A cyclic peptidylic inhibitor of murine urokinase-type plasminogen activator: changing species specificity by substitution of a single residue.
uPA (urokinase-type plasminogen activator) is a potential therapeutic target in a variety of pathological conditions, including cancer. In order to find new principles for inhibiting uPA in murine cancer models, we screened a phage-displayed peptide library with murine uPA as bait. We thereby isolated several murine uPA-binding peptide sequences, the predominant of which was the disulfide-bridged constrained sequence CPAYSRYLDC, which we will refer to as mupain-1. A chemically synthesized peptide corresponding to this sequence was found to be a competitive inhibitor of murine uPA, inhibiting its activity towards a low-molecular-mass chromogenic substrate as well as towards its natural substrate plasminogen. The K(i) value for inhibition as well as the K(D) value for binding were approx. 400 nM. Among a variety of other murine and human serine proteases, including trypsin, mupain-1 was found to be highly selective for murine uPA and did not even measurably inhibit human uPA. The cyclic structure of mupain-1 was indispensable for binding. Alanine scanning mutagenesis identified Arg(6) of mupain-1 as the P1 residue and indicated an extended binding interaction including the P5, P3, P2, P1 and P1' residues of mupain-1 and the specificity pocket, the catalytic triad and amino acids 41, 99 and 192 located in and around the active site of murine uPA. Exchanging His(99) of human uPA by a tyrosine residue, the corresponding residue in murine uPA, conferred mupain-1 susceptibility on to the latter. Peptide-derived inhibitors, such as mupain-1, may provide novel mechanistic information about enzyme-inhibitor interactions, provide alternative methodologies for designing effective protease inhibitors, and be used for target validation in murine model systems.
Andersen
Lisbeth M
LM
Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark. lma@mb.au.dk
Wind
Troels
T
Hansen
Hanne D
HD
Andreasen
Peter A
PA
D019943:Amino Acid Substitution; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology*; D013045:Species Specificity; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors* / Q000737:chemistry
D000970:Antineoplastic Agents; D010456:Peptides, Cyclic; C530075:mupain-1; D014568:Urokinase-Type Plasminogen Activator