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Chan YW, Tan CH, Heh CH, Tan KY. An immunoinformatic approach to assessing the immunogenic capacity of alpha-neurotoxins in elapid snake venoms. Front Pharmacol 2023; 14:1143437. [PMID: 37153801 PMCID: PMC10155835 DOI: 10.3389/fphar.2023.1143437] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 03/27/2023] [Indexed: 05/10/2023] Open
Abstract
Introduction: Most elapid snakes produce venoms that contain alpha-neurotoxins (α-NTXs), which are proteins that cause post-synaptic blockade and paralysis in snakebite envenoming. However, existing elapid antivenoms are known for their low potency in neutralizing the neurotoxic activity of α-NTXs, while the immunological basis has not been elucidated. Methods: In this study, a structure-based major histocompatibility complex II (MHCII) epitope predictor of horse (Equus caballus), complemented with DM-editing determinant screening algorithm was adopted to assess the immunogenicity of α-NTXs in the venoms of major Asiatic elapids (Naja kaouthia, Ophiophagus hannah, Laticauda colubrina, Hydrophis schistosus, Hydrophis curtus). Results: The scoring metric M2R, representing the relative immunogenic performance of respective α-NTXs, showed all α-NTXs have an overall low M2R of <0.3, and most of the predicted binders feature non-optimal P1 anchor residues. The M2R scores correlate strongly (R2 = 0.82) with the potency scores (p-score) generated based on the relative abundances of α-NTXs and the neutralization potency of commercial antivenoms. Discussion: The immunoinformatic analysis indicates that the inferior antigenicity of α-NTXs is not only due to their small molecular size but also the subpar immunogenicity affected by their amino acid composition. Structural modification with conjugation and synthetic epitope as immunogen may potentially enhance the immunogenicity for improved antivenom potency against α-NTXs of elapid snakes.
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Affiliation(s)
- Yi Wei Chan
- Protein and Interactomics Laboratory, Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Choo Hock Tan
- Venom Research and Toxicology Laboratory, Department of Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Choon Han Heh
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Malaya, Kuala Lumpur, Malaysia
| | - Kae Yi Tan
- Protein and Interactomics Laboratory, Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
- *Correspondence: Kae Yi Tan,
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Partnering for the major histocompatibility complex class II and antigenic determinant requires flexibility and chaperons. Curr Opin Immunol 2021; 70:112-121. [PMID: 34146954 DOI: 10.1016/j.coi.2021.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 05/12/2021] [Indexed: 11/22/2022]
Abstract
Cytotoxic, or helper T cells recognize antigen via T cell receptors (TCRs) that can see their target antigen as short sequences of peptides bound to the groove of proteins of major histocompatibility complex (MHC) class I, and class II respectively. For MHC class II epitope selection from exogenous pathogens or self-antigens, participation of several accessory proteins, molecular chaperons, processing enzymes within multiple vesicular compartments is necessary. A major contributing factor is the MHC class II structure itself that uniquely offers a dynamic and flexible groove essential for epitope selection. In this review, I have taken a historical perspective focusing on the flexibility of the MHC II molecules as the driving force in determinant selection and interactions with the accessory molecules in antigen processing, HLA-DM and HLA-DO.
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Welsh RA, Song N, Sadegh-Nasseri S. How Does B Cell Antigen Presentation Affect Memory CD4 T Cell Differentiation and Longevity? Front Immunol 2021; 12:677036. [PMID: 34177919 PMCID: PMC8224923 DOI: 10.3389/fimmu.2021.677036] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Accepted: 05/18/2021] [Indexed: 11/13/2022] Open
Abstract
Dendritic cells are the antigen presenting cells that process antigens effectively and prime the immune system, a characteristic that have gained them the spotlights in recent years. B cell antigen presentation, although less prominent, deserves equal attention. B cells select antigen experienced CD4 T cells to become memory and initiate an orchestrated genetic program that maintains memory CD4 T cells for life of the individual. Over years of research, we have demonstrated that low levels of antigens captured by B cells during the resolution of an infection render antigen experienced CD4 T cells into a quiescent/resting state. Our studies suggest that in the absence of antigen, the resting state associated with low-energy utilization and proliferation can help memory CD4 T cells to survive nearly throughout the lifetime of mice. In this review we would discuss the primary findings from our lab as well as others that highlight our understanding of B cell antigen presentation and the contributions of the MHC Class II accessory molecules to this outcome. We propose that the quiescence induced by the low levels of antigen presentation might be a mechanism necessary to regulate long-term survival of CD4 memory T cells and to prevent cross-reactivity to autoantigens, hence autoimmunity.
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Affiliation(s)
- Robin A Welsh
- Graduate Program in Immunology, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Nianbin Song
- Department of Biology, Krieger School of Arts & Sciences, Johns Hopkins University, Baltimore, MD, United States
| | - Scheherazade Sadegh-Nasseri
- Graduate Program in Immunology, Johns Hopkins School of Medicine, Baltimore, MD, United States.,Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD, United States
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4
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Álvaro-Benito M, Freund C. Revisiting nonclassical HLA II functions in antigen presentation: Peptide editing and its modulation. HLA 2020; 96:415-429. [PMID: 32767512 DOI: 10.1111/tan.14007] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 08/04/2020] [Indexed: 01/08/2023]
Abstract
The nonclassical major histocompatibility complex of class II molecules (ncMHCII) HLA-DM (DM) and HLA-DO (DO) feature essential functions for the selection of the peptides that are displayed by classical MHCII proteins (MHCII) for CD4+ Th cell surveillance. Thus, although the binding groove of classical MHCII dictates the main features of the peptides displayed, ncMHCII function defines the preferential loading of peptides from specific cellular compartments and the extent to which they are presented. DM acts as a chaperone for classical MHCII molecules facilitating peptide exchange and thereby favoring the binding of peptide-MHCII complexes of high kinetic stability mostly in late endosomal compartments. DO on the other hand binds to DM blocking its peptide-editing function in B cells and thymic epithelial cells, limiting DM activity in these cellular subsets. DM and DO distinct expression patterns therefore define specific antigen presentation profiles that select unique peptide pools for each set of antigen presenting cell. We have come a long way understanding the mechanistic underpinnings of such distinct editing profiles and start to grasp the implications for ncMHCII biological function. DM acts as filter for the selection of immunodominant, pathogen-derived epitopes while DO blocks DM activity under certain physiological conditions to promote tolerance to self. Interestingly, recent findings have shown that the unexplored and neglected ncMHCII genetic diversity modulates retroviral infection in mouse, and affects human ncMHCII function. This review aims at highlighting the importance of ncMHCII function for CD4+ Th cell responses while integrating and evaluating what could be the impact of distinct editing profiles because of natural genetic variations.
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Affiliation(s)
- Miguel Álvaro-Benito
- Laboratory of Protein Biochemistry, Institute für Chemie und Biochemie, Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Christian Freund
- Laboratory of Protein Biochemistry, Institute für Chemie und Biochemie, Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany
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5
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Reyes-Vargas E, Barker AP, Zhou Z, He X, Jensen PE. HLA-DM catalytically enhances peptide dissociation by sensing peptide-MHC class II interactions throughout the peptide-binding cleft. J Biol Chem 2020; 295:2959-2973. [PMID: 31969393 PMCID: PMC7062162 DOI: 10.1074/jbc.ra119.010645] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 01/13/2020] [Indexed: 11/06/2022] Open
Abstract
Human leukocyte antigen-DM (HLA-DM) is an integral component of the major histocompatibility complex class II (MHCII) antigen-processing and -presentation pathway. HLA-DM shapes the immune system by differentially catalyzing peptide exchange on MHCII molecules, thereby editing the peptide-MHCII (pMHCII) repertoire by imposing a bias on the foreign and self-derived peptide cargos that are presented on the cell surface for immune surveillance and tolerance induction by CD4+ T cells. To better understand DM selectivity, here we developed a real-time fluorescence anisotropy assay to delineate the pMHCII intrinsic stability, DM-binding affinity, and catalytic turnover, independent kinetic parameters of HLA-DM enzymatic activity. We analyzed prominent pMHCII contacts by differentiating the kinetic parameters in pMHCII homologs, observing that peptide interactions throughout the MHCII-binding cleft influence both the rate of peptide dissociation from the DM-pMHCII catalytic complex and the binding affinity of HLA-DM for a pMHCII. We show that the intrinsic stability of a pMHCII linearly correlates with DM catalytic turnover, but is nonlinearly correlated with its binding affinity. Surprisingly, interactions at the peptides N terminus up to and including MHCII position one (P1) anchor affected the catalytic turnover, suggesting that the active DM-pMHCII catalytic complex operates on pMHCII complexes with full peptide occupancy. Furthermore, interactions at the peptide C terminus modulated DM-binding affinity, suggesting distal communication between peptide interactions with the MHCII and the DM-pMHCII binding interface. Our results imply an intimate linkage between the DM-pMHCII interface and peptide-MHCII interactions throughout the peptide-binding cleft.
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Affiliation(s)
- Eduardo Reyes-Vargas
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Adam P Barker
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112; Department of Pathology, ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, Salt Lake City, Utah 84108
| | - Zemin Zhou
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112
| | - Xiao He
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112.
| | - Peter E Jensen
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84112; Department of Pathology, ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, Salt Lake City, Utah 84108.
