bims-celmim 2024-08-18 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2024–08–18
28 papers selected by
Marc Segarra Mondejar

Unique tau- and synuclein-dependent metabolic reprogramming in neurons distinct from normal aging.
Biofluorescence imaging-guided spatial metabolic tracing: In vivo tracking of metabolic activity in circulating tumor cell-mediated multi-organ metastases.
Mitochondrial-derived compartments are multilamellar domains that encase membrane cargo and cytosol.
Mitochondrial-derived compartments remove surplus proteins from the outer mitochondrial membrane.
3D Reconstruction of the Mitochondrial Network within the Neuronal Soma from SBF-SEM Volume Data.
Impaired microglial glycolysis promotes inflammatory responses after intracerebral haemorrhage via HK2-dependent mitochondrial dysfunction.
Flux Calculation for Primary Metabolism Reveals Changes in Allocation of Nitrogen to Different Amino Acid Families When Photorespiratory Activity Changes.
Deciphering the interaction between PKM2 and the built-in thermodynamic properties of the glycolytic pathway in cancer cells.
PDK4-mediated metabolic reprogramming is a potential therapeutic target for neovascular age-related macular degeneration.
Optogenetic manipulation of lysosomal physiology and autophagic activity.
An isotopically-labelled temporal mass spectrometry imaging data analysis workflow to reveal glucose spatial metabolism patterns in bovine lens tissue.
Mitochondrial Probe for Glutathione Depletion Reveals NME3 Essentiality for Mitochondrial Redox Response.
Mitochondrial network reorganization and transient expansion during oligodendrocyte generation.
Mitochondrial complex I promotes kidney cancer metastasis.
Dynamic interaction of REEP5-MFN1/2 enables mitochondrial hitchhiking on tubular ER.
Sulfur starvation-induced autophagy in Saccharomyces cerevisiae involves SAM-dependent signaling and transcription activator Met4.
Shifting redox reaction equilibria on demand using an orthogonal redox cofactor.
The significance of upper glycolytic components in regulating retinal pigment epithelial cellular behavior.
OPA1 promotes ferroptosis by augmenting mitochondrial ROS and suppressing an integrated stress response.
mTORC1 phosphorylates and stabilizes LST2 to negatively regulate EGFR.
Adapt and shape: metabolic features within the metastatic niche.
Intracellular pH differentially regulates transcription of metabolic and signaling pathways in normal epithelial cells.
GLUD1 determines murine muscle stem cell fate by controlling mitochondrial glutamate levels.
Malic enzymes in cancer: Regulatory mechanisms, functions, and therapeutic implications.
ScyNet: Visualizing interactions in community metabolic models.
The ratio of PKM1/PKM2 is the key factor affecting the glucose metabolism and biological function of colorectal cancer cells.
Predicting the Pathway Involvement of Metabolites in Both Pathway Categories and Individual Pathways.
DMT1 knockout abolishes ferroptosis induced mitochondrial dysfunction in C. elegans amyloid β proteotoxicity.

Aging Cell. 2024 Aug 13. e14277

Unique tau- and synuclein-dependent metabolic reprogramming in neurons distinct from normal aging.

Shweta Yadav, Aidan Graham, Farazdaq Al Hammood, Chris Garbark, Deepika Vasudevan, Udai Pandey, John M Asara, Dhivyaa Rajasundaram, Andrey A Parkhitko.

  Neuronal cells are highly specialized cells and have a specific metabolic profile to support their function. It has been demonstrated that the metabolic profiles of different cells/tissues undergo significant reprogramming with advancing age, which has often been considered a contributing factor towards aging-related diseases including Alzheimer's (AD) and Parkinson's (PD) diseases. However, it is unclear if the metabolic changes associated with normal aging predispose neurons to disease conditions or a distinct set of metabolic alterations happen in neurons in AD or PD which might contribute to disease pathologies. To decipher the changes in neuronal metabolism with age, in AD, or in PD, we performed high-throughput steady-state metabolite profiling on heads in wildtype Drosophila and in Drosophila models relevant to AD and PD. Intriguingly, we found that the spectrum of affected metabolic pathways is dramatically different between normal aging, Tau, or Synuclein overexpressing neurons. Genetic targeting of the purine and glutamate metabolism pathways, which were dysregulated in both old age and disease conditions partially rescued the neurodegenerative phenotype associated with the overexpression of wildtype and mutant tau. Our findings support a "two-hit model" to explain the pathological manifestations associated with AD where both aging- and Tau/Synuclein- driven metabolic reprogramming events cooperate with each other, and targeting both could be a potent therapeutic strategy.

Keywords:   Drosophila ; AD; GLS; PD; PRAT/PPAT; aging; glutaminase; metabolism; metabolomics; two‐hit model

DOI:  https://doi.org/10.1111/acel.14277
Talanta. 2024 Aug 10. pii: S0039-9140(24)01075-0. [Epub ahead of print]280 126696

Biofluorescence imaging-guided spatial metabolic tracing: In vivo tracking of metabolic activity in circulating tumor cell-mediated multi-organ metastases.

Hemi Luan, Shuailong Chen, Jingru Lian, Boxi Zhao, Xiaolong Xu, Yafei Chen, Yufang Yang, Zhuofeng Jiang, Min Qi, Jialing Liu, Wenyong Zhang, Tiangang Luan, Xin Hong.

  Circulating tumor cells (CTC) are considered metastatic precursors that are shed from the primary or metastatic deposits and navigate the bloodstream before undergoing extravasation to establish distant metastases. Metabolic reprogramming appears to be a hallmark of metastatic progression, yet current methods for evaluating metabolic heterogeneity within organ-specific metastases in vivo are limited. To overcome this challenge, we present Biofluorescence Imaging-Guided Spatial Metabolic Tracing (BIGSMT), a novel approach integrating in vivo biofluorescence imaging, stable isotope tracing, stain-free laser capture microdissection, and liquid chromatography-mass spectrometry. This innovative technology obviates the need for staining or intricate sample preparation, mitigating metabolite loss, and substantially enhances detection sensitivity and accuracy through chemical derivatization of polar metabolites in central carbon pathways. Application of BIGSMT to a preclinical CTC-mediated metastasis mouse model revealed significant heterogeneity in the in vivo carbon flux from glucose into glycolysis and the tricarboxylic acid (TCA) cycle across distinct metastatic sites. Our analysis indicates that carbon predominantly enters the TCA cycle through the enzymatic reaction catalyzed by pyruvate dehydrogenase. Thus, our spatially resolved BIGSMT technology provides fresh insights into the metabolic heterogeneity and evolution during melanoma CTC-mediated metastatic progression and points to novel therapeutic opportunities.

Keywords:  Biofluorescence imaging-guided spatial metabolic tracing (BIGSMT); Circulating tumor cell (CTC); Liquid chromatography-mass spectrometry (LC-MS); Melanoma metastasis; Metabolic reprogramming

DOI:  https://doi.org/10.1016/j.talanta.2024.126696
J Cell Biol. 2024 Nov 04. pii: e202307035. [Epub ahead of print]223(11):

Mitochondrial-derived compartments are multilamellar domains that encase membrane cargo and cytosol.

Zachary N Wilson, Matt West, Alyssa M English, Greg Odorizzi, Adam L Hughes.

Preserving the health of the mitochondrial network is critical to cell viability and longevity. To do so, mitochondria employ several membrane remodeling mechanisms, including the formation of mitochondrial-derived vesicles (MDVs) and compartments (MDCs) to selectively remove portions of the organelle. In contrast to well-characterized MDVs, the distinguishing features of MDC formation and composition remain unclear. Here, we used electron tomography to observe that MDCs form as large, multilamellar domains that generate concentric spherical compartments emerging from mitochondrial tubules at ER-mitochondria contact sites. Time-lapse fluorescence microscopy of MDC biogenesis revealed that mitochondrial membrane extensions repeatedly elongate, coalesce, and invaginate to form these compartments that encase multiple layers of membrane. As such, MDCs strongly sequester portions of the outer mitochondrial membrane, securing membrane cargo into a protected domain, while also enclosing cytosolic material within the MDC lumen. Collectively, our results provide a model for MDC formation and describe key features that distinguish MDCs from other previously identified mitochondrial structures and cargo-sorting domains.

DOI: https://doi.org/10.1083/jcb.202307035
J Cell Biol. 2024 Nov 04. pii: e202307036. [Epub ahead of print]223(11):

Mitochondrial-derived compartments remove surplus proteins from the outer mitochondrial membrane.

Zachary N Wilson, Sai Sangeetha Balasubramaniam, Sara Wong, Max-Hinderk Schuler, Mitchell J Wopat, Adam L Hughes.

The outer mitochondrial membrane (OMM) creates a boundary that imports most of the mitochondrial proteome while removing extraneous or damaged proteins. How the OMM senses aberrant proteins and remodels to maintain OMM integrity remains unresolved. Previously, we identified a mitochondrial remodeling mechanism called the mitochondrial-derived compartment (MDC) that removes a subset of the mitochondrial proteome. Here, we show that MDCs specifically sequester proteins localized only at the OMM, providing an explanation for how select mitochondrial proteins are incorporated into MDCs. Remarkably, selective sorting into MDCs also occurs within the OMM, as subunits of the translocase of the outer membrane (TOM) complex are excluded from MDCs unless assembly of the TOM complex is impaired. Considering that overloading the OMM with mitochondrial membrane proteins or mistargeted tail-anchored membrane proteins induces MDCs to form and sequester these proteins, we propose that one functional role of MDCs is to create an OMM-enriched trap that segregates and sequesters excess proteins from the mitochondrial surface.

DOI: https://doi.org/10.1083/jcb.202307036
Methods Mol Biol. 2024 ;2831 145-177

3D Reconstruction of the Mitochondrial Network within the Neuronal Soma from SBF-SEM Volume Data.

Jane Tweedy, Ross Laws, George Merces, Tracey Davey, Amy K Reeve, Amy E Vincent.

  Neurons contain three compartments, the soma, long axon, and dendrites, which have distinct energetic and biochemical requirements. Mitochondria feature in all compartments and regulate neuronal activity and survival, including energy generation and calcium buffering alongside other roles including proapoptotic signaling and steroid synthesis. Their dynamicity allows them to undergo constant fusion and fission events in response to the changing energy and biochemical requirements. These events, termed mitochondrial dynamics, impact their morphology and a variety of three-dimensional (3D) morphologies exist within the neuronal mitochondrial network. Distortions in the morphological profile alongside mitochondrial dysfunction may begin in the neuronal soma in ageing and common neurodegenerative disorders. However, 3D morphology cannot be comprehensively examined in flat, two-dimensional (2D) images. This highlights a need to segment mitochondria within volume data to provide a representative snapshot of the processes underpinning mitochondrial dynamics and mitophagy within healthy and diseased neurons. The advent of automated high-resolution volumetric imaging methods such as Serial Block Face Scanning Electron Microscopy (SBF-SEM) as well as the range of image software packages allow this to be performed.We describe and evaluate a method for randomly sampling mitochondria and manually segmenting their whole morphologies within randomly generated regions of interest of the neuronal soma from SBF-SEM image stacks. These 3D reconstructions can then be used to generate quantitative data about mitochondrial and cellular morphologies. We further describe the use of a macro that automatically dissects the soma and localizes 3D mitochondria into the subregions created.

Keywords:  3D reconstruction; Ageing; Mitochondria; Morphology; Neurodegeneration; SBF-SEM; Three-dimensional; Two-dimensional; mtDNA

DOI:  https://doi.org/10.1007/978-1-0716-3969-6_11
J Adv Res. 2024 Aug 12. pii: S2090-1232(24)00359-X. [Epub ahead of print]

Impaired microglial glycolysis promotes inflammatory responses after intracerebral haemorrhage via HK2-dependent mitochondrial dysfunction.

Yin Li, Hang Zhou, Xuchao He, Lingji Jin, Yuhan Zhu, Libin Hu, Majing Feng, Jun Zhu, Liang Wang, Yonghe Zheng, Shiwei Li, Zhiyuan Yan, Peili Cen, Junwen Hu, Zihang Chen, Xiaobo Yu, Xiongjie Fu, Chaoran Xu, Shenglong Cao, Yang Cao, Gao Chen, Lin Wang.

   INTRODUCTION: Intracerebral haemorrhage (ICH) is a devastating disease that leads to severe neurological deficits. Microglia are the first line of defence in the brain and play a crucial role in neurological recovery after ICH, whose activities are primarily driven by glucose metabolism. However, little is known regarding the status of glucose metabolism in microglia and its interactions with inflammatory responses after ICH.
OBJECTIVES: This study investigated microglial glycolysis and its mechanistic effects on microglial inflammation after ICH.
METHODS: We explored the status of glucose metabolism in the ipsilateral region and in fluorescence-activated-cell-sorting-isolated (FACS-isolated) microglia via 2-deoxy-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) analyses and gamma emission, respectively. Energy-related targeted metabolomics, along with 13C-glucose isotope tracing, was utilised to analyse glycolytic products in microglia. Mitochondrial membrane potential and mitochondrial reactive oxygen species (MitoROS) accumulation was assessed by flow cytometry. Behavioural, western blotting, gene regulation, and enzymatic activity analyses were conducted with a focus on microglia.
RESULTS: Neurological dysfunction was strongly correlated with decreased FDG-PET signals in the perihaematomal region, where microglial uptake of FDG was reduced. The decreased quantity of glucose-6-phosphate (G-6-P) in microglia was attributed to the downregulation of glucose transporter 1 (GLUT1) and hexokinase 2 (HK2). Enhanced inflammatory responses were driven by HK2 suppression via decreased mitochondrial membrane potential, which could be rescued by MitoROS scavengers. HK inhibitors aggravated neurological injury by suppressing FDG uptake and enhancing microglial inflammation in ICH mice.
CONCLUSION: These findings indicate an unexpected metabolic status in pro-inflammatory microglia after ICH, consisting of glycolysis impairment caused by the downregulation of GLUT1 and HK2. Additionally, HK2 suppression promotes inflammatory responses by disrupting mitochondrial function, providing insight into the mechanisms by which inflammation may be facilitated after ICH and indicating that metabolic enzymes as potential targets for ICH treatment.

Keywords:  Glycolysis; Hexokinase 2; Inflammation; Intracerebral haemorrhage; Microglia; Mitochondria

DOI:  https://doi.org/10.1016/j.jare.2024.08.016
Int J Mol Sci. 2024 Aug 01. pii: 8394. [Epub ahead of print]25(15):

Flux Calculation for Primary Metabolism Reveals Changes in Allocation of Nitrogen to Different Amino Acid Families When Photorespiratory Activity Changes.

Nils Friedrichs, Danial Shokouhi, Arnd G Heyer.

  Photorespiration, caused by oxygenation of the enzyme Rubisco, is considered a wasteful process, because it reduces photosynthetic carbon gain, but it also supplies amino acids and is involved in amelioration of stress. Here, we show that a sudden increase in photorespiratory activity not only reduced carbon acquisition and production of sugars and starch, but also affected diurnal dynamics of amino acids not obviously involved in the process. Flux calculations based on diurnal metabolite profiles suggest that export of proline from leaves increases, while aspartate family members accumulate. An immense increase is observed for turnover in the cyclic reaction of glutamine synthetase/glutamine-oxoglutarate aminotransferase (GS/GOGAT), probably because of increased production of ammonium in photorespiration. The hpr1-1 mutant, defective in peroxisomal hydroxypyruvate reductase, shows substantial alterations in flux, leading to a shift from the oxoglutarate to the aspartate family of amino acids. This is coupled to a massive export of asparagine, which may serve in exchange for serine between shoot and root.

Keywords:  Arabidopsis; alternative metabolic pathways; hpr1-1; photorespiration; photosynthesis–respiration interactions; plant carbon and nitrogen metabolism

DOI:  https://doi.org/10.3390/ijms25158394
J Biol Chem. 2024 Aug 07. pii: S0021-9258(24)02149-5. [Epub ahead of print] 107648

Deciphering the interaction between PKM2 and the built-in thermodynamic properties of the glycolytic pathway in cancer cells.

Chengmeng Jin, Wei Hu, Yuqi Wang, Hao Wu, Siying Zeng, Minfeng Ying, Xun Hu.

  Most cancer cells exhibit high glycolysis rates under conditions of abundant oxygen. Maintaining a stable glycolytic rate is critical for cancer cell growth as it ensures sufficient conversion of glucose carbons to energy, biosynthesis, and redox balance. Here we deciphered the interaction between PKM2 and the thermodynamic properties of the glycolytic pathway. Knocking down or knocking out PKM2 induced a thermodynamic equilibration in the glycolytic pathway, characterized by the reciprocal changes of the Gibbs free energy (ΔG) of the reactions catalyzed by PFK1 and PK, leading to a less exergonic PFK1-catalyzed reaction and a more exergonic PK-catalyzed reaction. The changes of the ΔGs of the two reactions causes the accumulation of intermediates, including the substrate PEP (the substrate of PK), in the segment between PFK1 and PK. The increased concentration of PEP in turn increased PK activity in the glycolytic pathway. Thus, the interaction between PKM2 and the thermodynamic properties of the glycolytic pathway maintains the reciprocal relationship between PK concentration and its substrate PEP concentration, by which, PK activity in the glycolytic pathway can be stabilized and effectively counteracts the effect of PKM2 KD or KO on glycolytic rate. In line with our previous reports, this study further validates the roles of the thermodynamics of the glycolytic pathway in stabilizing glycolysis in cancer cells. Deciphering the interaction between glycolytic enzymes and the thermodynamics of the glycolytic pathway will promote a better understanding of the flux control of glycolysis in cancer cells.

Keywords:  Gibbs free energy; PKM2; Warburg effect; allostery; cancer cells; cell metabolism; glycolysis; thermodynamics

DOI:  https://doi.org/10.1016/j.jbc.2024.107648
Cell Death Dis. 2024 Aug 09. 15(8): 582

PDK4-mediated metabolic reprogramming is a potential therapeutic target for neovascular age-related macular degeneration.

Juhee Kim, Yujin Jeon, Jinyoung Son, Haushabhau S Pagire, Suvarna H Pagire, Jin Hee Ahn, Akiyoshi Uemura, In-Kyu Lee, Sungmi Park, Dong Ho Park.

Age-related macular degeneration (AMD) causes severe blindness in the elderly due to choroidal neovascularization (CNV), which results from the dysfunction of the retinal pigment epithelium (RPE). While normal RPE depends exclusively on mitochondrial oxidative phosphorylation for energy production, the inflammatory conditions associated with metabolic reprogramming of the RPE play a pivotal role in CNV. Although mitochondrial pyruvate dehydrogenase kinase (PDK) is a central node of energy metabolism, its role in the development of CNV in neovascular AMD has not been investigated. In the present study, we used a laser-induced CNV mouse model to evaluate the effects of Pdk4 gene ablation and treatment with pan-PDK or specific PDK4 inhibitors on fluorescein angiography and CNV lesion area. Among PDK isoforms, only PDK4 was upregulated in the RPE of laser-induced CNV mice, and Pdk4 gene ablation attenuated CNV. Next, we evaluated mitochondrial changes mediated by PDK1-4 inhibition using siRNA or PDK inhibitors in inflammatory cytokine mixture (ICM)-treated primary human RPE (hRPE) cells. PDK4 silencing only in ICM-treated hRPE cells restored mitochondrial respiration and reduced inflammatory cytokine secretion. Likewise, GM10395, a specific PDK4 inhibitor, restored oxidative phosphorylation and decreased ICM-induced upregulation of inflammatory cytokine secretion. In a laser-induced CNV mouse model, GM10395 significantly alleviated CNV. Taken together, we demonstrate that specific PDK4 inhibition could be a therapeutic strategy for neovascular AMD by preventing mitochondrial metabolic reprogramming in the RPE under inflammatory conditions.

