title: Multiphasic dynamics of phosphatidylinositol 4-phosphate during phagocytosis.
abstract: We analyzed the distribution, fate, and functional role of phosphatidylinositol 4-phosphate (PtdIns4P) during phagosome formation and maturation. To this end, we used genetically encoded probes consisting of the PtdIns4P-binding domain of the bacterial effector SidM. PtdIns4P was found to undergo complex, multiphasic changes during phagocytosis. The phosphoinositide, which is present in the plasmalemma before engagement of the target particle, is transiently enriched in the phagosomal cup. Soon after the phagosome seals, PtdIns4P levels drop precipitously due to the hydrolytic activity of Sac2 and phospholipase C, becoming undetectable for ∼10 min. PtdIns4P disappearance coincides with the emergence of phagosomal PtdIns3P. Conversely, the disappearance of PtdIns3P that signals the transition from early to late phagosomes is accompanied by resurgence of PtdIns4P, which is associated with the recruitment of phosphatidylinositol 4-kinase 2A. The reacquisition of PtdIns4P can be prevented by silencing expression of the kinase and can be counteracted by recruitment of a 4-phosphatase with a heterodimerization system. Using these approaches, we found that the secondary accumulation of PtdIns4P is required for proper phagosomal acidification. Defective acidification may be caused by impaired recruitment of Rab7 effectors, including RILP, which were shown earlier to displace phagosomes toward perinuclear lysosomes. Our results show multimodal dynamics of PtdIns4P during phagocytosis and suggest that the phosphoinositide plays important roles during the maturation of the phagosome.
authors.affiliation: Division of Cell Biology, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.|Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
authors.forename: Roni
authors.initials: R
authors.lastname: Levin
authors.affiliation: Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261.
authors.forename: Gerald R V
authors.initials: GR
authors.lastname: Hammond
authors.affiliation: Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Tamas
authors.initials: T
authors.lastname: Balla
authors.affiliation: Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Kavli Institute for Neuroscience, Yale University Medical School, New Haven, CT 06510.
authors.forename: Pietro
authors.initials: P
authors.lastname: De Camilli
authors.affiliation: Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.|Department of Surgery, University of Toronto, Toronto, ON M5T 1P5, Canada.|Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Fairn
authors.affiliation: Division of Cell Biology, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada sergio.grinstein@sickkids.ca.|Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.|Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, ON M5B 1W8, Canada.
authors.forename: Sergio
authors.initials: S
authors.lastname: Grinstein
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism; D000818:Animals; D011992:Endosomes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D015778:Minor Histocompatibility Antigens / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology; D010588:Phagosomes / Q000378:metabolism* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D000067996:RAW 264.7 Cells; D020691:rab GTP-Binding Proteins / Q000378:metabolism
chemical_list: D015778:Minor Histocompatibility Antigens; D018129:Phosphatidylinositol Phosphates; C055525:phosphatidylinositol 3-phosphate; C037178:phosphatidylinositol 4-phosphate; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D019870:1-Phosphatidylinositol 4-Kinase; C000618292:PI4KIIIalpha protein, human; C402182:phosphatidylinositol phosphate 4-kinase; D020691:rab GTP-Binding Proteins