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Jame-Chenarboo Z, Gray TE, Macauley MS. Advances in understanding and exploiting Siglec-glycan interactions. Curr Opin Chem Biol 2024; 80:102454. [PMID: 38631213 DOI: 10.1016/j.cbpa.2024.102454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/18/2024] [Accepted: 03/21/2024] [Indexed: 04/19/2024]
Abstract
Sialic-acid-binding immunoglobulin-type lectins (Siglecs) are a family of cell-surface immunomodulatory receptors that recognize sialic-acid-containing glycans. The majority of Siglecs have an inhibitory motif in their intercellular domain and can regulate the cellular activation of immune cells. Importantly, the immunomodulatory role of Siglecs is regulated by engagement with distinct sialoglycan ligands. However, there are still many unanswered questions about the precise ligand(s) recognized by individual Siglec family members. New tools and approaches to study Siglec-ligand interactions are rapidly filling this knowledge gap. This review provides an overview of recent advances in discovering Siglec ligands as well as the development of approaches to modulate the function of Siglecs. In both aspects, chemical biology approaches are emphasized with a discussion on how these are complementing biochemical and genetic strategies.
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Affiliation(s)
| | - Taylor E Gray
- Department of Chemistry, University of Alberta, Canada
| | - Matthew S Macauley
- Department of Chemistry, University of Alberta, Canada; Department of Medical Microbiology and Immunology, University of Alberta, Canada.
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Boelaars K, van Kooyk Y. Targeting myeloid cells for cancer immunotherapy: Siglec-7/9/10/15 and their ligands. Trends Cancer 2024; 10:230-241. [PMID: 38160071 DOI: 10.1016/j.trecan.2023.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/17/2023] [Accepted: 11/28/2023] [Indexed: 01/03/2024]
Abstract
Advances in immunotherapy have revolutionized cancer treatment, yet many patients do not show clinical responses. While most immunotherapies target T cells, myeloid cells are the most abundant cell type in solid tumors and are key orchestrators of the immunosuppressive tumor microenvironment (TME), hampering effective T cell responses. Therefore, unraveling the immune suppressive pathways within myeloid cells could unveil new avenues for cancer immunotherapy. Over the past decade, Siglec receptors and their ligand, sialic acids, have emerged as a novel immune checkpoint on myeloid cells. In this review, we highlight key findings on how sialic acids modify immunity in the TME through engagement of Siglec-7/9/10/15 expressed on myeloid cells, and how the sialic acid-Siglec axis can be targeted for future cancer immunotherapies.
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Affiliation(s)
- Kelly Boelaars
- Amsterdam UMC location Vrije Universiteit Amsterdam, Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Institute for Infection and Immunity, De Boelelaan, 1117, Amsterdam, The Netherlands
| | - Yvette van Kooyk
- Amsterdam UMC location Vrije Universiteit Amsterdam, Molecular Cell Biology and Immunology, Cancer Center Amsterdam, Amsterdam Institute for Infection and Immunity, De Boelelaan, 1117, Amsterdam, The Netherlands.
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Conti G, Bärenwaldt A, Rabbani S, Mühlethaler T, Sarcevic M, Jiang X, Schwardt O, Ricklin D, Pieters RJ, Läubli H, Ernst B. Tetra- and Hexavalent Siglec-8 Ligands Modulate Immune Cell Activation. Angew Chem Int Ed Engl 2023; 62:e202314280. [PMID: 37947772 DOI: 10.1002/anie.202314280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/31/2023] [Accepted: 11/07/2023] [Indexed: 11/12/2023]
Abstract
Carbohydrate-binding proteins are generally characterized by poor affinities for their natural glycan ligands, predominantly due to the shallow and solvent-exposed binding sites. To overcome this drawback, nature has exploited multivalency to strengthen the binding by establishing multiple interactions simultaneously. The development of oligovalent structures frequently proved to be successful, not only for proteins with multiple binding sites, but also for proteins that possess a single recognition domain. Herein we present the syntheses of a number of oligovalent ligands for Siglec-8, a monomeric I-type lectin found on eosinophils and mast cells, alongside the thermodynamic characterization of their binding. While the enthalpic contribution of each binding epitope was within a narrow range to that of the monomeric ligand, the entropy penalty increased steadily with growing valency. Additionally, we observed a successful agonistic binding of the tetra- and hexavalent and, to an even larger extent, multivalent ligands to Siglec-8 on immune cells and modulation of immune cell activation. Thus, triggering a biological effect is not restricted to multivalent ligands but could be induced by low oligovalent ligands as well, whereas a monovalent ligand, despite binding with similar affinity, showed an antagonistic effect.
