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B Favre

Publications and source records attributed to B Favre.

At least 19 recordsLinked to original sources
PubMed2001

The hemidesmosomal protein bullous pemphigoid antigen 1 and the integrin beta 4 subunit bind to ERBIN. Molecular cloning of multiple alternative splice variants of ERBIN and analysis of their tissue expression.

The bullous pemphigoid antigen 1 (eBPAG1) is a constituent of hemidesmosomes (HDs), cell-substrate adhesion complexes in stratified epithelia. Although its COOH terminus interacts with intermediate filaments, its NH(2) terminus is important for its recruitment into HDs. To identify proteins that interact with the NH(2) terminus of human eBPAG1, we performed a yeast two-hybrid screen, which uncovered a protein belonging to the LAP/LERP (for LRR and PDZ domain) protein family with 16 NH(2)-terminal leucine-rich repeats and a COOH-terminal PDZ domain. The gene for this LAP/LERP protein comprises at least 26 exons located on the long arm of chromosome 5. In most human tissues, several transcripts were detected differing in the coding region situated upstream of or within the PDZ domain. One of the encoded variants was found to correspond to the recently described protein ERBIN. In yeast and in vitro binding experiments, ERBIN was shown to interact not only with eBPAG1 but also with the COOH-terminal region of the cytoplasmic domain of the integrin beta4 subunit, another component of HDs. Antibodies raised against the COOH terminus showed that ERBIN is expressed in keratinocytes. In transfected epithelial cells the protein, however, was not localized in HDs but was either diffusely distributed over the cytoplasm or concentrated at the basolateral plasma membrane. Because ERBIN had been shown previously to interact with the transmembrane tyrosine kinase receptor Erb-B2, which in turn associates with the integrin beta4 subunit, we suggest that ERBIN provides a link between HD assembly and Erb-B2 receptor signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Plectin, an unusual target antigen in bullous pemphigoid.

BACKGROUND: Bullous pemphigoid (BP) is a blistering disease associated with autoantibodies directed against two components of hemidesmosomes, BP180 and BP230. OBJECTIVES: To assess whether BP patients have autoantibodies targeting plectin, another hemidesmosomal component showing extensive homology to BP230. METHODS: Examination of sera from 16 patients with BP, using immunoprecipitation studies followed by immunoblotting. RESULTS: Serum of one of the 16 (6%) patients with BP contain autoantibodies binding to plectin, while no reactivity was found with sera from three control subjects. Sera from all 16 BP patients immunoprecipitated BP230 from extracts of biosynthetically radiolabelled human keratinocytes. CONCLUSIONS: Our results indicate that sera from BP patients might contain autoantibodies binding to plectin. Although this protein and BP230 are closely sequence-related, the occurrence of autoantibodies binding to plectin is a rare phenomenon in BP.

Autoantibodies↗
PubMed2001

Autoantibodies to the extracellular and intracellular domain of bullous pemphigoid 180, the putative key autoantigen in bullous pemphigoid, belong predominantly to the IgG1 and IgG4 subclasses.

BACKGROUND: Autoantibodies to the extracellular domain (ECD) of bullous pemphigoid (BP) antigen 180 (BP180) are thought to play a crucial part in the pathophysiology of BP. OBJECTIVES: As the various IgG subclasses have different biological properties, we have sought to assess the relative isotype distribution of IgG to BP180 and their reactivity against the ECD and intracellular domain (ICD) of BP180. METHODS: The reactivity of 27 sera from patients with BP was assayed by immunoblotting against recombinant proteins covering the ECD and ICD of BP180. RESULTS: Twenty-seven (100%) and 21 (77%) of 27 BP sera, respectively, contained IgG1 and IgG4 autoantibodies binding to the ECD of BP180. Fourteen (82%) and six (35%) of the 17 BP sera that were reactive with the ICD of BP180 had autoantibodies of the IgG1 and IgG4 subclass, respectively. The profile of the isotype restriction appeared to be similar when the response to the ECD vs. that to the ICD was compared. IgG2 and IgG3 reactivity with BP180 was found less frequently. Patients with BP of longer duration showed a tendency to have, in addition to IgG1, an IgG4 response. CONCLUSIONS: Consistent with prior evidence indicating that subepidermal blister formation in BP is dependent upon complement activation, the frequent finding of complement-fixing IgG1 autoantibodies to both the ECD and ICD of BP180 might have pathogenic relevance in BP. These findings provide new insights relevant for our understanding of the immune response to BP180, the putative key autoantigen in BP.

