bims-mitpro Biomed News
on Mitochondrial Proteostasis
Issue of 2024‒02‒18
ten papers selected by
Andreas Kohler, Umeå University
  1. Mitochondrial S-adenosylmethionine deficiency induces mitochondrial unfolded protein response and extends lifespan in Caenorhabditis elegans.
  2. Nutrient-dependent regulation of a stable intron modulates germline mitochondrial quality control.
  3. The HRI branch of the integrated stress response selectively triggers mitophagy.
  4. Renal aging and mitochondrial quality control.
  5. The role of mitophagy in metabolic diseases and its exercise intervention.
  6. Disruption of mitochondrial unfolded protein response results in telomere shortening in mouse oocytes and somatic cells.
  7. Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations.
  8. A system for inducible mitochondria-specific protein degradation in vivo.
  9. Structural basis for regulated assembly of the mitochondrial fission GTPase Drp1.
  10. A new family of bacterial ribosome hibernation factors.
  1. Aging Cell. 2024 Feb 15. e14103
    Mitochondrial S-adenosylmethionine deficiency induces mitochondrial unfolded protein response and extends lifespan in Caenorhabditis elegans.
    Tse Yu Chen, Feng-Yung Wang, Pin-Jung Lee, Ao-Lin Hsu, Tsui-Ting Ching.
      S-adenosylmethionine (SAM), generated from methionine and ATP by S-adenosyl methionine synthetase (SAMS), is the universal methyl group donor required for numerous cellular methylation reactions. In Caenorhabditis elegans, silencing sams-1, the major isoform of SAMS, genetically or via dietary restriction induces a robust mitochondrial unfolded protein response (UPRmt ) and lifespan extension. In this study, we found that depleting SAMS-1 markedly decreases mitochondrial SAM levels. Moreover, RNAi knockdown of SLC-25A26, a carrier protein responsible for transporting SAM from the cytoplasm into the mitochondria, significantly lowers the mitochondrial SAM levels and activates UPRmt , suggesting that the UPRmt induced by sams-1 mutations might result from disrupted mitochondrial SAM homeostasis. Through a genetic screen, we then identified a putative mitochondrial tRNA methyltransferase TRMT-10C.2 as a major downstream effector of SAMS-1 to regulate UPRmt and longevity. As disruption of mitochondrial tRNA methylation likely leads to impaired mitochondrial tRNA maturation and consequently reduced mitochondrial translation, our findings suggest that depleting mitochondrial SAM level might trigger UPRmt via attenuating protein translation in the mitochondria. Together, this study has revealed a potential mechanism by which SAMS-1 regulates UPRmt and longevity.
    Keywords:  S-adenosyl methionine; UPRmt; longevity; mitochondrial tRNA methyltransferase
    DOI:  https://doi.org/10.1111/acel.14103
  2. Nat Commun. 2024 Feb 10. 15(1): 1252
    Nutrient-dependent regulation of a stable intron modulates germline mitochondrial quality control.
    Annabel Qi En Ng, Seow Neng Chan, Jun Wei Pek.
      Mitochondria are inherited exclusively from the mothers and are required for the proper development of embryos. Hence, germline mitochondrial quality is highly regulated during oogenesis to ensure oocyte viability. How nutrient availability influences germline mitochondrial quality control is unclear. Here we find that fasting leads to the accumulation of mitochondrial clumps and oogenesis arrest in Drosophila. Fasting induces the downregulation of the DIP1-Clueless pathway, leading to an increase in the expression of a stable intronic sequence RNA called sisR-1. Mechanistically, sisR-1 localizes to the mitochondrial clumps to inhibit the poly-ubiquitination of the outer mitochondrial protein Porin/VDAC1, thereby suppressing p62-mediated mitophagy. Alleviation of the fasting-induced high sisR-1 levels by either sisR-1 RNAi or refeeding leads to mitophagy, the resumption of oogenesis and an improvement in oocyte quality. Thus, our study provides a possible mechanism by which fasting can improve oocyte quality by modulating the mitochondrial quality control pathway. Of note, we uncover that the sisR-1 response also regulates mitochondrial clumping and oogenesis during protein deprivation, heat shock and aging, suggesting a broader role for this mechanism in germline mitochondrial quality control.
    DOI:  https://doi.org/10.1038/s41467-024-45651-y
  3. Mol Cell. 2024 Feb 06. pii: S1097-2765(24)00052-2. [Epub ahead of print]
    The HRI branch of the integrated stress response selectively triggers mitophagy.
    Yogaditya Chakrabarty, Zheng Yang, Hsiuchen Chen, David C Chan.
