title: Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site.
abstract: The function of von Willebrand factor (VWF) is regulated by proteolysis, which limits its multimeric size and ability to tether platelets. The importance of ADAMTS13 metalloprotease in VWF regulation is demonstrated by the association between severe deficiency of ADAMTS13 and thrombotic thrombocytopenic purpura (TTP). However, ADAMTS13 activity levels do not always correlate with the clinical course of TTP, suggesting that other proteases could be important in regulating VWF. We identified 4 leukocyte proteases that cleave the synthetic VWF substrate FRETS-VWF73 and multimeric VWF. Elastase and proteinase 3 (PR3) cleave multimeric VWF and FRETS-VWF73 at the V(1607)-T(1608) peptide bond; cathepsin G and matrix metalloprotease 9 cleave VWF substrates at the Y(1605)-M(1606) and M(1606)-V(1607) bonds, respectively. Isolated intact human neutrophils cleave FRETS-VWF73 at the V(1607)-T(1608) peptide bond, suggesting that elastase or PR3 expressed on leukocyte surfaces might cleave VWF. In the presence of normal or ADAMTS13-deficient plasma, cleavage of FRETS-VWF73 by resting neutrophils is abolished. However, activated neutrophils retain proteolytic activity toward FRETS-VWF73 in the presence of plasma. Although the in vivo relevance remains to be established, these studies suggest the existence of a "hot spot" of VWF proteolysis in the VWF A2 domain, and support the possibility that activated leukocytes may participate in the proteolytic regulation of VWF.
authors.affiliation: Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, IA 52240, USA. thomas-raife@uiowa.edu
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Raife
authors.forename: Wenjing
authors.initials: W
authors.lastname: Cao
authors.forename: Bonnie S
authors.initials: BS
authors.lastname: Atkinson
authors.forename: Bruce
authors.initials: B
authors.lastname: Bedell
authors.forename: Robert R
authors.initials: RR
authors.lastname: Montgomery
authors.forename: Steven R
authors.initials: SR
authors.lastname: Lentz
authors.forename: George F
authors.initials: GF
authors.lastname: Johnson
authors.forename: X Long
authors.initials: XL
authors.lastname: Zheng
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism*; D000071120:ADAMTS13 Protein; D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D006801:Humans; D007962:Leukocytes / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010447:Peptide Hydrolases / Q000378:metabolism*; D011489:Protein Denaturation / Q000502:physiology; D055503:Protein Multimerization; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014841:von Willebrand Factor; D010447:Peptide Hydrolases; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human