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Zhou JZ, Huang B, Pei B, Sun GW, Pawlitz MD, Zhang W, Li X, Hokynar KC, Yao F, Perera MLW, Wei S, Zheng S, Polin LA, Poulik JM, Ranki A, Krohn K, Cunningham-Rundles C, Yang N, Bhagwat AS, Yu K, Peterson P, Kisand K, Vuong BQ, Cerutti A, Chen K. A Germinal Center Checkpoint of AIRE in B Cells Limits Antibody Diversification. bioRxiv 2024:2024.01.10.574926. [PMID: 38260362 PMCID: PMC10802573 DOI: 10.1101/2024.01.10.574926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
In response to antigens, B cells undergo affinity maturation and class switching mediated by activation-induced cytidine deaminase (AID) in germinal centers (GCs) of secondary lymphoid organs, but uncontrolled AID activity can precipitate autoimmunity and cancer. The regulation of GC antibody diversification is of fundamental importance but not well understood. We found that autoimmune regulator (AIRE), the molecule essential for T cell tolerance, is expressed in GC B cells in a CD40-dependent manner, interacts with AID and negatively regulates antibody affinity maturation and class switching by inhibiting AID function. AIRE deficiency in B cells caused altered antibody repertoire, increased somatic hypermutations, elevated autoantibodies to T helper 17 effector cytokines and defective control of skin Candida albicans. These results define a GC B cell checkpoint of humoral immunity and illuminate new approaches of generating high-affinity neutralizing antibodies for immunotherapy.
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Affiliation(s)
- Jordan Z Zhou
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI 48201, USA
- These authors contributed equally
| | - Bihui Huang
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
- The Seventh Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518107, China
- These authors contributed equally
| | - Bo Pei
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
| | - Guang Wen Sun
- School of Applied Science, Republic Polytechnic, Singapore 738984, Singapore
| | - Michael D Pawlitz
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
| | - Wei Zhang
- Beijing Genomics Institute (BGI)-Shenzhen, Guangdong 518083, China
| | - Xinyang Li
- Beijing Genomics Institute (BGI)-Shenzhen, Guangdong 518083, China
| | - Kati C Hokynar
- Department of Virology, University of Helsinki, Helsinki 00029, Finland
| | - Fayi Yao
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI 48201, USA
| | | | - Shanqiao Wei
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
| | - Simin Zheng
- School of Biological Sciences, Nanyang Technological University, Singapore 636921, Singapore
| | - Lisa A Polin
- Barbara Ann Karmanos Cancer Institute, Department of Oncology, Wayne State University, Detroit, MI 48201, USA
| | - Janet M Poulik
- Department of Pathology, Children's Hospital of Michigan, Detroit, MI 48201, USA
| | - Annamari Ranki
- Department of Dermatology and Allergic Diseases, University of Helsinki and Helsinki University Hospital, Helsinki 00250, Finland
| | - Kai Krohn
- Helsinki University Hospital Research Institute, Biomedicum, Helsinki 00290, Finland
| | | | - Naibo Yang
- Beijing Genomics Institute (BGI)-Shenzhen, Guangdong 518083, China
- Complete Genomics Inc., Mountain View, California 94043, USA
| | - Ashok S Bhagwat
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
- Department of Biochemistry, Microbiology and Immunology, Wayne State University, Detroit, MI 48201, USA
| | - Kefei Yu
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Pärt Peterson
- Department of Molecular Pathology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia
| | - Kai Kisand
- Department of Molecular Pathology, Institute of Biomedicine and Translational Medicine, University of Tartu, Tartu 50411, Estonia
| | - Bao Q Vuong
- Department of Biology, City College of New York, New York, NY 10031, USA
| | - Andrea Cerutti
- Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Mucosal Immunology Studies Team, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Maryland 20892, USA
| | - Kang Chen
- Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI 48201, USA
- School of Biological Sciences, Nanyang Technological University, Singapore 636921, Singapore
- Lead Contact
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Kabrani E, Saha T, Di Virgilio M. DNA repair and antibody diversification: the 53BP1 paradigm. Trends Immunol 2023; 44:782-791. [PMID: 37640588 DOI: 10.1016/j.it.2023.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/31/2023]
Abstract
The DNA double-strand break (DSB) repair factor 53BP1 has long been implicated in V(D)J and class switch recombination (CSR) of mammalian lymphocyte receptors. However, the dissection of the underlying molecular activities is hampered by a paucity of studies [V(D)J] and plurality of phenotypes (CSR) associated with 53BP1 deficiency. Here, we revisit the currently accepted roles of 53BP1 in antibody diversification in view of the recent identification of its downstream effectors in DSB protection and latest advances in genome architecture. We propose that, in addition to end protection, 53BP1-mediated end-tethering stabilization is essential for CSR. Furthermore, we support a pre-DSB role during V(D)J recombination. Our perspective underscores the importance of evaluating repair of DSBs in relation to their dynamic architectural contexts.
