title: Regulation of transferrin recycling kinetics by PtdIns[4,5]P2 availability.
abstract: Phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P2) is a phosphoinositide involved in a variety of cellular functions, including signal transduction, organelle trafficking, and actin dynamics. Although the role of PtdIns[4,5]P2 in endocytosis is well established, the precise trafficking steps relying on normal PtdIns[4,5]P2 balance in the endosomal pathway have not yet been elucidated. Here we show that decrease in intracellular PtdIns[4,5]P2 levels achieved by the overexpression of the 5-phosphatase domain of synaptojanin 1 or by siRNA knock-down of PIP5Ks expression lead to severe defects in the internalization of transferrin as well as in the recycling of internalized transferrin back to the cell surface in COS-7 cells. These defects suggest that PtdIns[4,5]P2 participates in multiple trafficking and/or sorting events during endocytosis. Coexpression of the PtdIns[4,5]P2 synthesizing enzyme, PIP5KI gamma, was able to rescue these endocytic defects. Furthermore, decreased levels of PtdIns[4,5]P2 caused delays in rapid and slow membrane recycling pathways as well as a severe backup of endocytosed membrane. Taken together, our results demonstrate that PtdIns[4,5]P2 availability regulates multiple steps in the endocytic cycle in non-neuronal cells.
authors.affiliation: Department of Life Science, Gwangju Institute of Science and Technology, 1 Oryong-dong Buk-gu, Gwangju, South Korea.
authors.forename: Sunyun
authors.initials: S
authors.lastname: Kim
authors.forename: Hyunmyung
authors.initials: H
authors.lastname: Kim
authors.forename: Belle
authors.initials: B
authors.lastname: Chang
authors.forename: Namhui
authors.initials: N
authors.lastname: Ahn
authors.forename: Suha
authors.initials: S
authors.lastname: Hwang
authors.forename: Gilbert
authors.initials: G
authors.lastname: Di Paolo
authors.forename: Sunghoe
authors.initials: S
authors.lastname: Chang
mesh_terms: D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002522:Chlorocebus aethiops; D002855:Chromatography, Thin Layer; D004705:Endocytosis; D007700:Kinetics; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014168:Transferrin / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D011994:Recombinant Proteins; D014168:Transferrin