1
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Rogers J, Bajur AT, Salaita K, Spillane KM. Mechanical control of antigen detection and discrimination by T and B cell receptors. Biophys J 2024:S0006-3495(24)00347-3. [PMID: 38794795 DOI: 10.1016/j.bpj.2024.05.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 05/10/2024] [Accepted: 05/21/2024] [Indexed: 05/26/2024] Open
Abstract
The adaptive immune response is orchestrated by just two cell types, T cells and B cells. Both cells possess the remarkable ability to recognize virtually any antigen through their respective antigen receptors-the T cell receptor (TCR) and B cell receptor (BCR). Despite extensive investigations into the biochemical signaling events triggered by antigen recognition in these cells, our ability to predict or control the outcome of T and B cell activation remains elusive. This challenge is compounded by the sensitivity of T and B cells to the biophysical properties of antigens and the cells presenting them-a phenomenon we are just beginning to understand. Recent insights underscore the central role of mechanical forces in this process, governing the conformation, signaling activity, and spatial organization of TCRs and BCRs within the cell membrane, ultimately eliciting distinct cellular responses. Traditionally, T cells and B cells have been studied independently, with researchers working in parallel to decipher the mechanisms of activation. While these investigations have unveiled many overlaps in how these cell types sense and respond to antigens, notable differences exist. To fully grasp their biology and harness it for therapeutic purposes, these distinctions must be considered. This review compares and contrasts the TCR and BCR, placing emphasis on the role of mechanical force in regulating the activity of both receptors to shape cellular and humoral adaptive immune responses.
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Affiliation(s)
- Jhordan Rogers
- Department of Chemistry, Emory University, Atlanta, Georgia
| | - Anna T Bajur
- Department of Physics, King's College London, London, United Kingdom; Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Khalid Salaita
- Department of Chemistry, Emory University, Atlanta, Georgia; Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia.
| | - Katelyn M Spillane
- Department of Physics, King's College London, London, United Kingdom; Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom; Department of Life Sciences, Imperial College London, London, United Kingdom.
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2
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Acuto O. T-cell virtuosity in ''knowing thyself". Front Immunol 2024; 15:1343575. [PMID: 38415261 PMCID: PMC10896960 DOI: 10.3389/fimmu.2024.1343575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Accepted: 01/17/2024] [Indexed: 02/29/2024] Open
Abstract
Major Histocompatibility Complex (MHC) I and II and the αβ T-cell antigen receptor (TCRαβ) govern fundamental traits of adaptive immunity. They form a membrane-borne ligand-receptor system weighing host proteome integrity to detect contamination by nonself proteins. MHC-I and -II exhibit the "MHC-fold", which is able to bind a large assortment of short peptides as proxies for self and nonself proteins. The ensuing varying surfaces are mandatory ligands for Ig-like TCRαβ highly mutable binding sites. Conserved molecular signatures guide TCRαβ ligand binding sites to focus on the MHC-fold (MHC-restriction) while leaving many opportunities for its most hypervariable determinants to contact the peptide. This riveting molecular strategy affords many options for binding energy compatible with specific recognition and signalling aimed to eradicated microbial pathogens and cancer cells. While the molecular foundations of αβ T-cell adaptive immunity are largely understood, uncertainty persists on how peptide-MHC binding induces the TCRαβ signals that instruct cell-fate decisions. Solving this mystery is another milestone for understanding αβ T-cells' self/nonself discrimination. Recent developments revealing the innermost links between TCRαβ structural dynamics and signalling modality should help dissipate this long-sought-after enigma.
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Affiliation(s)
- Oreste Acuto
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
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3
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Mo G, Lu X, Wu S, Zhu W. Strategies and rules for tuning TCR-derived therapy. Expert Rev Mol Med 2023; 26:e4. [PMID: 38095091 PMCID: PMC11062142 DOI: 10.1017/erm.2023.27] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 08/17/2023] [Accepted: 12/05/2023] [Indexed: 04/04/2024]
Abstract
Manipulation of T cells has revolutionized cancer immunotherapy. Notably, the use of T cells carrying engineered T cell receptors (TCR-T) offers a favourable therapeutic pathway, particularly in the treatment of solid tumours. However, major challenges such as limited clinical response efficacy, off-target effects and tumour immunosuppressive microenvironment have hindered the clinical translation of this approach. In this review, we mainly want to guide TCR-T investigators on several major issues they face in the treatment of solid tumours after obtaining specific TCR sequences: (1) whether we have to undergo affinity maturation or not, and what parameter we should use as a criterion for being more effective. (2) What modifications can be added to counteract the tumour inhibitory microenvironment to make our specific T cells to be more effective and what is the safety profile of such modifications? (3) What are the new forms and possibilities for TCR-T cell therapy in the future?
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Affiliation(s)
- Guoheng Mo
- State Key Laboratory of Organ Failure Research, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xinyu Lu
- State Key Laboratory of Organ Failure Research, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Sha Wu
- Department of Immunology/Guangdong Provincial Key Laboratory of Proteomics, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, People's Republic of China
| | - Wei Zhu
- State Key Laboratory of Organ Failure Research, Guangdong Provincial Key Laboratory of Viral Hepatitis Research, Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou, China
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4
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Ayres CM, Corcelli SA, Baker BM. The Energetic Landscape of Catch Bonds in TCR Interfaces. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2023; 211:325-332. [PMID: 37459192 PMCID: PMC10361606 DOI: 10.4049/jimmunol.2300121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 04/14/2023] [Indexed: 07/20/2023]
Abstract
Recognition of peptide/MHC complexes by αβ TCRs has traditionally been viewed through the lens of conventional receptor-ligand theory. Recent work, however, has shown that TCR recognition and T cell signaling can be profoundly influenced and tuned by mechanical forces. One outcome of applied force is the catch bond, where TCR dissociation rates decrease (half-lives increase) when limited force is applied. Although catch bond behavior is believed to be widespread in biology, its counterintuitive nature coupled with the difficulties of describing mechanisms at the structural level have resulted in considerable mystique. In this review, we demonstrate that viewing catch bonds through the lens of energy landscapes, barriers, and the ensuing reaction rates can help demystify catch bonding and provide a foundation on which atomic-level TCR catch bond mechanisms can be built.
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Affiliation(s)
- Cory M Ayres
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN
- The Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN
| | - Steve A Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN
| | - Brian M Baker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN
- The Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN
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5
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Lanz AL, Masi G, Porciello N, Cohnen A, Cipria D, Prakaash D, Bálint Š, Raggiaschi R, Galgano D, Cole DK, Lepore M, Dushek O, Dustin ML, Sansom MSP, Kalli AC, Acuto O. Allosteric activation of T cell antigen receptor signaling by quaternary structure relaxation. Cell Rep 2021; 36:109375. [PMID: 34260912 PMCID: PMC8293630 DOI: 10.1016/j.celrep.2021.109375] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 05/05/2021] [Accepted: 06/18/2021] [Indexed: 01/05/2023] Open
Abstract
The mechanism of T cell antigen receptor (TCR-CD3) signaling remains elusive. Here, we identify mutations in the transmembrane region of TCRβ or CD3ζ that augment peptide T cell antigen receptor (pMHC)-induced signaling not explicable by enhanced ligand binding, lateral diffusion, clustering, or co-receptor function. Using a biochemical assay and molecular dynamics simulation, we demonstrate that the gain-of-function mutations loosen the interaction between TCRαβ and CD3ζ. Similar to the activating mutations, pMHC binding reduces TCRαβ cohesion with CD3ζ. This event occurs prior to CD3ζ phosphorylation and at 0°C. Moreover, we demonstrate that soluble monovalent pMHC alone induces signaling and reduces TCRαβ cohesion with CD3ζ in membrane-bound or solubilised TCR-CD3. Our data provide compelling evidence that pMHC binding suffices to activate allosteric changes propagating from TCRαβ to the CD3 subunits, reconfiguring interchain transmembrane region interactions. These dynamic modifications could change the arrangement of TCR-CD3 boundary lipids to license CD3ζ phosphorylation and initiate signal propagation. Mutations in TCRβ and CD3ζ TMRs that reduce their interaction augment signaling pMHC and anti-CD3 binding to TCR-CD3 induce similar quaternary structure relaxation Soluble monovalent pMHC alone signals and reduces TCRαβ cohesion with CD3ζ Allosteric changes in TCR-CD3 dynamics instigate T cell activation
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Affiliation(s)
- Anna-Lisa Lanz
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Giulia Masi
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Nicla Porciello
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - André Cohnen
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Deborah Cipria
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Dheeraj Prakaash
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Štefan Bálint
- Kennedy Institute of Rheumatology, University of Oxford, Oxford OX3 7FY, UK
| | - Roberto Raggiaschi
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Donatella Galgano
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - David K Cole
- Division Infection & Immunity, Cardiff University, Cardiff CF14 4XN, UK; Immunocore Ltd., Abingdon OX14 4RY, UK
| | | | - Omer Dushek
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK
| | - Michael L Dustin
- Kennedy Institute of Rheumatology, University of Oxford, Oxford OX3 7FY, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
| | - Antreas C Kalli
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 9JT, UK; Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
| | - Oreste Acuto
- T-cell signalling laboratory, Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, UK.
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6
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Bingöl EN, Serçinoğlu O, Ozbek P. Unraveling the Allosteric Communication Mechanisms in T-Cell Receptor-Peptide-Loaded Major Histocompatibility Complex Dynamics Using Molecular Dynamics Simulations: An Approach Based on Dynamic Cross Correlation Maps and Residue Interaction Energy Calculations. J Chem Inf Model 2021; 61:2444-2453. [PMID: 33930270 DOI: 10.1021/acs.jcim.1c00338] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Antigen presentation by major histocompatibility complex (MHC) proteins to T-cell receptors (TCRs) plays a crucial role in triggering the adaptive immune response. Most of our knowledge on TCR-peptide-loaded major histocompatibility complex (pMHC) interaction stemmed from experiments yielding static structures, yet the dynamic aspects of this molecular interaction are equally important to understand the underlying molecular mechanisms and to develop treatment strategies against diseases such as cancer and autoimmune diseases. To this end, computational biophysics studies including all-atom molecular dynamics simulations have provided useful insights; however, we still lack a basic understanding of an overall allosteric mechanism that results in conformational changes in the TCR and subsequent T-cell activation. Previous hydrogen-deuterium exchange and nuclear magnetic resonance studies provided clues regarding these molecular mechanisms, including global rigidification and allosteric effects on the constant domain of TCRs away from the pMHC interaction site. Here, we show that molecular dynamics simulations can be used to identify how this overall rigidification may be related to the allosteric communication within TCRs upon pMHC interaction via essential dynamics and nonbonded residue-residue interaction energy analyses. The residues taking part in the rigidification effect are highlighted with an intricate analysis on residue interaction changes, which lead to a detailed outline of the complex formation event. Our results indicate that residues of the Cβ domain of TCRs show significant differences in their nonbonded interactions upon complex formation. Moreover, the dynamic cross correlations between these residues are also increased, in line with their nonbonded interaction energy changes. Altogether, our approach may be valuable for elucidating intramolecular allosteric changes in the TCR structure upon pMHC interaction in molecular dynamics simulations.
