title: Viral inhibitory peptide of TLR4, a peptide derived from vaccinia protein A46, specifically inhibits TLR4 by directly targeting MyD88 adaptor-like and TRIF-related adaptor molecule.
abstract: TLRs are critical pattern recognition receptors that recognize bacterial and viral pathogen-associated molecular patterns leading to innate and adaptive immune responses. TLRs signal via homotypic interactions between their cytoplasmic Toll/IL-1R (TIR) domains and TIR domain-containing adaptor proteins. Over the course of evolution, viruses have developed various immune evasion strategies, one of which involves inhibiting TLR signaling pathways to avoid immune detection. Thus, vaccinia virus encodes the A46 protein, which binds to multiple TIR-domain containing proteins, ultimately preventing TLRs from signaling. We have identified an 11-aa-long peptide from A46 (termed viral inhibitor peptide of TLR4, or VIPER), which, when fused to a cell-penetrating delivery sequence, potently inhibits TLR4-mediated responses. VIPER was TLR4 specific, being inert toward other TLR pathways, and was active in murine and human cells and in vivo, where it inhibited LPS-induced IL-12p40 secretion. VIPER also prevented TLR4-mediated MAPK and transcription factor activation, suggesting it acted close to the TLR4 complex. Indeed, VIPER directly interacted with the TLR4 adaptor proteins MyD88 adaptor-like (Mal) and TRIF-related adaptor molecule (TRAM). Viral proteins target host proteins using evolutionary optimized binding surfaces. Thus, VIPER possibly represents a surface domain of A46 that specifically inhibits TLR4 by masking critical binding sites on Mal and TRAM. Apart from its potential therapeutic and experimental use in suppressing TLR4 function, identification of VIPER's specific binding sites on TRAM and Mal may reveal novel therapeutic target sites. Overall, we demonstrate for the first time disruption of a specific TLR signaling pathway by a short virally derived peptide.
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity College Dublin, Ireland.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Lysakova-Devine
authors.forename: Brian
authors.initials: B
authors.lastname: Keogh
authors.forename: Barry
authors.initials: B
authors.lastname: Harrington
authors.forename: Kamalpreet
authors.initials: K
authors.lastname: Nagpal
authors.forename: Annett
authors.initials: A
authors.lastname: Halle
authors.forename: Douglas T
authors.initials: DT
authors.lastname: Golenbock
authors.forename: Tom
authors.initials: T
authors.lastname: Monie
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Bowie
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D005260:Female; D006801:Humans; D057131:Immune Evasion / Q000235:genetics / Q000276:immunology; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides; D020836:Protein Structure, Quaternary; D017472:Receptors, Interleukin-1 / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D014616:Vaccinia virus / Q000472:pathogenicity*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C413651:A46R protein, vaccinia virus; D048868:Adaptor Proteins, Signal Transducing; D008562:Membrane Glycoproteins; D010455:Peptides; D017472:Receptors, Interleukin-1; C480228:TICAM2 protein, human; C434984:TIRAP protein, human; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014764:Viral Proteins