科研之友
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摘要
Background: How LL-37 delivers double-stranded RNA (dsRNA) to activate TLR3 signaling is poorly understood. Results: LL-37 was found to traffic to endosomes with RNA and releases the dsRNA upon endosome acidification. A peptide derived from LL-37 could antagonize LL-37dsRNA trafficking. Conclusion: LL-37 trafficking of dsRNA is regulated by pH. Significance: This work establishes the mechanism of LL-37 enhancement of dsRNA-activated TLR3 signaling. LL-37 is a peptide secreted by human epithelial cells that can lyse bacteria, suppress signaling by Toll-like receptor 4 (TLR4), and enhance signaling to double-stranded RNA (dsRNA) by TLR3. How LL-37 interacts with dsRNA to affect signal transduction by TLR3 is not completely understood. We determined that LL-37 binds dsRNA and traffics to endosomes and releases the dsRNA in a pH-dependent manner. Using dynamic light scattering spectroscopy and cell-based FRET experiments, LL-37 was found to form higher order complexes independent of dsRNA binding. Upon acidification LL-37 will dissociate from a larger complex. In cells, LL-37 has a half-live of approximate to 1 h. LL-37 half-life was increased by inhibiting endosome acidification or inhibiting cathepsins, which include proteases whose activity are activated by endosome acidification. Residues in LL-37 that contact poly(I:C) and facilitate oligomerization in vitro were mapped. Peptide LL-29, which contains the oligomerization region of LL-37, inhibited LL-37 enhancement of TLR3 signal transduction. LL-29 prevented LL-37poly(I:C) co-localization to endosomes containing TLR3. These results shed light on the requirements for LL-37 enhancement of TLR3 signaling.
- 出版日期2014-10-3
