Selectivity of Human TLR9 for Double CpG Motifs and Implications for the Recognition of Genomic DNA

Abstract

TLR9 acts as a first-line host defense against pathogens recognizing DNA comprising unmethylated CpG motifs present in bacteria and viruses. Species- and sequence-specific recognition differences were demonstrated for TLR9 receptors. Activation of human (h)TLR9 requires a pair of closely positioned CpG motifs within oligodeoxyribonucleotides (ODNs), whereas mouse TLR9 is effectively activated by an ODN with a single CpG motif. Molecular model-directed mutagenesis identified two regions, site A and site B, as important for receptor activation. Amino acid residues Gln and Arg within site A contribute to the sequence-specific recognition by hTLR9 in determining the bias for two appropriately spaced CpG motifs within immunostimulatory ODNs. Mutation of Gln at site B, in combination with Gln and Arg mutations of mouse counterparts, increased activation of hTLR9 by mouse-specific ODN, mammalian genomic DNA, and bacterial DNA. We propose that the double CpG motif sequence-specificity of hTLR9 results in decreased activation by ODNs with a lower frequency of CpG motifs, such as from mammalian genomic DNA, which increases hTLR9 selectivity for pathogen versus host DNA.

Class A CpG Oligonucleotide Priming Rescues Mice from Septic Shock via Activation of Platelet-Activating Factor Acetylhydrolase

“…However, excessive cytokine production results in a “cytokine storm,” which can induce lethal endotoxin shock ( 4 , 5 ). TLR9 acts as a first-line host defense against pathogens recognizing DNA comprising unmethylated CpG motifs present in bacteria and viruses ( 6 ). Nucleic acid therapeutics including oligodeoxynucleotides (ODNs) from bacterial genomic DNA and microRNA are potential targeted therapies as they can strongly regulate gene expression and immune response ( 7 – 10 ).…”

The effect of anesthetics on toll like receptor 9

“…Isoflurane's electrostatic potential map showed a large negative charge potential surface ( Figure 4C), which could lead to charge interaction between isoflurane and positively charged residues of TLR9 ( Figure 4B alone. 23,27,28 In contrast, the degree of dimerization and activation of mouse TLR9 by CpG DNA alone is not different from by the combination of CpG DNA and 5′-xCx DNA. 29 Thus, we did not examine the role of isoflurane sites on mouse TLR9 despite we observed adducted residues ( Table 1, Supporting Figure S2).…”

Conservation and Divergence of Ligand Recognition and Signal Transduction Mechanisms in Toll-Like Receptors

“…[65][66][67][68][69][70] This species specificity cannot be explained by the current structural study, but it may be related to another DNA-binding site on TLR9. [71][72][73] Further structural studies will be needed to establish the basis for the species specificity of TLR9 activation. The structures of the inhibitory DNA-bound form of TLR9 were also determined 64) ( Fig.…”