bims-nenemi 2024-10-20 papers

bims-nenemi

Biomed News

on Neuroinflammation, neurodegeneration and mitochondria

Issue of 2024‒10‒20
25 papers selected by
Marco Tigano, Thomas Jefferson University

Mitophagy as a guardian against cellular aging.
Molecular mechanisms of mitochondrial dynamics.
LETMD1 regulates mitochondrial protein synthesis and import to guard brown fat mitochondrial integrity and function.
Visualizing VDAC1 in live cells using a tetracysteine tag.
Quantifying constraint in the human mitochondrial genome.
Somatic mitochondrial DNA mutations are a source of heterogeneity among primary leukemic cells.
The mitochondrial long non-coding RNA lncMtloop regulates mitochondrial transcription and suppresses Alzheimer's disease.
Inhibition of BAK-mediated apoptosis by the BH3-only protein BNIP5.
Post-transcriptional methylation of mitochondrial-tRNA differentially contributes to mitochondrial pathology.
Apoptosis-induced translocation of nesprin-2 from the nuclear envelope to mitochondria is associated with mitochondrial dysfunction.
Itaconate drives mtRNA-mediated type I interferon production through inhibition of succinate dehydrogenase.
Single-cell mitochondrial sequencing reveals low-frequency mitochondrial mutations in naturally aging mice.
A mitochondrial unfolded protein response-independent role of DVE-1 in longevity regulation.
Brown fat ATP-citrate lyase links carbohydrate availability to thermogenesis and guards against metabolic stress.
Farnesyl pyrophosphate potentiates dendritic cell migration in autoimmunity through mitochondrial remodelling.
A new gene signature for endothelial senescence identifies self-RNA sensing by retinoic acid-inducible gene I as a molecular facilitator of vascular aging.
Autophagy adaptors mediate Parkin-dependent mitophagy by forming sheet-like liquid condensates.
Regulation of the NLRP3 inflammasome by autophagy and mitophagy.
Monoamine oxidases: A missing link between mitochondria and inflammation in chronic diseases ?
cGAS deficient mice display premature aging associated with de-repression of LINE1 elements and inflammation.
A cross-disease resource of living human microglia identifies disease-enriched subsets and tool compounds recapitulating microglial states.
CRISPR screens unveil nutrient-dependent lysosomal and mitochondrial nodes impacting intestinal tissue-resident memory CD8+ T cell formation.
Mitophagy Defects Exacerbate Inflammation and Aberrant Proliferation in Lymphocytic Thyroiditis.
Type I interferon signaling and peroxisomal dysfunction contribute to enhanced inflammatory cytokine production in Irgm1-deficient macrophages.
Examining transfer of TERT to mitochondria under oxidative stress.

Autophagy. 2024 Oct 14. 1-3

Mitophagy as a guardian against cellular aging.

Tetsushi Kataura, Niall Wilson, Gailing Ma, Viktor I Korolchuk.

  Mitophagy, the selective autophagic clearance of damaged mitochondria, is considered vital for maintaining mitochondrial quality and cellular homeostasis; however, its molecular mechanisms, particularly under basal conditions, and its role in cellular physiology remain poorly characterized. We recently demonstrated that basal mitophagy is a key feature of primary human cells and is downregulated by immortalization, suggesting its dependence on the primary cell state. Mechanistically, we demonstrated that the PINK1-PRKN-SQSTM1 pathway regulates basal mitophagy, with SQSTM1 sensing superoxide-enriched mitochondria through its redox-sensitive cysteine residues, which mediate SQSTM1 oligomerization and mitophagy activation. We developed STOCK1N-57534, a small molecule that targets and promotes this SQSTM1 activation mechanism. Treatment with STOCK1N-57534 reactivates mitophagy downregulated in senescent and naturally aged donor-derived primary cells, improving cellular senescence(-like) phenotypes. Our findings highlight that basal mitophagy is protective against cellular senescence and aging, positioning its pharmacological reactivation as a promising anti-aging strategy.Abbreviation: IR: ionizing radiation; ROS: reactive oxygen species; SARs: selective autophagy receptors.

Keywords:  Aging; SQSTM1/p62; autophagy; mitochondria; mitophagy; senescence

DOI:  https://doi.org/10.1080/15548627.2024.2414461
Nat Rev Mol Cell Biol. 2024 Oct 17.

Molecular mechanisms of mitochondrial dynamics.

Luis-Carlos Tábara, Mayuko Segawa, Julien Prudent.

Mitochondria not only synthesize energy required for cellular functions but are also involved in numerous cellular pathways including apoptosis, calcium homoeostasis, inflammation and immunity. Mitochondria are dynamic organelles that undergo cycles of fission and fusion, and these transitions between fragmented and hyperfused networks ensure mitochondrial function, enabling adaptations to metabolic changes or cellular stress. Defects in mitochondrial morphology have been associated with numerous diseases, highlighting the importance of elucidating the molecular mechanisms regulating mitochondrial morphology. Here, we discuss recent structural insights into the assembly and mechanism of action of the core mitochondrial dynamics proteins, such as the dynamin-related protein 1 (DRP1) that controls division, and the mitofusins (MFN1 and MFN2) and optic atrophy 1 (OPA1) driving membrane fusion. Furthermore, we provide an updated view of the complex interplay between different proteins, lipids and organelles during the processes of mitochondrial membrane fusion and fission. Overall, we aim to present a valuable framework reflecting current perspectives on how mitochondrial membrane remodelling is regulated.

DOI: https://doi.org/10.1038/s41580-024-00785-1
iScience. 2024 Oct 18. 27(10): 110944

LETMD1 regulates mitochondrial protein synthesis and import to guard brown fat mitochondrial integrity and function.

Madigan Snyder, Yi-Kai Liu, Renjie Shang, Haowei Xu, Charlie Thrift, Xiyue Chen, Jingjuan Chen, Kun Ho Kim, Jiamin Qiu, Pengpeng Bi, W Andy Tao, Shihuan Kuang.

  Thermogenic brown adipocytes (BAs) catabolize lipids to generate heat, representing powerful agents against the growing global obesity epidemic. We and others reported recently that LETMD1 is a BA-specific protein essential for mitochondrial structure and function, but the mechanisms of action remain unclear. We performed sequential digestion to demonstrate that LETMD1 is a trans-inner mitochondrial membrane protein. We then generated UCP1Cre-driven BA-specific Letmd1 knockout (Letmd1 UKO ) mice to show that Letmd1 UKO leads to protein aggregation, reactive oxidative stress, hyperpolarization, and mitophagy in BAs. We further employed TurboID proximity labeling to identify LETMD1-interacting proteins. Many candidate proteins are associated with mitochondrial ribosomes, protein import machinery, and electron transport chain complexes (ETC-I and ETC-IV). Using quantitative proteomics, we confirmed the elevated aggregations of ETC and mitochondrial ribosomal proteins, impairing mitochondrial protein synthesis in the Letmd1 UKO BAs. Therefore, LETMD1 may function to maintain mitochondrial proteostasis through regulating import of nuclear-encoded proteins and local protein translation in brown fat mitochondria.

Keywords:  Cell; Cell biology; Cellular physiology; Molecular biology

DOI:  https://doi.org/10.1016/j.isci.2024.110944
PLoS One. 2024 ;19(10): e0311107

Visualizing VDAC1 in live cells using a tetracysteine tag.

Johannes Pilic, Furkan E Oflaz, Benjamin Gottschalk, Yusuf C Erdogan, Wolfgang F Graier, Roland Malli.

The voltage-dependent anion channel 1 (VDAC1) is a crucial gatekeeper in the outer mitochondrial membrane, controlling metabolic and energy homeostasis. The available methodological approaches fell short of accurate visualization of VDAC1 in living cells. To permit precise VDAC1 imaging, we utilized the tetracysteine (TC)-tag and visualized VDAC1 dynamics in living cells. TC-tagged VDAC1 had a cluster-like distribution on mitochondria. The labeling of TC-tagged VDAC1 was validated with immunofluorescence. The majority of VDAC1-TC-clusters were localized at endoplasmic reticulum (ER)-mitochondria contact sites. Notably, VDAC1 colocalized with BCL-2 Antagonist/Killer (BAK)-clusters upon apoptotic stimulation. Using this new tool, we were able to observe VDAC1-TC at mitochondrial fission sites. These findings highlight the suitability of the TC-tag for live-cell imaging of VDAC1, shedding light on the roles of VDAC1 in cellular processes.

DOI: https://doi.org/10.1371/journal.pone.0311107
Nature. 2024 Oct 16.

Quantifying constraint in the human mitochondrial genome.

Nicole J Lake, Kaiyue Ma, Wei Liu, Stephanie L Battle, Kristen M Laricchia, Grace Tiao, Daniela Puiu, Kenneth K Ng, Justin Cohen, Alison G Compton, Shannon Cowie, John Christodoulou, David R Thorburn, Hongyu Zhao, Dan E Arking, Shamil R Sunyaev, Monkol Lek.

Mitochondrial DNA (mtDNA) has an important yet often overlooked role in health and disease. Constraint models quantify the removal of deleterious variation from the population by selection and represent powerful tools for identifying genetic variation that underlies human phenotypes1-4. However, nuclear constraint models are not applicable to mtDNA, owing to its distinct features. Here we describe the development of a mitochondrial genome constraint model and its application to the Genome Aggregation Database (gnomAD), a large-scale population dataset that reports mtDNA variation across 56,434 human participants5. Specifically, we analyse constraint by comparing the observed variation in gnomAD to that expected under neutrality, which was calculated using a mtDNA mutational model and observed maximum heteroplasmy-level data. Our results highlight strong depletion of expected variation, which suggests that many deleterious mtDNA variants remain undetected. To aid their discovery, we compute constraint metrics for every mitochondrial protein, tRNA and rRNA gene, which revealed a range of intolerance to variation. We further characterize the most constrained regions within genes through regional constraint and identify the most constrained sites within the entire mitochondrial genome through local constraint, which showed enrichment of pathogenic variation. Constraint also clustered in three-dimensional structures, which provided insight into functionally important domains and their disease relevance. Notably, we identify constraint at often overlooked sites, including in rRNA and noncoding regions. Last, we demonstrate that these metrics can improve the discovery of deleterious variation that underlies rare and common phenotypes.

DOI: https://doi.org/10.1038/s41586-024-08048-x
medRxiv. 2024 Sep 27. pii: 2024.09.26.24314381. [Epub ahead of print]

Somatic mitochondrial DNA mutations are a source of heterogeneity among primary leukemic cells.

Kelly McCastlain, Catherine Welsh, Yonghui Ni, Liang Ding, Melissa Franco, Robert Autry, Besian Sejdiu, Ti-Cheng Chang, Wenan Chen, Huiyun Wu, Qingfei Pan, Veronica Gonzalez-Pena, Patrick Schreiner, Sasi Arunachalam, Joung Joo, Benshang Li, Shuhong Shen, Samuel Brady, Jinghui Zhang, Charles Gawad, William Evans, M Madan Babu, Konstantin Khrapko, Gang Wu, Jiyang Yu, Stanley Pounds, Mondira Kundu.

Somatic mitochondrial DNA (mtDNA) mutations are prevalent in tumors, yet defining their biological significance remains challenging due to the intricate interplay between selective pressure, heteroplasmy, and cell state. Utilizing bulk whole-genome sequencing data from matched tumor and normal samples from two cohorts of pediatric cancer patients, we uncover differences in the accumulation of synonymous and nonsynonymous mtDNA mutations in pediatric leukemias, indicating distinct selective pressures. By integrating single-cell sequencing (SCS) with mathematical modeling and network-based systems biology approaches, we identify a correlation between the extent of cell-state changes associated with tumor-enriched mtDNA mutations and the selective pressures shaping their distribution among individual leukemic cells. Our findings also reveal an association between specific heteroplasmic mtDNA mutations and cellular responses that may contribute to functional heterogeneity among leukemic cells and influence their fitness. This study highlights the potential of SCS strategies for distinguishing between pathogenic and passenger somatic mtDNA mutations in cancer.

DOI: https://doi.org/10.1101/2024.09.26.24314381
EMBO J. 2024 Oct 18.

The mitochondrial long non-coding RNA lncMtloop regulates mitochondrial transcription and suppresses Alzheimer's disease.

Wandi Xiong, Kaiyu Xu, Jacquelyne Ka-Li Sun, Siling Liu, Baizhen Zhao, Jie Shi, Karl Herrup, Hei-Man Chow, Lin Lu, Jiali Li.

  Maintaining mitochondrial homeostasis is crucial for cell survival and organismal health, as evidenced by the links between mitochondrial dysfunction and various diseases, including Alzheimer's disease (AD). Here, we report that lncMtDloop, a non-coding RNA of unknown function encoded within the D-loop region of the mitochondrial genome, maintains mitochondrial RNA levels and function with age. lncMtDloop expression is decreased in the brains of both human AD patients and 3xTg AD mouse models. Furthermore, lncMtDloop binds to mitochondrial transcription factor A (TFAM), facilitates TFAM recruitment to mtDNA promoters, and increases mitochondrial transcription. To allow lncMtDloop transport into mitochondria via the PNPASE-dependent trafficking pathway, we fused the 3'UTR localization sequence of mitochondrial ribosomal protein S12 (MRPS12) to its terminal end, generating a specified stem-loop structure. Introducing this allotropic lncMtDloop into AD model mice significantly improved mitochondrial function and morphology, and ameliorated AD-like pathology and behavioral deficits of AD model mice. Taken together, these data provide insights into lncMtDloop as a regulator of mitochondrial transcription and its contribution to Alzheimer's pathogenesis.

Keywords:   lncMtDloop ; Alzheimer’s Disease; Mitochondrial Homeostasis; TFAM; mtDNA

DOI:  https://doi.org/10.1038/s44318-024-00270-7
Cell Death Differ. 2024 Oct 15.

Inhibition of BAK-mediated apoptosis by the BH3-only protein BNIP5.

Sebastian Rühl, Zhenrui Li, Shagun Srivastava, Luigi Mari, Clifford S Guy, Mao Yang, Tudor Moldoveanu, Douglas R Green.

BCL-2 family proteins regulate apoptosis by initiating mitochondrial outer membrane permeabilization (MOMP). Activation of the MOMP effectors BAX and BAK is controlled by the interplay of anti-apoptotic BCL-2 proteins (e.g., MCL-1) and pro-apoptotic BH3-only proteins (e.g., BIM). Using a genome-wide CRISPR-dCas9 transactivation screen we identified BNIP5 as an inhibitor of BAK-, but not BAX-induced apoptosis. BNIP5 blocked BAK activation in different cell types and in response to various cytotoxic therapies. The BH3 domain of BNIP5 was both necessary and sufficient to block BAK activation. Mechanistically, the BH3 domain of BNIP5 acts as a selective BAK activator, but a poor de-repressor of complexes between BAK and pro-survival BCL-2 family proteins. By promoting the binding of activated BAK to MCL-1 or BCL-xL, BNIP5 inhibits apoptosis when BAX is absent. Based on our observations, BNIP5 can act functionally as an anti-apoptotic BH3-only protein.

DOI: https://doi.org/10.1038/s41418-024-01386-3
Nat Commun. 2024 Oct 18. 15(1): 9008

Post-transcriptional methylation of mitochondrial-tRNA differentially contributes to mitochondrial pathology.

Sunita Maharjan, Howard Gamper, Yuka Yamaki, Thomas Christian, Robert Y Henley, Nan-Sheng Li, Takeo Suzuki, Tsutomu Suzuki, Joseph A Piccirilli, Meni Wanunu, Erin Seifert, Douglas C Wallace, Ya-Ming Hou.

Human mitochondrial tRNAs (mt-tRNAs), critical for mitochondrial biogenesis, are frequently associated with pathogenic mutations. These mt-tRNAs have unusual sequence motifs and require post-transcriptional modifications to stabilize their fragile structures. However, whether a modification that stabilizes a wild-type (WT) mt-tRNA would also stabilize its pathogenic variants is unknown. Here we show that the N1-methylation of guanosine at position 9 (m1G9) of mt-Leu(UAA), while stabilizing the WT tRNA, has a destabilizing effect on variants associated with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes). This differential effect is further demonstrated, as removal of the m1G9 methylation, while damaging to the WT tRNA, is beneficial to the major pathogenic variant, improving the structure and activity of the variant. These results have therapeutic implications, suggesting that the N1-methylation of mt-tRNAs at position 9 is a determinant of pathogenicity and that controlling the methylation level is an important modulator of mt-tRNA-associated diseases.

DOI: https://doi.org/10.1038/s41467-024-53318-x
Nucleus. 2024 Dec;15(1): 2413501

Apoptosis-induced translocation of nesprin-2 from the nuclear envelope to mitochondria is associated with mitochondrial dysfunction.

