Biology subjects

LaVoie, M. J.

Publications and source records attributed to LaVoie, M. J..

4 recordsLinked to original sources

bioRxiv2025

Parkinson's disease LRRK2 mutations dysregulate iron homeostasis and promote oxidative stress and ferroptosis in human neurons and astrocytes

BackgroundIron accumulation is a hallmark of sporadic and familial Parkinsons disease (PD) and correlates with clinical motor symptom severity. The biochemical mechanisms driving iron dyshomeostasis in PD brain and whether these are early or late events in the neurodegenerative process remain unknown. Nigral iron levels in LRRK2-PD patients have been reported to be even higher than in idiopathic PD, and greater in non-manifesting LRRK2 carriers than controls, suggesting that iron accumulation precedes clinical onset in LRRK2-associated PD. However, the cells affected and mechanisms governing iron dyshomeostasis in PD remain unclear. MethodsHere, we investigated multiple independent measures of iron homeostasis in iPSCs, iPSC-derived cortical and dopaminergic neurons, and astrocytes from control and PD patient-derived iPSCs and an isogenic iPSC panel of three independent pathogenic PD mutations. High-content and super-resolution microscopy of iron-specific probes and ICP-MS were used to determine iron content and distribution across different cell types and LRRK2 genotypes. The upstream effectors and downstream consequences of iron dyshomeostasis on ferroptosis signaling were also examined. ResultsWe found that heterozygous LRRK2 mutations dysregulate cellular iron levels across iPSCs, neurons and astrocytes, in a kinase-dependent manner. Lysosomal ferrous iron was specifically and consistently elevated across iPSCs, iPSC-derived cortical and dopaminergic neurons, and astrocytes carrying LRRK2 mutations and rescued by treatment with the selective LRRK2 inhibitor, MLi-2. Importantly, we show that lipid peroxidation and ROS levels are elevated in isogenic LRRK2 mutant neurons, while iron chelation or MLi-2 reduced LRRK2-dependent ROS damage. LRRK2 regulates the function of over a dozen Rab GTPase proteins through direct phosphorylation, and our prior work revealed a unique correlation with Rab8a trafficking and iron. Here, we report that CRISPR/Cas9 knockout of Rab8a recapitulates LRRK2-driven effects on intracellular iron in different cell types and that exogenous Rab8a normalizes lysosomal iron levels in R1441C LRRK2 iPSCs. ConclusionsTogether, our findings demonstrate that LRRK2 mutations disrupt iron homeostasis across multiple cell types, including dopaminergic neurons, and establish a discrete biochemical pathway linking LRRK2 and vulnerability to ferroptosis signaling.

neuroscience↗

bioRxiv2025

Progressive Supranuclear Palsy PERK haplotype B selectively translates DLX1 promoting tau toxicity

The unfolded protein response (UPR) sensor PERK exists in two haplotypes termed A and B. PERK-B uniquely confers increased risk for tauopathies like progressive supranuclear palsy (PSP), but the mechanisms distinguishing its function from PERK-A and contributing to its association with tau pathology are not known. Here, we developed a controlled cellular model for a pair-wise comparison of the two PERK haplotypes, finding their UPR functions nearly indistinguishable. However, a careful examination employing puromycin-based proteomics revealed that a subset of mRNA translation events were permissible under PERK-B, but not PERK-A, dependent UPR. Critically, one of the targets that escaped PERK-B suppression was the transcription factor DLX1, which has been genetically linked to PSP risk. Here, we found a shift in the solubility of DLX1 in human PSP brain tissue, and report that silencing of DLX-1 reduced the aggregation of tau in mammalian cells. Furthermore, silencing of the fly homolog of DLX1 was sufficient to decrease tau-induced toxicity, in vivo. Our results detail the haplotype-specific PERK-B/DLX-1 pathway as a novel driver of tau pathology in cells, flies, and likely human brain, revealing new insights into PSP pathogenesis and potential therapeutic targets.

neuroscience↗

bioRxiv2023

The LRRK2 kinase substrates Rab8a and Rab10 contribute complementary but distinct disease-relevant phenotypes in human neurons

Mutations in the LRRK2 gene cause familial Parkinsons disease presenting with pleomorphic neuropathology that can involve -synuclein or tau accumulation. LRRK2 mutations are thought to converge toward a pathogenic increase in LRRK2 kinase activity. A subset of small Rab GTPases have been identified as LRRK2 substrates, with LRRK2-dependent phosphorylation resulting in Rab inactivation. We used CRISPR/Cas9 genome editing to generate a novel series of isogenic iPSC lines deficient in the two most well validated LRRK2 substrates, Rab8a and Rab10, from two independent, deeply phenotyped healthy control lines. Thorough characterization of NGN2-induced neurons revealed divergent effects of Rab8a and Rab10 deficiency on lysosomal pH, LAMP1 association with Golgi, -synuclein insolubility and tau phosphorylation, while parallel effects on lysosomal numbers and Golgi clustering were observed. Our data demonstrate largely antagonistic effects of genetic Rab8a or Rab10 inactivation which provide discrete insight into the pathologic features of their biochemical inactivation by pathogenic LRRK2 mutation. HighlightsO_LIRab8a and Rab10 deficiency induce lysosomal and Golgi defects C_LIO_LIRab8a and Rab10 deficiency induce opposing effects on lysosomal pH C_LIO_LIRab8a KO and Rab10 KO neurons show divergent effects on synuclein and tau proteostasis C_LIO_LIInactivation of different Rab GTPases can induce distinct disease-relevant phenotypes C_LI

neuroscience↗

bioRxiv2020

Parkinson Disease-Linked Parkin Mediates Redox Reactions That Lower Oxidative Stress In Mammalian Brain

We recently hypothesized that parkin plays a role in redox homeostasis and provided evidence that it directly reduces hydrogen peroxide (H2O2) in vitro. Here, we examined this anti-oxidant activity in vivo. Informed by findings in human brain, we demonstrate that elevated oxidative stress promotes parkin insolubility in mice. In normal mouse brain parkin was partially oxidized, e.g., at cysteines 195 and 252, which was augmented by oxidative stress. Although under basal conditions H2O2 levels were unchanged in adult prkn-/- brain, a parkin-dependent reduction of cytosolic H2O2 was observed when mitochondria were impaired, either due to neurotoxicant exposure (MPTP) or Sod2 haploinsufficiency. In accordance, markers of oxidative stress, e.g., protein carbonylation and nitrotyrosination, were elevated in the cytosol but not in mitochondria from prkn-/- mice. Nevertheless, this rise in oxidative stress led to changes in mitochondrial enzyme activities and the metabolism of glutathione in cells and mammalian brain. In parkins absence reduced glutathione concentrations were increased including in human cortex. This compensation was not due to new glutathione synthesis but attributed to elevated oxidized glutathione (GSSG)-reductase activity. Moreover, we discovered that parkin also recycled GSSG to its reduced form. With this reaction, parkin became S-glutathionylated, e.g., at cysteines 59 and human-specific 95. This oxidative modification was reversed by glutaredoxin. Our results demonstrate that cytosolic parkin mediates anti-oxidant reactions including H2O2 reduction and glutathione regeneration. These reducing activities lead to a range of oxidative modifications in parkin itself. In parkin-deficient brain oxidative stress rises despite changes to maintain redox balance.

neuroscience↗