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Bhattaram P, Penzo-Méndez A, Kato K, Bandyopadhyay K, Gadi A, Taketo MM, Lefebvre V. SOXC proteins amplify canonical WNT signaling to secure nonchondrocytic fates in skeletogenesis. ACTA ACUST UNITED AC 2014; 207:657-71. [PMID: 25452386 PMCID: PMC4259807 DOI: 10.1083/jcb.201405098] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In skeletogenic mesenchyme, SOXC proteins enter the APC–Axin destruction complex to inhibit β-catenin phosphorylation by GSK3 and thereby synergize with canonical WNT signaling to inhibit chondrogenesis. Canonical WNT signaling stabilizes β-catenin to determine cell fate in many processes from development onwards. One of its main roles in skeletogenesis is to antagonize the chondrogenic transcription factor SOX9. We here identify the SOXC proteins as potent amplifiers of this pathway. The SOXC genes, i.e., Sox4, Sox11, and Sox12, are coexpressed in skeletogenic mesenchyme, including presumptive joints and perichondrium, but not in cartilage. Their inactivation in mouse embryo limb bud caused massive cartilage fusions, as joint and perichondrium cells underwent chondrogenesis. SOXC proteins govern these cells cell autonomously. They replace SOX9 in the adenomatous polyposis coli–Axin destruction complex and therein inhibit phosphorylation of β-catenin by GSK3. This inhibition, a crucial, limiting step in canonical WNT signaling, thus becomes a constitutive event. The resulting SOXC/canonical WNT-mediated synergistic stabilization of β-catenin contributes to efficient repression of Sox9 in presumptive joint and perichondrium cells and thereby ensures proper delineation and articulation of skeletal primordia. This synergy may determine cell fate in many processes besides skeletogenesis.
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Affiliation(s)
- Pallavi Bhattaram
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
| | - Alfredo Penzo-Méndez
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
| | - Kenji Kato
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
| | - Kaustav Bandyopadhyay
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
| | - Abhilash Gadi
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
| | - Makoto M Taketo
- Department of Pharmacology, Kyoto University, Kyoto 606-8501, Japan
| | - Véronique Lefebvre
- Department of Cellular and Molecular Medicine, Orthopaedic and Rheumatologic Research Center, Cleveland Clinic Lerner Research Institute, Cleveland, OH 44195
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102
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Yu J, Virshup D. Updating the Wnt pathways. Biosci Rep 2014; 34:e00142. [PMID: 25208913 PMCID: PMC4201215 DOI: 10.1042/bsr20140119] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 09/05/2014] [Accepted: 09/11/2014] [Indexed: 12/12/2022] Open
Abstract
In the three decades since the discovery of the Wnt1 proto-oncogene in virus-induced mouse mammary tumours, our understanding of the signalling pathways that are regulated by the Wnt proteins has progressively expanded. Wnts are involved in an complex signalling network that governs multiple biological processes and cross-talk with multiple additional signalling cascades, including the Notch, FGF (fibroblast growth factor), SHH (Sonic hedgehog), EGF (epidermal growth factor) and Hippo pathways. The Wnt signalling pathway also illustrates the link between abnormal regulation of the developmental processes and disease manifestation. Here we provide an overview of Wnt-regulated signalling cascades and highlight recent advances. We focus on new findings regarding the dedicated Wnt production and secretion pathway with potential therapeutic targets that might be beneficial for patients with Wnt-related diseases.
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Key Words
- adenomatous polyposis coli
- planar cell polarity (pcp)
- wnt
- apc, adenomatous polyposis coli
- bar, bin-amphiphysin-rvs
- cbp, creb (camp response element-binding)-binding protein
- cop, coat protein complex
- crd, cysteine-rich domain
- ctd, c-terminal domain
- ck1α, casein kinase 1 α
- er, endoplasmic reticulum fap, familial adenomatous polyposis
- fdh, focal dermal hypoplasia
- gsk3β, glycogen synthase kinase 3β
- lef, lymphoid enhancer-binding factor
- lrp, lipoprotein receptor-related protein
- ntd, n-terminal domain
- pcp, planar cell polarity
- porcn, protein porcupine
- ror2, receptor tyrosine kinase-like orphan receptor 2
- rspo, r-spondin
- sfrp, secreted frizzled-related protein
- snx-1, sorting nexin-1
- swim, wingless-interacting molecule
- tcf, t cell-specific factor
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Affiliation(s)
- Jia Yu
- *Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - David M. Virshup
- *Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore
- †Institute of Medical Biology, A*STAR, Singapore 138648, Singapore
- ‡Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore
- §Department of Pediatrics, Duke University, Durham, NC 27710, U.S.A
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103
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Demagny H, Araki T, De Robertis EM. The tumor suppressor Smad4/DPC4 is regulated by phosphorylations that integrate FGF, Wnt, and TGF-β signaling. Cell Rep 2014; 9:688-700. [PMID: 25373906 DOI: 10.1016/j.celrep.2014.09.020] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 08/11/2014] [Accepted: 09/11/2014] [Indexed: 12/31/2022] Open
Abstract
Smad4 is a major tumor suppressor currently thought to function constitutively in the transforming growth factor β (TGF-β)-signaling pathway. Here, we report that Smad4 activity is directly regulated by the Wnt and fibroblast growth factor (FGF) pathways through GSK3 and mitogen-activated protein kinase (MAPK) phosphorylation sites. FGF activates MAPK, which primes three sequential GSK3 phosphorylations that generate a Wnt-regulated phosphodegron bound by the ubiquitin E3 ligase β-TrCP. In the presence of FGF, Wnt potentiates TGF-β signaling by preventing Smad4 GSK3 phosphorylations that inhibit a transcriptional activation domain located in the linker region. When MAPK is not activated, the Wnt and TGF-β signaling pathways remain insulated from each other. In Xenopus embryos, these Smad4 phosphorylations regulate germ-layer specification and Spemann organizer formation. The results show that three major signaling pathways critical in development and cancer are integrated at the level of Smad4.
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Affiliation(s)
- Hadrien Demagny
- Howard Hughes Medical Institute and Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA
| | - Tatsuya Araki
- Howard Hughes Medical Institute and Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA
| | - Edward M De Robertis
- Howard Hughes Medical Institute and Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA.
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104
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Gagliardi M, Hernandez A, McGough IJ, Vincent JP. Inhibitors of endocytosis prevent Wnt/Wingless signalling by reducing the level of basal β-catenin/Armadillo. J Cell Sci 2014; 127:4918-26. [PMID: 25236598 PMCID: PMC4231306 DOI: 10.1242/jcs.155424] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
A key step in the canonical Wnt signalling pathway is the inhibition of GSK3β, which results in the accumulation of nuclear β-catenin (also known as CTNNB1), and hence regulation of target genes. Evidence suggests that endocytosis is required for signalling, yet its role and the molecular understanding remains unclear. A recent and controversial model suggests that endocytosis contributes to Wnt signalling by causing the sequestration of the ligand-receptor complex, including LRP6 and GSK3 to multivesicular bodies (MVBs), thus preventing GSK3β from accessing β-catenin. Here, we use specific inhibitors (Dynasore and Dyngo-4a) to confirm the essential role of endocytosis in Wnt/Wingless signalling in human and Drosophila cells. However, we find no evidence that, in Drosophila cells or wing imaginal discs, LRP6/Arrow traffics to MVBs or that MVBs are required for Wnt/Wingless signalling. Moreover, we show that activation of signalling through chemical blockade of GSK3β is prevented by endocytosis inhibitors, suggesting that endocytosis impacts on Wnt/Wingless signalling downstream of the ligand-receptor complex. We propose that, through an unknown mechanism, endocytosis boosts the resting pool of β-catenin upon which GSK3β normally acts.
