title: Nucleotide-binding oligomerization domain proteins are innate immune receptors for internalized Streptococcus pneumoniae.
abstract: Streptococcus pneumoniae, the major cause of community-acquired pneumonia and bacterial meningitis, has been shown to transiently invade epithelial and endothelial cells. Innate immune receptors including Toll-like receptors recognize various pathogens, such as S. pneumoniae, by identifying conserved pathogen-associated molecular patterns. Recently, two members of a novel class of pattern recognition receptors, the cytosolic proteins nucleotide-binding oligomerization domain 1 (Nod1)/CARD4 and Nod2/CARD15, have been found to detect cell wall peptidoglycans. Here we tested the hypothesis that Nod proteins are involved in the intracellular recognition of pneumococci. Data indicate that pneumococci invade HEK293 cells. Genetic complementation studies in these cells demonstrate that NF-kappaB activation induced by S. pneumoniae depends on Nod2. Moreover, intracellular transfection of inactivated pneumococci yielded similar effects, confirming the Nod2 dependence of NF-kappaB activation by pneumococci in HEK293 cells. By dominant negative overexpression and small interfering RNA experiments, we show for the first time that interleukin-1 receptor-associated kinase participates in Nod2-dependent NF-kappaB activation. Additionally, dominant negative interleukin-1 receptor-associated kinase 2, tumor necrosis factor receptor-associated factor 6, NF-kappaB-inducing kinase, transforming growth factor-beta-activated kinase-binding protein 2, and transforming growth factor-beta-activated kinase 1 also inhibited Nod2-dependent NF-kappaB activation. We finally demonstrate that in C57BL/6 mouse lung tissue in vivo as well as in the bronchial epithelial cell line BEAS-2B, Nod1 and Nod2 mRNA expressions were up-regulated after pneumococcal infection. Data presented suggest that Nod proteins contribute to innate immune recognition of S. pneumoniae. Furthermore, Rip-2 and members of the Toll-like receptor-signaling cascade are involved in the Nod2-dependent activation of NF-kappaB induced by pneumococci.
authors.affiliation: Department of Internal Medicine/Infectious Diseases, Charité University Medicine Berlin, 1 Augustenburger Platz, 13353 Berlin, Germany.
authors.forename: Bastian
authors.initials: B
authors.lastname: Opitz
authors.forename: Anja
authors.initials: A
authors.lastname: Püschel
authors.forename: Bernd
authors.initials: B
authors.lastname: Schmeck
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Hocke
authors.forename: Simone
authors.initials: S
authors.lastname: Rosseau
authors.forename: Sven
authors.initials: S
authors.lastname: Hammerschmidt
authors.forename: Ralf R
authors.initials: RR
authors.lastname: Schumann
authors.forename: Norbert
authors.initials: N
authors.lastname: Suttorp
authors.forename: Stefan
authors.initials: S
authors.lastname: Hippenstiel
mesh_terms: D000818:Animals; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D009711:Nucleotides / Q000737:chemistry*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012293:Rifampin / Q000031:analogs & derivatives* / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D000097782:NF-kappaB-Inducing Kinase
chemical_list: D018076:DNA, Complementary; D053592:Interleukin-1 Receptor-Associated Kinases; D008156:Luciferases; D016328:NF-kappa B; D009711:Nucleotides; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012293:Rifampin; D000097782:NF-kappaB-Inducing Kinase; C084370:23-(O-(beta-glucopyranosyl))rifampicin