Von Willebrand factor A2 domain inhibits A1-DNA binding while preserving A1-platelet interaction under flow: evidence from recombinant domain constructs.

Background: Circulating cell-free DNA levels increase in the circulation during inflammation and thrombosis. During immunothrombosis, neutrophil extracellular traps provide long DNA fibers with prothrombotic properties. Von Willebrand factor (VWF) has been reported to interact with DNA via its A1 domain; however, the consequences of this interaction and its regulation by the adjacent A2 domain remain poorly understood. Objectives: Using recombinant VWF domain constructs, we aimed to characterize VWF-A1-DNA interactions and to determine whether the VWF-A2 domain modulates A1-DNA binding and its impact on platelet adhesion under flow. Methods: VWF-A1-DNA interactions were examined using atomic force microscopy, magnetic tweezers, ELISAs, and microfluidic flow assays. Both recombinant A1 and mammalian-expressed A1A2 constructs were employed to assess physiological relevance. Results: VWF-A1 bound to DNA and induced concentration-dependent DNA compaction. DNA binding to VWF-A1 significantly impaired platelet adhesion under flow conditions. In contrast, the A2 domain inhibited VWF-A1-DNA binding, as shown using both isolated A2 and A1A2 constructs, and mitigated DNA's inhibitory effect on A1-mediated platelet adhesion. Conclusion: These findings suggest that, within recombinant VWF domain constructs, VWF-A1 compacts DNA and that the A2 domain negatively regulates A1-DNA interactions while preserving A1-mediated platelet binding under flow. Although further validation in native multimeric VWF and physiologically relevant models is required, these results provide new insights into how the A2 domain differentially regulates VWF-A1 interactions with DNA and platelets.