Aged↗
PubMed2000

Immunophenotype of a transient myeloproliferative disorder in a newborn with trisomy 21.

Cytologic, immunologic, and cytogenetic studies were performed on the blast cells of a newborn with Down syndrome and transient myeloproliferative disease. This hematologic disorder is uncommon, and occurs primarily in infants with Down syndrome. This boy presented with a high white blood cell count and a high percentage of blast cells, without anemia or thrombocytopenia. Chromosome analysis showed a constitutional trisomy 21 without any other clonal abnormality. A three-color flow cytometric analysis was performed and revealed two different CD45 dim, CD34(+), CD117(+), CD56(+) immature subpopulations: the normal immature myeloid precursor and an immature blast cell population that expressed CD41, CD42, CD61, CD36, CD13, CD1a, and CD2. We postulate that this population could be the leukemic precursor involved in the acute megakaryoblastic leukemia frequently observed in children with Down syndrome.

Down Syndrome↗
PubMed2000

Acute myeloid leukemia with hypergranular cytoplasm: a differential diagnosis of acute promyelocytic leukemia.

We report here the case of a woman with acute myeloid leukemia with some blast cells exhibiting acute promyelocytic leukemia (APL)-like hypergranular cytoplasm. The cytologic and cytochemical aspects as well as the mature myeloid phenotype and hemostasis disorders were consistent with the diagnosis of APL. However, no t(15;17), or RARalpha gene, MLL gene or PML gene rearrangement was observed, or any other cytogenetic clonal abnormality. Coexpression on blast cells of CD33 and CD56 without CD34, CD16 or HLA-DR, suggested a myeloid/natural killer cell acute leukemia.

Blast Crisis↗
PubMed2000

IgG autoantibodies from bullous pemphigoid patients recognize multiple antigenic reactive sites located predominantly within the B and C subdomains of the COOH-terminus of BP230.

Bullous pemphigoid is a subepidermal bullous disorder characterized by an autoantibody response against the bullous pemphigoid antigen 230 (BP230) and the bullous pemphigoid antigen 180 (BP180), a cytoplasmic component and a transmembrane component, respectively, of hemidesmosomes. Although immunodominant sequences within the extracellular domain of BP180 have been identified, characterization of the antigenic sites on BP230 is still incomplete. To identify autoantibody-reactive sites on BP230 and to examine whether the targeted regions are contained within functionally important domains, recombinant fragments encompassing almost the entire BP230 were used to assess the reactivity of 25 bullous pemphigoid sera by immunoblotting. Our results demonstrate that (i) the region bearing the B and C subdomains of the COOH-terminus of BP230 contains immunodominant sequences recognized by the majority of bullous pemphigoid sera; (ii) additional autoantibody- reactive sites are present over extended regions of the NH2-terminal half of BP230 without evidence for antigenic cross-reactivity between the NH2- and COOH-termini of BP230; and, finally, (iii) autoantibodies reacting with the BP230 tail predominantly belong to the IgG4 and IgG1 subclasses, suggesting that both autoreactive TH2 and autoreactive TH1 cells regulate the autoantibody response to immunodominant sequences of BP230. As the COOH- terminus of BP230 mediates the attachment of keratin intermediate filaments to the hemidesmosomal plaque, whereas its NH2-terminus contains sequences important for its interaction with other constituents of hemidesmosomes, autoantibodies to BP230 might precipitate subepidermal blister formation and perpetuate the disease not only by eliciting an inflammatory reaction but also by interfering with the function of BP230 and thus the stability of hemidesmosomes.

Aged↗
PubMed1999

IgG autoantibodies from bullous pemphigoid (BP) patients bind antigenic sites on both the extracellular and the intracellular domains of the BP antigen 180.

Bullous pemphigoid (BP) and gestational pemphigoid (PG) are subepidermal blistering disorders associated with autoantibodies directed against two components of hemidesmosomes: the BP antigen 180 (BP180) and the BP antigen 230 (BP230). Autoantibodies against the extracellular domain (ECD) of BP180 are thought to play an initiatory role in subepidermal blister formation. To characterize the targeted antigenic sites on BP180, we have assessed the reactivity of sera from BP and PG patients against eukaryotic recombinant proteins encompassing various portions of the ECD and the intracellular domain (ICD) of BP180. Twenty-two of 22 (100%) BP sera that immunoblotted BP180 in keratinocyte extracts, bound a mutant form consisting of the entire ECD of BP180, whereas only three of these 22 sera (14%) reacted against the ECD of BP180 lacking the NC16A membrane proximal region. Thirteen out of the 22 (59%) BP sera recognized the ICD of BP180. Circulating IgG from a representative BP patient that was affinity purified against the ECD of BP180 did not bind the ICD when reblotted, indicating that there was no antigenic cross-reactivity between the ECD and the ICD of BP180. Reactivity against the ICD of BP180 was further ascertained by immunofluorescence microscopy studies showing that nine of the 22 (41%) BP sera stained COS-7 cells expressing the ICD of BP180. Using deletion mutants of the ICD of BP180, the majority of the sera was found to recognize the central region of the ICD of BP180. Specifically, an immunodominant region was localized to an 87-amino acid segment located towards the NH2-terminus of BP180. In contrast to BP sera, five of six (83%) PG sera contained IgG that recognized exclusively the NC16A region, whereas none bound to the ICD of BP180. Together, the results indicate that in BP, autoantibody reactivity to BP180 is not exclusively restricted to the NC16A region, but that additional antigenic determinants exist on the ICD of BP180. The observed heterogeneous immune response against BP180 might reflect intramolecular epitope spreading. Because the ICD ofBP180 harbors functionally important regions, it is possible that autoantibodies against the ICD of BP180 have pathogenic significance for the progression of the disease.

Adult↗
PubMed1999

Multiple amino acid substitutions in lanosterol 14alpha-demethylase contribute to azole resistance in Candida albicans.

Lanosterol 14alpha-demethylase (14DM) is the target of the azole antifungals, and alteration of the 14DM sequence leading to a decreased affinity of the enzyme for azoles is one of several potential mechanisms for resistance to these drugs in Candida albicans. In order to identify such alterations the authors investigated a collection of 19 C. albicans clinical isolates demonstrating either frank resistance (MICs > or = 32 microg ml(-1)) or dose-dependent resistance (MICs 8-16 microg ml(-1)) to fluconazole. In cell-free extracts from four isolates, including the Darlington strain ATCC 64124, sensitivity of sterol biosynthesis to inhibition by fluconazole was greatly reduced, suggesting that alterations in the activity or affinity of the 14DM could contribute to resistance. Cloning and sequencing of the 14DM gene from these isolates revealed 12 different alterations (two to four per isolate) leading to changes in the deduced amino acid sequence. Five of these mutations have not previously been reported. To demonstrate that these alterations could affect fungal susceptibility to azoles, the 14DM genes from one sensitive and three resistant C. albicans strains were tagged at the carboxyl terminus with a c-myc epitope and expressed in Saccharomyces cerevisiae under control of the endogenous promoter. Transformants receiving 14DM genes from resistant strains had fluconazole MICs up to 32-fold higher than those of transformants receiving 14DM from a sensitive strain, although Western blot analysis indicated that the level of expressed 14DM was similar in all transformants. Amino acid substitutions in the 14DM gene from the Darlington strain also conferred a strong cross-resistance to ketoconazole. In conclusion, multiple genetic alterations in C. albicans 14DM, including several not previously reported, can affect the affinity of the enzyme for azoles and contribute to resistance of clinical isolates.

Amino Acid Sequence↗
PubMed1999

Two cases of terminal deletion of chromosome 13: clinical features, conventional and molecular cytogenetic analysis.

