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Search Results: 1 - 10 of 307 matches for " Maryse Lebrun "
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ROP18 Is a Rhoptry Kinase Controlling the Intracellular Proliferation of Toxoplasma gondii
Hiba El Hajj,Maryse Lebrun,Stefan T Arold,Henri Vial,Gilles Labesse,Jean Fran?ois Dubremetz
PLOS Pathogens , 2007, DOI: 10.1371/journal.ppat.0030014
Abstract: Toxoplasma gondii is an obligate intracellular parasite for which the discharge of apical organelles named rhoptries is a key event in host cell invasion. Among rhoptry proteins, ROP2, which is the prototype of a large protein family, is translocated in the parasitophorous vacuole membrane during invasion. The ROP2 family members are related to protein-kinases, but only some of them are predicted to be catalytically active, and none of the latter has been characterized so far. We show here that ROP18, a member of the ROP2 family, is located in the rhoptries and re-localises at the parasitophorous vacuole membrane during invasion. We demonstrate that a recombinant ROP18 catalytic domain (amino acids 243–539) possesses a protein-kinase activity and phosphorylate parasitic substrates, especially a 70-kDa protein of tachyzoites. Furthermore, we show that overexpression of ROP18 in transgenic parasites causes a dramatic increase in intra-vacuolar parasite multiplication rate, which is correlated with kinase activity. Therefore, we demonstrate, to our knowledge for the first time, that rhoptries can discharge active protein-kinases upon host cell invasion, which can exert a long-lasting effect on intracellular parasite development and virulence.
Export of a Toxoplasma gondii Rhoptry Neck Protein Complex at the Host Cell Membrane to Form the Moving Junction during Invasion
Sébastien Besteiro equal contributor,Adeline Michelin equal contributor,Jo?l Poncet,Jean-Fran?ois Dubremetz,Maryse Lebrun
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000309
Abstract: One of the most conserved features of the invasion process in Apicomplexa parasites is the formation of a moving junction (MJ) between the apex of the parasite and the host cell membrane that moves along the parasite and serves as support to propel it inside the host cell. The MJ was, up to a recent period, completely unknown at the molecular level. Recently, proteins originated from two distinct post-Golgi specialised secretory organelles, the micronemes (for AMA1) and the neck of the rhoptries (for RON2/RON4/RON5 proteins), have been shown to form a complex. AMA1 and RON4 in particular, have been localised to the MJ during invasion. Using biochemical approaches, we have identified RON8 as an additional member of the complex. We also demonstrated that all RON proteins are present at the MJ during invasion. Using metabolic labelling and immunoprecipitation, we showed that RON2 and AMA1 were able to interact in the absence of the other members. We also discovered that all MJ proteins are subjected to proteolytic maturation during trafficking to their respective organelles and that they could associate as non-mature forms in vitro. Finally, whereas AMA1 has previously been shown to be inserted into the parasite membrane upon secretion, we demonstrated, using differential permeabilization and loading of RON-specific antibodies into the host cell, that the RON complex is targeted to the host cell membrane, where RON4/5/8 remain associated with the cytoplasmic face. Globally, these results point toward a model of MJ organization where the parasite would be secreting and inserting interacting components on either side of the MJ, both at the host and at its own plasma membranes.
Identification of a New Rhoptry Neck Complex RON9/RON10 in the Apicomplexa Parasite Toxoplasma gondii
Mauld H. Lamarque, Julien Papoin, Anne-Laure Finizio, Gaelle Lentini, Alexander W. Pfaff, Ermanno Candolfi, Jean-Fran?ois Dubremetz, Maryse Lebrun
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032457
Abstract: Apicomplexan parasites secrete and inject into the host cell the content of specialized secretory organelles called rhoptries, which take part into critical processes such as host cell invasion and modulation of the host cell immune response. The rhoptries are structurally and functionally divided into two compartments. The apical duct contains rhoptry neck (RON) proteins that are conserved in Apicomplexa and are involved in formation of the moving junction (MJ) driving parasite invasion. The posterior bulb contains rhoptry proteins (ROPs) unique to an individual genus and, once injected in the host cell act as effector proteins to co-opt host processes and modulate parasite growth and virulence. We describe here two new RON proteins of Toxoplasma gondii, RON9 and RON10, which form a high molecular mass complex. In contrast to the other RONs described to date, this complex was not detected at the MJ during invasion and therefore was not associated to the MJ complex RON2/4/5/8. Disruptions of either RON9 or RON10 gene leads to the retention of the partner in the ER followed by subsequent degradation, suggesting that the RON9/RON10 complex formation is required for proper sorting to the rhoptries. Finally, we show that the absence of RON9/RON10 has no significant impact on the morphology of rhoptry, on the invasion and growth in fibroblasts in vitro or on virulence in vivo. The conservation of RON9 and RON10 in Coccidia and Cryptosporidia suggests a specific relation with development in intestinal epithelial cells.
La précarité : une catégorie d’analyse pertinente des enjeux de la norme d’emploi et des situations sociales d’entre-deux
Maryse Bresson
SociologieS , 2011,
Abstract: Le présent article propose de prolonger le débat sur La précarité commencé dans la livraison de SociologieS mise en ligne le 27 septembre 2010. Il met en perspective les analyses d’Henri Eckert et Mircea Vultur, et propose une grille d’analyse de la précarité ou plus exactement, ici, des emplois dits atypiques . L’auteure invite à distinguer d’une part, les représentations sociales et les ressentis subjectifs des individus ; d’autre part, les processus économiques et sociaux associés aux transformations du marché du travail, afin de mieux articuler ensuite ces deux dimensions, en insistant sur l’enjeu de la norme d’emploi, et sur l’idée d’entre-deux proposée comme clé de lecture de la précarité. Precariousness: a pertinent analysis of the standard of employment issues and of "in-between" social situationsThis paper proposes to extend the debate on "Precariousness" started in SociologieS online on September 27, 2010. It puts into perspective analyses of Henry Eckert and Mircea Vultur, and offers an analysis of precariousness, or more precisely, here, jobs as "atypical". The author invites to distinguish, on the one hand, social representations and how individualsfeel subjectively the precariousness; on the other hand, economic and social processes associated to changes in the labour market, in order to better articulate these two dimensions, with particular emphasis on the issue of the standard of employment, and on the idea of "in-between" proposed as a key to reading the precariousness. Es la precariedad un concepto pertinente en lo que concierne la problemática del empleo y des situaciones sociales ambiguas?Este artículo es la continuación del debate sobe la precariedad publicado en la red en Sociologies el 27 septiembre de 2010. Pone en perspectiva los análisis de Henri Eckert y de Mircea Vultur y presenta un panel de análisis de la precariedad en particular de los empleos inhabituales. La autora distingue las representaciones sociales y las impresiones subjetivas de los individuos y por otra parte los procesos económicos y sociales asociados a las transformaciones del contexto laboral con el fin de articular estas dos dimensiones, insistiendo sobre la norma del trabajo y sobre el hecho que los empleos se sitúan frecuentemente en una encrucijada de la que parten direcciones y normas divergentes.
Camargue
Maryse CLARY
Mappemonde , 1989,
Abstract: Comment la représentation de l'espace camarguais dans un guide touristique fait état des représentations sur la Camargue et inverse la notion de centralité en Bas-Languedoc.
El rastro de tu sangre en la nieve : cuento de hadas sombrío o canción kitsch ?
Maryse Renaud
Amerika : Mémoires, Identités, Territoires , 2012, DOI: 10.4000/amerika.2920
Abstract: Este artículo propone una lectura del cuento El rastro de tu sangre en la nieve de Gabriel García Márquez (Doce cuentos peregrinos, 1992), observando las relaciones que el mismo establece con distintas formas de la cultura popular. Considerando el contexto del llamado realismo mágico , donde evoluciona habitualmente la producción de García Márquez, se estudian, en este relato, las múltiples relaciones inter-textuales con distintos tópicos populares, desde el cuento de hadas o de horror tradicional, hasta la cultura kitsch. Se estudia también la relación que García Márquez establece con el relato de aventuras, en modalidades como el road-movie del cine contemporáneo. El viaje que emprenden los personajes de la historia, de Espa a a Francia, que culmina en París, permite un replanteo de los lugares comunes de la oposición Civilización- Barbarie . Una suerte de revisión posmoderna de algunos mitos americanos, en un proceso de regreso a Europa o si se quiere de re-descubrimiento. Cet article propose une lecture de la nouvelle El rastro de tu sangre en la nieve ( La trace de ton sang dans la neige ) de Gabriel García Márquez (Douze contes vagabonds, 1992), en regardant les relations établies par le texte avec différentes formes de la culture populaire. Considérant le contexte du réalisme magique où évolue habituellement la production de Garcia Márquez, on étudie dans ce récit les multiples relations intertextuelles avec divers clichés de la culture populaire, des contes de fées ou d’horreur traditionnels, jusqu’à la culture kitsch. On y étudie aussi la relation établie par García Márquez avec le récit d’aventures, dans des modalités comme le road-movie du cinéma contemporain. Le voyage entrepris par les personnages de l’histoire, entre l’Espagne et la France, qui se termine à Paris, met en cause des lieux communs de l’opposition Civilisation-Barbarie . Une sorte de révision postmoderne des quelques mythes américaines dans ce retour vers l’Europe ou, d’une certaine fa on, une redécouverte. This article proposes an analysis of the short story The Trail of Your Blood in the Snow by Gabriel García Márquez (Strange Pilgrims) by looking at the associations the text makes with different forms from popular culture. We will study the short story within the context of Magic Realism, whose framework generally encompasses García Márquez’s works, and focus on the various intertextual links with various clichés, from popular culture, fairy tales, and traditional horror stories, to kitsch culture. We will also examine the relationship established
Communicating human biomonitoring results to ensure policy coherence with public health recommendations: analysing breastmilk whilst protecting, promoting and supporting breastfeeding
Arendt Maryse
Environmental Health , 2008,
Abstract: This article addresses the problem of how to ensure consistency in messages communicating public health recommendations on environmental health and on child health. The World Health Organization states that the protection, promotion and support of breastfeeding rank among the most effective interventions to improve child survival. International public health policy recommends exclusive breastfeeding for six months, followed by continued breastfeeding with the addition of safe and adequate complementary foods for two years and beyond. Biomonitoring of breastmilk is used as an indicator of environmental pollution ending up in mankind. This article will therefore present the biomonitoring results of concentrations of residues in breastmilk in a wider context. These results are the mirror that reflects the chemical substances accumulated in the bodies of both men and women in the course of a lifetime. The accumulated substances in our bodies may have an effect on male or female reproductive cells; they are present in the womb, directly affecting the environment of the fragile developing foetus; they are also present in breastmilk. Evidence of man-made chemical residues in breastmilk can provide a shock tactic to push for stronger laws to protect the environment. However, messages about chemicals detected in breastmilk can become dramatized by the media and cause a backlash against breastfeeding, thus contradicting the public health messages issued by the World Health Organization. Analyses of breastmilk show the presence of important nutritional components and live protective factors active in building up the immune system, in gastro intestinal maturation, in immune defence and in providing antiviral, antiparasitic and antibacterial activity. Through cohort studies researchers in environmental health have concluded that long-term breastfeeding counterbalances the effect of prenatal exposure to chemicals causing delay in mental and psychomotor development. Therefore caution should be exercised when presenting the results of biomonitoring of breastmilk. The results should be a motivation to enact strong legislation on chemicals and review the use of chemical substances present in breastmilk, but the results should not be used to undermine the confidence in breastmilk as the optimal food for infants and young children.
