ABSTRACT
Plasminogen activation, catalyzed by the serine proteases urokinase-type plasminogen activator (u-PA) and tissue plasminogen activator (t-PA), is thought to play an important role in a variety of physiological and pathological processes. The potency of the plasminogen activation system indicates that specific mechanisms must exist to control the initiation, progression, localization, and termination of the system. The principal role of u-PAR is to provide a facile mechanism for the confinement of u-PA to the cell surface, and this is accomplished by the high-affinity interaction between the growth factor domain of u-PA and the amino-terminal domain of u-PAR. The explanation for the discrepancy in the effects of u-PAR in purified and cell-associated systems lies in the binding of plasminogen to the cell surface. The cellular potentiation of plasminogen activation has been shown to involve effects on the activation of both plasminogen and pro-u-PA, which together account for the overall effect.
