1
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Santos-López J, de la Paz K, Fernández FJ, Vega MC. Structural biology of complement receptors. Front Immunol 2023; 14:1239146. [PMID: 37753090 PMCID: PMC10518620 DOI: 10.3389/fimmu.2023.1239146] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 08/16/2023] [Indexed: 09/28/2023] Open
Abstract
The complement system plays crucial roles in a wide breadth of immune and inflammatory processes and is frequently cited as an etiological or aggravating factor in many human diseases, from asthma to cancer. Complement receptors encompass at least eight proteins from four structural classes, orchestrating complement-mediated humoral and cellular effector responses and coordinating the complex cross-talk between innate and adaptive immunity. The progressive increase in understanding of the structural features of the main complement factors, activated proteolytic fragments, and their assemblies have spurred a renewed interest in deciphering their receptor complexes. In this review, we describe what is currently known about the structural biology of the complement receptors and their complexes with natural agonists and pharmacological antagonists. We highlight the fundamental concepts and the gray areas where issues and problems have been identified, including current research gaps. We seek to offer guidance into the structural biology of the complement system as structural information underlies fundamental and therapeutic research endeavors. Finally, we also indicate what we believe are potential developments in the field.
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Affiliation(s)
- Jorge Santos-López
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Karla de la Paz
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
- Research & Development, Abvance Biotech SL, Madrid, Spain
| | | | - M. Cristina Vega
- Centro de Investigaciones Biológicas Margarita Salas, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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2
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Arnaout MA. INTEGRINS: A BEDSIDE TO BENCH TO BEDSIDE STORY. TRANSACTIONS OF THE AMERICAN CLINICAL AND CLIMATOLOGICAL ASSOCIATION 2023; 133:34-55. [PMID: 37701613 PMCID: PMC10493766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
I provide a narrative of the path I took to discover the membrane receptors that mediate leukocyte adhesion, now known as β2 integrins or CD11/CD18. We followed this discovery with the first determination of the 3-D structures of integrins. The latter advance provided the foundation for understanding the unique features of integrins as divalent cation-dependent signaling receptors and as mechanosensitive conduits between the extracellular matrix and the intracellular cytoskeleton. Our structural studies are now opening new paths for taming overactive integrins in disease while minimizing the collateral damage associated with the faulty pharmacodynamics of current integrin inhibitory drugs.
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3
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Heterotropic roles of divalent cations in the establishment of allostery and affinity maturation of integrin αXβ2. Cell Rep 2022; 40:111254. [PMID: 36001965 PMCID: PMC9440770 DOI: 10.1016/j.celrep.2022.111254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 05/23/2022] [Accepted: 08/02/2022] [Indexed: 11/21/2022] Open
Abstract
Allosteric activation and silencing of leukocyte β2-integrins transpire through cation-dependent structural changes, which mediate integrin biosynthesis and recycling, and are essential to designing leukocyte-specific drugs. Stepwise addition of Mg2+ reveals two mutually coupled events for the αXβ2 ligand-binding domain-the αX I-domain-corresponding to allostery establishment and affinity maturation. Electrostatic alterations in the Mg2+-binding site establish long-range couplings, leading to both pH- and Mg2+-occupancy-dependent biphasic stability change in the αX I-domain fold. The ligand-binding sensorgrams show composite affinity events for the αX I-domain accounting for the multiplicity of the αX I-domain conformational states existing in the solution. On cell surfaces, increasing Mg2+ concentration enhanced adhesiveness of αXβ2. This work highlights how intrinsically flexible pH- and cation-sensitive architecture endows a unique dynamic continuum to the αI-domain structure on the intact integrin, thereby revealing the importance of allostery establishment and affinity maturation in both extracellular and intracellular integrin events.
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4
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Villanueva V, Li X, Jimenez V, Faridi HM, Gupta V. CD11b agonists offer a novel approach for treating lupus nephritis. Transl Res 2022; 245:41-54. [PMID: 35288363 PMCID: PMC9167730 DOI: 10.1016/j.trsl.2022.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/28/2022] [Accepted: 03/02/2022] [Indexed: 12/20/2022]
Abstract
Lupus nephritis (LN) develops in more than a third of all systemic lupus erythematosus (SLE) patients and is the strongest predictor of morbidity and mortality. Increased circulating levels of type I interferon (IFN I) and anti-double stranded DNA (anti-dsDNA) and anti-RNA binding protein (anti-RNP) antibodies lead to increased glomerular injury via leukocyte activation and glomerular infiltration. Uncontrolled Toll-like receptor (TLR) signaling in leukocytes results in increased production of IFN I and anti-dsDNA antibodies. ITGAM gene codes for integrin CD11b, the α-chain of integrin heterodimer CD11b/CD18, that is highly expressed in leukocytes and modulates TLR-dependent pro-inflammatory signaling. Three nonsynonymous SNPs in the ITGAM gene strongly correlate with increased risk for SLE and LN and with IFN I levels. Here we review the literature on the role of CD11b on leukocytes in LN. We also incorporate conclusions from several recent studies that show that these ITGAM SNPs result in a CD11b protein that is less able to suppress TLR-dependent pro-inflammatory pathways in leukocytes, that activation of CD11b via novel small molecule agonists suppresses TLR-dependent pathways, including reductions in circulating levels of IFN I and anti-dsDNA antibodies, and that CD11b activation reduces LN in model systems. Recent data strongly suggest that integrin CD11b is an exciting new therapeutic target in SLE and LN and that allosteric activation of CD11b is a novel therapeutic paradigm for effectively treating such autoimmune diseases.
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Affiliation(s)
- Veronica Villanueva
- Drug Discovery Center, Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Xiaobo Li
- Drug Discovery Center, Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Viviana Jimenez
- Drug Discovery Center, Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois
| | - Hafeez M Faridi
- Department of Pharmaceutical Sciences, College of Pharmacy, Chicago State University, Chicago, Illinois
| | - Vineet Gupta
- Drug Discovery Center, Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois.
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5
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Blythe EN, Weaver LC, Brown A, Dekaban GA. β2 Integrin CD11d/CD18: From Expression to an Emerging Role in Staged Leukocyte Migration. Front Immunol 2021; 12:775447. [PMID: 34858434 PMCID: PMC8630586 DOI: 10.3389/fimmu.2021.775447] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 10/08/2021] [Indexed: 12/12/2022] Open
Abstract
CD11d/CD18 is the most recently discovered and least understood β2 integrin. Known CD11d adhesive mechanisms contribute to both extravasation and mesenchymal migration – two key aspects for localizing peripheral leukocytes to sites of inflammation. Differential expression of CD11d induces differences in monocyte/macrophage mesenchymal migration including impacts on macrophage sub-set migration. The participation of CD11d/CD18 in leukocyte localization during atherosclerosis and following neurotrauma has sparked interest in the development of CD11d-targeted therapeutic agents. Whereas the adhesive properties of CD11d have undergone investigation, the signalling pathways induced by ligand binding remain largely undefined. Underlining each adhesive and signalling function, CD11d is under unique transcriptional control and expressed on a sub-set of predominately tissue-differentiated innate leukocytes. The following review is the first to capture the nearly three decades of CD11d research and discusses the emerging role of CD11d in leukocyte migration and retention during the progression of a staged immune response.
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Affiliation(s)
- Eoin N Blythe
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Microbiology and Immunology, University of Western Ontario, London, ON, Canada
| | - Lynne C Weaver
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, ON, Canada
| | - Arthur Brown
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Gregory A Dekaban
- Molecular Medicine Research Laboratories, Robarts Research Institute, University of Western Ontario, London, ON, Canada.,Department of Microbiology and Immunology, University of Western Ontario, London, ON, Canada
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6
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Jensen RK, Bajic G, Sen M, Springer TA, Vorup-Jensen T, Andersen GR. Complement Receptor 3 Forms a Compact High-Affinity Complex with iC3b. THE JOURNAL OF IMMUNOLOGY 2021; 206:3032-3042. [PMID: 34117107 DOI: 10.4049/jimmunol.2001208] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 04/13/2021] [Indexed: 11/19/2022]
Abstract
Complement receptor 3 (CR3, also known as Mac-1, integrin αMβ2, or CD11b/CD18) is expressed on a subset of myeloid and certain activated lymphoid cells. CR3 is essential for the phagocytosis of complement-opsonized particles such as pathogens and apoptotic or necrotic cells opsonized with the complement fragment iC3b and, to a lesser extent, C3dg. Although the interaction between the iC3b thioester domain and the ligand binding CR3 αM I-domain is structurally and functionally well characterized, the nature of additional CR3-iC3b interactions required for phagocytosis of complement-opsonized objects remains obscure. In this study, we analyzed the interaction between iC3b and the 150-kDa headpiece fragment of the CR3 ectodomain. Surface plasmon resonance experiments demonstrated a 30 nM affinity of the CR3 headpiece for iC3b compared with 515 nM for the iC3b thioester domain, whereas experiments monitoring binding of iC3b to CR3-expressing cells suggested an affinity of 50 nM for the CR3-iC3b interaction. Small angle x-ray scattering analysis revealed that iC3b adopts an extended but preferred conformation in solution. Upon interaction with CR3, iC3b rearranges to form a compact receptor-ligand complex. Overall, the data suggest that the iC3b-CR3 interaction is of high affinity and relies on minor contacts formed between CR3 and regions outside the iC3b thioester domain. Our results rationalize the more efficient phagocytosis elicited by iC3b than by C3dg and pave the way for the development of specific therapeutics for the treatment of inflammatory and neurodegenerative diseases that do not interfere with the recognition of noncomplement CR3 ligands.
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Affiliation(s)
- Rasmus K Jensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Goran Bajic
- Laboratory of Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA.,Department of Pediatrics, Harvard Medical School, Boston, MA.,Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Mehmet Sen
- Department of Biology and Biochemistry, University of Houston, Houston, TX
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA; and
| | | | - Gregers R Andersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark;
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7
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Siegel PM, Bojti I, Bassler N, Holien J, Flierl U, Wang X, Waggershauser P, Tonnar X, Vedecnik C, Lamprecht C, Stankova I, Li T, Helbing T, Wolf D, Anto-Michel N, Mitre LS, Ehrlich J, Orlean L, Bender I, Przewosnik A, Mauler M, Hollederer L, Moser M, Bode C, Parker MW, Peter K, Diehl P. A DARPin targeting activated Mac-1 is a novel diagnostic tool and potential anti-inflammatory agent in myocarditis, sepsis and myocardial infarction. Basic Res Cardiol 2021; 116:17. [PMID: 33721106 PMCID: PMC7960600 DOI: 10.1007/s00395-021-00849-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 01/18/2021] [Indexed: 12/15/2022]
Abstract
The monocyte β2-integrin Mac-1 is crucial for leukocyte–endothelium interaction, rendering it an attractive therapeutic target for acute and chronic inflammation. Using phage display, a Designed-Ankyrin-Repeat-Protein (DARPin) was selected as a novel binding protein targeting and blocking the αM I-domain, an activation-specific epitope of Mac-1. This DARPin, named F7, specifically binds to activated Mac-1 on mouse and human monocytes as determined by flow cytometry. Homology modelling and docking studies defined distinct interaction sites which were verified by mutagenesis. Intravital microscopy showed reduced leukocyte–endothelium adhesion in mice treated with this DARPin. Using mouse models of sepsis, myocarditis and ischaemia/reperfusion injury, we demonstrate therapeutic anti-inflammatory effects. Finally, the activated Mac-1-specific DARPin is established as a tool to detect monocyte activation in patients receiving extra-corporeal membrane oxygenation, as well as suffering from sepsis and ST-elevation myocardial infarction. The activated Mac-1-specific DARPin F7 binds preferentially to activated monocytes, detects inflammation in critically ill patients, and inhibits monocyte and neutrophil function as an efficient new anti-inflammatory agent.
