Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Gottschalk, B.
Application of structered illumination microscopy (SIM) in studying mitochondrial structure and function.
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Graz Medical University; 2020. pp. 126
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Graier Wolfgang
- Groschner Klaus
- Malli Roland
- Altmetrics:
- Abstract:
- Mitochondria are multifunctional organelles that essentially contribute to cell signaling by sophisticated mechanisms of communication. Morphological and structural properties of mitochondria often correlate with cellular functions and vice versa. Ca2+ plays an essential role as secondary messenger to transfer inter- and extracellular signals that modulate in particular mitochondrial shape, metabolism or stress response. Mitochondrial morphology was observed either in fixed cells with great spatial resolution using electron microscopy, or in living cells using fluorescence imaging approaches. Structured illumination microscopy (SIM) allows a compromise of both techniques combining enhanced spatial resolution compared to conventional fluorescence microscopy and the ability to observe dynamic processes in living cells. In this work two particular aspects of mitochondrial structure and function in relation to Ca2+ signaling were investigated: 1) The dynamics of the inner mitochondrial membrane (IMM) were quantified to investigate the influence of IP3-mediated endoplasmic reticulum (ER)-Ca2+ release on the sub-mitochondrial membrane organization. Dual-color SIM was used to quantitatively analyse cristae membrane (CM) dynamics in close proximity to mitochondria-associated ER membranes (MAMs). CM kinetics were spatially confined in MAMs by intracellular Ca2+ release independent of mitochondrial matrix Ca2+ signals. 2) Ca2+ movement across the IMM is strictly regulated by the mitochondrial Ca2+ uniporter complex (MCU-complex), which consists of multiple proteins like the pore forming mitochondrial Ca2+ uniporter (MCU), EMRE (an essential MCU regulator) and the Ca2+ gatekeeper MICU1 (mitochondrial Ca2+ uptake 1). Using SIM, MICU1 was found to localize at the inner boundary membrane (IBM) guarding mitochondria under resting conditions against Ca2+ overload, loss of membrane potential and cytochrome c release by cristae junction (CJ) stabilization. Upon intracellular Ca2+ elevation MICU1 functions as a Ca2+ dependent diffusion trap for MCU and EMRE, assembling the MCU-complex at the IBM to potentially increase Ca2+ uptake efficacy. Both aspects show how the interplay of structure and function of the mitochondrial membrane framework, dynamic sub-mitochondrial protein localization and Ca2+ signaling influence and regulate essential cellular processes.