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Identification of a new rhoptry neck complex RON9/RON10 in the Apicomplexa parasite Toxoplasma gondii.

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.

SUBMITTER: Lamarque MH

PROVIDER: S-EPMC3299665 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Identification of a new rhoptry neck complex RON9/RON10 in the Apicomplexa parasite Toxoplasma gondii.

Lamarque Mauld H MH Papoin Julien J Finizio Anne-Laure AL Lentini Gaelle G Pfaff Alexander W AW Candolfi Ermanno E Dubremetz Jean-François JF Lebrun Maryse M

PloS one 20120312 3

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 po ...[more]

PMID: 22427839

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Project description:Toxoplasmosis is a cosmopolitan zoonotic infection, caused by a unicellular protozoan parasite known as Toxoplasma gondii that belongs to the phylum Apicomplexa. It is estimated that over one-third of the world's population has been exposed and are latently infected with the parasite. In humans, toxoplasmosis is predominantly asymptomatic in immunocompetent persons, while among immunocompromised individuals may be cause severe and progressive complications with poor prognosis. Moreover, seronegative pregnant mothers are other risk groups for acquiring the infection. The life cycle of T. gondii is very complex, indicating the presence of a plurality of antigenic epitopes. Despite of great advances, recognize and construct novel vaccines for prevent and control of toxoplasmosis in both humans and animals is still remains a great challenge for researchers to select potential protein sequences as the ideal antigens. Notably, in several past years, constant efforts of researchers have made considerable advances to elucidate the different aspects of the cell and molecular biology of T. gondii mainly on microneme antigens, dense granule antigens, surface antigens, and rhoptry proteins (ROP). These attempts thereby provided great impetus to the present focus on vaccine development, according to the defined subcellular components of the parasite. Although, currently there is no commercial vaccine for use in humans. Among the main identified T. gondii antigens, ROPs appear as a putative vaccine candidate that are vital for invasion procedure as well as survival within host cells. Overall, it is estimated that they occupy about 1%-30% of the total parasite cell volume. In this review, we have summarized the recent progress of ROP-based vaccine development through various strategies from DNA vaccines, epitope or multi epitope-based vaccines, recombinant protein vaccines to vaccines based on live-attenuated vectors and prime-boost strategies in different mouse models.

Project description:UnlabelledIngestion of the obligate intracellular protozoan parasite Toxoplasma gondii causes an acute infection that leads to chronic infection of the host. To facilitate the acute phase of the infection, T. gondii manipulates the host response by secreting rhoptry organelle proteins (ROPs) into host cells during its invasion. A few key ROP proteins with signatures of kinases or pseudokinases (ROPKs) act as virulence factors that enhance parasite survival against host gamma interferon-stimulated innate immunity. However, the roles of these and other ROPK proteins in establishing chronic infection have not been tested. Here, we deleted 26 ROPK gene loci encoding 31 unique ROPK proteins of type II T. gondii and show that numerous ROPK proteins influence the development of chronic infection. Cyst burdens were increased in the ?rop16 knockout strain or moderately reduced in 11 ROPK knockout strains. In contrast, deletion of ROP5, ROP17, ROP18, ROP35, or ROP38/29/19 (ROP38, ROP29, and ROP19) severely reduced cyst burdens. ?rop5 and ?rop18 knockout strains were less resistant to host immunity-related GTPases (IRGs) and exhibited >100-fold-reduced virulence. ROP18 kinase activity and association with the parasitophorous vacuole membrane were necessary for resistance to host IRGs. The ?rop17 strain exhibited a >12-fold defect in virulence; however, virulence was not affected in the ?rop35 or ?rop38/29/19 strain. Resistance to host IRGs was not affected in the ?rop17, ?rop35, or ?rop38/29/19 strain. Collectively, these findings provide the first definitive evidence that the type II T. gondii ROPK proteome functions as virulence factors and facilitates additional mechanisms of host manipulation that are essential for chronic infection and transmission of T. gondiiImportanceReactivation of chronic Toxoplasma gondii infection in individuals with weakened immune systems causes severe toxoplasmosis. Existing treatments for toxoplasmosis are complicated by adverse reactions to chemotherapy. Understanding key parasite molecules required for chronic infection provides new insights into potential mechanisms that can interrupt parasite survival or persistence in the host. This study reveals that key secreted rhoptry molecules are used by the parasite to establish chronic infection of the host. Certain rhoptry proteins were found to be critical virulence factors that resist innate immunity, while other rhoptry proteins were found to influence chronic infection without affecting virulence. This study reveals that rhoptry proteins utilize multiple mechanisms of host manipulation to establish chronic infection of the host. Targeted disruption of parasite rhoptry proteins involved in these biological processes opens new avenues to interfere with chronic infection with the goal to either eliminate chronic infection or to prevent recrudescent infections.

Dataset Information

Identification of a new rhoptry neck complex RON9/RON10 in the Apicomplexa parasite Toxoplasma gondii.

Publications

Identification of a new rhoptry neck complex RON9/RON10 in the Apicomplexa parasite Toxoplasma gondii.

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