bims-mitdyn Biomed News
on Mitochondrial dynamics: mechanisms
Issue of 2024–11–17
twenty papers selected by
Edmond Chan, Queen’s University, School of Medicine
  1. Opposing roles for AMPK in regulating distinct mitophagy pathways.
  2. FMRP regulates MFF translation to locally direct mitochondrial fission in neurons.
  3. Structural basis of 3'-tRNA maturation by the human mitochondrial RNase Z complex.
  4. eIF5A controls mitoprotein import by relieving ribosome stalling at TIM50 translocase mRNA.
  5. HSF-1 promotes longevity through ubiquilin-1-dependent mitochondrial network remodelling.
  6. Nuclear localization of MTHFD2 is required for correct mitosis progression.
  7. Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission.
  8. A PRKN-independent Mechanism Regulating Cardiac Mitochondrial Quality Control.
  9. TAp73 regulates mitochondrial dynamics and multiciliated cell homeostasis through an OPA1 axis.
  10. The mitochondrial mRNA-stabilizing protein SLIRP regulates skeletal muscle mitochondrial structure and respiration by exercise-recoverable mechanisms.
  11. Mitochondria: great balls of fire.
  12. Understanding Mitochondrial and Lysosomal Dynamics by Fluorescent Microscopy.
  13. Metabolic Phenotyping of Synaptic Mitochondria Using MitoPlates™ and Synaptoneurosomes.
  14. Efficient PHB2 (prohibitin 2) exposure during mitophagy depends on VDAC1 (voltage dependent anion channel 1).
  15. Significantly reduced, but balanced, rates of mitochondrial fission and fusion are sufficient to maintain the integrity of yeast mitochondrial DNA.
  16. Simultaneous detection of membrane contact dynamics and associated Ca2+ signals by reversible chemogenetic reporters.
  17. Hepatic SerpinA1 improves energy and glucose metabolism through regulation of preadipocyte proliferation and UCP1 expression.
  18. PINK1-deficiency facilitates mitochondrial iron accumulation and colon tumorigenesis.
  19. Non-cell autonomous regulation of cell-cell signaling and differentiation by mitochondrial ROS.
  20. Methodologies for Mitochondrial Omic Profiling During Spaceflight.
  1. Mol Cell. 2024 Nov 05. pii: S1097-2765(24)00865-7. [Epub ahead of print]
    Opposing roles for AMPK in regulating distinct mitophagy pathways.
    Marianna Longo, Aniketh Bishnu, Pierpaolo Risiglione, Lambert Montava-Garriga, Joyceline Cuenco, Kei Sakamoto, Carol MacKintosh, Ian G Ganley.
      Mitophagy degrades damaged mitochondria, but we show here that it can also target functional mitochondria. This latter scenario occurs during programmed mitophagy and involves the mitophagy receptors NIX and BNIP3. Although AMP-activated protein kinase (AMPK), the energy-sensing protein kinase, can influence damaged-induced mitophagy, its role in programmed mitophagy is unclear. We found that AMPK directly inhibits NIX-dependent mitophagy by triggering 14-3-3-mediated sequestration of ULK1, via ULK1 phosphorylation at two sites: Ser556 and an additional identified site, Ser694. By contrast, AMPK activation increases Parkin phosphorylation and enhances the rate of depolarization-induced mitophagy, independently of ULK1. We show that this happens both in cultured cells and tissues in vivo, using the mito-QC mouse model. Our work unveils a mechanism whereby AMPK activation downregulates mitophagy of functional mitochondria but enhances that of dysfunctional/damaged ones.
    Keywords:  14-3-3; AMPK; NIX; Parkin; ULK1; autophagy; liver; mito-QC; mitophagy; skeletal muscle
    DOI:  https://doi.org/10.1016/j.molcel.2024.10.025
  2. Nat Cell Biol. 2024 Nov 15.
    FMRP regulates MFF translation to locally direct mitochondrial fission in neurons.
    Adam R Fenton, Ruchao Peng, Charles Bond, Siewert Hugelier, Melike Lakadamyali, Yi-Wei Chang, Erika L F Holzbaur, Thomas A Jongens.
      Fragile X messenger ribonucleoprotein (FMRP) is a critical regulator of translation, whose dysfunction causes fragile X syndrome. FMRP dysfunction disrupts mitochondrial health in neurons, but it is unclear how FMRP supports mitochondrial homoeostasis. Here we demonstrate that FMRP granules are recruited to the mitochondrial midzone, where they mark mitochondrial fission sites in axons and dendrites. Endolysosomal vesicles contribute to FMRP granule positioning around mitochondria and facilitate FMRP-associated fission via Rab7 GTP hydrolysis. Cryo-electron tomography and real-time translation imaging reveal that mitochondria-associated FMRP granules are ribosome-rich structures that serve as sites of local protein synthesis. Specifically, FMRP promotes local translation of mitochondrial fission factor (MFF), selectively enabling replicative fission at the mitochondrial midzone. Disrupting FMRP function dysregulates mitochondria-associated MFF translation and perturbs fission dynamics, resulting in increased peripheral fission and an irregular distribution of mitochondrial nucleoids. Thus, FMRP regulates local translation of MFF in neurons, enabling precise control of mitochondrial fission.
    DOI:  https://doi.org/10.1038/s41556-024-01544-2
  3. EMBO J. 2024 Nov 08.
    Structural basis of 3'-tRNA maturation by the human mitochondrial RNase Z complex.
    Genís Valentín Gesé, B Martin Hällberg.
      Maturation of human mitochondrial tRNA is essential for cellular energy production, yet the underlying mechanisms remain only partially understood. Here, we present several cryo-EM structures of the mitochondrial RNase Z complex (ELAC2/SDR5C1/TRMT10C) bound to different maturation states of mitochondrial tRNAHis, showing the molecular basis for tRNA-substrate selection and catalysis. Our structural insights provide a molecular rationale for the 5'-to-3' tRNA processing order in mitochondria, the 3'-CCA antideterminant effect, and the basis for sequence-independent recognition of mitochondrial tRNA substrates. Furthermore, our study links mutations in ELAC2 to clinically relevant mitochondrial diseases, offering a deeper understanding of the molecular defects contributing to these conditions.
    Keywords:  Cryo-EM; ELAC2; Mitochondria; RNA Processing; RNase Z
    DOI:  https://doi.org/10.1038/s44318-024-00297-w
  4. J Cell Biol. 2024 Dec 02. pii: e202404094. [Epub ahead of print]223(12):
    eIF5A controls mitoprotein import by relieving ribosome stalling at TIM50 translocase mRNA.
    Marina Barba-Aliaga, Vanessa Bernal, Cynthia Rong, Madeleine E Volfbeyn, Keguang Zhang, Brian M Zid, Paula Alepuz.
      Efficient import of nuclear-encoded proteins into mitochondria is crucial for proper mitochondrial function. The conserved translation factor eIF5A binds ribosomes, alleviating stalling at polyproline-encoding sequences. eIF5A impacts mitochondrial function across species, though the precise molecular mechanism is unclear. We found that eIF5A depletion in yeast reduces the translation and levels of the TCA cycle and oxidative phosphorylation proteins. Loss of eIF5A causes mitoprotein precursors to accumulate in the cytosol and triggers a mitochondrial import stress response. We identify an essential polyproline protein as a direct target of eIF5A: the mitochondrial inner membrane protein and translocase component Tim50. Thus, eIF5A controls mitochondrial protein import by alleviating ribosome stalling along Tim50 mRNA at the mitochondrial surface. Removal of polyprolines from Tim50 partially rescues the mitochondrial import stress response and translation of oxidative phosphorylation genes. Overall, our findings elucidate how eIF5A impacts the mitochondrial function by promoting efficient translation and reducing ribosome stalling of co-translationally imported proteins, thereby positively impacting the mitochondrial import process.
    DOI:  https://doi.org/10.1083/jcb.202404094
  5. Nat Commun. 2024 Nov 12. 15(1): 9797
    HSF-1 promotes longevity through ubiquilin-1-dependent mitochondrial network remodelling.
    Annmary Paul Erinjeri, Xunyan Wang, Rhianna Williams, Riccardo Zenezini Chiozzi, Konstantinos Thalassinos, Johnathan Labbadia.
      Increased activity of the heat shock factor, HSF-1, suppresses proteotoxicity and enhances longevity. However, the precise mechanisms by which HSF-1 promotes lifespan are unclear. Using an RNAi screen, we identify ubiquilin-1 (ubql-1) as an essential mediator of lifespan extension in worms overexpressing hsf-1. We find that hsf-1 overexpression leads to transcriptional downregulation of all components of the CDC-48-UFD-1-NPL-4 complex, which is central to both endoplasmic reticulum and mitochondria associated protein degradation, and that this is complemented by UBQL-1-dependent turnover of NPL-4.1. As a consequence, mitochondrial network dynamics are altered, leading to increased lifespan. Together, our data establish that HSF-1 mediates lifespan extension through mitochondrial network adaptations that occur in response to down-tuning of components associated with organellar protein degradation pathways.
    DOI:  https://doi.org/10.1038/s41467-024-54136-x
  6. Nat Commun. 2024 Nov 12. 15(1): 9529
    Nuclear localization of MTHFD2 is required for correct mitosis progression.
    Natalia Pardo-Lorente, Anestis Gkanogiannis, Luca Cozzuto, Antoni Gañez Zapater, Lorena Espinar, Ritobrata Ghose, Jacqueline Severino, Laura García-López, Rabia Gül Aydin, Laura Martin, Maria Victoria Neguembor, Evangelia Darai, Maria Pia Cosma, Laura Batlle-Morera, Julia Ponomarenko, Sara Sdelci.
      Subcellular compartmentalization of metabolic enzymes establishes a unique metabolic environment that elicits specific cellular functions. Indeed, the nuclear translocation of certain metabolic enzymes is required for epigenetic regulation and gene expression control. Here, we show that the nuclear localization of the mitochondrial enzyme methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) ensures mitosis progression. Nuclear MTHFD2 interacts with proteins involved in mitosis regulation and centromere stability, including the methyltransferases KMT5A and DNMT3B. Loss of MTHFD2 induces severe methylation defects and impedes correct mitosis completion. MTHFD2 deficient cells display chromosome congression and segregation defects and accumulate chromosomal aberrations. Blocking the catalytic nuclear function of MTHFD2 recapitulates the phenotype observed in MTHFD2 deficient cells, whereas restricting MTHFD2 to the nucleus is sufficient to ensure correct mitotic progression. Our discovery uncovers a nuclear role for MTHFD2, supporting the notion that translocation of metabolic enzymes to the nucleus is required to meet precise chromatin needs.
    DOI:  https://doi.org/10.1038/s41467-024-51847-z
  7. Sci Adv. 2024 Nov 15. 10(46): eadp7423
    Mitochondrial pyruvate transport regulates presynaptic metabolism and neurotransmission.
    Anupama Tiwari, Jongyun Myeong, Arsalan Hashemiaghdam, Marion I Stunault, Hao Zhang, Xiangfeng Niu, Marissa A Laramie, Jasmin Sponagel, Leah P Shriver, Gary J Patti, Vitaly A Klyachko, Ghazaleh Ashrafi.
      Glucose has long been considered the primary fuel source for the brain. However, glucose levels fluctuate in the brain during sleep or circuit activity, posing major metabolic stress. Here, we demonstrate that the mammalian brain uses pyruvate as a fuel source, and pyruvate can support neuronal viability in the absence of glucose. Nerve terminals are sites of metabolic vulnerability, and we show that mitochondrial pyruvate uptake is a critical step in oxidative ATP production in hippocampal terminals. We find that the mitochondrial pyruvate carrier is post-translationally modified by lysine acetylation, which, in turn, modulates mitochondrial pyruvate uptake. Our data reveal that the mitochondrial pyruvate carrier regulates distinct steps in neurotransmission, namely, the spatiotemporal pattern of synaptic vesicle release and the efficiency of vesicle retrieval-functions that have profound implications for synaptic plasticity. In summary, we identify pyruvate as a potent neuronal fuel and mitochondrial pyruvate uptake as a critical node for the metabolic control of neurotransmission in hippocampal terminals.
    DOI:  https://doi.org/10.1126/sciadv.adp7423
  8. Autophagy. 2024 Nov 09.
    A PRKN-independent Mechanism Regulating Cardiac Mitochondrial Quality Control.
    Wenjuan Wang, Jinbao Liu, Jie Li, Huabo Su.
      PRKN-dependent mitophagy plays a crucial role in maintaining mitochondrial health. Yet, PRKN-deficient mice do not exhibit mitochondrial and cardiac phenotypes at baseline, suggesting the existence of other mitochondrial ubiquitin (Ub) ligases. Here, we discuss our recent work identifying RNF7/RBX2 as a novel mitochondrial Ub ligase. Upon mitochondrial depolarization, RNF7 proteins are recruited to the mitochondria, where they directly ubiquitinate mitochondrial proteins and stabilize PINK1 expression, thereby promoting the clearance of damaged mitochondria and regulating mitochondrial turnover in the heart. The actions of RNF7 in mitochondria do not require PRKN. Ablation of Rnf7 in mouse hearts results in severe mitochondrial dysfunction and heart failure. Our findings demonstrate that RNF7 is indispensable for mitochondrial turnover and cardiac homeostasis. These results open new avenues for exploring new PRKN-independent pathways that regulate mitophagy, which could have significant implications for developing therapeutic interventions for cardiac diseases.
    Keywords:  Heart failure; RBX2/SAG; mitophagy; parkin; ubiquitination
    DOI:  https://doi.org/10.1080/15548627.2024.2423329
  9. Cell Death Dis. 2024 Nov 08. 15(11): 807
    TAp73 regulates mitochondrial dynamics and multiciliated cell homeostasis through an OPA1 axis.
    Niall A Buckley, Andrew Craxton, Xiao-Ming Sun, Emanuele Panatta, Lucia Giraldez Pinon, Sina Beier, Lajos Kalmar, Jaime Llodrá, Nobuhiro Morone, Ivano Amelio, Gerry Melino, L Miguel Martins, Marion MacFarlane.
      Dysregulated mitochondrial fusion and fission has been implicated in the pathogenesis of numerous diseases. We have identified a novel function of the p53 family protein TAp73 in regulating mitochondrial dynamics. TAp73 regulates the expression of Optic Atrophy 1 (OPA1), a protein responsible for controlling mitochondrial fusion, cristae biogenesis and electron transport chain function. Disruption of this axis results in a fragmented mitochondrial network and an impaired capacity for energy production via oxidative phosphorylation. Owing to the role of OPA1 in modulating cytochrome c release, TAp73-/- cells display an increased sensitivity to apoptotic cell death, e.g., via BH3-mimetics. We additionally show that the TAp73/OPA1 axis has functional relevance in the upper airway, where TAp73 expression is essential for multiciliated cell differentiation and function. Consistently, ciliated epithelial cells of Trp73-/- (global p73 knock-out) mice display decreased expression of OPA1 and perturbations of the mitochondrial network, which may drive multiciliated cell loss. In support of this, Trp73 and OPA1 gene expression is decreased in chronic obstructive pulmonary disease (COPD) patients, a disease characterised by alterations in mitochondrial dynamics. We therefore highlight a potential mechanism involving the loss of p73 in COPD pathogenesis. Our findings also add to the growing body of evidence for growth-promoting roles of TAp73 isoforms.
    DOI:  https://doi.org/10.1038/s41419-024-07130-6
  10. Nat Commun. 2024 Nov 13. 15(1): 9826
    The mitochondrial mRNA-stabilizing protein SLIRP regulates skeletal muscle mitochondrial structure and respiration by exercise-recoverable mechanisms.