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6
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Welsh R, Song N, Sadegh-Nasseri S. What to do with HLA-DO/H-2O two decades later? Immunogenetics 2019; 71:189-196. [PMID: 30683973 PMCID: PMC6377320 DOI: 10.1007/s00251-018-01097-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/20/2018] [Indexed: 10/27/2022]
Abstract
The main objective of antigen processing is to orchestrate the selection of immunodominant epitopes for recognition by CD4 T cells. To achieve this, MHC class II molecules have evolved with a flexible peptide-binding groove in need of a bound peptide. Newly synthesized MHC-II molecules bind a class II invariant chain (Ii) upon synthesis and are shuttled to a specialized compartment, where they encounter exogenous antigens. Ii serves multiple functions, one of which is to maintain the shape of the MHC-II groove so that it can readily bind exogenous antigens upon dissociation of the Ii peptide in MHC- II compartment. MIIC contains processing enzymes, one or both accessory molecules, HLA-DM/H2-M (DM) and HLA-DO/H2-O (DO), and optimal denaturing conditions. In a process known as "editing," DM facilitates the dissociation of the invariant chain peptide, CLIP, for exchange with exogenous antigens. Despite the availability of mechanistic insights into DM functions, understanding how DO contributes to epitope selection has proven to be more challenging. The current dogma assumes that DO inhibits DM, whereas an opposing model suggests that DO fine-tunes the epitope selection process. Understanding which of these, or potentially other models of DO function is important, as DO variants have been linked to autoimmunity, cancer, and the generation of broadly neutralizing antibodies to viruses. This review therefore attempts to evaluate experimental evidence in support of these hypotheses, with an emphasis on the less discussed model, and to explore intriguing questions about the importance of DO in biology.
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Affiliation(s)
- Robin Welsh
- Graduate Program in Immunology and Department of Pathology, Johns Hopkins University, Baltimore, MD, USA
| | - Nianbin Song
- Graduate Program in Immunology and Department of Pathology, Johns Hopkins University, Baltimore, MD, USA
| | - Scheherazade Sadegh-Nasseri
- Graduate Program in Immunology and Department of Pathology, Johns Hopkins University, Baltimore, MD, USA.
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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7
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Negroni MP, Stern LJ. The N-terminal region of photocleavable peptides that bind HLA-DR1 determines the kinetics of fragment release. PLoS One 2018; 13:e0199704. [PMID: 29965980 PMCID: PMC6028098 DOI: 10.1371/journal.pone.0199704] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
Major Histocompatibility Complex class II (MHC-II) molecules bind peptides and present them to receptors on CD4+ T cells as part of the immune system's surveillance of pathogens and malignancy. In the absence of peptide, MHC-II equilibrates between peptide-receptive and peptide-averse conformations. The conversion between these forms has been postulated to be important in regulating cellular antigen presentation but has been difficult to study. In order to generate the MHC-II molecule HLA-DR1 in the peptide-receptive form, we designed and tested a series of photocleavable peptides that included the UV-sensitive 3-amino-3-(2-nitrophenyl)-propionate amino acid analog. They were intended to bind tightly to the HLA-DR1 MHC molecule, but to generate low-affinity fragments after UV exposure that would be released to yield HLA-DR1 in the peptide-receptive conformation. We were able to identify photocleavable peptides that bound tightly to HLA-DR1 and generated the peptide-receptive conformation after UV exposure. However, slow release of photocleaved peptide fragments from the binding site limited the rate of binding of an incoming labeled peptide and complicated kinetic measurements of the individual steps of the overall peptide binding reaction. Modification of the N-terminal region of the photocleavable peptide to reduce MHC-II pocket or H-bonding interactions allowed for generation of the peptide receptive form immediately after UV exposure with peptide fragments neither retained within the site nor interfering with binding of an incoming peptide. However this was achieved only at the expense of a substantial reduction in overall peptide binding affinity, and these peptides had such weak interaction with HLA-DR1 that they were easily exchanged by incoming peptide without UV exposure. These results show that photocleavable peptides can be used to generate peptide-receptive HLA-DR1 and to facilitate peptide exchange in generation of specific peptide-MHC-II complexes, but that usage of these peptides for kinetic studies can be constrained by slow fragment release.
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Affiliation(s)
- Maria Pia Negroni
- Program in Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Lawrence J. Stern
- Program in Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
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8
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Afridi S, Hoessli DC, Hameed MW. Mechanistic understanding and significance of small peptides interaction with MHC class II molecules for therapeutic applications. Immunol Rev 2017; 272:151-68. [PMID: 27319349 DOI: 10.1111/imr.12435] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Major histocompatibility complex (MHC) class II molecules are expressed by antigen-presenting cells and stimulate CD4(+) T cells, which initiate humoral immune responses. Over the past decade, interest has developed to therapeutically impact the peptides to be exposed to CD4(+) T cells. Structurally diverse small molecules have been discovered that act on the endogenous peptide exchanger HLA-DM by different mechanisms. Exogenously delivered peptides are highly susceptible to proteolytic cleavage in vivo; however, it is only when successfully incorporated into stable MHC II-peptide complexes that these peptides can induce an immune response. Many of the small molecules so far discovered have highlighted the molecular interactions mediating the formation of MHC II-peptide complexes. As potential drugs, these small molecules open new therapeutic approaches to modulate MHC II antigen presentation pathways and influence the quality and specificity of immune responses. This review briefly introduces how CD4(+) T cells recognize antigen when displayed by MHC class II molecules, as well as MHC class II-peptide-loading pathways, structural basis of peptide binding and stabilization of the peptide-MHC complexes. We discuss the concept of MHC-loading enhancers, how they could modulate immune responses and how these molecules have been identified. Finally, we suggest mechanisms whereby MHC-loading enhancers could act upon MHC class II molecules.
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Affiliation(s)
- Saifullah Afridi
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
| | - Daniel C Hoessli
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
| | - Muhammad Waqar Hameed
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan
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9
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Nguyen TB, Jayaraman P, Bergseng E, Madhusudhan MS, Kim CY, Sollid LM. Unraveling the structural basis for the unusually rich association of human leukocyte antigen DQ2.5 with class-II-associated invariant chain peptides. J Biol Chem 2017; 292:9218-9228. [PMID: 28364043 DOI: 10.1074/jbc.m117.785139] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 03/28/2017] [Indexed: 11/06/2022] Open
Abstract
Human leukocyte antigen (HLA)-DQ2.5 (DQA1*05/DQB1*02) is a class-II major histocompatibility complex protein associated with both type 1 diabetes and celiac disease. One unusual feature of DQ2.5 is its high class-II-associated invariant chain peptide (CLIP) content. Moreover, HLA-DQ2.5 preferentially binds the non-canonical CLIP2 over the canonical CLIP1. To better understand the structural basis of HLA-DQ2.5's unusual CLIP association characteristics, better insight into the HLA-DQ2.5·CLIP complex structures is required. To this end, we determined the X-ray crystal structure of the HLA-DQ2.5· CLIP1 and HLA-DQ2.5·CLIP2 complexes at 2.73 and 2.20 Å, respectively. We found that HLA-DQ2.5 has an unusually large P4 pocket and a positively charged peptide-binding groove that together promote preferential binding of CLIP2 over CLIP1. An α9-α22-α24-α31-β86-β90 hydrogen bond network located at the bottom of the peptide-binding groove, spanning from the P1 to P4 pockets, renders the residues in this region relatively immobile. This hydrogen bond network, along with a deletion mutation at α53, may lead to HLA-DM insensitivity in HLA-DQ2.5. A molecular dynamics simulation experiment reported here and recent biochemical studies by others support this hypothesis. The diminished HLA-DM sensitivity is the likely reason for the CLIP-rich phenotype of HLA-DQ2.5.
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Affiliation(s)
- Thanh-Binh Nguyen
- the Bioinformatics Institute, Singapore 138671, Singapore.,the Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Priya Jayaraman
- the Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Elin Bergseng
- the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway
| | - M S Madhusudhan
- the Bioinformatics Institute, Singapore 138671, Singapore.,the Indian Institute of Science Education and Research, Pune 411008, India, and
| | - Chu-Young Kim
- From the Department of Chemistry and .,School of Pharmacy, University of Texas at El Paso, El Paso, Texas 79968.,Synthetic Biology for Clinical and Technological Innovation, Life Sciences Institute, National University of Singapore, 117456 Singapore, Singapore
| | - Ludvig M Sollid
- the Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, N-0372 Oslo, Norway
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10
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Zhou Z, Reyes-Vargas E, Escobar H, Chang KY, Barker AP, Rockwood AL, Delgado JC, He X, Jensen PE. Peptidomic analysis of type 1 diabetes associated HLA-DQ molecules and the impact of HLA-DM on peptide repertoire editing. Eur J Immunol 2016; 47:314-326. [PMID: 27861808 DOI: 10.1002/eji.201646656] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 10/21/2016] [Accepted: 11/10/2016] [Indexed: 11/08/2022]
Abstract
HLA-DM and class II associated invariant chain (Ii) are key cofactors in the MHC class II (MHCII) antigen processing pathway. We used tandem mass spectrometry sequencing to directly interrogate the global impact of DM and Ii on the repertoire of MHCII-bound peptides in human embryonic kidney 293T cells expressing HLA-DQ molecules in the absence or presence of these cofactors. We found that Ii and DM have a major impact on the repertoire of peptides presented by DQ1 and DQ6, with the caveat that this technology is not quantitative. The peptide repertoires of type 1 diabetes (T1D) associated DQ8, DQ2, and DQ8/2 are altered to a lesser degree by DM expression, and these molecules share overlapping features in their peptide binding motifs that are distinct from control DQ1 and DQ6 molecules. Peptides were categorized into DM-resistant, DM-dependent, or DM-sensitive groups based on the mass spectrometry data, and representative peptides were tested in competitive binding assays and peptide dissociation rate experiments with soluble DQ6. Our data support the conclusion that high intrinsic stability of DQ-peptide complexes is necessary but not sufficient to confer resistance to DM editing, and provide candidate parameters that may be useful in predicting the sensitivity of T-cell epitopes to DM editing.
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Affiliation(s)
- Zemin Zhou
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
| | | | | | - Kuan Y Chang
- Department of Computer Science and Engineering, National Taiwan Ocean University, Keelung, Taiwan
| | - Adam P Barker
- Department of Pathology, University of Utah, Salt Lake City, UT, USA.,ARUP Laboratories, University of Utah, Salt Lake City, UT, USA
| | - Alan L Rockwood
- Department of Pathology, University of Utah, Salt Lake City, UT, USA.,ARUP Laboratories, University of Utah, Salt Lake City, UT, USA
| | - Julio C Delgado
- Department of Pathology, University of Utah, Salt Lake City, UT, USA.,ARUP Laboratories, University of Utah, Salt Lake City, UT, USA
| | - Xiao He
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
| | - Peter E Jensen
- Department of Pathology, University of Utah, Salt Lake City, UT, USA
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11
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Sadegh-Nasseri S. A step-by-step overview of the dynamic process of epitope selection by major histocompatibility complex class II for presentation to helper T cells. F1000Res 2016; 5. [PMID: 27347387 PMCID: PMC4902097 DOI: 10.12688/f1000research.7664.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/27/2016] [Indexed: 11/25/2022] Open
Abstract
T cell antigen receptors (TCRs) expressed on cytotoxic or helper T cells can only see their specific target antigen as short sequences of peptides bound to the groove of proteins of major histocompatibility complex (MHC) class I, and class II respectively. In addition to the many steps, several participating proteins, and multiple cellular compartments involved in the processing of antigens, the MHC structure, with its dynamic and flexible groove, has perfectly evolved as the underlying instrument for epitope selection. In this review, I have taken a step-by-step, and rather historical, view to describe antigen processing and determinant selection, as we understand it today, all based on decades of intense research by hundreds of laboratories.
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12
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Yin L, Maben ZJ, Becerra A, Stern LJ. Evaluating the Role of HLA-DM in MHC Class II-Peptide Association Reactions. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2015; 195:706-16. [PMID: 26062997 PMCID: PMC4490944 DOI: 10.4049/jimmunol.1403190] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 05/15/2015] [Indexed: 01/07/2023]
Abstract
Ag presentation by MHC class II (MHC II) molecules to CD4(+) T cells plays a key role in the regulation of the adaptive immune response. Loading of antigenic peptides onto MHC II is catalyzed by HLA-DM (DM), a nonclassical MHC II molecule. The mechanism of DM-facilitated peptide loading is an outstanding problem in the field of Ag presentation. In this study, we systemically explored possible kinetic mechanisms for DM-catalyzed peptide association by measuring real-time peptide association kinetics using fluorescence polarization assays and comparing the experimental data with numerically modeled peptide association reactions. We found that DM does not facilitate peptide association by stabilizing peptide-free MHC II against aggregation. Moreover, DM does not promote transition of an inactive peptide-averse conformation of MHC II to an active peptide-receptive conformation. Instead, DM forms an intermediate with MHC II that binds peptide with faster kinetics than MHC II in the absence of DM. In the absence of peptides, interaction of MHC II with DM leads to inactivation and formation of a peptide-averse form. This study provides novel insights into how DM efficiently catalyzes peptide loading during Ag presentation.
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Affiliation(s)
- Liusong Yin
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01605; and
| | - Zachary J Maben
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01605; and
| | - Aniuska Becerra
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01605; and
| | - Lawrence J Stern
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01605; and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
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13
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Ferrante A, Templeton M, Hoffman M, Castellini MJ. The Thermodynamic Mechanism of Peptide-MHC Class II Complex Formation Is a Determinant of Susceptibility to HLA-DM. THE JOURNAL OF IMMUNOLOGY 2015; 195:1251-61. [PMID: 26116504 DOI: 10.4049/jimmunol.1402367] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 05/28/2015] [Indexed: 11/19/2022]
Abstract
Peptides bind MHC class II molecules through a thermodynamically nonadditive process consequent to the flexibility of the reactants. Currently, how the specific outcome of this binding process affects the ensuing epitope selection needs resolution. Calorimetric assessment of binding thermodynamics for hemagglutinin 306-319 peptide variants to the human MHC class II HLA-DR1 (DR1) and a mutant DR1 reveals that peptide/DR1 complexes can be formed with different enthalpic and entropic contributions. Complexes formed with a smaller entropic penalty feature circular dichroism spectra consistent with a non-compact form, and molecular dynamics simulation shows a more flexible structure. The opposite binding mode, compact and less flexible, is associated with greater entropic penalty. These structural variations are associated with rearrangements of residues known to be involved in HLA-DR (DM) binding, affinity of DM for the complex, and complex susceptibility to DM-mediated peptide exchange. Thus, the thermodynamic mechanism of peptide binding to DR1 correlates with the structural rigidity of the complex, and DM mediates peptide exchange by "sensing" flexible complexes in which the aforementioned residues are rearranged at a higher frequency than in more rigid ones.
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Affiliation(s)
- Andrea Ferrante
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775;
| | - Megan Templeton
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775; Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775; and
| | - Megan Hoffman
- Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, AK 99775
| | - Margaret J Castellini
- Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, AK 99775
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14
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Yin L, Stern LJ. Measurement of Peptide Binding to MHC Class II Molecules by Fluorescence Polarization. CURRENT PROTOCOLS IN IMMUNOLOGY 2014; 106:5.10.1-5.10.12. [PMID: 25081912 PMCID: PMC4151172 DOI: 10.1002/0471142735.im0510s106] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Peptide binding to major histocompatibility complex class II (MHCII) molecules is a key process in antigen presentation and CD4+ T cell epitope selection. This unit describes a fairly simple but powerful fluorescence polarization-based binding competition assay to measure peptide binding to soluble recombinant MHCII molecules. The binding of a peptide of interest to MHCII molecules is assessed based on its ability to inhibit the binding of a fluorescence-labeled probe peptide, with the strength of binding characterized as IC50 (concentration required for 50% inhibition of probe peptide binding). Data analysis related to this method is discussed. In addition, this unit includes a support protocol for fluorescence labeling peptide using an amine-reactive probe. The advantage of this protocol is that it allows simple, fast, and high-throughput measurements of binding for a large set of peptides to MHCII molecules.
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Affiliation(s)
- Liusong Yin
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA01605
| | - Lawrence J. Stern
- Department of Pathology, University of Massachusetts Medical School, Worcester, MA01605
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA01605
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15
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Yin L, Trenh P, Guce A, Wieczorek M, Lange S, Sticht J, Jiang W, Bylsma M, Mellins ED, Freund C, Stern LJ. Susceptibility to HLA-DM protein is determined by a dynamic conformation of major histocompatibility complex class II molecule bound with peptide. J Biol Chem 2014; 289:23449-64. [PMID: 25002586 DOI: 10.1074/jbc.m114.585539] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
HLA-DM mediates the exchange of peptides loaded onto MHCII molecules during antigen presentation by a mechanism that remains unclear and controversial. Here, we investigated the sequence and structural determinants of HLA-DM interaction. Peptides interacting nonoptimally in the P1 pocket exhibited low MHCII binding affinity and kinetic instability and were highly susceptible to HLA-DM-mediated peptide exchange. These changes were accompanied by conformational alterations detected by surface plasmon resonance, SDS resistance assay, antibody binding assay, gel filtration, dynamic light scattering, small angle x-ray scattering, and NMR spectroscopy. Surprisingly, all of those changes could be reversed by substitution of the P9 pocket anchor residue. Moreover, MHCII mutations outside the P1 pocket and the HLA-DM interaction site increased HLA-DM susceptibility. These results indicate that a dynamic MHCII conformational determinant rather than P1 pocket occupancy is the key factor determining susceptibility to HLA-DM-mediated peptide exchange and provide a molecular mechanism for HLA-DM to efficiently target unstable MHCII-peptide complexes for editing and exchange those for more stable ones.
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Affiliation(s)
- Liusong Yin
- From the Program in Immunology and Microbiology and
| | - Peter Trenh
- From the Program in Immunology and Microbiology and
| | - Abigail Guce
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Marek Wieczorek
- the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and
| | - Sascha Lange
- the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and
| | - Jana Sticht
- the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and
| | - Wei Jiang
- the Department of Pediatrics, Program in Immunology, Stanford University Medical Center, Stanford, California 94305
| | - Marissa Bylsma
- Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Elizabeth D Mellins
- the Department of Pediatrics, Program in Immunology, Stanford University Medical Center, Stanford, California 94305
| | - Christian Freund
- the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Thielallee 63, 14195 Berlin, Germany, and
| | - Lawrence J Stern
- From the Program in Immunology and Microbiology and Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01605,
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16
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Parra-López CA, Bernal-Estévez D, Vargas LE, Pulido-Calixto C, Salazar LM, Calvo-Calle JM, Stern LJ. An unstable Th epitope of P. falciparum fosters central memory T cells and anti-CS antibody responses. PLoS One 2014; 9:e100639. [PMID: 24983460 PMCID: PMC4077652 DOI: 10.1371/journal.pone.0100639] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 05/29/2014] [Indexed: 11/19/2022] Open
Abstract
Malaria is transmitted by Plasmodium-infected anopheles mosquitoes. Widespread resistance of mosquitoes to insecticides and resistance of parasites to drugs highlight the urgent need for malaria vaccines. The most advanced malaria vaccines target sporozoites, the infective form of the parasite. A major target of the antibody response to sporozoites are the repeat epitopes of the circumsporozoite (CS) protein, which span almost one half of the protein. Antibodies to these repeats can neutralize sporozoite infectivity. Generation of protective antibody responses to the CS protein (anti-CS Ab) requires help by CD4 T cells. A CD4 T cell epitope from the CS protein designated T* was previously identified by screening T cells from volunteers immunized with irradiated P. falciparum sporozoites. The T* sequence spans twenty amino acids that contains multiple T cell epitopes restricted by various HLA alleles. Subunit malaria vaccines including T* are highly immunogenic in rodents, non-human primates and humans. In this study we characterized a highly conserved HLA-DRβ1*04:01 (DR4) restricted T cell epitope (QNT-5) located at the C-terminus of T*. We found that a peptide containing QNT-5 was able to elicit long-term anti-CS Ab responses and prime CD4 T cells in HLA-DR4 transgenic mice despite forming relatively unstable MHC-peptide complexes highly susceptible to HLA-DM editing. We attempted to improve the immunogenicity of QNT-5 by replacing the P1 anchor position with an optimal tyrosine residue. The modified peptide QNT-Y formed stable MHC-peptide complexes highly resistant to HLA-DM editing. Contrary to expectations, a linear peptide containing QNT-Y elicited almost 10-fold lower long-term antibody and IFN-γ responses compared to the linear peptide containing the wild type QNT-5 sequence. Some possibilities regarding why QNT-5 is more effective than QNT-Y in inducing long-term T cell and anti-CS Ab when used as vaccine are discussed.
