bims-celmim Biomed News
on Cellular and mitochondrial metabolism
Issue of 2024–09–15
thirteen papers selected by
Marc Segarra Mondejar
  1. Chemiosmotic nutrient transport in synthetic cells powered by electrogenic antiport coupled to decarboxylation.
  2. Neuronal extracellular vesicles influence the expression, degradation and oligomeric state of fructose 1,6-bisphosphatase 2 in astrocytes affecting their glycolytic capacity.
  3. Cytosolic FKBPL and ER-resident CKAP4 co-regulates ER-phagy and protein secretion.
  4. Organization of a functional glycolytic metabolon on mitochondria for metabolic efficiency.
  5. Robust Mitochondrial Isolation from Rodent Cardiac Tissue.
  6. Mitophagy protects against ferroptosis.
  7. Oligodendroglial fatty acid metabolism as a central nervous system energy reserve.
  8. Destabilized near-infrared fluorescent nanobodies enable background-free targeting of GFP-based biosensors for imaging and manipulation.
  9. Disruption of nucleotide biosynthesis reprograms mitochondrial metabolism to inhibit adipogenesis.
  10. Glutaminolysis provides nucleotides and amino acids to regulate osteoclast differentiation in mice.
  11. Visualizing mitochondrial dynamics at the nanoscale.
  12. Non-invasive metabolic imaging of brown adipose tissue.
  13. Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer.
  1. Nat Commun. 2024 Sep 12. 15(1): 7976
    Chemiosmotic nutrient transport in synthetic cells powered by electrogenic antiport coupled to decarboxylation.
    Miyer F Patiño-Ruiz, Zaid Ramdhan Anshari, Bauke Gaastra, Dirk J Slotboom, Bert Poolman.
      Cellular homeostasis depends on the supply of metabolic energy in the form of ATP and electrochemical ion gradients. The construction of synthetic cells requires a constant supply of energy to drive membrane transport and metabolism. Here, we provide synthetic cells with long-lasting metabolic energy in the form of an electrochemical proton gradient. Leveraging the L-malate decarboxylation pathway we generate a stable proton gradient and electrical potential in lipid vesicles by electrogenic L-malate/L-lactate exchange coupled to L-malate decarboxylation. By co-reconstitution with the transporters GltP and LacY, the synthetic cells maintain accumulation of L-glutamate and lactose over periods of hours, mimicking nutrient feeding in living cells. We couple the accumulation of lactose to a metabolic network for the generation of intermediates of the glycolytic and pentose phosphate pathways. This study underscores the potential of harnessing a proton motive force via a simple metabolic network, paving the way for the development of more complex synthetic systems.
    DOI:  https://doi.org/10.1038/s41467-024-52085-z
  2. Sci Rep. 2024 09 09. 14(1): 20932
    Neuronal extracellular vesicles influence the expression, degradation and oligomeric state of fructose 1,6-bisphosphatase 2 in astrocytes affecting their glycolytic capacity.
    Daria Hajka, Bartosz Budziak, Dariusz Rakus, Agnieszka Gizak.
      Fructose 1,6-bisphosphatase 2 (Fbp2) is a regulatory enzyme of gluco- and glyconeogenesis which, in the course of evolution, acquired non-catalytic functions. Fbp2 promotes cell survival during calcium stress, regulates glycolysis via inhibition of Hif-1α activity, and is indispensable for the formation of long-term potentiation in hippocampus. In hippocampal astrocytes, the amount of Fbp2 protein is reduced by signals delivered in neuronal extracellular vesicles (NEVs) through an unknown mechanism. The physiological role of Fbp2 (determined by its subcellular localization/interactions) depends on its oligomeric state and thus, we asked whether the cargo of NEVs is sufficient to change also the ratio of Fbp2 dimer/tetramer and, consequently, influence astrocyte basal metabolism. We found that the NEVs cargo reduced the Fbp2 mRNA level, stimulated the enzyme degradation and affected the cellular titers of different oligomeric forms of Fbp2. This was accompanied with increased glucose uptake and lactate release by astrocytes. Our results revealed that neuronal signals delivered to astrocytes in NEVs provide the necessary balance between enzymatic and non-enzymatic functions of Fbp2, influencing not only its amount but also subcellular localization. This may allow for the metabolic adjustments and ensure protection of mitochondrial membrane potential during the neuronal activity-related increase in astrocytic [Ca2+].
    Keywords:  Astrocytes; Crosstalk; Extracellular vesicles; Fructose 1,6-bisphosphatase; Glycolysis; Neurons
    DOI:  https://doi.org/10.1038/s41598-024-71560-7
  3. Nat Commun. 2024 Sep 09. 15(1): 7886
    Cytosolic FKBPL and ER-resident CKAP4 co-regulates ER-phagy and protein secretion.
