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Papadaki GF, Woodward CH, Young MC, Winters TJ, Burslem GM, Sgourakis NG. A Chicken Tapasin ortholog can chaperone empty HLA-B∗37:01 molecules independent of other peptide-loading components. J Biol Chem 2023; 299:105136. [PMID: 37543367 PMCID: PMC10534222 DOI: 10.1016/j.jbc.2023.105136] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/26/2023] [Accepted: 07/29/2023] [Indexed: 08/07/2023] Open
Abstract
Human Tapasin (hTapasin) is the main chaperone of MHC-I molecules, enabling peptide loading and antigen repertoire optimization across HLA allotypes. However, it is restricted to the endoplasmic reticulum (ER) lumen as part of the protein loading complex (PLC), and therefore is highly unstable when expressed in recombinant form. Additional stabilizing co-factors such as ERp57 are required to catalyze peptide exchange in vitro, limiting uses for the generation of pMHC-I molecules of desired antigen specificities. Here, we show that the chicken Tapasin (chTapasin) ortholog can be expressed recombinantly at high yields in a stable form, independent of co-chaperones. chTapasin can bind the human HLA-B∗37:01 with low micromolar-range affinity to form a stable tertiary complex. Biophysical characterization by methyl-based NMR methods reveals that chTapasin recognizes a conserved β2m epitope on HLA-B∗37:01, consistent with previously solved X-ray structures of hTapasin. Finally, we provide evidence that the B∗37:01/chTapasin complex is peptide-receptive and can be dissociated upon binding of high-affinity peptides. Our results highlight the use of chTapasin as a stable scaffold for protein engineering applications aiming to expand the ligand exchange function on human MHC-I and MHC-like molecules.
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Affiliation(s)
- Georgia F Papadaki
- Center for Computational and Genomic Medicine, Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Claire H Woodward
- Center for Computational and Genomic Medicine, Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael C Young
- Center for Computational and Genomic Medicine, Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Trenton J Winters
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - George M Burslem
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Cancer Biology and Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nikolaos G Sgourakis
- Center for Computational and Genomic Medicine, Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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Papadaki GF, Woodward CH, Young MC, Winters TJ, Burslem GM, Sgourakis NG. A Chicken Tapasin ortholog can chaperone empty HLA molecules independently of other peptide-loading components. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.23.546255. [PMID: 37425753 PMCID: PMC10326978 DOI: 10.1101/2023.06.23.546255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Human Tapasin (hTapasin) is the main chaperone of MHC-I molecules, enabling peptide loading and antigen repertoire optimization across HLA allotypes. However, it is restricted to the endoplasmic reticulum (ER) lumen as part of the protein loading complex (PLC) and therefore is highly unstable when expressed in recombinant form. Additional stabilizing co-factors such as ERp57 are required to catalyze peptide exchange in vitro , limiting uses for the generation of pMHC-I molecules of desired antigen specificities. Here, we show that the chicken Tapasin (chTapasin) ortholog can be expressed recombinantly at high yields in stable form, independently of co-chaperones. chTapasin can bind the human HLA-B * 37:01 with low micromolar-range affinity to form a stable tertiary complex. Biophysical characterization by methyl-based NMR methods reveals that chTapasin recognizes a conserved β 2 m epitope on HLA-B * 37:01, consistent with previously solved X-ray structures of hTapasin. Finally, we provide evidence that the B * 37:01/chTapasin complex is peptide-receptive and can be dissociated upon binding of high-affinity peptides. Our results highlight the use of chTapasin as a stable scaffold for future protein engineering applications aiming to expand the ligand exchange function on human MHC-I and MHC-like molecules.
