title: Cathepsin G-regulated release of formyl peptide receptor agonists modulate neutrophil effector functions.
abstract: Neutrophil serine proteases play an important role in inflammation by modulating neutrophil effector functions. We have previously shown that neutrophils deficient in the serine proteases cathepsin G and neutrophil elastase (CG/NE neutrophils) exhibit severe defects in chemokine CXCL2 release and reactive oxygen species (ROS) production when activated on immobilized immune complex. Exogenously added active CG rescues these defects, but the mechanism remains undefined. Using a protease-based proteomic approach, we found that, in vitro, the addition of exogenous CG to immune complex-stimulated CG/NE neutrophils led to a decrease in the level of cell-associated annexin A1 (AnxA1) and cathelin-related antimicrobial peptide (CRAMP), both known inflammatory mediators. We further confirmed that, in vivo, CG was required for the extracellular release of AnxA1 and CRAMP in a subcutaneous air pouch model. In vitro, CG efficiently cleaved AnxA1, releasing the active N-terminal peptide Ac2-26, and processed CRAMP in limited fashion. Ac2-26 and CRAMP peptides enhanced the release of CXCL2 by CG/NE neutrophils in a dose-dependent manner via formyl peptide receptor (FPR) stimulation. Blockade of FPRs by an antagonist, Boc2 (t-Boc-Phe-d-Leu-Phe-d-Leu-Phe), abrogates CXCL2 release, whereas addition of FPR agonists, fMLF and F2L, relieves Boc2 inhibition. Furthermore, the addition of active CG, but not inactive CG, also relieves Boc2 inhibition. These findings suggest that CG modulates neutrophil effector functions partly by controlling the release (and proteolysis) of FPR agonists. Unexpectedly, we found that mature CRAMP, but not Ac2-26, induced ROS production through an FPR-independent pathway.
authors.affiliation: Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Josh C
authors.initials: JC
authors.lastname: Woloszynek
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu
authors.forename: Christine T N
authors.initials: CT
authors.lastname: Pham
mesh_terms: D000818:Animals; D017305:Annexin A1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D056649:Cathepsin G / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D054426:Chemokine CXCL2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002630:Chemotactic Factors / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008817:Mice, Mutant Strains; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D059748:Proteolysis; D017382:Reactive Oxygen Species / Q000276:immunology / Q000378:metabolism; D044042:Receptors, Formyl Peptide / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism
chemical_list: D017305:Annexin A1; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D054426:Chemokine CXCL2; D002630:Chemotactic Factors; C404915:Cxcl2 protein, mouse; C518154:F2L protein, mouse; D009842:Oligopeptides; D017382:Reactive Oxygen Species; D044042:Receptors, Formyl Peptide; C573274:annexin A1, mouse; D009240:N-Formylmethionine Leucyl-Phenylalanine; C033373:butyloxycarbonyl-phenylalanyl-leucyl-phenylalanyl-leucyl-phenylalanine; D056649:Cathepsin G; C534096:Ctsg protein, mouse