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Comprehensive Research Report: C. elegans mff-1 (Mitochondrial Fission Factor, UniProt Q19343)

1. Gene Identity and Protein Family

The gene mff-1 (ORF name F11C1.2, CELE_F11C1.2) in Caenorhabditis elegans encodes Mitochondrial Fission Factor (MFF-1), a member of the Tango11 protein family containing the Mff/Tango-11 domain (InterPro IPR008518). C. elegans possesses two paralogs of this family: mff-1 (F11C1.2) and mff-2, both of which have been proposed as candidate DRP-1 receptors on the mitochondrial outer membrane (lu2011amolecularswitch pages 7-8). The protein is the C. elegans ortholog of mammalian MFF and Drosophila Tango11 (CG3404), which was originally identified through siRNA screening for genes that affect mitochondrial morphology in Drosophila S2 cells (singh2023mechanisticanalysisof pages 28-32). Importantly, the MFF/Tango11 family is metazoan-specific and absent in yeast, which instead utilizes a different set of adaptor proteins (Fis1/Mdv1/Caf4) for Dnm1-mediated mitochondrial fission (yu2020regulationofmammalian pages 6-7, singh2023mechanisticanalysisof pages 28-32).

2. Primary Molecular Function

MFF-1 functions as a membrane-anchored receptor/adaptor protein that recruits the dynamin-related GTPase DRP-1 from the cytosol to the mitochondrial outer membrane, thereby promoting mitochondrial fission. This function is conserved from the well-characterized mammalian ortholog MFF. In mammalian cells, MFF is the principal DRP1 receptor and is essential for mitochondrial recruitment of DRP1; depletion of MFF severely inhibits mitochondrial fission and DRP1 recruitment, while overexpression extensively recruits DRP1 and induces mitochondrial fragmentation (otera2011discoveryofthe pages 1-3, yu2020regulationofmammalian pages 6-7). MFF binds DRP1 directly, although this interaction is transient and detectable only after chemical crosslinking (singh2023mechanisticanalysisof pages 28-32, singh2023mechanisticanalysisof pages 32-35). The interaction occurs through N-terminal repeat motifs (R1 and R2) in the first ~50 amino acids of MFF, which are essential for DRP1 binding (otera2011discoveryofthe pages 1-3, yu2020regulationofmammalian pages 6-7). Notably, MFF selectively recruits oligomerized, active forms of DRP1, distinguishing it from alternative DRP1 receptors such as MiD49/MiD51, which bind a wider range of DRP1 assembly states (yu2020regulationofmammalian pages 6-7).

In C. elegans, Lu et al. (2011) proposed that MFF-1 and MFF-2 serve as mitochondrial receptors for DRP-1, alongside the EGL-1–CED-9 complex. The rationale is that loss of egl-1 function only causes an approximately 20% increase in mitochondrial length, far less severe than the hyperfusion phenotype of drp-1 mutants, implying the existence of additional DRP-1 receptors such as MFF-1 and MFF-2 (lu2011amolecularswitch pages 7-8). Similarly, Qin et al. (2020) listed fis-2, mff-1, and mff-2 as candidate DRP-1 recruiters in C. elegans neurons (qin2020anendoplasmicreticulum pages 5-7).

MFF-1 is not an enzyme and does not catalyze a biochemical reaction. Rather, it functions as a structural adaptor that physically links cytosolic DRP-1 to the mitochondrial membrane, enabling the mechanochemical GTPase activity of DRP-1 to constrict and sever the outer mitochondrial membrane.