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Affiliation(s)
- Elif Naz Bingöl
- Department of Bioengineering, Institute of Pure and Applied Sciences, Marmara University, 34722 Istanbul, Turkey
| | - Onur Serçinoğlu
- Department of Bioengineering, Faculty of Engineering, Gebze Technical University, Kocaeli 41400, Turkey
| | - Pemra Ozbek
- Department of Bioengineering, Faculty of Engineering, Marmara University, Istanbul 34722, Turkey
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7
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Ma J, Ayres CM, Hellman LM, Devlin JR, Baker BM. Dynamic allostery controls the peptide sensitivity of the Ly49C natural killer receptor. J Biol Chem 2021; 296:100686. [PMID: 33891944 PMCID: PMC8138769 DOI: 10.1016/j.jbc.2021.100686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 04/14/2021] [Accepted: 04/19/2021] [Indexed: 11/30/2022] Open
Abstract
Using a variety of activating and inhibitory receptors, natural killer (NK) cells protect against disease by eliminating cells that have downregulated class I major histocompatibility complex (MHC) proteins, such as in response to cell transformation or viral infection. The inhibitory murine NK receptor Ly49C specifically recognizes the class I MHC protein H-2Kb. Unusual among NK receptors, Ly49C exhibits a peptide-dependent sensitivity to H-2Kb recognition, which has not been explained despite detailed structural studies. To gain further insight into Ly49C peptide sensitivity, we examined Ly49C recognition biochemically and through the lens of dynamic allostery. We found that the peptide sensitivity of Ly49C arises through small differences in H-2Kb-binding affinity. Although molecular dynamics simulations supported a role for peptide-dependent protein dynamics in producing these differences in binding affinity, calorimetric measurements indicated an enthalpically as opposed to entropically driven process. A quantitative linkage analysis showed that this emerges from peptide-dependent dynamic tuning of electrostatic interactions across the Ly49C–H-2Kb interface. We propose a model whereby different peptides alter the flexibility of H-2Kb, which in turn changes the strength of electrostatic interactions across the protein–protein interface. Our results provide a quantitative assessment of how peptides alter Ly49C-binding affinity, suggest the underlying mechanism, and demonstrate peptide-driven allostery at work in class I MHC proteins. Lastly, our model provides a solution for how dynamic allostery could impact binding of some, but not all, class I MHC partners depending on the structural and chemical composition of the interfaces.
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Affiliation(s)
- Jiaqi Ma
- Department of Chemistry & Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana, USA
| | - Cory M Ayres
- Department of Chemistry & Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana, USA
| | - Lance M Hellman
- Department of Physical and Life Sciences, Nevada State College, Henderson, Nevada, USA
| | - Jason R Devlin
- Department of Chemistry & Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana, USA
| | - Brian M Baker
- Department of Chemistry & Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana, USA.
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8
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Merkle PS, Trabjerg E, Hongjian S, Ferber M, Cuendet MA, Jørgensen TJD, Luescher I, Irving M, Zoete V, Michielin O, Rand KD. Probing the Conformational Dynamics of Affinity-Enhanced T Cell Receptor Variants upon Binding the Peptide-Bound Major Histocompatibility Complex by Hydrogen/Deuterium Exchange Mass Spectrometry. Biochemistry 2021; 60:859-872. [PMID: 33689297 DOI: 10.1021/acs.biochem.1c00035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Binding of the T cell receptor (TCR) to its cognate, peptide antigen-loaded major histocompatibility complex (pMHC) is a key interaction for triggering T cell activation and ultimately elimination of the target cell. Despite the importance of this interaction for cellular immunity, a comprehensive molecular understanding of TCR specificity and affinity is lacking. We conducted hydrogen/deuterium exchange mass spectrometry (HDX-MS) analyses of individual affinity-enhanced TCR variants and clinically relevant pMHC class I molecules (HLA-A*0201/NY-ESO-1157-165) to investigate the causality between increased binding affinity and conformational dynamics in TCR-pMHC complexes. Differential HDX-MS analyses of TCR variants revealed that mutations for affinity enhancement in TCR CDRs altered the conformational response of TCR to pMHC ligation. Improved pMHC binding affinity was in general observed to correlate with greater differences in HDX upon pMHC binding in modified TCR CDR loops, thereby providing new insights into the TCR-pMHC interaction. Furthermore, a specific point mutation in the β-CDR3 loop of the NY-ESO-1 TCR associated with a substantial increase in binding affinity resulted in a substantial change in pMHC binding kinetics (i.e., very slow kon, revealed by the detection of EX1 HDX kinetics), thus providing experimental evidence for a slow induced-fit binding mode. We also examined the conformational impact of pMHC binding on an unrelated TRAV12-2 gene-encoded TCR directed against the immunodominant MART-126-35 cancer antigen restricted by HLA-A*0201. Our findings provide a molecular basis for the observed TRAV12-2 gene bias in natural CD8+ T cell-based immune responses against the MART-1 antigen, with potential implications for general ligand discrimination and TCR cross-reactivity processes.
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Affiliation(s)
- Patrick S Merkle
- Department of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Esben Trabjerg
- Department of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Song Hongjian
- Department of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mathias Ferber
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Michel A Cuendet
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland.,Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065, United States
| | - Thomas J D Jørgensen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Immanuel Luescher
- Ludwig Branch for Cancer Research of the University of Lausanne, 8001 Zurich, Switzerland
| | - Melita Irving
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland.,Ludwig Branch for Cancer Research of the University of Lausanne, 8001 Zurich, Switzerland
| | - Vincent Zoete
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Olivier Michielin
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Kasper D Rand
- Department of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
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9
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Smith AR, Alonso JA, Ayres CM, Singh NK, Hellman LM, Baker BM. Structurally silent peptide anchor modifications allosterically modulate T cell recognition in a receptor-dependent manner. Proc Natl Acad Sci U S A 2021; 118:e2018125118. [PMID: 33468649 PMCID: PMC7848747 DOI: 10.1073/pnas.2018125118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Presentation of peptides by class I MHC proteins underlies T cell immune responses to pathogens and cancer. The association between peptide binding affinity and immunogenicity has led to the engineering of modified peptides with improved MHC binding, with the hope that these peptides would be useful for eliciting cross-reactive immune responses directed toward their weak binding, unmodified counterparts. Increasing evidence, however, indicates that T cell receptors (TCRs) can perceive such anchor-modified peptides differently than wild-type (WT) peptides, although the scope of discrimination is unclear. We show here that even modifications at primary anchors that have no discernible structural impact can lead to substantially stronger or weaker T cell recognition depending on the TCR. Surprisingly, the effect of peptide anchor modification can be sensed by a TCR at regions distant from the site of modification, indicating a through-protein mechanism in which the anchor residue serves as an allosteric modulator for TCR binding. Our findings emphasize caution in the use and interpretation of results from anchor-modified peptides and have implications for how anchor modifications are accounted for in other circumstances, such as predicting the immunogenicity of tumor neoantigens. Our data also highlight an important need to better understand the highly tunable dynamic nature of class I MHC proteins and the impact this has on various forms of immune recognition.
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MESH Headings
- Allosteric Regulation
- Binding Sites
- Cloning, Molecular
- Crystallography, X-Ray
- Escherichia coli/genetics
- Escherichia coli/metabolism
- Gene Expression
- Genetic Vectors/chemistry
- Genetic Vectors/metabolism
- HLA-A2 Antigen/chemistry
- HLA-A2 Antigen/genetics
- HLA-A2 Antigen/immunology
- Humans
- Jurkat Cells
- Kinetics
- Models, Molecular
- Peptides/chemistry
- Peptides/genetics
- Peptides/immunology
- Protein Binding
- Protein Conformation, alpha-Helical
- Protein Conformation, beta-Strand
- Protein Engineering
- Protein Interaction Domains and Motifs
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/immunology
- Th2 Cells/cytology
- Th2 Cells/immunology
- Thermodynamics
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Affiliation(s)
- Angela R Smith
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556
| | - Jesus A Alonso
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556
| | - Cory M Ayres
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556
| | - Nishant K Singh
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556
| | - Lance M Hellman
- Department of Physical and Life Sciences, Nevada State College, Henderson, NV 89002
| | - Brian M Baker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556;
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN 46556
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10
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Pathan-Chhatbar S, Drechsler C, Richter K, Morath A, Wu W, OuYang B, Xu C, Schamel WW. Direct Regulation of the T Cell Antigen Receptor's Activity by Cholesterol. Front Cell Dev Biol 2021; 8:615996. [PMID: 33490080 PMCID: PMC7820176 DOI: 10.3389/fcell.2020.615996] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 12/09/2020] [Indexed: 11/14/2022] Open
Abstract
Biological membranes consist of hundreds of different lipids that together with the embedded transmembrane (TM) proteins organize themselves into small nanodomains. In addition to this function of lipids, TM regions of proteins bind to lipids in a very specific manner, but the function of these TM region-lipid interactions is mostly unknown. In this review, we focus on the role of plasma membrane cholesterol, which directly binds to the αβ T cell antigen receptor (TCR), and has at least two opposing functions in αβ TCR activation. On the one hand, cholesterol binding to the TM domain of the TCRβ subunit keeps the TCR in an inactive, non-signaling conformation by stabilizing this conformation. This assures that the αβ T cell remains quiescent in the absence of antigenic peptide-MHC (the TCR's ligand) and decreases the sensitivity of the T cell toward stimulation. On the other hand, cholesterol binding to TCRβ leads to an increased formation of TCR nanoclusters, increasing the avidity of the TCRs toward the antigen, thus increasing the sensitivity of the αβ T cell. In mouse models, pharmacological increase of the cholesterol concentration in T cells caused an increase in TCR clustering, and thereby enhanced anti-tumor responses. In contrast, the γδ TCR does not bind to cholesterol and might be regulated in a different manner. The goal of this review is to put these seemingly controversial findings on the impact of cholesterol on the αβ TCR into perspective.
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Affiliation(s)
- Salma Pathan-Chhatbar
- Centre for Biological Signalling Studies and Centre for Integrative Biological Signalling Studies, University Freiburg, Freiburg, Germany.,Department of Immunology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Centre for Chronic Immunodeficiency (CCI), University of Freiburg, Freiburg, Germany
| | - Carina Drechsler
- Centre for Biological Signalling Studies and Centre for Integrative Biological Signalling Studies, University Freiburg, Freiburg, Germany.,Department of Immunology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Centre for Chronic Immunodeficiency (CCI), University of Freiburg, Freiburg, Germany
| | - Kirsten Richter
- Immunology, Infectious Diseases and Ophthalmology Disease Translational Area, Roche Innovation Center Basel, Basel, Switzerland
| | - Anna Morath
- Centre for Biological Signalling Studies and Centre for Integrative Biological Signalling Studies, University Freiburg, Freiburg, Germany.,Department of Immunology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Centre for Chronic Immunodeficiency (CCI), University of Freiburg, Freiburg, Germany
| | - Wei Wu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Bo OuYang
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China
| | - Chenqi Xu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Wolfgang W Schamel
- Centre for Biological Signalling Studies and Centre for Integrative Biological Signalling Studies, University Freiburg, Freiburg, Germany.,Department of Immunology, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Centre for Chronic Immunodeficiency (CCI), University of Freiburg, Freiburg, Germany
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11
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He Y, Agnihotri P, Rangarajan S, Chen Y, Kerzic MC, Ma B, Nussinov R, Mariuzza RA, Orban J. Peptide-MHC Binding Reveals Conserved Allosteric Sites in MHC Class I- and Class II-Restricted T Cell Receptors (TCRs). J Mol Biol 2020; 432:166697. [PMID: 33157083 DOI: 10.1016/j.jmb.2020.10.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/29/2020] [Accepted: 10/27/2020] [Indexed: 12/31/2022]
Abstract
T cells are vital for adaptive immune responses that protect against pathogens and cancers. The T cell receptor (TCR)-CD3 complex comprises a diverse αβ TCR heterodimer in noncovalent association with three invariant CD3 dimers. The TCR is responsible for recognizing antigenic peptides bound to MHC molecules (pMHC), while the CD3 dimers relay activation signals to the T cell. However, the mechanisms by which TCR engagement by pMHC is transmitted to CD3 remain mysterious, although there is growing evidence that mechanosensing and allostery both play a role. Here, we carried out NMR analysis of a human autoimmune TCR (MS2-3C8) that recognizes a self-peptide from myelin basic protein presented by the MHC class II molecule HLA-DR4. We observed pMHC-induced NMR signal perturbations in MS2-3C8 that indicate long-range effects on TCR β chain conformation and dynamics. Our results demonstrate that, in addition to expected changes in the NMR resonances of pMHC-contacting residues, perturbations extend to the Vβ/Vα, Vβ/Cβ, and Cβ/Cα interfacial regions. Moreover, the pattern of long-range perturbations is similar to that detected previously in the β chains of two MHC class I-restricted TCRs, thereby revealing a common allosteric pathway among three unrelated TCRs. Molecular dynamics (MD) simulations predict similar pMHC-induced effects. Taken together, our results demonstrate that pMHC binding induces long-range allosteric changes in the TCR β chain at conserved sites in both representative MHC class I- and class II-restricted TCRs, and that these sites may play a role in the transmission of signaling information.
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Affiliation(s)
- Yanan He
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Pragati Agnihotri
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Sneha Rangarajan
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Yihong Chen
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Melissa C Kerzic
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Buyong Ma
- Engineering Research Center of Cell & Therapeutic Antibody, MOE, School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China; Computational Structural Biology Section, Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Ruth Nussinov
- Computational Structural Biology Section, Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Roy A Mariuzza
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
| | - John Orban
- W.M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA; Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
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12
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Singh NK, Alonso JA, Harris DT, Anderson SD, Ma J, Hellman LM, Rosenberg AM, Kolawole EM, Evavold BD, Kranz DM, Baker BM. An Engineered T Cell Receptor Variant Realizes the Limits of Functional Binding Modes. Biochemistry 2020; 59:4163-4175. [PMID: 33074657 DOI: 10.1021/acs.biochem.0c00689] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
T cell receptors (TCRs) orchestrate cellular immunity by recognizing peptides presented by a range of major histocompatibility complex (MHC) proteins. Naturally occurring TCRs bind the composite peptide/MHC surface, recognizing peptides that are structurally and chemically compatible with the TCR binding site. Here we describe a molecularly evolved TCR variant that binds the human class I MHC protein HLA-A2 independent of the bound peptide, achieved by a drastic perturbation of the TCR binding geometry that places the molecule far from the peptide binding groove. This unique geometry is unsupportive of normal T cell signaling. A substantial divergence between affinity measurements in solution and in two dimensions between proximal cell membranes leads us to attribute the lack of signaling to steric hindrance that limits binding in the confines of a cell-cell interface. Our results provide an example of how receptor binding geometry can impact T cell function and provide further support for the view that germline-encoded residues in TCR binding loops evolved to drive productive TCR recognition and signaling.
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Affiliation(s)
- Nishant K Singh
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jesus A Alonso
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Daniel T Harris
- Department of Biochemistry and Cancer Center at Illinois, University of Illinois, Urbana, Illinois 61801, United States
| | - Scott D Anderson
- Department of Biochemistry and Cancer Center at Illinois, University of Illinois, Urbana, Illinois 61801, United States
| | - Jiaqi Ma
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Lance M Hellman
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Aaron M Rosenberg
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Elizabeth M Kolawole
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah 84112, United States
| | - Brian D Evavold
- Division of Microbiology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah 84112, United States
| | - David M Kranz
- Department of Biochemistry and Cancer Center at Illinois, University of Illinois, Urbana, Illinois 61801, United States
| | - Brian M Baker
- Department of Chemistry and Biochemistry and Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
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13
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Schamel WW, Alarcon B, Minguet S. The TCR is an allosterically regulated macromolecular machinery changing its conformation while working. Immunol Rev 2020; 291:8-25. [PMID: 31402501 DOI: 10.1111/imr.12788] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 05/30/2019] [Indexed: 12/13/2022]
Abstract
The αβ T-cell receptor (TCR) is a multiprotein complex controlling the activation of T cells. Although the structure of the complete TCR is not known, cumulative evidence supports that the TCR cycles between different conformational states that are promoted either by thermal motion or by force. These structural transitions determine whether the TCR engages intracellular effectors or not, regulating TCR phosphorylation and signaling. As for other membrane receptors, ligand binding selects and stabilizes the TCR in active conformations, and/or switches the TCR to activating states that were not visited before ligand engagement. Here we review the main models of TCR allostery, that is, ligand binding at TCRαβ changes the structure at CD3 and ζ. (a) The ITAM and proline-rich sequence exposure model, in which the TCR's cytoplasmic tails shield each other and ligand binding exposes them for phosphorylation. (b) The membrane-ITAM model, in which the CD3ε and ζ tails are sequestered inside the membrane and again ligand binding exposes them. (c) The mechanosensor model in which ligand binding exerts force on the TCR, inducing structural changes that allow signaling. Since these models are complementary rather than competing, we propose a unified model that aims to incorporate all existing data.
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Affiliation(s)
- Wolfgang W Schamel
- Department of Immunology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.,Center of Chronic Immunodeficiency CCI, University Clinics and Medical Faculty, Freiburg, Germany
| | - Balbino Alarcon
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | - Susana Minguet
- Department of Immunology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.,Center of Chronic Immunodeficiency CCI, University Clinics and Medical Faculty, Freiburg, Germany
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14
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Mariuzza RA, Agnihotri P, Orban J. The structural basis of T-cell receptor (TCR) activation: An enduring enigma. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49904-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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15
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Mariuzza RA, Agnihotri P, Orban J. The structural basis of T-cell receptor (TCR) activation: An enduring enigma. J Biol Chem 2019; 295:914-925. [PMID: 31848223 DOI: 10.1074/jbc.rev119.009411] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
T cells are critical for protective immune responses to pathogens and tumors. The T-cell receptor (TCR)-CD3 complex is composed of a diverse αβ TCR heterodimer noncovalently associated with the invariant CD3 dimers CD3ϵγ, CD3ϵδ, and CD3ζζ. The TCR mediates recognition of antigenic peptides bound to MHC molecules (pMHC), whereas the CD3 molecules transduce activation signals to the T cell. Whereas much is known about downstream T-cell signaling pathways, the mechanism whereby TCR engagement by pMHC is first communicated to the CD3 signaling apparatus, a process termed early T-cell activation, remains largely a mystery. In this review, we examine the molecular basis for TCR activation in light of the recently determined cryoEM structure of a complete TCR-CD3 complex. This structure provides an unprecedented opportunity to assess various signaling models that have been proposed for the TCR. We review evidence from single-molecule and structural studies for force-induced conformational changes in the TCR-CD3 complex, for dynamically-driven TCR allostery, and for pMHC-induced structural changes in the transmembrane and cytoplasmic regions of CD3 subunits. We identify major knowledge gaps that must be filled in order to arrive at a comprehensive model of TCR activation that explains, at the molecular level, how pMHC-specific information is transmitted across the T-cell membrane to initiate intracellular signaling. An in-depth understanding of this process will accelerate the rational design of immunotherapeutic agents targeting the TCR-CD3 complex.
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Affiliation(s)
- Roy A Mariuzza
- W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850 .,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742
| | - Pragati Agnihotri
- W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742
| | - John Orban
- W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850 .,Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
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16
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Knapp B, van der Merwe PA, Dushek O, Deane CM. MHC binding affects the dynamics of different T-cell receptors in different ways. PLoS Comput Biol 2019; 15:e1007338. [PMID: 31498801 PMCID: PMC6752857 DOI: 10.1371/journal.pcbi.1007338] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 09/19/2019] [Accepted: 08/20/2019] [Indexed: 12/13/2022] Open
Abstract
T cells use their T-cell receptors (TCRs) to scan other cells for antigenic peptides presented by MHC molecules (pMHC). If a TCR encounters a pMHC, it can trigger a signalling pathway that could lead to the activation of the T cell and the initiation of an immune response. It is currently not clear how the binding of pMHC to the TCR initiates signalling within the T cell. One hypothesis is that conformational changes in the TCR lead to further downstream signalling. Here we investigate four different TCRs in their free state as well as in their pMHC bound state using large scale molecular simulations totalling 26 000 ns. We find that the dynamical features within TCRs differ significantly between unbound TCR and TCR/pMHC simulations. However, apart from expected results such as reduced solvent accessibility and flexibility of the interface residues, these features are not conserved among different TCR types. The presence of a pMHC alone is not sufficient to cause cross-TCR-conserved dynamical features within a TCR. Our results argue against models of TCR triggering involving conserved allosteric conformational changes. The interaction between T-cells and other cells is one of the most important interactions in the human immune system. If T-cells are not triggered major parts of the immune system cannot be activated or are not working effectively. Despite many years of research the exact mechanism of how a T-cell is initially triggered is not clear. One hypothesis is that conformational changes within the T-cell receptor (TCR) can cause further downstream signalling within the T-cell. In this study we computationally investigate the dynamics of four different TCRs in their free and bound configuration. Our large scale simulations show that all four TCRs react to binding in different ways. In some TCRs mainly the areas close to the binding region are affected while in other TCRs areas further apart from the binding region are also affected. Our results argue against a conserved structural activation mechanism across different types of TCRs.
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Affiliation(s)
- Bernhard Knapp
- Department of Basic Sciences, International University of Catalonia, Barcelona, Spain
- Department of Statistics, University of Oxford, Oxford, United Kingdom
- * E-mail:
| | | | - Omer Dushek
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
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17
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Choi Y, Furlon JM, Amos RB, Griswold KE, Bailey-Kellogg C. DisruPPI: structure-based computational redesign algorithm for protein binding disruption. Bioinformatics 2019; 34:i245-i253. [PMID: 29949961 PMCID: PMC6022686 DOI: 10.1093/bioinformatics/bty274] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Motivation Disruption of protein–protein interactions can mitigate antibody recognition of therapeutic proteins, yield monomeric forms of oligomeric proteins, and elucidate signaling mechanisms, among other applications. While designing affinity-enhancing mutations remains generally quite challenging, both statistically and physically based computational methods can precisely identify affinity-reducing mutations. In order to leverage this ability to design variants of a target protein with disrupted interactions, we developed the DisruPPI protein design method (DISRUpting Protein–Protein Interactions) to optimize combinations of mutations simultaneously for both disruption and stability, so that incorporated disruptive mutations do not inadvertently affect the target protein adversely. Results Two existing methods for predicting mutational effects on binding, FoldX and INT5, were demonstrated to be quite precise in selecting disruptive mutations from the SKEMPI and AB-Bind databases of experimentally determined changes in binding free energy. DisruPPI was implemented to use an INT5-based disruption score integrated with an AMBER-based stability assessment and was applied to disrupt protein interactions in a set of different targets representing diverse applications. In retrospective evaluation with three different case studies, comparison of DisruPPI-designed variants to published experimental data showed that DisruPPI was able to identify more diverse interaction-disrupting and stability-preserving variants more efficiently and effectively than previous approaches. In prospective application to an interaction between enhanced green fluorescent protein (EGFP) and a nanobody, DisruPPI was used to design five EGFP variants, all of which were shown to have significantly reduced nanobody binding while maintaining function and thermostability. This demonstrates that DisruPPI may be readily utilized for effective removal of known epitopes of therapeutically relevant proteins. Availability and implementation DisruPPI is implemented in the EpiSweep package, freely available under an academic use license. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Yoonjoo Choi
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Jacob M Furlon
- Thayer School of Engineering, Dartmouth, Hanover, NH, USA
| | - Ryan B Amos
- Department of Computer Science, Princeton University, Princeton, NJ, USA
| | - Karl E Griswold
- Thayer School of Engineering, Dartmouth, Hanover, NH, USA.,Norris Cotton Cancer Center at Dartmouth, Lebanon, NH, USA.,Department of Biological Sciences, Dartmouth, Hanover, NH, USA
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18
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Karch R, Stocsits C, Ilieva N, Schreiner W. Intramolecular Domain Movements of Free and Bound pMHC and TCR Proteins: A Molecular Dynamics Simulation Study. Cells 2019; 8:cells8070720. [PMID: 31337065 PMCID: PMC6678086 DOI: 10.3390/cells8070720] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/02/2019] [Accepted: 07/12/2019] [Indexed: 12/11/2022] Open
Abstract
The interaction of antigenic peptides (p) and major histocompatibility complexes (pMHC) with T-cell receptors (TCR) is one of the most important steps during the immune response. Here we present a molecular dynamics simulation study of bound and unbound TCR and pMHC proteins of the LC13-HLA-B*44:05-pEEYLQAFTY complex to monitor differences in relative orientations and movements of domains between bound and unbound states of TCR-pMHC. We generated local coordinate systems for MHC α1- and MHC α2-helices and the variable T-cell receptor regions TCR Vα and TCR Vβ and monitored changes in the distances and mutual orientations of these domains. In comparison to unbound states, we found decreased inter-domain movements in the simulations of bound states. Moreover, increased conformational flexibility was observed for the MHC α2-helix, the peptide, and for the complementary determining regions of the TCR in TCR-unbound states as compared to TCR-bound states.