    Cathena Meiling Li, Jaemin Kang, Jongyeon Baek, Youbin Kim, Heemin Park, Yong-Keun Jung.
      Endoplasmic reticulum quality control is crucial for maintaining cellular homeostasis and adapting to stress conditions. Although several ER-phagy receptors have been identified, the collaboration between cytosolic and ER-resident factors in ER fragmentation and ER-phagy regulation remains unclear. Here, we perform a phenotype-based gain-of-function screen and identify a cytosolic protein, FKBPL, functioning as an ER-phagy regulator. Overexpression of FKBPL triggers ER fragmentation and ER-phagy. FKBPL has multiple protein binding domains, can self-associate and might act as a scaffold connecting CKAP4 and LC3/GABARAPs. CKAP4 serves as a bridge between FKBPL and ER-phagy cargo. ER-phagy-inducing conditions increase FKBPL-CKAP4 interaction followed by FKBPL oligomerization at the ER, leading to ER-phagy. In addition, FKBPL-CKAP4 deficiency leads to Golgi disassembly and lysosome impairment, and an increase in ER-derived secretory vesicles and enhances cytosolic protein secretion via microvesicle shedding. Taken together, FKBPL with the aid of CKAP4 induces ER fragmentation and ER-phagy, and FKBPL-CKAP4 deficiency facilitates protein secretion.
    DOI:  https://doi.org/10.1038/s41467-024-52188-7
  4. Nat Metab. 2024 Sep 11.
    Organization of a functional glycolytic metabolon on mitochondria for metabolic efficiency.
    Haoming Wang, John W Vant, Andrew Zhang, Richard G Sanchez, Youjun Wu, Mary L Micou, Vincent Luczak, Zachary Whiddon, Natasha M Carlson, Seungyoon B Yu, Mirna Jabbo, Seokjun Yoon, Ahmed A Abushawish, Majid Ghassemian, Takeya Masubuchi, Quan Gan, Shigeki Watanabe, Eric R Griffis, Marc Hammarlund, Abhishek Singharoy, Gulcin Pekkurnaz.
      Glucose, the primary cellular energy source, is metabolized through glycolysis initiated by the rate-limiting enzyme hexokinase (HK). In energy-demanding tissues like the brain, HK1 is the dominant isoform, primarily localized on mitochondria, and is crucial for efficient glycolysis-oxidative phosphorylation coupling and optimal energy generation. This study unveils a unique mechanism regulating HK1 activity, glycolysis and the dynamics of mitochondrial coupling, mediated by the metabolic sensor enzyme O-GlcNAc transferase (OGT). OGT catalyses reversible O-GlcNAcylation, a post-translational modification influenced by glucose flux. Elevated OGT activity induces dynamic O-GlcNAcylation of the regulatory domain of HK1, subsequently promoting the assembly of the glycolytic metabolon on the outer mitochondrial membrane. This modification enhances the mitochondrial association with HK1, orchestrating glycolytic and mitochondrial ATP production. Mutation in HK1's O-GlcNAcylation site reduces ATP generation in multiple cell types, specifically affecting metabolic efficiency in neurons. This study reveals a previously unappreciated pathway that links neuronal metabolism and mitochondrial function through OGT and the formation of the glycolytic metabolon, providing potential strategies for tackling metabolic and neurological disorders.
    DOI:  https://doi.org/10.1038/s42255-024-01121-9
  5. J Vis Exp. 2024 Aug 23.
    Robust Mitochondrial Isolation from Rodent Cardiac Tissue.
    Alyssa C Vadovsky, Melissa Quinn, Tianyi Xia, Yan Levitsky, Jason N Bazil.
      Mitochondrial isolation has been practiced for decades, following procedures established by pioneers in the fields of molecular biology and biochemistry to study metabolic impairments and disease. Consistent mitochondrial quality is necessary to properly investigate mitochondrial physiology and bioenergetics; however, many different published isolation methods are available for researchers. Although different experimental strategies require different isolation methods, the basic principles and procedures are similar. This protocol details a method capable of extracting well-coupled mitochondria from a variety of tissue sources, including small animals and cells. The steps outlined include organ dissection, mitochondrial purification, protein quantification, and various quality control checks. The primary quality control metric used to identify high-quality mitochondria is the respiratory control ratio (RCR). The RCR is the ratio of the respiratory rate during oxidative phosphorylation to the rate in the absence of ADP. Alternative metrics are discussed. While high RCR values relative to their tissue source are obtained using this protocol, several steps can be optimized to suit the individual needs of researchers. This procedure is robust and has consistently resulted in isolated mitochondria with above-average RCR values across animal models and tissue sources.
