151
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Caldon CE, Daly RJ, Sutherland RL, Musgrove EA. Cell cycle control in breast cancer cells. J Cell Biochem 2006; 97:261-74. [PMID: 16267837 DOI: 10.1002/jcb.20690] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In breast cancer, cyclins D1 and E and the cyclin-dependent kinase inhibitors p21 (Waf1/Cip1)and p27 (Kip1) are important in cell-cycle control and as potential oncogenes or tumor suppressor genes. They are regulated in breast cancer cells following mitogenic stimuli including activation of receptor tyrosine kinases and steroid hormone receptors, and their deregulation frequently impacts on breast cancer outcome, including response to therapy. The cyclin-dependent kinase inhibitor p16 (INK4A) also has a critical role in transformation of mammary epithelial cells. In addition to their roles in cell cycle control, some of these molecules, particularly cyclin D1, have actions that are not mediated through regulation of cyclin-dependent kinase activity but may be important for loss of proliferative control during mammary oncogenesis.
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Affiliation(s)
- C Elizabeth Caldon
- Cancer Research Program, Garvan Institute of Medical Research, St Vincent's Hospital, Sydney, NSW 2010, Australia
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152
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Borriello A, Cucciolla V, Criscuolo M, Indaco S, Oliva A, Giovane A, Bencivenga D, Iolascon A, Zappia V, Della Ragione F. Retinoic acid induces p27Kip1 nuclear accumulation by modulating its phosphorylation. Cancer Res 2006; 66:4240-8. [PMID: 16618747 DOI: 10.1158/0008-5472.can-05-2759] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
All-trans-retinoic acid (ATRA), the most biologically active metabolite of vitamin A, controls cell proliferation, apoptosis, and differentiation depending on the cellular context. These activities point to ATRA as a candidate for cancer therapy. A pivotal effect of the molecule is the modulation of p27Kip1, a cyclin-dependent kinase (CDK) inhibitor (CDKI). Here, we investigate the mechanisms by which ATRA regulates p27Kip1 level in LAN-5, a neuroblastoma cell line. When added to the cells, ATRA causes a rapid nuclear increase of p27Kip1, which clearly precedes growth arrest. The early buildup is not due to impairment of the CDKI degradation, in contrast to previous observations. Particularly, we did not detect the down-regulation of Skp2 and Cks1, two proteins involved in the nuclear ubiquitin-dependent p27Kip1 removal. Moreover, the morphogen does not impair the CDKI nuclear export and does not cause CDK2 relocalization. The characterization of CDKI isoforms by two-dimensional PAGE/immunoblotting showed that ATRA induces an early nuclear up-regulation of monophosphorylated p27Kip1. Immunologic studies established that this isoform corresponds to p27Kip1 phosphorylated on S10. The buildup of phospho(S10)p27Kip1 precedes the CDKI accumulation and increases its half-life. Finally, ATRA-treated nuclear LAN-5 extracts showed an enhanced capability of phosphorylating p27Kip1 on S10, thus explaining the nuclear up-regulation of the isoform. In conclusion, our data suggest a novel mechanism of ATRA antiproliferative activity, in which the morphogen rapidly up-regulates a nuclear kinase activity that phosphorylates p27Kip1 on S10. In turn, this event causes the stabilization of p27Kip1 and its accumulation in the nuclear compartment.
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Affiliation(s)
- Adriana Borriello
- Department of Biochemistry and Biophysics F. Cedrangolo, Second University of Naples, Italy
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153
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van Duijn PW, Trapman J. PI3K/Akt signaling regulates p27(kip1) expression via Skp2 in PC3 and DU145 prostate cancer cells, but is not a major factor in p27(kip1) regulation in LNCaP and PC346 cells. Prostate 2006; 66:749-60. [PMID: 16425184 DOI: 10.1002/pros.20398] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND We compared the involvement of PI3K/PTEN/Akt signaling in the regulation of the cell-cycle regulator p27(kip1) and investigated the mechanism of PI3K/PTEN/Akt modulation of p27(kip1) in the prostate cancer cell lines LNCaP, PC346, PC3, and DU145. METHODS PI3K/PTEN/Akt signaling was manipulated by wortmannin or specific siRNA. The effects on PI3K/Akt downstream effectors and p27(kip1) expression were monitored on RNA and protein levels. RESULTS PI3K/Akt inhibition in LNCaP and PC346 cells hardly affected p27(kip1) expression. As shown in LNCaP cells, p27(kip1) expression inversely correlated with Skp2 expression, but Skp2 was not regulated by Akt. Blocking PI3K/Akt signaling in PC3 cells resulted in decreased Skp2 protein expression and increased p27(kip1). Downregulation of PTEN in DU145 cells also showed PTEN/Akt-dependent regulation of Skp2 and p27(kip1). CONCLUSIONS In PC3 and DU145 cells, Skp2 is the main determinant in the PI3K/Akt-dependent regulation of p27(kip1). In LNCaP and PC346 cells, PI3K/Akt signaling is not a major factor in p27(kip1) regulation.
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Affiliation(s)
- Petra W van Duijn
- Department of Pathology, Josephine Nefkens Institute, Erasmus University Medical Center, Rotterdam, The Netherlands
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154
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Yoshimoto T, Boehm M, Olive M, Crook MF, San H, Langenickel T, Nabel EG. The arginine methyltransferase PRMT2 binds RB and regulates E2F function. Exp Cell Res 2006; 312:2040-53. [PMID: 16616919 DOI: 10.1016/j.yexcr.2006.03.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Revised: 02/25/2006] [Accepted: 03/06/2006] [Indexed: 11/30/2022]
Abstract
The retinoblastoma gene product (RB) is an important regulator of E2F activity. RB recruits a number of proteins, including HDACs, SWI/SNF complex, lysine methyl transferase (SUV39H1) and DNA methyltransferase (DNMT1), all of which negatively regulate E2F activity with RB. Here, we show that RB interacts with PRMT2, a member of the protein arginine methyltransferase family, to regulate E2F activity. PRMT2 directly bound and interacted with RB through its AdoMet binding domain, in contrast to other PRMT proteins, including PRMT1, PRMT3 and PRMT4. In reporter assays, PRMT2 repressed E2F1 transcriptional activity in an RB-dependent manner. PRMT2 formed a ternary complex with E2F1 in the presence of RB. To further explore the role of endogenous PRMT2 in the regulation of E2F activity, the PRMT2 gene was ablated in mice by gene targeting. Compared with PRMT2(+/+) mouse embryonic fibroblasts (MEFs), PRMT2(-/-) MEFs demonstrated increased E2F activity and early S phase entry following release of serum starvation. Vascular injury to PRMT2(-/-) arteries results in a hyperplastic response, consistent with increased G1-S phase progression. Taken together, these findings demonstrate a novel mechanism for the regulation of E2F activity by a member of the protein arginine methyltransferase family.
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Affiliation(s)
- Takanobu Yoshimoto
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, 31 Center Dr., 31/5A48, Bethesda, MD 20892, USA
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155
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Manceau V, Swenson M, Le Caer JP, Sobel A, Kielkopf CL, Maucuer A. Major phosphorylation of SF1 on adjacent Ser-Pro motifs enhances interaction with U2AF65. FEBS J 2006; 273:577-87. [PMID: 16420481 PMCID: PMC1949809 DOI: 10.1111/j.1742-4658.2005.05091.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Protein phosphorylation ensures the accurate and controlled expression of the genome, for instance by regulating the activities of pre-mRNA splicing factors. Here we report that splicing factor 1 (SF1), which is involved in an early step of intronic sequence recognition, is highly phosphorylated in mammalian cells on two serines within an SPSP motif at the junction between its U2AF65 and RNA binding domains. We show that SF1 interacts in vitro with the protein kinase KIS, which possesses a 'U2AF homology motif' (UHM) domain. The UHM domain of KIS is required for KIS and SF1 to interact, and for KIS to efficiently phosphorylate SF1 on the SPSP motif. Importantly, SPSP phosphorylation by KIS increases binding of SF1 to U2AF65, and enhances formation of the ternary SF1-U2AF65-RNA complex. These results further suggest that this phosphorylation event has an important role for the function of SF1, and possibly for the structural rearrangements associated with spliceosome assembly and function.
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Affiliation(s)
- Valérie Manceau
- INSERM U706, Institut du Fer à Moulin, 17, rue du Fer à Moulin, F-75005 Paris, France; UPMC, F-75005 Paris, France
| | - Matthew Swenson
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205,USA
| | - Jean-Pierre Le Caer
- Ecole Polytechnique, Laboratoire de Chimie des Mécanismes Réactionnels, Route de Saclay, F-91128 Palaiseau, France
| | - André Sobel
- INSERM U706, Institut du Fer à Moulin, 17, rue du Fer à Moulin, F-75005 Paris, France; UPMC, F-75005 Paris, France
| | - Clara L. Kielkopf
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205,USA
| | - Alexandre Maucuer
- INSERM U706, Institut du Fer à Moulin, 17, rue du Fer à Moulin, F-75005 Paris, France; UPMC, F-75005 Paris, France
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156
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Schiele TM. Current understanding of coronary in-stent restenosis. Pathophysiology, clinical presentation, diagnostic work-up, and management. ACTA ACUST UNITED AC 2006; 94:772-90. [PMID: 16258781 DOI: 10.1007/s00392-005-0299-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Accepted: 07/18/2005] [Indexed: 12/29/2022]
Abstract
In-stent restenosis is the limiting entity following coronary stent implantation. It is associated with significant morbidity and cost and thus represents a major clinical and economical problem. Worldwide, approximately 250 000 in-stent restenotic lesions per year have to be dealt with. The pathophysiology of instent restenosis is multifactorial and comprises inflammation, smooth muscle cell migration and proliferation and extracellular matrix formation, all mediated by distinct molecular pathways. Instent restenosis has been recognised as very difficult to manage, with a repeat restenosis rate of 50% regardless of the mechanical angioplasty device used. Much more favourable results were reported for the adjunctive irradiation of the in-stent restenotic lesion, with a consistent reduction of the incidence of repeat in-stent restenosis by 50%. Data from the first clinical trials on drug-eluting stents for the treatment of in-stent restenosis have shown very much promise yielding this strategy likely to become the treatment of choice. This review outlines the histological and molecular findings of the pathophysiology, the epidemiology, the predictors and the diagnostic work-up of in-stent restenosis and puts emphasis on the various treatment options for its prevention and therapy.
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Affiliation(s)
- T M Schiele
- Kardiologie, Klinikum der Ludwig-Maximilians-Universität München--Innenstadt, Ziemssenstrasse 1, 80336 München, Germany.
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157
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Wu FY, Wang SE, Sanders ME, Shin I, Rojo F, Baselga J, Arteaga CL. Reduction of Cytosolic p27Kip1Inhibits Cancer Cell Motility, Survival, and Tumorigenicity. Cancer Res 2006; 66:2162-72. [PMID: 16489017 DOI: 10.1158/0008-5472.can-05-3304] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We generated a p27(Kip1) mutant (p27deltaNLS) that localized exclusively in cell cytosol. Expression of p27deltaNLS in MCF7 breast cancer cells down-regulated RhoA and increased motility, survival, and Akt levels without an effect on cell cycle distribution. RNA interference of p27 in U87 glioma cells, which express p27 predominantly in the cytoplasm, inhibited motility and survival. Conversely, knockdown of p27 in COS7 cells, with >95% nuclear p27 expression, accelerated proliferation but had no effect on motility or survival. U87 cells in which p27 had been eliminated by RNA interference exhibited lower Akt levels, shorter Akt turnover, and markedly impaired tumorigenicity in vivo. These xenografts were less invasive and exhibited increased apoptosis compared with p27-expressing tumors. Expression of cytosolic p27 in primary human breast carcinomas correlated linearly with Akt content as measured by immunohistochemistry. These data suggest that cytoplasmic p27 can exert oncogenic functions by modulating Akt stability, cell survival, and tumorigenicity.
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Affiliation(s)
- Frederick Y Wu
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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158
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Dardick C, Ronald P. Plant and animal pathogen recognition receptors signal through non-RD kinases. PLoS Pathog 2006; 2:e2. [PMID: 16424920 PMCID: PMC1331981 DOI: 10.1371/journal.ppat.0020002] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 12/14/2005] [Indexed: 12/18/2022] Open
Abstract
Plants and animals mediate early steps of the innate immune response through pathogen recognition receptors (PRRs). PRRs commonly associate with or contain members of a monophyletic group of kinases called the interleukin-1 receptor-associated kinase (IRAK) family that include Drosophila Pelle, human IRAKs, rice XA21 and Arabidopsis FLS2. In mammals, PRRs can also associate with members of the receptor-interacting protein (RIP) kinase family, distant relatives to the IRAK family. Some IRAK and RIP family kinases fall into a small functional class of kinases termed non-RD, many of which do not autophosphorylate the activation loop. We surveyed the yeast, fly, worm, human, Arabidopsis, and rice kinomes (3,723 kinases) and found that despite the small number of non-RD kinases in these genomes (9%-29%), 12 of 15 kinases known or predicted to function in PRR signaling fall into the non-RD class. These data indicate that kinases associated with PRRs can largely be predicted by the lack of a single conserved residue and reveal new potential plant PRR subfamilies.
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Affiliation(s)
- Christopher Dardick
- United States Department of Agriculture, Agricultural Research Service, Appalachian Fruit Research Station, Kearneysville, West Virginia, United States of America
- * To whom correspondence should be addressed. E-mail: (CD); (PR)
| | - Pamela Ronald
- Department of Plant Pathology, University of California Davis, Davis, California, United States of America
- * To whom correspondence should be addressed. E-mail: (CD); (PR)
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159
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Sarek G, Järviluoma A, Ojala PM. KSHV viral cyclin inactivates p27KIP1 through Ser10 and Thr187 phosphorylation in proliferating primary effusion lymphomas. Blood 2006; 107:725-32. [PMID: 16160006 DOI: 10.1182/blood-2005-06-2534] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
AbstractKaposi sarcoma herpesvirus (KSHV) infection is consistently associated with primary effusion lymphomas (PELs) that are non-Hodgkin lymphomas of B-cell origin. All PEL cells are latently infected with KSHV and express latent viral proteins such as the viral cyclin (v-cyclin), which has previously been implicated in down-regulation of cell-cycle inhibitor p27KIP1 levels via phosphorylation on Thr187. PEL cells retain high levels of p27KIP1 but yet proliferate actively, which has left the biologic significance of this p27KIP1 destabilization somewhat elusive. We have recently demonstrated that v-cyclin and p27KIP1 stably associate in PEL cells. Here we demonstrate that v-cyclin together with its kinase partner CDK6 phosphorylates the associated p27KIP1 in PEL cells, which represent a biologically relevant model system for KSHV pathobiology. During latent viral replication p27KIP1 was phosphorylated by v-cyclin-CDK6 predominantly on Ser10, which enhances its cytoplasmic localization. Interestingly, upon reactivation of KSHV lytic cycle, v-cyclin-CDK6 phosphorylated p27KIP1 on Thr187, which resulted in down-regulation of p27KIP1 protein levels. These findings indicate that v-cyclin modulates the cell-cycle inhibitory function of p27KIP1 by phosphorylation in PELs, and also suggest a novel role for v-cyclin in the lytic reactivation of KSHV. (Blood. 2006;107:725-732)
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MESH Headings
- Cell Proliferation
- Cyclin-Dependent Kinase 6/metabolism
- Cyclin-Dependent Kinase Inhibitor p27/antagonists & inhibitors
- Cyclin-Dependent Kinase Inhibitor p27/metabolism
- Cyclins/pharmacology
- Cytoplasm/metabolism
- Fluorescent Antibody Technique, Indirect
- Herpesvirus 8, Human/genetics
- Herpesvirus 8, Human/metabolism
- Herpesvirus 8, Human/pathogenicity
- Humans
- Immunoblotting
- Immunoprecipitation
- Lymphoma, AIDS-Related/metabolism
- Lymphoma, AIDS-Related/virology
- Phosphorylation
- Protein Transport
- Sarcoma, Kaposi/metabolism
- Sarcoma, Kaposi/pathology
- Sarcoma, Kaposi/virology
- Serine/chemistry
- Subcellular Fractions
- Threonine/chemistry
- Tumor Cells, Cultured
- Viral Proteins/pharmacology
- Virus Replication
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Affiliation(s)
- Grzegorz Sarek
- Molecular Cancer Biology Program, Institute of Biomedicine, Biomedicum Helsinki, Finland
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160
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Kim TH, Oh S, Kim SS. Recombinant human prothrombin kringle-2 induces bovine capillary endothelial cell cycle arrest at G0-G1 phase through inhibition of cyclin D1/CDK4 complex: modulation of reactive oxygen species generation and up-regulation of cyclin-dependent kinase inhibitors. Angiogenesis 2006; 8:307-14. [PMID: 16400524 DOI: 10.1007/s10456-005-9020-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 09/09/2005] [Accepted: 09/23/2005] [Indexed: 01/05/2023]
Abstract
Prothrombin is a plasma glycoprotein involved in blood coagulation and, as we have previously reported, prothrombin kringles inhibit BCE (bovine capillary endothelial) cell proliferation. To reveal the mechanism, we investigated the influence of rk-2 (recombinant human prothrombin kringle-2) on the BCE cell cycle progression and ROS (reactive oxygen species) generation using FACS (fluorescence-activated cell sorter) analysis. Cell cycle analysis showed a decrease of G(1) phase cells in cells treated with bFGF (basic fibroblast growth factor) and an increase in cells treated with rk-2, as compared with the control cells. But, the portion of the S phase was reversed. In Western blot analysis, bFGF induced cytoplasmic translocation of p21(Waf1/Cip1) and p27(Kip1) and phosphorylation of p27(Kip1) but rk-2 treatment inhibited translocation of p21(Waf1/Cip1) and p27(Kip1) from nucleus to cytoplasm and phosphorylation of p27(Kip1). Also, rk-2 induced up-regulation of p53 and nuclear p21(Waf1/Cip1) and inhibited the cyclin D1/CDK4 (cyclin-dependent kinase 4) complex. The ROS level of rk-2-treated BCE cells was increased 2-fold when compared with the control, but treatment with NAC (N-Acetyl-L: -cysteine), an anti-oxidant, decreased ROS generation about 55% as compared with the rk-2 treatment. NAC treatment also restored cell cycle progression inhibited by rk-2 and down-regulated p53 and nuclear p21(Waf1/Cip1) expression induced by rk-2.These data suggest that rk-2 induces the BCE cell cycle arrest at G(0)-G(1) phase through inhibition of the cyclin D1/CDK4 complex caused by increase of ROS generation and nuclear cyclin-dependent kinase inhibitors.
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Affiliation(s)
- Tae Hyong Kim
- Department of Biochemistry, College of Science, Yonsei University, Seoul, Korea
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161
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Besson A, Gurian-West M, Chen X, Kelly-Spratt KS, Kemp CJ, Roberts JM. A pathway in quiescent cells that controls p27Kip1 stability, subcellular localization, and tumor suppression. Genes Dev 2006; 20:47-64. [PMID: 16391232 PMCID: PMC1356100 DOI: 10.1101/gad.1384406] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Accepted: 11/11/2005] [Indexed: 12/28/2022]
Abstract
We have created two knock-in mouse models to study the mechanisms that regulate p27 in normal cells and cause misregulation of p27 in tumors: p27(S10A), in which Ser10 is mutated to Ala; and p27(CK-), in which point mutations abrogate the ability of p27 to bind cyclins and CDKs. These two mutant alleles identify steps in a pathway that controls the proteasomal degradation of p27 uniquely in quiescent cells: Dephosphorylation of p27 on Ser10 inhibits p27 nuclear export and promotes its assembly into cyclin-CDK complexes, which is, in turn, necessary for p27 turnover. We further show that Ras-dependent lung tumorigenesis is associated with increased phosphorylation on Ser10 and cytoplasmic mislocalization of p27. Indeed, we find that p27(S10A) is refractory to Ras-induced cytoplasmic translocation and that p27(S10A) mice are tumor resistant. Thus, phosphorylation of p27 on Ser10 is an important event in the regulation of the tumor suppressor function of p27.
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Affiliation(s)
- Arnaud Besson
- Howard Hughes Medical Institute, Division of Basic Sciences, Seattle, Washington 98109, USA
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162
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Kawauchi T, Chihama K, Nabeshima YI, Hoshino M. Cdk5 phosphorylates and stabilizes p27kip1 contributing to actin organization and cortical neuronal migration. Nat Cell Biol 2005; 8:17-26. [PMID: 16341208 DOI: 10.1038/ncb1338] [Citation(s) in RCA: 217] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Accepted: 11/02/2005] [Indexed: 01/22/2023]
Abstract
p27(kip1), a cyclin-dependent kinase (CDK) inhibitor (CKI), generally suppresses CDK activity in proliferating cells. Although another role of p27 in cell migration has been recently suggested in vitro, the physiological importance of p27 in cell migration remains elusive, as p27-deficient mice have not shown any obvious migration-defect-related phenotypes. Here, we show that Cdk5, an unconventional neuronal CDK, phosphorylates and stabilizes p27 as an upstream regulator, maintaining the amount of p27 in post-mitotic neurons. In vivo RNA interference (RNAi) experiments showed that reduced amounts of p27 caused inhibition of cortical neuronal migration and decreased the amount of F-actin in the processes of migrating neurons. The Cdk5-p27 pathway activates an actin-binding protein, cofilin, which is also shown to be involved in cortical neuronal migration in vivo. Our findings shed light on a previously unknown new relationship between CDK and CKI in G0-arrested cells that regulates cytoskeletal reorganization and neuronal migration during corticogenesis.