DOI: https://doi.org/10.1038/s41419-024-06968-0
Autophagy. 2024 Aug 15.

Optogenetic manipulation of lysosomal physiology and autophagic activity.

Wenping Zeng, Canjun Li, Lili Qu, Chunlei Cang.

  Lysosomes are essential degradative organelles and signaling hubs within cells, playing a crucial role in the regulation of macroautophagy/autophagy. Dysfunction of lysosomes and impaired autophagy are closely associated with the development of various neurodegenerative diseases. Enhancing lysosomal activity and boosting autophagy levels holds great promise as effective strategies for treating these diseases. However, there remains a lack of methods to dynamically regulate lysosomal activity and autophagy levels in living cells or animals. In our recent work, we applied optogenetics to manipulate lysosomal physiology and function, developing three lysosome-targeted optogenetic tools: lyso-NpHR3.0, lyso-ArchT, and lyso-ChR2. These new actuators enable light-dependent regulation of key aspects such as lysosomal membrane potential, lumenal pH, hydrolase activity, degradation processes, and Ca2+ dynamics in living cells. Notably, lyso-ChR2 activation induces autophagy via the MTOR pathway while it promotes Aβ clearance through autophagy induction in cellular models of Alzheimer disease. Furthermore, lyso-ChR2 activation reduces Aβ deposition and alleviates Aβ-induced paralysis in Caenorhabditis elegans models of Alzheimer disease. Our lysosomal optogenetic actuators offer a novel method for dynamically regulating lysosomal physiology and autophagic activity in living cells and animals.

Keywords:  Alzheimer disease; MTOR; autophagy; lysosome; optogenetics

DOI:  https://doi.org/10.1080/15548627.2024.2392464
Sci Rep. 2024 08 14. 14(1): 18843

An isotopically-labelled temporal mass spectrometry imaging data analysis workflow to reveal glucose spatial metabolism patterns in bovine lens tissue.

Dingchang Shi, Angus C Grey, George Guo.

  Application of stable isotopically labelled (SIL) molecules in Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) over a series of time points allows the temporal and spatial dynamics of biochemical reactions to be tracked in a biological system. However, these large kinetic MSI datasets and the inherent variability of biological replicates presents significant challenges to the rapid analysis of the data. In addition, manual annotation of downstream SIL metabolites involves human input to carefully analyse the data based on prior knowledge and personal expertise. To overcome these challenges to the analysis of spatiotemporal MALDI-MSI data and improve the efficiency of SIL metabolite identification, a bioinformatics pipeline has been developed and demonstrated by analysing normal bovine lens glucose metabolism as a model system. The pipeline consists of spatial alignment to mitigate the impact of sample variability and ensure spatial comparability of the temporal data, dimensionality reduction to rapidly map regional metabolic distinctions within the tissue, and metabolite annotation coupled with pathway enrichment modules to summarise and display the metabolic pathways induced by the treatment. This pipeline will be valuable for the spatial metabolomics community to analyse kinetic MALDI-MSI datasets, enabling rapid characterisation of spatio-temporal metabolic patterns from tissues of interest.

Keywords:  Glucose; Kinetic MALDI imaging; Lens; MALDI imaging; Metabolomics; Stable isotope

DOI:  https://doi.org/10.1038/s41598-024-69507-z
ACS Chem Biol. 2024 Aug 12.

Mitochondrial Probe for Glutathione Depletion Reveals NME3 Essentiality for Mitochondrial Redox Response.

Piriththiv Dhavarasa, Tanja Sack, Carmine P Cerrato, Ashley P Cheng, Yi Y Zhang, Kangfu Chen, Shana O Kelley.

Maintenance of the mitochondrial thiol redox state is essential for cell survival. However, we lack a comprehensive understanding of the redox response to mitochondrial glutathione depletion. We developed a mitochondria-penetrating peptide, mtCDNB, to specifically deplete mitochondrial glutathione. A genome-wide CRISPR/Cas9 screen in tandem with mtCDNB treatment was employed to uncover regulators of the redox response to mitochondrial glutathione depletion. We identified nucleoside diphosphate kinase 3 (NME3) as a regulator of mitochondrial dynamics. We show that NME3 is recruited to the mitochondrial outer membrane when under redox stress. In the absence of NME3, there is impaired mitophagy, which leads to the accumulation of dysfunctional mitochondria. NME3 knockouts depleted of mitochondrial glutathione have increased mitochondrial ROS production, accumulate mtDNA lesions, and present a senescence-associated secretory phenotype. Our findings suggest a novel role for NME3 in selecting mitochondria for degradation through mitophagy under conditions of mitochondrial redox stress.

DOI: https://doi.org/10.1021/acschembio.4c00287
Nat Commun. 2024 Aug 14. 15(1): 6979

Mitochondrial network reorganization and transient expansion during oligodendrocyte generation.

Xhoela Bame, Robert A Hill.

Oligodendrocyte precursor cells (OPCs) give rise to myelinating oligodendrocytes of the brain. This process persists throughout life and is essential for recovery from neurodegeneration. To better understand the cellular checkpoints that occur during oligodendrogenesis, we determined the mitochondrial distribution and morphometrics across the oligodendrocyte lineage in mouse and human cerebral cortex. During oligodendrocyte generation, mitochondrial content expands concurrently with a change in subcellular partitioning towards the distal processes. These changes are followed by an abrupt loss of mitochondria in the oligodendrocyte processes and myelin, coinciding with sheath compaction. This reorganization and extensive expansion and depletion take 3 days. Oligodendrocyte mitochondria are stationary over days while OPC mitochondrial motility is modulated by animal arousal state within minutes. Aged OPCs also display decreased mitochondrial size, volume fraction, and motility. Thus, mitochondrial dynamics are linked to oligodendrocyte generation, dynamically modified by their local microenvironment, and altered in the aging brain.

DOI: https://doi.org/10.1038/s41467-024-51016-2
Nature. 2024 Aug 14.

Mitochondrial complex I promotes kidney cancer metastasis.

