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A relationship between the transient structure in the monomeric state and the aggregation propensities of α-synuclein and β-synuclein.

ABSTRACT: α-Synuclein is an intrinsically disordered protein whose aggregation is implicated in Parkinson's disease. A second member of the synuclein family, β-synuclein, shares significant sequence similarity with α-synuclein but is much more resistant to aggregation. β-Synuclein is missing an 11-residue stretch in the central non-β-amyloid component region that forms the core of α-synuclein amyloid fibrils, yet insertion of these residues into β-synuclein to produce the βSHC construct does not markedly increase the aggregation propensity. To investigate the structural basis of these different behaviors, quantitative nuclear magnetic resonance data, in the form of paramagnetic relaxation enhancement-derived interatomic distances, are combined with molecular dynamics simulations to generate ensembles of structures representative of the solution states of α-synuclein, β-synuclein, and βSHC. Comparison of these ensembles reveals that the differing aggregation propensities of α-synuclein and β-synuclein are associated with differences in the degree of residual structure in the C-terminus coupled to the shorter separation between the N- and C-termini in β-synuclein and βSHC, making protective intramolecular contacts more likely.

SUBMITTER: Allison JR

PROVIDER: S-EPMC4245978 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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 (?-syn) aggregation in the both laboratory animal and human. In this study, exposure to high METH doses increased the expression of ?-syn and the small ubiquitin-related modifier 1 (SUMO-1). Therefore, we hypothesized that SUMOylation of ?-syn is involved in high-dose METH-induced ?-syn aggregation. We measured the levels of ?-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 ?-syn SUMOylation on ?-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 ?-syn by transfecting a lentivirus containing the sequence of WT ?-syn or K96/102R ?-syn into SH-SY5Y cells and injecting an adenovirus containing the sequence of WT ?-syn or K96/102R ?-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 ?-syn, although the expression of ?-syn and SUMO-1 are increased. One possible cause is the reduction of UBC9 level. The increase in ?-syn SUMOylation by UBC9 overexpression relieves METH-induced ?-syn overexpression and aggregation, whereas the decrease in ?-syn SUMOylation by SUMO-1 silencing exacerbates the same pathology. Furthermore, mutations in the major SUMOylation acceptor sites of ?-syn also aggravate ?-syn overexpression and aggregation by impairing degradation through the UPS and the ALP in vitro and in vivo. These results suggest that SUMOylation of ?-syn plays a fundamental part in ?-syn overexpression and aggregation induced by METH and could be a suitable target for the treatment of neurodegenerative diseases.

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A relationship between the transient structure in the monomeric state and the aggregation propensities of α-synuclein and β-synuclein.

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