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Ampofo E, Pack M, Wrublewsky S, Boewe AS, Spigelman AF, Koch H, MacDonald PE, Laschke MW, Montenarh M, Götz C. CK2 activity is crucial for proper glucagon expression. Diabetologia 2024; 67:1368-1385. [PMID: 38503901 PMCID: PMC11153270 DOI: 10.1007/s00125-024-06128-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 02/07/2024] [Indexed: 03/21/2024]
Abstract
AIMS/HYPOTHESIS Protein kinase CK2 acts as a negative regulator of insulin expression in pancreatic beta cells. This action is mainly mediated by phosphorylation of the transcription factor pancreatic and duodenal homeobox protein 1 (PDX1). In pancreatic alpha cells, PDX1 acts in a reciprocal fashion on glucagon (GCG) expression. Therefore, we hypothesised that CK2 might positively regulate GCG expression in pancreatic alpha cells. METHODS We suppressed CK2 kinase activity in αTC1 cells by two pharmacological inhibitors and by the CRISPR/Cas9 technique. Subsequently, we analysed GCG expression and secretion by real-time quantitative RT-PCR, western blot, luciferase assay, ELISA and DNA pull-down assays. We additionally studied paracrine effects on GCG secretion in pseudoislets, isolated murine islets and human islets. In vivo, we examined the effect of CK2 inhibition on blood glucose levels by systemic and alpha cell-specific CK2 inhibition. RESULTS We found that CK2 downregulation reduces GCG secretion in the murine alpha cell line αTC1 (e.g. from 1094±124 ng/l to 459±110 ng/l) by the use of the CK2-inhibitor SGC-CK2-1. This was due to a marked decrease in Gcg gene expression through alteration of the binding of paired box protein 6 (PAX6) and transcription factor MafB to the Gcg promoter. The analysis of the underlying mechanisms revealed that both transcription factors are displaced by PDX1. Ex vivo experiments in isolated murine islets and pseudoislets further demonstrated that CK2-mediated reduction in GCG secretion was only slightly affected by the higher insulin secretion after CK2 inhibition. The kidney capsule transplantation model showed the significance of CK2 for GCG expression and secretion in vivo. Finally, CK2 downregulation also reduced the GCG secretion in islets isolated from humans. CONCLUSIONS/INTERPRETATION These novel findings not only indicate an important function of protein kinase CK2 for proper GCG expression but also demonstrate that CK2 may be a promising target for the development of novel glucose-lowering drugs.
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Affiliation(s)
- Emmanuel Ampofo
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Mandy Pack
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Selina Wrublewsky
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Anne S Boewe
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Aliya F Spigelman
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Hanna Koch
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Patrick E MacDonald
- Department of Pharmacology and Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Matthias W Laschke
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Mathias Montenarh
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Claudia Götz
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany.
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Ning Y, Wang C, Liu X, Du Y, Liu S, Liu K, Zhou J, Zhou C. CK2-mediated CCDC106 phosphorylation is required for p53 degradation in cancer progression. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2019; 38:131. [PMID: 30885251 PMCID: PMC6423756 DOI: 10.1186/s13046-019-1137-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/13/2019] [Indexed: 12/14/2022]
Abstract
BACKGROUND Dysfunction of p53 is a key cause of cancer development, while CCDC106 can reduce p53 stability and is associated with lung cancer. However, the roles of CCDC106 in other cancer types and its upstream regulators have not been investigated. METHODS The phosphorylation status was investigated by in vitro kinase assay and Western blotting using phosphorylation-specific antibodies. Co-immunoprecipitation assay and GST-pulldown were used to detect protein interaction. Cell viability, apoptosis, colony formation, wound-healing and invasion assays were measured for in vitro functional analyses. The in vivo effect of CCDC106 on tumor growth was investigated using a subcutaneous xenograft tumor mouse model. RESULTS We demonstrated that CCDC106 knockdown enhanced apoptosis by stabilizing p53 and suppressed cell viability, colony formation, migration and invasion in cervical cancer HeLa and breast cancer MCF7 cells with wild-type p53 (wtp53), whereas CCDC106 overexpression exerted the opposite effects in normal breast epithelial HBL100 and cervical cancer SiHa cells with wtp53. However, CCDC106 had no similar effects on p53-mutant cervical and breast cancer cells (C33A and MDA-MB-231). Further study showed that CK2 interacts with CCDC106 through its regulatory β subunit and then phosphorylates CCDC106 at Ser-130 and Ser-147. The phosphorylation of CCDC106 at Ser-130 and Ser-147 is required for its interaction with p53 and nuclear localization, respectively. Inhibiting CCDC106 phosphorylation by substituting both Ser-130 and Ser-147 with alanine or treating cells with the CK2 inhibitor CX-4945 abrogated CCDC106-induced p53 degradation and its oncogenic function in cells with wtp53. Wildtype CCDC106, but not Ser-130/- 147 mutant CCDC106, enhanced tumor growth and p53 degradation in a xenograft mouse model. Moreover, suppression of CCDC106 increased CX-4945 sensitivity of cancer cells with wtp53. CONCLUSION This study revealed a CK2/CCDC106/p53 signaling axis in the progression of breast and cervical cancers, which may provide a new therapeutic target for cancer treatment.
