Protein kinase CK2 ("casein kinase-2") and its implication in cell division and proliferation

Benzothiazole derivatives in the design of antitumor agents

Benzothiazoles are a class of heterocycles with multiple applications as anticancer, antibiotic, antiviral, and anti-inflammatory agents. Benzothiazole is a privileged scaffold in drug discovery programs for modulating a variety of biological functions. This review focuses on the design and synthesis of new benzothiazole derivatives targeting hypoxic tumors. Cancer is a major health problem, being among the leading causes of death. Tumor-hypoxic areas promote proliferation, malignancy, and resistance to drug treatment, leading to the dysregulation of key signaling pathways that involve drug targets such as vascular endothelial growth factor, epidermal growth factor receptor, hepatocyte growth factor receptor, dual-specificity protein kinase, cyclin-dependent protein kinases, casein kinase 2, Rho-related coil formation protein kinase, tunica interna endothelial cell kinase, cyclooxygenase-2, adenosine kinase, lysophosphatidic acid acyltransferases, stearoyl-CoA desaturase, peroxisome proliferator-activated receptors, thioredoxin, heat shock proteins, and carbonic anhydrase IX/XII. In turn, they regulate angiogenesis, proliferation, differentiation, and cell survival, controlling the cell cycle, inflammation, the immune system, and metabolic alterations. A wide diversity of benzothiazoles were reported over the last years to interfere with various proteins involved in tumorigenesis and, more specifically, in hypoxic tumors. Many hypoxic targets are overexpressed as a result of the hypoxia-inducible factor activation cascade and may not be present in normal tissues, providing a potential strategy for selectively targeting hypoxic cancers.

Curcumin in Cancer and Inflammation: An In-Depth Exploration of Molecular Interactions, Therapeutic Potentials, and the Role in Disease Management

This paper delves into the diverse and significant roles of curcumin, a polyphenolic compound from the Curcuma longa plant, in the context of cancer and inflammatory diseases. Distinguished by its unique molecular structure, curcumin exhibits potent biological activities including anti-inflammatory, antioxidant, and potential anticancer effects. The research comprehensively investigates curcumin's molecular interactions with key proteins involved in cancer progression and the inflammatory response, primarily through molecular docking studies. In cancer, curcumin's effectiveness is determined by examining its interaction with pivotal proteins like CDK2, CK2α, GSK3β, DYRK2, and EGFR, among others. These interactions suggest curcumin's potential role in impeding cancer cell proliferation and survival. Additionally, the paper highlights curcumin's impact on inflammation by examining its influence on proteins such as COX-2, CRP, PDE4, and MD-2, which are central to the inflammatory pathway. In vitro and clinical studies are extensively reviewed, shedding light on curcumin's binding mechanisms, pharmacological impacts, and therapeutic application in various cancers and inflammatory conditions. These studies are pivotal in understanding curcumin's functionality and its potential as a therapeutic agent. Conclusively, this review emphasizes the therapeutic promise of curcumin in treating a wide range of health issues, attributed to its complex chemistry and broad pharmacological properties. The research points towards curcumin's growing importance as a multi-faceted natural compound in the medical and scientific community.

GIMAP5 deficiency reveals a mammalian ceramide-driven longevity assurance pathway

Preserving cells in a functional, non-senescent state is a major goal for extending human healthspans. Model organisms reveal that longevity and senescence are genetically controlled, but how genes control longevity in different mammalian tissues is unknown. Here, we report a new human genetic disease that causes cell senescence, liver and immune dysfunction, and early mortality that results from deficiency of GIMAP5, an evolutionarily conserved GTPase selectively expressed in lymphocytes and endothelial cells. We show that GIMAP5 restricts the pathological accumulation of long-chain ceramides (CERs), thereby regulating longevity. GIMAP5 controls CER abundance by interacting with protein kinase CK2 (CK2), attenuating its ability to activate CER synthases. Inhibition of CK2 and CER synthase rescues GIMAP5-deficient T cells by preventing CER overaccumulation and cell deterioration. Thus, GIMAP5 controls longevity assurance pathways crucial for immune function and healthspan in mammals.

Site-specific phosphorylation of ZYG-1 regulates ZYG-1 stability and centrosome number

Spindle bipolarity is critical for genomic integrity. As centrosome number often dictates bipolarity, tight control of centrosome assembly is vital for faithful cell division. The master centrosome regulator ZYG-1/Plk4 plays a pivotal role in this process. In C. elegans, casein kinase II (CK2) negatively regulates centrosome duplication by controlling centrosome-associated ZYG-1 levels. Here, we investigated CK2 as a regulator of ZYG-1 and its impact on centrosome assembly. We show that CK2 phosphorylates ZYG-1 in vitro and physically interacts with ZYG-1 in vivo. Depleting CK2 or blocking ZYG-1 phosphorylation at CK2 target sites leads to centrosome amplification. Non-phosphorylatable ZYG-1 mutants exhibit elevated ZYG-1 levels, leading to increased ZYG-1 and downstream factors at centrosomes, thus driving centrosome amplification. Moreover, inhibiting the 26S proteasome prevents degradation of the phospho-mimetic ZYG-1. Our findings suggest that CK2-dependent phosphorylation of ZYG-1 controls ZYG-1 levels via proteasomal degradation to limit centrosome number.

Protein Kinase CK2α', More than a Backup of CK2α

The serine/threonine protein kinase CK2 is implicated in the regulation of fundamental processes in eukaryotic cells. CK2 consists of two catalytic α or α' isoforms and two regulatory CK2β subunits. These three proteins exist in a free form, bound to other cellular proteins, as tetrameric holoenzymes composed of CK2α2/β2, CK2αα'/β2, or CK2α'2/β2 as well as in higher molecular forms of the tetramers. The catalytic domains of CK2α and CK2α' share a 90% identity. As CK2α contains a unique C-terminal sequence. Both proteins function as protein kinases. These properties raised the question of whether both isoforms are just backups of each other or whether they are regulated differently and may then function in an isoform-specific manner. The present review provides observations that the regulation of both CK2α isoforms is partly different concerning the subcellular localization, post-translational modifications, and aggregation. Up to now, there are only a few isoform-specific cellular binding partners. The expression of both CK2α isoforms seems to vary in different cell lines, in tissues, in the cell cycle, and with differentiation. There are different reports about the expression and the functions of the CK2α isoforms in tumor cells and tissues. In many cases, a cell-type-specific expression and function is known, which raises the question about cell-specific regulators of both isoforms. Another future challenge is the identification or design of CK2α'-specific inhibitors.

Structure-guided discovery of adenosine triphosphate-competitive casein kinase 2 inhibitors

Casein kinase 2 (CK2) is a ubiquitous, highly pleiotropic serine-threonine kinase. CK2 has been identified as a potential drug target for the treatment of cancer and related disorders. Several adenosine triphosphate-competitive CK2 inhibitors have been identified and have progressed at different levels of clinical trials. This review presents details of CK2 protein, structural insights into adenosine triphosphate binding pocket, current clinical trial candidates and their analogues. Further, it includes the emerging structure-based drug design approaches, chemistry, structure-activity relationship and biological screening of potent and selective CK2 inhibitors. The authors tabulated the details of CK2 co-crystal structures because these co-crystal structures facilitated the structure-guided discovery of CK2 inhibitors. The narrow hinge pocket compared with related kinases provides useful insights into the discovery of CK2 inhibitors.

Site-Specific Phosphorylation of ZYG-1 Regulates ZYG-1 Stability and Centrosome Number

Spindle bipolarity is critical for genomic integrity. Given that centrosome number often dictates mitotic bipolarity, tight control of centrosome assembly is vital for the fidelity of cell division. The kinase ZYG-1/Plk4 is a master centrosome factor that is integral for controlling centrosome number and is modulated by protein phosphorylation. While autophosphorylation of Plk4 has been extensively studied in other systems, the mechanism of ZYG-1 phosphorylation in C. elegans remains largely unexplored. In C. elegans, Casein Kinase II (CK2) negatively regulates centrosome duplication by controlling centrosome-associated ZYG-1 levels. In this study, we investigated ZYG-1 as a potential substrate of CK2 and the functional impact of ZYG-1 phosphorylation on centrosome assembly. First, we show that CK2 directly phosphorylates ZYG-1 in vitro and physically interacts with ZYG-1 in vivo. Intriguingly, depleting CK2 or blocking ZYG-1 phosphorylation at putative CK2 target sites leads to centrosome amplification. In the non-phosphorylatable (NP)-ZYG-1 mutant embryo, the overall levels of ZYG-1 are elevated, leading to an increase in centrosomal ZYG-1 and downstream factors, providing a possible mechanism of the NP-ZYG-1 mutation to drive centrosome amplification. Moreover, inhibiting the 26S proteasome blocks degradation of the phospho-mimetic (PM)-ZYG-1, while the NP-ZYG-1 mutant shows partial resistance to proteasomal degradation. Our findings suggest that site-specific phosphorylation of ZYG-1, partly mediated by CK2, controls ZYG-1 levels via proteasomal degradation, limiting centrosome number. We provide a mechanism linking CK2 kinase activity to centrosome duplication through direct phosphorylation of ZYG-1, which is critical for the integrity of centrosome number.

Protein Kinase CK2 Contributes to Glucose Homeostasis by Targeting Fructose-1,6-Bisphosphatase 1

Glucose homeostasis is of critical importance for the survival of organisms. It is under hormonal control and often coordinated by the action of kinases and phosphatases. We have previously shown that CK2 regulates insulin production and secretion in pancreatic β-cells. In order to shed more light on the CK2-regulated network of glucose homeostasis, in the present study, a qRT-PCR array was carried out with 84 diabetes-associated genes. After inhibition of CK2, fructose-1,6-bisphosphatase 1 (FBP1) showed a significant lower gene expression. Moreover, FBP1 activity was down-regulated. Being a central enzyme of gluconeogenesis, the secretion of glucose was decreased as well. Thus, FBP1 is a new factor in the CK2-regulated network implicated in carbohydrate metabolism control.

Apigenin directly interacts with and inhibits topoisomerase 1 to upregulate CD26/DPP4 on colorectal carcinoma cells

Introduction: CD26/dipeptidyl peptidase IV (DPP4) is a cell-surface glycoprotein present on most epithelial cells that modulates the local response to external signals. We have previously shown that the dietary flavone apigenin (4',5,7-trihydroxyflavone) upregulates cell-surface CD26/DPP4 on human colorectal carcinoma (CRC) cells and regulates its activities. We observed a unique synergistic interaction with the CRC chemotherapeutic agent irinotecan, which through its metabolite SN38 elevates CD26 at doses that are sub-cytotoxic. As SN38 interacts with topoisomerase 1 (Topo1) we evaluated whether apigenin influences Topo1 activity. Methods: We used a radioimmunoassay to selectively measure CD26 at the cell surface of HT-29 cells following various treatments. Topoisomerase 1 mRNA expression was measured by q-RT-PCR and protein abundance by western blot analysis. Direct inhibition of topoisomerase activity was measured using an assay of DNA supercoil relaxation with recombinant human Topo1. The role of Topo1 in the effect of apigenin was shown both pharmacologically and by siRNA silencing of Topo1. Molecular docking analysis was done with SBD computational software using the CDOCKER algorithm. Results: The interplay between apigenin and irinotecan was not observed when apigenin was combined with other chemotherapeutic drugs including the topoisomerase 2 inhibitors doxorubicin or etoposide. There was no enhancement of irinotecan action if apigenin was replaced with its hydroxylated metabolite luteolin (3',4',5,7-tetrahydroxyflavone) or emodin (6-methyl-1,3,8-trihydroxyanthraquinone), which is an inhibitor of the principal kinase target of apigenin, casein kinase 2 (CK2). Apigenin did not alter Topo1 mRNA expression, but siRNA knockdown of functional Topo1 eliminated the effect of apigenin and itself increased CD26 levels. Apigenin inhibited Topo1 activity in intact HT-29 cells and showed comparable inhibition of purified recombinant human Topo1 enzyme activity to that of SN-38, the active metabolite of irinotecan. Apigenin fits into the complex of Topo1 with DNA to directly inhibit Topo1 enzyme activity. Discussion: We conclude that apigenin has a unique fit into the Topo1-DNA functional complex that leads to direct inhibition of Topo1 activity, and suggest that this is the basis for the exceptional interaction with the CRC drug irinotecan. A combined action of these two agents may therefore exert a role to limit local signals that facilitate tumour progression.

Minor Kinases with Major Roles in Cytokinesis Regulation

Cytokinesis, the conclusive act of cell division, allows cytoplasmic organelles and chromosomes to be faithfully partitioned between two daughter cells. In animal organisms, its accurate regulation is a fundamental task for normal development and for preventing aneuploidy. Cytokinesis failures produce genetically unstable tetraploid cells and ultimately result in chromosome instability, a hallmark of cancer cells. In animal cells, the assembly and constriction of an actomyosin ring drive cleavage furrow ingression, resulting in the formation of a cytoplasmic intercellular bridge, which is severed during abscission, the final event of cytokinesis. Kinase-mediated phosphorylation is a crucial process to orchestrate the spatio-temporal regulation of the different stages of cytokinesis. Several kinases have been described in the literature, such as cyclin-dependent kinase, polo-like kinase 1, and Aurora B, regulating both furrow ingression and/or abscission. However, others exist, with well-established roles in cell-cycle progression but whose specific role in cytokinesis has been poorly investigated, leading to considering these kinases as "minor" actors in this process. Yet, they deserve additional attention, as they might disclose unexpected routes of cell division regulation. Here, we summarize the role of multifunctional kinases in cytokinesis with a special focus on those with a still scarcely defined function during cell cleavage. Moreover, we discuss their implication in cancer.

CK2 and the Hallmarks of Cancer

Cancer is a leading cause of death worldwide. Casein kinase 2 (CK2) is commonly dysregulated in cancer, impacting diverse molecular pathways. CK2 is a highly conserved serine/threonine kinase, constitutively active and ubiquitously expressed in eukaryotes. With over 500 known substrates and being estimated to be responsible for up to 10% of the human phosphoproteome, it is of significant importance. A broad spectrum of diverse types of cancer cells has been already shown to rely on disturbed CK2 levels for their survival. The hallmarks of cancer provide a rationale for understanding cancer's common traits. They constitute the maintenance of proliferative signaling, evasion of growth suppressors, resisting cell death, enabling of replicative immortality, induction of angiogenesis, the activation of invasion and metastasis, as well as avoidance of immune destruction and dysregulation of cellular energetics. In this work, we have compiled evidence from the literature suggesting that CK2 modulates all hallmarks of cancer, thereby promoting oncogenesis and operating as a cancer driver by creating a cellular environment favorable to neoplasia.

CSNK2 in cancer: pathophysiology and translational applications

Protein kinase CSNK2 (CK2) is a pleiotropic serine/threonine kinase frequently dysregulated in solid and hematologic malignancies. To consolidate a wide range of biological and clinically oriented data from this unique kinase in cancer, this systematic review summarises existing knowledge from in vitro, in vivo and pre-clinical studies on CSNK2 across 24 different human cancer types. CSNK2 mRNA transcripts, protein levels and activity were found to be routinely upregulated in cancer, and commonly identified phosphotargets included AKT, STAT3, RELA, PTEN and TP53. Phenotypically, it frequently influenced evasion of apoptosis, enhancement of proliferation, cell invasion/metastasis and cell cycle control. Clinically, it held prognostic significance across 14 different cancers, and its inhibition in xenograft experiments resulted in a positive treatment response in 12. In conjunction with commentary on preliminary studies of CSNK2 inhibitors in humans, this review harmonises an extensive body of CSNK2 data in cancer and reinforces its emergence as an attractive target for cancer therapy. Continuing to investigate CSNK2 will be crucial to advancing our understanding of CSNK2 biology, and offers the promise of important new discoveries scientifically and clinically.

