Teasing apart active site contributions
Thrombus formation at sites of vascular injury is essential for the healing process. Protein disulfide isomerase (PDI) is a secreted enzyme that catalyzes disulfide bond formation and has been shown to both inhibit and promote coagulation. There are 2 redox-active catalytic sites, at the N- and C-terminus, respectively, within PDI; however, the roles of these sites in platelet function during coagulation are unclear. Junsong Zhou, Yi Wu, and colleagues at Soochow University and Temple University School of Medicine developed several mouse models to evaluate PDI in thrombosis and the contribution of the N- and C-terminal CGHC redox-active sites. Mice specifically lacking PDI within platelets had increased tail bleeding times and impaired platelet function but no defect in fibrin deposition, while animals lacking PDI within platelets and vessel walls had substantial defects both in platelet function and fibrin deposition at the site of injury. Platelet accumulation was attenuated in PDI-deficient animals with transgenic expression of PDI lacking the C-terminal CGHC motif (PDI(ss-oo)). In PDI-deficient mice and those expressing PDI(ss-oo), transfusion of PDI with a functional C-terminal CGHC motif, but lacking the N-terminal active site (PDI_ss-oo) rescued these defects. In human platelets, addition of PDI(ss-oo) inhibited aggregation, while PDI(oo-ss) enhanced aggregation. Moreover, the PDI C-terminal CGHC motif mediated P-selectin secretion from platelets in an αIIbβ3-independent manner. Together, these results demonstrate that the C-terminal redox-active site of PDI is essential for platelet function and coagulation. The accompanying movie shows that leukocytes are not involved in thrombus formation in the model used in this study (Videos 1 and 2) and that recombinant PDI(ss-oo) accumulates at the site of injury in both WT (Video 3) and PDI-deficient mice (Video 4).
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Abstract
Protein disulfide isomerase (PDI) has two distinct CGHC redox-active sites; however, the contribution of these sites during different physiologic reactions, including thrombosis, is unknown. Here, we evaluated the role of PDI and redox-active sites of PDI in thrombosis by generating mice with blood cells and vessel wall cells lacking PDI (
Authors
Junsong Zhou, Yi Wu, Lu Wang, Lubica Rauova, Vincent M. Hayes, Mortimer Poncz, David W. Essex
Copyright © 2019 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)