Mechanism Of Affinity Alterations In VWF-A3 Domain Mutant W1745C Studied By Molecular Dynamics Simulation

During physiological hemostasis process,circulating platelets tend to adhere to and then aggregate on the damaged blood vessels.They are key events in the process of hemostasis and thrombosis,and are mediated by collagen,von Willebrand factor(VWF),and glycoprotein Ib(GPIb)on the surface of platelets.They are also regulated by blood flow shear stress.Previous studies have shown that collagen can induce the up-regulation of binding affinity of A1 with GPIb on platelets,while W1745 C mutation on A3 can weaken the ability to adhere to platelets by down-regulating its affinity with collagen,leading to type II von Willebrand disease.However,the pathological mechanism has not been clear yet.Previously,our laboratory found that A1 mutation caused its local dynamic behavior change by molecular dynamics simulation,and revealed the molecular structure basis of A1/GPIbα affinity abnormality caused by mutation of one amino acid.At the same time,we got the the complex of GPIbα/6B4 by rigid docking and obtain the A2-α6/ADAMTS13-space by flexible docking,intensively studied the interaction between the receptor and the ligand.At present,the crystal structures of A3,A1 monomer and A3/Collagen complex have been resolved,at the same time,molecular dynamics simulation can observe the evolution of protein conformation and the details of atomic motion at the nanometer scale.To study the pathogenesis and structural basis of A3 mutant W1745 C under physiological conditions,a kind of 2 type of von Wilebrand disease(VWD),and to understand the interaction of A3/Collagen and A3/A1,in this paper,we constructed two systems of VWF-A3/Collagen and VWF-A1/VWF-A3 by molecular dynamics and docking method respectively.And by computer mutation,we obtained W1745C-A3/Collagen and W1745C-A3/A1.Equilibrium molecular dynamics simulations show that hydrogen bonds and salt bridges were critical for the formation of two complexes.Besides,the interaction of complex in the mechanical environment was investigated by constant velocity tensile simulation.we found that the dissociation force of VWF-A3/Collagen was significantly greater than that of VWF-A1/VWF-A3,but the dissociation forces of the two complexes after mutation were very close.These results suggest that the possible mechanism by which collagen activates VWF under high shear conditions is as follows: after the globular VWF in plasma binding to collagen,flow shear stress promotes the opening or stretching of the A1A2A3 ringy triplet and leading to A1A2A3 instability structure,thus accelerates the binding of VWF-A1 to platelet GPIb.The weakened W1745 C mutation decreased the mechanical stability of A3 and collagen,so the VWF ringy structure was not easy to open,which blocked VWF binding to platelets,and eventually caused von Willebrand disease.These results will help to strengthen the understanding of the pathological mechanism of coagulation and hemostasis disorders,and provide guidance for the development of related antithrombotic drugs and hemostatic drugs.