SIGNALS ELICITED FROM HUMAN PLATELETS BY SYNTHETIC, TRIPLE-HELICAL, COLLAGEN-LIKE PEPTIDES

Synthetic collagen-like peptides, of general structure [Gly-Pro-HyP](n ), adopt the triple-helical structure which is essential for the plate let-reactivity of native collagens. These peptides are potent activato rs of platelets, stimulating platelet aggregation at much lower dose t han collagen fibres, but, unlike collagen fibres, they are not recogni sed by the integrin alpha 2 beta 1. We have examined the ability of th e synthetic peptides to activate the various signalling pathways which regulate human platelet function. The peptides are potent activators of Ca2+ mobilisation and of protein kinase C, and they stimulate tyros ine phosphorylation of some substrates preferentially. However, in con trast with native type I collagen fibres, they are unable to inhibit p latelet adenylate cyclase. This suggests a mode of action for the synt hetic peptides which substantially overlaps, but which is not entirely identical with, that of native collagen.