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Different Camptothecin Sensitivities in Subpopulations of Colon Cancer Cells Correlate with Expression of Different Phospho-Isoforms of Topoisomerase I with Different Activities. Cancers (Basel) 2020; 12:cancers12051240. [PMID: 32423158 PMCID: PMC7281652 DOI: 10.3390/cancers12051240] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/08/2020] [Accepted: 05/13/2020] [Indexed: 12/25/2022] Open
Abstract
The heterogeneity of tumor cells and the potential existence of rare cells with reduced chemotherapeutic response is expected to play a pivotal role in the development of drug resistant cancers. Herein, we utilized the colon cancer cell lines, Caco2 and DLD1, to investigate heterogeneity of topoisomerase 1 (TOP1) activity in different cell subpopulations, and the consequences for the chemotherapeutic response towards the TOP1 targeting drug, camptothecin. The cell lines consisted of two subpopulations: one (the stem-cell-like cells) divided asymmetrically, was camptothecin resistant, had a differently phosphorylated TOP1 and a lower Casein Kinase II (CKII) activity than the camptothecin sensitive non-stem-cell-like cells. The tumor suppressor p14ARF had a different effect in the two cell subpopulations. In the stem-cell-like cells, p14ARF suppressed TOP1 activity and downregulation of this factor increased the sensitivity towards camptothecin. It had the opposite effect in non-stem-cell-like cells. Since it is only the stem-cell-like cells that have tumorigenic activity our results point towards new considerations for future cancer therapy. Moreover, the data underscore the importance of considering cell-to-cell variations in the analysis of molecular processes in cell lines.
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Nuclear Phosphoinositides: Their Regulation and Roles in Nuclear Functions. Int J Mol Sci 2019; 20:ijms20122991. [PMID: 31248120 PMCID: PMC6627530 DOI: 10.3390/ijms20122991] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/22/2019] [Accepted: 06/17/2019] [Indexed: 12/29/2022] Open
Abstract
Polyphosphoinositides (PPIns) are a family of seven lipid messengers that regulate a vast array of signalling pathways to control cell proliferation, migration, survival and differentiation. PPIns are differentially present in various sub-cellular compartments and, through the recruitment and regulation of specific proteins, are key regulators of compartment identity and function. Phosphoinositides and the enzymes that synthesise and degrade them are also present in the nuclear membrane and in nuclear membraneless compartments such as nuclear speckles. Here we discuss how PPIns in the nucleus are modulated in response to external cues and how they function to control downstream signalling. Finally we suggest a role for nuclear PPIns in liquid phase separations that are involved in the formation of membraneless compartments within the nucleus.
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Roy A, Tesauro C, Frøhlich R, Hede MS, Nielsen MJ, Kjeldsen E, Bonven B, Stougaard M, Gromova I, Knudsen BR. Decreased camptothecin sensitivity of the stem-cell-like fraction of Caco2 cells correlates with an altered phosphorylation pattern of topoisomerase I. PLoS One 2014; 9:e99628. [PMID: 24960044 PMCID: PMC4069021 DOI: 10.1371/journal.pone.0099628] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 05/17/2014] [Indexed: 12/27/2022] Open
Abstract
The CD44+ and CD44− subpopulations of the colorectal cancer cell line Caco2 were analyzed separately for their sensitivities to the antitumor drug camptothecin. CD44+ cells were less sensitive to camptothecin than CD44− cells. The relative resistance of CD44+ cells was correlated with (i) reduced activity of the nuclear enzyme topoisomerase I and (ii) insensitivity of this enzyme to camptothecin when analyzed in extracts. In contrast, topoisomerase I activity was higher in extracts from CD44− cells and the enzyme was camptothecin sensitive. Topoisomerase I from the two subpopulations were differentially phosphorylated in a manner that appeared to determine the drug sensitivity and activity of the enzyme. This finding was further supported by the fact that phosphorylation of topoisomerase I in CD44+ cell extract by protein kinase CK2 converted the enzyme to a camptothecin sensitive, more active form mimicking topoisomerase I in extracts from CD44− cells. Conversely, dephosphorylation of topoisomerase I in extracts from CD44− cells rendered the enzyme less active and camptothecin resistant. These findings add to our understanding of chemotherapy resistance in the Caco2 CD44+ cancer stem cell model.
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Affiliation(s)
- Amit Roy
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Cinzia Tesauro
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Rikke Frøhlich
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | | | - Maria J. Nielsen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Eigil Kjeldsen
- Hemodiagnostic Laboratory, Cancercytogenetic Section, Aarhus University Hospital, Aarhus, Denmark
| | - Bjarne Bonven
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Magnus Stougaard
- Department of Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - Irina Gromova
- Genome Integrity Unit, Proteomics in Cancer, Danish Cancer Research Center, Danish Cancer Society, Copenhagen, Denmark
| | - Birgitta R. Knudsen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
- * E-mail:
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Stougaard M, Ho YP. DNA-based nanosensors for next-generation clinical diagnostics via detection of enzyme activity. Expert Rev Mol Diagn 2013; 14:1-3. [PMID: 24308335 DOI: 10.1586/14737159.2014.863151] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Specific and sensitive detection of DNA-modifying enzymes represents a cornerstone in modern medical diagnostics. Many of the currently prevalent methods are not preferred in the clinics because they rely heavily on pre-amplification or post-separation steps. This editorial highlights the potential of adopting DNA-based nanosensors for the assessment of the activities of DNA-modifying enzymes, with emphasis on the topoisomerase and tyrosyl-DNA phosphodiesterase families. By underlining the existing challenges, we expect that the DNA-nanosensors may soon be promoted to clinical diagnostics via enzyme detection.
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Affiliation(s)
- Magnus Stougaard
- Department of Pathology, Aarhus University Hospital, Noerrebrogade 44, building 18B, 8000 Aarhus C, Denmark +45 7846 3672
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Bandyopadhyay K, Gjerset RA. Protein kinase CK2 is a central regulator of topoisomerase I hyperphosphorylation and camptothecin sensitivity in cancer cell lines. Biochemistry 2011; 50:704-14. [PMID: 21182307 DOI: 10.1021/bi101110e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Topoisomerase I (topo I) is required to unwind DNA during synthesis and provides the unique target for camptothecin-derived chemotherapeutic agents, including Irinotecan and Topotecan. While these agents are highly effective anticancer agents, some tumors do not respond due to intrinsic or acquired resistance, a process that remains poorly understood. Because of treatment toxicity, there is interest in identifying cellular factors that regulate tumor sensitivity and might serve as predictive biomarkers of therapy sensitivity. Here we identify the serine kinase, protein kinase CK2, as a central regulator of topo I hyperphosphorylation and activity and cellular sensitivity to camptothecin. In nine cancer cell lines and three normal tissue-derived cell lines we observe a consistent correlation between CK2 levels and camptothecin responsiveness. Two other topo I-targeted serine kinases, protein kinase C and cyclin-dependent kinase 1, do not show this correlation. Camptothecin-sensitive cancer cell lines display high CK2 activity, hyperphosphorylation of topo I, elevated topo I activity, and elevated phosphorylation-dependent complex formation between topo I and p14ARF, a topo I activator. Camptothecin-resistant cancer cell lines and normal cell lines display lower CK2 activity, lower topo I phosphorylation, lower topo I activity, and undetectable topo I/p14ARF complex formation. Experimental inhibition or activation of CK2 demonstrates that CK2 is necessary and sufficient for regulating these topo I properties and altering cellular responses to camptothecin. The results establish a cause and effect relationship between CK2 activity and camptothecin sensitivity and suggest that CK2, topo I phosphorylation, or topo I/p14ARF complex formation could provide biomarkers of therapy-responsive tumors.
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Affiliation(s)
- Keya Bandyopadhyay
- Torrey Pines Institute for Molecular Studies, 3550 General Atomics Court, San Diego, California 92121, United States
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Piazzi M, Bavelloni A, Faenza I, Blalock W, Urbani A, D'Aguanno S, Fiume R, Ramazzotti G, Maraldi NM, Cocco L. eEF1A phosphorylation in the nucleus of insulin-stimulated C2C12 myoblasts: Ser⁵³ is a novel substrate for protein kinase C βI. Mol Cell Proteomics 2010; 9:2719-28. [PMID: 20923971 DOI: 10.1074/mcp.m110.003152] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Recent data indicate that some PKC isoforms are translocated to the nucleus, in response to certain stimuli, where they play an important role in nuclear signaling events. To identify novel interacting proteins of conventional PKC (cPKC) at the nuclear level during myogenesis and to find new PKC isozyme-specific phosphosubstrates, we performed a proteomics analysis of immunoprecipitated nuclear samples from mouse myoblast C2C12 cells following insulin administration. Using a phospho(Ser)-PKC substrate antibody, specific interacting proteins were identified by LC-MS/MS spectrometry. A total of 16 proteins with the exact and complete motif recognized by the phospho-cPKC substrate antibody were identified; among these, particular interest was given to eukaryotic elongation factor 1α (eEF1A). Nuclear eEF1A was focalized in the nucleoli, and its expression was observed to increase following insulin treatment. Of the cPKC isoforms, only PKCβI was demonstrated to be expressed in the nucleus of C2C12 myocytes and to co-immunoprecipitate with eEF1A. In-depth analysis using site-directed mutagenesis revealed that PKCβI could phosphorylate Ser⁵³ of the eEF1A2 isoform and that the association between eEF1A2 and PKCβI was dependent on the phosphorylation status of eEF1A2.
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Affiliation(s)
- Manuela Piazzi
- Cellular Signaling Laboratory, Department of Human Anatomical Sciences, University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
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Balaña-Fouce R, García-Estrada C, Pérez-Pertejo Y, Reguera RM. Gene disruption of the DNA topoisomerase IB small subunit induces a non-viable phenotype in the hemoflagellate Leishmania major. BMC Microbiol 2008; 8:113. [PMID: 18611247 PMCID: PMC2492870 DOI: 10.1186/1471-2180-8-113] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 07/08/2008] [Indexed: 11/24/2022] Open
Abstract
Background The unusual heterodimeric leishmanial DNA topoisomerase IB consists of a large subunit containing the phylogenetically conserved "core" domain, and a small subunit harboring the C-terminal region with the characteristic tyrosine residue in the active site. RNAi silencing of any of both protomers induces a non-viable phenotype in the hemoflagelate Trypanosoma brucei. Unfortunately, this approach is not suitable in Leishmania where gene replacement with an antibiotic marker is the only approach to generate lack-of-function mutants. In this work, we have successfully generated null mutants in the small subunit of the L. major DNA topoisomerase IB using two selection markers, each conferring resistance to hygromycin B and puromycin, respectively. Results We have successfully replaced both topS loci with two selection markers. However, to achieve the second transfection round, we have had to rescue the null-homozygous with an episomal vector carrying the Leishmania major topS gene. Phenotypic characterization of the L. major rescued strain and a L. major strain, which co-overexpresses both subunits, shows few differences in DNA relaxation and camptothecin cytotoxicity when it was compared to the wild-type strain. Studies on phosphatidylserine externalization show a poor incidence of camptothecin-induced programmed cell death in L. major, but an effective cell-cycle arrest occurs within the first 24 h. S-Phase delay and G2/M reversible arrest was the main outcome at lower concentrations, but irreversible G2 arrest was detected at higher camptothecin pressure. Conclusion Results obtained in this work evidence the essentiality of the topS gene encoding the L. major DNA topoisomerase IB small subunit. Reversibility of the camptothecin effect points to the existence of effective checkpoint mechanisms in Leishmania parasites.
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Affiliation(s)
- Rafael Balaña-Fouce
- Departamento de Farmacología y Toxicología (INTOXCAL), Universidad de León, Campus de Vegazana s/n; 24071 León, Spain.
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Hackbarth JS, Galvez-Peralta M, Dai NT, Loegering DA, Peterson KL, Meng XW, Karnitz LM, Kaufmann SH. Mitotic phosphorylation stimulates DNA relaxation activity of human topoisomerase I. J Biol Chem 2008; 283:16711-22. [PMID: 18408216 PMCID: PMC2423254 DOI: 10.1074/jbc.m802246200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Revised: 03/20/2008] [Indexed: 11/06/2022] Open
Abstract
Human DNA topoisomerase I (topo I) is an essential mammalian enzyme that regulates DNA supercoiling during transcription and replication. In addition, topo I is specifically targeted by the anticancer compound camptothecin and its derivatives. Previous studies have indicated that topo I is a phosphoprotein and that phosphorylation stimulates its DNA relaxation activity. The locations of most topo I phosphorylation sites have not been identified, preventing a more detailed examination of this modification. To address this issue, mass spectrometry was used to identify four topo I residues that are phosphorylated in intact cells: Ser(10), Ser(21), Ser(112), and Ser(394). Immunoblotting using anti-phosphoepitope antibodies demonstrated that these sites are phosphorylated during mitosis. In vitro kinase assays demonstrated that Ser(10) can be phosphorylated by casein kinase II, Ser(21) can be phosphorylated by protein kinase Calpha, and Ser(112) and Ser(394) can be phosphorylated by Cdk1. When wild type topo I was pulled down from mitotic cells and dephosphorylated with alkaline phosphatase, topo I activity decreased 2-fold. Likewise, topo I polypeptide with all four phosphorylation sites mutated to alanine exhibited 2-fold lower DNA relaxation activity than wild type topo I after isolation from mitotic cells. Further mutational analysis demonstrated that Ser(21) phosphorylation was responsible for this change. Consistent with these results, wild type topo I (but not S21A topo I) exhibited increased sensitivity to camptothecin-induced trapping on DNA during mitosis. Collectively these results indicate that topo I is phosphorylated during mitosis at multiple sites, one of which enhances DNA relaxation activity in vitro and interaction with DNA in cells.
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Affiliation(s)
- Jennifer S. Hackbarth
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Marina Galvez-Peralta
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Nga T. Dai
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - David A. Loegering
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Kevin L. Peterson
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Xue W. Meng
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Larry M. Karnitz
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
| | - Scott H. Kaufmann
- Department of Biochemistry and Molecular
Biology and Division of Oncology Research, Mayo
Clinic, Mayo Graduate School, Rochester, Minnesota 55905
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St-Amant C, Lussier S, Lehoux J, Laberge RM, Boissonneault G. Altered phosphorylation of topoisomerase I following overexpression in an ovarian cancer cell line. Biochem Cell Biol 2006; 84:55-66. [PMID: 16462890 DOI: 10.1139/o05-157] [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] [Indexed: 11/22/2022] Open
Abstract
There is a growing interest regarding the use of camptothecins (CPTs) for the management of ovarian cancer. Since topoisomerase I has been established as a prime target of these drugs in other experimental models, it was important to determine whether sensitivity to CPTs in ovarian cancer cells is also correlated with the cellular level of this enzyme. Despite the 7-fold increase in topoisomerase expression achieved by adenovirus-mediated expression, the sensitivity to a CPT derivative (topotecan), was not improved compared with control cells harboring an endogenous level of the enzyme. This observation is in accordance with the similar level of topoisomerase I activity found in control and overexpressing cells and suggests that these cells may efficiently regulate the enzyme activity. Indeed, topoisomerase I overexpressing cells are characterized by a lack of alkaline phosphatase sensitivity and elimination of the hyperphosphorylated form of the protein. Taken together, these observations strongly suggest that an alteration in the phosphorylation state of topoisomerase I could limit its activity and prevent improvement of CPT response in ovarian cancer cells. In addition, a limited extent of topoisomerase I phosphorylating activity was found in nuclear extract of OVCAR-3 cells. Hence, providing enhancement in topoisomerase I expression may not result in improvement of CPT response in ovarian cancer cells because of an efficient control of the phosphorylation state of the enzyme.
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Affiliation(s)
- Christiane St-Amant
- Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, QC, Canada
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10
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Miura Y. Oxidative stress, radiation-adaptive responses, and aging. JOURNAL OF RADIATION RESEARCH 2004; 45:357-372. [PMID: 15613781 DOI: 10.1269/jrr.45.357] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Organisms living in an aerobic environment were forced to evolve effective cellular strategies to detoxify reactive oxygen species. Besides diverse antioxidant enzymes and compounds, DNA repair enzymes, and disassembly systems, which remove damaged proteins, regulation systems that control transcription, translation, and activation have also been developed. The adaptive responses, especially those to radiation, are defensive regulation mechanisms by which oxidative stress (conditioning irradiation) elicits a response against damage because of subsequent stress (challenging irradiation). Although many researchers have investigated these molecular mechanisms, they remain obscure because of their complex signaling pathways and the involvement of various proteins. This article reviews the factors concerned with radiation-adaptive response, the signaling pathways activated by conditioning irradiation, and the effects of aging on radiation-adaptive response. The proteomics approach is also introduced, which is a useful method for studying stress response in cells.
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Affiliation(s)
- Yuri Miura
- Redox regulation research group, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku. Tokyo, Japan.
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11
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Abstract
Topoisomerase I is a ubiquitous and essential enzyme in multicellular organisms. It is involved in multiple DNA transactions including DNA replication, transcription, chromosome condensation and decondensation, and probably DNA recombination. Besides its activity of DNA relaxation necessary to eliminate torsional stresses associated with these processes, topoisomerase I may have other functions related to its interaction with other cellular proteins. Topoisomerase I is the target of the novel anticancer drugs, the camptothecins. Recently a broad range of physiological and environmentally-induced DNA modifications have also been shown to poison topoisomerases. This review summarizes the various factors that enhance or suppress top1 cleavage complexes and discusses the significance of such effects. We also review the different mechanisms that have been proposed for the repair of topoisomerase I-mediated DNA lesions.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Vanhoefer U, Harstrick A, Achterrath W, Cao S, Seeber S, Rustum YM. Irinotecan in the treatment of colorectal cancer: clinical overview. J Clin Oncol 2001; 19:1501-18. [PMID: 11230497 DOI: 10.1200/jco.2001.19.5.1501] [Citation(s) in RCA: 235] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE AND METHODS For more than three decades, the therapeutic options for patients with advanced colorectal cancer have almost exclusively been based on fluoropyrimidines. With the recognition that topoisomerase-I (TOP-I) is an important therapeutic target in cancer therapy, irinotecan, a semisynthetic TOP-I-interactive camptothecin derivative, has been clinically established in the treatment of colorectal cancer. RESULTS Irinotecan was investigated as second-line chemotherapy after prior treatment with fluorouracil (FU)-based regimens in two large randomized phase III trials comparing irinotecan with either best supportive care or an infusional FU/leucovorin (LV) regimen. The outcomes of these trials established irinotecan as the standard therapy in the second-line treatment of colorectal cancer. The therapeutic value of irinotecan in the first-line treatment of metastatic colorectal cancer was investigated in two large randomized phase III trials comparing the combination of irinotecan and FU/LV with FU/LV alone. Both trials demonstrated significant superior efficacy for the combination of irinotecan and FU/LV in terms of response rate, median time to disease progression, and median survival time. Consequently, the combination of irinotecan and FU/LV has been approved as first-line chemotherapy for patients with metastatic colorectal cancer and constitutes the reference therapy against which other treatment options must be tested in the future. CONCLUSION In this review, the clinical rationale and update of the present clinical status of irinotecan in the treatment of colorectal cancer and future prospects of irinotecan-based combinations are discussed.
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Affiliation(s)
- U Vanhoefer
- Department of Internal Medicine (Cancer Research), West German Cancer Center, University of Essen Medical School, Essen, Germany
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Park SH, Lee SJ, Chung HY, Kim TH, Cho CK, Yoo SY, Lee YS. Inducible heat-shock protein 70 is involved in the radioadaptive response. Radiat Res 2000; 153:318-26. [PMID: 10669554 DOI: 10.1667/0033-7587(2000)153[0318:ihspii]2.0.co;2] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Park, S-H., Lee, S-J., Chung, H-Y., Kim, T-H., Cho, C-K., Yoo, S-Y. and Lee, Y-S. Inducible Heat-Shock Protein 70 Is Involved in the Radioadaptive Response. The thermoresistant (TR) clone of radiation-induced fibrosarcoma (RIF) cells showed an adaptive response, i.e. a reduced effect, after exposure to a higher challenging dose (4 Gy) when the priming dose (1 cGy) was given 4 or 7 h earlier, but RIF cells did not. Since inducible Hsp70 expression was different in cells of these two cell lines, the role of inducible Hsp70 in the adaptive response was examined. When inducible Hsp70 was transfected into RIF cells, the adaptive response was acquired. Transfection of inducible Hsp70 to NIH 3T3 mouse embryo cells also conferred radioresistance to the cells as assayed by clonogenic survival, [(3)H]thymidine incorporation, and an ELISA cell death detection kit. An increased tendency for the induction of an adaptive response was also observed. Interestingly, basal levels of Ca(2+)-dependent and independent Pkc activities were increased by transfection with inducible Hsp70 compared to those of control vector cells. Irradiation with gamma rays induced activation of Pkc within minutes in control vector cells, while transfection with inducible Hsp70 did not. Cellular redistribution to particulate fractions of Pkca, d and z after exposure gamma rays also was not detected. Furthermore, radioresistance by transfection with inducible Hsp70, as tested by clonogenic survival, disappeared after pretreatment with Pkc inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), prolonged treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA), and GF109203X. Taken together, these data suggest that radioresistance inducible by Hsp70 is associated with an elevated level of Pkc activity.
