Identification and Characterization of GTP-binding Inhibitors of LRRK2

Abstract

Parkinson's disease (PD) is one of the most common neurodegenerative disorders in aged adults, resulting from the loss of dopaminergic neurons in the substantia nigra and the accumulation of Lewy body aggregates in the brain. Currently there are no disease altering treatments for PD. Mutations in Leucine-rich repeat kinase 2 (LRRK2) are the most common contributors to both familial and sporadic PD cases, however the exact physiological role of LRRK2 is currently unclear. As a large protein (286 kDa) with both GTPase and kinase activities, LRRK2 represents a tractable target for PD intervention. The work in this dissertation focuses on the identification and characterization of GTP-binding inhibitors of LRRK2. Moreover, I further investigate the biopathological roles of LRRK2 on neural transport functions underlying neurdegeneration and test the neuroprotective effects of LRRK2 GTP-binding inhibitors. I discovered that the novel compound, 68, inhibits GTP-binding as well as kinase activities in LRRK2, and that optimized compound FX2149, a new analog of 68, shows significant improvements in blood brain barrier (BBB) penetration and in vivo efficacy in LRRK2 mutant brains. Furthermore, I demonstrate that the LRRK2 GTPase domain mutation, R1441C, impairs neural transport functions, however these impairments can be attenuated through treatment with our GTP-binding inhibitors. Lastly, I show that our GTP-binding inhibitors increase LRRK2 ubiquitination, with a preferential increase in atypical ubiquitin linkages. This work provides further insight into LRRK2 functions in the pathobiology of PD, as well as provides evidence for the applicability of GTP-binding inhibitors as pharmacological tools and potential therapeutic agents in the treatment of PD.