Bacterial RNA:DNA hybrids are activators of the NLRP3 inflammasome.
Enterohemorrhagic Escherichia coli (EHEC) is an extracellular pathogen that causes hemorrhagic colitis and hemolytic uremic syndrome. The proinflammatory cytokine, interleukin-1β, has been linked to hemolytic uremic syndrome. Here we identify the nucleotide-binding domain and leucine rich repeat containing family, pyrin domain containing 3 (NLRP3) inflammasome as an essential mediator of EHEC-induced IL-1β. Whereas EHEC-specific virulence factors were dispensable for NLRP3 activation, bacterial nucleic acids such as RNA:DNA hybrids and RNA gained cytosolic access and mediated inflammasome-dependent responses. Consistent with a direct role for RNA:DNA hybrids in inflammasome activation, delivery of synthetic EHEC RNA:DNA hybrids into the cytosol triggered NLRP3-dependent responses, and introduction of RNase H, which degrades such hybrids, into infected cells specifically inhibited inflammasome activation. Notably, an E. coli rnhA mutant, which is incapable of producing RNase H and thus harbors increased levels of RNA:DNA hybrid, induced elevated levels of NLRP3-dependent caspase-1 activation and IL-1β maturation. Collectively, these findings identify RNA:DNA hybrids of bacterial origin as a unique microbial trigger of the NLRP3 inflammasome.
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111;Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; and.
Sivapriya
S
Kailasan Vanaja
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; and.
Vijay A K
VA
Rathinam
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; and.
Maninjay K
MK
Atianand
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; and.
Parisa
P
Kalantari
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; and.
Brian
B
Skehan
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605; andCentre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway kate.fitzgerald@umassmed.edu John.Leong@tufts.edu.
Katherine A
KA
Fitzgerald
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111; kate.fitzgerald@umassmed.edu John.Leong@tufts.edu.
John M
JM
Leong
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D020170:Caspase 1 / Q000276:immunology; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D054324:Enterohemorrhagic Escherichia coli / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins / Q000235:genetics; D006463:Hemolytic-Uremic Syndrome / Q000276:immunology*; D015151:Immunoblotting; D058847:Inflammasomes / Q000276:immunology*; D053583:Interleukin-1beta / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D012313:RNA / Q000235:genetics / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics
D002352:Carrier Proteins; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D012269:Ribosomal Proteins; C436973:RimM protein, E coli; D012313:RNA; D020170:Caspase 1