Protein kinase CK2 is a common, evolutionarily conserved and ubiquitous protein kinase. In recent years, increasing evidences have shown that CK2 has a variety of phosphorylated protein substrates, which play important roles in growth, development and various diseases. Therefore, CK2 may participate in these physiological processes by regulating the phosphorylation of these substrates. This article briefly reviewed the structural characteristics of protein kinase CK2 and its physiological functions in growth, development, immunity, formation of tumor and other diseases, in order to provide knowledge basis for further research on the regulatory mechanism of CK2 and potential applications of its inhibitors.
Casein Kinase II/metabolism* ; Phosphorylation ; Proteins

The phosphorylation and dephosphorylation of proteins on tyrosyl residues are key regulatory mechanisms of cell growth and signal transduction and are controlled by opposing activities of protein tyrosine kinases and phosphotyrosyl phosphatases (PTPs). We have previously cloned and characterized a nontransmembrane chicken protein tyrosine phosphatase 1 (CPTP1) similar to human placental PTP1B (HPTP1B). CPTP1 contains several phosphorylation sequence motifs (S/T-X-X-D/E) for casein kinase II (CKII), [(I > E > V)-Y-(E > G)-(E > D > P > N)-(I/V > L)] for p56(1ck), and (P-E-S-P) for MAP kinase. To examine whether phosphatase activity of CPTP1 could be controlled by phosphorylation, CPTP1 and HPTP1B fusion proteins purified from E. coil were subjected to the in vitro phosphorylation by CKII. Phosphoamino acid analysis revealed that CPTP1 was phosphorylated on both serine and threonine residues by CKII in vitro. In addition, the degree of the phosphorylation of CPTP1 by CKII was shown to be five times higher than that of HPTP1B. Phosphorylation on both serine and threonine residues of CPTP1 in vitro results in an inhibition of its phosphatase activity. This result suggests that phosphorylation of CPTP1 and HPTP1B by CKII might be implicated in the regulation of their catalytic activities in the cell.
Casein Kinase II* ; Casein Kinases* ; Caseins* ; Chickens* ; Clone Cells ; Humans ; Phosphoric Monoester Hydrolases ; Phosphorylation* ; Phosphotransferases ; Protein Tyrosine Phosphatases* ; Protein-Tyrosine Kinases ; Serine ; Signal Transduction ; Threonine

Th17 cells promote inflammatory reactions, whereas regulatory T (Treg) cells inhibit them. Thus, the Th17/Treg cell balance is critically important in inflammatory diseases. However, the molecular mechanisms underlying this balance are unclear. Here, we demonstrate that casein kinase 2 (CK2) is a critical determinant of the Th17/Treg cell balance. Both the inhibition of CK2 with a specific pharmacological inhibitor, CX-4945, and its small hairpin RNA (shRNA)-mediated knockdown suppressed Th17 cell differentiation but reciprocally induced Treg cell differentiation in vitro. Moreover, CX-4945 ameliorated the symptoms of experimental autoimmune encephalomyelitis and reduced Th17 cell infiltration into the central nervous system. Mechanistically, CX-4945 inhibited the IL-6/STAT3 and Akt/mTOR signaling pathways. Thus, CK2 has a crucial role in regulating the Th17/Treg balance.
Casein Kinase II* ; Casein Kinases* ; Caseins* ; Central Nervous System ; Encephalomyelitis, Autoimmune, Experimental ; In Vitro Techniques ; RNA, Small Interfering ; T-Lymphocytes, Regulatory* ; Th17 Cells

BACKGROUND: Protein casein kinase 2 is involved in signal transduction, cell growth, and apoptosis. However, it has not been elucidated whether parkinsonian toxin 1-methyl-4-phenylpyridinium (MPP+)-induced neuronal cell death is mediated by a casein-kinase-2-mediated pathway. METHODS: We monitored apoptosis-related protein activation, changes in the level of casein kinase 2, nuclear damage, and apoptosis in differentiated PC12 cells exposed to MPP+ in combination with casein kinase 2 inhibitor. RESULTS: Casein kinase 2 inhibitors [4,5,6,7-tetrabromobenzotriazole (TBB), 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, and apigenin] reduced MPP+- and rotenone-induced cell death in differentiated PC12 cells. TBB inhibited the MPP+-induced activation of apoptosis-related proteins (decreases in Bid and Bcl-2 levels, increase in Bax levels, cytochrome c release, and caspase-3 activation), increase in casein kinase 2 levels, and nuclear damage. CONCLUSIONS: Administering casein kinase 2 inhibitor TBB at concentrations that do not induce toxic effects may reduce MPP+-induced cell death in differentiated PC12 cells by suppressing the apoptosis-related protein activation that leads to cytochrome c release and subsequent activation of caspase-3. The results suggest that MPP+-induced cell death process is mediated by a casein kinase 2 pathway.
1-Methyl-4-phenylpyridinium ; Animals ; Apoptosis ; Casein Kinase II ; Casein Kinases ; Caseins ; Caspase 3 ; Cell Death ; Cytochromes c ; Neurons ; PC12 Cells ; Proteins ; Signal Transduction ; Triazoles

