Title: Force Sensitivity of the von Willebrand Factor A2 Domain
Description: von Willebrand factor (VWF) is a multimeric glycoprotein that critically supports platelet aggregation in hemostasis. Disordered VWF function causes both thrombotic and bleeding disorders, and genetic defects in VWF are responsible for von Willebrand's disease (VWD), the most common inherited bleeding disorder in humans. Very large VWF multimers exhibit the greatest thrombogenic activity, which is attenuated by ADAMTS13 cleavage in the A2 domain. A2 cleavage is regulated by mechanical force, and pathologically high shear forces are known to enhance proteolysis and cause bleeding in patients. Enhanced cleavage is also described in patients with VWD 2A mutations. In contrast, VWF A2 is stabilized against cleavage by a calcium binding site within A2. Single molecule studies have demonstrated that mechanical unfolding is required for A2 cleavage to expose the scissile bond. In this dissertation, we aim to better understand the mechanosensitivity of A2 cleavage by characterizing the force sensitivity of A2 unfolding and refolding.