title: The endocytic pathway mediates cell entry of dsRNA to induce RNAi silencing.
abstract: Many metazoan cells can take up exogenous double-stranded (ds) RNA and use it to initiate an RNA silencing response, however, the mechanism for this uptake is ill-defined. Here, we identify the pathway for dsRNA uptake in Drosophila melanogaster S2 cells. Biochemical and cell biological analyses, and a genome-wide screen for components of the dsRNA-uptake machinery, indicated that dsRNA is taken up by an active process involving receptor-mediated endocytosis. Pharmacological inhibition of endocytic pathways disrupted exogenous dsRNA entry and the induction of gene silencing. This dsRNA uptake mechanism seems to be evolutionarily conserved, as knockdown of orthologues in Caenorhabditis elegans inactivated the RNA interference response in worms. Thus, this entry pathway is required for systemic RNA silencing in whole organisms. In Drosophila cells, pharmacological evidence suggests that dsRNA entry is mediated by pattern-recognition receptors. The possible role of these receptors in dsRNA entry may link RNA interference (RNAi) silencing to other innate immune responses.
authors.affiliation: Department of Microbiology and Immunology, University of California San Francisco, CA 94143-2280, USA.
authors.forename: Maria-Carla
authors.initials: MC
authors.lastname: Saleh
authors.forename: Ronald P
authors.initials: RP
authors.lastname: van Rij
authors.forename: Armin
authors.initials: A
authors.lastname: Hekele
authors.forename: Amethyst
authors.initials: A
authors.lastname: Gillis
authors.forename: Edan
authors.initials: E
authors.lastname: Foley
authors.forename: Patrick H
authors.initials: PH
authors.lastname: O'Farrell
authors.forename: Raul
authors.initials: R
authors.lastname: Andino
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D011134:Polysaccharides / Q000494:pharmacology; D034622:RNA Interference / Q000502:physiology*; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D011134:Polysaccharides; D012330:RNA, Double-Stranded; D004247:DNA; C007789:fucoidan; D008156:Luciferases