Alpha-Synuclein Aggregation Mechanism in the Presence of Nanomaterials.

Abstract

Parkinson's disease (PD) is characterized by the toxic oligomeric and fibrillar phases formed by monomeric alpha-synuclein (α-syn). Certain nanoparticles have been demonstrated to promote protein aggregation, while other nanomaterials have been found to prevent the process. In the current work, we use nuclear magnetic resonance spectroscopy in conjunction with isothermal titration calorimetry to investigate the cause and mechanism of these opposing effects at the amino acid protein level. The interaction of α-syn with two types of nanomaterials was considered: citrate-capped gold nanoparticles (AuNPs) and graphene oxide (GO). In the presence of AuNPs, α-syn aggregation is accelerated, whereas in the presence of GO, aggregation is prevented. The study indicates that GO sequesters the NAC region of α-syn monomers through electrostatic and hydrophobic interactions, leading to a reduced elongation rate, and AuNPs leave the NAC region exposed while binding the N-terminus, leading to higher aggregation. The protein's inclination toward quicker aggregation is explained by the binding of the N-terminus of α-syn with the gold nanoparticles. Conversely, a comparatively stronger interaction with GO causes the nucleation and growth phases to be postponed and inhibits intermolecular interactions. Our finding offers novel experimental insights at the residue level regarding the aggregation of α-syn in the presence of various nanomaterials and creates new opportunities for the development of suitably functionalized nanomaterial-based therapeutic reagents against Parkinson's and other neurodegenerative diseases.