Identification of a novel 14-3-3zeta binding site within the cytoplasmic tail of platelet glycoprotein Ibalpha.

The glycoprotein Ib-V-IX (GPIb-V-IX) complex interacts with subendothelial von Willebrand factor (VWF) to ensure recruitment of platelets at sites of vascular injury, a process that culminates in integrin alpha(IIb)beta(3)-dependent stable adhesion and spreading. Interaction of the 14-3-3zeta adaptor protein with the C-terminal 606-610 phosphoserine motif of the GPIbalpha subunit has been implicated in the control of alpha(IIb)beta(3) activation and cell spreading. In this study, we have examined potentially novel 14-3-3zeta binding sites by expressing mutant forms of GPIbalpha in Chinese-hamster-ovary (CHO) cells.