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Mitochondrial inner-membrane protease Yme1 degrades outer-membrane proteins Tom22 and Om45

Xi Wu1,2, Lanlan Li3, Hui Jiang4

  • 1School of Life Sciences, Peking University, Beijing, China wuxi@nibs.ac.cn.

The Journal of Cell Biology
|November 16, 2017
PubMed

Insights

Mitochondrial outer membrane proteins are degraded via a novel pathway involving the Yme1 AAA protease complex. This system monitors proteins from the intermembrane space, complementing known cytoplasmic degradation routes.

Area of Science:

  • Cell Biology
  • Mitochondrial Biology
  • Proteostasis

Background:

  • Mitochondria are vital organelles with essential metabolic and signaling roles.
  • Mitochondrial proteome quality control involves cytoplasmic and intramitochondrial proteolysis.
  • Previously, a Doa1-Cdc48-Ufd1-Npl4 complex was found to degrade outer membrane proteins.

Purpose of the Study:

  • To investigate novel proteolysis pathways for mitochondrial outer membrane proteins.
  • To identify the AAA proteases involved in degrading specific mitochondrial outer membrane proteins.
  • To elucidate the mechanism of Yme1-mediated degradation of mitochondrial outer membrane proteins.

Main Methods:

  • Immunoprecipitation assays to identify protein interactions.
  • In vivo site-specific photo-cross-linking to map protein interactions.
  • Biochemical assays to assess ATPase activity and substrate translocation.

Main Results:

  • Unexpectedly identified Yme1-Mgr1-Mgr3 AAA protease complex for mitochondrial outer membrane protein degradation.
  • Demonstrated that Mgr1 and Mgr3 adapters recognize intermembrane space domains of substrates.
  • Showed Yme1 ATPase activity mediates substrate dislocation into the intermembrane space.

Conclusions:

  • A novel proteolysis pathway monitors mitochondrial outer membrane proteins from the intermembrane space side.
  • The mitochondrial proteome is surveilled by parallel quality control systems.
  • This discovery expands our understanding of mitochondrial protein quality control mechanisms.

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