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Meléndez RA, Wynn DT, Merugu SB, Singh P, Kaplan KP, Robbins DJ. Exploring the role of casein kinase 1α splice variants across cancer cell lines. Biochem Biophys Res Commun 2024; 723:150189. [PMID: 38852281 DOI: 10.1016/j.bbrc.2024.150189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 05/20/2024] [Accepted: 05/28/2024] [Indexed: 06/11/2024]
Abstract
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.
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Affiliation(s)
- Ricardo A Meléndez
- Department of Biochemistry and Molecular Biology University of Miami Miller School of Medicine Miami FL, USA; Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA
| | - Daniel T Wynn
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA
| | - Siva Bharath Merugu
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA
| | - Prerna Singh
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA
| | - Kenton P Kaplan
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA
| | - David J Robbins
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C, USA.
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2
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Begum M, Paul P, Das D, Chakraborty K, Bhattacharjee A, Ghosh S. Genes regulating development and behavior exhibited altered expression in Drosophila melanogaster exposed to bisphenol A: use of real-time quantitative PCR (qRT-PCR) and droplet digital PCR (ddPCR) in genotoxicity study. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:7090-7104. [PMID: 33025430 DOI: 10.1007/s11356-020-10805-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
Toxicity of bisphenol A on morphological and life-history traits of model insect Drosophila melanogaster was reported in our previous work. In the present study, we have analyzed the adversity of bisphenol A on the reproductive behavior of adult and on the expression of selected genes in the larva and adult stage of fruit fly exposed to bisphenol A (0.007 g/2 ml. or 3.5 mg/ml), in addition to determination of LC50 value of bisphenol A in larva and pupal stage. We employed both the quantitative reverse transcriptase PCR and droplet digital PCR for analyzing the expression profile of seven genes namely, decapentaplegic, vestigial, wingless, foraging, insulin-like receptor, doublesex, and fruitless. We found bisphenol A has more adverse effects on male sexual behavior than females. Moreover, we observed significant downregulation of all the selected genes in treated larvae except, fruitless in male where it showed significant upregulation. On contrary among the treated adult flies, significant downregulation of all target genes in both sexes is evident, except, doublesex and fruitless in males which showed significant upregulation. We did not observe any deviation of male: female sex ratio from 1:1 under bisphenol A exposure. All these results suggest bisphenol A adversely affects the optimum functioning of genes which are involved in the regulation of metabolic pathways, behavioral pattern, stress response, endocrine homeostasis, neural functioning, and the development of the specific organ in Drosophila melanogaster. Our result not only provides a foundation to study further the bisphenol A toxicity on different pivotal genes in Drosophila but also suggests the use of the droplet digital PCR technology in toxicity measurement at the molecular level in eukaryotic model systems.
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Affiliation(s)
- Morium Begum
- Department of Zoology, Cytogenetics & Genomics Research Unit, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), 35, Ballygunge Circular Road.Kolkata, West Bengal, 700019, India
| | - Pallab Paul
- Department of Zoology, Cytogenetics & Genomics Research Unit, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), 35, Ballygunge Circular Road.Kolkata, West Bengal, 700019, India
| | - Debasmita Das
- Department of Zoology, Cytogenetics & Genomics Research Unit, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), 35, Ballygunge Circular Road.Kolkata, West Bengal, 700019, India
| | - Kaustav Chakraborty
- Amity Institute of Biotechnology, Amity-University Kolkata, Plot no 36, 37, and 38, Major Arterial Road (South-East), Action Area II, Newtown, Kolkata, West Bengal, 700135, India
| | - Ashima Bhattacharjee
- Amity Institute of Biotechnology, Amity-University Kolkata, Plot no 36, 37, and 38, Major Arterial Road (South-East), Action Area II, Newtown, Kolkata, West Bengal, 700135, India
| | - Sujay Ghosh
- Department of Zoology, Cytogenetics & Genomics Research Unit, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), 35, Ballygunge Circular Road.Kolkata, West Bengal, 700019, India.
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Sinha A, Fan VB, Ramakrishnan AB, Engelhardt N, Kennell J, Cadigan KM. Repression of Wnt/β-catenin signaling by SOX9 and Mastermind-like transcriptional coactivator 2. SCIENCE ADVANCES 2021; 7:7/8/eabe0849. [PMID: 33597243 PMCID: PMC7888933 DOI: 10.1126/sciadv.abe0849] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 01/05/2021] [Indexed: 05/06/2023]
Abstract
Wnt/β-catenin signaling requires inhibition of a multiprotein destruction complex that targets β-catenin for proteasomal degradation. SOX9 is a potent antagonist of the Wnt pathway and has been proposed to act through direct binding to β-catenin or the β-catenin destruction complex. Here, we demonstrate that SOX9 promotes turnover of β-catenin in mammalian cell culture, but this occurs independently of the destruction complex and the proteasome. This activity requires SOX9's ability to activate transcription. Transcriptome analysis revealed that SOX9 induces the expression of the Notch coactivator Mastermind-like transcriptional activator 2 (MAML2), which is required for SOX9-dependent Wnt/β-catenin antagonism. MAML2 promotes β-catenin turnover independently of Notch signaling, and MAML2 appears to associate directly with β-catenin in an in vitro binding assay. This work defines a previously unidentified pathway that promotes β-catenin degradation, acting in parallel to established mechanisms. SOX9 uses this pathway to restrict Wnt/β-catenin signaling.
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Affiliation(s)
- Abhishek Sinha
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA
| | - Vinson B Fan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA
| | - Aravinda-Bharathi Ramakrishnan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA
| | - Nicole Engelhardt
- Department of Biology, Vassar College, 124 Raymond Ave, Poughkeepsie, NY 12604, USA
| | - Jennifer Kennell
- Department of Biology, Vassar College, 124 Raymond Ave, Poughkeepsie, NY 12604, USA
| | - Ken M Cadigan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Biological Sciences Building, 1105 North University Avenue, Ann Arbor, MI 48109, USA.
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Lu Z, Chang L, Zhou H, Liu X, Li Y, Mi T, Tong D. Arctigenin Attenuates Tumor Metastasis Through Inhibiting Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma via Suppressing GSK3β-Dependent Wnt/β-Catenin Signaling Pathway In Vivo and In Vitro. Front Pharmacol 2019; 10:937. [PMID: 31555129 PMCID: PMC6726742 DOI: 10.3389/fphar.2019.00937] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 07/22/2019] [Indexed: 12/22/2022] Open
Abstract
Arctigenin (ARG) has been reported to be a bioactive lignan from Arctium lappa exerting various activities including anti-cancer and immune-regulation. The present study aimed to investigate the anti-metastasis activity and mechanism of ARG against hepatocellular carcinoma in vitro and in vivo. The results showed that ARG exhibited a significant cytotoxicity on Hep G2 and SMMC 7721 cells (but not on normal liver cells LO2). In addition, the migration and invasion of Hep G2 and SMMC 7721 cells were also remarkably repressed. Furthermore, ARG attenuated Wnt/β-catenin signaling activation, resulting in the down-regulation of β-catenin target genes including c-Myc, cyclin D1, MMP-9, and ZO-1. Noticeably, ARG attenuated the activation of Wnt/β-catenin through a GSK3β-dependent pathway. Besides, we also found that ARG potentially inhibited epithelial-mesenchymal transition by up-regulating the epithelial and down-regulating the mesenchymal marker proteins. In vivo, intraperitoneal injection of ARG not only significantly inhibited the growth of subcutaneous transplanted tumor but also dramatically alleviated the tumor metastasis in liver. Our data demonstrated that ARG exerted anti-epithelial-mesenchymal transition and anti-metastasis activities against hepatocellular carcinoma, which might make it a candidate as a preventive agent for cancer metastasis.
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Affiliation(s)
- Zheng Lu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Lingling Chang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Hongbo Zhou
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Xiaoqiang Liu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Yinqian Li
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Tiejun Mi
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Dewen Tong
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
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In vitro and in vivo anti-tumor activity of CoQ0 against melanoma cells: inhibition of metastasis and induction of cell-cycle arrest and apoptosis through modulation of Wnt/β-catenin signaling pathways. Oncotarget 2017; 7:22409-26. [PMID: 26968952 PMCID: PMC5008369 DOI: 10.18632/oncotarget.7983] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/23/2016] [Indexed: 12/13/2022] Open
Abstract
Coenzyme Q0 (CoQ0, 2,3-dimethoxy-5-methyl-1,4-benzoquinone), a novel quinone derivative, has been shown to modulate cellular redox balance. However, effect of this compound on melanoma remains unclear. This study examined the in vitro or in vivo anti-tumor, apoptosis, and anti-metastasis activities of CoQ0 (0-20 μM) through inhibition of Wnt/β-catenin signaling pathway. CoQ0 exhibits a significant cytotoxic effect on melanoma cell lines (B16F10, B16F1, and A2058), while causing little toxicity toward normal (HaCaT) cells. The suppression of β-catenin was seen with CoQ0 administration accompanied by a decrease in the expression of Wnt/β-catenin transcriptional target c-myc, cyclin D1, and survivin through GSK3β-independent pathway. We found that CoQ0 treatment caused G1 cell-cycle arrest by reducing the levels of cyclin E and CDK4. Furthermore, CoQ0 treatment induced apoptosis through caspase-9/-3 activation, PARP degradation, Bcl-2/Bax dysregulation, and p53 expression. Notably, non- or sub-cytotoxic concentrations of CoQ0 markedly inhibited migration and invasion, accompanied by the down-regulation of MMP-2 and -9, and up-regulation of TIMP-1 and -2 expressions in highly metastatic B16F10 cells. Furthermore, the in vivo study results revealed that CoQ0 treatment inhibited the tumor growth in B16F10 xenografted nude mice. Histological analysis and western blotting confirmed that CoQ0 significantly decreased the xenografted tumor progression as demonstrated by induction of apoptosis, suppression of β-catenin, and inhibition of cell cycle-, apoptotic-, and metastatic-regulatory proteins. The data suggest that CoQ0 unveils a novel mechanism by down-regulating Wnt/β-catenin pathways and could be used as a potential lead compound for melanoma chemotherapy.
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Hseu YC, Chao YH, Lin KY, Way TD, Lin HY, Thiyagarajan V, Yang HL. Antrodia camphorata inhibits metastasis and epithelial-to-mesenchymal transition via the modulation of claudin-1 and Wnt/β-catenin signaling pathways in human colon cancer cells. JOURNAL OF ETHNOPHARMACOLOGY 2017; 208:72-83. [PMID: 28688953 DOI: 10.1016/j.jep.2017.07.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Revised: 06/19/2017] [Accepted: 07/02/2017] [Indexed: 06/07/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Antrodia camphorata (AC) is a well known traditional Chinese medicinal mushroom in Taiwan, has been used to treat various diseases including cancer. MATERIALS AND METHODS In this study, we investigated the anti-metastatic and anti-EMT properties of a fermented culture broth of AC in human colon SW480claudin-1- and metastatic SW620claudin-1+ cancer cells in vitro. RESULTS AC down-regulates claudin-1 and inhibits the proliferation and colony-formation abilities of both SW620claudin-1+ and SW480claudin-1- cells. In highly metastatic SW620claudin-1+ cells, non-cytotoxic concentrations of AC significantly inhibited migration/invasion, accompanied by the down-regulation of MMP-2 and MMP-9 proteins. AC decreased nuclear translocation of Wnt/β-catenin through a GSK3β-dependent pathway. AC consistently inhibited EMT by up-regulating the epithelial and downregulating the mesenchymal marker proteins. In SW480claudin-1- cells, AC suppressed migration/invasion potentially through the inhibition of the PI3K/AKT/NFκB signaling pathways without altering the expression levels of β-catenin and GSK3β proteins. CONCLUSION Altogether, this study demonstrates the anti-metastatic and anti-EMT activities of AC, which may contribute to the development of a chemopreventive agent for colon cancer.
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Affiliation(s)
- You-Cheng Hseu
- Department of Cosmeceutics, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung 40402, Taiwan; Department of Health and Nutrition Biotechnology, Asia University, Taichung 41354, Taiwan
| | - Yu-Hsien Chao
- Institute of Nutrition, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung 40402, Taiwan
| | - Kai-Yuan Lin
- Department of Medical Research, Chi-Mei Medical Center, Tainan 710, Taiwan
| | - Tzong-Der Way
- Department of Life Sciences, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung 40402, Taiwan
| | - Hui-Yi Lin
- School of Pharmacy, College of Pharmacy, China Medical University, Taichung 40402, Taiwan
| | - Varadharajan Thiyagarajan
- Department of Cosmeceutics, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung 40402, Taiwan.
| | - Hsin-Ling Yang
- Institute of Nutrition, College of Biopharmaceutical and Food Sciences, China Medical University, Taichung 40402, Taiwan.
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Abstract
WNK (With-No-Lysine (K)) kinases are serine-threonine kinases characterized by an atypical placement of a catalytic lysine within the kinase domain. Mutations in human WNK1 or WNK4 cause an autosomal dominant syndrome of hypertension and hyperkalemia, reflecting the fact that WNK kinases are critical regulators of renal ion transport processes. Here, the role of WNKs in the regulation of ion transport processes in vertebrate and invertebrate renal function, cellular and organismal osmoregulation, and cell migration and cerebral edema will be reviewed, along with emerging literature demonstrating roles for WNKs in cardiovascular and neural development, Wnt signaling, and cancer. Conserved roles for these kinases across phyla are emphasized.
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Affiliation(s)
| | - Andreas Jenny
- Albert Einstein College of Medicine, New York, NY, United States.
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8
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Oncogenic KIT mutations in different exons lead to specific changes in melanocyte phospho-proteome. J Proteomics 2016; 144:140-7. [PMID: 27216642 DOI: 10.1016/j.jprot.2016.05.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Revised: 04/27/2016] [Accepted: 05/18/2016] [Indexed: 01/15/2023]
Abstract
UNLABELLED Mutations in the proto-oncogene c-KIT (KIT) are found in several cancers, and the site of these mutations differs markedly between cancer types. We used site directed mutagenesis to induce KIT(559), KIT(642) and KIT(816) mutations in primary human melanocytes (PHM) and we investigated the impact of each mutation on KIT function. We studied canonical KIT-signaling pathways by immunoblotting, and we used stable isotope labeling by amino acids in cell culture (SILAC) and kinase prediction models to identify kinases differently activated in respective mutants. We validated our results with the analysis of phosphorylation levels of selected substrates for each kinase. We concluded that CK1 ε and δ are more active in cell clones harboring KIT(559) and KIT(642) mutations, whereas PAK4 is more active in clones with KIT(816) mutation. Our findings might help to develop further therapeutic options for tumors with specific KIT mutations in different domains. BIOLOGICAL SIGNIFICANCE Different types of cancers harbor mutations in the oncogene KIT. The use of small molecules inhibitors directly targeting KIT had a limited success in the treatment of patients with KIT mutant cancers. Our study describes specific phospho-proteome changes due to different KIT mutations, and provides targets of further therapeutic options.
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Otto GP, Sharma D, Williams RS. Non-Catalytic Roles of Presenilin Throughout Evolution. J Alzheimers Dis 2016; 52:1177-87. [PMID: 27079701 PMCID: PMC4927835 DOI: 10.3233/jad-150940] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2016] [Indexed: 12/20/2022]
Abstract
Research into Alzheimer's disease pathology and treatment has often focused on presenilin proteins. These proteins provide the key catalytic activity of the γ-secretase complex in the cleavage of amyloid-β precursor protein and resultant amyloid tangle deposition. Over the last 25 years, screening novel drugs to control this aberrant proteolytic activity has yet to identify effective treatments for the disease. In the search for other mechanisms of presenilin pathology, several studies have demonstrated that mammalian presenilin proteins also act in a non-proteolytic role as a scaffold to co-localize key signaling proteins. This role is likely to represent an ancestral presenilin function, as it has been described in genetically distant species including non-mammalian animals, plants, and a simple eukaryotic amoeba Dictyostelium that diverged from the human lineage over a billion years ago. Here, we review the non-catalytic scaffold role of presenilin, from mammalian models to other biomedical models, and include recent insights using Dictyostelium, to suggest that this role may provide an early evolutionary function of presenilin proteins.
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Affiliation(s)
- Grant P. Otto
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Devdutt Sharma
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Robin S.B. Williams
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, UK
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Cruciat CM. Casein kinase 1 and Wnt/β-catenin signaling. Curr Opin Cell Biol 2014; 31:46-55. [PMID: 25200911 DOI: 10.1016/j.ceb.2014.08.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 08/21/2014] [Indexed: 12/12/2022]
Abstract
Casein kinase 1 (CK1) members play a critical and evolutionary conserved role in Wnt/β-catenin signaling. They phosphorylate several pathway components and exert a dual function, acting as both Wnt activators and Wnt inhibitors. Recent discoveries suggest that CK1 members act in a coordinated manner to regulate early responses to Wnt and notably that their enzymatic activity is regulated. Here, I provide a brief update of CK1 function and regulation in Wnt/β-catenin signaling.
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Affiliation(s)
- Cristina-Maria Cruciat
- Division of Molecular Embryology, DKFZ-ZMBH Alliance, DKFZ, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
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11
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Wnk kinases are positive regulators of canonical Wnt/β-catenin signalling. EMBO Rep 2013; 14:718-25. [PMID: 23797875 DOI: 10.1038/embor.2013.88] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 05/29/2013] [Accepted: 05/31/2013] [Indexed: 11/08/2022] Open
Abstract
Wnt/β-catenin signalling is central to development and its regulation is essential in preventing cancer. Using phosphorylation of Dishevelled as readout of pathway activation, we identified Drosophila Wnk kinase as a new regulator of canonical Wnt/β-catenin signalling. WNK kinases are known for regulating ion co-transporters associated with hypertension disorders. We demonstrate that wnk loss-of-function phenotypes resemble canonical Wnt pathway mutants, while Wnk overexpression causes gain-of-function canonical Wnt-signalling phenotypes. Importantly, knockdown of human WNK1 and WNK2 also results in decreased Wnt signalling in mammalian cell culture, suggesting that Wnk kinases have a conserved function in ensuring peak levels of canonical Wnt signalling.
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Abstract
The Wnt/β-catenin pathway is highly regulated to insure the correct temporal and spatial activation of its target genes. In the absence of a Wnt stimulus, the transcriptional coactivator β-catenin is degraded by a multiprotein "destruction complex" that includes the tumor suppressors Axin and adenomatous polyposis coli (APC), the Ser/Thr kinases GSK-3 and CK1, protein phosphatase 2A (PP2A), and the E3-ubiquitin ligase β-TrCP. The complex generates a β-TrCP recognition site by phosphorylation of a conserved Ser/Thr-rich sequence near the β-catenin amino terminus, a process that requires scaffolding of the kinases and β-catenin by Axin. Ubiquitinated β-catenin is degraded by the proteasome. The molecular mechanisms that underlie several aspects of destruction complex function are poorly understood, particularly the role of APC. Here we review the molecular mechanisms of destruction complex function and discuss several potential roles of APC in β-catenin destruction.
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Affiliation(s)
- Jennifer L Stamos
- Departments of Structural Biology and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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The Antitumor Activity of Antrodia camphorata in Melanoma Cells: Modulation of Wnt/β-Catenin Signaling Pathways. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:197309. [PMID: 23049605 PMCID: PMC3463817 DOI: 10.1155/2012/197309] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 08/14/2012] [Indexed: 12/16/2022]
Abstract
Antrodia camphorata (AC) is well known in Taiwan as a traditional Chinese medicine. The aim of this study was to investigate whether a fermented culture broth of AC could inhibit melanoma proliferation and progression via suppression of the Wnt/β-catenin signaling pathway. In this study, we observed that AC treatment resulted in decreased cell viability and disturbed Wnt/β-catenin cascade in B16F10 and/or B16F1 melanoma cells. This result was accompanied by a decrease in the expression of Wnt/β-catenin transcriptional targets, including c-Myc and survivin. Furthermore, treatment of melanoma cells with AC resulted in a significant increase in apoptosis, which was associated with DNA fragmentation, cytochrome c release, caspase-9 and -3 activation, PARP degradation, Bcl-2/Bax dysregulation, and p53 expression. We also observed that AC caused G1 phase arrest mediated by a downregulation of cyclin D1 and CDK4 and increased p21 and p27 expression. In addition, we demonstrated that non- and subcytotoxic concentrations of AC markedly inhibited migration and invasion of highly metastatic B16F10 cells. The antimetastatic effect of AC was further confirmed by reductions in the levels of MMP-2, MMP-9, and VEGF expression. These results suggest that Antrodia camphorata may exert antitumor activity by downregulating the Wnt/β-catenin pathways.
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Yano H, Yamamoto-Hino M, Awano W, Aoki-Kinoshita KF, Tsuda-Sakurai K, Okano H, Goto S. Identification of proteasome components required for apical localization of Chaoptin using functional genomics. J Neurogenet 2012; 26:53-63. [PMID: 22417167 DOI: 10.3109/01677063.2012.661497] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Abstract: the distinct localization of membrane proteins with regard to cell polarity is crucial for the structure and function of various organs in multicellular organisms. However, the molecules and mechanisms that regulate protein localization to particular subcellular domains are still largely unknown. To identify the genes involved in regulation of protein localization, the authors performed a large-scale screen using a Drosophila RNA interference (RNAi) library, by which Drosophila genes could be knocked down in a tissue- and stage-specific manner. Drosophila photoreceptor cells have a morphologically distinct apicobasal polarity, along which Chaoptin (Chp), a glycosylphosphatidylinositol (GPI)-anchored membrane protein, and the Na (+) , K(+) -ATPase are localized to the apical and basolateral domains, respectively. By examining the subcellular localization of these proteins, the authors identified 106 genes whose knockdown resulted in mislocalization of Chp and Na(+) , K(+) -ATPase. Gene ontology analysis revealed that the knockdown of proteasome components resulted in mislocalization of Chp to the basolateral plasma membrane. These results suggest that the proteasome is involved, directly or indirectly, in selective localization of Chp to the apical plasma membrane of Drosophila photoreceptor cells.
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Affiliation(s)
- Hiroyuki Yano
- Research Group of Glycobiology and Glycotechnology , Tokyo , Japan
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15
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A screen for X-linked mutations affecting Drosophila photoreceptor differentiation identifies Casein kinase 1α as an essential negative regulator of wingless signaling. Genetics 2011; 190:601-16. [PMID: 22095083 DOI: 10.1534/genetics.111.133827] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The Wnt and Hedgehog signaling pathways are essential for normal development and are misregulated in cancer. The casein kinase family of serine/threonine kinases regulates both pathways at multiple levels. However, it has been difficult to determine whether individual members of this family have distinct functions in vivo, due to their overlapping substrate specificities. In Drosophila melanogaster, photoreceptor differentiation is induced by Hedgehog and inhibited by Wingless, providing a sensitive system in which to identify regulators of each pathway. We used a mosaic genetic screen in the Drosophila eye to identify mutations in genes on the X chromosome required for signal transduction. We recovered mutations affecting the transcriptional regulator CREB binding protein, the small GTPase dynamin, the cytoskeletal regulator Actin-related protein 2, and the protein kinase Casein kinase 1α. Consistent with its reported function in the β-Catenin degradation complex, Casein Kinase 1α mutant cells accumulate β-Catenin and ectopically induce Wingless target genes. In contrast to previous studies based on RNA interference, we could not detect any effect of the same Casein Kinase 1α mutation on Hedgehog signaling. We thus propose that Casein kinase 1α is essential to allow β-Catenin degradation and prevent inappropriate Wingless signaling, but its effects on the Hedgehog pathway are redundant with other Casein kinase 1 family members.
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Drosophila homeodomain-interacting protein kinase inhibits the Skp1-Cul1-F-box E3 ligase complex to dually promote Wingless and Hedgehog signaling. Proc Natl Acad Sci U S A 2011; 108:9887-92. [PMID: 21628596 DOI: 10.1073/pnas.1017548108] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Drosophila Homeodomain-interacting protein kinase (Hipk) has been shown to regulate in vivo, the stability of Armadillo, the transcriptional effector of Wingless signaling. The Wingless pathway culminates in the stabilization of Armadillo that, in the absence of signaling, is sequentially phosphorylated, polyubiquitinated and degraded. Loss-of-function clones for hipk result in reduced stabilized Armadillo, whereas overexpression of hipk elevates Armadillo levels to promote Wingless-responsive target gene expression. Here, we show that overexpression of hipk can suppress the effects of negative regulators of Armadillo to prevent its degradation in the wing imaginal disc. Hipk acts to stabilize Armadillo by impeding the function of the E3 ubiquitin ligase Skp1-Cul1-F-box (SCF)(Slimb), thereby inhibiting Armadillo ubiquitination and subsequent degradation. Vertebrate Hipk2 displays a similar ability to prevent β-catenin ubiquitination in a functionally conserved mechanism. We find that Hipk's ability to inhibit SCF(Slimb)-mediated ubiquitination is not restricted to Armadillo and extends to other substrates of SCF(Slimb), including the Hedgehog signaling effector Ci. Thus, similar to casein kinase 1 and glycogen synthase kinase 3, Hipk dually regulates both Wingless and Hedgehog signaling by controlling the stability of their respective signaling effectors, but it is the first kinase to our knowledge identified that promotes the stability of both Armadillo and Ci.
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17
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Nyati S, Ranga R, Ross BD, Rehemtulla A, Bhojani MS. Molecular imaging of glycogen synthase kinase-3beta and casein kinase-1alpha kinases. Anal Biochem 2010; 405:246-54. [PMID: 20561505 DOI: 10.1016/j.ab.2010.06.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 06/10/2010] [Accepted: 06/11/2010] [Indexed: 01/07/2023]
Abstract
Glycogen synthase kinase-3beta (GSK3beta) and casein kinase-1alpha (CK1alpha) are multifunctional kinases that play critical roles in the regulation of a number of cellular processes. In spite of their importance, molecular imaging tools for noninvasive and real-time monitoring of their kinase activities have not been devised. Here we report development of the bioluminescent GSK3beta and CK1alpha reporter (BGCR) based on firefly luciferase complementation. Treatment of SW620 cells stably expressing the reporter with inhibitors of GSK3beta (SB415286 and LiCl) or CK1alpha (CKI-7) resulted in dose- and time-dependent increases in BGCR activity that were validated using Western blotting. No increase in bioluminescence was observed in the case of S37A mutant (GSK3beta inhibitors) or S45A mutant (CKI-7), demonstrating the specificity of the reporter. Imaging of mice tumor xenograft generated with BGCR-expressing SW620 cells following treatment with LiCl showed unique oscillations in GSK3beta activity that were corroborated by phosphorylated GSK3beta immunoblotting. Taken together, the BGCR is a novel molecular imaging tool that reveals unique insight into GSK3beta and CK1alpha kinase activities and may provide a powerful tool in experimental therapeutics for rapid optimization of dose and schedule of targeted therapies and for monitoring therapeutic response.
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Affiliation(s)
- Shyam Nyati
- Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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18
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Lin JL, Lin PL, Gu SH. Phosphorylation of glycogen synthase kinase-3beta in relation to diapause processing in the silkworm, Bombyx mori. JOURNAL OF INSECT PHYSIOLOGY 2009; 55:593-598. [PMID: 19418600 DOI: 10.1016/j.jinsphys.2009.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Glycogen synthase kinase-3 (GSK-3) is a multifunctional protein kinase that plays important roles in regulating both glycogen synthesis and protein synthesis. In the present study, we investigated GSK-3beta phosphorylation of silkworm eggs by immunoblotting with a conserved phospho-specific antibody to GSK-3beta. Results showed that the temporal changes in GSK-3beta phosphorylation were closely related to changes in glycogen levels previously reported by other researchers. In diapause eggs, an abrupt decrease in phosphorylation of GSK-3beta was found with the onset of diapause, and phosphorylation level of GSK-3beta reached a minimum level within 1 week after oviposition. However, when diapause eggs were incubated at 25 degrees C for 15 days and then transferred to 5 degrees C, a great increase in GSK-3beta phosphorylation was observed 5 days after transfer to 5 degrees C and high levels were maintained throughout the chilling period. In both non-diapause eggs and eggs whose diapause initiation was prevented by HCl, levels of GSK-3beta phosphorylation appeared to remain relatively high for several days and then greatly decreased 2 or 3 days before hatching. Moreover, GSK-3beta phosphorylation dramatically increased when dechorionated eggs were incubated in medium. The addition of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor, U0126, did not inhibit GSK-3beta phosphorylation in dechorionated eggs, although U0126 dose-dependently inhibited ERK phosphorylation. This result showed that ERK phosphorylation is not involved in upstream signaling for GSK-3beta phosphorylation and that there may be two distinct signaling pathways involved in diapause processing in Bombyx mori eggs.
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Affiliation(s)
- Ju-Ling Lin
- Department of Zoology, National Museum of Natural Science, Taiwan, ROC
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19
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Dahlberg CL, Nguyen EZ, Goodlett D, Kimelman D. Interactions between Casein kinase Iepsilon (CKIepsilon) and two substrates from disparate signaling pathways reveal mechanisms for substrate-kinase specificity. PLoS One 2009; 4:e4766. [PMID: 19274088 PMCID: PMC2651596 DOI: 10.1371/journal.pone.0004766] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Accepted: 02/10/2009] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Members of the Casein Kinase I (CKI) family of serine/threonine kinases regulate diverse biological pathways. The seven mammalian CKI isoforms contain a highly conserved kinase domain and divergent amino- and carboxy-termini. Although they share a preferred target recognition sequence and have overlapping expression patterns, individual isoforms often have specific substrates. In an effort to determine how substrates recognize differences between CKI isoforms, we have examined the interaction between CKIepsilon and two substrates from different signaling pathways. METHODOLOGY/PRINCIPAL FINDINGS CKIepsilon, but not CKIalpha, binds to and phosphorylates two proteins: Period, a transcriptional regulator of the circadian rhythms pathway, and Disheveled, an activator of the planar cell polarity pathway. We use GST-pull-down assays data to show that two key residues in CKIalpha's kinase domain prevent Disheveled and Period from binding. We also show that the unique C-terminus of CKIepsilon does not determine Dishevelled's and Period's preference for CKIepsilon nor is it essential for binding, but instead plays an auxillary role in stabilizing the interactions of CKIepsilon with its substrates. We demonstrate that autophosphorylation of CKIepsilon's C-terminal tail prevents substrate binding, and use mass spectrometry and chemical crosslinking to reveal how a phosphorylation-dependent interaction between the C-terminal tail and the kinase domain prevents substrate phosphorylation and binding. CONCLUSIONS/SIGNIFICANCE The biochemical interactions between CKIepsilon and Disheveled, Period, and its own C-terminus lead to models that explain CKIepsilon's specificity and regulation.
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Affiliation(s)
- Caroline Lund Dahlberg
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Elizabeth Z. Nguyen
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, United States of America
| | - David Goodlett
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington, United States of America
| | - David Kimelman
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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20
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The Drosophila p21-activated kinase Mbt modulates DE-cadherin-mediated cell adhesion by phosphorylation of Armadillo. Biochem J 2008; 416:231-41. [PMID: 18636970 DOI: 10.1042/bj20080465] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phosphorylation by tyrosine and serine/threonine kinases regulate the interactions between components of the cadherin-catenin cell-adhesion complex and thus can influence the dynamic modulation of cell adhesion under normal and disease conditions. Previous mutational analysis and localization experiments suggested an involvement of single members of the family of PAKs (p21-activated kinases) in the regulation of cadherin-mediated cell adhesion, but the molecular mechanism remained elusive. In the present study, we address this question using the Drosophila PAK protein Mbt, which is most similar to vertebrate PAK4. Previous phenotypic analysis showed that Mbt has a function to maintain adherens junctions during eye development and indicated a requirement of the protein in regulation of the actin cytoskeleton and the cadherin-catenin complex. Here we show that activation of Mbt leads to destabilization of the interaction of the Drosophila beta-catenin homologue Armadillo with DE-cadherin resulting in a decrease in DE-cadherin-mediated adhesion. Two conserved phosphorylation sites in Armadillo were identified that mediate this effect. The findings of the present study support the previous observation that activation of the human Mbt homologue PAK4 leads to anchorage-independent growth and provide a functional link between a PAK protein and the cadherin-catenin complex.
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21
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Abstract
How signaling cascades influence gene regulation at the level of chromatin modification is not well understood. We studied this process using the Wingless/Wnt pathway in Drosophila. When cells sense Wingless ligand, Armadillo (the fly beta-catenin) becomes stabilized and translocates to the nucleus, where it binds to the sequence-specific DNA binding protein TCF to activate transcription of target genes. Here, we show that Wingless signaling induces TCF and Armadillo recruitment to a select subset of TCF binding site clusters that act as Wingless response elements. Despite this localized TCF/Armadillo recruitment, histones are acetylated over a wide region (up to 30 kb) surrounding the Wingless response elements in response to pathway activation. This widespread histone acetylation occurs independently of transcription. In contrast to Wingless targets, other active genes not regulated by the pathway display sharp acetylation peaks centered on their core promoters. Widespread acetylation of Wingless targets is dependent upon CBP, a histone acetyltransferase known to bind to Armadillo and is correlated with activation of target gene expression. These data suggest that pathway activation induces localized recruitment of TCF/Armadillo/CBP to Wingless response elements, leading to widespread histone acetylation of target loci prior to transcriptional activation.
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22
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Sharma SK, Nirenberg M. Silencing of genes in cultured Drosophila neurons by RNA interference. Proc Natl Acad Sci U S A 2007; 104:12925-30. [PMID: 17646657 PMCID: PMC1937568 DOI: 10.1073/pnas.0704299104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Indexed: 11/18/2022] Open
Abstract
Cultures of neuroblasts that generate abundant neurons were established from Drosophila embryos to study silencing of genes by RNA interference (RNAi). Cultured cells expressed ELAV, a marker of neurons, Futsch, a marker of neurites, and Synapsin, Synaptobrevin, and Synaptogamin, proteins involved in neurotransmitter secretion. Conditions were found for efficient transfection of cells with siRNAs for ELAV or the insulin-like receptor, which resulted in marked decreases in neurons that express ELAV and Futsch. Cells also were successfully transfected with long-chain Sox-Neuro dsRNA resulting in a 55% reduction of neurons expressing Futsch. The results suggest that this cultured neural cell system can be used to study RNAi-dependent silencing of genes involved in many kinds of neural functions.
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Affiliation(s)
- Shail K. Sharma
- Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Marshall Nirenberg
- Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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23
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Kaladchibachi SA, Doble B, Anthopoulos N, Woodgett JR, Manoukian AS. Glycogen synthase kinase 3, circadian rhythms, and bipolar disorder: a molecular link in the therapeutic action of lithium. J Circadian Rhythms 2007; 5:3. [PMID: 17295926 PMCID: PMC1803776 DOI: 10.1186/1740-3391-5-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 02/12/2007] [Indexed: 11/25/2022] Open
Abstract
Background Bipolar disorder (BPD) is a widespread condition characterized by recurring states of mania and depression. Lithium, a direct inhibitor of glycogen synthase kinase 3 (GSK3) activity, and a mainstay in BPD therapeutics, has been proposed to target GSK3 as a mechanism of mood stabilization. In addition to mood imbalances, patients with BPD often suffer from circadian disturbances. GSK3, an essential kinase with widespread roles in development, cell survival, and metabolism has been demonstrated to be an essential component of the Drosophila circadian clock. We sought to investigate the role of GSK3 in the mammalian clock mechanism, as a possible mediator of lithium's therapeutic effects. Methods GSK3 activity was decreased in mouse embryonic fibroblasts (MEFs) genetically and pharmacologically, and changes in the cyclical expression of core clock genes – mPer2 in particular – were examined. Results We demonstrate that genetic depletion of GSK3 in synchronized oscillating MEFs results in a significant delay in the periodicity of the endogenous clock mechanism, particularly in the cycling period of mPer2. Furthermore, we demonstrate that pharmacological inhibition of GSK3 activity by kenpaullone, a known antagonist of GSK3 activity, as well as by lithium, a direct inhibitor of GSK3 and the most common treatment for BPD, induces a phase delay in mPer2 transcription that resembles the effect observed with GSK3 knockdown. Conclusion These results confirm GSK3 as a plausible target of lithium action in BPD therapeutics, and suggest the circadian clock mechanism as a significant modulator of lithium's clinical benefits.
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Affiliation(s)
- Sevag A Kaladchibachi
- Division of Signaling Biology, Ontario Cancer Institute, University Health Network, 610 University Avenue, Toronto, Ont. M5G 2M9, Canada
| | - Brad Doble
- Stem Cell and Cancer Research Institute, McMaster University, 1200 Main Street West, Hamilton, Ont. L8N 3Z5, Canada
| | - Norman Anthopoulos
- Division of Signaling Biology, Ontario Cancer Institute, University Health Network, 610 University Avenue, Toronto, Ont. M5G 2M9, Canada
| | - James R Woodgett
- Samuel Lunenfeld Research Institute, 600 University Avenue, Toronto, Ont. M5G 1X5, Canada
| | - Armen S Manoukian
- Division of Signaling Biology, Ontario Cancer Institute, University Health Network, 610 University Avenue, Toronto, Ont. M5G 2M9, Canada
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24
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Bryja V, Schulte G, Rawal N, Grahn A, Arenas E. Wnt-5a induces Dishevelled phosphorylation and dopaminergic differentiation via a CK1-dependent mechanism. J Cell Sci 2007; 120:586-95. [PMID: 17244647 DOI: 10.1242/jcs.03368] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Previously, we have shown that Wnt-5a strongly regulates dopaminergic neuron differentiation by inducing phosphorylation of Dishevelled (Dvl). Here, we identify additional components of the Wnt-5a-Dvl pathway in dopaminergic cells. Using in vitro gain-of-function and loss-of-function approaches, we reveal that casein kinase 1 (CK1) delta and CK1epsilon are crucial for Dvl phosphorylation by non-canonical Wnts. We show that in response to Wnt-5a, CK1epsilon binds Dvl and is subsequently phosphorylated. Moreover, in response to Wnt-5a or CK1epsilon, the distribution of Dvl changed from punctate to an even appearance within the cytoplasm. The opposite effect was induced by a CK1epsilon kinase-dead mutant or by CK1 inhibitors. As expected, Wnt-5a blocked the Wnt-3a-induced activation of beta-catenin. However, both Wnt-3a and Wnt-5a activated Dvl2 by a CK1-dependent mechanism in a cooperative manner. Finally, we show that CK1 kinase activity is necessary for Wnt-5a-induced differentiation of primary dopaminergic precursors. Thus, our data identify CK1 as a component of Wnt-5a-induced signalling machinery that regulates dopaminergic differentiation, and suggest that CK1delta/epsilon-mediated phosphorylation of Dvl is a common step in both canonical and non-canonical Wnt signalling.
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Affiliation(s)
- Vítezslav Bryja
- Laboratory of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden
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25
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Kimelman D, Xu W. beta-catenin destruction complex: insights and questions from a structural perspective. Oncogene 2007; 25:7482-91. [PMID: 17143292 DOI: 10.1038/sj.onc.1210055] [Citation(s) in RCA: 476] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
At the heart of the canonical Wnt signaling pathway is the beta-catenin destruction complex, which functions in the absence of Wnt signaling to keep the cytosolic and nuclear levels of beta-catenin very low by promoting the phosphorylation and ubiquitination of beta-catenin. Structural studies, combined with other experimental approaches, have begun to provide important insights into the mechanism of the destruction complex. We suggest a working model for the destruction complex based on the existing structural and experimental data, and focus on the questions that this model and other studies have raised about the function of the complex in both the normal and Wnt-inhibited states.
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Affiliation(s)
- D Kimelman
- Department of Biochemistry, University of Washington, Seattle, WA 98195-7350, USA.
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26
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Strutt H, Price MA, Strutt D. Planar polarity is positively regulated by casein kinase Iepsilon in Drosophila. Curr Biol 2006; 16:1329-36. [PMID: 16824921 DOI: 10.1016/j.cub.2006.04.041] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2006] [Revised: 04/07/2006] [Accepted: 04/10/2006] [Indexed: 10/24/2022]
Abstract
Members of the casein kinase I (CKI) family have been implicated in regulating canonical Wnt/Wingless (Wg) signaling by phosphorylating multiple pathway components. Overexpression of CKI in vertebrate embryos activates Wg signaling, and one target is thought to be the cytoplasmic effector Dishevelled (Dsh), which is an in vitro target of CKI phosphorylation. Phosphorylation of Dsh by CKI has also been suggested to switch its activity from noncanonical to canonical Wingless signaling. However, in vivo loss-of-function experiments have failed to identify a clear role for CKI in positive regulation of Wg signaling. By examining hypomorphic mutations of the Drosophila CKIepsilon homolog discs overgrown (dco)/double-time, we now show that it is an essential component of the noncanonical/planar cell polarity pathway. Genetic interactions indicate that dco acts positively in planar polarity signaling, demonstrating that it does not act as a switch between canonical and noncanonical pathways. Mutations in dco result in a reduced level of Dishevelled phosphorylation in vivo. Furthermore, in these mutants, Dishevelled fails to adopt its characteristic asymmetric subcellular localisation at the distal end of pupal wing cells, and the site of hair outgrowth is disrupted. Finally, we also find that dco function in polarity is partially redundant with CKIalpha.
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Affiliation(s)
- Helen Strutt
- Centre for Developmental and Biomedical Genetics, Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
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27
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Bryja V, Schulte G, Arenas E. Wnt-3a utilizes a novel low dose and rapid pathway that does not require casein kinase 1-mediated phosphorylation of Dvl to activate beta-catenin. Cell Signal 2006; 19:610-6. [PMID: 17027228 DOI: 10.1016/j.cellsig.2006.08.011] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Revised: 08/21/2006] [Accepted: 08/21/2006] [Indexed: 12/23/2022]
Abstract
The current view of canonical Wnt signalling is that following Wnt binding to its receptors (Frizzled-Lrp5/6), dishevelled (Dvl) becomes hyperphosphorylated, and the signal is transduced to the APC-GSK3beta-axin-beta-catenin multiprotein complex, which subsequently dissociates. As a result beta-catenin is not phosphorylated, escapes proteosomal degradation and activates its target genes after translocation to the nucleus. Here, we analyzed the importance of the Wnt-3a-induced phosphorylation and shift in electrophoretic migration of Dvl (PS-Dvl) for the activation of beta-catenin. Analysis of Wnt-3a time- and dose-responses in a dopaminergic cell line showed that beta-catenin is activated rapidly (within minutes) and at a low dose of Wnt-3a (1 ng/ml). Surprisingly, PS-Dvl appeared only after 30 min and at greater doses (> or =20 ng/ml) of Wnt-3a. Moreover, we found that a casein kinase 1 inhibitor (D4476) or siRNA for casein kinase 1 delta/epsilon (CK1delta/epsilon) blocked the Wnt-3a-induced PS-Dvl. Interestingly, CK1 inhibition or siRNA for CK1delta/epsilon did not ablate the activation of beta-catenin by Wnt-3a, indicating that there is a PS-Dvl-independent path to activate beta-catenin. The increase in beta-catenin activation by Wnt-3a (PS-Dvl-dependent or -independent) were blocked by Dickkopf1 (Dkk1), suggesting that the effect of Wnt-3a is in both cases mediated by Lrp5/6 receptors. Thus, our results show that Wnt-3a rapidly induce a partial activation of beta-catenin in the absence of PS-Dvl at low doses, while at high doses induce a full activation of beta-catenin in a PS-Dvl-dependent manner.
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Affiliation(s)
- Vítezslav Bryja
- Karolinska Institutet, Department Medical Biochemistry and Biophysics, Laboratory Molecular Neurobiology, S-171 77 Stockholm, Sweden
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28
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Zhang L, Jia J, Wang B, Amanai K, Wharton KA, Jiang J. Regulation of wingless signaling by the CKI family in Drosophila limb development. Dev Biol 2006; 299:221-37. [PMID: 16987508 PMCID: PMC1855185 DOI: 10.1016/j.ydbio.2006.07.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 07/24/2006] [Accepted: 07/25/2006] [Indexed: 12/22/2022]
Abstract
The Wingless (Wg)/Wnt signaling pathway regulates a myriad of developmental processes and its malfunction leads to human disorders including cancer. Recent studies suggest that casein kinase I (CKI) family members play pivotal roles in the Wg/Wnt pathway. However, genetic evidence for the involvement of CKI family members in physiological Wg/Wnt signaling events is lacking. In addition, there are conflicting reports regarding whether a given CKI family member functions as a positive or negative regulator of the pathway. Here we examine the roles of seven CKI family members in Wg signaling during Drosophila limb development. We find that increased CKIepsilon stimulates whereas dominant-negative or a null CKIepsilon mutation inhibits Wg signaling. In contrast, inactivation of CKIalpha by RNA interference (RNAi) leads to ectopic Wg signaling. Interestingly, hypomorphic CKIepsilon mutations synergize with CKIalpha RNAi to induce ectopic Wg signaling, revealing a negative role for CKIepsilon. Conversely, CKIalpha RNAi enhances the loss-of-Wg phenotypes caused by CKIepsilon null mutation, suggesting a positive role for CKIalpha. While none of the other five CKI isoforms can substitute for CKIalpha in its inhibitory role in the Wg pathway, several CKI isoforms including CG12147 exhibit a positive role based on overexpression. Moreover, loss of Gilgamesh (Gish)/CKIgamma attenuates Wg signaling activity. Finally, we provide evidence that several CKI isoforms including CKIalpha and Gish/CKIgamma can phosphorylate the Wg coreceptor Arrow (Arr), which may account, at least in part, for their positive roles in the Wg pathway.
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Affiliation(s)
- Lei Zhang
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Jianhang Jia
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Bing Wang
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Kazuhito Amanai
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Keith A. Wharton
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
- Department of Pathology and Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Jin Jiang
- Center for Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390
- *Correspondence:
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29
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Price MA. CKI, there's more than one: casein kinase I family members in Wnt and Hedgehog signaling. Genes Dev 2006; 20:399-410. [PMID: 16481469 DOI: 10.1101/gad.1394306] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Multiple members of the casein kinase I family of serine/threonine protein kinases are involved in positive and negative roles in Wnt and Hedgehog signaling. Here I review these roles, including recent results on casein kinase I (CKI) phosphorylation and activation of LRP6, and CKI phosphorylation of Ci and mediation of Ci-Slimb/beta-TrCP binding.
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Affiliation(s)
- Mary Ann Price
- Centre for Developmental and Biomedical Genetics, Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom.
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30
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Swiatek W, Kang H, Garcia BA, Shabanowitz J, Coombs GS, Hunt DF, Virshup DM. Negative regulation of LRP6 function by casein kinase I epsilon phosphorylation. J Biol Chem 2006; 281:12233-41. [PMID: 16513652 DOI: 10.1074/jbc.m510580200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Wnt signaling acts in part through the low density lipoprotein receptor-related transmembrane proteins LRP5 and LRP6 to regulate embryonic development and stem cell proliferation. Up-regulated signaling is associated with many forms of cancer. Casein kinase I epsilon (CKIepsilon) is a known component of the Wnt-beta-catenin signaling pathway. We find that CKIepsilon binds to LRP5 and LRP6 in vitro and in vivo and identify three CKIepsilon-specific phosphorylation sites in LRP6. Two of the identified phosphorylation sites, Ser1420 and Ser1430, influence Wnt signaling in vivo, since LRP6 with mutation of these sites is a more potent activator of both beta-catenin accumulation and Lef-1 reporter activity. Whereas Wnt3a regulates CKIepsilon kinase activity, LRP6 does not, placing CKIepsilon upstream of LRP6. Mutation of LRP6 Ser1420 and Ser1430 to alanine strengthens its interaction with axin, suggesting a mechanism by which CKIepsilon may negatively regulate Wnt signaling. The role of CKIepsilon is therefore more complex than was previously appreciated. Generation of active CKIepsilon may induce a negative feedback loop by phosphorylation of sites on LRP5/6 that modulate axin binding and hence beta-catenin degradation.
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Affiliation(s)
- Wojciech Swiatek
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112-5550, USA
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31
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Caricasole A, Bakker A, Copani A, Nicoletti F, Gaviraghi G, Terstappen GC. Two Sides of the Same Coin: Wnt Signaling in Neurodegeneration and Neuro-Oncology. Biosci Rep 2005; 25:309-27. [PMID: 16307379 DOI: 10.1007/s10540-005-2893-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Wnts function through the activation of at least three intracellular signal transduction pathways, of which the canonical β-catenin mediated pathway is the best understood. Aberrant canonical Wnt signaling has been involved in both neurodegeneration and cancer. An impairment of Wnt signals appears to be associated with aspects of neurodegenerative pathologies while overactivation of Wnt signaling is a common theme in several types of human tumors. Therefore, although therapeutic approaches aimed at modulating Wnt signaling in neurodegenerative and hyperproliferative diseases might impinge on the same molecular mechanisms, different pharmacological outcomes are required. Here we review recent developments on the understanding of the role of Wnt signaling in Alzheimer's disease and CNS tumors, and identify possible avenues for therapeutic intervention within a complex and multi-faceted signaling pathway.
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Affiliation(s)
- A Caricasole
- Sienabiotech S.p.A., Via Fiorentina 1, 53100, Siena, Italy
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Fujimuro M, Liu J, Zhu J, Yokosawa H, Hayward SD. Regulation of the interaction between glycogen synthase kinase 3 and the Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen. J Virol 2005; 79:10429-41. [PMID: 16051835 PMCID: PMC1182668 DOI: 10.1128/jvi.79.16.10429-10441.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA) protein stabilizes beta-catenin by the novel mechanism of binding to the negative regulator, glycogen synthase kinase 3 (GSK-3), and depleting cytoplasmic GSK-3 levels. The two domains of LANA required for interaction with GSK-3 were further characterized. Evidence for similarity between the C-terminal LANA interaction domain and the axin GSK-3 interaction domain was obtained using GSK-3 and LANA mutants. GSK-3(F291L), which does not interact with axin, also failed to bind to LANA, and a mutation in the axin homology domain of LANA, L1132P, destroyed binding to GSK-3. The N-terminal LANA interaction domain was found to mediate interaction by acting as a substrate for GSK-3. GSK-3(R96A), a priming pocket mutant, did not bind to LANA, suggesting that LANA was a primed GSK-3 substrate. Phosphorylation of endogenous LANA precipitated from primary effusion lymphoma cells was inhibited by the GSK-3 inhibitor LiCl. GST-LANA(1-340) was phosphorylated by GSK-3, and mitogen-activated protein kinase (MAPK) and casein kinase I functioned as priming kinases in vitro. Mutation of consensus GSK-3 sites revealed that sites between LANA amino acids 219 and 268 were important for GSK-3 phosphorylation. Immunoprecipitation assays revealed that loss of GSK-3 phosphorylation of this N-terminal domain correlated with loss of GSK-3 interaction. Although LANA-associated GSK-3 actively phosphorylated LANA, GSK-3 coprecipitated with LANA was unable to phosphorylate an exogenous peptide substrate. LANA sequestration of GSK-3 may explain the ability of KSHV-infected cells to tolerate increased levels of nuclear GSK-3.
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Affiliation(s)
- Masahiro Fujimuro
- Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Japan
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Takada R, Hijikata H, Kondoh H, Takada S. Analysis of combinatorial effects of Wnts and Frizzleds on beta-catenin/armadillo stabilization and Dishevelled phosphorylation. Genes Cells 2005; 10:919-28. [PMID: 16115200 DOI: 10.1111/j.1365-2443.2005.00889.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Both Wnt ligands and Frizzled (Fz) receptors each constitute a large family in vertebrates, but the receptor specificity of each Wnt has remained largely unknown. Here, we examined the receptor specificity of two typical Wnts, Wnt-3a and Wnt-5a, in signal transmission. To investigate systematically the combinatorial effects of these Wnts, various Fzs on canonical Wnt/beta-catenin signaling, we analyzed the ability of these Wnt proteins to increase stability of armadillo/beta-catenin proteins in Drosophila S2 cells expressing vertebrate Fzs. Wnt-3a increases the amount of armadillo proteins in cells expressing Fzs 4, 5 and 8, but not Fzs 3 and 6; whereas Wnt-5a does not increase it in any cell line. In contrast, both Wnt-3a and Wnt-5a increase the phosphorylation of Dsh in combination with most of the Fzs. This Dsh phosphorylation is abrogated by decreasing the levels of casein kinase I alpha by double-stranded RNA-mediated translational interference. These observations indicate that both Wnt proteins can interact with the majority of Fz receptors and elicit signaling reactions exemplified by Dsh phosphorylation but that the stabilization of beta-catenin/armadillo proteins in the Wnt/beta-catenin signaling occurs only when specific combinations of Wnt and Fz meet.
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Affiliation(s)
- Ritsuko Takada
- Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
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Ossipova O, Dhawan S, Sokol S, Green JBA. Distinct PAR-1 Proteins Function in Different Branches of Wnt Signaling during Vertebrate Development. Dev Cell 2005; 8:829-41. [PMID: 15935773 DOI: 10.1016/j.devcel.2005.04.011] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 04/11/2005] [Accepted: 04/14/2005] [Indexed: 11/24/2022]
Abstract
The kinase PAR-1 plays conserved roles in cell polarity. PAR-1 has also been implicated in axis establishment in C. elegans and Drosophila and in Wnt signaling, but its role in vertebrate development is unclear. Here we report that PAR-1 has two distinct and essential roles in axial development in Xenopus mediated by different PAR-1 isoforms. Depletion of PAR-1A or PAR-1BX causes dorsoanterior deficits, reduced Spemann organizer gene expression, and inhibition of canonical Wnt-beta-catenin signaling. By contrast, PAR-1BY depletion inhibits cell movements and localization of Dishevelled protein to the cell cortex, processes associated with noncanonical Wnt signaling. PAR-1 phosphorylation sites in Dishevelled are required for this translocation, but not for canonical Wnt signaling. We conclude that PAR-1BY is required in the PCP branch and mediates Dsh membrane localization while PAR-1A and PAR-1BX are essential for canonical signaling to beta-catenin, possibly via targets other than Dishevelled.
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Affiliation(s)
- Olga Ossipova
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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Patel S, Doble B, Woodgett JR. Glycogen synthase kinase-3 in insulin and Wnt signalling: a double-edged sword? Biochem Soc Trans 2005; 32:803-8. [PMID: 15494020 PMCID: PMC4485494 DOI: 10.1042/bst0320803] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Glycogen synthase kinase-3 is an unusual protein serine/threonine kinase that, unlike most of its 500-odd relatives in the genome, is active under resting conditions and is inactivated upon cell stimulation. The two mammalian isoforms, GSK-3alpha and beta, play largely overlapping roles and have been implicated in a variety of human pathologies, including Type II diabetes, Alzheimer's disease, bipolar disorder and cancer. Recently, the modes of regulation of this enzyme have been elucidated through a combination of structural and cell biological studies. A series of relatively selective small molecules have facilitated chemical manipulation of the enzyme in intact cells and tissues, and new roles for the protein kinase in embryonic stem cell differentiation and motility have emerged. Despite these advances, the therapeutic value of this enzyme as a drug target remains clouded by uncertainty over the potential of antagonists to promote tumorigenesis. This article describes the state of understanding of this intriguing enzyme, and weighs current evidence regarding whether there is a therapeutic window for amelioration of diseases in which it is implicated, in the absence of inducing new pathologies.
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Affiliation(s)
- S Patel
- Ontario Cancer Institute, 610 University Avenue, Toronto, Ontario M5G 2M9, Canada
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DasGupta R, Kaykas A, Moon RT, Perrimon N. Functional genomic analysis of the Wnt-wingless signaling pathway. Science 2005; 308:826-33. [PMID: 15817814 DOI: 10.1126/science.1109374] [Citation(s) in RCA: 281] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Wnt-Wingless (Wg) pathway is one of a core set of evolutionarily conserved signaling pathways that regulates many aspects of metazoan development. Aberrant Wnt signaling has been linked to human disease. In the present study, we used a genomewide RNA interference (RNAi) screen in Drosophila cells to screen for regulators of the Wnt pathway. We identified 238 potential regulators, which include known pathway components, genes with functions not previously linked to this pathway, and genes with no previously assigned functions. Reciprocal-Best-Blast analyses reveal that 50% of the genes identified in the screen have human orthologs, of which approximately 18% are associated with human disease. Functional assays of selected genes from the cell-based screen in Drosophila, mammalian cells, and zebrafish embryos demonstrated that these genes have evolutionarily conserved functions in Wnt signaling. High-throughput RNAi screens in cultured cells, followed by functional analyses in model organisms, prove to be a rapid means of identifying regulators of signaling pathways implicated in development and disease.
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Affiliation(s)
- Ramanuj DasGupta
- Department of Genetics, Howard Hughes Medical Institute (HHMI), Harvard Medical School, New Research Building, No. 339, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.
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Knippschild U, Gocht A, Wolff S, Huber N, Löhler J, Stöter M. The casein kinase 1 family: participation in multiple cellular processes in eukaryotes. Cell Signal 2005; 17:675-89. [PMID: 15722192 DOI: 10.1016/j.cellsig.2004.12.011] [Citation(s) in RCA: 420] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 12/22/2004] [Accepted: 12/22/2004] [Indexed: 12/11/2022]
Abstract
Phosphorylation of serine, threonine and tyrosine residues by cellular protein kinases plays an important role in the regulation of various cellular processes. The serine/threonine specific casein kinase 1 and 2 protein kinase families--(CK1 and CK2)--were among the first protein kinases that had been described. In recent years our knowledge of the regulation and function of mammalian CK1 kinase family members has rapidly increased. Extracellular stimuli, the subcellular localization of CK1 isoforms, their interaction with various cellular structures and proteins, as well as autophosphorylation and proteolytic cleavage of their C-terminal regulatory domains influence CK1 kinase activity. Mammalian CK1 isoforms phosphorylate many different substrates among them key regulatory proteins involved in the control of cell differentiation, proliferation, chromosome segregation and circadian rhythms. Deregulation and/or the incidence of mutations in the coding sequence of CK1 isoforms have been linked to neurodegenerative diseases and cancer. This review will summarize our current knowledge about the function and regulation of mammalian CK1 isoforms.
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Affiliation(s)
- Uwe Knippschild
- Department of Visceral and Transplantation Surgery, University of Ulm, Steinhövelstr. 9, 89075 Ulm, Germany.
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Ivanov AI, Rovescalli AC, Pozzi P, Yoo S, Mozer B, Li HP, Yu SH, Higashida H, Guo V, Spencer M, Nirenberg M. Genes required for Drosophila nervous system development identified by RNA interference. Proc Natl Acad Sci U S A 2004; 101:16216-21. [PMID: 15534205 PMCID: PMC528945 DOI: 10.1073/pnas.0407188101] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
RNA interference was used to screen 3,314 Drosophila double-stranded RNAs, corresponding to approximately 25% of Drosophila genes, for genes that affect the development of the embryonic nervous system. RNA-interference-mediated gene silencing in Drosophila embryos resulted in loss-of-function mutant phenotypes for 43 genes, which is 1.3% of the genes that were screened. We found 18 genes that were not known previously to affect the development of the nervous system. The functions of some of the genes are unknown. Other genes encode protein kinases, transcription factors, and signaling proteins, as well as proteins with other functions.
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Affiliation(s)
- Andrej I Ivanov
- Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Ha NC, Tonozuka T, Stamos JL, Choi HJ, Weis WI. Mechanism of Phosphorylation-Dependent Binding of APC to β-Catenin and Its Role in β-Catenin Degradation. Mol Cell 2004; 15:511-21. [PMID: 15327768 DOI: 10.1016/j.molcel.2004.08.010] [Citation(s) in RCA: 256] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 06/01/2004] [Accepted: 06/21/2004] [Indexed: 12/16/2022]
Abstract
The transcriptional coactivator beta-catenin mediates Wnt growth factor signaling. In the absence of a Wnt signal, casein kinase 1 (CK1) and glycogen synthase kinase-3beta (GSK-3beta) phosphorylate cytosolic beta-catenin, thereby flagging it for recognition and destruction by the ubiquitin/proteosome machinery. Phosphorylation occurs in a multiprotein complex that includes the kinases, beta-catenin, axin, and the Adenomatous Polyposis Coli (APC) protein. The role of APC in this process is poorly understood. CK1epsilon and GSK-3beta phosphorylate APC, which increases its affinity for beta-catenin. Crystal structures of phosphorylated and nonphosphorylated APC bound to beta-catenin reveal a phosphorylation-dependent binding motif generated by mutual priming of CK1 and GSK-3beta substrate sequences. Axin is shown to act as a scaffold for substrate phosphorylation by these kinases. Phosphorylated APC and axin bind to the same surface of, and compete directly for, beta-catenin. The structural and biochemical data suggest a novel model for how APC functions in beta-catenin degradation.
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Affiliation(s)
- Nam-Chul Ha
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94043, USA
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