168 shared publications
Institute of Pharmaceutical Sciences, Albert-Ludwigs-Universität Freiburg, Albertstraße 25, 79104 Freiburg, Germany
25 shared publications
Institute of Pharmaceutical SciencesAlbert-Ludwigs-Universität Freiburg Hermann-Herder-Str. 9 79104 Freiburg Germany
23 shared publications
Universitätsklinikum Freiburg, Klinik für Plastische und Handchirurgie
10 shared publications
Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
7 shared publications
BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
(2016 - 2018)
Mutations in mitochondrial membrane proteins could cause physiological and metabolic alterations in mitochondria as well as in cytosol. In order to address the origin of these alterations, mitochondria and cytosol of yeast wild-type BY4741 and two mutants, sdh2Δ and atp4Δ, were isolated from whole cells. These three compartments, namely mitochondria, cytosol and whole cell, were analyzed by gas chromatography-mass spectrometry based metabolic profiling, identifying seventy-three metabolites altogether, from which sixteen or ten were not detected either in mitochondria or cytosol. Compartment-specific distribution and regulation of metabolites were observed, showing the responses to the deletions of sdh2 and atp4. Based on the metabolic signature in mitochondrial matrix and cytosol, both mutants can be discriminated from wild-type by principal component analysis. De letions of electron chain transport components, sdh2 and atp4, altered not only citrate cycle related metabolites, but also diverse metabolites including amino acids, fatty acids, purine and pyrimidine intermediates and others. By applying metabolomics to isolated mitochondria and cytosol, compartment-specific metabolic regulation can be identified, which is helpful in understanding the molecular mechanism of mitochondrial homeostasis in response to genetic mutations.
SYM1 is an ortholog of the human MPV17 gene whose mutation causes mitochondrial DNA depletion syndrome. Sym1 protein is located in the inner mitochondrial membrane and its deletion results in impaired mitochondrial bioenergetic functions and morphological features under stress conditions. However, the functions of both Mpv17 and Sym1 have not been clearly characterized. Recently, compartment-specific metabolic alterations to mitochondrial mutations or inhibitors were revealed by analyzing isolated mitochondria. This development opens new doors for uncovering the function of Sym1. In order to find evidence for the molecular function of Sym1, mitochondria and the corresponding cytoplasmic fraction were isolated from wild type and sym1Δ cells through differential centrifugation. The samples were subjected to GC-MS profiling, after derivatization, or analyzed directly by LC-MS profiling, without derivatization. Eighty-nine metabolites were annotated by GC-MS profiling, while forty-five were annotated by LC-MS profiling. TCA cycle intermediates were reduced overall in sym1Δ. This correlates with the results of Dallabona et al. which showed severe OXPHOS defects of sym1Δ under stress conditions. At the same time, reduced glutathione was accumulated in mitochondria but reduced in cytosol, indicating an impaired redox balance in mutant cells. Interestingly, glutamine and aspartate, which can feed the TCA cycle, were up-regulated or maintained in mitochondria of sym1Δ. Furthermore, saccharopine was up-regulated while lysine was down-regulated in sym1Δ, exposing arrested lysine biosynthesis. Overall, GC- and LC-MS profiling in one workflow complement each other in identifying metabolites, which is helpful in understanding the metabolic dysregulations caused by deletion of sym1.