bims-mitdyn Biomed News
on Mitochondrial dynamics: mechanisms
Issue of 2023–11–26
seven papers selected by
Edmond Chan, Queen’s University, School of Medicine
  1. Mitochondrial fission drives neuronal metabolic burden to promote stress susceptibility in male mice.
  2. Inferring mitochondrial and cytosolic metabolism by coupling isotope tracing and deconvolution.
  3. Mitochondrial nucleoid condensates drive peripheral fission through high membrane curvature.
  4. Mitochondria-sequestered Aβ renders synaptic mitochondria vulnerable in the elderly with a risk of Alzheimer disease.
  5. Mitochondrial phosphoproteomes are functionally specialized across tissues.
  6. Mechanisms of stress management in mitochondrial protein import.
  7. c-Abl Phosphorylates MFN2 to Regulate Mitochondrial Morphology in Cells under Endoplasmic Reticulum and Oxidative Stress, Impacting Cell Survival and Neurodegeneration.
  1. Nat Metab. 2023 Nov 20.
    Mitochondrial fission drives neuronal metabolic burden to promote stress susceptibility in male mice.
    Wan-Ting Dong, Li-Hong Long, Qiao Deng, Duo Liu, Jia-Lin Wang, Fang Wang, Jian-Guo Chen.
      Neurons are particularly susceptible to energy fluctuations in response to stress. Mitochondrial fission is highly regulated to generate ATP via oxidative phosphorylation; however, the role of a regulator of mitochondrial fission in neuronal energy metabolism and synaptic efficacy under chronic stress remains elusive. Here, we show that chronic stress promotes mitochondrial fission in the medial prefrontal cortex via activating dynamin-related protein 1 (Drp1), resulting in mitochondrial dysfunction in male mice. Both pharmacological inhibition and genetic reduction of Drp1 ameliorates the deficit of excitatory synaptic transmission and stress-related depressive-like behavior. In addition, enhancing Drp1 fission promotes stress susceptibility, which is alleviated by coenzyme Q10, which potentiates mitochondrial ATP production. Together, our findings unmask the role of Drp1-dependent mitochondrial fission in the deficits of neuronal metabolic burden and depressive-like behavior and provides medication basis for metabolism-related emotional disorders.
    DOI:  https://doi.org/10.1038/s42255-023-00924-6
  2. Nat Commun. 2023 11 18. 14(1): 7525
    Inferring mitochondrial and cytosolic metabolism by coupling isotope tracing and deconvolution.
    Alon Stern, Mariam Fokra, Boris Sarvin, Ahmad Abed Alrahem, Won Dong Lee, Elina Aizenshtein, Nikita Sarvin, Tomer Shlomi.
      The inability to inspect metabolic activities within distinct subcellular compartments has been a major barrier to our understanding of eukaryotic cell metabolism. Previous work addressed this challenge by analyzing metabolism in isolated organelles, which grossly bias metabolic activity. Here, we describe a method for inferring physiological metabolic fluxes and metabolite concentrations in mitochondria and cytosol based on isotope tracing experiments performed with intact cells. This is made possible by computational deconvolution of metabolite isotopic labeling patterns and concentrations into cytosolic and mitochondrial counterparts, coupled with metabolic and thermodynamic modelling. Our approach lowers the uncertainty regarding compartmentalized fluxes and concentrations by one and three orders of magnitude compared to existing modelling approaches, respectively. We derive a quantitative view of mitochondrial and cytosolic metabolic activities in central carbon metabolism across cultured cell lines without performing cell fractionation, finding major variability in compartmentalized malate-aspartate shuttle fluxes. We expect our approach for inferring metabolism at a subcellular resolution to be instrumental for a variety of studies of metabolic dysfunction in human disease and for bioengineering.
    DOI:  https://doi.org/10.1038/s41467-023-42824-z
  3. Cell Rep. 2023 Nov 23. pii: S2211-1247(23)01484-5. [Epub ahead of print]42(12): 113472
    Mitochondrial nucleoid condensates drive peripheral fission through high membrane curvature.
    Qixin Chen, Liu-Yi Liu, Zhiqi Tian, Zhou Fang, Kang-Nan Wang, Xintian Shao, Chengying Zhang, Weiwei Zou, Fiona Rowan, Kangqiang Qiu, Baohua Ji, Jun-Lin Guan, Dechang Li, Zong-Wan Mao, Jiajie Diao.
