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Updated: Feb 12, 2026
HeLa Based Cell Free Expression Systems for Expression of Plasmodium Rhoptry Proteins
Published on: June 10, 2015
Identification of a novel rhoptry protein expressed predominantly in Plasmodium sporozoites
Sunti Oundavong1, Takashi Sekine1, Motomi Torii2
1Department of Parasitology and Tropical Medicine, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, Tokyo, Japan.
Abstract:
The infective stages of apicomplexan protozoans, such as the malaria parasite Plasmodium, possess apical organelles rhoptries and micronemes, which contain secretory proteins required for host cell invasion. The mechanisms mediating invasion are largely conserved among apicomplexan parasites; for example, rhoptry proteins are secreted to form a tight junction prior to invasion, which facilitates parasite entry into target cells. Stage-specific invasion mechanisms have also been described; such as those differentially mediating Plasmodium merozoite infection of erythrocytes versus sporozoite stage invasion of mosquito salivary glands and mammalian hepatocytes. Sporozoites are the transmission stage present within the salivary glands of infected mosquitoes, and can efficiently infect the mammalian liver after being deposited in the skin during a blood meal. While some sporozoite rhoptry proteins have been demonstrated to be critical for invasion of mosquito salivary glands and mammalian hepatocytes, their comprehensive molecular mechanisms have not been elucidated due to the limited availability of material. To screen for Plasmodium sporozoite-specific rhoptry proteins in the rodent malaria parasite, Plasmodium berghei, a proximity-dependent biotin identification method was employed combined with a genome editing strategy. Rhoptry neck protein 12 (RON12) was identified as a rhoptry molecule with the highest transcript levels in sporozoites; and was selected for use as a bait following tagging with UltraID. In RON12::ultraID expressing transgenic sporozoites, several secretory proteins were successfully biotinylated during parasite maturation in mosquitoes, including known rhoptry proteins. A novel rhoptry molecule was identified, PBANKA_1363400, which was localized to sporozoite rhoptries and was predominantly expressed in sporozoites rather than merozoites. This study demonstrates that the UltraID strategy enables highly sensitive and comprehensive protein identification in a species- or stage-specific manner in Plasmodium sporozoites.
Insights
Researchers identified novel proteins in malaria parasite sporozoites using a proximity-dependent biotin identification method. This technique aids in understanding Plasmodium parasite invasion mechanisms and developing new anti-malarial strategies.
Area of Science:
- Parasitology
- Molecular Biology
- Infectious Diseases
Background:
- Apicomplexan parasites like Plasmodium use apical organelles (rhoptries, micronemes) for host cell invasion.
- Sporozoites are key malaria transmission stages, infecting the liver, but their invasion mechanisms are not fully understood due to material limitations.
Purpose of the Study:
- To identify Plasmodium sporozoite-specific rhoptry proteins using a novel screening method.
- To elucidate the molecular mechanisms of Plasmodium sporozoite invasion.
Main Methods:
- Employed a proximity-dependent biotin identification method combined with genome editing in Plasmodium berghei.
- Utilized Rhoptry Neck Protein 12 (RON12) tagged with UltraID as bait in transgenic sporozoites.
Main Results:
- Successfully biotinylated several secretory proteins during parasite maturation, including known rhoptry proteins.
- Identified a novel rhoptry molecule, PBANKA_1363400, predominantly expressed in sporozoites.
- Demonstrated the UltraID strategy's effectiveness for sensitive, stage-specific protein identification in Plasmodium sporozoites.
Conclusions:
- The UltraID strategy is a powerful tool for comprehensive protein identification in Plasmodium sporozoites.
- This study identified a novel rhoptry protein potentially crucial for sporozoite invasion.
- Findings contribute to understanding malaria parasite transmission and host cell entry.
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