title: Interaction between ROCK II and nucleophosmin/B23 in the regulation of centrosome duplication.
abstract: Nucleophosmin (NPM)/B23 has been implicated in the regulation of centrosome duplication. NPM/B23 localizes between two centrioles in the unduplicated centrosome. Upon phosphorylation on Thr(199) by cyclin-dependent kinase 2 (CDK2)/cyclin E, the majority of centrosomal NPM/B23 dissociates from centrosomes, but some NPM/B23 phosphorylated on Thr(199) remains at centrosomes. It has been shown that Thr(199) phosphorylation of NPM/B23 is critical for the physical separation of the paired centrioles, an initial event of the centrosome duplication process. Here, we identified ROCK II kinase, an effector of Rho small GTPase, as a protein that localizes to centrosomes and physically interacts with NPM/B23. Expression of the constitutively active form of ROCK II promotes centrosome duplication, while down-regulation of ROCK II expression results in the suppression of centrosome duplication, especially delaying the initiation of centrosome duplication during the cell cycle. Moreover, ROCK II regulates centrosome duplication in its kinase and centrosome localization activity-dependent manner. We further found that ROCK II kinase activity is significantly enhanced by binding to NPM/B23 and that NPM/B23 acquires a higher binding affinity to ROCK II upon phosphorylation on Thr(199). Moreover, physical interaction between ROCK II and NPM/B23 in vivo occurs in association with CDK2/cyclin E activation and the emergence of Thr(199)-phosphorylated NPM/B23. All these findings point to ROCK II as the effector of the CDK2/cyclin E-NPM/B23 pathway in the regulation of centrosome duplication.
authors.affiliation: Department of Cell Biology, University of Cincinnati College of Medicine, 3125 Eden Avenue, Cincinnati, OH 45267-0521, USA.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Ma
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kanai
authors.forename: Kenji
authors.initials: K
authors.lastname: Kawamura
authors.forename: Kozo
authors.initials: K
authors.lastname: Kaibuchi
authors.forename: Keqiang
authors.initials: K
authors.lastname: Ye
authors.forename: Kenji
authors.initials: K
authors.lastname: Fukasawa
mesh_terms: D000818:Animals; D018385:Centrosome / Q000502:physiology*; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000502:physiology; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D000090243:Nucleophosmin; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012867:Skin / Q000166:cytology; D013912:Threonine / Q000378:metabolism; D014162:Transfection; D054460:rho-Associated Kinases
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D000090243:Nucleophosmin; D049452:Green Fluorescent Proteins; D013912:Threonine; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2