title: Granzyme B cleaves decorin, biglycan and soluble betaglycan, releasing active transforming growth factor-β1.
abstract: OBJECTIVE
  Granzyme B (GrB) is a pro-apoptotic serine protease that contributes to immune-mediated target cell apoptosis. However, during inflammation, GrB accumulates in the extracellular space, retains its activity, and is capable of cleaving extracellular matrix (ECM) proteins. Recent studies have implicated a pathogenic extracellular role for GrB in cardiovascular disease, yet the pathophysiological consequences of extracellular GrB activity remain largely unknown. The objective of this study was to identify proteoglycan (PG) substrates of GrB and examine the ability of GrB to release PG-sequestered TGF-β1 into the extracellular milieu.
  
  
  RESULTS
  Three extracellular GrB PG substrates were identified; decorin, biglycan and betaglycan. As all of these PGs sequester active TGF-β1, cytokine release assays were conducted to establish if GrB-mediated PG cleavage induced TGF-β1 release. Our data confirmed that GrB liberated TGF-β1 from all three substrates as well as from endogenous ECM and this process was inhibited by the GrB inhibitor 3,4-dichloroisocoumarin. The released TGF-β1 retained its activity as indicated by the induction of SMAD-3 phosphorylation in human coronary artery smooth muscle cells.
  
  
  CONCLUSIONS
  In addition to contributing to ECM degradation and the loss of tissue structural integrity in vivo, increased extracellular GrB activity is also capable of inducing the release of active TGF-β1 from PGs.
authors.affiliation: UBC James Hogg Research Centre, Institute for Heart+Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Boivin
authors.forename: Marlo
authors.initials: M
authors.lastname: Shackleford
authors.forename: Amanda
authors.initials: A
authors.lastname: Vanden Hoek
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhao
authors.forename: Tillie L
authors.initials: TL
authors.lastname: Hackett
authors.forename: Darryl A
authors.initials: DA
authors.lastname: Knight
authors.forename: David J
authors.initials: DJ
authors.lastname: Granville
mesh_terms: D058578:Biglycan / Q000378:metabolism*; D055162:Biocatalysis / Q000187:drug effects; D015153:Blotting, Western; D002478:Cells, Cultured; D003374:Coumarins / Q000494:pharmacology; D058575:Decorin / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D053804:Granzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D049934:Isocoumarins; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000737:chemistry / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D051900:Smad3 Protein / Q000378:metabolism; D012995:Solubility; D013379:Substrate Specificity; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D058578:Biglycan; D003374:Coumarins; D058575:Decorin; D049934:Isocoumarins; D011509:Proteoglycans; D018125:Receptors, Transforming Growth Factor beta; C497790:SMAD3 protein, human; D015842:Serine Proteinase Inhibitors; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; C071736:betaglycan; C046235:3,4-dichloroisocoumarin; D053804:Granzymes