familial mutations in DJ-1 may contribute to PD by disrupting these interactions.