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Affiliation(s)
- Rudolf Karch
- Section of Biosimulation and Bioinformatics, Center for Medical Statistics, Informatics and Intelligent Systems (CeMSIIS), Medical University of Vienna, Spitalgasse 23, A-1090 Vienna, Austria
| | - Claudia Stocsits
- Section of Biosimulation and Bioinformatics, Center for Medical Statistics, Informatics and Intelligent Systems (CeMSIIS), Medical University of Vienna, Spitalgasse 23, A-1090 Vienna, Austria
| | - Nevena Ilieva
- Institute of Information and Communication Technologies (IICT), Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 25A, 1113 Sofia, Bulgaria
- CERN-TH, Esplanade des Particules 1, 1211 Geneva, Switzerland
| | - Wolfgang Schreiner
- Section of Biosimulation and Bioinformatics, Center for Medical Statistics, Informatics and Intelligent Systems (CeMSIIS), Medical University of Vienna, Spitalgasse 23, A-1090 Vienna, Austria.
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19
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Ayres CM, Abualrous ET, Bailey A, Abraham C, Hellman LM, Corcelli SA, Noé F, Elliott T, Baker BM. Dynamically Driven Allostery in MHC Proteins: Peptide-Dependent Tuning of Class I MHC Global Flexibility. Front Immunol 2019; 10:966. [PMID: 31130956 PMCID: PMC6509175 DOI: 10.3389/fimmu.2019.00966] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 04/15/2019] [Indexed: 11/21/2022] Open
Abstract
T cell receptor (TCR) recognition of antigenic peptides bound and presented by class I major histocompatibility complex (MHC) proteins underlies the cytotoxic immune response to diseased cells. Crystallographic structures of TCR-peptide/MHC complexes have demonstrated how TCRs simultaneously interact with both the peptide and the MHC protein. However, it is increasingly recognized that, beyond serving as a static platform for peptide presentation, the physical properties of class I MHC proteins are tuned by different peptides in ways that are not always structurally visible. These include MHC protein motions, or dynamics, which are believed to influence interactions with a variety of MHC-binding proteins, including not only TCRs, but other activating and inhibitory receptors as well as components of the peptide loading machinery. Here, we investigated the mechanisms by which peptides tune the dynamics of the common class I MHC protein HLA-A2. By examining more than 50 lengthy molecular dynamics simulations of HLA-A2 presenting different peptides, we identified regions susceptible to dynamic tuning, including regions in the peptide binding domain as well as the distal α3 domain. Further analyses of the simulations illuminated mechanisms by which the influences of different peptides are communicated throughout the protein, and involve regions of the peptide binding groove, the β2-microglobulin subunit, and the α3 domain. Overall, our results demonstrate that the class I MHC protein is a highly tunable peptide sensor whose physical properties vary considerably with bound peptide. Our data provides insight into the underlying principles and suggest a role for dynamically driven allostery in the immunological function of MHC proteins.
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Affiliation(s)
- Cory M Ayres
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States.,Harper Cancer Research Institute, University of Notre Dame, South Bend, IN, United States
| | - Esam T Abualrous
- Computational Molecular Biology Group, Institute for Mathematics, Freie Universität Berlin, Berlin, Germany
| | - Alistair Bailey
- Institute for Life Sciences and Centre for Cancer Immunology, University of Southampton, Southampton, United Kingdom
| | - Christian Abraham
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States.,Harper Cancer Research Institute, University of Notre Dame, South Bend, IN, United States
| | - Lance M Hellman
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States.,Harper Cancer Research Institute, University of Notre Dame, South Bend, IN, United States
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States
| | - Frank Noé
- Computational Molecular Biology Group, Institute for Mathematics, Freie Universität Berlin, Berlin, Germany
| | - Tim Elliott
- Institute for Life Sciences and Centre for Cancer Immunology, University of Southampton, Southampton, United Kingdom
| | - Brian M Baker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States.,Harper Cancer Research Institute, University of Notre Dame, South Bend, IN, United States
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20
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Hellman LM, Foley KC, Singh NK, Alonso JA, Riley TP, Devlin JR, Ayres CM, Keller GLJ, Zhang Y, Vander Kooi CW, Nishimura MI, Baker BM. Improving T Cell Receptor On-Target Specificity via Structure-Guided Design. Mol Ther 2018; 27:300-313. [PMID: 30617019 DOI: 10.1016/j.ymthe.2018.12.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 12/05/2018] [Accepted: 12/08/2018] [Indexed: 12/30/2022] Open
Abstract
T cell receptors (TCRs) have emerged as a new class of immunological therapeutics. However, though antigen specificity is a hallmark of adaptive immunity, TCRs themselves do not possess the high specificity of monoclonal antibodies. Although a necessary function of T cell biology, the resulting cross-reactivity presents a significant challenge for TCR-based therapeutic development, as it creates the potential for off-target recognition and immune toxicity. Efforts to enhance TCR specificity by mimicking the antibody maturation process and enhancing affinity can inadvertently exacerbate TCR cross-reactivity. Here we demonstrate this concern by showing that even peptide-targeted mutations in the TCR can introduce new reactivities against peptides that bear similarity to the original target. To counteract this, we explored a novel structure-guided approach for enhancing TCR specificity independent of affinity. Tested with the MART-1-specific TCR DMF5, our approach had a small but discernible impact on cross-reactivity toward MART-1 homologs yet was able to eliminate DMF5 cross-recognition of more divergent, unrelated epitopes. Our study provides a proof of principle for the use of advanced structure-guided design techniques for improving TCR specificity, and it suggests new ways forward for enhancing TCRs for therapeutic use.
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Affiliation(s)
- Lance M Hellman
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Kendra C Foley
- Department of Surgery and the Cardinal Bernardin Cancer Center, Loyola University of Chicago, Maywood, IL, USA
| | - Nishant K Singh
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Jesus A Alonso
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Timothy P Riley
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Jason R Devlin
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Cory M Ayres
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Grant L J Keller
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Yuting Zhang
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA
| | - Craig W Vander Kooi
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Michael I Nishimura
- Department of Surgery and the Cardinal Bernardin Cancer Center, Loyola University of Chicago, Maywood, IL, USA
| | - Brian M Baker
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, Notre Dame, IN, USA.
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21
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Buckle AM, Borg NA. Integrating Experiment and Theory to Understand TCR-pMHC Dynamics. Front Immunol 2018; 9:2898. [PMID: 30581442 PMCID: PMC6293202 DOI: 10.3389/fimmu.2018.02898] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/26/2018] [Indexed: 11/13/2022] Open
Abstract
The conformational dynamism of proteins is well established. Rather than having a single structure, proteins are more accurately described as a conformational ensemble that exists across a rugged energy landscape, where different conformational sub-states interconvert. The interaction between αβ T cell receptors (TCR) and cognate peptide-MHC (pMHC) is no exception, and is a dynamic process that involves substantial conformational change. This review focuses on technological advances that have begun to establish the role of conformational dynamics and dynamic allostery in TCR recognition of the pMHC and the early stages of signaling. We discuss how the marriage of molecular dynamics (MD) simulations with experimental techniques provides us with new ways to dissect and interpret the process of TCR ligation. Notably, application of simulation techniques lags behind other fields, but is predicted to make substantial contributions. Finally, we highlight integrated approaches that are being used to shed light on some of the key outstanding questions in the early events leading to TCR signaling.
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Affiliation(s)
- Ashley M Buckle
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
| | - Natalie A Borg
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia
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22
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Rangarajan S, He Y, Chen Y, Kerzic MC, Ma B, Gowthaman R, Pierce BG, Nussinov R, Mariuzza RA, Orban J. Peptide-MHC (pMHC) binding to a human antiviral T cell receptor induces long-range allosteric communication between pMHC- and CD3-binding sites. J Biol Chem 2018; 293:15991-16005. [PMID: 30135211 DOI: 10.1074/jbc.ra118.003832] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 08/21/2018] [Indexed: 12/17/2022] Open
Abstract
T cells generate adaptive immune responses mediated by the T cell receptor (TCR)-CD3 complex comprising an αβ TCR heterodimer noncovalently associated with three CD3 dimers. In early T cell activation, αβ TCR engagement by peptide-major histocompatibility complex (pMHC) is first communicated to the CD3 signaling apparatus of the TCR-CD3 complex, but the underlying mechanism is incompletely understood. It is possible that pMHC binding induces allosteric changes in TCR conformation or dynamics that are then relayed to CD3. Here, we carried out NMR analysis and molecular dynamics (MD) simulations of both the α and β chains of a human antiviral TCR (A6) that recognizes the Tax antigen from human T cell lymphotropic virus-1 bound to the MHC class I molecule HLA-A2. We observed pMHC-induced NMR signal perturbations in the TCR variable (V) domains that propagated to three distinct sites in the constant (C) domains: 1) the Cβ FG loop projecting from the Vβ/Cβ interface; 2) a cluster of Cβ residues near the Cβ αA helix, a region involved in interactions with CD3; and 3) the Cα AB loop at the membrane-proximal base of the TCR. A biological role for each of these allosteric sites is supported by previous mutational and functional studies of TCR signaling. Moreover, the pattern of long-range, ligand-induced changes in TCR A6 revealed by NMR was broadly similar to that predicted by the MD simulations. We propose that the unique structure of the TCR β chain enables allosteric communication between the TCR-binding sites for pMHC and CD3.
