1
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Akasaka H, Sato D, Shihoya W, Nureki O, Kise Y. Cryo-EM structure of I domain-containing integrin αEβ7. Biochem Biophys Res Commun 2024; 721:150121. [PMID: 38781659 DOI: 10.1016/j.bbrc.2024.150121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024]
Abstract
The integrin family is a transmembrane receptor that plays critical roles in the cell-cell and cell-extracellular matrix adhesion, signal transduction such as cell cycle regulation, organization of the intracellular cytoskeleton, and immune responses. Consequently, dysfunction of integrins is associated with a wide range of human diseases, including cancer and immune diseases, which makes integrins therapeutic targets for drug discovery. Here we report the cryo-EM structure of the human α-I domain-containing full-length integrin αEβ7, which is expressed in the leukocytes of the immune system and a drug target for inflammatory bowel disease (IBD). The structure reveals the half-bent conformation, an intermediate between the close and the open conformation, while the α-I domain responsible for the ligand binding covers the headpiece domain by a unique spatial arrangement. Our results provide the structural information for the drug design targeting IBD.
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Affiliation(s)
- Hiroaki Akasaka
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan
| | - Dan Sato
- Curreio, Inc., Room 357, South Clinical Research Laboratory, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8485, Japan
| | - Wataru Shihoya
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan; Curreio, Inc., Room 357, South Clinical Research Laboratory, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8485, Japan.
| | - Yoshiaki Kise
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan; Curreio, Inc., Room 357, South Clinical Research Laboratory, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8485, Japan.
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2
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Nguyen H, Podolnikova NP, Ugarova TP, Wang X. α MI-domain of integrin Mac-1 binds the cytokine pleiotrophin using multiple mechanisms. Structure 2024; 32:1184-1196.e4. [PMID: 38729161 PMCID: PMC11316656 DOI: 10.1016/j.str.2024.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 03/21/2024] [Accepted: 04/15/2024] [Indexed: 05/12/2024]
Abstract
The integrin Mac-1 (αMβ2, CD11b/CD18, CR3) is an adhesion receptor expressed on macrophages and neutrophils. Mac-1 is also a promiscuous integrin that binds a diverse set of ligands through its αMI-domain. However, the binding mechanism of most ligands remains unclear. We have characterized the interaction of αMI-domain with the cytokine pleiotrophin (PTN), a protein known to bind αMI-domain and induce Mac-1-mediated cell adhesion and migration. Our data show that PTN's N-terminal domain binds a unique site near the N- and C-termini of the αMI-domain using a metal-independent mechanism. However, a stronger interaction is achieved when an acidic amino acid in a zwitterionic motif in PTN's C-terminal domain chelates the divalent cation in the metal ion-dependent adhesion site of active αMI-domain. These results indicate that αMI-domain can bind ligands using multiple mechanisms and that the active αMI-domain has a preference for motifs containing both positively and negatively charged amino acids.
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Affiliation(s)
- Hoa Nguyen
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA
| | | | - Tatiana P Ugarova
- School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA
| | - Xu Wang
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85281, USA.
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3
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Hou L, Sin YC, Chen Y, Yuki K. Integrin CD11c regulates B cell homeostasis. Front Immunol 2024; 15:1359608. [PMID: 38380335 PMCID: PMC10876775 DOI: 10.3389/fimmu.2024.1359608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 01/19/2024] [Indexed: 02/22/2024] Open
Abstract
CD11c is widely known as a cell surface marker for dendritic cells, but we recently showed that it regulates neutrophil and T cell functions. Because we found that CD11c knockout (KO) mice had lower blood B cell counts, we characterized B cell profile in developmental stages. We found that CD11c KO recirculating and mature B cells was significantly fewer compared with wild type, associated with exaggerated proliferation and apoptosis. Because they did not express CD11c, we sought for the possibility of CD11c-mediated non-intrinsic regulation of B cell proliferation and apoptosis. Here we hypothesized that dendritic cells, major cells expressing CD11c would regulate B cells indirectly. The proteomics of dendritic cells cultured in vitro indicated the downregulation of macrophage migration inhibitory factor (MIF). Less MIF was also confirmed by ELISA. Furthermore, plasma MIF level was significantly lower in naïve CD11c KO mice. Because MIF regulates B cell survival, we demonstrated a novel regulatory mechanism of naïve B cells via CD11c.
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Affiliation(s)
- Lifei Hou
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children’s Hospital, Boston, MA, United States
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, United States
| | - Yi-Cheng Sin
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
| | - Yue Chen
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
| | - Koichi Yuki
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children’s Hospital, Boston, MA, United States
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, United States
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4
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Cao Z, Garcia MJ, Sklar LA, Wandinger-Ness A, Fan Z. A Flow Cytometry-Based High-Throughput Technique for Screening Integrin-Inhibitory Drugs. J Vis Exp 2024:10.3791/64401. [PMID: 38372326 PMCID: PMC11172413 DOI: 10.3791/64401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024] Open
Abstract
This protocol aims to establish a method for identifying small molecular antagonists of β2 integrin activation, utilizing conformational-change-reporting antibodies and high-throughput flow cytometry. The method can also serve as a guide for other antibody-based high-throughput screening methods. β2 integrins are leukocyte-specific adhesion molecules that are crucial in immune responses. Neutrophils rely on integrin activation to exit the bloodstream, not only to fight infections but also to be involved in multiple inflammatory diseases. Controlling β2 integrin activation presents a viable approach for treating neutrophil-associated inflammatory diseases. In this protocol, a monoclonal antibody, mAb24, which specifically binds to the high-affinity headpiece of β2 integrins, is utilized to quantify β2 integrin activation on isolated primary human neutrophils. N-formylmethionyl-leucyl-phenylalanine (fMLP) is used as a stimulus to activate neutrophil β2 integrins. A high-throughput flow cytometer capable of automatically running 384-well plate samples was used in this study. The effects of 320 chemicals on β2 integrin inhibition are assessed within 3 h. Molecules that directly target β2 integrins or target molecules in the G protein-coupled receptor-initiated integrin inside-out activation signaling pathway can be identified through this approach.
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Affiliation(s)
- Ziming Cao
- Department of Immunology, School of Medicine, UConn Health
| | - Matthew J Garcia
- Center for Molecular Discovery, University of New Mexico Health Sciences Center
| | - Larry A Sklar
- Center for Molecular Discovery, University of New Mexico Health Sciences Center; Comprehensive Cancer Center, University of New Mexico Health Sciences Center; Department of Pathology, University of New Mexico Health Sciences Center; Autophagy, Inflammation, & Metabolism (AIM) Center, University of New Mexico
| | - Angela Wandinger-Ness
- Comprehensive Cancer Center, University of New Mexico Health Sciences Center; Department of Pathology, University of New Mexico Health Sciences Center
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health;
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5
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Hollis JA, Chan MC, Malik HS, Campbell MG. Evolutionary origin and structural ligand mimicry by the inserted domain of alpha-integrin proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.05.565221. [PMID: 37986796 PMCID: PMC10659397 DOI: 10.1101/2023.11.05.565221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Heterodimeric integrin proteins transmit signals through conformational changes upon ligand binding between their alpha (α) and beta (β) subunits. Early in chordate evolution, some α subunits acquired an "inserted" (I) domain, which expanded their ligand binding capacity but simultaneously obstructed the ancestral ligand-binding pocket. While this would seemingly impede conventional ligand-mediated integrin activation, it was proposed that the I domain itself could serve both as a ligand replacement and an activation trigger. Here, we provide compelling evidence in support of this longstanding hypothesis using high-resolution cryo-electron microscopy structures of two distinct integrin complexes: the ligand-free and E-cadherin-bound states of the αEβ7 integrin with the I domain, as well as the α4β7 integrin lacking the I domain in both a ligand-free state and bound to MadCAM-1. We trace the evolutionary origin of the I domain to an ancestral collagen-collagen interaction domain. Our analyses illuminate how the I domain intrinsically mimics an extrinsic ligand, enabling integrins to undergo the canonical allosteric cascade of conformational activation and dramatically expanding the range of cellular communication mechanisms in vertebrates.
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Affiliation(s)
- Jeremy A. Hollis
- Division of Basic Sciences, Fred Hutchinson Cancer Center; Seattle, WA 98109, USA
- Graduate Program in Molecular and Cellular Biology, University of Washington; Seattle, WA 98195, USA
| | - Matthew C. Chan
- Division of Basic Sciences, Fred Hutchinson Cancer Center; Seattle, WA 98109, USA
| | - Harmit S. Malik
- Division of Basic Sciences, Fred Hutchinson Cancer Center; Seattle, WA 98109, USA
- Howard Hughes Medical Institute; Seattle, WA 98109, USA
| | - Melody G. Campbell
- Division of Basic Sciences, Fred Hutchinson Cancer Center; Seattle, WA 98109, USA
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6
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. Comput Struct Biotechnol J 2023; 21:4497-4507. [PMID: 37753178 PMCID: PMC10518446 DOI: 10.1016/j.csbj.2023.09.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/17/2023] [Accepted: 09/17/2023] [Indexed: 09/28/2023] Open
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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7
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Zhang H, Zhu DS, Zhu J. Family-wide analysis of integrin structures predicted by AlphaFold2. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.02.539023. [PMID: 37205578 PMCID: PMC10187181 DOI: 10.1101/2023.05.02.539023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Recent advances in protein structure prediction using AlphaFold2, known for its high efficiency and accuracy, have opened new avenues for comprehensive analysis of all structures within a single protein family. In this study, we evaluated the capabilities of AphaFold2 in analyzing integrin structures. Integrins are heterodimeric cell surface receptors composed of a combination of 18 α and 8 β subunits, resulting in a family of 24 different members. Both α and β subunits consist of a large extracellular domain, a short transmembrane domain, and typically, a short cytoplasmic tail. Integrins play a pivotal role in a wide range of cellular functions by recognizing diverse ligands. Despite significant advances in integrin structural studies in recent decades, high-resolution structures have only been determined for a limited subsets of integrin members, thus limiting our understanding of the entire integrin family. Here, we first analyzed the single-chain structures of 18 α and 8 β integrins in the AlphaFold2 protein structure database. We then employed the newly developed AlphaFold2-multimer program to predict the α/β heterodimer structures of all 24 human integrins. The predicted structures show a high level of accuracy for the subdomains of both α and β subunits, offering high-resolution structure insights for all integrin heterodimers. Our comprehensive structural analysis of the entire integrin family unveils a potentially diverse range of conformations among the 24 members, providing a valuable structure database for studies related to integrin structure and function. We further discussed the potential applications and limitations of the AlphaFold2-derived integrin structures.
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Affiliation(s)
- Heng Zhang
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Daniel S. Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Jieqing Zhu
- Versiti Blood Research Institute, Milwaukee, WI, USA
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI, USA
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8
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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] [MESH Headings] [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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9
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Pinelo JEE, Manandhar P, Popovic G, Ray K, Tasdelen MF, Nguyen Q, Iavarone AT, Offenbacher AR, Hudson NE, Sen M. Systematic mapping of the conformational landscape and dynamism of soluble fibrinogen. J Thromb Haemost 2023; 21:1529-1543. [PMID: 36746319 PMCID: PMC10407912 DOI: 10.1016/j.jtha.2023.01.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/05/2023]
Abstract
BACKGROUND Fibrinogen is a soluble, multisubunit, and multidomain dimeric protein, which, upon its proteolytic cleavage by thrombin, is converted to insoluble fibrin, initiating polymerization that substantially contributes to clot growth. Fibrinogen contains numerous, transiently accessible "cryptic" epitopes for hemostatic and immunologic proteins, suggesting that fibrinogen exhibits conformational flexibility, which may play functional roles in its temporal and spatial interactions. Hitherto, there have been limited integrative approaches characterizing the solution structure and internal flexibility of fibrinogen. METHODS Here, utilizing a multipronged, biophysical approach involving 2 solution-based techniques, temperature-dependent hydrogen-deuterium exchange mass spectrometry and small angle X-ray scattering, corroborated by negative stain electron microscopy, we present a holistic, conformationally dynamic model of human fibrinogen in solution. RESULTS Our data reveal 4 major and distinct conformations of fibrinogen accommodated by a high degree of internal protein flexibility along its central scaffold. We propose that the fibrinogen structure in the solution consists of a complex, conformational landscape with multiple local minima. This is further supported by the location of numerous point mutations that are linked to dysfibrinogenemia and posttranslational modifications, residing near the identified fibrinogen flexions. CONCLUSION This work provides a molecular basis for the structural "dynamism" of fibrinogen that is expected to influence the broad swath of its functionally diverse macromolecular interactions and fine-tune the structural and mechanical properties of blood clots.
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Affiliation(s)
- Jose E E Pinelo
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Pragya Manandhar
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Grega Popovic
- Department of Chemistry, East Carolina University, Greenville, North Carolina, USA
| | - Katherine Ray
- Department of Chemistry, East Carolina University, Greenville, North Carolina, USA
| | - Mehmet F Tasdelen
- Department of Computer Science, University of Houston, Houston, Texas, USA
| | - Quoc Nguyen
- Department of Mathematics, University of Houston, Houston, Texas, USA
| | - Anthony T Iavarone
- QB3/Chemistry/Mass Spectrometry Facility, University of California, Berkeley, California, USA
| | - Adam R Offenbacher
- Department of Chemistry, East Carolina University, Greenville, North Carolina, USA
| | - Nathan E Hudson
- Department of Physics, East Carolina University, Greenville, North Carolina, USA
| | - Mehmet Sen
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA.
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10
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Tvaroška I, Kozmon S, Kóňa J. Molecular Modeling Insights into the Structure and Behavior of Integrins: A Review. Cells 2023; 12:cells12020324. [PMID: 36672259 PMCID: PMC9856412 DOI: 10.3390/cells12020324] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/09/2023] [Accepted: 01/11/2023] [Indexed: 01/18/2023] Open
Abstract
Integrins are heterodimeric glycoproteins crucial to the physiology and pathology of many biological functions. As adhesion molecules, they mediate immune cell trafficking, migration, and immunological synapse formation during inflammation and cancer. The recognition of the vital roles of integrins in various diseases revealed their therapeutic potential. Despite the great effort in the last thirty years, up to now, only seven integrin-based drugs have entered the market. Recent progress in deciphering integrin functions, signaling, and interactions with ligands, along with advancement in rational drug design strategies, provide an opportunity to exploit their therapeutic potential and discover novel agents. This review will discuss the molecular modeling methods used in determining integrins' dynamic properties and in providing information toward understanding their properties and function at the atomic level. Then, we will survey the relevant contributions and the current understanding of integrin structure, activation, the binding of essential ligands, and the role of molecular modeling methods in the rational design of antagonists. We will emphasize the role played by molecular modeling methods in progress in these areas and the designing of integrin antagonists.
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Affiliation(s)
- Igor Tvaroška
- Institute of Chemistry, Slovak Academy of Sciences, Dúbravska cesta 9, 845 38 Bratislava, Slovakia
- Correspondence:
| | - Stanislav Kozmon
- Institute of Chemistry, Slovak Academy of Sciences, Dúbravska cesta 9, 845 38 Bratislava, Slovakia
- Medical Vision o. z., Záhradnícka 4837/55, 821 08 Bratislava, Slovakia
| | - Juraj Kóňa
- Institute of Chemistry, Slovak Academy of Sciences, Dúbravska cesta 9, 845 38 Bratislava, Slovakia
- Medical Vision o. z., Záhradnícka 4837/55, 821 08 Bratislava, Slovakia
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11
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Pang X, He X, Qiu Z, Zhang H, Xie R, Liu Z, Gu Y, Zhao N, Xiang Q, Cui Y. Targeting integrin pathways: mechanisms and advances in therapy. Signal Transduct Target Ther 2023; 8:1. [PMID: 36588107 PMCID: PMC9805914 DOI: 10.1038/s41392-022-01259-6] [Citation(s) in RCA: 176] [Impact Index Per Article: 176.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/14/2022] [Accepted: 11/21/2022] [Indexed: 01/03/2023] Open
Abstract
Integrins are considered the main cell-adhesion transmembrane receptors that play multifaceted roles as extracellular matrix (ECM)-cytoskeletal linkers and transducers in biochemical and mechanical signals between cells and their environment in a wide range of states in health and diseases. Integrin functions are dependable on a delicate balance between active and inactive status via multiple mechanisms, including protein-protein interactions, conformational changes, and trafficking. Due to their exposure on the cell surface and sensitivity to the molecular blockade, integrins have been investigated as pharmacological targets for nearly 40 years, but given the complexity of integrins and sometimes opposite characteristics, targeting integrin therapeutics has been a challenge. To date, only seven drugs targeting integrins have been successfully marketed, including abciximab, eptifibatide, tirofiban, natalizumab, vedolizumab, lifitegrast, and carotegrast. Currently, there are approximately 90 kinds of integrin-based therapeutic drugs or imaging agents in clinical studies, including small molecules, antibodies, synthetic mimic peptides, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, imaging agents, etc. A serious lesson from past integrin drug discovery and research efforts is that successes rely on both a deep understanding of integrin-regulatory mechanisms and unmet clinical needs. Herein, we provide a systematic and complete review of all integrin family members and integrin-mediated downstream signal transduction to highlight ongoing efforts to develop new therapies/diagnoses from bench to clinic. In addition, we further discuss the trend of drug development, how to improve the success rate of clinical trials targeting integrin therapies, and the key points for clinical research, basic research, and translational research.
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Affiliation(s)
- Xiaocong Pang
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Xu He
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Zhiwei Qiu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Hanxu Zhang
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Ran Xie
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Zhiyan Liu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Yanlun Gu
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Nan Zhao
- grid.411472.50000 0004 1764 1621Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034 Beijing, China ,grid.411472.50000 0004 1764 1621Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191 Beijing, China
| | - Qian Xiang
- Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034, Beijing, China. .,Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191, Beijing, China.
| | - Yimin Cui
- Department of Pharmacy, Peking University First Hospital, Xishiku Street, Xicheng District, 100034, Beijing, China. .,Institute of Clinical Pharmacology, Peking University First Hospital, Xueyuan Road 38, Haidian District, 100191, Beijing, China.
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12
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Integrin Conformational Dynamics and Mechanotransduction. Cells 2022; 11:cells11223584. [PMID: 36429013 PMCID: PMC9688440 DOI: 10.3390/cells11223584] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 11/04/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022] Open
Abstract
The function of the integrin family of receptors as central mediators of cell-extracellular matrix (ECM) and cell-cell adhesion requires a remarkable convergence of interactions and influences. Integrins must be anchored to the cytoskeleton and bound to extracellular ligands in order to provide firm adhesion, with force transmission across this linkage conferring tissue integrity. Integrin affinity to ligands is highly regulated by cell signaling pathways, altering affinity constants by 1000-fold or more, via a series of long-range conformational transitions. In this review, we first summarize basic, well-known features of integrin conformational states and then focus on new information concerning the impact of mechanical forces on these states and interstate transitions. We also discuss how these effects may impact mechansensitive cell functions and identify unanswered questions for future studies.
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13
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Flow cytometry analysis of CD11c-positive peripheral blood mononuclear cells in horses. Vet Immunol Immunopathol 2022; 253:110504. [DOI: 10.1016/j.vetimm.2022.110504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/03/2022] [Accepted: 10/16/2022] [Indexed: 11/23/2022]
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14
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Lin FY, Li J, Xie Y, Zhu J, Huong Nguyen TT, Zhang Y, Zhu J, Springer TA. A general chemical principle for creating closure-stabilizing integrin inhibitors. Cell 2022; 185:3533-3550.e27. [PMID: 36113427 PMCID: PMC9494814 DOI: 10.1016/j.cell.2022.08.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 07/07/2022] [Accepted: 08/04/2022] [Indexed: 01/26/2023]
Abstract
Integrins are validated drug targets with six approved therapeutics. However, small-molecule inhibitors to three integrins failed in late-stage clinical trials for chronic indications. Such unfavorable outcomes may in part be caused by partial agonism, i.e., the stabilization of the high-affinity, extended-open integrin conformation. Here, we show that the failed, small-molecule inhibitors of integrins αIIbβ3 and α4β1 stabilize the high-affinity conformation. Furthermore, we discovered a simple chemical feature present in multiple αIIbβ3 antagonists that stabilizes integrins in their bent-closed conformation. Closing inhibitors contain a polar nitrogen atom that stabilizes, via hydrogen bonds, a water molecule that intervenes between a serine residue and the metal in the metal-ion-dependent adhesion site (MIDAS). Expulsion of this water is a requisite for transition to the open conformation. This change in metal coordination is general to integrins, suggesting broad applicability of the drug-design principle to the integrin family, as validated with a distantly related integrin, α4β1.
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Affiliation(s)
- Fu-Yang Lin
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Jing Li
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Yonghua Xie
- School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, PRC
| | - Jianghai Zhu
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Thi Thu Huong Nguyen
- Blood Research Institute, Versiti, Milwaukee, WI 53226, USA; Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Yonghui Zhang
- School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, PRC.
| | - Jieqing Zhu
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA; Blood Research Institute, Versiti, Milwaukee, WI 53226, USA; Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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15
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Abstract
Single-pass transmembrane receptors (SPTMRs) represent a diverse group of integral membrane proteins that are involved in many essential cellular processes, including signal transduction, cell adhesion, and transmembrane transport of materials. Dysregulation of the SPTMRs is linked with many human diseases. Despite extensive efforts in past decades, the mechanisms of action of the SPTMRs remain incompletely understood. One major hurdle is the lack of structures of the full-length SPTMRs in different functional states. Such structural information is difficult to obtain by traditional structural biology methods such as X-ray crystallography and nuclear magnetic resonance (NMR). The recent rapid development of single-particle cryo-electron microscopy (cryo-EM) has led to an exponential surge in the number of high-resolution structures of integral membrane proteins, including SPTMRs. Cryo-EM structures of SPTMRs solved in the past few years have tremendously improved our understanding of how SPTMRs function. In this review, we will highlight these progresses in the structural studies of SPTMRs by single-particle cryo-EM, analyze important structural details of each protein involved, and discuss their implications on the underlying mechanisms. Finally, we also briefly discuss remaining challenges and exciting opportunities in the field.
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Affiliation(s)
- Kai Cai
- Departments of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75231, USA
| | - Xuewu Zhang
- Departments of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75231, USA
- Departments of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75231, USA
- Corresponding Author: Xuewu Zhang, Department of pharmacology, UT Southwestern Medical Center, Dallas, TX 75390, USA;
| | - Xiao-chen Bai
- Departments of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75231, USA
- Departments of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75231, USA
- Corresponding Author: Xiao-chen Bai, Department of Biophysics, UT Southwestern Medical Center, Dallas, TX 75390, USA;
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16
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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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17
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Goldsmith JA, DiVenere AM, Maynard JA, McLellan JS. Structural basis for non-canonical integrin engagement by Bordetella adenylate cyclase toxin. Cell Rep 2022; 40:111196. [PMID: 35977491 PMCID: PMC9416875 DOI: 10.1016/j.celrep.2022.111196] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 06/08/2022] [Accepted: 07/20/2022] [Indexed: 11/29/2022] Open
Abstract
Integrins are ubiquitous cell-surface heterodimers that are exploited by pathogens and toxins, including leukotoxins that target β2 integrins on phagocytes. The Bordetella adenylate cyclase toxin (ACT) uses the αMβ2 integrin as a receptor, but the structural basis for integrin binding and neutralization by antibodies is poorly understood. Here, we use cryoelectron microscopy to determine a 2.7 Å resolution structure of an ACT fragment bound to αMβ2. This structure reveals that ACT interacts with the headpiece and calf-2 of the αM subunit in a non-canonical manner specific to bent, inactive αMβ2. Neutralizing antibody epitopes map to ACT residues involved in αM binding, providing the basis for antibody-mediated attachment inhibition. Furthermore, binding to αMβ2 positions the essential ACT acylation sites, which are conserved among toxins exported by type I secretion systems, at the cell membrane. These findings reveal a structural mechanism for integrin-mediated attachment and explain antibody-mediated neutralization of ACT intoxication.
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Affiliation(s)
- Jory A Goldsmith
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Andrea M DiVenere
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jennifer A Maynard
- Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
| | - Jason S McLellan
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA.
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18
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Su Y, Iacob RE, Li J, Engen JR, Springer TA. Dynamics of integrin α5β1, fibronectin, and their complex reveal sites of interaction and conformational change. J Biol Chem 2022; 298:102323. [PMID: 35931112 PMCID: PMC9483561 DOI: 10.1016/j.jbc.2022.102323] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 07/26/2022] [Accepted: 07/27/2022] [Indexed: 12/04/2022] Open
Abstract
Integrin α5β1 mediates cell adhesion to the extracellular matrix by binding fibronectin (Fn). Selectivity for Fn by α5β1 is achieved through recognition of an RGD motif in the 10th type III Fn domain (Fn10) and the synergy site in the ninth type III Fn domain (Fn9). However, details of the interaction dynamics are unknown. Here, we compared synergy-site and Fn-truncation mutations for their α5β1-binding affinities and stabilities. We also interrogated binding of the α5β1 ectodomain headpiece fragment to Fn using hydrogen-deuterium exchange (HDX) mass spectrometry to probe binding sites and sites of integrin conformational change. Our results suggest the synergistic effect of Fn9 requires both specific residues and a folded domain. We found some residues considered important for synergy are required for stability. Additionally, we show decreases in fibronectin HDX are localized to a synergy peptide containing contacting residues in two β-strands, an intervening loop in Fn9, and the RGD-containing loop in Fn10, indicative of binding sites. We also identified binding sites in the α5-subunit β-propeller domain for the Fn9 synergy site and in the β1-subunit βI domain for Fn10 based on decreases in α5β1 HDX. Interestingly, the dominant effect of Fn binding was an increase in α5β1 deuterium exchange distributed over multiple sites that undergo changes in conformation or solvent accessibility and appear to be sites where energy is stored in the higher-energy, open-integrin conformation. Together, our results highlight regions important for α5β1 binding to Fn and dynamics associated with this interaction.
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Affiliation(s)
- Yang Su
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115
| | - Roxana E Iacob
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA 02115
| | - Jing Li
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115
| | - John R Engen
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA 02115
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital; Departments of Biological Chemistry and Molecular Pharmacology and of Pediatrics, Harvard Medical School, Boston, MA 02115.
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19
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Caliandro MF, Schmalbein F, Todesca LM, Mörgelin M, Rezaei M, Meißner J, Siepe I, Grosche J, Schwab A, Eble JA. A redox-dependent thiol-switch and a Ca 2+ binding site within the hinge region hierarchically depend on each other in α7β1 integrin regulation. Free Radic Biol Med 2022; 187:38-49. [PMID: 35605898 DOI: 10.1016/j.freeradbiomed.2022.05.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/17/2022] [Indexed: 11/23/2022]
Abstract
Integrin-mediated cell contacts with the extracellular matrix (ECM) are essential for cellular adhesion, force transmission, and migration. Several effectors, such as divalent cations and redox-active compounds, regulate ligand binding activities of integrins and influence their cellular functions. To study the role of the Ca2+ binding site within the hinge region of the integrin α7 subunit, we genetically abrogated it in the α7hiΔCa mutant. This mutant folded correctly, associated with the β1 subunit and was exposed on the cell surface, but showed reduced ligand binding and weaker cell adhesion to laminin-111. Thus, it resembles the α7hiΔSS mutant, in which the redox-regulated pair of cysteines, closeby to the Ca2+ binding site within the hinge, was abrogated. Comparing both mutants in adhesion strength and cell migration revealed that both Ca2+ complexation and redox-regulation within the hinge interdepend on each other. Moreover, protein-chemical analyses of soluble integrin ectodomains containing the same α7 hinge mutations suggest that integrin activation via the subunit α hinge is primed by the formation of the cysteine pair-based crosslinkage. Then, this allows Ca2+ complexation within the hinge, which is another essential step for integrin activation and ligand binding. Thus, the α hinge is an allosteric integrin regulation site, in which both effectors, Ca2+ and redox-active compounds, synergistically and hierarchically induce far-ranging conformational changes, such as the extension of the integrin ectodomain, resulting in integrin activation of ECM ligand binding and altered integrin-mediated cell functions.
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Affiliation(s)
- Michele F Caliandro
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Felix Schmalbein
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Luca Matteo Todesca
- University of Münster, Institute of Physiology II, Robert-Koch-Str. 27b, 48149, Münster, Germany
| | | | - Maryam Rezaei
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Juliane Meißner
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Isabel Siepe
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Julius Grosche
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany
| | - Albrecht Schwab
- University of Münster, Institute of Physiology II, Robert-Koch-Str. 27b, 48149, Münster, Germany
| | - Johannes A Eble
- University of Münster, Institute of Physiological Chemistry and Pathobiochemistry, Waldeyerstr. 15, 48149, Münster, Germany.
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20
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Integrin Regulators in Neutrophils. Cells 2022; 11:cells11132025. [PMID: 35805108 PMCID: PMC9266208 DOI: 10.3390/cells11132025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 02/01/2023] Open
Abstract
Neutrophils are the most abundant leukocytes in humans and are critical for innate immunity and inflammation. Integrins are critical for neutrophil functions, especially for their recruitment to sites of inflammation or infections. Integrin conformational changes during activation have been heavily investigated but are still not fully understood. Many regulators, such as talin, Rap1-interacting adaptor molecule (RIAM), Rap1, and kindlin, are critical for integrin activation and might be potential targets for integrin-regulating drugs in treating inflammatory diseases. In this review, we outline integrin activation regulators in neutrophils with a focus on the above critical regulators, as well as newly discovered modulators that are involved in integrin activation.
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21
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Jensen RK, Pedersen H, Lorentzen J, Laursen NS, Vorup-Jensen T, Andersen GR. Structural insights into the function-modulating effects of nanobody binding to the integrin receptor α Mβ 2. J Biol Chem 2022; 298:102168. [PMID: 35738398 PMCID: PMC9287160 DOI: 10.1016/j.jbc.2022.102168] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 06/15/2022] [Accepted: 06/16/2022] [Indexed: 01/12/2023] Open
Abstract
The integrin receptor αMβ2 mediates phagocytosis of complement-opsonized objects, adhesion to the extracellular matrix, and transendothelial migration of leukocytes. However, the mechanistic aspects of αMβ2 signaling upon ligand binding are unclear. Here, we present the first atomic structure of the human αMβ2 headpiece fragment in complex with the nanobody (Nb) hCD11bNb1 at a resolution of 3.2 Å. We show that the receptor headpiece adopts the closed conformation expected to exhibit low ligand affinity. The crystal structure indicates that in the R77H αM variant, associated with systemic lupus erythematosus, the modified allosteric relationship between ligand binding and integrin outside–inside signaling is due to subtle conformational effects transmitted over a distance of 40 Å. Furthermore, we found the Nb binds to the αI domain of the αM subunit in an Mg2+-independent manner with low nanomolar affinity. Biochemical and biophysical experiments with purified proteins demonstrated that the Nb acts as a competitive inhibitor through steric hindrance exerted on the thioester domain of complement component iC3b attempting to bind the αM subunit. Surprisingly, we show that the Nb stimulates the interaction of cell-bound αMβ2 with iC3b, suggesting that it may represent a novel high-affinity proteinaceous αMβ2-specific agonist. Taken together, our data suggest that the iC3b–αMβ2 complex may be more dynamic than predicted from the crystal structure of the core complex. We propose a model based on the conformational spectrum of the receptor to reconcile these observations regarding the functional consequences of hCD11bNb1 binding to αMβ2.
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Affiliation(s)
- Rasmus K Jensen
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Henrik Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Josefine Lorentzen
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
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22
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Pourahmadi M, Shirdel A, Jamshidi N, Jafarian V, Khalifeh K. Comparing similar versions of a connecting helix on the structure of Chondroitinase ABC I. Enzyme Microb Technol 2022; 160:110073. [DOI: 10.1016/j.enzmictec.2022.110073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/20/2022] [Accepted: 06/02/2022] [Indexed: 11/16/2022]
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23
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Cappenberg A, Kardell M, Zarbock A. Selectin-Mediated Signaling-Shedding Light on the Regulation of Integrin Activity in Neutrophils. Cells 2022; 11:cells11081310. [PMID: 35455989 PMCID: PMC9025114 DOI: 10.3390/cells11081310] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/08/2022] [Accepted: 04/12/2022] [Indexed: 02/04/2023] Open
Abstract
As a consequence of tissue injury or infection, neutrophils are recruited in a stepwise recruitment process from the bloodstream into the surrounding tissue. Selectins are a family of adhesion molecules comprised of L-, E-, and P-selectin. Differences in expression patterns, protein structure, and ligand binding characteristics mediate distinct functions of each selectin. Interactions of selectins and their counter-receptors mediate the first contact of neutrophils with the endothelium, as well as subsequent neutrophil rolling along the endothelial surface. For efficient neutrophil recruitment, activation of β2-integrins on the cell surface is essential. Integrin activation can be elicited via selectin- as well as chemokine-mediated inside-out signaling resulting in integrin conformational changes and clustering. Dysregulation of selectin-induced integrin activation on neutrophils is involved in the development of severe pathological disease conditions including leukocyte adhesion deficiency (LAD) syndromes in humans. Here, we review molecular mechanisms involved in selectin-mediated signaling pathways in neutrophils and their impact on integrin activation, neutrophil recruitment, and inflammatory diseases.
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24
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The crystal structure of iC3b-CR3 αI reveals a modular recognition of the main opsonin iC3b by the CR3 integrin receptor. Nat Commun 2022; 13:1955. [PMID: 35413960 PMCID: PMC9005620 DOI: 10.1038/s41467-022-29580-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 03/15/2022] [Indexed: 12/27/2022] Open
Abstract
Complement activation on cell surfaces leads to the massive deposition of C3b, iC3b, and C3dg, the main complement opsonins. Recognition of iC3b by complement receptor type 3 (CR3) fosters pathogen opsonophagocytosis by macrophages and the stimulation of adaptive immunity by complement-opsonized antigens. Here, we present the crystallographic structure of the complex between human iC3b and the von Willebrand A inserted domain of the α chain of CR3 (αI). The crystal contains two composite interfaces for CR3 αI, encompassing distinct sets of contiguous macroglobulin (MG) domains on the C3c moiety, MG1-MG2 and MG6-MG7 domains. These composite binding sites define two iC3b-CR3 αI complexes characterized by specific rearrangements of the two semi-independent modules, C3c moiety and TED domain. Furthermore, we show the structure of iC3b in a physiologically-relevant extended conformation. Based on previously available data and novel insights reported herein, we propose an integrative model that reconciles conflicting facts about iC3b structure and function and explains the molecular basis for iC3b selective recognition by CR3 on opsonized surfaces. Complement activation on foreign cell surfaces leads to the generation of complement opsonins, which activate complement receptor type 3 (CR3) and pathogen clearance by macrophages. Here, the authors reveal structural basis of the interaction between human opsonin iC3b and the von Willebrand A inserted domain of the α chain of CR3.
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25
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Analysis of Integrin α IIb Subunit Dynamics Reveals Long-Range Effects of Missense Mutations on Calf Domains. Int J Mol Sci 2022; 23:ijms23020858. [PMID: 35055046 PMCID: PMC8776176 DOI: 10.3390/ijms23020858] [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: 11/29/2021] [Revised: 12/23/2021] [Accepted: 12/30/2021] [Indexed: 11/17/2022] Open
Abstract
Integrin αIIbβ3, a glycoprotein complex expressed at the platelet surface, is involved in platelet aggregation and contributes to primary haemostasis. Several integrin αIIbβ3 polymorphisms prevent the aggregation that causes haemorrhagic syndromes, such as Glanzmann thrombasthenia (GT). Access to 3D structure allows understanding the structural effects of polymorphisms related to GT. In a previous analysis using Molecular Dynamics (MD) simulations of αIIbCalf-1 domain structure, it was observed that GT associated with single amino acid variation affects distant loops, but not the mutated position. In this study, experiments are extended to Calf-1, Thigh, and Calf-2 domains. Two loops in Calf-2 are unstructured and therefore are modelled expertly using biophysical restraints. Surprisingly, MD revealed the presence of rigid zones in these loops. Detailed analysis with structural alphabet, the Proteins Blocks (PBs), allowed observing local changes in highly flexible regions. The variant P741R located at C-terminal of Calf-1 revealed that the Calf-2 presence did not affect the results obtained with isolated Calf-1 domain. Simulations for Calf-1 + Calf-2, and Thigh + Calf-1 variant systems are designed to comprehend the impact of five single amino acid variations in these domains. Distant conformational changes are observed, thus highlighting the potential role of allostery in the structural basis of GT.
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26
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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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27
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Arimori T, Miyazaki N, Mihara E, Takizawa M, Taniguchi Y, Cabañas C, Sekiguchi K, Takagi J. Structural mechanism of laminin recognition by integrin. Nat Commun 2021; 12:4012. [PMID: 34188035 PMCID: PMC8241838 DOI: 10.1038/s41467-021-24184-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 06/04/2021] [Indexed: 02/06/2023] Open
Abstract
Recognition of laminin by integrin receptors is central to the epithelial cell adhesion to basement membrane, but the structural background of this molecular interaction remained elusive. Here, we report the structures of the prototypic laminin receptor α6β1 integrin alone and in complex with three-chain laminin-511 fragment determined via crystallography and cryo-electron microscopy, respectively. The laminin-integrin interface is made up of several binding sites located on all five subunits, with the laminin γ1 chain C-terminal portion providing focal interaction using two carboxylate anchor points to bridge metal-ion dependent adhesion site of integrin β1 subunit and Asn189 of integrin α6 subunit. Laminin α5 chain also contributes to the affinity and specificity by making electrostatic interactions with large surface on the β-propeller domain of α6, part of which comprises an alternatively spliced X1 region. The propeller sheet corresponding to this region shows unusually high mobility, suggesting its unique role in ligand capture.
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Affiliation(s)
- Takao Arimori
- grid.136593.b0000 0004 0373 3971Laboratory for Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka Japan
| | - Naoyuki Miyazaki
- grid.136593.b0000 0004 0373 3971Laboratory for Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka Japan ,grid.20515.330000 0001 2369 4728Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, Japan
| | - Emiko Mihara
- grid.136593.b0000 0004 0373 3971Laboratory for Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka Japan
| | - Mamoru Takizawa
- grid.136593.b0000 0004 0373 3971Division of Matrixome Research and Application, Institute for Protein Research, Osaka University, Suita, Osaka Japan
| | - Yukimasa Taniguchi
- grid.136593.b0000 0004 0373 3971Division of Matrixome Research and Application, Institute for Protein Research, Osaka University, Suita, Osaka Japan
| | - Carlos Cabañas
- grid.465524.4Cell-cell Communication & Inflammation Unit, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain ,grid.4795.f0000 0001 2157 7667Department of Immunology, Ophthalmology and Otorhinolaryngology (IOO), Faculty of Medicine, Universidad Complutense de Madrid, Madrid, Spain ,grid.144756.50000 0001 1945 5329Instituto de Investigación Sanitaria Hospital 12 Octubre (i+12), Madrid, Spain
| | - Kiyotoshi Sekiguchi
- grid.136593.b0000 0004 0373 3971Division of Matrixome Research and Application, Institute for Protein Research, Osaka University, Suita, Osaka Japan
| | - Junichi Takagi
- grid.136593.b0000 0004 0373 3971Laboratory for Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka Japan
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Sun H, Hu L, Fan Z. β2 integrin activation and signal transduction in leukocyte recruitment. Am J Physiol Cell Physiol 2021; 321:C308-C316. [PMID: 34133240 DOI: 10.1152/ajpcell.00560.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Leukocyte recruitment is a critical step in the pathogenesis of inflammatory and immunological responses. Cell adhesion molecules (CAMs) are involved in controlling cell movements and the recruitment process, and the integrin family of CAMs plays a key role. During cell movement, integrin function is dynamically and precisely regulated. However, this balance might be broken under pathological conditions. Thus, the functional regulation and molecular mechanisms of integrins related to diseases are often a focus of research. Integrin β2 is one of the most commonly expressed integrins in leukocytes that mediate leukocyte adhesion and migration, and it plays an important role in immune responses and inflammation. In this review, we focus on specific functions of integrin β2 in leukocyte recruitment, the conformational changes and signal transduction of integrin β2 activation, the similarities between murine and human factors, and how new insights into these processes can inform future therapies for inflammation and immune diseases.
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Affiliation(s)
- Hao Sun
- Department of Medicine, University of California San Diego, La Jolla, California
| | - Liang Hu
- Cardiovascular Institute of Zhengzhou University, Department of Cardiology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health, Farmington, Connecticut
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29
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CD11c regulates hematopoietic stem and progenitor cells under stress. Blood Adv 2021; 4:6086-6097. [PMID: 33351105 DOI: 10.1182/bloodadvances.2020002504] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 11/09/2020] [Indexed: 12/28/2022] Open
Abstract
β2 integrins are well-known leukocyte adhesion molecules consisting of 4 members: CD11a-d. Their known biological functions range widely from leukocyte recruitment, phagocytosis, to immunological synapse formation, but the studies have been primarily focused on CD11a and CD11b. CD11c is 1 of the 4 members and is extremely homologous to CD11b. It has been well known as a dendritic cell marker, but the characterization of its function has been limited. We found that CD11c was expressed on the short-term hematopoietic stem cells and multipotent progenitor cells. The lack of CD11c did not affect the number of hematopoietic stem and progenitor cells (HSPCs) in healthy CD11c knockout mice. Different from other β2 integrin members, however, CD11c deficiency was associated with increased apoptosis and significant loss of HSPCs in sepsis and bone marrow transplantation. Although integrins are generally known for their overlapping and redundant roles, we showed that CD11c had a distinct role of regulating the expansion of HSPCs under stress. This study shows that CD11c, a well-known dendritic cell marker, is expressed on HSPCs and serves as their functional regulator. CD11c deficiency leads to the loss of HSPCs via apoptosis in sepsis and bone marrow transplantation.
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30
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Sun H, Zhi K, Hu L, Fan Z. The Activation and Regulation of β2 Integrins in Phagocytes and Phagocytosis. Front Immunol 2021; 12:633639. [PMID: 33868253 PMCID: PMC8044391 DOI: 10.3389/fimmu.2021.633639] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 03/11/2021] [Indexed: 01/10/2023] Open
Abstract
Phagocytes, which include neutrophils, monocytes, macrophages, and dendritic cells, protect the body by removing foreign particles, bacteria, and dead or dying cells. Phagocytic integrins are greatly involved in the recognition of and adhesion to specific antigens on cells and pathogens during phagocytosis as well as the recruitment of immune cells. β2 integrins, including αLβ2, αMβ2, αXβ2, and αDβ2, are the major integrins presented on the phagocyte surface. The activation of β2 integrins is essential to the recruitment and phagocytic function of these phagocytes and is critical for the regulation of inflammation and immune defense. However, aberrant activation of β2 integrins aggravates auto-immune diseases, such as psoriasis, arthritis, and multiple sclerosis, and facilitates tumor metastasis, making them double-edged swords as candidates for therapeutic intervention. Therefore, precise regulation of phagocyte activities by targeting β2 integrins should promote their host defense functions with minimal side effects on other cells. Here, we reviewed advances in the regulatory mechanisms underlying β2 integrin inside-out signaling, as well as the roles of β2 integrin activation in phagocyte functions.
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Affiliation(s)
- Hao Sun
- Department of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Kangkang Zhi
- Department of Vascular Surgery, Changzheng Hospital, Shanghai, China
| | - Liang Hu
- Department of Cardiology, Cardiovascular Institute of Zhengzhou University, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health, Farmington, CT, United States
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31
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Cai C, Sun H, Hu L, Fan Z. Visualization of integrin molecules by fluorescence imaging and techniques. ACTA ACUST UNITED AC 2021; 45:229-257. [PMID: 34219865 PMCID: PMC8249084 DOI: 10.32604/biocell.2021.014338] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Integrin molecules are transmembrane αβ heterodimers involved in cell adhesion, trafficking, and signaling. Upon activation, integrins undergo dynamic conformational changes that regulate their affinity to ligands. The physiological functions and activation mechanisms of integrins have been heavily discussed in previous studies and reviews, but the fluorescence imaging techniques -which are powerful tools for biological studies- have not. Here we review the fluorescence labeling methods, imaging techniques, as well as Förster resonance energy transfer assays used to study integrin expression, localization, activation, and functions.
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Affiliation(s)
- Chen Cai
- Department of Immunology, School of Medicine, UConn Health, Farmington, 06030, USA
| | - Hao Sun
- Department of Medicine, University of California, San Diego, La Jolla, 92093, USA
| | - Liang Hu
- Cardiovascular Institute of Zhengzhou University, Department of Cardiology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450051, China
| | - Zhichao Fan
- Department of Immunology, School of Medicine, UConn Health, Farmington, 06030, USA
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32
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Herbert A. Complement controls the immune synapse and tumors control complement. J Immunother Cancer 2020; 8:jitc-2020-001712. [PMID: 33323465 PMCID: PMC7745530 DOI: 10.1136/jitc-2020-001712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2020] [Indexed: 12/02/2022] Open
Abstract
The synapses between immune cells and their targets are 150 Å wide. They regulate immune cell responses (IRs) to cognate antigens. Here, I outline a potential mechanism for self-nonself discrimination based on the C3d and iC3b proteolytic fragments of complement protein C3. The proposed C3 checkpoint works through complement receptor 3 (CR3), which binds both C3d and iC3b. The CR3 conformations involved differ; the bent, cis-acting CR3 engages C3d, activating the immune cell expressing CR3; the extended, transacting CR3 conformer binds iC3b on another cell, inhibiting IRs. The CR3 complexes formed with iC3b and C3d vary greatly in size. Only bound C3d is small enough to fit within the synapse. It stimulates IRs by countering the inhibitory signals that iC3b generates at the synapse edge. The competition between C3d and iC3b dynamically determines whether or not an immune cell activates. Host cells use regulators of complement activation (RCA) to coat themselves with iC3b, silencing IRs against self by preventing synapse formation. Tumors exploit this process by overexpressing C3 and RCA to masquerade as ‘super-self’, with iC3b masking neoantigens. Enhancing synapse formation by specifically labeling cancer cells as nonself with targeted C3d therapeutics offers a new strategy for boosting tumor-specific immunity.
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Affiliation(s)
- Alan Herbert
- Discovery, InsideOutBio Inc, Charlestown, Massachusetts, USA
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33
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Mao D, Lü S, Zhang X, Long M. Mechanically Regulated Outside-In Activation of an I-Domain-Containing Integrin. Biophys J 2020; 119:966-977. [PMID: 32814058 DOI: 10.1016/j.bpj.2020.07.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 07/18/2020] [Accepted: 07/27/2020] [Indexed: 10/23/2022] Open
Abstract
Integrins are heterodimeric transmembrane proteins that mediate cellular adhesion and bidirectional mechanotransductions through their conformational allostery. The allosteric pathway of an I-domain-containing integrin remains unclear because of its complexity and lack of effective experiments. For a typical I-domain-containing integrin αXβ2, molecular dynamics simulations were employed here to investigate the conformational dynamics in the first two steps of outside-in activation, the bindings of both the external and internal ligands. Results showed that the internal ligand binding is a prerequisite to the allosteric transmission from the α- to β-subunits and the exertion of external force to integrin-ligand complex. The opening state of αI domain with downward movement and lower half unfolding of α7-helix ensures the stable intersubunit conformational transmission through external ligand binding first and internal ligand binding later. Reverse binding order induces a, to our knowledge, novel but unstable swingout of β-subunit Hybrid domain with the retained close states of both αI and βI domains. Prebinding of external ligand greatly facilitates the following internal ligand binding and vice versa. These simulations furthered the understanding in the outside-in activation of I-domain-containing integrins from the viewpoint of internal allosteric pathways.
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Affiliation(s)
- Debin Mao
- Center of Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory), Beijing Key Laboratory of Engineered Construction and Mechanobiology, and CAS Center for Excellence in Complex System Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Shouqin Lü
- Center of Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory), Beijing Key Laboratory of Engineered Construction and Mechanobiology, and CAS Center for Excellence in Complex System Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China.
| | - Xiao Zhang
- Center of Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory), Beijing Key Laboratory of Engineered Construction and Mechanobiology, and CAS Center for Excellence in Complex System Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Mian Long
- Center of Biomechanics and Bioengineering, Key Laboratory of Microgravity (National Microgravity Laboratory), Beijing Key Laboratory of Engineered Construction and Mechanobiology, and CAS Center for Excellence in Complex System Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China.
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34
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Ghosh DK, Ranjan A. The metastable states of proteins. Protein Sci 2020; 29:1559-1568. [PMID: 32223005 PMCID: PMC7314396 DOI: 10.1002/pro.3859] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/23/2020] [Accepted: 03/24/2020] [Indexed: 12/26/2022]
Abstract
The intriguing process of protein folding comprises discrete steps that stabilize the protein molecules in different conformations. The metastable state of protein is represented by specific conformational characteristics, which place the protein in a local free energy minimum state of the energy landscape. The native-to-metastable structural transitions are governed by transient or long-lived thermodynamic and kinetic fluctuations of the intrinsic interactions of the protein molecules. Depiction of the structural and functional properties of metastable proteins is not only required to understand the complexity of folding patterns but also to comprehend the mechanisms of anomalous aggregation of different proteins. In this article, we review the properties of metastable proteins in context of their stability and capability of undergoing atypical aggregation in physiological conditions.
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Affiliation(s)
- Debasish Kumar Ghosh
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and DiagnosticsUppal, HyderabadTelanganaIndia
| | - Akash Ranjan
- Computational and Functional Genomics Group, Centre for DNA Fingerprinting and DiagnosticsUppal, HyderabadTelanganaIndia
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35
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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: 43] [Impact Index Per Article: 10.8] [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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36
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Bednarczyk M, Stege H, Grabbe S, Bros M. β2 Integrins-Multi-Functional Leukocyte Receptors in Health and Disease. Int J Mol Sci 2020; 21:E1402. [PMID: 32092981 PMCID: PMC7073085 DOI: 10.3390/ijms21041402] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/11/2020] [Accepted: 02/14/2020] [Indexed: 12/25/2022] Open
Abstract
β2 integrins are heterodimeric surface receptors composed of a variable α (CD11a-CD11d) and a constant β (CD18) subunit and are specifically expressed by leukocytes. The α subunit defines the individual functional properties of the corresponding β2 integrin, but all β2 integrins show functional overlap. They mediate adhesion to other cells and to components of the extracellular matrix (ECM), orchestrate uptake of extracellular material like complement-opsonized pathogens, control cytoskeletal organization, and modulate cell signaling. This review aims to delineate the tremendous role of β2 integrins for immune functions as exemplified by the phenotype of LAD-I (leukocyte adhesion deficiency 1) patients that suffer from strong recurrent infections. These immune defects have been largely attributed to impaired migratory and phagocytic properties of polymorphonuclear granulocytes. The molecular base for this inherited disease is a functional impairment of β2 integrins due to mutations within the CD18 gene. LAD-I patients are also predisposed for autoimmune diseases. In agreement, polymorphisms within the CD11b gene have been associated with autoimmunity. Consequently, β2 integrins have received growing interest as targets in the treatment of autoimmune diseases. Moreover, β2 integrin activity on leukocytes has been implicated in tumor development.
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Affiliation(s)
| | | | | | - Matthias Bros
- Department of Dermatology, University Medical Center Mainz, Langenbeckstraße 1, 55131 Mainz, Germany; (M.B.); (H.S.); (S.G.)
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37
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Zheng Y, Leftheris K. Insights into Protein–Ligand Interactions in Integrin Complexes: Advances in Structure Determinations. J Med Chem 2020; 63:5675-5696. [DOI: 10.1021/acs.jmedchem.9b01869] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Yajun Zheng
- Pliant Therapeutics, South San Francisco, California 94080, United States
| | - Katerina Leftheris
- Pliant Therapeutics, South San Francisco, California 94080, United States
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38
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Juul-Madsen K, Qvist P, Bendtsen KL, Langkilde AE, Vestergaard B, Howard KA, Dehesa-Etxebeste M, Paludan SR, Andersen GR, Jensen PH, Otzen DE, Romero-Ramos M, Vorup-Jensen T. Size-Selective Phagocytic Clearance of Fibrillar α-Synuclein through Conformational Activation of Complement Receptor 4. THE JOURNAL OF IMMUNOLOGY 2020; 204:1345-1361. [PMID: 31969389 DOI: 10.4049/jimmunol.1900494] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 12/18/2019] [Indexed: 12/19/2022]
Abstract
Aggregation of α-synuclein (αSN) is an important histological feature of Parkinson disease. Recent studies showed that the release of misfolded αSN from human and rodent neurons is relevant to the progression and spread of αSN pathology. Little is known, however, about the mechanisms responsible for clearance of extracellular αSN. This study found that human complement receptor (CR) 4 selectively bound fibrillar αSN, but not monomeric species. αSN is an abundant protein in the CNS, which potentially could overwhelm clearance of cytotoxic αSN species. The selectivity of CR4 toward binding fibrillar αSN consequently adds an important αSN receptor function for maintenance of brain homeostasis. Based on the recently solved structures of αSN fibrils and the known ligand preference of CR4, we hypothesize that the parallel monomer stacking in fibrillar αSN creates a known danger-associated molecular pattern of stretches of anionic side chains strongly bound by CR4. Conformational change in the receptor regulated tightly clearance of fibrillar αSN by human monocytes. The induced change coupled concomitantly with phagolysosome formation. Data mining of the brain transcriptome in Parkinson disease patients supported CR4 as an active αSN clearance mechanism in this disease. Our results associate an important part of the innate immune system, namely complement receptors, with the central molecular mechanisms of CNS protein aggregation in neurodegenerative disorders.
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Affiliation(s)
- Kristian Juul-Madsen
- Biophysical Immunology Laboratory, Aarhus University, DK-8000 Aarhus C, Denmark.,Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Per Qvist
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.,iPSYCH, The Lundbeck Foundation Initiative for Integrative Psychiatric Research, Aarhus University, DK-8000 Aarhus C, Denmark.,iSEQ, Centre for Integrative Sequencing, Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Kirstine L Bendtsen
- Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Annette E Langkilde
- Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Bente Vestergaard
- Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark
| | - Kenneth A Howard
- Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Martxel Dehesa-Etxebeste
- Neuroscience Area, Biodonostia Research Institute, 20014 Donostia, San Sebastian, Spain.,CIBERNED, Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Søren R Paludan
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Gregers Rom Andersen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Poul Henning Jensen
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.,DANDRITE-Danish Research Institute of Translational Neuroscience, Aarhus University, DK-8000 Aarhus C, Denmark; and
| | - Daniel E Otzen
- Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Marina Romero-Ramos
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.,DANDRITE-Danish Research Institute of Translational Neuroscience, Aarhus University, DK-8000 Aarhus C, Denmark; and.,NEURODIN AU IDEAS Center, Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Thomas Vorup-Jensen
- Biophysical Immunology Laboratory, Aarhus University, DK-8000 Aarhus C, Denmark; .,Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.,Interdisciplinary Nanoscience Center, Aarhus University, DK-8000 Aarhus C, Denmark.,NEURODIN AU IDEAS Center, Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
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39
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Regulation of cell adhesion: a collaborative effort of integrins, their ligands, cytoplasmic actors, and phosphorylation. Q Rev Biophys 2019; 52:e10. [PMID: 31709962 DOI: 10.1017/s0033583519000088] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Integrins are large heterodimeric type 1 membrane proteins expressed in all nucleated mammalian cells. Eighteen α-chains and eight β-chains can combine to form 24 different integrins. They are cell adhesion proteins, which bind to a large variety of cellular and extracellular ligands. Integrins are required for cell migration, hemostasis, translocation of cells out from the blood stream and further movement into tissues, but also for the immune response and tissue morphogenesis. Importantly, integrins are not usually active as such, but need activation to become adhesive. Integrins are activated by outside-in activation through integrin ligand binding, or by inside-out activation through intracellular signaling. An important question is how integrin activity is regulated, and this topic has recently drawn much attention. Changes in integrin affinity for ligand binding are due to allosteric structural alterations, but equally important are avidity changes due to integrin clustering in the plane of the plasma membrane. Recent studies have partially solved how integrin cell surface structures change during activation. The integrin cytoplasmic domains are relatively short, but by interacting with a variety of cytoplasmic proteins in a regulated manner, the integrins acquire a number of properties important not only for cell adhesion and movement, but also for cellular signaling. Recent work has shown that specific integrin phosphorylations play pivotal roles in the regulation of integrin activity. Our purpose in this review is to integrate the present knowledge to enable an understanding of how cell adhesion is dynamically regulated.
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40
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Abstract
Integrins are heterodimeric cell surface receptors ensuring the mechanical connection between cells and the extracellular matrix. In addition to the anchorage of cells to the extracellular matrix, these receptors have critical functions in intracellular signaling, but are also taking center stage in many physiological and pathological conditions. In this review, we provide some historical, structural, and physiological notes so that the diverse functions of these receptors can be appreciated and put into the context of the emerging field of mechanobiology. We propose that the exciting journey of the exploration of these receptors will continue for at least another new generation of researchers.
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Affiliation(s)
- Michael Bachmann
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Sampo Kukkurainen
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Vesa P Hytönen
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
| | - Bernhard Wehrle-Haller
- Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire , Geneva , Switzerland ; and Faculty of Medicine and Health Technology, Tampere University, and Fimlab Laboratories , Tampere , Finland
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41
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Addressing the Compartmentalization of Specific Integrin Heterodimers in Mouse Sperm. Int J Mol Sci 2019; 20:ijms20051004. [PMID: 30813527 PMCID: PMC6429177 DOI: 10.3390/ijms20051004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 02/21/2019] [Accepted: 02/21/2019] [Indexed: 11/17/2022] Open
Abstract
Integrins are transmembrane cell receptors involved in two crucial mechanisms for successful fertilization, namely, mammalian intracellular signaling and cell adhesion. Integrins α6β4, α3β1 and α6β1 are three major laminin receptors expressed on the surface of mammalian cells including gametes, and the presence of individual integrin subunits α3, α6, β1 and β4 has been previously detected in mammalian sperm. However, to date, proof of the existence of individual heterodimer pairs in sperm and their detailed localization is missing. The major conclusion of this study is evidence that the β4 integrin subunit is expressed in mouse sperm and that it pairs with subunit α6; additionally, there is a detailed identification of integrin heterodimer pairs across individual membranes in an intact mouse sperm head. We also demonstrate the existence of β4 integrin mRNAs in round spermatids and spermatogonia by q-RT-PCR, which was further supported by sequencing the PCR products. Using super-resolution microscopy accompanied by colocalization analysis, we located integrin subunits as follows: α6/β4-inner apical acrosomal membrane and equatorial segment; α3, α6/β1, β4-plasma membrane overlaying the apical acrosome; and α3/β1-outer acrosomal membrane. The existence of α6β4, α3β1 and α6β1 heterodimers was further confirmed by proximity ligation assay (PLA). In conclusion, we delivered detailed characterization of α3, α6, β1 and β4 integrin subunits, showing their presence in distinct compartments of the intact mouse sperm head. Moreover, we identified sperm-specific localization for heterodimers α6β4, α3β1 and α6β1, and their membrane compartmentalization and the presented data show a complexity of membranes overlaying specialized microdomain structures in the sperm head. Their different protein compositions of these individual membrane rafts may play a specialized role, based on their involvement in sperm-epithelium and sperm-egg interaction.
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Cis interaction between sialylated FcγRIIA and the αI-domain of Mac-1 limits antibody-mediated neutrophil recruitment. Nat Commun 2018; 9:5058. [PMID: 30498196 PMCID: PMC6265255 DOI: 10.1038/s41467-018-07506-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 11/07/2018] [Indexed: 12/14/2022] Open
Abstract
Vascular-deposited IgG immune complexes promote neutrophil recruitment, but how this process is regulated is still unclear. Here we show that the CD18 integrin Mac-1, in its bent state, interacts with the IgG receptor FcγRIIA in cis to reduce the affinity of FcγRIIA for IgG and inhibit FcγRIIA-mediated neutrophil recruitment under flow. The Mac-1 rs1143679 lupus-risk variant reverses Mac-1 inhibition of FcγRIIA, as does a Mac-1 ligand and a mutation in Mac-1’s ligand binding αI-domain. Sialylated complex glycans on FcγRIIA interact with the αI-domain via divalent cations, and this interaction is required for FcγRIIA inhibition by Mac-1. Human neutrophils deficient in CD18 integrins exhibit augmented FcγRIIA-dependent recruitment to IgG-coated endothelium. In mice, CD18 integrins on neutrophils dampen IgG-mediated neutrophil accumulation in the kidney. In summary, cis interaction between sialylated FcγRIIA and the αI-domain of Mac-1 alters the threshold for IgG-mediated neutrophil recruitment. A disruption of this interaction may increase neutrophil influx in autoimmune diseases. Deposited immune complexes (IC) promote neutrophil recruitment, but the fine tuning of this process is still unclear. Here the authors show that the cis interaction of the IC receptor, FcγRIIA and CD18 integrin, Mac-1, on the neutrophil surface modulates neutrophil adhesion, with FcγRIIA sialylation specifically implicated in this interaction.
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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: 77] [Impact Index Per Article: 12.8] [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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Zhou D, Thinn AMM, Zhao Y, Wang Z, Zhu J. Structure of an extended β 3 integrin. Blood 2018; 132:962-972. [PMID: 30018079 PMCID: PMC6117741 DOI: 10.1182/blood-2018-01-829572] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 07/10/2018] [Indexed: 12/23/2022] Open
Abstract
Cells use adhesion receptor integrins to communicate with their surroundings. Integrin activation and cellular signaling are coupled with change from bent to extended conformation. β3 integrins, including αIIbβ3, which is essential for the function of platelets in hemostasis and thrombosis, and αVβ3, which plays multiple roles in diverse cell types, have been prototypes in understanding integrin structure and function. Despite extensive structural studies, a high-resolution integrin structure in an extended conformation remains to be determined. The human β3 Leu33Pro polymorphism, located at the PSI domain, defines human platelet-specific alloantigens 1a and 1b (HPA-1a/b), immune response to which is a cause of posttransfusion purpura and fetal/neonatal alloimmune thrombocytopenia. Leu33Pro substitution has also been suggested to be a risk factor for thrombosis. Here we report the crystal structure of the β3 headpiece in either Leu33 or Pro33 form, both of which reveal intermediate and fully extended conformations coexisting in 1 crystal. These were used to build high-resolution structures of full-length β3 integrin in the intermediate and fully extended states, agreeing well with the corresponding conformations observed by electron microscopy. Our structures reveal how β3 integrin becomes extended at its β-knee region and how the flexibility of β-leg domains is determined. In addition, our structures reveal conformational changes of the PSI and I-EGF1 domains upon β3 extension, which may affect the binding of conformation-dependent anti-HPA-1a alloantibodies. Our structural and functional data show that Leu33Pro substitution does not directly alter the conformation or ligand binding of β3 integrin.
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Affiliation(s)
- Dongwen Zhou
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
| | - Aye Myat Myat Thinn
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI; and
| | - Yan Zhao
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Physiology, School of Basic Medical Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Zhengli Wang
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
| | - Jieqing Zhu
- Blood Research Institute, BloodCenter of Wisconsin, part of Versiti, Milwaukee, WI
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, WI; and
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Miyazaki N, Iwasaki K, Takagi J. A systematic survey of conformational states in β1 and β4 integrins using negative-stain electron microscopy. J Cell Sci 2018; 131:jcs.216754. [PMID: 29700202 DOI: 10.1242/jcs.216754] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/19/2018] [Indexed: 01/23/2023] Open
Abstract
Structural analyses of β2 and β3 integrins have revealed that they generally assume a compact bent conformation in the resting state and undergo a global conformational transition involving extension during upregulation of ligand affinity, collectively called the 'switchblade model'. This hypothesis, however, has not been extensively tested for other classes of integrins. We prepared a set of recombinant integrin ectodomain fragments including αvβ3, α2β1, α3β1, α5β1, α6β1 and α6β4, and used negative-stain electron microscopy to examine their structures under various conditions. In contrast to αvβ3 integrin, which exhibited a severely bent conformation in low-affinity 5 mM Ca2+ conditions, all β1 integrin heterodimers displayed a mixed population of half-bent to fully extended conformations. Moreover, they did not undergo significant conformational change upon activation by Mn2+ Integrin α6β4 was even more resistant to conformational regulation, showing a completely extended structure regardless of the buffer conditions. These results suggest that the mechanisms of conformational regulation of integrins are more diverse and complex than previously thought, requiring more experimental scrutiny for each integrin subfamily member.
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Affiliation(s)
- Naoyuki Miyazaki
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kenji Iwasaki
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Junichi Takagi
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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46
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Sen M, Koksal AC, Yuki K, Wang J, Springer TA. Ligand- and cation-induced structural alterations of the leukocyte integrin LFA-1. J Biol Chem 2018; 293:6565-6577. [PMID: 29507098 DOI: 10.1074/jbc.ra117.000710] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/12/2018] [Indexed: 01/27/2023] Open
Abstract
In αI integrins, including leukocyte function-associated antigen 1 (LFA-1), ligand-binding function is delegated to the αI domain, requiring extra steps in the relay of signals that activate ligand binding and coordinate it with cytoplasmic signals. Crystal structures reveal great variation in orientation between the αI domain and the remainder of the integrin head. Here, we investigated the mechanisms involved in signal relay to the αI domain, including whether binding of the ligand intercellular adhesion molecule-1 (ICAM-1) to the αI domain is linked to headpiece opening and engenders a preferred αI domain orientation. Using small-angle X-ray scattering and negative-stain EM, we define structures of ICAM-1, LFA-1, and their complex, and the effect of activation by Mn2+ Headpiece opening was substantially stabilized by substitution of Mg2+ with Mn2+ and became complete upon ICAM-1 addition. These agents stabilized αI-headpiece orientation, resulting in a well-defined orientation of ICAM-1 such that its tandem Ig-like domains pointed in the opposite direction from the β-subunit leg of LFA-1. Mutations in the integrin βI domain α1/α1' helix stabilizing either the open or the closed βI-domain conformation indicated that α1/α1' helix movements are linked to ICAM-1 binding by the αI domain and to the extended-open conformation of the ectodomain. The LFA-1-ICAM-1 orientation described here with ICAM-1 pointing anti-parallel to the LFA-1 β-subunit leg is the same orientation that would be stabilized by tensile force transmitted between the ligand and the actin cytoskeleton and is consistent with the cytoskeletal force model of integrin activation.
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Affiliation(s)
- Mehmet Sen
- From the Program in Cellular and Molecular Medicine and .,the Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204
| | - Adem C Koksal
- From the Program in Cellular and Molecular Medicine and
| | - Koichi Yuki
- Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Jianchuan Wang
- From the Program in Cellular and Molecular Medicine and.,the Departments of Biological Chemistry and Molecular Pharmacology and of Medicine, Harvard Medical School, Boston, Massachusetts 02115, and
| | - Timothy A Springer
- From the Program in Cellular and Molecular Medicine and .,the Departments of Biological Chemistry and Molecular Pharmacology and of Medicine, Harvard Medical School, Boston, Massachusetts 02115, and
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47
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Nordenfelt P, Moore TI, Mehta SB, Kalappurakkal JM, Swaminathan V, Koga N, Lambert TJ, Baker D, Waters JC, Oldenbourg R, Tani T, Mayor S, Waterman CM, Springer TA. Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration. Nat Commun 2017; 8:2047. [PMID: 29229906 PMCID: PMC5725580 DOI: 10.1038/s41467-017-01848-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 10/20/2017] [Indexed: 12/31/2022] Open
Abstract
Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin, when engaged to an extracellular ligand and the cytoskeleton, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid, ligand-binding head of the integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin head, and measure orientation with fluorescence polarization microscopy. Cytoskeleton and ligand-bound integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. Our results place atomic, Å-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements.
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Affiliation(s)
- Pontus Nordenfelt
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA
- Division of Infection Medicine, Department of Clinical Sciences Lund, Faculty of Medicine, Lund University, Lund, 221 84, Sweden
| | - Travis I Moore
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Shalin B Mehta
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Chan Zuckerberg Biohub, San Francisco, CA, 94158, USA
| | - Joseph Mathew Kalappurakkal
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- National Center for Biological Sciences, Bangalore, 560065, India
| | - Vinay Swaminathan
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Nobuyasu Koga
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan
| | - Talley J Lambert
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - David Baker
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
| | - Jennifer C Waters
- Department of Cell Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Rudolf Oldenbourg
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Tomomi Tani
- Eugene Bell Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
| | - Satyajit Mayor
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- National Center for Biological Sciences, Bangalore, 560065, India
| | - Clare M Waterman
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA
- Cell Biology and Physiology Center, NHLBI, NIH, Bethesda, MD, 20824, USA
| | - Timothy A Springer
- Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
- Physiology Course, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
- Program in Cellular and Molecular Medicine, Children's Hospital, and Department of Biological Chemistry and Molecular Pharmacology and Medicine, Harvard Medical School, Boston, MA, 02115, USA.
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48
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Zhang X, Li L, Li N, Shu X, Zhou L, Lü S, Chen S, Mao D, Long M. Salt bridge interactions within the β 2 integrin α 7 helix mediate force-induced binding and shear resistance ability. FEBS J 2017; 285:261-274. [PMID: 29150976 DOI: 10.1111/febs.14335] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/23/2017] [Accepted: 11/14/2017] [Indexed: 01/13/2023]
Abstract
The functional performance of the αI domain α7 helix in β2 integrin activation depends on the allostery of the α7 helix, which axially slides down; therefore, it is critical to elucidate what factors regulate the allostery. In this study, we determined that there were two conservative salt bridge interaction pairs that constrain both the upper and bottom ends of the α7 helix. Molecular dynamics (MD) simulations for three β2 integrin members, lymphocyte function-associated antigen-1 (LFA-1; αL β2 ), macrophage-1 antigen (Mac-1; αM β2 ) and αx β2 , indicated that the magnitude of the salt bridge interaction is related to the stability of the αI domain and the strength of the corresponding force-induced allostery. The disruption of the salt bridge interaction, especially with double mutations in both salt bridges, significantly reduced the force-induced allostery time for all three members. The effects of salt bridge interactions of the αI domain α7 helix on β2 integrin conformational stability and allostery were experimentally validated using Mac-1 constructs. The results demonstrated that salt bridge mutations did not alter the conformational state of Mac-1, but they did increase the force-induced ligand binding and shear resistance ability, which was consistent with MD simulations. This study offers new insight into the importance of salt bridge interaction constraints of the αI domain α7 helix and external force for β2 integrin function.
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Affiliation(s)
- Xiao Zhang
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Linda Li
- College of Bioengineering, Chongqing University, China
| | - Ning Li
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Xinyu Shu
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Lüwen Zhou
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Shouqin Lü
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Shenbao Chen
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Debin Mao
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
| | - Mian Long
- Center of Biomechanics and Bioengineering, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China
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49
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Wang Z, Thinn AMM, Zhu J. A pivotal role for a conserved bulky residue at the α1-helix of the αI integrin domain in ligand binding. J Biol Chem 2017; 292:20756-20768. [PMID: 29079572 DOI: 10.1074/jbc.m117.790519] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Revised: 10/12/2017] [Indexed: 11/06/2022] Open
Abstract
The ligand-binding βI and αI domains of integrin are the best-studied von Willebrand factor A domains undergoing significant conformational changes for affinity regulation. In both βI and αI domains, the α1- and α7-helixes work in concert to shift the metal-ion-dependent adhesion site between the resting and active states. An absolutely conserved Gly in the middle of the α1-helix of βI helps maintain the resting βI conformation, whereas the homologous position in the αI α1-helix contains a conserved Phe. A functional role of this Phe is structurally unpredictable. Using αLβ2 integrin as a model, we found that the residue volume at the Phe position in the α1-helix is critical for αLβ2 activation because trimming the Phe by small amino acid substitutions abolished αLβ2 binding with soluble and immobilized intercellular cell adhesion molecule 1. Similar results were obtained for αMβ2 integrin. Our experimental and molecular dynamics simulation data suggested that the bulky Phe acts as a pawl that stabilizes the downward ratchet-like movement of β6-α7 loop and α7-helix, required for high-affinity ligand binding. This mechanism may apply to other von Willebrand factor A domains undergoing large conformational changes. We further demonstrated that the conformational cross-talk between αL αI and β2 βI could be uncoupled because the β2 extension and headpiece opening could occur independently of the αI activation. Reciprocally, the αI activation does not inevitably lead to the conformational changes of the β2 subunit. Such loose linkage between the αI and βI is attributed to the αI flexibility and could accommodate the αLβ2-mediated rolling adhesion of leukocytes.
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Affiliation(s)
- Zhengli Wang
- From the Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Aye Myat Myat Thinn
- From the Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin 53226 and.,the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jieqing Zhu
- From the Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, Wisconsin 53226 and .,the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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50
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Arimori T, Kitago Y, Umitsu M, Fujii Y, Asaki R, Tamura-Kawakami K, Takagi J. Fv-clasp: An Artificially Designed Small Antibody Fragment with Improved Production Compatibility, Stability, and Crystallizability. Structure 2017; 25:1611-1622.e4. [PMID: 28919443 DOI: 10.1016/j.str.2017.08.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/22/2017] [Accepted: 08/15/2017] [Indexed: 12/13/2022]
Abstract
Antibody fragments are frequently used as a "crystallization chaperone" to aid structural analysis of complex macromolecules that are otherwise crystallization resistant, but conventional fragment formats have not been designed for this particular application. By fusing an anti-parallel coiled-coil structure derived from the SARAH domain of human Mst1 kinase to the variable region of an antibody, we succeeded in creating a novel chimeric antibody fragment of ∼37 kDa, termed "Fv-clasp," which exhibits excellent crystallization compatibility while maintaining the binding ability of the original IgG molecule. The "clasp" and the engineered disulfide bond at the bottom of the Fv suppressed the internal mobility of the fragment and shielded hydrophobic residues, likely contributing to the high heat stability and the crystallizability of the Fv-clasp. Finally, Fv-clasp antibodies showed superior "chaperoning" activity over conventional Fab fragments, and facilitated the structure determination of an ectodomain fragment of integrin α6β1.
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Affiliation(s)
- Takao Arimori
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yu Kitago
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Masataka Umitsu
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Yuki Fujii
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Ryoko Asaki
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | | | - Junichi Takagi
- Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.
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