Phosphatidylinositol-phosphates mediate cytoskeletal reorganization during phagocytosis via a unique modular protein consisting of RhoGEF/DH and FYVE domains in the parasitic protozoon Entamoeba histolytica.
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.
Nakada-Tsukui
Kumiko
K
Department of Parasitology, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan.
Okada
Hiroyuki
H
Mitra
Biswa Nath
BN
Nozaki
Tomoyoshi
T
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004748:Entamoeba histolytica / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D018715:Microscopy, Video; D010587:Phagocytosis; D010588:Phagosomes / Q000737:chemistry; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors
D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D018129:Phosphatidylinositol Phosphates; D015800:Protozoan Proteins; D064067:Rho Guanine Nucleotide Exchange Factors