Friday, 21 August 2015

Mitotic redistribution of the mitochondrial network by Miro and Cenp-F

Kanfer G, Courthéoux T, Peterka M, Meier S, Soste M, Melnik A, Reis K, Aspenström P, Peter M, Picotti P, Kornmann B

If a cell divides, how do its mitochondria get segregated into the two daughter cells?  In general, mitochondria often move along microtubules with the help of molecular motors. Specialized adaptors on the mitochondrial outer membrane  recruit these motors, one of them being the GTPase Miro. But how exactly the segregation of mitochondria during mitosis is coordinated, is not well understood.

In this paper, they identify centromeric protein F (Cenp-F) which interacts with Miro. Cenp-F is a large protein that binds to the microtubules. It was found to be strongly recruited to mitochondria at the end of mitosis.  During S/G2, a fraction of Cenp-F is found on mitochondria, located mainly at the mitochondrial tips projecting away from the cell centre. The mitochondrial Cenp-F puncta that were visible in the S/G2 phase were all colocalized with microtubules.

They further find that Cenp-F directly interacts with the GTPase domains of both Miro1 and Miro2, leading to its recruitment to mitochondria. In wildtype cells, during cytokinesis mitochondria were parallel and extended away from the division plane, whereas in cells without Miro (or Cenp-F) the mitochondria were all clustered together around the nucleus.
The conclusion was that Cenp-F, recruiting by Miro, connects mitochondria to the tips of growing microtubules. The mitochondria then track the tips of the microtubules. Mitochondria were also seen to influence local microtubule dynamics, it can be that dragging forces caused by the attached mitochondria play a role in this.

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