bims-mitdyn Biomed News
on Mitochondrial dynamics: mechanisms
Issue of 2024–06–30
eleven papers selected by
Edmond Chan, Queen’s University, School of Medicine
  1. The extracellular matrix integrates mitochondrial homeostasis.
  2. Control of mitophagy initiation and progression by the TBK1 adaptors NAP1 and SINTBAD.
  3. Sequence-specific dynamic DNA bending explains mitochondrial TFAM's dual role in DNA packaging and transcription initiation.
  4. Lactate transported by MCT1 plays an active role in promoting mitochondrial biogenesis and enhancing TCA flux in skeletal muscle.
  5. Human mitochondrial carriers of the SLC25 family function as monomers exchanging substrates with a ping-pong kinetic mechanism.
  6. An aggregated mitochondrial distribution in preimplantation embryos disrupts nuclear morphology, function, and developmental potential.
  7. Raman micro-spectroscopy reveals the spatial distribution of fumarate in cells and tissues.
  8. Targeting DRP1 with Mdivi-1 to correct mitochondrial abnormalities in ADOA plus syndrome.
  9. IFNγ causes mitochondrial dysfunction and oxidative stress in myositis.
  10. Protocol for real-time assessment of mitochondrial and glycolytic ATP production in patient-derived glioma stem-like cells.
  11. The catalytic activity of methyltransferase METTL15 is dispensable for its role in mitochondrial ribosome biogenesis.
  1. Cell. 2024 Jun 24. pii: S0092-8674(24)00638-X. [Epub ahead of print]
    The extracellular matrix integrates mitochondrial homeostasis.
    Hanlin Zhang, C Kimberly Tsui, Gilberto Garcia, Larry K Joe, Haolun Wu, Ayane Maruichi, Wudi Fan, Sentibel Pandovski, Peter H Yoon, Brant M Webster, Jenni Durieux, Phillip A Frankino, Ryo Higuchi-Sanabria, Andrew Dillin.
      Cellular homeostasis is intricately influenced by stimuli from the microenvironment, including signaling molecules, metabolites, and pathogens. Functioning as a signaling hub within the cell, mitochondria integrate information from various intracellular compartments to regulate cellular signaling and metabolism. Multiple studies have shown that mitochondria may respond to various extracellular signaling events. However, it is less clear how changes in the extracellular matrix (ECM) can impact mitochondrial homeostasis to regulate animal physiology. We find that ECM remodeling alters mitochondrial homeostasis in an evolutionarily conserved manner. Mechanistically, ECM remodeling triggers a TGF-β response to induce mitochondrial fission and the unfolded protein response of the mitochondria (UPRMT). At the organismal level, ECM remodeling promotes defense of animals against pathogens through enhanced mitochondrial stress responses. We postulate that this ECM-mitochondria crosstalk represents an ancient immune pathway, which detects infection- or mechanical-stress-induced ECM damage, thereby initiating adaptive mitochondria-based immune and metabolic responses.
    Keywords:  TGF-β; TMEM2; extracellular matrix; hyaluronan; immunity; mitochondria
    DOI:  https://doi.org/10.1016/j.cell.2024.05.057
  2. Nat Struct Mol Biol. 2024 Jun 25.
    Control of mitophagy initiation and progression by the TBK1 adaptors NAP1 and SINTBAD.
    Elias Adriaenssens, Thanh Ngoc Nguyen, Justyna Sawa-Makarska, Grace Khuu, Martina Schuschnig, Stephen Shoebridge, Marvin Skulsuppaisarn, Emily Maria Watts, Kitti Dora Csalyi, Benjamin Scott Padman, Michael Lazarou, Sascha Martens.
      Mitophagy preserves overall mitochondrial fitness by selectively targeting damaged mitochondria for degradation. The regulatory mechanisms that prevent PTEN-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase Parkin (PINK1/Parkin)-dependent mitophagy and other selective autophagy pathways from overreacting while ensuring swift progression once initiated are largely elusive. Here, we demonstrate how the TBK1 (TANK-binding kinase 1) adaptors NAP1 (NAK-associated protein 1) and SINTBAD (similar to NAP1 TBK1 adaptor) restrict the initiation of OPTN (optineurin)-driven mitophagy by competing with OPTN for TBK1. Conversely, they promote the progression of nuclear dot protein 52 (NDP52)-driven mitophagy by recruiting TBK1 to NDP52 and stabilizing its interaction with FIP200. Notably, OPTN emerges as the primary recruiter of TBK1 during mitophagy initiation, which in return boosts NDP52-mediated mitophagy. Our results thus define NAP1 and SINTBAD as cargo receptor rheostats, elevating the threshold for mitophagy initiation by OPTN while promoting the progression of the pathway once set in motion by supporting NDP52. These findings shed light on the cellular strategy to prevent pathway hyperactivity while still ensuring efficient progression.
    DOI:  https://doi.org/10.1038/s41594-024-01338-y
  3. Nat Commun. 2024 Jun 27. 15(1): 5446
    Sequence-specific dynamic DNA bending explains mitochondrial TFAM's dual role in DNA packaging and transcription initiation.
    Hyun Huh, Jiayu Shen, Yogeeshwar Ajjugal, Aparna Ramachandran, Smita S Patel, Sang-Hyuk Lee.
      Mitochondrial transcription factor A (TFAM) employs DNA bending to package mitochondrial DNA (mtDNA) into nucleoids and recruit mitochondrial RNA polymerase (POLRMT) at specific promoter sites, light strand promoter (LSP) and heavy strand promoter (HSP). Herein, we characterize the conformational dynamics of TFAM on promoter and non-promoter sequences using single-molecule fluorescence resonance energy transfer (smFRET) and single-molecule protein-induced fluorescence enhancement (smPIFE) methods. The DNA-TFAM complexes dynamically transition between partially and fully bent DNA conformational states. The bending/unbending transition rates and bending stability are DNA sequence-dependent-LSP forms the most stable fully bent complex and the non-specific sequence the least, which correlates with the lifetimes and affinities of TFAM with these DNA sequences. By quantifying the dynamic nature of the DNA-TFAM complexes, our study provides insights into how TFAM acts as a multifunctional protein through the DNA bending states to achieve sequence specificity and fidelity in mitochondrial transcription while performing mtDNA packaging.
    DOI:  https://doi.org/10.1038/s41467-024-49728-6
  4. Sci Adv. 2024 Jun 28. 10(26): eadn4508
    Lactate transported by MCT1 plays an active role in promoting mitochondrial biogenesis and enhancing TCA flux in skeletal muscle.
    Lingling Zhang, Chenhao Xin, Shuo Wang, Shixuan Zhuo, Jing Zhu, Zi Li, Yuyi Liu, Lifeng Yang, Yan Chen.
      Once considered as a "metabolic waste," lactate is now recognized as a major fuel for tricarboxylic acid (TCA) cycle. Our metabolic flux analysis reveals that skeletal muscle mainly uses lactate to fuel TCA cycle. Lactate is transported through the cell membrane via monocarboxylate transporters (MCTs) in which MCT1 is highly expressed in the muscle. We analyzed how MCT1 affects muscle functions using mice with specific deletion of MCT1 in skeletal muscle. MCT1 deletion enhances running performance, increases oxidative fibers while decreasing glycolytic fibers, and enhances flux of glucose to TCA cycle. MCT1 deficiency increases the expression of mitochondrial proteins, augments cell respiration rate, and elevates mitochondrial activity in the muscle. Mechanistically, the protein level of PGC-1α, a master regulator of mitochondrial biogenesis, is elevated upon loss of MCT1 via increases in cellular NAD+ level and SIRT1 activity. Collectively, these results demonstrate that MCT1-mediated lactate shuttle plays a key role in regulating muscle functions by modulating mitochondrial biogenesis and TCA flux.
    DOI:  https://doi.org/10.1126/sciadv.adn4508
  5. EMBO J. 2024 Jun 27.
    Human mitochondrial carriers of the SLC25 family function as monomers exchanging substrates with a ping-pong kinetic mechanism.
    Camila Cimadamore-Werthein, Martin S King, Denis Lacabanne, Eva Pyrihová, Stephany Jaiquel Baron, Edmund Rs Kunji.
      Members of the SLC25 mitochondrial carrier family link cytosolic and mitochondrial metabolism and support cellular maintenance and growth by transporting compounds across the mitochondrial inner membrane. Their monomeric or dimeric state and kinetic mechanism have been a matter of long-standing debate. It is believed by some that they exist as homodimers and transport substrates with a sequential kinetic mechanism, forming a ternary complex where both exchanged substrates are bound simultaneously. Some studies, in contrast, have provided evidence indicating that the mitochondrial ADP/ATP carrier (SLC25A4) functions as a monomer, has a single substrate binding site, and operates with a ping-pong kinetic mechanism, whereby ADP is imported before ATP is exported. Here we reanalyze the oligomeric state and kinetic properties of the human mitochondrial citrate carrier (SLC25A1), dicarboxylate carrier (SLC25A10), oxoglutarate carrier (SLC25A11), and aspartate/glutamate carrier (SLC25A13), all previously reported to be dimers with a sequential kinetic mechanism. We demonstrate that they are monomers, except for dimeric SLC25A13, and operate with a ping-pong kinetic mechanism in which the substrate import and export steps occur consecutively. These observations are consistent with a common transport mechanism, based on a functional monomer, in which a single central substrate-binding site is alternately accessible.
