Biology subjects

Sanders, L. H.

Publications and source records attributed to Sanders, L. H..

7 recordsLinked to original sources

bioRxiv2026

Rab12 is a regulator of mitophagy and mitochondrial homeostasis

Rab GTPases orchestrate vesicular trafficking, but their contributions to mitochondrial quality control are not fully defined, despite links to multiple mitochondria-related human diseases. We conducted a family-wide siRNA-based screen using mt-mKeima/YFP-Parkin HeLa cells to identify regulators of depolarization-induced mitophagy. The screen identified several candidate Rabs, and follow-up studies validated Rab12 as a negative regulator of mitophagy. Rab12 knockdown or knockout augments clearance of damaged mitochondria basally and/or after FCCP-induced depolarization, with findings reproduced across distinct cell types. Rab12 depletion increased mitochondrial content, lowered mitochondrial membrane potential, and reduced mitochondrial DNA damage, without detectable changes in overall cellular bioenergetic capacity. Together, these results indicate that Rab12 restrains mitophagic engagement and its loss permits accumulation of lower-functioning mitochondria that are hypersensitive to mitophagy-inducing stress. Rab12 thus emerges as a novel effector linking vesicular trafficking machinery and mitochondrial homeostasis, with potential implications for neurodegenerative disorders and other Rab-associated diseases.

cell biology↗

bioRxiv2026

Parkinson's disease linked LRRK2 G2019S drives oxidative nuclear DNA damage and PARP1 hyperactive signaling

LRRK2 mutations are the most common cause of autosomal-dominant Parkinsons disease (PD), with G2019S linked to both familial and sporadic PD. Although LRRK2-mediated mitochondrial DNA damage is implicated in PD, the contribution of nuclear DNA damage is less understood. Using CRISPR/Cas9-generated LRRK2G2019S/G2019S knock-in cells, we discovered increased sensitivity to oxidative and alkylating DNA-damaging agents compared to wild-type, consistent with compromised tolerance/repair of lesions processed by base excision repair (BER). The oxRADD assay revealed elevated endogenous oxidative nuclear base damage in LRRK2 mutant cells. Concomitantly, PARP1-dependent poly(ADP-ribose) (PAR) levels were markedly increased, with chromatin enrichment of PARP1 and BER factors (XRCC1, DNA ligase III) only in LRRK2G2019S/G2019S cells, indicating BER initiation, without successful resolution. LRRK2G2019S/G2019S cells displayed synthetic lethality with PARP-trapping inhibitors (olaparib) but tolerated PARP1 knockdown, suggesting cytotoxicity from stabilized PARP-DNA complexes rather than loss of catalytic activity. The SOD/catalase mimetic EUK-134 abrogated LRRK2 G2019S-dependent PAR accumulation, whereas the mitochondrial complex I inhibitor rotenone exacerbated PAR levels, linking reactive oxygen species (ROS) to BER dysfunction and PARP1 hyperactivation. Overall, we have identified a ROS-dependent PARP1 hyperactivation pathway that underlies LRRK2 G2019S-associated cellular vulnerability.

cell biology↗

bioRxiv2025

Accumulation of LRRK2-associated phospho-Rab12 degenerative lysosomes in tauopathies

Parkinsons disease (PD) pathogenic mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with endolysosomal dysfunction across cell types, and carriers of LRRK2 mutations variably present with phosphorylated tau and -synuclein deposits in post-mortem analysis. LRRK2 mutations increase the phosphorylation of Rab substrates including Rab12. Rab12 is expressed in neuronal and non-neuronal cells with localization to membranes in the endolysosomal compartment. Under lysosomal stress, LRRK2 interaction with Rab12 upregulates LRRK2 kinase activity. In this study, using a recently developed monoclonal antibody directed to the LRRK2-mediated phosphorylation site on Rab12 at amino acid Ser106 (pS106-Rab12), we test whether aberrant LRRK2 phosphorylation is associated with tau and/or -synuclein pathology across clinically distinct neurodegenerative diseases. Analysis of brain tissue lysates and immunohistochemistry of pathology-susceptible brain regions demonstrate that pS106-Rab12 levels are increased in Dementia with Lewy bodies (DLB), Alzheimers disease (AD), and PD, and in LRRK2 mutation carriers. In early pathological stages, phosphorylated Rab12 localizes to granulovacuolar degeneration bodies (GVBs), which are thought to be active lysosomal-like structures, in neurons. pS106-Rab12-positive GVBs accumulate with pathological tau across brain tissues in DLB, AD, and PD, and in LRRK2 mutation carriers. In a mouse model of tauopathy, pS106-Rab12 localizes to GVBs during early tau deposition in an age-dependent manner. While GVBs are largely absent in neurons with mature protein pathology, subsets of both tau and -synuclein inclusions appear to incorporate pS106-Rab12 at later pathological stages. Finally, pS106-Rab12 labels GVBs in neurons and shows widespread co-pathology with tau inclusions in primary tauopathies including Picks disease, progressive supranuclear palsy and corticobasal degeneration. These results implicate LRRK2 kinase activity and Rab phosphorylation in endolysosomal dysfunction in both tau and -synuclein-associated neurodegenerative diseases.

