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Completion of mitochondrial division requires the intermembrane space protein Mdi1/Atg44

Olivia M Connor1, Srujan K Matta1, Jonathan R Friedman1

  • 1Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA.

The Journal of Cell Biology
|August 4, 2023
PubMed

Insights

Mitochondrial fission, crucial for organelle shape, requires the new protein Mdi1 (also named Atg44). This protein works with Dnm1 (dynamin-related protein 1) to ensure mitochondria divide properly.

Area of Science:

  • Cell Biology
  • Mitochondrial Dynamics

Background:

  • Mitochondria are dynamic organelles whose shape is regulated by fission and fusion.
  • Mitochondrial fission is mediated by Dnm1 (dynamin-related protein 1), but the complete mechanism, especially involving both membranes, remains unclear.

Purpose of the Study:

  • To investigate factors coordinating mitochondrial fission beyond Dnm1/Drp1 activity.
  • To identify proteins within the mitochondria that contribute to the completion of mitochondrial division.

Main Methods:

  • Genetic screening in yeast to identify novel fission factors.
  • Analysis of mitochondrial morphology in knockout strains.
  • Investigating protein localization and function using microscopy.

Main Results:

  • A novel intermembrane space protein, Mdi1 (Atg44), was identified as essential for mitochondrial fission in yeast.
  • Loss of Mdi1 leads to mitochondrial hyperfusion, indicating a fission defect, independent of Dnm1 recruitment.
  • Conserved homologs of Mdi1 possess an amphipathic α-helix critical for its function in mitochondrial morphology.

Conclusions:

  • Mdi1 plays a critical role in coordinating mitochondrial fission, likely by distorting membranes to facilitate Dnm1-mediated division.
  • Dnm1 alone is insufficient for efficient mitochondrial division; Mdi1 is required for robust fission completion.

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