1
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Wong MTY, Kelm S, Liu X, Taylor RD, Baker T, Essex JW. Higher Affinity Antibodies Bind With Lower Hydration and Flexibility in Large Scale Simulations. Front Immunol 2022; 13:884110. [PMID: 35707541 PMCID: PMC9190259 DOI: 10.3389/fimmu.2022.884110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/22/2022] [Indexed: 11/25/2022] Open
Abstract
We have carried out a long-timescale simulation study on crystal structures of nine antibody-antigen pairs, in antigen-bound and antibody-only forms, using molecular dynamics with enhanced sampling and an explicit water model to explore interface conformation and hydration. By combining atomic level simulation and replica exchange to enable full protein flexibility, we find significant numbers of bridging water molecules at the antibody-antigen interface. Additionally, a higher proportion of interactions excluding bulk waters and a lower degree of antigen bound CDR conformational sampling are correlated with higher antibody affinity. The CDR sampling supports enthalpically driven antibody binding, as opposed to entropically driven, in that the difference between antigen bound and unbound conformations do not correlate with affinity. We thus propose that interactions with waters and CDR sampling are aspects of the interface that may moderate antibody-antigen binding, and that explicit hydration and CDR flexibility should be considered to improve antibody affinity prediction and computational design workflows.
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Affiliation(s)
- Mabel T. Y. Wong
- School of Chemistry, University of Southampton, Southampton, United Kingdom
| | | | | | | | | | - Jonathan W. Essex
- School of Chemistry, University of Southampton, Southampton, United Kingdom
- *Correspondence: Jonathan W. Essex,
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2
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Lee DCP, Raman R, Ghafar NA, Budigi Y. An antibody engineering platform using amino acid networks: A case study in development of antiviral therapeutics. Antiviral Res 2021; 192:105105. [PMID: 34111505 DOI: 10.1016/j.antiviral.2021.105105] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 05/27/2021] [Accepted: 05/28/2021] [Indexed: 11/29/2022]
Abstract
We present here a case study of an antibody-engineering platform that selects, modifies, and assembles antibody parts to construct novel antibodies. A salient feature of this platform includes the role of amino acid networks in optimizing framework regions (FRs) and complementarity determining regions (CDRs) to engineer new antibodies with desired structure-function relationships. The details of this approach are described in the context of its utility in engineering ZAb_FLEP, a potent anti-Zika virus antibody. ZAb_FLEP comprises of distinct parts, including heavy chain and light chain FRs and CDRs, with engineered features such as loop lengths and optimal epitope-paratope contacts. We demonstrate, with different test antibodies derived from different FR-CDR combinations, that despite these test antibodies sharing high overall sequence similarity, they yield diverse functional readouts. Furthermore, we show that strategies relying on one dimensional sequence similarity-based analyses of antibodies miss important structural nuances of the FR-CDR relationship, which is effectively addressed by the amino acid networks approach of this platform.
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Affiliation(s)
| | - Rahul Raman
- Department of Biological Engineering, And Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
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3
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Fernández-Quintero ML, Heiss MC, Pomarici ND, Math BA, Liedl KR. Antibody CDR loops as ensembles in solution vs. canonical clusters from X-ray structures. MAbs 2021; 12:1744328. [PMID: 32264741 PMCID: PMC7153821 DOI: 10.1080/19420862.2020.1744328] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In the past decade, the relevance of antibodies as therapeutics has increased substantially. Therefore, structural and functional characterization, in particular of the complementarity-determining regions (CDRs), is crucial to the design and engineering of antibodies with unique binding properties. Various studies have focused on classifying the CDR loops into a small set of main-chain conformations to facilitate antibody design by assuming that certain sequences can only adopt a limited number of conformations. Here, we present a kinetic classification of CDR loop structures as ensembles in solution. Using molecular dynamics simulations in combination with strong experimental structural information, we observe conformational transitions between canonical clusters and additional dominant solution structures in the micro-to-millisecond timescale for all CDR loops, independent of length and sequence composition. Besides identifying all relevant conformations in solution, our results revealed that various canonical cluster medians actually belong to the same kinetic minimum. Additionally, we reconstruct the kinetics and probabilities of the conformational transitions between canonical clusters, and thereby extend the model of static canonical structures to reveal a dynamic conformational ensemble in solution as a new paradigm in the field of antibody structure design. Abbreviations: CDR: Complementary-determining region; Fv: Antibody variable fragment; PCCA: Perron cluster analysis; tICA: Time-lagged independent component analysis; VH: Heavy chain variable region; VL: Light chain variable region
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Affiliation(s)
- Monica L Fernández-Quintero
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Austria
| | - Martin C Heiss
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Austria
| | - Nancy D Pomarici
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Austria
| | - Barbara A Math
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Austria
| | - Klaus R Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innsbruck, Austria
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4
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Fan Z, Kiosses WB, Sun H, Orecchioni M, Ghosheh Y, Zajonc DM, Arnaout MA, Gutierrez E, Groisman A, Ginsberg MH, Ley K. High-Affinity Bent β 2-Integrin Molecules in Arresting Neutrophils Face Each Other through Binding to ICAMs In cis. Cell Rep 2020; 26:119-130.e5. [PMID: 30605669 PMCID: PMC6625519 DOI: 10.1016/j.celrep.2018.12.038] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 11/09/2018] [Accepted: 12/07/2018] [Indexed: 01/13/2023] Open
Abstract
Leukocyte adhesion requires β2-integrin activation. Resting integrins exist in a bent-closed conformation-i.e., not extended (E-) and not high affinity (H-)-unable to bind ligand. Fully activated E+H+ integrin binds intercellular adhesion molecules (ICAMs) expressed on the opposing cell in trans. E-H- transitions to E+H+ through E+H- or through E-H+, which binds to ICAMs on the same cell in cis. Spatial patterning of activated integrins is thought to be required for effective arrest, but no high-resolution cell surface localization maps of activated integrins exist. Here, we developed Super-STORM by combining super-resolution microscopy with molecular modeling to precisely localize activated integrin molecules and identify the molecular patterns of activated integrins on primary human neutrophils. At the time of neutrophil arrest, E-H+ integrins face each other to form oriented (non-random) nanoclusters. To address the mechanism causing this pattern, we blocked integrin binding to ICAMs in cis, which significantly relieved the face-to-face orientation.
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Affiliation(s)
- Zhichao Fan
- Division of Inflammation Biology, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA
| | - William Bill Kiosses
- Microscopy Core Facility, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA
| | - Hao Sun
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Marco Orecchioni
- Division of Inflammation Biology, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA
| | - Yanal Ghosheh
- Division of Inflammation Biology, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA
| | - Dirk M Zajonc
- Division of Immune Regulation, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA; Department of Internal Medicine, Faculty of Medicine and Health Sciences, Ghent University, 9000 Ghent, Belgium
| | - M Amin Arnaout
- Harvard Medical School, Boston, MA 02115, USA; Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, Boston, MA 02114, USA; Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA; Center for Regenerative Medicine, Medical Services, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Edgar Gutierrez
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Alex Groisman
- Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Mark H Ginsberg
- Department of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Klaus Ley
- Division of Inflammation Biology, La Jolla Institute for Immunology, 9420 Athena Circle Drive, La Jolla, CA 92037, USA; Department of Bioengineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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5
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Fernández-Quintero ML, Math BA, Loeffler JR, Liedl KR. Transitions of CDR-L3 Loop Canonical Cluster Conformations on the Micro-to-Millisecond Timescale. Front Immunol 2019; 10:2652. [PMID: 31803187 PMCID: PMC6877499 DOI: 10.3389/fimmu.2019.02652] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/25/2019] [Indexed: 01/02/2023] Open
Abstract
Sequence and structural diversity of antibodies are concentrated on six hypervariable loops, also known as the complementarity determining regions (CDRs). Five of six antibody CDR loops presumably adopt a so-called canonical structure out of a limited number of conformations. However, here we show for four antibody CDR-L3 loops differing in length and sequence, that each loop undergoes conformational transitions between different canonical structures. By extensive sampling in combination with Markov-state models we reconstruct the kinetics and probabilities of the transitions between canonical structures. Additionally, for these four CDR-L3 loops, we identify all relevant conformations in solution. Thereby we extend the model of static canonical structures to a dynamic conformational ensemble as a new paradigm in the field of antibody structure design.
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Affiliation(s)
| | | | | | - Klaus R. Liedl
- Center for Molecular Biosciences Innsbruck (CMBI), Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innsbruck, Austria
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6
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Samy KP, Anderson DA, Lo DJ, Mulvihill MS, Song M, Farris AB, Parker BS, MacDonald AL, Lu C, Springer TA, Kachlany SC, Reimann KA, How T, Leopardi FV, Franke KS, Williams KD, Collins BH, Kirk AD. Selective Targeting of High-Affinity LFA-1 Does Not Augment Costimulation Blockade in a Nonhuman Primate Renal Transplantation Model. Am J Transplant 2017; 17:1193-1203. [PMID: 27888551 PMCID: PMC5409867 DOI: 10.1111/ajt.14141] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2016] [Revised: 11/01/2016] [Accepted: 11/08/2016] [Indexed: 01/25/2023]
Abstract
Costimulation blockade (CoB) via belatacept is a lower-morbidity alternative to calcineurin inhibitor (CNI)-based immunosuppression. However, it has higher rates of early acute rejection. These early rejections are mediated in part by memory T cells, which have reduced dependence on the pathway targeted by belatacept and increased adhesion molecule expression. One such molecule is leukocyte function antigen (LFA)-1. LFA-1 exists in two forms: a commonly expressed, low-affinity form and a transient, high-affinity form, expressed only during activation. We have shown that antibodies reactive with LFA-1 regardless of its configuration are effective in eliminating memory T cells but at the cost of impaired protective immunity. Here we test two novel agents, leukotoxin A and AL-579, each of which targets the high-affinity form of LFA-1, to determine whether this more precise targeting prevents belatacept-resistant rejection. Despite evidence of ex vivo and in vivo ligand-specific activity, neither agent when combined with belatacept proved superior to belatacept monotherapy. Leukotoxin A approached a ceiling of toxicity before efficacy, while AL-579 failed to significantly alter the peripheral immune response. These data, and prior studies, suggest that LFA-1 blockade may not be a suitable adjuvant agent for CoB-resistant rejection.
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Affiliation(s)
- KP Samy
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - DA Anderson
- Emory Transplant Center, Emory University School of Medicine, Atlanta, GA 30322
| | - DJ Lo
- Emory Transplant Center, Emory University School of Medicine, Atlanta, GA 30322
| | - MS Mulvihill
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - M Song
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - AB Farris
- Department of Pathology & Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322
| | - BS Parker
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - AL MacDonald
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - C Lu
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| | - TA Springer
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115
| | - SC Kachlany
- Rutgers University, School of Medicine, Newark, NJ 07103,Actinobac Biomed, Inc., Kendall Park, NJ 08824
| | - KA Reimann
- Mass-Biologics, University of Massachusetts Medical School, Boston, MA 02126
| | - T How
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - FV Leopardi
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - KS Franke
- Division of Laboratory Animal Resources, Duke University, Durham, NC 27710
| | - KD Williams
- Division of Laboratory Animal Resources, Duke University, Durham, NC 27710
| | - BH Collins
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710
| | - AD Kirk
- Department of Surgery, Duke University School of Medicine, Durham, NC 27710,Emory Transplant Center, Emory University School of Medicine, Atlanta, GA 30322
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7
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Esser L, Shukla S, Zhou F, Ambudkar SV, Xia D. Crystal structure of the antigen-binding fragment of a monoclonal antibody specific for the multidrug-resistance-linked ABC transporter human P-glycoprotein. Acta Crystallogr F Struct Biol Commun 2016; 72:636-41. [PMID: 27487928 PMCID: PMC4973305 DOI: 10.1107/s2053230x16009778] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 06/16/2016] [Indexed: 12/19/2022] Open
Abstract
P-glycoprotein (P-gp) is a polyspecific ATP-dependent transporter linked to multidrug resistance in cancers that plays important roles in the pharmacokinetics of a large number of drugs. The drug-resistance phenotype of P-gp can be modulated by the monoclonal antibody UIC2, which specifically recognizes human P-gp in a conformation-dependent manner. Here, the purification, sequence determination and high-resolution structure of the Fab fragment of UIC2 (UIC2/Fab) are reported. Purified UIC2/Fab binds human P-gp with a 1:1 stoichiometry. Crystals of UIC2/Fab are triclinic (space group P1), with unit-cell parameters a = 40.67, b = 44.91, c = 58.09 Å, α = 97.62, β = 99.10, γ = 94.09°, and diffracted X-rays to 1.6 Å resolution. The structure was determined by molecular replacement and refined to 1.65 Å resolution. The asymmetric unit contains one molecule of UIC2/Fab, which exhibits a positively charged antigen-binding surface, suggesting that it might recognize an oppositely charged extracellular epitope of P-gp.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Amino Acid Motifs
- Animals
- Antibodies, Monoclonal/biosynthesis
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/isolation & purification
- Antigens/chemistry
- Antigens/metabolism
- Binding Sites
- Cloning, Molecular
- Crystallography, X-Ray
- Gene Expression
- Humans
- Hybridomas/chemistry
- Immunoglobulin Fab Fragments/biosynthesis
- Immunoglobulin Fab Fragments/chemistry
- Immunoglobulin Fab Fragments/isolation & purification
- Mice
- Mice, Inbred BALB C
- Models, Molecular
- Protein Binding
- Protein Interaction Domains and Motifs
- Protein Structure, Secondary
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/chemistry
- Recombinant Proteins/isolation & purification
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Affiliation(s)
- Lothar Esser
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Suneet Shukla
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Fei Zhou
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Suresh V. Ambudkar
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Di Xia
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
