Excellence in Research: Molecular mechanism of Tissue Factor encryption and decryption.

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This project is focused on the regulation of activity of a membrane protein Tissue Factor (TF) that serves as a cofactor for enzymes that initiate cascade reactions of blood coagulation. TF is inactive or encrypted in normal conditions, while in conditions of tissue damage, TF is exposed to coagulation enzymes and is turned into an activated or decrypted state. The primary mechanism of TF decryption is determined by the changes in membrane phospholipids leading to high-affinity binding of coagulation enzymes to the membrane surface and the TF, located on the membrane. However, mechanisms of encryption and decryption related directly to TF are not known. This project, with the state-of-the-art computational resources of the UT System, will provide training for undergraduate HBCU students. Outcomes of this project will have societal impact by providing new details about critical molecules with impacts in cardiovascular diseases and roles in viral infections. This project will develop a model of TF encryption and decryption based on the dimerization of TF. The model proposes an equilibrium between TF monomers and dimers. Dimers can be formed by two TF molecules bound in alternate configurations to produce encrypted, partially active, and fully active decrypted structures. This equilibrium depends on the lipid environment whereby specific lipids can selectively stabilize encrypted or decrypted dimers. The project will create models composed of full-length TF and other members of the coagulation cascade (Factor VIIa and Factor Xa)inserted into lipid bilayers of different phospholipid compositions. Molecular dynamics (MD) simulations and molecular docking will be carried out with the TF dimer models. Extensive comparative analysis of MD trajectories will be performed to reveal amino acids and membrane lipids essential for stabilizing TF dimers in an encrypted or decrypted state. In addition, amino acid residues involved in selective phospholipid binding and stabilization of encrypted or decrypted dimers will be selected for experimental validation of their role in TF encryption or decryption using mutational analysis combined with functional activity assays.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.