Biology subjects

Maio, N.

Publications and source records attributed to Maio, N..

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

Partial Bypass of Frataxin Deficiency by ISCU M141I Restores Cytosolic and Nuclear FeS Cluster Assembly

Iron-sulfur (Fe-S) clusters are essential cofactors required for the activity of numerous proteins involved in fundamental cellular processes, including DNA replication, metabolism and mitochondrial respiration. In eukaryotes, Fe-S cluster biogenesis is initiated in mitochondria by the ISC machinery, which assembles iron and sulfur, delivered by a cysteine desulfurase, onto the scaffold protein ISCU. Frataxin (FXN), a key regulator of this pathway, enhances Fe-S production by accelerating persulfide transfer to ISCU. FXN is essential in eukaryotes, and its loss results in "petite" phenotype in yeast, senescence in dividing mammalian cells and embryonic lethality in mice. Interestingly, in yeast, a methionine to isoleucine substitution at position 141 of the scaffold protein Isu1 can bypass the requirement of FXN. To test whether this bypass mechanism is conserved in mammals, we introduced the equivalent M141I substitution into the endogenous Iscu gene in murine fibroblasts carrying a conditional Fxn allele using CRISPR-Cas9. We show that the ISCU M141I variant enables cell survival in the absence of FXN, preventing cell cycle arrest and decreasing baseline DNA damage. However, these FXN-null survivor clones exhibit slower proliferation, persistent mitochondrial dysfunction and defective mitochondrial Fe-S cluster proteins. In contrast, nuclear and cytosolic Fe-S proteins are preserved, as is cellular iron homeostasis. Importantly, the ISCU M141I variant delays, but does not fully rescue, embryonic lethality in Fxn-deficient mice. Altogether, our results reveal a previously unrecognized compartment-specific rescue of Fe-S cluster dependent processes by the ISCU M141I variant in mammalian cells, raising for the first time the possibility of compartmental regulation of Fe-S cluster biogenesis.

cell biology↗

bioRxiv2025

Impaired oxidative phosphorylation drives primary tumor escape and metastasis

Metastasis causes most cancer deaths and reflects transitions from primary tumor escape to seeding and growth at metastatic sites. Epithelial-to-mesenchymal transition (EMT) is important early in metastasis to enable cancer cells to detach from neighboring cells, become migratory, and escape the primary tumor. While different phases of metastasis expose cells to variable nutrient environments and demands, the metabolic requirements and plasticity of each step are uncertain. Here we show that EMT and primary tumor escape are stimulated by disrupted oxidative metabolism. Using Renal Cell Carcinoma (RCC) patient samples, we identified the mitochondrial electron transport inhibitor NDUFA4L2 as upregulated in cells undergoing EMT. Deletion of NDUFA4L2 enhanced oxidative metabolism and prevented EMT and metastasis while NDUFA4L2 overexpression enhanced these processes. Mechanistically, NDUFA4L2 suppressed oxidative phosphorylation and caused citric acid cycle intermediates to accumulate, which modified chromatin accessibility of EMT-related loci to drive primary tumor escape. The effect of impaired mitochondrial metabolism to drive EMT appeared general, as renal cell carcinoma patient tumors driven by fumarate hydratase mutations with disrupted oxidative phosphorylation were highly metastatic and also had robust EMT. These findings highlight the importance of dynamic shifts in metabolism for cell migration and metastasis, with mitochondrial impairment driving early phases of this process. Understanding mitochondrial dynamics may have important implications in both basic and translational efforts to prevent cancer deaths.

cancer biology↗

bioRxiv2020

Pathogenic mutations in Leucine-rich repeat kinase 2 sequester Rab8a to damaged lysosomes and regulate transferrin-mediated iron uptake in microglia

Mutations in leucine-rich repeat kinase 2 (LRRK2) cause autosomal dominant Parkinsons disease (PD) while polymorphic LRRK2 variants are associated with sporadic PD. PD-linked mutations increase LRRK2 kinase activity and induce neurotoxicity in vitro and in vivo. The small GTPase Rab8a is a LRRK2 kinase substrate and is involved in receptor-mediated recycling and endocytic trafficking of transferrin, but the effect of PD-linked LRRK2 mutations on the function of Rab8a are poorly understood. Here, we show that gain-of-function mutations in LRRK2 induce sequestration of endogenous Rab8a into lysosomes in cells while pharmacological inhibition of LRRK2 kinase activity reverses this phenotype. Furthermore, we show that LRRK2 mutations drive accumulation of endocytosed transferrin into Rab8a-positive lysosomes leading to a dysregulation of iron transport. LRRK2 has been nominated as an integral part of cellular responses downstream of proinflammatory signals and is activated in microglia in post-mortem PD tissue. Here, we show that iPSC-derived microglia from patients carrying the most common LRRK2 mutation, G2019S, mistraffic transferrin to lysosomes proximal to the nucleus in proinflammatory conditions. Furthermore, G2019S knock-in mice show significant increase in iron deposition in microglia following intrastriatal LPS injection compared to wild type mice, accompanied by striatal accumulation of ferritin. Our data support a role of LRRK2 in modulating iron uptake and storage in response to proinflammatory stimuli in microglia.

cell biology↗