    Tang Cam Phung Pham, Steffen Henning Raun, Essi Havula, Carlos Henriquez-Olguín, Diana Rubalcava-Gracia, Emma Frank, Andreas Mæchel Fritzen, Paulo R Jannig, Nicoline Resen Andersen, Rikke Kruse, Mona Sadek Ali, Andrea Irazoki, Jens Frey Halling, Stine Ringholm, Elise J Needham, Solvejg Hansen, Anders Krogh Lemminger, Peter Schjerling, Maria Houborg Petersen, Martin Eisemann de Almeida, Thomas Elbenhardt Jensen, Bente Kiens, Morten Hostrup, Steen Larsen, Niels Ørtenblad, Kurt Højlund, Michael Kjær, Jorge L Ruas, Aleksandra Trifunovic, Jørgen Frank Pind Wojtaszewski, Joachim Nielsen, Klaus Qvortrup, Henriette Pilegaard, Erik Arne Richter, Lykke Sylow.
      Decline in mitochondrial function is linked to decreased muscle mass and strength in conditions like sarcopenia and type 2 diabetes. Despite therapeutic opportunities, there is limited and equivocal data regarding molecular cues controlling muscle mitochondrial plasticity. Here we uncovered that the mitochondrial mRNA-stabilizing protein SLIRP, in complex with LRPPRC, is a PGC-1α target that regulates mitochondrial structure, respiration, and mtDNA-encoded-mRNA pools in skeletal muscle. Exercise training effectively counteracts mitochondrial defects caused by genetically-induced LRPPRC/SLIRP loss, despite sustained low mtDNA-encoded-mRNA pools, by increasing mitoribosome translation capacity and mitochondrial quality control. In humans, exercise training robustly increases muscle SLIRP and LRPPRC protein across exercise modalities and sexes, yet less prominently in individuals with type 2 diabetes. SLIRP muscle loss reduces Drosophila lifespan. Our data points to a mechanism of post-transcriptional mitochondrial regulation in muscle via mitochondrial mRNA stabilization, offering insights into how exercise enhances mitoribosome capacity and mitochondrial quality control to alleviate defects.
    DOI:  https://doi.org/10.1038/s41467-024-54183-4
  11. FEBS J. 2024 Nov 14.
    Mitochondria: great balls of fire.
    Howard T Jacobs, Pierre Rustin, Paule Bénit, Dan Davidi, Mügen Terzioglu.
      Recent experimental studies indicate that mitochondria in mammalian cells are maintained at temperatures of at least 50 °C. While acknowledging the limitations of current experimental methods and their interpretation, we here consider the ramifications of this finding for cellular functions and for evolution. We consider whether mitochondria as heat-producing organelles had a role in the origin of eukaryotes and in the emergence of homeotherms. The homeostatic responses of mitochondrial temperature to externally applied heat imply the existence of a molecular heat-sensing system in mitochondria. While current findings indicate high temperatures for the innermost compartments of mitochondria, those of the mitochondrial surface and of the immediately surrounding cytosol remain to be determined. We ask whether some aspects of mitochondrial dynamics and motility could reflect changes in the supply and demand for mitochondrial heat, and whether mitochondrial heat production could be a factor in diseases and immunity.
    Keywords:  cold‐shock; eukaryote origins; heat‐shock; homeothermy; immunity; mitochondria; mitochondrial disease; mitochondrial dynamics; temperature gradients; thermogenesis
    DOI:  https://doi.org/10.1111/febs.17316
  12. Methods Mol Biol. 2025 ;2878 211-221
    Understanding Mitochondrial and Lysosomal Dynamics by Fluorescent Microscopy.
    Pedro A Dionísio, Vilma A Sardão, Nuno Raimundo.
      Live cell imaging is a robust method to visualize dynamic cellular structures, especially organelles with network-like structures such as mitochondria. In this regard, mitochondrial dynamics, namely mitochondrial fission and fusion, are highly dynamic processes that regulate mitochondrial size and morphology depending on a plethora of cellular cues. Likewise, lysosome size and distribution may hint at their function and state.Here, we describe how to perform live cell confocal imaging using commercially available organelle dyes (MitoTracker, LysoTracker), followed by either 2D or 3D analyses of mitochondrial morphology/network connectivity and lysosomal morphology using the freely available Mitochondria Analyzer plugin for ImageJ/Fiji.