Hila Zohar, Liora Lindenboim, Oren Gozlan, Gregg G Gundersen, Howard J Worman, Reuven Stein.

  Accumulating evidence suggests that the nuclear envelope (NE) is not just a target, but also a mediator of apoptosis. We showed recently that the NE protein nesprin-2 has pro-apoptotic activity, which involves its subcellular redistribution and Bcl-2 proteins. Here we further characterize the pro-apoptotic activity of nesprin-2 focusing on its redistribution. We assessed the redistribution kinetics of endogenous nesprin-2 tagged with GFP relative to apoptosis-associated mitochondrial dysfunction. The results show apoptosis-induced GFP-nesprin-2G redistribution occurred by two different modes - complete and partial, both lead to appearance of nesprin-2G near the mitochondria. Moreover, GFP-nesprin-2 redistribution is associated with reduction in mitochondrial membrane potential and mitochondrial outer membrane permeabilization and precedes the appearance of morphological features of apoptosis. Our results show that nesprin-2G redistribution and translocation near mitochondria is an early apoptotic effect associated with mitochondrial dysfunction, which may be responsible for the pro-apoptotic function of nesprin-2.

Keywords:  Apoptosis; LINC complex; mitochondria; nesprin-2; nuclear envelope; nucleus

DOI:  https://doi.org/10.1080/19491034.2024.2413501
Nat Metab. 2024 Oct 15.

Itaconate drives mtRNA-mediated type I interferon production through inhibition of succinate dehydrogenase.

Shane M O'Carroll, Christian G Peace, Juliana E Toller-Kawahisa, Yukun Min, Alexander Hooftman, Sara Charki, Louise Kehoe, Maureen J O'Sullivan, Aline Zoller, Anne F Mcgettrick, Emily A Day, Maria Simarro, Neali Armstrong, Justin P Annes, Luke A J O'Neill.

Itaconate is one of the most highly upregulated metabolites in inflammatory macrophages and has been shown to have immunomodulatory properties. Here, we show that itaconate promotes type I interferon production through inhibition of succinate dehydrogenase (SDH). Using pharmacological and genetic approaches, we show that SDH inhibition by endogenous or exogenous itaconate leads to double-stranded mitochondrial RNA (mtRNA) release, which is dependent on the mitochondrial pore formed by VDAC1. In addition, the double-stranded RNA sensors MDA5 and RIG-I are required for IFNβ production in response to SDH inhibition by itaconate. Collectively, our data indicate that inhibition of SDH by itaconate links TCA cycle modulation to type I interferon production through mtRNA release.

DOI: https://doi.org/10.1038/s42255-024-01145-1
Aging Cell. 2024 Sep;23(9): e14242

Single-cell mitochondrial sequencing reveals low-frequency mitochondrial mutations in naturally aging mice.

Fuyan Liu, Xiaolin Sun, Cai Wei, Liu Ji, Yali Song, Chenlu Yang, Yue Wang, Xin Liu, Daqing Wang, Jingmin Kang.

  Mitochondria play a crucial role in numerous biological processes; however, limited methods and research have focused on revealing mitochondrial heterogeneity at the single-cell level. In this study, we optimized the DNBelab C4 single-cell ATAC (assay for transposase-accessible chromatin) sequencing workflow for single-cell mitochondrial sequencing (C4_mtscATAC-seq). We validated the effectiveness of our C4_mtscATAC-seq protocol by sequencing the HEK-293T cell line with two biological replicates, successfully capturing both mitochondrial content (~68% of total sequencing data) and open chromatin status simultaneously. Subsequently, we applied C4_mtscATAC-seq to investigate two mouse tissues, spleen and bone marrow, obtained from two mice aged 2 months and two mice aged 23 months. Our findings revealed higher mitochondrial DNA (mtDNA) content in young tissues compared to more variable mitochondrial content in aged tissues, consistent with higher activity scores of nuclear genes associated with mitochondrial replication and transcription in young tissues. We detected a total of 22, 15, and 21 mtDNA mutations in the young spleen, aged spleen, and bone marrow, respectively, with most variant allele frequencies (VAF) below 1%. Moreover, we observed a higher number of mtDNA mutations with higher VAF in aged tissues compared to young tissues. Importantly, we identified three mtDNA variations (m.9821A>T, m.15219T>C, and m.15984C>T) with the highest VAF in both aged spleen and aged bone marrow. By comparing cells with and without these mtDNA variations, we analyzed differential open chromatin status to identify potential genes associated with these mtDNA variations, including transcription factors such as KLF15 and NRF1. Our study presents an alternative single-cell mitochondrial sequencing method and provides crude insights into age-related single-cell mitochondrial variations.

Keywords:  ATAC; aging; mitochondrial DNA (mtDNA); mitochondrial mutation; single cell sequencing

DOI:  https://doi.org/10.1111/acel.14242
Cell Rep. 2024 Oct 16. pii: S2211-1247(24)01240-3. [Epub ahead of print]43(11): 114889

A mitochondrial unfolded protein response-independent role of DVE-1 in longevity regulation.

Yi Sheng, Adriana Abreu, Zachary Markovich, Pearl Ebea, Leah Davis, Eric Park, Peike Sheng, Mingyi Xie, Sung Min Han, Rui Xiao.

