Quercetin-3-rutinoside Inhibits Protein Disulfide Isomerase by Binding to Its b'x Domain

Area of Science:

• Biochemistry
• Pharmacology
• Hematology

Background:

• Protein disulfide isomerase (PDI) is crucial for platelet thrombus formation and fibrin generation.
• PDI has been identified as a potential therapeutic target for antithrombotic agents.
• Quercetin-3-rutinoside has shown potential in inhibiting thrombus formation.

Purpose of the Study:

• To investigate the interaction between quercetin-3-rutinoside and PDI.
• To elucidate the mechanism by which quercetin-3-rutinoside inhibits thrombus formation.
• To identify potential strategies for reversing the antithrombotic effects of quercetin-3-rutinoside.

Main Methods:

• Fluorescence enhancement-based assay and isothermal calorimetry were used to study quercetin-3-rutinoside binding to PDI.
• Small angle X-ray scattering (SAXS) was employed to analyze conformational changes in PDI upon binding.
• Interaction studies with isolated PDI fragments were performed to map binding sites.

Main Results:

• Quercetin-3-rutinoside directly binds to the b' domain of PDI with a 1:1 stoichiometry.
• Binding induces a more compact conformation and restricts flexibility of PDI.
• Quercetin-3-rutinoside binds to the b'x domain of PDI, and this fragment can rescue inhibited thrombus formation in vivo.
• The isolated b' domain of PDI acts as an antidote by binding and neutralizing quercetin-3-rutinoside.

Conclusions:

• Quercetin-3-rutinoside exerts its antithrombotic effect by directly binding to the b'x domain of PDI.
• The PDI b'x fragment is essential for quercetin-3-rutinoside's inhibitory action.
• The isolated PDI b' domain shows promise as a potential antidote to reverse quercetin-3-rutinoside's antithrombotic activity.