Protease-activated receptors are a subfamily of related G protein-coupled receptors that are activated by cleavage of part of their extracellular domain. They are highly expressed in platelets, but also on endothelial cells, myocytes and neurons.Most of the PAR family act through the actions of G-proteins i (cAMP inhibitory), 12/13 (Rho and Ras activation) and q (calcium signalling) to cause cellular actions.