Staphylococcus aureus is carried by 30–70% of the general population as a commensal bacterium. It produces a special kind of peptides called phenol soluble modulins (PSMαs). And these PSMαs seem to affect the aggregation process of α-synuclein, a protein known to aggregate in Parkinson’s disease.
“We noticed that adding bacterial PSMαs accelerated the aggregation of α-synuclein”, tells Caroline Haikal, Ph.D. student in Professor Jia-Yi Li’s group and first author of the study.
Alone, the α-synuclein did not aggregate within the time-frame of the experiment, up to 14 days. When adding the bacterial PSMαs, this process started almost immediately. And even more interestingly, the PSMαs also facilitated the aggregation of α-synuclein inside cells. At least outside the body.
Thus, α-synuclein aggregation may happen in response to infections with this bacterium. Still, even though many persons carry around these bacteria, only about 1 % of the population develop Parkinson´s disease. This indicates there are other factors at play, like a genetic predisposition. So the authors do not think there is any reason for people to be generally worried regarding these findings.
“This aggregated α-synuclein would likely be cleared away after the infection is resolved. But in a subset of the population, instead, it may become chronic, seeding other α-synuclein leading to pathology”, explains Caroline Haikal.
It has long been thought that PD is a result of a dual hit: both a genetic predisposition for α-synuclein pathology and an environmental trigger are required for developing the disease. Infections could be one such environmental trigger. A deeper understanding of these environmental triggers can help researchers identify genetic risk factors that they have not previously studied. But first, the researchers also need to examine whether this bacteria-induced α-synuclein aggregation also happens inside the brain.
“Maybe in the future, we will be better able to identify who is at risk of developing PD and then try to prevent it by screening for these kinds of environmental triggers”, speculates Caroline Haikal.
“Our results suggest a possible trigger of Parkinson’s disease and could have implications for the prevention of the disease, even though our results need to be confirmed in human samples”, concludes Jia-Yi Li, the senior author of the study.