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Affiliation(s)
- S H Park
- Laboratory of Radiation Effect, Korea Cancer Center Hospital, 215-4 Gongneung-Dong, Nowon-Ku, Seoul 139-706, Korea
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14
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Abstract
Mammalian DNA topoisomerase I is a multifunctional enzyme which is essential for embryonal development. In addition to its classical DNA nicking-closing activities which are needed for relaxation of supercoiled DNA, topoisomerase I can phosphorylate certain splicing factors. The enzyme is also involved in transcriptional regulation through its ability to associate with other proteins in the TFIID-, and possibly TFIIH-, transcription complexes, and is implicated in the recognition of DNA lesions. Finally, topoisomerase I is a recombinase which can mediate illegitimate recombination. A crucial reaction intermediate during relaxation of DNA is the formation of a DNA-topoisomerase I complex (the cleavable complex) where topoisomerase I is covalently linked to a 3 -end of DNA thereby creating a single stranded DNA break. Cleavable complexes are also formed in the vicinity of DNA lesions and in the presence of the antitumor agent, camptothecin. While formation of cleavable complexes may be necessary for the initial stages of the DNA damage response, these complexes are also potentially dangerous to the cell due to their ability to mediate illegitimate recombination, which can lead to genomic instability and oncogenesis. Thus the levels and stability of these complexes have to be strictly regulated. This is obtained by maintaining the enzyme levels relatively constant, by limiting the stability of the cleavable complexes through physical interaction with the oncogene suppressor protein p53 and by degradation of the topoisomerase I by the proteasome system. Emerging evidence suggest that these regulatory functions are perturbed in tumor cells, explaining at the same time why topoisomerase I activities so often are increased in certain human tumors, and why these cells are sensitized to the cytotoxic effects of camptothecins.
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Affiliation(s)
- A K Larsen
- Institut Gustave-Roussy, Laboratory of Biology and Pharmacology of DNA Topoisomerases 39, Rue Camille Desmoulins, Villejuif, 94805, France.
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15
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Pommier Y, Pourquier P, Fan Y, Strumberg D. Mechanism of action of eukaryotic DNA topoisomerase I and drugs targeted to the enzyme. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1400:83-105. [PMID: 9748515 DOI: 10.1016/s0167-4781(98)00129-8] [Citation(s) in RCA: 422] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
DNA topoisomerase I is essential for cellular metabolism and survival. It is also the target of a novel class of anticancer drugs active against previously refractory solid tumors, the camptothecins. The present review describes the topoisomerase I catalytic mechanisms with particular emphasis on the cleavage complex that represents the enzyme's catalytic intermediate and the site of action for camptothecins. Roles of topoisomerase I in DNA replication, transcription and recombination are also reviewed. Because of the importance of topoisomerase I as a chemotherapeutic target, we review the mechanisms of action of camptothecins and the other topoisomerase I inhibitors identified to date.
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Affiliation(s)
- Y Pommier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, Bethesda, MD 20892-4255, USA.
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16
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Kovalszky I, Dudás J, Oláh-Nagy J, Pogány G, Töváry J, Timár J, Kopper L, Jeney A, Iozzo RV. Inhibition of DNA topoisomerase I activity by heparan sulfate and modulation by basic fibroblast growth factor. Mol Cell Biochem 1998; 183:11-23. [PMID: 9655174 DOI: 10.1023/a:1006898920637] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Eukaryotic DNA topoisomerase I catalyzes changes in the superhelical state of duplex DNA by transiently breaking single strands thereby allowing relaxation of both positively and negatively supercoiled DNA. Topoisomerase I is a nuclear enzyme localized at active sites of transcription, and abnormal levels of the enzyme have been observed in a variety of neoplasms. Because the enzyme binds heparin and, given the presence of heparan sulfate within the nuclei of mammalian cells, we sought to investigate the interaction between topoisomerase I and sulfated glycosaminoglycans isolated from normal and neoplastic human liver. The results demonstrated that low concentrations (approximately 100 nM) of heparan sulfate from normal liver but not from its malignant counterpart effectively blocked relaxation of supercoiled DNA driven by either purified holoenzyme or topoisomerase I activity present in nuclear extracts of three malignant cell lines. Heparin acted at even lower (approximately 10 nM) concentrations. Moreover, we show that basic fibroblast growth factor could interfere with this heparan sulfate/heparin-driven inhibition and that both basic fibroblast growth factor and heparin-binding sites co-localized in the nuclei of U937 leukemic cells. Our results suggest that DNA topoisomerase I activity may be modulated in vivo by specific heparan sulfate moieties present in normal cells but markedly reduced or absent in their transformed counterparts.
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Affiliation(s)
- I Kovalszky
- First Institute of Pathology and Experimental Cancer Research, Semmelweis Medical University, Budapest, Hungary
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17
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Mallia CM, Smith M, Clejan S, Beckman BS. Erythropoietin stimulates nuclear localization of diacylglycerol and protein kinase C beta II in B6SUt.EP cells. JOURNAL OF LIPID MEDIATORS AND CELL SIGNALLING 1997; 17:135-50. [PMID: 9524923 DOI: 10.1016/s0929-7855(97)00027-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Erythropoietin (EPO) is a hormone, as well as a hematopoietic growth factor, that specifically regulates the proliferation and differentiation of erythroid progenitor cells. Although the membrane-bound receptor for EPO has no intrinsic kinase activity, it triggers the activation of protein kinases via phospholipases A2, C, and D. A cascade of serine and threonine kinases, including Raf-1, MAP kinase and protein kinase C (PKC) is activated following tyrosine phosphorylation. In this study, we have examined whether changes in nuclear PKC and 1,2-diacylglycerol (DAG) are induced following EPO treatment of the murine target cell line, B6SUt.EP. Western blot analysis using isoform-specific antibodies demonstrated the presence of PKC beta II, but not PKC alpha, beta I, gamma, epsilon, delta, eta, or zeta in the nuclei of cells stimulated with EPO. The increase in nuclear beta II levels was accompanied by an immediate rise in DAG mass levels with both of the increases peaking by 1 min. These rapid increases in nuclear DAG and PKC beta II expression suggest a mechanism for EPO-induced changes in gene expression necessary for cell proliferation.
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Affiliation(s)
- C M Mallia
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112, USA
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18
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Affiliation(s)
- J P Liu
- Department of Medical Oncology, Newcastle Mater Misericordiae Hospital, New South Wales, Australia
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19
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Pantazis P. The water-insoluble camptothecin analogues: promising drugs for the effective treatment of haematological malignancies. Leuk Res 1995; 19:775-88. [PMID: 8551794 DOI: 10.1016/0145-2126(95)00048-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
After failing to exhibit benefits in clinical studies with cancer patients in the early 1970s, camptothecin (CPT) and its water-insoluble analogues are re-emerging as promising drugs with multiple actions in the treatment of human haematological malignancies. CPT analogues interfere with the mechanism of action of the nuclear enzyme topoisomerase I, while the cells progress through the S-phase of the cell cycle and this results in cell death by apoptosis. Modulations of topoisomerase I phosphorylation may indirectly modulate the cytotoxic activity of CPT analogues. In vitro, CPT analogues have exhibited increased or unaltered killing activity against leukaemia cells resistant to epipodophyllotoxins, anthracyclines, anthracenediones, and Vinca alkaloids, while development of resistance to CPT analogues renders leukaemia and lymphoma cells more sensitive to topoisomerase II-directed drugs, inducers of cell differentiation, and immunotoxins. Oral administration of the CPT analogues has circumvented the inconvenience of solubility of these drugs. Metabolic conversion of the CPT analogue 9-nitro-CPT to equally or more potent 9-amino-CPT practically makes unnecessary treatment of the patient with 9-amino-CPT, which, in addition, is costlier to prepare than 9-nitro-CPT. Considering the therapeutic, economic and handling viewpoints, the overall conclusion is that the water-insoluble CPT analogues are very promising antileukaemia/antilymphoma agents that warrant further preclinical and clinical studies.
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Affiliation(s)
- P Pantazis
- Stehlin Foundation for Cancer Research, St. Joseph Hospital, Houston, Texas, USA
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20
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Gupta M, Fujimori A, Pommier Y. Eukaryotic DNA topoisomerases I. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1262:1-14. [PMID: 7772596 DOI: 10.1016/0167-4781(95)00029-g] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- M Gupta
- Laboratory of Molecular Pharmacology, National Cancer Institute, National Institute of Health, Bethesda, MD 20892-4255, USA
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21
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Buchner K. Protein Kinase C in the Transduction of Signals Toward and within the Cell Nucleus. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.tb20252.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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22
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Kordiyak GJ, Jakes S, Ingebritsen TS, Benbow RM. Casein kinase II stimulates Xenopus laevis DNA topoisomerase I by physical association. Biochemistry 1994; 33:13484-91. [PMID: 7947757 DOI: 10.1021/bi00249a037] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A Xenopus laevis casein kinase II-like activity copurified with X. laevis DNA topoisomerase I activity during chromatography on DEAE-cellulose, phosphocellulose, and hydroxylapatite, but the two activities were resolved by chromatography on DNA-agarose [Kaiserman, H. B., Ingebritsen, T. S., & Benbow, R. M. (1988) Biochemistry 27, 3216-3222]. Phosphorylation of the catalytic polypeptides of dephosphorylated X. laevis DNA topoisomerase I by the endogenous X. laevis casein kinase II-like activity apparently resulted in a severalfold increase in catalytic activity. In this study, we show that incubation of purified X. laevis DNA topoisomerase I with electrophoretically homogeneous bovine brain casein kinase II and ATP strongly stimulated catalytic activity. Surprisingly, purified bovine casein kinase II stimulated X. laevis DNA topoisomerase I activity by more than an order of magnitude in the absence of ATP, although ATP resulted in additional stimulation. Other basic proteins, such as histone H1 and HMG proteins, also stimulated X. laevis DNA topoisomerase I catalytic activity 2-3-fold in the absence of ATP. Modulation of catalytic activity by direct physical association (protein-protein interactions) must, therefore, be considered in addition to phosphorylation in assessing the physiological role of casein kinase II and other basic proteins during regulation of X. laevis DNA topoisomerase I activity in vivo.
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Affiliation(s)
- G J Kordiyak
- Department of Zoology and Genetics, Iowa State University, Ames 50011-3223
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23
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Trubiani O, Borgatti P, Di Primio R. Protein kinase C modulation in apoptotic rat thymocytes: an ultrastructural analysis. HISTOCHEMISTRY 1994; 102:311-6. [PMID: 7843993 DOI: 10.1007/bf00269168] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Numerous events in the cell, such as gene expression, cell growth and metabolism are regulated by signal transduction pathways involving protein kinase C (PKC). Recent data indicate that a PKC-dependent mechanism also underlies the apoptotic death of cells induced by glucocorticoid hormones. In this report we have analysed the changes of PKC during dexamethasone-induced apoptosis in thymocytes by means of immunocytochemical and immunochemical analysis. The data obtained show an increase and intracellular movement of protein kinase C, which is translocated to the nucleus and linked to the nuclear matrix during the apoptotic process.
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Affiliation(s)
- O Trubiani
- Istituto di Citomorfologia Normale e Patologica del CNR, Chieti, Italy
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24
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Pizao PE, Smitskamp-Wilms E, Van Ark-Otte J, Beijnen JH, Peters GJ, Pinedo HM, Giaccone G. Antiproliferative activity of the topoisomerase I inhibitors topotecan and camptothecin, on sub- and postconfluent tumor cell cultures. Biochem Pharmacol 1994; 48:1145-54. [PMID: 7945408 DOI: 10.1016/0006-2952(94)90151-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have assessed the antiproliferative effects of a 24-hr exposure to the topoisomerase I inhibitors, topotecan and camptothecin, on two colon and one ovarian human tumor cell lines, cultured as subconfluent and as multilayered postconfluent cultures. Chemosensitivity was measured by the sulforhodamine B assay. In general, postconfluent cultures were less sensitive to these agents, yielding GI50S (drug concentrations inhibiting growth by 50%) from 1.2 to more than 6000 times higher than those of subconfluent cultures. Both compounds displayed similar effects on subconfluent cells, inducing complete growth inhibition at concentrations ranging from 0.03 to 0.5 microM. Topotecan, however, was more potent than camptothecin in two out of the three cell lines tested as multilayered postconfluent cultures. Topoisomerase I mRNA expression on postconfluent cultures was 50% lower than on subconfluent cultures in the three cell lines studied. However, we did not detect any reproducible differences in topoisomerase I protein expression and in relaxation activity of supercoiled DNA between the two types of cultures. From accumulation experiments it appeared that the peak concentration of the lactone form of topotecan as well as the area under the concentration-time curve (AUC) were 2-fold higher in the monolayer than in the multilayer cultures. Therefore, the differences in the activity of topoisomerase I inhibitors under our experimental conditions were likely due to a decreased rate of proliferation of postconfluent cells, associated with a reduction in drug uptake.
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Affiliation(s)
- P E Pizao
- Department of Oncology, Free University Hospital, Amsterdam, The Netherlands
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25
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Samuels DS, Shimizu Y, Nakabayashi T, Shimizu N. Phosphorylation of DNA topoisomerase I is increased during the response of mammalian cells to mitogenic stimuli. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1223:77-83. [PMID: 8061056 DOI: 10.1016/0167-4889(94)90075-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
DNA topoisomerase I is phosphorylated after mitogenic stimulation of 3T3-L1 mouse fibroblasts by 12-O-tetradecanoylphorbol 13-acetate (TPA), a phorbol ester tumor promoter. In vivo labeling with [32P]orthophosphate and immunoprecipitation with an anti-DNA topoisomerase I antibody has demonstrated an increase in the phosphorylation of DNA topoisomerase I in Swiss/3T3 mouse fibroblasts treated with epidermal growth factor (EGF) and H35 rat hepatoma cells treated with insulin. The only phosphorylated form of DNA topoisomerase I observed was the 100-kDa protein Digestion of DNA topoisomerase I with trypsin revealed two phosphopeptides. In addition, VT-1, a non-responsive genetic variant of 3T3-L1, and the DNA topoisomerase I inhibitor camptothecin were used to further study TPA-induced DNA topoisomerase I phosphorylation. Our results indicate that the phosphorylation of DNA topoisomerase I may be an ubiquitous response of cultured mammalian cells to mitogenic agents, even in the absence of DNA replication.
