Abstract - Lurz
Severing of reconstituted membrane tethers by single dynamin-related protein 1 complexes is MFF-dependent
Mitochondrial dynamics, including fission, fusion, and mitophagy, are crucial for cellular homeostasis. Dysfunctional fission is implicated in neurodegenerative and cardiovascular diseases. In mammals, Dynamin-related protein 1 (DRP1) drives fission by oligomerizing and constricting the mitochondrial outer membrane (MOM) in a GTP-dependent manner. DRP1, eventually assisted by the cytosolic dynamin Dyn2, severs the membrane completing the fission process. At mitochondrial preconstrictions, DRP1 is recruited to mitochondria by Fis1, MiD49, MiD51 and mitochondrial fission factor (MFF). Although removal of Fis1 or MiD49/51 reduces fission rates, removal of MFF has the most severe effect in mammalian systems.
Due to a complex regulation of the rare fission process and many redundancies regarding recruiters and effector proteins, in vivo studies remain challenging.
To resolve this, we reconstitute mitochondrial fission using purified proteins and defined membrane compositions in a fluorescence microscopy-based assay. Avoiding DRP1-tagging artifacts by utilizing a fluorescent DRP1-specific nanobody, we show that DRP1 alone is not sufficient to sever our membrane system; however, MFF tethering facilitates scission, with single, stable DRP1 complexes driving the process. We further explore the role of longer, potentially less active DRP1 and MFF isoforms found in the brain.