11 - Platelet receptors: collagen

Summary

Introduction

Platelet–collagen interaction is fundamental to both normal haemostasis and pathological thrombotic incidents. In recent years the complexity of platelet collagen receptors and their interplay has become better understood. However, further work is needed before the specific recognition sequences in collagens for each receptor are identified and the events leading from initial contact to primary adhesion and full-blown platelet activation become mapped. To achieve this will require knowledge of the relevant collagen receptors themselves, the signalling pathways they activate and the vascular collagens with which they interact. It is also becoming clear that accessory molecules on the platelet surface, together with adhesive proteins that bind both collagen and the platelet, can each modulate the interaction without being direct collagen receptors themselves. Finally, we envisage that the importance of employing experimental conditions which more accurately reflect the platelet–collagen interaction in vivo will become more widely recognised. Thus, the presentation of collagen in triple-helical conformation, as polymeric fibres rather than monomers, immobilized on a surface rather than in suspension, and finally under shear conditions which represent blood flow, will have a strong impact on the final understanding of collagen as an adhesive substrate and a platelet agonist. We aim here to pool current awareness of the various aspects of the plateletcollagen interaction introduced above. For recent reviews, see.

Early work, using tissue extracts in turbidimetric aggregometry, established the importance of collagen as a platelet agonist.