Department of Medicine, Division of Infectious Diseases and Immunology
Animals; Base Sequence; Carrier Proteins; Caspase 1; DNA, Single-Stranded; Enterohemorrhagic Escherichia coli; Enzyme-Linked Immunosorbent Assay; Escherichia coli Proteins; Hemolytic-Uremic Syndrome; Immunoblotting; Inflammasomes; Interleukin-1beta; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Confocal; Molecular Sequence Data; RNA; Ribosomal Proteins
Enterohemorrhagic Escherichia coli (EHEC) is an extracellular pathogen that causes hemorrhagic colitis and hemolytic uremic syndrome. The proinflammatory cytokine, interleukin-1beta, 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-1beta. 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-1beta maturation. Collectively, these findings identify RNA:DNA hybrids of bacterial origin as a unique microbial trigger of the NLRP3 inflammasome.
Vanaja, Sivapriya Kailasan; Rathinam, Vijay A. K.; Atianand, Maninjay K.; Kalantari, Parisa; Skehan, Brian M.; Fitzgerald, Katherine A.; and Leong, John M., "Bacterial RNA:DNA hybrids are activators of the NLRP3 inflammasome" (2014). Infectious Diseases and Immunology Publications and Presentations. 176.