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Schwerdtfeger F, Ter Beest M, Perez-Martinez CA, Raaijmakers K, Hagemann PM, Martí Juan A, Spruijt CG, Vermeulen M, van Deventer S, van Spriel AB. Identification of a sorting motif for Tspan3 to MHCII compartments in human B cells. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2025; 1867:184406. [PMID: 39689822 DOI: 10.1016/j.bbamem.2024.184406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 10/17/2024] [Accepted: 12/12/2024] [Indexed: 12/19/2024]
Abstract
Tetraspanins are four-transmembrane proteins that play fundamental roles in the immune system by enabling processes like migration, proliferation, signaling and protein trafficking. While the importance of cell surface tetraspanins has been established, the function of intracellular tetraspanins is less well understood. Here, we investigated the role of tetraspanin 3 (Tspan3) in lymphocytes. Tspan3 expression was low in T cells and high in B cells which increased during B cell activation. Tspan3 localized to late endosomal structures where it colocalized with major histocompatibility complex II (MHCII) in the MHCII compartment. There, inhibiting the formation of intraluminal vesicles (ILVs) showed that Tspan3 localization was not affected in contrast to its homologue CD63. Using a peptide-pulldown approach, we identified that Tspan3 interacts with AP2 via its C-terminus that harbors a YXXΦ-based sorting motif. Interestingly, mutating this motif did not impair Tspan3 localization. Instead, leucine 246 was required for its intracellular localization, identifying an unrecognized leucine-based sorting motif responsible for Tspan3 localization to MHCII compartment in B cells. Taken together, we report a new sorting motif for Tspan3 to MHCII compartments in human B cells.
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Affiliation(s)
- Fabian Schwerdtfeger
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands
| | - Martin Ter Beest
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands
| | - Cesar A Perez-Martinez
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands; Department of Physics, University of Sonora, Hermosillo, Mexico
| | - Kris Raaijmakers
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands; Department of Radiotherapy and OncoImmunology, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Philipp Michael Hagemann
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands
| | - Aina Martí Juan
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands
| | - Cornelia G Spruijt
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University Nijmegen, the Netherlands
| | - Michiel Vermeulen
- Department of Molecular Biology, Faculty of Science, Radboud Institute for Molecular Life Sciences, Oncode Institute, Radboud University Nijmegen, the Netherlands; Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Sjoerd van Deventer
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands
| | - Annemiek B van Spriel
- Department of Medical BioSciences, Radboud University Medical Center, Radboud Institute for Medical Innovation, Nijmegen, the Netherlands.
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Maiolo E, Bellesi S, Campana F, Iacovelli C, Malafronte R, Schiaffini G, Alma E, Bellisario F, Viscovo M, D'Innocenzo S, Toscano A, D'Alò F, De Stefano V, Larocca LM, Hohaus S. Heterogeneous Surface CD79b Expression in Aggressive B-Cell Lymphomas Assessed by Flow Cytometry on Lymph Node Biopsies. Cancers (Basel) 2024; 16:3968. [PMID: 39682155 DOI: 10.3390/cancers16233968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2024] [Revised: 11/18/2024] [Accepted: 11/22/2024] [Indexed: 12/18/2024] Open
Abstract
Background: CD79b is a B-cell-specific antigen that is crucial to the B-cell receptor and is considered a key target for treatment in aggressive B-cell lymphomas. Methods: While immunohistochemical studies have shown widespread expression of CD79b in mature B-cell-derived lymphomas, flow cytometry allows for precise measurement and differentiation between surface and intracellular localization. Results: In our comparative analysis, we discovered that CD79b expression percentages and mean fluorescence intensity (MFI) were lower in a group of 127 cases of aggressive B-cell lymphomas compared to a control group of benign reactive hyperplasia. We also observed significant variability in the surface expression of CD79b among lymphoma cases, with 18% showing predominantly intracellular positivity. There was a strong correlation between the surface expression of CD79b and clonal light chains. Notably, primary mediastinal B-cell lymphomas exhibited significantly lower surface CD79b expression compared to other lymphoma subtypes (median 0.8% IQR 0-48.5 vs. 80% IQR 24-97, p = 0.0005). Furthermore, patients over 60 years old and those with a higher Revised International Prognostic Index (R-IPI) had significantly higher CD79b expression, both of which are associated with a significant benefit from adding an anti-CD79b drug conjugate to first-line chemotherapy in diffuse large B-cell lymphomas. Conclusions: In conclusion, the quantitative flow cytometric analysis of CD79b surface expression in aggressive B-cell lymphomas provides clinically relevant information, highlighting its potential usefulness in guiding therapeutic decisions.