      Mitochondria are dynamic organelles that undergo fusion and fission events, in which the mitochondrial membrane and DNA (mtDNA) play critical roles. The spatiotemporal organization of mtDNA reflects and impacts mitochondrial dynamics. Herein, to study the detailed dynamics of mitochondrial membrane and mtDNA, we rationally develop a dual-color fluorescent probe, mtGLP, that could be used for simultaneously monitoring mitochondrial membrane and mtDNA dynamics via separate color outputs. By combining mtGLP with structured illumination microscopy to monitor mitochondrial dynamics, we discover the formation of nucleoid condensates in damaged mitochondria. We further reveal that nucleoid condensates promoted the peripheral fission of damaged mitochondria via asymmetric segregation. Through simulations, we find that the peripheral fission events occurred when the nucleoid condensates interacted with the highly curved membrane regions at the two ends of the mitochondria. Overall, we show that mitochondrial nucleoid condensates utilize peripheral fission to maintain mitochondrial homeostasis.
    Keywords:  CP: Cell biology; chemical biology
    DOI:  https://doi.org/10.1016/j.celrep.2023.113472
  4. JCI Insight. 2023 Nov 22. pii: e174290. [Epub ahead of print]8(22):
    Mitochondria-sequestered Aβ renders synaptic mitochondria vulnerable in the elderly with a risk of Alzheimer disease.
    Kun Jia, Jing Tian, Tienju Wang, Lan Guo, Zhenyu Xuan, Russell H Swerdlow, Heng Du.
      Mitochondria are critical for neurophysiology, and mitochondrial dysfunction constitutes a characteristic pathology in both brain aging and Alzheimer disease (AD). Whether mitochondrial deficiency in brain aging and AD is mechanistically linked, however, remains controversial. We report a correlation between intrasynaptosomal amyloid β 42 (Aβ42) and synaptic mitochondrial bioenergetics inefficiency in both aging and amnestic mild cognitive impairment, a transitional stage between normal aging and AD. Experiments using a mouse model expressing nonmutant humanized Aβ (humanized Aβ-knockin [hAβ-KI] mice) confirmed the association of increased intramitochondrial sequestration of Aβ42 with exacerbated synaptic mitochondrial dysfunction in an aging factor- and AD risk-bearing context. Also, in comparison with global cerebral Aβ, intramitochondrial Aβ was relatively preserved from activated microglial phagocytosis in aged hAβ-KI mice. The most parsimonious interpretation of our results is that aging-related mitochondrial Aβ sequestration renders synaptic mitochondrial dysfunction in the transitional stage between normal aging and AD. Mitochondrial dysfunction in both brain aging and the prodromal stage of AD may follow a continuous transition in response to escalated intraneuronal, especially intramitochondrial Aβ, accumulation. Moreover, our findings further implicate a pivotal role of mitochondria in harboring early amyloidosis during the conversion from normal to pathological aging.
    Keywords:  Aging; Alzheimer disease; Mitochondria; Mouse models; Neuroscience
    DOI:  https://doi.org/10.1172/jci.insight.174290
  5. Life Sci Alliance. 2024 Feb;pii: e202302147. [Epub ahead of print]7(2):
    Mitochondrial phosphoproteomes are functionally specialized across tissues.
    Fynn M Hansen, Laura S Kremer, Ozge Karayel, Isabell Bludau, Nils-Göran Larsson, Inge Kühl, Matthias Mann.
      Mitochondria are essential organelles whose dysfunction causes human pathologies that often manifest in a tissue-specific manner. Accordingly, mitochondrial fitness depends on versatile proteomes specialized to meet diverse tissue-specific requirements. Increasing evidence suggests that phosphorylation may play an important role in regulating tissue-specific mitochondrial functions and pathophysiology. Building on recent advances in mass spectrometry (MS)-based proteomics, we here quantitatively profile mitochondrial tissue proteomes along with their matching phosphoproteomes. We isolated mitochondria from mouse heart, skeletal muscle, brown adipose tissue, kidney, liver, brain, and spleen by differential centrifugation followed by separation on Percoll gradients and performed high-resolution MS analysis of the proteomes and phosphoproteomes. This in-depth map substantially quantifies known and predicted mitochondrial proteins and provides a resource of core and tissue-specific mitochondrial proteins (mitophos.de). Predicting kinase substrate associations for different mitochondrial compartments indicates tissue-specific regulation at the phosphoproteome level. Illustrating the functional value of our resource, we reproduce mitochondrial phosphorylation events on dynamin-related protein 1 responsible for its mitochondrial recruitment and fission initiation and describe phosphorylation clusters on MIGA2 linked to mitochondrial fusion.
