A point mutation in the amino terminus of TLR7 abolishes signaling without affecting ligand binding

J Immunol. 2011 Apr 1;186(7):4213-22. doi: 10.4049/jimmunol.1003585. Epub 2011 Mar 7.


TLR7 is the mammalian receptor for ssRNA and some nucleotide-like small molecules. We have generated a mouse by N-nitrose-N'-ethyl urea mutagenesis in which threonine 68 of TLR7 was substituted with isoleucine. Cells bearing this mutant TLR7 lost the sensitivity to the small-molecule TLR7 agonist resiquimod, hence the name TLR7(rsq1). In this work, we report the characterization of this mutant protein. Similar to the wild-type counterpart, TLR7(rsq1) localizes to the endoplasmic reticulum and is expressed at normal levels in both primary cells and reconstituted 293T cells. In addition to small-molecule TLR7 agonists, TLR7(rsq1) fails to be activated by ssRNA. Whole-transcriptome analysis demonstrates that TLR7 is the exclusive and indispensable receptor for both classes of ligands, consistent with the fact that both ligands induce highly similar transcriptional signatures in TLR7(wt/wt) splenocytes. Thus, TLR7(rsq1) is a bona fide phenocopy of the TLR7 null mouse. Because TLR7(rsq1) binds to ssRNA, our studies imply that the N-terminal portion of TLR7 triggers a yet to be identified event on TLR7. TLR7(rsq1) mice might represent a valuable tool to help elucidate novel aspects of TLR7 biology.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Cells, Cultured
  • HEK293 Cells
  • Humans
  • Imidazoles / pharmacology
  • Ligands
  • Membrane Glycoproteins / deficiency
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • Mutagenesis, Site-Directed
  • Point Mutation / immunology*
  • Protein Binding / drug effects
  • Protein Binding / genetics
  • Protein Binding / immunology
  • Signal Transduction / drug effects
  • Signal Transduction / genetics*
  • Signal Transduction / immunology*
  • Toll-Like Receptor 7 / deficiency
  • Toll-Like Receptor 7 / genetics*
  • Toll-Like Receptor 7 / metabolism*


  • Imidazoles
  • Ligands
  • Membrane Glycoproteins
  • TLR7 protein, human
  • Tlr7 protein, mouse
  • Toll-Like Receptor 7
  • resiquimod