Conformational quiescence of ADAMTS13 prevents proteolytic promiscuity

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Title: Conformational quiescence of ADAMTS13 prevents proteolytic promiscuity
Authors: South, K
Lane, DA
Freitas, MO
Item Type: Journal Article
Abstract: Background Recent work has revealed that ADAMTS13 circulates in a ‘closed’ conformation, only fully interacting with VWF following a conformational change. We hypothesised that this conformational quiescence also maintains the substrate specificity of ADAMTS13 and that the ‘open’ conformation of the protease might facilitate proteolytic promiscuity Objectives To identify a novel substrate for a constitutively active gain of function (GoF) ADAMTS13 variant (R568K/F592Y/R660K/Y661F/Y665F) Methods Fibrinogen proteolysis was characterised using SDS PAGE and LC-MS/MS. Fibrin formation was monitored by turbidity measurements and fibrin structure visualised by confocal microscopy Results ADAMTS13 exhibits proteolytic activity against the Aα chain of human fibrinogen, but this is only manifest on its conformational activation. Accordingly, the GoF ADAMTS13 variant and truncated variants such as MDTCS exhibit this activity. The cleavage site has been determined by LC-MS/MS to be Aα chain Lys225-Met226. Proteolysis of fibrinogen by GoF ADAMTS13 impairs fibrin formation in plasma based assays, alters clot structure and increases clot permeability. While GoF ADAMTS13 does not appear to proteolyse preformed cross-linked fibrin, its proteolytic activity against fibrinogen increases the susceptibility of fibrin to t-PA induced lysis by plasmin and increases the fibrin clearance rate more than 8 fold compared to WT ADAMTS13 (EC50 values of 3.0 ± 1.7 nM and 25.2 ± 9.7 nM, respectively) in in vitro thrombosis models Conclusion The ‘closed’ conformation of ADAMTS13 restricts its specificity and protects against fibrinogenolysis. Induced substrate promiscuity will be important as ADAMTS13 variants are developed as potential therapeutic agents against TTP and other cardiovascular diseases.
Issue Date: 23-Sep-2016
Date of Acceptance: 12-Aug-2016
ISSN: 1538-7933
Publisher: Wiley
Start Page: 2011
End Page: 2022
Journal / Book Title: Journal of Thrombosis and Haemostasis
Volume: 14
Issue: 10
Copyright Statement: © 2016 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis.This is an open access article under the terms of the Creative Commons Attribution License,which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: British Heart Foundation
British Heart Foundation
Funder's Grant Number: PG/12/55/29740
Keywords: ADAMTS-13 protein, human
allosteric regulation
protein conformation
von Willebrand factor
Cardiovascular System & Hematology
1102 Cardiovascular Medicine And Haematology
1103 Clinical Sciences
Publication Status: Published
Appears in Collections:Department of Medicine
Faculty of Medicine

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