An Exosite-specific ssDNA Aptamer Inhibits the Anticoagulant Functions of Activated Protein C and enhances Inhibition by Protein C Inhibitor

Müller, J. and Isermann, B. and Dücker, I. and Salehi, M. and Meyer, M. and Friedrich, Max and Madhusudhan, T. and Oldenburg, J. and Mayer, G. (2009) An Exosite-specific ssDNA Aptamer Inhibits the Anticoagulant Functions of Activated Protein C and enhances Inhibition by Protein C Inhibitor. Chemistry and Biology, 16 (4). pp. 442-451. ISSN 1074-5521 (http://dx.doi.org/10.1016/j.chembiol.2009.03.007)

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Abstract

Activated protein C (APC) is a serine protease with anticoagulant, anti-inflammatory, and cytoprotective properties. Using recombinant APC, we identified a class of single-stranded DNA aptamers (HS02) that selectively bind to APC with high affinity. Interaction of HS02 with APC modulates the protease activity in a way such that the anticoagulant functions of APC are inhibited and its reactivity toward the protein C inhibitor is augmented in a glysoaminoglycan-like fashion, whereas APC's antiapoptotic and cytoprotective functions remain unaffected. Based on these data, the binding site of HS02 was localized to the basic exosite of APC. These characteristics render the exosite-specific aptamers a promising tool for the development of APC assays and a potential therapeutic agent applicable for the selective control of APC's anticoagulant activity.