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Affiliation(s)
- Takeshi Kawauchi
- Department of Pathology and Tumor Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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163
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Seo DW, Li H, Qu CK, Oh J, Kim YS, Diaz T, Wei B, Han JW, Stetler-Stevenson WG. Shp-1 mediates the antiproliferative activity of tissue inhibitor of metalloproteinase-2 in human microvascular endothelial cells. J Biol Chem 2005; 281:3711-21. [PMID: 16326706 PMCID: PMC1361361 DOI: 10.1074/jbc.m509932200] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The tissue inhibitors of metalloproteinases (TIMPs) regulate matrix metalloproteinase activity required for cell migration/invasion associated with cancer progression and angiogenesis. TIMPs also modulate cell proliferation in vitro and angiogenesis in vivo independent of their matrix metalloproteinase inhibitory activity. Here, we show that TIMP-2 mediates G1 growth arrest in human endothelial cells through de novo synthesis of the cyclin-dependent kinase inhibitor p27Kip1. TIMP-2-mediated inhibition of Cdk4 and Cdk2 activity is associated with increased binding of p27Kip1 to these complexes in vivo. Protein-tyrosine phosphatase inhibitors or expression of a dominant negative Shp-1 mutant ablates TIMP-2 induction of p27Kip1. Finally, angiogenic responses to fibroblast growth factor-2 and vascular endothelial growth factor-A in "motheaten viable" Shp-1-deficient mice are resistant to TIMP-2 inhibition, demonstrating that Shp-1 is an important negative regulator of angiogenesis in vivo.
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MESH Headings
- Animals
- Blotting, Northern
- Blotting, Western
- Cell Cycle
- Cell Proliferation
- Cells, Cultured
- Cyclin-Dependent Kinase 2/metabolism
- Cyclin-Dependent Kinase 4/metabolism
- Cyclin-Dependent Kinase Inhibitor p27/metabolism
- Endothelium, Vascular/cytology
- G1 Phase
- Gene Expression Regulation
- Genes, Dominant
- Humans
- Immunoprecipitation
- Intracellular Signaling Peptides and Proteins/metabolism
- Intracellular Signaling Peptides and Proteins/physiology
- Mice
- Mice, Transgenic
- Microcirculation/enzymology
- Microscopy, Fluorescence
- Models, Biological
- Mutation
- Neovascularization, Physiologic
- Phosphorylation
- Polymerase Chain Reaction
- Protein Tyrosine Phosphatase, Non-Receptor Type 6
- Protein Tyrosine Phosphatases/metabolism
- Protein Tyrosine Phosphatases/physiology
- RNA, Small Interfering/metabolism
- Subcellular Fractions/metabolism
- Tissue Inhibitor of Metalloproteinase-2/biosynthesis
- Transfection
- Vascular Endothelial Growth Factor A/metabolism
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Affiliation(s)
- Dong-Wan Seo
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Hongmei Li
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Cheng-Kui Qu
- Department of Pathology, University of Maryland School of Medicine, Rockville, Maryland 20855
| | - Junseo Oh
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Young-Sik Kim
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Tere Diaz
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Beiyang Wei
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
| | - Jeung-Whan Han
- Department of Biochemistry and Molecular Biology, College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea
| | - William G. Stetler-Stevenson
- From the Cell and Cancer Biology Branch, CCR, NCI, NIH, Bethesda, Maryland 20892-1500, USA
- Address correspondence to: William G. Stetler-Stevenson, MD, Ph.D., NCI, NIH, Bldg 37, Room 1062B, Bethesda, MD 20892; Tel: 301-402-1521; Fax: 301-402-2628;
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164
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Nallamshetty S, Crook M, Boehm M, Yoshimoto T, Olive M, Nabel EG. The cell cycle regulator p27Kip1 interacts with MCM7, a DNA replication licensing factor, to inhibit initiation of DNA replication. FEBS Lett 2005; 579:6529-36. [PMID: 16289477 DOI: 10.1016/j.febslet.2005.10.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Revised: 10/06/2005] [Accepted: 10/17/2005] [Indexed: 10/25/2022]
Abstract
The G1/S phase restriction point is a critical checkpoint that interfaces between the cell cycle regulatory machinery and DNA replicator proteins. Here, we report a novel function for the cyclin-dependent kinase inhibitor p27Kip1 in inhibiting DNA replication through its interaction with MCM7, a DNA replication protein that is essential for initiation of DNA replication and maintenance of genomic integrity. We find that p27Kip1 binds the conserved minichromosome maintenance (MCM) domain of MCM7. The proteins interact endogenously in vivo in a growth factor-dependent manner, such that the carboxyl terminal domain of p27Kip1 inhibits DNA replication independent of its function as a cyclin-dependent kinase inhibitor. This novel function of p27Kip1 may prevent inappropriate initiation of DNA replication prior to S phase.
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Affiliation(s)
- Shriram Nallamshetty
- National Heart, Lung, and Blood Institute, National Institutes of Health, Building 50, Room 4523, 50 Center Drive, Bethesda, MD 20892, USA
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165
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Kfir S, Ehrlich M, Goldshmid A, Liu X, Kloog Y, Henis YI. Pathway- and expression level-dependent effects of oncogenic N-Ras: p27(Kip1) mislocalization by the Ral-GEF pathway and Erk-mediated interference with Smad signaling. Mol Cell Biol 2005; 25:8239-50. [PMID: 16135812 PMCID: PMC1234306 DOI: 10.1128/mcb.25.18.8239-8250.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Overactivation of Ras pathways contributes to oncogenesis and metastasis of epithelial cells in several ways, including interference with cell cycle regulation via the CDK inhibitor p27(Kip1) (p27) and disruption of transforming growth factor beta (TGF-beta) anti-proliferative activity. Here, we show that at high expression levels, constitutively active N-Ras induces cytoplasmic mislocalization of murine and human p27 via the Ral-GEF pathway and disrupts TGF-beta-mediated Smad nuclear translocation by activation of the Mek/Erk pathway. While human p27 could also be mislocalized via the phosphatidylinositol 3-kinase/Akt pathway, only Ral-GEF activation was effective for murine p27, which lacks the Thr157 Akt phosphorylation site of human p27. This establishes a novel role for the Ral-GEF pathway in regulating p27 localization. Interference with either Smad translocation or p27 nuclear localization was sufficient to disrupt TGF-beta growth inhibition. Moreover, expression of activated N-Ras or specific effector loop mutants at lower levels using retroviral vectors induced p27 mislocalization but did not inhibit Smad2/3 translocation, indicating that the effects on p27 localization occur at lower levels of activated Ras. These findings have important implications for the contribution of activated Ras to oncogenesis and for the conversion of TGF-beta from an inhibitory to a metastatic factor in some epithelial tumors.
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Affiliation(s)
- Shiri Kfir
- Department of Neurobiochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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166
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Kardinal C, Dangers M, Kardinal A, Koch A, Brandt DT, Tamura T, Welte K. Tyrosine phosphorylation modulates binding preference to cyclin-dependent kinases and subcellular localization of p27Kip1 in the acute promyelocytic leukemia cell line NB4. Blood 2005; 107:1133-40. [PMID: 16195327 DOI: 10.1182/blood-2005-05-1771] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have investigated the role of tyrosine phosphorylation of the cyclin-dependent kinase (cdk) inhibitor p27Kip1 using the acute promyelocytic leukemia cell line NB4 together with granulocyte colony-stimulating factor (G-CSF). Short-term G-CSF stimulation resulted in a rapid tyrosine dephosphorylation of p27Kip1 accompanied by a change in its binding preferences to cdks. On G-CSF stimulation, p27Kip1 dissociated from cdk4 and associated with cdk2. Binding assays with recombinant p27Kip1 confirmed that tyrosine-phosphorylated p27Kip1 preferentially bound to cdk4, whereas unphosphorylated protein preferentially associated with cdk2. In addition, studies with p27Kip1 point mutations revealed a decisive role of Tyr88 and Tyr89 in binding to cdk4. Furthermore, phosphorylation of Tyr88 and Tyr89 was accompanied by strong nuclear translocation of p27Kip1. Taken together, this report provides the first evidence that tyrosine phosphorylation of p27Kip1 plays a crucial role in binding to cdks and its subcellular localization. Moreover, both effects are mediated by application of G-CSF.
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Affiliation(s)
- Christian Kardinal
- Pädiatrische Hämatologie und Onkologie, Medizinische Hochschule Hannover (MHH), Hannover, Germany.
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167
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Schepers H, Wierenga ATJ, Eggen BJL, Vellenga E. Oncogenic Ras blocks transforming growth factor-beta-induced cell-cycle arrest by degradation of p27 through a MEK/Erk/SKP2-dependent pathway. Exp Hematol 2005; 33:747-57. [PMID: 15963850 DOI: 10.1016/j.exphem.2005.04.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 04/08/2005] [Accepted: 04/14/2005] [Indexed: 12/24/2022]
Abstract
OBJECTIVE To examine whether oncogenic Ras affects transforming growth factor (TGF)-beta-mediated cell-cycle arrest in hematopoietic cells and the downstream signal transduction pathway involved in the interference with TGF-beta-induced cell-cycle arrest. MATERIALS AND METHODS Two leukemic cell lines bearing N-Ras(L61) mutations; HL-60 and TF-1, and the M1 cell line with wt Ras were investigated for their response to TGF-beta. Signal transduction inhibitors, overexpression and RNA interference studies were performed to investigate the involvement of the various proteins. RESULTS Although TGF-beta signal transduction was not affected, G0-G1 arrest was absent in HL-60 and TF-1 cells due to the absence of p27. Overexpression of p27 restored TGF-beta-induced cell-cycle arrest, as well as interfering in Ras-mediated signaling. The farnesyl transferase inhibitor L744832 and the MEK inhibitor U0126 both restored p27 levels and cell-cycle arrest in response to TGF-beta. The absence of p27 protein is due to elevated levels of the ubiquitin ligase SKP2, which complexes with and targets p27 for degradation. RNA interference for SKP2 and treatment of these cells with the proteasome inhibitor MG132 restored p27 levels, corresponding with decreasing SKP2 levels after interfering in N-Ras signal transduction. P27, phosphorylated at threonine 187, is nuclear localized in N-Ras-containing cells. Mutation of this residue to alanine rendered p27 insensitive to degradation. CONCLUSION N-Ras(L61) transformed cells lack a G0-G1 arrest upon TGF-beta treatment due to absence of p27. p27 is degraded through a MapK-, and SKP2-dependent pathway. Overexpression of p27 results in restoration of cell-cycle arrest upon TGF-beta treatment.
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Affiliation(s)
- Hein Schepers
- Division of Hematology, Department of Medicine, University Medical Center Groningen, The Netherlands
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168
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Abstract
Approximately 50 years ago, researchers established conditions to maintain cells in tissue culture: Likely et al. (1952), Scherer et al. (1953), Eagle (1955). This simple model system set the stage for discovery of growth factors and the signaling systems that they engage to mediate cellular responses such as proliferation. The purpose of this review is to present the original view of how growth factors regulate cell cycle progression and an updated (priming/completion) version of how growth factors advance resting cells through the cell cycle.
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Affiliation(s)
- Andrius Kazlauskas
- Schepens Eye Research Institute, Harvard Medical School, 20 Staniford Street, Boston, MA 02114, USA.
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169
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Zhang Q, Tian L, Mansouri A, Korapati AL, Johnson TJ, Claret FX. Inducible expression of a degradation-resistant form of p27Kip1 causes growth arrest and apoptosis in breast cancer cells. FEBS Lett 2005; 579:3932-40. [PMID: 15996662 PMCID: PMC1366489 DOI: 10.1016/j.febslet.2005.06.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2005] [Revised: 06/03/2005] [Accepted: 06/05/2005] [Indexed: 01/15/2023]
Abstract
The cyclin-dependent kinase (CDK) inhibitor p27(Kip1) (p27) is an important regulator of cell cycle progression controlling the transition from G to S-phase. Low p27 levels or accelerated p27 degradation correlate with excessive cell proliferation and poor prognosis in several forms of cancer. Phosphorylation of p27 at Thr187 by cyclin E-CDK2 is required to initiate the ubiquitination-proteasomal degradation of p27. Protecting p27 from ubiquitin-mediated proteasomal degradation may increase its potential in cancer gene therapy. Here we constructed a non-phosphorylatable, proteolysis-resistant p27 mutant containing a Thr187-to-Ala substitution (T187A) which is not degraded by ubiquitin-mediated proteasome pathway, and compared its effects on cell growth, cell-cycle control, and apoptosis with those of wild-type p27. In muristerone A-inducible cell lines overexpressing wild-type or mutant p27, the p27 mutant was more resistant to proteolysis in vivo and more potent in inducing cell-cycle arrest and other growth-inhibitory effects such as apoptosis. Transduction of p27(T187A) in breast cancer cells with a doxycycline-regulated adenovirus led to greater inhibition of proliferation, more extensive apoptosis, with a markedly reduced protein levels of cyclin E and increased accumulation of cyclin D1, compared with wild-type p27. These findings support the potential effectiveness of a degradation-resistant form of p27 in breast cancer gene therapy.
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Affiliation(s)
| | | | | | | | | | - Francois X. Claret
- *Corresponding author. Fax: +1 713 563 4205. E-mail address: (F.X. Claret)
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170
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Qi CF, Xiang S, Shin MS, Hao X, Lee CH, Zhou JX, Torrey TA, Hartley JW, Fredrickson TN, Morse HC. Expression of the cyclin-dependent kinase inhibitor p27 and its deregulation in mouse B cell lymphomas. Leuk Res 2005; 30:153-63. [PMID: 16122798 DOI: 10.1016/j.leukres.2005.06.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Accepted: 06/13/2005] [Indexed: 01/04/2023]
Abstract
CDKN1B (p27) regulates cell-cycle progression at the G1-S transition by suppressing the cyclin E/CDK2 kinase complex. In normal lymphocytes and most human B cell non-Hodgkin lymphomas (NHL), there is an inverse correlation between proliferative activity and expression of p27; however, a subset of NHL with high mitotic indices expresses p27, which is inactive due to sequestration in nuclear protein complexes or due to cytoplasmic retention. Our studies of mouse B cell NHL also identified cases with high proliferative activity and high levels of p27 at a surprisingly high frequency. Here, p27 was complexed with D-type cyclins 1 and 3 and with the COPS9 protein, JAB1. In addition, we found cytoplasmic sequestration following phosphorylation by activated AKT.
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Affiliation(s)
- Chen-Feng Qi
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, Twinbrook I, Room 1421, National Institutes of Health, Rockville, MD, USA
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171
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Rohlfing AK, Schill T, Müller C, Hildebrandt P, Prowald A, Hildebrandt JP. Attenuation of cell cycle regulator p27(Kip1) expression in vertebrate epithelial cells mediated by extracellular signals in vivo and in vitro. J Comp Physiol B 2005; 175:511-22. [PMID: 16075271 DOI: 10.1007/s00360-005-0019-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Revised: 06/08/2005] [Accepted: 06/21/2005] [Indexed: 10/25/2022]
Abstract
Cell cycle arrest in potentially dividing cells is often mediated by inhibitors of G1/S-phase cyclin-dependent kinases. The cyclin E/CDK2-inhibitor p27(Kip1) has been implicated in this context in epithelial cells. We cloned and sequenced p27(Kip1) of ducklings (Anas platyrhynchos) and used an in vitro assay system to study the mechanism of p27(Kip1) downregulation in the nasal gland which precedes an increase in proliferation rate upon initial exposure of the animals to osmotic stress. Western blot studies revealed that p27(Kip1) is downregulated during 24 h of osmotic stress in ducklings with the steepest decline in protein levels between 5 and 8 h. As indicated by the results of Northern blot and semi-quantitative PCR studies, protein downregulation is not accompanied by similar changes in mRNA levels indicating that Kip1 is regulated mainly at the translational (synthesis) or posttranslational level (degradation). Using recombinant duck Kip1 protein expressed in E. coli, we showed that Kip1 is subject to polyubiquitinylation by cytosolic enzymes from nasal gland cells indicating that loss of Kip1 may be regulated, at least in part, by acceleration of protein degradation. In cultured nasal gland tissue, attenuation of Kip1 expression could be induced by activation of the muscarinic acetylcholine receptor indicating that mAChR-receptor signalling may play a role in the re-entry of quiescent gland cells into the cell cycle.
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Affiliation(s)
- Anne-Katrin Rohlfing
- Animal Physiology and Biochemistry, Ernst Moritz Arndt-University Greifswald, Biotechnikum, Walther Rathenau-Strasse 49 a, 17489 Greifswald, Germany
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172
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Xia L, Chen D, Han R, Fang Q, Waxman S, Jing Y. Boswellic acid acetate induces apoptosis through caspase-mediated pathways in myeloid leukemia cells. Mol Cancer Ther 2005. [PMID: 15767547 DOI: 10.1158/1535-7163] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The mechanism of the cytotoxic effect of boswellic acid acetate, a 1:1 mixture of alpha-boswellic acid acetate and beta-boswellic acid acetate, isolated from Boswellia carterri Birdw on myeloid leukemia cells was investigated in six human myeloid leukemia cell lines (NB4, SKNO-1, K562, U937, ML-1, and HL-60 cells). Morphologic and DNA fragmentation assays indicated that the cytotoxic effect of boswellic acid acetate was mediated by induction of apoptosis. More than 50% of the cells underwent apoptosis after treatment with 20 mug/mL boswellic acid for 24 hours. This apoptotic process was p53 independent. The levels of apoptosis-related proteins Bcl-2, Bax, and Bcl-XL were not modulated by boswellic acid acetate. Boswellic acid acetate induced Bid cleavage and decreased mitochondrial membrane potential without production of hydrogen peroxide. A general caspase inhibitor (Z-VAD-FMK) and a specific caspase-8 inhibitor II (Z-IETD-FMK) blocked boswellic acid acetate-induced apoptosis. The mRNAs of death receptors 4 and 5 (DR4 and DR5) were induced in leukemia cells undergoing apoptosis after boswellic acid acetate treatment. These data taken together suggest that boswellic acid acetate induces myeloid leukemia cell apoptosis through activation of caspase-8 by induced expression of DR4 and DR5, and that the activated caspase-8 either directly activates caspase-3 by cleavage or indirectly by cleaving Bid, which in turn decreases mitochondria membrane potential.
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MESH Headings
- Amino Acid Chloromethyl Ketones/pharmacology
- Apoptosis
- Blotting, Northern
- Blotting, Western
- Caspase 3
- Caspases/metabolism
- Cell Line, Tumor
- Cell Proliferation
- DNA Fragmentation
- HL-60 Cells
- Humans
- Hydrogen Peroxide/pharmacology
- Inhibitory Concentration 50
- K562 Cells
- Leukemia, Myeloid/drug therapy
- Leukemia, Myeloid/pathology
- Membrane Potentials
- Mitochondria/metabolism
- Models, Biological
- Models, Chemical
- Oligopeptides/pharmacology
- Protein Binding
- Proto-Oncogene Proteins c-bcl-2/metabolism
- RNA, Messenger/metabolism
- Receptors, TNF-Related Apoptosis-Inducing Ligand
- Receptors, Tumor Necrosis Factor/metabolism
- Triterpenes/pharmacology
- U937 Cells
- bcl-2-Associated X Protein
- bcl-X Protein
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Affiliation(s)
- Lijuan Xia
- Division of Hematology/Oncology, Department of Medicine, Box 1178, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029-6547.
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173
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Kudo Y, Kitajima S, Ogawa I, Miyauchi M, Takata T. Down-regulation of Cdk inhibitor p27 in oral squamous cell carcinoma. Oral Oncol 2005; 41:105-16. [PMID: 15695111 DOI: 10.1016/j.oraloncology.2004.05.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Revised: 04/07/2004] [Accepted: 05/12/2004] [Indexed: 12/19/2022]
Abstract
Oral squamous cell carcinoma (OSCC) is the most frequent malignant neoplasm of the head and neck region. Conversion of normal cells to cancer cells is achieved through a multi-step process that is closely associated with the accumulation of multiple gene changes including both oncogenes and tumour suppressor genes. The proliferation and progression of cancer may be caused by abnormalities of various positive and negative cell cycle regulators. Cell cycle progression is positively regulated by multiple cyclins and cyclin-dependent kinases (Cdks) and cyclin/Cdk complexes are negatively regulated by a number of Cdk inhibitors including p27. p27 is a Cdk inhibitor and plays an important role in negative regulation of the cell cycle during G0 and G1 phases. Degradation of p27 is a critical event for the G1/S transition and occurs through ubiquitination by SCF(Skp2) and subsequent degradation by the 26S proteasome. It has been revealed that down-regulation of p27 is frequently found in various cancers, including OSCC, and is due to an enhancement of its degradation. Importantly, down-regulation of p27 is well associated with its malignancy including poor prognosis in various cancers. Moreover, aggressive human cancers express low levels of p27 because of its decreased stability. More recent evidence suggests that Skp2 and Cks1, the specific recognition factors for p27 ubiquitination, have oncogenic properties. This review will focus on down-regulation of p27 and mechanism of its down-regulation in OSCC.
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Affiliation(s)
- Yasusei Kudo
- Department of Oral Maxillofacial Pathobiology, Division of Frontier Medical Science, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734, Japan.
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174
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Fasciano S, Patel RC, Handy I, Patel CV. Regulation of vascular smooth muscle proliferation by heparin: inhibition of cyclin-dependent kinase 2 activity by p27(kip1). J Biol Chem 2005; 280:15682-9. [PMID: 15731113 PMCID: PMC3972062 DOI: 10.1074/jbc.m411458200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Uncontrolled proliferation of vascular smooth muscle cells (VSMCs) contribute to intimal hyperplasia during atherosclerosis and restenosis. Heparin is an antiproliferative agent for VSMCs and has been shown to block VSMC proliferation both in tissue culture systems and in animals. Despite the well documented antiproliferative actions of heparin, its cellular targets largely remain unknown. In an effort to characterize the mechanism of the antiproliferative property of heparin, we have analyzed the effect of heparin on cell cycle in VSMC. Our results indicate that the heparin-induced block in G(1) to S phase transition is imposed by p27(kip1)-mediated inhibition of cyclin-dependent kinase 2 activity. Further analysis of p27(kip1) mRNA levels showed that the increase in p27(kip1) protein levels in heparin-treated VSMC occurs at posttranscriptional levels. We present evidence that heparin causes stabilization of p27(kip1) protein during G(1) phase and thereby prevents activation of cyclin-dependent kinase 2.
