Wednesday, April 16, 2008

Programmed Cell Death 5: A secreted molecule that exerts a pro-apoptotic effect on hosts

Mol Biochem Parasitol. 2008 Mar 6 [Epub ahead of print]

Programmed Cell Death 5 from Toxoplasma gondii: A secreted molecule that exerts a pro-apoptotic effect on host cells

Bannai H, Nishikawa Y, Matsuo T, Kawase O, Watanabe J, Sugimoto C, Xuan X.

National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.

Although parasite-infected host cells become resistant to apoptosis, uninfected bystander cells undergo apoptosis during Toxoplasma gondii infection. The Programmed Cell Death 5 (TgPDCD5) gene, a homologue of the human apoptosis-related molecule, was cloned from a T. gondii full-length cDNA database and subsequently characterized. The native TgPDCD5 was located in the cytosol and also detected in the secreted fraction. Immuno-electron microscopic analysis showed TgPDCD5 was primarily located close to the rhoptries or vesicle-like structures near the surface membrane of the parasite. Studies using recombinant TgPDCD5 (rTgPDCD5) demonstrated that host cells internalize the molecule in a heparan sulfate proteoglycan-binding motif-dependent manner. Furthermore, the addition of rTgPDCD5 to culture medium resulted in the enhancement of host-cell apoptosis triggered by etoposide in macrophage cell line J774A.1 and leukemic cell line HL-60 cells. Additionally, rTgPDCD5 induced apoptosis in J774A.1 cells in the presence of IFN-gamma. This report is the first to identify a parasitic molecule of T. gondii that has a pro-apoptotic effect on host cells.

PMID: 18406478 [PubMed - as supplied by publisher]

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