Requirement for deoxycytidine kinase in T and B lymphocyte development

Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 03/2010; 107(12):5551-6. DOI: 10.1073/pnas.0913900107
Source: PubMed


Deoxycytidine kinase (dCK) is a rate-limiting enzyme in deoxyribonucleoside salvage, a metabolic pathway that recycles products of DNA degradation. dCK phosphorylates and therefore activates nucleoside analog prodrugs frequently used in cancer, autoimmunity, and viral infections. In contrast to its well established therapeutic relevance, the biological function of dCK remains enigmatic. Highest levels of dCK expression are found in thymus and bone marrow, indicating a possible role in lymphopoiesis. To test this hypothesis we generated and analyzed dCK knockout (KO) mice. dCK inactivation selectively and profoundly affected T and B cell development. A 90-fold decrease in thymic cellularity was observed in the dCK KO mice relative to wild-type littermates. Lymphocyte numbers in the dCK KO mice were 5- to 13-fold below normal values. The severe impact of dCK inactivation on lymphopoiesis was unexpected given that nucleoside salvage has been thought to play a limited, "fine-tuning" role in regulating deoxyribonucleotide triphosphate pools produced by the de novo pathway. The dCK KO phenotype challenges this view and indicates that, in contrast to the great majority of other somatic cells, normal lymphocyte development critically requires the deoxyribonucleoside salvage pathway.

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    • "Finally, we hypothesized that endogenous cellular genotoxic stress could also trigger post-translational activation of dCK at Ser74. dCK knockout (KO) mice exhibit specific partial blocks in the early stages of T and B lymphocyte development [36]. Furthermore, complete dCK inactivation in mice induces endogenous DNA damage in lymphoid and erythroid lineages [37]. "
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    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 [18F]-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.
    Full-text · Article · Aug 2014 · PLoS ONE
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    • "DCK is highly expressed in the thymus and bone marrow, indicating a possible role in lymphopoiesis [16- 18]. Toy et al. had established DCK knockout (KO) mice and found that DCK inactivation selectively and profoundly affected T and B cell development [19]. Lymphocyte numbers in DCK KO mice were 5 to 13-fold below normal values. "
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    ABSTRACT: Rheumatoid arthritis (RA) is a complex, multi-system disease whose primary site of inflammatory tissue damage is the joint. The increasing evidences indicate that activated RA fibroblast-like synoviocytes (FLS) play a critical role in the development of pannus by migrating into cartilage and bone. Furthermore FLS and T cells can activate each other in vitro and in vivo, which is crucial for the progress of RA. Deoxycytidine kinase (DCK) has been linked to peripheral T cell homeostatic proliferation and survival, which is very important for RA. Yet, the function of DCK in FLS is still unknown. Here, we present a story that DCK could regulate the migration and invasion of FLS through AKT pathway in RA patients. Moreover, DCK seems to be the upstream of AKT and FAK, and AKT inhibitor exerted the similar effect on FLS motility. In summary, our study characterized the new role of DCK in human primary FLS cells, and figured out the possible pathway DCK involved in, and these findings might propose DCK as a novel target for controlling joint destruction of RA.
    Full-text · Article · Dec 2013 · International journal of clinical and experimental pathology
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    • "Analyses of dCK / (Toy et al., 2010) and TK1 / (Dobrovolsky et al., 2003) mice support the existence of a functional link between the NSP, RS, and hematopoietic development . Studies from our group (Toy et al., 2010), and confirmed independently by Choi et al. (2012), document severe developmental abnormalities affecting dCK / T cell, B cell, and erythroid lineages. TK1 / mice also display hematopoietic defects characterized by slightly abnormal secondary lymphoid structures and by elevated levels of micronucleated erythrocytes (Dobrovolsky et al., 2003, 2005). "
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    ABSTRACT: Nucleotide deficiency causes replication stress (RS) and DNA damage in dividing cells. How nucleotide metabolism is regulated in vivo to prevent these deleterious effects remains unknown. In this study, we investigate a functional link between nucleotide deficiency, RS, and the nucleoside salvage pathway (NSP) enzymes deoxycytidine kinase (dCK) and thymidine kinase (TK1). We show that inactivation of dCK in mice depletes deoxycytidine triphosphate (dCTP) pools and induces RS, early S-phase arrest, and DNA damage in erythroid, B lymphoid, and T lymphoid lineages. TK1(-/-) erythroid and B lymphoid lineages also experience nucleotide deficiency but, unlike their dCK(-/-) counterparts, they still sustain DNA replication. Intriguingly, dCTP pool depletion, RS, and hematopoietic defects induced by dCK inactivation are almost completely reversed in a newly generated dCK/TK1 double-knockout (DKO) mouse model. Using NSP-deficient DKO hematopoietic cells, we identify a previously unrecognized biological activity of endogenous thymidine as a strong inducer of RS in vivo through TK1-mediated dCTP pool depletion. We propose a model that explains how TK1 and dCK "tune" dCTP pools to both trigger and resolve RS in vivo. This new model may be exploited therapeutically to induce synthetic sickness/lethality in hematological malignancies, and possibly in other cancers.
    Full-text · Article · Nov 2012 · Journal of Experimental Medicine
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