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Affiliation(s)
- Gabriele Conti
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
- Chemical Biology and Drug Discovery Group, Department of Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands
| | - Anne Bärenwaldt
- Laboratory for Cancer Immunotherapy, Department of Biomedicine, University of Basel, Hebelstrasse 20, 4051, Basel, Switzerland
- Division of Medical Oncology, University Hospital Basel, Petersgraben 4, 4051, Basel, Switzerland
| | - Said Rabbani
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
| | - Tobias Mühlethaler
- Biophysics Facility, Department Biozentrum, University of Basel, Spitalstrasse 41, 4056, Basel, Switzerland
| | - Mirza Sarcevic
- Laboratory for Cancer Immunotherapy, Department of Biomedicine, University of Basel, Hebelstrasse 20, 4051, Basel, Switzerland
- Division of Medical Oncology, University Hospital Basel, Petersgraben 4, 4051, Basel, Switzerland
| | - Xiaohua Jiang
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
| | - Oliver Schwardt
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
| | - Daniel Ricklin
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
| | - Roland J Pieters
- Chemical Biology and Drug Discovery Group, Department of Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands
| | - Heinz Läubli
- Laboratory for Cancer Immunotherapy, Department of Biomedicine, University of Basel, Hebelstrasse 20, 4051, Basel, Switzerland
- Division of Medical Oncology, University Hospital Basel, Petersgraben 4, 4051, Basel, Switzerland
| | - Beat Ernst
- Molecular Pharmacy Group, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056, Basel, Switzerland
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Schnaar RL. Gangliosides as Siglec ligands. Glycoconj J 2023; 40:159-167. [PMID: 36701102 PMCID: PMC11000168 DOI: 10.1007/s10719-023-10101-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/09/2023] [Accepted: 01/13/2023] [Indexed: 01/27/2023]
Abstract
The structure of a sialoglycan can be translated into to a biological response when it binds to a specific endogenous lectin. Among endogenous sialic acid-binding lectins in humans are those comprising the 15-member Siglec family, most of which are expressed on overlapping sets of immune cells. Endogenous Siglec ligands are sialoglycolipids (gangliosides) and/or sialoglycoproteins, on cell surfaces or in the extracellular milieu, that bind to and initiate signaling by cell surface Siglecs. In the nervous system, where gangliosides are the predominant sialoglycans, Siglec-4 (myelin-associated glycoprotein) on myelinating cells binds to gangliosides GD1a and GT1b on nerve cell axons to ensure stable and productive axon-myelin interactions. In the immune system, Siglec-7 on natural killer cells binds to gangliosides GD3 and GD2 to inhibit immune signaling. Expression of GD3 and GD2 on cancer cells can lead to tumor immune evasion. Siglec-1 (sialoadhesin, CD169) on macrophages binds to gangliosides on tumors and enveloped viruses. This may enhance antigen presentation in some cases, or increase viral distribution in others. Several other Siglecs bind to gangliosides in vitro, the biological significance of which has yet to be fully established. Gangliosides, which are found on all human cells and tissues in cell-specific distributions, are functional Siglec ligands with varied roles driving Siglec-mediated signaling.
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Affiliation(s)
- Ronald L Schnaar
- Department of Pharmacology and Molecular Sciences, Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N Wolfe St, Baltimore, MD, 21205, USA.
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Siew JJ, Chern Y, Khoo KH, Angata T. Roles of Siglecs in neurodegenerative diseases. Mol Aspects Med 2023; 90:101141. [PMID: 36089405 DOI: 10.1016/j.mam.2022.101141] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/16/2022] [Accepted: 08/29/2022] [Indexed: 02/08/2023]
Abstract
Microglia are resident myeloid cells in the central nervous system (CNS) with a unique developmental origin, playing essential roles in developing and maintaining the CNS environment. Recent studies have revealed the involvement of microglia in neurodegenerative diseases, such as Alzheimer's disease, through the modulation of neuroinflammation. Several members of the Siglec family of sialic acid recognition proteins are expressed on microglia. Since the discovery of the genetic association between a polymorphism in the CD33 gene and late-onset Alzheimer's disease, significant efforts have been made to elucidate the molecular mechanism underlying the association between the polymorphism and Alzheimer's disease. Furthermore, recent studies have revealed additional potential associations between Siglecs and Alzheimer's disease, implying that the reduced signal from inhibitory Siglec may have an overall protective effect in lowering the disease risk. Evidences suggesting the involvement of Siglecs in other neurodegenerative diseases are also emerging. These findings could help us predict the roles of Siglecs in other neurodegenerative diseases. However, little is known about the functionally relevant Siglec ligands in the brain, which represents a new frontier. Understanding how microglial Siglecs and their ligands in CNS contribute to the regulation of CNS homeostasis and pathogenesis of neurodegenerative diseases may provide us with a new avenue for disease prevention and intervention.
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Affiliation(s)
- Jian Jing Siew
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yijuang Chern
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Kay-Hooi Khoo
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Takashi Angata
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
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