title: The O-fucosyltransferase O-fut1 is an extracellular component that is essential for the constitutive endocytic trafficking of Notch in Drosophila.
abstract: Notch is a transmembrane receptor that mediates the cell-cell interactions necessary for many cell-fate decisions. Endocytic trafficking of Notch plays important roles in the activation and downregulation of this receptor. A Drosophila O-FucT-1 homolog, encoded by O-fut1, catalyzes the O-fucosylation of Notch, a modification essential for Notch signaling and ligand binding. It was recently proposed that O-fut1 acts as a chaperon for Notch in the endoplasmic reticulum and is required for Notch to exit the endoplasmic reticulum. Here, we report that O-fut1 has additional functions in the endocytic transportation of Notch. O-fut1 was indispensable for the constitutive transportation of Notch from the plasma membrane to the early endosome, which we show was independent of the O-fucosyltransferase activity of O-fut1. We also found that O-fut1 promoted the turnover of Notch, which consequently downregulated Notch signaling. O-fut1 formed a stable complex with the extracellular domain of Notch. In addition, O-fut1 protein added to conditioned medium and endocytosed was sufficient to rescue normal Notch transportation to the early endosome in O-fut1 knockdown cells. Thus, an extracellular interaction between Notch and O-fut1 is essential for the normal endocytic transportation of Notch. We propose that O-fut1 is the first example, except for ligands, of a molecule that is required extracellularly for receptor transportation by endocytosis.
authors.affiliation: Precursory Research for Embryonic Science and Technology (PRESTO Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sasamura
authors.forename: Hiroyuki O
authors.initials: HO
authors.lastname: Ishikawa
authors.forename: Nobuo
authors.initials: N
authors.lastname: Sasaki
authors.forename: Syunsuke
authors.initials: S
authors.lastname: Higashi
authors.forename: Maiko
authors.initials: M
authors.lastname: Kanai
authors.forename: Shiho
authors.initials: S
authors.lastname: Nakao
authors.forename: Tomonori
authors.initials: T
authors.lastname: Ayukawa
authors.forename: Toshiro
authors.initials: T
authors.lastname: Aigaki
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Noda
authors.forename: Eiji
authors.initials: E
authors.lastname: Miyoshi
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsuno
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004330:Drosophila / Q000378:metabolism / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005647:Fucosyltransferases / Q000378:metabolism*; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D021381:Protein Transport / Q000502:physiology; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D016326:Extracellular Matrix Proteins; C497759:N protein, Drosophila; D051880:Receptors, Notch; D005647:Fucosyltransferases; C471275:O-fucosyltransferase 1, Drosophila