Platelet Protein Disulfide Isomerase Promotes Glycoprotein Ib?-Mediated Platelet-Neutrophil Interactions Under Thromboinflammatory Conditions.

ABSTRACT: BACKGROUND:Platelet-neutrophil interactions contribute to vascular occlusion and tissue damage in thromboinflammatory disease. Platelet glycoprotein Ib? (GPIb?), a key receptor for the cell-cell interaction, is believed to be constitutively active for ligand binding. Here, we established the role of platelet-derived protein disulfide isomerase (PDI) in reducing the allosteric disulfide bonds in GPIb? and enhancing the ligand-binding activity under thromboinflammatory conditions. METHODS:Bioinformatic analysis identified 2 potential allosteric disulfide bonds in GPIb?. Agglutination assays, flow cytometry, surface plasmon resonance analysis, a protein-protein docking model, proximity ligation assays, and mass spectrometry were used to demonstrate a direct interaction between PDI and GPIb? and to determine a role for PDI in regulating GPIb? function and platelet-neutrophil interactions. Also, real-time microscopy and animal disease models were used to study the pathophysiological role of PDI-GPIb? signaling under thromboinflammatory conditions. RESULTS:Deletion or inhibition of platelet PDI significantly reduced GPIb?-mediated platelet agglutination. Studies using PDI-null platelets and recombinant PDI or Anfibatide, a clinical-stage GPIb? inhibitor, revealed that the oxidoreductase activity of platelet surface-bound PDI was required for the ligand-binding function of GPIb?. PDI directly bound to the extracellular domain of GPIb? on the platelet surface and reduced the Cys4-Cys17 and Cys209-Cys248 disulfide bonds. Real-time microscopy with platelet-specific PDI conditional knockout and sickle cell disease mice demonstrated that PDI-regulated GPIb? function was essential for platelet-neutrophil interactions and vascular occlusion under thromboinflammatory conditions. Studies using a mouse model of ischemia/reperfusion-induced stroke indicated that PDI-GPIb? signaling played a crucial role in tissue damage. CONCLUSIONS:Our results demonstrate that PDI-facilitated cleavage of the allosteric disulfide bonds tightly regulates GPIb? function, promoting platelet-neutrophil interactions, vascular occlusion, and tissue damage under thromboinflammatory conditions.

SUBMITTER: Li J 

PROVIDER: S-EPMC6464389 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature