Mitochondria form networks. Formation of mitochondrial networks is important for maintaining mitochondrial DNA integrity and interchangingmitochondrial material, whereas disruption of the mitochondrialnetwork affects mitochondrial functions. According to the current view,mitochondrial networks are formed by fusion of individual mitochondria. Here, we report a new mechanism for formation of mitochondrial networks through KIF5B-mediated dynamictubulation of mitochondria. We found that KIF5B pulls thin, highly dynamic tubules out of mitochondria. Fusion of these dynamic tubules, which is mediated by mitofusins, gives rise to the mitochondrialnetwork. We further demonstrated that dynamictubulation and fusion is sufficient for mitochondrialnetworkformation, by reconstituting mitochondrial networks in vitro using purified fusion-competent mitochondria, recombinant KIF5B, and polymerized microtubules. Interestingly, KIF5B only controls networkformation in the peripheral zone of the cell, indicating that the mitochondrialnetwork is divided into subzones, which may be constructed by different mechanisms. Our data not only uncover an essential mechanism for mitochondrialnetworkformation, but also reveal that different parts of the mitochondrialnetwork are formed by different mechanisms.
Wang C, Du W, Su QP, Zhu M, Feng P, Li Y, Zhou Y, Mi N, Zhu Y, Jiang D, Zhang S, Zhang Z, Sun Y*, Yu L*. (2015) Dynamic tubulation of mitochondria drives mitochondrial network formation. Cell Research, 25(10):1108-1120.