bims-celmim 2024-08-04 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2024‒08‒04
twenty-two papers selected by
Marc Segarra Mondejar

A three-way organelle junction controls PI(4)P metabolism and mitochondrial division.
The significant role of amino acid metabolic reprogramming in cancer.
Inhibition of mitochondrial citrate shuttle alleviates metabolic syndromes induced by high-fat diet.
The potential role of gut microbiota-derived metabolites as regulators of metabolic syndrome-associated mitochondrial and endolysosomal dysfunction in Alzheimer's disease.
Remodeling of T-cell mitochondrial metabolism to treat autoimmune diseases.
Opa1 processing is dispensable in mouse development but is protective in mitochondrial cardiomyopathy.
Significantly reduced, but balanced, rates of mitochondrial fission and fusion are sufficient to maintain the integrity of yeast mitochondrial DNA.
Lactate-carried Mitochondrial Energy Overflow.
Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases.
Mitochondria-Targeted Multifunctional Nanoprodrugs by Inhibiting Metabolic Reprogramming for Combating Cisplatin-Resistant Lung Cancer.
Recent advances in fluorescent probes for ATP imaging.
The pyruvate dehydrogenase complex at the epigenetic crossroads of acetylation and lactylation.
ASCT2 is a major contributor to serine uptake in cancer cells.
The TOM complex from an evolutionary perspective and the functions of TOMM70.
Novel Imaging Tools to Study Mitochondrial Dynamics in Caenorhabditis elegans.
Epigenetic control of metabolic identity across cell types.
mTORC1 activity oscillates throughout the cell cycle, promoting mitotic entry and differentially influencing autophagy induction.
AutoMitoNetwork: Software for analyzing mitochondrial networks in autofluorescence images to enable label-free cell classification.
Mitochondrial bioenergetics and cardiolipin remodeling abnormalities in mitochondrial trifunctional protein deficiency.
Phosphorylation of PFKL regulates metabolic reprogramming in macrophages following pattern recognition receptor activation.
Stable isotope-resolved metabolomics analyses of metabolic phenotypes reveal variable glutamine metabolism in different patient-derived models of non-small cell lung cancer from a single patient.
Dissociating the metabolic and tumor-suppressive activity of p53.

J Cell Biol. 2024 Sep 02. pii: e202407125. [Epub ahead of print]223(9):

A three-way organelle junction controls PI(4)P metabolism and mitochondrial division.

York Posor, Volker Haucke.

Membrane contact sites (MCS) facilitate communication between organelles. Casler et al. (https://doi.org/10.1083/jcb.202308144) show that tripartite MCS between mitochondria, the endoplasmic reticulum (ER), and the plasma membrane (PM) regulate mitochondrial division and the distribution of phosphatidylinositol 4-phosphate [PI(4)P] on the PM.

DOI: https://doi.org/10.1083/jcb.202407125
Cell Commun Signal. 2024 Jul 29. 22(1): 380

The significant role of amino acid metabolic reprogramming in cancer.

Xiaohong Liu, Bo Ren, Jie Ren, Minzhi Gu, Lei You, Yupei Zhao.

  Amino acid metabolism plays a pivotal role in tumor microenvironment, influencing various aspects of cancer progression. The metabolic reprogramming of amino acids in tumor cells is intricately linked to protein synthesis, nucleotide synthesis, modulation of signaling pathways, regulation of tumor cell metabolism, maintenance of oxidative stress homeostasis, and epigenetic modifications. Furthermore, the dysregulation of amino acid metabolism also impacts tumor microenvironment and tumor immunity. Amino acids can act as signaling molecules that modulate immune cell function and immune tolerance within the tumor microenvironment, reshaping the anti-tumor immune response and promoting immune evasion by cancer cells. Moreover, amino acid metabolism can influence the behavior of stromal cells, such as cancer-associated fibroblasts, regulate ECM remodeling and promote angiogenesis, thereby facilitating tumor growth and metastasis. Understanding the intricate interplay between amino acid metabolism and the tumor microenvironment is of crucial significance. Expanding our knowledge of the multifaceted roles of amino acid metabolism in tumor microenvironment holds significant promise for the development of more effective cancer therapies aimed at disrupting the metabolic dependencies of cancer cells and modulating the tumor microenvironment to enhance anti-tumor immune responses and inhibit tumor progression.

Keywords:  Amino acid metabolism; Angiogenesis; Epigenetic regulation; Immune tolerance; Redox; Tumor microenvironment

DOI:  https://doi.org/10.1186/s12964-024-01760-1
Am J Physiol Cell Physiol. 2024 Jul 29.

Inhibition of mitochondrial citrate shuttle alleviates metabolic syndromes induced by high-fat diet.

Jun-Xian Wang, Yan-Yu Zhang, Yu-Cheng Qian, Yi-Fan Qian, An-Hui Jin, Mai Wang, Yuan Luo, Fang Qiao, Mei-Ling Zhang, Li-Qiao Chen, Zhen-Yu Du.

  The mitochondrial citrate shuttle, which relies on the solute carrier family 25 member 1 (SLC25A1), plays a pivotal role in transporting citrate from the mitochondria to the cytoplasm. This shuttle supports glycolysis, lipid biosynthesis, and protein acetylation. Previous research has primarily focused on Slc25a1 in pathological models, particularly high-fat diet (HFD)-induced obesity. However, the impact of Slc25a1 inhibition on nutrient metabolism under HFD remains unclear. To address this gap, we used zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus) to evaluate the effects of inhibiting Slc25a1. In zebrafish, we administered Slc25a1-specific inhibitors (CTPI-2) for four weeks, while Nile tilapia received intraperitoneal injections of dsRNA to knockdown slc25a1b for seven days. Inhibition of the mitochondrial citrate shuttle effectively protected zebrafish from HFD-induced obesity, hepatic steatosis, and insulin resistance. Notably, glucose tolerance was unaffected. Inhibition of Slc25a1 altered hepatic protein acetylation patterns, with decreased cytoplasmic acetylation and increased mitochondrial acetylation. Under HFD conditions, Slc25a1 inhibition promoted fatty acid oxidation and reduced hepatic triglyceride accumulation by deacetylating Cpt1a. Additionally, Slc25a1 inhibition triggered acetylation-induced inactivation of Pdhe1α, leading to a reduction in glucose oxidative catabolism. This was accompanied by enhanced glucose uptake and storage in zebrafish livers. Furthermore, Slc25a1 inhibition under HFD conditions activated the SIRT1/PGC1α pathway, promoting mitochondrial proliferation and enhancing oxidative phosphorylation for energy production. Our findings provide new insights into the role of non-histone protein acetylation via the mitochondrial citrate shuttle in the development of hepatic lipid deposition and hyperglycemia caused by HFD.

Keywords:  metabolic syndromes; mitochondrial citrate shuttle; nutrients metabolism; protein acetylation

DOI:  https://doi.org/10.1152/ajpcell.00194.2024
Exp Mol Med. 2024 Aug 01.

The potential role of gut microbiota-derived metabolites as regulators of metabolic syndrome-associated mitochondrial and endolysosomal dysfunction in Alzheimer's disease.

Young Hyun Jung, Chang Woo Chae, Ho Jae Han.

Although the role of gut microbiota (GMB)-derived metabolites in mitochondrial and endolysosomal dysfunction in Alzheimer's disease (AD) under metabolic syndrome remains unclear, deciphering these host-metabolite interactions represents a major public health challenge. Dysfunction of mitochondria and endolysosomal networks (ELNs) plays a crucial role in metabolic syndrome and can exacerbate AD progression, highlighting the need to study their reciprocal regulation for a better understanding of how AD is linked to metabolic syndrome. Concurrently, metabolic disorders are associated with alterations in the composition of the GMB. Recent evidence suggests that changes in the composition of the GMB and its metabolites may be involved in AD pathology. This review highlights the mechanisms of metabolic syndrome-mediated AD development, focusing on the interconnected roles of mitochondrial dysfunction, ELN abnormalities, and changes in the GMB and its metabolites. We also discuss the pathophysiological role of GMB-derived metabolites, including amino acids, fatty acids, other metabolites, and extracellular vesicles, in mediating their effects on mitochondrial and ELN dysfunction. Finally, this review proposes therapeutic strategies for AD by directly modulating mitochondrial and ELN functions through targeting GMB metabolites under metabolic syndrome.

DOI: https://doi.org/10.1038/s12276-024-01282-3
Autoimmun Rev. 2024 Jul 29. pii: S1568-9972(24)00074-0. [Epub ahead of print] 103583

Remodeling of T-cell mitochondrial metabolism to treat autoimmune diseases.

Liyan Lin, Ruyu Ren, Qiao Xiong, Chunfu Zheng, Bin Yang, Huiqing Wang.

  T cells are key drivers of the pathogenesis of autoimmune diseases by producing cytokines, stimulating the generation of autoantibodies, and mediating tissue and cell damage. Distinct mitochondrial metabolic pathways govern the direction of T-cell differentiation and function and rely on specific nutrients and metabolic enzymes. Metabolic substrate uptake and mitochondrial metabolism form the foundational elements for T-cell activation, proliferation, differentiation, and effector function, contributing to the dynamic interplay between immunological signals and mitochondrial metabolism in coordinating adaptive immunity. Perturbations in substrate availability and enzyme activity may impair T-cell immunosuppressive function, fostering autoreactive responses and disrupting immune homeostasis, ultimately contributing to autoimmune disease pathogenesis. A growing body of studies has explored how metabolic processes regulate the function of diverse T-cell subsets in autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), autoimmune hepatitis (AIH), inflammatory bowel disease (IBD), and psoriasis. This review describes the coordination of T-cell biology by mitochondrial metabolism, including the electron transport chain (ETC), oxidative phosphorylation, amino acid metabolism, fatty acid metabolism, and one‑carbon metabolism. This study elucidated the intricate crosstalk between mitochondrial metabolic programs, signal transduction pathways, and transcription factors. This review summarizes potential therapeutic targets for T-cell mitochondrial metabolism and signaling in autoimmune diseases, providing insights for future studies.

Keywords:  Autoimmune diseases; Fatty acid metabolism; Mitochondrial metabolism; OXPHOS; Regulatory T cells; T helper cells; Treatment

DOI:  https://doi.org/10.1016/j.autrev.2024.103583
Sci Adv. 2024 Aug 02. 10(31): eadp0443

Opa1 processing is dispensable in mouse development but is protective in mitochondrial cardiomyopathy.

Sofia Ahola, Lilli A Pazurek, Fiona Mayer, Philipp Lampe, Steffen Hermans, Lore Becker, Oana V Amarie, Helmut Fuchs, Valerie Gailus-Durner, Martin Hrabe de Angelis, Dietmar Riedel, Hendrik Nolte, Thomas Langer.

Mitochondrial fusion and fission accompany adaptive responses to stress and altered metabolic demands. Inner membrane fusion and cristae morphogenesis depends on optic atrophy 1 (Opa1), which is expressed in different isoforms and is cleaved from a membrane-bound, long to a soluble, short form. Here, we have analyzed the physiological role of Opa1 isoforms and Opa1 processing by generating mouse lines expressing only one cleavable Opa1 isoform or a non-cleavable variant thereof. Our results show that expression of a single cleavable or non-cleavable Opa1 isoform preserves embryonic development and the health of adult mice. Opa1 processing is dispensable under metabolic and thermal stress but prolongs life span and protects against mitochondrial cardiomyopathy in OXPHOS-deficient Cox10-/- mice. Mechanistically, loss of Opa1 processing disturbs the balance between mitochondrial biogenesis and mitophagy, suppressing cardiac hypertrophic growth in Cox10-/- hearts. Our results highlight the critical regulatory role of Opa1 processing, mitochondrial dynamics, and metabolism for cardiac hypertrophy.

DOI: https://doi.org/10.1126/sciadv.adp0443
bioRxiv. 2024 Jul 19. pii: 2024.07.18.604121. [Epub ahead of print]

Significantly reduced, but balanced, rates of mitochondrial fission and fusion are sufficient to maintain the integrity of yeast mitochondrial DNA.

Brett T Wisniewski, Laura L Lackner.

Mitochondria exist as dynamic tubular networks and the morphology of these networks impacts organelle function and cell health. Mitochondrial morphology is maintained in part by the opposing activities of mitochondrial fission and fusion. Mitochondrial fission and fusion are also required to maintain mitochondrial DNA (mtDNA) integrity. In Saccharomyces cerevisiae , the simultaneous inhibition of mitochondrial fission and fusion results in increased mtDNA mutation and the consequent loss of respiratory competence. The mechanism by which fission and fusion maintain mtDNA integrity is not fully understood. Previous work demonstrates that mtDNA is spatially linked to mitochondrial fission sites. Here, we extend this finding using live-cell imaging to localize mtDNA to mitochondrial fusion sites. While mtDNA is present at sites of mitochondrial fission and fusion, mitochondrial fission and fusion rates are not altered in cells lacking mtDNA. Using alleles that alter mitochondrial fission and fusion rates, we find that mtDNA integrity can be maintained in cells with significantly reduced, but balanced, rates of fission and fusion. In addition, we find that increasing mtDNA copy number reduces the loss of respiratory competence in double mitochondrial fission-fusion mutants. Our findings add novel insights into the relationship between mitochondrial dynamics and mtDNA integrity.

DOI: https://doi.org/10.1101/2024.07.18.604121
bioRxiv. 2024 Jul 20. pii: 2024.07.19.604361. [Epub ahead of print]

Lactate-carried Mitochondrial Energy Overflow.

