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Processing and secretion of ROP13: A unique Toxoplasma effector protein
Jay M Turetzky1, David K Chu, Bettina E Hajagos
1Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095-1489, USA.
International Journal for Parasitology
|April 3, 2010
Summary
Toxoplasma gondii rhoptry protein ROP13 is processed but not essential for infection. However, ROP13 can enter host cells and cause toxicity when overexpressed, indicating a potential role in host cell manipulation.
Area of Science:
- Cellular microbiology
- Parasitology
- Host-pathogen interactions
Background:
- Intracellular pathogens like Toxoplasma gondii secrete proteins via rhoptries to invade host cells.
- The precise functions of rhoptry proteins in host cell manipulation remain largely unknown.
Purpose of the Study:
- To investigate the processing, targeting, and function of the Toxoplasma gondii rhoptry protein ROP13.
- To determine the role of ROP13 in host cell invasion and intracellular survival.
Main Methods:
- Site-directed mutagenesis to analyze ROP13 processing at the SphiXE cleavage site.
- Gene disruption to assess ROP13 essentiality in vitro and in vivo.
- Exogenous expression in human cells to evaluate ROP13 localization and toxicity.
Main Results:
- ROP13 is synthesized as a pre-pro-protein, processed at a conserved SphiXE site, but prodomain processing is not required for secretion.
- ROP13 is not essential for Toxoplasma gondii growth in fibroblasts or virulence in mice.
- ROP13 is a soluble effector protein that localizes to the host cell cytoplasm and exhibits toxicity upon overexpression.
Conclusions:
- ROP13 processing is crucial for its maturation but not for rhoptry targeting or secretion.
- ROP13's non-essentiality for virulence suggests functional redundancy or specific roles not captured in standard assays.
- ROP13's cytoplasmic localization and toxicity in host cells suggest it acts as a soluble effector, potentially disrupting host cell functions.
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