Thrombin as procoagulant and anticoagulant

Area of Science:

• Biochemistry
• Molecular Biology
• Hematology

Background:

• Thrombin, a serine protease, is central to blood coagulation, exhibiting both procoagulant and anticoagulant functions.
• Sodium ion (Na+) binding allosterically modulates thrombin's activity, primarily driving its procoagulant and signaling roles.
• Cleavage of anticoagulant protein C by thrombin is independent of Na+ binding.

Purpose of the Study:

• To investigate the role of Na+ in thrombin's diverse functions.
• To engineer thrombin mutants with selectively altered substrate specificities.
• To develop novel anticoagulant and antithrombotic agents based on modified thrombin activity.

Main Methods:

• Characterization of Na+-dependent thrombin activity.
• Site-directed mutagenesis to engineer thrombin variants.
• Alanine scanning mutagenesis to map functional epitopes.
• In vivo evaluation of engineered thrombin mutants as therapeutic agents.

Main Results:

• Na+ binding is crucial for thrombin's procoagulant, prothrombotic, and signaling functions.
• Mutants with selectively compromised cleavage of fibrinogen and PAR1 were successfully engineered.
• These engineered thrombin mutants demonstrated efficacy as anticoagulant and antithrombotic agents in vivo.

Conclusions:

• The Na+-dependent allosteric regulation of thrombin provides a rational basis for enzyme engineering.
• Selective dissociation of procoagulant and anticoagulant activities is achievable through targeted mutagenesis.
• Engineered thrombin mutants represent a promising strategy for developing new antithrombotic therapies.