The aspartyl protease TgASP5 mediates the export of the Toxoplasma GRA16 and GRA24 effectors into host cells.
Toxoplasma gondii and Plasmodium species are obligatory intracellular parasites that export proteins into the infected cells in order to interfere with host-signalling pathways, acquire nutrients or evade host defense mechanisms. With regard to export mechanism, a wealth of information in Plasmodium spp. is available, while the mechanisms operating in T. gondii remain uncertain. The recent discovery of exported proteins in T. gondii, mainly represented by dense granule resident proteins, might explain this discrepancy and offers a unique opportunity to study the export mechanism in T. gondii. Here, we report that GRA16 export is mediated by two protein elements present in its N-terminal region. Because the first element contains a putative Plasmodium export element linear motif (RRLAE), we hypothesized that GRA16 export depended on a maturation process involving protein cleavage. Using both N- and C-terminal epitope tags, we provide evidence for protein proteolysis occurring in the N-terminus of GRA16. We show that TgASP5, the T. gondii homolog of Plasmodium plasmepsin V, is essential for GRA16 export and is directly responsible for its maturation in a Plasmodium export element-dependent manner. Interestingly, TgASP5 is also involved in GRA24 export, although the GRA24 maturation mechanism is TgASP5-independent. Our data reveal different modus operandi for protein export, in which TgASP5 should play multiple functions.
Laboratoire Adaptation et Pathogénie des Microorganismes, Centre National de la Recherche Scientifique, UMR5163, F-38041, Grenoble, France.|Université Joseph Fourier, F-38000, Grenoble Cedex 09, France.
Aurélie
A
Curt-Varesano
Laboratoire Adaptation et Pathogénie des Microorganismes, Centre National de la Recherche Scientifique, UMR5163, F-38041, Grenoble, France.|Université Joseph Fourier, F-38000, Grenoble Cedex 09, France.
Laurence
L
Braun
Bâtiment B - Biologie, BGene Genetics SAS, 2280 rue de la Piscine, 38400, Saint Martin d'Hères, France.
Caroline
C
Ranquet
Laboratoire Adaptation et Pathogénie des Microorganismes, Centre National de la Recherche Scientifique, UMR5163, F-38041, Grenoble, France.|Université Joseph Fourier, F-38000, Grenoble Cedex 09, France.
Mohamed-Ali
MA
Hakimi
Laboratoire Adaptation et Pathogénie des Microorganismes, Centre National de la Recherche Scientifique, UMR5163, F-38041, Grenoble, France.|Université Joseph Fourier, F-38000, Grenoble Cedex 09, France.
Alexandre
A
Bougdour
D057055:Aspartic Acid Proteases / Q000378:metabolism*; D002478:Cells, Cultured; D005347:Fibroblasts / Q000469:parasitology; D006801:Humans; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015800:Protozoan Proteins / Q000378:metabolism*; D014122:Toxoplasma / Q000201:enzymology / Q000378:metabolism*
D015800:Protozoan Proteins; D057055:Aspartic Acid Proteases
Apicomplexa; microbial-cell interaction; protein export; protein trafficking