# Characterization of an isoform specific anticoagulant function of TFPI-alpha

> **NIH NIH R01** · VERSITI BLOOD HEALTH, INC. · 2024 · $763,919

## Abstract

ABSTRACT
Tissue Factor Pathway Inhibitor (TFPI) is an anticoagulant protein with essential roles in hemostasis,
thrombosis, and embryonic development. TFPI was originally identified as the primary inhibitor of TF-FVIIa, the
catalytic complex that initiates blood coagulation. We recognized that the basic C-terminal region of TFPIα and
the basic region of the FV B-domain have homology and sought to define how TFPIα may specifically interact
with FV/FVa. In biochemical studies, we described an interaction between TFPIα and FVa that promotes
inhibition of nascent prothrombinase (FXa-FVa). This occurs at a previously unrecognized regulatory step in
the blood coagulation cascade when FV has been activated by FXa but before thrombin is generated. The
physiological importance of the TFPI-FV interaction is demonstrated by the following: 1) Bleeding disorders are
associated with FV variants that tightly bind TFPIα through this mechanism; 2) TFPIα has reduced ability to
inhibit prothrombinase assembled with FV Leiden (FVL) and likely contributes to the thrombotic disease
associated with this variant; and 3) Mice lacking TFPI activity have defects in cerebrovascular development
that contribute to their embryonic lethality, and removing FV from the embryos completely rescues the brain
pathology. We want to better understand how inhibition of prothrombinase by TFPIα impacts biological
processes. The proposed studies are based on recently published and new preliminary findings to define
extravascular locations where TFPIα interacts with FV and to probe how TFPI alters thrombotic disease,
placental development, and responses to endothelial damage. Aim 1 builds on our finding that heparin
releasable TFPIα originates from extracellular matrix (ECM) rather than the endothelial surface. Proposed
studies will define specific TFPIα binding proteins in ECM, the impact of binding ECM on TFPIα inhibitory
activity, and how TFPIα competes with growth factors for ECM binding. Aim 2 builds on our finding that TFPIα
and its interaction with FV modulates placental development, which will be probed using three mouse models
of TFPI deficiency. Aim 3 builds on our finding that platelet TFPIα modifies development of cardiac fibrosis
following irradiation. Proposed studies will further define the role of platelet TFPIα vs. other forms of TFPI in
this process. Together, the results of the proposed experiments will advance our understanding of how the
TFPIα-FV interaction modulates the pathophysiology of coagulation and coagulation-mediated cellular
signaling in important biological processes. They will potentially lead to new therapeutic approaches for
thrombotic diseases and bleeding disorders.

## Key facts

- **NIH application ID:** 10981641
- **Project number:** 2R01HL068835-17A1
- **Recipient organization:** VERSITI BLOOD HEALTH, INC.
- **Principal Investigator:** Alan E Mast
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $763,919
- **Award type:** 2
- **Project period:** 2002-08-01 → 2028-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10981641

## Citation

> US National Institutes of Health, RePORTER application 10981641, Characterization of an isoform specific anticoagulant function of TFPI-alpha (2R01HL068835-17A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10981641. Licensed CC0.

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