Author
Francis Biville
Other affiliations: Institut national de la recherche agronomique, California Institute of Technology, École nationale vétérinaire d'Alfort
Bio: Francis Biville is an academic researcher from Pasteur Institute. The author has contributed to research in topics: Riemerella anatipestifer & Pyrroloquinoline quinone. The author has an hindex of 22, co-authored 55 publications receiving 1436 citations. Previous affiliations of Francis Biville include Institut national de la recherche agronomique & California Institute of Technology.
Papers published on a yearly basis
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TL;DR: The has system is the only system thus far characterized in which the anti-sigma factor is submitted to the same signaling cascade as the target operon, and functions by pulses triggered by heme availability.
Abstract: Bacterial hemophores are secreted to the extracellular medium, where they scavenge heme from various hemoproteins due to their higher affinity for this compound, and return it to their specific outer membrane receptor. HasR, the outer membrane receptor of the HasA hemophore, assumes multiple functions which require various energy levels. Binding of heme and, of heme-free or heme-loaded hemophores is energy-independent. Heme transfer from the holo-hemophore to the outer membrane receptor is also energy-independent. In contrast, heme transport and hemophore release require basal or high levels of TonB and proton motive force, respectively. In addition, HasR is a component of a signaling cascade, regulating expression of the has operon via specific sigma and anti-sigma factors encoded by genes clustered at the has operon. The signal is the heme landing on HasR in the presence of the hemophore in its apo form. The has system is the only system thus far characterized in which the anti-sigma factor is submitted to the same signaling cascade as the target operon. Specific autoregulation of the has system, combined with negative regulation by the Fur protein, permits bacterial adaptation to the available iron source. In the presence of a heme-loaded hemophore, inactive anti-sigma factor is accumulated and can be activated as soon as the heme source dries up. Hence, the has system, instead of being submitted to amplification like other systems regulated by sigma anti-sigma factors, functions by pulses triggered by heme availability.
155 citations
TL;DR: It is reported that the protective and inhibitory effects of Hsp 90 depend on the activation state of the proteasome, and alpha-crystallin protects the trypsin-like activity of the MCP.
Abstract: Heat-shock protein 90 (Hsp 90) has been implicated in both protection against oxidative inactivation and inhibition of the multicatalytic proteinase (MCP, also known as 20 S proteasome). We report here that the protective and inhibitory effects of Hsp 90 depend on the activation state of the proteasome. Hsp 90 (and also alpha-crystallin) inhibits the N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activity (Cbz=benzyloxycarbonyl; MCA=7-amido-4-methylcoumarin) when the rat liver MCP is in its latent form, but no inhibitory effects are observed when the MCP is in its active form. Metal-catalysed oxidation of the active MCP inactivates the Ala-Ala-Phe-MCA-hydrolysing (chymotrypsin-like), N-Boc-Leu-Ser-Thr-Arg-MCA-hydrolysing (trypsin-like; Boc=t-butyloxycarbonyl), N-Cbz-Leu-Leu-Glu-beta-naphthylamine-hydrolysing (peptidylglutamyl-peptide hydrolase) and N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activities, whereas these activities are actually increased when the MCP is in its latent form. Hsp 90 protects against oxidative inactivation of the trypsin-like and N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activities of the MCP active form, and alpha-crystallin protects the trypsin-like activity. The specificity of the Hsp 90-mediated protection was assessed by a quantitative analysis of the two-dimensional electrophoretic pattern of MCP subunits before and after oxidation of the MCP, in the presence or absence of Hsp 90. Treatment of the FAO hepatoma cell line with iron and ascorbate was found to inactivate the MCP. Hsp 90 overexpression obtained by challenging the cells with iron was associated with a decreased susceptibility to oxidative inactivation of the MCP trypsin-like activity. Depletion of Hsp 90 by using antisense oligonucleotides resulted in an increased susceptibility to oxidative inactivation of the MCP trypsin-like activity, providing evidence for the physiological relevance of Hsp 90-mediated protection of the MCP.
129 citations
TL;DR: It is shown that the laterally acquired Trw T4SS diversified in the Bartonella lineage to facilitate host-restricted adhesion to erythrocytes in a wide range of mammals.
Abstract: Bacterial pathogens typically infect only a limited range of hosts; however, the genetic mechanisms governing host-specificity are poorly understood. The alpha-proteobacterial genus Bartonella comprises 21 species that cause host-specific intraerythrocytic bacteremia as hallmark of infection in their respective mammalian reservoirs, including the human-specific pathogens Bartonella quintana and Bartonella bacilliformis that cause trench fever and Oroya fever, respectively. Here, we have identified bacterial factors that mediate host-specific erythrocyte colonization in the mammalian reservoirs. Using mouse-specific Bartonella birtlesii, human-specific Bartonella quintana, cat-specific Bartonella henselae and rat-specific Bartonella tribocorum, we established in vitro adhesion and invasion assays with isolated erythrocytes that fully reproduce the host-specificity of erythrocyte infection as observed in vivo. By signature-tagged mutagenesis of B. birtlesii and mutant selection in a mouse infection model we identified mutants impaired in establishing intraerythrocytic bacteremia. Among 45 abacteremic mutants, five failed to adhere to and invade mouse erythrocytes in vitro. The corresponding genes encode components of the type IV secretion system (T4SS) Trw, demonstrating that this virulence factor laterally acquired by the Bartonella lineage is directly involved in adherence to erythrocytes. Strikingly, ectopic expression of Trw of rat-specific B. tribocorum in cat-specific B. henselae or human-specific B. quintana expanded their host range for erythrocyte infection to rat, demonstrating that Trw mediates host-specific erythrocyte infection. A molecular evolutionary analysis of the trw locus further indicated that the variable, surface-located TrwL and TrwJ might represent the T4SS components that determine host-specificity of erythrocyte parasitism. In conclusion, we show that the laterally acquired Trw T4SS diversified in the Bartonella lineage to facilitate host-restricted adhesion to erythrocytes in a wide range of mammals.
107 citations
TL;DR: AC2 is the first member of a new class of previously unrecognized ACs, and to date, no functional counterpart has been demonstrated in other organisms, however, scanning databases revealed a significant similarity between AC2 and the gene product of three hyperthermophilic archaebacteria: Methanobacterium thermoautotrophicum, Archaeglobus fulgidus, and Methanococcus jannaschii.
Abstract: Complementation of an Escherichia coli cya mutant with a genomic library from Aeromonas hydrophila allowed isolation of clones containing two different cya genes. Whereas one of these genes (cyaA) coded for an adenylyl cyclase (AC1) belonging to the previously described class I adenylyl cyclases (ACs), the second one (cyaB) coded for a protein (AC2) that did not match any previously characterized protein when compared to protein sequence databases. In particular, it did not align with any of members of the three known classes of ACs. The purified AC2 enzyme exhibited remarkable biochemical characteristics, namely, an optimum activity at a high temperature (65 degrees C) and at an alkalinic pH (9.5). In order to investigate the functions of both cyclases in A. hydrophila, each gene was inactivated in the chromosome and the resulting mutant strains were examined for physiological alterations. It was shown that, in contrast to cyaA, the cyaB gene was not expressed under usual laboratory growth conditions. However, introduction of a plasmid harboring the cyaB gene in a cyaA mutant, as well as in a cyaA cyaB mutant, allowed cyclic AMP production. AC2 is the first member of a new class of previously unrecognized ACs, and to date, no functional counterpart has been demonstrated in other organisms. However, scanning databases revealed a significant similarity between AC2 and the gene product of three hyperthermophilic archaebacteria: Methanobacterium thermoautotrophicum, Archaeglobus fulgidus, and Methanococcus jannaschii. The possibility of a gene transfer between such phylogenetically divergent bacteria is discussed.
86 citations
TL;DR: Six PQQ biosynthesis complementation groups were present in M. extorquens AM1 and M. organophilum DSM 760, and these have been designated pqqDGCBA and pqqEF, which had predicted gene products with substantial similarity to the gene products of corresponding pqq genes in Acinetobacter calcoaceticus and Klebsiella pneumoniae.
Abstract: Aerobic gram-negative methylotrophs oxidize methanol to formaldehyde by using a methanol dehydrogenase that has pyrroloquinoline quinone (PQQ) as a prosthetic group. Seventy-two mutants which are unable to grow on methanol unless the growth medium is supplemented with PQQ have been isolated in the facultative methanol utilizer Methylobacterium extorquens AM1. In addition, 12 previously isolated methanol oxidation mutants of M. extorquens AM1 were shown to be able to grow on methanol in the presence of PQQ. These putative PQQ biosynthesis mutants have been complemented by using previously isolated clones containing M. extorquens AM1 DNA, which were known to contain genes necessary for oxidation of methanol to formaldehyde (mox genes). Subcloning and transposon mutagenesis experiments have assigned these mutants to five complementation groups in two gene clusters. Representatives of each complementation group were shown to lack detectable PQQ in the growth medium and in cell extracts and to contain methanol dehydrogenase polypeptides that were inactive. Therefore, these mutants all appear to be defective in PQQ biosynthesis. PQQ biosynthesis mutants of Methylobacterium organophilum DSM 760 and M. organophilum XX were complemented by using M. extorquens AM1 subclones, and PQQ biosynthesis mutants of M. extorquens AM1 and M. organophilum XX were complemented by using M. organophilum DSM 760 subclones. This analysis suggested that a total of six PQQ biosynthesis complementation groups were present in M. extorquens AM1 and M. organophilum DSM 760. A 2-kb M. extorquens AM1 DNA fragment that complemented the MoxO class of PQQ biosynthesis mutants was sequenced and found to contain two complete open reading frames and the N-terminal sequence of a third. These genes designated pqqDGC, had predicted gene products with substantial similarity to the gene products of corresponding pqq genes in Acinetobacter calcoaceticus and Klebsiella pneumoniae. pqqD encodes a 29-amino-acid peptide which contains a tyrosine residue and glutamate residue that are conserved in the equivalent peptides of K. pneumoniae, PqqA (23 amino acids), and A. calcoaceticus, PqqIV (24 amino acids), and are thought to be the precursors for PQQ biosynthesis. The organizations of a cluster of five PQQ biosynthetic genes appear to be similiar in four different bacteria (M. extorquens AM1, M. organophilum DSM 760, K. pneumoniae, and A. calcoaceticus). Our results show that a total of seven pqq genes are present in M. extorquens AM1, and these have been designated pqqDGCBA and pqqEF.
69 citations
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations
TL;DR: The various signaling pathways known to be activated in response to oxidative stress in mammalian cells, the mechanisms leading to their activation, and their roles in influencing cell survival are discussed.
Abstract: Reactive oxygen species (ROS), whether produced endogenously as a consequence of normal cell functions or derived from external sources, pose a constant threat to cells living in an aerobic environment as they can result in severe damage to DNA, protein, and lipids. The importance of oxidative damage to the pathogenesis of many diseases as well as to degenerative processes of aging has becoming increasingly apparent over the past few years. Cells contain a number of antioxidant defenses to minimize fluctuations in ROS, but ROS generation often exceeds the cell's antioxidant capacity, resulting in a condition termed oxidative stress. Host survival depends upon the ability of cells and tissues to adapt to or resist the stress, and repair or remove damaged molecules or cells. Numerous stress response mechanisms have evolved for these purposes, and they are rapidly activated in response to oxidative insults. Some of the pathways are preferentially linked to enhanced survival, while others are more frequently associated with cell death. Still others have been implicated in both extremes depending on the particular circumstances. In this review, we discuss the various signaling pathways known to be activated in response to oxidative stress in mammalian cells, the mechanisms leading to their activation, and their roles in influencing cell survival. These pathways constitute important avenues for therapeutic interventions aimed at limiting oxidative damage or attenuating its sequelae.
2,222 citations
Alternatives1, John Innes Centre2, University of Bonn3, University of North Carolina at Chapel Hill4, University of Wisconsin-Madison5, University of Utah6, University of Southern California7, University of Edinburgh8, University of Warwick9, Harvard University10, University College Cork11, University of Queensland12, University of Hertfordshire13, University of Potsdam14, University of California, San Diego15, Goethe University Frankfurt16, University of California, San Francisco17, University of Delaware18, Uppsala University19, Medical University of Vienna20, J. Craig Venter Institute21, University of Hawaii at Manoa22, Leibniz Association23, University of Iowa24, University of Aberdeen25, Georgia Institute of Technology26, University of California, Berkeley27, University of Groningen28, Princeton University29, University of Marburg30, University of Illinois at Urbana–Champaign31, Saarland University32, Norwegian University of Life Sciences33, Massey University34, Toyama Prefectural University35, ETH Zurich36, University of Saskatchewan37, Rutgers University38, Scripps Research Institute39, University of Helsinki40, Texas A&M University41, National Institutes of Health42, Technical University of Berlin43, University of Otago44, University of Cambridge45, University of Alberta46, Michigan State University47, Hofstra University48
TL;DR: This review presents recommended nomenclature for the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs), a rapidly growing class of natural products.
1,560 citations
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TL;DR: In this article, Gray has written a book on diseases of poultry, Diseases of Poultry Their Aetiology, Diagnosis, Treatment and Control; with a Section on the Normal Anatomy and Physiology of the Fowl.
Abstract: VERY few veterinary surgeons have thought fit to write a book on diseases of poultry. Mr. Ernest Gray has done justice to the subject and is to be congratulated on his effort. A book of this size, written by one with specialized knowledge, will add to the value of any library or private bookshelf. Diseases of Poultry Their Aetiology, Diagnosis, Treatment and Control; with a Section on the Normal Anatomy and Physiology of the Fowl. By Ernest Gray. (Lockwood's Agricultural and Horticultural Handbooks.) Pp. x + 198 + 16 plates. (London: Crosby Lockwood and Son, Ltd., 1940.) 9s. 6d. net.
1,282 citations
TL;DR: This Review discusses established and emerging paradigms in nutrient metal homeostasis at the pathogen–host interface and investigates both the essentiality and toxicity of transition metals in biological systems.
Abstract: Transition metals occupy an essential niche in biological systems. Their electrostatic properties stabilize substrates or reaction intermediates in the active sites of enzymes, and their heightened reactivity is harnessed for catalysis. However, this heightened activity also renders transition metals toxic at high concentrations. Bacteria, like all living organisms, must regulate their intracellular levels of these elements to satisfy their physiological needs while avoiding harm. It is therefore not surprising that the host capitalizes on both the essentiality and toxicity of transition metals to defend against bacterial invaders. This Review discusses established and emerging paradigms in nutrient metal homeostasis at the pathogen-host interface.
1,206 citations