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Denorme F, Armstrong ND, Stoller ML, Portier I, Tugolukova EA, Tanner RM, Montenont E, Bhatlekar S, Cody M, Rustad JL, Ajanel A, Tolley ND, Murray DC, Boyle JL, Nieman MT, McKenzie SE, Yost CC, Lange LA, Cushman M, Irvin MR, Bray PF, Campbell RA. The predominant PAR4 variant in individuals of African ancestry worsens murine and human stroke outcomes. J Clin Invest 2023; 133:e169608. [PMID: 37471144 PMCID: PMC10503801 DOI: 10.1172/jci169608] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 07/18/2023] [Indexed: 07/22/2023] Open
Abstract
Protease-activated receptor 4 (PAR4) (gene F2RL3) harbors a functional dimorphism, rs773902 A/G (encoding Thr120/Ala120, respectively) and is associated with greater platelet aggregation. The A allele frequency is more common in Black individuals, and Black individuals have a higher incidence of ischemic stroke than White individuals. However, it is not known whether the A allele is responsible for worse stroke outcomes. To directly test the in vivo effect of this variant on stroke, we generated mice in which F2rl3 was replaced by F2RL3, thereby expressing human PAR4 (hPAR4) with either Thr120 or Ala120. Compared with hPAR4 Ala120 mice, hPAR4 Thr120 mice had worse stroke outcomes, mediated in part by enhanced platelet activation and platelet-neutrophil interactions. Analyses of 7,620 Black subjects with 487 incident ischemic strokes demonstrated the AA genotype was a risk for incident ischemic stroke and worse functional outcomes. In humanized mice, ticagrelor with or without aspirin improved stroke outcomes in hPAR4 Ala120 mice, but not in hPAR4 Thr120 mice. P selectin blockade improved stroke outcomes and reduced platelet-neutrophil interactions in hPAR4 Thr120 mice. Our results may explain some of the racial disparity in stroke and support the need for studies of nonstandard antiplatelet therapies for patients expressing PAR4 Thr120.
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Affiliation(s)
- Frederik Denorme
- Program in Molecular Medicine and
- Department of Neurology, Division of Vascular Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Nicole D. Armstrong
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | | | | | | | - Rikki M. Tanner
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | | | | | | | | | | | | | | | - Julie L. Boyle
- Bioinformatics Shared Resource, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
| | - Marvin T. Nieman
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Steven E. McKenzie
- Department of Medicine, The Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Christian Con Yost
- Program in Molecular Medicine and
- Department of Pediatrics, Division of Neonatology, University of Utah, Salt Lake City, Utah, USA
| | - Leslie A. Lange
- Division of Biomedical Informatics and Personalized Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Mary Cushman
- Department of Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont, USA
| | - Marguerite R. Irvin
- Department of Neurology, Division of Vascular Neurology, University of Utah, Salt Lake City, Utah, USA
| | - Paul F. Bray
- Program in Molecular Medicine and
- Department of Internal Medicine, Division of Hematology and Hematologic Malignancies, and
| | - Robert A. Campbell
- Program in Molecular Medicine and
- Department of Internal Medicine, Division of Hematology and Hematologic Malignancies, and
- Department of Pathology, Division of Microbiology and Immunology, University of Utah, Salt Lake City, Utah, USA
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2
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Dangelmaier C, Kunapuli SP. Protease-activated receptor 4 causes Akt phosphorylation independently of PI3 kinase pathways. Platelets 2021; 32:832-837. [PMID: 32811251 PMCID: PMC7889752 DOI: 10.1080/09537104.2020.1802415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 10/23/2022]
Abstract
PI-3 Kinase plays an important role in platelet activation mainly through regulation of RASA3. Akt phosphorylation is an indicator for the activity of PI3 kinase. The aim of this study is to characterize the pathways leading to Akt phosphorylation in platelets. We performed concentration response curves of LY294002, a pan-PI3 kinase inhibitor, on platelet aggregation and Akt phosphorylation, in washed human and mouse platelets. At concentrations as low as 3.12 µM, LY294002 abolished Akt phosphorylation induced by 2MeSADP and SFLLRN, but not by AYPGKF. It required much higher concentrations of LY294002 (12.5-25 µM) to abolish AYPGKF-induced Akt phosphorylation, both in wild type and P2Y12 null mouse platelets. We propose that 3.12 µM LY294002 is sufficient to inhibit PI3 kinase isoforms in platelets and higher concentrations might inhibit other pathways regulating Akt phosphorylation by AYPGKF. We conclude that Protease-activated receptor 4 (PAR4) might cause Akt phosphorylation through pathways distinctly different from those of Protease-activated receptor 1 (PAR1).
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Affiliation(s)
- Carol Dangelmaier
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
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3
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Xiang B, Zhang G, Zhang Y, Wu C, Joshi S, Morris AJ, Ware J, Smyth SS, Whiteheart SW, Li Z. Calcium Ion Chelation Preserves Platelet Function During Cold Storage. Arterioscler Thromb Vasc Biol 2021; 41:234-249. [PMID: 33176450 PMCID: PMC8158249 DOI: 10.1161/atvbaha.120.314879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Platelet transfusion is a life-saving therapy to prevent or treat bleeding in patients with thrombocytopenia or platelet dysfunction. However, for >6 decades, safe and effective strategies for platelet storage have been an impediment to widespread use of platelet transfusion. Refrigerated platelets are cleared rapidly from circulation, precluding cold storage of platelets for transfusion. Consequently, platelets are stored at room temperature with an upper limit of 5 days due to risks of bacterial contamination and loss of platelet function. This practice severely limits platelet availability for transfusion. This study is to identify the mechanism of platelet clearance after cold storage and develop a method for platelet cold storage. Approach and Results: We found that rapid clearance of cold-stored platelets was largely due to integrin activation and apoptosis. Deficiency of integrin β3 or caspase-3 prolonged cold-stored platelets in circulation. Pretreatment of platelets with EGTA, a cell impermeable calcium ion chelator, reversely inhibited cold storage-induced platelet activation and consequently prolonged circulation of cold-stored platelets. Moreover, transfusion of EGTA-treated, cold-stored platelets, but not room temperature-stored platelets, into the mice deficient in glycoprotein Ibα significantly shortened tail-bleeding times and diminished blood loss. CONCLUSIONS Integrin activation and apoptosis is the underlying mechanism of rapid clearance of platelets after cold storage. Addition of a cell impermeable calcium ion chelator to platelet products is potentially a simple and effective method to enable cold storage of platelets for transfusion.
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Affiliation(s)
- Binggang Xiang
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Guoying Zhang
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Yan Zhang
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Congqing Wu
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Smita Joshi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Andrew J. Morris
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
| | - Jerry Ware
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Susan S. Smyth
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
- Veterans Affairs Medical Center, Lexington, KY 40536, USA
| | - Sidney W. Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Zhenyu Li
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
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Zhao Y, Zheng K, Guan B, Guo M, Song L, Gao J, Qu H, Wang Y, Shi D, Zhang Y. DLDTI: a learning-based framework for drug-target interaction identification using neural networks and network representation. J Transl Med 2020; 18:434. [PMID: 33187537 PMCID: PMC7666529 DOI: 10.1186/s12967-020-02602-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 11/01/2020] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Drug repositioning, the strategy of unveiling novel targets of existing drugs could reduce costs and accelerate the pace of drug development. To elucidate the novel molecular mechanism of known drugs, considering the long time and high cost of experimental determination, the efficient and feasible computational methods to predict the potential associations between drugs and targets are of great aid. METHODS A novel calculation model for drug-target interaction (DTI) prediction based on network representation learning and convolutional neural networks, called DLDTI, was generated. The proposed approach simultaneously fused the topology of complex networks and diverse information from heterogeneous data sources, and coped with the noisy, incomplete, and high-dimensional nature of large-scale biological data by learning the low-dimensional and rich depth features of drugs and proteins. The low-dimensional feature vectors were used to train DLDTI to obtain the optimal mapping space and to infer new DTIs by ranking candidates according to their proximity to the optimal mapping space. More specifically, based on the results from the DLDTI, we experimentally validated the predicted targets of tetramethylpyrazine (TMPZ) on atherosclerosis progression in vivo. RESULTS The experimental results showed that the DLDTI model achieved promising performance under fivefold cross-validations with AUC values of 0.9172, which was higher than the methods using different classifiers or different feature combination methods mentioned in this paper. For the validation study of TMPZ on atherosclerosis, a total of 288 targets were identified and 190 of them were involved in platelet activation. The pathway analysis indicated signaling pathways, namely PI3K/Akt, cAMP and calcium pathways might be the potential targets. Effects and molecular mechanism of TMPZ on atherosclerosis were experimentally confirmed in animal models. CONCLUSIONS DLDTI model can serve as a useful tool to provide promising DTI candidates for experimental validation. Based on the predicted results of DLDTI model, we found TMPZ could attenuate atherosclerosis by inhibiting signal transductions in platelets. The source code and datasets explored in this work are available at https://github.com/CUMTzackGit/DLDTI .
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Affiliation(s)
- Yihan Zhao
- Department of Graduate School, Beijing University of Chinese Medicine, Beijing, China
| | - Kai Zheng
- School of Computer Science and Engineering, Central South University, Changsha, China
| | - Baoyi Guan
- National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital, Cardiovascular Diseases Center, China Academy of Chinese Medical Sciences, Beijing, China
| | - Mengmeng Guo
- Institute of Cardiovascular Sciences, Health Science Center, Peking University, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing, China
| | - Lei Song
- Department of Graduate School, Beijing University of Chinese Medicine, Beijing, China
| | - Jie Gao
- National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital, Cardiovascular Diseases Center, China Academy of Chinese Medical Sciences, Beijing, China
| | - Hua Qu
- National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital, Cardiovascular Diseases Center, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuhui Wang
- Institute of Cardiovascular Sciences, Health Science Center, Peking University, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing, China
| | - Dazhuo Shi
- National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital, Cardiovascular Diseases Center, China Academy of Chinese Medical Sciences, Beijing, China.
| | - Ying Zhang
- National Clinical Research Center for Chinese Medicine Cardiology, Xiyuan Hospital, Cardiovascular Diseases Center, China Academy of Chinese Medical Sciences, Beijing, China.
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Qasim H, Karim ZA, Hernandez KR, Lozano D, Khasawneh FT, Alshbool FZ. Arhgef1 Plays a Vital Role in Platelet Function and Thrombogenesis. J Am Heart Assoc 2019; 8:e011712. [PMID: 30994039 PMCID: PMC6512111 DOI: 10.1161/jaha.118.011712] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 03/25/2019] [Indexed: 01/09/2023]
Abstract
Background Platelets are the cellular mediators of hemostasis and thrombosis, and their function is regulated by a number of molecular mediators, such as small GTP ases. These small GTP ases are themselves regulated by guanine nucleotide exchange factors such as Arhgefs, several of which are found in platelets, including the highly expressed Arhgef1. However, the role of Arhgef1 in platelets has not yet been investigated. Methods and Results We employed mice with genetic deletion of Arhgef1 (ie, Arhgef1-/-) and investigated their platelet phenotype by employing a host of in vivo and in vitro platelet assays. Our results indicate that Arhgef1-/- mice had prolonged carotid artery occlusion and tail bleeding times. Moreover, platelets from these mice exhibited defective aggregation, dense and α granule secretion, α II bβ3 integrin activation, clot retraction and spreading, in comparison to their wild-type littermates. Finally, we also found that the mechanism by which Arhgef1 regulates platelets is mediated in part by a defect in the activation of the RhoA-Rho-associated kinase axis, but not Rap1b. Conclusions Our data demonstrate, for the first time, that Arhgef1 plays a critical role in platelet function, in vitro and in vivo.
