Role of Adaptor TRIF in the MyD88-Independent Toll-Like Receptor Signaling Pathway

Yamamoto, Masahiro; Sato, Shintaro; Hemmi, Hiroaki; Hoshino, Katsuaki; Kaisho, Tsuneyasu; Sanjo, Hideki; Takeuchi, Osamu; Sugiyama, Masanaka; Okabe, Masaru; Takeda, Kiyoshi; Akira, Shizuo

doi:10.1126/science.1087262

Cited by 2,819 publications

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“…Other well-known roles of the MyD88 pathway include the fact that all TLRs, except TLR3, signal via MyD88, leading to the expression of proinflammatory cytokines and chemokines. 24,25 In addition, MyD88 is a common TLR/IL-1 downstream adapter for IL-1 signaling and is also required for the expression of IL-1b. 26 However, disruption of MyD88 signaling does not protect against focal cerebral ischemia, in in vitro and in vivo models.…”

Section: Discussionmentioning

confidence: 99%

A New Role for Downstream Toll-like Receptor Signaling in Mediating Immediate Early Gene Expression during Focal Cerebral Ischemia

Famakin

Mou

Johnson

et al. 2013

J Cereb Blood Flow Metab

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To better understand the role of downstream Toll-like receptor (TLR) signaling during acute cerebral ischemia, we performed cDNA microarrays, on brain RNA, and cytokine arrays, on serum, from wild type (WT), MyD88 À / À and TRIF-mutant mice, at baseline and following permanent middle cerebral artery occlusion (pMCAO). The acute stress response pathway was among the top pathways identified by Ingenuity Pathway Analysis of microarray data. We used real-time polymerase chain reaction to confirm the expression of four immediate early genes; EGR1, EGR2, ARC, Nurr77, in this pathway, and insulin degrading enzyme (IDE). Compared to WT, baseline immediate early gene expression was increased up to10-fold in MyD88 À / À and TRIF-mutant mice. However, following pMCAO, immediate early gene expression remained unchanged, from this elevated baseline in these mice, but increased up to 12-fold in WT. Furthermore, expression of IDE, which also degrades b-amyloid, decreased significantly only in TRIF-mutant mice. Finally, sE-Selectin, sICAM, sVCAM-1, and MMP-9 levels were significantly decreased only in MyD88 À / À compared with WT mice. We thus report a new role for downstream TLR signaling in immediate early gene expression during acute cerebral ischemia. We also show that the TRIF pathway regulates IDE expression; a major enzyme that clears b-amyloid from the brain.

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Section: Discussionmentioning

confidence: 99%

A New Role for Downstream Toll-like Receptor Signaling in Mediating Immediate Early Gene Expression during Focal Cerebral Ischemia

Famakin

Mou

Johnson

et al. 2013

J Cereb Blood Flow Metab

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“…Tlr4 -/- [45], Tlr2 -/- [46], Myd88 -/- [30] and Tirap -/- [29] mice were generated in the C57BL/6 mouse background, and Trif -/- [47] and Tram -/-[48] mice were generated in the C57BL/6/129 mouse background and were made in the BIKEN animal facilities (Osaka, Japan). Lps2, a non-functional codominant allele of Trif, was induced by N-ethyl-N-nitrosourea mutagenesis on a pure C57BL/6 mouse background [49] in the Scripps Institute animal facilities (La Jolla CA).…”

Section: Mouse Strainsmentioning

confidence: 99%

Mechanism of pathogen‐specific TLR4 activation in the mucosa: Fimbriae, recognition receptors and adaptor protein selection

et al. 2006

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The mucosal host defence discriminates pathogens from commensals, and prevents infection while allowing the normal flora to persist. Paradoxically, Toll-like receptors (TLR) control the mucosal defence against pathogens, even though the TLR recognise conserved molecules like LPS, which are shared between pathogens and commensals. This study proposes a mechanism of pathogen-specific mucosal TLR4 activation, involving adhesive ligands and their host cell receptors. TLR4 signalling was activated in CD14-negative, LPS-unresponsive epithelial cells by P fimbriated, uropathogenic Escherichia coli but not by a mutant lacking fimbriae. Epithelial TLR4 signalling in vivo involved the glycosphingolipid receptors for P fimbriae and the adaptor proteins Toll/IL-1R (TIR) domain-containing adaptor inducing IFN-b (TRIF)/TRIF-related adaptor molecule (TRAM), but myeloid differentiation protein 88 (MyD88)/TIR domain-containing adaptor protein were not required for the epithelial response. Substituting the P fimbriae with type 1 fimbriae changed TLR4 signalling from the TRIF to the MyD88 adaptor pathway. In addition, the adaptor proteins and the fimbrial type were found to influence bacterial clearance. Trif -/-and Tram -/-mice remained infected with P fimbriated E. coli but cleared thetype 1 fimbriated strain, while Myd88 -/-mice became carriers of both the P and the type 1 fimbriated bacteria. Thus, TLR4 may be engaged specifically by pathogens, when the proper cell surface receptors are engaged by virulence ligands. IntroductionToll-like receptors (TLR) control the innate host defence at mucosal surfaces and yet commensals do not induce an inflammatory response at those sites. The relative inertia to the commensals is paradoxical, as the TLR recognise conserved pathogen-associated molecular patterns (PAMP), which are present on both pathogenic and commensal bacteria. Lipolysaccharide (LPS), flagellin, peptidoglycan or DNA may bind directly to the TLR but in addition, co-receptors are needed to enhance the TLR response to these conserved ligands [1][2][3]. Myeloid cells use CD14 and MD-2 as co-receptors for LPS in TLR4 signalling, and minute amounts of LPS may elicit a strong systemic inflammatory response [4,5]. However, the TLR response to pathogen attack at mucosal surfaces is controlled by different interactions. Epithelial cells must be protected from constant TLR activation by commensals and their PAMP, in order for mucosal integrity to be maintained. The epithelial cells thus lack co-receptors like CD14 [6][7][8][9][10][11], and in addition, commensals have been suggested to actively suppress epithelia responses through NF-jB [12,13]. Yet, mucosal pathogens evoke rapid TLR4-dependent responses at mucosal sites, suggesting that alternative ligands and receptors might be involved in mucosal TLR activation. Pathogens use adhesive surface ligands to break the inertia of the mucosal barrier [14][15][16]. The innate defence is activated as a direct result of these interactions and epithelial cells produce the first wave of me...

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“…In macrophages undergoing a UPR, synergistic IFN-b induction was observed with activators of TLR3, TLR4, and MDA5, but not TLR2 or TLR9. TLR3/4 use the TRIF-dependent pathway to activate IRF3 via Tank-binding kinase 1 and induce IFN-b, whereas TLR2 signals solely through MyD88, and does not cause significant up-regulation of type I IFN [39,40]. MDA5 recognizes cytoplasmic dsRNA [poly(I:C)] and activates IRF3 via IFN-b promoter stimulator-1 and Tank-binding kinase 1, suggesting that ER stress exerts its effect downstream of TRIF [10,34].…”

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confidence: 99%

Endoplasmic reticulum stress and the unfolded protein response are linked to synergistic IFN‐β induction via X‐box binding protein 1

et al. 2008

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Type I IFN are strongly induced upon engagement of certain pattern recognition receptors by microbial products, and play key roles in regulating innate and adaptive immunity. It has become apparent that the endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR), in addition to restoring ER homeostasis, also influences the expression of certain inflammatory cytokines. However, the extent to which UPR signaling regulates type I IFN remains unclear. Here we show that cells undergoing a UPR respond to TLR4 and TLR3 ligands, and intracellular dsRNA, with log-fold greater IFN-b induction. This synergy is not dependent on autocrine type I IFN signaling, but unexpectedly requires the UPR transcription factor X-box binding protein 1 (XBP-1). Synergistic IFN-b induction also occurs in HLA-B27/human b 2 m-transgenic rat macrophages exhibiting a UPR as a consequence of HLA-B27 up-regulation, where it correlates with activation of XBP-1 splicing. Together these findings indicate that the cellular response to endogenous 'danger' that disrupts ER homeostasis is coupled to IFN-b induction by XBP-1, which has implications for the immune response and the pathogenesis of diseases involving the UPR.Key words: HLA-B27 Á Interferons Á Protein misfolding Á Unfolded protein response IntroductionInitially identified as antiviral cytokines, type I IFN (IFN-a/b) are now recognized to have diverse immunoregulatory effects activating macrophages and NK cells, promoting T cell survival and dendritic cell (DC) maturation, and increasing the production of Th1-polarizing cytokines to mediate innate and adaptive immune responses [1]. Type I IFN also exert biological effects at low and even constitutive levels of expression [2]. For example, weak IFN-b-mediated signaling augments IFN-a/b induction in response to LPS through positive feedback involving autocrine/ paracrine up-regulation of IFN regulatory factor (IRF)7. In addition, low levels of IFN-a/b prime cells to respond to IFN-c and IL-6 by providing a phosphorylated type I IFN receptor 'niche' for commonly used signaling molecules in proximity to other cytokine receptor complexes [3,4]. Mice deficient in IFN-b are more susceptible to viral infection, have lower numbers of macrophages and mature B cells, and exhibit reduced bone mass [5], as IFN-b is a positive regulator of bone formation through inhibition of osteoclast differentiation [6]. Thus, even constitutive levels of this cytokine are important in osteo-immune homeostasis.IFN-b is produced by most cell types upon viral infection, and in large amounts by macrophages and DC, following engagement of pattern recognition receptors (PRR) by conserved molecular structures referred to as pathogen-associated molecular patterns [7, 8]. PRR that mediate IFN-b induction include cell surface TLR4 and endosomal TLR3 for LPS and dsRNA, respectively [9]. In both instances increased IFN-b gene transcription occurs via TLR/IL-1R domain-containing adapter inducing IFN-b (TRIF)-dependent IRF3 and NF-jB activation. PRR in the retinoic ...

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Role of Adaptor TRIF in the MyD88-Independent Toll-Like Receptor Signaling Pathway

Cited by 2,819 publications

References 20 publications

A New Role for Downstream Toll-like Receptor Signaling in Mediating Immediate Early Gene Expression during Focal Cerebral Ischemia

A New Role for Downstream Toll-like Receptor Signaling in Mediating Immediate Early Gene Expression during Focal Cerebral Ischemia

Mechanism of pathogen‐specific TLR4 activation in the mucosa: Fimbriae, recognition receptors and adaptor protein selection

Endoplasmic reticulum stress and the unfolded protein response are linked to synergistic IFN‐β induction via X‐box binding protein 1

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