Aggregation In Parkinson's Disease Research Articles

Lysophosphatidylcholine binds α-synuclein and prevents its pathological aggregation.

Accumulation of aggregated α-synuclein (α-syn) in Lewy bodies is the pathological hallmark of Parkinson's disease (PD). Genetic mutations in lipid metabolism are causative for a subset of patients with Parkinsonism. The role of α-syn's lipid interactions in its function and aggregation is recognized, yet the specific lipids involved and how lipid metabolism issues trigger α-syn aggregation and neurodegeneration remain unclear. Here, we found that α-syn shows a preference for binding to lysophospholipids (LPLs), particularly targeting lysophosphatidylcholine (LPC) without relying on electrostatic interactions. LPC is capable of maintaining α-syn in a compact conformation, significantly reducing its propensity to aggregate both in vitro and within cellular environments. Conversely, a reduction in the production of cellular LPLs is associated with an increase in α-syn accumulation. Our work underscores the critical role of LPLs in preserving the natural conformation of α-syn to inhibit improper aggregation, and establishes a potential connection between lipid metabolic dysfunction and α-syn aggregation in PD.

A crazy trio in Parkinson's disease: metabolism alteration, α-synuclein aggregation, and oxidative stress.

Parkinson's disease (PD) is an aging-associated neurodegenerative disorder, characterized by the progressive loss of dopaminergic neurons in the pars compacta of the substantia nigra and the presence of Lewy bodies containing α-synuclein within these neurons. Oligomeric α-synuclein exerts neurotoxic effects through mitochondrial dysfunction, glial cell inflammatory response, lysosomal dysfunction and so on. α-synuclein aggregation, often accompanied by oxidative stress, is generally considered to be a key factor in PD pathology. At present, emerging evidences suggest that metabolism alteration is closely associated with α-synuclein aggregation and PD progression, and improvement of key molecules in metabolism might be potentially beneficial in PD treatment. In this review, we highlight the tripartite relationship among metabolic changes, α-synuclein aggregation, and oxidative stress in PD, and offer updated insights into the treatments of PD, aiming to deepen our understanding of PD pathogenesis and explore new therapeutic strategies for the disease.

Palmitoylation of the Parkinson's disease-associated protein synaptotagmin-11 links its turnover to α-synuclein homeostasis.

Synaptotagmin-11 (Syt11) is a vesicle-trafficking protein that is linked genetically to Parkinson's disease (PD). Likewise, the protein α-synuclein regulates vesicle trafficking, and its abnormal aggregation in neurons is the defining cytopathology of PD. Because of their functional similarities in the same disease context, we investigated whether the two proteins were connected. We found that Syt11 was palmitoylated in mouse and human brain tissue and in cultured cortical neurons and that this modification to Syt11 disrupted α-synuclein homeostasis in neurons. Palmitoylation of two cysteines adjacent to the transmembrane domain, Cys39 and Cys40, localized Syt11 to digitonin-insoluble portions of intracellular membranes and protected it from degradation by the endolysosomal system. In neurons, palmitoylation of Syt11 increased its abundance and enhanced the binding of α-synuclein to intracellular membranes. As a result, the abundance of the physiologic tetrameric form of α-synuclein was decreased, and that of its aggregation-prone monomeric form was increased. These effects were replicated by overexpression of wild-type Syt11 but not a palmitoylation-deficient mutant. These findings suggest that palmitoylation-mediated increases in Syt11 amounts may promote pathological α-synuclein aggregation in PD.

Protective Association of HLA-DRB1*04 Subtypes in Neurodegenerative Diseases Implicates Acetylated Tau PHF6 Sequences

Objective To explore genetic association between human leukocyte antigen (HLA) and neurodegenerative diseases and investigate mechanisms behind the association. Background Pathophysiology of Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) involves accumulation of tau (neurofibrillary tangles) and amyloid-ß-rich (amyloid plaques) aggregates in AD, a-synuclein-rich aggregates (Lewy bodies) in PD and TDP-43 aggregates in ALS, although these aggregates may also co-occur. Likewise, consensus is growing that tau may play a key role in PD and ALS as well. Design/Methods We analyzed HLA associations in ∼176,000 individuals with PD or AD versus controls across ancestry groups. Pursuing this, we also compared postmortem brain density of neurofibrillary tangles and amyloid plaques in brain, tau and Aß42 levels in cerebrospinal fluid (CSF) of ∼8,000 individuals (controls and AD), and examined association of HLA in ∼2,500 patient with pathologically demonstrated Lewy Body Dementia. This was followed by HLA binding and tetramer T cell studies. Results A shared genetic association was observed across AD and PD at rs601945 (PD: odds ratio (OR) = 0.84; 95% confidence interval, [0.80; 0.88]; p = 2.2 x 10-13; AD: OR = 0.91[0.89; 0.93]; p = 1.8 x 10-22) and with a protective HLA association recently reported in ALS. Hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03 and absent for HLA-DRB1*04:05. The same signal was associated with decreased neurofibrillary tangle (but not neuritic plaque) density postmortem and was more associated with lower tau levels than Aß42 level changes in CSF. Furthermore, protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, but only when acetylated at K311, a modification central to aggregation. T cells recognizing this epitope were identified, showing relevance of this immune response in patients with neurodegenerative disorders. Conclusions An HLA-DRB1*04-mediated adaptive immune response, potentially against tau, decreases PD, AD and ALS risk, offering the possibility of new therapeutic avenues.

Baicalein exhibits differential effects and mechanisms towards disruption of α-synuclein fibrils with different polymorphs

Parkinson's disease (PD) is the second most common neurodegenerative diseases with no cure yet and its major hallmark is α-synuclein fibrillary aggregates. The crucial role of α-synuclein aggregation in PD makes it an attractive target for potential disease-modifying therapies. Disaggregation of α-synuclein fibrils is considered as one of the promising therapeutic strategies to treat PD. The wild type (WT) and mutant α-synuclein fibrils exhibit different polymorphs and provide therapeutic targets for PD. Recent experiments reported that a flavonoid baicalein can disrupt WT α-synuclein fibrils. However, the underlying disruptive mechanism remains largely elusive, and whether BAC is capable of disrupting mutant α-synuclein fibrils is also unknown. Herein, we performed microsecond molecular dynamics simulations on cryo-EM-determined WT and two familial PD-associated mutant (E46K and H50Q) α-synuclein fibrils with and without baicalein. We find that baicalein destructs WT fibril by disrupting E46-K80 salt-bridge and β-sheets, and by remodeling the inter-protofilament interface. And baicalein can also damage E46K and H50Q mutant fibrils, but to different extents and via different mechanisms. The E46K fibril disruption is initiated from E61-K80 salt-bridge and N-terminal β-sheet, while the H50Q fibril disruption starts from the inter-protofilament interface and N-terminal β-sheet. These results reveal that disruptive effects and modes of baicalein on α-synuclein fibrils are polymorphism-dependent. This study suggests that baicalein may be a potential drug candidate to disrupt both WT and E46K/H50Q mutant α-synuclein fibrils and alleviate the pathological process of PD.

A light-inducible protein clustering system for in vivo analysis of α-synuclein aggregation in Parkinson disease.

Neurodegenerative disorders refer to a group of diseases commonly associated with abnormal protein accumulation and aggregation in the central nervous system. However, the exact role of protein aggregation in the pathophysiology of these disorders remains unclear. This gap in knowledge is due to the lack of experimental models that allow for the spatiotemporal control of protein aggregation, and the investigation of early dynamic events associated with inclusion formation. Here, we report on the development of a light-inducible protein aggregation (LIPA) system that enables spatiotemporal control of α-synuclein (α-syn) aggregation into insoluble deposits called Lewy bodies (LBs), the pathological hallmark of Parkinson disease (PD) and other proteinopathies. We demonstrate that LIPA-α-syn inclusions mimic key biochemical, biophysical, and ultrastructural features of authentic LBs observed in PD-diseased brains. In vivo, LIPA-α-syn aggregates compromise nigrostriatal transmission, induce neurodegeneration and PD-like motor impairments. Collectively, our findings provide a new tool for the generation, visualization, and dissection of the role of α-syn aggregation in PD.

Assessment of LIN28A variants in Parkinson's disease in large European cohorts

Parkinson's disease (PD) is a complex neurodegenerative disease with a strong genetic component. To date, several genes have been associated with monogenic forms of the disease, but these only explain a small fraction of the observed familial aggregation in PD. Recently, a heterozygous loss-of-function variant in LIN28A was associated with PD pathogenesis in the Asian population. Here, we comprehensively investigate the role of LIN28A variants in PD patients of European ancestry and assess susceptibility using individual-level genotyping data from 14,671 PD cases and 17,667 controls, as well as whole-genome sequencing data from 1647 patients with PD and 1050 controls. In addition, we further assess the summary statistics from the most recent genome-wide association studies meta-analyses to date for PD risk and age at onset. After evaluating these data, we did not find evidence to support a role for LIN28A as a major causal gene for PD. However, additional large-scale familial and case-control studies in non-European ancestry populations are necessary to further evaluate the role of LIN28A in PD etiology.

Naphthoquinone-Dopamine Hybrids Inhibit α-Synuclein Aggregation, Disrupt Preformed Fibrils, and Attenuate Aggregate-Induced Toxicity.

Accumulation and aggregation of the intrinsically disordered protein α-synuclein (α-Syn) into amyloid fibrils are hallmarks of a series of heterogeneous neurodegenerative disorders, known as synucleinopathies and most notably Parkinson's disease (PD). The crucial role of α-Syn aggregation in PD makes it an attractive target for the development of disease-modifying therapeutics that would inhibit α-Syn aggregation or disrupt its preformed fibrillar assemblies. To this end, we have designed and synthesized two naphthoquinone-dopamine-based hybrid small molecules, NQDA and Cl-NQDA, and demonstrated their ability to inhibit in vitro amyloid formation by α-Syn using ThT assay, CD, TEM, and Congo red birefringence. Moreover, these hybrid molecules efficiently disassembled preformed fibrils of α-Syn into nontoxic species, as evident from LUV leakage assay. NQDA and Cl-NQDA were found to have low cytotoxicity and they attenuated the toxicity induced by α-Syn towards SH-SY5Y neuroblastoma cells. NQDA was found to efficiently cross an in vitro human blood-brain barrier model. These naphthoquinone-dopamine based derivatives can be an attractive scaffold for therapeutic design towards PD.

A simple, versatile and robust centrifugation-based filtration protocol for the isolation and quantification of α-synuclein monomers, oligomers and fibrils: Towards improving experimental reproducibility in α-synuclein research.

Increasing evidence suggests that the process of alpha‐synuclein (α‐syn) aggregation from monomers into amyloid fibrils and Lewy bodies, via oligomeric intermediates plays an essential role in the pathogenesis of different synucleinopathies, including Parkinson's disease (PD), multiple system atrophy and dementia with Lewy bodies (DLB). However, the nature of the toxic species and the mechanisms by which they contribute to neurotoxicity and disease progression remain elusive. Over the past two decades, significant efforts and resources have been invested in studies aimed at identifying and targeting toxic species along the pathway of α‐syn fibrillization. Although this approach has helped to advance the field and provide insights into the biological properties and toxicity of different α‐syn species, many of the fundamental questions regarding the role of α‐syn aggregation in PD remain unanswered, and no therapeutic compounds targeting α‐syn aggregates have passed clinical trials. Several factors have contributed to this slow progress, including the complexity of the aggregation pathways and the heterogeneity and dynamic nature of α‐syn aggregates. In the majority of experiment, the α‐syn samples used contain mixtures of α‐syn species that exist in equilibrium and their ratio changes upon modifying experimental conditions. The failure to quantitatively account for the distribution of different α‐syn species in different studies has contributed not only to experimental irreproducibility but also to misinterpretation of results and misdirection of valuable resources. Towards addressing these challenges and improving experimental reproducibility in Parkinson's research, we describe here a simple centrifugation‐based filtration protocol for the isolation, quantification and assessment of the distribution of α‐syn monomers, oligomers and fibrils, in heterogeneous α‐syn samples of increasing complexity. The protocol is simple, does not require any special instrumentation and can be performed rapidly on multiple samples using small volumes. Here, we present and discuss several examples that illustrate the applications of this protocol and how it could contribute to improving the reproducibility of experiments aimed at elucidating the structural basis of α‐syn aggregation, seeding activity, toxicity and pathology spreading. This protocol is applicable, with slight modifications, to other amyloid‐forming proteins.

Editors' note: Revisiting protein aggregation as pathogenic in sporadic Parkinson and Alzheimer diseases

Despite genetic data from families harboring APP mutations in Alzheimer disease (AD)—or SNCA gene multiplication in familial Parkinson disease (PD)—Dr. Espay et al. emphasized the limited evidence that implicates these protein products in the pathogenesis of sporadic cases of AD/PD. Instead, the authors argued, such proteins may be epiphenomena or could represent the nervous system response to cellular stress. Using established Bradford Hill criteria to determine a cause-and-effect relationship of these proteins and their respective diseases, the authors challenged the “age-old” notion that such proteins play a proximate role in disease pathogenesis. By summarizing the available evidence, the authors concluded “human studies of protein aggregation in AD and PD do not meet a minimum set of Bradford Hill's criteria to support a causal role.” Dr. Nelson respectfully disagrees with the conclusions drawn by the authors, citing evidence that nondemented patients with “preclinical” disease already exhibit abnormal protein deposits in the CNS, whereas demented patients without histopathologic evidence of AD or PD demonstrate pathology consistent with other degenerative conditions. As such, abnormally misfolded and aggregated proteins are more likely to be deleterious rather than protective or reactive. In response, Dr. Espay et al. emphasize the lack of evidence supporting the benefit of antiaggregation therapy (so far) in the treatment of patients with preclinical disease. Targeting these proteins, or preventing their aggregation, may fail to address the occult, proximate causes underlying these conditions. Although the jury may still be out regarding this chicken or the egg dilemma, it stands to reason that we should consider alternative hypotheses in the pathogenesis of sporadic AD or PD, if only to avoid perpetuating confirmation bias. Despite genetic data from families harboring APP mutations in Alzheimer disease (AD)—or SNCA gene multiplication in familial Parkinson disease (PD)—Dr. Espay et al. emphasized the limited evidence that implicates these protein products in the pathogenesis of sporadic cases of AD/PD. Instead, the authors argued, such proteins may be epiphenomena or could represent the nervous system response to cellular stress. Using established Bradford Hill criteria to determine a cause-and-effect relationship of these proteins and their respective diseases, the authors challenged the “age-old” notion that such proteins play a proximate role in disease pathogenesis. By summarizing the available evidence, the authors concluded “human studies of protein aggregation in AD and PD do not meet a minimum set of Bradford Hill's criteria to support a causal role.” Dr. Nelson respectfully disagrees with the conclusions drawn by the authors, citing evidence that nondemented patients with “preclinical” disease already exhibit abnormal protein deposits in the CNS, whereas demented patients without histopathologic evidence of AD or PD demonstrate pathology consistent with other degenerative conditions. As such, abnormally misfolded and aggregated proteins are more likely to be deleterious rather than protective or reactive. In response, Dr. Espay et al. emphasize the lack of evidence supporting the benefit of antiaggregation therapy (so far) in the treatment of patients with preclinical disease. Targeting these proteins, or preventing their aggregation, may fail to address the occult, proximate causes underlying these conditions. Although the jury may still be out regarding this chicken or the egg dilemma, it stands to reason that we should consider alternative hypotheses in the pathogenesis of sporadic AD or PD, if only to avoid perpetuating confirmation bias.

Melatonin and Parkinson Disease: Current Status and Future Perspectives for Molecular Mechanisms.

Parkinson disease (PD) is a chronic and neurodegenerative disease with motor and nonmotor symptoms. Multiple pathways are involved in the pathophysiology of PD, including apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and changes in the neurotransmitters. Preclinical and clinical studies have shown that melatonin supplementation is an appropriate therapy for PD. Administration of melatonin leads to inhibition of some pathways related to apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and dopamine loss in PD. In addition, melatonin improves some nonmotor symptom in patients with PD. Limited studies, however, have evaluated the role of melatonin on molecular mechanisms and clinical symptoms in PD. This review summarizes what is known regarding the impact of melatonin on PD in preclinical and clinical studies.

