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Sökning: WFRF:(Stefanis Leonidas)

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1.
  • Klionsky, Daniel J., et al. (författare)
  • Guidelines for the use and interpretation of assays for monitoring autophagy
  • 2012
  • Ingår i: Autophagy. - : Landes Bioscience. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
  • Forskningsöversikt (refereegranskat)abstract
    • In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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2.
  • Elbaz, Alexis, et al. (författare)
  • Independent and Joint Effects of the MAPT and SNCA Genes in Parkinson Disease
  • 2011
  • Ingår i: Annals of Neurology. - : John Wiley and Sons. - 1531-8249. ; 69:5, s. 778-792
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: We studied the independent and joint effects of the genes encoding alpha-synuclein (SNCA) and microtubule-associated protein tau (MAPT) in Parkinson disease (PD) as part of a large meta-analysis of individual data from case-control studies participating in the Genetic Epidemiology of Parkinson's Disease (GEO-PD) consortium. Methods: Participants of Caucasian ancestry were genotyped for a total of 4 SNCA (rs2583988, rs181489, rs356219, rs11931074) and 2 MAPT (rs1052553, rs242557) single nucleotide polymorphism (SNPs). Individual and joint effects of SNCA and MAPT SNPs were investigated using fixed- and random-effects logistic regression models. Interactions were studied on both a multiplicative and an additive scale, and using a case-control and case-only approach. Results: Fifteen GEO-PD sites contributed a total of 5,302 cases and 4,161 controls. All 4 SNCA SNPs and the MAPT H1-haplotype-defining SNP (rs1052553) displayed a highly significant marginal association with PD at the significance level adjusted for multiple comparisons. For SNCA, the strongest associations were observed for SNPs located at the 30 end of the gene. There was no evidence of statistical interaction between any of the 4 SNCA SNPs and rs1052553 or rs242557, neither on the multiplicative nor on the additive scale. Interpretation: This study confirms the association between PD and both SNCA SNPs and the H1 MAPT haplotype. It shows, based on a variety of approaches, that the joint action of variants in these 2 loci is consistent with independent effects of the genes without additional interacting effects. ANN NEUROL 2011; 69: 778-792
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3.
  • Heckman, Michael G., et al. (författare)
  • Population-specific Frequencies for LRRK2 Susceptibility Variants in the Genetic Epidemiology of Parkinson's Disease (GEO-PD) Consortium
  • 2013
  • Ingår i: Movement Disorders. - : John Wiley and Sons. - 0885-3185. ; 28:12, s. 1740-1744
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundVariants within the leucine-rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson's disease. Leucine-rich repeat kinase 2 variation related to disease susceptibility displays many features that reflect the nature of complex, late-onset sporadic disorders like Parkinson's disease. MethodsThe Genetic Epidemiology of Parkinson's Disease Consortium recently performed the largest genetic association study for variants in the leucine-rich repeat kinase 2 gene across 23 different sites in 15 countries. ResultsHerein, we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K-R1398H-K1423K) nominated in the original publication. Simple population allele frequencies not only can provide insight into the clinical relevance of specific variants but also can help genetically define patient groups. ConclusionsEstablishing individual patient-based genomic susceptibility profiles that incorporate both risk factors and protective factors will determine future diagnostic and treatment strategies. (c) 2013 International Parkinson and Movement Disorder Society
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4.
  • Ross, Owen A., et al. (författare)
  • Association of LRRK2 exonic variants with susceptibility to Parkinson's disease: a case-control study
  • 2011
  • Ingår i: Lancet Neurology. - : Lancet Ltd. - 1474-4465. ; 10:10, s. 898-908
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The leucine-rich repeat kinase 2 gene (LRRK2) harbours highly penetrant mutations that are linked to familial parkinsonism. However, the extent of its polymorphic variability in relation to risk of Parkinson's disease (PD) has not been assessed systematically. We therefore assessed the frequency of LRRK2 exonic variants in individuals with and without PD, to investigate the role of the variants in PD susceptibility. Methods LRRK2 was genotyped in patients with PD and controls from three series (white, Asian, and Arab-Berber) from sites participating in the Genetic Epidemiology of Parkinson's Disease Consortium. Genotyping was done for exonic variants of LRRK2 that were identified through searches of literature and the personal communications of consortium members. Associations with PD were assessed by use of logistic regression models. For variants that had a minor allele frequency of 0.5% or greater, single variant associations were assessed, whereas for rarer variants information was collapsed across variants. Findings 121 exonic LRRK2 variants were assessed in 15 540 individuals: 6995 white patients with PD and 5595 controls, 1376 Asian patients and 962 controls, and 240 Arab-Berber patients and 372 controls. After exclusion of carriers of known pathogenic mutations, new independent risk associations were identified for polymorphic variants in white individuals (M1646T, odds ratio 1.43, 95% CI 1.15-1.78; p=0.0012) and Asian individuals (A419V, 2.27, 1.35-3.83; p=0.0011). A protective haplotype (N551K-R1398H-K1423K) was noted at a frequency greater than 5% in the white and Asian series, with a similar finding in the Arab-Berber series (combined odds ratio 0.82, 0.72-0.94; p=0.0043). Of the two previously reported Asian risk variants, G2385R was associated with disease (1.73, 1.20-2.49; p=0.0026), but no association was noted for R1628P (0.62, 0.36-1.07; p=0.087). In the Arab-Berber series, Y2189C showed potential evidence of risk association with PD (4.48, 133-15.09; p=0.012). Interpretation The results for LRRK2 show that several rare and common genetic variants in the same gene can have independent effects on disease risk. LRRK2, and the pathway in which it functions, is important in the cause and pathogenesis of PD in a greater proportion of patients with this disease than previously believed. These results will help discriminate those patients who will benefit most from therapies targeted at LRRK2 pathogenic activity. Funding Michael J Fox Foundation and National Institutes of Health.
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5.
  • Sharma, Manu, et al. (författare)
  • Large-scale replication and heterogeneity in Parkinson disease genetic loci
  • 2012
  • Ingår i: Neurology. - : American Academy of Neurology. - 1526-632X. ; 79:7, s. 67-659
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The extent to which these genetic effects are consistent across different populations is unknown.METHODS: Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium were invited to participate in the study. A total of 11 SNPs were genotyped in 8,750 cases and 8,955 controls. Fixed as well as random effects models were used to provide the summary risk estimates for these variants. We evaluated between-study heterogeneity and heterogeneity between populations of different ancestry.RESULTS: In the overall analysis, single nucleotide polymorphisms (SNPs) in 9 loci showed significant associations with protective per-allele odds ratios of 0.78-0.87 (LAMP3, BST1, and MAPT) and susceptibility per-allele odds ratios of 1.14-1.43 (STK39, GAK, SNCA, LRRK2, SYT11, and HIP1R). For 5 of the 9 replicated SNPs there was nominally significant between-site heterogeneity in the effect sizes (I(2) estimates ranged from 39% to 48%). Subgroup analysis by ethnicity showed significantly stronger effects for the BST1 (rs11724635) in Asian vs Caucasian populations and similar effects for SNCA, LRRK2, LAMP3, HIP1R, and STK39 in Asian and Caucasian populations, while MAPT rs2942168 and SYT11 rs34372695 were monomorphic in the Asian population, highlighting the role of population-specific heterogeneity in PD.CONCLUSION: Our study allows insight to understand the distribution of newly identified genetic factors contributing to PD and shows that large-scale evaluation in diverse populations is important to understand the role of population-specific heterogeneity.
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6.
  • Refolo, Violetta, et al. (författare)
  • Progressive striatonigral degeneration in a transgenic mouse model of multiple system atrophy : translational implications for interventional therapies
  • 2018
  • Ingår i: Acta Neuropathologica Communications. - : BioMed Central (BMC). - 2051-5960. ; 6:1, s. 1-24
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disorder characterized by widespread oligodendroglial cytoplasmic inclusions of filamentous α-synuclein, and neuronal loss in autonomic centres, basal ganglia and cerebellar circuits. It has been suggested that primary oligodendroglial α-synucleinopathy may represent a trigger in the pathogenesis of MSA, but the mechanisms underlying selective vulnerability and disease progression are unclear. The post-mortem analysis of MSA brains provides a static final picture of the disease neuropathology, but gives no clear indication on the sequence of pathogenic events in MSA. Therefore, alternative methods are needed to address these issues. We investigated selective vulnerability and disease progression in the transgenic PLP-α-syn mouse model of MSA characterized by targeted oligodendroglial α-synuclein overexpression aiming to provide a neuropathological correlate of motor deterioration. We show progressive motor deficits that emerge at 6 months of age and deteriorate up to 18 months of follow-up. The motor phenotype was associated with dopaminergic cell loss in the substantia nigra pars compacta at 6 months, followed by loss of striatal dopaminergic terminals and DARPP32-positive medium sized projection neurons at 12 months. Olivopontocerebellar motor loops remained spared in the PLP-α-syn model of MSA. These findings replicate progressive striatonigral degeneration underlying Parkinson-variant MSA. The initiation of the degenerative process was linked to an increase of soluble oligomeric α-synuclein species between 2 and 6 months. Early region-specific α-synuclein-associated activation profile of microglia was found in MSA substantia nigra. The role of abnormal neuroinflammatory signalling in disease progression was further supported by increased levels of CD68, CCL3, CCL5 and M-CSF with a peak in aged PLP-α-syn mice. In summary, transgenic PLP-α-syn mice show a distinctive oligodendroglial α-synucleinopathy that is associated with progressive striatonigral degeneration linked to abnormal neuroinflammatory response. The model provides a relevant tool for preclinical therapeutic target discovery for human Parkinson-variant MSA.
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7.
  • Stefanis, Leonidas, et al. (författare)
  • How is alpha-synuclein cleared from the cell?
  • 2019
  • Ingår i: Journal of Neurochemistry. - : Wiley-Blackwell. - 0022-3042. ; 150:5, s. 577-590
  • Forskningsöversikt (refereegranskat)abstract
    • The levels and conformers of alpha-synuclein are critical in the pathogenesis of Parkinson's Disease and related synucleinopathies. Homeostatic mechanisms in protein degradation and secretion have been identified as regulators of alpha-synuclein at different stages of its intracellular trafficking and transcellular propagation. Here we review pathways involved in the removal of various forms of alpha-synuclein from both the intracellular and extracellular environment. Proteasomes and lysosomes are likely to play complementary roles in the removal of intracellular alpha-synuclein species, in a manner that depends on alpha-synuclein post-translational modifications. Extracellular alpha-synuclein is cleared by extracellular proteolytic enzymes, or taken up by neighboring cells, especially microglia and astrocytes, and degraded within lysosomes. Exosomes, on the other hand, represent a vehicle for egress of excess burden of the intracellular protein, potentially contributing to the transfer of alpha-synuclein between cells. Dysfunction in any one of these clearance mechanisms, or a combination thereof, may be involved in the initiation or progression of Parkinson's disease, whereas targeting these pathways may offer an opportunity for therapeutic intervention. (Figure presented.).
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8.
  • Xilouri, Maria, et al. (författare)
  • Boosting chaperone-mediated autophagy in vivo mitigates alpha-synuclein-induced neurodegeneration
  • 2013
  • Ingår i: Brain. - : Oxford University Press. - 1460-2156. ; 136, s. 2130-2146
  • Tidskriftsartikel (refereegranskat)abstract
    • alpha-Synuclein levels are critical to Parkinson's disease pathogenesis. Wild-type alpha-synuclein is degraded partly by chaperone-mediated autophagy, and aberrant alpha-synuclein may act as an inhibitor of the pathway. To address whether the induction of chaperone-mediated autophagy may represent a potential therapy against alpha-synuclein-induced neurotoxicity, we overexpressed lysosomal-associated membrane protein 2a, the rate-limiting step of chaperone-mediated autophagy, in human neuroblastoma SH-SY5Y cells, rat primary cortical neurons in vitro, and nigral dopaminergic neurons in vivo. Overexpression of the lysosomal-associated membrane protein 2a in cellular systems led to upregulation of chaperone-mediated autophagy, decreased alpha-synuclein turnover, and selective protection against adenoviral-mediated wild-type alpha-synuclein neurotoxicity. Protection was observed even when the steady-state levels of alpha-synuclein were unchanged, suggesting that it occurred through the attenuation of alpha-synuclein-mediated dysfunction of chaperone-mediated autophagy. Overexpression of the lysosomal receptor through the nigral injection of recombinant adeno-associated virus vectors effectively ameliorated alpha-synuclein-induced dopaminergic neurodegeneration by increasing the survival of neurons located in the substantia nigra as well as the axon terminals located in the striatum, which was associated with a reduction in total alpha-synuclein levels and related aberrant species. We conclude that induction of chaperone-mediated autophagy may provide a novel therapeutic strategy in Parkinson's disease and related synucleinopathies through two different mechanisms: amelioration of dysfunction of chaperone-mediated autophagy and lowering of alpha-synuclein levels.
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9.
  • Xilouri, Maria, et al. (författare)
  • LAMP2A as a therapeutic target in Parkinson disease
  • 2013
  • Ingår i: Autophagy. - : Landes Bioscience. - 1554-8635. ; 9:12, s. 2166-2168
  • Tidskriftsartikel (övrigt vetenskapligt)abstract
    • Abnormal aggregation of SNCA/-synuclein plays a crucial role in Parkinson disease (PD) pathogenesis. SNCA levels determine its toxicity, and its accumulation, even to a small extent, may be a risk factor for neurodegeneration. One of the main pathways for SNCA degradation is chaperone-mediated autophagy (CMA), a selective form of autophagy, while aberrant SNCA may act as a CMA inhibitor. In the current punctum we summarize our recent data showing that induction of CMA, via overexpression of the protein controlling its rate-limiting step, the lysosomal receptor LAMP2A, effectively decreases SNCA levels and ameliorates SNCA-induced neurodegeneration, both in neuronal cell culture systems and in the rat brain. Such findings suggest that modulation of LAMP2A and, consequently, CMA, represents a viable therapeutic target for PD and other synucleinopathies where SNCA accumulation and aggregation plays a fundamental role.
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10.
  • Xilouri, Maria, et al. (författare)
  • Selective neuroprotective effects of the S18Y polymorphic variant of UCH-L1 in the dopaminergic system
  • 2012
  • Ingår i: Human Molecular Genetics. - : Oxford University Press. - 0964-6906. ; 21:4, s. 874-889
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetic studies have implicated the neuronal ubiquitin C-terminal hydrolase (UCH) protein UCH-L1 in Parkinson's disease (PD) pathogenesis. Moreover, the function of UCH-L1 may be lost in the brains of PD and Alzheimer's disease patients. We have previously reported that the UCH-L1 polymorphic variant S18Y, potentially protective against PD in population studies, demonstrates specific antioxidant functions in cell culture. Albeit genetic, biochemical and neuropathological data support an association between UCH-L1, PD, synaptic degeneration and oxidative stress, the relationship between the dopaminergic system and UCH-L1 status remains obscure. In the current study, we have examined the dopaminergic system of mice lacking endogenous UCH-L1 protein (gracile axonal dystrophy mice). Our findings show that the lack of wild-type (WT) UCH-L1 does not influence to any significant degree the dopaminergic system at baseline or following injections of the neurotoxin methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, using a novel intrastriatal adenoviral injection protocol, we have found that mouse nigral neurons retrogradely transduced with S18Y UCH-L1, but not the WT protein, are significantly protected against MPTP toxicity. Overall, these data provide evidence for an antioxidant and neuroprotective effect of the S18Y variant of UCH-L1, but not of the WT protein, in the dopaminergic system, and may have implications for the pathogenesis of PD or related neurodegenerative conditions, in which oxidative stress might play a role.
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