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Affiliation(s)
- Eleni Kabrani
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany.
| | - Tannishtha Saha
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany; Freie Universität Berlin, Berlin 14195, Germany
| | - Michela Di Virgilio
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany; Charité-Universitätsmedizin Berlin, Berlin 10117, Germany.
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Luo S, Qiao R, Zhang X. DNA Damage Response and Repair in Adaptive Immunity. Front Cell Dev Biol 2022; 10:884873. [PMID: 35663402 PMCID: PMC9157429 DOI: 10.3389/fcell.2022.884873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 03/31/2022] [Indexed: 11/16/2022] Open
Abstract
The diversification of B-cell receptor (BCR), as well as its secreted product, antibody, is a hallmark of adaptive immunity, which has more specific roles in fighting against pathogens. The antibody diversification is from recombination-activating gene (RAG)-initiated V(D)J recombination, activation-induced cytidine deaminase (AID)-initiated class switch recombination (CSR), and V(D)J exon somatic hypermutation (SHM). The proper repair of RAG- and AID-initiated DNA lesions and double-strand breaks (DSBs) is required for promoting antibody diversification, suppressing genomic instability, and oncogenic translocations. DNA damage response (DDR) factors and DSB end-joining factors are recruited to the RAG- and AID-initiated DNA lesions and DSBs to coordinately resolve them for generating productive recombination products during antibody diversification. Recently, cohesin-mediated loop extrusion is proposed to be the underlying mechanism of V(D)J recombination and CSR, which plays essential roles in promoting the orientation-biased deletional end-joining . Here, we will discuss the mechanism of DNA damage repair in antibody diversification.
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Affiliation(s)
- Sha Luo
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
- Academy for Advanced Interdisciplinery Studies, Peking University, Beijing, China
| | - Ruolin Qiao
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
- Academy for Advanced Interdisciplinery Studies, Peking University, Beijing, China
| | - Xuefei Zhang
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
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Zhong X, D’Antona AM, Scarcelli JJ, Rouse JC. New Opportunities in Glycan Engineering for Therapeutic Proteins. Antibodies (Basel) 2022; 11:5. [PMID: 35076453 PMCID: PMC8788452 DOI: 10.3390/antib11010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 12/22/2021] [Accepted: 12/31/2021] [Indexed: 11/17/2022] Open
Abstract
Glycans as sugar polymers are important metabolic, structural, and physiological regulators for cellular and biological functions. They are often classified as critical quality attributes to antibodies and recombinant fusion proteins, given their impacts on the efficacy and safety of biologics drugs. Recent reports on the conjugates of N-acetyl-galactosamine and mannose-6-phosphate for lysosomal degradation, Fab glycans for antibody diversification, as well as sialylation therapeutic modulations and O-linked applications, have been fueling the continued interest in glycoengineering. The current advancements of the human glycome and the development of a comprehensive network in glycosylation pathways have presented new opportunities in designing next-generation therapeutic proteins.
