Abstract Number: PB1750
Meeting: ISTH 2020 Congress
Background: Pannexin-1 (Panx1) is a single membrane channel, which functions as an ion channel for small molecules. Recently, it was shown that platelet activation induces opening of Panx1 channels, amplifies [Ca2+]int and induces platelet aggregation. Panx1-deficient platelets show defects in hemostasis in in vitro and in vivo models.
Aims: To study Panx1 activation mechanisms in platelets and its impact on hemostasis and thrombosis.
Methods: Analysis of activation patterns of Panx1 phosphorylation after platelet activation, Panx1 inhibition by the specific inhibitor probenecid and ex vivo analysis of thrombus formation on collagen under flow.
Results: Western blot analysis demonstrated increased phosphorylation of tyrosine residue 198 (Tyr198) of Panx1 following platelet activation with classical platelet agonists. Tyrosine phosphorylation was shown to be fully dependent on Src – and partially dependent on PKC kinases. Interestingly, ADP does not phosphorylate Panx1 at Tyr198 but at Tyr308; another well-known phosphorylation site of Panx1. Here, Src kinases are only partially involved in phosphorylating Tyr308, which indicates other activation mechanisms of Panx1 channels. Blockage of Panx1 with probenecid led to reduced [ATP]ex after platelet activation with collagen-related peptide (CRP), Par4 peptide and thromboxane, but not with ADP. Panx1 inhibition leads to reduced thrombus formation on collagen at low (450 s-1) and moderate (1000 s-1) arterial shear rates ex vivo. Moreover, initial experiments provided evidence that low agonist activation of platelets lead to extracellular cleavage of Panx1 channels, which is known to irreversibly open the channel in inflammatory cells.
Conclusions: Panx1 channels function as ATP-release channels in platelets to support arterial thrombus formation. Panx1 activation is regulated by phosphorylation at different tyrosine residues following platelet activation. These results suggest an important role of Panx1 in hemostasis by releasing extracellular ATP to enable cell communication and to support thrombus formation.
To cite this abstract in AMA style:Metz LM, Elvers M. Phosphorylation and Activation of Pannexin-1 upon Platelet Activation and Thrombus Formation [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/phosphorylation-and-activation-of-pannexin-1-upon-platelet-activation-and-thrombus-formation/. Accessed January 21, 2022.
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