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Selected Publication:
Madreiter-Sokolowski, C.
PRMT1-mediated methylation of MICU1 is a key for the engagement of UCP2 in mitochondrial Ca2+ uptake
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Graz Medical University; 2016. pp.
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- Authors Med Uni Graz:
- Madreiter-Sokolowski Corina
- Advisor:
- Graier Wolfgang
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- Abstract:
- Mitochondria are supplying the cell with adenosine triphosphate (ATP) and are essential for cell differentiation, cell cycle, and intracellular signaling. The transfer of the ubiquitous second messenger Ca2+ into the matrix of mitochondria is an important process that substantially contributes to these cellular functions. Recent studies demonstrated that mitochondrial Ca2+ uptake is achieved by a macromolecular complex, which basically consists of the pore-forming mitochondrial Ca2+ uniporter (MCU) protein, the essential MCU regulator (EMRE) and the mitochondrial Ca2+ uptake 1 (MICU1). MICU1 is a Ca2+ sensing protein, which interacts with MCU in order to prevent mitochondrial Ca2+ overload potentially leading to cell stress and death. Before characterization of these proteins, uncoupling proteins 2 and 3 (UCP2/3) have been demonstrated to be crucial for mitochondrial Ca2+ uptake. Nevertheless, the mechanism how UCP2/3 contribute to mitochondrial Ca2+ uptake remained controversial. To clarify this issue we screened different cell types regarding the role of UCP2/3 in mitochondrial Ca2+ uptake by using genetically encoded fluorescent Ca2+ probes as well as fluorescent dyes. While modulation of UCP2/3 expression strongly affected mitochondrial Ca2+ uptake in HeLa and Ea.hy926, an UCP2/3-insensitive mitochondrial Ca2+ uptake could be identified in human umbilical vein endothelial cells (HUVECs) as well as in porcine aortic endothelial cells (PAECs). Western blots revealed a strongly increased asymmetric arginine dimethylation state of UCP2/3-dependent HeLa and Ea.hy926 in comparison to UCP2/3-independent HUVECs and PAECs. Förster resonance energy transfer (FRET)-based mitochondrial Ca2+ measurements and proteomic analyses demonstrated that protein arginine methyl transferase 1 (PRMT1) modulates mitochondrial Ca2+ uptake by asymmetrical methylation of MICU1. Methylation of MICU1 resulted in a decrease of its Ca2 sensitivity leading to attenuated mitochondrial Ca2+ uptake. It could be shown, that UCP2/3 normalized Ca2+ sensitivity of MICU1 and, thus, restored mitochondrial Ca2+ uptake in case of elevated PRMT1 activity. Since PRMT1 activity was reported to be highly elevated in certain types of cancer, these data not just provide novel insights in the complex regulation of the mitochondrial Ca2+ uptake, but also unveil possible targets for cancer treatments in the future.