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Yamamoto M, Morita R, Mizoguchi T, Matsuo H, Isoda M, Ishitani T, Chitnis AB, Matsumoto K, Crump JG, Hozumi K, Yonemura S, Kawakami K, Itoh M. Mib-Jag1-Notch signalling regulates patterning and structural roles of the notochord by controlling cell-fate decisions. Development 2010; 137:2527-37. [PMID: 20573700 DOI: 10.1242/dev.051011] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the developing embryo, cell-cell signalling is necessary for tissue patterning and structural organization. During midline development, the notochord plays roles in the patterning of its surrounding tissues while forming the axial structure; however, how these patterning and structural roles are coordinated remains elusive. Here, we identify a mechanism by which Notch signalling regulates the patterning activities and structural integrity of the notochord. We found that Mind bomb (Mib) ubiquitylates Jagged 1 (Jag1) and is essential in the signal-emitting cells for Jag1 to activate Notch signalling. In zebrafish, loss- and gain-of-function analyses showed that Mib-Jag1-Notch signalling favours the development of non-vacuolated cells at the expense of vacuolated cells in the notochord. This leads to changes in the peri-notochordal basement membrane formation and patterning surrounding the muscle pioneer cells. These data reveal a previously unrecognized mechanism regulating the patterning and structural roles of the notochord by Mib-Jag1-Notch signalling-mediated cell-fate determination.
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Affiliation(s)
- Mai Yamamoto
- Institute for Advanced Research, Nagoya University, Nagoya, Aichi 464-8602, Japan
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Benhra N, Vignaux F, Dussert A, Schweisguth F, Le Borgne R. Neuralized promotes basal to apical transcytosis of delta in epithelial cells. Mol Biol Cell 2010; 21:2078-86. [PMID: 20410139 PMCID: PMC2883951 DOI: 10.1091/mbc.e09-11-0926] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
In this article, it is shown that a pool of Delta localizes at the basolateral membrane of sensory organ precursor cells of Drosophila and of polarized MDCK cells and that Delta is endocytosed in a Neuralized-dependent manner from this basolateral membrane to allow for relocalization to the apical domain where it can bind and activate Notch. Notch receptors mediate short-range signaling controlling many developmental decisions in metazoans. Activation of Notch requires the ubiquitin-dependent endocytosis of its ligand Delta. How ligand endocytosis in signal-sending cells regulates receptor activation in juxtaposed signal-receiving cells remains largely unknown. We show here that a pool of Delta localizes at the basolateral membrane of signal-sending sensory organ precursor cells in the dorsal thorax neuroepithelium of Drosophila and that Delta is endocytosed in a Neuralized-dependent manner from this basolateral membrane. This basolateral pool of Delta is segregated from Notch that accumulates apically. Using a compartimentalized antibody uptake assay, we show that murine Delta-like 1 is similarly internalized by mNeuralized2 from the basolateral membrane of polarized Madin-Darby canine kidney cells and that internalized ligands are transcytosed to the apical plasma membrane where mNotch1 accumulates. Thus, endocytosis of Delta by Neuralized relocalizes Delta from the basolateral to the apical membrane domain. We speculate that this Neuralized-dependent transcytosis regulates the signaling activity of Delta by relocalizing Delta from a membrane domain where it cannot interact with Notch to another membrane domain where it can bind and activate Notch.
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Affiliation(s)
- Najate Benhra
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 6061, Institut de Génétique et Développement de Rennes, Université de Rennes 1, 35000 Rennes, France
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Ma D, Zhu Y, Ji C, Hou M. Targeting the Notch signaling pathway in autoimmune diseases. Expert Opin Ther Targets 2010; 14:553-65. [DOI: 10.1517/14728221003752750] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Wang Y, Chen Z, Bergmann A. Regulation of EGFR and Notch signaling by distinct isoforms of D-cbl during Drosophila development. Dev Biol 2010; 342:1-10. [PMID: 20302857 DOI: 10.1016/j.ydbio.2010.03.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 03/08/2010] [Accepted: 03/10/2010] [Indexed: 01/25/2023]
Abstract
Cells receive and interpret extracellular signals to regulate cellular responses such as proliferation, cell survival and differentiation. However, proper inactivation of these signals is critical for appropriate homeostasis. Cbl proteins are E3-ubiquitin ligases that restrict receptor tyrosine kinase (RTK) signaling, most notably EGFR (Epidermal Growth Factor Receptor), via the endocytic pathway. Consistently, many mutant phenotypes of Drosophila cbl (D-cbl) are due to inappropriate activation of EGFR signaling. However, not all D-cbl phenotypes can be explained by increased EGFR activity. Here, we report that D-Cbl also negatively regulates Notch activity during eye and wing development. D-cbl produces two isoforms by alternative splicing. The long isoform, D-CblL, regulates the EGFR. We found that the short isoform, D-CblS, preferentially restricts Notch signaling. Specifically, our data imply that D-CblS controls the activity of the Notch ligand Delta. Taken together, these data suggest that D-Cbl controls the EGFR and Notch/Delta signaling pathways through production of two alternatively spliced isoforms during development in Drosophila.
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Affiliation(s)
- Yuan Wang
- The University of Texas M.D. Anderson Cancer Center, Department of Biochemistry & Molecular Biology, 1515 Holcombe Blvd.-Unit 1000, Houston, TX 77030, USA
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Monastirioti M, Giagtzoglou N, Koumbanakis KA, Zacharioudaki E, Deligiannaki M, Wech I, Almeida M, Preiss A, Bray S, Delidakis C. Drosophila Hey is a target of Notch in asymmetric divisions during embryonic and larval neurogenesis. Development 2010; 137:191-201. [PMID: 20040486 DOI: 10.1242/dev.043604] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
bHLH-O proteins are a subfamily of the basic-helix-loop-helix transcription factors characterized by an 'Orange' protein-protein interaction domain. Typical members are the Hairy/E(spl), or Hes, proteins, well studied in their ability, among others, to suppress neuronal differentiation in both invertebrates and vertebrates. Hes proteins are often effectors of Notch signalling. In vertebrates, another bHLH-O protein group, the Hey proteins, have also been shown to be Notch targets and to interact with Hes. We have studied the single Drosophila Hey orthologue. We show that it is primarily expressed in a subset of newly born neurons, which receive Notch signalling during their birth. Unlike in vertebrates, however, Hey is not expressed in precursor cells and does not block neuronal differentiation. It rather promotes one of two alternative fates that sibling neurons adopt at birth. Although in the majority of cases Hey is a Notch target, it is also expressed independently of Notch in some lineages, most notably the larval mushroom body. The availability of Hey as a Notch readout has allowed us to study Notch signalling during the genesis of secondary neurons in the larval central nervous system.
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Affiliation(s)
- Maria Monastirioti
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 100 N. Plastira St., 70013 Heraklion, Crete, Greece
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Abstract
Notch signaling induced by canonical Notch ligands is critical for normal embryonic development and tissue homeostasis through the regulation of a variety of cell fate decisions and cellular processes. Activation of Notch signaling is normally tightly controlled by direct interactions with ligand-expressing cells, and dysregulated Notch signaling is associated with developmental abnormalities and cancer. While canonical Notch ligands are responsible for the majority of Notch signaling, a diverse group of structurally unrelated noncanonical ligands has also been identified that activate Notch and likely contribute to the pleiotropic effects of Notch signaling. Soluble forms of both canonical and noncanonical ligands have been isolated, some of which block Notch signaling and could serve as natural inhibitors of this pathway. Ligand activity can also be indirectly regulated by other signaling pathways at the level of ligand expression, serving to spatiotemporally compartmentalize Notch signaling activity and integrate Notch signaling into a molecular network that orchestrates developmental events. Here, we review the molecular mechanisms underlying the dual role of Notch ligands as activators and inhibitors of Notch signaling. Additionally, evidence that Notch ligands function independent of Notch is presented. We also discuss how ligand posttranslational modification, endocytosis, proteolysis, and spatiotemporal expression regulate their signaling activity.
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Affiliation(s)
- Brendan D'Souza
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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Kovall RA, Blacklow SC. Mechanistic insights into Notch receptor signaling from structural and biochemical studies. Curr Top Dev Biol 2010; 92:31-71. [PMID: 20816392 DOI: 10.1016/s0070-2153(10)92002-4] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Notch proteins are the receptors in a highly conserved signal transduction system used to communicate signals between cells that contact each other. Studies investigating structure-function relationships in Notch signaling have gained substantial momentum in recent years. Here, we summarize the current understanding of the molecular logic of Notch signal transduction, emphasizing structural and biochemical studies of Notch receptors, their ligands, and complexes of intracellular Notch proteins with their target transcription factors. Recent advances in the structure-based modulation of Notch-signaling activity are also discussed.
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Affiliation(s)
- Rhett A Kovall
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, OH, USA
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Abstract
Notch signaling occurs through direct interaction between Notch, the receptor, and its ligands, presented on the surface of neighboring cells. Endocytosis has been shown to be essential for Notch signal activation in both signal-sending and signal-receiving cells, and numerous genes involved in vesicle trafficking have recently been shown to act as key regulators of the pathway. Defects in vesicle trafficking can lead to gain- or loss-of-function defects in a context-dependent manner. Here, we discuss how endocytosis and vesicle trafficking regulate Notch signaling in both signal-sending and signal-receiving cells. We will introduce the key players in different trafficking steps, and further illustrate how they impact the signal outcome. Some of these players act as general factors and modulate Notch signaling in all contexts, whereas others modulate signaling in a context-specific fashion. We also discuss Notch signaling during mechanosensory organ development in the fly to exemplify how endocytosis and vesicle trafficking are effectively used to determine correct cell fates. In summary, endocytosis plays an essential role in Notch signaling, whereas intracellular vesicle trafficking often plays a context-dependent or regulatory role, leading to divergent outcomes in different developmental contexts.
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REST and CoREST modulate neuronal subtype specification, maturation and maintenance. PLoS One 2009; 4:e7936. [PMID: 19997604 PMCID: PMC2782136 DOI: 10.1371/journal.pone.0007936] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 10/18/2009] [Indexed: 11/19/2022] Open
Abstract
Background The repressor element-1 silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) is a master regulator of neuronal gene expression. REST functions as a modular scaffold for dynamic recruitment of epigenetic regulatory factors including its primary cofactor, the corepressor for element-1-silencing transcription factor (CoREST), to genomic loci that contain the repressor element-1 (RE1) binding motif. While REST was initially believed to silence RE1 containing neuronal genes in neural stem cells (NSCs) and non-neuronal cells, emerging evidence shows an increasingly complex cell type- and developmental stage-specific repertoire of REST target genes and functions that include regulation of neuronal lineage maturation and plasticity. Methodology/Principal Findings In this study, we utilized chromatin immunoprecipitation on chip (ChIP-chip) analysis to examine REST and CoREST functions during NSC-mediated specification of cholinergic neurons (CHOLNs), GABAergic neurons (GABANs), glutamatergic neurons (GLUTNs), and medium spiny projection neurons (MSNs). We identified largely distinct but overlapping profiles of REST and CoREST target genes during neuronal subtype specification including a disproportionately high percentage that are exclusive to each neuronal subtype. Conclusions/Significance Our findings demonstrate that the differential deployment of REST and CoREST is an important regulatory mechanism that mediates neuronal subtype specification by modulating specific gene networks responsible for inducing and maintaining neuronal subtype identity. Our observations also implicate a broad array of factors in the generation of neuronal diversity including but not limited to those that mediate homeostasis, cell cycle dynamics, cell viability, stress responses and epigenetic regulation.
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Gazave E, Lapébie P, Richards GS, Brunet F, Ereskovsky AV, Degnan BM, Borchiellini C, Vervoort M, Renard E. Origin and evolution of the Notch signalling pathway: an overview from eukaryotic genomes. BMC Evol Biol 2009; 9:249. [PMID: 19825158 PMCID: PMC2770060 DOI: 10.1186/1471-2148-9-249] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 10/13/2009] [Indexed: 12/20/2022] Open
Abstract
Background Of the 20 or so signal transduction pathways that orchestrate cell-cell interactions in metazoans, seven are involved during development. One of these is the Notch signalling pathway which regulates cellular identity, proliferation, differentiation and apoptosis via the developmental processes of lateral inhibition and boundary induction. In light of this essential role played in metazoan development, we surveyed a wide range of eukaryotic genomes to determine the origin and evolution of the components and auxiliary factors that compose and modulate this pathway. Results We searched for 22 components of the Notch pathway in 35 different species that represent 8 major clades of eukaryotes, performed phylogenetic analyses and compared the domain compositions of the two fundamental molecules: the receptor Notch and its ligands Delta/Jagged. We confirm that a Notch pathway, with true receptors and ligands is specific to the Metazoa. This study also sheds light on the deep ancestry of a number of genes involved in this pathway, while other members are revealed to have a more recent origin. The origin of several components can be accounted for by the shuffling of pre-existing protein domains, or via lateral gene transfer. In addition, certain domains have appeared de novo more recently, and can be considered metazoan synapomorphies. Conclusion The Notch signalling pathway emerged in Metazoa via a diversity of molecular mechanisms, incorporating both novel and ancient protein domains during eukaryote evolution. Thus, a functional Notch signalling pathway was probably present in Urmetazoa.
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Affiliation(s)
- Eve Gazave
- Aix-Marseille Universités, Centre d'Océanologie de Marseille, Station marine d'Endoume - CNRS UMR 6540-DIMAR, rue de Batterie des Lions, 13007 Marseille, France.
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61
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He F, Saito K, Kobayashi N, Harada T, Watanabe S, Kigawa T, Güntert P, Ohara O, Tanaka A, Unzai S, Muto Y, Yokoyama S. Structural and Functional Characterization of the NHR1 Domain of the Drosophila Neuralized E3 Ligase in the Notch Signaling Pathway. J Mol Biol 2009; 393:478-95. [DOI: 10.1016/j.jmb.2009.08.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2009] [Revised: 08/03/2009] [Accepted: 08/10/2009] [Indexed: 01/05/2023]
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Rizzo P, Osipo C, Pannuti A, Golde T, Osborne B, Miele L. Targeting Notch signaling cross-talk with estrogen receptor and ErbB-2 in breast cancer. ACTA ACUST UNITED AC 2009; 49:134-41. [PMID: 19344631 DOI: 10.1016/j.advenzreg.2009.01.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Paola Rizzo
- Breast Cancer Program, Cardinal Bernardin Cancer Center, Loyola University Chicago, Chicago, IL, USA
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63
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Matsuda M, Chitnis AB. Interaction with Notch determines endocytosis of specific Delta ligands in zebrafish neural tissue. Development 2008; 136:197-206. [PMID: 19056830 DOI: 10.1242/dev.027938] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Mind bomb1 (Mib1)-mediated endocytosis of the Notch ligand DeltaD is essential for activation of Notch in a neighboring cell. Although most DeltaD is localized in cytoplasmic puncta in zebrafish neural tissue, it is on the plasma membrane in mib1 mutants because Mib1-mediated endocytosis determines the normal subcellular localization of DeltaD. Knockdown of Notch increases cell surface DeltaA and DeltaD, but not DeltaC, suggesting that, like Mib1, Notch regulates endocytosis of specific ligands. Transplant experiments show that the interaction with Notch, both in the same cell (in cis) and in neighboring cells (in trans), regulates DeltaD endocytosis. Whereas DeltaD endocytosis following interaction in trans activates Notch in a neighboring cell, endocytosis of DeltaD and Notch following an interaction in cis is likely to inhibit Notch signaling by making both unavailable at the cell surface. The transplantation experiments reveal a heterogeneous population of progenitors: in some, cis interactions are more important; in others, trans interactions are more important; and in others, both cis and trans interactions are likely to contribute to DeltaD endocytosis. We suggest that this heterogeneity represents the process by which effective lateral inhibition leads to diversification of progenitors into cells that become specialized to deliver or receive Delta signals, where trans and cis interactions with Notch play differential roles in DeltaD endocytosis.
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Affiliation(s)
- Miho Matsuda
- Laboratory of Molecular Genetics, Section on Neural Developmental Dynamics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Rizzo P, Osipo C, Foreman K, Golde T, Osborne B, Miele L. Rational targeting of Notch signaling in cancer. Oncogene 2008; 27:5124-31. [PMID: 18758481 DOI: 10.1038/onc.2008.226] [Citation(s) in RCA: 314] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Accumulating preclinical and clinical evidence supports a pro-oncogenic function for Notch signaling in several solid tumors, particularly but not exclusively in breast cancer. Notch inhibitory agents, such as gamma-secretase inhibitors, are being investigated as candidate cancer therapeutic agents. Interest in therapeutic modulation of the Notch pathway has been increased by recent reports, indicating that its role is important in controlling the fate of putative 'breast cancer stem cells'. However, as is the case for most targeted therapies, successful targeting of Notch signaling in cancer will require a considerable refinement of our understanding of the regulation of this pathway and its effects in both normal and cancer cells. Notch signaling has bidirectional 'cross talk' interaction with multiple other pathways that include candidate therapeutic targets. Understanding these interactions will greatly increase our ability to design rational combination regimens. To determine which patients are most likely to benefit from treatment with Notch inhibitors, it will be necessary to develop molecular tests to accurately measure pathway activity in specific tumors. Finally, mechanism-based toxicities will have to be addressed by a careful choice of therapeutic agents, combinations and regimens. This article summarizes the current state of the field, and briefly describes opportunities and challenges for Notch-targeted therapies in oncology.
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Affiliation(s)
- P Rizzo
- Breast Cancer Program, Cardinal Bernardin Cancer Center, Loyola University Chicago, Chicago, IL 60163, USA
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Abstract
The Notch signaling pathway regulates a diverse array of cell types and cellular processes and is tightly regulated by ligand binding. Both canonical and noncanonical Notch ligands have been identified that may account for some of the pleiotropic nature associated with Notch signaling. This review focuses on the molecular mechanisms by which Notch ligands function as signaling agonists and antagonists, and discusses different modes of activating ligands as well as findings that support intrinsic ligand signaling activity independent of Notch. Post-translational modification, proteolytic processing, endocytosis and membrane trafficking, as well as interactions with the actin cytoskeleton may contribute to the recently appreciated multifunctionality of Notch ligands. The regulation of Notch ligand expression by other signaling pathways provides a mechanism to coordinate Notch signaling with multiple cellular and developmental cues. The association of Notch ligands with inherited human disorders and cancer highlights the importance of understanding the molecular nature and activities intrinsic to Notch ligands. Oncogene (2008) 27, 5148-5167; doi:10.1038/onc.2008.229.
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Affiliation(s)
- B D'Souza
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1737, USA
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Song R, Kim YW, Koo BK, Jeong HW, Yoon MJ, Yoon KJ, Jun DJ, Im SK, Shin J, Kong MP, Kim KT, Yoon K, Kong YY. Mind bomb 1 in the lymphopoietic niches is essential for T and marginal zone B cell development. ACTA ACUST UNITED AC 2008; 205:2525-36. [PMID: 18824586 PMCID: PMC2571928 DOI: 10.1084/jem.20081344] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Notch signaling regulates lineage decisions at multiple stages of lymphocyte development, and Notch activation requires the endocytosis of Notch ligands in the signal-sending cells. Four E3 ubiquitin ligases, Mind bomb (Mib) 1, Mib2, Neuralized (Neur) 1, and Neur2, regulate the Notch ligands to activate Notch signaling, but their roles in lymphocyte development have not been defined. We show that Mib1 regulates T and marginal zone B (MZB) cell development in the lymphopoietic niches. Inactivation of the Mib1 gene, but not the other E3 ligases, Mib2, Neur1, and Neur2, abrogated T and MZB cell development. Reciprocal bone marrow (BM) transplantation experiments revealed that Mib1 in the thymic and splenic niches is essential for T and MZB cell development. Interestingly, when BM cells from transgenic Notch reporter mice were transplanted into Mib1-null mice, the Notch signaling was abolished in the double-negative thymocytes. In addition, the endocytosis of Dll1 was impaired in the Mib1-null microenvironment. Moreover, the block in T cell development and the failure of Dll1 endocytosis were also observed in coculture system by Mib1 knockdown. Our study reveals that Mib1 is the essential E3 ligase in T and MZB cell development, through the regulation of Notch ligands in the thymic and splenic microenvironments.
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Affiliation(s)
- Ran Song
- Department of Life Science, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, South Korea
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Neuralized is expressed in the alpha/beta lobes of adult Drosophila mushroom bodies and facilitates olfactory long-term memory formation. Proc Natl Acad Sci U S A 2008; 105:14674-9. [PMID: 18794519 DOI: 10.1073/pnas.0801605105] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Memory formation involves multiple molecular mechanisms, the nature and components of which are essential to understand these processes. Drosophila is a powerful model to identify genes important for the formation and storage of consolidated memories because the molecular mechanisms and dependence of these processes on particular brain regions appear to be generally conserved. We present evidence that the highly conserved ubiquitin ligase Neuralized (Neur) is expressed in the adult Drosophila mushroom body (MB) alpha/beta lobe peripheral neurons and is a limiting factor for the formation of long-term memory (LTM). We show that loss of one copy of neur gene results in significant LTM impairment, whereas overexpression of Neur in the peripheral neurons of the alpha/beta lobes of the adult MBs results in a dosage-dependent enhancement of LTM. In contrast, learning, early memories, or anesthesia-resistant memory are not affected. We also demonstrate that the role of Neuralized in LTM formation is restricted within the neurons of the periphery of the alpha/beta lobes, and we suggest that this structural subdivision of the MBs participates in the formation of LTM.
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Diks SH, Sartori da Silva MA, Hillebrands JL, Bink RJ, Versteeg HH, van Rooijen C, Brouwers A, Chitnis AB, Peppelenbosch MP, Zivkovic D. d-Asb11 is an essential mediator of canonical Delta–Notch signalling. Nat Cell Biol 2008; 10:1190-8. [DOI: 10.1038/ncb1779] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 07/24/2008] [Indexed: 01/05/2023]
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Kandachar V, Bai T, Chang HC. The clathrin-binding motif and the J-domain of Drosophila Auxilin are essential for facilitating Notch ligand endocytosis. BMC DEVELOPMENTAL BIOLOGY 2008; 8:50. [PMID: 18466624 PMCID: PMC2391152 DOI: 10.1186/1471-213x-8-50] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Accepted: 05/08/2008] [Indexed: 11/24/2022]
Abstract
Background Ligand endocytosis plays a critical role in regulating the activity of the Notch pathway. The Drosophila homolog of auxilin (dAux), a J-domain-containing protein best known for its role in the disassembly of clathrin coats from clathrin-coated vesicles, has recently been implicated in Notch signaling, although its exact mechanism remains poorly understood. Results To understand the role of auxilin in Notch ligand endocytosis, we have analyzed several point mutations affecting specific domains of dAux. In agreement with previous work, analysis using these stronger dAux alleles shows that dAux is required for several Notch-dependent processes, and its function during Notch signaling is required in the signaling cells. In support of the genetic evidences, the level of Delta appears elevated in dAux deficient cells, suggesting that the endocytosis of Notch ligand is disrupted. Deletion analysis shows that the clathrin-binding motif and the J-domain, when over-expressed, are sufficient for rescuing dAux phenotypes, implying that the recruitment of Hsc70 to clathrin is a critical role for dAux. However, surface labeling experiment shows that, in dAux mutant cells, Delta accumulates at the cell surface. In dAux mutant cells, clathrin appears to form large aggregates, although Delta is not enriched in these aberrant clathrin-positive structures. Conclusion Our data suggest that dAux mutations inhibit Notch ligand internalization at an early step during clathrin-mediated endocytosis, before the disassembly of clathrin-coated vesicles. Further, the inhibition of ligand endocytosis in dAux mutant cells possibly occurs due to depletion of cytosolic pools of clathrin via the formation of clathrin aggregates. Together, our observations argue that ligand endocytosis is critical for Notch signaling and auxilin participates in Notch signaling by facilitating ligand internalization.
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Affiliation(s)
- Vasundhara Kandachar
- Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907-2054, USA.
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Commisso C, Boulianne GL. The neuralized homology repeat 1 domain of Drosophila neuralized mediates nuclear envelope association and delta-dependent inhibition of nuclear import. J Mol Biol 2008; 375:1125-40. [PMID: 18076903 DOI: 10.1016/j.jmb.2007.11.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 11/08/2007] [Accepted: 11/12/2007] [Indexed: 01/25/2023]
Abstract
Signaling by the Notch (N) pathway is critical for many developmental processes and requires complex trafficking of both the N receptor and its transmembrane ligands, Delta (Dl) and Serrate. neuralized encodes an E3 ubiquitin ligase required for N ligand internalization. Neuralized (Neur) is conserved from worms to humans and comprises two Neur homology repeat (NHR) domains, NHR1 and NHR2, and a carboxyl-terminal RING domain. We have previously shown that the RING domain is required for ubiquitin ligase activity and that NHR1 mediates binding to Dl, a ubiquitination target. In Drosophila, Neur associates with the plasma membrane and hepatocyte responsive serum phosphoprotein-positive endosomes. Here we demonstrate that Neur also exhibits nuclear envelope localization. We have determined that Neur subcellular localization is regulated by nuclear trafficking and that inhibition of chromosome region maintenance 1, a nuclear export receptor, interferes with Neur nuclear export, trapping Neur in the nucleus. Moreover, we demonstrate that nuclear envelope localization is mediated by the Neur NHR1 domain. Interestingly, Dl expression in Schneider cells is sufficient to inhibit Neur nuclear import and inhibition occurs in an NHR1-dependent manner, suggesting that Neur nuclear localization occurs in contexts where Dl expression is either low or absent. Consistent with this, we found that Neur exhibits nuclear trafficking and associates with the nuclear envelope in the secretory cells of the larval salivary gland and that overexpression of Dl can reduce Neur localization to the nucleus. Altogether, our data demonstrate that Neur localizes to the nuclear envelope and that this localization can be negatively regulated by Dl, suggesting a possible nuclear function for Neur in Drosophila.
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Affiliation(s)
- Cosimo Commisso
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada
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Neuralized contains a phosphoinositide-binding motif required downstream of ubiquitination for delta endocytosis and notch signaling. Dev Cell 2008; 13:783-95. [PMID: 18061562 DOI: 10.1016/j.devcel.2007.10.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 08/30/2007] [Accepted: 10/27/2007] [Indexed: 11/20/2022]
Abstract
The Notch signaling pathway, which plays a critical role in cell-fate decisions throughout development, is regulated by endocytosis of both the ligand and receptor. Endocytosis of the Drosophila ligands, Delta and Serrate, is required in the signaling cell for signal initiation and requires one of two ubiquitin ligases, Neuralized or Mind bomb. Through in vitro binding assays we have identified an interaction between Neuralized and phosphoinositides, modified membrane lipids that mediate membrane trafficking and signaling. We show that interactions between phosphoinositides and Neuralized contribute to the membrane localization of Neuralized in the absence of Delta, and that the phosphoinositide-binding motif is required for Neuralized to endocytose Delta downstream of Delta ubiquitination. Lastly, we provide evidence that this interaction may also be important for vertebrate Neuralized function. These results demonstrate that, through interactions with Neuralized, phosphoinositides may regulate Delta endocytosis and, by extension, Notch signal transduction.
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72
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Nagel AC, Wech I, Schwinkendorf D, Preiss A. Involvement of co-repressors Groucho and CtBP in the regulation of single-minded in Drosophila. Hereditas 2007; 144:195-205. [PMID: 18031354 DOI: 10.1111/j.2007.0018-0661.02020.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Dorso-ventral patterning results in the establishment of the two germ layers in the Drosophila embryo, mesoderm and mesectoderm, that are separated by a strip of cells giving rise to the mesectoderm and eventually to the ventral midline. The mesectoderm is specified by the expression of single-minded (sim) which is activated through the concerted action of Dorsal and Twist in addition to a Notch signal. In the mesoderm, sim is repressed by Snail together with the co-repressor C-terminal binding protein (CtBP). Here, we address the involvement of the two co-repressors CtBP and Groucho (Gro) in repression of sim in the neuroectoderm. It was shown earlier that sim is restricted in the neuroectoderm with help of Suppressor of Hairless [Su(H)] and Hairless. Using the female sterile technique, we generated germ line clones deficient for Gro, CtBP or Hairless and assayed sim mRNA relative to snail mRNA expression. We show that sim repression requires both co-repressors Gro and CtBP to be fully repressed in the neuroectoderm, suggesting that a repression complex is assembled including Su(H) and Hairless as was shown for other Notch target genes before. Moreover, our work implies that Gro is important for the repression of sim specifically within the mesoderm anlagen, indicating that Snail and CtBP are insufficient to entirely silence sim in this germ layer.
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Affiliation(s)
- Anja C Nagel
- Universität Hohenheim, Institut für Genetik, Stuttgart, Germany
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73
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Abstract
The positioning and elaboration of ectodermal veins in the wing of Drosophila melanogaster rely on widely utilized developmental signals, including those mediated by EGF, BMP, Hedgehog, Notch, and Wnt. Analysis of vein patterning mutants, using the molecular and genetic mosaic techniques available in Drosophila, has provided important insights into how a combination of short-range and long-range signaling can pattern a simple epidermal tissue. Moreover, venation has become a powerful system for isolating and analyzing novel components in these signaling pathways. I here review the basic events of vein patterning and give examples of how changes in venation have been used to identify important features of cell signaling pathways.
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Affiliation(s)
- Seth S Blair
- Department of Zoology, University of Wisconsin, Madison, WI 53706, USA.
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74
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Geffers I, Serth K, Chapman G, Jaekel R, Schuster-Gossler K, Cordes R, Sparrow DB, Kremmer E, Dunwoodie SL, Klein T, Gossler A. Divergent functions and distinct localization of the Notch ligands DLL1 and DLL3 in vivo. ACTA ACUST UNITED AC 2007; 178:465-76. [PMID: 17664336 PMCID: PMC2064846 DOI: 10.1083/jcb.200702009] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The Notch ligands Dll1 and Dll3 are coexpressed in the presomitic mesoderm of mouse embryos. Despite their coexpression, mutations in Dll1 and Dll3 cause strikingly different defects. To determine if there is any functional equivalence, we replaced Dll1 with Dll3 in mice. Dll3 does not compensate for Dll1; DLL1 activates Notch in Drosophila wing discs, but DLL3 does not. We do not observe evidence for antagonism between DLL1 and DLL3, or repression of Notch activity in mice or Drosophila. In vitro analyses show that differences in various domains of DLL1 and DLL3 individually contribute to their biochemical nonequivalence. In contrast to endogenous DLL1 located on the surface of presomitic mesoderm cells, we find endogenous DLL3 predominantly in the Golgi apparatus. Our data demonstrate distinct in vivo functions for DLL1 and DLL3. They suggest that DLL3 does not antagonize DLL1 in the presomitic mesoderm and warrant further analyses of potential physiological functions of DLL3 in the Golgi network.
