Open AccessIntervacuolar Transport and Unique Topology of GRA14, a Novel Dense Granule Protein inToxoplasma gondii
Author(s) -
Michael E. Rome,
Josh R. Beck,
Jay M. Turetzky,
Paul Webster,
Peter J. Bradley
Publication year - 2008
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.00782-08
Subject(s) - vacuole , biology , organelle , toxoplasma gondii , cytoplasm , microbiology and biotechnology , dense granule , intracellular parasite , membrane protein , transmembrane protein , transport protein , secretory pathway , granule (geology) , golgi apparatus , intracellular , biochemistry , endoplasmic reticulum , genetics , membrane , antibody , paleontology , receptor
Toxoplasma gondii is an obligate intracellular parasite that resides in the cytoplasm of its host in a unique membrane-bound vacuole known as the parasitophorous vacuole (PV). The membrane surrounding the parasite is remodeled by the dense granules, secretory organelles that release an array of proteins into the vacuole and to the PV membrane (PVM). Only a small portion of the protein constituents of the dense granules have been identified, and little is known regarding their roles in infection or how they are trafficked within the infected host cell. In this report, we identify a novel secreted dense granule protein, GRA14, and show that it is targeted to membranous structures within the vacuole known as the intravacuolar network and to the vacuolar membrane surrounding the parasite. We disruptedGRA14 and exploited the knockout strain to show that GRA14 can be transferred between vacuoles in a coinfection experiment with wild-type parasites. We also show that GRA14 has an unexpected topology in the PVM with its C terminus facing the host cytoplasm and its N terminus facing the vacuolar lumen. These findings have important implications both for the trafficking of GRA proteins to their ultimate destinations and for expectations of functional domains of GRA proteins at the host-parasite interface.