Hysteresis-like binding of coagulation factors X/Xa to procoagulant activated platelets and phospholipids results from multistep association and membrane-dependent multimerizationстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 9 июня 2016 г.
Аннотация:Binding of coagulation factors X (fX) and Xa (fXa) to activated platelets is required for the formation of
membrane-dependent enzymatic complexes of intrinsic tenase and prothrombinase. We carried out an
in-depth characterization of fX/fXa binding to phospholipids and gel-filtered, thrombin-activated platelets.
Flow cytometry, surface plasmon resonance, and computational modeling were used to investigate interactions
of fX/fXa with the membranes. Confocal microscopy was employed to study fXa binding to platelet thrombi
formed in flowing whole blood under arterial conditions. Binding of fX/fXa to either vesicles or procoagulant
platelets did not followa traditional one-step reversible binding model. Their dissociationwas a two-step process
resulting in a plateau that was up to 10-fold greater than the saturation value observed in the association experiments.
Computational modeling and experimental evidence suggested that thiswas caused by a combination of
two-step association (mainly for fX) and multimerization on the membrane (mainly for fXa). Importantly, fX
formed multimers with fXa, thereby improving its retention. The same binding/dissociation hysteresis was
observed for annexin V known to form trimers on the membranes. Experiments with platelets from gray
syndrome patients showed that alpha-granular factor Va provided an additional high-affinity binding site for
fXa that did not affect the hysteresis. Confocal microscopy observation of fXa binding to platelet thrombi in
a flow chamber and its wash-out confirmed that this phenomenon persisted under physiologically relevant
conditions. This suggests its possible role of “locking” coagulation factors on the membrane and preventing
their inhibition in plasma and removal from thrombi by flow