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Abstract
Reviewed are new concepts and models of Ca(2+) signalling originating from work with various animal cells, as well as the applicability of these models to the signalling systems used by blood platelets. The following processes and mechanisms are discussed: Ca(2+) oscillations and waves; Ca(2+) -induced Ca(2+) release; involvement of InsP(3)-receptors and quanta1 release of Ca(2+); different pathways of phospholipase C activation; heterogeneity in the intracellular Ca(2+) stores; store-and receptor-regulated Ca(2+) entry. Additionally, some typical aspects of Ca(2+) signalling in platelets are reviewed: involvement of protein serine/threonine and tyrosine kinases in the regulation of signal transduction; possible functions of platelet glycoproteins; and the importance of Ca(2+) for the exocytotic and procoagulant responses.
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Affiliation(s)
- J W Heemskerk
- Departments of Human Biology/ Biochemistry, University of Limburg, P.O. 616, 6200, MD, Maastricht, The Netherlands
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2
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Marrero MB, Schieffer B, Bernstein KE, Ling BN. SYMPOSIUM: Experimental Biology 1995 Role of Mesangial Cell Ion Transport in Glomerular Physiology and Disease: ANGIOTENSIN II-INDUCED TYROSINE PHOSPHORYLATION IN MESANGIAL AND VASCULAR SMOOTH MUSCLE CELLS. Clin Exp Pharmacol Physiol 2010. [DOI: 10.1111/j.1440-1681.1996.tb03067.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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3
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Jackson SP, Schoenwaelder SM. PI 3-Kinase p110β regulation of platelet integrin α(IIb)β3. Curr Top Microbiol Immunol 2010; 346:203-24. [PMID: 20517720 DOI: 10.1007/82_2010_61] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hemopoietic cells express relatively high levels of the type I phosphoinositide (PI) 3-kinase isoforms, with p110δ and γ exhibiting specialized signaling functions in neutrophils, monocytes, mast cells, and lymphocytes. In platelets, p110β appears to be the dominant PI 3-kinase isoform regulating platelet activation, irrespective of the nature of the primary platelet activating stimulus. Based on findings with isoform-selective p110β pharmacological inhibitors and more recently with p110β-deficient platelets, p110β appears to primarily signal downstream of G(i)- and tyrosine kinase-coupled receptors. Functionally, inhibition of p110β kinase function leads to a marked defect in integrin α(IIb)β₃ adhesion and reduced platelet thrombus formation in vivo. This defect in platelet adhesive function is not associated with increased bleeding, suggesting that therapeutic targeting of p110β may represent a safe approach to reduce thrombotic complications in patients with cardiovascular disease.
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Affiliation(s)
- Shaun P Jackson
- Australian Centre for Blood Diseases, Alfred Medical Research and Education Precinct (AMREP), Monash University, Melbourne, VIC, 3004, Australia.
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Schoenwaelder SM, Ono A, Nesbitt WS, Lim J, Jarman K, Jackson SP. Phosphoinositide 3-kinase p110 beta regulates integrin alpha IIb beta 3 avidity and the cellular transmission of contractile forces. J Biol Chem 2009; 285:2886-96. [PMID: 19940148 DOI: 10.1074/jbc.m109.029132] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide (PI) 3-kinase (PI3K) signaling processes play an important role in regulating the adhesive function of integrin alpha(IIb)beta(3), necessary for platelet spreading and sustained platelet aggregation. PI3K inhibitors are effective at reducing platelet aggregation and thrombus formation in vivo and as a consequence are currently being evaluated as novel antithrombotic agents. PI3K regulation of integrin alpha(IIb)beta(3) activation (affinity modulation) primarily occurs downstream of G(i)-coupled and tyrosine kinase-linked receptors linked to the activation of Rap1b, AKT, and phospholipase C. In the present study, we demonstrate an important role for PI3Ks in regulating the avidity (strength of adhesion) of high affinity integrin alpha(IIb)beta(3) bonds, necessary for the cellular transmission of contractile forces. Using knock-out mouse models and isoform-selective PI3K inhibitors, we demonstrate that the Type Ia p110 beta isoform plays a major role in regulating thrombin-stimulated fibrin clot retraction in vitro. Reduced clot retraction induced by PI3K inhibitors was not associated with defects in integrin alpha(IIb)beta(3) activation, actin polymerization, or actomyosin contractility but was associated with a defect in integrin alpha(IIb)beta(3) association with the contractile cytoskeleton. Analysis of integrin alpha(IIb)beta(3) adhesion contacts using total internal reflection fluorescence microscopy revealed an important role for PI3Ks in regulating the stability of high affinity integrin alpha(IIb)beta(3) bonds. These studies demonstrate an important role for PI3K p110 beta in regulating the avidity of high affinity integrin alpha(IIb)beta(3) receptors, necessary for the cellular transmission of contractile forces. These findings may provide new insight into the potential antithrombotic properties of PI3K p110 beta inhibitors.
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Affiliation(s)
- Simone M Schoenwaelder
- Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct, 89 Commercial Road, Melbourne, Victoria 3004, Australia.
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5
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Feijge MA, Lacabaratz-Porret C, van Pampus EC, Hamulyàk K, Lévy-Toledano S, Enouf J, Heemskerk JW. Contribution of thromboxane and endomembrane Ca2+-ATPases to variability in Ca2+ signalling of platelets from healthy volunteers. Platelets 2009; 9:179-83. [PMID: 16793698 DOI: 10.1080/09537109876654] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Inter-individual variability in Ca2+ signal generation was studied in platelets from 15 healthy volunteers. The possible involvement of variation in thromboxane A production and variation in sarco/endoplasmic reticulum Ca2+-ATPases (SERCAs) was investigated by using platelets isolated before and after intake of 500 mg aspirin, and by measuring the expression levels of two main SERCA isoforms (SERCA-2b and PL/IM 430-recognizable SERCA). Considerable difference in Ca2+ responses were detected after platelet stimulation with thrombin, collagen or the SERCA-2b inhibitor, thapsigargin (TG), with inter-individual coefficients of variance of 22-43% in the absence and 15-41% in the presence of aspirin. Differences in thromboxane A2 generation and SERCA expression contributed to this variability in various ways. In the absence of aspirin, the amount of formed thromboxane A2 partially explains the level of the Ca2+ response induced by TG. On the other hand, in the absence of thromboxane-dependent effects, the expression levels of SERCA-2b and SERCA PL/IM 430 were inversely related to the responses evoked by collagen and TG, respectively. None of these factors were related to the level of the thrombin-evoked Ca2+ signal.
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Affiliation(s)
- M A Feijge
- Department of Human Biology, University of Maastricht, The Netherlands
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6
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Derian CK, Santulli RJ, Tomko KA, Haertlein BJ, Andrade-Gordon P. Species differences in platelet responses to thrombin and SFLLRN. receptor-mediated calcium mobilization and aggregation, and regulation by protein kinases. Thromb Res 2005; 78:505-19. [PMID: 15714752 DOI: 10.1016/0049-3848(95)00084-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The thrombin receptor on human platelets is activated by thrombin to stimulate platelet aggregation through the tethered ligand SFLLRN. This study examined the effects of thrombin and SFLLRN on aggregation and calcium mobilization ([Ca2+]i) in rat, guinea pig, rabbit, dog, monkey, and human platelets, and the role of protein kinases in regulating these functions. Thrombin induced platelet aggregation and [Ca2+]i in all species studied; however, only guinea pig, monkey and human platelets were responsive to SFLLRN. Similar species specific effects were obtained with [Ca2+]i studies. The kinetic profile for [Ca2+]i differed among species, suggesting that regulatory mechanisms for calcium differed between agonists and among species. Staurosporine, a non-selective inhibitor of protein kinases, inhibited platelet aggregation induced by thrombin or SFLLRN in all species. Staurosporine inhibited thrombin-induced [Ca2+]i in guinea pigs, had no effect in rat, and increased [Ca2+]i in all other species. Staurosporine inhibited SFLLRN-induced [Ca2+]i in guinea pig, yet had no effect in monkey or human. Tyrphostin 23, a specific inhibitor of tyrosine protein kinases, inhibited thrombin-induced aggregation of rabbit, monkey, dog and human platelets. SFLLRN-induced aggregation was also inhibited by tyrphostin 23. Tyrphostin 23 inhibited [Ca2+]i induced by either thrombin or SFLLRN in all species. Based on the differential response to agonist stimulation, we propose that thrombin can activate platelets via SFLLRN-dependent and independent mechanisms, which could involve yet unrecognized subtypes of the thrombin receptor or distinct cellular activating mechanisms. Furthermore, differential regulation of calcium mobilization and aggregation was observed in those platelets responding to either thrombin or SFLLRN.
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Affiliation(s)
- C K Derian
- Drug Discovery Research, The R. W. Johnson Pharmaceutical Research Institute Spring House, PA 19477, USA
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7
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Larrucea S, González-Manchón C, Butta N, Arias-Salgado EG, Shen L, Ayuso MS, Parrilla R. Agonist-induced aggregation of Chinese hamster ovary cells coexpressing the human receptors for fibrinogen (integrin alphaIIbbeta3) and the platelet-activating factor: dissociation between adhesion and aggregation. Blood 2002; 99:2819-27. [PMID: 11929771 DOI: 10.1182/blood.v99.8.2819] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This work reports the establishment of a Chinese hamster ovary (CHO) cell line stably coexpressing the human alphaIIbbeta3 integrin and the platelet-activating factor receptor (PAFR). These cells aggregate in response to PAF in a Ca(++), alphaIIbbeta3, and soluble fibrinogen (Fg)-dependent manner that is prevented by PAF antagonists or alphaIIbbeta3 blockade. The aggregating response is accompanied by enhanced binding of fibrinogen and the activation-dependent IgM PAC1. This model has permitted us to identify, for the first time, intracellular signals distinctly associated with either alphaIIbbeta3-mediated adhesion or aggregation. Nonreceptor activation of protein kinase C (PKC) by phorbol ester produced cellular adhesion and spreading onto immobilized Fg, but it was not a sufficient signal to provoke cellular aggregation. Moreover, inhibition of PKC impeded the PAF stimulation of cellular adhesion, whereas the aggregation was not prevented. The PAF-induced cellular aggregation was distinctly associated with signaling events arising from the liganded Fg receptor and the agonist-induced stimulation of a calcium/calmodulin-dependent signaling pathway. Sustained tyrosine phosphorylation of both mitogen-activated protein kinase (MAPK) and an approximately 100-kd protein was associated with the PAF-induced aggregation, whereas phosphorylation of focal adhesion kinase (FAK) was preferably associated with cellular adherence and spreading onto immobilized Fg.
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Affiliation(s)
- Susana Larrucea
- Department of Physiopathology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Madrid, Spain
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8
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Ryals PE, Bae S, Patterson CE. Evidence for early signaling events in stomatin-induced differentiation of Tetrahymena vorax. J Eukaryot Microbiol 1999; 46:77-83. [PMID: 10188263 DOI: 10.1111/j.1550-7408.1999.tb04587.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of stomatin-induced differentiation of Tetrahymena vorax was investigated by in vivo protease degradation of cell surface proteins, the direct measurement of products formed from the activation of phospholipase C, and the use of an array of signal transduction inhibitors/activators. The data indicate that a surface-exposed protein is required for stomatin to signal the cells to differentiate and that the cells are committed to the differentiation pathway within two hours after exposure to stomatin. Analysis of radiolabeled polyphosphoinositols and inositol lipids from control and stomatin-treated populations in the presence of 10 mM LiCl were consistent with a rapid activation of phospholipase C. Within five min following addition of stomatin, this resulted in an increase in polyphosphoinositols and a concomitant decrease in the relative amounts of phosphatidylinositol bisphosphate and phosphatidylinositol trisphosphate.
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Affiliation(s)
- P E Ryals
- Department of Biochemistry and Molecular Biology, Mississippi State University 39762, USA.
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Pasquet JM, Dachary-Prigent J, Nurden AT. Microvesicle release is associated with extensive protein tyrosine dephosphorylation in platelets stimulated by A23187 or a mixture of thrombin and collagen. Biochem J 1998; 333 ( Pt 3):591-9. [PMID: 9677317 PMCID: PMC1219621 DOI: 10.1042/bj3330591] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phosphatidylserine exposure and microvesicle release give rise to procoagulant activity during platelet activation. We have previously shown that whereas the Ca2+ ionophore A23187 and 2,5-di-(t-butyl)-1, 4-benzohydroquinone, a Ca2+-ATPase inhibitor, induce phosphatidylserine exposure, only the former triggers microvesicle release. We now report that microvesicle formation with ionophore A23187 is specifically associated with mu-calpain activation, increased protein tyrosine phosphatase (PTP) activity and decreased tyrosine phosphorylation. The degree to which calpain and individual PTPs were activated in response to A23187 depended on the extent of bivalent cation chelation in the external medium. EGTA (2 mM) blocked or severely retarded their activation, and addition of extracellular Ca2+ in excess (2 mM) resulted in virtually immediate tyrosine dephosphorylation. Dephosphorylation was correlated with an increase in total PTP activity in platelet lysates. In platelets stimulated by a combination of thrombin and collagen, only the subpopulation undergoing microvesicle release and isolated by their binding to annexin-V-coated magnetic beads exhibited protein tyrosine dephosphorylation. Detection of PTP activity in an 'in-gel' assay showed the Ca2+-dependent appearance of active low-molecular-mass bands at 38, 36 and 27 kDa. Individual PTPs varied in their protease sensitivity to changes in intracellular Ca2+ levels. For example, PTP1B was a more sensitive substrate than SH2-domain-containing tyrosine phosphatase-1 for mu-calpain cleavage. Incubation of platelets with the PTP inhibitors, phenylarsine oxide and benzylphosphonic acid acetoxymethyl ester, led to increased tyrosine phosphorylation and the surface expression of aminophospholipids but little microvesicle formation. Furthermore, microvesicle release in response to ionophore A23187 was inhibited. We conclude that platelet microvesicle formation is associated with extensive protein tyrosine dephosphorylation.
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Affiliation(s)
- J M Pasquet
- UMR 5533 CNRS, Hôpital Cardiologique, 33604 Pessac, France
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10
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Lopez-Ilasaca M. Signaling from G-protein-coupled receptors to mitogen-activated protein (MAP)-kinase cascades. Biochem Pharmacol 1998; 56:269-77. [PMID: 9744561 DOI: 10.1016/s0006-2952(98)00059-8] [Citation(s) in RCA: 217] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Heterotrimeric GTP-binding protein (G-protein)-coupled receptors are able to induce a variety of responses including cell proliferation, differentiation, and activation of several intracellular kinase cascades. Prominent among these kinases are the activation of mitogen-activated protein (MAP) kinase, including the extracellular signal-regulated kinases (ERKs), ERK1 and ERK2 (p44mapk and p42mapk, respectively); stress-activated protein kinases (SAPKs/JNKs); and p38 kinase. These receptors signal through G-proteins. Recent data have shown that the activation of mitogen-activated protein/ERK kinase induced by G-protein-coupled receptors is mediated by both Galpha and Gbetagamma subunits involving a common signaling pathway with receptor-tyrosine-kinases. Gbetagamma-mediated mitogen-activated protein kinase activation is mediated by activation of phosphoinositide 3-kinase, followed by a tyrosine phosphorylation event, and proceeds in a sequence of events that involve functional association among the adaptor proteins Shc, Grb2, and Sos. SAPKs/JNKs and p38 are able to be activated by Gbetagamma proteins in a pathway involving Rho family proteins including RhoA, Rac1, and Cdc42.
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Affiliation(s)
- M Lopez-Ilasaca
- Max-Planck-Research Unit Molecular Cell Biology, Medical Faculty, University of Jena, Germany.
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11
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Déry O, Corvera CU, Steinhoff M, Bunnett NW. Proteinase-activated receptors: novel mechanisms of signaling by serine proteases. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C1429-52. [PMID: 9696685 DOI: 10.1152/ajpcell.1998.274.6.c1429] [Citation(s) in RCA: 594] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Although serine proteases are usually considered to act principally as degradative enzymes, certain proteases are signaling molecules that specifically regulate cells by cleaving and triggering members of a new family of proteinase-activated receptors (PARs). There are three members of this family, PAR-1 and PAR-3, which are receptors for thrombin, and PAR-2, a receptor for trypsin and mast cell tryptase. Proteases cleave within the extracellular NH2-terminus of their receptors to expose a new NH2-terminus. Specific residues within this tethered ligand domain interact with extracellular domains of the cleaved receptor, resulting in activation. In common with many G protein-coupled receptors, PARs couple to multiple G proteins and thereby activate many parallel mechanisms of signal transduction. PARs are expressed in multiple tissues by a wide variety of cells, where they are involved in several pathophysiological processes, including growth and development, mitogenesis, and inflammation. Because the cleaved receptor is physically coupled to its agonist, efficient mechanisms exist to terminate signaling and prevent uncontrolled stimulation. These include cleavage of the tethered ligand, receptor phosphorylation and uncoupling from G proteins, and endocytosis and lysosomal degradation of activated receptors.
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Affiliation(s)
- O Déry
- Department of Surgery, University of California, San Francisco 94143-0660, USA
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12
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Francischetti IM, Ghazaleh FA, Reis RA, Carlini CR, Guimarães JA. Convulxin induces platelet activation by a tyrosine-kinase-dependent pathway and stimulates tyrosine phosphorylation of platelet proteins, including PLC gamma 2, independently of integrin alpha IIb beta 3. Arch Biochem Biophys 1998; 353:239-50. [PMID: 9606958 DOI: 10.1006/abbi.1998.0598] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
1Convulxin (Cvx) is a well-characterized platelet aggregating glycoprotein isolated from Crotalus durissus terrificus and C. d. cascavella venoms. In the present report we show that Cvx induces tyrosine phosphorylation of human platelet proteins, including phospholipase C-gamma 2 (PLC gamma 2), and also stimulates [3H]arachidonic acid ([3H]AA) mobilization, pleckstrin phosphorylation, and an increase in the cytosolic Ca2+ concentration ([Ca2+]in) due to both Ca2+ entry and internal Ca2+ mobilization. Staurosporine, a potent protein kinase inhibitor, and genistein, a specific inhibitor of protein tyrosine kinases (PTK), were used to evaluate the role of protein tyrosine phosphorylation (PTP) in the signal transduction evoked by Cvx. Staurosporine and genistein inhibited in a dose-dependent manner platelet aggregation induced by Cvx. Both inhibitors significantly blocked to near basal levels breakdown of phosphatidylinositol 4,5-bisphosphate from [myo-2-3H]inositol-labeled platelets and the production of [3H]AA metabolites from [3H]AA-labeled platelets after challenge with Cvx. Cvx provokes an increase in [Ca2+]in in Fura-2-loaded platelets that was abolished by concentrations of staurosporine which also inhibited Cvx-induced platelet aggregation. In addition, Cvx stimulates a rapid increase in tyrosine phosphorylation of human platelets proteins with molecular masses of 40, 72/74, 78/80, 105, 120, and 145 kDa, followed by dephosphorylation. Furthermore, Cvx stimulates a rapid tyrosyl phosphorylation of a 145-kDa molecular mass protein that was identified as PLC gamma 2. PTP induced by Cvx was not inhibited when platelets were stimulated in the presence of indomethacin, apyrase, EDTA, or RGDS peptide. These results indicate that PTP is chronologically proximal to Cvx binding to platelets, and is independent of aggregation or fibrinogen binding to the integrin alpha IIb beta 3. On the other hand, the dephosphorylation step is inhibited by RGDS peptide or EDTA, suggesting that integrin alpha IIb beta 3 is envolved in this step. The profile obtained with Cvx resembles that obtained in platelets adherent to an immobilized ligand, such as immobilized collagen, in which PTP is independent on integrin alpha IIb beta 3. Thus, we suggest that Cvx is an example of a protein with adhesion molecule-like properties; i.e., it is an adhesin. In conclusion, our results show that Cvx induces multiple signaling pathways in platelets via a PTK-dependent pathway involving PLC gamma 2 tyrosyl phosphorylation, with the subsequent platelet responses. Cvx is unique among platelet soluble agonists because under test tube stirring conditions it induces a PTP profile independently of integrin alpha IIb beta 3.
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Affiliation(s)
- I M Francischetti
- Department of Medical Biochemistry, Federal University of Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Brazil
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13
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Hers I, Donath J, van Willigen G, Akkerman JW. Differential involvement of tyrosine and serine/threonine kinases in platelet integrin alphaIIbbeta3 exposure. Arterioscler Thromb Vasc Biol 1998; 18:404-14. [PMID: 9514409 DOI: 10.1161/01.atv.18.3.404] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The relative contributions of protein tyrosine kinases (PTKs) and protein kinase C isoenzymes (PKCs), a family of serine/threonine kinases, in integrin alpha(IIb)beta3 (glycoprotein IIb/IIIa) exposure are the subject of much controversy. In the present study we measured the effect of the PTK inhibitor herbimycin A and the PKC inhibitor bisindolylmaleimide I on 125I-fibrinogen binding to alpha(IIb)beta3 and on aggregation/secretion induced by different agonists. Dose-response studies showed complete inhibition of alpha(IIb)beta3 exposure by 30 micromol/L (ADP stimulation) and 35 to 40 micromol/L (alpha-thrombin stimulation) herbimycin A. In contrast, inhibition of exposure by bisindolylmaleimide I varied from none (for ADP and epinephrine), to 30% (for platelet-activating factor), and to approximately 80% (for alpha-thrombin). Studies with a submaximal dose of herbimycin A (approximately 50% inhibition of the ADP-response) and a maximal dose of bisindolylmaleimide I showed that optical aggregation had a similar sensitivity to the inhibitors as alpha(IIb)beta3 exposure with minimal interference by secreted ADP. Thus, the relative contributions of tyrosine and serine/threonine kinases in alpha(IIb)beta3 exposure and aggregation differ among the different agonists, with an exclusive role for PTKs in ADP- and epinephrine-induced responses and a role for both PTKs and PKCs in responses induced by platelet-activating factor and alpha-thrombin.
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Affiliation(s)
- I Hers
- Department of Haematology, University Hospital Utrecht, and the Institute for Biomembranes, Utrecht University, The Netherlands
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14
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Heemskerk JW, Feijge MA, Henneman L, Rosing J, Hemker HC. The Ca2+-mobilizing potency of alpha-thrombin and thrombin-receptor-activating peptide on human platelets -- concentration and time effects of thrombin-induced Ca2+ signaling. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 249:547-55. [PMID: 9370366 DOI: 10.1111/j.1432-1033.1997.00547.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In single platelets and in suspensions of platelets, alpha-thrombin evokes dose-dependent, transient increases in cytosolic Ca2+ concentration, [Ca2+]i, which are more prolonged than the [Ca2+]i transients evoked by other platelet agonists such as the thrombin-receptor-activating hexapeptide SFLLRN, thromboxane A2 analog U46619, and ADP. As a quantity taking into account both the magnitude and length of the Ca2+ response, we defined the Ca2+-mobilizing potency (CMP) of an agonist as the integrated rise in [Ca2+]i during the time of the Ca2+ signal. It was observed that: (a) the CMP increased with the agonist concentration in a saturating way, its maximal value being about four-times higher with alpha-thrombin than with SFLLRN; (b) the high CMP of alpha-thrombin was for only a small part due to endogenous production of ADP or thromboxane, and was mainly a consequence of prolonged influx of external Ca2+; (c) the CMP declined when alpha-thrombin was inactivated during the course of the Ca2+ signal; (d) CMP values increased with the agonist concentration upon sequential addition of increasing amounts of alpha-thrombin or SFLLRN; (e) when alpha-thrombin was gradually added to the platelets or formed by an in situ reconstituted prothrombinase system (with factor Xa, factor Va, and prothrombin), integrated Ca2+ responses were a function of the product of the alpha-thrombin concentration and the time of its presence. However, in these cases, the final CMP values were independent of the rate of alpha-thrombin addition or formation. We conclude that alpha-thrombin-induced Ca2+ signals in platelets rely largely upon Ca2+ influx, are not, or only slightly, subjected to homologous desensitization, and reflect the enzymatic capacity of alpha-thrombin to cleave protease-activated receptors. Thus, the high and prolonged Ca2+ signal induced by alpha-thrombin is due to continuous receptor cleavage without desensitizing effects of previously cleaved receptors.
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Affiliation(s)
- J W Heemskerk
- Department of Biochemistry, Maastricht University, The Netherlands.
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15
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Kashiwagi H, Schwartz MA, Eigenthaler M, Davis KA, Ginsberg MH, Shattil SJ. Affinity modulation of platelet integrin alphaIIbbeta3 by beta3-endonexin, a selective binding partner of the beta3 integrin cytoplasmic tail. J Cell Biol 1997; 137:1433-43. [PMID: 9182673 PMCID: PMC2132534 DOI: 10.1083/jcb.137.6.1433] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/1996] [Revised: 03/24/1997] [Indexed: 02/04/2023] Open
Abstract
Platelet agonists increase the affinity state of integrin alphaIIbbeta3, a prerequisite for fibrinogen binding and platelet aggregation. This process may be triggered by a regulatory molecule(s) that binds to the integrin cytoplasmic tails, causing a structural change in the receptor. beta3-Endonexin is a novel 111-amino acid protein that binds selectively to the beta3 tail. Since beta3-endonexin is present in platelets, we asked whether it can affect alphaIIbbeta3 function. When beta3-endonexin was fused to green fluorescent protein (GFP) and transfected into CHO cells, it was found in both the cytoplasm and the nucleus and could be detected on Western blots of cell lysates. PAC1, a fibrinogen-mimetic mAb, was used to monitor alphaIIbbeta3 affinity state in transfected cells by flow cytometry. Cells transfected with GFP and alphaIIbbeta3 bound little or no PAC1. However, those transfected with GFP/beta3-endonexin and alphaIIbbeta3 bound PAC1 specifically in an energy-dependent fashion, and they underwent fibrinogen-dependent aggregation. GFP/beta3-endonexin did not affect levels of surface expression of alphaIIbbeta3 nor did it modulate the affinity of an alphaIIbbeta3 mutant that is defective in binding to beta3-endonexin. Affinity modulation of alphaIIbbeta3 by GFP/beta3-endonexin was inhibited by coexpression of either a monomeric beta3 cytoplasmic tail chimera or an activated form of H-Ras. These results demonstrate that beta3-endonexin can modulate the affinity state of alphaIIbbeta3 in a manner that is structurally specific and subject to metabolic regulation. By analogy, the adhesive function of platelets may be regulated by such protein-protein interactions at the level of the cytoplasmic tails of alphaIIbbeta3.
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Affiliation(s)
- H Kashiwagi
- Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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16
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Schieffer B, Drexler H, Ling BN, Marrero MB. G protein-coupled receptors control vascular smooth muscle cell proliferation via pp60c-src and p21ras. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:C2019-30. [PMID: 9227431 DOI: 10.1152/ajpcell.1997.272.6.c2019] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The binding of vasoactive peptides to their respective G protein-coupled receptors has been implicated in the pathogenesis of vascular smooth muscle cell proliferation, leading to the development of hypertension, arteriosclerosis, and restenosis after vascular injury. We previously showed that the cytosolic tyrosine kinase pp60c-src is crucial for angiotensin II (ANG II)-induced activation of the protooncogene p21ras. Therefore, we investigated the role of pp60c-src and p21ras in rat aortic smooth muscle cell proliferation induced by several G protein-coupled receptors. ANG II, endothelin-1, or thrombin increased cell proliferation and DNA synthesis. Electroporation of anti-pp60c-src antibodies into cells abolished proliferation in response to these G protein-coupled receptor ligands but not in response to platelet-derived growth factor-BB (PDGF-BB). In contrast, electroporation of anti-p21ras antibody completely blocked DNA synthesis and cell proliferation in response to ANG II, endothelin-1, thrombin, and PDGF-BB. Our data indicate that the pp60c-src tyrosine kinase is necessary and specific for vascular smooth muscle cell proliferation and DNA synthesis in response to G protein-coupled receptors but not classic growth factor receptors.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Antibodies/pharmacology
- Aorta
- Becaplermin
- Biphenyl Compounds/pharmacology
- Cell Division/drug effects
- Cells, Cultured
- DNA/biosynthesis
- Electroporation
- Endothelin-1/pharmacology
- GTP-Binding Proteins/physiology
- Imidazoles/pharmacology
- Kinetics
- Losartan
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Platelet-Derived Growth Factor/pharmacology
- Proto-Oncogene Proteins c-sis
- Proto-Oncogene Proteins p21(ras)/metabolism
- Proto-Oncogene Proteins pp60(c-src)/metabolism
- Rats
- Receptors, Angiotensin/drug effects
- Receptors, Angiotensin/physiology
- Receptors, Cell Surface/drug effects
- Receptors, Cell Surface/physiology
- Receptors, Endothelin/drug effects
- Receptors, Endothelin/physiology
- Receptors, Platelet-Derived Growth Factor/drug effects
- Receptors, Platelet-Derived Growth Factor/physiology
- Receptors, Thrombin/drug effects
- Receptors, Thrombin/physiology
- Tetrazoles/pharmacology
- Thrombin/pharmacology
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Affiliation(s)
- B Schieffer
- Division of Cardiology, Hannover Medical School, Germany
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17
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Baldassare JJ, Henderson PA, Tarver A, Fisher GJ. Thrombin activation of human platelets dissociates a complex containing gelsolin and actin from phosphatidylinositide-specific phospholipase Cgamma1. Biochem J 1997; 324 ( Pt 1):283-7. [PMID: 9164868 PMCID: PMC1218428 DOI: 10.1042/bj3240283] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have examined the association of two cytoskeleton proteins, gelsolin and actin, with phosphatidylinositide-specific phospholipase Cgamma1 (PLCgamma1) in resting and thrombin-stimulated human platelets. In unstimulated platelets, gelsolin, actin and PLCgamma1 were immunoprecipitated as a complex by a polyclonal antibody to PLCgamma1. The association of gelsolin and actin was specific for PLCgamma1 because immunoprecipitates of PLCs beta2, beta3, gamma2 and delta1, which are also expressed in human platelets, did not contain detectable gelsolin or actin. Activation with thrombin resulted in platelet aggregation and the dissociation of gelsolin and actin from PLCgamma1. Inhibition of thrombin-induced platelet aggregation blocked the dissociation of gelsolin and actin from PLCgamma1. After stimulation with thrombin, PLCgamma1 activity in immunoprecipitates was increased 2-3-fold. This elevation in PLCgamma1 activity in response to thrombin activation was not observed when platelet aggregation was blocked. Although PLCgamma1 is tyrosine phosphorylated in response to many agonists, we could not detect, by Western analysis with anti-phosphotyrosine antibodies, tyrosine phosphorylation of PLCgamma1 immunoprecipitated from thrombin-stimulated platelets. These results demonstrate that PLCgamma1 is associated with gelsolin and actin in resting platelets, and that thrombin-induced platelet aggregation results in the dissociation of PLCgamma1 from gelsolin and actin, and the stimulation of PLCgamma1 activity.
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Affiliation(s)
- J J Baldassare
- Department of Pharmacological and Physiological Science, St. Louis Health Science Center, St. Louis, MO 63110, USA
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18
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Villar R, Alvariño MT, Flores R. Inhibition by ajoene of protein tyrosine phosphatase activity in human platelets. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1337:233-40. [PMID: 9048900 DOI: 10.1016/s0167-4838(96)00170-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The effects of ajoene (a potent antithrombotic agent obtained from garlic) on the tyrosine phosphorylation status of human platelet proteins were investigated by immunoblotting-based experiments using an anti-phosphotyrosine antibody. Incubation of platelets with ajoene enhanced the phosphorylation of at least four proteins (estimated MWs 76, 80, 84 and 120 kDa), both in resting platelets and in platelets subsequently stimulated with thrombin (0.1 U/ml). This effect was both dose- and incubation-time-dependent. High concentrations of ajoene (50 microM) or long periods of incubation (10 min) led to nonselective 'hyperphosphorylation' of numerous proteins. The effects of ajoene on protein tyrosine phosphatase (PTP) activity in platelet lysates were also investigated, PTP activity was inhibited when platelets were incubated with ajoene before lysis, but not when ajoene was added to lysates of platelets which had not been pre-exposed to ajoene.
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Affiliation(s)
- R Villar
- Departamento de Farmacoloxía, Facultade de Farmacia, Universidade de Santiago de Compostela, Spain.
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19
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Helgadóttir A, Halldórsson H, Magnúsdóttir K, Kjeld M, Thorgeirsson G. A role for tyrosine phosphorylation in generation of inositol phosphates and prostacyclin production in endothelial cells. Arterioscler Thromb Vasc Biol 1997; 17:287-94. [PMID: 9081683 DOI: 10.1161/01.atv.17.2.287] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have examined the effects of the protein tyrosine phosphatase inhibitor pervanadate on activation of signal transduction in human umbilical vein endothelial cells. Endothelial cells responded to pervanadate treatment by increasing tyrosine phosphorylation of cellular proteins, including phospholipase C (PLC) gamma 1, generating inositol phosphates (IPs), releasing arachidonic acid, and producing prostacyclin (prostaglandin [PG] I2). The dose and time responses for these events were similar. Tyrosine phosphorylation and formation of IPs in response to pervanadate were reduced by both staurosporine and genistein. Short-term incubation with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, which inhibits thrombin-induced IP generation, did not affect the IP response to pervanadate. To investigate the possible involvement of tyrosine phosphorylation in thrombin or histamine-induced IP generation and PGI2 production, we examined the effects of costimulation with pervanadate and either thrombin or histamine. These responses proved to be different. While the tyrosine phosphorylation of PLC gamma 1 was enhanced after cotreatment with thrombin and pervanadate compared with pervanadate alone, costimulation with pervanadate and histamine resulted in no more tyrosine phosphorylation of PLC gamma 1 than after pervanadate alone. Similarly, while cotreatment with pervanadate and thrombin caused synergistic increase in IP generation, costimulation with pervanadate and histamine resulted in an additive response. However, PGI2 responses to costimulation of pervanadate with either thrombin or histamine were both synergistic. Furthermore, stimulation with histamine, thrombin, or pervanadate all caused tyrosine phosphorylation of a mitogen-activated protein kinase (ERK1/p44). The results suggest that a tyrosine phosphorylation-dependent mechanism has a role in the phosphoinositide signal transduction pathway of human endothelial cells. Moreover, thrombin- but not histamine-induced generation of IPs appears to be partly caused by tyrosine phosphorylation of PLC gamma 1.
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Affiliation(s)
- A Helgadóttir
- Department of Pharmacology, University of Iceland, Reykjavik, Iceland
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20
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21
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Heemskerk JW, Farndale RW, Sage SO. Effects of U73122 and U73343 on human platelet calcium signalling and protein tyrosine phosphorylation. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1355:81-8. [PMID: 9030204 DOI: 10.1016/s0167-4889(96)00113-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have investigated the actions of the PLC inhibitor, U73122, and its close analogue, U73343, which does not inhibit PLC, in Fura-2-loaded human platelets. Rises in [Ca2+]i evoked by thrombin and collagen, and the TxA2-dependent rise in [Ca2+]i evoked by thapsigargin, were abolished by U73122, indicating that it inhibits the activity of both beta and gamma isoforms of PLC. The supposed control compound U73343, was found to inhibit TxA2 formation; it therefore partially inhibited the rise in [Ca2+]i evoked by low concentrations of thrombin, by thapsigargin or by collagen. U73343 had a greater effect than aspirin on the action of collagen, indicating an action on the TxA2-independent component of the signal, via PLC gamma-U73343 lowered TxA2 production by inhibiting the activation of cPLA2, probably at a tyrosine phosphorylation step. U73343 seems to inhibit only the tyrosine kinases involved in the activation of PLC gamma and the generation of TxA2. In contrast, U73122 increased tyrosine phosphorylation of platelet proteins, perhaps by inhibiting receptor independent tyrosine phosphatases, but inhibited all further tyrosine phosphorylation on addition of thrombin or other agonists.
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Affiliation(s)
- J W Heemskerk
- Department of Human Biology and Biochemistry, University of Limburg, Maastricht, The Netherlands
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22
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Mauco G, Artçanuthurry V, Pidard D, Grelac F, Maclouf J, Lévy-Tolédano S. Total inhibition of phospholipase C and phosphatidylinositol 3-kinase by okadaic acid in thrombin-stimulated platelets. Cell Signal 1997; 9:117-24. [PMID: 9067640 DOI: 10.1016/s0898-6568(96)00119-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The strong inhibition of thrombin-induced platelet functions induced by okadaic acid is not correlated with the partial modification of pleckstrin phosphorylation, which remains still phosphorylated two min after stimulation, indicating that protein kinase C is not affected by okadaic acid. We then investigated the effect of okadaic acid on platelet lipid metabolism. Our data indicate that inhibition indeed strongly affects phosphatidic acid as well as phosphatidylinositol 3,4-bisphosphate synthesis at low concentrations of okadaic acid, and phosphatidylinositol 4,5-bisphosphate at higher concentrations. Since thrombin-induced tyrosine phosphorylations were completely inhibited in the presence of okadaic acid, as a consequence, phosphatidylinositol 3-kinase was no longer detected in antiphosphotyrosine immunoprecipitates, thus explaining the absence of phosphatidylinositol, 3,4-bisphosphate synthesis. Finally, okadaic acid inhibited thrombin-induced fibrinogen binding, indicating that serine/threonine phosphatases may affect the inside-out signalling which regulates the alpha 11bb3 integrin, downstream protein kinase C activation.
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Affiliation(s)
- G Mauco
- INSERM Unité 326, Hôpital Purpan, Toulouse, France
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23
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Vostal JG, Shafer B, Mondoro TH, Fratantoni JC. Endogenous ADP prevents PGE1-induced tyrosine dephosphorylation of focal adhesion kinase in thrombin-activated platelets. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1314:1-12. [PMID: 8972712 DOI: 10.1016/s0167-4889(96)00066-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Prostaglandin E1(PGE1) inhibits tyrosine phosphorylation induced by low thrombin concentration (0.05 U/ml), but this is overcome by a high thrombin (2.0 U/ml) concentration. Thromboxane A2 and ADP are endogenous platelet agonists released during platelet activation which potentiate platelet responses. We investigated how these endogenous agonists influenced the effects of PGE1 on thrombin (2.0 U/ml)-induced tyrosine phosphorylation by removing released ADP with apyrase (2.0 U/ml) and by inhibiting thromboxane A2 synthesis with indomethacin (1 microM). Adding PGE1 (1 microM) before thrombin in apyrase/indomethacin(A/I)-treated platelets selectively prevented thrombin-induced tyrosine phosphorylation of a 117 kDa protein while other substrates were not affected. This selective effect was evident only in the presence of apyrase and was not dependent on indomethacin. Addition of PGE1 to A/I-treated platelets after thrombin also caused selective tyrosine dephosphorylation of the 117 kDa protein. Conditions which prevented thrombin-induced 117 kDa protein tyrosine phosphorylation also decreased fibrinogen binding to platelets. The 117 kDa protein was identified as the focal adhesion kinase (FAK) by immunoprecipitation with a monoclonal antibody to FAK and by absence of its tyrosine phosphorylation in the presence of RGDS peptide which inhibits fibrinogen binding and platelet aggregation. Thus, released endogenous ADP selectively prevents PGE1-mediated tyrosine dephosphorylation of platelet FAK most likely by stabilizing fibrinogen binding to platelets.
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Affiliation(s)
- J G Vostal
- Laboratory of Cellular Hematology, CBER-FDA, Bethesda, MD, USA.
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24
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Wheeler-Jones CP, May MJ, Morgan AJ, Pearson JD. Protein tyrosine kinases regulate agonist-stimulated prostacyclin release but not von Willebrand factor secretion from human umbilical vein endothelial cells. Biochem J 1996; 315 ( Pt 2):407-16. [PMID: 8615807 PMCID: PMC1217210 DOI: 10.1042/bj3150407] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The rapid synthesis and release of prostacyclin (PGI2) and the exocytotic secretion of von Willebrand Factor (vWF) elicited by activation of G-protein-coupled receptors on endothelium occur via signaling mechanisms which are incompletely defined. Activation of protein tyrosine kinases (PTKs) and modulation of the tyrosine-phosphorylation state of endogenous proteins have been implicated in several cellular processes including arachidonate release and exocytosis. In the present study we have examined the regulatory role of PTKs in agonist-stimulated release of PGI2 and vWF from human umbilical vein endothelial cells (HUVECs) using two chemically and mechanistically dissimilar PTK inhibitors (genistein and ST271). Genistein, but not the less active analogue daidzein, dose-dependently attenuated PGI2 release in response to thrombin and histamine (IC50 approx. 20 microM), and to the thrombin-receptor-activating peptide. A more potent inhibition of thrombin- and histamine-induced PGI2 synthesis was observed in cells exposed to ST271. In contrast, neither genistein nor ST271 modulated agonist-drive vWF secretion. At concentrations that abolished PGI2 release, genistein blocked thrombin- or histamine-evoked tyrosine phosphorylation of a 42 kDa protein. Ca2+ ionophore-induced PGI2 generation, but not vWF secretion, was also inhibited by both genistein and ST271, suggesting that these agents modulate PGI2 synthesis by acting at, or distal to, agonist-induced changes in intracellular CA2+ ([Ca2+]i). In fura-2-loaded HUVECs genistein partially reduced the histamine-induced peak [Ca2+]i but had no effect on the thrombin response. Ca(2+)-induced PGI2 release from electrically permeabilized HUVECs was abolished in the presence of ST271 or genistein, but not diadzein. The generation of PGI2 in response to exogenous arachidonic acid was not modulated by genistein or ST271, suggesting that PTK inhibitors do not directly inhibit cyclo-oxygenase activity. Taken together, these results suggest that PTKs regulate PGI2 synthesis and release in HUVECs by modulating, directly or indirectly, a CA(2+)-sensitive step upstream of cyclo-oxygenase.
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Affiliation(s)
- C P Wheeler-Jones
- Vascular Biology Research Centre, King's College London, Kensington, U.K
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25
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Zhang J, Zhang J, Shattil SJ, Cunningham MC, Rittenhouse SE. Phosphoinositide 3-kinase gamma and p85/phosphoinositide 3-kinase in platelets. Relative activation by thrombin receptor or beta-phorbol myristate acetate and roles in promoting the ligand-binding function of alphaIIbbeta3 integrin. J Biol Chem 1996; 271:6265-72. [PMID: 8626420 DOI: 10.1074/jbc.271.11.6265] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Platelets exposed to thrombin or thrombin receptor agonist peptide (SFLLRN) activate phospholipase C and protein kinase C (PKC), and accumulate 3-phosphorylated phosphoinositides (3-PPI) as a function of the activation and relocalization of two cytoskeletally-associated phosphoinositide 3-kinases (PI 3-K): p85/PI 3-K and PI 3-Kgamma. We now report that exposure of platelets to PKC-activating beta-phorbol myristate acetate (betaPMA) does not stimulate PI 3-Kgamma, but rather stimulates p85/PI 3-K, which associates with the cytoskeleton. Wortmannin is an inhibitor of both PI 3-Ks, known to act with more potency on p85/PI 3-K. betaPMA-stimulated 3-PPI accumulation is more sensitive to wortmannin (IC50 = 1.3 nM) than is SFLLRN- or thrombin-stimulated 3-PPI accumulation (IC50 = 10 nM). The activity of p85/PI 3-K in immunoprecipitates or in cytoskeletal fractions is inhibited more potently by exposure of platelets to wortmannin than is the activity of PI 3-Kgamma. betaPMA or SFLLRN promotes the conversion of platelet integrin alphaIIb/beta3 into a fibrinogen-binding form required for platelet aggregation. Activation of alphaIIb/beta3 in response to betaPMA or SFLLRN is inhibited by wortmannin with an IC50 of 1 nM in each case. Wortmannin inhibits neither activation of alphaIIb/beta3 by ligand-induced binding site antibody (anti-LIBS6 Fab) nor anti-LIBS6 Fab-induced platelet aggregation in the presence of fibrinogen, indicating that this type of "outside-in" signaling by alphaIIb/beta3 is largely PI 3-K-independent. We conclude that p85/PI 3-K, in preference to PI 3-Kgamma, contributes to activation of alphaIIb/beta3 when the thrombin receptor or PKC is stimulated.
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Affiliation(s)
- J Zhang
- Department of Pharmacology/Jefferson Cancer Institute, Philadelphia, Pennsylvania 19107, USA
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26
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Schieffer B, Paxton WG, Marrero MB, Bernstein KE. Importance of tyrosine phosphorylation in angiotensin II type 1 receptor signaling. Hypertension 1996; 27:476-80. [PMID: 8613189 DOI: 10.1161/01.hyp.27.3.476] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Angiotensin II is the major effector peptide of the renin-angiotensin system. In addition to its vasoconstrictor activity, angiotensin II stimulates smooth muscle cell growth in arterial hypertension and in models of vascular injury. The angiotensin II type 1 receptor is a seven-transmembrane receptor and is responsible for virtually all the physiological actions of angiotensin II. This class of receptor signals in part through its association with heterotrimeric G proteins. A newly developed concept for guanine nucleotide protein-coupled receptors is the activation of intracellular second-messenger proteins via tyrosine phosphorylation. For instance, angiotensin II stimulates the rapid tyrosine phosphorylation and activation of phospholipase C-gamma1. Also, angiotensin II stimulates the tyrosine phosphorylation of Janus kinases. In this review, we discuss early signaling events induced by angiotensin II with an emphasis on tyrosine phosphorylation. Understanding the importance of tyrosine phosphorylation in the signaling pathways of the angiotensin II type 1 receptor may lead to new treatment modalities for cardiovascular disease.
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Affiliation(s)
- B Schieffer
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 03022, USA
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27
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Abebe W, Ali N, Agrawal DK. Platelet-activating factor-induced inositol 1,4,5-trisphosphate generation in undifferentiated and differentiated U937 cells: role of tyrosine kinase. INTERNATIONAL JOURNAL OF IMMUNOPHARMACOLOGY 1996; 18:173-81. [PMID: 8796445 DOI: 10.1016/0192-0561(96)00004-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We compared the effect of platelet-activating factor (PAF) on inositol 1,4,5-trisphosphate (IP3) content in undifferentiated and differentiated U937 cells. In both cell types, PAF induced a rapid transient and concentration-dependent elevation of IP3 content. The production of IP3 in response to PAF was greater in differentiated than in undifferentiated cells. The increases in IP3 produced by PAF in both types of cell were inhibited by the PAF receptor antagonist, WEB 2086, as well as by the tyrosine kinase inhibitor, genistein. PAF also caused increased tyrosine phosphorylation of a 32 kDa protein substrate in both undifferentiated and differentiated cells. The magnitude of the phosphorylation was, however, greater in the differentiated cells. Genistein reduced the PAF-induced tyrosine phosphorylation of the substrate in both cell preparations. The specific binding of [3H]PAF was also markedly enhanced in differentiated cells. This effect was attenuated by genistein. The results indicate that PAF induces the production of IP3 in U937 cells via tyrosine kinase-mediated mechanisms and this process is augmented in differentiated cells.
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Affiliation(s)
- W Abebe
- Allergic Disease Center, Creighton University School of Medicine, Omaha, NE 68178, USA
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28
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Schieffer B, Bernstein KE, Marrero MB. The role of tyrosine phosphorylation in angiotensin II mediated intracellular signaling and cell growth. J Mol Med (Berl) 1996; 74:85-91. [PMID: 8820403 DOI: 10.1007/bf00196783] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Most cell types, including vascular smooth muscle cells and rat kidney mesangial cells, are controlled mainly by two types of cell surface receptors: (a) single membrane-spanning tyrosine kinase receptors for growth factors and (b) seven-transmembrane G-protein linked receptors for vasoactive peptides such as angiotensin II, vasopressin, and endothelin. These vasoactive peptide hormones also act as growth factors in normal and abnormal cell development. However, in contrast to the growth factor receptors (e.g., epidermal growth factor receptor and platelet-derived growth factor receptor), the G-protein linked receptors, such as the angiotensin II AT1 receptor, lack cytoplasmic tyrosine kinase domains. Nevertheless, angiotensin II has recently been demonstrated to cause increased tyrosine phosphorylation of numerous proteins in several cellular systems. For example, angiotensin II has been reported to induce the tyrosine phosphorylation of the gamma-isoform of phospholipase C, pp120, pp125FAK, and members of the janus kinase/signal transducer and activator of transcription pathway. Furthermore, angiotensin II seems to modulate the activity of the soluble cytoplasmic tyrosine kinase pp60c-src, and this tyrosine kinase has been implicated in the phosphorylation of some of the above proteins. Understanding the biochemistry of tyrosine phosphorylation involved in G-protein coupled receptors, such as the AT1 receptor, may therefore lead to the development of new pharmacological interventions important in cardiovascular diseases.
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Affiliation(s)
- B Schieffer
- Department of Pathology, Emory University, Atlanta, GA 30322, USA
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29
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Grand RJ, Turnell AS, Grabham PW. Cellular consequences of thrombin-receptor activation. Biochem J 1996; 313 ( Pt 2):353-68. [PMID: 8573065 PMCID: PMC1216916 DOI: 10.1042/bj3130353] [Citation(s) in RCA: 289] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- R J Grand
- CRC Institute for Cancer Studies, Medical School, University of Birmingham, Edgbaston, U.K
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30
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Dillon AM, Heath MF. Protein tyrosine phosphorylation in equine platelets: the effect of stimulation by thrombin and platelet-activating factor (PAF). Equine Vet J 1995; 27:448-58. [PMID: 8565942 DOI: 10.1111/j.2042-3306.1995.tb04426.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Protein tyrosine phosphorylation (PTP) in thrombin- and platelet-activating factor (PAF)-stimulated equine platelet activation was investigated in the absence and presence of 2 protein tyrosine kinase inhibitors (PTKIs), methyl 2,5-dihydroxycinnamate (MDHC) and genistein. Washed equine platelets aggregated irreversibly in response to thrombin or PAF in an agonist concentration dependent fashion. MDHC produced an MDHC concentration and time dependent inhibitory effect on rate and extent of thrombin- and PAF-induced aggregations, whereas the effect of genistein on the same parameters was only genistein concentration dependent. Western blotting demonstrated tyrosine phosphorylated proteins in resting platelets. Changes in the PTP pattern occurred both when platelets were stimulated with varying concentrations of thrombin or PAF for a standard time (3 min) or with a standard agonist concentration (0.17 u/ml thrombin or 10(-10) mol/l PAF) for varying times. Different patterns of PTP were produced by thrombin and PAF. 500 mumol/l MDHC and 300 mumol/l genistein each affected the PTP patterns produced in response to thrombin or PAF, but in different ways. PTP results with thrombin and PAF in the presence of 500 mumol/l MDHC were similar, as were those in the presence of 300 mumol/l genistein. However, there were many differences in the PTP results between thrombin (or PAF) in the presence of MDHC and between thrombin (or PAF) in the presence of genistein. Therefore, although both inhibitors are PTKIs, they have different effects on the PTP induced by either agonist. Our work has produced the first evidence of PTP in equine platelets. It is probable that the changes in PTP are related to events in the signal transduction pathway.
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Affiliation(s)
- A M Dillon
- University of Cambridge, Department of Clinical Veterinary Medicine, UK
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31
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Giesberts AN, van Willigen G, Lapetina EG, Akkerman JW. Regulation of platelet glycoprotein IIb/IIIa (integrin alpha IIB beta 3) function via the thrombin receptor. Biochem J 1995; 309 ( Pt 2):613-20. [PMID: 7542872 PMCID: PMC1135775 DOI: 10.1042/bj3090613] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Binding sites on glycoprotein (GP) IIb/IIIa exposed by 0.5 unit/ml alpha-thrombin are insensitive to prostaglandin I2 (PGI2), in contrast with sites exposed by ADP or platelet-activating factor. Here we show that the thrombin receptor agonist peptide (TRAP) (SFLLRN; 15 microM) opens almost the same number of GPIIb/IIIa molecules as 0.5 unit/ml alpha-thrombin (64840 +/- 8920 compared with 81050 +/- 6030 molecules of fibronectin bound/platelet), but these sites rapidly close on addition of PGI2. To investigate whether alpha-thrombin and TRAP initiate different signalling pathways, we measured phospholipase C (PLC)-mediated control of GPIIb/IIIa and its sensitivity to cyclic AMP. Optimal concentrations of alpha-thrombin and TRAP activated PLC maximally, but TRAP induced only about 50% protein kinase C PKC) activation after 10 min stimulation compared with alpha-thrombin. These concentrations also suppressed PGI2-induced cyclic AMP accumulation, with alpha-thrombin inducing complete inhibition and TRAP about 10% less. Direct activation of PKC by phorbol 12-myristate 13-acetate confirmed earlier observations that PGI2-induced cyclic AMP accumulation is partly inhibited via PKC. Applying different concentration of alpha-thrombin, TRAP or a combination of alpha-thrombin and the thrombin receptor inhibitory peptide (TRIP) (Mpr-F-Cha-Cha-RKPNDK-NH2; 800 microM) (Mpr, 3-mercaptopropionic acid; Cha, cyclohexylalanine), we show that the different means of stimulating the thrombin receptor all suppressed PGI2-induced cyclic AMP accumulation via (i) activation of PKC and (ii) activation of the heterotrimeric G-protein, Gi. We conclude that complete inhibition of cyclic AMP accumulation requires activation of both PKC and Gi, as observed with 0.5 unit/ml alpha-thrombin. Although TRAP almost fully exposes GPIIb/IIIa, its activation of PKC is incomplete, enabling PGI2 to raise cyclic AMP concentration from 1.4 +/- 0.7 to 4.1 +/- 1.3 nmol/10(11) platelets (P < 0.005) which is sufficient to close exposed GPIIb/IIIa molecules.
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Affiliation(s)
- A N Giesberts
- Department of Haematology, University Hospital Utrecht, The Netherlands
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32
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Turnell AS, Brant DP, Brown GR, Finney M, Gallimore PH, Kirk CJ, Pagliuca TR, Campbell CJ, Michell RH, Grand RJ. Regulation of neurite outgrowth from differentiated human neuroepithelial cells: a comparison of the activities of prothrombin and thrombin. Biochem J 1995; 308 ( Pt 3):965-73. [PMID: 8948457 PMCID: PMC1136817 DOI: 10.1042/bj3080965] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The mechanism by which thrombin and prothrombin control neurite retraction was studied in Ad12E1HER10 human neuroepithelial cells. Morphological changes in differentiated cells were apparent within minutes of the addition of very low concentrations of thrombin (3 pM). Higher concentrations (2 nM) of prothrombin were required to elicit a similar response. Doses of thrombin and prothrombin sufficient to cause neurite retraction stimulated protein tyrosine kinase activity. Protein tyrosine kinase activation also correlated positively with thrombin- and prothrombin-induced phosphoinositide 3-kinase activation and InsP6 dephosphorylation. However, thrombin-stimulated Ins(1,4,5)P3 generation and intracellular Ca2+ mobilization only occurred at concentrations in excess of those needed to induce retraction. No fluctuations in Ins(1,4,5)P3 were detected after stimulation with prothrombin, and no rapid synchronized release of Ca2+ was observed, even at very high concentrations. Prothrombin did, however, cause small oscillations in the intracellular Ca2+ concentration, similar to those produced by low concentrations of thrombin, after approximately 30 min. We conclude that prothrombin- and thrombin-induced neurite retractions are not dependent on PtdIns(4,5)P2 and Ca2+ mobilization, but are more probably mediated through an effector mechanism involving protein tyrosine kinase activation. No intracellular Ca2+ mobilization, protein tyrosine kinase activity or neurite retraction was observed after treatment of cells with proteolytically inactive mutant thrombin (S205-->A). Prothrombin-mediated intracellular Ca2+ mobilization and neurite retraction were inhibited by hirudin, which was shown to interact with thrombin but not prothrombin. It is concluded that cleavage of prothrombin to thrombin is a necessary prerequisite for biological activity on differentiated Ad12E1HER10 cells and that differences in agonist concentration are capable of coupling the thrombin receptor to different pathways within the cell.
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Affiliation(s)
- A S Turnell
- Centre for Clinical Research in Immunology and Signalling, Medical School, University of Birmingham, U.K
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33
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Torti M, Ramaschi G, Montsarrat N, Sinigaglia F, Balduini C, Plantavid M, Breton M, Chap H, Mauco G. Evidence for a glycoprotein IIb-IIIa- and aggregation-independent mechanism of phosphatidylinositol 3',4'-bisphosphate synthesis in human platelets. J Biol Chem 1995; 270:13179-85. [PMID: 7768914 DOI: 10.1074/jbc.270.22.13179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The synthesis of phosphatidylinositol 3',4'-bisphosphate (PtdIns(3,4)P2) in 32P-labeled human platelets induced by the tetrameric lectin concanavalin A and the physiological agonist thrombin were compared. Like thrombin, concanavalin A stimulated a time-dependent accumulation of PtdIns(3,4)P2, which reached maximal levels after 5 min of stimulation. However, while synthesis of PtdIns(3,4)P2 induced by thrombin was dependent on platelet aggregation, the production of PtdIns(3,4)P2 induced by concanavalin A was unchanged when aggregation was prevented by the omission of stirring or when fibrinogen binding to platelets was inhibited by the tetrapeptide RGDS. Accumulation of PtdIns(3,4)P2 was not observed in platelets stimulated with succinyl-concanavalin A, a dimeric derivative of the lectin that binds to the same receptors on the platelet surface but does not promote clustering of membrane glycoproteins. The synthesis of PtdIns(3,4)P2 induced by concanavalin A was also independent of the membrane glycoprotein IIb-IIIa, as normal accumulation of this lipid was observed in platelets from two patients affected by Glanzmann thrombasthenia. In contrast, thrombin showed a strongly reduced ability to stimulate PtdIns(3,4)P2 production in thrombasthenic platelets. Although concanavalin A was able to induce association of the regulatory subunit of the phosphatidylinositol 3-kinase with tyrosine-phosphorylated proteins, the tyrosine kinase inhibitor tyrphostin AG-213 did not inhibit the lectin-induced synthesis of PtdIns(3,4)P2. These results demonstrate the existence of a novel mechanism of PtdIns(3,4)P2 synthesis in human platelets, which is independent of glycoprotein IIb-IIIa and aggregation, but requires clustering of membrane glycoproteins. As clustering events occur during platelet aggregation promoted by physiological agonists, this new mechanism may also be involved in the aggregation-dependent production of PtdIns(3,4)P2 in thrombin-stimulated platelets.
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Affiliation(s)
- M Torti
- Department of Biochemistry, University of Pavia, Italy
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34
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Guinebault C, Payrastre B, Racaud-Sultan C, Mazarguil H, Breton M, Mauco G, Plantavid M, Chap H. Integrin-dependent translocation of phosphoinositide 3-kinase to the cytoskeleton of thrombin-activated platelets involves specific interactions of p85 alpha with actin filaments and focal adhesion kinase. J Cell Biol 1995; 129:831-42. [PMID: 7537275 PMCID: PMC2120444 DOI: 10.1083/jcb.129.3.831] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Thrombin-induced accumulation of phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) but not of PtdIns(3,4,5,)P3 is strongly correlated with the relocation to the cytoskeleton of 29% of the p85 alpha regulatory subunit of phosphoinositide 3-kinase (PtdIns 3-kinase) and is accompanied by a significant increase in PtdIns 3-kinase activity in this subcellular fraction. Actually, PtdIns(3,4)P2 accumulation and PtdIns 3-kinase, pp60c-src, and p125FAK translocations as well as aggregation were concomitant events occurring with a distinct lag after actin polymerization. The accumulation of PtdIns(3,4)P2 and the relocalization of PtdIns 3-kinase to the cytoskeleton were both dependent on tyrosine phosphorylation, integrin signaling, and aggregation. Furthermore, although p85 alpha was detected in anti-phosphotyrosine immunoprecipitates obtained from the cytoskeleton of thrombin-activated platelets, we failed to demonstrate tyrosine phosphorylation of cytoskeletal p85 alpha. Tyrphostin treatment clearly reduced its presence in this subcellular fraction, suggesting a physical interaction of p85 alpha with a phosphotyrosyl protein. These data led us to investigate the proteins that are able to interact with PtdIns 3-kinase in the cytoskeleton. We found an association of this enzyme with actin filaments: this interaction was spontaneously restored after one cycle of actin depolymerization-repolymerization in vitro. This association with F-actin appeared to be at least partly indirect, since we demonstrated a thrombin-dependent interaction of p85 alpha with a proline-rich sequence of the tyrosine-phosphorylated cytoskeletal focal adhesion kinase, p125FAK. In addition, we show that PtdIns 3-kinase is significantly activated by the p125FAK proline-rich sequence binding to the src homology 3 domain of p85 alpha subunit. This interaction may represent a new mechanism for PtdIns 3-kinase activation at very specific areas of the cell and indicates that the focal contact-like areas linked to the actin filaments play a critical role in signaling events that occur upon ligand engagement of alpha IIb/beta 3 integrin and platelet aggregation evoked by thrombin.
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Affiliation(s)
- C Guinebault
- Institut National de la Santé et de la Recherche Médicale, Unité 326, Hôpital Purpan, Toulouse, France
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Arkinstall S, Payton M, Maundrell K. Activation of phospholipase C gamma in Schizosaccharomyces pombe by coexpression of receptor or nonreceptor tyrosine kinases. Mol Cell Biol 1995; 15:1431-8. [PMID: 7862136 PMCID: PMC230367 DOI: 10.1128/mcb.15.3.1431] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The fission yeast Schizosaccharomyces pombe has no detectable endogenous receptor tyrosine kinases or associated signalling apparatus, and we have used this cell system to reconstitute mammalian platelet-derived growth factor beta (PDGF beta) receptor-linked activation of phospholipase C gamma 2 (PLC gamma 2). The PDGF beta receptor migrates as a glycosylated protein of 165 kDa associated exclusively with membrane fractions. No tyrosine autophosphorylation was detected when PDGF beta was expressed alone. PLC gamma 2 appears as a 140-kDa protein distributed between particulate and soluble fractions which exhibits characteristic selectivity for phosphatidylinositol 4,5-bisphosphate and is sensitive to powerful activation by Ca2+. When coexpressed, both PDGF beta and PLC gamma 2 undergo tyrosine phosphorylation, and this is accompanied by a > 26-fold increase in [3H]inositol 4,5-biphosphate ([3H]IP2) and [3H]inositol 1,4,5-triphosphate [3H]IP3 production. Treatment with the tyrosine phosphatase inhibitor pervanadate further increased PLC gamma 2 tyrosine phosphorylation as well as [3H]IP2 and [3H]IP3 generation. Phosphorylated PLC gamma 2 was found predominantly in membrane fractions. To test a nonreceptor tyrosine kinase, we then expressed the human proto-oncogene c-src together with its negative regulator Csk. These were immunodetectable as bands at 60 kDa (c-Src) and 50 kDa (Csk) and distributed between membrane and cytosolic fractions. When yeast coexpressing c-Src, Csk, and PLC gamma 2 was incubated with pervanadate, PLC gamma 2 was tyrosine phosphorylated and [3H]IP2 and [3H]IP3 production increased 11.0- and 7.0-fold, respectively. Csk expressed alone with PLC gamma 2 was ineffective. Similar PLC gamma 2 activation was observed upon in vitro mixing with the extracts expressing either c-Src or the PDGF beta receptor. In summary, this is the first report of a reconstitution of mammalian tyrosine kinase-linked effector activation in yeast cells and also the first demonstration of direct PLC gamma 2 activation by the proto-oncogene c-src. These observations indicate that S. pombe provides a powerful cell system in which to study critical molecular interactions and activities underlying receptor and nonreceptor tyrosine kinase-dependent cell signaling.
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Affiliation(s)
- S Arkinstall
- Glaxo Institute for Molecular Biology, Plan-les-Ouates, Geneva, Switzerland
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36
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Altmüller A, Presek P. Rapid protein tyrosine phosphorylation in the cytoskeleton of stimulated human platelets. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1265:61-6. [PMID: 7532010 DOI: 10.1016/0167-4889(94)00194-j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Upon activation platelets show elevated protein tyrosine phosphorylation, and translocation of the protein tyrosine kinase pp60c-src from the plasma membrane to the cytoskeleton occurs. We therefore investigated whether tyrosine phosphorylation also increases in the cytoskeletal compartment. Here we show that almost identical patterns of phosphotyrosine-containing proteins are detectable in the cytoskeleton after platelet stimulation with compounds that directly (phorbol 12-myristate, 13-acetate) or indirectly (thrombin, vasopressin, collagen, ADP) activate protein kinase C. The apparent molecular masses of the proteins phosphorylated at tyrosine residues are 145, 130, 100, 85, 80, 60, 56, 54 and 38 kDa. Elevation of cyclic AMP by prostaglandin E1 had no effect. Concentrations of thrombin as low as 0.01 units per ml are able to cause tyrosine phosphorylation of multiple proteins. The time course of protein tyrosine phosphorylation for thrombin- and vasopressin-stimulated platelets revealed a rapid increase in the cytoskeleton within 5 to 20 s following activation consistent with a role in early events of platelet function.
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Affiliation(s)
- A Altmüller
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, Giessen, Germany
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37
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Torti M, Ramaschi G, Sinigaglia F, Balduini C. Dual mechanism of protein-tyrosine phosphorylation in concanavalin A-stimulated platelets. J Cell Biochem 1995; 57:30-8. [PMID: 7721957 DOI: 10.1002/jcb.240570105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Treatment of human platelets with the lectin Concanavalin A (Con A) resulted in the tyrosine phosphorylation of several proteins with molecular masses 65, 80, 85, 95, 120, 135, and 150 kDa. These proteins were divided in two groups: the first group included the 65-, 85-, 95-, and 120-kDa bands, which were tyrosine phosphorylated also in thrombin-stimulated platelets; the second group (80-, 135-, and 150-kDa bands) included proteins whose tyrosine phosphorylation was exclusively promoted by Con A, but not by thrombin. Members of the second group were rapidly dephosphorylated when the lectin was displaced from the cell surface by methyl alpha-D-mannopyranoside. Pretreatment of intact platelets with the prostacyclin analog iloprost, inhibited Con A-induced tyrosine phosphorylation of the first group of proteins, but had no effect on the tyrosine phosphorylation of the proteins of the second group. Succinyl-Con A, a dimeric derivative of the lectin, which binds to the platelet surface but does not promote clustering of the receptor, did not induce tyrosine phosphorylation of the second group of proteins, although phosphorylation of some members of the first group was observed. Our results demonstrate the presence of two different mechanisms leading to protein-tyrosine phosphorylation in Con A-stimulated platelets, and identify a new signal transduction pathway, promoted by the clustering of membrane glycoproteins, that produces tyrosine phosphorylation of specific substrates. This new pathway may be activated by platelet interaction with multivalent ligands, such as adhesive proteins, during adhesion, spreading, and aggregation.
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Affiliation(s)
- M Torti
- Department of Biochemistry, Faculty of Science, University of Pavia, Italy
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38
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Greenwalt DE, Tandon NN. Platelet shape change and Ca2+ mobilization induced by collagen, but not thrombin or ADP, are inhibited by phenylarsine oxide. Br J Haematol 1994; 88:830-8. [PMID: 7819106 DOI: 10.1111/j.1365-2141.1994.tb05124.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In this report we have examined the effects of the protein tyrosine phosphatase inhibitor phenylarsine oxide (PAO) on receptor-mediated platelet shape change, secretion and aggregation. PAO was found to inhibit platelet aggregation induced by collagen, thrombin, ADP and epinephrine at IC50 values of 0.35 mumol/l, 2.5 mumol/l, 0.2 mumol/l and 0.3 mumol/l, respectively. Agonist-induced secretion of ATP was inhibited at similar or lower concentrations of PAO. The specificity of the interaction of PAO with platelet proteins was demonstrated by the ability of the disulfhydryl compound 2,3-dimercaptopropanol, which abstracts PAO from proteins to form a stable cyclic adduct, to reverse PAO inhibition of both agonist-induced platelet secretion and aggregation. Dimercaptopropanesulphonic acid, a membrane-impermeable analogue of dimercaptopropanol, did not reverse inhibition of collagen-induced shape change or aggregation by PAO, thereby demonstrating that PAO acted intracellularly. PAO inhibited collagen-induced shape change and internal Ca2+ mobilization but had no effect on these two phenomena when induced by thrombin or ADP. PAO was also unable to prevent arachidonic acid-induced shape change, indicating that PAO acts at a site prior to the phospholipase A2-mediated release of arachidonic acid to inhibit collagen-induced shape change. PAO induced the accumulation of a number of phosphotyrosine-containing proteins and inhibited the collagen-induced phosphorylation of a 40 kD protein. The potency and agonist-specific effects of PAO on platelet activation suggest that this inhibitor will be of value in elucidation of signal transduction pathways involved in receptor-mediated platelet function.
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Affiliation(s)
- D E Greenwalt
- American Red Cross, Holland Laboratory, Rockville, Maryland 20855
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39
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Tyrosine kinases regulate the cytoskeletal attachment of integrin alpha IIb beta 3 (platelet glycoprotein IIb/IIIa) and the cellular retraction of fibrin polymers. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)31660-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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40
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Blake RA, Schieven GL, Watson SP. Collagen stimulates tyrosine phosphorylation of phospholipase C-gamma 2 but not phospholipase C-gamma 1 in human platelets. FEBS Lett 1994; 353:212-6. [PMID: 7523195 DOI: 10.1016/0014-5793(94)01037-4] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Collagen is an important primary stimulus of platelets during the process of hemostasis. As with many other platelet stimuli, collagen signal transduction involves the hydrolysis of inositol phospholipids; however, the mechanisms which underlies this event is not well understood. Neither the collagen receptor nor the isoform of phospholipase C that is activated have been identified. We report that collagen-activation of platelets induces tyrosine phosphorylation of phospholipase C-gamma 2 but not phospholipase C-gamma 1. We also show that the platelet low affinity Fc receptor (Fc gamma RII), which mediates activation of platelets by immune complexes, and wheat germ agglutinin, which binds non-specifically to glycoprotein, stimulate phospholipase C-gamma 2 tyrosine phosphorylation. In contrast, we could not detect phospholipase C-gamma 2 tyrosine phosphorylation in platelets stimulated by either thrombin or a stable thromboxane A2 analogue, U46619.
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Affiliation(s)
- R A Blake
- Department of Pharmacology, Oxford, UK
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41
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Fry MJ. Structure, regulation and function of phosphoinositide 3-kinases. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1226:237-68. [PMID: 8054357 DOI: 10.1016/0925-4439(94)90036-1] [Citation(s) in RCA: 139] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- M J Fry
- Section of Cell Biology and Experimental Pathology, Institute of Cancer Research, Haddow Laboratories, Sutton, Surrey, UK
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42
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Furman MI, Grigoryev D, Bray PF, Dise KR, Goldschmidt-Clermont PJ. Platelet tyrosine kinases and fibrinogen receptor activation. Circ Res 1994; 75:172-80. [PMID: 8013076 DOI: 10.1161/01.res.75.1.172] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Platelet adhesion and aggregation during hemostasis and thrombosis are usually limited to sites where the integrity of the vessel wall is disrupted. The high concentration of platelet agonists within these sites represents a putative control mechanism for targeting platelet activation. Although much has been learned about the intracellular signaling systems controlling platelet activation, our understanding of the connection between signaling molecules and platelet aggregation remains limited. Tyrosine kinases are important signaling enzymes in cells and are abundant in platelets. Previous reports indicate that binding of glycoprotein IIb-IIIa (GPIIb-IIIa) to fibrinogen can induce the tyrosine phosphorylation of specific substrates. We show that, in turn, protein tyrosine kinase activity is necessary for agonist-induced activation of GPIIb-IIIa. Genistein and the tyrphostin AG-18 are two specific tyrosine kinase inhibitors, and the former has been shown to inhibit platelet aggregation. We use genistein and AG-18 in the present study to demonstrate that aggregation inhibition is due to suppression of GPIIb-IIIa activation. In contrast, genistin, an isoflavone compound related to genistein, and acetylsalicylic acid do not affect the tyrosine kinase-signaling pathway, nor do they inhibit GPIIb-IIIa activation induced by strong agonists. On identifying prominent tyrosine kinase substrates in activated platelets, we confirm that several substrates correspond to proteins associated with the cytoskeleton: the 85-kD subunit of phosphatidylinositol 3-kinase, the SH3-containing and actin-associating p85, pp60Src, and pp125FAK.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M I Furman
- Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, Md
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43
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Yatomi Y, Ozaki Y, Satoh K, Kume S. Synthesis of phosphatidylinositol 3,4-bisphosphate is regulated by protein-tyrosine phosphorylation but the p85 alpha subunit of phosphatidylinositol 3-kinase may not be a target for tyrosine kinases in thrombin-stimulated human platelets. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1212:337-44. [PMID: 8199204 DOI: 10.1016/0005-2760(94)90208-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To elucidate the mechanism involving synthesis of phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2), which is the main species of 3-phosphorylated phosphoinositides in activated blood platelets, we observed a correlation among protein-tyrosine phosphorylation, protein kinase C (PKC) activation, and PtdIns(3,4)P2 synthesis in these anucleate cells. Thrombin (1 U/ml) elicited marked protein-tyrosine phosphorylation, PKC activation, and PtdIns(3,4)P2 synthesis. In contrast, 1 microM 12-O-tetrade-canoylphorbol 13-acetate barely induced tyrosine phosphorylation and PtdIns(3,4)P2 synthesis although it strongly activated PKC. A variety of kinase inhibitors were tested for their ability to inhibit the thrombin effects. Both staurosporine and tyrphostin inhibited thrombin-stimulated tyrosine phosphorylation and PtdIns(3,4)P2 synthesis. H-7, which specifically, although weakly, inhibited PKC activation, had no effect on tyrosine phosphorylation and PtdIns(3,4)P2 production. Among the various kinase inhibitors tested, staurosporine was the most potent inhibitor of protein tyrosine phosphorylation and PtdIns(3,4)P2 synthesis, and there was a good correlation of the inhibition between these two parameters, although it also inhibited PKC activation. To examine the involvement of PtdIns 3-kinase, which is believed to play an important role in 3-phosphorylated phosphoinositide synthesis, we studied tyrosine phosphorylation and the association with tyrosine-phosphorylated proteins of the p85 alpha subunit of PtdIns 3-kinase in thrombin-stimulated platelets. We did not detect tyrosine-phosphorylated protein by Western blotting where p85 alpha was located. Similarly, when platelet lysates were precipitated with anti-p85 alpha antibodies and then blotted with anti-phosphotyrosine antibodies, tyrosine-phosphorylated p85 alpha was undetectable. Furthermore, when the cell lysates were precipitated with anti-phosphotyrosine antibodies, no p85 alpha was found in the immunoprecipitates. These results show that PtdIns(3,4)P2 synthesis in stimulated platelets is mediated by tyrosine phosphorylation, as it is in proliferating cells, but the p85 alpha subunit of PtdIns 3-kinase may not be a target for tyrosine kinases and that staurosporine, though non-specific, would be a useful tool for elucidating signal transduction involving D-3-phosphorylated phosphoinositide generation and protein-tyrosine phosphorylation in blood platelets.
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Affiliation(s)
- Y Yatomi
- Department of Laboratory Medicine, Yamanashi Medical College, Japan
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44
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Li RY, Gaits F, Ragab A, Ragab-Thomas JM, Chap H. Translocation of an SH2-containing protein tyrosine phosphatase (SH-PTP1) to the cytoskeleton of thrombin-activated platelets. FEBS Lett 1994; 343:89-93. [PMID: 7512933 DOI: 10.1016/0014-5793(94)80613-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A significant protein tyrosine phosphatase (PTP) activity was found to be associated with the cytoskeleton of thrombin-stimulated platelets. Translocation of the enzyme became maximal within 1-2 min of thrombin stimulation and was suppressed by cytochalasin D or upon inhibition of aggregation. Immunoblotting as well as immunoprecipitation revealed that a PTP with two SH2 domains (SH-PTP1) displayed the same behaviour, translocation to the cytoskeleton showing the same time course as that observed for pp60c-src. We conclude that SH-PTP1 might represent a critical enzyme in the complex interplay between the various proteins regulating protein tyrosine phosphorylation in the cytoskeletal matrix.
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Affiliation(s)
- R Y Li
- INSERM Unité 326, Phospholipides Membranaires, Signalisation Cellulaire et Lipoprotéines, Université Paul Sabatier, Hôpital Purpan, Toulouse, France
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45
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Payrastre B, Gironcel D, Plantavid M, Mauco G, Breton M, Chap H. Phosphoinositide 3-phosphatase segregates from phosphatidylinositol 3-kinase in EGF-stimulated A431 cells and fails to in vitro hydrolyse phosphatidylinositol(3,4,5)trisphosphate. FEBS Lett 1994; 341:113-8. [PMID: 8137909 DOI: 10.1016/0014-5793(94)80251-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Beside 4- and 5-phosphatases playing a role in the interconversion between the D-3 phosphorylated polyphosphoinositides, the only enzyme described so far to be responsible for a phosphomonesterasic activity on the D-3 position of inositol lipids is a specific 3-phosphatase that hydrolyzes PtdIns(3)P in NIH 3T3 cells. We report here the presence of a potent 3-phosphatase activity in different cell types. This activity is detected both in cytosol and membranes of A431 cells and is inhibited by VO4(-3) and Zn2+. Interestingly, the cytosolic activity from A431 cells selectively hydrolyzes in vitro PtdIns(3)P and PtdIns(3,4)P2, whereas PtdIns(3,4,5)P3 remains a very poor substrate under the same conditions. Finally, assays of phosphatidylinositol 3-kinase and 3-phosphatase activities in the pool of phosphotyrosine-containing proteins isolated from EGF-stimulated A431 cells suggest a compartmentation of these two antagonistic activities during cell activation.
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Affiliation(s)
- B Payrastre
- INSERM Unité 326, Hôpital Purpan, Toulouse, France
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46
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Membrane Receptors. Mol Endocrinol 1994. [DOI: 10.1016/b978-0-12-111231-8.50011-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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47
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Abstract
By virtue of their biological simplicity and widespread availability, platelets frequently have been used as a model system to study signal transduction. Such studies have revealed that changes in intracellular free calcium concentration are central to platelet functioning. The following article reviews current concepts of platelet structure and function, with particular emphasis on the mechanisms involved in platelet Ca2+ signalling.
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Affiliation(s)
- P Sargeant
- Physiological Laboratory, Cambridge University, U.K
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48
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