Urokinase-type Plasminogen Activator Receptor (uPAR) is a cell surface receptor that binds urokinase-type plasminogen activator (uPA) with high affinity, thereby facilitating the pericellular activation of plasminogen. It is multidomain glycoprotein tethered to the cell membrane with a glycosylphosphotidylinositol (GPI) anchor. uPAR was originally identified as a saturable binding site for urokinase on the cell surface.
uPAR binds urokinase and thus restricts plasminogen activation to the immediate vicinity of the cell membrane. Besides the primary ligand urokinase, uPAR interacts with several other proteins, among others: vitronectin, the uPAR associated protein and the integrin family of membrane proteins.
uPAR is a part of the plasminogen activation system, which in the healthy body is involved in tissue reorganization events such as mammary gland involution and wound healing. uPAR has been involved in various other processes related to cancer, such as cell migration, cell cycle regulation, and cell adhesion.