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Affiliation(s)
- Elena Maiolo
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Silvia Bellesi
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Fabrizia Campana
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
| | - Camilla Iacovelli
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Rosalia Malafronte
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Gabriele Schiaffini
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
| | - Eleonora Alma
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Flaminia Bellisario
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Marcello Viscovo
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
| | - Simone D'Innocenzo
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Alessia Toscano
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Francesco D'Alò
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
| | - Valerio De Stefano
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
| | - Luigi Maria Larocca
- Patologia Oncoematologica, Dipartimento di Scienze della Salute della Donna, del Bambino e di Sanità Pubblica, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
| | - Stefan Hohaus
- Dipartimento di Scienze di Laboratorio ed Ematologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
- Sezione di Ematologia, Dipartimento di Scienze Radiologiche ed Ematologiche, Università Cattolica del Sacro Cuore Facoltà di Medicina e Chirurgia, 00168 Rome, Italy
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Hoeger S, Drake LA, Drake JR. Proximity-Based Labeling Identifies MHC Class II and CD37 as B Cell Receptor-Proximal Proteins with Immunological Functions. Immunohorizons 2024; 8:326-338. [PMID: 38625120 PMCID: PMC11066716 DOI: 10.4049/immunohorizons.2400014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 04/03/2024] [Indexed: 04/17/2024] Open
Abstract
The BCR allows for Ag-driven B cell activation and subsequent Ag endocytosis, processing, and presentation to recruit T cell help. Core drivers of BCR signaling and endocytosis are motifs within the receptor's cytoplasmic tail (primarily CD79). However, BCR function can be tuned by other proximal cellular elements, such as CD20 and membrane lipid microdomains. To identify additional proteins that could modulate BCR function, we used a proximity-based biotinylation technique paired with mass spectrometry to identify molecular neighbors of the murine IgM BCR. Those neighbors include MHC class II molecules, integrins, various transporters, and membrane microdomain proteins. Class II molecules, some of which are invariant chain-associated nascent class II, are a readily detected BCR neighbor. This finding is consistent with reports of BCR-class II association within intracellular compartments. The BCR is also in close proximity to multiple proteins involved in the formation of membrane microdomains, including CD37, raftlin, and Ig superfamily member 8. Known defects in T cell-dependent humoral immunity in CD37 knockout mice suggest a role for CD37 in BCR function. In line with this notion, CRISPR-based knockout of CD37 expression in a B cell line heightens BCR signaling, slows BCR endocytosis, and tempers formation of peptide-class II complexes. These results indicate that BCR molecular neighbors can impact membrane-mediated BCR functions. Overall, a proximity-based labeling technique allowed for identification of multiple previously unknown BCR molecular neighbors, including the tetraspanin protein CD37, which can modulate BCR function.
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Affiliation(s)
- Sean Hoeger
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY
| | - Lisa A. Drake
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY
| | - James R. Drake
- Department of Immunology and Microbial Disease, Albany Medical College, Albany, NY
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Tkachenko A, Kupcova K, Havranek O. B-Cell Receptor Signaling and Beyond: The Role of Igα (CD79a)/Igβ (CD79b) in Normal and Malignant B Cells. Int J Mol Sci 2023; 25:10. [PMID: 38203179 PMCID: PMC10779339 DOI: 10.3390/ijms25010010] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 12/11/2023] [Accepted: 12/11/2023] [Indexed: 01/12/2024] Open
Abstract
B-cell receptor (BCR) is a B cell hallmark surface complex regulating multiple cellular processes in normal as well as malignant B cells. Igα (CD79a)/Igβ (CD79b) are essential components of BCR that are indispensable for its functionality, signal initiation, and signal transduction. CD79a/CD79b-mediated BCR signaling is required for the survival of normal as well as malignant B cells via a wide signaling network. Recent studies identified the great complexity of this signaling network and revealed the emerging role of CD79a/CD79b in signal integration. In this review, we have focused on functional features of CD79a/CD79b, summarized signaling consequences of CD79a/CD79b post-translational modifications, and highlighted specifics of CD79a/CD79b interactions within BCR and related signaling cascades. We have reviewed the complex role of CD79a/CD79b in multiple aspects of normal B cell biology and how is the normal BCR signaling affected by lymphoid neoplasms associated CD79A/CD79B mutations. We have also summarized important unresolved questions and highlighted issues that remain to be explored for better understanding of CD79a/CD79b-mediated signal transduction and the eventual identification of additional therapeutically targetable BCR signaling vulnerabilities.
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Affiliation(s)
- Anton Tkachenko
- BIOCEV, First Faculty of Medicine, Charles University, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Kristyna Kupcova
- BIOCEV, First Faculty of Medicine, Charles University, Prumyslova 595, 252 50 Vestec, Czech Republic
- First Department of Internal Medicine–Hematology, General University Hospital and First Faculty of Medicine, Charles University, 128 08 Prague, Czech Republic
| | - Ondrej Havranek
- BIOCEV, First Faculty of Medicine, Charles University, Prumyslova 595, 252 50 Vestec, Czech Republic
- First Department of Internal Medicine–Hematology, General University Hospital and First Faculty of Medicine, Charles University, 128 08 Prague, Czech Republic
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5
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Guldenpfennig C, Teixeiro E, Daniels M. NF-kB's contribution to B cell fate decisions. Front Immunol 2023; 14:1214095. [PMID: 37533858 PMCID: PMC10391175 DOI: 10.3389/fimmu.2023.1214095] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/03/2023] [Indexed: 08/04/2023] Open
Abstract
NF-κB signaling is essential to an effective innate and adaptive immune response. Many immune-specific functional and developmental outcomes depend in large on NF-κB. The formidable task of sorting out the mechanisms behind the regulation and outcome of NF-κB signaling remains an important area of immunology research. Here we briefly discuss the role of NF-κB in regulating cell fate decisions at various times in the path of B cell development, activation, and the generation of long-term humoral immunity.
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Affiliation(s)
- Caitlyn Guldenpfennig
- Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
- NextGen Precision Health, University of Missouri, Columbia, MO, United States
| | - Emma Teixeiro
- Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
- NextGen Precision Health, University of Missouri, Columbia, MO, United States
| | - Mark Daniels
- Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, United States
- NextGen Precision Health, University of Missouri, Columbia, MO, United States
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6
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Pasqualucci L, Klein U. NF-κB Mutations in Germinal Center B-Cell Lymphomas: Relation to NF-κB Function in Normal B Cells. Biomedicines 2022; 10:2450. [PMID: 36289712 PMCID: PMC9599362 DOI: 10.3390/biomedicines10102450] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/16/2022] [Accepted: 09/21/2022] [Indexed: 11/16/2022] Open
Abstract
Most B cell lymphomas arise from the oncogenic transformation of B cells that have undergone the germinal center (GC) reaction of the T cell-dependent immune response, where high-affinity memory B cells and plasma cells are generated. The high proliferation of GC B cells coupled with occasional errors in the DNA-modifying processes of somatic hypermutation and class switch recombination put the cell at a risk to obtain transforming genetic aberrations, which may activate proto-oncogenes or inactivate tumour suppressor genes. Several subtypes of GC lymphomas harbor genetic mutations leading to constitutive, aberrant activation of the nuclear factor-κB (NF-κB) signaling pathway. In normal B cells, NF-κB has crucial biological roles in development and physiology. GC lymphomas highjack these activities to promote tumour-cell growth and survival. It has become increasingly clear that the separate canonical and non-canonical routes of the NF-κB pathway and the five downstream NF-κB transcription factors have distinct functions in the successive stages of GC B-cell development. These findings may have direct implications for understanding how aberrant NF-κB activation promotes the genesis of various GC lymphomas corresponding to the developmentally distinct GC B-cell subsets. The knowledge arising from these studies may be explored for the development of precision medicine approaches aimed at more effective treatments of the corresponding tumours with specific NF-κB inhibitors, thus reducing systemic toxicity. We here provide an overview on the patterns of genetic NF-κB mutations encountered in the various GC lymphomas and discuss the consequences of aberrant NF-κB activation in those malignancies as related to the biology of NF-κB in their putative normal cellular counterparts.
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Affiliation(s)
- Laura Pasqualucci
- Institute for Cancer Genetics, Department of Pathology & Cell Biology, The Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA
| | - Ulf Klein
- Division of Haematology & Immunology, Leeds Institute of Medical Research at St. James’s, University of Leeds, Leeds LS9 7TF, UK
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7
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Roberts AD, Taraska JW. B cell receptor (BCR) endocytosis. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 194:159-177. [PMID: 36631191 PMCID: PMC11851869 DOI: 10.1016/bs.pmbts.2022.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The B cell receptor (BCR) interacts with foreign antigens to mediate B cell activation and secretion of antibodies. B cell activation begins with initiation of signaling pathways, such as NFAT, NF-κB, and MAPK, and endocytosis of the BCR-antigen complex. Many studies have investigated the signaling pathways associated with BCR activation, and this work has led to significant advances in drug therapies to treat cancer and autoimmune diseases that are linked to aberrant BCR signaling. Less is known, however, about the mechanisms of BCR endocytosis and the role endocytosis plays in B cell pathogenesis. This chapter will review key characteristics of the BCR, including a review of signaling pathways, and endocytic mechanisms associated with the activated BCR. We will also review recent studies investigating the role of BCR endocytosis disease pathogenesis.
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Affiliation(s)
- Aleah D Roberts
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States
| | - Justin W Taraska
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States.
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8
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McShane AN, Malinova D. The Ins and Outs of Antigen Uptake in B cells. Front Immunol 2022; 13:892169. [PMID: 35572544 PMCID: PMC9097226 DOI: 10.3389/fimmu.2022.892169] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 03/31/2022] [Indexed: 11/13/2022] Open
Abstract
A review of our current knowledge of B cell antigen uptake mechanisms, the relevance of these processes to pathology, and outstanding questions in the field. Specific antigens induce B cell activation through the B cell receptor (BCR) which initiates downstream signaling and undergoes endocytosis. While extensive research has shed light on the signaling pathways in health and disease, the endocytic mechanisms remain largely uncharacterized. Given the importance of BCR-antigen internalization for antigen presentation in initiating adaptive immune responses and its role in autoimmunity and malignancy, understanding the molecular mechanisms represents critical, and largely untapped, potential therapeutics. In this review, we discuss recent advancements in our understanding of BCR endocytic mechanisms and the role of the actin cytoskeleton and post-translational modifications in regulating BCR uptake. We discuss dysregulated BCR endocytosis in the context of B cell malignancies and autoimmune disorders. Finally, we pose several outstanding mechanistic questions which will critically advance our understanding of the coordination between BCR endocytosis and B cell activation.
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Affiliation(s)
- Adam Nathan McShane
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom
| | - Dessislava Malinova
- Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, United Kingdom
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9
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Characterization of interactions within the Igα/Igβ transmembrane domains of the human B-cell receptor provides insights into receptor assembly. J Biol Chem 2022; 298:101843. [PMID: 35307351 PMCID: PMC9018394 DOI: 10.1016/j.jbc.2022.101843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 03/10/2022] [Accepted: 03/11/2022] [Indexed: 12/04/2022] Open
Abstract
The B-cell receptor (BCR), a complex comprised of a membrane-associated immunoglobulin and the Igα/β heterodimer, is one of the most important immune receptors in humans and controls B-cell development, activity, selection, and death. BCR signaling plays key roles in autoimmune diseases and lymphoproliferative disorders, yet, despite the clinical significance of this protein complex, key regions (i.e., the transmembrane domains) have yet to be structurally characterized. The mechanism for BCR signaling also remains unclear and has been variously described by the mutually exclusive cross-linking and dissociation activation models. Common to these models is the significance of local plasma membrane composition, which implies that interactions between BCR transmembrane domains (TMDs) play a role in receptor functionality. Here we used an in vivo assay of TMD oligomerization called GALLEX alongside spectroscopic and computational methods to characterize the structures and interactions of human Igα and Igβ TMDs in detergent micelles and natural membranes. We observed weak self-association of the Igβ TMD and strong self-association of the Igα TMD, which scanning mutagenesis revealed was entirely stabilized by an E–X10–P motif. We also demonstrated strong heterotypic interactions between the Igα and Igβ TMDs both in vitro and in vivo, which scanning mutagenesis and computational models suggest is multiconfigurational but can accommodate distinct interaction sites for self-interactions and heterotypic interactions of the Igα TMD. Taken together, these results demonstrate that the TMDs of the human BCR are sites of strong protein–protein interactions that may direct BCR assembly, endoplasmic reticulum retention, and immune signaling.
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Malinova D, Wasim L, Newman R, Martínez-Riaño A, Engels N, Tolar P. Endophilin A2 regulates B-cell endocytosis and is required for germinal center and humoral responses. EMBO Rep 2021; 22:e51328. [PMID: 34323351 PMCID: PMC8419706 DOI: 10.15252/embr.202051328] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 06/22/2021] [Accepted: 07/09/2021] [Indexed: 12/26/2022] Open
Abstract
Antigen‐specific B‐cell responses require endosomal trafficking to regulate antigen uptake and presentation to helper T cells, and to control expression and signaling of immune receptors. However, the molecular composition of B‐cell endosomal trafficking pathways and their specific roles in B‐cell responses have not been systematically investigated. Here, we report high‐throughput identification of genes regulating B‐cell receptor (BCR)‐mediated antigen internalization using genome‐wide functional screens. We show that antigen internalization depends both on constitutive, clathrin‐mediated endocytosis and on antigen‐induced, clathrin‐independent endocytosis mediated by endophilin A2. Although endophilin A2‐mediated endocytosis is dispensable for antigen presentation, it is selectively required for metabolic support of B‐cell proliferation, in part through regulation of iron uptake. Consequently, endophilin A2‐deficient mice show defects in GC B‐cell responses and production of high‐affinity IgG. The requirement for endophilin A2 highlights a unique importance of clathrin‐independent intracellular trafficking in GC B‐cell clonal expansion and antibody responses.
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Affiliation(s)
- Dessislava Malinova
- Immune Receptor Activation Laboratory, The Francis Crick Institute, London, UK.,Wellcome-Wolfson Institute for Experimental Medicine, Queen's University Belfast, Belfast, UK
| | - Laabiah Wasim
- Immune Receptor Activation Laboratory, The Francis Crick Institute, London, UK
| | - Rebecca Newman
- Immune Receptor Activation Laboratory, The Francis Crick Institute, London, UK
| | - Ana Martínez-Riaño
- Immune Receptor Activation Laboratory, The Francis Crick Institute, London, UK
| | - Niklas Engels
- Institute of Cellular & Molecular Immunology, University Medical Center Göttingen, Göttingen, Germany
| | - Pavel Tolar
- Immune Receptor Activation Laboratory, The Francis Crick Institute, London, UK.,Institute of Immunity and Transplantation, University College London, London, UK
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11
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SARS-CoV-2 Cellular Entry Is Independent of the ACE2 Cytoplasmic Domain Signaling. Cells 2021; 10:cells10071814. [PMID: 34359983 PMCID: PMC8304749 DOI: 10.3390/cells10071814] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/10/2021] [Accepted: 07/15/2021] [Indexed: 12/16/2022] Open
Abstract
Recently emerged severe acute respiratory syndrome coronavirus (SARS-CoV)-1 and -2 initiate virus infection by binding of their spike glycoprotein with the cell-surface receptor angiotensin-converting enzyme 2 (ACE2) and enter into the host cells mainly via the clathrin-mediated endocytosis pathway. However, the internalization process post attachment with the receptor is not clear for both SARS-CoV-1 and -2. Understanding the cellular factor/s or pathways used by these CoVs for internalization might provide insights into viral pathogenesis, transmission, and development of novel therapeutics. Here, we demonstrated that the cytoplasmic tail of ACE2 is not essential for the entry of SARS-CoV-1 and -2 by using bioinformatics, mutational, confocal imaging, and pseudotyped SARS-CoVs infection studies. ACE2 cytoplasmic domain (cytACE2) contains a conserved internalization motif and eight putative phosphorylation sites. Complete cytoplasmic domain deleted ACE2 (∆cytACE2) was properly synthesized and presented on the surface of HEK293T and BHK21 cells like wtACE2. The SARS-CoVs S1 or RBD of spike protein binds and colocalizes with the receptors followed by internalization into the host cells. Moreover, pseudotyped SARS-CoVs entered into wtACE2- and ∆cytACE2-transfected cells but not into dipeptidyl peptidase 4 (DPP4)-expressing cells. Their entry was significantly inhibited by treatment with dynasore, a dynamin inhibitor, and NH4Cl, an endosomal acidification inhibitor. Furthermore, SARS-CoV antibodies and the soluble form of ACE2-treated pseudotyped SARS-CoVs were unable to enter the wtACE2 and ∆cytACE2-expressing cells. Altogether, our data show that ACE2 cytoplasmic domain signaling is not essential for the entry of SARS-CoV-1 and -2 and that SARS-CoVs entry might be mediated via known/unknown host factor/s.
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12
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Hammood M, Craig AW, Leyton JV. Impact of Endocytosis Mechanisms for the Receptors Targeted by the Currently Approved Antibody-Drug Conjugates (ADCs)-A Necessity for Future ADC Research and Development. Pharmaceuticals (Basel) 2021; 14:ph14070674. [PMID: 34358100 PMCID: PMC8308841 DOI: 10.3390/ph14070674] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/10/2021] [Accepted: 07/13/2021] [Indexed: 12/17/2022] Open
Abstract
Biologically-based therapies increasingly rely on the endocytic cycle of internalization and exocytosis of target receptors for cancer therapies. However, receptor trafficking pathways (endosomal sorting (recycling, lysosome localization) and lateral membrane movement) are often dysfunctional in cancer. Antibody-drug conjugates (ADCs) have revitalized the concept of targeted chemotherapy by coupling inhibitory antibodies to cytotoxic payloads. Significant advances in ADC technology and format, and target biology have hastened the FDA approval of nine ADCs (four since 2019). Although the links between aberrant endocytic machinery and cancer are emerging, the impact of dysregulated internalization processes of ADC targets and response rates or resistance have not been well studied. This is despite the reliance on ADC uptake and trafficking to lysosomes for linker cleavage and payload release. In this review, we describe what is known about all the target antigens for the currently approved ADCs. Specifically, internalization efficiency and relevant intracellular sorting activities are described for each receptor under normal processes, and when complexed to an ADC. In addition, we discuss aberrant endocytic processes that have been directly linked to preclinical ADC resistance mechanisms. The implications of endocytosis in regard to therapeutic effectiveness in the clinic are also described. Unexpectedly, information on endocytosis is scarce (absent for two receptors). Moreover, much of what is known about endocytosis is not in the context of receptor-ADC/antibody complexes. This review provides a deeper understanding of the pertinent principles of receptor endocytosis for the currently approved ADCs.
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Affiliation(s)
- Manar Hammood
- Departément de Medécine Nucléaire et Radiobiologie, Faculté de Medécine et des Sciences de la Santé, Centre Hospitalier Universitaire de Sherbrooke (CHUS), Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada;
| | - Andrew W. Craig
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada;
| | - Jeffrey V. Leyton
- Departément de Medécine Nucléaire et Radiobiologie, Faculté de Medécine et des Sciences de la Santé, Centre Hospitalier Universitaire de Sherbrooke (CHUS), Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada;
- Centre d’Imagerie Moleculaire, Centre de Recherche, CHUS, Sherbrooke, QC J1H 5N4, Canada
- Correspondence: ; Tel.: +1-819-346-1110
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13
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Sawalha Y, Maddocks K. Profile of Polatuzumab Vedotin in the Treatment of Patients with Relapsed/Refractory Non-Hodgkin Lymphoma: A Brief Report on the Emerging Clinical Data. Onco Targets Ther 2020; 13:5123-5133. [PMID: 32606733 PMCID: PMC7293382 DOI: 10.2147/ott.s219449] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 05/20/2020] [Indexed: 11/23/2022] Open
Abstract
Abstract Polatuzumab vedotin is an anti-CD79b antibody conjugated to monomethyl auristatin E that has shown significant clinical activity in follicular and diffuse large B-cell lymphoma (DLBCL) and is currently FDA-approved in combination with bendamustine and rituximab for patients with relapsed/refractory DLBCL. This review article summarizes data from clinical trials of polatuzumab and discusses its current role and future directions in the treatment of patients with B-cell non-Hodgkin lymphoma. Methods We conducted a literature search in PubMed and Google Scholar from inception to January 2020, using the following terms: polatuzumab and CD79. We also reviewed the package insert and available abstracts and posters presented at national and international meetings.
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Affiliation(s)
- Yazeed Sawalha
- Department of Internal Medicine, Division of Hematology, Arthur G. James Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, OH, USA
| | - Kami Maddocks
- Department of Internal Medicine, Division of Hematology, Arthur G. James Comprehensive Cancer Center, The Ohio State University Wexner Medical Center, Columbus, OH, USA
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14
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The role of actin and myosin in antigen extraction by B lymphocytes. Semin Cell Dev Biol 2019; 102:90-104. [PMID: 31862219 DOI: 10.1016/j.semcdb.2019.10.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 10/14/2019] [Accepted: 10/31/2019] [Indexed: 12/14/2022]
Abstract
B cells must extract antigens attached to the surface of antigen presenting cells to generate high-affinity antibodies. Antigen extraction requires force, and recent studies have implicated actomyosin-dependent pulling forces generated within the B cell as the major driver of antigen extraction. These actomyosin-dependent pulling forces also serve to test the affinity of the B cell antigen receptor for antigen prior to antigen extraction. Such affinity discrimination is central to the process of antibody affinity maturation. Here we review the evidence that actomyosin-dependent pulling forces generated within the B cell promote affinity discrimination and power antigen extraction. Our take on these critical B cell functions is influenced significantly by the recent identification of formin-generated, myosin-rich, concentric actin arcs in the medial portion of the T cell immune synapse, as B cells appear to contain a similar contractile actomyosin structure.
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Roe K, Shu GL, Draves KE, Giordano D, Pepper M, Clark EA. Targeting Antigens to CD180 but Not CD40 Programs Immature and Mature B Cell Subsets to Become Efficient APCs. THE JOURNAL OF IMMUNOLOGY 2019; 203:1715-1729. [PMID: 31484732 DOI: 10.4049/jimmunol.1900549] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/29/2019] [Indexed: 12/16/2022]
Abstract
Targeting Ags to the CD180 receptor activates both B cells and dendritic cells (DCs) to become potent APCs. After inoculating mice with Ag conjugated to an anti-CD180 Ab, B cell receptors were rapidly internalized. Remarkably, all B cell subsets, including even transitional 1 B cells, were programed to process, present Ag, and stimulate Ag-specific CD4+ T cells. Within 24-48 hours, Ag-specific B cells were detectable at T-B borders in the spleen; there, they proliferated in a T cell-dependent manner and induced the maturation of T follicular helper (TFH) cells. Remarkably, immature B cells were sufficient for the maturation of TFH cells after CD180 targeting: TFH cells were induced in BAFFR-/- mice (with only transitional 1 B cells) and not in μMT mice (lacking all B cells) following CD180 targeting. Unlike CD180 targeting, CD40 targeting only induced DCs but not B cells to become APCs and thus failed to efficiently induce TFH cell maturation, resulting in slower and lower-affinity IgG Ab responses. CD180 targeting induces a unique program in Ag-specific B cells and to our knowledge, is a novel strategy to induce Ag presentation in both DCs and B cells, especially immature B cells and thus has the potential to produce a broad range of Ab specificities. This study highlights the ability of immature B cells to present Ag to and induce the maturation of cognate TFH cells, providing insights toward vaccination of mature B cell-deficient individuals and implications in treating autoimmune disorders.
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Affiliation(s)
- Kelsey Roe
- Department of Immunology, University of Washington, Seattle, WA 98109
| | - Geraldine L Shu
- Department of Immunology, University of Washington, Seattle, WA 98109
| | - Kevin E Draves
- Department of Immunology, University of Washington, Seattle, WA 98109
| | - Daniela Giordano
- Department of Immunology, University of Washington, Seattle, WA 98109
| | - Marion Pepper
- Department of Immunology, University of Washington, Seattle, WA 98109
| | - Edward A Clark
- Department of Immunology, University of Washington, Seattle, WA 98109
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16
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Young RM, Phelan JD, Wilson WH, Staudt LM. Pathogenic B-cell receptor signaling in lymphoid malignancies: New insights to improve treatment. Immunol Rev 2019; 291:190-213. [PMID: 31402495 PMCID: PMC6693651 DOI: 10.1111/imr.12792] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 05/30/2019] [Indexed: 12/12/2022]
Abstract
Signals emanating from the B-cell receptor (BCR) promote proliferation and survival in diverse forms of B-cell lymphoma. Precision medicine strategies targeting the BCR pathway have been generally effective in treating lymphoma, but often fail to produce durable responses in diffuse large B-cell lymphoma (DLBCL), a common and aggressive cancer. New insights into DLBCL biology garnered from genomic analyses and functional proteogenomic studies have identified novel modes of BCR signaling in this disease. Herein, we describe the distinct roles of antigen-dependent and antigen-independent BCR signaling in different subtypes of DLBCL. We highlight mechanisms by which the BCR cooperates with TLR9 and mutant isoforms of MYD88 to drive sustained NF-κB activity in the activated B-cell-like (ABC) subtype of DLBCL. Finally, we discuss progress in detecting and targeting oncogenic BCR signaling to improve the survival of patients with lymphoma.
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MESH Headings
- Animals
- Autoantigens/immunology
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Germinal Center/immunology
- Germinal Center/metabolism
- Germinal Center/pathology
- Humans
- Leukemia, Lymphoid/diagnosis
- Leukemia, Lymphoid/etiology
- Leukemia, Lymphoid/metabolism
- Leukemia, Lymphoid/therapy
- Lymphoma/diagnosis
- Lymphoma/etiology
- Lymphoma/metabolism
- Lymphoma/therapy
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
- Signal Transduction
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Affiliation(s)
- Ryan M. Young
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD. 20892
| | - James D. Phelan
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD. 20892
| | - Wyndham H. Wilson
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD. 20892
| | - Louis M. Staudt
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD. 20892
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17
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Young RM, Phelan JD, Shaffer AL, Wright GW, Huang DW, Schmitz R, Johnson C, Oellerich T, Wilson W, Staudt LM. Taming the Heterogeneity of Aggressive Lymphomas for Precision Therapy. ANNUAL REVIEW OF CANCER BIOLOGY-SERIES 2019. [DOI: 10.1146/annurev-cancerbio-030518-055734] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genomic analyses of diffuse large B cell lymphoma (DLBCL) are revealing the genetic and phenotypic heterogeneity of these aggressive lymphomas. In part, this heterogeneity reflects the existence of distinct genetic subtypes that acquire characteristic constellations of somatic genetic alterations to converge on the DLBCL phenotype. In parallel, functional genomic screens and proteomic analyses have identified multiprotein assemblies that coordinate oncogenic survival signaling in DLBCL. In this review, we merge these recent insights into a unified conceptual framework with implications for the design of precision medicine trials in DLBCL.
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Affiliation(s)
- Ryan M. Young
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James D. Phelan
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Arthur L. Shaffer
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - George W. Wright
- Biometric Research Branch, Division of Cancer Diagnosis and Treatment, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Da Wei Huang
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Roland Schmitz
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Calvin Johnson
- Office of Intramural Research, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Thomas Oellerich
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Wyndham Wilson
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Louis M. Staudt
- Lymphoid Malignancies Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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18
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Mechanics of antigen extraction in the B cell synapse. Mol Immunol 2018; 101:319-328. [PMID: 30036798 DOI: 10.1016/j.molimm.2018.07.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 07/11/2018] [Indexed: 12/16/2022]
Abstract
B cell encounter with antigen displayed on antigen-presenting cells leads to B cell immune synapse formation, internalisation of the antigen, and stimulation of antibody responses. The sensitivity with which B cells detect antigen, and the quality and quantity of antigen that B cells acquire, depend upon mechanical properties of the immune synapse including interfacial tension, the strength of intermolecular bonds, and the compliance of the molecules and membranes that participate in antigen presentation. In this review, we discuss our current understanding of how these various physical parameters influence B cell antigen extraction in the immune synapse and how a more comprehensive understanding of B cell mechanics may promote the development of new approaches to stimulate the production of desired antibodies.
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19
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Drake JR. The immunobiology of ubiquitin-dependent B cell receptor functions. Mol Immunol 2018; 101:146-154. [PMID: 29940407 DOI: 10.1016/j.molimm.2018.05.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 04/29/2018] [Accepted: 05/24/2018] [Indexed: 02/01/2023]
Abstract
MHC class II-restricted antigen presentation by dendritic cells is necessary for activation of naïve CD4 T cells, whereas class II-restricted antigen presentation by B lymphocytes and macrophages is important for the recruitment of CD4+ helper and regulatory T cells. Antigen presentation by B cells is also important for induction of T cell tolerance. B cells are unique among these three types of MHC class II-expressing antigen presenting cells (APC) as they constitutively express high levels of cell surface class II molecules and express a clonally restricted antigen specific receptor, the B cell receptor (BCR). Here, I review our current understanding of three major steps that underlie the processing and presentation of BCR-bound cognate antigen: (1) endocytosis of antigen-BCR (Ag-BCR) complexes, (2) Ag-BCR trafficking to intracellular antigen processing compartments and (3) generation of antigenic peptide-MHC class II complexes, with a particular focus on the role of BCR ubiquitination in each. I will highlight potential topics for future research and briefly discuss the impact of the cell biology of BCR-mediated antigen processing on the response of the B cell and T cell to the cell-cell interactions mediated by B cell-expressed peptide-class II complexes.
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Affiliation(s)
- James R Drake
- Albany Medical College, Department of Immunology and Microbial Disease, 47 New Scotland Ave., MC-151, Albany, NY 12208-3479, United States.
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20
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Del Valle Batalla F, Lennon-Dumenil AM, Yuseff MI. Tuning B cell responses to antigens by cell polarity and membrane trafficking. Mol Immunol 2018; 101:140-145. [PMID: 29935436 DOI: 10.1016/j.molimm.2018.06.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 06/01/2018] [Accepted: 06/09/2018] [Indexed: 01/01/2023]
Abstract
The capacity of B lymphocytes to produce specific antibodies, particularly broadly neutralizing antibodies that provide immunity to viral pathogens has positioned them as valuable therapeutic targets for immunomodulation. To become competent as antibody secreting cells, B cells undergo a series of activation steps, which are triggered by the recognition of antigens frequently displayed on the surface of other presenting cells. Such antigens elicit the formation of an immune synapse (IS), where local cytoskeleton rearrangements coupled to mechanical forces and membrane trafficking orchestrate the extraction and processing of antigens in B cells. In this review, we discuss the molecular mechanisms that regulate polarized membrane trafficking and mechanical properties of the immune synapse, as well as the potential extracellular cues from the environment, which may impact the ability of B cells to sense and acquire antigens at the immune synapse. An integrated view of the diverse cellular mechanisms that shape the immune synapse will provide a better understanding on how B cells are efficiently activated.
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Affiliation(s)
- Felipe Del Valle Batalla
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
| | | | - María-Isabel Yuseff
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile.
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21
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Westbroek ML, Geahlen RL. Modulation of BCR Signaling by the Induced Dimerization of Receptor-Associated SYK. Antibodies (Basel) 2017; 6:antib6040023. [PMID: 31548538 PMCID: PMC6698873 DOI: 10.3390/antib6040023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 11/27/2017] [Accepted: 12/02/2017] [Indexed: 01/14/2023] Open
Abstract
Clustering of the B cell antigen receptor (BCR) by polyvalent antigens is transmitted through the SYK tyrosine kinase to the activation of multiple intracellular pathways that determine the physiological consequences of receptor engagement. To explore factors that modulate the quantity and quality of signals sent by the crosslinked BCR, we developed a novel chemical mediator of dimerization to induce clustering of receptor-associated SYK. To accomplish this, we fused SYK with E. coli dihydrofolate reductase (eDHFR), which binds the small molecule trimethoprim (TMP) with high affinity and selectivity and synthesized a dimer of TMP with a flexible linker. The TMP dimer is able to induce the aggregation of eDHFR-linked SYK in live cells. The induced dimerization of SYK bound to the BCR differentially regulates the activation of downstream transcription factors, promoting the activation of Nuclear Factor of Activated T cells (NFAT) without affecting the activation of NFκB. The dimerization of SYK enhances the duration but not the amplitude of calcium mobilization by enhancing the extent and duration of its interaction with the crosslinked BCR at the plasma membrane.
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Affiliation(s)
- Mark L Westbroek
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA.
| | - Robert L Geahlen
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA.
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22
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Abstract
Immune tolerance hinders the potentially destructive responses of lymphocytes to host tissues. Tolerance is regulated at the stage of immature B cell development (central tolerance) by clonal deletion, involving apoptosis, and by receptor editing, which reprogrammes the specificity of B cells through secondary recombination of antibody genes. Recent mechanistic studies have begun to elucidate how these divergent mechanisms are controlled. Single-cell antibody cloning has revealed defects of B cell central tolerance in human autoimmune diseases and in several human immunodeficiency diseases caused by single gene mutations, which indicates the relevance of B cell tolerance to disease and suggests possible genetic pathways that regulate tolerance.
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23
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Adler LN, Jiang W, Bhamidipati K, Millican M, Macaubas C, Hung SC, Mellins ED. The Other Function: Class II-Restricted Antigen Presentation by B Cells. Front Immunol 2017; 8:319. [PMID: 28386257 PMCID: PMC5362600 DOI: 10.3389/fimmu.2017.00319] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 03/07/2017] [Indexed: 12/31/2022] Open
Abstract
Mature B lymphocytes (B cells) recognize antigens using their B cell receptor (BCR) and are activated to become antibody-producing cells. In addition, and integral to the development of a high-affinity antibodies, B cells utilize the specialized major histocompatibility complex class II (MHCII) antigen presentation pathway to process BCR-bound and internalized protein antigens and present selected peptides in complex with MHCII to CD4+ T cells. This interaction influences the fate of both types of lymphocytes and shapes immune outcomes. Specific, effective, and optimally timed antigen presentation by B cells requires well-controlled intracellular machinery, often regulated by the combined effects of several molecular events. Here, we delineate and summarize these events in four steps along the antigen presentation pathway: (1) antigen capture and uptake by B cells; (2) intersection of internalized antigen/BCRs complexes with MHCII in peptide-loading compartments; (3) generation and regulation of MHCII/peptide complexes; and (4) exocytic transport for presentation of MHCII/peptide complexes at the surface of B cells. Finally, we discuss modulation of the MHCII presentation pathway across B cell development and maturation to effector cells, with an emphasis on the shaping of the MHCII/peptide repertoire by two key antigen presentation regulators in B cells: HLA-DM and HLA-DO.