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Affiliation(s)
- Hanan Qasim
- Department of Pharmaceutical SciencesSchool of PharmacyThe University of Texas El PasoEl PasoTX
| | - Zubair A. Karim
- Department of Pharmaceutical SciencesSchool of PharmacyThe University of Texas El PasoEl PasoTX
| | - Keziah R. Hernandez
- Department of Pharmaceutical SciencesSchool of PharmacyThe University of Texas El PasoEl PasoTX
| | | | - Fadi T. Khasawneh
- Department of Pharmaceutical SciencesSchool of PharmacyThe University of Texas El PasoEl PasoTX
| | - Fatima Z. Alshbool
- Department of Pharmaceutical SciencesSchool of PharmacyThe University of Texas El PasoEl PasoTX
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6
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Guidetti GF, Torti M, Canobbio I. Focal Adhesion Kinases in Platelet Function and Thrombosis. Arterioscler Thromb Vasc Biol 2019; 39:857-868. [DOI: 10.1161/atvbaha.118.311787] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The focal adhesion kinase family includes 2 homolog members, FAK and Pyk2 (proline-rich tyrosine kinase 2), primarily known for their roles in nucleated cells as regulators of cytoskeletal dynamics and cell adhesion. FAK and Pyk2 are also expressed in megakaryocytes and platelets and are activated by soluble agonists and on adhesion to the subendothelial matrix. Despite high sequence homology and similar molecular organization, FAK and Pyk2 play different roles in platelet function. Whereas FAK serves mostly as a traditional focal adhesion kinase activated downstream of integrins, Pyk2 coordinates multiple signals from different receptors. FAK, but not Pyk2, is involved in megakaryocyte maturation and platelet production. In circulating platelets, FAK is recruited by integrin αIIbβ3 to regulate hemostasis, whereas it plays minimal roles in thrombosis. By contrast, Pyk2 is implicated in platelet activation and is an important regulator of thrombosis. The direct activation of Pyk2 by calcium ions provides a connection between GPCRs (G-protein coupled receptors) and Src family kinases. In this review, we provide the comprehensive overview of >20 years of investigations on the role and regulation of focal adhesion kinases in blood platelets, highlighting common and distinctive features of FAK and Pyk2 in hemostasis and thrombosis.
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Affiliation(s)
| | - Mauro Torti
- From the Department of Biology and Biotechnology, University of Pavia, Italy
| | - Ilaria Canobbio
- From the Department of Biology and Biotechnology, University of Pavia, Italy
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7
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Minuz P, Meneguzzi A, Fumagalli L, Degan M, Calabria S, Ferraro R, Ricci M, Veneri D, Berton G. Calcium-Dependent Src Phosphorylation and Reactive Oxygen Species Generation Are Implicated in the Activation of Human Platelet Induced by Thromboxane A2 Analogs. Front Pharmacol 2018; 9:1081. [PMID: 30319416 PMCID: PMC6169403 DOI: 10.3389/fphar.2018.01081] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Accepted: 09/06/2018] [Indexed: 11/19/2022] Open
Abstract
The thromboxane (TX) A2 elicits TP-dependent different platelet responses. Low amounts activate Src kinases and the Rho–Rho kinase pathway independently of integrin αIIbβ3 and ADP secretion and synergize with epinephrine to induce aggregation. Aim of the present study was to investigate the role Src kinases and the interplay with calcium signals in reactive oxygen species (ROS) generation in the activatory pathways engaged by TXA2 in human platelets. All the experiments were performed in vitro or ex vivo. Washed platelets were stimulated with 50–1000 nM U46619 and/or 10 μM epinephrine in the presence of acetylsalicylic acid and the ADP scavenger apyrase. The effects of the ROS scavenger EUK-134, NADPH oxidase (NOX) inhibitor apocynin, Src kinase inhibitor PP2 and calcium chelator BAPTA were tested. Intracellular calcium and ROS generation were measured. Platelet rich plasma from patients treated with dasatinib was used to confirm the data obtained in vitro. We observed that 50 nM U46619 plus epinephrine increase intracellular calcium similarly to 1000 nM U46619. ROS generation was blunted by the NOX inhibitor apocynin. BAPTA inhibited ROS generation in resting and activated platelets. Phosphorylation of Src and MLC proteins were not significantly affected by antioxidants agents. BAPTA and antioxidants reduced P-Selectin expression, activation of integrin αIIbβ3and platelet aggregation. TXA2-induced increase in intracellular calcium is required for Src phosphorylation and ROS generation. NADPH oxidase is the source of ROS in TX stimulated platelets. The proposed model helps explain why an incomplete inhibition of TP receptor results in residual platelet activation, and define new targets for antiplatelet treatment.
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Affiliation(s)
- Pietro Minuz
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Alessandra Meneguzzi
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Laura Fumagalli
- Section of General Pathology, Department of Medicine, University of Verona, Verona, Italy
| | - Maurizio Degan
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Stefano Calabria
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Roberta Ferraro
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Marco Ricci
- Section of Internal Medicine, Department of Medicine, University of Verona, Verona, Italy
| | - Dino Veneri
- Section of Haematology, Department of Medicine, University of Verona, Verona, Italy
| | - Giorgio Berton
- Section of General Pathology, Department of Medicine, University of Verona, Verona, Italy
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Fu Q, Cheng J, Gao Y, Zhang Y, Chen X, Xie J. Protease-activated receptor 4: a critical participator in inflammatory response. Inflammation 2015; 38:886-95. [PMID: 25120239 DOI: 10.1007/s10753-014-9999-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Protease-activated receptors (PARs) are G protein-coupled receptors of which four members PAR1, PAR2, PAR3, and PAR4 have been identified, characterized by a typical mechanism of activation involving various related proteases. The amino-terminal sequence of PARs is cleaved by a broad array of proteases, leading to specific proteolytic cleavage which forms endogenous tethered ligands to induce agonist-biased PAR activation. The biological effect of PARs activated by coagulation proteases to regulate hemostasis and thrombosis plays an enormous role in the cardiovascular system, while PAR4 can also be activated by trypsin, cathepsin G, the activated factor X of the coagulation cascade, and trypsin IV. Irrespective of its role in thrombin-induced platelet aggregation, PAR4 activation is believed to be involved in inflammatory lesions, as show by investigations that have unmasked the effects of PAR4 on neutrophil recruitment, the regulation of edema, and plasma extravasation. This review summarizes the roles of PAR4 in coagulation and other extracellular protease pathways, which activate PAR4 to participate in normal regulation and disease.
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Affiliation(s)
- Qiang Fu
- Affiliated Cancer Hospital of Zhengzhou University, Henan Cancer Hospital, Zhengzhou, 450008, China
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9
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The focal adhesion kinase Pyk2 links Ca2+ signalling to Src family kinase activation and protein tyrosine phosphorylation in thrombin-stimulated platelets. Biochem J 2015; 469:199-210. [DOI: 10.1042/bj20150048] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/13/2015] [Indexed: 01/08/2023]
Abstract
We address the mechanism for Src family kinases activation downstream of G-protein-coupled receptors (GPCRs) in thrombin-stimulated blood platelets and we describe a novel interplay between Pyk2 and the Src kinases Fyn and Lyn in the regulation of Ca2+-dependent protein-tyrosine phosphorylation.
