title: A palmitoylated peptide, derived from the acidic carboxyl-terminal segment of the integrin alphaIIb cytoplasmic domain, inhibits platelet activation.
abstract: Platelet integrin alpha(IIb)beta(3) contains an acidic membrane distal motif, 1000LEEDDEEGE1008, in the cytoplasmic domain of the alpha(IIb) subunit. We showed that a lipid-modified peptide corresponding to the above region, palmitoyl-K-LEEDDEEGE (pal-K-1000-1008), is platelet permeable and has inhibited platelet aggregation induced by 0.4 U/ml of thrombin (IC50 = 164 microM). Moreover the peptide inhibited both Fibrinogen and PAC-1, binding to activated platelets. The non palmitoylated analog was inactive. A modified, scrambled acidic peptide (palmitoyl-K-GDDEELEEE), showed significant lower inhibitory activity than pal-K-1000-1008. A palmitoylated peptide corresponding to the membrane proximal cytoplasmic domain of alpha(IIb), 989KGVFFKR995 (pal-989-995), is known to specifically induce platelet aggregation. Pal-K-1000-1008 was an inhibitor of human washed platelet aggregation induced by pal-K-989-995 (IC50 = 15 microM). Moreover, pal-K-1000-1008 inhibited phosphorylation of ERK and FAK, two protein kinases involved in platelet activation and aggregation. Our results favour the assumption that the interaction of the membrane proximal sequence 989KGVFFKR995 of the cytoplasmic domain of alpha(IIb) with the acidic terminal 1000LEEDDEEGE1008 motif may be an important structural factor in platelet signaling, leading to platelet activation and aggregation.
authors.affiliation: Sector of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Koloka
authors.forename: Elena D
authors.initials: ED
authors.lastname: Christofidou
authors.forename: Spyros
authors.initials: S
authors.lastname: Vaxevanelis
authors.forename: Andromaxi A
authors.initials: AA
authors.lastname: Dimitriou
authors.forename: Vassilios
authors.initials: V
authors.lastname: Tsikaris
authors.forename: Alexandros D
authors.initials: AD
authors.lastname: Tselepis
authors.forename: Eugenia
authors.initials: E
authors.lastname: Panou-Pomonis
authors.forename: Maria
authors.initials: M
authors.lastname: Sakarellos-Daitsiotis
authors.forename: Demokritos C
authors.initials: DC
authors.lastname: Tsoukatos
mesh_terms: D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002463:Cell Membrane Permeability; D054641:Dual Specificity Phosphatase 2 / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D019308:Palmitic Acid; D010446:Peptide Fragments / Q000493:pharmacokinetics / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D015539:Platelet Activation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D040201:Platelet Membrane Glycoprotein IIb; D011485:Protein Binding / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism
chemical_list: D010446:Peptide Fragments; D010975:Platelet Aggregation Inhibitors; D040201:Platelet Membrane Glycoprotein IIb; D019308:Palmitic Acid; D005340:Fibrinogen; D011494:Protein Kinases; C517032:DUSP2 protein, human; D054641:Dual Specificity Phosphatase 2