neuroscience↗

bioRxiv2024

Single molecule array measures of LRRK2 kinase activity in serum link Parkinson's disease severity to peripheral inflammation

BackgroundLRRK2-targeting therapeutics that inhibit LRRK2 kinase activity have advanced to clinical trials in idiopathic Parkinsons disease (iPD). LRRK2 phosphorylates Rab10 on endolysosomes in phagocytic cells to promote some types of immunological responses. The identification of factors that regulate LRRK2-mediated Rab10 phosphorylation in iPD, and whether phosphorylated-Rab10 levels change in different disease states, or with disease progression, may provide insights into the role of Rab10 phosphorylation in iPD and help guide therapeutic strategies targeting this pathway. MethodsCapitalizing on past work demonstrating LRRK2 and phosphorylated-Rab10 interact on vesicles that can shed into biofluids, we developed and validated a high-throughput single-molecule array assay to measure extracellular pT73-Rab10. Ratios of pT73-Rab10 to total Rab10 measured in biobanked serum samples were compared between informative groups of transgenic mice, rats, and a deeply phenotyped cohort of iPD cases and controls. Multivariable and weighted correlation network analyses were used to identify genetic, transcriptomic, clinical, and demographic variables that predict the extracellular pT73-Rab10 to total Rab10 ratio. ResultspT73-Rab10 is absent in serum from Lrrk2 knockout mice but elevated by LRRK2 and VPS35 mutations, as well as SNCA expression. Bone-marrow transplantation experiments in mice show that serum pT73-Rab10 levels derive primarily from circulating immune cells. The extracellular ratio of pT73-Rab10 to total Rab10 is dynamic, increasing with inflammation and rapidly decreasing with LRRK2 kinase inhibition. The ratio of pT73-Rab10 to total Rab10 is elevated in iPD patients with greater motor dysfunction, irrespective of disease duration, age, sex, or the usage of PD-related or anti-inflammatory medications. pT73-Rab10 to total Rab10 ratios are associated with neutrophil activation, antigenic responses, and the suppression of platelet activation. ConclusionsThe extracellular ratio of pT73-Rab10 to total Rab10 in serum is a novel pharmacodynamic biomarker for LRRK2-linked innate immune activation associated with disease severity in iPD. We propose that those iPD patients with higher serum pT73-Rab10 levels may benefit from LRRK2-targeting therapeutics to mitigate associated deleterious immunological responses.

neuroscience↗

bioRxiv2023

Nuclease-dead S. aureus Cas9 downregulates alpha-synuclein and reduces mtDNA damage and oxidative stress levels in patient-derived stem cell model of Parkinson's disease

Parkinsons disease (PD) is one of the most common neurodegenerative diseases, but no disease modifying therapies have been successful in clinical translation presenting a major unmet medical need. A promising target is alpha-synuclein or its aggregated form, which accumulates in the brain of PD patients as Lewy bodies. While it is not entirely clear which alpha-synuclein protein species is disease relevant, mere overexpression of alpha-synuclein in hereditary forms leads to neurodegeneration. To specifically address gene regulation of alpha-synuclein, we developed a CRISPR interference (CRISPRi) system based on the nuclease dead S. aureus Cas9 (SadCas9) fused with the transcriptional repressor domain Krueppel-associated box to controllably repress alpha-synuclein expression at the transcriptional level. We screened single guide (sg)RNAs across the SNCA promoter and identified several sgRNAs that mediate downregulation of alpha-synuclein at varying levels. CRISPRi downregulation of alpha-synuclein in iPSC-derived neuronal cultures from a patient with an SNCA genomic triplication showed functional recovery by reduction of oxidative stress and mitochondrial DNA damage. Our results are proof-of-concept in vitro for precision medicine by targeting the SNCA gene promoter. The SNCA CRISPRi approach presents a new model to understand safe levels of alpha-synuclein downregulation and a novel therapeutic strategy for PD and related alpha-synucleinopathies.

neuroscience↗

bioRxiv2022

G2019S selective LRRK2 kinase inhibitor abrogates mitochondrial DNA damage

Pathogenic mutations in LRRK2 cause Parkinsons disease (PD). The G2019S variant is the most common, which results in abnormally high kinase activity. Compounds that target LRRK2 kinase activity are currently being developed and tested in clinical trials. We recently found that G2019S LRRK2 causes mitochondrial DNA (mtDNA) damage and treatment with multiple classes of LRRK2 kinase inhibitors at concentrations associated with dephosphorylation of LRRK2 reversed mtDNA damage to healthy control levels. Because maintaining the normal function of LRRK2 in heterozygous G2019S LRRK2 carriers while specifically targeting the G2019S LRRK2 activity could have an advantageous safety profile, we explored the efficacy of a G2019S mutant selective LRRK2 inhibitor to reverse mtDNA damage in G2019S LRRK2 models and patient cells relative to non-selective LRRK2 inhibitors. Potency of LRRK2 kinase inhibition by EB-42168, a G2019S mutant LRRK2 kinase inhibitor, and MLi-2, a nonselective inhibitor, was determined by measuring phosphorylation of LRRK2 at Ser935 and/or Ser1292 using quantitative western immunoblot analysis. The Mito DNADX assay, a novel system that allows for the accurate real-time quantification of mtDNA damage in a 96-well platform, was performed in parallel. We confirmed that EB-42168 selectively inhibits LRRK2 phosphorylation on G2019S LRRK2 relative to wild-type LRRK2. On the other hand, MLi-2 was equipotent for wild-type and G2019S LRRK2. Acute treatment with EB-42168 inhibited LRRK2 phosphorylation and also restored mtDNA damage to healthy control levels. Precision medicine is a common approach in modern day cancer research that is not yet routinely applied to neurodegenerative diseases. Abrogation of mtDNA damage with mutant selective tool inhibitor EB-42168 demonstrates the promise of a precision medicine approach for LRRK2 G2019S PD. Levels of mtDNA damage may serve as a potential pharmacodynamic biomarker of altered kinase activity that could be useful for small molecule development and clinical trials.

neuroscience↗

bioRxiv2022

A mitochondrial blood-based patient stratification candidate biomarker for Parkinson's disease

Parkinsons disease (PD) is the most common neurodegenerative movement disorder and neuroprotective interventions remain elusive. High throughput biomarkers aimed to stratify patients based on shared etiology is one critical path to the success of disease-modifying therapies in clinical trials. Mitochondrial dysfunction plays a prominent role in the pathogenesis of PD. Previously, we found brain region-specific mitochondrial DNA (mtDNA) damage accumulation in neuronal and in vivo PD models, as well as human PD postmortem brain tissue. In this study, to investigate mtDNA damage as a potential blood biomarker for PD, we describe a novel Mito DNADX assay that allows for the accurate real-time quantification of mtDNA damage in a 96-well platform, compatible with assessing large cohorts of patient samples. We found that levels of mtDNA damage were increased in blood derived from early-stage idiopathic PD patients or those harboring the pathogenic LRRK2 G2019S mutation compared to age-matched healthy controls. Given that increased mtDNA damage was also found in non-manifesting LRRK2 mutation carriers, mtDNA damage may begin to accumulate prior to a clinical PD diagnosis. LRRK2 kinase inhibition mitigated mtDNA damage in idiopathic PD models and patient-derived cells. The latter observations further substantiate a mechanistic role for wild-type LRRK2 kinase activity in idiopathic PD and support mtDNA damage reversal as a suitable approach to slow PD-related pathology. In light of recent advances in the field of precision medicine, the analysis of mtDNA damage as a blood-based patient stratification biomarker should be included in future clinical trials. One Sentence SummaryBlood test identifies Parkinsons patients most likely to respond to mitochondria-targeted therapeutics facilitating a precision medicine approach.

neuroscience↗