Platelet plasminogen activator inhibitor: purification and characterization of interaction with plasminogen activators and activated protein C

Fay, William P.; Owen, Whyte G.

doi:10.1021/bi00440a011

Cited by 50 publications

(19 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Platelets contain both a 2 AP 59 and PAI-1 15,[60][61][62][63] that are released upon stimulation. We found that a proportion of platelet PAI-1 colocalized with plasminogen binding in PS-exposing and spread platelets.…”

Section: Discussionmentioning

confidence: 99%

Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow

Whyte

Swieringa

Mastenbroek

et al. 2015

Blood

104

111

View full text Add to dashboard Cite

Key Points• Under physiological flow rates, plasminogen primarily accumulates on fibrin(ogen), emanating from platelets and initiates fibrinolysis.• Plasminogen is localized to defined "caps" on the surface of PS-exposing platelets in a fibrin(ogen)-dependent manner.The interaction of plasminogen with platelets and their localization during thrombus formation and fibrinolysis under flow are not defined. Using a novel model of whole blood thrombi, formed under flow, we examine dose-dependent fibrinolysis using fluorescence microscopy. Fibrinolysis was dependent upon flow and the balance between fibrin formation and plasminogen activation, with tissue plasminogen activator-mediated lysis being more efficient than urokinase plasminogen activator-mediated lysis. Fluorescently labeled plasminogen radiates from platelet aggregates at the base of thrombi, primarily in association with fibrin. Hirudin attenuates, but does not abolish plasminogen binding, denoting the importance of fibrin. Flow cytometry revealed that stimulation of platelets with thrombin/convulxin significantly increased the plasminogen signal associated with phosphatidylserine (PS)-exposing platelets. Binding was attenuated by tirofiban and GlyPro-Arg-Pro amide, confirming a role for fibrin in amplifying plasminogen binding to PSexposing platelets. Confocal microscopy revealed direct binding of plasminogen and fibrinogen to different platelet subpopulations. Binding of plasminogen and fibrinogen co-localized with PAC-1 in the center of spread platelets. In contrast, PS-exposing platelets were PAC-1 negative, and bound plasminogen and fibrinogen in a protruding "cap." These data show that different subpopulations of platelets harbor plasminogen by diverse mechanisms and provide an essential scaffold for the accumulation of fibrinolytic proteins that mediate fibrinolysis under flow. (Blood. 2015;125(16):2568-2578 IntroductionPlatelet accumulation is central to the hemostatic response. Platelets are activated in vivo by numerous agonists of varying potency, including thrombin, collagen, adenosine 59diphosphate, and thromboxane A2. Platelets exhibit a nonuniform response to activation, with distinct populations forming with different surface characteristics.1 Aggregating platelets are characterized by a spherical shape, binding of fibrinogen, and expression of the active integrin a IIb b 3, and predominantly function in clot retraction. Highly activated platelets are observed on collagen fibers 1 and in the core region of a thrombus nearest the vascular injury.2 These platelets are characterized by membrane exposure of phosphatidylserine (PS), a rounded balloon-like structure, sustained increase in cytosolic Ca 21, and binding of coagulation factors. 3,4 PS-exposing platelets, also termed procoagulant platelets, substantially enhance the activity of the prothrombinase complex, 5,6 and subsequent thrombin and fibrin formation. 7 An additional subpopulation of platelets, termed "coated" platelets, are generated in response to strong dual agonist stimulatio...

show abstract

Section: Discussionmentioning

confidence: 99%

Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow

Whyte

Swieringa

Mastenbroek

et al. 2015

Blood

104

111

View full text Add to dashboard Cite

show abstract

“…Upon activation by thrombin, activated protein C degrades factors V/Va and VIII/VIIIa and releases a tissue-type plasminogen activator. It also stimulates fi brinolysis through its interaction with plasminogen activator inhibitor [44][45][46] . A number of snake venoms specifi cally activate protein C [47] [47][48][49][50][51][52] , A. bilineatus [53] , A. h. halys [54] , and A. blomhoffi ussuriensis [55] .…”

Section: Protein C Activatorsmentioning

confidence: 99%

Serine Proteases Affecting Blood Coagulation and Fibrinolysis from Snake Venoms

Kini

2005

Pathophysiol Haemos Thromb

160

106

View full text Add to dashboard Cite

Snake venom proteases, in addition to their contribution to the digestion of the prey, affect various physiological functions. They affect platelet aggregation, blood coagulation, fibrinolysis, complement system, blood pressure and nervous system. This review provides a ready reference for serine proteases that interfere in blood coagulation and fibrinolysis. They exhibit their activity by activation of specific zymogens of coagulation factors. These serine proteases serve as tools to study molecular details in the activation of specific factors involved in coagulation and fibrinolytic cascades and are useful in treating various thrombotic and hemostatic conditions.

show abstract

“…4 -6 Consumption of PAI-1 by APC, however, is a kinetically unfavorable reaction when it is compared with inhibition of tPA by PAI-1. 7 Alternative explanations included APC inhibition of thrombin production, which would otherwise inhibit fibrinolysis either by the stimulation of PAI-1 release from platelets 8 or by some unknown mechanism. 9 We investigated the profibrinolytic effect of APC by use of a clot lysis assay that was based on a decrease in turbidity that occurs during fibrin dissolution.…”

Section: Discovery Of Tafimentioning

confidence: 99%

Thrombin Activatable Fibrinolysis Inhibitor and an Antifibrinolytic Pathway

Bajzar

2000

ATVB

188

140

View full text Add to dashboard Cite

Abstract-Coagulation and fibrinolysis are processes that form and dissolve fibrin, respectively. These processes are exquisitely regulated and protect the organism from excessive blood loss or excessive fibrin deposition. Regulation of these cascades is accomplished by a variety of mechanisms involving cellular responses, flow, and protein-protein interactions. With respect to regulation mediated by protein-protein interaction, the coagulation cascade appears to be more complex than the fibrinolytic cascade because it has more components. Yet each cascade is regulated by initiators, cofactors, feedback reactions, and inhibitors. Coagulation is also controlled by an anticoagulant pathway composed of (minimally) thrombin, thrombomodulin, and protein C. 1 Protein C is converted by the thrombin/thrombomodulin complex to activated protein C (APC), which catalyzes the proteolytic inactivation of the essential cofactors required for thrombin formation, factors Va and VIIIa. An analogous antifibrinolytic pathway has been identified recently. This pathway provides an apparent symmetry between coagulation and fibrinolysis and is also composed of thrombin, thrombomodulin, and a zymogen that is activated to an enzyme. The enzyme proteolytically inactivates a cofactor to attenuate fibrinolysis. However, unlike APC, which is a serine protease, the antifibrinolytic enzyme is a metalloprotease that exhibits carboxypeptidase B-like activity. Within a few years of each other, 5 groups independently described a molecule that accounts for this antifibrinolytic activity. We refer to this molecule as thrombin activatable fibrinolysis inhibitor (TAFI), a name that is based on functional properties by which it was identified, assayed, and purified.(Because of the preferences of some journals "activatable" is occasionally referred to as "activable.") This review will encompass a historical account of efforts to isolate TAFI and characterize it with respect to its activation, activity, regulation, and potential function in vivo. Discovery of TAFIOur initial efforts were directed toward understanding the apparent profibrinolytic effect of the anticoagulant APC, which had been reported previously. 2,3 In the work of Taylor and Lockhart, 2 the modest acceleration of fibrinolysis evoked by APC in a cell-free system was more pronounced in clots formed from either whole blood or platelet-poor plasma supplemented with leukocytes. Other investigators showed that APC can consume plasminogen activator inhibitor-1 (PAI-1), thereby sparing tissue plasminogen activator (tPA), and this was offered as an explanation for the apparent profibrinolytic properties of APC. 4 -6 Consumption of PAI-1 by APC, however, is a kinetically unfavorable reaction when it is compared with inhibition of tPA by PAI-1. 7 Alternative explanations included APC inhibition of thrombin production, which would otherwise inhibit fibrinolysis either by the stimulation of PAI-1 release from platelets 8 or by some unknown mechanism. 9 We investigated the profibrinolytic effect of A...

show abstract

Platelet plasminogen activator inhibitor: purification and characterization of interaction with plasminogen activators and activated protein C

Cited by 50 publications

References 28 publications

Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow

Plasminogen associates with phosphatidylserine-exposing platelets and contributes to thrombus lysis under flow

Serine Proteases Affecting Blood Coagulation and Fibrinolysis from Snake Venoms

Thrombin Activatable Fibrinolysis Inhibitor and an Antifibrinolytic Pathway

Contact Info

Product

Resources

About