Abstract
Neutrophils release their intracellular content, DNA included, into the bloodstream to form neutrophil extracellular traps (NETs) that confine and kill circulating pathogens. The mechanosensitive adhesive blood protein, von Willebrand Factor (vWF), interacts with the extracellular DNA of NETs to potentially immobilize them during inflammatory and coagulatory conditions. Here, we elucidate the previously unknown molecular mechanism governing the DNA-vWF interaction by integrating atomistic, coarse-grained, and Brownian dynamics simulations, with thermophoresis, gel electrophoresis, fluorescence correlation spectroscopy (FCS), and microfluidic experiments. We demonstrate that, independently of its nucleotide sequence, double-stranded DNA binds to a specific helix of the vWF A1 domain, via three arginines. This interaction is attenuated by increasing the ionic strength. Our FCS and microfluidic measurements also highlight the key role shear-stress has in enabling this interaction. Our simulations attribute the previously-observed platelet-recruitment reduction and heparin-size modulation, upon establishment of DNA-vWF interactions, to indirect steric hindrance and partial overlap of the binding sites, respectively. Overall, we suggest electrostatics-guiding DNA to a specific protein binding site-as the main driving force defining DNA-vWF recognition. The molecular picture of a key shear-mediated DNA-protein interaction is provided here and it constitutes the basis for understanding NETs-mediated immune and hemostatic responses.
Highlights
Release of DNA from neutrophils into the bloodstream to form neutrophil extracellular traps (NETs) is a key immune mechanism to trap and kill circulating pathogens [1,2]
We first studied the spontaneous association of the von Willebrand Factor (vWF) A1 domain to two different double stranded DNA (ds DNA) fragments, by performing multiple unbiased atomistic molecular dynamics (MD) simulations (84 runs, each one of 210 ns, for a total of 17.6 s cumulative simulation time)
The blood protein vWF was shown recently to interact with extracellular DNA from NETs [18]
Summary
Release of DNA from neutrophils into the bloodstream to form neutrophil extracellular traps (NETs) is a key immune mechanism to trap and kill circulating pathogens [1,2]. NETs are complex macro-molecular meshes, mainly composed of DNA, along with several scaffold proteins and highly-active antimicrobial agents. They efficiently ensnare and kill pathogens, triggered by diverse external stimuli. Since their discovery about 15 years ago, NETs have been attributed to provide a localized and timed immune response. Pregnancy complications and infertility have been linked to poor down-regulation of NETs [7]. NETs are found in patients with systemic infections (sepsis) [2,8,9] or in the res-
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