Divya Bezwada, Luigi Perelli, Nicholas P Lesner, Ling Cai, Bailey Brooks, Zheng Wu, Hieu S Vu, Varun Sondhi, Daniel L Cassidy, Stacy Kasitinon, Sherwin Kelekar, Feng Cai, Arin B Aurora, McKenzie Patrick, Ashley Leach, Rashed Ghandour, Yuanyuan Zhang, Duyen Do, Phyllis McDaniel, Jessica Sudderth, Dennis Dumesnil, Sara House, Tracy Rosales, Alan M Poole, Yair Lotan, Solomon Woldu, Aditya Bagrodia, Xiaosong Meng, Jeffrey A Cadeddu, Prashant Mishra, Javier Garcia-Bermudez, Ivan Pedrosa, Payal Kapur, Kevin D Courtney, Craig R Malloy, Giannicola Genovese, Vitaly Margulis, Ralph J DeBerardinis.

Most kidney cancers are metabolically dysfunctional1-4, but how this dysfunction affects cancer progression in humans is unknown. We infused 13C-labelled nutrients in over 80 patients with kidney cancer during surgical tumour resection. Labelling from [U-13C]glucose varies across subtypes, indicating that the kidney environment alone cannot account for all tumour metabolic reprogramming. Compared with the adjacent kidney, clear cell renal cell carcinomas (ccRCCs) display suppressed labelling of tricarboxylic acid (TCA) cycle intermediates in vivo and in ex vivo organotypic cultures, indicating that suppressed labelling is tissue intrinsic. [1,2-13C]acetate and [U-13C]glutamine infusions in patients, coupled with measurements of respiration in isolated human kidney and tumour mitochondria, reveal lower electron transport chain activity in ccRCCs that contributes to decreased oxidative and enhanced reductive TCA cycle labelling. However, ccRCC metastases unexpectedly have enhanced TCA cycle labelling compared with that of primary ccRCCs, indicating a divergent metabolic program during metastasis in patients. In mice, stimulating respiration or NADH recycling in kidney cancer cells is sufficient to promote metastasis, whereas inhibiting electron transport chain complex I decreases metastasis. These findings in humans and mice indicate that metabolic properties and liabilities evolve during kidney cancer progression, and that mitochondrial function is limiting for metastasis but not growth at the original site.

DOI: https://doi.org/10.1038/s41586-024-07812-3
J Cell Biol. 2024 Oct 07. pii: e202304031. [Epub ahead of print]223(10):

Dynamic interaction of REEP5-MFN1/2 enables mitochondrial hitchhiking on tubular ER.

Shue Chen, Yang Sun, Yuling Qin, Lan Yang, Zhenhua Hao, Zhihao Xu, Mikael Björklund, Wei Liu, Zhi Hong.

Mitochondrial functions can be regulated by membrane contact sites with the endoplasmic reticulum (ER). These mitochondria-ER contact sites (MERCs) are functionally heterogeneous and maintained by various tethers. Here, we found that REEP5, an ER tubule-shaping protein, interacts with Mitofusins 1/2 to mediate mitochondrial distribution throughout the cytosol by a new transport mechanism, mitochondrial "hitchhiking" with tubular ER on microtubules. REEP5 depletion led to reduced tethering and increased perinuclear localization of mitochondria. Conversely, increasing REEP5 expression facilitated mitochondrial distribution throughout the cytoplasm. Rapamycin-induced irreversible REEP5-MFN1/2 interaction led to mitochondrial hyperfusion, implying that the dynamic release of mitochondria from tethering is necessary for normal mitochondrial distribution and dynamics. Functionally, disruption of MFN2-REEP5 interaction dynamics by forced dimerization or silencing REEP5 modulated the production of mitochondrial reactive oxygen species (ROS). Overall, our results indicate that dynamic REEP5-MFN1/2 interaction mediates cytosolic distribution and connectivity of the mitochondrial network by "hitchhiking" and this process regulates mitochondrial ROS, which is vital for multiple physiological functions.

DOI: https://doi.org/10.1083/jcb.202304031
Nat Commun. 2024 Aug 13. 15(1): 6927

Sulfur starvation-induced autophagy in Saccharomyces cerevisiae involves SAM-dependent signaling and transcription activator Met4.

Magali Prigent, Hélène Jean-Jacques, Delphine Naquin, Stéphane Chédin, Marie-Hélène Cuif, Renaud Legouis, Laurent Kuras.

Autophagy is a key lysosomal degradative mechanism allowing a prosurvival response to stresses, especially nutrient starvation. Here we investigate the mechanism of autophagy induction in response to sulfur starvation in Saccharomyces cerevisiae. We found that sulfur deprivation leads to rapid and widespread transcriptional induction of autophagy-related (ATG) genes in ways not seen under nitrogen starvation. This distinctive response depends mainly on the transcription activator of sulfur metabolism Met4. Consistently, Met4 is essential for autophagy under sulfur starvation. Depletion of either cysteine, methionine or SAM induces autophagy flux. However, only SAM depletion can trigger strong transcriptional induction of ATG genes and a fully functional autophagic response. Furthermore, combined inactivation of Met4 and Atg1 causes a dramatic decrease in cell survival under sulfur starvation, highlighting the interplay between sulfur metabolism and autophagy to maintain cell viability. Thus, we describe a pathway of sulfur starvation-induced autophagy depending on Met4 and involving SAM as signaling sulfur metabolite.

DOI: https://doi.org/10.1038/s41467-024-51309-6
Nat Chem Biol. 2024 Aug 13.

Shifting redox reaction equilibria on demand using an orthogonal redox cofactor.

Derek Aspacio, Yulai Zhang, Youtian Cui, Emma Luu, Edward King, William B Black, Sean Perea, Qiang Zhu, Yongxian Wu, Ray Luo, Justin B Siegel, Han Li.

Nature's two redox cofactors, nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), are held at different reduction potentials, driving catabolism and anabolism in opposite directions. In biomanufacturing, there is a need to flexibly control redox reaction direction decoupled from catabolism and anabolism. We established nicotinamide mononucleotide (NMN+) as a noncanonical cofactor orthogonal to NAD(P)+. Here we present the development of Nox Ortho, a reduced NMN+ (NMNH)-specific oxidase, that completes the toolkit to modulate NMNH:NMN+ ratio together with an NMN+-specific glucose dehydrogenase (GDH Ortho). The design principle discovered from Nox Ortho engineering and modeling is facilely translated onto six different enzymes to create NMN(H)-orthogonal biocatalysts with a consistent ~103-106-fold cofactor specificity switch from NAD(P)+ to NMN+. We assemble these enzymes to produce stereo-pure 2,3-butanediol in cell-free systems and in Escherichia coli, enabled by NMN(H)'s distinct redox ratio firmly set by its designated driving forces, decoupled from both NAD(H) and NADP(H).

DOI: https://doi.org/10.1038/s41589-024-01702-5
Sci Rep. 2024 08 14. 14(1): 18862

The significance of upper glycolytic components in regulating retinal pigment epithelial cellular behavior.

Armaan Naghdi, Nicole Oska, Thangal Yumnamcha, Shaimaa Eltanani, Mohamed Shawky, Rao Me, Ahmed S Ibrahim.

  Cell adhesion to the extracellular matrix and its natural outcome of cell spreading, along with the maintenance of barrier activity, are essential behaviors of epithelial cells, including retinal pigment epithelium (RPE). Disruptions in these characteristics can result in severe vision-threatening diseases such as diabetic macular edema and age-related macular degeneration. However, the precise mechanisms underlying how RPE cells regulate their barrier integrity and cell spreading are not fully understood. This study aims to elucidate the relative importance of upper glycolytic components in governing these cellular behaviors of RPE cells. Electric Cell-Substrate Impedance Sensing (ECIS) technology was utilized to assess in real-time the effects of targeting various upper glycolytic enzymes on RPE barrier function and cell spreading by measuring cell resistance and capacitance, respectively. Specific inhibitors used included WZB117 for Glut1 inhibition, Lonidamine for Hexokinase inhibition, PFK158 for PFKFB3/PFK axis inhibition, and TDZD-8 for Aldolase inhibition. Additionally, the viability of RPE cells was evaluated using a lactate dehydrogenase (LDH) cytotoxicity assay. The most significant decrease in electrical resistance and increase in capacitance of RPE cells were observed due to dose-dependent inhibition of Glut1 using WZB117, as well as Aldolase inhibition with TDZD-8. LDH level analysis at 24-72 h post-treatment with WZB117 (1 and 10 μM) or TDZD-8 (1 μM) showed no significant difference compared to the control, indicating that the disruption of RPE functionality was not attributed to cell death. Lastly, inhibition of other upper glycolytic components, including PFKFB3/PFK with PFK158 or Hexokinase with Lonidamine, did not significantly affect RPE cell behavior. This study provides insights into the varied roles of upper glycolytic components in regulating the functionality of RPE cells. Specifically, it highlights the critical roles of Glut1 and Aldolase in preserving barrier integrity and promoting RPE cell adhesion and spreading. Such understanding will guide the development of safe interventions to treat RPE cell dysfunction in various retinal disorders.

Keywords:  Age-related macular degeneration (AMD); Barrier integrity; Capacitance; Cell adhesion; Cell spreading; Electric cell-substrate impedance sensing (ECIS); Glycolysis; Resistance

DOI:  https://doi.org/10.1038/s41598-024-68343-5
Mol Cell. 2024 Aug 09. pii: S1097-2765(24)00618-X. [Epub ahead of print]

OPA1 promotes ferroptosis by augmenting mitochondrial ROS and suppressing an integrated stress response.

Felix G Liang, Fereshteh Zandkarimi, Jaehoon Lee, Joshua L Axelrod, Ryan Pekson, Yisang Yoon, Brent R Stockwell, Richard N Kitsis.

  Ferroptosis, an iron-dependent form of nonapoptotic cell death mediated by lipid peroxidation, has been implicated in the pathogenesis of multiple diseases. Subcellular organelles play pivotal roles in the regulation of ferroptosis, but the mechanisms underlying the contributions of the mitochondria remain poorly defined. Optic atrophy 1 (OPA1) is a mitochondrial dynamin-like GTPase that controls mitochondrial morphogenesis, fusion, and energetics. Here, we report that human and mouse cells lacking OPA1 are markedly resistant to ferroptosis. Reconstitution with OPA1 mutants demonstrates that ferroptosis sensitization requires the GTPase activity but is independent of OPA1-mediated mitochondrial fusion. Mechanistically, OPA1 confers susceptibility to ferroptosis by maintaining mitochondrial homeostasis and function, which contributes both to the generation of mitochondrial lipid reactive oxygen species (ROS) and suppression of an ATF4-mediated integrated stress response. Together, these results identify an OPA1-controlled mitochondrial axis of ferroptosis regulation and provide mechanistic insights for therapeutically manipulating this form of cell death in diseases.

Keywords:  ATF4; GPx4; OPA1; cell death; ferroptosis; integrated stress response; mitochondria; system X(c)(−); xCT

DOI:  https://doi.org/10.1016/j.molcel.2024.07.020
Proc Natl Acad Sci U S A. 2024 Aug 20. 121(34): e2405959121

mTORC1 phosphorylates and stabilizes LST2 to negatively regulate EGFR.

Stefania Battaglioni, Louise-Marie Craigie, Sofia Filippini, Timm Maier, Michael N Hall.

  TORC1 (target of rapamycin complex 1) is a highly conserved protein kinase that plays a central role in regulating cell growth. Given the role of mammalian TORC1 (mTORC1) in metabolism and disease, understanding mTORC1 downstream signaling and feedback loops is important. mTORC1 recognizes some of its substrates via a five amino acid binding sequence called the TOR signaling (TOS) motif. mTORC1 binding to a TOS motif facilitates phosphorylation of a distinct, distal site. Here, we show that LST2, also known as ZFYVE28, contains a TOS motif (amino acids 401 to 405) and is directly phosphorylated by mTORC1 at serine 670 (S670). mTORC1-mediated S670 phosphorylation promotes LST2 monoubiquitination on lysine 87 (K87). Monoubiquitinated LST2 is stable and displays a broad reticular distribution. When mTORC1 is inactive, unphosphorylated LST2 is degraded by the proteasome. The absence of LST2 enhances EGFR (epidermal growth factor receptor) signaling. We propose that mTORC1 negatively feeds back on its upstream receptor EGFR via LST2.

Keywords:  LST2; TOS motif; mTOR signaling; negative feedback; phosphorylation substrate

DOI:  https://doi.org/10.1073/pnas.2405959121
Trends Endocrinol Metab. 2024 Aug 08. pii: S1043-2760(24)00197-8. [Epub ahead of print]

Adapt and shape: metabolic features within the metastatic niche.

Erica Pranzini, Luigi Ippolito, Elisa Pardella, Elisa Giannoni, Paola Chiarugi.

