Toll-like receptor 9 binds single-stranded CpG-DNA in a sequence- and pH-dependent manner.

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Rutz M, Metzger J, Gellert T, Luppa P, Lipford GB, Wagner H, Bauer S

Toll-like receptor 9 binds single-stranded CpG-DNA in a sequence- and pH-dependent manner.

Eur J Immunol. 2004 Sep;34(9):2541-50.

PubMed ID

15307186 [ View in PubMed

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Abstract

Toll-like receptors (TLR) recognize bacterial and viral components, but direct interaction of receptor and ligand is unclear. Here, we demonstrate that TLR9 binds directly and sequence-specifically to single-stranded unmethylated CpG-DNA containing a phosphodiester backbone. TLR9-CpG-DNA interaction occurs at the acidic pH (6.5-5.0) found in endosomes and lysosomes. By sequence comparison we identified a potential CpG-DNA binding domain homologous to that described for methyl-CpG-DNA binding proteins. Amino acid substitutions in this region abrogated CpG-DNA binding and led to loss of NF-kappaB activation. Furthermore, chloroquine and quinacrine, therapeutic agents for autoimmune diseases like rheumatoid arthritis and systemic lupus erythematosus, directly blocked TLR9-CpG-DNA interaction but not TLR2-Pam3Cys binding. Our results demonstrate direct binding of TLR9 to CpG-DNA and suggest that the therapeutic activity of chloroquine and quinacrine in autoimmune diseases may be due to its activity as a TLR9 antagonist and inhibitor of endosomal acidification.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Chloroquine	Toll-like receptor 9	Protein	Humans	Unknown	Inhibitor	Details