Exploring the role of casein kinase 1α splice variants across cancer cell lines.

Casein kinase 1α (CK1α) is a serine/threonine protein kinase that acts in various cellular processes affecting cell division and signal transduction. CK1α is present as multiple splice variants that are distinguished by the presence or absence of a long insert (L-insert) and a short carboxyl-terminal insert (S-insert). When overexpressed, zebrafish CK1α splice variants exhibit different biological properties, such as subcellular localization and catalytic activity. However, whether endogenous, alternatively spliced CK1α gene products also differ in their biological functions has yet to be elucidated. Here, we identify a panel of splice variant specific CK1α antibodies and use them to show that four CK1α splice variants are expressed in mammals. We subsequently show that the relative abundance of CK1α splice variants varies across distinct mouse tissues and between various cancer cell lines. Furthermore, we identify pathways whose expression is noticeably altered in cell lines enriched with select splice variants of CK1α. Finally, we show that the S-insert of CK1α promotes the growth of HCT 116 cells as cells engineered to lack the S-insert display decreased cell growth. Together, we provide tools and methods to identify individual CK1α splice variants, which we use to begin to uncover the differential biological properties driven by specific splice variants of mammalian CK1α.

CK1 and PP1 regulate Rift Valley fever virus genome replication through L protein phosphorylation.

Rift Valley fever virus (RVFV) is an arbovirus in the Phenuiviridae family identified initially by the large 'abortion storms' observed among ruminants; RVFV can also infect humans. In humans, there is a wide variation of clinical symptoms ranging from subclinical to mild febrile illness to hepatitis, retinitis, delayed-onset encephalitis, or even hemorrhagic fever. The RVFV is a tri-segmented negative-sense RNA virus consisting of S, M, and L segments. The L segment encodes the RNA-dependent RNA polymerase (RdRp), termed the L protein, which is responsible for both viral mRNA synthesis and genome replication. Phosphorylation of viral RdRps is known to regulate viral replication. This study shows that RVFV L protein is serine phosphorylated and identified Casein Kinase 1 alpha (CK1α) and protein phosphatase 1 alpha (PP1α) as L protein binding partners. Inhibition of CK1 and PP1 through small molecule inhibitor treatment, D4476 and 1E7-03, respectively, caused a change in the phosphorylated status of the L protein. Inhibition of PP1α resulted in increased L protein phosphorylation whereas inhibition of CK1α decreased L protein phosphorylation. It was also found that in RVFV infected cells, PP1α localized to the cytoplasmic compartment. Treatment of RVFV infected cells with CK1 inhibitors reduced virus production in both mammalian and mosquito cells. Lastly, inhibition of either CK1 or PP1 reduced viral genomic RNA levels. These data indicate that L protein is phosphorylated and that CK1 and PP1 play a crucial role in regulating the L protein phosphorylation cycle, which is critical to viral RNA production and viral replication.

Discovery of novel co-degradation CK1α and CDK7/9 PROTACs with p53 activation for treating acute myeloid leukemia.

Reactivating p53 activity to restore its anticancer function is an attractive cancer treatment strategy. In this study, we designed and synthesized a series of novel PROTACs to reactivate p53 via the co-degradation of CK1α and CDK7/9 proteins. Bioactivity studies showed that the selected PROTAC 13i exhibited potency antiproliferative activity in MV4-11 (IC50 = 0.096 ± 0.012 µM) and MOLM-13 (IC50 = 0.072 ± 0.014 µM) cells, and induced apoptosis of MV4-11 cells. Western-blot analysis showed that PROTAC 13i triple CK1α and CDK7/9 protein degradation resulted in the significantly increased expression of p53. At the same time, the transcriptional repression due to the degradation significantly reduced downstream gene expression of MYC, MDM2, BCL-2 and MCL-1, and reduced the inflammatory cytokine levels of TNF-α, IL-1ß and IL-6 in PMBCs. These results indicate the beneficial impact of simultaneous CK1α and CDK7/9 degradation for acute myeloid leukemia therapy.