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Affiliation(s)
- Maria Gagliardi
- MRC's National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK
| | - Ana Hernandez
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ian J McGough
- MRC's National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK
| | - Jean-Paul Vincent
- MRC's National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK
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105
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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: 99] [Impact Index Per Article: 9.0] [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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106
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Carotenuto M, De Antonellis P, Liguori L, Benvenuto G, Magliulo D, Alonzi A, Turino C, Attanasio C, Damiani V, Bello AM, Vitiello F, Pasquinelli R, Terracciano L, Federico A, Fusco A, Freeman J, Dale TC, Decraene C, Chiappetta G, Piantedosi F, Calabrese C, Zollo M. H-Prune through GSK-3β interaction sustains canonical WNT/β-catenin signaling enhancing cancer progression in NSCLC. Oncotarget 2014; 5:5736-49. [PMID: 25026278 PMCID: PMC4170634 DOI: 10.18632/oncotarget.2169] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 07/04/2014] [Indexed: 11/25/2022] Open
Abstract
H-Prune hydrolyzes short-chain polyphosphates (PPase activity) together with an hitherto cAMP-phosphodiesterase (PDE), the latest influencing different human cancers by its overexpression. H-Prune promotes cell migration in cooperation with glycogen synthase kinase-3 (Gsk-3β). Gsk-3β is a negative regulator of canonical WNT/β-catenin signaling. Here, we investigate the role of Gsk-3β/h-Prune complex in the regulation of WNT/β-catenin signaling, demonstrating the h-Prune capability to activate WNT signaling also in a paracrine manner, through Wnt3a secretion. In vivo study demonstrates that h-Prune silencing inhibits lung metastasis formation, increasing mouse survival. We assessed h-Prune levels in peripheral blood of lung cancer patients using ELISA assay, showing that h-Prune is an early diagnostic marker for lung cancer. Our study dissects out the mechanism of action of h-Prune in tumorigenic cells and also sheds light on the identification of a new therapeutic target in non-small-cell lung cancer.
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Affiliation(s)
- Marianeve Carotenuto
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Pasqualino De Antonellis
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Lucia Liguori
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | | | - Daniela Magliulo
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Alessandro Alonzi
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Cecilia Turino
- Dipartimento di Scienze Cardiotoraciche e Respiratorie, Clinica Seconda Università degli Studi di Napoli, Naples, Italy
| | - Carmela Attanasio
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Valentina Damiani
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Anna Maria Bello
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
| | - Fabiana Vitiello
- Dipartimento di Pneumologia e Tisiologia, Day Hospital Pneumologia e Pneumoncologico, AORN Vincenzo Monaldi, Naples, Italy
| | - Rosa Pasquinelli
- Functional Genomic Unit, National Cancer Institute, Fondazione G. Pascale, Naples, Italy
| | - Luigi Terracciano
- Institute of Pathology, Molecular Pathology Division, University of Basel, Switzerland
| | - Antonella Federico
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Istituto Di Endocrinologia e Oncologia Sperimentale del CNR, Naples, Italy
| | - Alfredo Fusco
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Istituto Di Endocrinologia e Oncologia Sperimentale del CNR, Naples, Italy
| | - Jamie Freeman
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Trevor C. Dale
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales, UK
| | - Charles Decraene
- Translational Research Dept, Institut Curie, Centre de recherche, Paris, France
- CNRS, UMR144, Paris, France
| | - Gennaro Chiappetta
- Functional Genomic Unit, National Cancer Institute, Fondazione G. Pascale, Naples, Italy
| | - Francovito Piantedosi
- Dipartimento di Pneumologia e Tisiologia, Day Hospital Pneumologia e Pneumoncologico, AORN Vincenzo Monaldi, Naples, Italy
| | - Cecilia Calabrese
- Dipartimento di Scienze Cardiotoraciche e Respiratorie, Clinica Seconda Università degli Studi di Napoli, Naples, Italy
| | - Massimo Zollo
- Centro di Ingegneria Genetica e Biotecnologie Avanzate (CEINGE), Naples, Italy
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università ‘Federico II’ di Naples, Italy
- Azienda Ospedaliera Federico II, DAI Medicina Trasfusional, Naples, Italy
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107
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Hagemann AIH, Kurz J, Kauffeld S, Chen Q, Reeves PM, Weber S, Schindler S, Davidson G, Kirchhausen T, Scholpp S. In vivo analysis of formation and endocytosis of the Wnt/β-catenin signaling complex in zebrafish embryos. J Cell Sci 2014; 127:3970-82. [PMID: 25074807 PMCID: PMC4163645 DOI: 10.1242/jcs.148767] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
After activation by Wnt/β-Catenin ligands, a multi-protein complex assembles at the clustering membrane-bound receptors and intracellular signal transducers into the so-called Lrp6-signalosome. However, the mechanism of signalosome formation and dissolution is yet not clear. Our imaging studies of live zebrafish embryos show that the signalosome is a highly dynamic structure. It is continuously assembled by Dvl2-mediated recruitment of the transducer complex to the activated receptors and partially disassembled by endocytosis. We find that, after internalization, the ligand-receptor complex and the transducer complex take separate routes. The Wnt–Fz–Lrp6 complex follows a Rab-positive endocytic path. However, when still bound to the transducer complex, Dvl2 forms intracellular aggregates. We show that this endocytic process is not only essential for ligand-receptor internalization but also for signaling. The μ2-subunit of the endocytic Clathrin adaptor Ap2 interacts with Dvl2 to maintain its stability during endocytosis. Blockage of Ap2μ2 function leads to Dvl2 degradation, inhibiton of signalosome formation at the plasma membrane and, consequently, reduction of signaling. We conclude that Ap2μ2-mediated endocytosis is important to maintain Wnt/β-catenin signaling in vertebrates.
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Affiliation(s)
- Anja I H Hagemann
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Jennifer Kurz
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Silke Kauffeld
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Qing Chen
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Patrick M Reeves
- Departments of Cell Biology and Pediatrics, Harvard Medical School and Program in Cellular and Molecular Medicine at Boston Children's Hospital, Boston, 02115 MA, USA
| | - Sabrina Weber
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Simone Schindler
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Gary Davidson
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
| | - Tomas Kirchhausen
- Departments of Cell Biology and Pediatrics, Harvard Medical School and Program in Cellular and Molecular Medicine at Boston Children's Hospital, Boston, 02115 MA, USA
| | - Steffen Scholpp
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics (ITG), 76021 Karsruhe, Germany
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108
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Sheng R, Kim H, Lee H, Xin Y, Chen Y, Tian W, Cui Y, Choi JC, Doh J, Han JK, Cho W. Cholesterol selectively activates canonical Wnt signalling over non-canonical Wnt signalling. Nat Commun 2014; 5:4393. [PMID: 25024088 PMCID: PMC4100210 DOI: 10.1038/ncomms5393] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 06/13/2014] [Indexed: 12/19/2022] Open
Abstract
Wnt proteins control diverse biological processes through β-catenin-dependent canonical signalling and β-catenin-independent non-canonical signalling. The mechanisms by which these signalling pathways are differentially triggered and controlled are not fully understood. Dishevelled (Dvl) is a scaffold protein that serves as the branch point of these pathways. Here, we show that cholesterol selectively activates canonical Wnt signalling over non-canonical signalling under physiological conditions by specifically facilitating the membrane recruitment of the PDZ domain of Dvl and its interaction with other proteins. Single-molecule imaging analysis shows that cholesterol is enriched around the Wnt-activated Frizzled and low-density lipoprotein receptor-related protein 5/6 receptors and plays an essential role for Dvl-mediated formation and maintenance of the canonical Wnt signalling complex. Collectively, our results suggest a new regulatory role of cholesterol in Wnt signalling and a potential link between cellular cholesterol levels and the balance between canonical and non-canonical Wnt signalling activities.
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Affiliation(s)
- Ren Sheng
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | | | | | - Yao Xin
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yong Chen
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Wen Tian
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yang Cui
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Jong-Cheol Choi
- Mechanical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Korea
| | - Junsang Doh
- Mechanical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Korea
| | | | - Wonhwa Cho
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
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109
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Pieters T, van Roy F. Role of cell–cell adhesion complexes in embryonic stem cell biology. J Cell Sci 2014; 127:2603-13. [DOI: 10.1242/jcs.146720] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
ABSTRACT
Pluripotent embryonic stem cells (ESCs) can self-renew or differentiate into any cell type within an organism. Here, we focus on the roles of cadherins and catenins – their cytoplasmic scaffold proteins – in the fate, maintenance and differentiation of mammalian ESCs. E-cadherin is a master stem cell regulator that is required for both mouse ESC (mESC) maintenance and differentiation. E-cadherin interacts with key components of the naive stemness pathway and ablating it prevents stem cells from forming well-differentiated teratomas or contributing to chimeric animals. In addition, depleting E-cadherin converts naive mouse ESCs into primed epiblast-like stem cells (EpiSCs). In line with this, a mesenchymal-to-epithelial transition (MET) occurs during reprogramming of somatic cells towards induced pluripotent stem cells (iPSCs), leading to downregulation of N-cadherin and acquisition of high E-cadherin levels. β-catenin exerts a dual function; it acts in cadherin-based adhesion and in WNT signaling and, although WNT signaling is important for stemness, the adhesive function of β-catenin might be crucial for maintaining the naive state of stem cells. In addition, evidence is rising that other junctional proteins are also important in ESC biology. Thus, precisely regulated levels and activities of several junctional proteins, in particular E-cadherin, safeguard naive pluripotency and are a prerequisite for complete somatic cell reprogramming.
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Affiliation(s)
- Tim Pieters
- Department of Biomedical Molecular Biology, Ghent University, B-9052 Ghent, Belgium
- Molecular and Cellular Oncology Unit, Inflammation Research Center, VIB, B-9052 Ghent, Belgium
| | - Frans van Roy
- Department of Biomedical Molecular Biology, Ghent University, B-9052 Ghent, Belgium
- Molecular Cell Biology Unit, Inflammation Research Center, VIB, B-9052 Ghent, Belgium
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110
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Maternal syntabulin is required for dorsal axis formation and is a germ plasm component in Xenopus. Differentiation 2014; 88:17-26. [PMID: 24798204 DOI: 10.1016/j.diff.2014.03.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/20/2014] [Accepted: 03/20/2014] [Indexed: 11/23/2022]
Abstract
In amphibians and teleosts, early embryonic axial development is driven by maternally deposited mRNAs and proteins, called dorsal determinants, which migrate to the presumptive dorsal side of the embryo in a microtubule-dependent manner after fertilization. Syntabulin is an adapter protein that binds to kinesin KIF5B and to the transmembrane protein Syntaxin1. In zebrafish, a mutation in Syntabulin causes complete embryo ventralization. It is unknown whether Syntabulin plays an analogous role during early development of other species, a question addressed here in Xenopus laevis. in situ hybridization of syntabulin mRNA was carried out at different stages of Xenopus development. In oocytes, syntabulin transcripts were localized to the vegetal cortex of large oocytes and the mitochondrial cloud of very young oocytes. We extended the zebrafish data by finding that during cleavage Xenopus syntabulin mRNA localized to the germ plasm and was later expressed in primordial germ cells (PGCs). This new finding suggested a role for Syntabulin during germ cell differentiation. The functional role of maternal syntabulin mRNA was investigated by knock-down with phosphorothioate DNA antisense oligos followed by oocyte transfer. The results showed that syntabulin mRNA depletion caused the complete loss of dorso-anterior axis formation in frog embryos. Consistent with the ventralized phenotype, syntabulin-depleted embryos displayed severe reduction of dorsal markers and ubiquitous transcription of the ventral marker sizzled. Syntabulin was required for the maternal Wnt/β-Catenin signal, since ventralization could be completely rescued by injection of β-catenin (or syntabulin) mRNA. The data suggest an evolutionarily conserved role for Syntabulin, a protein that bridges microtubule motors and membrane vesicles, during dorso-ventral axis formation in the vertebrates.
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111
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Acebron S, Karaulanov E, Berger B, Huang YL, Niehrs C. Mitotic Wnt Signaling Promotes Protein Stabilization and Regulates Cell Size. Mol Cell 2014; 54:663-74. [DOI: 10.1016/j.molcel.2014.04.014] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/27/2014] [Accepted: 04/08/2014] [Indexed: 10/25/2022]
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