Daniela Rauseo, Yasna Contreras-Baeza, Hugo Faurand, Nataly Cárcamo, Raibel Suárez, Alexandra von Faber-Castell, Franco Silva, Valentina Mora-González, Matthias T Wyss, Felipe Baeza-Lehnert, Iván Ruminot, Carlos Alvarez-Navarro, Alejandro San Martín, Bruno Weber, Pamela Y Sandoval, L Felipe Barros.

We addressed the question of mitochondrial lactate metabolism using genetically-encoded sensors. The organelle was found to contain a dynamic lactate pool that leads to dose- and time-dependent protein lactylation. In neurons, mitochondrial lactate reported blood lactate levels with high fidelity. The exchange of lactate across the inner mitochondrial membrane was found to be mediated by a high affinity H+-coupled transport system involving the mitochondrial pyruvate carrier MPC. Assessment of electron transport chain activity and determination of lactate flux showed that mitochondria are tonic lactate producers, a phenomenon driven by energization and stimulated by hypoxia. We conclude that an overflow mechanism caps the redox level of mitochondria, while saving energy in the form of lactate.

DOI: https://doi.org/10.1101/2024.07.19.604361
Diabetes Metab Syndr Obes. 2024 ;17 2789-2807

Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases.

Li-Ping Ou, Yong-Jian Liu, Shi-Tong Qiu, Chen Yang, Ji-Xin Tang, Xiao-Yu Li, Hua-Feng Liu, Zhen-Nan Ye.

  Metabolic reprogramming contributes to the progression and prognosis of various kidney diseases. Glutamine is the most abundant free amino acid in the body and participates in more metabolic processes than other amino acids. Altered glutamine metabolism is a prominent feature in different kidney diseases. Glutaminolysis converts glutamine into the TCA cycle metabolite, alpha-ketoglutarate, via a cascade of enzymatic reactions. This metabolic pathway plays pivotal roles in inflammation, maladaptive repair, cell survival and proliferation, redox homeostasis, and immune regulation. Given the crucial role of glutaminolysis in bioenergetics and anaplerotic fluxes in kidney pathogenesis, studies on this cascade could provide a better understanding of kidney diseases, thus inspiring the development of potential methods for targeted therapy. Emerging evidence has shown that targeting glutaminolysis is a promising therapeutic strategy for ameliorating kidney disease. In this narrative review, equation including keywords related to glutamine, glutaminolysis and kidney are subjected to an exhaustive search on Pubmed database, we identified all relevant articles published before 1 April, 2024. Afterwards, we summarize the regulation of glutaminolysis in major kidney diseases and its underlying molecular mechanisms. Furthermore, we highlight therapeutic strategies targeting glutaminolysis and their potential clinical applications.

Keywords:  glutamine; glutaminolysis; kidney diseases; therapeutic target

DOI:  https://doi.org/10.2147/DMSO.S471711
ACS Nano. 2024 Aug 01.

Mitochondria-Targeted Multifunctional Nanoprodrugs by Inhibiting Metabolic Reprogramming for Combating Cisplatin-Resistant Lung Cancer.

Haibin Lu, Weifang Tong, Meixu Jiang, Huimin Liu, Chen Meng, Kai Wang, Xupeng Mu.

  How to address the resistance of cisplatin (CDDP) has always been a clinical challenge. The resistance mechanism of platinum-based drugs is very complex, including nuclear DNA damage repair, apoptosis escape, and tumor metabolism reprogramming. Tumor cells can switch between mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis and develop resistance to chemotherapy drugs through metabolic variability. In addition, due to the lack of histone protection and a relatively weak damage repair ability, mitochondrial DNA (mtDNA) is more susceptible to damage, which in turn affects mitochondrial OXPHOS and can become a potential target for platinum-based drugs. Therefore, mitochondria, as targets of anticancer drugs, have become a hot topic in tumor resistance research. This study constructed a self-assembled nanotargeted drug delivery system LND-SS-Pt-TPP/HA-CD. β-Cyclodextrin-grafted hydronic acid (HA-CD)-encapsulated prodrug nanoparticles can target CD44 on the tumor surface and further deliver the prodrug to intracellular mitochondria through a triphenylphosphine group (TPP+). Disulfide bonds can be selectively degraded by glutathione (GSH) in mitochondria, releasing lonidamine (LND) and the cisplatin prodrug (Pt(IV)). Under the action of GSH and ascorbic acid, Pt(IV) is further reduced to cisplatin (Pt(II)). Cisplatin can cause mtDNA damage, induce mitochondrial dysfunction and mitophagy, and then affect mitochondrial OXPHOS. Meanwhile, LND can reduce the hexokinase II (HK II) level, induce destruction of mitochondria, and block energy supply by glycolysis inhibition. Ultimately, this self-assembled nano targeted delivery system can synergistically kill cisplatin-resistant lung cancer cells, which supplies an overcome cisplatin resistance choice via the disrupt mitochondria therapy.

