The urokinase receptor and regulation of cell surface plasminogen activation

Abstract

Urokinase-type plasminogen activator (u-PA) is a key enzyme involved in migration and invasiveness of cells, both in cancer and in several normal physiological processes (Reich, 1978; Dana et al., 1985; Saksela and Rifkin, 1988; Blasi and Verde, 1990). The application of modem biochemical and molecular biological techniques has identified some of the steps at which u-PA activity is regulated. A large number of studies have dealt with the biological roles of u-PA catalyzed plasminogen activation. These can be summarized as follows: (1) u-PA-dependent proteolysis can take place on cells with surface-bound reactants; physiologically, this may well be the most relevant form of plasminogen activation; (2) the plasminogen activating system and its regulation are complex and several molecules are known to be involved (activators, substrate, inhibitors, receptors), although other, as yet unidentified, components are also implicated and (3) on a biochemical basis the u-PA system exploited by cancer cells appears to be qualitatively identical to that used in normal