    Keywords:  Cell imaging; Fluorescent probes; LysoTracker; Lysosomes; Microscopy; MitoTracker; Mitochondria; Mitochondrial dynamics
    DOI:  https://doi.org/10.1007/978-1-0716-4264-1_11
  13. Methods Mol Biol. 2025 ;2878 67-74
    Metabolic Phenotyping of Synaptic Mitochondria Using MitoPlates™ and Synaptoneurosomes.
    Aleksandra Stawikowska, Magdalena Dziembowska, Bozena Kuzniewska.
      Mitochondrial functional assays using MitoPlates™ S-1 allow us to characterize mitochondria in terms of substrate metabolism. MitoPlates™ are 96-well microplates pre-coated with a diverse set of substrates. The electron flow from NADH and FADH2 producing mitochondrial substrates is measured based on the reduction of redox dye, that acts as a terminal electron acceptor. Here, we describe the application of MitoPlates™ to characterize the metabolism of synaptic mitochondria enclosed in isolated pre- and postsynaptic terminals (synaptoneurosomes).
    Keywords:  MitoPlates™; Mitochondrial substrate metabolism; Synaptic mitochondria; Synaptoneurosomes
    DOI:  https://doi.org/10.1007/978-1-0716-4264-1_4
  14. Autophagy. 2024 Nov 08.
    Efficient PHB2 (prohibitin 2) exposure during mitophagy depends on VDAC1 (voltage dependent anion channel 1).
    Moumita Roy, Sumangal Nandy, Elena Marchesan, Chayan Banerjee, Rupsha Mondal, Federico Caicci, Elena Ziviani, Joy Chakraborty.
      Exposure of inner mitochondrial membrane resident protein PHB2 (prohibitin 2) during autophagic removal of depolarized mitochondria (mitophagy) depends on the ubiquitin-proteasome system. This uncovering facilitates the PHB2 interaction with phagophore membrane-associated protein MAP1LC3/LC3. It is unclear whether PHB2 is exposed randomly at mitochondrial rupture sites. Prior knowledge and initial screening indicated that VDAC1 (voltage dependent anion channel 1) might play a role in this phenomenon. Through in vitro biochemical assays and imaging, we have found that VDAC1-PHB2 interaction increases during mitochondrial depolarization. Subsequently, this interaction enhances the efficiency of PHB2 exposure and mitophagy. To investigate the relevance in vivo, we utilized porin (equivalent to VDAC1) knockout Drosophila line. Our findings demonstrate that during mitochondrial stress, porin is essential for Phb2 exposure, Phb2-Atg8 interaction and mitophagy. This study highlights that VDAC1 predominantly synchronizes efficient PHB2 exposure through mitochondrial rupture sites during mitophagy. These findings may provide insights to understand progressive neurodegeneration.
    Keywords:  Neurodegeneration; PHB2-LC3 interaction; PINK1-PRKN; parkinson disease; porin; ubiquitin-proteasome system
    DOI:  https://doi.org/10.1080/15548627.2024.2426116
  15. Mol Biol Cell. 2024 Nov 13. mbcE24070306
    Significantly reduced, but balanced, rates of mitochondrial fission and fusion are sufficient to maintain the integrity of yeast mitochondrial DNA.
    Brett T Wisniewski, Jason C Casler, 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/10.1091/mbc.E24-07-0306
  16. Nat Commun. 2024 Nov 12. 15(1): 9775
    Simultaneous detection of membrane contact dynamics and associated Ca2+ signals by reversible chemogenetic reporters.
    Paloma García Casas, Michela Rossini, Linnea Påvénius, Mezida Saeed, Nikita Arnst, Sonia Sonda, Tânia Fernandes, Irene D'Arsiè, Matteo Bruzzone, Valeria Berno, Andrea Raimondi, Maria Livia Sassano, Luana Naia, Elisa Barbieri, Sara Sigismund, Patrizia Agostinis, Mattia Sturlese, Barbara A Niemeyer, Hjalmar Brismar, Maria Ankarcrona, Arnaud Gautier, Paola Pizzo, Riccardo Filadi.
