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 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 ARF tumor suppressor targets PPM1G/PP2Cγ to counteract NF-κB transcription tuning cell survival and the inflammatory response

2020 ◽  
Vol 117 (51) ◽  
pp. 32594-32605
Author(s):  
Usman Hyder ◽  
Jennifer L. McCann ◽  
Jinli Wang ◽  
Victor Fung ◽  
Juan Bayo ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Cell Survival ◽  
Cell Fate ◽  
Target Gene ◽  
Environmental Cues ◽  
Dependent Manner ◽  
Gene Promoters ◽  
Induced Apoptosis ◽  
Factor Α ◽  
Necrosis Factor

Inducible transcriptional programs mediate the regulation of key biological processes and organismal functions. Despite their complexity, cells have evolved mechanisms to precisely control gene programs in response to environmental cues to regulate cell fate and maintain normal homeostasis. Upon stimulation with proinflammatory cytokines such as tumor necrosis factor-α (TNF), the master transcriptional regulator nuclear factor (NF)-κB utilizes the PPM1G/PP2Cγ phosphatase as a coactivator to normally induce inflammatory and cell survival programs. However, how PPM1G activity is precisely regulated to control NF-κB transcription magnitude and kinetics remains unknown. Here, we describe a mechanism by which the ARF tumor suppressor binds PPM1G to negatively regulate its coactivator function in the NF-κB circuit thereby promoting insult resolution. ARF becomes stabilized upon binding to PPM1G and forms a ternary protein complex with PPM1G and NF-κB at target gene promoters in a stimuli-dependent manner to provide tunable control of the NF-κB transcriptional program. Consistently, loss of ARF in colon epithelial cells leads to up-regulation of NF-κB antiapoptotic genes upon TNF stimulation and renders cells partially resistant to TNF-induced apoptosis in the presence of agents blocking the antiapoptotic program. Notably, patient tumor data analysis validates these findings by revealing that loss ofARFstrongly correlates with sustained expression of inflammatory and cell survival programs. Collectively, we propose that PPM1G emerges as a therapeutic target in a variety of cancers arising from ARF epigenetic silencing, to loss of ARF function, as well as tumors bearing oncogenic NF-κB activation.

Increased levels of myocardial IκB-α protein promote tolerance to endotoxin

1998 ◽  
Vol 275 (3) ◽  
pp. H1084-H1091 ◽  
Author(s):  
Brian D. Shames ◽  
Daniel R. Meldrum ◽  
Craig H. Selzman ◽  
Edward J. Pulido ◽  
Brian S. Cain ◽  
...  
Keyword(s):  
Cardiac Toxicity ◽  
Cardiac Contractility ◽  
Nuclear Factor Κb ◽  
Protein Levels ◽  
Lps Challenge ◽  
Tnf Α ◽  
Initial Decrease ◽  
Myocardial Contractile ◽  
Factor Α ◽  
Necrosis Factor

Endotoxin [lipopolysaccharide (LPS)] causes tumor necrosis factor-α (TNF-α)-mediated myocardial contractile depression. Tolerance to the cardiac toxicity of LPS can be induced by a prior exposure to LPS or by pretreatment with glucocorticoids. The mechanisms by which the myocardium acquires tolerance to LPS remain unknown. LPS causes phosphorylation and degradation of inhibitory κB-α (IκB-α), releasing nuclear factor-κB (NF-κB) to activate TNF-α gene transcription. We hypothesized that LPS induces supranormal synthesis of myocardial IκB-α protein and thus renders the myocardium tolerant to subsequent LPS. Rats were challenged with LPS after pretreatment with LPS, dexamethasone, or saline. In saline-pretreated rats, LPS caused a rapid decrease in myocardial IκB-α protein levels, activation of NF-κB, and increased TNF-α production. These events were followed by myocardial contractile depression. After the initial decrease in myocardial IκB-α, IκB-α protein levels rebounded to a level greater than control levels by 24 h. Dexamethasone pretreatment similarly increased myocardial IκB-α protein levels. In rats pretreated with either LPS or dexamethasone, myocardial IκB-α protein levels remained similar to control levels after LPS challenge. The preserved level of myocardial IκB-α protein was associated with diminished NF-κB activation, attenuated myocardial TNF-α production, and improved cardiac contractility. We conclude that LPS and dexamethasone upregulate myocardial IκB-α protein expression and that an increased level of myocardial IκB-α protein may promote cardiac tolerance to LPS by inhibition of NF-κB intranuclear translocation and myocardial TNF-α production.

scholarly journals TNFα- and IKKβ-mediated TANK/I-TRAF phosphorylation: implications for interaction with NEMO/IKKγ and NF-κB activation

2006 ◽  
Vol 394 (3) ◽  
pp. 593-603 ◽  
Author(s):  
Marianne Bonif ◽  
Marie-Alice Meuwis ◽  
Pierre Close ◽  
Valérie Benoit ◽  
Karen Heyninck ◽  
...  
Keyword(s):  
Cellular Response ◽  
Target Genes ◽  
Nuclear Factor Κb ◽  
Signalling Molecules ◽  
Transactivation Potential ◽  
Ikk Complex ◽  
Subsequent Degradation ◽  
Factor Α ◽  
Necrosis Factor ◽  
Pro Inflammatory Cytokines

Pro-inflammatory cytokines trigger signalling cascades leading to NF-κB (nuclear factor-κB)-dependent gene expression through IKK [IκB (inhibitory κB) kinase]-dependent phosphorylation and subsequent degradation of the IκB proteins and via induced phosphorylation of p65. These signalling pathways rely on sequentially activated kinases which are assembled by essential and non-enzymatic scaffold proteins into functional complexes. Here, we show that the pro-inflammatory cytokine TNFα (tumour necrosis factor α) promotes TANK [TRAF (TNF receptor-associated factor) family member associated NF-κB activator] recruitment to the IKK complex via a newly characterized C-terminal zinc finger. Moreover, we show that TANK is phosphorylated by IKKβ upon TNFα stimulation and that this modification negatively regulates TANK binding to NEMO (NF-κB essential modulator). Interestingly, reduced TANK expression by RNA interference attenuates TNFα-mediated induction of a subset of NF-κB target genes through decreased p65 transactivation potential. Therefore the scaffold protein TANK is required for the cellular response to TNFα by connecting upstream signalling molecules to the IKKs and p65, and its subsequent IKKβ-mediated phosphorylation may be a mechanism to terminate the TANK-dependent wave of NF-κB activation.

scholarly journals FBXW7 mutations reduce binding of NOTCH1, leading to cleaved NOTCH1 accumulation and target gene activation in CLL

Blood ◽  
2019 ◽  
Vol 133 (8) ◽  
pp. 830-839 ◽  
Author(s):  
Viola Close ◽  
William Close ◽  
Sabrina Julia Kugler ◽  
Michaela Reichenzeller ◽  
Deyan Yordanov Yosifov ◽  
...  
Keyword(s):  
Target Gene ◽  
Hypoxia Inducible Factor ◽  
Gene Activation ◽  
Lymphocytic Leukemia ◽  
Negative Regulator ◽  
Missense Mutations ◽  
Protein Levels ◽  
In Silico Modeling ◽  
Functional Consequences ◽  
Wd40 Domain

Abstract NOTCH1 is mutated in 10% of chronic lymphocytic leukemia (CLL) patients and is associated with poor outcome. However, NOTCH1 activation is identified in approximately one-half of CLL cases even in the absence of NOTCH1 mutations. Hence, there appear to be additional factors responsible for the impairment of NOTCH1 degradation. E3-ubiquitin ligase F-box and WD40 repeat domain containing-7 (FBXW7), a negative regulator of NOTCH1, is mutated in 2% to 6% of CLL patients. The functional consequences of these mutations in CLL are unknown. We found heterozygous FBXW7 mutations in 36 of 905 (4%) untreated CLL patients. The majority were missense mutations (78%) that mostly affected the WD40 substrate binding domain; 10% of mutations occurred in the first exon of the α-isoform. To identify target proteins of FBXW7 in CLL, we truncated the WD40 domain in CLL cell line HG-3 via clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 (Cas9). Homozygous truncation of FBXW7 resulted in an increase of activated NOTCH1 intracellular domain (NICD) and c-MYC protein levels as well as elevated hypoxia-inducible factor 1-α activity. In silico modeling predicted that novel mutations G423V and W425C in the FBXW7-WD40 domain change the binding of protein substrates. This differential binding was confirmed via coimmunoprecipitation of overexpressed FBXW7 and NOTCH1. In primary CLL cells harboring FBXW7 mutations, activated NICD levels were increased and remained stable upon translation inhibition. FBXW7 mutations coincided with an increase in NOTCH1 target gene expression and explain a proportion of patients characterized by dysregulated NOTCH1 signaling.

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