Cholesterol-dependent cytolysins induce rapid release of mature IL-1beta from murine macrophages in a NLRP3 inflammasome and cathepsin B-dependent manner.
CDC are exotoxins secreted by many Gram-positive bacteria that bind cholesterol and oligomerize to form pores in eukaryotic cell membranes. We demonstrate that CDC TLO induces caspase-1 cleavage and the rapid release of IL-1beta from LPS-primed murine BMDM. IL-1beta secretion depends on functional toxin pore formation, as free cholesterol, which prevents TLO binding to cell membranes, blocks the cytokine release. Secretion of the mature forms of IL-1beta and caspase-1 occurs only at lower TLO doses, whereas at a higher concentration, cells release the biologically inactive proforms. IL-1beta release at a low TLO dose requires potassium efflux, calcium influx, and the activities of calcium-independent PLA(2), caspase-1, and cathepsin B. Additionally, mature IL-1beta release induced by a low TLO dose is dependent on the NLRP3 inflammasome, and pro-IL-1beta release induced by a high TLO dose occurs independently of NLRP3. These results further elucidate a mechanism of CDC-induced IL-1beta release and suggest a novel, immune evasion strategy in which IL-1beta-containing macrophages might release primarily inactive cytokine following exposure to high doses of these toxins.
Chu
Jessica
J
Immunology Graduate Program, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
Thomas
L Michael
LM
Watkins
Simon C
SC
Franchi
Luigi
L
Núñez
Gabriel
G
Salter
Russell D
RD
D000818:Animals; D002352:Carrier Proteins / Q000502:physiology*; D002401:Cathepsin B / Q000502:physiology*; D002784:Cholesterol / Q000494:pharmacology*; D003603:Cytotoxins / Q000494:pharmacology* / Q000633:toxicity; D004797:Enzyme-Linked Immunosorbent Assay; D005098:Exotoxins / Q000633:toxicity*; D005434:Flow Cytometry; D006094:Gram-Positive Bacteria / Q000502:physiology; D007249:Inflammation / Q000097:blood / Q000503:physiopathology; D053583:Interleukin-1beta / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010436:Pepstatins / Q000494:pharmacology
D002352:Carrier Proteins; D003603:Cytotoxins; D005098:Exotoxins; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D010436:Pepstatins; D002784:Cholesterol; D002401:Cathepsin B; C031375:pepstatin
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