1
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Off-target effect of the Epac agonist 8-pCPT-2'-O-Me-cAMP on P2Y12 receptors in blood platelets. Biochem Biophys Res Commun 2013; 437:603-8. [PMID: 23850619 DOI: 10.1016/j.bbrc.2013.07.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 07/02/2013] [Indexed: 11/21/2022]
Abstract
The primary target of the cAMP analogue 8-pCPT-2'-O-Me-cAMP is exchange protein directly activated by cAMP (Epac). Here we tested potential off-target effects of the Epac activator on blood platelet activation signalling. We found that the Epac analogue 8-pCPT-2'-O-Me-cAMP inhibits agonist-induced-GPCR-stimulated, but not collagen-stimulated, P-selectin surface expression on Epac1 deficient platelets. In human platelets, 8-pCPT-2'-O-Me-cAMP inhibited P-selectin expression elicited by the PKC activator PMA. This effect was abolished in the presence of the extracellular ADP scavenger system CP/CPK. In silico modelling of 8-pCPT-2'O-Me-cAMP binding into the purinergic platelet receptor P2Y12 revealed that the analogue docks similar to the P2Y12 antagonist 2MeSAMP. The 8-pCPT-2'-O-Me-cAMP analogue per se, did not provoke Rap 1 (Rap 1-GTP) activation or phosphorylation on the vasodilator-stimulated phosphoprotein (VASP) at Ser-157. In addition, the protein kinase A (PKA) antagonists Rp-cAMPS and Rp-8-Br-cAMPS failed to block the inhibitory effect of 8-pCPT-2'-O-Me-cAMP on thrombin- and TRAP-induced Rap 1 activation, thus suggesting that PKA is not involved. We conclude that the 8-pCPT-2'-O-Me-cAMP analogue is able to inhibit agonist-induced-GPCR-stimulated P-selectin independent from Epac1; the off-target effect of the analogue appears to be mediated by antagonistic P2Y12 receptor binding. This has implications when using cAMP analogues on specialised system involving such receptors. We found, however that the Epac agonist 8-Br-2'-O-Me-cAMP did not affect platelet activation at similar concentrations.
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Key Words
- (Rp)-adenosine-3′,5′-cyclic monophosphorothioate, Rp-isomer
- (β-phenyl-1), N(2)-etheno-8-bromoguanosine-3′,5′-cyclic monophosphate
- 2-methylthio-adenosine diphosphate
- 2-methylthio-adenosine monophosphate
- 2MeSADP
- 2MeSAMP
- 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole-3′,5′-cyclic monophosphorothioate, Sp-isomer
- 8-(4-chlorophenylthio)-2′-O-methyladenosine-3′,5′-cyclic monophosphate
- 8-(4-chlorophenylthio)-2′-O-methyladenosine-3′,5′-cyclic monophosphorothioate, Sp-isomer
- 8-Br-PET-cGMP
- 8-bromoadenosineadenosine-3′,5′-cyclic monophosphorothioate, Rp-isomer
- 8-pCPT-2′-O-Me-cAMP
- ADP
- Blood platelets
- CP/CPK
- Epac
- P2Y(12) receptor
- PI3K
- PKA
- PKG
- PMA
- Rp-8-Br-cAMPS
- Rp-cAMPS
- Sp-5, 6-DCL-cBIMPS
- Sp-8-pCPT-2′-O-Me-cAMPS
- Thromboxane
- TxA(2)
- adenosine diphosphate
- cAMP
- cAMP-activated protein kinase
- cGMP-activated protein kinase
- creatine phosphate/creatine phosphokinase
- cyclic adenosine monophosphate
- exchange factor directly activated by cAMP
- phorbol 12-myristate 13-acetate
- phosphatidyl-inositol-3 kinase
- thromboxane receptor A(2)
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2
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Bhavanasi D, Kim S, Goldfinger LE, Kunapuli SP. Protein kinase Cδ mediates the activation of protein kinase D2 in platelets. Biochem Pharmacol 2011; 82:720-7. [PMID: 21736870 DOI: 10.1016/j.bcp.2011.06.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 06/17/2011] [Accepted: 06/20/2011] [Indexed: 01/25/2023]
Abstract
Protein kinase D (PKD) is a subfamily of serine/threonine specific family of kinases, comprised of PKD1, PKD2 and PKD3 (PKCμ, PKD2 and PKCv in humans). It is known that PKCs activate PKD, but the relative expression of isoforms of PKD or the specific PKC isoform/s responsible for its activation in platelets is not known. This study is aimed at investigating the pathway involved in activation of PKD in platelets. We show that PKD2 is the major isoform of PKD that is expressed in human as well as murine platelets but not PKD1 or PKD3. PKD2 activation induced by AYPGKF was abolished with a G(q) inhibitor YM-254890, but was not affected by Y-27632, a RhoA/p160ROCK inhibitor, indicating that PKD2 activation is G(q)-, but not G₁₂/₁₃-mediated Rho-kinase dependent. Calcium-mediated signals are also required for activation of PKD2 as dimethyl BAPTA inhibited its phosphorylation. GF109203X, a pan PKC inhibitor abolished PKD2 phosphorylation but Go6976, a classical PKC inhibitor had no effect suggesting that novel PKC isoforms are involved in PKD2 activation. Importantly, Rottlerin, a non-selective PKCδ inhibitor, inhibited AYPGKF-induced PKD2 activation in human platelets. Similarly, AYPGKF- and Convulxin-induced PKD2 phosphorylation was dramatically inhibited in PKCδ-deficient platelets, but not in PKCθ- or PKCɛ-deficient murine platelets compared to that of wild type platelets. Hence, we conclude that PKD2 is a common signaling target downstream of various agonist receptors in platelets and G(q)-mediated signals along with calcium and novel PKC isoforms, in particular, PKCδ activate PKD2 in platelets.
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Affiliation(s)
- Dheeraj Bhavanasi
- Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
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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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4
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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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Gao G, Chen L, Dong B, Gu H, Dong H, Pan Y, Gao Y, Chen X. RhoA effector mDia1 is required for PI 3-kinase-dependent actin remodeling and spreading by thrombin in platelets. Biochem Biophys Res Commun 2009; 385:439-44. [DOI: 10.1016/j.bbrc.2009.05.090] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 05/20/2009] [Indexed: 10/20/2022]
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6
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Vorland M, Holmsen H. Phospholipase D in human platelets: presence of isoenzymes and participation of autocrine stimulation during thrombin activation. Platelets 2008; 19:211-24. [PMID: 18432522 DOI: 10.1080/09537100701777329] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Phospholipase D (PLD), which hydrolyzes phosphatidylcholine to phosphatidic acid (PA) and choline, is present in human platelets. Thrombin and other agonists have been shown to activate PLD but the precise mechanisms of activation and PLDs role in platelet activation remains unclear. We measured thrombin-stimulated PLD activity in platelets as formation of phosphatidylethanol. Since no specific PLD inhibitors exist, we investigated possible roles for PLD in platelets by correlating PLD activity with platelet responses such as thrombin-mediated secretion and F-actin formation (part of platelet shape change). Extracellular Ca2+ potentiated thrombin-stimulated PLD, but did not stimulate PLD in the absence of thrombin. Thrombin-induced PLD activity was enhanced by secreted ADP and binding of fibrinogen to its receptors. In contrast to others, we also found a basal PLD activity. Comparison of time courses and dose responses of platelets with PLD showed many points of correlation between PLD activation and lysosomal secretion and F-actin formation. The finding of different PLD activities suggested that different PLD isoenzymes exist in platelets as reported for other cells. Here we present evidence for the presence of both PLD1 and PLD2 in platelets by use of specific antibodies with immunoblotting and immunohistochemistry. Both isoforms were randomly localized in resting platelets, but became rapidly translocated to the proximity of the plasma membrane upon thrombin stimulation, thus indicating a role for PLD in platelet activation.
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Affiliation(s)
- M Vorland
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Norway.
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7
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Maayani S, Schwarz TE, Patel ND, Craddock-Royal BD, Tagliente TM. Agonist concentration-dependent differential responsivity of a human platelet purinergic receptor: pharmacological and kinetic studies of aggregation, deaggregation and shape change responses mediated by the purinergic P2Y1 receptor in vitro. Platelets 2004; 14:445-62. [PMID: 14713514 DOI: 10.1080/09537100310001612399] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Platelet shape change (SC), aggregation and deaggregation responses are integral components of hemostasis that are elicited and modulated in vivo by the simultaneous activation of several membrane receptors. Selective activation of the purinergic P2Y1 receptor in vivo elicits a sustained SC and a small, transient aggregation response that is reversed rapidly by a robust deaggregation response (Platelets 2003; 14: 89). Using a kinetics-based turbidimetric approach to study the modulation of these concurrent components of human platelet responses, we demonstrate that these P2Y1 receptor-related responses and a number of their kinetic and steady-state characteristics are differentially elicited and modulated. P2Y1 receptor agonist concentrations that elicited aggregation (pEC50 for ADP, 2-MeSADP; 5.88, 6.69) were 10-fold greater than those that elicited SC (7.33, 7.67). The magnitude of the aggregation response was agonist concentration-dependent, saturable and was associated with an agonist concentration-dependent deceleration of the deaggregation response. Gi-coupled receptor (alpha 2A-adrenoceptor, EP3 and P2Y12 receptors) agonists also enhanced aggregation through deceleration of the deaggregation response, and an inhibitor of PI3K activity (wortmannin) inhibited aggregation through acceleration of the deaggregation response. Neither treatment affected the extent or the kinetics of the SC response. The aggregation but not the SC response was rapidly desensitized by P2Y1 receptor activation by ADP. The affinity of the presence of a single P2Y1 receptor subtype. The differential characteristics and modulation of the SC and aggregation responses by a single receptor support the idea that different signaling pathways activated at different occupancy states of the same receptor underlie the two responses. P2Y1 receptor-mediated platelet aggregation and SC responses provide a convenient model for studying the phenomenon of agonist-directed signaling by differential occupancy of the same membrane receptor.
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Affiliation(s)
- Saul Maayani
- Department of Anesthesiology, Mount Sinai School of Medicine, New York, NY 10029, USA.
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8
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Ferreira IA, Eybrechts KL, Mocking AIM, Kroner C, Akkerman JWN. IRS-1 mediates inhibition of Ca2+ mobilization by insulin via the inhibitory G-protein Gi. J Biol Chem 2003; 279:3254-64. [PMID: 14602724 DOI: 10.1074/jbc.m305474200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Platelet agonists initiate aggregation and secretion by activating receptors coupled to the G-protein G(q), thereby raising cytosolic Ca(2+), [Ca(2+)](i). The rise in [Ca(2+)](i) is facilitated via inhibition of cAMP formation by the inhibitory G-protein of adenylyl cyclase, G(i). Since insulin attenuates platelet activation, we investigated whether insulin interferes with cAMP regulation. Here we report that insulin (0.5-200 nmol/liter) interferes with agonist-induced increases in [Ca(2+)](i) (ADP, thrombin), cAMP suppression (thrombin), and aggregation (ADP). The effects of insulin are as follows: (i) independent of the P2Y(12) receptor, which mediates ADP-induced cAMP lowering; (ii) not observed during G(s)-mediated cAMP formation; (iii) unaffected by treatments that affect phosphodiesterases (3-isobutyl-1-methylxanthine); and (iv) not changed by interfering with NO-mediated regulation of cAMP degradation (N(G)-monomethyl-l-arginine). Hence, insulin might interfere with G(i). Indeed, insulin induces the following: (i) tyrosine phosphorylation of the insulin receptor, the insulin receptor substrate-1 (IRS-1) and G(i)alpha(2); (ii) co-precipitation of IRS-1 with G(i)alpha(2) but not with other G alpha subunits. Despite persistent receptor activation, the association of IRS-1 with G(i)alpha(2) is transient, being optimal at 5 min and 1 nmol/liter insulin, which is sufficient to suppress Ca(2+) signaling by ADP, and at 10 min and 100 nmol/liter insulin, which is required to suppress Ca(2+) signaling by thrombin. Epinephrine, a known platelet sensitizer and antagonist of insulin, abolishes the effect of insulin on [Ca(2+)](i), tyrosine phosphorylation of G(i)alpha(2), and aggregation by interfering with the phosphorylation of the insulin receptor beta subunit. We conclude that insulin attenuates platelet functions by interfering with cAMP suppression through IRS-1 and G(i).
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Affiliation(s)
- Irlando Andrade Ferreira
- Thrombosis and Haemostasis Laboratory, Department of Hematology, University Medical Center Utrecht, and Institute for Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
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9
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Kim S, Foster C, Lecchi A, Quinton TM, Prosser DM, Jin J, Cattaneo M, Kunapuli SP. Protease-activated receptors 1 and 4 do not stimulate G(i) signaling pathways in the absence of secreted ADP and cause human platelet aggregation independently of G(i) signaling. Blood 2002; 99:3629-36. [PMID: 11986217 DOI: 10.1182/blood.v99.10.3629] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thrombin is an important agonist for platelet activation and plays a major role in hemostasis and thrombosis. Thrombin activates platelets mainly through protease-activated receptor 1 (PAR1), PAR4, and glycoprotein Ib. Because adenosine diphosphate and thromboxane A(2) have been shown to cause platelet aggregation by concomitant signaling through G(q) and G(i) pathways, we investigated whether coactivation of G(q) and G(i) signaling pathways is the general mechanism by which PAR1 and PAR4 agonists also activate platelet fibrinogen receptor (alphaIIbbeta3). A PAR1-activating peptide, SFLLRN, and PAR4-activating peptides GYPGKF and AYPGKF, caused inhibition of stimulated adenylyl cyclase in human platelets but not in the presence of either Ro 31-8220, a protein kinase C selective inhibitor that abolishes secretion, or AR-C66096, a P2Y12 receptor-selective antagonist; alpha-thrombin-induced inhibition of adenylyl cyclase was also blocked by Ro 31-8220 or AR-C66096. In platelets from a P2Y12 receptor-defective patient, alpha-thrombin, SFLLRN, and GYPGKF also failed to inhibit adenylyl cyclase. In platelets from mice lacking the P2Y12 receptor, neither alpha-thrombin nor AYPGKF caused inhibition of adenylyl cyclase. Furthermore, AR-C66096 caused a rightward shift of human platelet aggregation induced by the lower concentrations of alpha-thrombin and AYPGKF but had no effect at higher concentrations. Similar results were obtained with platelets from mice deficient in the P2Y12. We conclude that (1) thrombin- and thrombin receptor-activating peptide-induced inhibition of adenylyl cyclase in platelets depends exclusively on secreted adenosine diphosphate that stimulates G(i) signaling pathways and (2) thrombin and thrombin receptor-activating peptides cause platelet aggregation independently of G(i) signaling.
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MESH Headings
- Adenosine Diphosphate/metabolism
- Adenosine Diphosphate/physiology
- Adenosine Triphosphate/analogs & derivatives
- Adenosine Triphosphate/pharmacology
- Adenylyl Cyclases/metabolism
- Animals
- Blood Platelets/drug effects
- Blood Platelets/physiology
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Humans
- Membrane Proteins
- Mice
- Mice, Knockout
- Oligopeptides/antagonists & inhibitors
- Oligopeptides/pharmacokinetics
- Peptide Fragments/antagonists & inhibitors
- Peptide Fragments/pharmacology
- Platelet Aggregation/drug effects
- Platelet Aggregation Inhibitors/pharmacology
- Purinergic P2 Receptor Antagonists
- Receptor, PAR-1
- Receptor, PAR-2
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2/physiology
- Receptors, Purinergic P2Y12
- Receptors, Thrombin/agonists
- Receptors, Thrombin/antagonists & inhibitors
- Receptors, Thrombin/physiology
- Signal Transduction
- Thrombin/antagonists & inhibitors
- Thrombin/pharmacology
- Yohimbine/pharmacology
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Affiliation(s)
- Soochong Kim
- Department of Physiology and the Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
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10
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Cho MJ, Pestina TI, Steward SA, Lowell CA, Jackson CW, Gartner TK. Role of the Src family kinase Lyn in TxA2 production, adenosine diphosphate secretion, Akt phosphorylation, and irreversible aggregation in platelets stimulated with gamma-thrombin. Blood 2002; 99:2442-7. [PMID: 11895777 DOI: 10.1182/blood.v99.7.2442] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the Src family of kinases are abundant in platelets. Although their localization is known, their role(s) in platelet function are not well understood. Lyn is a Src-family kinase that participates in signal transduction pathways elicited by collagen-related peptide; it has also been implicated through biochemical studies in the regulation of von Willebrand factor signaling. Here, we provide evidence that Lyn plays a role in gamma-thrombin activation of platelets. Unlike the wild-type platelets, platelets from Lyn-deficient mice do not undergo irreversible aggregation, produce thromboxane A2, or secrete adenosine diphosphate in response to submaximal gamma-thrombin concentrations that cause secretion-dependent irreversible aggregation. Phosphorylation of Akt, a downstream effector of phosphatidylinositol 3-kinase, also requires a higher concentration of gamma-thrombin in Lyn-deficient platelets than in wild-type platelets. These findings demonstrate that Lyn signaling is required for thrombin induction of secretion-dependent platelet aggregation. Specifically, Lyn is required under these conditions to enable thrombin-induced TxA2 production and adenosine diphosphate secretion, necessary steps in secretion-dependent platelet aggregation.
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Affiliation(s)
- Moon J Cho
- Department of Microbiology and Molecular Cell Sciences, University of Memphis, Memphis, TN 38152, USA
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11
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Abstract
Platelets secrete platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) upon stimulation. We have demonstrated that platelets have functionally active PDGF alpha-receptors, a transmembrane tyrosine kinase involved in negative feedback regulation. Here we demonstrate the presence of the related VEGF receptors fms-like tyrosine kinase-1 and kinase-insert domain region on human platelets. VEGF itself did not cause platelet aggregation. However, addition of exogenous VEGF to SFRLLN or thrombin-stimulated platelets potentiated platelet aggregation. Moreover, thrombin-induced phosphoinositide 3-kinase and mitogen-activated protein kinase activity were enhanced in the presence of VEGF.
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Affiliation(s)
- Frode Selheim
- Department of Biochemistry and Molecular Biology, University of Bergen, Bergen, Norway.
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12
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Hirsch E, Bosco O, Tropel P, Laffargue M, Calvez R, Altruda F, Wymann M, Montrucchio G. Resistance to thromboembolism in PI3Kgamma-deficient mice. FASEB J 2001; 15:2019-21. [PMID: 11511514 DOI: 10.1096/fj.00-0810fje] [Citation(s) in RCA: 170] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Platelet aggregation and subsequent thrombosis are the major cause of ischemic diseases such as heart attack and stroke. ADP, acting via G protein-coupled receptors (GPCRs), is an important signal in thrombus formation and involves activation of phosphoinositide 3-kinases (PI3K). When platelets from mice lacking the G protein-activated PI3Kgamma isoform were stimulated with ADP, aggregation was impaired. Collagen or thrombin, however, evoked a normal response. ADP stimulation of PI3Kgamma-deficient platelets resulted in decreased PKB/Akt phosphorylation and alpha(IIb)beta(3) fibrinogen receptor activation. These effects did not influence bleeding time but protected PI3Kgamma-null mice from death caused by ADP-induced platelet-dependent thromboembolic vascular occlusion. This result demonstrates an unsuspected, well-defined role for PI3Kgamma downstream of ADP and suggests that pharmacological targeting of PI3Kgamma has a potential use as antithrombotic therapy.
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Affiliation(s)
- E Hirsch
- Dipartimento di Genetica, Biologia e Biochimica, Università di Torino, Via Santina 5 bis, 10126 Turin, Italy.
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13
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Selheim F, Frøyset AK, Strand I, Vassbotn FS, Holmsen H. Adrenaline potentiates PI 3-kinase in platelets stimulated with thrombin and SFRLLN: role of secreted ADP. FEBS Lett 2000; 485:62-6. [PMID: 11086166 DOI: 10.1016/s0014-5793(00)02188-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Adrenaline significantly potentiated late thrombin- and SFRLLN-induced PtdIns(3,4)P(2) production. Furthermore, the potentiating effect of adrenaline on thrombin-induced PtdIns(3, 4)P(2) production was independent on secreted ADP, whereas, the effect of adrenaline on SFRLLN-induced PtdIns(3,4)P(2) production was completely dependent of secreted ADP. However, the ADP-dependent accumulation of PtdIns(3,4)P(2) was not required for irreversible platelet aggregation induced by SFRLLN in the presence of adrenaline. It is concluded that adrenaline can replace secreted ADP to potentiate PtdIns(3,4)P(2) production in thrombin-stimulated but not in SFRLLN-stimulated platelets, thus demonstrating a qualitative difference between platelet stimulation by thrombin and the thrombin receptor activating peptide SFRLLN.
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Affiliation(s)
- F Selheim
- Department of Biochemistry and Molecular Biology, University of Bergen, Norway
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