Encryption and decryption of tissue factor

Area of Science:

• Biochemistry
• Hematology
• Cell Biology

Background:

• Tissue factor (TF) is a key initiator of blood coagulation, binding and activating factor VIIa (FVIIa).
• The TF/FVIIa complex generates thrombin, crucial for stable thrombus formation.
• TF exists in both extravascular and intravascular compartments, with distinct regulatory mechanisms.

Purpose of the Study:

• To investigate the mechanisms regulating intravascular TF activity, particularly its decryption on leucocytes.
• To explore the role of dithiol/disulfide bonds and phosphatidylserine exposure in TF decryption.
• To examine the involvement of purinergic receptors, complement activation, and protein disulfide isomerase in TF decryption.

Main Methods:

• Review of experimental observations on TF decryption.
• Analysis of the proposed dithiol/disulfide switch involving the Cys186-Cys209 bond in TF.
• Examination of studies implicating purinergic receptors, complement, and protein disulfide isomerase in TF regulation.

Main Results:

• Intravascular TF primarily originates from leucocytes (monocytes/neutrophils) and exists in a cryptic, non-coagulant form.
• Acute events trigger local TF decryption and subsequent FX activation.
• Decryption involves a dithiol/disulfide switch and phosphatidylserine exposure, with protein disulfide isomerase implicated.

Conclusions:

• TF decryption on myeloid cells is linked to purinergic receptor or complement activation.
• A dithiol/disulfide switch, potentially involving protein disulfide isomerase, is central to TF decryption.
• The precise molecular mechanism of protein disulfide isomerase in TF encryption/decryption remains to be elucidated.