  The success of disseminating cancer cells (DTCs) at specific metastatic sites is influenced by several metabolic factors. Even before DTCs arrival, metabolic conditioning from the primary tumor participates in creating a favorable premetastatic niche at distant organs. In addition, DTCs adjust their metabolism to better survive along the metastatic journey and successfully colonize their ultimate destination. However, the idea that the environment of the target organs may metabolically impact the metastatic fate is often underestimated. Here, we review the coexistence of two distinct strategies by which cancer cells shape and/or adapt to the metabolic profile of colonized tissues, ultimately creating a proper soil for their seeding and proliferation.

Keywords:  metabolic adaptation; metastatic niche; nutrient availability; organotropism; tissue metabolism

DOI:  https://doi.org/10.1016/j.tem.2024.07.016
J Biol Chem. 2024 Aug 09. pii: S0021-9258(24)02159-8. [Epub ahead of print] 107658

Intracellular pH differentially regulates transcription of metabolic and signaling pathways in normal epithelial cells.

Ricardo Romero-Moreno, Brandon J Czowski, Lindsey Harris, Jessamine F Kuehn, Katharine A White.

  Intracellular pH (pHi) dynamics regulate normal cell function, and dysregulated pHi dynamics is an emerging hallmark of cancer (constitutively increased pHi) and neurodegeneration (constitutively decreased pHi). However, the molecular mechanisms by which pHi dynamics regulate cell biology are poorly understood. Here, we discovered that altering pHi in normal human breast epithelial cells triggers global transcriptional changes. We identified 176 genes differentially regulated by pHi, with pHi-dependent genes clustering in signaling and glycolytic pathways. Using various normal epithelial cell models, we showed pH-dependent Notch1 expression, with increased protein abundance at high pHi. This resulted in pH-dependent downstream signaling, with increased Notch1 signaling at high pHi. We also found that high pHi increased the expression of glycolytic enzymes and regulators of pyruvate fate, including lactate dehydrogenase and pyruvate dehydrogenase kinase. These transcriptional changes were sufficient to alter lactate production, with high pHi shifting these normal epithelial cells toward a glycolytic metabolism and increasing lactate production. Thus, pHi dynamics transcriptionally regulate signaling and metabolic pathways in normal epithelial cells. Our data reveal new molecular regulators of pHi-dependent biology and a role for increased pHi in driving the acquisition of cancer-associated signaling and metabolic changes in normal human epithelial cells.

Keywords:  Intracellular pH; Notch1 signaling; glycolysis; lactate; metabolism; pyruvate

DOI:  https://doi.org/10.1016/j.jbc.2024.107658
Dev Cell. 2024 Aug 02. pii: S1534-5807(24)00455-6. [Epub ahead of print]

GLUD1 determines murine muscle stem cell fate by controlling mitochondrial glutamate levels.

Inés Soro-Arnáiz, Gillian Fitzgerald, Sarah Cherkaoui, Jing Zhang, Paola Gilardoni, Adhideb Ghosh, Ori Bar-Nur, Evi Masschelein, Pierre Maechler, Nicola Zamboni, Martin Poms, Alessio Cremonesi, Juan Carlos Garcia-Cañaveras, Katrien De Bock, Raphael Johannes Morscher.

  Muscle stem cells (MuSCs) enable muscle growth and regeneration after exercise or injury, but how metabolism controls their regenerative potential is poorly understood. We describe that primary metabolic changes can determine murine MuSC fate decisions. We found that glutamine anaplerosis into the tricarboxylic acid (TCA) cycle decreases during MuSC differentiation and coincides with decreased expression of the mitochondrial glutamate deaminase GLUD1. Deletion of Glud1 in proliferating MuSCs resulted in precocious differentiation and fusion, combined with loss of self-renewal in vitro and in vivo. Mechanistically, deleting Glud1 caused mitochondrial glutamate accumulation and inhibited the malate-aspartate shuttle (MAS). The resulting defect in transporting NADH-reducing equivalents into the mitochondria induced compartment-specific NAD+/NADH ratio shifts. MAS activity restoration or directly altering NAD+/NADH ratios normalized myogenesis. In conclusion, GLUD1 prevents deleterious mitochondrial glutamate accumulation and inactivation of the MAS in proliferating MuSCs. It thereby acts as a compartment-specific metabolic brake on MuSC differentiation.

Keywords:  GLUD1; glutamine metabolism; malate aspartate shuttle; metabolite compartmentalization; muscle stem cells; tricarboxylic acid cycle

DOI:  https://doi.org/10.1016/j.devcel.2024.07.015
Redox Biol. 2024 Jul 19. pii: S2213-2317(24)00251-9. [Epub ahead of print]75 103273

Malic enzymes in cancer: Regulatory mechanisms, functions, and therapeutic implications.

Huan Wang, Wanlin Cui, Song Yue, Xianglong Zhu, Xiaoyan Li, Lian He, Mingrong Zhang, Yan Yang, Minjie Wei, Huizhe Wu, Shuo Wang.

  Malic enzymes (MEs) are metabolic enzymes that catalyze the oxidation of malate to pyruvate and NAD(P)H. While researchers have well established the physiological metabolic roles of MEs in organisms, recent research has revealed a link between MEs and carcinogenesis. This review collates evidence of the molecular mechanisms by which MEs promote cancer occurrence, including transcriptional regulation, post-transcriptional regulation, post-translational protein modifications, and protein-protein interactions. Additionally, we highlight the roles of MEs in reprogramming energy metabolism, suppressing senescence, and modulating the tumor immune microenvironment. We also discuss the involvement of these enzymes in mediating tumor resistance and how the development of novel small-molecule inhibitors targeting MEs might be a good therapeutic approach. Insights through this review are expected to provide a comprehensive understanding of the intricate relationship between MEs and cancer, while facilitating future research on the potential therapeutic applications of targeting MEs in cancer management.

Keywords:  Cancer; Cancer therapy; Drug resistance; Malic enzyme inhibitors; Malic enzymes

DOI:  https://doi.org/10.1016/j.redox.2024.103273
Bioinform Adv. 2024 ;4(1): vbae104

ScyNet: Visualizing interactions in community metabolic models.

Michael Predl, Kilian Gandolf, Michael Hofer, Thomas Rattei.

Motivation: Genome-scale community metabolic models are used to gain mechanistic insights into interactions between community members. However, existing tools for visualizing metabolic models only cater to the needs of single organism models.
Results: ScyNet is a Cytoscape app for visualizing community metabolic models, generating networks with reduced complexity by focusing on interactions between community members. ScyNet can incorporate the state of a metabolic model via fluxes or flux ranges, which is shown in a previously published simplified cystic fibrosis airway community model.
Availability and implementation: ScyNet is freely available under an MIT licence and can be retrieved via the Cytoscape App Store (apps.cytoscape.org/apps/scynet). The source code is available at Github (github.com/univieCUBE/ScyNet).