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Affiliation(s)
- D S Samuels
- Department of Molecular and Cellular Biology, University of Arizona, Tucson
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26
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Affiliation(s)
- L Cocco
- Institute of Human Anatomy, University of Bologna
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27
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Samuels DS, Shimizu N. The predominant form of mammalian DNA topoisomerase I in vivo has a molecular mass of 100 kDa. Mol Biol Rep 1994; 19:99-103. [PMID: 8072496 DOI: 10.1007/bf00997154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
DNA topoisomerase I was purified to apparent homogeneity from human HeLa cells as a single polypeptide with a molecular mass of 100 kDa, as assayed by both gel filtration column chromatography and SDS-polyacrylamide gel electrophoresis. No smaller forms of the enzyme were detected in the purified fraction. Therefore, smaller forms, which have been observed by other investigators, are likely to be the result of proteolysis during isolation and are not relevant to the in vivo activity of DNA topoisomerase I.
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Affiliation(s)
- D S Samuels
- Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721
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28
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Isonishi S, Hom DK, Eastman A, Howell SB. Enhancement of sensitivity to platinum(II)-containing drugs by 12-O-tetradecanoyl-phorbol-13-acetate in a human ovarian carcinoma cell line. Br J Cancer 1994; 69:217-21. [PMID: 8297717 PMCID: PMC1968705 DOI: 10.1038/bjc.1994.42] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Sensitivity to platinum-containing drugs is believed to be a function of how much drug enters the cell, the extent of DNA adduct formation and the rate at which DNA is repaired. Activation of protein kinase C by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was found to enhance the sensitivity of human ovarian carcinoma 2008 cells to cisplatin (DDP), carboplatin (CBDCA) and (glycolato-O,O') diammineplatinum(II) (254-S). TPA was able to enhance the sensitivity of the DDP-resistant 2008/C13*5.25 subline to each of the three drugs to the same extent as for the 2008 cells. TPA produced no significant change in the uptake of [3H]cis-dichloro(ethylenediamine)-platinum(II). ([3H]DEP) or CBDCA. It did not alter glutathione content or glutathione-S-transferase activity, and induced rather than suppressed metallothionein IIA mRNA levels. TPA did increase the formation of intrastrand guanine-guanine cross-links by a factor of 1.5 +/- 0.3 (s.d.), and reduced the fraction of intrastrand adducts removed from DNA over the subsequent 24 h by a factor of 1.3 +/- 0.2 (s.d.) (n = 4; P < 0.05), however, these effects were too small to account for the degree of TPA-induced sensitisation. These results indicate that the mechanism of TPA-induced sensitisation is not specific to any one structural form of platinum-containing drug, and that it is not readily explicable on the basis of an effect on the four major parameters currently believed to regulate DDP sensitivity.
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Affiliation(s)
- S Isonishi
- Department of Obstetrics and Gynecology, Jikei University, Tokyo, Japan
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29
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Jarpe MB, Leach KL, Raben DM. Alpha-thrombin-induced nuclear sn-1,2-diacylglycerols are derived from phosphatidylcholine hydrolysis in cultured fibroblasts. Biochemistry 1994; 33:526-34. [PMID: 8286382 DOI: 10.1021/bi00168a018] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Diglycerides play an important role in a number of agonist-induced signal transduction pathways. We have recently demonstrated that alpha-thrombin induces a rapid increase in the level of diglyceride mass in the nucleus and a selective increase in nuclear PKC-alpha [Leach, K.L., Ruff, V.A., Jarpe, M.B., Fabbro, D., Adams, L.D., & Raben, D.M. (1992) J. Biol. Chem. 267, 21816-21822]. In the present report, we examined the potential source of the induced nuclear diglycerides by examining the molecular species profiles of both the induced diglycerides and nuclear phospholipids by capillary gas chromatography. The molecular species profiles of the nuclear diglycerides generated resemble the species profiles of PC, and not PI species, at all times. In addition, while our previous data indicated that the molecular species of whole-cell phospholipids did not change in response to alpha-thrombin, nuclear PE was altered in a dramatic and selective manner in response to this agonist. These results demonstrate that PC hydrolysis is the predominant, if not exclusive, source of the alpha-thrombin-induced nuclear diglycerides in these fibroblasts.
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Affiliation(s)
- M B Jarpe
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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30
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Pommier Y, Tanizawa A, Kohn KW. Mechanisms of topoisomerase I inhibition by anticancer drugs. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1994; 29B:73-92. [PMID: 8996602 DOI: 10.1016/s1054-3589(08)61132-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Y Pommier
- National Institutes of Health, Bethesda, Maryland 20892, USA
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31
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Cardellini E, Durban E. Phosphorylation of human topoisomerase I by protein kinase C in vitro and in phorbol 12-myristate 13-acetate-activated HL-60 promyelocytic leukaemia cells. Biochem J 1993; 291 ( Pt 1):303-7. [PMID: 8385936 PMCID: PMC1132517 DOI: 10.1042/bj2910303] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Topoisomerase I was phosphorylated in vitro by protein kinase C (PKC) purified from rat brain with high affinity (Km about 0.1 microM). Tryptic phosphopeptide mapping indicated that two major topoisomerase I peptides phosphorylated in vivo were comigrating with minor peptides phosphorylated by PKC in vitro. Topoisomerase I phosphorylation was stimulated 3-fold in HL-60 cells exposed to the tumour promoter phorbol 12-myristate 13-acetate. The results suggest that topoisomerase I phosphorylation in HL-60 cells is indirectly controlled by PKC.
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Affiliation(s)
- E Cardellini
- Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030
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32
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Zhang W, Hara A, Sakai N, Andoh T, Yamada H, Nozawa Y. Radiosensitization and inhibition of deoxyribonucleic acid repair in rat glioma cells by long-term treatment with 12-O-tetradecanoylphorbol 13-acetate. Neurosurgery 1993; 32:432-7; discussion 437. [PMID: 8455768 DOI: 10.1227/00006123-199303000-00015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Patients with brain tumors often undergo radiotherapy, and the cellular resistance is a major obstacle. It has been suggested that protein kinase C (PKC) may be one of a number of important regulatory enzymes in cell response to ionizing radiation. We therefore investigated the effect of PKC depletion on deoxyribonucleic acid (DNA) damage and repair after radiation in C6 cells using a microgel electrophoresis method to explore the role of PKC in glioma radioresistance. When cells are embedded in agarose on slides, lysed, and subjected to an electric field, broken DNA is able to migrate toward the anode. A significant increase in the length of DNA migration was observed in the cells exposed to irradiation. Inhibition of PKC activity by prolonged treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) or staurosporine, a potent PKC inhibitor, before irradiation enhanced radiation-induced DNA damage and attenuated the repair of damaged DNA. The half-times of DNA repair in parent C6 cells and PKC-depleted C6 cells were about 30 and 60 min, respectively, and the extent of DNA migration was still seen in the PKC-depleted cells even at 120 min after irradiation. In addition, the C6 cell clonogenicity after irradiation was also attenuated by long-term exposure of the cells to 12-O-tetradecanoylphorbol 13-acetate. These data suggest that PKC may play an important role in regulating the cell response to irradiation. The inhibitors of PKC might represent a new class of pharmacological agents to manipulate the radiosensitivity of gliomas.
