Export of a Toxoplasma gondii Rhoptry Neck Protein Complex at the Host Cell Membrane to Form the Moving Junction during Invasion

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

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

Autophagy Protein Atg3 is Essential for Maintaining Mitochondrial Integrity and for Normal Intracellular Development of Toxoplasma gondii Tachyzoites

Autophagy is a cellular process that is highly conserved among eukaryotes and permits the degradation of cellular material. Autophagy is involved in multiple survival-promoting processes. It not only facilitates the maintenance of cell homeostasis by degrading long-lived proteins and damaged organelles, but it also plays a role in cell differentiation and cell development. Equally important is its function for survival in stress-related conditions such as recycling of proteins and organelles during nutrient starvation. Protozoan parasites have complex life cycles and face dramatically changing environmental conditions; whether autophagy represents a critical coping mechanism throughout these changes remains poorly documented. To investigate this in Toxoplasma gondii, we have used TgAtg8 as an autophagosome marker and showed that autophagy and the associated cellular machinery are present and functional in the parasite. In extracellular T. gondii tachyzoites, autophagosomes were induced in response to amino acid starvation, but they could also be observed in culture during the normal intracellular development of the parasites. Moreover, we generated a conditional T. gondii mutant lacking the orthologue of Atg3, a key autophagy protein. TgAtg3-depleted parasites were unable to regulate the conjugation of TgAtg8 to the autophagosomal membrane. The mutant parasites also exhibited a pronounced fragmentation of their mitochondrion and a drastic growth phenotype. Overall, our results show that TgAtg3-dependent autophagy might be regulating mitochondrial homeostasis during cell division and is essential for the normal development of T. gondii tachyzoites

Regulation of peripheral blood flow in Complex Regional Pain Syndrome: clinical implication for symptomatic relief and pain management

Background. During the chronic stage of Complex Regional Pain Syndrome (CRPS), impaired microcirculation is related to increased vasoconstriction, tissue hypoxia, and metabolic tissue acidosis in the affected limb. Several mechanisms may be responsible for the ischemia and pain in chronic cold CPRS. Discussion. The diminished blood flow may be caused by either sympathetic dysfunction, hypersensitivity to circulating catecholamines, or endothelial dysfunction. The pain may be of neuropathic, inflammatory, nociceptive, or functional nature, or of mixed origin. Summary. The origin of the pain should be the basis of the symptomatic therapy. Since the difference in temperature between both hands fluctuates over time in cold CRPS, when in doubt, the clinician should prioritize the patient's report of a persistent cold extremity over clinical tests that show no difference. Future research should focus on developing easily applied methods for clinical use to differentiate between central and peripheral blood flow regulation disorders in individual patients

Une nouvelle inscription dans la salle à gradins du temple d'Artémis à Doura-Europos (information)

Leriche Pierre, El-Ajji Edmond. Une nouvelle inscription dans la salle à gradins du temple d'Artémis à Doura-Europos (information). In: Comptes rendus des séances de l'Académie des Inscriptions et Belles-Lettres, 143ᵉ année, N. 4, 1999. pp. 1309-1346

A middleware architecture for autonomic software deployment

International audienceAutonomic software deployment in open networked environments such as mobile and ad hoc networks is an open issue. Some solutions to software deployment exist; but, they are usable only within static topologies of devices. We propose a middleware architecture providing a constraint-based language guiding the deployment process at a high level and an autonomous agent-based system for establishing and maintaining a software deployment according to a deployment plan. Constraints solver generates the deployment plan from the initial specification and a network discovery service is used to automatically detect the target hosts. This paper presents middleware architecture that considers the challenges of deploying distributed software over mobile and ad hoc networks with minimal human oversight. We also present an implementation of a prototype and provide experimental results in both real environments

Validation of COSMOS DSL programs

International audienceCOSMOS DSL is a language dedicated to the domain of composition of context information. It allows, through its high-level constructions, to treat very large amounts of context data coming from distributed sources, whatsoever in ubiquitous systems or large-scale distributed systems. In this paper, we focus on the safety of programs developed in COSMOS DSL. We discuss the needs of reliability and validation of specific properties such as the lack of deadlocks and vivacity of context information. Then we propose an automatable modeling of COSMOS DSL using the Petri nets formalism to allow verification of behavioral properties in a software too

j-ASD : un middleware pour le déploiement logiciel autonomique

International audienceDans cet article nous nous intéressons à la problématique du déploiement autonomique de logiciel dans des infrastructures réparties à grande échelle à topologie variable, tels que les systèmes ubiquitaires et les systèmes pair-à-pair. Nous proposons j-ASD, un intergiciel pour l'automatisation du processus de déploiement. Le middleware est basé sur une spécification des contraintes de déploiement, qui sera résolue par la suite par un solveur de contraintes et un système d'agents mobiles adaptable pour l'exécution du plan de déploiement, la supervision et l'adaptation dynamique du processus de déploiement lors de l'exécution

Validation de programmes COSMOS DSL

National audienceCOSMOS DSL est un langage dédié au domaine de la composition d'informations de contexte. Il permet, grâce à ses constructions de haut niveau, de traiter de très grandes quantités de données de contexte provenant de sources réparties, que ce soit dans des systèmes ubiquitaires ou des systèmes répartis à grande échelle. Dans cet article, nous nous intéressons à la sûreté des programmes développés en COSMOS DSL. Nous discutons des besoins de fiabilité et de validation de propriétés spécifiques telles l'absence d'interblocages et de vivacité des informations de contexte. Nous proposons une modélisation de programmes COSMOS DSL au moyen du formalisme des réseaux de Petri. Cette nouvelle sémantique réseaux de Petri aux programmes COSMOS DSL est destinée à être automatisable pour permettre la vérification des propriétés comportementales dans un outil logicie