Ptpcd-1 is a novel cell cycle related phosphatase that regulates centriole duplication and cytokinesis Doaa H. Zineldeen, Midori Shimada, Hiroyuki Niida, Yuko Katsuno, Makoto Nakanishi * Department of Cell Biology and Biochemistry, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan article info Article history: Received 6 January 2009 Available online 24 January 2009 Keywords: Centrosome Phosphatase Mitosis Polo-like kinases Cytokinesis Cdc14 abstract Proper progression of mitosis requires spatio-temporal regulation of protein phosphorylation by orches- trated activities of kinases and phosphatases. Although many kinases, such as Aurora kinases, polo-like kinases (Plks), and cyclin B-Cdk1 are relatively well characterized in the context of their physiological functions at mitosis and regulation of their enzymatic activities during mitotic progression, phosphatases involved are largely unknown. Here we identified a novel protein tyrosine phosphatase containing domain 1 (Ptpcd 1) as a mitotic phosphatase, which shares sequence homology to Cdc14. Immunofluo- rescence studies revealed that Ptpcd1 partially colocalized with c-tubulin, an archetypical centrosomal marker. Overexpression of this phosphatase prevented unscheduled centrosomal amplification in hydroxyurea arrested U2OS cells. Intriguingly, Ptpcd 1-associated and colocalized with polo-like kinase 1(Plk1). Hence, overexpression of Ptpcd1 rescued prometaphase arrest of Plk-1 depleted cells, but resulted in aberrant cytokinesis as did as Plk1 overexpression. These results suggested that Ptpcd1 is involved in centrosomal duplication and cytokinesis. Ó 2009 Elsevier Inc. All rights reserved. Faithful transmission of genetic information relies on the coordi- nated regulatory system of the cell cycle [1]. In higher eukaryotes, mitosis involves many dynamic processes at chromosomes, includ- ing condensation and segregation, both of which are mainly regu- lated by protein phosphorylation and dephosphorylation [2]. Proper segregation of chromosomes requires centrosomal matura- tion, separation, spindle formation and alignment of chromosomes [2,3]. Centrosome is the major microtubule organizing center in ani- mal cells composed of two centrioles, which are barrel shaped struc- tures with nine triple microtubules and a pericentriolar matrix responsible for nucleating microtubules and organizing mitotic spindles for bipolar separation of sister chromatids [4,5]. The identi- fication of several centrosome-associated protein kinases has pro- posed the concept that multiple regulatory phosphorylation pathways tightly control centrosome cycle during cell cycle [6–8]. Around G1/S transition, a procentriole forms adjacent to each paren- tal centriole and continues growing during S phase. At the onset of mitosis, the two centrosomes separate and the daughter centriole matures and instructs mitotic spindle formation [4]. In post-mitotic cells, centrosome migrates to the cell surface and one of the centri- oles differentiates into a basal body that nucleates microtubules to form a cilium [5]. Polo-like kinases (Plks) regulate a multitude of several mitotic processes, including centrosome duplication, maturation [9], bipo- lar spindle formation [10], microtubule/kinetochore interactions, and cytokinesis [11,12]. Spatio-temporal coordination of Plks activities is achieved through binding to phosphorylated docking proteins with distinct subcellular localizations, such as centro- somes, kinetochore, and the midzone [12,13]. At early mitosis, Cdk1 creates the phosphorylated docking sites on the substrates [1], whereas Plks create their own docking sites on other partners after inactivation of Cdk1 [1,12,13]. In budding yeast, some parts of mitotic function of Plks appear to be mediated by Cdc14p. Cells lacking Cdc14p are unable to exit from mitosis, with defects in both movement of chromosomes to the spindle poles and elonga- tion of anaphase spindles [14]. Mammalian cells possess two Cdc14 paralogue, Cdc14A and Cdc14B, identified based on their se- quence similarity to Cdc14p [15]. Recent studies suggested that Cdc14A and Cdc14B might be involved in distinctive cellular func- tions; the former functioned in centrosomal separation and cytoki- nesis [3,16], and the latter in centrosomal duplication and microtubule stabilization [17]. However, Cdc14B deficient cells were viable and lacked apparent defects in chromosome segrega- tion and cytokinesis [18], suggesting that alternative phospha- tase(s) might be capable of complementing the mitotic functions of Cdc14B. Here, we identified Ptpcd1 as a possible functional iso- zyme of mammalian Cdc14B that is genetically linked to Plk1. Materials and methods Cloning of Ptpcd1. The complete ORF of Ptpcd1 (corresponding exactly to AW456874; No. NM 207232 and MGI: 2145430) was 0006-291X/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2009.01.113 * Corresponding author. Fax: +81 52 842 3955. E-mail address: mkt-naka@med.nagoya-cu.ac.jp (M. Nakanishi). Biochemical and Biophysical Research Communications 380 (2009) 460–466 Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc