Toll-like receptor 9

Toll-like receptor 9 (often abbreviated as TLR9) is a protein that in humans is encoded by the TLR9 gene. TLR9 is a member of the Toll-like receptor (TLR) family, which plays a fundamental role in pathogen recognition and activation of innate immunity.

Structure

TLR9 is a type I transmembrane protein characterized by an extracellular domain with leucine-rich repeats (LRRs) and a cytoplasmic domain with homology to the type I interleukin-1 receptor. This receptor is most closely related to TLR7 and TLR8, both of which, like TLR9, recognize nucleic acid-like structures.

Function

TLR9 recognizes unmethylated CpG motif, a common molecular pattern observed in various pathogens but not in the mammalian genome. Upon activation, TLR9 initiates a signaling pathway that includes MyD88, IRAK4, and TRAF6, resulting in the translocation of NF-κB to the nucleus, the production of pro-inflammatory cytokines, and the upregulation of co-stimulatory molecules.

Clinical significance

TLR9 has been implicated in various diseases such as systemic lupus erythematosus, rheumatoid arthritis, and allergy. It is also being studied for its potential role in the treatment of cancer and infectious diseases.

See also

• Toll-like receptor
• Innate immunity
• CpG motif
• NF-κB
• MyD88
• IRAK4
• TRAF6