Design and Development of IKZF2 and CK1α Dual Degraders.

Lenalidomide achieves its therapeutic efficacy by recruiting and removing proteins of therapeutic interest through the E3 ligase substrate adapter cereblon. Here, we report the design and characterization of 81 cereblon ligands for their ability to degrade the transcription factor Helios (IKZF2) and casein kinase 1 alpha (CK1α). We identified a key naphthamide scaffold that depleted both intended targets in acute myeloid leukemia MOLM-13 cells. Structure-activity relationship studies for degradation of the desired targets over other targets (IKZF1, GSPT1) afforded an initial lead compound DEG-35. A subsequent scaffold replacement campaign identified DEG-77, which selectively degrades IKZF2 and CK1α, and possesses suitable pharmacokinetic properties, solubility, and selectivity for in vivo studies. Finally, we show that DEG-77 has antiproliferative activity in the diffuse large B cell lymphoma cell line OCI-LY3 and the ovarian cancer cell line A2780 indicating that the dual degrader strategy may have efficacy against additional types of cancer.

Metabolic exhaustion and casein kinase 1α drive deguelin-induced premature red blood cell death.

1. Deguelin (DGN), a retinoid isolated from many plants, exhibits a potent anticancer activity against a wide spectrum of tumour cells. There is a dearth of evidence, however, regarding the toxicity of DGN to red blood cells (RBCs). This is relevant given the prevalent chemotherapy-associated anaemia observed in cancer patients.2. RBCs were exposed to 1-100 µM of DGN for 24 h at 37 °C. Haemolysis and related markers were photometrically measured while flow cytometry was employed to detect phosphatidylserine exposure through Annexin-V-FITC binding and light scatter properties. Additionally, cytosolic Ca2+ and reactive oxygen species were quantified using Fluo4/AM and H2DCFDA, respectively. DGN was also tested against specific signalling inhibitors in addition to vitamin C and ATP.3. DGN caused a significant increase in Annexin-V-positive cells which was accompanied by cell shrinkage without Ca2+ elevation or oxidative stress. DGN also elicited dose-responsive haemolysis which was ameliorated by preventing KCl efflux and in the presence of sucrose, D4476, and ATP. In whole blood, DGN significantly reduced the reticulocyte count and increased platelet distribution width and large cell count.4. DGN triggers premature RBC eryptosis and haemolysis through casein kinase 1α and ATP depletion, and exhibits a specific toxicity towards reticulocytes and platelets.

Dual IKZF2 and CK1α degrader targets acute myeloid leukemia cells.

Acute myeloid leukemia (AML) is a hematologic malignancy for which several epigenetic regulators have been identified as therapeutic targets. Here we report the development of cereblon-dependent degraders of IKZF2 and casein kinase 1α (CK1α), termed DEG-35 and DEG-77. We utilized a structure-guided approach to develop DEG-35 as a nanomolar degrader of IKZF2, a hematopoietic-specific transcription factor that contributes to myeloid leukemogenesis. DEG-35 possesses additional substrate specificity for the therapeutically relevant target CK1α, which was identified through unbiased proteomics and a PRISM screen assay. Degradation of IKZF2 and CK1α blocks cell growth and induces myeloid differentiation in AML cells through CK1α-p53- and IKZF2-dependent pathways. Target degradation by DEG-35 or a more soluble analog, DEG-77, delays leukemia progression in murine and human AML mouse models. Overall, we provide a strategy for multitargeted degradation of IKZF2 and CK1α to enhance efficacy against AML that may be expanded to additional targets and indications.

Casein Kinase 1α Regulates Testosterone Synthesis and Testis Development in Adult Mice.

Casein kinase 1α (CK1α) is a main component of the Wnt/ß-catenin signaling pathway, which participates in multiple biological processes. Our recent study demonstrated that CK1α is expressed in both germ cells and somatic cells of mouse testes and regulates spermatogenesis. However, little information is known about the role of CK1α in regulating the development of somatic cells in mouse testes. Our results demonstrated that conditional disruption of CK1α in murine Leydig cells sharply decreased testosterone levels; markedly affected testis development, sperm motility, and sperm morphology; and caused subfertility. The germ cell population was partially decreased in CK1α conditional knockout (cKO) mice, while the proliferation of Leydig cells and Sertoli cells was not affected. Furthermore, in vitro results verified that luteinizing hormone upregulates CK1α through the luteinizing hormone/protein kinase/Epidermal Growth Factor Receptor/extracellular regulated protein kinases/2 signaling pathway and that CK1α interacts with and phosphorylates EGFR, which subsequently activates the phosphorylation of ERK1/2, thereby promoting testosterone synthesis. In addition, high-dose testosterone propionate partially rescued the phenotype observed in cKO mice. This study provides new insights into the role of CK1α in steroidogenesis and male reproduction.

Casein kinase 1α mediates eryptosis: a review.

Eryptosis is a coordinated non-lytic cell death of erythrocytes characterized by cell shrinkage, cell membrane scrambling, Ca2+ influx, ceramide accumulation, oxidative stress, activation of calpain and caspases. Physiologically, it aims at removing damaged or aged erythrocytes from circulation. A plethora of diseases are associated with enhanced eryptosis, including metabolic diseases, cardiovascular pathology, renal and hepatic diseases, hematological disorders, systemic autoimmune pathology, and cancer. This makes eryptosis and eryptosis-regulating signaling pathways a target for therapeutic interventions. This review highlights the eryptotic signaling machinery containing several protein kinases and its small molecular inhibitors with a special emphasis on casein kinase 1α (CK1α), a serine/threonine protein kinase with a broad spectrum of activity. In this review article, we provide a critical analysis of the regulatory role of CK1α in eryptosis, highlight triggers of CK1α-mediated suicidal death of red blood cells, cover the knowledge gaps in understanding CK1α-driven eryptosis and discover the opportunity of CK1α-targeted pharmacological modulation of eryptosis. Moreover, we discuss the directions of future research focusing on uncovering crosstalks between CK1α and other eryptosis-regulating kinases and pathways.

Knockdown of Csnk1a1 results in preimplantation developmental arrest in mice.

Casein kinase 1, alpha 1 (CSNK1A1), is a member of the highly conserved serine/threonine protein kinase family. This study was established to analyze the expression and localization of CSNK1A1 and its function in early embryonic development in mice. Csnk1a1 mRNA and protein are expressed in multiple mouse tissues including the ovary. After ovulation and fertilization, Csnk1a1 mRNA and protein were detected in preimplantation embryos and their expression was highest in two-cell-stage embryos. CSNK1A1 protein was also mainly localized in the cytoplasm of preimplantation embryos. Moreover, knockdown of Csnk1a1 in zygotes led to a significant decrease in the rate of blastocyst formation. Furthermore, treatment of zygotes with the CSNK1A1-specific inhibitor D4476 also resulted in embryonic developmental arrest. These results provide the first evidence for a novel function of CSNK1A1 in early embryonic development in mice.

The Casein kinase 1α agonist pyrvinium attenuates Wnt-mediated CK1α degradation via interaction with the E3 ubiquitin ligase component Cereblon.

