Identification of PDI Substrates by Mechanism-Based Kinetic Trapping.

Area of Science:

• Biochemistry
• Molecular Biology
• Vascular Biology

Background:

• Protein disulphide isomerase (PDI) is secreted by activated platelets and endothelial cells, playing a crucial role in thrombus formation following vascular injury.
• PDI catalyzes critical redox reactions involving disulphide bonds in substrate proteins, but its specific extracellular substrates during thrombus formation remain largely unidentified due to transient interactions.

Purpose of the Study:

• To develop and detail a novel kinetic substrate trapping strategy for identifying extracellular substrates of PDI.
• To overcome the challenge of transient PDI-substrate interactions in identifying key players in thrombus formation.

Main Methods:

• Adaptation and development of a kinetic substrate trapping strategy.
• Generation of PDI variants with substituted active site amino acids to form stable PDI-substrate complexes.
• Detailed description of PDI variant characterization, kinetic trapping experiments, and substrate isolation/identification.

Main Results:

• Successful generation of PDI variants capable of forming stable complexes with their substrates.
• Establishment of a robust methodology for isolating and identifying extracellular PDI substrates.
• Demonstration of the protocol's adaptability for various biological fluids and applicability to other extracellular thiol isomerases.

Conclusions:

• The developed kinetic substrate trapping strategy is effective for identifying extracellular PDI substrates.
• This methodology provides new insights into the molecular mechanisms of thrombus formation.
• The protocol is versatile and can be applied broadly in the study of extracellular thiol isomerases and their substrates.