IκB Kinase Is an Essential Component of the Tpl2 Signaling Pathway

Waterfield, Michael; Jin, Wei; Reiley, William W.; Zhang, Minying; Sun, Shao Cong

doi:10.1128/mcb.24.13.6040-6048.2004

Cited by 127 publications

(149 citation statements)

References 41 publications

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“…It should be noted that no direct physical interaction was observed between ERK and IKK␣ or IKK␤ when we performed coimmunoprecipitation experiments (data not shown), implicating the involvement of an as-yet unidentified signaling intermediate. Recently, two separate studies have concluded that IKK␤ mediates LPS-or TNF-␣-induced ERK activation via tumor progression locus 2 (Tpl2) (53,54). However, by using Tpl2 siRNA knockdown, we found that Tpl2 is not involved in mediating MUC5AC induction or ERK activation by S. pneumoniae (data not shown).…”

Section: Discussionmentioning

confidence: 63%

A Novel Role for IκB Kinase (IKK) α and IKKβ in ERK-Dependent Up-Regulation of MUC5AC Mucin Transcription by Streptococcus pneumoniae

Lim

Jono

et al. 2007

The Journal of Immunology

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Epithelial cells represent the first line of host innate defense against invading microbes by elaborating a range of molecules involved in pathogen clearance. In particular, epithelial mucins facilitate the mucociliary clearance by physically trapping inhaled microbes. Up-regulation of mucin production thus represents an important host innate defense response against invading microbes. How mucin is induced in upper respiratory Streptococcus pneumoniae infections is unknown. In this study, we show that pneumolysin is required for up-regulation of MUC5AC mucin via TLR4-dependent activation of ERK in human epithelial cells in vitro and in mice in vivo. Interestingly, a “second wave” of ERK activation appears to be important in mediating MUC5AC induction. Moreover, IκB kinase (IKK) α and IKKβ are distinctly involved in MUC5AC induction via an ERK1-dependent, but IκBα-p65- and p100-p52-independent, mechanism, thereby revealing novel roles for IKKs in mediating up-regulation of MUC5AC mucin by S. pneumoniae.

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Section: Discussionmentioning

confidence: 63%

A Novel Role for IκB Kinase (IKK) α and IKKβ in ERK-Dependent Up-Regulation of MUC5AC Mucin Transcription by Streptococcus pneumoniae

Lim

Jono

et al. 2007

The Journal of Immunology

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“…In macrophages, pharmacological inhibition of the proteasome blocks both TPL-2 release from p105 and ERK activation following LPS stimulation [41,46], raising the possibility that IKK-induced p105 proteolysis might also regulate these processes. Consistent with this hypothesis, LPS-induced release of TPL-2 from p105, and its subsequent activation of MEK and ERK, are blocked by expression of p105 SSAA , which is resistant to IKK-induced proteolysis due to mutation of the IKK target serines to alanine.…”

Section: Regulation Of Tpl-2 Signaling By Nf-κb1 P105mentioning

confidence: 99%

Regulation and function of TPL-2, an IκB kinase-regulated MAP kinase kinase kinase

Gantke¹,

Sriskantharajah²,

Ley³

2010

Cell Res

135

158

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The IκB kinase (IKK) complex plays a well-documented role in innate and adaptive immunity. This function has been widely attributed to its role as the central activator of the NF-κB family of transcription factors. However, another important consequence of IKK activation is the regulation of TPL-2, a MEK kinase that is required for activation of ERK-1/2 MAP kinases in myeloid cells following Toll-like receptor and TNF receptor stimulation. In unstimulated cells, TPL-2 is stoichiometrically complexed with the NF-κB inhibitory protein NF-κB1 p105, which blocks TPL-2 access to its substrate MEK, and the ubiquitin-binding protein ABIN-2 (A20-binding inhibitor of NF-κB 2), both of which are required to maintain TPL-2 protein stability. Following agonist stimulation, the IKK complex phosphorylates p105, triggering its K48-linked ubiquitination and degradation by the proteasome. This releases TPL-2 from p105-mediated inhibition, facilitating activation of MEK, in addition to modulating NF-κB activation by liberating associated Rel subunits for translocation into the nucleus. IKK-induced proteolysis of p105, therefore, can directly regulate both NF-κB and ERK MAP kinase activation via NF-κB1 p105. TPL-2 is critical for production of the proinflammatory cytokine TNF during inflammatory responses. Consequently, there has been considerable interest in the pharmaceutical industry to develop selective TPL-2 inhibitors as drugs for the treatment of TNF-dependent inflammatory diseases, such as rheumatoid arthritis and inflammatory bowel disease. This review summarizes our current understanding of the regulation of TPL-2 signaling function, and also the complex positive and negative roles of TPL-2 in immune and inflammatory responses.

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“…In resting cells, Cot/tpl-2 forms a stable and inactive complex with p105 NF-kB and ABIN2 (A20-binding inhibitor of NF-kB2), among other proteins, protecting Cot/tpl-2 from degradation. The partial proteolysis of p105 NFkB to p50 NF-kB releases Cot/tpl-2 from the complex [15][16][17][18][19][20]. Dissociated and adequately phosphorylated Cot/tpl2 [21][22][23][24] fully activates MKK1 and consequently Erk1/2, prior to being rapidly degraded through the proteasome pathway [16,17,[25][26][27].…”

Section: Introductionmentioning

confidence: 99%

“…The partial proteolysis of p105 NFkB to p50 NF-kB releases Cot/tpl-2 from the complex [15][16][17][18][19][20]. Dissociated and adequately phosphorylated Cot/tpl2 [21][22][23][24] fully activates MKK1 and consequently Erk1/2, prior to being rapidly degraded through the proteasome pathway [16,17,[25][26][27]. Cot/tpl-2 (MAP3K8) is the sole MAP3K that activates the MKK1-Erk1/2 pathway in response to the activation of receptors of the TLR/IL-1 superfamily, as well as some of the TNF receptor family [17,[28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Cot/tpl2 activity is required for TLR‐induced activation of the Akt p70 S6k pathway in macrophages: Implications for NO synthase 2 expression

et al. 2011

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LPS stimulation activates IKK and different MAP kinase pathways, as well as the PI3K-AktmTOR-p70 S6k pathway, a negative regulator of these MyD88-dependent intracellular signals. Here, we show that Cot/tpl2, a MAP3K responsible for the activation of the MKK1-Erk1/2, controls P-Ser473 Akt and P-Thr389 p70 S6k phosphorylation in LPS-stimulated macrophages. Analysis of the intracellular signalling in Cot/tpl2 KO macrophages versus WT macrophages reveals lower IjBa recovery and higher phosphorylation of JNK and p38a after 1 h of LPS stimulation. Moreover, Cot/tpl2 deficiency increases LPS-induced NO synthase 2 (NOS2) expression in macrophages. Inhibition of the PI3K pathway abolishes the differences in IjBa and NOS2 expression between Cot/tpl2 KO and WT macrophages following LPS administration. Furthermore, in zymosan-and polyI:C-stimulated macrophages, Cot/tpl2 mediates P-Ser473 Akt phosphorylation, increases IjBa levels and decreases NOS2 expression. In conclusion, these data reveal a novel role for the Cot/tpl2 pathway in mediating TLR activation of the Akt-mTOR-p70 S6k pathway, allowing Cot/tpl2 to fine-control the activation state of other signalling pathways.Key words: Akt . Cot/tpl2 . Macrophage . NO synthase 2 . p70 S6k . TLR See accompanying Commentary by Martinez Supporting Information available online IntroductionStimulation of TLRs by the different PAMPs triggers macrophage activation, starting a specific functional program that culminates in the production of inflammatory mediators. With the exception of TLR3, TLRs use MyD88 as a central intracellular adaptor, thereby activating multiple downstream intracellular pathways including IKK. TLR3 and TLR4 recruit the TRIF adaptor, which also activates IKK, but specifically activating TBK1 and the transcription factor IRF3 (reviewed in [1,2]). Translocation of IRF3 to the nucleus is necessary, although not sufficient, to induce IFN-b expression [3]. Most TLRs also activate the PI3K-Akt-mTOR-p70 S6k pathway, which is considered to be a negative regulator of TLR activation in macrophages and myeloid dendritic cells. Inhibition of this PI3K-Akt-mTOR-p70 S6k pathway in TLR-activated cells augments NO synthase 2 (NOS2) expression [4][5][6][7][8].Adequate TLR4 stimulation induces the formation of a TLR receptor complex that recruits proteins such as MyD88 and p85 PI3 K [9]. PI3K subsequently activates the Akt-mTOR-p70 S6k pathway. Moreover, TLR-bound MyD88 recruits IRAK4 and IRAK1. The phosphorylation of IRAK1 by IRAK4 facilitates TRAF6 [1,10]). Activated IKK-b phosphorylates p105 NF-kB at multiple residues [11][12][13], which targets the rapid degradation of p105 NF-kB to p50 NF-kB [11][12][13][14]. In resting cells, Cot/tpl-2 forms a stable and inactive complex with p105 NF-kB and ABIN2 (A20-binding inhibitor of NF-kB2), among other proteins, protecting Cot/tpl-2 from degradation. The partial proteolysis of p105 NFkB to p50 NF-kB releases Cot/tpl-2 from the complex [15][16][17][18][19][20]. Dissociated and adequately phosphorylated Cot/tpl2 [21][22][23][24] fully...

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IκB Kinase Is an Essential Component of the Tpl2 Signaling Pathway

Cited by 127 publications

References 41 publications

A Novel Role for IκB Kinase (IKK) α and IKKβ in ERK-Dependent Up-Regulation of MUC5AC Mucin Transcription by Streptococcus pneumoniae

A Novel Role for IκB Kinase (IKK) α and IKKβ in ERK-Dependent Up-Regulation of MUC5AC Mucin Transcription by Streptococcus pneumoniae

Regulation and function of TPL-2, an IκB kinase-regulated MAP kinase kinase kinase

Cot/tpl2 activity is required for TLR‐induced activation of the Akt p70 S6k pathway in macrophages: Implications for NO synthase 2 expression

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