The Cullin-RING ligase 4 E3 ubiquitin ligase component Cereblon (CRBN) is a well-established target for a class of small molecules termed immunomodulatory drugs (IMiDs). These drugs drive CRBN to modulate the degradation of a number of neosubstrates required for the growth of multiple cancers. Whereas the mechanism underlying the activation of CRBN by IMiDs is well described, the normal physiological regulation of CRBN is poorly understood. We recently showed that CRBN is activated following exposure to Wnt ligands and subsequently mediates the degradation of a subset of physiological substrates. Among the Wnt-dependent substrates of CRBN is Casein kinase 1α (CK1α), a known negative regulator of Wnt signaling. Wnt-mediated degradation of CK1α occurs via its association with CRBN at a known IMiD binding pocket. Herein, we demonstrate that a small-molecule CK1α agonist, pyrvinium, directly prevents the Wnt-dependent interaction of CRBN with CK1α, attenuating the consequent CK1α degradation. We further show that pyrvinium disrupts the ability of CRBN to interact with CK1α at the IMiD binding pocket within the CRBN-CK1α complex. Of note, this function of pyrvinium is independent of its previously reported ability to enhance CK1α kinase activity. Furthermore, we also demonstrate that pyrvinium attenuates CRBN-induced Wnt pathway activation in vivo. Collectively, these results reveal a novel dual mechanism through which pyrvinium inhibits Wnt signaling by both attenuating the CRBN-mediated destabilization of CK1α and activating CK1α kinase activity.

Casein kinase 1α regulates murine spermatogenesis via p53-Sox3 signaling.

Casein kinase 1α (CK1α), acting as one member of the ß-catenin degradation complex, negatively regulates the Wnt/ß-catenin signaling pathway. CK1α knockout usually causes both Wnt/ß-catenin and p53 activation. Our results demonstrated that conditional disruption of CK1α in spermatogonia impaired spermatogenesis and resulted in male mouse infertility. The progenitor cell population was dramatically decreased in CK1α conditional knockout (cKO) mice, while the proliferation of spermatogonial stem cells (SSCs) was not affected. Furthermore, our molecular analyses identified that CK1α loss was accompanied by nuclear stability of p53 protein in mouse spermatogonia, and dual-luciferase reporter and chromatin immunoprecipitation assays revealed that p53 directly targeted the Sox3 gene. In addition, the p53 inhibitor pifithrin α (PFTα) partially rescued the phenotype observed in cKO mice. Collectively, our data suggest that CK1α regulates spermatogenesis and male fertility through p53-Sox3 signaling, and they deepen our understanding of the regulatory mechanism underlying the male reproductive system.

S100A16 promotes acute kidney injury by activating HRD1-induced ubiquitination and degradation of GSK3ß and CK1α.

The pathogenesis of acute kidney injury (AKI) is associated with the activation of multiple signaling pathways, including Wnt/ß-catenin signaling. However, the mechanism of Wnt/ß-catenin pathway activation in renal interstitial fibroblasts during AKI is unclear. S100 calcium-binding protein A16 (S100A16), a new member of calcium-binding protein S100 family, is a multi-functional signaling factor involved in various pathogenies, including tumors, glycolipid metabolism disorder, and chronic kidney disease (CKD). We investigated the potential participation of S100A16 in Wnt/ß-catenin pathway activation during AKI by subjecting wild-type (WT) and S100A16 knockout (S100A16+/-) mice to the ischemia-reperfusion injury (IRI), and revealed S100A16 upregulation in this model, in which knockout of S100A16 impeded the Wnt/ß-catenin signaling pathway activation and recovered the expression of downstream hepatocyte growth factor (HGF). We also found that S100A16 was highly expressed in Platelet-derived growth factor receptor beta (PDGFRß) positive renal fibroblasts in vivo. Consistently, in rat renal interstitial fibroblasts (NRK-49F cells), both hypoxia/reoxygenation and S100A16 overexpression exacerbated fibroblasts apoptosis and inhibited HGF secretion; whereas S100A16 knockdown or Wnt/ß-catenin pathway inhibitor ICG-001 reversed these changes. Mechanistically, we showed that S100A16 promoted Wnt/ß-catenin signaling activation via the ubiquitylation and degradation of ß-catenin complex members, glycogen synthase kinase 3ß (GSK3ß) and casein kinase 1α (CK1α), mediated by E3 ubiquitin ligase, the HMG-CoA reductase degradation protein 1 (HRD1). Our study identified the S100A16 as a key regulator in the activation of Wnt/ß-catenin signaling pathway in AKI.

