Ability of fibrinogen γ-derived dodecapeptides with different sequences to bind to rat platelets

A dodecapeptide (γ400-411) derived from a fibrinogen γ-chain carboxyl-terminal sequence recognizes specifically the active form of GPIIb/IIIa on the surface of activated platelets. For the purpose of efficient hemostasis, we previously developed ADP-encapsulated liposomes modified with human-dodecapeptide (HHLGGAKQAGDV, human-H12). On the other hand, the amino-acid sequence of H12 from rats is HHMGGSKQVGDM, having only 67% homology to that from humans. Here, we investigated the ability of rat-H12 in comparison with human-H12 to bind to platelets. Firstly, rat platelets were activated with phorbol-12-myristate-13-acetate (PMA), and the activation was confirmed by flow cytometry. Next, we evaluated the dissociation constant (K(d)) of human-H12 and rat-H12 for dissociation from rat platelets by using FACS. As a result, the K(d) of human-H12 and rat-H12 with respect to rat platelets was 2.78 ± 0.21 and 2.91 ± 0.22 μM, respectively. Furthermore, H12 from both species inhibited quite similarly the aggregation of rat platelets in platelet-rich plasma (PRP). These results suggest that H12 from different species with different amino acid sequences interacts similarly with GPIIb/IIIa on platelets.