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Establishing the signalling pathways regulating reversible platelet integrin activation

1Maastricht University, MAASTRICHT, Limburg, Netherlands, 2Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, The Netherlands; Institute for Cardiovascular and Metabolic Research, School of Biological sciences, University of Reading, Reading, UK, MAASTRICHT, Limburg, Netherlands, 3Departments of Biochemistry and Internal Medicine, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands;, Maastricht, Limburg, Netherlands, 4Department of Functional Coagulation, Synapse Research Institute, Maastricht, the Netherlands;, Maastricht, Limburg, Netherlands, 5Department of Biochemistry, CARIM, Maastricht University, Maastricht, the Netherlands; Synapse Research Institute Maastricht, The Netherlands, Maastricht, Limburg, Netherlands, 6Synapse Research Institute, Maastricht, the Netherlands, Maastricht, Limburg, Netherlands, 7Department of Functional Coagulation, Synapse Research Institute, Maastricht, the Netherlands, Maastricht, Limburg, Netherlands

Abstract Number: PB0407

Meeting: ISTH 2022 Congress

Theme: Platelets and Megakaryocytes » Platelet Signaling

Background: For long it is known that collagen- and thrombin-induced platelet signalling pathways are intrinsically reversible, and coupled to these the conformation change leading to integrin αIIbβ3 activation required for platelet aggregation. However, which signalling pathways contribute to a more or less persistent platelet aggregation in haemostasis and thrombosis is still not fully elucidated.

Aims: To establish the platelet signalling pathways induced by collagen or thrombin receptors that regulate early and late integrin αIIbβ3 activation.

Methods: Platelets were activated dose-dependently with the glycoprotein VI (GPVI) agonist CRP-XL or any of the PAR agonists thrombin, SFLLRN and AYPGKF. Flow cytometry was used to measure integrin αIIbβ3 activation (FITC-PAC1 mAb) and P-selectin expression over time. A panel of pharmacological inhibitors was used to block specific signalling pathways before or after the agonist addition.

Results: When pre-treated with blocking compounds, agonist-induced integrin αIIbβ3 activation decreased in the order: protein kinase C (PKC) > glycogen synthase kinase 3 (GSK3) > β-arrestin > phosphatidylinositol-3-kinase (PI3K) > [Ca2+]i elevation. Blocking compound application at 10-20 min after agonist CRP-XL or TRAP6 resulted in the same potency order of integrin closure. Expression of P-selectin was not antagonized by late application of compounds. After selective stimulation by PKC agonist PMA, integrin activation was prevented, and integrin closure was enhanced, again in the order of compounds blocking PKC > GSK3 > β-arrestin > PI3K > [Ca2+]i elevation. Induction of [Ca2+]i elevation by thapsigargin resulted in limited integrin activation that was only enhanced combined with weaker agonists such as TRAP6 or PMA.

Conclusion(s): Similarly, for GPVI and PAR agonists, PKC isoforms provided the strongest mechanism of short- and long-term integrin αIIbβ3 activation. This role is only enhanced by additional [Ca2+]i elevation with weak platelet agonists.

To cite this abstract in AMA style:

Zou J, Sun S, De Simone I, ten Cate H, de Groot P, Heemskerk J, Roest M, de Laat B. Establishing the signalling pathways regulating reversible platelet integrin activation [abstract]. https://abstracts.isth.org/abstract/establishing-the-signalling-pathways-regulating-reversible-platelet-integrin-activation/. Accessed October 1, 2023.

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