Previous and Current Research
Mitochondria are essential organelles of eukaryotic cells. They are involved in a number of anabolic and catabolic pathways and play a key role in cellular energy metabolism by oxidative generation of ATP. Biogenesis of mitochondria involves a complex interplay between the genetic systems of the organelle and the nucleus. The few, mostly hydrophobic proteins that are encoded by mitochondrial DNA and translated on mitochondrial ribosomes, constitute subunits of the oxidative phosphorylation system (OXPHOS). The proteins encoded in the nuclear DNA are translated on cytosolic ribosomes and imported into mitochondria. These proteins include structural proteins, enzymes or enzyme subunits, components of the import-, replication-, transcription- and translation-machinery and chaperones. Many basic studies on mitochondrial biogenesis employ yeast cells, because mutants with affected OXPHOS biogenesis can easily be isolated due to their inability to grow on non-fermentable carbon sources like glycerol.
Assembly of OXPHOS enzyme complexes requires a number of specific chaperones. Mutations interfering with the assembly often result in rapid degradation of unassembled subunits. Our group addresses the function of specific proteins in the process of the assembly of OXPHOS complexes. Complex IV (cytochrome c oxidase or COX) assembly depends on the formation of two copper centers (CuA and CuB). Some of the genes which are involved in this process have been identified. Current efforts aim at revealing the exact role of the gene products in this process, and to extend our knowledge to human homologues. To this end we study the effects of RNAi-mediated knockdown of the respective genes in cultured human cells. These findings will help to understand the pathology of human mitochondrial diseases.
Protein phosphorylation in mitochondria is another aspect of our research. Contrary to the situation in mammalian mitochondria, only few data on phosphorylated proteins and the enzymes engaged in the process of phosphorylation and dephosphorylation are available in yeast. We apply a reverse genetic approach by screening the phosphoproteome of mutants lacking candidate kinases and phosphatases with predicted mitochondrial localization. This strategy led to the identification of enzymes that regulate pyruvate dehydrogenase activity via phosphorylation.
A further research topic of our lab is the role of mitochondria in the differentiation of human stem cells (SC). We are studying various parameters of mitochondrial biogenesis and function in the course of SC differentiation and investigate the effects of mitochondrial dysfunction on the formation of mature cells.
Future Projects and Goals
Future prospects aim at the detailed characterization of the mitochondrial copper metabolism in yeasts (S. cerevisiae and S. pombe), Arabidopsis thaliana, and human cell lines, and the impact of mitochondrial dysfunction on stem cell differentiation.
Methodological and Technical Expertise
- Basic molecular biological methods, e.g. recombinant DNA technology, protein analysis
- Protein expression in E. coli and yeast (S. cerevisiae; S. pombe)
- Special protein analysis techniques (Blue Native PAGE, 2D-DIGE)
- Genetic analysis (tetrad analysis)
- Surface active self-assembling proteins (e.g. hydrophobins)
Radin I, Mansilla N, Rödel G and Steinebrunner I
The Arabidopsis COX11 homolog is essential for cytochrome c oxidase activity.
Front. Plant Sci. 6:1091. doi: 10.3389 (2015)
Gey U, Czupalla C, Hoflack B, Krause U, Rödel G
Proteomic Analysis Reveals a Novel Function of the Kinase Sat4p in Saccharomyces cerevisiae Mitochondria.
PLoS ONE 9(8): e103956 (2014)
Lauffer S, Mäbert K, Czupalla C, Pursche T, Hoflack B, Rödel G, Krause-Buchholz U
Saccharomyces cerevisiae porin pore forms complexes with the mitochondrial outer membrane proteins Om14p and Om45p.
J Biol Chem 287:17447–17458 (2012)
Hofmann AD, Beyer M, Krause-Buchholz U, Wobus M, Bornhäuser M, Rödel G
OXPHOS supercomplexes as a hallmark of the mitochondrial phenotype of adipogenic differentiated human MSCs.
Plos ONE 7: e35160 (2012)
Oswald C, Krause-Buchholz U, Rödel G
Knockdown of human COX17 affects assembly and supramolecular organization of cytochrome c oxidase.
J Mol Biology 389:470–479 (2009)