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Affiliation(s)
- Carlos A. Parra-López
- Department of Microbiology, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
- Graduate School in Biomedical Sciences, Universidad Nacional de Colombia, Bogotá, Colombia
- * E-mail: (CAP-L); (LJS)
| | - David Bernal-Estévez
- Department of Microbiology, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
- Graduate School in Biomedical Sciences, Universidad Nacional de Colombia, Bogotá, Colombia
- Fundación Salud de los Andes, Research Group of Immunology and Clinical Oncology - GIIOC, Bogotá, Colombia
| | - Luis Eduardo Vargas
- Department of Microbiology, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Carolina Pulido-Calixto
- Department of Microbiology, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Luz Mary Salazar
- Faculty of Sciences, Universidad Nacional de Colombia, Bogotá, Colombia
| | - J. Mauricio Calvo-Calle
- University of Massachusetts Medical School, Department of Pathology and Biochemistry and the Department of Molecular Pharmacology, Worcester, Massachusetts, United States of America
| | - Lawrence J. Stern
- University of Massachusetts Medical School, Department of Pathology and Biochemistry and the Department of Molecular Pharmacology, Worcester, Massachusetts, United States of America
- * E-mail: (CAP-L); (LJS)
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17
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Yin L, Stern LJ. A novel method to measure HLA-DM-susceptibility of peptides bound to MHC class II molecules based on peptide binding competition assay and differential IC(50) determination. J Immunol Methods 2014; 406:21-33. [PMID: 24583195 DOI: 10.1016/j.jim.2014.02.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 02/07/2014] [Accepted: 02/18/2014] [Indexed: 01/17/2023]
Abstract
HLA-DM (DM) functions as a peptide editor that mediates the exchange of peptides loaded onto MHCII molecules by accelerating peptide dissociation and association kinetics. The relative DM-susceptibility of peptides bound to MHCII molecules correlates with antigen presentation and immunodominance hierarchy, and measurement of DM-susceptibility has been a key effort in this field. Current assays of DM-susceptibility, based on differential peptide dissociation rates measured for individually labeled peptides over a long time base, are difficult and cumbersome. Here, we present a novel method to measure DM-susceptibility based on peptide binding competition assays performed in the presence and absence of DM, reported as a delta-IC(50) (change in 50% inhibition concentration) value. We simulated binding competition reactions of peptides with various intrinsic and DM-catalyzed kinetic parameters and found that under a wide range of conditions the delta-IC(50) value is highly correlated with DM-susceptibility as measured in off-rate assay. We confirmed experimentally that DM-susceptibility measured by delta-IC(50) is comparable to that measured by traditional off-rate assay for peptides with known DM-susceptibility hierarchy. The major advantage of this method is that it allows simple, fast and high throughput measurement of DM-susceptibility for a large set of unlabeled peptides in studies of the mechanism of DM action and for identification of CD4+ T cell epitopes.
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Affiliation(s)
- Liusong Yin
- Program in Immunology and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, United States
| | - Lawrence J Stern
- Program in Immunology and Microbiology, University of Massachusetts Medical School, Worcester, MA 01605, United States; Department of Pathology, University of Massachusetts Medical School, Worcester, MA 01605, United States; Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, United States.
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18
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Sant AJ, Chaves FA, Krafcik FR, Lazarski CA, Menges P, Richards K, Weaver JM. Immunodominance in CD4 T-cell responses: implications for immune responses to influenza virus and for vaccine design. Expert Rev Vaccines 2014; 6:357-68. [PMID: 17542751 DOI: 10.1586/14760584.6.3.357] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
CD4 T cells play a primary role in regulating immune responses to pathogenic organisms and to vaccines. Antigen-specific CD4 T cells provide cognate help to B cells, a requisite event for immunoglobulin switch and affinity maturation of B cells that produce neutralizing antibodies and also provide help to cytotoxic CD8 T cells, critical for their expansion and persistence as memory cells. Finally, CD4 T cells may participate directly in pathogen clearance via cell-mediated cytotoxicity or through production of cytokines. Understanding the role of CD4 T-cell immunity to viruses and other pathogens, as well as evaluation of the efficacy of vaccines, requires insight into the specificity of CD4 T cells. This review focuses on the events within antigen-presenting cells that focus CD4 T cells toward a limited number of peptide antigens within the pathogen or vaccine. The molecular events are discussed in light of the special challenges that the influenza virus poses, owing to the high degree of genetic variability, unpredictable pathogenicity and the repeated encounters that human populations face with this highly infectious pathogenic organism.
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Affiliation(s)
- Andrea J Sant
- David H Smith Center for Vaccine Biology and Immunology, Aab Institute and Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA.
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19
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Ji N, Somanaboeina A, Dixit A, Kawamura K, Hayward NJ, Self C, Olson GL, Forsthuber T. Small molecule inhibitor of antigen binding and presentation by HLA-DR2b as a therapeutic strategy for the treatment of multiple sclerosis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 191:5074-84. [PMID: 24123687 PMCID: PMC3891844 DOI: 10.4049/jimmunol.1300407] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The strong association of HLA-DR2b (DRB1*1501) with multiple sclerosis (MS) suggests this molecule as prime target for specific immunotherapy. Inhibition of HLA-DR2b-restricted myelin-specific T cells has the potential to selectively prevent CNS pathology mediated by these MHC molecules without undesired global immunosuppression. In this study, we report development of a highly selective small molecule inhibitor of peptide binding and presentation by HLA-DR2b. PV-267, the candidate molecule used in these studies, inhibited cytokine production and proliferation of myelin-specific HLA-DR2b-restricted T cells. PV-267 had no significant effect on T cell responses mediated by other MHC class II molecules, including HLA-DR1, -DR4, or -DR9. Importantly, PV-267 did not induce nonspecific immune activation of human PBMC. Lastly, PV-267 showed treatment efficacy both in preventing experimental autoimmune encephalomyelitis and in treating established disease. The results suggest that blocking the MS-associated HLA-DR2b allele with small molecule inhibitors may be a promising therapeutic strategy for the treatment of MS.
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Affiliation(s)
- Niannian Ji
- Department of Biology, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249
| | - Animesh Somanaboeina
- Department of Biology, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249
| | - Aakanksha Dixit
- Department of Biology, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249
| | - Kazuyuki Kawamura
- Department of Biology, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249
| | | | - Christopher Self
- Provid Pharmaceuticals Inc., 7 Deer Park Drive, Monmouth Junction, NJ 08852
| | - Gary L. Olson
- Provid Pharmaceuticals Inc., 7 Deer Park Drive, Monmouth Junction, NJ 08852
| | - Thomas Forsthuber
- Department of Biology, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249
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20
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Yin L, Stern LJ. HLA-DM Focuses on Conformational Flexibility Around P1 Pocket to Catalyze Peptide Exchange. Front Immunol 2013; 4:336. [PMID: 24146666 PMCID: PMC3797982 DOI: 10.3389/fimmu.2013.00336] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 10/03/2013] [Indexed: 11/13/2022] Open
Abstract
Peptides presented by major histocompatibility complex class II (MHCII) molecules to CD4+ T cells play a central role in the initiation of adaptive immunity. This antigen presentation process is characterized by the proteolytic cleavage of foreign and self proteins, and loading of the resultant peptides onto MHCII molecules. Loading and exchange of antigenic peptides is catalyzed by a non-classical MHCII molecule, HLA-DM. The impact of HLA-DM on epitope selection has been appreciated for a long time. However, the molecular mechanism by which HLA-DM mediates peptide exchange remains elusive. Here, we review recent efforts in elucidating how HLA-DM works, highlighted by two recently solved co-structures of HLA-DM bound to HLA-DO (a natural inhibitor of HLA-DM), or to HLA-DR1 (a common MHCII). In light of these efforts, a model for HLA-DM action in which HLA-DM utilizes conformational flexibility around the P1 pocket of the MHCII-peptide complex to catalyze peptide exchange is proposed.
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Affiliation(s)
- Liusong Yin
- Department of Pathology, University of Massachusetts Medical School , Worcester, MA , USA
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21
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Poluektov YO, Kim A, Hartman IZ, Sadegh-Nasseri S. HLA-DO as the optimizer of epitope selection for MHC class II antigen presentation. PLoS One 2013; 8:e71228. [PMID: 23951115 PMCID: PMC3738515 DOI: 10.1371/journal.pone.0071228] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 06/28/2013] [Indexed: 11/18/2022] Open
Abstract
Processing of antigens for presentation to helper T cells by MHC class II involves HLA-DM (DM) and HLA-DO (DO) accessory molecules. A mechanistic understanding of DO in this process has been missing. The leading model on its function proposes that DO inhibits the effects of DM. To directly study DO functions, we designed a recombinant soluble DO and expressed it in insect cells. The kinetics of binding and dissociation of several peptides to HLA-DR1 (DR1) molecules in the presence of DM and DO were measured. We found that DO reduced binding of DR1 to some peptides, and enhanced the binding of some other peptides to DR1. Interestingly, these enhancing and reducing effects were observed in the presence, or absence, of DM. We found that peptides that were negatively affected by DO were DM-sensitive, whereas peptides that were enhanced by DO were DM-resistant. The positive and negative effects of DO could only be measured on binding kinetics as peptide dissociation kinetics were not affected by DO. Using Surface Plasmon Resonance, we demonstrate direct binding of DO to a peptide-receptive, but not a closed conformation of DR1. We propose that DO imposes another layer of control on epitope selection during antigen processing.
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Affiliation(s)
- Yuri O. Poluektov
- Graduate Program in Immunology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - AeRyon Kim
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Isamu Z. Hartman
- Graduate Program in Immunology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Scheherazade Sadegh-Nasseri
- Graduate Program in Immunology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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22
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Schulze MSED, Anders AK, Sethi DK, Call MJ. Disruption of hydrogen bonds between major histocompatibility complex class II and the peptide N-terminus is not sufficient to form a human leukocyte antigen-DM receptive state of major histocompatibility complex class II. PLoS One 2013; 8:e69228. [PMID: 23976922 PMCID: PMC3743349 DOI: 10.1371/journal.pone.0069228] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 06/06/2013] [Indexed: 01/17/2023] Open
Abstract
Peptide presentation by MHC class II is of critical importance to the function of CD4+ T cells. HLA-DM resides in the endosomal pathway and edits the peptide repertoire of newly synthesized MHC class II molecules before they are exported to the cell surface. HLA-DM ensures MHC class II molecules bind high affinity peptides by targeting unstable MHC class II:peptide complexes for peptide exchange. Research over the past decade has implicated the peptide N-terminus in modulating the ability of HLA-DM to target a given MHC class II:peptide combination. In particular, attention has been focused on both the hydrogen bonds between MHC class II and peptide, and the occupancy of the P1 anchor pocket. We sought to solve the crystal structure of a HLA-DR1 molecule containing a truncated hemagglutinin peptide missing three N-terminal residues compared to the full-length sequence (residues 306-318) to determine the nature of the MHC class II:peptide species that binds HLA-DM. Here we present structural evidence that HLA-DR1 that is loaded with a peptide truncated to the P1 anchor residue such that it cannot make select hydrogen bonds with the peptide N-terminus, adopts the same conformation as molecules loaded with full-length peptide. HLA-DR1:peptide combinations that were unable to engage up to four key hydrogen bonds were also unable to bind HLA-DM, while those truncated to the P2 residue bound well. These results indicate that the conformational changes in MHC class II molecules that are recognized by HLA-DM occur after disengagement of the P1 anchor residue.
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Affiliation(s)
- Monika-Sarah E. D. Schulze
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Anne-Kathrin Anders
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
- Program in Immunology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Dhruv K. Sethi
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts, United States of America
| | - Melissa J. Call
- Structural Biology Division, the Walter and Eliza Hall Institute of Medical Research, the University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
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23
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Ferrante A. For many but not for all: how the conformational flexibility of the peptide/MHCII complex shapes epitope selection. Immunol Res 2013; 56:85-95. [PMID: 22753017 PMCID: PMC4197051 DOI: 10.1007/s12026-012-8342-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The adaptive immune response starts when CD4+ T cells recognize peptide antigens presented by class II molecules of the Major Histocompatibility Complex (MHCII). Two outstanding features of MHCII molecules are their polymorphism and the ability of each allele to bind a large panoply of peptides. The ability of each MHCII molecule to interact with a limited, though broad, range of amino acid sequences, or "permissive specificity" of binding, is the result of structural flexibility. This flexibility has been identified through biochemical and biophysical studies, and molecular dynamic simulations have modeled the conformational rearrangements that the peptide and the MHCII undergo during interaction. Moreover, there is evidence that the structural flexibility of the peptide/MHCII complex correlates with the activity of the "peptide-editing" molecule DM. In light of the impact that these recent findings have on our ability to predict MHCII epitopes, a review of the structural and thermodynamic determinants of peptide binding to MHCII is proposed.
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Affiliation(s)
- Andrea Ferrante
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA.
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24
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Ferrante A. HLA-DM: arbiter conformationis. Immunology 2013; 138:85-92. [PMID: 23113687 DOI: 10.1111/imm.12030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/16/2012] [Accepted: 10/17/2012] [Indexed: 12/31/2022] Open
Abstract
The recognition by CD4(+) T cells of peptides bound to class II MHC (MHCII) molecules expressed on the surface of antigen-presenting cells is a key step in the initiation of an adaptive immune response. Presentation of peptides is the outcome of an intracellular selection process occurring in dedicated endosomal compartments involving, among others, an MHCII-like molecule named HLA-DM (DM). The impact of DM on the epitope selection machinery has been known for more than 15 years. However, the mechanism by which DM skews the presented repertoire in favour of kinetically stable complexes has remained elusive. Here, a review of the most recent observations in the field is presented, pointing to the possibility that DM decides the survival of a peptide-MHCII complex (pMHCII) on the basis of its conformational flexibility, which is a function of the 'tightness' of interaction between the peptide and the MHCII at a specific region of the binding site.
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Affiliation(s)
- Andrea Ferrante
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA.
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25
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Painter CA, Stern LJ. Conformational variation in structures of classical and non-classical MHCII proteins and functional implications. Immunol Rev 2013; 250:144-57. [PMID: 23046127 DOI: 10.1111/imr.12003] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Recent structural characterizations of classical and non-classical major histocompatibility complex class II (MHCII) proteins have provided a view into the dynamic nature of the MHCII-peptide binding groove and the role that structural changes play in peptide loading processes. Although there have been numerous reports of crystal structures for MHCII-peptide complexes, a detailed analysis comparing all the structures has not been reported, and subtle conformational variations present in these structures may not have been fully appreciated. We compared the 91 MHCII crystal structures reported in the PDB to date, including an HLA-DR mutant particularly susceptible to DM-mediated peptide exchange, and reviewed experimental and computational studies of the effect of peptide binding on MHCII structure. These studies provide evidence for conformational lability in and around the α-subunit 3-10 helix at residues α48-51, a region known to be critical for HLA-DM-mediated peptide exchange. A biophysical study of MHC-peptide hydrogen bond strengths and a recent structure of the non-classical MHCII protein HLA-DO reveal changes in the same region. Conformational variability was observed also in the vicinity of a kink in the β-subunit helical region near residue β66 and in the orientation and loop conformation in the β2 Ig domain. Here, we provide an overview of the regions within classical and non-classical MHCII proteins that display conformational changes and the potential role that these changes may have in the peptide loading/exchange process.
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Affiliation(s)
- Corrie A Painter
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, USA
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26
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Schulze MSED, Wucherpfennig KW. The mechanism of HLA-DM induced peptide exchange in the MHC class II antigen presentation pathway. Curr Opin Immunol 2011; 24:105-11. [PMID: 22138314 DOI: 10.1016/j.coi.2011.11.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 11/13/2011] [Indexed: 12/13/2022]
Abstract
HLA-DM serves a critical function in the loading and editing of peptides on MHC class II (MHCII) molecules. Recent data showed that the interaction cycle between MHCII molecules and HLA-DM is dependent on the occupancy state of the peptide binding groove. Empty MHCII molecules form stable complexes with HLA-DM, which are disrupted by binding of high-affinity peptide. Interestingly, MHCII molecules with fully engaged peptides cannot interact with HLA-DM, and prior dissociation of the peptide N-terminus from the groove is required for HLA-DM binding. There are significant similarities to the peptide loading process for MHC class I molecules, even though it is executed by a distinct set of proteins in a different cellular compartment.
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Affiliation(s)
- Monika-Sarah E D Schulze
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
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27
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Conformational lability in the class II MHC 310 helix and adjacent extended strand dictate HLA-DM susceptibility and peptide exchange. Proc Natl Acad Sci U S A 2011; 108:19329-34. [PMID: 22084083 DOI: 10.1073/pnas.1108074108] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
HLA-DM is required for efficient peptide exchange on class II MHC molecules, but its mechanism of action is controversial. We trapped an intermediate state of class II MHC HLA-DR1 by substitution of αF54, resulting in a protein with increased HLA-DM binding affinity, weakened MHC-peptide hydrogen bonding as measured by hydrogen-deuterium exchange mass spectrometry, and increased susceptibility to DM-mediated peptide exchange. Structural analysis revealed a set of concerted conformational alterations at the N-terminal end of the peptide-binding site. These results suggest that interaction with HLA-DM is driven by a conformational change of the MHC II protein in the region of the α-subunit 3(10) helix and adjacent extended strand region, and provide a model for the mechanism of DM-mediated peptide exchange.
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28
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Call MJ. Small molecule modulators of MHC class II antigen presentation: Mechanistic insights and implications for therapeutic application. Mol Immunol 2011; 48:1735-43. [DOI: 10.1016/j.molimm.2011.05.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Revised: 05/23/2011] [Accepted: 05/24/2011] [Indexed: 02/02/2023]
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29
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Hou T, Macmillan H, Chen Z, Keech CL, Jin X, Sidney J, Strohman M, Yoon T, Mellins ED. An insertion mutant in DQA1*0501 restores susceptibility to HLA-DM: implications for disease associations. THE JOURNAL OF IMMUNOLOGY 2011; 187:2442-52. [PMID: 21775680 DOI: 10.4049/jimmunol.1100255] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
HLA-DM (DM) catalyzes CLIP release, stabilizes MHC class II molecules, and edits the peptide repertoire presented by class II. Impaired DM function may have profound effects on Ag presentation events in the thymus and periphery that are critical for maintenance of self-tolerance. The associations of the HLA-DQ2 (DQ2) allele with celiac disease and type 1 diabetes mellitus have been appreciated for a long time. The explanation for these associations, however, remains unknown. We previously found that DQ2 is a poor substrate for DM. In this study, to further characterize DQ2-DM interaction, we introduced point mutations into DQ2 on the proposed DQ2-DM interface to restore the sensitivity of DQ2 to DM. The effects of mutations were investigated by measuring the peptide dissociation and exchange rate in vitro, CLIP and DQ2 expression on the cell surface, and the presentation of α-II-gliadin epitope (residues 62-70) to murine, DQ2-restricted T cell hybridomas. We found that the three α-chain mutations (α+53G, α+53R, or αY22F) decreased the intrinsic stability of peptide-class II complex. More interestingly, the α+53G mutant restored DQ2 sensitivity to DM, likely due to improved interaction with DM. Our data also suggest that α-II-gliadin 62-70 is a DM-suppressed epitope. The DQ2 resistance to DM changes the fate of this peptide from a cryptic to an immunodominant epitope. Our findings elucidate the structural basis for reduced DQ2-DM interaction and have implications for mechanisms underlying disease associations of DQ2.
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Affiliation(s)
- Tieying Hou
- Department of Pediatrics, Program in Immunology, Stanford University, Stanford, CA 94305, USA
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Anders AK, Call MJ, Schulze MSED, Fowler KD, Schubert DA, Seth NP, Sundberg EJ, Wucherpfennig KW. HLA-DM captures partially empty HLA-DR molecules for catalyzed removal of peptide. Nat Immunol 2010; 12:54-61. [PMID: 21131964 PMCID: PMC3018327 DOI: 10.1038/ni.1967] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 11/09/2010] [Indexed: 11/20/2022]
Abstract
The mechanisms of HLA-DM catalyzed peptide exchange remain uncertain. We found that all stages of the interaction of DM with HLA-DR were dependent on the occupancy state of the peptide binding groove. High-affinity peptides were protected from removal by DM through two mechanisms: peptide binding induced dissociation of a long-lived complex of empty DR and DM, and high-affinity DR-peptide complexes bound DM only very slowly. Non-binding covalent DR-peptide complexes were converted to efficient DM binders upon truncation of an N-terminal peptide segment that emptied the P1 pocket and disrupted conserved hydrogen bonds to MHC. DM thus only binds to DR conformers in which a critical part of the binding site is vacant, due to spontaneous peptide motion.
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Affiliation(s)
- Anne-Kathrin Anders
- Department of Cancer Immunology & AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
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Peptide binding to MHC class I and II proteins: New avenues from new methods. Mol Immunol 2010; 47:649-57. [DOI: 10.1016/j.molimm.2009.10.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 10/08/2009] [Accepted: 10/13/2009] [Indexed: 01/27/2023]
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Ferrante A, Gorski J. Cutting edge: HLA-DM-mediated peptide exchange functions normally on MHC class II-peptide complexes that have been weakened by elimination of a conserved hydrogen bond. THE JOURNAL OF IMMUNOLOGY 2009; 184:1153-8. [PMID: 20038641 DOI: 10.4049/jimmunol.0902878] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The mechanism by which HLA-DM (DM) promotes exchange of peptides bound to HLA-DR (DR) is still unclear. We have shown that peptide interaction with DR1 can be considered a folding process as evidenced by cooperativity. However, in DM-mediated ligand exchange, prebound peptide release is noncooperative, which could be a function of the breaking of a critical interaction. The hydrogen bond (H-bond) between beta-chain His(81) and the peptide backbone at the -1 position is a candidate for such a target. In this study, we analyze the exchange of peptides bound to a DR1 mutant in which formation of this H-bond is impaired. We observe that DM still functions normally. However, as expected of a cooperative model, this H-bond contributes to the overall energetics of the complex and its disruption impacts the ability of the exchange ligand to fold with the binding groove into a stable complex.
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Affiliation(s)
- Andrea Ferrante
- Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI 53201, USA.
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Zhou Z, Callaway KA, Weber DA, Jensen PE. Cutting edge: HLA-DM functions through a mechanism that does not require specific conserved hydrogen bonds in class II MHC-peptide complexes. THE JOURNAL OF IMMUNOLOGY 2009; 183:4187-91. [PMID: 19767569 DOI: 10.4049/jimmunol.0901663] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
HLA-DM catalyzes peptide dissociation and exchange in class II MHC molecules through a mechanism that has been proposed to involve the disruption of specific components of the conserved hydrogen bond network in MHC-peptide complexes. HLA-DR1 molecules with alanine substitutions at each of the six conserved H- bonding positions were expressed in cells, and susceptibility to DM catalytic activity was evaluated by measuring the release of CLIP. The mutants alphaN62A, alphaN69A, alphaR76A, and betaH81A DR1 were fully susceptible to DM-mediated CLIP release, and betaN82A resulted in spontaneous release of CLIP. Using recombinant soluble DR1 molecules, the amino acid betaN82 was observed to contribute disproportionately in stabilizing peptide complexes. Remarkably, the catalytic potency of DM with each beta-chain mutant was equal to or greater than that observed with wild-type DR1. Our results support the conclusion that no individual component of the conserved hydrogen bond network plays an essential role in the DM catalytic mechanism.
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Affiliation(s)
- Zemin Zhou
- Department of Pathology, University of Utah, Salt Lake City, UT 84112, USA
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34
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Weaver JM, Sant AJ. Understanding the focused CD4 T cell response to antigen and pathogenic organisms. Immunol Res 2009; 45:123-43. [PMID: 19198764 DOI: 10.1007/s12026-009-8095-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Immunodominance is a term that reflects the final, very limited peptide specificity of T cells that are elicited during an immune response. Recent experiments in our laboratory compel us to propose a new paradigm for the control of immunodominance in CD4 T cell responses, stating that immunodominance is peptide-intrinsic and is dictated by the off-rate of peptides from MHC class II molecules. Our studies have revealed that persistence of peptide:class II complexes both predicts and controls CD4 T cell immunodominance and that this parameter can be rationally manipulated to either promote or eliminate immune responses. Mechanistically, we have determined that DM editing in APC is a key event that is influenced by the kinetic stability of class II:peptide complexes and that differential persistence of complexes also impacts the expansion phase of the immune response. These studies have important implications for rational vaccine design and for understanding the immunological mechanisms that limit the specificity of CD4 T cell responses.
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Affiliation(s)
- Jason M Weaver
- David H. Smith Center for Vaccine Biology and Immunology, AaB Institute of Biomedical Sciences, Department of Microbiology and Immunology, University of Rochester, NY 14642, USA
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35
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Yaneva R, Springer S, Zacharias M. Flexibility of the MHC class II peptide binding cleft in the bound, partially filled, and empty states: A molecular dynamics simulation study. Biopolymers 2009; 91:14-27. [DOI: 10.1002/bip.21078] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Deshaies F, Diallo DA, Fortin JS, O'Rourke HM, Pezeshki AM, Bellemare-Pelletier A, Raby N, Bédard N, Brunet A, Denzin LK, Thibodeau J. Evidence for a human leucocyte antigen-DM-induced structural change in human leucocyte antigen-DObeta. Immunology 2008; 127:408-17. [PMID: 19019088 DOI: 10.1111/j.1365-2567.2008.02984.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Human leucocyte antigen (HLA)-DO is a non-classical major histocompatibility complex class II molecule which modulates the function of HLA-DM and the loading of antigenic peptides on molecules such as HLA-DR. The bulk of HLA-DO associates with HLA-DM and this interaction is critical for HLA-DO egress from the endoplasmic reticulum. HLA-DM assists the early steps of HLA-DO maturation presumably through the stabilization of the interactions between the N-terminal regions of the alpha and beta chains. To evaluate a possible role for HLA-DM in influencing the conformation of HLA-DO, we made use of a monoclonal antibody, Mags.DO5, that was raised against HLA-DO/DM complexes. Using transfected cells expressing mismatched heterodimers between HLA-DR and -DO chains, we found that the epitope for Mags.DO5 is located on the DObeta chain and that Mags.DO5 reactivity was increased upon cotransfection with HLA-DM. Our results suggest that HLA-DM influences the folding of HLA-DO in the endoplasmic reticulum. A mutant HLA-DO showing reduced capacity for endoplasmic reticulum egress was better recognized by Mags.DO5 in the presence of HLA-DM. On the other hand, an HLA-DO mutant capable of endoplasmic reticulum egress on its own was efficiently recognized by Mags.DO5, irrespective of the presence of HLA-DM. Taken together, our results suggest that HLA-DM acts as a private chaperone, directly assisting the folding of HLA-DO to promote egress from the endoplasmic reticulum.
