title: Dissecting the role of Rho-mediated signaling in contractile ring formation.
abstract: In anaphase, microtubules provide a specification signal for positioning of the contractile ring. However, the nature of the signal remains unknown. The small GTPase Rho is a potent regulator of cytokinesis, but the involvement of Rho in contractile ring formation is disputed. Here, we show that Rho serves as a microtubule-dependent signal that specifies the position of the contractile ring. We found that Rho translocates to the equatorial region before furrow ingression. The Rho-specific inhibitor C3 exoenzyme and small interfering RNA to the Rho GDP/GTP exchange factor ECT2 prevent this translocation and disrupt contractile ring formation, indicating that active Rho is required for contractile ring formation. ECT2 forms a complex with the GTPase-activating protein MgcRacGAP and the kinesinlike protein MKLP1 at the central spindle, and the localization of ECT2 at the central spindle depends on MgcRacGAP and MKLP1. In addition, we show that the bundled microtubules direct Rho-mediated signaling molecules to the furrowing site and regulate furrow formation. Our study provides strong evidence for the requirement of Rho-mediated signaling in contractile ring formation.
authors.affiliation: Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA. kkamijo@ja3.so-net.ne.jp
authors.forename: Keiju
authors.initials: K
authors.lastname: Kamijo
authors.forename: Naoya
authors.initials: N
authors.lastname: Ohara
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Abe
authors.forename: Takashi
authors.initials: T
authors.lastname: Uchimura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoya
authors.forename: Jae-Seon
authors.initials: JS
authors.lastname: Lee
authors.forename: Toru
authors.initials: T
authors.lastname: Miki
mesh_terms: D000199:Actins / Q000378:metabolism; D048749:Cytokinesis; D005786:Gene Expression Regulation / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D034622:RNA Interference; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D008869:Microtubule-Associated Proteins; D009218:Myosins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins