Covalent α-synuclein dimers: chemico-physical and aggregation properties

• Published in: PloS one Vol. 7; no. 12; p. e50027
• Main Authors: Pivato, Micaela, De Franceschi, Giorgia, Tosatto, Laura, Frare, Erica, Kumar, Dhruv, Aioanei, Daniel, Brucale, Marco, Tessari, Isabella, Bisaglia, Marco, Samori, Bruno, de Laureto, Patrizia Polverino, Bubacco, Luigi
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 13-12-2012; Public Library of Science (PLoS)
• Subjects: Agglomeration; alpha-Synuclein - chemistry; Amyloid; Amyloid - chemistry; Amyloidogenesis; Animals; Biochemistry; Biology; Biotechnology; Chemistry, Physical - methods; Chromatography - methods; Circular Dichroism - methods; Cloning; Covalence; Dimerization; Dimers; Electrophoresis, Polyacrylamide Gel; Endopeptidase K - chemistry; Fibrillogenesis; Fluorescence; Fourier transforms; Infrared spectroscopy; Intermediates; Kinetics; Lewy bodies; Magnetic Resonance Spectroscopy - methods; Medicine; Microscopy, Atomic Force - methods; Microscopy, Electron, Transmission - methods; Molecular structure; Monomers; Morphometry; Movement disorders; Nanostructured materials; Neurodegenerative diseases; NMR; Nuclear magnetic resonance; Nucleotide sequence; Parkinson Disease - metabolism; Parkinson's disease; Physics; Physiology; Polypeptides; Properties (attributes); Protein structure; Protein Structure, Quaternary; Protein Structure, Tertiary; Proteins; Proteolysis; Secondary structure; Sodium Dodecyl Sulfate - chemistry; Species; Spectroscopy; Spectroscopy, Fourier Transform Infrared - methods; Spectrum analysis; Studies; Swine; Synuclein; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0050027

The aggregation of α-synuclein into amyloid fibrils constitutes a key step in the onset of Parkinson's disease. Amyloid fibrils of α-synuclein are the major component of Lewy bodies, histological hallmarks of the disease. Little is known about the mechanism of aggregation of α-synuclein. During this process, α-synuclein forms transient intermediates that are considered to be toxic species. The dimerization of α-synuclein could represent a rate-limiting step in the aggregation of the protein. Here, we analyzed four covalent dimers of α-synuclein, obtained by covalent link of the N-terms, C-terms, tandem cloning of two sequences and tandem juxtaposition in one protein of the 1-104 and 29-140 sequences. Their biophysical properties in solution were determined by CD, FT-IR and NMR spectroscopies. SDS-induced folding was also studied. The fibrils formation was analyzed by ThT and polarization fluorescence assays. Their morphology was investigated by TEM and AFM-based quantitative morphometric analysis. All dimers were found to be devoid of ordered secondary structure under physiological conditions and undergo α-helical transition upon interaction with SDS. All protein species are able to form amyloid-like fibrils. The reciprocal orientation of the α-synuclein monomers in the dimeric constructs affects the kinetics of the aggregation process and a scale of relative amyloidogenic propensity was determined. Structural investigations by FT IR spectroscopy, and proteolytic mapping of the fibril core did not evidence remarkable difference among the species, whereas morphological analyses showed that fibrils formed by dimers display a lower and diversified level of organization in comparison with α-synuclein fibrils. This study demonstrates that although α-synuclein dimerization does not imply the acquisition of a preferred conformation by the participating monomers, it can strongly affect the aggregation properties of the molecules. The results presented highlight a substantial role of the relative orientation of the individual monomer in the definition of the fibril higher structural levels.