    Keywords:  Bioenergetics; Kinetic Analysis; Mitochondria; SLC25 Mitochondrial Carrier Family; Transport
    DOI:  https://doi.org/10.1038/s44318-024-00150-0
  6. Proc Natl Acad Sci U S A. 2024 Jul 02. 121(27): e2317316121
    An aggregated mitochondrial distribution in preimplantation embryos disrupts nuclear morphology, function, and developmental potential.
    In-Won Lee, Abbas Pirpour Tazehkand, Zi-Yi Sha, Deepak Adhikari, John Carroll.
      A dispersed cytoplasmic distribution of mitochondria is a hallmark of normal cellular organization. Here, we have utilized the expression of exogenous Trak2 in mouse oocytes and embryos to disrupt the dispersed distribution of mitochondria by driving them into a large cytoplasmic aggregate. Our findings reveal that aggregated mitochondria have minimal impact on asymmetric meiotic cell divisions of the oocyte. In contrast, aggregated mitochondria during the first mitotic division result in daughter cells with unequal sizes and increased micronuclei. Further, in two-cell embryos, microtubule-mediated centering properties of the mitochondrial aggregate prevent nuclear centration, distort nuclear shape, and inhibit DNA synthesis and the onset of embryonic transcription. These findings demonstrate the motor protein-mediated distribution of mitochondria throughout the cytoplasm is highly regulated and is an essential feature of cytoplasmic organization to ensure optimal cell function.
    Keywords:  Meiosis; Mitosis; Nuclear morphology; TRAK2; mitochondrial aggregation
    DOI:  https://doi.org/10.1073/pnas.2317316121
  7. Nat Commun. 2024 Jun 25. 15(1): 5386
    Raman micro-spectroscopy reveals the spatial distribution of fumarate in cells and tissues.
    Marlous Kamp, Jakub Surmacki, Marc Segarra Mondejar, Tim Young, Karolina Chrabaszcz, Fadwa Joud, Vincent Zecchini, Alyson Speed, Christian Frezza, Sarah E Bohndiek.
      Aberrantly accumulated metabolites elicit intra- and inter-cellular pro-oncogenic cascades, yet current measurement methods require sample perturbation/disruption and lack spatio-temporal resolution, limiting our ability to fully characterize their function and distribution. Here, we show that Raman spectroscopy (RS) can directly detect fumarate in living cells in vivo and animal tissues ex vivo, and that RS can distinguish between Fumarate hydratase (Fh1)-deficient and Fh1-proficient cells based on fumarate concentration. Moreover, RS reveals the spatial compartmentalization of fumarate within cellular organelles in Fh1-deficient cells: consistent with disruptive methods, we observe the highest fumarate concentration (37 ± 19 mM) in mitochondria, where the TCA cycle operates, followed by the cytoplasm (24 ± 13 mM) and then the nucleus (9 ± 6 mM). Finally, we apply RS to tissues from an inducible mouse model of FH loss in the kidney, demonstrating RS can classify FH status. These results suggest RS could be adopted as a valuable tool for small molecule metabolic imaging, enabling in situ non-destructive evaluation of fumarate compartmentalization.
    DOI:  https://doi.org/10.1038/s41467-024-49403-w
  8. JCI Insight. 2024 Jun 25. pii: e180582. [Epub ahead of print]
    Targeting DRP1 with Mdivi-1 to correct mitochondrial abnormalities in ADOA plus syndrome.
    Yan Lin, Dongdong Wang, Busu Li, Jiayin Wang, Ling Xu, Xiaohan Sun, Kunqian Ji, Chuanzhu Yan, Fuchen Liu, Yuying Zhao.
      Autosomal dominant optic atrophy plus (ADOA+) is characterized by primary optic nerve atrophy accompanied by a spectrum of degenerative neurological symptoms. Despite ongoing research, no effective treatments are currently available for this condition. Our study provided evidence for the pathogenicity of an unreported c.1780T>C variant in the OPA1 gene through patient-derived skin fibroblasts and an engineered HEK293T cell line with OPA1 downregulation. We demonstrated that OPA1 insufficiency promoted mitochondrial fragmentation and increased DRP1 expression, disrupting mitochondrial dynamics. Consequently, this disruption enhanced mitophagy and caused mitochondrial dysfunction, contributing to the ADOA+ phenotype. Notably, the Drp1 inhibitor, mitochondrial division inhibitor-1 (Mdivi-1), effectively mitigated the adverse effects of OPA1 impairment. These effects included reduced Drp1 phosphorylation, decreased mitochondrial fragmentation, and balanced mitophagy. Thus, we propose that intervening in DRP1 with Mdivi-1 could correct mitochondrial abnormalities, offering a promising therapeutic approach for managing ADOA+.
    Keywords:  Autophagy; Drug therapy; Mitochondria; Neuroscience; Ophthalmology
    DOI:  https://doi.org/10.1172/jci.insight.180582
  9. Nat Commun. 2024 Jun 26. 15(1): 5403
    IFNγ causes mitochondrial dysfunction and oxidative stress in myositis.
    Catalina Abad, Iago Pinal-Fernandez, Clement Guillou, Gwladys Bourdenet, Laurent Drouot, Pascal Cosette, Margherita Giannini, Lea Debrut, Laetitia Jean, Sophie Bernard, Damien Genty, Rachid Zoubairi, Isabelle Remy-Jouet, Bernard Geny, Christian Boitard, Andrew Mammen, Alain Meyer, Olivier Boyer.
      Idiopathic inflammatory myopathies (IIMs) are severe autoimmune diseases with poorly understood pathogenesis and unmet medical needs. Here, we examine the role of interferon γ (IFNγ) using NOD female mice deficient in the inducible T cell co-stimulator (Icos), which have previously been shown to develop spontaneous IFNγ-driven myositis mimicking human disease. Using muscle proteomic and spatial transcriptomic analyses we reveal profound myofiber metabolic dysregulation in these mice. In addition, we report muscle mitochondrial abnormalities and oxidative stress in diseased mice. Supporting a pathogenic role for oxidative stress, treatment with a reactive oxygen species (ROS) buffer compound alleviated myositis, preserved muscle mitochondrial ultrastructure and respiration, and reduced inflammation. Mitochondrial anomalies and oxidative stress were diminished following anti-IFNγ treatment. Further transcriptomic analysis in IIMs patients and human myoblast in vitro studies supported the link between IFNγ and mitochondrial dysfunction observed in mice. These results suggest that mitochondrial dysfunction, ROS and inflammation are interconnected in a self-maintenance loop, opening perspectives for mitochondria therapy and/or ROS targeting drugs in myositis.
    DOI:  https://doi.org/10.1038/s41467-024-49460-1
  10. STAR Protoc. 2024 Jun 27. pii: S2666-1667(24)00324-1. [Epub ahead of print]5(3): 103159
    Protocol for real-time assessment of mitochondrial and glycolytic ATP production in patient-derived glioma stem-like cells.
    Pratibha Sharma, Vinay K Puduvalli.
      Glioma cells switch between energetic pathways to adapt and resist therapies. We present a protocol for measuring mitochondrial and glycolytic ATP rates in patient-derived glioma stem-like cells using a Seahorse XF ATP rate assay. We describe steps for growing 3D glioma stem-like cells, attaching cells to the assay plate, preparing drugs, and running the ATP rate assay. We also detail procedures for imaging viable cell numbers and normalization, with tips to overcome pitfalls in Agilent Seahorse assays.
    Keywords:  Cancer; Cell Biology; Cell culture; Cell-based Assays; Health Sciences; Metabolism; Neuroscience
    DOI:  https://doi.org/10.1016/j.xpro.2024.103159
  11. RNA Biol. 2024 Jan;21(1): 23-30
    The catalytic activity of methyltransferase METTL15 is dispensable for its role in mitochondrial ribosome biogenesis.
    Christian D Mutti, Lindsey Van Haute, Michal Minczuk.
      Ribosomes are large macromolecular complexes composed of both proteins and RNA, that require a plethora of factors and post-transcriptional modifications for their biogenesis. In human mitochondria, the ribosomal RNA is post-transcriptionally modified at ten sites. The N4-methylcytidine (m4C) methyltransferase, METTL15, modifies the 12S rRNA of the small subunit at position C1486. The enzyme is essential for mitochondrial protein synthesis and assembly of the mitoribosome small subunit, as shown here and by previous studies. Here, we demonstrate that the m4C modification is not required for small subunit biogenesis, indicating that the chaperone-like activity of the METTL15 protein itself is an essential component for mitoribosome biogenesis.
    Keywords:  Mitochondrial ribosome; chaperone; epitranscriptomics; methyltransferase; mitochondria; ribosomal RNA
    DOI:  https://doi.org/10.1080/15476286.2024.2369374
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