bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2024–12–08
twenty papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico
  1. OPA1 and disease-causing mutants perturb mitochondrial nucleoid distribution.
  2. Coordination of cytochrome bc1 complex assembly at MICOS.
  3. OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase.
  4. Mitochondrial respiratory supercomplexes gear up for heat generation in brown adipose tissue.
  5. Therapeutic hypoxia for mitochondrial disease via enhancement of hemoglobin affinity and inhibition of HIF-2α.
  6. SURF1 Deficiency: Expanding on Disease Phenotype and Assessing Disease Burden by Describing Clinical and Biochemical Phenotype.
  7. Placental nanoparticle-mediated IGF1 gene therapy corrects fetal growth restriction in a guinea pig model.
  8. Mitochondrial Transplantation in Brain Disorders: Achievements, Methods, and Challenges.
  9. Mitochondrial function in patients affected with fibromyalgia syndrome is impaired and correlates with disease severity.
  10. Skeletal muscle mitochondrial fragmentation predicts age-associated decline in physical capacity.
  11. Mitochondrial calcium uniporter complex controls T-cell-mediated immune responses.
  12. Two-stage binding of mitochondrial ferredoxin-2 to the core iron-sulfur cluster assembly complex.
  13. Mammalian mitochondrial inorganic polyphosphate (polyP) and cell signaling: Crosstalk between PolyP and the activity of AMPK.
  14. Understanding ubiquitination in neurodevelopment by integrating insights across space and time.
  15. Purification of mitochondria from skeletal muscle tissue for transcriptomic analyses reveals localization of nuclear-encoded noncoding RNAs.
  16. Stabilization of expandable DNA repeats by the replication factor Mcm10 promotes cell viability.
  17. Mitochondrial dysfunction in pregnancy loss: a review.
  18. Trehalose extricates impaired mitochondrial and autophagy dysregulation in patient iPSC-derived macular corneal dystrophy disease model.
  19. Alternative NADH dehydrogenase: A complex I backup, a drug target, and a tool for mitochondrial gene therapy.
  20. Neuronal PRDX-2-Mediated ROS Signaling Regulates Food Digestion via peripheral UPRmt Activation.
  1. Cell Death Dis. 2024 Nov 30. 15(11): 870
    OPA1 and disease-causing mutants perturb mitochondrial nucleoid distribution.
    J Macuada, I Molina-Riquelme, G Vidal, N Pérez-Bravo, C Vásquez-Trincado, G Aedo, D Lagos, P Yu-Wai-Man, R Horvath, T J Rudge, B Cartes-Saavedra, V Eisner.
      Optic atrophy protein 1 (OPA1) mediates inner mitochondrial membrane (IMM) fusion and cristae organization. Mutations in OPA1 cause autosomal dominant optic atrophy (ADOA), a leading cause of blindness. Cells from ADOA patients show impaired mitochondrial fusion, cristae structure, bioenergetic function, and mitochondrial DNA (mtDNA) integrity. The mtDNA encodes electron transport chain subunits and is packaged into nucleoids spread within the mitochondrial population. Nucleoids interact with the IMM, and their distribution is tightly linked to mitochondrial fusion and cristae shaping. Yet, little is known about the physio-pathological relevance of nucleoid distribution. We studied the effect of OPA1 and ADOA-associated mutants on nucleoid distribution using high-resolution confocal microscopy. We applied a novel model incorporating the mitochondrial context, separating nucleoid distribution into the array in the mitochondrial population and intramitochondrial longitudinal distribution. Opa1-null cells showed decreased mtDNA levels and nucleoid abundance. Also, loss of Opa1 led to an altered distribution of nucleoids in the mitochondrial population, loss of cristae periodicity, and altered nucleoids to cristae proximity partly rescued by OPA1 isoform 1. Overexpression of WT OPA1 or ADOA-causing mutants c.870+5 G > A or c.2713 C > T in WT cells, showed perturbed nucleoid array in the mitochondria population associated with cristae disorganization, which was partly reproduced in Skeletal muscle-derived fibroblasts from ADOA patients harboring the same mutants. Opa1-null and cells overexpressing ADOA mutants accumulated mitochondria without nucleoids. Interestingly, intramitochondrial nucleoid distribution was only altered in Opa1-null cells. Altogether, our results highlight the relevance of OPA1 in nucleoid distribution in the mitochondrial landscape and at a single-organelle level and shed light on new components of ADOA etiology.
    DOI:  https://doi.org/10.1038/s41419-024-07165-9
  2. EMBO Rep. 2024 Dec 02.
    Coordination of cytochrome bc1 complex assembly at MICOS.
    Ralf M Zerbes, Lilia Colina-Tenorio, Maria Bohnert, Karina von der Malsburg, Christian D Peikert, Carola S Mehnert, Inge Perschil, Rhena F U Klar, Rinse de Boer, Anita Kram, Ida van der Klei, Silke Oeljeklaus, Bettina Warscheid, Heike Rampelt, Martin van der Laan.
      The boundary and cristae domains of the mitochondrial inner membrane are connected by crista junctions. Most cristae membrane proteins are nuclear-encoded and inserted by the mitochondrial protein import machinery into the inner boundary membrane. Thus, they must overcome the diffusion barrier imposed by crista junctions to reach their final location. Here, we show that respiratory chain complexes and assembly intermediates are physically connected to the mitochondrial contact site and cristae organizing system (MICOS) that is essential for the formation and stability of crista junctions. We identify the inner membrane protein Mar26 (Fmp10) as a determinant in the biogenesis of the cytochrome bc1 complex (complex III). Mar26 couples a Rieske Fe/S protein-containing assembly intermediate to MICOS. Our data indicate that Mar26 maintains an assembly-competent Rip1 pool at crista junctions where complex III maturation likely occurs. MICOS facilitates efficient Rip1 assembly by recruiting complex III assembly intermediates to crista junctions. We propose that MICOS, via interaction with assembly factors such as Mar26, contributes to the spatial and temporal coordination of respiratory chain biogenesis.
    Keywords:   bc 1 Complex; Cristae; MICOS; Mitochondria; Respiratory Chain
    DOI:  https://doi.org/10.1038/s44319-024-00336-x
  3. Cell Rep. 2024 Dec 03. pii: S2211-1247(24)01389-5. [Epub ahead of print]43(12): 115038
    OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase.
    Praveenraj Elancheliyan, Klaudia K Maruszczak, Remigiusz Adam Serwa, Till Stephan, Ahmet Sadik Gulgec, Mayra A Borrero-Landazabal, Sonia Ngati, Aleksandra Gosk, Stefan Jakobs, Michal Wasilewski, Agnieszka Chacinska.
      Mitochondrial proteins are transported and sorted to the matrix or inner mitochondrial membrane by the presequence translocase TIM23. In yeast, this essential and highly conserved machinery is composed of the core subunits Tim23 and Tim17. The architecture, assembly, and regulation of the human TIM23 complex are poorly characterized. The human genome encodes two paralogs, TIMM17A and TIMM17B. Here, we describe an unexpected role of the ovarian cancer immunoreactive antigen domain-containing protein 1 (OCIAD1) and the prohibitin complex in the biogenesis of human TIM23. Prohibitins were required to stabilize both the TIMM17A- and TIMM17B-containing variants of the translocase. Interestingly, OCIAD1 assembled with the prohibitin complex to protect the TIMM17A variant from degradation by the YME1L protease. The expression of OCIAD1 was in turn regulated by the status of the TIM23 complex. We postulate that OCIAD1 together with prohibitins constitute a regulatory axis that differentially regulates variants of human TIM23.
    Keywords:  CP: Cell biology; OCIAD1; TIM23 translocase; biogenesis; mitochondria; prohibitin
    DOI:  https://doi.org/10.1016/j.celrep.2024.115038
  4. Cell Metab. 2024 Dec 03. pii: S1550-4131(24)00418-2. [Epub ahead of print]36(12): 2491-2492
    Mitochondrial respiratory supercomplexes gear up for heat generation in brown adipose tissue.
    Andreas Carlström, Martin Ott.
      Mitochondrial energy conversion supplies cellular energy but can also provide heat in brown adipose tissue (BAT). In a recent study, Shin and Latorre-Muro et al.1 show that respiratory supercomplexes in BAT are remodeled during cold to provide a tighter coupling, revealing a novel, physiologically important role for these supramolecular assemblies.
    DOI:  https://doi.org/10.1016/j.cmet.2024.10.022
  5. J Clin Invest. 2024 Dec 02. pii: e185569. [Epub ahead of print]134(23):
    Therapeutic hypoxia for mitochondrial disease via enhancement of hemoglobin affinity and inhibition of HIF-2α.
    Hong Wang, Maria Miranda, Eizo Marutani, Paul Lichtenegger, Gregory R Wojtkiewicz, Fumito Ichinose, Vamsi K Mootha.
      
    Keywords:  Genetics; Hypoxia
    DOI:  https://doi.org/10.1172/JCI185569
  6. Am J Med Genet A. 2024 Dec 05. e63947
    SURF1 Deficiency: Expanding on Disease Phenotype and Assessing Disease Burden by Describing Clinical and Biochemical Phenotype.
    Saima Kayani, Victor Daescu, Hamza Dahshi, Souad Messahel, Kasey Woleban, Berge A Minassian, Qinglan Ling, Steven J Gray.
      Leigh syndrome, a severe neurological disorder is commonly caused by homozygous or bi-allelic pathogenic variants in the SURF1 gene. SURF1 deficiency leads to dysfunction of Cytochrome C Oxidase (COX) activity, which is crucial for mitochondrial oxidative phosphorylation. Understanding COX activity's correlation with disease severity is essential for developing SURF1 Leigh Syndrome biomarkers. This study assesses the disease burden in SURF1 Leigh Syndrome and evaluates COX activity as a treatment biomarker. We reviewed records and questionnaires from 17 individuals, classifying them into phenotypic and genotypic groups. We compared COX activity assays in patient fibroblasts to age-matched controls, clinical data, and neuroimaging findings. Patient COX activity was at most 50% of controls, averaging 32% (p < 0.001). Common clinical features included brainstem abnormalities (93.3%), motor regression (92.3%), bi-allelic heterozygous SURF1 variants (88.2%), and delayed growth/development (35.7%). Homozygous and heterozygous nonsense/frameshift variants showed more severe phenotypes (p = 0.008) and more MRI abnormalities (p = 0.005). Significant COX activity reduction is linked to SURF1 Leigh Syndrome, with genotype influencing disease severity. Clinical and neuroimaging correlations show potential for prognostic indicators. This study lays the groundwork for future research and clinical application of COX activity as a SURF1 Leigh Syndrome biomarker.
    Keywords:  Leigh syndrome; SURF1 gene; biomarkers; cytochrome C oxidase; mitochondrial disorders; neuroimaging
    DOI:  https://doi.org/10.1002/ajmg.a.63947
  7. Gene Ther. 2024 Dec 04.
    Placental nanoparticle-mediated IGF1 gene therapy corrects fetal growth restriction in a guinea pig model.
    Baylea N Davenport, Rebecca L Wilson, Alyssa A Williams, Helen N Jones.
      Fetal growth restriction (FGR) caused by placental insufficiency is a major contributor to neonatal morbidity and mortality. There is currently no in utero treatment for placental insufficiency or FGR. The placenta serves as the vital communication, supply, exchange, and defense organ for the developing fetus and offers an excellent opportunity for therapeutic interventions. Here we show efficacy of repeated treatments of trophoblast-specific human insulin-like 1 growth factor (IGF1) gene therapy delivered in a non-viral, polymer nanoparticle to the placenta for the treatment of FGR. Using a guinea pig maternal nutrient restriction model (70% food intake) of FGR, nanoparticle-mediated IGF1 treatment was delivered to the placenta via ultrasound guidance across the second half of pregnancy, after establishment of FGR. This treatment resulted in correction of fetal weight in MNR + IGF1 animals compared to sham treated controls on an ad libitum diet, increased fetal blood glucose and decreased fetal blood cortisol levels compared to sham treated MNR, and showed no negative maternal side-effects. Overall, we show a therapy capable of positively impacting the entire pregnancy environment: maternal, placental, and fetal. This combined with our previous studies using this therapy at mid pregnancy in the guinea pig and in two different mouse model and three different human in vitro/ex vivo models, demonstrate the plausibility of this therapy for future human translation. Our overall goal is to improve health outcomes of neonates and decrease numerous morbidities associated with the developmental origins of disease.
    DOI:  https://doi.org/10.1038/s41434-024-00508-3
  8. Neurosci Biobehav Rev. 2024 Dec 03. pii: S0149-7634(24)00440-8. [Epub ahead of print] 105971
    Mitochondrial Transplantation in Brain Disorders: Achievements, Methods, and Challenges.
    Aurélien Riou, Aline Broeglin, Amandine Grimm.
      Mitochondrial transplantation is a new treatment strategy aimed at repairing cellular damage by introducing healthy mitochondria into injured cells. The approach shows promise in protecting brain function in various neurological disorders such as traumatic brain injury/ischemia, neurodegenerative diseases, cognitive disorders, and cancer. These conditions are often characterized by mitochondrial dysfunction, leading to impaired energy production and neuronal death. The review highlights promising preclinical studies where mitochondrial transplantation has been shown to restore mitochondrial function, reduce inflammation, and improve cognitive and motor functions in several animal models. It also addresses significant challenges that must be overcome before this therapy can be clinically applied. Current efforts to overcome these challenges, including advancements in isolation techniques, cryopreservation methods, finding an appropriate mitochondria source, and potential delivery routes, are discussed. Considering the rising incidence of neurological disorders and the limited effectiveness of current treatments, this review offers a comprehensive overview of the current state of mitochondrial transplantation research and critically assesses the remaining obstacles. It provides valuable insights that could steer future studies and potentially lead to more effective treatments for various brain disorders.
    Keywords:  Cognitive disorders; ischemia; mitochondrial transplantation; neurodegenerative diseases; traumatic brain injury
    DOI:  https://doi.org/10.1016/j.neubiorev.2024.105971
  9. Sci Rep. 2024 12 04. 14(1): 30247
    Mitochondrial function in patients affected with fibromyalgia syndrome is impaired and correlates with disease severity.
    Chiara Macchi, Andrea Giachi, Isabella Fichtner, Silvia Pedretti, Piercarlo Sarzi Puttini, Nico Mitro, Alberto Corsini, Massimiliano Ruscica, Roberta Gualtierotti.
      Fibromyalgia is a musculoskeletal syndrome characterized by chronic widespread pain that is often associated with systemic manifestations. Since mitochondria are the main source of cellular energy, we hypothesized that fibromyalgia syndrome (FMS) could be linked to mitochondrial impairment. Aim was to study mitochondrial dysfunction in peripheral blood mononuclear cells isolated from 50 patients with primary FMS and 20 apparently healthy controls. Although no differences in mitochondrial basal respiration were observed between patients with primary FMS and healthy controls, a lower median bioenergetic health index (BHI; - 22.1%, p = 0.03), a proxy of mitochondrial function, was found in patients. According to fibromyalgia severity score (FSS), a composite of widespread pain index and symptom severity scale, a lower median BHI (- 18.7%) was found in patients with a FSS ≥ 20 compared to those with a FSS < 20. Negative moderate correlations were found only between BHI and FSS (r = - 0.36) and widespread pain index (r = - 0.38). We demonstrated that patients with FMS had an impaired mitochondrial function. Additionally, we found a mild correlation between the widespread pain index and the BHI, possibly indicating that the altered mitochondrial function, in these patients, narrows musculoskeletal rather than central nervous system involvement.
    DOI:  https://doi.org/10.1038/s41598-024-81298-x
  10. Aging Cell. 2024 Dec 04. e14386
    Skeletal muscle mitochondrial fragmentation predicts age-associated decline in physical capacity.
    Richie P Goulding, Braeden T Charlton, Ellen A Breedveld, Matthijs van der Laan, Anne R Strating, Wendy Noort, Aryna Kolodyazhna, Brent Appelman, Michèle van Vugt, Anita E Grootemaat, Nicole N van der Wel, Jos J de Koning, Frank W Bloemers, Rob C I Wüst.
      Ageing substantially impairs skeletal muscle metabolic and physical function. Skeletal muscle mitochondrial health is also impaired with ageing, but the role of skeletal muscle mitochondrial fragmentation in age-related functional decline remains imprecisely characterized. Here, using a cross-sectional study design, we performed a detailed comparison of skeletal muscle mitochondrial characteristics in relation to in vivo markers of exercise capacity between young and middle-aged individuals. Despite similar overall oxidative phosphorylation capacity (young: 99 ± 17 vs. middle-aged: 99 ± 27 pmol O2.s-1.mg-1, p = 0.95) and intermyofibrillar mitochondrial density (young: 5.86 ± 0.57 vs. middle-aged: 5.68 ± 1.48%, p = 0.25), older participants displayed a more fragmented intermyofibrillar mitochondrial network (young: 1.15 ± 0.17 vs. middle-aged: 1.55 ± 0.15 A.U., p < 0.0001), a lower mitochondrial cristae density (young: 23.40 ± 7.12 vs. middle-aged: 13.55 ± 4.10%, p = 0.002) and a reduced subsarcolemmal mitochondrial density (young: 22.39 ± 6.50 vs. middle-aged: 13.92 ± 4.95%, p = 0.005). Linear regression analysis showed that 87% of the variance associated with maximal oxygen uptake could be explained by skeletal muscle mitochondrial fragmentation and cristae density alone, whereas subsarcolemmal mitochondrial density was positively associated with the capacity for oxygen extraction during exercise. Intramuscular lipid accumulation was positively associated with mitochondrial fragmentation and negatively associated with cristae density. Collectively, our work highlights the critical role of skeletal muscle mitochondria in age-associated declines in physical function.
    Keywords:  ageing; maximal oxygen uptake; mitochondrial morphology; mitochondrial respiration; skeletal muscle
    DOI:  https://doi.org/10.1111/acel.14386
  11. EMBO Rep. 2024 Dec 02.
    Mitochondrial calcium uniporter complex controls T-cell-mediated immune responses.
    Magdalena Shumanska, Dmitri Lodygin, Christine S Gibhardt, Christian Ickes, Ioana Stejerean-Todoran, Lena C M Krause, Kira Pahl, Lianne J H C Jacobs, Andrea Paluschkiwitz, Shuya Liu, Angela Boshnakovska, Niels Voigt, Tobias J Legler, Martin Haubrock, Miso Mitkovski, Gereon Poschmann, Peter Rehling, Sven Dennerlein, Jan Riemer, Alexander Flügel, Ivan Bogeski.
      T-cell receptor (TCR)-induced Ca2+ signals are essential for T-cell activation and function. In this context, mitochondria play an important role and take up Ca2+ to support elevated bioenergetic demands. However, the functional relevance of the mitochondrial-Ca2+-uniporter (MCU) complex in T-cells was not fully understood. Here, we demonstrate that TCR activation causes rapid mitochondrial Ca2+ (mCa2+) uptake in primary naive and effector human CD4+ T-cells. Compared to naive T-cells, effector T-cells display elevated mCa2+ and increased bioenergetic and metabolic output. Transcriptome and proteome analyses reveal molecular determinants involved in the TCR-induced functional reprogramming and identify signalling pathways and cellular functions regulated by MCU. Knockdown of MCUa (MCUaKD), diminishes mCa2+ uptake, mitochondrial respiration and ATP production, as well as T-cell migration and cytokine secretion. Moreover, MCUaKD in rat CD4+ T-cells suppresses autoimmune responses in an experimental autoimmune encephalomyelitis (EAE) multiple sclerosis model. In summary, we demonstrate that mCa2+ uptake through MCU is essential for proper T-cell function and has a crucial role in autoimmunity. T-cell specific MCU inhibition is thus a potential tool for targeting autoimmune disorders.
    Keywords:  Autoimmunity; Calcium; MCU; Mitochondria; T-cell
    DOI:  https://doi.org/10.1038/s44319-024-00313-4
  12. Nat Commun. 2024 Dec 04. 15(1): 10559
    Two-stage binding of mitochondrial ferredoxin-2 to the core iron-sulfur cluster assembly complex.
    Ralf Steinhilper, Linda Boß, Sven-A Freibert, Vinzent Schulz, Nils Krapoth, Susann Kaltwasser, Roland Lill, Bonnie J Murphy.
      Iron-sulfur (FeS) protein biogenesis in eukaryotes begins with the de novo assembly of [2Fe-2S] clusters by the mitochondrial core iron-sulfur cluster assembly (ISC) complex. This complex comprises the scaffold protein ISCU2, the cysteine desulfurase subcomplex NFS1-ISD11-ACP1, the allosteric activator frataxin (FXN) and the electron donor ferredoxin-2 (FDX2). The structural interaction of FDX2 with the complex remains unclear. Here, we present cryo-EM structures of the human FDX2-bound core ISC complex showing that FDX2 and FXN compete for overlapping binding sites. FDX2 binds in either a 'distal' conformation, where its helix F interacts electrostatically with an arginine patch of NFS1, or a 'proximal' conformation, where this interaction tightens and the FDX2-specific C terminus binds to NFS1, facilitating the movement of the [2Fe-2S] cluster of FDX2 closer to the ISCU2 FeS cluster assembly site for rapid electron transfer. Structure-based mutational studies verify the contact areas of FDX2 within the core ISC complex.
    DOI:  https://doi.org/10.1038/s41467-024-54585-4
  13. Mol Metab. 2024 Nov 30. pii: S2212-8778(24)00208-4. [Epub ahead of print] 102077
    Mammalian mitochondrial inorganic polyphosphate (polyP) and cell signaling: Crosstalk between PolyP and the activity of AMPK.
    Renata T Da Costa, Anna Nichenko, Matheus M Perez, Malgorzata Tokarska-Schlattner, Sheida Kavehmoghaddam, Vedangi Hambardikar, Ernest R Scoma, Erin L Seifert, Uwe Schlattner, Joshua C Drake, Maria E Solesio.
