The Urokinase receptor, also known as uPA receptor or uPAR or CD87 (Cluster of Differentiation 87), is a 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 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. In order to be able to reorganize tissue, the old tissue must be able to be degraded. An important mechanism in this degradation is the proteolysis cascade initiated by the plasminogen activation system. uPAR binds urokinase and thus restricts plasminogen activation to the immediate vicinity of the cell membrane. Thus uPAR seems to be an important player in the regulation of this process.
However the components of the plasminogen activation system have been found to be highly expressed in many malignanttumors, indicating that tumors are able to hijack the system, and use it in metastasis. Thus inhibitors of the various components of the plasminogen activation system have been sought as possible anticancer drugs.
uPAR has been involved in various other non-proteolytical processes related to cancer, such as cell migration, cell cycle regulation, and cell adhesion.
When uPA is bound to the receptor, there is cleavage between the GPI-anchor and the uPAR, releasing suPAR.[4]
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