Summary
Platelet glycoprotein (GP)Ib-IX-V mediates von Willebrand Factor (vWF)-dependent adhesion
to vascular subendothelium at high shear in (patho)physiological thrombus formation.
The ligand-binding domain of GPIb-IX-V is within the N-terminal 282 residues of GPIbα,
that contains seven tandem leucine-rich repeats (Leu36–Ala200). Repeats 2–4 are critical
for vWF binding. In this study, we have built molecular models of the seven leucine-rich
repeats of human, canine and mouse GPIbα, providing novel insights into the species-specific
interaction between human vWF and its receptor. Interestingly, a major difference
between the models was a large negatively charged patch on the concave face of human,
but not canine, repeats 2–4. In addition, five individual mutations within the leucine-rich
repeats of GPIbα associated with the bleeding disorder Bernard-Soulier syndrome, that
result in dysfunctional vWF binding, were mapped to the model of human GPIbα. This
provides the basis for relating these genetic lesions to abnormal function of the
receptor.
Keywords
Glycoprotein Ibα - platelets - leucine-rich repeats - Bernard-Soulier syndrome