Rhomboid 4 (ROM4) affects the processing of surface adhesins and facilitates host cell invasion by Toxoplasma gondii

Host cell attachment by Toxoplasma gondii is dependent on polarized secretion of apical adhesins released from the micronemes. Subsequent translocation of these adhesive complexes by an actin-myosin motor powers motility and host cell invasion. Invasion and motility are also accompanied by shedding of surface adhesins by intramembrane proteolysis. Several previous studies have implicated rhomboid proteases in this step; however, their precise roles in vivo have not been elucidated. Using a conditional knockout strategy, we demonstrate that TgROM4 participates in processing of surface adhesins including MIC2, AMA1, and MIC3. Suppression of TgROM4 led to decreased release of the adhesin MIC2 into the supernatant and concomitantly increased the surface expression of this and a subset of other adhesins. Suppression of TgROM4 resulted in disruption of normal gliding, with the majority of parasites twirling on their posterior ends. Parasites lacking TgROM4 bound better to host cells, but lost the ability to apically orient and consequently most failed to generate a moving junction; hence, invasion was severely impaired. Our findings indicate that TgROM4 is involved in shedding of micronemal proteins from the cell surface. Down regulation of TgROM4 disrupts the normal apical-posterior gradient of adhesins that is important for efficient cell motility and invasion of host cells by T. gondii

Eimeripain, a Cathepsin B-Like Cysteine Protease, Expressed throughout Sporulation of the Apicomplexan Parasite Eimeria tenella

The invasion and replication of Eimeria tenella in the chicken intestine is responsible for avian coccidiosis, a disease that has major economic impacts on poultry industries worldwide. E. tenella is transmitted to naïve animals via shed unsporulated oocysts that need contact with air and humidity to form the infectious sporulated oocysts, which contain the first invasive form of the parasite, the sporozoite. Cysteine proteases (CPs) are major virulence factors expressed by protozoa. In this study, we show that E. tenella expresses five transcriptionally regulated genes encoding one cathepsin L, one cathepsin B and three cathepsin Cs. Biot-LC-LVG-CHN2, a cystatin derived probe, tagged eight polypeptides in unsporulated oocysts but only one in sporulated oocysts. CP-dependant activities were found against the fluorescent substrates, Z-FR-AMC and Z-LR-AMC, throughout the sporulation process. These activities corresponded to a cathepsin B-like enzyme since they were inhibited by CA-074, a specific cathepsin B inhibitor. A 3D model of the catalytic domain of the cathepsin B-like protease, based on its sequence homology with human cathepsin B, further confirmed its classification as a papain-like protease with similar characteristics to toxopain-1 from the related apicomplexan parasite, Toxoplasma gondii; we have, therefore, named the E. tenella cathepsin B, eimeripain. Following stable transfection of E. tenella sporozoites with a plasmid allowing the expression of eimeripain fused to the fluorescent protein mCherry, we demonstrated that eimeripain is detected throughout sporulation and has a punctate distribution in the bodies of extra- and intracellular parasites. Furthermore, CA-074 Me, the membrane-permeable derivative of CA-074, impairs invasion of epithelial MDBK cells by E. tenella sporozoites. This study represents the first characterization of CPs expressed by a parasite from the Eimeria genus. Moreover, it emphasizes the role of CPs in transmission and dissemination of exogenous stages of apicomplexan parasites

Les coccidioses aviaires : importance et perspectives de recherche

Avian coccidial infections are associated with a heavy economic burden. They are caused by obligate intracellular parasites of the genus Eimeria. These parasites are host specific and invade epithelial cells of animal intestines, causing severe damages that can lead to the host’s death. Prophylaxis relies on the use of anticoccidial drugs and vaccination. However, the vaccines’ high costs and the emergence of anticoccidial drug resistance highlight the need to develop alternative control methods. A transgenic population of Eimeria has been developed recently, and this new tool will help study, for the first time, the molecular mechanisms involved in Eimeria infectious processes. Besides, this main advance in basic research could lead, in the longer time, to the development of new vaccine preparations. In this communication, we will also discuss the use of parasitic protease inhibitors as new putative anticoccidial drugs.Les coccidioses aviaires sont des maladies ayant de graves conséquences économiques. Elles sont provoquées par des parasites à développement intracellulaire obligatoire appelés Eimeria. Les Eimeria sont monoxènes et se développent spécifiquement dans les entérocytes de l’épithélium intestinal, ce qui engendre des perturbations de l’homéostasie pouvant conduire à la mort de l’animal. La prophylaxie repose sur l’utilisation d’anticoccidiens et sur la vaccination. Le coût élevé des vaccins, et l’apparition de résistances aux anticoccidiens soulignent la nécessité de trouver des moyens de lutte alternatif. Un système de transgenèse chez les Eimeria a été mis au point, ce qui permet d’envisager, pour la première fois, l’étude fine des mécanismes moléculaires impliqués dans les processus infectieux. Cette avancée capitale en recherche fondamentale pourrait aboutir, à plus long terme, à la création de nouvelles formulations vaccinales. Dans cette communication, nous discuterons de l’utilisation potentielle d’inhibiteurs de protéases parasitaires comme anticoccidiens de nouvelle génération.Naciri Muriel, Brossier Fabien. Les coccidioses aviaires : importance et perspectives de recherche. In: Bulletin de l'Académie Vétérinaire de France tome 162 n°1, 2009. pp. 47-50

Designing new compounds for a better comprehension of molecular mechanisms involved in the invasion of hosts cells by Eimeria parasites

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4,4,4-trifluoromethylpyrimido[1,2-b]pyridazin-2-ones systems and their analogs : inhibitors of<em> Eimeria</em> parasites

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Designing new compounds for to control the infection of hosts cells by Eimeria parasites

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Développement de nouvelles stratégies pour la mise au point d’anti-apicomplexes à visées thérapeutique et pharmacologique

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A PV-approach for dense water formation along fronts: Application to the Northwestern Mediterranean

Special Issue: Dense Water Formations in the North Western Mediterranean: From the Physical Forcings to the Biogeochemical ConsequencesInternational audienceThe mechanisms of dense water formation (r > 29:0 kg m 23) at work in the baroclinic cyclonic gyre of the NorthWestern Mediterranean basin are investigated through a PV-budget (PV: Potential Vortici-ty). The PV-budget is diagnosed from an eddy-resolving (1=36 o) ocean simulation driven in surface by hourly air-sea fluxes provided by a nonhydrostatic atmospheric model at 2:5 km resolution. The PV-budget is controlled by the diabatic, frictional, and advective PV-fluxes. Around the gyre the surface diabatic PV-flux dominates the PV-destruction, except along the northern branch of the North Current where the surface frictional PV-flux is strongly negative. In this region, the bathymetry stabilizes the front and maintains the current northerly in the same direction as the dominant northerly wind. This configuration leads to optimal wind-current interactions and explains the preponderance of frictional PV-destruction on diabatic PV-destruction. This mechanical forcing drives a cross-front ageostrophic circulation which subducts surface low-PV waters destroyed by wind on the dense side of the front and obducts high-PV waters from the pycnocline on the light side of the front. The horizontal PV-advections associated with the geostrophic cyclonic gyre and turbulent entrainment at the pycnocline also contribute to the PV-refueling in the frontal region. The surface nonadvective PV-flux involves energy exchanges down to 21400 W m 22 in the frontal zone: this flux is 3.5 times stronger than atmospheric buoyancy flux. These energy exchanges quantify the coupling effects between the surface atmospheric forcing with the oceanic frontal structures at submesoscale

Description de metallo-protease de la famille M1, impliquée dans le développement du parasite apicomplexe Eimeria tenella

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