Type 2M von Willebrand Disease Mutations Impair Platelet Adhesion Through Distinct Effects Involving Enhanced A1/A2...

Von Willebrand factor (VWF)-mediated platelet adhesion under flow conditions is tightly regulated by intramolecular autoinhibitory interactions, including the interaction between the A1 and A2 domains. Type 2M von Willebrand disease (VWD) is attributed to impaired binding of the A1 domain to platelet glycoprotein Ibα (GPIbα).

To investigate the effects of type 2M mutations on A1/A2 interactions and platelet adhesion.

Molecular dynamics (MD) simulations were performed to predict the effects of type 2M VWD mutations located at the A1/A2 interface on interdomain interactions. Atomic force microscopy (AFM) and biolayer interferometry (BLI) were used to validate the computational findings. Flow assays were used to evaluate platelet adhesion under flow conditions.

MD simulations identified eight reported type 2M mutations clustered at the A1/A2 binding interface. AFM and BLI experiments demonstrated that these mutations generally enhanced A1/A2 interactions. Platelet adhesion assays revealed these mutations impair platelet adhesion through distinct effects, including reduced A1/GPIbα binding and enhanced A1/A2 interaction. S1358N, V1360A, L1361W, K1362T, Y1363C, L1365R, and F1369I directly impaired platelet adhesion to VWF-A1. Notably, E1359K impaired platelet adhesion to isolated VWF-A1 under high shear conditions, whereas under low shear, the mutation markedly reduced platelet adhesion only in the presence of the A2 domain, suggesting a shear- and A2-dependent regulation of platelet adhesion.

Type 2M mutations located at the A1/A2 interface impair platelet adhesion through distinct effects on reduced A1/GPIbα binding and enhanced A1/A2 interaction. This study provides new insight into the regulatory role of the A1/A2 interaction in type 2M VWD.