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8
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Panousis C, Dhagat U, Edwards KM, Rayzman V, Hardy MP, Braley H, Gauvreau GM, Hercus TR, Smith S, Sehmi R, McMillan L, Dottore M, McClure BJ, Fabri LJ, Vairo G, Lopez AF, Parker MW, Nash AD, Wilson NJ, Wilson MJ, Owczarek CM. CSL311, a novel, potent, therapeutic monoclonal antibody for the treatment of diseases mediated by the common β chain of the IL-3, GM-CSF and IL-5 receptors. MAbs 2015; 8:436-53. [PMID: 26651396 PMCID: PMC4966837 DOI: 10.1080/19420862.2015.1119352] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 11/06/2015] [Accepted: 11/06/2015] [Indexed: 12/28/2022] Open
Abstract
The β common-signaling cytokines interleukin (IL)-3, granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-5 stimulate pro-inflammatory activities of haematopoietic cells via a receptor complex incorporating cytokine-specific α and shared β common (βc, CD131) receptor. Evidence from animal models and recent clinical trials demonstrate that these cytokines are critical mediators of the pathogenesis of inflammatory airway disease such as asthma. However, no therapeutic agents, other than steroids, that specifically and effectively target inflammation mediated by all 3 of these cytokines exist. We employed phage display technology to identify and optimize a novel, human monoclonal antibody (CSL311) that binds to a unique epitope that is specific to the cytokine-binding site of the human βc receptor. The binding epitope of CSL311 on the βc receptor was defined by X-ray crystallography and site-directed mutagenesis. CSL311 has picomolar binding affinity for the human βc receptor, and at therapeutic concentrations is a highly potent antagonist of the combined activities of IL-3, GM-CSF and IL-5 on primary eosinophil survival in vitro. Importantly, CSL311 inhibited the survival of inflammatory cells present in induced sputum from human allergic asthmatic subjects undergoing allergen bronchoprovocation. Due to its high potency and ability to simultaneously suppress the activity of all 3 β common cytokines, CSL311 may provide a new strategy for the treatment of chronic inflammatory diseases where the human βc receptor is central to pathogenesis. The coordinates for the βc/CSL311 Fab complex structure have been deposited with the RCSB Protein Data Bank (PDB 5DWU).
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Affiliation(s)
- Con Panousis
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Urmi Dhagat
- Australian Cancer Research Foundation Rational Drug Discovery Center, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, 3065, Australia
| | - Kirsten M. Edwards
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Veronika Rayzman
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Matthew P. Hardy
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Hal Braley
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | | | - Timothy R. Hercus
- Division of Human Immunology, the Center for Cancer Biology, SA Pathology and the University of South Australia, Frome Road, Adelaide, South Australia 5000 and the University of South Australia, Adelaide, South Australia 5001, Australia
| | - Steven Smith
- McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Roma Sehmi
- McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Laura McMillan
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Mara Dottore
- Division of Human Immunology, the Center for Cancer Biology, SA Pathology and the University of South Australia, Frome Road, Adelaide, South Australia 5000 and the University of South Australia, Adelaide, South Australia 5001, Australia
| | - Barbara J. McClure
- Division of Human Immunology, the Center for Cancer Biology, SA Pathology and the University of South Australia, Frome Road, Adelaide, South Australia 5000 and the University of South Australia, Adelaide, South Australia 5001, Australia
| | - Louis J. Fabri
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Gino Vairo
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Angel F Lopez
- Division of Human Immunology, the Center for Cancer Biology, SA Pathology and the University of South Australia, Frome Road, Adelaide, South Australia 5000 and the University of South Australia, Adelaide, South Australia 5001, Australia
| | - Michael W. Parker
- Australian Cancer Research Foundation Rational Drug Discovery Center, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, 3065, Australia
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Andrew D. Nash
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Nicholas J. Wilson
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Michael J. Wilson
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
| | - Catherine M. Owczarek
- Research and Development, CSL Limited; Bio21 Molecular Science and Biotechnology Institute, Parkville Victoria, 3010, Australia
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9
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Kukic P, Alvin Leung HT, Bemporad F, Aprile FA, Kumita JR, De Simone A, Camilloni C, Vendruscolo M. Structure and dynamics of the integrin LFA-1 I-domain in the inactive state underlie its inside-out/outside-in signaling and allosteric mechanisms. Structure 2015; 23:745-53. [PMID: 25773142 PMCID: PMC4396694 DOI: 10.1016/j.str.2014.12.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 12/04/2014] [Accepted: 12/06/2014] [Indexed: 01/13/2023]
Abstract
Lymphocyte function-associated antigen 1 (LFA-1) is an integrin that transmits information in two directions across the plasma membrane of leukocytes, in so-called outside-in and inside-out signaling mechanisms. To investigate the structural basis of these mechanisms, we studied the conformational space of the apo I-domain using replica-averaged metadynamics simulations in combination with nuclear magnetic resonance chemical shifts. We thus obtained a free energy landscape that reveals the existence of three conformational substates of this domain. The three substates include conformations similar to existing crystallographic structures of the low-affinity I-domain, the inactive I-domain with an allosteric antagonist inhibitor bound underneath α helix 7, and an intermediate affinity state of the I-domain. The multiple substates were validated with residual dipolar coupling measurements. These results suggest that the presence of three substates in the apo I-domain enables the precise regulation of the binding process that is essential for the physiological function of LFA-1.
