Acts as a receptor for urokinase plasminogen activator. Plays a role in localizing and promoting plasmin formation. Mediates the proteolysis-independent signal transduction activation effects of U-PA. Monomer (Probable). Interacts (via the UPAR/Ly6 domains) with SRPX2. Interacts with MRC2 (By similarity). Interacts with SORL1 (via N-terminal ectodomain); this interaction decreases PLAUR internalization (By similarity). The ternary complex composed of PLAUR-PLAU-SERPINE1 also interacts with SORL1 (By similarity). Expressed in angiogenic endothelial cells (at protein level). GPI-anchored form.