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Affiliation(s)
- Sneha Rangarajan
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.,the Departments of Cell Biology and Molecular Genetics and
| | - Yanan He
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.,Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, and
| | - Yihong Chen
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Melissa C Kerzic
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Buyong Ma
- the Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland 21702
| | - Ragul Gowthaman
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.,the Departments of Cell Biology and Molecular Genetics and
| | - Brian G Pierce
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.,the Departments of Cell Biology and Molecular Genetics and
| | - Ruth Nussinov
- the Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, National Cancer Institute at Frederick, Frederick, Maryland 21702
| | - Roy A Mariuzza
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, .,the Departments of Cell Biology and Molecular Genetics and
| | - John Orban
- From the W. M. Keck Laboratory for Structural Biology, University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, .,Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, and
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23
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Fodor J, Riley BT, Borg NA, Buckle AM. Previously Hidden Dynamics at the TCR-Peptide-MHC Interface Revealed. THE JOURNAL OF IMMUNOLOGY 2018; 200:4134-4145. [PMID: 29728507 DOI: 10.4049/jimmunol.1800315] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 04/10/2018] [Indexed: 12/28/2022]
Abstract
A structural characterization of the interaction between αβ TCRs and cognate peptide-MHC (pMHC) is central to understanding adaptive T cell-mediated immunity. X-ray crystallography, although the source of much structural data, traditionally provides only a static snapshot of the protein. Given the emerging evidence for the important role of conformational dynamics in protein function, we interrogated 309 crystallographic structures of pMHC complexes using ensemble refinement, a technique that can extract dynamic information from the x-ray data. Focusing on a subset of human pMHC class I systems, we found that in many cases, ensemble methods were able to uncover previously hidden evidence of significant conformational plasticity, thereby revealing additional information that can build upon and significantly enhance functional interpretations that are based on a single static structure. Notable examples include the interpretation of differences in the disease association of HLA subtypes, the relationship between peptide prominence and TCR recognition, the role of conformational flexibility in vaccine design, and the discrimination between induced fit and conformational selection models of TCR binding. We show that the currently widespread practice of analyzing pMHC interactions via the study of a single crystallographic structure does not make use of pertinent and easily accessible information from x-ray data concerning alternative protein conformations. This new analysis therefore not only highlights the capacity for ensemble methods to significantly enrich the interpretation of decades of structural data but also provides previously missing information concerning the dynamics of existing characterized TCR-pMHC interactions.
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Affiliation(s)
- James Fodor
- Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; and Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - Blake T Riley
- Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; and Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - Natalie A Borg
- Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; and Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - Ashley M Buckle
- Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia; and Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
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24
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van Hateren A, Anderson M, Bailey A, Werner JM, Skipp P, Elliott T. Direct evidence for conformational dynamics in major histocompatibility complex class I molecules. J Biol Chem 2017; 292:20255-20269. [PMID: 29021251 PMCID: PMC5724011 DOI: 10.1074/jbc.m117.809624] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 09/25/2017] [Indexed: 12/19/2022] Open
Abstract
Major histocompatibility complex class I molecules (MHC I) help protect jawed vertebrates by binding and presenting immunogenic peptides to cytotoxic T lymphocytes. Peptides are selected from a large diversity present in the endoplasmic reticulum. However, only a limited number of peptides complement the polymorphic MHC specificity determining pockets in a way that leads to high-affinity peptide binding and efficient antigen presentation. MHC I molecules possess an intrinsic ability to discriminate between peptides, which varies in efficiency between allotypes, but the mechanism of selection is unknown. Elucidation of the selection mechanism is likely to benefit future immune-modulatory therapies. Evidence suggests peptide selection involves transient adoption of alternative, presumably higher energy conformations than native peptide-MHC complexes. However, the instability of peptide-receptive MHC molecules has hindered characterization of such conformational plasticity. To investigate the dynamic nature of MHC, we refolded MHC proteins with peptides that can be hydrolyzed by UV light and thus released. We compared the resultant peptide-receptive MHC molecules with non-hydrolyzed peptide-loaded MHC complexes by monitoring the exchange of hydrogen for deuterium in solution. We found differences in hydrogen-deuterium exchange between peptide-loaded and peptide-receptive molecules that were negated by the addition of peptide to peptide-receptive MHC molecules. Peptide hydrolysis caused significant increases in hydrogen-deuterium exchange in sub-regions of the peptide-binding domain and smaller increases elsewhere, including in the α3 domain and the non-covalently associated β2-microglobulin molecule, demonstrating long-range dynamic communication. Comparing two MHC allotypes revealed allotype-specific differences in hydrogen-deuterium exchange, consistent with the notion that MHC I plasticity underpins peptide selection.
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Affiliation(s)
- Andy van Hateren
- Institute for Life Sciences and Centre for Cancer Immunology, Faculty of Medicine, Southampton SO17 1BJ
| | - Malcolm Anderson
- Waters Corporation, Stamford Avenue, Altrincham Road, Wilmslow SK9 4AX, United Kingdom
| | - Alistair Bailey
- Institute for Life Sciences and Centre for Cancer Immunology, Faculty of Medicine, Southampton SO17 1BJ; Centre for Proteomic Research, Biological Sciences, and Institute for Life Sciences, Southampton SO17 1BJ
| | - Jörn M Werner
- Institute for Life Sciences, Centre for Biological Sciences, and Faculty of Natural and Environmental Sciences, University of Southampton, Building 85, Southampton SO17 1BJ
| | - Paul Skipp
- Centre for Proteomic Research, Biological Sciences, and Institute for Life Sciences, Southampton SO17 1BJ
| | - Tim Elliott
- Institute for Life Sciences and Centre for Cancer Immunology, Faculty of Medicine, Southampton SO17 1BJ.
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25
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Merkle PS, Irving M, Hongjian S, Ferber M, Jørgensen TJD, Scholten K, Luescher I, Coukos G, Zoete V, Cuendet MA, Michielin O, Rand KD. The T-Cell Receptor Can Bind to the Peptide-Bound Major Histocompatibility Complex and Uncomplexed β2-Microglobulin through Distinct Binding Sites. Biochemistry 2017; 56:3945-3961. [DOI: 10.1021/acs.biochem.7b00385] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Patrick S. Merkle
- Department
of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Melita Irving
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
- Ludwig
Branch for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland
| | - Song Hongjian
- Department
of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Mathias Ferber
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Thomas J. D. Jørgensen
- Department
of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Kirsten Scholten
- Ludwig
Branch for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland
| | - Immanuel Luescher
- Ludwig
Branch for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland
| | - George Coukos
- Ludwig
Branch for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland
| | - Vincent Zoete
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Michel A. Cuendet
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
- Department
of Physiology and Biophysics, Weill Cornell Medical College, 1300
York Avenue, New York, New
York 10065, United States
| | - Olivier Michielin
- Swiss Institute of Bioinformatics, Bâtiment Génopode, UNIL Sorge, 1015 Lausanne, Switzerland
| | - Kasper D. Rand
- Department
of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
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26
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Natarajan K, McShan AC, Jiang J, Kumirov VK, Wang R, Zhao H, Schuck P, Tilahun ME, Boyd LF, Ying J, Bax A, Margulies DH, Sgourakis NG. An allosteric site in the T-cell receptor Cβ domain plays a critical signalling role. Nat Commun 2017; 8:15260. [PMID: 28508865 PMCID: PMC5440810 DOI: 10.1038/ncomms15260] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 03/14/2017] [Indexed: 12/21/2022] Open
Abstract
The molecular mechanism through which the interaction of a clonotypic αβ T-cell receptor (TCR) with a peptide-loaded major histocompatibility complex (p/MHC) leads to T-cell activation is not yet fully understood. Here we exploit a high-affinity TCR (B4.2.3) to examine the structural changes that accompany binding to its p/MHC ligand (P18-I10/H2-Dd). In addition to conformational changes in complementarity-determining regions (CDRs) of the TCR seen in comparison of unliganded and bound X-ray structures, NMR characterization of the TCR β-chain dynamics reveals significant chemical shift effects in sites removed from the MHC-binding site. Remodelling of electrostatic interactions near the Cβ H3 helix at the membrane-proximal face of the TCR, a region implicated in interactions with the CD3 co-receptor, suggests a possible role for an allosteric mechanism in TCR signalling. The contribution of these TCR residues to signal transduction is supported by mutagenesis and T-cell functional assays.
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MESH Headings
- Allosteric Site/immunology
- Animals
- Complementarity Determining Regions/chemistry
- Complementarity Determining Regions/metabolism
- Crystallography, X-Ray
- Major Histocompatibility Complex/immunology
- Mice
- Molecular Dynamics Simulation
- Mutagenesis
- Peptides/metabolism
- Protein Binding/immunology
- Protein Domains/immunology
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Signal Transduction/immunology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
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Affiliation(s)
- Kannan Natarajan
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Andrew C. McShan
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Jiansheng Jiang
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Vlad K Kumirov
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
| | - Rui Wang
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Huaying Zhao
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Peter Schuck
- Laboratory of Cellular Imaging and Macromolecular Biophysics, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Mulualem E. Tilahun
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Lisa F. Boyd
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Jinfa Ying
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - David H. Margulies
- Molecular Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Nikolaos G. Sgourakis
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California 95064, USA
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27
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Differential utilization of binding loop flexibility in T cell receptor ligand selection and cross-reactivity. Sci Rep 2016; 6:25070. [PMID: 27118724 PMCID: PMC4846865 DOI: 10.1038/srep25070] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 04/11/2016] [Indexed: 12/27/2022] Open
Abstract
Complementarity determining region (CDR) loop flexibility has been suggested to play an important role in the selection and binding of ligands by T cell receptors (TCRs) of the cellular immune system. However, questions remain regarding the role of loop motion in TCR binding, and crystallographic structures have raised questions about the extent to which generalizations can be made. Here we studied the flexibility of two structurally well characterized αβ TCRs, A6 and DMF5. We found that the two receptors utilize loop motion very differently in ligand binding and cross-reactivity. While the loops of A6 move rapidly in an uncorrelated fashion, those of DMF5 are substantially less mobile. Accordingly, the mechanisms of binding and cross-reactivity are very different between the two TCRs: whereas A6 relies on conformational selection to select and bind different ligands, DMF5 uses a more rigid, permissive architecture with greater reliance on slower motions or induced-fit. In addition to binding site flexibility, we also explored whether ligand-binding resulted in common dynamical changes in A6 and DMF5 that could contribute to TCR triggering. Although binding-linked motional changes propagated throughout both receptors, no common features were observed, suggesting that changes in nanosecond-level TCR structural dynamics do not contribute to T cell signaling.
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28
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Deredge D, Li J, Johnson KA, Wintrode PL. Hydrogen/Deuterium Exchange Kinetics Demonstrate Long Range Allosteric Effects of Thumb Site 2 Inhibitors of Hepatitis C Viral RNA-dependent RNA Polymerase. J Biol Chem 2016; 291:10078-88. [PMID: 27006396 DOI: 10.1074/jbc.m115.708370] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Indexed: 01/08/2023] Open
Abstract
New nonnucleoside analogs are being developed as part of a multi-drug regimen to treat hepatitis C viral infections. Particularly promising are inhibitors that bind to the surface of the thumb domain of the viral RNA-dependent RNA polymerase (NS5B). Numerous crystal structures have been solved showing small molecule non-nucleoside inhibitors bound to the hepatitis C viral polymerase, but these structures alone do not define the mechanism of inhibition. Our prior kinetic analysis showed that nonnucleoside inhibitors binding to thumb site-2 (NNI2) do not block initiation or elongation of RNA synthesis; rather, they block the transition from the initiation to elongation, which is thought to proceed with significant structural rearrangement of the enzyme-RNA complex. Here we have mapped the effect of three NNI2 inhibitors on the conformational dynamics of the enzyme using hydrogen/deuterium exchange kinetics. All three inhibitors rigidify an extensive allosteric network extending >40 Å from the binding site, thus providing a structural rationale for the observed disruption of the transition from distributive initiation to processive elongation. The two more potent inhibitors also suppress slow cooperative unfolding in the fingers extension-thumb interface and primer grip, which may contribute their stronger inhibition. These results establish that NNI2 inhibitors act through long range allosteric effects, reveal important conformational changes underlying normal polymerase function, and point the way to the design of more effective allosteric inhibitors that exploit this new information.
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Affiliation(s)
- Daniel Deredge
- From the Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201 and
| | - Jiawen Li
- Department of Molecular Biosciences, Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712
| | - Kenneth A Johnson
- Department of Molecular Biosciences, Institute for Cell and Molecular Biology, University of Texas, Austin, Texas 78712
| | - Patrick L Wintrode
- From the Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201 and
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29
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Bello M, Correa-Basurto J. Energetic and flexibility properties captured by long molecular dynamics simulations of a membrane-embedded pMHCII-TCR complex. MOLECULAR BIOSYSTEMS 2016; 12:1350-66. [PMID: 26926952 DOI: 10.1039/c6mb00058d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Although crystallographic data have provided important molecular insight into the interactions in the pMHC-TCR complex, the inherent features of this structural approach cause it to only provide a static picture of the interactions. While unbiased molecular dynamics simulations (UMDSs) have provided important information about the dynamic structural behavior of the pMHC-TCR complex, most of them have modeled the pMHC-TCR complex as soluble, when in physiological conditions, this complex is membrane bound; therefore, following this latter UMDS protocol might hamper important dynamic results. In this contribution, we performed three independent 300 ns-long UMDSs of the pMHCII-TCR complex anchored in two opposing membranes to explore the structural and energetic properties of the recognition of pMHCII by the TCR. The conformational ensemble generated through UMDSs was subjected to clustering and Cartesian principal component analyses (cPCA) to explore the dynamical behavior of the pMHCII-TCR association. Furthermore, based on the conformational population sampled through UMDSs, the effective binding free energy, per-residue free energy decomposition, and alanine scanning mutations were explored for the native pMHCII-TCR complex, as well as for 12 mutations (p1-p12MHCII-TCR) introduced in the native peptide. Clustering analyses and cPCA provide insight into the rocking motion of the TCR onto pMHCII, together with the presence of new electrostatic interactions not observed through crystallographic methods. Energetic results provide evidence of the main contributors to the pMHC-TCR complex formation as well as the key residues involved in this molecular recognition process.
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Affiliation(s)
- Martiniano Bello
- Laboratorio de Modelado Molecular, Bioinformática y Diseño de Fármacos de la Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis Y Diaz Mirón S/N, Col. Casco de Santo Tomas, Mexico City, CP: 11340, Mexico.
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30
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Sgourakis NG, May NA, Boyd LF, Ying J, Bax A, Margulies DH. A Novel MHC-I Surface Targeted for Binding by the MCMV m06 Immunoevasin Revealed by Solution NMR. J Biol Chem 2015; 290:28857-68. [PMID: 26463211 DOI: 10.1074/jbc.m115.689661] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Indexed: 12/21/2022] Open
Abstract
As part of its strategy to evade detection by the host immune system, murine cytomegalovirus (MCMV) encodes three proteins that modulate cell surface expression of major histocompatibility complex class I (MHC-I) molecules: the MHC-I homolog m152/gp40 as well as the m02-m16 family members m04/gp34 and m06/gp48. Previous studies of the m04 protein revealed a divergent Ig-like fold that is unique to immunoevasins of the m02-m16 family. Here, we engineer and characterize recombinant m06 and investigate its interactions with full-length and truncated forms of the MHC-I molecule H2-L(d) by several techniques. Furthermore, we employ solution NMR to map the interaction footprint of the m06 protein on MHC-I, taking advantage of a truncated H2-L(d), "mini-H2-L(d)," consisting of only the α1α2 platform domain. Mini-H2-L(d) refolded in vitro with a high affinity peptide yields a molecule that shows outstanding NMR spectral features, permitting complete backbone assignments. These NMR-based studies reveal that m06 binds tightly to a discrete site located under the peptide-binding platform that partially overlaps with the β2-microglobulin interface on the MHC-I heavy chain, consistent with in vitro binding experiments showing significantly reduced complex formation between m06 and β2-microglobulin-associated MHC-I. Moreover, we carry out NMR relaxation experiments to characterize the picosecond-nanosecond dynamics of the free mini-H2-L(d) MHC-I molecule, revealing that the site of interaction is highly ordered. This study provides insight into the mechanism of the interaction of m06 with MHC-I, suggesting a structural manipulation of the target MHC-I molecule at an early stage of the peptide-loading pathway.
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Affiliation(s)
| | - Nathan A May
- the Molecular Biology Section, Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Lisa F Boyd
- the Molecular Biology Section, Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Jinfa Ying
- From the Laboratory of Chemical Physics, NIDDK, and
| | - Ad Bax
- From the Laboratory of Chemical Physics, NIDDK, and
| | - David H Margulies
- the Molecular Biology Section, Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892
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31
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Hoffmann MM, Molina-Mendiola C, Nelson AD, Parks CA, Reyes EE, Hansen MJ, Rajagopalan G, Pease LR, Schrum AG, Gil D. Co-potentiation of antigen recognition: A mechanism to boost weak T cell responses and provide immunotherapy in vivo. SCIENCE ADVANCES 2015; 1:e1500415. [PMID: 26601285 PMCID: PMC4646799 DOI: 10.1126/sciadv.1500415] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/24/2015] [Indexed: 06/05/2023]
Abstract
Adaptive immunity is mediated by antigen receptors that can induce weak or strong immune responses depending on the nature of the antigen that is bound. In T lymphocytes, antigen recognition triggers signal transduction by clustering T cell receptor (TCR)/CD3 multiprotein complexes. In addition, it hypothesized that biophysical changes induced in TCR/CD3 that accompany receptor engagement may contribute to signal intensity. Nonclustering monovalent TCR/CD3 engagement is functionally inert despite the fact that it may induce changes in conformational arrangement or in the flexibility of receptor subunits. We report that the intrinsically inert monovalent engagement of TCR/CD3 can specifically enhance physiologic T cell responses to weak antigens in vitro and in vivo without stimulating antigen-unengaged T cells and without interrupting T cell responses to strong antigens, an effect that we term as "co-potentiation." We identified Mono-7D6-Fab, which biophysically altered TCR/CD3 when bound and functionally enhanced immune reactivity to several weak antigens in vitro, including a gp100-derived peptide associated with melanoma. In vivo, Mono-7D6-Fab induced T cell antigen-dependent therapeutic responses against melanoma lung metastases, an effect that synergized with other anti-melanoma immunotherapies to significantly improve outcome and survival. We conclude that Mono-7D6-Fab directly co-potentiated TCR/CD3 engagement by weak antigens and that such concept can be translated into an immunotherapeutic design. The co-potentiation principle may be applicable to other receptors that could be regulated by otherwise inert compounds whose latent potency is only invoked in concert with specific physiologic ligands.
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Affiliation(s)
- Michele M. Hoffmann
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Carlos Molina-Mendiola
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
- Department of Statistics, Polytechnic University of Catalonia, Barcelona 08034, Spain
| | - Alfreda D. Nelson
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Christopher A. Parks
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Edwin E. Reyes
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Michael J. Hansen
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Govindarajan Rajagopalan
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Larry R. Pease
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Adam G. Schrum
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
| | - Diana Gil
- Department of Immunology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA
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32
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Motozono C, Bridgeman JS, Price DA, Sewell AK, Ueno T. Clonotypically similar hybrid αβ T cell receptors can exhibit markedly different surface expression, antigen specificity and cross-reactivity. Clin Exp Immunol 2015; 180:560-70. [PMID: 25721491 PMCID: PMC4449784 DOI: 10.1111/cei.12610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/17/2015] [Accepted: 02/19/2015] [Indexed: 11/29/2022] Open
Abstract
Emerging data indicate that particular major histocompatibility complex (MHC)‐bound antigenic peptides can be recognized by identical or near‐identical αβ T cell receptors (TCRs) in different individuals. To establish the functional relevance of this phenomenon, we artificially paired α and β chains from closely related TCRs specific for the human leucocyte antigen (HLA)‐B*35:01‐restricted HIV‐1 negative regulatory factor (Nef)‐derived epitope VY8 (VPLRPMTY, residues 74–81). Several hybrid TCRs generated in this manner failed to express at the cell surface, despite near homology with naturally isolated αβ chain combinations. Moreover, a substantial proportion of those αβ TCRs that did express lost specificity for the index VY8 peptide sequence. One such hybrid αβ pair gained neo‐variant specificity in the context of the VY8 backbone. Collectively, these data show that clonotypically similar TCRs can display profound differences in surface expression, antigen specificity and cross‐reactivity with potential relevance for the control of mutable viruses.
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Affiliation(s)
- C Motozono
- Center for AIDS Research, Kumamoto University, Kumamoto, Japan.,Institute of Infection and Immunity, Cardiff University School of Medicine, Heath Park, Cardiff, UK
| | - J S Bridgeman
- Institute of Infection and Immunity, Cardiff University School of Medicine, Heath Park, Cardiff, UK
| | - D A Price
- Institute of Infection and Immunity, Cardiff University School of Medicine, Heath Park, Cardiff, UK
| | - A K Sewell
- Institute of Infection and Immunity, Cardiff University School of Medicine, Heath Park, Cardiff, UK
| | - T Ueno
- Center for AIDS Research, Kumamoto University, Kumamoto, Japan.,International Research Center for Medical Research, Kumamoto University, Kumamoto, Japan
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33
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Attaf M, Legut M, Cole DK, Sewell AK. The T cell antigen receptor: the Swiss army knife of the immune system. Clin Exp Immunol 2015; 181:1-18. [PMID: 25753381 PMCID: PMC4469151 DOI: 10.1111/cei.12622] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2015] [Indexed: 01/01/2023] Open
Abstract
The mammalian T cell receptor (TCR) orchestrates immunity by responding to many billions of different ligands that it has never encountered before and cannot adapt to at the protein sequence level. This remarkable receptor exists in two main heterodimeric isoforms: αβ TCR and γδ TCR. The αβ TCR is expressed on the majority of peripheral T cells. Most αβ T cells recognize peptides, derived from degraded proteins, presented at the cell surface in molecular cradles called major histocompatibility complex (MHC) molecules. Recent reports have described other αβ T cell subsets. These 'unconventional' T cells bear TCRs that are capable of recognizing lipid ligands presented in the context of the MHC-like CD1 protein family or bacterial metabolites bound to the MHC-related protein 1 (MR1). γδ T cells constitute a minority of the T cell pool in human blood, but can represent up to half of total T cells in tissues such as the gut and skin. The identity of the preferred ligands for γδ T cells remains obscure, but it is now known that this receptor can also functionally engage CD1-lipid, or immunoglobulin (Ig) superfamily proteins called butyrophilins in the presence of pyrophosphate intermediates of bacterial lipid biosynthesis. Interactions between TCRs and these ligands allow the host to discriminate between self and non-self and co-ordinate an attack on the latter. Here, we describe how cells of the T lymphocyte lineage and their antigen receptors are generated and discuss the various modes of antigen recognition by these extraordinarily versatile receptors.
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Affiliation(s)
- M Attaf
- Division of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
| | - M Legut
- Division of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
| | - D K Cole
- Division of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
| | - A K Sewell
- Division of Infection and Immunity, Cardiff University School of Medicine, Cardiff, UK
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34
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Affiliation(s)
- Gregory
F. Pirrone
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
| | - Roxana E. Iacob
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
| | - John R. Engen
- Department of Chemistry and
Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 United States
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35
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Understanding the structural dynamics of TCR-pMHC interactions. Trends Immunol 2014; 35:604-612. [DOI: 10.1016/j.it.2014.10.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 10/20/2014] [Accepted: 10/20/2014] [Indexed: 12/23/2022]
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36
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Abstract
αβ T-cell receptor (TCR) activation plays a crucial role for T-cell function. However, the TCR itself does not possess signaling domains. Instead, the TCR is noncovalently coupled to a conserved multisubunit signaling apparatus, the CD3 complex, that comprises the CD3εγ, CD3εδ, and CD3ζζ dimers. How antigen ligation by the TCR triggers CD3 activation and what structural role the CD3 extracellular domains (ECDs) play in the assembled TCR-CD3 complex remain unclear. Here, we use two complementary structural approaches to gain insight into the overall organization of the TCR-CD3 complex. Small-angle X-ray scattering of the soluble TCR-CD3εδ complex reveals the CD3εδ ECDs to sit underneath the TCR α-chain. The observed arrangement is consistent with EM images of the entire TCR-CD3 integral membrane complex, in which the CD3εδ and CD3εγ subunits were situated underneath the TCR α-chain and TCR β-chain, respectively. Interestingly, the TCR-CD3 transmembrane complex bound to peptide-MHC is a dimer in which two TCRs project outward from a central core composed of the CD3 ECDs and the TCR and CD3 transmembrane domains. This arrangement suggests a potential ligand-dependent dimerization mechanism for TCR signaling. Collectively, our data advance our understanding of the molecular organization of the TCR-CD3 complex, and provides a conceptual framework for the TCR activation mechanism.
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37
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Smith SN, Wang Y, Baylon JL, Singh NK, Baker BM, Tajkhorshid E, Kranz DM. Changing the peptide specificity of a human T-cell receptor by directed evolution. Nat Commun 2014; 5:5223. [PMID: 25376839 PMCID: PMC4225554 DOI: 10.1038/ncomms6223] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 09/10/2014] [Indexed: 11/09/2022] Open
Abstract
Binding of a T-cell receptor (TCR) to a peptide/major histocompatibility complex is the key interaction involved in antigen specificity of T cells. The recognition involves up to six complementarity determining regions (CDR) of the TCR. Efforts to examine the structural basis of these interactions and to exploit them in adoptive T-cell therapies has required the isolation of specific T-cell clones and their clonotypic TCRs. Here we describe a strategy using in vitro-directed evolution of a single TCR to change its peptide specificity, thereby avoiding the need to isolate T-cell clones. The human TCR A6, which recognizes the viral peptide Tax/HLA-A2, was converted to TCR variants that recognized the cancer peptide MART1/HLA-A2. Mutational studies and molecular dynamics simulations identified CDR residues that were predicted to be important in the specificity switch. Thus, in vitro engineering strategies alone can be used to discover TCRs with desired specificities.
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Affiliation(s)
- Sheena N. Smith
- Department of Biochemistry, University of Illinois, 600 S. Matthews Ave., Urbana, IL 61801, USA
| | - Yuhang Wang
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, IL 61802, USA
| | - Javier L. Baylon
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, IL 61802, USA
| | - Nishant K. Singh
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, 1234 Notre Dame Avenue, South Bend, IN 46557, USA
| | - Brian M. Baker
- Department of Chemistry and Biochemistry and the Harper Cancer Research Institute, University of Notre Dame, 1234 Notre Dame Avenue, South Bend, IN 46557, USA
| | - Emad Tajkhorshid
- Department of Biochemistry, University of Illinois, 600 S. Matthews Ave., Urbana, IL 61801, USA
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, IL 61802, USA
| | - David M. Kranz
- Department of Biochemistry, University of Illinois, 600 S. Matthews Ave., Urbana, IL 61801, USA
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38
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Hawse WF, Morel PA. An immunology primer for computational modelers. J Pharmacokinet Pharmacodyn 2014; 41:389-99. [PMID: 25238901 DOI: 10.1007/s10928-014-9384-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 09/09/2014] [Indexed: 11/30/2022]
Abstract
The immune system is designed to protect an organism from infection and damage caused by a pathogen. A successful immune response requires the coordinated function of multiple cell types and molecules in the innate and adaptive immune systems. Given the complexity of the immune system, it would be advantageous to build computational models to better understand immune responses and develop models to better guide the design of immunotherapies. Often, researchers with strong quantitative backgrounds do not have formal training in immunology. Therefore, the goal of this review article is to provide a brief primer on cellular immunology that is geared for computational modelers.
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Affiliation(s)
- William F Hawse
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA, USA,
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39
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Malecek K, Grigoryan A, Zhong S, Gu WJ, Johnson LA, Rosenberg SA, Cardozo T, Krogsgaard M. Specific increase in potency via structure-based design of a TCR. THE JOURNAL OF IMMUNOLOGY 2014; 193:2587-99. [PMID: 25070852 DOI: 10.4049/jimmunol.1302344] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Adoptive immunotherapy with Ag-specific T lymphocytes is a powerful strategy for cancer treatment. However, most tumor Ags are nonreactive "self" proteins, which presents an immunotherapy design challenge. Recent studies have shown that tumor-specific TCRs can be transduced into normal PBLs, which persist after transfer in ∼30% of patients and effectively destroy tumor cells in vivo. Although encouraging, the limited clinical responses underscore the need for enrichment of T cells with desirable antitumor capabilities prior to patient transfer. In this study, we used structure-based design to predict point mutations of a TCR (DMF5) that enhance its binding affinity for an agonist tumor Ag-MHC (peptide-MHC [pMHC]), Mart-1 (27L)-HLA-A2, which elicits full T cell activation to trigger immune responses. We analyzed the effects of selected TCR point mutations on T cell activation potency and analyzed cross-reactivity with related Ags. Our results showed that the mutated TCRs had improved T cell activation potency while retaining a high degree of specificity. Such affinity-optimized TCRs have demonstrated to be very specific for Mart-1 (27L), the epitope for which they were structurally designed. Although of somewhat limited clinical relevance, these studies open the possibility for future structural-based studies that could potentially be used in adoptive immunotherapy to treat melanoma while avoiding adverse autoimmunity-derived effects.
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Affiliation(s)
- Karolina Malecek
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016; Program in Structural Biology, New York University School of Medicine, New York, NY 10016
| | - Arsen Grigoryan
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016
| | - Shi Zhong
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016
| | - Wei Jun Gu
- Department of Chemistry, New York University, New York, NY 10012
| | - Laura A Johnson
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and
| | - Steven A Rosenberg
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and
| | - Timothy Cardozo
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016; Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016
| | - Michelle Krogsgaard
- Perlmutter Cancer Center, New York University School of Medicine, New York, NY 10016; Program in Structural Biology, New York University School of Medicine, New York, NY 10016; Interdisciplinary Melanoma Cooperative Group, New York University School of Medicine, New York, NY 10016
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40
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Hawse WF, De S, Greenwood AI, Nicholson LK, Zajicek J, Kovrigin EL, Kranz DM, Garcia KC, Baker BM. TCR scanning of peptide/MHC through complementary matching of receptor and ligand molecular flexibility. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2014; 192:2885-91. [PMID: 24523505 PMCID: PMC3992338 DOI: 10.4049/jimmunol.1302953] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Although conformational changes in TCRs and peptide Ags presented by MHC protein (pMHC) molecules often occur upon binding, their relationship to intrinsic flexibility and role in ligand selectivity are poorly understood. In this study, we used nuclear magnetic resonance to study TCR-pMHC binding, examining recognition of the QL9/H-2L(d) complex by the 2C TCR. Although the majority of the CDR loops of the 2C TCR rigidify upon binding, the CDR3β loop remains mobile within the TCR-pMHC interface. Remarkably, the region of the QL9 peptide that interfaces with CDR3β is also mobile in the free pMHC and in the TCR-pMHC complex. Determination of conformational exchange kinetics revealed that the motions of CDR3β and QL9 are closely matched. The matching of conformational exchange in the free proteins and its persistence in the complex enhances the thermodynamic and kinetic stability of the TCR-pMHC complex and provides a mechanism for facile binding. We thus propose that matching of structural fluctuations is a component of how TCRs scan among potential ligands for those that can bind with sufficient stability to enable T cell signaling.
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Affiliation(s)
- William F. Hawse
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46530, USA
| | - Soumya De
- Department of Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Alex I. Greenwood
- Department of Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Linda K. Nicholson
- Department of Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jaroslav Zajicek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46530, USA
| | | | - David M. Kranz
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana IL 61801, USA
| | - K. Christopher Garcia
- Departments of Molecular & Cellular Physiology and Structural Biology, Program in Immunology, and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Brian M. Baker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46530, USA
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41
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Pierce BG, Hellman LM, Hossain M, Singh NK, Vander Kooi CW, Weng Z, Baker BM. Computational design of the affinity and specificity of a therapeutic T cell receptor. PLoS Comput Biol 2014; 10:e1003478. [PMID: 24550723 PMCID: PMC3923660 DOI: 10.1371/journal.pcbi.1003478] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 01/02/2014] [Indexed: 01/15/2023] Open
Abstract
T cell receptors (TCRs) are key to antigen-specific immunity and are increasingly being explored as therapeutics, most visibly in cancer immunotherapy. As TCRs typically possess only low-to-moderate affinity for their peptide/MHC (pMHC) ligands, there is a recognized need to develop affinity-enhanced TCR variants. Previous in vitro engineering efforts have yielded remarkable improvements in TCR affinity, yet concerns exist about the maintenance of peptide specificity and the biological impacts of ultra-high affinity. As opposed to in vitro engineering, computational design can directly address these issues, in theory permitting the rational control of peptide specificity together with relatively controlled increments in affinity. Here we explored the efficacy of computational design with the clinically relevant TCR DMF5, which recognizes nonameric and decameric epitopes from the melanoma-associated Melan-A/MART-1 protein presented by the class I MHC HLA-A2. We tested multiple mutations selected by flexible and rigid modeling protocols, assessed impacts on affinity and specificity, and utilized the data to examine and improve algorithmic performance. We identified multiple mutations that improved binding affinity, and characterized the structure, affinity, and binding kinetics of a previously reported double mutant that exhibits an impressive 400-fold affinity improvement for the decameric pMHC ligand without detectable binding to non-cognate ligands. The structure of this high affinity mutant indicated very little conformational consequences and emphasized the high fidelity of our modeling procedure. Overall, our work showcases the capability of computational design to generate TCRs with improved pMHC affinities while explicitly accounting for peptide specificity, as well as its potential for generating TCRs with customized antigen targeting capabilities.
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Affiliation(s)
- Brian G. Pierce
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Lance M. Hellman
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Moushumi Hossain
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Nishant K. Singh
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Craig W. Vander Kooi
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Brian M. Baker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States of America
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana, United States of America
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42
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The basis for limited specificity and MHC restriction in a T cell receptor interface. Nat Commun 2013; 4:1948. [PMID: 23736024 PMCID: PMC3708045 DOI: 10.1038/ncomms2948] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 04/30/2013] [Indexed: 02/03/2023] Open
Abstract
αβ T cell receptors (TCRs) recognize peptides presented by major histocompatibility complex (MHC) proteins using multiple complementarity determining region (CDR) loops. TCRs display an array of poorly understood recognition properties, including specificity, cross-reactivity, and MHC restriction. Here we report a comprehensive thermodynamic deconstruction of the interaction between the A6 TCR and the Tax peptide presented by the class I MHC HLA-A*0201, uncovering the physical basis for the receptor's recognition properties. Broadly, our findings are in conflict with widely-held generalities regarding TCR recognition, such as the relative contributions of central and peripheral peptide residues and the roles of the hypervariable and germline CDR loops in engaging peptide and MHC. Instead we find that the recognition properties of the receptor emerge from the need to engage the composite peptide/MHC surface, with the receptor utilizing its CDR loops in a cooperative fashion such that specificity, cross-reactivity, and MHC restriction are inextricably linked.
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43
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Backbone flexibility of CDR3 and immune recognition of antigens. J Mol Biol 2013; 426:1583-99. [PMID: 24380763 DOI: 10.1016/j.jmb.2013.12.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 12/03/2013] [Accepted: 12/19/2013] [Indexed: 11/22/2022]
Abstract
Conformational entropy is an important component of protein-protein interactions; however, there is no reliable method for computing this parameter. We have developed a statistical measure of residual backbone entropy in folded proteins by using the ϕ-ψ distributions of the 20 amino acids in common secondary structures. The backbone entropy patterns of amino acids within helix, sheet or coil form clusters that recapitulate the branching and hydrogen bonding properties of the side chains in the secondary structure type. The same types of residues in coil and sheet have identical backbone entropies, while helix residues have much smaller conformational entropies. We estimated the backbone entropy change for immunoglobulin complementarity-determining regions (CDRs) from the crystal structures of 34 low-affinity T-cell receptors and 40 high-affinity Fabs as a result of the formation of protein complexes. Surprisingly, we discovered that the computed backbone entropy loss of only the CDR3, but not all CDRs, correlated significantly with the kinetic and affinity constants of the 74 selected complexes. Consequently, we propose a simple algorithm to introduce proline mutations that restrict the conformational flexibility of CDRs and enhance the kinetics and affinity of immunoglobulin interactions. Combining the proline mutations with rationally designed mutants from a previous study led to 2400-fold increase in the affinity of the A6 T-cell receptor for Tax-HLAA2. However, this mutational scheme failed to induce significant binding changes in the already-high-affinity C225-Fab/huEGFR interface. Our results will serve as a roadmap to formulate more effective target functions to design immune complexes with improved biological functions.
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44
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Computational design of protein–protein interactions. Curr Opin Struct Biol 2013; 23:903-10. [DOI: 10.1016/j.sbi.2013.08.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 08/06/2013] [Accepted: 08/08/2013] [Indexed: 11/23/2022]
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45
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Beerbaum M, Ballaschk M, Erdmann N, Schnick C, Diehl A, Uchanska-Ziegler B, Ziegler A, Schmieder P. NMR spectroscopy reveals unexpected structural variation at the protein-protein interface in MHC class I molecules. JOURNAL OF BIOMOLECULAR NMR 2013; 57:167-178. [PMID: 24006098 DOI: 10.1007/s10858-013-9777-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 08/28/2013] [Indexed: 06/02/2023]
Abstract
β2-Microglobulin (β2m) is a small, monomorphic protein non-covalently bound to the heavy chain (HC) in polymorphic major histocompatibility complex (MHC) class I molecules. Given the high evolutionary conservation of structural features of β2m in various MHC molecules as shown by X-ray crystallography, β2m is often considered as a mere scaffolding protein. Using nuclear magnetic resonance (NMR) spectroscopy, we investigate here whether β2m residues at the interface to the HC exhibit changes depending on HC polymorphisms and the peptides bound to the complex in solution. First we show that human β2m can effectively be produced in deuterated form using high-cell-density-fermentation and we employ the NMR resonance assignments obtained for triple-labeled β2m bound to the HLA-B*27:09 HC to examine the β2m-HC interface. We then proceed to compare the resonances of β2m in two minimally distinct subtypes, HLA-B*27:09 and HLA-B*27:05, that are differentially associated with the spondyloarthropathy Ankylosing Spondylitis. Each of these subtypes is complexed with four distinct peptides for which structural information is already available. We find that only the resonances at the β2m-HC interface show a variation of their chemical shifts between the different complexes. This indicates the existence of an unexpected plasticity that enables β2m to accommodate changes that depend on HC polymorphism as well as on the bound peptide through subtle structural variations of the protein-protein interface.
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Affiliation(s)
- Monika Beerbaum
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125, Berlin, Germany
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46
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Smith SN, Sommermeyer D, Piepenbrink KH, Blevins SJ, Bernhard H, Uckert W, Baker BM, Kranz DM. Plasticity in the contribution of T cell receptor variable region residues to binding of peptide-HLA-A2 complexes. J Mol Biol 2013; 425:4496-507. [PMID: 23954306 DOI: 10.1016/j.jmb.2013.08.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 08/05/2013] [Accepted: 08/06/2013] [Indexed: 11/29/2022]
Abstract
One hypothesis accounting for major histocompatibility complex (MHC) restriction by T cell receptors (TCRs) holds that there are several evolutionary conserved residues in TCR variable regions that contact MHC. While this "germline codon" hypothesis is supported by various lines of evidence, it has been difficult to test. The difficulty stems in part from the fact that TCRs exhibit low affinities for pep/MHC, thus limiting the range of binding energies that can be assigned to these key interactions using mutational analyses. To measure the magnitude of binding energies involved, here we used high-affinity TCRs engineered by mutagenesis of CDR3. The TCRs included a high-affinity, MART-1/HLA-A2-specific single-chain TCR and two other high-affinity TCRs that all contain the same Vα region and recognize the same MHC allele (HLA-A2), with different peptides and Vβ regions. Mutational analysis of residues in CDR1 and CDR2 of the three Vα2 regions showed the importance of the key germline codon residue Y51. However, two other proposed key residues showed significant differences among the TCRs in their relative contributions to binding. With the use of single-position, yeast-display libraries in two of the key residues, MART-1/HLA-A2 selections also revealed strong preferences for wild-type germline codon residues, but several alternative residues could also accommodate binding and, hence, MHC restriction. Thus, although a single residue (Y51) could account for a proportion of the energy associated with positive selection (i.e., MHC restriction), there is significant plasticity in requirements for particular side chains in CDR1 and CDR2 and in their relative binding contributions among different TCRs.
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Affiliation(s)
- Sheena N Smith
- Department of Biochemistry, University of Illinois, 600 South Mathews Avenue, Urbana, IL 61801, USA
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47
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Hawse WF, Gloor BE, Ayres CM, Kho K, Nuter E, Baker BM. Peptide modulation of class I major histocompatibility complex protein molecular flexibility and the implications for immune recognition. J Biol Chem 2013; 288:24372-81. [PMID: 23836912 DOI: 10.1074/jbc.m113.490664] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
T cells use the αβ T cell receptor (TCR) to recognize antigenic peptides presented by class I major histocompatibility complex proteins (pMHCs) on the surfaces of antigen-presenting cells. Flexibility in both TCRs and peptides plays an important role in antigen recognition and discrimination. Less clear is the role of flexibility in the MHC protein; although recent observations have indicated that mobility in the MHC can impact TCR recognition in a peptide-dependent fashion, the extent of this behavior is unknown. Here, using hydrogen/deuterium exchange, fluorescence anisotropy, and structural analyses, we show that the flexibility of the peptide binding groove of the class I MHC protein HLA-A*0201 varies significantly with different peptides. The variations extend throughout the binding groove, impacting regions contacted by TCRs as well as other activating and inhibitory receptors of the immune system. Our results are consistent with statistical mechanical models of protein structure and dynamics, in which the binding of different peptides alters the populations and exchange kinetics of substates in the MHC conformational ensemble. Altered MHC flexibility will influence receptor engagement, impacting conformational adaptations, entropic penalties associated with receptor recognition, and the populations of binding-competent states. Our results highlight a previously unrecognized aspect of the "altered self" mechanism of immune recognition and have implications for specificity, cross-reactivity, and antigenicity in cellular immunity.
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Affiliation(s)
- William F Hawse
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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48
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O'Donoghue GP, Pielak RM, Smoligovets AA, Lin JJ, Groves JT. Direct single molecule measurement of TCR triggering by agonist pMHC in living primary T cells. eLife 2013; 2:e00778. [PMID: 23840928 PMCID: PMC3701909 DOI: 10.7554/elife.00778] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/17/2013] [Indexed: 02/04/2023] Open
Abstract
T cells discriminate between self and foreign antigenic peptides, displayed on antigen presenting cell surfaces, via the TCR. While the molecular interactions between TCR and its ligands are well characterized in vitro, quantitative measurements of these interactions in living cells are required to accurately resolve the physical mechanisms of TCR signaling. We report direct single molecule measurements of TCR triggering by agonist pMHC in hybrid junctions between live primary T cells and supported lipid membranes. Every pMHC:TCR complex over the entire cell is tracked while simultaneously monitoring the local membrane recruitment of ZAP70, as a readout of TCR triggering. Mean dwell times for pMHC:TCR molecular binding of 5 and 54 s were measured for two different pMHC:TCR systems. Single molecule measurements of the pMHC:TCR:ZAP70 complex indicate that TCR triggering is stoichiometric with agonist pMHC in a 1:1 ratio. Thus any signal amplification must occur downstream of TCR triggering. DOI:http://dx.doi.org/10.7554/eLife.00778.001 The immune system identifies and combats foreign objects, including pathogens, in the body. T cells are key components of the immune system, and each has a unique variant of a signalling complex known as the T cell receptor on its surface. T cells scan the surfaces of other cells in search of antigens, which are peptides (fragments of proteins) that derive from foreign pathogens such as viruses. Successful recognition of a foreign peptide leads to an immune response that, in most cases, ultimately rids the body of the pathogen. Most importantly, however, the immune system must be able to discriminate between peptides that are produced naturally in the body (‘self’ peptides) and foreign or ‘non-self’ peptides. This is challenging because self peptides may have similar structures to non-self peptides and are often much more abundant. Many models have been proposed to explain how T cells are able to detect just a few molecules of foreign peptide. According to some hypotheses the T cell receptors get together in clusters to function cooperatively; alternatively, it has been suggested that rapid binding of a foreign peptide to multiple T cell receptors sequentially can build up a strong signal. However, none of these phenomena have been directly observed. O'Donoghue et al. now image the interactions between T cell receptors and peptides bound to molecules called major histocompatibility complexes (MHCs), and show that T cell activation can occur when a single foreign peptide binds to a single receptor. These interactions are long-lived and ultimately result in the recruitment of ZAP70, which has an important role in the activation of T cells, to the complex formed by the T cell, the peptide and the MHC molecule. Therefore, any amplification of the activating signal transmitted by non-self peptides occurs following receptor binding, in contrast to previous models. DOI:http://dx.doi.org/10.7554/eLife.00778.002
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Affiliation(s)
- Geoff P O'Donoghue
- Department of Chemistry , Howard Hughes Medical Institute, University of California, Berkeley , Berkeley , United States ; Physical Biosciences Division , Lawrence Berkeley National Laboratory, University of California, Berkeley , Berkeley , United States
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Cole DK, Sami M, Scott DR, Rizkallah PJ, Borbulevych OY, Todorov PT, Moysey RK, Jakobsen BK, Boulter JM, Baker BM, Yi Li. Increased Peptide Contacts Govern High Affinity Binding of a Modified TCR Whilst Maintaining a Native pMHC Docking Mode. Front Immunol 2013; 4:168. [PMID: 23805144 PMCID: PMC3693486 DOI: 10.3389/fimmu.2013.00168] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 06/12/2013] [Indexed: 12/15/2022] Open
Abstract
Natural T cell receptors (TCRs) generally bind to their cognate pMHC molecules with weak affinity and fast kinetics, limiting their use as therapeutic agents. Using phage display, we have engineered a high affinity version of the A6 wild-type TCR (A6wt), specific for the human leukocyte antigen (HLA-A∗0201) complexed with human T cell lymphotropic virus type 111–19 peptide (A2-Tax). Mutations in just 4 residues in the CDR3β loop region of the A6wt TCR were selected that improved binding to A2-Tax by nearly 1000-fold. Biophysical measurements of this mutant TCR (A6c134) demonstrated that the enhanced binding was derived through favorable enthalpy and a slower off-rate. The structure of the free A6c134 TCR and the A6c134/A2-Tax complex revealed a native binding mode, similar to the A6wt/A2-Tax complex. However, concordant with the more favorable binding enthalpy, the A6c134 TCR made increased contacts with the Tax peptide compared with the A6wt/A2-Tax complex, demonstrating a peptide-focused mechanism for the enhanced affinity that directly involved the mutated residues in the A6c134 TCR CDR3β loop. This peptide-focused enhanced TCR binding may represent an important approach for developing antigen specific high affinity TCR reagents for use in T cell based therapies.
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Affiliation(s)
- David K Cole
- Cardiff University School of Medicine, Heath Park , Cardiff , UK
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