title: Activation of deoxycytidine kinase by deoxyadenosine: implications in deoxyadenosine-mediated cytotoxicity.
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.
authors.affiliation: Institute of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, P.O. Box 260, H-1444 Budapest, Hungary. keszler@puskin.sote.hu
authors.forename: Gergely
authors.initials: G
authors.lastname: Keszler
authors.forename: Szula
authors.initials: S
authors.lastname: Virga
authors.forename: Tatjana
authors.initials: T
authors.lastname: Spasokoukotskaja
authors.forename: Pal I
authors.initials: PI
authors.lastname: Bauer
authors.forename: Maria
authors.initials: M
authors.lastname: Sasvari-Szekely
authors.forename: Maria
authors.initials: M
authors.lastname: Staub
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism*; D000243:Adenosine Deaminase / Q000172:deficiency / Q000378:metabolism; D058892:Adenosine Deaminase Inhibitors; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017338:Cladribine / Q000494:pharmacology; D003641:Deamination; D003839:Deoxyadenosines / Q000378:metabolism / Q000494:pharmacology*; D003842:Deoxycytidine Kinase / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008214:Lymphocytes / Q000378:metabolism*; D009700:Nucleoside Deaminases / Q000187:drug effects / Q000378:metabolism*; D015649:Pentostatin / Q000494:pharmacology; D011742:Pyrimidine Nucleotides / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000227:Adenine Nucleotides; D058892:Adenosine Deaminase Inhibitors; D000970:Antineoplastic Agents; D003839:Deoxyadenosines; D004791:Enzyme Inhibitors; D011742:Pyrimidine Nucleotides; D015649:Pentostatin; D017338:Cladribine; D000255:Adenosine Triphosphate; D003842:Deoxycytidine Kinase; D014357:Trypsin; D009700:Nucleoside Deaminases; D000243:Adenosine Deaminase