  The special AT-rich sequence-binding (SATB) protein DVE-1 is widely recognized for its pivotal involvement in orchestrating the retrograde mitochondrial unfolded protein response (mitoUPR) in C. elegans. In our study of downstream factors contributing to lifespan extension in sensory ciliary mutants, we find that DVE-1 is crucial for this longevity effect independent of its canonical mitoUPR function. Additionally, DVE-1 also influences lifespan under conditions of dietary restriction and germline loss, again distinct from its role in mitoUPR. Mechanistically, while mitochondrial stress typically prompts nuclear accumulation of DVE-1 to initiate the transcriptional mitoUPR program, these long-lived mutants reduce DVE-1 nuclear accumulation, likely by enhancing its cytosolic translocation. This observation suggests a cytosolic role for DVE-1 in lifespan extension. Overall, our study implies that, in contrast to the more narrowly defined role of the mitoUPR-related transcription factor ATFS-1, DVE-1 may possess broader functions than previously recognized in modulating longevity and defending against stress.

Keywords:  ATFS-1; C. elegans; CP: Cell biology; CP: Molecular biology; DVE-1; cilia; dietary restriction; germline signaling; longevity; mitoUPR

DOI:  https://doi.org/10.1016/j.celrep.2024.114889
Nat Metab. 2024 Oct 14.

Brown fat ATP-citrate lyase links carbohydrate availability to thermogenesis and guards against metabolic stress.

Ekaterina D Korobkina, Camila Martinez Calejman, John A Haley, Miranda E Kelly, Huawei Li, Maria Gaughan, Qingbo Chen, Hannah L Pepper, Hafsah Ahmad, Alexander Boucher, Shelagh M Fluharty, Te-Yueh Lin, Anoushka Lotun, Jessica Peura, Sophie Trefely, Courtney R Green, Paula Vo, Clay F Semenkovich, Jason R Pitarresi, Jessica B Spinelli, Ozkan Aydemir, Christian M Metallo, Matthew D Lynes, Cholsoon Jang, Nathaniel W Snyder, Kathryn E Wellen, David A Guertin.

Brown adipose tissue (BAT) engages futile fatty acid synthesis-oxidation cycling, the purpose of which has remained elusive. Here, we show that ATP-citrate lyase (ACLY), which generates acetyl-CoA for fatty acid synthesis, promotes thermogenesis by mitigating metabolic stress. Without ACLY, BAT overloads the tricarboxylic acid cycle, activates the integrated stress response (ISR) and suppresses thermogenesis. ACLY's role in preventing BAT stress becomes critical when mice are weaned onto a carbohydrate-plentiful diet, while removing dietary carbohydrates prevents stress induction in ACLY-deficient BAT. ACLY loss also upregulates fatty acid synthase (Fasn); yet while ISR activation is not caused by impaired fatty acid synthesis per se, deleting Fasn and Acly unlocks an alternative metabolic programme that overcomes tricarboxylic acid cycle overload, prevents ISR activation and rescues thermogenesis. Overall, we uncover a previously unappreciated role for ACLY in mitigating mitochondrial stress that links dietary carbohydrates to uncoupling protein 1-dependent thermogenesis and provides fundamental insight into the fatty acid synthesis-oxidation paradox in BAT.

DOI: https://doi.org/10.1038/s42255-024-01143-3
Nat Metab. 2024 Oct 18.

Farnesyl pyrophosphate potentiates dendritic cell migration in autoimmunity through mitochondrial remodelling.

Xiaomin Zhang, Yali Chen, Geng Sun, Yankang Fei, Ha Zhu, Yanfang Liu, Junyan Dan, Chunzhen Li, Xuetao Cao, Juan Liu.

Cellular metabolism modulates dendritic cell (DC) maturation and activation. Migratory dendritic cells (mig-DCs) travelling from the tissues to draining lymph nodes (dLNs) are critical for instructing adaptive immune responses. However, how lipid metabolites influence mig-DCs in autoimmunity remains elusive. Here, we demonstrate that farnesyl pyrophosphate (FPP), an intermediate of the mevalonate pathway, accumulates in mig-DCs derived from mice with systemic lupus erythematosus (SLE). FPP promotes mig-DC survival and germinal centre responses in the dLNs by coordinating protein geranylgeranylation and mitochondrial remodelling. Mechanistically, FPP-dependent RhoA geranylgeranylation promotes mitochondrial fusion and oxidative respiration through mitochondrial RhoA-MFN interaction, which subsequently facilitates the resolution of endoplasmic reticulum stress in mig-DCs. Simvastatin, a chemical inhibitor of the mevalonate pathway, restores mitochondrial function in mig-DCs and ameliorates systemic pathogenesis in SLE mice. Our study reveals a critical role for FPP in dictating mig-DC survival by reprogramming mitochondrial structure and metabolism, providing new insights into the pathogenesis of DC-dependent autoimmune diseases.

DOI: https://doi.org/10.1038/s42255-024-01149-x
Aging Cell. 2024 Sep;23(9): e14240

A new gene signature for endothelial senescence identifies self-RNA sensing by retinoic acid-inducible gene I as a molecular facilitator of vascular aging.

Jasenka Guduric-Fuchs, Edoardo Pedrini, Pietro M Bertelli, Shannon McDonnell, Varun Pathak, Kiran McLoughlin, Christina L O'Neill, Alan W Stitt, Reinhold J Medina.

  The number of senescent vascular endothelial cells increases during aging and their dysfunctional phenotype contributes to age-related cardiovascular disease. Identification of senescent cells is challenging as molecular changes are often tissue specific and occur amongst clusters of normal cells. Here, we established, benchmarked, and validated a new gene signature called EndoSEN that pinpoints senescent endothelial cells. The EndoSEN signature was enriched for interferon-stimulated genes (ISG) and correlated with the senescence-associated secretory phenotype (SASP). SASP establishment is classically attributed to DNA damage and cyclic GMP-AMP synthase activation, but our results revealed a pivotal role for RNA accumulation and sensing in senescent endothelial cells. Mechanistically, we showed that endothelial cell senescence hallmarks include self-RNA accumulation, RNA sensor RIG-I upregulation, and an ISG signature. Moreover, a virtual model of RIG-I knockout in endothelial cells underscored senescence as a key pathway regulated by this sensor. We tested and confirmed that RIG-I knockdown was sufficient to extend the lifespan and decrease the SASP in endothelial cells. Taken together, our evidence suggests that targeting RNA sensing is a potential strategy to delay vascular aging.

