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G Courtois

Publications and source records attributed to G Courtois.

At least 19 recordsLinked to original sources
PubMed2006

Mutations in the NF-kappaB signaling pathway: implications for human disease.

The nuclear factor-kappa B (NF-kappaB) signaling pathway is a multi-component pathway that regulates the expression of hundreds of genes that are involved in diverse and key cellular and organismal processes, including cell proliferation, cell survival, the cellular stress response, innate immunity and inflammation. Not surprisingly, mis-regulation of the NF-kappaB pathway, either by mutation or epigenetic mechanisms, is involved in many human and animal diseases, especially ones associated with chronic inflammation, immunodeficiency or cancer. This review describes human diseases in which mutations in the components of the core NF-kappaB signaling pathway have been implicated and discusses the molecular mechanisms by which these alterations in NF-kappaB signaling are likely to contribute to the disease pathology. These mutations can be germline or somatic and include gene amplification (e.g., REL), point mutations and deletions (REL, NFKB2, IKBA, CYLD, NEMO) and chromosomal translocations (BCL-3). In addition, human genetic diseases are briefly described wherein mutations affect protein modifiers or transducers of NF-kappaB signaling or disrupt NF-kappaB-binding sites in promoters/enhancers.

Genetic Diseases, Inborn↗
PubMed2006

NF-kappaB-related genetic diseases.

The recent identification of genetic diseases (incontinentia pigmenti, anhidrotic ectodermal dysplasia with immunodeficiency and cylindromatosis) resulting from mutations affecting components of the nuclear factor-kappaB (NF-kappaB) signaling pathway provides a unique opportunity to understand the function of NF-kappaB in vivo. Besides confirming the importance of NF-kappaB in innate and acquired immunity or bone mass control, analysis of these diseases has uncovered new critical roles played by this transcription factor in the development and homeostasis of the epidermis and the proper function of lymphatic vessels. In addition, the identified mutations will help understanding at the molecular level how NF-kappaB is activated in response to cell stimulation.

Animals↗
PubMed2003

[Molecular basis of the t(1;22)(p13;q13) specific for human acute megakaryoblastic leukemia].

The t(1;22)(p13;q13) translocation is specifically associated with infant acute megakaryoblastic leukemia (M7). We have recently characterized the two genes involved in this translocation: OTT (One Two Two) and MAL (Megakaryoblastic Acute Leukemia) respectively located on chromosome 1 and 22. The t(1;22) translocation results in the fusion of these genes in all the cases studied to date. We summarize here present knowledge regarding this translocation.

Chromosomes, Human, Pair 1↗
PubMed2001

Atypical forms of incontinentia pigmenti in male individuals result from mutations of a cytosine tract in exon 10 of NEMO (IKK-gamma).

Familial incontinentia pigmenti (IP [MIM 308310]), or Bloch-Sulzberger syndrome, is an X-linked dominant and male-lethal disorder. We recently demonstrated that mutations in NEMO (IKK-gamma), which encodes a critical component of the NF-kappaB signaling pathway, were responsible for IP. Virtually all mutations eliminate the production of NEMO, causing the typical skewing of X inactivation in female individuals and lethality in male individuals, possibly through enhanced sensitivity to apoptosis. Most mutations also give rise to classic signs of IP, but, in this report, we describe two mutations in families with atypical phenotypes. Remarkably, each family included a male individual with unusual signs, including postnatal survival and either immune dysfunction or hematopoietic disturbance. We found two duplication mutations in these families, at a cytosine tract in exon 10 of NEMO, both of which remove the zinc (Zn) finger at the C-terminus of the protein. Two deletion mutations were also identified in the same tract in additional families. However, only the duplication mutations allowed male individuals to survive, and affected female individuals with duplication mutations demonstrated random or slight skewing of X inactivation. Similarly, NF-kappaB activation was diminished in the presence of duplication mutations and was completely absent in cells with deletion mutations. These results strongly indicate that male individuals can also suffer from IP caused by NEMO mutations, and we therefore urge a reevaluation of the diagnostic criteria.

Amino Acid Sequence↗
PubMed2001

X-linked anhidrotic ectodermal dysplasia with immunodeficiency is caused by impaired NF-kappaB signaling.

The molecular basis of X-linked recessive anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) has remained elusive. Here we report hypomorphic mutations in the gene IKBKG in 12 males with EDA-ID from 8 kindreds, and 2 patients with a related and hitherto unrecognized syndrome of EDA-ID with osteopetrosis and lymphoedema (OL-EDA-ID). Mutations in the coding region of IKBKG are associated with EDA-ID, and stop codon mutations, with OL-EDA-ID. IKBKG encodes NEMO, the regulatory subunit of the IKK (IkappaB kinase) complex, which is essential for NF-kappaB signaling. Germline loss-of-function mutations in IKBKG are lethal in male fetuses. We show that IKBKG mutations causing OL-EDA-ID and EDA-ID impair but do not abolish NF-kappaB signaling. We also show that the ectodysplasin receptor, DL, triggers NF-kappaB through the NEMO protein, indicating that EDA results from impaired NF-kappaB signaling. Finally, we show that abnormal immunity in OL-EDA-ID patients results from impaired cell responses to lipopolysaccharide, interleukin (IL)-1beta, IL-18, TNFalpha and CD154. We thus report for the first time that impaired but not abolished NF-kappaB signaling in humans results in two related syndromes that associate specific developmental and immunological defects.

Adolescent↗
PubMed2000

ATM is required for IkappaB kinase (IKKk) activation in response to DNA double strand breaks.

Following challenge with proinflammatory stimuli or generation of DNA double strand breaks (DSBs), transcription factor NF-kappaB translocates from the cytoplasm to the nucleus to activate expression of target genes. In addition, NF-kappaB plays a key role in protecting cells from proapoptotic stimuli, including DSBs. Patients suffering from the genetic disorder ataxia-telangiectasia, caused by mutations in the ATM gene, are highly sensitive to inducers of DSBs, such as ionizing radiation. Similar hypersensitivity is displayed by cell lines derived from ataxia-telangiectasia patients or Atm knockout mice. The ATM protein, a member of the phosphatidylinositol 3-kinase (PI3K)-like family, is a multifunctional protein kinase whose activity is stimulated by DSBs. As both ATM and NF-kappaB deficiencies result in increased sensitivity to DSBs, we examined the role of ATM in NF-kappaB activation. We report that ATM is essential for NF-kappaB activation in response to DSBs but not proinflammatory stimuli, and this activity is mediated via the IkappaB kinase complex. DNA-dependent protein kinase, another member of the PI3K-like family, PI3K itself, and c-Abl, a nuclear tyrosine kinase, are not required for this response.

Androstadienes↗
PubMed2000

NF-kappa B defects in humans: the NEMO/incontinentia pigmenti connection.

The components of the nuclear factor-kappaB (NF-kappaB) family of transcription factors are critical for regulating the response to immune challenges. Recently, a role for NF-kappaB in skin biology has been revealed. Within the cascade of proteins whose activities impinge upon the activation of NF-kappaB, the NEMO (NF-kappaB essential modulator)/IKKgamma protein is required for the activation of the IkappaB kinases, which in turn, promote the degradation of IkappaB proteins, leading to the derepression of NF-kappaB activity. Courtois and Israël discuss the role of NEMO/IKKgamma in normal physiological activation of NF-kappaB and the consequences of defective NF-kappaB activation, as an effect of NEMO/IKKgamma mutations, which can lead to incontinentia pigmenti, a disease marked by alopecia, tooth eruption, skin lesions, and changes in skin pigmentation.

Animals↗
PubMed2000

Phorbol esters and cytokines regulate the expression of the NEMO-related protein, a molecule involved in a NF-kappa B-independent pathway.

The NF-kappaB signaling pathway plays a crucial role in the immune, inflammatory, and apoptotic responses. Recently, we identified the NF-kappaB Essential Modulator (NEMO) as an essential component of this pathway. NEMO is a structural and regulatory subunit of the high molecular kinase complex (IKK) responsible for the phosphorylation of NF-kappaB inhibitors. Data base searching led to the isolation of a cDNA encoding a protein we called NRP (NEMO-related protein), which shows a strong homology to NEMO. Here we show that NRP is present in a novel high molecular weight complex, that contains none of the known members of the IKK complex. Consistently, we could not observe any effect of NRP on NF-kappaB signaling. Nonetheless, we could demonstrate that treatment with phorbol esters induces NRP phosphorylation and decreases its half-life. This phosphorylation event could only be inhibited by K-252a and stauroporin. We also show that de novo expression of NRP can be induced by interferon and tumor necrosis factor alpha and that these two stimuli have a synergistic effect on NRP expression. In addition, we observed that endogenous NRP is associated with the Golgi apparatus. Analogous to NEMO, we find that NRP is associated in a complex with two kinases, suggesting that NRP could play a similar role in another signaling pathway.

Amino Acid Sequence↗
PubMed2000

High-performance liquid chromatographic determination of Maillard compounds in store-brand and name-brand ultra-high-temperature-treated cows' milk.

Furosine and furfural products of the Maillard reaction are used as specific indicators of the effect of heating treatments on milk quality. Their contents were measured in representative samples of store- and name-brand ultra-high-temperature-treated milks using RP-HPLC with UV detection. Furosine contents ranged from 40.32 to 50.67 and from 65.48 to 310.58 mg/100 g protein in name- and store-brand milks, respectively. Of the furfurals, only hydroxymethylfurfural was detected. The free hydroxymethylfurfural contents of store-brand milks ranged from 0.22 to 1.70 mg/100 g protein. Total hydroxymethylfurfural contents ranged from 0.29 to 0.41 and from 0.72 to 2.21 mg/100 g protein, for name- and store-brands, respectively.

Animals↗
PubMed2000

Genomic rearrangement in NEMO impairs NF-kappaB activation and is a cause of incontinentia pigmenti. The International Incontinentia Pigmenti (IP) Consortium.

Familial incontinentia pigmenti (IP; MIM 308310) is a genodermatosis that segregates as an X-linked dominant disorder and is usually lethal prenatally in males. In affected females it causes highly variable abnormalities of the skin, hair, nails, teeth, eyes and central nervous system. The prominent skin signs occur in four classic cutaneous stages: perinatal inflammatory vesicles, verrucous patches, a distinctive pattern of hyperpigmentation and dermal scarring. Cells expressing the mutated X chromosome are eliminated selectively around the time of birth, so females with IP exhibit extremely skewed X-inactivation. The reasons for cell death in females and in utero lethality in males are unknown. The locus for IP has been linked genetically to the factor VIII gene in Xq28 (ref. 3). The gene for NEMO (NF-kappaB essential modulator)/IKKgamma (IkappaB kinase-gamma) has been mapped to a position 200 kilobases proximal to the factor VIII locus. NEMO is required for the activation of the transcription factor NF-kappaB and is therefore central to many immune, inflammatory and apoptotic pathways. Here we show that most cases of IP are due to mutations of this locus and that a new genomic rearrangement accounts for 80% of new mutations. As a consequence, NF-kappaB activation is defective in IP cells.

Exons↗
PubMed2000

Protein kinase C-alpha is an upstream activator of the IkappaB kinase complex in the TPA signal transduction pathway to NF-kappaB in U2OS cells.

Inactive nuclear factor kappaB (NF-kappaB) complexes are retained in the cytoplasm by binding to inhibitory proteins, such as IkappaBalpha. Various stimuli lead to phosphorylation and subsequent processing of IkappaBalpha in the 26S proteasome and import of the active NF-kappaB transcription factor into the nucleus. In agreement with our previous finding that p90(rsk1) is essential for TPA-induced activation of NF-kappaB in Adenovirus 5E1-transformed Baby Rat Kidney cells, we now report that the MEK/ERK/p90(rsk1) inhibitor U0126 efficiently blocks TPA-induced IkappaBalpha processing in these cells. However, in U2OS cells, the cytokine-inducible IkappaB kinase complex (IKK) is the essential component of the TPA signal transduction pathway. Activation of the IKK complex in response to TPA is mediated by PKC-alpha, since both the PKC inhibitor GF109203 and a catalytically inactive PKC-alpha mutant inhibit activation of endogenous IKK by TPA, but not by tumor necrosis factor-alpha (TNF-alpha). We conclude that IKK is an integrator of TNF-alpha and TPA signal transduction pathways in U2OS cells.

Butadienes↗
PubMed2000

NEMO/IKK gamma-deficient mice model incontinentia pigmenti.

Disruption of the X-linked gene encoding NF-kappa B essential modulator (NEMO) produces male embryonic lethality, completely blocks NF-kappa B activation by proinflammatory cytokines, and interferes with the generation and/or persistence of lymphocytes. Heterozygous female mice develop patchy skin lesions with massive granulocyte infiltration and hyperproliferation and increased apoptosis of keratinocytes. Diseased animals present severe growth retardation and early mortality. Surviving mice recover almost completely, presumably through clearing the skin of NEMO-deficient keratinocytes. Male lethality and strikingly similar skin lesions in heterozygous females are hallmarks of the human genetic disorder incontinentia pigmenti (IP). Together with the recent discovery that mutations in the human NEMO gene cause IP, our results indicate that we have created a mouse model for that disease.

Animals↗
PubMed1998

Complementation cloning of NEMO, a component of the IkappaB kinase complex essential for NF-kappaB activation.

We have characterized a flat cellular variant of HTLV-1 Tax-transformed rat fibroblasts, 5R, which is unresponsive to all tested NF-kappaB activating stimuli, and we report here its genetic complementation. The recovered full-length cDNA encodes a 48 kDa protein, NEMO (NF-kappaB Essential MOdulator), which contains a putative leucine zipper motif. This protein is absent from 5R cells, is part of the high molecular weight IkappaB kinase complex, and is required for its formation. In vitro, NEMO can homodimerize and directly interacts with IKK-2. The NEMO cDNA was also able to complement another NF-kappaB-unresponsive cell line, 1.3E2, in which the protein is also absent, allowing us to demonstrate that this factor is required not only for Tax but also for LPS, PMA, and IL-1 stimulation of NF-kappaB activity.

Amino Acid Sequence↗
PubMed1997

Down-regulation of NF-kappaB activity and NF-kappaB p65 subunit expression by ras and polyoma middle T oncogenes in human colonic Caco-2 cells.

The products of ras and src proto-oncogenes are frequently activated in a constitutive state in human colorectal cancer. In this study we attempted to establish whether the tumorigenic progression induced by oncogenic activation of p21ras or pp60c-src in human colonic cells is associated with alterations of the activity and expression of nuclear factor kappaB (NF-kappaB), a transcription factor suspected to participate in the development of cancer. To this end, we used Caco-2 cells made highly tumorigenic by transfection with an activated Val-12 human Ha-ras gene or with the polyoma middle T (PyMT) oncogene, a constitutive activator of pp60c-src tyrosine kinase activity. Compared with control vector-transfected Caco-2 cells, both oncogene-transfected cell lines exhibited: (i) decreased constitutive NF-kappaB DNA-binding activity and NF-kappaB-mediated reporter gene expression, without alteration of their response to TNF-alpha for activation of these parameters; (ii) reduced NF-kappaB cytosolic stores along with a decreased p65 expression due, at least in part, to destabilization of p65 mRNA; (iii) a decrease in adhesion to extracellular matrix component-coated substrata which was partially corrected when stimulating NF-kappaB transcriptional activity with TNF-alpha. These results indicate that the tumorigenic progression induced by oncogenic p21ras or PyMT/pp60c-src in human colonic Caco-2 cells is associated with a down-regulation of p65 expression and NF-kappaB activity which could be responsible for the reduced adhesive properties of these cells after oncogene transfection.

Antigens, Polyomavirus Transforming↗
PubMed1997

Characterization of a mutant cell line that does not activate NF-kappaB in response to multiple stimuli.

Numerous genes required during the immune or inflammation response as well as the adhesion process are regulated by nuclear factor kappaB (NF-kappaB). Associated with its inhibitor, I kappaB, NF-kappaB resides as an inactive form in the cytoplasm. Upon stimulation by various agents, I kappaB is proteolyzed and NF-kappaB translocates to the nucleus, where it activates its target genes. The transduction pathways that lead to I kappaB inactivation remain poorly understood. In this study, we have characterized a cellular mutant, the 70/Z3-derived 1.3E2 murine pre-B cell line, that does not activate NF-kappaB in response to several stimuli. We demonstrate that upon stimulation by lipopolysaccharide, Taxol, phorbol myristate acetate, interleukin-1, or double-stranded RNA, I kappaB alpha is not degraded, as a result of an absence of induced phosphorylation on serines 32 and 36. Neither a mutation in I kappaB alpha nor a mutation in p50 or relA, the two major subunits of NF-kappaB in this cell line, accounts for this phosphorylation defect. As well as culminating in the inducible phosphorylation of I kappaB alpha on serines 32 and 36, all the stimuli that are inactive on 1.3E2 cells exhibit a sensitivity to the antioxidant pyrrolidine dithiocarbamate (PDTC). In contrast, stimuli such as hyperosmotic shock or phosphatase inhibitors, which use PDTC-insensitive pathways, induce I kappaB alpha degradation in 1.3E2. Analysis of the redox status of 1.3E2 does not reveal any difference from wild-type 70Z/3. We also report that the human T-cell leukemia virus type 1 (HTLV-1)-derived Tax trans-activator induces NF-kappaB activity in 1.3E2, suggesting that this viral protein does not operate via the defective pathway. Finally, we show that two other I kappaB molecules, I kappaB beta and the recently identified I kappaB epsilon, are not degraded in the 1.3E2 cell line following stimulation. Our results demonstrate that 1.3E2 is a cellular transduction mutant exhibiting a defect in a step that is required by several different stimuli to activate NF-kappaB. In addition, this analysis suggests a common step in the signaling pathways that trigger I kappaB alpha, I kappaB beta, and I kappaB epsilon degradation.

Animals↗
PubMed1995

Tyrosine phosphorylation of the erythropoietin receptor: role for differentiation and mitogenic signal transduction.

The erythropoietin (Epo) receptor belongs to the cytokine receptor superfamily. Although the cytokine receptors do not possess a tyrosine kinase consensus sequence in the intracellular domain, rapid stimulation of a tyrosine kinase activity occurs after activation by the ligand. We and others have shown that Epo induces the tyrosine phosphorylation of its cognate receptor as well as phosphorylation of other proteins. In this report, we examined the role of the receptor tyrosine residues in signal transduction. Eight tyrosine residues are located within the intracellular domain of the murine Epo receptor. A single tyrosine residue is present in the region previously shown to be sufficient for proliferative signal transduction. This tyrosine (Tyr 343) was mutated to phenylalanine. Moreover, mutant receptors were also generated with either a tyrosine residue or a phenylalanine residue at position 343 and with a COOH terminal truncation that removed the 7 other tyrosine residues. Expression vectors carrying these mutated receptors were transfected into the interleukin-3-dependent murine cell line Ba/F3. Epo-induced growth was sustained efficiently by all these receptors, although receptors without any tyrosine residues conferred a significantly reduced mitogenic activity. Moreover, all receptors were able to mediate Epo-dependant accumulation of beta-globin mRNA. The mutated receptors all induced the tyrosine phosphorylation of several cellular proteins after Epo stimulation. However, the truncated receptors induced the phosphorylation of a reduced number of proteins, suggesting that phosphorylated tyrosines of the receptor could have a role in the recruitment either of a tyrosine kinase or of tyrosine kinase substrate proteins. The receptors were all able to mediate Epo-induced activation of phosphatidylinositol 3-kinase, although truncated receptors no longer bound phosphatidylinositol 3-kinase.

Cell Differentiation↗
PubMed1995

Differentiation of murine pre-B cell line by an adjuvant muramyl peptide via NF-kappa B activation.

Muramyl dipeptide (MDP) induces NF-kappa B activation in the murine pre-B cell line 70Z/3, increases the expression of surface immunoglobulins, and potentiates the response to other inducers such as LPS or IL-1. In the present study we investigated whether NF-kappa B activation was related to the MDP-stimulated immunoglobulin expression. In a gel shift assay our results confirmed that MDP but not MDP(D,D), an adjuvant-inactive stereoisomer, could induce a kappa B-binding activity in 70Z/3 cells. The LPS or IL-1 induced NF-kappa B binding activity was increased in the presence of MDP but not of MDP(D,D). A mutant of the cell line called 1.3E2, defective in NF-kappa B activations by LPS, did not respond to MDP. The enhanced surface immunoglobulin expression induced in the wild type 70Z/3 cells by MDP alone or combined to LPS, IL-1 or IFN gamma was not obtained in this variant. The ability of various treatments to activate the kappa gene enhancer was quantitatively evaluated in cells transfected with a kappa-enhancer-luciferase expression plasmid. Treatment of transfected 70Z/3 cells with MDP resulted in a dose-dependent enhancement of luciferase activity, an additive effect to that induced by LPS or IL-1. Treatment of the defective variant transfected with the same construct did not result in luciferase expression after stimulation with the various agents. The transient transfection assays were used to compare the effectiveness of some MDP analogs. Two adjuvant-active compounds unable to enhance kappa light chain expression did not increase the basal response in the transfected 70Z/3 cells, indicating that NF-kappa B activation was not related to the adjuvant potency of MDP but correlated with the kappa induction.

Acetylmuramyl-Alanyl-Isoglutamine↗