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Platelet-derived microparticles express high affinity receptors for factor VIII.
G E Gilbert1, P J Sims, T Wiedmer
1Center for Hemostasis and Thrombosis Research, New England Medical Center, Boston, Massachusetts.
The Journal of Biological Chemistry
|September 15, 1991
Summary
Activated platelets and their microparticles bind factor VIII, a key cofactor in blood clotting. Platelet microparticles offer sustained factor VIII binding, crucial for tenase complex assembly.
Area of Science:
- Hematology
- Biochemistry
- Cell Biology
Background:
- Factor VIII is essential for the tenase enzyme complex, which assembles on activated platelet membranes.
- Membrane binding of factor VIII is critical for tenase complex assembly and blood coagulation.
Purpose of the Study:
- To characterize factor VIII-binding sites on activated platelets and their derived microparticles.
- To compare the binding kinetics and characteristics of factor VIII to factor V on platelet surfaces and microparticles.
Main Methods:
- Flow cytometry using labeled factor VIII and monoclonal antibodies.
- Characterization of microparticle shedding and factor VIII binding after platelet activation.
- Kinetic analysis of factor VIII and factor Va binding to microparticles.
Main Results:
- Activated platelets and shed microparticles bind factor VIII.
- Platelet microparticles exhibit sustained factor VIII binding, unlike platelets.
- Factor VIII and factor Va share similar binding kinetics and receptor characteristics on microparticles.
Conclusions:
- Activated platelets transiently increase high-affinity factor VIII receptors.
- Platelet-derived microparticles provide sustained high-affinity receptors for factor VIII.
- Factor VIII and factor Va binding mechanisms on activated platelets and microparticles are comparable.