Abstract
Aggregated α-synuclein (α-syn) is the main constituent of Lewy bodies, the main pathological hallmark of Parkinson’s disease (PD). Environmental factors are thought to be potential triggers capable of initiating the aggregation of the otherwise monomeric α-syn. Braak’s seminal work redirected attention to the intestine and recent reports of dysbiosis have highlighted the potential causative role that the microbiome might play in the pathology of PD. Staphylococcus aureus is a bacterium carried by 30-70% of the general population. It has been shown to produce functional amyloids, called Phenol Soluble Modulins (PSMαs). Here, we studied the kinetics of α-syn aggregation under quiescent conditions in the presence or absence of four different PSMα peptides and observed a remarkable shortening of the lag phase in their presence. Whereas pure α-syn monomer did not aggregate up to 450 h after initiation of the experiment in neither neutral nor mildly acidic buffer, the addition of different PSMα peptides resulted in an almost immediate increase in the Thioflavin T (ThT) fluorescence. Despite similar peptide sequences, the different PSMα peptides displayed distinct effects on the kinetics of α-syn aggregation. Kinetic analyses of the data suggest that while all four peptides catalyze α-syn aggregation, the underlying mechanisms might differ with a model of nucleation and elongation fitting the α-syn aggregation induced by PSMα2 but not PSMα1. The results of immunogold TEM imply that the aggregates are fibrillar and composed of α-syn. Addition of the co-aggregated materials to HEK cells expressing the A53T α-syn variant fused to GFP was found to catalyze α-syn aggregation and phosphorylation in the cells. Our results provide evidence of a potential trigger of synucleinopathies and could have implications for the prevention of the diseases.
Competing Interest Statement
The authors have declared no competing interest.