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Affiliation(s)
- Francis Deshaies
- Laboratoire d'Immunologie Moléculaire, Département de Microbiologie et Immunologie, Université de Montréal, Montréal, QC, Canada
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HLA-DM mediates epitope selection by a "compare-exchange" mechanism when a potential peptide pool is available. PLoS One 2008; 3:e3722. [PMID: 19005572 PMCID: PMC2580030 DOI: 10.1371/journal.pone.0003722] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Accepted: 10/27/2008] [Indexed: 11/19/2022] Open
Abstract
Background HLA-DM (DM) mediates exchange of peptides bound to MHC class II (MHCII) during the epitope selection process. Although DM has been shown to have two activities, peptide release and MHC class II refolding, a clear characterization of the mechanism by which DM facilitates peptide exchange has remained elusive. Methodology/Principal Findings We have previously demonstrated that peptide binding to and dissociation from MHCII in the absence of DM are cooperative processes, likely related to conformational changes in the peptide-MHCII complex. Here we show that DM promotes peptide release by a non-cooperative process, whereas it enhances cooperative folding of the exchange peptide. Through electron paramagnetic resonance (EPR) and fluorescence polarization (FP) we show that DM releases prebound peptide very poorly in the absence of a candidate peptide for the exchange process. The affinity and concentration of the candidate peptide are also important for the release of the prebound peptide. Increased fluorescence energy transfer between the prebound and exchange peptides in the presence of DM is evidence for a tetramolecular complex which resolves in favor of the peptide that has superior folding properties. Conclusion/Significance This study shows that both the peptide releasing activity on loaded MHCII and the facilitating of MHCII binding by a candidate exchange peptide are integral to DM mediated epitope selection. The exchange process is initiated only in the presence of candidate peptides, avoiding possible release of a prebound peptide and loss of a potential epitope. In a tetramolecular transitional complex, the candidate peptides are checked for their ability to replace the pre-bound peptide with a geometry that allows the rebinding of the original peptide. Thus, DM promotes a “compare-exchange” sorting algorithm on an available peptide pool. Such a “third party”-mediated mechanism may be generally applicable for diverse ligand recognition in other biological systems.
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38
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Fallang LE, Roh S, Holm A, Bergseng E, Yoon T, Fleckenstein B, Bandyopadhyay A, Mellins ED, Sollid LM. Complexes of two cohorts of CLIP peptides and HLA-DQ2 of the autoimmune DR3-DQ2 haplotype are poor substrates for HLA-DM. THE JOURNAL OF IMMUNOLOGY 2008; 181:5451-5461. [PMID: 18832702 DOI: 10.4049/jimmunol.181.8.5451] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Atypical invariant chain (Ii) CLIP fragments (CLIP2) have been found in association with HLA-DQ2 (DQ2) purified from cell lysates. We mapped the binding register of CLIP2 (Ii 96-104) to DQ2 and found proline at the P1 position, in contrast to the canonical CLIP1 (Ii 83-101) register with methionine at P1. CLIP1/2 peptides are the predominant peptide species, even for DQ2 from HLA-DM (DM)-expressing cells. We hypothesized that DQ2-CLIP1/2 might be poor substrates for DM. We measured DM-mediated exchange of CLIP and other peptides for high-affinity indicator peptides and found it is inefficient for DQ2. DM-DQ-binding and DM chaperone effects on conformation and levels of DQ are also reduced for DQ2, compared with DQ1. We suggest that the unusual interaction of DQ2 with Ii and DM may provide a basis for the known disease associations of DQ2.
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Affiliation(s)
- Lars-Egil Fallang
- Centre for Immune Regulation and Institute of Immunology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
| | - Sujin Roh
- Department of Pediatrics, Stanford University, Stanford, CA 94305, USA
| | - Anders Holm
- Centre for Immune Regulation and Institute of Immunology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
| | - Elin Bergseng
- Centre for Immune Regulation and Institute of Immunology, Rikshospitalet University Hospital, N-0027 Oslo, Norway
| | - Taejin Yoon
- Department of Pediatrics, Stanford University, Stanford, CA 94305, USA
| | - Burkhard Fleckenstein
- Centre for Immune Regulation and Institute of Immunology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
| | | | | | - Ludvig M Sollid
- Centre for Immune Regulation and Institute of Immunology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway.,Centre for Immune Regulation and Institute of Immunology, Rikshospitalet University Hospital, N-0027 Oslo, Norway
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39
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Sadegh-Nasseri S, Chen M, Narayan K, Bouvier M. The convergent roles of tapasin and HLA-DM in antigen presentation. Trends Immunol 2008. [PMID: 18261958 DOI: 10.1016/j.it.2008.01.001.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
Abstract
Cytotoxic and helper T cells respond to peptides derived from endogenous and exogenous sources that bind to major histocompatibility complex (MHC) class I and class II molecules and are presented on antigen-presenting cells. MHC class I and class II structures and maturation pathways have evolved to optimize antigen presentation to their respective T cells. The accessory proteins tapasin and HLA-DM (DM) crucially influence the selection of peptides that bind to the MHC molecules. We discuss here the dynamic interactions of tapasin and DM with their corresponding MHC molecules that indicate striking parallels. Utilization of a common mode of peptide selection by two different, but related, biological systems argue for its mechanistic validity.
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40
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Sadegh-Nasseri S, Chen M, Narayan K, Bouvier M. The convergent roles of tapasin and HLA-DM in antigen presentation. Trends Immunol 2008; 29:141-7. [PMID: 18261958 DOI: 10.1016/j.it.2008.01.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 12/21/2007] [Accepted: 01/02/2008] [Indexed: 02/02/2023]
Abstract
Cytotoxic and helper T cells respond to peptides derived from endogenous and exogenous sources that bind to major histocompatibility complex (MHC) class I and class II molecules and are presented on antigen-presenting cells. MHC class I and class II structures and maturation pathways have evolved to optimize antigen presentation to their respective T cells. The accessory proteins tapasin and HLA-DM (DM) crucially influence the selection of peptides that bind to the MHC molecules. We discuss here the dynamic interactions of tapasin and DM with their corresponding MHC molecules that indicate striking parallels. Utilization of a common mode of peptide selection by two different, but related, biological systems argue for its mechanistic validity.
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41
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Davies MN, Lamikanra A, Sansom CE, Flower DR, Moss DS, Travers PJ. Identification of the HLA-DM/HLA-DR interface. Mol Immunol 2008; 45:1063-70. [PMID: 17870168 DOI: 10.1016/j.molimm.2007.07.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 05/15/2007] [Accepted: 07/20/2007] [Indexed: 11/26/2022]
Abstract
Human leukocyte antigen (HLA)-DM is a critical participant in antigen presentation that catalyzes the dissociation of the Class II-associated Invariant chain-derived Peptide (CLIP) from the major histocompatibility complex (MHC) Class II molecules. There is competition amongst peptides for access to an MHC Class II groove and it has been hypothesised that DM functions as a 'peptide editor' that catalyzes the replacement of one peptide for another within the groove. It is established that the DM catalyst interacts directly with the MHC Class II but the precise location of the interface is unknown. Here, we combine previously described mutational data with molecular docking and energy minimisation simulations to identify a putative interaction site of >4000A2 which agrees with known point mutational data for both the DR and DM molecule. The docked structure is validated by comparison with experimental data and previously determined properties of protein-protein interfaces. A possible dissociation mechanism is suggested by the presence of an acidic cluster near the N terminus of the bound peptide.
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Affiliation(s)
- Matthew N Davies
- Edward Jenner Institute, Nuffield Department of Clinical Medicine, John Radcliffe Hospital, University of Oxford, Headley Way, Headington, Oxford OX3 9DU, UK
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42
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Bandyopadhyay A, Arneson L, Beeson C, Sant AJ. The relative energetic contributions of dominant P1 pocket versus hydrogen bonding interactions to peptide:class II stability: implications for the mechanism of DM function. Mol Immunol 2007; 45:1248-57. [PMID: 17980431 DOI: 10.1016/j.molimm.2007.09.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Accepted: 09/18/2007] [Indexed: 01/28/2023]
Abstract
Peptides are bound to MHC class II molecules by an array of hydrogen bonds between conserved MHC class II protein side-chains and the peptide backbone and through interactions between MHC protein pockets and peptide side-chain anchors. The crystal structure of murine I-A(k) protein with peptide shows a network of electrostatic interactions with the P1 aspartic acid anchor and an arginine in the P1 pocket that are thought to constitute the major stabilizing interaction between peptide and MHC. In this paper, have explored the relative energetic contribution of this dominant P1 pocket interaction with that made by a genetically conserved hydrogen bond which is formed by the beta 81 histidine residue and the main chain of the bound peptide. We have performed peptide dissociation experiments using antigenic peptides or variants that have altered side-chain interactions with the I-A(k) P1 pocket using either native I-A(k) or I-A(k) proteins mutated to disrupt the N-terminal hydrogen bond. The results demonstrate that the N-terminal hydrogen bonds in I-A(k) complexes make highly significant energetic contributions to the kinetic stabilities comparable to or greater than the energetic contribution of highly favorable P1 pocket interactions. Hence, we conclude that the kinetic stability of MHC class II:peptide complexes critically depends on two quite distinct molecular interactions between peptide and MHC located at the peptide's amino terminus. We discuss these results in light of the proposed mechanism for DM function.
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43
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Wearsch PA, Cresswell P. Selective loading of high-affinity peptides onto major histocompatibility complex class I molecules by the tapasin-ERp57 heterodimer. Nat Immunol 2007; 8:873-81. [PMID: 17603487 DOI: 10.1038/ni1485] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 06/06/2007] [Indexed: 11/09/2022]
Abstract
Major histocompatibility complex (MHC) class I glycoproteins bind peptides in the endoplasmic reticulum after incorporation into the peptide-loading complex, whose core is the transporter associated with antigen processing. Other components are the chaperone calreticulin, the thiol oxidoreductase ERp57, and tapasin. Tapasin and ERp57 have been shown to exist in the peptide-loading complex as a disulfide-linked heterodimer. Here, using a cell-free system, we demonstrate that although recombinant tapasin was ineffective in recruiting MHC class I molecules and facilitating peptide binding, recombinant tapasin-ERp57 conjugates accomplished both of those functions and also 'edited' the repertoire of bound peptides to maximize their affinity. Thus, the tapasin-ERp57 conjugate is the functional unit of the peptide-loading complex that generates MHC class I molecules with stably associated peptides.
