Parkinson's disease-associated LRRK2 risk variant, G2385R, enhances Rab substrate phosphorylation and impairs neuronal integrity.

Mutations in the LRRK2 gene are the most frequent cause of familial Parkinson's disease (PD) whereas common variants are associated with an increased risk for sporadic PD. LRRK2 encodes a multi-domain protein displaying two functional enzymatic activities: GTPase and kinase. In addition to familial mutations, several common LRRK2 coding variants have been associated with PD risk in different ethnic populations. Little is known about how these coding variants modulate the risk of developing PD. In this study, we aimed to evaluate the properties of a collection of LRRK2 coding risk variants (A419V, N551K, R1398H, R1628P, M1646T, S1647T, G2385R). With the exception of G2385R, we find that coding risk variants have minimal impact on LRRK2 protein levels, GTP-binding, LRRK2 phosphorylation, and subcellular localization in human cells and primary neurons. G2385R LRRK2 exhibits reduced phosphorylation at Ser910/Ser935 and Ser1292, consistent with diminished kinase activity. Notably, however, LRRK2 variants associated with increased PD risk (R1628P, M1646T, and G2385R) significantly elevate the levels of LRRK2-mediated Rab10 phosphorylation by >two-fold in cells. In contrast, LRRK2 variants associated with reduced PD risk (N551K, R1398H, and N551K-R1398H) do not alter pRab10 levels. The G2385R LRRK2 variant significantly inhibits neurite outgrowth in primary cortical neurons compared to wild-type LRRK2. Our study indicates that LRRK2-dependent Rab phosphorylation represents a relevant readout of PD risk induced by LRRK2 variants and demonstrates that the G2385R variant creates a hyperactive kinase that can impair neuronal integrity at comparable levels to the effects of G2019S LRRK2.