Discovery of small molecule interactors of human ArfGAP1 and their potential use for the treatment of Parkinson’s disease

Abstract

Parkinson’s disease (PD), a movement disorder affecting primarily elderly patients, is the second most common neurodegenerative disease. The majority of cases are idiopathic, however, a subset of patients have genetic variations that highly predispose them to the disease. The most common genetic variant is in the LRRK2 gene, encoding a protein with both GTPase and protein kinase enzymatic domains. All known PD predisposing variants result in an increase in its kinase activity. LRRK2 kinase inhibitors were trialed as a potential treatment but were found to be toxic to the kidney and lung. Thus, alternate approaches in treating LRRK2-mediated PD may offer benefit. The GTPase activating protein ArfGAP1 was identified as a regulator of LRRK2 activity. We hypothesized that inhibiting ArfGAP1 activity may be a viable approach to treat LRRK2-mediated PD. We performed a cell-based high-throughput small molecule screen testing over 100,000 compounds for potential inhibition of human ArfGAP1 in a cell-based assay. Five compounds consistently showed reversal of ArfGAP1 toxicity to cells. I tested three candidates for their ability to directly bind purified ArfGAP1 using microscale thermophoresis. The results suggest that all three compounds bind ArfGAP1. Fruit fly models expressing human LRRK2, and the most common PD pathogenic version LRRK2-G2019S, in dopaminergic neurons of the fly brain were used to test the efficacy of the three compounds using an age-related motor deficit phenotype. This proof of concept experiment determined that one of the compounds increased movement in flies expressing human LRRK2, but not the LRRK2-G2019S variant.