    DOI:  https://doi.org/10.3791/67093
  6. Nat Cell Biol. 2024 Sep;26(9): 1374
    Mitophagy protects against ferroptosis.
    Petra Gross.
      
    DOI:  https://doi.org/10.1038/s41556-024-01507-7
  7. Nat Neurosci. 2024 Sep 09.
    Oligodendroglial fatty acid metabolism as a central nervous system energy reserve.
    Ebrahim Asadollahi, Andrea Trevisiol, Aiman S Saab, Zoe J Looser, Payam Dibaj, Reyhane Ebrahimi, Kathrin Kusch, Torben Ruhwedel, Wiebke Möbius, Olaf Jahn, Jun Yup Lee, Anthony S Don, Michelle-Amirah Khalil, Karsten Hiller, Myriam Baes, Bruno Weber, E Dale Abel, Andrea Balabio, Brian Popko, Celia M Kassmann, Hannelore Ehrenreich, Johannes Hirrlinger, Klaus-Armin Nave.
      Brain function requires a constant supply of glucose. However, the brain has no known energy stores, except for glycogen granules in astrocytes. In the present study, we report that continuous oligodendroglial lipid metabolism provides an energy reserve in white matter tracts. In the isolated optic nerve from young adult mice of both sexes, oligodendrocytes survive glucose deprivation better than astrocytes. Under low glucose, both axonal ATP levels and action potentials become dependent on fatty acid β-oxidation. Importantly, ongoing oligodendroglial lipid degradation feeds rapidly into white matter energy metabolism. Although not supporting high-frequency spiking, fatty acid β-oxidation in mitochondria and oligodendroglial peroxisomes protects axons from conduction blocks when glucose is limiting. Disruption of the glucose transporter GLUT1 expression in oligodendrocytes of adult mice perturbs myelin homeostasis in vivo and causes gradual demyelination without behavioral signs. This further suggests that the imbalance of myelin synthesis and degradation can underlie myelin thinning in aging and disease.
    DOI:  https://doi.org/10.1038/s41593-024-01749-6
  8. Nat Commun. 2024 Sep 06. 15(1): 7788
    Destabilized near-infrared fluorescent nanobodies enable background-free targeting of GFP-based biosensors for imaging and manipulation.
    Natalia V Barykina, Erin M Carey, Olena S Oliinyk, Axel Nimmerjahn, Vladislav V Verkhusha.
      Near-infrared (NIR) probes are highly sought after as fluorescent tags for multicolor cellular and in vivo imaging. Here we develop small NIR fluorescent nanobodies, termed NIR-FbLAG16 and NIR-FbLAG30, enabling background-free visualization of various GFP-derived probes and biosensors. We also design a red-shifted variant, NIR-Fb(718), to simultaneously target several antigens within the NIR spectral range. Leveraging the antigen-stabilizing property of the developed NIR-Fbs, we then create two modular systems for precise control of gene expression in GFP-labeled cells. Applying the NIR-Fbs in vivo, we target cells expressing GFP and the calcium biosensor GCaMP6 in the somatosensory cortex of transgenic mice. Simultaneously tracking calcium activity and the reference signal from NIR-FbLAGs bound to GCaMP6 enables ratiometric deep-brain in vivo imaging. Altogether, NIR-FbLAGs present a promising approach for imaging and manipulating various processes in live cells and behaving animals expressing GFP-based probes.
    DOI:  https://doi.org/10.1038/s41467-024-51857-x
  9. J Lipid Res. 2024 Sep 06. pii: S0022-2275(24)00146-9. [Epub ahead of print] 100641
    Disruption of nucleotide biosynthesis reprograms mitochondrial metabolism to inhibit adipogenesis.
    Julia A Pinette, Jacob W Myers, Woo Yong Park, Heather G Bryant, Alex M Eddie, Genesis A Wilson, Claudia Montufar, Zayedali Shaikh, Zer Vue, Elizabeth R Nunn, Ryoichi Bessho, Matthew A Cottam, Volker H Haase, Antentor O Hinton, Jessica B Spinelli, Jean-Philippe Cartailler, Elma Zaganjor.
      A key organismal response to overnutrition involves the development of new adipocytes through the process of adipogenesis. Preadipocytes sense changes in the systemic nutrient status and metabolites can directly modulate adipogenesis. We previously identified a role of de novo nucleotide biosynthesis in adipogenesis induction, whereby inhibition of nucleotide biosynthesis suppresses the expression of the transcriptional regulators PPARγ and C/EBPα. Here, we set out to identify the global transcriptomic changes associated with the inhibition of nucleotide biosynthesis. Through RNA sequencing (RNAseq), we discovered that mitochondrial signatures were the most altered in response to inhibition of nucleotide biosynthesis. Blocking nucleotide biosynthesis induced rounded mitochondrial morphology, and altered mitochondrial function, and metabolism, reducing levels of tricarboxylic acid cycle intermediates, and increasing fatty acid oxidation (FAO). The loss of mitochondrial function induced by suppression of nucleotide biosynthesis was rescued by exogenous expression of PPARγ. Moreover, inhibition of FAO restored PPARγ expression, mitochondrial protein expression, and adipogenesis in the presence of nucleotide biosynthesis inhibition, suggesting a regulatory role of nutrient oxidation in differentiation. Collectively, our studies shed light on the link between substrate oxidation and transcription in cell fate determination.