Sequential Phosphorylation of Hepatitis C Virus NS5A Protein Requires the ATP-Binding Domain of NS3 Helicase.

The propagation of the hepatitis C virus (HCV) is regulated in part by the phosphorylation of its nonstructural protein NS5A that undergoes sequential phosphorylation on several highly conserved serine residues and switches from a hypo- to a hyperphosphorylated state. Previous studies have shown that NS5A sequential phosphorylation requires NS3 encoded on the same NS3-NS4A-NS4B-NS5A polyprotein. Subtle mutations in NS3 without affecting its protease activity could affect NS5A phosphorylation. Given the ATPase domain in the NS3 COOH terminus, we tested whether NS3 participates in NS5A phosphorylation similarly to the nucleoside diphosphate kinase-like activity of the rotavirus NSP2 nucleoside triphosphatase (NTPase). Mutations in the NS3 ATP-binding motifs blunted NS5A hyperphosphorylation and phosphorylation at serines 225, 232, and 235, whereas a mutation in the RNA-binding domain did not. The phosphorylation events were not rescued with wild-type NS3 provided in trans. When provided with an NS3 ATPase-compatible ATP analog, N6-benzyl-ATP-γ-S, thiophosphorylated NS5A was detected in the cells expressing the wild-type NS3-NS5B polyprotein. The thiophosphorylation level was lower in the cells expressing NS3-NS5B with a mutation in the NS3 ATP-binding domain. In vitro assays with a synthetic peptide and purified wild-type NS3 followed by dot blotting and mass spectrometry found weak NS5A phosphorylation at serines 222 and 225 that was sensitive to an inhibitor of casein kinase Iα but not helicase. When casein kinase Iα was included in the assay, much stronger phosphorylation was observed at serines 225, 232, and 235. We concluded that NS5A sequential phosphorylation requires the ATP-binding domain of the NS3 helicase and that casein kinase Iα is a potent NS5A kinase. IMPORTANCE For more than 20 years, NS3 was known to participate in NS5A sequential phosphorylation. In the present study, we show for the first time that the ATP-binding domain of NS3 is involved in NS5A phosphorylation. In vitro assays showed that casein kinase Iα is a very potent kinase responsible for NS5A phosphorylation at serines 225, 232, and 235. Our data suggest that ATP binding by NS3 probably results in conformational changes that recruit casein kinase Iα to phosphorylate NS5A, initially at S225 and subsequently at S232 and S235. Our discovery reveals intricate requirements of the structural integrity of NS3 for NS5A hyperphosphorylation and HCV replication.

Calcium-oxidative stress signaling axis and casein kinase 1α mediate eryptosis and hemolysis elicited by novel p53 agonist inauhzin.

Inauhzin (INZ) is a novel p53 agonist with antitumor activity. Anemia is a common side effect of chemotherapy and may arise from red blood cell (RBC) hemolysis or eryptosis. In this study, we investigate the mechanisms of INZ toxicity in human RBCs. RBCs were isolated from healthy donors and treated with antitumor concentrations of INZ (5-500 µM) for 24 h at 37 °C. Hemoglobin was photometrically measured, and cells were stained with Annexin-V-FITC for phosphatidylserine (PS), Fluo4/AM for calcium, and 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) for oxidative stress. INZ caused significant dose-responsive, calcium-dependent hemolysis starting at 40 µM. Furthermore, INZ significantly increased Annexin-positive cells and Fluo4 and DCF fluorescence. The cytotoxicity of INZ was also significantly mitigated in presence of D4476. INZ possesses hemolytic and eryptotic potential characterized by cell membrane scrambling, intracellular calcium overload, cell shrinkage, and oxidative stress secondary to calcium influx from the extracellular space.

CK1α protects WAVE from degradation to regulate cell shape and motility in the immune response.

