Mapping the fibrinogen binding sites of the GPIIb/IIIa receptor using synthetic peptides derived from the GPIIIa subunit

摘要

The formation of platelet-rich thrombus plays an important role in the pathophysiology of acute coronary syndromes(Acute Myocardial Infraction and Unstable Angina).This procedure requires activation of the platelets in which the heterodimeric complex of GPIIb/IIIa receptor changes its conformation and gains the ability to recognize fibrinogen.Fibrinogen binds to the receptor through the RGD sequence(alpha 95-97 and alpha 572-574)and the carboxy-terminal dodecapeptide HHLGGAKQAGDV of the gamma-chain(gamma 400-411).Several methods(chemical crosslinking,hydropathy complementary approaches and monoclonal antibody mapping)have been used for the determination of regions of GPIIb/IIla receptor which are involved in the platelet aggregation process.The regions 109-171,176-199,61-203,211-222 and 217-231 of GPIIIa have been reported as possible binding sites of fibrinogen.In our previous studies we managed to determine the binding regions within GPIIIa subunit,which are possibly involved in aggregation process,using synthetic 20-peptides,covering the extracellular region of the GPIIIa subunit.From the biological assays we concluded that some of the 20-peptides included in the GPIIIa:289-356(inhibitory activity 19%-61%),385-440(inhibitory activity 27%-62%),and 589-644(inhibitory activity 12%-41%)regions exhibit inhibitory activity which could characterize them as possible fibrinogen interacting regions.The aim of this work is to evaluate the participation of the GPIIIa:589-644 region in platelet aggregation process using synthetic peptides