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Affiliation(s)
- Stephen Fasciano
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
| | - Rekha C. Patel
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
| | - Indhira Handy
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
| | - Chandrashekhar V. Patel
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208
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175
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Kuiperij HB, van der Horst A, Raaijmakers J, Weijzen S, Medema RH, Bos JL, Burgering BMT, Zwartkruis FJT. Activation of FoxO transcription factors contributes to the antiproliferative effect of cAMP. Oncogene 2005; 24:2087-95. [PMID: 15688004 DOI: 10.1038/sj.onc.1208450] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
cAMP is a potent inhibitor of cell proliferation in a variety of cell lines. Downregulation of cyclin D1 and upregulation of the cell cycle inhibitor p27Kip1 are two mechanisms by which cAMP may induce a G1-arrest. Here we show that cAMP inhibits proliferation of cells that constitutively express cyclin D1 or are deficient for Rb, demonstrating that changes in these cell cycle regulators do not account for the cAMP-induced growth effects in mouse embryo fibroblasts (MEFs). Interestingly, the antiproliferative effect of cAMP mimics the effect previously observed for FoxO transcription factors. These transcription factors are under negative control of protein kinase B (PKB). We show that in MEFs cAMP strongly induces transcriptional activation of FoxO4 through the inhibition of PKB. Accordingly, not only p27Kip1 but also the FoxO target MnSOD is upregulated by cAMP. Importantly, introduction of dominant-negative FoxO partially rescues cAMP-induced inhibition of proliferation. From these results we conclude that inhibition of PKB and subsequent activation of FoxO transcription factors mediates an antiproliferative effect of cAMP.
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Affiliation(s)
- H Bea Kuiperij
- Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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176
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Abstract
The regulatory step in ubiquitin (Ub)-mediated protein degradation involves recognition and selection of the target substrate by an E3 Ub-ligase. E3 Ub-ligases evoke sophisticated mechanisms to regulate their activity temporally and spatially, including multiple post-translational modifications, combinatorial E3 Ub-ligase pathways, and subcellular localization. The phosphodegrons of many substrates incorporate the activities of multiple kinases, and ubiquitination only occurs when all necessary phosphorylation signals have been incorporated. In this manner, the precise timing of degradation can be controlled. Another way that the Ub pathway tightly controls the timing of proteolysis is with multiple E3 Ub-ligases acting upon a single target. Lastly, subcellular localization can either promote or prevent degradation by regulating the accessibility of kinases and E3 Ub-ligases. This review highlights recent findings that exemplify these emerging themes in the regulation of E3 Ub-ligase substrate recognition.
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Affiliation(s)
- Xiaolu L Ang
- Program in Biological and Biomedical Sciences, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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177
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Willems AR, Schwab M, Tyers M. A hitchhiker's guide to the cullin ubiquitin ligases: SCF and its kin. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1695:133-70. [PMID: 15571813 DOI: 10.1016/j.bbamcr.2004.09.027] [Citation(s) in RCA: 371] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The SCF (Skp1-Cullin-F-box) E3 ubiquitin ligase family was discovered through genetic requirements for cell cycle progression in budding yeast. In these multisubunit enzymes, an invariant core complex, composed of the Skp1 linker protein, the Cdc53/Cul1 scaffold protein and the Rbx1/Roc1/Hrt1 RING domain protein, engages one of a suite of substrate adaptors called F-box proteins that in turn recruit substrates for ubiquitination by an associated E2 enzyme. The cullin-RING domain-adaptor architecture has diversified through evolution, such that in total many hundreds of distinct SCF and SCF-like complexes enable degradation of myriad substrates. Substrate recognition by adaptors often depends on posttranslational modification of the substrate, which thus places substrate stability under dynamic regulation by intracellular signaling events. SCF complexes control cell proliferation through degradation of critical regulators such as cyclins, CDK inhibitors and transcription factors. A plethora of other processes in development and disease are controlled by other SCF-like complexes, including those based on Cul2-SOCS-box adaptor protein and Cul3-BTB domain adaptor protein combinations. Recent structural insights into SCF-like complexes have begun to illuminate aspects of substrate recognition and catalytic reaction mechanisms.
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Affiliation(s)
- Andrew R Willems
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Canada, M5G 1X5
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178
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Motti ML, Califano D, Troncone G, De Marco C, Migliaccio I, Palmieri E, Pezzullo L, Palombini L, Fusco A, Viglietto G. Complex regulation of the cyclin-dependent kinase inhibitor p27kip1 in thyroid cancer cells by the PI3K/AKT pathway: regulation of p27kip1 expression and localization. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 166:737-49. [PMID: 15743786 PMCID: PMC1602368 DOI: 10.1016/s0002-9440(10)62295-x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/01/2004] [Indexed: 01/03/2023]
Abstract
Functional inactivation of the tumor suppressor p27(kip1) in human cancer occurs either through loss of expression or through phosphorylation-dependent cytoplasmic sequestration. Here we demonstrate that dysregulation of the PI3K/AKT pathway is important in thyroid carcinogenesis and that p27(kip1) is a key target of the growth-regulatory activity exerted by this pathway in thyroid cancer cells. Using specific PI3K inhibitors (LY294002, wortmannin, and PTEN) and a dominant active AKT construct (myrAKT), we demonstrated that the PI3K/AKT pathway controlled thyroid cell proliferation by regulating the expression and subcellular localization of p27. Results obtained with phospho-specific antibodies and with transfection of nonphosphorylable p27(kip1) mutant constructs demonstrated that PI3K/AKT-dependent regulation of p27(kip1) mislocalization in thyroid cancer cells occurred via phosphorylation of p27(kip1) at T157 and T198 (but not at S10 or T187). Finally, we evaluated whether these results were applicable to human tumors. Analysis of 100 thyroid carcinomas indicated that p27(kip1) phosphorylation at T157/T198 and cytoplasmic mislocalization were preferentially associated with activation of the PI3K/AKT pathway. Thus the PI3/AKT pathway and its effector p27(kip1) play major roles in thyroid carcinogenesis.
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Affiliation(s)
- Maria Letizia Motti
- Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano, Università di Napoli Federico II, via S. Pansini 5, 80131 Napoli, Italy
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179
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Uchida T, Nakamura T, Hashimoto N, Matsuda T, Kotani K, Sakaue H, Kido Y, Hayashi Y, Nakayama KI, White MF, Kasuga M. Deletion of Cdkn1b ameliorates hyperglycemia by maintaining compensatory hyperinsulinemia in diabetic mice. Nat Med 2005; 11:175-82. [PMID: 15685168 DOI: 10.1038/nm1187] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Accepted: 01/04/2005] [Indexed: 12/31/2022]
Abstract
The protein p27(Kip1) regulates cell cycle progression in mammals by inhibiting the activity of cyclin-dependent kinases (CDKs). Here we show that p27(Kip1) progressively accumulates in the nucleus of pancreatic beta cells in mice that lack either insulin receptor substrate 2 (Irs2(-/-)) or the long form of the leptin receptor (Lepr(-/-) or db/db). Deletion of the gene encoding p27(Kip1) (Cdkn1b) ameliorated hyperglycemia in these animal models of type 2 diabetes mellitus by increasing islet mass and maintaining compensatory hyperinsulinemia, effects that were attributable predominantly to stimulation of pancreatic beta-cell proliferation. Thus, p27(Kip1) contributes to beta-cell failure during the development of type 2 diabetes in Irs2(-/-) and Lepr(-/-) mice and represents a potential new target for the treatment of this condition.
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Affiliation(s)
- Tohru Uchida
- Division of Diabetes and Digestive and Kidney Diseases, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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180
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Zhang W, Bergamaschi D, Jin B, Lu X. Posttranslational modifications of p27kip1 determine its binding specificity to different cyclins and cyclin-dependent kinases in vivo. Blood 2005; 105:3691-8. [PMID: 15665120 DOI: 10.1182/blood-2003-07-2558] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Using 2-dimensional gel electrophoresis (2D-gel) analysis, we show here that cell-cycle entry is associated with a significant increase in p27(kip1) phosphorylation in human primary B cells. A similar pattern of increase in p27(kip1) phosphorylation was also seen in 2 fast-growing tumor cell lines, Burkitt lymphoma cell line BL40 and breast carcinoma cell line Cal51, where inactive p27(kip1) is expressed at high levels. Detailed analysis revealed for the first time that different cyclins and cyclin-dependent kinases (cdk's) interact with distinct posttranslationally modified isoforms of p27(kip1) in vivo. Cyclin E but not cyclin A selectively interacts with phosphorylated p27(kip1) isoforms, while cyclin D1 and D2 favor unphosphorylated p27(kip1) isoforms in vivo. Interestingly, cyclin D3 and cdk4 selectively interact with phosphorylated p27(kip1) in BL40 cells. Among all D-type cyclin/cdk4 and cdk6 complexes, cyclin D3/cdk4 is most active in sequestering the inhibitory activity of p27(kip1) in vitro in a cyclinE/cdk2 kinase assay. This novel feature of the binding specificity of p27(kip1) to cyclins and cdk's in vivo is interpreted in the context of overexpression of cyclin D3 in the presence of high levels of p27(kip1) in human B-cell lymphomas with adverse clinical outcome.
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Affiliation(s)
- Wenqing Zhang
- Ludwig Institute for Cancer Research, University College London, 91 Riding House St, London W1W 7BS, United Kingdom
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181
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Baldassarre G, Belletti B, Nicoloso MS, Schiappacassi M, Vecchione A, Spessotto P, Morrione A, Canzonieri V, Colombatti A. p27(Kip1)-stathmin interaction influences sarcoma cell migration and invasion. Cancer Cell 2005; 7:51-63. [PMID: 15652749 DOI: 10.1016/j.ccr.2004.11.025] [Citation(s) in RCA: 229] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Revised: 10/14/2004] [Accepted: 11/04/2004] [Indexed: 12/31/2022]
Abstract
Emerging evidences suggest that cyclin-dependent kinase inhibitors (CKIs) can regulate cellular functions other than cell cycle progression, such as differentiation and migration. Here, we report that cytoplasmic expression of p27(kip1) affects microtubule (MT) stability following cell adhesion on extracellular matrix (ECM) constituents. This p27(kip1) activity is due to its ability to bind and impair the function of the MT-destabilizing protein stathmin. Accordingly, upregulation of p27(kip1) or downregulation of stathmin expression results in the inhibition of mesenchymal cell motility. Moreover, high stathmin and low cytoplasmic p27(kip1) expression correlate with the metastatic phenotype of human sarcomas in vivo. This study provides a functional link between proliferation and invasion of tumor cells based on diverse activities of p27(kip1) in different subcellular compartments.
