Funded Studies
Objective/Rationale:
The propagation of pathological alpha-synuclein in the central nervous system resembles a spreading viral infection. We have observed that alpha-synuclein can enter neurons by inducing the rupture of endocytic vesicles in a manner that is very similar to what is induced by many viruses. This study will establish if phosphorylation (addition of a phosphate group) or familial mutations of alpha-synuclein convey an increased ability to enter cells in this way, thus increasing the pathological potential of these forms of alpha-synuclein.
Project Description:
In this study, we will generate alpha-synuclein aggregates in vitro using typical alpha-synuclein, phosphorylated alpha-synuclein and alpha-synuclein harboring mutations associated with familial PD. Using these aggregates, we will assess their ability to induce the rupture of endocytic vesicles. We will also examine how vesicle rupture by these forms of alpha-synuclein induces mitochondrial stress by releasing digestive enzymes (called cathepsins) from these endocytic vesicles.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
We hypothesize that the stress induced by vesicle rupture will lead to the spread of alpha-synuclein between cells during the progression of Parkinson’s disease. Understanding how vesicle rupture governs the spread of alpha-synuclein pathology may reveal new targets to halt the development of symptoms that arise from neuronal death and dysfunction in Parkinson’s disease patients.
Anticipated Outcome:
It is well established that certain mutations in alpha-synuclein induce an early onset, familial form of Parkinson’s disease. Similarly, pathological forms of alpha-synuclein are known to be phosphorylated on a specific residue of the alpha-synuclein protein. This study will determine how these changes correlate with the ability of alpha-synuclein to induce vesicle rupture and cellular stress, which will provide critical insight into the molecular mechanisms underlying the pathological spread of alpha-synuclein in Parkinson’s disease.
Final Outcome
The gradual loss of dopamine-producing brain cells is the central feature of Parkinson's disease (PD). Responsible for the loss of brain cells and, consequently, the progressive nature of PD is the infection-like spread of toxic alpha-synuclein - a sticky protein that clumps in the brains of people with Parkinson's -- among neighboring brain cells. In this study, we followed alpha-synuclein clumps as they entered the cell. We noticed that the clumps travel much like some viruses: They enter the cell inside bubbles made of cell membranes and break out of the bubbles inside the cell, spreading like infection. We found that certain changes in chemical structure of alpha-synuclein can help the clumps enter the cell. Also, changes in alpha-synuclein structure caused by mutations (genetic changes), such as those associated with PD, help alpha-synuclein clumps break out of membrane bubbles inside the cell. This observation could explain the link between these mutations and Parkinson's. Our findings further explain how alpha-synuclein spreads in the brain and how this process induces inflammation akin to that accompanying viral infection.
November 2014
Presentations & Publications
Flavin WP, Freeman D, Campbell EM. Characterizing the properties and consequences of alpha-synuclein aggregation. Presented at: Annual American Physician Scientist Association/American Society for Clinical Investigation/Association of American Physicians Joint Meeting; 2014; Chicago, IL
Flavin WP, Samuel F, Fraser PE, Tandon A, Campbell EM. S129 Phosphorylation and A30P mutation increase efficacy of vesicle rupture following endocytosis of alpha-synuclein aggregates. Presented at: Grand Challenges in Parkinson's Disease; 2014; Grand Rapids, MI
Samuel F, Flavin WP, Pacelli C, et al. Alpha-synuclein serine 129 phosphorylation modulates self-assembly and cellular uptake. Presented at: Society for Neuroscience 44th Annual Meeting; 2014; Washington, DC