Tissue factor is a transmembrane single-chain glycoprotein composed of amino acid residues, which is indispensable for the human body.
Value:
Tissue factor is a transmembrane single-chain glycoprotein composed of 263 amino acid residues with a molecular weight of approximately 47 kDa. Among them, 219 amino acid residues at the amino end were located outside the cell membrane, followed by 23 amino acid residues across the cell membrane, and the remaining 21 amino acid residues were located in the cytoplasm.
Under normal circumstances, tissue factors are located in the adventitial cells of the blood vessel wall, the fibroblasts surrounding the blood vessels, the fibrous sacs of the liver, spleen, kidney and other organs, and the epidermal cells, glomerular epithelial cells, cerebral cortex, cardiomyocytes, alveolar macrophages, gastrointestinal walls, part of the genitourinary tract and endometrial stromal cells, but the vascular mestima or endometrial layer is very scarce.
Therefore, under normal circumstances, tissue factors do not exist in the circulation or come into contact with the circulating blood, and only when the integrity of the vessel wall is disrupted, TF is exposed to the circulating blood and acts as a hemostatic agent by activating the coagulation cascade.
What it does:
Tissue factors initiate the blood clotting cascade by binding to factor A. Moreover, TF relies on its close binding with the cell membrane to play an "anchor" role, so that the physiological coagulation process is limited to the injury site, and does not spread from the beginning of blood clotting to the distant place. TF initiates blood clotting by which TF sticks to a factor (f) with high affinity when TF expressed on the cell surface is exposed to plasma proteins.
Free factor A (Fa) and or formed TF2-A complexes activate the conversion of TF2F complexes to TF-A complexes, and TF-A complexes further activate free F. These mechanisms are known as TF-mediated activation of F itself. TF-A complexes rapidly catalyze factor activation. In addition, TF-A activates factors at a lower rate, and activated factor A converts the activator into factor A in the presence of a cofactor, a process that ultimately leads to thrombin production.
Thrombin then catalyzes the conversion of fibrinogen to fibrin and polymerization into fibrin blood clots. That is, TF can activate coagulation factors and at the same time, initiating two kinds of thrombin-linked amplification reactions, both endogenous and exogenous, and play an important role in the thrombosis process. However, at physiological concentrations, neither TF nor F alone has procoagulant activity.