Complement proteins C5b-9 stimulate procoagulant activity through platelet prothrombinase.

T Wiedmer; C T Esmon; P J Sims

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PubMed · 3092889

Complement proteins C5b-9 stimulate procoagulant activity through platelet prothrombinase.

T Wiedmer·C T Esmon·P J Sims

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Abstract

The capacity of platelets treated with nonlytic concentrations of the C5b-9 proteins to catalyze prothrombin activation and thereby trigger clot formation has been investigated. When suspended in the presence of exogenous factors Xa and Va, gel-filtered platelets treated with purified C5b-9 proteins catalyzed prothrombin to thrombin conversion at rates up to tenfold above controls, and exceeded by up to fourfold the prothrombinase activity observed for thrombin-stimulated platelets. In the absence of added factor Va, C5b-9 assembly on the platelet surface significantly shortened the lag period before prothrombinase expression that was observed for untreated platelets and increased the maximum catalytic rate of thrombin formation. A comparison with other platelet stimuli revealed that the C5b-9-induced activation of platelet prothrombinase closely paralleled the effects mediated by calcium ionophore A23187. Our data suggest that the C5b-9 proteins promote the release of platelet factor V and the assembly of the prothrombinase complex, thereby potentiating the effects of thrombin on the activation of prothrombinase. Membrane assembly of the C5b-9 proteins was also observed to markedly accelerate the rate of platelet-catalyzed plasma clotting, suggesting a direct link between C5b-9-mediated prothrombinase activation and procoagulant activity accompanying immunologic damage to the platelet.

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Blood Coagulation Blood Platelets Calcimycin Complement Membrane Attack Complex Complement System Proteins Enzyme Activation Humans Platelet Factor 4 Thrombin Thromboplastin Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S.

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T Wiedmer, C T Esmon, P J Sims. 1986. Complement proteins C5b-9 stimulate procoagulant activity through platelet prothrombinase.. https://pubmed.ncbi.nlm.nih.gov/3092889/

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