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Sachs L, Denker C, Greinacher A, Palankar R. Quantifying single-platelet biomechanics: An outsider's guide to biophysical methods and recent advances. Res Pract Thromb Haemost 2020; 4:386-401. [PMID: 32211573 PMCID: PMC7086474 DOI: 10.1002/rth2.12313] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/10/2019] [Accepted: 01/07/2020] [Indexed: 01/30/2023] Open
Abstract
Platelets are the key cellular components of blood primarily contributing to formation of stable hemostatic plugs at the site of vascular injury, thus preventing excessive blood loss. On the other hand, excessive platelet activation can contribute to thrombosis. Platelets respond to many stimuli that can be of biochemical, cellular, or physical origin. This drives platelet activation kinetics and plays a vital role in physiological and pathological situations. Currently used bulk assays are inadequate for comprehensive biomechanical assessment of single platelets. Individual platelets interact and respond differentially while modulating their biomechanical behavior depending on dynamic changes that occur in surrounding microenvironments. Quantitative description of such a phenomenon at single-platelet regime and up to nanometer resolution requires methodological approaches that can manipulate individual platelets at submicron scales. This review focusses on principles, specific examples, and limitations of several relevant biophysical methods applied to single-platelet analysis such as micropipette aspiration, atomic force microscopy, scanning ion conductance microscopy and traction force microscopy. Additionally, we are introducing a promising single-cell approach, real-time deformability cytometry, as an emerging biophysical method for high-throughput biomechanical characterization of single platelets. This review serves as an introductory guide for clinician scientists and beginners interested in exploring one or more of the above-mentioned biophysical methods to address outstanding questions in single-platelet biomechanics.
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Affiliation(s)
- Laura Sachs
- Institute of Immunology and Transfusion MedicineUniversity Medicine GreifswaldGreifswaldGermany
| | | | - Andreas Greinacher
- Institute of Immunology and Transfusion MedicineUniversity Medicine GreifswaldGreifswaldGermany
| | - Raghavendra Palankar
- Institute of Immunology and Transfusion MedicineUniversity Medicine GreifswaldGreifswaldGermany
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2
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Nguyen TH. Single-molecule force spectroscopy applied to heparin-induced thrombocytopenia. J Mol Recognit 2016; 30. [PMID: 27790761 DOI: 10.1002/jmr.2585] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 09/13/2016] [Accepted: 09/19/2016] [Indexed: 01/01/2023]
Abstract
Heparin-induced thrombocytopenia (HIT), occurring up to approximately 1% to 5% of patients receiving the antithrombotic drug heparins, has a complex pathogenesis involving multiple partners ranging from small molecules to cells/platelets. Recently, insights into the mechanism of HIT have been achieved by using single-molecule force spectroscopy (SMFS), a methodology that allows direct measurements of interactions among HIT partners. Here, the potential of SMFS in unraveling the mechanism of the initial steps in the pathogenesis of HIT at single-molecule resolution is highlighted. The new findings ranging from the molecular binding strengths and kinetics to the determination of the boundary between risk and non-risk heparin drugs or platelet-surface and platelet-platelet interactions will be reviewed. These novel results together have contributed to elucidate the mechanisms underlying HIT and demonstrate how SMFS can be applied to develop safer drugs with a reduced risk profile.
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Affiliation(s)
- Thi-Huong Nguyen
- Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475, Greifswald, Germany.,ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489, Greifswald, Germany
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3
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Nguyen TH, Palankar R, Bui VC, Medvedev N, Greinacher A, Delcea M. Rupture Forces among Human Blood Platelets at different Degrees of Activation. Sci Rep 2016; 6:25402. [PMID: 27146004 PMCID: PMC4857101 DOI: 10.1038/srep25402] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/18/2016] [Indexed: 11/21/2022] Open
Abstract
Little is known about mechanics underlying the interaction among platelets during activation and aggregation. Although the strength of a blood thrombus has likely major biological importance, no previous study has measured directly the adhesion forces of single platelet-platelet interaction at different activation states. Here, we filled this void first, by minimizing surface mediated platelet-activation and second, by generating a strong adhesion force between a single platelet and an AFM cantilever, preventing early platelet detachment. We applied our setup to measure rupture forces between two platelets using different platelet activation states, and blockade of platelet receptors. The rupture force was found to increase proportionally to the degree of platelet activation, but reduced with blockade of specific platelet receptors. Quantification of single platelet-platelet interaction provides major perspectives for testing and improving biocompatibility of new materials; quantifying the effect of drugs on platelet function; and assessing the mechanical characteristics of acquired/inherited platelet defects.
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Affiliation(s)
- Thi-Huong Nguyen
- Nanostructure Group, ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489 Greifswald, Germany.,Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Raghavendra Palankar
- Nanostructure Group, ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489 Greifswald, Germany.,Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Van-Chien Bui
- Nanostructure Group, ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489 Greifswald, Germany.,Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Nikolay Medvedev
- Nanostructure Group, ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489 Greifswald, Germany
| | - Andreas Greinacher
- Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany
| | - Mihaela Delcea
- Nanostructure Group, ZIK HIKE - Center for Innovation Competence, Humoral Immune Reactions in Cardiovascular Diseases, University of Greifswald, 17489 Greifswald, Germany.,Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, 17475 Greifswald, Germany
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4
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Yildirimer L, Seifalian AM. Sterilization-Induced Changes in Surface Topography of Biodegradable POSS-PCLU and the Cellular Response of Human Dermal Fibroblasts. Tissue Eng Part C Methods 2015; 21:614-30. [DOI: 10.1089/ten.tec.2014.0270] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Lara Yildirimer
- Division of Surgery & Interventional Science, UCL Centre for Nanotechnology & Regenerative Medicine, University College London, London, United Kingdom
| | - Alexander M. Seifalian
- Division of Surgery & Interventional Science, UCL Centre for Nanotechnology & Regenerative Medicine, University College London, London, United Kingdom
- Royal Free London NHS Foundation Trust Hospital, London, United Kingdom
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5
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Du Plooy JN, Buys A, Duim W, Pretorius E. Comparison of platelet ultrastructure and elastic properties in thrombo-embolic ischemic stroke and smoking using atomic force and scanning electron microscopy. PLoS One 2013; 8:e69774. [PMID: 23874998 PMCID: PMC3713049 DOI: 10.1371/journal.pone.0069774] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/16/2013] [Indexed: 11/23/2022] Open
Abstract
Thrombo-embolic ischemic stroke is a serious and debilitating disease, and it remains the second most common cause of death worldwide. Tobacco smoke exposure continues to be responsible for preventable deaths around the world, and is a major risk factor for stroke. Platelets play a fundamental role in clotting, and their pathophysiological functioning is present in smokers and stroke patients, resulting in a pro-thrombotic state. In the current manuscript, atomic force and scanning electron microscopy were used to compare the platelets of smokers, stroke patients and healthy individuals. Results showed that the elastic modulus of stroke platelets is decreased by up to 40%, whereas there is an elasticity decrease of up to 20% in smokers' platelets. This indicates a biophysical alteration of the platelets. Ultrastructurally, both the stroke patients and smokers' platelets are more activated than the healthy control group, with prominent cytoskeletal rearrangement involved; but to a more severe extent in the stroke group than in the smokers. Importantly, this is a confirmation of the extent of smoking as risk factor for stroke. We conclude by suggesting that the combined AFM and SEM analyses of platelets might give valuable information about the disease status of patients. Efficacy of treatment regimes on the integrity, cell shape, roughness and health status of platelets may be tracked, as this cell's health status is crucial in the over-activated coagulation system of conditions like stroke.
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Affiliation(s)
- Jeanette Noel Du Plooy
- Department of Physiology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Antoinette Buys
- Microscopy and Microanalysis, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Wiebren Duim
- Department of Neurology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
| | - Etheresia Pretorius
- Department of Physiology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
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6
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Whited AM, Park PSH. Atomic force microscopy: a multifaceted tool to study membrane proteins and their interactions with ligands. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:56-68. [PMID: 23603221 DOI: 10.1016/j.bbamem.2013.04.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/22/2013] [Accepted: 04/09/2013] [Indexed: 01/31/2023]
Abstract
Membrane proteins are embedded in lipid bilayers and facilitate the communication between the external environment and the interior of the cell. This communication is often mediated by the binding of ligands to the membrane protein. Understanding the nature of the interaction between a ligand and a membrane protein is required to both understand the mechanism of action of these proteins and for the development of novel pharmacological drugs. The highly hydrophobic nature of membrane proteins and the requirement of a lipid bilayer for native function have hampered the structural and molecular characterizations of these proteins under physiologically relevant conditions. Atomic force microscopy offers a solution to studying membrane proteins and their interactions with ligands under physiologically relevant conditions and can provide novel insights about the nature of these critical molecular interactions that facilitate cellular communication. In this review, we provide an overview of the atomic force microscopy technique and discuss its application in the study of a variety of questions related to the interaction between a membrane protein and a ligand. This article is part of a Special Issue entitled: Structural and biophysical characterization of membrane protein-ligand binding.
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Affiliation(s)
- Allison M Whited
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
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7
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E. Kehrel B, F. Brodde M. State of the art in platelet function testing. Transfus Med Hemother 2013; 40:73-86. [PMID: 23653569 PMCID: PMC3638976 DOI: 10.1159/000350469] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 03/05/2013] [Indexed: 12/20/2022] Open
Abstract
Platelets perform many functions in hemostasis but also in other areas of physiology and pathology. Therefore, it is obvious that many different function tests have been developed, each one conceived and standardized for a special purpose. This review will summarize the different fields in which platelet function testing is currently in use; diagnostics of patients with bleeding disorders, monitoring patients' response to anti-platelet therapy, monitoring in transfusion medicine (blood donors, platelet concentrates, and after transfusion), and monitoring in perioperative medicine to predict bleeding tendency. The second part of the review outlines different methods for platelet function testing, spanning bleeding time, and platelet counting as well as determining platelet adhesion, platelet secretion, platelet aggregation, platelet morphology, platelet signal transduction, platelet procoagulant activity, platelet apoptosis, platelet proteomics, and molecular biology.
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Affiliation(s)
- Beate E. Kehrel
- Department of Anesthesiology, Intensive Care and Pain Medicine, Experimental and Clinical Hemostasis, University of Münster, Germany
| | - Martin F. Brodde
- Department of Anesthesiology, Intensive Care and Pain Medicine, Experimental and Clinical Hemostasis, University of Münster, Germany
- OxProtect GmbH, Münster, Germany
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8
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Lackner JM, Waldhauser W, Hartmann P, Bruckert F, Weidenhaupt M, Major R, Sanak M, Wiesinger M, Heim D. Hemocompatibility of Inorganic Physical Vapor Deposition (PVD) Coatings on Thermoplastic Polyurethane Polymers. J Funct Biomater 2012; 3:283-97. [PMID: 24955532 PMCID: PMC4047937 DOI: 10.3390/jfb3020283] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Revised: 04/10/2012] [Accepted: 04/11/2012] [Indexed: 01/22/2023] Open
Abstract
Biocompatibility improvements for blood contacting materials are of increasing interest for implanted devices and interventional tools. The current study focuses on inorganic (titanium, titanium nitride, titanium oxide) as well as diamond-like carbon (DLC) coating materials on polymer surfaces (thermoplastic polyurethane), deposited by magnetron sputtering und pulsed laser deposition at room temperature. DLC was used pure (a-C:H) as well as doped with silicon, titanium, and nitrogen + titanium (a-C:H:Si, a-C:H:Ti, a-C:H:N:Ti). In-vitro testing of the hemocompatibility requires mandatory dynamic test conditions to simulate in-vivo conditions, e.g., realized by a cone-and-plate analyzer. In such tests, titanium- and nitrogen-doped DLC and titanium nitride were found to be optimally anti-thrombotic and better than state-of-the-art polyurethane polymers. This is mainly due to the low tendency to platelet microparticle formation, a high content of remaining platelets in the whole blood after testing and low concentration of platelet activation and aggregation markers. Comparing this result to shear-flow induced cell motility tests with e.g., Dictostelium discoideum cell model organism reveals similar tendencies for the investigated materials.
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Affiliation(s)
- Juergen M Lackner
- Joanneum Research Forschungsges.m.b.H., Institute for Surface Technologies and Photonics, Functional Surfaces, Leobner Straße 94, Niklasdorf A-8712, Austria.
| | - Wolfgang Waldhauser
- Joanneum Research Forschungsges.m.b.H., Institute for Surface Technologies and Photonics, Functional Surfaces, Leobner Straße 94, Niklasdorf A-8712, Austria.
| | - Paul Hartmann
- Joanneum Research Forschungsges.m.b.H., Institute for Surface Technologies and Photonics, Functional Surfaces, Leobner Straße 94, Niklasdorf A-8712, Austria.
| | - Franz Bruckert
- Grenoble Institute of Technology, Parvis Louis Néel, 38000 Grenoble Cedex 9, France.
| | - Marianne Weidenhaupt
- Grenoble Institute of Technology, Parvis Louis Néel, 38000 Grenoble Cedex 9, France.
| | - Roman Major
- Institute of Metallurgy and Materials Sciences, Polish Academy of Sciences, Reymonta 25, Krakow 30-059, Poland.
| | - Marek Sanak
- Department of Medicine, Jagiellonian University Medical College, Kopernika 23, Kraków 31-501, Poland.
| | - Martin Wiesinger
- Faculty of Technical and Environmental Sciences, University of Applied Sciences Upper Austria, Franz-Fritsch-Straße 11, Wels 4600, Austria.
| | - Daniel Heim
- Faculty of Technical and Environmental Sciences, University of Applied Sciences Upper Austria, Franz-Fritsch-Straße 11, Wels 4600, Austria.
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9
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Multiscale morphology of organic semiconductor thin films controls the adhesion and viability of human neural cells. Biophys J 2010; 98:2804-12. [PMID: 20550892 DOI: 10.1016/j.bpj.2010.03.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 02/15/2010] [Accepted: 03/15/2010] [Indexed: 11/20/2022] Open
Abstract
We investigate how multiscale morphology of functional thin films affects the in vitro behavior of human neural astrocytoma 1321N1 cells. Pentacene thin film morphology is precisely controlled by means of the film thickness, Theta (here expressed in monolayers (ML)). Fluorescence and atomic force microscopy allow us to correlate the shape, adhesion, and proliferation of cells to the morphological properties of pentacene films controlled by saturated roughness, sigma, correlation length, xi, and fractal dimension, d(f). At early incubation times, cell adhesion exhibits a transition from higher to lower values at Theta approximately 10 ML. This is explained using a model of conformal adhesion of the cell membrane onto the growing pentacene islands. From the model fitting of the data, we show that the cell explores the surface with a deformation of the membrane whose minimum curvature radius is 90 (+/- 45) nm. The transition in the adhesion at approximately 10 ML arises from the saturation of xi accompanied by the monotonic increase of sigma, which leads to a progressive decrease of the pentacene local radius of curvature and hence to the surface area accessible to the cell. Cell proliferation is also enhanced for Theta < 10 ML, and the optimum morphology parameter ranges for cell deployment and growth are sigma <or= 6 nm, xi > 500 nm, and d(f) > 2.45. The characteristic time of cell proliferation is tau approximately 10 +/- 2 h.
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10
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Karagkiozaki V, Logothetidis S, Lousinian S, Giannoglou G. Impact of surface electric properties of carbon-based thin films on platelets activation for nano-medical and nano-sensing applications. Int J Nanomedicine 2009; 3:461-9. [PMID: 19337414 PMCID: PMC2636585 DOI: 10.2147/ijn.s3607] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Electric surface properties of biomaterials, playing key role to various biointerfacial interactions, were related to hemocompatibility and biosensing phenomena. In this study, the examination of surface electric properties of amorphous hydrogenated carbon thin films (a-C:H) was carried out by means of electrostatic force microscope (EFM) and observation of differences in spatial charge distribution on the surface of the examined films during platelets adhesion was made. The thrombogenic potential of a-C:H thin films developed by magnetron sputtering with ~42% sp3 content and hydrogen partial pressure during deposition was evaluated, by in situ observation with atomic force microscope (AFM) of platelets’ activation and their subsequent adhesion. Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied. Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus. The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.
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Affiliation(s)
- Varvara Karagkiozaki
- Physics Department, Laboratory for Thin Films-Nanosystems and Nanometrology (LTFN), Medical School, AHEPA University General Hospital, 1st Cardiology Department, Aristotle University of Thessaloniki, Greece
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11
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Hantgan RR, Stahle MC, Horita DA. Entropy Drives Integrin αIIbβ3:Echistatin Binding—Evidence from Surface Plasmon Resonance Spectroscopy. Biochemistry 2008; 47:2884-92. [DOI: 10.1021/bi701877a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Roy R. Hantgan
- Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1016
| | - Mary C. Stahle
- Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1016
| | - David A. Horita
- Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157-1016
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12
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Hantgan RR, Stahle MC, Connor JH, Horita DA, Rocco M, McLane MA, Yakovlev S, Medved L. Integrin alphaIIbbeta3:ligand interactions are linked to binding-site remodeling. Protein Sci 2006; 15:1893-906. [PMID: 16877710 PMCID: PMC2242588 DOI: 10.1110/ps.052049506] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
This study tested the hypothesis that high-affinity binding of macromolecular ligands to the alphaIIbbeta3 integrin is tightly coupled to binding-site remodeling, an induced-fit process that shifts a conformational equilibrium from a resting toward an open receptor. Interactions between alphaIIbbeta3 and two model ligands-echistatin, a 6-kDa recombinant protein with an RGD integrin-targeting sequence, and fibrinogen's gamma-module, a 30-kDa recombinant protein with a KQAGDV integrin binding site-were measured by sedimentation velocity, fluorescence anisotropy, and a solid-phase binding assay, and modeled by molecular graphics. Studying echistatin variants (R24A, R24K, D26A, D26E, D27W, D27F), we found that electrostatic contacts with charged residues at the alphaIIb/beta3 interface, rather than nonpolar contacts, perturb the conformation of the resting integrin. Aspartate 26, which interacts with the nearby MIDAS cation, was essential for binding, as D26A and D26E were inactive. In contrast, R24K was fully and R24A partly active, indicating that the positively charged arginine 24 contributes to, but is not required for, integrin recognition. Moreover, we demonstrated that priming--i.e., ectodomain conformational changes and oligomerization induced by incubation at 35 degrees C with the ligand-mimetic peptide cHarGD--promotes complex formation with fibrinogen's gamma-module. We also observed that the gamma-module's flexible carboxy terminus was not required for alphaIIbbeta3 integrin binding. Our studies differentiate priming ligands, which bind to the resting receptor and perturb its conformation, from regulated ligands, where binding-site remodeling must first occur. Echistatin's binding energy is sufficient to rearrange the subunit interface, but regulated ligands like fibrinogen must rely on priming to overcome conformational barriers.
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Affiliation(s)
- Roy R Hantgan
- Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1019, USA.
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13
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Hussain MA, Agnihotri A, Siedlecki CA. AFM imaging of ligand binding to platelet integrin alphaIIbbeta3 receptors reconstituted into planar lipid bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:6979-86. [PMID: 16008412 DOI: 10.1021/la046943h] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The platelet integrin alphaIIbbeta3 plays a key role in platelet adhesion, activation, and aggregation at the subendothelium and at protein-coated synthetic biomaterials. In this study, interactions between alphaIIbbeta3 and both protein and peptide ligands for the receptor were imaged under physiological conditions by high-resolution atomic force microscopy (AFM). To directly image the ligand-receptor interactions, alphaIIbbeta3 receptors were reconstituted into a supported lipid bilayer formed on a mica surface in the AFM fluid cell assembly and subsequently activated with Mn2+. Fibrinogen, the natural protein ligand for the integrin, as well as a nanogold-labeled peptide ligand (an RGD-containing heptamer) were infused into the AFM fluid cell, incubated with the reconstituted and activated receptors, and imaged under buffer. Height images illustrating topographical features showed the integrin reconstituted in the bilayer. Fibrinogen molecules binding to the receptors were easily observed in the height images, with fibrinogen showing its characteristic trinodular structure and occasionally bridging integrin receptors. Fibrinogen was observed to bind to integrins at the D-domain consistent with the location of the gamma-chain dodecapeptide, while fibrinogen bridging integrins bound to receptors on opposite sides of the protein consistent with a 2-fold axis of symmetry. Peptide ligands were not visible in height images; however, phase images that map the mechanical properties detected the nanogold labels and demonstrated the presence of peptide ligands bound to the receptors. The results demonstrate the ability of this high-resolution microscopy technique to directly visualize single ligand/receptor interactions in a dynamic and physiologically relevant environment, and establish a framework for future fundamental studies of single protein/receptor interactions during normal pathological processes as well as biomaterial surface-induced thrombosis.
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Affiliation(s)
- Mohammad A Hussain
- Department of Surgery, Biomedical Engineering Institute, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania 17033, USA
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14
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Iwasaki K, Mitsuoka K, Fujiyoshi Y, Fujisawa Y, Kikuchi M, Sekiguchi K, Yamada T. Electron tomography reveals diverse conformations of integrin alphaIIbbeta3 in the active state. J Struct Biol 2005; 150:259-67. [PMID: 15890274 DOI: 10.1016/j.jsb.2005.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Revised: 03/02/2005] [Accepted: 03/09/2005] [Indexed: 10/25/2022]
Abstract
We used electron tomography to determine the three-dimensional (3D) structure of integrin alphaIIbbeta3 in the active state. We found that we obtained better density maps when we reconstructed a 3D volume for each individual particle in the tilt series rather than to extract the particle-containing subvolumes from a 3D reconstruction of the entire specimen area. The 3D tomographic reconstructions of 100 particles revealed that activated alphaIIbbeta3 adopts many different conformations. An average of all the individual 3D reconstructions nicely accommodated the crystal structure of the alphaVbeta3 headpiece, confirming the locations assigned to the alpha- and beta-subunit in the density map. The most striking finding of our study is the structural flexibility of the lower leg of the beta-subunit as opposed to the conformational stability of the leg of the alpha-subunit. The good fit of the atomic structure of the betaI domain and the hybrid domain in the active state showed that the hybrid domain swings out, and most particles used for tomography are in the active state. Multivariate statistical analysis and classification applied to the set of 3D reconstructions revealed that more than 90% reconstructions are grouped into the classes that show the active state. Our results demonstrate that electron tomography can be used to classify complexes with a flexible structure such as integrins.
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Affiliation(s)
- Kenji Iwasaki
- International Institute for Advanced Research, Matsushita Electric Industrial Co., Ltd, 3-4 Hikaridai, Seika, Soraku, Kyoto 619-02,
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