      Inorganic polyphosphate (polyP) is an evolutionary ancient polymer composed by orthophosphate units linked by phosphoanhydride bonds. In mammalian cells, polyP shows a high localization in mammalian mitochondria, and its regulatory role in various aspects of bioenergetics has already been demonstrated, via molecular mechanism(s) yet to be fully elucidated. In recent years, a role for polyP in signal transduction, from brain physiology to bloodstream, has also emerged. The intriguing possibility is that the effects of polyP on signal transduction could be mechanistically linked to those exerted on bioenergetics. Here, using a combination of cellular and animal models, we demonstrate for the first time the intimate crosstalk between the levels of polyP and the activation status of the AMPK signaling pathway, via a mechanism involving free phosphate homeostasis. AMPK is a key player in mammalian cell signaling, and a crucial regulator of cellular and mitochondrial homeostasis. Our results show that the depletion of mitochondrial polyP in mammalian cells downregulates the activity of AMPK. Moreover, increased levels of polyP activate AMPK. Accordingly, the genetic downregulation of AMPKα1 impairs polyP levels in both SH-SY5Y cells and in the brains of female mice. Our findings shed new light on the regulation of AMPK and position polyP as a potent regulator of mammalian cell physiology beyond mere bioenergetics, paving the road for using its metabolism as an innovative pharmacological target in pathologies characterized by dysregulated bioenergetics.
    Keywords:  AMPK; Bioenergetics; Cell signaling; Inorganic polyphosphate; Mammalian cells; Mitochondria
    DOI:  https://doi.org/10.1016/j.molmet.2024.102077
  14. Nat Struct Mol Biol. 2024 Dec 04.
    Understanding ubiquitination in neurodevelopment by integrating insights across space and time.
    Mateusz C Ambrozkiewicz, Sonja Lorenz.
      Ubiquitination regulates a myriad of eukaryotic signaling cascades by modifying substrate proteins, thereby determining their functions and fates. In this perspective, we discuss current challenges in investigating the ubiquitin system in the developing brain. We foster the concept that ubiquitination pathways are spatiotemporally regulated and tightly intertwined with molecular and cellular transitions during neurogenesis and neural circuit assembly. Focusing on the neurologically highly relevant class of homologous to E6AP C-terminus (HECT) ubiquitin ligases, we propose cross-disciplinary translational approaches bridging state-of-the-art cell biology, proteomics, biochemistry, structural biology and neuroscience to dissect ubiquitination in neurodevelopment and its specific perturbations in brain diseases. We highlight that a comprehensive understanding of ubiquitin signaling in the brain may reveal new horizons in basic neuroscience and clinical applications.
    DOI:  https://doi.org/10.1038/s41594-024-01422-3
  15. FASEB J. 2024 Dec 15. 38(23): e70223
    Purification of mitochondria from skeletal muscle tissue for transcriptomic analyses reveals localization of nuclear-encoded noncoding RNAs.
    Jessica Silver, Adam J Trewin, Stella Loke, Larry Croft, Mark Ziemann, Megan Soria, Hayley Dillon, Søren Nielsen, Séverine Lamon, Glenn D Wadley.
      Mitochondria are central to cellular function, particularly in metabolically active tissues such as skeletal muscle. Nuclear-encoded RNAs typically localize within the nucleus and cytosol but a small population may also translocate to subcellular compartments such as mitochondria. We aimed to investigate the nuclear-encoded RNAs that localize within the mitochondria of skeletal muscle cells and tissue. Intact mitochondria were isolated via immunoprecipitation (IP) followed by enzymatic treatments (RNase-A and proteinase-K) optimized to remove transcripts located exterior to mitochondria, making it amenable for high-throughput transcriptomic sequencing. Small RNA sequencing libraries were successfully constructed from as little as 1.8 ng mitochondrial RNA input. Small RNA sequencing of mitochondria from rat myoblasts revealed the enrichment of over 200 miRNAs. Whole-transcriptome RNA sequencing of enzymatically purified mitochondria isolated by IP from skeletal muscle tissue showed a striking similarity in the degree of purity compared to mitoplast preparations which lack an outer mitochondrial membrane. In summary, we describe a novel, powerful sequencing approach applicable to animal and human tissues and cells that can facilitate the discovery of nuclear-encoded RNA transcripts localized within skeletal muscle mitochondria.
