Abstract Number: PB0103
Meeting: ISTH 2021 Congress
Background: One of the major membrane-dependent reactions of blood coagulation is activation factor X by intrinsic tenase complex. However, it is not clear how these coagulation factors interact with each other and with the platelet membrane of different subpopulations.
Aims: To investigate the equilibrium and kinetics binding of factors IXa and X with subpopulations of activated platelets or phospholipid vesicles, as well as the effect of factor VIIIa on this binding.
Methods: Platelets were obtained from donor blood by gel filtration purification, and phospholipid vesicles were formed by extrusion. Native fIXa and fX were labeling with Alexa Fluor 647, commercial FITC-labeled antibodies were used for observation of recombinant fVIIIa. A flow cytometer BD FACSCanto II (BD Bioscience, San Jose, CA, USA) was used to assess the binding of factors to platelets and vesicles.
Results: The binding of factor IXa to the membrane of procoagulant platelets occurs through one low-affinity binding site, which is a negatively charged phosphatidylserine. In this case, the presence of factor VIII strongly increases the binding of factors IXa and X. At the same time, this binding was calcium-dependent and reversible. The association of intrinsic tenase factors with the PS- subpopulation was insignificant and linear in the studied range. There were obtained the equilibrium constants of binding of intrinsic tenase factors to the membrane of activated platelets PS+ subpopulation: fIXa 0,7 ± 0,1 μM, fIXa in the presence of fVIIIa 67 ± 16 nM, fX in the presence of fVIIIa 109 ± 10 nM; and to phospholipid vesicles: fIXa 1,0 ± 0,1 μM.
Conclusions: Here, we quantitatively characterized the interaction of fIXa in the presence and absence of fVIIIa with the two subpopulations of activated platelets.
The study was supported by the Russian Foundation for Basic Research grants 19-04-00615.
To cite this abstract in AMA style:Soloveva PA, Podoplelova NA, Ataullakhanov FI, Panteleev MA. Interaction of the Factor IXa with the Subpopulations of Activated Platelets [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 1). https://abstracts.isth.org/abstract/interaction-of-the-factor-ixa-with-the-subpopulations-of-activated-platelets/. Accessed September 24, 2021.
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