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Humphries BA, Zhang A, Buschhaus JM, Bevoor A, Farfel A, Rajendran S, Cutter AC, Luker GD. Enhanced mitochondrial fission inhibits triple-negative breast cancer cell migration through an ROS-dependent mechanism. iScience 2023; 26:106788. [PMID: 37235049 PMCID: PMC10206500 DOI: 10.1016/j.isci.2023.106788] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 01/27/2023] [Accepted: 04/26/2023] [Indexed: 05/28/2023] Open
Abstract
Mitochondria produce reactive oxygen species (ROS), which function in signal transduction. Mitochondrial dynamics, encompassing morphological shifts between fission and fusion, can directly impact ROS levels in cancer cells. In this study, we identified an ROS-dependent mechanism for how enhanced mitochondrial fission inhibits triple negative breast cancer (TNBC) cell migration. We found that enforcing mitochondrial fission in TNBC resulted in an increase in intracellular ROS levels and reduced cell migration and the formation of actin-rich migratory structures. Consistent with mitochondrial fission, increasing ROS levels in cells inhibited cell migration. Conversely, reducing ROS levels with either a global or mitochondrially targeted scavenger overcame the inhibitory effects of mitochondrial fission. Mechanistically, we found that the ROS sensitive SHP-1/2 phosphatases partially regulate inhibitory effects of mitochondrial fission on TNBC migration. Overall, our work reveals the inhibitory effects of ROS in TNBC and supports mitochondrial dynamics as a potential therapeutic target for cancer.
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Affiliation(s)
- Brock A. Humphries
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Anne Zhang
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Johanna M. Buschhaus
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Avinash Bevoor
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alex Farfel
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Shrila Rajendran
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alyssa C. Cutter
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gary D. Luker
- Center for Molecular Imaging, Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI 48109, USA
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2
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Humphries BA, Cutter AC, Buschhaus JM, Chen YC, Qyli T, Palagama DSW, Eckley S, Robison TH, Bevoor A, Chiang B, Haley HR, Sahoo S, Spinosa PC, Neale DB, Boppisetti J, Sahoo D, Ghosh P, Lahann J, Ross BD, Yoon E, Luker KE, Luker GD. Enhanced mitochondrial fission suppresses signaling and metastasis in triple-negative breast cancer. Breast Cancer Res 2020; 22:60. [PMID: 32503622 PMCID: PMC7275541 DOI: 10.1186/s13058-020-01301-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/20/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Mitochondrial dynamics underlies malignant transformation, cancer progression, and response to treatment. Current research presents conflicting evidence for functions of mitochondrial fission and fusion in tumor progression. Here, we investigated how mitochondrial fission and fusion states regulate underlying processes of cancer progression and metastasis in triple-negative breast cancer (TNBC). METHODS We enforced mitochondrial fission and fusion states through chemical or genetic approaches and measured migration and invasion of TNBC cells in 2D and 3D in vitro models. We also utilized kinase translocation reporters (KTRs) to identify single cell effects of mitochondrial state on signaling cascades, PI3K/Akt/mTOR and Ras/Raf/MEK/ERK, commonly activated in TNBC. Furthermore, we determined effects of fission and fusion states on metastasis, bone destruction, and signaling in mouse models of breast cancer. RESULTS Enforcing mitochondrial fission through chemical or genetic approaches inhibited migration, invasion, and metastasis in TNBC. Breast cancer cells with predominantly fissioned mitochondria exhibited reduced activation of Akt and ERK both in vitro and in mouse models of breast cancer. Treatment with leflunomide, a potent activator of mitochondrial fusion proteins, overcame inhibitory effects of fission on migration, signaling, and metastasis. Mining existing datasets for breast cancer revealed that increased expression of genes associated with mitochondrial fission correlated with improved survival in human breast cancer. CONCLUSIONS In TNBC, mitochondrial fission inhibits cellular processes and signaling pathways associated with cancer progression and metastasis. These data suggest that therapies driving mitochondrial fission may benefit patients with breast cancer.
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Affiliation(s)
- Brock A Humphries
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Alyssa C Cutter
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Johanna M Buschhaus
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
- Department of Biomedical Engineering, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Yu-Chih Chen
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
- Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI, USA
- Forbes Institute for Cancer Discovery, University of Michigan, Ann Arbor, MI, USA
| | - Tonela Qyli
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Dilrukshika S W Palagama
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Samantha Eckley
- Unit for Laboratory Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Tanner H Robison
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
- Department of Biomedical Engineering, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Avinash Bevoor
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Benjamin Chiang
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Henry R Haley
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Saswat Sahoo
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - Phillip C Spinosa
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Dylan B Neale
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, USA
| | - Jagadish Boppisetti
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Debashis Sahoo
- Department of Pediatrics, Department of Computer Science and Engineering, Jacob's School of Engineering, Rebecca and John Moore Comprehensive Cancer Center, University of California San Diego, La Jolla, CA, USA
| | - Pradipta Ghosh
- Department of Medicine, Department of Cellular and Molecular Medicine, Rebecca and John Moore Comprehensive Cancer Center, Veterans Affairs Medical Center, University of California San Diego, La Jolla, CA, USA
| | - Joerg Lahann
- Biointerfaces Institute, Departments of Chemical Engineering, Materials Science and Engineering, Biomedical Engineering, and Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Brian D Ross
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
- Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI, USA
| | - Eusik Yoon
- Department of Biomedical Engineering, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - Kathryn E Luker
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA
| | - Gary D Luker
- Center for Molecular Imaging, Department of Radiology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA.
- Department of Biomedical Engineering, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA.
- Department of Microbiology and Immunology, University of Michigan, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA.
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3
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Williams CF, George CH. Connect and Conquer: Collectivized Behavior of Mitochondria and Bacteria. Front Physiol 2019; 10:340. [PMID: 30984025 PMCID: PMC6450178 DOI: 10.3389/fphys.2019.00340] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/13/2019] [Indexed: 01/21/2023] Open
Abstract
The connectedness of signaling components in network structures is a universal feature of biologic information processing. Such organization enables the transduction of complex input stimuli into coherent outputs and is essential in modulating activities as diverse as the cooperation of bacteria within populations and the dynamic organization of mitochondria within cells. Here, we highlight some common principles that underpin collectivization in bacteria and mitochondrial populations and the advantages conferred by such behavior. We discuss the concept that bacteria and mitochondria act as signal transducers of their localized metabolic environments to bring about energy-dependent clustering to modulate higher-order function across multiple scales.
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4
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Nirwane A, Majumdar A. Understanding mitochondrial biogenesis through energy sensing pathways and its translation in cardio-metabolic health. Arch Physiol Biochem 2018; 124:194-206. [PMID: 29072101 DOI: 10.1080/13813455.2017.1391847] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Mitochondria play a pivotal role in physiological energy governance. Mitochondrial biogenesis comprises growth and division of pre-existing mitochondria, triggered by environmental stressors such as endurance exercise, caloric restriction, cold exposure and oxidative stress. For normal physiology, balance between energy intake, storage and expenditure is of utmost important for the coordinated regulation of energy homeostasis. In contrast, abnormalities in these regulations render the individual susceptible to cardiometabolic disorders. This review provides a comprehensive coverage and understanding on mitochondrial biogenesis achieved through energy-sensing pathways. This includes the complex coordination of nuclear, cytosolic and mitochondrial events involving energy sensors, transcription factors, coactivators and regulators. It focuses on the importance of mitochondrial biogenesis in cardiometabolic health. Lastly, converging on the benefits of caloric restriction and endurance exercise in achieving cardiometabolic health.
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Affiliation(s)
- Abhijit Nirwane
- a Department of Pharmacology , Bombay College of Pharmacy , Mumbai , India
- b Department of Pharmaceutical and Biomedical Sciences , University of Georgia , Athens , GA , USA
| | - Anuradha Majumdar
- a Department of Pharmacology , Bombay College of Pharmacy , Mumbai , India
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5
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Vincent AE, Turnbull DM, Eisner V, Hajnóczky G, Picard M. Mitochondrial Nanotunnels. Trends Cell Biol 2017; 27:787-799. [PMID: 28935166 PMCID: PMC5749270 DOI: 10.1016/j.tcb.2017.08.009] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/11/2017] [Accepted: 08/22/2017] [Indexed: 01/13/2023]
Abstract
Insight into the regulation of complex physiological systems emerges from understanding how biological units communicate with each other. Recent findings show that mitochondria communicate at a distance with each other via nanotunnels, thin double-membrane protrusions that connect the matrices of non-adjacent mitochondria. Emerging evidence suggest that mitochondrial nanotunnels are generated by immobilized mitochondria and transport proteins. This review integrates data from the evolutionarily conserved structure and function of intercellular projections in bacteria with recent developments in mitochondrial imaging that permit nanotunnel visualization in eukaryotes. Cell type-specificity, timescales, and the selective size-based diffusion of biomolecules along nanotunnels are also discussed. The joining of individual mitochondria into dynamic networks of communicating organelles via nanotunnels and other mechanisms has major implications for organelle and cellular behaviors.
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Affiliation(s)
- Amy E Vincent
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neurosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Doug M Turnbull
- Wellcome Trust Centre for Mitochondrial Research, Institute of Neurosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Veronica Eisner
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - György Hajnóczky
- MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Martin Picard
- Division of Behavioral Medicine, Department of Psychiatry, Columbia University Medical Center, New York, NY, USA; Department of Neurology, The Merritt Center and Columbia Translational Neuroscience Initiative, Columbia University Medical Center, New York, NY, USA; Columbia Aging Center, Columbia University Mailman School of Public Health, New York, NY 10032, USA.
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6
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Picard M, Wallace DC, Burelle Y. The rise of mitochondria in medicine. Mitochondrion 2016; 30:105-16. [PMID: 27423788 PMCID: PMC5023480 DOI: 10.1016/j.mito.2016.07.003] [Citation(s) in RCA: 294] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 07/04/2016] [Accepted: 07/12/2016] [Indexed: 12/11/2022]
Abstract
Once considered exclusively the cell's powerhouse, mitochondria are now recognized to perform multiple essential functions beyond energy production, impacting most areas of cell biology and medicine. Since the emergence of molecular biology and the discovery of pathogenic mitochondrial DNA defects in the 1980's, research advances have revealed a number of common human diseases which share an underlying pathogenesis involving mitochondrial dysfunction. Mitochondria undergo function-defining dynamic shape changes, communicate with each other, regulate gene expression within the nucleus, modulate synaptic transmission within the brain, release molecules that contribute to oncogenic transformation and trigger inflammatory responses systemically, and influence the regulation of complex physiological systems. Novel mitopathogenic mechanisms are thus being uncovered across a number of medical disciplines including genetics, oncology, neurology, immunology, and critical care medicine. Increasing knowledge of the bioenergetic aspects of human disease has provided new opportunities for diagnosis, therapy, prevention, and in connecting various domains of medicine. In this article, we overview specific aspects of mitochondrial biology that have contributed to - and likely will continue to enhance the progress of modern medicine.
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Affiliation(s)
- Martin Picard
- Department of Psychiatry, Division of Behavioral Medicine, Columbia University Medical Center, New York, NY, USA; Department of Neurology and CTNI, H Houston Merritt Center, Columbia University Medical Center, New York, NY, USA.
| | - Douglas C Wallace
- The Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Yan Burelle
- Faculty of Pharmacy, Université de Montreal, Montreal, QC, Canada
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7
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The Spectrum of Mitochondrial Ultrastructural Defects in Mitochondrial Myopathy. Sci Rep 2016; 6:30610. [PMID: 27506553 PMCID: PMC4978969 DOI: 10.1038/srep30610] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/07/2016] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial functions are intrinsically linked to their morphology and membrane ultrastructure. Characterizing abnormal mitochondrial structural features may thus provide insight into the underlying pathogenesis of inherited and acquired mitochondrial diseases. Following a systematic literature review on ultrastructural defects in mitochondrial myopathy, we investigated skeletal muscle biopsies from seven subjects with genetically defined mtDNA mutations. Mitochondrial ultrastructure and morphology were characterized using two complimentary approaches: transmission electron microscopy (TEM) and serial block face scanning EM (SBF-SEM) with 3D reconstruction. Six ultrastructural abnormalities were identified including i) paracrystalline inclusions, ii) linearization of cristae and abnormal angular features, iii) concentric layering of cristae membranes, iv) matrix compartmentalization, v) nanotunelling, and vi) donut-shaped mitochondria. In light of recent molecular advances in mitochondrial biology, these findings reveal novel aspects of mitochondrial ultrastructure and morphology in human tissues with implications for understanding the mechanisms linking mitochondrial dysfunction to disease.
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8
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Picard M. Mitochondrial synapses: intracellular communication and signal integration. Trends Neurosci 2015; 38:468-74. [PMID: 26187720 DOI: 10.1016/j.tins.2015.06.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/05/2015] [Accepted: 06/11/2015] [Indexed: 12/17/2022]
Abstract
Communication is a central theme in biology. Consequently, specialized structures have evolved to permit rapid communication among cells, tissues, organs, and physiological systems, thus enhancing the overall function and adaptation of the organism. A prime example is the neuronal synapse. In the brain, synaptic communication establishes neuronal networks with the capacity to integrate, process, and store information, giving rise to complex output signals capable of orchestrating functions across the organism. At the intracellular level, discoveries now reveal the existence of 'mitochondrial synapses' establishing mitochondrial networks, with defined chromatin-modifying mitochondrial output signals capable of orchestrating gene expression across the genome. These discoveries raise the possibility that in addition to their role as powerhouses and neuromodulators, mitochondria behave as intracellular signal-processing networks.
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Affiliation(s)
- Martin Picard
- Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia and the University of Pennsylvania, PA 19104, USA.
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9
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Hoitzing H, Johnston IG, Jones NS. What is the function of mitochondrial networks? A theoretical assessment of hypotheses and proposal for future research. Bioessays 2015; 37:687-700. [PMID: 25847815 PMCID: PMC4672710 DOI: 10.1002/bies.201400188] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondria can change their shape from discrete isolated organelles to a large continuous reticulum. The cellular advantages underlying these fused networks are still incompletely understood. In this paper, we describe and compare hypotheses regarding the function of mitochondrial networks. We use mathematical and physical tools both to investigate existing hypotheses and to generate new ones, and we suggest experimental and modelling strategies. Among the novel insights we underline from this work are the possibilities that (i) selective mitophagy is not required for quality control because selective fusion is sufficient; (ii) increased connectivity may have non-linear effects on the diffusion rate of proteins; and (iii) fused networks can act to dampen biochemical fluctuations. We hope to convey to the reader that quantitative approaches can drive advances in the understanding of the physiological advantage of these morphological changes.
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Affiliation(s)
- Hanne Hoitzing
- Department of Mathematics, Imperial College London, London, UK
| | - Iain G Johnston
- Department of Mathematics, Imperial College London, London, UK
| | - Nick S Jones
- Department of Mathematics, Imperial College London, London, UK
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10
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Trans-mitochondrial coordination of cristae at regulated membrane junctions. Nat Commun 2015; 6:6259. [PMID: 25687472 PMCID: PMC4332397 DOI: 10.1038/ncomms7259] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/09/2015] [Indexed: 01/22/2023] Open
Abstract
Reminiscent of bacterial quorum sensing, mammalian mitochondria participate in inter-organelle communication. However, physical structures that enhance or enable interactions between mitochondria have not been defined. Here we report that adjacent mitochondria exhibit coordination of inner mitochondrial membrane cristae at inter-mitochondrial junctions (IMJs). These electron-dense structures are conserved across species, resistant to genetic disruption of cristae organization, dynamically modulated by mitochondrial bioenergetics, independent of known inter-mitochondrial tethering proteins mitofusins and rapidly induced by the stable rapprochement of organelles via inducible synthetic linker technology. At the associated junctions, the cristae of adjacent mitochondria form parallel arrays perpendicular to the IMJ, consistent with a role in electrochemical coupling. These IMJs and associated cristae arrays may provide the structural basis to enhance the propagation of intracellular bioenergetic and apoptotic waves through mitochondrial networks within cells. Mammalian mitochondria are capable of inter-organelle communication, but connections between mitochondria have not been defined. Here, Picard et al. report the presence of inter-mitochondrial junctions, electron-dense regions with coordinated inner membrane cristae that do not depend on mitofusins for their formation.
