title: Comprehensive RNAi-based screening of human and mouse TLR pathways identifies species-specific preferences in signaling protein use.
abstract: Toll-like receptors (TLRs) are a major class of pattern recognition receptors, which mediate the responses of innate immune cells to microbial stimuli. To systematically determine the roles of proteins in canonical TLR signaling pathways, we conducted an RNA interference (RNAi)-based screen in human and mouse macrophages. We observed a pattern of conserved signaling module dependencies across species, but found notable species-specific requirements at the level of individual proteins. Among these, we identified unexpected differences in the involvement of members of the interleukin-1 receptor-associated kinase (IRAK) family between the human and mouse TLR pathways. Whereas TLR signaling in mouse macrophages depended primarily on IRAK4 and IRAK2, with little or no role for IRAK1, TLR signaling and proinflammatory cytokine production in human macrophages depended on IRAK1, with knockdown of IRAK4 or IRAK2 having less of an effect. Consistent with species-specific roles for these kinases, IRAK4 orthologs failed to rescue signaling in IRAK4-deficient macrophages from the other species, and only mouse macrophages required the kinase activity of IRAK4 to mediate TLR responses. The identification of a critical role for IRAK1 in TLR signaling in humans could potentially explain the association of IRAK1 with several autoimmune diseases. Furthermore, this study demonstrated how systematic screening can be used to identify important characteristics of innate immune responses across species, which could optimize therapeutic targeting to manipulate human TLR-dependent outputs.
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Kyu-Seon
authors.initials: KS
authors.lastname: Oh
authors.affiliation: Bioinformatics Team, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Dutta
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Sharat J
authors.initials: SJ
authors.lastname: Vayttaden
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Lin
authors.affiliation: Institute of Molecular Medicine, University Hospital, University of Bonn, 53127 Bonn, Germany.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Ebert
authors.affiliation: Institute of Innate Immunity, University Hospital, Biomedical Centre, University of Bonn, 53127 Bonn, Germany. Inflammation Division, Walter and Eliza Hall Institute, Parkville,Victoria 3052, Australia. Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Dominic
authors.initials: D
authors.lastname: De Nardo
authors.affiliation: Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Joie
authors.initials: J
authors.lastname: Davis
authors.affiliation: Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Rustam
authors.initials: R
authors.lastname: Bagirzadeh
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Nicolas W
authors.initials: NW
authors.lastname: Lounsbury
authors.affiliation: Department of Immunology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Chandrashekhar
authors.initials: C
authors.lastname: Pasare
authors.affiliation: Institute of Innate Immunity, University Hospital, Biomedical Centre, University of Bonn, 53127 Bonn, Germany. German Center for Neurodegenerative Diseases (DZNE), 53175 Bonn, Germany. Department of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Eicke
authors.initials: E
authors.lastname: Latz
authors.affiliation: Institute of Molecular Medicine, University Hospital, University of Bonn, 53127 Bonn, Germany.
authors.forename: Veit
authors.initials: V
authors.lastname: Hornung
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. fraseri@niaid.nih.gov.
authors.forename: Iain D C
authors.initials: ID
authors.lastname: Fraser
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D018345:Mice, Knockout; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics*; D013045:Species Specificity; D051193:Toll-Like Receptors / Q000235:genetics*
chemical_list: D007527:Isoenzymes; D051193:Toll-Like Receptors; D053592:Interleukin-1 Receptor-Associated Kinases