Thrombin-stimulated Human Platelets Express Molecular Forms of α-Granule Factor V (FV), which Differ from FVa

Wyshock, E G; Stewart, Gwendolyn J.; Colman, Robert W.

doi:10.1055/s-0038-1648989

Cited by 5 publications

(7 citation statements)

References 31 publications

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“…Additionally, neither 10 M hirudin nor 10 M r-TAP had any effect on the amidolytic activities of plasmin towards the three substrates. Thrombin translocates factor V from its storage granules to the surface of platelets where it is activated by thrombin to support prothrombinase formation on the platelets (Baruch et al, 1986;Wyschock et al, 1994). Plasmin did not directly activate prothrombin in platelet-rich plasmas in this study, in contrast to the proposal by Seitz et al (1993).…”

Section: Discussioncontrasting

confidence: 84%

Plasmin accelerates platelet‐dependent prothrombinase formation without activating the platelets

et al. 1996

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Patients with acute myocardial infarction who undergo thrombolytic therapy may shortly thereafter present evidence for increased platelet activation and thrombin activity, and recurrent thrombosis. This study investigated whether plasmin activates platelets and prothrombin in recalcified platelet-rich plasma (RPRP) to cause (at least in part) these side-effects of thrombolytic therapy. Plasmin (0.1 and 1.0 CU/ml) addition to RPRP with microM r-tick anticoagulant peptide (the latter a factor Xa inhibitor which abrogates prothrombin activation by prothrombinase at the concentration used) resulted in no change in the concentration of prothrombin fragment 1 + 2, or in the expression of GMP-140, the resting and activated GP IIb-IIIa conformers, and GPIb on platelets. Thus, plasmin neither activates platelets nor prothrombin in RPRP. However, plasmin accelerated platelet activation and secretion, and prothrombin fragment 1 + 2 production in RPRP. When combined with 1 microM r-tick anticoagulant peptide and 1 or 10 mM alpha-thrombin to RPRP, plasmin also increased the number of GMP-140 molecules expressed/platelet without enhancing alpha-thrombin binding to the platelets. Additionally, plasmin accelerated prothrombin activation when it was added to washed platelets resuspended in factor V depleted plasma simultaneously with 10 mM CaCl2, 10 nM alpha-thrombin for 10 s (to activate platelets and platelet factor V), followed by 4 microM hirudin and 1 nM factor Xa. Thus, plasmin potentiates the platelet release reaction in response to alpha-thrombin (probably by increasing the availability of factor V on the platelets) to enhance prothrombin activation in RPRP. These actions of plasmin may contribute to the increased platelet activation and thrombotic side-effects that can occur after thrombolytic therapy.

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Section: Discussioncontrasting

confidence: 84%

Plasmin accelerates platelet‐dependent prothrombinase formation without activating the platelets

et al. 1996

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“…However, since activated platelets can facilitate thrombin generation by providing a catalytic surface on which coagulation reactions occur (1) and by releasing an activated form of Factor V (2), it is possible that antiplatelet agents may also function as anticoagulants in vivo. Both quantitative and qualitative mechanisms may contribute to an anticoagulant effect of potent antiplatelet agents: ( a ) a decrease in platelet aggregation and platelet thrombus formation may result in a local decrease in both the mass of platelet membranes on which thrombin can be generated and the number of platelets available to release activated Factor V (quantitative effects), and ( b ) inhibition of the platelet "activation" process may prevent platelet membranes from developing an enhanced catalytic efficiency and may inhibit release and surface expression of activated Factor V (qualitative effects) (1,2).…”

Section: Introductionmentioning

confidence: 99%

Inhibition of platelet-mediated, tissue factor-induced thrombin generation by the mouse/human chimeric 7E3 antibody. Potential implications for the effect of c7E3 Fab treatment on acute thrombosis and "clinical restenosis".

Reverter¹,

Béguin²,

Kessels³

et al. 1996

J. Clin. Invest.

381

223

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The murine/human chimeric monoclonal antibody fragment (c7E3 Fab) blocks GPIIb/IIIa and ␣ v ␤ 3 receptors, inhibits platelet aggregation, and decreases the frequency of ischemic events after coronary artery angioplasty in patients at high risk of suffering such events. Although inhibition of platelet aggregation is likely to be the major mechanism of c7E3 Fab's effects, since activated platelets facilitate thrombin generation, it is possible that c7E3 Fab also decreases thrombin generation. To test this hypothesis, the effects of c7E3 Fab and other antiplatelet agents were tested in a thrombin generation assay triggered by tissue factor. c7E3 Fab produced dose-dependent inhibition of thrombin generation, reaching a plateau of 45-50% inhibition at concentrations Ն 15 g/ml. It also inhibited thrombin-antithrombin complex formation, prothrombin fragment F 1 ϩ 2 generation, platelet-derived growth factor and platelet factor 4 release, incorporation of thrombin into clots, and microparticle formation. Antibody 6D1, which blocks platelet GPIb binding of von Willebrand factor, had no effect on thrombin generation, whereas antibody 10E5, which blocks GPIIb/IIIa but not ␣ v ␤ 3 receptors decreased thrombin generation by ‫ف‬ 25%. Combining antibody LM609, which blocks ␣ v ␤ 3 receptors, with 10E5 increased the inhibition of thrombin generation to ‫ف‬ 32-41%. The platelets from three patients with Glanzmann thrombasthenia, who lacked GPIIb/IIIa receptors but had normal or increased ␣ v ␤ 3 receptors, supported ‫ف‬ 21% less thrombin generation than normal platelets. We conclude that thrombin generation initiated by tissue factor in the presence of platelets is significantly inhibited by c7E3 Fab, most likely in part through both GPIIb/IIIa and ␣ v ␤ 3 blockade, and that this effect may contribute to its antithrombotic properties. ( J. Clin. Invest. 1996. 98:863-874.)

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“…Platelet factor V is known to be heterogeneous in its molecular weight [11,12]. Similar to the ELISA assays, immunoblot analysis of lysates prepared from washed platelets (1 × 10 9 /ml), using polyclonal antiserum, indicated that factor V-New York platelets contained reduced quantities of variably sized factor V molecules that were normal in mobility (Fig.…”

Section: Immunoblot Studies Of Platelet Factor Vmentioning

confidence: 87%

“…Human factor V is secreted from agonist-stimulated platelets [8,10], and this secretion is inhibited by aspirin and metabolic inhibitors [10]. Factor V is present in platelets as a partially proteolyzed molecule [11,12] that, when activated by thrombin, yields peptides with molecular weights that appear to be electrophoretically indistinguishable from activated plasma factor V [13]. Recent studies have identified that, unlike plasma factor V, platelet factor V is stored complexed with multimerin, a soluble, massive, multimeric factor V binding protein that is found in platelets and endothelium, [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Platelet factor V New York: A defect in factor V distinct from that in factor V Quebec resulting in impaired prothrombinase generation

et al. 2001

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Studies were performed on a patient with a longstanding bleeding disorder whose major defects were impaired platelet prothrombinase activity in the absence of added factor Va, and a platelet factor V value that was either decreased or at the lower limit of normal when assayed on multiple occasions. In contrast, plasma factor V values were consistently normal. Unlike Scott Syndrome, in which platelet prothrombinase activity is decreased in both the presence and absence of added factor V, her platelets appeared to utilize added factor Va normally in supporting the generation of prothrombinase activity. These findings suggest an intrinsic defect in platelet factor V as the basis of her platelet prothrombinase defect. This defect appears to be different than that described in the Quebec platelet disorder (factor V Quebec). Immunoblot analyses of washed platelet lysates demonstrated a pattern of variably sized factor V molecules that was entirely similar to that observed in normal platelets, and both the heavy and light chains of her factor V after thrombin cleavage were of the same size as that observed in normal platelets. In addition, her platelet multimerin was normal and immunoblot analysis excluded the type of generalized granular protein defect and pathological proteolysis that has been suggested to explain the factor V defect in the Quebec platelet disorder. The findings in this patient thus suggest a new type of platelet factor V defect as the basis for the impaired capacity of her activated platelets to support prothrombinase generation. The findings further support an important role for platelet factor V in hemostasis.

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Thrombin-stimulated Human Platelets Express Molecular Forms of α-Granule Factor V (FV), which Differ from FVa

Cited by 5 publications

References 31 publications

Plasmin accelerates platelet‐dependent prothrombinase formation without activating the platelets

Plasmin accelerates platelet‐dependent prothrombinase formation without activating the platelets

Inhibition of platelet-mediated, tissue factor-induced thrombin generation by the mouse/human chimeric 7E3 antibody. Potential implications for the effect of c7E3 Fab treatment on acute thrombosis and "clinical restenosis".

Platelet factor V New York: A defect in factor V distinct from that in factor V Quebec resulting in impaired prothrombinase generation

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