Committee:  Dr. Larry McIntire (BioE, Gatech), Dr. Wilbur Lam (BioE, Gatech), Dr. Xiaoping Du(University of Illinois at Chicago) and Dr. Renhao Li (Emory University)
In hemostasis, platelet adhesion and signaling play key roles. Specifically, two platelet receptors: GPIbα and GPIIb/IIIa mediate the early and mid-stages of platelet adhesion. Platelet glycoprotein Ibα (GPIbα) is part of the GPIbα-V-IX complex that constitutes the receptor for von Willebrand factor (VWF). Its binding to VWF A1 domain enables rolling of platelets on the sites of vascular injury. GPIIb/IIIa is also known as integrin αIIbβ3 and is found exclusively on platelets; upon activation, it allows for platelet stable adhesion to VWF on the surface of sub-endothelium and promotes the expansion of the platelets plug by cross-linking via Arg-Gly-Asp (RGD) bearing ligands like soluble fibrinogen and VWF. Ligation of GPIbα and GPIIb/IIIa has been reported to trigger outside-in platelet-activating signals in a sequential fashion. In this proposal, I will study GPIbα and GPIIb/IIIa in the context of platelet adhesion and signal initiation. The goal is to address how ligand binding of GPIbα and GPIIb/IIIa initiates signaling in a mechanically dependent way and how GPIbα and GPIIb/IIIa trigger platelet activation. I propose to conduct single-molecular level experiments with a fluorescence biomembrane force probe (fBFP) to systematically correlate mechanically dependent GPIbα and GPIIb/IIIa ligation with readouts of platelet activation including GPIIb/IIIa up-regulation and unbending conformational change, platelet intracellular Ca²⁺ signal and lipid scrambling on the plasma membrane.