Structure of Human Urokinase Plasminogen Activator in Complex with Its Receptor

Abstract

The urokinase plasminogen activator binds to its cellular receptor with high affinity and initiates signaling cascades that are implicated in pathological processes including tumor growth, metastasis, and inflammation. We report the crystal structure at 1.9 angstroms of the urokinase receptor complexed with the urokinase amino-terminal fragment and an antibody against the receptor. The three domains of urokinase receptor form a concave shape with a central cone-shaped cavity where the urokinase fragment inserts. The structure provides insight into the flexibility of the urokinase receptor that enables its interaction with a wide variety of ligands and a basis for the design of urokinase-urokinase receptor antagonists.

Conformational Regulation of Urokinase Receptor Function

“…In the crystal structure solved for the SMB-uPAR-ATF complex (17), Trp 32 is thus buried in the vitronectin binding interface, and its mutation to alanine obviously impairs this interaction significantly, whereas the affinity for uPA is unaffected (18). In contrast, Tyr 57 is located at the bottom of the hydrophobic uPA binding cavity and is completely shielded from solvent in the corresponding uPAR-ATF complex (16,40). The affinity of uPAR Y57A for uPA is accordingly decreased by ϳ7-fold compared with both uPAR wt and uPAR W32A (34,39), whereas vitronectin binding is unaffected.…”

“…In the human genome, five genes are recognized so far to encode proteins with multiple LU domains, and these are all confined to a small gene cluster located on chromosome 19q13 (14). Among these modular proteins, the structure of only uPAR has presently been solved (7,(15)(16)(17), and it reveals that all three LU domains in this receptor adopt the archetypical three-finger fold that is found in the snake venom ␣-neurotoxins. More importantly, all three LU domains in uPAR cooperate to form a large hydrophobic ligand binding cavity for uPA.…”

“…More importantly, all three LU domains in uPAR cooperate to form a large hydrophobic ligand binding cavity for uPA. A notable flexibility in the modular assembly of uPAR is nevertheless displayed by these structures dependent on which ligand is actually buried in this ligand binding cavity (5,7,15,16). The functional binding epitope for vitronectin, another established uPAR ligand, is also confined to a composite receptor interface, which in this case is located between uPAR domain I (DI) and domain II (DII) as determined by alanine-scanning mutagenesis (18).…”

siRNA against plasminogen activator inhibitor-1 ameliorates bleomycin-induced lung fibrosis in rats

“…It is generally accepted that PAI-1 binding to uPA and the uPA receptor induces internalisation of the complex, thereby facilitating extracellular proteolysis as well as activation of growth factors and anti-apoptosis proteins [28,29] . Furthermore, these intermediates activate several signalling pathways.…”

A direct link between expression of urokinase plasminogen activator receptor, growth rate and oncogenic transformation in mouse embryonic fibroblasts

“…The amino terminus of the receptor, domain D1, is the primary site for binding urokinase (uPA), but binding occurs in a pocket formed by all three domains (Llinas et al, 2005;Huai et al, 2006). UPA converts plasminogen to the serine protease plasmin, which degrades fibrin and activates other zymogens like pro-matrix metalloproteinases (Blasi and Carmeliet, 2002).…”