      To maintain mitochondrial homeostasis, damaged or excessive mitochondria are culled in coordination with the physiological state of the cell. The integrated stress response (ISR) is a signaling network that recognizes diverse cellular stresses, including mitochondrial dysfunction. Because the four ISR branches converge to common outputs, it is unclear whether mitochondrial stress detected by this network can regulate mitophagy, the autophagic degradation of mitochondria. Using a whole-genome screen, we show that the heme-regulated inhibitor (HRI) branch of the ISR selectively induces mitophagy. Activation of the HRI branch results in mitochondrial localization of phosphorylated eukaryotic initiation factor 2, which we show is sufficient to induce mitophagy. The HRI mitophagy pathway operates in parallel with the mitophagy pathway controlled by the Parkinson's disease related genes PINK1 and PARKIN and is mechanistically distinct. Therefore, HRI repurposes machinery that is normally used for translational initiation to trigger mitophagy in response to mitochondrial damage.
    Keywords:  autophagy; integrated stress response; iron metabolism; mitochondria; mitophagy; organelle quality control
    DOI:  https://doi.org/10.1016/j.molcel.2024.01.016
  4. Biogerontology. 2024 Feb 13.
    Renal aging and mitochondrial quality control.
    Xiuli Guo, Jiao Wang, Yinjie Wu, Xinwang Zhu, Li Xu.
      Mitochondria are dynamic organelles that participate in different cellular process that control metabolism, cell division, and survival, and the kidney is one of the most metabolically active organs that contains abundant mitochondria. Perturbations in mitochondrial homeostasis in the kidney can accelerate kidney aging, and maintaining mitochondrial homeostasis can effectively delay aging in the kidney. Kidney aging is a degenerative process linked to detrimental processes. The significance of aberrant mitochondrial homeostasis in renal aging has received increasing attention. However, the contribution of mitochondrial quality control (MQC) to renal aging has not been reviewed in detail. Here, we generalize the current factors contributing to renal aging, review the alterations in MQC during renal injury and aging, and analyze the relationship between mitochondria and intrinsic renal cells. We also introduce MQC in the context of renal aging, and discuss the study of mitochondria in the intrinsic cells of the kidney, which is the innovation of our paper. In addition, during kidney injury and repair, the specific functions and regulatory mechanisms of MQC systems in resident and circulating cell types remain unclear. Currently, most of the studies we reviewed are based on animal and cellular models, the relationship between renal tissue aging and mitochondria has not been adequately investigated in clinical studies, and there is still a long way to go.
    Keywords:  Aging; Mitochondrial dysfunction; Mitochondrial quality control; Renal intrinsic cells
    DOI:  https://doi.org/10.1007/s10522-023-10091-6
  5. Front Physiol. 2024 ;15 1339128
    The role of mitophagy in metabolic diseases and its exercise intervention.
    Shaokai Tang, Yuanwen Geng, Qinqin Lin.
      Mitochondria are energy factories that sustain life activities in the body, and their dysfunction can cause various metabolic diseases that threaten human health. Mitophagy, an essential intracellular mitochondrial quality control mechanism, can maintain cellular and metabolic homeostasis by removing damaged mitochondria and participating in developing metabolic diseases. Research has confirmed that exercise can regulate mitophagy levels, thereby exerting protective metabolic effects in metabolic diseases. This article reviews the role of mitophagy in metabolic diseases, the effects of exercise on mitophagy, and the potential mechanisms of exercise-regulated mitophagy intervention in metabolic diseases, providing new insights for future basic and clinical research on exercise interventions to prevent and treat metabolic diseases.
    Keywords:  exercise; exerkine; metabolic disease; mitochondrial dysfunction; mitophagy
    DOI:  https://doi.org/10.3389/fphys.2024.1339128
  6. Aging (Albany NY). 2024 Feb 12. 16
    Disruption of mitochondrial unfolded protein response results in telomere shortening in mouse oocytes and somatic cells.
    Mauro Cozzolino, Yagmur Ergun, Emma Ristori, Akanksha Garg, Gizem Imamoglu, Emre Seli.
      Caseinolytic peptidase P (CLPP) plays a central role in mitochondrial unfolded protein response (mtUPR) by promoting the breakdown of misfolded proteins and setting in motion a cascade of reactions to re-establish protein homeostasis. Global germline deletion of Clpp in mice results in female infertility and accelerated follicular depletion. Telomeres are tandem repeats of 5'-TTAGGG-3' sequences found at the ends of the chromosomes. Telomeres are essential for maintaining chromosome stability during somatic cell division and their shortening is associated with cellular senescence and aging. In this study, we asked whether the infertility and ovarian aging phenotype caused by global germline deletion of Clpp is associated with somatic aging, and tested telomere length in tissues of young and aging mice. We found that impaired mtUPR caused by the lack of CLPP is associated with accelerated telomere shortening in both oocytes and somatic cells of aging mice. In addition, expression of several genes that maintain telomere integrity was decreased, and double-strand DNA breaks were increased in telomeric regions. Our results highlight how impaired mtUPR can affect telomere integrity and demonstrate a link between loss of mitochondrial protein hemostasis, infertility, and somatic aging.
    Keywords:  Clpp; aging; mitochondrial dysfunction; telomere length; unfolded protein response
    DOI:  https://doi.org/10.18632/aging.205543
  7. bioRxiv. 2024 Feb 01. pii: 2024.01.30.577830. [Epub ahead of print]
    Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations.
    Nicole Madrazo, Zinia Khattar, Evan T Powers, Jessica D Rosarda, R Luke Wiseman.
      Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically-diverse diseases. This has led to considerable interest in defining the biological mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress, including the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the specific stress signaling pathways activated in response to mitochondrial proteostasis stress by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of individual mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to mitochondrial proteostasis stress, with no other pathway showing significant activation. Further expanding this study, we show that broad depletion of mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to mitochondrial proteostasis disruption.
    DOI:  https://doi.org/10.1101/2024.01.30.577830
  8. Nat Commun. 2024 Feb 16. 15(1): 1454
    A system for inducible mitochondria-specific protein degradation in vivo.
    Swastika Sanyal, Anna Kouznetsova, Lena Ström, Camilla Björkegren.
      Targeted protein degradation systems developed for eukaryotes employ cytoplasmic machineries to perform proteolysis. This has prevented mitochondria-specific analysis of proteins that localize to multiple locations, for example, the mitochondria and the nucleus. Here, we present an inducible mitochondria-specific protein degradation system in Saccharomyces cerevisiae based on the Mesoplasma florum Lon (mf-Lon) protease and its corresponding ssrA tag (called PDT). We show that mitochondrially targeted mf-Lon protease efficiently and selectively degrades a PDT-tagged reporter protein localized to the mitochondrial matrix. The degradation can be induced by depleting adenine from the medium, and tuned by altering the promoter strength of the MF-LON gene. We furthermore demonstrate that mf-Lon specifically degrades endogenous, PDT-tagged mitochondrial proteins. Finally, we show that mf-Lon-dependent PDT degradation can also be achieved in human mitochondria. In summary, this system provides an efficient tool to selectively analyze the mitochondrial function of dually localized proteins.
    DOI:  https://doi.org/10.1038/s41467-024-45819-6
  9. Nat Commun. 2024 Feb 13. 15(1): 1328
    Structural basis for regulated assembly of the mitochondrial fission GTPase Drp1.
    Kristy Rochon, Brianna L Bauer, Nathaniel A Roethler, Yuli Buckley, Chih-Chia Su, Wei Huang, Rajesh Ramachandran, Maria S K Stoll, Edward W Yu, Derek J Taylor, Jason A Mears.
      Mitochondrial fission is a critical cellular event to maintain organelle function. This multistep process is initiated by the enhanced recruitment and oligomerization of dynamin-related protein 1 (Drp1) at the surface of mitochondria. As such, Drp1 is essential for inducing mitochondrial division in mammalian cells, and homologous proteins are found in all eukaryotes. As a member of the dynamin superfamily of proteins (DSPs), controlled Drp1 self-assembly into large helical polymers stimulates its GTPase activity to promote membrane constriction. Still, little is known about the mechanisms that regulate correct spatial and temporal assembly of the fission machinery. Here we present a cryo-EM structure of a full-length Drp1 dimer in an auto-inhibited state. This dimer reveals two key conformational rearrangements that must be unlocked through intramolecular rearrangements to achieve the assembly-competent state observed in previous structures. This structural insight provides understanding into the mechanism for regulated self-assembly of the mitochondrial fission machinery.
    DOI:  https://doi.org/10.1038/s41467-024-45524-4
  10. Nature. 2024 Feb 14.
    A new family of bacterial ribosome hibernation factors.
    Karla Helena-Bueno, Mariia Yu Rybak, Chinenye L Ekemezie, Rudi Sullivan, Charlotte R Brown, Charlotte Dingwall, Arnaud Baslé, Claudia Schneider, James P R Connolly, James N Blaza, Bálint Csörgő, Patrick J Moynihan, Matthieu G Gagnon, Chris H Hill, Sergey V Melnikov.
      To conserve energy during starvation and stress, many organisms use hibernation factor proteins to inhibit protein synthesis and protect their ribosomes from damage1,2. In bacteria, two families of hibernation factors have been described, but the low conservation of these proteins and the huge diversity of species, habitats and environmental stressors have confounded their discovery3-6. Here, by combining cryogenic electron microscopy, genetics and biochemistry, we identify Balon, a new hibernation factor in the cold-adapted bacterium Psychrobacter urativorans. We show that Balon is a distant homologue of the archaeo-eukaryotic translation factor aeRF1 and is found in 20% of representative bacteria. During cold shock or stationary phase, Balon occupies the ribosomal A site in both vacant and actively translating ribosomes in complex with EF-Tu, highlighting an unexpected role for EF-Tu in the cellular stress response. Unlike typical A-site substrates, Balon binds to ribosomes in an mRNA-independent manner, initiating a new mode of ribosome hibernation that can commence while ribosomes are still engaged in protein synthesis. Our work suggests that Balon-EF-Tu-regulated ribosome hibernation is a ubiquitous bacterial stress-response mechanism, and we demonstrate that putative Balon homologues in Mycobacteria bind to ribosomes in a similar fashion. This finding calls for a revision of the current model of ribosome hibernation inferred from common model organisms and holds numerous implications for how we understand and study ribosome hibernation.
    DOI:  https://doi.org/10.1038/s41586-024-07041-8
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