    Keywords:  adipocytes; adipogenesis; fatty acid oxidation; lipid droplets; metabolism; nucleotides; purine; pyrimidine
    DOI:  https://doi.org/10.1016/j.jlr.2024.100641
  10. EMBO Rep. 2024 Sep 13.
    Glutaminolysis provides nucleotides and amino acids to regulate osteoclast differentiation in mice.
    Guoli Hu, Yilin Yu, Yinshi Ren, Robert J Tower, Guo-Fang Zhang, Courtney M Karner.
      Osteoclasts are bone resorbing cells that are essential to maintain skeletal integrity and function. While many of the growth factors and molecular signals that govern osteoclastogenesis are well studied, how the metabolome changes during osteoclastogenesis is unknown. Using a multifaceted approach, we identified a metabolomic signature of osteoclast differentiation consisting of increased amino acid and nucleotide metabolism. Maintenance of the osteoclast metabolic signature is governed by elevated glutaminolysis. Mechanistically, glutaminolysis provides amino acids and nucleotides which are essential for osteoclast differentiation and bone resorption in vitro. Genetic experiments in mice found that glutaminolysis is essential for osteoclastogenesis and bone resorption in vivo. Highlighting the therapeutic implications of these findings, inhibiting glutaminolysis using CB-839 prevented ovariectomy induced bone loss in mice. Collectively, our data provide strong genetic and pharmacological evidence that glutaminolysis is essential to regulate osteoclast metabolism, promote osteoclastogenesis and modulate bone resorption in mice.
    Keywords:  Amino Acids; Glutaminolysis; Nucleotides; Osteoclast; Osteoporosis
    DOI:  https://doi.org/10.1038/s44319-024-00255-x
  11. Light Sci Appl. 2024 Sep 09. 13(1): 244
    Visualizing mitochondrial dynamics at the nanoscale.
    Till Stephan, Peter Ilgen, Stefan Jakobs.
      The study of mitochondria is a formidable challenge for super-resolution microscopy due to their dynamic nature and complex membrane architecture. In this issue, Ren et al. introduce HBmito Crimson, a fluorogenic and photostable mitochondrial probe for STED microscopy and investigate how mitochondrial dynamics influence the spatial organization of mitochondrial DNA.
    DOI:  https://doi.org/10.1038/s41377-024-01582-3
  12. Nat Methods. 2024 Sep;21(9): 1580
    Non-invasive metabolic imaging of brown adipose tissue.
    Jean Nakhle.
      
    DOI:  https://doi.org/10.1038/s41592-024-02422-3
  13. Nat Metab. 2024 Sep 09.
    Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer.
    Elena Buglakova, Måns Ekelöf, Michaela Schwaiger-Haber, Lisa Schlicker, Martijn R Molenaar, Mohammed Shahraz, Lachlan Stuart, Andreas Eisenbarth, Volker Hilsenstein, Gary J Patti, Almut Schulze, Marteinn T Snaebjornsson, Theodore Alexandrov.
      While heterogeneity is a key feature of cancer, understanding metabolic heterogeneity at the single-cell level remains a challenge. Here we present 13C-SpaceM, a method for spatial single-cell isotope tracing that extends the previously published SpaceM method with detection of 13C6-glucose-derived carbons in esterified fatty acids. We validated 13C-SpaceM on spatially heterogeneous models using liver cancer cells subjected to either normoxia-hypoxia or ATP citrate lyase depletion. This revealed substantial single-cell heterogeneity in labelling of the lipogenic acetyl-CoA pool and in relative fatty acid uptake versus synthesis hidden in bulk analyses. Analysing tumour-bearing brain tissue from mice fed a 13C6-glucose-containing diet, we found higher glucose-dependent synthesis of saturated fatty acids and increased elongation of essential fatty acids in tumours compared with healthy brains. Furthermore, our analysis uncovered spatial heterogeneity in lipogenic acetyl-CoA pool labelling in tumours. Our method enhances spatial probing of metabolic activities in single cells and tissues, providing insights into fatty acid metabolism in homoeostasis and disease.
    DOI:  https://doi.org/10.1038/s42255-024-01118-4
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