Low prevalence of known pathogenic mutations in dominant PD genes: A Swedish multicenter study

ObjectiveTo determine the frequency of mutations known to cause autosomal dominant Parkinson disease (PD) in a series with more than 10% of Sweden's estimated number of PD patients. MethodsThe Swedish Parkinson Disease Genetics Network was formed as a national multicenter consortium of clinical researchers who together have access to DNA from a total of 2,206 PD patients; 85.4% were from population-based studies. Samples were analyzed centrally for known pathogenic mutations in SNCA (duplications/triplications, p.Ala30Pro, p.Ala53Thr) and LRRK2 (p.Asn1437His, p.Arg1441His, p.Tyr1699Cys, p.Gly2019Ser, p.Ile2020Thr). We compared the frequency of these mutations in Swedish patients with published PD series and the gnomAD database. ResultsA family history of PD in first- and/or second-degree relatives was reported by 21.6% of participants. Twelve patients (0.54%) carried LRRK2 p.(Gly2019Ser) mutations, one patient (0.045%) an SNCA duplication. The frequency of LRRK2 p.(Gly2019Ser) carriers was 0.11% in a matched Swedish control cohort and a similar 0.098% in total gnomAD, but there was a marked difference between ethnicities in gnomAD, with 42-fold higher frequency among Ashkenazi Jews than all others combined. ConclusionsIn relative terms, the LRRK2 p.(Gly2019Ser) variant is the most frequent mutation among Swedish or international PD patients, and in gnomAD. SNCA duplications were the second most common of the mutations examined. In absolute terms, however, these known pathogenic variants in dominant PD genes are generally very rare and can only explain a minute fraction of familial aggregation of PD. Additional genetic and environmental mechanisms may explain the frequent co-occurrence of PD in close relatives.

Poloxamer 188 rescues MPTP-induced lysosomal membrane integrity impairment in cellular and mouse models of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). Rupture of lysosome is a major cellular stress condition leading to cell death in PD. We have previously shown that environmental oxidative toxins could impair autophagic flux and lysosomal functions in PD. Poloxamer 188 (P188) is an amphipathic polymer which has cytoprotective effect in traumatic brain injury and stroke. But whether Dyrk1A could rescue lysosome malfunction-mediated DA neuron death and α-synuclein aggregation in PD is still unknown. In the present study, MPTP mice models and MPP+-treated SH-SY5Y cells were used for study, and we found that P188 rescued MPP+-induced lysosomal dysfunction and impaired autophagy flux in mild MPP+-treated SH-SY5Y cells. P188 administration significantly restored lysosomal membrane integrity and prevented cathepsins leakage from the lysosomes into the cytoplasm, which triggered caspase-dependent apoptotic cell death in sub-acute MPTP mouse model and MPP+-treated SH-SY5Y cells. Furthermore, P188 ameliorated α-synuclein accumulation and behavioral impairment in chronic MPTP mouse model with MPTP and probenecid treatment. P188 could alleviate MPTP-induced DA neurons damage by restoring lysosome function.

LRRK2 G2019S Mutation Inhibits Degradation of α-Synuclein in an In Vitro Model of Parkinson's Disease.

The G2019S mutation of the leucine-rich repeat kinase 2 (LRRK2) is the most common genetic cause of Parkinson's disease (PD). However, the molecular mechanisms of LRRK2 mutation contributing to the onset and progression of PD have not been fully illustrated. We generated HEK293 cells stably transfected with α-synuclein and investigated the effect of LRRK2 G2019S mutation on the degradation of α-synuclein. The lysosomal activity was assessed by the protein degradation of glyceraldehyde-3-phosphate dehydrogenase and ribonuclease A. It was found that α-synuclein was mainly degraded in lysosomes. LRRK2 G2019S inhibited the degradation of α-synuclein, and promoted its aggregation. LRRK2 G2019S also decreased the activities of lysosomal enzymes including cathepsin B and cathepsin L. Furthermore, the inhibitory effect of LRRK2 G2019S on lysosomal functions did not depend on its kinase activity. These findings indicated that the inhibitory effect of LRRK2 G2019S on α-synuclein degradation could underlie the pathogenesis of aberrant α-synuclein aggregation in PD with LRRK2 mutation.

The Parkinson's Disease Protein α‐synuclein Alters the Microenvironment of the Endoplasmic Reticulum in Saccharomyces cerevisiae

The protein α‐synuclein forms aggregates in human dopaminergic neurons triggering apoptosis and Parkinson's Disease (PD). To better understand the link between protein aggregate formation and cell death, we have over expressed wild type and two mutant forms, A30P and A53T, of human α‐synuclein in the budding yeast, Saccharomyces cerevisiae. Our experiments suggest that these aggregates trigger the unfolded protein response (UPR) in yeast and that different clinically relevant variants of α‐synuclein up‐regulate the UPR to different degrees. Moreover, we show that the overexpression of α‐synuclein alters the redox state and the calcium dynamics of the yeast ER. Finally, our preliminary data suggests that sub‐lethal doses of tunicamycin and β‐mercaptoethanol, drugs that trigger the UPR, may alleviate the aggregation of α‐synuclein. Our results point to possible pharmacological interventions that may lower protein aggregation in PD. [Our laboratory is supported by grant NIGMS R15 GM110578, awarded to N. Austriaco.]Support or Funding Information[Our laboratory is supported by grant NIGMS R15 GM110578, awarded to N. Austriaco.]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

SUMOylation and ubiquitination reciprocally regulate α-synuclein degradation and pathological aggregation.

α-Synuclein accumulation is a pathological hallmark of Parkinson's disease (PD). Ubiquitinated α-synuclein is targeted to proteasomal or lysosomal degradation. Here, we identify SUMOylation as a major mechanism that counteracts ubiquitination by different E3 ubiquitin ligases and regulates α-synuclein degradation. We report that PIAS2 promotes SUMOylation of α-synuclein, leading to a decrease in α-synuclein ubiquitination by SIAH and Nedd4 ubiquitin ligases, and causing its accumulation and aggregation into inclusions. This was associated with an increase in α-synuclein release from the cells. A SUMO E1 inhibitor, ginkgolic acid, decreases α-synuclein levels by relieving the inhibition exerted on α-synuclein proteasomal degradation. α-Synuclein disease mutants are more SUMOylated compared with the wild-type protein, and this is associated with increased aggregation and inclusion formation. We detected a marked increase in PIAS2 expression along with SUMOylated α-synuclein in PD brains, providing a causal mechanism underlying the up-regulation of α-synuclein SUMOylation in the disease. We also found a significant proportion of Lewy bodies in nigral neurons containing SUMO1 and PIAS2. Our observations suggest that SUMOylation of α-synuclein by PIAS2 promotes α-synuclein aggregation by two mutually reinforcing mechanisms. First, it has a direct proaggregatory effect on α-synuclein. Second, SUMOylation facilitates α-synuclein aggregation by blocking its ubiquitin-dependent degradation pathways and promoting its accumulation. Therefore, inhibitors of α-synuclein SUMOylation provide a strategy to reduce α-synuclein levels and possibly aggregation in PD.

Glutamine promotes Hsp70 and inhibits α-Synuclein accumulation in pheochromocytoma PC12 cells.

