Peptides derived from MARCKS block coagulation complex assembly on phosphatidylserine.

Area of Science:

• Biochemistry
• Hematology
• Molecular Biology

Background:

• Blood coagulation is a complex process involving platelet activation and coagulation factors.
• Phosphatidylserine (PS) is a lipid crucial at the interface of platelet and coagulation factor activation.
• Activated platelets expose PS, serving as a platform for coagulation factor assembly and fibrin formation.

Purpose of the Study:

• To investigate the potential of small peptide and peptidomimetic probes derived from the myristoylated alanine-rich C-kinase substrate (MARCKS) lipid-binding domain.
• To determine if these MARCKS-derived probes can inhibit fibrin formation by targeting exposed phosphatidylserine on activated platelets.

Main Methods:

• Peptide synthesis and characterization.
• In vitro assays measuring factor Xa binding and prothrombinase activity.
• Whole blood flow assays to assess fibrin cross-linking.
• In vivo studies using animal models of thrombosis.

Main Results:

• MARCKS-derived peptides bind to phosphatidylserine on activated platelets.
• These peptides inhibit the binding of factor Xa and the enzymatic activity of prothrombinase.
• In flow conditions, peptides inhibit fibrin cross-linking of adherent platelets.
• In vivo, peptides localize to activated platelets within thrombi at remote injury sites.

Conclusions:

• MARCKS-derived peptides are effective inhibitors of platelet-mediated fibrin formation.
• These probes antagonize key steps in the coagulation cascade by targeting exposed phosphatidylserine.
• The findings suggest potential therapeutic applications for MARCKS-derived peptides in managing thrombotic disorders.