3. Subcellular Localization

MFF-1 localizes to the mitochondrial outer membrane (MOM). This was directly demonstrated in C. elegans by Head et al. (2011), who used MFF-1 as an outer membrane marker in protease protection experiments on isolated mitochondria. They showed that MFF-1 is digested by proteinase K in intact mitochondria (similar to other cytoplasmically exposed MOM proteins), whereas inner membrane protein EAT-3 and matrix protein F1β remain protease-protected. This confirms that MFF-1 is embedded in the mitochondrial outer membrane with a substantial portion of the protein exposed to the cytosol (head2011anovelmitochondrial pages 5-6). This topology is fully consistent with the mammalian ortholog, which is a C-tail-anchored MOM protein with its N-terminal functional domain facing the cytosol (singh2023mechanisticanalysisof pages 28-32, otera2011discoveryofthe pages 1-3).

4. Domain Architecture and Structural Features

Based on conserved domain architecture from the mammalian ortholog, the MFF/Tango-11 domain (IPR008518) protein is predicted to contain: (1) N-terminal repeat regions that serve as the DRP1-binding interface; (2) a coiled-coil domain that mediates protein oligomerization; and (3) a C-terminal transmembrane domain that anchors the protein in the outer mitochondrial membrane in a tail-anchored configuration (singh2023mechanisticanalysisof pages 28-32). In mammalian MFF, the coiled-coil domain enables oligomerization, most likely as a trimer with a dissociation constant of approximately 10 μM in solution. This dynamic oligomerization is essential for DRP1 activation and is significantly more favorable when the protein is membrane-anchored (liu2021mffoligomerizationis pages 7-8, liu2021mffoligomerizationis pages 1-2). Oligomerization-defective MFF mutants fail to rescue mitochondrial division, DRP1 recruitment to mitochondria, and peroxisome division in MFF-knockout cells (liu2021mffoligomerizationis pages 1-2, liu2021mffoligomerizationis pages 6-7).

5. Biochemical Pathway and Mechanism of Mitochondrial Fission

MFF-1 participates in the DRP1-mediated mitochondrial fission pathway. The current model, derived primarily from mammalian studies, proceeds as follows:

1. DRP1 recruitment: Cytosolic DRP1 exists as a mixture of dimers and higher-order oligomers. MFF on the outer mitochondrial membrane selectively binds pre-formed DRP1 oligomers through its N-terminal repeat motifs (singh2023mechanisticanalysisof pages 32-35, yu2020regulationofmammalian pages 6-7).
2. MFF oligomerization and Drp1 activation: MFF trimers assemble into higher-order puncta on the MOM. Actin filaments synergize with MFF by lowering the effective MFF concentration required for DRP1 activation by approximately 10-fold (liu2021mffoligomerizationis pages 7-8, liu2021mffoligomerizationis pages 1-2).
3. Membrane constriction and scission: Once recruited and activated, DRP1 self-assembles into ring-like oligomeric structures around mitochondria and hydrolyzes GTP, driving constriction and ultimately severing the outer mitochondrial membrane (otera2011discoveryofthe pages 1-3).

In C. elegans, the mitochondrial fission pathway additionally involves the EGL-1–CED-9 complex as a parallel DRP-1 receptor system. The BCL-2-like protein CED-9 can act as a molecular switch: in complex with the BH3-only protein EGL-1, it recruits GTP-bound DRP-1 to mitochondria and promotes fission, whereas CED-9 alone promotes FZO-1/EAT-3-dependent mitochondrial fusion (lu2011amolecularswitch pages 6-7, lu2011amolecularswitch pages 4-6, lu2011amolecularswitch pages 7-8). This dual-receptor system (EGL-1/CED-9 plus MFF-1/MFF-2) explains why loss of egl-1 alone only partially phenocopies drp-1 loss-of-function (lu2011amolecularswitch pages 7-8).

6. Role in Peroxisomal Fission

In mammalian cells, MFF is the sole DRP1 receptor essential for peroxisomal division. MFF-knockout cells display enlarged, elongated peroxisomes, and only wild-type MFF (but not oligomerization-deficient mutants) can rescue this phenotype (liu2021mffoligomerizationis pages 1-2, liu2021mffoligomerizationis pages 6-7, carmichael2022fissionimpossible(?)—new pages 9-10). Whether MFF-1 similarly participates in peroxisomal fission in C. elegans has not been directly tested in the retrieved literature, but this dual role is likely conserved given the family membership and the shared DRP1/MFF fission machinery.

7. Regulation by AMPK Phosphorylation

Mammalian MFF is regulated by phosphorylation by AMP-activated protein kinase (AMPK), the master cellular energy sensor. Key phosphorylation sites include Ser146 (involved in regulating MAVS-mediated innate immune responses), as well as Ser155, Ser172, and Ser275, which collectively link energy status to mitochondrial fission activity (hanada2021mavsisenergized pages 9-10, hanada2021mavsisenergized pages 7-8, tabara2025molecularmechanismsof pages 9-10). Under conditions of mitochondrial dysfunction or energy stress, AMPK phosphorylates MFF to promote mitochondrial fission, thereby facilitating the segregation and removal of damaged mitochondria via mitophagy (hanada2021mavsisenergized pages 1-2, carmichael2022fissionimpossible(?)—new pages 9-10). Additionally, protein kinase D (PKD) phosphorylates MFF during mitosis to coordinate mitochondrial division with cell division (tabara2025molecularmechanismsof pages 9-10). Whether AMPK-mediated regulation of MFF-1 is conserved in C. elegans remains to be determined experimentally.

8. Non-Canonical Function in Innate Immunity

A remarkable non-canonical function of MFF was discovered in its regulation of mitochondrial antiviral signaling (MAVS). Hanada et al. (2020) demonstrated that MFF is required for the formation of active MAVS clusters on mitochondria, independent of its role in mitochondrial fission and independent of DRP1. Under energy-replete conditions, MFF promotes MAVS cluster formation and a robust antiviral response. Under energy-depleted conditions, AMPK phosphorylates MFF at Ser146, leading to disorganization of MAVS clusters and suppression of the acute antiviral response (hanada2021mavsisenergized pages 9-10, hanada2021mavsisenergized pages 7-8, hanada2021mavsisenergized pages 1-2). This dual role positions MFF as a critical link between mitochondrial metabolism and innate immunity.

9. Evolutionary Conservation and the Tango11 Family

The Tango11/MFF family is conserved across metazoa but absent from yeast. The Drosophila ortholog, Tango11 (CG3404), was identified through genome-wide siRNA screening, and its knockdown causes perinuclear clustering of mitochondria similar to DRP1 knockdown, confirming a conserved fission function (singh2023mechanisticanalysisof pages 28-32). C. elegans has expanded this family to include two paralogs, mff-1 and mff-2, possibly reflecting functional diversification or partial redundancy in DRP-1 recruitment (lu2011amolecularswitch pages 7-8). In mammals, the single MFF gene generates at least nine splice variants through alternative exon usage, producing proteins of 25.1–38.5 kDa (singh2023mechanisticanalysisof pages 28-32).

10. Disease Relevance of the Mammalian Ortholog

Loss-of-function mutations in human MFF cause encephalopathy due to mitochondrial and peroxisomal fission defect (OMIM 617086), an autosomal recessive disorder. Clinical features include Leigh-like encephalopathy, developmental delay, epileptic seizures, optic atrophy, peripheral neuropathy, microcephaly, and intellectual disability (carmichael2022fissionimpossible(?)—new pages 22-23, carmichael2022fissionimpossible(?)—new pages 9-10, carmichael2022fissionimpossible(?)—new pages 21-22, OpenTargets Search: -MFF). Mutations are typically nonsense mutations that cause truncation before the C-terminal transmembrane domain. At the cellular level, patient fibroblasts show elongated, hyper-fused mitochondria and peroxisomes, reflecting impaired organellar fission, while metabolic functions of these organelles often remain surprisingly normal (carmichael2022fissionimpossible(?)—new pages 9-10, carmichael2022fissionimpossible(?)—new pages 10-12). This underscores that the primary pathology derives from disrupted organellar dynamics and distribution rather than metabolic failure per se.

