Receptor for activated thrombin or trypsin coupled to G proteins that stimulate phosphoinositide hydrolysis. May play a role in platelets activation. Highly expressed in the spleen. Slight expression in the heart, lung, skeletal muscle and kidney. No detectable expression in brain, liver or testis. Also detected in platelets. A proteolytic cleavage generates a new N-terminus that functions as a tethered ligand. Belongs to the G-protein coupled receptor 1 family.