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Affiliation(s)
- Insa Geffers
- Institut für Molekularbiologie, Medizinische Hochschule Hannover, Hannover, Germany
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75
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Koutelou E, Sato S, Tomomori-Sato C, Florens L, Swanson SK, Washburn MP, Kokkinaki M, Conaway RC, Conaway JW, Moschonas NK. Neuralized-like 1 (Neurl1) targeted to the plasma membrane by N-myristoylation regulates the Notch ligand Jagged1. J Biol Chem 2007; 283:3846-53. [PMID: 18077452 DOI: 10.1074/jbc.m706974200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Notch signaling constitutes an evolutionarily conserved mechanism that mediates cell-cell interactions in various developmental processes. Numerous regulatory proteins interact with the Notch receptor and its ligands and control signaling at multiple levels. Ubiquitination and endocytosis followed by endosomal sorting of both the receptor and its ligands is essential for Notch-mediated signaling. The E3 ubiquitin ligases, Neuralized (Neur) and Mind Bomb (Mib1), are crucial for regulating the activity and stability of Notch ligands in Drosophila; however, biochemical evidence that the Notch ligands are directly targeted for ubiquitination by Neur and/or Mib1 has been lacking. In this report, we explore the function of Neurl1, a mouse ortholog of Drosophila Neur. We show that Neurl1 can function as an E3 ubiquitin ligase to activate monoubiquitination in vitro of Jagged1, but not other mammalian Notch ligands. Neurl1 expression decreases Jagged1 levels in cells and blocks signaling from Jagged1-expressing cells to neighboring Notch-expressing cells. We demonstrate that Neurl1 is myristoylated at its N terminus, and that myristoylation of Neurl1 targets it to the plasma membrane. Point mutations abolishing either Neurl1 myristoylation and plasma membrane localization or Neurl1 ubiquitin ligase activity impair its ability to down-regulate Jagged1 expression and to block signaling. Taken together, our results argue that Neurl1 at the plasma membrane can affect the signaling activity of Jagged1 by directly enhancing its ubiquitination and subsequent turnover.
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Affiliation(s)
- Evangelia Koutelou
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
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76
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Nguyen HT, Voza F, Ezzeddine N, Frasch M. Drosophila mind bomb2 is required for maintaining muscle integrity and survival. ACTA ACUST UNITED AC 2007; 179:219-27. [PMID: 17954605 PMCID: PMC2064758 DOI: 10.1083/jcb.200708135] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We report that the Drosophila mind bomb2 (mib2) gene is a novel regulator of muscle development. Unlike its paralogue, mib1, zygotic expression of mib2 is restricted to somatic and visceral muscle progenitors, and their respective differentiated musculatures. We demonstrate that in embryos that lack functional Mib2, muscle detachment is observed beginning in mid stage 15 and progresses rapidly, culminating in catastrophic degeneration and loss of most somatic muscles by stage 17. Notably, the degenerating muscles are positive for apoptosis markers, and inhibition of apoptosis in muscles prevents to a significant degree the muscle defects. Rescue experiments with Mib1 and Neuralized show further that these E3 ubiquitin ligases are not capable of ameliorating the muscle mutant phenotype of mib2. Our data suggest strongly that mib2 is involved in a novel Notch- and integrin-independent pathway that maintains the integrity of fully differentiated muscles and prevents their apoptotic degeneration.
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Affiliation(s)
- Hanh T Nguyen
- Department of Medicine, Division of Cardiology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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77
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Koo BK, Yoon MJ, Yoon KJ, Im SK, Kim YY, Kim CH, Suh PG, Jan YN, Kong YY. An obligatory role of mind bomb-1 in notch signaling of mammalian development. PLoS One 2007; 2:e1221. [PMID: 18043734 PMCID: PMC2082076 DOI: 10.1371/journal.pone.0001221] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 10/31/2007] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The Notch signaling pathway is an evolutionarily conserved intercellular signaling module essential for cell fate specification that requires endocytosis of Notch ligands. Structurally distinct E3 ubiquitin ligases, Neuralized (Neur) and Mind bomb (Mib), cooperatively regulate the endocytosis of Notch ligands in Drosophila. However, the respective roles of the mammalian E3 ubiquitin ligases, Neur1, Neur2, Mib1, and Mib2, in mammalian development are poorly understood. METHODOLOGY/PRINCIPAL FINDINGS Through extensive use of mammalian genetics, here we show that Neur1 and Neur2 double mutants and Mib2(-/-) mice were viable and grossly normal. In contrast, conditional inactivation of Mib1 in various tissues revealed the representative Notch phenotypes: defects of arterial specification as deltalike4 mutants, abnormal cerebellum and skin development as jagged1 conditional mutants, and syndactylism as jagged2 mutants. CONCLUSIONS/SIGNIFICANCE Our data provide the first evidence that Mib1 is essential for Jagged as well as Deltalike ligand-mediated Notch signaling in mammalian development, while Neur1, Neur2, and Mib2 are dispensable.
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Affiliation(s)
- Bon-Kyoung Koo
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Mi-Jeong Yoon
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Ki-Jun Yoon
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Sun-Kyoung Im
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Yoon-Young Kim
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Cheol-Hee Kim
- Department of Biology, Chungnam National University, Daejeon, South Korea
| | - Pann-Ghill Suh
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
| | - Yuh Nung Jan
- Howard Hughes Medical Institute, Department of Physiology, University of California at San Francisco, San Francisco, California, United States of America
- Howard Hughes Medical Institute, Department of Biochemistry, University of California at San Francisco, San Francisco, California, United States of America
| | - Young-Yun Kong
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea
- * To whom correspondence should be addressed. E-mail:
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78
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Roca C, Adams RH. Regulation of vascular morphogenesis by Notch signaling. Genes Dev 2007; 21:2511-24. [PMID: 17938237 DOI: 10.1101/gad.1589207] [Citation(s) in RCA: 347] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Notch pathway is a versatile regulator of cell fate specification, growth, differentiation, and patterning processes in metazoan organisms. In the vertebrate cardiovascular system, multiple Notch family receptors and several of their Jagged and Delta-like ligands are expressed during critical stages of embryonic and postnatal development. Functional studies in mice, fish, tumor models, and cell culture systems have shown that the angiogenic growth of the blood vessel network, the proliferation of endothelial cells, and the differentiation of arteries and veins are controlled by Notch signaling. Moreover, Notch pathway components play important roles in human pathological conditions involving the vasculature, namely CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) and Alagille syndrome. Recent findings highlight the Notch ligand Delta-like 4 as a key regulator of tumor angiogenesis and suggest that this protein might be a promising target for cancer therapy.
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Affiliation(s)
- Cristina Roca
- Vascular Development Laboratory, Cancer Research UK London Research Institute, London WC2A 3PX, United Kingdom
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79
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Thomas GB, van Meyel DJ. The glycosyltransferase Fringe promotes Delta-Notch signaling between neurons and glia, and is required for subtype-specific glial gene expression. Development 2007; 134:591-600. [PMID: 17215308 DOI: 10.1242/dev.02754] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development, organization and function of central nervous systems depend on interactions between neurons and glial cells. However, the molecular signals that regulate neuron-glial communication remain elusive. In the ventral nerve cord of Drosophila, the close association of the longitudinal glia (LG) with the neuropil provides an excellent opportunity to identify and characterize neuron-glial signals in vivo. We have found that the activity and restricted expression of the glycosyltransferase Fringe (Fng)renders a subset of LG sensitive to activation of signaling through the Notch(N) receptor. This is the first report showing that modulation of N signaling by Fng is important for central nervous system development in any organism. In each hemisegment of the nerve cord the transcription factor Prospero (Pros) is selectively expressed in the six most anterior LG. Pros expression is specifically reduced in fng mutants, and is blocked by antagonism of the N pathway. The N ligand Delta (Dl), which is expressed by a subset of neurons, cooperates with Fng for N signaling in the anterior LG, leading to subtype-specific expression of Pros. Furthermore, ectopic Pros expression in posterior LG can be triggered by Fng, and by Dl derived from neurons but not glia. This effect can be mimicked by direct activation of the N pathway within glia. Our genetic studies suggest that Fng sensitizes N on glia to axon-derived Dl and that enhanced neuron-glial communication through this ligand-receptor pair is required for the proper molecular diversity of glial cell subtypes in the developing nervous system.