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Affiliation(s)
- W Zhang
- Department of Neurosurgery, Gifu University School of Medicine, Japan
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33
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Radiosensitization and Inhibition of Deoxyribonucleic Acid Repair in Rat Glioma Cells by Long-Term Treatment with 12-O-Tetradecanoylphorbol 13-Acetate. Neurosurgery 1993. [DOI: 10.1097/00006123-199303000-00015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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34
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Onishi Y, Azuma Y, Sato Y, Mizuno Y, Tadakuma T, Kizaki H. Topoisomerase inhibitors induce apoptosis in thymocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1175:147-54. [PMID: 8380339 DOI: 10.1016/0167-4889(93)90017-j] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The effects of the inhibitors of topoisomerase I and II, camptothecin and etoposide, as well as novobiocin and adriamycin, on the DNA fragmentation and viability of mouse thymocytes in primary culture were examined. All inhibitors were shown to produce dose-dependent internucleosomal DNA cleavage by resolving isolated DNA by agarose-gel electrophoresis. The DNA fragmentation seemed to precede cell death, determined on the basis of LDH release, by a few hours. Etoposide-induced DNA fragmentation progressively increased after incubation and was enhanced by pretreatment with phorbol 12,13-dibutyrate, a phorbol ester capable of activating protein kinase C, whereas camptothecin-induced DNA fragmentation increased progressively after 12 h incubation and was unaffected by phorbol 12,13-dibutyrate-pretreatment. The process was also energy-dependent and required RNA and protein synthesis and protein phosphorylation, since it was inhibited by sodium azide, actinomycin D, cycloheximide and 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine hydrochloride, a protein kinase inhibitor. DNA fragmentation was also inhibited by zinc ions, suggesting the involvement of a specific endonuclease in DNA cleavage. These phenomena are similar to those detected in thymocytes undergoing apoptosis following exposure to glucocorticoids (Cohen, J.J. and Duke, R.C. (1984) J. Immunol. 132, 38-42). Considering that topoisomerases function in cellular proliferation and differentiation by altering DNA topology, the results suggest that topoisomerases have important roles in T-lymphocyte ontogeny in the thymus and are in part involved in the elimination of autoreactive or harmful cells by an apoptotic process.
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Affiliation(s)
- Y Onishi
- Department of Biochemistry, Tokyo Dental College, Chiba, Japan
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35
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Zhang W, Yamada H, Sakai N, Nozawa Y. Sensitization of C6 glioma cells to radiation by staurosporine, a potent protein kinase C inhibitor. J Neurooncol 1993; 15:1-7. [PMID: 8455059 DOI: 10.1007/bf01050256] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The effect of staurosporine, a potent protein kinase C (PKC) inhibitor, on the sensitivity to radiation has been investigated in C6 glioma cells. Pretreatment of C6 cells with staurosporine at the concentrations over 1 nM resulted in an enhancement of sensitivity to irradiation. At a concentration of 5 nM, staurosporine caused significant radiosensitization of the cells, either it was administered 1) before and during irradiation, or 2) continuously before, during, and after irradiation, with a reduced D0 (the 37% survival dose) from 3.8 Gy to 2.9 Gy and 3.0 Gy, respectively, (p < 0.03). Since the viability of C6 cells was not affected by staurosporine alone at the concentrations tested, the radiosensitizing effect of staurosporine was considered to be mediated via suppression of PKC. Furthermore, another potent PKC inhibitor H-7, 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine dihydrochloride, also sensitized C6 cells to irradiation, while HA1004, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide hydrochloride a potent inhibitor for cAMP-dependent protein kinase, failed to affect the radiosensitivity in this cells. Therefore, staurosporine-induced sensitization of C6 cells to radiation may at least in part be mediated by its inhibitory activity for PKC. Staurosporine represents a new agent for radiosensitization and may prove usefulness in studying the mechanisms responsible for radio-resistance and -sensitivity in glioma cells.
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Affiliation(s)
- W Zhang
- Department of Neurosurgery, Gifu University School of Medicine, Japan
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36
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Tournier MF, Sobczak J, de Nechaud B, Duguet M. Comparison of biochemical properties of DNA-topoisomerase I from normal and regenerating liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 210:359-64. [PMID: 1332866 DOI: 10.1111/j.1432-1033.1992.tb17429.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Biochemical properties of topoisomerase I from normal and regenerating rat liver were analysed using crude or fractionated nuclear extracts. We could not detect significative change in topoisomerase I content or activity (magnesium stimulation and inhibition by ATP) during the course of liver regeneration. Topoisomerase I can be resolved into two species of 97 kDa and 100 kDa, with the same pI of 8.2-8.6 as shown by two dimensional gel electrophoresis. The two polypeptides contained a non-phosphorylated precursor and others forms with variable degrees of phosphorylation. In-vitro dephosphorylation with alkaline phosphatase leads to the disappearance of the phosphorylated forms and inactivation of the enzyme. The affinity of topoisomerase I for chromatin (measured by salt elution) differs markedly between normal and regenerating liver: nearly 50% of topoisomerase I remained bound to the chromatin from normal liver at 250 mM NaCl whereas it was completely eluted from 24-h-regenerating-liver nuclei. The biological significance of these results is discussed.
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Affiliation(s)
- M F Tournier
- Laboratoire d'Enzymologie des acides nucléiques, Université Pierre et Marie Curie, Paris, France
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37
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Leach K, Ruff V, Jarpe M, Adams L, Fabbro D, Raben D. Alpha-thrombin stimulates nuclear diglyceride levels and differential nuclear localization of protein kinase C isozymes in IIC9 cells. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36685-2] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Sakai K, Hirai M, Kudoh J, Minoshima S, Shimizu N. Molecular cloning and chromosomal mapping of a cDNA encoding human 80K-L protein: major substrate for protein kinase C. Genomics 1992; 14:175-8. [PMID: 1427823 DOI: 10.1016/s0888-7543(05)80301-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have isolated and sequenced complementary DNA (cDNA) for the human 80K-L protein, a major substrate for protein kinase C and the human homologue of an 80- to 87-kDa bovine protein named MARCKS (myristoylated alanine-rich C kinase substrate). The human 80K-L cDNA encodes a protein of 332 amino acids with a calculated molecular weight of 31,534. Homology comparisons of the nucleotide sequences of the cDNAs indicated that their 3'-untranslated regions are more homologous than the coding regions. Spot blot hybridization using flow-sorted human chromosomes indicated that the gene encoding the 80K-L protein, designated MACS, maps to the q15----qter region of human chromosome 6, and it also suggested that a genomic region with a sequence homologous to the 3'-untranslated region of the 80K-L mRNA exists on chromosome 21.