Keywords:  RNA sensing; cardiovascular diseases; cellular senescence; endothelial cells; senescence‐associated secretory phenotype

DOI:  https://doi.org/10.1111/acel.14240
EMBO J. 2024 Oct 17.

Autophagy adaptors mediate Parkin-dependent mitophagy by forming sheet-like liquid condensates.

Zi Yang, Saori R Yoshii, Yuji Sakai, Jing Zhang, Haruka Chino, Roland L Knorr, Noboru Mizushima.

  During PINK1- and Parkin-mediated mitophagy, autophagy adaptors are recruited to damaged mitochondria to promote their selective degradation. Autophagy adaptors such as optineurin (OPTN) and NDP52 facilitate mitophagy by recruiting the autophagy-initiation machinery, and assisting engulfment of damaged mitochondria through binding to ubiquitinated mitochondrial proteins and autophagosomal ATG8 family proteins. Here, we demonstrate that OPTN and NDP52 form sheet-like phase-separated condensates with liquid-like properties on the surface of ubiquitinated mitochondria. The dynamic and liquid-like nature of OPTN condensates is important for mitophagy activity, because reducing the fluidity of OPTN-ubiquitin condensates suppresses the recruitment of ATG9 vesicles and impairs mitophagy. Based on these results, we propose a dynamic liquid-like, rather than a stoichiometric, model of autophagy adaptors to explain the interactions between autophagic membranes (i.e., ATG9 vesicles and isolation membranes) and mitochondrial membranes during Parkin-mediated mitophagy. This model underscores the importance of liquid-liquid phase separation in facilitating membrane-membrane contacts, likely through the generation of capillary forces.

Keywords:  Autophagy; Liquid–Liquid Phase Separation; Mitophagy; Optineurin; Wetting

DOI:  https://doi.org/10.1038/s44318-024-00272-5
Immunol Rev. 2024 Oct 17.

Regulation of the NLRP3 inflammasome by autophagy and mitophagy.

Suman Gupta, Suzanne L Cassel, Fayyaz S Sutterwala, Jargalsaikhan Dagvadorj.

  The NLRP3 inflammasome is a multiprotein complex that upon activation by the innate immune system drives a broad inflammatory response. The primary initial mediators of this response are pro-IL-1β and pro-IL-18, both of which are in an inactive form. Formation and activation of the NLRP3 inflammasome activates caspase-1, which cleaves pro-IL-1β and pro-IL-18 and triggers the formation of gasdermin D pores. Gasdermin D pores allow for the secretion of active IL-1β and IL-18 initiating the organism-wide inflammatory response. The NLRP3 inflammasome response can be beneficial to the host; however, if the NLRP3 inflammasome is inappropriately activated it can lead to significant pathology. While the primary components of the NLRP3 inflammasome are known, the precise details of assembly and activation are less well defined and conflicting. Here, we discuss several of the proposed pathways of activation of the NLRP3 inflammasome. We examine the role of subcellular localization and the reciprocal regulation of the NLRP3 inflammasome by autophagy. We focus on the roles of mitochondria and mitophagy in activating and regulating the NLRP3 inflammasome. Finally, we detail the impact of pathologic NLRP3 responses in the development and manifestations of pulmonary disease.

Keywords:  NLRP3; caspase‐1; inflammasome; lung injury; mitochondria

DOI:  https://doi.org/10.1111/imr.13410
Redox Biol. 2024 Oct 11. pii: S2213-2317(24)00371-9. [Epub ahead of print]77 103393

Monoamine oxidases: A missing link between mitochondria and inflammation in chronic diseases ?

Lise Beucher, Claudie Gabillard-Lefort, Olivier R Baris, Jeanne Mialet-Perez.

  The role of mitochondria spans from the regulation of the oxidative phosphorylation, cell metabolism and survival/death pathways to a more recently identified function in chronic inflammation. In stress situations, mitochondria release some pro-inflammatory mediators such as ATP, cardiolipin, reactive oxygen species (ROS) or mitochondrial DNA, that are believed to participate in chronic diseases and aging. These mitochondrial Damage-Associated Molecular Patterns (mito-DAMPs) can modulate specific receptors among which TLR9, NLRP3 and cGAS-STING, triggering immune cells activation and sterile inflammation. In order to counter the development of chronic diseases, a better understanding of the underlying mechanisms of low grade inflammation induced by mito-DAMPs is needed. In this context, monoamine oxidases (MAO), the mitochondrial enzymes that degrade catecholamines and serotonin, have recently emerged as potent regulators of chronic inflammation in obesity-related disorders, cardiac diseases, cancer, rheumatoid arthritis and pulmonary diseases. The role of these enzymes in inflammation embraces their action in both immune and non-immune cells, where they regulate monoamines levels and generate toxic ROS and aldehydes, as by-products of enzymatic reaction. Here, we discuss the more recent advances on the role and mechanisms of action of MAOs in chronic inflammatory diseases.

Keywords:  Chronic diseases; DAMPs; Inflammation; Mitochondria; Monoamine oxidases; Oxidative stress

DOI:  https://doi.org/10.1016/j.redox.2024.103393
bioRxiv. 2024 Oct 11. pii: 2024.10.10.617645. [Epub ahead of print]

cGAS deficient mice display premature aging associated with de-repression of LINE1 elements and inflammation.