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Affiliation(s)
- Graham B Thomas
- Graduate Program in Neurological Sciences, Montreal, QC, Canada
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80
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Zhang C, Li Q, Lim CH, Qiu X, Jiang YJ. The characterization of zebrafish antimorphic mib alleles reveals that Mib and Mind bomb-2 (Mib2) function redundantly. Dev Biol 2007; 305:14-27. [PMID: 17331493 DOI: 10.1016/j.ydbio.2007.01.034] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 01/12/2007] [Accepted: 01/23/2007] [Indexed: 01/09/2023]
Abstract
Both mind bomb (mib) and mind bomb-2 (mib2) encode RING E3 ubiquitin ligases that promote Delta ubiquitylation and endocytosis in Notch activation. Detailed morphological and molecular examinations revealed that zebrafish mib(ta52b) (missense mutation in the C-terminal RING Finger (RF), M1013R) and mib(m132) (nonsense mutation resulting in a truncated protein that loses all three RFs, C785stop) are strong and weak antimorphic alleles, respectively, compared to the null allele, mib(tfi91) (nonsense mutation resulting in a truncated protein of only 60 amino acids, Y60stop). Zebrafish mib2 ortholog was identified in this study. Zebrafish Mib and Mib2 are colocalized in transfected cells and function redundantly in regulating Notch signaling in embryos. Mib(ta52b) and Mib(m132) have a dosage-dependent dominant-negative effect, at least, on Mib2, which is a molecular basis for the antimorphic phenotypes. It was also shown that Notch signaling negatively regulates mib expression in a Su(H)-dependent manner, forming a negative feedback loop in modulating Notch activation.
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Affiliation(s)
- Chengjin Zhang
- Laboratory of Developmental Signalling and Patterning, Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, 138673, Singapore
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81
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del Alamo D, Mlodzik M. Frizzled/PCP-dependent asymmetric neuralized expression determines R3/R4 fates in the Drosophila eye. Dev Cell 2007; 11:887-94. [PMID: 17141162 DOI: 10.1016/j.devcel.2006.09.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 08/07/2006] [Accepted: 09/19/2006] [Indexed: 01/10/2023]
Abstract
Planar cell polarity (PCP) is a common feature in many epithelia, reflected in cellular organization within the plane of an epithelium. In the Drosophila eye, Frizzled (Fz)/PCP signaling induces cell-fate specification of the R3/R4 photoreceptors through regulation of Notch activation in R4. Except for Dl upregulation in R3, the mechanism of how Fz/PCP signaling regulates Notch in this context is not understood. We demonstrate that the E3-ubiquitin ligase Neuralized (Neur), required for Dl-N signaling, is asymmetrically expressed within the R3/R4 pair. It is required in R3, where it is also upregulated in a Fz/PCP-dependent manner. As is the case for Dl, N activity in R4 further represses neur expression, thus, reinforcing the asymmetry. We demonstrate that Neur asymmetry is instructive in correct R3/R4 specification. Our data indicate that Fz/PCP-dependent Neur expression in R3 ensures the proper directionality of Dl-N signaling during R3/R4 specification.
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Affiliation(s)
- David del Alamo
- Department of Molecular, Cell, and Developmental Biology, Mount Sinai School of Medicine, New York, New York 10029, USA
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82
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Doroquez DB, Rebay I. Signal integration during development: mechanisms of EGFR and Notch pathway function and cross-talk. Crit Rev Biochem Mol Biol 2007; 41:339-85. [PMID: 17092823 DOI: 10.1080/10409230600914344] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Metazoan development relies on a highly regulated network of interactions between conserved signal transduction pathways to coordinate all aspects of cell fate specification, differentiation, and growth. In this review, we discuss the intricate interplay between the epidermal growth factor receptor (EGFR; Drosophila EGFR/DER) and the Notch signaling pathways as a paradigm for signal integration during development. First, we describe the current state of understanding of the molecular architecture of the EGFR and Notch signaling pathways that has resulted from synergistic studies in vertebrate, invertebrate, and cultured cell model systems. Then, focusing specifically on the Drosophila eye, we discuss how cooperative, sequential, and antagonistic relationships between these pathways mediate the spatially and temporally regulated processes that generate this sensory organ. The common themes underlying the coordination of the EGFR and Notch pathways appear to be broadly conserved and should, therefore, be directly applicable to elucidating mechanisms of information integration and signaling specificity in vertebrate systems.
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Affiliation(s)
- David B Doroquez
- Department of Biology, Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, MA, USA
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83
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Fischer JA, Eun SH, Doolan BT. Endocytosis, endosome trafficking, and the regulation of Drosophila development. Annu Rev Cell Dev Biol 2006; 22:181-206. [PMID: 16776558 DOI: 10.1146/annurev.cellbio.22.010605.093205] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Endocytosis and endosome trafficking regulate cell signaling in unexpected ways. Here we review the contribution that Drosophila research has made to this exciting field. In addition to attenuating signaling, endocytosis shapes morphogen gradients, activates ligands, and regulates spatially receptor activation within a single cell. Moreover, some receptors signal from within endosomes, and the ability of a specific type of endosome to form controls the ability of cells to signal. Experiments in Drosophila reveal that through regulation of a variety of cell signaling pathways, endocytosis controls cell patterning and cell fate.
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Affiliation(s)
- Janice A Fischer
- Institute for Cellular and Molecular Biology, Section of Molecular Cell and Development, University of Texas, Austin, Texas 78712, USA.
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84
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Zhang C, Li Q, Jiang YJ. Zebrafish Mib and Mib2 are mutual E3 ubiquitin ligases with common and specific delta substrates. J Mol Biol 2006; 366:1115-28. [PMID: 17196985 DOI: 10.1016/j.jmb.2006.11.096] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 11/23/2006] [Accepted: 11/28/2006] [Indexed: 12/12/2022]
Abstract
It was already known that both mind bomb (mib) and mind bomb-2 (mib2) encode E3 ubiquitin ligases that target Delta in Notch activation. Here we further demonstrated that zebrafish Mib and Mib2, similar to their mouse orthologs, have a C-terminal-most RING finger-dependent E3 ubiquitin ligase activity. Mib and Mib2 are reciprocal E3 ubiquitin ligases and substrates. They function similarly in Notch signaling by using DeltaC as a common substrate. However, Mib2 behaves differently from Mib in DeltaD internalization. In addition, Mib and Mib2 bind differently to extracellular and intracellular parts of DeltaA and DeltaC. Finally, mutant Mibs, Mib(ta52b) with a missense mutation in the C-terminal-most RING finger (M1013R) and Mib(m132) with a premature stop codon that leads to a deletion of three RING fingers (C785stop), act dominant-negatively and compete with Mib2 in DeltaC ubiquitylation and internalization, suggesting a molecular basis for the antimorphic phenotypes (stronger than the null phenotypes) observed in zebrafish mib(ta52b) and mib(m132) alleles.
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Affiliation(s)
- Chengjin Zhang
- Laboratory of Developmental Signalling and Patterning, Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, Singapore 138673, Singapore
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85
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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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86
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Ward EJ, Shcherbata HR, Reynolds SH, Fischer KA, Hatfield SD, Ruohola-Baker H. Stem cells signal to the niche through the Notch pathway in the Drosophila ovary. Curr Biol 2006; 16:2352-8. [PMID: 17070683 DOI: 10.1016/j.cub.2006.10.022] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 10/05/2006] [Accepted: 10/06/2006] [Indexed: 12/28/2022]
Abstract
Stem cells are maintained and retain their capacity to continue dividing because of the influence of a niche. Although niches are important to maintain "stemness" in a wide variety of tissues, control of these niches is poorly understood. The Drosophila germline stem cells (GSCs) reside in a somatic cell niche. We show that Notch activation can induce the expression of niche-cell markers even in an adult fly; overexpression of Delta in the germline, or activated Notch in the somatic cells, results in extra niche cells, up to 10-fold over the normal number. In turn, these ectopic niche cells induce ectopic GSCs. Conversely, when GCSs do not produce functional Notch ligands, Delta and Serrate, the TGF-beta pathway is not activated in the GSCs, and they differentiate and subsequently leave the niche. Importantly, clonal analysis reveals that the receiving end of the Notch pathway is required in the somatic cells. These data show that a feedback loop exists between the stem cells and niche cells. Demonstration that stem cells can contribute to niche function has far-reaching consequences for stem cell therapies and may provide insight into how cancer can spread throughout an organism via populations of cancer stem cells.
