Pharmacological inhibition of CK2 by silmitasertib mitigates sepsis-induced circulatory collapse, thus improving septic outcomes in mice.

Casein kinase II (CK2) has recently emerged as a pivotal mediator in the propagation of inflammation across various diseases. Nevertheless, its role in the pathogenesis of sepsis remains unexplored. Here, we investigated the involvement of CK2 in sepsis progression and the potential beneficial effects of silmitasertib, a selective and potent CK2α inhibitor, currently under clinical trials for COVID-19 and cancer. Sepsis was induced by caecal ligation and puncture (CLP) in four-month-old C57BL/6OlaHsd mice. One hour after the CLP/Sham procedure, animals were assigned to receive silmitasertib (50 mg/kg/i.v.) or vehicle. Plasma/organs were collected at 24 h for analysis. A second set of experiments was performed for survival rate over 120 h. Septic mice developed multiorgan failure, including renal dysfunction due to hypoperfusion (reduced renal blood flow) and increased plasma levels of creatinine. Renal derangements were associated with local overactivation of CK2, and downstream activation of the NF-ĸB-iNOS-NO axis, paralleled by a systemic cytokine storm. Interestingly, all markers of injury/inflammation were mitigated following silmitasertib administration. Additionally, when compared to sham-operated mice, sepsis led to vascular hyporesponsiveness due to an aberrant systemic and local release of NO. Silmitasertib restored sepsis-induced vascular abnormalities. Overall, these pharmacological effects of silmitasertib significantly reduced sepsis mortality. Our findings reveal, for the first time, the potential benefits of a selective and potent CK2 inhibitor to counteract sepsis-induced hyperinflammatory storm, vasoplegia, and ultimately prolonging the survival of septic mice, thus suggesting a pivotal role of CK2 in sepsis and silmitasertib as a novel powerful pharmacological tool for drug repurposing in sepsis.

CKIP-1 mediates CK2 translocation to regulate Nav1.5 and Kir2.1 channel complexes in cardiomyocytes.

Sodium and potassium channels, especially Nav1.5 and Kir2.1, play key roles in the formation of action potentials in cardiomyocytes. These channels interact with, and are regulated by, synapse-associated protein 97 (SAP97). However, the regulatory role of SAP97 in myocyte remains incompletely understood. Here, we investigate the function of SAP97 phosphorylation in the regulation of Nav1.5 and Kir2.1 channel complexes and the upstream regulation of SAP97. We found that SAP97 is phosphorylated by casein kinase II (CK2) in vitro. In addition, transfection of casein kinase 2 interacting protein-1 (CKIP-1) into cardiomyocytes to drive CK2 from the nucleus to the cytoplasm, increased SAP97 phosphorylation and Nav1.5 and Kir2.1 current activity. These findings demonstrated that CKIP-1 modulates the subcellular translocation of CK2, which regulates Nav1.5 and Kir2.1 channel complex formation and activity in cardiomyocytes.

Synthesis and evaluation of chemical linchpins for highly selective CK2α targeting.

Casein kinase-2 (CK2) are serine/threonine kinases with dual co-factor (ATP and GTP) specificity, that are involved in the regulation of a wide variety of cellular functions. Small molecules targeting CK2 have been described in the literature targeting different binding pockets of the kinase with a focus on type I inhibitors such as the recently published chemical probe SGC-CK2-1. In this study, we investigated whether known allosteric inhibitors binding to a pocket adjacent to helix αD could be combined with ATP mimetic moieties defining a novel class of ATP competitive compounds with a unique binding mode. Linking both binding sites requires a chemical linking moiety that would introduce a 90-degree angle between the ATP mimetic ring system and the αD targeting moiety, which was realized using a sulfonamide. The synthesized inhibitors were highly selective for CK2 with binding constants in the nM range and low micromolar activity. While these inhibitors need to be further improved, the present work provides a structure-based design strategy for highly selective CK2 inhibitors.

Calcineurin and CK2 Reciprocally Regulate Synaptic AMPA Receptor Phenotypes via α2δ-1 in Spinal Excitatory Neurons.

Calcineurin inhibitors, such as cyclosporine and tacrolimus (FK506), are commonly used immunosuppressants for preserving transplanted organs and tissues. However, these drugs can cause severe and persistent pain. GluA2-lacking, calcium-permeable AMPA receptors (CP-AMPARs) are implicated in various neurological disorders, including neuropathic pain. It is unclear whether and how constitutive calcineurin, a Ca2+/calmodulin protein phosphatase, controls synaptic CP-AMPARs. In this study, we found that blocking CP-AMPARs with IEM-1460 markedly reduced the amplitude of AMPAR-EPSCs in excitatory neurons expressing vesicular glutamate transporter-2 (VGluT2), but not in inhibitory neurons expressing vesicular GABA transporter, in the spinal cord of FK506-treated male and female mice. FK506 treatment also caused an inward rectification in the current-voltage relationship of AMPAR-EPSCs specifically in VGluT2 neurons. Intrathecal injection of IEM-1460 rapidly alleviated pain hypersensitivity in FK506-treated mice. Furthermore, FK506 treatment substantially increased physical interaction of α2δ-1 with GluA1 and GluA2 in the spinal cord and reduced GluA1/GluA2 heteromers in endoplasmic reticulum-enriched fractions of spinal cords. Correspondingly, inhibiting α2δ-1 with pregabalin, Cacna2d1 genetic knock-out, or disrupting α2δ-1-AMPAR interactions with an α2δ-1 C terminus peptide reversed inward rectification of AMPAR-EPSCs in spinal VGluT2 neurons caused by FK506 treatment. In addition, CK2 inhibition reversed FK506 treatment-induced pain hypersensitivity, α2δ-1 interactions with GluA1 and GluA2, and inward rectification of AMPAR-EPSCs in spinal VGluT2 neurons. Thus, the increased prevalence of synaptic CP-AMPARs in spinal excitatory neurons plays a major role in calcineurin inhibitor-induced pain hypersensitivity. Calcineurin and CK2 antagonistically regulate postsynaptic CP-AMPARs through α2δ-1-mediated GluA1/GluA2 heteromeric assembly in the spinal dorsal horn.

Active DNA Demethylase, TET1, Increases Oxidative Phosphorylation and Sensitizes Ovarian Cancer Stem Cells to Mitochondrial Complex I Inhibitor.

Ten-eleven translocation 1 (TET1) is a methylcytosine dioxygenase involved in active DNA demethylation. In our previous study, we demonstrated that TET1 reprogrammed the ovarian cancer epigenome, increased stem properties, and activated various regulatory networks, including metabolic networks. However, the role of TET1 in cancer metabolism remains poorly understood. Herein, we uncovered a demethylated metabolic gene network, especially oxidative phosphorylation (OXPHOS). Contrary to the concept of the Warburg effect in cancer cells, TET1 increased energy production mainly using OXPHOS rather than using glycolysis. Notably, TET1 increased the mitochondrial mass and DNA copy number. TET1 also activated mitochondrial biogenesis genes and adenosine triphosphate production. However, the reactive oxygen species levels were surprisingly decreased. In addition, TET1 increased the basal and maximal respiratory capacities. In an analysis of tricarboxylic acid cycle metabolites, TET1 increased the levels of α-ketoglutarate, which is a coenzyme of TET1 dioxygenase and may provide a positive feedback loop to modify the epigenomic landscape. TET1 also increased the mitochondrial complex I activity. Moreover, the mitochondrial complex I inhibitor, which had synergistic effects with the casein kinase 2 inhibitor, affected ovarian cancer growth. Altogether, TET1-reprogrammed ovarian cancer stem cells shifted the energy source to OXPHOS, which suggested that metabolic intervention might be a novel strategy for ovarian cancer treatment.

CKIP-1-Loaded Cartilage-Affinitive Nanoliposomes Reverse Osteoarthritis by Restoring Chondrocyte Homeostasis.

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage imbalance and disruption of cartilage extracellular matrix secretion. Identifying key genes that regulate cartilage differentiation and developing effective therapeutic strategies to restore their expression is crucial. In a previous study, we observed a significant correlation between the expression of the gene encoding casein kinase-2 interacting protein-1 (CKIP-1) in the cartilage of OA patients and OA severity scores, suggesting its potential involvement in OA development. To test this hypothesis, we synthesized a chondrocyte affinity plasmid, liposomes CKIP-1, to enhance CKIP-1 expression in chondrocytes. Our results demonstrated that injection of CAP-Lipos-CKIP-1 plasmid significantly improved OA joint destruction and restored joint motor function by enhancing cartilage extracellular matrix (ECM) secretion. Histological and cytological analyses confirmed that CKIP-1 maintains altered the phosphorylation of the signal transduction molecule SMAD2/3 of the transforming growth factor-ß (TGF-ß) pathway by promoting the phosphorylation of the 8T, 416S sit. Taken together, this work highlights a novel approach for the precise modulation of chondrocyte phenotype from an inflammatory to a noninflammatory state for the treatment of OA and may be broadly applicable to patients suffering from other arthritic diseases.

Chromatin modifier Hmga2 promotes adult hematopoietic stem cell function and blood regeneration in stress conditions.

The molecular mechanisms governing the response of hematopoietic stem cells (HSCs) to stress insults remain poorly defined. Here, we investigated effects of conditional knock-out or overexpression of Hmga2 (High mobility group AT-hook 2), a transcriptional activator of stem cell genes in fetal HSCs. While Hmga2 overexpression did not affect adult hematopoiesis under homeostasis, it accelerated HSC expansion in response to injection with 5-fluorouracil (5-FU) or in vitro treatment with TNF-α. In contrast, HSC and megakaryocyte progenitor cell numbers were decreased in Hmga2 KO animals. Transcription of inflammatory genes was repressed in Hmga2-overexpressing mice injected with 5-FU, and Hmga2 bound to distinct regions and chromatin accessibility was decreased in HSCs upon stress. Mechanistically, we found that casein kinase 2 (CK2) phosphorylates the Hmga2 acidic domain, promoting its access and binding to chromatin, transcription of anti-inflammatory target genes, and the expansion of HSCs under stress conditions. Notably, the identified stress-regulated Hmga2 gene signature is activated in hematopoietic stem progenitor cells of human myelodysplastic syndrome patients. In sum, these results reveal a TNF-α/CK2/phospho-Hmga2 axis controlling adult stress hematopoiesis.

RACK1 Promotes Meningioma Progression by Activation of NF-κB Pathway via Preventing CSNK2B from Ubiquitination Degradation.

Higher-grade meningiomas (WHO grade II and III) are characterized by aggressive invasiveness and high postoperative recurrence rates. The prognosis remains inadequate even with adjuvant radiotherapy and currently there is no definitive pharmacological treatment strategy and target for malignant meningiomas. This study aims to unveil the mechanisms driving the malignant progression of meningiomas and to identify potential inhibitory targets, with significant clinical implications. Implementing techniques such as protein immunoprecipitation, mass spectrometry, RNA interference, and transcriptome sequencing, we investigated the malignancy mechanisms in meningioma cell lines IOMM-LEE and CH157-MN. Additionally, in vivo experiments were carried out on nude mice. We discovered a positive correlation between meningioma malignancy and the levels of the receptor for activated C kinase 1 (RACK1), which interacts with CSNK2B, the ß subunit of casein kinase 2 (CK2), inhibiting its ubiquitination and subsequent degradation. This inhibition allows CK2 to activate the NF-κb pathway, which increases the transcription of CDK4 and cyclin D3, resulting in the transition of the cell cycle into the G2/M phase. The RACK1 inhibitor, harringtonolide (HA), significantly suppressed the malignant tendencies of meningioma cells. Our study suggests that RACK1 may play a role in the malignant progression of meningiomas, and therefore, targeting RACK1 could emerge as an effective strategy for reducing the malignancy of these tumors.

Subtype-selective prenylated isoflavonoids disrupt regulatory drivers of MYCN-amplified cancers.

Transcription factors have proven difficult to target with small molecules because they lack pockets necessary for potent binding. Disruption of protein expression can suppress targets and enable therapeutic intervention. To this end, we developed a drug discovery workflow that incorporates cell-line-selective screening and high-throughput expression profiling followed by regulatory network analysis to identify compounds that suppress regulatory drivers of disease. Applying this approach to neuroblastoma (NBL), we screened bioactive molecules in cell lines representing its MYC-dependent (MYCNA) and mesenchymal (MES) subtypes to identify selective compounds, followed by PLATESeq profiling of treated cells. This revealed compounds that disrupt a sub-network of MYCNA-specific regulatory proteins, resulting in MYCN degradation in vivo. The top hit was isopomiferin, a prenylated isoflavonoid that inhibited casein kinase 2 (CK2) in cells. Isopomiferin and its structural analogs inhibited MYC and MYCN in NBL and lung cancer cells, highlighting the general MYC-inhibiting potential of this unique scaffold.

Protein kinase CK2: An emerging regulator of cellular metabolism.

The protein kinase casein kinase 2 (CK2) exerts its influence on the metabolism of three major cellular substances by phosphorylating essential protein molecules involved in various cellular metabolic pathways. These substances include hormones, especially insulin, rate-limiting enzymes, transcription factors of key genes, and cytokines. This regulatory role of CK2 is closely tied to important cellular processes such as cell proliferation and apoptosis. Additionally, tumor cells undergo metabolic reprogramming characterized by aerobic glycolysis, accelerated lipid ß-oxidation, and abnormally active glutamine metabolism. In this context, CK2, which is overexpressed in various tumors, also plays a pivotal role. Hence, this review aims to summarize the regulatory mechanisms of CK2 in diverse metabolic pathways and tumor development, providing novel insights for the diagnosis, treatment, and prognosis of metabolism-related diseases and cancers.

Casein kinase-2 inhibition promotes retinal ganglion cell survival after acute intraocular pressure elevation.

Intraocular pressure elevation can induce retinal ganglion cell death and is a clinically reversible risk factor for glaucoma, the leading cause of irreversible blindness. We previously demonstrated that casein kinase-2 inhibition can promote retinal ganglion cell survival and axonal regeneration in rats after optic nerve injury. To investigate the underlying mechanism, in the current study we increased the intraocular pressure of adult rats to 75 mmHg for 2 hours and then administered a casein kinase-2 inhibitor (4,5,6,7-tetrabromo-2-azabenzimidazole or 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole) by intravitreal injection. We found that intravitreal injection of 4,5,6,7-tetrabromo-2-azabenzimidazole or 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole promoted retinal ganglion cell survival and reduced the number of infiltrating macrophages. Transcriptomic analysis showed that the mitogen activated protein kinase signaling pathway was involved in the response to intraocular pressure elevation but was not modulated by the casein kinase-2 inhibitors. Furthermore, casein kinase-2 inhibition downregulated the expression of genes (Cck, Htrsa, Nef1, Htrlb, Prph, Chat, Slc18a3, Slc5a7, Scn1b, Crybb2, Tsga10ip, and Vstm21) involved in intraocular pressure elevation. Our data indicate that inhibition of casein kinase-2 can enhance retinal ganglion cell survival in rats after acute intraocular pressure elevation via macrophage inactivation.

Erratum: Evaluation of a selective chemical probe validates that CK2 mediates neuroinflammation in a human induced pluripotent stem cell-derived microglial model.

[This corrects the article DOI: 10.3389/fnmol.2022.824956.].

Vacuolar ATPase Is a Possible Therapeutic Target in Acute Myeloid Leukemia: Focus on Patient Heterogeneity and Treatment Toxicity.

Vacuolar ATPase (V-ATPase) is regarded as a possible target in cancer treatment. It is expressed in primary acute myeloid leukemia cells (AML), but the expression varies between patients and is highest for patients with a favorable prognosis after intensive chemotherapy. We therefore investigated the functional effects of two V-ATPase inhibitors (bafilomycin A1, concanamycin A) for primary AML cells derived from 80 consecutive patients. The V-ATPase inhibitors showed dose-dependent antiproliferative and proapoptotic effects that varied considerably between patients. A proteomic comparison of primary AML cells showing weak versus strong antiproliferative effects of V-ATPase inhibition showed a differential expression of proteins involved in intracellular transport/cytoskeleton functions, and an equivalent phosphoproteomic comparison showed a differential expression of proteins that regulate RNA processing/function together with increased activity of casein kinase 2. Patients with secondary AML, i.e., a heterogeneous subset with generally adverse prognosis and previous cytotoxic therapy, myeloproliferative neoplasia or myelodysplastic syndrome, were characterized by a strong antiproliferative effect of V-ATPase inhibition and also by a specific mRNA expression profile of V-ATPase interactome proteins. Furthermore, the V-ATPase inhibition altered the constitutive extracellular release of several soluble mediators (e.g., chemokines, interleukins, proteases, protease inhibitors), and increased mediator levels in the presence of AML-supporting bone marrow mesenchymal stem cells was then observed, especially for patients with secondary AML. Finally, animal studies suggested that the V-ATPase inhibitor bafilomycin had limited toxicity, even when combined with cytarabine. To conclude, V-ATPase inhibition has antileukemic effects in AML, but this effect varies between patients.

Blockade of chemo-resistance to 5-FU by a CK2-targeted combination via attenuating AhR-TLS-promoted genomic instability in human colon cancer cells.

As highly expressed in several human cancers, Casein Kinase 2 (CK2) is involved in chemotherapy-induced resistance. As a new potent CK2 inhibitor, DN701 is used to overcome chemoresistance through its synergistic antitumor effect with 5-fluorouracil (5-FU). Translesion DNA synthesis (TLS) has drawn our attention because it is associated with the development of chemo-resistance and tumor recurrence. The in vitro biological properties of 5-FU-resistant colon cancer cells revealed that DN701 combined with 5-FU could overcome chemo-resistance via blocking CK2-mediated aryl hydrocarbon receptor (AhR) and TLS-induced DNA damage repair (DDR). Moreover, pharmacologic and genetic inhibitions of AhR potently reduced TLS-promoted genomic instability. The mechanistic studies showed that combined DN701 with 5-FU was investigated to inhibit CK2 expression level and AhR-TLS-REV1 pathway. Meanwhile, DN701 combined with 5-FU could reduce CK2-AhR-TLS genomic instability, thus leading to superior in vivo antitumor effect. The insights provide a rationale for combining DN701 with 5-FU as a therapeutic strategy for patients with colon cancer.

Inherited CSNK2A1 variants in families with Okur-Chung neurodevelopmental syndrome.

Pedigree showing the autosomal dominant inheritance pattern of CSNK21 variants in families presenting with OCNDS. (A) Maternal inheritance to two daughters in Family 1, (B) Paternal inheritance to a daughter in Family 2, and (C) Maternal inheritance to two sons in Family 3.

Genome-wide kinase-MAM interactome screening reveals the role of CK2A1 in MAM Ca2+ dynamics linked to DEE66.

The endoplasmic reticulum (ER) and mitochondria form a unique subcellular compartment called mitochondria-associated ER membranes (MAMs). Disruption of MAMs impairs Ca2+ homeostasis, triggering pleiotropic effects in the neuronal system. Genome-wide kinase-MAM interactome screening identifies casein kinase 2 alpha 1 (CK2A1) as a regulator of composition and Ca2+ transport of MAMs. CK2A1-mediated phosphorylation of PACS2 at Ser207/208/213 facilitates MAM localization of the CK2A1-PACS2-PKD2 complex, regulating PKD2-dependent mitochondrial Ca2+ influx. We further reveal that mutations of PACS2 (E209K and E211K) associated with developmental and epileptic encephalopathy-66 (DEE66) impair MAM integrity through the disturbance of PACS2 phosphorylation at Ser207/208/213. This, in turn, causes the reduction of mitochondrial Ca2+ uptake and the dramatic increase of the cytosolic Ca2+ level, thereby, inducing neurotransmitter release at the axon boutons of glutamatergic neurons. In conclusion, our findings suggest a molecular mechanism that MAM alterations induced by pathological PACS2 mutations modulate Ca2+-dependent neurotransmitter release.

Casein kinase 2 affects epilepsy by regulating ion channels: a potential mechanism.

Epilepsy, characterized by recurrent seizures and abnormal brain discharges, is the third most common chronic disorder of the Central Nervous System (CNS). Although significant progress has been made in the research on antiepileptic drugs (AEDs), approximately one-third of patients with epilepsy are refractory to these drugs. Thus, research on the pathogenesis of epilepsy is ongoing to find more effective treatments. Many pathological mechanisms are involved in epilepsy, including neuronal apoptosis, mossy fiber sprouting, neuroinflammation, and dysfunction of neuronal ion channels, leading to abnormal neuronal excitatory networks in the brain. CK2 (Casein kinase 2), which plays a critical role in modulating neuronal excitability and synaptic transmission, has been shown to be associated with epilepsy. However, there is limited research on the mechanisms involved. Recent studies have suggested that CK2 is involved in regulating the function of neuronal ion channels by directly phosphorylating them or their binding partners. Therefore, in this review, we will summarize recent research advances regarding the potential role of CK2 regulating ion channels in epilepsy, aiming to provide more evidence for future studies.

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.

MiR-93 alleviates DEHP plasticizer-induced neurotoxicity by negatively regulating TNFAIP1 and inhibiting ubiquitin-mediated degradation of CK2ß.

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer that is widely used in various products, such as plastic packaging in food industries. As an environmental endocrine disruptor, it induces adverse effects on brain development and function. However, the molecular mechanisms by which DEHP induces learning and memory impairment remain poorly understood. Herein, we found that DEHP impaired learning and memory in pubertal C57BL/6 mice, decreased the number of neurons, downregulated miR-93 and the ß subunit of casein kinase 2 (CK2ß), upregulated tumor necrosis factor-induced protein 1 (TNFAIP1), and inhibited Akt/CREB pathway in mouse hippocampi. Co-immunoprecipitation and western blotting assays revealed that TNFAIP1 interacted with CK2ß and promoted its degradation by ubiquitination. Bioinformatics analysis showed a miR-93 binding site in the 3'-untranslated region of Tnfaip1. A dual-luciferase reporter assay revealed that miR-93 targeted TNFAIP1 and negatively regulated its expression. MiR-93 overexpression prevented DEHP-induced neurotoxicity by downregulating TNFAIP1 and then activating CK2/Akt/CREB pathway. These data indicate that DEHP upregulates TNFAIP1 expression by downregulating miR-93, thus promoting ubiquitin-mediated degradation of CK2ß, subsequently inhibiting Akt/CREB pathway, and finally inducing learning and memory impairment. Therefore, miR-93 can relieve DEHP-induced neurotoxicity and may be used as a potential molecular target for prevention and treatment of related neurological disorders.