The microneme rhomboid protease TgROM1 is required for efficient intracellular growth of Toxoplasma

Eukaryot Cell. 2008 Feb 29 [Epub ahead of print]

The microneme rhomboid protease TgROM1 is required for efficient intracellular growth of Toxoplasma gondii

Brossier F, Starnes GL, Beatty WL, Sibley LD

Department of Molecular Microbiology, Washington University School of Medicine, 660. S Euclid Avenue, Saint Louis, MO, 63110-1093.

Rhomboids are serine proteases that cleave their substrates within the transmembrane domain. Toxoplasma gondii contains six rhomboids that are expressed in different life cycle stages and localized to different cellular compartments. Toxoplasma rhomboid protein 1 (TgROM1) has previously been shown to be active in vitro and the orthologue in Plasmodium falciparum processes the essential microneme protein AMA1 in a heterologous system. We investigated the role of TgROM1 to determine its role in during in vitro growth of T. gondii. TgROM1 was localized in the secretory pathway of the parasite including the Golgi and micronemes, which contain adhesive proteins involved in invasion of host cells. However, unlike other micronemal proteins, TgROM1 was not released onto the parasite surface during cell invasion, suggesting it does not play a critical role in cell invasion. Suppression of TgROM1 using the tetracycline-regulatable system revealed that ROM1 deficient parasites were out-competed by wide type T. gondii. ROM1 deficient parasites showed only modest decrease in invasion but replicated more slowly than wild type cells. Collectively, these results indicate that ROM1 is required for efficient intracellular growth by T. gondii.

PMID: 18310358 [PubMed - as supplied by publisher]