Enhanced vulnerability to oxidative stress by α-synuclein mutations and C-terminal truncation

Kanda, S; Bishop, John F.; Eglitis, Martin A.; Yang, Yanqin; Mouradian, M. Maral

doi:10.1016/s0306-4522(00)00077-4

Cited by 188 publications

(137 citation statements)

References 24 publications

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“…For instance, it exacerbates susceptibility of HEK293 and SH-SY5Y cells to DA toxicity (60,61), of primary DA neurons and N27 cells to 6-OHDA-induced apoptosis (59), and of SH-SY5Y cells to MPP ϩ -mediated cell death (62). In contrast to these studies, MESC2.10 cells overexpressing A53TSYN were resistant to AMPH-induced toxicity (Fig.…”

Section: Discussionmentioning

confidence: 84%

Effect of Mutant α-Synuclein on Dopamine Homeostasis in a New Human Mesencephalic Cell Line

Lotharius¹,

Barg²,

Wiekop³

et al. 2002

Journal of Biological Chemistry

320

266

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Mutations in ␣-synuclein have been linked to rare, autosomal dominant forms of Parkinson's disease. Despite its ubiquitous expression, mutant ␣-synuclein primarily leads to the loss of dopamine-producing neurons in the substantia nigra. ␣-Synuclein is a presynaptic nerve terminal protein of unknown function, although several studies suggest it is important for synaptic plasticity and maintenance. The present study utilized a new human mesencephalic cell line, MESC2.10, to study the effect of A53T mutant ␣-synuclein on dopamine homeostasis. In addition to expressing markers of mature dopamine neurons, differentiated MESC2.10 cells are electrically active, produce dopamine, and express wildtype human ␣-synuclein. Lentivirus-induced overexpression of A53T mutant ␣-synuclein in differentiated MESC2.10 cells resulted in down-regulation of the vesicular dopamine transporter (VMAT2), decreased potassium-induced and increased amphetamine-induced dopamine release, enhanced cytoplasmic dopamine immunofluorescence, and increased intracellular levels of superoxide. These results suggest that mutant ␣-synuclein leads to an impairment in vesicular dopamine storage and consequent accumulation of dopamine in the cytosol, a pathogenic mechanism that underlies the toxicity of the psychostimulant amphetamine and the parkinsonian neurotoxin 1-methyl-4-phenylpyridinium. Interestingly, cells expressing A53T mutant ␣-synuclein were resistant to amphetamine-induced toxicity. Because extravesicular, cytoplasmic dopamine can be easily oxidized into reactive oxygen species and other toxic metabolites, mutations in ␣-synuclein might lead to Parkinson's disease by triggering protracted, low grade dopamine toxicity resulting in terminal degeneration and ultimately cell death.

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Section: Discussionmentioning

confidence: 84%

Effect of Mutant α-Synuclein on Dopamine Homeostasis in a New Human Mesencephalic Cell Line

Lotharius¹,

Barg²,

Wiekop³

et al. 2002

Journal of Biological Chemistry

320

266

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“…The incremental aggregation process of ␣-synuclein involves several modifications (misfolding, dimer and oligomer formation, and self-aggregation) and is linked to Parkinson's disease-associated mutations (5,22,(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). In this study, we detected abnormal ␣-synuclein species based on their detergent solubility and electrophoretic mobility characteristics in three different systems: human DLB cortex, transgenic mice overexpressing wild type human ␣-synuclein, and a transiently transfected cell culture system.…”

Section: Discussionmentioning

confidence: 95%

Hsp70 Reduces α-Synuclein Aggregation and Toxicity

Klucken

Shin

Masliah

et al. 2004

Journal of Biological Chemistry

479

400

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Aggregation and cytotoxicity of misfolded ␣-synuclein is postulated to be crucial in the disease process of neurodegenerative disorders such as Parkinson's disease and DLB (dementia with Lewy bodies). In this study, we detected misfolded and aggregated ␣-synuclein in a Triton X-100 insoluble fraction as well as a high molecular weight product by gel electrophoresis of temporal neocortex from DLB patients but not from controls. We also found similar Triton X-100 insoluble forms of ␣-synuclein in an ␣-synuclein transgenic mouse model and in an in vitro model of ␣-synuclein aggregation. Introducing the molecular chaperone Hsp70 into the in vivo model by breeding ␣-synuclein transgenic mice with Hsp70-overexpressing mice led to a significant reduction in both the high molecular weight and detergent-insoluble ␣-synuclein species. Concomitantly, we found that Hsp70 overexpression in vitro similarly reduced detergent-insoluble ␣-synuclein species and protected cells from ␣-synuclein-induced cellular toxicity. Taken together, these data demonstrate that the molecular chaperone Hsp70 can reduce the amount of misfolded, aggregated ␣-synuclein species in vivo and in vitro and protect it from ␣-synuclein-dependent toxicity.␣-Synuclein is a natively unfolded molecule that can selfaggregate to form oligomers and fibrillar intermediates (1-5) that accumulate to form Lewy bodies (LBs) 1 and Lewy neurites in neurons at risk for degeneration in Parkinson's disease and dementia with Lewy bodies (DLB) (6 -14). For the most part, these ␣-synuclein aggregates are densely compact and can be immunostained for multiple additional components including ubiquitin, synphilin-1, and heat shock proteins (HSPs), which suggests that protein misfolding or degradation is altered in cells that develop LBs. Mouse models of ␣-synuclein aggregation exist that mimic the findings in human brains and show intracellular ␣-synuclein aggregates (15-17). Aggregated ␣-synuclein molecules are less detergent-soluble, and these detergent-insoluble species of ␣-synuclein can be detected in human brain, transgenic mouse models, and in vitro models (18 -21). Although it is known that the conformation of ␣-synuclein in LBs is significantly different from that in the neuropil (22), it is unclear which conformation of ␣-synuclein contributes to inclusion formation. In addition to the formation of intracellular aggregates, ␣-synuclein is also cytotoxic. It has been postulated that ␣-synuclein oligomers found in Parkinson's disease tissue by Western blot analysis represent the toxic species (5).HSPs belong to the family of chaperone proteins and are important in both refolding misfolded proteins and directing proteins toward proteasomal degradation (23-25). HSPs can be protective in several neurodegeneration models (26 -29), and recent data in the fly model suggest that overexpression of the molecular chaperone Hsp70 protects against ␣-synuclein-induced degeneration (26, 30). Hsp70 and its related co-chaperones may be important in ␣-synuclein misfolding. In fact, sever...

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“…In addition to influencing ␣-Syn aggregation͞ oligomerization, the C-terminal region of ␣-Syn appears to be important for the chaperone activity of ␣-Syn (39-41) and the stability of ␣-Syn (42). Further, the expression of ␣-Syn120 has been shown to increase cellular vulnerability to oxidative stress (43). Thus, normal presence of ␣-Syn⌬Cs in neurons may have other significant cellular effects.…”

Section: Discussionmentioning

confidence: 99%

Aggregation promoting C-terminal truncation of α-synuclein is a normal cellular process and is enhanced by the familial Parkinson's disease-linked mutations

West

Colla

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

417

451

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␣-synucleinopathy ͉ mass spectrometry ͉ proteolysis ͉ Lewy body P arkinson's disease (PD) is a common progressive neurodegenerative disease characterized by the loss of dopaminergic neurons of substantia nigra and the presence of the fibrillar cytoplasmic aggregates of ␣-synuclein (␣-Syn) in multiple brain regions (1, 2). Mutations in the ␣-Syn gene (3-7) and the abnormal aggregation of ␣-Syn are implicated in the pathogenesis of PD, and other related diseases are classified as ␣-synucleinopathies (1, 8-10). ␣-Syn is a highly conserved protein of 140 amino acids that is predominantly expressed in neurons, particularly in presynaptic terminals (11), and may have a role in synaptic plasticity and modulation of dopaminergic neurotransmission (11).Although the bulk of previous studies focused on the aggregation and the biology of the full-length ␣-Syn (␣-SynFL) (12, 13), the conspicuous presence of lower molecular mass ␣-Syn species in ␣-Syn aggregates (14, 15), and the enhanced in vitro fibril assembly of recombinant C-terminally truncated ␣-Syn (16, 17) suggests that the low-molecular mass ␣-Syn species may be of pathogenic significance. However, because postpathogenic and͞or postmortem processes could potentially generate a variety of ␣-Syn species, the significance of low-molecular mass ␣-Syn species to the development of ␣-synucleinopathy is uncertain.Herein, we demonstrate that C-terminally truncated lowmolecular mass ␣-Syn species (␣-Syn⌬C) with aggregationpromoting properties are normally generated in vivo. The expression of familial PD (FPD)-linked mutant human (Hu) ␣-Syn is associated with the higher cellular accumulation of ␣-Syn⌬C. Moreover, human cases with ␣-Syn lesions show preferential accumulation of ␣-Syn⌬C in aggregates and higher relative levels of soluble ␣-Syn⌬C. Our findings show that ␣-Syn⌬Cs are not an artifact of postpathologic processes and are likely to participate in the disease-linked aggregation of ␣-Syn. Materials and MethodsAdditional details are provided in Supporting Materials and Methods, which is published as supporting information on the PNAS web site.

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Enhanced vulnerability to oxidative stress by α-synuclein mutations and C-terminal truncation

Cited by 188 publications

References 24 publications

Effect of Mutant α-Synuclein on Dopamine Homeostasis in a New Human Mesencephalic Cell Line

Effect of Mutant α-Synuclein on Dopamine Homeostasis in a New Human Mesencephalic Cell Line

Hsp70 Reduces α-Synuclein Aggregation and Toxicity

Aggregation promoting C-terminal truncation of α-synuclein is a normal cellular process and is enhanced by the familial Parkinson's disease-linked mutations

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