1
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Zhang F, Luo W, Liu S, Zhao L, Su Y. Protein phosphatase 2A regulates blood cell proliferation and differentiation in Drosophila larval lymph glands. FEBS J 2024. [PMID: 39185698 DOI: 10.1111/febs.17247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 05/31/2024] [Accepted: 08/02/2024] [Indexed: 08/27/2024]
Abstract
Protein phosphatase 2A (PP2A), one of the most abundant protein phosphatases, has divergent functions in multiple types of cells. Its inactivation has been closely associated with leukemia diseases. However, the physiological function of PP2A for hematopoiesis has been poorly understood in organisms. Drosophila hematopoiesis parallels the vertebrate counterpart in developmental and functional features but involves a much simpler hematopoietic system. Here, utilizing the Drosophila major larval hematopoietic organ lymph gland, we studied the function of PP2A for hematopoiesis in vivo. By knocking down the expression of Pp2A-29B that encodes the scaffold subunit of the PP2A holoenzyme complex, we found that PP2A silencing in the differentiating hemocytes resulted in their excessive proliferation. Furthermore, this PP2A inhibition downregulated the expression of Smoothened (Smo), a crucial component in the Hedgehog pathway, and smo overexpression was able to rescue the phenotypes of PP2A depletion, indicating that Smo functions as a downstream effector of PP2A to restrict the hemocyte proliferation. PDGF/VEGF-receptor (Pvr) overexpression also restored the Smo expression and lymph gland morphology of PP2A silencing, suggesting a PP2A-Pvr-Smo axis to regulate lymph gland growth and hemocyte proliferation. Moreover, inhibiting PP2A activity in the blood progenitor cells promoted their differentiation, but which was independent with Smo. Together, our data suggested that PP2A plays a dual role in the Drosophila lymph gland by preserving the progenitor population and restraining the hemocyte proliferation, to properly regulate the hematopoietic process.
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Affiliation(s)
- Fang Zhang
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education) and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Wang Luo
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education) and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Sumin Liu
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education) and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Long Zhao
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education) and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
- Fisheries College, Ocean University of China, Qingdao, China
| | - Ying Su
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education) and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, China
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
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2
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Wu X, Zhang W, Long L, Wang Y, Chen H, Wang K, Wang Z, Bai J, Xue D, Pan Z. KDELR2 promotes bone marrow mesenchymal stem cell osteogenic differentiation via GSK3β/β-catenin signaling pathway. Cell Tissue Res 2024; 396:269-281. [PMID: 38470494 DOI: 10.1007/s00441-024-03884-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Accepted: 03/01/2024] [Indexed: 03/14/2024]
Abstract
Nonunion is a challenging complication of fractures for the surgeon. Recently the Lys-Asp-Glu-Leu (KDEL) endoplasmic reticulum protein retention receptor 2 (KDELR2) has been found that involved in osteogenesis imperfecta. However, the exact mechanism is still unclear. In this study, we used lentivirus infection and mouse fracture model to investigate the role of KDELR2 in osteogenesis. Our results showed that KDELR2 knockdown inhibited the osteogenic differentiation of mBMSCs, whereas KDELR2 overexpression had the opposite effect. Furthermore, the levels of active-β-catenin and phospho-GSK3β (Ser9) were upregulated by KDELR2 overexpression and downregulated by KDELR2 knockdown. In the fracture model, mBMSCs overexpressing KDELR2 promoted healing. In conclusion, KDELR2 promotes the osteogenesis of mBMSCs by regulating the GSK3β/β-catenin signaling pathway.
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Affiliation(s)
- Xiaoyong Wu
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Weijun Zhang
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Long Long
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
- Linping Hospital of Integrated Chinese and Western Medicine, No.60,Baojian Road, Hangzhou, 310009, China
| | - Yibo Wang
- Guangdong Provincial Key Laboratory of Orthopedics and Traumatology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou 510080, China
- Department of Spine Surgery, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Hongyu Chen
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Kanbin Wang
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Zhongxiang Wang
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Jinwu Bai
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China
| | - Deting Xue
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China.
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China.
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China.
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China.
| | - Zhijun Pan
- Department of Orthopedic Surgery of the Second Affiliated Hospital, School of Medicine, Zhejiang University, No. 88, Jiefang Road, Hangzhou 310009, China.
- Orthopedics Research Institute of Zhejiang University, No. 88, Jiefang Road, Hangzhou, 310009, China.
- Key Laboratory of Motor System Disease Research and Precision Therapy of Zhejiang Province, Hangzou City, Zhejiang Province, PR China.
- Clinical Research Center of Motor System Disease of Zhejiang Province, Hangzhou City, PR China.
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3
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He T, Fan Y, Wang Y, Liu M, Zhu AJ. Dissection of the microRNA Network Regulating Hedgehog Signaling in Drosophila. Front Cell Dev Biol 2022; 10:866491. [PMID: 35573695 PMCID: PMC9096565 DOI: 10.3389/fcell.2022.866491] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 04/08/2022] [Indexed: 11/13/2022] Open
Abstract
The evolutionarily conserved Hedgehog (Hh) signaling plays a critical role in embryogenesis and adult tissue homeostasis. Aberrant Hh signaling often leads to various forms of developmental anomalies and cancer. Since altered microRNA (miRNA) expression is associated with developmental defects and tumorigenesis, it is not surprising that several miRNAs have been found to regulate Hh signaling. However, these miRNAs are mainly identified through small-scale in vivo screening or in vitro assays. As miRNAs preferentially reduce target gene expression via the 3' untranslated region, we analyzed the effect of reduced expression of core components of the Hh signaling cascade on downstream signaling activity, and generated a transgenic Drosophila toolbox of in vivo miRNA sensors for core components of Hh signaling, including hh, patched (ptc), smoothened (smo), costal 2 (cos2), fused (fu), Suppressor of fused (Su(fu)), and cubitus interruptus (ci). With these tools in hand, we performed a genome-wide in vivo miRNA overexpression screen in the developing Drosophila wing imaginal disc. Of the twelve miRNAs identified, seven were not previously reported in the in vivo Hh regulatory network. Moreover, these miRNAs may act as general regulators of Hh signaling, as their overexpression disrupts Hh signaling-mediated cyst stem cell maintenance during spermatogenesis. To identify direct targets of these newly discovered miRNAs, we used the miRNA sensor toolbox to show that miR-10 and miR-958 directly target fu and smo, respectively, while the other five miRNAs act through yet-to-be-identified targets other than the seven core components of Hh signaling described above. Importantly, through loss-of-function analysis, we found that endogenous miR-10 and miR-958 target fu and smo, respectively, whereas deletion of the other five miRNAs leads to altered expression of Hh signaling components, suggesting that these seven newly discovered miRNAs regulate Hh signaling in vivo. Given the powerful effects of these miRNAs on Hh signaling, we believe that identifying their bona fide targets of the other five miRNAs will help reveal important new players in the Hh regulatory network.
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Affiliation(s)
- Tao He
- Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yu Fan
- Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, School of Life Sciences, Peking University, Beijing, China
| | - Yao Wang
- Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, School of Life Sciences, Peking University, Beijing, China
| | - Min Liu
- Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Alan Jian Zhu
- Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
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4
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Stapornwongkul KS, de Gennes M, Cocconi L, Salbreux G, Vincent JP. Patterning and growth control in vivo by an engineered GFP gradient. Science 2020; 370:321-327. [PMID: 33060356 PMCID: PMC7611032 DOI: 10.1126/science.abb8205] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 08/21/2020] [Indexed: 02/06/2023]
Abstract
Morphogen gradients provide positional information during development. To uncover the minimal requirements for morphogen gradient formation, we have engineered a synthetic morphogen in Drosophila wing primordia. We show that an inert protein, green fluorescent protein (GFP), can form a detectable diffusion-based gradient in the presence of surface-associated anti-GFP nanobodies, which modulate the gradient by trapping the ligand and limiting leakage from the tissue. We next fused anti-GFP nanobodies to the receptors of Dpp, a natural morphogen, to render them responsive to extracellular GFP. In the presence of these engineered receptors, GFP could replace Dpp to organize patterning and growth in vivo. Concomitant expression of glycosylphosphatidylinositol (GPI)-anchored nonsignaling receptors further improved patterning, to near-wild-type quality. Theoretical arguments suggest that GPI anchorage could be important for these receptors to expand the gradient length scale while at the same time reducing leakage.
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Affiliation(s)
| | - Marc de Gennes
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Luca Cocconi
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
- Imperial College, Department of Mathematics, London, UK
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5
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Kastl P, Manikowski D, Steffes G, Schürmann S, Bandari S, Klämbt C, Grobe K. Disrupting Hedgehog Cardin-Weintraub sequence and positioning changes cellular differentiation and compartmentalization in vivo. Development 2018; 145:145/18/dev167221. [PMID: 30242104 DOI: 10.1242/dev.167221] [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] [Received: 04/30/2018] [Accepted: 07/24/2018] [Indexed: 12/25/2022]
Abstract
Metazoan Hedgehog (Hh) morphogens are essential regulators of growth and patterning at significant distances from their source, despite being produced as N-terminally palmitoylated and C-terminally cholesteroylated proteins, which firmly tethers them to the outer plasma membrane leaflet of producing cells and limits their spread. One mechanism to overcome this limitation is proteolytic processing of both lipidated terminal peptides, called shedding, but molecular target site requirements for effective Hh shedding remained undefined. In this work, by using Drosophila melanogaster as a model, we show that mutagenesis of the N-terminal Cardin-Weintraub (CW) motif inactivates recombinant Hh proteins to variable degrees and, if overexpressed in the same compartment, converts them into suppressors of endogenous Hh function. In vivo, additional removal of N-palmitate membrane anchors largely restored endogenous Hh function, supporting the hypothesis that proteolytic CW processing controls Hh solubilization. Importantly, we also observed that CW repositioning impairs anterior/posterior compartmental boundary maintenance in the third instar wing disc. This demonstrates that Hh shedding not only controls the differentiation of anterior cells, but also maintains the sharp physical segregation between these receiving cells and posterior Hh-producing cells.
