[Inhibitory effect of AG1109 on recombinant human protein kinase CK2 holoenzyme].
OBJECTIVE
Protein kinase CK2 is an evolutionarily conserved serine/threonine kinase that is upregulated and can serve as an oncogene in many cancer cells. Targeted inhibition of CK2 could be useful in the treatment of many cancers. To search specific CK2 inhibitors we investigated the direct effect of tyrphostin AG1109 on recombinant human protein kinase CK2 holoenzyme and its kinetics.


METHODS
Recombinant human protein kinase CK2 alpha and beta subunits were cloned and expressed by gene engineering, and purified to homogeneous. The two subunits were mixed at the same molar ratio and reconstituted CK2 holoenzyme, which exerted the maximum biological activity. The CK2 activity was assayed by detecting incorporation of 32P of [gamma-32P]ATP or [gamma-32P]GTP into the substrate in various conditions.


RESULTS
The recombinant human CK2 was the second messengers (Ca2+, cAMP, and cGMP) independent protein kinase, the characterization and function of the reconstituted holoenzyme were consistent with those of native CK2. AG1109 strongly inhibited the holoenzyme activity of recombinant human protein kinase CK2 with an IC50 of 9.7 mumol/L, which was slightly more effective than 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and N-(2-aminoethyl)-5-chloronaphthalene-1-sulfonamide (A3), which were both known CK2 special inhibitors. Kinetic studies of AG1109 on recombinant human CK2 showed that the inhibition was mixed (competitive is dominant) with GTP and noncompetitive with casein.


CONCLUSIONS
AG1109 is an effective inhibitor of recombinant human protein kinase CK2 holoenzyme. The recombinant human protein kinase CK2 might be used as a molecular target for simpler screening and development of more effective inhibitors of CK2.
Liu
Xin-guang
XG
Institute of Biochemistry & Molecular Biology, Guangdong Medical College, Zhanjiang 524023, P. R. China. xgliu@gdmc.edu.cn
Liang
Nian-ci
NC
D047390:Casein Kinase II; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020035:Holoenzymes / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D020032:Tyrphostins / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D020035:Holoenzymes; D011994:Recombinant Proteins; D020032:Tyrphostins; C117081:tyrphostin AG 1109; D004004:Dichlororibofuranosylbenzimidazole; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases