1
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Thakur AK, Miller SE, Liau NPD, Hwang S, Hansen S, de Sousa E Melo F, Sudhamsu J, Hannoush RN. Synthetic Multivalent Disulfide-Constrained Peptide Agonists Potentiate Wnt1/β-Catenin Signaling via LRP6 Coreceptor Clustering. ACS Chem Biol 2023; 18:772-784. [PMID: 36893429 DOI: 10.1021/acschembio.2c00753] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Wnt ligands are critical for tissue homeostasis and form a complex with LRP6 and frizzled coreceptors to initiate Wnt/β-catenin signaling. Yet, how different Wnts achieve various levels of signaling activation through distinct domains on LRP6 remains elusive. Developing tool ligands that target individual LRP6 domains could help elucidate the mechanism of Wnt signaling regulation and uncover pharmacological approaches for pathway modulation. We employed directed evolution of a disulfide constrained peptide (DCP) to identify molecules that bind to the third β-propeller domain of LRP6. The DCPs antagonize Wnt3a while sparing Wnt1 signaling. Using PEG linkers with different geometries, we converted the Wnt3a antagonist DCPs to multivalent molecules that potentiated Wnt1 signaling by clustering the LRP6 coreceptor. The mechanism of potentiation is unique as it occurred only in the presence of extracellular secreted Wnt1 ligand. While all DCPs recognized a similar binding interface on LRP6, they displayed different spatial orientations that influenced their cellular activities. Moreover, structural analyses revealed that the DCPs exhibited new folds that were distinct from the parent DCP framework they were evolved from. The multivalent ligand design principles highlighted in this study provide a path for developing peptide agonists that modulate different branches of cellular Wnt signaling.
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Affiliation(s)
- Avinash K Thakur
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California 94080, United States
| | - Stephen E Miller
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California 94080, United States
| | - Nicholas P D Liau
- Department of Structural Biology, Genentech, South San Francisco, California 94080, United States
| | - Sunhee Hwang
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California 94080, United States
| | - Simon Hansen
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California 94080, United States
| | - Felipe de Sousa E Melo
- Department of Molecular Oncology, Genentech, South San Francisco, California 94080, United States
| | - Jawahar Sudhamsu
- Department of Structural Biology, Genentech, South San Francisco, California 94080, United States
| | - Rami N Hannoush
- Department of Early Discovery Biochemistry, Genentech, South San Francisco, California 94080, United States
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2
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Abstract
The WNT/β-catenin signalling pathway is a rich and complex network of cellular proteins that orchestrates diverse short-range cell-to-cell communication in metazoans and is essential for both embryonic development and adult homeostasis. Due to its fundamental importance in controlling cell behaviour at multiple levels, its deregulation is associated with a wide range of diseases in humans and identification of drugs targeting the pathway has attracted strong interest in the pharmaceutical sector. Transduction of WNT signals across the plasma membrane of cells involves a staggering degree of complexity and variety with respect to ligand-receptor, receptor-receptor and receptor-co-receptor interactions (Niehrs, Nat Rev Mol Cell Biol 13:767-779, 2012). Although the low-density-lipoprotein-receptor-related-protein (LRP) family is best known for its role in binding and endocytosis of lipoproteins, specific members appear to have additional roles in cellular communication. Indeed, for WNT/β-catenin signalling one apparently universal requirement is the presence of either LRP5 or LRP6 in combination with one of the ten Frizzled (FZD) WNT receptors (FZD1-10). In the 20 years since their discovery as WNT/FZD co-receptors, research on the LRP family has contributed greatly to our understanding of WNT signalling and LRPs have emerged as central players in WNT/β-catenin signalling. LRP5/6 are highly similar and represent the least redundant class of WNT receptor that transduce WNT/β-catenin signalling from a wide range of different WNT and FZD subtypes. This apparent simplicity however belies the complex arrangement of binding sites in the extracellular domain (ECD) of LRP5/6, which regulate interaction not only with WNTs but also with several inhibitors of WNT signalling. This chapter provides a historical overview, chronologically charting this remarkable progress in the field during the last 20 years of research on LRPs and their role in WNT/-catenin signalling. A more focused overview of the structural, functional and mechanistic aspects of LRP biology is also provided, together with the implications this has for pharmacological targeting of this notoriously intractable pathway.
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Affiliation(s)
- Gary Davidson
- Institute of Biological and Chemical Systems-Functional Molecular Systems (IBSC-FMS), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany.
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3
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Bosakova M, Abraham SP, Nita A, Hruba E, Buchtova M, Taylor SP, Duran I, Martin J, Svozilova K, Barta T, Varecha M, Balek L, Kohoutek J, Radaszkiewicz T, Pusapati GV, Bryja V, Rush ET, Thiffault I, Nickerson DA, Bamshad MJ, Rohatgi R, Cohn DH, Krakow D, Krejci P. Mutations in GRK2 cause Jeune syndrome by impairing Hedgehog and canonical Wnt signaling. EMBO Mol Med 2020; 12:e11739. [PMID: 33200460 PMCID: PMC7645380 DOI: 10.15252/emmm.201911739] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 09/08/2020] [Accepted: 09/15/2020] [Indexed: 12/15/2022] Open
Abstract
Mutations in genes affecting primary cilia cause ciliopathies, a diverse group of disorders often affecting skeletal development. This includes Jeune syndrome or asphyxiating thoracic dystrophy (ATD), an autosomal recessive skeletal disorder. Unraveling the responsible molecular pathology helps illuminate mechanisms responsible for functional primary cilia. We identified two families with ATD caused by loss-of-function mutations in the gene encoding adrenergic receptor kinase 1 (ADRBK1 or GRK2). GRK2 cells from an affected individual homozygous for the p.R158* mutation resulted in loss of GRK2, and disrupted chondrocyte growth and differentiation in the cartilage growth plate. GRK2 null cells displayed normal cilia morphology, yet loss of GRK2 compromised cilia-based signaling of Hedgehog (Hh) pathway. Canonical Wnt signaling was also impaired, manifested as a failure to respond to Wnt ligand due to impaired phosphorylation of the Wnt co-receptor LRP6. We have identified GRK2 as an essential regulator of skeletogenesis and demonstrate how both Hh and Wnt signaling mechanistically contribute to skeletal ciliopathies.
