Developmental change in translation initiation alters the localization of a common microbial protein necessary for
Kathryn Milligan-Myhre1, Sarah K Wilson2, Laura J Knoll2
1Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, 99508, USA.
Abstract:
The Toxoplasma gondii cyst stage is resistant to drug therapy. To identify potential targets for new therapeutics, we screened insertional mutants of T. gondii for a reduced ability to form cysts in the brains of mice. In one of these mutants, named 38C3, the mutagenesis plasmid inserted into the mRNA of a protein that is highly conserved in microbes but is not present in humans. The mutation in 38C3 causes reduced brain cyst production during chronic infection, but does not affect acute virulence, so the disrupted gene and protein are called T. gondii Brain Colonization Protein 1 (TgBCP1). TgBCP1 has three potential in frame start codons that produce 51, 33 or 25 kDa proteins. In rapidly replicating tachyzoites, translation initiates at the third methionine, producing the 25 kDa form that is conserved in many bacteria and protozoans. Brain cysts exclusively express the 51 kDa form of TgBCP1, which is secreted from the parasites and localizes to the cyst wall. Only expression of the long form of TgBCP1 restored cyst formation in the 38C3 mutant. TgBCP1 is essential for cyst formation and is the first example of a developmental regulation in translation initiation site preference for a T. gondii protein.
Insights
Researchers identified Toxoplasma gondii Brain Colonization Protein 1 (TgBCP1) as essential for cyst formation. This discovery offers a potential new target for treating drug-resistant Toxoplasma gondii infections.
Area of Science:
- Parasitology
- Molecular Biology
- Drug Discovery
Background:
- The cyst stage of Toxoplasma gondii is resistant to current drug therapies.
- Identifying novel drug targets is crucial for developing effective treatments against toxoplasmosis.
Purpose of the Study:
- To screen for Toxoplasma gondii mutants with reduced cyst formation to identify potential therapeutic targets.
- To characterize the role of a novel protein, TgBCP1, in T. gondii cyst development.
Main Methods:
- Insertional mutagenesis screening of T. gondii in a mouse model.
- Identification and characterization of the disrupted gene (TgBCP1) in a low-cyst forming mutant (38C3).
- Analysis of TgBCP1 protein expression and localization in different T. gondii life stages.
Main Results:
- A mutant (38C3) showed reduced brain cyst formation due to disruption of TgBCP1.
- TgBCP1 is essential for cyst formation, with the 51 kDa form specifically expressed and secreted to the cyst wall.
- TgBCP1 exhibits developmental regulation of translation initiation, with different forms produced in tachyzoites versus cysts.
Conclusions:
- Toxoplasma gondii Brain Colonization Protein 1 (TgBCP1) is essential for the formation of the drug-resistant cyst stage.
- TgBCP1 represents a promising new target for anti-toxoplasmosis therapeutics.
- The study reveals the first instance of developmental regulation of translation initiation site preference in T. gondii.
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