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Schulte G, Scharf MM, Bous J, Voss JH, Grätz L, Kozielewicz P. Frizzleds act as dynamic pharmacological entities. Trends Pharmacol Sci 2024; 45:419-429. [PMID: 38594145 DOI: 10.1016/j.tips.2024.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 03/07/2024] [Accepted: 03/13/2024] [Indexed: 04/11/2024]
Abstract
The Frizzled family of transmembrane receptors (FZD1-10) belongs to the class F of G protein-coupled receptors (GPCRs). FZDs bind to and are activated by Wingless/Int1 (WNT) proteins. The WNT/FZD signaling system regulates crucial aspects of developmental biology and stem-cell regulation. Dysregulation of WNT/FZD communication can lead to developmental defects and diseases such as cancer and fibrosis. Recent insight into the activation mechanisms of FZDs has underlined that protein dynamics and conserved microswitches are essential for FZD-mediated information flow and build the basis for targeting these receptors pharmacologically. In this review, we summarize recent advances in our understanding of FZD activation, and how novel concepts merge and collide with existing dogmas in the field.
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Affiliation(s)
- Gunnar Schulte
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
| | - Magdalena M Scharf
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Julien Bous
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Jan Hendrik Voss
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Lukas Grätz
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden
| | - Pawel Kozielewicz
- Section of Receptor Biology & Signaling, Dept. Physiology & Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden
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Dai E, Liu M, Li S, Zhang X, Wang S, Zhao R, He Y, Peng L, Lv L, Xiao H, Yang M, Yang Z, Zhao P. Identification of Novel FZD4 Mutations in Familial Exudative Vitreoretinopathy and Investigating the Pathogenic Mechanisms of FZD4 Mutations. Invest Ophthalmol Vis Sci 2024; 65:1. [PMID: 38558095 PMCID: PMC10996936 DOI: 10.1167/iovs.65.4.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 03/12/2024] [Indexed: 04/04/2024] Open
Abstract
Purpose The purpose of this study is to report five novel FZD4 mutations identified in familial exudative vitreoretinopathy (FEVR) and to analyze and summarize the pathogenic mechanisms of 34 of 96 reported missense mutations in FZD4. Methods Five probands diagnosed with FEVR and their family members were enrolled in the study. Ocular examinations and targeted gene panel sequencing were conducted on all participants. Plasmids, each carrying 29 previously reported FZD4 missense mutations and five novel mutations, were constructed based on the selection of mutations from each domain of FZD4. These plasmids were used to investigate the effects of mutations on protein expression levels, Norrin/β-catenin activation capacity, membrane localization, norrin binding ability, and DVL2 recruitment ability in HEK293T, HEK293STF, and HeLa cells. Results All five novel mutations (S91F, V103E, C145S, E160K, C377F) responsible for FEVR were found to compromise Norrin/β-catenin activation of FZD4 protein. After reviewing a total of 34 reported missense mutations, we categorized all mutations based on their functional changes: signal peptide mutations, cysteine mutations affecting disulfide bonds, extracellular domain mutations influencing norrin binding, transmembrane domain (TM) 1 and TM7 mutations impacting membrane localization, and intracellular domain mutations affecting DVL2 recruitment. Conclusions We expanded the spectrum of FZD4 mutations relevant to FEVR and experimentally demonstrated that missense mutations in FZD4 can be classified into five categories based on different functional changes.
