UC San Diego

Parkinson’s Disease (PD) is a progressive neurodegenerative disorder that affects more than 10 million people worldwide. While most cases of PD are sporadic, point mutations in Leucine-Rich Repeat Kinase (LRRK2) have been determined to be the most common cause of autosomal dominant late-onset PD. One key limitation within the field of LRRK2 biology lies within our inability to visualize endogenous LRRK2 due to its low expression. Without definitive evidence in endogenous systems, there remain questions surrounding how representative conclusions drawn from overexpression systems are regarding LRRK2 kinase activity, LRRK2 protein levels, and mechanisms underlying LRRK2-driven PD. Hence, it is crucial to develop a system to better understand endogenous LRRK2. Chapter I introduces LRRK2 biology by demonstrating the progress the field has made to unravel LRRK2’s complexities within the last 20 years. Chapter II tests the ability of novel HaloTag technology CRISPR-tagged to LRRK2 to better visualize endogenous LRRK2. Chapter III encompasses the use of a CRISPRi screen to identify pathways that potentially regulate endogenous LRRK2 degradation. Notably, the CRISPRi screen revealed two pathways modulating proteasomal degradation: SUMOylation and VCP/p97 system. Through validation of specific gene targets within a knockdown system, we found that the NPL4/UFD1L complex is involved in regulating endogenous LRRK2 degradation through an unknown mechanism. Future directions would include using microscopy to further corroborate the importance of the NPL4/UFD1L complex and establish its interaction to LRRK2 in the endogenous degradation pathway.