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Affiliation(s)
- Lital N Adler
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Wei Jiang
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | | | | | - Claudia Macaubas
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Shu-Chen Hung
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
| | - Elizabeth D Mellins
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Program in Immunology, Stanford University, Stanford, CA, USA
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24
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Abstract
The importance of understanding the genetic and biochemical basis of B-cell receptor (BCR) survival signaling in diffuse large B-cell lymphoma (DLBCL) is underscored by the recent clinical success of agents that target the BCR pathway. DLBCL is composed of multiple distinct molecular subtypes with divergent clinical outcomes. The activated B-cell-like (ABC) subtype is the most aggressive form of DLBCL and is often resistant to standard chemotherapies. ABC DLBCL expresses numerous genes found in antigen-activated B cells, and genetic and pharmacologic studies have demonstrated that ABC DLBCL tumors are addicted to NF-κB activity. The origins of this NF-κB activity remained obscure until RNA interference screens established that the majority of ABC DLBCL cell lines rely on expression of BCR components and downstream signaling effectors for NF-κB activation. Pharmacological inhibition with ibrutinib of Bruton's tyrosine kinase, a kinase that is required for BCR signaling to engage NF-κB, is selectively toxic for ABC DLBCL tumors; a finding that has now been translated to the clinic. These novel targets not only offer a promising new therapy option for ABC DLBCL, but also demonstrate the value of a deep molecular understanding of oncogenic signaling pathways.
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Affiliation(s)
- Ryan M Young
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - Arthur L Shaffer
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - James D Phelan
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD
| | - Louis M Staudt
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.
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25
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Hoogeboom R, Tolar P. Molecular Mechanisms of B Cell Antigen Gathering and Endocytosis. Curr Top Microbiol Immunol 2015; 393:45-63. [PMID: 26336965 DOI: 10.1007/82_2015_476] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Generation of high-affinity, protective antibodies requires B cell receptor (BCR) signaling, as well as antigen internalization and presentation to helper T cells. B cell antigen internalization is initiated by antigen capture, either from solution or from immune synapses formed on the surface of antigen-presenting cells, and proceeds via clathrin-dependent endocytosis and intracellular routing to late endosomes. Although the components of this pathway are still being discovered, it has become clear that antigen internalization is actively regulated by BCR signaling at multiple steps and, vice versa, that localization of the BCR along the endocytic pathway modulates signaling. Accordingly, defects in BCR internalization or trafficking contribute to enhanced B cell activation in models of autoimmune diseases and in B cell lymphomas. In this review, we discuss how BCR signaling complexes regulate each of the steps of this endocytic process and why defects along this pathway manifest as hyperactive B cell responses in vivo.
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Affiliation(s)
- Robbert Hoogeboom
- Division of Immune Cell Biology, National Institute for Medical Research, Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London, NW7 1AA, UK
| | - Pavel Tolar
- Division of Immune Cell Biology, National Institute for Medical Research, Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, London, NW7 1AA, UK.
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26
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Purdy AK, Alvarez Arias DA, Oshinsky J, James AM, Serebriiskii I, Campbell KS. The ap-2 clathrin adaptor mediates endocytosis of an inhibitory killer cell Ig-like receptor in human NK cells. THE JOURNAL OF IMMUNOLOGY 2014; 193:4675-83. [PMID: 25238755 DOI: 10.4049/jimmunol.1303406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Stable surface expression of human inhibitory killer cell Ig-like receptors (KIRs) is critical for controlling NK cell function and maintaining NK cell tolerance toward normal MHC class I(+) cells. Our recent experiments, however, have found that Ab-bound KIR3DL1 (3DL1) readily leaves the cell surface and undergoes endocytosis to early/recycling endosomes and subsequently to late endosomes. We found that 3DL1 internalization is at least partially mediated by an interaction between the μ2 subunit of the AP-2 clathrin adaptor complex and ITIM tyrosine residues in the cytoplasmic domain of 3DL1. Disruption of the 3DL1/μ2 interaction, either by mutation of the ITIM tyrosines in 3DL1 or mutation of μ2, significantly diminished endocytosis and increased surface expression of 3DL1 in human primary NK cells and cell lines. Furthermore, we found that the 3DL1/AP-2 interaction is diminished upon Ab engagement with the receptor, as compared with untreated cells. Thus, we have identified AP-2-mediated endocytosis as a mechanism regulating the surface levels of inhibitory KIRs through their ITIM domains. Based on our results, we propose a model in which nonengaged KIRs are internalized by this mechanism, whereas engagement with MHC class I ligand would diminish AP-2 binding, thereby prolonging stable receptor surface expression and promoting inhibitory function. Furthermore, this ITIM-mediated mechanism may similarly regulate the surface expression of other inhibitory immune receptors.
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Affiliation(s)
- Amanda K Purdy
- Immune Cell Development and Host Defense Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Diana A Alvarez Arias
- Immune Cell Development and Host Defense Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Jennifer Oshinsky
- Immune Cell Development and Host Defense Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Ashley M James
- Immune Cell Development and Host Defense Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111
| | - Ilya Serebriiskii
- Developmental Therapeutics Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111; and Kazan Federal University, Kazan 420008, Russia
| | - Kerry S Campbell
- Immune Cell Development and Host Defense Program, Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111;
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