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Sun Y, Young MC, Woodward CH, Danon JN, Truong H, Gupta S, Winters TJ, Burslem G, Sgourakis NG. Universal open MHC-I molecules for rapid peptide loading and enhanced complex stability across HLA allotypes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.18.533266. [PMID: 36993702 PMCID: PMC10055308 DOI: 10.1101/2023.03.18.533266] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The polymorphic nature and intrinsic instability of class I major histocompatibility complex (MHC-I) and MHC-like molecules loaded with suboptimal peptides, metabolites, or glycolipids presents a fundamental challenge for identifying disease-relevant antigens and antigen-specific T cell receptors (TCRs), hindering the development of autologous therapeutics. Here, we leverage the positive allosteric coupling between the peptide and light chain (β 2 microglobulin, β 2 m) subunits for binding to the MHC-I heavy chain (HC) through an engineered disulfide bond bridging conserved epitopes across the HC/β 2 m interface, to generate conformationally stable, open MHC-I molecules. Biophysical characterization shows that open MHC-I molecules are properly folded protein complexes of enhanced thermal stability compared to the wild type, when loaded with low- to intermediate-affinity peptides. Using solution NMR, we characterize the effects of the disulfide bond on the conformation and dynamics of the MHC-I structure, ranging from local changes in β 2 m interacting sites of the peptide binding groove to long-range effects on the α 2-1 helix and α 3 domain. The interchain disulfide bond stabilizes empty MHC-I molecules in a peptide-receptive, open conformation to promote peptide exchange across multiple human leucocyte antigen (HLA) allotypes, covering representatives from five HLA-A, six HLA-B supertypes, and oligomorphic HLA-Ib molecules. Our structural design, combined with conditional β-peptide ligands, provides a universal platform for generating ready-to-load MHC-I systems of enhanced stability, enabling a range of approaches to screen antigenic epitope libraries and probe polyclonal TCR repertoires in the context of highly polymorphic HLA-I allotypes, as well as oligomorphic nonclassical molecules. Significance Statement We outline a structure-guided approach for generating conformationally stable, open MHC-I molecules with enhanced ligand exchange kinetics spanning five HLA-A, all HLA-B supertypes, and oligomorphic HLA-Ib allotypes. We present direct evidence of positive allosteric cooperativity between peptide binding and β 2 m association with the heavy chain by solution NMR and HDX-MS spectroscopy. We demonstrate that covalently linked β 2 m serves as a conformational chaperone to stabilize empty MHC-I molecules in a peptide-receptive state, by inducing an open conformation and preventing intrinsically unstable heterodimers from irreversible aggregation. Our study provides structural and biophysical insights into the conformational properties of MHC-I ternary complexes, which can be further applied to improve the design of ultra-stable, universal ligand exchange systems in a pan-HLA allelic setting.
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Wu Y, Zhang N, Wei X, Lu S, Li S, Hashimoto K, Dijkstra JM, Xia C. The Structure of a Peptide-Loaded Shark MHC Class I Molecule Reveals Features of the Binding between β 2-Microglobulin and H Chain Conserved in Evolution. THE JOURNAL OF IMMUNOLOGY 2021; 207:308-321. [PMID: 34145057 DOI: 10.4049/jimmunol.2001165] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 04/23/2021] [Indexed: 12/22/2022]
Abstract
Cartilaginous fish are the most primitive extant species with MHC molecules. Using the nurse shark, the current study is, to the best of our knowledge, the first to present a peptide-loaded MHC class I (pMHC-I) structure for this class of animals. The overall structure was found to be similar between cartilaginous fish and bony animals, showing remarkable conservation of interactions between the three pMHC-I components H chain, β2-microglobulin (β2-m), and peptide ligand. In most previous studies, relatively little attention was given to the details of binding between the H chain and β2-m, and our study provides important new insights. A pronounced conserved feature involves the insertion of a large β2-m F56+W60 hydrophobic knob into a pleat of the β-sheet floor of the H chain α1α2 domain, with the knob being surrounded by conserved residues. Another conserved feature is a hydrogen bond between β2-m Y10 and a proline in the α3 domain of the H chain. By alanine substitution analysis, we found that the conserved β2-m residues Y10, D53, F56, and W60-each binding the H chain-are required for stable pMHC-I complex formation. For the β2-m residues Y10 and F56, such observations have not been reported before. The combined data indicate that for stable pMHC-I complex formation β2-m should not only bind the α1α2 domain but also the α3 domain. Knowing the conserved structural features of pMHC-I should be helpful for future elucidations of the mechanisms of pMHC-I complex formation and peptide editing.
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Affiliation(s)
- Yanan Wu
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
| | - Nianzhi Zhang
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
| | - Xiaohui Wei
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
| | - Shuangshuang Lu
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
| | - Shen Li
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
| | - Keiichiro Hashimoto
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Japan
| | - Johannes M Dijkstra
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Japan
| | - Chun Xia
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China; and
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Wu Y, Zhang N, Hashimoto K, Xia C, Dijkstra JM. Structural Comparison Between MHC Classes I and II; in Evolution, a Class-II-Like Molecule Probably Came First. Front Immunol 2021; 12:621153. [PMID: 34194421 PMCID: PMC8236899 DOI: 10.3389/fimmu.2021.621153] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 05/04/2021] [Indexed: 01/03/2023] Open
Abstract
Structures of peptide-loaded major histocompatibility complex class I (pMHC-I) and class II (pMHC-II) complexes are similar. However, whereas pMHC-II complexes include similar-sized IIα and IIβ chains, pMHC-I complexes include a heavy chain (HC) and a single domain molecule β2-microglobulin (β2-m). Recently, we elucidated several pMHC-I and pMHC-II structures of primitive vertebrate species. In the present study, a comprehensive comparison of pMHC-I and pMHC-II structures helps to understand pMHC structural evolution and supports the earlier proposed—though debated—direction of MHC evolution from class II-type to class I. Extant pMHC-II structures share major functional characteristics with a deduced MHC-II-type homodimer ancestor. Evolutionary establishment of pMHC-I presumably involved important new functions such as (i) increased peptide selectivity by binding the peptides in a closed groove (ii), structural amplification of peptide ligand sequence differences by binding in a non-relaxed fashion, and (iii) increased peptide selectivity by syngeneic heterotrimer complex formation between peptide, HC, and β2-m. These new functions were associated with structures that since their establishment in early pMHC-I have been very well conserved, including a shifted and reorganized P1 pocket (aka A pocket), and insertion of a β2-m hydrophobic knob into the peptide binding domain β-sheet floor. A comparison between divergent species indicates better sequence conservation of peptide binding domains among MHC-I than among MHC-II, agreeing with more demanding interactions within pMHC-I complexes. In lungfishes, genes encoding fusions of all MHC-IIα and MHC-IIβ extracellular domains were identified, and although these lungfish genes presumably derived from classical MHC-II, they provide an alternative mechanistic hypothesis for how evolution from class II-type to class I may have occurred.
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Affiliation(s)
- Yanan Wu
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Nianzhi Zhang
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Keiichiro Hashimoto
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Japan
| | - Chun Xia
- Department of Microbiology and Immunology, College of Veterinary Medicine, China Agricultural University, Beijing, China
| | - Johannes M Dijkstra
- Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Japan
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Differential scanning fluorimetry based assessments of the thermal and kinetic stability of peptide-MHC complexes. J Immunol Methods 2016; 432:95-101. [PMID: 26906089 DOI: 10.1016/j.jim.2016.02.016] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/17/2016] [Accepted: 02/17/2016] [Indexed: 11/20/2022]
Abstract
Measurements of thermal stability by circular dichroism (CD) spectroscopy have been widely used to assess the binding of peptides to MHC proteins, particularly within the structural immunology community. Although thermal stability assays offer advantages over other approaches such as IC50 measurements, CD-based stability measurements are hindered by large sample requirements and low throughput. Here we demonstrate that an alternative approach based on differential scanning fluorimetry (DSF) yields results comparable to those based on CD for both class I and class II complexes. As they require much less sample, DSF-based measurements reduce demands on protein production strategies and are amenable for high throughput studies. DSF can thus not only replace CD as a means to assess peptide/MHC thermal stability, but can complement other peptide-MHC binding assays used in screening, epitope discovery, and vaccine design. Due to the physical process probed, DSF can also uncover complexities not observed with other techniques. Lastly, we show that DSF can also be used to assess peptide/MHC kinetic stability, allowing for a single experimental setup to probe both binding equilibria and kinetics.
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7
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Montealegre S, Venugopalan V, Fritzsche S, Kulicke C, Hein Z, Springer S. Dissociation of β2-microglobulin determines the surface quality control of major histocompatibility complex class I molecules. FASEB J 2015; 29:2780-8. [PMID: 25782992 DOI: 10.1096/fj.14-268094] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 02/25/2015] [Indexed: 11/11/2022]
Abstract
Major histocompatibility complex class I proteins, which present antigenic peptides to cytotoxic T lymphocytes at the surface of all nucleated cells, are endocytosed and destroyed rapidly once their peptide ligand has dissociated. The molecular mechanism of this cellular quality control process, which prevents rebinding of exogenous peptides and thus erroneous immune responses, is unknown. To identify the nature of the decisive step in endocytic sorting of class I molecules and its location, we have followed the removal of optimally and suboptimally peptide-loaded murine H-2K(b) class I proteins from the cell surface. We find that the binding of their light chain, β2-microglobulin (β2m), protects them from endocytic destruction. Thus, the extended survival of suboptimally loaded K(b) molecules at 25°C is attributed to decreased dissociation of β2m. Because all forms of K(b) are constantly internalized but little β2m-receptive heavy chain is present at the cell surface, it is likely that β2m dissociation and recognition of the heavy chain for lysosomal degradation take place in an endocytic compartment.
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Affiliation(s)
- Sebastián Montealegre
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Vaishnavi Venugopalan
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Susanne Fritzsche
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Corinna Kulicke
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Zeynep Hein
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
| | - Sebastian Springer
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany
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Saini SK, Abualrous ET, Tigan AS, Covella K, Wellbrock U, Springer S. Not all empty MHC class I molecules are molten globules: Tryptophan fluorescence reveals a two-step mechanism of thermal denaturation. Mol Immunol 2013; 54:386-96. [DOI: 10.1016/j.molimm.2013.01.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 12/26/2012] [Accepted: 01/04/2013] [Indexed: 11/27/2022]
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9
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Fadel TR, Li N, Shah S, Look M, Pfefferle LD, Haller GL, Justesen S, Wilson CJ, Fahmy TM. Adsorption of multimeric T cell antigens on carbon nanotubes: effect on protein structure and antigen-specific T cell stimulation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:666-672. [PMID: 23090793 DOI: 10.1002/smll.201201684] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Revised: 08/21/2012] [Indexed: 06/01/2023]
Abstract
Antigen-specific activation of cytotoxic T cells can be enhanced up to three-fold more than soluble controls when using functionalized bundled carbon nanotube substrates ((b) CNTs). To overcome the denaturing effects of direct adsorption on (b) CNTs, a simple but robust method is demonstrated to stabilize the T cell stimulus on carbon nanotube substrates through non-covalent attachment of the linker neutravidin.
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Affiliation(s)
- Tarek R Fadel
- Department of Chemical and Biomedical Engineering, Yale University, P.O. Box 208284, New Haven, Connecticut, USA
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10
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Promiscuous binding of extracellular peptides to cell surface class I MHC protein. Proc Natl Acad Sci U S A 2012; 109:4580-5. [PMID: 22403068 DOI: 10.1073/pnas.1201586109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Algorithms derived from measurements of short-peptide (8-10 mers) binding to class I MHC proteins suggest that the binding groove of a class I MHC protein, such as K(b), can bind well over 1 million different peptides with significant affinity (<500 nM), a level of ligand-binding promiscuity approaching the level of heat shock protein binding of unfolded proteins. MHC proteins can, nevertheless, discriminate between similar peptides and bind many of them with high (nanomolar) affinity. Some insights into this high-promiscuity/high-affinity behavior and its impact on immunodominant peptides in T-cell responses to some infections and vaccination are suggested by results obtained here from testing a model developed to predict the number of cell surface peptide-MHC complexes that form on cells exposed to extracellular (exogenous) peptides.
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11
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Palankar R, Skirtach AG, Kreft O, Bédard M, Garstka M, Gould K, Möhwald H, Sukhorukov GB, Winterhalter M, Springer S. Controlled intracellular release of peptides from microcapsules enhances antigen presentation on MHC class I molecules. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2168-2176. [PMID: 19644923 DOI: 10.1002/smll.200900809] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
To understand the time course of action of any small molecule inside a single cell, one would deposit a defined amount inside the cell and initiate its activity at a defined moment. An elegant way to achieve this is to encapsulate the molecule in a micrometer-sized reservoir, introduce it into a cell, remotely open its wall by a laser pulse, and then follow the biological response by microscopy. The validity of this approach is validated here using microcapsules with defined walls that are doped with metallic nanoparticles so as to enable them to be opened with an infrared laser. The capsules are loaded with a fluorescent antigenic peptide and introduced into mammalian cultured cells where, upon laser-induced release, the peptide binds to major histocompatibility complex (MHC) class I proteins and elicits their cell surface transport. The concept of releasing a drug inside a cell and following its action is applicable to many problems in cell biology and medicine.
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Mareeva T, Martinez-Hackert E, Sykulev Y. How a T cell receptor-like antibody recognizes major histocompatibility complex-bound peptide. J Biol Chem 2008; 283:29053-9. [PMID: 18703505 PMCID: PMC2570882 DOI: 10.1074/jbc.m804996200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 07/30/2008] [Indexed: 11/06/2022] Open
Abstract
We determined the crystal structures of the T cell receptor (TCR)-like antibody 25-D1.16 Fab fragment bound to a complex of SIINFEKL peptide from ovalbumin and the H-2K(b) molecule. Remarkably, this antibody directly "reads" the structure of the major histocompatibility complex (MHC)-bound peptide, employing the canonical diagonal binding mode utilized by most TCRs. This is in marked contrast with another TCR-like antibody, Hyb3, bound to melanoma peptide MAGE-A1 in association with HLA-A1 MHC class I. Hyb3 assumes a non-canonical orientation over its cognate peptide-MHC and appears to recognize a conformational epitope in which the MHC contribution is dominant. We conclude that TCR-like antibodies can recognize MHC-bound peptide via two different mechanisms: one is similar to that exploited by the preponderance of TCRs and the other requires a non-canonical antibody orientation over the peptide-MHC complex.
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Affiliation(s)
- Tatiana Mareeva
- Department of Microbiology and Immunology and the Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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13
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Winkler K, Winter A, Rueckert C, Uchanska-Ziegler B, Alexiev U. Natural MHC class I polymorphism controls the pathway of peptide dissociation from HLA-B27 complexes. Biophys J 2007; 93:2743-55. [PMID: 17573425 PMCID: PMC1989716 DOI: 10.1529/biophysj.106.096602] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 04/20/2007] [Indexed: 01/22/2023] Open
Abstract
Analysis of antigen dissociation provides insight into peptide presentation modes of folded human leukocyte antigen (HLA) molecules, which consist of a heavy chain, beta2-microglobulin (beta2m), and an antigenic peptide. Here we have monitored peptide-HLA interactions and peptide dissociation kinetics of two HLA-B27 subtypes by fluorescence depolarization techniques. A single natural amino-acid substitution distinguishes the HLA-B*2705 subtype that is associated with the autoimmune disease ankylosing spondylitis from the non-disease-associated HLA-B*2709 subtype. Peptides with C-terminal Arg or Lys represent 27% of the natural B*2705 ligands. Our results show that dissociation of a model peptide with a C-terminal Lys (GRFAAAIAK) follows a two-step mechanism. Final peptide release occurs in the second step for both HLA-B27 subtypes. However, thermodynamics and kinetics of peptide-HLA interactions reveal different molecular mechanisms underlying the first step, as indicated by different activation energies of 95+/-8 kJ/mol (HLA-B*2705) and 150+/-10 kJ/mol (HLA-B*2709). In HLA-B*2709, partial peptide dissociation probably precedes fast final peptide release, while in HLA-B*2705 an allosteric mechanism based on long-range interactions between beta2m and the peptide binding groove controls the first step. The resulting peptide presentation mode lasts for days at physiological temperature, and determines the peptide-HLA-B*2705 conformation, which is recognized by cellular ligands such as T-cell receptors.
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Affiliation(s)
- Kathrin Winkler
- Physics Department, Freie Universität Berlin, Berlin, Germany
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14
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Bruder D, Nussbaum AK, Gakamsky DM, Schirle M, Stevanovic S, Singh-Jasuja H, Darji A, Chakraborty T, Schild H, Pecht I, Weiss S. Multiple synergizing factors contribute to the strength of the CD8+ T cell response against listeriolysin O. Int Immunol 2005; 18:89-100. [PMID: 16291651 DOI: 10.1093/intimm/dxh352] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Immunodominance in CD8+ T cell responses against Listeria monocytogenes is a well-recognized but still not fully understood phenomenon. From listeriolysin, the major virulence factor of L. monocytogenes, only a single epitope, pLLO91-99, is presented by MHC class I molecules in BALB/c mice which dominates the cytotoxic T cell response against this bacterial pathogen. To obtain more insights into the molecular and cellular mechanisms underlying immunodominance of this particular epitope, we compared the various steps involved in the presentation and recognition of pLLO91-99 derived from a wild-type toxin with an equivalent epitope from a mutated toxin. This fully functional variant contains within the pLLO91-99 epitope a conservative isoleucine to alanine replacement at the C-terminal anchor residue which results in loss of antigenicity. The binding properties of the variant peptide to soluble Kd remained unaffected and cytotoxic T cells capable of recognizing the pLLO99A/Kd complex were detectable in BALB/c mice. However, such T cells required higher concentrations of antigen in order to be optimally activated in vitro. A comparison between the TAP translocation efficiency of wild-type and mutant peptide demonstrated that the mutation at the C-terminus leads to a reduced transportation rate. Furthermore, the amino acid substitution changes the in vitro proteasomal cleavage pattern, resulting in a reduced liberation of the correct peptide from a polypeptide precursor. Thus, in all assays employed the immunodominant epitope performs optimally while the variant was found to be inferior. The synergy of all these steps most likely is the decisive factor in the immunodominance of pLLO91-99.
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Affiliation(s)
- Dunja Bruder
- Molecular Immunology, Department of Cell Biology and Immunology, German Research Centre for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany.
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15
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Borbulevych OY, Baxter TK, Yu Z, Restifo NP, Baker BM. Increased immunogenicity of an anchor-modified tumor-associated antigen is due to the enhanced stability of the peptide/MHC complex: implications for vaccine design. THE JOURNAL OF IMMUNOLOGY 2005; 174:4812-20. [PMID: 15814707 PMCID: PMC2241749 DOI: 10.4049/jimmunol.174.8.4812] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The use of "anchor-fixed" altered peptide ligands is of considerable interest in the development of therapeutic vaccines for cancer and infectious diseases, but the mechanism by which successful altered peptide ligands elicit enhanced immunity is unclear. In this study, we have determined the crystallographic structure of a major tumor rejection Ag, gp100(209-217), in complex with the HLA-A*0201 (HLA-A2) molecule, as well as the structure of a modified version of the peptide which substitutes methionine for threonine at position 2 (T2M; gp100(209-2M)). The T2M-modified peptide, which is more immunogenic in vitro and in vivo, binds HLA-A2 with a approximately 9-fold greater affinity and has a approximately 7-fold slower dissociation rate at physiological temperature. Within the limit of the crystallographic data, the T2M substitution does not alter the structure of the peptide/HLA-A2 complex. Consistent with this finding, in peripheral blood from 95 human subjects, we were unable to identify higher frequencies of T cells specific for either the native or modified peptide. These data strongly support the conclusion that the greater immunogenicity of the gp100(209-2M) peptide is due to the enhanced stability of the peptide/MHC complex, validating the anchor-fixing approach for generating therapeutic vaccine candidates. Thermodynamic data suggest that the enhanced stability of the T2M-modified peptide/HLA-A2 complex is attributable to the increased hydrophobicity of the modified peptide, but the gain due to hydrophobicity is offset considerably by the loss of a hydrogen bond made by the native peptide to the HLA-A2 molecule. Our findings have broad implications for the optimization of current vaccine-design strategies.
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Affiliation(s)
- Oleg Y Borbulevych
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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16
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Pecht I, Gakamsky DM. Spatial coordination of CD8 and TCR molecules controls antigen recognition by CD8+ T-cells. FEBS Lett 2005; 579:3336-41. [PMID: 15913613 DOI: 10.1016/j.febslet.2005.04.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2005] [Indexed: 11/28/2022]
Abstract
The interactions between the TCR and peptides bound to class I MHC encoded molecules (pMHC) and a mechanism for CD8 cooperation in this process are reviewed. Observation of two TCR/CD8 populations with different lateral diffusion rate constants as well as two distinct association phases of class I MHC tetramers ((pMHC)4) with T-cells suggest that the most efficient pMHC-T-cell association route corresponds to a fast tetramer binding to a colocalized CD8/TCR population, which apparently resides within membrane rafts. Thus, ligand-cell association starts by pMHC binding to the CD8. This rather fast step promotes pMHC association with CD8-proximal TCRs and thereby enhances the overall association process. The model suggests that this raft-associated CD8-TCR subpopulation is responsible for evoking T-cell activation.
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Affiliation(s)
- Israel Pecht
- Department of Immunology, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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17
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Berko D, Carmi Y, Cafri G, Ben-Zaken S, Sheikhet HM, Tzehoval E, Eisenbach L, Margalit A, Gross G. Membrane-anchored beta 2-microglobulin stabilizes a highly receptive state of MHC class I molecules. THE JOURNAL OF IMMUNOLOGY 2005; 174:2116-23. [PMID: 15699142 DOI: 10.4049/jimmunol.174.4.2116] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The magnitude of response elicited by CTL-inducing vaccines correlates with the density of MHC class I (MHC-I)-peptide complexes formed on the APC membrane. The MHC-I L chain, beta2-microglobulin (beta2m), governs complex stability. We reasoned that genetically converting beta2m into an integral membrane protein should exert a marked stabilizing effect on the resulting MHC-I molecules and enhance vaccine efficacy. In the present study, we show that expression of membranal human beta2m (hbeta2m) in mouse RMA-S cells elevates MHC-I thermal stability. RMA-S transfectants bind an exogenous peptide at concentrations 10(4)- to 10(6)-fold lower than parental RMA-S, as detected by complex-specific Abs and by T cell activation. Moreover, saturation of the transfectants' MHC-I by exogenous peptide occurs within 1 min, as compared with approximately 1 h required for parental cells. At saturation, however, level of peptide bound by modified cells is only 3- to 5-fold higher. Expression of native hbeta2m only results in marginal effect on the binding profile. Soluble beta2m has no effect on the accelerated kinetics, but the kinetics of transfectants parallel that of parental cells in the presence of Abs to hbeta2m. Ab inhibition and coimmunoprecipitation analyses suggest that both prolonged persistence of peptide-receptive H chain/beta2m heterodimers and fast heterodimer formation via lateral diffusion may contribute to stabilization. In vivo, peptide-loaded transfectants are considerably superior to parental cells in suppressing tumor growth. Our findings support the role of an allosteric mechanism in determining ternary MHC-I complex stability and propose membranal beta2m as a novel scaffold for CTL induction.
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MESH Headings
- Adjuvants, Immunologic/chemical synthesis
- Adjuvants, Immunologic/genetics
- Adjuvants, Immunologic/metabolism
- Animals
- Binding Sites, Antibody
- Binding, Competitive/immunology
- Cancer Vaccines/genetics
- Cancer Vaccines/immunology
- Cancer Vaccines/therapeutic use
- Cell Line, Tumor
- Histocompatibility Antigens Class I/metabolism
- Humans
- Jurkat Cells
- Kinetics
- Melanoma, Experimental/genetics
- Melanoma, Experimental/immunology
- Melanoma, Experimental/prevention & control
- Membrane Proteins/chemical synthesis
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Peptide Fragments/antagonists & inhibitors
- Peptide Fragments/metabolism
- Protein Binding/immunology
- Recombinant Fusion Proteins/chemical synthesis
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Thermodynamics
- Transfection
- beta 2-Microglobulin/chemical synthesis
- beta 2-Microglobulin/genetics
- beta 2-Microglobulin/immunology
- beta 2-Microglobulin/metabolism
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Affiliation(s)
- Dikla Berko
- Laboratory of Immunology, MIGAL-Galilee Technology Center, Kiryat Shmona, Israel
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18
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Baxter TK, Gagnon SJ, Davis-Harrison RL, Beck JC, Binz AK, Turner RV, Biddison WE, Baker BM. Strategic Mutations in the Class I Major Histocompatibility Complex HLA-A2 Independently Affect Both Peptide Binding and T Cell Receptor Recognition. J Biol Chem 2004; 279:29175-84. [PMID: 15131131 DOI: 10.1074/jbc.m403372200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutational studies of T cell receptor (TCR) contact residues on the surface of the human class I major histocompatibility complex (MHC) molecule HLA-A2 have identified a "functional hot spot" that comprises Arg(65) and Lys(66) and is involved in recognition by most peptide-specific HLA-A2-restricted TCRs. Although there is a significant amount of functional data on the effects of mutations at these positions, there is comparatively little biochemical information that could illuminate their mode of action. Here, we have used a combination of fluorescence anisotropy, functional assays, and Biacore binding experiments to examine the effects of mutations at these positions on the peptide-MHC interaction and TCR recognition. The results indicate that mutations at both position 65 and position 66 influence peptide binding by HLA-A2 to various extents. In particular, mutations at position 66 result in significantly increased peptide dissociation rates. However, these effects are independent of their effects on TCR recognition, and the Arg(65)-Lys(66) region thus represents a true "hot spot" for TCR recognition. We also made the observation that in vitro T cell reactivity does not scale with the half-life of the peptide-MHC complex, as is often assumed. Finally, position 66 is implicated in the "dual recognition" of both peptide and TCR, emphasizing the multiple roles of the class I MHC peptide-binding domain.
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Affiliation(s)
- Tiffany K Baxter
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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19
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Petrone PM, Garcia AE. MHC–Peptide Binding is Assisted by Bound Water Molecules. J Mol Biol 2004; 338:419-35. [PMID: 15066441 DOI: 10.1016/j.jmb.2004.02.039] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2003] [Revised: 02/02/2004] [Accepted: 02/02/2004] [Indexed: 10/26/2022]
Abstract
Water plays an important role in determining the high affinity of epitopes to the class I MHC complex. To study the energy and dynamics of water interactions in the complex we performed molecular dynamics simulation of the class I MHC-HLA2 complex bound to the HIV reverse transcriptase epitope, ILKEPVHGV, and in the absence of the epitope. Each simulation was extended for 5ns. We studied the processes of water penetration in the interface between MHC and peptide, and identified 14 water molecules that stay bound for periods longer than 1ns in regions previously identified by crystallography. These water molecules in the interface perform definite "tasks" contributing to the binding energy: hydrogen bond bridges between MHC and peptide and filling empty spaces in the groove which enhance affinity without contributing to epitope specificity. We calculate the binding energy for interfacial water molecules and find that there is an overall gain in free energy resulting from the formation of water clusters at the epitope-MHC interface. Water molecules serving the task of filling empty spaces bind at the interface with a net gain in entropy, relative to their entropy in bulk. We conclude that water molecules at the interface play the role of active mediators in the MHC-peptide interaction, and might be responsible for the large binding affinity of the MHC complex to a large number of epitope sequences.
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Affiliation(s)
- Paula M Petrone
- Theoretical Biology and Biophysics Group, T-10 MS K710, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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20
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Ge Q, Stone JD, Thompson MT, Cochran JR, Rushe M, Eisen HN, Chen J, Stern LJ. Soluble peptide-MHC monomers cause activation of CD8+ T cells through transfer of the peptide to T cell MHC molecules. Proc Natl Acad Sci U S A 2002; 99:13729-34. [PMID: 12374859 PMCID: PMC129758 DOI: 10.1073/pnas.212515299] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2002] [Indexed: 11/18/2022] Open
Abstract
T cell receptor (TCR)-mediated activation of CD4(+) T cells is known to require multivalent engagement of the TCR by, for example, oligomeric peptide-MHC complexes. In contrast, for CD8(+) T cells, there is evidence for TCR-mediated activation by univalent engagement of the TCR. We have here compared oligomeric and monomeric L(d) and K(b) peptide-MHC complexes and free peptide as stimulators of CD8(+) T cells expressing the 2C TCR. We found that the monomers are indeed effective in activating naive and effector CD8(+) T cells, but through an unexpected mechanism that involves transfer of peptide from soluble monomers to T cell endogenous MHC (K(b)) molecules. The result is that T cells, acting as antigen-presenting cells, are able to activate other naive T cells.
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Affiliation(s)
- Qing Ge
- Department of Biology, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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21
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Dédier S, Reinelt S, Rion S, Folkers G, Rognan D. Use of fluorescence polarization to monitor MHC-peptide interactions in solution. J Immunol Methods 2001; 255:57-66. [PMID: 11470286 DOI: 10.1016/s0022-1759(01)00423-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We describe here fluorescence polarization-based methods to investigate class I MHC-peptide interactions in solution. Fluorescein-labelled peptides were used to determine MHC/peptide complex association and dissociation constants as well as the equilibrium binding constant (KD). Furthermore, we developed a competition assay for the determination of IC50 values of nonlabelled compounds. Both kinetic and equilibrium parameters are of prime importance for the development of immunomodulating compounds. The assays described here show a good reproducibility and require only picomolar amounts of labelled tracers. A high ratio between the experimental values obtained for bound and free labelled ligand as well as a low standard deviation, permits the detection of class I MHC ligands with low affinity. Fluorescence polarization allows the direct measurement of the ratio between free and bound labelled ligand in solution without any separation step. Thus, in combination with microtiter-plates, the time for analysis is significantly decreased to 10 s per sample. Our assays represent versatile tools for characterizing the binding of single ligands as well as for rapid screening of large numbers of compounds.
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Affiliation(s)
- S Dédier
- Department of Applied BioSciences, Swiss Federal Institute of Technology, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
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22
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Davis DM, Chiu I, Fassett M, Cohen GB, Mandelboim O, Strominger JL. The human natural killer cell immune synapse. Proc Natl Acad Sci U S A 1999; 96:15062-7. [PMID: 10611338 PMCID: PMC24773 DOI: 10.1073/pnas.96.26.15062] [Citation(s) in RCA: 319] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/1999] [Accepted: 10/22/1999] [Indexed: 01/31/2023] Open
Abstract
Inhibitory killer Ig-like receptors (KIR) at the surface of natural killer (NK) cells induced clustering of HLA-C at the contacting surface of target cells. In this manner, inhibitory immune synapses were formed as human NK cells surveyed target cells. At target/NK cell synapses, HLA-C/KIR distributed into rings around central patches of intercellular adhesion molecule-1/lymphocyte function-associated antigen-1, the opposite orientation to mature murine T cell-activating synapses. This organization of protein was stable for at least 20 min. Cells could support multiple synapses simultaneously, and clusters of HLA-C moved as NK cells crawled over target cells. Clustering required a divalent metal cation, explaining how metal chelators inhibit KIR function. Surprisingly, however, formation of inhibitory synapses was unaffected by ATP depletion and the cytoskeletal inhibitors, colchicine and cytochalsins B and D. Clearly, supramolecular organization within plasma membranes is critical for NK cell immunosurveillance.
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Affiliation(s)
- D M Davis
- Department of Molecular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02143, USA
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23
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Chiu I, Davis DM, Strominger JL. Trafficking of spontaneously endocytosed MHC proteins. Proc Natl Acad Sci U S A 1999; 96:13944-9. [PMID: 10570178 PMCID: PMC24170 DOI: 10.1073/pnas.96.24.13944] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Class I MHC protein primarily presents endogenous antigen but also may present exogenous antigen. Here, we investigated the intracellular pathway of spontaneously internalized class I MHC protein by confocal microscopy. beta(2)-microglobulin (beta(2)m), labeled with a single fluorophore, was exchanged at the surface of B cell transfectants to specifically mark cell surface and endocytosed class I MHC protein. Intracellular beta(2)m colocalized with fluorophore-conjugated transferrin, implying that class I MHC protein endocytosed into early endosomes. These endosomes containing fluorescent beta(2)m were found close to or within the Golgi apparatus, marked by fluorescent ceramide. Even after 24 hr of incubation, very little fluorescent beta(2)m was found in intracellular organelles stained by DiOC(6), marking the endoplasmic reticulum, or fluorophore-conjugated low density lipoprotein, marking late endosomes and lysosomes. Fluorophore-conjugated superantigens (staphylococcal enterotoxin A and B), presumed to enter cells bound to class II MHC protein, also were found to endocytose into beta(2)m-containing early endosomes. Staining with mAb and use of transfectants expressing MHC protein attached to green fluorescent protein confirmed the presence of intracellular compartments rich in both class I and II MHC protein and demonstrated that class I and II MHC protein also colocalize in discrete microdomains at the cell surface. These cell surface microdomains also contained transferrin receptor and often were juxtaposed to cholesterol-rich lipid rafts. Thus, class I and II MHC protein meet in microdomains of the plasma membrane and endocytose into early endosomes, where both may acquire and present exogenous antigen.
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Affiliation(s)
- I Chiu
- Department of Molecular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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