Protein kinase CK2 phosphorylates and upregulates Akt/PKB

Abstract

Treatment of Jurkat cells with specific inhibitors of protein kinase CK2 induces apoptosis. Here we provide evidence that the antiapoptotic effect of CK2 can be at least partially mediated by upregulation of the Akt/PKB pathway. Such a conclusion is based on the following observations: (1) inhibition of CK2 by cell treatment with two structurally unrelated CK2 inhibitors induces downregulation of Akt/PKB, as judged from decreased phosphorylation of its physiological targets, and immunoprecipitate kinase assay; (2) similar results are observed upon reduction of CK2 catalytic subunit by the RNA-interference technique; (3) Akt/PKB Ser129 is phosphorylated by CK2 in vitro and in vivo; (4) such a phosphorylation of activated Akt/PKB correlates with a further increase in catalytic activity. These data disclose an unanticipated mechanism by which constitutive phosphorylation by CK2 may be required for maximal activation of Akt/PKB.

Pharmacological inhibition of protein kinase CK2 reverts the multidrug resistance phenotype of a CEM cell line characterized by high CK2 level

“…Similar results were obtained treating cells with other CK2 inhibitors, either structurally related or not to TBB (not shown). Figure 4 also shows that the phosphorylation degree of two CK2 target sites (Ser129 of Akt, Di Maira et al, 2005 and Thr 117 of BAD, Klumpp et al, 2004), detected by phospho-specific antibodies, is higher in R-CEM than in S-CEM. From all these data, it can be concluded that CK2-catalysed protein phosphorylation is much more pronounced in R-CEM cells, consistent with their higher content in CK2a.…”

“…CK2a-subunit antisera were raised in rabbit against the sequence of the human protein at C terminus (376-391), N terminus (2-15), or central region (188-202), CK2a-subunit monoclonal antibodies were from Calbiochem (Darmstadt, Germany) (1AD9), CK2b-subunit antibodies were raised in rabbit against the whole human protein, and also purchased from BD Transduction Laboratories (Erembodegen, Belgium), CK2a 0 -subunit, total Akt, actin, lactate dehydrogenase, and lamin B antibodies were from Santa Cruz Biotechnology (Santa Cruz, CA, USA), PARP antibodies were from Roche (Basel, Switzerland), Akt Sp129 phospho-specific antibodies were raised in rabbit as described elsewhere (Di Maira et al, 2005), BAD antibodies were from Cell Signaling Technology (Danvers, MA, USA), BAD Tp117 phosphospecific antibodies were kindly provided by Dr Klumpp (Munster, Germany).…”

“…For lanes 5 and 6, a quantitative analysis of radioactivity incorporated into the bands was performed by means of the OptiQuant Image Analysis software (Canberra-Packard, Schwadorf, Austria); bands whose intensity decrease by 50% or more in TBB-treated cells are pinpointed. (b) Upper part: equal amounts of Akt were immuno-precipitated from S-CEM and R-CEM lysates, and analysed by western blot with the CK2 target site Ser129 phospho-specific antibodies (Di Maira et al, 2005) and Akt total antibody, as indicated. Lower part: Ten microgram of total lysate from S-CEM and R-CEM were analysed by western blot with the CK2 target site BAD Thr117 phospho-specific antibodies (Klumpp et al, 2004) or BAD total antibody, as indicated.…”

“…For total lysate preparation, cells were lysed as described by Di Maira et al (2005). For soluble fraction and nuclear extract preparation, cells were lysed by the addition of hypertonic buffer, followed by extraction of nuclear proteins with a hypertonic buffer, as described by Ruzzene et al (2002).…”

Protein kinase CK2 in hematologic malignancies: reliance on a pivotal cell survival regulator by oncogenic signaling pathways

“…24,25 A number of studies have shown that CK2 phosphorylates PTEN in the C-terminal region, stabilizes the protein against ubiquitin-mediated proteasomal degradation and regulates PTEN activity in a negative manner. 26 --28 In addition to its direct regulation of PTEN, CK2 is able to activate AKT through direct phosphorylation 29 and through an indirect mechanism preventing the dephosphorylation of its active form. 30 CK2 regulation of other hematopoietic-specific transcription factors and molecules CK2 has also been described as a regulative kinase of a multitude of hematopoietic transcription factors and molecules.…”