Leucine-rich repeat kinase 2 (LRRK2) is a promising therapeutic target for the treatment of Parkinson’s disease (PD) and LRRK2 kinase inhibitors are currently being tested in early phase clinical trials. In order to ensure the highest chance of success, a biomarker-guided entry into clinical trials is key. LRRK2 phosphorylation, and phosphorylation of the LRRK2 substrate Rab10, have been proposed as target engagement biomarkers for LRRK2 kinase inhibition. However, a pharmacodynamic biomarker to demonstrate that a biological response has occurred is lacking. We previously discovered that the LRRK2 G2019S mutation causes mitochondrial DNA (mtDNA) damage and is LRRK2 kinase activity-dependent. Here, we have explored the possibility that measurement of mtDNA damage is a “surrogate” for LRRK2 kinase activity and consequently of kinase inhibitor activity. Mitochondrial DNA damage was robustly increased in PD patient-derived immune cells with LRRK2 G2019S mutations as compared with controls. Following treatment with multiple classes of LRRK2 kinase inhibitors, a full reversal of mtDNA damage to healthy control levels was observed and correlated with measures of LRRK2 dephosphorylation. Taken together, assessment of mtDNA damage levels may be a sensitive measure of altered kinase activity and provide an extended profile of LRRK2 kinase modulation in clinical studies.
Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting over one million people in the US. Mutations in leucine‐rich repeat kinase 2 (LRRK2) are the most common cause of inherited and idiopathic PD. We were the first to show that mitochondrial DNA (mtDNA) damage is caused by the most common mutation in LRRK2 (G2019S) and inhibition of LRRK2 kinase activity restores mtDNA integrity in PD models. However, whether aberrant LRRK2 kinase activity due to PD‐linked mutations has broad impact on nuclear genome integrity is unknown. Using LRRK2G2019S/G2019S knock‐in (KI) human embryonic kidney 293 (HEK293) cells obtained by CRISPR/Cas9 gene editing, our preliminary results indicate nuclear DNA damage is increased, including DNA double‐strand breaks (DSBs) as assayed by a neutral comet assay. Consistent with DSB accumulation, we observed significantly increased γ‐H2AX and 53BP1 foci. ATM is activated by DSBs and phosphorylates several key proteins that initiate the DNA damage response, cell cycle arrest, DNA repair or apoptosis. We found that basal levels of ATM pS1981 are increased in this in vitro LRRK2 G2019S model, which is an autophosphorylation site that correlates with DNA damage‐mediated activation. Additionally, downstream substrates CHK2 (pT68), and P53 (pS15) are similarly increased in LRRK2G2019S/G2019S KI cells compared to isogenic wild‐type control cells, substantiating that the ATM‐mediated DNA damage response pathway has been up‐regulated with the LRRK2 G2019S mutation. Blocking either LRRK2 or ATM kinase activity pharmacologically, significantly reversed LRRK2 G2019S‐induced γ‐H2AX foci. Overall these results suggest DSBs accumulate in LRRK2 PD, which in turn activate a sustained ATM mediated DNA damage response, which may lead to cell cycle arrest, aberrant DNA repair, and/or cell death. Further understanding of the functional relationship between LRRK2 and ATM offers new molecular insights into PD pathogenesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.