FIGURE 1.

Mitochondrial fission and fusion maintain a dynamic equilibrium via a series of molecules. The GTPase DRP1 located in the cytoplasm plays a dominant role in mitochondrial fission. The DRP1 receptor proteins FIS1, MFF, and MID49/51 are all distributed in the outer mitochondrial membrane. These receptor proteins can recruit DRP1 to the outer membrane to form a helical structure that hydrolyzes GTP, induces mitochondrial constriction and severing, and promotes mitochondrial fission. OPA1, MFN1, and MFN2 are three types of GTPases that govern mitochondrial fusion. MFN1 and MFN2 are localized in the outer mitochondrial membrane and form homologous or heterologous complexes that mediate mitochondrial coupling. OPA1 is involved in inner mitochondrial membrane fusion and the connection of cristae remodeling, and OPA1 mediates inner membrane fusion in turn after outer membrane fusion.