Differential binding of ICln in platelets to integrin-derived activating and inhibitory peptides

The capacity of platelets to form a thrombus is mediated by integrin αIIbβ3. The cytoplasmic tail of αIIb contains a highly conserved motif, 989KVGFFKR995, which plays a critical role in regulating integrin activation and acts as a recognition site for various intracellular proteins, e.g. CIB1, PP1, ICln and RN181. Previously, we demonstrated that a cell-permeable integrin-derived activating (IDA) peptide, KVGFFKR, induces platelet activation, whereas an integrin-derived inhibitory (IDI) peptide, KVGAAKR, is antithrombotic. To elucidate the molecular mechanism underlying these opposite effects we investigate the affinity of known integrin αIIb binding proteins for the two immobilized peptides in dependence on the activation state of platelets by means of peptide-affinity chromatography, blotting techniques and protein:peptide docking studies.Our results provide a model for the inhibition of ICln interaction with the integrin in activated platelets by the IDI-peptide. Thus, ICln:IDI-peptide interaction profiles can have a pivotal purpose in the search for consensus pharmacophores specifically inhibiting ICln function in platelets potentially leading to the development of integrin-derived antithrombotic drugs.