The plasminogen activator system: biology and regulation

The regulation of plasminogen activation involves genes for two plasminogen activators (tissue type and urokinase type), two specific inhibitors (type 1 and type 2), and a membrane-anchored urokinase-type plasminogen-activato r-specific receptor. This system plays an important role in various biologi cal processes involving extracellular proteolysis. Recent studies have reve aled that the system, through interplay with integrins and the extracellula r matrix protein vitronectin, is also involved in the regulation of cell mi gration and proliferation in a manner independent of proteolytic activity. The genes are expressed in many different cell types and their expression i s under the control of diverse extracellular signals. Gene expression resec ts the levels of the corresponding mRNA, which should be the net result of synthesis and degradation. Thus, modulation of mRNA stability is an importa nt factor in overall regulation. This review summarizes current understandi ng of the biology and regulation of genes involved in plasminogen activatio n at different levels.