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      The heat shock protein 90 of Toxoplasma gondii is essential for invasion of host cells and tachyzoite growth Translated title: La protéine de choc thermique 90 de Toxoplasma gondii est essentielle pour l’invasion des cellules hôtes et la croissance des tachyzoïtes

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          Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects almost all warm-blooded vertebrates. Heat shock proteins (HSP) regulate key signal transduction events in many organisms, and heat shock protein 90 (Hsp90) plays an important role in growth, development, and virulence in several parasitic protozoa. Here, we discovered increased transcription of the Hsp90 gene under conditions for bradyzoite differentiation, i.e. alkaline and heat shock conditions in vitro, suggesting that Hsp90 may be connected with bradyzoite development in T. gondii. A knockout of the TgHsp90 strain ( ΔHsp90) and a complementation strain were constructed. The TgHsp90 knockout cells were found to be defective in host-cell invasion, were not able to proliferate in vitro in Vero cells, and did not show long-time survival in mice in vivo. These inabilities of the knockout parasites were restored upon complementation of TgHsp90. These data unequivocally show that TgHsp90 contributes to bradyzoite development, and to invasion and replication of T. gondii in host cells.

          Translated abstract

          Toxoplasma gondii est un Apicomplexa parasite intracellulaire obligatoire qui infecte presque tous les vertébrés à sang chaud. Les protéines de choc thermique régulent les événements principaux de transduction du signal chez de nombreux organismes et la protéine de choc thermique 90 (Hsp90) joue un rôle important dans la croissance, le développement et la virulence chez plusieurs protozoaires parasites. Dans ce travail nous avons découvert une augmentation de la transcription du gène de Hsp90 dans les conditions de différenciation des bradyzoïtes et de chocs alcalins et thermiques in vitro, ce qui suggère que Hsp90 est lié au développement des bradyzoïtes chez T. gondii. Un knock-out de la souche TgHsp90 ( ΔHsp90) et une souche de complémentation ont été construits. Les cellules knock-out TgHsp90 se sont révélées défectueuses dans l’invasion des cellules hôtes, n’ont pas pu proliférer in vitro dans des cellules Vero et n’ont pas montré de survie de longue durée chez la souris in vivo. Ces défauts des parasites knock-out ont été restaurés lors de la complémentation de TgHsp90. Ces données montrent sans équivoque que TgHsp90 contribue au développement des bradyzoïtes, et à l’invasion et à la réplication de T. gondii dans les cellules hôtes.

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          Most cited references 48

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          Heat shock proteins and immune system.

           B Gao,  M F Tsan (2009)
          Heat shock proteins (HSPs) such as HSP 60 (Hsp60), Hsp70, Hsp90, and gp96, have been reported to play important roles in antigen presentation and cross-presentation, activation of macrophages and lymphocytes, and activation and maturation of dendritic cells. HSPs contain peptide-binding domains that bind exposed hydrophobic residues of substrate proteins. As part of their molecular chaperone functions, HSPs bind and deliver chaperoned, antigenic peptides to MHC class I molecules at the cell surface for presentation to lymphocytes. HSPs also bind nonprotein molecules with exposed hydrophobic residues including lipid-based TLR ligands. Recombinant HSP products may be contaminated with pathogen-associated molecules that contain exposed hydrophobic residues such as LPS (a TLR4 ligand), lipoprotein (a TLR2 ligand), and flagellin (a TLR5 ligand). These contaminants appear to be responsible for most, if not all, reported in vitro cytokine effects of HSPs, as highly purified HSPs do not show any cytokine effects. We propose that HSPs are molecular chaperones that bind protein and nonprotein molecules with exposed hydrophobic residues. The reported antigen presentation and cross-presentation and in vitro HSP cytokine functions are a result of molecules bound to or chaperoned by HSPs but not a result of HSPs themselves.
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            Foodborne toxoplasmosis.

            Toxoplasmosis can be due to congenital infection or acquired infection after birth and is one of the leading illnesses associated with foodborne hospitalizations and deaths. Undercooked meat, especially pork, lamb, and wild game meat, and soil contaminated with cat feces on raw fruits and vegetables are the major sources of foodborne transmission for humans. The new trend in the production of free-range organically raised meat could increase the risk of Toxoplasma gondii contamination of meat. Foodborne transmission can be prevented by production practices that reduce T. gondii in meat, adequate cooking of meat, washing of raw fruits and vegetables, prevention of cross contamination in the kitchen, and measures that decrease spread of viable oocysts into the environment.
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              Extracellular heat shock proteins in cell signaling.

              Extracellular stress proteins including heat shock proteins (Hsp) and glucose regulated proteins (Grp) are emerging as important mediators of intercellular signaling and transport. Release of such proteins from cells is triggered by physical trauma and behavioral stress as well as exposure to immunological "danger signals". Stress protein release occurs both through physiological secretion mechanisms and during cell death by necrosis. After release into the extracellular fluid, Hsp or Grp may then bind to the surfaces of adjacent cells and initiate signal transduction cascades as well as the transport of cargo molecules such as antigenic peptides. In addition Hsp60 and hsp70 are able to enter the bloodstream and may possess the ability to act at distant sites in the body. Many of the effects of extracellular stress proteins are mediated through cell surface receptors. Such receptors include Toll Like Receptors 2 and 4, CD40, CD91, CCR5 and members of the scavenger receptor family such as LOX-1 and SREC-1. The possession of a wide range of receptors for the Hsp and Grp family permits binding to a diverse range of cells and the performance of complex multicellular functions particularly in immune cells and neurones.

                Author and article information

                EDP Sciences
                19 June 2017
                : 24
                : ( publisher-idID: parasite/2017/01 )
                [1 ] Institute of Preventive Veterinary Medicine & Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, College of Animal Sciences, Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Zhejiang University Hangzhou 310058 PR China
                [2 ] Shenzhen Entry-exit Inspection and Quarantine Bureau Shenzhen 518045 PR China
                [3 ] Department of Biomedical Sciences and One Health Center for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine P.O. Box 334 Basseterre, St. Kitts West Indies
                Author notes
                [* ]Corresponding author: afdu@ 123456zju.edu.cn
                parasite170030 10.1051/parasite/2017023
                © H. Sun et al., published by EDP Sciences, 2017

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 8, Tables: 1, Equations: 0, References: 55, Pages: 11
                Research Article


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