Distinct molecular signatures of fission predict mitochondrial degradation or proliferation

Tatjana Kleele (1) , Timo Rey (1) , Julius Winter (1) , Sofia Zaganelli (1) , Dora Mahecic (1) , Hélène Perreten Lambert (1) , Francesco Ruberto (2) , Mohamed Nemir (2) , Timothy Wai (3) , Thierry Pedrazzini (2) , Suliana Manley (1)

1 EPFL - Ecole Polytechnique Fédérale de Lausanne
2 Experimental Cardiology Unit
3 G5 Biologie mitochondriale – Mitochondrial biology

Mitochondrial fission is a highly regulated process which, when disrupted, can alter metabolism, proliferation and apoptosis 1–3 . The downstream effects have implications for many diseases, from neurodegeneration 4–6 to cardiovascular disease 7,8 and cancer 9,10 . Key components of the fission machinery have been identified: constriction sites are initiated by the endoplasmic reticulum (ER) 11 and actin 12 before dynamin-related protein 1 (Drp1) 13 is recruited to the outer mitochondrial membrane via adaptor proteins 14–17 , where it drives constriction and scission of the membrane 18 . In the life cycle of mitochondria, fission is important for the biogenesis of new mitochondria as well as the clearance of dysfunctional mitochondria via mitophagy 3,19 . Global regulation of fission on the cellular level is insufficient to explain how fate decisions are made at the single organelle level, so it is unknown how those dual functions arise, blocking progress in developing therapies that target mitochondrial activity. However, systematically studying mitochondrial division to uncover fate determinants is challenging, since fission is unpredictable, and mitochondrial morphology is extremely heterogeneous. Furthermore, because their ultrastructure lies below the diffraction limit, the dynamic organization of mitochondria and their interaction partners are hard to study at the single organelle level. We used live-cell structured illumination microscopy (SIM) and instant SIM 20 for fast multi-colour acquisition of mitochondrial dynamics in Cos-7 cells and mouse cardiomyocytes. We analysed hundreds of fission events, and discovered two functionally and mechanistically distinct types of fission. Mitochondria divide peripherally to shed damaged material into smaller daughter mitochondria that subsequently undergo mitophagy, whereas healthy mitochondria proliferate via midzone division. Both types are Drp1-mediated, but they rely on different membrane adaptors to recruit Drp1, and ER and actin mediated pre-constriction is only involved in midzone fission.

Domaines: Santé publique et épidémiologie

Tatjana Kleele, Timo Rey, Julius Winter, Sofia Zaganelli, Dora Mahecic, et al.. Distinct molecular signatures of fission predict mitochondrial degradation or proliferation. 2021. ⟨pasteur-03101257⟩