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Localization of a Toxoplasma gondii rhoptry protein by immunoelectron microscopy during and after host cell
L D Saffer1, O Mercereau-Puijalon, J F Dubremetz
1Department of Pathology, University of Virginia School of Medicine, Charlottesville 22908.
Abstract:
We immunolocalized a Toxoplasma gondii rhoptry protein (ROP1) before and after parasite host cell invasion of human fibroblasts and TG180 murine sarcoma cells by electron microscopy and immunogold labeling using either a monoclonal antibody (Tg49) or a monospecific rabbit antiserum (alpha 249). At all stages of parasite growth ROP1 was found within the body but rarely within the peduncle of rhoptries, even in those that appeared empty. Immediately after host cell invasion ROP1 was associated with the parasitophorous vacuole membrane. Within hours after invasion the amount of ROP1 immunodetectable on the parasitophorous vacuole membrane was markedly decreased. The localization of ROP1 suggests a role in the early establishment of infection in host cells, consistent with previous work that has indicated that monoclonal antibodies to ROP1 (including the one used in these studies) interfere with the phenomenon of penetration enhancement.
Insights
Toxoplasma gondii rhoptry protein ROP1 localizes to the parasitophorous vacuole membrane after host cell invasion. This suggests ROP1 plays a role in the early stages of parasitic infection.
Area of Science:
- Cell Biology
- Parasitology
- Immunology
Background:
- Toxoplasma gondii is an intracellular parasite that invades host cells.
- Rhoptry proteins are crucial for host cell invasion and establishment of infection.
- ROP1 is a key rhoptry protein with a proposed role in invasion enhancement.
Purpose of the Study:
- To immunolocalize the Toxoplasma gondii rhoptry protein ROP1 before and after host cell invasion.
- To investigate the dynamic changes in ROP1 localization during the early stages of infection.
Main Methods:
- Immunoelectron microscopy and immunogold labeling were employed.
- Monoclonal antibody (Tg49) and rabbit antiserum (alpha 249) were used to detect ROP1.
- Localization was studied in human fibroblasts and TG180 murine sarcoma cells.
Main Results:
- ROP1 was consistently found within the body of rhoptries, rarely in the peduncle.
- Immediately post-invasion, ROP1 was associated with the parasitophorous vacuole membrane.
- Immunodetectable ROP1 on the parasitophorous vacuole membrane decreased significantly within hours after invasion.
Conclusions:
- ROP1 localization suggests a role in the early establishment of Toxoplasma gondii infection.
- The dynamic changes in ROP1 localization may be linked to its function in host cell penetration.
- Further research into ROP1's function could inform strategies to combat parasitic infections.