Uptake of extracellular double-stranded RNA by SID-2

Mol Cell. 2012 Sep 14;47(5):746-54. doi: 10.1016/j.molcel.2012.07.014. Epub 2012 Aug 16.

Abstract

Ingested dsRNAs trigger RNA interference (RNAi) in many invertebrates, including the nematode Caenorhabditis elegans. Here we show that the C. elegans apical intestinal membrane protein SID-2 is required in C. elegans for the import of ingested dsRNA and that, when expressed in Drosophila S2 cells, SID-2 enables the uptake of dsRNAs. SID-2-dependent dsRNA transport requires an acidic extracellular environment and is selective for dsRNAs with at least 50 base pairs. Through structure-function analysis, we identify several SID-2 regions required for this activity, including three extracellular, positively charged histidines. Finally, we find that SID-2-dependent transport is inhibited by drugs that interfere with vesicle transport. Therefore, we propose that environmental dsRNAs are imported from the acidic intestinal lumen by SID-2 via endocytosis and are released from internalized vesicles in a secondary step mediated by the dsRNA channel SID-1. Similar multistep mechanisms may underlie the widespread observations of environmental RNAi.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / antagonists & inhibitors
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Cells, Cultured
  • Drosophila / cytology
  • Drosophila / metabolism
  • Endocytosis
  • Histidine / metabolism
  • Hydrogen-Ion Concentration
  • Macrolides / pharmacology
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • RNA, Double-Stranded / chemical synthesis
  • RNA, Double-Stranded / chemistry
  • RNA, Double-Stranded / metabolism*
  • Structure-Activity Relationship
  • Thiazolidines / pharmacology

Substances

  • Bridged Bicyclo Compounds, Heterocyclic
  • Caenorhabditis elegans Proteins
  • Macrolides
  • Membrane Proteins
  • RNA, Double-Stranded
  • SID-2 protein, C elegans
  • Thiazolidines
  • Histidine
  • bafilomycin A1
  • latrunculin A