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Affiliation(s)
- Michaela Bosakova
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
- International Clinical Research CenterSt. Anne's University HospitalBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
| | - Sara P Abraham
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
| | - Alexandru Nita
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
| | - Eva Hruba
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
| | - Marcela Buchtova
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
| | - S Paige Taylor
- Department of Orthopaedic SurgeryDavid Geffen School of Medicine at UCLALos AngelesCAUSA
| | - Ivan Duran
- Department of Orthopaedic SurgeryDavid Geffen School of Medicine at UCLALos AngelesCAUSA
| | - Jorge Martin
- Department of Orthopaedic SurgeryDavid Geffen School of Medicine at UCLALos AngelesCAUSA
| | - Katerina Svozilova
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
| | - Tomas Barta
- Department of Histology and EmbryologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
| | - Miroslav Varecha
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
| | - Lukas Balek
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
| | | | - Tomasz Radaszkiewicz
- Institute of Experimental BiologyFaculty of ScienceMasaryk UniversityBrnoCzech Republic
| | - Ganesh V Pusapati
- Department of BiochemistryStanford UniversityPalo AltoCAUSA
- Department of MedicineStanford UniversityPalo AltoCAUSA
| | - Vitezslav Bryja
- Institute of Experimental BiologyFaculty of ScienceMasaryk UniversityBrnoCzech Republic
| | - Eric T Rush
- Children's Mercy Kansas City, Center for Pediatric Genomic MedicineKansas CityMOUSA
- Department of PediatricsUniversity of MissouriKansas CityMOUSA
| | - Isabelle Thiffault
- Children's Mercy Kansas City, Center for Pediatric Genomic MedicineKansas CityMOUSA
- Department of PediatricsUniversity of MissouriKansas CityMOUSA
| | | | - Michael J Bamshad
- Department of Genome SciencesUniversity of WashingtonSeattleWAUSA
- Department of PediatricsUniversity of WashingtonSeattleWAUSA
- Division of Genetic MedicineSeattle Children's HospitalSeattleWAUSA
| | | | - Rajat Rohatgi
- Department of BiochemistryStanford UniversityPalo AltoCAUSA
- Department of MedicineStanford UniversityPalo AltoCAUSA
| | - Daniel H Cohn
- Department of Orthopaedic SurgeryDavid Geffen School of Medicine at UCLALos AngelesCAUSA
- Department of Molecular Cell and Developmental BiologyUniversity of California at Los AngelesLos AngelesCAUSA
| | - Deborah Krakow
- Department of Orthopaedic SurgeryDavid Geffen School of Medicine at UCLALos AngelesCAUSA
- Department of Human GeneticsDavid Geffen School of Medicine at UCLALos AngelesCAUSA
- Department of Obstetrics and GynecologyDavid Geffen School of Medicine at UCLALos AngelesCAUSA
| | - Pavel Krejci
- Department of BiologyFaculty of MedicineMasaryk UniversityBrnoCzech Republic
- International Clinical Research CenterSt. Anne's University HospitalBrnoCzech Republic
- Institute of Animal Physiology and Genetics of the CASBrnoCzech Republic
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4
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Min Swe NM, Kobayashi Y, Kamimoto H, Moriyama K. Aberrantly activated Wnt/β-catenin pathway co-receptors LRP5 and LRP6 regulate osteoblast differentiation in the developing coronal sutures of an Apert syndrome (Fgfr2 S252W /+ ) mouse model. Dev Dyn 2020; 250:465-476. [PMID: 32822074 DOI: 10.1002/dvdy.239] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 08/13/2020] [Accepted: 08/13/2020] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Apert syndrome is an autosomal, dominant inherited disorder characterized by craniosynostosis and syndactyly caused by gain-of-function mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. Wnt/β-catenin signaling plays critical roles in regulating the skeletal development. Here, we analyzed the role of this pathway in the developing coronal sutures (CS) of a murine Apert syndrome model (Fgfr2S252W/+ ). RESULTS We observed aberrantly increased mRNA expression of Lrp5 and Lrp6 in CS of Fgfr2S252W/+ mice, whereas both wild type (WT) and Fgfr2S252W/+ mice showed similar expression of other Wnt/β-catenin-related genes, such as Wnt3, Wnt3a, Fzd4, Fzd6, Axin2, and Dkk1 as evidenced by in situ hybridization. Significantly increased Lrp5 and Lrp6 mRNA expression was observed by quantitative PCR analysis of cultured cells isolated from CS of Fgfr2S252W/+ mice. Phospho-LRP5, phospho-LRP6, and non-phospho-β-catenin were upregulated in Fgfr2S252W/+ CS compared with that in WT CS. Short-interfering RNA targeting Lrp5 and Lrp6 significantly reduced runt-related transcription factor 2, collagen type 1 alpha 1, and osteocalcin mRNA expression, and alkaline phosphatase activity in cultured cells. CONCLUSIONS The Wnt/β-catenin pathway was activated in the CS of Fgfr2S252W/+ mice during craniofacial development, suggesting the involvement of the Wnt/β-catenin pathway in the pathogenesis of CS synostosis in Fgfr2S252W/+ mice.
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Affiliation(s)
- Nay Myo Min Swe
- Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Yukiho Kobayashi
- Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Hiroyuki Kamimoto
- Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Keiji Moriyama
- Department of Maxillofacial Orthognathics, Division of Maxillofacial and Neck Reconstruction, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
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5
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Aghabozorgi AS, Ebrahimi R, Bahiraee A, Tehrani SS, Nabizadeh F, Setayesh L, Jafarzadeh-Esfehani R, Ferns GA, Avan A, Rashidi Z. The genetic factors associated with Wnt signaling pathway in colorectal cancer. Life Sci 2020; 256:118006. [PMID: 32593708 DOI: 10.1016/j.lfs.2020.118006] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/20/2020] [Accepted: 06/22/2020] [Indexed: 12/11/2022]
Abstract
Colorectal cancer (CRC) is a common cancer with poor prognosis and high mortality. There is growing information about the factors involved in the pathogenesis of CRC. However, the knowledge of the predisposing factors is limited. The development of CRC is strongly associated with the Wingless/Integrated (Wnt) signaling pathway. This pathway comprises several major target proteins, including LRP5/6, GSK3β, adenomatous polyposis coli (APC), axis inhibition protein (Axin), and β-catenin. Genetic variations in these components of the Wnt signaling pathway may lead to the activation of β-catenin, potentially increasing the proliferation of colorectal cells. Because of the potentially important role of the Wnt signaling pathway in CRC, we aimed to review the involvement of different mutations in the main downstream proteins of this pathway, including LRP5/6, APC, GSK3β, Axin, and β-catenin. Determination of the genetic risk factors involved in the progression of CRC may lead to novel approaches for the early diagnosis of CRC and the identification of potential therapeutic targets in the treatment of CRC.
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Affiliation(s)
- Amirsaeed Sabeti Aghabozorgi
- Medical Genetics Research Center, Basic Medical Sciences Institute, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Reyhane Ebrahimi
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Students' Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Bahiraee
- Department of Medical Genetics, Faculty of Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
| | - Sadra Samavarchi Tehrani
- Department of Clinical Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Students' Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran
| | - Fatemeh Nabizadeh
- Department of Medical Genetics, Faculty of Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
| | - Leila Setayesh
- Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences (TUMS), Tehran, Iran; Students' Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran
| | - Reza Jafarzadeh-Esfehani
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Gordon A Ferns
- Brighton & Sussex Medical School, Division of Medical Education, Falmer, Brighton, Sussex BN1 9PH, UK
| | - Amir Avan
- Student Research Committee, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran; Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
| | - Zahra Rashidi
- Fertility and Infertility Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran; Department of Anatomical Sciences, Medical School, Kermanshah University of Medical Sciences, Kermanshah, Iran.
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6
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Kan W, Enos MD, Korkmazhan E, Muennich S, Chen DH, Gammons MV, Vasishtha M, Bienz M, Dunn AR, Skiniotis G, Weis WI. Limited dishevelled/Axin oligomerization determines efficiency of Wnt/β-catenin signal transduction. eLife 2020; 9:e55015. [PMID: 32297861 PMCID: PMC7200158 DOI: 10.7554/elife.55015] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 04/15/2020] [Indexed: 12/16/2022] Open
Abstract
In Wnt/β-catenin signaling, the transcriptional coactivator β-catenin is regulated by its phosphorylation in a complex that includes the scaffold protein Axin and associated kinases. Wnt binding to its coreceptors activates the cytosolic effector Dishevelled (Dvl), leading to the recruitment of Axin and the inhibition of β-catenin phosphorylation. This process requires interaction of homologous DIX domains present in Dvl and Axin, but is mechanistically undefined. We show that Dvl DIX forms antiparallel, double-stranded oligomers in vitro, and that Dvl in cells forms oligomers typically <10 molecules at endogenous expression levels. Axin DIX (DAX) forms small single-stranded oligomers, but its self-association is stronger than that of DIX. DAX caps the ends of DIX oligomers, such that a DIX oligomer has at most four DAX binding sites. The relative affinities and stoichiometry of the DIX-DAX interaction provide a mechanism for efficient inhibition of β-catenin phosphorylation upon Axin recruitment to the Wnt receptor complex.
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Affiliation(s)
- Wei Kan
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - Michael D Enos
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - Elgin Korkmazhan
- Department of Chemical Engineering, Stanford UniversityStanfordUnited States
- Graduate Program in Biophysics, Stanford UniversityStanfordUnited States
| | - Stefan Muennich
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - Dong-Hua Chen
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
| | - Melissa V Gammons
- MRC Laboratory of Molecular Biology, Cambridge Biomedical CampusCambridgeUnited Kingdom
| | - Mansi Vasishtha
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - Mariann Bienz
- MRC Laboratory of Molecular Biology, Cambridge Biomedical CampusCambridgeUnited Kingdom
| | - Alexander R Dunn
- Department of Chemical Engineering, Stanford UniversityStanfordUnited States
- Graduate Program in Biophysics, Stanford UniversityStanfordUnited States
| | - Georgios Skiniotis
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
| | - William I Weis
- Department of Structural Biology and Stanford University School of MedicineStanfordUnited States
- Department of Molecular and Cellular Physiology, Stanford University School of MedicineStanfordUnited States
- Graduate Program in Biophysics, Stanford UniversityStanfordUnited States
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7
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A Role for the WNT Co-Receptor LRP6 in Pathogenesis and Therapy of Epithelial Cancers. Cancers (Basel) 2019; 11:cancers11081162. [PMID: 31412666 PMCID: PMC6721565 DOI: 10.3390/cancers11081162] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 02/06/2023] Open
Abstract
The WNT/β-catenin signaling pathway controls stem and progenitor cell proliferation, survival and differentiation in epithelial tissues. Aberrant stimulation of this pathway is therefore frequently observed in cancers from epithelial origin. For instance, colorectal and hepatic cancers display activating mutations in the CTNNB1 gene encoding β-catenin, or inactivating APC and AXIN gene mutations. However, these mutations are uncommon in breast and pancreatic cancers despite nuclear β-catenin localization, indicative of pathway activation. Notably, the low-density lipoprotein receptor-related protein 6 (LRP6), an indispensable co-receptor for WNT, is frequently overexpressed in colorectal, liver, breast and pancreatic adenocarcinomas in association with increased WNT/β -catenin signaling. Moreover, LRP6 is hyperphosphorylated in KRAS-mutated cells and in patient-derived colorectal tumours. Polymorphisms in the LRP6 gene are also associated with different susceptibility to developing specific types of lung, bladder and colorectal cancers. Additionally, recent observations suggest that LRP6 dysfunction may be involved in carcinogenesis. Indeed, reducing LRP6 expression and/or activity inhibits cancer cell proliferation and delays tumour growth in vivo. This review summarizes current knowledge regarding the biological function and regulation of LRP6 in the development of epithelial cancers—especially colorectal, liver, breast and pancreatic cancers.
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8
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Balmer P, Fellay AK, Sayar BS, Hariton WVJ, Wiener DJ, Galichet A, Müller EJ, Roosje PJ. FAM83G/Fam83g genetic variants affect canine and murine hair formation. Exp Dermatol 2018; 28:350-354. [PMID: 29963719 DOI: 10.1111/exd.13729] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/28/2018] [Indexed: 01/30/2023]
Abstract
FAM83G/Fam83g genetic variants have been described in dogs, mice and recently also in humans. They are associated with palmoplantar keratoderma and altered hair or coat phenotype, reported as wooly phenotype in mice. FAM83G/Fam83g is an unexplored effector of temporally and spatially coordinated Wnt and BMP signalling which are key pathways in pre- and postnatal hair follicle morphogenesis and differentiation. The aim of this study was to unravel phenotypic consequences of FAM83G/Fam83g variants on hair coat formation in dogs and mice. Our results show differences in hair types and hair shaft structures in both species. Additionally, mice exhibit deregulated hair cycle progression which timely correlates with defective Wnt signalling (Axin2) and Bmp2/4 expression. These results affirm the involvement of FAM83G in hair morphogenesis, hair follicle differentiation and cycling.
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Affiliation(s)
- Pierre Balmer
- Division of Clinical Dermatology, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Auxanne K Fellay
- Division of Clinical Dermatology, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Beyza S Sayar
- Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research, Molecular Dermatology and Stem Cell Research, University of Bern, Bern, Switzerland
| | - William V J Hariton
- Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research, Molecular Dermatology and Stem Cell Research, University of Bern, Bern, Switzerland
| | - Dominique J Wiener
- Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Arnaud Galichet
- Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research, Molecular Dermatology and Stem Cell Research, University of Bern, Bern, Switzerland.,Clinic for Dermatology, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Eliane J Müller
- Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Department of Clinical Research, Molecular Dermatology and Stem Cell Research, University of Bern, Bern, Switzerland.,Institute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Clinic for Dermatology, Inselspital, Bern University Hospital, Bern, Switzerland
| | - Petra J Roosje
- Division of Clinical Dermatology, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Dermfocus, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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9
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Foulquier S, Daskalopoulos EP, Lluri G, Hermans KCM, Deb A, Blankesteijn WM. WNT Signaling in Cardiac and Vascular Disease. Pharmacol Rev 2018; 70:68-141. [PMID: 29247129 PMCID: PMC6040091 DOI: 10.1124/pr.117.013896] [Citation(s) in RCA: 233] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
WNT signaling is an elaborate and complex collection of signal transduction pathways mediated by multiple signaling molecules. WNT signaling is critically important for developmental processes, including cell proliferation, differentiation and tissue patterning. Little WNT signaling activity is present in the cardiovascular system of healthy adults, but reactivation of the pathway is observed in many pathologies of heart and blood vessels. The high prevalence of these pathologies and their significant contribution to human disease burden has raised interest in WNT signaling as a potential target for therapeutic intervention. In this review, we first will focus on the constituents of the pathway and their regulation and the different signaling routes. Subsequently, the role of WNT signaling in cardiovascular development is addressed, followed by a detailed discussion of its involvement in vascular and cardiac disease. After highlighting the crosstalk between WNT, transforming growth factor-β and angiotensin II signaling, and the emerging role of WNT signaling in the regulation of stem cells, we provide an overview of drugs targeting the pathway at different levels. From the combined studies we conclude that, despite the sometimes conflicting experimental data, a general picture is emerging that excessive stimulation of WNT signaling adversely affects cardiovascular pathology. The rapidly increasing collection of drugs interfering at different levels of WNT signaling will allow the evaluation of therapeutic interventions in the pathway in relevant animal models of cardiovascular diseases and eventually in patients in the near future, translating the outcomes of the many preclinical studies into a clinically relevant context.
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Affiliation(s)
- Sébastien Foulquier
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
| | - Evangelos P Daskalopoulos
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
| | - Gentian Lluri
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
| | - Kevin C M Hermans
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
| | - Arjun Deb
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
| | - W Matthijs Blankesteijn
- Department of Pharmacology and Toxicology, Cardiovascular Research Institute, Maastricht University, Maastricht, The Netherlands (S.F., K.C.M.H., W.M.B.); Recherche Cardiovasculaire (CARD), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain, Brussels, Belgium (E.P.D.); Department of Medicine, Division of Cardiology, David Geffen School of Medicine (G.L., A.D.); and Department of Molecular Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California (A.D.)
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10
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Yao Q, An Y, Hou W, Cao YN, Yao MF, Ma NN, Hou L, Zhang H, Liu HJ, Zhang B. LRP6 promotes invasion and metastasis of colorectal cancer through cytoskeleton dynamics. Oncotarget 2017; 8:109632-109645. [PMID: 29312635 PMCID: PMC5752548 DOI: 10.18632/oncotarget.22759] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 10/28/2017] [Indexed: 12/14/2022] Open
Abstract
Low density lipoprotein (LDL) receptor-related protein-6 (LRP6) is an important co-receptor of Wnt pathway, which plays a predominant role in development and progression of colorectal cancer. Recently, dysregulation of LRP6 has proved to be involved in the progression of cancers, but its biological role and clinical significance in colorectal cancer remain unclear. In present study, we revealed that phosphorylation of LRP6 was aberrantly upregulated in colorectal carcinoma correlating with TNM or Dukes staging and worse prognosis. In addition, phosphorylated LRP6 was positively correlated with nuclear accumulation of β-catenin. Overexpression or activation of LRP6 could activate Wnt signaling and promote tumor cell migration in vitro. The activation of LRP6 could induce microtubule dynamics and actin remodeling, probably through regulation of microtubule-associated protein 1B (MAP1B), microtubule actin cross-linking factor 1 (MACF1) and Rho GTPase--RhoA and Rac1. The investigation suggests that LRP6 may be a potential prognostic marker and therapeutic target in the progression of colorectal cancers.
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Affiliation(s)
- Qian Yao
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Yu An
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Wei Hou
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Ya-Nan Cao
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Meng-Fei Yao
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Ning-Ning Ma
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Lin Hou
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Hong Zhang
- Department of Pathology, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
| | - Hai-Jing Liu
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Bo Zhang
- Department of Pathology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
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11
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Buchtova M, Oralova V, Aklian A, Masek J, Vesela I, Ouyang Z, Obadalova T, Konecna Z, Spoustova T, Pospisilova T, Matula P, Varecha M, Balek L, Gudernova I, Jelinkova I, Duran I, Cervenkova I, Murakami S, Kozubik A, Dvorak P, Bryja V, Krejci P. Fibroblast growth factor and canonical WNT/β-catenin signaling cooperate in suppression of chondrocyte differentiation in experimental models of FGFR signaling in cartilage. Biochim Biophys Acta Mol Basis Dis 2015; 1852:839-50. [PMID: 25558817 DOI: 10.1016/j.bbadis.2014.12.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 11/30/2014] [Accepted: 12/27/2014] [Indexed: 11/29/2022]
Abstract
Aberrant fibroblast growth factor (FGF) signaling disturbs chondrocyte differentiation in skeletal dysplasia, but the mechanisms underlying this process remain unclear. Recently, FGF was found to activate canonical WNT/β-catenin pathway in chondrocytes via Erk MAP kinase-mediated phosphorylation of WNT co-receptor Lrp6. Here, we explore the cellular consequences of such a signaling interaction. WNT enhanced the FGF-mediated suppression of chondrocyte differentiation in mouse limb bud micromass and limb organ cultures, leading to inhibition of cartilage nodule formation in micromass cultures, and suppression of growth in cultured limbs. Simultaneous activation of the FGF and WNT/β-catenin pathways resulted in loss of chondrocyte extracellular matrix, expression of genes typical for mineralized tissues and alteration of cellular shape. WNT enhanced the FGF-mediated downregulation of chondrocyte proteoglycan and collagen extracellular matrix via inhibition of matrix synthesis and induction of proteinases involved in matrix degradation. Expression of genes regulating RhoA GTPase pathway was induced by FGF in cooperation with WNT, and inhibition of the RhoA signaling rescued the FGF/WNT-mediated changes in chondrocyte cellular shape. Our results suggest that aberrant FGF signaling cooperates with WNT/β-catenin in suppression of chondrocyte differentiation.
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Affiliation(s)
- Marcela Buchtova
- Department of Anatomy, Histology and Embryology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic; Institute of Animal Physiology and Genetics AS CR, v.v.i., Brno, Czech Republic
| | - Veronika Oralova
- Institute of Animal Physiology and Genetics AS CR, v.v.i., Brno, Czech Republic
| | - Anie Aklian
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Jan Masek
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic
| | - Iva Vesela
- Department of Anatomy, Histology and Embryology, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
| | - Zhufeng Ouyang
- Department of Orthopaedics, Case Western Reserve University, Cleveland, OH, USA
| | - Tereza Obadalova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Zaneta Konecna
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Tereza Spoustova
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic
| | - Tereza Pospisilova
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic
| | - Petr Matula
- Centre for Biomedical Image Analysis, Faculty of Informatics, Masaryk University, Brno, Czech Republic
| | - Miroslav Varecha
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Lukas Balek
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic
| | - Iva Gudernova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Iva Jelinkova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Ivan Duran
- Department of Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Iveta Cervenkova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Shunichi Murakami
- Department of Orthopaedics, Case Western Reserve University, Cleveland, OH, USA
| | - Alois Kozubik
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic; Department of Cytokinetics, Institute of Biophysics AS CR, v.v.i., Brno, Czech Republic
| | - Petr Dvorak
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Vitezslav Bryja
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic; Department of Cytokinetics, Institute of Biophysics AS CR, v.v.i., Brno, Czech Republic
| | - Pavel Krejci
- Institute of Experimental Biology, Faculty of Sciences, Masaryk University, Brno, Czech Republic; Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic; International Clinical Research Center, St. Anne's University Hospital, Brno, Czech Republic.
