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Bury L, Falcinelli E, Chiasserini D, Springer TA, Italiano JE, Gresele P. Cytoskeletal perturbation leads to platelet dysfunction and thrombocytopenia in variant forms of Glanzmann thrombasthenia. Haematologica 2015; 101:46-56. [PMID: 26452979 DOI: 10.3324/haematol.2015.130849] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 10/01/2015] [Indexed: 11/09/2022] Open
Abstract
Several patients have been reported to have variant dominant forms of Glanzmann thrombasthenia, associated with macrothrombocytopenia and caused by gain-of-function mutations of ITGB3 or ITGA2B leading to reduced surface expression and constitutive activation of integrin αIIbβ3. The mechanisms leading to a bleeding phenotype of these patients have never been addressed. The aim of this study was to unravel the mechanism by which ITGB3 mutations causing activation of αIIbβ3 lead to platelet dysfunction and macrothrombocytopenia. Using platelets from two patients carrying the β3 del647-686 mutation and Chinese hamster ovary cells expressing different αIIbβ3-activating mutations, we showed that reduced surface expression of αIIbβ3 is due to receptor internalization. Moreover, we demonstrated that permanent triggering of αIIbβ3-mediated outside-in signaling causes an impairment of cytoskeletal reorganization arresting actin turnover at the stage of polymerization. The induction of actin polymerization by jasplakinolide, a natural toxin that promotes actin nucleation and prevents depolymerization of stress fibers, in control platelets produced an impairment of platelet function similar to that of patients with variant forms of dominant Glanzmann thrombasthenia. del647-686β3-transduced murine megakaryocytes generated proplatelets with a reduced number of large tips and asymmetric barbell-proplatelets, suggesting that impaired cytoskeletal rearrangement is the cause of macrothrombocytopenia. These data show that impaired cytoskeletal remodeling caused by a constitutively activated αIIbβ3 is the main effector of platelet dysfunction and macrothrombocytopenia, and thus of bleeding, in variant forms of dominant Glanzmann thrombasthenia.
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Affiliation(s)
- Loredana Bury
- Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Italy
| | - Emanuela Falcinelli
- Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Italy
| | - Davide Chiasserini
- Department of Medicine, Section of Neurology, University of Perugia, Italy
| | - Timothy A Springer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School and Program in Cellular and Molecular Medicine, Children's Hospital, Boston, MA, USA
| | - Joseph E Italiano
- Hematology Division, Department of Medicine, Brigham and Women's Hospital, Vascular Biology Program, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Paolo Gresele
- Department of Medicine, Section of Internal and Cardiovascular Medicine, University of Perugia, Italy
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55
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Soto-Pantoja DR, Kaur S, Roberts DD. CD47 signaling pathways controlling cellular differentiation and responses to stress. Crit Rev Biochem Mol Biol 2015; 50:212-30. [PMID: 25708195 DOI: 10.3109/10409238.2015.1014024] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CD47 is a widely expressed integral membrane protein that serves as the counter-receptor for the inhibitory phagocyte receptor signal-regulatory protein-α (SIRPα) and as a signaling receptor for the secreted matricellular protein thrombospondin-1. Recent studies employing mice and somatic cells lacking CD47 have revealed important pathophysiological functions of CD47 in cardiovascular homeostasis, immune regulation, resistance of cells and tissues to stress and chronic diseases of aging including cancer. With the emergence of experimental therapeutics targeting CD47, a more thorough understanding of CD47 signal transduction is essential. CD47 lacks a substantial cytoplasmic signaling domain, but several cytoplasmic binding partners have been identified, and lateral interactions of CD47 with other membrane receptors play important roles in mediating signaling resulting from the binding of thrombospondin-1. This review addresses recent advances in identifying the lateral binding partners, signal transduction pathways and downstream transcription networks regulated through CD47 in specific cell lineages. Major pathways regulated by CD47 signaling include calcium homeostasis, cyclic nucleotide signaling, nitric oxide and hydrogen sulfide biosynthesis and signaling and stem cell transcription factors. These pathways and other undefined proximal mediators of CD47 signaling regulate cell death and protective autophagy responses, mitochondrial biogenesis, cell adhesion and motility and stem cell self-renewal. Although thrombospondin-1 is the best characterized agonist of CD47, the potential roles of other members of the thrombospondin family, SIRPα and SIRPγ binding and homotypic CD47 interactions as agonists or antagonists of signaling through CD47 should also be considered.
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Affiliation(s)
- David R Soto-Pantoja
- a Laboratory of Pathology , Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda , MD , USA
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56
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Minagawa S, Lou J, Seed RI, Cormier A, Wu S, Cheng Y, Murray L, Tsui P, Connor J, Herbst R, Govaerts C, Barker T, Cambier S, Yanagisawa H, Goodsell A, Hashimoto M, Brand OJ, Cheng R, Ma R, McKnelly KJ, Wen W, Hill A, Jablons D, Wolters P, Kitamura H, Araya J, Barczak AJ, Erle DJ, Reichardt LF, Marks JD, Baron JL, Nishimura SL. Selective targeting of TGF-β activation to treat fibroinflammatory airway disease. Sci Transl Med 2015; 6:241ra79. [PMID: 24944194 DOI: 10.1126/scitranslmed.3008074] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Airway remodeling, caused by inflammation and fibrosis, is a major component of chronic obstructive pulmonary disease (COPD) and currently has no effective treatment. Transforming growth factor-β (TGF-β) has been widely implicated in the pathogenesis of airway remodeling in COPD. TGF-β is expressed in a latent form that requires activation. The integrin αvβ8 (encoded by the itgb8 gene) is a receptor for latent TGF-β and is essential for its activation. Expression of integrin αvβ8 is increased in airway fibroblasts in COPD and thus is an attractive therapeutic target for the treatment of airway remodeling in COPD. We demonstrate that an engineered optimized antibody to human αvβ8 (B5) inhibited TGF-β activation in transgenic mice expressing only human and not mouse ITGB8. The B5 engineered antibody blocked fibroinflammatory responses induced by tobacco smoke, cytokines, and allergens by inhibiting TGF-β activation. To clarify the mechanism of action of B5, we used hydrodynamic, mutational, and electron microscopic methods to demonstrate that αvβ8 predominantly adopts a constitutively active, extended-closed headpiece conformation. Epitope mapping and functional characterization of B5 revealed an allosteric mechanism of action due to locking-in of a low-affinity αvβ8 conformation. Collectively, these data demonstrate a new model for integrin function and present a strategy to selectively target the TGF-β pathway to treat fibroinflammatory airway diseases.
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Affiliation(s)
- Shunsuke Minagawa
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jianlong Lou
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Robert I Seed
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Anthony Cormier
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Shenping Wu
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Yifan Cheng
- The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Lynne Murray
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA. Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Cambridge CB21 6GH, UK
| | - Ping Tsui
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Jane Connor
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Ronald Herbst
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Gaithersburg, MD 20878, USA
| | - Cedric Govaerts
- Department of Respiratory, Inflammation and Autoimmunity, MedImmune, Cambridge CB21 6GH, UK
| | - Tyren Barker
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Stephanie Cambier
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Haruhiko Yanagisawa
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Amanda Goodsell
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Mitsuo Hashimoto
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Oliver J Brand
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Ran Cheng
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Royce Ma
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Kate J McKnelly
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Weihua Wen
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Arthur Hill
- Department of Surgery, University of California, San Francisco, San Francisco, CA 94110, USA
| | - David Jablons
- Department of Surgery, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Paul Wolters
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Hideya Kitamura
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jun Araya
- Department of Pulmonary Medicine, Jikei University, Tokyo 105 8461, Japan
| | - Andrea J Barczak
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - David J Erle
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Louis F Reichardt
- Genetics, Development, and Behavioral Sciences, University of California, San Francisco, San Francisco, CA 94110, USA
| | - James D Marks
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Jody L Baron
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94110, USA
| | - Stephen L Nishimura
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94110, USA.