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Affiliation(s)
- Gustavo Baldassarre
- Oncologia Sperimentale 2, Centro di Riferimento Oncologico, Istituto Nazionale Tumori, IRCCS, Aviano 33081, Italy.
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182
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Mirza AM, Gysin S, Malek N, Nakayama KI, Roberts JM, McMahon M. Cooperative regulation of the cell division cycle by the protein kinases RAF and AKT. Mol Cell Biol 2004; 24:10868-81. [PMID: 15572689 PMCID: PMC533961 DOI: 10.1128/mcb.24.24.10868-10881.2004] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The RAS-activated RAF-->MEK-->extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3'-kinase (PI3'-kinase)-->PDK1-->AKT signaling pathways are believed to cooperate to promote the proliferation of normal cells and the aberrant proliferation of cancer cells. To explore the mechanisms that underlie such cooperation, we have derived cells harboring conditionally active, steroid hormone-regulated forms of RAF and AKT. These cells permit the assessment of the biological and biochemical effects of activation of these protein kinases either alone or in combination with one another. Under conditions where activation of neither RAF nor AKT alone promoted S-phase progression, coactivation of both kinases elicited a robust proliferative response. Moreover, under conditions where high-level activation of RAF induced G(1) cell cycle arrest, activation of AKT bypassed the arrest and promoted S-phase progression. At the level of the cell cycle machinery, RAF and AKT cooperated to induce cyclin D1 and repress p27(Kip1) expression. Repression of p27(Kip1) was accompanied by a dramatic reduction in KIP1 mRNA and was observed in primary mouse embryo fibroblasts derived from mice either lacking SKP2 or expressing a T187A mutated form of p27(Kip1). Consistent with these observations, pharmacological inhibition of MEK or PI3'-kinase inhibited the effects of activated RAS on the expression of p27(Kip1) in NIH 3T3 fibroblasts and in a panel of bona fide human pancreatic cancer cell lines. Furthermore, we demonstrated that AKT activation led to sustained activation of cyclin/cdk2 complexes that occurred concomitantly with the removal of RAF-induced p21(Cip1) from cyclin E/cdk2 complexes. Cumulatively, these data strongly suggest that the RAF-->MEK-->ERK and PI3'K-->PDK-->AKT signaling pathways can cooperate to promote G(0)-->G(1)-->S-phase cell cycle progression in both normal and cancer cells.
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Affiliation(s)
- Amer M Mirza
- Cancer Research Institute and Department of Cellular and Molecular Pharmacology, UCSF Comprehensive Cancer Center, 2420 Sutter St., Box 0128, San Francisco, CA 94143-0128, USA
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183
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Shin I, Rotty J, Wu FY, Arteaga CL. Phosphorylation of p27Kip1 at Thr-157 interferes with its association with importin alpha during G1 and prevents nuclear re-entry. J Biol Chem 2004; 280:6055-63. [PMID: 15579463 DOI: 10.1074/jbc.m412367200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
We have studied mechanisms of Akt-mediated phosphorylation and regulation of cellular localization of p27. Akt phosphorylates Thr-157 in p27 and retains it in the cytosol. In cells arrested in G(1) and then synchronized to enter into S phase, Akt-mediated phosphorylation of Thr-157 p27 occurred in the cytosol during G(1) phase of the cell cycle. Both T157A and S10A p27 mutants localized in the nucleus in all phases of the cell cycle regardless of the expression of active Akt. Thr-157 phosphorylation was undetectable in S10A-p27, suggesting that Ser-10 phosphorylation is required for p27 localization in the cytosol and subsequent phosphorylation at Thr-157. Phosphorylation at Thr-157 interrupted the association of p27 with importin alpha. A T157A-p27 mutant protein exhibited higher association with importin alpha than wild-type-p27. Treatment of transfected and endogenous p27 with alkaline phosphatase rescued its association with importin alpha. Leptomycin B inhibited cytosolic Thr-157 P-p27 staining, implying that CRM1-dependent nuclear export is required for Akt-mediated Thr-157 phosphorylation. Heterokaryon shuttling assays with NIH3T3 (mouse) cells transfected with FLAG-p27 and HeLa (human) cells revealed that both wild type and T157A-p27 shuttled from NIH3T3 to HeLa cell nuclei with similar frequencies. However, S10A-p27 was found only in the NIH3T3 nuclei of NIH3T3-HeLa cell fusions. These results suggest that 1) Ser-10 phosphorylation is required for nuclear export of p27, 2) subsequent Akt-mediated phosphorylation at Thr-157 during G(1) phase corrals p27 in the cytosol, and 3) Thr-157 phosphorylation inhibits the association of p27 with importin alpha thus preventing its re-entry into the nucleus.
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Affiliation(s)
- Incheol Shin
- Department of Cancer Biology and Medicine, Vanderbilt-Ingram Comprehensive Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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184
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Slupianek A, Skorski T. NPM/ALK downregulates p27Kip1 in a PI-3K-dependent manner. Exp Hematol 2004; 32:1265-71. [PMID: 15588951 DOI: 10.1016/j.exphem.2004.11.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 10/19/2004] [Accepted: 11/05/2004] [Indexed: 11/28/2022]
Abstract
OBJECTIVES Anaplastic large-cell lymphomas (ALCL) are frequently associated with the chromosomal translocation t(2;5) (p23;q35) resulting in the NPM/ALK fusion gene that encodes a constitutively activated tyrosine kinase. We showed that NPM/ALK stimulated cell proliferation and that PI-3K/AKT pathway played an important role in this effect. p27Kip1 is a member of the CDK family inhibitory proteins regulating the entry into S phase. It was reported that p27Kip1 function is impaired in many tumors. In this study we investigated the role of PI-3K/AKT in NPM/ALK-dependent downregulation of p27Kip1 protein. MATERIALS AND METHODS To investigate this phenomenon the pro-B cell line BaF3, BaF3 cell line stably expressing NPM/ALK, and ALCL SUP-M2 cell line were used. The p27Kip1 protein expression before and after LY294002, wortmannin, or epoxomicin treatment and phosphorylation status of AKT were measured in parental and NPM/ALK+ cells by Western analysis. Also, the localization of p27Kip1 protein was analyzed by fractionation and immunoblotting. RESULTS p27Kip1 was found to be downregulated in NPM/ALK-transformed hematopoietic cells, but inhibition of proteasome-dependent degradation pathway by epoxomicin reversed this effect. In addition, treatment of NPM/ALK+ cells with LY294002, the PI-3K inhibitor, caused elevation of p27Kip1 protein expression and its nuclear localization. CONCLUSIONS Taken together, we postulate that NPM/ALK-PI-3K pathway stimulates cell proliferation by regulation of the expression and nuclear localization of p27Kip1.
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MESH Headings
- B-Lymphocytes/cytology
- B-Lymphocytes/metabolism
- B-Lymphocytes/pathology
- Blotting, Western
- Carrier Proteins/metabolism
- Cell Line, Transformed
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Cell Proliferation/drug effects
- Cell Transformation, Neoplastic/genetics
- Chromones/pharmacology
- Cyclin-Dependent Kinase Inhibitor p27
- Down-Regulation/drug effects
- Enzyme Inhibitors/pharmacology
- Gene Expression Regulation, Leukemic/drug effects
- Hematopoietic Stem Cells/metabolism
- Hematopoietic Stem Cells/pathology
- Humans
- Intracellular Signaling Peptides and Proteins/metabolism
- Lymphoma, Large B-Cell, Diffuse/genetics
- Lymphoma, Large B-Cell, Diffuse/metabolism
- Lymphoma, Large B-Cell, Diffuse/pathology
- Morpholines/pharmacology
- Oligopeptides/pharmacology
- Phosphatidylinositol 3-Kinases/metabolism
- Phosphorylation/drug effects
- Proteasome Endopeptidase Complex/metabolism
- Protein Transport/drug effects
- Protein-Tyrosine Kinases/genetics
- Protein-Tyrosine Kinases/metabolism
- S Phase/drug effects
- S Phase/genetics
- Signal Transduction/drug effects
- Transformation, Genetic
- Translocation, Genetic/genetics
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Affiliation(s)
- Artur Slupianek
- College of Science and Technology, Center for Biotechnology, Temple University, Philadelphia, Pa. 19008, USA.
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185
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Besson A, Assoian RK, Roberts JM. Regulation of the cytoskeleton: an oncogenic function for CDK inhibitors? Nat Rev Cancer 2004; 4:948-55. [PMID: 15573116 DOI: 10.1038/nrc1501] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Cyclin-dependent kinase inhibitors (CKIs) are well known inhibitors of cell proliferation. Their activity is disrupted in many tumour types. Recent studies show that some of these proteins have interesting alternative functions, acting in the cytoplasm to regulate Rho signalling and thereby controlling cytoskeletal organization and cell migration. The upregulation of CKIs in the cytoplasm of many cancer cells indicates that although loss of nuclear CKIs is important for cancer cell proliferation, gain of cytoplasmic CKI function might be involved in tumour invasion and metastasis.
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Affiliation(s)
- Arnaud Besson
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Division of Basic Science, Seattle, Washington 98109, USA
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186
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Sa G, Stacey DW. P27 expression is regulated by separate signaling pathways, downstream of Ras, in each cell cycle phase. Exp Cell Res 2004; 300:427-39. [PMID: 15475007 DOI: 10.1016/j.yexcr.2004.07.032] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 07/30/2004] [Indexed: 11/20/2022]
Abstract
The cyclin inhibitory protein p27Kip1 (p27) plays a vital role in regulating cell proliferation in response to the extracellular growth environment. Active proliferation requires the suppression of p27 levels throughout the cell cycle. Late in the cell cycle, p27 degradation requires phosphorylation of Thr 187 by cyclin dependent kinase 2, leading to recognition by the SCF ubiquitin ligase containing the Skp2 F-box protein. Suppression of p27 is also essential for cell proliferation early in the cell cycle, but this occurs independently of Skp2, whose expression is suppressed during G1 phase. In this study, we use a time lapse and quantitative imaging approach to study the connection between proliferative signaling and the degradation of p27 during each cell cycle period in actively cycling cells. Ras activity was required for the suppression of p27 levels throughout the cell cycle, but separate pathways downstream of Ras signaling were required in different cell cycle periods. For example, inhibitors of MEK and phosphatidylinositol-3-kinase induced p27 expression primarily in G1 phase, while inhibitors of AKT activity stimulated these levels primarily in S phase. Skp2 was expressed in a Ras-dependent manner at higher levels late in the cell cycle. Its ablation resulted in higher p27 levels primarily in G2 phase as expected. The fact that separate signaling pathways downstream of Ras function in each cell cycle phase to suppress p27 levels helps explain the vital connection between proliferative signaling, cell cycle control, and p27 expression.
