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Thrombin mutant W215A/E217A acts as a platelet GPIb antagonist
Michelle A Berny1, Tara C White, Erik I Tucker
1Department of Biomedical Engineering, Oregon Health & Science University, 3303 SW Bond Ave, Portland, OR 97239, USA.
Arteriosclerosis, Thrombosis, and Vascular Biology
|October 27, 2007
Summary
The Trp215Ala and Glu217Ala (WE) thrombin mutant binds platelets via GPIb, inhibiting von Willebrand factor-collagen interactions under shear. This reveals a novel mechanism for WE thrombin's antithrombotic effects.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Thrombin is a key enzyme in hemostasis.
- Mutant thrombins can exhibit altered functions.
- Understanding thrombin-platelet interactions is crucial for antithrombotic strategies.
Purpose of the Study:
- To investigate the molecular mechanism of direct WE-thrombin-platelet interactions.
- To analyze WE-thrombin's effects under static and shear conditions.
Main Methods:
- Studied purified platelets under static conditions.
- Utilized PPACK-anticoagulated blood under shear flow.
- Employed glycoprotein Ib (GPIb)-blocking antibodies.
- Assessed platelet deposition on collagen and von Willebrand factor.
Main Results:
- Platelets bound and spread on wild-type thrombin but not WE-thrombin statically.
- Under shear, platelets tethered and rolled on both wild-type and WE-thrombin, mediated by GPIb.
- WE-thrombin inhibited platelet deposition on collagen.
- WE-thrombin abrogated platelet tethering and rolling on von Willebrand factor under shear.
Conclusions:
- WE-thrombin interacts with platelets via GPIb, independent of its enzymatic activity.
- WE-thrombin inhibits GPIb-dependent platelet adhesion to von Willebrand factor and collagen under shear.
- These findings elucidate a novel mechanism for the antithrombotic activity of WE-thrombin.
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