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Oshinowo O, Azer SS, Lin J, Lam WA. Why platelet mechanotransduction matters for hemostasis and thrombosis. J Thromb Haemost 2023; 21:2339-2353. [PMID: 37331517 PMCID: PMC10529432 DOI: 10.1016/j.jtha.2023.06.010] [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: 05/31/2022] [Revised: 06/05/2023] [Accepted: 06/08/2023] [Indexed: 06/20/2023]
Abstract
Mechanotransduction is the ability of cells to "feel" or sense their mechanical microenvironment and integrate and convert these physical stimuli into adaptive biochemical cellular responses. This phenomenon is vital for the physiology of numerous nucleated cell types to affect their various cellular processes. As the main drivers of hemostasis and clot retraction, platelets also possess this ability to sense the dynamic mechanical microenvironments of circulation and convert those signals into biological responses integral to clot formation. Like other cell types, platelets leverage their "hands" or receptors/integrins to mechanotransduce important signals in responding to vascular injury to achieve hemostasis. The clinical relevance of cellular mechanics and mechanotransduction is imperative as pathologic alterations or aberrant mechanotransduction in platelets has been shown to lead to bleeding and thrombosis. As such, the aim of this review is to provide an overview of the most recent research related to platelet mechanotransduction, from platelet generation to platelet activation, within the hemodynamic environment and clot contraction at the site of vascular injury, thereby covering the entire "life cycle" of platelets. Additionally, we describe the key mechanoreceptors in platelets and discuss the new biophysical techniques that have enabled the field to understand how platelets sense and respond to their mechanical microenvironment via those receptors. Finally, the clinical significance and importance of continued exploration of platelet mechanotransduction have been discussed as the key to better understanding of both thrombotic and bleeding disorders lies in a more complete mechanistic understanding of platelet function by way of mechanotransduction.
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Affiliation(s)
- Oluwamayokun Oshinowo
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, USA; Children's Healthcare of Atlanta Inc, Aflac Cancer and Blood Disorders Center, Atlanta, Georgia, USA
| | - Sally S Azer
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, USA; Children's Healthcare of Atlanta Inc, Aflac Cancer and Blood Disorders Center, Atlanta, Georgia, USA
| | - Jessica Lin
- The Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Wilbur A Lam
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, USA; Children's Healthcare of Atlanta Inc, Aflac Cancer and Blood Disorders Center, Atlanta, Georgia, USA.
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2
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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: 12] [Impact Index Per Article: 12.0] [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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3
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Fischer NG, Aparicio C. Junctional epithelium and hemidesmosomes: Tape and rivets for solving the "percutaneous device dilemma" in dental and other permanent implants. Bioact Mater 2022; 18:178-198. [PMID: 35387164 PMCID: PMC8961425 DOI: 10.1016/j.bioactmat.2022.03.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/14/2022] [Accepted: 03/12/2022] [Indexed: 02/06/2023] Open
Abstract
The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the "device"/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant - as a model percutaneous device - placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists.
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Affiliation(s)
- Nicholas G. Fischer
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, 16-212 Moos Tower, 515 Delaware St. SE, Minneapolis, MN, 55455, USA
| | - Conrado Aparicio
- MDRCBB-Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, 16-212 Moos Tower, 515 Delaware St. SE, Minneapolis, MN, 55455, USA
- Division of Basic Research, Faculty of Odontology, UIC Barcelona – Universitat Internacional de Catalunya, C/. Josep Trueta s/n, 08195, Sant Cugat del Valles, Barcelona, Spain
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), C/. Baldiri Reixac 10-12, 08028, Barcelona, Spain
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4
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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: 8] [Impact Index Per Article: 4.0] [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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5
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Krylova NV, Silchenko AS, Pott AB, Ermakova SP, Iunikhina OV, Rasin AB, Kompanets GG, Likhatskaya GN, Shchelkanov MY. In Vitro Anti-Orthohantavirus Activity of the High-and Low-Molecular-Weight Fractions of Fucoidan from the Brown Alga Fucus evanescens. Mar Drugs 2021; 19:577. [PMID: 34677476 PMCID: PMC8538225 DOI: 10.3390/md19100577] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/08/2021] [Accepted: 10/13/2021] [Indexed: 01/19/2023] Open
Abstract
The Hantaan orthohantavirus (genovariant Amur-AMRV) is a rodent-borne zoonotic virus; it is the causative agent of haemorrhagic fever with renal syndrome in humans. The currently limited therapeutic options require the development of effective anti-orthohantavirus drugs. The ability of native fucoidan from Fucus evanescens (FeF) and its enzymatically prepared high-molecular-weight (FeHMP) and low-molecular-weight (FeLMP) fractions to inhibit different stages of AMRV infection in Vero cells was studied. The structures of derivatives obtained were determined using nuclear magnetic resonance (NMR) spectroscopy. We found that fucoidan and its derivatives exhibited significant antiviral activity by affecting the early stages of the AMRV lifecycle, notably virus attachment and penetration. The FeHMP and FeLMP fractions showed the highest anti-adsorption activity by inhibiting AMRV focus formation, with a selective index (SI) > 110; FeF had an SI of ~70. The FeLMP fraction showed a greater virucidal effect compared with FeF and the FeHMP fraction. It was shown by molecular docking that 2O-sulphated fucotetrasaccharide, a main component of the FeLMP fraction, is able to bind with the AMRV envelope glycoproteins Gn/Gc and with integrin β3 to prevent virus-cell interactions. The relatively small size of these sites of interactions explains the higher anti-AMRV activity of the FeLMP fraction.
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Affiliation(s)
- Natalia V. Krylova
- G.P. Somov Institute of Epidemiology and Microbiology, Rospotrebnadzor, Selskaya Street, 1, 690087 Vladivostok, Russia; (A.B.P.); (O.V.I.); (G.G.K.); (M.Y.S.)
| | - Artem S. Silchenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Science, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia; (A.S.S.); (S.P.E.); (A.B.R.); (G.N.L.)
| | - Anastasia B. Pott
- G.P. Somov Institute of Epidemiology and Microbiology, Rospotrebnadzor, Selskaya Street, 1, 690087 Vladivostok, Russia; (A.B.P.); (O.V.I.); (G.G.K.); (M.Y.S.)
| | - Svetlana P. Ermakova
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Science, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia; (A.S.S.); (S.P.E.); (A.B.R.); (G.N.L.)
| | - Olga V. Iunikhina
- G.P. Somov Institute of Epidemiology and Microbiology, Rospotrebnadzor, Selskaya Street, 1, 690087 Vladivostok, Russia; (A.B.P.); (O.V.I.); (G.G.K.); (M.Y.S.)
| | - Anton B. Rasin
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Science, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia; (A.S.S.); (S.P.E.); (A.B.R.); (G.N.L.)
| | - Galina G. Kompanets
- G.P. Somov Institute of Epidemiology and Microbiology, Rospotrebnadzor, Selskaya Street, 1, 690087 Vladivostok, Russia; (A.B.P.); (O.V.I.); (G.G.K.); (M.Y.S.)
| | - Galina N. Likhatskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far-Eastern Branch of the Russian Academy of Science, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia; (A.S.S.); (S.P.E.); (A.B.R.); (G.N.L.)
| | - Mikhail Y. Shchelkanov
- G.P. Somov Institute of Epidemiology and Microbiology, Rospotrebnadzor, Selskaya Street, 1, 690087 Vladivostok, Russia; (A.B.P.); (O.V.I.); (G.G.K.); (M.Y.S.)
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6
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Lietha D, Izard T. Roles of Membrane Domains in Integrin-Mediated Cell Adhesion. Int J Mol Sci 2020; 21:ijms21155531. [PMID: 32752284 PMCID: PMC7432473 DOI: 10.3390/ijms21155531] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/29/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022] Open
Abstract
The composition and organization of the plasma membrane play important functional and regulatory roles in integrin signaling, which direct many physiological and pathological processes, such as development, wound healing, immunity, thrombosis, and cancer metastasis. Membranes are comprised of regions that are thick or thin owing to spontaneous partitioning of long-chain saturated lipids from short-chain polyunsaturated lipids into domains defined as ordered and liquid-disorder domains, respectively. Liquid-ordered domains are typically 100 nm in diameter and sometimes referred to as lipid rafts. We posit that integrin β senses membrane thickness and that mechanical force on the membrane regulates integrin activation through membrane thinning. This review examines what we know about the nature and mechanism of the interaction of integrins with the plasma membrane and its effects on regulating integrins and its binding partners.
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Affiliation(s)
- Daniel Lietha
- Cell Signaling and Adhesion Group, Structural and Chemical Biology, Margarita Salas Center for Biological Research (CIB-CSIC), E-28040 Madrid, Spain;
| | - Tina Izard
- Cell Adhesion Laboratory, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, Jupiter, FL 33458, USA
- Correspondence:
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7
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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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8
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Gocheva G, Ivanova A. A Look at Receptor–Ligand Pairs for Active-Targeting Drug Delivery from Crystallographic and Molecular Dynamics Perspectives. Mol Pharm 2019; 16:3293-3321. [DOI: 10.1021/acs.molpharmaceut.9b00250] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Gergana Gocheva
- Sofia University “St. Kliment Ohridski”, Faculty of Chemistry and Pharmacy, 1 James Bourchier Blvd., 1164 Sofia, Bulgaria
| | - Anela Ivanova
- Sofia University “St. Kliment Ohridski”, Faculty of Chemistry and Pharmacy, 1 James Bourchier Blvd., 1164 Sofia, Bulgaria
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9
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Pagani G, Pereira JPV, Stoldt VR, Beck A, Scharf RE, Gohlke H. The human platelet antigen-1b (Pro 33) variant of α IIbβ 3 allosterically shifts the dynamic conformational equilibrium of this integrin toward the active state. J Biol Chem 2018; 293:4830-4844. [PMID: 29462793 DOI: 10.1074/jbc.ra118.002149] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 02/08/2018] [Indexed: 11/06/2022] Open
Abstract
Integrins are heterodimeric cell-adhesion receptors comprising α and β subunits that transmit signals allosterically in both directions across the membrane by binding to intra- and extracellular components. The human platelet antigen-1 (HPA-1) polymorphism in αIIbβ3 arises from a Leu → Pro exchange at residue 33 in the genu of the β3 subunit, resulting in Leu33 (HPA-1a) or Pro33 (HPA-1b) isoforms. Although clinical investigations have provided conflicting results, some studies have suggested that Pro33 platelets exhibit increased thrombogenicity. Under flow-dynamic conditions, the Pro33 variant displays prothrombotic properties, characterized by increased platelet adhesion, aggregate/thrombus formation, and outside-in signaling. However, the molecular events underlying this prothrombotic phenotype have remained elusive. As residue 33 is located >80 Å away from extracellular binding sites or transmembrane domains, we hypothesized that the Leu → Pro exchange allosterically shifts the dynamic conformational equilibrium of αIIbβ3 toward an active state. Multiple microsecond-long, all-atom molecular dynamics simulations of the ectodomain of the Leu33 and Pro33 isoforms provided evidence that the Leu → Pro exchange weakens interdomain interactions at the genu and alters the structural dynamics of the integrin to a more unbent and splayed state. Using FRET analysis of fluorescent proteins fused with αIIbβ3 in transfected HEK293 cells, we found that the Pro33 variant in its resting state displays a lower energy transfer than the Leu33 isoform. This finding indicated a larger spatial separation of the cytoplasmic tails in the Pro33 variant. Together, our results indicate that the Leu → Pro exchange allosterically shifts the dynamic conformational equilibrium of αIIbβ3 to a structural state closer to the active one, promoting the fully active state and fostering the prothrombotic phenotype of Pro33 platelets.
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Affiliation(s)
- Giulia Pagani
- Institute for Pharmaceutical and Medicinal Chemistry, 40225 Düsseldorf, Germany
| | - Joana P V Pereira
- Division of Experimental and Clinical Hemostasis, Hemotherapy and Transfusion Medicine, Institute of Transplantation Diagnostics and Cell Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany
| | - Volker R Stoldt
- Division of Experimental and Clinical Hemostasis, Hemotherapy and Transfusion Medicine, Institute of Transplantation Diagnostics and Cell Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany
| | - Andreas Beck
- Institute of Informatics, 40225 Düsseldorf, Germany
| | - Rüdiger E Scharf
- Division of Experimental and Clinical Hemostasis, Hemotherapy and Transfusion Medicine, Institute of Transplantation Diagnostics and Cell Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany; Biological Medical Research Center, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, 40225 Düsseldorf, Germany; John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), and Institute for Complex Systems-Structural Biochemistry (ICS 6), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
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10
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Bondu V, Wu C, Cao W, Simons PC, Gillette J, Zhu J, Erb L, Zhang XF, Buranda T. Low-affinity binding in cis to P2Y 2R mediates force-dependent integrin activation during hantavirus infection. Mol Biol Cell 2017; 28:2887-2903. [PMID: 28835374 PMCID: PMC5638590 DOI: 10.1091/mbc.e17-01-0082] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 08/08/2017] [Accepted: 08/17/2017] [Indexed: 12/22/2022] Open
Abstract
Atomic force microscopy is used to establish that low-affinity integrins bind in cis to P2Y2R. Integrin activation is initiated by a membrane-normal switchblade motion triggered by integrin priming after the virus binds to the integrin PSI domain. Tensile force between the P2Y2R and unbending integrin stimulates outside-in signaling. Pathogenic hantaviruses bind to the plexin-semaphorin-integrin (PSI) domain of inactive, β3 integrins. Previous studies have implicated a cognate cis interaction between the bent conformation β5/β3 integrins and an arginine-glycine-aspartic acid (RGD) sequence in the first extracellular loop of P2Y2R. With single-molecule atomic force microscopy, we show a specific interaction between an atomic force microscopy tip decorated with recombinant αIIbβ3 integrins and (RGD)P2Y2R expressed on cell membranes. Mutation of the RGD sequence to RGE in the P2Y2R removes this interaction. Binding of inactivated and fluorescently labeled Sin Nombre virus (SNV) to the integrin PSI domain stimulates higher affinity for (RGD)P2Y2R on cells, as measured by an increase in the unbinding force. In CHO cells, stably expressing αIIbβ3 integrins, virus engagement at the integrin PSI domain, recapitulates physiologic activation of the integrin as indicated by staining with the activation-specific mAB PAC1. The data also show that blocking of the Gα13 protein from binding to the cytoplasmic domain of the β3 integrin prevents outside-in signaling and infection. We propose that the cis interaction with P2Y2R provides allosteric resistance to the membrane-normal motion associated with the switchblade model of integrin activation, where the development of tensile force yields physiological integrin activation.
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Affiliation(s)
- Virginie Bondu
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Chenyu Wu
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Wenpeng Cao
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Peter C Simons
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Jennifer Gillette
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131
| | - Jieqing Zhu
- Blood Research Institute, Bloodcenter of Wisconsin, Milwaukee, WI 53226
| | - Laurie Erb
- Department of Biochemistry, 540F Bond Life Sciences Center, Columbia, MO 65211
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics and Department of Bioengineering, Lehigh University, Bethlehem, PA 18015
| | - Tione Buranda
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131 .,Center for Infectious Diseases and Immunity, University of New Mexico School of Medicine, Albuquerque, NM 87131
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11
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Wang L, Pan D, Yan Q, Song Y. Activation mechanisms of αVβ3 integrin by binding to fibronectin: A computational study. Protein Sci 2017; 26:1124-1137. [PMID: 28340512 PMCID: PMC5441423 DOI: 10.1002/pro.3163] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 03/13/2017] [Accepted: 03/19/2017] [Indexed: 01/29/2023]
Abstract
Integrin αVβ3 plays an important role in regulating cellular activities and in human diseases. Although the structure of αVβ3 has been studied by crystallography and electron microscopy, the detailed activation mechanism of integrin αVβ3 induced by fibronectin remains unclear. In this study, we investigated the conformational and dynamical motion changes of Mn2+ -bound integrin αVβ3 by binding to fibronectin with molecular dynamics simulations. Results showed that fibronectin binding to integrin αVβ3 caused the changes of the conformational flexibility of αVβ3 domains, the essential mode of motion for the domains of αV subunit and β3 subunit and the degrees of correlated motion of residues between the domains of αV subunit and β3 subunit of integrin αVβ3. The angle of Propeller domain with respect to the Calf-2 domain of αV subunit and the angle of Hybrid domain with respect to βA domain of β3 subunit significantly increased when integrin αVβ3 was bound to fibronectin. These changes could result in the conformational change tendency of αVβ3 from a bend conformation to an extended conformation and lead to the open swing of Hybrid domain relative to βA domain of β3 subunit, which have demonstrated their importance for αVβ3 activation. Fibronectin binding to integrin αVβ3 significantly decreased the relative position of α1 helix to βA domain and that to metal ion-dependent adhesion site, stabilized Mn2+ ions binding in integrin αVβ3 and changed fibronectin conformation, which are important for αVβ3 activation. Results from this study provide important molecular insight into the "outside-in" activation mechanism of integrin αVβ3 by binding to fibronectin.
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Affiliation(s)
- Lingyun Wang
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Di Pan
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Qi Yan
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
| | - Yuhua Song
- Department of Biomedical EngineeringThe University of Alabama at BirminghamBirminghamAlabama35294
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12
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The integrin PSI domain has an endogenous thiol isomerase function and is a novel target for antiplatelet therapy. Blood 2017; 129:1840-1854. [PMID: 28122739 DOI: 10.1182/blood-2016-07-729400] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 01/13/2017] [Indexed: 02/06/2023] Open
Abstract
Integrins are a large family of heterodimeric transmembrane receptors differentially expressed on almost all metazoan cells. Integrin β subunits contain a highly conserved plexin-semaphorin-integrin (PSI) domain. The CXXC motif, the active site of the protein-disulfide-isomerase (PDI) family, is expressed twice in this domain of all integrins across species. However, the role of the PSI domain in integrins and whether it contains thiol-isomerase activity have not been explored. Here, recombinant PSI domains of murine β3, and human β1 and β2 integrins were generated and their PDI-like activity was demonstrated by refolding of reduced/denatured RNase. We identified that both CXXC motifs of β3 integrin PSI domain are required to maintain its optimal PDI-like activity. Cysteine substitutions (C13A and C26A) of the CXXC motifs also significantly decreased the PDI-like activity of full-length human recombinant β3 subunit. We further developed mouse anti-mouse β3 PSI domain monoclonal antibodies (mAbs) that cross-react with human and other species. These mAbs inhibited αIIbβ3 PDI-like activity and its fibrinogen binding. Using single-molecular Biomembrane-Force-Probe assays, we demonstrated that inhibition of αIIbβ3 endogenous PDI-like activity reduced αIIbβ3-fibrinogen interaction, and these anti-PSI mAbs inhibited fibrinogen binding via different levels of both PDI-like activity-dependent and -independent mechanisms. Importantly, these mAbs inhibited murine/human platelet aggregation in vitro and ex vivo, and murine thrombus formation in vivo, without significantly affecting bleeding time or platelet count. Thus, the PSI domain is a potential regulator of integrin activation and a novel target for antithrombotic therapies. These findings may have broad implications for all integrin functions, and cell-cell and cell-matrix interactions.
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13
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Xu XR, Carrim N, Neves MAD, McKeown T, Stratton TW, Coelho RMP, Lei X, Chen P, Xu J, Dai X, Li BX, Ni H. Platelets and platelet adhesion molecules: novel mechanisms of thrombosis and anti-thrombotic therapies. Thromb J 2016; 14:29. [PMID: 27766055 PMCID: PMC5056500 DOI: 10.1186/s12959-016-0100-6] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Platelets are central mediators of thrombosis and hemostasis. At the site of vascular injury, platelet accumulation (i.e. adhesion and aggregation) constitutes the first wave of hemostasis. Blood coagulation, initiated by the coagulation cascades, is the second wave of thrombin generation and enhance phosphatidylserine exposure, can markedly potentiate cell-based thrombin generation and enhance blood coagulation. Recently, deposition of plasma fibronectin and other proteins onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that occurs prior to platelet accumulation (i.e. the classical first wave of hemostasis). These three waves of hemostasis, in the event of atherosclerotic plaque rupture, may turn pathogenic, and cause uncontrolled vessel occlusion and thrombotic disorders (e.g. heart attack and stroke). Current anti-platelet therapies have significantly reduced cardiovascular mortality, however, on-treatment thrombotic events, thrombocytopenia, and bleeding complications are still major concerns that continue to motivate innovation and drive therapeutic advances. Emerging evidence has brought platelet adhesion molecules back into the spotlight as targets for the development of novel anti-thrombotic agents. These potential antiplatelet targets mainly include the platelet receptors glycoprotein (GP) Ib-IX-V complex, β3 integrins (αIIb subunit and PSI domain of β3 subunit) and GPVI. Numerous efforts have been made aiming to balance the efficacy of inhibiting thrombosis without compromising hemostasis. This mini-review will update the mechanisms of thrombosis and the current state of antiplatelet therapies, and will focus on platelet adhesion molecules and the novel anti-thrombotic therapies that target them.
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Affiliation(s)
- Xiaohong Ruby Xu
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON Canada
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
- Guangdong Provincial Hospital of Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong People’s Republic of China
| | - Naadiya Carrim
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
- Canadian Blood Services, Toronto, ON Canada
| | - Miguel Antonio Dias Neves
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
| | - Thomas McKeown
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
| | - Tyler W. Stratton
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
| | - Rodrigo Matos Pinto Coelho
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
| | - Xi Lei
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
| | - Pingguo Chen
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
- Canadian Blood Services, Toronto, ON Canada
| | - Jianhua Xu
- CCOA Therapeutics Inc, Toronto, ON Canada
| | - Xiangrong Dai
- Lee’s Pharmaceutical holdings limited, Shatin Hong Kong, China
- Zhaoke Pharmaceutical co. limited, Hefei, Anhui China
| | - Benjamin Xiaoyi Li
- Lee’s Pharmaceutical holdings limited, Shatin Hong Kong, China
- Zhaoke Pharmaceutical co. limited, Hefei, Anhui China
- Hong Kong University of Science and technology, Hong Kong, China
| | - Heyu Ni
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON Canada
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON Canada
- Canadian Blood Services, Toronto, ON Canada
- CCOA Therapeutics Inc, Toronto, ON Canada
- Department of Medicine and Department of Physiology, University of Toronto, Toronto, ON Canada
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14
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Donner L, Fälker K, Gremer L, Klinker S, Pagani G, Ljungberg LU, Lothmann K, Rizzi F, Schaller M, Gohlke H, Willbold D, Grenegard M, Elvers M. Platelets contribute to amyloid-β aggregation in cerebral vessels through integrin αIIbβ3-induced outside-in signaling and clusterin release. Sci Signal 2016; 9:ra52. [PMID: 27221710 DOI: 10.1126/scisignal.aaf6240] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cerebral amyloid angiopathy (CAA) is a vascular dysfunction disorder characterized by deposits of amyloid-β (Aβ) in the walls of cerebral vessels. CAA and Aβ deposition in the brain parenchyma contribute to dementia and Alzheimer's disease (AD). We investigated the contribution of platelets, which accumulate at vascular Aβ deposits, to CAA. We found that synthetic monomeric Aβ40 bound through its RHDS (Arg-His-Asp-Ser) sequence to integrin αIIbβ3, which is the receptor for the extracellular matrix protein fibrinogen, and stimulated the secretion of adenosine diphosphate (ADP) and the chaperone protein clusterin from platelets. Clusterin promoted the formation of fibrillar Aβ aggregates, and ADP acted through its receptors P2Y1 and P2Y12 on platelets to enhance integrin αIIbβ3 activation, further increasing the secretion of clusterin and Aβ40 binding to platelets. Platelets from patients with Glanzmann's thrombasthenia, a bleeding disorder in which platelets have little or dysfunctional αIIbβ3, indicated that the abundance of this integrin dictated Aβ-induced clusterin release and platelet-induced Aβ aggregation. The antiplatelet agent clopidogrel, which irreversibly inhibits P2Y12, inhibited Aβ aggregation in platelet cultures; in transgenic AD model mice, this drug reduced the amount of clusterin in the circulation and the incidence of CAA. Our findings indicate that activated platelets directly contribute to CAA by promoting the formation of Aβ aggregates and that Aβ, in turn, activates platelets, creating a feed-forward loop. Thus, antiplatelet therapy may alleviate fibril formation in cerebral vessels of AD patients.
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Affiliation(s)
- Lili Donner
- Department of Clinical and Experimental Hemostasis, Hemotherapy and Transfusion Medicine, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Knut Fälker
- Cardiovascular Research Centre, Örebro University, SE-701 82 Örebro, Sweden
| | - Lothar Gremer
- Institute of Physical Biology, Heinrich Heine University, 40225 Düsseldorf, Germany. Institute of Structural Biochemistry (ICS-6), Research Centre Jülich, 52425 Jülich, Germany
| | - Stefan Klinker
- Institute of Physical Biology, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Giulia Pagani
- Institute for Pharmaceutical and Medicinal Chemistry, Department of Mathematics and Natural Sciences, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Liza U Ljungberg
- Cardiovascular Research Centre, Örebro University, SE-701 82 Örebro, Sweden
| | - Kimberley Lothmann
- Institute of Physical Biology, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Federica Rizzi
- Department of Biomedical, Biotechnological, and Translation Sciences, University of Parma, Via Volturno 39/a, 43126 Parma, Italy. Centre for Molecular and Translational Oncology (COMT), University of Parma, Parco Area delle Scienze 11/a, 43124 Parma, Italy. National Institute of Biostructure and Biosystems (INBB), Viale Medaglie d'Oro 305, 00136 Rome, Italy
| | - Martin Schaller
- Department of Dermatology, University of Tübingen, 72076 Tübingen, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Department of Mathematics and Natural Sciences, Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Dieter Willbold
- Institute of Physical Biology, Heinrich Heine University, 40225 Düsseldorf, Germany. Institute of Structural Biochemistry (ICS-6), Research Centre Jülich, 52425 Jülich, Germany
| | - Magnus Grenegard
- Cardiovascular Research Centre, Örebro University, SE-701 82 Örebro, Sweden
| | - Margitta Elvers
- Department of Clinical and Experimental Hemostasis, Hemotherapy and Transfusion Medicine, Heinrich Heine University, 40225 Düsseldorf, Germany.
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15
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Ni T, Harlos K, Gilbert R. Structure of astrotactin-2: a conserved vertebrate-specific and perforin-like membrane protein involved in neuronal development. Open Biol 2016; 6:rsob.160053. [PMID: 27249642 PMCID: PMC4892435 DOI: 10.1098/rsob.160053] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 04/07/2016] [Indexed: 11/30/2022] Open
Abstract
The vertebrate-specific proteins astrotactin-1 and 2 (ASTN-1 and ASTN-2) are integral membrane perforin-like proteins known to play critical roles in neurodevelopment, while ASTN-2 has been linked to the planar cell polarity pathway in hair cells. Genetic variations associated with them are linked to a variety of neurodevelopmental disorders and other neurological pathologies, including an advanced onset of Alzheimer's disease. Here we present the structure of the majority endosomal region of ASTN-2, showing it to consist of a unique combination of polypeptide folds: a perforin-like domain, a minimal epidermal growth factor-like module, a unique form of fibronectin type III domain and an annexin-like domain. The perforin-like domain differs from that of other members of the membrane attack complex-perforin (MACPF) protein family in ways that suggest ASTN-2 does not form pores. Structural and biophysical data show that ASTN-2 (but not ASTN-1) binds inositol triphosphates, suggesting a mechanism for membrane recognition or secondary messenger regulation of its activity. The annexin-like domain is closest in fold to repeat three of human annexin V and similarly binds calcium, and yet shares no sequence homology with it. Overall, our structure provides the first atomic-resolution description of a MACPF protein involved in development, while highlighting distinctive features of ASTN-2 responsible for its activity.
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Affiliation(s)
- Tao Ni
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Karl Harlos
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Robert Gilbert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
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16
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Huang Y, Zhao LL, Feng JL, Zhu HX, Huang X, Ren Q, Wang W. A novel integrin function in innate immunity from Chinese mitten crab (Eriocheir sinensis). DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2015; 52:155-165. [PMID: 26004499 DOI: 10.1016/j.dci.2015.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 05/15/2015] [Accepted: 05/18/2015] [Indexed: 06/04/2023]
Abstract
Integrins belong to a superfamily of conserved α β heterodimeric cell surface receptors that have critical function in cell migration, differentiation, and survival. In this study, an integrin called EsIntegrin was identified from Chinese mitten crab Eriocheir sinensis. EsIntegrin cDNA is 4415 bp long with a 2457 bp open reading frame that encodes an 818 amino acid protein. EsIntegrin contains a signal peptide, an integrin beta subunit (N-terminal portion of extracellular region) INB domain, an epidermal growth factor (hEGF) domain, an integrin B tail domain, a transmembrane region, and an integrin b cyt domain. EsIntegrin was mainly expressed in hemocytes and the heart, with a relatively lower expression level in gills, nerves, intestine, hepatopancreas, muscles, and eyestalk. When healthy crabs were challenged with LPS, PGN, Staphyloccocus aureus, or Vibrio parahaemolyticus, EsIntegrin expression level was upregulated significantly. Recombinant EsIntegrin has agglutination activity to Gram-positive (e.g., S. aureus and Bacillus subtilis) and Gram-negative bacteria (e.g., V. parahaemolyticus and Aeromonas hydrophila) in the presence of calcium. Furthermore, rEsIntegrin could not only bind to various bacteria such as S. aureus, Micrococcus luteus, B. subtilis, Bacillus megaterium, Bacillus thuringiensis, V. parahaemolyticus, Vibrio anguillarum, A. hydrophila, Vibrio natriegens, and Escherichia coli, but this compound also helped crabs in clearing virulent Gram-negative bacterium, V. parahaemolyticus, in vivo. These data suggested that EsIntegrin might function as cellular receptor that is involved in anti-bacterial immunity from E. sinensis.
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Affiliation(s)
- Ying Huang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China
| | - Ling-Ling Zhao
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China
| | - Jin-Ling Feng
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China
| | - Huan-Xi Zhu
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China
| | - Xin Huang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China
| | - Qian Ren
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China.
| | - Wen Wang
- Jiangsu Key Laboratory for Biodiversity & Biotechnology and Jiangsu Key Laboratory for Aquatic Crustacean Diseases, College of Life Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing 210046, China.
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17
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Abstract
Integrin α5β1 binds to an Arg-Gly-Asp (RGD) motif in its ligand fibronectin. We report high-resolution crystal structures of a four-domain α5β1 headpiece fragment, alone or with RGD peptides soaked into crystals, and RGD peptide affinity measurements. The headpiece crystallizes in a closed conformation essentially identical to that seen previously for α5β1 complexed with a Fab that allosterically inhibits ligand binding by stabilizing the closed conformation. Soaking experiments show that binding of cyclic RGD peptide with 20-fold higher affinity than a linear RGD peptide induces conformational change in the β1-subunit βI domain to a state that is intermediate between closed (low affinity) and open (high affinity). In contrast, binding of a linear RGD peptide induces no shape shifting. However, linear peptide binding induces shape shifting when Ca(2+) is depleted during soaking. Ca(2+) bound to the adjacent to metal ion-dependent adhesion site (ADMIDAS), at the locus of shape shifting, moves and decreases in occupancy, correlating with an increase in affinity for RGD measured when Ca(2+) is depleted. The results directly demonstrate that Ca(2+) binding to the ADMIDAS stabilizes integrins in the low-affinity, closed conformation. Comparisons in affinity between four-domain and six-domain headpiece constructs suggest that flexible integrin leg domains contribute to conformational equilibria. High-resolution views of the hybrid domain interface with the plexin-semaphorin-integrin (PSI) domain in different orientations show a ball-and-socket joint with a hybrid domain Arg side chain that rocks in a PSI domain socket lined with carbonyl oxygens.
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18
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Chouhan BS, Käpylä J, Denessiouk K, Denesyuk A, Heino J, Johnson MS. Early chordate origin of the vertebrate integrin αI domains. PLoS One 2014; 9:e112064. [PMID: 25409021 PMCID: PMC4237329 DOI: 10.1371/journal.pone.0112064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/11/2014] [Indexed: 12/17/2022] Open
Abstract
Half of the 18 human integrins α subunits have an inserted αI domain yet none have been observed in species that have diverged prior to the appearance of the urochordates (ascidians). The urochordate integrin αI domains are not human orthologues but paralogues, but orthologues of human αI domains extend throughout later-diverging vertebrates and are observed in the bony fish with duplicate isoforms. Here, we report evidence for orthologues of human integrins with αI domains in the agnathostomes (jawless vertebrates) and later diverging species. Sequence comparisons, phylogenetic analyses and molecular modeling show that one nearly full-length sequence from lamprey and two additional fragments include the entire integrin αI domain region, have the hallmarks of collagen-binding integrin αI domains, and we show that the corresponding recombinant proteins recognize the collagen GFOGER motifs in a metal dependent manner, unlike the α1I domain of the ascidian C. intestinalis. The presence of a functional collagen receptor integrin αI domain supports the origin of orthologues of the human integrins with αI domains prior to the earliest diverging extant vertebrates, a domain that has been conserved and diversified throughout the vertebrate lineage.
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Affiliation(s)
- Bhanupratap Singh Chouhan
- Structural Bioinformatics Laboratory, Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Jarmo Käpylä
- Department of Biochemistry, University of Turku, Turku, Finland
| | - Konstantin Denessiouk
- Structural Bioinformatics Laboratory, Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Alexander Denesyuk
- Structural Bioinformatics Laboratory, Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Jyrki Heino
- Department of Biochemistry, University of Turku, Turku, Finland
| | - Mark S. Johnson
- Structural Bioinformatics Laboratory, Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland
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19
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Rui X, Mehrbod M, Van Agthoven JF, Anand S, Xiong JP, Mofrad MRK, Arnaout MA. The α-subunit regulates stability of the metal ion at the ligand-associated metal ion-binding site in β3 integrins. J Biol Chem 2014; 289:23256-23263. [PMID: 24975416 DOI: 10.1074/jbc.m114.581470] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aspartate in the prototypical integrin-binding motif Arg-Gly-Asp binds the integrin βA domain of the β-subunit through a divalent cation at the metal ion-dependent adhesion site (MIDAS). An auxiliary metal ion at a ligand-associated metal ion-binding site (LIMBS) stabilizes the metal ion at MIDAS. LIMBS contacts distinct residues in the α-subunits of the two β3 integrins αIIbβ3 and αVβ3, but a potential role of this interaction on stability of the metal ion at LIMBS in β3 integrins has not been explored. Equilibrium molecular dynamics simulations of fully hydrated β3 integrin ectodomains revealed strikingly different conformations of LIMBS in unliganded αIIbβ3 versus αVβ3, the result of stronger interactions of LIMBS with αV, which reduce stability of the LIMBS metal ion in αVβ3. Replacing the αIIb-LIMBS interface residue Phe(191) in αIIb (equivalent to Trp(179) in αV) with Trp strengthened this interface and destabilized the metal ion at LIMBS in αIIbβ3; a Trp(179) to Phe mutation in αV produced the opposite but weaker effect. Consistently, an F191/W substitution in cellular αIIbβ3 and a W179/F substitution in αVβ3 reduced and increased, respectively, the apparent affinity of Mn(2+) to the integrin. These findings offer an explanation for the variable occupancy of the metal ion at LIMBS in αVβ3 structures in the absence of ligand and provide new insights into the mechanisms of integrin regulation.
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Affiliation(s)
- Xianliang Rui
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Mehrdad Mehrbod
- Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720
| | - Johannes F Van Agthoven
- Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and
| | - Saurabh Anand
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Jian-Ping Xiong
- Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and
| | - Mohammad R K Mofrad
- Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720.
| | - M Amin Arnaout
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129; Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and.
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20
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Oliver KH, Jessen T, Crawford EL, Chung CY, Sutcliffe JS, Carneiro AM. Pro32Pro33 mutations in the integrin β3 PSI domain result in αIIbβ3 priming and enhanced adhesion: reversal of the hypercoagulability phenotype by the Src inhibitor SKI-606. Mol Pharmacol 2014; 85:921-31. [PMID: 24695082 DOI: 10.1124/mol.114.091736] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The plasma-membrane integrin αIIbβ3 (CD41/CD61, GPIIbIIIa) is a major functional receptor in platelets during clotting. A common isoform of integrin β3, Leu33Pro is associated with enhanced platelet function and increased risk for coronary thrombosis and stroke, although these findings remain controversial. To better understand the molecular mechanisms by which this sequence variation modifies platelet function, we produced transgenic knockin mice expressing a Pro32Pro33 integrin β3. Consistent with reports utilizing human platelets, we found significantly reduced bleeding and clotting times, as well as increased in vivo thrombosis, in Pro32Pro33 homozygous mice. These alterations paralleled increases in platelet attachment and spreading onto fibrinogen resulting from enhanced integrin αIIbβ3 function. Activation with protease-activated receptor 4- activating peptide, the main thrombin signaling receptor in mice, showed no significant difference in activation of Pro32Pro33 mice as compared with controls, suggesting that inside-out signaling remains intact. However, under unstimulated conditions, the Pro32Pro33 mutation led to elevated Src phosphorylation, facilitated by increased talin interactions with the β3 cytoplasmic domain, indicating that the αIIbβ3 intracellular domains are primed for activation while the ligand-binding domain remains unchanged. Acute dosing of animals with a Src inhibitor was sufficient to rescue the clotting phenotype in knockin mice to wild-type levels. Together, our data establish that the Pro32Pro33 structural alteration modifies the function of integrin αIIbβ3, priming the integrin for outside-in signaling, ultimately leading to hypercoagulability. Furthermore, our data may support a novel approach to antiplatelet therapy by Src inhibition where hemostasis is maintained while reducing risk for cardiovascular disease.
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Affiliation(s)
- Kendra H Oliver
- Departments of Pharmacology (K.H.O., T.J., C.Y.C., A.M.C.) and Psychiatry, Molecular Physiology, and Biophysics (E.L.C., J.S.S.), Vanderbilt University Medical Center, Nashville, Tennessee
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21
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Upadhyay SK. Molecular Dynamics Simulations of Certain RGD-Based Peptides from Kistrin Provide Insight into the Higher Activity of REI-RGD34 Protein at Higher Temperature. Chem Biol Drug Des 2014; 83:600-9. [DOI: 10.1111/cbdd.12275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Sanjay K. Upadhyay
- Department of Biosciences and Bioengineering; Indian Institute of Technology Bombay; Powai Mumbai 400076 India
- Center for Bioinformatics; Shoolini University; Solan HP 173229 India
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22
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Lai C, Liu X, Tian C, Wu F. Integrin α1 has a long helix, extending from the transmembrane region to the cytoplasmic tail in detergent micelles. PLoS One 2013; 8:e62954. [PMID: 23646163 PMCID: PMC3639902 DOI: 10.1371/journal.pone.0062954] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/26/2013] [Indexed: 12/12/2022] Open
Abstract
Integrin proteins are very important adhesion receptors that mediate cell-cell and cell-extracellular matrix interactions. They play essential roles in cell signaling and the regulation of cellular shape, motility, and the cell cycle. Here, the transmembrane and cytoplasmic (TMC) domains of integrin α1 and β1 were over-expressed and purified in detergent micelles. The structure and backbone relaxations of α1-TMC in LDAO micelles were determined and analyzed using solution NMR. A long helix, extending from the transmembrane region to the cytoplasmic tail, was observed in α1-TMC. Structural comparisons of α1-TMC with reported αIIb-TMC domains indicated different conformations in the transmembrane regions and cytoplasmic tails. An NMR titration experiment indicated weak interactions between α1-TMC and β1-TMC through several α1-TMC residues located at its N-terminal juxta-transmembrane region and C-terminal extended helix region.
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Affiliation(s)
- Chaohua Lai
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xiaoxi Liu
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Changlin Tian
- Hefei National Laboratory for Physical Science at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
- * E-mail: (CT); (FW)
| | - Fangming Wu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
- * E-mail: (CT); (FW)
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23
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Ghemtio L, Muzet N. Retrospective molecular docking study of WY-25105 ligand to β-secretase and bias of the three-dimensional structure flexibility. J Mol Model 2013; 19:2971-9. [DOI: 10.1007/s00894-013-1821-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/10/2013] [Indexed: 01/04/2023]
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24
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Gohlke H, Schmitz B, Sommerfeld A, Reinehr R, Häussinger D. α5 β1-integrins are sensors for tauroursodeoxycholic acid in hepatocytes. Hepatology 2013; 57:1117-29. [PMID: 22865233 DOI: 10.1002/hep.25992] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 07/21/2012] [Indexed: 01/02/2023]
Abstract
UNLABELLED Ursodeoxycholic acid, which in vivo is converted to its taurine conjugate tauroursodeoxycholic acid (TUDC), is a mainstay for the treatment of cholestatic liver disease. Earlier work showed that TUDC exerts its choleretic properties in the perfused rat liver in an α5 β1 integrin-mediated way. However, the molecular basis of TUDC-sensing in the liver is unknown. We herein show that TUDC (20 μmol/L) induces in perfused rat liver and human HepG2 cells the rapid appearance of the active conformation of the β1 subunit of α5 β1 integrins, followed by an activating phosphorylation of extracellular signal-regulated kinases. TUDC-induced kinase activation was no longer observed after β1 integrin knockdown in isolated rat hepatocytes or in the presence of an integrin-antagonistic hexapeptide in perfused rat liver. TUDC-induced β1 integrin activation occurred predominantly inside the hepatocyte and required TUDC uptake by way of the Na(+) /taurocholate cotransporting peptide. Molecular dynamics simulations of a 3D model of α5 β1 integrin with TUDC bound revealed significant conformational changes within the head region that have been linked to integrin activation before. CONCLUSIONS TUDC can directly activate intrahepatocytic β1 integrins, which trigger signal transduction pathways toward choleresis. (HEPATOLOGY 2013).
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Affiliation(s)
- Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Department of Mathematics and Natural Sciences, Heinrich-Heine-University Düsseldorf, Germany
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25
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26
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Dong X, Mi LZ, Zhu J, Wang W, Hu P, Luo BH, Springer TA. α(V)β(3) integrin crystal structures and their functional implications. Biochemistry 2012; 51:8814-28. [PMID: 23106217 PMCID: PMC3495331 DOI: 10.1021/bi300734n] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many questions about the significance of structural features of integrin α(V)β(3) with respect to its mechanism of activation remain. We have determined and re-refined crystal structures of the α(V)β(3) ectodomain linked to C-terminal coiled coils (α(V)β(3)-AB) and four transmembrane (TM) residues in each subunit (α(V)β(3)-1TM), respectively. The α(V) and β(3) subunits with four and eight extracellular domains, respectively, are bent at knees between the integrin headpiece and lower legs, and the headpiece has the closed, low-affinity conformation. The structures differ in the occupancy of three metal-binding sites in the βI domain. Occupancy appears to be related to the pH of crystallization, rather than to the physiologic regulation of ligand binding at the central, metal ion-dependent adhesion site. No electron density was observed for TM residues and much of the α(V) linker. α(V)β(3)-AB and α(V)β(3)-1TM demonstrate flexibility in the linker between their extracellular and TM domains, rather than the previously proposed rigid linkage. A previously postulated interface between the α(V) and β(3) subunits at their knees was also not supported, because it lacks high-quality density, required rebuilding in α(V)β(3)-1TM, and differed markedly between α(V)β(3)-1TM and α(V)β(3)-AB. Together with the variation in domain-domain orientation within their bent ectodomains between α(V)β(3)-AB and α(V)β(3)-1TM, these findings are compatible with the requirement for large structural changes, such as extension at the knees and headpiece opening, in conveying activation signals between the extracellular ligand-binding site and the cytoplasm.
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Affiliation(s)
- Xianchi Dong
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Li-Zhi Mi
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Jianghai Zhu
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
| | - Wei Wang
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Ping Hu
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Bing-Hao Luo
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
- Department of Biological Sciences, 202 Life Sciences Building, Louisiana State University, Baton Rouge, LA 70803
| | - Timothy A. Springer
- Immune Disease Institute, Children's Hospital Boston and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
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Hota PK, Buck M. Plexin structures are coming: opportunities for multilevel investigations of semaphorin guidance receptors, their cell signaling mechanisms, and functions. Cell Mol Life Sci 2012; 69:3765-805. [PMID: 22744749 PMCID: PMC11115013 DOI: 10.1007/s00018-012-1019-0] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 04/09/2012] [Accepted: 04/11/2012] [Indexed: 01/13/2023]
Abstract
Plexin transmembrane receptors and their semaphorin ligands, as well as their co-receptors (Neuropilin, Integrin, VEGFR2, ErbB2, and Met kinase) are emerging as key regulatory proteins in a wide variety of developmental, regenerative, but also pathological processes. The diverse arenas of plexin function are surveyed, including roles in the nervous, cardiovascular, bone and skeletal, and immune systems. Such different settings require considerable specificity among the plexin and semaphorin family members which in turn are accompanied by a variety of cell signaling networks. Underlying the latter are the mechanistic details of the interactions and catalytic events at the molecular level. Very recently, dramatic progress has been made in solving the structures of plexins and of their complexes with associated proteins. This molecular level information is now suggesting detailed mechanisms for the function of both the extracellular as well as the intracellular plexin regions. Specifically, several groups have solved structures for extracellular domains for plexin-A2, -B1, and -C1, many in complex with semaphorin ligands. On the intracellular side, the role of small Rho GTPases has been of particular interest. These directly associate with plexin and stimulate a GTPase activating (GAP) function in the plexin catalytic domain to downregulate Ras GTPases. Structures for the Rho GTPase binding domains have been presented for several plexins, some with Rnd1 bound. The entire intracellular domain structure of plexin-A1, -A3, and -B1 have also been solved alone and in complex with Rac1. However, key aspects of the interplay between GTPases and plexins remain far from clear. The structural information is helping the plexin field to focus on key questions at the protein structural, cellular, as well as organism level that collaboratoria of investigations are likely to answer.
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Affiliation(s)
- Prasanta K. Hota
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
| | - Matthias Buck
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
- Department of Neuroscience, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
- Department of Pharmacology, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
- Comprehensive Cancer Center, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
- Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106 USA
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Conserved fiber-penton base interaction revealed by nearly atomic resolution cryo-electron microscopy of the structure of adenovirus provides insight into receptor interaction. J Virol 2012; 86:12322-9. [PMID: 22951835 DOI: 10.1128/jvi.01608-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Adenovirus (Ad) cell attachment is initiated by the attachment of the fiber protein to a primary receptor (usually CAR or CD46). This event is followed by the engagement of the penton base protein with a secondary receptor (integrin) via its loop region, which contains an Arg-Gly-Asp (RGD) motif, to trigger virus internalization. To understand the well-orchestrated adenovirus cell attachment process that involves the fiber and the penton base, we reconstructed the structure of an Ad5F35 capsid, comprising an adenovirus type 5 (Ad5) capsid pseudotyped with an Ad35 fiber, at a resolution of approximately 4.2 Å. The fiber-penton base interaction in the cryo-electron microscopic (cryo-EM) structure of Ad5F35 is similar to that in the cryo-EM structure of Ad5, indicating that the fiber-penton base interaction of adenovirus is conserved. Our structure also confirms that the C-terminal segment of the fiber tail domain constitutes the bottom trunk of the fiber shaft. Based on the conserved fiber-penton base interaction, we have proposed a model for the interaction of Ad5F35 with its primary and secondary receptors. This model could provide insight for designing adenovirus gene delivery vectors.
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β3 integrin interacts directly with GluA2 AMPA receptor subunit and regulates AMPA receptor expression in hippocampal neurons. Proc Natl Acad Sci U S A 2012; 109:1323-8. [PMID: 22232691 DOI: 10.1073/pnas.1113736109] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The integrins are transmembrane receptors for ECM proteins, and they regulate various cellular functions in the central nervous system. In hippocampal neurons, the β3 integrin subtype is required for homeostatic synaptic scaling of AMPA receptors (AMPARs) induced by chronic activity deprivation. The surface level of β3 integrin in postsynaptic neurons directly correlates with synaptic strength and the abundance of synaptic GluA2 AMPAR subunit. Although these observations suggest a functional link between β3 integrin and AMPAR, little is known about the mechanistic basis for the connection. Here we investigate the nature of β3 integrin and AMPAR interaction underlying the β3 integrin-dependent control of synaptic AMPAR expression and thus synaptic strength. We show that β3 integrin and GluA2 subunit form a complex in mouse brain that involves the direct binding between their cytoplasmic domains. In contrast, β3 integrin associates with GluA1 AMPAR subunit only weakly, and, in a heterologous expression system, the interaction requires the coexpression of GluA2. Surprisingly, in hippocampal pyramidal neurons, expressing β3 integrin mutants with either increased or decreased affinity for extracellular ligands has no differential effects in elevating excitatory synaptic currents and surface GluA2 levels compared with WT β3 integrin. Our findings identify an integrin family member, β3, as a direct interactor of an AMPAR subunit and provide molecular insights into how this cell-adhesion protein regulates the composition of cell-surface AMPARs.
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Chouhan B, Denesyuk A, Heino J, Johnson MS, Denessiouk K. Conservation of the human integrin-type beta-propeller domain in bacteria. PLoS One 2011; 6:e25069. [PMID: 22022374 PMCID: PMC3192720 DOI: 10.1371/journal.pone.0025069] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 08/26/2011] [Indexed: 11/18/2022] Open
Abstract
Integrins are heterodimeric cell-surface receptors with key functions in cell-cell and cell-matrix adhesion. Integrin α and β subunits are present throughout the metazoans, but it is unclear whether the subunits predate the origin of multicellular organisms. Several component domains have been detected in bacteria, one of which, a specific 7-bladed β-propeller domain, is a unique feature of the integrin α subunits. Here, we describe a structure-derived motif, which incorporates key features of each blade from the X-ray structures of human αIIbβ3 and αVβ3, includes elements of the FG-GAP/Cage and Ca(2+)-binding motifs, and is specific only for the metazoan integrin domains. Separately, we searched for the metazoan integrin type β-propeller domains among all available sequences from bacteria and unicellular eukaryotic organisms, which must incorporate seven repeats, corresponding to the seven blades of the β-propeller domain, and so that the newly found structure-derived motif would exist in every repeat. As the result, among 47 available genomes of unicellular eukaryotes we could not find a single instance of seven repeats with the motif. Several sequences contained three repeats, a predicted transmembrane segment, and a short cytoplasmic motif associated with some integrins, but otherwise differ from the metazoan integrin α subunits. Among the available bacterial sequences, we found five examples containing seven sequential metazoan integrin-specific motifs within the seven repeats. The motifs differ in having one Ca(2+)-binding site per repeat, whereas metazoan integrins have three or four sites. The bacterial sequences are more conserved in terms of motif conservation and loop length, suggesting that the structure is more regular and compact than those example structures from human integrins. Although the bacterial examples are not full-length integrins, the full-length metazoan-type 7-bladed β-propeller domains are present, and sometimes two tandem copies are found.
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Affiliation(s)
- Bhanupratap Chouhan
- Department of Biosciences, Åbo Akademi University, Turku, Finland
- Turku Center for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland
| | | | - Jyrki Heino
- Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland
| | - Mark S. Johnson
- Department of Biosciences, Åbo Akademi University, Turku, Finland
| | - Konstantin Denessiouk
- Turku Center for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland
- * E-mail:
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Abstract
Integrins are large, membrane-spanning, heterodimeric proteins that are essential for a metazoan existence. All members of the integrin family adopt a shape that resembles a large "head" on two "legs," with the head containing the sites for ligand binding and subunit association. Most of the receptor dimer is extracellular, but both subunits traverse the plasma membrane and terminate in short cytoplasmic domains. These domains initiate the assembly of large signaling complexes and thereby bridge the extracellular matrix to the intracellular cytoskeleton. To allow cells to sample and respond to a dynamic pericellular environment, integrins have evolved a highly responsive receptor activation mechanism that is regulated primarily by changes in tertiary and quaternary structure. This review summarizes recent progress in the structural and molecular functional studies of this important class of adhesion receptor.
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Affiliation(s)
- Iain D Campbell
- Department of Biochemistry, University of Oxford, United Kingdom.
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Molecular dynamics simulations of forced unbending of integrin α(v)β₃. PLoS Comput Biol 2011; 7:e1001086. [PMID: 21379327 PMCID: PMC3040657 DOI: 10.1371/journal.pcbi.1001086] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 01/18/2011] [Indexed: 11/24/2022] Open
Abstract
Integrins may undergo large conformational changes during activation, but the dynamic processes and pathways remain poorly understood. We used molecular dynamics to simulate forced unbending of a complete integrin αVβ3 ectodomain in both unliganded and liganded forms. Pulling the head of the integrin readily induced changes in the integrin from a bent to an extended conformation. Pulling at a cyclic RGD ligand bound to the integrin head also extended the integrin, suggesting that force can activate integrins. Interactions at the interfaces between the hybrid and β tail domains and between the hybrid and epidermal growth factor 4 domains formed the major energy barrier along the unbending pathway, which could be overcome spontaneously in ∼1 µs to yield a partially-extended conformation that tended to rebend. By comparison, a fully-extended conformation was stable. A newly-formed coordination between the αV Asp457 and the α-genu metal ion might contribute to the stability of the fully-extended conformation. These results reveal the dynamic processes and pathways of integrin conformational changes with atomic details and provide new insights into the structural mechanisms of integrin activation. Proteins can regulate their functions via conformational changes. One example is integrins, which are transmembrane receptors mediating cell-cell and cell-matrix adhesions. Inactive integrins may assume a bent conformation with low affinities for ligands unable to support adhesions. Intracellular or extracellular stimuli induce large scale changes from the bent to an extended conformation, resulting in active integrins with high affinities for ligands to mediate strong adhesions. We used molecular dynamics simulations to reveal the dynamics and pathways of integrin unbending in atomic details. Critical interactions in this process were identified. This study not only sheds light on the structural mechanisms of integrin activation, but also exemplifies allosteric regulations of protein functions.
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Castillo-Briceño P, Bihan D, Nilges M, Hamaia S, Meseguer J, García-Ayala A, Farndale RW, Mulero V. A role for specific collagen motifs during wound healing and inflammatory response of fibroblasts in the teleost fish gilthead seabream. Mol Immunol 2011; 48:826-34. [PMID: 21232799 PMCID: PMC3048961 DOI: 10.1016/j.molimm.2010.12.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 12/08/2010] [Accepted: 12/09/2010] [Indexed: 01/20/2023]
Abstract
Specific sites and sequences in collagen to which cells can attach, either directly or through protein intermediaries, were identified using Toolkits of 63-amino acid triple-helical peptides and specific shorter GXX'GEX″ motifs, which have different intrinsic affinity for integrins that mediate cell adhesion and migration. We have previously reported that collagen type I (COL-I) was able to prime in vitro the respiratory burst and induce a specific set of immune- and extracellular matrix-related molecules in phagocytes of the teleost fish gilthead seabream (Sparus aurata L.). It was also suggested that COL-I would provide an intermediate signal during the early inflammatory response in gilthead seabream. Since fibroblasts are highly involved in the initiation of wound repair and regeneration processes, in the present study SAF-1 cells (gilthead seabream fibroblasts) were used to identify the binding motifs in collagen by end-point and real-time cell adhesion assays using the collagen peptides and Toolkits. We identified the collagen motifs involved in the early magnesium-dependent adhesion of these cells. Furthermore, we found that peptides containing the GFOGER and GLOGEN motifs (where O is hydroxyproline) present high affinity for SAF-1 adhesion, expressed as both cell number and surface covering, while in cell suspensions, these motifs were also able to induce the expression of the genes encoding the proinflammatory molecules interleukin-1β and cyclooxygenase-2. These data suggest that specific collagen motifs are involved in the regulation of the inflammatory and healing responses of teleost fish.
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Affiliation(s)
| | - Dominique Bihan
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - Michael Nilges
- Department of Structural Biology and Chemistry, Institut Pasteur, 75724 Paris, France
| | - Samir Hamaia
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - José Meseguer
- Department of Cell Biology and Histology, University of Murcia, Murcia 30100, Spain
| | - Alfonsa García-Ayala
- Department of Cell Biology and Histology, University of Murcia, Murcia 30100, Spain
| | - Richard W. Farndale
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom
- Corresponding author. Tel.: +44 1223 766111; fax: +44 1223 333345.
| | - Victoriano Mulero
- Department of Cell Biology and Histology, University of Murcia, Murcia 30100, Spain
- Corresponding author. Tel.: +34 868887581; fax: +34 868883963.
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Abstract
Integrins are cell adhesion molecules that play important roles in many biological processes including hemostasis, immune responses, development, and cancer. Their adhesiveness is dynamically regulated through a process termed inside-out signaling. In addition, ligand binding transduces outside-in signals from the extracellular domain to the cytoplasm. Advances in the past several years have shed light on structural basis for integrin regulation and signaling, especially how the large-scale reorientations of the ectodomain are related to the inter-domain and intra-domain shape shifting that changes ligand-binding affinity. Experiments have also shown how the conformational changes of the ectodomain are linked to changes in the α- and β-subunit transmembrane and cytoplasmic domains.
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Affiliation(s)
- Guanyuan Fu
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA
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35
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Anthis NJ, Wegener KL, Critchley DR, Campbell ID. Structural diversity in integrin/talin interactions. Structure 2010; 18:1654-66. [PMID: 21134644 PMCID: PMC3157975 DOI: 10.1016/j.str.2010.09.018] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/25/2010] [Accepted: 09/01/2010] [Indexed: 10/18/2022]
Abstract
The adhesion of integrins to the extracellular matrix is regulated by binding of the cytoskeletal protein talin to the cytoplasmic tail of the β-integrin subunit. Structural studies of this interaction have hitherto largely focused on the β3-integrin, one member of the large and diverse integrin family. Here, we employ NMR to probe interactions and dynamics, revealing marked structural diversity in the contacts between β1A, β1D, and β3 tails and the Talin1 and Talin2 isoforms. Coupled with analysis of recent structures of talin/β tail complexes, these studies elucidate the thermodynamic determinants of this heterogeneity and explain why the Talin2/β1D isoforms, which are co-localized in striated muscle, form an unusually tight interaction. We also show that talin/integrin affinity can be enhanced 1000-fold by deleting two residues in the β tail. Together, these studies illustrate how the integrin/talin interaction has been fine-tuned to meet varying biological requirements.
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Affiliation(s)
- Nicholas J. Anthis
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3DR, UK
| | - Kate L. Wegener
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3DR, UK
| | - David R. Critchley
- Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Iain D. Campbell
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3DR, UK
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Hall PR, Leitão A, Ye C, Kilpatrick K, Hjelle B, Oprea TI, Larson RS. Small molecule inhibitors of hantavirus infection. Bioorg Med Chem Lett 2010; 20:7085-91. [PMID: 20951038 DOI: 10.1016/j.bmcl.2010.09.092] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 09/14/2010] [Accepted: 09/15/2010] [Indexed: 01/05/2023]
Abstract
Hantaviruses use α(v)β(3) integrins on the surface of human host cells as a gateway to invasion, hence compounds that target this receptor may be used as antiviral agents. To accomplish this aim, new peptidomimetic compounds were selected based on similarity to a cyclic peptide known to bind the α(v)β(3) receptor. This first round of biological screening identified peptidomimetic molecules which were effective hantavirus inhibitors in the low micromolar range, two thousand times more potent than the original cyclic peptide. Pharmacophore models were built to broaden the structural diversity of the second set of compounds screened. Structure-activity relationships (SAR) were drawn from the entire dataset. Further characterization by dose-response studies revealed that three compounds had potency in the nanomolar range. Selectivity assays with a panel of hantaviruses supported the mechanism of inhibition by targeting the α(v)β(3) receptor, through the β(3) integrin.
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Affiliation(s)
- Pamela R Hall
- Department of Pathology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
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37
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Reinehr R, Gohlke H, Sommerfeld A, Vom Dahl S, Häussinger D. Activation of integrins by urea in perfused rat liver. J Biol Chem 2010; 285:29348-56. [PMID: 20643649 DOI: 10.1074/jbc.m110.155135] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
High concentrations of urea were shown to induce a paradoxical regulatory volume decrease response with K(+) channel opening and subsequent hepatocyte shrinkage (Hallbrucker, C., vom Dahl, S., Ritter, M., Lang, F., and Häussinger, D. (1994) Pflügers Arch. 428, 552-560), although the hepatocyte plasma membrane is thought to be freely permeable to urea. The underlying mechanisms remained unclear. As shown in the present study, urea (100 mmol/liter) induced within 1 min an activation of β(1) integrins followed by an activation of focal adhesion kinase, c-Src, p38(MAPK), extracellular signal-regulated kinases, and c-Jun N-terminal kinase. Because α(5)β(1) integrin is known to act as a volume/osmosensor in hepatocytes, which becomes activated in response to hepatocyte swelling, the findings suggest that urea at high concentrations induces a nonosmotic activating perturbation of this osmosensor, thereby triggering a volume regulatory K(+) efflux. In line with this, similar to hypo-osmotic hepatocyte swelling, urea induced an inhibition of hepatic proteolysis, which was sensitive to p38(MAPK) inhibition. Molecular dynamics simulations of a three-dimensional model of the ectodomain of α(5)β(1) integrin in water, urea, or thiourea solutions revealed significant conformational changes of α(5)β(1) integrin in urea and thiourea solutions, in contrast to the simulation of α(5)β(1) in water. These changes lead to an unbending of the integrin structure around the genu, which may suggest activation, whereas the structures of single domains remained essentially unchanged. It is concluded that urea at high concentrations affects hepatic metabolism through direct activation of the α(5)β(1) integrin system.
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Affiliation(s)
- Roland Reinehr
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University Düsseldorf, D-40225 Düsseldorf, Germany
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Blue R, Li J, Steinberger J, Murcia M, Filizola M, Coller BS. Effects of limiting extension at the alphaIIb genu on ligand binding to integrin alphaIIbbeta3. J Biol Chem 2010; 285:17604-13. [PMID: 20363746 DOI: 10.1074/jbc.m110.107763] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Structural data of integrin alphaIIbbeta3 have been interpreted as supporting a model in which: 1) the receptor exists primarily in a "bent," low affinity conformation on unactivated platelets and 2) activation induces an extended, high affinity conformation prior to, or following, ligand binding. Previous studies found that "clasping" the alphaIIb head domain to the beta3 tail decreased fibrinogen binding. To study the role of alphaIIb extension about the genu, we introduced a disulfide "clamp" between the alphaIIb thigh and calf-1 domains. Clamped alphaIIbbeta3 had markedly reduced ability to bind the large soluble ligands fibrinogen and PAC-1 when activated with monoclonal antibody (mAb) PT25-2 but not when activated by Mn(2+) or by coexpressing the clamped alphaIIb with a beta3 subunit containing the activating mutation N339S. The clamp had little effect on the binding of the snake venom kistrin (M(r) 7,500) or alphaIIbbeta3-mediated adhesion to immobilized fibrinogen, but it did diminish the enhanced binding of mAb AP5 in the presence of kistrin. Collectively, our studies support a role for alphaIIb extension about the genu in the binding of ligands of 340,000 and 900,000 M(r) with mAb-induced activation but indicate that it is not an absolute requirement. Our data are consistent with alphaIIb extension resulting in increased access to the ligand-binding site and/or facilitating the conformational change(s) in beta3 that affect the intrinsic affinity of the binding pocket for ligand.
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Affiliation(s)
- Robert Blue
- Laboratory of Blood and Vascular Biology, The Rockefeller University, New York, New York 10021, USA
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Dotzauer D, Wolfenstetter S, Eibert D, Schneider S, Dietrich P, Sauer N. Novel PSI Domains in Plant and Animal H+-Inositol Symporters. Traffic 2010; 11:767-81. [DOI: 10.1111/j.1600-0854.2010.01057.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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41
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Integrin structure and functional relation with ion channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 674:1-7. [PMID: 20549935 DOI: 10.1007/978-1-4419-6066-5_1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Physical and functional link between cell adhesion molecules and ion channels provide a rapid connection between extracellular environment and cell physiology. Growing evidence does shows that frequent cross talk occurs between these classes of membrane proteins. These interactions are being addressed in ever increasing molecular detail. Recent advances have given X-ray resolved structure of the extracellular domains of integrin receptors. Such a level of resolution is still not available for the transmembrane and intracellular domains. Nonetheless, current molecular biological work is unraveling an intricate network connecting the cytoplasmic integrin domains with the cytoskeleton, ion channels and variety of cellular messengers. Overall, these studies show that integrins and ion channels both present bidirectional signaling features. Extracellular signals are usually transduced by integrins to trigger cellular responses that may involve ion fluxes, which can offer further relay. Intracellular processes and ion channel engagement can in turn affect integrin activation and expression and thus cell adhesion to the extracellular matrix. Moreover, ion channels themselves can communicate extracellular messages to both the cytoplasmic environment and integrin themselves. These interactions appear to often depend on formation of multiprotein membrane complexes that can recruit other elements, such as growth factor receptors and cytoplasmic signaling proteins. This chapter provides a general introduction to the field by giving a brief historical introduction and summarizing the main features of integrin structure and link to the cytoplasmic proteins. In addition, it outlines the main cellular processes inwhich channel-integrin interplay is known to exert clear physiological and pathological roles.
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42
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Provasi D, Murcia M, Coller BS, Filizola M. Targeted molecular dynamics reveals overall common conformational changes upon hybrid domain swing-out in beta3 integrins. Proteins 2009; 77:477-89. [PMID: 19455709 DOI: 10.1002/prot.22463] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The beta3 integrin family members alphaIIbeta3 and alphaVbeta3 signal bidirectionally through long-range allosteric changes, including a transition from a bent unliganded-closed low-affinity state to an extended liganded-open high-affinity state. To obtain an atomic-level description of this transition in an explicit solvent, we carried out targeted molecular dynamics simulations of the headpieces of alphaIIbeta3 and alphaVbeta3 integrins. Although minor differences were observed between these receptors, our results suggest a common transition pathway in which the hybrid domain swing-out is accompanied by conformational changes within the beta3 betaA (I-like) domain that propagate through the alpha7 helix C-terminus, and are followed by the alpha7 helix downward motion and the opening of the beta6-alpha7 loop. Breaking of contact interactions between the beta6-alpha7 loop and the alpha1 helix N-terminus results in helix straightening, internal rearrangements of the specificity determining loop (SDL), movement of the beta1-alpha1 loop toward the metal ion dependent adhesion site (MIDAS), and final changes at the interfaces between the beta3 betaA (I-like) domain and either the hybrid or the alpha beta-propeller domains. Taken together, our results suggest novel testable hypotheses of intradomain and interdomain interactions responsible for beta3 integrin activation.
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Affiliation(s)
- Davide Provasi
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029-6574, USA
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Gaillard T, Dejaegere A, Stote RH. Dynamics of beta3 integrin I-like and hybrid domains: insight from simulations on the mechanism of transition between open and closed forms. Proteins 2009; 76:977-94. [PMID: 19350618 DOI: 10.1002/prot.22404] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The conformational dynamics of the I-like and Hybrid domains from the beta3 integrin headpiece were studied by molecular dynamics simulation and normal mode analysis. Crystallographic structures of integrins show that the integrin headpiece can exist in largely different conformations manifested by a significant difference in the angle between the I-like and Hybrid domains. The relative orientation of these two domains is believed to be a crucial element of integrin function, as it may relate local structural modifications induced by ligand binding into large-scale conformational changes. To investigate the detailed mechanisms responsible for this coupling, we carried out molecular dynamics simulations of the I-like/Hybrid system and employed quasi-harmonic and normal mode analyses to characterize the large-scale motions. Our results show that the conformational transition of I-like and Hybrid domains inferred from crystallographic data is contained in the low-frequency dynamics of the system. Using targeted molecular dynamics simulations, we investigated the roles played by two structural elements of the I-like domain, the alpha7 and alpha1 helices, in the interdomain transition. From our results, we propose that these two helices function in tandem to initiate large-scale, interdomain conformational transition apparent in integrin activation and signaling.
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Affiliation(s)
- Thomas Gaillard
- Laboratoire de Biophysicochimie Moléculaire, Institut de Chimie de Strasbourg, Université de Strasbourg, Strasbourg, France
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Nogales A, García C, Pérez J, Callow P, Ezquerra TA, González-Rodríguez J. Three-dimensional model of human platelet integrin alphaIIb beta3 in solution obtained by small angle neutron scattering. J Biol Chem 2009; 285:1023-31. [PMID: 19897481 DOI: 10.1074/jbc.m109.050039] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Integrin alphaIIbbeta3 is the major membrane protein and adhesion receptor at the surface of blood platelets, which after activation plays a key role in platelet plug formation in hemostasis and thrombosis. Small angle neutron scattering (SANS) and shape reconstruction algorithms allowed formation of a low resolution three-dimensional model of whole alphaIIb beta3 in Ca(2+)/detergent solutions. Model projections after 90 degrees rotation along its long axis show an elongated and "arched" form (135 degrees) not observed before and a "handgun" form. This 20-nm-long structure is well defined, despite alphaIIb beta3 multidomain nature and expected segmental flexibility, with the largest region at the top, followed by two narrower and smaller regions at the bottom. Docking of this SANS envelope into the high resolution structure of alphaIIb beta3, reconstructed from crystallographic and NMR data, shows that the solution structure is less constrained, allows tentative assignment of the disposition of the alphaIIb and beta3 subunits and their domains within the model, and points out the structural analogies and differences of the SANS model with the crystallographic models of the recombinant ectodomains of alphaIIb beta3 and alphaV beta3 and with the cryo-electron microscopy model of whole alphaIIb beta3. The ectodomain is in the bent configuration at the top of the model, where alphaIIb and beta3 occupy the concave and convex sides, respectively, at the arched projection, with their bent knees at its apex. It follows the narrower transmembrane region and the cytoplasmic domains at the bottom end. AlphaIIb beta3 aggregated in Mn(2+)/detergent solutions, which impeded to get its SANS model.
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Affiliation(s)
- Aurora Nogales
- Departamento de Biofísica, Instituto de Química Física, Consejo Superior de Investigationes Científicas, Serrano 119, Madrid 28006, Spain
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45
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Cryo-electron microscopy structure of an adenovirus-integrin complex indicates conformational changes in both penton base and integrin. J Virol 2009; 83:11491-501. [PMID: 19726496 DOI: 10.1128/jvi.01214-09] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A structure of adenovirus type 12 (HAdV12) complexed with a soluble form of integrin alphavbeta5 was determined by cryo-electron microscopy (cryoEM) image reconstruction. Subnanometer resolution (8 A) was achieved for the icosahedral capsid with moderate resolution (27 A) for integrin density above each penton base. Modeling with alphavbeta3 and alpha(IIb)beta3 crystal structures indicates that a maximum of four integrins fit over the pentameric penton base. The close spacing (approximately 60 A) of the RGD protrusions on penton base precludes integrin binding in the same orientation to neighboring RGD sites. Flexible penton-base RGD loops and incoherent averaging of bound integrin molecules explain the moderate resolution observed for the integrin density. A model with four integrins bound to a penton base suggests that integrin might extend one RGD-loop in the direction that could induce a conformational change in the penton base involving clockwise untwisting of the pentamer. A global conformational change in penton base could be one step on the way to the release of Ad vertex proteins during cell entry. Comparison of the cryoEM structure with bent and extended models for the integrin ectodomain reveals that integrin adopts an extended conformation when bound to the Ad penton base, a multivalent viral ligand. These findings shed further light on the structural basis of integrin binding to biologically relevant ligands, as well as on the molecular events leading to HAdV cell entry.
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Xiong JP, Mahalingham B, Alonso JL, Borrelli LA, Rui X, Anand S, Hyman BT, Rysiok T, Müller-Pompalla D, Goodman SL, Arnaout MA. Crystal structure of the complete integrin alphaVbeta3 ectodomain plus an alpha/beta transmembrane fragment. J Cell Biol 2009; 186:589-600. [PMID: 19704023 PMCID: PMC2733745 DOI: 10.1083/jcb.200905085] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Accepted: 07/16/2009] [Indexed: 11/22/2022] Open
Abstract
We determined the crystal structure of 1TM-alphaVbeta3, which represents the complete unconstrained ectodomain plus short C-terminal transmembrane stretches of the alphaV and beta3 subunits. 1TM-alphaVbeta3 is more compact and less active in solution when compared with DeltaTM-alphaVbeta3, which lacks the short C-terminal stretches. The structure reveals a bent conformation and defines the alpha-beta interface between IE2 (EGF-like 2) and the thigh domains. Modifying this interface by site-directed mutagenesis leads to robust integrin activation. Fluorescent lifetime imaging microscopy of inactive full-length alphaVbeta3 on live cells yields a donor-membrane acceptor distance, which is consistent with the bent conformation and does not change in the activated integrin. These data are the first direct demonstration of conformational coupling of the integrin leg and head domains, identify the IE2-thigh interface as a critical steric barrier in integrin activation, and suggest that inside-out activation in intact cells may involve conformational changes other than the postulated switch to a genu-linear state.
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Affiliation(s)
- Jian-Ping Xiong
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Bhuvaneshwari Mahalingham
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Jose Luis Alonso
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Laura Ann Borrelli
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Xianliang Rui
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Saurabh Anand
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Bradley T. Hyman
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
| | - Thomas Rysiok
- Biologicals: Protein and Cell Science, Biologicals: Protein Purification, and Therapeutic Area Oncology: Biochemistry and Cellular Pharmacology, Merck-Serono Research, 64293 Darmstadt, Germany
| | - Dirk Müller-Pompalla
- Biologicals: Protein and Cell Science, Biologicals: Protein Purification, and Therapeutic Area Oncology: Biochemistry and Cellular Pharmacology, Merck-Serono Research, 64293 Darmstadt, Germany
| | - Simon L. Goodman
- Biologicals: Protein and Cell Science, Biologicals: Protein Purification, and Therapeutic Area Oncology: Biochemistry and Cellular Pharmacology, Merck-Serono Research, 64293 Darmstadt, Germany
| | - M. Amin Arnaout
- Program in Leukocyte Biology and Inflammation and Program in Structural Biology, Nephrology Division, Department of Medicine and Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129
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Abstract
Integrins are a ubiquitous family of non-covalently associated alpha/beta transmembrane heterodimers linking extracellular ligands to intracellular signaling pathways [1] [Cell, 2002; 110: 673]. Platelets contain five integrins, three beta1 integrins that mediate platelet adhesion to the matrix proteins collagen, fibronectin and laminin, and the beta3 integrins alphavbeta3 and alphaIIbbeta3 [2] [J Clin Invest, 2005; 115: 3363]. While there are only several hundred alphavbeta3 molecules per platelet, alphavbeta3 mediates platelet adhesion to osteopontin and vitronectin in vitro [3] [J Biol Chem, 1997; 272: 8137]; whether this occurs in vivo remains unknown. By contrast, the 80,000 alphaIIbbeta3 molecules on agonist-stimulated platelets bind fibrinogen, von Willebrand factor, and fibronectin, mediating platelet aggregation when the bound proteins crosslink adjacent platelets [2] [J Clin Invest, 2005; 115: 3363]. Although platelet integrins are poised to shift from resting to active conformations, tight regulation of their activity is essential to prevent the formation of intravascular thrombi. This review focuses on the structure and function of the intensively studied beta3 integrins, in particular alphaIIbbeta3, but reference will be made to other integrins where relevant.
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Affiliation(s)
- J S Bennett
- Hematology-Oncology Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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Abstract
Specific therapy is not available for hantavirus cardiopulmonary syndrome caused by Andes virus (ANDV). Peptides capable of blocking ANDV infection in vitro were identified using antibodies against ANDV surface glycoproteins Gn and Gc to competitively elute a cyclic nonapeptide-bearing phage display library from purified ANDV particles. Phage was examined for ANDV infection inhibition in vitro, and nonapeptides were synthesized based on the most-potent phage sequences. Three peptides showed levels of viral inhibition which were significantly increased by combination treatment with anti-Gn- and anti-Gc-targeting peptides. These peptides will be valuable tools for further development of both peptide and nonpeptide therapeutic agents.
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Zhu J, Luo BH, Xiao T, Zhang C, Nishida N, Springer TA. Structure of a complete integrin ectodomain in a physiologic resting state and activation and deactivation by applied forces. Mol Cell 2009; 32:849-61. [PMID: 19111664 DOI: 10.1016/j.molcel.2008.11.018] [Citation(s) in RCA: 370] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 08/08/2008] [Accepted: 11/25/2008] [Indexed: 12/01/2022]
Abstract
The complete ectodomain of integrin alpha(IIb)beta(3) reveals a bent, closed, low-affinity conformation, the beta knee, and a mechanism for linking cytoskeleton attachment to high affinity for ligand. Ca and Mg ions in the recognition site, including the synergistic metal ion binding site (SyMBS), are loaded prior to ligand binding. Electrophilicity of the ligand-binding Mg ion is increased in the open conformation. The beta(3) knee passes between the beta(3)-PSI and alpha(IIb)-knob to bury the lower beta leg in a cleft, from which it is released for extension. Different integrin molecules in crystals and EM reveal breathing that appears on pathway to extension. Tensile force applied to the extended ligand-receptor complex stabilizes the closed, low-affinity conformation. By contrast, an additional lateral force applied to the beta subunit to mimic attachment to moving actin filaments stabilizes the open, high-affinity conformation. This mechanism propagates allostery over long distances and couples cytoskeleton attachment of integrins to their high-affinity state.
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Affiliation(s)
- Jianghai Zhu
- The Immune Disease Institute and Department of Pathology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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50
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Socher I, Andrei-Selmer C, Bein G, Kroll H, Santoso S. Low-avidity HPA-1a alloantibodies in severe neonatal alloimmune thrombocytopenia are detectable with surface plasmon resonance technology. Transfusion 2009; 49:943-52. [PMID: 19175553 DOI: 10.1111/j.1537-2995.2008.02065.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is mostly caused by maternal alloantibodies directed against the human platelet alloantigen (HPA)-1a. Currently, the serologic diagnosis of FNAIT is based on the characterization of the HPA alloantibodies in monoclonal antibody-based antigen-capture assays (e.g., MAIPA assay). Accumulated current evidence indicated that such assays may overlook some HPA-1a antibodies. STUDY DESIGN AND METHODS This study employed surface plasmon resonance (SPR) technology using immunoaffinity-purified glycoprotein IIb/IIIa isoforms immobilized on biosensor chips to study the binding kinetics of HPA-1a alloantibodies from different FNAIT cases in real time. RESULTS Analysis of HPA-1a alloantibodies from FNAIT cases (n = 9) in SPR showed a moderate relative response (22.2-69.7 resonance units [RU]) and slow antibody dissociation. After the dissociation phase, varying amounts of bound antibodies (41%-79%) remained on the chip. In contrast in HPA-1a alloantibodies from a patient suffering from posttransfusion purpura, a high relative response (approximately 490 RU) was observed at the end of the association phase and no dissociation of antibody binding was detectable. Of particular relevance, by the use of this SPR technique, HPA-1a alloantibodies were detected in two severe FNAIT cases that had determined as false negative by MAIPA assay. In SPR, these HPA-1a alloantibodies showed low-avidity nature characterized by gradual dissociation of antibody during the association phase and complete detachment of antibody binding after the dissociation phase. This high "off-rate" character of low-avidity HPA-1a alloantibodies indicates that such antibody binding is easily detachable by the extensive washing procedure of the MAIPA. CONCLUSIONS Our results demonstrated that the SPR method can facilitate the diagnosis of clinically relevant low-avidity HPA-1a antibodies.
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Affiliation(s)
- Ines Socher
- Institute for Clinical Immunology and Transfusion Medicine, Giessen, Germany
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