title: A proteolytic cascade controls lysosome rupture and necrotic cell death mediated by lysosome-destabilizing adjuvants.
abstract: Recent studies have linked necrotic cell death and proteolysis of inflammatory proteins to the adaptive immune response mediated by the lysosome-destabilizing adjuvants, alum and Leu-Leu-OMe (LLOMe). However, the mechanism by which lysosome-destabilizing agents trigger necrosis and proteolysis of inflammatory proteins is poorly understood. The proteasome is a cellular complex that has been shown to regulate both necrotic cell death and proteolysis of inflammatory proteins. We found that the peptide aldehyde proteasome inhibitors, MG115 and MG132, block lysosome rupture, degradation of inflammatory proteins and necrotic cell death mediated by the lysosome-destabilizing peptide LLOMe. However, non-aldehyde proteasome inhibitors failed to prevent LLOMe-induced cell death suggesting that aldehyde proteasome inhibitors triggered a pleotropic effect. We have previously shown that cathepsin C controls lysosome rupture, necrotic cell death and the adaptive immune response mediated by LLOMe. Using recombinant cathepsin C, we found that aldehyde proteasome inhibitors directly block cathepsin C, which presumably prevents LLOMe toxicity. The cathepsin B inhibitor CA-074-Me also blocks lysosome rupture and necrotic cell death mediated by a wide range of necrosis inducers, including LLOMe. Using cathepsin-deficient cells and recombinant cathepsins, we demonstrate that the cathepsins B and C are not required for the CA-074-Me block of necrotic cell death. Taken together, our findings demonstrate that lysosome-destabilizing adjuvants trigger an early proteolytic cascade, involving cathepsin C and a CA-074-Me-dependent protease. Identification of these early events leading to lysosome rupture will be crucial in our understanding of processes controlling necrotic cell death and immune responses mediated by lysosome-destabilizing adjuvants.
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Brojatsch
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Heriberto
authors.initials: H
authors.lastname: Lima
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Alak K
authors.initials: AK
authors.lastname: Kar
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Lee S
authors.initials: LS
authors.lastname: Jacobson
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Muehlbauer
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Kartik
authors.initials: K
authors.lastname: Chandran
authors.affiliation: Albert Einstein College of Medicine, Department of Microbiology and Immunology, Bronx, New York, United States of America.
authors.forename: Felipe
authors.initials: F
authors.lastname: Diaz-Griffero
mesh_terms: D000277:Adjuvants, Pharmaceutic / Q000494:pharmacology*; D000447:Aldehydes / Q000494:pharmacology; D000818:Animals; D000942:Antigens, Bacterial / Q000494:pharmacology; D001427:Bacterial Toxins / Q000494:pharmacology; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism; D020789:Cathepsin C / Q000037:antagonists & inhibitors / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009336:Necrosis; D010455:Peptides / Q000494:pharmacology; D061988:Proteasome Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects*
chemical_list: D000277:Adjuvants, Pharmaceutic; D000447:Aldehydes; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D004151:Dipeptides; D007976:Leupeptins; D010455:Peptides; D061988:Proteasome Inhibitors; C030325:anthrax toxin; C089486:carbobenzoxy-leucyl-leucyl-norvalinal; C045139:leucyl-leucine-methyl ester; C068250:N-(3-propylcarbamoyloxirane-2-carbonyl)-isoleucyl-proline; D020789:Cathepsin C; D002401:Cathepsin B