The aim of this study is to determine the regulatory mechanism of PTEN-induced putative kinase protein 1 short isoform (PINK1S) in cytoplasm. By co-immunoprecipitation (Co-IP) assay, we identified that PINK1S interacted with the beta regulatory subunit of Casein Kinase 2 (CK2β), but not with the catalytic subunits CK2α1 and CK2α2. Furthermore, cells were transfected with PINK1S and CK2β, and then PINK1S was purified by immunoprecipitation. After detecting the phosphorylated proteins by Phos-tag Biotin, we found that CK2β overexpression increased auto-phosphorylation of PINK1S. Finally, we generated CK2β knockdown cell lines by RNA interference. Purified PINK1S from CK2β knockdown cells significantly reduced its auto-phosphorylation compared with control cells. These results suggested that CK2β functions as a regulatory subunit of PINK1S kinase complex promoted its activation by self-phosphorylation.
Biotin ; Casein Kinase II ; metabolism ; Cell Line ; Gene Knockdown Techniques ; Humans ; Phosphorylation ; Protein Kinases ; metabolism ; Pyridines ; RNA Interference ; Transfection

To explore the possible molecular interaction between CK2 and PrP, the full length sequences of human CK2alpha and CK2beta genes were amplified with RT-PCR using the mRNA from cell line SH-SY5Y as the template, and then the fusion proteins HIS-CK2alpha and GST-HIS-CK2beta were expressed in E. coli. The interaction between CK2 and PrP was evaluated with immunoprecipitation and pull-down assays. The results demonstrated that recombinant PrP bound specifically with CK2alpha, but not with CK2beta. The native CK2 and PrP in the hamster brains interacted each other, forming protein complexes. The domain responsible for interacting with CK2alpha was located at the C-terminal segment of PrP (residues 90-231). This study proposed reliable experimental data for the molecular interaction between PrP and CK2alpha, both in recombinant and native categories. These results supply scientific clues for further assessing the potential biological significance of the interaction of PrP with CK2 and possible role of CK2 in the pathogenesis of prion diseases.
Animals ; Casein Kinase II ; chemistry ; physiology ; Cricetinae ; Humans ; Immunoprecipitation ; Phosphorylation ; Prion Diseases ; etiology ; Prions ; chemistry ; Recombinant Proteins ; chemistry

OBJECTIVEMachado-Joseph disease (MJD)/Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant neurodegenerative disorder caused by an expansion of polyglutamine tract near the C-terminus of the MJD1 gene product, ataxin-3. The precise mechanism of the MJD/SCA3 pathogenesis remains unclear. A growing body of evidence demonstrates that phosphorylation plays an important role in the pathogenesis of many neurodegenerative diseases. However, few kinases are known to phosphorylate ataxin-3. The present study is to explore whether ataxin-3 is a substrate of casein kinase 2 (CK2).

METHODSThe interaction between ataxin-3 and CK2 was identified by glutathione S-transferase (GST) pull-down assay and co-immunoprecipition assay. The phosphorylation of ataxin-3 by CK2 was measured by in vitro phosphorylation assays. Results (1) Both wild type and expanded ataxin-3 interacted with CK2alpha and CK2beta in vitro. (2) In 293 cells, both wild type and expanded ataxin-3 interacted with CK2beta, but not CK2alpha. (3) CK2 phosphorylated wild type and expanded ataxin-3.

CONCLUSIONAtaxin-3 is a substrate of protein kinase CK2.

Ataxin-3 ; Casein Kinase II ; metabolism ; Cell Line, Transformed ; Glutathione Transferase ; metabolism ; Humans ; Immunoprecipitation ; methods ; Nerve Tissue Proteins ; metabolism ; Nuclear Proteins ; metabolism ; Phosphorylation ; Repressor Proteins ; metabolism ; Transfection ; methods

OBJECTIVETo investigate the expression of casein kinase 2β in esophageal carcinoma tissues and analyze its clinical significance.