    DOI:  https://doi.org/10.1096/fj.202401618R
  16. Nat Commun. 2024 Dec 03. 15(1): 10532
    Stabilization of expandable DNA repeats by the replication factor Mcm10 promotes cell viability.
    Chiara Masnovo, Zohar Paleiov, Daniel Dovrat, Laurel K Baxter, Sofia Movafaghi, Amir Aharoni, Sergei M Mirkin.
      Trinucleotide repeats, including Friedreich's ataxia (GAA)n repeats, become pathogenic upon expansions during DNA replication and repair. Here, we show that deficiency of the essential replisome component Mcm10 dramatically elevates (GAA)n repeat instability in a budding yeast model by loss of proper CMG helicase interaction. Supporting this conclusion, live-cell microscopy experiments reveal increased replication fork stalling at the repeat in mcm10-1 cells. Unexpectedly, the viability of strains containing a single (GAA)100 repeat at an essential chromosomal location strongly depends on Mcm10 function and cellular RPA levels. This coincides with Rad9 checkpoint activation, which promotes cell viability, but initiates repeat expansions via DNA synthesis by polymerase δ. When repair is inefficient, such as in the case of RPA depletion, breakage of under-replicated repetitive DNA can occur during G2/M, leading to loss of essential genes and cell death. We hypothesize that the CMG-Mcm10 interaction promotes replication through hard-to-replicate regions, assuring genome stability and cell survival.
    DOI:  https://doi.org/10.1038/s41467-024-54977-6
  17. Mol Cell Biochem. 2024 Dec 02.
    Mitochondrial dysfunction in pregnancy loss: a review.
    Lingjing Lu, Xinyue Huang, Yuqian Shi, Yue Jiang, Yanhua Han, Yuehui Zhang.
      A receptive endometrium, a healthy embryo, and harmonious communication between the mother and the embryo/fetus are necessary for a healthy and successful pregnancy. Pregnancy loss (PL) can be the outcome if there is a flaw in any of these critical developmental processes. Multiple risk factors contribute to PL, including genetic predispositions, uterine abnormalities, immune imbalances, endocrine dysfunctions, and environmental exposures, among others. Despite extensive investigations, more than half of women with recurrent pregnancy loss (RPL) lack identifiable risk factors, and causes of RPL remain elusive. To date, an accumulating body of evidence indicates that mitochondrial dysfunction in reproductive organs or cells is a potential underlying factor that may trigger PL. In this comprehensive review, we delve into the intricate relationship between mitochondrial dysfunction and PL, examining studies that focus on this connection in the context of diverse reproductive organs and cells, to unravel the interwoven links between these factors and gain a deeper understanding of their interconnectedness.
    Keywords:  Miscarriage; Mitochondrial dysfunction; Pregnancy loss; Spontaneous abortion
    DOI:  https://doi.org/10.1007/s11010-024-05171-1
  18. Stem Cell Res Ther. 2024 Dec 05. 15(1): 464
    Trehalose extricates impaired mitochondrial and autophagy dysregulation in patient iPSC-derived macular corneal dystrophy disease model.
    Divyani Nayak, Shivapriya Shivakumar, Rohit Shetty, K N Prashanthi, Arkasubhra Ghosh, Nallathambi Jeyabalan, Koushik Chakrabarty.
       BACKGROUND: Patient-derived induced pluripotent stem cell (iPSCs) represents a powerful tool for elucidating the underlying disease mechanisms. Macular corneal dystrophy (MCD) is an intractable and progressive bilateral corneal disease affecting the corneal stroma due to mutation/s in carbohydrate sulfotransferase 6 (CHST6) gene. The underlying molecular mechanisms leading to MCD are unclear due to a lack of human contextual model and limited access to affected corneal stromal keratocytes (CSKs) from MCD patients. This has restricted the current treatment option for MCD to restorative corneal transplantation thereby lending itself to the use of iPSCs.
    METHODS: induced pluripotent stem cells (iPSCs) were generated from two MCD patients and a healthy participant by senai virus based reprogramming of the peripheral mononuclear blood cells (PBMCs). The iPSCs were characterized based on the expression of pluripotent markers and formation of embryoid bodies possessing tri-lineage potential. Directed differentiation of the iPSCs to corneal stromal keratocytes (CSKs) was done via intermediate induction of neural crest cells. The iCSKs were characterized by immunocytochemistry and qPCR. Proteostat staining of the iCSKs was done to validate the disease phenotype invitro. Expression of autophagy markers in the iCSKs and JC staining were visualized by immunochemistry and live-cell imaging in trehalose treated iCSKs.
    RESULTS: We show that the MCD iPSC-derived CSKs (MCDiCSKs) exhibits impaired autophagy assessed by the profiles of autophagy-associated proteins (LAMP1, LC3II/I, p62 and Beclin-1) and mitochondrial membrane potential. Significantly higher protein aggregates in MCDiCSKs was seen compared with the control, which could be rescued upon autophagy modulation. Hence, we treated MCD-iCSKs with trehalose (autophagy inducer) and showed that it protects MCD-iCSKs from mitochondrial dysfunction and maintains autophagic degradation.
    CONCLUSION: Our study highlights the possible pathological mechanisms involved in MCD. We found trehalose ameliorate the impaired mitochondrial and autophagy dysregulation in patient iPSC-derived macular corneal dystrophy disease model, which could be a potential alternative for MCD management.
    Keywords:  Autophagy; Corneal stromal cells; Differentiation; Macular corneal dystrophy; Mitochondrial damage; Pluripotent stem cells
    DOI:  https://doi.org/10.1186/s13287-024-04016-4
  19. Biochim Biophys Acta Bioenerg. 2024 Nov 28. pii: S0005-2728(24)00499-7. [Epub ahead of print]1866(2): 149529
    Alternative NADH dehydrogenase: A complex I backup, a drug target, and a tool for mitochondrial gene therapy.
    Dmytro V Gospodaryov.
      Alternative NADH dehydrogenase, also known as type II NADH dehydrogenase (NDH-2), catalyzes the same redox reaction as mitochondrial respiratory chain complex I. Specifically, it oxidizes reduced nicotinamide adenine dinucleotide (NADH) while simultaneously reducing ubiquinone to ubiquinol. However, unlike complex I, this enzyme is non-proton pumping, comprises of a single subunit, and is resistant to rotenone. Initially identified in bacteria, fungi and plants, NDH-2 was subsequently discovered in protists and certain animal taxa including sea squirts. The gene coding for NDH-2 is also present in the genomes of some annelids, tardigrades, and crustaceans. For over two decades, NDH-2 has been investigated as a potential substitute for defective complex I. In model organisms, NDH-2 has been shown to ameliorate a broad spectrum of conditions associated with complex I malfunction, including symptoms of Parkinson's disease. Recently, lifespan extension has been observed in animals expressing NDH-2 in a heterologous manner. A variety of mechanisms have been put forward by which NDH-2 may extend lifespan. Such mechanisms include the activation of pro-longevity pathways through modulation of the NAD+/NADH ratio, decreasing production of reactive oxygen species (ROS) in mitochondria, or then through moderate increases in ROS production followed by activation of defense pathways (mitohormesis). This review gives an overview of the latest research on NDH-2, including the structural peculiarities of NDH-2, its inhibitors, its role in the pathogenicity of mycobacteria and apicomplexan parasites, and its function in bacteria, fungi, and animals.
    Keywords:  Hypoxia/reoxygenation; Mitochondrial diseases; Quinolones; Rossmann fold; Type II NADH dehydrogenase; iron‑sulfur clusters
    DOI:  https://doi.org/10.1016/j.bbabio.2024.149529
  20. Nat Commun. 2024 Dec 04. 15(1): 10582
    Neuronal PRDX-2-Mediated ROS Signaling Regulates Food Digestion via peripheral UPRmt Activation.
    Yating Liu, Qian Li, Guojing Tian, Xinyi Zhou, Panpan Chen, Bo Chen, Zhao Shan, Bin Qi.
      All organisms depend on food digestion for survival, yet the brain-gut signaling mechanisms that regulate this process are not fully understood. Here, using an established C. elegans digestion model, we uncover a pathway in which neuronal ROS (free radicals) signal the intestine to suppress digestion. Genetic screening reveals that reducing genes responsible for maintaining ROS balance increases free radicals and decreases digestion. PRDX-2 knockout in olfactory neurons (AWC) elevates ROS and reduces digestive capacity, mediated by the neuropeptide NLP-1 and activation of the mitochondrial unfolded protein response (UPRmt) in the intestine. Additionally, over-expressing nlp-1 or ablating AWC neurons both trigger UPRmt and inhibit digestion. These findings reveal a brain-gut connection in which neuronal PRDX-2-mediated ROS signaling modulates food digestion, highlighting a critical role of free radicals in shutting down digestion to alleviate stress and reduce food consumption.
    DOI:  https://doi.org/10.1038/s41467-024-55013-3
This page is being maintained by Thomas Krichel. It was last updated on 2024‒12‒08 at 10:32.