Estructuras y funciones del lenguaje: de los datos anatomo-clínicos a la imagen funcional
MARYSE SIKSOU
El Hombre y la Máquina , 2005,
Abstract: En este artículo queremos simplemente ilustrar el paralelismo de la evolución de las concepciones del lenguaje y de las estructuras implicadas en él; esta evolución tiene implicaciones en la evaluación y la toma en cuenta de los trastornos del lenguaje. Los aspectos estructurales son también una fuente de sugerencias. En efecto, es divertido pensar que los primeros pacientes de Broca y de Wernicke, respectivamente, no serían tenidos en cuenta hoy en un estudio anatómico debido a la extensión de su lesión o de la patología asociada y sin embargo sus paradigmas han sido productivos. He allí por qué es interesante observar la evolución de las teorías y los métodos de las estructuras y funciones del lenguaje del siglo XIX (los datos anatomo-clínicos) en relación con la imagen funcional del cerebro del siglo XXI.
Structural and Functional Insights into the Malaria Parasite Moving Junction Complex
Brigitte Vulliez-Le Normand equal contributor,Michelle L. Tonkin equal contributor,Mauld H. Lamarque equal contributor,Susann Langer,Sylviane Hoos,Magali Roques,Frederick A. Saul,Bart W. Faber,Graham A. Bentley ? ,Martin J. Boulanger ? ,Maryse Lebrun
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1002755
Abstract: Members of the phylum Apicomplexa, which include the malaria parasite Plasmodium, share many features in their invasion mechanism in spite of their diverse host cell specificities and life cycle characteristics. The formation of a moving junction (MJ) between the membranes of the invading apicomplexan parasite and the host cell is common to these intracellular pathogens. The MJ contains two key parasite components: the surface protein Apical Membrane Antigen 1 (AMA1) and its receptor, the Rhoptry Neck Protein (RON) complex, which is targeted to the host cell membrane during invasion. In particular, RON2, a transmembrane component of the RON complex, interacts directly with AMA1. Here, we report the crystal structure of AMA1 from Plasmodium falciparum in complex with a peptide derived from the extracellular region of PfRON2, highlighting clear specificities of the P. falciparum RON2-AMA1 interaction. The receptor-binding site of PfAMA1 comprises the hydrophobic groove and a region that becomes exposed by displacement of the flexible Domain II loop. Mutations of key contact residues of PfRON2 and PfAMA1 abrogate binding between the recombinant proteins. Although PfRON2 contacts some polymorphic residues, binding studies with PfAMA1 from different strains show that these have little effect on affinity. Moreover, we demonstrate that the PfRON2 peptide inhibits erythrocyte invasion by P. falciparum merozoites and that this strong inhibitory potency is not affected by AMA1 polymorphisms. In parallel, we have determined the crystal structure of PfAMA1 in complex with the invasion-inhibitory peptide R1 derived by phage display, revealing an unexpected structural mimicry of the PfRON2 peptide. These results identify the key residues governing the interactions between AMA1 and RON2 in P. falciparum and suggest novel approaches to antimalarial therapeutics.
Phosphatidylinositol 3-Monophosphate Is Involved in Toxoplasma Apicoplast Biogenesis
Lina Tawk,Jean-Fran?ois Dubremetz,Philippe Montcourrier,Ga?tan Chicanne,Fabrice Merezegue,Véronique Richard,Bernard Payrastre,Markus Meissner,Henri J. Vial,Christian Roy,Kai Wengelnik equal contributor ,Maryse Lebrun equal contributor
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1001286
Abstract: Apicomplexan parasites cause devastating diseases including malaria and toxoplasmosis. They harbour a plastid-like, non-photosynthetic organelle of algal origin, the apicoplast, which fulfils critical functions for parasite survival. Because of its essential and original metabolic pathways, the apicoplast has become a target for the development of new anti-apicomplexan drugs. Here we show that the lipid phosphatidylinositol 3-monophosphate (PI3P) is involved in apicoplast biogenesis in Toxoplasma gondii. In yeast and mammalian cells, PI3P is concentrated on early endosomes and regulates trafficking of endosomal compartments. Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles. Interference with regular PI3P function by over-expression of a PI3P specific binding module in the parasite led to the accumulation of vesicles containing apicoplast peripheral membrane proteins around the apicoplast and, ultimately, to the loss of the organelle. Accordingly, inhibition of the PI3P-synthesising kinase interfered with apicoplast biogenesis. These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast. This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.
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