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Affiliation(s)
- K Sakai
- Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan
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Bachs O, Agell N, Carafoli E. Calcium and calmodulin function in the cell nucleus. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1113:259-70. [PMID: 1510999 DOI: 10.1016/0304-4157(92)90041-8] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- O Bachs
- Department of Cell Biology, University of Barcelona, Spain
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Bhat NR, Hauser KF, Kindy MS. Cell proliferation and protooncogene induction in oligodendroglial progenitors. J Neurosci Res 1992; 32:340-9. [PMID: 1433384 DOI: 10.1002/jnr.490320306] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cell proliferation and the expression of the protooncogenes c-fos and c-jun have been examined in the primary cultures of oligodendroglial (OL) progenitor cells in response to phorbol 12-myristate 13-acetate (PMA), serum, insulin, insulin-like growth factor-I (IGF-I), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF). Combined [3H]thymidine autoradiography and immunocytochemistry was used to assess the mitogenic response of O4 (an oligodendrocyte-specific marker)-positive OL progenitors. In addition, the rate of DNA synthesis was measured by the incorporation of [3H]thymidine into acid-precipitable material. It was found that all of the agents tested stimulated DNA synthesis in OL progenitors and induced a rapid increase in c-fos and c-jun protooncogene expression. The induction of c-fos gene expression and DNA synthesis in response to PMA was completely blocked by 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7), a potent inhibitor of protein kinase C (PKC), thereby suggesting a role for PKC in the control of c-fos expression and cell proliferation in OL progenitors.
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Affiliation(s)
- N R Bhat
- Department of Biochemistry, Sanders-Brown Center on Aging, University of Kentucky School of Medicine, Lexington
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41
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DNA topoisomerase I phosphorylation in murine fibroblasts treated with 12-O-tetradecanoylphorbol-13-acetate and in vitro by protein kinase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49889-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Testori A, Burgoyne LA, Murray AW. Importance of substrate conformation in the phosphorylation of chromatin-associated proteins by exogenous protein kinase C. Cell Signal 1992; 4:145-51. [PMID: 1616821 DOI: 10.1016/0898-6568(92)90078-m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Protein kinase C (PKC)-mediated phosphorylation of chromatin-associated proteins was studied in vitro. HL-60 and HeLa nuclear proteins were notably unresponsive to exogenously added brain PKC. In contrast, 3T3 fibroblasts and lymphocytes from primary cultures exhibited PKC-dependent phosphorylation of chromatin-associated proteins when chromatin was induced to expand. Unexpanded nuclei in all cell lines were unresponsive. Responsiveness was particularly obvious in the decondensed chromatin of primary lymphocytes, where a large number of proteins were phosphorylated in response to exogenous PKC. DNAase-I and micrococcal nuclease strongly modulated these phosphorylation patterns indicating that the substrates were DNA-associated. It was concluded that although substrate conformation, i.e. condensation state, was the primary determining factor in control of PKC-dependent nuclear protein phosphorylation, different cell lines greatly differ in their overall responsiveness to exogenous PKC.
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Affiliation(s)
- A Testori
- School of Biological Sciences, Flinders University of South Australia, Adelaide
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43
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Hsieh JC, Jurutka PW, Galligan MA, Terpening CM, Haussler CA, Samuels DS, Shimizu Y, Shimizu N, Haussler MR. Human vitamin D receptor is selectively phosphorylated by protein kinase C on serine 51, a residue crucial to its trans-activation function. Proc Natl Acad Sci U S A 1991; 88:9315-9. [PMID: 1656468 PMCID: PMC52705 DOI: 10.1073/pnas.88.20.9315] [Citation(s) in RCA: 165] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The vitamin D receptor (VDR) is known to be a phosphoprotein and inspection of the deduced amino acid sequence of human VDR (hVDR) reveals the conservation of three potential sites of phosphorylation by protein kinase C (PKC)--namely, Ser-51, Ser-119, and Ser-125. Immunoprecipitated extracts derived from a rat osteoblast-like osteosarcoma cell line that contains the VDR in high copy number were incubated with the alpha, beta, and gamma isozymes of PKC, and VDR proved to be an effective substrate for PKC-beta, in vitro. When hVDR cDNAs containing single, double, and triple mutations of Ser-51, Ser-119, and Ser-125 were expressed in CV-1 monkey kidney cells, immunoprecipitated and phosphorylated by PKC-beta, in vitro, the mutation of Ser-51 selectively abolished phosphorylation. Furthermore, when transfected CV-1 cells were treated with phorbol 12-myristate 13-acetate, a PKC activator, phosphorylation of wild-type hVDR was enhanced, whereas that of the Ser-51 mutant hVDR was unaffected. Therefore, Ser-51 is the site of hVDR phosphorylation by PKC, both in vitro and in vivo. To evaluate the functional role of Ser-51 and its potential phosphorylation, hVDR-mediated transcription was tested using cotransfection with expression plasmids and a reporter gene that contained a vitamin D response element. Mutation of Ser-51 markedly inhibited transcriptional activation by the vitamin D hormone, suggesting that phosphorylation of Ser-51 by PKC could play a significant role in vitamin D-dependent transcriptional activation. Therefore, the present results link the PKC signal transduction pathway of growth regulation and tumor promotion to the phosphorylation and function of VDR.
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Affiliation(s)
- J C Hsieh
- Department of Biochemistry, University of Arizona, Tucson 85724
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Waybill MM, Yelamarty RV, Zhang YL, Scaduto RC, LaNoue KF, Hsu CJ, Smith BC, Tillotson DL, Yu FT, Cheung JY. Nuclear calcium gradients in cultured rat hepatocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 261:E49-57. [PMID: 1858874 DOI: 10.1152/ajpendo.1991.261.1.e49] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Ca2+ concentrations ([Ca2+]) in cytosol and nucleus in fura-2-loaded cultured rat hepatocytes were determined by three-dimensional (3-D) optical-sectioning microscopy. After determining the empirical 3-D point spread function of the fluorescence microscope-coupled digital video imaging system, contaminating light arising from optical planes above and below the plane of interest was removed by deconvolution using the nearest-neighboring approach (NNA) algorithm. Although deconvolution resulted in substantial improvement in accuracy of fluorescence intensity determinations in single-wavelength excitation images as well as sharper delineation of boundaries between cellular compartments, the complicated mathematical process did not significantly enhance the precision of [Ca2+] values derived from ratiometric (ratio of dual-wavelength excitation) images. In resting hepatocytes, cytosolic Ca2+ (210 +/- 15 nM) was 1.6- to 2-fold higher than nuclear Ca2+ (128 +/- 12 nM). This difference in Ca2+ between the two compartments was detected both in raw ratiometric images and in those processed with NNA algorithm. Addition of arginine vasopressin or epidermal growth factor resulted in significant increases (2- to 3-fold) in both cytosolic and nuclear Ca2+; however, the nuclear-to-cytosolic Ca2+ gradient was preserved in hepatocytes stimulated with mitogens. We conclude that the hepatocyte nuclear membrane contains Ca2+ permeability barriers and Ca2+ transport mechanisms that may be hormonally sensitive. We postulate that the increase in nuclear Ca2+ may be important in regulation of cell proliferation induced by mitogens, possibly by activating Ca(2+)-dependent endonucleases, nuclear calmodulin, or nuclear protein kinase C.
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Affiliation(s)
- M M Waybill
- Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033
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Malviya AN, Rogue P, Masmoudi A, Labourdette G, Vincendon G. Gene transcription: a role for nuclear protein kinase C? Int J Cancer 1990; 45:580-2. [PMID: 2307546 DOI: 10.1002/ijc.2910450335] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- A N Malviya
- Centre de Neurochimie du CNRS, Strasbourg, France
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