Figure 8.

Model for Plg-R_KT-dependent cell surface plasminogen activation. Plg-R_KT is located on the monocyte surface in close physical proximity to the uPAR. The uPAR brings uPA in close proximity to plasminogen bound to Plg-R_KT, thus promoting activation of the bound plasminogen to plasmin. In addition, t-PA also interacts specifically with Plg-R_KT, thus mimicking the interaction of t-PA with cellular binding sites. Despite sharing a binding site on Plg-R_KT, the relative concentrations of tPA and plasminogen in the circulation should permit simultaneous binding of both ligands to the cell surface, and each tPA molecule should be bound proximally to several plasminogen molecules, thus promoting plasminogen activation to plasmin on the cell surface.