Mechanisms and components of mitochondrial turnover and quality control by mitophagy

• Applicants: Professor Dr. Peter Rehling; Professor Dr. Michael Thumm
• Subject Area: Biochemistry
• Term: from 2011 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 200543882

• Final Report Year: 2017

Final Report Abstract

Turnover of entire mitochondria occurs through mitophagy. Here we aimed to assess the mechanism of mitophagy focusing on mitochondrial proteins implicated in targeting mitochondria to mitophagy. Our analyses showed that the yeast autophagy receptor Atg32 is required under all tested mitophagy-inducing conditions. A posttranslational regulation of Atg32 stability directs the protein to the vacuole during mitophagy. In contrast, Atg33 can be partially bypassed in post-log-phase and rapamycin-induced mitophagy. These findings reveal that at the level of mitochondria factors exist that are specific to discrete mitophagy stimuli. Uth1, which was considered a surface receptor for mitophagy is in fact dispensable for mitophagy and localizes to the inner mitochondrial membrane excluding a role as cytosol-exposed receptor protein. Our analyses in S. cerevisiae on mitophagy of damaged mitochondria showed that oxidative stress caused by H2O2 or paraquat only resulted in very moderately enhanced mitophagy. Taken together, in S. cerevisiae the so far best conditions to induce mitophagy are nutrient limitation or addition of the TOR kinase inhibitor rapamycin. In human mitochondria, we define a protein complex of activated Parkin upon mitophagy induction. This Parkin complex can be easily assessed by Blue Native PAGE and now be utilized as a marker for mitophagy induction.

Publications

• (2013) Uth1 is a mitochondrial inner membrane protein dispensable for post-log phase and rapamycin-induced mitophagy. FEBS J. 280: 4970-4982
  Welter, E., Montino, M., Reinhold, R., Schlotterhose, P., Krick, R., Dudek, J., Rehling, P., and Thumm, M.
  
• (2014) Cell biology. Powering the cell cycle. Science 346: 1059-1060
  Schulz C., and Rehling P.
  
• (2015). PI3P binding by Atg21 organises Atg8 lipidation. EMBO J. 34: 955–973
  Juris, L., Montino, M., Rube, P., Schlotterhose, P., Thumm, M., and Krick, R.
  
• (2016) Phospho-ubiquitin-Parkin complex as a marker for mitophagy signaling. Autophagy
  Callegari, S., Oeljeklaus, S., Warscheid, B., Dennerlein S., Thumm, M., Rehling, P., and Dudek, J.
  
• (2016). Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12: 1–222
  Klionsky, D. J., et al., Thumm, M., et al.