The rhoptry neck protein RON4 relocalizes at the moving junction during Toxoplasma gondii invasion

Abstract

SummaryHost cell invasion in the Apicomplexa is unique in its dependency on a parasite actin-driven machinery and in the exclusion of most host cell membrane proteins during parasitophorous vacuole (PV) formation. This exclusion occurs at a junction between host cell and parasite plasma membranes that has been called the moving junction, a circumferential zone which forms at the apical tip of the parasite, moves backward and eventually pinches the PV from the host cell membrane. Despite having been described by electron microscopic studies 30 years ago, the molecular nature of this singular structure is still enigmatic. We have obtained a monoclonal antibody that recognizes the moving junction of invading tachyzoites of Toxoplasma gondii , in a pattern clearly distinct from those described so far for microneme and rhoptry proteins. The protein recognized by this antibody has been affinity purified. Mass spectrometry analysis showed that it is a rhoptry neck protein (RON4), a hypothetical protein with homologues restricted to Apicomplexa. Our findings reveals for the first time the participation of rhoptry neck proteins in moving junction formation and strongly suggest the conservation of this structure at the molecular level among Apicomplexa.

Expression and localization of rhoptry neck protein 5 in merozoites and sporozoites of Plasmodium yoelii

“…SignalP 4.1 predicted a putative endoplasmic reticulum (ER) transport signal peptide at aa 1−20 at the PyRON5 N-terminus (Fig. 1) similar to TgRON5, PfRON5 [5,32] and TeRON5, suggesting that RON5 proteins are targeted to the secretory pathway. TM domains were not predicted by Phobius and OCTOPUS for PyRON5.…”

Molecular dissection of host cell invasion by the Apicomplexans: the glideosome

“…In addition, TgAMA1 has recently been shown to co-operates with rhoptry neck proteins in the formation and maintenance of the moving junction during host cell invasion ( Fig. 2A) (Alexander et al, 2005;Lebrun et al, 2005). We have recently dissected structurally and functionally the TgMIC4-1-6 complex and discovered interesting findings.…”

“…Immediately following microneme discharge the rhoptry organelles secrete their contents. Some rhoptry proteins (along with the microneme protein AMA1) have recently been demonstrated to contribute to the formation of the moving junction, although their precise role is unknown (Alexander et al, 2005;Carruthers & Boothroyd, 2007;Dubremetz, 2007;Lebrun et al, I ntracellular pathogens have evolved a great variety of smart strategies to establish infection, evading the host cellular and immune defences and adapting exquisitely to their intracellular niches. While bacterial pathogens can easily enter non-professional phagocytes by induced-phagocytosis, such a task is more challenging for the significantly larger protozoan parasites.…”

Un complexe moléculaire unique à l’origine de la motilité et de l’invasion des Apicomplexes

“…Il y a plus de 30 ans que cette structure a été observée par microscopie électronique en suivant l'entrée de mérozoïtes de P. knowlesi dans les globules rouges [35], mais les détails moléculaires n'ont commencé à émerger que récemment et se sont révélés en grande partie conservés chez les Apicomplexes. La jonction mobile est constituée de quatre protéines d'origine parasitaire : l'antigène de membrane apical AMA1, sécrété par les micronèmes, et trois protéines sécrétées par le col des rhoptries RON2, RON4 et RON5 [36,37] (Figure 4). Une fois sécrétée, AMA1 reste insérée dans la membrane plasmique du parasite et migre au niveau de la jonction mobile durant l'invasion.…”