A Patatin-Like Protein Protects Toxoplasma gondii from Degradation in a Nitric Oxide-Dependent Manner

Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Madison, Wisconsin, USA.
Infection and immunity (Impact Factor: 3.73). 01/2012; 80(1):55-61. DOI: 10.1128/IAI.05543-11
Source: PubMed


Toxoplasma gondii is an obligate intracellular parasite that uses immune cells to disseminate throughout its host. T. gondii can persist and even slowly replicate in activated host macrophages by reducing the antimicrobial effects of molecules such
as nitric oxide (NO). A T. gondii patatin-like protein called TgPL1 was previously shown to be important for survival in activated macrophages. Here we show
that a T. gondii mutant with a deletion of the TgPL1 gene (ΔTgPL1) is degraded in activated macrophages. This degradation phenotype is abolished by the removal of NO by the use
of an inducible NO synthase (iNOS) inhibitor or iNOS-deficient macrophages. The exogenous addition of NO to macrophages results
in reduced parasite growth but not the degradation of ΔTgPL1 parasites. These results suggest that NO is necessary but not
sufficient for the degradation of ΔTgPL1 parasites in activated macrophages. While some patatin-like proteins have phospholipase
A2 (PLA2) activity, recombinant TgPL1 purified from Escherichia coli does not have phospholipase activity. This result was not surprising, as TgPL1 contains a G-to-S change at the predicted
catalytic serine residue. An epitope-tagged version of TgPL1 partially colocalized with a dense granule protein in the parasitophorous
vacuole space. These results may suggest that TgPL1 moves to the parasitophorous vacuole to protect parasites from nitric
oxide by an undetermined mechanism.

Download full-text


Available from: Crystal Tobin Magle
  • Source
    • "Raw reads were aligned to either the T. gondii or M. musculus genomes, normalized and analyzed for differential gene expression. (B) To examine T. gondii in the brains of mice at the designated time points, mice were infected with 10,000 parasites of a bioluminescent T. gondii[62]. Shown are representative brains for 10 and 28 day post-infection mice, after the brains were soaked for 5 minutes in luciferin prior to imaging. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background The obligate intracellular parasite Toxoplasma gondii establishes a life-long chronic infection within any warm-blooded host. After ingestion of an encysted parasite, T. gondii disseminates throughout the body as a rapidly replicating form during acute infection. Over time and after stimulation of the host immune response, T. gondii differentiates into a slow growing, cyst form that is the hallmark of chronic infection. Global transcriptome analysis of both host and parasite during the establishment of chronic T. gondii infection has not yet been performed. Here, we conducted a dual RNA-seq analysis of T. gondii and its rodent host to better understand host and parasite responses during acute and chronic infection. Results We obtained nearly one billion paired-end RNA sequences from the forebrains of uninfected, acutely and chronically infected mice, then aligned them to the genomic reference files of both T. gondii and Mus musculus. Gene ontology (GO) analysis of the 100 most highly expressed T. gondii genes showed less than half were shared between acute and chronic infection. The majority of the highly expressed genes common in both acute and chronic infection were involved in transcription and translation, underscoring that parasites in both stages are actively synthesizing proteins. Similarly, most of the T. gondii genes highly expressed during chronic infection were involved in metabolic processes, again highlighting the activity of the cyst stage at 28 days post-infection. Comparative analyses of host genes using uninfected forebrain revealed over twice as many immune regulatory genes were more abundant during chronic infection compared to acute. This demonstrates the influence of parasite development on host gene transcription as well as the influence of the host environment on parasite gene transcription. Conclusions RNA-seq is a valuable tool to simultaneously analyze host and microbe transcriptomes. Our data shows that T. gondii is metabolically active and synthesizing proteins at 28 days post-infection and that a distinct subset of host genes associated with the immune response are more abundant specifically during chronic infection. These data suggest host and pathogen interplay is still present during chronic infection and provides novel T. gondii targets for future drug and vaccine development. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-806) contains supplementary material, which is available to authorized users.
    Full-text · Article · Sep 2014 · BMC Genomics
  • [Show abstract] [Hide abstract]
    ABSTRACT: The alveolate superphylum includes many free-living and parasitic organisms, which are united by the presence of alveolar sacs lying proximal to the plasma membrane, providing cell structure. All species comprising the apicomplexan group of alveolates are parasites and have adapted to the unique requirements of the parasitic lifestyle. Here the evolution of apicomplexan secretory organelles that are involved in the critical process of egress from one cell and invasion of another is explored. The variations within the Apicomplexa and how these relate to species-specific biology will be discussed. In addition, recent studies have identified specific calcium-sensitive molecules that coordinate the various events and regulate the release of these secretory organelles within apicomplexan parasites. Some aspects of this machinery are conserved outside the Apicomplexa, and are beginning to elucidate the conserved nature of the machinery. Briefly, the relationship of this secretion machinery within the Apicomplexa will be discussed, compared with free-living and predatory alveolates, and how these might have evolved from a common ancestor.
    No preview · Article · Oct 2012 · International journal for parasitology
  • [Show abstract] [Hide abstract]
    ABSTRACT: The intracellular protozoan parasite Toxoplasma gondii is capable of invading any nucleated cell and replicates within a parasitophorous vacuole (PV). This microenvironment is modified by secretory proteins from organelles named rhoptries and dense granules. In this report, we identify a novel dense granule protein, which we refer to as GRA22. GRA22 has no significant homology to any other known proteins. GRA22 possesses a signal peptide at the N-terminal end which is responsible for dense granule and PV localization. The RH strain GRA22 contains 12 copies of tandem repeats consisting each of 21 amino acids located between the 42nd and 293rd amino acid residues from a full length of 624 amino acids. On the other hand, ME49 strain GRA22 has 10 copies of tandem repeats. The Neospora caninum GRA22 ortholog completely lacks this repetitive sequence. GRA22 knock out parasites show a similar growth rate as the parental strain. However, the timing of egress is earlier than that of the parental strain. These results suggest that GRA22 is involved in regulating parasite egress in T. gondii.
    No preview · Article · Apr 2013 · Molecular and Biochemical Parasitology
Show more