title: Proteolytic inactivation of ADAMTS13 by thrombin and plasmin.
abstract: The multimeric size and the function of circulating von Willebrand factor are modulated via its proteolytic cleavage by the plasma metalloproteinase, ADAMTS13. It is unclear how ADAMTS13 activity is regulated within the vascular system. In the absence of a regulatory mechanism, ADAMTS13 activity might compromise platelet adhesion at sites of vascular injury. We hypothesized that at sites of vascular injury, ADAMTS13 activity could be regulated locally by coagulation proteinases. Initiation of coagulation in human plasma resulted in the disappearance of added full-length recombinant ADAMTS13. This loss was inhibited by hirudin. Using purified proteins, we showed that ADAMTS13 is proteolyzed at several cleavage sites by thrombin in a time- and concentration-dependent manner. Furthermore, this proteolysis ablated ADAMTS13 activity against purified von Willebrand factor. Preincubation of thrombin with soluble thrombomodulin, but not heparin, inhibited the proteolysis of ADAMTS13, suggesting the involvement of thrombin exosite I (and not exosite II) in ADAMTS13 recognition. Plasmin also cleaved ADAMTS13 into similar fragments, resulting in the loss of ADAMTS13 activity. This study demonstrates the susceptibility of ADAMTS13 to proteolytic inactivation and suggests possible roles for thrombin and plasmin at sites of vascular injury.
authors.affiliation: Haematology Department, Division of Investigative Sciences, Faculty of Medicine, Imperial College London, 5th Fl, Commonwealth Bldg, Hammersmith Hospital Campus, Du Cane Rd, London W12 0NN, United Kingdom. j.crawley@imperial.ac.uk
authors.forename: James T B
authors.initials: JT
authors.lastname: Crawley
authors.forename: Jonathan K
authors.initials: JK
authors.lastname: Lam
authors.forename: James B
authors.initials: JB
authors.lastname: Rance
authors.forename: Luigina R
authors.initials: LR
authors.lastname: Mollica
authors.forename: James S
authors.initials: JS
authors.lastname: O'Donnell
authors.forename: David A
authors.initials: DA
authors.lastname: Lane
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D003001:Cloning, Molecular; D017077:Culture Media, Conditioned; D005341:Fibrinolysin / Q000378:metabolism* / Q000494:pharmacology; D006629:Hirudins / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D017077:Culture Media, Conditioned; D006629:Hirudins; D011994:Recombinant Proteins; D013917:Thrombin; D005341:Fibrinolysin; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human