Murine embryonic fibroblasts lacking TC-PTP display delayed G1 phase through defective NF-kappaB activation.
Previous results suggested a potential role for T-cell protein tyrosine phosphatase (TC-PTP) in cell proliferation. However, no conclusive data has supported such a function in the modulation of this process. In order to clarify this issue, we isolated TC-PTP-/- murine embryonic fibroblasts (MEFs) as well as cell lines to characterize the role of TC-PTP in the control of cell proliferation and cell cycle. Both TC-PTP-/- primary MEFs and cell lines proliferate slower than TC-PTP+/+ cells. We also demonstrated that TC-PTP-/- cells have a slow progression through the G1 phase of the cell cycle. Further characterization of the G1 defect indicates that the kinetics of cyclin D1 induction was delayed and that p27(KIP1) remains at higher levels for an extended period of time. Moreover, cells lacking TC-PTP showed a delayed activation of CDK2. This slow progression through the early G1-phase resulted in decreased phosphorylation of the RB protein and subsequent delay into the S phase transition. In contrast, no further defects were detected in other phases of the cell cycle. Survey of the potential signaling pathways leading to this delayed cyclin D1 expression indicated that NF-kappaB activation was compromised and that IKKbeta activity was also reduced following PDGF stimulation. Reintroduction of wild-type TC-PTP into the TC-PTP-/- cells rescued the defective proliferation, cyclin D1 expression, NF-kappaB activation as well as IkappaB phosphorylation. Together, these results confirm that TC-PTP plays a positive role in the progression of early G1 phase of the cell cycle through the NF-kappaB pathway.
Ibarra-Sánchez
M J
MJ
McGill Cancer Centre and Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6.
Wagner
J
J
Ong
M T
MT
Lampron
C
C
Tremblay
M L
ML
D000818:Animals; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology*; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D016193:G1 Phase; D017353:Gene Deletion; D051550:I-kappa B Kinase; D007700:Kinetics; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein / Q000378:metabolism; D025521:Tumor Suppressor Proteins
C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D016328:NF-kappa B; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D019950:Mitogen-Activated Protein Kinase 1; D054578:Protein Tyrosine Phosphatase, Non-Receptor Type 2; D017027:Protein Tyrosine Phosphatases; C516653:Ptpn2 protein, mouse