title: Inhibition of the activation of multiple serine proteases with a cathepsin C inhibitor requires sustained exposure to prevent pro-enzyme processing.
abstract: Cathepsin C is a cysteine protease required for the activation of several pro-inflammatory serine proteases and, as such, is of interest as a therapeutic target. In cathepsin C-deficient mice and humans, the N-terminal processing and activation of neutrophil elastase, cathepsin G, and proteinase-3 is abolished and is accompanied by a reduction of protein levels. Pharmacologically, the consequence of cathepsin C inhibition on the activation of these serine proteases has not been described, due to the lack of stable and non-toxic inhibitors and the absence of appropriate experimental cell systems. Using novel reversible peptide nitrile inhibitors of cathepsin C, and cell-based assays with U937 and EcoM-G cells, we determined the effects of pharmacological inhibition of cathepsin C on serine protease activity. We show that indirect and complete inhibition of neutrophil elastase, cathepsin G, and proteinase-3 is achievable in intact cells with selective and non-cytotoxic cathepsin C inhibitors, at concentrations approximately 10-fold higher than those required to inhibit purified cathepsin C. The concentration of inhibitor needed to block processing of these three serine proteases was similar, regardless of the cell system used. Importantly, cathepsin C inhibition must be sustained to maintain serine protease inhibition, because removal of the reversible inhibitors resulted in the activation of pro-enzymes in intact cells. These findings demonstrate that near complete inhibition of multiple serine proteases can be achieved with cathepsin C inhibitors and that cathepsin C inhibition represents a viable but challenging approach for the treatment of neutrophil-based inflammatory diseases.
authors.affiliation: Department of Biochemistry and Molecular Biology, Merck Research Laboratories, 16711 Trans-Canada Highway, Kirkland Quebec H9H 3L1, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Méthot
authors.forename: Joel
authors.initials: J
authors.lastname: Rubin
authors.forename: Daniel
authors.initials: D
authors.lastname: Guay
authors.forename: Christian
authors.initials: C
authors.lastname: Beaulieu
authors.forename: Diane
authors.initials: D
authors.lastname: Ethier
authors.forename: T Jagadeeswar
authors.initials: TJ
authors.lastname: Reddy
authors.forename: Denis
authors.initials: D
authors.lastname: Riendeau
authors.forename: M David
authors.initials: MD
authors.lastname: Percival
mesh_terms: D000818:Animals; D020789:Cathepsin C / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007249:Inflammation; D007700:Kinetics; D019272:Leukocyte Elastase / Q000378:metabolism; D008956:Models, Chemical; D053146:Myeloblastin / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D010539:Permeability; D011817:Rabbits; D012697:Serine Endopeptidases / Q000737:chemistry*; D020298:U937 Cells
chemical_list: D004791:Enzyme Inhibitors; D020789:Cathepsin C; D012697:Serine Endopeptidases; D019272:Leukocyte Elastase; D053146:Myeloblastin; D003546:Cysteine Endopeptidases