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12
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Oncogenic KRAS signalling promotes the Wnt/β-catenin pathway through LRP6 in colorectal cancer. Oncogene 2014; 34:4914-27. [PMID: 25500543 PMCID: PMC4687460 DOI: 10.1038/onc.2014.416] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 11/04/2014] [Accepted: 11/08/2014] [Indexed: 12/14/2022]
Abstract
Aberrant regulation of the Wnt/β-catenin signaling pathway is one of the major causes of colorectal cancer (CRC). Loss-of-function mutations in APC are commonly found in CRC, leading to inappropriate activation of canonical Wnt signaling. Conversely, gain-of-function mutations in KRAS and BRAF genes are detected in up to 60% of CRCs. Whereas KRAS/mitogen-activated protein kinase (MAPK) and canonical Wnt/β-catenin pathways are critical for intestinal tumorigenesis, mechanisms integrating these two important signaling pathways during CRC development are unknown. Results herein demonstrate that transformation of normal intestinal epithelial cells (IECs) by oncogenic forms of KRAS, BRAF or MEK1 was associated with a marked increase in β-catenin/TCF4 and c-MYC promoter transcriptional activities and mRNA levels of c-Myc, Axin2 and Lef1. Notably, expression of a dominant-negative mutant of T-Cell Factor 4 (ΔNTCF4) severely attenuated IEC transformation induced by oncogenic MEK1 and markedly reduced their tumorigenic and metastatic potential in immunocompromised mice. Interestingly, the Frizzled co-receptor LRP6 was phosphorylated in a MEK-dependent manner in transformed IECs and in human CRC cell lines. Expression of LRP6 mutant in which serine/threonine residues in each particular ProlineProlineProlineSerine/ThreonineProline motif were mutated to alanines (LRP6-5A) significantly reduced β-catenin/TCF4 transcriptional activity. Accordingly, MEK inhibition in human CRC cells significantly diminished β-catenin/TCF4 transcriptional activity and c-MYC mRNA and protein levels without affecting β-catenin expression or stability. Lastly, LRP6 phosphorylation was also increased in human colorectal tumors, including adenomas, in comparison with healthy adjacent normal tissues. Our data indicate that oncogenic activation of KRAS/BRAF/MEK signaling stimulates the canonical Wnt/β-catenin pathway, which in turn promotes intestinal tumor growth and invasion. Moreover, LRP6 phosphorylation by ERK1/2 may provide a unique point of convergence between KRAS/MAPK and Wnt/β-catenin signalings during oncogenesis.
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13
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Abstract
The canonical Wnt/β-catenin pathway is an ancient and evolutionarily conserved signaling pathway that is required for the proper development of all metazoans, from the basal demosponge Amphimedon queenslandica to humans. Misregulation of Wnt signaling is implicated in many human diseases, making this pathway an intense area of research in industry as well as academia. In this review, we explore our current understanding of the molecular steps involved in the transduction of a Wnt signal. We will focus on how the critical Wnt pathway component, β-catenin, is in a "futile cycle" of constant synthesis and degradation and how this cycle is disrupted upon pathway activation. We describe the role of the Wnt pathway in major human cancers and in the control of stem cell self-renewal in the developing organism and in adults. Finally, we describe well-accepted criteria that have been proposed as evidence for the involvement of a molecule in regulating the canonical Wnt pathway.
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Affiliation(s)
- Kenyi Saito-Diaz
- Department of Cell and Developmental Biology and Program in Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA
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14
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MacDonald BT, He X. Frizzled and LRP5/6 receptors for Wnt/β-catenin signaling. Cold Spring Harb Perspect Biol 2012; 4:4/12/a007880. [PMID: 23209147 DOI: 10.1101/cshperspect.a007880] [Citation(s) in RCA: 421] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Frizzled and LRP5/6 are Wnt receptors that upon activation lead to stabilization of cytoplasmic β-catenin. In this study, we review the current knowledge of these two families of receptors, including their structures and interactions with Wnt proteins, and signaling mechanisms from receptor activation to the engagement of intracellular partners Dishevelled and Axin, and finally to the inhibition of β-catenin phosphorylation and ensuing β-catenin stabilization.
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Affiliation(s)
- Bryan T MacDonald
- The F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
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15
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Krejci P, Aklian A, Kaucka M, Sevcikova E, Prochazkova J, Masek JK, Mikolka P, Pospisilova T, Spoustova T, Weis M, Paznekas WA, Wolf JH, Gutkind JS, Wilcox WR, Kozubik A, Jabs EW, Bryja V, Salazar L, Vesela I, Balek L. Receptor tyrosine kinases activate canonical WNT/β-catenin signaling via MAP kinase/LRP6 pathway and direct β-catenin phosphorylation. PLoS One 2012; 7:e35826. [PMID: 22558232 PMCID: PMC3338780 DOI: 10.1371/journal.pone.0035826] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/22/2012] [Indexed: 12/27/2022] Open
Abstract
Receptor tyrosine kinase signaling cooperates with WNT/β-catenin signaling in regulating many biological processes, but the mechanisms of their interaction remain poorly defined. We describe a potent activation of WNT/β-catenin by FGFR2, FGFR3, EGFR and TRKA kinases, which is independent of the PI3K/AKT pathway. Instead, this phenotype depends on ERK MAP kinase-mediated phosphorylation of WNT co-receptor LRP6 at Ser1490 and Thr1572 during its Golgi network-based maturation process. This phosphorylation dramatically increases the cellular response to WNT. Moreover, FGFR2, FGFR3, EGFR and TRKA directly phosphorylate β-catenin at Tyr142, which is known to increase cytoplasmic β-catenin concentration via release of β-catenin from membranous cadherin complexes. We conclude that signaling via ERK/LRP6 pathway and direct β-catenin phosphorylation at Tyr142 represent two mechanisms used by various receptor tyrosine kinase systems to activate canonical WNT signaling.
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Affiliation(s)
- Pavel Krejci
- Medical Genetics Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America.
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16
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Modulation of canonical Wnt signaling by the extracellular matrix component biglycan. Proc Natl Acad Sci U S A 2011; 108:17022-7. [PMID: 21969569 DOI: 10.1073/pnas.1110629108] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Although extracellular control of canonical Wnt signaling is crucial for tissue homeostasis, the role of the extracellular microenvironment in modulating this signaling pathway is largely unknown. In the present study, we show that a member of the small leucine-rich proteoglycan family, biglycan, enhances canonical Wnt signaling by mediating Wnt function via its core protein. Immunoprecipitation analysis revealed that biglycan interacts with both the canonical Wnt ligand Wnt3a and the Wnt coreceptor low-density lipoprotein receptor-related protein 6 (LRP6), possibly via the formation of a trimeric complex. Biglycan-deficient cells treated with exogenous Wnt3a had less Wnt3a retained in cell layers compared with WT cells. Furthermore, the Wnt-induced levels of LRP6 phosphorylation and expression of several Wnt target genes were blunted in biglycan-deficient cells. Both recombinant biglycan proteoglycan and biglycan core protein increased Wnt-induced β-catenin/T cell-specific factor-mediated transcriptional activity, and this activity was completely inhibited by Dickkopf 1. Interestingly, recombinant biglycan was able to rescue impaired Wnt signaling caused by a previously described missense mutation in the extracellular domain of human LRP6 (R611C). Furthermore, biglycan's modulation of canonical Wnt signaling affected the functional activities of osteoprogenitor cells, including the RUNX2-mediated transcriptional activity and calcium deposition. Use of a transplant system and a fracture healing model revealed that expression of Wnt-induced secreted protein 1 was decreased in bone formed by biglycan-deficient cells, further suggesting reduced Wnt signaling in vivo. We propose that biglycan may serve as a reservoir for Wnt in the pericellular space and modulate Wnt availability for activation of the canonical Wnt pathway.
