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Dual-localized PPTC7 limits mitophagy through proximal and dynamic interactions with BNIP3 and NIX

Lianjie Wei1, Mehmet Oguz Gok2, Jordyn D Svoboda1

  • 1Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine in St. Louis, St. Louis, MO, USA.

Life Science Alliance
|July 11, 2024
PubMed

Insights

Protein phosphatase 7 (PPTC7) regulates mitophagy by promoting the turnover of BNIP3 and NIX proteins. This mitochondrial phosphatase targets these proteins for proteasomal degradation, controlling basal mitophagy levels.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitophagy is a crucial cellular process for maintaining mitochondrial homeostasis.
  • BNIP3 and NIX are key proteins that mediate mitophagy.
  • The precise mechanisms by which PPTC7 regulates mitophagy are not fully understood.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which PPTC7 suppresses BNIP3- and NIX-mediated mitophagy.
  • To investigate the role of PPTC7 in the post-transcriptional regulation of BNIP3 and NIX.
  • To determine the subcellular localization and functional relevance of PPTC7 in mitophagy regulation.

Main Methods:

  • Western blotting to assess protein levels and half-life.
  • Proteasomal inhibition assays.
  • Overexpression and localization studies of PPTC7.
  • Proximity labeling and co-localization experiments.

Main Results:

  • Loss of PPTC7 leads to post-transcriptional upregulation of BNIP3 and NIX.
  • PPTC7 promotes the ubiquitin-mediated turnover of BNIP3 and NIX.
  • PPTC7's catalytic activity is required for regulating BNIP3 and NIX levels, but mitochondrial localization is not essential.
  • PPTC7 is dual-localized to the outer mitochondrial membrane and matrix.
  • Anchoring PPTC7 to the outer mitochondrial membrane effectively reduces BNIP3 and NIX accumulation.
  • PPTC7 dynamically associates with BNIP3 and NIX.

Conclusions:

  • PPTC7 functions in the outer mitochondrial compartment to promote proteasomal turnover of BNIP3 and NIX.
  • This action of PPTC7 limits basal mitophagy.
  • PPTC7 acts as a critical regulator of mitophagy through targeted protein degradation.

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