Hsp70 regulates α-Synuclein (α-Syn) degeneration in Parkinson's disease (PD), indicating that Hsp70 promotion may be able to prevent or reverse α-Syn-induced toxicity in PD. Additionally, it has been demonstrated that glutamine (Gln) enhances Hsp70 expression. In the present study, Gln-induced Hsp70 promotion in pheochromocytoma was investigated with reverse transcription- quantitative polymerase chain reaction and western blotting methods. Then it was observed whether heat shock factor (HSF)-1 was required for this phenomenon with an RNA interference strategy. The regulatory role of Gln on α-Syn degeneration was also determined in the α-Syn-overexpressed PC12 [PC12 (α-Syn+)] cells, which were treated with or without the proteasomal inhibitor lactacystin (Lac). The results demonstrated that treatment with ≥10 mM Gln significantly increased Hsp70 mRNA and protein levels (P<0.05) and that this promotion was HSF-1-dependent, as HSF-1 knockout with HSF-1-specific small interfering RNA abrogated Hsp70 promotion in PC12 (α-Syn+) cells. Furthermore, Gln treatment markedly upregulated α-Syn degeneration in PC12 (α-Syn+) cells, which was significantly reduced (P<0.05) in the presence of Lac. Therefore, the present study suggests that Gln is able to induce the promotion of Hsp70 expression in PC12 cells in an HSF-1-dependent manner and that Gln-mediated Hsp70 promotion may increase α-Syn degradation even in the presence of proteasomal inhibitor. Thus, glutamine may be a potential therapeutic agent to prevent α-Syn aggregation in PD.

Ubiquitin and Parkinson's disease through the looking glass of genetics.

Biochemical alterations found in the brains of Parkinson's disease (PD) patients indicate that cellular stress is a major driver of dopaminergic neuronal loss. Oxidative stress, mitochondrial dysfunction, and ER stress lead to impairment of the homeostatic regulation of protein quality control pathways with a consequent increase in protein misfolding and aggregation and failure of the protein degradation machinery. Ubiquitin signalling plays a central role in protein quality control; however, prior to genetic advances, the detailed mechanisms of how impairment in the ubiquitin system was linked to PD remained mysterious. The discovery of mutations in the α-synuclein gene, which encodes the main protein misfolded in PD aggregates, together with mutations in genes encoding ubiquitin regulatory molecules, including PTEN-induced kinase 1 (PINK1), Parkin, and FBX07, has provided an opportunity to dissect out the molecular basis of ubiquitin signalling disruption in PD, and this knowledge will be critical for developing novel therapeutic strategies in PD that target the ubiquitin system.

Cross-linking for the analysis of α-synuclein in the enteric nervous system.

Since the observation that aggregated α-synuclein, the pathological hallmark of Parkinson's disease (PD), is found in the gut in almost all patients, it has been suggested that the enteric nervous system (ENS) could be a starting point for α-synuclein pathology. α-synuclein has long been thought to occur as a monomer in living cells, but recent studies reported that it instead exists as a tetramer in non-neuronal cells and in neurons. Given the possible key role of the ENS in PD pathophysiology, we undertook the current research to characterize the native state of α-synuclein in rat primary culture of ENS and in adult human healthy ENS. Using amine-reactive cross-linking, we showed that, by contrast to cell lines and brain neurons, α-synuclein exists primarily as a monomer in intact enteric neurons, suggesting that the native state of α-synuclein is different between the ENS and the brain. Our results provide new insights into the widely discussed concepts of α-synuclein aggregation and misfolding in PD and raise issue about the possible transmission of α-synuclein from the ENS to the brain.

Ubiqutination via K27 and K29 chains signals aggregation and neuronal protection of LRRK2 by WSB1.

A common genetic form of Parkinson's disease (PD) is caused by mutations in LRRK2. We identify WSB1 as a LRRK2 interacting protein. WSB1 ubiquitinates LRRK2 through K27 and K29 linkage chains, leading to LRRK2 aggregation and neuronal protection in primary neurons and a Drosophila model of G2019S LRRK2. Knocking down endogenous WSB1 exacerbates mutant LRRK2 neuronal toxicity in neurons and the Drosophila model, indicating a role for endogenous WSB1 in modulating LRRK2 cell toxicity. WSB1 is in Lewy bodies in human PD post-mortem tissue. These data demonstrate a role for WSB1 in mutant LRRK2 pathogenesis, and suggest involvement in Lewy body pathology in sporadic PD. Our data indicate a role in PD for ubiquitin K27 and K29 linkages, and suggest that ubiquitination may be a signal for aggregation and neuronal protection in PD, which may be relevant for other neurodegenerative disorders. Finally, our study identifies a novel therapeutic target for PD.