uPAR was originally identified as a saturable binding site for urokinase (also known as uPA) on the cell surface.

[5] The structure of uPAR has been solved by X-ray crystallography in complex with a peptide antagonist[6] and with its native ligand, urokinase.

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.

When urokinase is bound to the receptor, there is cleavage between the GPI-anchor and the uPAR, releasing a soluble form of the protein known as suPAR.

[8][9] Soluble urokinase plasminogen activator receptor (suPAR) has been found to be a biomarker of inflammation.