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Title: Investigating vesicular trafficking function and dysfunction of the Parkinson's disease kinase LRRK2
Author: Heaton, George
ISNI:       0000 0004 8508 0344
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Mutations in the LRRK2 gene represent a major cause of Parkinson's disease (PD), a common age dependent neurodegenerative disease characterised by nigral neuronal loss and motor symptoms. Despite intensive study, a consensus on how LRRK2 acts within cells and how pathogenic mutations compromise this function has yet to be achieved. Identifying functional interactors of LRRK2 can offer key insights into cellular mecha-nisms leading to neurodegeneration. In this study, I employed an unbiased protein-protein interaction screen to identify LRRK2 ROC domain binding partners. A comple-mentary siRNA screen was also employed to determine whether any candidate interac-tors could modify the sub-cellular localisation LRRK2. From this analysis, I discovered a functional interaction between LRRK2 and clathrin adaptor protein complex 2 (AP2). Analysis of LRRK2 KO tissue further revealed significant dysregulation of AP2 complex components, suggesting LRRK2 acts as an upstream modifier. The AP2 complex functions as a cytosolic bridge for cargo molecules and clathrin during the early stages of clathrin mediated endocytosis (CME). Experiments in cellular models demonstrated expression of LRRK2 is capable of modifying recruitment and phosphory-lation of AP2 in a mutation-dependent manner. Relative to WT LRRK2, expression of pathogenic mutation also resulted in impaired CME. Slowed endocytosis was also ob-served following depletion of endogenous LRRK2, suggesting pathogenic variants impair the physiological activity of LRRK2. I also report a decrease in activity-dependent syn-aptic vesicle endocytosis within pathogenic LRRK2 knock-in neurons. Alongside LRRK2, several PD-associated genes intersect with membrane-trafficking pathways. To probe for additional genetic associations, polygenic risk profiling was performed on IPDGC GWAS datasets. Clathrin-dependent endocytosis genes were found to be associated with Park-inson's disease across multiple cohorts, suggesting common variants at these loci repre-sent cumulative risk factors for disease. Taken together, these findings suggest CME is a LRRK2-mediated, PD relevant pathway.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available