Reactome: A Curated Pathway Database

Toll Like Receptor 9 (TLR9) Cascade (R-HSA-168138)

Species Homo sapiens

Summation

CpG DNA is an unusual Pathogen-Associated Molecular Pattern (PAMP). Cytosine methylation exists in mammalian but not bacterial cells, and most (but not all) CpG in the mammalian genome is methylated. Therefore, unmethylated CpG DNA may signal the presence of microbial infection. Evidence of CpG recognition by TLR9 was demonstrated both in human and mouse, and this type of signaling requires its internalization into late endosomal/lysosomal compartments. TLR9 has been reported to be able to discern different types of CpG motifs, and therefore that it presumably recognizes CpG DNA directly. It appears that over evolutionary periods, TLR9 molecules expressed by different species have diverged. This has led to differences in the precise sequence motif (CpG dinucleotide plus flanking regions) that optimally stimulate the innate immune system of different animals.

Locations in the PathwayBrowser
Additional Information
Compartment cytosol , endosome membrane , nucleoplasm
GO Biological Process toll-like receptor 9 signaling pathway (0034162)
Cross References
Database Identifier
BioModels Database BIOMD0000000477
Literature References
pubMedId Title Journal Year
14751759 Signal transduction pathways mediated by the interaction of CpG DNA with Toll-like receptor 9 Semin Immunol 2004