title: CARD4/Nod1 mediates NF-kappaB and JNK activation by invasive Shigella flexneri.
abstract: Epithelial cells are refractory to extracellular lipopolysaccharide (LPS), yet when presented inside the cell, it is capable of initiating an inflammatory response. Using invasive Shigella flexneri to deliver LPS into the cytosol, we examined how this factor, once intracellular, activates both NF-kappaB and c-Jun N-terminal kinase (JNK). Surprisingly, the mode of activation is distinct from that induced by toll-like receptors (TLRs), which mediate LPS responsiveness from the outside-in. Instead, our findings demonstrate that this response is mediated by a cytosolic, plant disease resistance-like protein called CARD4/Nod1. Biochemical studies reveal enhanced oligomerization of CARD4 upon S. flexneri infection, an event necessary for NF-kappaB induction. Dominant-negative versions of CARD4 block activation of NF-kappaB and JNK by S. flexneri as well as microinjected LPS. Finally, we showed that invasive S. flexneri triggers the formation of a transient complex involving CARD4, RICK and the IKK complex. This study demonstrates that in addition to the extracellular LPS sensing system mediated by TLRs, mammalian cells also possess a cytoplasmic means of LPS detection via a molecule that is related to plant disease-resistance proteins.
authors.affiliation: Unité des Virus Oncogènes, and Unité INSERM 389, Institut Pasteur, 28 rue du Dr Roux, Paris, Cédex 15, 75724 France.
authors.forename: S E
authors.initials: SE
authors.lastname: Girardin
authors.forename: R
authors.initials: R
authors.lastname: Tournebize
authors.forename: M
authors.initials: M
authors.lastname: Mavris
authors.forename: A L
authors.initials: AL
authors.lastname: Page
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: G R
authors.initials: GR
authors.lastname: Stark
authors.forename: J
authors.initials: J
authors.lastname: Bertin
authors.forename: P S
authors.initials: PS
authors.lastname: DiStefano
authors.forename: M
authors.initials: M
authors.lastname: Yaniv
authors.forename: P J
authors.initials: PJ
authors.lastname: Sansonetti
authors.forename: D J
authors.initials: DJ
authors.lastname: Philpott
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D029721:Drosophila Proteins; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D007375:Interleukin-1 / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D008070:Lipopolysaccharides / Q000008:administration & dosage / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008845:Microinjections; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D053474:Nod1 Signaling Adaptor Protein; D011233:Precipitin Tests; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D012763:Shigella flexneri / Q000472:pathogenicity / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D047992:TNF Receptor-Associated Factor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D029721:Drosophila Proteins; D007375:Interleukin-1; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; C119067:NOD1 protein, human; D053474:Nod1 Signaling Adaptor Protein; D011506:Proteins; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D047992:TNF Receptor-Associated Factor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C506253:RIPK2 protein, human; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases