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Bunimovich YL, Nair-Gill E, Riedinger M, McCracken MN, Cheng D, McLaughlin J, Radu CG, Witte ON. Deoxycytidine kinase augments ATM-Mediated DNA repair and contributes to radiation resistance. PLoS One 2014; 9:e104125. [PMID: 25101980 PMCID: PMC4125169 DOI: 10.1371/journal.pone.0104125] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 07/10/2014] [Indexed: 11/19/2022] Open
Abstract
Efficient and adequate generation of deoxyribonucleotides is critical to successful DNA repair. We show that ataxia telangiectasia mutated (ATM) integrates the DNA damage response with DNA metabolism by regulating the salvage of deoxyribonucleosides. Specifically, ATM phosphorylates and activates deoxycytidine kinase (dCK) at serine 74 in response to ionizing radiation (IR). Activation of dCK shifts its substrate specificity toward deoxycytidine, increases intracellular dCTP pools post IR, and enhances the rate of DNA repair. Mutation of a single serine 74 residue has profound effects on murine T and B lymphocyte development, suggesting that post-translational regulation of dCK may be important in maintaining genomic stability during hematopoiesis. Using [(18)F]-FAC, a dCK-specific positron emission tomography (PET) probe, we visualized and quantified dCK activation in tumor xenografts after IR, indicating that dCK activation could serve as a biomarker for ATM function and DNA damage response in vivo. In addition, dCK-deficient leukemia cell lines and murine embryonic fibroblasts exhibited increased sensitivity to IR, indicating that pharmacologic inhibition of dCK may be an effective radiosensitization strategy.
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Affiliation(s)
- Yuri L. Bunimovich
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
- Crump Institute for Molecular Imaging, University of California Los Angeles, Los Angeles, California, United States of America
| | - Evan Nair-Gill
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Mireille Riedinger
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Melissa N. McCracken
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Donghui Cheng
- Howard Hughes Medical Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jami McLaughlin
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Caius G. Radu
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
- Crump Institute for Molecular Imaging, University of California Los Angeles, Los Angeles, California, United States of America
- Ahmanson Translational Imaging Division, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Owen N. Witte
- Department of Molecular and Medical Pharmacology, University of California Los Angeles, Los Angeles, California, United States of America
- Howard Hughes Medical Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
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Noninvasive prediction of tumor responses to gemcitabine using positron emission tomography. Proc Natl Acad Sci U S A 2009; 106:2847-52. [PMID: 19196993 DOI: 10.1073/pnas.0812890106] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and cytosine arabinoside (cytarabine, ara-C) represent a class of nucleoside analogs used in cancer chemotherapy. Administered as prodrugs, dFdC and ara-C are transported across cell membranes and are converted to cytotoxic derivatives through consecutive phosphorylation steps catalyzed by endogenous nucleoside kinases. Deoxycytidine kinase (DCK) controls the rate-limiting step in the activation cascade of dFdC and ara-C. DCK activity varies significantly among individuals and across different tumor types and is a critical determinant of tumor responses to these prodrugs. Current assays to measure DCK expression and activity require biopsy samples and are prone to sampling errors. Noninvasive methods that can detect DCK activity in tumor lesions throughout the body could circumvent these limitations. Here, we demonstrate an approach to detecting DCK activity in vivo by using positron emission tomography (PET) and (18)F-labeled 1-(2'-deoxy-2'-fluoroarabinofuranosyl) cytosine] ([(18)F]FAC), a PET probe recently developed by our group. We show that [(18)F]FAC is a DCK substrate with an affinity similar to that of dFdC. In vitro, accumulation of [(18)F]FAC in murine and human leukemia cell lines is critically dependent on DCK activity and correlates with dFdC sensitivity. In mice, [(18)F]FAC accumulates selectively in DCK-positive vs. DCK-negative tumors, and [(18)F]FAC microPET scans can predict responses to dFdC. We suggest that [(18)F]FAC PET might be useful for guiding treatment decisions in certain cancers by enabling individualized chemotherapy.
