Title : Plasmin Cleaves Von Willebrand Factor at K1491-R1492 in the A1-A2 Linker Region in a Shear- and Glycan-Dependent Manner In Vitro
Abstract :
Previous studies have demonstrated a role for plasmin in regulating plasma von Willebrand factor ( VWF ) multimer com position
Moreover, emerging data have shown that plasmin-induced cleavage of VWF is of particular importance in specific pathological states
Interestingly, plasmin has been successfully used as an alternative to ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif ) in a mouse model of thrombotic thrombocytopenic purpura
Consequently, elucidating the molecular mechanisms through which plasmin binds and cleaves VWF is not only of basic scientific interest but also of direct clinical importance
Our aim was to investigate factors that modulate the susceptibility of human VWF to proteolysis by plasmin
We have adapted the VWF vortex proteolysis assay to allow for time-dependent shear exposure studies
We show that globular VWF is resistant to plasmin cleavage under static conditions, but is readily cleaved by plasmin under shear
Although both plasmin and ADAMTS13 cleave VWF in a shear-dependent manner, plasmin does not cleave at the Tyr1605-Met1606 ADAMTS13 proteolytic site in the A2 domain
Rather under shear stress conditions, or in the presence of denaturants, such as urea or ristocetin, plasmin cleaves the K1491-R1492 peptide bond within the VWF A1-A2 linker region
Finally, we demonstrate that VWF susceptibility to plasmin proteolysis at K1491-R1492 is modulated by local N-linked glycan expression within A1A2A3, and specifically inhibited by heparin binding to the A1 domain
Improved understanding of the plasmin- VWF interaction offers exciting opportunities to develop novel adjunctive therapies for the treatment of refractory thrombotic thrombocytopenic purpura