Keywords:  cisplatin; glutathione; glycolysis; mitochondrial; oxidative phosphorylation; triphenylphosphine group

DOI:  https://doi.org/10.1021/acsnano.4c04024
Talanta. 2024 Jul 28. pii: S0039-9140(24)01001-4. [Epub ahead of print]279 126622

Recent advances in fluorescent probes for ATP imaging.

Chen Zhang, Guanzhao Wu.

  Adenosine-5'-triphosphate (ATP) is a critical biological molecule that functions as the primary energy currency within cells. ATP synthesis occurs in the mitochondria, and variations in its concentration can significantly influence mitochondrial and cellular performance. Prior studies have established a link between ATP levels and a variety of diseases, such as cancer, neurodegenerative conditions, ischemia, and hypoglycemia. Consequently, researchers have developed many fluorescent probes for ATP detection, recognizing the importance of monitoring intracellular ATP levels to understand cellular processes. These probes have been effectively utilized for visualizing ATP in living cells and biological samples. In this comprehensive review, we categorize fluorescent sensors developed in the last five years for ATP detection. We base our classification on fluorophores, structure, multi-response channels, and application. We also evaluate the challenges and potential for advancing new generations of fluorescence imaging probes for monitoring ATP in living cells. We hope this summary motivates researchers to design innovative and effective probes tailored to ATP sensing. We foresee imminent progress in the development of highly sophisticated ATP probes.

Keywords:  ATP detection; Adenosine-5′-triphosphate; Fluorescence imaging; Nanoprobes; Small-molecule probes

DOI:  https://doi.org/10.1016/j.talanta.2024.126622
Mol Genet Metab. 2024 Jul 16. pii: S1096-7192(24)00424-4. [Epub ahead of print]143(1-2): 108540

The pyruvate dehydrogenase complex at the epigenetic crossroads of acetylation and lactylation.

Peter W Stacpoole, Carolyn O Dirain.

  The pyruvate dehydrogenase complex (PDC) is remarkable for its size and structure as well as for its physiological and pathological importance. Its canonical location is in the mitochondrial matrix, where it primes the tricarboxylic acid (TCA) cycle by decarboxylating glycolytically-derived pyruvate to acetyl-CoA. Less well appreciated is its role in helping to shape the epigenetic landscape, from early development throughout mammalian life by its ability to "moonlight" in the nucleus, with major repercussions for human healthspan and lifespan. The PDC's influence on two crucial modifiers of the epigenome, acetylation and lactylation, is the focus of this brief review.

Keywords:  Acetylation; Epigenetics; Glycolysis; Histones; Inborn metabolic disorders; Lactylation; Nuclear translocation; Pyruvate dehydrogenase complex; Tricarboxylic acid cycle

DOI:  https://doi.org/10.1016/j.ymgme.2024.108540
Cell Rep. 2024 Jul 26. pii: S2211-1247(24)00881-7. [Epub ahead of print]43(8): 114552

ASCT2 is a major contributor to serine uptake in cancer cells.

Kelly O Conger, Christopher Chidley, Mete Emir Ozgurses, Huiping Zhao, Yumi Kim, Svetlana E Semina, Philippa Burns, Vipin Rawat, Lina Lietuvninkas, Ryan Sheldon, Issam Ben-Sahra, Jonna Frasor, Peter K Sorger, Gina M DeNicola, Jonathan L Coloff.

  The non-essential amino acid serine is a critical nutrient for cancer cells due to its diverse biosynthetic functions. While some tumors can synthesize serine de novo, others are auxotrophic and therefore reliant on serine uptake. Importantly, despite several transporters being known to be capable of transporting serine, the transporters that mediate serine uptake in cancer cells are not known. Here, we characterize the amino acid transporter ASCT2 (SLC1A5) as a major contributor to serine uptake in cancer cells. ASCT2 is well known as a glutamine transporter in cancer, and our work demonstrates that serine and glutamine compete for uptake through ASCT2. We further show that ASCT2-mediated serine uptake is essential for purine nucleotide biosynthesis and that estrogen receptor α (ERα) promotes serine uptake by directly activating SLC1A5 transcription. Collectively, our work defines an additional important role for ASCT2 as a serine transporter in cancer and evaluates ASCT2 as a potential therapeutic target.

