1
|
Ventura E, Iannuzzi CA, Pentimalli F, Giordano A, Morrione A. RBL1/p107 Expression Levels Are Modulated by Multiple Signaling Pathways. Cancers (Basel) 2021; 13:cancers13195025. [PMID: 34638509 PMCID: PMC8507926 DOI: 10.3390/cancers13195025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/29/2021] [Accepted: 10/02/2021] [Indexed: 11/16/2022] Open
Abstract
The members of the retinoblastoma (RB) protein family, RB1/p105, retinoblastoma-like (RBL)1/p107 and RBL2/p130 are critical modulators of the cell cycle and their dysregulation has been associated with tumor initiation and progression. The activity of RB proteins is regulated by numerous pathways including oncogenic signaling, but the molecular mechanisms of these functional interactions are not fully defined. We previously demonstrated that RBL2/p130 is a direct target of AKT and it is a key mediator of the apoptotic process induced by AKT inhibition. Here we demonstrated that RBL1/p107 levels are only minorly modulated by the AKT signaling pathway. In contrast, we discovered that RBL1/p107 levels are regulated by multiple pathways linked directly or indirectly to Ca2+-dependent signaling. Inhibition of the multifunctional calcium/calmodulin-dependent kinases (CaMKs) significantly reduced RBL1/p107 expression levels and phosphorylation, increased RBL1/p107 nuclear localization and led to cell cycle arrest in G0/G1. Targeting the Ca2+-dependent endopeptidase calpain stabilized RBL1/p107 levels and counteracted the reduction of RBL1/p107 levels associated with CaMKs inhibition. Thus, these novel observations suggest a complex regulation of RBL1/p107 expression involving different components of signaling pathways controlled by Ca2+ levels, including CaMKs and calpain, pointing out a significant difference with the mechanisms modulating the close family member RBL2/p130.
Collapse
Affiliation(s)
- Elisa Ventura
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
| | - Carmelina Antonella Iannuzzi
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, I-80131 Napoli, Italy; (C.A.I.); (F.P.)
| | - Francesca Pentimalli
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, I-80131 Napoli, Italy; (C.A.I.); (F.P.)
| | - Antonio Giordano
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
- Department of Medical Biotechnologies, University of Siena, I-53100 Siena, Italy
| | - Andrea Morrione
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA; (E.V.); (A.G.)
- Correspondence: ; Tel.: +215-204-2450
| |
Collapse
|
2
|
Verdugo-Sivianes EM, Carnero A. Role of the Holoenzyme PP1-SPN in the Dephosphorylation of the RB Family of Tumor Suppressors During Cell Cycle. Cancers (Basel) 2021; 13:cancers13092226. [PMID: 34066428 PMCID: PMC8124259 DOI: 10.3390/cancers13092226] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/29/2021] [Accepted: 05/03/2021] [Indexed: 11/16/2022] Open
Abstract
Simple Summary Cell cycle progression is highly regulated by modulating the phosphorylation status of retinoblastoma (RB) family proteins. This process is controlled by a balance in the action of kinases, such as the complexes formed by cyclin-dependent kinases (CDKs) and cyclins, and phosphatases, mainly the protein phosphatase 1 (PP1). However, while the phosphorylation of the RB family has been largely studied, its dephosphorylation is less known. Recently, the PP1-Spinophilin (SPN) holoenzyme has been described as the main phosphatase responsible for the dephosphorylation of RB proteins during the G0/G1 transition and at the end of G1. Here, we describe the regulation of the phosphorylation status of RB family proteins, giving importance not only to their inactivation by phosphorylation but also to their dephosphorylation to restore the cell cycle. Abstract Cell cycle progression is highly regulated by modulating the phosphorylation status of the retinoblastoma protein (pRB) and the other two members of the RB family, p107 and p130. This process is controlled by a balance in the action of kinases, such as the complexes formed by cyclin-dependent kinases (CDKs) and cyclins, and phosphatases, mainly the protein phosphatase 1 (PP1). However, while the phosphorylation of the RB family has been largely studied, its dephosphorylation is less known. Phosphatases are holoenzymes formed by a catalytic subunit and a regulatory protein with substrate specificity. Recently, the PP1-Spinophilin (SPN) holoenzyme has been described as the main phosphatase responsible for the dephosphorylation of RB proteins during the G0/G1 transition and at the end of G1. Moreover, SPN has been described as a tumor suppressor dependent on PP1 in lung and breast tumors, where it promotes tumorigenesis by increasing the cancer stem cell pool. Therefore, a connection between the cell cycle and stem cell biology has also been proposed via SPN/PP1/RB proteins.
Collapse
Affiliation(s)
- Eva M. Verdugo-Sivianes
- Instituto de Biomedicina de Sevilla, IBIS, Hospital Universitario Virgen del Rocio, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Avda. Manuel Siurot s/n, 41013 Seville, Spain;
- CIBERONC, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Amancio Carnero
- Instituto de Biomedicina de Sevilla, IBIS, Hospital Universitario Virgen del Rocio, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Avda. Manuel Siurot s/n, 41013 Seville, Spain;
- CIBERONC, Instituto de Salud Carlos III, 28029 Madrid, Spain
- Correspondence: ; Tel.: +34-955-92-31-11
| |
Collapse
|
3
|
Cunarro J, Buque X, Casado S, Lugilde J, Vidal A, Mora A, Sabio G, Nogueiras R, Aspichueta P, Diéguez C, Tovar S. p107 Deficiency Increases Energy Expenditure by Inducing Brown-Fat Thermogenesis and Browning of White Adipose Tissue. Mol Nutr Food Res 2018; 63:e1801096. [PMID: 30383332 DOI: 10.1002/mnfr.201801096] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 10/24/2018] [Indexed: 11/07/2022]
Abstract
SCOPE The tumor suppressor p107, a pocket protein member of the retinoblastoma susceptibility protein family, plays an important role in the cell cycle and cellular adipocyte differentiation. Nonetheless, the mechanism by which it influences whole body Energy homeostasis is unknown. METHODS AND RESULTS The phenotype of p107 knockout (KO) mixed-background C57BL6/129 mice phenotype is studied by focusing on the involvement of white and brown adipose tissue (WAT and BAT) in energy metabolism. It is shown that p107 KO mice are leaner and have high-fat diet resistence. This phenomenon is explained by an increase of energy expenditure. The higher energy expenditure is caused by the activation of thermogenesis and may be mediated by both BAT and the browning of WAT. Consequently, it leads to the resistance of p107 KO mice to high-fat diet effects, prevention of liver steatosis, and improvement of the lipid profile and glucose homeostasis. CONCLUSION These data allowed the unmasking of a mechanism by which a KO of p107 prevents diet-induced obesity by increasing energy expenditure via increased thermogenesis in BAT and browning of WAT, indicating the relevance of p107 as a modulator of metabolic activity of both brown and white adipocytes. Therefore, it can be targeted for the development of new therapies to ameliorate the metabolic syndrome.
Collapse
Affiliation(s)
- Juan Cunarro
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
- CIBER Fisiopatología, de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Xabier Buque
- Department of Physiology, University of the Basque Country UPV/EHU, 48940, Leioa, Spain
- Biocruces Research Institute, 48903, Barakaldo, Bizkaia, Spain
| | - Sabela Casado
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
- CIBER Fisiopatología, de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Javier Lugilde
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
| | - Anxo Vidal
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
| | - Alfonso Mora
- Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029, Madrid, Spain
| | - Guadalupe Sabio
- Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029, Madrid, Spain
| | - Rubén Nogueiras
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
- CIBER Fisiopatología, de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Patricia Aspichueta
- Department of Physiology, University of the Basque Country UPV/EHU, 48940, Leioa, Spain
- Biocruces Research Institute, 48903, Barakaldo, Bizkaia, Spain
| | - Carlos Diéguez
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
- CIBER Fisiopatología, de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| | - Sulay Tovar
- Centro de Investigación en Medicina Molecular (CIMUS), Universidade de Santiago de Compostela and Instituto de Investigaciones Sanitarias de Santiago de Compostela (IDIS), 15782, Santiago de Compostela, Spain
- CIBER Fisiopatología, de la Obesidad y Nutrición (CIBERobn), 15706, Spain
| |
Collapse
|
4
|
Liban TJ, Thwaites MJ, Dick FA, Rubin SM. Structural Conservation and E2F Binding Specificity within the Retinoblastoma Pocket Protein Family. J Mol Biol 2016; 428:3960-3971. [PMID: 27567532 DOI: 10.1016/j.jmb.2016.08.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 06/24/2016] [Accepted: 08/17/2016] [Indexed: 11/24/2022]
Abstract
The human pocket proteins retinoblastoma (Rb), p107, and p130 are critical negative regulators of the cell cycle and contribute to tumor suppression. While strong structural conservation within the pocket protein family provides for some functional redundancy, important differences have been observed and may underlie the reason that Rb is a uniquely potent tumor suppressor. It has been proposed that distinct pocket protein activities are mediated by their different E2F transcription factor binding partners. In humans, Rb binds E2F1-E2F5, whereas p107 and p130 almost exclusively associate with E2F4 and E2F5. To identify the molecular determinants of this specificity, we compared the crystal structures of Rb and p107 pocket domains and identified several key residues that contribute to E2F selectivity in the pocket family. Mutation of these residues in p107 to match the analogous residue in Rb results in an increase in affinity for E2F1 and E2F2 and an increase in the ability of p107 to inhibit E2F2 transactivation. Additionally, we investigated how phosphorylation by Cyclin-dependent kinase on distinct residues regulates p107 affinity for the E2F4 transactivation domain. We found that phosphorylation of residues S650 and S975 weakens the E2F4 transactivation domain binding. Our data reveal molecular features of pocket proteins that are responsible for their similarities and differences in function and regulation.
Collapse
Affiliation(s)
- Tyler J Liban
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Michael J Thwaites
- Department of Biochemistry, Western University, London Regional Cancer Program and Children's Health Research Institute, London, Ontario, Canada
| | - Frederick A Dick
- Department of Biochemistry, Western University, London Regional Cancer Program and Children's Health Research Institute, London, Ontario, Canada
| | - Seth M Rubin
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
| |
Collapse
|
5
|
Effector mechanisms of sunitinib-induced G1 cell cycle arrest, differentiation, and apoptosis in human acute myeloid leukaemia HL60 and KG-1 cells. Ann Hematol 2012. [PMID: 23180436 DOI: 10.1007/s00277-012-1627-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Acute myeloid leukaemia (AML) is a heterogeneous disease with dismal outcome. Sunitinib is an orally active inhibitor of multiple tyrosine kinase receptors approved for renal cell carcinoma and gastrointestinal stromal tumour that has also been studied for AML in several clinical trials. However, the precise mechanism of sunitinib action against AML remains unclear and requires further investigation. For this purpose, this study was conducted using human AML cell lines (HL60 and KG-1) and AML patients' mononucleated cells. Sunitinib induced G1 phase arrest associated with decreased cyclin D1, cyclin D3, and cyclin-dependent kinase (Cdk)2 and increased p27(Kip1), pRb1, and p130/Rb2 expression and phosphorylated activation of protein kinase C alpha and beta (PKCα/β). Selective PKCα/β inhibitor treatment abolished sunitinib-elicited AML differentiation, suggesting that PKCα/β may underlie sunitinib-induced monocytic differentiation. Furthermore, sunitinib increased pro-apoptotic molecule expression (Bax, Bak, PUMA, Fas, FasL, DR4, and DR5) and decreased anti-apoptotic molecule expression (Bcl-2 and Mcl-1), resulting in caspase-2, caspase-3, caspase-8, and caspase-9 activation and both death receptor and mitochondria-dependent apoptosis. Taken together, these findings provide evidence that sunitinib targets AML cells through both differentiation and apoptosis pathways. More clinical studies are urgently needed to demonstrate its optimal clinical applications in AML.