METHODSThe expression of CK2β in a tissue chip containing 60 normal esophageal mucosa and 60 colorectal cancer specimens were detected immunohistochemically. Ten human esophageal carcinoma and adjacent normal tissues were examined for the expression of CK2β protein and mRNA using Western blotting and real-time quantitative PCR, respectively.

RESULTSA strong expression of CK2β was found in 85.71% of the esophageal cancer tissues; 1.79% of the cancer tissues were negative for CK2β expression, and 1.79% and 10.71% of the cancer tissues were weakly and moderately positive, respectively. In the normal mucosal tissues, 96.67% of the tissues were negative for CK2β and 3.33% showed weak CK2β expression, showing a significant difference in the distribution of CK2β between normal and esophageal carcinoma tissues (P<0.001). The expression level of CK2β in esophageal cancers was associated with the pathological stage (TNM) (P=0.010). Western blotting and real-time quantitative PCR also confirmed an increased CK2β expression in the esophageal cancer tissues.

CONCLUSIONThe high expression of protein kinase CK2β is closely related to the carcinogenesis and malignancy of esophageal cancer.

Adult ; Aged ; Carcinoma, Squamous Cell ; metabolism ; pathology ; Casein Kinase II ; metabolism ; Esophageal Neoplasms ; metabolism ; pathology ; Female ; Gene Expression Regulation, Neoplastic ; Humans ; Male ; Middle Aged ; Neoplasm Staging

PTEN-induced putative kinase 1 (PINK1), a Parkinson's disease (PD)-related protein, has two isoforms, the mitochondria-localized full-length isoform PINK1FL and the cytoplasm-localized short isoform PINK1-cyto. Studies have suggested that PINK1FL can selectively accumulate at the surface of damaged mitochondria and cooperate with another Parkinson's Disease-related protein PARKIN to trigger the degradation of MIRO1, a mitochondria trafficking regulator. The functions of PINK1-cyto are, however, not yet clear. To investigate the functions of PINK1-cyto, we expressed different proteins in cultured HEK293 cells by transfecting it with different plasmids, and detected the protein levels by Western blot after expressing for 24 h. We found that in cultured HEK293 cells, PINK1-cyto could also cooperate with PARKIN degrade MIRO1 in the presence of CK23, and the regulatory subunit of Casein Kinase II. Interestingly, this function of CK2P was not dependent on CK2alpha, the catalytic subunit of Casein Kinase II. We also found that CK2P could promote the direct interaction between PINK1-cyto and MIRO1 by immunocoprecipitation analysis. This result suggested that in addition to CK2alpha, CK2beta could also form a kinase complex.
Casein Kinase II ; metabolism ; HEK293 Cells ; Humans ; Mitochondrial Proteins ; metabolism ; Parkinson Disease ; Protein Kinases ; metabolism ; Protein Transport ; Ubiquitin-Protein Ligases ; metabolism ; rho GTP-Binding Proteins ; metabolism

OBJECTIVETo assess the effect of small interfering RNA (siRNA) specific to protein kinase CK2a on proliferation and apoptosis of Hep-2 cell line.

METHODSsiRNA expression plasmid psiRNA-hH1neo-CK2 specific to protein kinase CK2a and non-specific siRNA expression plasmid psiRNA-hH1neo-cont were constructed respectively, and then were transfected into Hep-2 cells by lipofectamine methods. Protein kinase CK2a mRNA and protein of the transfected cells were detected by reverse transcription polymerase chain reaction (RT-PCR) and Western Blot, respectively. Proliferation and apoptosis of the transfected cells were observed by methyl thiazolyl tetrazolium (MTT) method and flow cytometry (FCM), respectively.

RESULTSProtein kinase CK2a mRNA and protein expressions were significantly decreased in the cells transfected with psiRNA-hH1neo-CK2 (P < 0.05). The Hep-2 cells grew slowly after transfected with psiRNA-hH1neo-CK2(P < 0.05). Obvious subdiploid peaks were found in the cells transfected with psiRNA-hH1neo-CK2 (P < 0.05).

CONCLUSIONSsiRNA expression plasmid specific to protein kinase CK2a suppressed the protein kinase CK2a expression and the proliferation of Hep-2, and induced apoptosis of Hep-2 cells.

Carcinoma ; genetics ; pathology ; Casein Kinase II ; genetics ; Cell Line, Tumor ; Cell Proliferation ; Humans ; Laryngeal Neoplasms ; genetics ; pathology ; Plasmids ; RNA, Messenger ; genetics ; RNA, Small Interfering ; Transfection