scholarly journals FAF1 Suppresses IκB Kinase (IKK) Activation by Disrupting the IKK Complex Assembly

2007 ◽  
Vol 282 (38) ◽  
pp. 27572-27577 ◽  
Author(s):  
Min-Young Park ◽  
Ji-hyun Moon ◽  
Ki-Sung Lee ◽  
Hye-In Choi ◽  
Jongkyeong Chung ◽  
...  
Keyword(s):  
Leucine Zipper ◽  
Physical Interaction ◽  
Inhibitory Mechanism ◽  
Complex Assembly ◽  
Downstream Signaling ◽  
Leucine Zipper Domain ◽  
Iκb Kinase ◽  
Ikk Complex ◽  
Factor Α ◽  
Necrosis Factor

This study presents a molecular inhibitory mechanism by Fas-associated factor 1 (FAF1) on IκB kinase (IKK) activation, where divergent NF-κB-activating stimuli converge. FAF1 interacts with IKKβ in response to proinflammatory stimuli (such as tumor necrosis factor-α, interleukin-1β, and lipopolysaccharide) and suppresses IKK activation. Interaction of the leucine-zipper domain of IKKβ with FAF1 affected the IKK heterocomplex (IKKα/β) and homocomplex (IKKα/α, IKKβ/β) formations and attenuated IKKγ recruitment to IKKβ. Overexpression of FAF1 reduced the level of IKKβ activity, whereas FAF1 depletion increased the activity. These results indicate that FAF1 inhibits IKK activation and its downstream signaling by interrupting the IKK complex assembly through physical interaction with IKKβ. Taken together, FAF1 robustly suppresses NF-κB activation through the inhibition of IKK activation in combination with previously reported cytoplasmic retention of NF-κB p65 (Park, M. Y., Jang, H. D., Lee, S. Y., Lee, K. J., and Kim, E. (2004) J. Biol. Chem. 279, 2544–2549). Such redundant suppression would prevent inadvertent activation of the NF-κB pathway.

scholarly journals Myosin motor Myo1c and its receptor NEMO/IKK-γ promote TNF-α–induced serine307 phosphorylation of IRS-1

2006 ◽  
Vol 173 (5) ◽  
pp. 665-671 ◽  
Author(s):  
Yoshitaka Nakamori ◽  
Masahiro Emoto ◽  
Naofumi Fukuda ◽  
Akihiko Taguchi ◽  
Shigeru Okuya ◽  
...  
Keyword(s):  
Motor Protein ◽  
Nuclear Factor Κb ◽  
Receptor Protein ◽  
Cytoskeletal Network ◽  
Iκb Kinase ◽  
Tnf Α ◽  
Ikk Complex ◽  
Factor Α ◽  
And Function ◽  
Necrosis Factor

Tumor necrosis factor-α (TNF-α) signaling through the IκB kinase (IKK) complex attenuates insulin action via the phosphorylation of insulin receptor substrate 1 (IRS-1) at Ser307. However, the precise molecular mechanism by which the IKK complex phosphorylates IRS-1 is unknown. In this study, we report nuclear factor κB essential modulator (NEMO)/IKK-γ subunit accumulation in membrane ruffles followed by an interaction with IRS-1. This intracellular trafficking of NEMO requires insulin, an intact actin cytoskeletal network, and the motor protein Myo1c. Increased Myo1c expression enhanced the NEMO–IRS-1 interaction, which is essential for TNF-α– induced phosphorylation of Ser307–IRS-1. In contrast, dominant inhibitory Myo1c cargo domain expression diminished this interaction and inhibited IRS-1 phosphorylation. NEMO expression also enhanced TNF-α–induced Ser307–IRS-1 phosphorylation and inhibited glucose uptake. In contrast, a deletion mutant of NEMO lacking the IKK-β–binding domain or silencing NEMO blocked the TNF-α signal. Thus, motor protein Myo1c and its receptor protein NEMO act cooperatively to form the IKK–IRS-1 complex and function in TNF-α–induced insulin resistance.

scholarly journals The IKKβ Subunit of IκB Kinase (IKK) is Essential for Nuclear Factor κB Activation and Prevention of Apoptosis

1999 ◽  
Vol 189 (11) ◽  
pp. 1839-1845 ◽  
Author(s):  
Zhi-Wei Li ◽  
Wenming Chu ◽  
Yinling Hu ◽  
Mireille Delhase ◽  
Tom Deerinck ◽  
...  
Keyword(s):  
Interleukin 1 ◽  
Nuclear Factor Κb ◽  
Regulatory Subunit ◽  
Nuclear Factor ◽  
Catalytic Subunits ◽  
Iκb Kinase ◽  
Ikk Complex ◽  
Factor Α ◽  
Necrosis Factor

The IκB kinase (IKK) complex is composed of three subunits, IKKα, IKKβ, and IKKγ (NEMO). While IKKα and IKKβ are highly similar catalytic subunits, both capable of IκB phosphorylation in vitro, IKKγ is a regulatory subunit. Previous biochemical and genetic analyses have indicated that despite their similar structures and in vitro kinase activities, IKKα and IKKβ have distinct functions. Surprisingly, disruption of the Ikkα locus did not abolish activation of IKK by proinflammatory stimuli and resulted in only a small decrease in nuclear factor (NF)-κB activation. Now we describe the pathophysiological consequence of disruption of the Ikkβ locus. IKKβ-deficient mice die at mid-gestation from uncontrolled liver apoptosis, a phenotype that is remarkably similar to that of mice deficient in both the RelA (p65) and NF-κB1 (p50/p105) subunits of NF-κB. Accordingly, IKKβ-deficient cells are defective in activation of IKK and NF-κB in response to either tumor necrosis factor α or interleukin 1. Thus IKKβ, but not IKKα, plays the major role in IKK activation and induction of NF-κB activity. In the absence of IKKβ, IKKα is unresponsive to IKK activators.

scholarly journals The α and β Subunits of IκB Kinase (IKK) Mediate TRAF2-Dependent IKK Recruitment to Tumor Necrosis Factor (TNF) Receptor 1 in Response to TNF

2001 ◽  
Vol 21 (12) ◽  
pp. 3986-3994 ◽  
Author(s):  
Anne Devin ◽  
Yong Lin ◽  
Shoji Yamaoka ◽  
Zhiwei Li ◽  
Michael Karin ◽  
...  
Keyword(s):  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Leucine Zipper ◽  
Nuclear Translocation ◽  
Ring Finger ◽  
Tnf Receptor ◽  
Death Domain ◽  
Iκb Kinase ◽  
Cytokine Tumor Necrosis Factor ◽  
Necrosis Factor

ABSTRACT The activation of IκB kinase (IKK) is a key step in the nuclear translocation of the transcription factor NF-κB. IKK is a complex composed of three subunits: IKKα, IKKβ, and IKKγ (also called NEMO). In response to the proinflammatory cytokine tumor necrosis factor (TNF), IKK is activated after being recruited to the TNF receptor 1 (TNF-R1) complex via TNF receptor-associated factor 2 (TRAF2). We found that the IKKα and IKKβ catalytic subunits are required for IKK-TRAF2 interaction. This interaction occurs through the leucine zipper motif common to IKKα, IKKβ, and the RING finger domain of TRAF2, and either IKKα or IKKβ alone is sufficient for the recruitment of IKK to TNF-R1. Importantly, IKKγ is not essential for TNF-induced IKK recruitment to TNF-R1, as this occurs efficiently in IKKγ-deficient cells. Using TRAF2−/− cells, we demonstrated that the TNF-induced interaction between IKKγ and the death domain kinase RIP is TRAF2 dependent and that one possible function of this interaction is to stabilize the IKK complex when it interacts with TRAF2.

scholarly journals Akt-Dependent Phosphorylation Specifically Regulates Cot Induction of NF-κB-Dependent Transcription

2002 ◽  
Vol 22 (16) ◽  
pp. 5962-5974 ◽  
Author(s):  
Lawrence P. Kane ◽  
Marianne N. Mollenauer ◽  
Zheng Xu ◽  
Christoph W. Turck ◽  
Arthur Weiss
Keyword(s):  
Protein Kinase ◽  
Signaling Pathways ◽  
Cellular Transformation ◽  
Dominant Negative ◽  
Mitogen Activated Protein Kinase ◽  
Iκb Kinase ◽  
Ikk Complex ◽  
Mitogen Activated Protein ◽  
Tumor Necrosis Factor Induction ◽  
Necrosis Factor

ABSTRACT The Akt (or protein kinase B) and Cot (or Tpl-2) serine/threonine kinases are associated with cellular transformation. These kinases have also been implicated in the induction of NF-κB-dependent transcription. As a member of the mitogen-activated protein kinase kinase kinase (MAP3K) family, Cot can also activate MAP kinase signaling pathways that target AP-1 and NFAT family transcription factors. Here we show that Akt and Cot physically associate and functionally cooperate. Akt appears to function upstream of Cot, as Akt can enhance Cot induction of NF-κB-dependent transcription, and dominant-negative Cot blocks the activation of this element by Akt. Furthermore, deletion analysis shows that binding to Akt is critical for Cot function. The regulation of NF-κB-dependent transcription by Cot requires Akt-dependent phosphorylation of serine 400 (S400), near the carboxy terminus of Cot. However, phosphorylation at this site is not required for Cot kinase activity or AP-1 induction, suggesting it specifically regulates Cot effector function at the level of the NF-κB pathway. Mutation of S400 in Cot does indeed abolish its ability to activate IκB-kinase (IKK) complexes, but paradoxically it allows for increased Cot association with the IKK complex. This mutated form of Cot also acts as a dominant negative for T-cell antigen receptor/CD28- or Akt/phorbol myristate acetate-induced NF-κB induction, while having relatively little effect on tumor necrosis factor induction of NF-κB. These findings suggest that the activation of different signaling pathways by MAP3Ks may be regulated separately and may provide evidence for how such discrimination by one member of this kinase family occurs.

Adiponectin suppresses IκB kinase activation induced by tumor necrosis factor-α or high glucose in endothelial cells: role of cAMP and AMP kinase signaling

2007 ◽  
Vol 293 (6) ◽  
pp. E1836-E1844 ◽  
Author(s):  
Xiangdong Wu ◽  
Kalyankar Mahadev ◽  
Lauren Fuchsel ◽  
Raogo Ouedraogo ◽  
Shi-qiong Xu ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Tumor Necrosis Factor ◽  
High Glucose ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Amp Kinase ◽  
Inflammatory Signaling ◽  
Iκb Kinase ◽  
Factor Α ◽  
Necrosis Factor

Adiponectin is a protein secreted from adipocytes that exhibits salutary effects in the vascular endothelium by signaling mechanisms that are not well understood. In obesity-related disease states and type 2 diabetes, circulating substances, including tumor necrosis factor-α (TNFα) and high glucose, activate IκB kinase (IKK)β and reduce the abundance of its substrate, inhibitor of κB (IκB)α, leading to nuclear translocation of the transcription factor NF-κB and stimulation of an inflammatory signaling cascade closely associated with endothelial dysfunction. The present study demonstrates that the globular domain of adiponectin (gAd) potently suppresses the activation of IKKβ by either TNFα or high glucose in human umbilical vein endothelial cells and ameliorates the associated loss of IκBα protein. Interestingly, activation of AMP kinase was substantially more effective than cAMP signaling in suppressing high glucose-induced IKKβ activity, whereas both pathways were comparably active in suppressing the TNFα-induced increase in IKKβ. Both cAMP/protein kinase A signaling and activation of the AMP kinase pathway played a role in the suppression by gAd of TNFα- and high glucose-mediated IKKβ activation. These findings support an important role for adiponectin in anti-inflammatory signaling in the endothelium and also imply that multiple pathways are involved in the cellular effects of adiponectin.

scholarly journals TfR1 interacts with the IKK complex and is involved in IKK–NF-κB signalling

2012 ◽  
Vol 449 (1) ◽  
pp. 275-284 ◽  
Author(s):  
Niall S. Kenneth ◽  
Sharon Mudie ◽  
Sanne Naron ◽  
Sonia Rocha
Keyword(s):  
Target Gene ◽  
Gene Activation ◽  
Nuclear Factor Κb ◽  
Gene Promoters ◽  
Protein Levels ◽  
Transferrin Receptor 1 ◽  
The Family ◽  
Ikk Complex ◽  
Factor Α ◽  
Necrosis Factor

The IKK [inhibitor of NF-κB (nuclear factor κB) kinase] complex has an essential role in the activation of the family of NF-κB transcription factors in response to a variety of stimuli. To identify novel IKK-interacting proteins, we performed an unbiased proteomics screen where we identified TfR1 (transferrin receptor 1). TfR1 is required for transferrin binding and internalization and ultimately for iron homoeostasis. TfR1 depletion does not lead to changes in IKK subunit protein levels; however, it does reduce the formation of the IKK complex, and inhibits TNFα (tumour necrosis factor α)-induced NF-κB-dependent transcription. We find that, in the absence of TfR1, NF-κB does not translocate to the nucleus efficiently, and there is a reduction in the binding to target gene promoters and consequentially less target gene activation. Significantly, depletion of TfR1 results in an increase in apoptosis in response to TNFα treatment, which is rescued by elevating the levels of RelA/NF-κB. Taken together, these results indicate a new function for TfR1 in the control of IKK and NF-κB. Our data indicate that IKK–NF-κB responds to changes in iron within the cell.

scholarly journals βTrCP-Mediated Proteolysis of NF-κB1 p105 Requires Phosphorylation of p105 Serines 927 and 932

2003 ◽  
Vol 23 (1) ◽  
pp. 402-413 ◽  
Author(s):  
Valerie Lang ◽  
Julia Janzen ◽  
Gregory Zvi Fischer ◽  
Yasmina Soneji ◽  
Sören Beinke ◽  
...  
Keyword(s):  
Target Sequence ◽  
Double Knockout ◽  
Necrosis Factor Alpha ◽  
Ubiquitin E3 Ligase ◽  
Iκb Kinase ◽  
Tnf Α ◽  
Ikk Complex ◽  
Factor Alpha ◽  
Necrosis Factor

ABSTRACT NF-κB1 p105 functions both as a precursor of NF-κB1 p50 and as a cytoplasmic inhibitor of NF-κB. Following the stimulation of cells with tumor necrosis factor alpha (TNF-α), the IκB kinase (IKK) complex rapidly phosphorylates NF-κB1 p105 on serine 927 in the PEST region. This phosphorylation is essential for TNF-α to trigger p105 degradation, which releases the associated Rel/NF-κB subunits to translocate into the nucleus and regulate target gene transcription. Serine 927 resides in a conserved motif (Asp-Ser927-Gly-Val-Glu-Thr-Ser932) homologous to the IKK target sequence in IκBα. In this study, TNF-α-induced p105 proteolysis was revealed to additionally require the phosphorylation of serine 932. Experiments with IKK1−/− and IKK2−/− double knockout embryonic fibroblasts demonstrate that the IKK complex is essential for TNF-α to stimulate phosphorylation on p105 serines 927 and 932. Furthermore, purified IKK1 and IKK2 can each phosphorylate a glutathione S-transferase-p105758-967 fusion protein on both regulatory serines in vitro. IKK-mediated p105 phosphorylation generates a binding site for βTrCP, the receptor subunit of an SCF-type ubiquitin E3 ligase, and depletion of βTrCP by RNA interference blocks TNF-α-induced p105 ubiquitination and proteolysis. Phosphopeptide competition experiments indicate that βTrCP binds p105 more effectively when both serines 927 and 932 are phosphorylated. Interestingly, however, βTrCP affinity for the IKK-phosphorylated sequence on p105 is substantially lower than that on IκBα. Thus, it appears that reduced p105 recruitment of βTrCP and subsequent ubiquitination may contribute to delayed p105 proteolysis after TNF-α stimulation relative to that for IκBα.

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