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Affiliation(s)
- Xiaotian Zhong
- BioMedicine Design, Medicinal Sciences, Pfizer Worldwide R&D, 610 Main Street, Cambridge, MA 02139, USA;
| | - Aaron M. D’Antona
- BioMedicine Design, Medicinal Sciences, Pfizer Worldwide R&D, 610 Main Street, Cambridge, MA 02139, USA;
| | - John J. Scarcelli
- BioProcess R&D, Biotherapeutics Pharmaceutical Sciences, Medicinal Sciences, Pfizer Worldwide R&D, 1 Burtt Road, Andover, MA 01810, USA;
| | - Jason C. Rouse
- Analytical R&D, Biotherapeutics Pharmaceutical Sciences, Medicinal Sciences, Pfizer Worldwide R&D, 1 Burtt Road, Andover, MA 01810, USA;
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Mueller S. Rarely Recognized Antibody Diversification in Covid-19 Evolution to Counteract Advanced SARS-CoV-2 Evasion Strategies, and Implications for Prophylactic Treatment. Front Physiol 2021; 12:624675. [PMID: 34413782 PMCID: PMC8369989 DOI: 10.3389/fphys.2021.624675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 07/06/2021] [Indexed: 11/13/2022] Open
Abstract
The ongoing Covid-19 pandemic underscores the importance of finding effective and safe ways to combat the virus, and to optimally understand the immune response elicited upon natural infection. This likely involves all components of the immune system, both innate and adaptive. The impetus for the rapid development of prophylactic treatment options has led to an intense focus on neutralizing antibodies (Abs), and many novel and specialized platforms have been designed to achieve that goal. B-cell immunity relies on the generation of a diverse repertoire of Abs. Their structural variation is defined in terms of amino acid composition that is encoded in the genome or acquired through somatic mutations. Yet, key examples of frequently neglected antibody diversification mechanisms involving post-translational modifications such as N- or O-linked glycosylation are present in significant portions of the population. During the last few years, these and other beyond gene sequence determined humoral immune response mechanisms have in some specific cases revealed their potent immunomodulatory effects. Nonetheless, such more unusual mechanisms have not received much attention in the context of SARS-CoV-2. Thus, with specific focus on the latter, this paper presents, (1) the rationale for considering beyond sequence determined strategies, (2) evidence for their possible involvement in Covid-19 disease evolution, (3) consequences for vaccine design exemplified by one of the vaccine candidates that is currently undergoing trial, and (4) more general implications. Based on a critical interpretation of published literature, the hypotheses developed in this study point to a crucial role of non-genetic antibody diversification mechanisms in disease evolution to counteract unique immunogenicity determinants of SARS-CoV-2 infection. The involvement of post translational mechanisms may also help explain the widely varied immune response observed, not only among different patient groups, but also in terms of their observed incompatibility with SARS-CoV-2 infection in several human cell types. The article highlights potentials and challenges of these refined humoral immune response mechanisms to most optimally target non-genetic viral evasion strategies.
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Liu LD, Huang M, Dai P, Liu T, Fan S, Cheng X, Zhao Y, Yeap LS, Meng FL. Intrinsic Nucleotide Preference of Diversifying Base Editors Guides Antibody Ex Vivo Affinity Maturation. Cell Rep 2019; 25:884-892.e3. [PMID: 30355495 DOI: 10.1016/j.celrep.2018.09.090] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/13/2018] [Accepted: 09/27/2018] [Indexed: 12/27/2022] Open
Abstract
Base editors (BEs) are emerging tools used for precision correction or diversifying mutation. It provides a potential way to recreate somatic hypermutations (SHM) for generating high-affinity antibody, which is usually screened from antigen-challenged animal models or synthetic combinatorial libraries. By comparing somatic mutations in the same genomic context, we screened engineered deaminases and CRISPR-deaminase coupling approaches and updated diversifying base editors (DBEs) to generate SHM. The deaminase used in DBEs retains its intrinsic nucleotide preference and mutates cytidines at its preferred motifs. DBE with AID targets the same hotspots as physiological AID does in vivo, while DBE with other deaminases generates distinct mutation profiles from the same DNA substrate. Downstream DNA repair pathways further diversified the sequence, while Cas9-nickase restricted mutation spreading. Finally, application of DBE in an antibody display system achieved antibody affinity maturation ex vivo. Our findings provide insight of DBE working mechanism and an alternative antibody engineering approach.
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Affiliation(s)
- Liu Daisy Liu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Min Huang
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Pengfei Dai
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Tingting Liu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Shuangshuang Fan
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Xueqian Cheng
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Yaofeng Zhao
- State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing 100193, China
| | - Leng-Siew Yeap
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Fei-Long Meng
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China.
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Tan J, Piccoli L, Lanzavecchia A. The Antibody Response to Plasmodium falciparum: Cues for Vaccine Design and the Discovery of Receptor-Based Antibodies. Annu Rev Immunol 2018; 37:225-246. [PMID: 30566366 DOI: 10.1146/annurev-immunol-042617-053301] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Plasmodium falciparum remains a serious public health problem and a continuous challenge for the immune system due to the complexity and diversity of the pathogen. Recent advances from several laboratories in the characterization of the antibody response to the parasite have led to the identification of critical targets for protection and revealed a new mechanism of diversification based on the insertion of host receptors into immunoglobulin genes, leading to the production of receptor-based antibodies. These advances have opened new possibilities for vaccine design and passive antibody therapies to provide sterilizing immunity and control blood-stage parasites.
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Affiliation(s)
- Joshua Tan
- Institute for Research in Biomedicine, Università della Svizzera italiana, 6500 Bellinzona, Switzerland; .,Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom.,Current affiliation: National Institute of Allergy and Infectious Diseases, Rockville, Maryland 20852, USA
| | - Luca Piccoli
- Institute for Research in Biomedicine, Università della Svizzera italiana, 6500 Bellinzona, Switzerland;
| | - Antonio Lanzavecchia
- Institute for Research in Biomedicine, Università della Svizzera italiana, 6500 Bellinzona, Switzerland; .,VIR Biotechnology, San Francisco, California 94158, USA
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van de Bovenkamp FS, Derksen NIL, Ooijevaar-de Heer P, van Schie KA, Kruithof S, Berkowska MA, van der Schoot CE, IJspeert H, van der Burg M, Gils A, Hafkenscheid L, Toes REM, Rombouts Y, Plomp R, Wuhrer M, van Ham SM, Vidarsson G, Rispens T. Adaptive antibody diversification through N-linked glycosylation of the immunoglobulin variable region. Proc Natl Acad Sci U S A 2018; 115:1901-6. [PMID: 29432186 DOI: 10.1073/pnas.1711720115] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A hallmark of B-cell immunity is the generation of a diverse repertoire of antibodies from a limited set of germline V(D)J genes. This repertoire is usually defined in terms of amino acid composition. However, variable domains may also acquire N-linked glycans, a process conditional on the introduction of consensus amino acid motifs (N-glycosylation sites) during somatic hypermutation. High levels of variable domain glycans have been associated with autoantibodies in rheumatoid arthritis, as well as certain follicular lymphomas. However, the role of these glycans in the humoral immune response remains poorly understood. Interestingly, studies have reported both positive and negative effects on antibody affinity. Our aim was to elucidate the role of variable domain glycans during antigen-specific antibody responses. By analyzing B-cell repertoires by next-generation sequencing, we demonstrate that N-glycosylation sites are introduced at positions in which glycans can affect antigen binding as a result of a specific clustering of progenitor glycosylation sites in the germline sequences of variable domain genes. By analyzing multiple human monoclonal and polyclonal (auto)antibody responses, we subsequently show that this process is subject to selection during antigen-specific antibody responses, skewed toward IgG4, and positively contributes to antigen binding. Together, these results highlight a physiological role for variable domain glycosylation as an additional layer of antibody diversification that modulates antigen binding.
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Affiliation(s)
- Stephen P Methot
- Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
- Department of Medicine, McGill University, Montreal, QC, Canada
| | - Javier M Di Noia
- Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
- Department of Medicine, McGill University, Montreal, QC, Canada
- Department of Medicine, Université de Montréal, Montréal, QC, Canada
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Bak ST, Sakellariou D, Pena-Diaz J. The dual nature of mismatch repair as antimutator and mutator: for better or for worse. Front Genet 2014; 5:287. [PMID: 25191341 PMCID: PMC4139959 DOI: 10.3389/fgene.2014.00287] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 08/04/2014] [Indexed: 01/19/2023] Open
Abstract
DNA is constantly under attack by a number of both exogenous and endogenous agents that challenge its integrity. Among the mechanisms that have evolved to counteract this deleterious action, mismatch repair (MMR) has specialized in removing DNA biosynthetic errors that occur when replicating the genome. Malfunction or inactivation of this system results in an increase in spontaneous mutability and a strong predisposition to tumor development. Besides this key corrective role, MMR proteins are involved in other pathways of DNA metabolism such as mitotic and meiotic recombination and processing of oxidative damage. Surprisingly, MMR is also required for certain mutagenic processes. The mutagenic MMR has beneficial consequences contributing to the generation of a vast repertoire of antibodies through class switch recombination and somatic hypermutation processes. However, this non-canonical mutagenic MMR also has detrimental effects; it promotes repeat expansions associated with neuromuscular and neurodegenerative diseases and may contribute to cancer/disease-related aberrant mutations and translocations. The reaction responsible for replication error correction has been the most thoroughly studied and it is the subject to numerous reviews. This review describes briefly the biochemistry of MMR and focuses primarily on the non-canonical MMR activities described in mammals as well as emerging research implicating interplay of MMR and chromatin.