The WAVE regulatory complex (WRC) is the main activator of the Arp2/3 complex, promoting lamellipodial protrusions in migrating cells. The WRC is basally inactive but can be activated by Rac1 and phospholipids, and through phosphorylation. However, the in vivo relevance of the phosphorylation of WAVE proteins remains largely unknown. Here, we identified casein kinase I alpha (CK1α) as a regulator of WAVE, thereby controlling cell shape and cell motility in Drosophila macrophages. CK1α binds and phosphorylates WAVE in vitro. Phosphorylation of WAVE by CK1α appears not to be required for activation but, rather, regulates its stability. Pharmacologic inhibition of CK1α promotes ubiquitin-dependent degradation of WAVE. Consistently, loss of Ck1α but not ck2 function phenocopies the depletion of WAVE. Phosphorylation-deficient mutations in the CK1α consensus sequences within the VCA domain of WAVE can neither rescue mutant lethality nor lamellipodium defects. By contrast, phosphomimetic mutations rescue all cellular and developmental defects. Finally, RNAi-mediated suppression of 26S proteasome or E3 ligase complexes substantially rescues lamellipodia defects in CK1α-depleted macrophages. Therefore, we conclude that basal phosphorylation of WAVE by CK1α protects it from premature ubiquitin-dependent degradation, thus promoting WAVE function in vivo. This article has an associated First Person interview with the first author of the paper.

The E3 ubiquitin ligase component, Cereblon, is an evolutionarily conserved regulator of Wnt signaling.

Immunomodulatory drugs (IMiDs) are important for the treatment of multiple myeloma and myelodysplastic syndrome. Binding of IMiDs to Cereblon (CRBN), the substrate receptor of the CRL4CRBN E3 ubiquitin ligase, induces cancer cell death by targeting key neo-substrates for degradation. Despite this clinical significance, the physiological regulation of CRBN remains largely unknown. Herein we demonstrate that Wnt, the extracellular ligand of an essential signal transduction pathway, promotes the CRBN-dependent degradation of a subset of proteins. These substrates include Casein kinase 1α (CK1α), a negative regulator of Wnt signaling that functions as a key component of the ß-Catenin destruction complex. Wnt stimulation induces the interaction of CRBN with CK1α and its resultant ubiquitination, and in contrast with previous reports does so in the absence of an IMiD. Mechanistically, the destruction complex is critical in maintaining CK1α stability in the absence of Wnt, and in recruiting CRBN to target CK1α for degradation in response to Wnt. CRBN is required for physiological Wnt signaling, as modulation of CRBN in zebrafish and Drosophila yields Wnt-driven phenotypes. These studies demonstrate an IMiD-independent, Wnt-driven mechanism of CRBN regulation and provide a means of controlling Wnt pathway activity by CRBN, with relevance for development and disease.

Csnk1a1 inhibition modulates the inflammatory secretome and enhances response to radiotherapy in glioma.

Glioblastoma multiforme (GBM), a fatal brain tumour with no available targeted therapies, has a poor prognosis. At present, radiotherapy is one of the main methods to treat glioma, but it leads to an obvious increase in inflammatory factors in the tumour microenvironment, especially IL-6 and CXCL1, which plays a role in tumour to resistance radiotherapy and tumorigenesis. Casein kinase 1 alpha 1 (CK1α) (encoded on chromosome 5q by Csnk1a1) is considered an attractive target for Tp53 wild-type acute myeloid leukaemia (AML) treatment. In this study, we evaluated the anti-tumour effect of Csnk1a1 suppression in GBM cells in vitro and in vivo. We found that down-regulation of Csnk1a1 or inhibition by D4476, a Csnk1a1 inhibitor, reduced GBM cell proliferation efficiently in both Tp53 wild-type and Tp53-mutant GBM cells. On the contrary, overexpression of Csnk1a1 promoted cell proliferation and colony formation. Csnk1a1 inhibition improved the sensitivity to radiotherapy. Furthermore, down-regulation of Csnk1a1 reduced the production and secretion of pro-inflammatory factors. In the preclinical GBM model, treatment with D4476 significantly inhibited the increase in pro-inflammatory factors caused by radiotherapy and improved radiotherapy sensitivity, thus inhibiting tumour growth and prolonging animal survival time. These results suggest targeting Csnk1a1 exert an anti-tumour role as an inhibitor of inflammatory factors, providing a new strategy for the treatment of glioma.

Reversible modulation of circadian time with chronophotopharmacology.

The circadian clock controls daily rhythms of physiological processes. The presence of the clock mechanism throughout the body is hampering its local regulation by small molecules. A photoresponsive clock modulator would enable precise and reversible regulation of circadian rhythms using light as a bio-orthogonal external stimulus. Here we show, through judicious molecular design and state-of-the-art photopharmacological tools, the development of a visible light-responsive inhibitor of casein kinase I (CKI) that controls the period and phase of cellular and tissue circadian rhythms in a reversible manner. The dark isomer of photoswitchable inhibitor 9 exhibits almost identical affinity towards the CKIα and CKIδ isoforms, while upon irradiation it becomes more selective towards CKIδ, revealing the higher importance of CKIδ in the period regulation. Our studies enable long-term regulation of CKI activity in cells for multiple days and show the reversible modulation of circadian rhythms with a several hour period and phase change through chronophotopharmacology.

Targeting Protein Kinases in Blood Cancer: Focusing on CK1α and CK2.

Disturbance of protein kinase activity may result in dramatic consequences that often lead to cancer development and progression. In tumors of blood origin, both tyrosine kinases and serine/threonine kinases are altered by different types of mutations, critically regulating cancer hallmarks. CK1α and CK2 are highly conserved, ubiquitously expressed and constitutively active pleiotropic kinases, which participate in multiple biological processes. The involvement of these kinases in solid and blood cancers is well documented. CK1α and CK2 are overactive in multiple myeloma, leukemias and lymphomas. Intriguingly, they are not required to the same degree for the viability of normal cells, corroborating the idea of "druggable" kinases. Different to other kinases, mutations on the gene encoding CK1α and CK2 are rare or not reported. Actually, these two kinases are outside the paradigm of oncogene addiction, since cancer cells' dependency on these proteins resembles the phenomenon of "non-oncogene" addiction. In this review, we will summarize the general features of CK1α and CK2 and the most relevant oncogenic and stress-related signaling nodes, regulated by kinase phosphorylation, that may lead to tumor progression. Finally, we will report the current data, which support the positioning of these two kinases in the therapeutic scene of hematological cancers.

FAM83F regulates canonical Wnt signalling through an interaction with CK1α.

The function of the FAM83F protein, like the functions of many members of the FAM83 family, is poorly understood. Here, we show that injection of Fam83f mRNA into Xenopus embryos causes axis duplication, a phenotype indicative of enhanced Wnt signalling. Consistent with this, overexpression of FAM83F activates Wnt signalling, whereas ablation of FAM83F from human colorectal cancer (CRC) cells attenuates it. We demonstrate that FAM83F is farnesylated and interacts and co-localises with CK1α at the plasma membrane. This interaction with CK1α is essential for FAM83F to activate Wnt signalling, and FAM83F mutants that do not interact with CK1α fail to induce axis duplication in Xenopus embryos and to activate Wnt signalling in cells. FAM83F acts upstream of GSK-3ß because the attenuation of Wnt signalling caused by loss of FAM83F can be rescued by GSK-3 inhibition. Introduction of a farnesyl-deficient mutant of FAM83F in cells through CRISPR/Cas9 genome editing redirects the FAM83F-CK1α complex away from the plasma membrane and significantly attenuates Wnt signalling, indicating that FAM83F exerts its effects on Wnt signalling at the plasma membrane.