1
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Bender M, Palankar R. Platelet Shape Changes during Thrombus Formation: Role of Actin-Based Protrusions. Hamostaseologie 2021; 41:14-21. [PMID: 33588449 DOI: 10.1055/a-1325-0993] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Platelet activation and aggregation are essential to limit blood loss at sites of vascular injury but may also lead to occlusion of diseased vessels. The platelet cytoskeleton is a critical component for proper hemostatic function. Platelets change their shape after activation and their contractile machinery mediates thrombus stabilization and clot retraction. In vitro studies have shown that platelets, which come into contact with proteins such as fibrinogen, spread and first form filopodia and then lamellipodia, the latter being plate-like protrusions with branched actin filaments. However, the role of platelet lamellipodia in hemostasis and thrombus formation has been unclear until recently. This short review will briefly summarize the recent findings on the contribution of the actin cytoskeleton and lamellipodial structures to platelet function.
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Affiliation(s)
- Markus Bender
- Institute of Experimental Biomedicine - Chair I, University Hospital and Rudolf Virchow Center, Würzburg, Germany
| | - Raghavendra Palankar
- Department of Transfusion Medicine, Institute for Immunology and Transfusion Medicine, University Medicine Greifswald, Greifswald, Germany
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2
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Nicolai L, Schiefelbein K, Lipsky S, Leunig A, Hoffknecht M, Pekayvaz K, Raude B, Marx C, Ehrlich A, Pircher J, Zhang Z, Saleh I, Marel AK, Löf A, Petzold T, Lorenz M, Stark K, Pick R, Rosenberger G, Weckbach L, Uhl B, Xia S, Reichel CA, Walzog B, Schulz C, Zheden V, Bender M, Li R, Massberg S, Gaertner F. Vascular surveillance by haptotactic blood platelets in inflammation and infection. Nat Commun 2020; 11:5778. [PMID: 33188196 PMCID: PMC7666582 DOI: 10.1038/s41467-020-19515-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 10/14/2020] [Indexed: 12/21/2022] Open
Abstract
Breakdown of vascular barriers is a major complication of inflammatory diseases. Anucleate platelets form blood-clots during thrombosis, but also play a crucial role in inflammation. While spatio-temporal dynamics of clot formation are well characterized, the cell-biological mechanisms of platelet recruitment to inflammatory micro-environments remain incompletely understood. Here we identify Arp2/3-dependent lamellipodia formation as a prominent morphological feature of immune-responsive platelets. Platelets use lamellipodia to scan for fibrin(ogen) deposited on the inflamed vasculature and to directionally spread, to polarize and to govern haptotactic migration along gradients of the adhesive ligand. Platelet-specific abrogation of Arp2/3 interferes with haptotactic repositioning of platelets to microlesions, thus impairing vascular sealing and provoking inflammatory microbleeding. During infection, haptotaxis promotes capture of bacteria and prevents hematogenic dissemination, rendering platelets gate-keepers of the inflamed microvasculature. Consequently, these findings identify haptotaxis as a key effector function of immune-responsive platelets. Breakdown of vascular barriers is a major complication of inflammatory diseases. However, the mechanisms underlying platelet recruitment to inflammatory micro-environments remains unclear. Here, the authors identify haptotaxis as a key effector function of immune-responsive platelets
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Affiliation(s)
- Leo Nicolai
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, 80802, Munich, Germany
| | - Karin Schiefelbein
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Silvia Lipsky
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Alexander Leunig
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Marie Hoffknecht
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Kami Pekayvaz
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Ben Raude
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Charlotte Marx
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Andreas Ehrlich
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Joachim Pircher
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Zhe Zhang
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Inas Saleh
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | | | - Achim Löf
- Ludwig-Maximilians-Universität, 80799, Munich, Germany
| | - Tobias Petzold
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Michael Lorenz
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Konstantin Stark
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Robert Pick
- Walter-Brendel-Centre of Experimental Medicine, University Hospital, München, Germany.,Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center, Planegg-Martinsried, Munich, Germany
| | - Gerhild Rosenberger
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Ludwig Weckbach
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany
| | - Bernd Uhl
- Department of Otorhinolarynology, Ludwig-Maximilians-Universität Munich, Munich, Germany
| | - Sheng Xia
- Department of Cell Biology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD, 21205, USA
| | | | - Barbara Walzog
- Walter-Brendel-Centre of Experimental Medicine, University Hospital, München, Germany.,Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center, Planegg-Martinsried, Munich, Germany
| | - Christian Schulz
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, 80802, Munich, Germany
| | - Vanessa Zheden
- Institute of Science and Technology (IST) Austria, 3400, Klosterneuburg, Austria
| | - Markus Bender
- Institute of Experimental Biomedicine I, University Hospital and Rudolf Virchow Center, Würzburg, Germany
| | - Rong Li
- Department of Cell Biology, Johns Hopkins University School of Medicine, 855 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Steffen Massberg
- Medizinische Klinik und Poliklinik I, Klinikum der Ludwig-Maximilians-Universität, 81377, Munich, Germany. .,DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, 80802, Munich, Germany.
| | - Florian Gaertner
- DZHK (German Centre for Cardiovascular Research), Partner Site Munich Heart Alliance, 80802, Munich, Germany. .,Institute of Science and Technology (IST) Austria, 3400, Klosterneuburg, Austria.
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3
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Schurr Y, Sperr A, Volz J, Beck S, Reil L, Kusch C, Eiring P, Bryson S, Sauer M, Nieswandt B, Machesky L, Bender M. Platelet lamellipodium formation is not required for thrombus formation and stability. Blood 2019; 134:2318-2329. [PMID: 31697813 DOI: 10.1182/blood.2019002105] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 09/30/2019] [Indexed: 11/20/2022] Open
Abstract
During platelet spreading, the actin cytoskeleton undergoes rapid rearrangement, forming filopodia and lamellipodia. Controversial data have been published on the role of lamellipodia in thrombus formation and stability. The Wiskott-Aldrich syndrome protein-family verprolin-homologous protein (WAVE)-regulatory complex, which has been shown in other cells to drive lamellipodium formation by enhancing actin nucleation via the actin-related protein 2/3 (Arp2/3) complex, is activated by Ras-related C3 botulinum toxin substrate 1 (Rac1) interaction with the WAVE complex subunit cytoplasmic fragile X mental retardation 1-interacting protein 1 (Cyfip1). We analyzed Cyfip1flox/floxPf4-Cre mice to investigate the role of Cyfip1 in platelet function. These mice displayed normal platelet counts and a slight reduction in platelet volume. Activation of mutant platelets was only moderately reduced to all tested agonists as measured by αIIbβ3 integrin activation and P-selectin surface exposure. However, lamellipodium formation of mutant platelets was completely abolished on different matrices. Nevertheless, Cyfip1-deficient platelets formed stable thrombi on collagen fibers ex vivo and in 2 models of occlusive arterial thrombosis in vivo. Similarly, the hemostatic function and maintenance of vascular integrity during inflammation of the skin and lung were unaltered in the mutant mice. Investigation of platelet morphology in an induced thrombus under flow revealed that platelets rather form filopodia in the thrombus shell, and are flattened with filopodium-like structures when in direct contact to collagen fibers at the bottom of the thrombus. We provide for the first time direct evidence that platelet lamellipodium formation is not required for stable thrombus formation, and that morphological changes of platelets differ between a static spreading assay and thrombus formation under flow.
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Affiliation(s)
- Yvonne Schurr
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Andreas Sperr
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Julia Volz
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Sarah Beck
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Lucy Reil
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Charly Kusch
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Patrick Eiring
- Department of Biotechnology and Biophysics, Biocenter, Julius Maximilian University of Würzburg, Würzburg, Germany
| | - Sheila Bryson
- Beatson Institute, Cancer Research UK, Glasgow, United Kingdom; and
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius Maximilian University of Würzburg, Würzburg, Germany
| | - Bernhard Nieswandt
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
| | - Laura Machesky
- Beatson Institute, Cancer Research UK, Glasgow, United Kingdom; and
- Institute of Cancer Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Markus Bender
- Institute of Experimental Biomedicine-Chair I, University Hospital
- Rudolf Virchow Center, and
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4
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5
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Barwari T, Eminaga S, Mayr U, Lu R, Armstrong PC, Chan MV, Sahraei M, Fernández-Fuertes M, Moreau T, Barallobre-Barreiro J, Lynch M, Yin X, Schulte C, Baig F, Pechlaner R, Langley SR, Zampetaki A, Santer P, Weger M, Plasenzotti R, Schosserer M, Grillari J, Kiechl S, Willeit J, Shah AM, Ghevaert C, Warner TD, Fernández-Hernando C, Suárez Y, Mayr M. Inhibition of profibrotic microRNA-21 affects platelets and their releasate. JCI Insight 2018; 3:123335. [PMID: 30385722 PMCID: PMC6238735 DOI: 10.1172/jci.insight.123335] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 09/26/2018] [Indexed: 12/22/2022] Open
Abstract
Fibrosis is a major contributor to organ disease for which no specific therapy is available. MicroRNA-21 (miR-21) has been implicated in the fibrogenetic response, and inhibitors of miR-21 are currently undergoing clinical trials. Here, we explore how miR-21 inhibition may attenuate fibrosis using a proteomics approach. Transfection of miR-21 mimic or inhibitor in murine cardiac fibroblasts revealed limited effects on extracellular matrix (ECM) protein secretion. Similarly, miR-21–null mouse hearts showed an unaltered ECM composition. Thus, we searched for additional explanations as to how miR-21 might regulate fibrosis. In plasma samples from the community-based Bruneck Study, we found a marked correlation of miR-21 levels with several platelet-derived profibrotic factors, including TGF-β1. Pharmacological miR-21 inhibition with an antagomiR reduced the platelet release of TGF-β1 in mice. Mechanistically, Wiskott-Aldrich syndrome protein, a negative regulator of platelet TGF-β1 secretion, was identified as a direct target of miR-21. miR-21–null mice had lower platelet and leukocyte counts compared with littermate controls but higher megakaryocyte numbers in the bone marrow. Thus, to our knowledge this study reports a previously unrecognized effect of miR-21 inhibition on platelets. The effect of antagomiR-21 treatment on platelet TGF-β1 release, in particular, may contribute to the antifibrotic effects of miR-21 inhibitors. MicroRNA-21 inhibition may convey its therapeutic benefits in fibrosis through its action in bone marrow cells rather than targeting fibroblasts directly.
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Affiliation(s)
- Temo Barwari
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Seda Eminaga
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Ursula Mayr
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Ruifang Lu
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Paul C Armstrong
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Melissa V Chan
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Mahnaz Sahraei
- Department of Comparative Medicine and Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Marta Fernández-Fuertes
- Department of Comparative Medicine and Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Thomas Moreau
- Department of Haematology, University of Cambridge, National Health Blood Service Centre, Cambridge, United Kingdom
| | | | - Marc Lynch
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Xiaoke Yin
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Christian Schulte
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Ferheen Baig
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Raimund Pechlaner
- Department of Neurology, Medical University Innsbruck, Innsbruck, Austria
| | - Sarah R Langley
- Duke-NUS Medical School, Singapore.,National Heart Centre Singapore, Singapore
| | - Anna Zampetaki
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | | | - Martin Weger
- Department of Internal Medicine, Bruneck Hospital, Bruneck, Italy
| | - Roberto Plasenzotti
- Medical University of Vienna, Institute of Biomedical Research, Vienna, Austria
| | - Markus Schosserer
- Christian Doppler Laboratory on Biotechnology of Skin Aging, Department of Biotechnology, BOKU - University of Natural Resources and Life Sciences, Vienna, Austria
| | - Johannes Grillari
- Christian Doppler Laboratory on Biotechnology of Skin Aging, Department of Biotechnology, BOKU - University of Natural Resources and Life Sciences, Vienna, Austria
| | - Stefan Kiechl
- Department of Neurology, Medical University Innsbruck, Innsbruck, Austria
| | - Johann Willeit
- Department of Neurology, Medical University Innsbruck, Innsbruck, Austria
| | - Ajay M Shah
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
| | - Cedric Ghevaert
- Department of Haematology, University of Cambridge, National Health Blood Service Centre, Cambridge, United Kingdom
| | - Timothy D Warner
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Carlos Fernández-Hernando
- Department of Comparative Medicine and Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Yajaira Suárez
- Department of Comparative Medicine and Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Manuel Mayr
- King's British Heart Foundation Centre, King's College London, London, United Kingdom
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6
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Pleines I, Cherpokova D, Bender M. Rho GTPases and their downstream effectors in megakaryocyte biology. Platelets 2018; 30:9-16. [DOI: 10.1080/09537104.2018.1478071] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Irina Pleines
- Institute of Experimental Biomedicine I, University Hospital and Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
| | - Deya Cherpokova
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, and Department of Pediatrics, Harvard Medical School, Boston, MA, USA
| | - Markus Bender
- Institute of Experimental Biomedicine I, University Hospital and Rudolf Virchow Center, University of Würzburg, Würzburg, Germany
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7
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Messaoudi K, Ali A, Ishaq R, Palazzo A, Sliwa D, Bluteau O, Souquère S, Muller D, Diop KM, Rameau P, Lapierre V, Marolleau JP, Matthias P, Godin I, Pierron G, Thomas SG, Watson SP, Droin N, Vainchenker W, Plo I, Raslova H, Debili N. Critical role of the HDAC6-cortactin axis in human megakaryocyte maturation leading to a proplatelet-formation defect. Nat Commun 2017; 8:1786. [PMID: 29176689 PMCID: PMC5702605 DOI: 10.1038/s41467-017-01690-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 10/10/2017] [Indexed: 01/08/2023] Open
Abstract
Thrombocytopenia is a major side effect of a new class of anticancer agents that target histone deacetylase (HDAC). Their mechanism is poorly understood. Here, we show that HDAC6 inhibition and genetic knockdown lead to a strong decrease in human proplatelet formation (PPF). Unexpectedly, HDAC6 inhibition-induced tubulin hyperacetylation has no effect on PPF. The PPF decrease induced by HDAC6 inhibition is related to cortactin (CTTN) hyperacetylation associated with actin disorganization inducing important changes in the distribution of megakaryocyte (MK) organelles. CTTN silencing in human MKs phenocopies HDAC6 inactivation and knockdown leads to a strong PPF defect. This is rescued by forced expression of a deacetylated CTTN mimetic. Unexpectedly, unlike human-derived MKs, HDAC6 and CTTN are shown to be dispensable for mouse PPF in vitro and platelet production in vivo. Our results highlight an unexpected function of HDAC6–CTTN axis as a positive regulator of human but not mouse MK maturation. Histone deacetylase (HDAC) inhibitors, a class of cancer therapeutics, cause thrombocytopenia via an unknown mechanism. Here, the authors show that HDAC6 inhibition impairs proplatelet formation in human megakaryocytes, and show that this is linked to hyperacetylation of the actin-binding protein cortactin.
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Affiliation(s)
- Kahia Messaoudi
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France.,Paris7 Diderot University, 75013, Paris, France
| | - Ashfaq Ali
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France.,Paris7 Diderot University, 75013, Paris, France
| | - Rameez Ishaq
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France.,Paris7 Diderot University, 75013, Paris, France
| | - Alberta Palazzo
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France.,Paris7 Diderot University, 75013, Paris, France
| | - Dominika Sliwa
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Olivier Bluteau
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Sylvie Souquère
- CNRS-UMR-9196, Institut Gustave Roussy, 94805, Villejuif, France
| | - Delphine Muller
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Khadija M Diop
- Genomic Platform, Institut Gustave Roussy, 94805, Villejuif, France
| | - Philippe Rameau
- Gustave Roussy, Integrated Biology Core Facility, 94805, Villejuif, France
| | | | - Jean-Pierre Marolleau
- Clinical Hematology and Cell Therapy Department, Amiens Hospital, UPJV University EA4666, 80054, Amiens, France
| | - Patrick Matthias
- Friedrich Miescher Institute for Biomedical Research, 4002, Basel, Switzerland
| | - Isabelle Godin
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Gérard Pierron
- CNRS-UMR-9196, Institut Gustave Roussy, 94805, Villejuif, France
| | - Steven G Thomas
- Institute of Cardiovascular Sciences, The Medical School, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.,Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands, UK
| | - Stephen P Watson
- Institute of Cardiovascular Sciences, The Medical School, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.,Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Midlands, UK
| | - Nathalie Droin
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France.,Genomic Platform, Institut Gustave Roussy, 94805, Villejuif, France
| | - William Vainchenker
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Isabelle Plo
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Hana Raslova
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France.,Paris-Saclay University, UMR 1170, 94805, Villejuif, France.,Gustave Roussy, 94805, Villejuif, France
| | - Najet Debili
- Institut National de la Santé et de la Recherche Médicale, UMR 1170, Equipe labellisée par la Ligue Nationale contre le Cancer, 94805, Villejuif, France. .,Paris-Saclay University, UMR 1170, 94805, Villejuif, France. .,Gustave Roussy, 94805, Villejuif, France.
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8
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Abstract
Actin reorganization regulates key processes in platelet activation. Here we examined the role of the Arp2/3 complex, an essential component in actin filament branching, in platelet function. The Arpc2 gene, encoding the p34 subunit of the Arp2/3 complex, was deleted in the megakaryocyte lineage (Arpc2fl/flPF4-Cre). Deletion of the Arp2/3 complex resulted in marked microthrombocytopenia in mice, caused by premature platelet release into the bone marrow compartment and impaired platelet survival in circulation. Arpc2fl/flPF4-Cre platelets exhibited alterations in their actin cytoskeleton and their peripheral microtubule coil. Thrombocytopenia was alleviated following clodronate liposome-induced macrophage depletion in Arpc2fl/flPF4-Cre mice. Arpc2fl/flPF4-Cre platelets failed to spread and showed a mild defect in integrin activation and aggregation. However, no significant differences in hemostasis or thrombosis were observed between Arpc2fl/flPF4-Cre and control mice. Thus, Arp2/3 is critical for platelet homeostasis but plays only a minor role for vascular hemostasis.
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9
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Kahr WHA, Pluthero FG, Elkadri A, Warner N, Drobac M, Chen CH, Lo RW, Li L, Li R, Li Q, Thoeni C, Pan J, Leung G, Lara-Corrales I, Murchie R, Cutz E, Laxer RM, Upton J, Roifman CM, Yeung RSM, Brumell JH, Muise AM. Loss of the Arp2/3 complex component ARPC1B causes platelet abnormalities and predisposes to inflammatory disease. Nat Commun 2017; 8:14816. [PMID: 28368018 PMCID: PMC5382316 DOI: 10.1038/ncomms14816] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 01/31/2017] [Indexed: 12/19/2022] Open
Abstract
Human actin-related protein 2/3 complex (Arp2/3), required for actin filament branching, has two ARPC1 component isoforms, with ARPC1B prominently expressed in blood cells. Here we show in a child with microthrombocytopenia, eosinophilia and inflammatory disease, a homozygous frameshift mutation in ARPC1B (p.Val91Trpfs*30). Platelet lysates reveal no ARPC1B protein and greatly reduced Arp2/3 complex. Missense ARPC1B mutations are identified in an unrelated patient with similar symptoms and ARPC1B deficiency. ARPC1B-deficient platelets are microthrombocytes similar to those seen in Wiskott–Aldrich syndrome that show aberrant spreading consistent with loss of Arp2/3 function. Knockout of ARPC1B in megakaryocytic cells results in decreased proplatelet formation, and as observed in platelets from patients, increased ARPC1A expression. Thus loss of ARPC1B produces a unique set of platelet abnormalities, and is associated with haematopoietic/immune symptoms affecting cell lineages where this isoform predominates. In agreement with recent experimental studies, our findings suggest that ARPC1 isoforms are not functionally interchangeable. ARPC1B is a component of the actin-related protein 2/3 complex (Arp2/3), which is required for actin filament branching. Kahr et al. show that ARPC1B deficiency in humans is associated with severe multisystem disease that includes platelet abnormalities, eosinophilia, eczema and other indicators of immune disease.
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Affiliation(s)
- Walter H A Kahr
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Division of Haematology/Oncology, Department of Paediatrics, University of Toronto and The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Fred G Pluthero
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Abdul Elkadri
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Neil Warner
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Marko Drobac
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Chang Hua Chen
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Richard W Lo
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Ling Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Ren Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4
| | - Qi Li
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Cornelia Thoeni
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Jie Pan
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Gabriella Leung
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Irene Lara-Corrales
- Division of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ryan Murchie
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ernest Cutz
- Division of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Ronald M Laxer
- Division of Rheumatology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Medicine, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Julia Upton
- Division of Immunology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Chaim M Roifman
- Division of Immunology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
| | - Rae S M Yeung
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,Division of Rheumatology, Department of Paediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Department of Immunology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - John H Brumell
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Aleixo M Muise
- Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 0A4.,Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8.,SickKids Inflammatory Bowel Disease Center and Division of Gastroenterology, Hepatology, and Nutrition, Department of Paediatrics, University of Toronto, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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10
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Rondina MT, Freitag M, Pluthero FG, Kahr WHA, Rowley JW, Kraiss LW, Franks Z, Zimmerman GA, Weyrich AS, Schwertz H. Non-genomic activities of retinoic acid receptor alpha control actin cytoskeletal events in human platelets. J Thromb Haemost 2016; 14:1082-94. [PMID: 26848712 PMCID: PMC5497578 DOI: 10.1111/jth.13281] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Indexed: 12/29/2022]
Abstract
UNLABELLED Essentials Platelets employ proteins/signaling pathways traditionally thought reserved for nuclear niche. We determined retinoic-acid-receptor alpha (RARα) expression and function in human platelets. RARα/actin-related protein-2/3 complex (Arp2/3) interact via non-genomic signaling in platelets. RARα regulates Arp2/3-mediated actin cytoskeletal dynamics and platelet spreading. SUMMARY Background Platelets utilize proteins and pathways classically reserved for the nuclear niche. Methods We determined whether human platelets express retinoic-acid-receptor family members, traditionally thought of as nuclear transcription factors, and deciphered the function of RARα. Results We found that RARα is robustly expressed in human platelets and megakaryocytes and interacts directly with actin-related protein-2/3 complex (Arp2/3) subunit 5 (Arp2/3s5). Arp2/3s5 co-localized with RARα in situ and regulated platelet cytoskeletal processes. The RARα ligand all-trans retinoic acid (atRA) disrupted RARα-Arp2/3 interactions. When isolated human platelets were treated with atRA, rapid cytoskeletal events (e.g. platelet spreading) were inhibited. In addition, when platelets were cultured for 18 h in the presence of atRA, actin-dependent morphological changes (e.g. extended cell body formation) were similarly inhibited. Using in vitro actin branching assays, RARα and Arp2/3-regulated complex actin branch formation was demonstrated. Consistent with inhibition of cytoskeletal processes in platelets, atRA, when added to this branching assay, resulted in dysregulated actin branching. Conclusion Our findings identify a previously unknown mechanism by which RARα regulates Arp2/3-mediated actin cytoskeletal dynamics through a non-genomic signaling pathway. These findings have broad implications in both nucleated and anucleate cells, where actin cytoskeletal events regulate cell morphology, movement and division.
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Affiliation(s)
- M T Rondina
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
- Department of Internal Medicine, George E. Wahlen Salt Lake City VAMC, Salt Lake City, UT, USA
| | - M Freitag
- Department of Immunology and Transfusion Medicine, University of Greifswald, Greifswald, Germany
| | - F G Pluthero
- Program in Cell Biology, Research Institute, Hospital for Sick Children, Toronto, ON, Canada
| | - W H A Kahr
- Program in Cell Biology, Research Institute, Hospital for Sick Children, Toronto, ON, Canada
- Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, ON, Canada
| | - J W Rowley
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
| | - L W Kraiss
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
- Division of Vascular Surgery, Department of Surgery, University of Utah, Salt Lake City, UT, USA
| | - Z Franks
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
| | - G A Zimmerman
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - A S Weyrich
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - H Schwertz
- Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA
- Department of Immunology and Transfusion Medicine, University of Greifswald, Greifswald, Germany
- Division of Vascular Surgery, Department of Surgery, University of Utah, Salt Lake City, UT, USA
- Lichtenberg-Professor for Experimental Hemostasis, University of Greifswald, Greifswald, Germany
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Ye S, Huang Y, Joshi S, Zhang J, Yang F, Zhang G, Smyth SS, Li Z, Takai Y, Whiteheart SW. Platelet secretion and hemostasis require syntaxin-binding protein STXBP5. J Clin Invest 2014; 124:4517-28. [PMID: 25244094 DOI: 10.1172/jci75572] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 07/24/2014] [Indexed: 01/22/2023] Open
Abstract
Genome-wide association studies (GWAS) have linked genes encoding several soluble NSF attachment protein receptor (SNARE) regulators to cardiovascular disease risk factors. Because these regulatory proteins may directly affect platelet secretion, we used SNARE-containing complexes to affinity purify potential regulators from human platelet extracts. Syntaxin-binding protein 5 (STXBP5; also known as tomosyn-1) was identified by mass spectrometry, and its expression in isolated platelets was confirmed by RT-PCR analysis. Coimmunoprecipitation studies showed that STXBP5 interacts with core secretion machinery complexes, such as syntaxin-11/SNAP23 heterodimers, and fractionation studies suggested that STXBP5 also interacts with the platelet cytoskeleton. Platelets from Stxbp5 KO mice had normal expression of other key secretory components; however, stimulation-dependent secretion from each of the 3 granule types was markedly defective. Secretion defects in STXBP5-deficient platelets were confirmed via lumi-aggregometry and FACS analysis for P-selectin and LAMP-1 exposure. Interestingly, STXBP5-deficient platelets had altered granule cargo levels, despite having normal morphology and granule numbers. Consistent with secretion and cargo deficiencies, Stxbp5 KO mice showed dramatic bleeding in the tail transection model and defective hemostasis in the FeCl3-induced carotid injury model. Transplantation experiments indicated that these defects were due to loss of STXBP5 in BM-derived cells. Our data demonstrate that STXBP5 is required for normal arterial hemostasis, due to its contributions to platelet granule cargo packaging and secretion.
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12
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Abstract
WIP plays an important role in the remodeling of the actin cytoskeleton, which controls cellular activation, proliferation, and function. WIP regulates actin polymerization by linking the actin machinery to signaling cascades. WIP binding to WASp and to its homolog, N-WASp, which are central activators of the actin-nucleating complex Arp2/3, regulates their cellular distribution, function, and stability. By binding to WASp, WIP protects it from degradation and thus, is crucial for WASp retention. Indeed, most mutations that result in WAS, an X-linked immunodeficiency caused by defective/absent WASp activity, are located in the WIP-binding region of WASp. In addition, by binding directly to actin, WIP promotes the formation and stabilization of actin filaments. WASp-independent activities of WIP constitute a new research frontier and are discussed extensively in this article. Here, we review the current information on WIP in human and mouse systems, focusing on its associated proteins, its molecular-regulatory mechanisms, and its role as a key regulator of actin-based processes in the immune system.
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Affiliation(s)
- Sophia Fried
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Omri Matalon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Elad Noy
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Mira Barda-Saad
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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13
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Megakaryocyte-specific Profilin1-deficiency alters microtubule stability and causes a Wiskott–Aldrich syndrome-like platelet defect. Nat Commun 2014; 5:4746. [DOI: 10.1038/ncomms5746] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 07/20/2014] [Indexed: 11/08/2022] Open
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Karmakar S, Saha S, Banerjee D, Chakrabarti A. Differential proteomics study of platelets in asymptomatic constitutional macrothrombocytopenia: altered levels of cytoskeletal proteins. Eur J Haematol 2014; 94:43-50. [PMID: 24934967 DOI: 10.1111/ejh.12398] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2014] [Indexed: 12/27/2022]
Abstract
OBJECTIVES Harris platelet syndrome (HPS), also known as asymptomatic constitutional macrothrombocytopenia (ACMT), is an autosomal dominant platelet disorder characterized by mild-to-severe thrombocytopenia and giant platelets with normal platelet aggregation and absence of bleeding symptoms. We have attempted a comparative proteomics study for profiling of platelet proteins in healthy vs. pathological states to discover characteristic protein expression changes in macrothrombocytes and decipher the factors responsible for the functionally active yet morphologically distinct platelets. METHODS We have used 2-D gel-based protein separation techniques coupled with MALDI-ToF/ToF-based mass spectrometric identification and characterization of the proteins to investigate the differential proteome profiling of platelet proteins isolated from the peripheral blood samples of patients and normal volunteers. RESULTS AND CONCLUSION Our study revealed altered levels of actin-binding proteins such as myosin light chain, coactosin-like protein, actin-related protein 2/3 complex, and transgelin2 that hint toward the cytoskeletal changes necessary to maintain the structural and functional integrity of macrothrombocytes. We have also observed over expressed levels of peroxiredoxin2 that signifies the prevailing oxidative stress in these cells. Additionally, altered levels of protein disulfide isomerase and transthyretin provide insights into the measures adapted by the macrothrombocytes to maintain their normal functional activity. This first proteomics study of platelets from ACMT may provide an understanding of the structural stability and normal functioning of these platelets in spite of their large size.
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Affiliation(s)
- Shilpita Karmakar
- Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
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15
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Kim H, Falet H, Hoffmeister KM, Hartwig JH. Wiskott-Aldrich syndrome protein (WASp) controls the delivery of platelet transforming growth factor-β1. J Biol Chem 2013; 288:34352-63. [PMID: 24133214 DOI: 10.1074/jbc.m113.459750] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Platelets are immunologically competent cells containing cytokines such as TGF-β1 that regulate cell-mediated immunity. However, the mechanisms underlying cytokine secretion from platelets are undefined. The Wiskott-Aldrich syndrome protein (WASp) regulates actin polymerization in nucleated hematopoietic cells but has other role(s) in platelets. WASp-null (WASp(-/-)) platelets stimulated with a PAR-4 receptor agonist had increased TGF-β1 release compared with WT platelets; inhibiting WASp function with wiskostatin augmented TRAP-induced TGF-β1 release in human platelets. TGF-β1 release is dissociated from α-granule secretion (P-selectin up-regulation) and occurs more gradually, with ∼10-15% released after 30-60 min. Blockade of Src family kinase-mediated WASp Tyr-291/Tyr-293 phosphorylation increased TGF-β1 release, with no additive effect in WASp(-/-) platelets, signifying that phosphorylation is critical for WASp-limited TGF-β1 secretion. Inhibiting F-actin assembly with cytochalasin D enhanced secretion in WT platelets and further increased TGF-β1 release in WASp(-/-) platelets, indicating that WASp and actin assembly independently regulate TGF-β1 release. A permeabilized platelet model was used to test the role of upstream small GTPases in TGF-β1 release. N17Cdc42, but not Rac1 mutants, increased TGF-β1 secretion and abrogated WASp phosphorylation. We conclude that WASp function restricts TGF-β1 secretion in a Cdc42- and Src family kinase-dependent manner and independently of actin assembly.
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Affiliation(s)
- Hugh Kim
- From the Division of Translational Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
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16
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Paul DS, Albers CA, Rendon A, Voss K, Stephens J, van der Harst P, Chambers JC, Soranzo N, Ouwehand WH, Deloukas P. Maps of open chromatin highlight cell type-restricted patterns of regulatory sequence variation at hematological trait loci. Genome Res 2013; 23:1130-41. [PMID: 23570689 PMCID: PMC3698506 DOI: 10.1101/gr.155127.113] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Nearly three-quarters of the 143 genetic signals associated with platelet and erythrocyte phenotypes identified by meta-analyses of genome-wide association (GWA) studies are located at non-protein-coding regions. Here, we assessed the role of candidate regulatory variants associated with cell type–restricted, closely related hematological quantitative traits in biologically relevant hematopoietic cell types. We used formaldehyde-assisted isolation of regulatory elements followed by next-generation sequencing (FAIRE-seq) to map regions of open chromatin in three primary human blood cells of the myeloid lineage. In the precursors of platelets and erythrocytes, as well as in monocytes, we found that open chromatin signatures reflect the corresponding hematopoietic lineages of the studied cell types and associate with the cell type–specific gene expression patterns. Dependent on their signal strength, open chromatin regions showed correlation with promoter and enhancer histone marks, distance to the transcription start site, and ontology classes of nearby genes. Cell type–restricted regions of open chromatin were enriched in sequence variants associated with hematological indices. The majority (63.6%) of such candidate functional variants at platelet quantitative trait loci (QTLs) coincided with binding sites of five transcription factors key in regulating megakaryopoiesis. We experimentally tested 13 candidate regulatory variants at 10 platelet QTLs and found that 10 (76.9%) affected protein binding, suggesting that this is a frequent mechanism by which regulatory variants influence quantitative trait levels. Our findings demonstrate that combining large-scale GWA data with open chromatin profiles of relevant cell types can be a powerful means of dissecting the genetic architecture of closely related quantitative traits.
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Affiliation(s)
- Dirk S Paul
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1SA, United Kingdom.
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Massaad MJ, Ramesh N, Geha RS. Wiskott-Aldrich syndrome: a comprehensive review. Ann N Y Acad Sci 2013; 1285:26-43. [DOI: 10.1111/nyas.12049] [Citation(s) in RCA: 229] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Michel J. Massaad
- Division of Immunology, Boston Children's Hospital, and Department of Pediatrics; Harvard Medical School; Boston; Massachusetts
| | - Narayanaswamy Ramesh
- Division of Immunology, Boston Children's Hospital, and Department of Pediatrics; Harvard Medical School; Boston; Massachusetts
| | - Raif S. Geha
- Division of Immunology, Boston Children's Hospital, and Department of Pediatrics; Harvard Medical School; Boston; Massachusetts
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Yang C, Svitkina T. Filopodia initiation: focus on the Arp2/3 complex and formins. Cell Adh Migr 2012; 5:402-8. [PMID: 21975549 DOI: 10.4161/cam.5.5.16971] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Filopodia are long, slender, actin-rich cellular protrusions, which recently have become a focus of cell biology research because of their proposed roles as sensory and exploratory organelles that allow for "intelligent" cell behavior. Actin nucleation, elongation and bundling are believed to be essential for filopodia formation and functions. However, the identity of actin filament nucleators responsible for the initiation of filopodia remains controversial. Two alternative models, the convergent elongation and tip nucleation, emphasize two different actin filament nucleators, the Arp2/3 complex or formins, respectively, as key players during filopodia initiation. Although these two models in principle are not mutually exclusive, it is important to understand which of them is actually employed by cells. In this review, we discuss the existing evidence regarding the relative roles of the Arp2/3 complex and formins in filopodia initiation.
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Affiliation(s)
- Changsong Yang
- Department of Biology; University of Pennsylvania; Philadelphia, PA, USA
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20
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Abstract
PURPOSE OF REVIEW Blood platelets are involved in primary and secondary hemostasis and thus maintain the integrity of the vasculature. They circulate with an average lifespan of 5-9 days in humans. Thus, the body must generate and clear platelets daily to maintain normal physiological blood platelet counts. Known platelet clearance mechanisms include antibody-mediated clearance by spleen macrophages, as in immune thrombocytopenia, and platelet consumption due to massive blood loss. RECENT FINDINGS New concepts in the clearance mechanisms of platelets have recently emerged. New evidence shows that platelets desialyted due to chilling or sepsis are cleared in the liver by macrophages, that is Kupffer cells, as well as hepatocytes, through lectin-mediated recognition of platelet glycans. On the contrary, platelet-associated antibodies normalize the clearance of platelets in a mouse model for Wiskott-Aldrich syndrome. SUMMARY The goal of this review is to summarize the latest findings in platelet clearance mechanisms with a focus on lectin-mediated recognition of platelet glycans. Transfusion medicine and treatments of hematopoietic disorders associated with severe thrombocytopenia may benefit from a better understanding of these mechanisms.
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Isaac BM, Ishihara D, Nusblat LM, Gevrey JC, Dovas A, Condeelis J, Cox D. N-WASP has the ability to compensate for the loss of WASP in macrophage podosome formation and chemotaxis. Exp Cell Res 2010; 316:3406-16. [PMID: 20599953 DOI: 10.1016/j.yexcr.2010.06.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/09/2010] [Accepted: 06/10/2010] [Indexed: 10/24/2022]
Abstract
Wiskott-Aldrich syndrome protein (WASP) and its homologue neural-WASP (N-WASP) are nucleation promoting factors that integrate receptor signaling with actin cytoskeleton rearrangement. While hematopoietic cells express both WASP and N-WASP, WASP deficiency results in altered cell morphology, loss of podosomes and defective chemotaxis. It was determined that cells from a mouse derived monocyte/macrophage cell line and primary cells of myeloid lineage expressed approximately 15-fold higher levels of WASP relative to N-WASP. To test whether N-WASP can compensate for the loss of WASP and restore actin cytoskeleton integrity, N-WASP was overexpressed in macrophages, in which endogenous WASP expression was reduced by short hairpin RNA (shWASP cells). Many of the defects associated with the loss of WASP, such as podosome-dependent matrix degradation and chemotaxis were corrected when N-WASP was expressed at equimolar level to that of the wild-type WASP. Furthermore, the ability of N-WASP to partially compensate for the loss of WASP may be physiologically relevant since activated murine WASP-deficient peritoneal macrophages, which show enhanced N-WASP expression, also show an increase in matrix degradation. Our study suggests that expression levels of WASP and N-WASP may influence their roles in actin cytoskeleton rearrangement and shed light to the complex intertwining roles WASP and N-WASP play in macrophages.
