Platelets contain tissue factor pathway inhibitor-2 derived from megakaryocytes and inhibits fibrinolysis.
Publication/Presentation Date
11-7-2014
Abstract
Tissue factor pathway inhibitor-2 (TFPI-2) is a homologue of TFPI-1 and contains three Kunitz-type domains and a basic C terminus region. The N-terminal domain of TFPI-2 is the only inhibitory domain, and it inhibits plasma kallikrein, factor XIa, and plasmin. However, plasma TFPI-2 levels are negligible (≤20 pM) in the context of influencing clotting or fibrinolysis. Here, we report that platelets contain significant amounts of TFPI-2 derived from megakaryocytes. We employed RT-PCR, Western blotting, immunohistochemistry, and confocal microscopy to determine that platelets, MEG-01 megakaryoblastic cells, and bone marrow megakaryocytes contain TFPI-2. ELISA data reveal that TFPI-2 binds factor V (FV) and partially B-domain-deleted FV (FV-1033) with K(d) ~9 nM and binds FVa with K(d) ~100 nM. Steady state analysis of surface plasmon resonance data reveal that TFPI-2 and TFPI-1 bind FV-1033 with K(d) ~36-48 nM and bind FVa with K(d) ~252-456 nM. Further, TFPI-1 (but not TFPI-1161) competes with TFPI-2 in binding to FV. These data indicate that the C-terminal basic region of TFPI-2 is similar to that of TFPI-1 and plays a role in binding to the FV B-domain acidic region. Using pull-down assays and Western blots, we show that TFPI-2 is associated with platelet FV/FVa. TFPI-2 (~7 nM) in plasma of women at the onset of labor is also, in part, associated with FV. Importantly, TFPI-2 in platelets and in plasma of pregnant women inhibits FXIa and tissue-type plasminogen activator-induced clot fibrinolysis. In conclusion, TFPI-2 in platelets from normal or pregnant subjects and in plasma from pregnant women binds FV/Va and regulates intrinsic coagulation and fibrinolysis.
Volume
289
Issue
45
First Page
31647
Last Page
31661
ISSN
1083-351X
Published In/Presented At
Vadivel, K., Ponnuraj, S. M., Kumar, Y., Zaiss, A. K., Bunce, M. W., Camire, R. M., Wu, L., Evseenko, D., Herschman, H. R., Bajaj, M. S., & Bajaj, S. P. (2014). Platelets contain tissue factor pathway inhibitor-2 derived from megakaryocytes and inhibits fibrinolysis. The Journal of biological chemistry, 289(45), 31647–31661. https://doi.org/10.1074/jbc.M114.569665
Disciplines
Medicine and Health Sciences
PubMedID
25262870
Department(s)
Department of Medicine
Document Type
Article