PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “NF-KappaB Inhibitor alpha”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1995

Activation of transcription factor NF-kappa B is suppressed by curcumin (diferuloylmethane) [corrected].

When activated, NF-kappa B, a ubiquitous transcription factor, binds DNA as a heterodimeric complex composed of members of the Rel/NF-kappa B family of polypeptides. Because of its intimate involvement in host defense against disease, this transcription factor is an important target for therapeutic intervention. In the present report we demonstrate that curcumin (diferuloylmethane), a known anti-inflammatory and anticarcinogenic agent, is a potent inhibitor of NF-kappa B activation. Treatment of human myeloid ML-1a cells with tumor necrosis factor (TNF) rapidly activated NF-kappa B, which consists of p50 and p65 subunits, and this activation was inhibited by curcumin. AP-1 binding factors were also found to be down-modulated by curcumin, whereas the Sp1 binding factor was unaffected. Besides TNF, curcumin also blocked phorbol ester- and hydrogen peroxide-mediated activation of NF-kappa B. The TNF-dependent phosphorylation and degradation of I kappa B alpha was not observed in curcumin-treated cells; the translocation of p65 subunit to the nucleus was inhibited at the same time. The mechanism of action of curcumin was found to be different from that of protein tyrosine phosphatase inhibitors. Our results indicate that curcumin inhibits NF-kappa B activation pathway at a step before I kappa B alpha phosphorylation but after the convergence of various stimuli.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Cupric ion blocks NF kappa B activation through inhibiting the signal-induced phosphorylation of I kappa B alpha.

A transcription factor NF kappa B, which regulates expression of various cellular genes involved in immune responses and viral genes including HIV, is sequestered in the cytoplasm as a complex with an inhibitory protein I kappa B. Various extracellular signals induce phosphorylation and rapid degradation of I kappa B alpha to release NF kappa B. Cu2+ was found to inhibit the activation of NF kappa B induced by TNF-alpha, TPA, or H2O2. Deoxycholate treatment of the cytoplasmic extract prepared from cells stimulated by TNF-alpha in the presence of Cu2+ resulted in the release of NF kappa B from I kappa B alpha, indicating that Cu2+ interferes with the dissociation of the NF kappa B-I kappa B complex. Neither phosphorylation nor degradation of I kappa B alpha was observed upon TNF-alpha stimulation in the presence of Cu2+. These results indicate that Cu2+ inhibits the release of NF kappa B by blockade of a signal leading to the phosphorylation of I kappa B alpha.

Animals↗
PubMed1995

Identification of an I kappa B alpha-associated protein kinase in a human monocytic cell line and determination of its phosphorylation sites on I kappa B alpha.

Nuclear factor kappa B (NF-kappa B) is stored in the cytoplasm as an inactive form through interaction with I kappa B. Stimulation of cells leads to a rapid phosphorylation of I kappa B alpha, which is presumed to be important for the subsequent degradation. We have recently reported the establishment of a lipopolysaccharide (LPS)-dependent cell-free activation system of NF-kappa B in association with the induction of I kappa B alpha phosphorylation. In this study, we have identified a kinase in cell extracts from the LPS-stimulated human monocytic cell line, THP-1, that specifically binds and phosphorylates I kappa B alpha. LPS stimulation transiently enhanced the I kappa B alpha-bound kinase activity in THP-1 cells. Mutational analyses of I kappa B alpha and competition experiments with the synthetic peptides identified major phosphorylation sites by the bound kinase as Ser and Thr residues in the C-terminal acidic domain of I kappa B alpha. Moreover, we show that the peptide, corresponding to the C-terminal acidic domain of I kappa B alpha, blocked the LPS-induced NF-kappa B activation as well as inducible phosphorylation of endogenous I kappa B alpha in a cell-free system using THP-1 cells. These results suggested that the bound kinase is involved in the signaling pathway of LPS by inducing the phosphorylation of the C-terminal region of I kappa B alpha and subsequent dissociation of the NF-kappa B.I kappa B alpha complex.

Amino Acid Sequence↗
PubMed1994

NF-kappa B and I kappa B alpha: an inducible regulatory system in endothelial activation.

Structural analysis of the promoters of several endothelial genes induced at sites of inflammatory or immune responses reveals binding sites for the transcription factor nuclear factor kappa B (NF-kappa B). Endothelial cells express transcripts encoding the p50/p105 and p65 components of NF-kappa B and the rel-related proto-oncogene c-rel; steady state levels of these transcripts are transiently increased by tumor necrosis factor alpha (TNF-alpha). Western blotting revealed that stimulation of endothelial cells with TNF-alpha resulted in nuclear accumulation of the p50 and p65 components of NF-kappa B. Ultraviolet crosslinking and immunoprecipitation demonstrated binding of the p50 and p65 components of NF-kappa B to the E-selectin kappa B site. Endothelial cells express an inhibitor of NF-kappa B activation, I kappa B-alpha (MAD-3). Protein levels of this inhibitor fall rapidly after TNF-alpha stimulation. In parallel, p50 and p65 accumulate in the nucleus and RNA transcript levels for I kappa B-alpha are dramatically upregulated. Recombinant p65 stimulates expression of E-selectin promoter-reporter constructs. I kappa B-alpha inhibits p65 or TNF-alpha-stimulated E-selectin promoter-reporter gene expression in transfected endothelial cells. The NF-kappa B and I kappa B-alpha system may be an inducible regulatory mechanism in endothelial activation.

Animals↗
PubMed1995

Selective inhibition of E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 expression by inhibitors of I kappa B-alpha phosphorylation.

The promoters of the E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) genes contain recognition sequences for the inducible nuclear transcription factor kappa B (NF-kappa B). We demonstrate that the appearance of NF-kappa B DNA-binding activity in the nucleus of TNF-alpha-stimulated HUVEC is associated with the rapid phosphorylation and subsequent degradation of I kappa B-alpha, the cytoplasmic inhibitor of NF-kappa B. Serine protease inhibitors prevented the TNF-alpha-induced accumulation of phosphorylated I kappa B-alpha, and prevented I kappa B-alpha degradation and the appearance of NF-kappa B DNA-binding activity. These inhibitors had no direct effect upon the ability of NF-kappa B to bind its cognate recognition sequences, nor upon the DNA-binding activities of other transcription factors. Inhibition of I kappa B-alpha proteolysis resulted in the inhibition of the cytokine- and LPS-induced transcriptional up-regulation and cell-surface expression of E-selectin, VCAM-1, and ICAM-1. In contrast, the TNF-alpha-induced expression of plasminogen activator inhibitor-1 and the constitutive expression of ICAM-2 were unaffected. These inhibitors also had no effect on cellular viability or rates of RNA or protein synthesis. Inhibitors of other proteases and various protein kinases had no effect on the cytokine-induced expression of these endothelial adhesion molecules. These findings indicate that it is possible, using a single pharmacologic agent, to selectively inhibit the expression of the E-selectin, VCAM-1, and ICAM-1 genes without affecting the constitutive or inducible expression of other genes. Pharmacologic inhibition of I kappa B-alpha proteolysis represents a novel approach to the development of anti-inflammatory therapeutics.

Cells, Cultured↗
PubMed1995

Stimulation-dependent I kappa B alpha phosphorylation marks the NF-kappa B inhibitor for degradation via the ubiquitin-proteasome pathway.

The nuclear translocation of NF-kappa B follows the degradation of its inhibitor, I kappa B alpha, an event coupled with stimulation-dependent inhibitor phosphorylation. Prevention of the stimulation-dependent phosphorylation of I kappa B alpha, either by treating cells with various reagents or by mutagenesis of certain putative I kappa B alpha phosphorylation sites, abolishes the inducible degradation of I kappa B alpha. Yet, the mechanism coupling the stimulation-induced phosphorylation with the degradation has not been resolved. Recent reports suggest a role for the proteasome in I kappa B alpha degradation, but the mode of substrate recognition and the involvement of ubiquitin conjugation as a targeting signal have not been addressed. We show that of the two forms of I kappa B alpha recovered from stimulated cells in a complex with RelA and p50, only the newly phosphorylated form, pI kappa B alpha, is a substrate for an in vitro reconstituted ubiquitin-proteasome system. Proteolysis requires ATP, ubiquitin, a specific ubiquitin-conjugating enzyme, and other ubiquitin-proteasome components. In vivo, inducible I kappa B alpha degradation requires a functional ubiquitin-activating enzyme and is associated with the appearance of high molecular weight adducts of I kappa B alpha. Ubiquitin-mediated protein degradation may, therefore, constitute an integral step of a signal transduction process.

Adenosine Triphosphate↗
PubMed1994

Coordinate induction of I kappa B alpha and NF kappa B genes.

The NF kappa B transcription factor exists in an inactive state when complexed with I kappa B alpha in the cytosol. Upon stimulation by a variety of agents, NF kappa B is released from I kappa B alpha and is translocated to the nucleus to induce kappa B motif-containing promoters. Once I kappa B alpha is dissociated from NF kappa B, I kappa B alpha is rapidly degraded. Few studies have been reported concerning the molecular basis for the regulation of I kappa B alpha gene expression. The current studies now show: (1) the expression of I kappa B alpha can be induced by protein synthesis inhibitors including cycloheximide, anisomycin, and puromycin; (2) cycloheximide-dependent induction can be blocked by a transcriptional inhibitor; (3) double-stranded RNA and tumor necrosis factor alpha, which are both known to induce NF kappa B, induce the expression of I kappa B alpha, whereas L-cysteine, which is known to inhibit NF kappa B expression, inhibits I kappa B alpha expression; and (4) the induction of I kappa B alpha gene expression is transient, as is the induction of other NF kappa B-inducible genes. These findings suggest that I kappa B alpha is a NF kappa B-inducible gene. The current results also show a concomitant induction of both subunits of NF kappa B (p50 and p65) after the treatment of cells with double-stranded RNA. Based on these results, a model is proposed suggesting the existence of integrated pathways for the positive and negative autoregulation of I kappa B alpha and NF kappa B.

Amino Acid Sequence↗
PubMed1991

Characterization of an immediate-early gene induced in adherent monocytes that encodes I kappa B-like activity.

We have cloned a group of cDNAs representing mRNAs that are rapidly induced following adherence of human monocytes. One of the induced transcripts (MAD-3) encodes a protein of 317 amino acids with one domain containing five tandem repeats of the cdc10/ankyrin motif, which is 60% similar (46% identical) to the ankyrin repeat region of the precursor of NF-kappa B/KBF1 p50. The C-terminus has a putative protein kinase C phosphorylation site. In vitro translated MAD-3 protein was found to specifically inhibit the DNA-binding activity of the p50/p65 NF-kappa B complex but not that of the p50/p50 KBF1 factor or of other DNA-binding proteins. The MAD-3 cDNA encodes an I kappa B-like protein that is likely to be involved in regulation of transcriptional responses to NF-kappa B, including adhesion-dependent pathways of monocyte activation.

Amino Acid Sequence↗
PubMed1992

Chromosomal localization of the genes encoding the p50/p105 subunits of NF-kappa B (NFKB2) and the I kappa B/MAD-3 (NFKBI) inhibitor of NF-kappa B to 4q24 and 14q13, respectively.

The regulation of expression of a variety of genes involved in immune function, inflammation, and cellular growth control, as well as control of expression of certain viruses such as the human immunodeficiency virus (HIV), is dependent on the transcription factor NF-kappa B. In many cells, NF-kappa B is found in the cytoplasm where it is associated with an inhibitor protein known as I kappa B. Recently the genes encoding the p50 and p65 subunits of NF-kappa B, as well as one form of I kappa B/MAD-3 (NFKBI), have been cloned. As part of our goal to determine the chromosomal organization of members of the REL/NFKB family, as well as their inhibitors, we localized the NFKBp50/p105 (NFKB2) and I kappa B/MAD-3 (NFKBI) genes to human chromosome bands 4q24 and 14q13, respectively.

Chromosome Mapping↗
PubMed1992

I kappa B/MAD-3 masks the nuclear localization signal of NF-kappa B p65 and requires the transactivation domain to inhibit NF-kappa B p65 DNA binding.

The active nuclear form of the NF-kappa B transcription factor complex is composed of two DNA binding subunits, NF-kappa B p65 and NF-kappa B p50, both of which share extensive N-terminal sequence homology with the v-rel oncogene product. The NF-kappa B p65 subunit provides the transactivation activity in this complex and serves as an intracellular receptor for a cytoplasmic inhibitor of NF-kappa B, termed I kappa B. In contrast, NF-kappa B p50 alone fails to stimulate kappa B-directed transcription, and based on prior in vitro studies, is not directly regulated by I kappa B. To investigate the molecular basis for the critical regulatory interaction between NF-kappa B and I kappa B/MAD-3, a series of human NF-kappa B p65 mutants was identified that functionally segregated DNA binding, I kappa B-mediated inhibition, and I kappa B-induced nuclear exclusion of this transcription factor. Results from in vivo expression studies performed with these NF-kappa B p65 mutants revealed the following: 1) I kappa B/MAD-3 completely inhibits NF-kappa B p65-dependent transcriptional activation mediated through the human immunodeficiency virus type 1 kappa B enhancer in human T lymphocytes, 2) the binding of I kappa B/MAD-3 to NF-kappa B p65 is sufficient to retarget NF-kappa B p65 from the nucleus to the cytoplasm, 3) selective deletion of the functional nuclear localization signal present in the Rel homology domain of NF-kappa B p65 disrupts its ability to engage I kappa B/MAD-3, and 4) the unique C-terminus of NF-kappa B p65 attenuates its own nuclear localization and contains sequences that are required for I kappa B-mediated inhibition of NF-kappa B p65 DNA binding activity. Together, these findings suggest that the nuclear localization signal and transactivation domain of NF-kappa B p65 constitute a bipartite system that is critically involved in the inhibitory function of I kappa B/MAD-3. Unexpectedly, our in vivo studies also demonstrate that I kappa B/MAD-3 binds directly to NF-kappa B p50. This interaction is functional as it leads to retargeting of NF-kappa B p50 from the nucleus to the cytoplasm. However, no loss of DNA binding activity is observed, presumably reflecting the unique C-terminal domain that is distinct from that present in NF-kappa B p65.

Animals↗
PubMed1992

The C terminus of the NF-kappa B p50 precursor and an I kappa B isoform contain transcription activation domains.

The p50 subunit of the NF-kappa B transcription complex is derived from the N-terminal half of a larger precursor protein, p105. Although a fair amount is known about functions located within the p50 sequences, less is known about the C-terminal half of p105. In this report, we have identified a potent transcription activation domain located in the C terminus of mouse p105. In addition, the I kappa B beta proteins chicken p40 and human MAD-3, proteins that are related to the p105 C terminus, strongly activated transcription in chicken cells and yeast when fused to GAL4 DNA-binding sequences. Furthermore, chicken p40 is primarily located in the nucleus of chicken cells when overexpressed from a retroviral vector. Our results suggest novel models for the function and regulation of NF-kappa B transcription complexes.

Amino Acid Sequence↗
PubMed1992

I kappa B interacts with the nuclear localization sequences of the subunits of NF-kappa B: a mechanism for cytoplasmic retention.

NF-kappa B is an inducible transcription factor comprised of a 50-kD (p50) and a 65-kD (p65) subunit. Induction of NF-kappa B activity, which is a critical event in many signal transduction pathways, involves release from a cytoplasmic inhibitory protein, I kappa B, followed by translocation of the active transcription factor complex into the nucleus. Earlier studies suggested that I kappa B targets the p65 subunit of NF-kappa B. However, we demonstrate by in vitro and in vivo methods that the recently cloned I kappa B/MAD-3 interacts with both the p50 and p65 subunits of NF-kappa B, as well as c-Rel. Furthermore, an alternatively spliced, dimerization-deficient transforming variant of p65 (p65 delta) interacts extremely weakly with I kappa B/MAD-3, suggesting that dimerization is important for interaction. We demonstrate that the conserved nuclear localization sequences (NLSs) of NF-kappa B and c-Rel are the targets for I kappa B/MAD-3 interaction. Indirect immunofluorescence experiments demonstrate that I kappa B/MAD-3 expression retains both p65 and p50 in the cytoplasm. Furthermore, and most important, a p65 that contains an SV40 large T antigen NLS in addition to its own NLS is no longer retained in the cytoplasm in the presence of I kappa B/MAD-3. We propose that I kappa B/MAD-3 masks the NLSs of NF-kappa B and c-Rel and that this constitutes the mechanism for cytoplasmic retention of these proteins.

Alternative Splicing↗
PubMed1995

Role of transcriptional activation of I kappa B alpha in mediation of immunosuppression by glucocorticoids.

Glucocorticoids are potent immunosuppressive drugs, but their mechanism is poorly understood. Nuclear factor kappa B (NF-kappa B), a regulator of immune system and inflammation genes, may be a target for glucocorticoid-mediated immunosuppression. The activation of NF-kappa B involves the targeted degradation of its cytoplasmic inhibitor, I kappa B alpha, and the translocation of NF-kappa B to the nucleus. Here it is shown that the synthetic glucocorticoid dexamethasone induces the transcription of the I kappa B alpha gene, which results in an increased rate of I kappa B alpha protein synthesis. Stimulation by tumor necrosis factor causes the release of NF-kappa B from I kappa B alpha. However, in the presence of dexamethasone this newly released NF-kappa B quickly reassociates with newly synthesized I kappa B alpha, thus markedly reducing the amount of NF-kappa B that translocates to the nucleus. This decrease in nuclear NF-kappa B is predicted to markedly decrease cytokine secretion and thus effectively block the activation of the immune system.

Cell Line↗
PubMed1995

Immunosuppression by glucocorticoids: inhibition of NF-kappa B activity through induction of I kappa B synthesis.

Glucocorticoids are among the most potent anti-inflammatory and immunosuppressive agents. They inhibit synthesis of almost all known cytokines and of several cell surface molecules required for immune function, but the mechanism underlying this activity has been unclear. Here it is shown that glucocorticoids are potent inhibitors of nuclear factor kappa B (NF-kappa B) activation in mice and cultured cells. This inhibition is mediated by induction of the I kappa B alpha inhibitory protein, which traps activated NF-kappa B in inactive cytoplasmic complexes. Because NF-kappa B activates many immunoregulatory genes in response to pro-inflammatory stimuli, the inhibition of its activity can be a major component of the anti-inflammatory activity of glucocorticoids.

Animals↗
PubMed1992

Rapid induction in regenerating liver of RL/IF-1 (an I kappa B that inhibits NF-kappa B, RelB-p50, and c-Rel-p50) and PHF, a novel kappa B site-binding complex.

The liver is one of the few adult tissues that has the capacity to regenerate following hepatectomy or toxic damage. In examining the early growth response during hepatic regeneration, we found that a highly induced immediate-early gene in regenerating liver encodes RL/IF-1 (regenerating liver inhibitory factor) and is the rat homolog of human MAD-3 and probably of chicken pp40. RL/IF-1 has I kappa B activity of broad specificity in that it inhibits the binding of p50-p65 NF-kappa B, c-Rel-p50, and RelB-p50, but not p50 homodimeric NF-kappa B, to kappa B sites. Like RL/IF-1, several members of the NF-kappa B and rel family of transcription factors are immediate-early genes in regenerating liver and mitogen-treated cells. We examined changes in kappa B site binding activity during liver regeneration and discovered a rapidly induced novel kappa B site-binding complex designated PHF [posthepatectomy factor(s)]. PHF is induced over 1,000-fold within minutes posthepatectomy in a protein synthesis-independent manner, with peak activity at 30 min, and is not induced by sham operation. PHF is distinct from p50-p65 NF-kappa B, which is present only in the inactive form in liver posthepatectomy. Although early PHF complexes do not interact strongly with anti-p50 antibodies, PHF complexes present later (3 to 5 h) posthepatectomy react strongly, suggesting that they contain a p50 NF-kappa B subunit. Unlike p50-p65 NF-kappa B, c-Rel-p50, and RelB-p50 complexes, PHF binding to kappa B sites is not inhibited by RL/IF-1. One role of RL/IF-1 in liver regeneration may be to inhibit p50-p65 NF-kappa B activity present in hepatic cells, allowing for the preferential binding of PHF to kappa B sites. Because PHF is induced immediately posthepatectomy in the absence of de novo protein synthesis, PHF could have a role in the regulation of liver-specific immediate-early genes in regenerating liver.

Animals↗
PubMed1995

N- and C-terminal sequences control degradation of MAD3/I kappa B alpha in response to inducers of NF-kappa B activity.

The proteolytic degradation of the inhibitory protein MAD3/I kappa B alpha in response to extracellular stimulation is a prerequisite step in the activation of the transcription factor NF-kappa B. Analysis of the expression of human I kappa B alpha protein in stable transfectants of mouse 70Z/3 cells shows that, as for the endogenous murine protein, exogenous I kappa B alpha is degraded in response to inducers of NF-kappa B activity, such as phorbol myristate acetate or lipopolysaccharide. In addition, pretreatment of the cells with the proteasome inhibitor N-Ac-Leu-Leu-norleucinal inhibits this ligand-induced degradation and, in agreement with previous studies, stabilizes a hyperphosphorylated form of the human I kappa B alpha protein. By expressing mutant forms of the human protein in this cell line, we have been able to delineate the sequences responsible for both the ligand-induced phosphorylation and the degradation of I kappa B alpha. Our results show that deletion of the C terminus of the I kappa B alpha molecule up to amino acid 279 abolishes constitutive but not ligand-inducible phosphorylation and inhibits ligand-inducible degradation. Further analysis reveals that the inducible phosphorylation of I kappa B alpha maps to two serines in the N terminus of the protein (residues 32 and 36) and that the mutation of either residue is sufficient to abolish ligand-induced degradation, whereas both residues must be mutated to abolish inducible phosphorylation of the protein. We propose that treatment of 70Z/3 cells with either phorbol myristate acetate or lipopolysaccharide induces a kinase activity which phosphorylates serines 32 and that these phosphorylations target the protein for rapid proteolytic degradation, possibly by the ubiquitin-26S proteasome pathway, thus allowing NF-kappa B to translocate to the nucleus and to activate gene expression.

Amino Acid Sequence↗