1
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Kremer J, Brendel C, Mack EKM, Mack HID. Expression of β-1,4-galactosyltransferases during Aging in Caenorhabditis elegans. Gerontology 2020; 66:571-581. [PMID: 33171474 DOI: 10.1159/000510722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 08/03/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Altered plasma activity of β-1,4-galac-tosyl-transferases (B4GALTs) is a novel candidate biomarker of human aging. B4GALT1 is assumed to be largely responsible for this activity increase, but how it modulates the aging process is unclear at present. OBJECTIVES To determine how expression of B4GALT1 and other B4GALT enzymes changes during aging of an experimentally tractable model organism, Caenorhabditis elegans. METHODS Targeted analysis of mRNA levels of all 3 C. elegans B4GALT family members was performed by qPCR in wild-type and in long-lived daf-2 (insulin/IGF1-like receptor)-deficient or germline-deficient animals. RESULTS bre-4 (B4GALT1/2/3/4) is the only B4GALT whose expression increases during aging in wild-type worms. In addition, bre-4 levels also rise during aging in long-lived daf-2-deficient worms, but not in animals that are long-lived due to the lack of germline stem cells. On the other hand, expression of sqv-3 (B4GALT7) and of W02B12.11 (B4GALT5/6) appears decreased or constant, respectively, in all backgrounds during aging. CONCLUSIONS The age-dependent bre-4 mRNA increase in C. elegans parallels the age-dependent B4GALT activity increase in humans and is consistent with C. elegans being a suitable experimental organism to define potentially conserved roles of B4GALT1 during aging.
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Affiliation(s)
- Jennifer Kremer
- Department of Hematology, Oncology and Immunology, Philipps-University Marburg, and University Hospital Gießen and Marburg, Marburg, Germany
| | - Cornelia Brendel
- Department of Hematology, Oncology and Immunology, Philipps-University Marburg, and University Hospital Gießen and Marburg, Marburg, Germany
| | - Elisabeth Karin Maria Mack
- Department of Hematology, Oncology and Immunology, Philipps-University Marburg, and University Hospital Gießen and Marburg, Marburg, Germany,
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2
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Baron M. Combining genetic and biophysical approaches to probe the structure and function relationships of the notch receptor. Mol Membr Biol 2018; 34:33-49. [PMID: 30246579 DOI: 10.1080/09687688.2018.1503742] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Notch is a conserved cell signalling receptor regulating many aspects of development and tissue homeostasis. Notch is activated by ligand-induced proteolytic cleavages that release the Notch intracellular domain, which relocates to the nucleus to regulate gene transcription. Proteolytic activation first requires mechanical force to be applied to the Notch extracellular domain through an endocytic pulling mechanism transmitted through the ligand/receptor interface. This exposes the proteolytic cleavage site allowing the signal to be initiated following removal of the Notch extracellular domain. Ligands can also act, when expressed in the same cell, through non-productive cis-interactions to inhibit Notch activity. Furthermore, ligand selectivity and Notch activation are regulated by numerous post-translational modifications of the extracellular domain. Additional non-canonical trans and cis interactions with other regulatory proteins may modulate alternative mechanisms of Notch activation that depend on endocytic trafficking of the full-length receptor and proteolytic release of the intracellular domain from endo-lysosomal surface. Mutations of Notch, located in different regions of the protein, are associated with a spectrum of different loss and gain of function phenotypes and offer the possibility to dissect distinct regulatory interactions and mechanisms, particularly when combined with detailed structural analysis of Notch in complex with various regulatory partners.
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Affiliation(s)
- Martin Baron
- a School of Biological Sciences , University of Manchester , Manchester , UK
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3
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Ratliff M, Hill-Harfe KL, Gleason EJ, Ling H, Kroft TL, L'Hernault SW. MIB-1 Is Required for Spermatogenesis and Facilitates LIN-12 and GLP-1 Activity in Caenorhabditis elegans. Genetics 2018; 209:173-193. [PMID: 29531012 PMCID: PMC5935030 DOI: 10.1534/genetics.118.300807] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 02/26/2018] [Indexed: 12/11/2022] Open
Abstract
Covalent attachment of ubiquitin to substrate proteins changes their function or marks them for proteolysis, and the specificity of ubiquitin attachment is mediated by the numerous E3 ligases encoded by animals. Mind Bomb is an essential E3 ligase during Notch pathway signaling in insects and vertebrates. While Caenorhabditis elegans encodes a Mind Bomb homolog (mib-1), it has never been recovered in the extensive Notch suppressor/enhancer screens that have identified numerous pathway components. Here, we show that C. elegans mib-1 null mutants have a spermatogenesis-defective phenotype that results in a heterogeneous mixture of arrested spermatocytes, defective spermatids, and motility-impaired spermatozoa. mib-1 mutants also have chromosome segregation defects during meiosis, molecular null mutants are intrinsically temperature-sensitive, and many mib-1 spermatids contain large amounts of tubulin. These phenotypic features are similar to the endogenous RNA intereference (RNAi) mutants, but mib-1 mutants do not affect RNAi. MIB-1 protein is expressed throughout the germ line with peak expression in spermatocytes followed by segregation into the residual body during spermatid formation. C. elegans mib-1 expression, while upregulated during spermatogenesis, also occurs somatically, including in vulva precursor cells. Here, we show that mib-1 mutants suppress both lin-12 and glp-1 (C. elegans Notch) gain-of-function mutants, restoring anchor cell formation and a functional vulva to the former and partly restoring oocyte production to the latter. However, suppressed hermaphrodites are only observed when grown at 25°, and they are self-sterile. This probably explains why mib-1 was not previously recovered as a Notch pathway component in suppressor/enhancer selection experiments.
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Affiliation(s)
- Miriam Ratliff
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Katherine L Hill-Harfe
- Department of Biology, Emory University, Atlanta, Georgia 30322
- Program in Genetics and Molecular Biology, Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia 30322
| | | | - Huiping Ling
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Tim L Kroft
- Department of Biology, Emory University, Atlanta, Georgia 30322
| | - Steven W L'Hernault
- Department of Biology, Emory University, Atlanta, Georgia 30322
- Program in Genetics and Molecular Biology, Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia 30322
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4
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Suckling RJ, Korona B, Whiteman P, Chillakuri C, Holt L, Handford PA, Lea SM. Structural and functional dissection of the interplay between lipid and Notch binding by human Notch ligands. EMBO J 2017; 36:2204-2215. [PMID: 28572448 PMCID: PMC5538765 DOI: 10.15252/embj.201796632] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/06/2017] [Accepted: 04/07/2017] [Indexed: 12/30/2022] Open
Abstract
Recent data have expanded our understanding of Notch signalling by identifying a C2 domain at the N-terminus of Notch ligands, which has both lipid- and receptor-binding properties. We present novel structures of human ligands Jagged2 and Delta-like4 and human Notch2, together with functional assays, which suggest that ligand-mediated coupling of membrane recognition and Notch binding is likely to be critical in establishing the optimal context for Notch signalling. Comparisons between the Jagged and Delta family show a huge diversity in the structures of the loops at the apex of the C2 domain implicated in membrane recognition and Jagged1 missense mutations, which affect these loops and are associated with extrahepatic biliary atresia, lead to a loss of membrane recognition, but do not alter Notch binding. Taken together, these data suggest that C2 domain binding to membranes is an important element in tuning ligand-dependent Notch signalling in different physiological contexts.
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Affiliation(s)
| | | | - Pat Whiteman
- Department of BiochemistryUniversity of OxfordOxfordUK
| | | | - Laurie Holt
- Department of BiochemistryUniversity of OxfordOxfordUK
| | | | - Susan M Lea
- Sir William Dunn School of PathologyUniversity of OxfordOxfordUK
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5
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Promotion of bone morphogenetic protein signaling by tetraspanins and glycosphingolipids. PLoS Genet 2015; 11:e1005221. [PMID: 25978409 PMCID: PMC4433240 DOI: 10.1371/journal.pgen.1005221] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/14/2015] [Indexed: 02/08/2023] Open
Abstract
Bone morphogenetic proteins (BMPs) belong to the transforming growth factor β (TGFβ) superfamily of secreted molecules. BMPs play essential roles in multiple developmental and homeostatic processes in metazoans. Malfunction of the BMP pathway can cause a variety of diseases in humans, including cancer, skeletal disorders and cardiovascular diseases. Identification of factors that ensure proper spatiotemporal control of BMP signaling is critical for understanding how this pathway is regulated. We have used a unique and sensitive genetic screen to identify the plasma membrane-localized tetraspanin TSP-21 as a key new factor in the C. elegans BMP-like “Sma/Mab” signaling pathway that controls body size and postembryonic M lineage development. We showed that TSP-21 acts in the signal-receiving cells and genetically functions at the ligand-receptor level. We further showed that TSP-21 can associate with itself and with two additional tetraspanins, TSP-12 and TSP-14, which also promote Sma/Mab signaling. TSP-12 and TSP-14 can also associate with SMA-6, the type I receptor of the Sma/Mab pathway. Finally, we found that glycosphingolipids, major components of the tetraspanin-enriched microdomains, are required for Sma/Mab signaling. Our findings suggest that the tetraspanin-enriched membrane microdomains are important for proper BMP signaling. As tetraspanins have emerged as diagnostic and prognostic markers for tumor progression, and TSP-21, TSP-12 and TSP-14 are all conserved in humans, we speculate that abnormal BMP signaling due to altered expression or function of certain tetraspanins may be a contributing factor to cancer development. The bone morphogenetic protein (BMP) signaling pathway is required for multiple developmental processes during metazoan development. Various diseases, including cancer, can result from mis-regulation of the BMP pathway. Thus, it is critical to identify factors that ensure proper regulation of BMP signaling. Using the nematode C. elegans, we have devised a highly specific and sensitive genetic screen to identify new modulators in the BMP pathway. Through this screen, we identified three conserved tetraspanin molecules as novel factors that function to promote BMP signaling in a living organism. We further showed that these three tetraspanins likely form a complex and function together with glycosphingolipids to promote BMP signaling. Recent studies have implicated several tetraspanins in cancer initiation, progression and metastasis in mammals. Our findings suggest that the involvement of tetraspanins in cancer may partially be due to their function in modulating the activity of BMP signaling.
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6
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Chen Y, Greenwald I. hecd-1 modulates notch activity in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2014; 5:353-9. [PMID: 25552605 PMCID: PMC4349089 DOI: 10.1534/g3.114.015321] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 12/23/2014] [Indexed: 12/02/2022]
Abstract
Notch is a receptor that mediates cell-cell interactions that specify binary cell fate decisions in development and tissue homeostasis. Inappropriate Notch signaling is associated with cancer, and mutations in Notch pathway components have been associated with developmental diseases and syndromes. In Caenorhabditis elegans, suppressors of phenotypes associated with constitutively active LIN-12/Notch have identified many conserved core components and direct or indirect modulators. Here, we molecularly identify sel(ar584), originally isolated as a suppressor of a constitutively active allele of lin-12. We show that sel(ar584) is an allele of hecd-1, the ortholog of human HECDT1, a ubiquitin ligase that has been implicated in several different mammalian developmental events. We studied interactions of hecd-1 with lin-12 in the somatic gonad and with the other C. elegans Notch gene, glp-1, in the germ line. We found that hecd-1 acts as a positive modulator of lin-12/Notch activity in a somatic gonad context--the original basis for its isolation--but acts autonomously as a negative modulator of glp-1/Notch activity in the germ line. As the yeast ortholog of HECD-1, Ufd4p, has been shown to function in quality control, and C. elegans HECD-1 has been shown to affect mitochondrial maintenance, we propose that the different genetic interactions between hecd-1 and Notch genes we observed in different cell contexts may reflect differences in quality control regulatory mechanisms or in cellular metabolism.
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Affiliation(s)
- Yunting Chen
- Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York 10025 Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, New York 10025
| | - Iva Greenwald
- Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, New York 10025 Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, New York 10025 Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, New York, New York 10025
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7
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Zhu H, Han M. Exploring developmental and physiological functions of fatty acid and lipid variants through worm and fly genetics. Annu Rev Genet 2014; 48:119-48. [PMID: 25195508 DOI: 10.1146/annurev-genet-041814-095928] [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] [Indexed: 11/09/2022]
Abstract
Lipids are more than biomolecules for energy storage and membrane structure. With ample structural variation, lipids critically participate in nearly all aspects of cellular function. Lipid homeostasis and metabolism are closely related to major human diseases and health problems. However, lipid functional studies have been significantly underdeveloped, partly because of the difficulty in applying genetics and common molecular approaches to tackle the complexity associated with lipid biosynthesis, metabolism, and function. In the past decade, a number of laboratories began to analyze the roles of lipid metabolism in development and other physiological functions using animal models and combining genetics, genomics, and biochemical approaches. These pioneering efforts have not only provided valuable insights regarding lipid functions in vivo but have also established feasible methodology for future studies. Here, we review a subset of these studies using Caenorhabditis elegans and Drosophila melanogaster.
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Affiliation(s)
- Huanhu Zhu
- Howard Hughes Medical Institute and Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309;
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8
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Heuss SF, Tarantino N, Fantini J, Ndiaye-Lobry D, Moretti J, Israël A, Logeat F. A glycosphingolipid binding domain controls trafficking and activity of the mammalian notch ligand delta-like 1. PLoS One 2013; 8:e74392. [PMID: 24069306 PMCID: PMC3771905 DOI: 10.1371/journal.pone.0074392] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 08/01/2013] [Indexed: 01/12/2023] Open
Abstract
The activity of Notch ligands is tightly regulated by trafficking events occurring both before and after ligand-receptor interaction. In particular endocytosis and recycling have been shown to be required for full signaling activity of the ligands before they encounter the Notch receptor. However little is known about the precise endocytic processes that contribute to ligand internalization. Here we demonstrate that endocytosis contributes to Dll1 signaling activity by preserving the ligand from shedding and degradation. We further show that the glycosphingolipid-binding motif originally identified in Drosophila Notch ligands is conserved in mammals and is necessary for Dll1 internalization. Mutation of its conserved tryptophan residue results in a Dll1 molecule which is rapidly inactivated by shedding and degradation, does not recycle to the cell surface and does not activate Notch signaling. Finally, silencing in the signal-sending cells of glucosylceramide synthase, the enzyme implicated in the initial phase of glycosphingolipid synthesis, down-regulates Notch activation. Our data indicate that glycosphingolipids, by interacting with Dll1, may act as functional co-factors to promote its biological activity.
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Affiliation(s)
- Sara Farrah Heuss
- Unité de Signalisation Moléculaire et Activation Cellulaire, URA CNRS 2582, Institut Pasteur, Paris, France
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9
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Pontier SM, Schweisguth F. Glycosphingolipids in signaling and development: From liposomes to model organisms. Dev Dyn 2011; 241:92-106. [DOI: 10.1002/dvdy.22766] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2011] [Indexed: 01/05/2023] Open
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10
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Gravato-Nobre MJ, Stroud D, O'Rourke D, Darby C, Hodgkin J. Glycosylation genes expressed in seam cells determine complex surface properties and bacterial adhesion to the cuticle of Caenorhabditis elegans. Genetics 2011; 187:141-55. [PMID: 20980242 PMCID: PMC3018313 DOI: 10.1534/genetics.110.122002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 10/19/2010] [Indexed: 11/18/2022] Open
Abstract
The surface of the nematode Caenorhabditis elegans is poorly understood but critical for its interactions with the environment and with pathogens. We show here that six genes (bus-2, bus-4, and bus-12, together with the previously cloned srf-3, bus-8, and bus-17) encode proteins predicted to act in surface glycosylation, thereby affecting disease susceptibility, locomotory competence, and sexual recognition. Mutations in all six genes cause resistance to the bacterial pathogen Microbacterium nematophilum, and most of these mutations also affect bacterial adhesion and biofilm formation by Yersinia species, demonstrating that both infection and biofilm formation depend on interaction with complex surface carbohydrates. A new bacterial interaction, involving locomotory inhibition by a strain of Bacillus pumilus, reveals diversity in the surface properties of these mutants. Another biological property--contact recognition of hermaphrodites by males during mating--was also found to be impaired in mutants of all six genes. An important common feature is that all are expressed most strongly in seam cells, rather than in the main hypodermal syncytium, indicating that seam cells play the major role in secreting surface coat and consequently in determining environmental interactions. To test for possible redundancies in gene action, the 15 double mutants for this set of genes were constructed and examined, but no synthetic phenotypes were observed. Comparison of the six genes shows that each has distinctive properties, suggesting that they do not act in a linear pathway.