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Affiliation(s)
- Beth M Isaac
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Shcherbina A, Cooley J, Lutskiy MI, Benarafa C, Gilbert GE, Remold-O'Donnell E. WASP plays a novel role in regulating platelet responses dependent on alphaIIbbeta3 integrin outside-in signalling. Br J Haematol 2009; 148:416-27. [PMID: 19863535 DOI: 10.1111/j.1365-2141.2009.07959.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The most consistent feature of Wiskott Aldrich syndrome (WAS) is profound thrombocytopenia with small platelets. The responsible gene encodes WAS protein (WASP), which functions in leucocytes as an actin filament nucleating agent -yet- actin filament nucleation proceeds normally in patient platelets regarding shape change, filopodia and lamellipodia generation. Because WASP localizes in the platelet membrane skeleton and is mobilized by alphaIIbbeta3 integrin outside-in signalling, we questioned whether its function might be linked to integrin. Agonist-induced alphaIIbbeta3 activation (PAC-1 binding) was normal for patient platelets, indicating normal integrin inside-out signalling. Inside-out signalling (fibrinogen, JON/A binding) was also normal for wasp-deficient murine platelets. However, adherence/spreading on immobilized fibrinogen was decreased for patient platelets and wasp-deficient murine platelets, indicating decreased integrin outside-in responses. Another integrin outside-in dependent response, fibrin clot retraction, involving contraction of the post-aggregation actin cytoskeleton, was also decreased for patient platelets and wasp-deficient murine platelets. Rebleeding from tail cuts was more frequent for wasp-deficient mice, suggesting decreased stabilisation of the primary platelet plug. In contrast, phosphatidylserine exposure, a pro-coagulant response, was enhanced for WASP-deficient patient and murine platelets. The collective results reveal a novel function for WASP in regulating pro-aggregatory and pro-coagulant responses downstream of integrin outside-in signalling.
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Affiliation(s)
- Anna Shcherbina
- Immune Disease Institute, Harvard Medical School, Boston, MA, USA
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23
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Abstract
In the first report of the concurrent immunodeficiency, thrombocytopenia, and eczema that we now call the Wiskott-Aldrich Syndrome (WAS), Alfred Wiskott asked whether it could be a familial form of Werlhof's disease (now called ITP). This review summarizes what is known about platelet production, consumption, and function in clinical and murine WAS. Both platelet production and consumption are affected by WASP deficiency. Likely molecular mechanisms have been identified for the former process, but remain problematic for the latter. Recent data in a murine model suggest that WASP deficiency could increase both the incidence of antiplatelet antibodies and susceptibility to their enhancement of platelet consumption. Wiskott's original speculation about the relationship between WAS and ITP may need to be reconsidered.
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Marathe BM, Prislovsky A, Astrakhan A, Rawlings DJ, Wan JY, Strom TS. Antiplatelet antibodies in WASP(-) mice correlate with evidence of increased in vivo platelet consumption. Exp Hematol 2009; 37:1353-63. [PMID: 19733207 DOI: 10.1016/j.exphem.2009.08.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 08/10/2009] [Accepted: 08/27/2009] [Indexed: 10/20/2022]
Abstract
OBJECTIVE To study the role of antiplatelet antibodies in the thrombocytopenia of murine Wiskott-Aldrich syndrome (WAS). MATERIALS AND METHODS A flow cytometric method was developed for detection of serum antiplatelet antibodies via their binding to intact target platelets lacking surface antibodies. Platelets were labeled with 5-chloromethylfluorescein diacetate (CMFDA) in order to track their clearance from the circulation. WASP(-)muMT(-/-) mice were generated by standard breeding methods. RESULTS Serum antiplatelet antibodies were detected in approximately 40% of WASP(-) males. The mean level of reticulated platelets is significantly increased in these antibody(+) males. While WASP(-) males show an approximately 50% reduction in platelet counts, 5% to 10% show a more severe thrombocytopenia associated with increased reticulated platelets, suggesting the presence of clearance-inducing antiplatelet antibodies. In support of that inference, 90% of the latter mice show detectable serum antiplatelet antibodies. The antibodies are primarily immunoglobulin G, and are also detected in >30% of CD47(-/-) males. WASP(-)muMT(-/-) males, which demonstrate no serum- or platelet-associated antibodies, show a degree of thrombocytopenia similar to that of WASP(-) males. Their platelet clearance rates remain accelerated--more so in WASP(-)muMT(-/-) than WASP(+)muMT(-/-) recipients. CONCLUSIONS These findings suggest that platelet WASP deficiency results in an increase in platelet clearance rates by two mechanisms: an antibody-independent mechanism that largely requires WASP deficiency in trans, and an antibody-dependent mechanism that does not. Both an increased incidence of antiplatelet antibodies and an increased susceptibility to their effects contribute to antibody-dependent clearance of WASP(-) platelets.
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Affiliation(s)
- Bindumadhav M Marathe
- Department of Pathology and Laboratory Medicine, University of Tennessee Health Sciences Center, Memphis, Tenn., USA
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Calaminus SDJ, Thomas S, McCarty OJT, Machesky LM, Watson SP. Identification of a novel, actin-rich structure, the actin nodule, in the early stages of platelet spreading. J Thromb Haemost 2008; 6:1944-52. [PMID: 18761725 DOI: 10.1111/j.1538-7836.2008.03141.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND During platelet spreading, the actin cytoskeleton undergoes marked changes, forming filopodia, lamellipodia and stress fibres. In the present study, we report the identification of a novel actin-rich structure, termed an actin nodule, which appears prior to lamellipodia and stress fibre formation. METHODS Platelet spreading was monitored using human platelets and mouse GFP-actin platelets using real-time and end-point DIC, and fluorescent and electron microscopy (EM). RESULTS We identified a small, novel actin structure, the actin nodule, in the early stages of adhesion and spreading, which we hypothesize to be a precursor of lamellipodia and stress fibres. Nodule formation shows an inverse correlation to Rho kinase and myosin-II activity, is independent of PI3-kinase, but dependent on Src kinase activity. Actin nodules contain multiple proteins, including Arp2/3, Fyn, Rac, and beta1- and beta3- integrins, but not Src. EM analysis revealed that actin filaments extend in all directions from the nodules. Actin nodules are present on multiple matrices, including fibrinogen, laminin and VWF + botrocetin. CONCLUSION This work identifies a novel platelet actin structure, which we propose is a precursor to both lamellipodia and stress fibres and acts to drive platelet spreading.
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Affiliation(s)
- S D J Calaminus
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham, UK.
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Cvejic A, Hall C, Bak-Maier M, Flores MV, Crosier P, Redd MJ, Martin P. Analysis of WASp function during the wound inflammatory response--live-imaging studies in zebrafish larvae. J Cell Sci 2008; 121:3196-206. [PMID: 18782862 DOI: 10.1242/jcs.032235] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Wiskott-Aldrich syndrome protein (WASp) is haematopoietically restricted, and is the causative protein underlying a severe human disorder that can lead to death due to immunodeficiency and haemorrhaging. Much is known about the biochemistry of WASp and the migratory capacity of WASp-defective cells in vitro, but in vivo studies of immune-cell behaviour are more challenging. Using the translucency of zebrafish larvae, we live-imaged the effects of morpholino knockdown of WASp1 (also known as Was) on leukocyte migration in response to a wound. In embryos at 22 hours post-fertilisation, primitive macrophages were impaired in their migration towards laser wounds. Once a circulatory system had developed, at 3 days post-fertilisation, we observed significantly reduced recruitment of neutrophils and macrophages to ventral fin wounds. Cell-tracking studies indicated that fewer leukocytes leave the vessels adjacent to a wound and those that do exhibit impaired navigational capacity. Their cell morphology appears unaltered but their choice of leading-edge pseudopodia is more frequently incorrect, leading to impaired chemotaxis. We also identified two zebrafish mutants in WASp1 by TILLING, one of which was in the WIP-binding domain that is the hotspot for human lesions, and mutants exhibited the same deficiencies in wound inflammation and thrombus formation as WASp1 morphants.
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Affiliation(s)
- Ana Cvejic
- Departments of Biochemistry and Physiology, School of Medical Sciences, University of Bristol, Bristol, UK
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Prislovsky A, Marathe B, Hosni A, Bolen AL, Nimmerjahn F, Jackson CW, Weiman D, Strom TS. Rapid platelet turnover in WASP(-) mice correlates with increased ex vivo phagocytosis of opsonized WASP(-) platelets. Exp Hematol 2008; 36:609-23. [PMID: 18346836 DOI: 10.1016/j.exphem.2007.12.019] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Revised: 12/04/2007] [Accepted: 12/31/2007] [Indexed: 12/01/2022]
Abstract
OBJECTIVE Our objective was to determine a mechanism for the thrombocytopenia of murine Wiskott-Aldrich syndrome (WAS). MATERIALS AND METHODS Consumption rates of WAS protein (WASP)(-) and wild-type (WT) platelets were measured by injection of 5-chloromethylfluorescein diacetate (CMFDA)-labeled platelets into WT or WASP(-) recipients, and by in vivo biotinylation. Platelet and reticulated platelet counts were performed using quantitative flow cytometry. Bone marrow megakaryocyte number and ploidy was assessed by flow cytometry. Phagocytosis of CMFDA-labeled, opsonized platelets was assessed using bone marrow-derived macrophages. Serum antiplatelet antibodies were assayed via their binding to WT platelets. RESULTS CMFDA-labeled WASP(-) platelets are consumed more rapidly than WT platelets in either WT or WASP(-) recipients. In vivo biotinylation studies corroborate these findings and show a normal consumption rate for WASP(-) reticulated platelets. The number of reticulated platelets is reduced in WASP(-) mice, but a significant number of the mice show an increased proportion of reticulated platelets and more severe thrombocytopenia. Sera from some of the latter group contain antiplatelet antibodies. Compared to WT platelets, WASP(-) platelets opsonized with anti-CD61 or 6A6 antibody are taken up more rapidly by bone marrow-derived macrophages. In vivo consumption rates of WASP(-) platelets are more accelerated by opsonization than are those of WT platelets. CONCLUSION Both rapid clearance and impaired production contribute to the thrombocytopenia of murine WAS. Increased susceptibility of opsonized WASP(-) platelets to phagocytosis leads to increased in vivo clearance. This correlates with a higher incidence of individuals with an elevated fraction of reticulated platelets, a more severe thrombocytopenia, and antiplatelet antibodies.
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Affiliation(s)
- Amanda Prislovsky
- Department of Pathology and Laboratory Medicine, Memphis Veterans Administration Medical Center, Memphis, TN 38104, USA
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Lutskiy MI, Shcherbina A, Bachli ET, Cooley J, Remold-O'Donnell E. WASP localizes to the membrane skeleton of platelets. Br J Haematol 2007; 139:98-105. [PMID: 17854313 DOI: 10.1111/j.1365-2141.2007.06745.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Patients with Wiskott-Aldrich syndrome (WAS), an X-linked blood cell disease, suffer from severe thrombocytopenia due to accelerated loss of defective platelets. The affected gene encodes WASP, an actin regulatory protein thought to reside in the cytoplasm of resting leucocytes. In contrast, this study showed that, for platelets, one-quarter of WASP molecules fractionate in the detergent-insoluble high speed pellet characterized as the membrane skeleton, the scaffold structure that underlies the lipid bilayer and stabilizes the surface membrane. Following treatment of platelets with thrombin and stirring, which induces cytoarchitectural remodelling, WASP and other membrane skeletal components sedimented at lower g force and partitioned in the low-speed pellet. Thrombin and stirring also induced WASP tyrosine phosphorylation, a rapid activating reaction, and proteolytic inactivation by cysteine protease calpain. Both the alteration of the sedimentation profile and the proteolytic inactivation were specific for the membrane skeletal pool of WASP and were abrogated in alphaIIb beta3 integrin-deficient platelets and in normal platelets treated with an integrin antagonist. The findings demonstrate that WASP is a component of the resting platelet membrane skeleton and participates in membrane skeletal rearrangements downstream of integrin outside-in signalling. The possible implications for the platelet defect in WAS are discussed.
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Affiliation(s)
- Maxim I Lutskiy
- The CBR Institute for Biomedical Research and the Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
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Calaminus SD, McCarty OJ, Auger JM, Pearce AC, Insall RH, Watson SP, Machesky LM. A major role for Scar/WAVE-1 downstream of GPVI in platelets. J Thromb Haemost 2007; 5:535-41. [PMID: 17319906 PMCID: PMC1880834 DOI: 10.1111/j.1538-7836.2007.02377.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND The small GTPase Rac1 plays a critical role in lamellipodia assembly in platelets on matrix proteins in the absence or presence of G protein-coupled receptor (GPCR) agonists. Rac mediates actin assembly via Scar/WAVE, a family of scaffolding proteins that direct actin reorganization by relaying signals from Rac to the Arp2/3 complex. OBJECTIVE To evaluate the role of Scar/WAVE-1 in mediating platelet activation and cytoskeletal reorganization. METHODS AND RESULTS Using specific antibodies, we demonstrate that murine platelets, like human platelets, express Scar/WAVE-1 and Scar/WAVE-2. Lamellipodia formation in Scar/WAVE-1(-/-) platelets is markedly inhibited on immobilized collagen-related peptide (CRP) and on laminin, both of which signal through the collagen receptor GPVI. In contrast, lamellipodia formation on collagen, which requires release of the GPCR agonists ADP and thromboxane A(2), is not altered. Immobilized fibrinogen supports limited formation of lamellipodia in murine platelets, which is not altered in Scar/WAVE-1(-/-) platelets. As with Rac1(-/-) platelets, Scar/WAVE-1(-/-) platelets exhibit a marked inhibition of aggregation in response to CRP, whereas the response to the GPCR agonist thrombin is not altered. Platelet aggregation on immobilized collagen under shear, which is dependent on signaling by matrix and GPCR agonists, was unaltered in the absence of Scar/WAVE-1. CONCLUSION This study demonstrates a major role for Scar/WAVE-1 in mediating platelet cytoskeletal reorganization and aggregate formation downstream of activation by GPVI but not by GPCR agonists.
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Affiliation(s)
- Simon D.J. Calaminus
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
| | - Owen J.T. McCarty
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR 97239, USA
| | - Jocelyn M. Auger
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
| | - Andrew C. Pearce
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
| | - Robert H. Insall
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Steve P. Watson
- Centre for Cardiovascular Sciences, Institute of Biomedical Research, The Medical School, University of Birmingham, Birmingham B15 2TT, UK
| | - Laura M. Machesky
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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Thornber K, McCarty OJT, Watson SP, Pears CJ. Distinct but critical roles for integrin ?IIb?3in platelet lamellipodia formation on fibrinogen, collagen-related peptide and thrombin. FEBS J 2006; 273:5032-43. [PMID: 17032352 DOI: 10.1111/j.1742-4658.2006.05500.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Integrins are the major receptor type known to facilitate cell adhesion and lamellipodia formation on extracellular matrix proteins. However, collagen-related peptide and thrombin have recently been shown to mediate platelet lamellipodia formation when presented as immobilized surfaces. The aims of this study were to establish if there exists a role for the platelet integrin alpha(IIb)beta(3) in this response; and if so, whether signalling from the integrin is required for lamellipodia formation on these surfaces. Real-time analysis was used to compare platelet morphological changes on surfaces of fibrinogen, collagen-related peptide or thrombin in the presence of various pharmacological inhibitors and platelets from 'knockout' mice. We demonstrate that collagen-related peptide and thrombin stimulate distinct patterns of platelet lamellipodia formation and elevation of intracellular Ca(2+) to that induced by the integrin alpha(IIb)beta(3) ligand, fibrinogen. Nevertheless, lamellipodia formation on collagen-related peptide and thrombin is dependent upon engagement of alpha(IIb)beta(3), consistent with release of alpha(IIb)beta(3) ligand(s) from platelet granules. However, the requirement for signalling by the integrin on fibrinogen can be bypassed by the addition of thrombin to the solution. These observations reveal a critical role for alpha(IIb)beta(3) in forming lamellipodia on collagen-related peptide and thrombin which is dependent on its ability to function as an adhesive receptor but not necessarily on its ability to signal. These results suggest that integrins may play an important role in lamellipodia formation triggered by nonintegrin ligands in platelets and possibly in other cell types.
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Krzewski K, Chen X, Orange JS, Strominger JL. Formation of a WIP-, WASp-, actin-, and myosin IIA-containing multiprotein complex in activated NK cells and its alteration by KIR inhibitory signaling. ACTA ACUST UNITED AC 2006; 173:121-32. [PMID: 16606694 PMCID: PMC2063796 DOI: 10.1083/jcb.200509076] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The tumor natural killer (NK) cell line YTS was used to examine the cytoskeletal rearrangements required for cytolysis. A multiprotein complex weighing approximately 1.3 mD and consisting of WASp-interacting protein (WIP), Wiskott-Aldrich syndrome protein (WASp), actin, and myosin IIA that formed during NK cell activation was identified. After induction of an inhibitory signal, the recruitment of actin and myosin IIA to a constitutive WIP-WASp complex was greatly decreased. Both actin and myosin IIA were recruited to WIP in the absence of WASp. This recruitment correlated with increased WIP phosphorylation, which was mediated by PKCtheta. Furthermore, the disruption of WIP expression by WIP RNA interference prevented the formation of this protein complex and led to almost complete inhibition of cytotoxic activity. Thus, the multiprotein complex is important for NK cell function, killer cell immunoglobulin-like receptor inhibitory signaling affects proteins involved in cytoskeletal rearrangements, and WIP plays a central role in the formation of the complex and in the regulation of NK cell activity.
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Affiliation(s)
- Konrad Krzewski
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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33
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McCarty OJT, Calaminus SDJ, Berndt MC, Machesky LM, Watson SP. von Willebrand factor mediates platelet spreading through glycoprotein Ib and alpha(IIb)beta3 in the presence of botrocetin and ristocetin, respectively. J Thromb Haemost 2006; 4:1367-78. [PMID: 16706984 DOI: 10.1111/j.1538-7836.2006.01966.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND von Willebrand factor (VWF) plays a critical role in the process of hemostasis by mediating flow-dependent adhesion and spreading of platelets on exposed extracellular matrix proteins following vascular injury. To accomplish this, VWF binds to two distinct platelet receptors: glycoprotein (GP)Ib-IX-V and integrin alpha(IIb)beta3. OBJECTIVE To evaluate the ability of GPIb and alpha(IIb)beta3 to mediate platelet adhesion and lamellipodia formation on immobilized VWF in the presence of the biochemical modulators, ristocetin and botrocetin. RESULTS In the presence of botrocetin and inhibitors of adenosine diphosphate (ADP) and thromboxane A2 (TxA2), VWF is able to support formation of lamellipodia through a GPIb-dependent mechanism that is independent of alpha(IIb)beta3 and PI3-kinase. Lamellipodia formation under these conditions is incomplete. In marked contrast, in the presence of ristocetin, VWF stimulates formation of fully spread lamellipodia through a pathway that is dependent upon alpha(IIb)beta3 and PI3-kinase. Furthermore, alpha(IIb)beta3 also supports platelet spreading on VWF alone, but only in the absence of inhibitors of ADP and TxA2. The localization of filamentous actin and the Arp2/3 complex in platelets on VWF in the presence of botrocetin and ristocetin are distinct, yielding disparate lamellipodium kinetic signatures. Interestingly, botrocetin significantly enhances platelet adhesion to VWF under flow in whole blood in an alpha(IIb)beta3-independent manner, while ristocetin augments washed platelet adhesion and spreading to VWF under flow in an alpha(IIb)beta3-dependent manner. CONCLUSIONS These observations demonstrate that VWF is able to induce lamellipodia formation through distinct receptors, and has important consequences for investigation of the role of VWF-GPIb interactions in the context of platelet regulation.
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Affiliation(s)
- O J T McCarty
- Centre for Cardiovascular Sciences, University of Birmingham, Birmingham, UK.
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34
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Abstract
Platelets are small subcellular fragments that are released from megakaryocytes. They are composed of a concentrate of megakaryocyte membrane, cytoplasm, granules, and organelles, and circulate throughout blood vessels and survey the integrity of the vascular system. They circulate as discs, a form specified by their internal microtubule and actin cytoskeleton. When encountering vascular damage, platelets rapidly convert into their active forms, which function to seal off the injury and prevent fluid loss. To assume the active shape, the internal cytoskeleton of each platelet is rapidly disassembled and replaced. New actin filament assembly provides the force that spreads platelets across damaged surfaces and allows the formation of filopodia, which are used to interconnect platelets in solution. In this review, we discuss the role of the cytoskeleton in defining the resting and active forms of the platelet.
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Affiliation(s)
- John H Hartwig
- Division of Hematology, Karp Family Research Laboratories, Brigham and Women's Hospital, Boston, MA 02115, USA.
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35
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van Rossum AGSH, Moolenaar WH, Schuuring E. Cortactin affects cell migration by regulating intercellular adhesion and cell spreading. Exp Cell Res 2006; 312:1658-70. [PMID: 16527272 DOI: 10.1016/j.yexcr.2006.01.033] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 01/15/2006] [Accepted: 01/30/2006] [Indexed: 12/18/2022]
Abstract
Cortactin is an F-actin binding protein that stabilizes F-actin networks and promotes actin polymerization by activating the Arp2/3 complex. Overexpression of cortactin, as observed in several human cancers, stimulates cell migration, invasion, and experimental metastasis; however, the underlying mechanism is not understood. To investigate the importance of cortactin in cell migration, we downregulated its expression using RNA interference (RNAi). Stable downregulation of cortactin in HBL100 breast epithelial cells resulted in (i) decreased cell migration and invasion, (ii) enhanced cell-cell adhesion, and (iii) accelerated cell spreading. These phenotypic changes were reversed by expression of RNAi-resistant mouse cortactin. Cortactin colocalized with cadherin and beta-catenin in adherens junctions, consistent with its role in intercellular adhesion. Remarkably, cortactin deficiency did not affect lamellipodia formation. Instead, downregulation of cortactin in human squamous carcinoma cells that overexpress cortactin changed the cytoskeletal organization. We conclude that increased levels of cortactin, as found in human carcinomas, promote cell migration and invasion by reducing cell spreading and intercellular adhesive strength.
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Affiliation(s)
- Agnes G S H van Rossum
- Department of Pathology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden, The Netherlands
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Soriani A, Moran B, de Virgilio M, Kawakami T, Altman A, Lowell C, Eto K, Shattil SJ. A role for PKCtheta in outside-in alpha(IIb)beta3 signaling. J Thromb Haemost 2006; 4:648-55. [PMID: 16460447 DOI: 10.1111/j.1538-7836.2006.01806.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Fibrinogen binding to platelets triggers alpha(IIb)beta3-dependent outside-in signals that promote actin rearrangements and cell spreading. Studies with chemical inhibitors or activators have implicated protein kinase C (PKC) in alpha(IIb)beta3 function. However, the role of individual PKC isoforms is poorly understood. Biochemical and genetic approaches were used to determine whether PKCtheta is involved in alpha(IIb)beta3 signaling. PKCtheta was constitutively associated with alpha(IIb)beta3 in human and murine platelets. Fibrinogen binding to alpha(IIb)beta3 stimulated the association of PKCtheta with tyrosine kinases Btk and Syk, and tyrosine phosphorylation of PKCtheta, Btk and the actin regulator, Wiskott-Aldrich syndrome protein (WASP). Mouse platelets deficient in PKCtheta or Btk failed to spread on fibrinogen. Furthermore, PKCtheta was required for phosphorylation of WASP-interacting protein on Ser-488, an event that has been linked to WASP activation of the Arp2/3 complex and actin polymerization in lymphocytes. Neither PKCtheta nor Btk were required for agonist-induced inside-out signaling and fibrinogen binding to alpha(IIb)beta3. Thus, PKCtheta is a newly identified, essential member of a dynamic outside-in signaling complex that includes Btk and that couples alpha(IIb)beta3 to the actin cytoskeleton.
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Affiliation(s)
- A Soriani
- Division of Hematology-Oncology, Department of Medicine, University of California San Diego, La Jolla, CA, USA.
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Hardy AR, Hill DJ, Poole AW. Evidence that the purinergic receptor P2Y12 potentiates platelet shape change by a Rho kinase-dependent mechanism. Platelets 2005; 16:415-29. [PMID: 16236603 DOI: 10.1080/09537100500163424] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
ADP activates human platelets through two G-protein coupled receptors, P2Y1 and P2Y12, to induce a range of functional responses. Here we have addressed the role and mechanism of P2Y12 in modulating ADP-induced platelet shape change. Although the response depended upon activation of P2Y1, it was potentiated by P2Y12 as the P2Y12-selective antagonists AR-C69931MX and 2MeSAMP partially inhibited shape change in the later phase of the response. This was paralleled by inhibition of pseudopod formation, platelet spheration, actin polymerisation and myosin light chain phosphorylation. P2Y12 is known to couple to activation of PI3 kinase and inhibition of adenylate cyclase, but we showed that neither of these signalling events couples to regulation of shape change by this receptor. However, by assessment of phosphorylation of its major substrate myosin light chain phosphatase, we provide direct evidence for activation of Rho kinase by ADP, and that although P2Y1 is required for activation of Rho kinase, P2Y12 is able to potentiate its activity. We conclude that P2Y12 plays a potentiatory role in ADP-induced shape change through regulation of the Rho kinase pathway, potentiating both myosin phosphorylation and actin polymerisation, and this forms part of an important signalling pathway additional to its well-established Gi-coupled pathways.
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Affiliation(s)
- Adam R Hardy
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK
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McCarty OJT, Larson MK, Auger JM, Kalia N, Atkinson BT, Pearce AC, Ruf S, Henderson RB, Tybulewicz VLJ, Machesky LM, Watson SP. Rac1 is essential for platelet lamellipodia formation and aggregate stability under flow. J Biol Chem 2005; 280:39474-84. [PMID: 16195235 PMCID: PMC1395485 DOI: 10.1074/jbc.m504672200] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The role of Rac family proteins in platelet spreading on matrix proteins under static and flow conditions has been investigated by using Rac-deficient platelets. Murine platelets form filopodia and undergo limited spreading on fibrinogen independent of Rac1 and Rac2. In the presence of thrombin, marked lamellipodia formation is observed on fibrinogen, which is abrogated in the absence of Rac1. However, Rac1 is not required for thrombin-induced aggregation or elevation of F-actin levels. Formation of lamellipodia on collagen and laminin is also Rac1-dependent. Analysis of platelet adhesion dynamics on collagen under flow conditions in vitro revealed that Rac1 is required for platelet aggregate stability at arterial rates of shear, as evidenced by a dramatic increase in platelet embolization. Furthermore, studies employing intravital microscopy demonstrated that Rac1 plays a critical role in the development of stable thrombi at sites of vascular injury in vivo. Thus, our data demonstrated that Rac1 is essential for lamellipodia formation in platelets and indicated that Rac1 is required for aggregate integrity leading to thrombus formation under physiologically relevant levels of shear both in vitro and in vivo.
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Affiliation(s)
- Owen J T McCarty
- Centre for Cardiovascular Sciences, the Institute of Biomedical Research, School of Biosciences, University of Birmingham, United Kingdom.
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Kashiwagi H, Shiraga M, Kato H, Honda S, Sako M, Kurata Y, Kanakura Y, Tomiyama Y. Expression and subcellular localization of WAVE isoforms in the megakaryocyte/platelet lineage. J Thromb Haemost 2005; 3:361-8. [PMID: 15670045 DOI: 10.1111/j.1538-7836.2004.01082.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
WAVE isoforms, which consist of WAVE-1, WAVE-2 and WAVE-3, are members of the Wiskott-Aldrich syndrome protein (WASP) family. They are implicated in the regulation of actin-cytoskeletal reorganization downsteam of the small GTPase, Rac. Since platelet attachment to extracellular matrices leads to filopodial and lamellipodial extension, we examined the expression and subcellular localization of WAVEs in platelets. Employing primary megakaryocytic cells derived from cord blood as well as megakaryocytic cell lines, we also examined their expression during megakaryocytic differentiation. Immunoblotting and immunohistochemical analysis revealed that platelets expressed WAVE-1 and WAVE-2, whereas WAVE-3 expression was hardly to be detected. WAVE-1 expression was associated with megakaryocytic differentiation, whereas WAVE-2 and WAVE-3 expression was not changed by the differentiation. In adhered platelets both WAVE-1 and WAVE-2 were localized at the edge of the lamellipodia and at the tips of filopodia. In WASP-deficient platelets we found normal lamellipodial formation and localization of WAVE-1 and WAVE-2 at the edges of lamellipodia. Furthermore, we demonstrated that WAVE-1 and WAVE-2 moved from a detergent-soluble cytosolic fraction to insoluble cytoskeleton fraction after platelet aggregation. These results suggest that WAVE-1 and WAVE-2 regulate actin reorganization during platelet spreading and aggregate formation.
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Affiliation(s)
- H Kashiwagi
- Department of Hematology, Osaka University Graduate School of Medicine, 2-2, Yamada-oka, Suita, Osaka 565-0871, Japan.
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Burns S, Cory GO, Vainchenker W, Thrasher AJ. Mechanisms of WASp-mediated hematologic and immunologic disease. Blood 2004; 104:3454-62. [PMID: 15308573 DOI: 10.1182/blood-2004-04-1678] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Wiskott-Aldrich syndrome protein (WASp) is a key regulator of actin polymerization in hematopoietic cells. The dynamic nature of cytoskeletal changes during a variety of cellular processes demands complex mechanisms for coordinated integration of input signals, precise localization within the cell, and regulated activation of the Arp2/3 complex. Mutations in the Wiskott-Aldrich syndrome gene either inhibit or dysregulate normal WASp function, resulting in clinical diseases with complex and disparate phenotypes. This review highlights recent advances that have enhanced our understanding of the mechanisms by which these molecular defects cause hematologic and immunologic disease.
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Affiliation(s)
- Siobhan Burns
- Molecular Immunology Unit, Institute of Child Health, University College London, 30 Guilford St, London, WC1N 1EH, United Kingdom.
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41
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Abstract
Arp2/3 complex nucleates the formation of dendritic actin filament arrays, which are especially prominent at the leading edges of motile cells. Recent genetic and other loss-of-function studies have highlighted the importance of the Arp2/3 complex for normal cell functions, and especially for cell motility. WASP/Scar family proteins regulate the activity of the Arp2/3 complex, and also link it to several signaling pathways. Recent studies suggest that Scar is a more important regulator of Arp2/3 activity in actin-dependent morphological processes than WASP, which may have a more restricted role in specialized cellular events. It has also become clear that precise regulation of both Scar and WASP activity is of the utmost importance for their physiological functions.
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Affiliation(s)
- Maria K Vartiainen
- Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, Transcription Laboratory, London, WC2A 3PX, UK
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Biyasheva A, Svitkina T, Kunda P, Baum B, Borisy G. Cascade pathway of filopodia formation downstream of SCAR. J Cell Sci 2004; 117:837-48. [PMID: 14762109 DOI: 10.1242/jcs.00921] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The protrusion of two distinct actin-containing organelles, lamellipodia and filopodia, is thought to be regulated by two parallel pathways: from Rac1 through Scar/WAVEs to lamellipodia, and from Cdc42 through N-WASP to filopodia. We tested this hypothesis in Drosophila, which contains a single gene for each WASP subfamilies, SCAR and WASp. We performed targeted depletion of SCAR or WASp by dsRNA-mediated interference in two Drosophila cultured cell lines expressing lamellipodial and filopodial protrusion. Knockdown was verified by laser capture microdissection and RT-PCR, as well as western blotting. Morphometrical, kinetic and electron microscopy analyses of the SCAR-depleted phenotype in both cell types revealed strong inhibition of lamellipodial formation and cell spreading, as expected. More importantly, filopodia formation was also strongly inhibited, which is not consistent with the parallel pathway hypothesis. By contrast, depletion of WASp did not produce any significant phenotype, except for a slight inhibition of spreading, showing that both lamellipodia and filopodia in Drosophila cells are regulated predominantly by SCAR. We propose a new, cascade pathway model of filopodia regulation in which SCAR signals to lamellipodia and then filopodia arise from lamellipodia in response to additional signal(s).
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Affiliation(s)
- Assel Biyasheva
- Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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Geddis AE, Kaushansky K. Inherited thrombocytopenias: toward a molecular understanding of disorders of platelet production. Curr Opin Pediatr 2004; 16:15-22. [PMID: 14758109 DOI: 10.1097/00008480-200402000-00005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW To review the defined syndromes of inherited thrombocytopenia and discuss new genetic data for several disorders that shed light on the process of megakaryopoiesis. RECENT FINDINGS The genes responsible for several inherited thrombocytopenias have been recently discovered, including congenital amegakaryocytic leukemia, amegakaryocytic thrombocytopenia with radio-ulnar synostosis, familial platelet syndrome with predisposition to acute myelogenous leukemia, Paris-Trousseau, Wiskott-Aldrich syndrome, and the May-Hegglin, Sebastian, Epstein, and Fechner syndromes. These clinical syndromes, combined with studies in mouse and in vitro models, reveal the importance of these genes for normal hematopoiesis. SUMMARY Although inherited syndromes of thrombocytopenia are rare, characterization of mutations in these disorders has contributed greatly to our understanding of megakaryocyte and platelet development. A systematic registry of congenitally thrombocytopenic individuals would almost certainly lead to new genetic discoveries.
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Affiliation(s)
- Amy E Geddis
- Department of Pediatrics, University of California, San Diego, USA.
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Notarangelo LD, Ochs HD. Wiskott—Aldrich Syndrome: a model for defective actin reorganization, cell trafficking and synapse formation. Curr Opin Immunol 2003; 15:585-91. [PMID: 14499269 DOI: 10.1016/s0952-7915(03)00112-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Wiskott-Aldrich Syndrome (WAS) is an X-linked immunodeficiency characterized by thrombocytopenia with small platelets, eczema, recurrent infections, autoimmune disorders and increased incidence of malignancies. Classic WAS, and a milder form, X-linked thrombocytopenia, are caused by mutations of the WAS protein (WASP) gene. Recent investigations have provided evidence that WASP and several related proteins are involved in the reorganization of the actin cytoskeleton by activating Arp2/3-mediated actin polymerization. This function is controlled by the small GTPase Cdc42, which regulates the autoinhibitory loop formation of WASP. In addition, WASP is involved in cytoplasmic signaling via its interaction with a variety of adaptor molecules. Mutation analysis of large cohorts of WAS/X-linked thrombocytopenia patients has provided evidence for a strong correlation between phenotype and genotype.
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Affiliation(s)
- Luigi D Notarangelo
- Department of Pediatrics, University of Brescia, Spedali Civili, 25123 Brescia,
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Hoffmeister KM, Felbinger TW, Falet H, Denis CV, Bergmeier W, Mayadas TN, von Andrian UH, Wagner DD, Stossel TP, Hartwig JH. The clearance mechanism of chilled blood platelets. Cell 2003; 112:87-97. [PMID: 12526796 DOI: 10.1016/s0092-8674(02)01253-9] [Citation(s) in RCA: 308] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Platelet transfusion is a very common lifesaving medical procedure. Not widely known is the fact that platelets, unlike other blood cells, rapidly leave the circulation if refrigerated prior to transfusion. This peculiarity requires blood services to store platelets at room temperature, limiting platelet supplies for clinical needs. Here, we describe the mechanism of this clearance system, a longstanding mystery. Chilling platelets clusters their von Willebrand (vWf) receptors, eliciting recognition of mouse and human platelets by hepatic macrophage complement type 3 (CR3) receptors. CR3-expressing but not CR3-deficient mice exposed to cold rapidly decrease platelet counts. Cooling primes platelets for activation. We propose that platelets are thermosensors, primed at peripheral sites where most injuries occurred throughout evolution. Clearance prevents pathologic thrombosis by primed platelets. Chilled platelets bind vWf and function normally in vitro and ex vivo after transfusion into CR3-deficient mice. Therefore, GPIb modification might permit cold platelet storage.
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Affiliation(s)
- Karin M Hoffmeister
- Division of Hematology, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
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