Collapse
|
6
|
Kolupaeva V, Janssens V. PP1 and PP2A phosphatases--cooperating partners in modulating retinoblastoma protein activation. FEBS J 2012; 280:627-43. [PMID: 22299668 DOI: 10.1111/j.1742-4658.2012.08511.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The retinoblastoma/pocket protein family is one of the master regulators of the eukaryotic cell cycle. It includes the retinoblastoma protein (Rb) and the related p107 and p130 proteins. The importance of the Rb pathway for homeostasis and tumour suppression is evident from the fact that inactivating mutations in Rb are frequently associated with many cancers. Rbs regulate the cell cycle by controlling the activity of the E2F family of transcription factors. The activity of Rb proteins themselves is modulated by their phosphorylation status at several Ser/Thr residues: phosphorylation by cyclin-dependent kinases inactivates Rb proteins and positively influences the transcription of genes necessary for cell cycle progression. Although the mechanisms of cyclin-dependent kinase-mediated inactivation of Rb proteins are understood in great detail, our knowledge of the process that counteracts Rb phosphorylation is still quite limited. The present review focuses on the Ser/Thr phosphatases that are responsible for the dephosphorylation and thus activation of Rb proteins. Two major scenarios are considered: (a) when pocket proteins are dephosphorylated during regular cell cycle progression and (b) when rapid dephosphorylation is dictated by external stress or growth inhibitory conditions, such as oxidative stress, UV radiation or other DNA-damaging stimuli, and cell differentiation factors. It transpires that protein phosphatase 1 and protein phosphatase 2A can efficiently modulate pocket protein activity in a highly context-dependent manner and both are tightly regulated by the presence of different regulatory subunits or interacting proteins.
Collapse
Affiliation(s)
- Victoria Kolupaeva
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
| | | |
Collapse
|
7
|
Chen H, Lin YW, Mao YQ, Wu J, Liu YF, Zheng XY, Xie LP. MicroRNA-449a acts as a tumor suppressor in human bladder cancer through the regulation of pocket proteins. Cancer Lett 2012; 320:40-7. [PMID: 22266187 DOI: 10.1016/j.canlet.2012.01.027] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 01/13/2012] [Accepted: 01/14/2012] [Indexed: 01/27/2023]
Abstract
Frequent downregulation of microRNA-449a (miR-449a) was detected in 14 human bladder cancer tissues. The restoration of miR-449a inhibited cell growth and induced G1-phase arrest in T24 and 5637 human bladder cancer cells. CDK6 and CDC25a were downregulated after miR-449a treatment, resulting in the functional accumulation of the pocket proteins Rb and p130. The growth of T24 tumor xenografts was suppressed by exogenous miR-449a, and the nuclear proliferation antigen Ki-67 was downregulated in miR-449a-treated tumors. These results suggest a tumor-suppressive role for miR-449a in human bladder cancer.
Collapse
Affiliation(s)
- Hong Chen
- Department of Urology, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China
| | | | | | | | | | | | | |
Collapse
|
8
|
Petrov N, Zhidkova O, Serikov V, Zenin V, Popov B. Induction of Wnt/β-catenin signaling in mouse mesenchymal stem cells is associated with activation of the p130 and E2f4 and formation of the p130/Gsk3β/β-catenin complex. Stem Cells Dev 2011; 21:589-97. [PMID: 21631154 DOI: 10.1089/scd.2011.0048] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Proteins p130 and E2f4, members of the retinoblastoma protein (pRb) family/E2F transcription factor family, are the key elements in regulation of cell cycle and differentiation. The functional role of the p130/E2f4 in mesenchymal stem cells (MSC) is unclear. We demonstrate here that activation of the Wnt/β-catenin pathway in mouse MSC is associated with accumulation of active forms of the p130, E2f4, and β-catenin but does not result in inhibition of cell cycle progression. The levels and phosphorylation patterns of p130, E2f4, and β-catenin in MSC do not change during cell cycle progression. This is different from control T98G glyoblastoma cells that accumulated differently phosphorylated forms of the p130 in quiescence, and under active proliferation. In MSC, synchronized at G0/G1 and S cell cycle phases, the p130 and β-catenin physically interact each other, whereas Gsk3β was associated and co-precipitated with both p130 and β-catenin. Our results indicate that Wnt/β-catenin and pRb signal pathways interact with each other and form common p130/Gsk3β/β-catenin complex during MSC cycle progression. Physiological relevance of such complex may be associated with coupling of the cell cycle and differentiation in MSC, which is related to a wide differentiation potential of these stem cells.
Collapse
Affiliation(s)
- Nikolay Petrov
- Laboratory of Cell Pathology, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | | | | | | | | |
Collapse
|
9
|
Burkhart DL, Wirt SE, Zmoos AF, Kareta MS, Sage J. Tandem E2F binding sites in the promoter of the p107 cell cycle regulator control p107 expression and its cellular functions. PLoS Genet 2010; 6:e1001003. [PMID: 20585628 PMCID: PMC2891812 DOI: 10.1371/journal.pgen.1001003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Accepted: 05/26/2010] [Indexed: 11/19/2022] Open
Abstract
The retinoblastoma tumor suppressor (Rb) is a potent and ubiquitously expressed cell cycle regulator, but patients with a germline Rb mutation develop a very specific tumor spectrum. This surprising observation raises the possibility that mechanisms that compensate for loss of Rb function are present or activated in many cell types. In particular, p107, a protein related to Rb, has been shown to functionally overlap for loss of Rb in several cellular contexts. To investigate the mechanisms underlying this functional redundancy between Rb and p107 in vivo, we used gene targeting in embryonic stem cells to engineer point mutations in two consensus E2F binding sites in the endogenous p107 promoter. Analysis of normal and mutant cells by gene expression and chromatin immunoprecipitation assays showed that members of the Rb and E2F families directly bound these two sites. Furthermore, we found that these two E2F sites controlled both the repression of p107 in quiescent cells and also its activation in cycling cells, as well as in Rb mutant cells. Cell cycle assays further indicated that activation of p107 transcription during S phase through the two E2F binding sites was critical for controlled cell cycle progression, uncovering a specific role for p107 to slow proliferation in mammalian cells. Direct transcriptional repression of p107 by Rb and E2F family members provides a molecular mechanism for a critical negative feedback loop during cell cycle progression and tumorigenesis. These experiments also suggest novel therapeutic strategies to increase the p107 levels in tumor cells. The retinoblastoma tumor suppressor Rb belongs to a family of cell cycle inhibitors along with the related proteins p107 and p130. Strong evidence indicates that the three family members have both specific and overlapping functions and expression patterns in mammalian cells, including in cancer cells. However, the molecular mechanisms underlying the functional differences and similarities among Rb, p107, and p130 are still poorly understood. One proposed mechanism of compensation is a negative feedback loop involving increased p107 transcription in Rb-deficient cells. To dissect the mechanisms controlling p107 expression in both wild-type and Rb-deficient cells, we have engineered inactivating point mutations into the E2F binding sites in the endogenous p107 promoter using gene targeting in mouse embryonic stem cells. Gene expression and DNA binding assays revealed that these two sites are essential for the control of p107 transcription in wild-type and Rb mutant cells, and cell cycle assays showed their importance for normal functions of p107. These experiments identify a key node in cell cycle regulatory networks.
Collapse
Affiliation(s)
- Deborah L. Burkhart
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, California, United States of America
- Cancer Biology Program, Stanford Medical School, Stanford, California, United States of America
| | - Stacey E. Wirt
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, California, United States of America
- Cancer Biology Program, Stanford Medical School, Stanford, California, United States of America
| | - Anne-Flore Zmoos
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, California, United States of America
| | - Michael S. Kareta
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, California, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford Medical School, Stanford, California, United States of America
| | - Julien Sage
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, California, United States of America
- Cancer Biology Program, Stanford Medical School, Stanford, California, United States of America
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford Medical School, Stanford, California, United States of America
- * E-mail:
| |
Collapse
|
10
|
Wirt SE, Sage J. p107 in the public eye: an Rb understudy and more. Cell Div 2010; 5:9. [PMID: 20359370 PMCID: PMC2861648 DOI: 10.1186/1747-1028-5-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 04/02/2010] [Indexed: 11/25/2022] Open
Abstract
p107 and its related family members Rb and p130 are critical regulators of cellular proliferation and tumorigenesis. Due to the extent of functional overlap within the Rb family, it has been difficult to assess which functions are exclusive to individual members and which are shared. Like its family members, p107 can bind a variety of cellular proteins to affect the expression of many target genes during cell cycle progression. Unlike Rb and p130, p107 is most highly expressed during the G1 to S phase transition of the cell cycle in actively dividing cells and accumulating evidence suggests a role for p107 during DNA replication. The specific roles for p107 during differentiation and development are less clear, although emerging studies suggest that it can cooperate with other Rb family members to control differentiation in multiple cell lineages. As a tumor suppressor, p107 is not as potent as Rb, yet studies in knockout mice have revealed some tumor suppressor functions in mice, depending on the context. In this review, we identify the unique and overlapping functions of p107 during the cell cycle, differentiation, and tumorigenesis.
Collapse
Affiliation(s)
- Stacey E Wirt
- Departments of Pediatrics and Genetics, Stanford Medical School, Stanford, CA 94305, USA.
| | | |
Collapse
|
11
|
Burkhart DL, Viatour P, Ho VM, Sage J. GFP reporter mice for the retinoblastoma-related cell cycle regulator p107. Cell Cycle 2008; 7:2544-52. [PMID: 18719374 DOI: 10.4161/cc.7.16.6441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The RB tumor suppressor gene is mutated in a broad range of human cancers, including pediatric retinoblastoma. Strikingly, however, Rb mutant mice develop tumors of the pituitary and thyroid glands, but not retinoblastoma. Mouse genetics experiments have demonstrated that p107, a protein related to pRB, is capable of preventing retinoblastoma, but not pituitary tumors, in Rb-deficient mice. Evidence suggests that the basis for this compensatory function of p107 is increased transcription of the p107 gene in response to Rb inactivation. To begin to address the context-dependency of this compensatory role of p107 and to follow p107 expression in vivo, we have generated transgenic mice carrying an enhanced GFP (eGFP) reporter inserted into a bacterial artificial chromosome (BAC) containing the mouse p107 gene. Expression of the eGFP transgene parallels that of p107 in these transgenic mice and identifies cells with a broad range of expression level for p107, even within particular organs or tissues. We also show that loss of Rb results in the upregulation of p107 transcription in specific cell populations in vivo, including subpopulations of hematopoietic cells. Thus, p107 BAC-eGFP transgenic mice serve as a useful tool to identify distinct cell types in which p107 is expressed and may have key functions in vivo, and to characterize changes in cellular networks accompanying Rb deficiency.
Collapse
Affiliation(s)
- Deborah L Burkhart
- Department of Pediatrics and Genetics, Cancer Biology Program, Stanford Medical School, Stanford, California, USA
| | | | | | | |
Collapse
|
12
|
Luzo ACM, Duarte ASS, Salles TSI, Queiroz MLS, Lorand-Metze I, Costa FF, Saad STO. Early proliferation of umbilical cord blood cells from premature neonates. Vox Sang 2007; 93:145-53. [PMID: 17683358 DOI: 10.1111/j.1423-0410.2007.00936.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND AND OBJECTIVE Human umbilical cord blood (UCB) is an important source of haematopoietic stem cells; however, the behaviour of progenitor cells obtained from premature and full-term neonates is still a controversy subject. Thus, the aim of this study was to evaluate cell cycle parameters and the proliferative capacity of UCB progenitor cells from premature and full-term neonates. MATERIAL AND METHODS Clonogenic assays were performed with methylcellulose, medium supplemented with recombinant stimulating growth factors and the colonies were scored on the seventh day and the 14th day of culture. A cell cycle study was carried out by DNA analysis using flow cytometry and 30 000 events were acquired; p107 and p130 expressions were analysed by Western blotting. RESULTS Cultures obtained from UCB of premature neonates showed an early growth of colony-forming unit (CFU)-burst forming unit erythroid/CFU-granulocyte, erythrocyte, macrophage and megakaryocyte (BFU-E/GEMM), and CFU-granulocyte, macrophage (GM) by the seventh day of culture (P < 0.001). Therefore, the number and morphological characteristics of these colonies were comparable with those obtained from full-term neonates, on the 14th day of culture. At the 14th day, a large amount of CFU-GM was detected in the premature group (P < 0.0032). The premature culture on the 14th day showed fibroblasts and was comparable to those of full-term neonates on the 21st day in terms of number and morphology of the colonies. DNA analysis showed that the number of cells in S-phase was also higher in premature samples when compared to full-term neonates, P < 0.0021 (0 h = 12.8 vs. 2.5%; 16 h = 10.5 vs. 5.9%; 20 h = 13.5 vs. 10.3%; 24 h = 13.8 vs. 9.1%; 48 h = 14.0 vs. 5.4%; 72 h = 20.5 vs. 8.9%; 96 h = 13.8 vs. 7.7%). The Western blotting results demonstrated that p107 and p130 cell cycle protein expressions were higher in premature cells than in full-term cells. CONCLUSION These results suggest that the higher capacity of proliferation and early differentiation of premature UCB might not be related only to the amount of stem/progenitor cells but also to a different timing of cell cycle entry.
Collapse
Affiliation(s)
- A C M Luzo
- Hemocentro and Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), CEP 13083-970 Campinas, São Paulo, Brazil
| | | | | | | | | | | | | |
Collapse
|
13
|
Williamson AJK, Smith DL, Blinco D, Unwin RD, Pearson S, Wilson C, Miller C, Lancashire L, Lacaud G, Kouskoff V, Whetton AD. Quantitative proteomics analysis demonstrates post-transcriptional regulation of embryonic stem cell differentiation to hematopoiesis. Mol Cell Proteomics 2007; 7:459-72. [PMID: 18045800 DOI: 10.1074/mcp.m700370-mcp200] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Embryonic stem (ES) cells can differentiate in vitro to produce the endothelial and hematopoietic precursor, the hemangioblasts, which are derived from the mesoderm germ layer. Differentiation of Bry(GFP/+) ES cell to hemangioblasts can be followed by the expression of the Bry(GFP/+) and Flk1 genes. Proteomic and transcriptomic changes during this differentiation process were analyzed to identify mechanisms for phenotypic change during early differentiation. Three populations of differentiating Bry(GFP) ES cells were obtained by flow cytometric sorting, GFP-Flk1- (epiblast), GFP+Flk1- (mesoderm), and GFP+Flk1+ (hemangioblast). Microarray analyses and relative quantification two-dimensional LCLC-MS/MS on nuclear extracts were performed. We identified and quantified 2389 proteins, 1057 of which were associated to their microarray probe set. These included a variety of low abundance transcription factors, e.g. UTF1, Sox2, Oct4, and E2F4, demonstrating a high level of proteomic penetrance. When paired comparisons of changes in the mRNA and protein expression levels were performed low levels of correlation were found. A strong correlation between isobaric tag-derived relative quantification and Western blot analysis was found for a number of nuclear proteins. Pathway and ontology analysis identified proteins known to be involved in the regulation of stem cell differentiation, and proteins with no described function in early ES cell development were also shown to change markedly at the proteome level only. ES cell development is regulated at the mRNA and protein level.
Collapse
Affiliation(s)
- Andrew J K Williamson
- Stem Cell and Leukemia Proteomics Laboratory, Faculty of Medical and Human Sciences, University of Manchester, Kinnaird House, Kinnaird Road, Manchester M20 4QL, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Abstract
Emerging evidence indicates that the tumor microenvironmental stress of hypoxia can induce genetic instability in cancer cells. We and others have found that the expression levels of key genes within the DNA mismatch repair (MMR) and homologous recombination (HR) pathways are coordinately repressed by hypoxia. These decreases are associated with functional impairments in both MMR and HR repair under hypoxic conditions, and thus they represent a possible mechanistic explanation for the observed phenomenon of hypoxia-induced genetic instability. In parallel, studies also indicate that several DNA damage response factors are activated in response to hypoxia and subsequent reoxygenation, including ATM/ATR, Chkl/Chk2 and BRCA1. Taken together, these findings reveal that hypoxia induces a unique cellular stress response involving an initial, acute DNA damage response to hypoxia and reoxygenation, followed by a chronic response to prolonged hypoxia in which selected DNA repair pathways are coordinately suppressed. In this review, we discuss these pathways and the possible mechanisms involved, as well as the consequences for genetic instability and tumor progression within the tumor microenvironment.
Collapse
Affiliation(s)
- Ranjit S Bindra
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520-8040, USA
| | | | | |
Collapse
|
15
|
Wang N, Xie K, Huo S, Zhao J, Zhang S, Miao J. Suppressing phosphatidylcholine-specific phospholipase C and elevating ROS level, NADPH oxidase activity and Rb level induced neuronal differentiation in mesenchymal stem cells. J Cell Biochem 2007; 100:1548-57. [PMID: 17211851 DOI: 10.1002/jcb.21139] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In the previous research, we found that D609 (tricyclodecan-9-yl-xanthogenate) could induce human marrow stromal cell (hMSC) differentiation to neuron-like cells. In this study, to understand the possible mechanism, we sequentially investigated the changes of phosphatidylcholine-specific phospholipase C (PC-PLC) activity, the expression of Rb, the intracellular reactive oxygen species (ROS) levels, NADPH oxidase and superoxide dismutase (SOD) activities when D609 induced neuronal differentiation in rat mesenchymal stem cells (MSCs). The results showed that D609 obviously inhibited the activity of PC-PLC when it induced neuronal differentiation in rat MSCs. Simultaneously, ROS level and the activity of NADPH oxidase increased significantly, but the MnSOD and Cu/ZnSOD activities were not altered. Furthermore, the level of Rb protein was evidently elevated. Our data suggested that PC-PLC mediated neuronal differentiation of rat MSCs by elevating NADPH oxidase activity, ROS level, and up-regulating the expression of Rb protein.
Collapse
Affiliation(s)
- Nan Wang
- Institute of Developmental Biology, School of Life Science, Shandong University, Jinan, China
| | | | | | | | | | | |
Collapse
|
16
|
Mangan JK, Tantravahi RV, Rane SG, Reddy EP. Granulocyte colony-stimulating factor-induced upregulation of Jak3 transcription during granulocytic differentiation is mediated by the cooperative action of Sp1 and Stat3. Oncogene 2006; 25:2489-99. [PMID: 16518416 DOI: 10.1038/sj.onc.1209280] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We previously demonstrated that Jak3 is a primary response gene for G-CSF and ectopic overexpression of Jak3 can accelerate granulocytic differentiation of normal mouse bone marrow cells induced by G-CSF and GM-CSF. To gain insight into the regulation of G-CSF-induced transcription of Jak3, we constructed deletion and linker scanning mutants of the Jak3 promoter sequences and performed luciferase reporter assays in the murine myeloid cell line 32Dcl3, with and without G-CSF stimulation. These experiments showed that mutation of a -67 to -85 element, which contained a putative Sp1 binding site, or mutation of a -44 to -53 GAS element resulted in a marked reduction of Jak3 promoter activity. Electrophoretic mobility shift assays revealed that Sp1 and Stat3 present in nuclear lysates of 32Dcl3 cells stimulated with G-CSF can bind to the -67 to -85 element and -44 to -53 GAS element, respectively. In addition, cotransfection of a constitutively active mutant of Stat3 along with a Jak3 promoter/luciferase reporter resulted in enhanced Jak3 promoter activity. Together, these results demonstrate that activation of Jak3 transcription during G-CSF- induced granulocytic differentiation is mediated by the combined action of Sp1 and Stat3, a mechanism also shown to be important in IL-6-induced monocytic differentiation.
Collapse
Affiliation(s)
- J K Mangan
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA, USA
| | | | | | | |
Collapse
|
17
|
Tamrakar S, Kapasi AJ, Spector DH. Human cytomegalovirus infection induces specific hyperphosphorylation of the carboxyl-terminal domain of the large subunit of RNA polymerase II that is associated with changes in the abundance, activity, and localization of cdk9 and cdk7. J Virol 2006; 79:15477-93. [PMID: 16306619 PMCID: PMC1316045 DOI: 10.1128/jvi.79.24.15477-15493.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus infection in the presence of the cyclin-dependent kinase (cdk) inhibitor roscovitine leads to changes in differential splicing and the polyadenylation of immediate early IE1/IE2 and UL37 transcripts (V. Sanchez, A. K. McElroy, J. Yen, S. Tamrakar, C. L. Clark, R. A. Schwartz, and D. H. Spector, J. Virol. 78:11219-11232, 2004). To determine if this was associated with specific phosphorylation of the C-terminal domain (CTD) of the RNA polymerase II (RNAP II) large subunit by cdk7/cyclin H and cdk9/cyclin T1, we examined the expression and localization of these kinases and the various phosphorylated forms of RNAP II. Infection resulted in increased RNAP II CTD phosphorylated on serines 2 and 5 and increased levels of activity of cdk7 and cdk9. At early times, cdk9 localizes with input viral DNA, and aggregates of cdk9 and cdk7 and a subset of Ser2-phosphorylated RNAP II colocalize with IE1/IE2 proteins adjacent to promyelocytic leukemia protein oncogenic domains. Later, cdk9 and Ser2-phosphorylated RNAP II form a nuclear punctate pattern; cdk7 resides in replication centers, and Ser5-phosphorylated RNAP II clusters at the peripheries of replication centers. Roscovitine treatment leads to decreased levels of hyperphosphorylated RNAP II (RNAP IIo) in infected cells and of hypophosphorylated RNAP II in mock-infected and infected cells. The RNAP IIo decrease does not occur if roscovitine is added 8 h postinfection, as was previously observed for processing of IE transcripts. These results suggest that accurate IE gene expression requires specific phosphorylation of the RNAP II CTD early in infection.
Collapse
Affiliation(s)
- Sama Tamrakar
- Cellular and Molecular Medicine East, Room 2059, Mail Code 0712, 9500 Gilman Drive, University of California, San Diego, La Jolla, California 92093-0712, USA
| | | | | |
Collapse
|
18
|
Macaluso M, Montanari M, Marshall CM, Gambone AJ, Tosi GM, Giordano A, Massaro-Giordano M. Cytoplasmic and nuclear interaction between Rb family proteins and PAI-2: a physiological crosstalk in human corneal and conjunctival epithelial cells. Cell Death Differ 2006; 13:1515-22. [PMID: 16397580 DOI: 10.1038/sj.cdd.4401835] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Extracellular plasminogen activator inhibitor type-2 (PAI-2) is a potent inhibitor of urokinase-type plasminogen activator (u-PA) and also acts as a multifunctional protein. However, the biological activity of intracellular PAI-2, as well as its intracellular targets, until now remain an enigma. Here, we show that pRb2/p130 and Rb1/p105, but not p107, interact with PAI-2 in both the cytoplasm and nucleus of normal primary human corneal and conjunctival epithelial cells. We provided the first in vivo evidence that a specific fragment of the PAI-2 promoter is bound simultaneously by pRb2/ p130, PAI-2, E2F5, histone deacetylase 1 (HDAC1), DNA methyltransferase 1 (DNMT1), and histone methyltransferase (SUV39H1), in normal primary human corneal epithelial cells, and by pRb2/p130, PAI-2, E2F5, HDAC1, and DNMT1, in normal primary human conjunctiva epithelial cells. Our results strongly indicate a physiological interaction between pRb family members and PAI-2, suggesting the hypothesis that pRb2/p130 and PAI-2 may cooperate in modulating PAI-2 gene expression by chromatin remodeling, in normal corneal and conjunctival cells.
Collapse
Affiliation(s)
- M Macaluso
- Sbarro Institute for Cancer Research and Molecular Medicine, Center of Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA.
| | | | | | | | | | | | | |
Collapse
|
19
|
Jori FP, Melone MAB, Napolitano MA, Cipollaro M, Cascino A, Giordano A, Galderisi U. RB and RB2/p130 genes demonstrate both specific and overlapping functions during the early steps of in vitro neural differentiation of marrow stromal stem cells. Cell Death Differ 2005; 12:65-77. [PMID: 15459751 DOI: 10.1038/sj.cdd.4401499] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Marrow stromal stem cells (MSCs) are stem-like cells that are currently being tested for their potential use in cell therapy for a number of human diseases. MSCs can differentiate into both mesenchymal and nonmesenchymal lineages. In fact, in addition to bone, cartilage and fat, it has been demonstrated that MSCs are capable of differentiating into neurons and astrocytes. RB and RB2/p130 genes are involved in the differentiation of several systems. For this reason, we evaluated the role of RB and RB2/p130 in the differentiation and apoptosis of MSCs under experimental conditions that allow for MSC differentiation toward the neuron-like phenotype. To this end, we ectopically expressed either RB or RB2/p130 and monitored proliferation, differentiation and apoptosis in rat primary MSC cultures induced to differentiate toward the neuron-like phenotype. Both RB and RB2/P130 decreased cell proliferation rate. In pRb-overexpressing cells, the arrest of cell growth was also observed in the presence of the HDAC-inhibitor TSA, suggesting that its antiproliferative activity does not rely upon the HDAC pathway, while the addition of TSA to pRb2/p130-overexpressing cells relieved growth inhibition. TUNEL reactions and studies on the expression of genes belonging to the Bcl-2 family showed that while RB protected differentiating MSCs from apoptosis, RB2/p130 induced an increase of apoptosis compared to controls. The effects of both RB and RB2/p130 on programmed cell death appeared to be HDAC- independent. Molecular analysis of neural differentiation markers and immunocytochemistry revealed that RB2/p130 contributes mainly to the induction of generic neural properties and RB triggers cholinergic differentiation. Moreover, the differentiation potentials of RB2/p130 and RB appear to rely, at least in part, on the activity of HDACs.
Collapse
Affiliation(s)
- F P Jori
- Department of Neurological Sciences, Second University of Naples, Naples, Italy
| | | | | | | | | | | | | |
Collapse
|
20
|
Fox BC, Crew TE, Welham MJ. Phosphoinositide 3-kinases can act independently of p27Kip1 to regulate optimal IL-3-dependent cell cycle progression and proliferation. Cell Signal 2005; 17:473-87. [PMID: 15601625 DOI: 10.1016/j.cellsig.2004.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Accepted: 09/08/2004] [Indexed: 12/01/2022]
Abstract
We have examined the role of phosphoinositide 3-kinases (PI3K) in interleukin (IL)-3-dependent cell cycle progression and compared the effects of LY294002 with expression of a dominant negative form of p85, termed Deltap85, which more specifically inhibits class I(A) PI3Ks. Inhibition of PI3Ks in BaF/3 led to accumulation of cells in G1 and extension of cell cycle transit times. Biochemically, both LY294002 and Deltap85 decreased levels of p107 and cyclins D2, D3 and E and reduced retinoblastoma protein (pRb) phosphorylation. Significantly, only LY294002 treatment increased expression of p27(Kip1). Interestingly, LY294002 decreased IL-3-induced proliferation of primary bone marrow-derived mast cells (BMMC) derived from both wild-type and p27(Kip1)-deficient mice and importantly, LY294002 treatment failed to upregulate p27(Kip1) in wild-type BMMC. These data support a role for class I(A) PI3K in regulating optimal cell cycle progression in response to IL-3 and demonstrate that upregulation of p27(Kip1) is not essential for attenuation of the cell cycle resulting from PI3K inhibition.
Collapse
Affiliation(s)
- Bridget C Fox
- Department of Pharmacy and Pharmacology, The University of Bath, Claverton Down, Bath BA2 7AY, UK
| | | | | |
Collapse
|
21
|
McCabe MT, Azih OJ, Day ML. pRb-Independent growth arrest and transcriptional regulation of E2F target genes. Neoplasia 2005; 7:141-51. [PMID: 15802019 PMCID: PMC1501127 DOI: 10.1593/neo.04394] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Revised: 09/02/2004] [Accepted: 09/13/2004] [Indexed: 01/28/2023]
Abstract
The retinoblastoma tumor suppressor (pRb) has traditionally been studied as a negative regulator of cell cycle progression through its interactions with the E2F family of transcription factors. Utilizing prostate epithelial cell lines established from Rb+/+ and Rb-/- prostate tissues, we previously demonstrated that Rb-/- epithelial cells were not transformed and retained the ability to differentiate in vivo despite the lack of pRb. To further study the effects of pRb loss in an epithelial cell population, we utilized oligonucleotide microarrays to identify any pRb-dependent transcriptional regulation during serum depletion-induced growth arrest. These studies identified 120 unique transcripts regulated by growth arrest in Rb+/+ cells. In these wild-type cells, the majority (80%) of altered transcripts were downregulated, including 40 previously identified E2F target genes. Although the transcriptional repression of E2F target genes is characteristic of pRb pocket protein family activity, further analysis revealed that, compared to Rb+/+ cells, Rb-/- cells exhibited a nearly identical response for all transcripts including those of E2F target genes. These findings demonstrate that pRb is not strictly required for the vast majority of transcriptional alterations associated with growth arrest.
Collapse
Affiliation(s)
- Michael T McCabe
- Department of Urology, University of Michigan, Ann Arbor, MI 48109-0944, USA
| | | | | |
Collapse
|
22
|
Litovchick L, Chestukhin A, DeCaprio JA. Glycogen synthase kinase 3 phosphorylates RBL2/p130 during quiescence. Mol Cell Biol 2004; 24:8970-80. [PMID: 15456871 PMCID: PMC517894 DOI: 10.1128/mcb.24.20.8970-8980.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phosphorylation of the retinoblastoma-related or pocket proteins RB1/pRb, RBL1/p107, and RBL2/p130 regulates cell cycle progression and exit. While all pocket proteins are phosphorylated by cyclin-dependent kinases (CDKs) during the G1/S-phase transition, p130 is also specifically phosphorylated in G0-arrested cells. We have previously identified several phosphorylated residues that match the consensus site for glycogen synthase kinase 3 (GSK3) in the G0 form of p130. Using small-molecule inhibitors of GSK3, site-specific mutants of p130, and phospho-specific antibodies, we demonstrate here that GSK3 phosphorylates p130 during G0. Phosphorylation of p130 by GSK3 contributes to the stability of p130 but does not affect its ability to interact with E2F4 or cyclins. Regulation of p130 by GSK3 provides a novel link between growth factor signaling and regulation of the cell cycle progression and exit.
Collapse
Affiliation(s)
- Larisa Litovchick
- Dana-Farber Cancer Institute, Mayer 457, 44 Binney St., Boston, MA 02115, USA
| | | | | |
Collapse
|
23
|
Li Q, Sakurai Y, Ryu T, Azuma K, Yoshimura K, Yamanouchi Y, Ikehara S, Kawamoto K. Expression of Rb2/p130 protein correlates with the degree of malignancy in gliomas. Brain Tumor Pathol 2004; 21:121-5. [PMID: 15696973 DOI: 10.1007/bf02482187] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
It has been reported that there is an inverse correlation between the immunohistochemical expression of Rb2/p130, a member of the retinoblastoma gene family, and the degree of malignancy in at least some histological types. In order to investigate the expression of this protein in gliomas, we evaluated 58 samples from patients with resected gliomas. We focused on the relationship between the degree of malignancy of the glioma and the immunohistochemical detection of Rb2/p130. Expression of Rb2/p130 was observed in 38 glioma specimens (65.5%), including a high expression level in low-grade glioma specimens (> 30% positive cells in 84% of tumors) and a low expression level in high-grade glioma specimens (> 30% positive cells in 12% of tumors). The most aggressive of the gliomas exhibited very low to undetectable levels of Rb2/p130. Moreover, we observed an inverse correlation between Rb2/p130 expression and the degree of malignancy. These findings suggest that the differentiation of gliomas might be partially mediated by the Rb2/p130 gene, and that Rb2/ p130 expression can additionally be an indicator of a better prognosis in patients with gliomas.
Collapse
Affiliation(s)
- Qiang Li
- Department of Neurosurgery, Kansai Medical University, Moriguchi, Osaka, Japan
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Li G, Domenico J, Lucas JJ, Gelfand EW. Identification of multiple cell cycle regulatory functions of p57Kip2 in human T lymphocytes. THE JOURNAL OF IMMUNOLOGY 2004; 173:2383-91. [PMID: 15294951 DOI: 10.4049/jimmunol.173.4.2383] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The specific functions of p57(Kip2) in lymphocytes have not yet been fully elucidated. In this study, it is shown that p57(Kip2), which is a member of the Cip/Kip family of cyclin-dependent kinase inhibitors, is present in the nuclei of normal resting (G(0)) T cells from peripheral blood and in the nuclei of the T cell-derived Jurkat cell line. Activation through the TCR results in rapid transport of cytoplasmic cyclin-dependent kinase 6 (cdk6) to nuclei, where it associates with cyclin D and p57(Kip2) in active enzyme complexes. Using purified recombinant proteins, it was shown in vitro that addition of p57(Kip2) protein to a mixture of cyclin D2 and cdk6 enhanced the association of the latter two proteins and resulted in phosphorylation of p57(Kip2). To probe further the function of p57(Kip2), Jurkat cells stably transfected with a plasmid encoding p57(Kip2) under control of an inducible (tetracycline) promoter were made. Induction of p57(Kip2) resulted in increased association of cdk6 with cyclin D3, without receptor-mediated T cell stimulation. The overall amounts of cdk6 and cyclin D3, and also of cdk4 and cyclin E, remained unchanged. Most notably, increased p57(Kip2) levels resulted in marked inhibition of both cyclin E- and cyclin A-associated cdk2 kinase activities and a decrease in cyclin A amounts. Therefore, although facilitating activation of cdk6, the ultimate outcome of p57(Kip2) induction was a decrease in DNA synthesis and cell proliferation. The results indicate that p57(Kip2) is involved in the regulation of several aspects of the T cell cycle.
Collapse
Affiliation(s)
- Guiming Li
- Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO 80206, USA
| | | | | | | |
Collapse
|
25
|
Calbó J, Serna C, Garriga J, Graña X, Mazo A. The fate of pancreatic tumor cell lines following p16 overexpression depends on the modulation of CDK2 activity. Cell Death Differ 2004; 11:1055-65. [PMID: 15309028 DOI: 10.1038/sj.cdd.4401481] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Restitution of lost tumor-suppressor activities may be a promising strategy to target specifically cancer cells. However, the action of ectopically expressed tumor-suppressor genes depends on genetic background of tumoral cells. Ectopic expression of p16(INK4a) induces either cell cycle arrest or apoptosis in different pancreatic cancer cell lines. We examined the molecular mechanisms mediating these two different cellular responses to p16 overexpression. Ectopic expression of p16 leads to G1 arrest in NP-9 cells by redistributing p21/p27 CKIs and inhibiting cyclin-dependent kinase CDK2 activity. In contrast, in NP-18 cells cyclin E (CycE)/CDK2 activity is significantly higher and is not downregulated by p16-mediated redistribution of p21/p27. Moreover, inhibition of CDK4 activity with fascaplysine, which does not affect CycE/CDK2 activity, reduces pocket protein phosphorylation in both cell lines, but fails to induce growth arrest. Like overexpression of p16, fascaplysine induces apoptosis in NP-18 cells, suggesting that inhibition of D-type cyclin/CDK activity in cells with high levels of CycE/CDK2 activity activates an apoptotic pathway. Inhibition of CycE/CDK2 activity via ectopic expression of p21 in NP-18 cells overexpressing p16 induces growth arrest and prevents p16-mediated apoptosis. Accordingly, silencing of p21 expression by using small interfering RNA switches the fate of p16-expressing NP-9 cells from cell cycle arrest to apoptosis. Our data suggest that, after CDK4/6 inactivation, the fate of pancreatic tumor cells depends on the ability to modulate CDK2 activity.
