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Journal ArticleDOI

IRAK-4: A novel member of the IRAK family with the properties of an IRAK-kinase

TL;DR: IRAK-4 is the closest human homolog to Pelle and depends on its kinase activity to activate NF-κB, suggesting a role of IRAK- 4 as a central element in the early signal transduction of Toll/IL-1 receptors, upstream of IRAk-1.
Abstract: Toll/IL-1 receptor family members are central components of host defense mechanisms in a variety of species. One well conserved element in their signal transduction is Ser/Thr kinases, which couple early signaling events in a receptor complex at the plasma membrane to larger signalosomes in the cytosol. The fruit fly Drosophila melanogaster has one member of this family of kinases, termed Pelle. The complexity of this pathway is vastly increased in vertebrates, and several Pelle homologs have been described and termed IL-1 receptor-associated kinase (IRAK). Here we report the identification of a novel and distinct member of the IRAK family, IRAK-4. IRAK-4 is the closest human homolog to Pelle. Endogenous IRAK-4 interacts with IRAK-1 and TRAF6 in an IL-1-dependent manner, and overexpression of IRAK-4 can activate NF-κB as well as mitogen-activated protein (MAP) kinase pathways. Most strikingly, and in contrast to the other IRAKs, IRAK-4 depends on its kinase activity to activate NF-κB. In addition, IRAK-4 is able to phosphorylate IRAK-1, and overexpression of dominant-negative IRAK-4 is blocking the IL-1-induced activation and modification of IRAK-1, suggesting a role of IRAK-4 as a central element in the early signal transduction of Toll/IL-1 receptors, upstream of IRAK-1.
Citations
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Journal ArticleDOI
24 Feb 2006-Cell
TL;DR: New insights into innate immunity are changing the way the way the authors think about pathogenesis and the treatment of infectious diseases, allergy, and autoimmunity.

10,685 citations


Cites background from "IRAK-4: A novel member of the IRAK ..."

  • ...After IRAK-1 associates with MyD88, it is phosphorylated by the activated IRAK-4 and subsequently associates with TNFR-associated factor 6 (TRAF6), which acts as an ubiquitin protein ligase (E3) (Li et al., 2002)....

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Journal ArticleDOI
TL;DR: Rapid progress that has recently improved the understanding of the molecular mechanisms that mediate TLR signalling is reviewed.
Abstract: One of the mechanisms by which the innate immune system senses the invasion of pathogenic microorganisms is through the Toll-like receptors (TLRs), which recognize specific molecular patterns that are present in microbial components. Stimulation of different TLRs induces distinct patterns of gene expression, which not only leads to the activation of innate immunity but also instructs the development of antigen-specific acquired immunity. Here, we review the rapid progress that has recently improved our understanding of the molecular mechanisms that mediate TLR signalling.

7,906 citations


Cites background from "IRAK-4: A novel member of the IRAK ..."

  • ...It has also been shown that IRAK1 is a direct substrate of IRAK4 but not vice vers...

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Journal ArticleDOI
TL;DR: This unit discusses mammalian Toll receptors (TLR1‐10) that have an essential role in the innate immune recognition of microorganisms and are discussed are TLR‐mediated signaling pathways and antibodies that are available to detect specific TLRs.
Abstract: The innate immune system in drosophila and mammals senses the invasion of microorganisms using the family of Toll receptors, stimulation of which initiates a range of host defense mechanisms. In drosophila antimicrobial responses rely on two signaling pathways: the Toll pathway and the IMD pathway. In mammals there are at least 10 members of the Toll-like receptor (TLR) family that recognize specific components conserved among microorganisms. Activation of the TLRs leads not only to the induction of inflammatory responses but also to the development of antigen-specific adaptive immunity. The TLR-induced inflammatory response is dependent on a common signaling pathway that is mediated by the adaptor molecule MyD88. However, there is evidence for additional pathways that mediate TLR ligand-specific biological responses.

5,915 citations

Journal ArticleDOI
TL;DR: This review presents current knowledge on pathogen recognition through different families of PRRs and the increasingly complex signaling pathways responsible for activation of an inflammatory and antimicrobial response and medical implications are discussed.
Abstract: Summary: The innate immune system constitutes the first line of defense against invading microbial pathogens and relies on a large family of pattern recognition receptors (PRRs), which detect distinct evolutionarily conserved structures on pathogens, termed pathogen-associated molecular patterns (PAMPs). Among the PRRs, the Toll-like receptors have been studied most extensively. Upon PAMP engagement, PRRs trigger intracellular signaling cascades ultimately culminating in the expression of a variety of proinflammatory molecules, which together orchestrate the early host response to infection, and also is a prerequisite for the subsequent activation and shaping of adaptive immunity. In order to avoid immunopathology, this system is tightly regulated by a number of endogenous molecules that limit the magnitude and duration of the inflammatory response. Moreover, pathogenic microbes have developed sophisticated molecular strategies to subvert host defenses by interfering with molecules involved in inflammatory signaling. This review presents current knowledge on pathogen recognition through different families of PRRs and the increasingly complex signaling pathways responsible for activation of an inflammatory and antimicrobial response. Moreover, medical implications are discussed, including the role of PRRs in primary immunodeficiencies and in the pathogenesis of infectious and autoimmune diseases, as well as the possibilities for translation into clinical and therapeutic applications.

2,565 citations


Cites background from "IRAK-4: A novel member of the IRAK ..."

  • ...protein ligase (E3) (214) that, together with the ubiquitination...

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Journal ArticleDOI
TL;DR: Toll-like receptors have been established to play an essential role in the activation of innate immunity by recognizing specific patterns of microbial components and TIR domain-containing adaptors provide specificity of TLR signaling.

2,291 citations


Cites background from "IRAK-4: A novel member of the IRAK ..."

  • ...A biochemical study revealed that IRAK-4 acts upstream of, and phosphorylates, IRAK-1 upon stimulation [22]....

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References
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Journal ArticleDOI
15 Mar 1996-Blood
TL;DR: This is a lengthy review, with 586 citations chosen to illustrate specific areas of interest rather than a compendium of references, which summarizes what the author considers established or controversial topics linking the biology of IL-1 to mechanisms of disease.

4,354 citations

Journal ArticleDOI
03 Oct 1996-Nature
TL;DR: The identification of a new TRAF family member is reported, designated TRAF6, which indicates that TRAF proteins may function as signal transducers for distinct receptor families and that TRAf6 participates in IL-1 signalling.
Abstract: Many cytokines signal through different cell-surface receptors to activate the transcription factor NF-kappaB. Members of the TRAF protein family have been implicated in the activation of NF-kappaB by the tumour-necrosis factor (TNF)-receptor superfamily. Here we report the identification of a new TRAF family member, designated TRAF6. When overexpressed in human 293 cells, TRAF6 activates NF-kappaB. A dominant-negative mutant of TRAF6 inhibits NF-kappaB activation signalled by interleukin-1 (IL-1) but not by TNF. IL-1 treatment of 293 cells induces the association of TRAF6 with IRAK, a serine/threonine kinase that is rapidly recruited to the IL-1 receptor after IL-1 induction. These findings indicate that TRAF proteins may function as signal transducers for distinct receptor families and that TRAF6 participates in IL-1 signalling.

1,324 citations

Journal ArticleDOI
06 Feb 1997-Nature
TL;DR: The findings indicate that NIK participates in an NF-KB-inducing signalling cascade common to receptors of the TNF/NGF family and to the interleukin-1 type-I receptor.
Abstract: Several members of the tumour-necrosis/nerve-growth factor (TNF/NGF) receptor family activate the transcription factor NF-kappaB through a common adaptor protein, Traf2 (refs 1-5), whereas the interleukin 1 type-I receptor activates NF-kappaB independently of Traf2 (ref. 4). We have now cloned a new protein kinase, NIK, which binds to Traf2 and stimulates NF-kappaB activity. This kinase shares sequence similarity with several MAPKK kinases. Expression in cells of kinase-deficient NIK mutants fails to stimulate NF-kappaB and blocks its induction by TNF, by either of the two TNF receptors or by the receptor CD95 (Fas/Apo-1), and by TRADD, RIP and MORT1/FADD, which are adaptor proteins that bind to these receptors. It also blocked NF-kappaB induction by interleukin-1. Our findings indicate that NIK participates in an NF-kappaB-inducing signalling cascade common to receptors of the TNF/NGF family and to the interleukin-1 type-I receptor.

1,319 citations

Journal ArticleDOI
06 Sep 2001-Nature
TL;DR: A protein is described, Mal (MyD88-adapter-like), which joins MyD88 as a cytoplasmic TIR-domain-containing protein in the human genome, which is therefore an adapter in TLR-4 signal transduction.
Abstract: The recognition of microbial pathogens by the innate immune system involves Toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns. Different TLRs recognize different pathogen-associated molecular patterns, with TLR-4 mediating the response to lipopolysaccharide from Gram-negative bacteria. All TLRs have a Toll/IL-1 receptor (TIR) domain, which is responsible for signal transduction. MyD88 is one such protein that contains a TIR domain. It acts as an adapter, being involved in TLR-2, TLR-4 and TLR-9 signalling; however, our understanding of how TLR-4 signals is incomplete. Here we describe a protein, Mal (MyD88-adapter-like), which joins MyD88 as a cytoplasmic TIR-domain-containing protein in the human genome. Mal activates NF-kappaB, Jun amino-terminal kinase and extracellular signal-regulated kinase-1 and -2. Mal can form homodimers and can also form heterodimers with MyD88. Activation of NF-kappaB by Mal requires IRAK-2, but not IRAK, whereas MyD88 requires both IRAKs. Mal associates with IRAK-2 by means of its TIR domain. A dominant negative form of Mal inhibits NF-kappaB, which is activated by TLR-4 or lipopolysaccharide, but it does not inhibit NF-kappaB activation by IL-1RI or IL-18R. Mal associates with TLR-4. Mal is therefore an adapter in TLR-4 signal transduction.

1,250 citations

Journal ArticleDOI
31 Oct 1997-Science
TL;DR: Overexpression of a catalytically inactive form of IKK-β blocked cytokine-induced NF-κB activation and suggested that an active IκB kinase complex may require three distinct protein kinases.
Abstract: Activation of the transcription factor nuclear factor kappa B (NF-kappaB) by inflammatory cytokines requires the successive action of NF-kappaB-inducing kinase (NIK) and IkappaB kinase-alpha (IKK-alpha). A widely expressed protein kinase was identified that is 52 percent identical to IKK-alpha. IkappaB kinase-beta (IKK-beta) activated NF-kappaB when overexpressed and phosphorylated serine residues 32 and 36 of IkappaB-alpha and serines 19 and 23 of IkappaB-beta. The activity of IKK-beta was stimulated by tumor necrosis factor and interleukin-1 treatment. IKK-alpha and IKK-beta formed heterodimers that interacted with NIK. Overexpression of a catalytically inactive form of IKK-beta blocked cytokine-induced NF-kappaB activation. Thus, an active IkappaB kinase complex may require three distinct protein kinases.

1,186 citations