title: Effect of synthetic peptides corresponding to residues 313-332 of the alphaIIb subunit on platelet activation and fibrinogen binding to alphaIIbbeta3.
abstract: The platelet integrin receptor alphaIIbbeta3 plays a critical role in thrombosis and haemostasis by mediating interactions between platelets and several ligands but primarily fibrinogen. It has been shown previously that the YMESRADR KLAEVGRVYLFL (313-332) sequence of the alphaIIb subunit plays an important role in platelet activation, fibrinogen binding and alphaIIbbeta3-mediated outside-in signalling. Furthermore, we recently showed that the 20-residue peptide (20-mer) alphaIIb 313-332, is a potent inhibitor of platelet aggregation and fibrinogen binding to alphaIIbbeta3, interacting with fibrinogen rather than the receptor. In an effort to determine the sequence and the minimum length required for the biological activity of the above 20-mer, we synthesized seven octapeptides, each overlapping by six residues, covering the entire sequence and studied their effect on platelet activation as well as fibrinogen binding to activated platelets. We show for the first time that octapeptides containing the RAD sequence are capable of inhibiting platelet aggregation and secretion as well as fibrinogen binding to the activated alphaIIbbeta3, possibly interacting with the ligand rather than the receptor. This suggests that the RAD sequence, common to all the inhibitory peptides, is critical for their biological activity. However, the presence of the YMES sequence, adjacent to RAD, significantly increases the peptide's biological potency. The development of such inhibitors derived from the 313-332 region of the alphaIIb subunit may be advantageous against the RGD-like antagonists as they could inhibit platelet activation without interacting with alphaIIbbeta3, thus failing to further induce alphaIIbbeta3-mediated outside-in signalling.
authors.affiliation: Department of Chemistry Medical School, University of Ioannina, Greece.
authors.forename: John V
authors.initials: JV
authors.lastname: Mitsios
authors.forename: Afroditi P
authors.initials: AP
authors.lastname: Tambaki
authors.forename: Morfis
authors.initials: M
authors.lastname: Abatzis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Biris
authors.forename: Maria
authors.initials: M
authors.lastname: Sakarellos-Daitsiotis
authors.forename: Constantinos
authors.initials: C
authors.lastname: Sakarellos
authors.forename: Ketty
authors.initials: K
authors.lastname: Soteriadou
authors.forename: John
authors.initials: J
authors.lastname: Goudevenos
authors.forename: Moses
authors.initials: M
authors.lastname: Elisaf
authors.forename: Demokritos
authors.initials: D
authors.lastname: Tsoukatos
authors.forename: Vassilios
authors.initials: V
authors.lastname: Tsikaris
authors.forename: Alexandros D
authors.initials: AD
authors.lastname: Tselepis
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D054641:Dual Specificity Phosphatase 2; D005340:Fibrinogen / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000235:genetics* / Q000494:pharmacology*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015539:Platelet Activation / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D009842:Oligopeptides; D010446:Peptide Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D005340:Fibrinogen; D003094:Collagen; D054648:Protein Phosphatase 2; C517032:DUSP2 protein, human; D054641:Dual Specificity Phosphatase 2; D017027:Protein Tyrosine Phosphatases; D013917:Thrombin