The activation of factor XI by meizothrombin was investigated using recombinant meizothrombin (R155A meizothrombin) that is resistant to autocatalytic removal of fragment 1. Meizothrombin was capable of activating factor XI at an activation rate similar to that of thrombin. Dextran sulphate and heparin, known cofactors of thrombin-mediated factor XI activation, did not stimulate the activation of factor XI by meizothrombin. However, the activation of factor XI by meizothrombin was markedly enhanced by vesicles containing phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylethanolamine (PE), whereas PC/PS or PC/PE vesicles only had a minor effect on the activation. Thrombin-mediated factor XI activation was not influenced by phospholipids.
The effect of PC/PS/PE and PC/PS vesicles was studied in a factor XI dependent clot lysis assay. In this assay, factor XI inhibits clot lysis by a feedback loop in the intrinsic pathway via thrombin-mediated factor XI activation. Removal of endogenous phospholipids in plasma by centrifugation resulted in an increased clot lysis, which could be restored to the pre-centrifugation level by the addition of PC/PS/PE vesicles, but not by PC/PS vesicles. When clot lysis was initiated by factor IXa in the presence of a factor XIa blocking antibody, there was no difference in inhibitory effect of PC/PS/PE or PC/PS vesicles. These data suggested that the differences in clot lysis inhibition observed between PC/PS/PE and PC/PS vesicles were caused by factor XI activation by meizothrombin. Meizothrombin-mediated factor XI activation may therefore play an important role in the antifibrinolytic feedback loop in the intrinsic pathway.
References
1
Naito K,
Fujikawa K.
Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces. J Biol Chem 1991; 266: 7353-7358
4
Naito K,
Fujikawa K.
Activation of human blood coagulation factor XI independent of factor XII. Factor XI is activated by thrombin and factor XIa in the presence of negatively charged surfaces. Thromb Haemost 1991; 65: 144 (Abstract).
5
Gailani D,
Broze GJ.
Factor XH-independent activation of factor XI in plasma: effect of sulfatides on tissue factor-induced coagulation. Blood 1993; 82: 813-819
6
von demBome PAK,
Koppelman SJ,
Bouma BN,
Meijers JCM.
Surface independent activation of factor XI by thrombin in the presence of high molecular weight kininogen. Thromb Haemost 1994; 72: 397-402
7
von demBome PAK,
Meijers JCM,
Bouma BN.
Feedback activation of factor XI by thrombin in plasma results in additional formation of thrombin that protects fibrin clots from fibrinolysis. Blood 1995; 86: 3035-3042
11
Doyle M,
Haley PE.
Meizothrombin: active intermediate formed during prothrombinase-catalyzed activation of prothrombin. Methods Enzymol 1993; 222: 299-312
12
Rosing J,
Zwaal RFA,
Tans G.
Formation of meizothrombin as intermediate in factor Xa-catalyzed prothrombin activation. J Biol Chem 1986; 261: 4224-4228
14
Tans G,
Nicolaes GAF,
Christella M,
Thomassen LGD,
Hemker HC,
van ZonneveldAJ,
Pannekoek H,
Rosing J.
Activation of human factor V by meizothrombin. J Biol Chem 1994; 269: 15969-15972
15
Schoen P,
Lindhout T.
The in situ inhibition of prothrombinase formed human α-thrombin and meizothrombin (desFl) by antithrombin III and heparin. J Biol Chem 1987; 262: 11268-11274
16
Krishnaswamy S,
Mann KG,
Nesheim ME.
The prothrombinase-catalyzed activation of prothrombin proceeds through the intermediate meizothrombin in an ordered, sequential reaction. J Biol Chem 1986; 261: 8977-8984
17
Tijburg PNM,
van HeerdeWL,
Leenhouts HM,
Hessing M,
Bouma BN,
de GrootPhG.
Formation of meizothrombin as intermediate in factor Xa-catalyzed prothrombin activation on endothelial cells. The influence of thrombin on the reaction mechanism. J Biol Chem 1991; 266: 4017-4022
18
Tans G,
Janssen-Claessen T,
Hemker HC,
Zwaal RFA,
Rosing J.
Meizothrombin formation during factor Xa-catalyzed prothrombin activa-tion. Formation in a purified system and in plasma. J Biol Chem 1991; 266: 21864-21873
19
Bovill EG,
Tracy RP,
Hayes TE,
Jenny RJ,
Bhushan FH,
Mann KG.
Evidence that meizothrombin is an intermediate product in clotting whole blood. Arterioscler Thromb Vase Biol 1995; 15: 754-758
21
van derGraaf F,
Greengard JS,
Bouma BN,
Kerbiriou DM,
Griffin JH.
Isolation and functional characterization of the active light chain of activated human blood coagulation factor XI. J Biol Chem 1983; 258: 9669-9675
24
Rouser G,
Fleisher S,
Yamamoto A.
Two dimensional thin layer chromatographic separation of polar lipids and determination of phospholipid by phosphorus analysis of spots. Lipids 1970; 5: 494-496
25
Meijers JCM.
Regulation of the blood coagulation mechanism by plasma proteinase inhibitors. PhD Thesis, State University of Utrecht, The Netherlands. 1988 pp. 93-108
27
Rhee MJ,
Morris S,
Kosow DP.
Role of meizothrombin and meizothrom-bin(desFl) in the conversion of prothrombin to thrombin by the Echis carinatus venom coagulant. Biochemistry 1988; 21: 3437-3443
28
Pei G,
Laue TM,
Aulabaugh A,
Fowlkes DM,
Lentz BR.
Structural comparisons of meizothrombin and its precursor prothrombin in the presence or absence of membranes. Biochemistry 1992; 31: 6990-6996
32
Smirnov MD,
Esmon CT.
Phosphatidylethanolamine incorporation into vesicles selectively enhances factor Va inactivation by activated protein C. J Biol Chem 1994; 269: 816-819
