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

Synergy between GPIb and GPVI signaling machineries has been suggested previously, however its molecular mechanism remains unclear. We generated a novel GPIb transgenic mouse (GPIb{Delta}sig/{Delta}sig) by CRISPR-Cas9 technology to delete the last 24 residues of the GPIb intracellular tail important for VWF-mediated signaling. GPIb{Delta}sig/{Delta}sig 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 GPIb{Delta}sig/{Delta}sig mice, GPIb{Delta}sig/{Delta}sig 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 IIb{beta}3-or GPVI-blockers suggested reduced IIb{beta}3 activation contributes to the phenotype of the GPIb{Delta}sig/{Delta}sig platelets. Together, these results reveal a new role for the intracellular tail of GPIb in transducing both VWF-GPIb and collagen-GPVI signaling events in platelets. Summary statementGPIb and GPVI are two key receptors on the platelet surface. Using a novel transgenic mouse (GPIb{Delta}sig/{Delta}sig) that lacks the last 24 amino acids of the GPIb intracellular tail, we demonstrate the importance of this region not only in transducing signals in response to GPIb binding to VWF, but also for collagen-GPVI-mediated platelet responses revealing previously underappreciated receptor crosstalk between GPIb and GPVI.