Summary

The following table provides a cross-species comparison of MFF-1/MFF/Tango11:

Table: This table compares the key features of worm mff-1, human MFF, and Drosophila Tango11 to support functional annotation by orthology. It highlights what is directly shown in C. elegans versus what is inferred from better-characterized metazoan orthologs.

In summary, C. elegans MFF-1 (F11C1.2, UniProt Q19343) is a mitochondrial outer membrane protein belonging to the metazoan-specific Tango11/MFF family. It functions as a receptor/adaptor for the dynamin-related GTPase DRP-1, recruiting it from the cytosol to the mitochondrial surface to promote organellar fission. While direct functional studies on mff-1 in C. elegans are limited, its identification as a protease-sensitive outer mitochondrial membrane protein (head2011anovelmitochondrial pages 5-6), its classification within the Tango11 family (singh2023mechanisticanalysisof pages 28-32), and its proposal as a DRP-1 receptor alongside its paralog MFF-2 (lu2011amolecularswitch pages 7-8) strongly support functional conservation with the well-characterized mammalian MFF, which serves as the principal DRP1 adaptor for both mitochondrial and peroxisomal fission.

References

1. (lu2011amolecularswitch pages 7-8): Yun Lu, Stéphane G. Rolland, and Barbara Conradt. A molecular switch that governs mitochondrial fusion and fission mediated by the bcl2-like protein ced-9 of caenorhabditis elegans. Proceedings of the National Academy of Sciences, 108:E813-E822, Sep 2011. URL: https://doi.org/10.1073/pnas.1103218108, doi:10.1073/pnas.1103218108. This article has 48 citations and is from a highest quality peer-reviewed journal.

2. (singh2023mechanisticanalysisof pages 28-32): Abeer Prakash Singh. Mechanistic analysis of mitochondrial fission mediators. Text, Jan 2023. URL: https://doi.org/10.26181/21844440.v1, doi:10.26181/21844440.v1. This article has 0 citations and is from a peer-reviewed journal.

3. (yu2020regulationofmammalian pages 6-7): Rong Yu, Urban Lendahl, Monica Nistér, and Jian Zhao. Regulation of mammalian mitochondrial dynamics: opportunities and challenges. Frontiers in Endocrinology, Jun 2020. URL: https://doi.org/10.3389/fendo.2020.00374, doi:10.3389/fendo.2020.00374. This article has 222 citations.

4. (otera2011discoveryofthe pages 1-3): Hidenori Otera and Katsuyoshi Mihara. Discovery of the membrane receptor for mitochondrial fission gtpase drp1. Small GTPases, 2:167-172-51, May 2011. URL: https://doi.org/10.4161/sgtp.2.3.16486, doi:10.4161/sgtp.2.3.16486. This article has 108 citations and is from a peer-reviewed journal.

5. (singh2023mechanisticanalysisof pages 32-35): Abeer Prakash Singh. Mechanistic analysis of mitochondrial fission mediators. Text, Jan 2023. URL: https://doi.org/10.26181/21844440.v1, doi:10.26181/21844440.v1. This article has 0 citations and is from a peer-reviewed journal.

6. (qin2020anendoplasmicreticulum pages 5-7): Qing Qin, Ting Zhao, Wei Zou, Kang Shen, and Xiangming Wang. An endoplasmic reticulum atpase safeguards endoplasmic reticulum identity by removing ectopically localized mitochondrial proteins. Cell reports, 33 6:108363, Nov 2020. URL: https://doi.org/10.1016/j.celrep.2020.108363, doi:10.1016/j.celrep.2020.108363. This article has 48 citations and is from a highest quality peer-reviewed journal.

