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Insight into the moving junctiondependent invasion in Apicomplexa parasites

Vendredi 11 octobre 2013 14:00 - Duree : 1 heure
Lieu : Institut Jean Roget, Salle de Conférence du 5ème Etage, Faculté de Médecine-Pharmacie, Domaine de la Merci, La Tronche. Pour y accéder : Prenez l’ascenseur sud

Orateur : Maryse LEBRUN (CNRS UMR 5235, Université de Montpellier 2)

The phylum Apicomplexa includes some of the most important pathogenic parasites of man and animals, the deadliest of which is the malaria parasite Plasmodium falciparum, responsible for a toll of one million human deaths per year. Being obligatory intracellular organisms, Apicomplexa have developed a unique invasion mechanism that is conserved across the phylum involving a tight interaction formed between the host cell and the parasite surfaces called Moving Junction (MJ). The MJ appears as a punctuate focus at the apical tip of the parasite, then rapidly resolves into a ring that moves posteriorly over the parasite in conjunction with host membrane invagination and eventual engulfment of the invading parasite. The MJ is essential for this process, as it anchors the parasite to the host surface while the parasite’s actin-myosin motor provides forward motion into the host cell. By combining cell biology, structural biology and gene targeting approaches, we have deciphered the core machinery of the MJ. We showed that the actors of the MJ are proteins unique to the phylum and conserved between most members. MJ proteins are secreted from two distinct secretory organelles of the parasite : the micronemes and the rhoptries. MJ formation relies on secretion and export in the host cell of a rhoptry neck proteins (RONs) complex, including at least RONs 2, 4, and 5. RON2 is integrated into the host plasma membrane, exposing its N-terminal domain within the cytosol of the host cell, likely retaining RONs 4, 5 and 8 near the cytosolic face of this membrane. RON2 also exposes an ectodomain on the cell surface that serves as a receptor for the secreted micronemal apical membrane antigen 1 (AMA1) which is displayed on the parasite cell surface. The organization of this AMA1-RON complex points towards a model whereby the parasite secretes and inserts the interacting components on both sides of the MJ, i.e. the plasma membranes of the host (RON2) and the parasite (AMA1). In this model, RON4/5/8 would allow the anchoring of the junction complex to the host cell cytoskeleton.

Contact : cordelia.bisanz@ujf-grenoble.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (Institut Jean Roget)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire IJR)
Site de l'évènement : Pôle Santé / La Tronche

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