Inhibition of CK2 mitigates Alzheimer's tau pathology by preventing NR2B synaptic mislocalization

Alzheimer’s disease (AD) is a neurodegenerative disorder that exhibits pathological changes in both tau and synaptic function. AD patients display increases in hyperphosphorylated tau and synaptic activity. Previous studies have individually identified the role of NR2B subunit-containing NMDA receptors in AD related synaptic dysfunction and aggregated tau without reconciling the conflicting differences and implications of NR2B expression. Inhibition of extrasynaptically located NR2B mitigates tau pathology in AD models, whereas the inhibition of synaptic NR2B replicates tau-associated hyperactivity. This suggests that a simultaneous increase in extrasynaptic NR2B and decrease in synaptic NR2B may be responsible for tau pathology and synaptic dysfunction, respectively. The synaptic location of NR2B is regulated by casein kinase 2 (CK2), which is highly expressed in AD patients. Here, we used patient brains diagnosed with AD, corticobasal degeneration, progressive supranuclear palsy or Pick’s disease to characterize CK2 expression across these diverse tauopathies. Human derived material was also utilized in conjunction with cultured hippocampal neurons in order to investigate AD-induced changes in NR2B location. We further assessed the therapeutic effect of CK2 inhibition on NR2B synaptic distribution and tau pathology. We found that aberrant expression of CK2, and synaptically translocated NR2B, is unique to AD patients compared to other tauopathies. Increased CK2 was also observed in AD-tau treated neurons in addition to the mislocalization of NR2B receptors. Tau burden was alleviated in vitro by correcting synaptic:extrasynaptic NR2B function. Restoring NR2B physiological expression patterns with CK2 inhibition and inhibiting the function of excessive extrasynaptic NR2B with Memantine both mitigated tau accumulation in vitro. However, the combined pharmacological treatment promoted the aggregation of tau. Our data suggests that the synaptic:extrasynaptic balance of NR2B function regulates AD-tau pathogenesis, and that the inhibition of CK2, and concomitant prevention of NR2B mislocalization, may be a useful therapeutic tool for AD patients.

SGC-CK2-1 Is an Efficient Inducer of Insulin Production and Secretion in Pancreatic β-Cells

The pyrazolopyrimidine based compound SGC-CK2-1 is a potent and highly specific CK2 inhibitor and a new tool to study the biological functions of protein kinase CK2 irrespective from off-target effects. We used this compound in comparison with the well-established CK2 inhibitor CX-4945 to analyze the importance of CK2 for insulin production and secretion from pancreatic β-cells. Both inhibitors affected the proliferation and viability of MIN6 cells only marginally and downregulated the endogenous CK2 activity to a similar level. Furthermore, both inhibitors increased the message for insulin and boosted the secretion of insulin from storage vesicles. Thus, regarding the high specificity of SGC-CK2-1, we can clearly attribute the observed effects to biological functions of protein kinase CK2.

Targeting of Protein Kinase CK2 in Acute Myeloid Leukemia Cells Using the Clinical-Grade Synthetic-Peptide CIGB-300

Protein kinase CK2 has emerged as an attractive therapeutic target in acute myeloid leukemia (AML), an advent that becomes particularly relevant since the treatment of this hematological neoplasia remains challenging. Here we explored for the first time the effect of the clinical-grade peptide-based CK2 inhibitor CIGB-300 on AML cells proliferation and viability. CIGB-300 internalization and subcellular distribution were also studied, and the role of B23/nucleophosmin 1 (NPM1), a major target for the peptide in solid tumors, was addressed by knock-down in model cell lines. Finally, pull-down experiments and phosphoproteomic analysis were performed to study CIGB-interacting proteins and identify the array of CK2 substrates differentially modulated after treatment with the peptide. Importantly, CIGB-300 elicited a potent anti-proliferative and proapoptotic effect in AML cells, with more than 80% of peptide transduced cells within three minutes. Unlike solid tumor cells, NPM1 did not appear to be a major target for CIGB-300 in AML cells. However, in vivo pull-down experiments and phosphoproteomic analysis evidenced that CIGB-300 targeted the CK2α catalytic subunit, different ribosomal proteins, and inhibited the phosphorylation of a common CK2 substrates array among both AML backgrounds. Remarkably, our results not only provide cellular and molecular insights unveiling the complexity of the CIGB-300 anti-leukemic effect in AML cells but also reinforce the rationale behind the pharmacologic blockade of protein kinase CK2 for AML-targeted therapy.

TMEM2 binds to CSNK2A3 to inhibit HBV infection via activation of the JAK/STAT pathway

To investigate mechanisms that TMEM2 activation inhibits hepatitis B virus (HBV) infection in hepatocarcinoma (HCC) cells, co-immunoprecipitation (Co-IP) and mass spectrometry were used in screening interacting proteins for TMEM2. Levels of casein kinase 2 subunit α3 (CSNK2A3) in HCC cells were found to be inhibited or overexpressed using siRNAs and pcDNA3.1-CSNK2A3, respectively. Effect of CSNK2A3 expression on cell proliferation was analyzed using MTS, while its effect on HBV infection was measured using ddPCR and IHC. Western blotting and JAK inhibitor ruxolitinib were also used to determine whether TMEM2-regulated CSNK2A3 expression and HBV infection were affected by JAK-STAT signaling. Co-IP and mass spectrometry results showed that CSNK2A3 interacts with TMEM2. Moreover, overexpression of CSNK2A3 significantly inhibited cell proliferation, while inhibition of CSNK2A3 promoted proliferation of HCC cells. In addition, overexpression of CSNK2A3 was observed to significantly enhance HBV infection, while siRNA knockdown of CSNK2A3 inhibited HBV infection. Notably, effect of CSNK2A3 overexpression on HBV infection was suppressed by TMEM2 overexpression. Further mechanistic analyses have revealed that TMEM2 could antagonize the effects of CSNK2A3 on cell proliferation and HBV infection via JAK-STAT pathway activation. In conclusion, TMEM2 has been determined to bind to CSNK2A3 to inhibit HBV infection via activation of the JAK-STAT pathway.

Dysregulation of phosphoproteins in hepatocellular carcinoma revealed via quantitative analysis of the phosphoproteome

Hepatocellular carcinoma (HCC) is one of the most frequently diagnosed types of cancer in the world. Post-translational modifications, such as phosphorylation, serve an essential role during cancer development. To identify aberrant phosphorylation in HCC, a multiplexed tandem mass tag approach combined with liquid chromatography tandem-mass spectrometry was used in the present study. The results are available via ProteomeXchange (identifier no. PXD013934). A total of 4,780 phosphorylated sites distributed on 2,209 proteins were identified and quantified, including 74 and 459 phosphorylated upregulated and downregulated proteins, respectively. Bioinformatic analysis revealed differences and similarities between HCC and normal tissues. Gene Ontology enrichment analysis provided information on biological processes, molecular functions, cellular components and sub-cellular localizations. Protein domains enrichment of differentially expressed proteins was analyzed using InterPro database. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed pathways that may potentially be involved in HCC. Integrative analysis of the functions, pathways, motifs of phosphorylated peptides, protein domains and protein interactions established a profile of the phosphoproteome of HCC, which may contribute to identify novel biomarkers for the diagnosis and prognosis of HCC, as well as novel therapeutic targets for HCC treatment.