John C Martinez, Francesco Morandini, Lucinda Fitzgibbons, Natasha Sieczkiewicz, Sung Jae Bae, Michael E Meadow, Eric Hillpot, Joseph Cutting, Victoria Paige, Seyed Ali Biashad, Matthew Simon, John Sedivy, Andrei Seluanov, Vera Gorbunova.

Aging-associated inflammation, or 'inflammaging" is a driver of multiple age-associated diseases. Cyclic GMP-AMP Synthase (cGAS) is a cytosolic DNA sensor that functions to activate interferon response upon detecting viral DNA in the cytoplasm. cGAS contributes to inflammaging by responding to endogenous signals such as damaged DNA or LINE1 (L1) cDNA which forms in aged cells. While cGAS knockout mice are viable their aging has not been examined. Unexpectedly, we found that cGAS knockout mice exhibit accelerated aging phenotype associated with induction of inflammation. Transcription of L1 elements was increased in both cGAS knockout mice and in cGAS siRNA knockdown cells associated with high levels of cytoplasmic L1 DNA and expression of ORF1 protein. Cells from cGAS knockout mice showed increased chromatin accessibility and decreased DNA methylation on L1 transposons. Stimulated emission depletion microscopy (STED) showed that cGAS forms nuclear condensates that co-localize with H3K9me3 heterochromatin marks, and H3K9me3 pattern is disrupted in cGAS knockout cells. Taken together these results suggest a previously undescribed role for cGAS in maintaining heterochromatin on transposable elements. We propose that loss of cGAS leads to loss of chromatin organization, de-repression of transposable elements and induction of inflammation resulting in accelerated aging.

DOI: https://doi.org/10.1101/2024.10.10.617645
Nat Neurosci. 2024 Oct 15.

A cross-disease resource of living human microglia identifies disease-enriched subsets and tool compounds recapitulating microglial states.

John F Tuddenham, Mariko Taga, Verena Haage, Victoria S Marshe, Tina Roostaei, Charles White, Annie J Lee, Masashi Fujita, Anthony Khairallah, Ya Zhang, Gilad Green, Bradley Hyman, Matthew Frosch, Sarah Hopp, Thomas G Beach, Geidy E Serrano, John Corboy, Naomi Habib, Hans-Ulrich Klein, Rajesh Kumar Soni, Andrew F Teich, Richard A Hickman, Roy N Alcalay, Neil Shneider, Julie Schneider, Peter A Sims, David A Bennett, Marta Olah, Vilas Menon, Philip L De Jager.

Human microglia play a pivotal role in neurological diseases, but we still have an incomplete understanding of microglial heterogeneity, which limits the development of targeted therapies directly modulating their state or function. Here, we use single-cell RNA sequencing to profile 215,680 live human microglia from 74 donors across diverse neurological diseases and CNS regions. We observe a central divide between oxidative and heterocyclic metabolism and identify microglial subsets associated with antigen presentation, motility and proliferation. Specific subsets are enriched in susceptibility genes for neurodegenerative diseases or the disease-associated microglial signature. We validate subtypes in situ with an RNAscope-immunofluorescence pipeline and high-dimensional MERFISH. We also leverage our dataset as a classification resource, finding that induced pluripotent stem cell model systems capture substantial in vivo heterogeneity. Finally, we identify and validate compounds that recapitulate certain subtypes in vitro, including camptothecin, which downregulates the signature of disease-enriched subtypes and upregulates a signature previously associated with Alzheimer's disease.

DOI: https://doi.org/10.1038/s41593-024-01764-7
Immunity. 2024 Oct 09. pii: S1074-7613(24)00457-6. [Epub ahead of print]

CRISPR screens unveil nutrient-dependent lysosomal and mitochondrial nodes impacting intestinal tissue-resident memory CD8+ T cell formation.

Jana L Raynor, Nicholas Collins, Hao Shi, Cliff Guy, Jordy Saravia, Seon Ah Lim, Nicole M Chapman, Peipei Zhou, Yan Wang, Yu Sun, Isabel Risch, Haoran Hu, Anil Kc, Renqiang Sun, Sharad Shrestha, Hongling Huang, Jon P Connelly, Shondra M Pruett-Miller, Miguel Reina-Campos, Ananda W Goldrath, Yasmine Belkaid, Hongbo Chi.

  Nutrient availability and organelle biology direct tissue homeostasis and cell fate, but how these processes orchestrate tissue immunity remains poorly defined. Here, using in vivo CRISPR-Cas9 screens, we uncovered organelle signaling and metabolic processes shaping CD8+ tissue-resident memory T (TRM) cell development. TRM cells depended on mitochondrial translation and respiration. Conversely, three nutrient-dependent lysosomal signaling nodes-Flcn, Ragulator, and Rag GTPases-inhibited intestinal TRM cell formation. Depleting these molecules or amino acids activated the transcription factor Tfeb, thereby linking nutrient stress to TRM programming. Further, Flcn deficiency promoted protective TRM cell responses in the small intestine. Mechanistically, the Flcn-Tfeb axis restrained retinoic acid-induced CCR9 expression for migration and transforming growth factor β (TGF-β)-mediated programming for lineage differentiation. Genetic interaction screening revealed that the mitochondrial protein Mrpl52 enabled early TRM cell formation, while Acss1 controlled TRM cell development under Flcn deficiency-associated lysosomal dysregulation. Thus, the interplay between nutrients, organelle signaling, and metabolic adaptation dictates tissue immunity.

Keywords:  CD8 T cell; adaptive immunity; dietary intervention; immunometabolism; lysosome; mitochondria; tissue-resident memory

DOI:  https://doi.org/10.1016/j.immuni.2024.09.013
Thyroid. 2024 Oct 14.

Mitophagy Defects Exacerbate Inflammation and Aberrant Proliferation in Lymphocytic Thyroiditis.

Han Sai Lee, Jinju Lee, Hyun-Ju An, Min-Ji Sung, Jin-Hyung Heo, So-Young Lee, Young Shin Song.

  Background: Mitochondrial dysfunction in the thyroid due to defective mitophagy has been observed in lymphocytic thyroiditis (LT). However, the effect of impaired mitophagy on the pathogenesis of LT is not well understood. The aim of this study is to investigate the role of mitophagy dysregulation in the thyroid gland. Methods: We analyzed RNA sequencing data of human thyroid glands with/without LT from Genotype-Tissue Expression (GTEx; n = 653) and performed RNA sequencing in thyroid glands of phosphatase and tensin homolog-induced putative protein kinase 1 (Pink1) knock-out and wild-type mice. We evaluated the phenotypic and histopathologic characteristics of the human (n = 16) and mouse thyroids. Additionally, we assessed cell proliferation, reactive oxygen species (ROS) production, and cytokine secretion of human thyroid epithelial cells (HTori-3) treated with PINK1 siRNA or a mitophagy inhibitor. Results: We found that expression of PINK1, a key regulator of mitophagy, was compromised in human thyroids with LT. Thyroid glands of Pink1-deficient mice exhibited increased inflammatory responses and nodular hyperplasia. Furthermore, mitophagy defects led to the production of pro-inflammatory cytokines and ROS in thyroid cells, resulting in immune cell recruitment. Notably, these mitophagy defects upregulated both the RNA expression and protein secretion of amphiregulin (AREG), an epidermal growth factor receptor (EGFR) ligand, in thyroid cells, while decreasing the protein expression of cAMP response element-binding protein (CREB), a transcription factor that suppresses AREG transcription. Finally, we demonstrated that aberrant cell proliferation in thyroid cells, driven by mitophagy defects, was mitigated after treatment with cetuximab, an EGFR inhibitor. Conclusions: In this study, we observed that mitophagy defects in the thyroid not only intensify inflammation through the accumulation of ROS, cytokine production, and immune cell recruitment but also contribute to hyperplasia via the EGFR pathway, facilitated by increased secretion of AREG from thyroid cells.

Keywords:  PINK1; RNA sequencing; hyperplasia; inflammation; lymphocytic thyroiditis; mitophagy

DOI:  https://doi.org/10.1089/thy.2024.0125
J Biol Chem. 2024 Oct 10. pii: S0021-9258(24)02385-8. [Epub ahead of print] 107883

Type I interferon signaling and peroxisomal dysfunction contribute to enhanced inflammatory cytokine production in Irgm1-deficient macrophages.

Brian E Fee, Lanette R Fee, Mark Menechella, Bethann Affeldt, Aemilia R Sprouse, Amina Bounini, Yazan Alwarawrah, Caitlyn T Molloy, Olga R Ilkayeva, Joseph A Prinz, Devi Swain Lenz, Nancie J MacIver, Prashant Rai, Michael B Fessler, Jörn Coers, Gregory A Taylor.

  The human IRGM gene has been linked to inflammatory diseases including sepsis and Crohn's disease. Decreased expression of human IRGM, or of the mouse orthologues Irgm1 and Irgm2, leads to increased production of a number of inflammatory chemokines and cytokines in vivo and/or in cultured macrophages. Prior work has indicated that increased cytokine production is instigated by metabolic alterations and by changes in mitochondrial homeostasis; however, a comprehensive mechanism has not been elucidated. In the studies presented here, RNA deep sequencing and quantitative PCR were used to show that increases in cytokine production, as well as most changes in the transcriptional profile of Irgm1-/- bone marrow-derived macrophages (BMM), are dependent on increased type I IFN production seen in those cells. Metabolic alterations that drive increased cytokines in Irgm1-/- BMM - specifically increases in glycolysis and increased accumulation of acyl-carnitines - were unaffected by quenching type I IFN signaling. Dysregulation of peroxisomal homeostasis was identified as a novel upstream pathway that governs type I IFN production and inflammatory cytokine production. Collectively, these results enhance our understanding of the complex biochemical changes that are triggered by lack of Irgm1 and contribute to inflammatory disease seen with Irgm1-deficiency.

Keywords:  GTPase; cytokine induction; interferon; macrophage; peroxisome

DOI:  https://doi.org/10.1016/j.jbc.2024.107883
Sci Rep. 2024 10 15. 14(1): 24185

Examining transfer of TERT to mitochondria under oxidative stress.

Dmitrii Burkatovskii, Andrey Bogorodskiy, Ivan Maslov, Olga Moiseeva, Roman Chuprov-Netochin, Ekaterina Smirnova, Nikolay Ilyinsky, Alexey Mishin, Sergey Leonov, Georg Bueldt, Valentin Gordeliy, Thomas Gensch, Valentin Borshchevskiy.

  The primary role of telomerase is the lengthening of telomeres. Nonetheless, emerging evidence highlights additional functions of telomerase outside of the nucleus. Specifically, its catalytic subunit, TERT (Telomerase Reverse Transcriptase), is detected in the cytosol and mitochondria. Several studies have suggested an elevation in TERT concentration within mitochondria in response to oxidative stress. However, the origin of this mitochondrial TERT, whether transported from the nucleus or synthesized de novo, remains uncertain. In this study, we investigate the redistribution of TERT, labeled with a SNAP-tag, in response to oxidative stress using laser scanning fluorescence microscopy. Our findings reveal that, under our experimental conditions, there is no discernible transport of TERT from the nucleus to the mitochondria due to oxidative stress.

Keywords:  Mitochondria; Oxidative stress; Protein transport; SNAP-tag; TERT

DOI:  https://doi.org/10.1038/s41598-024-75127-4