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Affiliation(s)
- Philipp Kastl
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Dominique Manikowski
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Georg Steffes
- Institute of Neurobiology and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Sabine Schürmann
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Shyam Bandari
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Christian Klämbt
- Institute of Neurobiology and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
| | - Kay Grobe
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, D-48149 Münster, Germany
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6
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Liu C, Rodriguez KF, Brown PR, Yao HHC. Reproductive, Physiological, and Molecular Outcomes in Female Mice Deficient in Dhh and Ihh. Endocrinology 2018; 159:2563-2575. [PMID: 29788357 PMCID: PMC6287595 DOI: 10.1210/en.2018-00095] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 04/11/2018] [Indexed: 02/05/2023]
Abstract
Ovarian development requires coordinate communications among oocytes, granulosa cells, and theca cells. Two Hedgehog (Hh) pathway ligands, Desert hedgehog (Dhh) and Indian hedgehog (Ihh), are produced by the granulosa cells and work together to regulate theca cell specification and development. Mice lacking both Dhh and Ihh had loss of normal ovarian function, which raised the question of which biological actions are specifically controlled by each ligand during folliculogenesis. By comparing the reproductive fitness, hormonal profiles, and ovarian transcriptomes among control, Dhh single-knockout (KO), Ihh KO, and Dhh/Ihh double-knockout (DKO) mice, we examined the specific roles of Dhh and Ihh in these processes. Dhh/Ihh DKO female mice were infertile because of a lack of theca cells and their steroid product androgen. Although Dhh and Ihh KO mice were fertile with normal folliculogenesis, they had decreased androgen production and alterations in their ovarian transcriptomes. Absence of Ihh led to aberrant steroidogenesis and elevated inflammation responses, which were not found in Dhh KO mouse ovaries, implicating that IHH has a greater impact than DHH on the activation of the Hh signaling pathway in the ovary. Our findings provide insight into not only how the Hh pathway influences folliculogenesis but also the distinct and overlapping roles of Dhh and Ihh in supporting ovarian development.
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Affiliation(s)
- Chang Liu
- Reproductive and Developmental Biology Group, National Institute of
Environmental Health Sciences, Durham, North Carolina
| | - Karina F Rodriguez
- Reproductive and Developmental Biology Group, National Institute of
Environmental Health Sciences, Durham, North Carolina
| | - Paula R Brown
- Reproductive and Developmental Biology Group, National Institute of
Environmental Health Sciences, Durham, North Carolina
| | - Humphrey H-C Yao
- Reproductive and Developmental Biology Group, National Institute of
Environmental Health Sciences, Durham, North Carolina
- Correspondence: Humphrey H.-C. Yao, PhD, Reproductive Developmental Biology Laboratory, National
Institute of Environmental Health Sciences, 111 T.W. Alexander Drive, Mail Drop C4-10,
Research Triangle Park, North Carolina 27709. E-mail:
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7
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Schürmann S, Steffes G, Manikowski D, Kastl P, Malkus U, Bandari S, Ohlig S, Ortmann C, Rebollido-Rios R, Otto M, Nüsse H, Hoffmann D, Klämbt C, Galic M, Klingauf J, Grobe K. Proteolytic processing of palmitoylated Hedgehog peptides specifies the 3-4 intervein region of the Drosophila wing. eLife 2018. [PMID: 29522397 PMCID: PMC5844694 DOI: 10.7554/elife.33033] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cell fate determination during development often requires morphogen transport from producing to distant responding cells. Hedgehog (Hh) morphogens present a challenge to this concept, as all Hhs are synthesized as terminally lipidated molecules that form insoluble clusters at the surface of producing cells. While several proposed Hh transport modes tie directly into these unusual properties, the crucial step of Hh relay from producing cells to receptors on remote responding cells remains unresolved. Using wing development in Drosophila melanogaster as a model, we show that Hh relay and direct patterning of the 3–4 intervein region strictly depend on proteolytic removal of lipidated N-terminal membrane anchors. Site-directed modification of the N-terminal Hh processing site selectively eliminated the entire 3–4 intervein region, and additional targeted removal of N-palmitate restored its formation. Hence, palmitoylated membrane anchors restrict morphogen spread until site-specific processing switches membrane-bound Hh into bioactive forms with specific patterning functions. Each cell in a developing embryo receives information that determines what type of body structure it will form. In fruit flies, this information is partly given by a protein called Hedgehog. In the embryo cells that receive it, Hedgehog can trigger a series of events which activate certain genes and thereby regulate structure formation. The Hedgehog proteins are produced by a different organizing group of cells: from there they transport within the embryo, creating a gradient. Depending on where a responding cell is in the embryo, it receives a different amount of Hedgehog, which gives the cell its identity. For example, Hedgehog proteins form a gradient across a fruit fly’s developing wing, which creates a visible vein pattern. How Hedgehog proteins form gradients is enigmatic, however, because once produced, they cling to the cells that created them. The reason for this unusual behavior is that the two ends of the Hedgehog protein are attached to a different fat molecule. In particular, one extremity is linked to a fat molecule called palmitate. These ends’ fatty additions anchor Hedgehog to the cells that produced them. Then, the tethered proteins gather together to form chain-like clusters where they inactivate each other: the extremity with the palmitate ‘hides’ the portion of the neighboring protein that binds to the receiving cells. It is still unclear how Hedgehog can be activated and released to reach these faraway cells. One hypothesis is that an enzyme comes to the clusters and frees the proteins by cutting both of Hedgehog’s fatty anchors. Thanks to how the palmitate tethers Hedgehog to the cell, the protein is positioned in such a way that when the enzyme makes its snip, the binding site on the neighboring Hedgehog gets exposed: this protein is activated and, when also cut by the enzyme, released. Here, Schürmann et al. create an array of mutant Hedgehog proteins – for example some without palmitate, some with palmitate that cannot be removed by the enzyme – and study how they affect the development of the wing’s pattern in the fruit fly. Coupled with the imaging of the clusters, these experiments support the hypothesis that the palmitate anchor is necessary so that Hedgehog proteins can be turned on before diffusing away. The Hedgehog family of proteins is also present in humans, where it presides over the development of the embryo but is also involved in cancer. Understanding how Hedgehog works in the fruit fly could lead to new discoveries in humans too.
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Affiliation(s)
- Sabine Schürmann
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Georg Steffes
- Center for Medical Biotechnology, University of Duisburg-Essen, Essen, Germany.,Institute of Neurobiology, University of Münster, Münster, Germany
| | - Dominique Manikowski
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Philipp Kastl
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Ursula Malkus
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Shyam Bandari
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Stefanie Ohlig
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Corinna Ortmann
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | | | - Mandy Otto
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
| | - Harald Nüsse
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Daniel Hoffmann
- Center for Medical Biotechnology, University of Duisburg-Essen, Essen, Germany
| | - Christian Klämbt
- Institute of Neurobiology, University of Münster, Münster, Germany
| | - Milos Galic
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Jürgen Klingauf
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Kay Grobe
- Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
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8
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Manikowski D, Kastl P, Grobe K. Taking the Occam's Razor Approach to Hedgehog Lipidation and Its Role in Development. J Dev Biol 2018; 6:jdb6010003. [PMID: 29615552 PMCID: PMC5875562 DOI: 10.3390/jdb6010003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 01/01/2023] Open
Abstract
All Hedgehog (Hh) proteins signal from producing cells to distant receiving cells despite being synthesized as N-and C-terminally lipidated, membrane-tethered molecules. To explain this paradoxical situation, over the past 15 years, several hypotheses have been postulated that tie directly into this property, such as Hh transport on cellular extensions called cytonemes or on secreted vesicles called lipophorins and exosomes. The alternative situation that tight membrane association merely serves to prevent unregulated Hh solubilization has been addressed by biochemical and structural studies suggesting Hh extraction from the membrane or proteolytic Hh release. While some of these models may act in different organisms, tissues or developmental programs, others may act together to specify Hh short- and long-range signaling in the same tissues. To test and rank these possibilities, we here review major models of Hh release and transport and hypothesize that the (bio)chemical and physical properties of firmly established, homologous, and functionally essential biochemical Hh modifications are adapted to specify and determine interdependent steps of Hh release, transport and signaling, while ruling out other steps. This is also described by the term “congruence”, meaning that the logical combination of biochemical Hh modifications can reveal their true functional implications. This combined approach reveals potential links between models of Hh release and transport that were previously regarded as unrelated, thereby expanding our view of how Hhs can steer development in a simple, yet extremely versatile, manner.
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Affiliation(s)
- Dominique Manikowski
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence, University of Münster, D-48149 Münster, Germany.
| | - Philipp Kastl
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence, University of Münster, D-48149 Münster, Germany.
| | - Kay Grobe
- Institute of Physiological Chemistry and Pathobiochemistry and Cells-in-Motion Cluster of Excellence, University of Münster, D-48149 Münster, Germany.
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9
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Abstract
The Hedgehog (Hh) signalling pathway plays many important roles in development, homeostasis and tumorigenesis. The critical function of Hh signalling in bone formation has been identified in the past two decades. Here, we review the evolutionarily conserved Hh signalling mechanisms with an emphasis on the functions of the Hh signalling pathway in bone development, homeostasis and diseases. In the early stages of embryonic limb development, Sonic Hedgehog (Shh) acts as a major morphogen in patterning the limb buds. Indian Hedgehog (Ihh) has an essential function in endochondral ossification and induces osteoblast differentiation in the perichondrium. Hh signalling is also involved intramembrane ossification. Interactions between Hh and Wnt signalling regulate cartilage development, endochondral bone formation and synovial joint formation. Hh also plays an important role in bone homeostasis, and reducing Hh signalling protects against age-related bone loss. Disruption of Hh signalling regulation leads to multiple bone diseases, such as progressive osseous heteroplasia. Therefore, understanding the signalling mechanisms and functions of Hh signalling in bone development, homeostasis and diseases will provide important insights into bone disease prevention, diagnoses and therapeutics.
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10
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Hartl TA, Scott MP. Wing tips: The wing disc as a platform for studying Hedgehog signaling. Methods 2014; 68:199-206. [PMID: 24556557 DOI: 10.1016/j.ymeth.2014.02.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 02/03/2014] [Accepted: 02/06/2014] [Indexed: 12/26/2022] Open
Abstract
Hedgehog (Hh) signal transduction is necessary for the development of most mammalian tissues and can go awry and cause birth defects or cancer. Hh signaling was initially described in Drosophila, and much of what we know today about mammalian Hh signaling was directly guided by discoveries in the fly. Indeed, Hh signaling is a wonderful example of the use of non-vertebrate model organisms to make basic discoveries that lead to new disease treatment. The first pharmaceutical to treat hyperactive Hh signaling in Basal Cell Carcinoma was released in 2012, approximately 30 years after the isolation of Hh mutants in Drosophila. The study of Hh signaling has been greatly facilitated by the imaginal wing disc, a tissue with terrific experimental advantages. Studies using the wing disc have led to an understanding of Hh ligand processing, packaging into particles for transmission, secretion, reception, signal transduction, target gene activation, and tissue patterning. Here we describe the imaginal wing disc, how Hh patterns this tissue, and provide methods to use wing discs to study Hh signaling in Drosophila. The tools and approaches we highlight form the cornerstone of research efforts in many laboratories that use Drosophila to study Hh signaling, and are essential for ongoing discoveries.
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Affiliation(s)
- Tom A Hartl
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Bioengineering, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Matthew P Scott
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Bioengineering, Stanford University School of Medicine, Stanford, CA 94305, USA.
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11
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Gao L, Wu L, Hou X, Zhang Q, Zhang F, Ye X, Yang Y, Lin X. Drosophila miR-932 modulates hedgehog signaling by targeting its co-receptor Brother of ihog. Dev Biol 2013; 377:166-76. [PMID: 23453925 DOI: 10.1016/j.ydbio.2013.02.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/14/2013] [Accepted: 02/05/2013] [Indexed: 02/08/2023]
Abstract
Hedgehog (Hh) proteins act as morphogens in a variety of developmental contexts to control cell fates and growth in a concentration-dependent manner. Therefore, secretion, distribution, and reception of Hh proteins must be tightly regulated and deregulation of these processes contributes to numerous human diseases. Brother of ihog (Boi) and its close relative Ihog (Interference hedgehog) are cell surface proteins that act as Hh co-receptors required for Hh signaling response and cell-surface maintenance of Hh protein. MicroRNAs (miRNAs) are a group of widely expressed 21-23 nucleotides non-coding RNAs that repress gene function through interactions with target mRNAs. Here, we have identified a novel miRNA, miR-932, as an important regulator for Boi. We show that overexpression of miR-932 in the wing disc can enhance Hh signaling strength, but reduce its signaling range, a phenotype similar to that of boi knockdown. In both in vivo sensor assay and in vitro luciferase assay, miR-932 can suppress Boi by directly binding to its 3'UTR. Meanwhile, down-regulation of miR-932 by sponge elevates the protein level of Boi, confirming that miR-932 is an in vivo regulator of Boi expression. Further, we demonstrate that miR-932 can block Hh signaling when co-expressed with ihog-RNAi. Moreover, we find that other predicted miRNAs of Boi fail to suppress it as strong as miR-932. Taken together, our data demonstrate that miR-932 can modulate Hh activity by specifically targeting Boi in Drosophila, illustrating the important roles of miRNAs in fine regulation of the Hh signaling pathway.
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Affiliation(s)
- Lei Gao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
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12
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Geisbrecht ER, Sawant K, Su Y, Liu ZC, Silver DL, Burtscher A, Wang X, Zhu AJ, McDonald JA. Genetic interaction screens identify a role for hedgehog signaling in Drosophila border cell migration. Dev Dyn 2013; 242:414-31. [PMID: 23335293 DOI: 10.1002/dvdy.23926] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 12/22/2012] [Accepted: 12/28/2012] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Cell motility is essential for embryonic development and physiological processes such as the immune response, but also contributes to pathological conditions such as tumor progression and inflammation. However, our understanding of the mechanisms underlying migratory processes is incomplete. Drosophila border cells provide a powerful genetic model to identify the roles of genes that contribute to cell migration. RESULTS Members of the Hedgehog signaling pathway were uncovered in two independent screens for interactions with the small GTPase Rac and the polarity protein Par-1 in border cell migration. Consistent with a role in migration, multiple Hh signaling components were enriched in the migratory border cells. Interference with Hh signaling by several different methods resulted in incomplete cell migration. Moreover, the polarized distribution of E-Cadherin and a marker of tyrosine kinase activity were altered when Hh signaling was disrupted. Conservation of Hh-Rac and Hh-Par-1 signaling was illustrated in the wing, in which Hh-dependent phenotypes were enhanced by loss of Rac or par-1. CONCLUSIONS We identified a pathway by which Hh signaling connects to Rac and Par-1 in cell migration. These results further highlight the importance of modifier screens in the identification of new genes that function in developmental pathways.
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Affiliation(s)
- Erika R Geisbrecht
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
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13
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Gao L, Hou X, Wu L, Zhang F, Zhang Q, Ye X, Yang Y, Lin X. Drosophila miR-960 negatively regulates Hedgehog signaling by suppressing Smoothened, Costal-2 and Fused. Cell Signal 2013; 25:1301-9. [PMID: 23385085 DOI: 10.1016/j.cellsig.2013.01.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 01/16/2013] [Indexed: 12/19/2022]
Abstract
MicroRNAs (miRNAs) are endogenous small non-coding RNAs that post-transcriptionally regulate gene expression in eukaryotes. In Drosophila melanogaster, up to 240 miRNAs have been identified by computational methods or experimental approaches. However, most of their biological functions are still unknown. Here, we identified miR-960 as a suppressor of Hedgehog (Hh) signaling pathway. Ectopic miR-960 obviously represses the expression levels of target genes. This activity is mediated by direct inhibition of Smoothened (Smo), Costal-2 (Cos2) and Fused (Fu), which are essential signaling transduction components of Hh pathway. Through in vivo sensor assay and in vitro luciferase assay, we found that miR-960 directly binds to the 3'UTRs of smo, cos2 and fu mRNAs to block their translation. Additionally, we demonstrated that miR-960 cannot suppress Wg and Dpp signaling pathways. Together, our results indicate that miR-960 can specifically suppress Hh pathway by directly targeting three important signaling transducers Smo, Cos2 and Fu.
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Affiliation(s)
- Lei Gao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China
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14
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Abstract
Hedgehog (Hh) signaling plays pivotal roles in embryonic development and adult tissue homeostasis, and its deregulation leads to numerous human disorders including cancer. Binding of Hh to Patched (Ptc), a twelve-transmembrane protein, alleviates its inhibition of Smoothened (Smo), a seven-transmembrane protein related to G-protein-coupled receptors (GPCRs), leading to Smo phosphorylation and activation. Smo acts through intracellular signaling complexes to convert the latent transcription factor Cubitus interruptus (Ci)/Gli from a truncated repressor to a full-length activator, leading to derepression/activation of Hh target genes. Increasing evidence suggests that phosphorylation participates in almost every step in the signal relay from Smo to Ci/Gli, and that differential phosphorylation of several key pathway components may be crucial for translating the Hh morphogen gradient into graded pathway activities. In this review, we focus on the multifaceted roles that phosphorylation plays in Hh signal transduction, and discuss the conservation and difference between Drosophila and mammalian Hh signaling mechanisms.
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15
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Abstract
Hedgehog (Hh) proteins regulate the development of a wide range of metazoan embryonic and adult structures, and disruption of Hh signaling pathways results in various human diseases. Here, we provide a comprehensive review of the signaling pathways regulated by Hh, consolidating data from a diverse array of organisms in a variety of scientific disciplines. Similar to the elucidation of many other signaling pathways, our knowledge of Hh signaling developed in a sequential manner centered on its earliest discoveries. Thus, our knowledge of Hh signaling has for the most part focused on elucidating the mechanism by which Hh regulates the Gli family of transcription factors, the so-called "canonical" Hh signaling pathway. However, in the past few years, numerous studies have shown that Hh proteins can also signal through Gli-independent mechanisms collectively referred to as "noncanonical" signaling pathways. Noncanonical Hh signaling is itself subdivided into two distinct signaling modules: (i) those not requiring Smoothened (Smo) and (ii) those downstream of Smo that do not require Gli transcription factors. Thus, Hh signaling is now proposed to occur through a variety of distinct context-dependent signaling modules that have the ability to crosstalk with one another to form an interacting, dynamic Hh signaling network.