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Affiliation(s)
- Predrag Kukic
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK
| | - Hoi Tik Alvin Leung
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK; Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel 4056, Switzerland
| | - Francesco Bemporad
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK; Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, Viale G. B. Morgagni 50, 50134, Firenze, Italy
| | - Francesco A Aprile
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK
| | - Janet R Kumita
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK
| | - Alfonso De Simone
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
| | - Carlo Camilloni
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK
| | - Michele Vendruscolo
- Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK.
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10
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Abstract
Pili of Gram-positive bacteria are unique structures on the bacterial surface, assembled from covalently linked polypeptide subunits. Pilus assembly proceeds by transpeptidation reactions catalyzed by sortases, followed by covalent anchoring of the filament in the peptidoglycan layer. Another distinctive property is the presence of intramolecular isopeptide bonds, conferring extraordinary chemical and mechanical stability to these elongated structures. Besides their function in cell adhesion and biofilm formation, this section discusses possible application of pilus constituents as vaccine components against Gram-positive pathogens.
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11
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Leung HTA, Kukic P, Camilloni C, Bemporad F, De Simone A, Aprile FA, Kumita JR, Vendruscolo M. NMR characterization of the conformational fluctuations of the human lymphocyte function-associated antigen-1 I-domain. Protein Sci 2014; 23:1596-606. [PMID: 25147050 DOI: 10.1002/pro.2538] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/13/2014] [Accepted: 08/19/2014] [Indexed: 01/13/2023]
Abstract
Lymphocyte function-associated antigen-1 (LFA-1) is an integrin protein that transmits information across the plasma membrane through the so-called inside-out and outside-in signaling mechanisms. To investigate these mechanisms, we carried out an NMR analysis of the dynamics of the LFA-1 I-domain, which has enabled us to characterize the motions of this domain on a broad range of timescales. We studied first the internal motions on the nanosecond timescale by spin relaxation measurements and model-free analysis. We then extended this analysis to the millisecond timescale motions by measuring (15) N-(1) H residual dipolar couplings of the backbone amide groups. We analyzed these results in the context of the three major conformational states of the I-domain using their corresponding X-ray crystallographic structures. Our results highlight the importance of the low-frequency motions of the LFA-1 I-domain in the inactive apo-state. We found in particular that α-helix 7 is in a position in the apo-closed state that cannot be fully described by any of the existing X-ray structures, as it appears to be in dynamic exchange between different conformations. This type of motion seems to represent an inherent property of the LFA-1 I-domain and might be relevant for controlling the access to the allosteric binding pocket, as well as for the downward displacement of α-helix 7 that is required for the activation of LFA-1.
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Affiliation(s)
- Hoi Tik Alvin Leung
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom; Biozentrum, University of Basel, Basel, CH-4056, Switzerland
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Krishnan V, Dwivedi P, Kim BJ, Samal A, Macon K, Ma X, Mishra A, Doran KS, Ton-That H, Narayana SVL. Structure of Streptococcus agalactiae tip pilin GBS104: a model for GBS pili assembly and host interactions. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1073-89. [PMID: 23695252 PMCID: PMC3663123 DOI: 10.1107/s0907444913004642] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 02/18/2013] [Indexed: 11/10/2022]
Abstract
The crystal structure of a 75 kDa central fragment of GBS104, a tip pilin from the 2063V/R strain of Streptococcus agalactiae (group B streptococcus; GBS), is reported. In addition, a homology model of the remaining two domains of GBS104 was built and a model of full-length GBS104 was generated by combining the homology model (the N1 and N4 domains) and the crystal structure of the 75 kDa fragment (the N2 and N3 domains). This rod-shaped GBS104 model is constructed of three IgG-like domains (the N1, N2 and N4 domains) and one vWFA-like domain (the N3 domain). The N1 and N2 domains of GBS104 are assembled with distinct and remote segments contributed by the N- and C-termini. The metal-binding site in the N3 domain of GBS104 is in the closed/low-affinity conformation. Interestingly, this domain hosts two long arms that project away from the metal-binding site. Using site-directed mutagenesis, two cysteine residues that lock the N3 domain of GBS104 into the open/high-affinity conformation were introduced. Both wild-type and disulfide-locked recombinant proteins were tested for binding to extracellular matrix proteins such as collagen, fibronectin, fibrinogen and laminin, and an increase in fibronectin binding affinity was identified for the disulfide-locked N3 domain, suggesting that induced conformational changes may play a possible role in receptor binding.
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Affiliation(s)
- Vengadesan Krishnan
- UNESCO Regional Centre for Biotechnology (RCB), Gurgaon 122 016, Haryana, India
| | - Prabhat Dwivedi
- University of Texas Health Science Center, Houston, TX 77030, USA
| | - Brandon J. Kim
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
| | - Alexandra Samal
- Center for Biophysical Sciences and Engineering, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kevin Macon
- Center for Biophysical Sciences and Engineering, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Xin Ma
- University of Texas Health Science Center, Houston, TX 77030, USA
| | - Arunima Mishra
- University of Texas Health Science Center, Houston, TX 77030, USA
| | - Kelly S. Doran
- Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
| | - Hung Ton-That
- University of Texas Health Science Center, Houston, TX 77030, USA
| | - Sthanam V. L. Narayana
- Center for Biophysical Sciences and Engineering, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Faridi MH, Altintas MM, Gomez C, Duque JC, Vazquez-Padron RI, Gupta V. Small molecule agonists of integrin CD11b/CD18 do not induce global conformational changes and are significantly better than activating antibodies in reducing vascular injury. Biochim Biophys Acta Gen Subj 2013; 1830:3696-710. [PMID: 23454649 DOI: 10.1016/j.bbagen.2013.02.018] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Revised: 02/15/2013] [Accepted: 02/19/2013] [Indexed: 01/08/2023]
Abstract
BACKGROUND CD11b/CD18 is a key adhesion receptor that mediates leukocyte adhesion, migration and immune functions. We recently identified novel compounds, leukadherins, that allosterically enhance CD11b/CD18-dependent cell adhesion and reduce inflammation in vivo, suggesting integrin activation to be a novel mechanism of action for the development of anti-inflammatory therapeutics. Since a number of well-characterized anti-CD11b/CD18 activating antibodies are currently available, we wondered if such biological agonists could also become therapeutic leads following this mechanism of action. METHODS We compared the two types of agonists using in vitro cell adhesion and wound-healing assays and using animal model systems. We also studied effects of the two types of agonists on outside-in signaling in treated cells. RESULTS Both types of agonists similarly enhanced integrin-mediated cell adhesion and decreased cell migration. However, unlike leukadherins, the activating antibodies produced significant CD11b/CD18 macro clustering and induced phosphorylation of key proteins involved in outside-in signaling. Studies using conformation reporter antibodies showed that leukadherins did not induce global conformational changes in CD11b/CD18 explaining the reason behind their lack of ligand-mimetic outside-in signaling. In vivo, leukadherins reduced vascular injury in a dose-dependent fashion, but, surprisingly, the anti-CD11b activating antibody ED7 was ineffective. CONCLUSIONS Our results suggest that small molecule allosteric agonists of CD11b/CD18 have clear advantages over the biologic activating antibodies and provide a mechanistic basis for the difference. GENERAL SIGNIFICANCE CD11b/CD18 activation represents a novel strategy for reducing inflammatory injury. Our study establishes small molecule leukadherins as preferred agonists over activating antibodies for future development as novel anti-inflammatory therapeutics.
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Weinreb PH, Li S, Gao SX, Liu T, Pepinsky RB, Caravella JA, Lee JH, Woods VL. Dynamic structural changes are observed upon collagen and metal ion binding to the integrin α1 I domain. J Biol Chem 2012; 287:32897-912. [PMID: 22847004 PMCID: PMC3463359 DOI: 10.1074/jbc.m112.354365] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 07/11/2012] [Indexed: 02/05/2023] Open
Abstract
We have applied hydrogen-deuterium exchange mass spectrometry, in conjunction with differential scanning calorimetry and protein stability analysis, to examine solution dynamics of the integrin α1 I domain induced by the binding of divalent cations, full-length type IV collagen, or a function-blocking monoclonal antibody. These studies revealed features of integrin activation and α1I-ligand complexes that were not detected by static crystallographic data. Mg(2+) and Mn(2+) stabilized α1I but differed in their effects on exchange rates in the αC helix. Ca(2+) impacted α1I conformational dynamics without altering its gross thermal stability. Interaction with collagen affected the exchange rates in just one of three metal ion-dependent adhesion site (MIDAS) loops, suggesting that MIDAS loop 2 plays a primary role in mediating ligand binding. Collagen also induced changes consistent with increased unfolding in both the αC and allosteric C-terminal helices of α1I. The antibody AQC2, which binds to α1I in a ligand-mimetic manner, also reduced exchange in MIDAS loop 2 and increased exchange in αC, but it did not impact the C-terminal region. This is the first study to directly demonstrate the conformational changes induced upon binding of an integrin I domain to a full-length collagen ligand, and it demonstrates the utility of the deuterium exchange mass spectrometry method to study the solution dynamics of integrin/ligand and integrin/metal ion interactions. Based on the ligand and metal ion binding data, we propose a model for collagen-binding integrin activation that explains the differing abilities of Mg(2+), Mn(2+), and Ca(2+) to activate I domain-containing integrins.
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Affiliation(s)
| | - Sheng Li
- the Department of Medicine and Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0656
| | - Sharon X. Gao
- From Biogen Idec, Inc., Cambridge, Massachusetts 02142 and
| | - Tong Liu
- the Department of Medicine and Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0656
| | | | | | - Jun H. Lee
- the Department of Medicine and Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0656
| | - Virgil L. Woods
- the Department of Medicine and Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0656
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Mahalingam B, Ajroud K, Alonso JL, Anand S, Adair B, Horenstein AL, Malavasi F, Xiong JP, Arnaout MA. Stable coordination of the inhibitory Ca2+ ion at the metal ion-dependent adhesion site in integrin CD11b/CD18 by an antibody-derived ligand aspartate: implications for integrin regulation and structure-based drug design. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2011; 187:6393-401. [PMID: 22095715 PMCID: PMC3237904 DOI: 10.4049/jimmunol.1102394] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A central feature of integrin interaction with physiologic ligands is the monodentate binding of a ligand carboxylate to a Mg(2+) ion hexacoordinated at the metal ion-dependent adhesion site (MIDAS) in the integrin A domain. This interaction stabilizes the A domain in the high-affinity state, which is distinguished from the default low-affinity state by tertiary changes in the domain that culminate in cell adhesion. Small molecule ligand-mimetic integrin antagonists act as partial agonists, eliciting similar activating conformational changes in the A domain, which has contributed to paradoxical adhesion and increased patient mortality in large clinical trials. As with other ligand-mimetic integrin antagonists, the function-blocking mAb 107 binds MIDAS of integrin CD11b/CD18 A domain (CD11bA), but in contrast, it favors the inhibitory Ca(2+) ion over the Mg(2+) ion at MIDAS. We determined the crystal structures of the Fab fragment of mAb 107 complexed to the low- and high-affinity states of CD11bA. Favored binding of the Ca(2+) ion at MIDAS is caused by the unusual symmetric bidentate ligation of a Fab-derived ligand Asp to a heptacoordinated MIDAS Ca(2+) ion. Binding of the Fab fragment of mAb 107 to CD11bA did not trigger the activating tertiary changes in the domain or in the full-length integrin. These data show that the denticity of the ligand Asp/Glu can modify the divalent cation selectivity at MIDAS and hence integrin function. Stabilizing the Ca(2+) ion at MIDAS by bidentate ligation to a ligand Asp/Glu may provide one approach for designing pure integrin antagonists.
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Affiliation(s)
- Bhuvaneshwari Mahalingam
- Structural Biology Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129,Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - Kaouther Ajroud
- Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - Jose Luis Alonso
- Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - Saurabh Anand
- Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - Brian Adair
- Structural Biology Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129,Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - Alberto L Horenstein
- Lab of Immunogenetics, University of Torino Medical School, 10126, Torino, Italy
| | - Fabio Malavasi
- Lab of Immunogenetics, University of Torino Medical School, 10126, Torino, Italy
| | - Jian-Ping Xiong
- Structural Biology Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129,Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129
| | - M. Amin Arnaout
- Structural Biology Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129,Leukocyte Biology and Inflammation Program, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, 02129,Address correspondence to: M. Amin Arnaout, Division of Nephrology, Massachusetts General Hospital, 149 13th Street, Charlestown, MA, 02129, Tel: 617-726-5663, Fax: 617-726-5671.
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Sevoflurane binds and allosterically blocks integrin lymphocyte function-associated antigen-1. Anesthesiology 2010; 113:600-9. [PMID: 20693879 DOI: 10.1097/aln.0b013e3181e89a77] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Volatile anesthetics have been shown to modify immune cell functions via several mechanisms, some of which have been only partially elucidated. We demonstrated that isoflurane inhibits primary leukocyte integrin lymphocyte function-associated antigen-1 (LFA-1) by binding to the allosteric cavity critical for conformational activation to its high-affinity form. It remains to be determined whether the allosteric inhibition of LFA-1 by isoflurane can be generalized to other anesthetics such as sevoflurane. METHODS The effects of sevoflurane on the ability of LFA-1 to bind to its counter-ligand, intercellular adhesion molecule-1, was studied in leukocytes by flow cytometry. To examine whether sevoflurane acts directly on LFA-1, we measured ligand-binding using beads coated with purified LFA-1 protein. To distinguish between competitive versus allosteric inhibition, we analyzed the effects of sevoflurane on both wild-type and mutant-locked high-affinity LFA-1. One-way analysis of variance was employed for statistical analysis of the data. Nuclear magnetic resonance spectroscopy was used to identify sevoflurane binding site(s). RESULTS Sevoflurane at clinically relevant concentrations inhibited the ligand-binding function of LFA-1 in leukocytes as well as in cell-free assays (P<0.05). Sevoflurane blocked wild-type but not locked high-affinity LFA-1, thereby demonstrating an allosteric mode of inhibition. Nuclear magnetic resonance spectroscopy revealed that sevoflurane bound to the allosteric cavity, to which LFA-1 allosteric antagonists and isoflurane also bind. CONCLUSIONS This study suggests that sevoflurane also blocks the activation-dependent conformational changes of LFA-1 to the high-affinity form. The allosteric mode of action exemplified by sevoflurane and isoflurane via LFA-1 might represent one of the underlying mechanisms of anesthetic-mediated immunomodulation.
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Carreño R, Brown WS, Li D, Hernandez JA, Wang Y, Kim TK, Craft JW, Komanduri KV, Radvanyi LG, Hwu P, Molldrem JJ, Legge GB, McIntyre BW, Ma Q. 2E8 binds to the high affinity I-domain in a metal ion-dependent manner: a second generation monoclonal antibody selectively targeting activated LFA-1. J Biol Chem 2010; 285:32860-32868. [PMID: 20724473 DOI: 10.1074/jbc.m110.111591] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activation of leukocyte function-associated antigen-1 (LFA-1) plays a critical role in regulating immune responses. The metal ion-dependent adhesion site on the I-domain of LFA-1 α(L) subunit is the key recognition site for ligand binding. Upon activation, conformation changes in the I-domain can lead LFA-1 from the low affinity state to the high affinity (HA) state. Using the purified HA I-domain locked by disulfide bonds for immunization, we developed an mAb, 2E8, that specifically binds to cells expressing the HA LFA-1. The surface plasmon resonance analysis has shown that 2E8 only binds to the HA I-domain and that the dissociation constant (K(D)) for HA I-domain is 197 nm. The binding of 2E8 to the HA I-domain is metal ion-dependent, and the affinity decreased as Mn(2+) was replaced sequentially by Mg(2+) and Ca(2+). Surface plasmon resonance analysis demonstrates that 2E8 inhibits the interaction of HA I-domain and ICAM-1. Furthermore, we found that 2E8 can detect activated LFA-1 on both JY and Jurkat cells using flow cytometry and parallel plate adhesion assay. In addition, 2E8 inhibits JY cell adhesion to human umbilical vein endothelial cells and homotypic aggregation. 2E8 treatment reduces the proliferation of both human CD4(+) and CD8(+) T cells upon OKT3 stimulation without the impairment of their cytolytic function. Taken together, these data demonstrate that 2E8 is specific for the high affinity form of LFA-1 and that 2E8 inhibits LFA-1/ICAM-1 interactions. As a novel activation-specific monoclonal antibody, 2E8 is a potentially useful reagent for blocking high affinity LFA-1 and modulating T cell activation in research and therapeutics.
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Affiliation(s)
- Roberto Carreño
- From the Section of Transplantation Immunology, Department of Stem Cell Transplantation and Cellular Therapy, Houston, Texas 77030
| | | | - Dan Li
- From the Section of Transplantation Immunology, Department of Stem Cell Transplantation and Cellular Therapy, Houston, Texas 77030
| | - Jessica A Hernandez
- Department of Melanoma Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Yang Wang
- From the Section of Transplantation Immunology, Department of Stem Cell Transplantation and Cellular Therapy, Houston, Texas 77030
| | - Tae Kon Kim
- Adult Stem Cell Transplant Program, University of Miami Sylvester Comprehensive Cancer Center, Miami, Florida 33136
| | - John W Craft
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | - Krishna V Komanduri
- Adult Stem Cell Transplant Program, University of Miami Sylvester Comprehensive Cancer Center, Miami, Florida 33136
| | - Laszlo G Radvanyi
- Department of Melanoma Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Patrick Hwu
- Department of Melanoma Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Jeffrey J Molldrem
- From the Section of Transplantation Immunology, Department of Stem Cell Transplantation and Cellular Therapy, Houston, Texas 77030
| | - Glen B Legge
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | | | - Qing Ma
- From the Section of Transplantation Immunology, Department of Stem Cell Transplantation and Cellular Therapy, Houston, Texas 77030.
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