Docking and stability defects in mitofusin highlight the proteasome as a potential therapeutic target

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Published on: January 11, 2017

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Ira Buntenbroich1, Vincent Anton1, Daniel Perez-Hernandez2

  • 1Institute for Genetics,University of Cologne, Cologne 50931, Germany.

Iscience
|July 7, 2023
PubMed

Insights

Mitochondrial fusion defects cause disease. This study reveals two conserved cysteines in mitofusins are crucial for outer membrane fusion, uncovering new steps and potential therapeutic targets like proteasomal inhibition.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitochondrial fusion is essential for cellular health, and defects are linked to numerous diseases.
  • Mitofusins (MFN proteins) are key regulators of mitochondrial outer membrane fusion, utilizing GTP hydrolysis for membrane remodeling.
  • The precise mechanism by which mitofusins mediate outer membrane fusion remains incompletely understood.

Purpose of the Study:

  • To elucidate the specific roles of conserved cysteine residues in yeast and mammalian mitofusins during the mitochondrial fusion process.
  • To identify novel intermediate steps in the mitofusin-mediated outer membrane fusion cycle.
  • To explore potential therapeutic strategies targeting mitofusin function and stability.

Main Methods:

  • Site-directed mutagenesis of conserved cysteine residues in Fzo1 (yeast mitofusin).
  • Analysis of mitochondrial morphology and fusion in yeast strains expressing mutated Fzo1.
  • Investigation of protein complex formation and stability using biochemical assays.
  • Assessment of the impact of proteasomal inhibition on Fzo1 function and mitochondrial fusion.

Main Results:

  • The two conserved cysteines in mitofusins are essential for efficient mitochondrial fusion.
  • Cysteine 381 is critical for the formation of the trans-tethering complex prior to GTP hydrolysis.
  • Cysteine 805 stabilizes the Fzo1 protein and the trans-tethering complex immediately before membrane fusion.
  • Proteasomal inhibition rescues the fusion defect caused by the Fzo1 C805S mutation, restoring Fzo1 levels and membrane fusion.

Conclusions:

  • This study identifies two novel, cysteine-dependent steps in the mitochondrial outer membrane fusion cycle.
  • Understanding these steps provides insights into mitofusin-associated diseases caused by protein assembly or stability defects.
  • Targeting the proteasome presents a potential therapeutic avenue for treating mitofusin-related disorders.
Keywords:
Biological sciencesCell biologyGeneticsMolecular biology

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