The urokinase-type-plasminogen-activator receptor (CD87) is a pleiotropic molecule.

Since its discovery over a decade ago, evidence has accumulated implicating the cell-surface urokinase receptor (u-PAR), in numerous biological processes. Most notable has been the identification of a critical role for u-PAR in the regulation of cell-surface plasminogen activation in physiological and pathological conditions. Recent evidence suggests that u-PAR, a glycosylphosphatidylinositol-linked receptor, lacking transmembrane and cytoplasmic domains, is also involved in processes not related to plasminogen activation, including cellular adhesion and the transmission of extracellular signals across the plasma membrane. Involvement of activated u-PAR in these events identifies previously unsuspected roles for this molecule and defines a new field of research in u-PAR biology. We discuss the molecular biology of u-PAR together with the underlying mechanisms responsible for the novel functional roles recently ascribed to this pleiotropic molecule.