@article{KunzGoetzGaoetal.2020,
  author    = {Kunz, Tobias C. and G{\"o}tz, Ralph and Gao, Shiqiang and Sauer, Markus and Kozjak-Pavlovic, Vera},
  title     = {Using Expansion Microscopy to Visualize and Characterize the Morphology of Mitochondrial Cristae},
  series = {Frontiers in Cell and Developmental Biology},
  volume    = {8},
  journal   = {Frontiers in Cell and Developmental Biology},
  issn      = {2296-634X},
  doi       = {10.3389/fcell.2020.00617},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208296},
  year      = {2020},
  abstract  = {Mitochondria are double membrane bound organelles indispensable for biological processes such as apoptosis, cell signaling, and the production of many important metabolites, which includes ATP that is generated during the process known as oxidative phosphorylation (OXPHOS). The inner membrane contains folds called cristae, which increase the membrane surface and thus the amount of membrane-bound proteins necessary for the OXPHOS. These folds have been of great interest not only because of their importance for energy conversion, but also because changes in morphology have been linked to a broad range of diseases from cancer, diabetes, neurodegenerative diseases, to aging and infection. With a distance between opposing cristae membranes often below 100 nm, conventional fluorescence imaging cannot provide a resolution sufficient for resolving these structures. For this reason, various highly specialized super-resolution methods including dSTORM, PALM, STED, and SIM have been applied for cristae visualization. Expansion Microscopy (ExM) offers the possibility to perform super-resolution microscopy on conventional confocal microscopes by embedding the sample into a swellable hydrogel that is isotropically expanded by a factor of 4-4.5, improving the resolution to 60-70 nm on conventional confocal microscopes, which can be further increased to ∼ 30 nm laterally using SIM. Here, we demonstrate that the expression of the mitochondrial creatine kinase MtCK linked to marker protein GFP (MtCK-GFP), which localizes to the space between the outer and the inner mitochondrial membrane, can be used as a cristae marker. Applying ExM on mitochondria labeled with this construct enables visualization of morphological changes of cristae and localization studies of mitochondrial proteins relative to cristae without the need for specialized setups. For the first time we present the combination of specific mitochondrial intermembrane space labeling and ExM as a tool for studying internal structure of mitochondria.},
  language  = {en}
}
@article{NanguneriFlottmannHorstmannetal.2012,
  author    = {Nanguneri, Siddharth and Flottmann, Benjamin and Horstmann, Heinz and Heilemann, Mike and Kuner, Thomas},
  title     = {Three-Dimensional, Tomographic Super-Resolution Fluorescence Imaging of Serially Sectioned Thick Samples},
  series = {PLoS One},
  volume    = {7},
  journal   = {PLoS One},
  number    = {5},
  doi       = {10.1371/journal.pone.0038098},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-134434},
  pages     = {e38098},
  year      = {2012},
  abstract  = {Three-dimensional fluorescence imaging of thick tissue samples with near-molecular resolution remains a fundamental challenge in the life sciences. To tackle this, we developed tomoSTORM, an approach combining single-molecule localization-based super-resolution microscopy with array tomography of structurally intact brain tissue. Consecutive sections organized in a ribbon were serially imaged with a lateral resolution of 28 nm and an axial resolution of 40 nm in tissue volumes of up to 50 \(\mu\)mx50\(\mu\)mx2.5\(\mu\)m. Using targeted expression of membrane bound (m)GFP and immunohistochemistry at the calyx of Held, a model synapse for central glutamatergic neurotransmission, we delineated the course of the membrane and fine-structure of mitochondria. This method allows multiplexed super-resolution imaging in large tissue volumes with a resolution three orders of magnitude better than confocal microscopy.},
  language  = {en}
}
@article{MambrettiKistnerMayeretal.2016,
  author    = {Mambretti, Egle M. and Kistner, Katrin and Mayer, Stefanie and Massotte, Dominique and Kieffer, Brigitte L. and Hoffmann, Carsten and Reeh, Peter W. and Brack, Alexander and Asan, Esther and Rittner, Heike L.},
  title     = {Functional and structural characterization of axonal opioid receptors as targets for analgesia},
  series = {Molecular Pain},
  journal   = {Molecular Pain},
  number    = {12},
  doi       = {10.1177/1744806916628734},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145917},
  pages     = {1-17},
  year      = {2016},
  abstract  = {Background Opioids are the gold standard for the treatment of acute pain despite serious side effects in the central and enteric nervous system. µ-opioid receptors (MOPs) are expressed and functional at the terminals of sensory axons, when activated by exogenous or endogenous ligands. However, the presence and function of MOP along nociceptive axons remains controversial particularly in na{\"i}ve animals. Here, we characterized axonal MOPs by immunofluorescence, ultrastructural, and functional analyses. Furthermore, we evaluated hypertonic saline as a possible enhancer of opioid receptor function. Results Comparative immunolabeling showed that, among several tested antibodies, which all provided specific MOP detection in the rat central nervous system (CNS), only one monoclonal MOP-antibody yielded specificity and reproducibility for MOP detection in the rat peripheral nervous system including the sciatic nerve. Double immunolabeling documented that MOP immunoreactivity was confined to calcitonin gene-related peptide (CGRP) positive fibers and fiber bundles. Almost identical labeling and double labeling patterns were found using mcherry-immunolabeling on sciatic nerves of mice producing a MOP-mcherry fusion protein (MOP-mcherry knock-in mice). Preembedding immunogold electron microscopy on MOP-mcherry knock-in sciatic nerves indicated presence of MOP in cytoplasm and at membranes of unmyelinated axons. Application of [D-Ala\(^2\), N-MePhe\(^4\), Gly-ol]-enkephalin (DAMGO) or fentanyl dose-dependently inhibited depolarization-induced CGRP release from rat sciatic nerve axons ex vivo, which was blocked by naloxone. When the lipophilic opioid fentanyl was applied perisciatically in na{\"i}ve Wistar rats, mechanical nociceptive thresholds increased. Subthreshold doses of fentanyl or the hydrophilic opioid DAMGO were only effective if injected together with hypertonic saline. In vitro, using β-arrestin-2/MOP double-transfected human embryonic kidney cells, DAMGO as well as fentanyl lead to a recruitment of β-arrestin-2 to the membrane followed by a β-arrestin-2 reappearance in the cytosol and MOP internalization. Pretreatment with hypertonic saline prevented MOP internalization. Conclusion MOPs are present and functional in the axonal membrane from na{\"i}ve animals. Hypertonic saline acutely decreases ligand-induced internalization of MOP and thereby might improve MOP function. Further studies should explore potential clinical applications of opioids together with enhancers for regional analgesia.},
  language  = {en}
}