Protease activated receptors: theme and variations

The four PAR family members are G protein coupled receptors that are normal ly activated by proteolytic exposure of an occult tethered ligand, Three of the family members are thrombin receptors, The fourth (PAR2) is not activa ted by thrombin, but can be activated by other proteases, including trypsin , tryptase and Factor Xa, This review focuses on recent information about t he manner in which signaling through these receptors is initiated and termi nated, including evidence for inter- as well as intramolecular modes of act ivation, and continuing efforts to identify additional, biologically-releva nt proteases that can activate PAR family members.