Cyclo19,31[D-Cys19]-uPA19-31 Is a Potent Competitive Antagonist of the Interaction of Urokinase-Type Plasminogen Activator with Its Receptor (CD87)

Abstract

IntroductionThe serine proteases urokinase-type plasminogen activator (uPA) and plasmin, in concert with other proteolytic enzymes (e. g. matrix metalloproteases, cysteine proteases), are involved in tumor-associated processes such as cell invasion and regulation of cell/cell and cell/matrix contacts Schmitt et al., 2000;Andreasen et al., 2000). (pro-)uPA binds to a specific, high-affinity cell surface receptor, uPAR (CD87), which is composed of three structurally homologous, independently folded domains (Dear and Medcalf, 1998). In addition, there are also cellular binding sites for plasmin(ogen) (Félez, 1998). In consequence, binding of (pro-) uPA to cell membrane-anchored uPAR significantly increases plasmin generation due to a distinct increase of reciprocal activation of pro-uPA and plasminogen (Ellis et al., 1991). Plasmin not only degrades a variety of components of the extracellular matrix (e. g. fibrin and laminin), but also activates certain matrix metalloproteases (in addition to pro-uPA) which break down additional structural proteins of the extracellular matrix such as various collagens. Thus, cell surface-triggered plasminogen activation plays a fundamental role in tissue remodeling, which is a prerequisite for tumor cell invasion and metastasis Schmitt et al., 2000;Andreasen et al., 2000).The interaction of pro-uPA or its activated form high molecular weight (HMW-)uPA with uPAR has been characterised in detail. Although the N-terminal domain I of uPAR contains major determinants for uPA-binding, high affinity interaction with uPA is dependent on the multidomain structure of the receptor, indicating that all three protein domains are involved in the formation of a composite ligand binding site (Ploug, 1998;Gårdsvoll et al., 1999;Bdeir et al., 2000). In contrast, uPA binds to uPAR via a defined continuous peptide sequence

Conformational Regulation of Urokinase Receptor Function

“…One peptide antagonist (AE234) is designed to mimic the ␤-hairpin region of GFD, which is responsible for the tight receptor binding properties of uPA (41,42). This compound is a small 10-mer cyclic peptide, and it inhibited the uPA-uPAR interaction with an IC 50 value of 150 nM ( Table 1 and Fig.…”

The kringle stabilizes urokinase binding to the urokinase receptor

“…It is clear, however, that such dynamic biologic activities are unlikely to be explained by a simple binding process mediated exclusively through a limited portion of the growth factor domain. [28][29][30][31][32][33] The results of the present study show that the kringle contributes to the interaction of uPA with uPAR and that this contribution For personal use only. on May 10, 2018. by guest www.bloodjournal.org From is dependent on the GFD.…”

“…26 There is compelling evidence to indicate that scuPA binds to uPAR through its GFD. [28][29][30][31][32][33][34] However, the potential involvement of other sites in uPA in receptor binding has not been studied in detail.…”

“…26 There is compelling evidence to indicate that scuPA binds to uPAR through its GFD. [28][29][30][31][32][33][34] However, the potential involvement of other sites in uPA in receptor binding has not been studied in detail.Evidence favoring the existence of such auxiliary sites comes from studies in which uPA-induced, uPAR-mediated adhesion to vitronectin (Vn) and other integrin ligands has been examined using purified proteins 7,35,36 or whole cells. 7,8,31,36,37 For example, we have reported that ATF enhances the binding of soluble uPAR (suPAR) to cellular Vn to a considerably greater extent than does GFD, 35 and similar observations have been made by others.…”

Novel Bi- and Trifunctional Inhibitors of Tumor-Associated Proteolytic Systems

“…The short distance between Cys19 and Cys31 in the native molecule allowed cycling of the linear uPA 19-31 using disulfide bridge formation giving rise to the cyclic peptides such as cyclo 19,31 uPA 19-31 and cyclo 21,29 uPA [21][22][23][24][25][26][27][28][29][30] (Fig. 10B,C) (Burgle et al, 1997;Magdolen et al, 2001). These cyclic peptides were able to compete with Sato et al, 2002).…”