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Enhanced activity of ADAMTS13 variant (R568K/F592Y/R660K/Y661F/Y665F) against platelet agglutination in vitro and in a murine model of acute ischaemic stroke

Authors
  • South, K
  • Denorme, F
  • Salles, I
  • De Meyer, S
  • Lane, D
Publication Date
Aug 03, 2018
Source
Spiral - Imperial College Digital Repository
Keywords
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Unknown
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Abstract

Background ADAMTS13 circulates in a closed conformation, only achieving full proteolytic activity against von Willebrand Factor (VWF) following a substrate‐induced conformational change. A gain of function (GoF) ADAMTS13 variant (R568K/F592Y/R660K/Y661F/Y665F) is conformationally pre‐activated. Objectives To establish how the hyperactivity of GoF ADAMTS13 is manifest in experimental models mimicking the occlusive arterial thrombi present in acute ischaemic stroke. Methods The ability of GoF ADAMTS13 to dissolve VWF‐platelet agglutinates was examined using an assay of ristocetin‐induced platelet agglutination and in parallel flow models of arterial thrombosis. A murine model of focal ischaemia was used to assess the thrombolytic potential of GoF ADAMTS13. Results WT ADAMTS13 required conformational activation to attain full activity against VWF‐mediated platelet capture under flow. In this assay GoF ADAMTS13 had an EC50 value >5‐fold lower than wild type (WT) (0.73±0.21 nM and 3.81±0.97 nM, respectively). The proteolytic activity of GoF ADAMTS13 against pre‐formed platelet agglutinates under flow was enhanced >4‐fold compared to WT (EC50 values of 2.5±1.1 nM and 10.2±5.6 nM, respectively). In a murine stroke model GoF ADAMTS13 restored cerebral blood flow at a lower dose than WT ADAMTS13 and partially retained the ability to recanalise vessels when administration was delayed by 1 hour. Conclusion The limited proteolytic activity of WT ADAMTS13 in in vitro models of arterial thrombosis suggests an in vivo requirement for conformational activation. The enhanced activity of the GoF ADAMTS13 variant translates to a more pronounced protective effect in experimental stroke.

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