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Yu S, Han R, Gan R. The Wnt/β-catenin signalling pathway in Haematological Neoplasms. Biomark Res 2022; 10:74. [PMID: 36224652 PMCID: PMC9558365 DOI: 10.1186/s40364-022-00418-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 11/10/2022] Open
Abstract
Leukaemia and lymphoma are common malignancies. The Wnt pathway is a complex network of proteins regulating cell proliferation and differentiation, as well as cancer development, and is divided into the Wnt/β-catenin signalling pathway (the canonical Wnt signalling pathway) and the noncanonical Wnt signalling pathway. The Wnt/β-catenin signalling pathway is highly conserved evolutionarily, and activation or inhibition of either of the pathways may lead to cancer development and progression. The aim of this review is to analyse the mechanisms of action of related molecules in the Wnt/β-catenin pathway in haematologic malignancies and their feasibility as therapeutic targets.
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Affiliation(s)
- Siwei Yu
- Cancer Research Institute, Key Laboratory of Cancer Cellular and Molecular Pathology in Hunan Province, Hengyang Medical School, University of South China, 421001, Hengyang, Hunan, P. R. China
| | - Ruyue Han
- Cancer Research Institute, Key Laboratory of Cancer Cellular and Molecular Pathology in Hunan Province, Hengyang Medical School, University of South China, 421001, Hengyang, Hunan, P. R. China
| | - Runliang Gan
- Cancer Research Institute, Key Laboratory of Cancer Cellular and Molecular Pathology in Hunan Province, Hengyang Medical School, University of South China, 421001, Hengyang, Hunan, P. R. China.
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2
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Jin T, Peng G, Wu E, Mendiratta S, Elul T. N-terminal and central domains of APC function to regulate branch number, length and angle in developing optic axonal arbors in vivo. Brain Res 2018; 1697:34-44. [PMID: 29856981 DOI: 10.1016/j.brainres.2018.05.045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 05/07/2018] [Accepted: 05/28/2018] [Indexed: 11/24/2022]
Abstract
During formation of neuronal circuits, axons navigate long distances to reach their target locations in the brain. When axons arrive at their target tissues, in many cases, they extend collateral branches and/or terminal arbors that serve to increase the number of synaptic connections they make with target neurons. Here, we investigated how Adenomatous Polyposis Coli (APC) regulates terminal arborization of optic axons in living Xenopus laevis tadpoles. The N-terminal and central domains of APC that regulate the microtubule cytoskeleton and stability of β-catenin in the Wnt pathway, were co-expressed with GFP in individual optic axons, and their terminal arbors were then imaged in tectal midbrains of intact tadpoles. Our data show that the APCNTERM and APCβ-cat domains both decreased the mean number, and increased the mean length, of branches in optic axonal arbors relative to control arbors in vivo. Additional analysis demonstrated that expression of the APCNTERM domain increased the average bifurcation angle of branching in optic axonal arbors. However, the APCβ-cat domain did not significantly affect the mean branch angle of arbors in tecta of living tadpoles. These data suggest that APC N-terminal and central domains both modulate number and mean length of branches optic axonal arbors in a compensatory manner, but also define a specific function for the N-terminal domain of APC in regulating branch angle in optic axonal arbors in vivo. Our findings establish novel mechanisms for the multifunctional protein APC in shaping terminal arbors in the visual circuit of the developing vertebrate brain.
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Affiliation(s)
- Taegun Jin
- Touro University California, Vallejo, CA, United States
| | - Gregory Peng
- Touro University California, Vallejo, CA, United States
| | - Esther Wu
- Touro University California, Vallejo, CA, United States
| | | | - Tamira Elul
- Touro University California, Vallejo, CA, United States.
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3
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Mannava AG, Tolwinski NS. Membrane bound GSK-3 activates Wnt signaling through disheveled and arrow. PLoS One 2015; 10:e0121879. [PMID: 25848770 PMCID: PMC4388798 DOI: 10.1371/journal.pone.0121879] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 02/17/2015] [Indexed: 01/22/2023] Open
Abstract
Wnt ligands and their downstream pathway components coordinate many developmental and cellular processes. In adults, they regulate tissue homeostasis through regulation of stem cells. Mechanistically, signal transduction through this pathway is complicated by pathway components having both positive and negative roles in signal propagation. Here we examine the positive role of GSK-3/Zw3 in promoting signal transduction at the plasma membrane. We find that targeting GSK-3 to the plasma membrane activates signaling in Drosophila embryos. This activation requires the presence of the co-receptor Arrow-LRP5/6 and the pathway activating protein Disheveled. Our results provide genetic evidence for evolutionarily conserved, separable roles for GSK-3 at the membrane and in the cytosol, and are consistent with a model where the complex cycles from cytosol to membrane in order to promote signaling at the membrane and to prevent it in the cytosol.
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Affiliation(s)
- Anirudh G. Mannava
- Yale-NUS College and Department of Biological Sciences, National University of Singapore, Block MD6, Centre for Translational Medicine, Yong Loo Lin School of Medicine, 14 Medical Drive, Level 10 South, 10-02M, Singapore 117599, Singapore
| | - Nicholas S. Tolwinski
- Yale-NUS College and Department of Biological Sciences, National University of Singapore, Block MD6, Centre for Translational Medicine, Yong Loo Lin School of Medicine, 14 Medical Drive, Level 10 South, 10-02M, Singapore 117599, Singapore
- * E-mail:
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4
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Zhang W, Zhang H, Wang N, Zhao C, Zhang H, Deng F, Wu N, He Y, Chen X, Zhang J, Wen S, Liao Z, Zhang Q, Zhang Z, Liu W, Yan Z, Luu HH, Haydon RC, Zhou L, He TC. Modulation of β-catenin signaling by the inhibitors of MAP kinase, tyrosine kinase, and PI3-kinase pathways. Int J Med Sci 2013; 10:1888-98. [PMID: 24324366 PMCID: PMC3856380 DOI: 10.7150/ijms.6019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 10/17/2013] [Indexed: 12/12/2022] Open
Abstract
Aberrant activation of β-catenin signaling plays an important role in human tumorigenesis. However, molecular mechanisms behind the β-catenin signaling deregulation are mostly unknown because genetic alterations in this pathway only account for a small fraction of tumors. Here, we investigator if other major pathways can regulate β-catenin signaling activity. By employing a panel of chemical activators and/or inhibitors of several cellular signaling pathways, we assess these modulators' effects on luciferase reporter driven by β-catenin/TCF4-responsive elements. We find that lithium-stimulated β-catenin activity is synergistically enhanced by protein kinase C activator PMA. However, β-catenin-regulated transcriptional (CRT) activity is significantly inhibited by casein kinase II inhibitor DRB, MEK inhibitor PD98059, G-proteins and their receptor uncoupling agent suramin, protein tyrosine kinase inhibitor genistein, and PI-3 kinase inhibitor wortmannin, suggesting that these cellular pathways may participate in regulating β-catenin signaling. Interestingly, the Ca⁺⁺/calmodulin kinase II inhibitor HDBA is shown to activate β-catenin activity at low doses. Furthermore, Wnt3A-stimulated and constitutively activated CRT activities, as well as the intracellular accumulation of β-catenin protein in human colon cancer cells, are effectively suppressed by PD98059, genistein, and wortmannin. We further demonstrate that EGF can activate TCF4/β-catenin activity and induce the tyrosine phosphorylation of β-catenin protein. Thus, our results should provide important insights into the molecular mechanisms underlying Wnt/β-catenin activation. This knowledge should facilitate our efforts to develop efficacious and novel therapeutics by targeting these pathways.
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Affiliation(s)
- Wenwen Zhang
- 1. Ministry of Education Key Laboratory of Diagnostic Medicine and School of Clinical Diagnostic Medicine, and the Affiliated Hospitals of Chongqing Medical University, Chongqing 400016, China; ; 2. Molecular Oncology Laboratory, Department of Orthopaedic Surgery, The University of Chicago Medical Center, 5841 South Maryland Avenue, MC 3079, Chicago, IL 60637, USA; ; 3. Department of Laboratory Medicine of the Affiliated Hospital, Bingzhou Medical University, Yantai, Shandong, China
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5
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Houston DW. Cortical rotation and messenger RNA localization in Xenopus axis formation. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:371-88. [PMID: 23801488 DOI: 10.1002/wdev.29] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In Xenopus eggs, fertilization initiates a rotational movement of the cortex relative to the cytoplasm, resulting in the transport of critical determinants to the future dorsal side of the embryo. Cortical rotation is mediated by microtubules, resulting in activation of the Wnt/β-catenin signaling pathway and expression of organizer genes on the dorsal side of the blastula. Similar cytoplasmic localizations resulting in β-catenin activation occur in many chordate embryos, suggesting a deeply conserved mechanism for patterning early embryos. This review summarizes the experimental evidence for the molecular basis of this model, focusing on recent maternal loss-of-function studies that shed light on two main unanswered questions: (1) what regulates microtubule assembly during cortical rotation and (2) how is Wnt/β-catenin signaling activated dorsally? In addition, as these processes depend on vegetally localized molecules in the oocyte, the mechanisms of RNA localization and novel roles for localized RNAs in axis formation are discussed. The work reviewed here provides a beginning framework for understanding the coupling of asymmetry in oogenesis with the establishment of asymmetry in the embryo.
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6
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Mutations in the human naked cuticle homolog NKD1 found in colorectal cancer alter Wnt/Dvl/beta-catenin signaling. PLoS One 2009; 4:e7982. [PMID: 19956716 PMCID: PMC2776356 DOI: 10.1371/journal.pone.0007982] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 10/19/2009] [Indexed: 12/27/2022] Open
Abstract
Background Mutation of Wnt signal antagonists Apc or Axin activates β-catenin signaling in many cancers including the majority of human colorectal adenocarcinomas. The phenotype of apc or axin mutation in the fruit fly Drosophila melanogaster is strikingly similar to that caused by mutation in the segment-polarity gene, naked cuticle (nkd). Nkd inhibits Wnt signaling by binding to the Dishevelled (Dsh/Dvl) family of scaffold proteins that link Wnt receptor activation to β-catenin accumulation and TCF-dependent transcription, but human NKD genes have yet to be directly implicated in cancer. Methodology/Principal Findings We identify for the first time mutations in NKD1 - one of two human nkd homologs - in a subset of DNA mismatch repair-deficient colorectal tumors that are not known to harbor mutations in other Wnt-pathway genes. The mutant Nkd1 proteins are defective at inhibiting Wnt signaling; in addition, the mutant Nkd1 proteins stabilize β-catenin and promote cell proliferation, in part due to a reduced ability of each mutant Nkd1 protein to bind and destabilize Dvl proteins. Conclusions/Significance Our data raise the hypothesis that specific NKD1 mutations promote Wnt-dependent tumorigenesis in a subset of DNA mismatch-repair-deficient colorectal adenocarcinomas and possibly other Wnt-signal driven human cancers.
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7
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Kennell J, Cadigan KM. APC and beta-catenin degradation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 656:1-12. [PMID: 19928348 DOI: 10.1007/978-1-4419-1145-2_1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jennifer Kennell
- Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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8
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Huang H, He X. Wnt/beta-catenin signaling: new (and old) players and new insights. Curr Opin Cell Biol 2008; 20:119-25. [PMID: 18339531 DOI: 10.1016/j.ceb.2008.01.009] [Citation(s) in RCA: 349] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 01/30/2008] [Indexed: 12/21/2022]
Abstract
Wnt/beta-catenin signaling has central roles in embryogenesis and human diseases including cancer. A central scheme of the Wnt pathway is to stabilize the transcription coactivator beta-catenin by preventing its phosphorylation-dependent degradation. Significant progress has been made toward the understanding of this crucial regulatory pathway, including the protein complex that promotes beta-catenin phosphorylation-degradation, and the mechanism by which the extracellular Wnt ligand engages cell surface receptors to inhibit beta-catenin phosphorylation-degradation. Here we review some recent discoveries in these two areas, and highlight some crucial questions that remain to be resolved.
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Affiliation(s)
- He Huang
- The F M Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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Takacs CM, Baird JR, Hughes EG, Kent SS, Benchabane H, Paik R, Ahmed Y. Dual positive and negative regulation of wingless signaling by adenomatous polyposis coli. Science 2008; 319:333-6. [PMID: 18202290 DOI: 10.1126/science.1151232] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The evolutionarily conserved Wnt/Wingless signal transduction pathway directs cell proliferation, cell fate, and cell death during development in metazoans and is inappropriately activated in several types of cancer. The majority of colorectal carcinomas contain truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor, a negative regulator of Wnt/Wingless signaling. Here, we demonstrate that Drosophila Apc homologs also have an activating role in both physiological and ectopic Wingless signaling. The Apc amino terminus is important for its activating function, whereas the beta-catenin binding sites are dispensable. Apc likely promotes Wingless transduction through down-regulation of Axin, a negative regulator of Wingless signaling. Given the evolutionary conservation of APC in Wnt signal transduction, an activating role may also be present in vertebrates with relevance to development and cancer.
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Affiliation(s)
- Carter M Takacs
- Department of Genetics and the Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH 03755, USA
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10
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Abstract
Xenopus is an established and powerful model system for the study of Wnt signaling in vertebrates. Above all, the relatively large size of the embryos enables microinjection experiments, which have led to key discoveries not only about the functional role of Wnt signaling in vertebrate embryos, but also about the molecular mechanisms of Wnt signaling in vertebrate cells. A major advantage of the Xenopus model is the ability to obtain large numbers of embryos, which develop relatively rapidly and which can be studied in natural separation from sentient adult parental animals. In order to obtain Xenopus embryos, ovulation in females is induced with a simple hormone injection, the eggs collected and fertilized with sperm from males. The Xenopus model system has been further strengthened by recent advances such as morpholino technology and efficient transgenic methods, as well as the development of Xenopus tropicalis as a diploid genetic model system with a shorter generation time and a genome similar to higher vertebrates.
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Affiliation(s)
- Stefan Hoppler
- School of Medical Sciences, University of Aberdeen, Aberdeen, Scotland, UK
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11
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Mahadevaiyer S, Xu C, Gumbiner BM. Characterization of a 60S complex of the adenomatous polyposis coli tumor suppressor protein. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1773:120-30. [PMID: 17126424 PMCID: PMC1808328 DOI: 10.1016/j.bbamcr.2006.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 09/27/2006] [Accepted: 10/13/2006] [Indexed: 10/24/2022]
Abstract
The tumor suppressor protein adenomatous polyposis coli (APC) is a multifunctional protein with a well characterized role in the Wnt signal transduction pathway and roles in cytoskeletal regulation and cell polarity. The soluble pool of APC protein in colon epithelial tumor cells exists in two distinct complexes fractionating at approximately 20S and approximately 60S in size. The 20S complex contains components of the beta-catenin destruction complex and probably functions in the Wnt pathway. In this study, we characterized the molecular nature of the 60S APC- containing complex by examining known potential binding partners of APC. 60S APC did not contain EB1 or diaphanous, proteins that have been reported to interact with APC and are implicated in microtubule plus end stabilization. Nor did the two other microtubule associated proteins, MAP4 or KAP3, which is thought to link APC to kinesin motor proteins, associate with the 60S complex. Minor fractions of alpha-tubulin, gamma-tubulin and IQGAP1, a Rac1 and CDC42 effector that interacts with APC, specifically associated with APC in the 60S fraction. We propose that 60S APC is a discrete high molecular weight complex with a novel function in cytoskeletal regulation in epithelial cells apart from its well established role in targeting catenin destruction or its proposed role in microtubule plus end stabilization.
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Affiliation(s)
- Sreekala Mahadevaiyer
- Department of Cell Biology, University of Virginia Health Sciences Center, 1300 Jefferson Park Avenue, Charlottesville, VA 22908, USA
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12
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Scully C, Bagan JV, Black M, Carrozzo M, Eisen D, Escudier M, Farthing P, Kuffer R, Lo Muzio L, Mignogna M, Porter SR. Number 1Epithelial biology. Oral Dis 2005; 11:58-71. [PMID: 15752078 DOI: 10.1111/j.1601-0825.2004.01078.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The oral mucous membrane has features similar to skin but also differs in several ways. This paper reviews the aspects of epithelial biology necessary for an understanding of the vesiculoerosive disorders.
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Affiliation(s)
- C Scully
- Eastman Dental Institute, University College London, 256 Grays Inn Road, London WC1X, UK.
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13
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Abstract
The Adenomatous Polyposis coli (APC) gene is mutated or lost in most colon cancers, and the APC protein has emerged as a multifunctional protein that is not only involved in the Wnt-regulated degradation of -catenin, but also regulates cytoskeletal proteins and thus plays a role in cell migration, cell adhesion, and mitosis. The gut epithelium is uniquely dependent on an intricate balance between a number of fundamental cellular processes including migration, differentiation, adhesion, apoptosis, and mitosis. In this review, I discuss the molecular mechanisms that govern the various functions of APC and their relationship to the role of APC in colon cancer.
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Affiliation(s)
- Inke S Näthke
- Cell and Developmental Biology, University of Dundee Dundee DD1 5EH, Scotland, United Kingdom.
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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: 423] [Impact Index Per Article: 22.3] [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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Deroo T, Denayer T, Van Roy F, Vleminckx K. Global Inhibition of Lef1/Tcf-dependent Wnt Signaling at Its Nuclear End Point Abrogates Development in Transgenic Xenopus Embryos. J Biol Chem 2004; 279:50670-5. [PMID: 15371453 DOI: 10.1074/jbc.m408969200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Analysis of canonical Wnt signaling during vertebrate development by means of knock-out or transgenic approaches is often hampered by functional redundancy as well as pathway bifurcations downstream of the manipulated components. We report the design of an optimized chimera capable of blocking transcriptional activation of Lef1/Tcf-beta-catenin target genes, thus enabling intervention with the canonical Wnt pathway at its nuclear end point. This construct was made hormone-inducible, both functionally and transcriptionally, and was transgenically integrated in Xenopus embryos. Down-regulation of target genes was clearly observed upon treatment of these embryos with dexamethasone. In addition, exposure of variously aged transgenic embryos to dexamethasone caused complex phenotypes with many new but also several recognizable features stemming from inhibition of canonical Wnt signaling. At least in some tissues, a significant reduction in cell proliferation and an increase in programmed cell death appeared to underlie these phenotypes. Our inducible transgenic system can serve a broad range of experimental settings designed to unveil new functional aspects of Lef1/Tcf-beta-catenin signaling during vertebrate embryogenesis.
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MESH Headings
- Animals
- Animals, Genetically Modified
- Antineoplastic Agents, Hormonal/pharmacology
- Apoptosis
- Blotting, Western
- Bromodeoxyuridine/pharmacology
- Cell Nucleus/metabolism
- Cell Proliferation
- DNA-Binding Proteins/antagonists & inhibitors
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Dexamethasone/pharmacology
- Down-Regulation
- Drosophila
- Embryo, Nonmammalian/metabolism
- Gene Expression Regulation, Developmental
- Genes, Reporter
- Genetic Techniques
- Genetic Vectors
- Homeodomain Proteins/genetics
- Humans
- In Situ Nick-End Labeling
- Lymphoid Enhancer-Binding Factor 1
- Mice
- Microscopy, Fluorescence
- Phenotype
- Plasmids/metabolism
- Promoter Regions, Genetic
- Protein Structure, Tertiary
- Proto-Oncogene Proteins/metabolism
- RNA/chemistry
- RNA/metabolism
- Receptors, Glucocorticoid/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Transcription Factors/antagonists & inhibitors
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription, Genetic
- Transcriptional Activation
- Transgenes
- Wnt Proteins
- Xenopus laevis
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Affiliation(s)
- Tom Deroo
- Developmental Biology Unit, Ghent University-Flanders Interuniversity Institute for Biotechnology, Belgium
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16
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Choi J, Park SY, Costantini F, Jho EH, Joo CK. Adenomatous Polyposis Coli Is Down-regulated by the Ubiquitin-Proteasome Pathway in a Process Facilitated by Axin. J Biol Chem 2004; 279:49188-98. [PMID: 15355978 DOI: 10.1074/jbc.m404655200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adenomatous polyposis coli (APC) protein and Axin form a complex that mediates the down-regulation of beta-catenin, a key effector of Wnt signaling. Truncation mutations in APC are responsible for familial and sporadic colorectal tumors due to failure in the down-regulation of beta-catenin. While the regulation of beta-catenin by APC has been extensively studied, the regulation of APC itself has received little attention. Here we show that the level of APC is down-regulated by the ubiquitin-proteasome pathway and that Wnt signaling inhibits the process. The domain responsible for the down-regulation and direct ubiquitination was identified. We also show an unexpected role for Axin in facilitating the ubiquitination-proteasome-mediated down-regulation of APC through the oligomerization of Axin. Our results suggest a new mechanism for the regulation of APC by Axin and Wnt signaling.
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Affiliation(s)
- Jongkyu Choi
- Laboratory of Ophthalmology and Visual Science, The Catholic University of Korea, 505 Banpo-dong, Seocho-ku, Seoul, 137-701, Korea
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17
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Roura S, Martínez D, Piedra J, Miravet S, García de Herreros A, Duñach M. APC 3×15 β-catenin-binding domain potentiates β-catenin association to TBP and upregulates TCF-4 transcriptional activity. Biochem Biophys Res Commun 2003; 309:830-5. [PMID: 13679048 DOI: 10.1016/j.bbrc.2003.08.075] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Beta-catenin plays a dual role as a regulatory component of adherens junctions and as a transcriptional cofactor. The nuclear activity of this protein is controlled by adenomatous polyposis coli (APC) protein. We have analyzed the effect on beta-catenin-dependent transcription of a beta-catenin binding domain present in APC, consisting in three 15-amino acid repeats (APC 3 x 15). Association of this fragment prevents the interaction of beta-catenin with E-cadherin but not with TCF-4. Transfection of this fragment to several cell lines increases the transcriptional activity of the beta-catenin-TCF-4 complex and promotes the translocation of beta-catenin to the nucleus. Moreover, previous binding of APC 3 x 15 facilitates the association of beta-catenin to the TATA box-associated protein. Therefore, APC 3 x 15 domain plays a positive role in the control of transcriptional activity of beta-catenin-TCF-4 and can contribute to explain the role of the truncated forms of APC in colon tumorigenesis.
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Affiliation(s)
- Santiago Roura
- Unitat de Biologia Cel.lular i Molecular, Institut Municipal d'Investigació Mèdica, Universitat Pompeu Fabra, 08003, Barcelona, Spain.
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18
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Landesman Y, Goodenough DA, Paul DL. Xwnt-2 (Xwnt-2b) is maternally expressed in Xenopus oocytes and embryos. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1576:265-8. [PMID: 12084573 DOI: 10.1016/s0167-4781(02)00344-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Xwnt-2 (formerly Xwnt-2b) is a member of the Xwnt-8 class of axis-inducing Wnts. Its zygotic expression is at the prosencephalic-mesencephalic border of the early tadpole brain and above the heart primordium [Mech. Dev. 63 (1997) 199]. Here, we report that Xwnt-2 has an earlier, maternal pattern of expression. It is detected in the oocyte, egg and the developing embryo. Studies of the spatial localization of maternal Xwnt-2 show transcripts in both vegetal and animal blastomeres with enrichment in the animal hemisphere. The identification of maternal Xwnt-2 raises questions about possible roles of dorsalizing Xwnts in axial patterning of the Xenopus embryo.
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Affiliation(s)
- Yosef Landesman
- Department of Neurobiology, Harvard Medical School, 220 Longwood Ave., Boston, MA 02115, USA.
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19
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Cassimeris L, Spittle C. Regulation of microtubule-associated proteins. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 210:163-226. [PMID: 11580206 DOI: 10.1016/s0074-7696(01)10006-9] [Citation(s) in RCA: 158] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Microtubule-associated proteins (MAPs) function to regulate the assembly dynamics and organization of microtubule polymers. Upstream regulation of MAP activities is the major mechanism used by cells to modify and control microtubule assembly and organization. This review summarizes the functional activities of MAPs found in animal cells and discusses how these MAPs are regulated. Mechanisms controlling gene expression, isoform-specific expression, protein localization, phosphorylation, and degradation are discussed. Additional regulatory mechanisms include synergy or competition between MAPs and the activities of cofactors or binding partners. For each MAP it is likely that regulation in vivo reflects a composite of multiple regulatory mechanisms.
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Affiliation(s)
- L Cassimeris
- Department of Biological Sciences, Lehigh University Bethlehem, Pennsylvania 18015, USA
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20
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Yanagawa SI, Matsuda Y, Lee JS, Matsubayashi H, Sese S, Kadowaki T, Ishimoto A. Casein kinase I phosphorylates the Armadillo protein and induces its degradation in Drosophila. EMBO J 2002; 21:1733-42. [PMID: 11927557 PMCID: PMC125941 DOI: 10.1093/emboj/21.7.1733] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Casein kinase I (CKI) was recently reported as a positive regulator of Wnt signaling in vertebrates and Caenorhabditis elegans. To elucidate the function of Drosophila CKI in the wingless (Wg) pathway, we have disrupted its function by double-stranded RNA-mediated interference (RNAi). While previous findings were mainly based on CKI overexpression, this is the first convincing loss-of-function analysis of CKI. Surprisingly, CKIalpha- or CKIepsilon-RNAi markedly elevated the Armadillo (Arm) protein levels in Drosophila Schneider S2R+ cells, without affecting its mRNA levels. Pulse-chase analysis showed that CKI-RNAi stabilizes Arm protein. Moreover, Drosophila embryos injected with CKIalpha double-stranded RNA showed a naked cuticle phenotype, which is associated with activation of Wg signaling. These results indicate that CKI functions as a negative regulator of Wg/Arm signaling. Overexpression of CKIalpha induced hyper-phosphorylation of both Arm and Dishevelled in S2R+ cells and, conversely, CKIalpha-RNAi reduced the amount of hyper-modified forms. His-tagged Arm was phosphorylated by CKIalpha in vitro on a set of serine and threonine residues that are also phosphorylated by Zeste-white 3. Thus, we propose that CKI phosphorylates Arm and stimulates its degradation.
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Affiliation(s)
- Shin-ichi Yanagawa
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-Ku, Kyoto 606-8507 and
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-Ku, Nagoya 464-8601, Japan Present address: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA Corresponding author e-mail:
| | | | - Jong-Seo Lee
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-Ku, Kyoto 606-8507 and
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-Ku, Nagoya 464-8601, Japan Present address: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA Corresponding author e-mail:
| | | | | | - Tatsuhiko Kadowaki
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-Ku, Kyoto 606-8507 and
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-Ku, Nagoya 464-8601, Japan Present address: Department of Pathology, Harvard Medical School, Boston, MA 02115, USA Corresponding author e-mail:
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21
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Lo Muzio L, Pannone G, Staibano S, Mignogna MD, Serpico R, Fanali S, De Rosa G, Piattelli A, Mariggiò MA. p120(cat) Delocalization in cell lines of oral cancer. Oral Oncol 2002; 38:64-72. [PMID: 11755823 DOI: 10.1016/s1368-8375(01)00027-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
UNLABELLED p120(cat) is a novel component of the catenin family, a cytoplasmic molecule closely associated with the cell-cell adhesion molecule E (epithelial)-cadherin, by forming complexes between the cytoplasmic domain of E-cadherin and the cytoskeleton. Recent studies suppose a role for this molecule in human cancers and to date none report its expression in oral squamous cell carcinomas (SCCs). The goal of this study was to evaluate the role of this protein in the oral carcinogenetic process. A linked streptavidin-biotin-alkaline phosphatase technique was used to examine the immunoreactivity and cellular localisation of p120(cat) in five oral epithelial cell lines (NCTC 2544, normal and immortalized keratinocytes; KB, a poorly differentiated SCC cell line; OSC 20, a well differentiated oral SCC cell line; CAL 33 and CAL 27, moderately differentiated oral SCC cell lines) and 10 normal oral epithelium biopsies. RESULTS As already reported for E-cadherin, beta- and gamma-catenin, p120 expression showed a homogeneous membranous localization in normal oral specimens. The intensity of staining for p120 progressively increased from basal and parabasal layers toward the intermediate spinous layer. No staining for p120 was observed in the upper layer. NCTC showed a membranous positivity. OSC 20, CAL 33 and CAL 27 showed a membranous positivity, even if polarized to cell-cell adhesion sites, in 40-50% of cells. OSC 20, CAL 33 and CAL 27 cells showed also a cytoplasmic delocalization. All positive KB cells showed a prevalent cytoplasmic staining and 10% of these cells showed a nuclear delocalization. In cancer cells, p120 showed an inverse relationship with the degree of differentiation for a progressive displacement of the signal toward the cytoplasm or nucleus in dedifferentiated cells. In conclusions, this nuclear delocalization for p120 could suppose its potential involvement in signalling and cancer transformation.
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Affiliation(s)
- L Lo Muzio
- Institute of Dental Sciences, University of Ancona, Ancona, Italy.
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22
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Lo Muzio L. A possible role for the WNT-1 pathway in oral carcinogenesis. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2001; 12:152-65. [PMID: 11345525 DOI: 10.1177/10454411010120020501] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Reductions in cell-cell adhesion and stromal and vascular invasion are essential steps in the progression from localized malignancy to metastatic disease for all cancers. Proteins involved in intercellular adhesion, such as E-cadherin and catenin, probably play an important role in metastatic processes and cellular differentiation. While E-cadherin and beta-catenin expression has been extensively studied in many forms of human cancers, less is known about the role of the Wingless-Type-1 (WNT-1) pathway in human tumors. A large body of genetic and biochemical evidence has identified beta-catenin as a key downstream component of the WNT signaling pathway, and recent studies of colorectal tumors have shown a functional link among beta-catenin, adenomatous polyposis coli gene product (APC), and other components of the WNT-1 pathway. WNT-1 pathway signaling is thought to be mediated via interactions between beta-catenin and members of the LEF-1/TCF family of transcription factors. The WNT signal stabilizes beta-catenin protein and promotes its accumulation in the cytoplasm and nucleus. In the nucleus, beta-catenin associates with TCF to form a functional transcription factor which mediates the transactivation of target genes involved in the promotion of tumor progression, invasion, and metastasis, such as C-Myc, cyclin D1, c-jun, fra-1, and u-PAR. There is a strong correlation between the ability of the WNT-1 gene to induce beta-catenin accumulation and its transforming potential in vivo, suggesting that the WNT-1 gene activates an intracellular signaling pathway that can induce the morphological transformation of cells. For these reasons, data obtained from the study of the WNT-1 pathway could be important in our understanding of the mechanisms of epithelial tumors, in general, and probably also of oral squamous cell carcinoma, in particular.
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Affiliation(s)
- L Lo Muzio
- Institute of Dental Sciences, University of Ancona, Italy.
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23
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Abstract
Xenopus has been widely used to study early embryogenesis because the embryos allow for efficient functional assays of gene products by the overexpression of RNA. The first asymmetry of the embryo is initiated during oogenesis and is manifested by the darkly pigmented animal hemisphere and lightly pigmented vegetal hemisphere. Upon fertilization a second asymmetry, the dorsal-ventral asymmetry, is established, with the sperm entry site defining the prospective ventral region. During the cleavage stage, a vegetal cortical cytoplasm (VCC)/beta-catenin signaling pathway is differentially activated on the prospective dorsal side of the embryo. The overlapping of the VCC/beta-catenin and transforming growth factor beta (TGF-beta) pathways in the dorsal vegetal quadrant specifies dorsal-vental axis formation by regulating formation of the Spemann organizer, including the anterior endomesoderm. The organizer initiates gastrulation to form a triploblastic embryo in which the mesoderm layer is located between the ectoderm layer and the endoderm layer. The interplay between maternal and zygotic TGF-beta s and the T-box transcription factors in the vegetal hemisphere initiates the specification of germ-layer lineages. TGF-beta signaling originating from the vegetal region induces mesoderm in the equatorial region, and initiates endoderm differentiation directly in the vegetal region. The ectoderm develops from the animal region, which does not come into contact with the vegetal TGF-beta signals. A large number of the downstream components and transcriptional targets of early developmental pathways have been identified and characterized. This review gives an overview of recent advances in the understanding of the functional roles and interactions of the molecular players important for axis determination and germ-layer specification during early Xenopus embryogenesis.
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Affiliation(s)
- A P Chan
- Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA
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24
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Reinacher-Schick A, Gumbiner BM. Apical membrane localization of the adenomatous polyposis coli tumor suppressor protein and subcellular distribution of the beta-catenin destruction complex in polarized epithelial cells. J Cell Biol 2001; 152:491-502. [PMID: 11157977 PMCID: PMC2196003 DOI: 10.1083/jcb.152.3.491] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2000] [Accepted: 12/13/2000] [Indexed: 02/06/2023] Open
Abstract
The adenomatous polyposis coli (APC) protein is implicated in the majority of hereditary and sporadic colon cancers. APC is known to function as a tumor suppressor through downregulation of beta-catenin as part of a high molecular weight complex known as the beta-catenin destruction complex. The molecular composition of the intact complex and its site of action in the cell are still not well understood. Reports on the subcellular localization of APC in various cell systems have differed significantly and have been consistent with an association with a cytosolic complex, with microtubules, with the nucleus, or with the cortical actin cytoskeleton. To better understand the role of APC and the destruction complex in colorectal cancer, we have begun to characterize and isolate these complexes from confluent polarized human colon epithelial cell monolayers and other epithelial cell types. Subcellular fractionation and immunofluorescence microscopy reveal that a predominant fraction of APC associates tightly with the apical plasma membrane in a variety of epithelial cell types. This apical membrane association is not dependent on the mutational status of either APC or beta-catenin. An additional pool of APC is cytosolic and fractionates into two distinct high molecular weight complexes, 20S and 60S in size. Only the 20S fraction contains an appreciable portion of the cellular axin and small but detectable amounts of glycogen synthase kinase 3beta and beta-catenin. Therefore, it is likely to correspond to the previously characterized beta-catenin destruction complex. Dishevelled is almost entirely cytosolic, but does not significantly cofractionate with the 20S complex. The disproportionate amount of APC in the apical membrane and the lack of other destruction complex components in the 60S fraction of APC raise questions about whether these pools of APC take part in the degradation of beta-catenin, or alternatively, whether they could be involved in other functions of the protein that still must be determined.
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Affiliation(s)
- Anke Reinacher-Schick
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021
| | - Barry M. Gumbiner
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021
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25
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Abstract
The Wnt signaling pathway plays critical roles in embryonic development and tumorigenesis. Stimulation of the Wnt pathway results in the accumulation of a nuclear beta-catenin/Tcf complex, activating Wnt target genes. A crystal structure of beta-catenin bound to the beta-catenin binding domain of Tcf3 (Tcf3-CBD) has been determined. The Tcf3-CBD forms an elongated structure with three binding modules that runs antiparallel to beta-catenin along the positively charged groove formed by the armadillo repeats. Structure-based mutagenesis defines three sites in beta-catenin that are critical for binding the Tcf3-CBD and are differentially involved in binding APC, cadherin, and Axin. The structural and mutagenesis data reveal a potential target for molecular drug design studies.
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Affiliation(s)
- T A Graham
- Department of Biological Structure University of Washington 98195, Seattle, WA, USA
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26
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Abstract
The Wnt/Wingless signaling transduction pathway plays an important role in both embryonic development and tumorigenesis. beta-Catenin, a key component of the Wnt signaling pathway, interacts with the TCF/LEF family of transcription factors and activates transcription of Wnt target genes. Recent studies have revealed that a number of proteins such as, the tumor suppressor APC and Axin are involved in the regulation of the Wnt signaling pathway. Furthermore, mutations in APC or beta-catenin have been found to be responsible for the genesis of human cancers.
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Affiliation(s)
- T Akiyama
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, 113-0032, Tokyo, Japan.
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27
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Ratcliffe MJ, Itoh K, Sokol SY. A positive role for the PP2A catalytic subunit in Wnt signal transduction. J Biol Chem 2000; 275:35680-3. [PMID: 11007767 DOI: 10.1074/jbc.c000639200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase-2A (PP2A) is a multisubunit serine/threonine phosphatase involved in intracellular signaling, gene regulation, and cell cycle progression. Different subunits of PP2A bind to Axin and Adenomatous Polyposis Coli, components of the Wnt signal transduction pathway. Using early Xenopus embryos, we studied how PP2A functions in Wnt signal transduction. The catalytic subunit of PP2A (PP2A-C) potentiated secondary axis induction and Siamois reporter gene activation by Dishevelled, a component of the Wnt pathway, indicating a positive regulatory role of this enzyme in Wnt signaling. In contrast, small t antigen, an antagonist of PP2A-C, inhibited Dishevelled-mediated signal transduction, as did the regulatory PP2A-B'epsilon subunit, consistent with the requirement of PP2A function in this pathway. Although Wnt signaling is thought to occur via regulation of beta-catenin degradation, PP2A-C did not significantly affect beta-catenin stability. Moreover, the pathway activated by a stabilized form of beta-catenin was sensitive to PP2A-C and its inhibitors, suggesting that PP2A-C acts downstream of beta-catenin. Because previous work has suggested that PP2A can act upstream of beta-catenin, we propose that PP2A regulates the Wnt pathway at multiple levels.
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Affiliation(s)
- M J Ratcliffe
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Molecular Medicine Unit, Beth Israel Deaconess Medical Center, Boston, Massachessetts 02215, USA.
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28
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Fukui A, Kishida S, Kikuchi A, Asashima M. Effects of rat Axin domains on axis formation in Xenopus embryos. Dev Growth Differ 2000; 42:489-98. [PMID: 11041490 DOI: 10.1046/j.1440-169x.2000.00536.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Wnt signaling plays an important role in axis formation in early vertebrate development. Axin is one Wnt signaling regulator that inhibits this pathway. The effects of the injection of mRNA of several rat Axin (rAxin) mutants on axis formation in Xenopus embryos were examined. It was found that rAxin mutants containing only a regulation of G-protein signaling (RGS) domain fragment or with deletion of the RGS domain induced axis formation. Because the RGS domain is a major adenomatous polyposis coli gene product (APC)-binding domain, APC association with glycogen synthase kinase 3beta (GSK3beta) on the Axin molecule may be important in inhibition of axis formation. The ventralizing activities of wild-type rAxin and a mutant in which the Dishevelled and Axin (DIX) domain was deleted (deltaDIX mutant) were examined. Histological examination and gene expression revealed that the ventralizing activity of the deltaDIX mutant was weaker than that of wild-type rAxin. This finding suggests that the C-terminus of rAxin contributes to the inhibition of Wnt signaling in Xenopus embryos. Furthermore, an rAxin mutant that contained both the RGS and GSK3beta-binding domains affected both the dorsal and ventral sides of blastomeres, mediated ectodermal fate and induced expansion of notochord and/or endoderm, but did not induce axis formation.
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Affiliation(s)
- A Fukui
- Departmetn of Life Sciences (Biology), University of Tokyo, Japan
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29
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Affiliation(s)
- P Polakis
- Department of Molecular Oncology, Genentech Inc., South San Francisco, California 94080 USA.
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30
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Young J, Simms LA, Tarish J, Buttenshaw R, Knight N, Anderson GJ, Bell A, Leggett B. A family with attenuated familial adenomatous polyposis due to a mutation in the alternatively spliced region of APC exon 9. Hum Mutat 2000; 11:450-5. [PMID: 9603437 DOI: 10.1002/(sici)1098-1004(1998)11:6<450::aid-humu5>3.0.co;2-p] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A family is presented with attenuated familial adenomatous polyposis of variable phenotype. The clinical features range from sparse right-sided polyposis and cancer in the proximal colon at the age of 34 to pan-colonic polyposis and cancer at the age of 68. Rectal sparing is common to all affected members. Heteroduplex analysis detected bands of altered mobility in exon 9 of the APC gene in all affected family members. Subsequently, a frameshift mutation was found in the alternatively spliced region of exon 9 at codon 398 which resulted in a stop signal 4 codons downstream. Alternatively spliced transcripts that delete the mutation were readily amplified from normal colonic mucosa and therefore create a mechanism for the attenuated phenotype seen in this family.
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Affiliation(s)
- J Young
- Glaxo Conjoint Gastroenterology Laboratory, Royal Brisbane Hospital Foundation Clinical Research Centre, Australia.
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31
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Abstract
The adenomatous polyposis coli (APC) gene was first identified as the gene mutated in an inherited syndrome of colon cancer predisposition known as familial adenomatous polyposis coli (FAP). Mutation of APC is also found in 80% of all colorectal adenomas and carcinomas and is one of the earliest mutations in colon cancer progression. Similar to other tumor suppressor genes, both APC alleles are inactivated by mutation in colon tumors, resulting in the loss of full-length protein in tumor cells. The functional significance of altering APC is the dysregulation of several physiologic processes that govern colonic epithelial cell homeostasis, which include cell cycle progression, migration, differentiation, and apoptosis. Roles for APC in some of these processes are in large part attributable to its ability to regulate cytosolic levels of the signaling molecule beta-catenin and to affect the transcriptional profile in cells. This article summarizes numerous genetic, biochemical, and cell biologic studies on the mechanisms of APC-mediated tumor suppression. Mouse models of FAP, in which the APC gene has been genetically inactivated, have been particularly useful in testing therapeutic and chemopreventive strategies. These data have significant implications for colorectal cancer treatment approaches as well as for understanding other disease genes and cancers of other tissue types.
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Affiliation(s)
- K H Goss
- Howard Hughes Medical Institute, Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
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32
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Hoier EF, Mohler WA, Kim SK, Hajnal A. The Caenorhabditis elegans APC-related gene apr-1 is required for epithelial cell migration and Hox gene expression. Genes Dev 2000. [DOI: 10.1101/gad.14.7.874] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Inactivation of the Caenorhabditis elegans APC-related gene (apr-1) has pointed at two separate functions of apr-1. First, apr-1 is required for the migration of epithelial cells during morphogenesis of the embryo. In this process, APR-1 may act in a Cadherin/α-Catenin/β-Catenin complex as a component of adherens junctions. Second, apr-1 is required for Hox gene expression, most likely by positively regulating the activity of the Wingless signaling pathway. During embryogenesis, apr-1 is required for the expression ofceh-13 labial in anterior seam and muscle cells and during larval development, apr-1 is necessary for the expression of lin-39 deformed in the vulval precursor cells. Thus, APR-1 may positively regulate the activity of the β-Catenin/Armadillo-related proteins HMP-2 in migrating epithelial cells and BAR-1 in the vulval precursor cells.
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33
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Hoier EF, Mohler WA, Kim SK, Hajnal A. The Caenorhabditis elegans APC-related gene apr-1 is required for epithelial cell migration and Hox gene expression. Genes Dev 2000; 14:874-86. [PMID: 10766743 PMCID: PMC316495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Inactivation of the Caenorhabditis elegans APC-related gene (apr-1) has pointed at two separate functions of apr-1. First, apr-1 is required for the migration of epithelial cells during morphogenesis of the embryo. In this process, APR-1 may act in a Cadherin/alpha-Catenin/beta-Catenin complex as a component of adherens junctions. Second, apr-1 is required for Hox gene expression, most likely by positively regulating the activity of the Wingless signaling pathway. During embryogenesis, apr-1 is required for the expression of ceh-13 labial in anterior seam and muscle cells and during larval development, apr-1 is necessary for the expression of lin-39 deformed in the vulval precursor cells. Thus, APR-1 may positively regulate the activity of the beta-Catenin/Armadillo-related proteins HMP-2 in migrating epithelial cells and BAR-1 in the vulval precursor cells.
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Affiliation(s)
- E F Hoier
- Division of Cancer Research, Department of Pathology, University of Zürich, CH-8091 Zürich, Switzerland
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34
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Giannini AL, Vivanco MM, Kypta RM. Analysis of beta-catenin aggregation and localization using GFP fusion proteins: nuclear import of alpha-catenin by the beta-catenin/Tcf complex. Exp Cell Res 2000; 255:207-20. [PMID: 10694436 DOI: 10.1006/excr.1999.4785] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
beta-Catenin plays essential roles in cell adhesion, by associating with cadherins, and as a signaling molecule, by interacting with the Tcf/LEF-1 family of transcription factors. In order to study the protein-protein interactions of beta-catenin in living cells, we fused it to green fluorescent protein (GFP). GFP-beta-catenin was incorporated into cell junctions but also accumulated in the nucleus, where it formed rod-like structures. The carboxyl-terminal armadillo repeats of GFP-beta-catenin were sufficient for nuclear localization, but formation of rods required the armadillo repeats and sequences in both the amino- and the carboxyl-terminal domains. Rod formation was prevented by coexpression of N-cadherin, APC, and Tcf-4, which bind to the armadillo repeats of beta-catenin, but not by coexpression of alpha-catenin, although alpha-catenin expression did prevent accumulation of beta-catenin in the nucleus. Interestingly, when alpha-catenin, beta-catenin, and Tcf-4 were coexpressed they colocalized in the nucleus, and this correlated with a decrease in beta-catenin/Tcf-dependent transcriptional activity. These results indicate that binding of beta-catenin to Tcf-4 overrides the function of alpha-catenin to sequester beta-catenin in the cytoplasm and suggest that alpha-catenin can regulate beta-catenin signaling in the nucleus.
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Affiliation(s)
- A L Giannini
- MRC Laboratory for Molecular Cell Biology, University College London, London, WC1E 6BT
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35
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Salic A, Lee E, Mayer L, Kirschner MW. Control of beta-catenin stability: reconstitution of the cytoplasmic steps of the wnt pathway in Xenopus egg extracts. Mol Cell 2000; 5:523-32. [PMID: 10882137 DOI: 10.1016/s1097-2765(00)80446-3] [Citation(s) in RCA: 297] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulation of beta-catenin degradation by intracellular components of the wnt pathway was reconstituted in cytoplasmic extracts of Xenopus eggs and embryos. The ubiquitin-dependent beta-catenin degradation in extracts displays a biochemical requirement for axin, GSK3, and APC. Axin dramatically accelerates while dishevelled inhibits beta-catenin turnover. Through another domain, dishevelled recruits GBP/Frat1 to the APC-axin-GSK3 complex. Our results confirm and extend models in which inhibition of GSK3 has two synergistic effects: (1) reduction of APC phosphorylation and loss of affinity for beta-catenin and (2) reduction of beta-catenin phosphorylation and consequent loss of its affinity for the SCF ubiquitin ligase complex. Dishevelled thus stabilizes beta-catenin, which can dissociate from the APC/axin complex and participate in transcriptional activation.
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Affiliation(s)
- A Salic
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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36
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Farr GH, Ferkey DM, Yost C, Pierce SB, Weaver C, Kimelman D. Interaction among GSK-3, GBP, axin, and APC in Xenopus axis specification. J Cell Biol 2000; 148:691-702. [PMID: 10684251 PMCID: PMC2169372 DOI: 10.1083/jcb.148.4.691] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/1999] [Accepted: 01/10/2000] [Indexed: 11/22/2022] Open
Abstract
Glycogen synthase kinase 3 (GSK-3) is a constitutively active kinase that negatively regulates its substrates, one of which is beta-catenin, a downstream effector of the Wnt signaling pathway that is required for dorsal-ventral axis specification in the Xenopus embryo. GSK-3 activity is regulated through the opposing activities of multiple proteins. Axin, GSK-3, and beta-catenin form a complex that promotes the GSK-3-mediated phosphorylation and subsequent degradation of beta-catenin. Adenomatous polyposis coli (APC) joins the complex and downregulates beta-catenin in mammalian cells, but its role in Xenopus is less clear. In contrast, GBP, which is required for axis formation in Xenopus, binds and inhibits GSK-3. We show here that GSK-3 binding protein (GBP) inhibits GSK-3, in part, by preventing Axin from binding GSK-3. Similarly, we present evidence that a dominant-negative GSK-3 mutant, which causes the same effects as GBP, keeps endogenous GSK-3 from binding to Axin. We show that GBP also functions by preventing the GSK-3-mediated phosphorylation of a protein substrate without eliminating its catalytic activity. Finally, we show that the previously demonstrated axis-inducing property of overexpressed APC is attributable to its ability to stabilize cytoplasmic beta-catenin levels, demonstrating that APC is impinging upon the canonical Wnt pathway in this model system. These results contribute to our growing understanding of how GSK-3 regulation in the early embryo leads to regional differences in beta-catenin levels and establishment of the dorsal axis.
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Affiliation(s)
- Gist H. Farr
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
| | - Denise M. Ferkey
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
| | - Cynthia Yost
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
| | - Sarah B. Pierce
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
| | - Carole Weaver
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
| | - David Kimelman
- Department of Biochemistry and Center for Developmental Biology, University of Washington, Seattle, Washington 98195-7350
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37
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Seidensticker MJ, Behrens J. Biochemical interactions in the wnt pathway. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1495:168-82. [PMID: 10656974 DOI: 10.1016/s0167-4889(99)00158-5] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The wnt signal transduction pathway is involved in many differentiation events during embryonic development and can lead to tumor formation after aberrant activation of its components. The cytoplasmic component beta-catenin is central to the transmission of wnt signals to the nucleus: in the absence of wnts beta-catenin is constitutively degraded in proteasomes, whereas in the presence of wnts beta-catenin is stabilized and associates with HMG box transcription factors of the LEF/TCF family. In tumors, beta-catenin degradation is blocked by mutations of the tumor suppressor gene APC (adenomatous polyposis coli), or of beta-catenin itself. As a consequence, constitutive TCF/beta-catenin complexes are formed and activate oncogenic target genes. This review discusses the mechanisms that silence the pathway in cells that do not receive a wnt signal and goes on to describe the regulatory steps involved in the activation of the pathway.
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Affiliation(s)
- M J Seidensticker
- Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13122, Berlin, Germany
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Thorpe CJ, Schlesinger A, Bowerman B. Wnt signalling in Caenorhabditis elegans: regulating repressors and polarizing the cytoskeleton. Trends Cell Biol 2000; 10:10-7. [PMID: 10603471 DOI: 10.1016/s0962-8924(99)01672-4] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Wnt proteins are secreted, cysteine-rich glycoprotein ligands with numerous roles during animal development. Recent studies of endoderm induction during embryogenesis in the nematode Caenorhabditis elegans challenge the prevailing view that Wnt signalling specifies cell fate by converting transcriptional repressors into activators. Instead, a mitogen-activated protein kinase (MAPK)-related pathway converges with Wnt signalling in C. elegans to relieve transcriptional repression. Furthermore, Wnt signalling induces endoderm in part by aligning the mitotic spindle in a responding cell along the anterior-posterior body axis. To orient mitotic spindles, Wnt signalling might directly target the cytoskeleton, prior to any regulation of gene transcription in responding cells.
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Affiliation(s)
- C J Thorpe
- Howard Hughes Medical Institute and the Dept of Pharmacology, University of Washington, Pharmacology Box 357370, Seattle, WA 98195-7370, USA
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Miller JR, Hocking AM, Brown JD, Moon RT. Mechanism and function of signal transduction by the Wnt/beta-catenin and Wnt/Ca2+ pathways. Oncogene 1999; 18:7860-72. [PMID: 10630639 DOI: 10.1038/sj.onc.1203245] [Citation(s) in RCA: 533] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Communication between cells is often mediated by secreted signaling molecules that bind cell surface receptors and modulate the activity of specific intracellular effectors. The Wnt family of secreted glycoproteins is one group of signaling molecules that has been shown to control a variety of developmental processes including cell fate specification, cell proliferation, cell polarity and cell migration. In addition, mis-regulation of Wnt signaling can cause developmental defects and is implicated in the genesis of several human cancers. The importance of Wnt signaling in development and in clinical pathologies is underscored by the large number of primary research papers examining various aspects of Wnt signaling that have been published in the past several years. In this review, we will present a synopsis of current research with particular attention paid to molecular mechanism of Wnt signal transduction and how the mis-regulation of Wnt signaling leads to cancer.
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Affiliation(s)
- J R Miller
- Department of Pharmacology and Center for Developmental Biology, Howard Hughes Medical Institute, University of Washington, Seattle 98195, USA
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40
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Strovel ET, Sussman DJ. Transient overexpression of murine dishevelled genes results in apoptotic cell death. Exp Cell Res 1999; 253:637-48. [PMID: 10585287 DOI: 10.1006/excr.1999.4700] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Dishevelled (Dvl) gene family encodes cytoplasmic proteins that are implicated in Wnt signal transduction. In mammals, the manner in which Wnt signals are transduced remains unclear. The biochemical and molecular mechanisms defining the Wnt-1 pathway are of great interest because of its important role in development and its activation in murine breast tumors. In order to elucidate Dvl's role in Wnt signaling, we attempted to overexpress Dvl in cells, but were unable to obtain stable cell lines. We show here that the overexpression of Dvl genes alters nuclear and cellular morphology of COS-1 and C57MG cells and causes cell death due to the induction of apoptosis. Deletion studies demonstrate that all three conserved domains of Dvl (DIX, PDZ, and DEP) are required for Dvl-mediated cell death. Coexpression of protein phosphatase 2Calpha, a Dvl-interacting protein identified in yeast two-hybrid studies, protects cells from the cell death observed in cells overexpressing Dvl alone. Furthermore, the adenomatous polyposis coli (APC) gene product appears to be required for Dvl-mediated cell death. The relevance of these findings to Wnt signal transduction, as well as to developmental processes and disease, are discussed.
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Affiliation(s)
- E T Strovel
- Division of Human Genetics, University of Maryland at Baltimore, 655 West Baltimore Street, Room 11-049, Baltimore, Maryland 21201, USA
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Baker JC, Beddington RS, Harland RM. Wnt signaling in Xenopus embryos inhibits bmp4 expression and activates neural development. Genes Dev 1999; 13:3149-59. [PMID: 10601040 PMCID: PMC317181 DOI: 10.1101/gad.13.23.3149] [Citation(s) in RCA: 253] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/1999] [Accepted: 10/12/1999] [Indexed: 11/24/2022]
Abstract
We report a new role for Wnt signaling in the vertebrate embryo: the induction of neural tissue from ectoderm. Early expression of mouse wnt8, Xwnt8, beta-catenin, or dominant-negative GSK3 induces the expression of neural-specific markers and inhibits the expression of Bmp4 in Xenopus ectoderm. We show that Wnt8, but not the BMP antagonist Noggin, can inhibit Bmp4 expression at early gastrula stages. Furthermore, inhibition of beta-catenin activity in the neural ectoderm of whole embryos by a truncated TCF results in a decrease in neural development. Therefore, we suggest that a cleavage-stage Wnt signal normally contributes to an early repression of Bmp4 on the dorsal side of the embryo and sensitizes the ectoderm to respond to neural inducing signals from the organizer. The Wnt targets Xnr3 and siamois have been shown previously to have neuralizing activity when overexpressed. However, antagonists of Wnt signaling, dnXwnt8 and Nxfrz8, inhibit Wnt-mediated Xnr3 and siamois induction, but not neural induction, suggesting an alternative mechanism for Bmp repression and neuralization. Conversely, dnTCF blocks both Wnt-mediated Xnr3 and neural induction, suggesting that both pathways require this transcription factor.
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Affiliation(s)
- J C Baker
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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Marikawa Y, Elinson RP. Relationship of vegetal cortical dorsal factors in the Xenopus egg with the Wnt/beta-catenin signaling pathway. Mech Dev 1999; 89:93-102. [PMID: 10559484 DOI: 10.1016/s0925-4773(99)00210-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In Xenopus, the dorsal factor in the vegetal cortical cytoplasm (VCC) of the egg is responsible for axis formation of the embryo. Previous studies have shown that VCC dorsal factor has properties similar to activators of the Wnt/beta-catenin-signaling pathway. In this study, we examined the relationship of the VCC dorsal factor with components of the pathway. First, we tested whether beta-catenin protein, which is known to be localized on the dorsal side of early embryos, accounts for the dorsal axis activity of VCC. Reduction of beta-catenin mRNA and protein in oocytes did not diminish the activity of VCC to induce a secondary axis in recipient embryos. The amount of beta-catenin protein was not enriched in VCC compared to animal cortical cytoplasm, which has no dorsal axis activity. These results indicate that beta-catenin is unlikely to be the VCC dorsal axis factor. Secondly, we examined the effects of four Wnt-pathway-interfering constructs (dominant-negative Xdsh, XGSK3, Axin, and dominant-negative XTcf3) on the ability of VCC to induce expression of the early Wnt target genes, Siamois and Xnr3. The activity of VCC was inhibited by Axin and dominant negative XTcf3 but not by dominant negative Xdsh or XGSK3. We also showed that VCC decreased neither the amount nor the activity of exogenous XGSK3, suggesting that the VCC dorsal factor does not act by affecting XGSK3 directly. Finally, we tested six Wnt-pathway activating constructs (Xwnt8, Xdsh, dominant negative XGSK3, dominant negative Axin, XAPC and beta-catenin) for their responses to the four Wnt-pathway-interfering constructs. We found that only XAPC exhibited the same responses as VCC; it was inhibited by Axin and dominant negative XTcf3 but not by dominant negative Xdsh or XGSK3. Although the connection between XAPC and the VCC dorsal factor is not yet clear, the fact that APC binds Axin suggests that the VCC dorsal factor could act on Axin rather than XGSK3.
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Affiliation(s)
- Y Marikawa
- Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Canada
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Abstract
Wingless/Wnt signaling directs cell-fate choices during embryonic development. In Drosophila, Wingless signaling mediates endoderm induction and the establishment of segment polarity in the developing embryo. The fly Wingless cascade is strikingly similar to the vertebrate Wnt signaling pathway, which controls a number of key developmental decisions such as dorsal-ventral patterning in Xenopus. Factors of the TCF/LEF HMG domain family (Tcfs) have recently been established as the downstream effectors of the Wingless/Wnt signal transduction pathways. Upon Wingless/Wnt signaling, a cascade is initiated that results in the accumulation of cytoplasmic beta-catenin (or its fly homolog, Armadillo). There is also a concomitant translocation of beta-catenin/Armadillo to the nucleus, where it interacts with a specific sequence motif at the N terminus of Tcfs to generate a transcriptionally active complex. This bipartite transcription factor is targeted to the upstream regulatory regions of Tcf target genes including Siamois and Nodal related gene-3 in Xenopus, engrailed and Ultrabithorax in Drosophila via the sequence-specific HMG box, and mediates their transcriptional activation by virtue of transactivation domains contributed by beta-catenin/Armadillo. In the absence of Wingless/Wnt signals, a key negative regulator of the pathway, GSK3 beta, is activated, which mediates the downregulation of cytoplasmic beta-catenin/Armadillo via the ubiquitin-proteasome pathway. In the absence of nuclear beta-catenin, the Tcfs recruit the corepressor protein Groucho to the target gene enhancers and actively repress their transcription. An additional corepressor protein, CREB-binding protein (CBP), may also be involved in this repression of Tcf target gene activity. Several other proteins, including adenomatous polyposis coli (APC), GSK3 beta, and Axin/Conductin, are instrumental in the regulation of beta-catenin/Armadillo. In APC-deficient colon carcinoma cell lines, beta-catenin accumulates and is constitutively complexed with nuclear Tcf-4. A proportion of APC wild-type colon carcinomas and melanomas also contains constitutive nuclear Tcf-4/beta-catenin complexes as a result of dominant mutations in the N terminus of beta-catenin that render it insensitive to downregulation by APC, GSK3 beta, and Axin/Conductin. This results in the unregulated expression of Tcf-4 target genes such as c-myc. Based on the established role for Tcf-4 in maintaining intestinal stem cells it is likely that deregulation of c-myc expression as a result of constitutive Tcf-4/beta-catenin activity promotes uncontrolled intestinal cell proliferation. This would readily explain the formation of intestinal polyps during colon carcinogenesis. Similar mechanisms leading to deregulation of Tcf target gene activity are likely to be involved in melanoma and other forms of cancer.
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Affiliation(s)
- N Barker
- Department of Immunology, University Hospital, Utrecht, The Netherlands
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Abstract
Adenomatous polyposis coli (APC) is an important tumour suppressor in the human colon. It is conserved between human and flies, and promotes, together with Axin and glycogen synthase kinase 3 (GSK3), the degradation of the Wnt-signalling effector beta-catenin. Recent experiments have shaped our understanding of how Axin and GSK3 function but the role of APC in this process remains elusive.
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Affiliation(s)
- M Bienz
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, UK.
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McCartney BM, Dierick HA, Kirkpatrick C, Moline MM, Baas A, Peifer M, Bejsovec A. Drosophila APC2 is a cytoskeletally-associated protein that regulates wingless signaling in the embryonic epidermis. J Cell Biol 1999; 146:1303-18. [PMID: 10491393 PMCID: PMC2156123 DOI: 10.1083/jcb.146.6.1303] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/1999] [Accepted: 08/09/1999] [Indexed: 01/11/2023] Open
Abstract
The tumor suppressor adenomatous polyposis coli (APC) negatively regulates Wingless (Wg)/Wnt signal transduction by helping target the Wnt effector beta-catenin or its Drosophila homologue Armadillo (Arm) for destruction. In cultured mammalian cells, APC localizes to the cell cortex near the ends of microtubules. Drosophila APC (dAPC) negatively regulates Arm signaling, but only in a limited set of tissues. We describe a second fly APC, dAPC2, which binds Arm and is expressed in a broad spectrum of tissues. dAPC2's subcellular localization revealed colocalization with actin in many but not all cellular contexts, and also suggested a possible interaction with astral microtubules. For example, dAPC2 has a striking asymmetric distribution in neuroblasts, and dAPC2 colocalizes with assembling actin filaments at the base of developing larval denticles. We identified a dAPC2 mutation, revealing that dAPC2 is a negative regulator of Wg signaling in the embryonic epidermis. This allele acts genetically downstream of wg, and upstream of arm, dTCF, and, surprisingly, dishevelled. We discuss the implications of our results for Wg signaling, and suggest a role for dAPC2 as a mediator of Wg effects on the cytoskeleton. We also speculate on more general roles that APCs may play in cytoskeletal dynamics.
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Affiliation(s)
- Brooke M. McCartney
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280
| | - Herman A. Dierick
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500
| | - Catherine Kirkpatrick
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280
| | - Melissa M. Moline
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500
| | - Annette Baas
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280
| | - Mark Peifer
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280
| | - Amy Bejsovec
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500
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Willert K, Logan CY, Arora A, Fish M, Nusse R. A Drosophila Axin homolog, Daxin, inhibits Wnt signaling. Development 1999; 126:4165-73. [PMID: 10457025 DOI: 10.1242/dev.126.18.4165] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The vertebrate Axin protein, the product of the mouse fused gene, binds to beta-catenin to inhibit Wnt signaling. We have identified a homolog of Axin in Drosophila, Daxin. Using double-stranded RNA interference, we generated loss-of-function phenotypes that are similar to overexpression of the Drosophila Wnt gene wingless (wg). Overexpression of Daxin produces phenotypes similar to loss of wg. In addition, we show that Daxin overexpression can modify phenotypes elicited by wg and another Drosophila Wnt gene, DWnt-2. Using immunoprecipitation of endogenous Daxin protein from embryos we show that Daxin interacts with Armadillo and Zeste-white 3. The loss-of-function and overexpression phenotypes show that Daxin, like its mammalian counterpart, acts as a negative regulator of wg/Wnt signaling.
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Affiliation(s)
- K Willert
- Howard Hughes Medical Institute, Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
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47
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Affiliation(s)
- D Gradl
- Department of Biochemistry, University of Ulm, Albert Einstein Allee 11, D-89081, Ulm, Germany
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48
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Hamada F, Murata Y, Nishida A, Fujita F, Tomoyasu Y, Nakamura M, Toyoshima K, Tabata T, Ueno N, Akiyama T. Identification and characterization of E-APC, a novel Drosophila homologue of the tumour suppressor APC. Genes Cells 1999; 4:465-74. [PMID: 10526234 DOI: 10.1046/j.1365-2443.1999.00272.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Mutations in the adenomatous polyposis coli (APC) tumour suppressor gene are implicated in the genesis of colorectal cancers. The product of the APC gene forms a complex with beta-catenin, glycogen synthase kinase 3beta (GSK-3beta) and Axin/conductin, and induces the degradation of beta-catenin. RESULTS We have identified a novel Drosophila homologue of APC, E-APC, which is similar to but differs in several respects from D-APC. The E-APC cDNA encodes a protein of predicted 1067 amino acids, with seven armadillo repeats, two copies of the 15-amino acid repeat, five copies of the 20-amino acid repeat, and one Axin/conductin binding site. E-APC directly interacts with D-Axin and Armadillo (Arm, the Drosophila homologue of beta-catenin) in vitro, destabilizes intracellular beta-catenin, and suppresses beta-catenin/TCF-regulated transcription in APC-/- colon cancer cells. The E-APC mRNA is ubiquitously expressed throughout all developmental stages in Drosophila. CONCLUSION Our findings suggest that E-APC may be universally involved in the regulation of the Wingless signalling pathway by down-regulating the level of Arm in Drosophila.
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Affiliation(s)
- F Hamada
- Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita 565-0871, Japan. and
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Abstract
Mutations in the adenomatous polyposis coli (APC) gene are associated with most colorectal cancers. The APC protein has been implicated in many aspects of tumour development. This article will discuss recent data suggesting that APC may have multiple functions in the cell. First, APC is a component of the Wnt signalling pathway; second, APC may have a role in cell migration; finally, APC may regulate proliferation and apoptosis.
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Affiliation(s)
- I S Näthke
- Department of Anatomy and Physiology, University of Dundee, UK.
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50
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Yu X, Waltzer L, Bienz M. A new Drosophila APC homologue associated with adhesive zones of epithelial cells. Nat Cell Biol 1999; 1:144-51. [PMID: 10559900 DOI: 10.1038/11064] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Adenomatous polyposis coli protein (APC) is an important tumour suppressor in the human colon epithelium. In a complex with glycogen synthase kinase-3 (GSK-3), APC binds to and destabilizes cytoplasmic ('free') beta-catenin. Here, using a yeast two-hybrid screen for proteins that bind to the Drosophila beta-catenin homologue, Armadillo, we identify a new Drosophila APC homologue, E-APC. E-APC also binds to Shaggy, the Drosophila GSK-3 homologue. Interference with E-APC function produces embryonic phenotypes like those of shaggy mutants. Interestingly, E-APC is concentrated in apicolateral adhesive zones of epithelial cells, along with Armadillo and E-cadherin, which are both integral components of the adherens junctions in these zones. Various mutant conditions that cause dissociation of E-APC from these zones also obliterate the segmental modulation of free Armadillo levels that is normally induced by Wingless signalling. We propose that the Armadillo-destabilizing protein complex, consisting of E-APC, Shaggy, and a third protein, Axin, is anchored in adhesive zones, and that Wingless signalling may inhibit the activity of this complex by causing dissociation of E-APC from these zones.
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Affiliation(s)
- X Yu
- MRC Laboratory of Molecular Biology, Cambridge, UK
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