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Affiliation(s)
- Erkuan Dai
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Min Liu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Shujin Li
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Xiang Zhang
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shiyuan Wang
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Rulian Zhao
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Yunqi He
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Li Peng
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Liting Lv
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Haodong Xiao
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Mu Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Zhenglin Yang
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Center for Medical Genetics and Department of Laboratory Medicine, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
- Research Unit for Blindness Prevention, Chinese Academy of Medical Sciences (2019RU026), Sichuan Provincial People's Hospital, Chengdu, Sichuan, China
| | - Peiquan Zhao
- Department of Ophthalmology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Familial Exudative Vitreoretinopathy-Related Disease-Causing Genes and Norrin/ β-Catenin Signal Pathway: Structure, Function, and Mutation Spectrums. J Ophthalmol 2019; 2019:5782536. [PMID: 31827910 PMCID: PMC6885210 DOI: 10.1155/2019/5782536] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 09/07/2019] [Accepted: 09/26/2019] [Indexed: 02/06/2023] Open
Abstract
Familial exudative vitreoretinopathy (FEVR) is a hereditary ocular disorder characterized by incomplete vascularization/abnormality of peripheral retina. Four of the identified disease-causing genes of FEVR were NDP, FZD4, LRP5, and TSPAN12, the protein coded by which were the components of the Norrin/β-catenin signal pathway. In this review, we summarized and discussed the spectrum of mutations involving these four genes. By the end of 2017, the number of FEVR causing mutations reported for NDP, FZD4, LRP5, and TSPAN12 was, respectively, 26, 121, 58, and 40. Three most frequently reported mutations were c. 362G > A (p.R121Q) of NDP, c. 313A > G (p.M105V), and c.1282_1285delGACA (p.D428SfsX2) of FZD4. Mutations have a tendency to cluster in some “hotspots” domains which may be responsible for protein interactions.
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Kozielewicz P, Turku A, Schulte G. Molecular Pharmacology of Class F Receptor Activation. Mol Pharmacol 2019; 97:62-71. [PMID: 31591260 DOI: 10.1124/mol.119.117986] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/25/2019] [Indexed: 12/29/2022] Open
Abstract
The class Frizzled (FZD) or class F of G protein-coupled receptors consists of 10 FZD paralogues and Smoothened (SMO). FZDs coordinate wingless/Int-1 signaling and SMO mediates Hedgehog signaling. Class F receptor signaling is intrinsically important for embryonic development and its dysregulation leads to diseases, including diverse forms of tumors. With regard to the importance of class F signaling in human disease, these receptors provide an attractive target for therapeutics, exemplified by the use of SMO antagonists for the treatment of basal cell carcinoma. Here, we review recent structural insights in combination with a more detailed functional understanding of class F receptor activation, G protein coupling, conformation-based functional selectivity, and mechanistic details of activating cancer mutations, which will lay the basis for further development of class F-targeting small molecules for human therapy. SIGNIFICANCE STATEMENT: Stimulated by recent insights into the activation mechanisms of class F receptors from structural and functional analysis of Frizzled and Smoothened, we aim to summarize what we know about the molecular details of ligand binding, agonist-driven conformational changes, and class F receptor activation. A better understanding of receptor activation mechanisms will allow us to engage in structure- and mechanism-driven drug discovery with the potential to develop more isoform-selective and potentially pathway-selective drugs for human therapy.
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Affiliation(s)
- Pawel Kozielewicz
- Section of Receptor Biology and Signaling, Department Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Ainoleena Turku
- Section of Receptor Biology and Signaling, Department Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Gunnar Schulte
- Section of Receptor Biology and Signaling, Department Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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5
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Seemab S, Pervaiz N, Zehra R, Anwar S, Bao Y, Abbasi AA. Molecular evolutionary and structural analysis of familial exudative vitreoretinopathy associated FZD4 gene. BMC Evol Biol 2019; 19:72. [PMID: 30849938 PMCID: PMC6408821 DOI: 10.1186/s12862-019-1400-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/22/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Frizzled family members belong to G-protein coupled receptors and encode proteins accountable for cell signal transduction, cell proliferation and cell death. Members of Frizzled receptor family are considered to have critical roles in causing various forms of cancer, cardiac hypertrophy, familial exudative vitreoretinopathy (FEVR) and schizophrenia. RESULTS This study investigates the evolutionary and structural aspects of Frizzled receptors, with particular focus on FEVR associated FZD4 gene. The phylogenetic tree topology suggests the diversification of Frizzled receptors at the root of metazoans history. Moreover, comparative structural data reveals that FEVR associated missense mutations in FZD4 effect the common protein region (amino acids 495-537) through a well-known phenomenon called epistasis. This critical protein region is present at the carboxyl-terminal domain and encompasses the K-T/S-XXX-W, a PDZ binding motif and S/T-X-V PDZ recognition motif. CONCLUSION Taken together these results demonstrate that during the course of evolution, FZD4 has acquired new functions or epistasis via complex patter of gene duplications, sequence divergence and conformational remodeling. In particular, amino acids 495-537 at the C-terminus region of FZD4 protein might be crucial in its normal function and/or pathophysiology. This critical region of FZD4 protein may offer opportunities for the development of novel therapeutics approaches for human retinal vascular disease.
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Affiliation(s)
- Suman Seemab
- National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320 Pakistan
| | - Nashaiman Pervaiz
- National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320 Pakistan
| | - Rabail Zehra
- National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320 Pakistan
| | - Saneela Anwar
- National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320 Pakistan
| | - Yiming Bao
- BIG Data Center & CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101 China
| | - Amir Ali Abbasi
- National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320 Pakistan
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Valnohova J, Kowalski-Jahn M, Sunahara RK, Schulte G. Functional dissection of the N-terminal extracellular domains of Frizzled 6 reveals their roles for receptor localization and Dishevelled recruitment. J Biol Chem 2018; 293:17875-17887. [PMID: 30237173 PMCID: PMC6240854 DOI: 10.1074/jbc.ra118.004763] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 09/18/2018] [Indexed: 11/06/2022] Open
Abstract
The Frizzled (FZD) proteins belong to class F of G protein-coupled receptors (GPCRs) and are essential for various pathways involving the secreted lipoglycoproteins of the wingless/int-1 (WNT) family. A WNT-binding cysteine-rich domain (CRD) in FZDs is N-terminally located and connected to the seven transmembrane domain-spanning receptor core by a linker domain that has a variable length in different FZD homologs. However, the function and importance of this linker domain are poorly understood. Here we used systematic mutagenesis of FZD6 to define the minimal N-terminal domain sufficient for receptor surface expression and recruitment of the intracellular scaffold protein Dishevelled (DVL). Further, we identified a triad of evolutionarily conserved cysteines in the FZD linker domain that is crucial for receptor membrane expression and recruitment of DVL. Our results are in agreement with the concept that the conserved cysteines in the linker domain of FZDs assist with the formation of a common secondary structure in this region. We propose that this structure could be involved in agonist binding and receptor activation mechanisms that are similar to the binding and activation mechanisms known for other GPCRs.
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Affiliation(s)
- Jana Valnohova
- From the Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, 171 65 Stockholm, Sweden
| | - Maria Kowalski-Jahn
- From the Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, 171 65 Stockholm, Sweden
| | - Roger K Sunahara
- Department of Pharmacology, University of California San Diego School of Medicine, La Jolla, California 92093
| | - Gunnar Schulte
- From the Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, 171 65 Stockholm, Sweden.
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Strakova K, Kowalski-Jahn M, Gybel T, Valnohova J, Dhople VM, Harnos J, Bernatik O, Ganji RS, Zdrahal Z, Mulder J, Lindskog C, Bryja V, Schulte G. Dishevelled enables casein kinase 1-mediated phosphorylation of Frizzled 6 required for cell membrane localization. J Biol Chem 2018; 293:18477-18493. [PMID: 30309985 DOI: 10.1074/jbc.ra118.004656] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 10/05/2018] [Indexed: 11/06/2022] Open
Abstract
Frizzleds (FZDs) are receptors for secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family, initiating an important signal transduction network in multicellular organisms. FZDs are G protein-coupled receptors (GPCRs), which are well known to be regulated by phosphorylation, leading to specific downstream signaling or receptor desensitization. The role and underlying mechanisms of FZD phosphorylation remain largely unexplored. Here, we investigated the phosphorylation of human FZD6 Using MS analysis and a phospho-state- and -site-specific antibody, we found that Ser-648, located in the FZD6 C terminus, is efficiently phosphorylated by casein kinase 1 ϵ (CK1ϵ) and that this phosphorylation requires the scaffolding protein Dishevelled (DVL). In an overexpression system, DVL1, -2, and -3 promoted CK1ϵ-mediated FZD6 phosphorylation on Ser-648. This DVL activity required an intact DEP domain and FZD-mediated recruitment of this domain to the cell membrane. Substitution of the CK1ϵ-targeted phosphomotif reduced FZD6 surface expression, suggesting that Ser-648 phosphorylation controls membrane trafficking of FZD6 Phospho-Ser-648 FZD6 immunoreactivity in human fallopian tube epithelium was predominantly apical, associated with cilia in a subset of epithelial cells, compared with the total FZD6 protein expression, suggesting that FZD6 phosphorylation contributes to asymmetric localization of receptor function within the cell and to epithelial polarity. Given the key role of FZD6 in planar cell polarity, our results raise the possibility that asymmetric phosphorylation of FZD6 rather than asymmetric protein distribution accounts for polarized receptor signaling.
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Affiliation(s)
- Katerina Strakova
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic.,Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, Biomedicum (6D), Tomtebodavägen 16, SE-17165 Stockholm, Sweden
| | - Maria Kowalski-Jahn
- Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, Biomedicum (6D), Tomtebodavägen 16, SE-17165 Stockholm, Sweden
| | - Tomas Gybel
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
| | - Jana Valnohova
- Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, Biomedicum (6D), Tomtebodavägen 16, SE-17165 Stockholm, Sweden
| | - Vishnu M Dhople
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, Ernst Moritz Arndt University of Greifswald, Friedrich-Ludwig-Jahn-Strasse 15, 17487 Greifswald, Germany
| | - Jakub Harnos
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
| | - Ondrej Bernatik
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic
| | - Ranjani Sri Ganji
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic.,Central European Institute for Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Zbynek Zdrahal
- Central European Institute for Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Jan Mulder
- Science for Life Laboratory, Department of Neuroscience, Karolinska Institute, Tomtebodavägen 16 17165 Stockholm, Sweden, and
| | - Cecilia Lindskog
- Department of Immunology, Genetics and Pathology, Rudbeck Laboratory, Science for Life Laboratory, Uppsala University, Dag Hammarskjölds väg 20, 751 85 Uppsala, Sweden
| | - Vitezslav Bryja
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic,
| | - Gunnar Schulte
- From the Laboratory of WNT Signaling, Institute of Experimental Biology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic, .,Section for Receptor Biology and Signaling, Department of Physiology and Pharmacology, Karolinska Institutet, Biomedicum (6D), Tomtebodavägen 16, SE-17165 Stockholm, Sweden
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8
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Crystal structure of the Frizzled 4 receptor in a ligand-free state. Nature 2018; 560:666-670. [DOI: 10.1038/s41586-018-0447-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 07/10/2018] [Indexed: 01/07/2023]
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9
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Wang Y, Mahesh P, Wang Y, Novo SG, Shihan MH, Hayward-Piatkovskyi B, Duncan MK. Spatiotemporal dynamics of canonical Wnt signaling during embryonic eye development and posterior capsular opacification (PCO). Exp Eye Res 2018; 175:148-158. [PMID: 29932883 DOI: 10.1016/j.exer.2018.06.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 06/14/2018] [Accepted: 06/18/2018] [Indexed: 02/07/2023]
Abstract
The appropriate spatial and temporal regulation of canonical Wnt signaling is vital for eye development. However, the literature often conflicts on the distribution of canonical Wnt signaling in the eye. Here, using a sensitive mouse transgenic reporter line, we report a detailed re-evaluation of the spatiotemporal dynamics of canonical Wnt signaling in the developing eye. Canonical Wnt activity was dynamic in the optic vesicle and later in the retina, while it was absent from the ectodermal precursors of the lens and corneal epithelium. However, later in corneal development, canonical Wnt reporter activity was detected in corneal stroma and endothelium precursors as they form from the neural crest, although this was lost around birth. Interestingly, while no canonical Wnt signaling was detected in the corneal limbus or basal cells at any developmental stage, it was robust in adult corneal wing and squamous epithelial cells. While canonical Wnt reporter activity was also absent from the postnatal lens, upon lens injury intended to model cataract surgery, it upregulated within 12 h in remnant lens epithelial cells, and co-localized with alpha smooth muscle actin in fibrotic lens epithelial cells from 48 h post-surgery onward. This pattern correlated with downregulation of the inhibitor of canonical Wnt signaling, Dkk3. These data demonstrate that canonical Wnt signaling is dynamic within the developing eye and upregulates in lens epithelial cells in response to lens injury. As canonical Wnt signaling can collaborate with TGFβ to drive fibrosis in other systems, these data offer the first evidence in a lens-injury model that canonical Wnt may synergize with TGFβ signaling to drive fibrotic posterior capsular opacification (PCO).
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Affiliation(s)
- Yichen Wang
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States
| | - Priyha Mahesh
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States
| | - Yan Wang
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States
| | - Samuel G Novo
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States
| | - Mahbubul H Shihan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States
| | | | - Melinda K Duncan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, United States.
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