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Affiliation(s)
- Maria J. Gravato-Nobre
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom and Department of Cell and Tissue Biology, University of California, San Francisco, California 94143
| | - Dave Stroud
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom and Department of Cell and Tissue Biology, University of California, San Francisco, California 94143
| | - Delia O'Rourke
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom and Department of Cell and Tissue Biology, University of California, San Francisco, California 94143
| | - Creg Darby
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom and Department of Cell and Tissue Biology, University of California, San Francisco, California 94143
| | - Jonathan Hodgkin
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom and Department of Cell and Tissue Biology, University of California, San Francisco, California 94143
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11
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Hamel S, Fantini J, Schweisguth F. Notch ligand activity is modulated by glycosphingolipid membrane composition in Drosophila melanogaster. ACTA ACUST UNITED AC 2010; 188:581-94. [PMID: 20176925 PMCID: PMC2828914 DOI: 10.1083/jcb.200907116] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Endocytosis of the transmembrane ligands Delta (Dl) and Serrate (Ser) is required for the proper activation of Notch receptors. The E3 ubiquitin ligases Mindbomb1 (Mib1) and Neuralized (Neur) regulate the ubiquitination of Dl and Ser and thereby promote both ligand endocytosis and Notch receptor activation. In this study, we identify the alpha1,4-N-acetylgalactosaminyltransferase-1 (alpha4GT1) gene as a gain of function suppressor of Mib1 inhibition. Expression of alpha4GT1 suppressed the signaling and endocytosis defects of Dl and Ser resulting from the inhibition of mib1 and/or neur activity. Genetic and biochemical evidence indicate that alpha4GT1 plays a regulatory but nonessential function in Notch signaling via the synthesis of a specific glycosphingolipid (GSL), N5, produced by alpha4GT1. Furthermore, we show that the extracellular domain of Ser interacts with GSLs in vitro via a conserved GSL-binding motif, raising the possibility that direct GSL-protein interactions modulate the endocytosis of Notch ligands. Together, our data indicate that specific GSLs modulate the signaling activity of Notch ligands.
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Affiliation(s)
- Sophie Hamel
- Institut Pasteur, Centre National de la Recherche Scientifique URA2578, 75724 Paris, Cedex 15, France
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12
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Short B. Glycosphingolipids keep signaling in top-Notch condition. J Biophys Biochem Cytol 2010. [PMCID: PMC2828930 DOI: 10.1083/jcb.1884if] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Membrane lipids promote the endocytosis and signaling capacity of Notch receptor ligands.
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13
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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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14
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Intracellular trafficking of Notch receptors and ligands. Exp Cell Res 2009; 315:1549-55. [DOI: 10.1016/j.yexcr.2008.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 09/08/2008] [Accepted: 09/09/2008] [Indexed: 11/23/2022]
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15
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Marza E, Simonsen KT, Faergeman NJ, Lesa GM. Expression of ceramide glucosyltransferases, which are essential for glycosphingolipid synthesis, is only required in a small subset of C. elegans cells. J Cell Sci 2009; 122:822-33. [PMID: 19240113 DOI: 10.1242/jcs.042754] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Glycosphingolipids (GSLs) are glycosylated derivatives of ceramide in the lipid bilayer. Their ubiquitous distribution and complexity suggest that they have important functions, but what these are in vivo is still poorly understood. Here, we characterize the phenotype of Caenorhabditis elegans mutants with essentially no GSLs. The C. elegans genome encodes three ceramide glucosyltransferase (CGT) genes, which encode enzymes required for GSL biosynthesis. Animals lacking CGT do not synthesize GSLs, arrest growth at the first larval stage, and display defects in a subset of cells in their digestive tract; these defects impair larval feeding, resulting in a starvation-induced growth arrest. Restoring CGT function in these digestive tract cells - but not in a variety of other tissues - is sufficient to rescue the phenotypes associated with loss of CGT function. These unexpected findings suggest that GSLs are dispensable in most C. elegans cells, including those of the nervous system.
