Truncation of ADAMTS13 by Plasmin Enhances Its Activity in Plasma

Abstract

ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) cleaves von Willebrand Factor (VWF) multimers to control their thrombogenicity. The fibrinolytic enzyme plasmin can cleave VWF in a similar manner. However, plasmin can also cleave ADAMTS13, which ultimately inactivates it. This leaves the overall role of plasmin in primary haemostasis uncertain.We investigated the combined molecular effects of plasmin on VWF and ADAMTS13. We first identified that plasmin destroys FRETS-VWF73 substrate by cleaving the ADAMTS13 binding region in a buffered system. We next investigated how plasmin affects both VWF and ADAMTS13 under static conditions in plasma by western blotting. We found that globular VWF is largely protected from plasmin cleavage. However, ADAMTS13 is rapidly cleaved under these conditions, suggesting inactivation. Surprisingly, we observed that plasmin enhances ADAMTS13 activity in a modified two-stage FRETS-VWF73 assay that protects FRETS-VWF73 substrate from degradation. In direct binding studies under the same conditions, we found that plasmin generates multiple C-terminally truncated forms of ADAMTS13 with VWF-binding capacity. In an effort to seek evidence for this mechanism in vivo, we analysed plasma from patients with systemic amyloidosis, which is hallmarked by a hyperfibrinolytic state. We found that their plasma contained increased levels of C-terminally truncated forms of ADAMTS13, which correlated with their hyperfibrinolytic state.We propose that truncation of ADAMTS13 by plasmin abolishes intramolecular self-association, which improves interaction with unfolded VWF.

Structural analysis of ischemic stroke thrombi: histological indications for therapy resistance

“…18,34 Of note, plasmin can also cleave VWF, and plasmin activity was shown to regulate ADAMTS13 activity. [35][36][37] It will be interesting to further elucidate the interplay between plasmin and ADAMTS13 in the degradation of fibrin/VWF structures that are present in ischemic stroke thrombi.…”

Effect of tranexamic acid on endothelial von Willebrand factor/ADAMTS-13 response to in vitro shock conditions

“…In vivo where ADAMTS-13 activity is low, plasmin activity may support cleavage of ULvWF. However, plasmin may also cleave ADAMTS-13 31–33 . The relative effects of plasmin on the vWF-ADAMTS-13 axis is uncertain.…”

“…However, plasmin may also cleave ADAMTS-13. [31][32][33] The relative effects of plasmin on the vWF-ADAMTS-13 axis is uncertain. It is likely that the beneficial effects of TXA administration following trauma are in part related to protection of the glycocalyx layer and resultant impact on the ADAMTS-13-vWF axis.…”

Platelet dysfunction after trauma: From mechanisms to targeted treatment

“…However, specific proteolysis of CUB domains of ADAMTS13 can enhance ADAMTS13 activity and remove substrate specificity for VWF 85,88 . Hyperactive ADAMTS13 can cleave fibrinogen, potentially impairing platelet adhesion and aggregation 85,88 . The CUB domains of ADAMTS13 also directly inhibit platelet adhesion to collagen under flow 89 .…”

“…Several proteases that are elevated after traumatic injury (e.g., thrombin, plasmin) can degrade ADAMTS13, decreasing its activity 86,87 . However, specific proteolysis of CUB domains of ADAMTS13 can enhance ADAMTS13 activity and remove substrate specificity for VWF 85,88 . Hyperactive ADAMTS13 can cleave fibrinogen, potentially impairing platelet adhesion and aggregation 85,88 .…”