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F Brouillard

Publications and source records attributed to F Brouillard.

10 recordsLinked to original sources
PubMed2002

Tryptophan missense mutation in the ligand-binding domain of the vitamin D receptor causes severe resistance to 1,25-dihydroxyvitamin D.

In this study, two related young children, brother and sister, exhibited severe vitamin D-resistant rickets without alopecia. Sequence analysis of the total vitamin D receptor (VDR) cDNA from skin fibroblasts revealed a substitution of the unique tryptophan of the VDR by arginine at amino acid 286 (W286R). Cultured skin fibroblasts of the two patients expressed normal-size VDR protein (immunocytochemistry and Western blotting) and normal length VDR mRNA (Northern blotting). But, these fibroblasts, as well as COS-7 cells transfected with the W286R mutant, failed to bind 3H 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The tryptophan substitution did not affect VDR trafficking toward the nucleus but abolished the 24-hydroxylase gene response to 1,25(OH)2D3, even at 10(-6) M concentrations. In conclusion, this case report of a new family with hereditary vitamin D-resistant rickets (HVDRR) emphasizes the crucial role of the VDR tryptophan for ligand binding and for transactivation of 1,25(OH)2D3 target genes. It clearly shows the clinical significance of this VDR amino acid for calcium homeostasis and bone mineralization. This observation suggests further that the presence of a stable VDR-bound ligand may not be obligatory for normal hair follicle development.

Amino Acid Sequence↗
PubMed2001

Drug resistance induced by ouabain via the stimulation of MDR1 gene expression in human carcinomatous pulmonary cells.

The inhibition of the Na+/K+-ATPase by cardiotonic drugs like ouabain deeply perturbs both the properties of the cell membrane and the ionic composition of the cytoplasm and hence alters fundamental cell reactions. These three types of reactions may be involved in the stimulation of multidrug resistance 1 (MDR-1) gene expression and the synthesis of permeability glycoprotein [P-glycoprotein (P-gp)]. We have determined whether ouabain, which binds to an extracellular motif of the Na+/K+-ATPase, stimulates MDR-1 gene expression by measuring both mRNA and protein and whether the resulting P-gp extrudes hydrophobic compounds and causes resistance to antimitotic agents. The experiments were performed on Calu-3 cells, a human cell line from a pulmonary carcinoma. Northern blotting showed that treating the cells with submicromolar concentrations of ouabain stimulated MDR-1 gene expression within 24 h. The ouabain-induced stimulation of MDR-1 expression was not restricted to Calu-3 cells but also occurred in human carcinomatous colon (T-84 and HT-29) and hepatic (H7V3) cells. However, it is not ubiquitous because it was not found in HeLa cells. The stimulation was reproduced by other Na+/K+-ATPase inhibitors and occurred via enhanced gene transcription, apparently due to the increased cytosolic calcium concentration. Ouabain also increased the membrane content of P-gp, as detected by immunoblotting and immunohistology. We have developed a microvideo assay based on the properties of acetoxymethyl ester calcein and calcein to show that this P-gp extruded the hydrophobic acetoxymethyl ester calcein. Ouabain also caused the Calu-3 cells to become resistant to doxorubicin and vinblastine. Thus, although ouabain acts extracellularly, it may stimulate MDR-1 gene expression and P-gp synthesis and make cells resistant to hydrophobic cytotoxic compounds.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

NF-kappa B mediates up-regulation of CFTR gene expression in Calu-3 cells by interleukin-1beta.

Inflammation of the airways is a major feature of the inherited disease cystic fibrosis. Previous studies have shown that the pro-inflammatory cytokines tumor necrosis factor alpha and interferon gamma reduce the expression of the cystic fibrosis transmembrane conductance regulator (CFTR) gene (CFTR) in HT-29 and T84 cells by acting post-transcriptionally. We have investigated the effect of the pro-inflammatory peptide interleukin 1beta (IL-1beta) on the expression of the CFTR in Calu-3 cells. IL-1beta increased the production of CFTR mRNA in a dose- and time-dependent manner. Its action was inhibited by inhibitors of the NF-kappaB pathway, including N-acetyl-l-cysteine, pyrrolidine dithiocarbamate, and a synthetic cell-permeable peptide containing the NF-kappaB nuclear localization signal sequence. Gel shift analysis showed that IL-1beta activated NF-kappaB in Calu-3 cells, and transfection experiments using p50 and RelA expressing vectors showed that exogenous transfected NF-kappaB subunits increased the concentration of CFTR mRNA. Gel shift analysis with antibody supershifting also showed that IL-1beta caused the binding of NF-kappaB to a kappaB-like response element at position -1103 to -1093 in the CFTR 5'-flanking region. Transfection experiments using -2150 to +52 CFTR reporter gene constructs showed that the activity of the CFTR promoter is enhanced by exogenous transfected NF-kappaB and IL-1beta and that this enhancement is due, at least in part, to the -1103 to -1093 kappaB site. We conclude that the intracellular signaling that leads to increased CFTR mRNA in response to IL-1beta in Calu-3 cells includes the binding of NF-kappaB to the -1103 kappaB element and a subsequent increase in CFTR promoter activity.

Cell Line↗
PubMed2000

New summation rules for coulomb wave functions

Sums of products of the Coulomb wave functions over degenerate manifolds have been obtained in a closed form. These sums appear in many atomic and molecular problems. The sums have been obtained making use of the properties of the Coulomb Green's function G(r, r('),E), in the limit E-->E(n), where E(n) is the eigenenergy of the hydrogenlike atomic ion. The closed Hostler-Pratt form of G in the coordinate representation has been used. The sums calculated are a consequence of the n degeneracy of the Coulomb atomic energy levels. This itself, as is well known, follows from the four-dimensional symmetry of the Coulomb problem for the hydrogen atom.

Journal Article↗
PubMed2000

Modulation of CFTR gene expression in HT-29 cells by extracellular hyperosmolarity.

Hypertonicity has pleiotropic effects on cell function, including activation of transporters and regulation of gene expression. It is important to investigate the action of hypertonicity on cystic fibrosis gene expression because cystic fibrosis transmembrane conductance regulator (CFTR), the cAMP-regulated Cl(-) channel, regulates ion transport across the secretory epithelia, which are often in a hypertonic environment. We found that adding >150 mosmol/l NaCl, urea, or mannitol to the culture medium reduced the amount of CFTR mRNA in colon-derived HT-29 cells in a time-dependent manner. Studies with inhibitors of various kinases [H-89 (protein kinase A inhibitor), bisindolylmaleimide (protein kinase C inhibitor), staurosporine (serine/threonine kinase inhibitor) and herbimycin A (tyrosine kinase inhibitor), SB-203580 and PD-098059 (mitogen-activated protein kinase inhibitors)] showed that CFTR gene expression and its decrease by added NaCl required p38 kinase cascade activity. The CFTR gene activity is regulated at the transcriptional level, since adding NaCl diminished the luciferase activity of HeLa cells transiently transfected with the CFTR promoter. This regulation requires protein synthesis. The complexity of the reactions involved in blocking CFTR gene transcription by NaCl strongly suggests that the decrease in CFTR mRNA is part of a general cell response to hyperosmolar stress.

Blotting, Northern↗
PubMed1999

Aspirin and some other nonsteroidal anti-inflammatory drugs inhibit cystic fibrosis transmembrane conductance regulator protein gene expression in T-84 cells.

Cystic fibrosis (CF) is caused by mutations in the CF gene, which encodes CF transmembrane conductance regulator protein (CFTR), a transmembrane protein that acts as a cAMP-regulated chloride channel The disease is characterized by inflammation but the relationship between inflammation, abnormal transepithelial ion transport, and the clinical manifestations of CF are uncertain. The present study was undertaken to determine whether three nonsteroidal anti-inflammatory drugs (NSAIDs) (aspirin, ibuprofen, and indomethacin) modulate CFTR gene expression in T-84 cells. Treatment with NSAIDs reduced CFTR transcripts, and decreased cAMP-stimulated anion fluxes, an index of CFTR function. However, the two phenomena occurred at different concentrations of both drugs. The results indicate that NSAIDs can regulate both CFTR gene expression and the function of CFTR-related chloride transport, and suggest that NSAIDs act via multiple transduction pathways.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Expression of the surface antigen A2B7 in adult and developing honeybee olfactory pathway.

In order to identify molecules involved in the development of the honeybee olfactory pathway, hybridoma technology has been used. Among different cell lines, A2B7 has been selected. It produces a specific antibody for a surface glycoprotein of 91 kDa. This protein is mainly expressed by both the antennal receptor cells and mushroom body neurons. Based on (i) the spatio-temporal pattern of expression during pupal development; (ii) the cell surface location of the antigen; and (iii) the partial molecular characterization of the antigen, a putative role for this protein in axonal fasciculation and guidance is discussed.

Animals↗