DOI: https://doi.org/10.1093/bioadv/vbae104
Transl Cancer Res. 2024 Jul 31. 13(7): 3522-3535

The ratio of PKM1/PKM2 is the key factor affecting the glucose metabolism and biological function of colorectal cancer cells.

Liang Ma, Xue Zhang, Yan Liu, Hui Jin, Dan Li, Hui Zhang, Li Feng, Jing Zuo, Yudong Wang, Jiayin Liu, Jing Han.

   Background: Despite evidence suggesting a significant role of pyruvate kinase muscle isozyme (PKM) in cancer development, its particular function in colorectal cancer (CRC) remains unclear. This study aimed to elucidate the specific role and mechanism of PKM and its isoforms, PKM1 and PKM2, in the progression of CRC.
Methods: We analyzed PKM, PKM1, and PKM2 expression in CRC tissues and their correlation with clinicopathological features. Plasmids were constructed to modulate these isoforms' expression in CRC cells. Cellular behavior changes, including glucose metabolism alterations, were assessed using the Seahorse Energy Meter, and the Cell Counting Kit-8 (CCK8) assay to determine the inhibitory concentration of 5-fluorouracil (5-FU) on different CRC cell groups.
Results: Our results showed significant PKM overexpression in CRC tissues, which was correlated with negative prognostic factors such as advanced T stages and lymph node metastasis. A lower PKM1/PKM2 ratio was associated with these adverse outcomes. Functionally, PKM1 overexpression decreased cell migration and invasion, increasing 5-FU sensitivity. Conversely, PKM2 overexpression promoted malignant traits and reduced 5-FU sensitivity. Intriguingly, the introduction of glycolysis inhibitors attenuated the impact of PKM on the biological functions of CRC cells, suggesting a glycolysis-dependent mechanism.
Conclusions: This study establishes the PKM1/PKM2 ratio as crucial in CRC progression and 5-FU response. PKM1 overexpression reduces CRC malignancy and increases 5-FU sensitivity, while PKM2 does the opposite. Notably, glycolysis inhibitors lessen PKM's impact on CRC cells, highlighting a glycolysis-dependent mechanism. These insights suggest targeting PKM isoforms and glycolysis pathways as a promising CRC therapeutic strategy, potentially enhancing treatment efficacy.

Keywords:  Pyruvate kinase; chemotherapy sensitivity; clinicopathological features; glucose metabolism

DOI:  https://doi.org/10.21037/tcr-24-154
bioRxiv. 2024 Aug 09. pii: 2024.08.07.607025. [Epub ahead of print]

Predicting the Pathway Involvement of Metabolites in Both Pathway Categories and Individual Pathways.

Erik D Huckvale, Hunter N B Moseley.

Metabolism is the network of chemical reactions that sustain cellular life. Parts of this metabolic network are defined as metabolic pathways containing specific biochemical reactions. Products and reactants of these reactions are called metabolites, which are associated with certain human-defined metabolic pathways. Metabolic knowledgebases, such as the Kyoto Encyclopedia of Gene and Genomes (KEGG) contain metabolites, reactions, and pathway annotations; however, such resources are incomplete due to current limits of metabolic knowledge. To fill in missing metabolite pathway annotations, past machine learning models showed some success at predicting KEGG Level 2 pathway category involvement of metabolites based on their chemical structure. Here, we present the first machine learning model to predict metabolite association to more granular KEGG Level 3 metabolic pathways. We used a feature and dataset engineering approach to generate over one million metabolite-pathway entries in the dataset used to train a single binary classifier. This approach produced a mean Matthews correlation coefficient (MCC) of 0.806 ± 0.017 SD across 100 cross-validations iterations. The 172 Level 3 pathways were predicted with an overall MCC of 0.726. Moreover, metabolite association with the 12 Level 2 pathway categories were predicted with an overall MCC of 0.891, representing significant transfer learning from the Level 3 pathway entries. These are the best metabolite-pathway prediction results published so far in the field.

DOI: https://doi.org/10.1101/2024.08.07.607025
bioRxiv. 2024 Aug 09. pii: 2024.08.08.607074. [Epub ahead of print]

DMT1 knockout abolishes ferroptosis induced mitochondrial dysfunction in C. elegans amyloid β proteotoxicity.

Wilson Peng, Kaitlin B Chung, B Paige Lawrence, M Kerry O'Banion, Robert T Dirksen, Andrew P Wojtovich, John O Onukwufor.

Iron is critical for neuronal activity and metabolism, and iron dysregulation alters these functions in age-related neurodegenerative disorders, such as Alzheimer's disease (AD). AD is a chronic neurodegenerative disease characterized by progressive neuronal dysfunction, memory loss and decreased cognitive function. AD patients exhibit elevated iron levels in the brain compared to age-matched non-AD individuals. However, the degree to which iron overload contributes to AD pathogenesis is unclear. Here, we evaluated the involvement of ferroptosis, an iron-dependent cell death process, in mediating AD-like pathologies in C. elegans . Results showed that iron accumulation occurred prior to the loss of neuronal function as worms age. In addition, energetic imbalance was an early event in iron-induced loss of neuronal function. Furthermore, the loss of neuronal function was, in part, due to increased mitochondrial reactive oxygen species mediated oxidative damage, ultimately resulting in ferroptotic cell death. The mitochondrial redox environment and ferroptosis were modulated by pharmacologic processes that exacerbate or abolish iron accumulation both in wild-type worms and worms with increased levels of neuronal amyloid beta (Aβ). However, neuronal Aβ worms were more sensitive to ferroptosis-mediated neuronal loss, and this increased toxicity was ameliorated by limiting the uptake of ferrous iron through knockout of divalent metal transporter 1 (DMT1). In addition, DMT1 knockout completely suppressed phenotypic measures of Aβ toxicity with age. Overall, our findings suggest that iron-induced ferroptosis alters the mitochondrial redox environment to drive oxidative damage when neuronal Aβ is overexpressed. DMT1 knockout abolishes neuronal Aβ-associated pathologies by reducing neuronal iron uptake.
Highlights: Energetic imbalance is an early event in iron-induced loss of neuronal functionNeuronal Aβ increases susceptibility to ferroptosis mediated oxidative damageDivalent metal transporter 1 knockout protects against iron-induced oxidative damage and ferroptosis.

DOI: https://doi.org/10.1101/2024.08.08.607074