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Affiliation(s)
- Ellen J Ward
- Department of Biochemistry, Institute for Stem Cell and Regenerative Medicine, School of Medicine, Box 357350, 1959 NE Pacific Street, University of Washington, Seattle, Washington 98195, USA
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87
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Commisso C, Boulianne GL. The NHR1 domain of Neuralized binds Delta and mediates Delta trafficking and Notch signaling. Mol Biol Cell 2006; 18:1-13. [PMID: 17065551 PMCID: PMC1751308 DOI: 10.1091/mbc.e06-08-0753] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Notch signaling, which is crucial to metazoan development, requires endocytosis of Notch ligands, such as Delta and Serrate. Neuralized is a plasma membrane-associated ubiquitin ligase that is required for neural development and Delta internalization. Neuralized is comprised of three domains that include a C-terminal RING domain and two neuralized homology repeat (NHR) domains. All three domains are conserved between organisms, suggesting that these regions of Neuralized are functionally important. Although the Neuralized RING domain has been shown to be required for Delta ubiquitination, the function of the NHR domains remains elusive. Here we show that neuralized, a well-characterized neurogenic allele, exhibits a mutation in a conserved residue of the NHR1 domain that results in mislocalization of Neuralized and defects in Delta binding and internalization. Furthermore, we describe a novel isoform of Neuralized and show that it is recruited to the plasma membrane by Delta and that this is mediated by the NHR1 domain. Finally, we show that the NHR1 domain of Neuralized is both necessary and sufficient to bind Delta. Altogether, our data demonstrate that NHR domains can function in facilitating protein-protein interactions and in the case of Neuralized, mediate binding to its ubiquitination target, Delta.
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Affiliation(s)
- Cosimo Commisso
- The Hospital for Sick Children, Program in Developmental Biology and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada M5G 1X8
| | - Gabrielle L. Boulianne
- The Hospital for Sick Children, Program in Developmental Biology and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada M5G 1X8
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88
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Abstract
A small number of signalling pathways are used iteratively to regulate cell fates, cell proliferation and cell death in development. Notch is the receptor in one such pathway, and is unusual in that most of its ligands are also transmembrane proteins; therefore signalling is restricted to neighbouring cells. Although the intracellular transduction of the Notch signal is remarkably simple, with no secondary messengers, this pathway functions in an enormous diversity of developmental processes and its dysfunction is implicated in many cancers.
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Affiliation(s)
- Sarah J Bray
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK.
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89
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Glittenberg M, Pitsouli C, Garvey C, Delidakis C, Bray S. Role of conserved intracellular motifs in Serrate signalling, cis-inhibition and endocytosis. EMBO J 2006; 25:4697-706. [PMID: 17006545 PMCID: PMC1618092 DOI: 10.1038/sj.emboj.7601337] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Accepted: 08/16/2006] [Indexed: 11/09/2022] Open
Abstract
Notch is the receptor in a signalling pathway that operates in a diverse spectrum of developmental processes. Its ligands (e.g. Serrate) are transmembrane proteins whose signalling competence is regulated by the endocytosis-promoting E3 ubiquitin ligases, Mindbomb1 and Neuralized. The ligands also inhibit Notch present in the same cell (cis-inhibition). Here, we identify two conserved motifs in the intracellular domain of Serrate that are required for efficient endocytosis. The first, a dileucine motif, is dispensable for trans-activation and cis-inhibition despite the endocytic defect, demonstrating that signalling can be separated from bulk endocytosis. The second, a novel motif, is necessary for interactions with Mindbomb1/Neuralized and is strictly required for Serrate to trans-activate and internalise efficiently but not for it to inhibit Notch signalling. Cis-inhibition is compromised when an ER retention signal is added to Serrate, or when the levels of Neuralized are increased, and together these data indicate that cis-inhibitory interactions occur at the cell surface. The balance of ubiquitinated/unubiquitinated ligand will thus affect the signalling capacity of the cell at several levels.
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Affiliation(s)
- Marcus Glittenberg
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Chrysoula Pitsouli
- Institute of Molecular Biology and Biotechnology, FORTH, and Department of Biology, University of Crete, Heraklion, Greece
| | - Clare Garvey
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Christos Delidakis
- Institute of Molecular Biology and Biotechnology, FORTH, and Department of Biology, University of Crete, Heraklion, Greece
| | - Sarah Bray
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
- Department of Physiology Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK. Tel.: +44 1223 333792; Fax: +44 1223 333786; E-mail:
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90
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Song R, Koo BK, Yoon KJ, Yoon MJ, Yoo KW, Kim HT, Oh HJ, Kim YY, Han JK, Kim CH, Kong YY. Neuralized-2 regulates a Notch ligand in cooperation with Mind bomb-1. J Biol Chem 2006; 281:36391-400. [PMID: 17003037 DOI: 10.1074/jbc.m606601200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in Drosophila neuralized (Dneur) result in a variety of developmental defects that closely resemble those of Notch mutants and other Notch pathway mutants. However, mice with disrupted neur1 do not show any aberrant cell fate specifications in neurogenesis and somitogenesis. Thus, we speculated that other vertebrate neur homolog(s) might compensate for loss of the neur gene. Here, we report the paralog of mouse Neur1, named Neuralized-2 (Neur2), which is a ubiquitin-protein isopeptide ligase (E3) that interacts with and ubiquitinates Delta. Both murine Neur1 and Neur2 have similar degrees of homology to DNeur, and neur2 is expressed in patterns similar to those of neur1 in embryos, suggesting potential functional redundancy. Interestingly, two distinct classes of E3 ligases, Mind bomb-1 (Mib1) and Neur2, have cooperative but distinct roles in Delta endocytosis to Hrs-positive vesicles, i.e. Mib1 functions in the initial step of Delta endocytosis, and Neur2 is required for targeting endocytosed Delta to Hrs-positive vesicles. Thus, our study provides a new insight into how distinct E3 ligases work together in the endocytic pathways for Notch signaling.
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Affiliation(s)
- Ran Song
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, South Korea
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91
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Hagedorn EJ, Bayraktar JL, Kandachar VR, Bai T, Englert DM, Chang HC. Drosophila melanogaster auxilin regulates the internalization of Delta to control activity of the Notch signaling pathway. ACTA ACUST UNITED AC 2006; 173:443-52. [PMID: 16682530 PMCID: PMC2063844 DOI: 10.1083/jcb.200602054] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have isolated mutations in the Drosophila melanogaster homologue of auxilin, a J-domain-containing protein known to cooperate with Hsc70 in the disassembly of clathrin coats from clathrin-coated vesicles in vitro. Consistent with this biochemical role, animals with reduced auxilin function exhibit genetic interactions with Hsc70 and clathrin. Interestingly, the auxilin mutations interact specifically with Notch and disrupt several Notch-mediated processes. Genetic evidence places auxilin function in the signal-sending cells, upstream of Notch receptor activation, suggesting that the relevant cargo for this auxilin-mediated endocytosis is the Notch ligand Delta. Indeed, the localization of Delta protein is disrupted in auxilin mutant tissues. Thus, our data suggest that auxilin is an integral component of the Notch signaling pathway, participating in the ubiquitin-dependent endocytosis of Delta. Furthermore, the fact that auxilin is required for Notch signaling suggests that ligand endocytosis in the signal-sending cells needs to proceed past coat disassembly to activate Notch.
