How does the coagulation protease thrombin regulate cellular behaviour? The protease-
activated receptors (PARs) provide one answer. In concert with the coagulation cascade,
these receptors provide an elegant mechanism linking mechanical information in the form of
tissue injury or vascular leakage to cellular responses. Roles for PARs are beginning to
emerge in haemostasis and thrombosis, inflammation, and perhaps even blood vessel
development.