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17
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Dissecting molecular differences between Wnt coreceptors LRP5 and LRP6. PLoS One 2011; 6:e23537. [PMID: 21887268 PMCID: PMC3160902 DOI: 10.1371/journal.pone.0023537] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 07/19/2011] [Indexed: 01/14/2023] Open
Abstract
Low-density lipoprotein receptor-related proteins 5 and 6 (LRP5 and LRP6) serve as Wnt co-receptors for the canonical β-catenin pathway. While LRP6 is essential for embryogenesis, both LRP5 and LRP6 play critical roles for skeletal remodeling, osteoporosis pathogenesis and cancer formation, making LRP5 and LRP6 key therapeutic targets for cancer and disease treatment. LRP5 and LRP6 each contain in the cytoplasmic domain five conserved PPPSPxS motifs that are pivotal for signaling and serve collectively as phosphorylation-dependent docking sites for the scaffolding protein Axin. However existing data suggest that LRP6 is more effective than LRP5 in transducing the Wnt signal. To understand the molecular basis that accounts for the different signaling activity of LRP5 and LRP6, we generated a series of chimeric receptors via swapping LRP5 and LRP6 cytoplasmic domains, LRP5C and LRP6C, and studied their Wnt signaling activity using biochemical and functional assays. We demonstrate that LRP6C exhibits strong signaling activity while LRP5C is much less active in cells. Recombinant LRP5C and LRP6C upon in vitro phosphorylation exhibit similar Axin-binding capability, suggesting that LRP5 and LRP6 differ in vivo at a step prior to Axin-binding, likely at receiving phosphorylation. We identified between the two most carboxyl PPPSPxS motifs an intervening "gap4" region that appears to account for much of the difference between LRP5C and LRP6C, and showed that alterations in this region are sufficient to enhance LRP5 PPPSPxS phosphorylation and signaling to levels comparable to LRP6 in cells. In addition we provide evidence that binding of phosphorylated LRP5 or LRP6 to Axin is likely direct and does not require the GSK3 kinase as a bridging intermediate as has been proposed. Our studies therefore uncover a new and important molecular tuning mechanism for differential regulation of LRP5 and LRP6 phosphorylation and signaling activity.
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18
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Schulte G. International Union of Basic and Clinical Pharmacology. LXXX. The class Frizzled receptors. Pharmacol Rev 2011; 62:632-67. [PMID: 21079039 DOI: 10.1124/pr.110.002931] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The receptor class Frizzled, which has recently been categorized as a separate group of G protein-coupled receptors by the International Union of Basic and Clinical Pharmacology, consists of 10 Frizzleds (FZD(1-10)) and Smoothened (SMO). The FZDs are activated by secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family, whereas SMO is indirectly activated by the Hedgehog (HH) family of proteins acting on the transmembrane protein Patched (PTCH). Recent years have seen major advances in our knowledge about these seven-transmembrane-spanning proteins, including: receptor function, molecular mechanisms of signal transduction, and the receptor's role in embryonic patterning, physiology, cancer, and other diseases. Despite intense efforts, many question marks and challenges remain in mapping receptor-ligand interaction, signaling routes, mechanisms of specificity and how these molecular details underlie disease and also the receptor's important role in physiology. This review therefore focuses on the molecular aspects of WNT/FZD and HH/SMO signaling discussing receptor structure, mechanisms of signal transduction, accessory proteins, receptor dynamics, and the possibility of targeting these signaling pathways pharmacologically.
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Affiliation(s)
- Gunnar Schulte
- Section of Receptor Biology & Signaling, Dept. of Physiology & Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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19
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Mitogen-activated protein kinases promote WNT/beta-catenin signaling via phosphorylation of LRP6. Mol Cell Biol 2010; 31:179-89. [PMID: 20974802 DOI: 10.1128/mcb.00550-10] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
LDL-related protein 6 (LRP6) is a coreceptor of WNTs and a key regulator of the WNT/β-catenin pathway. Upon activation, LRP6 is phosphorylated within its intracellular PPPS/TP motifs. These phosphorylated motifs are required to recruit axin and to inhibit glycogen synthase kinase 3 (GSK3), two basic components of the β-catenin destruction complex. On the basis of a kinome-wide small interfering RNA (siRNA) screen and confirmative biochemical analysis, we show that several proline-directed mitogen-activated protein kinases (MAPKs), such as p38, ERK1/2, and JNK1 are sufficient and required for the phosphorylation of PPPS/TP motifs of LRP6. External stimuli, which control the activity of MAPKs, such as phorbol esters and fibroblast growth factor 2 (FGF2) control the choice of the LRP6-PPPS/TP kinase and regulate the amplitude of LRP6 phosphorylation and WNT/β-catenin-dependent transcription. Our findings suggest that cells not only recruit one dedicated LRP6 kinase but rather select their LRP6 kinase depending on cell type and the external stimulus. Moreover, direct phosphorylation of LRP6 by MAPKs provides a unique point for convergence between WNT/β-catenin signaling and mitogenic pathways.
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20
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Niehrs C, Shen J. Regulation of Lrp6 phosphorylation. Cell Mol Life Sci 2010; 67:2551-62. [PMID: 20229235 PMCID: PMC11115861 DOI: 10.1007/s00018-010-0329-3] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/08/2010] [Accepted: 02/19/2010] [Indexed: 12/14/2022]
Abstract
The Wnt/beta-catenin signaling pathway plays important roles in embryonic development and tissue homeostasis, and is implicated in human disease. Wnts transduce signals via transmembrane receptors of the Frizzled (Fzd/Fz) family and the low density lipoprotein receptor-related protein 5/6 (Lrp5/6). A key mechanism in their signal transduction is that Wnts induce Lrp6 signalosomes, which become phosphorylated at multiple conserved sites, notably at PPSPXS motifs. Lrp6 phosphorylation is crucial to beta-catenin stabilization and pathway activation by promoting Axin and Gsk3 recruitment to phosphorylated sites. Here, we summarize how proline-directed kinases (Gsk3, PKA, Pftk1, Grk5/6) and non-proline-directed kinases (CK1 family) act upon Lrp6, how the phosphorylation is regulated by ligand binding and mitosis, and how Lrp6 phosphorylation leads to beta-catenin stabilization.
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Affiliation(s)
- Christof Niehrs
- Division of Molecular Embryology, DKFZ-ZMBH Alliance, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 581, Heidelberg, Germany.
