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Molecular mechanism of the interaction of subendothelial microfibrils with blood platelets
1INSERM U353, Institut d'Hématologie, Hôpital Saint-Louis, Paris, France.
Abstract:
This short review summarizes the present state of our knowledge concerning the mechanisms of the interaction between subendothelial microfibrils and blood platelets. Microfibrils associated with elastin and with basement membranes have been shown to be able to promote platelet adhesion and subsequent activation and aggregation. A 128 kDa thrombospondin (TSP)-like glycoprotein of microfibrils (GP 128) is involved in their reactivity towards platelets, as established from specific inhibition by antibodies against GP 128 and against TSP of the microfibril-platelet interaction. This interaction only occurs in the presence of plasma von Willebrand factor (vWF). VWF effectively binds to microfibrils; this binding does not implicate GP 128, but a 97 kDa protein of microfibrils not yet characterized. In addition, from data based on inhibition of platelet adhesion and aggregation by monoclonal antibodies against platelet membrane glycoprotein Ib (GP Ib), it appears that GP Ib, a platelet membrane receptor for vWF, acts in the vWF dependent microfibril-platelet interaction as a receptor for VWF bound to protein 97 kDa in microfibrils. A tentative model is presented to illustrate the complex mechanism of the microfibril-platelet interactions: recognition of vWF bound to microfibrils by GP Ib would be the first step, which would then allow subsequent binding of GP 128 to its receptor on the platelet membrane.
Insights
Subendothelial microfibrils promote platelet adhesion and aggregation via von Willebrand factor (vWF) binding. Platelet glycoprotein Ib (GP Ib) acts as the receptor for vWF on microfibrils, initiating this interaction.
Area of Science:
- Biochemistry
- Hematology
- Cell Biology
Background:
- Subendothelial microfibrils, components of elastic and basement membranes, interact with blood platelets.
- This interaction is crucial for platelet adhesion, activation, and aggregation.
Purpose of the Study:
- To review the mechanisms underlying the interaction between subendothelial microfibrils and blood platelets.
- To elucidate the roles of specific proteins and receptors in this process.
Main Methods:
- Review of existing literature on microfibril-platelet interactions.
- Analysis of data involving antibody inhibition studies against specific proteins (GP 128, TSP, GP Ib) and von Willebrand factor (vWF).
Main Results:
- A 128 kDa thrombospondin (TSP)-like glycoprotein (GP 128) on microfibrils is involved in platelet reactivity.
- The interaction requires plasma von Willebrand factor (vWF), which binds to a 97 kDa microfibril protein, not GP 128.
- Platelet glycoprotein Ib (GP Ib), a vWF receptor, mediates the interaction with vWF bound to the 97 kDa microfibril protein.
Conclusions:
- A model for microfibril-platelet interaction is proposed, starting with GP Ib recognizing vWF bound to microfibrils.
- This initial recognition facilitates subsequent binding of GP 128 to its platelet receptor, driving platelet activation and aggregation.