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MESH Headings
- Animals
- Auxilins/genetics
- Auxilins/physiology
- Body Patterning/genetics
- Body Patterning/physiology
- Clathrin/genetics
- Clathrin/metabolism
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/physiology
- Endocytosis/genetics
- Endocytosis/physiology
- ErbB Receptors/genetics
- ErbB Receptors/physiology
- Eye Abnormalities/genetics
- Eye Abnormalities/ultrastructure
- Gene Expression Regulation, Developmental
- Genotype
- HSC70 Heat-Shock Proteins/genetics
- HSC70 Heat-Shock Proteins/metabolism
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Microscopy, Electron, Scanning
- Mutation/genetics
- Nervous System/embryology
- Nervous System/metabolism
- Phenotype
- Photoreceptor Cells, Invertebrate/embryology
- Photoreceptor Cells, Invertebrate/metabolism
- RNA, Small Interfering/genetics
- Receptors, Notch/genetics
- Receptors, Notch/physiology
- Signal Transduction/genetics
- Signal Transduction/physiology
- Wings, Animal/embryology
- Wings, Animal/metabolism
- Wings, Animal/ultrastructure
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Affiliation(s)
- Elliott J Hagedorn
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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92
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Bernard F, Dutriaux A, Silber J, Lalouette A. Notch pathway repression by vestigial is required to promote indirect flight muscle differentiation in Drosophila melanogaster. Dev Biol 2006; 295:164-77. [PMID: 16643882 DOI: 10.1016/j.ydbio.2006.03.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Accepted: 03/02/2006] [Indexed: 01/28/2023]
Abstract
Drosophila dorsal longitudinal muscles develop during metamorphosis by fusion of myoblasts with larval templates. It has been shown that both vestigial and Notch are crucial for correct formation of these muscles. We investigated the relationship between vestigial and the Notch pathway during this process. Using Enhancer of Split Region Transcript m6 gene expression as a reporter of Notch pathway activity, we were able to demonstrate that this pathway is only active in myoblasts. Moreover, close examination of the cellular location of several of the main actors of the N pathway (Notch, Delta, neuralized, Serrate, Mind bomb1 and fringe) during dorsal longitudinal muscle development enabled us to find that Notch receptor can play multiple roles in adult myogenesis. We report that the locations of the two Notch ligands (Delta and Serrate) are different. Interestingly, we found that fringe, which encodes a glycosyltransferase that modifies the affinity of the Notch receptor for its ligands, is expressed in muscle fibers and in a subset of myoblasts. In addition, we demonstrate that fringe expression is essential for Notch pathway inhibition and muscle differentiation. Lastly, we report that, in vestigial mutants, fringe expression is lost, and when fringe is overexpressed, a significant rescue of indirect flight muscle degeneration is obtained. Altogether, our data show that a vestigial-differentiating function is achieved through the inhibition of the Notch pathway.
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Affiliation(s)
- F Bernard
- Institut Jacques Monod, UMR7592, CNRS Universités Paris 7 et 6, Tour 43, 2, place Jussieu, 75251 Cedex 05, Paris, France
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93
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Abstract
A number of recent studies have shown that endocytosis of Notch ligands is required for activation of Notch. There are at least two broad models that account for how Delta endocytosis in one cell might contribute to activation of Notch in the neighboring cell. The first class of models is related to the possibility that Delta endocytosis facilitates S2 cleavage and removal of the Notch extracellular domain, a critical step in Notch activation. A second class of models is related to the possibility that Delta ubiquitylation and endocytosis facilitates interactions between Delta and Notch. In the second set of models, Delta undergoes endocytosis and its subsequent trafficking back to the surface, following modifications or some change in the context in which it is presented, makes Delta a more effective ligand. Though it is still not clear how either or both mechanisms contribute, recent evidence points to the importance of both endocytosis and recycling in Delta signaling.
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Affiliation(s)
- Ajay Chitnis
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, 6 Center Drive, 3B 315, Bethesda, MD 20892, USA.
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94
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Takeuchi T, Adachi Y, Sonobe H, Furihata M, Ohtsuki Y. A ubiquitin ligase, skeletrophin, is a negative regulator of melanoma invasion. Oncogene 2006; 25:7059-69. [PMID: 16715130 DOI: 10.1038/sj.onc.1209688] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Skeletrophin (mindbomb homolog 2 (MIB2)) is a RING (Really Interesting New Gene) finger-dependent ubiquitin ligase, which targets the intracellular region of Notch ligands. A previous immunohistochemical study demonstrated that skeletrophin was downregulated in many melanomas. In the present study, we have identified a promoter region of skeletrophin on a CpG island and detected aberrant methylation of this region in six of 31 invasive melanomas, but in none of 25 benign nevi or five non-invasive superficial spreading melanomas. Subsequently, we found that a zinc-finger transcriptional factor Snail, which is overexpressed in many melanoma cells, repressed the skeletrophin promoter activity via an E-box-related element and was involved in downregulation of skeletrophin. An activator protein-2, which has a tumor suppressor-like role in melanoma, increased skeletrophin expression. Interestingly, exogenously expressed skeletrophin reduced melanoma cell invasion in vitro and in vivo. Colony formation in soft agar was also reduced in a RING motif-dependent manner, without affecting cell growth. We also found that skeletrophin downregulated transcription of the Met oncogene, which encodes the hepatocyte growth factor receptor and plays a role in the determination of the invasive phenotype of many malignant tumors. Finally, exogenously expressed skeletrophin, but not its RING mutant, increased transcription of Hes1 gene, a downstream effector of Notch pathway in melanoma cells. The present findings indicate that skeletrophin might be a novel suppressor factor for melanoma invasion.
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Affiliation(s)
- T Takeuchi
- Department of Pathology, Kochi Medical School, Kochi, Japan.
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95
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Bardin AJ, Schweisguth F. Bearded family members inhibit Neuralized-mediated endocytosis and signaling activity of Delta in Drosophila. Dev Cell 2006; 10:245-55. [PMID: 16459303 DOI: 10.1016/j.devcel.2005.12.017] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 12/16/2005] [Accepted: 12/28/2005] [Indexed: 11/26/2022]
Abstract
Endocytosis of Notch receptor ligands in signaling cells is essential for Notch receptor activation. In Drosophila, the E3 ubiquitin ligase Neuralized (Neur) promotes the endocytosis and signaling activity of the ligand Delta (Dl). In this study, we identify proteins of the Bearded (Brd) family as interactors of Neur. We show that Tom, a prototypic Brd family member, inhibits Neur-dependent Notch signaling. Overexpression of Tom inhibits the endocytosis of Dl and interferes with the interaction of Dl with Neur. Deletion of the Brd gene complex results in ectopic endocytosis of Dl in dorsal cells of stage 5 embryos. This defect in Dl trafficking is associated with ectopic expression of the single-minded gene, a direct Notch target gene that specifies the mesectoderm. We propose that inhibition of Neur by Brd proteins is important for precise spatial regulation of Dl signaling.
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Affiliation(s)
- Allison J Bardin
- CNRS UMR 8542, Ecole Normale Supérieure, 46, rue d'Ulm, 75230 Paris Cedex, France
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96
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Le Borgne R. Regulation of Notch signalling by endocytosis and endosomal sorting. Curr Opin Cell Biol 2006; 18:213-22. [PMID: 16488590 DOI: 10.1016/j.ceb.2006.02.011] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Accepted: 02/08/2006] [Indexed: 01/31/2023]
Abstract
Cell-cell signalling is an essential process in the formation of multicellular organisms. Notch is the receptor of an evolutionarily conserved signalling pathway regulating numerous developmental decisions. Indeed, its misregulation is linked to multiple developmental and physiological disorders. Notch and its ligands are distributed widely throughout development, yet Notch activity is highly controlled and restricted in time and space. Recent advances have highlighted that endocytosis followed by endosomal sorting of both the Notch receptor and its ligands is an essential mechanism by which Notch-mediated signalling is developmentally controlled.
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Affiliation(s)
- Roland Le Borgne
- CNRS UMR 6061, Faculté de Médecine, 2 avenue du Professeur Léon Bernard, CS 34317, 35043 Rennes Cedex, France.
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