MIEF2

MIEF2 (MiD49) is a mitochondrial outer membrane receptor for the dynamin-related GTPase DRP1, serving as a central organizer of mitochondrial fission that couples metabolic and apoptotic signals to organelle dynamics and cell cycle progression. MIEF2 recruits cytosolic DRP1 to the mitochondrial surface through a surface loop within its nucleotidyl transferase domain, functioning independently of the alternative receptors Fis1 and Mff, and its oligomerization upon binding long-chain acyl-CoAs stimulates DRP1 GTPase activity to drive fission (PMID:21508961, PMID:25581164, PMID:38594588). MIEF2 protein abundance is tightly controlled by MARCH5 E3 ubiquitin ligase–mediated ubiquitination and proteasomal degradation, a process negatively regulated by Mff and Drp1, while its transcription is suppressed by Foxo3a (PMID:26564796, PMID:27932492, PMID:28137654). DRP1-dependent fission specifically through MIEF2/MiD51 (rather than Mff) is required for apoptotic cristae remodeling and cytochrome c release, and silencing MIEF2 causes G1 cell cycle arrest through ERK1/2–CDK4 signaling, linking mitochondrial fission to proliferative control (PMID:26903540, PMID:29431643).

1. 2011 High

   Identification of MIEF2 as a mitochondrial outer membrane protein that directly recruits DRP1 established a new class of fission receptor independent of previously known adaptors.

   Evidence Immunofluorescence, knockdown/overexpression, and subcellular fractionation in mammalian cells

   PMID:21508961

   Open questions at the time

   • Structural basis of DRP1–MiD49 interaction unknown
   • Relationship to other DRP1 receptors (Mff, Fis1) not yet resolved genetically
2. 2013 High

   Genetic epistasis using Fis1/Mff-null cells demonstrated that MIEF2 can recruit DRP1 and drive fission independently of all other known receptors, resolving the question of receptor redundancy.

   Evidence Fis1-null, Mff-null, and Fis1/Mff double-null cell lines with DRP1 puncta quantification and organelle-targeting experiments

   PMID:23283981 PMID:23921378

   Open questions at the time

   • Molecular determinants on MIEF2 that contact DRP1 not yet mapped
   • Functional distinction between MIEF2 and MiD51 unclear
3. 2015 High

   The 2.4 Å crystal structure of MIEF2 revealed a nucleotidyl transferase fold and identified a specific surface loop required for DRP1 recruitment, providing the first structural framework for receptor-mediated fission.

   Evidence X-ray crystallography with surface entropy reduction mutagenesis and biochemical DRP1 recruitment assays

   PMID:25581164

   Open questions at the time

   • No co-structure of the MIEF2–DRP1 complex
   • Ligand binding capacity of the nucleotidyl transferase pocket in MIEF2 unresolved
4. 2015 High

   Discovery that MARCH5 E3 ligase ubiquitinates MIEF2 for proteasomal degradation revealed the principal mechanism controlling MIEF2 abundance and explained how excess MIEF2 drives pathological fragmentation and apoptosis sensitization.

   Evidence MARCH5-KO cells, ubiquitination assays, MiD49-KO epistasis, and proteasome inhibitor experiments

   PMID:26564796

   Open questions at the time

   • Specific ubiquitin chain type on MIEF2 not determined
   • Signals that regulate MARCH5 activity toward MIEF2 unknown
5. 2016 High

   Demonstration that DRP1-dependent cristae remodeling and cytochrome c release require MIEF2/MiD51 but not Mff distinguished the apoptotic fission pathway from homeostatic fission and positioned MIEF2 as a specific mediator of intrinsic apoptosis.

   Evidence MiD49/51-KO, Drp1-KO, Mff-KO cell lines with cytochrome c release assays, OPA1 epistasis, and electron microscopy

   PMID:26903540 PMID:27076521

   Open questions at the time

   • How MIEF2/MiD51 selectively remodel cristae versus simply fragmenting mitochondria is mechanistically unclear
   • Whether MIEF2 and MiD51 are individually sufficient for apoptotic remodeling not separated
6. 2016 High

   Double-knockout studies showed that Mff and Drp1 negatively regulate MARCH5-mediated ubiquitination of MIEF2, revealing a feedback circuit among fission components that tunes receptor abundance.

   Evidence Drp1−/−/MARCH5−/− and Mff−/−/MARCH5−/− double knockouts, co-immunoprecipitation, pulse-chase half-life measurement

   PMID:27932492

   Open questions at the time

   • Mechanism by which Drp1 and Mff restrain MARCH5 activity toward MIEF2 is unclear
   • Role of the p97/Npl4 complex in MIEF2 extraction not fully dissected
7. 2017 Medium

   Identification of Foxo3a as a direct transcriptional repressor of the MIEF2 promoter linked stress-responsive transcription factor signaling to mitochondrial fission control, with in vivo relevance to doxorubicin-induced cardiotoxicity.

   Evidence ChIP/promoter assay, Foxo3a transgenic mice, MIEF2 siRNA knockdown, in vivo cardiotoxicity model

   PMID:28137654

   Open questions at the time

   • Other transcriptional regulators of MIEF2 not surveyed
   • Whether Foxo3a regulation is tissue-specific or general is unknown
8. 2018 High

   Silencing MIEF2 caused G1-phase arrest through ERK1/2–CDK4 signaling, establishing that MIEF2-mediated mitochondrial fission is coupled to cell cycle progression and proliferative control in vascular smooth muscle cells.

   Evidence siRNA knockdown, flow cytometry, microRNA profiling, in vivo nebulized siRNA in monocrotaline-PAH rat model

   PMID:29431643

   Open questions at the time

   • Direct mechanistic link between mitochondrial morphology and ERK1/2 activation not identified
   • Whether this cell cycle coupling operates in non-vascular cell types is unknown
9. 2023 Medium

   A co-crystal structure of DRP1 with a small-molecule inhibitor that disrupts the DRP1–MIEF2 interface identified this interaction as an allosteric regulatory site, opening a pharmacological avenue.

   Evidence X-ray co-crystallography of DRP1 with inhibitor compound, in vitro mitochondrial fragmentation assay

   PMID:37583827

   Open questions at the time

   • No direct co-crystal of MIEF2 bound to DRP1 is available
   • In vivo efficacy of the DRP1–MIEF2 interface inhibitor not tested
10. 2024 High

    Long-chain acyl-CoAs were identified as activating ligands that bind the nucleotidyl transferase pocket and induce MIEF2 oligomerization, which stimulates DRP1 GTPase activity, directly coupling lipid metabolic status to mitochondrial fission.

    Evidence In vitro oligomerization and DRP1 GTPase assays, point mutagenesis, live-cell imaging with oleic acid treatment and MiD49/51 knockdown

    PMID:38594588

    Open questions at the time

    • Structural basis of LCACA binding to MIEF2 specifically (versus MiD51) not resolved
    • Physiological range of acyl-CoA concentrations at the OMM in different metabolic states not established
11. 2025 Medium

    MIEF2 knockdown impaired PINK1–Parkin-dependent mitophagy and CPT-1A-mediated fatty acid β-oxidation, extending MIEF2 function beyond fission into mitophagy and metabolic regulation.

    Evidence siRNA knockdown in fibroblast-like synoviocytes, mitophagy and fatty acid oxidation assays, CIA mouse model

    PMID:40846102

    Open questions at the time

    • MIEF2–PINK1/Parkin interaction is computationally inferred rather than biochemically validated
    • Whether the mitophagy role is secondary to fission defects or a direct function is unresolved

• The structural basis of the MIEF2–DRP1 complex at atomic resolution, the mechanism by which MIEF2-dependent fission specifically remodels cristae during apoptosis, and the in vivo physiological functions of MIEF2 in tissue-specific contexts remain unresolved.
• No co-crystal structure of the MIEF2–DRP1 complex exists
• Mechanism distinguishing apoptotic cristae remodeling from homeostatic fission through MIEF2 is unclear
• Tissue-specific in vivo knockout phenotypes of MIEF2 have not been systematically characterized