The GPIbα intracellular tail - role in transducing VWF- and Collagen/GPVI-mediated signaling

Abstract

AbstractSynergy between GPIbα and GPVI signaling machineries has been suggested previously, however its molecular mechanism remains unclear. We generated a novel GPIbα transgenic mouse (GPIbαΔsig/Δsig) by CRISPR-Cas9 technology to delete the last 24 residues of the GPIbα intracellular tail important for VWF-mediated signaling. GPIbαΔsig/Δsig platelets bound VWF normally under flow but formed fewer filopodia on VWF/botrocetin, demonstrating that the deleted region does not affect ligand binding but appreciably impairs VWF-dependent signaling. Notably, while haemostasis was normal in GPIbαΔsig/Δsig mice, GPIbαΔsig/Δsig platelets exhibited defective responses after collagen-related-peptide stimulation and formed smaller aggregates on collagen-coated microchannels at low and high shears. 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. Together, these results reveal a new role for the intracellular tail of GPIbα in transducing both VWF-GPIbα and collagen-GPVI signaling events in platelets.Summary statementGPIbα and GPVI are two key receptors on the platelet surface. Using a novel transgenic mouse (GPIbαΔsig/Δsig) that lacks the last 24 amino acids of the GPIbα intracellular tail, we demonstrate the importance of this region not only in transducing signals in response to GPIbα binding to VWF, but also for collagen-GPVI-mediated platelet responses revealing previously underappreciated receptor crosstalk between GPIbα and GPVI.