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Infection and Immunity, December 2008, p. 5853-5861, Vol. 76, No. 12
0019-9567/08/$08.00+0     doi:10.1128/IAI.01667-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Toxoplasma gondii Dense Granule Protein GRA7 Is Phosphorylated upon Invasion and Forms an Unexpected Association with the Rhoptry Proteins ROP2 and ROP4{triangledown}

Joe Dan Dunn,{dagger} Sandeep Ravindran, Seon-Kyeong Kim,{ddagger} and John C. Boothroyd*

Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305-5124

Received 14 December 2007/ Returned for modification 5 February 2008/ Accepted 12 September 2008

The obligate intracellular parasite Toxoplasma gondii infects warm-blooded animals throughout the world and is an opportunistic pathogen of humans. As it invades a host cell, Toxoplasma forms a novel organelle, the parasitophorous vacuole, in which it resides during its intracellular development. The parasite modifies the parasitophorous vacuole and its host cell with numerous proteins delivered from rhoptries and dense granules, which are secretory organelles unique to the phylum Apicomplexa. For the majority of these proteins, little is known other than their localization. Here we show that the dense granule protein GRA7 is phosphorylated but only in the presence of host cells. Within 10 min of invasion, GRA7 is present in strand-like structures in the host cytosol that contain rhoptry proteins. GRA7 strands also contain GRA1 and GRA3. Independently of its phosphorylation state, GRA7 associates with the rhoptry proteins ROP2 and ROP4 in infected host cells. This is the first report of interactions between proteins secreted from rhoptries and dense granules.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Stanford University School of Medicine, 299 Campus Drive, Stanford, CA 94305-5124. Phone: (650) 723-7984. Fax: (650) 725-6757. E-mail: jboothr{at}stanford.edu

{triangledown} Published ahead of print on 22 September 2008.

Editor: J. F. Urban, Jr.

{dagger} Present address: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710.

{ddagger} Present address: Institute for OneWorld Health, 50 California ST, Suite 500, San Francisco, CA 94111.

Infection and Immunity, December 2008, p. 5853-5861, Vol. 76, No. 12
0019-9567/08/$08.00+0     doi:10.1128/IAI.01667-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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