How Toxoplasma injects rhoptry proteins into the host cell


Principal Investigator: FELICE DEBORAH KELLY
Abstract: DESCRIPTION (provided by applicant): The obligate intracellular parasite Toxoplasma gondii can infect an extremely broad range of host species. This promiscuity may be enabled by the parasite's ability to inject its own invasion proteins into target cells. To invade a host cell the infective form of the parasite, the tachyzoite, attaches to a target cell, injects parasite protein into that cell, and then enters the cell, creating the parasitophorous vacuole in which it will replicate. The proteins that are introduced into the target cell are stored in specialized vacuolar organelles called rhoptries. Some of the rhoptry proteins are required for formation of the moving junction, a structure that is essential for invasion and may propel the parasite into the host cell. Host cell defenses are modified by other injected rhoptry proteins, such as protein kinases that act on host STAT and p47 GTPase functions. Despite the importance of these rhoptry proteins, it is completely unknown how they are introduced into the host cell. I hypothesize that there is a specific protein structure that is required for injection of parasite proteins into host cells, and that it will be possible to generate temperature-sensitive mutants where that structure is disrupted. The goal of this project is to discover the mechanism of protein injection by looking for a specific class of invasion mutants. To find genes that are essential for invasion, I will isolate and identify temperature-sensitive mutants of Toxoplasma gondii that are defective in host cell invasion. I will then determine whether any of these mutants have a defect in protein injection into the host cell, using a previously published FRET-disruption assay. Characterization and sequencing of identified injection mutants will allow me to identify important new elements of the host cell invasion machinery. Once injection proteins are identified they will be tagged for localization and affinity purification to identify binding partnrs. This machinery is likely to be conserved throughout the Apicomplexa family, just as the invasion machinery is, and proteins identified here may help us understand the invasion of Plasmodium falciparum as well.
Funding Period: 2013-01-01 - 2014-12-31
more information: NIH RePORT

Detail Information

Research Grants30

  1. The plant-like vacuole of Toxoplasma gondii
    Silvia N Moreno; Fiscal Year: 2013
    ..We think that the PLV plays a central role during the extracellular phase of the parasite not only in resisting environmental stress but also as it prepares itself for invading the next host cell. ..
  2. New infection-related proteins of Plasmodium sporozoites and liver stages
    Stefan H I Kappe; Fiscal Year: 2013
    ..Identifying major liver stage-host hepatocyte interactions and elucidating their functional significance will reveal fundamental principles of malaria parasite liver infection and provide new avenues for preventive drug design. ..
  3. A host protein network necessary for parasite cytolysis
    Doron Greenbaum; Fiscal Year: 2013
    ..We herein propose to integrate cell biological, molecular genetics, and pharmacological approaches to elucidate the activation, function, and significance of this host network for parasite cytolysis. ..
  4. Phosphoproteome of Toxoplasma
    John C Boothroyd; Fiscal Year: 2013
    ..Finally, we will take advantage of our expertise in mass spectrometry to innovate new methods for phosphoproteomic analyses of samples where the amount available is too small for conventional analyses. ..
  5. Novel rhoptry effector proteins in Toxoplasma host-pathogen interaction
    PETER JOHN BRADLEY; Fiscal Year: 2013
    ..Together, these complementary approaches promise to reveal novel mechanistic insights into how Toxoplasma uses this unique set of effector proteins to modulate its mammalian host cell. ..
  6. The Role of Toxoplasma Rhoptries in Host Cell Infection
    PETER JOHN BRADLEY; Fiscal Year: 2013
    ..These studies will open completely new insight into the mechanism by which apicomplexan parasites use this novel invasion machine to infect their mammalian hosts and cause disease. ..
  7. Essential Cell Cycle Mechanisms in Toxoplasma
    Michael W White; Fiscal Year: 2013
    ..Therefore, through this investigation of the molecular basis of the parasite cell cycle, new potential drug targets will be identified upon which novel therapies may be developed. ..
  8. A novel approach to characterize the Toxoplasma gondii secretome in vivo
    Jon P Boyle; Fiscal Year: 2013
    ..Such effectors may represent new potential targets for therapeutic intervention. ..
  9. Unique functions of the mitochondrial tRNA import machinety in T. gondii
    Lilach Sheiner; Fiscal Year: 2013
    ..gondii mitochondrion and hence contribute to the design of new countermeasures, also of relevance to other apicomplexan parasites such as the causative agent of malaria, Plasmodium falciparum. ..
  10. The AP2 factors required for Toxoplasma replication
    Michael W White; Fiscal Year: 2013
    ..These studies will provide fundamental knowledge of a new set of mechanisms required to produce parasite replication that is relevant to acute disease caused by the growth of Toxoplasma in the immunocompromised human host. ..
  11. Toxoplasma Epigenomics and Gene Expression
    Kami Kim; Fiscal Year: 2013
    ..Understanding the function of AP2 proteins may lead to new treatments that will prevent of treat T. gondii infection in individuals with AIDS. ..
  12. Pacific NorthWest Regional Center of Excellence (PNWRCE)
    Jay A Nelson; Fiscal Year: 2013
    ..pseudomallei host pathogen response during both the septicemic as well as the intracellular phases of the disease. ..
  13. The role of the DOC2.1 protein in Toxoplasma gondii Ca2+- dependent exocytosis
    Marc Jan Gubbels; Fiscal Year: 2013
    ..Putative TgDOC2.1 interaction partners identified by either method will be validated by co-localization studies in the parasite. Altogether, we will define the mechanism behind the conserved microneme secretion process. ..