title: The T-cell protein tyrosine phosphatase is phosphorylated on Ser-304 by cyclin-dependent protein kinases in mitosis.
abstract: Two alternatively spliced forms of the human protein tyrosine phosphatase TCPTP (T-cell protein tyrosine phosphatase) exist: a 48 kDa form that is targeted to the endoplasmic reticulum (TC48) and a shorter 45 kDa form that is targeted to the nucleus (TC45). In this study we have identified Ser-304 (Phe301-Asp-His-Ser304-Pro-Asn-Lys307) as a major TCPTP phosphory-lation site and demonstrate that TC45, but not TC48, is phosphorylated on this site in vivo. Phosphorylation of TC45 on Ser-304 was cell cycle-dependent, and increased as cells progressed from G2 into mitosis, but subsided upon mitotic exit. Ser-304 phosphorylation was increased when cells were arrested in mitosis by microtubule poisons such as nocodazole, but remained unaltered when cells were arrested at the G2/M checkpoint by adriamycin. Phosphorylation of Ser-304 did not alter significantly the phosphatase activity or the protein stability of TC45, and had no apparent effect on TC45 localization. Ser-304 phosphorylation was ablated when cells were treated with the CDK (cyclin-dependent protein kinase) inhibitors roscovitine or SU9516, but remained unaltered when ERK1/2 activation was inhibited with the MEK (mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase) inhibitor PD98059. In addition, recombinant CDKs, but not the Polo-like kinase Plk1, phosphorylated Ser-304 in vitro. Our studies identify Ser-304 as a major phosphorylation site in human TCPTP, and the TC45 variant as a novel mitotic CDK substrate.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria 3800, Australia.
authors.forename: Patricia
authors.initials: P
authors.lastname: Bukczynska
authors.forename: Manuela
authors.initials: M
authors.lastname: Klingler-Hoffmann
authors.forename: Kenneth I
authors.initials: KI
authors.lastname: Mitchelhill
authors.forename: Mark H C
authors.initials: MH
authors.lastname: Lam
authors.forename: Melissa
authors.initials: M
authors.lastname: Ciccomancini
authors.forename: Nicholas K
authors.initials: NK
authors.lastname: Tonks
authors.forename: Boris
authors.initials: B
authors.lastname: Sarcevic
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Kemp
authors.forename: Tony
authors.initials: T
authors.lastname: Tiganis
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D019556:COS Cells / Q000201:enzymology; D002453:Cell Cycle / Q000502:physiology; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes; D007668:Kidney / Q000166:cytology / Q000196:embryology / Q000201:enzymology; D008938:Mitosis / Q000502:physiology*; D008970:Molecular Weight; D010766:Phosphorylation; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D014162:Transfection / Q000379:methods
chemical_list: D007527:Isoenzymes; D012694:Serine; D018844:Cyclin-Dependent Kinases; C516649:PTPN2 protein, human; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases