Oxidative Stress Induces Nuclear DNA Damage and PARP1 Activation in LRRK2 Parkinson’s Disease Models

Abstract

Parkinson’s disease (PD) is the most common movement neurodegenerative disorder, with over 10 million cases worldwide. PD is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta, which causes a myriad of motor impairments including tremor, rigidity, bradykinesia, and postural instability. Mutations in LRRK2 are a common cause of PD, with the G2019S variant being the most frequent pathogenic mutation. Although considerable work has been done to define cellular functions of LRRK2, the precise molecular mechanisms by which LRRK2 G2019S promotes neuronal dysfunction are not well understood. Emerging evidence highlights the importance of genome maintenance in PD pathogenesis; however, the roles of DNA damage and repair in PD remain unclear. We found that the PD-linked mutant impacts the cell’s ability to process specific DNA lesions by demonstrating that LRRK2G2019S/G2019S knock-in (KI) cells are more sensitive than wild-type control to oxidative stress and DNA alkylation. In the absence of exogenous stress, LRRK2G2019S/G2019S KI cells accumulate greater levels of oxidative DNA lesions than the wild-type control. Given that oxidative lesions and strand breaks activate base excision repair (BER) and PARP1, we examined PARP1 activity and found that LRRK2 G2019S causes a nearly 250 percent increase in PARP1 activation compared to the wild-type control. PARP1 activation was also elevated in midbrain lysates from 4-6-month-old Lrrk2 G2019S KI heterozygous mice compared to controls. Furthermore, LRRK2G2019S/G2019S KI cells are more sensitive to PARP1 inhibition via trapping compared to the wild-type control. The SOD/catalase mimetic (EUK 134) rescues PAR accumulation, and the mitochondrial complex I inhibitor rotenone further exacerbates PAR generation in LRRK2G2019S/G2019S cells, implicating reactive oxygen species (ROS) as a driver of BER dysfunction and increased PARP1 signaling. Finally, to better understand the underlying mechanisms of PARP1 activation caused by LRRK2 G2019S, we performed proximity labeling and mass spectrometry, identifying significant enrichment of gene ontology terms related to cell cycle processes and chromosomal and organelle organization in LRRK2G2019S/G2019S KI cells compared to the wild-type control. Together, these findings reveal genome integrity is disrupted as a consequence of oxidative stress in LRRK2 G2019S PD and highlight PARP1 signaling as an important response to genome instability in PD pathogenesis.