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Smal C, Vertommen D, Bertrand L, Rider MH, van den Neste E, Bontemps F. Identification of phosphorylation sites on human deoxycytidine kinase after overexpression in eucaryotic cells. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2007; 25:1141-6. [PMID: 17065079 DOI: 10.1080/15257770600890194] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Compelling evidence suggests that deoxycytidine kinase (dCK), a key enzyme in the salvage of deoxyribonucleosides and in the activation of clinically relevant nucleoside analogues, can be regulated by reversible phosphorylation. In this study, we show that dCK overexpressed in HEK-293T cells was labelled after incubation of the cells with [32P]orthophosphate. Tandem mass spectrometry allowed the identification of 4 in vivo phosphorylation sites, Thr3, Ser11, Ser15, and Ser74. These results provide the first evidence that dCK is constitutively multiphosphorylated in intact cells. In addition, site-directed mutagenesis demonstrated that phosphorylation of Ser74, the major in vivo phosphorylation site, is crucial for dCK activity.
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Affiliation(s)
- C Smal
- Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology, Brussels, Belgium
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Keszler G, Spasokoukotskaja T, Sasvári-Székely M, Eriksson S, Staub M. Deoxycytidine kinase is reversibly phosphorylated in normal human lymphocytes. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2007; 25:1147-51. [PMID: 17065080 DOI: 10.1080/15257770600894345] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The activity of deoxycytidine kinase (dCK) has been shown to be enhanced upon genotoxic stress in human lymphocytes, and reversible phosphorylation of the enzyme has been implicated in the activation process. Here, we provide compelling evidence that dCK is a cytosolic phosphoprotein. Two-dimensional gel electrophoresis revealed that dCK has several differentially charged isoforms in cells. One-third of total cellular dCK was bound to a phosphoprotein-binding column irrespective of its activity levels, indicating that other mechanisms rather than phosphorylation alone might also be involved in the stimulation of enzyme activity. We excluded the possibility that activated dCK is translocated to the nucleus, but identified a dCK isoform of low abundance with a higher molecular weight in the nuclear fractions.
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Affiliation(s)
- G Keszler
- Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Budapest, Hungary.
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Keszler G, Virga S, Spasokoukotskaja T, Bauer PI, Sasvari-Szekely M, Staub M. Activation of deoxycytidine kinase by deoxyadenosine: implications in deoxyadenosine-mediated cytotoxicity. Arch Biochem Biophys 2005; 436:69-77. [PMID: 15752710 DOI: 10.1016/j.abb.2005.01.009] [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] [Received: 10/22/2004] [Revised: 01/13/2005] [Indexed: 11/17/2022]
Abstract
The inborn deficiency of adenosine deaminase is characterised by accumulation of excess amounts of cytotoxic deoxyadenine nucleotides in lymphocytes. Formation of dATP requires phosphorylation of deoxyadenosine by deoxycytidine kinase (dCK), the main nucleoside salvage enzyme in lymphoid cells. Activation of dCK by a number of genotoxic agents including 2-chlorodeoxyadenosine, a deamination-resistant deoxyadenosine analogue, was found previously. Here, we show that deoxyadenosine itself is also a potent activator of dCK if its deamination was prevented by the adenosine deaminase inhibitor deoxycoformycin. In contrast, deoxycytidine was found to prevent stimulation of dCK by various drugs. The activated form of dCK was more resistant to tryptic digestion, indicating that dCK undergoes a substrate-independent conformational change upon activation. Elevated dCK activities were accompanied by decreased pyrimidine nucleotide levels whereas cytotoxic dATP pools were selectively enhanced. dCK activity was found to be downregulated by growth factor and MAP kinase signalling, providing a potential tool to slow the rate of dATP accumulation in adenosine deaminase deficiency.
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Affiliation(s)
- Gergely Keszler
- Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, P.O. Box 260, H-1444 Budapest, Hungary.
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Smal C, Bertrand L, Van Den Neste E, Cardoen S, Veiga-da-Cunha M, Marie S, Race V, Ferrant A, Van den Berghe G, Bontemps F. New Evidences for a Regulation of Deoxycytidine Kinase Activity by Reversible Phosphorylation. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/chin.200511208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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