Collapse
Affiliation(s)
- J Calbó
- Department of Biochemistry and Molecular Biology, University of Barcelona, Avda. Diagonal 645, Barcelona 08028, Spain
| | | | | | | | | |
Collapse
|
26
|
Wikenheiser-Brokamp KA. Rb family proteins differentially regulate distinct cell lineages during epithelial development. Development 2004; 131:4299-310. [PMID: 15294860 DOI: 10.1242/dev.01232] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
pRb, p107 and p130 are important regulators of cell cycle and have extensive overlapping functions; however, only Rb has been shown to be a bone fide tumor suppressor. Defining the overlapping versus distinct pocket protein functions is therefore an important step to understanding the unique role of Rb. Using lung as a model, the present studies demonstrate that pocket proteins are important not only in regulating cell cycle and survival but also in cell lineage specification. An inducible lung-specific Rb knockout strategy was used to demonstrate that Rb is specifically required for restricting neuroendocrine cell fate despite functional compensation for Rb deficiency in other cell types. Ablation of total Rb family function resulted in opposing effects in specification along distinct cell lineages, providing evidence that pocket proteins inhibit neuroendocrine cell fate while being required for differentiation in other cell types. These findings identify a novel role for pocket proteins in cell fate determination, and establish a unique cell lineage-specific function for Rb that explains, at least in part, why Rb and p16 are inactivated in phenotypically distinct carcinomas.
Collapse
Affiliation(s)
- Kathryn A Wikenheiser-Brokamp
- Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO 63110, USA.
| |
Collapse
|
27
|
Lakshman M, Subramaniam V, Rubenthiran U, Jothy S. CD44 promotes resistance to apoptosis in human colon cancer cells. Exp Mol Pathol 2004; 77:18-25. [PMID: 15215046 DOI: 10.1016/j.yexmp.2004.03.002] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Indexed: 11/28/2022]
Abstract
Overexpression of CD44, especially its variant isoforms, occurs consistently in colon cancer, as compared to autologous normal colon, and this change occurs also in most other types of cancer. One of the basic features of malignant transformation is the acquisition of resistance to apoptosis. In this study, we asked whether the expression of CD44 and some of its variant isoforms commonly found in colon cancer participate in resistance to apoptosis and what are the mechanisms involved. A human colon cancer cell line, SW620, which does not express CD44 was stably transfected with standard, v3-10, and v8-10 containing isoforms of CD44. Mock-transfected and CD44-transfected cells were exposed to etoposide to induce apoptosis. Apoptotic and concomitant changes relevant to the mechanisms of apoptosis were monitored by flow cytometry, DNA fragmentation, and immunoblot analyses. It was observed that resistance to apoptosis induced by etoposide is promoted by CD44 expression in SW620, and this resistance is better sustained by the full variant isoform, v3-10. Concomitant alterations in caspase 9, caspase 3, Bcl-xl, and Bak indicated that the resistance to apoptosis in this model involved the mitochondrial pathway. The differential response of CD44 transfectants was associated with a downregulation of pRb and phosphorylated AKT. The results of this study are consistent with the conclusion that expression of variant CD44 isoforms which is characteristic of colon cancer, and most other types of cancer, confers a selective advantage to resist apoptosis, thereby promoting cell transformation into a malignant phenotype, in conjunction with other anti-apoptotic factors.
Collapse
Affiliation(s)
- Minalini Lakshman
- Department of Laboratory Medicine and Pathobiology, St. Michael's Hospital and University of Toronto, Toronto, Ontario, Canada M5B 1W8
| | | | | | | |
Collapse
|
28
|
Lakshman M, Subramaniam V, Jothy S. CD44 negatively regulates apoptosis in murine colonic epithelium via the mitochondrial pathway. Exp Mol Pathol 2004; 76:196-204. [PMID: 15126101 DOI: 10.1016/j.yexmp.2003.12.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Indexed: 11/23/2022]
Abstract
Regulation of epithelial cell proliferation and apoptosis are important determinants of colonic crypt homeostasis, and their dysregulations are key features of colon cancer. In this study, we investigated whether CD44, an adhesion protein overexpressed in colon cancer, plays a role in colonocyte proliferation and apoptosis, and the molecular mechanisms involved in these processes. Using a CD44 knockout mouse model devoid of a gross phenotype, we found that CD44 null colonocytes have alterations at the ultrastructural and molecular levels. Mitochondria in CD44 null colonocytes at the top of the crypt have disrupted cristae. The ratio of anti-apoptotic Bcl-xl to pro-apoptotic Bak was shifted toward apoptosis in CD44 null colon due to decreased Bcl-xl expression. Caspase 9 was upregulated and active in CD44 null colon. Its expression shifted from a location restricted to the top of the control crypts to the whole crypt axis in CD44 null colon. Caspase 3 was also activated in CD44 null colon suggesting that CD44 null colonocytes are apoptotic via the intrinsic pathway. Cell cycle regulators, cyclin A, p21, and pRb protein were abrogated in CD44 null mice. Overall, CD44 negatively regulates apoptosis via the mitochondrial pathway in the colonic epithelium through the regulators/effectors of cell cycle and apoptosis.
Collapse
Affiliation(s)
- Minalini Lakshman
- Department of Laboratory Medicine and Pathobiology, St. Michael's Hospital and University of Toronto, Toronto, ON, Canada M5B 1W8
| | | | | |
Collapse
|
29
|
Mangan JK, Rane SG, Kang AD, Amanullah A, Wong BC, Reddy EP. Mechanisms associated with IL-6-induced up-regulation of Jak3 and its role in monocytic differentiation. Blood 2004; 103:4093-101. [PMID: 14976041 DOI: 10.1182/blood-2003-06-2165] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report here that Janus kinase 3 (Jak3) is a primary response gene for interleukin-6 (IL-6) in macrophage differentiation, and ectopic overexpression of Jak3 accelerates monocytic differentiation of normal mouse bone marrow cells stimulated with cytokines. Furthermore, we show that incubation of normal mouse bone marrow cells with a JAK3-specific inhibitor results in profound inhibition of myeloid colony formation in response to granulocyte-macrophage colony-stimulating factor or the combination of stem cell factor, IL-3, and IL-6. In addition, mutagenesis of the Jak3 promoter has revealed that Sp1 binding sites within a -67 to -85 element and a signal transducer and activator of transcription (Stat) binding site at position -44 to -53 are critical for activation of Jak3 transcription in murine M1 myeloid leukemia cells stimulated with IL-6. Electrophoretic mobility shift assay (EMSA) analysis has demonstrated that Sp1 can bind to the -67 to -85 element and Stat3 can bind to the -44 to -53 STAT site in IL-6-stimulated M1 cells. Additionally, ectopic overexpression of Stat3 enhanced Jak3 promoter activity in M1 cells. This mechanism of activation of the murine Jak3 promoter in myeloid cells is distinct from a recently reported mechanism of activation of the human JAK3 promoter in activated T cells.
Collapse
Affiliation(s)
- James K Mangan
- Temple University School of Medicine, Fels Institute for Cancer Research and Molecular Biology, 3307 N Broad St, AHP Room 154, Philadelphia, PA 19140, USA
| | | | | | | | | | | |
Collapse
|
30
|
Lucas JJ, Domenico J, Gelfand EW. Cyclin-Dependent Kinase 6 Inhibits Proliferation of Human Mammary Epithelial Cells. Mol Cancer Res 2004. [DOI: 10.1158/1541-7786.105.2.2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Many defects in cancer cells are in molecules regulating G1-phase cyclin-dependent kinases (cdks), which are responsible for modulating the activities of Rb family growth-suppressing proteins. Models for understanding how such defects affect proliferation assume that cdks are responsible for sequentially phosphorylating, and hence inactivating, the growth-suppressing functions of Rb family proteins, thus promoting cell cycle progression. However, cdks also play a role in formation of growth-suppressing forms of pRb family molecules, including the “hypophosphorylated” species of pRb itself. Here, it is shown that normal human mammary epithelial cells have a high amount of cdk6 protein and activity, but all breast tumor-derived cell lines analyzed had reduced levels, with several having little or no cdk6. Immunohistochemical studies showed reduced levels of cdk6 in breast tumor cells as compared with normal breast tissue in vivo. Cdk6 levels in two breast tumor cell lines were restored to those characteristic of normal human mammary epithelial cells by DNA transfection. The cells had a reduced growth rate compared with parental tumor cells; cells that lost ectopic expression of cdk6 reverted to the faster growth rate of parental cells. Cell lines with restored cdk6 levels accumulated higher amounts of the Rb family protein p130 as well as E2F4, a suppressing member of the E2F family of transcription factors, in their nuclei. The results suggest that cdk6 restrains rather than stimulates breast epithelial cell proliferation and that its loss or down-regulation could play a role in breast tumor development.
Collapse
Affiliation(s)
- Joseph J. Lucas
- Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO
| | - Joanne Domenico
- Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO
| | - Erwin W. Gelfand
- Division of Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, Denver, CO
| |
Collapse
|
31
|
Ashe M, Pabon-Peña L, Dees E, Price KL, Bader D. LEK1 is a potential inhibitor of pocket protein-mediated cellular processes. J Biol Chem 2003; 279:664-76. [PMID: 14555653 DOI: 10.1074/jbc.m308810200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
LEK1, a member of the LEK family of proteins, is ubiquitously expressed in developing murine tissues. Our current studies are aimed at identifying the role of LEK1 during cell growth and differentiation. Little is known about the function of LEK proteins. Recent studies in our laboratory have focused on the characterization of the LEK1 atypical Rb-binding domain that is conserved among all LEK proteins. Our findings suggest that LEK1 potentially functions as a universal regulator of pocket protein activity. Pocket proteins exhibit distinct expression patterns during development and function to regulate cell cycle, apoptosis, and tissue-specific gene expression. We show that LEK1 interacts with all three pocket proteins, p107, p130, and pRb. Additionally, this interaction occurs specifically between the LEK1 Rb-binding motif and the "pocket domain" of Rb proteins responsible for Rb association with other targets. Analyses of the effects of disruption of LEK1 protein expression by morpholino oligomers demonstrate that LEK1 depletion decreases cell proliferation, disrupts cell cycle progression, and induces apoptosis. Given its expression in developing cells, its association with pocket proteins, and its effects on proliferation, cell cycle, and viability of cells, we suggest that LEK1 functions in a similar manner to phosphorylation to disrupt association of Rb proteins with appropriate binding targets. Thus, the LEK1/Rb interaction serves to retain cells in a pre-differentiative, actively proliferative state despite the presence of Rb proteins during development. Our data suggest that LEK1 is unique among LEK family members in that it specifically functions during murine development to regulate the activity of Rb proteins during cell division and proliferation. Furthermore, we discuss the distinct possibility that a yet unidentified splice variant of the closely related human CENP-F, serves a similar function to LEK1 in humans.
