title: Drosophila S2 cells secrete wingless on exosome-like vesicles but the wingless gradient forms independently of exosomes.
abstract: Wingless acts as a morphogen in Drosophila wing discs, where it specifies cell fates and controls growth several cell diameters away from its site of expression. Thus, despite being acylated and membrane associated, Wingless spreads in the extracellular space. Recent studies have focussed on identifying the route that Wingless follows in the secretory pathway and determining how it is packaged for release. We have found that, in medium conditioned by Wingless-expressing Drosophila S2 cells, Wingless is present on exosome-like vesicles and that this fraction activates signal transduction. Proteomic analysis shows that Wingless-containing exosome-like structures contain many Drosophila proteins that are homologous to mammalian exosome proteins. In addition, Evi, a multipass transmembrane protein, is also present on exosome-like vesicles. Using these exosome markers and a cell-based RNAi assay, we found that the small GTPase Rab11 contributes significantly to exosome production. This finding allows us to conclude from in vivo Rab11 knockdown experiments, that exosomes are unlikely to contribute to Wingless secretion and gradient formation in wing discs. Consistent with this conclusion, extracellularly tagged Evi expressed from a Bacterial Artificial Chromosome is not released from imaginal disc Wingless-expressing cells.
authors.affiliation: Division of Developmental Biology, MRC National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK. kbecket@nimr.mrc.ac.uk
authors.forename: Karen
authors.initials: K
authors.lastname: Beckett
authors.forename: Solange
authors.initials: S
authors.lastname: Monier
authors.forename: Lucy
authors.initials: L
authors.lastname: Palmer
authors.forename: Cyrille
authors.initials: C
authors.lastname: Alexandre
authors.forename: Hannah
authors.initials: H
authors.lastname: Green
authors.forename: Eric
authors.initials: E
authors.lastname: Bonneil
authors.forename: Graca
authors.initials: G
authors.lastname: Raposo
authors.forename: Pierre
authors.initials: P
authors.lastname: Thibault
authors.forename: Roland
authors.initials: R
authors.lastname: Le Borgne
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vincent
mesh_terms: D000818:Animals; D002460:Cell Line; D022202:Chromosomes, Artificial, Bacterial; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D055354:Exosomes / Q000378:metabolism*; D060227:Imaginal Discs / Q000166:cytology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering; D022142:Secretory Vesicles / Q000378:metabolism; D051155:Wnt1 Protein / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D051155:Wnt1 Protein; D020691:rab GTP-Binding Proteins; C511046:Wls protein, Drosophila; C074622:wg protein, Drosophila; C559123:Rab11 protein, Drosophila; D000099193:rab11 GTP-Binding Proteins