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Affiliation(s)
- Patrick M Siegel
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia
| | - István Bojti
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Nicole Bassler
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia
| | - Jessica Holien
- ACRF Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Melbourne, Australia
| | - Ulrike Flierl
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia
| | - Xiaowei Wang
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia.,Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia.,Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia
| | - Philipp Waggershauser
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Xavier Tonnar
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christopher Vedecnik
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Constanze Lamprecht
- BIOSS Centre for Biological Signalling Studies/Synthetic Biology of Signalling Processes, University of Freiburg, Freiburg, Germany
| | - Ivana Stankova
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tian Li
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thomas Helbing
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Dennis Wolf
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Nathaly Anto-Michel
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Lucia Sol Mitre
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Julia Ehrlich
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Lukas Orlean
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ileana Bender
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Anne Przewosnik
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Maximilian Mauler
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Laura Hollederer
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Martin Moser
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christoph Bode
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael W Parker
- ACRF Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Melbourne, Australia.,Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia.,Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Australia
| | - Karlheinz Peter
- Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia. .,Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia. .,Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia. .,Baker Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC, 3004, Australia.
| | - Philipp Diehl
- Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Atherothrombosis and Vascular Biology Laboratory, Baker Heart and Diabetes Institute, Melbourne, Australia.,Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia
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8
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Lietha D, Izard T. Roles of Membrane Domains in Integrin-Mediated Cell Adhesion. Int J Mol Sci 2020; 21:ijms21155531. [PMID: 32752284 PMCID: PMC7432473 DOI: 10.3390/ijms21155531] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022] Open
Abstract
The composition and organization of the plasma membrane play important functional and regulatory roles in integrin signaling, which direct many physiological and pathological processes, such as development, wound healing, immunity, thrombosis, and cancer metastasis. Membranes are comprised of regions that are thick or thin owing to spontaneous partitioning of long-chain saturated lipids from short-chain polyunsaturated lipids into domains defined as ordered and liquid-disorder domains, respectively. Liquid-ordered domains are typically 100 nm in diameter and sometimes referred to as lipid rafts. We posit that integrin β senses membrane thickness and that mechanical force on the membrane regulates integrin activation through membrane thinning. This review examines what we know about the nature and mechanism of the interaction of integrins with the plasma membrane and its effects on regulating integrins and its binding partners.
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Affiliation(s)
- Daniel Lietha
- Cell Signaling and Adhesion Group, Structural and Chemical Biology, Margarita Salas Center for Biological Research (CIB-CSIC), E-28040 Madrid, Spain;
| | - Tina Izard
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, FL 33458, USA
- Correspondence:
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9
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Structural basis of the leukocyte integrin Mac-1 I-domain interactions with the platelet glycoprotein Ib. Blood Adv 2020; 3:1450-1459. [PMID: 31053572 DOI: 10.1182/bloodadvances.2018027011] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 03/10/2019] [Indexed: 12/14/2022] Open
Abstract
Cell-surface receptor interactions between leukocyte integrin macrophage-1 antigen (Mac-1, also known as CR3, αMβ2, CD11b/CD18) and platelet glycoprotein Ibα (GPIbα) are critical to vascular inflammation. To define the key residues at the binding interface, we used nuclear magnetic resonance (NMR) to assign the spectra of the mouse Mac-1 I-domain and mapped the residues contacting the mouse GPIbα N-terminal domain (GPIbαN) to the locality of the integrin metal ion-dependant adhesion site (MIDAS) surface. We next determined the crystal structures of the mouse GPIbαN and Mac-1 I-domain to 2 Å and 2.5 Å resolution, respectively. The mouse Mac-1 I-domain crystal structure reveals an active conformation that is stabilized by a crystal contact from the α7-helix with a glutamate side chain completing the octahedral coordination sphere of the MIDAS Mg2+ ion. The amino acid sequence of the α7-helix and disposition of the glutamic acid matches the C-terminal capping region α-helix of GPIbα effectively acting as a ligand mimetic. Using these crystal structures in combination with NMR measurements and docking analysis, we developed a model whereby an acidic residue from the GPIbα leucine-rich repeat (LRR) capping α-helix coordinates directly to the Mac-1 MIDAS Mg2+ ion. The Mac-1:GPIbαN complex involves additional interactions consolidated by an elongated pocket flanking the GPIbαN LRR capping α-helix. The GPIbαN α-helix has an HxxxE motif, which is equivalent by homology to RxxxD from the human GPIbαN. Subsequent mutagenesis of residues at this interface, coupled with surface plasmon resonance studies, confirmed the importance of GPIbαN residues H218, E222, and the Mac-1 MIDAS residue T209 to formation of the complex.