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10
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Moroi AJ, Watson SP. Impact of the PI3-kinase/Akt pathway on ITAM and hemITAM receptors: haemostasis, platelet activation and antithrombotic therapy. Biochem Pharmacol 2015; 94:186-94. [PMID: 25698506 DOI: 10.1016/j.bcp.2015.02.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 02/09/2015] [Accepted: 02/09/2015] [Indexed: 01/16/2023]
Abstract
Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that are activated in response to various stimulants, and they regulate many processes including inflammation; the stress response; gene transcription; and cell proliferation, differentiation, and death. Increasing reports have shown that the PI3Ks and their downstream effector Akt are activated by several platelet receptors that regulate platelet activation and haemostasis. Platelets express two immunoreceptor tyrosine based activation motif (ITAM) receptors, collagen receptor glycoprotein VI (GPVI) and Fcγ receptor IIA (FcγRIIA), which are characterized by two YxxL sequences separated by 6-12 amino acids. Activation of an ITAM receptor initiates a reaction cascade via its YxxL sequence in which signaling molecules such as spleen tyrosine kinase (Syk), linker for activation of T cells (LAT) and phospholipase C γ2 (PLCγ2) become activated, leading to platelet activation. Platelets also express another receptor, C-type lectin 2 (CLEC-2), which has a single YxxL sequence, so it is appropriately called a hemITAM receptor. ITAM receptors and the hemITAM receptor share many signaling features. Here we will summarize our current knowledge about how the PI3K/Akt pathway regulates (hem)ITAM receptor-mediated platelet activation and haemostasis and discuss the possible benefits of targeting PI3K/Akt as an antithrombotic therapy.
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Affiliation(s)
- Alyssa J Moroi
- Centre for Cardiovascular Sciences, Institute for Biomedical Research, The College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
| | - Steve P Watson
- Centre for Cardiovascular Sciences, Institute for Biomedical Research, The College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
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11
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Khan A, Li D, Ibrahim S, Smyth E, Woulfe DS. The physical association of the P2Y12 receptor with PAR4 regulates arrestin-mediated Akt activation. Mol Pharmacol 2014; 86:1-11. [PMID: 24723492 DOI: 10.1124/mol.114.091595] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is now well accepted that protease activated receptor (PAR) 1 and PAR4 have differential roles in platelet activation. PAR4, a low-affinity thrombin receptor in human platelets, participates in sustained platelet activation in a P2Y12-dependent manner; however, the mechanisms are not defined. Our previous studies demonstrated that thrombin induces the association of PAR4 with P2Y12, together with arrestin recruitment to the complex. Here we show that PAR4 and P2Y12 directly interact to coregulate Akt signaling after PAR4 activation. We observed direct and specific interaction of P2Y12 with PAR4 but not PAR1 by bioluminescent resonance energy transfer when the receptors were coexpressed in human embryonic kidney 293T cells. PAR4-P2Y12 dimerization was promoted by PAR4-AP and inhibited by P2Y12 antagonist. By using sequence comparison of the transmembrane domains of PAR1 and PAR4, we designed a mutant form of PAR4, "PAR4SFT," by replacing LGL194-196 at the base of transmembrane domain 4 with the corresponding aligned PAR1 residues SFT 220-222. PAR4SFT supported only 8.74% of PAR4-P2Y12 interaction, abolishing P2Y12-dependent arrestin recruitment to PAR4 and Akt activation. Nonetheless, PAR4SFT still supported homodimerization with PAR4. PAR4SFT failed to induce a calcium flux when expressed independently; however, coexpression of increasing concentrations of PAR4SFT, together with PAR4 potentiated PAR4-mediated calcium flux, suggested that PAR4 act as homodimers to signal to Gq-coupled calcium responses. In conclusion, PAR4 LGL (194-196) governs agonist-dependent association of PAR4 with P2Y12 and contributes to Gq-coupled calcium responses. PAR4-P2Y12 association supports arrestin-mediated sustained signaling to Akt. Hence, PAR4-P2Y12 dimerization is likely to be important for the PAR4-P2Y12 dependent stabilization of platelet thrombi.
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Affiliation(s)
- Aasma Khan
- Department of Biological Sciences, University of Delaware, Newark, Delaware (A.K., D.L., D.S.W.); and Institute for Translational Medicine and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania (S.I., E.S.)
| | - Dongjun Li
- Department of Biological Sciences, University of Delaware, Newark, Delaware (A.K., D.L., D.S.W.); and Institute for Translational Medicine and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania (S.I., E.S.)
| | - Salam Ibrahim
- Department of Biological Sciences, University of Delaware, Newark, Delaware (A.K., D.L., D.S.W.); and Institute for Translational Medicine and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania (S.I., E.S.)
| | - Emer Smyth
- Department of Biological Sciences, University of Delaware, Newark, Delaware (A.K., D.L., D.S.W.); and Institute for Translational Medicine and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania (S.I., E.S.)
| | - Donna S Woulfe
- Department of Biological Sciences, University of Delaware, Newark, Delaware (A.K., D.L., D.S.W.); and Institute for Translational Medicine and Pharmacology, University of Pennsylvania, Philadelphia, Pennsylvania (S.I., E.S.)
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12
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Ogawa A, Firth AL, Ariyasu S, Yamadori I, Matsubara H, Song S, Fraidenburg DR, Yuan JXJ. Thrombin-mediated activation of Akt signaling contributes to pulmonary vascular remodeling in pulmonary hypertension. Physiol Rep 2013; 1:e00190. [PMID: 24744867 PMCID: PMC3970741 DOI: 10.1002/phy2.190] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 11/27/2013] [Indexed: 12/11/2022] Open
Abstract
Chronic thromboembolic pulmonary hypertension (CTEPH) has been increasingly recognized as a common source of elevated pulmonary vascular resistance and pulmonary hypertension. It is clear that development of pulmonary thromboemboli is the inciting event for this process, yet it remains unclear why some patients have persistent pulmonary artery occlusion leading to distal pulmonary vascular remodeling and CTEPH. Thrombin, a serine protease, is an integral part of the common coagulation cascade, yet thrombin also has direct cellular effects through interaction with the family of PAR membrane receptors. This study is designed to determine the effects of thrombin on Akt signaling in pulmonary artery smooth muscle cells (PASMC) from normal humans and pulmonary hypertension patients. Thrombin treatment of PASMC resulted in a transient increase in Akt phosphorylation and had similar effects on the downstream targets of the Akt/mTOR pathway. Ca2+ is shown to be required for Akt phosphorylation as well as serum starvation, a distinct effect compared to platelet‐derived growth factor. Thrombin treatment was associated with a rise in intracellular [Ca2+] and enhanced store‐operated calcium entry (SOCE). These effects lead to enhanced proliferation, which is more dramatic in both IPAH and CTEPH PASMC. Enhanced proliferation is also shown to be attenuated by inhibition of Akt/mTOR in CTEPH PASMC. Thrombin has direct effects on PASMC increasing intracellular [Ca2+] and PASMC proliferation, an effect attributed to Akt phosphorylation. The current results implicate the effects of thrombin in the pathogenesis of idiopathic pulmonary arterial hypertension (IPAH) and CTEPH, which may potentially be a novel therapeutic target. Thrombin is known to play an important role in thrombotic events including pulmonary embolism. In this manuscript, we show a direct effect of thrombin on pulmonary artery smooth muscle cells in both normal and diseased states through Akt signaling, which leads to increased store‐operated calcium entry and cellular proliferation. These direct effects of thrombin may play a role in the development and progression of chronic thromboembolic pulmonary hypertension.
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Affiliation(s)
- Aiko Ogawa
- Department of Clinical Science, National Hospital Organization Okayama Medical CenterTamasu, Kita-kuOkayama, Japan
| | - Amy L Firth
- The Salk Institute of Biological Studies, La Jolla, California
| | - Sanae Ariyasu
- Clinical Pathology, National Hospital Organization Okayama Medical Center, TamasuKita-kuOkayama, Japan
| | - Ichiro Yamadori
- Clinical Pathology, National Hospital Organization Okayama Medical Center, TamasuKita-kuOkayama, Japan
| | - Hiromi Matsubara
- Department of Clinical Science, National Hospital Organization Okayama Medical CenterTamasu, Kita-kuOkayama, Japan
| | - Shanshan Song
- Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy Medicine, University of Illinois at Chicago, Chicago, Illinois ; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois
| | - Dustin R Fraidenburg
- Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy Medicine, University of Illinois at Chicago, Chicago, Illinois ; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois
| | - Jason X-J Yuan
- Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy Medicine, University of Illinois at Chicago, Chicago, Illinois ; Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois ; Department of Pharmacology, University of Illinois at Chicago, Chicago, Illinois
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13
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Zhang SH, Zhang Y, Shen J, Zhang S, Chen L, Gu J, Mruk JS, Cheng G, Zhu L, Kunapuli SP, Ding Z. Tumor vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid inhibits platelet activation and thrombosis via inhibition of thromboxane A2 signaling and phosphodiesterase. J Thromb Haemost 2013; 11:1855-66. [PMID: 23902231 DOI: 10.1111/jth.12362] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Indexed: 12/01/2022]
Abstract
BACKGROUND 5,6-Dimethylxanthenone-4-acetic acid (DMXAA) is a tumor vascular disrupting agent under clinical trials as an adjacent antitumor agent. DMXAA is structurally similar to flavone-8-acetic acid (FAA), an old tumor vascular disrupting agent with antiplatelet and antithrombotic effects. In contrast to FAA, which causes bleeding in tumor patients, no bleeding has been reported in patients receiving DMXAA. Whether DMXAA also affects platelet function is not clear. OBJECTIVES To determine the effects of DMXAA on platelet function and explore the underlying mechanisms. METHODS AND RESULTS DMXAA concentration-dependently inhibited human platelet aggregation and ATP release induced by U46619, arachidonic acid, ADP, collagen, or ristocetin. Furthermore, DMXAA inhibited phosphorylation of Erk1/2 and Akt downstream of thromboxane A2 signaling inhibition. DMXAA also inhibited human platelet phosphodiesterase. The antiplatelet effects were further confirmed using mice administered DMXAA intravenously. DMXAA dramatically inhibited thrombus formation in FeCl3 -injured mouse mesenteric arterial thrombus model and laser-injured mouse cremaster arteriole thrombus model. Notably, at a dose exhibiting antithrombotic effects similar to those of clopidogrel in mice, DMXAA did not significantly increase bleeding. CONCLUSIONS For the first time, we found that tumor vascular disrupting agent DMXAA has potent antiplatelet and antithrombotic effects without any bleeding diathesis. As DMXAA inhibits platelet activity with safe profile, DMXAA could be used as an efficacious and safe antiplatelet drug.
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Affiliation(s)
- S H Zhang
- Key Laboratory of Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai, China
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14
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Mischnik M, Boyanova D, Hubertus K, Geiger J, Philippi N, Dittrich M, Wangorsch G, Timmer J, Dandekar T. A Boolean view separates platelet activatory and inhibitory signalling as verified by phosphorylation monitoring including threshold behaviour and integrin modulation. MOLECULAR BIOSYSTEMS 2013; 9:1326-39. [DOI: 10.1039/c3mb25597b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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15
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The P2Y(12) antagonists, 2MeSAMP and cangrelor, inhibit platelet activation through P2Y(12)/G(i)-dependent mechanism. PLoS One 2012; 7:e51037. [PMID: 23236426 PMCID: PMC3516503 DOI: 10.1371/journal.pone.0051037] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 10/29/2012] [Indexed: 11/19/2022] Open
Abstract
Background ADP is an important physiological agonist that induces integrin activation and platelet aggregation through its receptors P2Y1 (Gαq-coupled) and P2Y12 (Gαi-coupled). P2Y12 plays a critical role in platelet activation and thrombosis. Adenosine-based P2Y12 antagonists, 2-methylthioadenosine 5′-monophosphate triethylammonium salt hydrate (2MeSAMP) and Cangrelor (AR-C69931MX) have been widely used to demonstrate the role of P2Y12 in platelet function. Cangrelor is being evaluated in clinical trials of thrombotic diseases. However, a recent study reported that both 2MeSAMP and Cangrelor raise intra-platelet cAMP levels and inhibit platelet aggregation through a P2Y12-independent mechanism. Methodology/Principal Findings The present work, using P2Y12 deficient mice, sought to clarify previous conflicting reports and to elucidate the mechanisms by which 2MeSAMP and Cangrelor inhibit platelet activation and thrombosis. 2MeSAMP and Cangrelor inhibited aggregation and ATP release of wild-type but not P2Y12 deficient platelets. 2MeSAMP and Cangrelor neither raised intracellular cAMP concentrations nor induced phosphorylation of vasodilator-stimulated phosphoprotein (VASP) in washed human or mouse platelets. Furthermore, unlike the activators (PGI2 and forskolin) of the cAMP pathway, 2MeSAMP and Cangrelor failed to inhibit Ca2+ mobilization, Akt phosphorylation, and Rap1b activation in P2Y12 deficient platelets. Importantly, while injection of Cangrelor inhibited thrombus formation in a FeCl3-induced thrombosis model in wild-type mice, it failed to affect thrombus formation in P2Y12 deficient mice. Conclusions These data together demonstrate that 2MeSAMP and Cangrelor inhibit platelet function through the P2Y12-dependent mechanism both in vitro and in vivo.
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16
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Niu H, Chen X, Gruppo RA, Li D, Wang Y, Zhang L, Wang K, Chai W, Sun Y, Ding Z, Gartner TK, Liu J. Integrin αIIb-mediated PI3K/Akt activation in platelets. PLoS One 2012; 7:e47356. [PMID: 23082158 PMCID: PMC3474815 DOI: 10.1371/journal.pone.0047356] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
Integrin αIIbβ3 mediated bidirectional signaling plays a critical role in thrombosis and haemostasis. Signaling mediated by the β3 subunit has been extensively studied, but αIIb mediated signaling has not been characterized. Previously, we reported that platelet granule secretion and TxA2 production induced by αIIb mediated outside-in signaling is negatively regulated by the β3 cytoplasmic domain residues R(724)KEFAKFEEER(734). In this study, we identified part of the signaling pathway utilized by αIIb mediated outside-in signaling. Platelets from humans and gene deficient mice, and genetically modified CHO cells as well as a variety of kinase inhibitors were used for this work. We found that aggregation of TxA2 production and granule secretion by β3Δ724 human platelets initiated by αIIb mediated outside-in signaling was inhibited by the Src family kinase inhibitor PP2 and the PI3K inhibitor wortmannin, respectively, but not by the MAPK inhibitor U0126. Also, PP2 and wortmannin, and the palmitoylated β3 peptide R(724)KEFAKFEEER(734), each inhibited the phosphorylation of Akt residue Ser473 and prevented TxA2 production and storage granule secretion. Similarly, Akt phosphorylation in mouse platelets stimulated by the PAR4 agonist peptide AYPGKF was αIIbβ3-dependent, and blocked by PP2, wortmannin and the palmitoylated peptide p-RKEFAKFEEER. Akt was also phosphorylated in response to mAb D3 plus Fg treatment of CHO cells in suspension expressing αIIbβ3-Δ724 or αIIbβ3E(724)AERKFERKFE(734), but not in cells expressing wild type αIIbβ3. In summary, SFK(s) and PI3K/Akt signaling is utilized by αIIb-mediated outside-in signaling to activate platelets even in the absence of all but 8 membrane proximal residues of the β3 cytoplasmic domain. Our results provide new insight into the signaling pathway used by αIIb-mediated outside-in signaling in platelets.
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Affiliation(s)
- Haixia Niu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xue Chen
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ralph A. Gruppo
- Hematology-Oncology Department, Cincinnati Children’s Hospital, Cincinnati, Ohio, United States of America
| | - Ding Li
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanhua Wang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Lin Zhang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Kemin Wang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weiran Chai
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yueping Sun
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhongren Ding
- Key Laboratory of Molecular Medicine, Ministry of Education, and Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai, China
| | - T. Kent Gartner
- Department of Biological Sciences, University of Memphis, Memphis, Tennessee, United States of America
| | - Junling Liu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- * E-mail:
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17
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Xiang B, Zhang G, Stefanini L, Bergmeier W, Gartner TK, Whiteheart SW, Li Z. The Src family kinases and protein kinase C synergize to mediate Gq-dependent platelet activation. J Biol Chem 2012; 287:41277-87. [PMID: 23066026 DOI: 10.1074/jbc.m112.393124] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Src family kinases (SFKs) play essential roles in collagen- and von Willebrand factor (VWF)-mediated platelet activation. However, the roles of SFKs in G protein-coupled receptor-mediated platelet activation and the molecular mechanisms whereby SFKs are activated by G protein-coupled receptor stimulation are not fully understood. Here we show that the thrombin receptor protease-activated receptor 4 agonist peptide AYPGKF elicited SFK phosphorylation in P2Y(12) deficient platelets but stimulated minimal SFK phosphorylation in platelets lacking G(q). We have previously shown that thrombin-induced SFK phosphorylation was inhibited by the calcium chelator 5,5'-dimethyl-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (dimethyl-BAPTA). The calcium ionophore A23187 induced SFK phosphorylation in both wild-type and G(q) deficient platelets. Together, these results indicate that SFK phosphorylation in response to thrombin receptor stimulation is downstream from G(q)/Ca(2+) signaling. Moreover, A23187-induced thromboxane A(2) synthesis, platelet aggregation, and secretion were inhibited by preincubation of platelets with a selective SFK inhibitor, PP2. AYPGKF-induced thromboxane A(2) production in wild-type and P2Y(12) deficient platelets was abolished by PP2, and AYPGKF-mediated P-selectin expression, integrin α(IIb)β(3) activation, and aggregation of P2Y(12) deficient platelets were partially inhibited by the PKC inhibitor Ro-31-8220, PP2, dimethyl-BAPTA, or LY294002, but were abolished by Ro-31-8220 plus PP2, dimethyl-BAPTA, or LY294002. These data indicate that Ca(2+)/SFKs/PI3K and PKC represent two alternative signaling pathways mediating G(q)-dependent platelet activation.
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Affiliation(s)
- Binggang Xiang
- Saha Cardiovascular Research Center, College of Medicine, University of Kentucky, Lexington, Kentucky 40536, USA
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18
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O'Brien KA, Gartner TK, Hay N, Du X. ADP-stimulated activation of Akt during integrin outside-in signaling promotes platelet spreading by inhibiting glycogen synthase kinase-3β. Arterioscler Thromb Vasc Biol 2012; 32:2232-40. [PMID: 22814751 DOI: 10.1161/atvbaha.112.254680] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Integrins mediate platelet adhesion and transmit outside-in signals leading to platelet spreading. Phosphoinositide 3-kinases (PI3Ks) play a critical role in outside-in signaling and platelet spreading; however, the mechanisms of PI3K activation and function in outside-in signaling are unclear. We sought to determine the role of the Akt family of serine/threonine kinases and activation mechanisms of the PI3K/Akt pathway in outside-in signaling. METHODS AND RESULTS Akt inhibitors and Akt3 knockout inhibited platelet spreading on fibrinogen, indicating that Akt is important in integrin outside-in signaling. Akt inhibitors and Akt3 knockout also diminished integrin-dependent phosphorylation of glycogen synthase kinase-3β. Inhibition of glycogen synthase kinase-3β reversed the inhibitory effects of Akt3 knockout and inhibitors of Akt or PI3K on platelet spreading, indicating that glycogen synthase kinase-3β is a downstream target of Akt in outside-in signaling. Integrin-dependent activation of the PI3K-Akt pathway requires Src family kinase. Akt phosphorylation is also significantly inhibited in ADP receptor P2Y12 knockout platelets and further inhibited in P2Y12 knockout platelets treated with a P2Y1 antagonist. Consistently, P2Y12 knockout and P2Y1 inhibition together reduced platelet spreading. CONCLUSIONS These results demonstrate that integrin outside-in signaling and platelet spreading requires Src family kinase-dependent and ADP receptor-amplified activation of the PI3K-Akt-GSK-3β pathway.
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Affiliation(s)
- Kelly A O'Brien
- Department of Pharmacology, University of Illinois College of Medicine, 835 S. Wolcott Avenue, Chicago, IL 60612, USA
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19
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Abstract
Integrin α2β1-mediated adhesion of human platelets to monomeric type I collagen or to the GFOGER peptide caused a time-dependent activation of PI3K and Akt phosphorylation. This process was abrogated by pharmacologic inhibition of PI3Kβ, but not of PI3Kγ or PI3Kα. Moreover, Akt phosphorylation was undetectable in murine platelets expressing a kinase-dead mutant of PI3Kβ (PI3Kβ(KD)), but occurred normally in PI3Kγ(KD) platelets. Integrin α2β1 failed to stimulate PI3Kβ in platelets from phospholipase Cγ2 (PLCγ2)-knockout mice, and we found that intracellular Ca(2+) linked PLCγ2 to PI3Kβ activation. Integrin α2β1 also caused a time-dependent stimulation of the focal kinase Pyk2 downstream of PLCγ2 and intracellular Ca(2+). Whereas activation of Pyk2 occurred normally in PI3Kβ(KD) platelets, stimulation of PI3Kβ was strongly reduced in Pyk2-knockout mice. Neither Pyk2 nor PI3Kβ was required for α2β1-mediated adhesion and spreading. However, activation of Rap1b and inside-out stimulation of integrin αIIbβ3 were reduced after inhibition of PI3Kβ and were significantly impaired in Pyk2-deficient platelets. Finally, both PI3Kβ and Pyk2 significantly contributed to thrombus formation under flow. These results demonstrate that Pyk2 regulates PI3Kβ downstream of integrin α2β1, and document a novel role for Pyk2 and PI3Kβ in integrin α2β1 promoted inside-out activation of integrin αIIbβ3 and thrombus formation.
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20
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Zhang G, Xiang B, Dong A, Skoda RC, Daugherty A, Smyth SS, Du X, Li Z. Biphasic roles for soluble guanylyl cyclase (sGC) in platelet activation. Blood 2011; 118:3670-9. [PMID: 21803853 PMCID: PMC3186338 DOI: 10.1182/blood-2011-03-341107] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 07/12/2011] [Indexed: 12/15/2022] Open
Abstract
Nitric oxide (NO) stimulates cGMP synthesis by activating its intracellular receptor, soluble guanylyl cyclase (sGC). It is a currently prevailing concept that No and cGMP inhibits platelet function. However, the data supporting the inhibitory role of NO/sGC/cGMP in platelets have been obtained either in vitro or using whole body gene deletion that affects vessel wall function. Here we have generated mice with sGC gene deleted only in megakaryocytes and platelets. Using the megakaryocyte- and platelet-specific sGC-deficient mice, we identify a stimulatory role of sGC in platelet activation and in thrombosis in vivo. Deletion of sGC in platelets abolished cGMP production induced by either NO donors or platelet agonists, caused a marked defect in aggregation and attenuated secretion in response to low doses of collagen or thrombin. Importantly, megakaryocyte- and platelet-specific sGC deficient mice showed prolonged tail-bleeding times and impaired FeCl₃-induced carotid artery thrombosis in vivo. Interestingly, the inhibitory effect of the NO donor SNP on platelet activation was sGC-dependent only at micromolar concentrations, but sGC-independent at millimolar concentrations. Together, our data demonstrate important roles of sGC in stimulating platelet activation and in vivo thrombosis and hemostasis, and sGC-dependent and -independent inhibition of platelets by NO donors.
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Affiliation(s)
- Guoying Zhang
- Division of Cardiovascular Medicine, Saha Cardiovascular Center, University of Kentucky, Lexington, KY, USA
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21
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Zhang G, Xiang B, Ye S, Chrzanowska-Wodnicka M, Morris AJ, Gartner TK, Whiteheart SW, White GC, Smyth SS, Li Z. Distinct roles for Rap1b protein in platelet secretion and integrin αIIbβ3 outside-in signaling. J Biol Chem 2011; 286:39466-77. [PMID: 21940635 DOI: 10.1074/jbc.m111.239608] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rap1b is activated by platelet agonists and plays a critical role in integrin α(IIb)β(3) inside-out signaling and platelet aggregation. Here we show that agonist-induced Rap1b activation plays an important role in stimulating secretion of platelet granules. We also show that α(IIb)β(3) outside-in signaling can activate Rap1b, and integrin outside-in signaling-mediated Rap1b activation is important in facilitating platelet spreading on fibrinogen and clot retraction. Rap1b-deficient platelets had diminished ATP secretion and P-selectin expression induced by thrombin or collagen. Importantly, addition of low doses of ADP and/or fibrinogen restored aggregation of Rap1b-deficient platelets. Furthermore, we found that Rap1b was activated by platelet spreading on immobilized fibrinogen, a process that was not affected by P2Y(12) or TXA(2) receptor deficiency, but was inhibited by the selective Src inhibitor PP2, the PKC inhibitor Ro-31-8220, or the calcium chelator demethyl-1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis. Clot retraction was abolished, and platelet spreading on fibrinogen was diminished in Rap1b-deficient platelets compared with wild-type controls. The defects in clot retraction and spreading on fibrinogen of Rap1b-deficient platelets were not rescued by addition of MnCl(2), which elicits α(IIb)β(3) outside-in signaling in the absence of inside-out signaling. Thus, our results reveal two different activation mechanisms of Rap1b as well as novel functions of Rap1b in platelet secretion and in integrin α(IIb)β(3) outside-in signaling.
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Affiliation(s)
- Guoying Zhang
- Division of Cardiovascular Medicine, The Gill Heart Institute, University of Kentucky, Lexington, Kentucky 40536, USA
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22
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Akbar H, Shang X, Perveen R, Berryman M, Funk K, Johnson JF, Tandon NN, Zheng Y. Gene targeting implicates Cdc42 GTPase in GPVI and non-GPVI mediated platelet filopodia formation, secretion and aggregation. PLoS One 2011; 6:e22117. [PMID: 21789221 PMCID: PMC3138762 DOI: 10.1371/journal.pone.0022117] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 06/16/2011] [Indexed: 11/22/2022] Open
Abstract
Background Cdc42 and Rac1, members of the Rho family of small GTPases, play critical roles in actin cytoskeleton regulation. We have shown previously that Rac1 is involved in regulation of platelet secretion and aggregation. However, the role of Cdc42 in platelet activation remains controversial. This study was undertaken to better understand the role of Cdc42 in platelet activation. Methodology/Principal Findings We utilized the Mx-cre;Cdc42lox/lox inducible mice with transient Cdc42 deletion to investigate the involvement of Cdc42 in platelet function. The Cdc42-deficient mice exhibited a significantly reduced platelet count than the matching Cdc42+/+ mice. Platelets isolated from Cdc42−/−, as compared to Cdc42+/+, mice exhibited (a) diminished phosphorylation of PAK1/2, an effector molecule of Cdc42, (b) inhibition of filopodia formation on immobilized CRP or fibrinogen, (c) inhibition of CRP- or thrombin-induced secretion of ATP and release of P-selectin, (d) inhibition of CRP, collagen or thrombin induced platelet aggregation, and (e) minimal phosphorylation of Akt upon stimulation with CRP or thrombin. The bleeding times were significantly prolonged in Cdc42−/− mice compared with Cdc42+/+ mice. Conclusion/Significance Our data demonstrate that Cdc42 is required for platelet filopodia formation, secretion and aggregation and therefore plays a critical role in platelet mediated hemostasis and thrombosis.
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Affiliation(s)
- Huzoor Akbar
- Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America.
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Abstract
Upon vascular injury, platelets are activated by adhesion to adhesive proteins, such as von Willebrand factor and collagen, or by soluble platelet agonists, such as ADP, thrombin, and thromboxane A(2). These adhesive proteins and soluble agonists induce signal transduction via their respective receptors. The various receptor-specific platelet activation signaling pathways converge into common signaling events that stimulate platelet shape change and granule secretion and ultimately induce the "inside-out" signaling process leading to activation of the ligand-binding function of integrin α(IIb)β(3). Ligand binding to integrin α(IIb)β(3) mediates platelet adhesion and aggregation and triggers "outside-in" signaling, resulting in platelet spreading, additional granule secretion, stabilization of platelet adhesion and aggregation, and clot retraction. It has become increasingly evident that agonist-induced platelet activation signals also cross talk with integrin outside-in signals to regulate platelet responses. Platelet activation involves a series of rapid positive feedback loops that greatly amplify initial activation signals and enable robust platelet recruitment and thrombus stabilization. Recent studies have provided novel insight into the molecular mechanisms of these processes.
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Affiliation(s)
- Zhenyu Li
- Department of Medicine, University of Kentucky
| | | | | | - Xiaoping Du
- Department of Pharmacology, University of Illinois at Chicago
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24
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Li D, D'Angelo L, Chavez M, Woulfe DS. Arrestin-2 differentially regulates PAR4 and ADP receptor signaling in platelets. J Biol Chem 2010; 286:3805-14. [PMID: 21106537 DOI: 10.1074/jbc.m110.118018] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Arrestins can facilitate desensitization or signaling by G protein-coupled receptors (GPCR) in many cells, but their roles in platelets remain uncharacterized. Because of recent reports that arrestins can serve as scaffolds to recruit phosphatidylinositol-3 kinases (PI3K)s to GPCRs, we sought to determine whether arrestins regulate PI3K-dependent Akt signaling in platelets, with consequences for thrombosis. Co-immunoprecipitation experiments demonstrate that arrestin-2 associates with p85 PI3Kα/β subunits in thrombin-stimulated platelets, but not resting cells. The association is inhibited by inhibitors of P2Y12 and Src family kinases (SFKs). The function of arrestin-2 in platelets is agonist-specific, as PAR4-dependent Akt phosphorylation and fibrinogen binding were reduced in arrestin-2 knock-out platelets compared with WT controls, but ADP-stimulated signaling to Akt and fibrinogen binding were unaffected. ADP receptors regulate arrestin recruitment to PAR4, because co-immunoprecipitates of arrestin-2 with PAR4 are disrupted by inhibitors of P2Y1 or P2Y12. P2Y1 may regulate arrestin-2 recruitment to PAR4 through protein kinase C (PKC) activation, whereas P2Y12 directly interacts with PAR4 and therefore, may help to recruit arrestin-2 to PAR4. Finally, arrestin2(-/-) mice are less sensitive to ferric chloride-induced thrombosis than WT mice, suggesting that arrestin-2 can regulate thrombus formation in vivo. In conclusion, arrestin-2 regulates PAR4-dependent signaling pathways, but not responses to ADP alone, and contributes to thrombus formation in vivo.
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Affiliation(s)
- Dongjun Li
- Department of Biological Sciences, University of Delaware, Newark, Delaware 19716, USA
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