title: Phosphatidylinositol-4,5-bisphosphate hydrolysis directs actin remodeling during phagocytosis.
abstract: The Rho GTPases play a critical role in initiating actin polymerization during phagocytosis. In contrast, the factors directing the disassembly of F-actin required for fission of the phagocytic vacuole are ill defined. We used fluorescent chimeric proteins to monitor the dynamics of association of actin and active Cdc42 and Rac1 with the forming phagosome. Although actin was found to disappear from the base of the forming phagosome before sealing was complete, Rac1/Cdc42 activity persisted, suggesting that termination of GTPase activity is not the main determinant of actin disassembly. Furthermore, fully internalized phagosomes engineered to associate constitutively with active Rac1 showed little associated F-actin. The disappearance of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)) from the phagosomal membrane closely paralleled the course of actin disassembly. Furthermore, inhibition of PI(4,5)P(2) hydrolysis or increased PI(4,5)P(2) generation by overexpression of phosphatidylinositol phosphate kinase I prevented the actin disassembly necessary for the completion of phagocytosis. These observations suggest that hydrolysis of PI(4,5)P(2) dictates the remodeling of actin necessary for completion of phagocytosis.
authors.affiliation: Division of Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
authors.forename: Cameron C
authors.initials: CC
authors.lastname: Scott
authors.forename: Wendy
authors.initials: W
authors.lastname: Dobson
authors.forename: Roberto J
authors.initials: RJ
authors.lastname: Botelho
authors.forename: Natasha
authors.initials: N
authors.lastname: Coady-Osberg
authors.forename: Philippe
authors.initials: P
authors.lastname: Chavrier
authors.forename: David A
authors.initials: DA
authors.lastname: Knecht
authors.forename: Colin
authors.initials: C
authors.lastname: Heath
authors.forename: Philip
authors.initials: P
authors.lastname: Stahl
authors.forename: Sergio
authors.initials: S
authors.lastname: Grinstein
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D019281:Dimerization; D004912:Erythrocytes / Q000166:cytology; D049452:Green Fluorescent Proteins; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D010587:Phagocytosis / Q000502:physiology*; D010588:Phagosomes / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D019269:Phosphatidylinositol 4,5-Diphosphate; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein