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Adamson K, Spain E, Prendergast U, Moran N, Forster RJ, Keyes TE. Fibrinogen Motif Discriminates Platelet and Cell Capture in Peptide-Modified Gold Micropore Arrays. Langmuir 2018; 34:715-725. [PMID: 29240434 DOI: 10.1021/acs.langmuir.7b03279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Human blood platelets and SK-N-AS neuroblastoma cancer-cell capture at spontaneously adsorbed monolayers of fibrinogen-binding motifs, GRGDS (generic integrin adhesion), HHLGGAKQAGDV (exclusive to platelet integrin αIIbβ3), or octanethiol (adhesion inhibitor) at planar gold and ordered 1.6 μm diameter spherical cap gold cavity arrays were compared. In all cases, arginine/glycine/aspartic acid (RGD) promoted capture, whereas alkanethiol monolayers inhibited adhesion. Conversely only platelets adhered to alanine/glycine/aspartic acid (AGD)-modified surfaces, indicating that the AGD motif is recognized preferentially by the platelet-specific integrin, αIIbβ3. Microstructuring of the surface effectively eliminated nonspecific platelet/cell adsorption and dramatically enhanced capture compared to RGD/AGD-modified planar surfaces. In all cases, adhesion was reversible. Platelets and cells underwent morphological change on capture, the extent of which depended on the topography of the underlying substrate. This work demonstrates that both the nature of the modified interface and its underlying topography influence the capture of cancer cells and platelets. These insights may be useful in developing cell-based cancer diagnostics as well as in identifying strategies for the disruption of platelet cloaks around circulating tumor cells.
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Affiliation(s)
- Kellie Adamson
- School of Chemical Sciences, Dublin City University , Dublin 9, Ireland
| | - Elaine Spain
- School of Chemical Sciences, Dublin City University , Dublin 9, Ireland
| | - Una Prendergast
- School of Chemical Sciences, Dublin City University , Dublin 9, Ireland
| | - Niamh Moran
- Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland , Dublin 2, Ireland
| | - Robert J Forster
- School of Chemical Sciences, Dublin City University , Dublin 9, Ireland
| | - Tia E Keyes
- School of Chemical Sciences, Dublin City University , Dublin 9, Ireland
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2
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Zafar H, Shang Y, Li J, David GA 3rd, Fernandez JP, Molina H, Filizola M, Coller BS. αIIbβ3 binding to a fibrinogen fragment lacking the γ-chain dodecapeptide is activation dependent and EDTA inducible. Blood Adv 2017; 1:417-28. [PMID: 29296957 DOI: 10.1182/bloodadvances.2017004689] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 01/24/2017] [Indexed: 12/24/2022] Open
Abstract
Platelet integrin receptor αIIbβ3 supports platelet aggregation by binding fibrinogen. The interaction between the fibrinogen C-terminal γ-chain peptide composed of residues γ-404-411 (GAKQAGDV) and the Arg-Gly-Asp (RGD) binding pocket on αIIbβ3 is required for fibrinogen-mediated platelet aggregation, but data suggest that other ancillary binding sites on both fibrinogen and αIIbβ3 may lead to higher-affinity fibrinogen binding and clot retraction. To identify additional sites, we analyzed the ability of platelets and cells expressing normal and mutant αIIbβ3 to adhere to an immobilized fibrinogen plasmin fragment that lacks intact γ-404-411 ('D98'). We found the following: (1) Activated, but not unactivated, platelets adhere well to immobilized 'D98.' (2) Cells expressing constitutively active αIIbβ3 mutants, but not cells expressing normal αIIbβ3 or αVβ3, adhere well to 'D98.' (3) Monoclonal antibodies 10E5 and 7E3 inhibit the adhesion to 'D98' of activated platelets and cells expressing constitutively active αIIbβ3, as do small-molecule inhibitors that bind to the RGD pocket. (4) EDTA paradoxically induces normal αIIbβ3 to interact with 'D98.' Because molecular modeling and molecular dynamics simulations suggested that the αIIb L151-D159 helix may contribute to the interaction with 'D98,' we studied an αIIbβ3 mutant in which the αIIb 148-166 loop was swapped with the corresponding αV loop; it failed to bind to fibrinogen or 'D98.' Our data support a model in which conformational changes in αIIbβ3 and/or fibrinogen after platelet activation and the interaction between γ-404-411 and the RGD binding pocket make new ancillary sites available that support higher-affinity fibrinogen binding and clot retraction.
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3
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Kundu SK, Heilmann EJ, Sio R, Garcia C, Ostgaard RA. Characterization of an In Vitro Platelet Function Analyzer, PFA-100™. Clin Appl Thromb Hemost 1996; 2:241-9. [DOI: 10.1177/107602969600200404] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A new in vitro system for the evaluation of platelet function, PFA-100 (currently under evaluation) is characterized. The system monitors platelet aggrega tion on a collagen-epinephrine-coated membrane as whole blood sample is aspirated under controlled flow conditions through a microscopic aperture cut into the membrane. The time required for the platelet plug to oc clude the aperture (closure time) is indicative of the plate let function in the sample. Incubation of normal blood samples with antibodies to glycoprotein (GP) Ib, GPIIb- IIIa, von Willebrand factor, or with the peptide Arg-Gly- Asp-Ser, resulted in a concentration-dependent prolonga tion in closure time. An anti-fibrinogen antibody did not impact the closure time. Closure time was also prolonged when the hematocrit or the platelet count was lowered to pathological values. The study indicates that PFA-100 could detect defects in platelet adhesion or aggregation. The simplicity of the test makes PFA-100 unique for rapid screening of a variety of platelet dysfunction.
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Hashimoto M, Taguchi K, Ogaki S, Watanabe H, Kinoshita M, Nishikawa K, Takeoka S, Ikeda Y, Handa M, Otagiri M, Maruyama T. Pharmacokinetic Properties of Single and Repeated Injection of Liposomal Platelet Substitute in a Rat Model of Red Blood Cell Transfusion-Induced Dilutional Thrombocytopenia. J Pharm Sci 2015; 104:3968-3976. [PMID: 26249543 DOI: 10.1002/jps.24607] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 07/10/2015] [Accepted: 07/16/2015] [Indexed: 01/08/2023]
Abstract
A preclinical study of dodecapeptide ((400)HHLGGAKQAGDV(411)) (H12)-(adenosine diphosphate, ADP)-liposomes for use as a synthetic platelet (PLT) substitute under conditions of red blood cell (RBC) transfusion-induced dilutional thrombocytopenia is limited to pharmacological effect. In this study, the pharmacokinetics of H12-(ADP)-liposomes in RBC transfusion-induced dilutional thrombocytopenic rats were evaluated. As evidenced by the use of (14) C, (3) H double-radiolabeled H12-(ADP)-liposomes in which the encapsulated ADP and liposomal membrane were labeled with (14) C and (3) H, respectively, the H12-(ADP)-liposomes remained intact in the blood circulation for up to 3 h after injection, and were mainly distributed to the liver and spleen. The encapsulated ADP was mainly eliminated in the urine, whereas the outer membrane was mainly eliminated in the feces. These successive pharmacokinetic properties of the H12-(ADP)-liposomes in RBC transfusion-induced dilutional thrombocytopenic rats were similar to those in healthy rats, except for the shorter retention time in the circulation. When H12-(ADP)-liposomes were repeatedly injected into RBC transfusion-induced dilutional thrombocytopenic rats at intervals of 5 days at a dose of 10 mg lipids/kg, the second dose of injected H12-(ADP)-liposomes were rapidly cleared from the circulation, namely, via the accelerated blood clearance phenomenon. These novel pharmacokinetic findings provide useful information for the further development of H12-(ADP)-liposomes as a PLT substitute.
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Affiliation(s)
- Mai Hashimoto
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan
| | - Kazuaki Taguchi
- Faculty of Pharmaceutical Sciences, Sojo University, Nishi-ku, Kumamoto 862-0082, Japan
| | - Shigeru Ogaki
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan
| | - Hiroshi Watanabe
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan; Center for Clinical Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan
| | - Manabu Kinoshita
- Department of Immunology and Microbiology, National Defense Medical College, Tokorozawa, Saitama 359-8513, Japan
| | - Kahoko Nishikawa
- Department of Traumatology and Critical Care Medicine, National Defense Medical College, Tokorozawa, Saitama, 359-8513, Japan
| | - Shinji Takeoka
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yasuo Ikeda
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Makoto Handa
- Center for Transfusion Medicine and Cell Therapy, Keio University, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Masaki Otagiri
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan; Faculty of Pharmaceutical Sciences, Sojo University, Nishi-ku, Kumamoto 862-0082, Japan; DDS Research Institute, Sojo University, 4-22-1 Ikeda, Nishi-ku, Kumamoto 862-0082, Japan
| | - Toru Maruyama
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan; Center for Clinical Pharmaceutical Sciences, Kumamoto University, Kumamoto 862-0973, Japan.
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Abstract
Excessive bleeding and the resulting complications are a leading killer of young people globally. There are many successful methods to halt bleeding in the extremities, including compression, tourniquets, and dressings. However, current treatments for internal hemorrhage (including from head or truncal injuries), termed non-compressible bleeding, are inadequate. For these non-compressible injuries, blood transfusions are the current treatment standard. However, they must be refrigerated, may potentially transfer disease, and are of limited supply. In addition, time is of the essence for halting hemorrhage, since more than a third of civilian deaths due to hemorrhage from trauma occur before the patient even reaches the hospital. As a result, particles that can cross-link activated platelets through the glycoprotein IIb/IIIa receptor expressed on activated platelets are being investigated as an alternative treatment for non-compressible bleeding. Ideally, these particles would interact specifically with platelets to stabilize the platelet plug. Initial designs used biologically derived microparticles with red blood cell fragment or albumin cores decorated with RGD or fibrinogen, which bind to GPIIb/IIIa. More recently there has been research into the use of fully synthetic nanoparticles with liposomal or polymer cores that crosslink platelets through a targeting peptide bound to the surface. Some of the challenges for the development of these particles include appropriate sizing to prevent blocking the capillaries of the lungs, immune system evasion to prevent strong reactions and increase circulation time, and storage and resuspension so that first responders can easily use the particles. In addition, the effectiveness of the variety of animal bleeding models in predicting outcomes must be examined before test results can be fully understood. Progress has been made in the development of particles to combat hemorrhage, but issues of immune sensitivity and storage must be resolved before these types of particles can be translated for human use.
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Taguchi K, Ujihira H, Ogaki S, Watanabe H, Fujiyama A, Doi M, Okamura Y, Takeoka S, Ikeda Y, Handa M, Otagiri M, Maruyama T. Pharmacokinetic study of the structural components of adenosine diphosphate-encapsulated liposomes coated with fibrinogen γ-chain dodecapeptide as a synthetic platelet substitute. Drug Metab Dispos 2013; 41:1584-91. [PMID: 23735758 DOI: 10.1124/dmd.112.050005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV, H12)-coated, ADP-encapsulated liposomes [H12-(ADP)-liposomes] were developed as a synthetic platelet alternative that specifically accumulates at bleeding sites as the result of interactions with activated platelets via glycoprotein IIb/IIIa and augments platelet aggregation by releasing ADP. The aim of this study is to characterize the pharmacokinetic properties of H12-(ADP)-liposomes and structural components in rats, and to predict the blood retention of H12-(ADP)-liposomes in humans. With use of H12-(ADP)-liposomes in which the encapsulated ADP and liposomal membrane cholesterol were radiolabeled with (14)C and (3)H, respectively, it was found that the time courses for the plasma concentration curves of (14)C and (3)H radioactivity showed that the H12-(ADP)-liposomes remained intact in the blood circulation for up to 24 hours after injection, and were mainly distributed to the liver and spleen. However, the (14)C and (3)H radioactivity of H12-(ADP)-liposomes disappeared from organs within 7 days after injection. The encapsulated ADP was metabolized to allantoin, which is the final metabolite of ADP in rodents, and was mainly eliminated in the urine, whereas the cholesterol was mainly eliminated in feces. In addition, the half-life of the H12-(ADP)-liposomes in humans was predicted to be approximately 96 hours from pharmacokinetic data obtained for mice, rats, and rabbits using an allometric equation. These results suggest that the H12-(ADP)-liposome has potential with proper pharmacokinetic and acceptable biodegradable properties as a synthetic platelet substitute.
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Affiliation(s)
- Kazuaki Taguchi
- Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
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7
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Wang YY, Lü LX, Shi JC, Wang HF, Xiao ZD, Huang NP. Introducing RGD Peptides on PHBV Films through PEG-Containing Cross-Linkers to Improve the Biocompatibility. Biomacromolecules 2011; 12:551-9. [DOI: 10.1021/bm100886w] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yan-Yan Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
| | - Lan-Xin Lü
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
| | - Jun-Cai Shi
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
| | - Hai-Feng Wang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
| | - Zhong-Dang Xiao
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
| | - Ning-Ping Huang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, P.R. China
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8
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Okamura Y, Katsuno S, Suzuki H, Maruyama H, Handa M, Ikeda Y, Takeoka S. Release abilities of adenosine diphosphate from phospholipid vesicles with different membrane properties and their hemostatic effects as a platelet substitute. J Control Release 2010; 148:373-9. [PMID: 20875473 DOI: 10.1016/j.jconrel.2010.09.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Revised: 07/08/2010] [Accepted: 09/14/2010] [Indexed: 10/19/2022]
Abstract
We have constructed phospholipid vesicles with hemostatic activity as a platelet substitute. The vesicles were conjugated with a dodecapeptide (HHLGGAKQAGDV, H12), which is a fibrinogen γ-chain carboxy-terminal sequence (γ400-411). We have recently exploited these vesicles as a potential drug delivery system by encapsulation of adenosine 5'-diphosphate (ADP) (H12-(ADP)-vesicles). Here we explore the relationship between the ADP release from H12-(ADP)-vesicles with different membrane properties and their hemostatic effects. In total, we prepared five kinds of H12-(ADP)-vesicles with different lamellarities and membrane flexibilities. By radioisotope-labeling, we directly show that H12-(ADP)-vesicles were capable of augmenting platelet aggregation by releasing ADP in an aggregation-dependent manner. The amount of ADP released from the vesicles was dependent on their membrane properties. Specifically, the amount of ADP released increased with decreasing lamellarity and tended to increase with increasing membrane flexibility. Our in vivo results clearly demonstrated that H12-(ADP)-vesicles with the ability to release ADP exert considerable hemostatic action in terms of correcting prolonged bleeding time in a busulphan-induced thrombocytopenic rat model. We propose a recipe to control the hemostatic abilities of H12-(ADP)-vesicles by modulating ADP release based on membrane properties. We believe that this concept will be invaluable to the development of platelet substitutes and other drug carriers.
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Affiliation(s)
- Yosuke Okamura
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo 162-8480, Japan
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9
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Okamura Y, Eto K, Maruyama H, Handa M, Ikeda Y, Takeoka S. Visualization of liposomes carrying fibrinogen γ-chain dodecapeptide accumulated to sites of vascular injury using computed tomography. Nanomedicine: Nanotechnology, Biology and Medicine 2010; 6:391-6. [DOI: 10.1016/j.nano.2009.07.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Revised: 06/28/2009] [Accepted: 07/13/2009] [Indexed: 10/20/2022]
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10
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Sánchez-Cortés J, Mrksich M. The platelet integrin alphaIIbbeta3 binds to the RGD and AGD motifs in fibrinogen. ACTA ACUST UNITED AC 2010; 16:990-1000. [PMID: 19778727 DOI: 10.1016/j.chembiol.2009.08.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 08/27/2009] [Accepted: 08/27/2009] [Indexed: 10/20/2022]
Abstract
Fibrinogen (Fbg) mediates platelet aggregation by binding the alphaIIbbeta3 integrin receptor, but the interaction of the receptor with peptide motifs of Fbg remains unresolved. This paper describes the use of self-assembled monolayers (SAMs) to study the adhesion of alphaIIbbeta3-transfected CHO cells to the GRGDS and HHLGGAKQAGDV motifs within Fbg. Cells adhered to and spread on monolayers presenting either peptide. Cell adhesion could be inhibited by either soluble peptide, demonstrating that the peptides bind competitively to the integrin. A peptide array was used to show that AGD was the minimal binding sequence in HHLGGAKQAGDV and that the receptor recognizes ligands of the form GXGDSC, where X is a hydrophobic or basic residue. This work revises our understanding of the alphaIIbbeta3 specificity and also suggests a new class of antithrombotic agents.
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Affiliation(s)
- Juan Sánchez-Cortés
- Department of Chemistry and Howard Hughes Medical Institute, The University of Chicago, Chicago, IL 60637, USA
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11
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Okamura Y, Fukui Y, Kabata K, Suzuki H, Handa M, Ikeda Y, Takeoka S. Novel platelet substitutes: disk-shaped biodegradable nanosheets and their enhanced effects on platelet aggregation. Bioconjug Chem 2009; 20:1958-65. [PMID: 19788180 DOI: 10.1021/bc900325w] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have studied biocompatible spherical carriers carrying a dodecapeptide, HHLGGAKQAGDV (H12), on their surface as platelet substitutes. This peptide is a fibrinogen γ-chain carboxy-terminal sequence (γ400-411) and specifically recognizes the active form of glycoprotein IIb/IIIa on activated platelets. Our purpose is to assess the possibility of making a novel platelet substitute consisting of disk-shaped nanosheets having a large contact area for the targeting site, rather than conventional small contact area spherical carriers. The H12 peptide was conjugated to the surface of the free-standing nanosheets made of biodegradable poly(d,l-lactide-co-glycolide) (PLGA). These H12-PLGA nanosheets were fabricated onto 3 μm disk-shaped patterned hydrophobic octadecyl regions on a SiO(2) substrate. By way of comparison, spherical H12-PLGA microparticles with the same surface area and conjugation number of H12 were also prepared. The resulting H12-PLGA nanosheets specifically interacted with the activated platelets adhered on the collagen surface at twice the rate of the H12-PLGA microparticles under flow conditions, and showed platelet thrombus formation in a two-dimensional spreading manner. Thus, H12-PLGA nanosheets might be a suitable candidate novel platelet alternative substitute for infused human platelet concentrates for the treatment of bleeding in patients with severe thrombocytopenia.
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Affiliation(s)
- Yosuke Okamura
- Department of Life Science and Medical Bioscience, Graduate School of Advanced Science and Engineering, Waseda University, TWIns, Tokyo, Japan
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12
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Abstract
Hemostasis and thrombosis (blood clotting) involve fibrinogen binding to integrin αIIbβ3 on platelets, resulting in platelet aggregation. αvβ3 binds fibrinogen via an Arg-Asp-Gly (RGD) motif in fibrinogen's α subunit. αIIbβ3 also binds to fibrinogen; however, it does so via an unstructured RGD-lacking C-terminal region of the γ subunit (γC peptide). These distinct modes of fibrinogen binding enable αIIbβ3 and αvβ3 to function cooperatively in hemostasis. In this study, crystal structures reveal the integrin αIIbβ3–γC peptide interface, and, for comparison, integrin αIIbβ3 bound to a lamprey γC primordial RGD motif. Compared with RGD, the GAKQAGDV motif in γC adopts a different backbone configuration and binds over a more extended region. The integrin metal ion–dependent adhesion site (MIDAS) Mg2+ ion binds the γC Asp side chain. The adjacent to MIDAS (ADMIDAS) Ca2+ ion binds the γC C terminus, revealing a contribution for ADMIDAS in ligand binding. Structural data from this natively disordered γC peptide enhances our understanding of the involvement of γC peptide and integrin αIIbβ3 in hemostasis and thrombosis.
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Affiliation(s)
- Timothy A Springer
- Department of Pathology, Immune Disease Institute, Harvard Medical School, Boston, MA 02115, USA
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13
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Okamura Y, Fujie T, Nogawa M, Maruyama H, Handa M, Ikeda Y, Takeoka S. Haemostatic effects of polymerized albumin particles carrying fibrinogen γ-chain dodecapeptide as platelet substitutes in severely thrombocytopenic rabbits. Transfus Med 2008; 18:158-66. [DOI: 10.1111/j.1365-3148.2008.00860.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Feuerstein GZ, Ruffolo RR. The antiplatelet GPIIb/IIIa antibody, 7E3: A pioneer drug for the treatment of arterial thrombotic disorders. Expert Opin Investig Drugs 2008. [DOI: 10.1517/13543784.3.7.745] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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15
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Humphries MJ, Doyle PM, Harris CJ. Overview Biologicals and Immunologicals: Integrin antagonists as modulators of adhesion. Expert Opin Ther Pat 2008. [DOI: 10.1517/13543776.4.3.227] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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16
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Sun CX, Chen P, Lu W, Liu JN. Tyr178 of beta3 is critical for alphaIIb maturation and macromolecular ligand binding to alphaIIbbeta3. Thromb Res 2008; 122:203-10. [PMID: 18201749 DOI: 10.1016/j.thromres.2007.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2007] [Revised: 10/14/2007] [Accepted: 11/12/2007] [Indexed: 11/17/2022]
Abstract
To explore the structural basis of ligand binding to alphaIIbbeta3, we conducted a site-directed mutagenesis of Y178, which is located in the ligand-specificity region (C177-C184) of the beta3 subunit. Two mutant beta3 constructs, Y178A and Y178I, were transfected into CHO cells and co-expressed with human alphaIIb subunit on the cell surface. Our results showed that the Y178A mutation affected processing and cell surface exposure of recombinant alphaIIbbeta3 receptor, abrogated the binding of PAC-1, a ligand-mimetic antibody, to alphaIIbbeta3 pre-treated with the known activator DTT. The Y178A mutation also resulted in reduced adhesion of alphaIIbbeta3 on immobilized fibrinogen. In contrast, the interaction of alphaIIbbeta3 with the small molecular ligand RGDS was unaffected by Y178A mutation, as evidenced by the elevated LIBS-1 epitope expression following RGDS addition. Interestingly however, Y178I mutation did not affect the receptor synthesis and function at all. As for post-receptor occupancy, neither Y178A nor Y178I prevented alphaIIbbeta3 translocation to focal adhesion contacts. These results suggest that Y178 is involved in alphaIIb maturation and alphaIIbbeta3 complex expression. This residue is also critical for alphaIIbbeta3 interaction with its macromolecular ligand or ligand-mimetic mAb, possibly due to its involvement in other ligand-binding sites distinct from the RGD-binding pocket. We also propose that a residue with appropriate side-chain size and hydrophobicity at position 178 is spatially required for formation of the correct tertiary structure of the site.
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Affiliation(s)
- Chong-Xiu Sun
- Institute of Molecular Medicine and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, 22 Hankou Road, Nanjing, 210093, China
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17
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Blue R, Murcia M, Karan C, Jirousková M, Coller BS. Application of high-throughput screening to identify a novel alphaIIb-specific small- molecule inhibitor of alphaIIbbeta3-mediated platelet interaction with fibrinogen. Blood 2008; 111:1248-56. [PMID: 17978171 DOI: 10.1182/blood-2007-08-105544] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Small-molecule alphaIIbbeta3 antagonists competitively block ligand binding by spanning between the D224 in alphaIIb and the MIDAS metal ion in beta3. They variably induce conformational changes in the receptor, which may have undesirable consequences. To identify alphaIIbbeta3 antagonists with novel structures, we tested 33 264 small molecules for their ability to inhibit the adhesion of washed platelets to immobilized fibrinogen at 16 muM. A total of 102 compounds demonstrated 50% or more inhibition, and one of these (compound 1, 265 g/mol) inhibited ADP-induced platelet aggregation (IC(50): 13+/- 5 muM), the binding of soluble fibrinogen to platelets induced by mAb AP5, and the binding of soluble fibrinogen and a cyclic RGD peptide to purified alphaIIbbeta3. Compound 1 did not affect the function of GPIb, alpha2beta1, or the other beta3 family receptor alphaVbeta3. Molecular docking simulations suggest that compound 1 interacts with alphaIIb but not beta3. Compound 1 induced partial exposure of an alphaIIb ligand-induced binding site (LIBS), but did not induce exposure of 2 beta3 LIBS. Transient exposure of purified alphaIIbbeta3 to eptifibatide, but not compound 1, enhanced fibrinogen binding ("priming"). Compound 1 provides a prototype for small molecule selective inhibition of alphaIIbbeta3, without receptor priming, via targeting alphaIIb.
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Pesho MM, Bledzka K, Michalec L, Cierniewski CS, Plow EF. The Specificity and Function of the Metal-binding Sites in the Integrin β3 A-domain. J Biol Chem 2006; 281:23034-41. [PMID: 16723352 DOI: 10.1074/jbc.m602856200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The A-domains within integrin beta subunits contain three metal sites termed the metal ion-dependent adhesion site (MIDAS), site adjacent to the metal ion-dependent adhesion site (ADMIDAS), and ligand-induced metal-binding site (LIMBS), and these sites are involved in ligand engagement. The selectivity of these metal sites and their role in ligand binding have been investigated by expressing a fragment corresponding to the beta3 A-domain, beta3-(109-352), and single point mutants in which each of the cation-binding sites has been disabled. Equilibrium dialysis experiments identified three Mn2+- and two Ca2+-binding sites with the LIMBS being the site that did not bind Ca2+. Although the ADMIDAS could bind Ca2+, it did not bind Mg2+. These results indicate that the Ca2+-specific site that inhibits ligand binding is the ADMIDAS. Two different assay systems, surface plasmon resonance and a microtiter plate assay, demonstrated that the beta3 A-domain fragment bound fibrinogen in the presence of 0.1 mm Ca2+ but not in 3 mm Ca2+. This behavior recapitulated the effects of Ca2+ on fibrinogen binding to alphavbeta3 but not alphaIIbbeta3. Disabling any of the three cation-binding sites abrogated fibrinogen binding. These results indicate that the specificities of the three metal-binding sites for divalent cations are distinct and that each site can regulate the ligand binding potential of the beta3 A-domain.
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Affiliation(s)
- Michelle M Pesho
- Joseph J. Jacobs Center for Thrombosis and Vascular Biology and Department of Molecular Cardiology, Cleveland Clinic, Cleveland, Ohio 44195, USA
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19
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Abstract
Fibrinogen molecules are comprised of two sets of disulfide-bridged Aalpha-, Bbeta-, and gamma-chains. Each molecule contains two outer D domains connected to a central E domain by a coiled-coil segment. Fibrin is formed after thrombin cleavage of fibrinopeptide A (FPA) from fibrinogen Aalpha-chains, thus initiating fibrin polymerization. Double-stranded fibrils form through end-to-middle domain (D:E) associations, and concomitant lateral fibril associations and branching create a clot network. Fibrin assembly facilitates intermolecular antiparallel C-terminal alignment of gamma-chain pairs, which are then covalently 'cross-linked' by factor XIII ('plasma protransglutaminase') or XIIIa to form 'gamma-dimers'. In addition to its primary role of providing scaffolding for the intravascular thrombus and also accounting for important clot viscoelastic properties, fibrin(ogen) participates in other biologic functions involving unique binding sites, some of which become exposed as a consequence of fibrin formation. This review provides details about fibrinogen and fibrin structure, and correlates this information with biological functions that include: (i) suppression of plasma factor XIII-mediated cross-linking activity in blood by binding the factor XIII A2B2 complex. (ii) Non-substrate thrombin binding to fibrin, termed antithrombin I (AT-I), which down-regulates thrombin generation in clotting blood. (iii) Tissue-type plasminogen activator (tPA)-stimulated plasminogen activation by fibrin that results from formation of a ternary tPA-plasminogen-fibrin complex. Binding of inhibitors such as alpha2-antiplasmin, plasminogen activator inhibitor-2, lipoprotein(a), or histidine-rich glycoprotein, impairs plasminogen activation. (iv) Enhanced interactions with the extracellular matrix by binding of fibronectin to fibrin(ogen). (v) Molecular and cellular interactions of fibrin beta15-42. This sequence binds to heparin and mediates platelet and endothelial cell spreading, fibroblast proliferation, and capillary tube formation. Interactions between beta15-42 and vascular endothelial (VE)-cadherin, an endothelial cell receptor, also promote capillary tube formation and angiogenesis. These activities are enhanced by binding of growth factors like fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF), and cytokines like interleukin (IL)-1. (vi) Fibrinogen binding to the platelet alpha(IIb)beta3 receptor, which is important for incorporating platelets into a developing thrombus. (vii) Leukocyte binding to fibrin(ogen) via integrin alpha(M)beta2 (Mac-1), which is a high affinity receptor on stimulated monocytes and neutrophils.
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Affiliation(s)
- M W Mosesson
- The Blood Research Institute, The Blood Center of Southeastern Wisconsin, Milwaukee, WI 53201-2178, USA.
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20
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Choi ET, Khan MF, Leidenfrost JE, Collins ET, Boc KP, Villa BR, Novack DV, Parks WC, Abendschein DR. Beta3-integrin mediates smooth muscle cell accumulation in neointima after carotid ligation in mice. Circulation 2004; 109:1564-9. [PMID: 15007005 DOI: 10.1161/01.cir.0000121733.68724.ff] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Pharmacological blockade of beta3-integrins inhibits neointimal lesion formation in nonmouse animal models of arterial injury. In contrast, beta3-integrin-deficient (beta3-/-) mice are not protected from neointimal lesion formation after arterial injury. We investigated this discrepancy in beta3-/- and wild-type (beta3+/+) mice using different models of injury. METHODS AND RESULTS After disruption of the carotid with a transluminal probe, there was no significant difference in neointimal thickening between beta3-/- and beta3+/+ mice. However, after ligation of the carotid without medial disruption, there was reduced neointimal thickening in beta3-/- mice compared with beta3+/+ mice at intervals up to 3 months. Lesion reduction in beta3-/- mice was associated with fewer intimal smooth muscle cells (SMCs) without a difference in SMC apoptosis or proliferation rate compared with beta3+/+ mice, consistent with reduced SMC migration from the media into the intima of beta3-/- mice. Moreover, combined eccentric medial disruption and ligation of the carotid in beta3-/- mice resulted in neointimal lesion formation only at the site of medial disruption. Transplantation of bone marrow cells harvested from beta3+/+ mice into irradiated beta3-/- mice resulted in reduced neointimal lesion formation after carotid ligation injury, confirming the importance of alpha(v)beta3 and not alpha(IIb)beta3 in the attenuated response. CONCLUSIONS The alpha(v)beta3-integrin mediates intimal SMC accumulation that contributes to neointimal thickening in the setting of arterial ligation.
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Affiliation(s)
- Eric T Choi
- Department of Surgery, Washington University School of Medicine, St Louis, Mo, USA.
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21
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Takeoka S, Okamura Y, Teramura Y, Watanabe N, Suzuki H, Tsuchida E, Handa M, Ikeda Y. Function of fibrinogen γ-chain dodecapeptide-conjugated latex beads under flow. Biochem Biophys Res Commun 2003; 312:773-9. [PMID: 14680832 DOI: 10.1016/j.bbrc.2003.10.184] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Indexed: 10/26/2022]
Abstract
In order to perform a fundamental study of platelet substitutes, novel particles that bound to activated platelets were prepared using two oligopeptides conjugated to latex beads. The oligopeptides were CHHLGGAKQAGDV (H12), which is a fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411), and CGGRGDF (RGD), which contains a fibrinogen alpha-chain sequence (alpha 95-98 RGDF). Both peptides contained an additional amino-terminal cysteine to enable conjugation. Human serum albumin was adsorbed onto the surface of latex beads (average diameter 1microm) and pyridyldisulfide groups were chemically introduced into the adsorbed protein. H12 or RGD peptides were then chemically linked to the modified surface protein via disulfide linkages. H12- or RGD-conjugated latex beads prepared in this way enhanced the in vitro thrombus formation of activated platelets on collagen-immobilized plates under flowing thrombocytopenic-imitation blood. Based on the result of flow cytometric analyses of agglutination, PAC-1 binding, antiP-selectin antibody binding, and annexin V binding, the H12-conjugated latex beads showed minimal interaction with non-activated platelets. These results indicate the excellent potential of H12-conjugated particles as a candidate for a platelet substitute.
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Affiliation(s)
- Shinji Takeoka
- Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555, Japan
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22
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Abstract
Fibroblast growth factor-2 (FGF-2) binds to fibrin(ogen) with high affinity, and fibrinogen potentiates FGF-2-stimulated proliferation of endothelial cells. Because plasmin degrades fibrin(ogen) physiologically and could liberate growth factor from fibrin deposits or alter its activity, we have now investigated the effect of plasmic degradation on the activity of fibrin(ogen)-bound FGF-2. Fibrinogen with bound FGF-2 was incubated with plasmin, the products characterized by SDS-PAGE, and the proliferative activity determined by (3)H-thymidine incorporation into endothelial cells. Before plasmin exposure, proliferation was increased 3.7 +/- 0.6-fold with fibrinogen-bound FGF-2 compared with medium alone (P < 0.005). Plasmic degradation resulted in progressive decrease in the proliferative capacity, with the 60-min digest showing predominantly fragment D1 and E and (3)H-thymidine uptake of only 1.2 +/- 0.2-fold, significantly less than the activity of an equal concentration of free FGF-2 (P < 0.02). However, further degradation increased activity, and proliferation with a 90-min digest increased to 2.6 +/- 0.5-fold, significantly greater than the 60-min digest (P < 0.02). Plasmic degradation in the presence of 10 mm calcium chloride prevented degradation of D1 to D2 and D3, and the activity did not increase with extended degradation. Immunoprecipitation of the digests with antifibrinogen antibody showed 70 +/- 8% of fibrinogen-bound FGF-2 in the presence of calcium but only 15 +/- 4% in its absence, indicating that cleavage of D1 to D2 and D3 is critical in binding. Fragment D1 and D2, but not D3, bound to a column containing immobilized FGF-2, indicating that a binding site is lost upon degradation to D3. The results demonstrate that plasmic degradation of fibrinogen modulates the activity and binding of FGF-2 that involves a site near the carboxyl terminus of the gamma chain.
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Affiliation(s)
- A Sahni
- Hematology/Oncology Unit, Department of Medicine, University of Rochester School of Medicine & Dentistry, University Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA.
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23
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24
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Abstract
This review covers the functional features of the fibrinogen gamma chains including their participation in fibrin polymerization and cross-linking, their role in the initiation of fibrinolysis, their binding and regulation of factor XIII activity, their interactions with platelets and other cells, and their role in mediating thrombin binding to fibrin, a thrombin inhibitory function termed 'antithrombin I'.
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Affiliation(s)
- M W Mosesson
- The Blood Research Institute of the Blood Center of Southeastern Wisconsin, PO Box 2178, Milwaukee, Wisconsin 53201-2178, USA.
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25
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Abstract
Integrins are alphabeta heterodimeric cell-surface receptors that are vital to the survival and function of nucleated cells. They recognize aspartic-acid- or a glutamic-acid-based sequence motifs in structurally diverse ligands. Integrin recognition of most ligands is divalent cation dependent and conformationally sensitive. In addition to this common property, there is an underlying binding specificity between integrins and ligands for which there has been no structural basis. The recently reported crystal structures of the extracellular segment of an integrin in its unliganded state and in complex with a prototypical Arg-Gly-Asp (RGD) ligand have provided an atomic basis for cation-mediated binding of aspartic-acid-based ligands to integrins. They also serve as a basis for modelling other integrins in complex with larger physiologic ligands. These models provide new insights into the molecular basis for ligand binding specificity in integrins and its regulation by activation-driven tertiary and quaternary changes.
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Affiliation(s)
- M Amin Arnaout
- Renal Unit, Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA 02129, USA.
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26
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Cierniewska-Cieslak A, Cierniewski CS, Bledzka K, Blecka K, Papierak M, Michalec L, Zhang L, Haas TA, Plow EF. Identification and characterization of two cation binding sites in the integrin beta 3 subunit. J Biol Chem 2002; 277:11126-34. [PMID: 11796735 DOI: 10.1074/jbc.m112388200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The midsegment of the beta(3) subunit has been implicated in the ligand and cation binding functions of the beta(3) integrins. This region may contain a metal ion-dependent adhesion site (MIDAS) and fold into an I domain-like structure. Two recombinant fragments, beta(3)-(95-373) and beta(3)-(95-301), were expressed and found to bind fibrinogen. Whereas 0.1 mm Ca(2+) supported ligand binding to both recombinant fragments, 1.0 mm Ca(2+) suppressed binding to the longer but not the shorter fragment. These properties suggest that beta(3)-(95-373) contains both the ligand-competent (LC) and inhibitory (I) cation binding sites, and beta(3)-(95-301) lacks the I site. In equilibrium dialysis experiments, beta(3)-(95-373) contained two divalent cation binding sites, one reactive with either Mg(2+) or Ca(2+) and one Ca(2+)-specific, whereas beta(3)-(95-301) lacked the Ca(2+)-specific site. Mutant forms of beta(3)-(95-373) suggested that the LC site is a MIDAS motif involving Asp(119), Ser(121), Ser(123), Asp(217), and/or Glu(220) as coordination sites, and the I site was dependent upon residues within beta(3)-(301-323). In a molecular model of beta(3)-(95-373), a second Ca(2+) could be docked onto a flexible loop in close proximity to the MIDAS. These results indicate that the ligand competent and Ca(2+)-specific inhibitory cation binding sites are distinct and reside in beta(3)-(95-373).
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27
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Abstract
Upon vascular injury, platelets initiate interaction with exposed subendothelial matrices through various receptors such as glycoprotein (GP) Ib/IX/V complex, alpha2beta1 integrin, and GPVI/FcRgamma. Although these interactions cannot sustain stable platelet thrombus formation by themselves, they ultimately lead to the activation of alphaIIbbeta3 integrin (GPIIb-IIIa complex [GPIIb-IIIa]), the most abundant receptor in platelets. The alphaIIbbeta3 integrin plays a central role in primary hemostasis by serving as a receptor for fibrinogen and von Willebrand factor (vWf). It establishes a stable interaction with vWf bound to the extracellular matrices and uses fibrinogen as a bridging molecule in platelet aggregate formation. The alphaIIbbeta3 integrin also plays an important role in the pathogenesis of thrombosis. Over the past decades, a tremendous amount of effort has been made to elucidate the ligand-binding mechanisms of alphaIIbbeta3, in part because of its clinical significance. Most of the studies have relied on biochemical analyses of purified alphaIIbbeta3 or recombinant proteins generated in vitro. With the lack of actual 3-dimensional structure, molecular modeling has provided a useful framework for interpreting such experimental data on structure-function correlation of integrin molecules. However, it has also generated disagreement between different models. The aim of this minireview is to summarize the past efforts as well as the recent accomplishments in elucidating the structure/function of alphaIIbbeta3. Finally, we will try to explain all those experimental data using the recently published crystal structure of the extracellular domains of the alphaVbeta3 heterodimeric complex.
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Affiliation(s)
- T Kamata
- Department of Anatomy, Keio University School of Medicine, Tokyo, Japan.
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28
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Abstract
Fibrinogen and fibrin play important, overlapping roles in blood clotting, fibrinolysis, cellular and matrix interactions, inflammation, wound healing, and neoplasia. These events are regulated to a large extent by fibrin formation itself and by complementary interactions between specific binding sites on fibrin(ogen) and extrinsic molecules including proenzymes, clotting factors, enzyme inhibitors, and cell receptors. Fibrinogen is comprised of two sets of three polypeptide chains termed A alpha, B beta, and gamma, that are joined by disulfide bridging within the N-terminal E domain. The molecules are elongated 45-nm structures consisting of two outer D domains, each connected to a central E domain by a coiled-coil segment. These domains contain constitutive binding sites that participate in fibrinogen conversion to fibrin, fibrin assembly, crosslinking, and platelet interactions (e.g., thrombin substrate, Da, Db, gamma XL, D:D, alpha C, gamma A chain platelet receptor) as well as sites that are available after fibrinopeptide cleavage (e.g., E domain low affinity non-substrate thrombin binding site); or that become exposed as a consequence of the polymerization process (e.g., tPA-dependent plasminogen activation). A constitutive plasma factor XIII binding site and a high affinity non-substrate thrombin binding site are located on variant gamma' chains that comprise a minor proportion of the gamma chain population. Initiation of fibrin assembly by thrombin-mediated cleavage of fibrinopeptide A from A alpha chains exposes two EA polymerization sites, and subsequent fibrinopeptide B cleavage exposes two EB polymerization sites that can also interact with platelets, fibroblasts, and endothelial cells. Fibrin generation leads to end-to-middle intermolecular Da to EA associations, resulting in linear double-stranded fibrils and equilaterally branched trimolecular fibril junctions. Side-to-side fibril convergence results in bilateral network branches and multistranded thick fiber cables. Concomitantly, factor XIII or thrombin-activated factor XIIIa introduce intermolecular covalent epsilon-(gamma glutamyl)lysine bonds into these polymers, first creating gamma dimers between properly aligned C-terminal gamma XL sites, which are positioned transversely between the two strands of each fibrin fibril. Later, crosslinks form mainly between complementary sites on alpha chains (forming alpha-polymers), and even more slowly among gamma dimers to create higher order crosslinked gamma trimers and tetramers, to complete the mature network structure.
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Affiliation(s)
- M W Mosesson
- Blood Research Institute, Blood Center of Southeastern Wisconsin, P.O. Box 2178, Milwaukee, Wisconsin 53201, USA.
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29
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Abstract
Binding of fibrinogen to GPIIb-IIIa on agonist-stimulated platelets results in platelet aggregation, presumably by crosslinking adjacent activated platelets. Although unactivated platelets express numerous copies of GPIIb-IIIa on their surface, spontaneous, and potentially deleterious, platelet aggregation is prevented by tightly regulating the fibrinogen binding activity of GPIIb-IIIa. Preliminary evidence suggests that it is the submembranous actin or actin-associated proteins that constrains GPIIb-IIIa in a low affinity state and that relief of this constraint by initiating actin filament turnover enables GPIIb-IIIa to bind fibrinogen. Two regions of the fibrinogen alpha chain that contain an RGD motif, as well as the carboxyl-terminus of the fibrinogen gamma chain, represent potential binding sites for GPIIb-IIIa in the fibrinogen molecule. However, ultrastructural studies using purified fibrinogen and GPIIb-IIIa, and studies using recombinant fibrinogen in which the RGD and relevant gamma chain motifs were mutated indicate that sequences located at the carboxyl-terminal end of the gamma chain mediates fibrinogen binding to GPIIb-IIIa. There is evidence that fibrinogen itself binds to regions in the amino terminal portions of both GPIIb and GPIIIa and that the sites interacting with the fibrinogen gamma chain and with RGD-containing peptides are spatially distinct. Nonetheless, there appears to be allosteric linkage between these sites, accounting for the ability of RGD-containing peptides to inhibit platelet aggregation and arterial thrombosis.
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Affiliation(s)
- J S Bennett
- Hematology-Oncology Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
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30
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Rosado JA, Meijer EM, Hamulyak K, Novakova I, Heemskerk JW, Sage SO. Fibrinogen binding to the integrin alpha(IIb)beta(3) modulates store-mediated calcium entry in human platelets. Blood 2001; 97:2648-56. [PMID: 11313254 DOI: 10.1182/blood.v97.9.2648] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Effects of the occupation of integrin alpha(IIb)beta(3) by fibrinogen on Ca(++) signaling in fura-2-loaded human platelets were investigated. Adding fibrinogen to washed platelet suspensions inhibited increases in cytosolic [Ca(++)] concentrations ([Ca(++)](i)) evoked by adenosine diphosphate (ADP) and thrombin in a concentration-dependent manner in the presence of external Ca(++) but not in the absence of external Ca(++) or in the presence of the nonselective cation channel blocker SKF96365, indicating selective inhibition of Ca(++) entry. Fibrinogen also inhibited store-mediated Ca(++) entry (SMCE) activated after Ca(++) store depletion using thapsigargin. The inhibitory effect of fibrinogen was reversed if fibrinogen binding to alpha(IIb)beta(3) was blocked using RDGS or abciximab and was absent in platelets from patients homozygous for Glanzmann thrombasthenia. Fibrinogen was without effect on SMCE once activated. Activation of SMCE in platelets occurs through conformational coupling between the intracellular stores and the plasma membrane and requires remodeling of the actin cytoskeleton. Fibrinogen inhibited actin polymerization evoked by ADP or thapsigargin in control cells and in cells loaded with the Ca(++) chelator dimethyl BAPTA. It also inhibited the translocation of the tyrosine kinase p60(src) to the cytoskeleton. These results indicate that the binding of fibrinogen to integrin alpha(IIb)beta(3) inhibits the activation of SMCE in platelets by a mechanism that may involve modulation of the reorganization of the actin cytoskeleton and the cytoskeletal association of p60(src). This action may be important in intrinsic negative feedback to prevent the further activation of platelets subjected.
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Affiliation(s)
- J A Rosado
- Department of Physiology, University of Cambridge, Cambridge, United Kingdom
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31
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Ward CM, Kestin AS, Newman PJ. A Leu262Pro mutation in the integrin β3 subunit results in an αIIb-β3 complex that binds fibrin but not fibrinogen. Blood 2000; 96:161-9. [DOI: 10.1182/blood.v96.1.161] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractPlatelet retraction of a fibrin clot is mediated by the platelet fibrinogen receptor, IIbβ3. In certain forms of the inherited platelet disorder, Glanzmann thrombasthenia (GT), mutant IIbβ3 may interact normally with fibrin yet fail to support fibrinogen-dependent aggregation. We describe a patient (LD) with such a form of GT. Platelets from LD supported normal clot retraction but failed to bind fibrinogen. Platelet analysis using flow cytometry and immunoblotting showed reduced but clearly detectable IIbβ3, findings consistent with type II GT. Genotyping of LD revealed 2 novel β3 mutations: a deletion of nucleotides 867 to 868, resulting in a premature stop codon at amino acid residue 267, and a T883C missense mutation, resulting in a leucine (Leu) 262-to-proline (Pro) substitution. Leu262 is highly conserved among β integrin subunits and lies within an intrachain loop implicated in subunit association. Leu262Proβ3 cotransfected with wild-type IIb into COS-7 cells showed delayed intracellular maturation and reduced surface expression of easily dissociable complexes. In human embryonic kidney 293 cells, Leu262Proβ3 formed a complex with endogenous av and retracted fibrin clots similarly to wild-type β3. The same cells, however, were unable to bind immobilized fibrinogen. The molecular requirements for IIbβ3 to interact with fibrin compared with fibrinogen, therefore, appear to differ. The region surrounding β3 Leu262 may maintain β3 in a fibrinogen-binding, competent form, but it appears not to be required for receptor interactions with fibrin.
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32
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Ward CM, Kestin AS, Newman PJ. A Leu262Pro mutation in the integrin β3 subunit results in an αIIb-β3 complex that binds fibrin but not fibrinogen. Blood 2000; 96:161-9. [DOI: 10.1182/blood.v96.1.161.013k50_161_169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Platelet retraction of a fibrin clot is mediated by the platelet fibrinogen receptor, IIbβ3. In certain forms of the inherited platelet disorder, Glanzmann thrombasthenia (GT), mutant IIbβ3 may interact normally with fibrin yet fail to support fibrinogen-dependent aggregation. We describe a patient (LD) with such a form of GT. Platelets from LD supported normal clot retraction but failed to bind fibrinogen. Platelet analysis using flow cytometry and immunoblotting showed reduced but clearly detectable IIbβ3, findings consistent with type II GT. Genotyping of LD revealed 2 novel β3 mutations: a deletion of nucleotides 867 to 868, resulting in a premature stop codon at amino acid residue 267, and a T883C missense mutation, resulting in a leucine (Leu) 262-to-proline (Pro) substitution. Leu262 is highly conserved among β integrin subunits and lies within an intrachain loop implicated in subunit association. Leu262Proβ3 cotransfected with wild-type IIb into COS-7 cells showed delayed intracellular maturation and reduced surface expression of easily dissociable complexes. In human embryonic kidney 293 cells, Leu262Proβ3 formed a complex with endogenous av and retracted fibrin clots similarly to wild-type β3. The same cells, however, were unable to bind immobilized fibrinogen. The molecular requirements for IIbβ3 to interact with fibrin compared with fibrinogen, therefore, appear to differ. The region surrounding β3 Leu262 may maintain β3 in a fibrinogen-binding, competent form, but it appears not to be required for receptor interactions with fibrin.
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33
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Abstract
The alpha(v)beta(3) integrin is a non-covalent, heterodimeric, cell-surface protein that is expressed with varying density on numerous cell types, including osteoclasts, vascular smooth muscle cells, endothelial cells and a variety of tumour cells. Functionally, alpha(v)beta(3) mediates a diverse range of biological events including the adhesion of osteoclasts to bone matrix, smooth muscle cell migration and angiogenesis. Specifically, there has been significant attention focused on the preparation of inhibitors of alpha(v)beta(3) for use as inhibitors of bone resorption, in recognition of the medical need for improved prevention and treatment of osteoporosis. Herein, we summarise the pertinent chemistry and biological advances in the medicinal design and biological evaluation of peptide and small molecule alpha(v)beta(3) antagonists as inhibitors of bone resorption.
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Affiliation(s)
- G D Hartman
- Department of Medicinal Chemistry, Merck Research Laboratories, WP14-2, West Point, PA 19486, USA
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34
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Beumer S, Heijnen-Snyder GJ, IJsseldijk MJ, Sixma JJ. Fibronectin in an extracellular matrix of cultured endothelial cells supports platelet adhesion via its ninth type III repeat : A comparison with platelet adhesion to isolated fibronectin. Arterioscler Thromb Vasc Biol 2000; 20:E16-25. [PMID: 10764693 DOI: 10.1161/01.atv.20.4.e16] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We investigated the involvement of different domains of fibronectin in mediating platelet adhesion to fibronectin in the extracellular matrix (ECM) of cultured endothelial cells under flow conditions. Polyclonal anti-fibronectin antibodies were absorbed with Sepharose to which no protein, intact fibronectin, or different fibronectin fragments had been coupled to obtain supernatants (Sups) (Sup(0), Sup(FN), and Sup(name of the fragment), respectively) from which a specific part of the antibodies had been removed. Treatment of the ECM before perfusion with Sup(0) resulted in a 36% decrease in platelet coverage, whereas treatment with Sup(FN) resulted in maximal adhesion. Treatment of the ECM with supernatants from which antibodies directed against the gelatin- or heparin-binding domain had been removed showed the same inhibition as treatment with Sup(0). Removal of antibodies directed to the 120-kDa cell-binding domain resulted in a level of adhesion equal to the level found when the ECM was treated with Sup(FN). Further analysis of this central region showed that only treatment with supernatants from which antibodies directed to the ninth type III repeat (III-9) of fibronectin had been removed resulted in a significantly higher adhesion than treatment with Sup(0). Studies of adhesion to the fragments themselves showed that only fragments containing III-10 were able to support adhesion. Mutation of the Arg-Gly-Asp (RGD) sequence into Arg-Gly-Glu (RGE) in one of those fragments resulted in a complete loss of adhesive capacity. These data suggest that platelet adhesion to fibronectin in the ECM depends on III-9, whereas III-10 does not seem to be required. For platelet adhesion to isolated fibronectin, an intact RGD sequence seems to be crucial.
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Affiliation(s)
- S Beumer
- University Hospital Utrecht, Department of Hematology, Utrecht, Netherlands
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35
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Abstract
The B chain of beta-bungarotoxin 1-6 sequence, RGRHGD, presents the highest local average hydrophilicity measured by Kyte and Doolittle modeling analysis. The RGRHGD holds parts of both RGD and KGD peptides, which have been reported as having high binding affinity to GPIIb-IIIa. The present study evaluates whether the synthesized hexapeptide, RGRHGD, has an antiplatelet effect and further elucidates the possible mechanisms of action. RGRHGD dose-dependently inhibited rabbit platelet aggregation and adenosine triphosphate release induced by arachidonic acid, collagen, platelet-activating factor, thrombin, or U46619 with the IC50 range of 82.7 to 510 microg/mL. The platelet thromboxane B2 formation induced by collagen or thrombin was also significantly decreased by RGRHGD, but there was no effect on arachidonic acid-induced thromboxane B2 formation. In addition, RGRHGD also inhibited the rise of intracellular calcium level stimulated by arachidonic acid, collagen, or thrombin in Fura 2-AM-loaded platelets. The adenosine 3',5'-cyclic monophosphate level of washed platelets was not affected by RGRHGD. In conclusion, these data indicate that the inhibitory effect of RGRHGD on platelet aggregation may be due to the attenuation of thromboxane A2 formation and intracellular calcium mobilization. In addition, this study may provide a useful method of finding potential therapeutic agents by using molecular modeling analysis.
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Affiliation(s)
- T M Wu
- Department of Biology, National Taiwan Normal University, Republic of China
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36
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Mohri H, Iwamatsu A, Ohkubo T. Heparin Binding Sites Are Located in a 40-kD gamma-Chain and a 36-kD beta-Chain Fragment Isolated from Human Fibrinogen. J Thromb Thrombolysis 1994; 1:49-54. [PMID: 10603512 DOI: 10.1007/BF01061996] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Objective: We have previously shown that (125)I-fibrinogen binds to heparin sepharose CL-6B. To identify the localization of the heparin binding domain in human fibrinogen, reduced and alkylated fibrinogen was digested by limited-Staphylococcus aureus V8 protease. Methods/Results: Two fragments have now been isolated and purified to apparent homogeneity by heparin-affinity chromatography. These fragments, denoted the 40-kD and 36-kD fragments, contain NH(2)-terminal sequences of Ala-Ser-Ile-Leu-Thr-Hb;-Asp and Thr-Val-Asn-Ser-Asn-Ile-Pro, respectively. These fragments established the positions of these peptides within the gamma chain of fibrinogen as beginning with the residue tentatively designated 124 and within the beta chain as beginning with the residue designated 186. Binding of (125)I-fibrinogen to heparin-sepharose CL-6B was completely inhibited by a mixture of these fragments, with an IC(50) of 3.2 µM. The synthetic peptide of the gamma chain carboxy-terminal 15 residues (GQQHHLGGAKQAGDV;G15) partially inhibited fibrinogen binding. The mixture of these fragments partially inhibited the ADP-induced aggregation of platelets. Conclusions: These data indicate that the domains for heparin binding may be present on both the gamma chain and the beta chain of fibrinogen, and that the domain on the gamma chain may be close to the binding domain on the carboxy terminus of the fibrinogen gamma chain to glycoprotein IIb-IIIa.
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Jedsadayanmata A, Chen CC, Kireeva ML, Lau LF, Lam SC. Activation-dependent adhesion of human platelets to Cyr61 and Fisp12/mouse connective tissue growth factor is mediated through integrin alpha(IIb)beta(3). J Biol Chem 1999; 274:24321-7. [PMID: 10446209 DOI: 10.1074/jbc.274.34.24321] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Cyr61 and connective tissue growth factor (CTGF), members of a newly identified family of extracellular matrix-associated signaling molecules, are found to mediate cell adhesion, promote cell migration and enhance growth factor-induced cell proliferation in vitro, and induce angiogenesis in vivo. We previously showed that vascular endothelial cell adhesion and migration to Cyr61 and Fisp12 (mouse CTGF) are mediated through integrin alpha(v)beta(3). Both Cyr61 and Fisp12/mCTGF are present in normal blood vessel walls, and it has been demonstrated that CTGF is overexpressed in advanced atherosclerotic lesions. In the present study, we examined whether Cyr61 and Fisp12/mCTGF could serve as substrates for platelet adhesion. Agonist (ADP, thrombin, or U46619)-stimulated but not resting platelets adhered to both Cyr61 and Fisp12/mCTGF, and this process was completely inhibited by prostaglandin I(2), which prevents platelet activation. The specificity of Cyr61- and Fisp12/mCTGF-mediated platelet adhesion was demonstrated by specific inhibition of this process with polyclonal anti-Cyr61 and anti-Fisp12/mCTGF antibodies, respectively. The adhesion of ADP-activated platelets to both proteins was divalent cation-dependent and was blocked by RGDS, HHLGGAKQAGDV, or echistatin, but not by RGES. Furthermore, this process was specifically inhibited by the monoclonal antibody AP-2 (anti-alpha(IIb)beta(3)), but not by LM609 (anti-alpha(v)beta(3)), indicating that the interaction is mediated through integrin alpha(IIb)beta(3). In a solid phase binding assay, activated alpha(IIb)beta(3), purified by RGD affinity chromatography, bound to immobilized Cyr61 and Fisp12/mCTGF in a dose-dependent and RGD-inhibitable manner. In contrast, unactivated alpha(IIb)beta(3) failed to bind to either protein. Collectively, these findings identify Cyr61 and Fisp12/mCTGF as two novel activation-dependent adhesive ligands for the integrin alpha(IIb)beta(3) on human platelets, and implicate a functional role for these proteins in hemostasis and thrombosis.
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Affiliation(s)
- A Jedsadayanmata
- Department of Pharmacology, University of Illinois, Chicago, Illinois 60612, USA
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Affiliation(s)
- Y Shimizu
- Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455, USA
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Cierniewski CS, Byzova T, Papierak M, Haas TA, Niewiarowska J, Zhang L, Cieslak M, Plow EF. Peptide ligands can bind to distinct sites in integrin alphaIIbbeta3 and elicit different functional responses. J Biol Chem 1999; 274:16923-32. [PMID: 10358039 DOI: 10.1074/jbc.274.24.16923] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The spatial relationship between the binding sites for two cyclic peptides, cyclo(S,S)KYGCRGDWPC (cRGD) and cyclo(S,S)KYGCHarGDWPC (cHarGD), high affinity analogs for the RGD and HLGGAKQAGDV peptide ligands, in integrin alphaIIbbeta3 (GPIIb-IIIa) has been characterized. For this purpose, cRGD and cHarGD were labeled with fluorescein isothiocyanate and tetramethylrhodamine 5-isothiocyanate, respectively. Both cyclic peptides were potent inhibitors of fibrinogen binding to alphaIIbbeta3, particularly in the presence of Mn2+; IC50 values for cRGD and cHarGD were 1 and <0.1 nM in the presence of Mn2+. Direct binding experiments and fluorescence resonance energy transfer analysis using the purified receptor showed that both peptides interacted simultaneously with distinct sites in alphaIIbbeta3. The distance between these sites was estimated to be 6.1 +/- 0.5 nm. Although cRGD bound preferentially to one site and cHarGD to the other, the sites were not fully specific, and each cyclic peptide or its linear counterpart could displace the other to some extent. The binding affinity of the cHarGD site was dramatically affected by Mn2+. cRGD, but not cHarGD, bound to recombinant beta3-(95-373) in a cation-dependent manner, indicating that the cRGD site is located entirely within this fragment. With intact platelets, binding of c-RGD and cHarGD to alphaIIbbeta3 resulted in distinct conformational alterations in the receptor as indicated by the differential exposure of ligand-induced binding site epitopes and also induced the opposite on membrane fluidity as shown by electron paramagnetic resonance analyses using 5-doxylstearic acid as a spin probe. These data support the concept the two peptide ligands bind to distinct sites in alphaIIbbeta3 and initiate different functional consequences within the receptor itself and within platelets.
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Affiliation(s)
- C S Cierniewski
- Department of Biophysics, Medical University in Lodz, 90-131 Lodz, Poland
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40
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Affiliation(s)
- L F Lau
- Department of Molecular Genetics, Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois, 60607-7170, USA.
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41
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Hu DD, White CA, Panzer-Knodle S, Page JD, Nicholson N, Smith JW. A new model of dual interacting ligand binding sites on integrin alphaIIbbeta3. J Biol Chem 1999; 274:4633-9. [PMID: 9988699 DOI: 10.1074/jbc.274.8.4633] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The platelet integrin alphaIIbbeta3 mediates platelet aggregation and platelet adhesion. This integrin is the key to hemostasis and also to pathologic vascular occlusion. A key domain on alphaIIbbeta3 is the ligand binding site, which can bind to plasma fibrinogen and to a number of Arg-Gly-Asp (RGD)-type ligands. However, the nature and function of the ligand binding pocket on alphaIIbbeta3 remains controversial. Some studies suggest the presence of two ligand binding pockets, whereas other reports indicate a single binding pocket. Here we use surface plasmon resonance to show that alphaIIbbeta3 contains two distinct ligand binding pockets. One site binds to fibrinogen, and a separate site binds to RGD-type ligands. More importantly, however, the two ligand binding pockets are interactive. RGD-type ligands are capable of binding to alphaIIbbeta3 even when it is already occupied by fibrinogen. Once bound, RGD-type ligands induce the dissociation of fibrinogen from alphaIIbbeta3. This allosteric cross-talk has important implications for anti-platelet therapy because it suggests a novel approach for the dissolution of existing platelet thrombi.
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Affiliation(s)
- D D Hu
- Program on Cell Adhesion, Cancer Research Center, The Burnham Institute, La Jolla, California 92037, USA
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42
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Tozer EC, Baker EK, Ginsberg MH, Loftus JC. A Mutation in the Subunit of the Platelet Integrin IIbβ3 Identifies a Novel Region Important for Ligand Binding. Blood 1999; 93:918-24. [DOI: 10.1182/blood.v93.3.918] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractAn unbiased genetic approach was used to identify a specific amino acid residue in the IIb subunit important for the ligand binding function of the integrin IIbβ. Chemically mutagenized cells were selected by flow cytometry based on their inability to bind the ligand mimetic antibody PAC1 and a cell line containing a single amino acid substitution in IIb at position 224 (D→V) was identified. Although well expressed on the surface of transfected cells, IIbD224Vβ3 as well as IIbD224Aβ3 did not bind IIbβ3-specific ligands or a RGD peptide, a ligand shared in common with vβ3. Insertion of exon 5 of IIb, residues G193-W235, into the backbone of the v subunit did not enable the chimeric receptor to bind IIbβ3-specific ligands. However, the chimeric receptor was still capable of binding to a RGD affinity matrix. IIbD224 is not well conserved among other integrin subunits and is located in a region of significant variability. In addition, amino acid D224 lies within a predicted loop of the recently proposed β-propeller model for integrin subunits and is adjacent to a loop containing amino acid residues previously implicated in receptor function. These data support a role for this region in ligand binding function of the IIbβ3 receptor.
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43
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Tozer EC, Baker EK, Ginsberg MH, Loftus JC. A Mutation in the Subunit of the Platelet Integrin IIbβ3 Identifies a Novel Region Important for Ligand Binding. Blood 1999; 93:918-924. [DOI: 10.1182/blood.v93.3.918.403k26_918_924] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An unbiased genetic approach was used to identify a specific amino acid residue in the IIb subunit important for the ligand binding function of the integrin IIbβ. Chemically mutagenized cells were selected by flow cytometry based on their inability to bind the ligand mimetic antibody PAC1 and a cell line containing a single amino acid substitution in IIb at position 224 (D→V) was identified. Although well expressed on the surface of transfected cells, IIbD224Vβ3 as well as IIbD224Aβ3 did not bind IIbβ3-specific ligands or a RGD peptide, a ligand shared in common with vβ3. Insertion of exon 5 of IIb, residues G193-W235, into the backbone of the v subunit did not enable the chimeric receptor to bind IIbβ3-specific ligands. However, the chimeric receptor was still capable of binding to a RGD affinity matrix. IIbD224 is not well conserved among other integrin subunits and is located in a region of significant variability. In addition, amino acid D224 lies within a predicted loop of the recently proposed β-propeller model for integrin subunits and is adjacent to a loop containing amino acid residues previously implicated in receptor function. These data support a role for this region in ligand binding function of the IIbβ3 receptor.
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45
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Chen YX, Zhang XZ, Zheng K, Chen SM, Wang QC, Wu XX. Protease-catalyzed synthesis of precursor dipeptides of RGD with reverse micelles. Enzyme Microb Technol 1998. [DOI: 10.1016/s0141-0229(98)00037-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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46
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O'Connell DP, Nanavaty T, McDevitt D, Gurusiddappa S, Höök M, Foster TJ. The fibrinogen-binding MSCRAMM (clumping factor) of Staphylococcus aureus has a Ca2+-dependent inhibitory site. J Biol Chem 1998; 273:6821-9. [PMID: 9506984 DOI: 10.1074/jbc.273.12.6821] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The clumping factor (ClfA) is a cell surface-associated protein of Staphylococcus aureus that promotes binding of fibrinogen or fibrin to the bacterial cell. Previous studies have shown that ClfA and the platelet integrin alphaIIbbeta3 recognize the same domain at the extreme C terminus of the fibrinogen gamma-chain. alphaIIbbeta3 interaction with this domain is known to occur in close proximity to a Ca2+-binding EF-hand structure in the alpha-subunit. Analysis of the primary structure of ClfA indicated the presence of a potential Ca2+-binding EF-hand-like motif at residues 310-321 within the fibrinogen-binding domain. Deletion mutagenesis and site-directed mutagenesis of this EF-hand in recombinant truncated ClfA proteins (Clf40, residues 40-559; and Clf41, residues 221-559) resulted in a significant reduction of affinity for native fibrinogen and a fibrinogen gamma-chain peptide. Furthermore, Ca2+ (or Mn2+) could inhibit the binding of the fibrinogen gamma-chain peptide to Clf40-(40-559) and the adhesion of S. aureus cells to immobilized fibrinogen with an IC50 of 2-3 mM. In contrast, Mg2+ (or Na+) at similar concentrations had no effect on the ClfA-fibrinogen interaction. Far-UV CD analysis of Clf40-(40-559) and Clf41-(221-559) in the presence of metal ions indicated Ca2+- and Mn2+-induced differences in secondary structure. These data suggest that Ca2+ binds to an inhibitory site(s) within ClfA and induces a conformational change that is incompatible with binding to the C terminus of the gamma-chain of fibrinogen. Mutagenesis studies indicate that the Ca2+-dependent inhibitory site is located within the EF-hand motif at residues 310-321.
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Affiliation(s)
- D P O'Connell
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Republic of Ireland
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47
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Huang C, Wong GW, Ghildyal N, Gurish MF, Sali A, Matsumoto R, Qiu WT, Stevens RL. The tryptase, mouse mast cell protease 7, exhibits anticoagulant activity in vivo and in vitro due to its ability to degrade fibrinogen in the presence of the diverse array of protease inhibitors in plasma. J Biol Chem 1997; 272:31885-93. [PMID: 9395536 DOI: 10.1074/jbc.272.50.31885] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Mouse mast cell protease (mMCP) 7 is a tryptase of unknown function expressed by a subpopulation of mast cells that reside in numerous connective tissue sites. Because enzymatically active mMCP-7 is selectively released into the plasma of V3 mastocytosis mice undergoing passive systemic anaphylaxis, we used this in vivo model system to identify a physiologic substrate of the tryptase. Plasma samples taken from V3 mastocytosis mice that had been sensitized with immunoglobulin (Ig) E and challenged with antigen were found to contain substantial amounts of four 34-55-kDa peptides, all of which were derived from fibrinogen. To confirm the substrate specificity of mMCP-7, a pseudozymogen form of the recombinant tryptase was generated that could be activated after its purification. The resulting recombinant mMCP-7 exhibited potent anticoagulant activity in the presence of normal plasma and selectively cleaved the alpha-chain of fibrinogen to fragments of similar size as that seen in the plasma of the IgE/antigen-treated V3 mastocytosis mouse. Subsequent analysis of a tryptase-specific, phage display peptide library revealed that recombinant mMCP-7 preferentially cleaves an amino acid sequence that is nearly identical to that in the middle of the alpha-chain of rat fibrinogen. Because fibrinogen is a physiologic substrate of mMCP-7, this tryptase can regulate clot formation and fibrinogen/integrin-dependent cellular responses during mast cell-mediated inflammatory reactions.
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Affiliation(s)
- C Huang
- Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA
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48
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Sow MA, Molla A, Lamaty F, Lazaro R. Synthesis of RGD amphiphilic cyclic peptide as fibrinogen or fibronectin antagonist. Int J Pept Res Ther 1997. [DOI: 10.1007/bf02442916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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49
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Tselepis VH, Green LJ, Humphries MJ. An RGD to LDV motif conversion within the disintegrin kistrin generates an integrin antagonist that retains potency but exhibits altered receptor specificity. Evidence for a functional equivalence of acidic integrin-binding motifs. J Biol Chem 1997; 272:21341-8. [PMID: 9261147 DOI: 10.1074/jbc.272.34.21341] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Integrin ligands almost invariably employ a variant of either the RGD or LDV motif as a key element of their receptor recognition site. These short acidic peptide sequences collaborate with specific nonhomologous flanking residues and spatially separate "synergy" sequences to determine receptor binding specificity. Although the consensus sequences for RGD and LDV motifs are quite different, their common use suggests that they might share a critical role in receptor-ligand engagement. To date, the effects of interconversion of the two motifs within a natural protein framework have not been tested; however, in this study, we have converted the natural RGD site found in the snake venom disintegrin kistrin into an LDV motif and examined the effects of the change on the specificity of integrin recognition and on disintegrin potency. While an assessment of receptor binding using cell adhesion and purified integrin solid-phase assays demonstrated recognition of recombinant RGD kistrin by alphaVbeta3 and alpha5beta1, a series of LDV kistrin chimeras did not bind to these integrins, but instead were recognized specifically by alpha4beta1. The minimal change to elicit this distinct switch in receptor specificity was found to involve alteration of only three residues within kistrin. Alanine scanning mutagenesis was used to provide further information on the functional contribution of the three residues. More important, the LDV kistrin chimeras also retained much of the characteristic potency of RGD kistrin, indicating that the kistrin scaffold is optimized for presentation of both RGD and LDV sequences. These findings provide evidence for similarities in motif pharmacophore and reinforce the hypothesis that RGD and LDV sites have an equivalent functional role in receptor binding. They also demonstrate the potential for other disintegrin-containing proteins, perhaps from the ADAM family, to employ LDV sequences for integrin binding.
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Affiliation(s)
- V H Tselepis
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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50
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Abrams C, Shattil SJ. The Platelet Integrin, GP IIb-IIIa (αIIbß3). The Platelet. Elsevier; 1997. pp. 67-108. [DOI: 10.1016/s1569-2558(08)60411-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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