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Affiliation(s)
- Gaurisankar Sa
- Department of Molecular Biology, The Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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187
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Kotake Y, Nakayama K, Ishida N, Nakayama KI. Role of serine 10 phosphorylation in p27 stabilization revealed by analysis of p27 knock-in mice harboring a serine 10 mutation. J Biol Chem 2004; 280:1095-102. [PMID: 15528185 DOI: 10.1074/jbc.m406117200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The inhibition of cyclin-dependent kinase activity by p27 contributes to regulation of cell cycle progression. Serine 10 is the major phosphorylation site of p27, and its phosphorylation has been shown to affect the stability and nuclear export of p27 at the G0-G1 transition in transfected cultured cells. To investigate the physiological relevance of p27 phosphorylation on Ser10, we generated p27 "knock-in" mice that harbor an S10A mutation in this protein. Mice homozygous for the mutation (p27(S10A/S10A) mice) were normal in body size, but the abundance of p27 was decreased in many organs, including brain, thymus, spleen, and testis. The stability of p27 in G0 phase was markedly reduced in lymphocytes of p27(S10A/S10A) mice compared with that in wild-type cells, whereas p27 stability in S phase was similar in cells of the two genotypes. The degradation of p27 in cells of the mutant mice at G0 phase was prevented by a proteasome inhibitor. These data indicate that the physiological role of p27 phosphorylation on Ser10 is to stabilize the protein in G0 phase. Unexpectedly, the nuclear export of p27 at the G0-G1 transition occurred normally in p27(S10A/S10A) mouse embryonic fibroblasts, indicating that phosphorylation of Ser10 is dispensable for this process.
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Affiliation(s)
- Yojiro Kotake
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Fukuoka 812-8582, Japan
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188
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Min YH, Cheong JW, Kim JY, Eom JI, Lee ST, Hahn JS, Ko YW, Lee MH. Cytoplasmic mislocalization of p27Kip1 protein is associated with constitutive phosphorylation of Akt or protein kinase B and poor prognosis in acute myelogenous leukemia. Cancer Res 2004; 64:5225-31. [PMID: 15289327 DOI: 10.1158/0008-5472.can-04-0174] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cyclin-dependent kinase inhibitor p27Kip1 functions at the nuclear level by binding to cyclin E/cyclin-dependent kinase-2. It was shown that Akt or protein kinase B (Akt/PKB)-dependent phosphorylation of p27Kip1 led to the cytoplasmic mislocalization of p27Kip1, suggesting the potential abrogation of its activity. Here, we evaluated the localization of p27Kip1 protein in leukemic blasts in relation to Akt/PKB phosphorylation and clinical outcomes in acute myelogenous leukemia (AML). Western blot analysis of the nuclear and cytoplasmic fractions revealed a heterogenous localization pattern of p27Kip1 in AML. Cytoplasmic mislocalization of p27Kip1 was significantly associated with the constitutive serine(473) Akt/PKB phosphorylation in AML cells (P < 0.05). Transfection of U937 cells with an expression construct encoding the constitutively active form of Akt/PKB resulted in a remarkable increase in the levels of cytoplasmic p27Kip1. Whereas the transfection of U937 cells with a construct encoding dominant-negative Akt/PKB resulted in a recovery of nuclear localization of p27Kip1. Both the disease-free survival and overall survival are significantly shorter in AML cases with high cytoplasmic to nuclear ratio of p27Kip1 localization compared with the cases with low cytoplasmic to nuclear ratio (P = 0.0353, P = 0.0023, respectively). Multivariate analysis indicated that the cytoplasmic to nuclear ratio of p27Kip1 localization was an independent prognostic variable for both disease-free survival and overall survival (P = 0.043, P = 0.008, respectively). These findings additionally extend our understanding of the role of p27Kip1 in AML, and buttress the case of p27Kip1 mislocalization as a prognostic indicator and Akt/PKB/p27Kip1 pathway as a ready target for antileukemia therapy.
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Affiliation(s)
- Yoo Hong Min
- Department of Internal Medicine, Yonsei University College of Medicine, Seodaemun-ku Shinchon-dong 134, Seoul 120-752, Korea.
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189
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Yiu SM, Wong PWH, Lam TW, Mui YC, Kung HF, Lin M, Cheung YT. Filtering of Ineffective siRNAs and Improved siRNA Design Tool. Bioinformatics 2004; 21:144-51. [PMID: 15333460 DOI: 10.1093/bioinformatics/bth498] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
MOTIVATION Short interfering RNAs (siRNAs) can be used to suppress gene expression and possess many potential applications in therapy, but how to design an effective siRNA is still not clear. Based on the MPI (Max-Planck-Institute) basic principles, a number of siRNA design tools have been developed recently. The set of candidates reported by these tools is usually large and often contains ineffective siRNAs. In view of this, we initiate the study of filtering ineffective siRNAs. RESULTS The contribution of this paper is 2-fold. First, we propose a fair scheme to compare existing design tools based on real data in the literature. Second, we attempt to improve the MPI principles and existing tools by an algorithm that can filter ineffective siRNAs. The algorithm is based on some new observations on the secondary structure, which we have verified by AI techniques (decision trees and support vector machines). We have tested our algorithm together with the MPI principles and the existing tools. The results show that our filtering algorithm is effective. AVAILABILITY The siRNA design software tool can be found in the website http://www.cs.hku.hk/~sirna/ CONTACT smyiu@cs.hku.hk
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Affiliation(s)
- S M Yiu
- Department of Computer Science, University of Hong Kong, Hong Kong.
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190
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Abstract
Recent structures of the heterodimeric splicing factor U2 snRNP auxiliary factor (U2AF) have revealed two unexpected examples of RNA recognition motif (RRM)-like domains with specialized features for protein recognition. These unusual RRMs, called U2AF homology motifs (UHMs), represent a novel class of protein recognition motifs. Defining a set of rules to distinguish traditional RRMs from UHMs is key to identifying novel UHM family members. Here we review the critical sequence features necessary to mediate protein-UHM interactions, and perform comprehensive database searches to identify new members of the UHM family. The resulting implications for the functional and evolutionary relationships among candidate UHM family members are discussed.
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Affiliation(s)
- Clara L. Kielkopf
- Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
- Corresponding author. E-MAIL ; FAX (410) 955-2926
| | - Stephan Lücke
- Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Michael R. Green
- Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
- Corresponding author. E-MAIL ; FAX (508) 856-5473
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191
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Abstract
Ubiquitin-mediated proteolysis has emerged as a paramount mechanism for regulating the cell division cycle. Changes in the activities of certain E3 ligases can promote the interconversion of cell cycle states or transitions. Recent studies have revealed how distinct E3 ligases control the activity of other E3 ligases and how the interplay between these degradation machines sets up the timing of cell cycle transitions. For example, during G1, the anaphase-promoting complex in conjunction with Cdh1 (APC(Cdh1)) catalyzes destruction of the S-phase activator Skp2, helping to define the G1 state. In response to poorly defined signals, APC(Cdh1) activity is reduced, allowing accumulation of Skp2 and therefore entry into S phase. In many cases, E3 ligases also function to ubiquitinate proteins that negatively regulate cell cycle transitions. Recent work indicates that cyclin-dependent kinase 2 and Polo kinase collaborate to phosphorylate Wee1, thereby promoting its ubiquitination by SCF(beta-TRCP). Thus, activation of the mitotic transition produces feedback signals that help to turn off the negative upstream pathway to further reenforce the transition.
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Affiliation(s)
- Xiaolu L Ang
- Program in Biological and Biomedical Sciences, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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192
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Snøve O, Holen T. Many commonly used siRNAs risk off-target activity. Biochem Biophys Res Commun 2004; 319:256-63. [PMID: 15158470 DOI: 10.1016/j.bbrc.2004.04.175] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 02/07/2023]
Abstract
Using small interfering RNA (siRNA) to induce sequence specific gene silencing is fast becoming a standard tool in functional genomics. As siRNAs in some cases tolerate mismatches with the mRNA target, knockdown of genes other than the intended target could make results difficult to interpret. In an investigation of 359 published siRNA sequences, we have found that about 75% of them have a risk of eliciting non-specific effects. A possible cause for this is the popular BLAST search engine, which is inappropriate for such short oligos as siRNAs. Furthermore, we used new special purpose hardware to do a transcriptome-wide screening of all possible siRNAs, and show that many unique siRNAs exist per target even if several mismatches are allowed. Hence, we argue that the risk of off-target effects is unnecessary and should be avoided in future siRNA design.
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Affiliation(s)
- Ola Snøve
- Interagon AS, Medisinsk-teknisk senter, NO-7489, Trondheim, Norway
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193
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Vitagliano D, Carlomagno F, Motti ML, Viglietto G, Nikiforov YE, Nikiforova MN, Hershman JM, Ryan AJ, Fusco A, Melillo RM, Santoro M. Regulation of p27Kip1 Protein Levels Contributes to Mitogenic Effects of the RET/PTC Kinase in Thyroid Carcinoma Cells. Cancer Res 2004; 64:3823-9. [PMID: 15172989 DOI: 10.1158/0008-5472.can-03-3918] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We show that treatment of a panel of thyroid carcinoma cell lines naturally harboring the RET/PTC1 oncogene, with the RET kinase inhibitors PP1 and ZD6474, results in reversible G(1) arrest. This is accompanied by interruption of Shc and mitogen-activated protein kinase (MAPK) phosphorylation, reduced levels of G(1) cyclins, and increased levels of the cyclin-dependent kinase inhibitor p27Kip1 because of a reduced protein turnover. MAP/extracellular signal-regulated kinase 1/2 inhibition by U0126 caused G(1) cyclins down-regulation and p27Kip1 up-regulation as well. Forced expression of RET/PTC in normal thyroid follicular cells caused a MAPK- and proteasome-dependent down-regulation of p27Kip1. Reduction of p27Kip1 protein levels by antisense oligonucleotides abrogated the G(1) arrest induced by RET/PTC blockade. Therefore, in thyroid cancer, RET/PTC-mediated MAPK activation contributes to p27Kip1 deregulation. This pathway is implicated in cell cycle progression and in response to small molecule kinase inhibitors.
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Affiliation(s)
- Donata Vitagliano
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, University 'Federico II' c/o Istituto di Endocrinologia ed Oncologia Sperimentale, Consiglio Nazionale delle Ricerche, Naples, Italy
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194
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Deng X, Mercer SE, Shah S, Ewton DZ, Friedman E. The cyclin-dependent kinase inhibitor p27Kip1 is stabilized in G(0) by Mirk/dyrk1B kinase. J Biol Chem 2004; 279:22498-504. [PMID: 15010468 DOI: 10.1074/jbc.m400479200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Elevated levels of the cyclin-dependent kinase (CDK) inhibitor p27 block the cell in G(0)/G(1) until mitogenic signals activate G(1) cyclins and initiate proliferation. Post-translational regulation of p27 by different phosphorylation events is critical in allowing cells to proceed through the cell cycle. We now demonstrate that the arginine-directed kinase, Mirk/dyrk1B, is maximally active in G(0) in NIH3T3 cells, when it stabilizes p27 by phosphorylating it at Ser-10. The phospho-mimetic mutant p27-S10D was more stable, and the non-phosphorylatable mutant p27-S10A was less stable than wild-type when expressed in G(0)-arrested cells. Following phosphorylation by Mirk, p27 remains a functional CDK inhibitor, capable of binding to CDK2. Mirk did not induce the translocation of p27 from the nucleus in G(0), but instead co-localized with nuclear p27. Depletion of Mirk by RNA interference decreased the phosphorylation of p27 at Ser-10 and the stability of endogenous p27. RNA(i) to Mirk increased cell entry from G(0) into G(1) as shown by increased expression of proliferating cell nuclear antigen and decreased expression of p27. These data suggest a model in which Mirk increases the amount of nuclear p27 by stabilizing it during G(0) when Mirk is most abundant. Mitogen stimulation then causes cells to enter G(1), reduces Mirk levels (Deng, X., Ewton, D., Pawlikowski, B., Maimone, M., and Friedman, E. (2003) J. Biol. Chem. 278, 41347-41354), and initiates the translocation of p27 to the cytoplasm. In addition, depletion of Mirk by RNA(i) in postmitotic C2C12 myoblasts decreased protein but not mRNA levels of p27, suggesting that stabilization of p27 by Mirk also occurs during differentiation.
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Affiliation(s)
- Xiaobing Deng
- Upstate Medical University, State University of New York, Syracuse, New York 13210, USA
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195
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Han HC, Austin KJ, Nathanielsz PW, Ford SP, Nijland MJ, Hansen TR. Maternal nutrient restriction alters gene expression in the ovine fetal heart. J Physiol 2004; 558:111-21. [PMID: 15133065 PMCID: PMC1664914 DOI: 10.1113/jphysiol.2004.061697] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adequate maternal nutrient supply is critical for normal fetal organogenesis. We previously demonstrated that a global 50% nutrient restriction during the first half of gestation causes compensatory growth of both the left and right ventricles of the fetal heart by day 78 of gestation. Thus, it was hypothesized that maternal nutrient restriction significantly altered gene expression in the fetal cardiac left ventricle (LV). Pregnant ewes were randomly grouped into control (100% national research council (NRC) requirements) or nutrient-restricted groups (50% NRC requirements) from day 28 to day 78 of gestation, at which time fetal LV were collected. Fetal LV mRNA was used to construct a suppression subtraction cDNA library from which 11 cDNA clones were found by differential dot blot hybridization and virtual Northern analysis to be up-regulated by maternal nutrient restriction: caveolin, stathmin, G-1 cyclin, alpha-actin, titin, cardiac ankyrin repeat protein (CARP), cardiac-specific RNA-helicase activated by MEF2C (CHAMP), endothelial and smooth muscle derived neuropilin (ESDN), prostatic binding protein, NADH dehydrogenase subunit 2, and an unknown protein. Six of these clones (cardiac alpha-actin, cyclin G1, stathmin, NADH dehydrogenase subunit 2, titin and prostatic binding protein) have been linked to cardiac hypertrophy in other species including humans. Of the remaining clones, caveolin, CARP and CHAMP have been shown to inhibit remodelling of hypertrophic tissue. Compensatory growth of fetal LV in response to maternal undernutrition is concluded to be associated with increased transcription of genes related to cardiac hypertrophy, compensatory growth or remodelling. Counter-regulatory gene transcription may be increased, in part, as a response to moderating the degree of cardiac remodelling. The short- and long-term consequences of these changes in fetal heart gene expression and induction of specific homeostatic mechanisms in response to maternal undernutrition remain to be determined.
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Affiliation(s)
- Hyung-Chul Han
- Center for the Study of Fetal Programming and Department of Animal Science, University of Wyoming, Laramie, WY 82071, USA
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196
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Affiliation(s)
- Catherine Denicourt
- Howard Hughes Medical Institute, and Department of Cellular and Molecular Medicine, University of California San Diego School of Medicine, La Jolla, CA 92093-0686, USA
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197
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Besson A, Gurian-West M, Schmidt A, Hall A, Roberts JM. p27Kip1 modulates cell migration through the regulation of RhoA activation. Genes Dev 2004; 18:862-76. [PMID: 15078817 PMCID: PMC395846 DOI: 10.1101/gad.1185504] [Citation(s) in RCA: 412] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The tumor suppressor p27(Kip1) is an inhibitor of cyclin/cyclin-dependent kinase (CDK) complexes and plays a crucial role in cell cycle regulation. However, p27(Kip1) also has cell cycle-independent functions. Indeed, we find that p27(Kip1) regulates cell migration, as p27(Kip1)-null fibroblasts exhibit a dramatic decrease in motility compared with wild-type cells. The regulation of motility by p27(Kip1) is independent of its cell-cycle regulatory functions, as re-expression of both wild-type p27(Kip1) and a mutant p27(Kip1) (p27CK(-)) that cannot bind to cyclins and CDKs rescues migration of p27(-/-) cells. p27(-/-) cells have increased numbers of actin stress fibers and focal adhesions. This is reminiscent of cells in which the Rho pathway is activated. Indeed, active RhoA levels were increased in cells lacking p27(Kip1). Moreover, inhibition of ROCK, a downstream effector of Rho, was able to rescue the migration defect of p27(-/-) cells in response to growth factors. Finally, we found that p27(Kip1) binds to RhoA, thereby inhibiting RhoA activation by interfering with the interaction between RhoA and its activators, the guanine-nucleotide exchange factors (GEFs). Together, the data suggest a novel role for p27(Kip1) in regulating cell migration via modulation of the Rho pathway.
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Affiliation(s)
- Arnaud Besson
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Division of Basic Science, Seattle, WA 98109, USA
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198
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Sekimoto T, Fukumoto M, Yoneda Y. 14-3-3 suppresses the nuclear localization of threonine 157-phosphorylated p27(Kip1). EMBO J 2004; 23:1934-42. [PMID: 15057270 PMCID: PMC404318 DOI: 10.1038/sj.emboj.7600198] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Accepted: 03/11/2004] [Indexed: 01/12/2023] Open
Abstract
p27(Kip1) (p27), a CDK inhibitor, migrates into the nucleus, where it controls cyclin-CDK complex activity for proper cell cycle progression. We report here that the classical bipartite-type basic amino-acid cluster and the two downstream amino acids of the C-terminal region of p27 function as a nuclear localization signal (NLS) for its full nuclear import activity. Importin alpha3 and alpha5, but not alpha1, transported p27 into the nucleus in conjunction with importin beta, as evidenced by an in vitro transport assay. It is known that Akt phosphorylates Thr 157 of p27 and this reduces the nuclear import activity of p27. Using a pull-down experiment, 14-3-3 was identified as the Thr157-phosphorylated p27NLS-binding protein. Although importin alpha5 bound to Thr157-phosphorylated p27NLS, 14-3-3 competed with importin alpha5 for binding to it. Thus, 14-3-3 sequestered phosphorylated p27NLS from importin alpha binding, resulting in cytoplasmic localization of NLS-phosphorylated p27. These findings indicate that 14-3-3 suppresses importin alpha/beta-dependent nuclear localization of Thr157-phosphorylated p27, suggesting implications for cell cycle disorder in Akt-activated cancer cells.
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Affiliation(s)
- Toshihiro Sekimoto
- Department of Cell Biology and Neuroscience, Graduate School of Medicine, Osaka University, Yamada-oka, Suita, Osaka, Japan
| | - Masahiro Fukumoto
- Department of Cell Biology and Neuroscience, Graduate School of Medicine, Osaka University, Yamada-oka, Suita, Osaka, Japan
| | - Yoshihiro Yoneda
- Department of Cell Biology and Neuroscience, Graduate School of Medicine, Osaka University, Yamada-oka, Suita, Osaka, Japan
- Laboratories for Biomolecular Networks, Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, Yamada-oka, Suita, Osaka, Japan
- Laboratories for Biomolecular Networks, Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan. Tel.: +81 6 6879 3210; Fax: +81 6 6879 3219; E-mail:
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199
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Abstract
p27Kip1 is an important regulator of the G1 to S transition. While a potent inhibitor of cyclin-dependent-kinase (Cdk)2, p27 is also involved in assembly of cyclin D/Cdk4 complexes. Although rarely mutated, p27 is functionally downregulated in many human cancers by mechanisms involving enhanced degradation, cytoplasmic mislocalization, and/or sequestration by cyclin D/Cdk complexes in response to oncogenic signals. Therefore, low levels and/or cytoplasmic localized p27 have been associated with enhanced malignancy and poor patient prognosis in many neoplasias including breast cancer. Recent data discussed below suggest that a threshold of p27 is required for response to antiestrogens and, conversely, that low levels predict for antiestrogen resistance. These results imply that hormone receptor-positive tumors with low and/or cytosolic p27 respond poorly to antiestrogens and should be considered for alternative therapeutic strategies.
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Affiliation(s)
- Carlos L Arteaga
- Departments of Medicine and Cancer Biology and Breast Cancer Program, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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200
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Brown KA, Roberts RL, Arteaga CL, Law BK. Transforming growth factor-beta induces Cdk2 relocalization to the cytoplasm coincident with dephosphorylation of retinoblastoma tumor suppressor protein. Breast Cancer Res 2004; 6:R130-9. [PMID: 14979923 PMCID: PMC400660 DOI: 10.1186/bcr762] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2003] [Revised: 01/05/2004] [Accepted: 01/15/2004] [Indexed: 01/07/2023] Open
Abstract
Background The transforming growth factor-β (TGF-β) signaling pathway functions to prevent tumorigenesis, and loss of sensitivity to TGF-β-mediated cell cycle arrest is nearly ubiquitous among human cancers. Our previous studies demonstrated that rapamycin potentiates TGF-β-induced cell cycle arrest in nontransformed epithelial cells and partially restores TGF-β-induced growth arrest of some human cancer cell lines. Growth arrest correlated with increased binding of p21 and p27 to cyclin-dependent kinase-2 (Cdk2), and inhibition of Cdk2 kinase activity. However, it was unclear how TGF-β caused increased binding of p21 and p27 to Cdk2. Methods Cell fractionation and immunofluorescence microscopy experiments were performed to examine the effect of TGF-β on the intracellular localization of Cdk2, p21, and p27. Kinase assays were performed on cytoplasmic and nuclear extracts to determine how TGF-β altered Cdk2 activity in both subcellular compartments. Results In breast epithelial cells treatment with TGF-β induced a decrease in nuclear Cdk2 concentrations and relocalization of Cdk2 to the cytoplasm. Cdk2 relocalization to the cytoplasm correlated with dephosphorylation of nuclear retinoblastoma tumor suppressor protein and decreased nuclear Cdk2 activity. In these epithelial cell lines, p21 and p27 were localized primarily in the cytoplasm. Decreases in nuclear Cdk2 concentrations correlated with increased binding of Cdk2 to cytoplasmic p21 and p27. Conclusion Cooperative growth arrest induced by treatment with TGF-β + rapamycin causes inhibition of nuclear Cdk2 activity through multiple mechanisms, including Cdk2 relocalization to the cytoplasm, increased p27 and p21 binding to Cdk2, and increased phosphorylation of nuclear Cdk2 on its inhibitory site, Tyr15.
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Affiliation(s)
- Kimberly A Brown
- Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Richard L Roberts
- Department of Pathology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Carlos L Arteaga
- Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Brian K Law
- Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, USA
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