Abstract Number: OC 37.4
Meeting: ISTH 2021 Congress
Background: The platelet GPIbα-VWF A1 domain interaction is essential for platelet tethering under high shear conditions. Under flow, VWF binding to GPIb-IX-V complex induces intracellular calcium fluxes and activation of tyrosine kinases that culminate in the activation of αIIbβ3. GPIbα and GPVI signaling machineries have previously been suggested to be linked, but the molecular basis of their signaling overlap remains unclear.
Aims: To evaluate the importance of the GPIbα intracellular tail in platelet function and thrombus formation.
Methods: GpIbαΔsig/Δsig mice, in which the last 24 amino acids of the intracellular tail were deleted, were generated via CRISPR-Cas9 technology. Platelet function was assessed ex vivo by flow cytometry, platelet aggregometry, immunostaining, microfluidic assays, and in vivo by tail bleeding and thrombosis models.
Results: GpIbαΔsig/Δsig mice exhibited mildly reduced platelet count and slightly enlarged platelets compared to GpIbα+/+ littermates. Activation of GpIbαΔsig/Δsig platelets with ADP, thrombin and rhodocytin was normal, but GpIbαΔsig/Δsig platelets stimulated with collagen-related-peptide (CRP) exhibited markedly decreased P-selectin exposure and αIIbβ3 activation, suggesting a role for the GpIbα intracellular tail in GPVI-mediated signaling. Consistent with this, while hemostasis was normal in GpIbαΔsig/Δsig mice, diminished tyrosine-phosphorylation, particularly pSYK was detected in CRP-stimulated GpIbαΔsig/Δsig platelets as well as reduced platelet spreading on CRP. Although GpIbαΔsig/Δsig platelets bound VWF normally under flow, they formed smaller aggregates than wild-type platelets on collagen-coated microchannels at low, medium and high shears. In response to both VWF and collagen binding, flow assays performed with plasma-free blood or in the presence of αIIbβ3– or GPVI-blockers suggested reduced αIIbβ3 activation contributes to the phenotype of the GpIbαΔsig/Δsig platelets.
Conclusions: Together, our data reveal the importance of the intracellular tail of GPIbα in transducing VWF-GPIbα signals and also a previously uncharacterized role for this region in collagen-GPVI signaling events in platelets.
To cite this abstract in AMA style:Constantinescu-Bercu A, A Wang Y, J Woollard K, Mangin P, Vanhoorelbeke K, Crawley JT, I Salles-Crawley I. The Intracellular Tail of GPIbα Augments GPVI-mediated Signaling in Mice [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/the-intracellular-tail-of-gpib%ce%b1-augments-gpvi-mediated-signaling-in-mice/. Accessed December 10, 2023.
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