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Kowaltowski AJ, Abdulkader F. How and when to measure mitochondrial inner membrane potentials. Biophys J 2024:S0006-3495(24)00176-0. [PMID: 38454598 DOI: 10.1016/j.bpj.2024.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/21/2024] [Accepted: 03/05/2024] [Indexed: 03/09/2024] Open
Abstract
The scientific literature on mitochondria has increased significantly over the years due to findings that these organelles have widespread roles in the onset and progression of pathological conditions such as metabolic disorders, neurodegenerative and cardiovascular diseases, inflammation, and cancer. Researchers have extensively explored how mitochondrial properties and functions are modified in different models, often using fluorescent inner mitochondrial membrane potential (ΔΨm) probes to assess functional mitochondrial aspects such as protonmotive force and oxidative phosphorylation. This review provides an overview of existing techniques to measure ΔpH and ΔΨm, highlighting their advantages, limitations, and applications. It discusses drawbacks of ΔΨm probes, especially when used without calibration, and conditions where alternative methods should replace ΔΨm measurements for the benefit of the specific scientific objectives entailed. Studies investigating mitochondria and their vast biological roles would be significantly advanced by the understanding of the correct applications as well as limitations of protonmotive force measurements and use of fluorescent ΔΨm probes, adopting more precise, artifact-free, sensitive, and quantitative measurements of mitochondrial functionality.
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Affiliation(s)
- Alicia J Kowaltowski
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
| | - Fernando Abdulkader
- Departmento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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2
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Neikirk K, Lopez EG, Marshall AG, Alghanem A, Krystofiak E, Kula B, Smith N, Shao J, Katti P, Hinton A. Call to action to properly utilize electron microscopy to measure organelles to monitor disease. Eur J Cell Biol 2023; 102:151365. [PMID: 37864884 DOI: 10.1016/j.ejcb.2023.151365] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 10/14/2023] [Accepted: 10/15/2023] [Indexed: 10/23/2023] Open
Abstract
This review provides an overview of the current methods for quantifying mitochondrial ultrastructure, including cristae morphology, mitochondrial contact sites, and recycling machinery and a guide to utilizing electron microscopy to effectively measure these organelles. Quantitative analysis of mitochondrial ultrastructure is essential for understanding mitochondrial biology and developing therapeutic strategies for mitochondrial-related diseases. Techniques such as transmission electron microscopy (TEM) and serial block face-scanning electron microscopy, as well as how they can be combined with other techniques including confocal microscopy, super-resolution microscopy, and correlative light and electron microscopy are discussed. Beyond their limitations and challenges, we also offer specific magnifications that may be best suited for TEM analysis of mitochondrial, endoplasmic reticulum, and recycling machinery. Finally, perspectives on future quantification methods are offered.
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Affiliation(s)
- Kit Neikirk
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Edgar-Garza Lopez
- Department of Internal Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Andrea G Marshall
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Ahmad Alghanem
- King Abdullah International Medical Research Center (KAIMRC), Ali Al Arini, Ar Rimayah, Riyadh 11481, Saudi Arabia
| | - Evan Krystofiak
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Bartosz Kula
- Del Monte Institute for Neuroscience, Department of Neuroscience, University of Rochester, School of Medicine and Dentistry, Rochester 14642, USA
| | - Nathan Smith
- Del Monte Institute for Neuroscience, Department of Neuroscience, University of Rochester, School of Medicine and Dentistry, Rochester 14642, USA
| | - Jianqiang Shao
- Central Microscopy Research Facility, University of Iowa, Iowa City, IA, USA
| | - Prasanna Katti
- National Heart, Lung and Blood Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Antentor Hinton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.
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3
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Liu T, Stephan T, Chen P, Keller-Findeisen J, Chen J, Riedel D, Yang Z, Jakobs S, Chen Z. Multi-color live-cell STED nanoscopy of mitochondria with a gentle inner membrane stain. Proc Natl Acad Sci U S A 2022; 119:e2215799119. [PMID: 36534799 PMCID: PMC9907107 DOI: 10.1073/pnas.2215799119] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Accepted: 10/21/2022] [Indexed: 12/24/2022] Open
Abstract
Capturing mitochondria's intricate and dynamic structure poses a daunting challenge for optical nanoscopy. Different labeling strategies have been demonstrated for live-cell stimulated emission depletion (STED) microscopy of mitochondria, but orthogonal strategies are yet to be established, and image acquisition has suffered either from photodamage to the organelles or from rapid photobleaching. Therefore, live-cell nanoscopy of mitochondria has been largely restricted to two-dimensional (2D) single-color recordings of cancer cells. Here, by conjugation of cyclooctatetraene (COT) to a benzo-fused cyanine dye, we report a mitochondrial inner membrane (IM) fluorescent marker, PK Mito Orange (PKMO), featuring efficient STED at 775 nm, strong photostability, and markedly reduced phototoxicity. PKMO enables super-resolution (SR) recordings of IM dynamics for extended periods in immortalized mammalian cell lines, primary cells, and organoids. Photostability and reduced phototoxicity of PKMO open the door to live-cell three-dimensional (3D) STED nanoscopy of mitochondria for 3D analysis of the convoluted IM. PKMO is optically orthogonal with green and far-red markers, allowing multiplexed recordings of mitochondria using commercial STED microscopes. Using multi-color STED microscopy, we demonstrate that imaging with PKMO can capture interactions of mitochondria with different cellular components such as the endoplasmic reticulum (ER) or the cytoskeleton, Bcl-2-associated X protein (BAX)-induced apoptotic process, or crista phenotypes in genetically modified cells, all at sub-100 nm resolution. Thereby, this work offers a versatile tool for studying mitochondrial IM architecture and dynamics in a multiplexed manner.
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Affiliation(s)
- Tianyan Liu
- College of Future Technology, Institute of Molecular Medicine, National Biomedical Imaging Center, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing100871, China
- Peking-Tsinghua Center for Life Science, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing100871, China
| | - Till Stephan
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
- Clinic of Neurology, University Medical Center Göttingen, Göttingen37075, Germany
| | - Peng Chen
- Peking University-Nanjing Institute of Translational Medicine, Nanjing211800, China
- Genvivo Biotech, Nanjing211800, China
| | - Jan Keller-Findeisen
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology, Translational Neuroinflammation and Automated Microscopy, Göttingen37075, Germany
| | - Jingting Chen
- College of Future Technology, Institute of Molecular Medicine, National Biomedical Imaging Center, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing100871, China
| | - Dietmar Riedel
- Laboratory of Electron Microscopy, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
| | - Zhongtian Yang
- Peking-Tsinghua Center for Life Science, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing100871, China
| | - Stefan Jakobs
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
- Clinic of Neurology, University Medical Center Göttingen, Göttingen37075, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology, Translational Neuroinflammation and Automated Microscopy, Göttingen37075, Germany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells”, University of Göttingen, Göttingen37099, Germany
| | - Zhixing Chen
- College of Future Technology, Institute of Molecular Medicine, National Biomedical Imaging Center, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Peking University, Beijing100871, China
- Peking-Tsinghua Center for Life Science, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing100871, China
- Peking University-Nanjing Institute of Translational Medicine, Nanjing211800, China
- Genvivo Biotech, Nanjing211800, China
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4
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Rieger B, Arroum T, Borowski M, Villalta J, Busch KB. Mitochondrial F 1 F O ATP synthase determines the local proton motive force at cristae rims. EMBO Rep 2021; 22:e52727. [PMID: 34595823 PMCID: PMC8647149 DOI: 10.15252/embr.202152727] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 08/31/2021] [Accepted: 09/10/2021] [Indexed: 12/25/2022] Open
Abstract
The classical view of oxidative phosphorylation is that a proton motive force (PMF) generated by the respiratory chain complexes fuels ATP synthesis via ATP synthase. Yet, under glycolytic conditions, ATP synthase in its reverse mode also can contribute to the PMF. Here, we dissected these two functions of ATP synthase and the role of its inhibitory factor 1 (IF1) under different metabolic conditions. pH profiles of mitochondrial sub-compartments were recorded with high spatial resolution in live mammalian cells by positioning a pH sensor directly at ATP synthase's F1 and FO subunits, complex IV and in the matrix. Our results clearly show that ATP synthase activity substantially controls the PMF and that IF1 is essential under OXPHOS conditions to prevent reverse ATP synthase activity due to an almost negligible ΔpH. In addition, we show how this changes lateral, transmembrane, and radial pH gradients in glycolytic and respiratory cells.
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Affiliation(s)
- Bettina Rieger
- Institute of Molecular Cell BiologySchool of BiologyUniversity of MünsterMünsterGermany
| | - Tasnim Arroum
- Institute of Molecular Cell BiologySchool of BiologyUniversity of MünsterMünsterGermany
| | - Marie‐Theres Borowski
- Institute of Molecular Cell BiologySchool of BiologyUniversity of MünsterMünsterGermany
| | - Jimmy Villalta
- Institute of Molecular Cell BiologySchool of BiologyUniversity of MünsterMünsterGermany
| | - Karin B Busch
- Institute of Molecular Cell BiologySchool of BiologyUniversity of MünsterMünsterGermany
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Farkas DL. Biomedical Applications of Translational Optical Imaging: From Molecules to Humans. Molecules 2021; 26:molecules26216651. [PMID: 34771060 PMCID: PMC8587670 DOI: 10.3390/molecules26216651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 08/24/2021] [Accepted: 08/24/2021] [Indexed: 11/16/2022] Open
Abstract
Light is a powerful investigational tool in biomedicine, at all levels of structural organization. Its multitude of features (intensity, wavelength, polarization, interference, coherence, timing, non-linear absorption, and even interactions with itself) able to create contrast, and thus images that detail the makeup and functioning of the living state can and should be combined for maximum effect, especially if one seeks simultaneously high spatiotemporal resolution and discrimination ability within a living organism. The resulting high relevance should be directed towards a better understanding, detection of abnormalities, and ultimately cogent, precise, and effective intervention. The new optical methods and their combinations needed to address modern surgery in the operating room of the future, and major diseases such as cancer and neurodegeneration are reviewed here, with emphasis on our own work and highlighting selected applications focusing on quantitation, early detection, treatment assessment, and clinical relevance, and more generally matching the quality of the optical detection approach to the complexity of the disease. This should provide guidance for future advanced theranostics, emphasizing a tighter coupling-spatially and temporally-between detection, diagnosis, and treatment, in the hope that technologic sophistication such as that of a Mars rover can be translationally deployed in the clinic, for saving and improving lives.
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Affiliation(s)
- Daniel L. Farkas
- PhotoNanoscopy and Acceleritas Corporations, 13412 Ventura Boulevard, Sherman Oaks, CA 91423, USA; ; Tel.: +1-310-600-7102
- Clinical Photonics Corporation, 8591 Skyline Drive, Los Angeles, CA 90046, USA
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
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6
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Segawa M, Wolf DM, Hultgren NW, Williams DS, van der Bliek AM, Shackelford DB, Liesa M, Shirihai OS. Quantification of cristae architecture reveals time-dependent characteristics of individual mitochondria. Life Sci Alliance 2020; 3:e201900620. [PMID: 32499316 PMCID: PMC7283135 DOI: 10.26508/lsa.201900620] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 05/14/2020] [Accepted: 05/26/2020] [Indexed: 02/06/2023] Open
Abstract
Recent breakthroughs in live-cell imaging have enabled visualization of cristae, making it feasible to investigate the structure-function relationship of cristae in real time. However, quantifying live-cell images of cristae in an unbiased way remains challenging. Here, we present a novel, semi-automated approach to quantify cristae, using the machine-learning Trainable Weka Segmentation tool. Compared with standard techniques, our approach not only avoids the bias associated with manual thresholding but more efficiently segments cristae from Airyscan and structured illumination microscopy images. Using a cardiolipin-deficient cell line, as well as FCCP, we show that our approach is sufficiently sensitive to detect perturbations in cristae density, size, and shape. This approach, moreover, reveals that cristae are not uniformly distributed within the mitochondrion, and sites of mitochondrial fission are localized to areas of decreased cristae density. After a fusion event, individual cristae from the two mitochondria, at the site of fusion, merge into one object with distinct architectural values. Overall, our study shows that machine learning represents a compelling new strategy for quantifying cristae in living cells.
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Affiliation(s)
- Mayuko Segawa
- Department of Medicine, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Dane M Wolf
- Department of Medicine, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- Graduate Program in Nutrition and Metabolism, Graduate Medical Sciences, Boston University School of Medicine, Boston, MA, USA
| | - Nan W Hultgren
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - David S Williams
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Alexander M van der Bliek
- Molecular Biology Institute at University of California, Los Angeles, Los Angeles, CA, USA
- Department of Biological Chemistry, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, USA
| | - David B Shackelford
- Department of Pulmonary and Critical Care Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA; Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Marc Liesa
- Department of Medicine, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Orian S Shirihai
- Department of Medicine, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
- Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
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