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21
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Differential modulation of TCF/LEF-1 activity by the soluble LRP6-ICD. PLoS One 2010; 5:e11821. [PMID: 20676368 PMCID: PMC2911377 DOI: 10.1371/journal.pone.0011821] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 07/05/2010] [Indexed: 12/28/2022] Open
Abstract
The canonical Wnt/β-catenin (Wnt) pathway is a master transcriptional regulatory signaling pathway that controls numerous biological processes including proliferation and differentiation. As such, transcriptional activity of the Wnt pathway is tightly regulated and/or modulated by numerous proteins at the level of the membrane, cytosol and/or nucleus. In the nucleus, transcription of Wnt target genes by TCF/LEF-1 is repressed by the long Groucho/TLE co-repressor family. However, a truncated member of the Groucho/TLE family, amino terminal enhancer of Split (AES) can positively modulate TCF/LEF-1 activity by antagonizing long Groucho/TLE members in a dominant negative manner. We have previously shown the soluble intracellular domain of the LRP6 receptor, a receptor required for activation of the Wnt pathway, can positively regulate transcriptional activity within the Wnt pathway. In the current study, we show the soluble LRP6 intracellular domain (LRP6-ICD) can also translocate to the nucleus in CHO and HEK 293T cells and in contrast to cytosolic LRP6-ICD; nuclear LRP6-ICD represses TCF/LEF-1 activity. In agreement with previous reports, we show AES enhances TCF/LEF-1 mediated reporter transcription and further we demonstrate that AES activity is spatially regulated in HEK 293T cells. LRP6-ICD interacts with AES exclusively in the nucleus and represses AES mediated TCF/LEF-1 reporter transcription. These results suggest that LRP6-ICD can differentially modulate Wnt pathway transcriptional activity depending upon its subcellular localization and differential protein-protein interactions.
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22
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Davidson G, Niehrs C. Emerging links between CDK cell cycle regulators and Wnt signaling. Trends Cell Biol 2010; 20:453-60. [PMID: 20627573 DOI: 10.1016/j.tcb.2010.05.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 05/03/2010] [Accepted: 05/04/2010] [Indexed: 01/09/2023]
Abstract
Wnt/beta-catenin signaling controls many aspects of cell behavior throughout development and in adults. One of its best-known and cancer-relevant functions is to stimulate cell proliferation. Recent work has implicated Wnt components in regulating mitotic events, suggesting that the cell cycle and Wnt signaling are directly linked. This concept has now been substantially strengthened with the finding that the mitotic CDK14/cyclin Y complex promotes Wnt signaling through phosphorylation of the LRP6 co-receptor, a key regulatory nexus in the Wnt/beta-catenin pathway. Thus, an unexpectedly tight collaboration between the mitotic cell cycle machinery and Wnt signaling is emerging, suggesting that this pathway might orchestrate mitotic processes.
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Affiliation(s)
- Gary Davidson
- Karlsruhe Institute of Technology (KIT), Institute of Toxicology and Genetics, H. v. Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
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23
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Beagle B, Mi K, Johnson GVW. Phosphorylation of PPP(S/T)P motif of the free LRP6 intracellular domain is not required to activate the Wnt/beta-catenin pathway and attenuate GSK3beta activity. J Cell Biochem 2010; 108:886-95. [PMID: 19711366 DOI: 10.1002/jcb.22318] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The canonical Wnt/beta-catenin signaling pathway plays a critical role in numerous physiological and pathological processes. LRP6 is an essential co-receptor for Wnt/beta-catenin signaling; as transduction of the Wnt signal is strongly dependent upon GSK3beta-mediated phosphorylation of multiple PPP(S/T)P motifs within the membrane-anchored LRP6 intracellular domain. Previously, we showed that the free LRP6 intracellular domain (LRP6-ICD) can activate the Wnt/beta-catenin pathway in a beta-catenin and TCF/LEF-1 dependent manner, as well as interact with and attenuate GSK3beta activity. However, it is unknown if the ability of LRP6-ICD to attenuate GSK3beta activity and modulate activation of the Wnt/beta-catenin pathway requires phosphorylation of the LRP6-ICD PPP(S/T)P motifs, in a manner similar to the membrane-anchored LRP6 intracellular domain. Here we provide evidence that the LRP6-ICD does not have to be phosphorylated at its PPP(S/T)P motif by GSK3beta to stabilize endogenous cytosolic beta-catenin resulting in activation of TCF/LEF-1 and the Wnt/beta-catenin pathway. LRP6-ICD and a mutant in which all 5 PPP(S/T)P motifs were changed to PPP(A)P motifs equivalently interacted with and attenuated GSK3beta activity in vitro, and both constructs inhibited the in situ GSK3beta-mediated phosphorylation of beta-catenin and tau to the same extent. These data indicate that the LRP6-ICD attenuates GSK3beta activity similar to other GSK3beta binding proteins, and is not a result of it being a GSK3beta substrate. Our findings suggest the functional and regulatory mechanisms governing the free LRP6-ICD may be distinct from membrane-anchored LRP6, and that release of the LRP6-ICD may provide a complimentary signaling cascade capable of modulating Wnt-dependent gene expression.
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Affiliation(s)
- Brandon Beagle
- Department of Anesthesiology, University of Rochester, Rochester, New York 14642, USA
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24
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Davidson G, Shen J, Huang YL, Su Y, Karaulanov E, Bartscherer K, Hassler C, Stannek P, Boutros M, Niehrs C. Cell cycle control of wnt receptor activation. Dev Cell 2010; 17:788-99. [PMID: 20059949 DOI: 10.1016/j.devcel.2009.11.006] [Citation(s) in RCA: 204] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 11/02/2009] [Accepted: 11/23/2009] [Indexed: 10/20/2022]
Abstract
Low-density lipoprotein receptor related proteins 5 and 6 (LRP5/6) are transmembrane receptors that initiate Wnt/beta-catenin signaling. Phosphorylation of PPPSP motifs in the LRP6 cytoplasmic domain is crucial for signal transduction. Using a kinome-wide RNAi screen, we show that PPPSP phosphorylation requires the Drosophila Cyclin-dependent kinase (CDK) L63. L63 and its vertebrate homolog PFTK are regulated by the membrane tethered G2/M Cyclin, Cyclin Y, which mediates binding to and phosphorylation of LRP6. As a consequence, LRP6 phosphorylation and Wnt/beta-catenin signaling are under cell cycle control and peak at G2/M phase; knockdown of the mitotic regulator CDC25/string, which results in G2/M arrest, enhances Wnt signaling in a Cyclin Y-dependent manner. In Xenopus embryos, Cyclin Y is required in vivo for LRP6 phosphorylation, maternal Wnt signaling, and Wnt-dependent anteroposterior embryonic patterning. G2/M priming of LRP6 by a Cyclin/CDK complex introduces an unexpected new layer of regulation of Wnt signaling.
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Affiliation(s)
- Gary Davidson
- Division of Molecular Embryology, Karlsruhe Institute of Technology, Institute of Toxicology and Genetics, Hermann von Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
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25
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Abstract
Signaling by the Wnt family of secreted glycolipoproteins via the transcriptional coactivator beta-catenin controls embryonic development and adult homeostasis. Here we review recent progress in this so-called canonical Wnt signaling pathway. We discuss Wnt ligands, agonists, and antagonists, and their interactions with Wnt receptors. We also dissect critical events that regulate beta-catenin stability, from Wnt receptors to the cytoplasmic beta-catenin destruction complex, and nuclear machinery that mediates beta-catenin-dependent transcription. Finally, we highlight some key aspects of Wnt/beta-catenin signaling in human diseases including congenital malformations, cancer, and osteoporosis, and discuss potential therapeutic implications.
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Affiliation(s)
- Bryan T MacDonald
- F. M. Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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26
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MacDonald BT, Tamai K, He X. Wnt/beta-catenin signaling: components, mechanisms, and diseases. Dev Cell 2009. [PMID: 19619488 DOI: 10.1016/j.devcel] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Signaling by the Wnt family of secreted glycolipoproteins via the transcriptional coactivator beta-catenin controls embryonic development and adult homeostasis. Here we review recent progress in this so-called canonical Wnt signaling pathway. We discuss Wnt ligands, agonists, and antagonists, and their interactions with Wnt receptors. We also dissect critical events that regulate beta-catenin stability, from Wnt receptors to the cytoplasmic beta-catenin destruction complex, and nuclear machinery that mediates beta-catenin-dependent transcription. Finally, we highlight some key aspects of Wnt/beta-catenin signaling in human diseases including congenital malformations, cancer, and osteoporosis, and discuss potential therapeutic implications.
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Affiliation(s)
- Bryan T MacDonald
- F. M. Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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27
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Abstract
Signaling by the Wnt family of secreted glycolipoproteins via the transcriptional coactivator beta-catenin controls embryonic development and adult homeostasis. Here we review recent progress in this so-called canonical Wnt signaling pathway. We discuss Wnt ligands, agonists, and antagonists, and their interactions with Wnt receptors. We also dissect critical events that regulate beta-catenin stability, from Wnt receptors to the cytoplasmic beta-catenin destruction complex, and nuclear machinery that mediates beta-catenin-dependent transcription. Finally, we highlight some key aspects of Wnt/beta-catenin signaling in human diseases including congenital malformations, cancer, and osteoporosis, and discuss potential therapeutic implications.
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Affiliation(s)
- Bryan T MacDonald
- F. M. Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, Boston, MA 02115, USA
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28
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Abstract
The Wnt family of secreted ligands act through many receptors to stimulate distinct intracellular signalling pathways in embryonic development, in adults and in disease processes. Binding of Wnt to the Frizzled family of receptors and to low density lipoprotein receptor-related protein 5 (LRP5) or LRP6 co-receptors stimulates the intracellular Wnt-beta-catenin signalling pathway, which regulates beta-cateninstability and context-dependent transcription. This signalling pathway controls many processes, such as cell fate determination, cell proliferation and self-renewal of stem and progenitor cells. Intriguingly, the transmembrane receptor Tyr kinases Ror2 and Ryk, as well as Frizzledreceptors that act independently of LRP5 or LRP6, function as receptors for Wnt and activate beta-catenin-independent pathways. This leads to changes in cell movement and polarity and to the antagonism of the beta-catenin pathway.
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Affiliation(s)
- Stephane Angers
- Leslie Dan Faculty of Pharmacy and the Department of Biochemistry, University of Toronto, Ontario, M5S 3M2, Canada.
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29
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Inhibition of GSK3 phosphorylation of beta-catenin via phosphorylated PPPSPXS motifs of Wnt coreceptor LRP6. PLoS One 2009; 4:e4926. [PMID: 19293931 PMCID: PMC2654145 DOI: 10.1371/journal.pone.0004926] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2008] [Accepted: 02/05/2009] [Indexed: 11/24/2022] Open
Abstract
The Wnt/β-catenin signaling pathway plays essential roles in cell proliferation and differentiation, and deregulated β-catenin protein levels lead to many types of human cancers. On activation by Wnt, the Wnt co-receptor LDL receptor related protein 6 (LRP6) is phosphorylated at multiple conserved intracellular PPPSPXS motifs by glycogen synthase kinase 3 (GSK3) and casein kinase 1 (CK1), resulting in recruitment of the scaffolding protein Axin to LRP6. As a result, β-catenin phosphorylation by GSK3 is inhibited and β-catenin protein is stabilized. However, how LRP6 phosphorylation and the ensuing LRP6-Axin interaction lead to the inhibition of β-catenin phosphorylation by GSK3 is not fully understood. In this study, we reconstituted Axin-dependent β-catenin phosphorylation by GSK3 and CK1 in vitro using recombinant proteins, and found that the phosphorylated PPPSPXS peptides directly inhibit β-catenin phosphorylation by GSK3 in a sequence and phosphorylation-dependent manner. This inhibitory effect of phosphorylated PPPSPXS motifs is direct and specific for GSK3 phosphorylation of β-catenin at Ser33/Ser37/Thr41 but not for CK1 phosphorylation of β-catenin at Ser45, and is independent of Axin function. We also show that a phosphorylated PPPSPXS peptide is able to activate Wnt/β-catenin signaling and to induce axis duplication in Xenopus embryos, presumably by inhibition of GSK3 in vivo. Based on these observations, we propose a working model that Axin recruitment to the phosphorylated LRP6 places GSK3 in the vicinity of multiple phosphorylated PPPSPXS motifs, which directly inhibit GSK3 phosphorylation of β-catenin. This model provides a possible mechanism to account, in part, for inhibition of β-catenin phosphorylation by Wnt-activated LRP6.
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30
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MacDonald BT, Yokota C, Tamai K, Zeng X, He X. Wnt signal amplification via activity, cooperativity, and regulation of multiple intracellular PPPSP motifs in the Wnt co-receptor LRP6. J Biol Chem 2008; 283:16115-23. [PMID: 18362152 DOI: 10.1074/jbc.m800327200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Low density lipoprotein receptor-related protein 6 (LRP6) and its homologue LRP5 serve as Wnt co-receptors that are essential for the Wnt/beta-catenin pathway. Wnt activation of LRP6 leads to recruitment of the scaffolding protein Axin and inhibition of Axin-mediated phosphorylation/destruction of beta-catenin. We showed that five conserved PPPSP motifs in the LRP6 intracellular domain are required for LRP6 function, and mutation of these motifs together abolishes LRP6 signaling activity. We further showed that Wnt induces the phosphorylation of a prototypic PPPSP motif, which provides a docking site for Axin and is sufficient to transfer signaling activity to a heterologous receptor. However, the activity, regulation, and functionality of multiple PPPSP motifs in LRP6 have not been characterized. Here we provide a comprehensive analysis of all five PPPSP motifs in LRP6. We define the core amino acid residues of a prototypic PPPSP motif via alanine scanning mutagenesis and demonstrate that each of the five PPPSP motifs exhibits signaling and Axin binding activity in isolation. We generated two novel phosphorylation-specific antibodies to additional PPPSP motifs and show that Wnt induces phosphorylation of these motifs in the endogenous LRP6 through glycogen synthase kinase 3. Finally, we uncover the critical cooperativity of PPPSP motifs in the full-length LRP6 by demonstrating that LRP6 mutants lacking a single PPPSP motif display compromised function, whereas LRP6 mutants lacking two of the five PPPSP motifs are mostly inactive. This cooperativity appears to reflect the ability of PPPSP motifs to promote the phosphorylation of one another and to interact with Axin synergistically. These results establish the critical role and a common phosphorylation/activation mechanism for the PPPSP motifs in LRP6 and suggest that the conserved multiplicity and cooperativity of the PPPSP motifs represents a built-in amplifier for Wnt signaling by the LRP6 family of receptors.
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Affiliation(s)
- Bryan T MacDonald
- F. M. Kirby Neurobiology Center, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA
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31
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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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