      Membrane contact sites (MCSs) are hubs allowing various cell organelles to coordinate their activities. The dynamic nature of these sites and their small size hinder analysis by current imaging techniques. To overcome these limitations, we here design a series of reversible chemogenetic reporters incorporating improved, low-affinity variants of splitFAST, and study the dynamics of different MCSs at high spatiotemporal resolution, both in vitro and in vivo. We demonstrate that these versatile reporters suit different experimental setups well, allowing one to address challenging biological questions. Using these probes, we identify a pathway in which calcium (Ca2+) signalling dynamically regulates endoplasmic reticulum-mitochondria juxtaposition, characterizing the underlying mechanism. Finally, by integrating Ca2+-sensing capabilities into the splitFAST technology, we introduce PRINCESS (PRobe for INterorganelle Ca2+-Exchange Sites based on SplitFAST), a class of reporters to simultaneously detect MCSs and measure the associated Ca2+ dynamics using a single biosensor.
    DOI:  https://doi.org/10.1038/s41467-024-52985-0
  17. Nat Commun. 2024 Nov 12. 15(1): 9585
    Hepatic SerpinA1 improves energy and glucose metabolism through regulation of preadipocyte proliferation and UCP1 expression.
    Shota Okagawa, Masaji Sakaguchi, Yuma Okubo, Yuri Takekuma, Motoyuki Igata, Tatsuya Kondo, Naoki Takeda, Kimi Araki, Bruna Brasil Brandao, Wei-Jun Qian, Yu-Hua Tseng, Rohit N Kulkarni, Naoto Kubota, C Ronald Kahn, Eiichi Araki.
      Lipodystrophy and obesity are associated with insulin resistance and metabolic syndrome accompanied by fat tissue dysregulation. Here, we show that serine protease inhibitor A1 (SerpinA1) expression in the liver is increased during recovery from lipodystrophy caused by the adipocyte-specific loss of insulin signaling in mice. SerpinA1 induces the proliferation of white and brown preadipocytes and increases the expression of uncoupling protein 1 (UCP1) to promote mitochondrial activation in mature white and brown adipocytes. Liver-specific SerpinA1 transgenic mice exhibit increased browning of adipose tissues, leading to increased energy expenditure, reduced adiposity and improved glucose tolerance. Conversely, SerpinA1 knockout mice exhibit decreased adipocyte mitochondrial function, impaired thermogenesis, obesity, and systemic insulin resistance. SerpinA1 forms a complex with the Eph receptor B2 and regulates its downstream signaling in adipocytes. These results demonstrate that SerpinA1 is an important hepatokine that improves obesity, energy expenditure and glucose metabolism by promoting preadipocyte proliferation and activating mitochondrial UCP1 expression in adipocytes.
    DOI:  https://doi.org/10.1038/s41467-024-53835-9
  18. Autophagy. 2024 Nov 08.
    PINK1-deficiency facilitates mitochondrial iron accumulation and colon tumorigenesis.
    Mariella Arcos, Lavanya Goodla, Hyeoncheol Kim, Sharina P Desai, Rui Liu, Kunlun Yin, Zhaoli Liu, David R Martin, Xiang Xue.
      Mitophagy, the process by which cells eliminate damaged mitochondria, is mediated by PINK1 (PTEN induced kinase 1). Our recent research indicates that PINK1 functions as a tumor suppressor in colorectal cancer by regulating cellular metabolism. Interestingly, PINK1 ablation activated the NLRP3 (NLR family pyrin domain containing 3) inflammasome, releasing IL1B (interleukin 1 beta). However, inhibiting the NLRP3-IL1B signaling pathway with an IL1R (interleukin 1 receptor) antagonist or NLRP3 inhibitor did not hinder colon tumor growth after PINK1 loss. To identify druggable targets in PINK1-deficient tumors, ribonucleic acid sequencing analysis was performed on colon tumors from pink1 knockout and wild-type mice. Gene Set Enrichment Analysis highlighted the enrichment of iron ion transmembrane transporter activity. Subsequent qualitative polymerase chain reaction and western blot analysis revealed an increase in mitochondrial iron transporters, including mitochondrial calcium uniporter, in PINK1-deficient colon tumor cells and tissues. Live-cell iron staining demonstrated elevated cellular and mitochondrial iron levels in PINK1-deficient cells. Clinically used drugs deferiprone and minocycline reduced mitochondrial iron and superoxide levels, resulting in decreased colon tumor cell growth in vitro and in vivo. Manipulating the mitochondrial iron uptake protein MCU (mitochondrial calcium uniporter) also affected cell and xenograft tumor growth. This study suggests that therapies aimed at reducing mitochondrial iron levels may effectively inhibit colon tumor growth, particularly in patients with low PINK1 expression.
    Keywords:  Colorectal cancer; deferiprone; iron chelation; minocycline; mitochondrial iron; mitophagy
    DOI:  https://doi.org/10.1080/15548627.2024.2425594
  19. J Cell Biol. 2024 Dec 02. pii: e202401084. [Epub ahead of print]223(12):
    Non-cell autonomous regulation of cell-cell signaling and differentiation by mitochondrial ROS.
    Yipeng Du, Lei Wang, Lizbeth Perez-Castro, Maralice Conacci-Sorrell, Matthew Sieber.
      Mitochondrial reactive oxygen species (ROS) function intrinsically within cells to induce cell damage, regulate transcription, and cause genome instability. However, we know little about how mitochondrial ROS production non-cell autonomously impacts cell-cell signaling. Here, we show that mitochondrial dysfunction inhibits the plasma membrane localization of cell surface receptors that drive cell-cell communication during oogenesis. Within minutes, we found that mitochondrial ROS impairs exocyst membrane binding and leads to defective endosomal recycling. This endosomal defect impairs the trafficking of receptors, such as the Notch ligand Delta, during oogenesis. Remarkably, we found that overexpressing RAB11 restores ligand trafficking and rescues the developmental defects caused by ROS production. ROS production from adjacent cells acutely initiates a transcriptional response associated with growth and migration by suppressing Notch signaling and inducing extra cellualr matrix (ECM) remodeling. Our work reveals a conserved rapid response to ROS production that links mitochondrial dysfunction to the non-cell autonomous regulation of cell-cell signaling.
    DOI:  https://doi.org/10.1083/jcb.202401084
  20. Methods Mol Biol. 2025 ;2878 273-291
    Methodologies for Mitochondrial Omic Profiling During Spaceflight.
    Joseph W Guarnieri, JangKeun Kim, Douglas C Wallace, Christopher E Mason, Masafumi Muratani, Afshin Beheshti.
      To be able to understand how spaceflight can affect human biology, there is a need for maximizing the amount of information that can be obtained from experiments flown to space. Recently there has been an influx of data obtained from astronauts through multi-omics approaches based on both governmental and commercial spaceflight missions. In addition to data from humans, mitochondrial specific data is gathered for other experiments from rodents and other organisms that are flown in space. This data has started to universally demonstrate that mitochondrial dysfunction is the key regulator associated with increasing health risks associated with spaceflight. This mitochondrial dysfunction can have influence downstream on immune suppression, inflammation, circadian rhythm issues, and more. Due to the space environment, standard methodologies have to be altered for performing mitochondrial specific analysis and in general sample collection for omics. To perform mitochondrial specific analysis and data collection from samples flown to space we will outline the current sample collection methods, processing of the samples, and specific analysis. Specifically we will highlight the different mitochondrial methodologies and challenges involved with research associated with spaceflight.
    Keywords:  Astronauts; ImmunoblottingImmunoblotting; Mitochondria; Mitochondrial DNA; Multi-omics; Omics; PBMCs; RNA-sequence; Transcriptomics; mtDNA
    DOI:  https://doi.org/10.1007/978-1-0716-4264-1_15
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