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Franzkoch R, Anand A, Breitsprecher L, Psathaki OE, Barisch C. Resolving exit strategies of mycobacteria in Dictyostelium discoideum by combining high-pressure freezing with 3D-correlative light and electron microscopy. Mol Microbiol 2024; 121:593-604. [PMID: 38063129 DOI: 10.1111/mmi.15205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 11/21/2023] [Accepted: 11/23/2023] [Indexed: 03/12/2024]
Abstract
The infection course of Mycobacterium tuberculosis is highly dynamic and comprises sequential stages that require damaging and crossing of several membranes to enable the translocation of the bacteria into the cytosol or their escape from the host. Many important breakthroughs such as the restriction of mycobacteria by the autophagy pathway and the recruitment of sophisticated host repair machineries to the Mycobacterium-containing vacuole have been gained in the Dictyostelium discoideum/M. marinum system. Despite the availability of well-established light and advanced electron microscopy techniques in this system, a correlative approach integrating both methods with near-native ultrastructural preservation is currently lacking. This is most likely due to the low ability of D. discoideum to adhere to surfaces, which results in cell loss even after fixation. To address this problem, we improved the adhesion of cells and developed a straightforward and convenient workflow for 3D-correlative light and electron microscopy. This approach includes high-pressure freezing, which is an excellent technique for preserving membranes. Thus, our method allows to monitor the ultrastructural aspects of vacuole escape which is of central importance for the survival and dissemination of bacterial pathogens.
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Affiliation(s)
- Rico Franzkoch
- iBiOs-integrated Bioimaging Facility, University of Osnabrück, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück, Germany
- Division of Microbiology, Department of Biology, University of Osnabrück, Osnabrück, Germany
| | - Aby Anand
- Center of Cellular Nanoanalytics, Osnabrück, Germany
- Division of Molecular Infection Biology, Department of Biology, University of Osnabrück, Osnabrück, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Division of Host-Microbe Interactome, Research Center Borstel - Leibniz Lung Center (FZB), Borstel, Germany
- Department of Biology, University of Hamburg, Hamburg, Germany
| | - Leonhard Breitsprecher
- iBiOs-integrated Bioimaging Facility, University of Osnabrück, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück, Germany
- Division of Microbiology, Department of Biology, University of Osnabrück, Osnabrück, Germany
| | - Olympia E Psathaki
- iBiOs-integrated Bioimaging Facility, University of Osnabrück, Osnabrück, Germany
- Center of Cellular Nanoanalytics, Osnabrück, Germany
| | - Caroline Barisch
- Center of Cellular Nanoanalytics, Osnabrück, Germany
- Division of Molecular Infection Biology, Department of Biology, University of Osnabrück, Osnabrück, Germany
- Centre for Structural Systems Biology, Hamburg, Germany
- Division of Host-Microbe Interactome, Research Center Borstel - Leibniz Lung Center (FZB), Borstel, Germany
- Department of Biology, University of Hamburg, Hamburg, Germany
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Newman LE, Weiser Novak S, Rojas GR, Tadepalle N, Schiavon CR, Grotjahn DA, Towers CG, Tremblay MÈ, Donnelly MP, Ghosh S, Medina M, Rocha S, Rodriguez-Enriquez R, Chevez JA, Lemersal I, Manor U, Shadel GS. Mitochondrial DNA replication stress triggers a pro-inflammatory endosomal pathway of nucleoid disposal. Nat Cell Biol 2024; 26:194-206. [PMID: 38332353 PMCID: PMC11026068 DOI: 10.1038/s41556-023-01343-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 12/20/2023] [Indexed: 02/10/2024]
Abstract
Mitochondrial DNA (mtDNA) encodes essential subunits of the oxidative phosphorylation system, but is also a major damage-associated molecular pattern (DAMP) that engages innate immune sensors when released into the cytoplasm, outside of cells or into circulation. As a DAMP, mtDNA not only contributes to anti-viral resistance, but also causes pathogenic inflammation in many disease contexts. Cells experiencing mtDNA stress caused by depletion of the mtDNA-packaging protein, transcription factor A, mitochondrial (TFAM) or during herpes simplex virus-1 infection exhibit elongated mitochondria, enlargement of nucleoids (mtDNA-protein complexes) and activation of cGAS-STING innate immune signalling via mtDNA released into the cytoplasm. However, the relationship among aberrant mitochondria and nucleoid dynamics, mtDNA release and cGAS-STING activation remains unclear. Here we show that, under a variety of mtDNA replication stress conditions and during herpes simplex virus-1 infection, enlarged nucleoids that remain bound to TFAM exit mitochondria. Enlarged nucleoids arise from mtDNA experiencing replication stress, which causes nucleoid clustering via a block in mitochondrial fission at a stage when endoplasmic reticulum actin polymerization would normally commence, defining a fission checkpoint that ensures mtDNA has completed replication and is competent for segregation into daughter mitochondria. Chronic engagement of this checkpoint results in enlarged nucleoids trafficking into early and then late endosomes for disposal. Endosomal rupture during transit through this endosomal pathway ultimately causes mtDNA-mediated cGAS-STING activation. Thus, we propose that replication-incompetent nucleoids are selectively eliminated by an adaptive mitochondria-endosomal quality control pathway that is prone to innate immune system activation, which might represent a therapeutic target to prevent mtDNA-mediated inflammation during viral infection and other pathogenic states.
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Affiliation(s)
- Laura E Newman
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Gladys R Rojas
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | | | | | | | | | - Matthew P Donnelly
- Salk Institute for Biological Studies, La Jolla, CA, USA
- Medical Scientist Training Program, University of California, San Diego, La Jolla, CA, USA
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA, USA
| | - Sagnika Ghosh
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Sienna Rocha
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Joshua A Chevez
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Ian Lemersal
- La Jolla Institute for Immunology, La Jolla, CA, USA
| | - Uri Manor
- Salk Institute for Biological Studies, La Jolla, CA, USA.
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA.
- Department of Cell & Developmental Biology, University of California, San Diego, La Jolla, CA, USA.
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