Apigenin upregulation of CD26/DPPIV on colon epithelial cells requires inhibition of casein kinase 2

CD26/DPPIV is a cell surface glycoprotein found on cells of the intestinal epithelium including those of the colon. We have previously shown that the dietary flavone apigenin (4',5,7-trihydroxyflavone) upregulates CD26/DPPIV on colon cells. Flavonoids such as apigenin interfere with the action of multiple cellular protein kinases and have the capacity to modulate the cell exterior and its ability to interface with the local environment through different signaling pathways. We show here that the ability of apigenin to upregulate CD26/DPPIV is exerted through and requires the activity of casein kinase 2 (CK2). Inhibitors of CK2 that are distinct from apigenin (emodin, 6-methyl-1,3,8-trihydroxyanthraquinone; TBB, 4,5,6,7-tetrabromobenzotriazole; and DRB, 5,6-dichlorobenzimidazole 1-β-D-ribofuranoside) showed a dose-dependent ability to increase CD26/DPPIV and had the same maximal effect when combined with apigenin at submaximal concentrations. Knockdown of CK2 with siRNA abrogated the ability of apigenin to upregulate CD26/DPPIV. Apigenin treatment of cells had no effect on the levels of CK2 protein, consistent with an inhibition of activity of the enzyme. Apigenin's upregulation of CD26/DPPIV in differentiated human colon epithelial cells depends upon inhibition of CK2 activity. This is a key step in enabling apigenin's ability to regulate the functions of intestinal epithelial cells.

Hyperphosphorylation of fetal liver IGFBP-1 precedes slowing of fetal growth in nutrient-restricted baboons and may be a mechanism underlying IUGR

In cultured fetal liver cells, insulin-like growth factor (IGF) binding protein (IGFBP)-1 hyperphosphorylation in response to hypoxia and amino acid deprivation is mediated by inhibition of mechanistic target of rapamycin (mTOR) and activation of amino acid response (AAR) signaling and casein kinase (CK)2. We hypothesized that fetal liver mTOR inhibition, activation of AAR and CK2, and IGFBP-1 hyperphosphorylation occur before development of intrauterine growth restriction (IUGR). Pregnant baboons were fed a control (C) or a maternal nutrient restriction (MNR; 70% calories of control) diet starting at gestational day (GD) 30 (term GD 185). Umbilical blood and fetal liver tissue were obtained at GD 120 (C, n = 7; MNR, n = 10) and 165 (C, n = 7; MNR, n = 8). Fetal weights were unchanged at GD 120 but decreased at GD 165 in the MNR group (-13%, P = 0.03). IGFBP-1 phosphorylation, as determined by parallel reaction monitoring mass spectrometry (PRM-MS), immunohistochemistry, and/or Western blot, was enhanced in MNR fetal liver and umbilical plasma at GD 120 and 165. IGF-I receptor autophosphorylation^Tyr1135 (-64%, P = 0.05) was reduced in MNR fetal liver at GD 120. Furthermore, fetal liver CK2 (α/α'/β) expression, CK2β colocalization, proximity with IGFBP-1, and CK2 autophosphorylation^Tyr182 were greater at GD 120 and 165 in MNR vs. C. Additionally, mTOR complex (mTORC)1 (p-P70S6K^Thr389, -52%, P = 0.05) and mTORC2 (p-Akt^Ser473, -56%, P < 0.001) activity were decreased and AAR was activated (p-GCN2^Thr898, +117%, P = 0.02; p-eIF2α^Ser51, +294%, P = 0.002; p-ERK^Thr202, +111%, P = 0.03) in MNR liver at GD 120. Our data suggest that fetal liver IGFBP-1 hyperphosphorylation, mediated by mTOR inhibition and both AAR and CK2 activation, is a key link between restricted nutrient and oxygen availability and the development of IUGR.

Protein Kinase CK2 in Cancer Energetics

Protein kinase CK2 (formerly known as casein kinase 2) is abnormally elevated in many cancers. This may increase tumor aggressiveness through CK2-dependent phosphorylation of key proteins in several signaling pathways. In this work, we have compiled evidence from the literature to suggest that CK2 also modulates a metabolic switch characteristic of cancer cells that enhances resistance to death, due to either drugs or to a microenvironment deficient in oxygen or nutrients. Concurrently, CK2 may help to preserve mitochondrial activity in a PTEN-dependent manner. PTEN, widely recognized as a tumor suppressor, is another CK2 substrate in the PI3K/Akt signaling pathway that promotes cancer viability and aerobic glycolysis. Given that CK2 can regulate Akt as well as two of its main effectors, namely mTORC1 and β-catenin, we comprehensively describe how CK2 may modulate cancer energetics by regulating expression of key targets and downstream processes, such as HIF-1 and autophagy, respectively. Thus, the specific inhibition of CK2 may lead to a catastrophic death of cancer cells, which could become a feasible therapeutic strategy to beat this devastating disease. In fact, ATP-competitive inhibitors, synthetic peptides and antisense oligonucleotides have been designed as CK2 inhibitors, some of them used in preclinical models of cancer, of which TBB and silmitasertib are widely known. We will finish by discussing a hypothetical scenario in which cancer cells are "addicted" to CK2; i.e., in which many proteins that regulate signaling pathways and metabolism-linked processes are highly dependent on this kinase.

Crystal structure of Arabidopsis thaliana casein kinase 2 α1

Casein kinase 2 (CK2) is a ubiquitous pleiotropic enzyme that is highly conserved across eukaryotic kingdoms. CK2 is singular amongst kinases as it is highly rigid and constitutively active. Arabidopsis thaliana is widely used as a model system in molecular plant research; the biological functions of A. thaliana CK2 are well studied in vivo and many of its substrates have been identified. Here, crystal structures of the α subunit of A. thaliana CK2 in three crystal forms and of its complex with the nonhydrolyzable ATP analog AMppNHp are presented. While the C-lobe of the enzyme is highly rigid, structural plasticity is observed for the N-lobe. Small but significant displacements within the active cleft are necessary in order to avoid steric clashes with the AMppNHp molecule. Binding of AMppNHp is influenced by a rigid-body motion of the N-lobe that was not previously recognized in maize CK2.

Comparative analysis of two brine shrimps revealed differential expression pattern and functional characterization of CK2α under bacterial stimulation from different geographical distribution

Understanding how the brine shrimp responds to different geographical populations can provide novel insights on response to bacterial stimulation. In the paper, Artemia sinica from lower altitudes and Artemia parthenogenetica from higher altitudes of the Tibetan Plateau, were used to illustrate different defense against bacteria mechanisms that these organisms used to adapt to different geographical environments. Protein kinase CK2 is a serine/threonine kinase with a multitude of protein substrates. It is a ubiquitous enzyme essential for the viability of eukaryotic cells, where its functions in a variety of cellular processes, including cell cycle progression, apoptosis, transcription, and viral infection. The gene encodes the same mRNA sequence in A. sinica and A. parthenogenetica, named AsCK2α and ApCK2α, respectively. The open reading frame was obtained, a 1047-bp sequence encoding a predicted protein of 349 amino acids. To systematically analyze the expression of AsCK2α and ApCK2α during embryonic development and bacterial challenge, real-time PCR, Western blotting and immunohistochemistry were performed. The results showed that AsCK2α was higher than ApCK2α at different developmental stages. Under bacterial challenge, the expression of ApCK2α was significantly higher than AsCK2α. Protein localization analysis showed that AsCK2α and ApCK2α were mainly distributed in the head and chest. Our research revealed that CK2α plays a vital role in the growth, development and bacterial stimulation of the brine shrimp.

Design, synthesis and biological evaluation of new embelin derivatives as CK2 inhibitors

A new series of furan embelin derivatives was synthesized and characterized as ATP-competitive CK2 inhibitors. The new compounds were efficiently synthesized using a multicomponent approach from embelin (1), aldehydes and isonitriles through a Knoevenagel condensation/Michael addition/heterocyclization. Several compounds with inhibitory activities in the low micromolar or even submicromolar were identified. The most active derivative was compound 4l (2-(tert-butylamino)-3-(furan-3-yl)-5-hydroxy-6-undecylbenzofuran-4,7-dione) with an IC₅₀ value of 0.63 μM. It turned out to be an ATP competitive CK2 inhibitor with a K_i value determined to be 0.48 μM. Docking studies allowed the identification of key ligand-CK2 interactions, which could help to further optimize this family of compounds as CK2 inhibitors.

Cellular signaling and epigenetic regulation of gene expression in leukemia

Alterations in normal regulation of gene expression is one of the key features of hematopoietic malignancies. In order to gain insight into the mechanisms that regulate gene expression in these diseases, we dissected the role of the Ikaros protein in leukemia. Ikaros is a DNA-binding, zinc finger protein that functions as a transcriptional regulator and a tumor suppressor in leukemia. The use of ChIP-seq, RNA-seq, and ATAC-seq—coupled with functional experiments—revealed that Ikaros regulates both the global epigenomic landscape and epigenetic signature at promoter regions of its target genes. Casein kinase II (CK2), an oncogenic kinase that is overexpressed in leukemia, directly phosphorylates Ikaros at multiple, evolutionarily-conserved residues. Phosphorylation of Ikaros impairs the protein's ability to regulate both the transcription of its target genes and global epigenetic landscape in leukemia. Treatment of leukemia cells with a specific inhibitor of CK2 restores Ikaros function, resulting in cytotoxicity of leukemia cells. Here, we review the mechanisms through which the CK2-Ikaros signaling axis regulates the global epigenomic landscape and expression of genes that control cellular proliferation in leukemia.

Protein kinase CK2 subunits exert specific and coordinated functions in skeletal muscle differentiation and fusogenic activity

Casein kinase 2 (CK2) is a tetrameric protein kinase composed of 2 catalytic (α and α') and 2 regulatory β subunits. Our study provides the first molecular and cellular characterization of the different CK2 subunits, highlighting their individual roles in skeletal muscle specification and differentiation. Analysis of C2C12 cell knockout for each CK2 subunit reveals that: 1) CK2β is mandatory for the expression of the muscle master regulator myogenic differentiation 1 in proliferating myoblasts, thus controlling both myogenic commitment and subsequent muscle-specific gene expression and myotube formation; 2) CK2α is involved in the activation of the muscle-specific gene program; and 3) CK2α' activity regulates myoblast fusion by mediating plasma membrane translocation of fusogenic proteins essential for membrane coalescence, like myomixer. Accordingly, CK2α' overexpression in C2C12 cells and in mouse regenerating muscle is sufficient to increase myofiber size and myonuclei content via enhanced satellite cell fusion. Consistent with these results, pharmacological inhibition of CK2 activity substantially blocks the expression of myogenic markers and muscle cell fusion both in vitro in C2C12 and primary myoblasts and in vivo in mouse regenerating muscle and zebrafish development. Overall, our work describes the specific and coordinated functions of CK2 subunits in orchestrating muscle differentiation and fusogenic activity, highlighting CK2 relevance in the physiopathology of skeletal muscle tissue.-Salizzato, V., Zanin, S., Borgo, C., Lidron, E., Salvi, M., Rizzuto, R., Pallafacchina, G., Donella-Deana, A. Protein kinase CK2 subunits exert specific and coordinated functions in skeletal muscle differentiation and fusogenic activity.

The effect of ionizing radiation on the subcellular localization and kinase activity of protein kinase CK2 in human non-small cell lung cancer cells

Protein kinase CK2 is a ubiquitously expressed kinase in eukaryotes, which is known to phosphorylate many protein substrates. Because CK2 is involved in the regulation of various signaling pathways, we wondered whether CK2 participated in the regulation of ionizing radiation (IR) induced biological process. In this study, we investigated the effect of IR on the subcellular localization and kinase activity in human non-small cell lung cancer (NSCLC) cells. Immunofluorescent results showed that CK2 subunits shuttle into the nucleus mostly beginning 1 h after IR and lasting more than 6 h. We also conducted in vitro kinase assay and observed an increase in CK2 kinase activity at 6 h after IR. Furthermore, an increase in S phase was observed at 6 h after IR. Colony formation assay results demonstrated that CK2 inhibitor CX-4945 significantly enhanced the effect of irradiation in NSCLC cells. These results indicated that CK2 may be implicated in the regulation of IR-induced biological process.

IUGR Is Associated With Marked Hyperphosphorylation of Decidual and Maternal Plasma IGFBP-1

CONTEXT

The mechanisms underpinning intrauterine growth restriction (IUGR), as a result of placental insufficiency, remain poorly understood, no specific treatment is available, and clinically useful biomarkers for early detection are lacking.

OBJECTIVE

We hypothesized that human IUGR is associated with inhibition of mechanistic target of rapamycin (mTOR) and activation of amino acid response (AAR) signaling, increased protein kinase casein kinase-2 (CK2) activity, and increased insulin-like growth factor-binding protein 1 (IGFBP-1) expression and phosphorylation in decidua and that maternal plasma IGFBP-1 hyperphosphorylation in the first trimester predicts later development of IUGR.

DESIGN, SETTING, AND PARTICIPANTS

Decidua [n = 16 appropriate-for-gestational age (AGA); n = 16 IUGR] and maternal plasma (n = 13 AGA; n = 13 IUGR) were collected at delivery from two different cohorts. In addition, maternal plasma was obtained in the late first trimester from a third cohort of women (n = 7) who later delivered an AGA or IUGR infant.

MAIN OUTCOME MEASURES

Total IGFBP-1 expression and phosphorylation (Ser101/Ser119/Ser169), mTOR, AAR, and CK2 activity in decidua and IGFBP-1 concentration and phosphorylation in maternal plasma.

RESULTS

We show that decidual IGFBP-1 expression and phosphorylation are increased, mTOR is markedly inhibited, and AAR and CK2 are activated in IUGR. Moreover, IGFBP-1 hyperphosphorylation in first-trimester maternal plasma is associated with the development of IUGR.

CONCLUSIONS

These data are consistent with the possibility that the decidua functions as a nutrient sensor linking limited oxygen and nutrient availability to increased IGFBP-1 phosphorylation, possibly mediated by mTOR and AAR signaling. IGFBP-1 hyperphosphorylation in first-trimester maternal plasma may serve as a predictive IUGR biomarker, allowing early intervention.

Protein Kinase CK2, a Potential Therapeutic Target in Carcinoma Management

The Protein kinase CK2 (formerly known as casein kinase 2) is a highly conserved serine/ threonine kinase overexpressed in various human carcinomas and its high expression often correlates with poor prognosis. CK2 protein is localized in the nucleus of many tumor cells and correlates with clinical features in many cases. Increased expression of CK2 in mice results in the development of various types of carcinomas (both solids and blood related tumors, such as (breast carcinoma, lymphoma, etc), which reveals its carcinogenic properties. CK2 plays essential roles in many key biological processes related to carcinoma, including cell apoptosis, DNA damage responses and cell cycle regulation. CK2 has become a potential anti-carcinoma target. Various CK2 inhibitors have been developed with anti-neoplastic properties against a variety of carcinomas. Some CK2 inhibitors have showed good results in in vitro and pre-clinical models, and have even entered in clinical trials. This article will review effects of CK2 and its inhibitors on common carcinomas in in vitro and pre-clinical studies.

Casein kinase II-mediated phosphorylation of lipin 1β phosphatidate phosphatase at Ser-285 and Ser-287 regulates its interaction with 14-3-3β protein

The mammalian lipin 1 phosphatidate phosphatase is a key regulatory enzyme in lipid metabolism. By catalyzing phosphatidate dephosphorylation, which produces diacylglycerol, the enzyme plays a major role in the synthesis of triacylglycerol and membrane phospholipids. The importance of lipin 1 to lipid metabolism is exemplified by cellular defects and lipid-based diseases associated with its loss or overexpression. Phosphorylation of lipin 1 governs whether it is associated with the cytoplasm apart from its substrate or with the endoplasmic reticulum membrane where its enzyme reaction occurs. Lipin 1β is phosphorylated on multiple sites, but less than 10% of them are ascribed to a specific protein kinase. Here, we demonstrate that lipin 1β is a bona fide substrate for casein kinase II (CKII), a protein kinase that is essential to viability and cell cycle progression. Phosphoamino acid analysis and phosphopeptide mapping revealed that lipin 1β is phosphorylated by CKII on multiple serine and threonine residues, with the former being major sites. Mutational analysis of lipin 1β and its peptides indicated that Ser-285 and Ser-287 are both phosphorylated by CKII. Substitutions of Ser-285 and Ser-287 with nonphosphorylatable alanine attenuated the interaction of lipin 1β with 14-3-3β protein, a regulatory hub that facilitates the cytoplasmic localization of phosphorylated lipin 1. These findings advance our understanding of how phosphorylation of lipin 1β phosphatidate phosphatase regulates its interaction with 14-3-3β protein and intracellular localization and uncover a mechanism by which CKII regulates cellular physiology.