We report the cases of two unrelated patients with psychomotor retardation and craniofacial abnormalities, in whom cytogenetic studies have revealed a terminal deletion of chromosome 13 confirmed by fluorescence in situ hybridization (FISH). This del(13)(q33.2) is the smallest terminal deletion of the 13q reported so far. Interestingly enough, the serum level of coagulation factors VII and X, whose genes are located in 13q34, were reduced in both patients. These cases illustrate the difficulties in identifying precisely chromosome deletions and demonstrate that FISH techniques allow to obtain a more precise correlation between clinical phenotype and cytogenetic abnormalities.

Child, Preschool↗
PubMed1997

Modulation of the enzymatic properties of protein phosphatase 2A catalytic subunit by the recombinant 65-kDa regulatory subunit PR65alpha.

All protein phosphatase 2A (PP2A) holoenzymes contain a 36-kDa catalytic subunit (PP2Ac) and a regulatory subunit of 65 kDa (PR65). We have studied the interaction between PP2Ac and PR65 in an in vitro system, using PP2Ac isolated from rabbit skeletal muscle and recombinant PR65alpha expressed in bacteria or insect cells. Bacterially expressed PR65alpha exhibited identical biochemical properties to the protein expressed and isolated from the baculoviral expression system. The association of recombinant PR65 with PP2Ac was very tight (K(D)app = 85 pM) and led to a suppression of PP2A activity, which was maximal (70-80%) when phosphoproteins were used as substrates. When less-structured or smaller substrates (such as phosphopeptides) were used, this inhibition was only 30%. PR65 stimulated PP2Ac activity when the assays were performed in the presence of polycations. This indicates that the PR65 not only serves the previously predicted structural role as a molecular scaffold, but also allosterically modulates the enzymatic properties of PP2Ac. Furthermore, we identified a site of interaction between PP2Ac and PR65alpha by disruption of a stretch of basic amino acids by introduction of a glutamate at position 416. This produced an almost 100-fold reduced affinity for PP2Ac and indicated that this basic motif is an important determinant for the interaction of PR65 and PP2Ac.

Amino Acid Sequence↗
PubMed1997

Differential inhibition and posttranslational modification of protein phosphatase 1 and 2A in MCF7 cells treated with calyculin-A, okadaic acid, and tautomycin.

Calyculin-A (CA), okadaic acid (OA), and tautomycin (TAU) are potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A) and are widely used on cells in culture. Despite their well characterized selectivity in vitro, their exact intracellular effects on PP1 and PP2A cannot be directly deduced from their extracellular concentration because their cell permeation properties are not known. Here we demonstrate that, due to the tight binding of the inhibitors to PP1 and/or PP2A, their cell penetration could be monitored by measuring PP1 and PP2A activities in cell-free extracts. Treatment of MCF7 cells with 10 nM CA for 2 h simultaneously inhibited PP1 and PP2A activities by more than 50%. A concentration of 1 microM OA was required to obtain a similar time course of PP2A inhibition in MCF7 cells to that observed with 10 nM CA, whereas PP1 activity was unaffected. PP1 was predominantly inhibited in MCF7 cells treated with TAU but even at 10 microM TAU PP1 inhibition was much slower than that observed with 10 nM CA. Furthermore, binding of inhibitors to PP2Ac and/or PP1c in MCF7 cells led to differential posttranslational modifications of the carboxyl termini of the proteins as demonstrated by Western blotting. OA and CA, in contrast to TAU, induced demethylation of the carboxyl-terminal Leu309 residue of PP2Ac. On the other hand, CA and TAU, in contrast to OA, elicited a marked decrease in immunoreactivity of the carboxyl terminus of the alpha-isoform of PP1c, probably reflecting proteolysis of the protein. These results suggest that in MCF7 cells OA selectively inhibits PP2A and TAU predominantly affects PP1, a conclusion supported by their differential effects on cytokeratins in this cell line.

Antifungal Agents↗
PubMed1997

Differential inhibition of fungal amd mammalian squalene epoxidases by the benzylamine SDZ SBA 586 in comparison with the allylamine terbinafine.

The allylamine class of antifungal compounds are specific inhibitors of squalene epoxidase (SE). However, depending on their chemical structure, allylamine derivatives can be highly selective for either fungal or mammalian SEs. All allylamines tested previously, irrespective of their selectivity, inhibit fungal SEs in a noncompetitive manner and mammalian SEs in a competitive manner. Here we have analyzed the inhibitory properties of the benzylamine SDZ SBA 586 toward fungal and mammalian SEs in comparison to the systemic antimycotic terbinafine, SDZ SBA 586 was, like terbinafine a selective inhibitor of fungal SE. Microsomal SE from the pathogenic yeast candida albicans was sixfold more sensitive to SDZ SBA 586 than to terbinafine, C50: 8 nM versus 44 nM, while the enzyme from the dermatophyte fungus Trichophyton rubrum was slightly less sensitive to SDZ SBA 586 than to terbinafine, IC50: 39 and 18 nM, respectively. Similarly to terbinafine, SDZ SBA 586 inhibited the yeast enzyme in non competitive manner, SDZ SBA 586 also inhibited mammalian microsomal SEs, but only at micromolar concentrations. It was more active than terbinafine toward both guinea pig SE, IC50: 2 microM versus 4 microM, and rat SE, IC50: 11 microM versus 87 microM. However, in contrast to terbinafine as well as allylamines selective for mammalian SE, SDZ SBA 586 was a noncompetitive inhibitor of rat microsomal SE. Interestingly, depending on the source of microsomal SE, binding of terbinafine and SDZ SBA 586 exhibited a positive, indifferent, or negative cooperativity, suggesting that SE is an oligomeric enzyme.

Allosteric Regulation↗
PubMed1997

Cloning and expression of squalene epoxidase from the pathogenic yeast Candida albicans.

The allylamine antimycotic terbinafine prevents the formation of sterols by specifically inhibiting squalene epoxidase (SE). The biological and biochemical action of terbinafine on fungal pathogens has been well investigated, but little is known at the molecular level. Here we report the cloning, sequencing and expression of the target of terbinafine from the major pathogen Candida albicans. A C. albicans genomic DNA library was constructed in gamma ZAP Express and screened with a DNA fragment obtained by polymerase chain reaction with two primers designed from sequences common to Saccharomyces cerevisiae and rodent SEs. Two types of clone, approximately 3.9 kbp and 4.1 kbp, were isolated. Both contained an identical open reading frame of 1488 nucleotides, while a few sequence differences were found in the flanking regions, suggesting an allelic heterogeneity. The deduced protein sequence of C. albicans SE, 496 amino acids (55324 Da), is 54% and 41% identical to those of S. cerevisiae and rat, respectively. A 1.8-kb transcript was observed on Northern blots of C. albicans mRNA. Polyclonal antibodies, raised against an internal peptide of C. albicans SE, recognized a protein associated with the particulate fraction of M(r) 55000 on Western blots of C. albicans extracts. C. albicans SE was overexpressed in S. cerevisiae with the expression vector pYES2. In homogenates from S. cerevisiae overexpressing the C. albicans protein SE activity was 10-fold higher than the endogenous activity from controls.

Amino Acid Sequence↗
PubMed1997

Pulsed gradient analysis using a dedicated magnetometer.

In magnetic resonance imaging and spectroscopy, knowledge of the magnetic field gradient behavior is very important. This work describes a simple way to characterize the temporal and spatial dependence of the main magnetic field when a gradient is switched. Records are performed with a home-built magnetometer. This device is controlled by a personal computer for recording and processing the NMR signals from an array of small probes spatially distributed and switched by the magnetometer. We present results of measurements on a 2-T superconducting magnet. These results show the residual defects of an active shielded gradient coils system.

Magnetic Resonance Imaging↗
PubMed1997

Translocation 1;19 in two brain tumors.

We report two-cases of brain tumors, one childhood medulloblastoma and one adult glioblastoma with an unusual chromosomal abnormality: a t(1;19)(q23;q13). We analyzed these karyotypes using fluorescence in situ hybridization (FISH) and wonder if this chromosomal aberration could represent a particular entity in these brain tumors like t(1;19) in ALL.

Brain Neoplasms↗