2009 Fiscal Year Final Research Report
Analysis of phosphatidylinositol mediated molecular mechanisms that related to phagocytosis process of the Entamoeba histolytica.
| Project/Area Number |
20790323
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Parasitology (including Sanitary zoology)
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| Research Institution | National Institute of Infectious Diseases |
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Principal Investigator |
TSUKUI Kumiko National Institute of Infectious Diseases, 寄生動物部, 主任研究官 (00420092)
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| Project Period (FY) |
2008 – 2009
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| Keywords | 原虫 |
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| Research Abstract |
To understand the roles of phosphoinositides [PtdIns] in phagocytosis of parasitic eukaryotes, we examined the interaction of phosphatidylinositol-3-phosphate [PtdIns(3)P] and putative PtdIns-P-binding proteins during phagocytosis in the enteric protozoan parasite Entamoeba histolytica. It was previously shown that phagocytosis in E. histolytica is indispensable for virulence and is inhibited by PtdIns 3-kinase inhibitors. We demonstrated by time-lapse live imaging that during the initiation of phagocytosis, the PtdIns(3)P biomarker GFP-Hrs-FYVE, was translocated to the phagocytic cup, phagosome, and to tunnel-like structures connecting the plasma membrane and phagosomes. E. histolytica possesses 12 FYVE domain-containing proteins (EhFP1-12), 11 of which also contain the RhoGEF/DH domain. Among them EhFP4 was shown to be recruited to the tunnel-like structures and to the proximal region of the phagosome. We further demonstrated that EhFP4 physically interacted with 4 of 10 predominant Rho/Rac small GTPases. Phosphoinositide binding assay showed that EhFP4 unexpectedly bound to PtdIns(4)P via the carboxyl-terminal domain and that the FYVE domain modulates the binding specificity of EhFP4 to PtdIns-P. Expression of the FYVE domain from EhFP4 inhibited phagocytosis while enhancement was observed when mammalian Hrs-FYVE domain was expressed. Altogether, we demonstrated that PtdIns(3)P, PtdIns(4)P and EhFP4 coordinately regulate phagocytosis and phagosome maturation in this parasitic eukaryote.
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