OMA1 protease eliminates arrested protein import intermediates upon mitochondrial depolarization

Area of Science:

• Cellular Biology
• Mitochondrial Biology
• Protein Transport

Background:

• Mitochondrial proteins synthesized in the cytosol must be imported into the organelle.
• Protein unfolding is necessary for translocation through mitochondrial membranes.
• Misfolded proteins can stall import, disrupting mitochondrial function and cellular proteostasis.

Purpose of the Study:

• To investigate the molecular mechanisms resolving failed protein import in human cells.
• To compare human mechanisms with those previously described in yeast.
• To establish a cell line-based translocase clogging model for human import failure studies.

Main Methods:

• Development of a cell line-based translocase clogging model.
• Analysis of cellular responses to protein import stalling.
• Identification of key proteases and factors involved in resolving translocation blockage.

Main Results:

• Human cells utilize mitochondrial factors to clear blocked translocases, differing from fungal mechanisms.
• Mitochondrial membrane depolarization triggers OMA1-mediated cleavage of stalled proteins.
• Cleavage releases blocked translocases, and fragments are cleared by cytosolic VCP/p97 and the proteasome.

Conclusions:

• Human cells employ a distinct mechanism involving mitochondrial proteolysis to resolve protein import failures.
• OMA1 plays a crucial role in releasing stalled proteins from mitochondrial translocases.
• This process ensures the maintenance of mitochondrial function and cellular proteostasis.