The role of Fis1p-Mdv1p interactions in mitochondrial fission complex assembly

Area of Science:

• Cell Biology
• Mitochondrial Dynamics
• Protein Interactions

Background:

• Mitochondrial division is crucial for cellular health and is mediated by protein complexes on the outer mitochondrial membrane.
• The Fis1p protein, an integral outer membrane protein, plays a key role in recruiting other proteins, including Mdv1p and Dnm1p GTPase, to form fission complexes.
• The precise molecular mechanisms governing the assembly of these fission complexes, particularly the Fis1p-Mdv1p interaction, remain incompletely understood.

Purpose of the Study:

• To elucidate the direct interaction between Fis1p and Mdv1p.
• To investigate the role of the Fis1p tetratricopeptide repeat (TPR)-like domain in fission complex assembly.
• To define the distinct functional contributions of the Fis1p NH(2)-terminal arm and TPR-like fold in mitochondrial fission.

Main Methods:

• Investigated the Fis1p-Mdv1p interaction using biochemical assays to confirm direct binding.
• Utilized conditional mutations in the Fis1p TPR-like domain to assess effects on fission complex assembly.
• Employed suppressor mutations in the Mdv1p coiled-coil region to analyze genetic interactions and functional relationships.

Main Results:

• Provided direct evidence for a physical interaction between Fis1p and Mdv1p.
• Demonstrated that mutations in the Fis1p TPR-like domain disrupt fission complex assembly.
• Showed that these assembly defects can be rescued by specific mutations in Mdv1p, highlighting functional interdependence.

Conclusions:

• The Fis1p TPR-like fold directly binds to Mdv1p, mediating its recruitment.
• Mdv1p acts as a scaffold, facilitating the subsequent recruitment of Dnm1p GTPase into functional mitochondrial fission complexes.
• The Fis1p NH(2)-terminal arm and TPR-like fold possess separable functions critical for regulating mitochondrial division.