Keywords:  ASCT2; CP: Cancer; ERα; SLC1A5; amino acid uptake; breast cancer; cancer metabolism; diet; purine biosynthesis; serine starvation; serine transporter

DOI:  https://doi.org/10.1016/j.celrep.2024.114552
Biol Chem. 2024 Aug 02.

The TOM complex from an evolutionary perspective and the functions of TOMM70.

Metin Özdemir, Sven Dennerlein.

  In humans, up to 1,500 mitochondrial precursor proteins are synthesized at cytosolic ribosomes and must be imported into the organelle. This is not only essential for mitochondrial but also for many cytosolic functions. The majority of mitochondrial precursor proteins are imported over the translocase of the outer membrane (TOM). In recent years, high-resolution structure analyses from different organisms shed light on the composition and arrangement of the TOM complex. Although significant similarities have been found, differences were also observed, which have been favored during evolution and could reflect the manifold functions of TOM with cellular signaling and its response to altered metabolic situations. A key component within these regulatory mechanisms is TOMM70, which is involved in protein import, forms contacts to the ER and the nucleus, but is also involved in cellular defense mechanisms during infections.

Keywords:  TOM complex; mitochondria; mitochondrial import

DOI:  https://doi.org/10.1515/hsz-2024-0043
bioRxiv. 2024 Jul 16. pii: 2024.07.16.603730. [Epub ahead of print]

Novel Imaging Tools to Study Mitochondrial Dynamics in Caenorhabditis elegans.

Miriam Valera-Alberni, Pallas Yao, Silvia Romero-Sanz, Anne Lanjuin, William B Mair.

Mitochondria exhibit a close interplay between their structure and function. Understanding this intricate relationship requires advanced imaging techniques that can capture the dynamic nature of mitochondria and their impact on cellular processes. However, much of the work on mitochondrial dynamics has been done in single celled organisms or in vitro cell culture. Here, we introduce novel genetic tools for live imaging of mitochondrial networks in the nematode Caenorhabditis elegans , addressing a pressing need for advanced techniques in studying organelle dynamics within live intact multicellular organisms. Through a comprehensive analysis, we directly compare our tools with existing methods, demonstrating their advantages for visualizing mitochondrial morphology and contrasting their impact on organismal physiology. We reveal limitations of conventional techniques, while showcasing the utility and versatility of our approaches, including endogenous CRISPR tags and ectopic labeling. By providing a guide for selecting the most suitable tools based on experimental goals, our work advances mitochondrial research in C. elegans and enhances the strategic integration of diverse imaging modalities for a holistic understanding of organelle dynamics in living organisms.

DOI: https://doi.org/10.1101/2024.07.16.603730
bioRxiv. 2024 Jul 24. pii: 2024.07.24.604914. [Epub ahead of print]

Epigenetic control of metabolic identity across cell types.

Maria Pires Pacheco, Déborah Gerard, Riley J Mangan, Alec R Chapman, Dennis Hecker, Manolis Kellis, Marcel H Schulz, Lasse Sinkkonen, Thomas Sauter.

Constraint-based network modelling is a powerful tool for analysing cellular metabolism at genomic scale. Here, we conducted an integrative analysis of metabolic networks reconstructed from RNA-seq data with paired epigenomic data from the EpiATLAS resource of the International Human Epigenome Consortium (IHEC). Applying a state-of-the-art contextualisation algorithm, we reconstructed metabolic networks across 1,555 samples corresponding to 58 tissues and cell types. Analysis of these networks revealed the distribution of metabolic functionalities across human cell types and provides a compendium of human metabolic activity. This integrative approach allowed us to define, across tissues and cell types, i) reactions that fulfil the basic metabolic processes (core metabolism), and ii) cell type-specific functions (unique metabolism), that shape the metabolic identity of a cell or a tissue. Integration with EpiATLAS-derived cell type-specific gene-level chromatin states and enhancer-gene interactions identified enhancers, transcription factors, and key nodes controlling core and unique metabolism. Transport and first reactions of pathways were enriched for high expression, active chromatin state, and Polycomb-mediated repression in cell types where pathways are inactive, suggesting that key nodes are targets of repression. This integrative analysis forms the basis for identifying regulation points that control metabolic identity in human cells.

DOI: https://doi.org/10.1101/2024.07.24.604914
Cell Rep. 2024 Jul 26. pii: S2211-1247(24)00872-6. [Epub ahead of print]43(8): 114543

mTORC1 activity oscillates throughout the cell cycle, promoting mitotic entry and differentially influencing autophagy induction.

Jay N Joshi, Ariel D Lerner, Frank Scallo, Alexandra N Grumet, Paul Matteson, James H Millonig, Alexander J Valvezan.

