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Uptake of extracellular double-stranded RNA by SID-2.
Deborah L McEwan1, Alexandra S Weisman, Craig P Hunter
1Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
Molecular Cell
|August 21, 2012
Summary
The C. elegans protein SID-2 facilitates the uptake of ingested double-stranded RNA (dsRNA) into cells, a process crucial for RNA interference (RNAi). This uptake occurs via endocytosis in an acidic environment, requiring specific SID-2 regions.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- RNA interference (RNAi) is a conserved gene-silencing mechanism triggered by double-stranded RNA (dsRNA).
- In invertebrates like C. elegans, ingested dsRNA can induce systemic RNAi, but the uptake mechanism remains unclear.
Purpose of the Study:
- To elucidate the mechanism of ingested dsRNA uptake in C. elegans.
- To identify the role of the SID-2 protein in dsRNA import and RNAi.
Main Methods:
- Expression of C. elegans SID-2 in Drosophila S2 cells.
- Structure-function analysis of SID-2.
- Treatment with drugs affecting vesicle transport.
- Analysis of dsRNA uptake under varying pH conditions.
Main Results:
- SID-2 is essential for the uptake of ingested dsRNA in C. elegans.
- Expressed SID-2 enables dsRNA uptake in Drosophila S2 cells.
- SID-2-mediated dsRNA transport requires an acidic extracellular environment and dsRNAs of at least 50 base pairs.
- Specific extracellular histidines in SID-2 are critical for its function.
- Vesicle transport inhibitors block SID-2-dependent dsRNA uptake.
Conclusions:
- SID-2 mediates dsRNA import from the acidic intestinal lumen via endocytosis.
- A two-step mechanism involving SID-2 and SID-1 facilitates environmental RNAi.
- This mechanism provides insight into the widespread phenomenon of environmental RNAi.
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