Mitochondrial fission
Mitochondrial fission is the process where
Mechanism
FtsZ Localization
The
Drp1
The
The mitochondria forms a contact site with the endoplasmic reticulum (ER), and the ER in turn associates with the mitochondria to form preconstriction sites which are necessary but insufficient for mitochondrial fission to take place. Inverted formin 2 (INF2), a protein localized on the ER, and with the help of SPIRE1C localized on the mitochondria,[10] causes actin to polymerize where bundles of actin diagonally cross each other and recruit myosin II, which assists in localizing Drp1 onto mitochondria.[11] Actin bundles are reservoirs of Drp1 proteins and their polymerization helps enable provide a pool of Drp1 proteins to assemble onto the mitochondria. Actin polymerzation also helps trigger a calcium ion influx from the ER and into the mitochondria, which results in the dephosphorylation of the Ser637 residue on Drp1 and then a scission that cleaves the inner mitochondrial membrane will. Drp1 most commonly forms rings of 16 monomers around the mitochondrial membrane, and this in turn deeply constricts the membrane. Several 16-unit Drp1 rings can assemble and form helical structures that tubulate the mitochondrial membrane.[12] Nearby rings of Drp1 will experience interactions between their G domains (or G-G interactions). G-G interactions reposition catalytic sites to cause GTP hydrolysis, and GTP hydrolysis leads to conformational changes that further assist in the final separation at the constriction site to produce two different mitochondria. The exact process by which the final separation takes place is not yet fully understood.[5]
Role of other organelles
PI(4)P needs to be delivered to the mitochondrial membrane and is necessary for fission to proceed. One mode of delivery of PI(4)P to the mitochondria-ER contact sites is from the Golgi apparatus. Golgi contain ARF1 proteins localized on their membranes, which are capable of recruiting kinases that trigger the synthesis of PI(4)P. PI(4)P is then delivered through a vesicle to mitochondria-ER contact sites.[13] Lysosomes are also often involved in but not necessary for mitochondrial fission. Contact between mitochondria and lysosomes are possible because the Rab7 protein can both form associates with lysosomes and a protein embedded on the outer mitochondrial membrane called TBC1D15. Before fission proceeds, Rab7 will dissociate from lysosomes by hydrolyzing GTP. Contact between the ER and lysosomes also takes place and these contacts also depend on Rab7. A subset of these contacts is also mediated by oxysterol binding protein related protein 1L (ORP1L). ORP1L forms associations with lysosomes via Rab7 and also forms associations with ER via VAMP-associated proteins (VAPs). Overall, this allows for three-way contact between the mitochondria, ER, and lysosomes. The ER recruits lysosomes only after Drp1 has already been recruited (whereas Drp1 itself is recruited after the preconstriction takes place). ORP1L is also required in the transfer of PI(4)P from lysosomes to the mitochondria. PI(4)P is therefore delivered to the mitochondria from both Golgi and lysosomes, and it is possible (though not currently known) that the two organelles provide PI(4)P for different purposes during fission or at different steps in the process, or whether they contribute PI(4)P for entirely distinct forms of mitochondrial fission.[14]
Peripheral and Midzone Division
Recent findings suggest that mitochondria undergo two different mechanisms of fission. In an elongated mitochondrial network, mitochondria are capable of dividing near the center (at the midzone) or towards one of the two ends (or the periphery). Midzone division and peripheral division in mitochondrial networks appears to be involved in two different cellular activities. Midzone division is promoted by biogenesis, when the cell is proliferating and more mitochondria are needed. Peripheral division results in the removal of damaged mitochondrial units from the network formed at the periphery, these mitochondria being destined for autophagy (or mitophagy), destined for destruction. Peripheral division appears to be preceded by elevated concentrations of reactive oxygen species and reduced membrane potential and pH. These two types of fission appear to be regulated by different molecular mechanisms. The adaptor protein FIS1 appears to be the involved adaptor protein recruiting Drp1 in peripheral division, whereas the adaptor MFF seems to be the involved adaptor protein recruiting Drp1 during midzone division. On the other hand, MiD49 and MiD51 appear to both be involved in both forms of division. Furthermore, the lysosomal contact sites with mitochondria only appear during peripheral division.[15]
See also
- Mitochondrial fusion
- Binary fission
References
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- ^ Otera, Hidenori, and Katsuyoshi Mihara. "Discovery of the membrane receptor for mitochondrial fission GTPase Drp1." Small GTPases 2.3 (2011): 241-251.
- PMID 22934639.
- ^ a b c d Kraus, Felix, et al. "Function and regulation of the divisome for mitochondrial fission." Nature 590.7844 (2021): 57-66.
- ^ Huang, Pinwei, Chad A. Galloway, and Yisang Yoon. "Control of mitochondrial morphology through differential interactions of mitochondrial fusion and fission proteins." PLOS ONE 6.5 (2011): e20655.
- ^ Dikov, Daniel, and Andreas S. Reichert. "How to split up: lessons from mitochondria." The EMBO journal 30.14 (2011): 2751-2753.
- ^ Otera, Hidenori, et al. "Mff is an essential factor for mitochondrial recruitment of Drp1 during mitochondrial fission in mammalian cells." Journal of Cell Biology 191.6 (2010): 1141-1158.
- ^ Zhao, Jian, et al. "Human MIEF1 recruits Drp1 to mitochondrial outer membranes and promotes mitochondrial fusion rather than fission." The EMBO journal 30.14 (2011): 2762-2778.
- ^ Manor, U., Bartholomew, S., Golani, G., Christenson, E., Kozlov, M., Higgs, H., Spudich, J., Lippincott-Schwartz, J. A mitochondria-anchored isoform of the actin-nucleating spire protein regulates mitochondrial division. (2015) Elife. 4. DOI: 10.7554/eLife.08828
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- ^ Basu, Kaustuv, et al. "Molecular mechanism of DRP1 assembly studied in vitro by cryo-electron microscopy." PLOS ONE 12.6 (2017): e0179397.
- ^ Nagashima, S., Tábara, L. C., Tilokani, L., Paupe, V., Anand, H., Pogson, J. H., Zunino, R., McBride, H. M., & Prudent, J. (2020). Golgi-derived PI(4)P-containing vesicles drive late steps of mitochondrial division. Science, 367(6484), 1366–1371. https://doi.org/10.1126/science.aax6089
- ^ Boutry, Maxime, and Peter K. Kim. "ORP1L mediated PI (4) P signaling at ER-lysosome-mitochondrion three-way contact contributes to mitochondrial division." Nature communications 12.1 (2021): 1-18.
- ^ Kleele, T., Rey, T., Winter, J., Zaganelli, S., Mahecic, D., Lambert, H. P., ... & Manley, S. (2021). Distinct fission signatures predict mitochondrial degradation or biogenesis. Nature, 593(7859), 435-439.