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Reversible Platelet Integrin αIIbβ3 Activation and Thrombus Instability. Int J Mol Sci 2022; 23:ijms232012512. [PMID: 36293367 PMCID: PMC9604507 DOI: 10.3390/ijms232012512] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 11/28/2022] Open
Abstract
Integrin αIIbβ3 activation is essential for platelet aggregation and, accordingly, for hemostasis and arterial thrombosis. The αIIbβ3 integrin is highly expressed on platelets and requires an activation step for binding to fibrinogen, fibrin or von Willebrand factor (VWF). A current model assumes that the process of integrin activation relies on actomyosin force-dependent molecular changes from a bent-closed and extended-closed to an extended-open conformation. In this paper we review the pathways that point to a functional reversibility of platelet αIIbβ3 activation and transient aggregation. Furthermore, we refer to mouse models indicating that genetic defects that lead to reversible platelet aggregation can also cause instable thrombus formation. We discuss the platelet agonists and signaling pathways that lead to a transient binding of ligands to integrin αIIbβ3. Our analysis points to the (autocrine) ADP P2Y1 and P2Y12 receptor signaling via phosphoinositide 3-kinases and Akt as principal pathways linked to reversible integrin activation. Downstream signaling events by protein kinase C, CalDAG-GEFI and Rap1b have not been linked to transient integrin activation. Insight into the functional reversibility of integrin activation pathways will help to better understand the effects of antiplatelet agents.
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Jayakumar T, Hsu CY, Khamrang T, Hsia CH, Hsia CW, Manubolu M, Sheu JR. Possible Molecular Targets of Novel Ruthenium Complexes in Antiplatelet Therapy. Int J Mol Sci 2018; 19:ijms19061818. [PMID: 29925802 PMCID: PMC6032250 DOI: 10.3390/ijms19061818] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 06/13/2018] [Accepted: 06/15/2018] [Indexed: 12/19/2022] Open
Abstract
In oncotherapy, ruthenium (Ru) complexes are reflected as potential alternatives for platinum compounds and have been proved as encouraging anticancer drugs with high efficacy and low side effects. Cardiovascular diseases (CVDs) are mutually considered as the number one killer globally, and thrombosis is liable for the majority of CVD-related deaths. Platelets, an anuclear and small circulating blood cell, play key roles in hemostasis by inhibiting unnecessary blood loss of vascular damage by making blood clot. Platelet activation also plays a role in cancer metastasis and progression. Nevertheless, abnormal activation of platelets results in thrombosis under pathological settings such as the rupture of atherosclerotic plaques. Thrombosis diminishes the blood supply to the heart and brain resulting in heart attacks and strokes, respectively. While currently used anti-platelet drugs such as aspirin and clopidogrel demonstrate efficacy in many patients, they exert undesirable side effects. Therefore, the development of effective therapeutic strategies for the prevention and treatment of thrombotic diseases is a demanding priority. Recently, precious metal drugs have conquered the subject of metal-based drugs, and several investigators have motivated their attention on the synthesis of various ruthenium (Ru) complexes due to their prospective therapeutic values. Similarly, our recent studies established that novel ruthenium-based compounds suppressed platelet aggregation via inhibiting several signaling cascades. Our study also described the structure antiplatelet-activity relationship (SAR) of three newly synthesized ruthenium-based compounds. This review summarizes the antiplatelet activity of newly synthesized ruthenium-based compounds with their potential molecular mechanisms.
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Affiliation(s)
- Thanasekaran Jayakumar
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
| | - Chia-Yuan Hsu
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
- Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan.
| | - Themmila Khamrang
- Department of Chemistry, North Eastern Hill University, Shillong 793022, India.
| | - Chih-Hsuan Hsia
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
| | - Chih-Wei Hsia
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
| | - Manjunath Manubolu
- Department of Evolution, Ecology and Organismal Biology, Ohio State University, Columbus, OH 43212, USA.
| | - Joen-Rong Sheu
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
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Stefanini L, Bergmeier W. Negative regulators of platelet activation and adhesion. J Thromb Haemost 2018; 16:220-230. [PMID: 29193689 PMCID: PMC5809258 DOI: 10.1111/jth.13910] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Indexed: 12/29/2022]
Abstract
Platelets are small anucleated cells that constantly patrol the cardiovascular system to preserve its integrity and prevent excessive blood loss where the vessel lining is breached. Their key challenge is to form a hemostatic plug under conditions of high shear forces. To do so, platelets have evolved a molecular machinery that enables them to sense trace amounts of signals at the site of damage and to rapidly shift from a non-adhesive to a pro-adhesive state. However, this highly efficient molecular machinery can also lead to unintended platelet activation and cause clinical complications such as thrombocytopenia and thrombosis. Thus, several checkpoints are in place to tightly control platelet activation and adhesiveness in space and time. In this review, we will discuss select negative regulators of platelet activation, which are critical to maintain patrolling platelets in a quiescent, non-adhesive state and/or to limit platelet adhesion to sites of injury.
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Affiliation(s)
- L Stefanini
- Department of Internal Medicine and Medical Specialties, Sapienza University of Rome, Rome, Italy
| | - W Bergmeier
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Unsworth AJ, Bye AP, Gibbins JM. Platelet-Derived Inhibitors of Platelet Activation. PLATELETS IN THROMBOTIC AND NON-THROMBOTIC DISORDERS 2017. [PMCID: PMC7123044 DOI: 10.1007/978-3-319-47462-5_37] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Jayakumar T, Yang CH, Geraldine P, Yen TL, Sheu JR. The pharmacodynamics of antiplatelet compounds in thrombosis treatment. Expert Opin Drug Metab Toxicol 2016; 12:615-32. [DOI: 10.1080/17425255.2016.1176141] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Thanasekaran Jayakumar
- Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chih-Hao Yang
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Pitchairaj Geraldine
- Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, India
| | - Ting-Lin Yen
- Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan
| | - Joen-Rong Sheu
- Graduate Institute of Medical Sciences, Taipei Medical University, Taipei, Taiwan
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- College of Medicine, Taipei Medical University, Taipei, Taiwan
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Raslan Z, Aburima A, Naseem KM. The Spatiotemporal Regulation of cAMP Signaling in Blood Platelets-Old Friends and New Players. Front Pharmacol 2015; 6:266. [PMID: 26617518 PMCID: PMC4639615 DOI: 10.3389/fphar.2015.00266] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 10/26/2015] [Indexed: 11/22/2022] Open
Abstract
Atherothrombosis, the pathology underlying numerous cardiovascular diseases, is a major cause of death globally. Hyperactive blood platelets play a key role in the atherothrombotic process through the release of inflammatory mediators and formation of thrombi. In healthy blood vessels, excessive platelet activation is restricted by endothelial-derived prostacyclin (PGI2) through cyclic adenosine-5′-monophosphate (cAMP) and protein kinase A (PKA)-dependent mechanisms. Elevation in intracellular cAMP is associated with the control of a number of distinct platelet functions including actin polymerisation, granule secretion, calcium mobilization and integrin activation. Unfortunately, in atherosclerotic disease the protective effects of cAMP are compromised, which may contribute to pathological thrombosis. The cAMP signaling network in platelets is highly complex with the presence of multiple isoforms of adenylyl cyclase (AC), PKA, and phosphodiesterases (PDEs). However, a precise understanding of the relationship between specific AC, PKA, and PDE isoforms, and how individual signaling substrates are targeted to control distinct platelet functions is still lacking. In other cells types, compartmentalisation of cAMP signaling has emerged as a key mechanism to allow precise control of specific cell functions. A-kinase anchoring proteins (AKAPs) play an important role in this spatiotemporal regulation of cAMP signaling networks. Evidence of AKAP-mediated compartmentalisation of cAMP signaling in blood platelets has begun to emerge and is providing new insights into the regulation of platelet function. Dissecting the mechanisms that allow cAMP to control excessive platelet activity without preventing effective haemostasis may unleash the possibility of therapeutic targeting of the pathway to control unwanted platelet activity.
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Affiliation(s)
- Zaher Raslan
- Centre for Cardiovascular and Metabolic Research, Hull-York Medical School, University of Hull , Hull, UK
| | - Ahmed Aburima
- Centre for Cardiovascular and Metabolic Research, Hull-York Medical School, University of Hull , Hull, UK
| | - Khalid M Naseem
- Centre for Cardiovascular and Metabolic Research, Hull-York Medical School, University of Hull , Hull, UK
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Knebel SM, Sprague RS, Stephenson AH. Prostacyclin receptor expression on platelets of humans with type 2 diabetes is inversely correlated with hemoglobin A1c levels. Prostaglandins Other Lipid Mediat 2015; 116-117:131-5. [DOI: 10.1016/j.prostaglandins.2014.12.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 12/23/2014] [Accepted: 12/23/2014] [Indexed: 02/02/2023]
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Goubau C, Buyse GM, Van Geet C, Freson K. The contribution of platelet studies to the understanding of disease mechanisms in complex and monogenetic neurological disorders. Dev Med Child Neurol 2014; 56:724-31. [PMID: 24579816 DOI: 10.1111/dmcn.12421] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/05/2014] [Indexed: 01/03/2023]
Abstract
Platelets, known for their role in primary haemostasis, prevent excessive bleeding after injury. The study of platelets has, therefore, traditionally focused on bleeding disorders. It has recently become evident, however, that platelet research can contribute to unravelling the disease mechanisms that underlie neuropathological disorders that have a subtle subclinical platelet phenotype. Platelets and neurosecretory cells have common gene expression profiles and share several biological features. This review provides a literature update on the use of platelets as easily accessible cells to study neurological disorders. We provide examples of the use of different platelet-based tests to understand the underlying pathophysiological mechanisms for both complex and monogenetic neuropathological disorders. In addition to the well-studied regulated granule secretion and serotonin metabolism, more recent studies have shown that defects in transcription factors, membrane transporters, G-protein signal transduction, and cytoskeletal proteins can be investigated using platelets to gain information on their role in neuropathology.
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Affiliation(s)
- Christophe Goubau
- Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium; Department of Child Neurology, University Hospitals Leuven, Leuven, Belgium
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Time-resolved characterization of cAMP/PKA-dependent signaling reveals that platelet inhibition is a concerted process involving multiple signaling pathways. Blood 2013; 123:e1-e10. [PMID: 24324209 DOI: 10.1182/blood-2013-07-512384] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
One of the most important physiological platelet inhibitors is endothelium-derived prostacyclin which stimulates the platelet cyclic adenosine monophosphate/protein kinase A (cAMP/PKA)-signaling cascade and inhibits virtually all platelet-activating key mechanisms. Using quantitative mass spectrometry, we analyzed time-resolved phosphorylation patterns in human platelets after treatment with iloprost, a stable prostacyclin analog, for 0, 10, 30, and 60 seconds to characterize key mediators of platelet inhibition and activation in 3 independent biological replicates. We quantified over 2700 different phosphorylated peptides of which 360 were significantly regulated upon stimulation. This comprehensive and time-resolved analysis indicates that platelet inhibition is a multipronged process involving different kinases and phosphatases as well as many previously unanticipated proteins and pathways.
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Nurden AT, Nurden P. Congenital platelet disorders and understanding of platelet function. Br J Haematol 2013; 165:165-78. [DOI: 10.1111/bjh.12662] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Alan T. Nurden
- L'Institut de Rhythmologie et Modélisation Cardiaque (LIRYC); Plateforme Technologique et d'Innovation Biomédicale; Hôpital Xavier Arnozan; Pessac France
| | - Paquita Nurden
- L'Institut de Rhythmologie et Modélisation Cardiaque (LIRYC); Plateforme Technologique et d'Innovation Biomédicale; Hôpital Xavier Arnozan; Pessac France
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Louwette S, Van Geet C, Freson K. Regulators of G protein signaling: role in hematopoiesis, megakaryopoiesis and platelet function. J Thromb Haemost 2012; 10:2215-22. [PMID: 22908964 DOI: 10.1111/j.1538-7836.2012.04903.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Regulators of G protein signaling (RGS) are intracellular signaling regulators that bind activated G protein α subunits (Gα) and increase their intrinsic GTPase activity via their common RGS homology domain. In addition to their GTPase accelerating activity (GAP), RGS proteins also contain other domains that regulate their receptor selectivity, their interaction with other proteins such as adenylyl cyclase or their subcellular localization via interaction with scaffold proteins such as tubulin, 14-3-3 or spinophilin. There are at least 37 different RGS family members in humans and numerous physiological functions have been assigned to these proteins, which have rather a tissue-specific expression pattern. The role of some RGS proteins was shown to be important for hematopoiesis. More recent studies also focused on their expression in platelets, and for R4 RGS subfamily members RGS2, RGS16 and RGS18, it could be demonstrated that they regulate megakaryopoiesis and/or platelet function. These functional studies mostly comprised in vitro experiments and in vivo studies using small animal models. Their role in human pathology related to platelet dysfunction remains still largely unknown, except for a case report with a RGS2 gain of function mutation. In addition to an introduction on RGS signaling and different effectors with a special focus on the R4 subfamily members, we here will give an overview of the studies related to the role of RGS proteins in hematopoiesis, megakaryopoiesis and platelet function.
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Affiliation(s)
- S Louwette
- Center for Molecular and Vascular Biology Departement of Pediatrics, University of Leuven, Leuven, Belgium
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Abstract
Inherited diseases of the megakaryocyte lineage give rise to bleeding when platelets fail to fulfill their hemostatic function upon vessel injury. Platelet defects extend from the absence or malfunctioning of adhesion (GPIb-IX-V, Bernard-Soulier syndrome) or aggregation receptors (integrin αIIbβ3, Glanzmann thrombasthenia) to defects of primary receptors for soluble agonists, secretion from storage organelles, activation pathways and the generation of procoagulant activity. In disorders such as the Chediak-Higashi, Hermansky-Pudlak, Wiskott-Aldrich and Scott syndromes the molecular lesion extends to other cells. In familial thrombocytopenia (FT), platelets are produced in insufficient numbers to assure hemostasis. Some FT affect platelet morphology and give rise to the 'giant platelet' syndromes (e.g. MYH9-related diseases) with changes in megakaryocyte maturation within the bone marrow and premature release of platelets. Diseases of platelet production may also affect other cells and in some cases interfere with development and/or functioning of major organs. Diagnosis of platelet disorders requires platelet function testing, studies often aided by the quantitative analysis of receptors by flow cytometry and fluorescence and electron microscopy. New generation DNA-based procedures including whole exome sequencing offer an exciting new perspective. Transfusion of platelets remains the most common treatment of severe bleeding, management with desmopressin is often used for mild disorders. Substitute therapies are available including rFVIIa and the potential use of thrombopoietin analogues for FT. Stem cell or bone marrow transplantation has been successful for several diseases while gene therapy shows promise in the Wiskott-Aldrich syndrome.
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Affiliation(s)
- A T Nurden
- Centre de Référence des Pathologies Plaquettaires, Plateforme Technologique et d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France.
