195 research outputs found
First person – Agathe Chaigne
No full textFirst Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Agathe Chaigne is first author on ‘ Three-dimensional geometry controls division symmetry in stem cell colonies’, published in JCS. Agathe is a postdoc in the lab of Ewa Paluch at the MRC Laboratory for Molecular Cell Biology (LMCB), University College London, London, UK, investigating the crosstalk between cell division and cell fate transitions during development
Manipulation des nucléotides par la bactérie intracellulaire obligatoire Chlamydia trachomatis
No full textChlamydia trachomatis est une bactérie intracellulaire obligatoire qui infecte les cellules épithéliales humaines du tractus uro-génital. Ce pathogène est connu comme étant l'infection sexuellement transmissible la plus courante. Certaines souches peuvent aussi infecter la conjonctive oculaire, qui peut évoluer en trachome, constituant la principale cause de cécité d'origine bactérienne. Le développement intracellulaire de la bactérie dans un compartiment membranaire, appelé inclusion, au sein du cytoplasme de la cellule a rendu C. trachomatis dépendant de l'hôte pour l'acquisition des nucléosides triphosphates (NTP), les éléments constitutifs de l'ARN et de l'ADN (sous la forme de désoxynucléotides, dNTP). Les membranes n'étant pas perméables aux nucléotides, ces métabolites, ou leurs précurseurs, sont transportés par des transporteurs spécifiques. Seuls les transporteurs de NTP bactériens, Npt1 et Npt2, ont été identifiés pour importer les NTP de l'inclusion vers les bactéries, ce qui soulève la question de savoir comment les nucléotides de l'hôte deviennent accessibles dans l'inclusion. Cette thèse porte sur deux aspects principaux : premièrement, les stratégies mises en œuvre par C. trachomatis pour accéder aux nucléotides de l'hôte, et deuxièmement, la caractérisation de la protéine bactérienne CtMazG, qui présente une fonction hypothétique de nucléotide pyrophosphohydrolase. Dans la cellule hôte, les nucléotides sont synthétisés par deux voies : la voie de sauvetage, qui synthétise des nucléotides (formes phosphorylées de nucléosides) à partir de nucléosides importés, et la voie de novo, où les nucléotides sont synthétisés à partir d'autres métabolites cellulaires. Nos données démontrent que les deux voies de synthèse des nucléotides contribuent à l'approvisionnement de C. trachomatis. De plus, nous montrons que les nucléotides, et non les nucléosides, sont importés dans l'inclusion. Cependant, nos efforts pour identifier les transporteurs responsables de cet import ont été infructueux.En parallèle, nous avons exploré le rôle de la protéine bactérienne CtMazG dans l'infection par C. trachomatis. Nous avons confirmé l'activité pyrophosphohydrolase de nucléotides, en particulier pour les dNTP puriques (dATP et dGTP), ce qui entraîne la génération de formes monophosphate de désoxynucléosides puriques. Nos données montrent que CtMazG est nécessaire au développement optimal de la bactérie et que son absence résulte en l'accumulation de mutations. Dans plusieurs autres organismes, le rôle de MazG dans la préservation du génome est lié à sa spécialisation vis-à-vis de nucléotides oxydés, mais ce n'est pas le cas de CtMazG. Nos données suggèrent plutôt que CtMazG équilibre les niveaux relatifs de dNTP, participant par ce biais à la fidélité de l'étape de réplication du génome. CtMazG a en outre un rôle important pour l'entrée des bactéries dans leur phase proliférative, là encore possiblement en équilibrant les dNTP.En conclusion, ce projet a permis de mieux comprendre des stratégies employées par C. trachomatis pour accéder aux nucléotides de l'hôte et d'élucider le rôle d'une enzyme bactérienne modulant les dNTP dans le développement de C. trachomatis.Chlamydia trachomatis is an obligate intracellular bacterium that infects human epithelial cells of the urogenital tract. This pathogen is known as the most common sexually transmitted infection. Certain strains can also infect the ocular conjunctiva, which can develop into trachoma, the leading cause of bacterial blindness.The intracellular development of the bacterium in a membrane compartment, called an inclusion, within the cell cytoplasm has made C. trachomatis dependent on the host for the acquisition of nucleoside triphosphates (NTP), the