Grants and Contracts Details
Description
Thrombosis is a leading cause of death in the United States. It is caused by excessive production of the blood
clotting factor thrombin. During normal hemostasis, thrombin generation is tightly regulated by several
anticoagulant proteins, including protein S (PS). PS is an important anticoagulant protein in humans with total
deficiency producing severe, life-threatening thrombosis at birth. However, the biochemical mechanism(s) by
which PS mediates its anticoagulant activity are poorly understood. PS is a cofactor for two other endogenous
anticoagulants, tissue factor pathway inhibitor alpha (TFPIá) and activated protein C (APC). PS/TFPIá inhibits
coagulation factor Xa (FXa), while PS/APC proteolytically inactivates factor Va (FVa). FVa and FXa combine to
form prothrombinase, the powerful enzymatic complex that converts prothrombin to thrombin. Prothrombinase
is resistant to inactivation by either PS/APC or PS/TFPIá during the propagation phase of blood clotting, yet its
activity is clearly regulated because thrombi do not spread throughout the entire vasculature during normal
hemostasis. PS promotes the inactivation of both protein components of prothrombinase, FVa (as an APC
cofactor) and FXa (as a TFPIá cofactor), suggesting that it may modulate prothrombinase activity. We
hypothesize that coordinated action of the PS/TFPIá and PS/APC anticoagulant systems will produce
efficient inhibition of prothrombinase. This hypothesis will be tested via complimentary biochemical and
structural studies. The K99 will focus on biochemical studies using assays established during my post-doctoral
research. They will further define the mechanism by which PS enhances TFPIá inhibitory activity (Specific Aim
1.1) and determine how FXa inhibition by PS/TFPIá alters the ability of PS/APC to proteolytically inactivate
FVa and vice versa (Specific Aim 1.2). The R00 will extend this work further by assessing the contribution of
different physiologic membrane surfaces to the regulation of thrombin generation (Specific Aim 1.3). These
functional studies will be correlated with structural studies. The K99 will focus on development of molecular
models of the PS/TFPIá and PS/APC complexes (Specific Aim 2.1). The R00 will extend this work by
producing crystal structures of individual domains of PS, TFPIá, and APC, separately and in complex (Specific
Aims 2.2 and 2.3). These studies will coincide with career development training, which will include a focus on
training in structural biology, through a combination of courses and work in the laboratory of Dr. Stephen
Everse. This will differentiate my work from that of my mentor and enable me to establish an independent
research career studying the biochemistry of hemostatic proteins.
Status | Finished |
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Effective start/end date | 9/15/15 → 9/30/21 |
Funding
- National Heart Lung and Blood Institute: $736,045.00
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