TY - JOUR A1 - Johann, Kornelia A1 - Kleinert, Maximilian A1 - Klaus, Susanne T1 - The role of GDF15 as a myomitokine JF - Cells N2 - Growth differentiation factor 15 (GDF15) is a cytokine best known for affecting systemic energy metabolism through its anorectic action. GDF15 expression and secretion from various organs and tissues is induced in different physiological and pathophysiological states, often linked to mitochondrial stress, leading to highly variable circulating GDF15 levels. In skeletal muscle and the heart, the basal expression of GDF15 is very low compared to other organs, but GDF15 expression and secretion can be induced in various stress conditions, such as intense exercise and acute myocardial infarction, respectively. GDF15 is thus considered as a myokine and cardiokine. GFRAL, the exclusive receptor for GDF15, is expressed in hindbrain neurons and activation of the GDF15-GFRAL pathway is linked to an increased sympathetic outflow and possibly an activation of the hypothalamic-pituitary-adrenal (HPA) stress axis. There is also evidence for peripheral, direct effects of GDF15 on adipose tissue lipolysis and possible autocrine cardiac effects. Metabolic and behavioral outcomes of GDF15 signaling can be beneficial or detrimental, likely depending on the magnitude and duration of the GDF15 signal. This is especially apparent for GDF15 production in muscle, which can be induced both by exercise and by muscle disease states such as sarcopenia and mitochondrial myopathy. KW - anorexia KW - appetite regulation KW - cardiokine KW - cytokine KW - exercise KW - mitochondria KW - muscle KW - myokine KW - myopathy KW - sarcopenia Y1 - 2021 U6 - https://doi.org/10.3390/cells10112990 SN - 2073-4409 VL - 10 IS - 11 PB - MDPI CY - Basel ER - TY - JOUR A1 - Westbury, Michael V. A1 - Dalerumb, Fredrik A1 - Noren, Karin A1 - Hofreiter, Michael T1 - Complete mitochondrial genome of a bat-eared fox (Otocyon megalotis), along with phylogenetic considerations JF - Mitochondrial DNA. Part B N2 - The bat-eared fox, Otocyon megalotis, is the only member of its genus and is thought to occupy a basal position within the dog family. These factors can lead to challenges in complete mitochondrial reconstructions and accurate phylogenetic positioning. Here, we present the first complete mitochondrial genome of the bat-eared fox recovered using shotgun sequencing and iterative mapping to three distantly related species. Phylogenetic analyses placed the bat-eared fox basal in the Canidae family within the clade including true foxes (Vulpes) and the raccoon dog (Nyctereutes) with high support values. This position is in good agreement with previously published results based on short fragments of mitochondrial and nuclear genes, therefore adding more support to the basal positioning of the bat-eared fox within Canidae. KW - Phylogenetics KW - mitochondria KW - iterative mapping KW - Canidae Y1 - 2017 U6 - https://doi.org/10.1080/23802359.2017.1331325 SN - 2380-2359 VL - 2 IS - 1 SP - 298 EP - 299 PB - Routledge, Taylor & Francis Group CY - London ER - TY - JOUR A1 - Geroldinger, Gerald A1 - Tonner, Matthias A1 - Fudickar, Werner A1 - De Sarkar, Sritama A1 - Dighal, Aishwarya A1 - Monzote, Lianet A1 - Staniek, Katrin A1 - Linker, Torsten A1 - Chatterjee, Mitali A1 - Gille, Lars T1 - Activation of anthracene endoperoxides in leishmania and impairment of mitochondrial functions JF - Molecules N2 - Leishmaniasis is a vector-borne disease caused by protozoal Leishmania. Because of resistance development against current drugs, new antileishmanial compounds are urgently needed. Endoperoxides (EPs) are successfully used in malaria therapy, and experimental evidence of their potential against leishmaniasis exists. Anthracene endoperoxides (AcEPs) have so far been only technically used and not explored for their leishmanicidal potential. This study verified the in vitro efficiency and mechanism of AcEPs against both Leishmania promastigotes and axenic amastigotes (L. tarentolae and L. donovani) as well as their toxicity in J774 macrophages. Additionally, the kinetics and radical products of AcEPs’ reaction with iron, the formation of radicals by AcEPs in Leishmania, as well as the resulting impairment of parasite mitochondrial functions were studied. Using electron paramagnetic resonance combined with spin trapping, photometry, and fluorescence-based oximetry, AcEPs were demonstrated to (i) show antileishmanial activity in vitro at IC50 values in a low micromolar range, (ii) exhibit host cell toxicity in J774 macrophages, (iii) react rapidly with iron (II) resulting in the formation of oxygen- and carbon-centered radicals, (iv) produce carbon-centered radicals which could secondarily trigger superoxide radical formation in Leishmania, and (v) impair mitochondrial functions in Leishmania during parasite killing. Overall, the data of different AcEPs demonstrate that their structures besides the peroxo bridge strongly influence their activity and mechanism of their antileishmanial action. KW - Leishmania KW - endoperoxides KW - EPR spectroscopy KW - mitochondria KW - radicals Y1 - 2018 U6 - https://doi.org/10.3390/molecules23071680 SN - 1420-3049 VL - 23 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wardelmann, Kristina A1 - Rath, Michaela A1 - Castro, José Pedro A1 - Blümel, Sabine A1 - Schell, Mareike A1 - Hauffe, Robert A1 - Schumacher, Fabian A1 - Flore, Tanina A1 - Ritter, Katrin A1 - Wernitz, Andreas A1 - Hosoi, Toru A1 - Ozawa, Koichiro A1 - Kleuser, Burkhard A1 - Weiß, Jürgen A1 - Schürmann, Annette A1 - Kleinridders, André T1 - Central acting Hsp10 regulates mitochondrial function, fatty acid metabolism and insulin sensitivity in the hypothalamus JF - Antioxidants N2 - Mitochondria are critical for hypothalamic function and regulators of metabolism. Hypothalamic mitochondrial dysfunction with decreased mitochondrial chaperone expression is present in type 2 diabetes (T2D). Recently, we demonstrated that a dysregulated mitochondrial stress response (MSR) with reduced chaperone expression in the hypothalamus is an early event in obesity development due to insufficient insulin signaling. Although insulin activates this response and improves metabolism, the metabolic impact of one of its members, the mitochondrial chaperone heat shock protein 10 (Hsp10), is unknown. Thus, we hypothesized that a reduction of Hsp10 in hypothalamic neurons will impair mitochondrial function and impact brain insulin action. Therefore, we investigated the role of chaperone Hsp10 by introducing a lentiviral-mediated Hsp10 knockdown (KD) in the hypothalamic cell line CLU-183 and in the arcuate nucleus (ARC) of C57BL/6N male mice. We analyzed mitochondrial function and insulin signaling utilizing qPCR, Western blot, XF96 Analyzer, immunohistochemistry, and microscopy techniques. We show that Hsp10 expression is reduced in T2D mice brains and regulated by leptin in vitro. Hsp10 KD in hypothalamic cells induced mitochondrial dysfunction with altered fatty acid metabolism and increased mitochondria-specific oxidative stress resulting in neuronal insulin resistance. Consequently, the reduction of Hsp10 in the ARC of C57BL/6N mice caused hypothalamic insulin resistance with acute liver insulin resistance. KW - brain insulin signaling KW - mitochondria KW - oxidative stress KW - fatty acid metabolism Y1 - 2021 U6 - https://doi.org/10.3390/antiox10050711 SN - 2076-3921 VL - 10 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Schell, Mareike A1 - Chudoba, Chantal A1 - Leboucher, Antoine A1 - Alfine, Eugenia A1 - Flore, Tanina A1 - Ritter, Katrin A1 - Weiper, Katharina A1 - Wernitz, Andreas A1 - Henkel, Janin A1 - Kleinridders, André T1 - Interplay of Dietary Fatty Acids and Cholesterol Impacts Brain Mitochondria and Insulin Action JF - Nutrients N2 - Overconsumption of high-fat and cholesterol-containing diets is detrimental for metabolism and mitochondrial function, causes inflammatory responses and impairs insulin action in peripheral tissues. Dietary fatty acids can enter the brain to mediate the nutritional status, but also to influence neuronal homeostasis. Yet, it is unclear whether cholesterol-containing high-fat diets (HFDs) with different combinations of fatty acids exert metabolic stress and impact mitochondrial function in the brain. To investigate whether cholesterol in combination with different fatty acids impacts neuronal metabolism and mitochondrial function, C57BL/6J mice received different cholesterol-containing diets with either high concentrations of long-chain saturated fatty acids or soybean oil-derived poly-unsaturated fatty acids. In addition, CLU183 neurons were stimulated with combinations of palmitate, linoleic acid and cholesterol to assess their effects on metabolic stress, mitochondrial function and insulin action. The dietary interventions resulted in a molecular signature of metabolic stress in the hypothalamus with decreased expression of occludin and subunits of mitochondrial electron chain complexes, elevated protein carbonylation, as well as c-Jun N-terminal kinase (JNK) activation. Palmitate caused mitochondrial dysfunction, oxidative stress, insulin and insulin-like growth factor-1 (IGF-1) resistance, while cholesterol and linoleic acid did not cause functional alterations. Finally, we defined insulin receptor as a novel negative regulator of metabolically stress-induced JNK activation. KW - cholesterol KW - insulin signaling KW - mitochondria KW - brain KW - inflammation KW - fatty acids KW - JNK KW - insulin receptor Y1 - 2020 U6 - https://doi.org/10.3390/nu12051518 SN - 2072-6643 VL - 12 IS - 5 PB - MDPI CY - Basel ER - TY - THES A1 - Riedel, Simona T1 - Characterization of Mitochondrial ABC Transporter Homologues in Rhodobacter capsulatus T1 - Charakterisierung von Homologen zu mitochondrialen ABC Transportern in Rhodobacter capsulatus N2 - ABC-Transporter (ABC abgeleitet von ATP-Binding Cassette) gehören zur Klasse der Transmembran-Proteine und kommen in allen drei Domänen des Lebens vor. Ihr struktureller Aufbau ist dabei stets ähnlich, wohingegen konservierte Proteinsequenzen selten vorkommen. Die Transporter sind aus zwei lipophilen, membran-durchspannenden Domänen, welche auch TMDs (abgeleitet von Transmembrane spanning Domains) genannt werden, und zwei hydrophilen Domänen, die auch NBDs (abgeleitet von Nucleotide Binding Domains) genannt werden, aufgebaut. Die Vielzahl der durch ABC-Transporter beförderten Moleküle erklärt dabei die enorme Anzahl diverser TMDs. In den Mitochondrien des Menschen findet man vier ABC-Transporter (ABCB6, ABCB7, ABCB8 und ABCB10) mit funktionellen Homologen in Hefen und Pflanzen. In Bakterien hingegen können, mit Ausnahme von Rickettsiae und verwandten Bakterien, keine Homologen zu mitochondrialen ABC-Transportern identifiziert werden. Die transportierten Moleküle sowie die damit verbundenen Funktionen sind im Einzelnen bislang weitgehend unbekannt. ABCB7 und die entsprechenden Homologen in Hefen (Atm1) und in Pflanzen (ATM3) konnten mit der cytosolischen Eisen-Schwefel-Cluster-Biosynthese in Zusammenhang gebracht werden. Eine schwefelhaltige Verbindung der mitochondrialen Matrix wird mit Hilfe dieses Transporters der cytosolischen Eisen-Schwefel-Cluster-Assemblierung zur Verfügung gestellt. Die 2014 publizierten Kristallstrukturen von Atm1 (Hefe) und Atm1 aus Novosphingobium aromaticivorans offenbarten dabei eine hoch konservierte Glutathion-Bindetasche innerhalb der TMDs für ABCB7 Homologe. In der Modellpflanze Arabidopsis thaliana konnte ATM3 zusätzlich mit der Biosynthese des Molybdän-Cofaktors in Verbindung gebracht werden. In der vorliegenden Arbeit wurde das α-Proteobacterium Rhodobacter capsulatus als Modellorganismus genutzt, um mitochondriale ABC-Transporter Homologe zu untersuchen. Das Bakterium enthält zwei ABC-Transporter-Gene, rcc03139 und rcc02305, die mit den humanen mitochondrialen Transportern große Sequenzübereinstimmungen aufweisen (rcc03139: 41 % respektive 38 % Identität mit ABCB8 und ABCB10, rcc02305: 47 % identisch mit ABCB7 und ABCB6). Mit Hilfe erzeugter Interposon-Mutanten (Δrcc02305I und Δrcc03139I) konnte erstmals gezeigt werden, dass bakterielle Transporter funktionell sehr ähnliche Aufgaben wie die mitochondrialen ABC-Transporter übernehmen. Beispielsweise akkumulierten beide Interposon-Mutanten reaktive Sauerstoff-Spezies (ROS) ohne gleichzeitige Akkumulation von Glutathion oder Eisen. Weiterhin konnten wir zeigen, dass, ähnlich wie bereits für ATM3 postuliert, die Biosynthese des Molybdän-Cofaktors in Δrcc02305I verändert ist. Mit Hilfe einer lebensfähigen Doppelmutante, in der beide ABC-Transporter-Gene gleichzeitig deletiert wurden, konnten wir ausschließen, dass die beiden bakteriellen ABC-Transporter grundsätzlich redundante Funktionen haben. Durch die Analyse des Proteoms von Δrcc03139I im Vergleich zu der des Wildtyps, konnte eine extreme Beeinflussung der Tetrapyrrol Biosynthese sowie entsprechender Zielproteine identifiziert werden. Dies konnte zusätzlich durch die Quantifizierung einzelner Zwischenprodukte der Biosynthese bestätigt werden. Im Gegensatz dazu konnte anhand der Analyse des Proteoms in Verbindung mit analytischen Methoden in Δrcc02305I ein Ungleichgewicht in der Schwefelverteilung identifiziert werden. Zusammen mit der Entdeckung einer Pyridoxalphosphat (PLP) Bindestelle in Rcc02305 und anderen ABCB7-artigen Transportern, welche direkt mit dem Walker-A-Motiv der NBD überlappt, ermöglichte dies eine völlig neue Theorie, wie die schwefelhaltige Verbindung transportiert werden kann. Wir gehen davon aus, dass an PLP zunächst ein Persulfid produziert wird, welches unmittelbar mit dem Glutathion der transmembranen Bindetasche zu einem gemischten Polysulfid reagiert. Im Anschluss daran wird die ATP-Bindestelle frei und die Hydrolyse des ATPs löst eine Konformationsänderung aus, welche das gemischte Polysulfid ins Periplasma bzw. in den intermembranen Raum freigibt. N2 - ATP-binding cassette (ABC) transporters are present in all kingdoms of life and enable active transport of various different molecules across biological membranes. They all share an overall architecture of two lipophilic transmembrane spanning domains (TMDs) traversing the membrane and two hydrophilic nucleotide binding domains (NBDs) usually lacking sequence identity. The multiplicity in transported molecules is accompanied by extreme diversity in TMDs. Human mitochondria harbor four ABC transporters, namely ABCB6, ABCB7, ABCB8 and ABCB10 with functional homologues in yeast and plants. Except the ones found in Rickettsiae and related bacteria mitochondrial ABC transporters are absent in bacteria. In addition to converting energy mitochondria are important platforms for biosynthesizing various cofactors as iron sulfur clusters, molybdenum cofactor (Moco) or heme. ABCB7 (Atm1 in yeast) has been shown to connect mitochondrial with cytosolic iron sulfur cluster assembly by exporting a yet unknown sulfur containing molecule. In addition, TMDs of Atm1 display a glutathione binding pocket accessible from the matrix which has been identified in all ABCB7-like transporters and also exists in a bacterial ABC transporter homologue of Atm1 in Novosphingobium aromaticivorans. In addition, ATM3, a plant mitochondrial homologous ABC transporter to human ABCB7, has been associated with biosynthesizing Moco. In this study we used the α-proteobacterium Rhodobacter capsulatus as a model organism to characterize mitochondrial ABC transporter homologues. R. capsulatus contains two homologues to mitochondrial ABC transporters with the corresponding gene loci rcc03139 and rcc02305. They share 38 to 47 % sequence identities to human mitochondrial ABC transporters ABCB8/ABCB10 and ABCB7/ABCB6, respectively. We created interposon mutants lacking either rcc03139 or rcc02305, analyzed the physiological effects on R. capsulatus and compared the findings especially to eukaryotic deletion studies. A viable bacterial double mutant strain lacking both mitochondrial ABC transporters was constructed to investigate possible overlapping functions. Both R. capsulatus single mutants showed a severe accumulation of intracellular reactive oxygen species (ROS) in comparison to ∆nifDK which revealed to be additive in the double mutant. In the proteome of ∆rcc03139I abundancies of tetrapyrrole related proteins were significantly increased in comparison to the proteome of parental strain, which was further validated by reduced amounts of tetrapyrrole intermediates in ∆rcc03139. In contrast, in ∆rcc02305I total glutathione (GSH) was elevated when endogenous GSH biosynthesis was inhibited. In conjunction with proteomic studies we uncovered misbalanced sulfur distribution in ∆rcc02305I. Furthermore, strains lacking Rcc02305 accumulated cyclic pyranopterin monophosphate (cPMP), an intermediate of Moco biosynthesis, as it was already shown for the deletion strain of the eukaryotic counterpart ATM3 in plants. In contrast single mutant strain Δrcc03139I neither accumulated cPMP nor glutathione. Bioinformatic analysis of the amino acid sequence of Rcc02305 revealed a pyridoxal 5´phosphate (PLP) binding site which overlaps with Walker A within the NBDs of Rcc02305 and other ABCB7-like transporters. The PLP cofactor is well studied in C-DES (L-cysteine/cystine lyase from Synechocystis) for persulfide production and in L-cysteine desulfurases such as IscS and NFS1 for its role in formation of protein-bound persulfides. Based on our findings we are able to propose a new modality for the transport of the sulfur containing molecule: first of all, the transporter produces a highly reactive persulfide which is then subsequently trapped by glutathione polysulfide, already bound within the binding pocket in TMDs. Walker A becomes accessible for ATP and after hydrolysis the mixed polysulfide is released. Based on our studies we are convinced that both mitochondrial ABC transporter homologues fulfil distinct roles in R. capsulatus: Rcc02305 is a representative of Atm1/ABCB7-like transporters and important for proper sulfur distribution by exporting persulfides. In contrast Rcc03139 is a representative of ABCB6/ABCB10 related transporters and involved in biosynthesizing tetrapyrroles. KW - Rhodobacter capsulatus KW - ABC Transporter KW - ABCB7 KW - Mitochondrien KW - PLP-Walker A-Überlagerung KW - Rhodobacter capsulatus KW - ABC transporter KW - ABCB7 KW - mitochondria KW - PLP-Walker A-overlap Y1 - 2019 ER -