Dynamic regulation of the modular assembly of the mitochondrial respiratory chain

• Applicant: Professorin Dr. Friederike-Nora Vögtle
• Subject Area: Biochemistry ; Cell Biology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504289590

The mitochondrial respiratory chain plays a central role in cellular energy metabolism by generating ATP through oxidative phosphorylation (OXPHOS). Various proteins and co-factors build up the individual respiratory chain complexes, which assemble into larger structures known as supercomplexes. The biogenesis of these complexes and their subsequent assembly into supercomplexes requires several assembly factors. Deficiencies in the assembly or function of the OXPHOS machinery can lead to increased production of reactive oxygen species and oxidative stress, resulting in severe human diseases. How the correct stoichiometry between the respiratory chain complexes and the ATP synthase is achieved remained unexplored. During the first funding period, we identified a stop-and-go mechanisms that temporarily halts the assembly of the respiratory chain complexes until positive signals from complex IV and the mitoribosome remove the molecular brake, allowing the synchronized progression of complex IV and ATP synthase biogenesis. We identified the key protein components Mra1 and Rcf2 and their mechanism in molecular detail, however, the role of phospholipids and the integration of the stop-and-go-mechanism into metabolic pathways have yet to be investigated. In the second funding period, we aim to achieve a comprehensive understanding of this fundamental process to ensure efficient energy conversion through synchronized complex assembly. We plan to extend our analysis beyond proteins to include lipids and metabolic pathways. Specifically, we aim to identify the mitochondrial proteases that play central roles in the stoichiometric control mechanism by degrading the molecular brake Mra1. We will investigate the role of phospholipids, in particular of the mitochondrial signature lipid cardiolipin, which is crucial for OXPHOS activity. Additionally, it remains unknown how cells synchronize the biogenesis of the OXPHOS machinery with the activity of metabolic pathways that generate substrates for the respiratory chain complexes. Therefore, our third aim is to assess the regulation of the TCA cycle in response to metabolic rewiring. Here, we will focus on the uncharacterized protein Fmp16, which may function as a second molecular brake based on our preliminary data.

• DFG Programme: Research Grants