  Mechanistic Target of Rapamycin Complex 1 (mTORC1) is a master metabolic regulator that is active in nearly all proliferating eukaryotic cells; however, it is unclear whether mTORC1 activity changes throughout the cell cycle. We find that mTORC1 activity oscillates from lowest in mitosis/G1 to highest in S/G2. The interphase oscillation is mediated through the TSC complex but is independent of major known regulatory inputs, including Akt and Mek/Erk signaling. By contrast, suppression of mTORC1 activity in mitosis does not require the TSC complex. mTORC1 has long been known to promote progression through G1. We find that mTORC1 also promotes progression through S and G2 and is important for satisfying the Chk1/Wee1-dependent G2/M checkpoint to allow entry into mitosis. We also find that low mTORC1 activity in G1 sensitizes cells to autophagy induction in response to partial mTORC1 inhibition or reduced nutrient levels. Together, these findings demonstrate that mTORC1 is differentially regulated throughout the cell cycle, with important phase-specific consequences for proliferating cells.

Keywords:  CDK1; CP: Cell biology; G2/M checkpoint; TSC complex; TSC2; autophagy; cell cycle; mTOR; mTORC1; mitosis

DOI:  https://doi.org/10.1016/j.celrep.2024.114543
Cytometry A. 2024 Jul 30.

AutoMitoNetwork: Software for analyzing mitochondrial networks in autofluorescence images to enable label-free cell classification.

Shannon Handley, Ayad G Anwer, Aline Knab, Akanksha Bhargava, Ewa M Goldys.

  High-resolution mitochondria imaging in combination with image analysis tools have significantly advanced our understanding of cellular function in health and disease. However, most image analysis tools for mitochondrial studies have been designed to work with fluorescently labeled images only. Additionally, efforts to integrate features describing mitochondrial networks with machine learning techniques for the differentiation of cell types have been limited. Herein, we present AutoMitoNetwork software for image-based assessment of mitochondrial networks in label-free autofluorescence images using a range of interpretable morphological, intensity, and textural features. To demonstrate its utility, we characterized unstained mitochondrial networks in healthy retinal cells and in retinal cells exposed to two types of treatments: rotenone, which directly inhibited mitochondrial respiration and ATP production, and iodoacetic acid, which had a milder impact on mitochondrial networks via the inhibition of anaerobic glycolysis. For both cases, our multi-dimensional feature analysis combined with a support vector machine classifier distinguished between healthy cells and those treated with rotenone or iodoacetic acid. Subtle changes in morphological features were measured including increased fragmentation in the treated retinal cells, pointing to an association with metabolic mechanisms. AutoMitoNetwork opens new options for image-based machine learning in label-free imaging, diagnostics, and mitochondrial disease drug development.

Keywords:  autofluorescence; biological image analysis; label‐free imaging; machine learning; mitochondria; mitochondria network

DOI:  https://doi.org/10.1002/cyto.a.24889
JCI Insight. 2024 Aug 01. pii: e176887. [Epub ahead of print]

Mitochondrial bioenergetics and cardiolipin remodeling abnormalities in mitochondrial trifunctional protein deficiency.

Eduardo Vieira Neto, Meicheng Wang, Austin J Szuminsky, Lethicia Ferraro, Erik Koppes, Yudong Wang, Clinton Van't Land, Al-Walid Mohsen, Geancarlo Zanatta, Areeg H El-Gharbawy, Tamil S Anthonymuthu, Yulia Y Tyurina, Vladimir A Tyurin, Valerian Kagan, Hülya Bayir, Jerry Vockley.

  Mitochondrial trifunctional protein (TFP) deficiency is an inherited metabolic disorder leading to a block in long-chain fatty acid β-oxidation. Mutations in either HADHA and HADHB, which encode the TFPα and β subunits, respectively, usually result in combined TFP deficiency. A single common mutation, HADHA c.1528G>C (p.E510Q), leads to isolated 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency. TFP also catalyzes a step in the remodeling of cardiolipin (CL), a phospholipid critical to mitochondrial membrane stability and function. We explored the effect of mutations in TFP subunits on CL and other phospholipid content and composition and the consequences of these changes on mitochondrial bioenergetics in patient-derived fibroblasts. Abnormalities in these parameters varied extensively among different fibroblasts, and some cells were able to maintain basal oxygen consumption rates similar to controls. Although CL reduction was universally identified, a simultaneous increase in monolysocardiolipins was discrepant among cells. A similar profile was seen in liver mitochondria isolates from a TFP-deficient mouse model. Response to new potential drugs targeting cardiolipin metabolism might be dependent on patient genotype.