    DOI:  https://doi.org/10.26508/lsa.202302147
  6. Biochem Soc Trans. 2023 Nov 21. pii: BST20230377. [Epub ahead of print]
    Mechanisms of stress management in mitochondrial protein import.
    Maryam Mukhtar, Krutika Thakkur, Agnieszka Chacinska, Piotr Bragoszewski.
      Mitochondria are vital to the functions of eukaryotic cells. Most mitochondrial proteins are transported into the organelle following their synthesis by cytoplasmic ribosomes. However, precise protein targeting is complex because the two diverse lipid membranes encase mitochondria. Efficient protein translocation across membranes and accurate sorting to specific sub-compartments require the cooperation of multiple factors. Any failure in mitochondrial protein import can disrupt organelle fitness. Proteins intended for mitochondria make up a significant portion of all proteins produced in the cytosol. Therefore, import defects causing their mislocalization can significantly stress cellular protein homeostasis. Recognition of this phenomenon has increased interest in molecular mechanisms that respond to import-related stress and restore proteostasis, which is the focus of this review. Significantly, disruptions in protein homeostasis link strongly to the pathology of several degenerative disorders highly relevant in ageing societies. A comprehensive understanding of protein import quality control will allow harnessing this machinery in therapeutic approaches.
    Keywords:  mitochondria; protein degradation; protein transport; proteostasis; proteotoxicity; stress
    DOI:  https://doi.org/10.1042/BST20230377
  7. Antioxidants (Basel). 2023 Nov 16. pii: 2007. [Epub ahead of print]12(11):
    c-Abl Phosphorylates MFN2 to Regulate Mitochondrial Morphology in Cells under Endoplasmic Reticulum and Oxidative Stress, Impacting Cell Survival and Neurodegeneration.
    Alexis Martinez, Cristian M Lamaizon, Cristian Valls, Fabien Llambi, Nancy Leal, Patrick Fitzgerald, Cliff Guy, Marcin M Kamiński, Nibaldo C Inestrosa, Brigitte van Zundert, Gonzalo I Cancino, Andrés E Dulcey, Silvana Zanlungo, Juan J Marugan, Claudio Hetz, Douglas R Green, Alejandra R Alvarez.
      The endoplasmic reticulum is a subcellular organelle key in the control of synthesis, folding, and sorting of proteins. Under endoplasmic reticulum stress, an adaptative unfolded protein response is activated; however, if this activation is prolonged, cells can undergo cell death, in part due to oxidative stress and mitochondrial fragmentation. Here, we report that endoplasmic reticulum stress activates c-Abl tyrosine kinase, inducing its translocation to mitochondria. We found that endoplasmic reticulum stress-activated c-Abl interacts with and phosphorylates the mitochondrial fusion protein MFN2, resulting in mitochondrial fragmentation and apoptosis. Moreover, the pharmacological or genetic inhibition of c-Abl prevents MFN2 phosphorylation, mitochondrial fragmentation, and apoptosis in cells under endoplasmic reticulum stress. Finally, in the amyotrophic lateral sclerosis mouse model, where endoplasmic reticulum and oxidative stress has been linked to neuronal cell death, we demonstrated that the administration of c-Abl inhibitor neurotinib delays the onset of symptoms. Our results uncovered a function of c-Abl in the crosstalk between endoplasmic reticulum stress and mitochondrial dynamics via MFN2 phosphorylation.
    Keywords:  amyotrophic lateral sclerosis; apoptosis; c-Abl; endoplasmic reticulum stress; mitochondrial fusion; mitofusin 2
    DOI:  https://doi.org/10.3390/antiox12112007
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