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10
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Berry KN, Brett TJ. Structural and Biophysical Analysis of the CLCA1 VWA Domain Suggests Mode of TMEM16A Engagement. Cell Rep 2020; 30:1141-1151.e3. [PMID: 31995732 PMCID: PMC7050472 DOI: 10.1016/j.celrep.2019.12.059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/14/2019] [Accepted: 12/16/2019] [Indexed: 01/09/2023] Open
Abstract
The secreted protein calcium-activated chloride channel regulator 1 (CLCA1) utilizes a von Willebrand factor type A (VWA) domain to bind to and potentiate the calcium-activated chloride channel TMEM16A. To gain insight into this unique potentiation mechanism, we determined the 2.0-Å crystal structure of human CLCA1 VWA bound to Ca2+. The structure reveals the metal-ion-dependent adhesion site (MIDAS) in a high-affinity "open" conformation, engaging in crystal contacts that likely mimic how CLCA1 engages TMEM16A. The CLCA1 VWA contains a disulfide bond between α3 and α4 in close proximity to the MIDAS that is invariant in the CLCA family and unique in VWA structures. Further biophysical studies indicate that CLCA1 VWA is preferably stabilized by Mg2+ over Ca2+ and that α6 atypically extends from the VWA core. Finally, an analysis of TMEM16A structures suggests residues likely to mediate interaction with CLCA1 VWA.
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Affiliation(s)
- Kayla N Berry
- Immunology Program and Medical Scientist Training Program, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Internal Medicine, Division of Pulmonary and Critical Care, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tom J Brett
- Department of Internal Medicine, Division of Pulmonary and Critical Care, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
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11
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Molecular mechanism of leukocidin GH-integrin CD11b/CD18 recognition and species specificity. Proc Natl Acad Sci U S A 2019; 117:317-327. [PMID: 31852826 PMCID: PMC6955338 DOI: 10.1073/pnas.1913690116] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Staphylococcus aureus is one of the most virulent bacterial pathogens and, in particular, has the richest repertoire of cytotoxins: A single bacterium can secrete 6 different β-barrel pore-forming toxins, with different cell type and species specificities. Each toxin engages specific receptors on target cells, but the role the receptor plays in the pore-formation process is poorly understood. Here, we determine the crystal structures of a very potent S. aureus leukocidin (LukGH) in complex with its receptor (CD11b) from a sensitive (human) and an insensitive (murine) host, and track the receptor involvement in different steps on the pore-formation pathway. These results advance the knowledge of receptor-mediated leukocidin pore formation and open ways for antileukocidin and anti-S. aureus approaches. Host–pathogen interactions are central to understanding microbial pathogenesis. The staphylococcal pore-forming cytotoxins hijack important immune molecules but little is known about the underlying molecular mechanisms of cytotoxin–receptor interaction and host specificity. Here we report the structures of a staphylococcal pore-forming cytotoxin, leukocidin GH (LukGH), in complex with its receptor (the α-I domain of complement receptor 3, CD11b-I), both for the human and murine homologs. We observe 2 binding interfaces, on the LukG and the LukH protomers, and show that human CD11b-I induces LukGH oligomerization in solution. LukGH binds murine CD11b-I weakly and is inactive toward murine neutrophils. Using a LukGH variant engineered to bind mouse CD11b-I, we demonstrate that cytolytic activity does not only require binding but also receptor-dependent oligomerization. Our studies provide an unprecedented insight into bicomponent leukocidin–host receptor interaction, enabling the development of antitoxin approaches and improved animal models to explore these approaches.
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12
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Vorup-Jensen T, Jensen RK. Structural Immunology of Complement Receptors 3 and 4. Front Immunol 2018; 9:2716. [PMID: 30534123 PMCID: PMC6275225 DOI: 10.3389/fimmu.2018.02716] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 11/05/2018] [Indexed: 01/10/2023] Open
Abstract
Complement receptors (CR) 3 and 4 belong to the family of beta-2 (CD18) integrins. CR3 and CR4 are often co-expressed in the myeloid subsets of leukocytes, but they are also found in NK cells and activated T and B lymphocytes. The heterodimeric ectodomain undergoes considerable conformational change in order to switch the receptor from a structurally bent, ligand-binding in-active state into an extended, ligand-binding active state. CR3 binds the C3d fragment of C3 in a way permitting CR2 also to bind concomitantly. This enables a hand-over of complement-opsonized antigens from the cell surface of CR3-expressing macrophages to the CR2-expressing B lymphocytes, in consequence acting as an antigen presentation mechanism. As a more enigmatic part of their functions, both CR3 and CR4 bind several structurally unrelated proteins, engineered peptides, and glycosaminoglycans. No consensus motif in the proteinaceous ligands has been established. Yet, the experimental evidence clearly suggest that the ligands are primarily, if not entirely, recognized by a single site within the receptors, namely the metal-ion dependent adhesion site (MIDAS). Comparison of some recent identified ligands points to CR3 as inclined to bind positively charged species, while CR4, by contrast, binds strongly negative-charged species, in both cases with the critical involvement of deprotonated, acidic groups as ligands for the Mg2+ ion in the MIDAS. These properties place CR3 and CR4 firmly within the realm of modern molecular medicine in several ways. The expression of CR3 and CR4 in NK cells was recently demonstrated to enable complement-dependent cell cytotoxicity toward antibody-coated cancer cells as part of biological therapy, constituting a significant part of the efficacy of such treatment. With the flexible principles of ligand recognition, it is also possible to propose a response of CR3 and CR4 to existing medicines thereby opening a possibility of drug repurposing to influence the function of these receptors. Here, from advances in the structural and cellular immunology of CR3 and CR4, we review insights on their biochemistry and functions in the immune system.
