The N-terminal flanking region of the A1 domain regulates the force-dependent binding of von Willebrand factor to platelet glycoprotein Ibα.
Binding of platelet glycoprotein Ibα (GPIbα) to von Willebrand factor (VWF) initiates platelet adhesion to disrupted vascular surface under arterial blood flow. Flow exerts forces on the platelet that are transmitted to VWF-GPIbα bonds, which regulate their dissociation. Mutations in VWF and/or GPIbα may alter the mechanical regulation of platelet adhesion to cause hemostatic defects as found in patients with von Willebrand disease (VWD). Using a biomembrane force probe, we observed biphasic force-decelerated (catch) and force-accelerated (slip) dissociation of GPIbα from VWF. The VWF A1 domain that contains the N-terminal flanking sequence Gln(1238)-Glu(1260) (1238-A1) formed triphasic slip-catch-slip bonds with GPIbα. By comparison, using a short form of A1 that deletes this sequence (1261-A1) abolished the catch bond, destabilizing its binding to GPIbα at high forces. Importantly, shear-dependent platelet rolling velocities on these VWF ligands in a flow chamber system mirrored the force-dependent single-bond lifetimes. Adding the Gln(1238)-Glu(1260) peptide, which interacted with GPIbα and 1261-A1 but not 1238-A1, to whole blood decreased platelet attachment under shear stress. Soluble Gln(1238)-Glu(1260) reduced the lifetimes of GPIbα bonds with VWF and 1238-A1 but rescued the catch bond of GPIbα with 1261-A1. A type 2B VWD 1238-A1 mutation eliminated the catch bond by prolonging lifetimes at low forces, a type 2M VWD 1238-A1 mutation shifted the respective slip-catch and catch-slip transition points to higher forces, whereas a platelet type VWD GPIbα mutation enhanced the bond lifetime in the entire force regime. These data reveal the structural determinants of VWF activation by hemodynamic force of the circulation.
From the Coulter Department of Biomedical Engineering.
Lining
L
Ju
the Puget Sound Blood Research Institute; Department of Medicine, University of Washington, Seattle, Washington 98104.
Jing-Fei
JF
Dong
Cardiovascular Sciences-Thrombosis, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030.
Miguel A
MA
Cruz
From the Coulter Department of Biomedical Engineering; Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332,. Electronic address: cheng.zhu@bme.gatech.edu.
Cheng
C
Zhu
D019943:Amino Acid Substitution; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D010973:Platelet Adhesiveness; D019038:Platelet Glycoprotein GPIb-IX Complex; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014841:von Willebrand Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D008562:Membrane Glycoproteins; D019038:Platelet Glycoprotein GPIb-IX Complex; C094990:adhesion receptor; D014841:von Willebrand Factor
Biomembrane Force Probe; Catch Bond; Glycoprotein Ibα; Kinetics; Platelets; Single Molecule Biophysics; Thrombosis; von Willebrand Factor