Lentivirus-mediated down-regulation of CK2α inhibits proliferation and induces apoptosis of malignant lymphoma and leukemia cells

Casein kinase II subunit alpha (CK2α) is highly expressed in many malignant tumor tissues, including lymphomas and leukemia. To investigate the role of CK2α in cell proliferation and apoptosis of malignant lymphomas and leukemia, 2 lymphoma cell lines and one leukemia cell line were infected with CK2α shRNA lentivirus or negative control shRNA lentivirus, and stably infected cell lines were established. Real-time PCR and Western blot results showed that the mRNA and protein levels of CK2α were significantly reduced in CK2α knockdown cells. The tetrazolium-based colorimetric (MTT) assay found that down-regulation of CK2α inhibited the proliferation of these cells. Flow cytometry analysis showed that inhibition of CK2α induced cell cycle arrest and apoptosis of lymphoma and leukemia cells. In accordance with these, down-regulation of CK2α also reduced the protein levels of proliferating cell nuclear antigen (PCNA), cyclinD1, and bcl-2, and increased the protein expression of bax, cleaved caspase-3, cleaved caspase-9, and cleaved poly(ADP ribose) polymerase (PARP). Moreover, knockdown of CK2α impeded the growth of xenograft tumors in vivo. In summary, our study revealed that CK2α may contribute to the development of malignant lymphoma and leukemia, and serve as the therapeutic target of these malignant tumors.

CIGB-300: A peptide-based drug that impairs the Protein Kinase CK2-mediated phosphorylation

Protein kinase CK2, formerly referred to as casein kinase II, is a serine/threonine kinase often found overexpressed in solid tumors and hematologic malignancies that phosphorylates many substrates integral to the hallmarks of cancer. CK2 has emerged as a viable oncology target having been experimentally validated with different kinase inhibitors, including small molecule ATP-competitors, synthetic peptides, and antisense oligonucleotides. To date only two CK2 inhibitors, CIGB-300 and CX-4945, have entered the clinic in phase 1-2 trials. This review provides information on CIGB-300, a cell-permeable cyclic peptide that inhibits CK2-mediated phosphorylation by targeting the substrate phosphoacceptor domain. We review data that support the concept of CK2 as an anticancer target, address the mechanism of action, and summarize preclinical studies showing antiangiogenic and antimetastatic effects as well as synergism with anticancer drugs in preclinical models. We also summarize early clinical research (phase 1/2 trials) of CIGB-300 in cervical cancer, including data in combination with chemoradiotherapy. The clinical data demonstrate the safety, tolerability, and clinical effects of intratumoral injections of CIGB-300 and provide the foundation for future phase 3 clinical trials in locally advanced cervical cancer in combination with standard chemoradiotherapy.

Nuclear localization of the CK2α-subunit correlates with poor prognosis in clear cell renal cell carcinoma

Protein kinase CK2α, one of the two catalytic isoforms of the protein kinase CK2 has been shown to contribute to tumor development, tumor proliferation and suppression of apoptosis in various malignancies. We conducted this study to investigate CK2 expression in different subtypes of Renal Cell Carcinoma (RCC) and in the benign oncocytoma. qRT-PCR, immunohistochemistry and Western blot analyses revealed that CK2α expression was significantly increased at the mRNA and protein levels in clear cell RCC (ccRCC). Also the kinase activity of CK2 was significantly increased in ccRCC compared to normal renal cortex. Nuclear protein expression of CK2α correlated in univariate analysis with poor Progression Free Survival (HR = 8.11, p = 0.016). Functional analyses (cell proliferation assay) revealed an inhibitory effect of Caki-2 cell growth following CK2 inhibition with CX-4945. Our results suggest that CK2α promotes migration and invasion of ccRCC and therefore could serve as a novel prognostic biomarker and molecular therapeutic target in this type of cancer.

Okur-Chung neurodevelopmental syndrome: Eight additional cases with implications on phenotype and genotype expansion

Okur-Chung syndrome is a neurodevelopmental condition attributed to germline CSNK2A1 pathogenic missense variants. We present 8 unreported subjects with the above syndrome, who have recognizable dysmorphism, varying degrees of developmental delay and multisystem involvement. Together with 6 previously reported cases, we present a case series of 7 female and 7 male subjects, highlighting the recognizable facial features of the syndrome (microcephaly, hypertelorism, epicanthic fold, ptosis, arched eyebrows, low set ears, ear fold abnormality, broad nasal bridge and round face) as well as frequently occurring clinical features including neurodevelopmental delay (93%), gastrointestinal (57%), musculoskeletal (57%) and immunological (43%) abnormalities. The variants reported in this study are evolutionary conserved and absent in the normal population. We observed that the CSNK2A1 gene is relatively intolerant to missense genetic changes, and most variants are within the protein kinase domain. All except 1 variant reported in this cohort are spatially located on the binding pocket of the holoenzyme. We further provide key recommendations on the management of Okur-Chung syndrome. To conclude, this is the second case series on Okur-Chung syndrome, and an in-depth review of the phenotypic features and genomic findings of the condition with suggestions on clinical management.

Cancer-type dependent expression of CK2 transcripts

A multitude of proteins are aberrantly expressed in cancer cells, including the oncogenic serine-threonine kinase CK2. In a previous report, we found increases in CK2 transcript expression that could explain the increased CK2 protein levels found in tumors from lung and bronchus, prostate, breast, colon and rectum, ovarian and pancreatic cancers. We also found that, contrary to the current notions about CK2, some CK2 transcripts were downregulated in several cancers. Here, we investigate all other cancers using Oncomine to determine whether they also display significant CK2 transcript dysregulation. As anticipated from our previous analysis, we found cancers with all CK2 transcripts upregulated (e.g. cervical), and cancers where there was a combination of upregulation and/or downregulation of the CK2 transcripts (e.g. sarcoma). Unexpectedly, we found some cancers with significant downregulation of all CK2 transcripts (e.g. testicular cancer). We also found that, in some cases, CK2 transcript levels were already dysregulated in benign lesions (e.g. Barrett’s esophagus). We also found that CK2 transcript upregulation correlated with lower patient survival in most cases where data was significant. However, there were two cancer types, glioblastoma and renal cell carcinoma, where CK2 transcript upregulation correlated with higher survival. Overall, these data show that the expression levels of CK2 genes is highly variable in cancers and can lead to different patient outcomes.

Inhibitory influence of natural flavonoids on human protein kinase CK2 isoforms: effect of the regulatory subunit

CK2 is a pleiotropic, constitutively active protein kinase responsible for the phosphorylation of more than 300 physiological substrates. Typically, this enzyme is found in tetrameric form consisting of two regulatory subunits CK2β and two catalytic subunits CK2α or CK2α′. Several natural occurring flavonoids were tested for their ability to inhibit both CK2 holoenzymes, CK2α₂β₂ and CK2α′₂β₂. We identified few substances selectively inhibiting only the α′ subunit. Other compounds showed similar effect towards all four isoforms. In some cases, like chrysoeriol, pedalitin, apigenin, and luteolin, the α₂β₂ holoenzyme was at least six times better inhibited than the free α subunit. Otherwise, we have found a luteolin derivative decreased the kinase activity of CK2α′ with an IC₅₀ value of 0.8 μM, but the holoenzyme only with 9.5 µM.

Association of protein kinase CK2 inhibition with cellular radiosensitivity of non-small cell lung cancer

Protein kinase CK2 is a highly conserved protein Ser/Thr protein kinase and plays important roles in cell proliferation, protein translation and cell survival. This study investigated the possibility of using CK2 inhibition as a new approach for increasing the efficacy of radiotherapy in non-small cell lung cancer (NSCLC) and its underlying mechanisms. Kinase inhibition of CK2 was attempted either by using the specific CK2 inhibitor, Quinalizarin or by applying siRNA interference technology to silence the expression of the catalytic subunit of CK2 in A549 and H460 cells. The results showed that CK2α knockdown or Quinalizarin significantly enhanced the radiosensitivity of various NSCLC cells. The notable findings we observed after exposure to both CK2 inhibition and ionizing radiation (IR) were a prolonged delay in radiation-induced DNA double-strand breaks (DSB) repair, robust G2/M checkpoint arrest and increased apoptosis. In vivo studies further demonstrated that compared with each treatment alone, CK2 inhibition combined with IR reduced tumor growth in the H460 cell xenograft model. In conclusion, CK2 is a promising target for the enhancement of radiosensitivity in NSCLC.

Identification of Candidate Casein Kinase 2 Substrates in Mitosis by Quantitative Phosphoproteomics

Protein phosphorylation is a crucial regulatory mechanism that controls many aspects of cellular signaling. Casein kinase 2 (CK2), a constitutively expressed and active kinase, plays key roles in an array of cellular events including transcription and translation, ribosome biogenesis, cell cycle progression, and apoptosis. CK2 is implicated in cancerous transformation and is a therapeutic target in anti-cancer therapy. The specific and selective CK2 ATP competitive inhibitor, CX-4945 (silmitaseratib), is currently in phase 2 clinical trials. While many substrates and interactors of CK2 have been identified, less is known about CK2 substrates in mitosis. In the present work, we utilize CX-4945 and quantitative phosphoproteomics to inhibit CK2 activity in mitotically arrested HeLa cells and determine candidate CK2 substrates. We identify 330 phosphorylation sites on 202 proteins as significantly decreased in abundance upon inhibition of CK2 activity. Motif analysis of decreased sites reveals a linear kinase motif with aspartic and glutamic amino acids downstream of the phosphorylated residues, which is consistent with known substrate preferences for CK2. To validate specific candidate CK2 substrates, we perform in vitro kinase assays using purified components. Furthermore, we identified CK2 interacting proteins by affinity purification-mass spectrometry (AP-MS). To investigate the biological processes regulated by CK2 in mitosis, we perform network analysis and identify an enrichment of proteins involved in chromosome condensation, chromatin organization, and RNA processing. We demonstrate that overexpression of CK2 in HeLa cells affects proper chromosome condensation. Previously, we found that phosphoprotein phosphatase 6 (PP6), but not phosphoprotein phosphatase 2A (PP2A), opposes CK2 phosphorylation of the condensin I complex, which is essential for chromosome condensation. Here, we extend this observation and demonstrate that PP6 opposition of CK2 is a more general cellular regulatory mechanism.

Casein kinase 2 is a critical determinant of the balance of Th17 and Treg cell differentiation

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.

Effect of Phosphorylation on a Human-like Osteopontin Peptide

The last decade established that the dynamic properties of the phosphoproteome are central to function and its modulation. The temporal dimension of phosphorylation effects remains nonetheless poorly understood, particularly for intrinsically disordered proteins. Osteopontin, selected for this study due to its key role in biomineralization, is expressed in many species and tissues to play a range of distinct roles. A notable property of highly phosphorylated isoforms of osteopontin is their ability to sequester nanoclusters of calcium phosphate to form a core-shell structure, in a fluid that is supersaturated but stable. In Biology, this process enables soft and hard tissues to coexist in the same organism with relative ease. Here, we extend our understanding of the effect of phosphorylation on a disordered protein, the recombinant human-like osteopontin rOPN. The solution structures of the phosphorylated and unphosphorylated rOPN were investigated by small-angle x-ray scattering and no significant changes were detected on the radius of gyration or maximum interatomic distance. The picosecond-to-nanosecond dynamics of the hydrated powders of the two rOPN forms were further compared by elastic and quasi-elastic incoherent neutron scattering. Phosphorylation was found to block some nanosecond side-chain motions while increasing the flexibility of other side chains on the faster timescale. Phosphorylation can thus selectively change the dynamic behavior of even a highly disordered protein such as osteopontin. Through such an effect on rOPN, phosphorylation can direct allosteric mechanisms, interactions with substrates, cofactors and, in this case, amorphous or crystalline biominerals.

Gene expression profiles and signaling mechanisms in α2B-adrenoceptor-evoked proliferation of vascular smooth muscle cells

BACKGROUND

α2-adrenoceptors are important regulators of vascular tone and blood pressure. Regulation of cell proliferation is a less well investigated consequence of α2-adrenoceptor activation. We have previously shown that α2B-adrenoceptor activation stimulates proliferation of vascular smooth muscle cells (VSMCs). This may be important for blood vessel development and plasticity and for the pathology and therapeutics of cardiovascular disorders. The underlying cellular mechanisms have remained mostly unknown. This study explored pathways of regulation of gene expression and intracellular signaling related to α2B-adrenoceptor-evoked VSMC proliferation.

RESULTS

The cellular mechanisms and signaling pathways of α2B-adrenoceptor-evoked proliferation of VSMCs are complex and include redundancy. Functional enrichment analysis and pathway analysis identified differentially expressed genes associated with α2B-adrenoceptor-regulated VSMC proliferation. They included the upregulated genes Egr1, F3, Ptgs2 and Serpine1 and the downregulated genes Cx3cl1, Cav1, Rhoa, Nppb and Prrx1. The most highly upregulated gene, Lypd8, represents a novel finding in the VSMC context. Inhibitor library screening and kinase activity profiling were applied to identify kinases in the involved signaling pathways. Putative upstream kinases identified by two different screens included PKC, Raf-1, Src, the MAP kinases p38 and JNK and the receptor tyrosine kinases EGFR and HGF/HGFR. As a novel finding, the Src family kinase Lyn was also identified as a putative upstream kinase.

CONCLUSIONS

α2B-adrenoceptors may mediate their pro-proliferative effects in VSMCs by promoting the activity of bFGF and PDGF and the growth factor receptors EGFR, HGFR and VEGFR-1/2. The Src family kinase Lyn was also identified as a putative upstream kinase. Lyn is known to be expressed in VSMCs and has been identified as an important regulator of GPCR trafficking and GPCR effects on cell proliferation. Identified Ser/Thr kinases included several PKC isoforms and the β-adrenoceptor kinases 1 and 2. Cross-talk between the signaling mechanisms involved in α2B-adrenoceptor-evoked VSMC proliferation thus appears to involve PKC activation, subsequent changes in gene expression, transactivation of EGFR, and modulation of kinase activities and growth factor-mediated signaling. While many of the identified individual signals were relatively small in terms of effect size, many of them were validated by combining pathway analysis and our integrated screening approach.

Casein Kinase II (CK2), Glycogen Synthase Kinase-3 (GSK-3) and Ikaros mediated regulation of leukemia

Signaling networks that regulate cellular proliferation often involve complex interactions between several signaling pathways. In this manuscript we review the crosstalk between the Casein Kinase II (CK2) and Glycogen Synthase Kinase-3 (GSK-3) pathways that plays a critical role in the regulation of cellular proliferation in leukemia. Both CK2 and GSK-3 are potential targets for anti-leukemia treatment. Previously published data suggest that CK2 and GSK-3 act synergistically to promote the phosphatidylinositol-3 kinase (PI3K) pathway via phosphorylation of PTEN. More recent data demonstrate another mechanism through which CK2 promotes the PI3K pathway - via transcriptional regulation of PI3K pathway genes by the newly-discovered CK2-Ikaros axis. Together, these data suggest that the CK2 and GSK-3 pathways regulate AKT/PI3K signaling in leukemia via two complementary mechanisms: a) direct phosphorylation of PTEN and b) transcriptional regulation of PI3K-promoting genes. Functional interactions between CK2, Ikaros and GSK3 define a novel signaling network that regulates proliferation of leukemia cells. This regulatory network involves both direct posttranslational modifications (by CK and GSK-3) and transcriptional regulation (via CK2-mediated phosphorylation of Ikaros). This information provides a basis for the development of targeted therapy for leukemia.