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Affiliation(s)
- Pamela A Wearsch
- Department of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA
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44
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Narayan K, Chou CL, Kim A, Hartman IZ, Dalai S, Khoruzhenko S, Sadegh-Nasseri S. HLA-DM targets the hydrogen bond between the histidine at position beta81 and peptide to dissociate HLA-DR-peptide complexes. Nat Immunol 2006; 8:92-100. [PMID: 17143275 PMCID: PMC3019572 DOI: 10.1038/ni1414] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 10/24/2006] [Indexed: 11/08/2022]
Abstract
The peptide editor HLA-DM (DM) mediates exchange of peptides bound to major histocompatibility (MHC) class II molecules during antigen processing; however, the mechanism by which DM displaces peptides remains unclear. Here we generated a soluble mutant HLA-DR1 with a histidine-to-asparagine substitution at position 81 of the beta-chain (DR1betaH81N) to perturb an important hydrogen bond between MHC class II and peptide. Peptide-DR1betaH81N complexes dissociated at rates similar to the dissociation rates of DM-induced peptide-wild-type DR1, and DM did not enhance the dissociation of peptide-DR1betaH81N complexes. Reintroduction of an appropriate hydrogen bond (DR1betaH81N betaV85H) restored DM-mediated peptide dissociation. Thus, DR1betaH81N might represent a 'post-DM effect' conformation. We suggest that DM may mediate peptide dissociation by a 'hit-and-run' mechanism that results in conformational changes in MHC class II molecules and disruption of hydrogen bonds between betaHis81 and bound peptide.
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Affiliation(s)
- Kedar Narayan
- Graduate Program in Immunology, Johns Hopkins University Baltimore, Maryland 21205, USA
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45
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Lazarski CA, Chaves FA, Sant AJ. The impact of DM on MHC class II-restricted antigen presentation can be altered by manipulation of MHC-peptide kinetic stability. ACTA ACUST UNITED AC 2006; 203:1319-28. [PMID: 16682499 PMCID: PMC2121212 DOI: 10.1084/jem.20060058] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
DM edits the peptide repertoire presented by major histocompatibility complex class II molecules by professional antigen-presenting cells (APCs), favoring presentation of some peptides over others. Despite considerable research by many laboratories, there is still significant uncertainty regarding the biochemical attributes of class II–peptide complexes that govern their susceptibility to DM editing. Here, using APCs that either do or do not express DM and a set of unrelated antigens, we found that the intrinsic kinetic stability of class II–peptide complexes is tightly correlated with the effects of DM editing within APCs. Furthermore, through the use of kinetic stability variants of three independent peptides, we demonstrate that increasing or decreasing the kinetic stability of class II–peptide complexes causes a corresponding alteration in DM editing. Finally, we show that the spontaneous kinetic stability of class II complexes correlates directly with the efficiency of presentation by DM+ APCs and the immunodominance of that class II–peptide complex during an immune response. Collectively, these results suggest that the pattern of DM editing in APCs can be intentionally changed by modifying class II–peptide interactions, leading to the desired hierarchy of presentation on APCs, thereby promoting recruitment of CD4 T cells specific for the preferred peptides during an immune response.
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Affiliation(s)
- Christopher A Lazarski
- David H. Smith Center for Vaccine Biology and Immunology, Aab Institute and Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA
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46
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Lovitch SB, Pu Z, Unanue ER. Amino-terminal flanking residues determine the conformation of a peptide-class II MHC complex. THE JOURNAL OF IMMUNOLOGY 2006; 176:2958-68. [PMID: 16493054 DOI: 10.4049/jimmunol.176.5.2958] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The peptide spanning residues 48-62 of hen egg white lysozyme presented by I-A(k) molecules gives rise to two T cell populations, types A and B, that recognize distinct conformers of the complex generated in late and recycling endosomes. The class II-like accessory molecule H2-DM functions as a conformational editor, eliminating the type B conformer in late endosomes. Here, we show that the conformation of the complex, and its susceptibility to editing by H2-DM, are determined by peptide amino-terminal flanking residues. Elimination of these residues abolished editing, permitting formation of the type B conformer in late endosomes. Substitutions at P(-2) affected the stability of the type B conformer, preventing its formation and/or editing, without hindering peptide binding or formation of the type A conformer of the complex. We conclude that interactions involving amino-terminal flanking residues stabilize peptide-MHC conformers and confer resistance to editing by H2-DM, influencing the nature of the T cell repertoire.
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Affiliation(s)
- Scott B Lovitch
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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47
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Suri A, Lovitch SB, Unanue ER. The wide diversity and complexity of peptides bound to class II MHC molecules. Curr Opin Immunol 2005; 18:70-7. [PMID: 16316750 DOI: 10.1016/j.coi.2005.11.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Accepted: 11/10/2005] [Indexed: 01/25/2023]
Abstract
The identification and quantitation of peptides selected by class II MHC molecules during natural processing of proteins is of key importance in understanding the repertoire and distribution of T cells. The examination of peptides selected by class II MHC molecules has depended greatly on mass spectrometry, a powerful technique that identifies and sequences peptides in complex mixtures with great sensitivity and precision. Such analysis has resulted in the identification of several factors, including the repertoire of peptides selected by MHC molecules during natural processing of proteins, motifs important for selection of processed peptides, conformational isomers of peptide-MHC complexes, and post-translational changes to the peptides.
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Affiliation(s)
- Anish Suri
- Washington University School of Medicine, Department of Pathology and Immunology, 660 South Euclid Avenue, St. Louis, MO 63110, USA
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48
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Abstract
The relative plasticity of peptide binding to class II major histocompatibility complex (MHC) molecules permits formation of multiple conformational isomers by the same peptide and MHC molecule; such conformers are specifically recognized by distinct subsets of T cells. Here, we review current knowledge and recent advances in our understanding of peptide-class II MHC conformational isomerism and the mechanisms that generate distinct MHC-peptide conformers. We focus on our studies of two T-cell subsets, type A and B, which recognize distinct conformers of the dominant epitope of hen egg white lysozyme presented by I-A(k). These conformers form via different pathways and in distinct intracellular vesicles: the type A conformer forms in late endosomes upon processing of native protein, while the more flexible type B conformer forms in early endosomes and at the cell surface. In this process, H2-DM acts as a conformational editor, eliminating the type B conformer in late endosomes. Type B T cells constitute a significant component of the naïve T-cell repertoire; furthermore, self-reactive type B T cells escape negative selection and are present in abundance in the periphery. Ongoing studies should elucidate the role of type B T cells in immunity to pathogens and in autoimmune pathology.
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Affiliation(s)
- Scott B Lovitch
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO 63110, USA
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Busch R, Rinderknecht CH, Roh S, Lee AW, Harding JJ, Burster T, Hornell TMC, Mellins ED. Achieving stability through editing and chaperoning: regulation of MHC class II peptide binding and expression. Immunol Rev 2005; 207:242-60. [PMID: 16181341 DOI: 10.1111/j.0105-2896.2005.00306.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In antigen-presenting cells (APCs), loading of major histocompatibility complex class II (MHC II) molecules with peptides is regulated by invariant chain (Ii), which blocks MHC II antigen-binding sites in pre-endosomal compartments. Several molecules then act upon MHC II molecules in endosomes to facilitate peptide loading: Ii-degrading proteases, the peptide exchange factor, human leukocyte antigen-DM (HLA-DM), and its modulator, HLA-DO (DO). Here, we review our findings arguing that DM stabilizes a globally altered conformation of the antigen-binding groove by binding to a lateral surface of the MHC II molecule. Our data imply changes in the interactions between specificity pockets and peptide side chains, complementing data from others that suggest DM affects hydrogen bonds. Selective weakening of peptide/MHC interactions allows DM to alter the peptide repertoire. We also review our studies in cells that highlight the ability of several factors to modulate surface expression of MHC II molecules via post-Golgi mechanisms; these factors include MHC class II-associated Ii peptides (CLIP), DM, and microbial products that modulate MHC II traffic from endosomes to the plasma membrane. In this context, we discuss possible mechanisms by which the association of some MHC II alleles with autoimmune diseases may be linked to their low CLIP affinity.
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Affiliation(s)
- Robert Busch
- Division of Pediatric Immunology and Transplantation Biology, Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94705, USA
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50
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Sant AJ, Chaves FA, Jenks SA, Richards KA, Menges P, Weaver JM, Lazarski CA. The relationship between immunodominance, DM editing, and the kinetic stability of MHC class II:peptide complexes. Immunol Rev 2005; 207:261-78. [PMID: 16181342 DOI: 10.1111/j.0105-2896.2005.00307.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Immunodominance refers to the restricted antigen specificity of T cells detected in the immune response after immunization with complex antigens. Despite the presence of many potential peptide epitopes within these immunogens, the elicited T-cell response apparently focuses on a very limited number of peptides. Over the last two decades, a number of distinct explanations have been put forth to explain this very restricted specificity of T cells, many of which suggest that endosomal antigen processing restricts the array of peptides available to recruit CD4 T cells. In this review, we present evidence from our laboratory that suggest that immunodominance in CD4 T-cell responses is primarily due to an intrinsic property of the peptide:class II complexes. The intrinsic kinetic stability of peptide:class II complexes controls DM editing within the antigen-presenting cells and thus the initial epitope density on priming dendritic cells. Additionally, we hypothesize that peptides that possess high kinetic stability interactions with class II molecules display persistence at the cell surface over time and will more efficiently promote T-cell signaling and differentiation than competing, lower-stability peptides contained within the antigen. We discuss this model in the context of the existing data in the field of immunodominance.
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Affiliation(s)
- Andrea J Sant
- David H. Smith Center for Vaccine Biology and Immunology, Aab Institute and Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA.
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