The Pathological G51D Mutation in Alpha-Synuclein Oligomers Confers Distinct Structural Attributes and Cellular Toxicity.

Catherine Xu,Nunilo Cremades,Laura Itzhaki,Aviad Levin,Marta Castellana-Cruz,Zhen Du,Christopher Dobson,Janet Kumita,Benedetta Mannini,Serene Chen,Georg Meisl,Tuomas Knowles

doi:10.3390/molecules27041293

Catherine Xu, Nunilo Cremades + Show 10 more

Open Access

https://doi.org/10.3390/molecules27041293

Copy DOI

Abstract

A wide variety of oligomeric structures are formed during the aggregation of proteins associated with neurodegenerative diseases. Such soluble oligomers are believed to be key toxic species in the related disorders; therefore, identification of the structural determinants of toxicity is of upmost importance. Here, we analysed toxic oligomers of α-synuclein and its pathological variants in order to identify structural features that could be related to toxicity and found a novel structural polymorphism within G51D oligomers. These G51D oligomers can adopt a variety of β-sheet-rich structures with differing degrees of α-helical content, and the helical structural content of these oligomers correlates with the level of induced cellular dysfunction in SH-SY5Y cells. This structure–function relationship observed in α-synuclein oligomers thus presents the α-helical structure as another potential structural determinant that may be linked with cellular toxicity in amyloid-related proteins.

Highlights

The misfolding of proteins and their aggregation into amyloid fibrils has been implicated in numerous neurodegenerative disorders, including Parkinson’s disease (PD) and Alzheimer’s disease (AD) [1]
Deconvolution of circular dichroism (CD) spectra of WT oligomers suggests that they contain around 11% of α-helical structure, which was not detected by solid-state NMR analysis [13], indicating that the percentage of α-helical content we report here should only be used as a relative quantification between oligomer samples
Detailed work on the WT oligomers generated through our methods has identified the mechanistic features of α-synuclein oligomer-induced membrane disruption: first, the disordered N-terminal regions of the oligomers were found to act as anchors to the membrane by folding into α-helices, allowing the structured hydrophobic β-sheet core of the oligomer to insert into the interior of the lipid bilayer [13]

Summary

Introduction

The misfolding of proteins and their aggregation into amyloid fibrils has been implicated in numerous neurodegenerative disorders, including Parkinson’s disease (PD) and Alzheimer’s disease (AD) [1]. Α-synuclein is intrinsically disordered; upon interaction with membranes, the protein has been observed to adopt an α-helical structure [2], associated with the functional role of the protein in neuronal cells [3]. Oligomeric species with varying degrees of β-sheet structure are observable in the early stages of aggregation [7]. It is these early oligomeric species, rather than the mature amyloid fibrils, that are believed to be key toxic species in the context of disease [1,8,9,10,11]. While a range of mechanisms have been proposed by which the toxic effect could be mediated, interactions with cell membranes are likely to be a main contributor to the observed cytotoxicity [12,13,14]

Methods

Results

Conclusion