1
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Suganuma Y, Imamura A, Ando H, Kiso M, Takematsu H, Tsubata T, Ishida H. Improved synthesis of CD22-binding sialosides and its application for further development of potent CD22 inhibitors. Glycoconj J 2023; 40:225-246. [PMID: 36708410 DOI: 10.1007/s10719-023-10098-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 11/28/2022] [Accepted: 01/02/2023] [Indexed: 01/29/2023]
Abstract
CD22, one of the sialic acid-binding immunoglobulin-like lectins (Siglecs), regulates B lymphocyte signaling via its interaction with glycan ligands bearing the sequence Neu5Ac/Gcα(2→6)Gal. We have developed the synthetic sialoside GSC-718 as a ligand mimic for CD22 and identified it as a potent CD22 inhibitor. Although the synthesis of CD22-binding sialosides including GSC-718 has been reported by our group, the synthetic route was unfortunately not suitable for large-scale synthesis. In this study, we developed an improved scalable synthetic procedure for sialosides which utilized 1,5-lactam formation as a key step. The improved procedure yielded sialosides incorporating a series of aglycones at the C2 position. Several derivatives with substituted benzyl residues as aglycones were found to bind to mouse CD22 with affinity comparable to that of GSC-718. The new procedure developed in this study affords sialosides in sufficient quantities for cell-based assays, and will facilitate the search for promising CD22 inhibitors that have therapeutic potential.
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Affiliation(s)
- Yuki Suganuma
- Department of Applied Bioorganic Chemistry, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Akihiro Imamura
- Department of Applied Bioorganic Chemistry, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Institute for Glyco-core Research (iGCORE), Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
| | - Hiromune Ando
- Institute for Glyco-core Research (iGCORE), Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Makoto Kiso
- Department of Applied Bioorganic Chemistry, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiromu Takematsu
- Faculty of Medical Technology, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Takeshi Tsubata
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, 113-8510, Tokyo, Japan
| | - Hideharu Ishida
- Department of Applied Bioorganic Chemistry, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Institute for Glyco-core Research (iGCORE), Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
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2
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Cooper O, Waespy M, Chen D, Kelm S, Li Q, Haselhorst T, Tiralongo J. Sugar-decorated carbon dots: a novel tool for targeting immunomodulatory receptors. NANOSCALE ADVANCES 2022; 4:5355-5364. [PMID: 36540112 PMCID: PMC9729803 DOI: 10.1039/d2na00364c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 10/14/2022] [Indexed: 06/17/2023]
Abstract
Interactions between sialic acid (Sia) and sialic acid-binding immunoglobulin-like lectins (siglecs) regulate the immune system, with aberrations contributing to pathologies such as autoimmunity, infectious disease and cancer. Over the last decade, several multivalent Sia ligands have been synthesized to modulate the Sia-binding affinity of proteins/lectins. Here, we report a novel class of multivalent siglec probes through the decoration of α(2,6)-sialyllactose ligands on inherently fluorescent carbon dots (CD). We show that the preference of α(2,3)-linked Sia for siglec-1 can be altered by increasing the multivalence of Sia ligands present on the CD, and that a locally high glycan concentration can have a direct effect on linkage specificity. Additionally, micromolar (IC50 ∼ 70 μM) interaction of α(2,6)-sialyllactose-CD (6-CD) with siglec-2 (CD22) revealed it was capable of generating a significant cytotoxic effect on Burkitt's Lymphoma (BL) Daudi B cells. This phenonomen was attributed to 6-CD's ability to form trans interactions with CD22 on masked BL Daudi cells as a direct result of clustering of the Sia moiety on the CD surface. Overall, our glycoengineered carbon dots represent a novel high affinity molecular probe with multiple applications in sialoglycoscience and medicine.
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Affiliation(s)
- Oren Cooper
- Institute for Glycomics, Gold Coast Campus, Griffith University Queensland 4222 Australia
| | - Mario Waespy
- Centre for Biomolecular Interactions Bremen, Department of Biology and Chemistry, University of Bremen 28334 Bremen Germany
| | - Dechao Chen
- School of Engineering and Built Environment, Nathan Campus, Griffith University QLD 4111 Australia
| | - Sørge Kelm
- Centre for Biomolecular Interactions Bremen, Department of Biology and Chemistry, University of Bremen 28334 Bremen Germany
| | - Qin Li
- School of Engineering and Built Environment, Nathan Campus, Griffith University QLD 4111 Australia
- Queensland Micro- and Nanotechnology Centre, Australia, Nathan Campus, Griffith University QLD 4111 Australia
| | - Thomas Haselhorst
- Institute for Glycomics, Gold Coast Campus, Griffith University Queensland 4222 Australia
| | - Joe Tiralongo
- Institute for Glycomics, Gold Coast Campus, Griffith University Queensland 4222 Australia
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3
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Srivastava S, Verhagen A, Sasmal A, Wasik BR, Diaz S, Yu H, Bensing BA, Khan N, Khedri Z, Secrest P, Sullam P, Varki N, Chen X, Parrish CR, Varki A. Development and applications of sialoglycan-recognizing probes (SGRPs) with defined specificities: exploring the dynamic mammalian sialoglycome. Glycobiology 2022; 32:1116-1136. [PMID: 35926090 PMCID: PMC9680117 DOI: 10.1093/glycob/cwac050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 06/20/2022] [Accepted: 07/14/2022] [Indexed: 01/07/2023] Open
Abstract
Glycans that are abundantly displayed on vertebrate cell surface and secreted molecules are often capped with terminal sialic acids (Sias). These diverse 9-carbon-backbone monosaccharides are involved in numerous intrinsic biological processes. They also interact with commensals and pathogens, while undergoing dynamic changes in time and space, often influenced by environmental conditions. However, most of this sialoglycan complexity and variation remains poorly characterized by conventional techniques, which often tend to destroy or overlook crucial aspects of Sia diversity and/or fail to elucidate native structures in biological systems, i.e. in the intact sialome. To date, in situ detection and analysis of sialoglycans has largely relied on the use of plant lectins, sialidases, or antibodies, whose preferences (with certain exceptions) are limited and/or uncertain. We took advantage of naturally evolved microbial molecules (bacterial adhesins, toxin subunits, and viral hemagglutinin-esterases) that recognize sialoglycans with defined specificity to delineate 9 classes of sialoglycan recognizing probes (SGRPs: SGRP1-SGRP9) that can be used to explore mammalian sialome changes in a simple and systematic manner, using techniques common in most laboratories. SGRP candidates with specificity defined by sialoglycan microarray studies were engineered as tagged probes, each with a corresponding nonbinding mutant probe as a simple and reliable negative control. The optimized panel of SGRPs can be used in methods commonly available in most bioscience labs, such as ELISA, western blot, flow cytometry, and histochemistry. To demonstrate the utility of this approach, we provide examples of sialoglycome differences in tissues from C57BL/6 wild-type mice and human-like Cmah-/- mice.
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Affiliation(s)
- Saurabh Srivastava
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Andrea Verhagen
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Aniruddha Sasmal
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Brian R Wasik
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Sandra Diaz
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Hai Yu
- Department of Chemistry, University of California at Davis, Davis, CA, USA
| | - Barbara A Bensing
- Department of Medicine, University of California, San Francisco, CA, USA,VA Medical Center, San Francisco, CA, USA
| | - Naazneen Khan
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Zahra Khedri
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Patrick Secrest
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Paul Sullam
- Department of Medicine, University of California, San Francisco, CA, USA,VA Medical Center, San Francisco, CA, USA
| | - Nissi Varki
- Department of Cellular and Molecular Medicine, School of Medicine, University of California at San Diego, San Diego, CA, USA,Glycobiology Research and Training Center, University of California at San Diego, San Diego, CA, USA
| | - Xi Chen
- Department of Chemistry, University of California at Davis, Davis, CA, USA
| | - Colin R Parrish
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
| | - Ajit Varki
- Corresponding author: UCSD School of Medicine, La Jolla, CA 92093-0687, USA.
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4
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Prescher H, Schweizer A, Frank M, Kuhfeldt E, Ring J, Nitschke L. Targeting Human CD22/Siglec-2 with Dimeric Sialosides as Novel Oligosaccharide Mimetics. J Med Chem 2022; 65:10588-10610. [PMID: 35881556 DOI: 10.1021/acs.jmedchem.2c00765] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Significant interest in the development of high-affinity ligands for Siglecs exists due to the various therapeutically relevant functions of these proteins. Here, we report a new strategy to develop and design Siglec ligands as disialyl-oligosaccharide mimetics exemplified on Siglec-2 (CD22). We report insights into development of dimeric ligands with high affinity and avidity to cell surface-expressed CD22, assay development, tool compounds, structure activity relationships, and biological data on calcium flux regulation in B-cells. The binding modes of selected ligands have been modeled based on state-of-the-art molecular dynamics simulations on the microsecond timescale, providing detailed views on ligand binding and opening a new perspective on drug design efforts for Siglecs. High-avidity dimeric ligands containing a linker opening the way towards bispecifics are presented as well.
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Affiliation(s)
| | - Astrid Schweizer
- Chair of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany
| | - Martin Frank
- Biognos AB, Generatorsgatan 1, 40274 Göteborg, Sweden
| | | | - Julia Ring
- Chair of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany
| | - Lars Nitschke
- Chair of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany
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5
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Jiang HS, Zhuang SC, Lam CH, Chang LY, Angata T. Recent Progress in the Methodologies to Identify Physiological Ligands of Siglecs. Front Immunol 2021; 12:813082. [PMID: 34956244 PMCID: PMC8702521 DOI: 10.3389/fimmu.2021.813082] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 11/23/2021] [Indexed: 11/28/2022] Open
Abstract
Siglecs, a family of receptor-like lectins, recognize glycoproteins and/or glycolipids containing sialic acid in the extracellular space and transduce intracellular signaling. Recently, researchers uncovered significant contributions of Siglecs in cancer immunity, renewing interest in this family of proteins. Previous extensive studies have defined how Siglecs recognize glycan epitopes (glycotopes). Nevertheless, the biological role of these glycotopes has not been fully evaluated. Recent studies using live cells have begun unraveling the constituents of Siglec ligands. These studies demonstrated that glycoprotein scaffolds (counter-receptors) displaying glycotopes are sometimes just as important as the glycotope itself. These new insights may guide future efforts to develop therapeutic agents to target the Siglec – ligand axis.
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Affiliation(s)
- Huei-Syuan Jiang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.,Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan.,Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Shao-Chien Zhuang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.,Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Chak Hin Lam
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Lan-Yi Chang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Takashi Angata
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.,Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan.,Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
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6
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van Houtum EJH, Büll C, Cornelissen LAM, Adema GJ. Siglec Signaling in the Tumor Microenvironment. Front Immunol 2021; 12:790317. [PMID: 34966391 PMCID: PMC8710542 DOI: 10.3389/fimmu.2021.790317] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 11/23/2021] [Indexed: 12/16/2022] Open
Abstract
Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of receptors that recognize sialoglycans - sialic acid containing glycans that are abundantly present on cell membranes. Siglecs are expressed on most immune cells and can modulate their activity and function. The majority of Siglecs contains immune inhibitory motifs comparable to the immune checkpoint receptor PD-1. In the tumor microenvironment (TME), signaling through the Siglec-sialoglycan axis appears to be enhanced through multiple mechanisms favoring tumor immune evasion similar to the PD-1/PD-L1 signaling pathway. Siglec expression on tumor-infiltrating immune cells appears increased in the immune suppressive microenvironment. At the same time, enhanced Siglec ligand expression has been reported for several tumor types as a result of aberrant glycosylation, glycan modifications, and the increased expression of sialoglycans on proteins and lipids. Siglec signaling has been identified as important regulator of anti-tumor immunity in the TME, but the key factors contributing to Siglec activation by tumor-associated sialoglycans are diverse and poorly defined. Among others, Siglec activation and signaling are co-determined by their expression levels, cell surface distribution, and their binding preferences for cis- and trans-ligands in the TME. Siglec binding preference are co-determined by the nature of the proteins/lipids to which the sialoglycans are attached and the multivalency of the interaction. Here, we review the current understanding and emerging conditions and factors involved in Siglec signaling in the TME and identify current knowledge gaps that exist in the field.
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Affiliation(s)
- Eline J. H. van Houtum
- Radiotherapy & OncoImmunology Laboratory, Department of Radiation Oncology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Christian Büll
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW), Utrecht, Netherlands
- Copenhagen Center for Glycomics, Departments of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lenneke A. M. Cornelissen
- Radiotherapy & OncoImmunology Laboratory, Department of Radiation Oncology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Gosse J. Adema
- Radiotherapy & OncoImmunology Laboratory, Department of Radiation Oncology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
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7
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Pluvinage JV, Sun J, Claes C, Flynn RA, Haney MS, Iram T, Meng X, Lindemann R, Riley NM, Danhash E, Chadarevian JP, Tapp E, Gate D, Kondapavulur S, Cobos I, Chetty S, Pașca AM, Pașca SP, Berry-Kravis E, Bertozzi CR, Blurton-Jones M, Wyss-Coray T. The CD22-IGF2R interaction is a therapeutic target for microglial lysosome dysfunction in Niemann-Pick type C. Sci Transl Med 2021; 13:eabg2919. [PMID: 34851695 PMCID: PMC9067636 DOI: 10.1126/scitranslmed.abg2919] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Lysosome dysfunction is a shared feature of rare lysosomal storage diseases and common age-related neurodegenerative diseases. Microglia, the brain-resident macrophages, are particularly vulnerable to lysosome dysfunction because of the phagocytic stress of clearing dying neurons, myelin, and debris. CD22 is a negative regulator of microglial homeostasis in the aging mouse brain, and soluble CD22 (sCD22) is increased in the cerebrospinal fluid of patients with Niemann-Pick type C disease (NPC). However, the role of CD22 in the human brain remains unknown. In contrast to previous findings in mice, here, we show that CD22 is expressed by oligodendrocytes in the human brain and binds to sialic acid–dependent ligands on microglia. Using unbiased genetic and proteomic screens, we identify insulin-like growth factor 2 receptor (IGF2R) as the binding partner of sCD22 on human myeloid cells. Targeted truncation of IGF2R revealed that sCD22 docks near critical mannose 6-phosphate–binding domains, where it disrupts lysosomal protein trafficking. Interfering with the sCD22-IGF2R interaction using CD22 blocking antibodies ameliorated lysosome dysfunction in human NPC1 mutant induced pluripotent stem cell–derived microglia-like cells without harming oligodendrocytes in vitro. These findings reinforce the differences between mouse and human microglia and provide a candidate microglia-directed immunotherapeutic to treat NPC.
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Affiliation(s)
- John V. Pluvinage
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Jerry Sun
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Christel Claes
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697, USA
| | - Ryan A. Flynn
- Stem Cell Program, Children’s Hospital Boston, Boston, MA 02115, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138, USA
| | - Michael S. Haney
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Tal Iram
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Xiangling Meng
- Stanford Brain Organogenesis, Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA 94305, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Rachel Lindemann
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Nicholas M. Riley
- Department of Chemistry and ChEM-H, Stanford University, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304, USA
| | - Emma Danhash
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92697, USA
| | - Jean Paul Chadarevian
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697, USA
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92697, USA
- Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92697, USA
| | - Emma Tapp
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - David Gate
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Sravani Kondapavulur
- Medical Scientist Training Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Inma Cobos
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Sundari Chetty
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
- Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Anca M. Pașca
- Division of Neonatology, Department of Pediatrics, Stanford University, Stanford, CA 94304, USA
| | - Sergiu P. Pașca
- Stanford Brain Organogenesis, Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA 94305, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | | | - Carolyn R. Bertozzi
- Department of Chemistry and ChEM-H, Stanford University, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94304, USA
| | - Mathew Blurton-Jones
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA 92697, USA
- Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92697, USA
- Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA 92697, USA
| | - Tony Wyss-Coray
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
- Paul F. Glenn Center for the Biology of Aging, Stanford University School of Medicine, Stanford, CA 94304, USA
- Wu Tsai Neurosciences Institute, Stanford, CA, 94305, USA
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8
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Geissner A, Baumann L, Morley TJ, Wong AKO, Sim L, Rich JR, So PPL, Dullaghan EM, Lessard E, Iqbal U, Moreno M, Wakarchuk WW, Withers SG. 7-Fluorosialyl Glycosides Are Hydrolysis Resistant but Readily Assembled by Sialyltransferases Providing Easy Access to More Metabolically Stable Glycoproteins. ACS CENTRAL SCIENCE 2021; 7:345-354. [PMID: 33655072 PMCID: PMC7908025 DOI: 10.1021/acscentsci.0c01589] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Indexed: 05/04/2023]
Abstract
The maintenance of therapeutic glycoproteins within the circulatory system is associated, in large part, with the integrity of sialic acids as terminal sugars on the glycans. Glycoprotein desialylation, either by spontaneous cleavage or through host sialidases, leads to protein clearance, mainly through the liver. Thus, the installation of minimally modified sialic acids that are hydrolysis-resistant yet biologically equivalent should lead to increased circulatory half-lives and improved pharmacokinetic profiles. Here we describe the chemoenzymatic synthesis of CMP-sialic acid sugar donors bearing fluorine atoms at the 7-position, starting from the corresponding 4-deoxy-4-fluoro-N-acetylhexosamine precursors. For the derivative with natural stereochemistry we observe efficient glycosyl transfer by sialyltransferases, along with improved stability of the resultant 7-fluorosialosides toward spontaneous hydrolysis (3- to 5-fold) and toward cleavage by GH33 sialidases (40- to 250-fold). Taking advantage of the rapid transfer of 7-fluorosialic acid by sialyltransferases, we engineered the O-glycan of Interferon α-2b and the N-glycans of the therapeutic glycoprotein α1-antitrypsin. Studies of the uptake of the glyco-engineered α1-antitrypsin by HepG2 liver cells demonstrated the bioequivalence of 7-fluorosialic acid to sialic acid in suppressing interaction with liver cell lectins. In vivo pharmacokinetic studies reveal enhanced half-life of the protein decorated with 7-fluorosialic acid relative to unmodified sialic acid in the murine circulatory system. 7-Fluorosialylation therefore offers considerable promise as a means of prolonging circulatory half-lives of glycoproteins and may pave the way toward biobetters for therapeutic use.
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Affiliation(s)
- Andreas Geissner
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Lars Baumann
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Thomas J. Morley
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Andrew K. O. Wong
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Lyann Sim
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Jamie R. Rich
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Pauline P. L. So
- AdMare
BioInnovations, 2405
Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Edie M. Dullaghan
- AdMare
BioInnovations, 2405
Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Etienne Lessard
- National
Research Council Canada, Human Health Therapeutics, Ottawa, ON K1A 0R6, Canada
| | - Umar Iqbal
- National
Research Council Canada, Human Health Therapeutics, Ottawa, ON K1A 0R6, Canada
| | - Maria Moreno
- National
Research Council Canada, Human Health Therapeutics, Ottawa, ON K1A 0R6, Canada
| | - Warren W. Wakarchuk
- Department
of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Stephen G. Withers
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
- Tel.: (604) 822-3402. Fax: (604) 822-8869. E-mail:
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9
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Sialic acid and biology of life: An introduction. SIALIC ACIDS AND SIALOGLYCOCONJUGATES IN THE BIOLOGY OF LIFE, HEALTH AND DISEASE 2020. [PMCID: PMC7153325 DOI: 10.1016/b978-0-12-816126-5.00001-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Sialic acids are important molecule with high structural diversity. They are known to occur in higher animals such as Echinoderms, Hemichordata, Cephalochorda, and Vertebrata and also in other animals such as Platyhelminthes, Cephalopoda, and Crustaceae. Plants are known to lack sialic acid. But they are reported to occur in viruses, bacteria, protozoa, and fungi. Deaminated neuraminic acid although occurs in vertebrates and bacteria, is reported to occur in abundance in the lower vertebrates. Sialic acids are mostly located in terminal ends of glycoproteins and glycolipids, capsular and tissue polysialic acids, bacterial lipooligosaccharides/polysaccharides, and in different forms that dictate their role in biology. Sialic acid play important roles in human physiology of cell-cell interaction, communication, cell-cell signaling, carbohydrate-protein interactions, cellular aggregation, development processes, immune reactions, reproduction, and in neurobiology and human diseases in enabling the infection process by bacteria and virus, tumor growth and metastasis, microbiome biology, and pathology. It enables molecular mimicry in pathogens that allows them to escape host immune responses. Recently sialic acid has found role in therapeutics. In this chapter we have highlighted the (i) diversity of sialic acid, (ii) their occurrence in the diverse life forms, (iii) sialylation and disease, and (iv) sialic acid and therapeutics.
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10
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Fan CY, Hou YR, Adak AK, Waniwan JT, Dela Rosa MAC, Low PY, Angata T, Hwang KC, Chen YJ, Lin CC. Boronate affinity-based photoactivatable magnetic nanoparticles for the oriented and irreversible conjugation of Fc-fused lectins and antibodies. Chem Sci 2019; 10:8600-8609. [PMID: 31803435 PMCID: PMC6844280 DOI: 10.1039/c9sc01613a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 07/31/2019] [Indexed: 12/29/2022] Open
Abstract
The utilization of immuno-magnetic nanoparticles (MNPs) for the selective capture, enrichment, and separation of specific glycoproteins from complicated biological samples is appealing for the discovery of disease biomarkers. Herein, MNPs were designed and anchored with abundant boronic acid (BA) and photoreactive alkyl diazirine (Diaz) functional groups to obtain permanently tethered Fc-fused Siglec-2 and antiserum amyloid A (SAA) mAb with the assistance of reversible boronate affinity and UV light activation in an orientation-controlled manner. The Siglec-2-Fc-functionalized MNPs showed excellent stability in fetal bovine serum (FBS) and excellent efficiency in the extraction of cell membrane glycoproteins. The anti-SAA mAb-functionalized MNPs maintained active Ab orientation and preserved antigen recognition capability in biological samples. Thus, the BA-Diaz-based strategy holds promise for the immobilization of glycoproteins, such as antibodies, with the original protein binding activity maintained, which can provide better enrichment for the sensitive detection of target proteins.
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Affiliation(s)
- Chen-Yo Fan
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan .
| | - Yi-Ren Hou
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan .
| | - Avijit K Adak
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan .
| | | | | | - Penk Yeir Low
- Institute of Biological Chemistry , Academia Sinica , Taipei , Taiwan
| | - Takashi Angata
- Institute of Biological Chemistry , Academia Sinica , Taipei , Taiwan
| | - Kuo-Chu Hwang
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan .
| | - Yu-Ju Chen
- Institute of Chemistry , Academia Sinica , Taipei , Taiwan .
| | - Chun-Cheng Lin
- Department of Chemistry , National Tsing Hua University , Hsinchu , Taiwan .
- Frontier Research Center on Fundamental and Applied Sciences of Matters , Hsinchu , Taiwan
- Department of Medicinal and Applied Chemistry , Kaohsiung Medical University , Kaohsiung , Taiwan
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11
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Peng W, Paulson JC. CD22 Ligands on a Natural N-Glycan Scaffold Efficiently Deliver Toxins to B-Lymphoma Cells. J Am Chem Soc 2017; 139:12450-12458. [PMID: 28829594 DOI: 10.1021/jacs.7b03208] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
CD22 is a sialic acid-binding immunoglobulin-like lectin (Siglec) that is highly expressed on B-cells and B cell lymphomas, and is a validated target for antibody and nanoparticle based therapeutics. However, cell targeted therapeutics are limited by their complexity, heterogeneity, and difficulties in production. We describe here a chemically defined natural N-linked glycan scaffold that displays high affinity CD22 glycan ligands and outcompetes the natural ligand for the receptor, resulting in single molecule binding to CD22 and endocytosis into cells. Binding affinity is increased by up to 1500-fold compared to the monovalent ligand, while maintaining the selectivity for hCD22 over other Siglecs. Conjugates of these multivalent ligands with auristatin and saporin toxins are efficiently internalized via hCD22 resulting in killing of B-cell lymphoma cells. This single molecule ligand targeting strategy represents an alternative to antibody- and nanoparticle-mediated approaches for delivery of agents to cells expressing CD22 and other Siglecs.
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Affiliation(s)
- Wenjie Peng
- Departments of Molecular Medicine and Immunology & Microbiology, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - James C Paulson
- Departments of Molecular Medicine and Immunology & Microbiology, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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12
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Prescher H, Schweizer A, Kuhfeldt E, Nitschke L, Brossmer R. New Human CD22/Siglec-2 Ligands with a Triazole Glycoside. Chembiochem 2017; 18:1216-1225. [PMID: 28374962 DOI: 10.1002/cbic.201600707] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Indexed: 12/15/2022]
Abstract
CD22 is a member of the Siglec family. Considerable attention has been drawn to the design and synthesis of new Siglec ligands to explore target biology and innovative therapies. In particular, CD22-ligand-targeted nanoparticles with therapeutic functions have proved successful in preclinical settings for blood cancers, autoimmune diseases, and tolerance induction. Here we report the design, synthesis and affinity evaluation of a new class of Siglec ligands: namely sialic acid derivatives with a triazole moiety replacing the natural glycoside oxygen atom. In addition, we describe important and surprising differences in binding to CD22 expressed at the cell surface for compounds with distinct valences. The new class of compounds might serve as a template for the design of ligands for other members of the Siglec family and next-generation CD22-ligand-based targeted therapies.
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Affiliation(s)
| | - Astrid Schweizer
- Division of Genetics, Department of Biology, University of Erlangen, 91058, Erlangen, Germany
| | | | - Lars Nitschke
- Division of Genetics, Department of Biology, University of Erlangen, 91058, Erlangen, Germany
| | - Reinhard Brossmer
- Biochemistry Center, University of Heidelberg, 69120, Heidelberg, Germany.,G3-BioTec, 69207, Sandhausen, Germany
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13
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Siddiqui S, Schwarz F, Springer S, Khedri Z, Yu H, Deng L, Verhagen A, Naito-Matsui Y, Jiang W, Kim D, Zhou J, Ding B, Chen X, Varki N, Varki A. Studies on the Detection, Expression, Glycosylation, Dimerization, and Ligand Binding Properties of Mouse Siglec-E. J Biol Chem 2016; 292:1029-1037. [PMID: 27920204 DOI: 10.1074/jbc.m116.738351] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 12/02/2016] [Indexed: 12/20/2022] Open
Abstract
CD33-related Siglecs are a family of proteins widely expressed on innate immune cells. Binding of sialylated glycans or other ligands triggers signals that inhibit or activate inflammation. Immunomodulation by Siglecs has been extensively studied, but relationships between structure and functions are poorly explored. Here we present new data relating to the structure and function of Siglec-E, the major CD33-related Siglec expressed on mouse neutrophils, monocytes, macrophages, and dendritic cells. We generated nine new rat monoclonal antibodies specific to mouse Siglec-E, with no cross-reactivity to Siglec-F. Although all antibodies detected Siglec-E on transfected human HEK-293T cells, only two reacted with mouse bone marrow neutrophils by flow cytometry and on spleen sections by immunohistochemistry. Moreover, whereas all antibodies recognized Siglec-E-Fc on immunoblots, binding was dependent on intact disulfide bonds and N-glycans, and only two antibodies recognized native Siglec-E within spleen lysates. Thus, we further investigated the impact of Siglec-E homodimerization. Homology-based structural modeling predicted a cysteine residue (Cys-298) in position to form a disulfide bridge between two Siglec-E polypeptides. Mutagenesis of Cys-298 confirmed its role in dimerization. In keeping with the high level of 9-O-acetylation found in mice, sialoglycan array studies indicate that this modification has complex effects on recognition by Siglec-E, in relationship to the underlying structures. However, we found no differences in phosphorylation or SHP-1 recruitment between dimeric and monomeric Siglec-E expressed on HEK293A cells. Phylogenomic analyses predicted that only some human and mouse Siglecs form disulfide-linked dimers. Notably, Siglec-9, the functionally equivalent human paralog of Siglec-E, occurs as a monomer.
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Affiliation(s)
- Shoib Siddiqui
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Flavio Schwarz
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Stevan Springer
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Zahra Khedri
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Hai Yu
- the Department of Chemistry, University of California, Davis, California 95616, and
| | - Lingquan Deng
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Andrea Verhagen
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Yuko Naito-Matsui
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | | | - Daniel Kim
- BioLegend, Inc., San Diego, California 92121
| | - Jie Zhou
- BioLegend, Inc., San Diego, California 92121
| | - Beibei Ding
- BioLegend, Inc., San Diego, California 92121
| | - Xi Chen
- the Department of Chemistry, University of California, Davis, California 95616, and
| | - Nissi Varki
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687
| | - Ajit Varki
- From the Departments of Medicine and Cellular & Molecular Medicine, Glycobiology Research and Training Center (GRTC), University of California San Diego, La Jolla, California 92093-0687,
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14
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Akatsu C, Shinagawa K, Numoto N, Liu Z, Ucar AK, Aslam M, Phoon S, Adachi T, Furukawa K, Ito N, Tsubata T. CD72 negatively regulates B lymphocyte responses to the lupus-related endogenous toll-like receptor 7 ligand Sm/RNP. J Exp Med 2016; 213:2691-2706. [PMID: 27810925 PMCID: PMC5110020 DOI: 10.1084/jem.20160560] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 08/05/2016] [Accepted: 09/26/2016] [Indexed: 01/03/2023] Open
Abstract
Akatsu and colleagues show that CD72 specifically recognizes Sm/RNP, a lupus-related self-antigen and an endogenous TLR7 ligand, and inhibits B cell responses to Sm/RNP. In mice, CD72 prevents production of anti-Sm/RNP antibodies crucial for lupus development. Toll-like receptor 7 (TLR7) plays an essential role in development of systemic lupus erythematosus by co-stimulating B cells reactive to the endogenous TLR7 ligand Sm/ribonucleoprotein (RNP), a crucial lupus self-antigen. However, how the TLR7-mediated autoimmune response is regulated is not yet known. In this study, we demonstrate that CD72, an inhibitory B cell co-receptor known to prevent development of lupus, recognizes Sm/RNP at the extracellular C-type lectin-like domain (CTLD) and specifically inhibits B cell response to Sm/RNP. Moreover, the CTLD of CD72c, a lupus-susceptible allele, binds to Sm/RNP less strongly than that of lupus-resistant CD72a. Reduced binding of CD72c is supported by x-ray crystallographic analysis that reveals a considerable alteration in charge at the putative ligand-binding site. Thus, CD72 appears to specifically inhibit B cell response to the endogenous TLR7 ligand Sm/RNP through CTLD-mediated recognition of Sm/RNP, thereby preventing production of anti-Sm/RNP antibody crucial for development of lupus.
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Affiliation(s)
- Chizuru Akatsu
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Kenro Shinagawa
- Department of Structural Biology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Nobutaka Numoto
- Department of Structural Biology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Zhihong Liu
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan.,Emergency Department, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning Province 110001, China
| | - Ayse Konuskan Ucar
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Mohammad Aslam
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Shirly Phoon
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Takahiro Adachi
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Koji Furukawa
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566, Japan
| | - Nobutoshi Ito
- Department of Structural Biology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
| | - Takeshi Tsubata
- Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo, Tokyo 113-8510, Japan
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15
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Kaltner H, García Caballero G, Sinowatz F, Schmidt S, Manning JC, André S, Gabius HJ. Galectin-related protein: An integral member of the network of chicken galectins. Biochim Biophys Acta Gen Subj 2016; 1860:2298-312. [DOI: 10.1016/j.bbagen.2016.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 05/12/2016] [Accepted: 06/02/2016] [Indexed: 10/21/2022]
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16
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Abstract
An important underlying mechanism that contributes to autoimmunity is the loss of inhibitory signaling in the immune system. Sialic acid-recognizing Ig superfamily lectins or Siglecs are a family of cell surface proteins largely expressed in hematopoietic cells. The majority of Siglecs are inhibitory receptors expressed in immune cells that bind to sialic acid-containing ligands and recruit SH2-domain-containing tyrosine phosphatases to their cytoplasmic tails. They deliver inhibitory signals that can contribute to the constraining of immune cells, and thus protect the host from autoimmunity. The inhibitory functions of CD22/Siglec-2 and Siglec-G and their contributions to tolerance and autoimmunity, primarily in the B lymphocyte context, are considered in some detail in this review. The relevance to autoimmunity and unregulated inflammation of modified sialic acids, enzymes that modify sialic acid, and other sialic acid-binding proteins are also reviewed.
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Affiliation(s)
- Vinay S Mahajan
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA.,Departments of Medicine and Pathology, Harvard Medical School, Boston, MA, USA.,Deaprtment of Pathology, Brigham and Women's Hospital, Boston, MA, USA
| | - Shiv Pillai
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA.,Departments of Medicine and Pathology, Harvard Medical School, Boston, MA, USA
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17
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Deng L, Chen X, Varki A. Exploration of sialic acid diversity and biology using sialoglycan microarrays. Biopolymers 2013; 99:650-65. [PMID: 23765393 PMCID: PMC7161822 DOI: 10.1002/bip.22314] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 06/04/2013] [Indexed: 12/13/2022]
Abstract
Sialic acids (Sias) are a group of α-keto acids with a nine-carbon backbone, which display many types of modifications in nature. The diversity of natural Sia presentations is magnified by a variety of glycosidic linkages to underlying glycans, the sequences and classes of such glycans, as well as the spatial organization of Sias with their surroundings. This diversity is closely linked to the numerous and varied biological functions of Sias. Relatively large libraries of natural and unnatural Sias have recently been chemically/chemoenzymatically synthesized and/or isolated from natural sources. The resulting sialoglycan microarrays have proved to be valuable tools for the exploration of diversity and biology of Sias. Here we provide an overview of Sia diversity in nature, the approaches used to generate sialoglycan microarrays, and the achievements and challenges arising.
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Affiliation(s)
- Lingquan Deng
- Departments of Medicine and Cellular & Molecular MedicineGlycobiology Research and Training Center, University of CaliforniaSan Diego, La JollaCA92093‐0687
| | - Xi Chen
- Department of ChemistryUniversity of CaliforniaDavisCA95616
| | - Ajit Varki
- Departments of Medicine and Cellular & Molecular MedicineGlycobiology Research and Training Center, University of CaliforniaSan Diego, La JollaCA92093‐0687
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18
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Abstract
Why exactly some individuals develop autoimmune disorders remains unclear. The broadly accepted paradigm is that genetic susceptibility results in some break in immunological tolerance, may enhance the availability of autoantigens, and may enhance inflammatory responses. Some environmental insults that occur on this background of susceptibility may then contribute to autoimmunity. In this review we discuss some aspects related to inhibitory signaling and rare genetic variants, as well as additional factors that might contribute to autoimmunity including the possible role of clonal somatic mutations, the role of epigenetic events and the contribution of the intestinal microbiome. Genetic susceptibility alleles generally contribute to the loss of immunological tolerance, the increased availability of autoantigens, or an increase in inflammation. Apart from common genetic variants, rare loss-of-function genetic variants may also contribute to the pathogenesis of autoimmunity. Studies of an inhibitory signaling pathway in B cells helped identify a negative regulatory enzyme called sialic acid acetyl esterase. The study of rare genetic variants of this enzyme provides an illustrative example showing the importance of detailed functional analyses of variant alleles and the need to exclude functionally normal common or rare genetic variants from analysis. It has also become clear that pathways that are functionally impacted by either common or rare defective variants can also be more significantly compromised by gene expression changes that may result from epigenetic alterations. Another important and evolving area that has been discussed relates to the role of the intestinal microbiome in influencing helper T cell polarization and the development of autoimmunity.
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Affiliation(s)
- Shiv Pillai
- Massachusetts General Hospital, Center for Cancer Research, Harvard Medical School, Boston, MA 02129, USA.
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19
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Abstract
CD22 is a 140-kDa member of the Siglec family of cell surface proteins that is expressed by most mature B-cell lineages. As a co-receptor of the B-cell receptor (BCR), it is known to contribute to the sensitive control of the B-cell response to antigen. Cross-linking of CD22 and the BCR by antigen triggers the phosphorylation of CD22, which leads to activation of signaling molecules such as phosphatases. Signal transduction pathways involving CD22 have been explored in a number of mouse models, some of which have provided evidence that in the absence of functional CD22, B cells have a "hyperactivated" phenotype, and suggest that loss of CD22 function could contribute to the pathogenesis of autoimmune diseases. Modulating CD22 activity has therefore been suggested as a possible therapeutic approach to such diseases. For example, the novel CD22-targeting monoclonal antibody epratuzumab is currently under investigation as a treatment for the connective tissue disorder systemic lupus erythematosus (SLE).
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Affiliation(s)
- Thomas Dörner
- Charité University Medicine Berlin, CC12, Dept. Medicine/Rheumatology and Clinical Immunology and German Rheumatism Research Center Berlin (DRFZ), Berlin, Germany.
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20
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Walker JA, Hall AM, Kotsopoulou E, Espeli M, Nitschke L, Barker RN, Lyons PA, Smith KGC. Increased red cell turnover in a line of CD22-deficient mice is caused by Gpi1c: a model for hereditary haemolytic anaemia. Eur J Immunol 2012; 42:3212-22. [PMID: 22930244 DOI: 10.1002/eji.201242633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Revised: 08/02/2012] [Accepted: 08/24/2012] [Indexed: 11/06/2022]
Abstract
CD22, an inhibitory co-receptor of the BCR, has been identified as a potential candidate gene for the development of autoimmune haemolytic anaemia in mice. In this study, we have examined Cd22(tm1Msn) CD22-deficient mice and identified an increase in RBC turnover and stress erythropoiesis, which might be consistent with haemolysis. We then, however, eliminated CD22 deficiency as the cause of accelerated RBC turnover and established that enhanced RBC turnover occurs independently of B cells and anti-RBC autoanti-bodies. Accelerated RBC turnover in this particular strain of CD22-deficient mice is red cell intrinsic and appears to be the consequence of a defective allele of glucose phosphate isomerase, Gpi1(c). This form of Gpi1 was originally derived from wild mice and results in a substantial reduction in enzyme activity. We have identified the polymorphism that causes impaired catalytic activity in the Gpi1(c) allele, and biochemically confirmed an approximate 75% reduction of GPI1 activity in Cd22(-/-) RBCs. The Cd22(-/-).Gpi1(c) congenic mouse provides a novel animal model of GPI1-deficiency, which is one of the most common causes of chronic non-spherocytic haemolytic anaemia in humans.
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Affiliation(s)
- Jennifer A Walker
- Cambridge Institute for Medical Research and Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK
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21
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Paulson JC, Macauley MS, Kawasaki N. Siglecs as sensors of self in innate and adaptive immune responses. Ann N Y Acad Sci 2012; 1253:37-48. [PMID: 22288608 DOI: 10.1111/j.1749-6632.2011.06362.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Siglecs are expressed on most white blood cells of the immune system and are known to modulate the activity of cell signaling receptors via regulatory motifs in their cytoplasmic domains. This immunoglobulin subfamily of coreceptors recognize sialic acid containing glycans as ligands, which are found on glycoproteins and glycolipids of all mammalian cells. By virtue of their ability to recognize this common structural element, siglecs are increasingly recognized for their ability to help immune cells distinguish between self and nonself, and dampen autoimmune responses.
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Affiliation(s)
- James C Paulson
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California 92037, USA.
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22
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Rigato PO, Fusaro AE, Victor JR, Sato MN. Maternal immunization to modulate the development of allergic response and pathogen infections. Immunotherapy 2011; 1:141-56. [PMID: 20635979 DOI: 10.2217/1750743x.1.1.141] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
This article reviews recent experimental approaches of preventive strategies regarding allergy and infections by pathogens, particularly in early childhood, by targeting maternal immunomodulation. Basic research is essential to understand maternal vaccination as a strategy to control allergic disease and bacterial and viral infections; thus, providing support for future translational research. The environmental stimuli and host genetic factors, along with maternal influences in early life when immune systems are developing and during postnatal life, are essential for the decision between tolerance induction or allergen sensitization. Maternal immunomodulation strategies should serve as a challenge when attempting to halt the spread of allergy responses and viral infections, until the innate and adaptive arms of the immune system of the neonates are competent.
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Affiliation(s)
- Paula Ordonhez Rigato
- Laboratório de Dermatologia e Imunodeficiências - LIM56, Faculdade de Medicina da Universidade de São Paulo, Instituto de Medicina Tropical - Prédio II, Av Dr Enéas de Carvalho Aguiar, 500, 3 masculine andar, 05403-05000, São Paulo, Brazil
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23
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24
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Abdu-Allah HHM, Watanabe K, Hayashizaki K, Takaku C, Tamanaka T, Takematsu H, Kozutsumi Y, Tsubata T, Ishida H, Kiso M. Potent small molecule mouse CD22-inhibitors: exploring the interaction of the residue at C-2 of sialic acid scaffold. Bioorg Med Chem Lett 2009; 19:5573-5. [PMID: 19720531 DOI: 10.1016/j.bmcl.2009.08.044] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 08/08/2009] [Accepted: 08/12/2009] [Indexed: 10/20/2022]
Abstract
Our previous study revealed that compound 1 (9-(4'-hydroxy-4-biphenyl)acetamido-9-deoxy-Neu5Gcalpha2-6GalOMP) has the most promising affinity for mCD22. Replacing the subterminal galactose residue of 1 with benzyl or biphenylmethyl as aglycone led to 38- and 20-fold higher potency, respectively. This discovery represents a new direction in inhibitor design suitable for pharmaceutical development.
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Affiliation(s)
- Hajjaj H M Abdu-Allah
- Department of Applied Bio-organic Chemistry, The United Graduate School of Agricultural Sciences, Gifu University, Gifu 501-1193, Japan.
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25
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26
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Abdu-Allah HHM, Tamanaka T, Yu J, Zhuoyuan L, Sadagopan M, Adachi T, Tsubata T, Kelm S, Ishida H, Kiso M. Design, synthesis, and structure-affinity relationships of novel series of sialosides as CD22-specific inhibitors. J Med Chem 2008; 51:6665-81. [PMID: 18841881 DOI: 10.1021/jm8000696] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Sialosides incorporating substituted amides or amines at 9-position of sialic acid moiety have been synthesized and evaluated as CD22 inhibitors. Several derivatives exhibited inhibitory potency in sub- to low micromolar range (e. g., 8o, 9d, 9g, and 9k showed IC 50 values 0.40, 0.47, 0.24, and 0.23 microM, respectively, for hCD22, while 8p, 8q, and 9f, showed IC 50 values 1.70, 2.90, and 4.10 microM, respectively, for mCD22). The most significant result was the strongly enhanced affinity of 9g and 9k containing 9-(2' or 4'-hydroxy-4-biphenyl) methylamino substituents (600-fold more potent for hCD22 than the corresponding 9-hydroxy derivative; 7a). Molecular modeling study was carried out to get some insights into the molecular basis of CD22 inhibition. To the best of our knowledge, this is the first systematic structure-affinity relationship study on inhibition of CD22.
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Affiliation(s)
- Hajjaj H M Abdu-Allah
- Department of Applied Bio-organic Chemistry, The United Graduate School of Agricultural Sciences, Gifu University, Gifu 501-1193, Japan
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27
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Abstract
Frontal affinity chromatography using fluorescence detection (FAC-FD) is a versatile technique for the precise determination of dissociation constants (Kd) between glycan-binding proteins (lectins) and fluorescent-labeled glycans. A series of glycan-containing solutions is applied to a lectin-immobilized column, and the elution profile of each glycan (termed the 'elution front', V) is compared with that (V0) for an appropriate control. Here we describe our standard protocol using an automated FAC system (FAC-1), consisting of two isocratic pumps, an autosampler, a column oven and two miniature columns connected to a fluorescence detector. Analysis time for 100 sugar-protein interactions is approximately 10 h, using as little as 2.5 pmol of pyridylaminated (PA) oligosaccharide per analysis. Using FAC-FD, we have so far obtained quantitative interaction data of >100 lectins for >100 PA oligosaccharides.
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28
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Tanaka Y, Bond MR, Kohler JJ. Photocrosslinkers illuminate interactions in living cells. MOLECULAR BIOSYSTEMS 2008; 4:473-80. [DOI: 10.1039/b803218a] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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29
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Abstract
CD22 is an inhibitory coreceptor of the B-cell receptor (BCR), and plays a critical role in establishing signalling thresholds for B-cell activation. Like other coreceptors, the ability of CD22 to modulate B-cell signalling is critically dependent upon its proximity to the BCR, and this in turn is governed by the binding of its extracellular domain to alpha2,6-linked sialic acid ligands. Manipulation of CD22 ligand binding in various experimental settings has profound effects on B-cell signalling, but as yet there is no complete model for how ligand binding in vivo controls normal CD22 function. Several elegant studies have recently shed light on this issue, although the results appear to suggest two mutually exclusive models for the role of ligand binding; in either promoting or inhibiting, CD22 function. We shall therefore discuss these results in detail, and suggest possible approaches by which these conflicting experimental findings might be reconciled. We shall also consider a second important issue in CD22 biology, which relates to the role that defects in this receptor might play in mediating autoimmune disease. We review the current evidence for this, and discuss the importance of genetic background in modifying CD22 function and predisposition to autoimmunity.
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Affiliation(s)
- Jennifer A Walker
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Cambridge CB2 0XY, United Kingdom.
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30
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Crocker PR, Paulson JC, Varki A. Siglecs and their roles in the immune system. Nat Rev Immunol 2007; 7:255-66. [PMID: 17380156 DOI: 10.1038/nri2056] [Citation(s) in RCA: 1444] [Impact Index Per Article: 84.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell surfaces in the immune system are richly equipped with a complex mixture of glycans, which can be recognized by diverse glycan-binding proteins. The Siglecs are a family of sialic-acid-binding immunoglobulin-like lectins that are thought to promote cell-cell interactions and regulate the functions of cells in the innate and adaptive immune systems through glycan recognition. In this Review, we describe recent studies on signalling mechanisms and discuss the potential role of Siglecs in triggering endocytosis and in pathogen recognition. Finally, we discuss the postulated functions of the recently discovered CD33-related Siglecs and consider the factors that seem to be driving their rapid evolution.
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Affiliation(s)
- Paul R Crocker
- Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dundee DD 15EH, UK.
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31
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Eichler W. Characteristics of two CD75-related cell-surface expressed antigens of human lymphocytes. Mol Immunol 2006; 44:2047-55. [PMID: 17067678 DOI: 10.1016/j.molimm.2006.09.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 09/11/2006] [Indexed: 11/18/2022]
Abstract
The structure of cell surface carbohydrates expressed on human leukocytes is dependent on the cell's developmental stage, differentiation, and activation. Although modification of oligosaccharide side chains by sialylation is quite common, antigenic determinants on lymphocytes associated with the presence of sialoglycans are still incompletely defined. In the study presented here, monoclonal antibodies (mAbs) were used to characterize two novel but related cell surface carbohydrate antigens. One antigen, denominated as B8, is largely masked by sialyl residues on most lymphocytes, while it is detectable on the majority of B cells. Treatment with sialidase resulted in the exposure of B8 on the surface of blood cells including lymphocytes. Although the second carbohydrate antigen, C1, was sialidase-sensitive, its molecular properties and cellular distribution place it in close vicinity to B8. B8(+) as well as C1(+) lymphocytes were found predominantly in the mantle zone of secondary follicles of tonsillar tissue. These findings raised the possibility that B8 and C1 are closely related to a category of carbohydrate antigens previously classified as CDw76 (recently assigned to CD75s). MAbs directed against B8 or C1 precipitated 34, 37, 43, and 200kDa glycoproteins from tonsillar lymphocytes, indicating that identical cell surface proteins are associated with both antigens. In contrast to B8, however, the expression of C1 was increased on lymphocytes upon activation. Together the results suggest that CD75-related epitopes are distinct molecular entities which may be exposed on glycoproteins and are differently expressed on lymphocytes.
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Affiliation(s)
- Wolfram Eichler
- University of Leipzig, Eye Hospital, Liebigstrasse 10-14, D-04103 Leipzig, Germany.
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32
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Collins BE, Blixt O, Han S, Duong B, Li H, Nathan JK, Bovin N, Paulson JC. High-affinity ligand probes of CD22 overcome the threshold set by cis ligands to allow for binding, endocytosis, and killing of B cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:2994-3003. [PMID: 16920935 DOI: 10.4049/jimmunol.177.5.2994] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
CD22 (Siglec-2) is a key regulator of B cell signaling whose function is modulated by interaction with extracellular glycan ligands mediated through its N-terminal Ig domain. Its preferred ligand is the sequence Sia alpha2-6Gal that is abundantly expressed on N-linked glycans of B cell glycoproteins, and by binding to CD22 in cis causes CD22 to appear "masked" from binding to synthetic sialoside probes. Yet, despite the presence of cis ligands, CD22 redistributes to sites of cell contact by binding to trans ligands on neighboring cells. In this study, we demonstrate the dynamic equilibrium that exists between CD22 and its cis and trans ligands, using a high-affinity multivalent sialoside probe that competes with cis ligands and binds to CD22 on native human and murine B cells. Consistent with the constitutive endocytosis reported for CD22, the probes are internalized once bound, demonstrating that CD22 is an endocytic receptor that can carry ligand-decorated "cargo" to intracellular compartments. Conjugation of the sialoside probes to the toxin saporin resulted in toxin uptake and toxin-mediated killing of B lymphoma cell lines, suggesting an alternative approach for targeting CD22 for treatment of B cell lymphomas.
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Affiliation(s)
- Brian E Collins
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92024, USA
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33
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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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34
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Grewal PK, Boton M, Ramirez K, Collins BE, Saito A, Green RS, Ohtsubo K, Chui D, Marth JD. ST6Gal-I restrains CD22-dependent antigen receptor endocytosis and Shp-1 recruitment in normal and pathogenic immune signaling. Mol Cell Biol 2006; 26:4970-81. [PMID: 16782884 PMCID: PMC1489171 DOI: 10.1128/mcb.00308-06] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The ST6Gal-I sialyltransferase produces Siglec ligands for the B-cell-specific CD22 lectin and sustains humoral immune responses. Using multiple experimental approaches to elucidate the mechanisms involved, we report that ST6Gal-I deficiency induces immunoglobulin M (IgM) antigen receptor endocytosis in the absence of immune stimulation. This coincides with increased antigen receptor colocalization with CD22 in both clathrin-deficient and clathrin-enriched membrane microdomains concurrent with diminished tyrosine phosphorylation of Igalpha/beta, Syk, and phospholipase C-gamma2 upon immune activation. Codeficiency with CD22 restores IgM antigen receptor half-life at the cell surface in addition to reversing alterations in membrane trafficking and immune signaling. Diminished immune responses due to ST6Gal-I deficiency further correlate with constitutive recruitment of Shp-1 to CD22 in unstimulated B cells independent of Lyn tyrosine kinase activity and prevent autoimmune disease pathogenesis in the Lyn-deficient model of systemic lupus erythematosus, resulting in a significant extension of life span. Protein glycosylation by ST6Gal-I restricts access of antigen receptors and Shp-1 to CD22 and operates by a CD22-dependent mechanism that decreases the basal rate of IgM antigen receptor endocytosis in altering the threshold of B-cell immune activation.
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MESH Headings
- Animals
- B-Lymphocytes/chemistry
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Endocytosis/genetics
- Glycoproteins/metabolism
- Glycosylation
- Immunity/genetics
- Immunoglobulin M/analysis
- Immunoglobulin M/immunology
- Intracellular Signaling Peptides and Proteins/analysis
- Intracellular Signaling Peptides and Proteins/metabolism
- Lupus Erythematosus, Systemic/genetics
- Lupus Erythematosus, Systemic/immunology
- Lymphocyte Activation
- Membrane Microdomains/chemistry
- Mice
- Mice, Mutant Strains
- N-Acetylneuraminic Acid/metabolism
- Phosphorylation
- Protein Tyrosine Phosphatase, Non-Receptor Type 6
- Protein Tyrosine Phosphatases/analysis
- Protein Tyrosine Phosphatases/metabolism
- Receptors, Antigen, B-Cell/analysis
- Receptors, Antigen, B-Cell/metabolism
- Receptors, Fc/analysis
- Receptors, Fc/metabolism
- Sialic Acid Binding Ig-like Lectin 2/analysis
- Sialic Acid Binding Ig-like Lectin 2/genetics
- Sialic Acid Binding Ig-like Lectin 2/metabolism
- Sialyltransferases/genetics
- Sialyltransferases/metabolism
- Signal Transduction
- Tyrosine/metabolism
- src-Family Kinases/genetics
- src-Family Kinases/metabolism
- beta-D-Galactoside alpha 2-6-Sialyltransferase
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Affiliation(s)
- Prabhjit K Grewal
- Department of Cellular and Molecular Medicine and Howard Hughes Medical Institute, 9500 Gilman Drive MC0625, University of California-San Diego, La Jolla, CA 92093, USA
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35
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Collins BE, Smith BA, Bengtson P, Paulson JC. Ablation of CD22 in ligand-deficient mice restores B cell receptor signaling. Nat Immunol 2005; 7:199-206. [PMID: 16369536 DOI: 10.1038/ni1283] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 10/24/2005] [Indexed: 12/17/2022]
Abstract
CD22 is a negative regulator of B cell signaling, an activity modulated by its interaction with glycan ligands containing alpha2-6-linked sialic acids. B cells deficient in the enzyme (ST6Gal I) that forms the CD22 ligand show suppressed BCR signaling. Here we report that mice deficient in both CD22 and its ligand (Cd22-/- St6gal1-/- mice) showed restored B cell receptor (BCR) signaling, suggesting that the suppressed signaling of St6gal1-/- cells is mediated through CD22. Coincident with suppressed BCR signaling, B cells lacking ST6Gal I showed a net redistribution of the BCR to clathrin-rich microdomains containing most of the CD22, resulting in a twofold increase in the localization of CD22 together with the BCR. These studies suggest an important function for the CD22-ligand interaction in regulating BCR signaling and microdomain localization.
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Affiliation(s)
- Brian E Collins
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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36
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Nitschke L, Lajaunias F, Moll T, Ho L, Martinez-Soria E, Kikuchi S, Santiago-Raber ML, Dix C, Parkhouse RME, Izui S. Expression of aberrant forms of CD22 on B lymphocytes in Cd22a lupus-prone mice affects ligand binding. Int Immunol 2005; 18:59-68. [PMID: 16291654 DOI: 10.1093/intimm/dxh349] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CD22 functions primarily as a negative regulator of B-cell receptor signaling. The Cd22a allele has been proposed as a candidate allele for murine systemic lupus erythematosus. In this study, we explored the possible expression of aberrant forms of CD22, which differ in the N-terminal sequences constituting the ligand-binding site due to synthesis of abnormally processed Cd22 mRNA, in several Cd22a mouse strains, including C57BL/6 Cd22 congenic mice. The staining pattern of splenic B cells obtained with CY34 anti-CD22 mAb, which was expected to bind poorly to the aberrant CD22, was more heterogeneous in Cd22(a) mice than in Cd22b mice. Moreover, CD22 detected on B cells of Cd22a mice was expressed more weakly and as a smaller-sized protein, compared with Cd22b mice. Significantly, analysis with a synthetic CD22 ligand demonstrated that Cd22a mice carried a larger proportion of CD22 that was not bound by cis ligands on the B-cell surface than Cd22b mice. Finally, the study of C57BL/6 Cd22 congenic mice revealed that Cd22a B cells displayed a phenotype reminiscent of constitutively activated B cells (reduced surface IgM expression and augmented MHC class II expression), as reported for B cells expressing a mutant CD22 lacking the ligand-binding domain. Our demonstration that Cd22a B cells express aberrant forms of CD22, which can potentially deregulate B-cell signaling because of their decreased ligand-binding capacity, provides further support for Cd22a as a potential candidate allele for murine systemic lupus erythematosus.
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MESH Headings
- Alleles
- Animals
- B-Lymphocytes/immunology
- Gene Expression Regulation/genetics
- Gene Expression Regulation/immunology
- Genes, MHC Class II/genetics
- Genes, MHC Class II/immunology
- Immunoglobulin M/genetics
- Immunoglobulin M/immunology
- Ligands
- Lupus Erythematosus, Systemic/genetics
- Lupus Erythematosus, Systemic/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Mice, Inbred NZB
- Mice, Knockout
- RNA Processing, Post-Transcriptional/genetics
- RNA Processing, Post-Transcriptional/immunology
- Sialic Acid Binding Ig-like Lectin 2/genetics
- Sialic Acid Binding Ig-like Lectin 2/immunology
- Signal Transduction/genetics
- Signal Transduction/immunology
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Affiliation(s)
- Lars Nitschke
- Department of Genetics, University of Erlangen, 91058 Erlangen, Germany
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37
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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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38
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Han S, Collins BE, Bengtson P, Paulson JC. Homomultimeric complexes of CD22 in B cells revealed by protein-glycan cross-linking. Nat Chem Biol 2005; 1:93-7. [PMID: 16408005 DOI: 10.1038/nchembio713] [Citation(s) in RCA: 223] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 05/23/2005] [Indexed: 02/05/2023]
Abstract
CD22 is a negative regulator of B-cell receptor signaling, an activity mediated by recruitment of SH2 domain-containing phosphatase 1 through a phosphorylated immunoreceptor tyrosine inhibitory motif in its cytoplasmic domain. As in other members of the sialic acid-binding immunoglobulin-like lectin, or siglec, family, the extracellular N-terminal immunoglobulin domain of CD22 binds to glycan ligands containing sialic acid, which are highly expressed on B-cell glycoproteins. B-cell glycoproteins bind to CD22 in cis and 'mask' the ligand-binding domain, modulating its activity as a regulator of B-cell signaling. To assess cell-surface cis ligand interactions, we developed a new method for in situ photoaffinity cross-linking of glycan ligands to CD22. Notably, CD45, surfaceIgM (sIgM) and other glycoproteins that bind to CD22 in vitro do not appear to be important cis ligands of CD22 in situ. Instead, CD22 seems to recognize glycans of neighboring CD22 molecules as cis ligands, forming homomultimeric complexes.
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Affiliation(s)
- Shoufa Han
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, MEM-L71, La Jolla, California 92037, USA
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39
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Nitschke L, Tsubata T. Molecular interactions regulate BCR signal inhibition by CD22 and CD72. Trends Immunol 2004; 25:543-50. [DOI: 10.1016/j.it.2004.08.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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40
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Collins BE, Blixt O, DeSieno AR, Bovin N, Marth JD, Paulson JC. Masking of CD22 by cis ligands does not prevent redistribution of CD22 to sites of cell contact. Proc Natl Acad Sci U S A 2004; 101:6104-9. [PMID: 15079087 PMCID: PMC395930 DOI: 10.1073/pnas.0400851101] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CD22, a negative regulator of B cell signaling, is a member of the siglec family that binds to alpha2-6-linked sialic acids on glycoproteins. Previous reports demonstrated that binding of multivalent sialoside probes to CD22 is blocked, or "masked," by endogenous (cis) ligands, unless they are first destroyed by sialidase treatment. These results suggest that cis ligands on B cells make CD22 functionally unavailable for binding to ligands in trans. Through immunofluorescence microscopy, however, we observed that CD22 on resting B cells redistributes to the site of contact with other B or T lymphocytes. Redistribution is mediated by interaction with trans ligands on the opposing cell because it does not occur with ligand-deficient lymphocytes from ST6GalI-null mice. Surprisingly, CD45, proposed as both a cis and trans ligand of CD22, was not required for redistribution to sites of cell contact, given that redistribution of CD22 was independent of CD45 and was observed with lymphocytes from CD45-deficient mice. Furthermore, CD45 is not required for CD22 masking as similar levels of masking were observed in the WT and null mice. Comparison of the widely used sialoside-polyacrylamide probe with a sialoside-streptavidin probe revealed that the latter bound a subset of B cells without sialidase treatment, suggesting that cis ligands differentially impacted the binding of these two probes in trans. The combined results suggest that equilibrium binding to cis ligands does not preclude binding of CD22 to ligands in trans, and allows for its redistribution to sites of contact between lymphocytes.
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Affiliation(s)
- Brian E Collins
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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41
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Blixt O, Collins BE, van den Nieuwenhof IM, Crocker PR, Paulson JC. Sialoside specificity of the siglec family assessed using novel multivalent probes: identification of potent inhibitors of myelin-associated glycoprotein. J Biol Chem 2003; 278:31007-19. [PMID: 12773526 DOI: 10.1074/jbc.m304331200] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Ten of the 11 known human siglecs or their murine orthologs have been evaluated for their specificity for over 25 synthetic sialosides representing most of the major sequences terminating carbohydrate groups of glycoproteins and glycolipids. Analysis has been performed using a novel multivalent platform comprising biotinylated sialosides bound to a streptavidin-alkaline phosphatase conjugate. Each siglec was found to have a unique specificity for binding 16 different sialoside-streptavidin-alkaline phosphatase probes. The relative affinities of monovalent sialosides were assessed for each siglec in competitive inhibition studies. The quantitative data obtained allows a detailed analysis of each siglec for the relative importance of sialic acid and the penultimate oligosaccharide sequence on binding affinity and specificity. Most remarkable was the finding that myelin-associated glycoprotein (Siglec-4) binds with 500-10,000-fold higher affinity to a series of mono- and di-sialylated derivatives of the O-linked T-antigen (Galbeta(1-3)-GalNAc(alpha)OThr) as compared with alpha-methyl-NeuAc.
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MESH Headings
- Alkaline Phosphatase
- Animals
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Antigens, Differentiation, B-Lymphocyte/genetics
- Antigens, Differentiation, B-Lymphocyte/metabolism
- Antigens, Differentiation, Myelomonocytic/genetics
- Antigens, Differentiation, Myelomonocytic/metabolism
- CHO Cells
- Carbohydrate Sequence
- Cell Adhesion Molecules
- Chimera
- Cricetinae
- Enzyme-Linked Immunosorbent Assay
- Galactosides/chemical synthesis
- Galactosides/metabolism
- Glycolipids/chemical synthesis
- Glycolipids/metabolism
- Glycoproteins/chemical synthesis
- Glycoproteins/metabolism
- Humans
- Lectins/genetics
- Lectins/metabolism
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Molecular Sequence Data
- N-Acetylneuraminic Acid/metabolism
- Protein Binding
- Receptors, Immunologic/genetics
- Receptors, Immunologic/metabolism
- Sialic Acid Binding Ig-like Lectin 1
- Sialic Acid Binding Ig-like Lectin 2
- Sialic Acid Binding Immunoglobulin-like Lectins
- Streptavidin
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Affiliation(s)
- Ola Blixt
- Scripps Research Institute, Department of Molecular Biology, La Jolla, California 92037, USA
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42
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Yang ZQ, Puffer EB, Pontrello JK, Kiessling LL. Synthesis of a multivalent display of a CD22-binding trisaccharide. Carbohydr Res 2002; 337:1605-13. [PMID: 12423961 DOI: 10.1016/s0008-6215(02)00270-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Multivalent interactions have been implicated in the binding of B-cell surface glycoprotein CD22 to its physiological ligands. Because CD22 can influence B-cell antigen receptor (BCR) signaling, multivalent ligands that cluster CD22 may influence B-cell responses. Here, we report an efficient synthesis of a fluorophore-labeled multivalent display of a CD22-binding trisaccharide, Neu5Acalpha2,6Galbeta1,4Glc, using the ring-opening metathesis polymerization (ROMP). Our synthetic strategy involves the modification of an N-hydroxysuccinimide (NHS) ester-substituted polymer generated by ROMP with the aminopropyl glycoside of the trisaccharide. The conjugation efficiency for the coupling is high; when 0.3 equiv of the trisaccharide derivative were used relative to NHS ester groups, the mole fraction (chi) of trisaccharide ligand incorporated onto the backbone was 0.3. A fluorescein-labeled version of the multivalent ligand binds to cells expressing CD22.
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Affiliation(s)
- Zhi-Qiang Yang
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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43
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Collins BE, Blixt O, Bovin NV, Danzer CP, Chui D, Marth JD, Nitschke L, Paulson JC. Constitutively unmasked CD22 on B cells of ST6Gal I knockout mice: novel sialoside probe for murine CD22. Glycobiology 2002; 12:563-71. [PMID: 12213789 DOI: 10.1093/glycob/cwf067] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The interaction of CD22 with glycoprotein ligands bearing the Siaalpha2,6Gal-R sequence is believed to modulate its function as a regulator of B cell signaling. Although a commercial sialoside-polyacrylamide (PAA) probe, NeuAc- alpha2,6Gal-PAA, has facilitated studies on ligand binding by human CD22, murine CD22 binds instead with high affinity to NeuGcalpha2,6Gal-R. A multivalent probe with this sequence was constructed to facilitate investigations of ligand binding in CD22 function using genetically defined murine models. The probe is based on the sialoside-PAA platform, which is then biotinylated for easy detection. A series of sialoside probes were constructed with two different length linker arms between the sialoside and the backbone and three different sialoside to PAA molar ratios. The NeuGcalpha2,6Gal-PAA probe is specific for CD22: it binds to sialidase-treated B cells of wild-type mice but not B cells of CD22-null mice. Additionally, because the probe only binds to sialidase-treated wild-type cells, it confirms that CD22 is constitutively "masked" on most B cells from wild-type mice by binding to ligands in cis. In contrast, the probe bound equally well to native or sialidase-treated B cells from the immunocompromised ligand-deficient ST6Gal I knockout mice, demonstrating that CD22 is constitutively "unmasked" in these cells.
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Affiliation(s)
- Brian E Collins
- Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., MEM-L71, La Jolla, CA 92075, USA
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44
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Angata T, Kerr SC, Greaves DR, Varki NM, Crocker PR, Varki A. Cloning and characterization of human Siglec-11. A recently evolved signaling molecule that can interact with SHP-1 and SHP-2 and is expressed by tissue macrophages, including brain microglia. J Biol Chem 2002; 277:24466-74. [PMID: 11986327 DOI: 10.1074/jbc.m202833200] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Siglecs are sialic acid-recognizing animal lectins of the immunoglobulin superfamily. We have cloned and characterized a novel human molecule, Siglec-11, that belongs to the subgroup of CD33/Siglec-3-related Siglecs. As with others in this subgroup, the cytosolic domain of Siglec-11 is phosphorylated at tyrosine residue(s) upon pervanadate treatment of cells and then recruits the protein-tyrosine phosphatases SHP-1 and SHP-2. However, Siglec-11 has several novel features relative to the other CD33/Siglec-3-related Siglecs. First, it binds specifically to alpha2-8-linked sialic acids. Second, unlike other CD33/Siglec-3-related Siglecs, Siglec-11 was not found on peripheral blood leukocytes. Instead, we observed its expression on macrophages in various tissues, such as liver Kupffer cells. Third, it was also expressed on brain microglia, thus becoming the second Siglec to be found in the nervous system. Fourth, whereas the Siglec-11 gene is on human chromosome 19, it lies outside the previously described CD33/Siglec-3-related Siglec cluster on this chromosome. Fifth, analyses of genome data bases indicate that Siglec-11 has no mouse ortholog and that it is likely to be the last canonical human Siglec to be reported. Finally, although Siglec-11 shows marked sequence similarity to human Siglec-10 in its extracellular domain, the cytosolic tail appears only distantly related. Analysis of genomic regions surrounding the Siglec-11 gene suggests that it is actually a chimeric molecule that arose from relatively recent gene duplication and recombination events, involving the extracellular domain of a closely related ancestral Siglec gene (which subsequently became a pseudogene) and a transmembrane and cytosolic tail derived from another ancestral Siglec.
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MESH Headings
- Amino Acid Sequence
- Antigens, CD/analysis
- Antigens, CD/chemistry
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Antigens, Differentiation, Myelomonocytic/analysis
- Antigens, Differentiation, Myelomonocytic/chemistry
- Antigens, Differentiation, Myelomonocytic/genetics
- Antigens, Differentiation, Myelomonocytic/metabolism
- Appendix/cytology
- Appendix/metabolism
- Base Sequence
- Brain/physiology
- Cloning, Molecular
- Evolution, Molecular
- Humans
- Intracellular Signaling Peptides and Proteins
- Lectins/chemistry
- Lectins/genetics
- Lectins/metabolism
- Macrophages/physiology
- Membrane Proteins
- Microglia/physiology
- Molecular Sequence Data
- Organ Specificity
- Palatine Tonsil/cytology
- Palatine Tonsil/metabolism
- Protein Tyrosine Phosphatase, Non-Receptor Type 11
- Protein Tyrosine Phosphatase, Non-Receptor Type 6
- Protein Tyrosine Phosphatases/metabolism
- Pseudogenes
- RNA, Messenger/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Alignment
- Sequence Homology, Amino Acid
- Sialic Acid Binding Ig-like Lectin 3
- Transcription, Genetic
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Affiliation(s)
- Takashi Angata
- Glycobiology Research and Training Center, Department of Medicine, University of California, San Diego, La Jolla, California 92093-0687, USA
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45
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Brinkman-Van der Linden ECM, Sonnenburg JL, Varki A. Effects of sialic acid substitutions on recognition by Sambucus nigra agglutinin and Maackia amurensis hemagglutinin. Anal Biochem 2002; 303:98-104. [PMID: 11906157 DOI: 10.1006/abio.2001.5539] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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46
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47
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Azuma Y, Sakanashi M, Matsumoto K. The effect of alpha2,6-linked sialic acid on anti-IgM antibody-induced apoptosis in Ramos cells. Glycoconj J 2001; 18:419-24. [PMID: 11925509 DOI: 10.1023/a:1014820316267] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Apoptosis in B cells is induced through the B cell antigen receptor (BCR) and affects the sialic acid recognition molecules on B cells. We investigated the effects of alpha(1)-acid glycoprotein (AGP), which mainly contains alpha2,6-linked sialic acid, on anti-IgM antibody (Ab)-induced apoptosis in Ramos cells, which are derived from Burkitt's lymphoma. When Ramos cells were incubated with anti-IgM-Ab in plates coated with AGP, neuraminidase-digested AGP (asAGP) or alpha2,3-sialylated AGP (2,3AGP), apoptosis was suppressed only in those coated with AGP. We also studied the effects of CD22, which is expressed on the surface of mature B cells and binds to sugar chains containing alpha2,6-linked sialic acid, with anti-CD22 monoclonal antibody (mAb). Anti-CD22mAb enhanced anti-IgM Ab-induced apoptosis in Ramos cells. These contradictory results suggested that the recognition molecules for alpha2,6-linked sialic acid on AGP, which inhibits B-cell apoptosis, is distinct from CD22, or that different binding domains of CD22 between alpha2,6-linked sialic acid and anti-CD22 mAb exert opposite functions of suppression or enhancement to anti-IgM Ab-induced B cells.
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MESH Headings
- Antibodies, Anti-Idiotypic/pharmacology
- Antibodies, Monoclonal/immunology
- Antibodies, Monoclonal/pharmacology
- Antigens, CD/immunology
- Antigens, CD/metabolism
- Antigens, Differentiation, B-Lymphocyte/immunology
- Antigens, Differentiation, B-Lymphocyte/metabolism
- Apoptosis/drug effects
- B-Lymphocytes/cytology
- B-Lymphocytes/drug effects
- B-Lymphocytes/immunology
- Carbohydrate Conformation
- Cell Adhesion Molecules
- Cell Survival/drug effects
- DNA Fragmentation/drug effects
- Flow Cytometry
- Humans
- Lectins
- N-Acetylneuraminic Acid/chemistry
- N-Acetylneuraminic Acid/pharmacology
- Orosomucoid/chemistry
- Orosomucoid/pharmacology
- Sialic Acid Binding Ig-like Lectin 2
- Tumor Cells, Cultured
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Affiliation(s)
- Y Azuma
- Department of Clinical Chemistry, School of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan.
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48
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van Rossenberg SM, Sliedregt LA, Autar R, Piperi C, Van Der Merwe AP, van Berkel TJ, Kuiper J, Biessen EA. A structure-function study of ligand recognition by CD22beta. J Biol Chem 2001; 276:12967-73. [PMID: 11152460 DOI: 10.1074/jbc.m009276200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
B-cell-specific CD22 is a member of a group of cell adhesion molecules within the immunoglobulin superfamily that display binding to glycans with terminal sialic acid residues. Binding of endogenous ligands to CD22 triggers B-cell activation and proliferation. It is therefore conceivable that high affinity ligands for CD22 may be of value as inhibitors of B-cell activation in allergy and chronic inflammation. In this study, we aimed to delineate the structural requirements for ligand binding to CD22. A library of 20 mono-, di-, and trisaccharide analogs of the basic binding motif Neu5Ac(alpha2,6)Lac was synthesized and screened for affinity for CD22beta. In general, CD22 ligand recognition appeared to be rather tolerant with respect to structural modifications of the anomeric sugar on a mono-, di-, and trisaccharide level, although affinity was increased by the presence of a nitro aromatic group at C-2. The most potent monovalent ligand, Neu5Ac-4-nitrobenzoyl-Glc, was selected to generate multivalent ligands based on either a glutamate or Tris cluster core. All multivalent ligands displayed at least a 10-fold increased affinity for CD22 compared with the corresponding monovalent glycoside. Interestingly, a maximal gain in affinity was already obtained for bivalent ligands, regardless of the terminal glycoside. A trivalent Tris-based cluster of Neu5Ac-4-nitrobenzoyl-Glc displayed a 300-fold higher affinity compared with the basic binding motif, which makes it, to our knowledge, the most potent antagonist for CD22 yet synthesized. As our in vitro fluorescence-activated cell sorting studies demonstrated efficient cellular uptake of a CD22 substrate, the most potent ligand in this study may hold promise as a homing device for immunomodulatory compounds and cytostatics.
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Affiliation(s)
- S M van Rossenberg
- Leiden/Amsterdam Center for Drug Research, Division of Biopharmaceutics, Sylvius Laboratories, Leiden University, 2300 RA Leiden, The Netherlands.
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49
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Affiliation(s)
- S Kelm
- Institute of Biochemistry, University of Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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50
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Sliedregt LA, van Rossenberg SM, Autar R, Valentijn AR, van der Marel GA, van Boom JH, Piperi C, van der Merwe PA, Kuiper J, van Berkel TJ, Biessen EA. Design and synthesis of a multivalent homing device for targeting to murine CD22. Bioorg Med Chem 2001; 9:85-97. [PMID: 11197350 DOI: 10.1016/s0968-0896(00)00224-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
CD22 is a cell-surface glycoprotein uniquely located on mature B-cells and B-cell derived tumour cells. Current evidence suggests that binding of endogenous ligands to CD22 leads to modulation of B-cell activation by antigen. Incidentally, however, B-cell activation may derail. and lead to an undesired immune response, for example in cases of allergy, rheumatoid arthritis and Crohn's disease. In this situation, synthetic high-affinity ligands for CD22 may be of therapeutic value as inhibitors of B-cell activation. Recent studies have revealed that natural ligands for CD22 contain the trisaccharide NeuAc alpha-2,6-Lac as the basic binding motif. In addition, it has been demonstrated that binding to CD22 is strongly enhanced by multivalent presentation of the basic binding motif (cluster effect). In this paper. the stepwise development of a novel multivalent high-affinity ligand for CD22 is described. In the first stage, a series of monovalent NeuAc alpha-2,6-Glc(Y)X type binding motifs was prepared, and their affinity for murine CD22 was monitored, to obtain more insight into the effect of separate structure elements on ligand recognition. In the second stage, we prepared a trivalent cluster, based on the monovalent motif that displayed the highest affinity for CD22, NeuAc alpha-2,6-GlcNBzNO2OMe (7). This cluster, TRIS(NeuAc alpha-2,6-GlcNBzNO2)3 (52), displayed a more than 58-fold higher affinity for CD22 than the reference structure NeuAc alpha-2,6-LacOMe (10). To our knowledge, the cluster 52 is one of the most potent antagonists for CD22 yet synthesised.
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Affiliation(s)
- L A Sliedregt
- Leiden/Amsterdam Center for Drug Research, Division of Biopharmaceutics, Sylvius Laboratories, Leiden University, The Netherlands
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