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The Toxoplasma gondii rhoptry protein ROP4 is secreted into the parasitophorous vacuole and becomes phosphorylated in infected cells.

ABSTRACT: Many intracellular pathogens are separated from the cytosol of their host cells by a vacuole membrane. This membrane serves as a critical interface between the pathogen and the host cell, across which nutrients are imported, wastes are excreted, and communication between the two cells takes place. Very little is known about the vacuole membrane proteins mediating these processes in any host-pathogen interaction. During a screen for monoclonal antibodies against novel surface or secreted proteins of Toxoplasma gondii, we identified ROP4, a previously uncharacterized member of the ROP2 family of proteins. We report here on the sequence, posttranslational processing, and subcellular localization of ROP4, a type I transmembrane protein. Mature, processed ROP4 is localized to the rhoptries, secretory organelles at the apical end of the parasite, and is secreted from the parasite during host cell invasion. Released ROP4 associates with the vacuole membrane and becomes phosphorylated in the infected cell. Similar results are seen with ROP2. Further analysis of ROP4 showed it to be phosphorylated on multiple sites, a subset of which result from the action of either host cell protein kinase(s) or parasite kinase(s) activated by host cell factors. The localization and posttranslational modification of ROP4 and other members of the ROP2 family of proteins within the infected cell make them well situated to play important roles in vacuole membrane function.

SUBMITTER: Carey KL

PROVIDER: S-EPMC522600 | biostudies-literature | 2004 Oct

REPOSITORIES: biostudies-literature

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The Toxoplasma gondii rhoptry protein ROP4 is secreted into the parasitophorous vacuole and becomes phosphorylated in infected cells.

Carey Kimberly L KL Jongco Artemio M AM Kim Kami K Ward Gary E GE

Eukaryotic cell 20041001 5

Many intracellular pathogens are separated from the cytosol of their host cells by a vacuole membrane. This membrane serves as a critical interface between the pathogen and the host cell, across which nutrients are imported, wastes are excreted, and communication between the two cells takes place. Very little is known about the vacuole membrane proteins mediating these processes in any host-pathogen interaction. During a screen for monoclonal antibodies against novel surface or secreted proteins ...[more]

PMID: 15470260

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Project description:Toxoplasma gondii tachyzoites co-opt host cell functions through introduction of a large set of rhoptry- and dense granule-derived effector proteins. These effectors reach the host cytosol through different means: direct injection for rhoptry effectors and translocation across the parasitophorous vacuolar membrane (PVM) for dense granule (GRA) effectors. The machinery that translocates these GRA effectors has recently been partially elucidated, revealing three components, MYR1, MYR2, and MYR3. To determine whether other proteins might be involved, we returned to a library of mutants defective in GRA translocation and selected one with a partial defect, suggesting it might be in a gene encoding a new component of the machinery. Surprisingly, whole-genome sequencing revealed a missense mutation in a gene encoding a known rhoptry protein, a serine/threonine protein kinase known as ROP17. ROP17 resides on the host cytosol side of the PVM in infected cells and has previously been known for its activity in phosphorylating and thereby inactivating host immunity-related GTPases. Here, we show that null or catalytically dead mutants of ROP17 are defective in GRA translocation across the PVM but that translocation can be rescued "in trans" by ROP17 delivered by other tachyzoites infecting the same host cell. This strongly argues that ROP17's role in regulating GRA translocation is carried out on the host cytosolic side of the PVM, not within the parasites or lumen of the parasitophorous vacuole. This represents an entirely new way in which the different secretory compartments of Toxoplasma tachyzoites collaborate to modulate the host-parasite interaction.IMPORTANCE When Toxoplasma infects a cell, it establishes a protective parasitophorous vacuole surrounding it. While this vacuole provides protection, it also serves as a barrier to the export of parasite effector proteins that impact and take control of the host cell. Our discovery here that the parasite rhoptry protein ROP17 is necessary for export of these effector proteins provides a distinct, novel function for ROP17 apart from its known role in protecting the vacuole. This will enable future research into ways in which we can prevent the export of effector proteins, thereby preventing Toxoplasma from productively infecting its animal and human hosts.

Dataset Information

The Toxoplasma gondii rhoptry protein ROP4 is secreted into the parasitophorous vacuole and becomes phosphorylated in infected cells.

Publications

The Toxoplasma gondii rhoptry protein ROP4 is secreted into the parasitophorous vacuole and becomes phosphorylated in infected cells.

Similar Datasets

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