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Louwette S, Régal L, Wittevrongel C, Thys C, Vandeweeghde G, Decuyper E, Leemans P, De Vos R, Van Geet C, Jaeken J, Freson K. NPC1 defect results in abnormal platelet formation and function: studies in Niemann-Pick disease type C1 patients and zebrafish. Hum Mol Genet 2012; 22:61-73. [PMID: 23010472 DOI: 10.1093/hmg/dds401] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Niemann-Pick type C is a lysosomal storage disease associated with mutations in NPC1 or NPC2, resulting in an accumulation of cholesterol in the endosomal-lysosomal system. Niemann-Pick type C has a clinical spectrum that ranges from a neonatal rapidly fatal disorder to an adult-onset chronic neurodegenerative disease combined with remarkably, in some cases, hematological defects such as thrombocytopenia, anemia and petechial rash. A role of NPC1 in hematopoiesis was never shown. Here, we describe platelet function abnormalities in three unrelated patients with a proven genetic and biochemical NPC1 defect. Their platelets have reduced aggregations, P-selectin expression and ATP secretions that are compatible with the observed abnormal alpha and reduced dense granules as studied by electron microscopy and CD63 staining after platelet spreading. Their blood counts were normal. NPC1 expression was shown in platelets and megakaryocytes (MKs). In vitro differentiated MKs from NPC1 patients exhibit hyperproliferation of immature MKs with different CD63(+) granules and abnormal cellular accumulation of cholesterol as shown by filipin stainings. The role of NPC1 in megakaryopoiesis was further studied using zebrafish with GFP-labeled thrombocytes or DsRed-labeled erythrocytes. NPC1 depletion in zebrafish resulted in increased cell death in the brain and abnormal cellular accumulation of filipin. NPC1-depleted embryos presented with thrombocytopenia and mild anemia as studied by flow cytometry and real-time QPCR for specific blood cell markers. In conclusion, this is the first report, showing a role of NPC1 in platelet function and formation but further studies are needed to define how cholesterol storage interferes with these processes.
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Affiliation(s)
- Sophie Louwette
- Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium
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Apostolidis PA, Lindsey S, Miller WM, Papoutsakis ET. Proposed megakaryocytic regulon of p53: the genes engaged to control cell cycle and apoptosis during megakaryocytic differentiation. Physiol Genomics 2012; 44:638-50. [PMID: 22548738 DOI: 10.1152/physiolgenomics.00028.2012] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
During endomitosis, megakaryocytes undergo several rounds of DNA synthesis without division leading to polyploidization. In primary megakaryocytes and in the megakaryocytic cell line CHRF, loss or knock-down of p53 enhances cell cycling and inhibits apoptosis, leading to increased polyploidization. To support the hypothesis that p53 suppresses megakaryocytic polyploidization, we show that stable expression of wild-type p53 in K562 cells (a p53-null cell line) attenuates the cells' ability to undergo polyploidization during megakaryocytic differentiation due to diminished DNA synthesis and greater apoptosis. This suggested that p53's effects during megakaryopoiesis are mediated through cell cycle- and apoptosis-related target genes, possibly by arresting DNA synthesis and promoting apoptosis. To identify candidate genes through which p53 mediates these effects, gene expression was compared between p53 knock-down (p53-KD) and control CHRF cells induced to undergo terminal megakaryocytic differentiation using microarray analysis. Among substantially downregulated p53 targets in p53-KD megakaryocytes were cell cycle regulators CDKN1A (p21) and PLK2, proapoptotic FAS, TNFRSF10B, CASP8, NOTCH1, TP53INP1, TP53I3, DRAM1, ZMAT3 and PHLDA3, DNA-damage-related RRM2B and SESN1, and actin component ACTA2, while antiapoptotic CKS1B, BCL2, GTSE1, and p53 family member TP63 were upregulated in p53-KD cells. Additionally, a number of cell cycle-related, proapoptotic, and cytoskeleton-related genes with known functions in megakaryocytes but not known to carry p53-responsive elements were differentially expressed between p53-KD and control CHRF cells. Our data support a model whereby p53 expression during megakaryopoiesis serves to control polyploidization and the transition from endomitosis to apoptosis by impeding cell cycling and promoting apoptosis. Furthermore, we identify a putative p53 regulon that is proposed to orchestrate these effects.
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Affiliation(s)
- Pani A Apostolidis
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA.
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Louwette S, Labarque V, Wittevrongel C, Thys C, Metz J, Gijsbers R, Debyser Z, Arnout J, Van Geet C, Freson K. Regulator of G-protein signaling 18 controls megakaryopoiesis and the cilia-mediated vertebrate mechanosensory system. FASEB J 2012; 26:2125-36. [PMID: 22308195 DOI: 10.1096/fj.11-198739] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
RGS18 was originally identified as a R4 subfamily member of regulators of G-protein signaling (RGS) with specific expression in hematopoietic progenitors, myeloerythroid cells, and megakaryocytes, though its physiological role in hematopoiesis remained unknown. Here, we show that lentiviral RGS18 overexpression during differentiation of mouse Sca1(+) hematopoietic stem cells induced a 50% increase of megakaryocyte proliferation. RGS18 depletion in zebrafish results in thrombocytopenia, as 66 to 88% of the embryos lack thrombocytes after injection of an ATG or splice-blocking morpholino, respectively. These embryos have no defects in early hematopoiesis, erythropoiesis, or leukocyte number and migration. In addition, all RGS18 depleted embryos have curly tails and an almost absent response to acoustic stimuli. In situ hybridization in zebrafish, Xenopus, and mouse embryos shows RGS18 expression in thrombocytes and/or hematological tissues but also in brain and otic vesicles. RGS18 interferes with development of cilia in hair cells of the inner ear and neuromast cells. On the basis of literature evidence that RGS-R4 members interact with the G-protein-modulated Wnt/calcium pathway, Wnt5b- but not Wnt5a-depleted embryos phenocopy all RGS18 knockdown effects. In summary, our study is the first to show that RGS18 regulates megakaryopoiesis but also reveals its unexpected role in ciliogenesis, at least in lower vertebrates, via interference with Wnt signaling.
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Affiliation(s)
- Sophie Louwette
- Center for Molecular and Vascular Biology, KU Leuven, Campus Gasthuisberg, O&N1, Herestraat 49, Box 911, 3000 Leuven, Belgium
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Abstract
Endothelial prostacyclin and nitric oxide potently inhibit platelet functions. Prostacyclin and nitric oxide actions are mediated by platelet adenylyl and guanylyl cyclases, which synthesize cyclic AMP (cAMP) and cyclic GMP (cGMP), respectively. Cyclic nucleotides stimulate cAMP-dependent protein kinase (protein kinase A [PKA]I and PKAII) and cGMP-dependent protein kinase (protein kinase G [PKG]I) to phosphorylate a broad panel of substrate proteins. Substrate phosphorylation results in the inactivation of small G-proteins of the Ras and Rho families, inhibition of the release of Ca(2+) from intracellular stores, and modulation of actin cytoskeleton dynamics. Thus, PKA/PKG substrates translate prostacyclin and nitric oxide signals into a block of platelet adhesion, granule release, and aggregation. cAMP and cGMP are degraded by phosphodiesterases, which might restrict signaling to specific subcellular compartments. An emerging principle of cyclic nucleotide signaling in platelets is the high degree of interconnection between activating and cAMP/cGMP-dependent inhibitory signaling pathways at all levels, including cAMP/cGMP synthesis and breakdown, and PKA/PKG-mediated substrate phosphorylation. Furthermore, defects in cAMP/cGMP pathways might contribute to platelet hyperreactivity in cardiovascular disease. This article focuses on recent insights into the regulation of the cAMP/cGMP signaling network and on new targets of PKA and PKG in platelets.
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Affiliation(s)
- A Smolenski
- UCD Conway Institute, UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin, Ireland.