CK2 in Cancer: Cellular and Biochemical Mechanisms and Potential Therapeutic Target

CK2 genes are overexpressed in many human cancers, and most often overexpression is associated with worse prognosis. Site-specific expression in mice leads to cancer development (e.g., breast, lymphoma) indicating the oncogenic nature of CK2. CK2 is involved in many key aspects of cancer including inhibition of apoptosis, modulation of signaling pathways, DNA damage response, and cell cycle regulation. A number of CK2 inhibitors are now available and have been shown to have activity against various cancers in vitro and in pre-clinical models. Some of these inhibitors are now undergoing exploration in clinical trials as well. In this review, we will examine some of the major cancers in which CK2 inhibition has promise based on in vitro and pre-clinical studies, the proposed cellular and signaling mechanisms of anti-cancer activity by CK2 inhibitors, and the current or recent clinical trials using CK2 inhibitors.

Exploring the CK2 Paradox: Restless, Dangerous, Dispensable

The history of protein kinase CK2 is crowded with paradoxes and unanticipated findings. Named after a protein (casein) that is not among its physiological substrates, CK2 remained in search of its targets for more than two decades after its discovery in 1954, but it later came to be one of the most pleiotropic protein kinases. Being active in the absence of phosphorylation and/or specific stimuli, it looks unsuitable to participate in signaling cascades, but its “lateral” implication in a variety of signaling pathways is now soundly documented. At variance with many “onco-kinases”, CK2 is constitutively active, and no oncogenic CK2 mutant is known; still high CK2 activity correlates to neoplasia. Its pleiotropy and essential role may cast doubts on the actual “druggability” of CK2; however, a CK2 inhibitor is now in Phase II clinical trials for the treatment of cancer, and cell clones viable in the absence of CK2 are providing information about the mechanism by which cancer becomes addicted to high CK2 levels. A phosphoproteomics analysis of these CK2 null cells suggests that CK2 pleiotropy may be less pronounced than expected and supports the idea that the phosphoproteome generated by this kinase is flexible and not rigidly pre-determined.

The New Role for an Old Kinase: Protein Kinase CK2 Regulates Metal Ion Transport

The pleiotropic serine/threonine protein kinase CK2 was the first kinase discovered. It is renowned for its role in cell proliferation and anti-apoptosis. The complexity of this kinase is well reflected by the findings of past decades in terms of its heterotetrameric structure, subcellular location, constitutive activity and the extensive catalogue of substrates. With the advent of non-biased high-throughput functional genomics such as genome-wide deletion mutant screening, novel aspects of CK2 functionality have been revealed. Our recent discoveries using the model organism Saccharomyces cerevisiae and mammalian cells demonstrate that CK2 regulates metal toxicity. Extensive literature search reveals that there are few but elegant works on the role of CK2 in regulating the sodium and zinc channels. As both CK2 and metal ions are key players in cell biology and oncogenesis, understanding the details of CK2’s regulation of metal ion homeostasis has a direct bearing on cancer research. In this review, we aim to garner the recent data and gain insights into the role of CK2 in metal ion transport.

Comparing Drug Images and Repurposing Drugs with BioGPS and FLAPdock: The Thymidylate Synthase Case

Repurposing and repositioning drugs has become a frequently pursued and successful strategy in the current era, as new chemical entities are increasingly difficult to find and get approved. Herein we report an integrated BioGPS/FLAPdock pipeline for rapid and effective off-target identification and drug repurposing. Our method is based on the structural and chemical properties of protein binding sites, that is, the ligand image, encoded in the GRID molecular interaction fields (MIFs). Protein similarity is disclosed through the BioGPS algorithm by measuring the pockets' overlap according to which pockets are clustered. Co-crystallized and known ligands can be cross-docked among similar targets, selected for subsequent in vitro binding experiments, and possibly improved for inhibitory potency. We used human thymidylate synthase (TS) as a test case and searched the entire RCSB Protein Data Bank (PDB) for similar target pockets. We chose casein kinase IIα as a control and tested a series of its inhibitors against the TS template. Ellagic acid and apigenin were identified as TS inhibitors, and various flavonoids were selected and synthesized in a second-round selection. The compounds were demonstrated to be active in the low-micromolar range.

Protein kinase CK2 in breast cancer: the CK2β regulatory subunit takes center stage in epithelial plasticity

Structurally, protein kinase CK2 consists of two catalytic subunits (α and α') and two regulatory subunits (β), which play a critical role in targeting specific CK2 substrates. Compelling evidence shows the complexity of the CK2 cellular signaling network and supports the view that this enzyme is a key component of regulatory protein kinase networks that are involved in several aspects of cancer. CK2 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, and its expression and activity are upregulated in blood tumors and virtually all solid tumors. The prognostic significance of CK2α expression in association with various clinicopathological parameters highlighted this kinase as an adverse prognostic marker in breast cancer. In addition, several recent studies reported its implication in the regulation of the epithelial-to-mesenchymal transition (EMT), an early step in cancer invasion and metastasis. In this review, we briefly overview the contribution of CK2 to several aspects of cancer and discuss how in mammary epithelial cells, the expression of its CK2β regulatory subunit plays a critical role in maintaining an epithelial phenotype through CK2-mediated control of key EMT-related transcription factors. Importantly, decreased CK2β expression in breast tumors is correlated with inefficient phosphorylation and nuclear translocation of Snail1 and Foxc2, ultimately leading to EMT induction. This review highlights the pivotal role played by CK2β in the mammary epithelial phenotype and discusses how a modest alteration in its expression may be sufficient to induce dramatic effects facilitating the early steps in tumor cell dissemination through the coordinated regulation of two key transcription factors.

Topoisomerase-I PS506 as a Dual Function Cancer Biomarker

Novel biomarkers for cancer diagnosis and therapy selection are urgently needed to facilitate early detection and improve therapy outcomes. We have previously identified a novel phosphorylation site at serine 506 (PS506) on topoisomerase-I (topo-I) and have shown that it is widely expressed in cell lines derived from several cancers, including lung cancer, but is low in cell lines derived from non-cancerous tissues. Here we have investigated how PS506 expression in lung tissue specimens correlates with their malignant status. We find that PS506 expression is significantly elevated in malignant tumors of non-small cell lung cancer (NSCLC) compared to adjacent, non-cancerous lung tissue and benign lung tumors. PS506 expression was up to 6-fold higher in malignant specimens than in paired non-malignant tissue. Using the well-characterized NIH/NCI 60-cell line panel, we correlate the most elevated expression levels of PS506 in lung, ovarian, and colon cancer cells lines with increased sensitivity to camptothecin, a plant alkaloid that targets topo-I. This is consistent with our earlier studies in a smaller sampling of cell lines and with our finding that PS506 increases topo-I DNA binding. Two widely used chemotherapeutic drugs for ovarian and colon cancer, topotecan and irinotecan, respectively, are derived from camptothecin. Irinotecan has also displayed efficacy in clinical trials of NSCLC. Our results suggest that elevated PS506 expression may correlate with clinical chemosensitivity to these agents in ovarian, colon, and NSCLC. PS506 may therefore serve as a biomarker for diagnosis or therapy selection.

Benzotriazole: An overview on its versatile biological behavior

Discovered in late 1960, azoles are heterocyclic compounds class which constitute the largest group of available antifungal drugs. Particularly, the imidazole ring is the chemical component that confers activity to azoles. Triazoles are obtained by a slight modification of this ring and similar or improved activities as well as less adverse effects are reported for triazole derivatives. Consequently, it is not surprising that benzimidazole/benzotriazole derivatives have been found to be biologically active. Since benzimidazole has been widely investigated, this review is focused on defining the place of benzotriazole derivatives in biomedical research, highlighting their versatile biological properties, the mode of action and Structure Activity Relationship (SAR) studies for a variety of antimicrobial, antiparasitic, and even antitumor, choleretic, cholesterol-lowering agents.