Specific targeting of uPA activity with a monoclonal antibody neutralizeS uPA-dependent effects
Urokinase-type plasminogen activator (uPA) plays a central role in tissue remodeling processes. Most of our understanding of the role of uPA in vivo is derived from studies using gene-targeted uPA deficient mice. To enable in vivo studies on the specific interference with uPA functionality in mouse models, we have now developed murine monoclonal antibodies (mAbs) directed against murine uPA by immunization of uPA deficient mice with the recombinant protein. Guided by ELISA, Western blotting, Surface Plasmon Resonance and enzyme kinetic analyses, we have selected two highly potent and inhibitory anti-uPA mAbs (mU1 and mU3). Both mAbs recognized epitopes located on low molecular weight uPA. In enzyme activity assays in vitro, mU1 blocked uPA-catalyzed plasminogen activation as well as plasmin-mediated pro-uPA activation, whereas mU3 only was directed against the first of these reactions. We additionally provide evidence that mU1, but not mU3, successfully targeted uPA-dependent processes in vivo. Hence, systemic administration of mU1 (i) rescued mice treated with a uPA-activatable anthrax pro-toxin, and (ii) impaired uPA-mediated hepatic fibrinolysis in tPA deficient mice, resulting in a phenotype mimicking that of uPA;tPA double deficient mice. Importantly, this is the first report demonstrating specific antagonist-directed targeting of mouse uPA at the enzyme activity level in a normal physiological process in vivo.
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Document Type: Abstract
Publication date: May 1, 2008