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Alpha-synuclein aggregation involves a bafilomycin A 1-sensitive autophagy pathway.

ABSTRACT: Synucleinopathies like Parkinson disease and dementia with Lewy bodies (DLB) are characterized by ?-synuclein aggregates within neurons (Lewy bodies) and their processes (Lewy neurites). Whereas ?-synuclein has been genetically linked to the disease process, the pathological relevance of ?-synuclein aggregates is still debated. Impaired degradation is considered to result in aggregation of ?-synuclein. In addition to the ubiquitin-proteasome degradation, the autophagy-lysosomal pathway (ALP) is involved in intracellular degradation processes for ?-synuclein. Here, we asked if modulation of ALP affects ?-synuclein aggregation and toxicity. We have identified an induction of the ALP markers LAMP-2A and LC3-II in human brain tissue from DLB patients, in a transgenic mouse model of synucleinopathy, and in a cell culture model for ?-synuclein aggregation. ALP inhibition using bafilomycin A 1 (BafA1) significantly potentiates toxicity of aggregated ?-synuclein species in transgenic mice and in cell culture. Surprisingly, increased toxicity is paralleled by reduced aggregation in both in vivo and in vitro models. The dichotomy of effects on aggregating and nonaggregating species of ?-synuclein was specifically sensitive to BafA1 and could not be reproduced by other ALP inhibitors. The present study expands on the accumulating evidence regarding the function of ALP for ?-synuclein degradation by isolating an aggregation specific, BafA1-sensitive, ALP-related pathway. Our data also suggest that protein aggregation may represent a detoxifying event rather than being causal for cellular toxicity.

SUBMITTER: Klucken J

PROVIDER: S-EPMC3378419 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Alpha-synuclein aggregation involves a bafilomycin A 1-sensitive autophagy pathway.

Klucken Jochen J Poehler Anne-Maria AM Ebrahimi-Fakhari Darius D Schneider Jacqueline J Nuber Silke S Rockenstein Edward E Schlötzer-Schrehardt Ursula U Hyman Bradley T BT McLean Pamela J PJ Masliah Eliezer E Winkler Juergen J

Autophagy 20120501 5

Synucleinopathies like Parkinson disease and dementia with Lewy bodies (DLB) are characterized by α-synuclein aggregates within neurons (Lewy bodies) and their processes (Lewy neurites). Whereas α-synuclein has been genetically linked to the disease process, the pathological relevance of α-synuclein aggregates is still debated. Impaired degradation is considered to result in aggregation of α-synuclein. In addition to the ubiquitin-proteasome degradation, the autophagy-lysosomal pathway (ALP) is ...[more]

PMID: 22647715

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Project description:Methamphetamine (METH) is an illegal and widely abused psychoactive stimulant. METH abusers are at high risk of neurodegenerative disorders, including Parkinson's disease (PD). Previous studies have demonstrated that METH causes alpha-synuclein (α-syn) aggregation in the both laboratory animal and human. In this study, exposure to high METH doses increased the expression of α-syn and the small ubiquitin-related modifier 1 (SUMO-1). Therefore, we hypothesized that SUMOylation of α-syn is involved in high-dose METH-induced α-syn aggregation. We measured the levels of α-syn SUMOylation and these enzymes involved in the SUMOylation cycle in SH-SY5Y human neuroblastoma cells (SH-SY5Y cells), in cultures of C57 BL/6 primary mouse neurons and in brain tissues of mice exposure to METH. We also demonstrated the effect of α-syn SUMOylation on α-syn aggregation after METH exposure by overexpressing the key enzyme of the SUMOylation cycle or silencing SUMO-1 expression in vitro. Then, we make introduced mutations in the major SUMOylation acceptor sites of α-syn by transfecting a lentivirus containing the sequence of WT α-syn or K96/102R α-syn into SH-SY5Y cells and injecting an adenovirus containing the sequence of WT α-syn or K96/102R α-syn into the mouse striatum. Levels of the ubiquitin-proteasome system (UPS)-related makers ubiquitin (Ub) and UbE1, as well as the autophagy-lysosome pathway (ALP)-related markers LC3, P62 and lysosomal associated membrane protein 2A (LAMP2A), were also measured in SH-SY5Y cells transfected with lentivirus and mice injected with adenovirus. The results showed that METH exposure decreases the SUMOylation level of α-syn, although the expression of α-syn and SUMO-1 are increased. One possible cause is the reduction of UBC9 level. The increase in α-syn SUMOylation by UBC9 overexpression relieves METH-induced α-syn overexpression and aggregation, whereas the decrease in α-syn SUMOylation by SUMO-1 silencing exacerbates the same pathology. Furthermore, mutations in the major SUMOylation acceptor sites of α-syn also aggravate α-syn overexpression and aggregation by impairing degradation through the UPS and the ALP in vitro and in vivo. These results suggest that SUMOylation of α-syn plays a fundamental part in α-syn overexpression and aggregation induced by METH and could be a suitable target for the treatment of neurodegenerative diseases.

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Alpha-synuclein aggregation involves a bafilomycin A 1-sensitive autophagy pathway.

Publications

Alpha-synuclein aggregation involves a bafilomycin A 1-sensitive autophagy pathway.

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