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Affiliation(s)
- Yichong Ning
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China
| | - Chunqing Wang
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Present address: Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, 87131, USA
| | - Xin Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Present address: Reproductive & Genetic Hospital CITIC-XIANGYA, Human, Changsha, 410008, China
| | - Yan Du
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China
| | - Shunlian Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China
| | - Kaili Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China
| | - Jianlin Zhou
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China. .,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.
| | - Chang Zhou
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China. .,Key Laboratory of Protein Chemistry and Developmental Biology of the Ministry of Education, College of Life Science, Hunan Normal University, Changsha, 410081, Hunan, China.
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Lupp S, Götz C, Khadouma S, Horbach T, Dimova EY, Bohrer AM, Kietzmann T, Montenarh M. The upstream stimulatory factor USF1 is regulated by protein kinase CK2 phosphorylation. Cell Signal 2014; 26:2809-17. [PMID: 25194820 DOI: 10.1016/j.cellsig.2014.08.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 08/29/2014] [Indexed: 11/17/2022]
Abstract
The upstream stimulatory factors 1 (USF1) and 2 (USF2) are transcription factors which bind to E-box motifs of various promoters regulating a variety of different cellular processes. Only little is known about the regulation of USFs. Here, we identified protein kinase CK2 as an enzyme that phosphorylates USF1 but not USF2. Using deletion mutants and point mutants we were able to identify threonine 100 as the major phosphorylation site for CK2. It is well known that USF1 and USF2 form hetero-dimers. Binding studies revealed that the inhibition of CK2 kinase activity by a specific inhibitor enhanced binding of USF1 to USF2. Furthermore, transactivation studies showed that the inhibition of CK2 phosphorylation of USF1 stimulated transcription from the glucokinase promoter as well as the fatty acid synthetase promoter but not from the heme oxygenase-1 promoter. Thus, we have shown for the first time that CK2 phosphorylation of USF1 modulates two functionally important properties of USF1, namely hetero-dimerization and transactivation.
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Affiliation(s)
- Sarah Lupp
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Claudia Götz
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany.
| | - Sunia Khadouma
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Tina Horbach
- Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Elitsa Y Dimova
- Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Anna-Maria Bohrer
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Thomas Kietzmann
- Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Mathias Montenarh
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
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Ren P, Sheng Z, Wang Y, Yi X, Zhou Q, Zhou J, Xiang S, Hu X, Zhang J. RNF20 promotes the polyubiquitination and proteasome-dependent degradation of AP-2α protein. Acta Biochim Biophys Sin (Shanghai) 2014; 46:136-40. [PMID: 24374663 DOI: 10.1093/abbs/gmt136] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Transcription factor activator protein 2α (AP-2α) is a negative regulator of adipogenesis by repressing the transcription of CCAAT/enhancer binding protein (C/EBPα) gene. During adipogenesis, AP-2α is degraded, leading to transcriptional up-regulation of C/EBPα. However, the mechanism for AP-2α degradation is not clear. Here, using immunoprecipitation assay and mass spectrometry, we identified ring finger protein 20 (RNF20) as an AP-2α-interacting protein in 3T3-L1 preadipocytes. RNF20 has been proved to be an E3 ubiquitin ligase for both histone H2B and tumor suppressor ErbB3-binding protein 1 (Ebp1). In this study, we demonstrated that RNF20 co-localized and interacted with AP-2α, and promoted its polyubiquitination and proteasome-dependent degradation. Over-expression of RNF20 inhibited the activity of AP-2α and rescued the C/EBPα expression which was inhibited by AP-2α. These results suggested that RNF20 may play roles in adipocyte differentiation by stimulating ubiquitin-proteasome-dependent degradation of AP-2α.
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Affiliation(s)
- Peng Ren
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Science, Hunan Normal University, Changsha 410081, China
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