Summary

P-selectin is translocated from the α-granules to the surface ofactivated platelets where it participates in thrombosis andinflammation.We investigated the signaling pathways involvedin thrombin-induced human platelet P-selectin expression.Assessed by flow cytometry, inhibition of protein kinase C(PKC) with chelerythrine reduced P-selectin expression by66%, platelet/neutrophil binding, GPIIb/IIIa activation and aggregation(p<0.05). Gö 6976, an inhibitor of the conventionalPKCs (α and β), did not alter P-selectin expression. However, rottlerin inhibited by 50% its expression (p<0.05), but only atdoses that interfere with the novel ( ε, η) and atypical (ζ) PKCs.Inhibition of protein tyrosine kinase (PTK) and phosphoinositide3-kinase (PI3-K) did not significantly affect P-selectinexpression. In conclusion, thrombin-induced P-selectin expressionis PKC-sensitive, but PTK and PI3-K-insensitive.The novel ε and η and atypical ζ, but not the conventional α and β andthe novel δ PKCs, may be involved in this process.