building blocks of RNA and DNA (in the form of deoxynucleotides, dNTP). As membranes are not permeable to nucleotides, these metabolites, or their precursors, are transported by specific transporters. Only bacterial NTP transporters, Npt1 and Npt2, have been identified to import NTP from the inclusion into bacteria, raising the question of how host nucleotides become accessible in the inclusion.This thesis focuses on two main aspects: firstly, the strategies implemented by C. trachomatis to access host nucleotides, and secondly, the characterization of the bacterial protein CtMazG, which exhibits a hypothetical nucleotide pyrophosphohydrolase function. In the host cell, nucleotides are synthesized by two pathways: the salvage pathway, which synthesizes nucleotides (phosphorylated forms of nucleosides) from imported nucleosides, and the de novo pathway, where nucleotides are synthesized from other cellular metabolites. Our data demonstrate that both nucleotide synthesis pathways contribute to the supply of C. trachomatis. In addition, we show that nucleotides, not nucleosides, are imported into the inclusion. However, our efforts to identify the transporters responsible for this import were unsuccessful.In parallel, we explored the role of the bacterial protein CtMazG in C. trachomatis infection. We confirmed the nucleotide pyrophosphohydrolase activity, particularly for purine dNTPs (dATP and dGTP), leading to the generation of monophosphate forms of purine deoxynucleosides. Our data show that CtMazG is necessary for optimal bacterial development, and that its absence results in the accumulation of mutations. In many other organisms, MazG's role in genome preservation is linked to its specialization in oxidized nucleotides, but this is not the case for CtMazG. Instead, our data suggest that CtMazG balances the relative levels of dNTP, thereby contributing to the fidelity of the genome replication step. CtMazG also plays an important role in the entry of bacteria into their proliferative phase, again possibly by balancing dNTP.In conclusion, this project has enabled us to gain a better understanding of the strategies employed by C. trachomatis to access host nucleotides, and to elucidate the role of a bacterial enzyme modulating dNTP in the development of C. trachomatis
Rerouting of host lipids by bacteria: are you CERTain you need a vesicle?
No full textInternational audienceComment on The lipid transfer protein CERT interacts with the Chlamydia inclusion protein IncD and participates to ER-Chlamydia inclusion membrane contact sites. [PLoS Pathog. 2011] Chlamydia trachomatis co-opts GBF1 and CERT to acquire host sphingomyelin for distinct roles during intracellular development. [PLoS Pathog. 2011
Identificaion and characterization of a novel early effector protein of Chlamydia trachomatis
No full textC. trachomatis est une bactérie Gram-négative intracellulaire obligatoire et un pathogène humain. Première cause de maladie sexuellement transmissible d'origine bactérienne, elle est également responsable, dans les pays en développement, d'infections oculaires pouvant conduire à la cécité (trachome). Son cycle de développement bi-phasique a lieu au sein d'un compartiment appelé inclusion. Grâce à un système de sécrétion de type 3 (SST3), Chlamydia sécrète des protéines dans le cytosol de la cellule afin de promouvoir sa survie et sa multiplication. Ces protéines sont désignées sous le terme d'effecteurs.C. trachomatis is an obligate intracellular Gram-negative bacteria and a human pathogen. It is the most prevalent cause of sexually transmitted diseases of bacterial origin and a leading cause of preventable blindness in the developing world. During their biphasic developmental cycle the bacteria remains in a membrane-bounded cellular compartment called an inclusion. Using a type 3 secretion system (T3SS) they translocate effector proteins inside the cytosol of the cell to promote its survival and multiplication.The aim of the PhD was to study the function of CT622, a hypothetic protein from C. trachomatis. We showed that CT622 is an effector protein from the T3SS and that it is secreted early during the infection. We identified a bacterial protein that binds to CT622, and we showed that it acts as a chaperone, stabilizing CT622 and enhancing its secretion. We obtained bacteria lacking CT622 expression, thus demonstrating that CT622 is not essential for bacterial growth in vitro. However, preliminary studies indicate that in the absence of CT622 bacterial development is delayed and T3SS is defective.We identified several molecules interacting with CT622: geranylgeranyl diphosphate, Rab39 and Atg16L1 proteins. Future work will aim at understanding how these identified interactions, or other bacterial or cellular partners still to be discovered, contribute to the establishment of a niche favorable to bacterial development