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Affiliation(s)
- Sara Thornby Bak
- Department of Neuroscience and Pharmacology and Center for Healthy Aging, University of Copenhagen Copenhagen, Denmark
| | - Despoina Sakellariou
- Department of Neuroscience and Pharmacology and Center for Healthy Aging, University of Copenhagen Copenhagen, Denmark
| | - Javier Pena-Diaz
- Department of Neuroscience and Pharmacology and Center for Healthy Aging, University of Copenhagen Copenhagen, Denmark
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Li G, Pone EJ, Tran DC, Patel PJ, Dao L, Xu Z, Casali P. Iron inhibits activation-induced cytidine deaminase enzymatic activity and modulates immunoglobulin class switch DNA recombination. J Biol Chem 2012; 287:21520-9. [PMID: 22556412 PMCID: PMC3375573 DOI: 10.1074/jbc.m112.366732] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 04/26/2012] [Indexed: 12/31/2022] Open
Abstract
Immunoglobulin (Ig) class switch DNA recombination (CSR) and somatic hypermutation (SHM) are critical for the maturation of the antibody response. Activation-induced cytidine deaminase (AID) initiates CSR and SHM by deaminating deoxycytidines (dCs) in switch (S) and V(D)J region DNA, respectively, to generate deoxyuracils (dUs). Processing of dUs by uracil DNA glycosylase (UNG) yields abasic sites, which are excised by apurinic/apyrimidinic endonucleases, eventually generating double strand DNA breaks, the obligatory intermediates of CSR. Here, we found that the bivalent iron ion (Fe(2+), ferrous) suppressed CSR, leading to decreased number of switched B cells, decreased postrecombination Iμ-C(H) transcripts, and reduced titers of secreted class-switched IgG1, IgG3, and IgA antibodies, without alterations in critical CSR factors, such as AID, 14-3-3γ, or PTIP, or in general germline I(H)-S-C(H) transcription. Fe(2+) did not affect B cell proliferation or plasmacytoid differentiation. Rather, it inhibited AID-mediated dC deamination in a dose-dependent fashion. The inhibition of intrinsic AID enzymatic activity by Fe(2+) was specific, as shown by lack of inhibition of AID-mediated dC deamination by other bivalent metal ions, such as Zn(2+), Mn(2+), Mg(2+), or Ni(2+), and the inability of Fe(2+) to inhibit UNG-mediated dU excision. Overall, our findings have outlined a novel role of iron in modulating a B cell differentiation process that is critical to the generation of effective antibody responses to microbial pathogens and tumoral cells. They also suggest a possible role of iron in dampening AID-dependent autoimmunity and neoplastic transformation.
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Affiliation(s)
- Guideng Li
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Egest J. Pone
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Daniel C. Tran
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Pina J. Patel
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Lisa Dao
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Zhenming Xu
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
| | - Paolo Casali
- From the Institute for Immunology and Department of Medicine, School of Medicine, University of California, Irvine, California 92697-4120
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Ellyard JI, Benk AS, Taylor B, Rada C, Neuberger MS. The dependence of Ig class-switching on the nuclear export sequence of AID likely reflects interaction with factors additional to Crm1 exportin. Eur J Immunol 2011; 41:485-90. [PMID: 21268017 PMCID: PMC3437479 DOI: 10.1002/eji.201041011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 10/21/2010] [Accepted: 11/09/2010] [Indexed: 01/31/2023]
Abstract
Activation-induced deaminase (AID) is a B lymphocyte-specific DNA deaminase that triggers Ig class-switch recombination (CSR) and somatic hypermutation. It shuttles between cytoplasm and nucleus, containing a nuclear export sequence (NES) at its carboxyterminus. Intriguingly, the precise nature of this NES is critical to AID's function in CSR, though not in somatic hypermutation. Many alterations to the NES, while preserving its nuclear export function, destroy CSR ability. We have previously speculated that AID's ability to potentiate CSR may critically depend on the affinity of interaction between its NES and Crm1 exportin. Here, however, by comparing multiple AID NES mutants, we find that - beyond a requirement for threshold Crm1 binding - there is little correlation between CSR and Crm1 binding affinity. The results suggest that CSR, as well as the stabilisation of AID, depend on an interaction between the AID C-terminal decapeptide and factor(s) additional to Crm1.
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Affiliation(s)
- Julia I Ellyard
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge, UK
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Abstract
Activation induced deaminase (AID) is a unique enzyme that directly introduces mutations in the immunoglobulin genes to generate antibody diversity during the humoral immune response. Since this mutator enzyme poses a measurable risk of off-target mutation, which can be deleterious or transforming for a cell, several regulatory mechanisms exist to control its activity. At least three of these mechanisms affect AID subcellular localization. It was recently found that AID is actively imported into the nucleus, most likely through importin-α/β recognizing a structural nuclear localization signal. However, AID is largely excluded from the nucleus in steady state thanks to two mechanisms. In addition to nuclear export through the exportin CRM1, a mechanism retaining AID in the cytoplasm exists. Cytoplasmic retention hinders the passive diffusion of AID into the nucleus playing an important role in the nuclear exclusion of AID. Subcellular localization of AID also determines its stability. The regulation of the nuclear fraction of AID by these many mechanisms has functional implications for antibody diversification.
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