7. (head2011anovelmitochondrial pages 5-6): Brian P. Head, Miren Zulaika, Sergey Ryazantsev, and Alexander M. van der Bliek. A novel mitochondrial outer membrane protein, moma-1, that affects cristae morphology in caenorhabditis elegans. Molecular Biology of the Cell, 22:831-841, Mar 2011. URL: https://doi.org/10.1091/mbc.e10-07-0600, doi:10.1091/mbc.e10-07-0600. This article has 95 citations and is from a domain leading peer-reviewed journal.

8. (liu2021mffoligomerizationis pages 7-8): Ao Liu, Frieda Kage, and Henry N. Higgs. Mff oligomerization is required for drp1 activation and synergy with actin filaments during mitochondrial division. Oct 2021. URL: https://doi.org/10.1091/mbc.e21-04-0224, doi:10.1091/mbc.e21-04-0224. This article has 41 citations and is from a domain leading peer-reviewed journal.

9. (liu2021mffoligomerizationis pages 1-2): Ao Liu, Frieda Kage, and Henry N. Higgs. Mff oligomerization is required for drp1 activation and synergy with actin filaments during mitochondrial division. Oct 2021. URL: https://doi.org/10.1091/mbc.e21-04-0224, doi:10.1091/mbc.e21-04-0224. This article has 41 citations and is from a domain leading peer-reviewed journal.

10. (liu2021mffoligomerizationis pages 6-7): Ao Liu, Frieda Kage, and Henry N. Higgs. Mff oligomerization is required for drp1 activation and synergy with actin filaments during mitochondrial division. Oct 2021. URL: https://doi.org/10.1091/mbc.e21-04-0224, doi:10.1091/mbc.e21-04-0224. This article has 41 citations and is from a domain leading peer-reviewed journal.

11. (lu2011amolecularswitch pages 6-7): Yun Lu, Stéphane G. Rolland, and Barbara Conradt. A molecular switch that governs mitochondrial fusion and fission mediated by the bcl2-like protein ced-9 of caenorhabditis elegans. Proceedings of the National Academy of Sciences, 108:E813-E822, Sep 2011. URL: https://doi.org/10.1073/pnas.1103218108, doi:10.1073/pnas.1103218108. This article has 48 citations and is from a highest quality peer-reviewed journal.

12. (lu2011amolecularswitch pages 4-6): Yun Lu, Stéphane G. Rolland, and Barbara Conradt. A molecular switch that governs mitochondrial fusion and fission mediated by the bcl2-like protein ced-9 of caenorhabditis elegans. Proceedings of the National Academy of Sciences, 108:E813-E822, Sep 2011. URL: https://doi.org/10.1073/pnas.1103218108, doi:10.1073/pnas.1103218108. This article has 48 citations and is from a highest quality peer-reviewed journal.

13. (carmichael2022fissionimpossible(?)—new pages 9-10): Ruth E. Carmichael, Markus Islinger, and Michael Schrader. Fission impossible (?)—new insights into disorders of peroxisome dynamics. Cells, 11:1922, Jun 2022. URL: https://doi.org/10.3390/cells11121922, doi:10.3390/cells11121922. This article has 28 citations.

14. (hanada2021mavsisenergized pages 9-10): Yuki Hanada, Naotada Ishihara, Lixiang Wang, Hidenori Otera, Takaya Ishihara, Takumi Koshiba, Katsuyoshi Mihara, Yoshihiro Ogawa, and Masatoshi Nomura. Mavs is energized by mff which senses mitochondrial metabolism via ampk for acute antiviral immunity. Nature Communications, Nov 2020. URL: https://doi.org/10.1038/s41467-020-19287-7, doi:10.1038/s41467-020-19287-7. This article has 79 citations and is from a highest quality peer-reviewed journal.

15. (hanada2021mavsisenergized pages 7-8): Yuki Hanada, Naotada Ishihara, Lixiang Wang, Hidenori Otera, Takaya Ishihara, Takumi Koshiba, Katsuyoshi Mihara, Yoshihiro Ogawa, and Masatoshi Nomura. Mavs is energized by mff which senses mitochondrial metabolism via ampk for acute antiviral immunity. Nature Communications, Nov 2020. URL: https://doi.org/10.1038/s41467-020-19287-7, doi:10.1038/s41467-020-19287-7. This article has 79 citations and is from a highest quality peer-reviewed journal.

16. (tabara2025molecularmechanismsof pages 9-10): Luis-Carlos Tábara, Mayuko Segawa, and Julien Prudent. Molecular mechanisms of mitochondrial dynamics. Nature reviews. Molecular cell biology, 26:123-146, Oct 2025. URL: https://doi.org/10.1038/s41580-024-00785-1, doi:10.1038/s41580-024-00785-1. This article has 390 citations.

17. (hanada2021mavsisenergized pages 1-2): Yuki Hanada, Naotada Ishihara, Lixiang Wang, Hidenori Otera, Takaya Ishihara, Takumi Koshiba, Katsuyoshi Mihara, Yoshihiro Ogawa, and Masatoshi Nomura. Mavs is energized by mff which senses mitochondrial metabolism via ampk for acute antiviral immunity. Nature Communications, Nov 2020. URL: https://doi.org/10.1038/s41467-020-19287-7, doi:10.1038/s41467-020-19287-7. This article has 79 citations and is from a highest quality peer-reviewed journal.

18. (carmichael2022fissionimpossible(?)—new pages 22-23): Ruth E. Carmichael, Markus Islinger, and Michael Schrader. Fission impossible (?)—new insights into disorders of peroxisome dynamics. Cells, 11:1922, Jun 2022. URL: https://doi.org/10.3390/cells11121922, doi:10.3390/cells11121922. This article has 28 citations.

19. (carmichael2022fissionimpossible(?)—new pages 21-22): Ruth E. Carmichael, Markus Islinger, and Michael Schrader. Fission impossible (?)—new insights into disorders of peroxisome dynamics. Cells, 11:1922, Jun 2022. URL: https://doi.org/10.3390/cells11121922, doi:10.3390/cells11121922. This article has 28 citations.

20. (OpenTargets Search: -MFF): Open Targets Query (-MFF, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

21. (carmichael2022fissionimpossible(?)—new pages 10-12): Ruth E. Carmichael, Markus Islinger, and Michael Schrader. Fission impossible (?)—new insights into disorders of peroxisome dynamics. Cells, 11:1922, Jun 2022. URL: https://doi.org/10.3390/cells11121922, doi:10.3390/cells11121922. This article has 28 citations.

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Citations

1. lu2011amolecularswitch pages 7-8
2. singh2023mechanisticanalysisof pages 28-32
3. yu2020regulationofmammalian pages 6-7
4. qin2020anendoplasmicreticulum pages 5-7
5. head2011anovelmitochondrial pages 5-6
6. otera2011discoveryofthe pages 1-3
7. tabara2025molecularmechanismsof pages 9-10
8. singh2023mechanisticanalysisof pages 32-35
9. liu2021mffoligomerizationis pages 7-8
10. liu2021mffoligomerizationis pages 1-2
11. liu2021mffoligomerizationis pages 6-7
12. lu2011amolecularswitch pages 6-7
13. lu2011amolecularswitch pages 4-6
14. hanada2021mavsisenergized pages 9-10
15. hanada2021mavsisenergized pages 7-8
16. hanada2021mavsisenergized pages 1-2
17. https://doi.org/10.1073/pnas.1103218108,
18. https://doi.org/10.26181/21844440.v1,
19. https://doi.org/10.3389/fendo.2020.00374,
20. https://doi.org/10.4161/sgtp.2.3.16486,
21. https://doi.org/10.1016/j.celrep.2020.108363,
22. https://doi.org/10.1091/mbc.e10-07-0600,
23. https://doi.org/10.1091/mbc.e21-04-0224,
24. https://doi.org/10.3390/cells11121922,
25. https://doi.org/10.1038/s41467-020-19287-7,
26. https://doi.org/10.1038/s41580-024-00785-1,