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Affiliation(s)
- David J Robbins
- Molecular Oncology Program, Department of Surgery, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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16
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Wu LF, Gao L, Hou XM, Zhang QH, Li S, Yang YF, Lin XH. Drosophila
miR-5 suppresses Hedgehog signaling by directly targeting Smoothened. FEBS Lett 2012; 586:4052-60. [DOI: 10.1016/j.febslet.2012.10.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/29/2012] [Accepted: 10/02/2012] [Indexed: 12/21/2022]
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17
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Anderson E, Peluso S, Lettice LA, Hill RE. Human limb abnormalities caused by disruption of hedgehog signaling. Trends Genet 2012; 28:364-73. [DOI: 10.1016/j.tig.2012.03.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/26/2012] [Accepted: 03/26/2012] [Indexed: 12/23/2022]
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18
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Pignot G, Vieillefond A, Vacher S, Zerbib M, Debre B, Lidereau R, Amsellem-Ouazana D, Bieche I. Hedgehog pathway activation in human transitional cell carcinoma of the bladder. Br J Cancer 2012; 106:1177-86. [PMID: 22361633 PMCID: PMC3304423 DOI: 10.1038/bjc.2012.55] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/27/2012] [Accepted: 02/03/2012] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The Hedgehog (Hh) signalling pathway functions as an organiser in embryonic development. Recent studies have shown constitutive activation of this pathway in various malignancies, but its role in bladder cancer remains poorly studied. METHODS Expression levels of 31 genes and 9 microRNAs (miRNAs) involved in the Hh pathway were determined by quantitative real-time RT-PCR in 71 bladder tumour samples (21 muscle-invasive (MIBC) and 50 non-muscle-invasive (NMIBC) bladder cancers), as well as in 6 bladder cancer cell lines. RESULTS The SHH ligand gene and Gli-inducible target genes (FOXM1, IGF2, OSF2, H19, and SPP1) were overexpressed in tumour samples as compared with normal bladder tissue. SHH overexpression was found in 96% of NMIBC and 52% of MIBC samples, as well as in two bladder cancer cell lines. Altered expression of miRNAs supported their oncogene or tumour-suppressor gene status. In univariate analysis, high expression levels of PTCH2, miRNA-92A, miRNA-19A, and miRNA-20A were associated with poorer overall survival in MIBC (P=0.02, P=0.012, P=0.047, and P=0.036, respectively). CONCLUSION We observed constitutive activation of the Hh pathway in most NMIBC and about 50% of MIBC. We also found that some protein-coding genes and miRNAs involved in the Hh pathway may have prognostic value at the individual level.
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Affiliation(s)
- G Pignot
- Department of Urology, Service d'Urologie, Université Paris Descartes, Sorbonne Paris Cité, 27 rue du Faubourg Saint Jaques, Paris F-75014, France.
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19
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Ranieri N, Ruel L, Gallet A, Raisin S, Thérond PP. Distinct phosphorylations on kinesin costal-2 mediate differential hedgehog signaling strength. Dev Cell 2012; 22:279-94. [PMID: 22306085 DOI: 10.1016/j.devcel.2011.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 10/11/2011] [Accepted: 12/07/2011] [Indexed: 10/14/2022]
Abstract
The graded Hedgehog (Hh) signal is transduced by the transmembrane Smoothened (Smo) proteins in both vertebrates and invertebrates. In Drosophila, associations between Smo and the Fused (Fu)/Costal-2 (Cos2)/Cubitus Interruptus (Ci) cytoplasmic complex lead to pathway activation, but it remains unclear how the cytoplasmic complex responds to and transduces different levels of Hh signaling. We show here that, within the Hh gradient field, low- and high-magnitude Smo activations control differentially the phosphorylation of Cos2 on two distinct serines. We also provide evidence that these phosphorylations depend on the Fu kinase activity and lead to a shift of Cos2 distribution from the cytoplasm to the plasma membrane. Moreover, the distinct Cos2 phosphorylation states mediate differential Hh signaling magnitude, suggesting that phosphorylation and relocation of Cos2 to the plasma membrane facilitate high-level Hh signaling through the control of Ci nuclear translocation and transcriptional activity.
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Affiliation(s)
- Nadia Ranieri
- CNRS, UMR6543, Institut de Biologie du Développement et du Cancer-IBDC, Nice 06108, France
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20
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Abstract
The study of posttranslational regulation of proteins has occupied biochemists for well over a half century. Understanding balanced phosphorylation and dephosphorylation of the proteins may be the key to meeting some of the most pressing scientific challenges. A detailed examination of the phosphorylation of many components in the Hedgehog (Hh) pathway leads to a better understanding of the Hh signaling mechanisms. This chapter describes the precise phosphorylation that evolves during the phosphorylation/dephosphorylation of players in the Hh signaling cascade, including the signal transducer Smoothened and the transcription factor Ci/Gli.
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Affiliation(s)
- Jianhang Jia
- Department of Molecular and Cellular Biochemistry, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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21
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Shi Q, Li S, Jia J, Jiang J. The Hedgehog-induced Smoothened conformational switch assembles a signaling complex that activates Fused by promoting its dimerization and phosphorylation. Development 2011; 138:4219-31. [PMID: 21852395 DOI: 10.1242/dev.067959] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hedgehog (Hh) transduces signal by regulating the subcellular localization and conformational state of the GPCR-like protein Smoothened (Smo) but how Smo relays the signal to cytoplasmic signaling components remains poorly understood. Here, we show that Hh-induced Smo conformational change recruits Costal2 (Cos2)/Fused (Fu) and promotes Fu kinase domain dimerization. We find that induced dimerization through the Fu kinase domain activates Fu by inducing multi-site phosphorylation of its activation loop (AL) and phospho-mimetic mutations of AL activate the Hh pathway. Interestingly, we observe that graded Hh signals progressively increase Fu kinase domain dimerization and AL phosphorylation, suggesting that Hh activates Fu in a dose-dependent manner. Moreover, we find that activated Fu regulates Cubitus interruptus (Ci) by both promoting its transcriptional activator activity and inhibiting its proteolysis into a repressor form. We provide evidence that activated Fu exerts these regulations by interfering with the formation of Ci-Sufu and Ci-Cos2-kinase complexes that normally inhibit Ci activity and promote its processing. Taken together, our results suggest that Hh-induced Smo conformational change facilitates the assembly of active Smo-Cos2-Fu signaling complexes that promote Fu kinase domain dimerization, phosphorylation and activation, and that Fu regulates both the activator and repressor forms of Ci.
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Affiliation(s)
- Qing Shi
- Department of Developmental Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
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22
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Su Y, Ospina JK, Zhang J, Michelson AP, Schoen AM, Zhu AJ. Sequential phosphorylation of smoothened transduces graded hedgehog signaling. Sci Signal 2011; 4:ra43. [PMID: 21730325 PMCID: PMC3526344 DOI: 10.1126/scisignal.2001747] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The correct interpretation of a gradient of the morphogen Hedgehog (Hh) during development requires phosphorylation of the Hh signaling activator Smoothened (Smo); however, the molecular mechanism by which Smo transduces graded Hh signaling is not well understood. We show that regulation of the phosphorylation status of Smo by distinct phosphatases at specific phosphorylated residues creates differential thresholds of Hh signaling. Phosphorylation of Smo was initiated by adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase (PKA) and further enhanced by casein kinase I (CKI). We found that protein phosphatase 1 (PP1) directly dephosphorylated PKA-phosphorylated Smo to reduce signaling mediated by intermediate concentrations of Hh, whereas PP2A specifically dephosphorylated PKA-primed, CKI-phosphorylated Smo to restrict signaling by high concentrations of Hh. We also established a functional link between sequentially phosphorylated Smo species and graded Hh activity. Thus, we propose a sequential phosphorylation model in which precise interpretation of morphogen concentration can be achieved upon versatile phosphatase-mediated regulation of the phosphorylation status of an essential activator in developmental signaling.
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Affiliation(s)
| | | | | | - Andrew P. Michelson
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Adam M. Schoen
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Alan Jian Zhu
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
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23
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Hogan J, Valentine M, Cox C, Doyle K, Collier S. Two frizzled planar cell polarity signals in the Drosophila wing are differentially organized by the Fat/Dachsous pathway. PLoS Genet 2011; 7:e1001305. [PMID: 21379328 PMCID: PMC3040658 DOI: 10.1371/journal.pgen.1001305] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Accepted: 01/12/2011] [Indexed: 11/18/2022] Open
Abstract
The regular array of distally pointing hairs on the mature Drosophila wing is evidence for the fine control of Planar Cell Polarity (PCP) during wing development. Normal wing PCP requires both the Frizzled (Fz) PCP pathway and the Fat/Dachsous (Ft/Ds) pathway, although the functional relationship between these pathways remains under debate. There is strong evidence that the Fz PCP pathway signals twice during wing development, and we have previously presented a Bidirectional-Biphasic Fz PCP signaling model which proposes that the Early and Late Fz PCP signals are in different directions and employ different isoforms of the Prickle protein. The goal of this study was to investigate the role of the Ft/Ds pathway in the context of our Fz PCP signaling model. Our results allow us to draw the following conclusions: (1) The Early Fz PCP signals are in opposing directions in the anterior and posterior wing and converge precisely at the site of the L3 wing vein. (2) Increased or decreased expression of Ft/Ds pathway genes can alter the direction of the Early Fz PCP signal without affecting the Late Fz PCP signal. (3) Lowfat, a Ft/Ds pathway regulator, is required for the normal orientation of the Early Fz PCP signal but not the Late Fz PCP signal. (4) At the time of the Early Fz PCP signal there are symmetric gradients of dachsous (ds) expression centered on the L3 wing vein, suggesting Ds activity gradients may orient the Fz signal. (5) Localized knockdown or over-expression of Ft/Ds pathway genes shows that boundaries/gradients of Ft/Ds pathway gene expression can redirect the Early Fz PCP signal specifically. (6) Altering the timing of ds knockdown during wing development can separate the role of the Ft/Ds pathway in wing morphogenesis from its role in Early Fz PCP signaling. Planar Cell Polarity (PCP) describes the orientation of a cell within the plane of a cell layer. The precise control of PCP has been shown to be vital for normal development in both vertebrates and invertebrates, and failures of PCP have been implicated in human disease. Studies in the fruit fly Drosophila have identified two genetic pathways, the Frizzled and Fat/Dachsous pathways, that are required to organize PCP, although the functional relationship between the two pathways remains unresolved. We have previously proposed a model of Frizzled pathway activity in the Drosophila wing that invokes two consecutive Frizzled signaling events oriented in different directions. The Early and Late Fz PCP signals use different isoforms of the Prickle protein. The goal of this study was to define the activity of the Fat/Dachsous pathway in the context of our Frizzled signaling model. Our results suggest that the Fat/Dachsous pathway has a different functional relationship with each of the Frizzled signaling events. Specifically, we find that by altering Fat/Dachsous pathway activity, we can reorient the Early Frizzled signal without affecting the Late Frizzled signal. This suggests that the functional relationship between the Fat/Dachsous pathway and the Frizzled pathway can vary, even between consecutive Frizzled signaling events within the same set of cells.