Keywords:  Fatty acid oxidation; Genetics; Intermediary metabolism; Metabolism; Mitochondria

DOI:  https://doi.org/10.1172/jci.insight.176887
Nat Commun. 2024 Jul 31. 15(1): 6438

Phosphorylation of PFKL regulates metabolic reprogramming in macrophages following pattern recognition receptor activation.

Meiyue Wang, Heinrich Flaswinkel, Abhinav Joshi, Matteo Napoli, Sergi Masgrau-Alsina, Julia M Kamper, Antonia Henne, Alexander Heinz, Marleen Berouti, Niklas A Schmacke, Karsten Hiller, Elisabeth Kremmer, Benedikt Wefers, Wolfgang Wurst, Markus Sperandio, Jürgen Ruland, Thomas Fröhlich, Veit Hornung.

Innate immune responses are linked to key metabolic pathways, yet the proximal signaling events that connect these systems remain poorly understood. Here we show that phosphofructokinase 1, liver type (PFKL), a rate-limiting enzyme of glycolysis, is phosphorylated at Ser775 in macrophages following several innate stimuli. This phosphorylation increases the catalytic activity of PFKL, as shown by biochemical assays and glycolysis monitoring in cells expressing phosphorylation-defective PFKL variants. Using a genetic mouse model in which PFKL Ser775 phosphorylation cannot take place, we observe that upon activation, glycolysis in macrophages is lower than in the same cell population of wild-type animals. Consistent with their higher glycolytic activity, wild-type cells have higher levels of HIF1α and IL-1β than PfklS775A/S775A after LPS treatment. In an in vivo inflammation model, PfklS775A/S775A mice show reduced levels of MCP-1 and IL-1β. Our study thus identifies a molecular link between innate immune activation and early induction of glycolysis.

DOI: https://doi.org/10.1038/s41467-024-50104-7
Metabolomics. 2024 Jul 27. 20(4): 87

Stable isotope-resolved metabolomics analyses of metabolic phenotypes reveal variable glutamine metabolism in different patient-derived models of non-small cell lung cancer from a single patient.

Connor J Kinslow, Michael Bousamra Ll, Yihua Cai, Jun Yan, Pawel K Lorkiewicz, Ahmad Al-Attar, Jinlian Tan, Richard M Higashi, Andrew N Lane, Teresa W-M Fan.

  INTRODUCTION: Stable isotope tracers have been increasingly used in preclinical cancer model systems, including cell culture and mouse xenografts, to probe the altered metabolism of a variety of cancers, such as accelerated glycolysis and glutaminolysis and generation of oncometabolites. Comparatively little has been reported on the fidelity of the different preclinical model systems in recapitulating the aberrant metabolism of tumors.OBJECTIVES: We have been developing several different experimental model systems for systems biochemistry analyses of non-small cell lung cancer (NSCLC1) using patient-derived tissues to evaluate appropriate models for metabolic and phenotypic analyses.
METHODS: To address the issue of fidelity, we have carried out a detailed Stable Isotope-Resolved Metabolomics study of freshly resected tissue slices, mouse patient derived xenografts (PDXs), and cells derived from a single patient using both 13C6-glucose and 13C5,15N2-glutamine tracers.
RESULTS: Although we found similar glucose metabolism in the three models, glutamine utilization was markedly higher in the isolated cell culture and in cell culture-derived xenografts compared with the primary cancer tissue or direct tissue xenografts (PDX).
CONCLUSIONS: This suggests that caution is needed in interpreting cancer biochemistry using patient-derived cancer cells in vitro or in xenografts, even at very early passage, and that direct analysis of patient derived tissue slices provides the optimal model for ex vivo metabolomics. Further research is needed to determine the generality of these observations.

Keywords:  Cancer metabolism; Non-small cell lung cancer; Patient-derived xenografts; Preclinical models; Primary cell culture; Stable isotope-resolved metabolomics

DOI:  https://doi.org/10.1007/s11306-024-02126-x
Trends Endocrinol Metab. 2024 Aug 01. pii: S1043-2760(24)00199-1. [Epub ahead of print]

Dissociating the metabolic and tumor-suppressive activity of p53.

Yoshitaka Sakurai, Naoto Kubota, Takashi Kadowaki.

  The tumor suppressor p53 regulates metabolic homeostasis. Recently, Tsaousidou et al. reported that selective activation of p53 via downregulation of Tudor interacting repair regulator (TIRR) confers protection against cancer despite obesity and insulin resistance, providing new insights into the role of p53 at the intersection of oncogenesis and systemic metabolism.

Keywords:  cancer; inflammation; insulin resistance; obesity; oncogenesis; p53

DOI:  https://doi.org/10.1016/j.tem.2024.07.018