Dataset Information

Toxoplasma GRA protein identification

ABSTRACT: Toxoplasma gondii is an opportunistic pathogen infecting humans and a variety of vertebrate animals. Secretory dense granule proteins (GRA) are important effectors that mediate host-parasite interactions and facilitate parasitism. Due to the wide host range, T. gondii needs diverse GRA proteins to accommodate parasite survival in different hosts. In this study, we used two proximity based protein labeling techniques to identify novel GRA proteins. Using GRA1 as bait, two transgenic strains expressing GRA1-BirA* or GRA1-APEX were used to biotinylate GRA candidate proteins. Using these methods, 90 proteins were identified by APEX based labeling and 56 by the BirA* approach. Twenty-three were identified by both techniques, among which 13 are known GRA proteins. In combination 98 novel GRA candidates were identified by these two approaches and 25 are known GRAs. The majority of them are only present in coccidian parasites and dispensable for parasite growth in vitro, they likely mediate interactions with hosts and play roles during animal infections.

INSTRUMENT(S): Q-Tof Ultima

ORGANISM(S): Toxoplasma

TISSUE(S): Cell Culture, Fibroblast

DISEASE(S): Toxoplasmosis

SUBMITTER: Bang Shen

LAB HEAD: Bang Shen

PROVIDER: PXD009604 | Pride | 2018-11-02

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	20171107_ML_BirA1 (F007276).mzid_20171107_ML_BirA1_(F007276).pride.mgf.gz	Mzid
	20171107_ML_BirA1 (F007276).pride.mztab.gz	Mztab
	20171107_ML_BirA1-C (F007277).mzid_20171107_ML_BirA1-C_(F007277).pride.mgf.gz	Mzid
	20171107_ML_BirA1-C (F007277).pride.mztab.gz	Mztab
	20171107_ML_BirA1-CF007277.mzid.gz	Mzid

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Publications

Identification of Novel Dense-Granule Proteins in Toxoplasma gondii by Two Proximity-Based Biotinylation Approaches.

Pan Ming M Li Mingjun M Li Longjiao L Song Yongle Y Hou Lun L Zhao Junlong J Shen Bang B

Journal of proteome research 20181026 1

Toxoplasma gondii is an opportunistic pathogen infecting humans and a variety of vertebrate animals. Secretory dense-granule proteins (GRAs) play diverse roles in the mediation of host-parasite interactions and facilitate parasitism, but many of them still remain to be identified. Here, we used two proximity-based protein labeling techniques to identify novel GRA proteins. Taking GRA1 as bait, transgenic strains expressing GRA1-BirA* or GRA1-APEX were constructed to biotinylate GRAs. Using these ...[more]

PMID: 30362762

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Project description:The phylum Apicomplexa comprises an ancient group of early divergent eukaryotes, including some of the most deadly pathogens of medical and veterinary importance. Plasmodium species are responsible for malaria, which causes as many as 700,000 deaths per year, while Toxoplasma gondii chronically infects up to 30% of the human population, with immunocompromised patients and pregnant women at risk for adverse outcomes, such as toxoplasmic encephalitis and spontaneous abortion, respectively. T. gondii is considered a model system not only for its pathogenic relatives but also for intracellular parasitism and infection biology in general. T. gondii has common eukaryotic organelles, including the nucleus, endoplasmic reticulum (ER), and a single Golgi stack, but also specific secretory organelles named dense granules, micronemes, and rhoptries that contain parasite-derived factors required for host infection. Rhoptries and micronemes are formed de novo during parasite replication, and this process requires significant protein and lipid trafficking through the secretory pathway. The trafficking mechanisms employed by T. gondii retain several typical eukaryote components as well as evolving divergent features. Protein trafficking of this parasite is mediated by entry into a canonical ER followed by vesicle packaging through a single Golgi complex. Post-Golgi protein sorting to specific organelles requires the function of dynamin-related protein B, which is involved in fission events. Downstream Rab-GTPases function throughout the parasite secretory pathway. T. gondii soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins in docking and fusion at target membranes have also been described. However, unlike in mammalian cells, T. gondii ER is reduced so that the nuclear envelope itself contributes to a substantial proportion of its total volume. Whereas in mammalian cells hundreds of Golgi stacks occupy the perinuclear area, the Golgi apparatus is limited to a single discrete structure in T.gondii. The post-Golgi system also named the endosome-like compartment (ELC) is involved in the trafficking of microneme proteins. The ELC is decorated by the small GTPases, Rab5 and Rab7, which are typically associated with the endosomal system. Nevertheless, classical endocytosis has not yet been validated in T. gondii. This parasite has no lysosomes; rather the parasite harbors acidic vesicles that were thought to be precursors of the rhoptry organelles. The parasite lacks most components of endosomal sorting complexes (ESCRT), which are known for their roles in forming multivesicular bodies that deliver ubiquitinated membrane proteins and lipids to lysosomes for degradation. The machinery required for caveogenesis and caveola-dependent invaginations have not yet been identified in the parasite. Furthermore, while evidence of conventional clathrin-dependent endocytosis by T.gondii is lacking, clathrin is present exclusively in post-Golgi compartments where its function is restricted to post-Golgi trafficking, and the uptake of cytosol proteins by the tachyzoites of T. gondii has recently been described using an endocytosis assay. However, the mechanisms underlying the events of this unconventional endocytosis in the parasite remain to be determined. Clearly, the secretory pathway of T. gondii can be considered a stripped-down version of the more complex trafficking machinery that characterizes higher eukaryotes. Despite this minimal trafficking machinery, the parasites actively rely on a membrane vesicle formation and transport during its intracellular lifecycle; however, to date, comparatively little is known about the mechanisms involved in trafficking pathways in T. gondii. We previously reported a T. gondii sortilin-like receptor (TgSORTLR) that regulates protein transport and is essential for apical secretory organelle biogenesis and host infection17. Moreover, the C-terminal tail of TgSORTLR was shown to be involved in recruiting many cytosolic cargo proteins including two homologues of the core retromer components, Vps26 and Vps35, which are known to regulate retrograde transport from endosomes to the trans-Golgi Network (TGN) in yeast and mammals. Here, we report that a singular architecture with a trimer Vps35-Vps26-Vps29 core complex acts as the major cargo endosomal recycling machinery and is required for parasite integrity and more specifically for secretory organelle biogenesis and maintenance of a multiple ligand-binding transporter at the T. gondii membrane. Our findings provide strong evidence that the unconventional TgSORTLR-containing endosome-like compartment is involved in distinct mechanisms for the delivery of major retromer-dependent cargo. In this current work, we demonstrate a definitive role for the endocytic recycling pathway in T. gondii pathogenesis.

Project description:Toxoplasma gondii is a widely prevalent parasite of animals and humans that causes a broad spectrum of conditions ranging from asymptomatic or mild cold-like infections to abortion, severe ocular disease, encephalitis, and sometimes death. It is a member of the phylum Apicomplexa that also includes such significant human pathogens as Plasmodium spp. and Cryptosporidium spp. causing malaria and diarrheal disease, respectively. The toxoplasma cell has a multilayered pellicle: under the plasma membrane lies the inner membrane complex (IMC) comprised of flat membrane sacks supported by cortical microtubules and a meshwork of cytoskeletal filaments. The IMC acts as a mechanical barrier for membrane vesicles trafficking to and from the plasma membrane, necessitating the existence of dedicated cites for endo- and exocytosis where the IMC is interrupted. One such site is located at the apical end of the cell where the contents of the apical secretory organelles is exocytosed upon invasion. However, endocytosis in Toxoplasma and other apicomplexans is poorly understood, although conspicuous invaginations of the plasma membrane observed microscopically have been dubbed the micropore and postulated to be involved in endocytosis. We found that the endocytic markers including the subunits α and μ of the AP2 adaptor complex, dynamin-related protein C (DrpC), an Eps15 homology domain-containing protein, and the kelch-domain protein K13 localise to distinct persistent foci in the pellicle of Toxoplasma. Another type of persistent punctate structures found in the IMC are the enigmatic apical annuli whose function is completely unknown. We have discovered a new component of the annuli which is a putative LMBR1 family region protein embedded into the plasma membrane. Our experiments indicate that this protein – and annuli by extension – has a role in exocytosis. To better understand the molecular composition of these endocytic and exocytic structures and gain an insight into their function, we genetically fused them with a promiscuous bacterial biotin-ligase BirA* and used them as baits in proximity-dependent biotin identification experiments (BioID). We employed TMT10plex labelling and MS3-level tandem mass spectrometry with synchronous precursor selection (SPS-MS3) to achieve accurate quantification of multiple samples. Several hundred proteins have been identified and quantified in three biological replicates for every bait and the parental cell line control. Proteins significantly enriched in the BirA*-tagged cells relative to the control have been identified using linear modelling with LIMMA.