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Affiliation(s)
- Thomas Vorup-Jensen
- Biophysical Immunology Laboratory, Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark
| | - Rasmus Kjeldsen Jensen
- Department of Molecular Biology and Genetics-Structural Biology, Aarhus University, Aarhus, Denmark
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13
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Liu Y, Ma S, Wang X, Feng Y, Zhang S, Wang S, Zhang X. The role of β2 integrin associated heparin-binding protein release in ARDS. Life Sci 2018; 203:92-98. [PMID: 29679701 DOI: 10.1016/j.lfs.2018.04.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/13/2018] [Accepted: 04/17/2018] [Indexed: 01/18/2023]
Abstract
AIMS PMNs (polymorphonuclear neutrophil) play important roles in early stage of inflammation induced ARDS (Acute Respiratory Distress Syndrome). Both HBP (Heparin-Binding Protein) released from active PMNs and β2 integrins on the surface of PMNs are involved in vascular leakage. The role and relationship of HBP and β2 integrins on ARDS still requires study. MATERIALS AND METHODS We established ARDS model using C57BL/6 mice with cecal ligation and puncture and eliminating HBP and β2 integrin with respective antibodies. The mice were also challenged with HBP endotracheal instillation. Histopathology score, lung wet/dry ratio, bronchoalveolar lavage fluid protein, plasma HBP and β2 integrin on PMNs from all groups were measured. β2 integrin and HBP were analyzed after incubated PMNs with streptococcal and pretreat with anti-CD18, anti-HBP, 1-phosphatidylinositol 3-kinase (PI3K) inhibitor and p38 mitogen-activated protein kinase (MAPK) inhibitor. KEY FINDINGS All lung injury indicatrix accompanied with HBP and β2 integrin elevated in CLP group, and HBP and β2 integrin were in correlation with each other and both were in correlation with the severity of lung injury. Endotracheal instillation HBP induced lung injury in CLP mice. Inhibiting both HBP and integrin ameliorated lung injury. HBP release was suppressed by inhibiting integrin and PI3K pathway, while integrin level did not decrease after eliminating HBP. SIGNIFICANCE Both HBP and β2 integrin play important roles in ARDS. HBP released from PMNs is β2 integrin-PI3K signaling pathway dependent process revealing potential novel therapeutic targets for ARDS treatment.
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Affiliation(s)
- Yang Liu
- Department of Critical Care Medicine, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China; Department of Critical Care Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Shaolin Ma
- Department of Critical Care Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xuebin Wang
- Department of Critical Care Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yajing Feng
- Department of Critical Care Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Shouqin Zhang
- Department of Critical Care Medicine, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Sheng Wang
- Department of Critical Care Medicine, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiangyu Zhang
- Department of Critical Care Medicine, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
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14
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Briot J, Mailhot O, Bourdin B, Tétreault MP, Najmanovich R, Parent L. A three-way inter-molecular network accounts for the Ca Vα2δ1-induced functional modulation of the pore-forming Ca V1.2 subunit. J Biol Chem 2018; 293:7176-7188. [PMID: 29588365 DOI: 10.1074/jbc.ra118.001902] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/09/2018] [Indexed: 12/17/2022] Open
Abstract
L-type CaV1.2 channels are essential for the excitation-contraction coupling in cardiomyocytes and are hetero-oligomers of a pore-forming CaVα1C assembled with CaVβ and CaVα2δ1 subunits. A direct interaction between CaVα2δ1 and Asp-181 in the first extracellular loop of CaVα1 reproduces the native properties of the channel. A 3D model of the von Willebrand factor type A (VWA) domain of CaVα2δ1 complexed with the voltage sensor domain of CaVα1C suggests that Ser-261 and Ser-263 residues in the metal ion-dependent adhesion site (MIDAS) motif are determinant in this interaction, but this hypothesis is untested. Here, coimmunoprecipitation assays and patch-clamp experiments of single-substitution variants revealed that CaVα2δ1 Asp-259 and Ser-261 are the two most important residues in regard to protein interactions and modulation of CaV1.2 currents. In contrast, mutating the side chains of CaVα2δ1 Ser-263, Thr-331, and Asp-363 with alanine did not completely prevent channel function. Molecular dynamics simulations indicated that the carboxylate side chain of CaVα2δ1 Asp-259 coordinates the divalent cation that is further stabilized by the oxygen atoms from the hydroxyl side chain of CaVα2δ1 Ser-261 and the carboxylate group of CaVα1C Asp-181. In return, the hydrogen atoms contributed by the side chain of Ser-261 and the main chain of Ser-263 bonded the oxygen atoms of CaV1.2 Asp-181. We propose that CaVα2δ1 Asp-259 promotes Ca2+ binding necessary to produce the conformation of the VWA domain that locks CaVα2δ1 Ser-261 and Ser-263 within atomic distance of CaVα1C Asp-181. This three-way network appears to account for the CaVα2δ1-induced modulation of CaV1.2 currents.
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Affiliation(s)
- Julie Briot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Olivier Mailhot
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Biochimie et Médecine Moléculaire, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Benoîte Bourdin
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Marie-Philippe Tétreault
- Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada
| | - Rafael Najmanovich
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada
| | - Lucie Parent
- Départements de Pharmacologie et Physiologie, Faculté de Médecine, Montréal, Québec H1T 1C8, Canada; Centre de Recherche de l'Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec H1T 1C8, Canada.
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15
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Brown KL, Banerjee S, Feigley A, Abe H, Blackwell TS, Pozzi A, Hudson BG, Zent R. Salt-bridge modulates differential calcium-mediated ligand binding to integrin α1- and α2-I domains. Sci Rep 2018; 8:2916. [PMID: 29440721 PMCID: PMC5811549 DOI: 10.1038/s41598-018-21231-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 01/31/2018] [Indexed: 11/11/2022] Open
Abstract
Integrins are transmembrane cell-extracellular matrix adhesion receptors that impact many cellular functions. A subgroup of integrins contain an inserted (I) domain within the α–subunits (αI) that mediate ligand recognition where function is contingent on binding a divalent cation at the metal ion dependent adhesion site (MIDAS). Ca2+ is reported to promote α1I but inhibit α2I ligand binding. We co-crystallized individual I-domains with MIDAS-bound Ca2+ and report structures at 1.4 and 2.15 Å resolution, respectively. Both structures are in the “closed” ligand binding conformation where Ca2+ induces minimal global structural changes. Comparisons with Mg2+-bound structures reveal Mg2+ and Ca2+ bind α1I in a manner sufficient to promote ligand binding. In contrast, Ca2+ is displaced in the α2I domain MIDAS by 1.4 Å relative to Mg2+ and unable to directly coordinate all MIDAS residues. We identified an E152-R192 salt bridge hypothesized to limit the flexibility of the α2I MIDAS, thus, reducing Ca2+ binding. A α2I E152A construct resulted in a 10,000-fold increase in Mg2+ and Ca2+ binding affinity while increasing binding to collagen ligands 20%. These data indicate the E152-R192 salt bridge is a key distinction in the molecular mechanism of differential ion binding of these two I domains.
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Affiliation(s)
- Kyle L Brown
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA. .,Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA. .,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.
| | - Surajit Banerjee
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA.,Northeastern Collaborative Access Team, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Andrew Feigley
- Leadership Alliance, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA
| | - Hanna Abe
- Aspirnaut Summer research program, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA
| | - Timothy S Blackwell
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
| | - Ambra Pozzi
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
| | - Billy G Hudson
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Structural Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Aspirnaut Summer research program, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Department of Biochemistry, Vanderbilt University, Nashville, TN, 37232-2372, USA
| | - Roy Zent
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, TN, 37232-2372, USA.,Veterans Affairs Hospital, Nashville, TN, 37232, USA
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16
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Raab-Westphal S, Marshall JF, Goodman SL. Integrins as Therapeutic Targets: Successes and Cancers. Cancers (Basel) 2017; 9:E110. [PMID: 28832494 PMCID: PMC5615325 DOI: 10.3390/cancers9090110] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 08/11/2017] [Accepted: 08/14/2017] [Indexed: 12/12/2022] Open
Abstract
Integrins are transmembrane receptors that are central to the biology of many human pathologies. Classically mediating cell-extracellular matrix and cell-cell interaction, and with an emerging role as local activators of TGFβ, they influence cancer, fibrosis, thrombosis and inflammation. Their ligand binding and some regulatory sites are extracellular and sensitive to pharmacological intervention, as proven by the clinical success of seven drugs targeting them. The six drugs on the market in 2016 generated revenues of some US$3.5 billion, mainly from inhibitors of α4-series integrins. In this review we examine the current developments in integrin therapeutics, especially in cancer, and comment on the health economic implications of these developments.
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Affiliation(s)
- Sabine Raab-Westphal
- Translational In Vivo Pharmacology, Translational Innovation Platform Oncology, Merck KGaA, Frankfurter Str. 250, 64293 Darmstadt, Germany.
| | - John F Marshall
- Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.
| | - Simon L Goodman
- Translational and Biomarkers Research, Translational Innovation Platform Oncology, Merck KGaA, 64293 Darmstadt, Germany.
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17
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Dehnadi A, Benedict Cosimi A, Neal Smith R, Li X, Alonso JL, Means TK, Arnaout MA. Prophylactic orthosteric inhibition of leukocyte integrin CD11b/CD18 prevents long-term fibrotic kidney failure in cynomolgus monkeys. Nat Commun 2017; 8:13899. [PMID: 28071653 PMCID: PMC5234083 DOI: 10.1038/ncomms13899] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 11/10/2016] [Indexed: 12/21/2022] Open
Abstract
Ischaemic acute kidney injury (AKI), an inflammatory disease process, often progresses to chronic kidney disease (CKD), with no available effective prophylaxis. This is in part due to lack of clinically relevant CKD models in non-human primates. Here we demonstrate that inhibition of the archetypal innate immune receptor CD11b/CD18 prevents progression of AKI to CKD in cynomolgus monkeys. Severe ischaemia-reperfusion injury of the right kidney, with subsequent periods of the left ureter ligation, causes irreversible right kidney failure 3, 6 or 9 months after AKI. Moreover, prophylactic inactivation of CD11b/CD18, using the orthosteric CD11b/CD18 inhibitor mAb107, improves microvascular perfusion and histopathology, reduces intrarenal pro-inflammatory mediators and salvages kidney function long term. These studies reveal an important early role of CD11b+ leukocytes in post-ischaemic kidney fibrosis and failure, and suggest a potential early therapeutic intervention to mitigate progression of ischaemic AKI to CKD in humans.
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Affiliation(s)
- Abbas Dehnadi
- Division of Transplant Surgery, Department of Surgery, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - A Benedict Cosimi
- Division of Transplant Surgery, Department of Surgery, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Rex Neal Smith
- Harvard Medical School, Boston, Massachusetts 02115, USA.,Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Xiangen Li
- Harvard Medical School, Boston, Massachusetts 02115, USA.,Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - José L Alonso
- Harvard Medical School, Boston, Massachusetts 02115, USA.,Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Terry K Means
- Harvard Medical School, Boston, Massachusetts 02115, USA.,Division of Rheumatology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - M Amin Arnaout
- Harvard Medical School, Boston, Massachusetts 02115, USA.,Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Center For Regenerative Medicine, Medical Services, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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18
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Abstract
Integrins comprise a large family of αβ heterodimeric cell adhesion receptors that are expressed on all cells except red blood cells and that play essential roles in the regulation of cell growth and function. The leukocyte integrins, which include members of the β
1, β
2, β
3, and β
7 integrin family, are critical for innate and adaptive immune responses but also can contribute to many inflammatory and autoimmune diseases when dysregulated. This review focuses on the β
2 integrins, the principal integrins expressed on leukocytes. We review their discovery and role in host defense, the structural basis for their ligand recognition and activation, and their potential as therapeutic targets.
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Affiliation(s)
- M Amin Arnaout
- Leukocyte Biology & Inflammation Program, Structural Biology Program, Nephrology, Center for Regenerative Medicine, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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19
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Celik E, Faridi MH, Kumar V, Deep S, Moy VT, Gupta V. Agonist leukadherin-1 increases CD11b/CD18-dependent adhesion via membrane tethers. Biophys J 2014; 105:2517-27. [PMID: 24314082 DOI: 10.1016/j.bpj.2013.10.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 10/09/2013] [Accepted: 10/18/2013] [Indexed: 01/13/2023] Open
Abstract
Integrin CD11b/CD18 is a key adhesion receptor that mediates leukocyte migration and immune functions. Leukadherin-1 (LA1) is a small molecule agonist that enhances CD11b/CD18-dependent cell adhesion to its ligand ICAM-1. Here, we used single-molecule force spectroscopy to investigate the biophysical mechanism by which LA1-activated CD11b/CD18 mediates leukocyte adhesion. Between the two distinct populations of CD11b/CD18:ICAM-1 complex that participate in cell adhesion, the cytoskeleton(CSK)-anchored elastic elements and the membrane tethers, we found that LA1 enhanced binding of CD11b/CD18 on K562 cells to ICAM-1 via the formation of long membrane tethers, whereas Mn(2+) additionally increased ICAM-1 binding via CSK-anchored bonds. LA1 activated wild-type and LFA1(-/-) neutrophils also showed longer detachment distances and time from ICAM-1-coated atomic force microscopy tips, but significantly lower detachment force, as compared to the Mn(2+)-activated cells, confirming that LA1 primarily increased membrane-tether bonds to enhance CD11b/CD18:ICAM-1 binding, whereas Mn(2+) induced additional CSK-anchored bond formation. The results suggest that the two types of agonists differentially activate integrins and couple them to the cellular machinery, providing what we feel are new insights into signal mechanotransduction by such agents.
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Affiliation(s)
- Emrah Celik
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida
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20
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Teplyakov A, Luo J, Obmolova G, Malia TJ, Sweet R, Stanfield RL, Kodangattil S, Almagro JC, Gilliland GL. Antibody modeling assessment II. Structures and models. Proteins 2014; 82:1563-82. [PMID: 24633955 DOI: 10.1002/prot.24554] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 02/23/2014] [Accepted: 03/06/2014] [Indexed: 12/12/2022]
Abstract
To assess the state-of-the-art in antibody structure modeling, a blinded study was conducted. Eleven unpublished Fab crystal structures were used as a benchmark to compare Fv models generated by seven structure prediction methodologies. In the first round, each participant submitted three non-ranked complete Fv models for each target. In the second round, CDR-H3 modeling was performed in the context of the correct environment provided by the crystal structures with CDR-H3 removed. In this report we describe the reference structures and present our assessment of the models. Some of the essential sources of errors in the predictions were traced to the selection of the structure template, both in terms of the CDR canonical structures and VL/VH packing. On top of this, the errors present in the Protein Data Bank structures were sometimes propagated in the current models, which emphasized the need for the curated structural database devoid of errors. Modeling non-canonical structures, including CDR-H3, remains the biggest challenge for antibody structure prediction.
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Affiliation(s)
- Alexey Teplyakov
- Janssen Research & Development, LLC, 1400 McKean Road, Spring House, Pennsylvania, 19477
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21
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Jiao Y, Legge FS, Zeng X, Treutlein HR, Zeng J. Antibody recognition of Shiga toxins (Stxs): computational identification of the epitopes of Stx2 subunit A to the antibodies 11E10 and S2C4. PLoS One 2014; 9:e88191. [PMID: 24516609 PMCID: PMC3917601 DOI: 10.1371/journal.pone.0088191] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/04/2014] [Indexed: 11/18/2022] Open
Abstract
We have recently developed a new method to predict the epitopes of the antigens that are
recognized by a specific antibody. In this work, we applied the method to identify the epitopes of
the Shiga toxin (Stx2 subunit A) that were bound by two specific antibodies 11E10 and S2C4. The
predicted epitopes of Stx2 binding to the antibody 11E10 resembles the recognition surface
constructed by the regions of Stx2 identified experimentally. For the S2C4, our results indicate
that the antibody recognizes the Stx2 at two different regions on the protein surface. The first
region (residues 246-254: ARSVRAVNE) is similar to the recognition region of the 11E10, while the
second region is formed by two epitopes. The second region is particularly significant because it
includes the amino acid sequence region that is diverse between Stx2 and other Stx (residues
176-188: QREFRQALSETAPV). This new recognition region is believed to play an important role in the
experimentally observed selectivity of S2C4 to the Stx2.
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Affiliation(s)
- Yongjun Jiao
- Institute of Pathogenic Microbiology, Jiangsu Provincial
Center for Disease Prevention and Control, Key Laboratory of Enteric Pathogenic Microbiology,
Ministry Health, Nanjing, China
| | - Fiona S. Legge
- Computist Bio-Nanotech, Small Technology Clusters,
Scoresby, Victoria, Australia
| | - Xiaoyan Zeng
- Institute of Pathogenic Microbiology, Jiangsu Provincial
Center for Disease Prevention and Control, Key Laboratory of Enteric Pathogenic Microbiology,
Ministry Health, Nanjing, China
| | - Herbert R. Treutlein
- Monash Institute of Pharmaceutical Sciences, Monash
University, Parkville, Victoria, Australia
- Computist Bio-Nanotech, Small Technology Clusters,
Scoresby, Victoria, Australia
- * E-mail: (HRT); (JZ)
| | - Jun Zeng
- Monash Institute of Pharmaceutical Sciences, Monash
University, Parkville, Victoria, Australia
- Computist Bio-Nanotech, Small Technology Clusters,
Scoresby, Victoria, Australia
- * E-mail: (HRT); (JZ)
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22
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Mason L, Amani P, Cross M, Baker J, Bailey UM, Jones MK, Gasser RB, Hofmann A. The Relevance of Structural Biology in Studying Molecules Involved in Parasite–Host Interactions: Potential for Designing New Interventions. Aust J Chem 2014. [DOI: 10.1071/ch14304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
New interventions against infectious diseases require a detailed knowledge and understanding of pathogen–host interactions and pathogeneses at the molecular level. The combination of the considerable advances in systems biology research with methods to explore the structural biology of molecules is poised to provide new insights into these areas. Importantly, exploring three-dimensional structures of proteins is central to understanding disease processes, and establishing structure–function relationships assists in identification and assessment of new drug and vaccine targets. Frequently, the molecular arsenal deployed by invading pathogens, and in particular parasites, reveals a common theme whereby families of proteins with conserved three-dimensional folds play crucial roles in infectious processes, but individual members of such families show high levels of specialisation, which is often achieved through grafting particular structural features onto the shared overall fold. Accordingly, the applicability of predictive methodologies based on the primary structure of proteins or genome annotations is limited, particularly when thorough knowledge of molecular-level mechanisms is required. Such instances exemplify the need for experimental three-dimensional structures provided by protein crystallography, which remain an essential component of this area of research. In the present article, we review two examples of key protein families recently investigated in our laboratories, which could represent intervention targets in the metabolome or secretome of parasites.
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23
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Adair BD, Xiong JP, Alonso JL, Hyman BT, Arnaout MA. EM structure of the ectodomain of integrin CD11b/CD18 and localization of its ligand-binding site relative to the plasma membrane. PLoS One 2013; 8:e57951. [PMID: 23469114 PMCID: PMC3585415 DOI: 10.1371/journal.pone.0057951] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 01/27/2013] [Indexed: 11/19/2022] Open
Abstract
One-half of the integrin α-subunit Propeller domains contain and extra vWFA domain (αA domain), which mediates integrin binding to extracellular physiologic ligands via its metal-ion-dependent adhesion site (MIDAS). We used electron microscopy to determine the 3D structure of the αA-containing ectodomain of the leukocyte integrin CD11b/CD18 (αMβ2) in its inactive state. A well defined density for αA was observed within a bent ectodomain conformation, while the structure of the ectodomain in complex with the Fab fragment of mAb107, which binds at the MIDAS face of CD11b and stabilizes the inactive state, further revealed that αA is restricted to a relatively small range of orientations relative to the Propeller domain. Using Fab 107 as probe in fluorescent lifetime imaging microscopy (FLIM) revealed that αA is positioned relatively far from the membrane surface in the inactive state, and a systematic orientation search revealed that the MIDAS face would be accessible to extracellular ligand in the inactive state of the full-length cellular integrin. These studies are the first to define the 3D EM structure of an αA-containing integrin ectodomain and to position the ligand-binding face of αA domain in relation to the plasma membrane, providing new insights into current models of integrin activation.
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Affiliation(s)
- Brian D. Adair
- Structural Biology Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Jian-Ping Xiong
- Structural Biology Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - José Luis Alonso
- Leukocyte Biology and Inflammation Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Bradley T. Hyman
- Division of Nephrology, and Institute for Neurodegenerative Disease, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - M. Amin Arnaout
- Structural Biology Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
- Leukocyte Biology and Inflammation Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States of America
- * E-mail:
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24
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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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25
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26
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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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Alonso JL, Goldmann WH. Influence of divalent cations on the cytoskeletal dynamics of K562 cells determined by nano-scale bead tracking. Biochem Biophys Res Commun 2012; 421:245-8. [DOI: 10.1016/j.bbrc.2012.03.145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 03/28/2012] [Indexed: 02/07/2023]
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