@article{BartelPeinPopperetal.2019, author = {Bartel, Karin and Pein, Helmut and Popper, Bastian and Schmitt, Sabine and Janaki-Raman, Sudha and Schulze, Almut and Lengauer, Florian and Koeberle, Andreas and Werz, Oliver and Zischka, Hans and M{\"u}ller, Rolf and Vollmar, Angelika M. and Schwarzenberg, Karin von}, title = {Connecting lysosomes and mitochondria - a novel role for lipid metabolism in cancer cell death}, series = {Cell Communication and Signaling}, volume = {17}, journal = {Cell Communication and Signaling}, doi = {10.1186/s12964-019-0399-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-221524}, year = {2019}, abstract = {Background The understanding of lysosomes has been expanded in recent research way beyond their view as cellular trash can. Lysosomes are pivotal in regulating metabolism, endocytosis and autophagy and are implicated in cancer. Recently it was discovered that the lysosomal V-ATPase, which is known to induce apoptosis, interferes with lipid metabolism in cancer, yet the interplay between these organelles is poorly understood. Methods LC-MS/MS analysis was performed to investigate lipid distribution in cells. Cell survival and signaling pathways were analyzed by means of cell biological methods (qPCR, Western Blot, flow cytometry, CellTiter-Blue). Mitochondrial structure was analyzed by confocal imaging and electron microscopy, their function was determined by flow cytometry and seahorse measurements. Results Our data reveal that interfering with lysosomal function changes composition and subcellular localization of triacylglycerids accompanied by an upregulation of PGC1α and PPARα expression, master regulators of energy and lipid metabolism. Furthermore, cardiolipin content is reduced driving mitochondria into fission, accompanied by a loss of membrane potential and reduction in oxidative capacity, which leads to a deregulation in cellular ROS and induction of mitochondria-driven apoptosis. Additionally, cells undergo a metabolic shift to glutamine dependency, correlated with the fission phenotype and sensitivity to lysosomal inhibition, most prominent in Ras mutated cells. Conclusion This study sheds mechanistic light on a largely uninvestigated triangle between lysosomes, lipid metabolism and mitochondrial function. Insight into this organelle crosstalk increases our understanding of mitochondria-driven cell death. Our findings furthermore provide a first hint on a connection of Ras pathway mutations and sensitivity towards lysosomal inhibitors.}, language = {en} } @article{OttDorschFraunholzetal.2015, author = {Ott, Christine and Dorsch, Eva and Fraunholz, Martin and Straub, Sebastian and Kozjak-Pavlovic, Vera}, title = {Detailed Analysis of the Human Mitochondrial Contact Site Complex Indicate a Hierarchy of Subunits}, series = {PLoS One}, volume = {10}, journal = {PLoS One}, number = {3}, doi = {10.1371/journal.pone.0120213}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125347}, pages = {e0120213}, year = {2015}, abstract = {Mitochondrial inner membrane folds into cristae, which significantly increase its surface and are important for mitochondrial function. The stability of cristae depends on the mitochondrial contact site (MICOS) complex. In human mitochondria, the inner membrane MICOS complex interacts with the outer membrane sorting and assembly machinery (SAM) complex, to form the mitochondrial intermembrane space bridging complex (MIB). We have created knockdown cell lines of most of the MICOS and MIB components and have used them to study the importance of the individual subunits for the cristae formation and complex stability. We show that the most important subunits of the MIB complex in human mitochondria are Mic60/Mitofilin, Mic19/CHCHD3 and an outer membrane component Sam50. We provide additional proof that ApoO indeed is a subunit of the MICOS and MIB complexes and propose the name Mic23 for this protein. According to our results, Mic25/CHCHD6, Mic27/ApoOL and Mic23/ApoO appear to be periphery subunits of the MICOS complex, because their depletion does not affect cristae morphology or stability of other components.}, language = {en} } @phdthesis{Ott2013, author = {Ott, Christine Kornelia}, title = {Diverse Aspects of the Sorting and Assembly Machinery in Human Mitochondria}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-85462}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {Mitochondria are organelles of endosymbiotic origin, which play many important roles in eukaryotic cells. Mitochondria are surrounded by two membranes and, considering that most of the mitochondrial proteins are produced in the cytosol, possess import machineries, which transport mitochondria-targeted proteins to their designated location. A special class of outer mitochondrial membrane (OMM) proteins, the β-barrel proteins, require the sorting and assembly machinery (SAM) for their OMM integration. Both mitochondrial β-barrel proteins and the central component of the SAM complex, Sam50, have homologs in gram-negative bacteria. In yeast mitochondria, bacterial β-barrel proteins can be imported and assembled into the OMM. Our group demonstrated that this, however, is not the case for human mitochondria, which import only neisserial β barrel proteins, but not those of Escherichia coli and Salmonella enterica. As a part of this study, I could demonstrate that β-barrel proteins such as Omp85 and PorB of different Neisseria species are targeted to human mitochondria. Interestingly, only proteins belonging to the neisserial Omp85 family were integrated into the OMM, whereas PorB was imported into mitochondria but not assembled. By exchanging parts of homologous neisserial Omp85 and E. coli BamA and, similarly, of neisserial PorB and E. coli OmpC, it could be demonstrated in this work that the mitochondrial import signal of bacterial β barrel proteins cannot be limited to one short linear sequence, but rather secondary structure and protein charge seem to play an important role, as well as specific residues in the last β-strand of Omp85. Omp85 possesses five conserved POTRA domains in its amino-terminal part. This work additionally demonstrated that in human mitochondria, at least two POTRA domains of Omp85 are necessary for membrane integration and functionality of Omp85. In the second part of this work, the influence of Sam50 on the mitochondrial cristae structure was investigated. This work contributed to a study performed by our group in which it was confirmed that Sam50 is present in a high molecular weight complex together with mitofilin, CHCHD3, CHCHD6, DnaJC11, metaxin 1 and metaxin 2. This connection between the inner and outer mitochondrial membrane was shown to be crucial for the maintenance of the mitochondrial cristae structure. In addition, a role of Sam50 in respiratory complex assembly, suggested by a SILAC experiment conducted in our group, could be confirmed by in vitro import studies. An influence of Sam50 not only on respiratory complexes but also on the recently described respiratory complex assembly factor TTC19 was demonstrated. It was shown that TTC19 not only plays a role in complex III assembly as published, but also influences the assembly of respiratory complex IV. Thus, in this part of the work a connection between the OMM protein Sam50 and maintenance of cristae structure, respiratory complex assembly and an assembly factor could be established.}, subject = {Mitochondrien}, language = {en} } @unpublished{HennigPrustyKauferetal.2021, author = {Hennig, Thomas and Prusty, Archana B. and Kaufer, Benedikt and Whisnant, Adam W. and Lodha, Manivel and Enders, Antje and Thomas, Julius and Kasimir, Francesca and Grothey, Arnhild and Herb, Stefanie and J{\"u}rges, Christopher and Meister, Gunter and Erhard, Florian and D{\"o}lken, Lars and Prusty, Bhupesh K.}, title = {Selective inhibition of microRNA processing by a herpesvirus-encoded microRNA triggers virus reactivation from latency}, edition = {submitted version}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-267858}, year = {2021}, abstract = {Herpesviruses have mastered host cell modulation and immune evasion to augment productive infection, life-long latency and reactivation thereof 1,2. A long appreciated, yet elusively defined relationship exists between the lytic-latent switch and viral non-coding RNAs 3,4. Here, we identify miRNA-mediated inhibition of miRNA processing as a novel cellular mechanism that human herpesvirus 6A (HHV-6A) exploits to disrupt mitochondrial architecture, evade intrinsic host defense and drive the latent-lytic switch. We demonstrate that virus-encoded miR-aU14 selectively inhibits the processing of multiple miR-30 family members by direct interaction with the respective pri-miRNA hairpin loops. Subsequent loss of miR-30 and activation of miR-30/p53/Drp1 axis triggers a profound disruption of mitochondrial architecture, which impairs induction of type I interferons and is necessary for both productive infection and virus reactivation. Ectopic expression of miR-aU14 was sufficient to trigger virus reactivation from latency thereby identifying it as a readily drugable master regulator of the herpesvirus latent-lytic switch. Our results show that miRNA-mediated inhibition of miRNA processing represents a generalized cellular mechanism that can be exploited to selectively target individual members of miRNA families. We anticipate that targeting miR-aU14 provides exciting therapeutic options for preventing herpesvirus reactivations in HHV-6-associated disorders like myalgic encephalitis/chronic fatigue syndrome (ME/CFS) and Long-COVID.}, language = {en} } @article{GoosDejungJanzenetal.2017, author = {Goos, Carina and Dejung, Mario and Janzen, Christian J. and Butter, Falk and Kramer, Susanne}, title = {The nuclear proteome of Trypanosoma brucei}, series = {PLoS ONE}, volume = {12}, journal = {PLoS ONE}, number = {7}, doi = {10.1371/journal.pone.0181884}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158572}, pages = {e0181884}, year = {2017}, abstract = {Trypanosoma brucei is a protozoan flagellate that is transmitted by tsetse flies into the mammalian bloodstream. The parasite has a huge impact on human health both directly by causing African sleeping sickness and indirectly, by infecting domestic cattle. The biology of trypanosomes involves some highly unusual, nuclear-localised processes. These include polycistronic transcription without classical promoters initiated from regions defined by histone variants, trans-splicing of all transcripts to the exon of a spliced leader RNA, transcription of some very abundant proteins by RNA polymerase I and antigenic variation, a switch in expression of the cell surface protein variants that allows the parasite to resist the immune system of its mammalian host. Here, we provide the nuclear proteome of procyclic Trypanosoma brucei, the stage that resides within the tsetse fly midgut. We have performed quantitative label-free mass spectrometry to score 764 significantly nuclear enriched proteins in comparison to whole cell lysates. A comparison with proteomes of several experimentally characterised nuclear and non-nuclear structures and pathways confirmed the high quality of the dataset: the proteome contains about 80\% of all nuclear proteins and less than 2\% false positives. Using motif enrichment, we found the amino acid sequence KRxR present in a large number of nuclear proteins. KRxR is a sub-motif of a classical eukaryotic monopartite nuclear localisation signal and could be responsible for nuclear localization of proteins in Kinetoplastida species. As a proof of principle, we have confirmed the nuclear localisation of six proteins with previously unknown localisation by expressing eYFP fusion proteins. While proteome data of several T. brucei organelles have been published, our nuclear proteome closes an important gap in knowledge to study trypanosome biology, in particular nuclear-related processes.}, language = {en} } @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} }