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11
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Picard M, Shirihai OS, Gentil BJ, Burelle Y. Mitochondrial morphology transitions and functions: implications for retrograde signaling? Am J Physiol Regul Integr Comp Physiol 2013; 304:R393-406. [PMID: 23364527 DOI: 10.1152/ajpregu.00584.2012] [Citation(s) in RCA: 212] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In response to cellular and environmental stresses, mitochondria undergo morphology transitions regulated by dynamic processes of membrane fusion and fission. These events of mitochondrial dynamics are central regulators of cellular activity, but the mechanisms linking mitochondrial shape to cell function remain unclear. One possibility evaluated in this review is that mitochondrial morphological transitions (from elongated to fragmented, and vice-versa) directly modify canonical aspects of the organelle's function, including susceptibility to mitochondrial permeability transition, respiratory properties of the electron transport chain, and reactive oxygen species production. Because outputs derived from mitochondrial metabolism are linked to defined cellular signaling pathways, fusion/fission morphology transitions could regulate mitochondrial function and retrograde signaling. This is hypothesized to provide a dynamic interface between the cell, its genome, and the fluctuating metabolic environment.
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Affiliation(s)
- Martin Picard
- Center for Mitochondrial and Epigenomic Medicine, Children’s Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA
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12
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Picard M, White K, Turnbull DM. Mitochondrial morphology, topology, and membrane interactions in skeletal muscle: a quantitative three-dimensional electron microscopy study. J Appl Physiol (1985) 2012; 114:161-71. [PMID: 23104694 DOI: 10.1152/japplphysiol.01096.2012] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Dynamic remodeling of mitochondrial morphology through membrane dynamics are linked to changes in mitochondrial and cellular function. Although mitochondrial membrane fusion/fission events are frequent in cell culture models, whether mitochondrial membranes dynamically interact in postmitotic muscle fibers in vivo remains unclear. Furthermore, a quantitative assessment of mitochondrial morphology in intact muscle is lacking. Here, using electron microscopy (EM), we provide evidence of interacting membranes from adjacent mitochondria in intact mouse skeletal muscle. Electron-dense mitochondrial contact sites consistent with events of outer mitochondrial membrane tethering are also described. These data suggest that mitochondrial membranes interact in vivo among mitochondria, possibly to induce morphology transitions, for kiss-and-run behavior, or other processes involving contact between mitochondrial membranes. Furthermore, a combination of freeze-fracture scanning EM and transmission EM in orthogonal planes was used to characterize and quantify mitochondrial morphology. Two subpopulations of mitochondria were studied: subsarcolemmal (SS) and intermyofibrillar (IMF), which exhibited significant differences in morphological descriptors, including form factor (means ± SD for SS: 1.41 ± 0.45 vs. IMF: 2.89 ± 1.76, P < 0.01) and aspect ratio (1.97 ± 0.83 vs. 3.63 ± 2.13, P < 0.01) and circularity (0.75 ± 0.16 vs. 0.45 ± 0.22, P < 0.01) but not size (0.28 ± 0.31 vs. 0.27 ± 0.20 μm(2)). Frequency distributions for mitochondrial size and morphological parameters were highly skewed, suggesting the presence of mechanisms to influence mitochondrial size and shape. In addition, physical continuities between SS and IMF mitochondria indicated mixing of both subpopulations. These data provide evidence that mitochondrial membranes interact in vivo in mouse skeletal muscle and that factors may be involved in regulating skeletal muscle mitochondrial morphology.
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Affiliation(s)
- Martin Picard
- Mitochondrial Research Group, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, United Kingdom.
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