1
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Lossos A, Elazar N, Lerer I, Schueler-Furman O, Fellig Y, Glick B, Zimmerman BE, Azulay H, Dotan S, Goldberg S, Gomori JM, Ponger P, Newman JP, Marreed H, Steck AJ, Schaeren-Wiemers N, Mor N, Harel M, Geiger T, Eshed-Eisenbach Y, Meiner V, Peles E. Myelin-associated glycoprotein gene mutation causes Pelizaeus-Merzbacher disease-like disorder. Brain 2015; 138:2521-36. [PMID: 26179919 DOI: 10.1093/brain/awv204] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/27/2015] [Indexed: 01/07/2023] Open
Abstract
Pelizaeus-Merzbacher disease is an X-linked hypomyelinating leukodystrophy caused by mutations or rearrangements in PLP1. It presents in infancy with nystagmus, jerky head movements, hypotonia and developmental delay evolving into spastic tetraplegia with optic atrophy and variable movement disorders. A clinically similar phenotype caused by recessive mutations in GJC2 is known as Pelizaeus-Merzbacher-like disease. Both genes encode proteins associated with myelin. We describe three siblings of a consanguineous family manifesting the typical infantile-onset Pelizaeus-Merzbacher disease-like phenotype slowly evolving into a form of complicated hereditary spastic paraplegia with mental retardation, dysarthria, optic atrophy and peripheral neuropathy in adulthood. Magnetic resonance imaging and spectroscopy were consistent with a demyelinating leukodystrophy. Using genetic linkage and exome sequencing, we identified a homozygous missense c.399C>G; p.S133R mutation in MAG. This gene, previously associated with hereditary spastic paraplegia, encodes myelin-associated glycoprotein, which is involved in myelin maintenance and glia-axon interaction. This mutation is predicted to destabilize the protein and affect its tertiary structure. Examination of the sural nerve biopsy sample obtained in childhood in the oldest sibling revealed complete absence of myelin-associated glycoprotein accompanied by ill-formed onion-bulb structures and a relatively thin myelin sheath of the affected axons. Immunofluorescence, cell surface labelling, biochemical analysis and mass spectrometry-based proteomics studies in a variety of cell types demonstrated a devastating effect of the mutation on post-translational processing, steady state expression and subcellular localization of myelin-associated glycoprotein. In contrast to the wild-type protein, the p.S133R mutant was retained in the endoplasmic reticulum and was subjected to endoplasmic reticulum-associated protein degradation by the proteasome. Our findings identify involvement of myelin-associated glycoprotein in this family with a disorder affecting the central and peripheral nervous system, and suggest that loss of the protein function is responsible for the unique clinical phenotype.
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Affiliation(s)
- Alexander Lossos
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Nimrod Elazar
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Israela Lerer
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Ora Schueler-Furman
- 4 Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University, Jerusalem, Israel
| | - Yakov Fellig
- 5 Department of Pathology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Benjamin Glick
- 6 Paediatric Neuromuscular Service, Alyn Paediatric Rehabilitation Centre, Jerusalem, Israel
| | - Bat-El Zimmerman
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Haim Azulay
- 5 Department of Pathology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Shlomo Dotan
- 7 Department of Ophthalmology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Sharon Goldberg
- 7 Department of Ophthalmology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - John M Gomori
- 8 Department of Radiology, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Penina Ponger
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - J P Newman
- 1 Department of Neurology and Agnes Ginges Centre for Human Neurogenetics, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Hodaifah Marreed
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Andreas J Steck
- 9 Department of Biomedicine, University Hospital Basel, University of Basel, Switzerland
| | | | - Nofar Mor
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Michal Harel
- 10 Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Tamar Geiger
- 10 Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yael Eshed-Eisenbach
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Vardiella Meiner
- 3 Department of Genetics and Metabolic Diseases, Hebrew University-Hadassah Medical Centre, Jerusalem, Israel
| | - Elior Peles
- 2 Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
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2
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Schwardt O, Kelm S, Ernst B. SIGLEC-4 (MAG) Antagonists: From the Natural Carbohydrate Epitope to Glycomimetics. Top Curr Chem (Cham) 2013; 367:151-200. [DOI: 10.1007/128_2013_498] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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3
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Molecular basis of the interactions of the Nogo-66 receptor and its homolog NgR2 with myelin-associated glycoprotein: development of NgROMNI-Fc, a novel antagonist of CNS myelin inhibition. J Neurosci 2009; 29:5768-83. [PMID: 19420245 DOI: 10.1523/jneurosci.4935-08.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Myelin-associated glycoprotein (MAG) is a sialic acid-binding Ig-family lectin that functions in neuronal growth inhibition and stabilization of axon-glia interactions. The ectodomain of MAG is comprised of five Ig-like domains and uses neuronal cell-type-specific mechanisms to signal growth inhibition. We show that the first three Ig-like domains of MAG bind with high affinity and in a sialic acid-dependent manner to the Nogo-66 receptor-1 (NgR1) and its homolog NgR2. Domains Ig3-Ig5 of MAG are sufficient to inhibit neurite outgrowth but fail to associate with NgR1 or NgR2. Nogo receptors are sialoglycoproteins comprised of 8.5 canonical leucine-rich repeats (LRR) flanked by LRR N-terminal (NT) and C-terminal (CT)-cap domains. The LRR cluster is connected through a stalk region to a membrane lipid anchor. The CT-cap domain and stalk region of NgR2, but not NgR1, are sufficient for MAG binding, and when expressed in neurons, exhibit constitutive growth inhibitory activity. The LRR cluster of NgR1 supports binding of Nogo-66, OMgp, and MAG. Deletion of disulfide loop Cys(309)-Cys(336) of NgR1 selectively increases its affinity for Nogo-66 and OMgp. A chimeric Nogo receptor variant (NgR(OMNI)) in which Cys(309)-Cys(336) is deleted and followed by a 13 aa MAG-binding motif of the NgR2 stalk, shows superior binding of OMgp, Nogo-66, and MAG compared with wild-type NgR1 or NgR2. Soluble NgR(OMNI) (NgR(OMNI)-Fc) binds strongly to membrane-bound inhibitors and promotes neurite outgrowth on both MAG and CNS myelin substrates. Thus, NgR(OMNI)-Fc may offer therapeutic opportunities following nervous system injury or disease where myelin inhibits neuronal regeneration.
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4
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Quarles RH. A Hypothesis About the Relationship of Myelin-Associated Glycoprotein’s Function in Myelinated Axons to its Capacity to Inhibit Neurite Outgrowth. Neurochem Res 2008; 34:79-86. [DOI: 10.1007/s11064-008-9668-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Accepted: 03/12/2008] [Indexed: 12/30/2022]
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5
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Abstract
The myelin-associated glycoprotein (MAG) is a type I transmembrane glycoprotein localized in periaxonal Schwann cell and oligodendroglial membranes of myelin sheaths where it functions in glia-axon interactions. It contains five immunoglobulin (Ig)-like domains and is in the sialic acid-binding subgroup of the Ig superfamily. It appears to function both as a ligand for an axonal receptor that is needed for the maintenance of myelinated axons and as a receptor for an axonal signal that promotes the differentiation, maintenance and survival of oligodendrocytes. Its function in the maintenance of myelinated axons may be related to its role as one of the white matter inhibitors of neurite outgrowth acting through a receptor complex involving the Nogo receptor and/or gangliosides containing 2,3-linked sialic acid. MAG is expressed as two developmentally regulated isoforms with different cytoplasmic domains that may activate different signal transduction pathways in myelin-forming cells. MAG contains a carbohydrate epitope shared with other glycoconjugates that is a target antigen in autoimmune peripheral neuropathy associated with IgM gammopathy and has been implicated in a dying back oligodendrogliopathy in multiple sclerosis.
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Affiliation(s)
- Richard H Quarles
- Myelin and Brain Development Section, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland 20892, USA.
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6
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Abstract
Sialic acids are a family of acidic sugars with a 9-carbon backbone, prominently expressed in animals of deuterostome lineage. Siglecs are the largest family of vertebrate endogenous receptors that recognize glycoconjugates containing sialic acids. Although a few Siglecs are well-conserved throughout vertebrate evolution and show similar binding preference regardless of the species of origin, most others, particularly the CD33-related subfamily of Siglecs, show marked inter-species differences in repertoire, sequence, and binding preference. The diversification of CD33-related Siglecs may be driven by direct competition against pathogens, and/or by necessity to catch up with the changing landscape of endogenous glycans, which may in turn be changing to escape exploitation by other pathogens.
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Affiliation(s)
- Takashi Angata
- Research Center for Glycoscience, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki, Japan.
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7
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Yu XL, Jiang JL, Li L, Feng Q, Xu J, Chen ZN. The glycosylation characteristic of hepatoma-associated antigen HAb18G/CD147 in human hepatoma cells. Int J Biochem Cell Biol 2006; 38:1939-45. [PMID: 16824781 DOI: 10.1016/j.biocel.2006.05.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 05/17/2006] [Accepted: 05/18/2006] [Indexed: 11/27/2022]
Abstract
HAb18G/CD147 is a highly glycosylated transmembrane protein belonging to the immunoglobulin superfamily. Our previous studies have demonstrated that overexpressing HAb18G/CD147 enhances the metastatic potentials of human hepatoma cells. In the present study, to investigate the glycosylation characteristic of HAb18G/CD147 in human hepatoma cells, HAb18G/CD147 was first purified from human FHCC-98 hepatoma cells by immunoaffinity chromatography, and then introduced into human fibroblasts culture system for matrix metalloproteinases induction. As a result, the elevated levels of matrix metalloproteinases secreted by fibroblasts were detected by gelatin zymography. The lysates of human hepatoma FHCC-98 cell revealed two major forms of HAb18G/CD147 (43-66 and 35 kDa) by western blot assay. To elucidate whether the variation of molecule size were caused by different glycosylation, two different approaches were employed to accomplish this goal: deglycosylation with N-glycosylation inhibitor tunicamycin or endoglycosidases. A single deglycosylated core protein with molecular weight approximately 27 kDa was obtained from both methods. Furthermore, the results of endoglycosidases treatment also showed that two forms of HAb18G/CD147 contain different types of oligosaccharide chains, thus sensitive to different endoglycosidase. In conclusion, the present study demonstrated that purified native HAb18G/CD147 has the bioactivity of stimulating human fibroblasts to produce elevated levels of matrix metalloproteinases, and that the two different forms of HAb18G/CD147 are derived from the single core protein but differ in their degree and types of glycosylation.
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Affiliation(s)
- Xiao-Ling Yu
- Cell Engineering Research Centre & Department of Cell Biology, State Key Laboratory of Cancer Biology, Fourth Military Medical University, Xi'an 710032, PR China
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8
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Abstract
Animal glycan-recognizing proteins can be broadly classified into two groups-lectins (which typically contain an evolutionarily conserved carbohydrate-recognition domain [CRD]) and sulfated glycosaminoglycan (SGAG)-binding proteins (which appear to have evolved by convergent evolution). Proteins other than antibodies and T-cell receptors that mediate glycan recognition via immunoglobulin (Ig)-like domains are called "I-type lectins." The major homologous subfamily of I-type lectins with sialic acid (Sia)-binding properties and characteristic amino-terminal structural features are called the "Siglecs" (Sia-recognizing Ig-superfamily lectins). The Siglecs can be divided into two groups: an evolutionarily conserved subgroup (Siglecs-1, -2, and -4) and a CD33/Siglec-3-related subgroup (Siglecs-3 and -5-13 in primates), which appear to be rapidly evolving. This article provides an overview of historical and current information about the Siglecs.
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Affiliation(s)
- Ajit Varki
- Research Center for Glycoscience, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan.
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9
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McKerracher L. Ganglioside rafts as MAG receptors that mediate blockade of axon growth. Proc Natl Acad Sci U S A 2002; 99:7811-3. [PMID: 12060723 PMCID: PMC122973 DOI: 10.1073/pnas.132280299] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Lisa McKerracher
- Département de Pathologie et Biologie Cellulaire, Université de Montréal, 2900 Edouard-Montpetit, Montréal, Quebec, Canada H3T 1J4.
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10
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Dashiell SM, Tanner SL, Pant HC, Quarles RH. Myelin-associated glycoprotein modulates expression and phosphorylation of neuronal cytoskeletal elements and their associated kinases. J Neurochem 2002; 81:1263-72. [PMID: 12068074 DOI: 10.1046/j.1471-4159.2002.00927.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Decreased phosphorylation of neurofilaments in mice lacking myelin-associated glycoprotein (MAG) was shown to be associated with decreased activities of extracellular-signal regulated kinases (ERK1/2) and cyclin-dependent kinase-5 (cdk5). These in vivo changes could be caused directly by the absence of a MAG-mediated signaling pathway or secondary to a general disruption of the Schwann cell-axon junction that prevents signaling by other molecules. Therefore, in vitro experimental paradigms of MAG interaction with neurons were used to determine if MAG directly influences expression and phosphorylation of cytoskeletal proteins and their associated kinases. COS-7 cells stably transfected with MAG or with empty vector were co-cultured with primary dorsal root ganglion (DRG) neurons. Total amounts of the middle molecular weight neurofilament subunit (NF-M), microtubule-associated protein 1B (MAP1B), MAP2, and tau were up-regulated significantly in DRG neurons in the presence of MAG. There was also increased expression of phosphorylated high molecular weight neurofilament subunit (NF-H), NF-M, and MAP1B. Additionally, in similar in vitro paradigms, total and phosphorylated NF-M were increased significantly in PC12 neurons co-cultured with MAG-expressing COS cells or treated with a soluble MAG Fc-chimera. The increased expression of phosphorylated cytoskeletal proteins in the presence of MAG in vitro was associated with increased activities of ERK 1/2 and cdk5. We propose that interaction of MAG with an axonal receptor(s) induces a signal transduction cascade that regulates expression of cytoskeletal proteins and their phosphorylation by these proline-directed protein kinases.
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Affiliation(s)
- Suzanne M Dashiell
- Laboratory of Molecular and Cellular Neurobiology, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland 20892, USA
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11
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Li N, Zhang W, Wan T, Zhang J, Chen T, Yu Y, Wang J, Cao X. Cloning and Characterization of Siglec-10, a Novel Sialic Acid Binding Member of the Ig Superfamily, from Human Dendritic Cells. J Biol Chem 2001; 276:28106-12. [PMID: 11358961 DOI: 10.1074/jbc.m100467200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Siglecs (sialic acid-binding Ig-like lectins) are a subfamily of I-type lectins, which specifically recognize sialic acids. Nine members of the family have been identified thus far. We have obtained a novel cDNA clone from a human dendritic cell cDNA library encoding a protein with sequence and structural features of the Siglec family, hence designated as Siglec-10. The full-length Siglec-10 cDNA encodes a type 1 transmembrane protein containing four extracellular immunoglobulin-like domains, a transmembrane region, and a cytoplasmic tail with two classical immunoreceptor tyrosine-based inhibitory motifs. The N-terminal V-set Ig domain has most of the amino acid residues typical of the Siglecs. Siglec-10 shows the closest homology to Siglec-5 and Siglec-3/CD33. Various cells and cell lines including monocytes and dendritic cells express Siglec-10. High levels of mRNA expression were seen in peripheral blood leukocytes, spleen, and liver. When expressed on COS-7 cells, Siglec-10 was able to bind human red blood cells and soluble sialoglycoconjugates in a sialic acid-dependent manner. The identification of Siglec-10 as a new Siglec family member and its expression profile, together with its sialic acid-dependent binding capacity, suggest that it may be involved in cell-cell recognition by interacting with sialylated ligands expressed on specific cell populations.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Antigens, CD/metabolism
- Antigens, Differentiation, Myelomonocytic/metabolism
- Blotting, Northern
- COS Cells
- Cell Line
- Cell Membrane/metabolism
- Cloning, Molecular
- DNA, Complementary/metabolism
- Dendritic Cells/metabolism
- Erythrocytes/metabolism
- Gene Library
- HL-60 Cells
- HeLa Cells
- Humans
- Immunoglobulins/chemistry
- Immunoglobulins/genetics
- Lectins/chemistry
- Lectins/genetics
- Leukocytes/metabolism
- Liver/metabolism
- Models, Biological
- Molecular Sequence Data
- Monocytes/metabolism
- Neuraminidase/metabolism
- Protein Binding
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- Receptors, Cell Surface
- Recombinant Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Sialic Acids/metabolism
- Spleen/metabolism
- Tissue Distribution
- Transfection
- Tumor Cells, Cultured
- U937 Cells
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Affiliation(s)
- N Li
- Institute of Immunology, Second Military Medical University, 800 Xiangyin Road, Shanghai 200433, China
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12
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Affiliation(s)
- S Kelm
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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13
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Yoshida S, Shibata M, Yamamoto S, Hagihara M, Asai N, Takahashi M, Mizutani S, Muramatsu T, Kadomatsu K. Homo-oligomer formation by basigin, an immunoglobulin superfamily member, via its N-terminal immunoglobulin domain. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4372-80. [PMID: 10880960 DOI: 10.1046/j.1432-1327.2000.01482.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Basigin (Bsg) is a highly glycosylated transmembrane protein with two immunoglobulin (Ig)-like domains. A number of studies, including gene targeting, have demonstrated that Bsg plays pivotal roles in spermatogenesis, implantation, neural network formation and tumor progression. In the present study, to understand the mechanism of action of Bsg, we determined its expression status on the plasma membrane. Cotransfection of Bsg expression vectors with two different tags clarified that Bsg forms homo-oligomers in a cis-dependent manner on the plasma membrane. If the disulfide bond of the more N-terminally located Ig-like domain was destroyed by mutations, Bsg could not form oligomers. In contrast, the mutations of the C-terminal Ig-like domain or N-glycosylation sites did not affect the association. The association of mouse and human Bsgs, which exhibit high homology in the transmembrane and intracellular domains but low homology in the extracellular domain, was very weak as compared with that within the same species, suggesting the importance of the extracellular domain in the association. If the extracellular domain of the human Ret protein was replaced with the N-terminal Ig-like domain of Bsg, the resulting chimera protein was associated with intact wild-type Bsg, but not if the C-terminal Ig-like domain, instead of the N-terminal one, of Bsg was used. No oligomer formation took place between the intact wild-type Ret and Bsg proteins. In conclusion, these data indicate that the N-terminal Ig-like domain is necessary and sufficient for oligomer formation by Bsg on the plasma membrane.
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MESH Headings
- Animals
- Antigens, CD
- Antigens, Neoplasm
- Antigens, Surface/chemistry
- Avian Proteins
- Basigin
- Biotinylation
- Blood Proteins
- Blotting, Western
- COS Cells
- Cell Membrane/metabolism
- DNA, Complementary/metabolism
- Disulfides
- Electrophoresis, Polyacrylamide Gel
- Glycosylation
- Humans
- Immunoglobulins/chemistry
- Male
- Membrane Glycoproteins/biosynthesis
- Membrane Glycoproteins/chemistry
- Membrane Glycoproteins/genetics
- Mice
- Mice, Inbred C57BL
- Models, Biological
- Mutagenesis, Site-Directed
- Mutation
- Plasmids/metabolism
- Precipitin Tests
- Protein Structure, Tertiary
- Recombinant Fusion Proteins/metabolism
- Testis/metabolism
- Transfection
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Affiliation(s)
- S Yoshida
- Departments of Biochemistry, Obstetrics and Gynecology, and Pathology, Nagoya University School of Medicine, Japan
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14
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Abstract
The Siglecs are a recently discovered family of sialic acid-binding lectins of the immunoglobulin (Ig) superfamily. We report a molecule showing homology to the six first reported Siglecs, with the closest relationship to Siglec-3(CD33), Siglec-5, and Siglec-6(OBBP-1). The extracellular portion has two Ig-like domains, with the amino-terminal V-set Ig domain including amino acid residues known to be involved in sialic acid recognition by other Siglecs. The cytoplasmic domain has putative sites of tyrosine phosphorylation shared with some Siglecs, including an Immuno-receptor Tyrosine-based Inhibitory Motif (ITIM). Expression of the full-length cDNA induces sialic acid-dependent binding to human erythrocytes. A recombinant chimeric form containing the extracellular Ig domains selectively recognizes the sequence Neu5Acalpha2-6Galbeta1-4Glc, and binding requires the side chain of sialic acid. Mutation of an arginine residue predicted to be critical for sialic acid binding abolishes both interactions. Taken together, our findings justify designation of the molecule as Siglec-7. Analysis of bacterial artificial chromosome (BAC) clones spanning the known human genomic location of Siglec-3 indicates that the Siglec-7 gene is also located on chromosome 19q13.3-13.4. Human tissues show strong expression of Siglec-7 mRNA in spleen, peripheral blood leukocytes, and liver. The combination of an extracellular sialic acid binding site and an intracellular ITIM motif suggests that this molecule is involved in trans-membrane regulatory signaling reactions.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, Differentiation, Myelomonocytic/chemistry
- Antigens, Differentiation, Myelomonocytic/genetics
- Base Sequence
- COS Cells
- Chromosomes, Human, Pair 19
- DNA, Complementary/chemistry
- Erythrocytes/metabolism
- Gene Expression
- Humans
- Lectins
- Leukocytes/chemistry
- Liver/chemistry
- Molecular Sequence Data
- N-Acetylneuraminic Acid/metabolism
- N-Acetylneuraminic Acid/pharmacology
- RNA, Messenger/analysis
- Sequence Homology
- Spleen/chemistry
- Transfection
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Affiliation(s)
- T Angata
- Glycobiology Research and Training Center, Department of Medicine and Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
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15
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Brinkman-Van der Linden EC, Varki A. New aspects of siglec binding specificities, including the significance of fucosylation and of the sialyl-Tn epitope. Sialic acid-binding immunoglobulin superfamily lectins. J Biol Chem 2000; 275:8625-32. [PMID: 10722702 DOI: 10.1074/jbc.275.12.8625] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The siglecs (sialic acid-binding immunoglobulin superfamily lectins) are immunoglobulin superfamily members recognizing sialylated ligands. Most prior studies of siglec specificities focused on alpha2-3- and alpha2-6-sialyllactos(amin)es and on one or two of the siglecs at a time. Here, we explore several new aspects of specificities of the first six reported siglecs, using sialylated glycans presented in multivalent form, on synthetic polyacrylamide backbones, or on mucin polypeptides. First, we report that binding of siglec-1 (sialoadhesin), siglec-3 (CD33), siglec-4a (myelin-associated glycoprotein), and siglec-5 to alpha2-3 sialyllactosamine is affected markedly by the presence of an alpha1-3-linked fucose. Thus, while siglecs may not interfere with selectin-mediated recognition, fucosylation could negatively regulate siglec binding. Second, in contrast to earlier studies, we find that siglec-3 prefers alpha2-6-sialyllactose. Third, siglec-5 binds alpha2-8-linked sialic acid, making it the siglec least specific for linkage recognition. Fourth, siglecs-2 (CD22), -3, -5, and -6 (obesity-binding protein 1) showed significant binding to sialyl-Tn (Neu5Acalpha2-6-GalNAc), a tumor marker associated with poor prognosis. Fifth, siglec-6 is an exception among siglecs in not requiring the glycerol side chain of sialic acid for recognition. Sixth, all siglecs require the carboxyl group of sialic acid for binding. Finally, the presentation of the sialyl-Tn epitope and/or more extended structures that include this motif may be important for optimal recognition by the siglecs. This was concluded from studies using ovine, bovine, and porcine submaxillary mucins and Chinese hamster ovary cells transfected with ST6GalNAc-I and/or the mucin polypeptide MUC1.
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Affiliation(s)
- E C Brinkman-Van der Linden
- Glycobiology Research and Training Center and Department of Medicine, University of California San Diego, La Jolla, California 92093, USA
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16
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Abstract
The myelin-associated glycoprotein, a minor component of myelin in the central and peripheral nervous system, has been implicated in the formation and maintenance of myelin. Although the analysis of MAG null mutants confirms this view, the phenotype of this mutant is surprisingly subtle. In the CNS of MAG-deficient mice, initiation of myelination, formation of morphologically intact myelin sheaths and to a minor extent, integrity of myelin is affected. In the PNS, in comparison, only maintenance of myelin is impaired. Recently, the large isoform of MAG has been identified as the functionally important isoform in the CNS, whereas the small MAG isoform is sufficient to maintain the integrity of myelinated fibers in the PNS. Remarkably, none of the different defects in the MAG mutant is consistently associated with each myelinated fiber. These observations suggest that other molecules performing similar functions as MAG might compensate, at least partially, for the absence of MAG in the null mutant.
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Affiliation(s)
- M Schachner
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, Hamburg, Germany.
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17
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Razi N, Varki A. Cryptic sialic acid binding lectins on human blood leukocytes can be unmasked by sialidase treatment or cellular activation. Glycobiology 1999; 9:1225-34. [PMID: 10536038 DOI: 10.1093/glycob/9.11.1225] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We recently reported that the sialic acid-specific binding sites of CD22 molecules on B cells are masked by endogenous ligands, and can be unmasked by sialidase treatment or cellular activation. Here, we show that many other human blood leukocyte types have endogenous sialic acid binding sites that can be unmasked by sialidase treatment. Truncation of sialic acid side chains on the soluble probes used for detection abolishes all binding, indicating the specificity of the interaction for the details of sialic acid structure. There is limited overlap between alpha2-6- and alpha2-3-sialic acid-specific binding sites, which are unmasked on monocytes, natural killer cells, a minority of mature T cells, neutrophils, and some cultured human leukemic cell lines. Activation with phorbol ester and calcium ionophore causes spontaneous exposure of some of the binding sites, occurring over a period of minutes on neutrophils and several hours on monocytes and U937 leukemia cells. Activation is accompanied by some evidence for desialylation of cell surface molecules. Thus, many human blood cells have specific binding sites for sialic acids, masked by endogenous sialylated ligands. Cellular activation can unmask these sites, possibly by the action of an endogenous sialidase. The nearly universal masking of such sites in unactivated blood cells could explain why many of these sialic acid-binding lectins have not been previously discovered. Similar considerations may apply to sialic acid binding lectins of other cell types and tissues.
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Affiliation(s)
- N Razi
- Glycobiology Program and Cancer Center, Divisions of Hematology-Oncology, and Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
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Abstract
The past year has provided the X-ray crystal structures of both the N-terminal domain of sialoadhesin and the extracytoplasmic domain of the cation-dependent mannose 6-phosphate receptor. These structures represent the first examples from the I- and P-type lectin families and provide important insights into how these transmembrane-spanning receptors function. In addition, structures of galectin-7 and of the carbohydrate-recognition domain of galectin-3 have given evidence of a new galectin quaternary structure. Finally, the structure of tachylectin-2, the first example of a fivefold symmetric beta-propeller protein, sheds light on the role played by this lectin in horseshoe crab host defense.
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Affiliation(s)
- J M Rini
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.
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Turnley AM, Bartlett PF. Nerve growth factor modulates myelin-associated glycoprotein binding to sensory neurons. Int J Dev Neurosci 1999; 17:109-19. [PMID: 10221670 DOI: 10.1016/s0736-5748(98)00068-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Myelin-associated glycoprotein (MAG) is a molecule expressed by myelinating cells at the myelin/axon interface, which binds to an as yet unidentified molecule on neurons. We have used a MAG-immunoglobulin Fc fusion protein to examine the expression and regulation of the MAG binding molecule on sensory neurons in culture. Binding of the MAG-Fc reached a maximum at 24-48 h and was higher on neurons which expressed high levels of neurofilament. Nerve growth factor (NGF) upregulated expression of the MAG binding molecule in a dose dependent manner. Schwann cells co-cultured with sensory neurons in serum-free medium stimulated maximal expression of the MAG binding molecule, which was decreased by addition of anti-NGF to the co-cultures. This indicated that Schwann cells can modulate expression of the MAG binding molecule via production of NGF and may represent a physiological mechanism for regulation of MAG-MAG binding molecule interactions during myelination and remyelination.
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Affiliation(s)
- A M Turnley
- The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital, Victoria, Australia.
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Sialylation of the Sialic Acid Binding Lectin Sialoadhesin Regulates Its Ability to Mediate Cell Adhesion. Blood 1999. [DOI: 10.1182/blood.v93.4.1245] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe macrophage-specific cell surface receptor sialoadhesin, which is a member of the newly recognized family of sialic acid binding lectins called siglecs, binds glycoprotein and glycolipid ligands containing a2-3–linked sialic acid on the surface of several leukocyte subsets. Recently, the sialic acid binding activity of the siglec CD22 has been demonstrated to be regulated by sialylation of the CD22 receptor molecule. In the present work, we show that desialylation of in vivo macrophage sialylconjugates enhances sialoadhesin-mediated lectin activity. Herein, we show that receptor sialylation of soluble sialoadhesin inhibits its binding to Jurkat cell ligands, and that charge-dependent repulsion alone cannot explain this inhibition. Furthermore, we show that the inhibitory effect of sialic acid is partially dependent on the presence of an intact exocyclic side chain. These results, in conjunction with previous findings, suggest that sialylation of siglecs by specific glycosyltransferases may be a common mechanism by which siglec-mediated adhesion is regulated.
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Abstract
The macrophage-specific cell surface receptor sialoadhesin, which is a member of the newly recognized family of sialic acid binding lectins called siglecs, binds glycoprotein and glycolipid ligands containing a2-3–linked sialic acid on the surface of several leukocyte subsets. Recently, the sialic acid binding activity of the siglec CD22 has been demonstrated to be regulated by sialylation of the CD22 receptor molecule. In the present work, we show that desialylation of in vivo macrophage sialylconjugates enhances sialoadhesin-mediated lectin activity. Herein, we show that receptor sialylation of soluble sialoadhesin inhibits its binding to Jurkat cell ligands, and that charge-dependent repulsion alone cannot explain this inhibition. Furthermore, we show that the inhibitory effect of sialic acid is partially dependent on the presence of an intact exocyclic side chain. These results, in conjunction with previous findings, suggest that sialylation of siglecs by specific glycosyltransferases may be a common mechanism by which siglec-mediated adhesion is regulated.
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Abstract
We describe the characterization of siglec-5 (sialic acid-binding Ig-like lectin-5), a novel transmembrane member of the immunoglobulin superfamily, highly related to the myeloid antigen, CD33. A full-length cDNA encoding siglec-5 was isolated from a human activated monocyte cDNA library. Sequencing predicted that siglec-5 contains four extracellular immunoglobulin-like domains, the N-terminal two of which are 57% identical to the corresponding region of CD33. The cytoplasmic tail is also related to that of CD33, containing two tyrosine residues embodied in immunoreceptor tyrosine-based inhibitory motif-like motifs. The siglec-5 gene was shown to map to chromosome 19q13.41-43, closely linked to the CD33 gene. When siglec-5 was expressed on COS cells or as a recombinant protein fused to the Fc region of human IgG1, it was able to mediate sialic acid–dependent binding to human erythrocytes and soluble glycoconjugates, suggesting that it may be involved in cell-cell interactions. By using specific antibodies, siglec-5 was found to have an expression pattern distinct from that of CD33, being present at relatively high levels on neutrophils but absent from leukemic cell lines representing early stages of myelomonocytic differentiation. Western blot analysis of neutrophil lysates indicated that siglec-5 exists as a disulfide-linked dimer of approximately 140 kD.© 1998 by The American Society of Hematology.
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Abstract
AbstractWe describe the characterization of siglec-5 (sialic acid-binding Ig-like lectin-5), a novel transmembrane member of the immunoglobulin superfamily, highly related to the myeloid antigen, CD33. A full-length cDNA encoding siglec-5 was isolated from a human activated monocyte cDNA library. Sequencing predicted that siglec-5 contains four extracellular immunoglobulin-like domains, the N-terminal two of which are 57% identical to the corresponding region of CD33. The cytoplasmic tail is also related to that of CD33, containing two tyrosine residues embodied in immunoreceptor tyrosine-based inhibitory motif-like motifs. The siglec-5 gene was shown to map to chromosome 19q13.41-43, closely linked to the CD33 gene. When siglec-5 was expressed on COS cells or as a recombinant protein fused to the Fc region of human IgG1, it was able to mediate sialic acid–dependent binding to human erythrocytes and soluble glycoconjugates, suggesting that it may be involved in cell-cell interactions. By using specific antibodies, siglec-5 was found to have an expression pattern distinct from that of CD33, being present at relatively high levels on neutrophils but absent from leukemic cell lines representing early stages of myelomonocytic differentiation. Western blot analysis of neutrophil lysates indicated that siglec-5 exists as a disulfide-linked dimer of approximately 140 kD.© 1998 by The American Society of Hematology.
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Razi N, Varki A. Masking and unmasking of the sialic acid-binding lectin activity of CD22 (Siglec-2) on B lymphocytes. Proc Natl Acad Sci U S A 1998; 95:7469-74. [PMID: 9636173 PMCID: PMC22653 DOI: 10.1073/pnas.95.13.7469] [Citation(s) in RCA: 201] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
CD22 is a B cell-restricted glycoprotein involved in signal transduction and modulation of cellular activation. It is also an I-type lectin (now designated Siglec-2), whose extracellular domain can specifically recognize alpha2-6-linked sialic acid (Sia) residues. This activity is postulated to mediate intercellular adhesion and/or to act as a coreceptor in antigen-induced B cell activation. However, studies with recombinant CD22 indicate that the lectin function can be inactivated by expression of alpha2-6-linked Sia residues on the same cell surface. To explore whether this masking phenomenon affects native CD22 on B cells, we first developed a probe to detect the lectin activity of recombinant CD22 expressed on Chinese hamster ovary cells (which have no endogenous alpha2-6-linked Sia residues). This probe is inactive against CD22-positive B lymphoma cells and Epstein-Barr virus-transformed lymphoblasts which express high levels of alpha2-6-linked Sia residues. Enzymatic desialylation unmasks the CD22 lectin activity, indicating that endogenous Sia residues block the CD22 lectin-binding site. Truncation of the side chains of cell surface Sia residues by mild periodate oxidation (known to abrogate Sia recognition by CD22) also had this unmasking effect, indicating that the effects of desialylation are not due to a loss of negative charge. Normal resting B cells from human peripheral blood gave similar findings. However, the lectin is partially unmasked during in vitro activation of these cells. Thus, the lectin activity of CD22 is restricted by endogenous sialylation in resting B cells and may be transiently unmasked during in vivo activation, perhaps to modulate intercellular or intracellular interactions at this critical stage in the humoral response.
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Affiliation(s)
- N Razi
- Glycobiology Program, University of California, San Diego Cancer Center, Divisions of Hematology-Oncology and Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093-0687, USA
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