Dynactin Targets Pavarotti-KLP to the Central Spindle during Anaphase and Facilitates Cytokinesis in Drosophila S2 Cells

JCS 119:4431 (2006)
Regis Giet @ Universite de Rennes, France

One big problem for cytokinesis study is usually its player also participate earlier mitosis steps. Here is another example. Author used siRNA knocking down p150-Glued, a component of dynactin complex, in Drosophila S2 cells. They found that defects appeared in both mitosis and cytokinesis. Authors concluded that p150-Glued is required for the localized redistribution of the centromeric and/or kinetochore proteins MEI-S332 (homologue of mammalian Shogusin), BubR1, and Aurora B for chromatid disjunction and subsequent segregation. For the cytokinesis, p150-Glued is needed for efficient recruitment of Aurora B, Polo kinase and Pavarotti-KLP (homologue of mammalian MKLP1) to central spindle.

I want to focus on the cytokinesis part since that is what I am studying right now. Authors said p150-Glued enhances but is not essential for recruitment of Aurora B, Polo kinase, and Pavarotti-KLP is because they eventually appeared at the central spindle / MT plus-end at later cytokinesis stages. I am conserved on this conclusion. Those experiments were done by using siRNA. I ever used PRC1 siRNA in my systems. I got the result midzone-like structure is no longer properly aligned or bundled, a typical PRC1 depleted phenotype. But it is very difficult to really get rid ALL the target proteins by siRNA. For proteins like PRC1 which intends to concentrate at the MT plus end, you can always see some dim signal on plus-end since it is concentrated.

Several interesting phenotypes have been found in this paper. One of them is Glued RNAi cells lack stable microtubule bundles. Obviously It can be a secondary effect from Aurora B, Polo kinase, and/or Pavarotti-KLP. But it at least suggests possible players involved in the midzone stabilization which I very much interested recently.