Work

OC 61.5 Plasma Growth Factors Drive Constitutive Translation in Circulating Platelets to Maintain Protein Homeostasis and Regulate Platelet GPCR Reactivity and the Hemostatic and Thrombotic Balance

Year: 2023

Type: article

Abstract: Background: Increased levels of the circulating form of human endoglin (sEng) have been reported in several cardiovascular-related conditions including preeclampsia, as a consequence of a cleavage product of membrane bound endoglin, present on endothelial cells.However, the role of sEng in platelet-dependent hemostasis in vivo is unknown.Aims: Because sEng encompasses an RGD motif involved in integrin binding, we hypothesized that sEng would be able to bind integrin αIIbβ3, therefore compromising platelet binding to fibrinogen and thrombus stability.Methods: To address this question, in vitro washed human platelet aggregation, thrombus retraction and secretion-competition assays were performed in the presence of sEng.Surface plasmon resonance (SPR) binding and computational (docking) analyses were carried out to evaluate protein-protein interactions.Transgenic mice overexpressing human sEng (hsEng+) were used to measure bleeding/rebleeding, prothrombin time (PT), blood stream and embolus formation after FeCl3-induced injury of carotid artery.Results: Adding sEng to human whole blood under flow conditions, a smaller thrombus size compared to controls was observed.Also, we found that sEng inhibited platelet aggregation and thrombus retraction, interfering with fibrinogen binding, but without affecting platelet activation.SPR binding studies demonstrated the specific interaction between αIIbβ3 and sEng, and molecular modelling showed a good fitting between αIIbβ3 and sEng structures involving the endoglin RGD motif, suggesting the possible formation of a highly stable αIIbβ3/sEng complex.hsEng+ mice showed increased bleeding time and number of re-bleedings compared to wild-type mice.No differences in PT were denoted between genotypes.After FeCl3 injury, the number of released emboli in hsEng+ mice was higher and the occlusion was slower compared to controls.Conclusion(s): These results show that sEng interferes with thrombus formation and stabilization, likely via its binding to platelet αIIbβ3, demonstrating its involvement in primary hemostasis control and suggesting that sEng could be a new tool for antithrombotic therapy.

Source: Research and Practice in Thrombosis and Haemostasis

DOI: 10.1016/j.rpth.2023.100571