Toxoplasma gondii is a protozoan parasite that poses a significant risk to AIDS patients and is listed by NIAID as a Category B Priority Pathogen for biodefense. Fundamental to the pathogenic process is the ability of the parasite to develop into a latent tissue cyst that can re-emerge as a rapidly growing form upon impairment of immunity. Increased understanding of this developmental process will provide new opportunities for therapeutic intervention. The work in our first award period focused on GCN5 histone acetyltransferases (HATs) and led to the discovery that histone acetylation correlates with gene expression pertinent to Toxoplasma development. We have taken genetic approaches to define the roles of two distinct GCN5-family HATs we have characterized in Toxoplasma (TgGCN5-A and -B). We have found that the loss of TgGCN5 impairs the ability of Toxoplasma to up-regulate key developmentally expressed genes. We have also determined that some of the proteins interacting with TgGCN5 in a yeast two-hybrid screen have domains typical of transcriptional regulators;this is significant because the lack of DNA-binding transcription factors detectable in the Toxoplasma genome has hampered efforts to understand how gene expression is regulated. How Toxoplasma regulates transcription to grow effectively during the acute stage, and develop into a latent cyst during stress, represent major gaps in our knowledge that hinder our ability to fight the opportunistic infection. The data generated by the first award allow us to focus this renewal on defining mechanisms of GCN5- mediated gene regulation in the context of parasite development, which underlies pathogenesis. We hypothesize that the TgGCN5 HATs play key roles in Toxoplasma pathogenesis by forming distinct complexes with novel proteins that regulate developmental gene expression.
Our specific aims i nclude (1) Determine the roles of TgGCN5 HATs in pathogenesis;(2) Elucidate differences in TgGCN5 complexes during Toxoplasma development;(3) Define the mechanism by which each TgGCN5 is recruited to target gene promoters to coordinate developmental gene expression. The proposed research capitalizes on the novel reagents, techniques, and transgenic parasites that we have developed. The data generated will illuminate the mechanism behind developmental transitions in Toxoplasma that are responsible for disease progression, thus exposing novel points of therapeutic intervention.

Public Health Relevance

Toxoplasma gondii is a protozoan parasite that causes significant disease as an opportunistic infection of AIDS patients. Chronic toxoplasmosis is currently incurable because the parasite is able to develop into cysts that remain latent until immunosuppression. The mechanisms driving the development of these cysts are the focus of our studies, as learning how Toxoplasma develops will identify novel points of therapeutic intervention. We are taking an innovative approach to use transcriptional regulators as a means to elucidate the mechanisms of parasite development. The regulation of gene expression plays a key role in this pathogenic process;therefore, our results stand a high probability of translating into useful new therapies to combat opportunistic infectious diseases like Toxoplasma.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI077502-10
Application #
8452684
Study Section
AIDS-associated Opportunistic Infections and Cancer Study Section (AOIC)
Program Officer
Mcgugan, Glen C
Project Start
2009-05-01
Project End
2014-04-30
Budget Start
2013-05-01
Budget End
2014-04-30
Support Year
10
Fiscal Year
2013
Total Cost
$354,549
Indirect Cost
$124,225
Name
Indiana University-Purdue University at Indianapolis
Department
Pharmacology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Radke, Joshua B; Lucas, Olivier; De Silva, Erandi K et al. (2013) ApiAP2 transcription factor restricts development of the Toxoplasma tissue cyst. Proc Natl Acad Sci U S A 110:6871-6
Xue, Bin; Jeffers, Victoria; Sullivan, William J et al. (2013) Protein intrinsic disorder in the acetylome of intracellular and extracellular Toxoplasma gondii. Mol Biosyst 9:645-57
Joyce, Bradley R; Tampaki, Zoi; Kim, Kami et al. (2013) The unfolded protein response in the protozoan parasite Toxoplasma gondii features translational and transcriptional control. Eukaryot Cell 12:979-89
Stilger, Krista L; Sullivan Jr, William J (2013) Elongator protein 3 (Elp3) lysine acetyltransferase is a tail-anchored mitochondrial protein in Toxoplasma gondii. J Biol Chem 288:25318-29
Miao, Jun; Lawrence, Matthew; Jeffers, Victoria et al. (2013) Extensive lysine acetylation occurs in evolutionarily conserved metabolic pathways and parasite-specific functions during Plasmodium falciparum intraerythrocytic development. Mol Microbiol 89:660-75
Figueras, Maria J; Martin, Osvaldo A; Echeverria, Pablo C et al. (2012) Toxoplasma gondii Sis1-like J-domain protein is a cytosolic chaperone associated to HSP90/HSP70 complex. Int J Biol Macromol 50:725-33
Sullivan Jr, William J; Jeffers, Victoria (2012) Mechanisms of Toxoplasma gondii persistence and latency. FEMS Microbiol Rev 36:717-33
Dixon, Stacy E; Bhatti, Micah M; Uversky, Vladimir N et al. (2011) Regions of intrinsic disorder help identify a novel nuclear localization signal in Toxoplasma gondii histone acetyltransferase TgGCN5-B. Mol Biochem Parasitol 175:192-5
Konrad, Christian; Wek, Ronald C; Sullivan Jr, William J (2011) A GCN2-like eukaryotic initiation factor 2 kinase increases the viability of extracellular Toxoplasma gondii parasites. Eukaryot Cell 10:1403-12
Sullivan Jr, William J; Smith, Aaron T; Joyce, Bradley R (2009) Understanding mechanisms and the role of differentiation in pathogenesis of Toxoplasma gondii: a review. Mem Inst Oswaldo Cruz 104:155-61

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