Mitochondria continually change shape through the combined actions of fission, fusion, and movement along cytoskeletal tracks. The lengths of mitochondria and the degree to which they form closed networks are determined by the balance between fission and fusion rates. These rates are influenced by metabolic and pathogenic conditions inside mitochondria and by their cellular environment. Fission and fusion are important for growth, for mitochondrial redistribution, and for maintenance of a healthy mitochondrial network. In addition, mitochondrial fission and fusion play prominent roles in disease-related processes such as apoptosis and mitophagy. Three members of the Dynamin family are key components of the fission and fusion machineries. Their functions are controlled by different sets of adaptor proteins on the surface of mitochondria and by a range of regulatory processes. Here, we review what is known about these proteins and the processes that regulate their actions.
The mitochondrial fission protein Drp1 binds to Mff on mitochondria, followed by entry into a complex with Fis1 at the ER–mitochondrial interface. Mutations in Fis1 disrupt disposal of defective mitochondria when fission is induced by stress. Fis1 thus acts in sequence with Mff to couple mitochondrial fission with downstream degradation processes.
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