title: Proteolysis of the endothelial cell protein C receptor by neutrophil proteinase 3.
abstract: BACKGROUND
  The endothelial cell protein C receptor (EPCR) presents protein C to the thrombin:thrombomodulin complex on the endothelium of large vessels, and enhances the generation of activated protein C (APC) and activation of protease-activated receptor-1. A previous report has demonstrated binding of soluble (s) EPCR to activated neutrophils via surface proteinase 3 (PR3).
  
  
  METHODS
  We now report further characterization of this interaction. Activated neutrophils and purified PR3 both decrease endothelial cell (EC) surface EPCR, suggestive of its proteolysis.
  
  
  RESULTS
  When added to purified recombinant sEPCR, PR3 produced multiple cleavages, with early products including 20 kDa N-terminal and C-terminal (after Lys(176)) fragments. The binding of active site blocked PR3 to sEPCR was studied by surface plasmon resonance. Estimates of the K(D) of 18.5-102 nM were obtained with heterogeneous binding, suggestive of more than a single interaction site.
  
  
  CONCLUSIONS
  This work demonstrates PR3 binding to and proteolysis of EPCR and suggests a mechanism by which anticoagulant and cell protective pathways can be down-regulated during inflammation.
authors: Department of Haematology, Imperial College London, London, UK. villegas@ujf-grenoble.fr
authors: A
authors: A
authors: Villegas-Mendez
authors: R
authors: R
authors: Montes
authors: L R
authors: LR
authors: Ambrose
authors: A N
authors: AN
authors: Warrens
authors: M
authors: M
authors: Laffan
authors: D A
authors: DA
authors: Lane
mesh_terms: D001779:Blood Coagulation Factors / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D018920:Coculture Techniques; D005434:Flow Cytometry; D006801:Humans; D006868:Hydrolysis; D053146:Myeloblastin / Q000378:metabolism*; D018375:Neutrophil Activation; D040901:Proteomics; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D001779:Blood Coagulation Factors; D011956:Receptors, Cell Surface; C091963:activated protein C receptor; D053146:Myeloblastin