A palmitoylated peptide, derived from the acidic carboxyl-terminal segment of the integrin alphaIIb cytoplasmic domain, inhibits platelet activation.
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.
Koloka
Vassiliki
V
Sector of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece.
Christofidou
Elena D
ED
Vaxevanelis
Spyros
S
Dimitriou
Andromaxi A
AA
Tsikaris
Vassilios
V
Tselepis
Alexandros D
AD
Panou-Pomonis
Eugenia
E
Sakarellos-Daitsiotis
Maria
M
Tsoukatos
Demokritos C
DC
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
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