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Affiliation(s)
- Esther Marza
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
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16
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The intracellular region of Notch ligands Dll1 and Dll3 regulates their trafficking and signaling activity. Proc Natl Acad Sci U S A 2008; 105:11212-7. [PMID: 18676613 DOI: 10.1073/pnas.0800695105] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic studies have shown that ubiquitination and endocytosis of the Drosophila ligand Delta in signal-sending cells are required for activation of Notch signaling, but how these events promote Notch activation remains poorly understood. Here, we show that an ubiquitination-defective mutant of the murine Delta-homologue Dll1 is endocytosed but, in contrast to the wild-type Dll1, is unable to subsequently recycle back to the cell surface or to bind Notch1 efficiently. These results demonstrate that ubiquitination, although not required for endocytosis, is essential for Dll1 recycling and that recycling is required to acquire affinity for the receptor. On the other hand, a chimeric molecule encompassing the extracellular domain of Dll1 and the transmembrane/intracellular domain of Dll3, which contains no lysine, is endocytosed, recycled, and interacts with Notch1 but is unable to induce transendocytosis of the extracellular region of Notch1 or to signal. These observations suggest that the chimera uses an ubiquitination-independent signal to recycle, allowing it to acquire affinity for Notch1. Our results support the idea that ligand recycling determines its competence to bind efficiently to the receptor but that this is insufficient to allow it to perform transendocytosis, an event required for activation of Notch signaling. Finally, the present study indicates that Dll1 partially localizes to lipid microdomains, whereas both ubiquitination-defective Dll1 and the Dll1-3 chimera are excluded from these compartments, suggesting that these microdomains provide the environment necessary for Dll1 to activate Notch signaling.
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17
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Partridge FA, Tearle AW, Gravato-Nobre MJ, Schafer WR, Hodgkin J. The C. elegans glycosyltransferase BUS-8 has two distinct and essential roles in epidermal morphogenesis. Dev Biol 2008; 317:549-59. [PMID: 18395708 DOI: 10.1016/j.ydbio.2008.02.060] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 02/22/2008] [Accepted: 02/29/2008] [Indexed: 12/22/2022]
Abstract
Ventral enclosure in Caenorhabditis elegans involves migration of epidermal cells over a neuroblast substrate and subsequent adhesion at the ventral midline. Organisation of the neuroblast layer by ephrins and their receptors is essential for this migration. We show that bus-8, which encodes a predicted glycosyltransferase, is essential for embryonic enclosure and acts in or with ephrin signalling to mediate neuroblast organisation and to permit epidermal migration. BUS-8 acts non-cell-autonomously in this process, and likely modifies an extracellular regulator of ephrin signalling and cell organisation. Weak and cold-sensitive alleles of bus-8 show that the gene has a separate and distinct post-embryonic role, being essential for epidermal integrity and production of the cuticle surface. This disorganisation of the epidermis and cuticle layers causes increased drug sensitivity, which could aid the growing use of C. elegans in drug screening and chemical genomics. The viable mutants are also resistant to infection by the pathogen Microbacterium nematophilum, due to failure of the bacterium to bind to the host surface. The two separate essential roles of BUS-8 in epidermal morphogenesis add to our growing understanding of the widespread importance of glycobiology in development.
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Affiliation(s)
- Frederick A Partridge
- Genetics Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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18
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Investigating the genetic circuitry of mastermind in Drosophila, a notch signal effector. Genetics 2008; 177:2493-505. [PMID: 18073442 DOI: 10.1534/genetics.107.080994] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Notch signaling regulates multiple developmental processes and is implicated in various human diseases. Through use of the Notch transcriptional co-activator mastermind, we conducted a screen for Notch signal modifiers using the Exelixis collection of insertional mutations, which affects approximately 50% of the Drosophila genome, recovering 160 genes never before associated with Notch, extending the previous roster of genes that interact functionally with the Notch pathway and mastermind. As the molecular identity for most recovered genes is known, gene ontology (GO) analysis was applied, grouping genes according to functional classifications. We identify novel Notch-associated GO categories, uncover nodes of integration between Notch and other signaling pathways, and unveil groups of modifiers that suggest the existence of Notch-independent mastermind functions, including a conserved ability to regulate Wnt signaling.
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Cormier S, Souilhol C, Babinet C, Cohen-Tannoudji M. Voie de signalisation Notch et développement précoce des mammifères. Med Sci (Paris) 2007; 23:26-8. [PMID: 17212926 DOI: 10.1051/medsci/200723126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Sarah Cormier
- Unité de Génétique fonctionnelle de la souris, CNRS URA 2578, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France
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Yook K, Hodgkin J. Mos1 mutagenesis reveals a diversity of mechanisms affecting response of Caenorhabditis elegans to the bacterial pathogen Microbacterium nematophilum. Genetics 2006; 175:681-97. [PMID: 17151260 PMCID: PMC1800622 DOI: 10.1534/genetics.106.060087] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A specific host-pathogen interaction exists between Caenorhabditis elegans and the gram-positive bacterium Microbacterium nematophilum. This bacterium is able to colonize the rectum of susceptible worms and induces a defensive tail-swelling response in the host. Previous mutant screens have identified multiple loci that affect this interaction. Some of these loci correspond to known genes, but many bus genes [those with a bacterially unswollen (Bus) mutant phenotype] have yet to be cloned. We employed Mos1 transposon mutagenesis as a means of more rapidly cloning bus genes and identifying new mutants with altered pathogen response. This approach revealed new infection-related roles for two well-characterized and much-studied genes, egl-8 and tax-4. It also allowed the cloning of a known bus gene, bus-17, which encodes a predicted galactosyltransferase, and of a new bus gene, bus-19, which encodes a novel, albeit ancient, protein. The results illustrate advantages and disadvantages of Mos1 transposon mutagenesis in this system.
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Affiliation(s)
- Karen Yook
- Genetics Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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Souilhol C, Cormier S, Tanigaki K, Babinet C, Cohen-Tannoudji M. RBP-Jkappa-dependent notch signaling is dispensable for mouse early embryonic development. Mol Cell Biol 2006; 26:4769-74. [PMID: 16782866 PMCID: PMC1489163 DOI: 10.1128/mcb.00319-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Notch signaling pathway is an evolutionarily conserved signaling system which has been shown to be essential in cell fate specification and in numerous aspects of embryonic development in all metazoans thus far studied. We recently demonstrated that several components of the Notch signaling pathway, including the four Notch receptors and their five ligands known in mammals, are expressed in mouse oocytes, in mouse preimplantation embryos, or both. This suggested a possible implication of the Notch pathway in the first cell fate specification of the dividing mouse embryo, which results in the formation of the blastocyst. To address this issue directly, we generated zygotes in which both the maternal and the zygotic expression of Rbpsuh, a key element of the core Notch signaling pathway, were abrogated. We find that such zygotes give rise to blastocysts which implant and develop normally. Nevertheless, after gastrulation, these embryos die around midgestation, similarly to Rbpsuh-null mutants. This demonstrates that the RBP-Jkappa-dependent pathway, otherwise called the canonical Notch pathway, is dispensable for blastocyst morphogenesis and the establishment of the three germ layers, ectoderm, endoderm, and mesoderm. These results are discussed in the light of recent observations which have challenged this conclusion.
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Affiliation(s)
- Céline Souilhol
- Unité Biologie du Développement, CNRS URA 2578, Institut Pasteur, Paris, France
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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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