title: Stabilization of anaphase midzone microtubules is regulated by Rho during cytokinesis in human fibrosarcoma cells.
abstract: The dynamics of astral and midzone microtubules (MTs) must be separately regulated during cell division, but the mechanism of selective stabilization of midzone MTs is poorly understood. Here we show that, in HT1080 cells, activation of Rho is required to stabilize midzone MTs, and to maintain the midzone structures after anaphase onset or during cytokinesis. Ect2-depleted cells undergoing conventional cytokinesis (cytokinesis A) or contractile ring-independent cytokinesis (cytokinesis B) formed abnormally thin bundles of midzone MTs. C3-loaded mitotic cells with inactivated Rho showed similar but more severe disorganization of midzone MTs. In addition, the bundles of astral MTs were abnormally abundant along the cell periphery in both Ect2-depleted and C3-loaded mitotic cells. Mitotic kinesin-like protein 1 (MKLP1), a component of the spindle midzone required for bundling of MTs, was localized only in the narrower equatorial regions in Ect2-depleted cells, and disappeared from the midzone accompanying the progression of the mitotic phase in C3-loaded cells. Stabilization of MTs by taxol was sufficient to maintain the midzone structures in C3-loaded mitotic cells. These results, when combined with a preceding analysis on another, microtubule-associated Rho GEF (C.J. Bakal, D. Finan, J. LaRose, C.D. Wells, G. Gish, S. Kulkarni, P. DeSepulveda, A. Wilde, R. Rottapel, The Rho GTP exchange factor Lfc promotes spindle assembly in early mitosis, Proc. Natl. Acad. Sci. U. S. A. 102 (2005) 9529-9534), suggest that mammalian cells have two potential steps that require active Rho for the stabilization of midzone MTs during mitosis and cytokinesis.
authors: Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.
authors: Masamitsu
authors: M
authors: Kanada
authors: Akira
authors: A
authors: Nagasaki
authors: Taro Q P
authors: TQ
authors: Uyeda
mesh_terms: D000705:Anaphase / Q000502:physiology*; D000818:Animals; D045744:Cell Line, Tumor; D048749:Cytokinesis / Q000502:physiology*; D004789:Enzyme Activation; D005354:Fibrosarcoma / Q000378:metabolism / Q000473:pathology; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D008941:Spindle Apparatus / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C489850:ECT2 protein, human; D006576:Heterocyclic Compounds, 4 or More Rings; C092935:KIF23 protein, human; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D050257:Tubulin Modulators; C472645:blebbistatin; D020741:rho GTP-Binding Proteins; D017239:Paclitaxel; D015739:Nocodazole