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Nurden A, Nurden P. Advances in our understanding of the molecular basis of disorders of platelet function. J Thromb Haemost 2011; 9 Suppl 1:76-91. [PMID: 21781244 DOI: 10.1111/j.1538-7836.2011.04274.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Genetic defects of platelet function give rise to mucocutaneous bleeding of varying severity because platelets fail to fulfil their haemostatic role after vessel injury. Abnormalities of pathways involving glycoprotein (GP) mediators of adhesion (Bernard-Soulier syndrome, platelet-type von Willebrand disease) and aggregation (Glanzmann thrombasthenia) are the most studied and affect the GPIb-IX-V complex and integrin αIIbβ3, respectively. Leukocyte adhesion deficiency-III combines Glanzmann thrombasthenia with infections and defects of kindlin-3, a mediator of integrin activation. Agonist-specific deficiencies in platelet aggregation relate to mutations of primary receptors for ADP (P2Y(12)), thromboxane A(2) (TXA2R) and collagen (GPVI); however, selective abnormalities of intracellular signalling pathways remain better understood in mouse models. Defects of secretion from δ-granules are accompanied by pigment defects in the Hermansky-Pudlak and Chediak-Higashi syndromes; they concern multiple genes and protein complexes involved in secretory organelle biogenesis and function. Quebec syndrome is linked to a tandem duplication of the urokinase plasminogen activator (PLAU) gene while locus assignment to chromosome 3p has advanced the search for the gene(s) responsible for α-granule deficiency in the gray platelet syndrome. Defects of α-granule biosynthesis also involve germline VPS33B mutations in the ARC (arthrogryposis, renal dysfunction and cholestasis) syndrome. A mutation in transmembrane protein 16F (TMEM16F) has been linked to a defective procoagulant activity and phosphatidylserine expression in the Scott syndrome. Cytoskeletal dysfunction (with platelet anisotrophy) occurs not only in the Wiskott-Aldrich syndrome but also in filamin A deficiency or MYH9-related disease while GATA1 mutations or RUNX1 haploinsufficiency can affect expression of multiple platelet proteins.
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Affiliation(s)
- A Nurden
- Centre de Référence des Pathologies Plaquettaires, Plateforme Technologique d'Innovation Biomédicale, Hôpital Xavier Arnozan, Pessac, France.
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Horstman LL, Jy W, Ahn YS, Zivadinov R, Maghzi AH, Etemadifar M, Steven Alexander J, Minagar A. Role of platelets in neuroinflammation: a wide-angle perspective. J Neuroinflammation 2010; 7:10. [PMID: 20128908 PMCID: PMC2829540 DOI: 10.1186/1742-2094-7-10] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 02/03/2010] [Indexed: 01/03/2023] Open
Abstract
OBJECTIVES This review summarizes recent developments in platelet biology relevant to neuroinflammatory disorders. Multiple sclerosis (MS) is taken as the "Poster Child" of these disorders but the implications are wide. The role of platelets in inflammation is well appreciated in the cardiovascular and cancer research communities but appears to be relatively neglected in neurological research. ORGANIZATION After a brief introduction to platelets, topics covered include the matrix metalloproteinases, platelet chemokines, cytokines and growth factors, the recent finding of platelet PPAR receptors and Toll-like receptors, complement, bioactive lipids, and other agents/functions likely to be relevant in neuroinflammatory diseases. Each section cites literature linking the topic to areas of active research in MS or other disorders, including especially Alzheimer's disease. CONCLUSION The final section summarizes evidence of platelet involvement in MS. The general conclusion is that platelets may be key players in MS and related disorders, and warrant more attention in neurological research.
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Affiliation(s)
- Lawrence L Horstman
- Wallace Coulter Platelet Laboratory, Division of Hematology and Oncology, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Wenche Jy
- Wallace Coulter Platelet Laboratory, Division of Hematology and Oncology, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Yeon S Ahn
- Wallace Coulter Platelet Laboratory, Division of Hematology and Oncology, Department of Medicine, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Robert Zivadinov
- Buffalo Neuroimaging Analysis Center, The Jacobs Neurological Institute, Department of Neurology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo NY, USA
| | - Amir H Maghzi
- Department of Neurology, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Masoud Etemadifar
- Department of Neurology, Isfahan University of Medical Sciences, Isfahan, Iran
| | - J Steven Alexander
- Department of Cellular and Molecular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
| | - Alireza Minagar
- Department of Neurology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA
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