Collapse
Affiliation(s)
- Mabelle Ashe
- Stahlman Cardiovascular Research Laboratories, Program for Developmental Biology and the Division of Cardiovascular Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA
| | | | | | | | | |
Collapse
|
32
|
Abstract
The general mechanisms that control the cell cycle in mammalian cells have been studied in depth and several proteins that are involved in the tight regulation of cell cycle progression have been identified. However, the analysis of which molecules participate in cell cycle exit of specific cell lineages is not exhaustive yet. Moreover, the strict relation between cell cycle exit and induction of differentiation has not been fully understood and seems to depend on the cell type. Several in vivo and in vitro studies have been performed in the last few years to address these issues in cells of the nervous system. In this review, we focus our attention on cyclin-cyclin-dependent kinase complexes, cyclin kinase inhibitors, genes of the retinoblastoma family, p53 and N-Myc, and we aim to summarize the latest evidence indicating their involvement in the control of the cell cycle and induction of differentiation in different cell types of the peripheral and central nervous systems. Studies on nervous system tumors and a possible contributory role in tumorigenesis of polyomavirus T antigen are reported to point out the critical contribution of some cell cycle regulators to normal neural and glial development.
Collapse
Affiliation(s)
- Umberto Galderisi
- Department of Experimental Medicine, School of Medicine, Second University of Naples, Naples, Italy
| | | | | |
Collapse
|
33
|
Bhattacharya S, Garriga J, Calbó J, Yong T, Haines DS, Graña X. SKP2 associates with p130 and accelerates p130 ubiquitylation and degradation in human cells. Oncogene 2003; 22:2443-51. [PMID: 12717421 DOI: 10.1038/sj.onc.1206339] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
p130 is a member of the retinoblastoma family of pocket proteins, which includes pRB and p107. Unlike pRB and p107, p130 protein levels decrease dramatically following its hyperphosphorylation starting in the mid-G1 phase of the cell cycle. However, the mechanism leading to p130 downregulation is unknown. We have found that the proteasome inhibitor, lactacystin, inhibited p130 downregulation in T98G cells progressing through the G1/S transition and S phase and that p130 is multiubiquitylated in 293 cells. We have previously shown that ectopic expression of both cyclin D and E induces phosphorylation and downregulation of p130. Since the SKP1/Cul1/SKP2 E3 ubiquitin ligase complex mediates ubiquitylation of substrates previously phosphorylated by cyclin-dependent kinases, we investigated the potential role of this ubiquitin ligase in mediating p130 downregulation. We found that p130 interacts with SKP1, Cul-1 and SKP2 in human 293 cells. We also found that ectopic coexpression of SKP2 and p130 leads to dose-dependent downregulation of p130, reduces p130 protein half-life and induces p130 ubiquitylation in these cells. Moreover, adenoviral-mediated expression of SKP2 accelerates downregulation of endogenous hyperphosphorylated p130 in mitogen-stimulated T98G cells and primary WI38 fibroblasts. We conclude that p130 is a substrate of the SCF(SKP2) ubiquitin ligase and this E3 ligase regulates p130 abundance during the cell cycle.
Collapse
Affiliation(s)
- Sabyasachi Bhattacharya
- Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, PA 19140, USA
| | | | | | | | | | | |
Collapse
|
34
|
Calbó J, Parreño M, Sotillo E, Yong T, Mazo A, Garriga J, Grana X. G1 cyclin/cyclin-dependent kinase-coordinated phosphorylation of endogenous pocket proteins differentially regulates their interactions with E2F4 and E2F1 and gene expression. J Biol Chem 2002; 277:50263-74. [PMID: 12401786 DOI: 10.1074/jbc.m209181200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitogenic stimulation leads to activation of G(1) cyclin-dependent kinases (CDKs), which phosphorylate pocket proteins and trigger progression through the G(0)/G(1) and G(1)/S transitions of the cell cycle. However, the individual role of G(1) cyclin-CDK complexes in the coordinated regulation of pocket proteins and their interaction with E2F family members is not fully understood. Here we report that individually or in concert cyclin D1-CDK and cyclin E-CDK complexes induce distinct and coordinated phosphorylation of endogenous pocket proteins, which also has distinct consequences in the regulation of pocket protein interactions with E2F4 and the expression of p107 and E2F1, both E2F-regulated genes. The up-regulation of these two proteins and the release of p130 and pRB from E2F4 complexes allows formation of E2F1 complexes not only with pRB but also with p130 and p107 as well as the formation of p107-E2F4 complexes. The formation of these complexes occurs in the presence of active cyclin D1-CDK and cyclin E-CDK complexes, indicating that whereas phosphorylation plays a role in the abrogation of certain pocket protein/E2F interactions, these same activities induce the formation of other complexes in the context of a cell expressing endogenous levels of pocket and E2F proteins. Of note, phosphorylated p130 "form 3," which does not interact with E2F4, readily interacts with E2F1. Our data also demonstrate that ectopic overexpression of either cyclin is sufficient to induce mitogen-independent growth in human T98G and Rat-1 cells, although the effects of cyclin D1 require downstream activation of cyclin E-CDK2 activity. Interestingly, in T98G cells, cyclin D1 induces cell cycle progression more potently than cyclin E. This suggests that cyclin D1 activates pathways independently of cyclin E that ensure timely progression through the cell cycle.
Collapse
Affiliation(s)
- Joaquim Calbó
- Fels Institute for Cancer Research and Molecular Biology and Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
| | | | | | | | | | | | | |
Collapse
|
35
|
Tibudan SS, Wang Y, Denning MF. Activation of protein kinase C triggers irreversible cell cycle withdrawal in human keratinocytes. J Invest Dermatol 2002; 119:1282-9. [PMID: 12485429 DOI: 10.1046/j.1523-1747.2002.19625.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Irreversible cell cycle withdrawal occurs as normal keratinocytes detach from the basement membrane and initiate their terminal differentiation program. To investigate which signaling pathways regulate this permanent cell cycle withdrawal, we added inhibitors of kinases implicated in integrin signaling and keratinocyte differentiation to normal human keratinocytes induced to differentiate in suspension culture, and assayed the growth capacity of the recovered cells. Keratinocytes suspended in methylcellulose for 24 h underwent approximately 1000-fold loss of proliferative capacity. Of the kinase inhibitors tested, only the protein kinase C inhibitor Bisindolylmaleimide I (GF109203X) caused dramatic protection from loss of growth potential. Direct activation of protein kinase C by 12-O-tetradecanoyl-phorbol-13-acetate was also sufficient to trigger irreversible growth arrest. Protein kinase C inhibitors selective for protein kinase Calpha, the only Ca2+-dependent protein kinase C isoform in keratinocytes, protected keratinocytes from suspension-induced cell cycle withdrawal. Consistent with this finding, we measured a specific induction of Ca2+-dependent protein kinase C activity 2-3 h after keratinocytes were placed into suspension culture. Furthermore, protein kinase Calpha was strongly localized to cell membranes in the suprabasal keratinocytes of human epidermis, suggesting translocation and activation in vivo. Coordinated changes in cell cycle regulators (p21, p27, pRb, p107, p130) consistent with cells exiting the cell cycle were observed in suspended keratinocytes, and these changes were blocked by protein kinase C inhibition. These results indicate that the loss of cell matrix adhesion triggers protein kinase C activation, which is an early event required for cell cycle withdrawal of terminally differentiating normal human keratinocytes.
Collapse
Affiliation(s)
- Shalini S Tibudan
- Loyola University Medical Center, Department of Pathology and the Cardinal Bernardin Cancer Center, 2160 S. First Avenue, Maywood, IL 60153, USA
| | | | | |
Collapse
|
36
|
Tedesco D, Lukas J, Reed SI. The pRb-related protein p130 is regulated by phosphorylation-dependent proteolysis via the protein-ubiquitin ligase SCF(Skp2). Genes Dev 2002; 16:2946-57. [PMID: 12435635 PMCID: PMC187481 DOI: 10.1101/gad.1011202] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
p130 is a tumor suppressor of the pocket protein family whose expression is posttranscriptionally regulated and largely G0 restricted. The mechanism of down-regulation of p130 expression in proliferating cells was investigated. Our results indicate that the decline of p130 expression as G0 cells reenter the cell cycle is due to a decrease in protein stability. The enhancement of p130 turnover in late G1 and S phase compared with G0 and early G1 phase was dependent on Cdk4/6-specific phosphorylation of p130 on Serine 672, and independent of Cdk2 activity. The activity of the ubiquitin ligase complex Skp1-Cul1/Cdc53-F-box protein Skp2 (SCF(Skp2)) and the proteasome were necessary for p130 degradation. In vitro, recombinant Skp2 was able to bind hyperphosphorylated but not dephosphorylated p130. Furthermore, in vitro polyubiquitination of p130 by SCF(Skp2) was specifically dependent on phosphorylation of p130 on Serine 672. Thus, like the Cdk inhibitor p27(Kip1), p130 turnover is regulated by Cdk-dependent G1 phosphorylation leading to ubiquitin-dependent proteolysis.
Collapse
Affiliation(s)
- Donato Tedesco
- Department of Molecular Biology, MB-7, The Scripps Research Institute, La Jolla, California 92037, USA
| | | | | |
Collapse
|
37
|
Sivamurthy N, Stone DH, LoGerfo FW, Quist WC. Attenuated retinoblastoma gene product and associated E2F/retinoblastoma imbalance in anastomotic intimal hyperplasia. J Vasc Surg 2002; 35:1233-41. [PMID: 12042736 DOI: 10.1067/mva.2002.124378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVE The retinoblastoma gene product is a cell cycle control protein that when inhibited allows cell proliferation to progress by releasing E2F. Retinoblastoma manipulation has been attempted to prevent intimal hyperplasia (IH) in injured native vessels by arresting vascular smooth muscle cell proliferation. However, no studies have identified the role, if any, of retinoblastoma in anastomotic IH formation after prosthetic arterial grafting. The goal of this study was to describe the relation of retinoblastoma and E2F to anastomotic IH with analyzing retinoblastoma/E2F levels, retinoblastoma phosphorylation, and transcription of retinoblastoma and E2F in prosthetic arterial grafting. METHODS Six-mm-diameter expanded polytetrafluoroethylene carotid interposition grafts (n = 12) were implanted in 25-kg mongrel dogs. The intervening arterial segments were harvested as controls. The distal anastomoses were harvested at 14 and 30 days after implantation for immunoblot, messenger RNA (mRNA), and immunohistochemistry analyses. Tissue homogenate was separated with sodium dodecylsulfate-polyacrylamide gel electrophoresis and probed with antibody to total retinoblastoma, phosphorylated retinoblastoma at serine 795, serine 780, and serine 807/811, and E2F-1. Bands at each time point were quantitated and compared with control artery (n = 12). Each lane was standardized with reprobing with antibody to beta-tubulin. Immunohistochemistry was performed with antibody to retinoblastoma. Retinoblastoma and E2F mRNA expression levels in anastomotic IH and control artery were analyzed with an oligonucleotide microarray. RESULTS Total retinoblastoma, from immunoblot analysis, was decreased at the 14-day and 30-day distal anastomoses by 35.7% and 33.6%, respectively, compared with control (P <.01). Furthermore, retinoblastoma at these time points was unphosphorylated at phosphorylation sites serine 795, serine 780, and serine 807/811. E2F-1 levels at 14 days and 30 days were unchanged compared with control. Positive staining for retinoblastoma was seen in endothelial and vascular smooth muscle cell from control, 14-day, and 30-day tissue. A qualitative decrease appeared to be seen in retinoblastoma in the neointima at 14 and 30 days compared with the native wall. No differential expression of retinoblastoma and E2F mRNA was seen in anastomotic IH compared with control. CONCLUSION This study showed that total retinoblastoma levels are decreased and E2F-1 levels remain unchanged in anastomotic IH. Attenuated retinoblastoma is a novel concept to anastomotic IH after prosthetic arterial grafting. Retinoblastoma/E2F imbalance may not be the result of transcriptional regulation and may increase unbound E2F to promote cell proliferation. Hypophosphorylation of remaining retinoblastoma may minimize uncontrolled proliferation by preventing further increases in unbound E2F. Therefore, retinoblastoma/E2F imbalance may lead to the early but limited increase in cell proliferation seen after prosthetic arterial grafting and appears to contribute to the development and progression of anastomotic IH.
Collapse
Affiliation(s)
- Nayan Sivamurthy
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, 4 Blackfan Circle, Boston, MA 02115, USA
| | | | | | | |
Collapse
|
38
|
Motamed K, Funk SE, Koyama H, Ross R, Raines EW, Sage EH. Inhibition of PDGF-stimulated and matrix-mediated proliferation of human vascular smooth muscle cells by SPARC is independent of changes in cell shape or cyclin-dependent kinase inhibitors. J Cell Biochem 2002; 84:759-71. [PMID: 11835401 DOI: 10.1002/jcb.10095] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Interactions among growth factors, cells, and extracellular matrix regulate proliferation during normal development and in pathologies such as atherosclerosis. SPARC (secreted protein, acidic, and rich in cysteine) is a matrix-associated glycoprotein that modulates the adhesion and proliferation of vascular cells. In this study, we demonstrate that SPARC inhibits human arterial smooth muscle cell proliferation stimulated by platelet-derived growth factor or by adhesion to monomeric type I collagen. Binding studies with SPARC and SPARC peptides indicate specific and saturable interaction with smooth muscle cells that involves the C-terminal Ca2+-binding region of the protein. We also report that SPARC arrests monomeric collagen-supported smooth muscle cell proliferation in the late G1-phase of the cell cycle in the absence of an effect on cell shape or on levels of cyclin-dependent kinase inhibitors. Cyclin-dependent kinase-2 activity, p107 and cyclin A levels, and retinoblastoma protein phosphorylation are markedly reduced in response to the addition of exogenous SPARC and/or peptides derived from specific domains of SPARC. Thus, SPARC, previously characterized as an inhibitor of platelet-derived growth factor binding to its receptor, also antagonizes smooth muscle cell proliferation mediated by monomeric collagen at the level of cyclin-dependent kinase-2 activity.
Collapse
Affiliation(s)
- Kouros Motamed
- Department of Vascular Biology, The Hope Heart Institute, Seattle, Washington 98104, USA
| | | | | | | | | | | |
Collapse
|
39
|
Vail ME, Chaisson ML, Thompson J, Fausto N. Bcl-2 expression delays hepatocyte cell cycle progression during liver regeneration. Oncogene 2002; 21:1548-55. [PMID: 11896583 DOI: 10.1038/sj.onc.1205212] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2001] [Revised: 11/28/2001] [Accepted: 11/28/2001] [Indexed: 11/09/2022]
Abstract
Bcl-2 is the prototype of a family of genes that prevent apoptosis. However, several reports indicate that Bcl-2 may also act as a cell cycle modulator. In several human tumors, Bcl-2 expression correlates with a more favorable prognosis and lower tumor proliferative activity. We have shown that Bcl-2 expression delays liver tumor development in transgenic mice even when the gene is turned on shortly before the time of tumor development. We hypothesized that Bcl-2 may delay liver tumorigenesis by interfering with hepatocyte proliferation. To test whether Bcl-2 expression may act on hepatocyte replication we studied liver regeneration in Bcl-2 transgenic mice and wild-type littermates. DNA replication was delayed by approximately 8 h in Bcl-2 transgenic mice compared to the timing of the response in wild-type littermates. Cyclin D expression showed no alterations in the regenerating liver of Bcl-2 transgenic mice. In contrast, there was a delay in the expression of p107, cyclin E and in the activity of cyclin E/cdk 2 activity. These results show that Bcl-2 expression delays cell cycle progression in hepatocytes and suggests that it acts at a step involving cyclin E and p107.
Collapse
Affiliation(s)
- Mary E Vail
- Department of Pathology, University of Washington, Seattle, Washington, WA 98195-7705, USA
| | | | | | | |
Collapse
|
40
|
Jori FP, Galderisi U, Piegari E, Peluso G, Cipollaro M, Cascino A, Giordano A, Melone MA. RB2/p130 ectopic gene expression in neuroblastoma stem cells: evidence of cell-fate restriction and induction of differentiation. Biochem J 2001; 360:569-77. [PMID: 11736646 PMCID: PMC1222259 DOI: 10.1042/0264-6021:3600569] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The activity of the RB2/p130 gene, which is a member of the retinoblastoma gene family, is cell-cycle-regulated and plays a key role in growth inhibition and differentiation. We used neuroblastoma cell lines as a model for studies on neural crest progenitor cell differentiation. We show that Rb2/p130 ectopic protein expression induces morphological and molecular modifications, promoting differentiation of intermediate (I) phenotype SK-N-BE(2)-C neuroblastoma cells towards a neuroblastic (N) rather than a Schwann/glial/melanocytic (S) phenotype. These modifications are stable as they persist even after treatment with an S-phenotype inducer. Rb2/p130 ectopic expression also induces a more differentiated phenotype in N-type SH-SY-5Y cells. Further, this function appears to be independent of cell-cycle withdrawal. The data reported suggest that the Rb2/p130 protein is able to induce neuronal lineage specification and differentiation in neural crest stem and committed neuroblastoma cells, respectively. Thus, the Rb2/p130 protein seems to be required throughout the full neural maturation process.
Collapse
Affiliation(s)
- F P Jori
- Department of Neurological Sciences, Second University of Naples, Via Pansini 5, 80100 Naples, Italy
| | | | | | | | | | | | | | | |
Collapse
|
41
|
Cuenca AG, Cress WD, Good RA, Marikar Y, Engelman RW. Calorie restriction influences cell cycle protein expression and DNA synthesis during liver regeneration. Exp Biol Med (Maywood) 2001; 226:1061-7. [PMID: 11743143 DOI: 10.1177/153537020122601114] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Calorie restriction without essential nutrient deficiency (calorie restriction, CR) abrogates experimental carcinogenesis and extends healthful life span. To test whether CR influences cell-cycle protein expression during the hepatocellular proliferation induced by 70% partial hepatectomy (PH), BALB/c mice were separated into two groups, fed comparable semi-purified diets for 10 weeks that differed 40% in caloric offering, and were then subjected to PH. When PH was performed, CR mice weighed 36% less than ad libitum (AL)-fed mice (P < 0.01), but liver-to-body weight ratios were similar. During the regenerative hyperplasia, hepatocytes of CR mice demonstrated evidence of accelerated entrance and passage through G1 and S phases, and an earlier exit from the cell cycle. The first peak of DNA synthesis occurred 6 hr earlier, and the second peak was significantly greater among CR mice with 38% +/- 13% bromodeoxyuridine (BrdU)-positive hepatocytes, compared with 14% +/- 4% in AL mice (P < 0.01). More E2F-1 expression was induced at the hepatic G1/S boundary just prior to each peak of DNA synthesis in regenerating livers of CR mice (P < 0.01), and 8 hr earlier among CR mice. More hyperphosphorylated retinoblastoma p110 was detected during hepatic G1 and the G1-S transition among CR mice, coincident with the early hepatocellular proliferative wave. Cyclin A was induced during the first peak of DNA synthesis 4 hr earlier among CR mice, and it continued 4 hr longer in AL mice, indicating an earlier post-replicative exit by hepatocytes in CR mice. p21 was induced during the G1 phase at 4 hr post-PH, and was maximally expressed during and after peak DNA synthesis in both dietary groups. These results indicate that CR influences cell cycle protein expression levels, causing hepatocytes to enter into S phase earlier and exit abruptly from the cell cycle, and they support the premise that CR enhances induced cell responsiveness by influencing cell cycle regulatory controls.
Collapse
Affiliation(s)
- A G Cuenca
- Department of Pediatrics, College of Medicine, University of South Florida, Tampa, Florida 33612, USA
| | | | | | | | | |
Collapse
|
42
|
Clarke KO, Feinman R, Harrison LE. Tributyrin, an oral butyrate analogue, induces apoptosis through the activation of caspase-3. Cancer Lett 2001; 171:57-65. [PMID: 11485828 DOI: 10.1016/s0304-3835(01)00574-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The purpose of this study was to investigate the anti-proliferative and pro-apoptotic effects of the butyrate analogues, tributyrin (TB) and phenylbutyrate (PB), in a colon cancer model. We demonstrate that HT-29 colon cancer cells exposed to PB and TB result in growth inhibition associated with an induction of apoptosis mediated through the activation of caspase-3 activity. A block in the G1/S cell cycle traverse associated with a decrease in CDK2 (cyclin dependent kinase) protein levels and retinoblastoma protein hypophosphorylation was also noted after PB and TB exposure. Importantly, TB proved to be the most potent agent in its ability to induce these phenotypic changes, and potentially may represent a novel therapy for patients with advanced colorectal cancer.
Collapse
Affiliation(s)
- K O Clarke
- Department of Surgery, UMDNJ--New Jersey Medical School, 185 South Orange Avenue, MSB G588, Newark, NJ 07103, USA
| | | | | |
Collapse
|
43
|
Parreño M, Garriga J, Limón A, Albrecht JH, Graña X. E1A modulates phosphorylation of p130 and p107 by differentially regulating the activity of G1/S cyclin/CDK complexes. Oncogene 2001; 20:4793-806. [PMID: 11521191 DOI: 10.1038/sj.onc.1204644] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2001] [Revised: 05/10/2001] [Accepted: 05/17/2001] [Indexed: 11/08/2022]
Abstract
We have previously shown that the adenoviral 12S E1A protein modulates the phosphorylation status of p130 and p107 without apparent changes in the cell cycle dependent phosphorylation of the retinoblastoma protein. Here we report on the mechanisms by which E1A modifies differentially the phosphorylation status of pocket proteins. In human U-2 OS osteosarcoma cells transiently expressing E1A, ectopic expression of D-type cyclins alone or combined, but not cyclins E and/or A, fully rescues E1A-mediated block in hyperphosphorylation of p130 to form 3. However, cyclins E and A, individually or together, induce hyperphosphorylation of p130 to species with intermediate mobility. Phosphopeptide maps indicate that E1A inhibits phosphorylation of sites phosphorylatable by CDKs. One of these sites is Ser-1044. The effects of blocking the activities of endogenous and exogenous cyclins with p16 and dominant negative CDK2 in E1A expressing cells further indicate that p130 is phosphorylated by both D-type cyclin and cyclin E/CDK complexes and that E1A modulates the activity of these G1/S CDKs by independent mechanisms. Stable expression of E1A in MC3T3-E1 cells leads to downregulation of D-type cyclins, and upregulation of cyclins E and A. This is accompanied by increased CDK2 kinase activity. Downregulation of D-type cyclins in these cells correlates with a block on both p130 hyperphosphorylation to form 3 and hyperphosphorylation of p107. This is rescued by D-type cyclins but not by cyclin E. In addition, we show that the upregulation of cyclins E and A is at least partially dependent on an intact pocket protein/E2F pathway, but downregulation of D-type cyclins is not. Moreover, we provide evidence that while the lack of a functional pRB pathway also results in a block on hyperphosphorylation of p130 to form 3, this is not sufficient to induce constitutive expression of p130 form 2b.