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Affiliation(s)
- Justin Hogan
- Department of Biological Sciences, Marshall University, Huntington, West Virginia, United States of America
| | - Meagan Valentine
- Department of Biological Sciences, Marshall University, Huntington, West Virginia, United States of America
| | - Chris Cox
- Department of Biological Sciences, Marshall University, Huntington, West Virginia, United States of America
| | - Kristy Doyle
- Department of Biological Sciences, Marshall University, Huntington, West Virginia, United States of America
| | - Simon Collier
- Department of Biological Sciences, Marshall University, Huntington, West Virginia, United States of America
- * E-mail:
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Terriente-Félix A, Molnar C, Gómez-Skarmeta JL, de Celis JF. A conserved function of the chromatin ATPase Kismet in the regulation of hedgehog expression. Dev Biol 2010; 350:382-92. [PMID: 21146514 DOI: 10.1016/j.ydbio.2010.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 11/24/2010] [Accepted: 12/01/2010] [Indexed: 12/31/2022]
Abstract
The development of the Drosophila melanogaster wing depends on its subdivision into anterior and posterior compartments, which constitute two independent cell lineages since their origin in the embryonic ectoderm. The anterior-posterior compartment boundary is the place where signaling by the Hedgehog pathway takes place, and this requires pathway activation in anterior cells by ligand expressed exclusively in posterior cells. Several mechanisms ensure the confinement of hedgehog expression to posterior cells, including repression by Cubitus interruptus, the co-repressor Groucho and Master of thick veins. In this work we identified Kismet, a chromodomain-containing protein of the SNF2-like family of ATPases, as a novel component of the hedgehog transcriptional repression mechanism in anterior compartment cells. In kismet mutants, hedgehog is ectopically expressed in a domain of anterior cells close to the anterior-posterior compartment boundary, causing inappropriate activation of the pathway and changes in the development of the central region of the wing. The contribution of Kismet to the silencing of hedgehog expression is limited to anterior cells with low levels of the repressor form of Cubitus interruptus. We also show that knockdown of CHD8, the kismet homolog in Xenopus tropicalis, is also associated with ectopic sonic hedgehog expression and up-regulation of one of its target genes in the eye, Pax2, indicating the evolutionary conservation of Kismet/CHD8 function in negatively controlling hedgehog expression.
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Affiliation(s)
- Ana Terriente-Félix
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid Cantoblanco, Madrid, Spain
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25
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Farzan SF, Stegman MA, Ogden SK, Ascano M, Black KE, Tacchelly O, Robbins DJ. A quantification of pathway components supports a novel model of Hedgehog signal transduction. J Biol Chem 2009; 284:28874-84. [PMID: 19717563 PMCID: PMC2781433 DOI: 10.1074/jbc.m109.041608] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 08/25/2009] [Indexed: 11/06/2022] Open
Abstract
The secreted protein Hedgehog (Hh) plays a critical instructional role during metazoan development. In Drosophila, Hh signaling is interpreted by a set of conserved, downstream effectors that differentially localize and interact to regulate the stability and activity of the transcription factor Cubitus interruptus. Two essential models that integrate genetic, cell biological, and biochemical information have been proposed to explain how these signaling components relate to one another within the cellular context. As the molar ratios of the signaling effectors required in each of these models are quite different, quantitating the cellular ratio of pathway components could distinguish these two models. Here, we address this important question using a set of purified protein standards to perform a quantitative analysis of Drosophila cell lysates for each downstream pathway component. We determine each component's steady-state concentration within a given cell, demonstrate the molar ratio of Hh signaling effectors differs more than two orders of magnitude and that this ratio is conserved in vivo. We find that the G-protein-coupled transmembrane protein Smoothened, an activating component, is present in limiting amounts, while a negative pathway regulator, Suppressor of Fused, is present in vast molar excess. Interestingly, despite large differences in the steady-state ratio, all downstream signaling components exist in an equimolar membrane-associated complex. We use these quantitative results to re-evaluate the current models of Hh signaling and now propose a novel model of signaling that accounts for the stoichiometric differences observed between various Hh pathway components.
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Affiliation(s)
- Shohreh F. Farzan
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - Melanie A. Stegman
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - Stacey K. Ogden
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - Manuel Ascano
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - Kendall E. Black
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - Ofelia Tacchelly
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
| | - David J. Robbins
- From the Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755 and
- the Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03756
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Carreira-Barbosa F, Kajita M, Kajita M, Morel V, Wada H, Okamoto H, Martinez Arias A, Fujita Y, Wilson SW, Tada M. Flamingo regulates epiboly and convergence/extension movements through cell cohesive and signalling functions during zebrafish gastrulation. Development 2008; 136:383-92. [PMID: 19091770 DOI: 10.1242/dev.026542] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During vertebrate gastrulation, the body axis is established by coordinated and directional movements of cells that include epiboly, involution, and convergence and extension (C&E). Recent work implicates a non-canonical Wnt/planar cell polarity (PCP) pathway in the regulation of C&E. The Drosophila atypical cadherin Flamingo (Fmi) and its vertebrate homologue Celsr, a 7-pass transmembrane protein with extracellular cadherin repeats, regulate several biological processes, including C&E, cochlear cell orientation, axonal pathfinding and neuronal migration. Fmi/Celsr can function together with molecules involved in PCP, such as Frizzled (Fz) and Dishevelled (Dsh), but there is also some evidence that it may act as a cell adhesion molecule in a PCP-pathway-independent manner. We show that abrogation of Celsr activity in zebrafish embryos results in epiboly defects that appear to be independent of the requirement for Celsr in PCP signalling during C&E. Using a C-terminal truncated form of Celsr that inhibits membrane presentation of wild-type Celsr through its putative pro-region, a hanging drop assay reveals that cells from embryos with compromised Celsr activity have different cohesive properties from wild-type cells. It is disruption of this ability of Celsr to affect cell cohesion that primarily leads to the in vivo epiboly defects. In addition, Lyn-Celsr, in which the intracellular domain of Celsr is fused to a membrane localisation signal (Lyn), inhibits Fz-Dsh complex formation during Wnt/PCP signalling without affecting epiboly. Fmi/Celsr therefore has a dual role in mediating two separate morphogenetic movements through its roles in mediating cell cohesion and Wnt/PCP signalling during zebrafish gastrulation.
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Affiliation(s)
- Filipa Carreira-Barbosa
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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Abstract
The Hedgehog (Hh) family of proteins control cell growth, survival, and fate, and pattern almost every aspect of the vertebrate body plan. The use of a single morphogen for such a wide variety of functions is possible because cellular responses to Hh depend on the type of responding cell, the dose of Hh received, and the time cells are exposed to Hh. The Hh gradient is shaped by several proteins that are specifically required for Hh processing, secretion, and transport through tissues. The mechanism of cellular response, in turn, incorporates multiple feedback loops that fine-tune the level of signal sensed by the responding cells. Germline mutations that subtly affect Hh pathway activity are associated with developmental disorders, whereas somatic mutations activating the pathway have been linked to multiple forms of human cancer. This review focuses broadly on our current understanding of Hh signaling, from mechanisms of action to cellular and developmental functions. In addition, we review the role of Hh in the pathogenesis of human disease and the possibilities for therapeutic intervention.
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Affiliation(s)
- Markku Varjosalo
- Department of Molecular Medicine, National Public Health Institute (KTL), and Genome-Scale Biology Program, Biomedicum Helsinki, Institute of Biomedicine and High Throughput Center, Faculty of Medicine, University of Helsinki, Helsinki FI-00014, Finland
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Dessaud E, McMahon AP, Briscoe J. Pattern formation in the vertebrate neural tube: a sonic hedgehog morphogen-regulated transcriptional network. Development 2008; 135:2489-503. [PMID: 18621990 DOI: 10.1242/dev.009324] [Citation(s) in RCA: 512] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Neuronal subtype specification in the vertebrate neural tube is one of the best-studied examples of embryonic pattern formation. Distinct neuronal subtypes are generated in a precise spatial order from progenitor cells according to their location along the anterior-posterior and dorsal-ventral axes. Underpinning this organization is a complex network of multiple extrinsic and intrinsic factors. This review focuses on the molecular mechanisms and general strategies at play in ventral regions of the forming spinal cord, where sonic hedgehog-based morphogen signaling is a key determinant. We discuss recent advances in our understanding of these events and highlight unresolved questions.
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Affiliation(s)
- Eric Dessaud
- Developmental Neurobiology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK
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29
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Costal2 functions as a kinesin-like protein in the hedgehog signal transduction pathway. Curr Biol 2008; 18:1215-20. [PMID: 18691888 DOI: 10.1016/j.cub.2008.07.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 07/02/2008] [Accepted: 07/04/2008] [Indexed: 11/21/2022]
Abstract
The Hedgehog (Hh) signaling pathway initiates an evolutionarily conserved developmental program required for the proper patterning of many tissues [1]. Although Costal2 (Cos2) is a requisite component of the Hh pathway, its mechanistic role is not well understood. Because of its primary sequence, Cos2 was initially predicted to function as a kinesin-like protein [2]. However, evidence showing that Cos2 function might require kinesin-like properties has been lacking [2-6]. Thus, the prevailing dogma in the field is that Cos2 functions solely as a scaffolding protein [7, 8]. Here, we show that Cos2 motility is required for its biological function and that this motility may be Hh regulated. We show that Cos2 motility requires an active motor domain, ATP, and microtubules. Additionally, Cos2 recruits and transports other components of the Hh signaling pathway, including the transcription factor Cubitus interruptus (Ci). Drosophila expressing cos2 mutations that encode proteins that lack motility are attenuated in their ability to regulate Ci activity and exhibit phenotypes consistent with attenuated Cos2 function [9]. Combined, these results demonstrate that Cos2 motility plays an important role in its function, regulating the amounts and activity of Ci that ultimately interpret the level of Hh to which cells are exposed.
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30
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Low WC, Wang C, Pan Y, Huang XY, Chen JK, Wang B. The decoupling of Smoothened from Galphai proteins has little effect on Gli3 protein processing and Hedgehog-regulated chick neural tube patterning. Dev Biol 2008; 321:188-96. [PMID: 18590719 DOI: 10.1016/j.ydbio.2008.06.014] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 06/04/2008] [Accepted: 06/06/2008] [Indexed: 11/30/2022]
Abstract
The Hedgehog (Hh) signal is transmitted by two receptor molecules, Patched (Ptc) and Smoothened (Smo). Ptc suppresses Smo activity, while Hh binds Ptc and alleviates the suppression, which results in activation of Hh targets. Smo is a seven-transmembrane protein with a long carboxyl terminal tail. Vertebrate Smo has been previously shown to be coupled to Galpha(i) proteins, but the biological significance of the coupling in Hh signal transduction is not clear. Here we show that although inhibition of Galpha(i) protein activity appears to significantly reduce Hh pathway activity in Ptc(-/-) mouse embryonic fibroblasts and the NIH3T3-based Shh-light cells, it fails to derepress Shh- or a Smo-agonist-induced inhibition of Gli3 protein processing, a known in vivo indicator of Hh signaling activity. The inhibition of Galpha(i) protein activity also cannot block the Sonic Hedgehog (Shh)-dependent specification of neural progenitor cells in the neural tube. Consistent with these results, overexpression of a constitutively active Galpha(i) protein, Galpha(i2)QL, cannot ectopically specify the neural cell types in the spinal cord, whereas an active Smo, SmoM2, can. Thus, our results indicate that the Smo-induced Galpha(i) activity plays an insignificant role in the regulation of Gli3 processing and Shh-regulated neural tube patterning.
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Affiliation(s)
- Wee-Chuang Low
- Department of Genetic Medicine, Weill Medical College of Cornell University, 1300 York Avenue, W404, New York, NY 10021, USA
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31
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Molnar C, Holguin H, Mayor F, Ruiz-Gomez A, de Celis JF. The G protein-coupled receptor regulatory kinase GPRK2 participates in Hedgehog signaling in Drosophila. Proc Natl Acad Sci U S A 2007; 104:7963-8. [PMID: 17483466 PMCID: PMC1876555 DOI: 10.1073/pnas.0702374104] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Indexed: 11/18/2022] Open
Abstract
Signaling by Smoothened (Smo) plays fundamental roles during animal development and is deregulated in a variety of human cancers. Smo is a transmembrane protein with a heptahelical topology characteristic of G protein-coupled receptors. Despite such similarity, the mechanisms regulating Smo signaling are not fully understood. We show that Gprk2, a Drosophila member of the G protein-coupled receptor kinases, plays a key role in the Smo signal transduction pathway. Lowering Gprk2 levels in the wing disc reduces the expression of Smo targets and causes a phenotype reminiscent of loss of Smo function. We found that Gprk2 function is required for transducing the Smo signal and that when Gprk2 levels are lowered, Smo still accumulates at the cell membrane, but its activation is reduced. Interestingly, the expression of Gprk2 in the wing disc is regulated in part by Smo, generating a positive feedback loop that maintains high Smo activity close to the anterior-posterior compartment boundary.
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Affiliation(s)
| | - Helena Holguin
- *Centro de Biología Molecular “Severo Ochoa” and
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Federico Mayor
- *Centro de Biología Molecular “Severo Ochoa” and
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Ana Ruiz-Gomez
- *Centro de Biología Molecular “Severo Ochoa” and
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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32
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Ruiz-Gómez A, Molnar C, Holguín H, Mayor F, de Celis JF. The cell biology of Smo signalling and its relationships with GPCRs. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:901-12. [PMID: 17094938 DOI: 10.1016/j.bbamem.2006.09.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 09/20/2006] [Accepted: 09/25/2006] [Indexed: 12/11/2022]
Abstract
The Smoothened (Smo) signalling pathway participates in many developmental processes, contributing to the regulation of gene expression by controlling the activity of transcription factors belonging to the Gli family. The key elements of the pathway were identified by means of genetic screens carried out in Drosophila, and subsequent analysis in other model organisms revealed a high degree of conservation in both the proteins involved and in their molecular interactions. Recent analysis of the pathway, using a combination of biochemical and cell biological approaches, is uncovering the intricacies of Smo signalling, placing its elements in particular cellular compartments and qualifying the molecular processes involved. These include the synthesis, secretion and diffusion of the ligand, the activation of the receptor and the modifications in the activity of nuclear effectors. In this review we discuss recent advances in understanding biochemical and cellular aspects of Smo signalling, with particular focus in the similarities in the mechanism of signal transduction between Smo and other transmembrane proteins belonging to the G-Protein coupled receptors superfamily (GPCR).
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Affiliation(s)
- Ana Ruiz-Gómez
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
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33
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Walthall SL, Moses M, Horabin JI. A large complex containing Patched and Smoothened initiates Hedgehog signaling in Drosophila. J Cell Sci 2007; 120:826-37. [PMID: 17284519 DOI: 10.1242/jcs.03382] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hedgehog acts as an organizer during development. Its signaling involves the receptor Patched, signal transducer Smoothened and a cytoplasmic complex containing the transcription factor Cubitus interruptus tethered to the Smoothened carboxyl tail. Without Hedgehog, Patched represses Smoothened resulting in proteolysis of Cubitus interruptus to its repressor form. With Hedgehog, Patched repression of Smoothened is relieved and Cubitus interruptus is activated. Sex-lethal, the master switch for sex determination in Drosophila, has been shown to associate with Cubitus interruptus and the cytoplasmic components of the Hedgehog signaling pathway. Additionally, Sex-lethal responds to the presence of Hedgehog in a Patched-dependent manner. The latter prompted us to examine the role of Patched in signaling. We find that Cubitus interruptus, Sex-lethal, Patched and Smoothened co-immunoprecipitate and co-fractionate, suggesting a large complex of both membrane and cytoplasmic components of the Hedgehog pathway. The entire complex is present at the plasma membrane and the association of Patched changes depending on the activation state of the pathway; it also is not female specific. Colocalization analyses suggest that Sex-lethal alters the endocytic cycling of the Hedgehog components and may augment the Hedgehog signal in females by decreasing the proteolytic cleavage of Cubitus interruptus, availing more of it for activation.
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Affiliation(s)
- Sabrina L Walthall
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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34
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Abstract
To fully understand how animals develop, it is often necessary to remove the function of a particular gene in a specific cell type or subset of cells. In Drosophila melanogaster, mosaic animals have been widely utilized to study cell fate, growth and patterning, and restriction of cell fate. This chapter describes using FLP recombinase to generate mosaic Drosophila, discussing the chromosomes and cross scheme, how to induce the clones, how to properly identify the appropriate progeny, and how to prepare and analyze the tissues, clones, and phenotypes. It then presents three examples, applying this technique to study Hedgehog signaling. The first example describes moderate-sized costal clones in imaginal discs, using green fluorescent protein (GFP) as a marker and dppLacZ and Engrailed expression as phenotypic reporters. The second describes filling the adult eye with roadkill mutant clones, using white as a marker and scoring morphology. The third describes clonal misexpression of a truncated form of Smoothened, using GFP and yellow as markers.
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35
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Busson D, Pret AM. GAL4/UAS targeted gene expression for studying Drosophila Hedgehog signaling. Methods Mol Biol 2007; 397:161-201. [PMID: 18025721 DOI: 10.1007/978-1-59745-516-9_13] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The GAL4/upstream activating sequence (UAS) system is one of the most powerful tools for targeted gene expression. It is based on the properties of the yeast GAL4 transcription factor which activates transcription of its target genes by binding to UAS cis-regulatory sites. In Drosophila, the two components are carried in separate lines allowing for numerous combinatorial possibilities. The driver lines provide tissue-specific GAL4 expression and the responder lines carry the coding sequence for the gene of interest under the control of UAS sites. In this chapter, the basic GAL4/UAS system and its extensions, namely those allowing precise temporal control and reversible expression, are described. In addition, a list of GAL4 and UAS lines and schematic maps of GAL4 and UAS vectors useful in the study of Hedgehog (Hh) signaling is given. Finally, uses of the GAL4/UAS system to resolve some of the questions addressed in the study of the Hh pathway are presented.
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36
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Walton KD, Croce JC, Glenn TD, Wu SY, McClay DR. Genomics and expression profiles of the Hedgehog and Notch signaling pathways in sea urchin development. Dev Biol 2006; 300:153-64. [PMID: 17067570 PMCID: PMC1880897 DOI: 10.1016/j.ydbio.2006.08.064] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 08/18/2006] [Accepted: 08/28/2006] [Indexed: 12/22/2022]
Abstract
The Hedgehog (Hh) and Notch signal transduction pathways control a variety of developmental processes including cell fate choice, differentiation, proliferation, patterning and boundary formation. Because many components of these pathways are conserved, it was predicted and confirmed that pathway components are largely intact in the sea urchin genome. Spatial and temporal location of these pathways in the embryo, and their function in development offer added insight into their mechanistic contributions. Accordingly, all major components of both pathways were identified and annotated in the sea urchin Strongylocentrotus purpuratus genome and the embryonic expression of key components was explored. Relationships of the pathway components, and modifiers predicted from the annotation of S. purpuratus, were compared against cnidarians, arthropods, urochordates, and vertebrates. These analyses support the prediction that the pathways are highly conserved through metazoan evolution. Further, the location of these two pathways appears to be conserved among deuterostomes, and in the case of Notch at least, display similar capacities in endomesoderm gene regulatory networks. RNA expression profiles by quantitative PCR and RNA in situ hybridization reveal that Hedgehog is produced by the endoderm beginning just prior to invagination, and signals to the secondary mesenchyme-derived tissues at least until the pluteus larva stage. RNA in situ hybridization of Notch pathway members confirms that Notch functions sequentially in the vegetal-most secondary mesenchyme cells and later in the endoderm. Functional analyses in future studies will embed these pathways into the growing knowledge of gene regulatory networks that govern early specification and morphogenesis.
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Affiliation(s)
- Katherine D Walton
- Developmental, Cellular, and Molecular Biology Group, Duke University, Durham, NC 27710, USA.
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37
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Malpel S, Claret S, Sanial M, Brigui A, Piolot T, Daviet L, Martin-Lannerée S, Plessis A. The last 59 amino acids of Smoothened cytoplasmic tail directly bind the protein kinase Fused and negatively regulate the Hedgehog pathway. Dev Biol 2006; 303:121-33. [PMID: 17182028 DOI: 10.1016/j.ydbio.2006.10.042] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 10/27/2006] [Accepted: 10/27/2006] [Indexed: 01/28/2023]
Abstract
The Hedgehog (HH) signaling pathway is crucial for the development of many organisms and its inappropriate activation is involved in numerous cancers. HH signal controls the traffic and activity of the seven-pass transmembrane protein Smoothened (SMO), leading to the transcriptional regulation of HH-responsive genes. In Drosophila, the intracellular transduction events following SMO activation depend on cytoplasmic multimeric complexes that include the Fused (FU) protein kinase. Here we show that the regulatory domain of FU physically interacts with the last 52 amino acids of SMO and that the two proteins colocalize in vivo to vesicles. The deletion of this region of SMO leads to a constitutive activation of SMO, promoting the ectopic transcription of HH target genes. This activation is partially dependent of FU activity. Thus, we identify a novel link between SMO and the cytoplasmic complex(es) and reveal a negative role of the SMO C-terminal region that interacts with FU. We propose that FU could act as a switch, activator in presence of HH signal or inhibitor in absence of HH.
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Affiliation(s)
- Sébastien Malpel
- Génétique du Développement et Evolution, Institut Jacques Monod, UMR 7592, CNRS/Universités Paris 6 and 7, 2 Place Jussieu, 75251 Paris cedex 05, France
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38
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Kent D, Bush EW, Hooper JE. Roadkill attenuates Hedgehog responses through degradation of Cubitus interruptus. Development 2006; 133:2001-10. [PMID: 16651542 DOI: 10.1242/dev.02370] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The final step in Hedgehog (Hh) signal transduction is post-translational regulation of the transcription factor, Cubitus interruptus (Ci). Ci resides in the cytoplasm in a latent form, where Hh regulates its processing into a transcriptional repressor or its nuclear access as a transcriptional activator. Levels of latent Ci are controlled by degradation, with different pathways activated in response to different levels of Hh. Here, we describe the roadkill (rdx) gene, which is expressed in response to Hh. The Rdx protein belongs to a conserved family of proteins that serve as substrate adaptors for Cullin3-mediated ubiquitylation. Overexpression of rdx reduced Ci levels and decreased both transcriptional activation and repression mediated by Ci. Loss of rdx allowed excessive accumulation of Ci. rdx manipulation in the eye revealed a novel role for Hh in the organization and survival of pigment and cone cells. These studies identify rdx as a limiting factor in a feedback loop that attenuates Hh responses through reducing levels of Ci. The existence of human orthologs for Rdx raises the possibility that this novel feedback loop also modulates Hh responses in humans.
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Affiliation(s)
- David Kent
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, PO Box 6511, Aurora, CO 80045, USA
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Huangfu D, Anderson KV. Signaling from Smo to Ci/Gli: conservation and divergence of Hedgehog pathways from Drosophila to vertebrates. Development 2006; 133:3-14. [PMID: 16339192 DOI: 10.1242/dev.02169] [Citation(s) in RCA: 375] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although the framework of the Hedgehog (Hh) signaling pathway is evolutionarily conserved, recent studies indicate that fundamental differences exist between Drosophila and vertebrates in the way signals are transduced from the membrane protein Smoothened (Smo) to the Ci/Gli transcription factors. For example, Smo structure and the roles of fused and Suppressor of fused have diverged. Recently, many vertebrate-specific components have been identified that act between Smo and Gli. These include intra-flagellar transport proteins, which link vertebrate Hh signaling to cilia. Because abnormal Hh signaling can cause birth defects and cancer, these vertebrate-specific components may have roles in human health.
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Affiliation(s)
- Danwei Huangfu
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY 10021, USA
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40
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Molnar C, de Celis JF. Independent roles of Drosophila Moesin in imaginal disc morphogenesis and hedgehog signalling. Mech Dev 2006; 123:337-51. [PMID: 16682173 DOI: 10.1016/j.mod.2006.02.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2005] [Revised: 02/17/2006] [Accepted: 02/20/2006] [Indexed: 12/31/2022]
Abstract
The three ERM proteins (Ezrin, Radixin and Moesin) form a conserved family required in many developmental processes involving regulation of the cytoskeleton. In general, the molecular function of ERM proteins is to link specific membrane proteins to the actin cytoskeleton. In Drosophila, loss of moesin (moe) activity causes incorrect localisation of maternal determinants during oogenesis, failures in rhabdomere differentiation in the eye and alterations of epithelial integrity in the wing imaginal disc. Some aspects of Drosophila Moe are related to the activity of the small GTPase RhoA, because the reduction of RhoA activity corrects many phenotypes of moe mutant embryos and imaginal discs. We have analysed the phenotype of moesin loss-of-function alleles in the wing disc and adult wing, and studied the effects of reduced Moesin activity on signalling mediated by the Notch, Decapentaplegic, Wingless and Hedgehog pathways. We found that reductions in Moesin levels in the wing disc cause the formation of wing-tissue vesicles and large thickenings of the vein L3, corresponding to breakdowns of epithelial continuity in the wing base and modifications of Hedgehog signalling in the wing blade, respectively. We did not observe any effect on signalling pathways other than Hedgehog, indicating that the moe defects in epithelial integrity have not generalised effects on cell signalling. The effects of moe mutants on Hedgehog signalling depend on the correct gene-dose of rhoA, suggesting that the requirements for Moesin in disc morphogenesis and Hh signalling in the wing disc are mediated by its regulation of RhoA activity. The mechanism linking Moesin activity with RhoA function and Hedgehog signalling remains to be elucidated.
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Affiliation(s)
- Cristina Molnar
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
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41
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Varjosalo M, Li SP, Taipale J. Divergence of hedgehog signal transduction mechanism between Drosophila and mammals. Dev Cell 2006; 10:177-86. [PMID: 16459297 DOI: 10.1016/j.devcel.2005.12.014] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 11/24/2005] [Accepted: 12/27/2005] [Indexed: 11/27/2022]
Abstract
The Hedgehog (Hh) signaling pathway has conserved roles in development of species ranging from Drosophila to humans. Responses to Hh are mediated by the transcription factor Cubitus interruptus (Ci; GLIs 1-3 in mammals), and constitutive activation of Hh target gene expression has been linked to several types of human cancer. In Drosophila, the kinesin-like protein Costal2 (Cos2), which associates directly with the Hh receptor component Smoothened (Smo), is essential for suppression of the transcriptional activity of Ci in the absence of ligand. Another protein, Suppressor of Fused (Su(Fu)), exerts a weak negative influence on Ci activity. Based on analysis of functional and sequence conservation of Cos2 orthologs, Su(Fu), Smo, and Ci/GLI proteins, we find here that Drosophila and mammalian Hh signaling mechanisms have diverged, and that, in mouse cells, major Cos2-like activities are absent and the inhibition of the Hh pathway in the absence of ligand critically depends on Su(Fu).
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Affiliation(s)
- Markku Varjosalo
- Molecular and Cancer Biology Program, Biomedicum, University of Helsinki and Department of Molecular Medicine, National Public Health Institute, P.O. Box 63, Helsinki FIN-00014, Finland
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42
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Ogden SK, Casso DJ, Ascano M, Yore MM, Kornberg TB, Robbins DJ. Smoothened regulates activator and repressor functions of Hedgehog signaling via two distinct mechanisms. J Biol Chem 2006; 281:7237-43. [PMID: 16423832 PMCID: PMC3677211 DOI: 10.1074/jbc.m510169200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The secreted protein Hedgehog (Hh) plays an important role in metazoan development and as a survival factor for many human tumors. In both cases, Hh signaling proceeds through the activation of the seven-transmembrane protein Smoothened (Smo), which is thought to convert the Gli family of transcription factors from transcriptional repressors to transcriptional activators. Here, we provide evidence that Smo signals to the Hh signaling complex, which consists of the kinesin-related protein Costal2 (Cos2), the protein kinase Fused (Fu), and the Drosophila Gli homolog cubitus interruptus (Ci), in two distinct manners. We show that many of the commonly observed molecular events following Hh signaling are not transmitted in a linear fashion but instead are activated through two signals that bifurcate at Smo to independently affect activator and repressor pools of Ci.
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Affiliation(s)
- Stacey K. Ogden
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - David J. Casso
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143
| | - Manuel Ascano
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755
- Department of Molecular Genetics Graduate Program, University of Cincinnati Medical Center, Cincinnati, Ohio 45267
| | - Mark M. Yore
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755
| | - Thomas B. Kornberg
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143
| | - David J. Robbins
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755
- To whom correspondence should be addressed: Dept. of Pharmacology and Toxicology, Dartmouth Medical School, HB 7650 Remsen, Hanover, NH, 03755-7650. Tel.: 603-650-1716; Fax: 603-650-1129;
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Croker JA, Ziegenhorn SL, Holmgren RA. Regulation of the Drosophila transcription factor, Cubitus interruptus, by two conserved domains. Dev Biol 2006; 291:368-81. [PMID: 16413529 DOI: 10.1016/j.ydbio.2005.12.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 12/06/2005] [Accepted: 12/08/2005] [Indexed: 12/23/2022]
Abstract
Hedgehog signaling is required for the development of many organisms, including Drosophila. In flies, Hh patterns the embryonic epidermis and larval imaginal discs by regulating the transcription factor, Cubitus interruptus (Ci). To date, three levels of regulation have been identified: proteolytic processing into a repressor, nuclear import, and activation. In this report, we characterize the function of two Ci domains that are conserved in the vertebrate homologues, GLI1, GLI2, and GLI3. One domain includes the first two of five C(2)-H(2) zinc-fingers. While conserved in all members of the GLI/Ci family, the first two fingers do not appear to make significant contacts with the DNA target sequence. Ci protein lacking this region is still able to interact with the cytoplasmic complex and activate transcription in embryos and wing imaginal discs, but it is no longer processed into the repressor form. The second domain, termed NR for "N-terminal Regulatory", binds Suppressor of Fused. Deletion of this region has little effect on embryonic patterning, but compromises cytoplasmic retention of Ci. Analysis of the amino acid sequence of this domain identifies 11 perfectly conserved serines and one tyrosine. We propose that this region may be modified, possibly by phosphorylation, to regulate Ci nuclear import.
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Affiliation(s)
- Jennifer A Croker
- Department of Biochemistry, Molecular Biology, and Cell Biology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL 60208, USA
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Torroja C, Gorfinkiel N, Guerrero I. Mechanisms of Hedgehog gradient formation and interpretation. ACTA ACUST UNITED AC 2005; 64:334-56. [PMID: 16041759 DOI: 10.1002/neu.20168] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Morphogens are molecules that spread from localized sites of production, specifying distinct cell outcomes at different concentrations. Members of the Hedgehog (Hh) family of signaling molecules act as morphogens in different developmental systems. If we are to understand how Hh elicits multiple responses in a temporally and spatially specific manner, the molecular mechanism of Hh gradient formation needs to be established. Moreover, understanding the mechanisms of Hh signaling is a central issue in biology, not only because of the role of Hh in morphogenesis, but also because of its involvement in a wide range of human diseases. Here, we review the mechanisms affecting the dynamics of Hh gradient formation, mostly in the context of Drosophila wing development, although parallel findings in vertebrate systems are also discussed.
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Affiliation(s)
- Carlos Torroja
- Centro de Biología Molecular Severo Ochoa, CSIC, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain
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May SR, Ashique AM, Karlen M, Wang B, Shen Y, Zarbalis K, Reiter J, Ericson J, Peterson AS. Loss of the retrograde motor for IFT disrupts localization of Smo to cilia and prevents the expression of both activator and repressor functions of Gli. Dev Biol 2005; 287:378-89. [PMID: 16229832 DOI: 10.1016/j.ydbio.2005.08.050] [Citation(s) in RCA: 329] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 08/24/2005] [Accepted: 08/29/2005] [Indexed: 10/25/2022]
Abstract
Sonic Hedgehog (Shh) signals are transduced into nuclear ratios of Gli transcriptional activator versus repressor. The initial part of this process is accomplished by Shh acting through Patched (Ptc) to regulate Smoothened (Smo) activity. The mechanisms by which Ptc regulates Smo, and Smo activity is transduced to processing of Gli proteins remain unclear. Recently, a forward genetic approach in mice identified a role for intraflagellar transport (IFT) genes in Shh signal transduction, downstream of Patched (Ptc) and Rab23. Here, we show that the retrograde motor for IFT is required in the mouse for the phenotypic expression of both Gli activator and repressor function and for effective proteolytic processing of Gli3. Furthermore, we show that the localization of Smo to primary cilia is disrupted in mutants. These data indicate that primary cilia act as specialized signal transduction organelles required for coupling Smo activity to the biochemical processing of Gli3 protein.
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Affiliation(s)
- Scott R May
- Ernest Gallo Clinic and Research Center, Emeryville, CA 94608, USA
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46
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Abstract
The Hedgehog (Hh)-signaling pathway is essential for numerous developmental processes in Drosophila and vertebrate embryos. Hh signal transduction encompasses a complex series of regulatory events, including the generation of the mature Hh ligand, propagation of the ligand from source of production as well as the reception and interpretation of the signal in Hh-receiving cells. Many congenital malformations in humans are known to involve mutations in various components of the Hh-signaling pathway. This mini review summarizes some recent findings about the regulation of Hh signal transduction and describes the spectrum of human congenital malformations that are associated with aberrant Hh signaling. Based on a comparison of mouse-mutant phenotypes and human syndromes, we discuss how Hh-dependent Gli activator and repressor functions contribute to some of the congenital malformations.
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Affiliation(s)
- E Nieuwenhuis
- Program in Developmental Biology, The Hospital for Sick Children, Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario MG5 1X8, Canada
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47
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Abstract
Signalling by secreted Hedgehog (Hh) proteins is important for the development of many tissues and organs. Damage to components of the Hh signal-transduction pathway can lead to birth defects and cancer. The Hh proteins are distributed in tissues in a gradient, and cells respond to different thresholds of Hh with distinct responses. The cellular machinery that is responsible for the unique molecular mechanisms of Hh signal transduction has been largely conserved during metazoan evolution.
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Affiliation(s)
- Joan E Hooper
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, 12801 East 17th Avenue, Box 8018, Aurora, Colorado 80045, USA.
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Zhang W, Zhao Y, Tong C, Wang G, Wang B, Jia J, Jiang J. Hedgehog-regulated Costal2-kinase complexes control phosphorylation and proteolytic processing of Cubitus interruptus. Dev Cell 2005; 8:267-78. [PMID: 15691767 DOI: 10.1016/j.devcel.2005.01.001] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 01/10/2005] [Accepted: 01/10/2005] [Indexed: 12/21/2022]
Abstract
Hedgehog (Hh) proteins control animal development by regulating the Gli/Ci family of transcription factors. In Drosophila, Hh counteracts phosphorylation by PKA, GSK3, and CKI to prevent Cubitus interruptus (Ci) processing through unknown mechanisms. Here, we show that these kinases physically interact with the kinesin-like protein Costal2 (Cos2) to control Ci processing and that Hh inhibits such interaction. Cos2 is required for Ci phosphorylation in vivo, and Cos2-immunocomplexes (Cos2IPs) phosphorylate Ci and contain PKA, GSK3, and CKI. By using a Kinesin-Cos2 chimeric protein that carries Cos2-interacting proteins to the microtubule plus end, we demonstrated that these kinases bind Cos2 in intact cells. PKA, GSK3, and CKI directly bind the N- and C-terminal regions of Cos2, both of which are essential for Ci processing. Finally, we showed that Hh signaling inhibits Cos2-kinase complex formation. We propose that Cos2 recruits multiple kinases to efficiently phosphorylate Ci and that Hh inhibits Ci phosphorylation by specifically interfering with kinase recruitment.
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Affiliation(s)
- Wensheng Zhang
- Center for Developmental Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Nakano Y, Nystedt S, Shivdasani AA, Strutt H, Thomas C, Ingham PW. Functional domains and sub-cellular distribution of the Hedgehog transducing protein Smoothened in Drosophila. Mech Dev 2005; 121:507-18. [PMID: 15172682 DOI: 10.1016/j.mod.2004.04.015] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 03/30/2004] [Accepted: 04/15/2004] [Indexed: 10/26/2022]
Abstract
The Hedgehog signalling pathway is deployed repeatedly during normal animal development and its inappropriate activity is associated with various tumours in human. The serpentine protein Smoothened (Smo) is essential for cells to respond to the Hedeghog (Hh) signal; oncogenic forms of Smo have been isolated from human basal cell carcinomas. Despite similarities with ligand binding G-protein coupled receptors, the molecular basis of Smo activity and its regulation remains unclear. In non-responding cells, Smo is suppressed by the activity of another multipass membrane spanning protein Ptc, which acts as the Hh receptor. In Drosophila, binding of Hh to Ptc has been shown to cause an accumulation of phosphorylated Smo protein and a concomitant stabilisation of the activated form of the Ci transcription factor. Here, we identify domains essential for Smo activity and investigate the sub-cellular distribution of the wild type protein in vivo. We find that deletion of the amino terminus and the juxtamembrane region of the carboxy terminus of the protein result in the loss of normal Smo activity. Using Green Fluorescent Protein (GFP) and horseradish peroxidase fusion proteins we show that Smo accumulates in the plasma membrane of cells in which Ptc activity is abrogated by Hh but is targeted to the degradative pathway in cells where Ptc is active. We further demonstrate that Smo accumulation is likely to be a cause, rather than a consequence, of Hh signal transduction.
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Affiliation(s)
- Y Nakano
- MRC Intercellular Signalling Group, Centre for Developmental Genetics, University School of Medicine and Biomedical Science, Firth Court, Western Bank, Sheffield S10 2TN, UK
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Besse F, Busson D, Pret AM. Hedgehog signaling controls Soma-Germen interactions duringDrosophila ovarian morphogenesis. Dev Dyn 2005; 234:422-31. [PMID: 16145667 DOI: 10.1002/dvdy.20537] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The genetic analysis of Drosophila adult oogenesis has provided insights into the molecular mechanisms that control cell proliferation, differentiation, migration, and intercellular signaling. However, little is known about the larval and pupal cellular events leading to the formation of the highly organized adult ovary, which is composed of ovarioles each containing germline cells enveloped by specialized somatic cells. We describe here the presence of ovarioles devoid of any germ cells in adult females mutant for fused, which encodes a Hedgehog signal transducing serine/threonine kinase. We show that this phenotype corresponds to a requirement for fused function for the organization of germ cells with respect to ovarian somatic cells during ovariole formation specifically during pupal stages and provide some evidence by means of clonal analysis suggesting that fused function may be necessary in the germline. hedgehog is expressed specifically in somatic terminal filament cells in pupal ovaries, and females bearing hedgehog strong loss-of-function mutations also exhibit aberrant germ cell distribution and formation of agametic ovarioles. These results indicate a positive role for Fused in the transduction of somatic Hedgehog signaling instructing ovariole morphogenesis. We also provide evidence for the use of noncanonical Hedgehog signal transducer(s) within germline cells.
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Affiliation(s)
- Florence Besse
- Institut J. Monod, UMR 7592-CNRS/Université Pierre et Marie Curie/Université Denis Diderot, Laboratoire de Génétique du Développement et Evolution 2, place Jussieu, Paris, France
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