Untersuchung der sub-mitochondrialen Lokalisation des MINOS-Komplexes in humanen Zellen

Abstract

MINOS (mitochondrial inner membrane organizing structure) is a large hetero-oligomeric complex in the inner mitochondrial membrane. Originally identified in mitochondria of yeast cells, components of the complex were found to be enriched at cristae junctions, where they have been shown to be essential in maintaining these connections between the inner boundary membrane and the cristae membrane. Additionally, it has been speculated that the MINOS-complex is the core of an extended network that controls both the structure and the function of mitochondria. So far, however, the spatial arrangement of the complex remained ill-defined. In this dissertation I used super-resolution microscopy (nanoscopy) to show that core components of the MINOS-complex are localized in distinct clusters within the mitochondria of mammalian cells. The distribution of these clusters exhibits an inner cellular gradient from the center to the rim of the cells. The arrangement of the clusters is highly ordered forming a regularly spaced pattern parallel to the growth surface. No such pattern could be determined for interaction partners of the MINOS-complex. Using quantitative immuno-electron microcopy, this study shows that the human protein mitofilin is localized at cristae junctions. Electron tomography revealed a highly ordered arrangement of the cristae. The cristae junctions are shown to be aligned parallel to the growth surface, thereby reflecting the spatial arrangement of the MINOS-clusters. Conclusively, I showed in this study that the MINOS-complex is localized in distinct clusters at cristae junctions and that the complex demonstrates an unexpectedly high level of regularity. This strongly suggests that MINOS plays a central role in the structural organization and the regulation of mitochondria.