The chlamydial OTU domain-containing protein ChlaOTU is an early type III secretion effector targeting ubiquitin and NDP52
No full textChlamydia are obligate intracellular pathogens. Upon contact with the host, they use type III secretion to deliver proteins into the cell, thereby triggering actin-dependent entry and establishing the infection. We observed that Chlamydia caviae elicited a local and transient accumulation of ubiquitinated proteins at the entry sites, which disappeared within 20 min. We investigated the mechanism for the rapid clearance of ubiquitin. We showed that the OTU-like domain containing protein CCA00261, predicted to have deubiquitinase activity, was detected in infectious particles and was a type III secretion effector. This protein is present in several Chlamydia strains, including the human pathogen Chlamydia pneumoniae, and we further designate it as ChlaOTU. We demonstrated that ChlaOTU bound ubiquitin and NDP52, and we mapped these interactions to distinct domains. NDP52 was recruited to Chlamydia entry sites and was dispensable for infection and for bacterial growth. ChlaOTU functioned as a deubiquitinase in vitro. Heterologousexpression of ChlaOTU reduced ubiquitin accumulation at the entry sites, while a catalytic mutant of the deubiquitinase activity had the opposite effect. Altogether, we have identified a novel secreted protein of chlamydiae. ChlaOTU targets both ubiquitin and NDP52 and likely participates in the clearance of ubiquitin at the invasion sites.Fil: Furtado, Ana Rita. Institut Pasteur. Unité de Biologie des Interactions Cellulaires; FranciaFil: Essid, Miriam. Institut Pasteur. Unité de Biologie des Interactions Cellulaires; FranciaFil: Perrinet, Stéphenie. Institut Pasteur. Unité de Biologie des Interactions Cellulaires; FranciaFil: Balaña, Maria Eugenia. Institut Pasteur. Unité de Biologie des Interactions Cellulaires; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ciencias y Tecnología "Dr. Cesar Milstein"; ArgentinaFil: Yoder, Nicholas. Nine Cambridge Center. Whitehead Institute for Biomedical Research; Estados UnidosFil: Dehoux, Pierre. Institut Pasteur. Plateforme Intégration et Analyse Génomique; FranciaFil: Subtil, Agathe. Institut Pasteur. Unité de Biologie des Interactions Cellulaires; Franci
Chlamydia Trachomatis détourne l'énergie stockée de l'hôte et accumule le glycogène dans le lumen de l'inclusion par un chemin double
No full textThe human pathogen Chlamydia trachomatis is an obligate intracellular bacterium, which develops in a parasitophorous compartment called inclusion. The inclusion membrane serves as a barrier to host defense mechanisms, but limits access to nutrients. One essential nutrient for C. trachomatis is glucose, and its polymer, glycogen, is highly abundant in the inclusion lumen. This work aimed to reconstitute the glucose flow in C. trachomatis infected cells and to understand the mechanisms for glycogen accumulation. In summary, our work demonstrates that glycogen storage in C. trachomatis inclusions is the result of two different strategies, bulk acquisition of host glycogen through invagination of the inclusion membrane, and de novo synthesis of glycogen within the inclusion lumen. The latter mechanism implicates the import of host UDP-glucose through a host transporter that is recruited to the inclusion membrane, and the secretion of bacterial glycogen enzymes into the inclusion lumen. These processes allow the bacteria to build an energy store within the inclusion lumen, out of reach for the host.Chlamydia trachomatis est une bactérie intracellulaire obligatoire pathogène pour l'homme, qui se développe dans un compartiment appelé inclusion. La membrane de l'inclusion constitue une protection contre les défenses de l'hôte, mais limite l'accès aux nutriments. Un élément essentiel pour C. trachomatis est le glucose. Son polymère, le glycogène, est abondant dans le lumen de l'inclusion. Ce travail a eu pour objectif de reconstituer le flux de glucose dans des cellules infectées et d'expliquer l'accumulation du glycogène. En résumé, notre travail démontre que l'accumulation de glycogène dans la lumière de l'inclusion est le résultat de deux processus, l'import de glycogène " brut " de l'hôte par invagination de la membrane de l'inclusion, et la synthèse de novo de glycogène dans le lumen de l'inclusion. Ce dernier implique l'import d'UDP-glucose par un transporteur de la cellule hôte qui est recruté dans la membrane de l'inclusion, et la sécrétion d'enzymes bactériennes dans le lumen de l'inclusion. Ces mécanismes permettent aux bactéries de stocker des molécules énergétique, inaccessibles à l'hôte
Det ulmer under overflaten. Agathe Backer Grøndahl (1847-1907). Genus, sjanger og norskhet
No full textAbstract Ph.D. dissertation at Göteborg University, Sweden, 2008 Author: Camilla Hambro Title: Det ulmer under overflaten. Agathe Backer Grøndahl (1847–1907), genus, sjanger og norskhet English title: What smoulders beneath the surface. Agathe Backer Grøndahl (1847–1907), gender, genre and Norwegianness Language: Norwegian, with an English summary Department: Department of Culture, Aesthetics and Media Series: Skrifter från musikvetenskap, Göteborgs universitet, nr 91, 2008 ISSN 1654-6261 ISBN 978-91-85974-07-8 My dissertation is a problem oriented one. The composer pianist Agathe Backer Grøndahl (1847–1907) has always been a self-evident figure in chapters of Norwegian music history books that cover music, musicians and composers in "Grieg’s shadow". Extensive historical source materials (reception materials connected to Backer Grøndahl’s concerts and compositions; her letters, notebooks, workbooks and sketches) form the basis of the study. The problems studied are what kind of expectations are connected to three intertwined core concepts connected to Backer Grøndahl, namely: "femininity", "genre", and "Norwegianness" (the folk-influenced Norwegian tradition). Musical and material, as well as institutional, sociological and economical, ”Agathe Backer Grøndahl” discourses are examined. The arenas where the three core concepts and discourses unfold, sound, develop, are moulded and understood, are threefold: •Musical culture with which the pianist composer and her compositions interacted from 1866–1903. •Presentations of her in monographs and music history books. •Various attempts to revise this kind of music historiography. The musical analysis starts out from reception materials connected to her performances of her own works and tries to trace the critics’ descriptions in the scores. The works analyzed are: One of her two orchestral compositions, Andante quasi allegretto for piano and orchestra (1869) in sonata form. (I rediscovered this "lost" work in the National Library in Oslo.) The song "To the queen of my heart" (Op. 1/3, 1870), the descriptively titled lyrical piece Wood Nymph’s Dance (1887), the feminist cantata Nytaarsgry (1901) performed at the Scandinavian Women’s Convention 1902 and the singable and (in)famous song "Eventide" Op. 42/7 1899). Performed compositions become performative via the reception materials, hers, the listeners’ and amateur performers "producerly texts" connected to them
ATG16L1 functions in cell homeostasis beyond autophagy
No full textInternational audienceAtg16-like (ATG16L) proteins were identified in higher eukaryotes for their resemblance to Atg16, a yeast protein previously characterized as a subunit of the Atg12-Atg5/Atg16 complex. In yeast, this complex catalyzes the lipidation of Atg8 on pre-autophagosomal structures and is therefore required for the formation of autophagosomes. In higher eukaryotes, ATG16L1 is also almost exclusively present as part of an ATG12-ATG5/ATG16L1 complex and has the same essential function in autophagy. However, ATG16L1 is three times bigger than Atg16. It displays, in particular, a carboxy-terminal extension, including a WD40 domain, which provides a platform for interaction with a variety of proteins, and allows for the recruitment of the ATG12-ATG5/ATG16L1 complex to membranes under different contexts. Furthermore, detailed analyses at the cellular level have revealed that some of the ATG16L1-driven activities are independent of the lipidation reaction catalyzed by the ATG12-ATG5/ATG16L1 complex. At the organ level, the use of mice that are hypomorphic for Atg16l1, or with cell-specific ablation of its expression, revealed a large panel of consequences of ATG16L1 dysfunctions. In this review, we recapitulate the current knowledge on ATG16L1 expression and functions. We emphasize, in particular, how it broadly acts as a brake on inflammation, thereby contributing to maintaining cell homeostasis. We also report on independent studies that converge to show that ATG16L1 is an important player in the regulation of intracellular traffic. Overall, autophagy-independent functions of ATG16L1 probably account for more of the phenotypes associated with ATG16L1 deficiencies than currently appreciated
Étude du rôle de la transglutaminase tissulaire (TG2) dans l'infection par Chlamydia trachomatis : un effecteur clé dans le détournement du métabolisme de la cellule hôte
No full textChlamydia trachomatis is an obligate intracellular pathogenic bacterium infecting humans, causing sexually transmitted infections or ocular infections. During its biphasic developmental cycle, C. trachomatis remains in a membrane-bound compartment, separated from the cytoplasm. The bacterium has acquired strategies to highjack cellular functions to meet its metabolic needs. Here we focused on the impact of a cellular enzyme called TG2 on C. trachomatis development. The activity of this enzyme is a transamidating activity, i.e. the catalysis of a covalent bound between two proteins or with a small amine present in the cell. We have shown that TG2 expression and transamidating activity increased upon C. trachomatis infection, necessary for optimal bacterial growth. At the cellular level, we focused our work on the impact of TG2 on cellular metabolism modification during infection. We showed that TG2 played a central role in the control of glucose import in infected cells. In addition, we identified GFPT1, as a target of TG2. GFPT1 is the rate-limiting enzyme of the hexosamine biosynthetic pathway, regulating the synthesis of UDP-N-acetylglucosamine. This metabolite is used for post-translational modification of proteins by O-GlcNAcylation. Our work uncovered a link between TG2 transamidating activity and O-GlcNAcylation. This link was disrupted in infected cells likely because UDP-N-acetylglucosamine is consumed by the bacteria to assist division. In conclusion, our work established TG2 as a key player in controlling glucose-derived metabolic pathways in mammalian cells, themselves hijacked by C. trachomatis to sustain its own metabolic needs.Chlamydia trachomatis est une bactérie pathogène intracellulaire obligatoire infectant l'Homme causant des infections sexuellement transmissibles et des infections oculaires. Au cours de son cycle infectieux biphasique, elle réside au sein d'un compartiment séparé du cytoplasme par une membrane. Afin d'assurer ses besoins métaboliques, cette bactérie a développé des stratégies variées lui permettant de détourner des fonctions cellulaires. Nous avons étudié l'impact d'une enzyme cellulaire, TG2, sur le développement de C. trachomatis. Cette enzyme possède une activité transamidase consistant en la catalyse d'un lien covalent entre deux protéines ou entre une protéine et une petite amine. Nous avons montré que l'activité de TG2 ainsi que sa quantité augmentent au cours de l'infection par Chlamydia, favorisant la croissance bactérienne. Au niveau cellulaire, nous avons pu mettre en évidence un rôle clé de TG2 dans le contrôle de l'import de glucose dans les cellules infectées. De plus, nous avons identifié GFPT1 comme cible de TG2. GFPT1 est l'enzyme cinétiquement limitante de la voie de biosynthèse des hexosamines, régulant la synthèse d'UDP-GlcNAc. Ce métabolite est utilisé pour la modification de protéines par O-GlcNAcylation. Notre travail a révélé un lien inattendu entre l'activité de TG2 et l'O-GlcNAcylation, interrompu dans les cellules infectées probablement car l'UDP-GlcNAc est utilisé par la bactérie pour sa division. En conclusion, ce travail présente TG2 comme un effecteur clé dans le contrôle de voies métaboliques dérivées du glucose, rôle détourné par C. trachomatis afin de subvenir à ses propres besoins
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