Collapse
Affiliation(s)
- M Parreño
- Department of Biochemistry, Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, Pennsylvania, PA19140, USA
| | | | | | | | | |
Collapse
|
44
|
Nagasawa M, Gelfand EW, Lucas JJ. Accumulation of high levels of the p53 and p130 growth-suppressing proteins in cell lines stably over-expressing cyclin-dependent kinase 6 (cdk6). Oncogene 2001; 20:2889-99. [PMID: 11420701 DOI: 10.1038/sj.onc.1204396] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/1998] [Revised: 02/07/2001] [Accepted: 02/13/2001] [Indexed: 11/09/2022]
Abstract
Cyclin-dependent kinase 6(cdk6) is present in randomly proliferating cultures of 3T3 cells but has little detectable enzymatic activity. Significant activity is detected only during a short period in early G1 phase. To examine the possible functions of cdk6 in 3T3 cells, lines stably over-expressing cdk6 were constructed and compared to normal 3T3 cells or cell lines with reduced cdk6 levels due to expression of a dominant-negative form of the protein. Over-expression of cdk6 in cells, which led to high levels of activity even in proliferating cultures, had dramatic effects. Cell lines stably over-expressing wild-type cdk6 had a markedly reduced growth rate compared to parental 3T3 cells or lines expressing a dominant-negative form of cdk6. They also over-produced the p53 and p130 proteins and had increased sensitivity to UV-irradiation. Irradiation resulted in accumulation of the Bax protein and rapid cell death. Levels of p53 and p130 proteins were down-regulated and the growth rate of the cells was increased by introduction of the dominant-negative form of cdk6 into cells over-expressing cdk6, indicating that cdk6 is involved in the overproduction of p53 and p130. The results suggest that cdk6, through regulation of growth-suppressing molecules, may play a role in halting cellular growth when proliferation is inappropriate.
Collapse
Affiliation(s)
- M Nagasawa
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado, CO 80206, USA
| | | | | |
Collapse
|
45
|
Paggi MG, Bonetto F, Severino A, Baldi A, Battista T, Bucci F, Felsani A, Lombardi D, Giordano A. The retinoblastoma-related Rb2/p130 gene is an effector downstream of AP-2 during neural differentiation. Oncogene 2001; 20:2570-8. [PMID: 11420667 DOI: 10.1038/sj.onc.1204356] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2000] [Revised: 01/31/2001] [Accepted: 02/05/2001] [Indexed: 11/08/2022]
Abstract
Rb2/p130, a member of the Retinoblastoma family of growth and tumour suppressor genes, is extensively implicated in the control of cell cycle and differentiation. The minimal promoter region of Rb2/p130 in T98G human glioblastoma cells was identified and its analysis revealed the presence of a KER1 palindromic sequence able to bind the transcription factor AP-2, a regulatory protein that plays a crucial role in ectodermal differentiation. This KER1 site interacted in vitro with AP-2, and AP-2 overexpression increased Rb2/p130 transcription and translation. We also found that rat PC12 pheochromocytoma cells, when induced to differentiate by NGF, displayed an increase of AP-2 protein levels and of Rb2/p130 transcription and protein levels. AP-2-transfected PC12 cells displayed enhanced transcription and translation of Rb2/p130 and of the cdk inhibitor p21(WAF1/CIP1), a gene known to be under the control of AP-2, but unable by itself to elicit PC12 differentiation. Overexpression of either AP-2 or Rb2/p130 elicited per se cell differentiation in the absence of NGF, while coexpression of AP-2B, a negative regulator of AP-2 transcriptional activity, inhibited only AP-2-induced differentiation. Altogether, these results indicate that Rb2/p130 is a critical effector of AP-2 in sustaining ectodermal differentiation.
Collapse
Affiliation(s)
- M G Paggi
- Laboratory of Cell Metabolism and Pharmacokinetics, Centre for Experimental Research, Regina Elena Cancer Institute, Via delle Messi d'Oro 156, 00158 Rome, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Abstract
Flavopiridol inhibits phosphokinases. Its activity is strongest on cyclin dependent kinases (cdk-1, -2, -4, -6, -7) and less on receptor tyrosine kinases (EGFR), receptor associates tyrosine kinases (pp60 Src) and on signal transducing kinases (PKC and Erk-1). Although the inhibiting activity of flavopiridol is strongest for cdk, the cytotoxic activity of flavopiridol is not limited to cycling cells. Resting cells are also killed. This fact suggests that inhibition of cdks involved in the control of cell cycle is not the only mechanism of action. Inhibition of cdk's with additional functions (i.e. involved in the control of transcription or function of proteins that do not control cell cycle) may contribute to the antitumoral effect. Moreover, direct and indirect inhibition of receptor activation (EGFR) and/or a direct inhibition of kinases (pp60 Src, PKC, Erk-1) involved in the signal transduction pathway could play a role in the antiproliferative activity of flavopiridol. From pharmacokinetic data in patients it can be concluded that the inhibitory activity (IC50) of flavopiridol on these kinases is in the range of concentrations that might be achieved intracellularly after systemic application of non-toxic doses of flavopiridol. However, no in situ data from flavopiridol treated cells have been published yet that prove that by inhibition of EGFR, pp60 Src, PKC and/or Erk-1 (in addition to inhibition of cdk's) flavopiridol is able to induce apoptosis. Thus many questions regarding the detailed mechanism of antitumoral action of flavopiridol are still open. For the design of protocols for future clinical studies this review covers the essential information available on the mechanism of antitumoral activity of flavopiridol. The characteristics of this antitumoral activity include: High rate of apoptosis, especially in leukemic cells; synergy with the antitumoral activity of many cytostatics; independence of its efficacy on pRb, p53 and Bcl-2 expression; lack of interference with the most frequent multidrug resistance proteins (P-glycoprotein and MRP-190); and a strong antiangiogenic activity. Based on these pharmacological data it can be concluded that flavopiridol could be therapeutically active in tumor patients: independent on the genetic status of their tumors or leukemias (i.e. mutations of the pRb and/or p53, amplification of bcl-2); in spite of drug resistance of their tumors induced by first line treatment (and caused by enhanced expression of multidrug resistance proteins); in combination with conventional chemotherapeutics preferentially given prior to flavopiridol; and due to a complex mechanism involving cytotoxicity on cycling and on resting tumor cells, apoptosis and antiangiogenic activity. In consequence, flavopiridol is a highly attractive, new antitumoral compound and deserves further elucidation of its clinical potency.
Collapse
Affiliation(s)
- H H Sedlacek
- Aventis Pharma Deutschland GmbH, Central Biotechnology, P.O. Box 1140, 35001, Marburg, Germany.
| |
Collapse
|
47
|
Yan W, Kero J, Suominen J, Toppari J. Differential expression and regulation of the retinoblastoma family of proteins during testicular development and spermatogenesis: roles in the control of germ cell proliferation, differentiation and apoptosis. Oncogene 2001; 20:1343-56. [PMID: 11313878 DOI: 10.1038/sj.onc.1204254] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2000] [Revised: 01/05/2001] [Accepted: 01/09/2001] [Indexed: 11/09/2022]
Abstract
Normal spermatogenesis is highly dependent on well-balanced germ cell proliferation, differentiation, and apoptosis. However, the molecular mechanisms that govern these processes are largely unknown. Retinoblastoma family proteins (pRb, p107 and p130) are potentially important regulators of cell growth, differentiation and apoptosis. pRb has been shown to be expressed in the rat testis and involved in the regulation of spermatogenesis. In the present study, the expression and localization of the other two pRb family members, p107 and p130, were analysed at both mRNA and protein levels during testicular development and spermatogenesis using Northern, Western blotting, immunohistochemistry, and in situ hybridization. Furthermore, changes of levels and phosphorylation status of pRb family proteins in response to growth suppression and/or apoptosis induction were investigated using a seminiferous tubule culture system and three animal models. Our data suggest that: (1) pRb family proteins are differentially expressed in the rat testis and they function in a cell-type-specific manner during testicular development and spermatogenesis; (2) they participate in the control of germ cell cycle and act in a cell cycle-phase-specific fashion during germ cell proliferation, and (3) they are also involved in the regulation of apoptosis of germ cells and Leydig cells.
Collapse
Affiliation(s)
- W Yan
- Department of Physiology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | | | | | | |
Collapse
|
48
|
Frey MR, Clark JA, Leontieva O, Uronis JM, Black AR, Black JD. Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium. J Cell Biol 2000; 151:763-78. [PMID: 11076962 PMCID: PMC2169440 DOI: 10.1083/jcb.151.4.763] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Members of the protein kinase C (PKC) family of signal transduction molecules have been widely implicated in regulation of cell growth and differentiation, although the underlying molecular mechanisms involved remain poorly defined. Using combined in vitro and in vivo intestinal epithelial model systems, we demonstrate that PKC signaling can trigger a coordinated program of molecular events leading to cell cycle withdrawal into G(0). PKC activation in the IEC-18 intestinal crypt cell line resulted in rapid downregulation of D-type cyclins and differential induction of p21(waf1/cip1) and p27(kip1), thus targeting all of the major G(1)/S cyclin-dependent kinase complexes. These events were associated with coordinated alterations in expression and phosphorylation of the pocket proteins p107, pRb, and p130 that drive cells to exit the cell cycle into G(0) as indicated by concomitant downregulation of the DNA licensing factor cdc6. Manipulation of PKC isozyme levels in IEC-18 cells demonstrated that PKCalpha alone can trigger hallmark events of cell cycle withdrawal in intestinal epithelial cells. Notably, analysis of the developmental control of cell cycle regulatory molecules along the crypt-villus axis revealed that PKCalpha activation is appropriately positioned within intestinal crypts to trigger this program of cell cycle exit-specific events in situ. Together, these data point to PKCalpha as a key regulator of cell cycle withdrawal in the intestinal epithelium.
Collapse
Affiliation(s)
- M R Frey
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
| | | | | | | | | | | |
Collapse
|
49
|
Iuliano R, Trapasso F, Stella A, Le Pera I, Melillo RM, Bruni P, Baldassarre G, Chiariotti L, Santoro M, Viglietto G, Fusco A. Pivotal role of the RB family proteins in in vitro thyroid cell transformation. Exp Cell Res 2000; 260:257-67. [PMID: 11035920 DOI: 10.1006/excr.2000.5023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Rat thyroid differentiated cells (PC Cl 3) are an excellent model system with which to study the interaction between differentiation and cell transformation. We previously demonstrated that PC Cl 3 cells expressing the adenovirus E1A gene no longer depend on thyrotropin for growth and do not express thyroid differentiation markers. Here we show that an E1A mutant unable to bind the RB protein failed to transform the PC Cl 3 cells. Conversely, mutations in the E1A p300 interacting region did not affect its transforming ability. The pivotal role of RB family proteins in the thyroid cell transformation is supported by the thyrotropin independence induced by the E7 gene of human papilloma virus type 16, but not by a mutated form in the RB-binding region.
Collapse
Affiliation(s)
- R Iuliano
- Dipartimento di Medicina Sperimentale e Clinica, Università degli Studi di Catanzaro "Magna Graecia,", Catanzaro, 88100, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Canhoto AJ, Chestukhin A, Litovchick L, DeCaprio JA. Phosphorylation of the retinoblastoma-related protein p130 in growth-arrested cells. Oncogene 2000; 19:5116-22. [PMID: 11042701 DOI: 10.1038/sj.onc.1203893] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The retinoblastoma family of proteins including pRB, p107 and p130 undergoes cell cycle dependent phosphorylation during the mid-G1 to S phase transition. This phosphorylation is dependent upon the activity of cyclin D/cdk4. In contrast to pRB and p107, p130 is phosphorylated during G0 and the early G1 phase of the cell cycle. We observed that p130 is specifically phosphorylated on serine and threonine residues in T98G cells arrested in G0 by serum deprivation or density arrest. Identification of the phospho-serine and phospho-threonine residues revealed that most were clustered within a short co-linear region unique to p130, defined as the Loop. Deletion of the Loop region resulted in a change in the phosphorylation status of p130 under growth arrest conditions. Notably, deletion of the Loop did not affect the ability of p130 to bind to E2F-4 or SV40 Large T antigen, to induce growth arrest in Saos-2 cells, and to become hyperphosphorylated during the proliferative phase of the cell cycle. p130 undergoes specific G0 phosphorylation in a manner that distinguishes it from pRB and p107.
Collapse
Affiliation(s)
- A J Canhoto
- Department of Adult Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, MA 02115, USA
| | | | | | | |
Collapse
|