The applicant, Lilach Sheiner, is highly accomplished in Toxoplasma gondii genetic manipulation, and has recently developed a pipeline to identify and characterize genes encoding unique components of parasite endosymbiotic organelles. During the mentored phase, the applicant will utilize this system and focus on the identification and disruption of parasite-specific components of mitochondrial tRNA import (MITI) that are likely suitable as new drug targets. Furthermore the candidate will develop tools to characterize the biological function of MITI components, and will master the relevant biochemical skills, with the help of the mentors. As an independent investigator at an institution of basic biomedical research, she will apply these molecular and biochemical tools to study MITI and other parasite-specific aspects of mitochondrial biogenesis, as a promising source for drug targets. The CTEGD fosters a highly collaborative research environment with 19 faculty members interested in various aspects of parasite biology and with excellent core facilities. The mentor, Boris Striepen, is an expert on endosymbiont biology in T. gondii and is one of the leading scientists in the field of molecular research in these parasites. The co-mentor, Stephen Hajduk, is an expert biochemist with wide ranging experience in parasite mitochondria biogenesis, and who has specific interest in MITI in parasites. The T. gondii mitochondrion is essential and shows several unique features. Recent data suggests that MITI in these parasites is likely to be dependent on a divergent machinery. The goal of this proposal is to identify the components responsible for this divergence, utilizing a novel bioinformatics search strategy, and to address their function by reverse genetics, using a new streamlined system to generate conditional mutants. While some tools to characterize tRNA import and mitochondrial function in T. gondii are at hand, others await development and adaptation. Isolation of pure mitochondria has not been established, which limits the extent of biochemical research available. This challenge will be addressed in the proposed project. These studies will open new perspectives on the biogenesis of the T. 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.

Public Health Relevance

Toxoplasma gondii, a protozoan parasite, causes mortality in immunocompromised individuals (e.g. HIV patients or organ transplant recipients) and fatal congenital infections. In the USA, it is a neglected infection of poverty and a biodefense concern. It is also a close relative of the malaria parasite. No known vaccines or drugs can eradicate persistent T. gondii infection in humans. The goal of this research is to study the details of the unusual T. gondii mitochondrial tRNA import path, to identify new parasite specific targets for intervention.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Career Transition Award (K99)
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Microbiology and Infectious Diseases B Subcommittee (MID)
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Mcgugan, Glen C
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University of Georgia
Public Health & Prev Medicine
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United States
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Sheiner, Lilach; Fellows, Justin D; Ovciarikova, Jana et al. (2015) Toxoplasma gondii Toc75 Functions in Import of Stromal but not Peripheral Apicoplast Proteins. Traffic 16:1254-69
Sheiner, Lilach; Vaidya, Akhil B; McFadden, Geoffrey I (2013) The metabolic roles of the endosymbiotic organelles of Toxoplasma and Plasmodium spp. Curr Opin Microbiol 16:452-8