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61
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Rui X, Mehrbod M, Van Agthoven JF, Anand S, Xiong JP, Mofrad MRK, Arnaout MA. The α-subunit regulates stability of the metal ion at the ligand-associated metal ion-binding site in β3 integrins. J Biol Chem 2014; 289:23256-23263. [PMID: 24975416 DOI: 10.1074/jbc.m114.581470] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aspartate in the prototypical integrin-binding motif Arg-Gly-Asp binds the integrin βA domain of the β-subunit through a divalent cation at the metal ion-dependent adhesion site (MIDAS). An auxiliary metal ion at a ligand-associated metal ion-binding site (LIMBS) stabilizes the metal ion at MIDAS. LIMBS contacts distinct residues in the α-subunits of the two β3 integrins αIIbβ3 and αVβ3, but a potential role of this interaction on stability of the metal ion at LIMBS in β3 integrins has not been explored. Equilibrium molecular dynamics simulations of fully hydrated β3 integrin ectodomains revealed strikingly different conformations of LIMBS in unliganded αIIbβ3 versus αVβ3, the result of stronger interactions of LIMBS with αV, which reduce stability of the LIMBS metal ion in αVβ3. Replacing the αIIb-LIMBS interface residue Phe(191) in αIIb (equivalent to Trp(179) in αV) with Trp strengthened this interface and destabilized the metal ion at LIMBS in αIIbβ3; a Trp(179) to Phe mutation in αV produced the opposite but weaker effect. Consistently, an F191/W substitution in cellular αIIbβ3 and a W179/F substitution in αVβ3 reduced and increased, respectively, the apparent affinity of Mn(2+) to the integrin. These findings offer an explanation for the variable occupancy of the metal ion at LIMBS in αVβ3 structures in the absence of ligand and provide new insights into the mechanisms of integrin regulation.
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Affiliation(s)
- Xianliang Rui
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Mehrdad Mehrbod
- Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720
| | - Johannes F Van Agthoven
- Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and
| | - Saurabh Anand
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129
| | - Jian-Ping Xiong
- Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and
| | - Mohammad R K Mofrad
- Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720.
| | - M Amin Arnaout
- Leukocyte Biology and Inflammation Program and Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129; Structural Biology Program, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129 and.
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62
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Yu YP, Wang Q, Liu YC, Xie Y. Molecular basis for the targeted binding of RGD-containing peptide to integrin αVβ3. Biomaterials 2013; 35:1667-75. [PMID: 24268666 DOI: 10.1016/j.biomaterials.2013.10.072] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 10/27/2013] [Indexed: 12/11/2022]
Abstract
Integrin αVβ3-targeting peptides with an exposed arginine-glycine-aspartate (RGD) sequence play a crucial role in targeted anticancer drug delivery. The effects of RGD-containing peptide structure and quantity on mechanism of targeted binding of RGD-containing peptide to integrin αVβ3 were studied intensively at the molecular level via molecular dynamic simulations. Targeted recognization was mainly driven by the electrostatic interactions between the residues in RGD and the metal ions in integrin αVβ3, and cyclic arginine-glycine-aspartate-phenylalanine-valine (RGDFV) peptide appeared to be a better vector than the linear RGD-containing peptides. In addition, the optimal molar concentration ratio of RGD peptides to integrin αVβ3 appeared to be 2:1. These results will help improve the current understanding on the mechanism of interactions between RGD and integrin αVβ3, and promote the application prospects of RGD-based vectors in tumor imaging, diagnosis, and cancer therapy.
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Affiliation(s)
- Yu-Ping Yu
- Soft Matter Research Center, Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China
| | - Qi Wang
- Soft Matter Research Center, Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China
| | - Ying-Chun Liu
- Soft Matter Research Center, Department of Chemistry, Zhejiang University, Hangzhou 310027, PR China.
| | - Ying Xie
- Department of Pharmaceutics, Peking University, Beijing 100191, PR China.
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