Nature Cell Biology
- 8, 793 - 802 (2006)
Published online: 23 July 2006; | doi:10.1038/ncb1439
The endocytic pathway mediates cell entry of dsRNA to induce RNAi silencingMaria-Carla Saleh1, 4, Ronald P. van Rij1, 4, Armin Hekele1, Amethyst Gillis1, Edan Foley2, 3, Patrick H. O'Farrell2 & Raul Andino11
Department of Microbiology and Immunology, University of California San Francisco, CA 94143–2280, USA. 2
Department of Biochemistry and Biophysics, University of California San Francisco, CA 94143-2200, USA. 3
Current address: Canada Research Chair in Innate Immunity, Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Canada. 4
These authors contributed equally to this work.
Correspondence should be addressed to Raul Andino Raul.Andino@UCSF.edu 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.
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